Solvothermal and hydrothermal processes: the main physico-chemical factors involved and new trends

Hydro- and solvothermal processes play an important role in the different scientific domains involving either basic or applied research. During the last years, such processes have been strongly developed, in particular with the elaboration of nanocrystallites. This review article presents a brief history of their development, an analysis of the key factors governing such processes, and the recent trends

Solvothermal processes : definition, key factors governing the involved chemical reactions and new trends

Solvothermal processes are defined, and the different domains of applications are described. The main physico-chemical factors playing a key role in such processes are then analyzed. The trends characterizing the current development of solvothermal processes are outlined

High pressure and chemical bonding in materials chemistry

Materials chemistry under high pressures is an important research area opening new routes for stabilizing novel materials or original structures with different compositions (oxides, oxoborates, nitrides, nitridophosphates, sulfides,. . .). Due to the varieties of chemical compositions and structures involved, high pressure technology is also an important tool for improving the investigations on chemical bonding and consequently the induced physico-chemical properties. Two different approaches can be described: (i) the chemical bond is pre-existing and in such a case, high pressures lead to structural transformations, (ii) the chemical bond does not exist and high pressures are able to help the synthesis of novel materials. In both cases the condensation effect (ΔV < 0 between precursors and the final product) is the general rule. In addition, through the improvement of the reactivity, high pressures can lead to materials that are not reachable through other chemical routes

Solvothermal processes : definition, key factors governing the involved chemical reactions and new trends

Solvothermal processes are defined, and the different domains of applications are described. The main physico-chemical factors playing a key role in such processes are then analyzed. The trends characterizing the current development of solvothermal processes are outlined

Solvothermal and hydrothermal processes: the main physico-chemical factors involved and new trends

Hydro- and solvothermal processes play an important role in the different scientific domains involving either basic or applied research. During the last years, such processes have been strongly developed, in particular with the elaboration of nanocrystallites. This review article presents a brief history of their development, an analysis of the key factors governing such processes, and the recent trends

How high pressure can be involved in chemical bonding

In a first approach, between two atoms A and B, two different types of chemical bonds can be possibly involved : (i) a strong with electronic change, (ii) a weak involving electrostatic or Van der Waals interactions..

Solvothermal processes: new trends in Materials Chemistry

Solvothermal processes are characterized by mild temperature conditions. The use of high pressure appears important for enhancing chemical reactivity. The roles of the solvent and the reagents in the mechanisms governing the formation of a specific material are underlined. Some new directions of research, at the interface with others scientific domains, are discussed

Un siècle de hautes pressions : développements technologiques et scientifiques

A century of high pressure: technological and scientific developments. This paper is devoted to the development of high pressures during approximately one century and the main scientific domains concerned by such a development. Roughly three main periods have been considered: (i) the early period at the beginning of XXth century (1900 → 1970), the second period (1970 → 2005) taking into account some important technical developments (the high pressure vessels with a large volume, the diamond anvil cell associated with the laser heating...), and a prospective concerning, on the basis of recent results, the possible developments during the next 10 years. The early period was mainly characterized by some industrial problems: the improvement of the mechanical properties of alloys and consequently the requirement for performant cutting and machining tools (leading to the diamond synthesis), the synthesis of ammonia (initiated both by the development of explosives and the requirement of fertilisers), the preservation of foods (correlated to a new organization of the Society), the elaboration of single crystals characterized by specific physical properties with functional properties for the development of some industrial sectors (telecommunications, computer science...). The more recent period (1970–2005) has been characterized by the development of new performant tools able to improve the development of scientific domains (diamond-anvil-cell and Geosciences, Belt-type, multi-anvils and toroïd equipments and the Chemistry of Materials, high pressure vessels and Food-Science...). During these last years roughly three main tendances have been observed: (i) the investigation of researches at extreme (P, T) conditions, (ii) the improvement of researches involving mild (P, T) conditions mainly in liquid phase (hydrothermal and solvothermal synthesis), (iii) the development of high pressures in Biology and Biotechnology. During the next years the extension of high pressure level and also the development of the next scientific domains would improve research involving different planets. In parallel the development of chemical reactions in mild P, T conditions in a liquid phase would allow to prepare new hybrid nano-systems at the interface between inorganic and organic chemistry, inorganic and biological chemistry or new supramolecular systems. The applications of high pressures in Biotechnology – due in particular to the low energy conveyed by pressure – would lead to new research domains or industrial processes involving either the inactivation of pathogen microorganisms with the development of new vaccines or the domain of the proteins..

High pressure and chemical bonding in materials chemistry

Materials chemistry under high pressures is an important research area opening new routes for stabilizing novel materials or original structures with different compositions (oxides, oxoborates, nitrides, nitridophosphates, sulfides,. . .). Due to the varieties of chemical compositions and structures involved, high pressure technology is also an important tool for improving the investigations on chemical bonding and consequently the induced physico-chemical properties. Two different approaches can be described: (i) the chemical bond is pre-existing and in such a case, high pressures lead to structural transformations, (ii) the chemical bond does not exist and high pressures are able to help the synthesis of novel materials. In both cases the condensation effect (ΔV < 0 between precursors and the final product) is the general rule. In addition, through the improvement of the reactivity, high pressures can lead to materials that are not reachable through other chemical routes

Solvothermal processes: a route to the stabilization of new materials

Solvothermal processes are a powerful route for preparing materials. Different examples are given, either in water as solvent or in non-aqueous solvents such as alcohols, liquid NH 3 and NH 2 NH 2 . This quite new approach for materials synthesis will probably be strongly developed in the near future provided that the role of solvents in the supercritical conditions can be better understood from the chemical reactivity point of view