Crystallographic and electrical study of the chromium substituted ferrous zinc copper ferrites

The structural and electrical properties of the oxidic spinel Zn_0·5Cu_0·5Fe _x Cr_2−x O₄ (x=0·8, 0·9, 1·0, 1·1) have been investigated through X-ray diffraction, electrical resistivity, and thermoelectric measurements. X-ray diffraction data showed formation of single spinel phase with cubic structure. D.C. resistivity measurements from room temperature to 850 K was carried out and activation energy for all the compositions evaluated. Thermoelectric measurements showedp-type semiconducting nature in all the samples.     

中子活化分析法作为标准物质元素定值权威方法的研究

中子活化分析全面参量化方法与传统的相对比较法相结合，初步满足了国际标准化组织对标准物质元素定值权威方法的定义。首次担子同中子活化分析法可作为ＲＭ一批元素定值的权威方法。对典型的地质、岩石圈环境有证标准物质ＣＲＭ的分析结果表明：Ａｌ，Ａｓ，Ｃｅ，Ｃｏ，Ｃｒ，Ｃｓ，Ｅｕ，Ｆｅ，Ｈｆ，Ｌａ，Ｌｕ，Ｍｎ，Ｎａ，ｒＢ，ｓＢ，ｓＣ，Ｔａ，Ｔｂ，Ｔｈ，Ｙｂ等２０种元素的的实验测定值与推荐值与误差范围符合得很好，     

Viscosity of Some Binary Mixtures of Arenes

The viscosity of 12 binary mixtures of benzene+toluene, +ethylbenzene, +isopropylbenzene, +tert-butylbenzene; toluene+ethylbenzene, +isopro- pylbenzene, +tert-butylbenzene; ethylbenzene+isopropylbenzene; isopropylbenzene+tert-butylbenzene; o-xylene+m-xylene; m-xylene+p-xylene; and p-xylene+o-xylene has been measured over the entire range of composition. The viscosity deviations and excess Gibbs energy of activation G ^*E of viscous flow based on Eyring's theory have been calculated. The results have been analyzed in terms of the change in the structure of pure component molecules. The viscosity data have been correlated with the equations of Grunberg and Nissan; Hind, McLaughlin, and Ubbelohde; Tamura and Kurata; Katti and Chaudhri; McAllister; and Heric and Brewer. The Prigogine–Flory–Patterson– Bloomfield–Dewan (PFPBD) theory has been applied to analyze the excess viscosity of the present binary mixtures.     

甲烷活化机理研究进展

对近年来CH4活化机理方面的研究做了综述。在甲烷氧化偶联(OCM)反应中,催化剂表面上究竟何种氧负离子(O2-(超氧)、O22-(过氧)、表面晶格氧O2-)是参与活化CH4的活性氧物种仍然是一个存在争议的问题。在不同金属表面上CH4的直接活化模式被认为有两种,一种是形变模式,另一种是伸缩模式。在通过中间体途径活化CH4的研究中,发现“三中心两电子”脱氢反应和与有机金属阳离子络合物的络合交换反应是两种在温和条件下活化CH4的很有前景的活化方式。     

Apparent solubility of drugs in partially crystalline systems

Using several griseofulvin samples, representing different solid-state structures, the solubility behavior of drugs in both one-state (totally ordered, semiordered or disordered) and two-state systems was studied. Special attention was directed towards the surface structure of the particles. The partially crystalline samples were obtained by milling the raw material (crystalline standard) or storing the quenched sample (amorphous standard). The solid-state structure of the materials was studied using x-ray diffraction (XRD), differential scanning calorimetry (DSC), isothermal microcalorimetry (IMC), and scanning electron microscopy (SEM). The saturation concentration of the materials was studied in suspensions containing different dispersion concentrations of drug after centrifugation and filtration, using spectrophotometry. In all cases these dispersion concentrations exceeded the solubility of the drug. The solubilities were plotted vs. dispersion concentrations for each sample. Several solubility plateaus were found. The lowest and highest solubility plateaus corresponded to the solubilities of crystalline and amorphous standards. These plateaus were reached at 8 and 44 µg/mL for crystalline and amorphous griseofulvin standards, respectively. An intermediate plateau served as an indication of the existence of a totally semiordered structure. This was reached at 19 µg/mL for griseofulvin. Any deviation from these plateaus was suggested to be indicative of the existence of heterogeneity on the surface structure, which in most cases could be described as a two state system. In such cases, the apparent solubility was a function of dispersion concentration, until at very high dispersion concentrations (4000-20,000 µg/mL) the saturation concentration of the totally disordered (44 µg/mL) or semiordered (19 µg/mL) one-state phase was reached. No reduction in these values was observed during storage for 50 days. It is thus concluded that, in partially crystalline systems, the saturation concentration is an interfacial phenomenon, which depends on the amount, reactivity, and solid-state structure of the exposed solid surfaces in equilibrium with the solution. A simplified solubility model is proposed to qualitatively describe the relationship between established apparent solubilities (saturation concentrations) and different combinations of solid-state structures.     

Viscosities of Nonelectrolyte Liquid Mixtures Containing Acrylonitrile

The measurements of viscosity are reported for seven binary mixtures of acrylonitrile (AN) with ethanenitrile (EN), methyl acetate (MA), ethyl acetate (EA), n-butyl acetate (BA), dimethylformamide (DMF), dimethylacetamide (DMA), and dimethyl sulphoxide (DMSO) at 303.15 K temperature. The viscosity data have been correlated with the equations of Grunberg and Nissan; Hind, McLaughlin, and Ubbelohde; Tamura and Kurata; Katti and Chaudhri; McAllister; Heric and Brewer; and of Auslaender. The relations between the viscosity deviations , excess Gibbs energy of activation G*^E of viscous flow, and the intermolecular interaction in these mixtures are discussed.     

高铁闪锌矿加压浸出过程中Fe的动力学研究

进行了高铁闪锌矿加压浸出过程Fe的动力学研究。考察了温度、压力、始酸浓度、矿样粒度、溶液中Fe ~(2+)浓度对Fe浸出率的影响。结果表明,在试验条件下,浸出初期Fe的漫出速率受化学反应控制,遵循“未反应核减缩型”表面化学反应控制的动力学规律,浸出后期受固膜扩散控制,浸出中期由二者共同控制。     

活化法测量197Au等核素的14MeV中子反应截面

采用活化法测量了197Au等核素的14MeV中子反应截面.当入射中子能量为14.75MeV时,197Au(n,2n)196Au反应截面测量结果为(2175±76)×10-31m2,并与其他测量结果和ENDF/B-6评价数据库数据进行了比较.对于结果的一些不确定度因素,采用MCNP程序进行了分析.