Hydrothermal chemistry, synthesis

I would like to describe hydrothermal quartz synthesis and commercialization as an example of synergistic interaction between synthesis and processing physical chemistry leading to better materials and more cost-effective devices. My discussions here and in the subsequent section on hydrothermal KTP will be at somewhat greater length because the role of chemists in hydrothermal synthesis and processing is perhaps not very well known and because of my familiarity with the subjects due to personal involvement. 

Due to their interesting magnetic and electronic properties, the hydrothermal chemistry of transition metal oxides has been studied to a considerable extent. It appears that iron oxides are especially amenable to hydrothermal synthesis, and tiheir chemistry is quite rich and promising. The simplest iron oxides such as magnetite and hematite can be prepared [51], as well as substantially more... 

Such reactions are discussed at appropriate points throughout the book as each individual compound is being considered. A particularly important set of reactions in this category is the synthesis of element hydrides by hydrolysis of certain sulfides (to give H2S), nitrides (to give NH3), phosphides (PH3), carbides (C Hm), borides (B Hm), etc. Useful reviews are available on hydrometallurgy (the recovery of metals by use of aqueous solutions at relatively low temperatures), hydrothermal syntheses and the use of supercritical water as a reaction medium for chemistry. 

Hu, S., Wang, A., Li, X., Wang, Y., and Lowe, H. (2010) Hydrothermal synthesis of ionic liquid [Bmim]OH-modified Ti02 nanoparticles with enhanced photocatalytic activity under visible light. Chemistry - An Asian Journal, 5 (5), 1171-1177. 

Li, X., Gao, Y., Yu, L., and Zheng, L. (2010) Template-free synthesis of CdS hollow nanospheres based on an ionic liquid assisted hydrothermal process and their application in photocatalysis. Journal of Solid State Chemistry, 183 (6), 1423-1432. 

Reflux synthesis methods in wet chemistry include techniques that normally involve relatively lower reaction temperatures compared with hydrothermal synthesis, a very... 

Sheets, W.C., Mugnier, E., Barnabe, A., Marks, T.J. and Poeppelmeier, K.R. (2006) Hydrothermal synthesis of delafossite-type oxides. Chemistry of Materials, 18, 7-20. 

Lu, C. and Shen, B. (2010) Electrochemical characteristics of LiNijy 3Coi/3Mni/302 powders prepared from microwave-hydrothermally derived precursors. Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 497, 159-165. 

Microwave hydrothermal synthesis and visible-light photocatalytic activity of y-Bi2Mo06 nanoplates. Materials Chemistry and Physics, 110, 332-336. 

Simultaneous to the understanding of some basics of hydrothermal carbonization using pure carbohydrate models, the synthesis of hydrothermal carbon materials using raw biomass was continued. It has been analyzed whether complex biomass - hy-drothermally carbonized - can also be directed to complex structural motifs with distinct surface polarities. Ideally, for this purpose one can use the structures and functionalization components already included in the biomass. We specifically selected waste biomass for material synthesis, starting products which are known to be hard to use otherwise, rich in ternary components, and applied different HTC conditions [29]. That way, one can avoid the food-raw materials competition, a prerequisite we regard as crucial for the development of a fully sustainable chemistry. 

A. Rabenau, The role of hydrothermal synthesis in preparative chemistry. Angew. Chem. Int. Ed. Engl. 24, 1026-1040 (1985). 

Chesnut, D.J., Kusnetzow, A., Birge, R.R. and Zubieta, J. (1999) Solid state coordination chemistry of the copper halide- and pseudo-halide-organoamine system, Cu-X-[(bis-2,3-(2-pyridyl) pyrazine)] (X = C1, Br, CN) Hydrothermal synthesis and structural characterization. Inoig. Chem., 38, 2663—2671. 

Qi, Y.-F., Li, Y.-G., Wang, E. et al. (2007) Hydrothermal synthesis and structures of organic-inorganic hybrid solids based on arsenic-vanadate building blocks. Journal of Coordination Chemistry, 60(13), 1403-18. 

Fowler, B. O. (1974). Hydrothermal synthesis of hydroxyl apatite. Inorganic Chemistry, 13(1) 191-214. 

Ataie, A. et al. (1995) Effect of hydrothermal synthesis environment on the particle morphology, chemistry and magnetic properties of barium hexaferrite, J. Mater. Sci., 30, 5600-6. 

The recent descriptions of the ALPO-n, SAPO-n and MeAPO-n families of microporous materials illustrate that hydrothermal syntheses can afford a wide and diverse range of four-coordinate framework structures based on nearregular tetrahedra [1,2]. As building blocks, octahedra and tetrahedra can also be combined, in various proportions, into a variety of structure types [3,4]. Reflecting the conditions used for conventional synthesis [3,4], most of these structures are condensed, with little accessible pore volume. There are, however, examples of both synthetic [5-7] and natural materials [8-11] that have microporous crystalline structures. Further, the formation chemistry of silicates and aluminosilicates [12,13] illustrates that the more open structures are generally produced under relatively mild conditions. Open octahedral-tetrahedral structures with large pore systems might therefore also be accessible under appropriate low temperature hydrothermal conditions. 

Wakihara T, Okubo T. Hydrothermal synthesis and characterization of zeolites. Chemistry Letters. 2005 34(3) 276-281. 

Adschiri T. Supercritical hydrothermal synthesis of organic-inorganic hybrid nanoparticles. Chemistry Letters. 2007 36 1188-1193. 

The literature on inorganic open-framework materials abounds in the synthesis and characterization of metal silicates, phosphates and carboxylates. Most of these materials have an organic amine as the template. In the last few years, it has been shown that anions such as sulfate, selenite and selenate can also be employed to obtain organically templated open-framework materials. This tutorial review provides an up-to-date survey of organically templated metal sulfates, selenites and selenates, prepared under hydrothermal conditions. The discussion includes one-, two-, and three-dimensional structures of these materials, many of which possess open architectures, The article should be useful to practitioners of inorganic and materials chemistry, besides students and teachers. The article serves to demonstrate how most oxy-anions can be used to build complex structures with metal-oxygen polyhedra. 

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