Melting of Au and Al in nanometer Fe/Au and Fe/Al multilayers under swift heavy ions: A thermal spike study

Knowing that Fe is sensitive to swift heavy ion irradiations whereas Au and Al are not, the behavior of nanometric metallic multilayer systems, like [Fe(3 nm)/Au(x)](y) and [Fe(3 nm)/Al(x)](y) with x ranging between 1 and 10 mn, were studied within the inelastic thermal spike model. In addition to the usual cylindrical geometry of energy dissipation perpendicular to the ion projectile direction, the heat transport along the ion path was implemented in the electronic and atomic sub-systems. The simulations were performed using three different values of linear energy transfer corresponding to 3 MeV/u of Pb-208, Xe-132 and Kr-84 ions. For the Fe/Au system, evidence of appearance of a molten phase was found in the entire Au layer, provided the Au thickness is less than 7 nm and 3 nm for Pb and Xe ions, respectively. For the Fe/Al(x) system irradiated with Pb ions, the Al layers with a thickness less than 4 nm melt along the entire ion track. Surprisingly, the Fe layer does not melt if the Al thickness is larger than 2 nm, although the deposited energy surpasses the electronic stopping power threshold of track formation in Fe. For Kr ions melting does not occur in any of the multilayer systems.

The luminescence of Eu2+ in mixed phase system

The dependence of the structure of the hosts on the M ion radius in MMgAl10O17 (M = Be, Mg, Ca, Sr, Ba, Pb, Eu, Mn, Fe, Co, Ni, Zn, Cd, Sn) system was studied and the luminescence of Eu2+ the mixed phase system was discussed. When M ion radius is less than 0.10 nm, the system MMgAl10O17 constructs by the mixed phases consisting of manegtoplumbite and spinel, alpha-alumina or spinel and alpha-alumina. In the mixed phase of manegtoplumbite and spinel and alpha-alumina, Eu2+ ion preferentially occupies lattice site of the cations in manegtoplumbite well matched with the radius and charge of Eu2+. There exists only d-->f transition emission of Eu2+ and no characteristic emission of Eu3+ occurs in those hosts. In the mixed phase of spinel and alpha-alumina, Eu2+ can enter the lattice site of Mg2+ ion or Al3+ ion and the d-->f and f-->f transition of Eu2+ can been observed respectively. Meanwhile, since the radius and charge of matrix lattice ions substituted by Eu2+ do not match with those of Eu2+, the valence state of Eu2+ is unstable. Eu2+ is partly changed into Eu3+ and the emission of Eu3+ is obviously observed even under the condition of reduction atmosphere. If reaction temperature is more than 1 150 degrees C, Al2O3 forms alpha-Al2O3 structure, the f-->f transition of Eu2+ appears. If reaction temperature is less than 1 150 degrees C, a mixed phase of alpha-Al2O3 and gamma-Al2O3 is formed, the f-->f transition of Eu2+ disappears and a new band emission from d-->f transition of Eu2+ occurs.

Applications of improved 2-D numerical wave tanks in wave breaking

Song and Banner (2002, henceforth referred to as SB02) used a numerical wave tank (developed by Drimer and Agnon, and further refined by Segre, henceforth referred to as DAS) to study the wave breaking in the deep water, and proposed a dimensionless breaking threshold that based on the behaviour of the wave energy modulation and focusing during the evolution of the wave group. In this paper, two modified DAS models are used to further test the SB02's results, the first one (referred to MDAS1) corrected many integral calculation errors appeared in the DAS code, and the second one (referred to MDAS2) replaced the linear boundary element approximation of DAS into the cubic element on the free surface. Researches show that the results of MDAS1 are the same with those of DAS for the simulations of deep water wave breaking, but, the different values of the wavemaker amplitude, the breaking time and the maximum local average energy growth rate delta(max) for the marginal breaking cases are founded by MDAS2 and MDAS1. However, MDAS2 still satisfies the SB02' s breaking threshold. Furthermore, MDAS1 is utilized to study the marginal breaking case in the intermediate water depth when wave passes over a submerged slope, where the slope is given by 1 : 500, 1 : 300, 1 : 150 or 1 : 100. It is found that the maximum local energy density U increases significantly if the slope becomes steeper, and the delta(max) decreases weakly and increases intensively for the marginal recurrence case and marginal breaking case respectively. SB02's breaking threshold is still valid for the wave passing over a submerged slope gentler than 1 : 100 in the intermediate water depth.

湖北徐家山锑矿床地球化学和成矿机理研究

　　湖北省通山县的徐家山锑矿床赋存于上震旦统灯影组和陡山沱组的海相碳酸盐岩中，该矿床是华南锑矿带内典型代表性锑矿之一，也是湖北最具经济价值的锑矿床。本论文以该矿床为研究对象，在系统整理前人工作的基础上，进行了深入细致的野外地质考察和系统采样，选取有代表性的样品，运用流体地球化学、元素地球化学、同位素地球化学（C、O、Sr、S、Pb、Sm-Nd）等方法手段，对其成矿流体来源、成矿物质来源、成矿时代、矿床成因等主要矿床学问题进行了系统研究，探讨了该矿床的成矿机理，并对华南锑矿带内上震旦统锑资源潜力进行了初步评价。本论文主要取得以下几点认识： 1）通过对该矿床成矿期脉石矿物（石英、重晶石和方解石）中包裹体镜下观察、显微测温和激光拉曼探针分析，表明该矿床为典型的中低温（150～200℃）热液锑矿床，其热液属NaCl + H2O + CO2 ± N2型，具低盐度（3～6% NaCl）和中等密度（0.90～0.96 g/cm3）特征。结合氢、氧、锶、铅同位素等研究结果，进一步推断这种成矿流体主要来源于经深部循环演化的大气降水，不支持其主要来源于岩浆期后热液的观点。 2）该矿床成矿前和成矿期方解石碳、氧同位素研究结果，表明成矿流体中的溶解碳以H2CO3为主，该流体与围岩发生水－岩相互作用是导致成矿期方解石和辉锑矿沉淀的主要机制。结合方解石的稀土元素地球化学研究，可推断该矿床的两期方解石为同源不同期的产物。 3）微量元素、碳、氧、硫同位素研究结果，表明徐家山矿床的成矿物质与赋矿围岩具有亲缘性；其中最主要的矿石矿物—辉锑矿，其硫同位素组成（+11.2‰～+14.4‰）相对较高（平均值可能在华南锑矿带内最高）、极其均一，且塔式效应明显等为特征，指示该矿的赋矿围岩—震旦纪海相地层是硫的唯一来源。 4）对徐家山锑矿床首次利用锶、铅同位素示踪其成矿物质来源。利用铅同位素示踪手段，首次明确提出该锑矿床存在两个矿源层，部分成矿物质来自赋矿围岩，部分成矿物质来自下伏基底地层，突破了前人对成矿物质仅来源于赋矿围岩的传统认识；并从锶同位素角度，进一步论证了下伏的中元古界冷家溪群基底是成矿元素锑的重要提供者。 5）首次对徐家山矿区成矿期方解石的Sm-Nd同位素组成进行了测定，并初步获得三条等时线年龄（323Ma、348Ma和402Ma）。结合该矿辉锑矿的正常铅模式年龄及成矿地质背景，可推断出该矿床应形成于加里东期。该结论否定了前人燕山期成矿的观点，为重新认识该矿的矿床成因和成矿机理提供新的契机。 6）徐家山锑矿床的成矿时代与那些江南古陆中赋存于前寒武系的锑（和/或金）矿床一致，其成矿流体特征与华南锑矿带其它典型锑矿床相似，揭示出华南锑矿带内不同地段、不同层位产出的锑矿床存在某种共性，这有助于揭示我国华南锑矿带不同锑矿床之间的内在联系以及该矿带锑大规模成矿的机制。 7）根据前人和本文的研究成果，重新厘定了徐家山锑矿床的成因类型，明确提出该锑矿为沉积－改造型矿床，层控特征非常明显。 8）初步评估华南地区上震旦统中锑矿的找矿潜力。认为华南锑矿床带中上震旦统，尤其是鄂南、赣西北、湘西等地的该套地层，锑资源潜力巨大。华南锑矿带中的上震旦统有可能成为我国将来找锑矿取得突破的重要层位之一。

有机质在贵州晴隆大厂锑矿成矿过程中的作用

锑成矿中有机作用的研究国内外进行得极少，本文首先运用（有机）包裹体探讨了大厂锑成矿流体的一系列物理化学性质和主要成矿特征：1．成矿温度与盐度分别为150-180℃ 和10-12 Wt%，2．主成矿阶段水质类型属 F-SO_4Ca－K型，气相成份中甲烷含量较高(C_1/C_2～C_4 > 1)，3. 成矿介质水主要来自大气降水，δD＝-63～-66‰, δ~(18)O = -3.5～-0.6‰)。有机地球化学研究显示岭好组有机碳含量高（平均 Corg = 0.71% > 0.5%)，完全具备生油能力，是一重要的烃源层。有机质反射率（Ro）达1.87-2.93%，演化程序较高，热变沥青多呈充填状，具明显的运移特征。模拟实验证明石油对锑有较强的萃取能力，可作为 Sb 迁移的良好载体；且按萃取实验结果，有机迁移与无机迁移同等重要。对腐殖酸（质）和高硫原油作了较详细的讨论－－腐殖酸（质）在形成矿源层中有重要作用，高硫原油热裂解本身可以产生H_2S，提供部份硫；而辉锑矿的最终形成则缘于大气降水的加入，温度降低和氧化等因素综合作用的结构。总结不同阶段不同有机质的不同作用，提出了有机－无机综合成矿模式。