Mahesh Kumar Talari

Effect of (Ba0.6Sr0.4)TiO3 (BST) Doping on Dielectric Properties of CaCu3Ti4O12 (CCTO)

The effect of (Ba 0.6 Sr 0.4 )TiO 3 (BST) addition on dielectric properties of CaCu 3 Ti 4 O 12 (CCTO) ceramic was investigated. Ceramic samples with the chemical formula (1– x )CaCu 3 Ti 4 O 12 + x (Ba 0 . 6 , Sr 0.4 )TiO 3 ( x =0, 0.05, 0.1, and 0.2) were synthesized from high purity oxide powders by the conventional solid-state synthesis method. X-ray diffraction (XRD) analysis showed the existence of BST as a secondary phase alongside CCTO. Scanning electron microscopy (SEM) investigation showed a slight decrease in grain size of doped CCTO samples. Density measurements showed that porosity content increased with increasing BST addition indicating low densification due to high melting point secondary phase addition. Dielectric constant of undoped CCTO ( x =0) showed lack of stability with frequency which dropped drastically between 10 4 and 10 5 Hz and accompanied by high dielectric loss. Addition of BST into CCTO caused the dielectric constant to slightly decrease but improved stability with frequency compared to the undoped sample. The decrease in dielectric constant of doped CCTO samples was suggested to be partly due to the decrease in average grain size and increase in porosity with BST addition. Nevertheless, a high value of dielectric constant was still maintained around ∼10 4 range for all doped samples. The dielectric loss (tanδ) of all BST-doped samples was lower than that of pure CCTO sample at the frequency range of 10 3 to 10 5 Hz probably due to the increase of grains boundary resistivity. The activation energy of grains boundary ( E gb ) showed higher values as compared to the activation energy of grains ( E g ) for all samples and conforms to the internal barrier layer capacitor (IBLC) model.

Conductometric Study of Nimesulide in Aqueous Solutions of Hydrotropic Agents at Different Temperatures

Conductance values of nimesulide have been determined in water in 0.1, 0.2, 0.4, 0.6, 0.8, 1 and 2 mol dm-3 aqueous solutions of hydrotropic agents (sodium benzoate, sodium salicylate, sodium bromide and nicotinamide) at temperatures 298.15, 303.15, 308.15 and 313.15 K. The conductance values have been used to evaluate the limiting molar conductance and association constants by means of Shedlovsky extrapolation technique. Thermodynamic parameters for the association process of nimesulide in aqueous solutions of hydrotropic agents have also been calculated.

Effect of Mo on the High-Temperature Creep Resistance and Machinability of a Recycled Al-Alloy with High Iron Impurity

Reported work focuses on the effect of morphology of the Fe-rich intermetallic phases on the machinability of Al-alloy containing >2wt.% Fe, obtained from automotive scrap. Effect of Mo addition on the microstructure, high-temperature impression creep and thereby the machinability of the Al-recycled alloy were studied. The machinability of the recycled alloy was estimated by investigating the built-up-edge (BUE) and surface roughness (Ra). SEM-EDS and TEM-SADP studies have shown that the crystal structure (BCC) of the Al8Fe2Si phase remained unchanged; however, Mo replaced few Fe atoms with little effect on the lattice dimension. It has been found that the addition of Mo to the recycled alloy suppresses the formation of β-phase (Al5FeSi) by suppressing the peritectic transformation of α (Al8Fe2Si) phase. Such suppression is found to improve the high-temperature creep resistance and the machinability with the increase in the Mo addition level.

Effect of titanium-boron additions on grain refinement of AA 2219 gas tungsten arc welds

Abstract Grain refinement of aluminium weld metal involves the transition from coarse columnar grains to smaller, more equiaxed grains (sometimes referred to as columnar to equiaxed transition). This refinement in grain size and shape results in both improved mechanical properties (ductility and toughness) and significant improvement in weldability. The present study has investigated the influence of Tibor additions on the structure and mechanical properties of AA 2219 gas tungsten arc (GTA) weldments. Controlled amounts of Tibor grain refiner (containing Ti and B in a ratio of 5∶1) were introduced into the molten pool of AA 2219 by predeposited cast inserts under different welding conditions by GTA welding. Full penetration GTA welds were prepared using alternating current. It was observed that grain size was decreased with increasing amounts of Tibor. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength and ductility. It is also found that welds subjected to post-weld aging treatment displayed superior mechanical properties.

Synthesis and structural characterization of nano-hydroxyapatite biomaterials prepared by microwave processing

Synthetic hydroxyapatite, (HA, Ca10(PO4)6(OH)2), is an attractive and widely utilized bio-ceramic material for orthopedic and dental implants because of its close resemblance of native tooth and bone crystal structure. Synthetic HA exhibits excellent osteoconductive properties. Osteoconductivity means the ability to provide the appropriate scaffold or template for bone formation. Calcium phosphate biomaterials [(HA), tri-calcium phosphate (TCP) and biphasic calcium phosphate (HA/TCP)] with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive and can be effective carriers of bone cell seeds. This HA can be used in bio-implants as well as drug delivery application due to the unique properties of HA. Biomaterials synthesized from the natural species like mussel shells have additional benefits such as high purity, less expensive and high bio compatibility. In this project, HA-nanoparticles of different crys...

Structural and Optical Properties: Mn Doped Nano ZnO Synthesized by Mechanochemical Synthesis

Manganese doped ZnO nanoparticles were synthesized by mechanochemical processing in a high energy ball mill (Zn1−xMnxO, x = 0, 0.02, 0.04, 0.06, 0.08, 0.1). ZnO nano particles were synthesized by milling corresponding chemical precursors in a planetary ball mill for different periods of time. Diluents were used to control the agglomeration and reaction kinetics during the milling. Diluents were removed from the milled powders by selective leaching technique and the samples were dried at 100 °C for 24 hours. Phase identification and crystallite size investigations were carried out from the data obtained by X‐ray Diffraction (XRD) analysis of the samples. The peak shifting in XRD patterns showed that Mn ions were successfully doped into the ZnO crystal lattice with successive increase in dopant levels. Average crystallite size of the nano particles is seen to vary from 16 to 30 nm. Morphology of the samples was investigated by field emission scanning electron microscope (FESEM). It can be seen from FESEM images that the nano particles did not tend to agglomerate. Uv‐Visible spectroscopic (Uv‐Vis) technique was used for the optical properties characterization of the samples. Band gap values of the ZnO nano particles were determined from Tauc plots of UV‐Vis data. The energy gap is seen to decrease with increase in Mn.Manganese doped ZnO nanoparticles were synthesized by mechanochemical processing in a high energy ball mill (Zn1−xMnxO, x = 0, 0.02, 0.04, 0.06, 0.08, 0.1). ZnO nano particles were synthesized by milling corresponding chemical precursors in a planetary ball mill for different periods of time. Diluents were used to control the agglomeration and reaction kinetics during the milling. Diluents were removed from the milled powders by selective leaching technique and the samples were dried at 100 °C for 24 hours. Phase identification and crystallite size investigations were carried out from the data obtained by X‐ray Diffraction (XRD) analysis of the samples. The peak shifting in XRD patterns showed that Mn ions were successfully doped into the ZnO crystal lattice with successive increase in dopant levels. Average crystallite size of the nano particles is seen to vary from 16 to 30 nm. Morphology of the samples was investigated by field emission scanning electron microscope (FESEM). It can be seen from FESEM im...

Study of Sintering Temperature for Nano-Hydroxyapatite with Addition of Titanium

Synthetic Hydroxyapatite (HA, Ca10(PO4)6(OH)2) have the ability to provide the appropriate, scaffold or template for bone formation because of similar chemical and crystallographic structures to bone. The addition of 10wt. % of Ti powder in nano-HA powder was done by using ball milling. The different sintering temperatures at 1000, 1050, 1100, 1150 and 1200°C of nano-HA-Ti pallet were studied. Nano-HA-Ti pallet after vary sintering temperature were tested by hardness and compression strength tests. The optimum sintering temperature to sintered nano-Ha-Ti was at 1200°C because it gave the highest hardness and compression values which were 290.80HV and 78.49MPa. From Scanning Electron Microscopy (SEM) analyzed, nano-HA-Ti particles at 1200°C showed the attachment of nano-HA powder with Ti powder at grain boundary and some crack had form.

Effect of Aluminium Doping on Structural and Optical Properties of ZnO Nanoparticles Prepared by Mechanochemical Synthesis

Optical properties of metal ion doped zinc oxide (ZnO) nanoparticles synthesized by various methods were reported to display different properties. Nevertheless, there are limited reports on metal ion doped ZnO prepared by mechanochemical synthesis. This paper reports the effect of aluminium doping on structural and optical properties of ZnO (Zn1‐xAlxO, x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) nanoparticles prepared by mechanochemical synthesis in a high‐energy ball mill. The samples were synthesized by milling corresponding chemical precursors in a planetary ball mill for 5 h. Diluents were used to control the agglomeration and reaction kinetics during the milling. The shifting of X‐Ray Diffraction (XRD) peaks indicated that Al ions have been successfully doped into the crystal lattice of ZnO host. Average crystallite size, was calculated based on Scherrer’s equation, was found to vary from 22 to 29 nm. Blue shift in energy gap (Eg) with increasing Al concentration (x<0.08) could be attributed to either the Bu...

Effect of Milling Time on Properties of Mechanochemically Synthesized Nano ZnO

This paper presents the characterization results of nanocrystalline Zinc Oxide with different crystallite sizes prepared by mechanochemical synthesis. Nano ZnO particles of different crystallite size were synthesized by high energy milling of precursor powders for various periods of time. Diluents were added to the precursor powders to reduce the agglomeration of product phase and to avoid the spontaneous reaction of precursor powders. After the milling process, diluents were selectively leached out using distilled water. X‐ray Diffraction data was used to analyze the crystallite size of the nanoparticles and also to analyze the progress of the chemical reaction during milling process. Crystallite sizes were calculated from the XRD peak broadening using the Sherrer’s formula. Crystallite sizes were seen to increase at a faster rate after 5h of milling where as bellow 5h of milling, little increase was observed. This increase in crystallite size at higher milling time could be attributed to cold welding an...

Microstructure and Mechanical Properties of Ti-15-3 Alloy Gas Tungsten Arc Welds Prepared Using CP-Titanium Filler

Strength and ductility of fusion zone of metastable β titanium alloy welds can be improved by choosing suitable fillers. This paper reports the effects of using CP-Ti filler on the microstructural and mechanical properties of Ti-15-3 weldments. Full penetration autogenous and CP-Ti filler welds were produced by pulsed gas tungsten arc welding. X-ray diffraction analysis revealed small amounts of α-Ti phase in the diffraction pattern obtained for welds prepared using CP-Ti filler. Transmission electron microscopy analysis showed presence of grain boundary and intragranular α in the fusion zone of the welds prepared using CP-Ti filler. The welds prepared with CP-Ti filler showed higher hardness, higher UTS and lower % strain compared to autogenous welds.