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961.
962.
包覆型纳米铜-银双金属粉研究 总被引:21,自引:0,他引:21
目前,导电胶或者电磁波屏蔽涂料用的导电性填料主要有三类,一是铜粉,二是银粉,三是铜-银双金属粉。铜粉具有来源广、价格低廉、导电性好等优点,但其抗氧化性能弱;银粉导电性与抗氧化性好,但其资源日益匮乏。大量的研究试图通过对铜粉进行表面改性来提高其性能。表面改性有两种方法,一是包膜处理,用SiO2溶胶处理铜粉,铜粉抗氧化性能提高,但其表面导电性能大大降低犤1犦;另一类方法是在铜粉表面覆盖一层导电性能与抗氧化性能均佳的银或金而制成双金属粉末犤2~5犦。制取高性能的铜-银双金属粉是该领域的研究重点。目前获得铜-银双金属粉的方… 相似文献
963.
Six palladium(Ⅱ) complexes with isonitrosoethylacetoacetate imine Schiff base ligands, Pd(R-IEAI)2, were prepared and characterized by IR, Raman and electronic spectra. Complex tran Pd(p-CH3C6H4-IEAI)2 (2) cry- stallizes in the monoclinic system, space group P21/c,with a=1.2002(2),b=0.9972(2),c=1.1121(2)nm,β=90.43(3)°,Z=2,F(000)=616,μ=7.44cm-1. The final R and wR are 0.0244 and 0.0625 for 2620 ob-served reflections with I≥2σ(I), respectively. The geometry around the Pd(Ⅱ) ions in those complexes has a distorted PdN4 square plane, the Schiff base ligands R-IEAI- being coordinated through their oximino-nitrogen atoms and imino-nitrogen atoms. 相似文献
964.
The complex Cu2(μ-dppb)2(μ-Cl)2 has been synthesized from the reaction of CuCl, dppb and (n-Bu)4NCl. The crystal belongs to the triclinic with space group P1. The unit cell parameters are: a=9.939(4)?, b=10.083(6)?, c=14.104(5)?, α=76.46(3)°, β=71.02(2)°, γ=70.87(5)°. The single crystal X-ray diffraction analysis reveals that it has a bi-ring structure with a symmetry center at the middle of two Copper atoms. The outer ring is a 14-membered ring of Cu-dppb-Cu-dppb, and the inner ring is a 4-membered ring composed of two Cl- and two Cu(Ⅰ). Investigation of third-order optical nonlinearity shows that it exhibits considerable nonlinear absorptive and self-defocusing effect with α2=1.75×10-13m·W-1 and n2=3.19×10-18m2·W-1. CCDC: 193113. 相似文献
965.
L.M. Ilharco A.M. Santos M.J. Silva J.M.G. Martinho 《Journal of Sol-Gel Science and Technology》1997,8(1-3):877-882
The influence of the acid catalyst concentration on the structural evolution of a sol-gel system was studied by doping TEOS
based starting solutions with two fluorescent probes: a polystyrene chain (M
n
=1700) and a much shorter alkane chain (M=172), both of them labeled at both ends with 1-pyrenyl. For this purpose, each probe was incorporated in two TEOS∶H2O∶C2H5OH mixtures (molar ratios 1∶4∶1), one at pH 1.2 and the other at pH 2.5 (respectively below and above the isoelectric point
of silica). Very low concentrations of the probes were used (≤10−6
M), so the pyrene dimmers and excimers were formed only intramolecularly. The ratios of excimer to monomer fluorescence intensities
at excitation wavelength of 360 nm (where mainly the ground state pyrene dimmers are excited) were studied as a function of
time. Different evolutions of these ratios were observed, which allowed us to predict that the silica structure developsvia the formation of primary particles, even at pH values below the isoelectric point of silica, where it is not possible to
directly detect their formation. 相似文献
966.
967.
Kim C. Pich Roger Bishop Donald C. Craig Ian G. Dance A. David Rae Marcia L. Scudder 《Structural chemistry》1993,4(1):41-51
In a further exploration of the structural factors causing alicyclic diols such asexo-2,exo-6-dihydroxy-2,6-dimethylbicyclo[3.3.1]nonane (1) to adopt the helical tubuland inclusion host structure, the title compound (8) has been synthesized and its crystal structure determined. This 9-oxa analogue of (1) has a totally different structure [C10H18O3; orthorhombic;P21212;a 18.989(4),b 19.064(3),c 14.256(3) Å;Z 20; with finalR 0.065] due to involvement of the ether oxygen atom in the hydrogen bonding network. The structure of the diol (8) approximatesP¯421
c symmetry, and 16 of the 20 molecules per cell create a hostlike structure of this symmetry, which consists of tightly bound hydrogen bonded pillars parallel toc. The remaining guestlike molecules occupy inequivalent pseudo ¯4 sites separated byc/2 to form weakly bound columns parallel toc. Hydrogen bonds also occur between the pillars and columns. An ordered structure with sensible intermolecular contacts can be formed inP212121 with thec axis doubled. A difference betweena andb axial lengths correlates with a difference in occupancies of pseudo-¯4-related sites for the guest-like component of the structure. 相似文献
968.
The enthalpies of dissolution, transfer, and axial coordination for the Cd(II), Co(II), Mn(III), Fe(III), and Cr(III) complexes of tetraphenylporphine, H2(TPP), in nonpolar (C6H6, CCl4) and electron-donating solvents (DMF, DMSO, Py,c-C5H10NH) have been determined calorimetrically at 298.15 K. On the basis of thermogravimetrical data for the corresponding crystallosolvates the composition, thermal stability, and energy of intermolecular interaction of the metal-porphine complexes with pyridine have been calculated. Complexing in noncoordinating solvents brings about no radical change in the physicochemical characteristics of axial coordination which depend critically on the electron structure of the complex-forming metal.Translated fromfzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 846–850, May, 1993. 相似文献
969.
Refinement of the Crystal Structure of K2O2 The crystal structure of K2O2 has been refined using 241 diffractometer data (Cmca; a = 6.733(1), b = 6.996(1), c = 6.474(1) Å; Z = 4; Rw = 0.050). The distance O? O (1.541(6) Å) is significantly larger than that one assumed for alkali metal peroxides, so far. 相似文献
970.
交联聚异丁烯酸甲酯型负载树脂的孔结构与分离稀土性能的关系 总被引:3,自引:0,他引:3
本文报导异丁烯酸甲酯型负载树脂的交联度、致孔剂组成和含量对负载树脂孔结构的影响.结果指出,良溶剂和劣溶剂按一定比例混合作为致孔剂,可制备不同孔结构的树脂.致孔剂量增加,树脂表观比重减小,而比表面积、孔体积与平均孔径均增加.交联度从10%增加到35%,表观比重和比表面积增加,而孔体积与平均孔径减小.增加致孔剂所含良溶剂的比例,树脂的表观比重、比表面积增加,而孔体积与平均孔径减小.已制备一系列不同孔结构的2-乙己基膦酸单2-乙己基酯(P507)负载树脂,比较了它们分离La、Ce、Pr、Nd的性能.结果表明,适当孔结构的负载树脂用于萃取色层分离稀土元素具有优良的分离性能. 相似文献