R. Wiśniewski

High Pressure Apparatus for Gaseous Hydrogen and Deuterium up to 25 Kilobars and Temperature Range −50 to 100°C

A high pressure device for gaseous hydrogen and deuterium in form of a double piston‐cylinder system is described. Any contact between gaseous volume and the pressure transmitting liquid is avoided. The device has 15 electrical leads from gaseous volume to the outside of the apparatus. Resistance data for palladium under hydrogen and deuterium pressures are presented.

On the improvement of the metrological properties of manganin sensors

The paper presents the recent progress made in the accuracy improvement of the manganin pressure sensors at the Warsaw University of Technology (WUT) and at the Institute of Nuclear Energy. The efforts of the authors were concentrated on three problems: The improvement of the temperature characteristics by the design of a manganin sensor with the temperature compensation achieved by the application of two manganin coils with two different temperature characteristics; The improvement of the calibration process by using a high pressure deadweight piston gauge (with the correction of effective area versus pressure dependence, built at WUT), measurements of the manganin resistance as a function of the temperature and of the pressure using a precise multimeter and application of statistical methods for long series of measurements. The modification of the thermal characteristic by implantation of bismuth and krypton ions.

Optical effects observed in pressure-induced phase transition for some liquid molecular system

Abstract Pressure has a specific influence on the light scattering, electrical permittivity of some liquids in which all molecules have the unsaturated double bond CC. The changes of the intensity of the transmitted light and permittivity of these liquids observed during their transition to the high-pressure phase are discussed. This paper presents analyses of possible structures of these liquids in the high-pressure states.

Changes of liquid structure under pressure in oleic acid

In this study, we show that in the case of oleic acid, the transition to the high-pressure phase, strong scattering of light phase is observed. Before this state is reached, the investigated liquid goes into a stable intermediate state at lower pressures showing weaker light scattering. Molecules of the liquid in the high-pressure states are more ordered and the time to reach these states is relatively long. On the basis of measurements of the changes of permittivity, the intensity of the transmitted light and temperature in oleic acid as a function of time after the application of pressure, this paper presents an analysis of changes of the structure of the investigated liquid during its transformation. †Presented at the 42nd EHPRG conference, Lausanne, September 1–4, 2004.

Linear unbalanced dc bridge

A modification of the classic Wheatstone bridge is presented in which the output voltage is exactly proportional to the increase in measured resistance. This modification is based on a special system of connection with the power supply. In its original version the circuit was successfully applied to high‐pressure measurement by the manganin sensor method.

Viscosity measurements of some castor oil based mixtures under high-pressure conditions†

The measurements of the viscosity of castor oil and its methyl alcohol mixtures have shown abnormal rise of viscosity due to the high-pressure phase transition. The dependence of viscosity on pressure has been compared with the pressure dependence of dielectric constant. This comparison has been done for both directions of the phase transition showing some similarity of these dependencies. Because of the very high viscosity at the pressure range, corresponding to the phase transition PVT region, the capillary viscometer, based on the Hagen–Poiseuille’s method, has been designed, built and applied. The new high-pressure phase of castor oil has structural viscosity (is strongly non-Newtonian liquid). †Presented at the 42nd EHPRG Conference, Lausanne, Switzerland, September 1–4, 2004.

On the structure of a pressure-induced new phase in castor oil

Abstract It is known, that pressure has a specific effect on the permittivity of some liquids in which all molecules have an unsaturated double bond CC. Castor oil, one of these liquids, exhibits a strong increase of scattering of radiation in the visible region, and significant decrease of permittivity some hours after application of pressure above 0.36 GPa. This paper presents further analysis from a microscopic point of view of the structure of the new high-pressure state in castor oil on the basis of changes of permittivity with an increase of pressure observed during its transition to the high-pressure phase. These analyses indicate that the tendency towards anti-parallel orientation between dipoles of neighbouring molecules of castor oil in high-pressure state is greater than in the original state.

Influence of technology on the metrological properties of gold–chromium alloy pressure gauges

This paper discusses the technological processing of the gold–chromium (with 1.95±0.05% Cr) alloy pressure gauge, optimized to get the best metrological properties. It also presents experimental results of thermal and pressure measurements of the alloy. It was found that the Au–Cr pressure gauge, properly seasoned in the controlled seasoning process, is completely free of hysteresis in resistance due to pressure changes, with uncertainty of less than 0.4 bar in 6000 bars range. Resistance‐pressure and resistance‐temperature characteristics didn’t change during the pressure or temperature cycling. It is also shown in the paper that there is a possibility of employing Au–Cr pressure gauges for measurements of high pressures up to about 20 000 bars.

VISCOSITY OF THE METHYL ALCOHOL DOPED CASTOR OIL HIGH-PRESSURE PHASE

High-pressure apparatus (up to 1 GPa) for viscosity measurements (using the capillary method) of a high-viscous medium has been constructed. High-pressure phases of pure castor oil and methyl alcohol doped castor oil, which had been obtained earlier, were generated and their viscosity measured. Values of viscosity as high as 160kPas for pure castor oil and 60kPas for methyl alcohol doped castor oil (about 5 of volume%), at a small shear rate parameter equal to about 0.1s−1, were measured and their structural (tixotropic) type viscosity (consistency) were discovered.

Hybridized dead‐weight piston gauge up to 1 GPa

A hybridized dead‐weight piston gauge consisting of a simple and a re‐entrant piston‐cylinder system is described. The device has an accuracy of 0.1% and can operate up to 1 GPa. The nominal diameter of the gauge piston is 2 mm, initial clearances 4 and 10 μm. The expression for effective area, experimental results confirming the idea of the gauge, and some meterological data determining their accuracy are given.