Thermal Diffusivity and Electrical Conductivity Studies of Polyaniline Based Materials and Selected Ceramics

In this work, the photoflash and four-point probe techniques were respectively applied for thermal diffusivity and electrical conductivity measurement on polyaniline, polyaniline blends, polyaniline composite and ceramic at room temperature. In the photoflash technique, the signal was initially generated by a high intensity camera flash as an excitation source. A fast response K -type thermocouple was used as a detector to monitor the temperature at the rear surface of the sample. The photoflash signal was captured as a function of time and the half rise time; t₀.₅ of each sample was then analyzed to determine the thermal diffusivity. The photoflash setup was first calibrated with the sample of known thermal diffusivity. The results indicate that the thermal diffusivity of the calibration sample correlated well with the results from literature

Cation/Anion substitution into spinel LiMn2O4 cathode material for Li-ion battery application: a review of recent progress

Spinel LiMn2O4 is a positive electrode material with a robust structure. It has a three-dimensional network of channels for fast lithium-ion diffusion in state-of-the-art lithium rechargeable batteries. It is commercialized because of its high-power and cost-effective natural abundant element. However, its capacity fading and cycle performance, originating from Mn dissolution, still need improvement. In this review, the recent development of the effect of cation and anion doped into the spinel LiMn2O4 cathode material is thoroughly investigated. The effect of anion substitution on the morphology and electrochemical properties were investigated. Cation/anion substitution shows improvement in the structural stability and suppresses lattice deformation of the material. Finally, some insight into the future prospects for spinel cathode developments is provided

Thermal Diffusivity Measurement of La Doped SrSn0 3(Sr1_xLaxSn03 ) Ceramics by Photoflash Method

Thermal diffusivity, a of a medium is the thermophysicaJ property which determines the speed of heat propagation by conduction during changes of temperature with time. The measurement of thermal diffusivity can be carried out at room temperature by photoflash method, which employs a high intensity camera flash as the excitation source. In this paper, Sr1 _ xLaxSn0 3 ceramics doped with different compositions of La (x = 0.1, 0.4, 0.6, 0.8, 1.0) was investigated for their thermal diffusivity. The thermal diffusivity values varied from 0.44 x 10-2 - 1.15 X 10-2 cm2/s corresponding to x = 0.1 to x = 1.0. The morphology and structure of Sr1 _xLaxSn03 ceramics were analysed from SEM and XRD measurements to support the thermal diffusivity behaviour

Synthesis and electrical studies of quaternary chalcogenide semiconductor Cu2ZnSnSe4

Quaternary chalcogenide semiconductor has attracted much attention as absorber-layer materials in solar cells. The absorber-layer material, Cu2ZnSnSe4 (CZTSe) which is a p-type semiconductor that has high absorption coefficient, had been synthesized by using solvothermal method. The variation of concentrations of the Copper (II) Chloride dihydrate have brought some effects towards producing the stoichiometry and non-stoichiometry copper zinc tin selenide that may lead to the improvement of efficiency of solar cells. The synthesized reaction was conducted at 250°C for 24 hours. Properties of the samples have been characterized by X-ray diffraction (XRD) to determine the crystal structure of the sample and X-ray Fluorescence (XRF) to determine the elemental composition of the sample. The electrical properties such as resistance and conductivity have been studied through Van der Pauw configuration. The CZTSe has been successfully synthesized at concentrations of 0.15 M with no impurities phases existed

The annealing effect on thermal diffusivity of polyaniline (emeraldine base) measured using photoflash technique

In this paper, we present the annealing effect on thermal diffusivity of Emeraldine Base−Polyaniline (EB). The thermal diffusivity was measured at room temperature using photoflash technique. The excitation source used consists of a high intensity camera flash. A series of samples annealed at different temperature (25°C, 100°C, 150°C, 200°C, 250°C and 300°C) were investigated and the annealing effect on the thermal diffusivity was discussed in detail. The Scanning Electron Microscopy (SEM) and X−ray Diffraction (XRD) measurement was done to analyze the annealing effect on morphology and sample structure

Concentration effect of Zinc Acetate dihydrate as precursor in preparing Zinc Selenide through hydrothermal method

Zinc Selenide has been synthesized through hydrothermal method using Zinc Acetate Dihydrate (Zn(O2CCH3)2(H2O)2) and Se powder as the precursor. In a typical synthesis, Zn2+ and Se2- ion have been prepared separately and charged into a teflon-lined stainless steel autoclave. The ZnSe are characterized by X-ray diffraction (XRD), Field Emission Microscopy (FESEM), ultraviolet–visible spectroscopy (UV-Vis) and photoluminescence (PL). From the Pure ZnSe with main XRD peak at 2θ = 27.29°, 45.30°, 53.62°, 65.88°, 72.68° has been synthesized with the optical band gap energy (Eg) of 2.50 eV with emission peak at 486 nm

Effects of aging time on microstructure, hydrophobic and optical properties of BiFeO3 thin films synthesized via sol-gel method

BiFeO3 (BFO) films were synthesized with the sol-gel method followed by the spin coating technique using 2-methoxyethanol as solvent and acetylacetone as chelating agent. The effects of aging time (t = 0, 1, 3, 6 days) of the BFO sol on the microstructure, wettability and optical properties of BFO films were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle (CA) measurement, Uv-vis and photoluminescence. The crystallinity of films was affected by t. Crystallite size of the films changed slightly in the range of 14.2 – 15.2 nm while the lattice parameters clearly varied with t. The average particle size of BFO films ranged between 45.9 and 52.7 nm while the mean square roughness (Rq) varied between 1.0 and 4.2 nm. The films showed maximum optical transmittance (81 – 90 %) in the range 600 – 800 nm. The band gap of the films was also affected with t, and it has a value of 2.85 to 2.76 eV. The films showed a hydrophobic property with CA ranging between 95.3 to 104.7 °. The best crystallinity, lowest Rq and highest Eg = 2.85 eV were obtained for the film with t = 1 day. The results demonstrate possible development of a superhydrophobic coating using BiFeO3 coating

Influence of tartaric acid concentration on structural and optical properties of CuSe nanoparticles synthesized via microwave assisted method

The influence of chelating agent on structural and optical properties of copper selenide nanoparticle has been the subject of ongoing debate in copper selenide based material research. In this project we developed a straightforward microwave irradiation technique for the synthesis of copper selenide nanoparticles. Copper selenide nanoparticles were successfully synthesized using CuCl2·2H2O and Na2SeO3 as copper and selenium sources respectively while, the reducing and chelating agents were hydrazine hydrate and tartaric acid respectively. The effect of concentration of tartaric acid on structural and optical properties of CuSe NPs were investigated. The as-prepared product were characterized by means of an X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron spectroscopy (FESEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), UV–visible absorption spectroscopy (UV–Vis.), Raman spectroscopy and photoluminescence spectroscopy (PL). XRD results reveal a hexagonal (Klockmannite) crystal structure with size in the range between 73.10 nm and 16.10 nm. The band gap of the as-prepared CuSe NPs were found to increase between 1.80 eV and 2.10 eV. The wavelength of the maximum PL emission was at 600 nm with 400 nm excitation wavelength. Three characteristics vibrational modes belonging to CuSe NPs were detected in the Raman spectra. Therefore, the results obtained in this study provide a new pathway of understanding the effect of tartaric acid concentration on structural and optical properties of CuSe NPs and can explain the use of this novel product as a potential candidate for optoelectronic and solar cell applications

Preparation of polycrystalline FeTe1−xSx (x = 0.00–0.30) via solid-state reaction method at ambient pressure

Polycrystalline samples with nominal composition FeTe1−x S x (x = 0.00–0.30) were synthesized via solid state reaction method with intermittent grinding in argon gas flow. X-ray diffraction (XRD) patterns revealed the tetragonal structure (space group P4/nmm) of the samples with the presence of impurities Fe3O4 and FeTe2. By substitution with S, the a and c lattice parameters shrink probably due to the smaller ionic radius of S2− compared to Te2−. Scanning electron microscopy images showed that the samples developed plate-like grains with increasing S substitution. Substitution of Te with S suppresses the structural transition of the parent compound FeTe as shown by both the temperature dependence of resistance and magnetic moment measurements. All of the S-substituted samples showed a rapid drop of resistance at around 9–10 K but zero resistance down to 4 K was not observed. In addition, negative magnetic moment corresponds to diamagnetism was detected in the samples for x = 0.25 and 0.30 suggesting the coexistence of magnetic and superconducting phase in these samples. The magnetization hysteresis loops measured at room temperature showed ferromagnetic behavior for the pure and S substituted samples. However, the magnetization, rentivity and coercivity decreased with S content