Showing papers by "Pushan Ayyub published in 1993"
TL;DR: In this article, a microstructural study of a new water-in-oil microemulsion composed of cetyltrimethylammonium bromide (CTAB), butanol, octane and an aqueous phase is presented.
Abstract: We present a microstructural study of a new water-in-oil microemulsion composed of cetyltrimethylammonium bromide (CTAB), butanol, octane and an aqueous phase. The system solubilizes relatively large proportions of metal salt solutions such as Y(NO3)3 and Cu(NO3)2. The properties studied include electrical conductivity, viscosity and effective hydrodynamic diameter (from dynamic light scattering). The non-monotonic dependence of the hydrodynamic diameter on the aqueous phase fraction has been explained by a simple equipartition model with variable surfactant aggregation number. The presence of Cu2+ ions in very small water-in-oil droplets (<5 nm) is found to lead to the formation of a [CuBr3]– complex, but the complex is destroyed with an increase in the size of the droplets.
28 citations
TL;DR: In this article, it was shown that diamond particulates in the form of a film were deposited on tungsten surfaces by laser-induced reactive quenching of cyclohexane and decalin liquids whose stereostructure is closely related to that of diamond.
19 citations
TL;DR: In this article, it was shown that bulk La1.85Sr0.15CuO4−δ (LSCO) superconducts below 36K. But microcrystalline LSCO with mean particle size ≤700nm (prepared by rapid liquid dehydration) is not superconducting down to 4.2K.
Abstract: Bulk La1.85Sr0.15CuO4−δ (LSCO) superconducts below 36K. But microcrystalline LSCO with mean particle size ≤700nm (prepared by rapid liquid dehydration) is not superconducting down to 4.2K. This may be due to a size-induced structural distortion and an accompanying reduction in the oxygen occupancy.
7 citations
TL;DR: In this article, the nucleation and growth processes that occur during the irreversible structural transformation of metastable oxide phases to their thermodynamically stable polymorphs were studied, which can be correlated to the change in the specific volume at the transition.
Abstract: We have studied the nucleation and growth processes that occur during the irreversible structural transformation of metastable oxide phases to their thermodynamically stable polymorphs. The transformations examined were: (i) cubic pyrochlore Pb2Ti2O6 (metastable) to tetragonal perovskite PbTiO3; (ii) hexagonal BaFe2O4 (metastable) to orthorhombic BaFe2O4; and (iii) orthorhombic stibiotantalite BiNbO4 (metastable) to triclinic BiNbO4. In each case the irreversible transformation was accompanied by a marked reduction in the particle size, which can be correlated to the change in the specific volume at the transition. Solids which undergo a relatively large change in specific volume during structural transformation can therefore be obtained in fine-particle form by controlled heating of their metastable polymorphs just above the transformation temperature.
4 citations