In this paper is presented consolidation of nanometer-sized molybdenum powders to form bulk samples by the technique of Plasma Pressure Compaction ðP 2 CÞ. The nanocrystalline powders, consolidated at a temperature of 1400 C and pressure of 48 MPa for a time period of 3 min, had a theoretical density of 97%. The presence of distributed agglomerates in the nanocrystalline powders has an influence on density and microstructure of the bulk metal sample. To facilitate comparison micrometer-sized powders of molybdenum were also consolidated, at a temperature of 1650 C, and had a theoretical density of 98.5%. The bulk sample obtained by consolidating nanocrystalline powders had a higher microhardness (2.95 GPa) than the sample obtained by consolidating from micron-sized powders (2.16 GPa). 2002 Elsevier Science Ltd. All rights reserved.

The microhardness and microstructural characteristics of bulk molybdenum samples obtained by consolidating nanopowders by plasma pressure compaction

Effect of solvent on structure and optical properties of PZT nanoparticles prepared by sol–gel method, in infrared region

A novel Fe−Mn−Zn−Ti−O mixed metal oxide has been developed for efficient low-temperature (25−50 °C) removal of H2S from a gas mixture containing 600 ppm H2S, 25 vol% H2, 7.5 vol % CO2, and 1−3 vol% H2O that simulates typical conditions experienced at the outlet of a bioreactor loaded with sulfate metal reducing bacteria (SMRB) that converts toxic Cr6+ and As5+ present in ground and surface waters and soils into nontoxic elements. During the latter conversion H2S gas is produced and has to be treated. In the present work it is demonstrated for the first time that by using the sol−gel synthesis route at given experimental conditions (e.g., metal precursor salts, solvent system, and solution pH), optimum structural properties for the Fe−Mn−Zn−Ti−O solid can be obtained for maximization of H2S uptake. In particular, at 25 °C an H2S uptake (0.085 g H2S/g solid) larger by at least a factor of 3 compared to a commercial Ni-based H2S absorbent material was obtained.

Effects of Sol−Gel Synthesis on 5Fe−15Mn−40Zn−40Ti−O Mixed Oxide Structure and its H2S Removal Efficiency from Industrial Gas Streams

Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle-particle and macromolecule-macromolecule interactions was carried out.  2004 Society of Chemical Industry

G Hare'l

Papers

Effects of solvent and agitation on microstructural characteristics of sol-gel derived nanocrystalline Y-TZP powders