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doi: 10.1007/bf02749913pmid: N/A
Supramolecular synthesis is being increasingly employed in materials design. In this article, the design of porous solids is discussed as a case study. Examples from recent work in the areas of open-framework inorganic materials, mesoporous solids and organic porous solids are presented to illustrate this important aspect of materials chemistry.
Chidambaram, R; Sharma, Surinder M
doi: 10.1007/bf02749914pmid: N/A
There are many fascinating areas of research related to the response of materials at high static and dynamic pressures. The experimental range of compression achievable in the condensed state under pressure is much larger than the range of expansion achievable before melting by variation of temperature. The advances in the experimental techniques have been matched by the developments in the first principles theories and in computational resources. Studies of equation of state and of phase transitions in materials have helped to increase our basic understanding of the condensed state of matter, with possible applications in many fields, including nuclear technology. The current status of high pressure research is briefly reviewed, taking examples mainly from the work of our group at Trombay.
Chidambaram, R; Sharma, Surinder
doi: 10.1007/BF02749914pmid: N/A
There are many fascinating areas of research related to the response of materials at high static and dynamic pressures. The experimental range of compression achievable in the condensed state under pressure is much larger than the range of expansion achievable before melting by variation of temperature. The advances in the experimental techniques have been matched by the developments in the first principles theories and in computational resources. Studies of equation of state and of phase transitions in materials have helped to increase our basic understanding of the condensed state of matter, with possible applications in many fields, including nuclear technology. The current status of high pressure research is briefly reviewed, taking examples mainly from the work of our group at Trombay.
doi: 10.1007/BF02749915pmid: N/A
The most common method used for synthesizing inorganic solids is the so-called ‘ceramic method’ which involves synthesizing at elevated temperatures and leads to thermodynamically stable phases. This method has a serious limitation because many inorganic solids of current interest are rather metastable and consequently their preparation requires low temperature methods. In this article, we have reported some methods of synthesis which also include methods that belong to soft-chemistry routes. The selected examples presented in this paper are: (i) the intercalation and or deintercalation of oxygen in oxides by electrochemical oxidation or reduction in aqueous or nonaqueous solutions, (ii) the use of chemical agents such as NO 2 or borohydrides for obtaining oxides with tunneled and lamellar structures, (iii) a multistage synthesis processing for intercalating, in layered oxygenated materials, anionic species and acrylic monomers and polymers, (iv) the supercritical fluid processing for preparing nitrides, carbon-nitrides, lamellar oxides and oxy-(hydroxy-) fluorides, and (v) the mechanical alloying for synthesizing new Mg-based binary intermetallics.
doi: 10.1007/bf02749915pmid: N/A
The most common method used for synthesizing inorganic solids is the so-called ‘ceramic method’ which involves synthesizing at elevated temperatures and leads to thermodynamically stable phases. This method has a serious limitation because many inorganic solids of current interest are rather metastable and consequently their preparation requires low temperature methods. In this article, we have reported some methods of synthesis which also include methods that belong to soft-chemistry routes. The selected examples presented in this paper are: (i) the intercalation and or deintercalation of oxygen in oxides by electrochemical oxidation or reduction in aqueous or nonaqueous solutions, (ii) the use of chemical agents such as NO2 or borohydrides for obtaining oxides with tunneled and lamellar structures, (iii) a multistage synthesis processing for intercalating, in layered oxygenated materials, anionic species and acrylic monomers and polymers, (iv) the supercritical fluid processing for preparing nitrides, carbon-nitrides, lamellar oxides and oxy-(hydroxy-) fluorides, and (v) the mechanical alloying for synthesizing new Mg-based binary intermetallics.
doi: 10.1007/BF02749916pmid: N/A
High-energy mechanical working of ordered alloys has the twin effects of refining the grain size to the nano-range, and reducing (or even eliminating) the long-range order (LRO). In this way, states of order can be achieved that cannot be obtained by heat-teatment. Subsequent annealing will re-establish the order. Some experiments in this field, notably with Ni 3 Al, will be outlined.
doi: 10.1007/bf02749916pmid: N/A
High-energy mechanical working of ordered alloys has the twin effects of refining the grain size to the nano-range, and reducing (or even eliminating) the long-range order (LRO). In this way, states of order can be achieved that cannot be obtained by heat-teatment. Subsequent annealing will re-establish the order. Some experiments in this field, notably with Ni3Al, will be outlined.
doi: 10.1007/bf02749917pmid: N/A
The alloying behaviour in nanometer (nm)-sized particles was studied by transmission electron microscopy (TEM). When solute atoms are vapour-deposited onto nm-sized particles at room temperature, rapid dissolution of solute atoms into particles occur, and solid solution or compound particles are successfully formed. Such spontaneous alloying occurs even between nm-sized particles of different elements. Our results can be summarized as: (i) spontaneous alloying takes place via a solid-state process, (ii) spontaneous alloying becomes more difficult with increasing particle size, (iii) spontaneous alloying is not an artifact originating from the temperature rise in particles which might be induced by heat of condensation and (iv) remarkable enhancement of solubility is observed in nm-sized compound particles.
Lang, C; Shechtman, D; Gonzalez, E
doi: 10.1007/BF02749918pmid: N/A
Quasicrystalline (QC) materials are of interest not only because of their unique structure, but also because they exhibit unusual properties which are potentially useful in industrial applications. In the present study a range of aluminium-based QC alloys, in the form of plasma-sprayed coatings, has been produced and evaluated. For the first time the influence of heat treatment on the structure and properties of these coatings has been systematically investigated. Of the nine QC coatings investigated, those of the Al-Cu-Fe-Cr system and the Al-Pd-Mn system showed the most promising combination of good hardness with low coefficient of friction.
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