Aluminizing definition

It is also of interest to use MAS NMR for the study of the thermal treatment of zeolites which are not in the ammonium-exchanged form. In an X-ray study, Pluth and Smith (179) found electron density at the center of the sodalite cages in dehydrated zeolites Ca-A and Sr-A and attributed this to a partial occupancy of these sites by a four-coordinated aluminous species. No such effect was found in zeolite A exchanged with monovalent cations. Corbin et al. (180) used 27A1 MAS NMR to examine commercial samples of K-A, Na-A and (Ca,Na)-A, as received (see Fig. 41). For K-A and Na-A, only framework tetrahedral Al species were observed, with chemical shifts of 57 and 52 ppm respectively. However, in (Ca,Na)-A an additional intense resonance at 78 ppm, typical of AlfOH) but definitely not due to framework aluminum, was also found (see Fig. 41). A much weaker signal, also at 78 ppm, was detected in zeolite Sr-A its intensity increased greatly on heating the sample to 550°C. Freude et al. (183) came to very similar conclusions in their NMR study of heat-treated zeolite Ca-A. They found that maximum framework dealumination occurs at 500°C and corresponds to ac. 17% of total Al. 

Variants of preparation have been proposed [135, 248] including sintering [391] or co-electrodeposition of the precursors [138, 407], and aluminization of the surface of Ni at high temperature whose nature has a definite effect on the resulting electrocatalytic activity [408]. The main features of Raney Ni have been evaluated, including the pore size distribution and the real surface area [93, 135]. It has been found that the composition of the precursor alloys and their particle size have important influence on the adsorption properties of the resulting Raney metal, hence on its electrocatalytic properties [409]. 

By definition, peridotites contain greater than 40% olivine with lesser amounts of orthopyroxene and clinopyroxene. An aluminous phase, plagio-clase, spinel, or garnet may be present depending on the pressure of equilibration and defines the facies from which the peridotite xenolith was sampled (Figure 2). Plagioclase-peridotites are generally rare in continental xenolith suites... 

For periodic systems, an ad hoc partitioning of their absolute hardnesses into atomic contributions results in the definition of reactivity indices for such extended compounds [205] which proves useful in order to understand the chemical behavior of solid-state materials [206]. For example, the differing reactivities of various polymorphs of lithium aluminate may be rationalized in terms of their acid-base behavior [207], and the quantum-chemical explanation is in accordance with the principle of Le Chatelier. 

In the past the division of cements on the basis of phase composition was applied, as follows alite, alite-celite (Tdmebohm called brownmillerite celite), alite-aluminate and others (Fig. 1.5) [31]. Such division, although fully justified, gives few information to the user— properties of several classes are very approximate, it has no application to cements with additions and for these reasons has no practical use. However, the chemists use it frequently enough for cement kind definition, especially in the case of special cements, which are discussed in Chap. 9. 

Photograph 3-5 Large, round, slightly ragged belite blue subhedral to anhedral alite and matrix of aluminate (CjA, arrow) and ferrite. Superimposed nital over KOH produces increased clarity in matrix phase definition. (S A6615)... 

Definition Primarily sodium aluminate (hydrated), sodium phosphate (ortho), and sm. amts, of sodium carbonate and sodium silicate Properties Wh. powd. 

Both SEM/EDX and petrographic techniques were able to identify the secondary zirconia in the stones. In addition, in both stones, EDX was also able to identify the composition of the highly aluminous background material around the crystals. Not all refractories that contain zirconium also have alumina in their matrix. Therefore being able to distinguish the presence of alumina provided additional information that was used to definitively identify the source of the stones. 

In order to resolve the issues surrounding the liquid-liquid phase transition in the yttria aluminates, it is essential that these suggested indications are thoroughly corroborated. If a liquid-liquid phase transition can be definitively continued in the yttria aluminates, it would be the first conclusive demonstration of such phenomena. This would in turn further stimulate research into other possible systems exhibiting polyamorphous behaviour. 

The mechanical behavior of concrete should be viewed from the point of view of a composite material. A composite material is a three dimensional combination of at least two chemically and mechanically distinct materials with a definite interface separating the components. This multiphase material will have different properties from the original components. Concrete qualifies as such a multiphase material. Concrete is composed of hydrated cement paste (C-S-H, CH, aluminate, and ferrite-based compounds) and imhydrated cement, containing a network of a mixture of different materials. In dealing with cement paste behavior, basically it is considered that the paste consists of C-S-H and CH with a capillary system. The model of concrete is simplified by treating it as a matrix containing aggregate embedded in a matrix of cement paste. This model provides information on the mechanical properties of concrete. 

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