Silicones dust control

Dust control is a major problem in corrosion control by silicone polymers. Dust particles which may bridge, or meerly lay upon conductors will absorb moisture diffusing through the silicone and result in a localized site of corrosion. We found this to be the case in a number of our early saunples. Following the results of this study, all of our encapsulated assemblies will be cleaned and encapsulated in a clean room which is serviced by HEPA filters. 

Another prominent application of FBCVD is in the manufacture of high purity silicon. Silicon seed particles are fluidized in a bed, in which a mixture of silane and hydrogen is introduced. Decomposition of silane on the silicon particles results in the formation of a pure silicon film. It is of importance to control the process in order to minimize homogeneous nucleation of silicon dust by appropriately designing gas distribution system and controlling process parameters.7,8... 

X-ray fluorescence can be used to analyse all types of samples. Its applications are numerous, whether in research and development or in quality control of production. Initially, X-ray fluorescence was used in industries that treat metals of primary fusion or alloys and, more generally, in the mineral industry (for use one ceramics, cements, steel, glass, etc.). Because of the ease of use of common X-ray fluorescence instruments, its scope of application has expanded into other areas the photographic industry and semi-conductors (for impurity control in silicon chips), the petroleum industry, geology, paper mills, gas analyses (such as nitrogen), toxicology and environmental applications (dust, fumes from combustion, heavy metals, and dangerous materials in waste such as Pb, As, Cr, Cd, etc.). 

However, emission control dust or sludge from ferrochromium and ferrochromium-silicon production is listed as hazardous waste by EPA (1988b). The processed wastes from several chromium chemical industries are designated as hazardous wastes as well (EPA 1981), and disposal of process wastes is regulated by the EPA. Land filling appears to be the most important method for the disposal of chromium wastes generated by chemical industries. Of the total chromium released in the environment by chemical industries, 82.3% is released on land. An equally large amount of chromium waste is transferred off-site (see Section 5.2). It is anticipated that most of this off-site waste will be disposed of in landfills after proper treatment. It is important to convert chromium wastes into forms of chromium... 

The performance targets, such as reactivity of the reaction mixture, selectivity, extension of a production campaign or reproducibility, are controlled by quite a number of parameters. The most important parameters are temperature, pressure, catalyst and promoters, poisons and inhibitors, silicon composition and structure, particle size distribution of solids, dust removal from fluidized-bed reactor, homogeneity of fluidized-bed and the purity of chloromethane. 

The silicone film responsible for the nonspreading was not removed by repeated washing in benzene. It appears desirable to use a silicone of relatively high molecular weight to reduce volatility and to decrease the rate of lateral flow. The film should be kept below 300 A.to reduce lateral flow as well as to minimize dust collection by the treated surface. The utilization of thicker resin-type films for the control of oil spreading is described in another report from this laboratory [3],... 

The initial alloy coatings deposited on to polymers showed a tendency to exhibit pinhole defects most of which have since been attributed to the presence of dust particles. Polymer films have a propensity to accumulate an electrostatic charge that attracts fine particles. As an alternative, interim method to address the issue of defects in the Pd-Cu alloy membrane films, films were deposited onto smooth, silicon wafers. Particulate and other contaminants can be more readily controlled (i.e., minimized) on a silicon surface, in comparison to plastic, and is considerably smoother than plastic. In experiments using magnetron sputtering, we were able to produce defect-free Pd-Cu films on 12 in. diameter silicon and 4 in. square glass plates. A released film, 4 p.m thick, is shown in Fig. 11.4. Films as thin as 0.7 p.m have been produced in this way. 

The inorganic silicates form a class of binders which are either dissolved in water or solvent and which react with water to give an inorganic film. They are prepared by fusing a mixture of sand or silicon oxide and typically a mixture of potassiiun or sodium carbonate. The main use of the silicate binders is in conjunction with a high loading zinc dust as a corrosion control primer. They can be classified in three groups ... 

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