Oxide Powder Synthesis

The hydrolysis reaction usually occurs at room temperature and dehydration occurs below 600°C, resulting in the formation of very fine ceramic particles, that is, 2-5 nm [22]. This method has been successfully used to make high-purity submicrometer-sized oxides from several metal alkoxides [23,24]. Focus on multicomponent oxide powder synthesis through the two-step hydrolysis and dehydration of metal alkoxides constitutes the remainder of this chapter. 

Keywords Oxide Powder Synthesis/Organic Steric Entrapment/Doped Lanthanum... 

Figure 1. Flow chart for mixed oxide powder synthesis by the organic, steric entrapment...

Gulgun M.A., Kriven W.M. A simple solution polymerizaion route for oxide powder synthesis. Ceramic transactions, 1995, v. 62, p.57-66... 

T. Tani, K. Takatori, N. Watanabe, N. Kamiya Metal oxide powder synthesis by emulsion combustion method, Material Research Society 13(5), 1099-1102 (1998). 

Segadaes AM. Oxide powder synthesis by the combustion route. Eur Ceram News Lett... 

The corresponding preparation methods may be grouped into two main streams based upon the gas-solid and liquid-solid nature of the transformations. Gas-solid transformation methodsare broadly used in the context of ultrafme oxide powder synthesis. Liquid-solid transformation methods follow a bottom-up approach. A number of methods have been developed, among which some generally used are discussed below ... 

Co-reduction of mixed oxides. A two-stage preparation of an alloy through the synthesis of a suitable precursor may be exemplified by the chemical route used by Jena et al. (2004) in the preparation of a copper-nickel alloy. The alloy was prepared from an aqueous solution of the nitrates of copper and nickel dissolved in a minimum amount of water and allowed to dehydrate and decompose to their oxides at a temperature around 350°C for an hour. Samples of the mixed oxide powders thus formed were subjected to reduction by pure hydrogen. The reduced powder (apparently containing partially alloyed metals) was sintered at 1000°C. The effect of temperature (250-450°C) on the reduction of the co-formed oxides was studied. 

One approach to making such powders is the sol-gel method, in which a metal oxide powder is synthesized from a metal alkoxide, a compound derived from a metal and an alcohol. In the synthesis of titania (Ti02) from titanium ethoxide, Ti(OCH2CH3)4, for example, the Ti(OCH2CH3)4 starting material is made by the reaction of titanium(IV) chloride with ethanol and ammonia in a benzene solution ... 

K. Song, J. Kim, Synthesis of high surface area tin (Sn) oxide powders via water-in-oil microemulsions, Powder Technol. 103 (3) (2000) 268-272. 

Contrary to the above mentioned technologies, which are based on arc plasma furnaces, a radiofrequency (RF) plasma system can process fine powders without granulation in a continuous operation. This possibility, together with the advantageous features of the thermal plasmas mentioned above, offer great perspectives for the synthesis of special ceramic powders such as spinel ferrites [5]. The RF plasma treatment produces nanosized metal and/or oxide powders depending on the parameters of processing. In this paper application of an RF thermal plasma system for the treat-... 

CHEMICAL SYNTHESIS OF MIXED OXIDE POWDERS FOR SOLID OXIDE FUEL CELL (SOFC) ELECTROLYTE AND ELECTRODES... 

Every organic carrier material has exhibited a different performance for the synthesis of mixed oxide powders. Moreover, the performance of one organic carrier material varied for each type of mixed oxide powder... 

This chapter discusses the fluid-solid and solid-solid reactions used to produce ceramic powders. The first aspect of this discussion is the spontaneity of a particular reaction for a given temperature and atmosphere. Thermodynamics is used to determine whether a reaction is spontaneous. The thermod3mamics of the thermal decomposition of minerals and metal salts, oxidation reactions, reduction reactions, and nitridation reactions is discussed because these are often used for ceramic powder synthesis. After a discussion of thermodynamics, the kinetics of reaction is given to determine the time necessary to complete the reaction. Reaction kinetics are discussed in terms of the various rate determining steps of mass and heat transfer, as well as surface reaction. After this discussion of reaction kinetics, a brief discussion of the types of equipment used for the synthesis of ceramic powders is presented. Finally, the kinetics of solid—solid interdiffusion is discussed. 

A classic example of a solid—fluid ceramic powder synthesis reaction is that of calcination and dehydration of natural or synthetic raw materials. Calcination reactions are common for the production of many oxides from carbonates, hydrates, sulfates, nitrates, acetates, oxalates, citrates, and so forth. In general, the reactions produce an oxide and a volatile gaseous reaction product, such as CO2, SOg, or HgO. The most extensively studied reactions of this type are the decompositions of magnesium hydroxide, magnesium carbonate, and calcium carbonate. Depending on the particular conditions of time, temperature, ambient pressure of CO2, relative humidity, particle size, and so on, the process may be controlled by a surface reaction, gas diffusion to the reacting... 

The reduction of oxides in reducing atmospheres is also an important industrial fluid—solid reaction that produces a powder. Because these types of reactions can affect ceramic powder synthesis, they are included in this chapter. However, these reduction reactions are frequently used to produce metal powders and are not often used to produce ceramic powders. These reduction reaction can, however, be the first step in a sequence of steps to produce carbide and nitride powders. Several examples of fluid—solid reduction reactions are... 

THE SYNTHESIS AND THERMAL STABILITY STUDY OF MESOPOROUS CERIUM (IV) OXIDE POWDERS... 

Exclusion of water and oxygen is the primary criterion in rare earth oxysulfide synthesis procedures. This is generally analogous to the case of rare earth sulfides. The industry synthesis technology depends on sulfurizing rare earth oxide powders via solid-state reactions. For instance, the classical sulfide fusion method follows the schematic reaction ... 

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