Partial molar volume of FeO, NiG and CoO liquid at high pressure

为了测定高压下亲铁氧化物液体的偏摩尔体积，我们开发了高压x射线吸收技术，利用同步x射线和多砧仪测量高压下硅酸盐熔体的密度。用I=I_0 exp（-ρμt）计算样品的x射线吸收曲线的密度（ρ），其中land分别为透射x射线强度和入射x射线强度，μ为样品的质量吸收系数，t为样品厚度。在本研究中，我们使用单晶金刚石圆柱体作为样品胶囊，因为它具有低x射线吸收，硬度和与硅酸盐熔体的惰性。金刚石胶囊使硅酸盐金属在压力下的密度测量成为可能。在日本spring8的BL22XU上，利用dia型立方砧仪和高亮度单色x射线进行了高压x射线吸收实验。我们用含铁二硅酸钠和含铁二硅酸钠的玻璃作为原料。虽然在5gpa和1873 K下测定了玻璃、结晶固体和熔体的密度，但我们还没有测定液体的偏摩尔体积。然而，这种方法可以在高压和高温下产生一系列密度数据，误差在1%以内，足以评估硅酸盐液体的部分摩尔体积。

We have developed the high-pressure X-ray absorption technique to measure density of silicate melts at high-pressure using synchrotron X-ray and a multi-anvil apparatus, in order to determine partial molar volume of siderophile oxide liquid at high pressure. Density (ρ) is evaluated from X-ray absorption profile of a sample using the equation of I=I_0 exp(-ρμt), where land are intensities of transmitted and incident X-rays, respectively, μ is mass absorption coefficient of sample, and t is sample thickness. In this study, we used a single crystalline diamond cylinder as a sample capsule, because its low X-ray absorption, hardness, and inertness with silicate melts. Diamond capsule makes the densiy measurement of silciate metls under pressure possible.High-pressure X-ray absorption experiments were conducted by using a DIA-type cubic anvil apparatus and a highly brilliant monochromatic X-ray at BL22XU of SPring-8,Japan. We used glasses with the compositions both of the MORB and of the Fe-bearing sodium disilicate for starting materials. Although densities of glasses, crystalline solids, and melts were determined up to 5 GPa and 1873 K, we have not determined the partial molar volume of liquid. This method can, however, yield a series of density data at high pressures and temperatures within an error of 1% enough to evaluate the partial molar volume of silicate liquid.