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排序方式: 共有226条查询结果,搜索用时 15 毫秒
221.
Ashish Pandey Anoop Kelkar R. K. Singhal Chetan Baghra Amrit Prakash Mohd. Afzal J. P. Panakkal 《Journal of Radioanalytical and Nuclear Chemistry》2012,293(3):743-749
Pyrohydrolysis is a fast, reliable and convenient method for the decomposition of solid refractory samples. Thoria based mixed oxide nuclear fuels requires more than 1,200?°C reaction temperature to lose its structural integrity so as to release the halides. In the present paper, we report WO3 accelerated pyrohydrolytic extraction technique for the separation of F? and Cl? from thoria based fuels along with the feasibility of using MoO3 and V2O5. The mechanism of extraction has been investigated in detail using X-ray diffraction and recovery studies. ThO2 along with its halides undergo high temperature solid state reaction with WO3 forming Th(WO4)2 and releasing the halides for their subsequent hydrolysis. The quantification was carried out by ion chromatography with suppressed ion conductivity detection. The average recoveries of the spiked samples for F? and Cl? were 93?C99%. The method was successfully applied for simultaneous determination of F? and Cl? in thorium based nuclear fuel samples at 950?°C. 相似文献
222.
Zhang D Gao R Afzal S Vargas M Sharma S McCurdy A Yousufuddin M Stewart T Bau R Selke M 《Organic letters》2006,8(22):5125-5128
Singlet oxygen reacts with binaphthyl phosphine derivatives such as 1,1'-binaphthyl di-tert-butyl phosphine to form the corresponding binaphthyl-2-oxide phosphine oxides. This new intramolecular arene epoxidation reaction proceeds with complete retention of stereochemistry. The binaphthyl-2-oxide di-tert-butyl phosphine oxide undergoes a slow "NIH-rearrangement" to form the corresponding hydroxylated product. A transient phosphadioxirane intermediate has been directly observed by low-temperature NMR. Kinetic analyses show that all of the phosphadioxirane intermediate is converted to product. [reaction: see text] 相似文献
223.
Anoop Kelkar Amrit Prakash Mohd. Afzal J. P. Panakkal H. S. Kamath 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(2):443-449
An ion chromatographic method has been developed for the determination of traces of Li+, Na+, K+, Ca2+, Mg2+, Sr2+, Fe3+, Cu2+, Ni2+, Co2+, Zn2+, Cd2+, Mn2+ in UO2, ThO2 powders and sintered (Th,U)O2 pellets. This new method utilizes poly-(butadiene-maleic acid) (PBDMA) coated silica cation exchange column and mixed functionality
column of anion and cation exchange to achieve the separation of alkali, alkaline earths and transition metal ions, respectively.
It involves matrix separation after sample dissolution by solvent extraction with TBP (tri butyl phosphate)-TOPO (tri octyl
phosphine oxide)/CCl4. Interference of transition metal ions in the determination of alkali, alkaline earth metal ions are removed by using pyridine
2,6-dicarboxylic acid (PDCA) in the tartaric acid mobile phase. Mobile phase composition is optimized for the base line separation
of alkali, alkaline earth and transition metal ions. Linear calibration graphs in the range 0.01–20 μg mL−1 were obtained with regression coefficients better than 0.999. The respective relative standard deviations were also determined.
Recoveries of the spiked samples are within ±10% of the expected value. The developed method is authenticated by comparison
with certified standards of UO2 and ThO2 powders. 相似文献
224.
Afzal M. Yasmeen G. Saleem M. Butt P. K. Khattak A. K. Afzal J. 《Journal of Thermal Analysis and Calorimetry》2000,59(3):721-727
Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work,
the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the
temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated.
It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The
loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA
graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures
as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of
reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to
follow first-order kinetics.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
225.
David M. Haddleton Alex M. Heming Adam P. Jarvis Afzal Khan Andrew Marsh Sebastien Perrier Stefan A.F. Bon Stuart G. Jackson Ryan Edmonds Elizabeth Kelly Dax Kukulj Carl Waterson 《Macromolecular Symposia》2000,157(1):201-208
The use of copper(I) Schiff base complex catalysed atom transfer polymerisation of methacrylates is described. The use of a range of functional and multi‐functional initiators enables the synthesis of a range of functional and star polymers to be prepared under undemanding synthetic conditions. End capping with silyl enol ethers allows for ω‐functional polymers. The combination of novel initiators, functional monomers and end capping allows an unprecedented array of macromolecular structures to be produced with limited need for protecting group chemistry. 相似文献
226.
Hassan Haseebul Iqbal Muhammad Waqas Afzal Amir Muhammad Asghar Mazia Aftab Sikandar 《Journal of Solid State Electrochemistry》2023,27(1):125-137
Journal of Solid State Electrochemistry - A hybrid supercapacitor, also known as a supercapattery, combines the high power density of supercapacitors with the high energy density of batteries. In... 相似文献