Compositions and crystal structures

AFt (Al20j-Fe203-tri) phases have the general constitutional formula 

Midgley and Rosaman (M57) concluded from DTA evidence that SO4 can be partly replaced by OH in the AFt phase of cement pastes. Pollman et al. (P22a) showed that the fully OH -substituted phase, C AHj, exists but is easily carbonated. Material described as a silicate analogue was later shown to have also contained (C28) but a product identified by X- 

Thaumasite, [Ca3Si(0H)g l2H20](S04)(C03) or C3SSCH,j, has a structure similar to those of the AFt phases, with Si replacing AF and S04 and groups in the channel sites (E2,E3). The octahedral coordination 

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The precise control of size, its distribution, shape, composition, and crystal structure of bimetallic nanoparticles is crucial in this field. Some strategies to prepare bimetallic nanoparticles were proposed and subsequently the corresponding methods were developed for the purpose of controlled nanoparticles. These methods enable us to find novel chemical and physical properties of bimetallic nanoparticles depending on their structures. 

Any two samples of a particular mineral, whatever their source or place of origin, have the same basic composition and characteristic crystal structure moreover, no two different minerals have identical chemical composition and crystal structure (see Textboxes 8 and 21). Quartz, for example, is a common and abundant mineral composed of silicon dioxide, a compound that occurs naturally not only as quartz but also in other crystal structures, known as polymorphs (polymorphs are minerals that have the same chemical composition but different crystal structure), some of which, listed in Table 23, have been used for a variety of purposes. The crystal structure, which is essential for the characterization of solid materials, is just one of a wide range of physical properties, that is, properties not involving chemical differences, which provide convenient criteria for characterizing and identifying solids. 

The chemical composition and crystal structure of a mineral determine its physical and optical properties. The diamond crystalline lattice structure (Fig. 4.3.2)... 

Naturally occurring iron oxide pigments are widely distributed geographically and can be found in a wide range of colours from black to reds and yellows, depending on composition and crystal structure. Ochres of many kinds and from different sources were often used in oil... 

A mineral is a naturally occurring, crystalline inorganic compound with a specific chemical composition and crystal structure. Minerals are commonly named to honor a person, to indicate the geographic area where the mineral was discovered, or to highlight some distinctive chemical, crystallographic, or physical characteristic of the substance. Each mineral sample has some obvious properties color, shape, texture, and perhaps odor or taste. However, to determine the precise composition and crystal structure necessary to accurately identify the species, one or several of the following techniques must be employed optical, x-ray diffraction, transmission electron microscopy and diffraction, and chemical and spectral analyses. 

The long history of bestowing names on minerals has provided some confusing legacies. Many mineral names end with the suffix ite, although not most of the common species no standard naming practice has ever been adopted. Occasionally different names have been applied to samples of the same mineral that differ only in color or shape, but are identical to each other in chemical composition and crystal structure. These names, usually of the common rock-forming minerals, are often encountered and are therefore accepted as synonyms or as varieties of bona fide mineral species. The Fibrous Minerals list (Appendix 1) includes synonyms. 

MMMF are synthetics that have crystalline rather than amorphous structures. Not surprizingly, early examples are reminiscent of the naturally occurring fibers synthetic chrysotile (lander and Wuhrer, 1938) and needles of amphibolelike composition and crystal structure (Shell et al., 1958). However, the bulk of the crystalline synthetic fibers, both in use and under investigation, do not have mineral equivalents therefore, we chose to use the term whiskers to distinguish crystalline man-made inorganic fibers from their natural relatives. 

Whiskers are synthetic crystalline fibers of variable size, but with diameters of usually less than 25 microns. An upper limit in diameter exists because the physical and chemical properties approach those of the bulk material as the diameter of fibrous sample increases. Since the purpose of synthesis is to take advantage of some characteristic property of the material in fibrous form, such as enhanced strength for small volume, the optimum material has a small diameter. For similar reasons the aspect ratio of useful whiskers is often well over 100. Whiskers can be single crystals, but many are polycrystalline aggregates of fibrils with preferred orientations. The compositions and crystal structures of the compounds synthesized as crystalline fibers also have the broadest possible variety (Brenner, 1958). 

Mineral A naturally occurring element or compound defined by its chemical composition and crystal structure (see chapter 2). By custom in recent times, mineral species have been given names ending in ite. Each year, about 100 new species are proposed, and usually about half are accepted by the International Mineralogical Association Commission on New Names as bona fide new species. The Glossary of Mineral Species (Fleischer, 1987) is a current source of information. Updates are published annually in the Mineralogical Record. 

Mineral group A collection of mineral species and mineral series that have common basic chemical and structural units and related compositions and crystal structures. 

In spite of the fact that the isothermal sections have been investigated for the 18 ternary systems from 448 possible 7 -d-element-Sb combinations, a considerable number of publications is devoted to the crystal structure investigations of ternary compounds that enables one to consider more thoroughly the effect of / -element and d-element interaction as well as the formation, composition and crystal structure of ternary antimonides. 

R-Mn(Cd, Zn)-Sb. Analysis of the compositions and crystal structures of the investigated 7 -3d-element-Sb systems established a vague similarity between /J-Mn-Sb and the cadmium and zinc containing systems (table 59) ... 

Microabrasion using compressed air is a modification based on sandblasting, the micropowder blasting. This process enables all types of glass, ceramics and semiconductor materials, irrespective of their chemical composition and crystal structure, to be inexpensively processed down to the micrometer scale. The micropowder blasting is a masked procedure and works quasi-parallel on the whole substrate. A powder jet drives systematically over the substrate. Material is removed at the mask openings (see Figure 2.17). 

An empirical set of effective ionic radii in oxides and fluorides, taking into account the electronic spin state and coordination of both the cation and anion, have been calculated (114). For six-coordinate Bk(III), the radii values are 0.096 nm, based on a six-coordinate oxide ion radius of 0.140 nm, and 0.110 nm, based on a six-coordinate fluoride ion radius of 0.119 nm. For eight-coordinate Bk(IV), the corresponding values are 0.093 and 0.107 nm, based on the same anion radii (114). Other self-consistent sets of trivalent and tetravalent lanthanide and actinide ionic radii, based on isomorphous series of oxides (145, 157) and fluorides (148, 157), have been published. Based on a crystal radius for Cf(III), the ionic radius of isoelectronic Bk(II) was calculated to be 0.114 nm (158). It is important to note, however, that meaningful comparisons of ionic radii can be made only if the values compared are calculated in like fashion from the same type of compound, both with respect to composition and crystal structure. 

Mineral species a mineral substance having a specific chemical formula and characteristic physical and optical properties that distinguish it from all others defined by composition and crystal structure. 

Alite is the most important constituent of all normal Portland cement clinkers, of which it constitutes 50-70%. It is tricalcium silicate (CajSiOj) modified in composition and crystal structure by incorporation of foreign ions, especially Mg ", AP and Fe. It reacts relatively quickly with water, and in normal Portland cements is the most important of the constituent phases for strength development at ages up to 28 days, it is by far the most important. 

Extrinsic dielectric loss in the microwave Ereqnency range is related to microstructure, secondary phases, and processing conditions. Intrinsic loss, however, represents the minimnm loss related to the lattice anharmonicity that can be expected for a particnlar material composition and crystal structure. It plays a... 

With these restrictions, almost 4,000 different minerals are known, with several dozen new minerals identified each year. Every mineral possesses a combination of chemical composition and crystal structure that makes it unique, and by which it is classified (grouped with similar minerals) and identified. These minerals make up the solid Earth, the moon, and even meteorites. However, only 20 or so minerals compose the bulk of Earth s crust, that is, the part of the solid Earth accessible to human beings, extending from the surface downward to a maximum depth of about 55 mi (90 km). These minerals are often called the rock-forming minerals. 

Mineral— A naturally occurring solid substance of nonbiological origin, having definite chemical composition and crystal structure. 

The second attractive feature of bimetallic nanoparticles is their magnetic property. In addition to the fact that the size control of bimetallic nanoparticles composed of noble and 3d-transition metals is easier than that of 3d-transition monometallic nanoparticles, recent technology makes it possible to control the compositions and crystal structures of such bimetallic nanoparticles. Some examples are provided in Section 11.3.2. 

Ceramic materials of the clay family occur widely in nature, and the many different forms of clay differ in both their composition and crystal structure. In general, the structure of clay is noted for its layered arrangement of aluminosilicate sheets. Upon addition... 

The Bacterial Photosynthetic Reaction Center Chemical Composition and Crystal Structure... 

Today we find shape selective catalysis 30 years old but far from mature. Synthesis and preparation of molecular sieves has expanded to over 200 combinations of chemical compositions and crystal structures. 

Filinchuk Y E, Vyon K, Meisner G P, Pinkerton F E and Balogh MP (2006), On the composition and crystal structure of the new quaternary hydride phase Li4BN3Hio, Inorg. Chem. 45, 1433-1435. 

Composition and crystal structures of stable and metastable compounds... 

Only a limited amount of information is available on the magnetic properties of ternary R-Fe-B or R-Co-B compounds having compositions and crystal structures different from Nd2Fe14B. Compounds of the composition RFe4B were studied... 

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