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Electronic Structure Effect on Model Cluster for L1_2 Structure of Al_3Ti Intermetallic Compound with an Addition of Alloying Elements Fe, Ni and Cu

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Journal of materials Science & Technology 1995年第5期11卷 369-372页

作者： Senying LIU Rongze HU Dongliang ZHAO and Chongyu WANG(Central Iron and Steel research Institute, Beijing, 100081, China)(To whom correspondence should be addressed)Ping LUO(National research Cent or certified materials, Beijing, 100013, China)Zhongjie P natl res ctr certified mat BEIJING 100013PEOPLES R CHINA FLORIDA INT UNIV MIAMIFL 33199

By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.

关键词： Fe Electronic Structure Effect on Model Cluster for L12 Structure of Al3Ti Intermetallic Compound with an Addition of Alloying Elements Fe Al Ti Cu

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Bonding Characteristics of the Intermetallic Compound Al_3Ti+Cr

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Journal of materials Science & Technology 1996年第3期12卷 180-184页

作者： Senying LIU Rongze HU Dongliang ZHAO and Chongyu WANG (Central Iron and Steel research Institute, Beijing 100081, China)Ping LUO (National research Center for certified material, Beijing 100013, China)Zhongjie PU (Florida International University, Miami natl res ctr certified mat BEIJING 100013PEOPLES R CHINA FLORIDA INT UNIV MIAMIFL 33199

Based on our structural model and a tight-binding Hamiltonian the eIectronic structure has been calculated by use of a recursion method (RM) for two models of the tetragonal DO22 and the cubic Ll2 crystal structures in Al3Ti+Cr for contrast, from which bonding characteristics have been discussed. The results for the interaction energy (IE) show that Cr prefers to replacing Al site. Cr partly replacing Al can change the IE between the atoms and make the constriction of lattice constant c and the elongation of lattice constant a for the DO22 and thereby may induce the change of crystal structure from DO22 to L12. The results for bond order integral (BOI) and IE between the atoms also show that the strong (110) directional Cr-Ti bondings are ***, Al3Ti-base intermetallic compounds with addition of the Cr atom still remain brittle.

关键词： Ti II Al Bonding Characteristics of the Intermetallic Compound Al3Ti+Cr res

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Molecular Weight and Aggregation of Erwinia Gum in Aqueous Solutions

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Chemical research in Chinese Universities 2000年第2期16卷 156-162页

作者： ZHANG Lina XU Xiaojuan ZHU RongPing Iijima Hideki Wuhan Univ Dept Chem Wuhan 430072 Peoples R China natl res ctr certified reference mat Beijing 100013 Peoples R China Asahi Chem Ind Co Ltd Chem Technol Dept 4 Miyazaki 8828847 Japan

Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weightaverage molecular weights M w, numberaverage molecular weights M n and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.

关键词： Erwinia gum Light scattering SEC Membrane osmometry Viscometry Molecular weight Aggregation

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Photooxidation　of　hydrochlorofluocarbons　and　hydrofluorocarbons　initiated　by　OH　radicals

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Journal of Environmental Sciences 1996年第2期8卷 228-234页

作者： Zhong Jinxian Mu Yujing Yang Wenxiang(research Center for Eco-Environmental Sciences Chinese Academy of Sciences, Beijing 100085, China)Chen Dazhou(Chinese Center for certified reference materials, Beijing 100013, China) res. ctr. for Eco-Environ. Sciences Chinese Academy of Sciences Beijing 100085 China Chinese ctr. for certified Ref. mat. Beijing 100013 China

Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH radicals. The OH radicals can initiate photooxidation of HCFC-22 and 134A. The products of photooxidation were determined by a Fourier Transform infrared Spectroscopy with a 20ml long path cell. The products were COF2,CO2, HCI, H2O and HF for HCFC-22 + H2O2 system, HO, CO2, HCI and HF for HCFC-22 +H2O2 +O2 system, HCOF, CF3OOCF3,CO2, H2O and HF for HFC-134A +H2O2 system, HCOF, CO2, H2O, and HF for HFC-134A + H2O2+ O2 system. Based on those results, the mechanisms of photooxidation were suggested.

关键词： hydrochlorofluorocarbons hydrofluorocarbons photooxidation OH radicals FTIR.

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