31 No. 3
Teaching High-Temperature Materials Chemistry at University (IUPAC Technical Report)
by Giovanni Balducci, Andrea Ciccioli, Giovanni de Maria, Fiqiri Hoda, and Gerd M. Rosenblatt
Pure and Applied Chemistry, 2009
Vol. 81, No. 2, pp. 299–338
Over the last four to five decades, high-temperature materials chemistry (HTMC) has flourished and expanded as a challenging area of scientific and applied research, spurred by a growing demand for new inorganic materials (such as neoceramics, intermetallics, superalloys) able to withstand extreme thermal and chemical environments. Such high-temperature environments are ubiquitous in combustion, nuclear energy, and space technologies and are also encountered in new, more efficient processes for the synthesis, recycling, and refining of materials. The advancement of HTMC has seen a synergic interchange between basic and applied research, with the application of thermodynamics, kinetics, and a variety of physical, chemical, and modeling techniques. This fertile field of interdisciplinary research has its origins in modern high-temperature chemistry, which led to an understanding of the fundamental ways in which chemical properties and behaviors differ at high temperatures from those encountered at more moderate temperatures.
As systematic knowledge of the chemical and physical behavior of materials at high temperatures accumulated—accompanying progress in the production, control, and measurement of temperatures up to 3 000 degrees K and beyond, and by the extension of the high-temperature regime to most measurement and diagnostic techniques—the unusual high-temperature behavior of materials’ properties and reactivity emerged, often dramatically different from those expected near to room temperature. Accepted generalizations in chemical behavior at ordinary temperatures are no longer valid at high temperature: The high-temperature reactivity of materials is ruled by thermodynamic properties rather than kinetics; condensed phase–gas phase processes become increasingly important in the number and complexity of chemical species; reactions tend to be entropy rather than enthalpy, controlled with increasing temperature; and unusual new compounds and molecular species appear with unfamiliar oxidation states stabilized by the high-temperature conditions. Also, stoichiometric solids extend their range of homogeneity, and often unstable, nonstoichiometric phases are stabilized in the high-temperature domain. This chemical behavior influences the physical properties of materials and renders invalid predictions based on extrapolation from room-temperature properties.
Despite the important role played by HTMC in modern advanced technology and the considerable progress by research in the field, HTMC topics are rarely addressed in chemistry and materials science programs at the university level, and no textbook exists that is specifically devoted to HTMC topics. It is therefore important to make efforts to fill this educational gap and to introduce students of chemistry and materials science to the concepts underlying the behavior of materials and chemical bonding at high temperatures. IUPAC project 2000-024-2-200 (Teaching High-Temperature Materials Chemistry at University), under the auspices of the IUPAC Inorganic Chemistry Division, aimed to fulfill this function. The final report of the project task group is a resource book on the properties and behavior of high-temperature materials for those teaching materials science or physical or inorganic chemistry at various levels. The report includes an introduction and seven sections covering historical background, chemical behavior of condensed phase–gas phase systems at high temperatures, basic concepts of materials thermodynamics, experimental techniques, use of thermodynamic data and modeling, vaporization and decomposition processes, and gas-solid reactions. The ninth section covers more specific topics, mostly concerning applications of high-temperature materials and processes. Each recommended topic is accompanied by a bibliography of helpful references, a short introduction or explanation that includes areas of application, and some relevant teaching suggestions. An extensive annotated resource bibliography is an appendix to the report.
last modified 28 April 2009.
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