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11.
H. F. Aly M. A. El-Haggan A. A. Abdel-Rassoul 《Journal of Radioanalytical and Nuclear Chemistry》1976,30(1):81-92
Three different alternatives are applied for the determination of the stability constants of zirconium and hafnium complexes
with 2-methyl lactic acid using cation exchange. Calculations based on the exchange equilibria of the highly charged metal
cations and the positively charged ligand complexes rather than that of the hydrolysed complex species are worked out according
to SCHUBERT and FRONAEUS, respectively. The third alternative adopted in this work, is principally based on the consideration
of all complexed species produced by hydrolyses in the aqueous phase. The B-values obtained by the different methods are intercorrelated
and discussed. 相似文献
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15.
胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响. 相似文献
16.
Amita Gupta Alexei Yu Ganin Parmanand Sharma Vikrant Agnihotri LM Belova KV Rao Mikhail E Kozlov AA Zakhidov RH Baughman 《Pramana》2002,58(5-6):1051-1059
We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show
a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are
found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there
exists no report in literature on any BiNi compound which is magnetic. 相似文献
17.
A. A. Abdel-Rassoul H. F. Aly R. Madbouly 《Journal of Radioanalytical and Nuclear Chemistry》1970,5(2):193-200
A high purity grade palladium matrix used for production of isotopes has been analyzed for Ru, Co, Fe, Zn, Cd and Hg by neutron
activation. The chemical procedure is based on the addition of respective carriers followed by the simultaneous separation
of different elemental impurities by anion exchange chromatography. The method is free from chemical interference.
Self-shielding of the matrix material has been considered and proved to be within the acceptable experimental error. Secondary
nuclear reactions are discussed and found to be negligible under the experimental conditions used.
Part I:Intern. J. Appl. Radiation Isotopes, 17 (1966) 309. 相似文献
18.
Darshan C Kundaliya Reeta Vij AA Tulapurkar U Vaidya R Pinto RG Kulkarni 《Pramana》2002,58(5-6):1041-1044
Electrical resistance (R) measurements of a bulk La0.33Nd0.33Ca0.33MnO3 perovskite in magnetic fields up to 40 kOe have revealed anomalous temperature hysteretic effects both in 0 Oe and 20 kOe
magnetic fields. The sharp peak observed in the R vs. T plot indicates the occurrence of metal-to-insulator (M-I) transition at a temperature of T
MI=110 K and 140 K, for cooling and warming paths, respectively. An applied magnetic field of 20 kOe reduces the resistance
and shifts T
MI to 160 K and 185 K for cooling and warming, respectively. We have observed a much higher resistance in the cooling path than
in the warming path leading to the hysteretic resistance ratio (R
cool/R
warm) of 200 at 110 K and 1.8 at 160 K for 0 Oe and 20 kOe, respectively. Record values of colossal magnetoresistance (CMR) have
been achieved. The CMR value reaches nearly 99% in the temperature ranges of 90 K to 140 K and 90 K to 170 K for 20 kOe and
40 kOe magnetic fields in the cooling mode, respectively. The observed unusual behavior is attributed to the co-existence
of La-rich and Nd-rich domains assumed to be distributed randomly in the compound. 相似文献
19.
We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu2 and 2H-NbS2. 2H-NbS2 is iso-structural and iso-electronic to 2H-NbSe2, whose similarity with CeRu2 as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We
report on the step change in equilibrium magnetization across the peak effect in CeRu2. We also present the vortex phase diagram of 2H-NbS2 obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS2 and 2H-NbSe2. 相似文献
20.
Activation analysis is applied for the simultaneous determination of manganese, nickel and copper in different uranium samples, including metallic uranium, uranium concentrates, oxide, acetate, nitrate and sodium uranate. The analytical scheme developed is based on separation of the uranium by paper chromatography and subsequent determination of these elements in the pile-irradiated residues by simple radiochemical operations. The reliability of the scheme proposed is tested, and the limits of sensitivity of the methods worked out are ascertained. Accordingly, microgram concentrations of the elements studied could be assayed in limited quantities of the samples analysed with a precision of +/- 15%. Reagent-blank determinations are also considered. 相似文献