Carbonized silica

Table 14-16 lists t)pical grades of porous carbon, silica, alumina, stainless steel (t)pe 316y and polymers commercially available. 

Fillers. Some fillers, such as short fibres or flakes of inorganic materials, improve the mechanical properties of a plastic. Others, called extenders, permit a large volume of a plastic to be produced with relatively little actual resin. Calcium carbonate, silica and clay are frequently used extenders. 

Formerly derived from the natural mineral lapis lazuli, ultramarine blue pigments have, for more than a century, been manufactured synthetically. The materials used in the manufacture of ultramarines are china clay (a hydrated aluminosilicate), sodium carbonate, silica, sulfur and a carbonaceous reducing material such as coal tar pitch. For the manufacture of the blue pigments, the blend of ingredients is heated to a temperature of 750 800 °C over a period of 50-100 h, and the reaction... 

The adsorption systems involve the adsorption of the pollutant on the surface of a solid. The solid can then be regenerated by passing hot gases such as steam through the system. A concentrated pollutant is then recovered hopefully it can be converted into a by-product or fuel. The most common adsorbents are activated carbon, silica gel, alumina, and molecular sieves.29... 

Porous natural clays, alumina, magnesia, activated carbon, silica, asbestos... 

S. Sampath and O. Lev, Renewable, reagentless glucose sensor based on a redox-modified enzyme and carbon-silica composite. Electroanalysis 8, 1112-1116 (1996). 

Ostwald s step rule holds that a thermodynamically unstable mineral reacts over time to form a sequence of progressively more stable minerals (e.g., Morse and Casey, 1988 Steefel and Van Cappellen, 1990 Nordeng and Sibley, 1994). The step rule is observed to operate, especially at low temperature, in a number of min-eralogic systems, including the carbonates, silica polymorphs, iron and manganese oxides, iron sulfides, phosphates, clay minerals, and zeolites. 

Extended studies demonstrated that Pt [31-73] and, to a lesser degree, Pd [107,121,127,217-225], Rh [131,226], and Ir [227] are the most suitable active metals. With one exception (colloidal Pt [111,125,228]) all these metals have been used in supported form. The most used supports are alumina, carbon, silica, and titania [56,226], and more recently zeolites [106,229-230],... 

Only with silica was the nature of the surface groups studied as extensively as with carbon. Silica, like carbon, has several polymorphs. Apart from the amorphous state, it is known to exist in numerous crystalline modifications. The most important forms are quartz, tridymite, and cristobalite. Each of these can occur in a low-temperature form and in a high-temperature form of somewhat higher symmetry. Tridymite is only stable if small amounts of alkali ions are present in the lattice 159). Ar. Weiss and Al. Weiss 160) discovered an unstable fibrous modification with the SiSj structure. Recently, a few high-pressure modifications have been synthesized keatite 161), coesite 162), and stishovite 16S). The high-pressure forms have been found in nature in impact craters of meteorites, e.g., in the Arizona crater or in the Ries near Nbrdlingen (Bavaria). 

The principal types of industrial adsorbent can be divided into amorphous and the crystalline types. The former includes activated carbon, silica gel, and activated alumina the latter includes zeolites and their aluminum phosphate, AIPO4 (or ALPO), analogs. Yang (2003) wrote that, since the invention of synthetic zeolites in 1959, adsorption has become a key separation tool in the chemical, petrochemical, and pharmaceutical industries. Adsorptive separation of different molecules can be achieved by three mechanisms equilibrium adsorption differences, diffusion kinetics differences. 

The rubber compound usually requires an inert inoiganic filler and small particle size carbon particle for reinforcement. The rubber polymers vary in inherent tensile strength from very high in the case of natural mbber to almost nonexistent for some synthetic polymers, eg, SBR. The fillers most commonly used for mbber compounds include carbon black, day, calcium carbonate, silica, talc (qv), and several other inorganic fillers. 

Most of the adsorbents used in the adsorption process are also useful to catalysis, because they can act as solid catalysts or their supports. The basic function of catalyst supports, usually porous adsorbents, is to keep the catalytically active phase in a highly dispersed state. It is obvious that the methods of preparation and characterization of adsorbents and catalysts are very similar or identical. The physical structure of catalysts is investigated by means of both adsorption methods and various instrumental techniques derived for estimating their porosity and surface area. Factors such as surface area, distribution of pore volumes, pore sizes, stability, and mechanical properties of materials used are also very important in both processes—adsorption and catalysis. Activated carbons, silica, and alumina species as well as natural amorphous aluminosilicates and zeolites are widely used as either catalyst supports or heterogeneous catalysts. From the above, the following conclusions can be easily drawn (Dabrowski, 2001) ... 

Activated carbon, silica gel, and alumina are the most popular adsorbent materials in industry due to the fact that they provide large surface areas per unit weight. Activated carbon is produced from coconut shell, wood, and bone, whereas silica gel is made of hydrated silicon dioxide. Alumina can be either mined or produced by precipitated aluminum oxide and hydroxide. In the following sections, the most important adsorbents are presented in detail. 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

CSDPF 2124 Carbon/silica dual 171 phase filler 9% silica Cabot... 

CSDPF 4210 Carbon/silica dual 154 phase filler 55% silica Cabot... 

Discussion - Some surface modification does take place on all carbon black samples. On the other hand, in the case of the oxidized gas black, its larger oxygen functionality clearly increases its capability to be modified. The case of carbon/ silica dual-phase fillers is similar. The TGA data show that the higher silica content... 

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