InxAl1-xN/Al0.53Ga0.47N multiple quantum wells on Al0.5Ga0.5N buffer with variable in-plane lattice parameter

The structural and luminescent properties of InxAl1-xN/Al0.53Ga0.47N multiple quantum wells (MQW) grown on an Al0.5Ga0.5N buffer partially relaxed with respect to an underlying AlN-template are reported. A significant redshift and improvement of ultraviolet (UV) photoluminescence (PL) intensity is found for InAlN MQWs grown on AlGaN buffers with higher relaxation degree. This is attributed to a higher QW indium incorporation as confirmed also by X-ray diffraction (XRD). The nature of room temperature time resolved PL is studied and discussed from the point of view of the possibility of a type I-type II band lineup transition in the InAlN-AlGaN system

Effect of Post-Annealing Treatment on Mechanical Properties of ZnO Thin Films

The present work was focused to study nanomechanical properties of ZnO thin films deposited on different substrates (Corning Glass and Fused Quartz) using DC-sputtering. The crystallinity and microstructure are correlated with process conditions and post annealing treatment in NH3 environment, which in turn affects the mechanical performance. The structural growth accompanied a change in crystalline nature and microstructure as the substrate is altered from corning glass substrate to fused quartz at similar synthesis conditions. The post deposition annealed ZnO thin films demonstrated agglomerated particles with no clear grain boundaries having nano-cracks present in the morphology, which is attributed as NH3 effect on microstructure. The mechanical properties such as hardness (6.89-7.76 GPa), Young’s modulus (94.9-124.6 GPa), and coefficient of friction ̴ (1.0-3.0) of ZnO thin films were measured using three sided pyramidal Berkovich nanoindentation. Load-unload segment of indentation curve of thin films which is measured at continuous loading revealed no event of discontinuity (≥ 2 nm) during loading/unloading, indicating no fracture or delamination during indentation. The critical load of ZnO thin films failure was analysed using scratch testing ramp loading and the value of critical load was found around ̴535.6 µN to ̴668.4 µN

Efficacy of dispersion of magnesium silicate (talc) in papermaking

The understanding of the dispersion chemistry of papermaking grade fillers is as important as their effect on paper. Magnesium silicate (talc) is one of the major fillers used for papermaking. It is hydrophobic and chemically inert. The dispersion chemistry of talc of different particle sizes was studied with wetting agent (non-ionic triblock copolymer) and anionic dispersant (sodium salt of polyacrylic acid). Both wetting agent and dispersant were added in talc slurry separately and in combination. The dispersion behavior was studied through measuring the Brookfield viscosity. The wetted and dispersed talc was also added to paper to understand its effect on papermaking process and paper properties. Wetting and dispersion changed the colloidal charge chemistry of talc making it more anionic which reduced the talc retention in paper. Lowering the particle size of talc significantly improved the light scattering coefficient (LSC) of paper and decreased its retention. Controlling colloidal charge of papermaking suspension with cationic polyacrylamide polymer helped in protecting the retention of talc without affecting the LSC of both filler and paper

Application of response surface methodology and central composite design for the optimization of talc filler and retention aid in papermaking

121-127Cationic polyacrylamide (CPAM) has been used as a retention aid with talc (hydrous magnesium silicate) filler to get the variation of ash in paper using response surface methodology based central composite design. The need of CPAM for varying dosage of talc filler is calculated statistically through the data of first pass ash retention (FPAR) using analysis of variance. The design is employed by selecting the dosages of talc filler and CPAM as model factors to get the variation of ash in paper. The dosages of talc and CPAM range from 250 g/t to 750 g/t and from 50 g/t to 400 g/t pulp respectively. The results of first order factorial design show that both independent variables have significant effect on increasing the ash in paper. At any particular filler addition level, the increase in CPAM addition enhances the ash and FPAR. Optimum conditions to get around 55% FPAR and 15% ash in paper are found to be 382 kg/t talc and 230 g/t CPAM. The linear equations obtained from the designed experiments can be used to predict the dosage of inputs (talc and CPAM) on the basis of desired outputs (ash content and FPAR)