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An analytical procedure for the determination of uranium and thorium in the sub-ng/g range as well as of other trace elements in the ng/g to g/g range in high purity quartz samples is described. The results obtained by inductively coupled plasma mass spectroscopy (ICP-MS) are compared to those obtained by other analytical techniques (instrumental neutron activation analysis, INAA; flame atomic absorption spectrometry, AAS; Zeeman graphite furnace atomic absorption spectrometry, ZGFAAS; total reflection X-ray fluorescence analysis, TRFA; direct current arc optical emission spectrometry, DC-arc OES; and X-ray fluorescence analysis, XRFA). For the ICP-MS measurements, the decomposition of the samples is carried out with HF/HNO3/H2SO4-mixtures. The results obtained by the different methods show reasonable agreement. For uranium and thorium, ICP-MS proves to be the most sensitive method: detection limits of about 50 pg/g can be achieved for both elements.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
65.
O. Martins J.Y. Buzaré J. Emery P. Claudy J.M. LéTOFFé V. Brandel M. Genet 《Journal of Sol-Gel Science and Technology》1997,8(1-3):315-319
Different transparent phosphate xerogels were synthesized using concentrated solutions of metal chlorides and phosphoric acid
with a proper mole ratio of both components. By this method we prepared bulk samples of thorium and tin(IV) phosphate xerogels
by drying at room temperature or at 350 K. Some properties of these amorphous materials were studied by means of differential
scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) techniques. Depending on mole ratio metal/phosphate,
these xerogels show, near 180 K, inflection points which we interpret asT
g
. Samples dried at 425 K lose their transparency and have noT
g
. Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties were confirmed
by EPR studies of the xerogels doped with Cr3+ and Fe3+ ions as probes. These results show the existence of two different phases in the xerogels: a liquid-like one, in the range
from 190 K to 350 K and a solid-like one, in the range from 4 K to 190 K. 相似文献
66.
T. A. Mastryukova O. I. Artyushin M. P. Pasechnik E. V. Sharova I. L. Odinets V. P. Morgalyuk I. G. Tananaev G. V. Myasoedova B. F. Myasoedov 《Russian Chemical Bulletin》2005,54(11):2540-2544
The composition of complexes formed upon the extraction of UVI and ThIV nitrates with O-n-nonyl(N,N-dibutylcarbamoylmethyl) methyl phosphinate (L) from solutions of nitric acid without additional solvent was determined by 31P NMR spectroscopy. The structures of the complexes formed were studied by IR spectroscopy. Uranium(VI) is extracted from 3 and 5 M solutions of HNO3 as the [UO2(L)2(NO3)2] complex, while thorium(IV) is extracted from 5 M HNO3 as the [Th(L)3(NO3)3]+·NO
3
−
complex. In both cases, ligand L has bidentate coordination. Ligand L contacts with 3 and 5 M nitric acid to form adducts L·HNO3 and L· (HNO3)2, respectively.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2460–2464, November, 2005. 相似文献
67.
Employing an Unsaturated Th4+ Site in a Porous Thorium–Organic Framework for Kr/Xe Uptake and Separation
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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
68.
Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)
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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
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