Effects of pre-carbonization treatment on the sintering process and Jc performance of sugar-doped MgB2 superconductors

The carbonization treatment was employed to the sugar-coated B powders before it mixed with Mg powders. It is found that the pre-carbonization treatment could effectively suppress the formation of MgO and Mg₂C₃ impurity in the sugar-doped samples and thus result in an improved J_c at low fields in the sugar-doped samples. Besides, the sintering process of sugar-doped samples was also investigated combined with the thermal analysis and it is found that the sugar addition could obviously lower the onset temperature of the solid–solid reaction between Mg and B.     

聚缩醛螺胞二醚的合成及结构表征

在I₂催化剂的作用下, 利用苯甲醛与季戊四醇反应, 制备了聚缩醛螺胞二醚的模型化合物3,9-二苯基-2,4,8,10-四氧杂螺[5.5]十一烷(1). 在此基础上, 利用1,3-苯二甲醛与不同摩尔比的季戊四醇合成了化合物1,3-二(2,6-二氧杂-4,4-二羟甲基环己基)苯(2)和2,4,8,10-四氧杂-3,9-二(3'-甲酰基苯基)螺[5.5]十一烷(3). 化合物2与化合物3反应, 制成标题化合物聚缩醛螺胞二醚4, 收率为95.4%. 用FTIR, ¹H NMR对化合物1～4的结构进行了表征. 发现在含有手性轴化合物1, 3, 4的¹H NMR谱中, 4个亚甲基中的8个氢原子裂分为4组双峰, 而不含有手性轴化合物中的4个亚甲基中的8个氢原子不裂分, 是个单峰. 这种不同不是由于化合物中刚性环所致, 而是由于有无手性轴造成的.     

有机锡聚醚酯、聚胺酯的合成及性质的研究

将二烷基二氯化锡，二（β－烷氧羰烷基）二氯化锡与有机羟基酸，氨基酸通过界面缩聚，制成了一系列新的有机锡聚醚酯，聚胺酯化合物，讨论了影响反应的因素与产率及分子量关系，测试了有机锡聚合物阻止聚氯乙烯（ＰＶＣ）树脂热分解性能，取得了有意义的结果．     

支载型分子印迹聚合物膜的制备及其透过选择性研究

以2-氨基吡啶为模板,采用聚四氟乙烯微孔膜为支载膜,甲基丙烯酸为功能单体,偶氮二异丁腈为引发剂,紫外光引发聚合,制备出支载型分子印迹膜,并研究了分子印迹膜对2-氨基吡啶及其结构类似物的透过选择性,并对甲基丙烯酸与2-氨基吡啶之间的相互作用和膜的形貌进行了表征。结果表明,甲基丙烯酸对模板分子能够形成摩尔比为1∶2的配合物,分子印迹膜能够实现2-氨基吡啶与其类似物的分离。     

Temperature dependence of photoluminescence in MEH-PPV blend films

The temperature dependence of the optical properties in poly [2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) blending with 2-(4-biphenyl)-5-(4-tertbutylphenyl)-1,3,4-oxadiazole (PBD) has been investigated. The blending influence on the chain conformation and exciton energy migration in blend film is described. The PL emission from the pure and blend films are all blue shifted with increasing temperature. An addition of PBD in MEH-PPV films suppresses the relative intensity of 0-1 vibronic peaks at lower temperature. This phenomenon will not be promoted with increasing temperature, attributed to a temperature-dependent migration process of singlet excitons.     

大型滑坡滑带土剪切流变特性研究

利用重力压密原理制样, 采用“陈氏加载法”, 对某大型滑坡滑带土剪切流变特性进行研究。选择伯格粘弹性本构模型描述滑带土的流变性状, 获得了滑带土的长期强度值, 并论述了长期强度在滑坡稳定性研究中的意义。     

Reinforcement of Biodegradable Poly(DL-lactic acid) Material by Equal-Channel Angular Extrusion

The purpose of this study was to reinforce biodegradable poly(DL -lactic acid) (PDLLA) material using a new method, equal-channel angular extrusion (ECAE). Different processing parameters, including the number of extrusion passes and the process temperature, were investigated to analyze their effect on the PDLLA properties. Experimental results indicate that the mechanical strength of PDLLA increased with the number of extrusion passes. The extrusion temperature also affected the mechanical strength of the PDLLA. After two ECAE passes, the bending strength of PDLLA increased from 83.3 to 178.7 MPa. The bending fracture mode for PDLLA changed from brittle failure for initial specimens to ductile fracture after ECAE processing. SEM micrographs showed that the longitudinal split surfaces of PDLLA are of a fibrillar structure. Taken together, the results suggest that ECAE might represent a useful approach for the preparation of reinforced PDLLA.     

Extension of isometries between the unit spheres of complex l(Γ)(p>1)spaces

In this paper, we study the extension of isometries between the unit spheres of complex Banach spaces l^p(Γ) and l^p(Δ)(p > 1). We first derive the representation of isometries between the unit spheres of complex Banach spaces l^p(Γ) and l^p(Δ). Then we arrive at a conclusion that any surjective isometry between the unit spheres of complex Banach spaces l^p(Γ)and l^p(Δ) can be extended to be a linear isometry on the whole space.     

Pd修饰对Cd0.8Zn0.2S/SiO2光催化甘油水溶液制氢性能的影响

用等体积浸渍法制备了不同Pd负载量的Pd/Cd_0.8Zn_0.2S/SiO₂光催化材料,采用XRD、H₂-TPR、XPS、UV-vis DRS和光催化反应评价等方法对光催化材料的表面结构、光吸收性能以及光催化甘油水溶液制氢反应性能进行了考察。研究结果表明,ZnS与CdS在SiO₂表面形成了Cd_0.8Zn_0.2S固溶体,金属Pd负载未对固溶体Cd_0.8Zn_0.2S/SiO₂的结构造成影响;金属Pd修饰明显地提高了原固溶体的光响应性能,拓展了其吸光域,增强了吸光效率。金属Pd修饰后,Cd_0.8Zn_0.2S/SiO₂的光解甘油水溶液产氢速率显著提高,Pd负载量为0.5%的Pd/Cd_0.8Zn_0.2S/SiO₂具有最佳的光催化甘油水溶液制氢性能,其在紫外光照射下的氢气生成速率为831 μmol/h,较未负载时提高了近四倍;模拟太阳光下为153 μmol/h,较未负载时提高了近两倍。     

Acetate coverage effect on the reactivity of vinyl acetate synthesis on Pd/Au alloy surfaces

Vinyl acetate (VA) synthesis on Pd/Au(111) and Pd/Au(100) surfaces has been systematically investigated through first-principles density functional theory (DFT) calculations. The DFT results showed that for VA synthesis, the ‘Samanos’ reaction mechanism (i.e., direct coupling of coadsorbed ethylene and acetate species and subsequent β-hydride elimination to form VA) is more favorable than the ‘Moiseev’ mechanism (i.e., ethylene first dehydrogenates to form vinyl species which then couple with the coadsorbed acetate species to form VA). More importantly, it was found the surface coverage of acetate has a significant effect on the reactivity of VA synthesis, and the activation energy of the rate-controlling step on Pd/Au(100) surface is smaller than that on Pd/Au(111) surface (0.88 vs. 0.95 eV), indicating the former is more active than the latter.