We have conducted synchrotron x-ray diffraction studies on high purity zirconium metal at pressures $\left(P\right)$ up to $17\mathrm{GPa}$ and temperatures $\left(T\right)$ up to $973\mathrm{K}$. Unit cell volumes $\left(V\right)$ were derived from the refinements of x-ray diffraction data for the $\alpha$, $\beta$, and $\omega$ phases of zirconium and fitted to a Birch-Murnaghan equation of state with the pressure derivative of the bulk modulus, $K_0{}^{\prime }$, fixed at 4.0. The derived thermoelastic parameters for $\alpha$ zirconium are isothermal bulk modulus $K_0=92\left(3\right)\mathrm{GPa}$, temperature derivative of bulk modulus ${(\partial K∕\partial T)}_P=-2.3\left(8\right)\times {10}^{-2}\mathrm{GPa}∕\mathrm{K}$, volumetric thermal expansivity ${\alpha }_T=a+bT$ with $a=1.5(\pm 0.8)\times {10}^{-5}{\mathrm{K}}^{-1}$ and $b=1.7(\pm 1.4)\times {10}^{-8}{\mathrm{K}}^{-2}$, and the pressure derivative of thermal expansion ${(\partial \alpha ∕\partial P)}_T=-2.7\left(9\right)\times {10}^{-6}{\mathrm{GPa}}^{-1}{\mathrm{K}}^{-1}$. For the $\beta$ phase we obtained an isothermal bulk modulus of $K_T=66\left(3\right)\mathrm{GPa}$ at $973\mathrm{K}$ and a unit-cell volume of $V\left(973\mathrm{K}\right)=47.7\left(3\right){\mathrm{\AA }}^3$ at ambient pressure. For the $\omega$ zirconium we obtained $K_0=90\left(5\right)\mathrm{GPa}$. Within the experimental errors, the $K_0$ values we determined for the $\alpha$ and $\omega$ phases and volumetric thermal expansion for the $\alpha$ phase are in agreement with previous experimental results, whereas all other thermoelastic parameters represent the first determinations for the three crystalline phases of zirconium metal.

We synthesized diamond–SiC nanocomposites with superhardness and greatly enhanced fracture toughness through a synthetic approach based on high-energy ball milling to form amorphous Si precursors followed by rapid reactive sintering at high pressure (P) and high temperature (T). We show how the simultaneous $\mathrm{P–T}$ application allows for better control of the reactive sintering of a nanocrystalline SiC matrix in which diamond crystals are embedded. The measured fracture toughness $K_{\mathrm{IC}}$ of the synthesized composites has been enhanced greatly, as much as 50% from 8.2 to 12.0 MPa m^1/2, as the crystal size of the SiC matrix decreases from 10 μm to 20 nm. Our result contradicts a commonly held belief of an inverse correlation between hardness and fracture toughness. We demonstrate the importance of nanostructure for the enhancement of mechanical properties of the composite materials.

We investigate the manipulation of 5 nm diamond nanoparticles in a user-defined pattern on a substrate using the acoustic radiation force associated with a bulk acoustic standing wave. Both concentric and rectangular patterns are studied and the experimental results are compared with theoretical predictions. The effect of drag force acting on a nanoparticle is evaluated and limits for particle speed and particle size that can be moved by acoustic radiation force are determined. We found good agreement between our experimental results and existing theoretical models and demonstrate that nanosized particles can be manipulated effectively by means of bulk wave acoustic radiation force.