Ca3Co4O9陶瓷的固相法制备及分析

本实验采用固相合成法成功地制备了Ca3Co4O9热电材料。通过对样品的显微结构与物相组成等进行分析研究,优化了制备工艺。实验结果表明:由固相法制得的Ca3Co4O9为取向无规则的片状组织;适当提高煅烧温度、延长保温时间有利于片状组织的生长。     

Partial oxidation of methane to synthesis gas over α-Al2O3-supported bimetallic Pt–Co catalysts

The partial oxidation of methane to synthesis gas was studied at atmospheric pressure and in the temperature range of 550–800°C over -Al₂O₃-supported bimetallic Pt–Co, and monometallic Pt and Co catalysts, respectively. Both methane conversion and CO selectivity over a bimetallic Pt_0.5Co₁ catalyst were higher than those over monometallic Pt_0.5 and Co₁ catalysts. Furthermore, the addition of platinum in Pt–Co bimetallic catalysts effectively improved their resistance to carbon deposition with no coking occurring on Pt_0.5Co₁ during 80 h reaction. The FTIR study of CO adsorption observed only linearly bonded CO on bimetallic Pt–Co catalysts. TPR and XPS showed enhanced formation of a cobalt surface phase (CSP) in bimetallic Pt–Co catalysts. The origins of the good coking resistivity of bimetallic Pt–Co catalysts were discussed.     

负载型钴铜双金属氮化物催化氨分解研究

Co and Mo bimetallic nitrides supported on Mg（Al）O, MgO and γ-Al2O3 were prepared in temperatureprogrammed reactions with NH3. The surface morphology, chemical composition and catalytic activity for NH3 decomposition on the supported Co and Mo bimetallic nitrides were studied by X-ray diffractometer （XRD）, NH3 temperature-programmed desorption and mass spectrometer （NH3-TPD-MS）, temperature-programmed desorption and mass spectrometer （TPD-MS）, H2 temperature-programmed surface reaction （H2-TPSR） and activity test. The phases of Co3Mo3N and MoN could be formed on Mg（Al）O, MgO and Al2O3 during the nitridation, and they might be more uniformly dispersed on Mg（Al）O and MgO than on γ-Al2O3. Transition metallic nitrides are generally considered as potential catalysts for hydrogen-involving reactions due to the entrance of hydrogen atoms into subsurface and the lattice of metallic nitrides. The diffusion of nitrogen in the bulk and the structure transformation of Co and Mo nitride compounds occur during NH3-TPD, but the supported Co and Mo bimetallic nitrides are not easily reduced at H2 atmosphere. Co3Mo3N/Mg（Al）O catalyst exhibits the highest activity, while Co3Mo3N/Al2O3 exhibits the lowest activity for NH3 decomposition. Furthermore, the catalytic activity of Co and Mo bimetallic nitrides is not only much higher than that of supported single metallic nitride, but also highly dependent upon the surface acidity and BET surface area of support.     

微波共沉淀法制备锂离子电池正极材料LiNi0.8Co0.2O2

采用微波共沉淀法合成了制备LiNi0.8Co0.2O2的前驱体球形α-Ni0.8Co0.2(OH)2，将其与LiOH·H2O混合，在氧气氛围下，用不同的烧结温度分别烧结10小时获得LiNi0.8Co0.2O2正极材料。用XRD、SEM对所制备的正极材料进行结构和形貌分析，用恒流充放电测试材料的电化学性能。结果表明，烧结温度对材料结构和电化学性能影响较大，所合成材料均具有α-NaFeO2的层状结构，烧结温度越高材料结晶越完善。900℃烧结的LiNi0.8Co0.2O2材料初级颗粒结晶最完善而且其二次团聚粒子的平均粒径最小，其表现出的电化学性能也最好，首次放电容量为189.1mA·h·g-1，首次循环放电效率达到92.5%。30循环后放电容量保持在148 mA·h·g-1，显示出较好的循环稳定性。     

Parameter Estimation for Periodically Stationary Time Series

Abstract. The innovations algorithm can be used to obtain parameter estimates for periodically stationary time series models. In this paper, we compute the asymptotic distribution for these estimates in the case, where the innovations have a finite fourth moment. These asymptotic results are useful to determine which model parameters are significant. In the process, we also develop asymptotics for the Yule–Walker estimates.     

Characterization and tests of planar Co3O4 model catalysts prepared by chemical vapor deposition

The chemical vapor deposition method was used to deposit thin films of cobalt oxide starting with cobalt (II) acetylacetonate and oxygen. The deposition process was investigated and the obtained films were identified as a cubic spinel-type polycrystalline Co₃O₄ with a crystallite size of 30–40 nm. The coating was carbon-free and the surface oxygen concentration was measured to be 66 at.% with AES analysis. Smooth and highly uniform thin films were deposited on planar stainless steel substrates and subjected to TPR and catalysis tests that show positive correlation. The apparent activation energy of Co₃O₄ reduction to CoO was measured to be (33±5) kJ/mol. The catalytic activity of Co₃O₄ was investigated toward the conversion of both propane and ethanol to carbon dioxide. Though the catalytic action was registered at the same temperature, the deactivation process was seen to be different. The catalytic conversion of ethanol induces a fast deactivation process, which was linked to its high ability to reduce Co₃O₄.     

CO2 hydrogenation over micro‐ and mesoporous oxides supported Ru catalysts

We prepared relatively uniform supported Ru catalysts by ion‐exchange and CVD methods, using an NaY zeolite and a mesoporous FSM‐16 as substrates, and carried out CO₂ hydrogenation. They showed high activity for CO₂ hydrogenation. A Ru‐ion‐exchanged catalyst showed high activity for methanol production. Co addition promoted methanol formation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spreading of Cobalt Phase and Silicate Formation in Co/SiO2 Model Catalyst

The electron microscopy technique was used to characterize the cobalt–silica interaction in a model catalyst at high temperature in air. The samples were in the form of thin cobalt films (1 and 4 nm thick) supported on an amorphous layer of SiO₂. It was concluded that cobalt loading determines the evolution of the microstructure, morphology and phase composition. The spreading of the cobalt oxide phase and formation of cobalt silicate was established.     

添加剂对Cu/Co多层膜电结晶成核机理及磁性的影响

在硼酸镀液中以单晶S i(111)为基底用双槽法制备Cu/Co多层膜,在镀液中分别加入了镀铜添加剂2000#和镀钴添加剂5#。探讨了镀层电结晶成核机理,在基础镀液中铜电结晶为三维连续成核过程,钴电结晶在较低电位下为三维连续成核,在较高电位下为三维瞬时成核过程。加入添加剂后,铜、钴电结晶均为三维瞬时成核过程。测试了Cu/Co多层膜的磁性能;添加剂能提高多层膜的磁性能,无添加剂的Cu/Co多层膜的巨磁阻(GMR)值约为5%,而在加入了添加剂后,其GMR值高达52%。     

糠醛加氢制糠醇中γ-Al2O3负载Cu-Zn催化剂的改性研究

采用浸渍法制备Co改性γ-Al₂O₃负载的Cu-Zn催化剂，考察Cu-Zn负载量、Co含量及反应温度等对催化剂性能的影响。结果表明，在413 K、氢气流速0.5 mL·s^－1 和糠醛空速2 h^-1 条件下,当催化剂Cu-Zn/γ-Al₂O₃（Co）中n(Cu)∶n(Zn)∶n(Al)∶n(Co)＝1.0∶2.0∶3.0∶0.51时，糠醇的选择性100％，糠醛转化率94.6％，比使用单纯Cu-Zn/γ-Al₂O₃催化剂的最佳转化率提高11％。