微波硬化表面包覆低共熔体锂盐水玻璃砂抗吸湿性初步研究

介绍了一种在水玻璃砂型表面生成低共熔体锂盐包覆层的方法。首先在水玻璃砂型表面喷涂0．38LiOH-0．62LiNO，混合锂盐饱和水溶液，再将喷涂后的砂型放入微波炉加热硬化，因为配比的混合锂盐共熔点温度只有175．7℃，饱和水溶液中的溶质在微波加热时迅速析出，溶质在微波作用下在砂型表面形成低共熔体。经过低共熔体锂盐表面包覆处理的砂型微波硬化温度能达到370℃，远高于普通微波硬化砂型（110℃），因而包覆处理的砂型强度更高；在相对湿度为98％~100％恒湿条件下存放4h后，表面包覆处理的砂型强度较未处理的提高了将近2倍。SEM分析表明，混合锂盐在砂型表面和内层之间的过渡层上生成了一层致密低共熔体物质，该物质阻挡了水分的入侵而保护了内部高强度的粘结桥。

氧化钕在氟盐体系中的溶解度

本文研究了氧化钕在LiF-NdF_3-BaF_2系熔体中的溶解度。讨论了氟化锂、氟化钡、温度对溶解度的影响及氟化钡对稳定熔体组成的作用。实验结果表明:在氟化锂为20～30%;氯化钡为5～10%;温度为800～900C实验范围内,氧化钕的溶解度可达7～10%。

氟盐体系中Sc^(3+)在Ag电极上的阴极还原过程

采用循环伏安法和计时电位法研究了钪离子在１０４３Ｋ下、ＬｉＦＮａＦ体系中银电极上的阴极还原过程。结果表明，Ｓｃ３＋在Ａｇ电极上的还原过程是可逆的简单电荷传递的三电子反应，阴极过程受扩散控制。

萤石中流体-熔融包裹体的研究

在四川冕宁稀土矿床霓辉重晶石伟晶岩型矿体早期萤石中笔者发现了大量的流体-熔融包裹体。矿物的光学性质及激光拉曼光谱特征表明,流体-溶融包裹体内晶体矿物为重晶石。萤石中流体-熔融包裹体的“均一化”温度为493.7—502.3℃,其捕获温度更高,这说明主矿物萤石的形成温度很高,笔者认为这类萤石是由富含挥发分,以氟化钙、硫酸钡为主要成分的盐熔体直接结晶而成的,即该类萤石以及与之共生的重晶石具有岩浆成因的特征。

四川冕宁稀土矿床包裹体研究

在四川冕宁稀土矿床霓辉重晶伟晶岩和碳酸岩矿体的早期萤石、石英中发现了大量的流体－熔融包裹体。包裹体的捕获温度高于５００℃，说明两类矿体为典型的盐熔体结晶产物。研究还显示，在矿石矿物氟碳铈矿中，存在着大量的流体包裹体，这说明矿床的稀土矿化与热液作用有成因联系，成矿温度为１５０－２７０℃。所有研究结果均证明，四川冕宁矿床是一个与盐熔体有关的热液稀土矿床。

Copper partitioning between granitic silicate melt and coexisting aqueous fluid at 850°C and 100 MPa

Experiments on the partitioning of Cu between different granitic silicate melts and the respective coexisting aqueous fluids have been performed under conditions of 850 ℃, 100 MPa and oxygen fugacity （fO2） buffered at approaching Ni-NiO （NNO）. Partition coefficients of Cu （Dcu = Cfluid/Cmelt） were varied with different alumina/alkali mole ratios [Al2O3/（Na2O ＋ K2O）, abbreviated as Al/ Alk], Na/K mole ratios, and SiO2 mole contents. The DCu increased from 1.28 ± 0.01 to 22.18 ±0.22 with the increase of Al/Alk mole ratios （ranging from 0.64 to 1.20） and Na/K mole ratios （ranging from 0.58 to 2.56）. The experimental results also showed that Dcu was positively correlated with the HCl concentration of the starting fluid. The Dcu was independent of the SiO2 mole content in the range of SiO2 content considered. No Dcu value was less than 1 in our experiments at 850 ℃ and 100 MPa, indicating that Cu preferred to enter the fluid phase rather than the coexisting melt phase under most conditions in the melt-fluid system, and thus a significant amount of Cu could be transported in the fluid phase in the magmatichydrothermal environment. The results indicated that Cu favored partitioning into the aqueous fluid rather than the melt phase if there was a high Na/K ratio, Na-rich, peraluminous granitic melt coexisting with the high Cl^- fluid.

Diffraction and luminescence analysis of extremely rapidly cooled molten system(LiF-CaF)-xLnF(Ln=Sm and Gd)

Samples of(LiF-CaF2)eut-x SmF3(-x GdF3)(x=0.03-0.50) were prepared by spontaneous cooling as well by very fast cooling(using the rapid solidification processing(RSP) method) which provide two types of sample morphology: riffle-like and sphere-like fragments. All types of samples were studied by XRD, optical absorption and fluorescence spectroscopy. The presence of LiF stabilises the cubic cell dimension, and the content of lanthanide fluorides presents influence on phases formed, as well as the crystallinity of the system, in both the spontaneously and rapidly-cooled systems. The photoluminescence properties of the investigated systems are dependent on the lanthanide fluoride content. The intensity of the emission bands, corresponding to the Sm3+ ion, reaches the maximum when the Sm content is x(SmF3)=0.03. An even stronger dependence is observed of optical properties on the morphology of the samples, i.e. whether the samples are spontaneously cooled or processed by the RSP method followed by mechanical grinding. Mechanical grinding enhances the luminescent properties and leads to higher emission intensities. It is also shown that the photoluminescent spectroscopy is suitable for detection/approval of lowered local symmetry via significant splitting of spectral bands.

Characterization of polysulfone hollow-fiber ultrafiltration membrane and its cleaning efficiency by streaming potential and flux method

Polysulfone(PS)hollow-fiber ultrafiltration membrane was characterized combined with flux and streaming potential in single electrolyte solutions.The effects of trans-membrane pressure,electrolyte concentration,ion valence and pH value of electrolyte solution on the streaming potential(SP)of the membrane were investigated.The zeta potential and surface charge density of the membrane were calculated on the basis of Helmholtz-Smoluchowski equation and Gouy-Chapmann theory.The results indicate that the valence and concentration of cation have a greater influence on the SP and surface charge density of PS membrane than those of anion,and the pH value of electrolyte solution has great effects on the SP and zeta potential of the membrane surface. Both the absolute value of the streaming potential and water flux of the adsorbed membrane decrease,compared with those of the clean membrane.The streaming potential and flux of the cleaned membrane can be completely recovered by cleaning with the mass fraction of 0.8%EDTA at pH=10.

Water and partial melting of Earth's mantle

Water plays a crucial role in the melting of Earth's mantle. Mantle magmatisms mostly occur at plate boundaries(including subduction zones and mid-ocean ridges) and in some intraplate regions with thermal anomaly. At oceanic subduction zones, water released by the subducted slab may induce melting of the overlying mantle wedge or even the slab itself, giving rise to arc magmatism, or may evolve into a supercritical fluid. The physicochemical conditions for the formation of slab melt and supercritical fluid are still under debate. At mid-ocean ridges and intraplate hot zones, water and CO_2 cause melting of the upwelling mantle to occur at greater depths and in greater extents. Low degree melting of the mantle may occur at boundaries between Earth's internal spheres, including the lithosphere-asthenosphere boundary(LAB), the upper mantletransition zone boundary, and the transition zone-lower mantle boundary, usually attributed to contrasting water storage capacity across the boundary. The origin for the stimulating effect of water on melting lies in that water as an incompatible component has a strong tendency to be enriched in the melt(i.e., with a mineral-melt partition coefficient much smaller than unity), thereby lowering the Gibbs free energy of the melt. The partitioning of water between melt and mantle minerals such as olivine, pyroxenes and garnet has been investigated extensively, but the effects of hydration on the density and transport properties of silicate melts require further assessments by experimental and computational approaches.

Electrical conductivity of hydrous silicate melts and aqueous fluids: Measurement and applications

The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous silicate melts and aqueous fluids is sensitive to composition, temperature, and pressure, making it useful for understanding partial melting and fluid activity at great depths. This study presents a review on the experimental studies of electrical conductivity of silicate melts and aqueous fluids, and introduces some important applications of experimental results. For silicate melts, electrical conductivity increases with increasing temperature but decreases with pressure. With a similar Na^+ concentration, along the calc-alkaline series electrical conductivity generally increases from basaltic to rhyolitic melt, accompanied by a decreasing activation enthalpy. Electrical conductivity of silicate melts is strongly enhanced with the incorporation of water due to promoted cation mobility. For aqueous fluids, research is focused on dilute electrolyte solutions. Electrical conductivity typically first increases and then decreases with increasing temperature, and increases with pressure before approaching a plateau value. The dissociation constant of electrolyte can be derived from conductivity data. To develop generally applicable quantitative models of electrical conductivity of melt/fluid addressing the dependences on temperature, pressure, and composition, it requires more electrical conductivity measurements of representative systems to be implemented in an extensive P-T range using up-to-date methods.

Occurrence andmineral chemistry of chromite and xieite in the Suizhou L6 chondrite

The occurrence and mineral chemistry of chromite and its high-pressure phase xieite in the Suizhou meteorite were studied by different modem micromineralogical techniques. Three types of occurrences for chromite were observed in the Suizhou L6 chondrite： coarse chromite grains, cluster of chromite fragments in molten plagioclase, and exsolution lamellar chromite in oli- vine. All the chromite grains of the first two types are remarkably similar in chemical compositions, but the composition of exsolution chromite is inhomogeneous and variable in A1203 content. Xieite is a post-spinel CT-phase of chromite firstly found in the Suizhou meteorite. Three types of occurrences of xieite have also been revealed in this meteorite： coarse xieite grains, complex three-zone-grains consisting of the inner xieite, the intermediate lamellae-like CF-phase and the outer chromite phase, and two-phase-grains consisting of xieite and one of the high-pressure silicate minerals lingunite, ringwoodite or majorite. The curved boundary between xieite and the silicate half in two-phase grains is indicative of some partial or even full melting of the silicate phase. EPMA and EDS results show that the compositions of xieite inside/contacting the shock veins are also identical to that of chromite outside the veins. However, some element diffusion appeared in between the xieite and the silicate half in the two-phase grains, namely, some of Al^3＋ from lingunite, or Fe^2＋ from ringwoodite migrated to xieite, and some of Cr^3＋ migrated from xieite to lingunite or ringwoodite. Majorite in two-phase grains shows remarkable decrease of SiO2 and MgO, and notable increase of Al2O3 and CaO, indicating that its host mineral pyroxene was fully molten and mixed with the surrounding silicate melt of the vein matrix. The complexity in mineral chemistry of these two-phase grains in shock veins can be explained by the much higher shock peak temperature in shock veins （1800-2000℃） than in unmelted main body （-1000℃）, and by the much lower density of the silicate minerals （2.6-3.3 g/cm3） than that of chromite （4.43 g/cm^3）. Being a refractory and a rela-tively high-impedance material, chromite is chemically more stable and easier to reflect shock wave into the silicate half causing the partial or even full melting of silicate phases, upon which some diffusion of elements between the two phases them-selves, or even mixing of molten pyroxene and the surrounding silicate melt.