Materials synthesis and processing

G.E. Duvall, Shock Compression Chemistry in Materials Synthesis and Processing, National Materials Advisory Board NMAB-414, National Academy Press, Washington, DC, 1984. 

In the words of a recent paper on MSE education (Flemings and Cahn 2000), chemistry departments have historically been interested in individual atoms and molecules, but increasingly they are turning to condensed phases . A report by the National Research Council (of the USA) in 1985 highlighted the opportunities for chemists in the materials field, and this was complemented by the NRC s later analysis (MSE 1989) which, inter alia, called for much increased emphasis on materials synthesis and processing. As a direct consequence of this recommendation, the National Science Foundation (of the USA) soon afterwards issued a formal call for research proposals in materials synthesis and processing (Lapporte 1995), and by that time it can be said that materials chemistry had well and truly arrived, in the... 

Porous samples would appear on the surface to provide such a complex and uncontrolled local environment for deformation of solids that they would be of little interest in scientific investigations. Indeed, the principal interest in their responses is technologically driven they are very effective attenuators of wave profiles and much of materials synthesis and processing is carried out on powders. Duvall [86D01] has summarized the difficulty of work with porous powder samples as follows ... 

Shock-compression science, which has developed and matured since its inception in 1955. has never before been documented in book form. Over this period, shock-compression research has provided numerous major contributions to scientific and industrial technology. As a result, our knowledge of geophysics, planetary physics, and astrophysics has substantially improved, and shock processes have become standard industrial methods in materials synthesis and processing. Characterizations of shock-compressed matter have been broadened and enriched with involvements of the fields of physics, electrical engineering, solid mechanics, metallurgy, geophysics, and materials science... 

Besides the classical search for linear, one-dimensional electronically active materials, synthetic approaches are now also focussed on the generation and characterization of two- and three-dimensional structures, especially shape-persistent molecules with a well-defined size and geometry on a nanometer-scale. It is therefore timely and adequate to extend concepts of materials synthesis and processing to meet the needs defined by nanochcmislry since the latter is now emerging as a subdiscipline of material sciences. 

The Intimate Connection Between Materials Synthesis and Processing... 

It is particularly important to study process phenomena under dynamic (rather than static) conditions. Most current analytical techniques are designed to determine the initial and final states of a material or process. Instmments must be designed for the analysis of materials processing in real time, so that the cmcial chemical reactions in materials synthesis and processing can be monitored as they occur. Recent advances in nuclear magnetic resonance and laser probes indicate valuable lines of development for new techniques and comparable instmmentation for the study of interfaces, complex hquids, microstmctures, and hierarchical assemblies of materials. Instmmentation needs for the study of microstmctured materials are discussed in Chapter 9. 

A.W. Weimer, Carbide, Nitride and Boride Materials, Synthesis and Processing, 1st Ed. Chapman Hall, London, 1997. 

Materials Synthesis and Processing Research at the Interfaces of Materials Research, Engineering, Chemistry, and Biology NSF 91—75, National Science Foundation Washington, DC, 1991. 

Figure 3.35 Classification of chemical vapor infiltration processes. From Carbide, Nitride, and Boride Materials Synthesis and Processing, A. W. Weimer, ed. p. 563. Copyright 1997 by Chapman Hall, London, UK, with kind permission of Kluwer Academic Publishers.

Novel synthesis often unlocks the door to novel materials, phenomena and applications. Materials processing in the laboratory and its transfer to the factory is the key to high quality, high yield, low cost materials. Indeed materials synthesis and processing were identified in the recent National Research Council "Materials Science and Engineering Study"(7) as key to U.S. industrial competitiveness in the 1990 s. 

Frequently we define a porous medium as a solid material that contains voids and pores. The notion of pore requires some observations for an accurate description and characterization. If we consider the connection between two faces of a porous body we can have opened and closed or blind pores between these two faces we can have pores which are not interconnected or with simple or multiple connections with respect to other pores placed in their neighborhood. In terms of manufacturing a porous solid, certain pores can be obtained without special preparation of the raw materials whereas designed pores require special material synthesis and processing technology. We frequently characterize a porous structure by simplified models (Darcy s law model for example) where parameters such as volumetric pore fraction, mean pore size or distribution of pore radius are obtained experimentally. Some porous synthetic structures such as zeolites have an apparently random internal arrangement where we can easily identify one or more cavities the connection between these cavities gives a trajectory for the flow inside the porous body (see Fig. 4.30). 

---