• S H MOHAMED

Articles written in Bulletin of Materials Science

• Change in properties upon thermal treatment of copper sulphide powder and thin films

The thermal oxidation of CuS powder was examined under flow of nitrogen and dry air using thermogravimetry/differential thermal analysis. After 473 K, the oxidation of CuS occurred as a weight loss and accompanied with two overlapped exothermic peaks. The melting temperature delayed due to the formation of oxide and sulphate on the surface of the particles. X-ray diffraction revealed that the as-prepared thin films are mixed phases of hexagonal CuS, orthorhombic Cu$_2$S and orthorhombic CuSO$_4$. After annealing at 573 or 773 K, the films oxidized and new orthorhombic Cu$_8$O phase appeared, and its intensity became dominant upon increasing the temperature and time. Nanoparticles morphology was observed for as-prepared films and upon annealing the nanoparticle became more rounded and bigger. The transmittance of the as-prepared films was almost zero over the entire measured range and it increased with increase in the annealing temperature and time, whereas the reflectance decreased. Both refractive and extinction coefficient values decreased with increase in annealing temperature and annealing time, while the bandgap virtually increased. The resistivity of the as-prepared film remained nearly constant until 543 K. Above 543 K the resistivity increased sharply. Negative and positive temperature coefficients in resistivity phenomena were explored in the annealed films and they were strongly dependent on both annealing temperature and time.

• ZnO thin films prepared by RF plasma chemical vapour transport for self-cleaning and transparent conducting coatings

ZnO thin films were prepared by chemical vapour transport method in inductively coupled plasma (ICP). The films were synthesized at different substrate positions and various oxygen/argon ratios. X-ray diffraction (XRD) revealed that all the synthesized films at different positions are mixture of hexagonal ZnO and hexagonal Zn phases. The relative peak integrated intensity (RPII) of the ZnO phase is 83.6, 25.3 and 45.3%, for positions 1, 2 and 3, respectively. Morphology of ZnO films was found to be sensitive to substrate position. Flat flakes, bended nanowires (NWs) and nanoparticles morphologies are observed for positions 1, 2 and 3, respectively. The sample synthesized at 1 is stoichiometric, whereas the samples prepared in positions 2 and 3 are sub-stoichiometric. The films prepared at positions 1 and 3 have relatively high transmittance and low reflectance values, whereas the film prepared at position 2 has low transmittance and high reflectance. The ZnO film prepared at position 2 is hydrophobic with water contact angle of $112.2^\circ$, which can be used as self-cleaning coating. For ZnO films prepared with various O$_2$ ratios, the RPII was 83.2, 88.0, 96.4 and 100% for films prepared with 10, 20, 30 and 40%, respectively. With increasing O$_2$ ratio, the nanograins became bigger and the stoichiometry improved. The transmittance and optical bandgap increased, whereas the reflectance and refractive index decreased with increase in O$_2$ ratio. The ZnO film synthesized with 30% O$_2$ ratio has the highest figure ofmerit (F$_{OM}$) value; thus, this film may be considered as the best ZnO film for transparent conducting coating applications.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020