R. G. Munro

Material Properties of Titanium Diboride

The physical, mechanical, and thermal properties of polycrystalline TiB2 are examined with an emphasis on the significant dependence of the properties on the density and grain size of the material specimens. Using trend analysis, property relations, and interpolation methods, a coherent set of trend values for the properties of polycrystalline TiB2 is determined for a mass fraction of TiB2 ⩾ 98 %, a density of (4.5±0.1) g/cm3, and a mean grain size of (9±1) µm.

Model line‐shape analysis for the ruby R lines used for pressure measurement

An empirical model spectral line shape has been considered for the R1 and R2 fluorescence lines of ruby to investigate the possibility of improvements in the precision and the reproducibility of pressure measurements at high temperature using the ruby fluorescence technique. Other advantages, such as using the ruby method to obtain a simultaneous measurement of pressure and temperature or to obtain quantitative estimates of pressure distributions under nonhydrostatic conditions, have also been considered.

Quantitative wear maps as a visualization of wear mechanism transitions in ceramic materials

Abstract The materials properties of advanced structural ceramics are providing new technological opportunities for improved wear-resistant components in heat engines. Use of ceramics could result in higher efficiency, increased power output and longer lifetimes. However, the successful application of these new materials may be inhibited by the need for evaluated materials properties and the availability of appropriate design criteria. Among the crucial properties of ceramics for use in new engine designs are the friction and wear characteristics of the wear couples. The screening of materials for friction and wear performance usually requires empirical field trials which may be very expensive. Laboratory testing of tribological properties would be much less expensive. What is lacking in laboratory tests, however, is a good correlation between the specific wear test conducted in the laboratory and the specific operating conditions of the industrial application. Basic to such a correlation is an understanding of the mechanisms of the wear process and how the mechanisms change with variations in the operating conditions. This paper describes a new methodology for the wear testing of ceramics that is intended to enable materials screening and designing to be based on laboratory results. The methodology prescribes a systematic effort to measure and represent the wear characteristics of ceramics in a uniform and unified manner. The result is a set of wear maps that collectively provide a comprehensive representation of the wear properties of the materials. Presentation of the wear results in three-dimensional representations allows simultaneous parametric dependencies to be visualized more readily than the traditional two-dimensional graphs. The resulting visual structures of different regions of wear space may indicate the effective limits of competing wear mechanisms and, hence, may provide a basis for wear model development.

Isothermal equations of state for H2O‐VII and D2O‐VII

Lattice parameters and cell volumes at room temperature are reported for H2O‐VII to 36 GPa and for D2O‐VII to 32 GPa. The data are fitted to seven isothermal equations of state from which are derived averaged values of the isothermal bulk moduli (B) and their pressure derivatives (dB/dP) as a function of pressure. For H2O over the range 2.33⩽P⩽30.9 GPa, B increases from 22.3 to 141.0 GPa while dB/dP decreases from 4.9 to 3.7. For D2O over the range 2.8⩽P⩽30.27 GPa, B increases from 30.0 to 129.0 GPa while dB/dP decreases from 4.1 to 3.1. An independent determination of B and dB/dP using a piecewise regression analysis gives B = 15.78+4.11 P, GPa with no distinction between H2O and D2O over the observed pressure ranges. The procedures employed for treating the data and the reliability of the derived results are assessed for both materials.

Reliability of the isothermal bulk modulus deduced from model equations of state

The evaluation of the isothermal bulk modulus of a material by the technique of fitting model isothermal equations of state to experimental data is discussed. A sometimes serious difficulty in this application of model equations is identified, and the relationship between the error in the measured lattice parameter or the pressure and the error in the deduced value of the bulk modulus is investigated.

Correlation of the glass transition and the pressure dependence of viscosity in liquids

The determination of the glass‐transition pressure by the ruby R1 line‐broadening method is quantitatively confirmed to within 10% by an independent method. The procedure utilizes a model which describes the pressure dependence of the viscosity and contains the glass‐transition pressure as a parameter. The two methods are compared for three liquids, n‐butyl chloride, 4 : 1 methanol‐ethanol, and isopropyl alcohol. Data from earlier works are used for 4 : 1 methanol‐ethanol and isopropyl alcohol. The viscosity of n‐butyl chloride at room temperature is measured as a function of pressure to 36 kbars in a diamond‐anvil falling‐sphere viscometer, and the glass‐transition pressure is determined by a separate measurement using the ruby R1 line‐broadening method.

Temperature distribution in the diamond anvil pressure cell at high temperature

The temperature distribution in a diamond anvil pressure cell is investigated theoretically for a model cell having a cylindrical external heater. For a heater surface at 1000 absolute degrees above the ambient temperature, it is found, at steady state, that the region of the sample chamber is, for all practical purposes, isothermal at a temperature of about 11 degrees below the temperature of the heater. When the heater temperature is subsequently incremented instantaneously by 10 degrees, a new steady state is reached in about 30 sec.

Wall effects in a diamond‐anvil pressure‐cell falling‐sphere viscometer

A geometric correction factor γ due to the close proximity of the walls and sphere in a diamond‐anvil pressure‐cell falling‐sphere viscometer is evaluated in order to determine a liquid’s viscosity μ from the measured apparent viscosity μA. μ=γμA. Approximate values of γ are presented for a finite right circular cylindrical cell in which a sphere falls along a centrally located diameter. The results are used in conjunction with measurements on a fluid of known viscosity to estimate that the accuracy obtainable in a diamond‐anvil pressure‐cell falling‐sphere viscometer is better than 30%.

Compression studies of a nickel‐based superalloy, MAR‐M200, and of Ni3Al

The lattice parameter of a cubic nickel‐based alloy, MAR‐M200, has been determined as a function of pressure for 0<p<14 GPa at room temperature. A similar study was made for Ni3Al in the range 0<p<11 GPa at room temperature. In both cases, the diamond anvil pressure cell was used in conjunction with the energy dispersive method of x‐ray diffraction. The data were analyzed in the context of model equations of state and in comparison with other results from ultrasonic studies.

Diamond Anvil Cell Technology For P,T Studies Of Ceramics: ZrO2 (8 mol% Y2O3)

We are undertaking a systematic study of the structural and bulk properties of zirconia and other ceramic materials as functions of pressure and temperature. This paper describes the experimental approach that is being taken and discusses some of the results already obtained for ZrO2 with 8 mol% Y2O3.