Materials Today: Proceedings

Online ISSN: 2214-7853
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Article
We analyze the heat current flowing across interacting quantum dots within the Coulomb blockade regime. Power can be generated by either voltage or temperature biases. In the former case, we find nonlinear contributions to the Peltier effect that are dominated by conventional Joule heating for sufficiently high voltages. In the latter case, the differential thermal conductance shows maxima or minima depending on the energy level position. Furthermore, we discuss departures from the Kelvin-Onsager reciprocity relation beyond linear response.
 
Article
Phase change materials (PCMs) are preferred in thermal energy storage applications due to their excellent storage and discharge capacity through melting and solidifications. PCMs store energy as a Latent heat-base which can be used back whenever required. The liquefying rate (melting rate) is a significant parameter that decides the suitability of. PCMs in applications where there is a notable difference in temperature within the device for discontinuous warm storage capacities. A few studies have also been conducted to integrate PCMs in buildings as it upgrades building warm idleness, decreases maximum heat flux. This review paper summarizes some of the applications of PCMs. For future developments, some of the recommendations can be summarised as: in few of the listed applications, stability of the PCM needed to be explored since very few literature are available. The use of multiple phase change materials in a coupled or conjugate applications may also be further explored. In these applications, cost analysis and payback period of thermal storage systems empolyed with phase change materials also need exploration.
 
Article
Thermoelectric power (TEP) along with temperature dependent resistivity of Ti doped Gd-Sr manganite (Gd0.7Sr0.3Mn1-xTixO3 (x = 0, 0.1 and 0.15) denoted by G, G0.1 and G0.15 respectively) are studied systematically. Significant Seebeck coefficients (S) are exhibited by all the three samples which is a most desirable quality of a good thermoelectric material. In the case of sample G, highest attained value of S is −35.57mVK⁻¹ at 91 K. For G0.1 and G0.15 highest attained values are −31.60 mVK⁻¹ at 114 K and –33.76 mVK⁻¹ at 133 K respectively. This reveals that Ti doping shifts the highest value of S to higher temperatures. Diffusion and magnon drag contribute to TEP at lower temperatures. Temperature dependence of thermopower at comparatively higher temperature region gives an insight of combined SPH and VRH models. Temperature dependent electrical resistivity is successfully analyzed within the interesting framework of variable range hopping of small polarons.
 
Article
Nano ferrite particles were synthesized by oxalate precursor method, characterized by TGA/DTA analysis to know the pattern of decomposition, an elemental stoichiometry confirmed by EDAX method. The X-ray diffraction (XRD) and Infra-Red patterns were used to determine structural parameters, indicate the formation of single-phase cubic spinal structure. The average crystalline size was calculated from FWHM of most intensive pick 311, also confirmed from TEM analysis observe in the range of 29–34 nm. The structural parameters like lattice constant, X-ray density, bulk density and porosity increases with Cr³⁺ ion concentration. The magnetic parameters like saturation magnetizations and magnetic moments shown decreasing tendency. Bis-(4-hydroxycoumarin) methane derivatives successfully synthesized from 4 hydroxycoumarin 1) aromatic aldehydes 2, and using 20 mol % NiFe2−xCrxO4 nanoparticles as magnetically recoverable and reusable catalyst.
 
Article
The present work is based upon the investigation of structural properties of technologically important compound SrxCd1-xO (x= 0.00, 0.25, 0.50, 0.75 and 1.00) of group II-VI semiconductors. The Linear Combination of Atomic Orbital method has been used within density functional theory as embodied in CRYSTAL code. The Hybrid scheme B3LYP is used for making the Kohn-Sham Hamiltonian. The effect of the composition on lattice constant, bulk modulus is investigated. The deviations of the lattice constant from the Vegard’s law were observed for three cases
 
Results of refinement process of Nd x-1 Yb x FeO 3 at x = a) 0.01, b) 0.05 and c) 0.10, respectively. (+ = observed data, -= calculated data, -= difference line between observed and calculated data) .
Evolution of the lattice parameters with an increasing dopant of Yb at x = 0.01, 0.05, and 0.10, respectively.
Figures-of-merit of Rietveld refinement process of Nd 1-x Yb x FeO 3.
Article
The XRD data of NdFeO3 doped Yb has been successfully analyzed by Rietveld refinement method. The Nd1-xYbxFeO3 crystallographic data used base on X-ray diffraction results to obtain their crystal structure and phase. The Rietveld refinement method in Rietica software was used to analyze the lattice parameters of the samples. The result of X-ray diffraction shows that the presence of Yb did not affect the crystal structure of NdFeO3. The Rietveld refinement process shows that all samples have a good refinement indicating by the value of χ² ranging from 1.2 to 1.4 and the good visualization of the graph between experimental and calculation patterns. Further analyses of lattice parameter results then explained in this paper.
 
Article
In this study, the hardness values were analyzed to compare the micro-alloying (0.02 and 0.04 wt%) effect of Titanium (Ti) in 2xxx series Aluminium (Al) alloys. Al-Cu-Mg (alloy-A), Al-Cu-Mg-0.02Ti (alloy-B) and Al-Cu-Mg-0.04Ti (alloy-C) were the alloys which were prepared using standard casting process. Different conditions of heat treatment were applied on the alloys. Using Rockwell Hardness tester hardness was investigated for the said alloys under as-cast and heat treated conditions. Addition of 0.02 wt% of Ti to the investigated alloy improves the hardness value by about 3.61% when the alloy was naturally aged and water-cooled (NAW). After adding 0.04 wt% of Ti to the investigated alloy improves the hardness value by about 15.66% when the alloy was naturally aged and water-cooled (NAW). In the study the hardness values were recorded for 31 days at different time intervals such as at Day 1, 7, 15, 21 and 31. The hardness of the alloys was maximum when it reaches Day 15 and gradually decreases after that. The hardness of the water-cooled samples (Alloy A, B and C) was seen to be decreasing in a specific order in all the days the hardness test was performed. The order observed is, NAW > AC > AAW > NAWSH > NAWS > AAWH.
 
Article
Pure and modified lead titanate PbTiO3 (PT) by 3% of the lanthanum iron oxide LaFeO3 (LF) samples were prepared by a sol-gel process. The calcined powders (at 700 °C for 2h) were structurally characterized by X-ray diffraction and Raman spectroscopy, it has been proven that these materials have a single phase as a perovskite-type. Furthermore, DRX and Raman spectrum revealed local lattice distortions from tetragonal structure (P4/mmm) for non-doped sample (PT-LF0%) to pseudo-cubic structure (Pm-3m) for doped sample (PT-LF3%). Optical properties were investigated by UV visible (UV-vis) absorption spectroscopy at room temperature. The UV-vis spectrum indicated that the studied powder has an optical band gap of 2.032 eV making of this material a good candidate for photovoltaic applications. In order to investigate their electrical properties, we have pressed the calcined powder into the pellets and heat treated at 1100 °C for 4h. The compound exhibited a high dielectric constant and a low dielectric loss. Empirical laws of the Curie-Weiss and of the Uchino were performed to extract electrical parameters in wide frequency range.
 
Article
A formidable amount of work has been devoted aiming towards the understanding of the structure and properties of colossal magnetoresistance (CMR) manganites. Mixed valent manganites with the general formula R1-xAxMnO3 (R = trivalent rare earth ion and A = divalent ion like Sr⁺², Ba⁺², Pb⁺², Ca⁺² etc.) are found to exhibit variety of phenomena such as charge, spin and orbit ordering, electronic, magnetic and structural transitions depending on the type and amount of doping (x). In this paper, doping dependent modifications in the microstructure polycrystalline La0.7Sr0.3Mn1-xTixO3 (LSMTO) (x = 0.03, 0.06 and 0.12) compounds synthesized by hybrid method (sol gel method + solid state reaction method) have been discussed in detail. In the present work, the powder X-ray diffraction patterns reveals that the samples are single phase in nature and the samples show a rhombohedral structure in hexagonal lattice with the space group R3-c. The Rietveld refinement was performed using FullProf software for the detailed structural investigation. In this context, the lattice parameters, unit cell volume and χ² were obtained for LSMTO samples. On the substitution of Mn⁺⁴ by Ti⁺⁴, the structure does not undergo any phase transformation, but lattice parameters steadily increase as Ti⁺⁴ doping concentration increases. It can be related to the larger ionic radius of Ti⁺⁴ (rTi⁺⁴ = 0.605 Å) ion compared to that of Mn⁺⁴ (rMn⁺⁴ = 0.540 Å) ion. FT-IR spectra for LSMTO of different concentration show the four peaks around 400–500 cm⁻¹ (Mn-O-Mn bending mode), 610–670 cm⁻¹ (Mn-O stretching mode), 2330–2400 cm⁻¹ (moisture contain) and 540 cm⁻¹ (Ti-O stretching modes). Weight loss % versus temperature plot (TGA) for the x = 0.06 sample confirms that the precursor shows three step weight loss profiles and does not melt up to the temperature of 1050 °C. A quantitative analysis of the energy dispersive spectroscopy (EDS) data indicates that the observed concentration of elements is very close to the calculated values from its chemical formula. Typical SEM micrographs for all the three samples show that each sample possesses fine and clear grain boundaries (GBs). From the R-T measurements, an increase in resistivity and a decrease in metal to insulator transition temperature (TMI) were observed by increasing doping level of Ti for Mn. All the LSMTO samples show the resistivity suppression under applied magnetic field. The maximum MR % (89%) was observed for x = 0.12 at 5 T compare to other doped samples. This result suggests that the magnetoresistance behavior is improved by addition of Ti at Mn. These results prove that concentration Ti substitution at Mn site enhances the various properties of this manganite system.
 
Article
(Ta2O5)1-x-(TiO2)x (TTO) thin films, with x = 0.035, were deposited onto the P/boron-silicon (100) semiconducting substrates by reactive direct current (DC) magnetron sputtering of mosaic Ta and Ti metal targets, at ambient temperature. As-deposited films have been passed through the process of annealing at the temperatures, ranging from 500 to 800 °C. X-ray diffraction measurements, generally, show the formation of Ta2O5 structure of the annealed films. Metal–oxide–semiconductor (MOS) structure of Ag/(Ta2O5)1-x-(TiO2)x/p-Si (Ag/TTO/p-Si), with x = 0.035, was formed, and capacitance of the structure was measured, at room temperature and 1 MHz. Capacitance of prepared MOS structure was measured, and found generally, increasing with annealing temperature. Among the prepared films, maximum value of dielectric constant was found 45, at 1 MHz, for the films annealed at 700 °C. Frequency dependent behaviour of dielectric loss was observed, and was found minimum value of 0.022, at 200 kHz, for the films deposited at room temperature.
 
Article
The morphological and visual properties of Magnesium Zinc Aluminate (Mg0.67Zn0.3 Al2O4) nanophosphor impured with Dysprosium (Dy³⁺) of 0.03 mol were reported in the present paper. Urea (NH2-CO-NH2) was used as fuel, Mg0.67Zn0.3 Al2O4(Pure)& Mg0.67Zn0.3 Al2O4 doped with 0.03 mol of Dysprosium (Dy³⁺) nanophosphors were synthesized through a solution combustion technique. The emergence of Mg1-xZnx Al2O4(Pure) & Mg1−x−yZnx Al2O4:YDy(x = 0.3 & Y = 0.03 mol) were confirmed by urea-nitrate incorporation through combustion synthesis manner at 550◦C. The morphological properties of Pure and impure MgZnAl2O4 nanocrystallites were investigated through X-ray diffraction (XRD) having Cu Kα [40 kV,15 mA X-ray] at λ = 1.541862°A,the stage rec- ognization and interposed stage emergence were established through the appearance of the heterojunctions peak at 2θ = 36.73◦ and Fourier Trans- form Infrared (FT-IR) Spectroscopy(PEService).An Optical energy gap(Eg) of 1.23 eV calculated by Tauc Plot Method confirmed that Mg1−x−yZnxAl2O4, may be semiconducting materials.The result proved that the MgZnAl2O4 with an average particle size of 28.34 nm and 21.99 nm for pure and impure nanophosphors are crystalline in nature.The nanophosphors size were calculated by Scherer’s equation.
 
Article
The morphological and visual properties of Zinc Magnesium Aluminate (Zn0.67 Mg0.3 Al2O4) nanophosphor impured with Dysprosium (Dy³⁺) of 0.03 mol were reported in the present paper. Urea (NH2-CO-NH2) was used as fuel, Zn0.67Mg0.3 Al2O4(Pure)& Zn0.67Mg0.3 Al2O4 doped with 0.03 mol of Dysprosium (Dy³⁺) nanophosphors were synthesized through a solution combustion technique. The emergence of Zn1−xMgx Al2O4(Pure) & Zn1−x−yMgxAl2O4:YDy (x = 0.3 & Y = 0.03 mol) were confirmed by urea-nitrate incorporation through combustion synthesis manner at 550 °C. The morphological properties of Pure and impure ZnMgAl2O4 nanocrystallites were investigated through X-ray diffraction (XRD) having Cu Kα [40 kV, 15 mA X-ray] at λ = 1.541862°A, the stage recognization and interposed stage emergence were established through the appearance of the heterojunctions peak at 2θ = 36.68◦ and Fourier Transform Infrared (FT-IR) Spectroscopy (PEService). An Optical energy gap(Eg) of 1.499 eV calculated by Tauc Plot Method confirmed that Zn1-x-yMgxAl2O4, may be semiconducting materials. The result proved that the Zn-MgAl2O4 with an average particle size of 25.12 nm and 24.90 nm for pure and impure nanophosphors are crystalline in nature. The nanophosphors size were calculated by Scherer’s equation.
 
Article
We have succeeded to increase the absorption capacity of microwaves by substituting La³⁺ ions with Sr²⁺ ions (Ba0.6Sr0.4-xLaxFe10MnTiO19). Samples are made by the solid reaction method through milling. XRD is used to characterize phase formation and crystal structure. SEM is used to see the surface morphology. VNA is used to measure the ability to absorb microwaves. The results obtained indicate that the sample is single phase with a hexagonal structure. The shape and size of the particles are still heterogeneous. The ability to absorb microwaves is −20.1 dB, −24.7 dB, and −20.3 dB for × = 0.05, 0.10, and 0.15 respectively.
 
Article
This paper presents the preparation and characterization of Ca1-xBaxCu3Ti4O12 (x = 0 & 0.05) materials by Wet chemical method using CuSO4, BaCl2, TiO2, and CaCO3 as starting precursors. X-ray diffraction patterns recorded by using X-ray diffractometer employing Cu-Kα radiation with a Ni-filter show that the materials are formed in single phase in cubic perovskite crystal system with nominal impurities. DSC/TGA curves show that the phase stabilization of the samples is occurring around 1000 °C temperature. From scanning electron micrographs it is observed that the typical grain size is found to be 1–3 µm. Further, bonding information of samples has been gained by Fourier Transform Infrared (FTIR) spectroscopy patterns.
 
Article
Multiferroic composites (1-x) Bi 0.9Sm 0.1FeO 3/ (x) La 0.7Sr 0.3MnO3 (x = 0, 0.05, 0.1) have been synthesized and their dielectric and magnetoelectric (ME) properties were measured at room temperature. X-ray diffraction patterns show peaks corresponding to both Bi 0.9Sm 0.1FeO 3 (BSFO) and La 0.7Sr 0.3MnO3 (LSMO) phase, which indicates the successful formation of composites. The frequency responses of dielectric properties have been investigated over a wide range of frequencies at room temperature. The dielectric constant and AC conductivity of the samples enhances with increasing content of LSMO. Furthermore, the ME responses of the samples were analyzed at room temperature shows highest ME coupling value of 24.67 mV/cm Oe for composite with x = 0.05. It could generate up to 2.05 V/cm for a magnetic field of 86 Oe. The voltage generation in the composite with modulating AC field maintains a linear relation and point towards the direct application of the material in a variety of next generation low power consuming devices working at room temperature.
 
Article
Lead-free ternary 0.72Na0.5Bi0.5TiO3-0.2SrTiO3-0.08K0.5Na0.5NbO3 (NBT-ST-KNN) ferroelectric relaxor is prepared by conventional solid state reaction route. The ceramic with dense microstructure is studied by complex impedance spectroscopy over a temperature range from 400 °C to 650 °C. A clear contribution of grain and grain boundaries to the relaxation mechanism is confirmed from the Nyquist plot as a function of frequency and temperature and are investigated using empirical relations. The relaxation time is evaluated from Im Z* plot using Arrhenius law. Existence of two different activation energy values depicts the presence of two different relaxation processes. This investigation on complex impedance and ac conductivity values will provide useful information about the temperature and frequency dependent relaxation and conduction process.
 
Article
Na0.5Bi0.5TiO3 (NBT) and CoFe2O4 (CFO) ceramics were synthesized by sol–gel and metallo – organic chemical solution methods respectively. Structural, electrical, dielectric and magnetic properties of (1-x) NBT-(x) CFO (x = 0.1, 0.2) multiferroic particulate composite prepared by mixing NBT and CFO powders in required stoichiometric concentration were studied. The presence of ferroelectric (NBT) and ferrite (CFO) phases had been confirmed by X-ray diffraction analysis (XRD). Room temperature dielectric behavior was studied with varying frequencies. Ferromagnetic behavior was also confirmed by M−H hysteresis loops. The current–voltage (I–V) characteristics were studied by using Keithley 2611 Source Meter.
 
Article
Phosphates materials are low in cost, environmental friendly, have good thermal stability and good photoluminescence properties. In the present work Eu²⁺ doped (Ca5-xSrx)(PO4)3Cl (x = 0.1, 2.4) novel phosphors are prepared using wet chemical synthesis method. Intense blue emission is observed when characterised for photoluminescence spectrum. Photoluminescence spectrum of (Ca5-xSrx)(PO4)3Cl exhibit emission peak cantered at around 449 nm attributed to 4f⁶5d to 4f⁷ transition of Eu²⁺ upon excitation by 365 nm radiations. Excitation spectrum of the phosphors shows efficient response in near UV region. CIE chromaticity coordinates for (Ca2.55Eu0.05)Sr2.4(PO4)3Cl are x = 0.1508 to and y = 0.0331 and those for (Ca4.85Eu0.05)Sr0.1(PO4)3Cl are x = 0.1510 and y = 0.0321 (red dot), indicating the emitting colour is tunable in blue region. Thus, results showed that (Ca5-xSrx) (PO4)3Cl:Eu²⁺ phosphors can be used as a blue host for white LED.
 
Article
Magnesium Titanate-based ceramics is one of the popular microwave dielectric materials. These are widely used as dielectrics in resonators and filters for communication, capacitors and radar systems operating at microwave frequencies. The pure and Calcium doped Magnesium Titanate ceramic materials are synthesised by conventional Solid-state route diffusion method. High purity chemicals of MgO, TiO2 and CaO which are taken in according to their compositions for the preparation of Mg1-xCaxTiO3 (x=0,0.1,0.2 and 0.3) ceramics. They are grounded well for 12h in a Ball Mill. Then the powders are calcined at 1175°C to 1200°C for 36h and are pressed into pellets. These pellets are sintered at 1270°C to 1300°C for 6h. The dielectric constant from room temperature to 350°C is calculated using HIOKI 3532-50 LCR HiTESTER in the frequency range of 100Hz-5MHz. The dielectric constant at room temperature at a frequency of 0.1KHz for pure Magnesium Titanate is found to be 14.13 and as the concentration of Calcium increases dielectric constant increases. The AC conductivity and Dielectric loss of the samples are measured. XRD studies revealed that the compound exhibits major phase of MgTiO3 with Hexagonal structure and space group 148: R-3.
 
Article
Bi3+-substituted Li0.35Zn0.3BixFe2.35-xO4 (x = 0.1) nanocrystallites of ∼32 nm synthesized via a citrate-gel combustion and then annealed at 400 °C for 2 h in air shows a saturation magnetization Ms = 11.25 emu/g (with a high coercivity Hc = 273 Oe) at 5 K. Frequency (f) dependence of dielectric properties describes a mechanism of polarization. Granular crystallites offers a high polarization Ps = 1.956 μC/cm2 at 9 kV/cm applied field.
 
Article
The novel La0.7Ce0.2Sr0.1Fe0.5Mn0.4Co0.1O3 (LCSFMCO) perovskite nanoparticles were successfully synthesised using sol-gel method at a temperature around 350°C. The obtained powder was further calcinated at 700°C for a predetermined span of time. Samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Electron Dispersive Spectrometry (EDS) for its structural, morphological, and compositional analysis respectively. The electrochemical behaviour of the synthesised LCSFMCO perovskite nanoparticles were studied by measuring the cyclic voltammetry. The Capacitance, charge- discharge, impedance results were studied using the electrochemical analysis.
 
Article
La0.7Sr0.3Fe0.1Mn0.9O3 and La0.7Sr0.3Fe0.4Mn0.6O3 perovskite were prepared via solid state reaction method for cathode application in solid oxide fuel cell. XRD analysis confirmed single phase and crystalline nature of the both compounds. Density was calculated by Archimedes Principle and surface morphologies were investigated via Scanning Electron Microscope. Thermal behavior of the compounds was studied by thermo gravimetric analysis and dilatometer. Above 350 ⁰C temperature, material started gaining weight and increased content of Fe decreased its thermal expansion coefficient. Impedance spectroscope confirmed the non-Debye relaxation behaviour. Fe substitution enhanced the dielectric constant as well as conductivity and decreased the activation energy of the material. Maximum value of conductivity was found to be 116.31 S/cm for La0.7Sr0.3Fe0.4Mn0.6O3 compound. Investigated parameters recommended that as prepared materials are suitable materials for cathode of SOFCs.
 
Article
In this paper, (ZnO)x-(MgO)1-x composites were deposited on glass and silicon substrate using E-Beam Deposition Technique. Doping of MgO is in atomic percentage for various compositions from 0% to 90%. XRD results show that MgO has been doped successfully. The investigation of Band gap has been done and the result displays as the MgO content is increased, the band gap is tuned from 3.16 eV to 3.55 eV and transmission band edge is blue shifted about 36 meV to the higher energy direction, this is closely related to formation of mesoporous structure. The Band Gap has been calculated using UV–Vis Spectroscopy. Investigation confirms that defects in surface have been increased with the increase in MgO Content.
 
Article
We investigate the influence of Ce substitution on the magnetic and magnetocaloric properties in CexNi1-x amorphous alloys with x = 0.12, 0.34 and 0.43, synthesized using ultrahigh vacuum evaporation method. The Ni magnetic moment decreases from 0.033µB, 0.0087µB to 0.002µB when Ce content increases from 0.12, 0.34 to 0.43. The same trend was found for Curie temperature TC which decreases from 40 K, 12 K to 2 K. The magnetic behavior and the magnetic transition were analyzed using Landau theory around the transition temperature. The magnetic transition nature is of a second order from ferromagnetic to paramagnetic state. Good agreement was found between the magnetic entropy (−ΔSM) values estimated by Landau theory and those obtained using classical Maxwell relation.
 
Article
This study compares the conventional T6 (“solution-quenching-aging”) treatment with an innovative one, in terms of high temperature response of the EN AW-2618A alloy, containing 0.12wt% Zr. The new treatment is aimed to stimulate Zr-based precipitates with optimal size, shape and distribution, in order to completely take advantage of Zr anti-recrystallization effect. To assess alloy's thermal stability, samples subjected to both heat treatments were soaked at 250 °C, up to 50h. Hardness measurements, microstructural characterization and high temperature compression tests have been carried out, giving evidence of significant improvements connected to controlled formation of Zr-based precipitates.
 
Article
Perovskite La1-xCaxFe0.75Co0.25O3 {x = 0.15 & 0.25} cathode material for solid oxide fuel cell has been prepared by solid state reaction method. Material has been calcined and sintered at 900 °C for 12 h and 1250 °C for 4 h respectively. X-ray diffractometer has been used to study the structural properties. Archimedes principle has been used to calculate the density and scanning electron microscope has been used to study morphology of the material. Change in weight during sintering process studied by themogravimetric analysis and temperature expansion coefficient determined by dilatometer. Impedance analyser has been used to study the dielectric and electric behavior of the material. Conductivity of the material has been calculated more than 100 Scm⁻¹. Doping of Ca²⁺ increased the conductivity of the material. Obtained parameter confirmed that present prepared perovskite is appropriate to be used as cathode electrode of solid oxide fuel cell.
 
Article
In this work, the effect of graphene addition on the transport critical current density of (Tl0.85Cr0.15) Sr2CaCu2O7-δ (Tl-1212) superconductor was investigated. Thallium-based high temperature superconductor (HTS) with nominal starting composition (Tl0.85Cr0.15) Sr2CaCu2O7-δ was prepared using high purity oxide powders via solid state reaction method. 0.001 – 0.005 wt.% of graphene were added into Tl-1212 superconductors. The characteristic of the samples were determined by powder X-ray diffraction method, scanning electron microscopy (SEM), energy dispersive X-Ray analysis (EDX), electrical resistance measurements and transport critical current density measurements. The zero-resistance temperature, Tc-zero was found to decrease from 95 K to 84 K with the increase of graphene. The temperature dependence transport critical current density (Jc) of the pure and graphene added bulk samples were investigated. Jc of the non-added bulk sample was 1320 mA/cm² at 30 K while the Jc of sample with 0.001 wt.% graphene was 3660 mA/cm² at 30 K. Results showed that the Jc of the Tl-1212 samples decreased with increasing graphene addition. Graphene acted as impurity which is believed to perform the flux pinning effect to Tl-1212. Thus, the Jc of Tl-1212 superconductors was enhanced. The phase formation and morphology of samples Tl-1212 were also discussed in this paper.
 
Article
Probing in to the electrical behavior of ceramics is very essential for casting them in to real life applications. In this work, we report the temperature dependence of dielectric permittivity and impedance spectroscopic studies of 0.7Na0.5Bi0.5TiO3-0.2SrTiO3-0.1BaTiO3 to investigate its electrical properties. A Lorentz type law was found to well describe the diffused permittivity peak by two independent fitting processes. Such a peculiarity was related to the temperature response of the PNRs. This was ascertained from the temperature and frequency dependent Z* and M′′ spectra respectively. Combined graphs of normalized Z′′(f) and M′′(f) in the range 50 – 200 °C predict short ranged dipolar relaxations within the grains.
 
Article
Nb-1Zr-0.1C is a Niobium based refractory metal alloy having an excellent combination of high temperature properties like high melting point (∼2500°C), adequate high temperature strength (∼200 MPa) and creep strength for long duration, better compatibility for alkali liquid metal, resistance to thermal shock & radiation and low ductile to brittle transition temperature (DBTT). These properties make this alloy a potential candidate for several structural applications including compact high temperature reactors. Welding of this alloy is a difficult task due to its high melting point and its reactive nature. In comparison to the conventional welding processes, high energy density sources like electron beam and laser beam which can produce deep penetrations with narrow heat affected zones are more suitable to weld the components made of Nb-1Zr-0.1C alloy. This paper describes the development of electron beam welding procedure for Nb-1Zr-0.1C alloy. Welding parameters were developed and weld bead was characterized by metallography and different zones of the weld bead were identified and studied. The results of the welding trials and the tests performed on the welds and the major observations & conclusions drawn from the experience of welding Nb-1Zr-0.1C alloy are presented in this paper.
 
Article
An eco-friendly magneto-electric material of 0.1LaFeO3-0.9HoMnO3 has been prepared with different weight percentage of LaFeO3 and HoMnO3 concentration by a chemical “Pyrophoric reaction technique”. The formation of both LaFeO3 and HoMnO3phases is confirmed through X-ray diffraction technique. The magneto-electric coupling and electrical transport have been carried out at room temperature and selected temperatures. The observed magneto-electric coefficient attributes the presence of strain mediated magnetostriction properties of the piezomagnetic material. The AC electrical response is investigated by impedance spectroscopy technique, which shows the contribution of grains and grain boundaries of the material. The impedance value is decreasing with rise in temperature, which signifies the negative temperature coefficient resistance effect of the sample. The Nyquist plot shows the existence of non-Debye type relaxation mechanism in the composite. This study is developing an urge to know the details of the magneto-electric coupling and electrical transport properties of a system for its technological applications.
 
Article
Dual phase (Bi4Ti3O12)0.2-(CaCu3Ti4O12)0.8 {(BTO)0.2-(CCTO)0.8} nanocomposite powder was synthesized via a low cost auto-combustion method. Nancomposite powder was modified in the form of a thick layer (50 μm) over the alumina ceramic substrate using screen printing technique. The structural, morphological, functional and electrical properties of the dielectric thick film have been observed. The XRD spectra confirm the coexistence of dual phase composite systems with proper ratios. The particle size was significantly smaller and very few un-melted particles were observed from FESEM analysis of the thick film. Vibrational modes present in the composite film were confirmed with the help of FTIR spectrum. The (BTO)0.2-(CCTO)0.8 shows an unusual behaviour of high dielectric constant (∼243) and dielectric loss (∼5.9) at low frequency as well as room temperature. The understanding of this amazing dielectric behaviour opens the new way of nanocomposite thick films which can be used as a dielectric substrate for microstrip antenna fabrication.
 
Article
Aluminium 6063 alloy is widely utilized as a structural membrane among automobile and aircraft sectors because of its excellent specific strength and formability characteristics. Aluminium alloys which have been employed in the form of aerospace structural components will undergo dynamic loading which leads to the fatigue which is due to mechanical stress and thermal conditions. Considering studies toward the low cycle fatigue behavior of aluminium alloys are particularly narrowed, this investigation sighted to the analysis of fatigue behavior of Al 6063 alloy at the various strain amplitude of 0.4% and 0.8% which performed through the low cycle fatigue testing machine at the frequency rate of 0.2 Hz. The test reveals that for the higher magnitude of 0.8% strain amplitude the fatigue life was shorter as 291 cycles. Mean Stress of the Al6063 samples relies on the crack initiation and value of the mean stress is a vital parameter for determining the fatigue limits. For 0.4% strain amplitude, it took 1735 cycles to fail but there was only cyclic softening has happened, whereas for 0.8% despite the shorter life.
 
Article
The optoelectronics properties of Gallium Nitride and its alloys are attracting increasing interest due to the potential application of these materials for UV photodetectors and high electron mobility transistors. However, the persistent photoconductivity (PPC) in the GaN based photoconductive devices affects the light sensitive characteristics and with temperature these photoinduced effects are different in ternary alloys such as that of the AlxGa1-xN layers. In order to study the temperature dependent PPC effect, we have performed photoconductivity measurements on two heterostructures constituting unintentional n-type GaN and n-type Al0.2Ga0.8N layers on GaN buffer on Mo back-coated c-plane sapphire substrate using UV monochromatic light. Low temperature PPC measurements have shown that trap levels exist in both AlGaN and GaN layers. In our samples PPC decay behavior in n-Al0.2Ga0.8N layer was found to better than the n-GaN layer at low temperatures. Broad distribution of trap (defect) levels with energies lower than the bandgap energies were observed in both n-Al0.2Ga 0.8N layer and GaN layer as evident from room temperature photoluminescence spectra. In ternary nitrides, the presence of 2DEG channel dominates the photoresponse at low temperature whereas in binary nitrides, the photoresponse is majorly affected by the trap levels. This study enabled us to propose AlxGa1-xN based UV photodetector for low-temperature applications.
 
Article
Stopping force formula for heavy ions with ZHI=3-36, in the energy region ∼0.2–3.0 MeV/n, is developed. For this, fitting parameters involved in effective charge parameterization of Hubert et al. formulation are modified. Other parameters, used for stopping force calculations, are computed by utilizing Ziegler’s fitting formulae. To check the reliability/validity of the present stopping force formula, the computed results are compared with the recently measured values. The comparison reveals that the predicted values are in good agreement (within experimental errors) with the recently measured values. The study is significantly important because low energy ions are widely used in material science particularly in ion implantation/irradiation along with other fields like atomic and molecular physics, health physics, bio-science and medical science etc. In addition, the study is also important to understand the fundamental aspects involved in interaction of ion with matter. The predicted values based on the present formula can be used as an input parameter for all those experiments where these combinations are used.
 
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The (1 − x)CoFe2O4 + xBaTiO3 (x = 0.2, 0.5, 0.8) magnetoelectric (ME) composites were prepared by solid state method. The structural feature of as-prepared ceramics were characterized and studied systematically by using XRD, and Raman. The dielectric properties were measured by LCR Meter Bridge. Variation of dielectric properties (dielectric constant and dielectric loss) with frequency range of 1000 Hz–1 MHz were studied. The AC conductivity were calculated from dielectric constant (ε’) and loss tangent (tanδ). The conduction phenomenon was explained on the basis of small polaron hopping model. The composites show excellent ferroelectric properties. The morphological feature of the selected composites; fractured as well as thermally etched has been studied by scanning electron microscopy. The relationship between such properties, chemical composition and sintering temperatures are thoroughly discussed.
 
Article
The effect of strain rates on 0.24 percent C carbon steel under tensile loading has been discussed in this study. To perform the test by adjusting the strain rates, an electronic tensiometer was used. Before and after research, the microstructural orientations and stiffness around the necking area were defined by an optical microscope and a micro-hardness tester. At room temperature, the mechanical properties of carbon steel are investigated, such as ultimate tensile strength, yield strength and hardness. The lowest ultimate tensile strength (429.14 MPa) and lowest yield strength from the data were observed to have a strain rate of 1 mm/min (292.8 MPa). Strain intensity of 5.75 mm/min. The maximum ultimate strength (525.54 MPa) and highest yield strength are given (376.35 MPa). If the strain rate increases, the ultimate strength, and yield strength will rise and vice versa, the results showed. It can be observed that the hardness value improved to a reasonable level of 3.5 mm/min from 1.5 mm/min and decreased to 5.75 mm/min as the strain rate increased. The ANN model demonstrated an impressive contrast between the coefficient of correlation (R = 0.997) and the error in the mean square (MSE = 1.24 10-5) and the experimental findings. This analysis shows that the ANN model is capable of predicting the impact on Carbon steel’s mechanical properties of different rates for the strain.
 
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Bi1–xSbx solid solutions are the best n-type thermoelectric materials for use at temperatures ≤200 K. An important parameter determining material’s figure of merit is charge carrier concentration. To determine it correctly, one should carry out measurements in a weak magnetic field. On the basis of the magnetic field dependences of the Hall coefficient and magnetoresistance, the dependences of the weak magnetic field boundary Bc on composition (x = 0–0.25) and temperature (T = 77–300 K) for polycrystalline Bi1–xSbx alloys were plotted. It was established that the Bc(x) dependences exhibit a non-monotonic behavior which is attributed to the existence of electronic phase transitions.
 
Article
Ti1-xZnxO2 {0 ≤ x ≤ 0.25} nano material has been synthesized by solid state reaction method. X-ray diffractometer (XRD) has been used to study the structural properties of the nanomaterial which confirmed orthorhombic structure with space group Pbcn. Scherer formula has been used to calculate the crystalline size of the nanomaterial which has been found to be decreased from 30 nm to 19 nm with Zn substitutions. William Hall plots confirmed tensile strain in the unit cell of the crystalline material. Scanning electron microscope (SEM) has been used to study the morphology of the as prepared nanomaterial which confirmed that gains are unequal in size and randomly oriented in the material. Archimedes principle has been used to study the density of material which observed to be increased with Zn doping. Thermo gravimetric analysis confirmed the weight loss of the material at low temperature and material become stable at higher temperature. Vibrating sample magnetometer confirmed diamagnetic character of the material. Impedance analyser has been used to study the dielectric and electric properties of the nano-material. Dielectric constant of the material is high at low frequency and decreased at high frequency confirmed the polarization loss inside the material at higher value of frequency. Electric conductivity of the as prepared materials has been increased with temperature and decreased with Zn atom substitution.
 
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The structural, ferroelectric, dielectric and conduction mechanism of Pb0.75La0.25TiO3 ceramics synthesized using solid state reaction route & Auto Combustion method have been reported. X-ray diffraction data reveals that prepared ceramics using both the methods crystallizes into tetragonal phase whereas ferroelectric loop confirms the presence ferroelectric ordering. Frequency dependent ε′ and ε″ at different temperature shows the Cole-Cole relaxation behaviour. The Jonscher’s power law fitted parameter ‘n’ vs. temperature explains the conduction mechanism in prepared ceramics.
 
Top-cited authors
T. Sathish
  • Saveetha School of Engineering, SIMATS
Karthikeyan Sathasivam
  • Syed Ammal Engineering College
Rajesh Purohit
  • Birla Institute of Technology and Science Pilani
Mathivananq Periyasamy
  • Vilnius Gediminas Technical University
Manoj Kumar Pasupathi
  • KPR Institute of Engineering and Technology, Coimbatore, India