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71.
Transition metal containing hafnium phosphates forms has layered monoclinic structure. In general these materials have similar route of thermal decomposition; i.e. they loss their crystal water first then at a higher temperature their structural one. At least the result HfP2O7 goes through phase change at about 1000 K. In detail among their thermal decomposition some differences occur. The Mn and Zn containing samples have similar behaviour as pure hafnium phosphate. The Cu and Ni containing materials have an additional exo-process connected with the transition metal oxide forms. In case of Co containing sample similar to that of Zn containing one (but very weak) processes were observed. 相似文献
72.
Utko J Przybylak S Jerzykiewicz LB Szafert S Sobota P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(1):181-190
Reactions of [Mg(thffo)(2)] (1) or [Ca(thffo)(2)] (2) with ZrCl(4) or HfCl(4) in a CH(2)Cl(2)/THF/CH(3)CN mixture give thermally stable neutral heterobimetallic tetranuclear complexes [M(3)M'(mu(x)-O)(mu,eta(2)-thffo)(6)(Cl)(6)] (thffo=tetrahydrofurfuroxide; M/M'/x: 3, Zr/Mg/3; 4, Hf/Mg/3; 5, Zr/Ca/4; 6, Hf/Ca/4) as colorless crystals in 75-82 % yield. X-ray diffraction studies show complexes 3-5 to contain oxo-bridged M(3) triangles that are capped by an alkaline earth metal-containing moiety to form species of C(3) symmetry. Reactions of ZrCl(4) and HfCl(4) with pure tetrahydrofurfuryl alcohol in EtOH and MeOH provide ionic complexes [M(3)(mu(3)-O)(mu,eta(2)-thffo)(3)(L)(3)(Cl)(6)]Cl (M/L: 8, Zr/EtOH; 9, Hf/EtOH; 10, Zr/MeOH) in 66-79 % yield. Complexes 8-10 consist of M(3) triangles that are analogous to those in 3-6 and possess similar overall symmetry, as shown by X-ray crystallography. Changes in the reaction conditions afforded the asymmetric neutral dimer [Zr(2)(mu-thffo)(2)(thffoH)(Cl)(6)] (7) and the homometallic [Zr(3)(mu(3)-O)(mu,eta(2)-thp)(3)(thf)(2)(Cl)(7)] (11). 相似文献
73.
Piyush Deokar Dr. Monica Vasiliu Prof. Dr. David A. Dixon Prof. Dr. Karl O. Christe Prof. Dr. Ralf Haiges 《Angewandte Chemie (International ed. in English)》2016,55(46):14350-14354
The binary zirconium and hafnium polyazides [PPh4]2[M(N3)6] (M=Zr, Hf) were obtained in near quantitative yields from the corresponding metal fluorides MF4 by fluoride–azide exchange reactions with Me3SiN3 in the presence of two equivalents of [PPh4][N3]. The novel polyazido compounds were characterized by their vibrational spectra and their X‐ray crystal structures. Both anion structures provide experimental evidence for near‐linear M‐N‐N coordination of metal azides. The species [M(N3)4], [M(N3)5]? and [M(N3)6]2? (M=Ti, Zr, Hf) were studied by quantum chemical calculations at the electronic structure density functional theory and MP2 levels. 相似文献
74.
Y. Arita T. Ogawa B. Tsuchiya T. Matsui 《Journal of Thermal Analysis and Calorimetry》2008,92(2):403-406
Heat capacities, electrical conductivities and phase transition temperature of hafnium hydrides, HfHx (0.99≤x≤1.83), were studied using a direct heating pulse calorimeter and a differential scanning calorimeter from room temperature
to above 500 K. The heat capacity of HfH1.83 was larger than that of pure hafnium and showed no anomaly of heat capacity. In contrast, there were λ-type peaks for the
heat capacity and DSC curves for HfHx (1.1≤x≤1.6) near 385 and 356 K. The anomalies of heat capacity and electrical conductivity of HfHx (1.1≤x≤1.6) were considered the result of phase transition and order-disorder phase transition for hydrogen in the hafnium hydride
lattice for HfHx (1.1≤x≤1.3). 相似文献
75.
A liquid-liquid extraction study has been conducted to separate hafnium from zirconium, using Cyanex 301 in kerosene. Noticeably, it is the first time that Cyanex 301 is utilized to separate Hf(IV) from Zr(IV). In this series of experiments, several parameters influencing the separation have been investigated, such as the initial pH, the extractant concentration, the metal ion concentration, the temperature, the type of the diluents and the salt addition. Regarding the aging of the Zr(IV) and Hf(IV) solutions, the solutions with a maximum 3 d aging time could be used with no difficulties. It was observed that the initial pH increase caused an increase in the Zr(IV)/Hf(IV) separation factor. Moreover, the distribution decreased with the temperature increase, suggesting that the reaction is exothermic. In agreement with the resulting data, the optimum separation factor illustrates the value of 7 at a pH of 4.00 in the presence of NaCl as an added salt. The attractive characteristics of the presently designed method are the use of low acidic nitrate solutions, the lack of using thiocyanate and a higher extractability of hafnium-Cyanex 301 relative to zirconium-Cyanex 301 complexes. 相似文献
76.
利用基于进化算法的晶体结构预测软件USPEX,并结合第一性原理方法对HfB的稳定晶体结构进行全局搜索。在基态条件下,新发现2个HfB晶体结构(空间群:P6m2和R3m)。其中,P6m2结构比已报道的Hf B晶体结构(空间群:Pnma、Cmcm、I41/amd和Fm3m)具有最低的基态能量。这些结构中,B原子分别以二维类石墨烯(P6m2和R3m结构),zig-zag链(Pnma、Cmcm和41/amd结构)和孤立原子(Fm3m结构)3种形式存在,从而导致它们具有显著的化学键合特征、高温稳定性和强韧特性差异。 相似文献
77.
新试剂7-(2,4,6-三羟基苯偶氮)-8-羟基喹啉-5-磺酸光度法同时测定微量锆和铪 总被引:1,自引:0,他引:1
本文研究了新试剂7-(2,4,6-三羟基苯偶氮)-8-羟基喹啉-5-磺酸(THBAQS)与锆、铪的显色反应.酸性条件下锆、铪均可形成 M-THBAQS-CTMAB三元络合物,ε_(315nm)~(Zr)=3. 27×10~4,ε_(515nm)~(HI)=3.8×10~4,适量H_2O_2使锆络合物吸光度显著降低,据此实现了锆铪的同时测定.本法简便快速、适用范围为0~30μgZr/25 mL,0~25μg Hf/25 mL,且X_(Zr)+X_(Hf)<35μg/25 mL. 相似文献
78.
79.
Electron-induced Hf-, W-L-shell partial, total production cross sections, mean ionization cross sections and Hf-L_3-shell ionization cross sections (at two energies) have been measured as functions of electron energies (from near threshold to 36keV). The influence of electrons reflected from the backing of the thin targets on measured results was corrected using a model to relate to the electron transport process. The mean paths of electron multi-scattered in the target itself (including forward and backward scattering) were calculated by means of Monte Carlo program (EGS4) and they were used to correct measured results. A comparison with both theoretical predictions was given. 相似文献
80.
E. Malhotra N. K. Kaushik G. S. Sodhi 《Journal of Thermal Analysis and Calorimetry》2001,65(3):859-864
Ionic chelate complexes of kojic acid(I) and hafnium(IV) of the type [(η5-C5H5)2HfL]+[MCl3]– (II)[HL=kojic acid; M=Zn(II), Cd(II), Hg(II), Cu(II)] have been synthesised and characterised by spectral studies (IR, UV, 1H NMR and 13CNMR). Thermogravimetric (TG) and differential thermal analytical (DTA) studies have been carried out for these complexes
and from the TG curves, the order and apparent activation energy for the thermal decomposition reactions have been elucidated.
The various thermal studies have been correlated with some structural aspects of the complexes concerned. From DTA curves,
the heat of reaction has been calculated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献