Synthesis of Nano-Crystalline Ceramic powders by Chemical Process

Several processes were developed by our research group to synthesise nanocrystalline ceramic materials. Amongst them, the im,estigation of the new, simple and versatile technique to generate ultra fine powders of advanced ceramic oxides using a chemical pyrophoric reaction and sot-gel techniques are noteworthy. In the solution comb-ustion technique, the role of pH on the morphology of the synthesised powder was attributedto the redox reaction. These pyrophoricallp generated precursors could also be utilised to synthesise nano-crystalline aluminium nitride powders at low temperatures using carbotherntic process. An economically feasible alkoxide based solgel process for the production of high purity nano-crystalline alumina powders was established and several subsequent processes to generate nanospheres to micro spheres were investi-gated. This increased the potential of these high pure nano-crystalline spherical alumina powders for practical applications in spray coating on industrial components, fabrication of envelope for sodium vapour lamp, hip joints and IC substrate

Self-Propagating High-Temperature Synthesis(SHS) of Advanced High Temperature Materials

Over the last few years, our research group at National Metallurgical Laboratory Jamshedpur had contributed significantly on the fabrication of various advanced high temperature materials monolithic and composites namely ZrB2, TiC, ZrB;-A1zO 3 and AlzO3-SiC by self-propagating hightemperature synthesis (SHS) technique. In this paper, the SHS processes developed at National Metallurgical Laboratory, Jamshedpur are reviewed Ultra fine ZrB2, TiC, TiC-Ni powder were prepared. New in-situ composites in the ZrBz-A1203, Alz03-SiC,., TiC-Ni were prepared by the SHS techniques.The studies were focused on the SHS processing, mechanism of phase formation, microstructure evaluation, sintering of SHS produced powder and their property eval-uation. A new combustion synthesis technique using a rapid heating self-propagating high temperature synthesis (RH-SHS) was made for the fabrication of in-situ AlzO3-SiCu, composite. Process for the in-situ preparation of 96% dense ZrBz-Al103 by the SHS was developed

Effect of Silver on the Sintering Characteristics of High T Ceramic Superconductors

A detailed investigation on the densification behaviour of Y-Ba-Cu-oxide (YBCO)-AgX and Bi-Pb-Sr-Ca-Cu-oxide (BPSCCO)-AgX composite powder synthesised by a chemical pyrophoric decomposition technique is made. It has been observed that Ag plays a significant role on the lowering of sintering temperatures and melting points of these superconductors. In YBCO-AgX, for 0< x<_0.6 the rate of densification increases and for 0.6<x<1.2 the rate of densification decreases. The densification behaviour is due to oxygen absorption at the interface of YBCO and Ag grains and a low temperature eutectic Ag,,OX formed which promotes liquid phase sintering. Studies on the sintering characteristics under inert atmosphere indicate increased densification with the silver addition. The removal of oxygen from Ag,OX to the inert sintering atmosphere enhances the densification rates . This is also confirmed from the weight loss of the pellets observed in the TG experiments. Sintering studies of BPSCCO-AgX composites show decrease of densification with the Ag content in the matrix. The degradation of superconducting properties is attributed to the change of chemical compositions of the composites. The evaporation loss of Bi, Pb, Sr and Cu during sintering is observed to be the cause of degradation. The evaporation losses are increased with x

The sensitivity of frog hearts to acetylcholine and other neurohumoral transmitter and allied substances and the comparative toxicity of modern plastic and silicone connecting tubing tested on frog hearts

The thesis is divided into two parts dealing with separate topics: Part I - The Sensitivity of Frog Hearts to Acetylcholine and Other Neurohumoral Transmitter and Allied Substances. Part II - The Toxicity of Modern Plastic and Silicone Connecting Tubing, Tested on Frog Hearts. The aim of the present work was to investigate the threshold sensitivity (minimum effective concentrations) of frog hearts to some well documented substances of physiological importance under critically controlled experimental conditions. Acetylcholine, adrenaline, noradrenaline, 5-hydroxytryptamine and nicotine were selected for this purpose. Very sensitive electronic equipment specially designed and adapted to suit the frog heart was developed over a period of several years. The equipment permits a well controlled perfusion of frog heart and records the perfusion pressure (venous pressure) heart rate, arterial pressures (systolic, diastolic and pulse pressure) and cardiac output simultaneously and continuously. The electronic part of the equipment essentially consists of a specially designed 4 channel direct ink writing recorder. Photographs of different parts of equipment and operational details are given in the section on Methods. The perfusion of frog heart was conducted by introducing a cannula into the inferior vena cava without opening the pericardium. The perfusate coming out of the two aortic cannulae passed through an 'arterial system' consisting of elastic connecting tubing and artificial resistance, and finally escaped out in the form of drops which were counted and integrated electronically. Since the constancy of venous pressure was a crucial point in providing a stable record and also in preventing the occurrence of undesirable changes in the different recorded parameters during a critical test perfusion, special care was exercised in designing and developing the venous pressure recorder. The venous pressure recorder and the carriages for the different sources of perfusion have been so developed that the venous pressure can be kept constant at any desired value throughout the period of experiment lasting from 1 to 3 days. At the same time unavoidable minor changes in the venous pressure (of course quite insufficient to influence the stability of record) of the order of 0.05 cm of even less, were recorded and displayed very prominently. A venous pressure monitoring meter constantly guided the operator. Special methods of precaution and control were introduced at several stages of the experiment so that the effect of test solutions were well controlled and it was clearly shown on the record that there could be no possibility of unrecognised changes in the record due to artefacts - electronic or otherwise. The distilled water used for preparing solutions, the ionic composition of fluids, the type of glass containers, the connecting tubing, the minor variations in temperature from standing at different places), minor variations in the pH of the solutions and bacterial, chemical or organic contamination of glassware and tubing, all were liable to influence the behaviour of the preparation. With conventional crude methods the influence of such factors would never be detected. Most of these variables were easily controlled once their importance was realised, though a considerable time was devoted to analysing and controlling them. (Abstract shortened by ProQuest.)

Role of templating agents on the growth morphology of AIPO4

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Positioning and Surveying Requirements for Exploration and Exploitation of Ocean Wealth

Deep sea mining, such as is now being planned to be carried out in the Indian Ocean, requires an accurate positioning system for navigation and for the control of the equipment. Short range systems using electromagnetic principles cover only a limited area while the longer range systems which can be used for offshore, deep ocean work although covering large areas, have limited accuracy. This paper reviews the requirements for position fixing systems for deep ocean mining and the ways to reach the best solution at the most reasonable cost

Development of Aluminium based Metal Matrix Composites

A detailed study on the processing of Al-metal matrix comp, cites with the reinforcement of different parti-culates such as SiC, TiN and Ti02 was carried out. The Al-SiC composite powder prepared through atomisation route is expected to limit the interfacial reaction bet-ween the matrix and the ceramic particulate and help in making customer tailored components by powder metallurgy route. An attempt to avoid the interfacial reaction of matrix and ceramic is investigated by impregnating the Al matrix with TiN particulates. Similarly, Al-Ti02.composite is investigated by new spray forming technique, where the interfacial reaction between Al and Ti02 is expected to form intermetallic compounds and improve the bonding and mechanical properties. The results of the present studies show that the Al based composites prepared through various techniques exhibits excellent mechanical, physical and tribological properties and could emerge as promising materials for defence, aerospace and other engineering applications

Synthesis and structural characterisation of bismuth(III) hydroxamates and their activity against Helicobacter pylori

Seven new bismuth(III) hydroxamate complexes derived from the hydroxamic acids N-methylfurohydroxamic acid (H-MFHA), N-benzoyl-N-phenylhydroxamic acid (H-BPHA), salicylhydroxamic acid (H2-SHA), benzohydroxamic acid (H2-BHA), and acetohydroxamic acid (H2-AHA) have been synthesized and characterized. The complexes formed are either tris-hydroxamato complexes containing only mono-anionic ligands, [Bi(H-SHA)3], [Bi(MFHA)3] and [Bi(BPHA)3]; mixed-anion complexes, [Bi(SHA)(H-SHA)] and [Bi(AHA)(H-AHA)]; and potassium bismuthate complexes, K[Bi(SHA)2] and K[Bi(BHA)2]. The solid-state structure of three complexes has been determined through single crystal X-ray diffraction; [Bi(MFHA)3]2·Me2C[double bond, length as m-dash]O, {[Bi(SHA)(H-SHA)(DMSO)2][Bi(SHA)(H-SHA)(DMSO)]·DMSO}∞ and [Bi(BPHA)3]2·2EtOH. All the complexes and their parent acids were assessed for the bactericidal activity against three strains of Helicobacter pylori (26695, B128 and 251). Of the acids, only acetohydroxamic acid showed any activity at low concentrations (MIC 6.25 μg mL−1; 83.26 µM) while the others were not toxic below 25 μg mL−1. In contrast, their bismuth(III) complexes all showed excellent activity across all three strains (e.g. 0.28 μM for [Bi(H-SHA)3] to 6.01 μM for K[Bi(BHA)2] against strain 251) with only minor variations in activity being both ligand and composition dependant

Loss of α-Synuclein Does Not Affect Mitochondrial Bioenergetics in Rodent Neurons.

Increased α-synuclein (αsyn) and mitochondrial dysfunction play central roles in the pathogenesis of Parkinson's disease (PD), and lowering αsyn is under intensive investigation as a therapeutic strategy for PD. Increased αsyn levels disrupt mitochondria and impair respiration, while reduced αsyn protects against mitochondrial toxins, suggesting that interactions between αsyn and mitochondria influences the pathologic and physiologic functions of αsyn. However, we do not know if αsyn affects normal mitochondrial function or if lowering αsyn levels impacts bioenergetic function, especially at the nerve terminal where αsyn is enriched. To determine if αsyn is required for normal mitochondrial function in neurons, we comprehensively evaluated how lowering αsyn affects mitochondrial function. We found that αsyn knockout (KO) does not affect the respiration of cultured hippocampal neurons or cortical and dopaminergic synaptosomes, and that neither loss of αsyn nor all three (α, β and γ) syn isoforms decreased mitochondria-derived ATP levels at the synapse. Similarly, neither αsyn KO nor knockdown altered the capacity of synaptic mitochondria to meet the energy requirements of synaptic vesicle cycling or influenced the localization of mitochondria to dopamine (DA) synapses in vivo. Finally, αsyn KO did not affect overall energy metabolism in mice assessed with a Comprehensive Lab Animal Monitoring System. These studies suggest either that αsyn has little or no significant physiological effect on mitochondrial bioenergetic function, or that any such functions are fully compensated for when lost. These results implicate that αsyn levels can be reduced in neurons without impairing (or improving) mitochondrial bioenergetics or distribution

Development and Characterization of Ag-Cu-Ti Alloys for Ceramic Brazing

In the present investigation, silver and copper base alloys with varying compositions of Ag:Cu = 72:28, 60:40, 50:50 and 30:70 (by wt%) are prepared. In each set, 1, 2 and 3w1% of active filler element, i.e. titanium is incorporated by powder metallurgical route. The samples are characterised by XRD, DTA-TGA, SEM and EDX. The XRD results show that titanium and its related phases are not present due to the lower concentration of Ti in these samples. Energy dispersive X-ray analyses reveal that most of the titanium is present in the copper rich phase and very little in the silver rich phase. The rolled brazing alloys are used for./pining the alumina to alumina, that showed excellent joining characteristics