排序方式: 共有26条查询结果,搜索用时 312 毫秒
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经洗净烘干并磨碎的试样在硝酸中浸泡过夜后在硝酸-高氯酸中消解,蒸发至冒白烟并继续蒸至近干,加入一定量的盐酸微沸1~2min,使硒(Ⅵ)还原为硒(Ⅳ),溶液用盐酸(5+95)定容至50mL。此溶液由载流盐酸(5+95)溶液送入氢化物发生器,与还原剂10g.L-1 KBH4溶液混合并反应生成硒的氢化物,样品中汞则生成原子态汞蒸气。两者由载气引入原子化器,在选定的仪器工作条件下,测定硒及汞的荧光强度。在实际样品中,硒、汞共存的浓度比未超过10,在同时测定中两者之间互不干扰。按所提出的条件测定,硒、汞的质量浓度在1.0~5.0μg.L-1范围内与相应的荧光强度值之间呈线性关系,方法的检出限(3s/k)依次为0.077,0.009 8μg.L-1。对仪器测定精密度做了试验,测得其相对标准偏差(n=7)依次为1.98%,1.31%。 相似文献
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Laser multilayer deposition of Rene88DT superalloy on DD3 single-crystal substrate is conducted.The influences of the crystal orientation of the substrate and the profile of the solid/liquid interface of the molten pool on the deposited microstructure are investigated.A unique strategy is proposed by adjusting the angle between the substrate surface and the substrate crystal orientation.This approach prevents the formation of the turned dendrite,thus obtaining a fully directional microstructure in the deposits. 相似文献
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在借鉴已有科学史融入其他学科教学模式的基础上,针对目前化学史融入中学化学课程的实际教学现状,经过多次教学实践的检验,提出了一种将化学史有效融入中学化学教学实践的“历史线”“探究线”“知识线”和“应用线”的四线式教学模式,该模式可将化学核心素养的培养贯穿于整个教学之中。 相似文献
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高T_c氧化物 Bi_(2-x)Pb_xSr_2Ca_2Cu_3O_y(x=0.2,0.3,0.4,0.5)大块超导体的 Meissner 效应表明存在110K 和85K 两个超导相,并且以110K 相为主,抗磁转变起始于103K 附近.不同样品在77.3K 的磁化实验表明,当 x≤0.3时,H_(Cl)≈28Oe,当 x>0.3时,H_(cl)=25Oe.x=0.3的样品在不同温度下的磁化实验结果表明,在 T=77.3—95K 之间,H_(Cl)与 T 成线性关系,且 dH_(Cl)/dT=-1.07Oe/K.两个超导相的存在导致磁化曲线峰的拉宽,且拉宽程度与85K 相所占的比例有关. 相似文献
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超延伸高分子量聚乙烯力学性能的研究王维泮,张凤英(北京化工大学高分子系北京100029)关键词超高分子量聚乙烯,冷拉伸,超延伸,延伸比随着高科技的发展,对材料性能的要求越来越高.目前一些发达国家正在致力于高机能、超强力的塑料.使高分子高度取向是获得高... 相似文献
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Laser solid forming (LSF) from blended elemental powders is an advanced technique to investigate new alloy systems and to create innovative materials. Accurate composition control is critical for the applications of this technique. In this letter, the composition analysis is performed on LSF titanium alloys from blended Ti, Al, and V powders. It is found that the composition of as-deposited sample can be controlled by keeping the identity of the divergence angle of each elemental powder stream. Based on the consistency condition for divergence angles of different elemental powder streams, the matching relation among the Ti, Al, and V powder characteristics (particle size and density) can be obtained, which ensures the consistency in composition between the laser deposits and the blended elemental powders under different laser processing parameters. 相似文献