Vikram V. Dabhade

Synthesis of nanosized titanium powder by high energy milling

Titanium powders of about 2 μ particle size were subjected to high energy attrition milling in an argon atmosphere. Selecting suitable milling parameters, nanosize (<100 nm) titanium powders were prepared after 15 h of milling. An average particle size of 35 nm was obtained at 30 h of milling after which the particle size stabilized with continuation of milling to 75 h. The powders after milling for various durations were characterized by TEM, ICP and XRD, and these results are reported and discussed.

Sintering mechanisms of attrition milled titanium nano powder

Detailed sintering studies have been carried out on attrition milled nanocrystalline titanium powder through isothermal dilatometry over a temperature range of 300–1250 °C along with microstructural and x-ray diffraction studies. The sintering behavior of attrition milled nanocrystalline titanium appears to be characterized by: (i) very low activation energies, (ii) high shrinkage anisotropy, (iii) very rapid grain growth in the beta range, and (iv) two kinds of densification processes, namely, intra-agglomerate and inter-agglomerate. Analysis of the kinetic data through sintering diagram approach indicates the operation of particle sliding and grain boundary rotation, type of mechanism in addition to the grain-boundary diffusion, and lattice diffusion as the dominant mass transport mechanisms.

Dilatometric sintering study of titanium-titanium nitride nano/nanocomposite powders

Abstract The sintering behaviour of titanium–titanium nitride nano/nanocomposite powders has been investigated by dilatometry. The nanosized titanium powders (40 nm) were produced by the attrition milling of micron sized titanium powders (12 μm) in Ar atmosphere while the nanosized titanium nitride powders (50 nm) were as procured. Two compositions of the nano/nanocomposite powders, i.e. Ti–8TiN and Ti–15TiN (wt-%) were produced by physical mixing and ultrasonification. Dilatometry was carried out at a constant rate of 10 K min−1 heating to various temperatures in the range of 450–1250°C followed by holding for 1 h. The effect of nanoTiN reinforcement on the sintering onset temperature, linear shrinkage, shrinkage rate, activation energy for sintering, microstructure and grain growth has been reported and discussed.

Effect of Al particle size on the reaction kinetics and densification of TiAl intermetallics

The present investigation deals with response of the particle size of aluminum on the reactive sintering of Ti–Al intermetallics and subsequently on their reaction kinetics and densification behavior. Aluminum powders of initial average particle size of 44 μm were milled for various durations in a planetary ball mill to produce average particles sizes of 100, 28 and 7 μm. These aluminum powders of various particle sizes i.e. 100, 28 and 7 μm were mixed with titanium powder of average particles size of 44 μm in the ratio of 1:1 corresponding to the Ti–Al intermetallic composition. The reactive sintering temperatures of the mixtures were determined by DTA and the effect of change in particle Al particle size has been determined for the activation energy ofthe self-propagating reaction. The effect of Al particle size on the sintering was determined by studying density and microstructure.

Metallography of Fe–P–C and Fe–P–C–Si–N Alloys

The microstructures of Fe–P–C and Fe–P–C–Si–N alloys have been studied to understand the phase distributions and phase transformations during heat treatment. Iron–phosphorus alloys show ghosting features when etched with Nital, since it attacks iron with lower phosphorus content preferentially. The ghostlines mark the boundaries of phosphorus content as it existed at higher temperatures in the austenite–ferrite duplex phase region. Oberhoffer’s reagent reveals the dual-phase microstructure by depositing copper on the low-phosphorus region. The ferrite-to-austenite and reverse transformations were studied and found to occur by nucleation and growth along with diffusion of phosphorus. The morphologies of the phases conform to the Dube system. The phase distribution in dual-phase microstructures was studied using quantitative metallography and compared with the phase fractions obtained from phase diagram calculated using a thermodynamic software. Silicon and nitrogen were added to improve the toughness of the base alloy. Providing homogenization treatment in the upper ferrite region will take less time.

Initial sintering kinetics of titanium-titanium nitride nano/nanocomposite powders

Abstract The present investigation deals with the mass transport mechanisms operating during the initial sintering of titanium–titanium nitride nano/nanocomposite powders. Two compositions of the nano/nanocomposite powders, i.e. nano Ti–8 wt-% nano TiN and nano Ti–15 wt-% nano TiN along with nano Ti were used in the present study. Sintering studies have been carried out by dilatometry of the powder compacts using a constant rate of heating (CRH) and employing model equations to the initial sintering portion. The shrinkage values obtained were analysed using Young and Cutlers equations and a model proposed by Johnson and Berrin. Based on the analysis of experimental data the effect of second phase TiN on the mass transport mechanisms of nano Ti was determined.

Characterization of Automobile Shredder Residues for Chlorine Content and Estimation of it’s Circulation in Cement Kiln

The possible utilization of automobile shredder residue as a fuel in the cement kiln process was investigated. The detailed characteristics of the automobile shredder residues were investigated in terms of it’s chlorine content as a fuel feed and its circulation in cement kiln. For estimation of the chlorine content in the cement kiln system, the Weber model which is one of the circulation material’s forecast model was used. From the results, we estimated the chlorine by-pass rate should be 1 ~ 2 percent, for maintaining the present level of chlorine content’s on the hot-meal of the cement kiln system.

Studies on alloying process of a ferritic/martensitic oxide dispersion strengthened (ODS) steel prepared by mechanical alloying of elemental powders

Ferritic/martensitic oxide dispersion strengthened steel with a nominal composition of Fe–9Cr–2W–0.2Ti–0.12C–0.35Y2O3 was produced by mechanical alloying in a high energy horizontal Simoloyer attritor. Powder samples were collected at intervals of 0.5, 1, 2, 3, 5, 7 and 10 h and analysed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and differential thermal analysis. The alloying elements (Cr and W) got dissolved in the matrix in 7 h milled powder. Crystallite size decreased rapidly with milling time up to 5 h milling and reached a stable size of ∼12 nm after 7 h, whereas strain and lattice parameter were found to increase with milling time. The particle size increased up to 2 h milling and then decreased with milling time. A fine and uniform particle size of ∼25 nm was obtained after 7 h milling. The alloying process and distribution of alloying elements/Y2O3 is studied in the present work.

Nanoporous SiC Membrane Derived from Preceramic Polymer

Ceramic membranes having nano sized pores have great potential for gas separation at high temperature due to their good thermal stability. Moreover, nanoporous silicon carbide membrane has potential application under hydrothermal condition at high temperature. In this research, nanoporous SiC membrane has been developed on the porous alumina plate using preceramic polymers as CVD precursor at 850oC. The preceramic polymer was characterized with Si29 NMR, FT-IR, GC and TGA. The prepared SiC membrane was characterized with SEM and EDS. The hydrogen permeability and selectivity toward nitrogen gas were measured using a GC.

Hydrothermal Synthesis of Hydroxyapatite Powders Using Alkyl Ammonium Bromides as Surfactants

Rod shaped nanocrystalline powders of hydroxyapatite (HAp) were synthesized by a low temperature chemical route involving calcium nitrate tetrahydrate and sodium phosphate. Three types of alkyl ammonium bromide surfactants i.e. tetrapropylammonium bromide, tetraethylammonium bromide and tetramethylammonium bromide were used to regulate the nucleation and crystal growth. The synthesized powders were characterized by XRD, SEM and FTIR. The effect of the various alkyl ammonium bromide surfactants on the phase formation, particle size and morphology of the hydroxyapatite powders has been investigated and reported.