Amit Mallik

Direct amide bond formation from carboxylic acids and amines using activated alumina balls as a new, convenient, clean, reusable and low cost heterogeneous catalyst

For the first time, we have used activated alumina balls (3–5 mm diameter) for amide synthesis from carboxylic acids (unactivated) and amines (unactivated) under neat reaction conditions that produce no toxic by-products and has the advantages of being low-cost, easily available, heterogeneous, reusable and environmentally benign with no troublesome/hazardous disposal of the catalyst.

Retracted Article: Self-limited growth of Pr3+-doped LaF3 nanocrystals in oxyfluoride glass and glass-ceramics

Transparent oxyfluoride glass-ceramics of heavy metals doped with rare earth metal ions are important materials in optoelectronics. In the present study, we report the preparation of a glass and a glass-ceramic with composition 16.52Al2O3·1.5 AlF3·12.65LaF3·4.33Na2O·64.85 SiO2 (mol%), where both the materials were doped with 1 mol% Pr2O3. All four species were structurally characterized by Transmission Electron Microscopy (TEM). Pr2O3 affected the phase separation in the glass and deferred crystallization compared to the undoped glass. The crystallization mechanism and the location of various components in the glass/glass-ceramics were ascertained through advanced STEM/EDX techniques. The phase separated regions in the mother glass were mostly populated by F and La and also by Pr, Al and Si. The phase separated droplets, after annealing, turned into 10–20 nm LaF3 nanocrystals, which were found to partly include the doping Pr3+ ions in the crystals themselves. The interphase crystal/glassy matrix was thoroughly characterized by EDX. The results suggest that the inner LaF3 crystal core is engulfed by an Al enriched layer that follows a Si enriched surrounding shell as the outer core. This finding also indicates that the crystal surface is too viscous to further enhance the crystal growth, and therefore the overall crystal formation is limited to the nanosize.

Comparative studies on physico-mechanical properties of composite materials of low density polyethylene and raw/calcined kaolin

Abstract The paper describes the preparation of the composite materials of low density polyethylene (LDPE) as the base mixed separately with raw kaolin and the same calcined at 800 °C under the same variation in weight percentage using single-screw extruder and a mixing machine operated at a temperature between 190 and 200 °C. Some of the mechanical and physical properties such as Youngs modulus, elongation at break, shore hardness and water absorption were determined at different weight fractions of filler (0, 2, 7, 10 and 15%). It was found that the addition of filler increases the mechanical properties. Absorption test was done in water at different immersion times for different composites. The degree of water absorption of composite materials was found to decrease with increasing wt% of kaolin filler (0–15%) according to Ficks law. Calcined kaolin produces better mechanical properties than raw kaolin.