Silicon elemental composition

Table 3.1 gives the local elemental composition of three different tubercles from three different systems formed under different chemical treatments. At the floor of each tubercle, the concentration of chlorine and sulfur is higher than in the crust. The concentration of most crust elements, except that of iron, also decreases near the tubercle floor. The crust contains traces of treatment chemicals including zinc, phosphorus, and silicon. Tubercle 1 contains up to 40% silicon in the crust, which strongly suggests accumulation of silt by settling of particulate. 

In the design of preceramic polymers, achievement of the desired elemental composition in the ceramic obtained from them (SiC and Si3N4 in the present cases) is a major problem. For instance, in the case of polymers aimed at the production of SiC on pyrolysis, it is more usual than not to obtain solid residues after pyrolysis which, in addition to SiC, contain an excess either of free carbon or free silicon. In order to get close to the desired elemental composition, two approaches have been found useful in our research (1) The use of two comonomers in the appropriate ratio in preparation of the polymer, and (2) the use of chemical or physical combinations of two different polymers in the appropriate ratio. 

Determination of the elemental composition should be started with the M + 2 peak. Chlorine, bromine, sulfur, and silicone are easily detected due to characteristic signal multiplicity for each of these elements. There is a simple mle to check the presence of the main A + 2 elements. If the intensity of the M + 2 peak constitutes less than 3% of the intensity of the M peak, the compound does not contain chlorine, bromine, sulfur, or silicon atoms. This rule is valid for the fragment ions as well, while its applicability is confirmed by the data summarized in Table 5.4. 

Brown and coworkers (18,35) used X-ray fluorescence to analyze the elemental composition of total dusts from five cottonseed oil mills. The dusts were removed from high volume samplers by forceps followed by brushing. Samples from cleaning, delintering, hulling and baling areas were taken. A summary of the data is shown in Table XIV. Silicon is the most abundant element detected in all areas except hulling. 

Elemental composition Si 16.52%, Cl 83.48%. The compound maybe added slowly to water and decomposed. The aqueous solution may be analyzed for silicon (see Silicon). An aliquot of the solution may be measured for chloride... 

Elemental composition Si 26.97%, F 73.03%. The gas is bubbled slowly through water to decompose into silicic acid and hydrofluoric acid. HE is analyzed for fluoride ion by fluoride-selective electrode or by ion chromatography. Silicon in the aqueous solution can be measured by AA or ICP. 

Various SiC-type fibres with elemental compositions of Si-C, Si-N-C-O, Si-B-N, Si-C-0 and Si-Ti-C-0 are commercially available. These fibres are made from polymeric precursors. A multifilament SiC fibre, called Tyranno, is produced by Ube Industries, Japan [29], This fibre is made by the pyrolysis of poly(titano carbosilanes) and contains 1.5-40 titanium by weight. Another multifilament fibre is called silicon carbonitride, trade name HPZ, produced by Dow Coming Corporation, USA. 

The elemental composition is useful for characterisation of inorganic pigments and organic dyes. However, a database is needed for their identification. In all ballpoint pen inks, sulfur, copper, silicon and phosphorus are present in the elemental composition. Some samples also contain zinc, chlorine, bromine and calcium. In black inks, chromium and lead are additionally found. Samples differ with respect to the elemental composition quantitatively rather than the qualitatively. A greater variability in elemental content is observed for gel inks. 

Silicon constitutes 28% of the elemental composition of the earth s crust and is the most abundant crustal element after oxygen (47%). Silicates, compounds which contain Si04 tetrahedra in the crystal lattice, account for about one-third of all known mineral species and about 95% of the earth s crust. In view of this high abundance of silicate minerals in the near-surface crustal regime, it is perhaps not surprising that organisms (which also inhabit the near-surface environments of the earth) have found numerous ways of interacting with siliceous materials. 

There have been many measurements of the elemental composition of urban aerosols stimulated by the need for large databases in aerosol source apportionment (discussed in a later section). Table 13.2 compares concentrations in the fine and coarse fractions for various U.S. cities. The results show remarkable similarities in the order of magnitude of the concentrations from city to city for each element. Soil dust is a major component of the coarse fraction as indicated by the strong enrichment in aluminum and silicon in every city. The coarse fraction is much less active chemically both with respect to its mechanisms of formation and as a site for reaction, compared to the fine fraction discussed next. 

An appropriate choice of reference elements is required, as well as a tabulation of elemental compositions of source materials. Elements that are useful as reference elements for crustal material include silicon, aluminum,... 

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