Shiv Brat Singh

Magnetic Ni/Ag core–shell nanostructure from prickly Ni nanowire precursor and its catalytic and antibacterial activity

A microemulsion template assisted hydrazine hydrate mediated wet chemical reduction of nickel chloride hexahydrate at 70 °C has been used for the fabrication of prickly nickel nanowires. Subsequently, the nanowire surfaces are modified with silver using the well known Tollens reagent to form Ni/Ag core–shell nanostructures. X-Ray diffraction studies confirm the formation of face centered cubic type structures of nickel as well as silver in Ni/Ag nanostructures individually and they are found to be devoid of any trace of contamination. Low magnification field emission scanning electron microscope (FESEM) images confirm the wire-like morphology of nickel as well as Ni/Ag core–shell nanostructures. However, the high magnification FESEM and transmission electron microscopy images show the prickly surface of nickel nanowires consisting of cone-like nanostructures, where small spherical silver particles are deposited. Vibrating sample magnetometer (VSM) studies show well defined ferromagnetic behavior of the Ni as well as core–shell Ni/Ag structures. In addition, these nanostructures have been proved to be efficient catalysts at room temperature for the reduction of p-nitrophenol compared to bare Ni nanowires, and the magnetic behaviour serves as an added advantage in its easy separation from the reaction mixture so that it can be reused. Furthermore, Ni/Ag nanostructures also exhibit excellent antibacterial properties, which are significantly better than commercially available antibacterial materials.

Osteo-maturation of adipose-derived stem cells required the combined action of vitamin D3, β-glycerophosphate, and ascorbic acid

This study investigated the effects of various components [vitamin D3 (VD3), beta-glycerophosphate (BGP), and ascorbic acid (AA)] on the potential of human adipose-derived progenitor cells (ADPCs) to transdifferentiate into osteoblast-like cells. ADPCs were induced under four different supplement groups: (1) VD3+BGP+AA, (2) VD3 alone, (3) BGP+AA, and (4) no VD3, BGP or AA. Mineralization studies and presence of bone matrix-related proteins by immunostaining showed that the Group 1 ADPCs showed their ability to undergo osteoblastic differentiation. Further evaluation was made by estimation of levels of RUNX-2 and TAZ genes. Group 1 ADPCs showed the consistent expression of RUNX-2 and TAZ levels over the study period of 28days. The study showed good correlation among various parameters evaluated to conclude that ADPCs could be an alternative source for generating osteoblast-like cells.

SERS active Ag encapsulated Fe@SiO2 nanorods in electromagnetic wave absorption and crystal violet detection.

The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (-14.7dB) compared with Fe@SiO2 (-9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10(-10)M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation.

The influence of heat treatment and role of boron on sliding wear behaviour of β-type Ti–35Nb–7.2Zr–5.7Ta alloy in dry condition and in simulated body fluids

The wear behaviour of heat-treated Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys (all compositions are in wt%) was investigated in dry condition and in simulated body fluids. It has been found that there is no straightforward relationship between the wear rate and the microstructure. The hardness has no appreciable effect on the wear behaviour of these alloys. The presence of boron in the TNZT alloy deteriorates its wear properties. The wear rate of TNZT and TNZTB alloys in various media increases in the following sequence: dry condition < Hanks solution < bovine serum.

Understanding the complexities of bake hardening

Abstract The basic science behind bake hardening steels is well understood in terms of the interactions between interstitial solutes and dislocations. However, the manufacture of such alloys involves a variety of other variables, the interactions between which are influential in controlling the extent of hardening. In the present work, a model which includes the chemical composition of the steel, the strain before aging and the annealing and aging conditions is developed and used to explore certain anomalies in the published literature. It is found that whereas the roles of deformation and aging can be rationalised, the generic effect of niobium is associated with large uncertainties and warrants further experimental work.

Ultra Fast Cooling and Its Effect on the Mechanical Properties of Steel

The objective of this work is to study about the ultrafast cooling of a hot static 6 mm thick steel plate (AISI-1020) by air assisted spray cooling. The study covers the effect of air flow rate and the water impingement density on the cooling rate. The initial temperature of the plate, before the cooling starts, is kept at 900 °C. The spray was produced from a full cone high mass flux and low turn down ratio air atomizer at a fixed nozzle to plate distance. The cooling rate shows that low turn down ratio air atomized spray can generate ultra fast cooling (UFC) rate for a 6 mm thick steel plate. After cooling, the tensile strength and hardness of the cooled steel plate were examined. The surface heat flux and surface temperature calculations have been performed by using INTEMP software. The result of this study could be applied in designing of fast cooling system especially for the run-out table cooling.

Friction Stir Welding: Scope and Recent Development

Friction Stir Welding (FSW) is a new solid-state welding technique which finds application in various industries. This chapter introduces the process, basic mechanism, application, and recent research developments. Research work in this book chapter is broadly divided in two parts: experimental-based, and finite element modeling (FEM)-based approaches of the FSW process. In the experimental studies, three recent developments are presented in this chapter: first, a unique twin-tool concept to modify the FSW process and provide alternative to multi-pass FSW; second, feasibility of using ultrasonic coupled with FSW is studied to reduce the amount of force generated during the process and improve the process efficiency; and finally, formability study of friction stir welded blank is presented. Formability of welded blank plays a vital factor for different industrial application, especially in automobile industry. In the second part, FEM method is implemented to simulate the process. Different modeling techniques are also discussed. A case study in each case is presented with sample results, to have a better understanding on the process and development.

Influence of in situ TiB reinforcements and role of heat treatment on mechanical properties and biocompatibility of β Ti-alloys

The effect of heat treatment on the mechanical properties of Ti-35Nb-5.7Ta-7.2Zr (TNZT) and Ti-35Nb-5.7Ta-7.2Zr-0.5B (TNZTB) alloys has been investigated. In the case of TNZT alloy, the presence of ω phase in the matrix has a greater effect on strength and hardness than the presence of secondary α precipitates. The TNZTB alloy shows higher hardness and tensile strength than the TNZT alloy due to the formation of hard TiB precipitates in the matrix of the former. However, the boron free alloy offers higher ductility than the boron containing alloy. Presence of TiB precipitates in the matrix increases the strength of the TNZTB alloy when ω precipitates are present in the matrix. However, the boride precipitates have no substantial influence on the strength of the TNZTB alloy when ω phase in the matrix is replaced by the α phase. The elastic modulus of the TNZT samples shows a very small variation with different heat treatment conditions. The TNZT alloy samples containing β and ω phases show higher elastic modulus than the samples containing β and α phases. The elastic modulus of the TNZTB alloy is higher than that of the TNZT alloy due to the formation of high modulus TiB particles in the matrix. Both the alloys show better cell adhesion and spreading than the control material (polystyrene). However, the boron free Ti-alloy shows better cell attachment than the boron containing Ti-alloy.

Models for Austenite to Martensite Transformation in TRIP-Aided Steels: A Comparative Study

Low alloy transformation induced plasticity (TRIP)-aided steels are of particular interest to the automotive industry as they offer an excellent combination of strength and ductility at affordable costs. These unique properties depend primarily on the deformation induced transformation behavior of retained austenite to martensite, which is therefore, the most important aspect of TRIP-aided steels. As such, it is important to develop a mathematical model for the transformation of retained austenite. This would not only help in a better understanding of the deformation induced transformation behavior of retained austenite but also aid in a better design of the microstructure of TRIP-aided steels. A large number of empirical as well as semi-empirical models have been developed over the years to describe and predict the variation of retained austenite with strain. A comparative study of the different available models will be presented in this article.

Corrosion behaviour of heat treated boron free and boron containing Ti–13Zr–13Nb (wt%) alloy in simulated body fluid

The corrosion behaviour of heat treated Ti–13Zr–13Nb (TZN) and Ti–13Zr–13Nb–0.5B (TZNB) alloys in Hank’s solution has been investigated. The microstructure of the heat treated TZN alloy consisted of α, β or martensite. Addition of boron to TZN alloy led to the formation of dispersed TiB particles and modification of microstructure. In general, the furnace cooled TZN sample showed lower corrosion potential (Ecorr) than the air cooled sample. Aging of water quenched samples decreased the Ecorr value. The passive current density of TZN samples varied within a narrow range. Presence of boron in TZN alloy decreased the corrosion potential and substantially increased the passive current density. Results showed that boron deteriorated the corrosion resistance of TZN alloy.