Cubic hydrothermal synthesis

Hydrothermal Method. Iron [Fe(III)], barium, and the dopants are precipitated as their hydroxides and reacted with an excess of sodium hydroxide solution (up to 6 mol/L) at 250-350 °C in an autoclave. This is generally followed by an annealing treatment at 750-800°C to obtain products with the desired magnetic properties. Many variations of the process have been described [5.36]-[5.40], the earliest report being from 1969 [5.41], In later processes, hydrothermal synthesis is followed by coating with cubic ferrites, a process resembling the cobalt modification of iron oxides (see Section 5.1.2). The object is to increase the saturation magnetization of the material [5.42]-[5.44],... 

Microwave-assisted hydrothermal methods can also be used for preparing ceramics. This involves placing a sealed vessel containing the reagents into the micro-wave cavity. One example of the use of microwave-assisted hydrothermal synthesis involves the preparation of cubic-shaped In(OH)3 particles from a mixed aqueous solution of InClj and urea. These particles were then used to probe the kinetics of the thermal decomposition of ln(OH)3 to cubic-In203. 

The carried-out theoretical analysis is confirmed by the works of the scientists from New Jersey University and California University in Berkeley who experimentally found the self-organization of the cubic microparticles of plumbum zirconate-titanate (PZT) [28] the ordered groups of cubic micro-crystals from PZT obtained by hydrothermal synthesis formed a fiat layer of particles on the air-water interface, where the particle occupied the more stable position corresponding to position 2-3 in Figure 9.15. 

Synthesis of zeolites from polysilicates has been examined for two reasons. First, the particle sizes and shapes can be very different from those formed by conventional synthesis. For instance, the solid-state transformation of kanemite gels yields distinctly smaller silicalite particles that are more cubic in shape than by using hydrothermal synthesis. A second reason is the search of zeolite systems that can be shaped without needing binding additives. A possibility would be the transformation of raw materials into a zeolite after being shaped, as illustrated by Shimizu et al. [232]. 

Yin, C.Y., Mnakshi, M., Ralph, D.E., Jiang, Z.T., Xie, Z., Guo, H. Hydrothermal synthesis of cubic a-Fe203 microparticles using glycine Surface characterization, reaction mechtmism tmd electrochemical activity. J. Alloy. Compd. 509,9821-9825 (2011)... 

In the present study low temperature (373 K) hydrothermal technique has been employed for the synthesis of Na8[GaSi04]6(C104)2, containing perchlorate as a guest anion. The product obtained was characterized by x-ray powder diffraction, IR and Raman spectroscopy. The product crystallizes with the cubic sodalite in the space... 

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