Ceramic particle , thermal shock resistance

Nieto, M.I., Martinez, R., Mazerolles, L., Baudin, C. (2004), Improvement in the thermal shock resistance of alumina through the addition of submicron-sized aluminium nitride particles , J. Eur. Ceram. Soc., 24, 2293-2301. 

Sbaizero, O., Pezzotti, G. (2003), Influence of molybdenum particles on thermal shock resistance of alumina matrix ceramics , Mater. Sci. Eng., A343, 273-281. 

The important properties of aluminum oxide ceramics are their high temperature stability (melting point of AI2O3 2050°C), their good thermal conductivity, their high electrical resistivity and their high chemical resistance. Their mediocre thermal shock resistance is a disadvantage. All these properties are dependent upon the chemical purity and particle size distribution of the oxide powder and the density, structure and pore size di.stribution of the ceramic. 

Chapters 8 and 9 consider the mechanical properties of rubber- and ceramic-particle toughened-epoxy materials. The importance of rubber cavitation is highlighted in Chapter 8. It is well known that this mechanism can relieve the high degree of triaxiality at a crack tip in the material and enable subsequent plastic hole growth of the epoxy resin, which is a major toughening mechanism. We return to rigid particles in Chapter 9, which examines their use to increase the thermal shock resistance of epoxy resins. 

The effects of ceramic particles and filler content on the thermal shock behavior of toughened epoxy resins have been studied. Resins filled with stiff and strong particles, such as silicon nitride and silicon carbide, show high thermal shock resistance, and the effect of filler content is remarkable. At higher volume fractions (Vf > 40%), the thermal shock resistance of these composites reaches 140 K, whereas that of neat resin is about 90 K. The highest thermal shock resistance is obtained with silicon nitride. The thermal shock resistance of silica-filled composites also increases with increasing filler content, but above 30% of volume fraction it comes close to a certain value. On the contrary, in alumina-filled resin, the thermal shock resistance shows a decrease with increasing filler content. 

Any ceramic particles may be used. In-fact, due to its cost effectiveness, as well as environmental impact, ash from power plants is a very attractive candidate. Preliminary results validate ash to be a viable candidate. Since the filler is the dominant phase in the composition, ranging between 40 - 90 wt.%, a low CTE material would lead to a better thermal shock resistance (TSR) for the extruded ware, if the application requires considerable thermal gradients. To ameliorate thermal shock, especially when using materials with high intrinsic CTE, segmentation may also be considered. 

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