Michael D. Rutter

Investigation of pressure-induced amorphization in hydrated zeolite Li-A and Na-A using synchrotron X-ray diffraction

High pressure synchrotron X-ray diffraction measurements of hydrated zeolite Li-A and Na-A were carried out at pressures up to 4.1 GPa and at room temperature in a large volume press. Energy dispersive X-ray diffraction measurements showed progressive pressure-induced amorphization of both Li-A and Na-A samples. The most rapid loss in long-range ordering occurred at pressures up to 2.2 GPa followed by a gradual, continued decrease in ordering up to the maximum pressure. At 4.1 GPa the samples appeared to be X-ray amorphous. After decompression, diffraction patterns at 1 atm indicated that the sample reverted back to their initial crystal structure. q 2001 Elsevier Science Ltd. All rights reserved.

Ionic conduction in hydrated zeolite Li-, Na- and K-A at high pressures

Abstract Ionic conductivities of hydrated zeolite Li-, Na- and K-A at room temperature and at pressures up to 4.8 GPa have been measured. Anomalous increases in conductivity with pressure up to 1.7–1.9 GPa were observed for all zeolites. In this pressure range, activation volumes of conduction are −1.4, −3.9 and −6.8 cm 3 /mol for Li-, Na- and K-A zeolites, respectively. The conductivity goes through a maximum, where pressure-induced amorphization occurs. Following the maximum, there is a rapid decrease in conductivity due to the collapse of long-range ordering. On decompression, conductivity increases to values that are higher than the conductivity values at equal pressures on compression.

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.

Tailoring sphere density for high pressure physical property measurements on liquids

We present a new method of tailoring the density of a sphere for use as a probe in high pressure-temperature physical property experiments on liquids. The method consists of a composite sphere made of an inner, high density, metallic, spherical core and an exterior, low density, refractory, spherical shell or mantle. Micromechanical techniques are used to fabricate the composite sphere. We describe a relatively simple mechanical device that can grind hemispherical recesses as small as 200 μm in diameter in sapphire and as small as 500 μm in diameter in ruby hemispheres. Examples of composite spheres made with a Pt or WC core and Al2O3 shell used in metallic liquids pressurized to 16 GPa and 1900 K are shown.

Pressure-induced increase in the ionic conductivity of Li, Na, and K zeolites of type A

The effect of pressure on the ionic conductivity of hydrated A-zeolites containing Li, Na, and K cations was investigated. Room-temperature experiments at pressures to 4.8 GPa show an increase in the conductivity, which attains its maximum value in the range of 1.7–1.8 GPa for the three zeolites. Further compression leads to a drastic decrease in the conductivity at 2.5–3.5 GPa. The decrease in the conductivity is associated with the pressure-induced transition to the amorphous state, as follows from previously reported IR spectroscopy data. It is believed that the increase in the conductivity with pressure and the subsequent transition to the amorphous state follow one or several of the following mechanisms: (1) cation conductivity involving hydroxyls, (2) hydroxyl-proton conductivity, and (3) enhanced cation mobility due to pressure-induced change in the degree of hydration. With decreasing pressure, the conductivity does not follow the compression curve. For pressure-cycled samples, the low-pressure conductivity during decompression is two orders of magnitude higher than its value at the same pressure during compression. Compression provides a new way for conductivity optimization in hydrated A-zeolites.