Silicon-aluminum ordering

Klinowski, J., Thomas, J. M., Fyfe, C. A. and Parzaile, V. E. (1981) Application of Magic Angle Spinning Silicon-29 Nuclear Magnetic Resonance. Evidence for Two Different Kinds of Silicon-Aluminum Ordering in Zeolite Structures, J. Phys. Chem., 85, 2590-2594. 

Another characteristic of 2 1 clays is isomorphous substitution, where iso means same and morphous means shape. During the formation of clay, cations other than aluminum and silicon become incorporated into the structure. In order for this to work and still ensure a stable clay, the cation must be about the same size as either aluminum or silicon, hence the term isomorphous. There are a limited number of cations that satisfy this requirement. For silicon, aluminum as Al3+ and iron as Fe3+ will tit without causing too much distortion of the clay structure. For aluminum, iron as Fe3+, magnesium as Mg2+, zinc as Zn2+, and iron as Fe2+ will fit without causing too much structural distortion (see Figure 3.4). 

When 1,2-dichlorobenzene in hydrogen-saturated deionized water was exposed to a slurry of palladium catalyst (1%) at room temperature, benzene formed via the intermediate chlorobenzene. The reaction rate decreased in the order of MCM-41 (mesoporous oxide having a silicon aluminum ratio of 35) > alumina > Y (dealuminated zeolite having a silicon aluminum ratio of 15). It appeared the reaction rate was directly proportional to the surface area of the support catalyst used (Schiith and Reinhard, 1997). 

The results are shown in Tables I, II, and III. The major elements in coal and in the derived products are, in order of decreasing abundance in the materials studied, silicon, aluminum, calcium, iron, and magnesium. With the minor and trace elements, the detection limits vary with the ash content of each type of material about 1-5 ppm for the coals and residues and 1-3 ppb for the oils. The elements thallium, bismuth, germanium, and gallium were sought but not detected. 

In order to substantiate further the mineral matter content information received from the x-ray diffraction analyses, several coke pellets were scanned for sulfur, iron, calcium, silicon, aluminum and potassium in the electron microprobe. Electron probe results showed abundant silicon, suggesting quartz (Si02), considerable aluminum, suggesting kaolinite [Ali>Sii Oii(OH)4] and, relatively speaking, little iron, sulfur, calcium, or potassium. 

Silicon and Aluminum Ordering of Zeolites Interpretation of Silicon-29 NMR Data for Faujasite and ZK4... 

Transition metal carbides can be used as diffusion barriers like transition metal nitrides in multilayer metallization schemes for integrated circuits. Layers on the order of lOOnm are applied and are produced by sputtering methods. The high chemical stability of these transition metal carbides, especially those of group 4, are exploited to prevent interaction of metal or component layers such as silicon, aluminum, and silicides upon thermal load in production processes. This load would cause electrical or even structural deterioration of the multilayer packages. 

We have been investigating the nature of these novel solids in order to ascertain information which may lead to new catalytic applications. Two important questions to be addressed are (i) what are the local T-atom (tetrahedral atom) arrangements (silicon, aluminum, and phosphorus), and (ii) what is the elemental homogeneity Questions (i) has been addressed mainly through the use of solid-state NMR while the answer to question (ii) is most appropriately obtained from surface to bulk elemental analyses. 

The NZ was supplied by Nemetali , Vranjska Banja, Serbia Montenegro. The mineralogical composition of the natural zeolite is 90% clinoptiolite and the rest is mordenite and haylandrite. The chemical analysis of the natural zeolite shows that the oxides of silicon, aluminum, calcium and iron are the main constituents while other oxides are present in trace amounts (Table 1). Prior to the experiments, the NZ was dried at 300°C for 48 h in order to remove any traces of moisture or other constituents. The properties of the adsorbents used are listed in Table 2. 

At project Inception, approx. 1975, the accumulative cost of encapsulation materials In popular use, such as RTV silicones, aluminum panels, etc., greatly exceeded 14.00 per m2. Accordingly, the FSA project established a group called the "Environmental Isolation Task", to Identify and/or develop as necessary new materials, and new material technologies in order to achieve the cost and life goal. 

The earth metals and the earths themselves were in the same place, according to their similarities, hut one had not successfiilly ordered them. It is true that they form boron and silicon, aluminum and beryllium, yttrium and cerium, which are special groups, hut each of them lacked in the third member. The magnesium stayed alone and the zirconium belongs to the titanium and the tin. 

Steel is aluminized (i.e., coated with aluminum) by hot dipping or spraying and, to a lesser extent, by cementation. Molten baths of aluminum for hot dipping usually contain dissolved silicon in order to retard formation of a brittle alloy layer. Hot-dipped coatings are used for oxidation resistance at moderately elevated temperatures, such as for oven construction and for automobile mufflers. They are unaffected by temperatures up to 480°C (900°F). At still higher temperatures, the coatings become refractory, but continue to be protective up to about 680 °C (1250 °F) [34]. 

Values for the abundance of the element in the earth s crust and in sea are reported in many publicahons and different values are quoted for the same element. This book uses values from CRC Handbook of Chemistry and Physics [1.2]. These values are collected in Tables 1.6a and 1.6b, and the elements are ranked in order of abundance in the earth s crust. Oxygen, silicon, aluminum, iron and calcium are the most abundant elements and are ranked 1-5. Two elements with the same abundance, as for instance gallium and nitrogen, have both been given the ranking 34-35. For technetium, promethium, francium and astahne no abundance values are available and all four are ranked 89-92. 

Calibration of an arc or spark source is linear over three orders of magnitude, and detection limits are good, often within the region of a few micrograms per gram for elements such as vanadium, aluminum, silicon, and phosphorus. Furthermore, the nature of the matrix material composing the bulk of the sample appears to have little effect on the accuracy of measurement. 

Refining. In order to produce silicon that meets the requirements of the chemical, ie, siUcones, and primary aluminum markets, the siUcon produced in the arc furnace requires further purification. The quaUty of siUcon for the chemical siUcones industry is critical with respect to the levels of aluminum and calcium present, and the primary aluminum grade of siUcon requires low levels of calcium, iron, and phosphoms. The impurity requirements for the secondary aluminum market are not as stringent, so long as the siUcon content is >98.5%. 

---