Zhang Baisheng

Neutron diffraction study on site occupation of substitutional elements at sub lattices in Fe3 Al intermetallics

Abstract The site occupation of substitutional elements Cr, Mo, Ti, Mn, Ni and Si at sublattices in DO3-type stoichiometric Fe3Al intermetallics, effect of the elements on magnetic moment of the unit cell, and tensile properties at room temperature have been determined my means of neutron diffractometry and mechanical measurement in vacuum. The experimental results indicate that Cr, Mo, and Ti atoms all occupy the next nearest neighbors of Al atoms, Ni and Mn atoms the nearest neighbors, while Si atoms occupy the positions of Al atoms. All the alloying elements investigated in the present work modify the magnetic moment of the two types of Fe atoms in the unit cell. Based on the above results and corresponding mechanical measurements, the effects of the substitutional alloying elements on the intrinsic tensile properties are discussed.

CHARACTERISTICS OF BIOMARKERS IN THE RECENT SEDIMENT FROM QINGHAI LAKE, NORTHWEST CHINA

The occurrence of biomarker hydrocarbons in the Recent sediment of Qinghai Lake was investigated. It was found that the distribution of these biomarkers in Qinghai Lake, a semi-saline water lake, is unusual. The distribution of n-alkanes is predominated by high carbon-numbered alkanes with a high OEP (CPI) value. Two series of bicyclic sesquiterpanes derived from micro-organisms, e.g. algae or bacteria, were detected. The occurrence of tricyclic and tetracyclic terpenoids is characterized by the input of the organic matter from aquatic organisms. The conversion from hopenes existing in bacteria and blue-green algae into hopanes is put forward in this paper. C27C29 regular steranes, 4-methylsteroids, diasteranes, pregnanes, norsteroids and secosteranes were found in abundance in the sedimentary samples. Another important contribution of this paper is towards the geochemistry of amino acids in the Recent sediment of Qinghai Lake. The composition, distribution and evolution of the amino acids in the lacustrine sediments will be discussed in detail. It was found that several ratios of different amino acids have a clear diagenesis trend in the two cores studied. The racemization reaction of amino acids and their application in the geochemistry will also be discussed. The racemization of alanine and leucine were employed in this study to calculate the age of the sediment samples, with satisfactory result.

Biomarker characteristics of nonmarine oils in China

Abstract The present paper deals with the origin of non-marine oils in China. Since the formation of their source rocks, is greatly affected by paleoclimate and sedimentary environments, crude oils originated from such source rocks display different molecular characteristics. This paper attempts to identify these continental environments by using various geochemical parameters (OEP, Pr/Ph and biomarkers). In fact the distribution of hopanes with different carbon numbers is influenced by the characteristics of the original organic matter and by diagenetic transformations of sedimentary environments. As for biological markers, tricyclic terpanes, progesteranes and 4 methyl steranes are particularly abundant in saline depositional environments. On the other hand, onoceranes, 8,14-secohopanes, spirotriterpanes, tarxeranes, γ-lupanes and oleananes are specifically found in crude oils derived from swamp or very shallow lagoon facies. By studying recent sediments of different depositional environments it is therefore possible to establish effective models for reconstructing paleoenvironments.

NEUTRON DIFFRACTION STUDY ON (Bi−Pb)2Sr2Ca2Cu3O10

The polycrystalline sample of (Bi–Pb)2Sr2Ca2Cu3O10 with Tc=107 K was prepared. The X-ray diffraction proved that the sample is single phase. The crystal structure study on the sample has been carried out by neutron diffraction. The result shows that its structure is tetragonal body-centre structure with space group of I4/mmm, containing a few oxygen atoms at 4e site in Bi–Pb layers.

Petroleum geochemistry of the Talimu Basin

Abstract The Talimu Basin in China consists of a Paleozoic platform and a Meso-Cenozoic land block series. On the basis of sedimentological and tectonic studies of the Talimu Basin, it is proposed in this paper that two different kinds of oil-generating sub-basins and source beds are present, and responsible for the formation and accumulation of both marine and nonmarine hydrocarbons. A preliminary evaluation for different source beds within the basin has been carried out using the disciplines of sedimentology, lithofacies-paleogeography and organic geochemistry. We distinguish various depositional settings, with different oxidation and/or reduction features, by showing systematic differences in relative molecular distributions. These include characteristic facies-related biomarkers, such as tricyclic terpanes, pregpanes, fluorenes, dibenzofurans and dibenzothiophenes. Types of organic matter in source rocks are revealed by the presence/absence of land plant-derived biomarkers, including pimarane, abietane, dehydroabietane, fluoranthenes, chrysenes and perylenes. Kerogens, from black mudstones of the Saergan Formation and the Yingan Formation at the northwestern margin of the basin, have been selected for detailed examination of their hydrocarbon potential. Favorable regions for hydrocarbon prospecting in the basin are also discussed.

Neutron Scattering Study of Sr Substitution for Ba in YBa2Cu3O7-y

Neutron diffraction and inelastic scattering were carried out on YBa2-xSrxCu3O7-y (x=0.5, 1.0, 1.25). It was confirmed that the substitution of Sr for Ba in YBa2Cu3O7-y increases the oxygen vacancies in the Cu O chain. Moreover, the substitution strengthens the coupling between the Ba O plane and the Cu O chain, and reduces the crystal stability. These are the possible causes of Tc depression for Sr substituted YBa2Cu3O7-y.

Crystallographic structure and intrinsic magentic properties of R2Fe14BNx

We found that the nitrogen atoms can enter into the R2Fe14B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R2Fe14BNx, R=Nd and Y, have been investigated by using x-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffraction data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The relationship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed.

Structure Refinement of Bi2Sr1.855Ca1.145Cu2O8 from Neutron Data

Neutron diffraction study on the structure of Bi2Sr1.855Ca1.145Cu2O8 was carried out. Data refinements show that the average subcell structure for Bi2Sr1.855Ca1.145Cu2O8 is in the best fit of the space group Fmmm and the structure is described by alternate stacking of SrO-CuO2-Ca-CuO2-SrO slab and a double BiO layers. An oxygen layer sandwiched by the bismuth layers was confirmed.