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A high-temperature pressure calibration technique using Sm-doped Y3Al5O12 (Sm:YAG) crystal as the pressure calibrant has been developed by studying its Y1 through Y10 fluorescence peaks (frequencies from 15 600 to 17 200 cm−1) at pressures (p) from 1 bar to 19 GPa and temperatures (T) from 20 to 850 °C in externally heated diamond anvil cells. The entire spectrum was fit to a sum of ten Lorentzians plus a linear background. The positions, relative intensities and widths were represented by empirical functions of p and T. Several fitting routines for p determination were created based on these dependences, and were tested on various high-p and high-T experimental Sm:YAG fluorescence spectra. The p values obtained from the fitting routines are compared with those obtained from the ruby and the nitrogen (N2) vibron pressure scales. A fitting routine is proposed that can determine p from 20 to 850 °C within an estimated uncertainty of 0.4 GPa.

The diffusivity of Sb in Si is retarded by pressure, characterized at 860 °C by an activation volume of V*=+0.07±0.02 times the Si atomic volume. V* is close to values inferred from atomistic calculations for a vacancy mechanism. Our results for hydrostatic pressure are used to predict the effect of biaxial strain on Sb diffusion. The prediction matches measured behavior for Sb diffusion in biaxially strained Si and Si–Ge films. This work lends additional support to the predominance of the vacancy mechanism for Sb diffusion and demonstrates the first steps in the development of a capability for predicting the effect of nonhydrostatic stress on diffusion.

The in-situ mixing zone represents dynamic characteristics of CO2 miscible displacement flows, which is important for carbon dioxide enhanced oil recovery (CO2-EOR) projects. However, the migration characteristics of the in-situ mixing zone under reservoir conditions has been neither well studied nor fully understood. The in-situ mixing zone with the flowing mixture of supercritical CO2 and n-decane (nC10) was investigated by using a magnetic resonance imaging apparatus at a reservoir condition of 8.5 MPa and 37.8 °C in porous media. The experimental results showed that the CO2-frontal velocity was larger than the mixing-frontal velocity. The mixing zone length was linearly declined in the miscible displacement process. And the declining rate of the mixing zone length was increased with injection rate. It indicates that the mixing zone length is not constant in a vertically stable CO2 misible displacement and a volume contraction due to phase behavior effects may occur. Then, an error function based on th...

CO2 flooding is one of the most popular secondary or tertiary recoveries for oil production. It is also significant for studying the mechanisms of the two-phase and multiphase flow in porous media. In this study, an experimental study was carried out by using magnetic resonance imaging technique to examine the detailed effects of pressure and rates on CO2/decane flow in a bead-pack porous media. The displacing processes were conducted under various pressures in a region near the minimum miscibility pressure (the system tuned from immiscible to miscible as pressure is increasing in this region) and the temperature of 37.8 °C at several CO2 injection volumetric rates of 0.05, 0.10, and 0.15 ml/min (or linear rates of 3.77, 7.54, and 11.3 ft/day). The evolution of the distribution of decane and the characteristics of the two phase flow were investigated and analyzed by considering the pressure and rate. The area and velocity of the transition zone between the two phases were calculated and analyzed to quantify mixing. The area of transition zone decreased with pressure at near miscible region and a certain injection rate and the velocity of the transition zone was always less than the “volumetric velocity” due to mutual solution and diffusion of the two phases. Therefore, these experimental results give the fundamental understanding of tertiary recovery processes at near miscible condition.

The hydrostatic pressure dependence of the diffusivity of P in compressively strained Si0.93Ge0.07 and unalloyed Si has been measured. In both cases the diffusivity is almost independent of pressure, characterized by an activation volume V* of (+0.09±0.11) times the atomic volume Ω for the unalloyed Si, and (+0.01±0.06) Ω for Si0.93Ge0.07. The results are used in conjunction with the reported effect of biaxial strain on diffusion normal to the surface to test the prediction for an interstitialcy-based mechanism of Aziz’s phenomenological thermodynamic treatment of diffusion under uniform nonhydrostatic stress states. The prediction agrees well with measured behavior, lending additional credence to the interstitial-based mechanism and supporting the nonhydrostatic thermodynamic treatment.