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Thermal conductivity is one of significant physical properties of engineering materials. It has been confirmed through the thermal conductivity measurements of natural and synthetic materials, and from theoretical calculations that the theoretical conductivities of diamond, BN, SiC, BeO, BP and AlN are larger than 300W·m-1·K-1 at room temperature, being classed as high thermal conductivity solids. Non-oxide ceramic polycrystals with conductivities close to those of single crystals have been developed through the advances in ceramic processing. In recent years, the thermal conductivity exceeding 150W·m-1·K-1 has been reported for β-Si3N4 ceramics, joining a group of high thermal conductivity solids. The non-oxide ceramics have been progressively used as heat-dissipating substrates for highly integrated circuits and optoelectronics, structural components for producing semi-conductors, engine-related material components and so on. Accordingly, the significance of high thermal conductivity non-oxide ceramics has been highly recognized in many industrial fields. In this review, the test results of thermal conductivity of non-oxide ceramics, such as SiC, AlN and Si3N4, are summarized, and then, the effects of processing and microstructural parameters on their thermal conductivities are discussed. Based on the experimental data, the mechanisms of thermal conduction in non-oxide ceramics are examined. The processing strategy leading to high thermal conductivity non-oxide ceramics is also addressed.

Seven kinds of ceramics, β-Si3N4, α′/β′-Sialon, TZP, SiC, three kinds of Al2O3, were worn using three kinds of abrasive particles having different hardnesses by abrasive water jet (AWJ). Wear mechanisms and wear rates of the worn ceramics depend strongly on the ratio of the hardness of abrasive particles (Hp) to that of target ceramics (Ht) as well as on the fracture toughness of target materials (Kt). Kt affects the wear mechanism and rate more strongly in AWJ than in sand erosion. The erosive wear map, which has been proposed based on the experimental results of sand erosion, was found to be qualitatively applicable to AWJ.

The characteristic low brittle-ductile transition temperature of TiC was utilized to toughen SiC matrix composites at high temperatures. AlN, Ti and C powders were used as a dopant to alter the intrinsic properties of SiC matrix or dispersed TiC particles. The fracture toughness of the SiC matrix was improved in the temperature from room temperature to 1600°C by the incorporation of dispersed TiC particles. At low temperatures, the toughening mechanism in SiC/TiC composites was crack deflection or crack bridging while above 1200°C, it was plastic deformation of TiC particles.

On a utilise des eprouvettes entaillees en chevron pour mesurer le travail de rupture a haute temperature de Si 3 N 4 presse a chaud. On examine l'influence de la vitesse de deplacement sur l'energie effective de rupture. La contrainte de pontage a l'interface des fissures est evaluee a partir de l'increment de resistance a la rupture en fonction de l'extension de la fissure, et elle est comparee a la resistance a la traction

Aluminum nitride (AlN) was formed by two-step pyrolysis of poly(isopropyliminoalane) in Ar. The product pyrolyzed at 1000°C was an amorphous material. Solid-state 27 Al-nuclear magnetic resonance spectroscopy (NMR) showed that an AlN-like structure was present in the product. Heat treatment of the pyrolyzed product at 1600°C yielded crystalline AlN from the amorphous material.

Du nitrure de silicium fritte a ete assemble avec du molybdene a l'aide d'intercouches metalliques par pressage chaud et pressage isostatique chaud. On etudie la structure et la resistance interfaciales, les contraintes residuelles, la resistance a la chaleur

On a fabrique des ceramiques poreuses de SiC avec environ 60% de densite relative par frittage de poudres de β-SiC a l'aide d'additifs (B, AlN) a 1900-2100 o C pendant 0,5 a 5 h sous azote. On etudie les masses frittees par diffraction RX et MEB. Une certaine quantite de B est incorporee dans le reseau de SiC, le bore en exces formant du BN. Une quantite de N superieure a celle de B est incorporee dans β-SiC lors du frittage. AlN accroit la transformation de phase β→4H. L'addition de B et AlN diminue la conductivite electrique et accroit le coefficient de Seebeck

On a prepare des composites denses SiC-TiB 2 par pressage chaud reactif de melanges de poudres SiC-TiO 2 -B 4 C-C sechees par pulverisation. On etudie la resistance a la flexion, la tenacite et la resistivite electrique en fonction de la teneur en TiB 2 . Ces composites peuvent etre usines facilement par electroerosion

Examen de la surface de rupture apres essai de fatigue statique et comparaison avec la surface de rupture apres essai statique