Papers by Author: Rajat Kanti Paul

Abstract: Novel continuously porous alumina (25%monoclinic-Zirconia) (Al2O3-(m-ZrO2)) and tetragonal Zirconia (t-ZrO2) composites were fabricated with concentric multilayer shells of Al2O3-(m-ZrO2) and t-ZrO2 by the multi-pass extrusion process. Nanocrystaline Al2O3-(m-ZrO2)/ t-ZrO2 powders and graphite powder as a pore forming agent were mixed with polymer in extrudable form. The microstructure was tailored in the green bodies by the extrusion process with high flexibility of control. The green body was burnt-out and sintered to obtain the continuously porous ceramics. The pore diameter and pore frame thickness were around 198±10.5 μm and 158.5±10.2 μm, respectively. The pore frame region was furnished with 9 alternating shells of Al2O3-(m-ZrO2) and t-ZrO2 with uniform thickness of about 17.6±1.1 μm. The interfaces of the alternate layers were designed corrugated shape. The detailed microstructure of the porous bodies was characterized by SEM techniques.

Abstract: Using 6wt%Y2O3-2wt%Al2O3 as sintering additives and Si as a raw powder, the continuously porous in-situ Si2N2O-Si3N4 bodies were fabricated by multi-pass extrusion process and their microstructures were investigated depending on the addition of carbon (0-9wt %) in the mixture powder. The introduction of Si2N2O fibers observed in the unidirectional continuous pores as well as in the pore-frame regions of the nitrided bodies can be an effective method in increasing the filtration efficiency. In the case of no carbon addition, the network type Si2N2O fibers with high aspect ratio appeared in the continuous pores with diameters of 150-200nm. However, in the case of 9wt% C addition, the fibers were found without any network type and had diameters of 200-250nm.

Abstract: Using microwave synthesized HAp nano powder and polymethyl methacrylate (PMMA) as a pore-forming agent, the porous biphasic calcium phosphate (BCP) ceramics were fabricated depending on the sintering temperature. The synthesized HAp powders was about 70-90 nm in diameter. In the porous sintered bodies, the pores having 150-180 μm were homogeneously dispersed in the BCP matrix. Some amounts of pores interconnected due the necking of PMMA powders which will increase the osteoconductivity and ingrowth of bone-tissues while using as a bone substrate. As the sintering temperature increased, the relative density increased and showed the maximum value of 79.6%. From the SBF experiment, the maximum resorption of Ca2+ ion was observed in the sample sintered at 1000°C.