C. Pavithran

Studies on electroless nickel boride coating on boron carbide particles

Abstract Ni–B alloy deposits were successfully formed over alkali surface treated boron carbide by electroless technique and the effects of processing parameters such as reduction bath pH, temperature and post-heat treatment were investigated. Microstructural studies show remarkable changes in structural morphology from mesh-like structure to platelet type Ni–B coating. The main Ni–B phases observed were NiB, Ni2B, Ni3B and Ni4B3. An effective Ni–B alloy coating with better surface characteristics was formed at pH 8 under 75°C reaction bath temperature in the presence of bath stabiliser. The post-heat treatment of Ni–B coated particles under varying bath reaction temperatures at 400°C showed remarkable Ni–B phase transformation from metastable NiB and Ni2B to stable crystalline Ni3B phase. The NiB coated particle shows lower particle–matrix interfacial reaction, better wettability and enhanced dispersion in aluminium composites compared to uncoated particles.

Structure and Properties of Electroless Cu and Ni-B Coated B4C Particle Dispersed Aluminum Composites by Powder Metallurgy Technique

The widespread demand for light-weight materials in various emerging industrial sectors lead to the fabrication of aluminum- boron carbide composites. In this study, the B4C particles were coated copper and Ni-B through electroless process using formaldehyde and sodium borohydride respectively as reducing agents under optimized condition. The microstructural and hardness behavior were investigated for powder metallurgy processed 20 vol. % of B4C and coated B4C particles in the aluminum matrix. Microscopic observation revealed that coating improved the dispersibility of B4C particles in the matrix. The coated particles showed an increase in hardness and particle compaction with reduced porosity.

Micropatterning of Polystyrene-Alumina Nanocomposite Film by Non-Solvent Induced Phase Separation

The objective of the present study is to fabricate micropatterned polystyrene-alumina nanocomposite (PAN) film by immersing the casted PAN/toluene solution into the bath of a non-solvent of the polymer. Immediate precipitation occurs and creates concavities on the surface of PAN cast after drying due to phase separation induced by solvent non-solvent exchange mechanism assisted by amphiphilic modified alumina particle. PAN film with relatively uniform micropatterns is formed which have the maximum dispersion limit of particles. The effect of particle loading and dispersion on the morphology of pattern is investigated, and a possible mechanism is discussed.