表面脱β层梯度结构硬质合金研究进展

随着涂层技术在硬质合金领域的日益广泛应用,制备可防止涂层裂纹向基体扩展的具有表面脱立方相碳化物(即β相)的梯度结构的硬质合金基体成为需要。文中概述了此类结构合金的形成机理、影响因素以及发展现状和方向等。     

A study of function mechanism of hemxamethyl tetra-amine in gelation process of uranium

The UO2 ceramic microspheres are the most important materials in the spherical fuel elements for high temperature reactor (HTR). A process for preparation of UO2 kernels known as total gelation process of uranium (TGU) was developed as the production process of 10 mW HTR at Tsinghua University. The TGU process is based on the traditional sol-gel process, external gelation process and internal gelation process of uranium (EGU and IGU), which implies that the gelation action is initiated both by ammonia out of the gel particles and hemxamethyl tetra-amine (HMTA) inside the gel particles. The gelation behavior and the properties of uranium microspheres were investigated of the solution with and without HMTA. It is observed that good spherical particles can be obtained without HMTA in the sol, which indicates a more controllable and industrialized route will be set up. Contrasts between this route and the traditional EGU were also listed .     

RADIOIMMUNOTOXICOLOGICAL EFFECT OF ENRICHED URANIUM ON CENTRAL AND PERIPHERAL IMMUNE CELLS AND THE PROTECTIVE ACTION OF IL－1 AND IL－2

ＲＡＤＩＯＩＭＭＵＮＯＴＯＸＩＣＯＬＯＧＩＣＡＬＥＦＦＥＣＴＯＦＥＮＲＩＣＨＥＤＵＲＡＮＩＵＭＯＮＣＥＮＴＲＡＬＡＮＤＰＥＲＩＰＨＥＲＡＬＩＭＭＵＮＥＣＥＬＬＳＡＮＤＴＨＥＰＲＯＴＥＣＴＩＶＥＡＣＴＩＯＮＯＦＩＬ－１ＡＮＤＩＬ－２￥ＺｈｕＳｈｏｕｐｅ...     

改进的QPSO-BP算法的铀价格预测模型及应用

铀产品价格的变化直接决定了铀矿项目的价值,铀产品价格的预测,可提高企业的经营决策能力和抗风险能力。为提高预测的精度,采用基于改进的量子粒子群算法优化训练BP神经网络的学习算法,对铀价格进行建模预测。采用改进的QPSO算法优化BP网络的权值与阈值。将通过优化搜索得到的粒子的位置向量解码作为网络的权值与阈值,选择网络结构5．11—1对铀价格进行预测。结果表明：QPSO—BP模型的预测精度（0．15％）高于PSO-BP模型（4．55％）与BP模型（30．86％）。泛化能力指标平均相对变动值为O．0025,预测结果的泛化能力提高。相对误差分布集中,预测结果稳定。说明该模型在铀价格预测中有效,对项目投资决策有一定的参考价值。     

Premelting transition in uranium dioxide

Thermal analysis of the cooling curves of small samples of uranium dioxide, laser heated in a high-pressure autoclave on a subsecond time scale to a temperature just below the melting point, reveals, in the case of nominally stoichiometric UO_2.00, a significant -like heat capacity peak, indicating a premelting transition in this material. The results are discussed and a simple model is presented in terms of which the observed behavior can be described.Summary of a paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria. Because of its length, the full paper was published in a regular issue of this journal (Vol. 14, No. 2, 1993).     

Premelting transition in uranium dioxide

Thermal analysis of the cooling curves of small samples of UO_2±x —initially laser heated (in a high-pressure autoclave to inhibit evaporation) on a subsecond time scale to temperatures just below their melting points [T _m(x)]—reveals, in the case of nominally stoichiometric UO_2.00, a significant, -like, heat capacity [C _p(T)] peak near 2670 K; the cooling curves of samples exposed to a reducing environment, on the other hand, exhibit undercooling, characteristic of a first-order phase transition, while under oxidizing conditions it is found that the premelting transition readily disappears. These findings confirm Bredig's original prediction of a premelting transition in this material, in common with that found in other (nonactinide) fluorites near 0.85T _m. A simple model is presented in terms of which the observed behavior can be rationalized. The model is based on the hypothesis that the premelting transition is due to Frenkel disordering of the oxygen sublattice—a process which is rendered cooperative by attractive interactions between complementary Frenkel defects (oxygen interstitials and vacancies); these interactions are treated in a mean-field approximation. The quantitative degree of maximum disorder (realized just above the transition) is, on the other hand, controlled by repulsive interactions between like defects—the inclusion of which, solely through their effect on the configurational entropy, satisfactorily reproduces the values inferred from recent high-temperature neutron diffraction experiments. Assuming that the phase transition in stoichiometric UO_2.00 is of second order, the model predicts a divergent heat capacity, C _v, which approximates well to the experimental (-like) C _p peak. Crucial to reproducing the observed behavior away from stoichiometry is the introduction of a (linear) dependence of the nonconfigurational partial entropy of formation on the prevailing concentration of intrinsic Frenkel defects in UO_2±x; interestingly, it is found that the line of calculated (but unrealized) second-order transitions in UO_2+x intersects the U₄O₉ phase boundary near to where a high-temperature diffuse order-disorder transition has been observed in the oxygen superlattice, suggesting that the second-order, -transition in UO_2.00 is the stoichiometric counterpart of this transition in U₄O₉.     

我国南方某铀矿井通风系统优化改造研究

在全面分析总结我国南方某铀矿井通风系统存在的问题基础上,以按需分风的通风网络优化技术,对原有通风系统进行优化,提出了矿井通风系统总体改造方案.通过方案实施,氡及氡子体浓度达到了国家辐射防护标准要求,各采掘面平均氡子体浓度下降了22.9%.     

高山开采铀矿山安全防护研究

某铀矿山位于海拔3000 m以上,属于高山采矿,由于高山采矿不但存在地质灾害频发、工业场地安全性较差的问题,更重要的是高山铀矿山开采过程中还有具有高山病和放射性危害。在矿山设计中,应充分考虑高原采矿的特殊性,采取有针对性的安全措施,降低矿山开采中风险,使井下生产能够安全、顺利的进行。     

鄂尔多斯盆地银东地区层间氧化带特征分析

层间氧化带是矿床形成的直接控制因素,铀矿化位于层间氧化带的尖灭部位,产于相邻氧化带发育的灰色砂体中,层间氧化带是找矿的地球化学标志和矿床形成的直接控制因素。通过对该区地质构造和沉积演化历史的系统分析,重点描述中侏罗统直罗组和下白垩统华池—环河组层间氧化带的特征,进而确定本区具备形成层间氧化带砂岩型铀矿的条件。     

某铀矿床碱法地浸溶浸液配方探讨

结合某铀矿床碱法地浸室内试验，进行了氧化剂的种类、质量分数和溶浸剂的种类、质量分数选择试验，研究了反应时间、矿石粒度对铀浸出率的影响。结果表明，碳酸（碳酸氢）钠盐或铵盐是良好的溶浸剂，铀浸出率可达到70％～80％；加入质量分数为0．1％的双氧水和质量分数为0.02％的高锰酸钾，铀浸出率明显提高，可满足铀浸出需求。