Kanchan S. Mahato

Catalytic action of CuAlS2 microparticles and nanoparticles in cellulose pyrolysis

This paper explores the catalytic action of as-synthesized CuAlS2 microparticles and nanoparticles on cellulose pyrolysis. The CuAlS2 microparticles were synthesized by heating precursor elements at high temperatures in an evacuated quartz ampoule. CuAlS2 nanoparticles were synthesized at ambient temperature by using a simple wet chemical technique. Before using the microparticles and nanoparticles for catalytic study, they were comprehensively characterized. The thermal analysis, including catalytic study of both the CuAlS2 microparticles and nanoparticles on cellulose pyrolysis, was carried out by thermogravimetric (TG), differential thermogravimetric (DTG) and differential thermal analysis (DTA) techniques. Prior to studying their role as catalysts in cellulose pyrolysis, the CuAlS2 microparticles and nanoparticles were characterized by thermal analysis in an inert N2 atmosphere. The TG analysis of as-synthesized CuAlS2 microparticles and nanoparticles showed three and five steps of decomposition, with total weight losses of 6.89% and 53.37%, respectively. The TG analysis of pure cellulose and cellulose mixed with 10%, 5% and 2.5% CuAlS2 microparticles and nanoparticles demonstrated that the nanoparticles are better catalysts in cellulose pyrolysis than the microparticles. The TG analysis results of cellulose pyrolysis have been supported by the DTA and DTG curves recorded simultaneously. The obtained results are explored in detail.

Synthesis and electrical transport properties of SnS nanoparticles

The SnS nanoparticles were synthesized at ambient temperature by simple wet chemical method. The stoichiometric and structural characterization was done by EDAX and XRD techniques respectively. The crystallite size was determined using Scherrers formula and Hall-Williamson plot using XRD data. The electrical transport properties studies were carried out on pellets prepared by hydraulic pressing of SnS nanoparticles. The thermoelectric power and dc resistivity variation with temperature was studied on the pellets. Room temperature Hall effect measurement was made on the pellet. The obtained results are discussed in details.

Wet Chemical Synthesis and Characterization of MnS Nanoparticles

The manganese sulfide, MnS, is a wide bandgap (Eg = 3.1eV) diluted magnetic semiconductor belonging to the VIIB-VIA family with outstanding magneto-optical properties. The authors report the synthesis and characterization of MnS nanoparticles. The MnS nanoparticles were synthesized by simple wet chemical method at ambient temperature. Manganese acetate (C4H6MnO4.4H2O) was used as source for Mn+2 ions and thioacetamide (C2H5NS) was used as source for S-2 ions. The energy dispersive analysis of X-ray (EDAX) and X-ray diffraction (XRD) were used for stoichiometric and structural characterization of the synthesized nanoparticles respectively. The crystallite size calculated from XRD using Scherrer’s formula and Hall-Williamson relation came out to be of 6.81 nm and 5.27 nm respectively. The optical absorption spectra showed absorption edge at 325 nm corresponding to energy of 3.82 eV, which acknowledged the occurrence of blue shift. The photoluminescence spectra recorded for five different excitation wavelengths viz 250, 275, 280, 300 and 325 nm showed three emission peaks at 463 nm, 550 nm and 821 nm. The TEM and SEM analysis of the particles clearly shows the particles are spherical in shape. The selected area electron diffraction (SAED) pattern showed ring pattern, stating the nanoparticles to be polycrystalline. The obtained results are discussed in details.

Structural, Electrical, and Thermal Properties Study of CVT Grown CuAlS_2 Single Crystals

CuAlS_2 single crystals were grown by the chemical vapour transport (CVT) technique using iodine as a transporting agent in a close-spaced geometry. The crystal structure, lattice constants, Miller indices, density and %d errors of as grown CuAlS_2 were determined from X-ray diffraction (XRD). The crystalline nature was confirmed by the selected area electron diffraction (SAED) pattern of transmission electron microscopy (TEM). The Scanning Electron Microscopy (SEM) images of the as grown surfaces of the single crystals showed the layer growth mechanism. The variation of resistivity with temperature was studied along the perpendicular to the c-axis using the four probes technique. The activation energy values were evaluated from the slopes of the resistivity variation with temperature plot. The Hall measurement data at ambient temperature were used to determine the resistivity (ρ), Hall coefficient (R_H), carrier concentration (η), Hall mobility (μ), and conductivity type of the grown crystals. The hot probe method was used to confirm the conductivity type. Values of the Fermi energy (E_f ), constant values (A), scattering parameter (s), Seebeck coefficient (S), effective density of states (N_A) and effective mass (m_e∗) were determined by the data of the Seebeck coefficient variation with temperature. The I-V characteristics study was carried out in dark as well as under white and UV illumination. The high pressure electrical resistance measurements have been performed on as grown single crystals up to a pressure of 5 GPa. It was observed that the resistance decreases with pressure up to some point, then afterward increases gradually with pressure. Thermogravimetric (TG), differential thermal analysis (DTA), and differential thermogravimetric (DTG) analysis were carried out on the as grown CuAlS_2 single crystals in an inert nitrogen atmosphere in the temperature range from room temperature to 1223 K. The kinetic parameters were determined employing nonmechanistic equations using the Broido and Coats-Redfern (C-R) relations. All the obtained results are discussed in this paper.

Study of surface microstructure and optical properties of as-grown Mo0.6W0.4Se2 single crystals

The surface microstructures and optical properties of as-grown Mo0.6W0.4Se2 single crystals were studied. The microstructures on the as-grown crystal surface reveals that spirals and Frank-Read dislocations are prominent. The study of the variation of refractive index (η), extinction coefficient (k), real and imaginary dielectric constants (er and ei), and the optical conductivity (σ0) with incident photon energy from the analysis of optical absorption spectrum of Mo0.6W0.4Se2 single crystals, showed that near the bandgap energy value all sharply increases.