Self propagating high temperature synthesis

Combustion synthesis also termed self-propagating high-temperature synthesis (SHS) is a strong exothermic chemical reaction that leads to the formation of new thermodynamically stable materials with structures often not obtained under different reaction conditions. In some way or the other, both Goldschmidt and Matignon (Chapter 2) can be considered to be the first to have apphed this concept successfully to synthesize materials. However, the term SHS in today s perception is linked mainly to the work of Russian Chemist Alexander G. Merzhanov ( 1931) who has been working on this concept since the 1960s [1, 2]. 

In the SHS, the reaction occurs in a narrow zone (designated the combustion wave) of high temperature that travels at a rate ranging from a few milhmetres per second to several ten metres per second. 

Now metal/fluorocarbon reactions beside their use in flares and igniters constitute a versatile toolbox for the synthesis of new materials. Depending on the metallic substrate, reactions of fluorocarbons with metals and their alloys and compounds yield materials such as 

In accordance with the general simplified reactions, where w describes the maximum valency of the metal and omega describes the maximum valency of the element X. 

Metal-Fluorocarhon Based Energetic Materials, First Edition. Emst-Christian Koch. 

Some whiskers have a hollow, tubular structure none have metal droplets at their tips. This and other factors suggest [75] that whisker growth does not proceed by a VLS, but by a VS transformation whereby the ammonium fluoride catalyst plays an important role in the growth process. 

---

International Journal of Self-propagating High-temperature Synthesis, Allerton Press, New York, from 1992. 

Intermetallic compound formation may be observed as the result from the diffusion across an interface between the two solids. The transient formation of a liquid phase may aid the synthesis and densification processes. A further aid to the reaction speed and completeness may come from the non-negligible volatility of the component(s). An important factor influencing the feasibility of the reactions between mixed powders is represented by the heat of formation of the desired alloy the reaction will be easier if it is more exothermic. Heat must generally be supplied to start the reaction but then an exothermic reaction can become self-sustaining. Such reactions are also known as combustion synthesis, reactive synthesis, self-propagating high-temperature synthesis. 

Figure 6.12. Self-propagating high-temperature synthesis of NiAl (Fan etal. 2001). The temperature- time profile observed during the passage of a combustion wave is shown.

TABLE 9.5 Compounds Produced by Self-Propagating, High-Temperature Synthesis (SHS)a... 

SIDMT. Metal Hydrides Manufacturing. Coals Increase the Hydrogen content in the Metallic Hydrides. Synthesize Metallic Hydrides by conventional techniques and by Self-propagation High Temperature Synthesis. 

Combustion synthesis, also known as self-propagating high temperature synthesis,... 

In addition to conventional sintering, reactive powder processing, also called combustion synthesis or self-propagating high-temperature synthesis (SHS), can be used if the target compounds can be synthezised from the starting powder mixture (Stangle and Miyamoto, 1995). This process comprises a rapid and exothermic chemical reaction to simultaneously synthesize some or all of the constituent phases in the FGM and density the component. 

Self-Propagating High-Temperature Synthesis (SHS) Conventional methods of synthesizing materials via solid reactions involve... 

---