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排序方式: 共有88条查询结果,搜索用时 10 毫秒
61.
J.A.H. Coaquira L.B. Carvalho A.W. Carbonari S. Quezado 《Physica B: Condensed Matter》2009,404(19):3116-3118
Structural, magnetic and hyperfine interaction measurements have been carried out on the novel compound La3.5Ru4O13 prepared under two different atmospheres (air and oxygen flow). This compound is formed in the orthorhombic structure (space group Pmmm, # 47). The coexistence of the triple-layered perovskite-type planes (quasi-2D structure) and the rutile-like slabs (1D structure) leads to interesting magnetic and electronic properties in this compound. The magnetic susceptibility of this system shows a peak at T~47 K associated with antiferromagnetic interactions. The Curie-Weiss behaviour of the susceptibility provides an effective magnetic moment consistent with Ru ions in low-spin state. Perturbed angular correlation measurements carried out with 111Cd probe in the temperature range 10-60 K reveal only quadrupole interactions and indicate the occurrence of structural distortions for T<40 K. 相似文献
62.
In order to study the binding of the toxic heavy metal ion Hg2+ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction
of 199Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold,
three-fold and four-fold coordinations.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
63.
M. W. Raynor I. L. Davies K. D. Bartle A. A. Clifford A. Williams J. M. Chalmers B. W. Cook 《Journal of separation science》1988,11(11):766-775
The combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter-face for subsequent infrared analysis involving the use of an infra-red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers. 相似文献
64.
R. Caruso N. Pellegri O. de Sanctis P.C. Rivas M.C. Caracoche 《Journal of Sol-Gel Science and Technology》1997,8(1-3):223-227
Powders and thin films of zirconia doped with 2.5 and 11.3 mole% Y2O3 have been fabricated via the sol-gel route. The phase structure and its thermal evolution have been investigated using mainly
the hyperfine nuclear technique of Perturbed Angular Correlations. Both resulting structures, tetragonal and cubic, exhibited
at least two different configurations around zirconium sites. The tetragonal powder involves an activation energy for vacancy
fast diffusion lower than the cubic powder. Conclusions have also been drawn regarding the thermal stability of the ceramics
under different heat treatments.
Member of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
Member of Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), Argentina. 相似文献
65.
Perturbed γγ-angular correlation spectroscopy (PAC) was used to investigate nanocrystalline Ni and NiCu alloys, which are
prepared by pulsed electrodeposition (PED). Using diffusion for doping nanocrystalline Ni with 111In four different ordered grain boundary structures are observed, which are characterized by unique electric field gradients.
The incorporation of 111In on substitutional bulk sites of Ni is caused by moving grain boundaries below 1000 K and by volume diffusion above 1000
K. The nanocrystalline NiCu alloys prepared by PED are microscopically inhomogeneous as observed by PAC. In contrast, this
inhomogeneity cannot be detected by X-ray diffraction. The influence of the temperature of the electrolyte, the current density
during deposition, and the optional addition of saccharin to the electrolyte on the homogeneity of nanocrystalline NiCu alloys
was investigated.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
66.
Katalin Barkcs Ildik Bohuss Andrs Bukovszky Imre Varga Gyula Zray 《Microchemical Journal》2000,67(1-3)
The applicability of an inorganic, polyaluminium-type flocculent was tested comparing to polyacrylamides — an organic-type flocculent — used in the drinking water treatment process. The efficiency of this inorganic flocculent in the removal of suspended solids and also in minimizing the residual concentrations of the dissolved organic and inorganic micro-pollutants was checked in the case of purifying filter backwash water. Experimental data showed the advantage of the inorganic flocculent applying procedure as a part of recent water treatment technology. The applied polyaluminium-salt was economically competitive, improved the process stability and also ensured good water quality parameters. 相似文献
67.
Long Zhao Matthew B. Prendergast Ralf I. Kaiser Bo Xu Utuq Ablikim Musahid Ahmed Bing‐Jian Sun Yue‐Lin Chen Agnes H. H. Chang Rana K. Mohamed Felix R. Fischer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17603-17611
Polycyclic aromatic hydrocarbons (PAHs) represent the link between resonance‐stabilized free radicals and carbonaceous nanoparticles generated in incomplete combustion processes and in circumstellar envelopes of carbon rich asymptotic giant branch (AGB) stars. Although these PAHs resemble building blocks of complex carbonaceous nanostructures, their fundamental formation mechanisms have remained elusive. By exploring these reaction mechanisms of the phenyl radical with biphenyl/naphthalene theoretically and experimentally, we provide compelling evidence on a novel phenyl‐addition/dehydrocyclization (PAC) pathway leading to prototype PAHs: triphenylene and fluoranthene. PAC operates efficiently at high temperatures leading through rapid molecular mass growth processes to complex aromatic structures, which are difficult to synthesize by traditional pathways such as hydrogen‐abstraction/acetylene‐addition. The elucidation of the fundamental reactions leading to PAHs is necessary to facilitate an understanding of the origin and evolution of the molecular universe and of carbon in our galaxy. 相似文献
68.
69.
Al13形态的分离纯化与表征 总被引:23,自引:0,他引:23
采用乙醇-丙酮沉淀法提取了聚合氰化铝(PAC)中的Al13形态并采用Al-Ferron逐时络合比色法、27Al NMR,SEM,TEM和XRD等方法对所获得的水溶性Al13形态进行了分析表征.结果表明,通过向聚合氯化铝溶液中不断加入乙醇和丙酮,聚合氯化铝中各形态组分便会按照在混合溶剂中溶解度由小到大的顺序,依次从溶液中析出.截取中间组分得到Al13 形态.Al-Ferron逐时络合比色法和27Al NMR的鉴定结果表明,采用该方法分离提纯得到的样品中Al13 的含量达95%以上.SEM和TEM的鉴定结果表明,固体Al13聚集体主要为棱柱、单斜长方体和四面体等多面晶粒,小的聚集体粒径约 200mm,大的可达 2μm.溶液中的Al13 形态聚集成束并以枝状排列.XRD结果表明,Al13的特征衍射峰出现在2θ为5°~25°的范围内. 相似文献
70.
Karel Jank Conny
stman Hkan Carlsson Agneta Bemgrd Anders Colmsj 《Journal of separation science》1994,17(3):135-140
Peak splitting of high molecular weight polycyclic aromatic compounds originating from the microwave plasma of an atomic emission detector (AED) coupled to a GC has been described and evaluated. The influence of the solute structure, solute concentration, and physical conditions in the AED (such as detector temperature, make-up gas flow, concentration of reagent gases and distance of column end from the plasma) have been studied. An explanation is presented for peak splitting, which is based on an insufficient solute decomposition and solute mass flow in the discharge tube. Modification of the instrument by introduction of additional make-up gas applied through the transfer line has been shown to improve peak shape and solute response. 相似文献