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Polypyrrole (pure) and polypyrrole doped with different protonic acids (HCl and H3PO4) have been synthesized using NaOH as reducing agent in aqueous HCl medium and ammonium persulphate (APS) as an oxidant, respectively. These pure and doped samples were named as S1, S2, and S3 for further investigations. These pure and doped samples were annealed at 200oC for 4 hr. The amorphous nature of these annealed and as-prepared polypyrrole samples was confirmed by XRD. FTIR spectra and SEM images of all the samples were taken at room temperature, which indicate: significant change in annealed samples. To calculate the energy band gap of all the samples, the absorption spectra were recorded by USB-2000 spectrophotometer at room temperature in the wavelength range 300–800 nm. From the analysis of absorption spectra, optical band gap of as-prepared samples (S1–S3) was determined to be 2.64, 2.43, and 2.29 eV, respectively and for annealed samples A1–A3 values obtained were 2.30, 2.25, and 2.17 eV. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers

A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density.

The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.

The thin films of Cd1-x Zn x S (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) have been prepared by the vacuum evaporation method using a mechanically alloyed mixture of CdS and ZnS. The structural, optical and electrical properties have been investigated through the X-ray diffractometer, spectrophotometer and Keithley electrometer. The X-ray diffraction patterns of these films show that films are polycrystalline in nature having preferential orientation along the (002) plane. In the absorption spectra of these films, absorption edge shifts towards lower wavelength with the increase of Zn concentration. The energy band gap has been determined using these spectra. It is found that the energy band gap increases with increasing Zn concentration. The electrical conductivity of so prepared thin films has been determined using a I–V characteristic curve for these films. The result indicates that the electrical conductivity decreases with increasing Zn content and increases with temperature. An effort has also been made to o...

A flame retardant composition was prepared from phosphorus-melamine-urea-formaldehyde (PMUF) reaction. The flame retardancy of rigid polyurethane foam (RPUF) was studied by impregnating it with various concentrations of PMUF. Optimum impregnation time, retention and density of RPUF samples with PMUF were also studied. The morphology, elemental analysis, and thermal stability of RPUF and RPUF-PMUF samples were studied with scanning electron microscopy (SEM), CHNS analyzer, and energy dispersive X-rays (EDX) and, thermogravimetric analysis (TGA), derivative thermogravimetric (DTG), differential thermal analysis (DTA), respectively. The deposition of PMUF on the cell walls and surfaces was exhibited by decreased cell size from 357 to 285 (±5) μm. CHNS and EDX studies show the introduction of phosphorus and nitrogen into the RPUF-PMUF samples. The degradation of RPUF and RPUF-PMUF samples was occurred through two and three stages in nitrogen and air, respectively. RPUF-PMUF samples are decomposed comparatively at lower temperature than RPUF which is resulted into large amount of high temperature stable char residue. This char residue acts as insulating blanket and protects RPUF-PMUF from fire. Fire performance and smoke density of RPUF and RPUF-PMUF samples were investigated with BS: 4735, ASTM D2863 and ASTM E662, respectively. RPUF-PMUF samples demonstrate reduced extent burnt from 125 to 27 mm, burning rate 2.23–0.44 mm/s and percent mass loss (PML) from 100 to 8.82%. Oxygen index was also increased from 17.8 to 23.8. Dm results obtained during smoke density tests show that RPUF-PMUF generates less and delayed smoke than RPUF under flaming and nonflaming mode. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Using a Dynamic Mechanical Analyzer (DMA), mechanical properties like modulus and phase transition temperature of polyester composites of banana fibers (treated and untreated) are measured simultaneously. The shifting of phase transition temperature is observed in some treatments. The performance of the composite depends to a large extent on the adhesion between polymer matrix and the reinforcement. This is often achieved by surface modification of the matrix or the filler. Banana fiber was modified chemically to achieve improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkalies were used to modify the fiber surface. Chemical modification was found to have a profound effect on the fiber/matrix interaction, which is evident from the values of phase transition temperatures. Of the various chemical treatments, simple alkali treatment with 1% NaOH was found to be the most effective.

A thick film of aniline-formaldehyde copolymer and PMMA is synthesized via dispersion of aniline-formaldehyde copolymer powder as filler particles in PMMA with two different concentrations. Variation of the complex elastic modulus and mechanical loss factor (tanδ) with temperature is studied. It is observed that the complex elastic modulus decreases with temperature owing to thermal expansion of films. On the other hand, tanδ increases up to a characteristic temperature beyond which it shows a decreasing trend toward melting. Transition temperature T g of sample S1 (pure PMMA) is found to be 80°C. In sample S2 (1 wt % aniline formaldehyde copolymer), the peak of tanδ at a lower temperature (66°C) corresponds to glass transition temperature T g of the PMMA matrix, while the peak of tanδ at a higher temperature (107.8°C) corresponds to T g of a polymer chain restricted by filler particles of aniline-formaldehyde copolymer. A further increase (10 wt % aniline-formaldehyde copolymer) in the concentration of filler particles of aniline-formaldehyde copolymer results in a more compact structure and a shift of T g to a higher temperature, 122.2°C. This shift in the glass transition temperature of thick films of aniline-formaldehyde copolymer and PMMA is dependent upon the concentration of filler particles in the sample.

The II-VI polycrystalline semiconducting materials have come under increased scrutiny because of their wide use in the cost reduction of devices for photovoltaic applications.Cd1−XZnXTe is one of the II-VI ternary semiconductor materials whose bandgap can be tailored to any value between 1.48–2.26 eV as X varies from 0 to 1. It is promising material for high-efficiency solar cells, switching, and other optoelectronic devices. Polycrystalline thin film ofCd1−XZnXTe with variable composition (0≤X≤1) has been deposited on ultraclean glass substrates by screen printing method followed by sintering process. The optical and structural properties ofCd1−XZnXTe thin films have been examined. The optical bandgap of these films is studied using reflection spectra in wavelength range of 350–900 nm by using double beam spectrophotometer. The structure of sample was determined from X-ray diffraction patterns. The films were polycrystalline in nature having wurtzite (Hexagonal) structure over the whole range studied. The lattice parameters vary almost linearly with the composition parameterX, following Vegard's law. Sintering is a very simple and viable method compared to other cost-intensive methods. The results of the present investigation will be useful in characterizing the material CdZnTe for its applications in photovoltaics.

Pure polypyrrole and polypyrrole in salt form were synthesized using NaOH as reducing agent in aqueous HCl, respectively. Electrical conduction in these pure and doped polypyrrole samples was studied through the I-V characteristics of these materials. I-V characteristic curves for both pure and doped polypyrrole were found to be linear. The conductivity of chlorine-doped polypyrrole is about 104 times that of pure polypyrrole. An attempt has been made to study the dependence of conductivity on temperature, in order to understand the application of these systems. It has been observed from the variation of conductivity vs. temperature curve in both the samples that the conductivity increases with the increase in temperature. This behaviour is indicative of semiconducting nature of the samples with a variation in electrical conductivity of each, which is a strong function of doping and temperature of the environment. Activation energies for both the samples have been found to be in millielectron-volt range, 101.94 meV and 121.68 meV for pure and doped polypyrrole, respectively. An effort has also been made to understand the charge transport in these conductive polymers through models.

Chemical method has been used to prepare cadmium sulphide by using cadmium, hydrochloric acid and H2S. The reflection spectra of covered and uncovered sintered films of CdS have been recorded by ‘Hitachi spectrophotometer’ over the wavelength range 300–700 nm. The energy band gaps of these films have been calculated from reflection spectra. It is found that the energy band gap of both films is same as 2.41 eV. It is indicated that energy band gap of these films does not change. This value of band gap is in good agreement with the value reported by other workers. The measurement of photocurrent has also been carried out using Keithley High Resistance meter/ Electrometer. This film shows the high photosensitivity and high photocurrent decay. Thus so obtained films are suitable for fabrication of photo detectors and solar cells.

Measurements of I – V characteristics and DC electrical conductivity of Se 85− x Te 15 Sb x (where x = 2, 4, 6, 8 and 10) glassy thin pellets, prepared by well established melt quenching technique in bulk (pellets of diameter 12 mm and thickness ≈1 mm were prepared under a constant load of 5 tons), have been carried out at room temperature using Keithley High Resistance Meter/Electrometer 6517A. For the recording of I – V characteristics, this equipment was used in FVMI (Force Voltage Measure Current) mode. It is found evident from the I – V characteristics that the glass containing 4 at. wt.% of Sb has the minimum resistance allowing maximum current through the sample as compared to the other at. wt.% of Sb contents e.g. 2, 6, 8 and 10. At 4 at. wt.% of Sb, conductivity rises to 76% of the value obtained for 2 at. wt.% of Sb. Composition dependence of DC conductivity is discussed in terms of the bond formation between Se and Sb at different compositions. The conduction mechanism is discussed qualitatively on the basis of Poole–Frenkel conduction mechanism. Also the linear relation between ln ( I ) and V 1/2 verifies that the conduction mechanism is of Poole–Frenkel type for both low and high voltage range. The deviation of ohmic behaviour at lower voltage range towards the non-ohmic at higher voltage range is due to the high voltage induced temperature effects in the sample.

TheI—Vcharacterization and the electrical resistivity of selenium rich Se85Cd15-xZnx (x = 0, 3, 7, 11 and 15) system at room temperature have been studied. Samples were obtained using melt cooling technique. So prepared samples were then characterized in terms of their crystal structure and lattice parameter using X-ray diffraction method. The materials were found to be poly crystalline in nature, having zinc blend structure over the whole range of zinc concentration. The measurements ofI—V bdcharacteristics have been carried out at different temperatures from room to 140°C. The electrical resistivity of the samples with composition at room temperature has been found to vary between maximum 2.7 x 108 Ωm and minimum 7.3 x 105 Ωm and shows a maximum at 3 at. wt.% of Zn. The carrier activation energy of the samples with composition has also been determined and found to vary from 0.026 eV to 0.111 eV.

Simultaneous measurements of effective thermal conductivity (λe) and effective thermal diffusivity (χe) of four samples S1 (polyaniline mixed with 100% Ni), S2 (polyaniline mixed with 90% Ni and 10% Al), S3 (polyaniline mixed with 80% Ni and 20% Al) and S4 (polyaniline mixed with 70% Ni and 30% Al) of polyaniline mix with metal Ni and Al in different percentage have been made using transient plane source technique. In the temperature range from room temperature to 170 °C. Both λe and χe increase with increase in temperature. Addition of aluminium concentration at the cost of nickel in the composite increases the value of λe and χe over the entire range of temperature under investigation. It has been found that the values of λe and χe are maximum when 70% of Ni and 30% of Al are mixed in polyaniline matrix. This behaviour is also predicted by an empirical relation, which is obtained from polynomial fit of the experimental data and is explained on the basis of bond formation between metal (Ni and Al) and nitrogen of polyaniline matrix.

The paper reports influence of samarium substitution on the properties of a PZT composition near MPB. Samarium (Sm) was varied from 0 to 0.02/FU. The samples were prepared by standard double sinter...

Measurements of thermophysical properties of Zn x Te 100− x ( x = 5, 10, 30 and 50) chalcogenide material in pellet form have been made in the temperature range from room temperature (15 °C) to 200 °C and in cooling cycle from 200 °C to 15 °C using transient plane source (TPS) technique. In heating mode the values of effective thermal conductivity ( λ e ) and effective thermal diffusivity ( χ e ) increase from 15 °C to 200 °C. During the cooling mode λ e and χ e decrease slightly in the temperature range from 200 °C to 160 °C below which λ e and χ e remain almost constant at all temperatures. Such type of behaviour shows thermal hysteresis in this sample, which can be explained on the basis of the change in structure of the material. XRD studies suggest that the material is polycrystalline in nature.

Nanocomposites of Ni-Zn with copolymer matrix of aniline and formaldehyde in presence of varying concentrations of zinc ions have been studied at room temperature and normal pressure. The energy band gap of these materials are determined by reflection spectra in the wavelength range 400–850 nm by spectrophotometer at room temperature. From the analysis of reflection spectra, nanocomposites of copolymer of aniline and formaldehyde with Ni1-xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 10) have been found to have direct band gaps ranging from 1.50–1.66 eV.

The optical and electrical properties of BF[sup [minus]][sub 4] doped polypyrrole (PPY) have been studied in detail. The effect of annealing on the optical and electrical properties of BF[sup [minus]][sub 4] doped PPY is reported. Interestingly, these properties are modified with annealing and it is observed that PPY is similar to other inorganic amorphous semiconductors. It is also seen that the electrical and optical properties of BF[sup [minus]][sub 4] doped PPY are stabilized after 70 h of annealing at 70 C.

Amorphous selenium alloy films have been found to exhibit excellent photosensitive properties from 300 to 700 nm. These films constitute the essential part of xerographic photoreceptors. Optical absorption, energy band gap and X-ray structural analysis of Se85 Te15 and Se85 As15 films are reported. The effect of annealing on these parameters has also been indicated.

In the present work, Differential Scanning Calorimetry (DSC) has been performed at different heating rates under non‐isothermal conditions to study the crystallizalion kinetics of the Ge0.5Sn0.5Se2.5 chalcogenide glass. Four different methods of analysis (Kissinger equation, Ozawa equation, Matusita equation and Augis and Bennett method) of the non‐isothermal DSC data and various kinetic parameters i.e the activation energy of glass transition (Et), the activation energy of crystallization (Ec), order parameter, rate constant, frequency factor have been determined. The rate constant K (indicator of the rate of to crystalline phase transformation) has been evaluated using the method of Augis and Bannett. Further, the rate of crystallization and dimensionality of growth has also been investigated for the above system.

Cd 1- X Zn X Te is one of the II-VI ternary semiconductor materials whose band gap can be tailored to any value between 1.48 eV to 2.26 eV as X varies from 0 to 1. It is promising material for high efficiency solar cells, switching and other optoelectronic devices. Cd 0.4 Zn 0.6 Te thin films have been deposited on ultra-clean glass substrates by screen printing method followed by sintering process. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal) structure with strong preferential orientation of grains along the (101) direction. The optical band gap of the films has been studied using absorption spectra by using double beam spectrophotometer. The dc conductivity of the films was measured in vacuum by two probe technique. The results of present investigation will be useful in characterizing the material Cd 1- X Zn X Te for its applications in photovoltaics. Sintering is a very simple and viable method compared to other cost intensive methods.

Sophistication in the aviation and warfare technologies has significantly increased the use of metals such as aluminium, magnesium and their alloys for numerous applications. The resulting fires of such metals are probably one of the most dominating and devastating risks if the metals are in the form of fine particles. The work consists of determination of the constituents of the various combustion products after the burning of the magnesium, aluminium and aluminium-magnesium alloy powder heaps on the sand bed. The analysis of the ground products of burnt metal powders on the sand bed has been carried out by using X-ray diffractometer. It is found that oxides and nitrides were the predominant fractions of the combustion products of the metal powders. Interestingly, it is also found that the combustion products of the aluminium, and the aluminium-magnesium alloy powder heap on the sand bed contain free aluminium also.

A deformation dipole model for the lattice dynamics of KCN in an orientationally disordered phase has been formulated. The model includes the rotational-translational coupling effect based on the theory of Michel and Naudts (1977). The authors report phonon dispersion curves of KCN at 300 K and compare them with the available experimental data. The agreement is very good. The one-phonon density of states of KCN is also reported.

As part of a study of the thermodynamical properties of interstitial elements in refractory metals, the free energy of formation of Mo2C is determined, and the thermodynamical properties of C in solution in solid Mo evaluated. The activity of C in the two-phase region Mo + Mo2C is obtained from the C content of iron rods equilibrated with metal + carbide powder mixtures. The free energy of formation of alpha-Mo2C is determined from the activity data. The thermodynamic properties of C in the terminal solid solution are calculated from available data on the solid solubility of C in Mo. Lattice distortion due to misfit of the C atoms in the interstitial sites appears to play a significant role in determining the thermodynamic properties of C in solid Mo.

We present theoretical and experimental second-order Raman spectra for NaF, KF, RbF, and CsF. The theoretical calculation follows the formalism of Born and Bradburn. For the lattice-dynamic calculation we use the deformation-dipole model and present comparisons with measured dispersion curves. For the polarizability calculation, we retain all eight first-neighbor and all thirty second-neighbor polarizability codficients. We find that, in addition to all of the first-neighbor coefficients, only three of the second-neighbor coefficients are needed to obtain good agreement between the calculated and observed spectra both as regards peak positions and over-all shape. Comparison with other types of calculations are made.

We present here a new technique, called vapour phase spray pyrolysis, for deposition ofto andito films. Undopedto film showed semiconducting nature, a sheet resistance of 1088 Ω/□, a donor ionization energy level of 40 meV, average visible transmittance of 75·4% andn-type conductivity. The indium doped (ito) film 10 wt % showed metallic nature, a sheet resistance of 15 Ω/□, average visible transmittance of 80·4 % andp-type conductivity. Thus theto andito films showed fairly good electro-optical qualities, comparable to those obtained by sophisticated and costly techniques.

Lead sulphide thin films have been deposited by conventional chemical bath technique. The effect of Cu doping is studied on the resistivity and the band gap of these films. An anamolous behavior is obtained in the case of variation of band gap with impurity (mol%) which shows that certain values of impurity have prominent features. While the resistivity decreases first with the increase in impurity, after a particular value the resistivity adopts a rising trend, and on still higher doping the decreased resistivity again starts to take place.

We have studied experimentally and theoretically the second-order Raman spectra of LiF. Theoretical calculations based on Born and Bradburn's approach explain the observed spectra fairly well when all the eight-nearest-neighbor, only two of the fifteen-next-nearest-neighbor negative-negative, and none of the fifteen next-nearest-neighbor positive-positive polarizability coefficients are used as adjustable parameters.

The theoretical calculations for the diode quality factor n for a metal‐insulator‐n‐semiconductor solar cell under illumination are presented here. These calculations show that, under illumination, n increases with increasing d and decreases slightly for d>18 A at JL =36 mA cm−2. Results of the calculations compare well with experimental results observed by H. C. Card [Solid‐State Electron. 20, 971 (1977)].

The theoretical calculations for the diode quality factor ‘‘n’’ for a metal‐insulator‐n‐semiconductor solar cell in the dark are presented here by taking proper account of the effective mass for the holes. These calculations show that in the dark the diode quality factor ‘‘n’’ increases with increasing insulator layer thickness ‘‘d.’’ Results of the calculations agree well with experimental values observed by Card [Solid State Electron. 20, 971 (1977)].

Y. K. Agrawal, Health Physics Division, Environmental Studies Bombay 400085, India at 370 nm is used for measurement. The method is sensitive, precise and equally applicable for the extraction of micrograms of titanium. A thorough investigation of the reaction conditions resulted in opt imum parameters, which are incorporated in the working instruction given below. Beer's law is obeyed with the range of 5 2 0 gg of Ti/ml. The molar absorptivity is 2.4 x 103. Moderate amounts of commonly occurring ions are tolerated. Strong interference is shown by V 5+, Ce *+, Mo 6 and Fe 3+.