Showing papers by "Sampat Raj Vadera published in 2018"

Ni/graphitic carbon core–shell nanostructure-based light weight elastomeric composites for Ku-band microwave absorption applications

Abstract: Graphitic carbon-coated Ni metal core nanoparticles are synthesized using controlled thermal treatment of Ni-hydroxide in an aniline–formaldehyde copolymer matrix under a N2 atmosphere. The structural and microstructural studies substantiate the formation of a graphitic shell on the metallic nickel core. The 850 °C heat-treated core–shell structured material is ferromagnetic in nature with high saturation magnetization. The sample with the highest value of magnetic moment is impregnated in a rubber matrix to prepare composite samples with core–shell nanomaterials of different weight fractions. The sample with 70 wt% Ni/graphitic carbon core–shell powder in the elastomeric rubber matrix showed the optimal microwave absorption at a fairly low thickness of ∼1 mm. This is attributed to the optimized combination of the effective impedance matching and interfacial polarization losses. Further increase in the Ni/graphitic carbon filler material resulted in reduced microwave absorption due to the greater mismatch of impedance as compared to the desired free space impedance of ∼377 Ω. Thus, the optimized composite material is of great potential for microwave absorption in the Ku band.

Synthesis of Various Ferrite (MFe₂O₄) Nanoparticles and Their Application as Efficient and Magnetically Separable Catalyst for Biginelli Reaction.

Abstract: Herein, we reports the application of various spinel ferrite nanoparticles, MFe2O4 (M = Co, Ni, Cu, Zn), as efficient catalyst for Biginelli reaction. All ferrite nanoparticles were synthesized using a novel aqueous solution based method. It was observed that, the catalytic activity of the ferrite nanoparticles followed the decreasing order of CoFe2O4 > CuFe2O4 > NiFe2O4 > ZnFe2O4. The most important feature of these ferrite nanocatalysts is that, these nanoparticles can directly be used as catalyst and no surface modification or functionalization is required. These ferrite nanoparticles are easily separable from reaction mixture after reaction by using a magnet externally. Easy synthesis methodology, high catalytic activity, easy magnetic separation and good reusability make these ferrite nanoparticles attractive catalysts for Biginelli reaction.