Silica carbon mixtures

The reactants are fine-scaled silica/carbon mixtures formed as a decomposition product of silicon- and carbon-containing synthetic polymers or naturally occurring precursors. 

Hydraulic limes (84) may be used for mortar, stucco, or the scratch coat for plaster. They harden slowly under water, whereas high calcium limes, after slaking with water, harden in air to form the carbonate but not under water at ordinary temperatures. However, at elevated temperatures achieved with steam curing, lime—silica sand mixtures do react to produce durable products such as sand—lime bricks. 

Titanium tetrachloride is produced on an industrial scale by the chlorination of titanium dioxide-carbon mixtures in reactors lined with silica. During the reactor operation, the lining comes into contact not only with chlorine but also with titanium tetrachloride. There appears to be no attack on silica by either of these as the lining remains intact. However, the use of such a reactor for chlorinating beryllium oxide by the carbon-chlorine reduction chlorination procedure is not possible because the silica lining is attacked in this case. This corrosion of silica can be traced to the attack of beryllium chloride on silica. The interaction of beryllium chloride with silica results in the formation of silicon tetrachloride in accordance with the reaction... 

Lycoramine. Lycoramine (300)[79] synthesised by Parker et al [80] utilised an intramolecular 5-exo radical addition to an appropriately located double bond to generate the quaternary carbon centre (Scheme 46). The starting material, the silyloxybromo ketone 301, was secured initially as a mixture of isomers from 4-methoxy-3-cyclohexen-l-ol (302) by silylation to 303 followed by bromination. On standing or in contact with silica, the mixture was converted essentially into 304. The overwhelming preference for the substance 301 to exist... 

To etch away silica, carbonization product samples were treated with a mixture of concentrated sulfuric and hydrofluoric acids (5 drops of H2S04 and 1 mL of HF), boiled dry and washed with water. From the precipitate obtained were prepared dispersions in acetone, which were used to determine the size and shape of particles on a JEM100CX-II transmission electron microscope by a commonly used procedure[10]. 

The Metallurgy of Iron. The ores of iron are usually first roasted, in order to remove water, to decompose carbonates, and to oxidize sulfides. They are then reduced with coke, in a structure called a blast furnace (Fig. 26-2). Ores containing limestone or magnesium carbonate are mixed with an acidic flux (containing an, excess of silica), such as sand or clay, in order to make a liquid slag. Limestone is used as flux for ores containing an excess o silica. The mixture of ore, flux, and coke is introduced at the top of the blast furnace, and pre heated air is blown in at the bottom through tuyeres. As the solid... 

M. Sopicka-Lizer, R. A. Terpstra and R. Metselaar, Carbothermal Production of P-Sialon from Alumina Silica and Carbon Mixture. J. Mater. Soc., 30, 6363-9 (1995). 

Complex fluids composed of several pseudophases with a liquid-liquid interface (emulsions, macroemul-sions, cells, liposomes) or liquid-solid interface (suspensions of silica, carbon black, latex, etc.) can, from a dielectric point of view, be considered as classical heterogeneous systems. Several basic theoretical approaches have been developed in order to describe the dielectric behavior of such systems. Depending on the concentration, the shape of the dispersed phase, and the conductivity of both the media and disperse phase, different mixture formulas can be applied to describe the electric property of the complex liquids (11-15). 

Similar results were obtained for mixtures of polyurethane and PVC and poly(e-caprolactone) with styrene-acrylonitrile copolymer. It was found that fillers (silica, carbon black, and talc) broaden the rubbery PU transition, shifting it to higher temperatures. This effect was found to be less pronounced for the high temperature PVC relaxation. The positions of the relaxation maxima are shifted... 

Ivanov and co-workers [4] also pyrolysed scrap tyres in the presence of water vapour to produce a solid product. This product was then characterised by Fourier-Transform infrared and energy-dispersive XRF spectroscopy and evaluated for use as a filler in SBR cured compounds. These vulcanisates were then tested and the results obtained compared with SBR compounds that had been prepared using conventional fillers such as silica and mixtures of silica and carbon black... 

This is an acid-base reaction, in which the base is the oxide ion (p. 89) the acidic oxide SiOj displaces the weaker acidic oxide CO2 in the fused mixture. But in aqueous solution, where the 0 ion cannot function as a strong basefp. 89),carbon dioxide displaces silica, which, therefore, precipitates when the gas is passed through the aqueous silicate solution. In a fused mixture of silica and a nitrate or phosphate, the silica again displaces the weaker acidic oxides N2O5 and P4OJ0 ... 

Both the Toth and Alcoa processes provide aluminum chloride for subsequent reduction to aluminum. Pilot-plant tests of these processes have shown difficulties exist in producing aluminum chloride of the purity needed. In the Toth process for the production of aluminum chloride, kaolin [1332-58-7] clay is used as the source of alumina (5). The clay is mixed with sulfur and carbon, and the mixture is ground together, pelletized, and calcined at 700°C. The calcined mixture is chlorinated at 800°C and gaseous aluminum chloride is evolved. The clay used contains considerable amounts of silica, titania, and iron oxides, which chlorinate and must be separated. Silicon tetrachloride and titanium tetrachloride are separated by distillation. Resublimation of aluminum chloride is requited to reduce contamination from iron chloride. 

Coesite. Coesite, the second most dense (3.01 g/cm ) phase of silica, was first prepared ia the laboratory by heating a mixture of sodium metasibcate and diammonium hydrogen phosphate or another mineraliser at 500—800°C and 1.5—3.5 GPa (14,800—34,540 atm). Coesite has also been prepared by oxidation of silicon with silver carbonate under pressure (67). The stmcture is monoclinic = 717 pm, Cg = 1.238 pm, and 7 = 120°. 

In the course of mixture separation, the composition and properties of both mobile phase (MP) and stationary phase (SP) are purposefully altered by means of introduction of some active components into the MP, which are absorbed by it and then sorbed by the SP (e.g. on a silica gel layer). This procedure enables a new principle of control over chromatographic process to be implemented, which enhances the selectivity of separation. As a possible way of controlling the chromatographic system s properties in TLC, the pH of the mobile phase and sorbent surface may be changed by means of partial air replacement by ammonia (a basic gaseous component) or carbon dioxide (an acidic one). 

Carbon soot from resistive heating of a carbon rod in a partial helium atmosphere (0.3bar) under specified conditions is extracted with boiling C H or toluene, filtered and the red-brown soln evapd to give crystalline material in 14% yield which is mainly a mixture of fullerenes C q and C70. Chromatographic filtration of the crude mixture with allows no separation of components, but some separation was observed on silica gel... 

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