Solution-precursor-solid

Among the three polymorphs of crystalline calciiun carbonate, calcite is the equilibrium phase, most commonly adopting a rhombohedral morphology. In biologically produced minerals, however, the rhombohedral morphology is rarely adopted. Single-crystalline calcite fibers are observed most prominently in sea-urchin teeth and bacterial deposits [67-69]. They do not follow the crystallographic symmetry of calcite. Such calcite fibers were prepared in vitro via a solution-precursor-solid mechanism [70]. 

Trentler T J ef a/1997 Solution-liquid-solid growth of indium phosphide fibers from organometallic precursors elucidation of molecular and non-molecular components of the pathway J. Am. Chem. Soc. 119 2172... 

Solution-Liquid-Solid (SLS) growth of semiconductor nanowires by Wang etal. (2006). The synthesis proceeds by a solution-based catalysed growth mechanism in which nanometer-scale metallic droplets catalyse the decomposition of metallo-organic precursors and crystalline nanowire growth. 

Decomposition and reforming of methanol on Au/ZnO and Au/TiC>2 catalysts have been intensively studied using FT-IR and quadrupole mass-spectrometry.73 Unlike the Cu-ZnO system, no formate groups were observed on Au/ZnO because of the larger size of the gold atom, the same kind of solid solution precursor is not formed, and gold is therefore unable to activate the support in the same way. 

The methods most commonly used for preparing catalysts are precipitation (Section A 2 1 3) and impregnation (Section A 2 2 1 1) In both of them, the catalyti cally active material is transferred from a liquid phase, usually an aqueous solution, to a solid By contrast, other catalysts are obtained from solid precursors Solid state reactions, namely solid-to-solid reactions in which both the starting material (the catalyst precursor) and the catalyst are solids, offer convenient methods to prepare several industrial catalysts, especially those con taming two or more metallic elements or their oxides The reason of the conspicuous efficiency of these methods to prepare phases containing two or several metallic elements is due to special features of solid-state reactions, compared to liquid-to-solid or gas-to-solid reactions This section briefly outlines these peculiarities and presents the most frequent types of solid-state processes used in preparing catalysts... 

A good example of multistep solid state synthesis achieved starting from carbonate solid solution precursors is provided by the Ca2Fe2 xMnx05 series of oxides. The structures of both the end members, Ca2Fe205 and Ca2Mn205, are derived from that of the perovskite (Fig. 2). Solid solutions between the two oxides would be expected to show oxygen vacancy... 

A number of ternary and quaternary metal oxides of perovskite and related structures can be prepared by employing hydroxide, nitrate and cyanide solid solution precursors as well [20]. For example, hydroxide solid solutions of the general formula Lnj-jMj/OHJj where Ln = La or Nd and M = Al, Cr, Fe, Co or Ni) and La where (where M Ni and... 

Precursor solid solutions or compounds can be used to prepare metal alloys. Thus, Mo-W alloys have been prepared [23] by the hydrogen reduction of (NH4)6[Mo7 Metal alloys can be used as pre-... 

Because both CaC03 and MnC03 have the calcite crystal structure, it is possible to prepare a complete series of Ca-Mn carbonate solid solutions. These solid solutions are then used as precursors for subsequent reaction to Ca-Mn oxides. In this way, precursors are obtained in which the reactant cations are on the order of 10 A apart, regardless of the precursor particle size. Since solid... 

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