Silicon actions/effects

Pour 50 cc. of concentrated sulfuric acid slowly into about 1 liter of water in an evaporating dish and add 50 g. of iron nails or turnings. When the action becomes slow heat the dish until the acid is practically all neutralized, as indicated by the fact that evolution of hydrogen ceases. Filter from the undissolved iron, carbon, silicon, and other residues, using a folded filter, and evaporate to crystallization. If the solution oxidizes appreciably in the operation additional iron and acid must be added to effect reduction. Oxidation will be indicated by a change in color from bottle green to a yellowish shade of green, or by the formation of a rusty precipitate. 

It is well known that the elements in framework of zeolite molecular sieves greatly influence the properties and behaviors of these materials [1-3], The introduction of heteroatoms into the framework has become one of most active fields in study of zeolites. The investigations were mostly focused on the methods to introduce heteroatoms into the framework (for examples, hydrothermal synthesis and post-synthesis), the mechanisms for incorporations, the effect of heteroatoms on the acid-base properties and the catalytic features of modified samples [1-10]. Relatively less attention was paid to the effect of treatment process on the porous properties of samples although the incorporation of heteroatoms, especially by the so-called post-synthesis, frequently changes the distribution of pore size. Recently, we incorporated Al, Ga and B atoms into zeolites (3 by the post-synthesis in an alkaline medium named alumination, galliation and boronation, respectively. It was found that different trivalent elements inserted into the [3 framework at quite different level. The heteroatoms with unsuitable atom size and poor stability in framework were less introduced, leading to that a considerable amount of framework silicon were dissolved under the action of base and the mesopores in zeolite crystal were developed. As a typical case, the boronation of zeolites (3 and the accompanied formation of mesopores are reported in the present paper. 

Arsenic does not combine directly with carbon, silicon or boron. The reaction with metals to form definite arsenides or alloys is described no pp. 57-78. The presence of small quantities of arsenic or of its compounds in certain catalysts has a poisoning effect. The first traces added to the catalyst have the greatest effect thus the activity of 0-35 g. of platinum was reduced linearly by the addition of arsenic up to 0-7 mg., this quantity reducing the catalytic activity to 45 per cent, of its original value the addition of 10 mg. of arsenic, however, depressed the activity only to 26 per cent, of the original value.3 Vanadium catalysts are poisoned by the presence of arsenic, although the action is slow arsenic pentoxide is formed.4... 

With reference to this point of view a large amount of bioactive silicon compounds with a short duration of action was synthesized and investigated in pharmacological and toxicological effects. 

Complete cleavage of the silicon-silicon bond in permethylated polysilanes is effected by the action of excess bromine in carbon tetrachloride at room temperature. 

Such a behavior is evidence for the lability of the electronic structure of the silicon atom, because it undergoes rearrangement under the action of both chemical and geometric factors. These factors are comparable in their effect the substitution of the F atom for H brings about almost the same changes in the characteristics of the silicon atom as does the cis-trans conversion of the substituent (OH group). 

Cobalt Disilicide, CoSi2, results when cobalt is heated in the electric furnace with excess of silicon or with a mixture of copper silicide and silicon.8 It forms dark crystals, probably belonging to the cubic system density 5 3 hardness 4-5. Sulphur has no action on it, and oxygen at 1200° C. only effects a superficial oxidation. It incandesces in fluorine if gently wanned chlorine attacks it at 300° C., and bromine and iodine at dull red heat. Concentrated hydrogen... 

Other types of damage may be produced through thermomechanical effects. For example, when being annealed at 450°C a CVD aluminum film on a Si substrate is subjected to compressive thermoelastic stresses owing to the considerable difference between the thermal expansion coefficients of aluminum (a = 23 x 10 °C 0 and the silicon substrate (a. = 3.5 x 10 °C 0-When cooling, the film may therefore contract by as much as 1%. Due to the combined action... 

The rp.action described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons. Reactions of /-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons, - esters, dialkyl and aryl alkyl ethers, benzylic ethers, cyclic ethers, straight-chain and benzylic sul-fides, cyclic sulfides, amides, and certain organo-silicon compounds. ... 

The causes for roughness may be grouped into two categories, process dependent and material dependent as shown in Fig. 35 [3, 127]. The process-dependent causes are the deposition of metal or nonmetal particles (Fig. 35a,b) or bubbles (Fig. 35c) which provide masking to the deposited areas. The difference in the masking effect between a metal and a non-metal particle is that metal can actively participate in the dissolution reaction by a galvanic action. The material-dependent causes, such as preferential dissolution at lattice defects (Fig. 35d), anisotropic dissolution associated with terraces and steps (Fig. 35e), and formation of pores (Fig. 35f) are associated with the structure and property of silicon crystal. 

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