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Silicon nitride (Si3N4) materials with preferentially aligned β-Si3N4 grains were tribologically characterized with respect to their possible application in a high-pressure gasoline pump. Tribological tests were performed under oscillating sliding conditions lubricated with isooctane as a substitute for gasoline using Si3N4 counterbodies. Performance in terms of wear of the aligned materials surpassed that of nonaligned reference Si3N4, as well as that of self-mated silicon carbide, zirconia, alumina, and a steel sliding pair. The plane perpendicular to the extruding direction and parallel to the hot-pressing axis was the most wear resistant. [ABSTRACT FROM AUTHOR]

Rare-earth zirconates have been identified as a class of low-thermal-conductivity ceramics for possible use in thermal barrier coatings (TBCs) for gas-turbine engine applications. To document and compare the thermal conductivities of important rare-earth zirconates, we have measured the thermal conductivities of the following hot-pressed ceramics: (i) Gd[sub 2]Zr[sub 2]O[sub 7] (pyrochlore phase), (ii) Gd[sub 2]Zr[sub 2]O[sub 7] (fluorite phase), (iii) Gd[sub 2.58]Zr[sub 1.57]O[sub 7] (fluorite phase), (iv) Nd[sub 2]Zr[sub 2]O[sub 7] (pyrochlore phase), and (v) Sm[sub 2]Zr[sub 2]O[sub 7] (pyrochlore phase). We have also measured the thermal conductivity of pressureless-sintered 7 wt% yttria-stabilized zirconia (7YSZ)—the commonly used composition in current TBCs. All rare-earth zirconates investigated here showed nearly identical thermal conductivities, all of which were ∼30% lower than the thermal conductivity of 7YSZ in the temperature range 25°-700°C. This finding is discussed qualitatively with reference to thermal-conductivity theory. [ABSTRACT FROM AUTHOR]

Examines the silicon nitride joining using silica and yttria ceramic interlayers. Distinction of the joining interlayer from the Si&sub3;N&sub4; bulk; Description of the microstructure and reaction products; Assessment of the controlled crystallization of refractory secondary phrase.

Investigates the effect of microstructure on the thermal conductivity of silicon nitride materials. Thermal conductivity of the materials; Percentage on the secondary phases of the materials; Grain size of the materials.

The ability of boehmite to form printable inks has sparked interest in the manufacturing of 3D alumina (Al2O3) and composite structures by enabling direct ink writing methods while avoiding the use of printing additives. These materials may exhibit high porosity due to the printing and sintering procedures, depending on the intended application. The 3D-printed porous composite structures of γ-Al2O3 and α-Al2O3 containing 2 wt.% of carbon nanotubes or reduced graphene oxide ribbons were fabricated from boehmite gels, followed by different heat treatments. The reinforcing effect of these carbon nanostructures was evidenced by compression tests carried out on the different alumina structures. A maximum relative increase of 50% in compressive strength was achieved for the γ-Al2O3 composite structure reinforced with reduced graphene oxide ribbons, which was also accompanied by an increase in the specific surface area. [ABSTRACT FROM AUTHOR]