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Thermophysical properties were investigated for zirconium diboride (ZrB 2 ) and ZrB 2 -30 vol% silicon carbide (SiC) ceramics. Thermal conductivities were calculated from measured thermal diffusivities, heat capacities, and densities. The thermal conductivity of ZrB 2 increased from 56 W (m K) À1 at room temperature to 67 W (m K) À1 at 1675 K, whereas the thermal conductivity of ZrB 2 -SiC decreased from 62 to 56 W (m K) À1 over the same temperature range. Electron and phonon contributions to thermal conductivity were determined using electrical resistivity measurements and were used, along with grain size models, to explain the observed trends. The results are compared with previously reported thermal conductivities for ZrB 2 and ZrB 2 -SiC.

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In this study, we discovered that a small addition of Y is very effective in improving glass-forming ability of Fe-based alloys. As-cast bulk amorphous alloys containing 2 at. % Y showed large thermal stability, with glass transition temperatures above 900 K and supercooled liquid regions above 55 K, and high strength, with Vickers hardnesses larger than HV 1200. The beneficial effect of Y on glass formation is twofold: (1) Y adjusted the compositions closer to the eutectic and thus lowered their liquidus temperatures, and (2) Y improved the manufacturability of these alloys by scavenging the oxygen impurity from it via the formation of innocuous yttrium oxides.

The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 lm and 80 nm. The powder-ethanol suspensions made with 15-lm diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k th ) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200°C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k th values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k th of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k th increase was less than has been observed in APS coatings.

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Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist's dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

In this article we report on the atomic displacement parameters, lattice expansions, heat capacity, and thermal conductivity of samples of Ti4AlN3 in the 298–1370 K temperature range. Rietveld refinement of high temperature neutron diffraction data shows that the nitrogen is substoichiometric and the formula is Ti4AlN2.9. In this structure, the atomic displacement parameters of the Al atoms are higher than those of either the Ti or N atoms. The Ti–N bonds adjacent to the Al planes are about 2.5% shorter than the Ti–N bonds in the inner layers. The thermal expansion coefficients along the a and c axes are, respectively, (9.6±0.1)×10−6 and (8.8±0.1)×10−6 K−1. The unit cell expansivity, (9.4±0.1)×10−6 K−1, is in agreement with the dilatometric bulk thermal expansivity (9.7±0.2)×10−6 K−1. The heat capacity, cp, is 150 J/mol K at ambient temperatures and extrapolates to ≈220 J/mol K at 1300 K. At all temperatures cp equals four times the molar heat capacity of TiN. The room temperature thermal conductivity is 12 W/m K and increases linearly to ≈20 W/m K at 1300 K.