Powder controlled crystalline, precipitation

The oxide and the sulfide are more stable than the corresponding Cu11 compounds at high temperatures. Copper(I) oxide (Cu20) is made as a yellow powder by controlled reduction of an alkaline solution of a Cu2+ salt with hydrazine or, as red crystals, by thermal decomposition of CuO. A yellow hydroxide is precipitated from the metastable Cu+ solution mentioned previously. Copper(I) sulfide (Cu2S) is a black crystalline solid prepared by heating copper and sulfur in the absence of air. 

The introduction to the section Silica Gels and Powders by W. Welsh constitutes an introduction to the study of silica powders. Detailed accounts of the synthetic processes and applications of fumed silicas, silica gels, and precipitated silicas are given by Ferch (Chapter 24) and Patterson (Chapter 32). For scientists, silica powders are of special interest because they offer the opportunity of working with very pure systems with well-controlled ultimate particle size and specific surface area. One of the most important aspects of silica powders is their adsorptive properties. These properties are the subject of the work by Kenny and Sing (Chapter 25), which includes the crystalline zeolitic silica known as silicalite. 

If the level of supersaturation is carefully controlled, it is often possible to avoid crystallization when a water-soluble salt of a weak acid is precipitated with a base, or when a water-soluble salt of a weak base is precipitated with an acid. When crystalline iopanoic acid is dissolved in 0.1 N NaOH, and 0.1 N HCI is added, an amorphous powder is precipitated [43]. A similar phenomenon is observed in the case of the precipitation of piretanide [155]. Another example in this genre is the... 

When creating supersaturation levels sufficient to induce particle formation, precipitation of sparingly soluble salts and sol-gel processes are viewed differently. Precipitation normally involves mixing a cation solution with a precipitant solution. For example, consider preparation of an oxalate precursor to a CoO- and MnO-doped ZnO powder. In this process, the Zn, Mn, and Co are coprecipitated with controlled stoichiometry and the precipitate is calcined to the oxide. To form the oxalate, a state of supersaturation is created by mixing an aqueous solution of the metal nitrates or chlorides with an oxalate precipitant solution. The system is supersaturated with respect to the different metal oxalate phases and a crystalline coprecipitate forms. Depending on precipitation conditions (pH, concentrations, temperature, etc.), different metal complexes are present in solution. The form and concentration of these complexes determine the phase, morphology, and particle size distribution of the resulting precipitate. 

State of the atomized powders during preparation and consolidation in a well-controlled atmosphere. Furthermore, considering that no distinct contrast revealing the precipitation of a crystalline phase is seen in the cross-sectional structure, extrusion at 373 K is suitable enough to keep the nonequilibrium phase in the as-quenched state. The absence of a crystalline phase in the extruded bulk alloy has been confirmed by X-ray diffraction and differential scaiming calorimetric analyses for the bulk MggsYioCus alloy extruded at 373 K. 

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