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排序方式: 共有149条查询结果,搜索用时 31 毫秒
81.
研究了磷酸三丁酯萃淋树脂色层分离,电感耦合等离子体质谱法测定富稀土样中微量铀、钍的方法。样品经消解后,以磷酸三丁酯萃淋树脂为固定相、8 mol/L硝酸为流动相过柱分离,样品中的大部分稀土元素随流动相流出,而铀和钍则被固定相吸附,用去离子水洗脱后,再用电感耦合等离子体质谱仪测定。铀、钍的检出限分别为0.06,0.16μg/L,测定结果的相对标准偏差均小于10%(n=5),加标回收率为98%~105%。对稀土矿石标准物质进行测定,测定值与推荐值相符。该法操作简便,测定结果可靠,适于富稀土样中微量铀、钍的测定。 相似文献
82.
Employing an Unsaturated Th4+ Site in a Porous Thorium–Organic Framework for Kr/Xe Uptake and Separation 下载免费PDF全文
Dr. Yanlong Wang Wei Liu Zhuanling Bai Tao Zheng Prof. Mark A. Silver Yuxiang Li Yaxing Wang Xia Wang Prof. Juan Diwu Prof. Zhifang Chai Prof. Shuao Wang 《Angewandte Chemie (International ed. in English)》2018,57(20):5783-5787
Actinide based metal–organic frameworks (MOFs) are unique not only because compared to the transition‐metal and lanthanide systems they are substantially less explored, but also owing to the uniqueness of actinide ions in bonding and coordination. Now a 3D thorium–organic framework ( SCU‐11 ) contains a series of cages with an effective size of ca. 21×24 Å. Th4+ in SCU‐11 is 10‐coordinate with a bicapped square prism coordination geometry, which has never been documented for any metal cation complexes. The bicapped position is occupied by two coordinated water molecules that can be removed to afford a very unique open Th4+ site, confirmed by X‐ray diffraction, color change, thermogravimetry, and spectroscopy. The degassed phase ( SCU‐11‐A ) exhibits a Brunauer–Emmett–Teller surface area of 1272 m2 g?1, one of the highest values among reported actinide materials, enabling it to sufficiently retain water vapor, Kr, and Xe with uptake capacities of 234 cm3 g?1, 0.77 mmol g?1, 3.17 mmol g?1, respectively, and a Xe/Kr selectivity of 5.7. 相似文献
83.
Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi) 下载免费PDF全文
Thomas M. Rookes Dr. Elizabeth P. Wildman Dr. Gábor Balázs Dr. Benedict M. Gardner Dr. Ashley J. Wooles Dr. Matthew Gregson Dr. Floriana Tuna Prof. Dr. Manfred Scheer Prof. Dr. Stephen T. Liddle 《Angewandte Chemie (International ed. in English)》2018,57(5):1332-1336
The synthesis and characterisation is presented of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS=N(CH2CH2NSiMe2But)3, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; TrenTIPS=N(CH2CH2NSiPri3)3, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route. 相似文献
84.
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86.
钍含量对Co/HMS催化剂结构和费托合成的影响 总被引:3,自引:1,他引:2
详细研究了钍含量对15% Co/HMS催化剂结构、费托合成CO转化率和烃分布的影响, 结果表明: 钍助剂的添加降低了催化剂的钴还原度, 并可使催化剂钴晶粒减小, 且存在钍物种对钴物种的覆盖; 钴晶粒的减小、较高钍含量时催化剂里钍物种对钴物种的覆盖和钴物种还原性能的降低, 使催化剂存在最优的钍含量, 此时催化剂表面暴露的金属钴原子最多, 较好地解释了钍含量达到1.5 wt%时, 催化剂CO转化率最高的实验现象. 烃分布研究表明: 反应温度较低时钍助剂将促进产物链的增长和高碳烃选择性的增加, 但反应温度较高时难以促进产物链的增长. 相似文献
87.
经辉 《中国无机分析化学》2015,5(3):34-40
建立了X射线荧光光谱法测定矿石样品中铀、钍含量的快速分析方法。采用高压粉末制样法,对不同含量的放射性样品的压片压力、粒径、含水率、用量等处理条件到进行单因素实验。在400 MPa压力下压制,克服了低压制样的弊端,制备的样片表面光滑、致密,大幅改善了制样重现性,有效地减少了部分基体效应,铀校准曲线的标准偏差从0.053%降到0.0071%,钍校准曲线的标准偏差从0.062%降到0.0057%。经国家一级标准物质验证,表明方法准确、可靠,能满足样品中铀、钍含量日常分析要求。 相似文献
88.
L. W. Komlew 《Isotopes in environmental and health studies》2013,49(11-12):409-412
89.
Thorium may not be determined by direct atomic absorption spectroscopy in flame media with appreciable sensitivity because of inefficient atomisation. Earlier papers from this laboratory have described indirect amplification procedures for similarly difficult elements e.g. niobium1 and titanium2 by atomic absorption spectroscopy· Madison and Guyon3 have developed a solution spectrophotometric procedure for thorium in which the heteropoly acid complex of thorium with phosphomolybdic acid is formed and reduced to the ‘heteropoly blue’. Strict adherence to time of addition of reagents is required in this procedure, and. it is necessary to effect an initial separation of the thorium from most other cations present in the sample. 相似文献
90.
F. Abou El-Nour N. Belacy M. Abdel-Khalik T. Khalil H. F. Aly 《Isotopes in environmental and health studies》2013,49(11):529-531
Thoriumdioxide was selected as a second promoter for nickel catalyst in addition to chromium oxide which was proved to be suitable to accelerate the H/D isotopic exchange reaction between hydrogen and water vapour. A series of Ni/Cr2O3/ThO2 catalysts were prepared by the co-precipitation technique. The amount of Ni was 70 … 90 mol%, while that of Cr2O3 was 0 … 20 mol% and that of ThO2 ranges from 0 … 30 mol%. This type of catalysts is sensitive for water condensation on its surface. The total surface area, total pore volume and pore radius of the catalysts were calculated from nitrogen adsorption on their surfaces at 77 K and application of the BET-equation. 相似文献