Material synthesis

Various microstructures and configurations are possible for useful solid materials, including bulk single crystals and epitaxial layers, polycrystalline articles or thin films with controlled grain size (including micro- and nanocrystalline 

Traditional solid-state synthesis involves the direct reaction of stoichiometric quantities of pure elements and precursors in the solid state, at relatively high temperatures (ca. 1,000 °C). Briefly, reactants are measured out in a specific ratio, ground together, pressed into a pellet, and heated in order to facilitate interdiffusion and compound formation. The products are often in powdery and multiphase form, and prolonged annealing is necessary in order to manufacture larger crystals and pure end-products. In this manner, thermodynamically stable products under the reaction conditions are obtained, while rational design of desired products is limited, as little, if any, control is possible over the formation of metastable intermediates.  

Low-temperature solid-state synthesis is preferred in most cases, where appropriate, for obvious reasons such as energy and cost economy and process safety or for critical concerns regarding the accessibility of compounds that are stable only at low temperatures or non-equilibrium phases, i.e., compounds thermodynamically unstable with respect to the obtained phase (e.g., a ternary instead of binary phase). The use of low-temperature eutectics as solvents for the reactants, hydrothermal growth 

Metal chalcogenides, apart from their technological significance in industrial applications, have played an important role in the development of new synthetic concepts and methods in the area of solid-state chemistry. A great example is alkali metal intercalation into TiS2 (Chap. 6) first reported three decades ago, which highlighted the then-novel synthetic approach called soft chemistry chimie douce). This low-temperature process allows for new compounds to be obtained while retaining the structural framework of the precursor. Related to this concept is the 

As a result of the advances in catalyst discovery for aqueous ethylene polymerization, silica-polyethylene nancomposites have been prepared with structures that vary with changing catalyst structure and silica composition. It is likely that many more advances in the area of high-tech composites with potential biological and nanotechnology applications will be made in the next few years through aqueous polymerization processes. In addition to free radical polymerizations and catalytic polymerizations, it should be noted that oxidative polymerizations can also be performed in aqueous media to yield conducting polymers. Recently, this has been used to prepare polypyrrole-coated latex particles that are expected to be interesting synthetic mimics for micrometeorites. 

Silver nanoparticles have also been prepared in aqueous solution using Capsicum annum L. extract. It is thought in this example that Ag(i) is reduced to Ag(0) by proteins within the natural extract and that these proteins also act to stabilize the particles. The size of the nanoparticles was found to increase with reaction time 5 h, 10 2 nm 9 h, 25 3 nm 13 h, 40 5 nm. It should be noted that gold and silver nanoparticles have potential pharmaceutical and biomedical applications, and it is therefore highly desirable to use natural stabilizing agents (starch, glucose or plant extracts) and biocompatible solvents such as water. 

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Storhoff J J and Mirkin C A 1999 Programmed materials synthesis with DNA Chem. Rev. 99 1849... 

Table 4. Techniques for Commercial Gemstone Material Synthesis...

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

In other materials synthesis applications, the utilization of the strong bonding of fullerenes to clean silicon surfaces, has led to the application of a monolayer... 

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... 

United States at least. The huge field of inorganic materials synthesis is not further discussed in this chapter, but the interested reader will benefit from reading a survey entitled Inorganic materials synthesis learning from case studies (Roy 1996). 

Materials chemistry is now served by a whole range of journals, ranging from the venerable Journal of Solid-State Chemistry and Materials Researeh Bulletin (already mentioned) to Materials Chemistry and Physies (which, interestingly, now incorporates The International Journal of the Chinese Soeiety for Materials Seienee... which appears to be distinct from the Chinese MRS) and Journal of Materials Chemistry (published by the RSC in London) - also Chemistry of Materials, published by the ACS. In France, Annales de Chimie Seienee des Materiaux is an offshoot of a journal originally founded by Lavoisier in 1789 (shortly before he lost his head). Journal of Materials Synthesis and Proeessing is an interesting periodical with somewhat narrower focus. 

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 ... 

Alternately (and showing the versatility of the impact technique), impac-tors can be designed to achieve structured loading. The pillow technique of Barker used a graded shock impedance to achieve a small amplitude shock followed by a slowly increasing pressure [88C04]. Materials synthesis studies... 

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... 

These two research areas share the common characteristic of involving inorganic solids in the combustion process. Catalytic combustion research focuses on using the solid to facilitate the oxidation of well-known fuels such as hydrogen and methane. Materials synthesis research focuses on using combustion as a means to react the solids either with each other or a gas, such as nitrogen (which in this case acts as an oxidizer), to make new solid materials. 

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. 

State-of-the-art polymer LEDs now have operating lifetimes and luminous efficiencies suitable for a wide variety of commercial applications. Furthermore, it is clear that the fundamental limits of polymer LED performance have not yet been reached. With improvements in material synthesis, fabrication techniques, and device design, significant increases in LED performance are to be expected. These improvements should lead to the extensive use of polymer LEDs in future display applications. 

In the field of materials synthesis, T8[CH = CH2]8 has been used to prepare three-dimensional (meso)porous polymers with high surface area via reactions with TgHg or T8[OSiMe2H]8 in the presence of a Pt catalyst as described in Section Xu et al. prepared a POSS-based monomer by reaction... 

Table 19 Compounds Ts[OSiMe2R]8 for hybrid material synthesis obtained from T8[OSiMe2H]s... 

Combining materials synthesis and materials processing. These areas have traditionally been considered separate research areas. Future advances in materials require a fusion of these topics in research and practice. 

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. 

Neirynck, J. M., Yang, G. R., Murarka, S. P., et al., Low Dielectric Constant Materials-Synthesis and Applications in Microelectronics, Materials Research Society Symposium Proceedings, Vol. 381,1995,pp. 229-234. 

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

Modeling, Simulation and Control of Chemical Reaction Systems Nano Materials Synthesis and Application Novel Reactors and Processes Polymer Reaction Engineering... 

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