Controlling grain size

The ammonium perchlorate solution is spray-dried to the desired crystal size at air temperatures below 150°C and crystal temperatures of about 110°C. This procedure provides a pure product having a controlled grain size. Prior mechanical and thermal treatment affects the isothermal... 

Various microstructures and configurations are possible for useful solid materials, including bulk single crystals and epitaxial layers, polycrystalline articles or thin films with controlled grain size (including micro- and nanocrystalline... 

However, for modern electronic circuits, it is important to have a product of controlled grain size and the precursor method is one way to achieve this. (Another way is the sol-gel method which has also been applied to this material.) The precursor used is an oxalate. The first step in the preparation is to prepare an oxo-oxalate of titanium. Excess oxalic acid solution is added to titanium butoxide which initially hydrolyses to give a precipitate which then redissolves in the excess oxalic acid. 

Le et al. (2006) employed "amorphous citrate" gel method to prepare single phase ceramic powders of LaNiOs with controlled grain size by thermal annealing. The target product was obtained at 650 °C with particle sizes from 30 to 65 ran at annealing temperatures from 650 to 750 °C, while the crystalline sized varied from 10 to 15 ran. Accordingly, a wide... 

Varying the rate of cooling (quenching) of the metal controls grain size and grain patterns. 

The polymer pyrolysis technology has several advantages over the conventional methods and some of these include the ability to purify precursors at low cost lower processing temperature versatility of precursors to form complex shapes, films, fibers, etc the opportunity to prepare novel materials such as ceramic-ceramic and ceramic-metal composites and modify chemical, physical, optical, mechanical, and electrical properties and at least some ability to control grain size, microstructure, and crystallinity, thereby allowing densification at temperature lower than traditional processing temperatures. 

Popov KI, Pavlovic MG (1993) Electrodeposition of metal powdtas with controlled grain size and morphology. In White RE, Bockris JO M, Cratway BE (eds) Modem aspects of electrochemistry, vol 24. Plenum Press, New York, pp 299-391... 

The microstructure refinement from the modified thermomechanical treatment is responsible for enhancement of tensile strength and ductility by 18% and 25% respectively. Simultaneously, the stress rupture life as well as ductility is enhanced by virtue of controlled grain size and uniform carbide distribution brought about by the thermo-mechanical treatment. 

Because of their influence on the boundary mobility, the use of fine second-phase particles and, in particular, the use of dopants form two of the most effective approaches for controlling grain size during solid-state sintering. Prior to considering their practical use, we examine the mechanism by which they influence Mh. 

Solid solution additives or dopants provide an effective approach for the fabrication, by sintering, of ceramics with high densities and controlled grain size, but as discussed in Chapter 9, the role of the dopant is not well understood. This gap in understanding limits the applicability of the approach. The major roles of the dopant and the parameters that control the effectiveness of a dopant in a given role form important issues in the solid solution additive approach. 

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