• Rakesh Kumar

Articles written in Bulletin of Materials Science

• Preparation and studies of some thermal, mechanical and optical properties of 𝑥Al2O3(1 – 𝑥)NaPO3 glass system

Sodium aluminophosphate glasses having compositions of 𝑥Al2O3(1 – 𝑥)NaPO3 (𝑥 = 0.05–0.2) were prepared using conventional melt-quench technique. Density, glass transition temperature, microhardness (MH), thermal expansion coefficient (TEC) and transmission characteristics were measured as a function of alumina content for different samples. They were found to depend on O/P ratio with pronounced changes taking place for O/P ratio ≥ 3.5. Density, glass transition temperature and microhardness were found to increase up to 15 mol% of alumina and then they showed a decreasing trend. Thermal expansion coefficient decreased continuously with alumina content. Optical gaps for different glass samples as measured from transmission characteristics were found to be in the range 3.13–3.51 eV. It initially decreased with alumina content up to 15 mol% and then increased. The behaviour was explained on the basis of change in the average aluminum coordination number from six Al(6) to four Al(4) (i.e. Al(OP)6/Al(OP)4 ratio) along with the changes in polyhedra linkages in the glass network due to change in O/P ratio.

• Effect of mechanical activation on cordierite synthesis through solid-state sintering method

Synthesis of cordierite (5SiO2.2MgO.2Al2O3) has attracted special attention from researchers for its special characteristics. Most common method of cordierite preparation is solid-state reaction using source of alumina, silica and magnesia, which requires temperature of 1350 °C or above. This study deals with the effect of mechanical activation on cordierite synthesis at lower temperature. Talc, kaolinite clay and alumina powder were taken as precursor materials and the batches were formulated on the basis of stoichometric cordierite formation. Particle size distribution (PSD) was measured to get the distribution pattern of milled powder. Pellets were prepared by compaction of dried milled powders and fired at 1200 °C temperature. X-ray diffraction (XRD) technique was used to characterize crystalline phases. Microstructural analysis was done under scanning electron microscope (SEM). It was observed that properties were improved with milling time. Dense and uniform microstructures were formed when samples were milled for 45 and 60 min.

• Material-specific properties and applications of additive manufacturing techniques: a comprehensive review

Additive manufacturing (AM) has emerged as a powerful tool of manufacturing over conventional manufacturing techniques due to its customization features, design flexibility, waste minimization and ability to create intrinsic shapes. This technology involves the fabrication of parts by layer-by-layer printing and thus offers robust mechanical properties. This study aims to provide a comprehensive overview of distinct AM processes, history, materials, comparison and their applications in different fields. In addition, this study also summarizes the mechanical properties of distinct parts fabricated by distinct AM methods, so that this research could become the torch bearer for the futuristic researchers working in this area.

• Influence of MgO and ZnO nanofillers on morphology, structural, thermal and mechanical properties of polylactic acid films

This study is about the influence of magnesium oxide (MgO) and zinc oxide (ZnO) nanoparticles on the morphology, structural, thermal and mechanical properties of the polylactic acid (PLA) films. The pure PLA and PLA nanocomposites were prepared using a cost-effective film applicator at 2 and 5 wt% of nanofillers. The dispersity and elements were examined by scanning electron microscopy with energy dispersive spectroscopy. For 2 wt% of nanofiller in the film, the agglomeration of nanoparticles was not observed, whereas for higher weight percentages agglomeration took place. X-ray diffraction study confirms the improved crystallinity of PLA at 2 wt% nanofillers. Thermal analysis of PLA composite films confirms that the values of glass transition ($T_g$), crystallization ($T_c$) and melting temperature ($T_m$) increased for 2 wt% and decreased for 5 wt% nanofillers. At 2 wt%, the glass transition temperatures of PLA/ZnO andPLA/MgO nanocomposite films are 63 and 62°C, respectively. Further, the tensile test confirms that 2 wt% of nanofiller incorporated PLA films have better properties than 5 wt% of nanofiller due to the better dispersion of nanoparticles. At 2 wt% of MgO and ZnO nanoparticles, tensile strength ($T_s$) was increased to 19.4 ± 0.97 and 22 ± 1.1 MPa, respectively. The prepared PLA nanocomposite films with improved thermal and mechanical properties can be utilized in food packaging applications.

• Bulletin of Materials Science

Volume 46, 2023
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