Hydrated-type materials

Wiebeke, M., and Hoebbel, D. (1992) Structural Links between ZeoUte-lype and Clathrate Hydrate-type Materials Synthesis and Crystal Structure of... 

A comparison of boehmite with other raw materials is included in Table 6. In this table the soda and lithia contents of compositions based on a range of raw materials and the resultant properties are detailed. The level of / "-alumina was always higher with the hydrate-type raw material the hydrothermally prepared raw materials gave the highest content of / " -alumina. 

The earliest of these studies was on PbS. PbS can have either p- or n-type conductivity, although CD PbS is usually p-type. Based on the belief that the p-type conductivity may be due to alkali metal cations from the deposition solution, an alkali metal—free deposition, using lead acetate, thiourea, and hydrazine hydrate was used [33]. While initially n-type, the film converted to p-type in air. Attempts to stabilize the p-type material by adding trivalent cations to the deposition solution were unsuccessful. However, deposition of the PbS on a trivalent metal, such as Al, did stabilize the n-PbS, at least for a time. In this way, p-n junctions were made (the PbS close to the trivalent metal was n-type, while the rest of the film was p-type). Photovoltages up to 100 mV were obtained from these junctions at room temperature and almost 300 mV at low temperatures (90 K). 

We have previously analyzed the photo-assisted corrosion of n-type materials during photoanode applications (8). This work suggested that the H+ ions produced during the electrolysis reaction underwent desorption from the photoanode surface much less readily than would be suspected for fully hydrated H+ ions, and is summarized in Appendix I. 

The principle of ion exchange is based on the fact that some solid materials exchange ions when in contact with a solution. The most commonly used materials are the resin ion exchangers. These have replaced most of the older aluminosilicate or hydrated oxide materials, and are available in a number of types and particle sizes. 

For SAPO-11 type materials it was observed (29) that the as synthesized SYN (with di-n propylamine template) the calcined (CAL), hydrated (WAT) and cyclohexane (CYC) saturated samples exhibit different XRD patterns as shown in fig.5. As for other molecular sieves it was important to determine if silicon was incorporated into the AIPO4 framework or not and subsequently if basic or acidic properties were induced depending if Si " was substituting Al or P ", respectively. The X-ray diffraction pattern analysis allowed us to show that A1 and P atoms are strictly alternate and that the material crystallizes in the non centro symmetric Ima2 space group with a = 1.867 (2), b= 1.3373 (2) and c = 0.84220 (9) nm (33). The channels along c axis are elliptical and are occupied by the di-n propylamine molecules. Disordered domains were also evidenced presumably... 

The best starting materials are active oxides, possibly produced in situ, preferably from hydroxides, hydrated oxides or carbonates. In some cases it may be necessary to start with a very well-defined oxide modification in order to obtain an active catalyst [29]. Occasionally, the required starting oxides are produced by thermal decomposition of nitrates. However, the activity of such products is not very high and their maximum specific surface does not exceed a few m. /g. For this reason, nitrate decomposition Is Important only for the production of supported catalysts (see below). Oxides calcined at a high temperature, as well as spinel-type materials, should be avoided, since their reduction times tend to be extremely long [2]. 

Type of Flexible Waterproofing Material Figure 8.1 Elongation of hydrated-type flexible waterproofing materials. 

Figure 8.2 Polymer-cement ratio vs. elongation, adhesion and water permeability of hydrated-type flexible waterproofing materials. ( 1993, ASTM, reprinted with permission.)...

Increasing Demand for Hydrated-Type Liquid- plied Membrane Waterproofing Materials (in Japanese), The Bosui Journal, 21(10) 43-46 (Nov. 1990)... 

Pocket Plate Electrode. This is the same type of electrode used in pocket plate nickel-cadmium and nickel-iron batteries. Electrodes are prepared by loading nickel hydroxide hydrate active material and a conductive additive (graphite and/or nickel flake) into tubular flat pockets which are then assembled into electrodes. Little interest currently exists in using this type of electrode in nickel-zinc cells since modern cells attempt to utilize lightweight electrode construction. 

Soils and clays, in general, when calcined give off adsorbed, interlayer, and hydrated types of water. These effects produce endothermal peaks or loss of weight in DTA and TG, respectively. The endothermal peaks are followed by exothermal peaks that are caused by re-crystalliza-tion. Although many types of clay minerals such as montmorillonite, illite, and some shales show these effects, they are not suitable as pozzolans in concrete. Metakaolin, formed by heating kaolinite, seems to be the most suitable additive material for cement. Heating of kaolinite involves removal of adsorbed water at about 100°C and dehydroxylation at above 600°C, followed by the formation of metakaolinite, an almost amorphous product. The sequence of reactions is as follows ... 

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