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Structure, electrical, dielectric, and optical investigation on polyvinyl alcohol/metal chloride nanocomposites
Journal of Applied Polymer Science
Abstract
Different concentrations of metal chlorides/polyvinyl alcohol nanocomposites have been prepared by the typical solvent cast technique. The prepared samples were investigated by different techniques such as X‐ray diffraction, differential scanning calorimetry, and scanning electron microscope. DC and AC conductivities are examined at different temperatures and frequencies. An activation process was found in the DC conductivity versus temperature relation and the activation energy was calculated. The AC conductivity obeyed the ωS power law. The behavior of S with temperature was studied. Various dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″) and loss tangent (tan δ) have been determined in the temperature range 303–443 K at different frequencies. The dielectric parameters were found to decrease with increasing frequency. The study of dielectric relaxation as a function of temperature at constant frequency shows two relaxation mechanisms. The optical band gaps and band tails were estimated from the measured absorption spectra. The applied photon energy found to affect the observed optical band gaps. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
... In recent years, due to the technological importance of the organic/polymeric materials play an important role in electronic and optoelectronic device applications such as Schottky type diode, solar cells, light-emitting diodes, transistors, sensors and capacitors [1][2][3][4][5][6]. In order to improve the performance and reliability of metal-semiconductor (MS) type Schottky barrier diodes (SBDs), a thin polymer layer with and without metal doped are inserted between metal and semiconductor instead of traditional insulator materials such as SiO 2 and SnO 2 . ...
... Usually, metal-polymer-semiconductor (MPS) structure shows similar behavior of metal-insulator-semiconductor (MIS) type Schottky diodes. Especially, polyvinyl alcohol (PVA) has an important place among organics/ polymers and it has low cost, low weight, flexible and easy fabrication processes such as electrostatic spraying, electrochemical deposition, sol-gel, dip coating, and spin coating [1][2][3][4]. PVA is also water soluble and it has a semi-crystalline polymer exhibit more important applications due to the role of OH group and hydrogen bonds [4]. On the other hand, PVA has normally poor electrical conductivity and may be conductive upon doping with some dopants such as Zn, Ni, Co, graphene, (Cu 2 O-CuO) due to the high physical interaction between polymer chains [5,6]. ...
... Especially, polyvinyl alcohol (PVA) has an important place among organics/ polymers and it has low cost, low weight, flexible and easy fabrication processes such as electrostatic spraying, electrochemical deposition, sol-gel, dip coating, and spin coating [1][2][3][4]. PVA is also water soluble and it has a semi-crystalline polymer exhibit more important applications due to the role of OH group and hydrogen bonds [4]. On the other hand, PVA has normally poor electrical conductivity and may be conductive upon doping with some dopants such as Zn, Ni, Co, graphene, (Cu 2 O-CuO) due to the high physical interaction between polymer chains [5,6]. ...
In this study, the electrical characteristics of the prepared Au/(Cu2O–CuO–PVA)/n-Si (MPS) structures have been investigated in detail by using the frequency dependent C–V and G/ω–V measurements by taking into account the interfacial polymer layer, surface states (Nss), polarization and series resistance (Rs). The electric parameters such as the diffusion potential (VD), the concentration of donor atoms (ND), and barrier height (BH) values were obtained from C⁻²–V plots for each frequency and they were found as 0.33 eV, 7.60 × 10¹³cm⁻³, 0.65 eV at 10 kHz and 0.70 eV, 6.99 × 10¹³cm⁻³, 1.02 eV at 3 MHz. The energy dependent profiles of Nss and their relaxation time (τ) were found by using admittance method and they ranged from 1.09 × 10¹¹ to 1.60 × 10¹¹ eV⁻¹ cm⁻² and 7.75 × 10⁻⁶ to 9.93 × 10⁻⁵ s, respectively. These low values of Nss are indicated that the (Cu2O–CuO)-doped PVA interfacial layer considerably enhances the performance of the Au/n-Si (MS) structure and so it can be successfully utilized instead of the traditional insulator/dielectric layer due to its passivized the surface states. The Rs versus V plot was obtained from the C–V and G/ω–V data using Nicollian and Brews method and it shows a distinctive peak, while the magnitude of the peak decreases with increasing frequency, its position shift towards lower or negative bias voltage with decreasing frequency due to the reordering and restructuring of surface states and their relaxation time under applied bias voltage. The impedance measurements were also performed in the wide range of frequency (100 Hz–1 MHz) at room temperature. The equivalent circuit model parameters such as parallel resistor (Rp), capacitor (Cp) and a series resistance (Rs) were calculated from Cole–Cole plots. The values of Rs, Rp and Cp decrease with increases dc voltage. The decrease of Rp is because of the increasing in the number of injected charge carriers into the device.
... However, the poor conductivity of organic/polymer materials compared to inorganic materials is the most challenging issue in their use of them for this purpose. On the other hand, polymers with suitable dopants can easily overcome this problem [3][4][5][6][21][22][23][24][25][26][27]. ...
... Among polymers, such as low weight, flexibility, and water solubility and application areas such as pharmaceutical, biomedical, chemical sensor, electroluminescent devices, and batteries highlight PVA [26][27][28][29]. PVA is a semi-crystalline and consisting of crystalline, amorphous phases, and generally, the properties of the amorphous regions are dominant. ...
Variation in the electrical parameters depending on illumination and the formation of negative capacitance (NC), and inductive behavior (IB) of Schottky structures interlaid with Zn:PVA, were executed by current/impedance-voltage (I/Z-V) measurements in the dark and under 200 mW/cm2 illuminance. To designate the voltage or calculation method effects on the ideality factor (n), barrier height (BH-B), and series resistance (Rs), these parameters were extracted from different methods. These parameters extracted through the Thermionic-emission (TE) theory, Ohm's law, Norde and Cheung functions were compared with each other. The reverse bias ln(IR) – VR0.5 plots were also drawn to designate the validity of Poole-Frenkel and Schottky emissions. In Z-V measurements, NC and related IB phenomena were observed at 500 kHz-fixed frequency in the dark and under illuminance. The interface states (Dit) variation depending on energy and voltage was obtained using current and capacitance measurements and related equations. The calculations of the diffusion-potential (VD), acceptor-atoms (NA), Fermi-energy (EF), and B(C-V) values were performed by fitting the observed linear in the reverse bias C-2-V plot. A detailed analysis of NC and IB was performed via the drawn C/G/-I plots for positive voltages. All experimental results show that the used calculation method, illumination, and voltage are highly effective on the electrical parameters.
... As doping concentration increases the intensity increases. The emission peaks were observed around 771 nm in fluorescence spectra giving a value of energy band gap around 1.62 eV [12,[20][21][22][23][24][25][26][27][28][29]. ...
Pure and transition metal doped calcium titanate (CaTi1 − xMxO3 where M = Cr) was prepared by solid state reaction technique to study effect of doping on the structural, optical and electrical properties of calcium titanate. Structural properties were investigated by XRD. Also XRD pattern revealed the orthorhombic phase with Pbnm space group which was confirmed by calculating different parameters. SEM results showed the variation of grain size distribution ranging from 470 to 371 nm. FTIR studies confirmed the presence of the functional group modes of vibrations. Optical properties were studied by UV and FL techniques. Furthermore, from optical analysis shows that energy gap of the pure sample increased from 1.8 to 2.9 eV respectively. VSM revealed the presence of magnetic property in the sample and with substitution the magnetic behaviour first decreased for x = 0.2 then enhanced for x = 0.4 and VSM analyze that our material is a ferromagnetic in nature.
... (hv) as presented in Fig. 8C. The Urbach energy increased on increasing the SNPs contents in the nanocomposite which confirmed the presence of the localized state in the forbidden band that caused the shifting of the Fermi level [29]. The band tail energy of the pristine PVA film was reported as 0.22 eV [24] which increased to 0.27 eV after loading 1 (%, w/w) SNPs. ...
The present investigation dealt with the fabrication and opto-structural characterization of silica nanoparticles (SNPs) incorporated polyvinyl alcohol (PVA)-based nanocomposite films. The said films were prepared via the solution casting approach followed by characterization using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray diffraction (XRD) and water contact angle (WCA) analyses. Moreover, the optical parameters including direct/indirect bandgaps, absorption coefficient and the Urbach energy of the test films were determined using UV visible spectroscopy. The SEM results indicated the spherical morphology of the as-prepared SNPs and their regular distribution of them in the PVA-based composite film. The WCA of the pristine PVA film increased from 50.2 to 94.4º for the resultant nanocomposite film. This indicated that the prepared nanocomposite films exhibited surface non-wetting, which could be ascribed to their enhanced crystallinity due to certain physicochemical and structural rearrangements. The results of mechanical properties demonstrated that the tensile strength increased and elongation at the break decreased by adding the SNPs in the PVA matrix. The overall direct, indirect and optical bandgap values significantly decreased on 1 (%, w/w) loading of SNPs in the nanocomposite film. The prepared nanocomposite films might be useful in fabricating optoelectronic devices workable even in mild humid environments.
... (11) Table 4 shows the addition of CaTiO3 into pure PS resulted in a decrease in σ and enhance Ee-p. This is likely due to the increase in charge carrier mobility, which facilitated transitions between the highest occupied molecular orbital of PS and the defect states (trap levels) of CaTiO3 filler [31]. ...
Polystyrene (PS) thin films containing 4% and 8% calcium titanate (CaTiO3) perovskite nanofiller were prepared by film casting techniques. The influence of CaTiO3 loading on the structure and optical characteristic of PS were studied by using X-ray diffraction and UV-absorption spectroscopy. The XRD analysis showed the addition of CaTiO3 into PS enhanced the formation of crystal structure and resulted in the formation of nano-crystal with a smaller diameter. The optical characterizations showed that the addition of CaTiO3 reduced the transmission and increased the reflection of PS films for UV and visible wavelength of the incident light. Absorption of pure PS films was limited to less than 270 nm, while the absorption of PS/CaTiO3 composites film covered the whole UV -range. The values of the optical energy gap were calculated by using Tauc equation. It was found that the addition of 8% CaTiO3 decreased the values of optical energy gaps from 4.42 eV to 4.26 eV. This is suggested the formation of extra energy levels in the bandgap tails, which aided the transition of electrons from the valence band to these new energy levels in the conduction band.
The dielectric properties of nanocomposites based on isotactic polypropylene (iPP) and atactic polystyrene (aPS) obtained by novel, simple, and environmentally friendly treatment technique have been analyzed in this study. The best treatment conditions to obtain nanocomposites with embedded core‐shell particles with enhanced dielectric properties were considered. Treatment of polymer matrices in water solution iron(II)‐chloride had the most pronounced precipitation effect, that was directly related to the appearance of higher transition metal concentrations in the iPP and aPS matrices, in comparison to treatments in the other two transition metal salts, MnCl 2 and NiCl 2 . Relative dielectric constant and loss tangent have been studied in the frequency range from 20 Hz to 9 MHz. Embedded core‐shell nanoparticles (from 15 to 150 nm in diameter) in a very small amount (1.72E‐8 mol/cm ³ to 1.17E‐5 mol/cm ³ ) resulted in significant improvement (2.5% up to 9.1%) and stabilization of relative dielectric constant value toward higher frequencies and also lowering loss tangent in compare to starting polymer matrices. These properties indicate that materials obtained with the presented treatment technique can be applied as microelectronic packing and with further development of the method in order to obtain a higher concentration of metal ions as energy storage devices.
NiCl2-filled polyvinyl alcohol (PVA) films filled prepared by casting process. X-ray diffraction (XRD) revealed that crystalline nature of PVA was reduced with NiCl2 content. The transmittance spectra of NiCl2 filled PVA films were reduced with NiCl2 content, confirming the increase of amorphous phase noticed by XRD for high NiCl2 content samples. In addition, the indirect band gap for PVA film is enhanced by NiCl2 content. However, the direct band gap for PVA film is decreased by NiCl2 content. It is recommended that NiCl2 filled PVA films are useful for packaging community.
In this research, a casting method has been used to prepare (PVA-codoped with (Al(NO3)3 and Fe(NO3)3) as trivalent metal ions. The Fe³⁺-ions with different concentrations (i.e., 0.1, 0.4, 0.8, 4, and 8 wt%) were added to the 5 wt% of Al³⁺/PVA solution to form a codoped composite film. The as-prepared sample was characterized by FT-IR, X-ray diffraction, optical absorption, electrical properties studies, and optical limiting effect. FTIR results showed the interlinked of Fe³⁺-ions with the OH group in the PVA matrix. The investigation of (XRD) indicates that the pure PVA and the doped films are semi-crystalline. The optical bandgap of PVA decreases with raising the concentration of Fe³⁺-ions. The dielectric properties and AC electrical conductivity were studied and dependent on the Fe³⁺-contents. The analyzed material displayed great performance for the optical limiting for two laser sources of 632.8 and 533 nm. The plots of the field-dependent magnetization measured at room temperature showed a weak room temperature ferromagnetism with the significant paramagnetic components. Consequently, this study has successfully discovered that Fe³⁺-codoped Al³⁺/PVA composites are good candidates for use in different electronic, optoelectronic, and CUT-OFF laser device applications.
Polyvinyl alcohol/Zinc oxide (PVA/ZnO) nanocomposite films with various weight percentages of ZnO nanoparticles (0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%) were prepared by solution casting method. The structural, optical and morphological properties of the synthesized samples were characterized by X-ray diffraction (XRD), UV–Visible spectroscopy, Fourier transform Infrared spectroscopy (FTIR) and Scanning electron microscope (SEM). X-ray diffraction studies confirms the formation of PVA/ZnO nanocomposites. From the UV–vis absorbance spectra, the band gap energy of the samples was calculated and its value decreases with increasing the wt% of ZnO into the PVA matrix. The transmittance of the nanocomposites in the visible region is decreased with increasing the concentration of ZnO into the PVA matrix and completely blocked in the UV region. These behaviours suggests that the nanocomposite materials could be used as UV shielding materials. The FTIR analysis indicates physical interaction between hydroxyl group of PVA and ZnO. SEM shows the dispersion of ZnO on the surface of PVA matrix. The dielectric properties and AC conductivity measurement in the frequency range 100 Hz to 1 MHz reveals the maximum dielectric constant at PVA/5 wt% ZnO nanocomposite.
The solution casting method was used to prepare nanocomposite films of chitosan/TiO2 nanoparticles (NPs) because of their applications in various fields. The effects of TiO2NP concentration on the structural, morphological, thermal, mechanical, and optical properties of such films were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, and thermal analysis (thermogravimetric analysis [TGA] and differential scanning calorimetry [DSC]). The XRD patterns reveal miscibility between the amorphous components of chitosan and TiO2NPs. The HRTEM and FESEM images illustrate the distribution and dispersion of TiO2NPs on the film surface. Data from FTIR spectroscopy, DSC, and TGA and the mechanical properties indicate the dependence of chitosan properties on the presence of TiO2NPs and the existence of interactions between chitosan and TiO2NPs. The reflectance and transmittance values obtained were used to calculate the CIE tristimulus values, color parameters, refractive index, absorption coefficient, dielectric spectra, optical conductivity, volume energy loss function (VELF), and surface energy loss function (SELF). The dependence of the absorption coefficient on the photon energy demonstrated that the optical transfer is permissible and direct. The variations of the dielectric spectra and optical conductivity indicate different interactions between photons and electrons in the films produced and relate to the electronic structure. The values of the VELF were found to be greater than those of the SELF, which confirms that the energy loss occurred mostly within the material. Films were also examined for water vapor transmission (WVT) and water vapor permeability (WVP), and the results showed that incorporation of TiO2NPs onto chitosan caused a decrease of WVT and WVP. In addition, the antimicrobial activity of the nanocomposite films against Gram-positive and Gram-negative bacteria was studied, and good antimicrobial activity was found, indicating their ability to inhibit bacterial proliferation at the culture site. The developed chitosan thin films supporting an optimized amount of TiO2NPs could be used to treat various diseases.
In this research, the solution casting technique has been used to synthesize composite with different weights of VCl3 embedded in polyvinyl alcohol (PVA), in the form of films. X-ray diffraction (XRD) patterns display a broad peak with low intensity of high doping composite films, reflecting an increase in the non-crystallinity and the internal strain. The complex formation between the OH– groups and the V³⁺ ions has been outlined through Fourier transform IR spectroscopy (FTIR). The film’s surface morphology via SEM images shows an increase in the agglomeration with the doping ratio of VCl3. The optical band gap and the width of localized states were changed from 4.86 to 3.03 eV and 0.85 to 2.54 eV. The average refractive index was estimated from band gap energy, as it increased to 2.46 for a composite of high doping ratio (VPVA6). Moreover, the optical susceptibilities χ⁽¹⁾ and χ⁽³⁾ and the non-linear refractive index n⁽²⁾ values indicate the possibility of applying this novel composite material on a wide scale of optoelectronic applications. The samples have reduced the power of the two lasers (632.8 and 532 nm) to 25 and 21%. The AC electrical conductivity was increased with doping ratio, and its relation with frequency is following Jounscher’s law. The improved characteristics, optical performance, and low band gap make them promising in UV-protector and linear/non-linear optoelectronic instruments.
In this study, (CuO doped PVA) composite material was deposited using spin coating technique on n-Si and the Au/CuO-PVA/n-Si Metal/Polymer/Semiconductor type Schottky Barrier Diodes (MPS type SBDs) were fabricated. The electrical measurements of Au/CuO-PVA/n-Si SBDs were realized in the dark and under various UV (365 nm) light intensities ranging from 50 to 250 mW/cm². The basic parameters of the MPS type SBDs such as leakage current (I0), zero bias barrier height (ΦB0), barrier height (ΦB), ideality factor (n), series resistance (Rs), shunt resistance (Rsh), rectification rate (RR), photocurrent (Ipc) and surface states (Nss) were obtained Current-Voltage (I–V) plot based on Thermionic Emission (TE) theory, and Norde function depending on the UV light intensity. As the light intensity increases, RR, Rsh, ΦB0, and ΦB decreased but the n and I0 increased. In addition, the increase of UV light intensity caused the increase of photocurrent in MPS type SBDs and thus MPS type SBDs exhibited more ohmic behavior.
Different wt.% of Ni²⁺- doped Poly (vinyl alcohol), PVA, films are synthesized by a low-cost casting method. XRD, SEM and FTIR spectroscopy are used to study the microstructure of the composite samples. The degree of semi-crystallinity for all Ni²⁺-doped PVA (NPVA) and pure PVA films decreases and the amorphous order dominated in 3.7 wt% Ni²⁺-doped PVA (NPVA5) film as established by studying the spectroscopy of XRD and FT-IR. The increment of the Ni²⁺-doping level in PVA led to a formation of non-homogeneous particle size with an average value range from 1.03 μm to 4.47 μm for 0.027 wt% Ni²⁺-doped PVA (NPVA1), and NPVA5 films, respectively. UV–Vis-IR transmittance and absorption spectroscopies are specified for measuring the optical parameters. The indirect energy gap (Eig) decreases to 4.85 eV for NPVA5 film, and the direct energy gap, Eg, to 1.36 eV for the same sample. However, owing to the complex construction between Ni²⁺-ions and the matrix of PVA, the transition strength (Ed), the indices of refraction (n, n∞), and oscillator wavelength (λ0) increase, while the excitation energy (Es) decreases with further wt.% of Ni²⁺-ions. Due to the optical properties of the films, they are suitable to be inserted in different optoelectronic applications.
Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23o with increased intensity as PEG ratio increases. However, doping with La³⁺, Fe³⁺ or Ir³⁺ eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe³⁺ or Ir³⁺. There are a consistency between Eg values obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasing σac of films to higher values that candidates them in semiconductors industry.
In order to increase the capacitance of Au/n‐Si (MS) structure, 7% graphene doped PVA was coated on n‐Si as an interfacial layer. The measured data of capacitance (C) and conductance (G/ω) of Au/7% graphene doped‐PVA/n‐Si (MPS) structure was utilized for the calculation of real and imaginary parts of complex permittivity (ε* = ε′ − jε″), loss tangent (tanδ), complex electric modulus (M* = M′ + jM″), and electrical conductivity (σ). The admittance measurements (C and G/ω) were carried out in the frequency range of 0.5 kHz to 1 MHz at room temperature. Frequency dependence of the dielectric constant (ε′), dielectric loss (ε″) and tanδ shows a dispersive behavior at low frequencies. This behavior was explained by Maxwell–Wagner relaxation. Due to the dipolar and the interfacial polarizations, as well as the surface states (Nss) and the interfacial PVA layer, the parameters exhibited a strong dependence on frequency and applied bias voltage. The σ versus log(f) plot exhibited both low and high frequency dispersion phenomena such that at low frequencies σ value corresponding to the dc conductivity (σdc), but at high frequencies it corresponds to the ac conductivity (σac). M′ and M″, both, have low values in the low frequency region. However, an increase is observed with the increasing frequency due to the short‐range mobility of charge carriers. As a result, the change in dielectric parameters and electric modulus with frequency is the result of relaxation phenomena and surface states. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43827.
Electrical conductivity of Nylon 66 thin films prepared by alternating vapor deposition polymerization (AVDP) and interfacial polymerization (IFP) were measured as a function of temperature and humidity. AVDP films had highly ordered structures with the molecular orientation normal to the substrate with the tilting angle of about 54°. Electrical properties of AVDP and IFP films were made along the film thickness direction and parallel to the film surface. The conductivity of AVDP film was anisotropic over temperature ranges of 50–200°C. The conductivity of AVDP film perpendicular to the film thickness was larger than that along the film thickness direction. Temperature dependence of the conductivity showed three temperature ranges: (1) below Tg, (2) Tg~100°C, (3) above 100°C. The activation energy for the conductivity decreased with humidity in the range of Tg~100°C but was almost constant above 100°C. Carriers were supposed to be impurities, such as hydrochloric acid in AVDP films and sodium chloride in IFP films. The ionic jump distance was estimated to be about 3.5 nm above Tg.
Films of PVA/PVP blend (50/50) filled with different concentrations of LiBr were prepared. The prepared films were investigated by different techniques. XRD scans demonstrate that complexation between the filler and the blend takes place in the amorphous region. UV–VIS analysis revealed that the values of the optical energies are changed with increase Li-ions content. This indicates that there is a charge transfer complexes arise between the polymer blend and Li-ions. The thermal stability of the product samples has improved after filling LiBr increases, this indicates that the filler acts as a plasticizer. The rise of the conductivity is significant with increased concentration of LiBr, this is means the decrease in the degree of crystallinity and increase in the degree of amorphosity. This suggests the choice of LiBr as filler to improve the electrical conductivity of PVA/PVP.
Polyvinylchloride (PVC) films containing different amounts of NiCl2 have been prepared using a casting method. The UV/VIS (200-800 nm) and IR (200-4000 cm−1) spectra and dc electric conductivity have been investigated. One optical absorption edge was found for pure PVC, while the addition of NiCl2 led to the appearance of a second edge at lower photon energy. The change of the calculated values of the optical energy gaps with increasing NiCl2 content has been interpreted in terms of the structural modifications of the PVC matrix. The spectral analysis indicated that the Ni+2 ions are present in its octahedral symmetrical forms. The infrared analysis revealed that there is a change of the NiCl2 chliation mode beyond 0.25 filling level. The electric conduction was attributed to an intrachain one dimensional interpolaron hopping mechanism. The calculated hopping distance was R0 ≥ five monomer unit lengths. R0 depends linearly on both temperature and filling level.
Polyvinylchloride (PVC) films containing different amounts of NiCl2 have been prepared using a casting method. The UV/VIS (200-800 nm) and IR (200-4000 cm-1) spectra and dc electric conductivity have been investigated. One optical absorption edge was found for pure PVC, while the addition of NiCl2 led to the appearance of a second edge at lower photon energy. The change of the calculated values of the optical energy gaps with increasing NiCl2 content has been interpreted in terms of the structural modifications of the PVC matrix. The spectral analysis indicated that the Ni+2 ions are present in its octahedral symmetrical forms. The infrared analysis revealed that there is a change of the NiCl2 chliation mode beyond 0.25 filling level. The electric conduction was attributed to an intrachain one dimensional interpolaron hopping mechanism. The calculated hopping distance was R0 ≥ five monomer unit lengths. R0 depends linearly on both temperature and filling level.
Thermal analysis of semicrystalline poly(vinyl alcohol) reveals the existence of up to three energetically distinct states of water within the polymer structure. Wide angle X-ray studies indicate that diffusion of water into semicrystalline samples of the polymer gradually destroys the crystalline regions of the polymer, although water is found to not inhabit intact crystallites. The nonfreezing water is responsible for the destruction of crystalline regions by a mechanism of disruption of intermolecular hydrogen bonds in the interface region between the crystalline and swollen amorphous regions. Water does not inhabit the polymer in clusters as freezable water until most of the inter and intra molecular hydrogen bonding has been disrupted by the nonfreezing water.
Filled and unfilled polyvinylalcohol (PVA) films were prepared by the casting technique. Films of equal amounts with various concentrations of two fillers (CoBr2 and MgCl2) were prepared. Spectroscopic, structural and some physical properties of these films were studied with different techniques. Fourier-transform infrared (FTIR) revealed that the syndiotacticity structure of the PVA samples causes dense molecular packing in the crystal and also stronger intermolecular hydrogen bonds, which are responsible for the disappearance of the molecular motion. X-ray diffraction (XRD) scans evidenced the presence of some semicrystalline structure of PVA films. The optical absorption spectra suggested the presence of an optical gap (Eg), which depends on filler concentration for all the filling levels. Differential thermal analysis (DTA) suggests that the segmental mobility of an amorphous pure PVA increases as a result of the addition of mixed fillers, becoming less-rigid segments. This indicates that the mixed fillers act as plasticizers.
A series CdS/PVA nanocomposite films with different amount of Cd salt have been prepared by means of the in situ synthesis method via the reaction of Cd2+-dispersed poly vinyl-alcohol (PVA) with H2S. The as-prepared films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) absorption, photoluminescence (PL) spectra, Fourier transform infrared spectroscope (FTIR) and thermogravimetric analysis (TGA). The XRD results indicated the formation of CdS nanoparticles with hexagonal phase in the PVA matrix. The primary FTIR spectra of CdS/PVA nanocomposite in different processing stages have been discussed. The vibrational absorption peak of CdS bond at 405 cm−1 was observed, which further testified the generation of CdS nanoparticles. The TGA results showed incorporation of CdS nanoparticles significantly altered the thermal properties of PVA matrix. The photoluminescence and UV–vis spectroscopy revealed that the CdS/PVA films showed quantum confinement effect.
The electrical conductivity, current–voltage (I–V) characteristics and optical absorption of pure and AgNO3-doped polyvinyl alcohol (PVA) films have been studied under different conditions. The electrical conductivity increased with increasing dopant concentration up to 0.5 wt.% of the dopant and then showed a decrease beyond this concentration. The increase in conductivity for dopant concentration up to 0.5 wt.% is attributed to formation of charge transfer complexes while the decrease for concentrations above 0.5 wt.% may be due to segregation. The variation of electrical conductivity with temperature showed two regions of activation with activation energies 0.8 and 0.3 eV for undoped films and 1.3 and 0.3 eV for doped films. I–V characteristics indicated that Schottky emission is the dominant charge transport mechanism in both undoped and AgNO3-doped films. Optical absorption studies in the wavelength range 190–600 nm showed additional peaks in the wavelength region 391–417 nm for differently doped films, in addition to the peak at 273 nm for undoped PVA. The optical energy gaps and band edge values shifted to lower energies on doping up to a dopant concentration of 0.5 wt.% but showed an increasing tendency for further increase in dopant concentration.
An electrical conductivity having a frequency dependence ∼ωs , where s < 1, has been reported for many amorphous semiconductors and chalcogenide glasses. It is the purpose of this paper to point out that the mechanism normally postulated for this behaviour, namely, thermally assisted quantum-mechanical tunnelling, is inappropriate for the case of the chalcogenide glasses. Instead, a mechanism is proposed in which two electrons hop over a potential barrier between defect sites, the height of the barrier being correlated with the intersite separation. The theory of this effect is seen to explain many features observed experimentally; in particular, the variation of the exponent a between different materials and its temperature dependence. New estimates for the spatial densities of states of these materials are made and are in reasonably close agreement with values inferred from other experimental data.
The various origins of a frequency-dependent conductivity in amorphous semiconductors are reviewed, stressing particularly recent advances and the influences that factors such as correlation and non-random spatial distributions of electrically active centres can have on the a.c. conductivity. A comprehensive survey is given of the experimental a.c. data for two types of amorphous semiconductor, namely chalcogenide and pnictide materials. It is concluded that the a.c. behaviour at intermediate to high temperatures is well accounted for by the correlated-barrier-hopping model, whereas the low-temperature behaviour is probably due to atomic tunnelling.
Nanocomposites of poly(vinyl alcohol) (PVA)/ZnS and PVA/CdS was prepared by in situ hydrothermal reaction. The intensity of the PVA crystalline diffraction peaks decreased after 8 h of treatment at 120 °C. The diffraction of PVA crystal resulted from the strong intermolecular interaction between PVA chains through the intermolecular hydrogen bonding. The intensity of the diffraction peaks and also the size of the crystals were determined by the number of PVA chains packing together. After being composited with sulfides, the intensity of PVA diffraction peaks was further decreased. This is because the interactions of PVA with ZnS and CdS led to a decreased in the intermolecular interaction between the PVA chains and thus the degree of crystallinity.
Electrical conduction and dielectric relaxation in (V2O5)1 − x(P2O5)x glasses (where x = 0.12, 0.18 and 0.24) have been investigated in the temperature range 300–560 K and frequency range 50 Hz-10 kHz. The temperature dependences of both bulk and d.c. conductivities are described by the Mott and Davis equation for conduction in amorphous solids with activation energies of 0.0355–0.0546 eV and 0.4–0.47 eV, respectively. The results of d.c. conductivity are discussed on the basis of small polaron hopping between V4+ and V5+ sites beyond θD/2, whereas the results of bulk conductivity are discussed according to the electron hopping between filled and empty localized states at the Fermi level. The a.c. conductivity is found to obey the power relation σ = Aωn. Reasonable values of both hopping rate and relaxation time are obtained and discussed. The results of conduction as well as dielectric properties are discussed on the basis of both bulk and domain interfaces, which play a significant role in both conduction and relaxation processes in the glass matrix.
An in situ and single-step route to creating a uniform dispersion of lanthanum(III) oxide nanoparticles in a polyimide is described. The process of thermally evolving, from the diaquotris(2,4-pentanedionato)lanthanum(III) complex, to a homogeneous dispersion of lanthanum(III) oxide nanoparticles within a 6FDA/1,3(3)-APB polyimide matrix has been characterized. The report also describes the resulting changes in the final properties of the hybrid material relative to the neat polyimide. Characterization techniques include dielectric spectroscopy, small angle X-ray scattering, X-ray photoelectron spectroscopy, and gas permeability.
In this study, the electrical and optical properties of newly prepared Ni(L1H2) and Ni(L2H2) complexes have been investigated and the results obtained were analyzed. It is seen that these complexes have inorganic semiconductor properties. The activation energies (Ea) for the complexes were calculated by using Arrhenius plots and their optical band gaps have been determined through the optical spectra. Thermal probe measurements indicated that these samples have n-type of electrical conductivity.
The experimental evidence concerning the density of states in amorphous semiconductors and the ranges of energy in which states are localized is reviewed; this includes d.c. and a.c. conductivity, drift mobility and optical absorption. There is evidence that for some chalcogenide semiconductors the model proposed by Cohen, Fritzsche and Ovshinsky (1969) should be modified by introducing a band of localized states, near the centre of the gap. The values of C, when the d.c. conductivity is expressed as C exp (- E/kT), are considered. The behaviour of the optical absorption coefficient near the absorption edge and its relation to exciton formation are discussed. Finally, an interpretation of some results on photoconductivity is offered.
The present paper describes the effect of superconductors on the sintering process, apparent cross-linking density, sintering factor, hardness and volume fraction of butyl rubber (IIR) composites. Electrical conductivity and I–V characteristics at various processing conditions of IIR with different concentrations of superconductor were measured. The stability and reproducibility of IIR composites were tested. Also, the conduction mechanism of electrical conductivity is discussed. Specific heat and the amount of heat transferred by radiation and convection were calculated via the proposed model and calorimetry as a function of superconductor content. It was found that superconductor accelerates the driving force during the sintering process and the characteristic time constant during sintering decreases while the sintering factor, the apparent cross-linking density, hardness and volume fraction of rubber increases as the content of superconductor increases. In addition, it was proved that the superconductor and Joule heating effect improves the electrical and thermal properties of IIR.
Polyvinyl alcohol films, with various AgNO3 filler mass fractions (≤5%), were prepared. The structural and morphological variations, due to filling and UV-irradiation, were investigated using the following techniques; differential scanning calorimetry (DSC), UV/VIS optical absorption spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). Two different crystalline phases (one is due to the PVA matrix and the other is attributed to the PVA–Ag+ chelates) were detected besides the PVA amorphous phase, for the non-irradiated and the UV-irradiated (for 4 and 6h) films. The PVA–Ag+ chelates disappeared at 2h UV-irradiation. It is implied that the structural morphology changes vastly due to the changes in filling level and/or UV-irradiation time. The observed morphological patterns were discussed.
Exponential absorption edges α=Aeg(ℏω-ℏω0) have been observed in both ionic (Urbach's rule: g=σ/kBT* and covalent materials. Arguments are given to show that a unified theory of exponetial absorption edges must (i) rely on electric microfields as the cause, (ii) include exciton effects and the final-state interaction between the electron and the hole, and (iii) ascribe Urbach's rule to the relative, internal motion of the exciton. An approximate calculation has been made in which the nonuniform microfields are replaced by a statistical distribution of uniform microfields; this calculation is a generalization to physically relevant intermediate-strength fields of previous strong- and weak-field theories of Redfield and Dexter. In contrast with the other microfield models, which obtain the exponential spectral shape by averaging over microfield distributions, the present theory obtains a quantitatively exponential edge as an inherent feature. The temperature dependences of the edges in various materials follow qualitatively from the nature of the microfield sources. The specific temperature dependence of Urbach's rule in ionic crystals is obtained from this model, with supplementary arguments to account for nonuniformity of the fields.
DOI:https://doi.org/10.1103/PhysRev.92.1324
A review of dielectric data for a wide range of solids proves the
existence of a remarkable `universality' of frequency and time responses
which is essentially incompatible with the multiplicity of currently
accepted detailed interpretations. Certain unique features of the
universal behaviour strongly suggest the dominant role of many-body
interactions.
Polyvinyl alcohol (PVA) films filled with different filling levels (FLs) of XFeCL3(15−X)MnCl2 were studied. The DSC thermograms exhibited an increase in the melting temperature with filling, indicating better thermal stability of the filled polymer of interesting industrial applications. The amorphous feature of the filled polymer was depicted using XRD scans. Vibrational studies displayed significant structural deformations. The FL dependence of certain IR absorption peaks was discussed. The dc electrical conduction mechanism was interpreted on the basis of the modified interpolaron hopping model. The present results of the dc magnetic susceptibility (χ) suggested the temperature dependence of Curie–Weiss behavior characterized by localized magnetic moments. The effective paramagnetic moment (μeff) was estimated; its dependence on the FL exhibited a non-linear character. The electron spin resonance (ESR) study revealed unresolved broad distorted signals characterized by the hyperfine structure. The ESR parameters were evaluated. A correlation between the above-mentioned studies was discussed to relate the structural, electrical and magnetic properties of the filled PVA polymer.
The influence of silver (Ag) nanoparticles on the properties of poly(vinyl alcohol) (PVA) was investigated. The nanocomposite was prepared by mixing a colloidal solution consisting of silver nanoparticles with a water solution of PVA in appropriate ratios. Composite films with different contents of inorganic phase were obtained after solvent evaporation. The contents of the inorganic phase in the nanocomposites were determined by using atomic absorption spectroscopy (AA) for silver, and were found to be 0.19, 0.33, and 0.73 wt %. Transmission electron microscopy (TEM) of the nanocomposite films revealed the presence of Ag particles with average diameter of 20 nm. Comparison of the thermal properties of the pure polymer and the nanocomposite films showed that the thermal stability is improved by about 40 °C, and the glass transition temperature is shifted to a higher temperature up to 20 °C for the highest content of the nanofiller. An increase in Young's modulus and strength of the nanocomposite was also observed with an increase in Ag content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Stress relaxation measurements revealed reduced stability of the nanocomposite upon prolonged loading, compared to the pure PVA matrix.
Polyvinylalcohol (PVA) films, filled with mass fractions % of , were prepared. The x-ray diffraction spectra indicated the partial crystallinity of PVA, which decays as w increases. The infrared analysis implied that the degree of syndiotacticity depends, nonmonotonically, on w. The observed peak at 520 nm, in the ultraviolet-visible spectra, revealed (i) the transition . (ii) the octahedral coordination of , (iii) the trapped electrons of the OH group of PVA and (iv) the spin-cluster excitation. The dependence on the temperature T of the dc electrical conduction was attributed to phonon-assisted interpolaron one-dimensional (1D) hopping of charge carriers. The temperature dependence of the dc magnetic susceptibility fits the 1D Ising antiferromagnetic equation well. The obtained electron spin resonance spectra exhibit the main features of the spectrum of the unfilled PVA. The dependence on the filling level of the logarithm of the calculated average rotational correlation frequency of mobile spins was compared with the corresponding dependences of the Ising coupling factor and the degree of syndiotacticity. The spin configuration of the present system was discussed in detail; it differs from the spin configuration of the -filled PVA films. The 1% -filled PVA film is the most suitable for its response to electromagnetic waves.
Polyvinylidene fluoride and polymethylmethacrylate (PVDF/PMMA) films were blended with different concentrations by casting method. Structural, spectroscopic, and morphological characteristics of both the interface and the surface of the films have been investigated. The blends were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible, differential thermal analysis (DTA), and scanning electron microscopy (SEM). All measurements reveal that the blends take place based on the influence of PMMA content on PVDF. FTIR results indicate the possible interactions between carbonyl group of PMMA and CH2 groups of PVDF which indicates the formation of blends. Optical absorption spectra suggested the presence of an optical gap (Eg) which decreased with increasing PMMA content. UV/VIS spectra were characterized by a sharp edge and a window of wavelength range 290–350 nm for some blends. The optical window can be used as an optical sensor or band pass filter. The degree of crystallinity was found to decrease with increasing PMMA content, which was confirmed by XRD and DTA analysis. SEM micrograph shows spherulites which increase with the addition of PMMA and it becomes sharper and contains a longitudinal shape. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity ( NTCC ) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS) , conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined.
© 2002 Society of Chemical Industry
The epitaxial growths of titanium dioxide (TiO2) thin films were prepared by pulsed laser deposition. The dependencies of the crystalline structure of prepared films upon buffer O2 gas pressure, laser power and substrate were studied. The crystalline structures were found by the X-ray diffraction method to be a mixture of rutile and anatase on α-Al2O3, and anatase on LaAlO3. The crystallite sizes were calculated to be about 10 nm by applying the Scherrer equation to the diffraction peaks. The sizes were increased by collisions between evaporated particles and O2. The growth of mixed crystal is caused by the competitive process between lattice misfit-induced epitaxy and thermodynamic stability.
We have studied the effect of BaCl2 dopant on the optical and microstructural properties of a polymer poly(vinyl alcohol) (PVA). Pure and BaCl2 doped PVA films were prepared using solvent casting method. These films were characterized using FTIR, UV–visible, XRD and DSC techniques. The observed peaks around 3425 cm−1, at 1733 cm−1 and 1640 cm−1 in the FTIR spectra were assigned to O–H, CC stretching and acetyle CO group vibrations, respectively. In the doped PVA shift in these bands can be understood on the basis of intra/inter molecular hydrogen bonding with the adjacent OH group of PVA. The UV–visible spectra shows the absorption bands around 196 nm and shoulders around 208 nm with different absorption intensities for doped PVA, which are assigned to n→π* transition. This indicates the presence of unsaturated bonds mainly in the tail–head of the polymer. Optical band energy gap is estimated using UV–visible spectra and it decreases with increasing dopant concentration. The powder XRD shows an increase in crystallinity in the doped PVA, which arises due to the interaction of dopant with PVA causing a molecular rearrangement within the amorphous phase of polymer. These modifications also influence the optical property of the doped polymer. The DSC study also supports increasing crystalline thickness and degree of crystallinity due to doping.
The real part of the dielectric constant () of pure and doped polyvinyl alcohol (PVA) with 1, 2 and 3 wt% vanadate was measured as a function of temperature and frequency. () decreases with increasing frequency due to a rapid variation of the field accompanied with the applied frequency as well as the disordering of the segmental parts of the polymer chain. The vanadate effects appear in a form of increasing the crystallinity in the sample leading to a decrease in (), except in the case of 2 wt% vanadate in which () is drastically increased. The d.c. conductivity for the vanadate doped PVA is measured as a function of temperature. The values of the activation energy as obtained from the experimental data give information about the presence of more than one conduction mechanism as well as the useful applications of PVA, especially in the field of electronics. 1998 Kluwer Academic Publishers
Charge transport properties, such as the temperature dependent dc conductivity and the frequency dependent conductance, of polymer matrix–metal particles composites, are investigated in the present study. Dc and ac conductivity is examined with varying parameters the filler content, temperature and the frequency in the case of ac field. The examined systems, though they are characterized as dielectrics, exhibit considerable conductivity, which alters by several orders of magnitude with temperature and frequency. The temperature and frequency dependence of conductivity gives evidence for the charge carriers transport mechanism via the occurred agreement of experimental results with the employed hopping models (variable range hopping model and random free-energy barrier model).
Silver filled antimicrobial polymers were produced from composites comprising polyamide and elementary silver powder possessing various specific surface area (SSA) by melt compounding. Different concentrations (2%, 4% and 8%) of the silver powder were incorporated in the polyamide to investigate the effect of silver loading on the mechanical properties. As the water uptake imparts antimicrobial properties, the influence of the diffused water on the mechanical properties of the composites is discussed. Scanning electron microscopy (SEM) is employed to investigate the morphology of the composites. The composite morphology found to be dependent on the SSA of the silver powder employed within the polyamide matrix. DMTA measurements were performed to follow the visco elastic behaviour of the composites. The crystallinities of the composites were evaluated using Differential Scanning Calorimetry (DSC).
A nanocomposite of poly (vinyl alcohol) (PVA) reinforced with various contents of CdS was synthesized by organosols reaction with particle size in the range of nanoscale. The influence of CdS content on the network structure of PVA matrix such as particle size distribution, gel fraction (GF), equilibrium water content (EWC), water absorption (WA), extent of filler reinforcement (γ), volume fraction of polymer (Vs) number of elastically effective chains (NEC), and X-ray diffraction (XRD) were investigated. The affine and phantom models for physical crosslinks were used to predict the nature of crosslinks. The thermal behavior of PVA–CdS composites has been studied by differential thermal analysis (DTA), Thermogravimetry (TG) and differential scanning calorimetry (DSC). The dc conductivity of the PVA system reinforced with CdS as a function of concentration and temperature has been presented. The PVA composite exhibits considerably high electronic conductivity which increases linearly with the increase of CdS content. The conduction mechanism in PVA–CdS composites is governing by hopping mechanism. The effects of CdS loading and temperature on the thermal conductivity (λ) and specific heats (Cp) were investigated. The antistatic properties and electromagnetic wave shielding effectiveness (EMI) of PVA–CdS composites has been also investigated. The optical properties such as absorbance and transient photo current under applied voltage of PVA–CdS composites were tested. The mechanical properties of PVA–CdS composites were investigated in details. It is proved that the PVA–CdS composites can be effectively used for linear thermistors, antistatic charge dissipation, EMI in the encapsulation of electronic devices, in woven texturing, optical switch and solar cell fabrication.
- H Wang
- P Fang
- Z Chen
- S Wang
Wang, H.; Fang, P.; Chen, Z.; Wang, S. Appl. Surf. Sci.
2007, 253, 8495.
- J D Dow
- D Redfield
Dow, J. D.; Redfield, D. Phys. Rev. B. 1972, 5, 594.
ARTICLE
WWW.MATERIALSVIEWS.COM
WILEYONLINELIBRARY.COM/APP
- Y Aydogdu
- F Yakuphanoglu
- A Aydogdu
- E Tas
- A Cukuraval
Aydogdu, Y.; Yakuphanoglu, F.; Aydogdu, A.; Tas, E.;
Cukuraval, A. Solid State Sci. 2002, 4, 879.
- A Tawansi
- H M Zidan
- A H Oraby
- M E Dorgham
Tawansi, A.; Zidan, H. M.; Oraby, A. H.; Dorgham, M. E. J.
Phys. D: Appl. Phys. 1998, 31, 3428.
- Li Shao
- H Okui
Li Shao, H.; Okui, N. Polym. J. 1999, 31, 1083.
- F Urbach
Urbach, F. Phys. Rev. 1953, 92, 1324.
- M K El Mansy
- Mater
El Mansy, M. K. Mater. Chem. Phys. 1998, 56, 238.
- M H Harun
- E Saion
- A Kassim
- M Y Hussain
- I S Mustafa
- M A A Omer
- Malaysian
Harun, M. H.; Saion, E.; Kassim, A.; Hussain, M. Y.;
Mustafa, I. S.; Omer, M. A. A. Malaysian Polym. J. 2008, 3,
27.
- M A Ahmed
- M S Abo-Ellil
- Mater
Ahmed, M. A.; Abo-Ellil, M. S. Mater. Electron. 1998, 9,
391.
- R F Bhajantri
- V Ravindrachary
- A Harisha
- V Crasta
Bhajantri, R. F.; Ravindrachary, V.; Harisha, A.; Crasta, V.;
Nayak, P. S. Poojary, B. Polymer 2006, 47, 3591.
- A Tawansi
- H M Zidan
- Y M Mostafa
- A H Eldumiatty
Tawansi, A.; Zidan, H. M.; Mostafa, Y. M.; Eldumiatty, A.
H. Phys. Script. 1997, 55, 243.
- E M Abdelrazek
- I S Elashmawi
- A El-Khodary
- A Yassin
- Curr
Abdelrazek, E. M.; Elashmawi, I. S.; El-khodary, A.; Yassin,
A. Curr. Appl. Phys. 2010, 10, 607.
- E M Abdelrazek
Abdelrazek, E. M. Phys. B 2008, 403, 2137.
- I S Elashmawi
- N A Hakeem
Elashmawi, I. S.; Hakeem, N. A. Polym. Eng. Sci. 2008, 895,
48.
- F El-Tantawy
- K Kamada
- H Ohnabe
El-Tantawy, F.; Kamada, K.; Ohnabe, H. Polym. Int. 2002,
51, 635.
- E A Davis
- N F Mott
Davis, E. A.; Mott, N. F. Philos. Mag. 1970, 22, 903.
- Z H Mbhele
- M G Salemane
- C G C E Van Sittert
- J M W Van Sittert
- V Djoković
Mbhele, Z. H.; Salemane, M. G.; van Sittert, C. G. C. E.;
van Sittert, J. M. W.; Djoković, V. Chem. Mater. 2003, 15,
5019.