Experimental observation of deep crust fluid-NaCl aqueous solution at elevated temperatures and pressures and its significance

In order to reveal the nature of deep crust fluids, the phase relations of NaCI-saturat-ed solution at high temperatures and pressures in a hydrothermal diamond anvil cell (HDAC) are investigated. Salinity of the solutions observed is about 35%-50% . The temperatures for the observation range from 25 to 850℃ and the pressures from 1 atm to about 1 GPa. A supercritical single phase, liquid phase (L), vapor phase (V), solid phase (H), L+H, H + V+L and the near-critical phases L + V can be observed. A two-phase (L + V) immiscibility field for the NaCI solution has been discovered to lie in a wide range of temperatures and pressures: from 250( ±3) to 721℃. Within this field there are two parts, where the upper high temperature part of the two-phase regions is very unstable in character. It is possible to observe a "critical phenomenon". In some of our experiments an "explosion" almost constantly occurred at the interface between the liquid and vapor phases, making the interface obscure, and a continuous transition between the two phases could be found. By a visual microscope it was found that in the two-phase immiscible field near to the critical state the vapor phase and liquid phase compose a crystal structure geometry. It is a special solution structure that was found under a microscope. This discovery is important for us to understand the reason of increasing electronic conductivity of NaCI aqueous solution with respect to temperatures and pressures. And also, it will be easy to interpret the variation of electronic conductivity in the earth crust.     

Pressure Dependence of Molar Volume near the Melting Point in Benzene

The pressure dependence of the molar volume was at constant temperatures close to the melting point in benzene. The molar volume of benzene was calculated using experimental data for the thermal expansivity for constant temperatures of 25℃, 28.5℃, 40℃, and 51℃ at various pressures for both the solid and liquid phases. The predictions are in good agreement with the observed volumes in both the solid and liquid phases of benzene. The predicted values of the molar volume for a constant temperature of 28.5℃ in the liquid phase of benzene agree well with experimental data in the literature.     

Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

At 1.0?4.0 GPa and 1123?1473 K and under oxygen fugacity-controlled conditions (Ni+NiO, Fe+Fe₃O₄, Fe+FeO and Mo+MoO₂ buffers), a YJ-3000t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (10³?10⁶ Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2) with the rise of temperature (T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3) under the control of oxygen buffer Fe+Fe₃O₄, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1.25±0.08) eV and (0.105±0.025) cm³/mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and (5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.     

Transient photoconductivity in a-(Se80Te20)100 xAgx (0rxr4) thin films

Bulk material of (Se80Te20)100 xAgx (0rxr4) system was prepared by using a conventional melt quenching technique. Thin films of a-(Se80Te20)100 xAgx (0rxr4) were deposited by the vacuum evaporation technique at a base pressure of 10 4 mbar onto well-cleaned glass substrates. Temperature dependence of electrical conductivity in the temperature range of 263–333 K has been studied. There is increase in the value of conductivity with increase in temperature as well as with Ag content. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0, representing the continuous distribution of traps. Rise and decay of photocurrent with time at room temperature at different light intensities for (Se80Te20)98Ag2 thin film samples have also been reported. The results have been explained on the basis of the Dember voltage and interaction between photoexcited holes and the trapped electrons on the surface.     

Synthesis of Ta C and Ta_2C from tantalum and graphite in the laser-heated diamond anvil cell

The pressure dependence of the onset of the formation of Ta C and Ta2 C from the elements has been investigated by in situ X-ray diffraction and pyrometry.Ta C has been synthesized by the reaction of Ta and graphite at pressures between 8.6 and 14.3 GPa and at temperatures up to 2,300 K using a laser-heated diamond anvil cell. The products were characterized by X-ray diffraction. Ta and graphite begin to react around 1,100 K at ambient pressure conditions, and the reaction temperature increases with increasing pressure. A linear extrapolation of these data is consistent with recent observations of the formation of Ta C at 90 GPa and 3,600 K. We show that diffusion of carbon into tantalum significantly changes the lattice parameter of up to 2 % in the pressure range of up to19 GPa. In some experiments, Ta2 C was formed concomitantly. The experimentally determined bulk modulus of Ta2 C is B0;exp：= 286（5） GPa. Other tantalum carbide phases were not observed.     

Thermal conductivity measurements on xonotlite-type calcium silicate by the transient hot-strip method

The experimental results of the thermal conductivities of xonotlite-type calcium silicate insulation materials were presented at different temperatures and pressures. Two appropriative surroundings, i.e. an elevated temperature surrounding from ambient temperature to 1450 K and a vacuum surrounding from atmosphere pressure to 10-3 Pa, were designed for the transient hot-strip (THS) method. The thermal conductivities of xonotlite-type calcium silicate with four densities from ambient temperature to 1000 K and 0.045 Pa to atmospheric pressure were measured. The results show that the thermal conductivity of xonotlite-type calcium silicate decreases apparently with the fall of density, and decreases apparently with the drop of pressure, and reaches the least value at about 100 Pa. The thermal conductivity of xonotlite-type calcium silicate increases almost linearly with T3, and increases more abundantly with low density than with high density. The thermal conductivity measurement uncertainty is estimated to be approximately 3% at ambient temperature, and 6% at 800 K.     

Effect of sintering parameters on the microstructure and thermal conductivity of diamond/Cu composites prepared by high pressure and high temperature infiltration

Pure Cu composites reinforced with diamond particles were fabricated by a high pressure and high temperature (HPHT) infiltration technique. Their microstructural evolution and thermal conductivity were presented as a function of sintering parameters (temperature, pressure, and time). The improvement in interfacial bonding strength and the maximum thermal conductivity of 750 W/(m·K) were achieved at the optimal sintering parameters of 1200℃, 6 GPa and 10 min. It is found that the thermal conductivity of the composites depends strongly on sintering pressure. When the sintering pressure is above 6 GPa, the diamond skeleton is detected, which greatly contributes to the excellent thermal conductivity.     

An experimental study of dehydration melting of phengite-bearing eclogite at 1.5―3.0 GPa

Dehydration melting experiments were performed on ultrahigh-pressure eclogite from Bixiling in the Dabie orogen at 1.5--3.0 GPa and 800--950℃ using piston cylinder apparatus. The results show that （1） eclogite with -5% phengite started to melt at T≤800--850℃ and P = 1.5--2.0 GPa and produced about 3% granitic melt; （2） the products of dehydration melting of phengite-bearing eclogite vary with temperature and pressure. Fluid released from dehydration of phengite and zoisite leads to partial melting of eclogite and formation of plagioclase reaction rim around kyanite at pressures of 1.5--2.0 GPa and temperatures of 800--850℃; （3） phengite reacted with omphacite and quartz and produced oligoclase, kyanite and melt at elevated temperatures. Oligoclase is the primary reaction product produced by partial melting of phengite in the eclogite; and （4） the dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa and temperatures ≥900℃ results in formation of garnets with higher molar fraction of pyrope （37.67 wt.%--45.94 wt.%）. Potassium feldspar and jadeite occur at P = 2.4--3.0 GPa and T≥900℃, indicating higher pressure and fluid-absent conditions. Our results constrain the solidus for dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa. Combining experi- mental results with field observations of partial melting in natural eclogites, we concluded that phengite-bearing eclogites from the Dabie-Sulu orogen were able to partially molten at P= 1.5--2.0 GPa and T= 800--850℃ during exhumation. The ultrahigh-high pressure eclogites would have experienced partial melting in association with metamorphic phase transformation under different fluid conditions.     

Ultrasonic measurements of single-crystal gold under hydrostatic pressures up to 8 GPa in a Kawai-type multi-anvil apparatus

Ultrasonic measurements were conducted on single-crystal gold at ambient condition and hydrostatic pressures up to 8 GPa at room temperature in a Kawai-type multi-anvil apparatus. The P-wave velocities measured at high pressures were in good agreement with Daniels and Smith’s ultrasonic study. The three independent elastic constants of gold at ambient condition were determined to be C11=192.7 GPa, C12=162.9 GPa, and C44=42.4 GPa. On the basis of an analysis of previous elastic data and the present ultrasonic data, the pressure derivatives of three elastic constants were estimated to be C1 ′1= 7.12,C 1′2 = 6.24,and C4′4 = 1.82. The calculated values of isothermal bulk modulus (KT0) and its pressure derivatives ( KT ′0) are KT0 = 166.44 GPa and KT ′0= 6.56. This indicates that Anderson et al.’s model of equation of state of gold might underestimates pressure about 1 GPa at pressure around 23 GPa and ambient temperature. Our results explained the discrepancies among the models of equation of state of gold proposed previously.     

AN APPROACH TO CALCULATE THE SURFACE TENSION OF THE LIQUID NITROGEN FILM ON SOLIDS FROM AN ADSORPTION ISOTHERM

The equations, used in this paper to calculate the surface tension of the liquid nitrogen film formed by the physical adsorption on many different model solids (e.g. spherical partiele, plane particle and spherical cavity pores or cylindrical pores at the openings of both ends in solid bodies), have been derived on the thermodynamie principle. The calculated results have shown that the surface tension (γ) of the adsorbed liquid nitrogen film on most of non-porous solid surfaces diminishes with the rise of the nitrogen gas pressure (p) or of the adsorbed layers (n) at 77.3K; when p reaches the vapour pressure (p_s) of the bulk liquid nitrogen, y turns into the surface tension (γ_o) of the bulk liquid nitrogen; whgn p /p, <0.98, there is an obvious difference between γ and γ_O.     

Radiation theory comparison for magnetoacoustic tomography with magnetic induction （MAT-MI）

Based on the principle of Lorentz force induced acoustic vibration, radiation theory comparison between acoustic point and dipole sources was conducted for magnetoacoustic tomography with magnetic induction （MAT-MI）. It is proved that each acoustic source of MAT- MI is produced by the divergence of the magnetically induced Lorentz force, and the detected acoustic pressure is the integral of all diffraction sources inside the object. Wave clusters are produced by abrupt pressure changes at conductivity boundaries, and only the configurations in terms of shape and size of phantom models can be recon- structed. However, different from point source, positive and negative pressures are generated by the radiation pat- tern of dipole sources. Reverse vibration phases of wave clusters in collected waveforms and opposite polarities of borderline stripes in reconstructed images are produced at conductivity boundaries, representing the direction of conductivity changes. The experimentally collected wave- forms and reconstructed images of the aluminum foil cylinder and cylindrical saline gel phantom model agree well with simulated results. The favorable results prove the validity of the radiation theory of acoustic dipole source and provide basis for further investigation of conductivity reconstruction for MAT-MI.     

An experimental study on the solubility of copper bichloride in water vapor

Using the solubility method, the solubility of CuCl2 in liquid-undersaturated HCl-bearing water vapor was investigated experimentally at temperatures of 330-370 ℃ and pressures of 4.2-10 MPa. The re-sults have shown that hydration could significantly enhance copper solubility and the concentrations of copper were positively correlated with PH2O. The solubility of copper in vapor phase increased with increasing PH2O at the constant temperature. CuCl2 was transported as hydrated species CuCl2(H2O)ngas in water vapor. The formation of complexes is proposed to be the result of the following reaction: CuCl2solid nH2Ogas = CuCl2 (H2O)ngas The hydration number n decreased slightly with increasing temperature. Statistical hydration numbers are 4.0, 3.6 and 3.3 at 330, 350 and 370 ℃ , respectively.     

Structural and spectroscopic analysis of wurtzite (ZnO)1-x(Sb2O3)x composite semiconductor

The structural, vibrational and impedance analysis for(Zn O)1 x(Sb2O3)xcomposite synthesized by solid state reaction technique were carried out in the present investigation. X-ray diffraction(XRD) study showed that(Zn O)1 x(Sb2O3)xcomposite has hexagonal(wurtzite) crystal structure. Variation in lattice constants with Sb-doping indicated the proper incorporation of Sb dopant in Zn O host matrix. The results of Raman spectroscopy test suggested the signature of E2(high) and E1(TO) Raman modes, and verified the wurtzite structure of(Zn O)1 x(Sb2O3)x composite. Two additional phonon bands(671, 712) cm 1appeared in Raman spectra of composite samples due to the existence of the lattice defects caused by Sb doping or may be other intrinsic lattice defects formed during the synthesis of(Zn O)1 x(Sb2O3)xcomposite. The frequency dependent on the electrical characteristics, such as, impedance(Z), dielectric constant(ε) and AC conductivity(σ) have been studied in a range of frequencies for different Sb concentration at room temperature. The electrical measurement results showed that the impedance increased with Sb dopant concentration, while dielectric constant and AC conductivity decreased with Sb dopant concentration.     

Characteristics of flame spread over the surface of charring solid combustibles at high altitude

To explore the characteristics of flame spread over the surface of charring solid combustibles at high altitude, the whitewood with uniform texture was chosen to conduct a series of experiments in Lhasa and Hefei, with altitude of 3658 m and 50 m respectively. Several parameters, including the flame height, flame spread rate, flame temperature, surface temperature, were measured on samples with different width and inclinations. A quantitative analysis of flame spread characteristics over sample surface at high altitude was performed. Results showed that, in the environment of lower pressure and oxygen concentration at high altitude, the flame height and flame spread rate over sample surface decreased, but the flame temperature increased slightly. However, with increasing of sample width, the relative difference between the flame spread rates at different altitudes decreased.     

Relation between powder size and electrolyte properties in nano YSZ system

YSZ (yttria stabilized zirconia) electrolyte properties made from different sizes of nano powders were investigated. As a result, the sample marked KD with the smallest size (10 nm) of first particles and the sample marked TH with narrow distribution and the smallest median diameter M_med of 0.49 μm have the best sintering properties and the highest electrical conductivity. There is a very well correlation between the density and the electrical conductivity of YSZ, that is, the samples with a higher density have a higher electrical conductivity. The area resistance of YSZ electrolyte made in the experiment, such as TH of 0.483 Ω·cm2, is much lower than that of the sample D of 1.300 Ω·cm2 made in Germany at 850℃. The complex resistance of YSZ electrolyte made in the experiment at the grain, grain boundary and electrode in the range of 300-750℃ decreases greatly compared to the sample made in Germany by shown in the complex impedance plot.     

Microstructure evolution and thixoforming behavior of 7075 aluminum alloy in the semi-solid state prepared by RAP method

The effects of isothermal treatments on the microstructural evolution and coarsening rate of semi-solid 7075 aluminum alloy produced via the recrystallization and partial remelting (RAP) process were investigated. Samples of 7075 aluminum alloy were subjected to cold extrusion, and semi-solid treatment was carried out for 5–30 min at temperatures ranging from 580 to 605°C. A backward-extrusion experiment was conducted to investigate liquid segregation during the thixoforming process. The results revealed that obvious grain coarsening and spheroidization occurred during prolonged isothermal treatments. In addition, higher soaking temperatures promoted the spheroidization and coarsening process because of the increased liquid fraction and the melting of second phases. Segregation of the liquid phase caused by the difference in fluidity between the liquid and the solid phases was observed in different regions of the thixoformed specimens.     

Effect of sintering temperature on phase evolution of Al_(86)Ni_6Y_(4.5)Co_2La_(1.5) bulk amorphous composites synthesized via mechanical alloying and spark plasma sintering

Al_(86)Ni_6Y_(4.5)Co_2La_(1.5) amorphous powders were synthesized by mechanical alloying for 200 h. Subsequent consolidation was performed via spark plasma sintering in the temperature range of 250 ℃ to 500 ℃ at the pressure of 500 MPa. The role of viscous flow on densification was investigated by studying the viscosity change of the amorphous phase at different consolidation temperatures. The decrease in viscosity at higher sintering temperatures resulted in better particle bonding and densification of consolidated samples. The formation of only FCC Al was observed in the consolidated samples at sintering temperatures ≤ 300 ℃ and the intermetallic phases formed at temperatures ≥ 400 ℃. The mechanical properties of the bulk samples were measured by Vickers microhardness and nanoindentation tests. The testing results showed that the average values of microhardness, nanohardness and elastic modulus of the sample consolidated at 500 ℃ were 3.06 ± 0.14 GPa,4.85 ± 1.14 GPa and 89.53 ± 9.25 GPa, respectively. The increase in hardness and elastic modulus of the higher temperature consolidated samples is attributed to the improvement in particle bonding, densification and distribution of various hard intermetallic phases in the amorphous matrix.     

Extraction of vanadium from high calcium vanadium slag using direct roasting and soda leaching

The extraction of vanadium from high calcium vanadium slag was attempted by direct roasting and soda leaching. The oxidation process of the vanadium slag at different temperatures was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effects of roasting temperature, roasting time, Na₂CO₃ concentration, leaching temperature, leaching time, and liquid to solid ratio on the extraction of vanadium were studied. The results showed that olivine phases and spinel phases in the vanadium slag were completely decomposed at 500 and 800℃, respectively. Vanadium-rich phases were formed at above 850℃. The leaching rate of vanadium reached above 90% under the optimum conditions:roasting temperature of 850℃, roasting time of 60 min, Na₂CO₃ concentration of 160 g/L, leaching temperature of 95℃, leaching time of 150 min, and liquid to solid ratio of 10:1 mL/g. The main impurities were Si and P in the leach liquor.     

Thickness of compound layer in steel-aluminum solid to liquid bonding

The bonding of solid steel plate to liquid aluminum was studied using rapid solidification. The surface of solid steel plate was defatted, descaled, immersed (in K₂ZrF₆ flux aqueous solution) and stoved. In order to determine the thickness of Fe-Al compound layer at the interface of steel-aluminum solid to liquid bonding under rapid solidification, the interface of bonding plate was investigated by SEM (Scanning Electron Microscope) experiment. The relationship between bonding parameters (such as preheat temperature of steel plate, temperature of aluminum liquid and bonding time) and thickness of Fe-Al compound layer at the interface was established by artificial neural networks (ANN) perfectly. The maximum of relative error between the output and the desired output of the ANN is only 5.4%. From the bonding parameters for the largest interfacial shear strength of bonding plate (226℃ for preheat temperature of steel plate, 723℃ for temperature of aluminum liquid and 15.8 s for bonding time), the reasonable thickness of Fe-Al compound layer 10.8 μm was got.     

Structural characteristics and mechanism of hydrogen-induced disproportionation of the ZrCo alloy

The intermetallic compound ZrCo was prepared, and its hydrogen-induced disproportionation in hydrogen desorption processes was investigated. The hydrogenation-dehydrogenation thermodynamics of the ZrCo alloy was evaluated by pressure-composition isotherm measurements at different temperatures. The kinetic processes of hydrogen-induced disproportionation at different temperatures under certain pressures were detailedly studied. The disproportionation rate of the ZrCo alloy increased with the increases of temperature and initial hydrogen pressure under experimental conditions. However, the maximum attainable extent of disproportionation did not change much with an increase in temperature or initial hydrogen pressure. The crystallographic structure analysis of the ZrCo alloy combining with its corresponding dehydrogenation kinetic curves under the conditions of an initial hydrogen pressure of 0.2 MPa and a temperature of 723 K indicated that the basic process of disproportionation reactions was composed of four stages:rapid dehydrogenation of ZrCoH₃, equilibrium of dehydrogenation, simultaneity of dehydrogenation and disproportionation, and completion of disproportionation.