Mantravadi Krishna Mohan

Lime-enhanced carbon monoxide reduction of cuprous sulfide

Kinetic studies were conducted on the carbon monoxide reduction of cuprous sulfide powder in the presence of lime as a function of quantity of lime in the charge, CO flowrate, temperature, and time of reduction and particle size of the sulfide. Lime was found to enhance drastically the rate of reduction as well as reduce the COS emission into the off-gas to negligible levels. Both temperature and flowrate of the reducing gas were found to influence the reduction rate, and best results were obtained at 1273 K and at a CO flowrate of 3.33 cm3 s−1. The overall reaction seems to be governed by the intrinsic kinetics of the Cu2S-CO reaction. Kinetic analysis reveals the observance of the Valensi’s equation, indicating diffusional control through the product layer formed over reacting Cu2S particles. The calculated experimental activation energy of 169.6 kJ/mole in the termperature range of 1123 to 1273 K is in good agreement with that reported in the literature for sulfur diffusion in copper. A critical comparison has been made of the lime-scavenged reduction of Cu2S by different reagents, namely, hydrogen, carbon monoxide, and carbon.

Synthesis and characterization of copper nanoparticles by chemical reduction method

Copper nanoparticles were synthesized using chemical reduction method by reduction of copper sulphate as a metal precursor and sodium borohydride as reducing agent. The particles are characterized and assessed by UV-Vis spectrometer, SEM-EDS and particle size analysis. SEM-EDS and particle size analysis contributed to the analysis of size, shape and composition of copper nanoparticles. UV-Vis spectrometer contributed to analysis of optical properties of the nanoparticles which showed a 550nm and 800nm copper band. The SEM images are also observed and found to be in agreement with the UV-Vis result, confirming the formation of metallic copper nanoparticles. The average particle size at room temperature was less than 16nm. The sizes of the nanoparticles are more controllable by the chemical reduction method.

Microstructure, Texture, and Mechanical Behavior of As-cast Ni-Fe-W Matrix Alloy

This article describes the tensile properties, flow, and work-hardening behavior of an experimental alloy 53Ni-29Fe-18W in as-cast condition. The microstructure of the alloy 53Ni-29Fe-18W displays single phase (fcc) in as-cast condition along with typical dendritic features. The bulk texture of the as-cast alloy reveals the triclinic sample symmetry and characteristic nature of coarse-grained materials. The alloy exhibits maximum strength (σYS and σUTS) values along the transverse direction. The elongation values are maximum and minimum along the transverse and longitudinal directions, respectively. Tensile fracture surfaces of both the longitudinal and transverse samples display complete ductile fracture features. Two types of slip lines, namely, planar and intersecting, are observed in deformed specimens and the density of slip lines increases with increasing the amount of deformation. The alloy displays moderate in-plane anisotropy (AIP) and reasonably low anisotropic index (δ) values, respectively. The instantaneous or work-hardening rate curves portray three typical stages (I through III) along both the longitudinal and transverse directions. The alloy exhibits dislocation-controlled strain hardening during tensile testing, and slip is the predominant deformation mechanism.

Surface modification of Magnesium and its alloy as orthopedic biomaterials with biopolymers

Abstract Magnesium (Mg) and its alloys, as biodegradable materials, have received a huge interest in biomedical applications, especially, in the manufacturing of orthopedic implants (e.g., plates and pins). However, they are prone to rapid corrosion and degradation, and hence they do not fulfil all the essential clinical requirements. Consequently, plenty of surface modification approaches have been introduced for the improvement of corrosion resistance and biocompatibility, including metal coatings, nanoporous in organic coatings and biopolymer depositions. Compared to other permanent coating materials, biopolymers are promising candidates for the surface modification of implants, in regard of their high biocompatibility, moderate biodegradability and high corrosion inhibition ability. In this chapter, the use of cationic chitosan and cellulose/cellulose derivatives, naturally occurring polymers, as coating materials for magnesium-based implants, are summarized.