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951.
A new series of metal (II) organophosphates with the formula M(II) 2(H2O)2[O3PCH2(C6H4)CH2PO3] (M=Mn, Fe and Ni) have been prepared by hydrothermal synthesis. The structure consisted of two-dimensional metal–oxygen inorganic layers is pillared by p-xylylenediphosphonate to form a three dimensional framework. The layers are constructed by corner-sharing metal oxygen polyhedron. A study on the magnetism of the materials indicates the presence of spin canted antiferromagnetc interactions. The manganese and iron compounds represent the interesting 3D metal organophosphate molecular metamagnet due to spin canted antiferromagnetic with high critical temperature (40 K for Mn; 16 K for Fe). The infinite M–O–M layers are believed to be responsible for this high performance. 相似文献
952.
Effect of co-doping Yb, Gd and Ce in scandia stabilized zirconia (SSZ) on the phase stability, high temperature aging behavior and ionic conductivity was studied. Both binary (10 mol% SSZ) and the ternary (co-doped) compositions were found to be in single cubic phase in the as-processed condition. However, the binary composition exhibited the rhombohedral ‘β’ phase after sintering whereas the ternary compositions remained in the single cubic phase. The sintered pellets were aged at 900 °C for 500 h in air to study the phase stability at high temperature. Transmission electron microscopy revealed that the aged samples of Yb and Gd co-doped compositions contain small amount of the tetragonal phase which resulted in considerable degradation in conductivity (more than 20%). The Ce co-doped sample, on the other hand, was in single cubic phase after aging and this ensured that conductivity reduction was minimal in this composition. The co-doped samples however, showed higher conductivity before and after aging compared to the binary composition. The rhombohedral ‘β’ phase was absent in all the co-doped ternary compositions even after high temperature aging. 相似文献
953.
Sayantani Das Alo Dutta Binita Ghosh Sourish Banerjee T.P. Sinha 《Journal of Physics and Chemistry of Solids》2014
Nanoparticles of cadmium selenide (CdSe) have been synthesized by soft chemical route using mercaptoethanol as a capping agent. X-ray diffraction and transmission electron microscope measurements show that the prepared sample belongs to sphalerite structure with the average particle size of 25 nm. The band gap of the material is found to be 2.1 eV. The photoluminescence (PL) emission spectra of the sample are measured at various excitation wavelengths. The PL spectra appear in the visible region, and the emission feature depends on the wavelength of the excitation. Impedance spectroscopy is applied to investigate the dielectric relaxation of the sample in a temperature range from 323 to 473 K and in a frequency range from 42 Hz to 1.1 MHz. The complex impedance plane plot has been analyzed by an equivalent circuit consisting of two serially connected R-CPE units, each containing a resistance (R) and a constant phase element (CPE). The dielectric relaxation of the sample is investigated in the electric modulus formalism. The temperature dependent relaxation times obey the Arrhenius law. The Havriliak–Negami model is used to investigate the dielectric relaxation mechanism in the sample. The frequency dependent conductivity spectra are found to obey the power law. 相似文献
954.
Nickel nanoparticles have been synthesized by chemical reduction method. By the analysis of X-ray diffraction, the resultant particles are characterized and found to be pure crystalline nickel with a face-centered cubic (FCC) structure. The morphology and size of the nanoparticles are studied by scanning electron microscopy (SEM) and micrographs reveal that the nanoparticles are mostly spherical. The compositional analysis has been carried out by using EDAX. The quantum size confinement of the crystallites is evident from the blue-shift of the absorption edge in the UV–vis absorption spectrum. 相似文献
955.
In this paper, a hybrid Particle Chemical Reaction Optimization (PCRO) algorithm and lateral inhibition is proposed to solve the image matching problem. Lateral inhibition has the ability to enhance the characters of image, which can help to improve the accuracy of image matching. In order to overcome the shortcomings of basic Chemical Reaction Optimization (CRO) algorithm, we improve CRO by proposing PCRO which inspired from the thought of Particle Swarm Optimization (PSO). Comparative experimental results in image matching show that our proposed hybrid method performs much better than other bio-inspired algorithms. 相似文献
956.
傅里叶红外光谱法鉴别部分胡椒属生药的研究 总被引:1,自引:0,他引:1
利用共有峰率和变异峰率双指标,以胡椒属七种药用植物的红外指纹图谱为依据,计算出所测样品的共有峰率和变异峰率。建立了胡椒属七种药用植物共有峰率和变异峰率双指标序列,结果揭示了胡椒属七种药用植物的亲缘关系。中药海风藤与石南藤、大叶蒟根茎的共有峰率均在77%以上,变异峰率均在30%以下,此三种胡椒属药用植物亲缘关系较近;海风藤与胡椒根茎、十八症根的共有峰率在61%左右,亲缘关系稍远;海风藤与蒌叶根茎的共有峰率仅为44%。亲缘关系较远。利用红外二阶导数谱图,可以鉴别中药海风藤及其伪品石南藤、十八症根、大叶蒟根茎、胡椒根茎等品种。傅里叶红外光谱法可以对样品进行无损处理,不需要对药材进行复杂的提取分离过程即可提供化合物的官能团、类别、氢键等信息。该法能从整体水平分析谱图特征峰,具有分析速度快,重现性好,非破坏性和样品量小,制样简单,专属性强,节约成本,保护环境等优点。可以解决中药海风藤因资源短缺,伪品较多,鉴别困难等问题,也可为临床用药的安全、有效提供保障。傅里叶红外光谱法为胡椒属药用植物亲缘关系的探讨和真伪鉴别提供了一种新方法。符合中药向综合分析和整体分析发展的趋势。 相似文献
957.
958.
960.
E.V.Tretyachenko A.V.Gorokhovsky G.Y.Yurkov F.S.Fedorov M.A.Vikulova D.S.Kovaleva E.E.Orozaliev 《Particuology》2014,(6):22-28
TiO2 compounds possess relatively high adsorption abilities and exhibit high photocatalytic activities that exhibit potential for the destruction of organic pollutants in natural and waste waters.Nanostructured potassium polytitanates modified using transition metals and their oxides/hydroxides generate new nanomaterials that operate in the visible spectral range.This study presents the synthesis and investigation of the structure,composition and photocatalytic activity of powdered nanoscale quasi-amorphous potassium polytitanates particles modified with iron,zinc,copper,cobalt and nickel sulfate in aqueous solutions.All of the powders investigated in this work exhibit a high adsorption capacity for methylene blue dye(15-20mg/g) related to the welldeveloped surface of the layered potassium polytitanate particles.Introducing transition metals and their oxides/hydroxides influences the electronic structure of the obtained systems.A high photocatalytic activity was observed for systems containing iron,zinc,nickel and their oxides/hydroxides in the ultraviolet and visible ranges. 相似文献