Oxide powders, metal

Carburization by Thermal Diffusion. Carburization of chemically processed metal or metal-compound powders is carried out through sohd-state, thermal diffusion processes, either in protective gas or vacuum. Carbide soHd solutions are prepared by the same methods. Most carbides are made by these processes, using loose or compacted mixtures of carbon and metal or metal-oxide powders. HaUdes of Group 5 (VB) metals recovered from ores by chlorination are similarly carburized. 

In a second paper from Kirillov et al., synthetic aspects of liquid phase precipitation reactions are discussed in relation to the factors responsible for metal-oxide formation. In particular the Pechini reaction, a sol-gel process, was examined. A good reference section is provided to introduce the reader to previous literature. The authors stress that more work needs to be done to establish what factors are important for producing the highest quality metal-oxide powders from such reactions. The conclusion specifically lists the criteria needed in order to accomplish this task. 

Hydrous metal oxide powders, 25 100 Hydrous oxides, zirconium, 26 647 Hydrous silicates, in silica/silicate... 

Some features of the spectra obtained with conventional equipment are illustrated with unsaturated hydrocarbons as fluorophores that have been adsorbed from gas or liquid phase on highly porous metal oxide powders as scattering substrates. 

In 1988, Tanaka et al. first reported the use of ultrafine metal powder in protein analysis. Since then, many inorganic materials, including graphite particles, fine metal or metal oxide powder, silver thin-film substrates or particles,and silica gel, have been used in the MALDI-TOF analysis of low-mass molecules. 

R.S. (1993) Surface sites on spinel type of corundum type metal oxide powders. Langmuir 9 92-99... 

In an early experiment, metal/graphite composite anodes were made of bored graphite rods that were packed with pressed mixtures of metal oxide powder, graphite powder, and pitch (12,13). The packed graphite rods had to be heated to about 1600°C for several hours under vacuum in order to cure the pitch. Subsequently the preparation of composite anodes was simplified by simply packing with a mixed powder of metal oxide (or metal) and carbon. Several kinds of composite rods, in which metal particles are uniformly dispersed in graphite, are now commercially available (31). 

The reaction of metal oxide in powders in the presence of solid carbon. Carbides are obtained by closely mixing metal oxide powders with carbon, and heating, again as with the pure metals, at temperatures... 

APPENDIX 2. PREPARATION AND ANALYSIS OF ISOOCTYL THIOGLYCOLATE-COATED METAL OXIDE POWDERS... 

One approach to making such powders is the sol-gel method, in which a metal oxide powder is synthesized from a metal alkoxide, a compound derived from a metal and an alcohol. In the synthesis of titania (Ti02) from titanium ethoxide, Ti(OCH2CH3)4, for example, the Ti(OCH2CH3)4 starting material is made by the reaction of titanium(IV) chloride with ethanol and ammonia in a benzene solution ... 

Powders possessing relatively high surface area and active sites can be intrinsically catalytically active themselves. Powders of nickel, platinum, palladium, and copper chromites find broad use in various hydrogenation reactions, whereas zeolites and metal oxide powders are used primarily for cracking and isomerization. All of the properties important for supported powdered catalysts such as particle size, resistance to attrition, pore size, and surface area are likewise important for unsupported catalysts. Since no additional catalytic species are added, it is difficult to control active site location however, intuitively it is advantageous to maximize the area of active sites within the matrix. This parameter can be influenced by preparative procedures. 

Hashimoto, K. Hiramoto, M. Lever, A. B. P. Sakata, T. Luminescence decay of ruthenium(II) complexes adsorbed on metal oxide powders in vacuo Energy gap dependence of the electron-transfer rate, J. Phys. Chem. 1988, 92, 1016. 

Hollow polymer spheres Talcum Metal oxide/-powder Blowing agents Bonding agents Peroxide Flame retardants... 

Hydrous metal oxide powders, such as sodium titanate, NaT O, can be prepared by treating TYZOR TPT with sodium hydroxide in methanol solvent to form a soluble intermediate, which is hydrolyzed in acetone—water to form an ion-exchange material useful in treating radioactive waste (158). Exchange of the sodium ion with an active metal such as Ni, Pt, or Pd gives heterogeneous catalysts useful in olefin polymerization, coal liquification, and hydrotreating. 

To modify 1 g of metal or metal oxide powder 50 g of an aqueous polymer or copolymer solution containing 1 w/w % polymer were used. Because the polymer was used in excess, the largest possible amount of polymer should be adsorbed on the surface (adsorption temperature t ads = 20 °C). Three pH-values were under investigation pH = 5, 8 and 11. They were adjusted with 0.1 moll-1 NaOH or HC1 and measured with the pH-equipment by HANNA-Instruments. 

This transformation is carried out by intimately mixing metal oxide powders with carbon, again as with the pure metals, at temperatures between 1500-2300 K, with or without the presence of a hydrocarbon gas. The reactions of oxides with carbon are thermodynamically favored, but high temperatures are again needed because the transformations are limited by diffusion. The direct transformation of oxides to carbides is economically advantageous over the use of metals since the need to separately reduce the oxide phases is avoided. Wide application is found for the commercial production of carbides of molybdenum, tungsten, and tantalum. 

Most of our experiments used large (millimeter-sized) polyhedral, polymeric objects that could be easily manipulated by hand. These objects were cast from molds, and the sides were readily differentiated into hydrophobic and hydrophilic sets. By working at a relatively large size scale, we were able to fabricate objects of a complexity difficult to achieve on a smaller, sub-millimeter scale. We could control the colors of the faces of the objects, the densities of the water phase (by adding a salt), and the densities of the objects (by adding a dense metal oxide powder). 

First-principles calculation on lithium transition metal oxides of positive electrodes for lithium-ion batteries have been done by many researchers [17-20]. In general the open-circuit voltage EocvM depends on the difference in the Li chemical potential between anode Li metal and cathode. In this paper, we have investigated the possibility of using the metal oxide powders for anodic electrode as active materials and find out their electrochemical performance through the calculation. The first-principles calculation in this paper for the voltages was carried out as follows ... 

Figure 16.3 A flow chart of a typical sol-gel process for preparing nano-scale metal oxide powder.

K. Tajiri, H. Matsubara, T. Asahina and M. Kosaka, Thermal Conduction of Powders ( I ) - Some Metal Oxide Powders - (in Japanese), Energy Resources, 7, No. 5, 79-83 (1886). 

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