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Electrochemical deposition regimes and critical influence of organic additives on the structure of Bifilms
... The efficiency of electrochemical deposition significantly depends on the chemical composition of the electrolyte. A large number of studies have been devoted to the electrodeposition of Bi films from silicate, pyrophosphate, nitrate, citric, stearic, sulfate, lactate, and other electrolytes [29][30][31][32][33]. Besides, for a specific electrolyte composition, organic additives provide additional control over the film structure [34,35]. ...
... A well-known nitrate electrolyte can allow the electrodeposition of uniform coatings in specific conditions, but the deposition is limited in speed down to 12 µm/h [30,39]. In this work, we used a recently developed [36,40] perchlorate electrolyte, which is more suitable for practical applications due to a higher growth speed (up to 200 µm/h) and comparable quality of deposits [34]. ...
... The change in dominating texture of Bi film synthesized under j = 70.0 mA/cm 2 probably is attributed to different adsorption of atomic hydrogen and beginning of electrochemical reaction of hydrogen ions reduction: such a high cathode current density causes the reduction of Bi 3+ in the diffusion-limited mode [34]. ...
The study is devoted to the electronic properties and structure of bismuth films obtained by electrodeposition from high-speed perchlorate electrolyte. Polycrystalline samples were synthesized in acidic perchlorate electrolyte under the (0.18 – 70.0) mA/cm² cathode current density and annealed at 265 oC in the He gas atmosphere. The structure, microstructure and electron properties of Bi films were characterized using X-Ray diffraction analysis, scanning electron microscopy, and electron backscattered diffraction. Electrical resistance, magnetoresistance, and Hall coefficient were studied at the 5 – 300 K temperature range under magnetic field up to 8 T. A specific and unexpected behavior has been found concerning the average size and shape of Bi grains with increasing of the current density: the increase in deposition current density up to 70.0 mA/cm² contributes to Bi films formation with more isotropic and reduced average grains size. Samples synthesized under 0.18 mA/cm² current density after annealing showed electronic properties, including magnetoresistance, similar to those of flawless single-crystals. The differences in the electronic characteristics of Bi films electrodeposited under different currents and electrolyte composition were explained by changes in electronic mobility due to scattering on grain boundaries.
... Many previous studies have been dedicated to Bi films electrodeposition from lactate, tartrate, silicate, nitrate, citric, hydrochloric, stearic, sulfate, and pyrophosphate electrolytes [13,27,32,41,[46][47][48][49][50]. However, the literature on the perchlorate electrolytes study is not comprehensive enough [51,52]. This electrolyte has several advantages: Homogeneous and dense coatings obtaining, high deposition rates, and it also approximates 100% current efficiency. ...
... Then, a change in the morphology of the grains to a granular form was observed ( Figure 4D-F). Finally, after 15 s of deposition, a layered granular morphology of Bi grains was observed, which was characteristic of rhombohedral Bi [52]. ...
... Then, a change in the morphology of the grains to a granular form was observed ( Figure 4D-F). Finally, after 15 s of deposition, a layered granular morphology of Bi grains was observed, which was characteristic of rhombohedral Bi [52]. The layering of granular Bi grains occurs due to the growth texture (preferential orientation of the grains). ...
Bi nanocrystalline films were formed from perchlorate electrolyte (PE) on Cu substrate via electrochemical deposition with different duration and current densities. The microstructural, morphological properties, and elemental composition were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray microanalysis (EDX). The optimal range of current densities for Bi electrodeposition in PE using polarization measurements was demonstrated. For the first time, it was shown and explained why, with a deposition duration of 1 s, co-deposition of Pb and Bi occurs. The correlation between synthesis conditions and chemical composition and microstructure for Bi films was discussed. The analysis of the microstructure evolution revealed the changing mechanism of the films’ growth from pillar-like (for Pb-rich phase) to layered granular form (for Bi) with deposition duration rising. This abnormal behavior is explained by the appearance of a strong Bi growth texture and coalescence effects. The investigations of porosity showed that Bi films have a closely-packed microstructure. The main stages and the growth mechanism of Bi films in the galvanostatic regime in PE with a deposition duration of 1–30 s are proposed.
... The semiconducting photocatalyst has appeared as useful automation because of diverse favors counting modest, low energy depletion, non-toxicity, and the ability to efficiently use UV and/or visible light productively [6][7][8]. Among the abundant and various multifunctional semiconductor photocatalysts [9,10], ZnO sticks out as the most encouraging matter due to its high photosensitivity, non-toxic/stable nature, low cost, competing for photocatalytic performance, and ability to handle amply accessible sunlight as well as extraordinary physical/chemical properties [11]. ...
... The interspace between the lamp and the glass beaker was kept at 10 cm for all cases. The pH of the mixture was regulated by NaOH to 10. In prior to the irradiation, the total mixture containing MB solution and photocatalysts was thoroughly mixed by a magnetic stirrer and maintained in dark conditions for 30 min, to get adsorption-desorption equilibrium. ...
Herein, to investigate the photodegradation of methylene blue (MB) under UV light irradiation and the photocatalytic activity of chemically derived ZnO, ZnO: Co 5% nano rod-like thin films and ZnO/ZnO: Co 5% homojunction, the role of grain size and microstrain on their structural, optical, electrical and photocatalytic properties were studied. Hexagonal wurtzite structure, the doping of Co²⁺ into ZnO host lattice, reduced crystallite/grain size, and enhanced microstrain have been confirmed by structural and morphological analysis. The presence and the atomic content of Zn/Zn²⁺, Co/Co²⁺, O/O²⁻ elements, and ions have been confirmed by EDS and XPS measurements. The n/p-type conductivity in nano rod-like film and p-n bilayers have been verified by Hall and I-V characterizations. The PL analysis showed that the decreased luminescence intensity and the formation of defect/trapping centers by Co²⁺ doping and formation of p-n homojunction as crystallite/grain size decreased while microstrain increased. With 5% Co-doping and the emergence of p-n homojunction, the photocatalytic efficiency (ղ %) was reduced compared with parent ZnO photocatalyst, while the crystallite/grain size decreases and microstrain enhances. The decreased ղ % was attributed to the reduced crystallite/grain size, increment of microstrain, and the generation of defects/trapping centers via 5% Co-doing and formation of ZnO/ZnO:Co 5% nano rod-like homojunction. These results demonstrate that the fabrication of p-n homojunction will not always result in an enhanced ղ % even if it puts down the recombination of light-induced charge transporters.
... μm thick, while the Zn-10ZnO-10MgO coating was 223.5 μm thick. Although the thicknesses of Zn-10ZnO-10MgO-2UPP and Zn-10ZnO-10MgO-4UPP coatings are comparatively lower; however, these coating thicknesses were still observed to be comparable to most coating thicknesses in the literature [31]. While the thickness of coatings could sometimes affect their thermal stability, mechanical properties, and interfacial structure, the most stable coating might not be the thickest coating [32]. ...
The numerous industrial application of mild steel despite its susceptibility to degradation on exposure to the environment has called for the continuous search for materials that can protect its surface from contaminants which could affect its inherent properties. This paper therefore examined the corrosion-resistance, hardness, and microstructure properties of unripe plantain peel (UPP) nanoparticle-reinforced Zn–ZnO–MgO composite coatings deposited on the surface of mild steel (AISI 1015 Carbon Steel). The corrosion properties of the coated steel samples were investigated using the potentiodynamic polarization technique, utilizing simulated seawater (3.65% NaCl solution) as the test medium. The hardness of the coated steel samples was studied using the Brinell hardness method, while the microstructure properties were investigated using XRD and SEM/EDS. The as-received mild steel sample was observed to exhibit a hardness value and corrosion rate of 136.8 kgf/mm2 and 8.6272 mm/year, respectively, while the Zn–10ZnO–10MgO-coated mild steel sample exhibited a hardness value and corrosion rate of 246.53 and 1.7698 mm/year, respectively. Relative to the other samples, the Zn–10ZnO–10MgO–6UPP-coated mild steel (sample coated with 10 g/L of ZnO, 10 g/L of MgO and 6 g/L of UPP) exhibited a highest hardness value and lowest corrosion rate of 254.77 kgf/mm2 and 0.6645 mm/year, respectively. These corrosion rate and hardness values of the Zn–10ZnO–10MgO–6UPP-coated mild steel sample showed that the unripe plantain peel nanoparticles further enhanced the strengthening and passivating ability of Zn–ZnO–MgO–UPP coating. The SEM micrographs revealed that the Zn–ZnO–MgO–UPP coating possessed a more refined microstructure relative to the Zn–ZnO–MgO coating, signifying the grain refining ability of the unripe plantain peel nanoparticles. The EDS additionally indicated the occurrence of crucial and dispersion strengthening elements in the coatings. The XRD profile of the coatings exhibited high intensities, which signified that the coatings have high stability and good texture with microstructural and chemical homogeneity.
... The polar hydroxyl groups of the polymer chain form intermolecular and intramolecular hydrogen bonds with transition metal ions. Therefore, PVA-added Tellurium electrolyte might produce microstructures with uniform crystal grain [47]. Fig. 5 shows the morphology results of Tellurium films with PVA additives. ...
Thin film technologies in terms of preparation and fabrication are of great importance in various fields, such as integrated circuits (IC), LCD monitors, photovoltaics, solar cells and sensors. Tellurium, as a narrow bandgap semiconductor, has attracted much attention due to its rich optical and electrical properties. Taking advantage of these properties, its films have been explored in recent years as saturable absorbers, gas sensors, and thermoelectric materials. However, it is challenging to control the growth of the specific morphology of tellurium films. In this work, based on the electrodeposition challenge, we systematically investigated the electrodeposition process of tellurium films. It was found that the CV curves of electrodeposited tellurium shift in the positive direction with increasing deposition time. In addition, the stabilized potential was determined based on the stable deposition peak potential after a certain deposition time. Moreover, three different additives, namely polyvinyl alcohol (PVA), tartaric acid (TA) and sodium lignosulfonate (SLS), were adopted to manipulate the morphology of as-deposited tellurium films. A rational route to deposit tellurium films with various morphologies have been established.
... A spray jet tends to work mainly with crack arresters, thus improving coating toughness [148]. The Effect on Energy Efficiency of Yttria-Stabilized Zirconia non Brass, Copper and Hardened Steel Nozzle in Additive Manufacturing was analyzed, which is the recent advancement of the application of TBCs in additive manufacturing [149][150][151][152]. Other methods can also be used, such as electrochemical deposition regimes, to develop thin films [153,154]. ...
Thermal barrier coating is critical for thermal insulation technology, making the underlying base metal capable of operating at a melting temperature of 1150 °C. By increasing the temperature of incoming gases, engineers can improve the thermal and mechanical performance of gas turbine blades and the piston cylinder arrangement. Recent developments in the field of thermal barrier coatings (TBCs) have made this material suitable for use in a variety of fields, including the aerospace and diesel engine industries. Changes in the turbine blade microstructure brought on by its operating environment determine how long and reliable it will be. In addition, the effectiveness of multi-layer, composite and functionally graded coatings depends heavily on the deposition procedures used to create them. This research aims to clarify the connection between workplace conditions, coating morphology and application methods. This article presents a high-level overview of the many coating processes and design procedures employed for TBCs to enhance the coating’s surface quality. To that end, this review is primarily concerned with the cultivation, processing and characteristics of engineered TBCs that have aided in the creation of specialized coatings for use in industrial settings.
... In this case the following can be noted: sufficiently high mechanical strength and thermal conductivity [45], high electrochemical resistance [13], resistant to the high temperatures [46]. Moreover, as already mentioned, its geometric characteristics can be easily adjusted by synthesis conditions' changing [47,48]. Such templates are considered as the most relevant for integration into microelectronic technologies [1,[49][50][51]. ...
The results of studies on the wettability properties and preparation of porous anodic alumina (PAA) membranes with a 3.3 ± 0.2 μm thickness and a variety of pore sizes are presented in this article. The wettability feature results, as well as the fabrication processing characteristics and morphology, are presented. The microstructure effect of these surfaces on wettability properties is analyzed in comparison to outer PAA surfaces. The interfacial contact angle was measured for amorphous PAA membranes as-fabricated and after a modification technique (pore widening), with pore sizes ranging from 20 to 130 nm. Different surface morphologies of such alumina can be obtained by adjusting synthesis conditions, which allows the surface properties to change from hydrophilic (contact angle is approximately 13°) to hydrophobic (contact angle is 100°). This research could propose a new method for designing functional surfaces with tunable wettability. The potential applications of ordinary alumina as multifunctional films are demonstrated.
... Single crystals, especially from metal oxides, received enormous attention worldwide in the past few decades due to their distinguished optoelectronic and gas sensing properties over a large scale [1][2][3][4]. Single crystals of zinc oxide, a wide and direct bandgap (~3.37 eV) semiconductor, gained extra interest among other counterparts due to its unique luminescence feature at 378 nm wavelength and large exciton binding energy (60 meV) [5][6][7]. The intense near band edge emission and the large exciton binding energy make ZnO a promising candidate for optoelectronic devices such as laser diodes [8], light-emitting diodes [9], and photodetectors [10]. ...
Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with <0001> orientation exhibits strong and sharp emission intensity with suppressed deep level defects (mostly caused by oxygen vacancies Vo). Furthermore, Raman analysis reveals that <0001> orientation has dominant E2 (high) and E2 (low) modes, indicating that this direction has better crystallinity. At low temperature, the neutral donor-to-bound exciton (DoX) transition dominates, regardless of the orientation, according to the temperature-dependent PL spectra. Moreover, free-exciton (FX) transition emerges at higher temperatures in all orientations. The PL intensity dependence on the excitation power has been described in terms of power-law (I~Lα). Our results demonstrate that the α for <0001>, <1120>, and <1010> is (1.148), (1.180), and (1.184) respectively. In short, the comprehensive PL analysis suggests that DoX transitions are dominant in the NBE region, whereas oxygen vacancies (Vo) are the dominant deep levels in ZnO. In addition, the <0001> orientation contains fewer Vo-related defects with intense excitonic emission in the near band edge region than other counterparts, even at high temperature (~543 K). These results indicate that <0001> growth direction is favorable for fabricating ZnO-based highly efficient optoelectronic devices.
... While Zn-10ZnO-10MgO-6UPP coating was observed to be 224 µm thick, Zn-10ZnO-10MgO coating was 223.5 µm thick. Although the thicknesses of Zn-10ZnO-10MgO-2UPP and Zn-10ZnO-10MgO-4UPP coatings are comparatively lower, however, these coating thicknesses were still observed to be comparable to most coating thicknesses in literature [31]. While the thickness of coatings could sometimes affect its thermal stability, mechanical properties and interfacial structure the most stable coating might not be the thickest coating [32]. ...
The numerous industrial application of mild steel despite its susceptibility to degradation on exposure to the environment has called for the continuous search for materials that can protect its surface from contaminants which could affect its inherent properties. This paper therefore examined the corrosion-resistance, hardness and microstructure properties of unripe plantain peel (UPP) nanoparticles reinforced Zn-ZnO-MgO composite coatings deposited on the surface of mild steel. The corrosion properties of the coated steel samples were investigated using the potentiodynamic polarization technique, utilizing simulated seawater (3.65% NaCl solution) as the test medium. The hardness of the coated steel samples was studied using the Brinell hardness method, while the microstructure properties were investigated using XRD and SEM/EDS. The as-received mild steel sample was observed to exhibit a hardness value and corrosion rate of 136.8 kgf/mm ² and 8.6272 mm/year, respectively, while the Zn-10ZnO-10MgO coated mild steel sample exhibited a hardness value and corrosion rate of 246.5 and 1.7698 mm/year, respectively. Relative to the other samples, the Zn-10ZnO-10MgO-6UPP coated mild steel (sample coated with 10 g/L of ZnO, 10 g/L of MgO and 6 g/L of UPP) exhibited a highest hardness value and lowest corrosion rate of 254.8 kgf/mm ² and 0.6645 mm/year, respectively. These corrosion rate and hardness values of the Zn-10ZnO-10MgO-6UPP coated mild steel sample showed that the unripe plantain peel nanoparticles further enhanced the strengthening and passivating ability of Zn-ZnO-MgO-UPP coating. The SEM micrographs revealed that the Zn-ZnO-MgO-UPP coating possessed a more refined microstructure relative to the Zn-ZnO-MgO coating, signifying the grain refining ability of the unripe plantain peel nanoparticles. The EDS additionally indicated the occurrence of crucial and dispersion strengthening elements in the coatings. The XRD profile of the coatings exhibited high intensities, which signified that the coatings have high stability, good texture with microstructural and chemical homogeneity.
... For example, Nb-doped SnO 2 thin films possess stable cycling life of 200 cycles at 0.5C with a discharge specific capacity about 982.7 mA h g -1 [38]; Fe-doped Li 0.5 La 0.5 TiO 3 with a nano-sphere structure is a novel n-type H 2 S sensing material, which has ultra-fast response/recovery properties [39]. Numerous techniques for fabricating thin films of metal-containing materials are successfully developed so far [40][41][42][43]. Single-layer MoS 2 , which can be easily fabricated by means of the exfoliation technique [44][45][46][47][48][49], is a typical promising film material possessing many extraordinary properties such as high electrical conductivity [50][51][52], superior mechanical strength [53,54], and excellent thermal stability [55,56], that lead to important applications as field-effect transistors [57][58][59][60], sensors [61][62][63], and phototransistors [64,65]. ...
The transport property of a four-terminal MoS2NR/V7(Bz)8 device is computed within the framework of density functional theory combined with the nonequilibrium Green’s function (NEGF) technique. This device is constructed by a MoS2 nanoribbon (MoS2NR) as the source-to-drain channel and a spin-polarized V7(Bz)8 nanowire grafted on the MoS2NR surface as the double gate channel, where the four terminals are all connected to a semi-infinite one-dimensional (1D) Au lead. The transport characteristic is explored by investigating the conductance, currents, local density of states (LDOS), and scattering states. The currents of different leads are dissimilar due to the complex interplay between the four terminals that is otherwise not present in a two-terminal setup. The most interesting feature we articulate is that the induced promising properties including negative differential resistance (NDR) behavior, input/output current switching, as well as spin-polarized lead currents can be fine-tuned by the magnitude of either source bias or gate bias. These features can be utilized in designing multi-terminal nanoelectronic devices.
Graphical abstract
... As the VO content increases in the growth solutions of the SILAR process, the energy of nucleus formation decreases. Therefore, the nucleus density increases, and the crystallite size of the ZnO samples decreases [48]. ...
In the present study, nanostructured zinc oxide (ZnO) films have been successfully synthesized using fruit extract of Viburnum opulus L. (VO) on glass slides by successive ionic layer adsorption and reaction (SILAR) procedure. The impact of VO concentrations on the structural, morphological, optical, electrical, and antibacterial attributes of ZnO films has been investigated in detail. The samples' XRD patterns present a hexagonal crystal structure with a preferential orientation along the (002) plane. The crystallite size values of ZnO samples were found to be in the ranges from 14.88 to 9.23 nm. The supplementation of VO to the synthesis solution remarkably affected the surface morphological features of the ZnO films. The optical results demonstrated that band gap energy values of the ZnO films at room temperature were decreased from 3.20 to 3.07 eV as a function of VO content in the bath solution. The films' electrical properties were determined by impedance analysis in the frequency range of 20Hz -1 MHz. Impedance-frequency measurements showed VO insertion to ZnO thin films cause an increase in impedance value at the low frequencies. Cole-Cole plots with a single semi-circle confirmed the contribution of grain and grain boundary for the electrical conduction process. The agar disk diffusion method was used to test the antibacterial properties of ZnO/VO inserted ZnO and inhibition zones were measured. VO inserted ZnO showed a stronger inhibitory effect on gram-positive bacteria Staphylococcus aureus (ATCC 25923) and gram-negative bacteria Escherichia coli (ATCC 35218) than ampicillin antibiotic used as a control group. In line with the promising bactericidal results of a new generation, VO inserted ZnO, the nanostructured product with this study, it can also be applied in multidrug-resistant clinical isolates obtained from patients.
... Various materials including graphene family, transition metal dichalcogenides, metal selenides and sulfides, metal carbides, metal halides, oxide compounds have been synthesized or revisited as 2D layers, continuously expanding 2D materials library [3][4][5][6][7][8][9][10][11][12][13][14]. There are many methods to fabricate monolayer 2D atomic crystal materials, including mechanical stripping, electrochemical deposition, chemical vapor deposition and molecular beam epitaxy (MBE) [15][16][17][18][19][20]. Comparing with other methods, MBE method is more competitive because of its advantages in epitaxial thickness and doping control at single atom level [21][22][23][24][25][26][27][28][29][30]. ...
CuSe monolayer possesses intrinsically patterned triangular nanopores with uniform
size and can serve as a template for selective adsorptions for molecules and nanoclusters.
Here, we prepare the CuSe monolayer on Cu(111) substrate by molecular beam epitaxy
method and characterize CuSe monolayer in detail by bond-resolved scanning
tunneling microscopy and non-contact atomic force microscopy. The results further
confirm the honeycomb feature and triangular nanopores existence of CuSe monolayer.
In addition, scanning tunneling spectroscopy measurements reveal the semiconducting
features of CuSe monolayer with a band gap of 2.40 eV. This work helps to understand
the structure and electronic properties of those intrinsically patterned two-dimensional
materials.
... as well as greater photoconductivity to reduce the electrical losses [14]. Recently, CdS thin films have been fabricated by varieties of deposition methods including the chemical vapour deposition (CVD) [15], the physical vapour deposition (PVD) [16], the metal-organic CVD (MOCVD) [17], the chemical bath deposition (CBD) [18,19], sol-gel [20], spray pyrolysis [21], the molecular beam epitaxy (MBE) [22], pulsed electrolyte deposition [23][24][25], electrochemical deposition [26,27], electrodeposition [28,29] etc. However, these methods always involve expensive equipments and a special protective environment together with strict operational conditions. ...
We demonstrate the direct synthesis of CdS thin films by spin coating method with thiol-amine co-solvents system. Anneal-ing of the films at various temperatures has been performed in the air using simple glass protector. The XRD patterns show a strong peak along (110) plane related to cubic lattice while two weak peaks at (002) and (100) planes indicate the hexagonal symmetry for the CdS thin films. The Raman peak at 305 cm −1 also confirms the formation of crystalline CdS thin films. The FTIR study also reveals the formation of CdS thin films. The SEM images reveal the surface uniformity and homogeneity of the CdS thin films. The EDX results indicate nearly stoichiometric CdS thin films. The optical band gap of CdS thin films is ~ 2.4 eV when coated at 2000 rpm and annealed at 300 °C for 5 min. These findings indicate that synthesized CdS films are potential candidates for solution-processed CdTe/CdS solar cells.
... The SAED patterns and HR-TEM imaging of SrY x Nb x Fe 12−2x O 19 (x=0.04) HFs was displayed in figure S4 the hexagonal grain with the SrFe 12 O 19 structure with relative lattice spacing [17]. ...
Series of Sr hexaferrites (HFs) co-substituted with Nb³⁺ and Y³⁺ ions (SrYxNbxFe12−2xO19 (x ≤ 0.05) were prepared via sol-gel combustion method. In addition to their optical, low temperature, magnetic properties and hyperfine interactions were investigated in detail. X-ray diffraction (XRD) patterns were considered proving both the formation and pureness of products. Mossbauer analysis indicated that the hyperfine field on iron nuclei at all sites decrease with substitution of Y³⁺–Nb³⁺ ions into Sr-hexaferrite as a result of changing the magnetic Fe³⁺ (5 μB) ions by nonmagnetic Y³⁺ and Nb³⁺ ions. This leads to decreasing of the magnetic super exchange interaction between the ions. Measurements of AC susceptibility and ZFC-FC magnetizations implemented in a range from room temperature (RT) down to around 2 K. The analysis of MFC–MZFC data proves the ferrimagnetic performance of different prepared HFs in the whole range of 2–325 K and a super-spin glass-like behavior was identified at minimal temperatures. The investigation of AC susceptibility revealed a weakening in the magnetic exchange interactions with the rise in the Nb³⁺ and Y³⁺ ions ratios.
... [28][29][30][31] Electrodeposition is usually performed at room conditions, which makes it cheaper with respect to other techniques and more attractive for large-scale production; moreover, it can provide highly ordered and crystalline deposits. [32][33][34][35] Unfortunately, in the case of bismuth, only few works manage to obtain a continuous and uniform deposit through electrochemical methods, [36][37][38] while most electronic applications require smooth deposits to maximise the charge transfer and other performances. To overcome this drawback, we investigated the possibility of exploiting the underpotential deposition (UPD) to obtain a bismuth layer of controlled uniformity. ...
In this work, the electrodeposition of smooth bismuth thin films was investigated. Bismuth is known for its peculiar magnetic, thermal and electrical properties but the deposition of a uniform and flat film, which are features required for its application in electronic devices, is not trivial. We investigated the morphology of Bi film electrodeposited at increasing overpotential on a monocrystalline silver electrode. We found that the presence of an underpotential deposition (UPD) layer, previously deposited on the surface, drives the overpotential deposition to a smoother growth. The samples were investigated by means of different techniques: atomic force microscopy (AFM) and scanning electron microscopy combined with energy dispersive X‐ray spectroscopy (SEM‐EDS) to study the morphology, X‐ray photoemission spectroscopy (XPS) to assess the composition and X‐ray diffraction spectroscopy (XRD) to check the crystallinity. We also found an unexpected form birefringence behaviour, which has been preliminary investigated with cross polarized light microscopy (CPL). Be‐smooth: Bismuth thin films have many interesting properties and applications in electronic devices, but a smooth and controlled growth is required. Combining underpotential deposition and overpotential deposition it is possible to obtain these characteristics. In this way smooth thin film of bismuth was obtained and even an unexpected form birefringence behaviour emerged.
... Fig. 3cef are the interior structure of SA/N-Co x O y -700 which was prepared through introducing melamine. Similar to the framework structure of SA/PEI-Co x O y -700, SA/N-Co x O y -700 has expanded hexagonal framework and developed channel structures, which would realize a good matching of dielectric loss and magnetic loss [40,41]. The cross profile of SA/N-Co x O y -700 is consist of many cell-like textures with core-shell structure, which are assembled by cell wall-like interconnection. ...
In order to solve the pollution of electromagnetic interference (EMI), hierarchical Co/N-co-doped carbonaceous compounds with absorption promoting nanostructures were prepared as absorbing materials via a seaweed-based hydrogel strategy. XRD, Raman, SEM, TEM, VSM and XPS were used to characterize the resultant samples. All the tests indicated that the absorber carbonized at 700 °C (SA/N-CoxOy-700, among, SA represents sodium alginate and 700 means that the carbonization temperature was 700 °C) has an excellent performance, which minimal RL can reach to −47.31 dB at 16.16 GHz and the effective absorption bandwidth (RL < -10 dB) is 4.56 GHz from 13.44 to 18 GHz. The relative superior performance is mainly attributed to the cooperative effect of nitrogen-doped carbon skeleton, expanded surface, multiple defects, various phase interface and hierarchal pore structures, thus leading to the improvement in multiple reflections and scattering, nature resonance, eddy-current effect, the consumption of thermal energy, dipoles and interfacial polarization.
... In the case of ion implantation, when the largest amount of implanted substance is distributed at a certain depth, which depends on the maximum length of the incident ions in ceramics, a strengthening layer is formed that prevents degradation of ceramics under external influences by introducing implanted ions into the crystal structure and reducing the porosity of the surface layer [42][43][44][45]. In turn, the use of low-energy metal ions allows not only modifying the surface layer of ceramics due to changes in dislocation and defective concentrations, but also for large fluences of irradiation, implantation of incident ions into the crystal structure of ceramics [46][47][48]. ...
The paper presents results of studying the applicability of ion implantation to increase the strength characteristics and corrosion resistance of carbide ceramics. According to the X-ray phase analysis, it was found that an increase in the irradiation fluence leads to a slight change in the magnitudes of displacements and defect concentration, which indicates the absence of amorphization processes of the crystal structure. It is established that a decrease in the lattice volume leads to an increase in ceramics density and a decrease in porosity. In this case, a change in the average crystallite size leads to a change in the concentration of dislocation defects near the grain boundaries, which also indicates a change in the defect structure as a result of irradiation. A decrease in the integral porosity of the surface layer, as well as changes in the dislocation and vacancy densities in the surface layer of ceramics, leads to an increase in the strength and crack resistance of the surface layer. That has a significant effect on reducing the rate of degradation of ceramics in aggressive media.
In the present study, Eu ³⁺ -doped zinc fluoro-telluroborate transparent glasses were prepared by the conventional melt−quench technique. Their density and refractive index values were measured, and using these values, different physical parameters (number density, oxygen packing density, no. of bonds/vol, etc.) were calculated and analysed. The XRD pattern displayed a disordered atomic arrangement in the glass network. The EDS spectra proved the purity of the samples exhibiting only those elements used during the synthesis. The good solubility of Eu ³⁺ ions in zinc fluoro-telluroborate glasses was analysed through fine absorption peaks in the UV−Vis−NIR range. The absorption intensities increased in all samples up to 3.0 mol% of Eu ³⁺ -doping concentration. The stabilities of the samples, such as ∆ T ~ (144–156) °C and H r ~ 2.33–4.00, calculated using characteristic temperatures ( T g , T x , T c , T m ) from DSC studies exhibited their promising candidature in a high-temperature environment. The Eu7 (Eu ³⁺ with 3.0 mol%) glass confirmed better attenuation properties (LAC, Z eff , HVL, MFP) compared to other composition (0–2.5 mol%) glasses.
This article deals with the effects of current modes on saccharin adsorption during NiFe electrodeposition, and, as a consequence, its effect on chemical composition, crystal structure, and microstructure of deposited films. For this purpose, we obtained NiFe films using direct, pulse, and pulse-reverse electrodeposition modes. The deposit composition, crystal structure, and surface microstructure are studied. Direct current (DC) and pulse current (PC) films have a smooth surface, while a pulse-reverse current (PRC) film surface is covered by a volumetric cauliflower-like microstructure. The mechanism of the film surface development was considered from the point of view of saccharin adsorption and its action as an inhibitor of vertical grain growth during different current modes. During the DC and PC modes, saccharin is freely adsorbed on the growth centers and restrains their vertical growth. Whereas in the case of the PRC electrodeposition, saccharin adsorbs during cathodic pulses and desorbs during anodic pulses. Therefore, its inhibiting action decreases, vertical grain growth rises, and a rougher surface develops.
Polymer composite (PC) films comprising polyvinyl alcohol (PVA) and poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with manganese dioxide (MnO2) as filler were prepared by simple solution casting method. The structural confirmation of PCs was investigated by Fourier transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The morphological and thermal properties were analyzed using scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Under the frequency range, 50 Hz to 20 MHz, and temperature from 40 to 150 °C, the dielectric properties and Q-factor values for the as-synthesized PC films were investigated by an impedance analyzer. PVA/PEDOT:PSS/MnO2 having wt% 50:35:15 revealed high dielectric constant (ε) at 1949 and low dielectric loss(tanδ) at 8.13. The obtained results suggest that the titled PC films are effective materials for energy storage applications.
Reasonable construction of multi-pore heterogeneous structures and enhancement of synergistic interaction between metal ions are important means to improve the performance of supercapacitors. This work selected metal organic frameworks (MOF) as the sacrificial template, and Se-doped needle-like nanosphere heterostructures Se-CoSe2@ZnSe were successfully prepared by in situ growth and selenization treatment. The specific capacity of the Se-CoSe2@ZnSe-5 (CZS-5) electrode is up to 2469.12 F g⁻¹ at 1 A g⁻¹, and the capacity retention rate of 3000 cycles at a current density of 10 A g⁻¹ is 85.39%. The CZS-5//AC hybrid supercapacitor has a high power density of 1280.00 W kg⁻¹ at an energy density of 68.88 Wh kg⁻¹. The excellent electrochemical properties are attributed to the construction of Se-CoSe2@ZnSe heterostructure of needle-shaped nanospheres enhances the synergy between Zn and Co ions; the doping of selenium effectively improves the conductivity of the electrode material; selenium vacancies produced during selenization increase the activity of the active site. In addition, the density functional theory (DFT) calculation shows that Se-CoSe2@ZnSe-5 has higher density of states (DOS) near the Fermi energy level, which provides additional theoretical support for the improvement of electrochemical performance.
The heterostructure of bismuth (Bi) and Bi2Sr2CaCu2O8+δ (Bi2212) is considered as a potential type of quantum material. The strain-engineering controls the band structure in the composite films, which is applied in the high-temperature quantum spin Hall materials. In this work, Bi/Bi2212 composite film is synthesized using a two-step method to reduce the fabrication cost. The microstructure and transport properties of the composite films are characterized and analyzed. Experimental results demonstrate that the Bi/Bi2212 composite film obtains the high-quality crystallinity and excellent connectivity. The transport property measurement results show that the band structure changes due to the coupled effects of the strain and electric field. The origin is the compensation between the electron and hole charge carriers. The above band gap change leads to a shift in the metal-semiconductor transition temperature. Functionally coupled composite films exhibit new properties in magnetoresistance devices.
A comprehensive study of the present work aimed to investigate the radiation shielding features for W–Cu composites materials with high density. Isostatic hot pressing technique was applied to obtain W85 wt%Cu15 wt% and W75 wt%Cu25 wt% composites with various thickness (0.6, 0.9, 1.2, 1.5 and 2.7 cm). Composites were the pollycristalline samples with well packed microstructure. The statistical grain size distribution performed that the size of an agrolemerated copper grains increases with the Cu content rising. X-ray diffraction (XRD) analysis showed that the main spectrum lines of the composites are corresponded to the bcc phase of tungsten and fcc phase of copper. The linear attenuation coefficient (LAC) was detected experimentally using a NaI detector at various incoming photon energy. The highest values of LAC are found 2.11 and 4.33 cm⁻¹ for W75 wt%Cu25 wt% and W85 wt%Cu15 wt%, respectively, at low energy 0.266 MeV while the lowest values (0.44 and 0.48 cm⁻¹ for W75 wt%Cu25 wt% and W85 wt%Cu15 wt%, respectively) are observed at high energy 1.25 MeV. From the obtained results, it can deduce the discussed W–Cu composites are suitable to be used in several applications of radiation protection.
Active metals, such as platinum and palladium, were doped in TiZrHfMoNb high-entropy alloy to tune its electronic structure. The electronic structure, activation, and kinetic properties were experimentally investigated. The results indicate that electron transfer occurred between the active metal atoms and other metal atoms after platinum or palladium doping, and that the oxide on the surface was destabilized by active metal doping due to improved activation performance. Therefore, TiZrHfMoNbPt0.0025 could reach a maximum hydrogen storage capacity of 1.749 wt% (1.80 H/M) at around 100 s on the first absorption curve. The electron transfer process is believed to aid in optimizing the electron density of interstitial sites, allowing additional interstitial sites to accommodate additional hydrogen atoms. The presented results provide new insights into the hydrogen storage properties of high-entropy alloys, and it is expected that hydrogen storage capacity can be increased by tuning the concentration and type of doping elements.
In this work, pre-lithiated VO2(B) nanobelts are synthesized by a two-step hydrothermal method. After pre-lithiation, the VO2(B) nanobelts exhibit a uniformly dispersed morphology with a large specific surface area. Compared to pure VO2(B) nanobelts, the pre-lithiated VO2(B) nanobelts show much better electrochemical performance in terms of cycling stability and high-rate capability. The lithium-ion diffusivity in the pre-lithiated VO2(B) nanobelts is enhanced due to enlargement of the crystal lattice after pre-lithiation. The pre-lithiated VO2(B) nanobelt cathode delivers an initial specific capacity of 264 mAh g–1 at 0.1 A g–1 with a capacity retention of 81.6% after 100 cycles, which is superior to that obtained for pure VO2(B) under the same conditions (initial capacity of 221.5 mAh g–1 and capacity retention of 63.3%). Moreover, the pre-lithiated VO2(B) nanobelt electrode exhibits outstanding long-term cycling stability (capacity retention of 87.2% after 800 cycles at 1000 mA g–1). These results indicate that pre-lithiated VO2(B) nanobelts have great potential to be applied as an advanced cathode material for next-generation lithium-ion batteries.
Hierarchical ZnO/CuO nanorods were grown on RF sputtered ZnO seed layer via the hydrothermal method and their characteristics are analyzed by high resolution scanning electron microscope (HRSEM) and X-ray diffraction (XRD) techniques to confirm the elemental composition, crystal structure, and morphology of the sensing material. The sensing performance of the carbon dioxide sensor was evaluated at room temperature under the various concentration of carbon dioxide gas from 150 ppm to 1000 ppm. The result obtained shows that the sensor yields a high response of 9.7% for 1000 ppm of carbon dioxide gas with fast response and recovery time varied in the range of 1 min to 4 min. The above results indicate the accomplishment of room temperature sensing with good reversibility and repeatability compared to conventional previously reported high temperature carbon dioxide sensors.
In this work, a two-nearest-neighbor structure model, named the 3-1 model, of the face-centered cubic (FCC) solid solution alloy is found based on the Cowley short-range order parameter and the Friedel’s periodic spherical oscillated (FPSO) model. The proposed 3-1 model has high symmetry, high density, and large separation. The model error between the 3-1 model and the standard spherical periodic model is only 0.004 nm. Besides, the chemical composition formula of the present model is applied to analyze the common grade compositions of various alloys. This work shows that the 3-1 model has universality in mature industrial grades of Au–Ag and Au–Cu alloys, and provides a simplified method to design the composition of alloys.
Arylazopyrazoles (AAPs) show significant potential as a new family of molecular photoswitches owing to their efficient reversible trans -to- cis photoisomerization behavior and the high thermal stability of their metastable cis -isomer. In this study, AAPs have been used for the fabrication of solid-state photoswitchable polydimethylsiloxane (PDMS) based composite thin films. The thin films were prepared by using PDMS as a polymer matrix and different concentrations of AAPs as chromophores at 150 °C via spin-coating. The photoswitching behavior of the AAPPDMS composite films and the pristine AAP samples induced by irradiation with specific wavelength of light were investigated. We found that the as prepared AAPPDMS composite films showed rapid and near-quantitative (>98%) reversible trans -to- cis isomerization upon alternating irradiation with UV (λ = 365 nm) and green (λ = 525 nm) light which is comparable to the isomerization behavior of the pristine AAP chromophores in solution. This indicates that the excellent photoswitching property of the AAPs is preserved in the solid-state of the AAP-PDMS composite films. The results also show that the optical properties of the AAP-PDMS composite films can be tuned by using different ratios of the AAP chromophores and exposure to UV-light irradiation. Additionally, the thin films were tested for their photo-actuation behavior by UV–vis spectroscopy. Irradiation of the thin film with alternating 365 nm UV and 525 nm green light lead to a slight reversible bending behavior. This is presumably caused by the light-induced conformational change of the AAP moiety embedded within the PDMS matrix and the soft nature of the PDMS. This methodology provides a new approach for exploring the fabrication of polymers with enhanced mechanical behavior and solidstate photoswitching properties. Arylazopyrazoles (AAPs) show significant potential as a new family of molecular photoswitches owing to their efficient reversible trans -tocis photoisomerization behavior and the high thermal stability of their metastable cis - isomer. In this study, AAPs have been used for the fabrication of solid-state photoswitchable polydimethylsiloxane (PDMS) based composite thin films. The thin films were prepared by using PDMS as a polymer matrix and different concentrations of AAPs as chromophores at 150 °C via spin-coating. The photoswitching behavior of the AAP-PDMS composite films and the pristine AAP samples induced by irradiation with specific wavelength of light were investigated. We found that the as prepared AAP-PDMS composite films showed rapid and near-quantitative (>98%) reversible trans -to- cis isomerization upon alternating irradiation with UV (λ = 365 nm) and green (λ= 525 nm) light which is comparable to the isomerization behavior of the pristine AAP chromophores in solution. This indicates that the excellent photoswitching property of the AAPs is preserved in the solid-state of the AAP-PDMS composite films. The results also show that the optical properties of the AAP-PDMS composite films can be tuned by using different ratios of the AAP chromophores and exposure to UV-light irradiation. Additionally, the thin films were tested for their photo-actuation behavior by UV–vis spectroscopy. Irradiation of the thin film with alternating 365 nm UV and 525 nm green light lead to a slight reversible bending behavior. This is presumably caused by the light-induced conformational change of the AAP moiety embedded within the PDMS matrix and the soft nature of the PDMS. This methodology provides a new approach for exploring the fabrication of polymers with enhanced mechanical behavior and solid-state photoswitching properties.
Commercial AA-7075-T6 material was subjected to thermal exposure for 60 min in the temperature range 100–300 °C with an interval of 20 °C. There was no noticeable effect of exposure temperature on the yield stress, ultimate tensile stress, fracture stress, and surface hardness in the temperature range 100–200 °C. However, each strength parameter decreased rapidly with the increase in exposure temperature from 200 to 300 °C. This behavior was accounted for in terms of dislocation glide by Orowan mechanism in an atmosphere of semi-coherent ή precipitates (MgZn2) in the main matrix. Stress relaxation at a fixed strain for 1000 s was recorded at various stress levels over the entire stress – strain curve of a given AA-7075-T6 specimen. The stress relaxation rate s increased linearly with the strain εo at which initial stress σo was allowed to relax in the specimen. The stress relaxation parameter (ds/dεo) varied with exposure temperature in a manner similar to that of the strength parameters. The rate process of stress relaxation in the low-strain region was precipitate – dislocation interaction whereas that in the high-strain region was recovery by cross-slip mechanism.
Transparent conductive tin-doped zinc oxide (ZTO) thin films were deposited on glass substrate by using radio frequency (RF) magnetron sputtering method. The effect of sputtering power on crystalline structure, morphology, optical and electrical properties of the ZTO film was systematically studied. XRD results showed that the as-deposited ZTO thin films had a hexagonal wurtzite structure, with (002) orientation. Combining with SEM images, it was found that the grain size was increased with increasing sputtering power. The AFM images revealed that low sputtering powers of <210 W should be used to have ZTO films with small roughness (Rq). The optimized sample exhibited an average transmittance of 93.4% in the wavelength range of 400-900 nm, while the band gap had a significant red shift relative to that of the intrinsic ZnO. Carrier concentration and mobility of the ZTO films were decreased, whereas the resistivity was increased, with increasing sputtering power. The sample sputtered at 120 W had the maximized figure of merit (ФTC) of 11.87 × 10⁻⁴ Ω⁻¹·sq, with the variation trend to nearly mirror-symmetrical with that of surface roughness of the films.
Five kinds of phenolic acid-chitosan composite films including p-coumaric acid-chitosan, ferulic acid-chitosan, gallic acid-chitosan, vanillic acid-chitosan and salicylic acid-chitosan composite films with same content of phenolic acids were prepared, respectively. Their physical, mechanical and biological properties were investigated. Further, the preservative effect of ferulic acid-chitosan composite films and p-coumaric acid-chitosan composite films on Penaeus vannamei was evaluated. The results indicated that phenolic acids changed physical properties, decreased the mechanical properties, and increased biological properties of chitosan film. Among the phenolic acid-chitosan composite films, gallic acid-chitosan composite films possessed the best physical properties, mechanical properties, antioxidant and antimicrobial activities, which may be related to three phenolic hydroxyl groups in its molecule. In the shrimp preservation experiment, ferulic acid-chitosan composite films showed better preservative effect on shrimps in terms of weight loss, pH value, total volatile basic nitrogen, thiobarbituric acid value, total bacterial count and sensory score of shrimps during storage. The results may be related to the methoxy group in ferulic acid. The work revealed that the properties and preservative effect on shrimp of chitosan film were influenced by structures of phenolic acids.
In this work, a new Ultraviolet Optically Controlled Graphene Field-Effect Transistor (UV-OC-GFET) based on Graded Band-Gap (GBG) ZnMgO photosensitive-gate is proposed. The device drain current model is numerically developed by self-consistently solving the Schrödinger/Poisson equations based on non-equilibrium Green's function (NEGF) formalism. The influence of GBG strategy with different profiles on the device sensing performances is analyzed. Our investigation reveals that the use of both GBG ZnMgO photo-gate and graphene nanoribbon channel offers the dual-benefit of improved electric field distribution in the photosensitive layer and enhanced drain current. This leads to outperforming the device Figure of Merits (FoMs). In this context, it is found that the proposed UV sensor with optimized band-gap profile exhibits giant responsivity exceeding 1.5 × 10⁶ A/W with superb detectivity of 7 × 10¹⁴ Jones, far surpassing that of the conventional Si-channel based phototransistors. Therefore, this innovative strategy based on graphene nanoribbon channel combined with GBG sensitive-gate pinpoints a new path towards achieving high-performance visible-blind UV-phototransistor, making it a potential alternative photoreceiver for chip-level optical communication and optoelectronic applications.
Hydrogen storage alloys of La2-xYxMg16Ni (x = 0, 0.1, 0.2, 0.3, 0.4) were smelted by vacuum induction melting furnace. The microstructure of the cast alloys were observed by scanning electron microscope, and the alloys structure were analyzed by X-ray Diffractometer (XRD) before and after hydrogen absorption. The electrochemical capacity, cyclic stability, high-rate discharge, potentiodynamic polarization curves, and constant potential crossing curves were tested. Besides, the limited current density and diffusion coefficient were calculated. The results show that the main phase of the as-cast alloy is La2Mg17, and a little amount of the second phase Mg2Ni exist. In addition, LaH3 and MgH2 and a small amount of Mg2NiH4 phases were formed in the alloy after saturated hydrogen absorption. With the increasing of La element substituted by Y element in La2Mg16Ni alloy, the discharge specific capacity of alloy shows a decreasing tendency, it’s unconspicuous, though. The cyclic stability and high rate discharge of hydrogen storage alloys increase first and then decrease with the increasing of La element substituted by Y element in La2Mg16Ni alloy. When S50 is 34.01%, the cyclic stability of La1.8Y0.2Mg16Ni alloy is best. Both the limited discharge current density and hydrogen diffusion coefficient of the alloy increase first and then decrease with the increasing of the La element of La2Mg16Ni alloy replaced by Y element. The maximum current density of La1.8Y0.2Mg16Ni alloy is IL = 325.11 mA/g, and the maximum diffusion coefficient is D = 1.849 × 10⁻⁸ cm²/s.
Addition of D-Asp in the electrochemical deposition process of Bismuth film resulted the generation of a new diffraction peak in X-ray diffraction (XRD) spectrum. This phenomenon was not observed in the situation of L-Asp. The new diffraction peak might suggest D-Asp could result in the generation of a specific Bismuth structure. Enantioselective recognition of D- and L-Asp can be realized based on this new XRD peak. The limit of detection was determined to be 3.5 × 10⁻⁸ and 1.7 × 10⁻⁸ mol L⁻¹ for D- and L-Asp, respectively. The XRD spectra of electrodeposited Copper films fabricated in the presence of D- or L-Asp showed different lattice plane diffraction peak intensity ratios. The reason was believed to be chirality induced different binding capabilities of Asp enantiomers that influenced Copper film growth. Therefore, the combination of electrochemical deposition using Copper as metal source and XRD technology can be used to achieve enantioselective recognition of Asp. The limit of detection for D- and L-Asp were determined to be 1.5 × 10⁻¹⁰ and 1.2 × 10⁻¹¹ mol L⁻¹, respectively.
The two conventional aluminate precursor preparation methods are liquid-state co-precipitation and mechanical mixture, needing high temperature to fabricate thermionic cathodes for vacuum devices. Herein, we introduce the room temperature solid states (RTSS) approach to fabricate the precursors of barium calcium aluminates (BCA). For this, crystalline hydrates are used to prepare the precursor through mechanical grinding. The resulting product comprises of crystallized α-(Ba,Ca)CO3 solid solution and Al³⁺-contained amorphous precipitants. After sintering at 1200 °C, the active phases of Ba3CaAl2O7 and Ba3Al2O6 were obtained. The direct current (dc) emission measurements in a close-space diode configuration revealed that the divergent current density (Jdiv) of the test cathode reaches 7.2 A/cm² at 1130 °CB, which is comparable to that of the co-precipitation liquid phase method. Considering the virtue of an environmentally-friendly and low-temperature preparation approach, the preparation of aluminates using the RTSS technique has great potential for the fabrication of dispenser cathodes for vacuum devices.
The thermal stability of Cu/W nano-multilayers deposited on a Si substrate using ion beam deposition was analyzed in situ by GISAXS and transmission EDX—a combination of methods permitting the observation of diffusion processes within buried layers. Further supporting techniques such as XRR, TEM, WAXS, and AFM were employed to develop an extensive microstructural understanding of the multilayer before and during heating. It was found that the pronounced in-plane compressive residual stress and defect population induced by ion beam deposition result in low thermal stability driven by thermally activated self-interstitial and vacancy diffusion, ultimately leading to complete degradation of the layered structure at moderate temperatures. The formation of Cu protrusions was observed, and a model was formulated for stress-assisted Cu diffusion driven by Coble creep along W grain boundaries, along with the interaction with Si substrate, which showed excellent agreement with the observed experimental data. The model provided the explanation for the experimentally observed strong correlation between thin film deposition conditions, microstructural properties, and low thermal stability that can be applied to other multilayer systems.
We report the effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer-assisted deposition on c-cut sapphire (Al2O3). The films show a superconducting transition temperature of 10.4 K and an upper critical field Hc2(0) perpendicular to the film surface around 3 T. The latter corresponds to a relatively large coherence length ξ, which enhances the two-dimensional limit when the magnetic field is applied parallel to the film surface. In comparison with pure δ-MoN films, the inclusion of Co2N impurity in the δ-MoN films could significantly modify the critical current density at the vortex-free state. The ability to tune the superconducting properties of metal-nitride superconductors by introducing chemically and structurally compatible impurity may find potential applications for superconducting single-photon detectors.
The defect creation on the surface of the metal oxide structure by infrared laser irradiation played a vital role in enhancing its optical properties. Herein, Zn/ZnO thin film was synthesized by pulsed laser deposition of Zn metal, followed by creating oxygen vacant by infrared laser irradiation, then the Ag layer was used to coat the irradiated ZnO thin film by pulsed laser deposition of Ag metal to produce Ag/ir-Zn/ZnO nanocomposite structure. The effect of creating vacancies on the thin films of ZnO has appeared on the optical and structural properties of Ag/ir-Zn/ZnO thin film was studied by X-ray diffraction, X-ray photoelectron spectrometer, and energy dispersive X-ray diffraction. The response of nonlinearity of Ag/ir-Zn/ZnO thin film was enhanced in compared with that of thin films of a single layer of CdO, single layer Ag, or CdO/Ag thin film.
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This work studies the relationship between the electrochemical synthesis temperature and the potential of Ni nanotubes obtained in polyethylene terephthalate template pores with their structure and morphological peculiarities. Based on established regularities in the evolution of morphology and structural parameters, the dynamics of the Ni nanotubes main magnetic characteristics are analyzed.
Self-organized nanoporous oxide layer was successively prepared on the Ti6Al4V surface in an ethylene glycol electrolyte containing 0.1 mol dm⁻³ NH4F, 5 wt% H2O and 0.1 mol dm⁻³ lactic acid solution. Morphology, composition and crystal structure of the developed oxide layer were evaluated using FESEM, EDX and XRD analysis. FESEM study shows that the average diameter of the nanopores is ~ 89 nm and the thickness of the developed oxide layer is ~ 5.412 µm. XRD and EDX analyses indicate that the as-anodized nanoporous oxide layer are mainly amorphous in nature and contained significant amount of fluoride species. To remove the fluoride species and formed more chemical stable oxide layer thermal treatment is performed at 723 K for 3 h duration. XPS study confirms the presence of TiO2 and Al2O3 in the oxide layer. Potentiodynamic polarization study has been carried out to evaluate the corrosion inhibition property of the developed nanoporous oxide layer in an 8 g/l NaCl medium. It was concluded that the nanoporous oxide layer fabricated on Ti6Al4V surfaces shows good corrosion inhibition property than that of bare Ti6Al4V.
A novel synthesis of (E)-4-(4-carboxy-3-hydroxystyryl)-1-methylquinolin-1-ium iodide nanostructure thin film has been doped with zinc oxide nanoparticles to study the optical properties of nanocomposite films. Different characterization techniques for nanocomposite film such as Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, x-ray diffraction, scanning electron microscopy and optical properties have been used. The scanning electron microscopy showed a good dispersion of zinc oxide nanoparticles on nanocomposite film surface. The dielectric constant and optical conductivity increased and demonstrated wave-like performance with increasing zinc oxide nanoparticles ratio at hν range of 0.7eV – 5.0 eV. zinc oxide nanoparticles content increases lead to the formation of a wide variety of three dimension-semiconductor networks within nanocomposite film matrix which increase optical conductivity. The density functional theory by thee dimension molecular simulation software and Cambridge serial total energy package was used for optimization of novel cyanine dye and nanocomposite as isolated molecule. From the ultraviolet–visible spectrum of nanocomposite thin film, the direct and indirect optical energy gap values are 2.041 eV and 1938 eV by using Tauc`s equation, respectively, related to direct and indirect transitions of electrons. By using thee dimension molecular simulation software mothed with density functional theory simulation, the highest occupied molecular orbital and lowest unoccupied molecular orbital values for nanocomposite as isolated molecule are 4.735 eV and 3.531 eV, respectively. The simulated Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, x-ray diffraction and optical properties by Gaussian software and Cambridge serial total energy package are in great agreement with the experimental study. A successful choice for optoelectronics and solar cell applications are the novel cyanine dye thin film and its nanocomposite.
A facile synthetic method was reported to synthesis nanostructured alloy from SnO2/Au in just one step without further purification or washing by a dual ultra-fast pulsed laser ablation in liquid media technique. The dual ultra-fast technique was based on splitting the laser irradiation by beam splatter to produce two paths. Each path makes a laser ablation process on each target immersed in ultra-pure water. The physicochemical properties of the prepared sample were investigated by XRD, UV–visible spectrometer, TEM, and EDX. XRD technique showed the formation of crystalline structure from Au and SnO2, while UV-visible spectrometer showed the formation of the absorption peaks of SPR of Au and the metal oxide of SnO2, whereas TEM revealed the nanostructure formation of nanostructured alloy structure, but EDX confirmed that the formation alloy had the composition structure from Au and SnO2. Furthermore, its antibacterial activity showed the highly efficient against E. coli rather than Bacillus subtilis.
The work presents data on changes in the structural and strength characteristics of tantalum carbide ceramics as a result of irradiation with heavy Kr¹⁴⁺ ions with an energy comparable in magnitude to the energy of fission fragments of uranium nuclei. The irradiation fluence was 10¹³, 5 × 10¹³ и 10¹⁴ ion/cm². The choice of irradiation fluences is due to the possibility of modeling the defect structure in ceramics at various degrees of overlapping of the ion trajectories in the target. It was found that an increase in the irradiation fluence above 5 × 10¹³ ion/cm² leads not only to an increase in distortions and deformations in the structure, but also to an increase in the area of regions containing an increased carbon content, thereby changing the stoichiometric ratio of elements in the surface layer and having a negative effect on the strength characteristics of ceramics.
The dynamics of phase transformations in CoZnO/CoZn nanostructures of the Zn – Hexagonal/ZnCo2O4 – spinel → Zn – Hexagonal/Co2.34Zn10.63 → Co– Hexagonal/Co2.34Zn10.63 type depending on the difference of the applied potentials is presented. As a production method, the method of electrochemical synthesis was used, in which polymer track membranes with pore diameters of 400 nm and a length of 12 μm were used as templates. The study found that at small potential differences (1.25–1.75 V), the presence of oxygen is observed in the structure of nanowires, which is introduced into the crystalline structure during the synthesis. In this case, an increase in the difference in the applied potentials above 1.75 V leads to an increase in the cobalt concentration in the structure of the nanowires accompanied by the displacement of oxygen and the formation of the Co/Zn structure with a stoichiometric ratio of 1:1. It was found that all the nanostructures under study during the life tests of the applicability of these nanostructures as cathode materials of lithium-ion batteries retained their operability after 400 cycles of life tests, which indicates their high resistance to degradation. Moreover, for samples containing a high concentration of cobalt in the structure, the lifetime reaches more than 800 cycles, which is explained by the high stability of these nanostructures to degradation processes.
Ni nanopillars (Ni NPs) composite materials formation technology was presented. The morphological and structural properties of the composite material were investigated using scanning electron microscopy, atomic force microscopy, X-ray diffraction. The corrosion resistance of the nanocomposite materials has been studied by potentiodynamic polarization curves analysis. The composite represents the array of vertically ordered Ni NPs with the identical size in alumina matrix. XRD investigation indicates that Ni NPs are polynanocrystalline material. It has been shown that Ni NPs and the composite material have sufficient corrosion resistance in a 0.9% aqueous NaCl solution. Porous alumina matrix is the neutral and protective component of the composite. These nanocomposite materials can be excellent candidates for practical use in different applications.
The influence of bath concentration, electrodeposition potential, and hydrodynamic conditions in the electrolytic cell on the morphology, chemical composition, and crystal structure of synthesized Zn, Sb, and Zn-Sb thin films was demonstrated based on FE-SEM, EDS, XRD, and Raman measurements. It was found that an increase in the working electrode potential leads to the formation of thin films with a higher atomic percentage (at.%) of zinc. Contrary, increasing SbCl3 concentration in the citrate bath and application of electrolyte stirring, lead to the preferential electrodeposition of thin films containing a higher content of antimony. From the point of view of thermoelectric applications, the most promising material was that containing the ZnSb crystal phase with the Zn/Sb atomic ratio of 1. The best results for electrodeposition of Zn-Sb thin films were observed at −1.5 V vs. Ag/AgCl (3 M KCl) in the citrate bath containing 0.045 M ZnCl2 and 0.045 M SbCl3 in the absence of electrolyte stirring. As a result, an amorphous ZnSb thin film with the Zn/Sb atomic ratio of 1.03 was obtained. The sample with a composition very close to stoichiometric ZnSb was annealed in an inert atmosphere in order to transform it into a crystalline thin film.
The results of the synthesis and subsequent phase transformations of FeCo nanowires depending on the annealing temperature are presented. An annealing temperature range of 200–800 °C was chosen to initialize the processes of annihilation of point defects at low temperatures, as well as phase transformations as a result of oxidation of nanostructures at high annealing temperatures. In the course of the research, a three-stage process of phase transformations was established, accompanied by oxidation of the structure followed by the formation of oxide phases of the spinel type Fe2CoO4 and Co3O4. It was found that at temperatures of 400 °C and 600 °C, the introduction of oxygen occurs nonuniformly along grain boundaries with the subsequent formation of oxide compounds, and in the case of annealing at a temperature of 800 °C, the oxygen distribution in the structure of nanowires becomes uniform, which indicates the complete oxidation of nanowires with isotropic the formation of oxide phases in the entire volume of nanowires. The prospects of using oxide biphasic nanowires for catalytic reduction reactions para-nitroaniline - para-phenyldiamine are shown.
Co/Cu multilayer nanowires (MNWs) were ac pulsed electrodeposited into the 50 nm diameter nanopores of anodic aluminum oxide (AAO) templates in 2.5, 3.8 and 5.25 pH values using the single bath technique. In each acidity, thickness of the Co magnetic layers (tCo) was kept constant (∼45 nm) and that of the non-magnetic Cu layers (tCu) was changed (3, 15, 32, 65, 160 and 260 nm) by adjustment of pulse numbers. Structural and magnetic properties of the samples were studied by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), hysteresis loops and first order reversal curve (FORC) diagrams. TEM images confirm the formation of multilayer structure and uniformity in thickness of the layers. XRD patterns show strong effect of the acidity and Cu-layer thickness on crystallographic characteristics. The acidity along with Cu-layer thickness caused the c-axis direction to change from parallel to perpendicular to the wires axis. A strong relation between crystalline features as preferred orientation and magnetic properties of the samples was also observed by hysteresis loops and FORC diagrams. As shown, both the acidity and tCu affect magnetic response of the magnetic system. FORC diagrams also showed that magnetostatic interactions between the magnetic layers significantly decrease with the increase in tCu, regardless of the electrolyte acidity. The coercivity distribution was also seen to vary through both crystalline structure and magnetostatic interactions.
The paper presents the results of a study of changes in structural and magnetic characteristics, as well as phase transformations in Fe–Ni/Fe–Ni–O nanoparticles obtained by chemical synthesis and subsequent thermal annealing. It was found that the initial nanoparticles are a three-phase system consisting of Fe–Ni–O oxide with a spinel structure and a Fe–Ni alloy with a face- and body-centered cubic lattices. As a result of thermal annealing, a decrease in the Fe–Ni phase was established with subsequent ordering of the Fe–Ni–O phase with a decrease in the crystal lattice parameter and an increase in the degree of crystallinity. During resurces tests, it was found that for single-phase Fe–Ni–O nanoparticles, the lifetime is close to 500 discharge/charge cycles, which is a good indicator of the working life and makes it promising to use Fe–Ni/Fe–Ni–O nanoparticles as anode materials for lithium-ion batteries.
For the large volumes of dye wastewater treatment, the development of novel adsorbents with high adsorption capacity and good separation is of great significance. Here, a simple method is used to prepare a magnetic adsorbent for the efficient removal of acid blue 80 (AB‐80) and methylene blue (MB). The magnetic adsorption results show that as‐obtained MEL−Fe‐C exhibits good magnetic properties in AB‐80 and MB removal experiments. Importantly, this material shows good AB‐80 and MB removal property after ten times of repeated use. Therefore, as‐prepared MEL−Fe‐C is an ideal adsorbent candidate for removal of dyes in wastewater treatment applications. Development of novel adsorbents with high adsorption capacity and good separation is an absolute requirement for treating large volumes of dye wastewater. Here, an economic magnetic adsorbent, MEL−Fe‐C, was prepared by a simple process. MEL−Fe‐C exhibits good magnetic properties and removes acid blue 80 and methylene blue to a large extent from water even after ten times of repeated use. Hence, it would be an ideal adsorbent candidate for removal of dyes during wastewater treatment.
Valley polarization of multi-valleyed materials is of significant interest for potential applications in electronic devices. The main challenge is removing the valley degeneracy in some controllable way. The unique properties of bismuth, including its anisotropic electronic structure and Dirac valley degeneracy, make this material an excellent system for valleytronics. It is demonstrated theoretically that the direction of an externally applied magnetic field in the binary-bisectrix plane has a profound effect not only on the charge, but also on the thermal transport along the trigonal direction. The rotating field probes the electronic mass anisotropy and tunes the contribution from a particular Dirac valley in the electrical resistivity, Seebeck coefficient, and thermal conductivity at moderate temperatures and field strengths. It is further shown that the field polarization of the transport properties is accompanied by selective filtering of the carriers type providing further opportunities for thermoelectric transport control.
We have observed a large increase in the magnetoresistance (MR) of polycrystalline and epitaxial thin Bi films, which were subjected to a post-annealing procedure at 3°C below the Bi melting point. We have achieved an increase in the MR by a factor of 2560 at 5K as compared with 343 for an as-grown epitaxial film due to enhanced carrier mobilities.
Polycrystalline Bi films were deposited onto p-GaAs(100) by electrochemical deposition. Annealing resulted in the formation of large grains with a preferred [012] orientation. The p-GaAs/Bi junctions were rectifying and the barrier height and ideality factor decreased with increasing film thickness. For films greater than 0.5 μm in thickness, the barrier height was about 0.56 eV and the ideality factor was between 1.1–1.2 for both as-deposited and annealed films. The resistance of the as-deposited films exhibited a negative temperature coefficient whereas the annealed films exhibited a positive temperature coefficient due to the limiting carrier mean free path. The magnetoresistance (MR) exhibited a quasilinear field dependence with an MR effect as large as 5600 (560 000%) at 5 K and 2.2 (220%) at room temperature. © 2000 American Institute of Physics.
The electrochemical deposition of bismuth on n-GaAs(100),
and p-GaAs(100) from
solution is characterized by cyclic voltammetry and impedance measurements. Electron capture at the conduction band forms
the rate-determining step in the reduction of
at n-type GaAs. The morphology of the bismuth films is related to the deposition kinetics. The rectifying n-GaAs/Bi Schottky
barrier formed on low-doped substrates prevents oxidation of bismuth, whereas tunneling through the space-charge layer allows
anodic stripping of Bi on highly doped substrates. Under illumination, electroless deposition of Bi is observed on n-GaAs.
Surface-state mediated hole injection is responsible for the slow deposition of Bi on p-GaAs in the dark. Photoassisted nucleation
and subsequent growth in the dark results in the formation of continuous thin Bi films on p-GaAs. © 2001 The Electrochemical
Society. All rights reserved.
Bismuth thin films are formed electrochemically on n- Ga As (110). Bismuth films up to a few hundred nanometers in thickness exhibit a strong (018) texture, while thicker films are polycrystalline. The barrier height of the n- Ga As / Bi Schottky contacts is 0.62 eV , about 0.2 eV lower than for electrodeposited bismuth films on GaAs (100).
Single-crystal bismuth thin films 1 to 20 micrometers thick were fabricated by electrodeposition and suitable annealing. Magnetoresistance
up to 250 percent at 300 kelvin and 380,000 percent at 5 kelvin as well as clean Shubnikov–de Haas oscillations were observed,
indicative of the high quality of these films. A hybrid structure was also made that showed a large magnetoresistive effect
of 30 percent at 200 oersted and a field sensitivity of 0.2 percent magnetoresistance per oersted at room temperature.
Multilayered Ni80Fe20/Cu film shields were obtained via electrochemistry method with different thickness and number of partial magnetic layers. Magnetic properties and shielding characteristics were investigated as well as function of thickness and number of layers. Difference in magnetic properties for Ni80Fe20 films with different thickness is due to formation of defect layers on the top and bottom film surfaces during electrodeposition processes. These layers can be characterized as layers with high density defects (as a result poor iron content). Main deviation in magnetic properties is typical for thinner films. It was measured DC and AC shielding and results discussed. Maximal value of DC-shielding effectiveness was observed for multilayered samples with small number magnetic layers with large thickness (80–400 μm). The minimal value of DC-shielding effectiveness was observed for the multilayered sample with the minimum thickness of the magnetic layer (5 μm) and maximal number of the layers (80 layers). It is in good agreement with shunting mechanism. In low frequency range maximal values of AC-shielding effectiveness were observed like in case of DC-shielding for samples with small number magnetic layers with large thickness. With frequency increasing the situation was radically changed and AC- shielding effectiveness was higher for samples with maximal number of layers. In the frequency range above 40 kHz AC- shielding effectiveness was sharply decreased due to sharply decreasing of permeability value. As a result it leads to decrease of absorption loses (SEabs.). It was discussed the main shielding mechanisms for multilayered Ni80Fe20/Cu film samples under different external influences. Main contribution in electromagnetic shielding in the range 300 Hz – 20 kHz is absorption and reflection processes. In the range 20 kHz – 50 kHz main shielding mechanisms are reflection and re-reflection. For 300 Hz – 50 kHz frequency range most appropriate to use multilayered structures with large number of thin layers with cardinally different values of magnetic permeability and electrical conductivity.
The BaFe12-xGaxO19 (x = 0.1-1.2) solid solutions of the barium hexagonal ferrite of M-type were synthesized and attested by the powder X-ray diffraction method at 300 K. The unit cell parameters were refined. With increase of substitution level the parameters of unit cell monotonically decrease. These samples were investigated by the vibration magnetometry method. With increase of substitution level the magnetic parameters monotonically decrease. The concentration dependence of the TC Curie temperature as well as the MS spontaneous specific magnetization and the HC coercive force at 300 K is constructed. The microwave properties of the considered samples in the external magnetic bias field were also investigated at 300 K. It is shown that with increase of Ga³⁺ concentration from x = 0.1 to x = 0.6 the frequency value of the natural ferromagnetic resonance decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With increase in Ga³⁺ concentration the line width of the natural ferromagnetic resonance increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation. At the same time the peak amplitude of the resonant curve changes slightly. The frequency shift of the natural ferromagnetic resonance in the external magnetic bias field takes place more intensively for the samples with small Ga³⁺ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency electromagnetic radiation.
The lightly doped BaFe12-xDxO19 (D = Al³⁺, In³⁺; x = 0.1 and 0.3) polycrystalline hexaferrite samples have been investigated by powder neutron diffractometry as well as by vibration sample magnetometry in a wide temperature range from 4 K up to 740 K and in magnetic field up to 14 T to establish the nature of Fe³⁺(Al³⁺, In³⁺) – O²⁻ - Fe³⁺(Al³⁺, In³⁺) indirect exchange interactions. The crystal structure features such as the ionic coordinates and lattice parameters have been defined and Rietveld refined. The Invar effect has been observed in low temperature range below 150 K. It was explained by the thermal oscillation anharmonicity of ions. It is established that the ferrimagnet-paramagnet phase transition is a standard second-order one. From the macroscopic magnetization measurement the Curie temperature and ordered magnetic moment per nominal iron ion are obtained. From the microscopic diffraction measurement the magnetic moments at all the nonequivalent ionic positions and total magnetic moment per iron ion have been obtained at different temperatures down to 4 K. The light diamagnetic doping mechanism and magnetic structure model are proposed. The effect of light diamagnetic doping on nature of Fe³⁺(Al³⁺, In³⁺) – O²⁻ - Fe³⁺(Al³⁺, In³⁺) indirect exchange interactions with temperature increase is discussed.
M-type BaFe11.9Al0.1O19 hexaferrite was successfully synthesized by solid state reactions. Precision investigations of crystal and magnetic structures of BaFe11.9Al0.1O19 powder by neutron diffraction in the temperature range 4.2 – 730 К have been performed. Magnetic and electrical properties investigations were carried out in the wide temperature range. Neutron powder diffraction data were successfully refined in approximation for both space groups (SG): centrosymmetric #194 (standard non-polar phase) and non-centrosymmetric #186 (polar phase). It has been shown that at low temperatures (below room temperature) better fitting results (value χ²) were for the polar phase (SG: #186) or for the two phases coexistence (SG: #186 and SG: #194). At high temperatures (400–730 K) better fitting results were for SG: #194. It was established coexistence of the dual ferroic properties (specific magnetization and spontaneous polarization) at room temperature. Strong correlation between magnetic and electrical subsystems was demonstrated (magnetoelectrical effect). Temperature dependences of the spontaneous polarization, specific magnetization and magnetoelectrical effect were investigated.
Electroanalysis with bismuth film electrodes and other Bi electrodes is reviewed. The review offers a retrospective insight into a short history, reminding of all the important milestones in the field and the basic characteristics of all hitherto known types of Bi electrodes and including inevitable comparison with related mercury electrodes. Furthermore, special attention has been paid to discussion on specific features of bismuth-based electrodes in electrochemical stripping analysis. The text is illustrated by numerous examples mostly based on author's results and includes also tables summarising the individual studies and methods mentioned in the review. Last but not least, the most important achievements are critically evaluated and future prospects outlined. A review with 100 references.
Well dispersed RuCu nanoparticles (NPs) supported on graphene were in situ synthesized by a one-step co-reduction of aqueous solution of ruthenium (III) chloride, cupric (II) chloride, and graphite oxide (GO) with ammonia borane (AB) under ambient condition. The nature of the NPs was fully characterized by TEM, HRTEM, XRD, energy dispersive spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The as-synthesized NPs exhibit much higher catalytic activity for hydrolytic dehydrogenation of AB than the monometallic Ru and Cu, bimetallic RuCu/graphene reduced by NaBH4, and graphene free RuCu counterparts. Additionally, the as-synthesized NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as SiO2, γ-Al2O3, and carbon black. The activity of Ru1Cu7.5/graphene NPs in terms of turnover frequency (TOF) is 135 mol H2 min−1 (mol Ru)−1, which is higher than Ru/graphene, and most reported Ru-based or other noble metal-based NPs for the catalytic hydrolysis of AB. The activation energy for hydrolysis of AB in the presence of Ru1Cu7.5/graphene NPs was determined as 30.59 kJ mol−1, which is lower than most of the reported catalysts. Furthermore, the as-prepared NPs exert satisfied durable stability for the hydrolytic dehydrogenation of AB.
Reversible electrodeposition of metallic bismuth onto transparent conducting substrates was studied with interest in the electrochromic phenomena produced by plating and stripping a thin metallic film. Different bismuth films were prepared potentiostatically by applying potential steps of different amplitude (whilst maintaining the electric charge at a constant value), and the change in transmittance was followed in situ simultaneously during the electrodeposition process. A large change of transmittance was observed for constant charge films prepared at different deposition potentials. As the absorbance is related to the deposition charge (amount of metallic bismuth electrodeposited), changes in optical properties of equivalent films must be related to large changes in film morphology; this was corroborated by scanning electron microscopy. The effect of copper additives was also analyzed: this produced changes in film morphology, leading to bidimensional deposition being predominant over the tridimensional process.
The effect of controlled amounts of irreversibly adsorbed bismuth on a Pt (111) oriented electrode surface on the electrocatalytic oxidation of formic acid has been studied in the whole range of coverage. The experimental method used in this work enables us to maintain a constant surface coverage in heteroatoms while the electrode is cycled in the whole range of potential of oxidation of the organics. For a coverage range from 0 up to 0.8 the electroactivity of the surface for the direct oxidation of formic acid is enhanced by a factor of 40, while in the whole range of coverage the accumulation of the blocking intermediate is lowered to an undetectable level.
The effect of adsorbing submonolayers of bismuth and tin onto single-crystal, polycrystalline and dispersed platinum electrodes on the oxidation of formic acid and methanol was investigated. While the oxidation of formic acid on Pt(111) was found to be enhanced by adsorbed sub-monolayers of bismuth, the oxidation of methanol was inhibited by all adsorbed coverages of both tin and bismuth on all electrodes. The adsorbed tin was found to be more stable on the dispersed Pt electrodes than on the smooth electrodes.
The status of electrochromic devices based upon the reversible electrodeposition of thin bismuth–copper films is reported. The electrochemistry and interface chemistry of the system relevant to information display applications are briefly described. Low information content displays are currently being produced in small quantities with saturated black and white contrast ratio of 25:1 and lifetimes of greater than ten million cycles. Electrochemical scanning tunneling microscopy (ECSTM) studies on highly ordered pyrolytic graphite (HOPG) substrates were undertaken as a first step in the unraveling of the detailed nucleation and growth behavior of the Bi–Cu system at the atomic level. The results obtained support previous studies using scanning electron microscopy and surface spectroscopy. Preliminary results on the plating current efficiency of the system using a quartz crystal microbalance (QCM) are reported.
Bismuth films (200-1400 Å) were grown epitaxially on freshly cleaved mica substrates. These films consisted of a mosaic of equally oriented crystallites averaging several microns in diameter. The plane of the films coincided with the trigonal plane of Bi. We have studied the thickness dependence of the resistivity, the Hall coefficient, and the transverse magneto-resistance, by gradually varying the thickness of a single film which was kept under high vacuum during the entire experiment. The resistivity at 360 and 77 °K is a smooth monotonic function of the thickness. At 12 °K, we observed small oscillations in the resistivity and in the magnetoresistance. These oscillations are regarded as probable manifestations of the quantum size effect (QSE). The thickness dependence of the Hall coefficient is in striking disagreement with the predictions of the infinite-potential-well model. Better agreement between the theory and experimental results is obtained when we assume a less rigid boundary condition. Also for several films we have investigated the temperature dependence of these three transport coefficients and found it to be quite different from that of bulk bismuth. We have attempted to explain these results in terms of the behavior of the carrier concentration and of the different scattering mechanisms that can come into play in these films.
The voltammetric profile in sulfuric acid electrolytes of high coverage bismuth monolayers on Pt(111) having a fractional coverage (θ) of 0.39 exhibits two pairs of peaks located positive and negative, respectively, of the redox peak associated with the 0.33 coverage Bi/Pt(111) adlayer. The ΔEfwhm (full width at half-maximum) values for these peaks are 10 and 20 mV, respectively, suggesting that the redox events involve significant near-neighbor interactions and may correspond to phase transitions within the bismuth adlayer. The formal potentials of these redox peaks shift by 65 mV per pH unit, suggesting that two protons are involved in the two-electron redox reaction of the bismuth adatoms. This provides evidence that the two pairs of redox peaks could correspond to the abrupt formation of [Bi(OH)2]ad and [BiO]ad from Biad. Upon continuous potential scanning in sulfuric acid electrolyte, these peaks decay while two new peaks grow in, with an isopotential point forming between the two anodic peaks. The new, latter peak corresponds to that found for the 0.33 coverage Bi/Pt(111) adlayer. The peaks that grow in upon potential scanning could arise from the interconversion of the hydroxide and oxide network to a stable, long-range hydrogen-bonded (bi)sulfate network upon bismuth oxidation. The peak associated with the 0.33 coverage Bi/Pt(111) adlayer could then be ascribed to the abrupt formation of this (bi)sulfate network upon bismuth oxidation. In perchloric acid electrolytes the two pairs of high coverage bismuth redox peaks are also present, but one increases monotonically while the other decreases upon potential scanning, without the appearance of any new peaks. The high coverage peaks are thus associated with the formation of a long-range hydroxide and oxide network upon bismuth oxidation. The presence of halide anions (Cl-, Br-, I-) dramatically affects the voltammetric profile of Bi/Pt(111). Initially, chloride appears to form a complex with the bismuth adlayer. Upon potential scanning, the redox peak ascribed to the chloride complex decays while that associated with the stable bismuth adlayer reemerges. Bromide and iodide anions both cause the complete desorption of the bismuth adlayer, suggesting that they have significantly stronger bonding interactions to Pt(111) than does bismuth.
This paper reports an investigation of the large magnetoresistance (MR) of 0.3–1.5 µm thick polycrystalline Bi films deposited in vacuum on non-crystalline substrates and annealed at critical temperatures. The occurrence of critical temperatures is associated with intensive growth of crystallites. It is demonstrated that such films consist of large 50–200 µm high-quality crystallites and exhibit a large transverse MR. At temperatures higher than 77 K the magnitude of the MR can exceed that of epitaxial Bi films. The experimental results are interpreted on the basis of a polycrystalline Bi thin-film model. The data suggest that in Te-doped Bi films the MR can be larger than that in pure Bi films. It is found that the grain-boundary scattering is weak. However, there exist rather isotropic extra carrier scattering channels which reduce the anisotropy of electrical conductivity and MR. The relative importance of this extra scattering changes with temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
In this article, the decade of electroanalysis with bismuth-based electrodes is reviewed (with 222 refs.). Emphasis is put on the environmentally friendly (“green”) character of bismuth electrodes, their versatility and variability in use, as well as the actual classification of the individual types of electrodes, sensors, and detectors that utilize the unique properties of metallic bismuth. Of particular interest is the genesis of the field, when the respective activities and achievements are monitored year by year over the whole period of 2000–2009, including the circumstances of the introduction of bismuth-coated electrodes into electrochemical stripping analysis. The review highlights all the significant milestones and break-points that had directed the experimental work around the globe, outlining the present day's position of this lively, inspiring, and still highly prospective area. Finally, it provides a special insight into electroanalysis with bismuth electrodes through numerous surveys, summaries, and detailed statistical data obtained by analyzing the accessible literature database.
The underpotential deposition (UPD) and overpotential deposition (OPD) of bismuth on Au(1 1 1) have been studied with in situ scanning tunneling microscopy (STM). Large area STM images obtained in the UPD region indicate that adsorbed bismuth lifts the reconstruction of the Au(1 1 1) surface. This results in the formation of gold islands at potentials less than 0.170 VSCE. In situ STM images of the Bi OPD process reveal needle growth across the gold surface, beginning at step edges and proceeding to form relatively uniform films. This growth behavior is observed at −0.070 VSCE, after stepping the potential to −0.120 VSCE for 4 s. Atomic resolution images of the OPD bismuth layer indicate that the unit cell is nearly rectangular with dimensions of 3.9±0.2 and 4.3±0.2 Å. This corresponds to having the shorter side of the Bi unit cell along the long edge of the bismuth needles. The reduced spacing hinders the incorporation of atoms diffusing along these edges. Instead, diffusing atoms become incorporated at the needle end where the structure is more open, resulting in the observed Bi growth anisotropy.
Metal bismuth with various morphologies, with particle size from nanometer to micrometer, has been successfully prepared by electrodeposition onto Pt, Au, Al and ITO electrodes at room temperature. The size and morphology of the deposits are strongly dependent on preparation conditions, such as deposition potential, current density, electrode and electrolyte. As observed by scanning and transmission electron microscopes, the deposited Bi particles exhibit plentiful appearances, such as prickly rod, banch, skeleton and strip-like shapes. A significant positive magnetoresistence effect is observed even at room temperature.
Single crystalline bismuth nanowire arrays in anodic alumina membrane have been fabricated by pulsed electro-deposition. The nanowires of different diameters were obtained by changing the electrical parameter of the pulsed electrodeposition using anodic alumina membrane as template with the same pore size. X-ray diffraction and TEM analysis show that the bismuth nanowires are single crystalline with highly preferential orientation, and the diameter of nanowires increases with increasing the relaxation time of pulse. The growth mechanism of nanowires was discussed.
For many years mercury electrodes were the transducer of choice in stripping voltammetry of trace metals owing to their high sensitivity, reproducibility, and renewability. However, because of the toxicity of mercury, alternative (‘environmentally friendly’) electrode materials are highly desired for both centralized and field applications. Recently introduced bismuth electrodes offer a very attractive alternative to commonly used mercury electrodes. Such electrodes display well-defined, undistorted and highly reproducible response, favorable resolution of neighboring peaks, high hydrogen evolution, with good signal-to-background characteristics comparable to those of common mercury electrodes. The attractive stripping behavior of bismuth electrodes reflects the ability of bismuth to form ‘fused’ multicomponent alloys with heavy metals. Bismuth stripping electrodes thus hold great promise for decentralized metal testing, with applications ranging from continuous remote sensing to single-use measurements. Fundamental studies aimed at understanding the behavior of bismuth film electrodes should lead to rational preparation and operation of reliable alternative (‘non–mercury’) stripping electrodes that would have a major impact upon electroanalysis of trace metals. This article reviews the development, behavior, scope and prospects of bismuth electrodes for stripping-based electrochemical measurements of trace metals.
The electrocatalytic effect of underpotential deposition (UPD) of bismuth on the cathodic reduction of oxygen and hydrogen peroxide has been investigated on poly- and mono-crystalline (111) and (100) gold electrodes in 0.5 M HClO4 solution. On the bare gold substrates an incomplete 2-electron reduction of O2 to H2O2 predominates, which in the presence of Bi3+ in the solution is positively catalysed indicated by a decrease of the overvoltage and an increase of the rate of H2O2 reduction. The catalytic effects can be correlated with the degree of Bi adsorbate coverage and the structural arrangement of Bi adatoms depending on the crystallographic orientation of the substrate. The effect of a mixed anion (Cl−) and cation (Bi3+) adsorption on the reduction process was also studied.
The electrodeposition of bismuth on glassy carbon electrodes (GCEs) from nitrate solutions was studied by cyclic voltammetry, chronoamperometry, and scanning electron microscopy. Cyclic voltammograms exhibit a crossover between the cathodic and anodic branches, characteristic of the formation of bismuth nuclei on GCEs. The bismuth electrodeposition on GCEs is a diffusion-controlled reaction. The current transients for bismuth electrodeposition were analyzed according to the Scharifker–Hills models, the Scharifker’s general equation and the Heerman–Tarallo equation. For 1 and 5 mM Bi3+, the nucleation and growth mechanism is independent of deposition potential and follows the three-dimensional (3D) progressive nucleation and growth model. However, a deposition potential dependence of nucleation and growth mechanism can be found in the cases of 10 and 20 mM Bi3+. The quantitative analysis by the two equations shows that A and N0 exponentially grow with the increase of deposition potential, while D decays in an exponential mode. It should be noted that the two equations produced the very close N0 and D values and the distinct A values (especially at −300 and −350 mV). However, the critical size of the nuclei (Nc) estimated by using the two equations was all zero. Both of the equations can be used for describing the electrodeposition of bismuth on GCEs in this work. SEM images show that high deposition potential as well as high concentration can enhance the nuclei density of bismuth on GCEs and favors the formation of small crystallites with a less defined structure.
The properties of the bismuth film electrode designed for adsorptive stripping voltammetry were examined by electrochemical and microscopic techniques. The various bismuth plating solutions containing bromide ions were tested in bismuth film generation on glassy carbon. The composition of the plating solution, the influence of accumulation potential, and the stability of bismuth coating as well as the memory effect is discussed. The analytical usefulness of the BiFEs obtained by the proposal procedure was estimated for adsorptive stripping measurement of cobalt traces in a solution of 1 × 10−4 M DMG and 0.1 M ammonia buffer. It has been found that the plating solution of 0.02 M Bi(NO3)3, 1 M HCl and 0.5 M LiBr as well as −0.28 V plating potential and 20 s plating time ensure the finest quality bismuth film deposited on the glassy carbon support for analytical purposes. The electrode-to-electrode reproducibility of the described plating procedure was characterized by the relative standard deviation (RSD) equal to 12%. The repeatability of the cobalt response for 30 subsequent adsorptive stripping measurements of the same BiFE amounted RSD=6%.
Dissociative adsorption of formic acid and methanol on adatom-modified Pt(111) electrodes has been carried out as a way of studying poison formation reactions on these surfaces. The electrodes were prepared using irreversible adsorption of Bi and As. A modification of the dissociative adsorption technique used for poison formation studies has been employed. For clean Pt(111) surfaces the behaviour of the poison formation reaction of the two organic molecules is almost the same, but on adatom-modified Pt(111) electrodes different results are found. Bi and As show an important long-range electronic effect which inhibits poison formation from the dissociative adsorption of formic acid at very low adatom coverage. However, for methanol, the inhibition due to the presence of Bi adatoms on the surface can be explained by a simple third-body effect. A computer simulation of the dissociative adsorption of formic acid on Bi-modified Pt(111) electrodes has been carried out in order to calculate the width of the domains affected by the presence of Bi adatoms.
We report an investigation of the low-temperature electrical transport properties of bismuth films under applied hydrostatic pressure. Films with their trigonal axis perpendicular to the film plane and thicknesses of 30, 50, and 500 nm were grown by molecular-beam epitaxy on BaF2 substrates. At 500 nm thickness the behavior resembles that of bulk Bi. From the observed Shubnikov-de Haas oscillations we find a pressure-induced decrease in extremal Fermi cross section. For the 30-nm film, we obtain the low-temperature carrier densities for electrons and holes together with the corresponding mobilities from magnetoconductance data at pressures up to 20 kbar. We find that pressure strongly reduces the surface-induced excess hole concentration, clearly revealing a finite electron concentration at high pressures. We discuss our results within the context of a possible semimetal-semiconductor transition in thin Bi films.
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