Black ceramics

Pyrolysis of the white solids obtained in these KH-catalyze< dehydrocyclodimerization reactions (under argon from 50-950°C) produced black ceramic residues, with the exception of the 1 1 THF ammonolysis-derived solid which left a brown residue. The ceramic yields were excellent (all greater than or equal to 82%, with the highest being 88%). 

Further experiments showed that the "combined" polymers may be converted to black ceramic fibers. Pyrolysis of pressed bars of the "combined" polymer to 1000°C gave a black product of irregular shape (74-76% ceramic yield). In other experiments, SiC powder was dispersed in toluene containing 20% by weight of the "combined" polymer. The solution was evaporated and the residue, a fine powder of SiC with the "combined" polymer binder, was pressed into bars and pyrolyzed at 1000°C. A ceramic bar (6% weight loss, slightly shrunk in size) was obtained. 

Currently, besides catering to the pharmaceutical industry, Luid energy milling is employed for size reduction of agricultural chemicals, carbon black, ceramics, cosmetics, pigments, precious metals, propellants, resins, and toner materials. 

Ebonex electrodes — When Ti02 is placed into an atmosphere of hydrogen at a temperature higher than 1000 °C partial reduction and formation of Ti02 x phases occurs. Of particular interest is Ti407, a black ceramic material of high electrical conductivity and chemical inertness. This material, Ebonex, has been formed into ceramic electrodes for applications as -+ dimension-ally stable anode [ii] or - cathode [iii]. 

Fibers could be drawn from concentrated syrups of these products in toluene. The drawn fibers could not directly be converted to ceramic fibers, because they melted on being heated, and a cure step was required to render them infusible. The required cure could be accomplished by UV irradiation of the fibers. Following this treatment, pyrolysis of the fibers in a stream of argon gave black ceramic fibers, and pyrolysis in a stream of ammonia gave white ceramic fibers. 

On pyrolysis under argon to 1000 °C, the polysilazanes prepared from the systems just discussed gave black ceramic products whose elemental analysis could be explained in terms of the following formal compositions (in weight percent) 62-65% Si3N4, 15-20% SiC, and 14-16% free carbon. In general, the white materials obtained on pyrolysis in a stream of ammonia contained less than 1% carbon. 

Summary The stepwise synthesis of the polycarbosilanes (Cl2SiCH2CH2) (5) and (H2SiCH2CH2)n (6) are described. On addition of catalytical amounts of transition metal complexes to polymer 6 dehydrogenation occurs and a further crosslinked carbosilane (8) is obtained by formation of new silicon-silicon bonds. Pyrolysis of carbosilane 8 produces a black ceramic material, containing P-SiC together with carbon. The ceramic yield after pyrolysis of 8 is approximately four times the yield obtained when 6 is employed as the starting material. From polymeric 8 preceramic fibers are accessible subsequent pyrolysis yields ceramic fibers. Moreover, the carbosilane 8 can be utilized as a binder for ceramic powders. 

In a similar way, the wipe can be used on a glossy surface (such as black ceramic tiles) or on a mirror surface to test for streaking. The testing would be done in the manner previously outlined. 

The trapping of absorbing particles was performed using irregular black ceramic particles and CuO particles dispersed in kerosene. We have also trapped slightly absorbing latex spheres which were in clumps so that their rotation could be more easily observed. 

Soap scum tends to be built up as fine layers of calcium or magnesium fatty acids on the bathroom surfaces, gradually dulling the surface and serving as a matrix for trapping other soils, such as sloughed skin cells, dirt, lint, and mildew. Many bathroom surfaces are fabricated to be shiny, and the soap scum, which is white or cream colored, tends to become apparent when the shine is dulled. As the more popular bathroom colors are pale or white, it is hard to see the soap scum itself on the surface, owing to the lack of color contrast. Soap scum is much more apparent on dark surfaces (like black ceramic tiles) or on transparent surfaces (like transparent shower doors). It is therefore somewhat hard for the consumer to determine that the soap scum has been completely removed from the surface except by the reappearance of the native shine of the surfaces. 

The earliest HTCC structures were produced using 92% alumina [17]. Today, this composition remains a "workhorse" material. As shown in Table 6.1, there is a variety of AI2O3 formulations in commercial production. Manufacturers tend to maintain some secrecy as to the specific ingredients however, in addition to purity, the color of alumina ceramics is a distinguishing characteristic. Kyocera s "black" ceramic (90%) is actually a deep-red composition resulting from the inclusion of a small amount of Cr203. Other additives (W, Mo, and Ti) have also been included in HTCC to darken the ceramic. This opacification has no functional benefit although it eliminates the visibility of subsurface metallization. Ceramic vendors introduced this... 

The reflectance spectra for highly absorbing or black ceramics contain more noise than do other spectra due to the much lower signal-to-noise ratio. In black ceramics, the higher power Xe lamp (300 W) tends to compensate for the small amount of reflected light. Several other techniques can be utilized in order to improve the signal-to-noise ratio. One is to open the slits (widen the bandpass) of the monochromator in order to let more light... 

A reasonable practice is to match the spectral characteristics of the reference material to that of the spedmen being measured, such that there is not a very large difference in reflected light between the specimen and the reference. If a black ceramic is being measured, then it is generally helpful to use a black reference material. Carbon black powder is a possible reference. For other various neutral (gray) ceramics and for colored ceramics, the Spectra-lon materials are also available as calibrated references having a variety of spectral characteristics. 

Spot plate A plate, typically in the range of 3 X 4" made of white or black ceramic or glass. Spot plates have depressions in which the sample is placed and color test reagents are added. The design and color helps with interpretation of colors produced. 

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