Hongjian Liu

A large-volume press facility at the Advanced Photon Source: diffraction and imaging studies on materials relevant to the cores of planetary bodies

A new large-volume, high-pressure facility is being utilized and developed as part of GeoSoilEnviroCARS at a third-generation synchrotron, the Advanced Photon Source. This user facility consists of two large-volume presses (LVP), a 2.5 MN (250 ton) LVP installed at the bending magnet beamline, and a 10 MN (1000 ton) LVP at the insertion device beamline. Here we report some techniques currently being developed with the 10 MN LVP and the latest scientific results obtained using the 2.5 MN LVP.

Viscosity and density of Fe–S liquids at high pressures

High P, T measurements of viscosity and density of Fe–S liquids are reported. Viscosity was measured using Stokes method and synchrotron radiographic techniques for real-time imaging of a falling/rising composite sphere in Fe–S liquids. For P up to 4 GPa and T up to 1523 K, measured viscosities are of the order of 10−2–10−3 Pa s. Density of Fe–10 wt% S liquids was measured using the sink/float method with composite spheres. The high P density data indicate a density increase of 29% between 1 atm and 15 GPa at 1923 K.

Anomalous ionic conductivity of Sc2(WO4)3mediated by structural changes at high pressures and temperatures

The ionic conductivity of Sc2(WO4)3 at 400 °C shows a normal decrease with increase in pressure up to 2.9 GPa but then increases anomalously at pressures up to 4.3 GPa. Synchrotron in situ x-ray diffraction results show that Sc2(WO4)3 undergoes pressure-induced amorphization at pressures coincident with the reversal in conductivity behaviour. The loss of crystal structure at high pressure may be associated with the property of negative thermal expansion in Sc2(WO4)3.

Amorphization and post-amorphous phases of NaA Zeolite at high P–T conditions

Hydrated NaA (hyd-NaA) and dehydrated NaA (deh-NaA) zeolites were studied at high P–T conditions (up to 4.5 GPa and 400 °C) by ex situ X-ray powder diffraction and in situ impedance spectroscopy. At compression of both synthetic zeolites in 1000-ton cubic press, the amorphization was observed in a wide pressure range at room T. At heating to 200–250 °C and compression to 2–3 GPa, a complete amorphous material was obtained from deh-NaA. After amorphization at high P–T, hyd-NaA zeolite transforms to new crystalline phases: carnegieite and nepheline. These amorphous-to-crystalline transformations in a low pressure range suggest the correlation of short-scale order parameters in both materials. The presence of water in hyd-NaA essentially changes the phase diagram. Phase transformations in zeolites may be studied by in situ impedance spectroscopy. Unusual ionic AC conductivity of hyd-NaA, characterized by high value and the Cole–Cole plot with broken line without any semicircle, was observed. The pressure range of high-conducting state increases with temperature and may be broader the measured interval of 0.8–4.5 GPa at 400 °C.