Solid Sis

At 577°C the eutectic reaction takes place the liquid decomposes into solid (Al) mixed with solid Si, but on a finer scale than before (bottom of Fig. A1.32). This intimate mixture of secondary (Al) with secondary Si is the eutectic structure. 

Figure 1 (a) Energy level diagram of solid Si, including the density of states of the... 

In contrast to the relative inertness of solid Si to gaseous and liquid reagents, molten Si is an extremely reactive material it forms alloys or... 

Figure 3.12 The integral molar Gibbs energy of liquid Ge-Si at 1500 K with pure liquid Ge and solid Si as standard states. Data are taken from reference [4].

Direct formation of fj-FeSiy A preparation method for 3-FeSi2 was proposed by Oikawa and Ozaki (2002) to activate the interfacial reaction between Fe and Si powders through a heat process in a sealed ampoule. The mechanism of the reaction process was investigated by using sputtered Fe films on Si substrate (and on sapphire substrates). It was found that Si vapour reacts, in sealed ampoules, with solid Fe, and it is saturated to form e-FeSi. Reaction of FeSi with solid Si then takes place to form FeSi2. It was suggested that this process has a potential interest in the activation of reactions with Si of other refractory metals. 

We need to convert solid Si particles to SiCU by reacting them with CI2 gas at 300°C in a... 

Hexazidostannate-Sodium Salt. Na2Sn(N3)6, probably Sn(N3)4 -2NaN3 mw416.85, N 60.50% white solid, si sol in eth or benz. Prepd by heating a tetrahydrofuran soln of SnCl4 NaN3. Hydrolyzes in moist air. Explodes on boiling over an open flame... 

Use the data of Appendix C to answer the following questions. (Assume that ACp is negligible—but would this affect your answer ) (a) At what temperature does CVD of silicon from SiH4 become thermodynamically feasible (b) Would CVD of solid Si (mp 1410 °C) from SiCU (g) be feasible under any circumstances, assuming that the liberated chlorine could be tolerated ... 

These compds are liquids or low melting solids, si sol in w and sol in common org solvents... 

When there are many species involved, the problem becomes much more complex and species partial pressures have to be calculated by approximate numerical techniques. As an illustration, consider the Si-CI-H system3 with only eight gaseous species (H2, HCI, SiH4, SiH3CI, SiH2Cl2, SiHCU, SiCI4 and Si Cl ) allowed, where the deposition of solid Si on the surface of the container must be allowed for. 

Figure 3 shows the X-ray diffraction patterns observed with the sodium aluminosilicate solid (Si/Al - 1.33) in NaOH. All the data were collected after - eight hours (within a span of 30 minutes) of heating and are plotted on the same intensity scale, so they can be compared directly. The yield of total solids in the pure water system was very small (<100 mg) and no crystals were evident. At 10% alcohol, mostly zeolite A and small diffraction peaks due to zeolite X crystals are observed. With 25% alcohol, the crystallization is complete for zeolite X. Fifty percent alcohol shows peaks due to zeolites A, X and cancrinite, whereas at 75% alcohol, cancrinite is the only product. 

A measure of the attraction of two solids Si and S2 across an interface is the reversible work of adhesion This quantity is given by the relationship of Dupre... 

The explosion limit dropped to lower laser fluence upon increasing the pressure of the (fluoromethyl)silanes. Below the explosion limit, chemical changes of the (fluoromethyl)silanes could only be detected after irradiation with as many as 10 laser pulses. The reaction products revealed an almost quantitative reduction of the CF bond and afforded the gaseous fluorosilanes Sip4 and Sip3H, the hydrocarbons CH4 and C2H2, and different solid Si/C/F/H materials. 

The results of thermal analysis show that the temperature of the solid state transformation in MoFe is higher —5°C.) in UFe mixtures than it is in pure MoFe. An increase of the transformation temperature of a component A in mixture with another component B indicates that component B is more soluble in the low temperature form of component A (13). It is concluded, on the basis of the observed raising of the transformation temperature (not on the basis of a chemical analysis of solids Si and S3), that UFe is more soluble in the low temperature form of MoFe than in the high temperature form. 

Young s equation can also be used to determine wetting. The derivation of this venerable expression is based upon a consideration of the three-phase equilibrium that exists at a partially wet surface. The three equilibria present are chosen to be liquid droplets (or regions of thick film) in equilibrium with the vapor (/v), regions of thin adsorption in equilibrium with the solid si, because the thin layer is adsorbed on the solid), and regions of thick film in equilibrium with the solid (sv). 

Change in Ci selectivity, as a function of time on stream for the 3 catalysts studied artd for pure HZSM-5 (A- solid, Si/AI = 14). 

As a part of solar grade Si production, it is necessary to cast the material after refining. A substantial refining effect can be attained, if planar front is achieved during the solidification. The solubility of many impurities is higher in liquid Si than in solid Si. In directional solidification with a planar front, there will be a clearly defined interface observed between solid and liquid Si. 

During solidification of a Al-Si melt, the first phase that precipitated is solid Si. Most of the impurity elements have higher solubility in the liquid alloy than in solid Si and can, therefore, effectively be removed by the solvent refining method. The Si will of course be saturated with Al, which has to be removed at a later stage. 

Over the past decades, several papers were published regarding purification of Si using molten aluminium as solvent [13-16]. Yoshikawa and Morita [17] have estimated the segregation coefficient for various elements between solid Si and the Si-Al melt (Table 1.3). 

Table 1.3. Segregation ratio between solid Si and Si-Al melt...

The liquid Si-based solution, here abbreviated as 1 , is described using a simple polynomial expression based on a substitutional solution with random mixing. The same model is employed for the diamond-structured Si-rich solid phase, denoted as s. The Gibbs energies of the liquid and solid Si-based phases are given by the following equation ... 

The assessed thermodynamic properties of liquid and solid Si-based solution can be directly applied to evaluate the influence of third element on the solubility of the main impurity in silicon melt. For example, the effect of the impurity element on the solubility of C in pure Si melt can be evaluated by the following equation ... 

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