Luminescence and energy transfer between Ce3+ and Mn2+ in alkaline earth borates

The luminescence of Ce3+ and Ce3+, Mn2+ co-doped BaB8O13 and SrB4O7 prepared in air is studied. The results show that tetravalent cerium ion can he reduced to trivalent state in the hosts and gives rise to efficient luminescence. Energy transfer between Ce3+ and Mn2+ is possible. Mn2+ ions can be efficiently sensitized by Ce3+ and exhibit green and red emissions which implied that Mn2+ occupied the crystallographic sites of cations and boron sites of the anoins, respectively. The intensity ratio of red to Been emission in matrix increases with the increasing of manganese concentration.

Formation of epsilon-FeXN/BN magnetic nanocomposite and its thermodynamic and kinetic analyses

A nanocomposite of nanometer-sized magnetic granular epsilon-FeXN embedded in a nonmagnetic amorphous boron nitride matrix was prepared by ball milling mixture of alpha-Fe and hexagonal boron nitride in argon atmosphere. The grain size of the epsilon-FeXN alloy was about 10-20 nm. The nitrogen concentration in the epsilon-FeXN alloy increases with extending milling time. Both thermodynamic calculation and the present experiment show that iron and nitrogen atoms have higher alloying driving force than iron and boron atoms. Analyses of thermodynamics and kinetics about formation of the epsilon-FeXN alloy suggested that the formation of the epsilon-FeXN alloy is related to amorphization of the hexagonal boron nitride and refinement of the alpha-Fe. II was found from the present experiment that a critical grain size of the alpha-Fe reacting with nitrogen in the amorphous boron nitride is about 8 nm.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .2. Chemorheological modeling

Chemorheology and corresponding models for an epoxy-terminated poly(phenylene ether ketone) (E-PEK) and 4,4'-diaminodiphenyl sulfone (DDS) system were investigated using a differential scanning calorimeter (DSC) and a cone-and-plate rheometer. For this system, the reported four-parameter chemorheological model and modified WLF chemorheological model can only be used in an isothermal or nonisothermal process, respectively. In order to predict the resin viscosity variation during a stepwise temperature cure cycle actually used, a new model based on the combination of the four-parameter model and the modified WLF model was developed. The combined model can predict the resin viscosity variation during a stepwise temperature cure cycle more accurately than the above two models. In order to simplify the establishment of this model, a new five-parameter chemorheological model was then developed. The parameters in this five-parameter model can be determined through very few rheology and DSC experiments. This model is practicable to describe the resin viscosity variation for isothermal, nonisothermal, or stepwise temperature cure cycles accurately. The five-parameter chemorheological model has also successfully been used in the E-PEK systems with two other curing agents, i.e., the diamine curing agent with the addition of a boron trifluride monoethylamine (BF3-MEA) accelerator and an anhydride curing agent (hexahydrophthalic acid anhydride). (C) 1997 John Wiley & Sons, Inc.

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF DIVALENT SAMARIUM ACTIVATED BINARY FLUORIDES

A simple technique for preparation of powder binary fluorides activated with divalent samarium ions is described. The samarium impurity is introduced as samarium trifluoride SmF3 and hydrogen acts as the reducing agent to transform Sm3+ into Sm2+. Using this method, samarium has been stabilized in the divalent state in some fluorides: KMgF3, LiBaF3, BaBeF4, SrMgF4 and BaMgF4. Moreover, BaBeF4, SrMgF4 and BaMgF4 have never been activated with Sm2+ ions up to now. We also find that under the same synthetic conditions samarium can not be stabilized in the divalent state in some fluorides: KCaF3, CaBeF4 and CaMgF4, but the characteristic luminescence of trivalent samarium Sm3+ appears in these matrices. The emission and excitation spectra of samarium (Sm2+ and Sm3+) in these binary fluorides are presented and briefly discussed. The relationship between the oxidation state of samarium and the composition, the structure of matrices is also analyzed.

VALENCY AND ITS CHANGE PROCESS OF SAMARIUM ION IN SAMARIUM FLUORIDE SYSTEM

Nonstoichiometric series SmF(x) (2.0 less-than-or-equal-to x less-than-or-equal-to 3.0) have been synthesized by reduction of samarium trifluoride with hydrogen for several times, and the stoichiometric samarium difluoride has been obtained. The structure of nonstoichiometric samarium fluoride series and the valency of samarium ion are briefly discussed. The valent change process of samarium ion at high temperatures in different atmospheres is investigated.

INVESTIGATION ON THE LUMINESCENCE PROPERTIES OF DY-3+ AND EU-3+ IN ALKALINE-EARTH BORATES

In this paper, the yellow-to-blue intensity ratio of Dy3+ (Y/B) and the red-to-orange intensity ratio of Eu3+ (R/O) were studied in relation to the compositions and structures of alkaline-earth borates. The dependence of the energy of the Eu3+ charge-transfer band (CTB) and of the emission intensity of Dy3+ on the alkaline-earth ions and the boron content of the hosts is discussed.

大洋有孔虫微量元素研究

The most novel aspect of this thesis is the combination analysis of the boron isotopes and trace elements. What’s more, it also provides a reliable analytical technique, which is suitable for both boron isotopes and trace elements. Al/Ca values can be used to monitor the clay removal during the sample preparation. It is found that when Al/Ca>100 mol/mol, the measured boron isotopic compositions are always several permil lower than those properly cleaned. B/Ca ratios can be used to calculate the exact boron loaded for each sample. Otherwise, too much loading will lead to too long time for the whole analytical sequence, and too less loading might incur serious blank problem. One other benefit besides those discussed above is that the combination analysis of boron isotopes and trace elements on the same sample allows reconstruction of the marine carbonate system and atmospheric pCO2 without assumption of the other parameter. In the marine carbonate system, with the seawater pH from the foraminiferal 11B, one has to make an assumption on the other variable to obtain the rest four variables. A series studies found that U/Ca and B/Ca are potential proxies for seawater [CO32-]and [HCO3-], respectively. Since they are measured on the same sample with boron isotopes, hence, there is no spatial or temporal ambiguity in the incorporation of the two controlling parameters. With 11B and U/Ca, the reconstructed atmospheric pCO2 variations match the atmospheric pCO2 record from the Vostok ice core within ±20 ppm. The incorporations of U and B into foraminiferal carbonates are controlled by the overall growth rate of individual foraminifers and other possible factors. The reliable application of these proxies still require further calibrations. In a similar fashion, the combination analysis of boron isotopes and Mg/Ca also has great advantages. Mg/Ca has been proved to be a reliable proxy for the surface seawater temperature. With the combination analysis, one can determine the phase between changes in atmospheric pCO2 and surface seawater temperature, thus explore the cause and mechanism of the changes in atmospheric pCO2. .

利用MC-ICP-MS测定硼同位素及其在西藏地热和盐湖中的初步应用

Based on previous studies, boron can be separated from aqueous samples with Amberlite IRA-743 resin. Experiments on the elute temperature, elute volume and the dynamic resin exchange capacity have been performed in this study. Results show that the dynamic exchange capacity of the resin is 4.2mg B/g and at room temperature, boron fixed on the resin within this capacity level can be extracted quantitatively by using 5ml 2%HNO3. A new procedure has been developed for the measurement of boron isotope ratios in water samples using a Neptune MC-ICP-MS, after resolving the memory effect, which is a key problem, and investigating the impacts of mass bias and Si matrix effect. Using this method, it usually takes 20 min to perform one measurement on 0.1ppm boron solution with a precision of 0.23‰ (SD). If the relative deviation between a sample and the standard is large, the washout time needs to be doubled to achieve a higher precision. δ11B values of water samples from Yangbajing geothermal field vary from -10.53 to -9.13‰. Owing to the large difference B concentration and the small B isotope difference between deep geothermal water and surface water, B isotope ratios of the shallow geothermal fluids are dominated by the deep end member rather than the shallower one in the mixing process. As a consequence, δ11B-B relation is indicative basically of a dilution process. Vapor-liquid separation and calcite scaling also greatly influence B isotope fractionation. δ11B values of water samples from Dagejia geothermal field are from -15.98‰ to -11.67‰. Boron in Changma River near the field has two sources, freshwater lakes (Dajiamang Lake and Canke Lake) and geothermal waters. Finally, a preliminary discussion is included on boron geochemical characteristics of the salt lakes in Shuanghu area and other geothermal fields, to provide information for future studies on boron isotope geochemistry of geothermal systems and salt lakes in Tibet.

海洋生物碳酸盐硼同位素技术研究及其应用

近些年来，利用海洋生物碳酸盐硼同位素重建古海水pH，计算当时大气CO2含量，进而推测古气候的变化已成为国际同位素地球化学界研究的热点问题，被称为δ11B-pH技术。古海水的δ11Bsw是否恒定、B(OH)4−和B(OH)3间理论的硼同位素分馏系数4/3是多少以及碳酸盐的δ11Bcarb是否等于海水B(OH)4−的δ11B4值是该技术成功的三个关键。但到目前为止以上三项问题还没得到完全证实。 为确定方解石的硼同位素组成与海水pH的依赖关系，已进行过大量实验研究。他们的结果与预期的假设一致，支持了B(OH)4-是掺入方解石结构主要形式的假设。但近期 Pagani(2005)指出B(OH)4-也许不是掺入方解石结构的主要形式，B(OH)3也可能同时掺入进碳酸盐。肖应凯等(2006)的无机碳酸盐沉积实验发现碳酸盐沉积和母液间的硼同位素分馏系数大于1的异常现象，认为碳酸钙中镁或其它微量元素的存在是重要原因，推断这是在高pH生成Mg(OH)2沉积后11B优先掺入的缘故，推断有B(OH)3掺入碳酸盐的可能。 以前进行的沉积实验，只考虑到碳酸钙本身，确实证明了硼只以或主要以B(OH)4-参与进生物碳酸钙。但天然的海洋生物碳酸盐含有镁、锶、铁等微量元素，这些微量元素的存在可能会改变硼的参与行为，从而对硼同位素分馏产生影响。现代珊瑚礁中水镁石普遍存在，这是否会影响珊瑚的硼同位素组成而导致δ11B-pH技术的误差还值得研究。 针对以上问题，主要对硼掺入进Mg(OH)2的形式及分馏机理，现代珊瑚中镁、锶等微量元素与硼浓度及硼同位素的关系进行研究，并用生物碳酸盐的硼同位素对陆相产出有孔虫的沉积环境进行判别。 通过研究，得到以下几点认识： 1. 在Mg(OH)2从pH9.5～13的含硼合成海水中沉积时，Mg(OH)2沉积11B的变化范围为-1.20‰～28.26‰，高于合成海水的11B (-7.00±0.07‰)，沉积和海水间的硼同位素分馏系数固/液变化范围为1.0177～1.0569，平均值为1.0329，这是H3BO3优先掺入的结果，造成11B在Mg(OH)2沉积中富集。 2. Mg(OH)2沉积的硼浓度和硼在Mg(OH)2沉积与滤液间的分配系数Kd的变化范围分别为228.61 g/g～937.79 g/g和9.31～494.20。高pH值时硼掺入Mg(OH)2的过程中吸附作用占有重要位置。 3. Mg(OH)2吸附实验表明，硼掺入Mg(OH)2非常迅速，4 h能达到平衡。平衡后Mg(OH)2中硼浓度[B]固和固相与溶液相间的分配系数Kd随pH设定的升高和固液比的降低而降低。而且最高的[B]固和Kd均远高于硼被金属氧化物或粘土矿物吸附时的对应值，表硼具有很强的掺入Mg(OH)2的能力。 4. 吸附平衡时溶液相的11B液f (-19.2‰～-17.8‰)均低于原始溶液的11B液i (-7.00±0.07‰)，计算的Mg(OH)2与平衡溶液间的硼同位素分馏系数固-液变化范围为1.0186～1.0220，平均值为1.0203。这充分表明，硼掺入Mg(OH)2时11B优先进入固相，这是B(OH)3优先掺入的结果。 5. 硼以B(OH)3和B(OH)4-两种形式同时掺入Mg(OH)2，并以B(OH)3优先掺入为主，pH设定越低掺入的B(OH)3比例越高。 6. 硼将通过吸附和与Mg(OH)2的沉淀反应而掺入Mg(OH)2，两者共同决定了Mg(OH)2中硼同位素分馏特征。 7. Ca、Sr、B和Na在珊瑚中均得到富集，而Mg在珊瑚中却是贫化的。珊瑚的B浓度主要不是由这几种元素决定的。 8. 珊瑚δ11Bcarb的变化范围为22.8‰～27.9‰，平均为25.2‰。除与B浓度相关性明显外，珊瑚δ11Bcarb与其它四种元素的相关性不强。北海涠洲岛、灯楼角和三亚三地珊瑚与海水间的分馏系数carb-sw分别为0.9839、0.9847和0.9850。珊瑚与海水B(OH)3间的分馏系数carb-3的变化范围为0.9772～0.9800，平均值为0.9788，随pH升高carb-3减小。珊瑚的平均δ11Bcarb基本位于采用=0.9772时理论计算的δ11B4曲线之上，而且都低于原始合成海水的δ11Bcarb，表明硼是以B(OH)3和B(OH)4-两种形式同时掺入进珊瑚中的，并以B(OH)4-优先掺入为主。 9. 由于B(OH)4- 和B(OH)3同时进入到珊瑚中，d11Bcarb=d11B4的假设不能成立，由所测定生物碳酸盐的δ11Bcarb值计算的海水pH值会产生误差，使δ11B-pH技术变得更为复杂。 10. 实验模拟与自然的真实情况是有差距的，不能完全用实验模拟来代替自然的真实情况。 11.杨户庄剖面的第四纪早期有孔虫的生存环境是非海相环境，不是“海侵”或“海泛”的结果；同时也表明有孔虫并非是特有的海洋生物，它完全可以在陆相环境中存在。

地表环境过程的硼同位素地球化学研究

硼同位素作为灵敏的地质示踪剂,被成功地用于解决一些地球化学问题.如壳一幔演化和板块俯冲过程的研究、判别沉积环境和物质来源、研究成矿作用和矿床成因、古海洋和古气候研究、水环境污染研究等.但地表风过程的硼同位素地球化学研究非常少,其分馏机理和分馏程度还很不清楚.为此该论文着眼于大陆风化过程的硼同位素地球化学特征的研究.在硼同位素分析方法研究的基础上,成功地测定了洛川黄土剖面酸溶相样品和西江河水样品的硼同位素组成.对典型陆相条件风化过程和流域侵蚀过程的硼同位素地球化学特征进行了探讨.