Articles written in Bulletin of Materials Science
Volume 5 Issue 3-4 August 1983 pp 343-363
Properties of materials exhibiting cooperative phenomena are likely to be modified on restricting the lattice size. Several such microcrystalline materials have been studied to infer general underlying principles. Ferroelectricity, ferromagnetism, superconductivity, and superfluidity in limited lattice sometimes not only show modified behaviour but also new behaviour not present in bulk. Microcrystals are considered to be free, coupled, grain-boundary-separated, or domain-wall-separated.
Volume 6 Issue 2 May 1984 pp 327-338 Microparticle Materials
Microparticles and micrograin ceramics show features distinct from the usual-sized polycrystalline materials. Amorphous state material combined with microparticle size for Pb(Zr0.51 Ti0.49)O3 mimics the dielectric behaviour of crystalline ferroelectricity in ABO3 compounds. Fine-grained Y3Fe5O12 (
Volume 9 Issue 3 August 1987 pp 193-202
Optical properties of transparent alumina prepared through gel process at room temperature and coloured with dopants have been studied. The absorption bands, molar absorptivity, effect of concentration and the dependence of oxidation state of copper on the copper content and water content are similar to the random network glasses. The ultraviolet absorption edge at lower energies confirm the disordered nature of the transition phase aluminas
Volume 9 Issue 4 November 1987 pp 287-294
The load dependence of Vicker’s indentation hardness has been measured in some non-metallic materials and thin foils. A load of 100 g appears to be appropriate for comparing materials. Foil thickness, especially for soft metals like copper, must be at least twenty times the impression diagonal to get a correct value of hardness. The Meyer index varies for materials and can be used for comparison because it seems to pertain to the nature of chemical bonds. The index for boron carbide is similar to glass as was expected by Rice.
Volume 11 Issue 1 September 1988 pp 1-9
The process of gelation through chemical polymerization is described for the preparation of transparent alumina. The nature of disorder in the transition phases of alumina is discussed using the results of XRD, IR, optical absorption and NMR. The microstructures in the monolithic porous xerogels are observed to be fractals arising due to instabilities while drying. Phase separation noticed in copper and chromium-doped xerogels is attributed to fluctuations in polymer density.
Volume 11 Issue 1 September 1988 pp 11-19
Optical properties of chromium-doped transparent alumina xerogels have been studied in the ultraviolet, visible and near infra-red regions. The coordination, valence state and symmetry of crystal field around the transition metal ion is found to change in different transition phases of the xerogel in accordance with the earlier conclusion that the metal ion penetrates into the alumina matrix and occupies aluminium sites. In boehmite and α-Al2O3 chromium is essentially in trivalent state, octahedrally coordinated, whereas in the transition
Volume 13 Issue 4 September 1990 pp 271-282
Boehmite gel-coated SiC whiskers have been studied as discs and as dispersed in gel and commercial alumina. The coated whiskers oxidize and react to some extent in alumina-rich composite compacts when heated in vacuum. In the absence of alumina as matrix, discs of coated whiskers turned brittle on heating above 1600°C. A density of 3.7g/cc was obtained for compacts of SiC whiskers in submicron alumina when sintered pressureless for 2 h at 1600°C. A smooth interface, compatible with the matrix, has resulted in good mechanical properties.
Volume 13 Issue 4 September 1990 pp 283-291
The growth of crystalline mica in K2O-SiO2-MgO-MgF2 glass has been studied and characterised through various techniques, viz. differential thermal analysis (DTA), X-ray diffraction (XRD), microscopy (SEM), and microhardness tests. It is observed that the addition of titania has a stronger influence on the growth of mica crystallites as compared to variation in heat treatment schedules.
Volume 17 Issue 2 April 1994 pp 171-179
In this paper we describe the toxicological tests done on a machinable glassceramic, prepared at the Defence Metallurgical Research Laboratory. Tests show no toxicity and biocompatibility is inferred.
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