Structural and magnetic properties and hyperfine interaction in La3.5Ru4O13 compound

Structural, magnetic and hyperfine interaction measurements have been carried out on the novel compound La_3.5Ru₄O₁₃ 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.     

Synthesis of Polycyclic Aromatic Hydrocarbons by Phenyl Addition–Dehydrocyclization: The Third Way

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.     

Al13形态的分离纯化与表征

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．     

氢化物发生原子荧光法测定聚氯化铝中的砷含量

建立了氢化物发生原子荧光法测定聚氯化铝中砷含量的检测方法。将聚氯化铝样品用硫酸溶解,蒸至近干,用氢化物发生原子荧光法测定其中的砷含量。在最佳测定条件下,砷的质量浓度在0~10.0μg/L范围内与荧光强度呈良好的线性关系,相关系数r=0.999 3,砷的检出限为0.03μg/g,样品加标回收率为82.5%~90.0%,测定结果的相对标准偏差为1.5%~1.9%。该法具有快速、准确、灵敏度高等优点。     

Comparative Study of Sol-Gel Derived 2.5% and 11.3% Y2O3-ZrO2 by Perturbed Angular Correlations Spectroscopy

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.     

硫酸根型阴离子交换树脂法改善PAC絮凝性能的研究

体系以聚合氯化铝溶液为原料、以硫酸型强碱性阴离子交换树脂为载体， 进行离子交换反应．结果表明，在保持氧化铝含量基本不变的情况下，能有效 地提高聚合铝的碱化度。同时生成含ＳＯ_４~（２－）的聚合氯化铝（简称ＰＡＣＳ），实验证明它的絮凝效果优于聚合氯化铝（简称ＰＡＣ）．     

Supercritical fluid extraction / capillary supercritical fluid chromatography / Fourier transform infrared microspectrometry of polycyclic aromatic compounds in a coal tar pitch

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.     

Instrument-induced effects in the analysis of polycyclic aromatic compounds by capillary gas chromatography with atomic emission detection (GC-AED)

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.     

Comparison of polyelectrolytes applied in drinking water treatment

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.     

Magnetic Properties of Grain Boundaries of Nanocrystalline Ni and of Ni Precipitates in Nanocrystalline NiCu Alloys

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.