Prasenjit Barick

Bio: Prasenjit Barick is an academic researcher from Arc International. The author has contributed to research in topics: Microstructure & Fracture toughness. The author has an hindex of 7, co-authored 15 publications receiving 201 citations. Previous affiliations of Prasenjit Barick include Government College of Engineering and Ceramic Technology.

Dense β-SiAlONs consolidated by a modified hydrolysis-assisted solidification route

Abstract: Dense β-Si 4 Al 2 O 2 N 6 materials were fabricated by a modified hydrolysis-assisted solidification (HAS) route from aqueous slurries containing 48–50 vol.% solids, in which 5–22 wt.% of the required α-Al 2 O 3 was replaced by equivalent amounts of unprotected aluminium nitride (AlN) powder to promote consolidation via AlN hydrolysis. A fixed amount (9.37 wt.%) of AlN passivated against hydrolysis with a coating phosphate layer was also added to all the samples consolidated by the modified HAS method. The aqueous slurries were cast in non-porous moulds, allowed to set and dried before sintering at 1675 °C for 4 h. For comparison purposes, ceramics with the same predicted final composition (having 64.33% α-Si 3 N 4 , 23.36% α-Al 2 O 3 , 9.37% AlN and 7% Y 2 O 3 as starting materials) were also consolidated by a conventional dry-powder pressing (CDPP). The β-Si 4 Al 2 O 2 N 6 ceramics consolidated by the modified HAS route exhibited superior outstanding properties (bulk density, apparent porosity, water absorption capacity, hardness and fracture toughness) in comparison to the traditional dry-powder pressing route.

A review on magnesium aluminate (MgAl2O4) spinel: synthesis, processing and applications

Abstract: Magnesium aluminate (MgAl2O4) spinel (MAS) is a synthetic material with cubic crystal structure and excellent chemical, thermal, dielectric, mechanical and optical properties. These properties made MAS an indispensable material for optically transparent windows, domes and armours, and for certain refractory applications. High processing cost of dense MAS ceramics is in the main responsible for its limited usage in certain important applications despite its excellent performance in them. The volume expansion (∼8%) associated with MAS phase formation from alumina and magnesia does not allow obtaining dense MAS bodies in a single-stage reaction sintering process. Therefore, dense MAS bodies are made by following a double stage firing process, which is expensive. The existing literature suggests that the processing cost of dense MAS ceramics could be reduced to a great extent by decisive selection of starting raw materials, powder processing and densification conditions, and by understanding the under...

X-ray Linear Dichroism in cubic compounds: the case of Cr3+ in MgAl2O4

Abstract: The angular dependence (x-ray linear dichroism) of the $\text{Cr}\text{ }K$ pre-edge in ${\text{MgAl}}_{2}{\text{O}}_{4}:{\text{Cr}}^{3+}$ spinel is measured by means of x-ray absorption near-edge structure spectroscopy and compared to calculations based on density functional theory (DFT) and ligand field multiplet (LFM) theory. We also present an efficient method, based on symmetry considerations, to compute the dichroism of the cubic crystal starting from the dichroism of a single substitutional site. DFT shows that the electric dipole transitions do not contribute to the features visible in the pre-edge and provides a clear vision of the assignment of the $1s\ensuremath{\rightarrow}3d$ transitions. However, DFT is unable to reproduce quantitatively the angular dependence of the pre-edge, which is, on the other side, well reproduced by LFM calculations. The most relevant factors determining the dichroism of $\text{Cr}\text{ }K$ pre-edge are identified as the site distortion and $3d\text{\ensuremath{-}}3d$ electronic repulsion. From this combined DFT, LFM approach is concluded that when the pre-edge features are more intense than 4% of the edge jump, pure quadrupole transitions cannot explain alone the origin of the pre-edge. Finally, the shape of the dichroic signal is more sensitive than the isotropic spectrum to the trigonal distortion of the substitutional site. This suggests the possibility to obtain quantitative information on site distortion from the x-ray linear dichroism by performing angular dependent measurements on single crystals.