Synthesis and Characterization of Advanced Materials (1984) / Chapter Skim
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Panel 1: Problems Related to the Character of SACAM Research
Panel 1: Problems Related to the Character of SACAM Research
Pages 31-43
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From page 31... ...
The tradition of evaluating principal scientists primarily in terms of their individual contributions; 3. The emphasis on molecular science in undergraduate curricula, especially in chemistry, which is a key discipline in advanced materials synthesis and characterization; 4.
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From page 32... ...
The preparation and study of materials that are of interest for their mechanical properties, especially durability, present a broad range of problems in basic research. Materials such as fiber composites, ultrahard boron compounds, high-temperature alloys, and spinodal compositions deserve basic study by metallurgists, ceramists, and chemists.
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From page 33... ...
These areas, which have direct bearing on many technological needs, offer substantial challenges and opportunities for basic research in the synthesis and characterization of solids. We consider the current status of basic research in advanced materials synthesis and characterization using the following breakdown: electronic structure of solids, inorganic solids: new classes of compounds and their impact on solid-state concepts, highly conducting molecular solids, ceramics and amorphous solids, and predicting the lifetimes of materials.
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From page 34... ...
Descriptions of electronic behavior in solids are based primarily on two extreme models: the localized model applies to electrons about discrete atomic centers, and the Itinerant model applies to electrons distributed over the entire sol ido Many materials exhibit intermediate behavior, thus efforts are under way to establish ~ theoretical bridge between the extremes of localized and itinerant electron behavior. The general problem is known as the "narrow-band" problem; its solution requires the introduction in zero order of electron-lattice interactions and electron-electron correlations.
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From page 35... ...
'it" A..: .2'~.2._. '' i" 35 attempt to predict synthesis behavior or properties of materials in new configurations frequently lead to the application of more rigorous or ab initio methods; these then provide a basis for the evaluation and refinement of the empirical theories.
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From page 36... ...
Not only do these compounds imply the occurrence of new phenomena, but they also promise direct use as catalytic substrates, media for hydrogen storage, new electronic environments for nonmetals or for metal ions in electronic and magnetic applications, and as intermediates potentially important in corrosion of active and refractory metals and significant for their mechanical properties (e.g., stress corrosion cracking of zirconium by iodine)
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From page 37... ...
We expect that other new phenomena will be found that will further stimulate advances in this area. The results of work in this field have played a crucial role in developing concepts related to onedimensional band theory, charge density waves, Peierls instability effects, Coulomb interactions, incommensurate lattice effects, and effects of defects.
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From page 38... ...
These compounds have already resulted in new concepts of electronic conduction in solids, which will undoubtedly continue as new materials are prepared and studied. The discovery in Hg2.84AsF6 of a sublattice that is incommensurate with the main crystal lattice has evoked considerable theoretical interest.
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From page 39... ...
Examples of opportunities for significant new developments in ceramic materials include metallic oxides for use as electrode materials in electrochemical cells, for example, oxygen electrodes in fuel/electrolysis cells and solid-solution electrodes in high-specific-energy batteries; catalytic substrates and mixed ceramic-metal catalyst systems; high-temperature structural materials for heat engines and turbines; radiation-hardened and corrosion-resistant materials for nuclear fusion containment; photosensitized ceramics for photography and photoelectrolysis of water; controlled surface-reactive glasses and glass ceramics for replacement of bones or teeth; and tailor-made crystal chemicals for long-term encapsulation of nuclear wastes. Because of the multicomponent and polyphase nature of these materials, characterization and synthesis are often highly complex and difficult.
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From page 40... ...
Such research has been made possible by the recent development of a variety of new experimental approaches, including Fourier transform NMR, laser Raman spectroscopy, and XAFS. Such studies would lead to a better understanding of a variety of materials: amorphous solids with solutions of second and third components, for example, hydrogenated amorphous silicon and selenium hybrid crystalline materials with amorphous sublattices, such as 6-alumina with an ordered A1O lattice and disordered Na+; stabilized unusual oxidation states in invert glasses; mete stable Volubility gap materials; and microphage separated oxide and chalcogenide glasses.
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From page 41... ...
~ for the use of this new instrumentation for the characterization of surfaces and interphase boundaries, intermediate-range order, and the environment-structure interactions of ceramics and amorphous solids. The complexities that result from the polyphase and multicomponent nature of ceramic materials often make the new characterization techniques difficult to apply; however, the understanding of dynamic mechanisms in structural and atomic detail probably will yield new ceramic materials and improvements in properties and processing of existing materials.
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From page 42... ...
Our perception Gut the problems and our recommendations follow. 10 The techniques required for synthesis research are ger~erally suff iciently demanding and specialized that efforts to develop a synthesis program frequently preclude the development in the same group of the expertise required for the incisive investigation of properties or f ront-1 ine theoret ical analys is .
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From page 43... ...
We recommend that an effort be made to attract first-rate minds into the area by emphasizing the intellectually stimulating character of the problems and by better disseminating news of the field and the continuing substantial accomplishments and applications of solid-state research.
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