Advanced Materials Proceedings

Abstract AIN thin films were grown by ion beam sputter deposition in reactive assistance of N⁺/N₂⁺ ions on Si (100) substrates. During deposition, assisted ion energy (E_A) was varied as 90 eV and 120 eV with a post deposition exposure to N₂ plasma. The resultant films were characterized by grazing incidence x-ray diffraction (GIXRD) for their structure and atomic force microscopy (AFM) for their root mean square (rms) surface roughness (δ). UV-VIS spectrophotometry was carried out to explore their optical band-gap with associated Urbach (E_U) and weak absorption tail (E_WAT) energies. Our results show that, AlN thin film grown with 90 eV reactive ion assistance possesses larger optical band gap (E_g) of 5.3 eV associated with comparatively narrower band tails when compared to those AlN thin film samples which were grown for 120 eV reactive ion assistance. These optical band-gaps are further correlated with corresponding Urbach energy tails which can be used as a measure of disorder in microstructure of the film. Also, appropriate optimization of energy tails substantiates the possibility of band gap engineering as per the requirement of different thin film devices. Copyright © 2017 VBRI Press.

Abstract The p-type thermoelectric material Ca₃Co₄O₉ were synthesized by the sol-gel synthesis in the presence of complexing agent of citric acid and dispersant of polyethylene glycol 400, and followed by the uni-axial hot-pressing (HP) technique. Observation by X-ray diffraction revealed that the formation of phase pure sample on calcination at 1073 K for 4 h. Scanning electron microscopy indicated that the significant enhancement of the grain growth through HP technique. The density of the sintered pellets increased with an increase of applied pressure. The electrical resistivity was greatly reduced with an increase of the applied pressure, whereas the Seebeck coefficient was little increased with an increase of the applied pressure. As a result, the pellet treated by the HP technique under the condition of 1098 K, 25 MPa and 30 min showed a maximum power factor of about 498 μWm^-1K^-2 at 950K. Copyright © 2017 VBRI Press.

Abstract Manganese ferrite nanoparticles with chemical formula MnFe₂O₄ have been synthesized by low temperature chemical co-precipitation method. The structural and optical properties of the nanoparticles were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), fourier transform infra-red spectroscopy (FTIR) and UV-visible absorption spectroscopy. XRD confirm pure spinel phase formation of the prepared sample. All the observed peaks correspond to the standard diffraction pattern of manganese ferrite having JCPDS card number 74-2403. From the XRD data, the average crystallite size was calculated and found to be 27.40 nm. The FTIR spectrum shows the characteristic bands of the spinel ferrite. Morphology of the nanoferrites was given by SEM image revealing that the particles are approximately spherical in shape. The elemental composition along with their relative ratios was given by EDAX and was found to be in agreement with their initial calculated values. UV- visible absorption spectrum of the prepared sample shows characteristic absorption in visible range and from the UV-visible absorption data the band gap of the prepared sample was determined. MnFe₂O₄ nanoparticles were found to possess a narrow band gap of 1.4 eV which may find applications in photocatalytic degradation of pollutants. The simple co-precipitation method proves to be an effective method for synthesis of pure phase manganese ferrite nanoparticles. Copyright © 2017 VBRI Press.

Abstract In the present study nanoparticles of zinc oxide (ZnO) were synthesized by simple solution based approach and used as an adsorbent for the removal of Cu(II) ions from aqueous solution. ZnO nanoparticles were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). TEM confirmed the formation of zinc oxide nanoparticles in the size range of 10-11 nm. Adsorption capacity of ZnO for removing Cu(II) ions from aqueous solutions was investigated at different pH, as a function of contact time, metal ion concentration and the amount of adsorbent. Moreover, adsorption isotherms and kinetics was studied to understand the nature and mechanism of adsorption. A high percentage removal  (98.71%) of Cu(II) from its aqueous solutions at pH 5 and  at initial heavy metal ion concentration of 300 mg/l by ZnO particles was achieved. The adsorption isotherm was well described by Freundlich isotherm model
(R²= 0.999). The adsorption kinetics data was well fitted by the pseudo-second-order rate model with a high regression coefficient. The  above results suggest that ZnO nanoparticles can be used as  potential adsorbent for the efficient removal of heavy metals from aqueous solutions. Copyright © 2017 VBRI Press

Abstract Mn₂O₃ nanoparticles have been synthesized using chemical co-precipitation method. The as synthesized nanoparticles were characterized by X-ray diffractometer (XRD), UV-Visible spectrophotometer (UV-Vis) and Fourier Transform Infra-Red (FTIR) spectrophotometer method. The results indicate that synthesized Mn₂O₃ nanoparticles possessed crystallites having sizes 12.56 nm and 11.90 nm with cubic and orthorhombic structures respectively. The two samples are named as M1 and M2. The gas response of both the samples was investigated for different concentrations of NH₃ gas at room temperature. Sample M2 based thick film sensor showed enhanced sensing performance in comparison to sample M1. This is attributed to smaller crystallite size of sample M2. The sample M2 based sensor showed the response of 67.1% with the response and recovery times 65 and 71 sec respectively. The fabricated nanoparticles show promising use as room temperature NH₃ sensors.