纳米TiO_2膜电极上乙醛酸的电催化合成研究

运用电化学循环伏安法 (CV)对纳米TiO2 膜电极 (Ti/nano TiO2 )在硫酸和草酸溶液中的电化学行为进行了研究。在c(H2 SO4 ) =1mol/L溶液中的循环伏安图上Epac1=- 0 .5 6V(vs.SCE)和Epac2 =- 0 96V(vs.SCE)处 ,出现两对可逆氧化还原峰 ,而在相同扫描速度下草酸溶液中的循环伏安曲线上 ,这两对电极反应氧化峰基本消失 ,还原峰电流增大 ,表明Ti/nano TiO2 膜电极对电还原草酸成为乙醛酸的反应具有较高的电催化活性和选择性。常温常压下 ,控制电位Epc=- 1 0V左右电解合成乙醛酸 ,乙醛酸的产率和电流效率分别达到 96 5 %和 90 %。     

超级电容器电极材料二氧化锰的合成和性能研究

高锰酸钾和硫酸锰混合液,在高压反应釜内通过不同的水热时间合成了纳米级α-二氧化锰。借助X射线衍射(XRD)、扫描电镜(SEM)和比表面积(BET法)分析手段,对样品的结构和性能进行了表征。研究结果表明:水热时间为9 h的样品,扫描电镜检测结果显示,合成的粉体是纳米粉体,粒径为50~60 nm;X射线衍射检测结果表明,合成的粉体为α-二氧化锰;合成粉体的比表面积达到53.66 m2/g。以该二氧化锰为工作电极、饱和甘汞电极(SCE)为参比电极、铂丝电极为辅助电极的三电极体系中,以1 mol/L的硫酸钠溶液为电解液,通过循环伏安和计时电位法研究电化学行为,结果表明:在电位窗口为0~0.8 V(相对于饱和甘汞电极)、扫描速度为2 mV/s时,其比电容达到76 F/g,循环伏安曲线接近于矩形。     

钒酸铋的制备及可见光降解罗丹明B的研究

以偏钒酸铵和碳酸铋为原料,用NaOH调节体系pH,水热法合成钒酸铋(BiVO4)光催化剂。利用XRD和UV-Vis漫反射对样品的晶型结构和光吸收特性进行表征分析。以罗丹明B为目标降解物,卤素灯(λ>400 nm)为光源,探讨水热温度、水热时间对合成BiVO4催化剂的可见光催化活性影响。结果表明,在水热温度为200℃、水热时间为8 h的条件下合成的钒酸铋光解效率最高。实验还研究了罗丹明B水溶液pH、催化剂投加量对光催化罗丹明B降解率的影响。结果表明,在罗丹明B水溶液pH为3、初始质量浓度为10 mg/L、每60 mL溶液催化剂投加量为0.4 g时能达到较好的光催化效果,反应2 h后降解率可达97%。     

氨基化倍半硅氧烷/石墨烯的合成及性能研究

通过改进的Hummers法来制备氧化石墨烯,然后在氧化石墨烯中插入氨基倍半硅氧烷,再将得到的产物进行还原,制备氨基化倍半硅氧烷复合石墨烯的杂化材料,最后通过红外光谱、扫描电镜、拉曼光谱、紫外-可见吸收光谱等手段对制得的材料进行了表征。分别用氧饱和的0.5 mol/L硫酸溶液和0.1 mol/L氢氧化钾溶液作为电解液,光催化体系,通过循环伏安法和线性扫描伏安法研究了合成催化剂的氧还原性能,并计算了制备的催化剂在氧化原反应中的转移电子数,从而了解其氧还原性能。研究结果表明:在3 443 cm~(-1)处产生氨基的伸缩振动吸收峰,证明氨基化倍半硅氧烷被成功引入石墨烯片层中。氨基化倍半硅氧烷/石墨烯在1 567 cm~(-1)处有一个C=C的吸收峰,证明了复合材料中的氧化石墨烯成功地被还原成了石墨烯。拉曼光谱表征出氧化石墨烯的氧化程度较高。Pt-GO-POSS在相同条件下的转移电子数为3.81,其氧还原性能高于RGO-POSS。     

Mn掺杂ZnCo2O4纳米片阵列的制备及电化学性能研究

通过水热合成再煅烧的方法在泡沫镍表面生长出了Mn掺杂的ZnCo2O4纳米片阵列。利用XRD、SEM、EDS-面扫描、XPS对样品的结构/形貌和掺入的Mn元素的分布情况进行了表征。然后,再进一步对样品进行了循环伏安曲线、恒电流充放电和循环稳定性的测试。结果表明,样品在电流密度为3 mA/cm2时,比电容达到了2 134.1 F/g;在电流密度为10 mA/cm2时,循环1 000圈,电容保持率为98.59%。因此,合成的样品比电容较高且循环稳定,是一种较为理想的超级电容器的电极材料。     

剑状Bi_2O_3的微波合成及其循环伏安特性

以五水合硝酸铋和乙二醇为原料采用微波辐照法合成了剑状结构的Bi2O3。利用X射线粉末衍射(XRD)、扫描电镜(SEM)和氮气吸附实验对产物进行了表征。循环伏安法测试结果表明,该氧化铋的电化学反应活性很高,在微电极上所作的循环伏安曲线中还原/氧化峰电位、峰电流变化规律等方面有较好的一致性,可以吸附到电极上面改善其性能。     

电合成法制备纳米材料及纳米材料电极上的电催化合成

通过电化学合成前驱体直接水解法制备纳米TiO2 粉体和纳米TiO2 膜电极。用循环伏安法、循环方波伏安法和电解合成法研究了纳米TiO2 膜电极对有机合成反应的电催化活性。发现纳米TiO2 膜电极在 0 2～ - 1 2V扫描电位区间有两对氧化还原峰 (峰电位Epc1=- 0 5 6V ,峰电位Epc2 =- 0 95V ,扫描速度 10 0mV·s-1) ,具有异相氧化还原催化行为。电解结果表明 ,纳米TiO2 膜中的Ti(Ⅳ ) /Ti(Ⅲ )氧化还原电对作为媒质 ,异相间接电还原硝基苯为对氨基苯酚 (收率91 6 % ,电流效率 95 2 % )和草酸为乙醛酸 (收率 96 5 % ,电流效率 90 % )。     

单斜镍锰酸锂在不同离子电解液中的性能研究

采用高温固相合成法合成正极材料单斜镍锰酸锂(Li_2Mn_(0.5)Ni_(0.5)O_3),采用X射线衍射技术确定电极材料晶型结构,以循环伏安法及恒流充放电法测试了该材料在中性水溶液中的电化学性能,探讨了电解液中不同离子组合对电池性能的影响。循环伏安法测试表明,在硫酸锂+硫酸锌+硫酸锰电解液中,该电极材料具有更加明显的氧化/还原峰,峰型更尖锐,峰电流更高;恒流充放电测试表明,该电极材料在硫酸锂+硫酸锌+硫酸锰电解液中具有较为明显的放电平台,放电中值电压为1.3 V。首次放电比容量达287.4 mA·h/g,库伦效率为94.8%,循环50次一直稳定在300 mA·h/g左右,并且库伦效率一直稳定在90%以上,表现出优异的电化学性能。     

钛酸锂/石墨烯复合材料及电化学性能

通过固相法制备出钛酸锂(LTO)样品，再将LTO和氧化石墨烯通过水热法制得钛酸锂/还原石墨烯复合材料(LTO-RGO)。通过XRD、SEM、TEM对材料的结构、形貌进行表征，并进行充放电性能测试、交流阻抗测试来检测其电化学性能。结果表明，石墨烯对钛酸锂进行包覆处理不影响钛酸锂材料的晶型结构、无杂相出现。钛酸锂/石墨烯复合材料表现出了比钛酸锂材料更为优异的电化学性能，0.2C倍率下的放电比容量为208.7mA·h/g，50次循环后容量保持率为98.10%；20C倍率下的放电比容量为136.1mA·h/g。     

改进的共沉淀-微波法合成正极材料LiFePO_4/C

采用改进的共沉淀-微波法,利用自制加料装甓合成了橄榄石型LiFePO_4/C复合正极材料.应用X射线衍射(XRD)、循环伏安(CV)以及恒电流充放电测试等方法对目标材料进行了结构表征和电化学性能测试.实验结果表明微波烧结8 min的样品具有单一的橄榄石型晶体结构和较好的电化学性能,0.2 C倍率下充放电测试表明,其首次放电比容量158.09 mAh/g,20次循环后,容量没有明显衰减.0.5、1、2C倍率下的平均放电容量分别为135.42、98.40、83.79 mAh/g,循环过程中样品表现出较好的循环稳定性.     

静电纺丝射流分裂过程的探讨

以质量分数28％再生蚕丝素蛋白水溶液进行静电纺丝，结合拉曼光谱和广角X射线分析测试纤维的构象和晶体结构，探讨了纺丝过程中射流发生情况。结果表明，静电纺丝所得纤维中，仅部分丝素蛋白分子转变为β折叠构象，丝素Ⅱ晶型含量少，纤维只经历了有限的拉伸，说明静电纺丝中射流不是单一细化，而是发生了分裂。     

Crystalline transition behavior of sisal in cycle process

In this study, the effects of cycle process on crystalline transition behavior of sisal fiber were investigated in various conditions (in air, in composites and in argon) by XRD analysis. The results indicated that the sisal cellulose falls into cellulose I, and the polymorphic transformation didn't occur for sisal cellulose after cycle process. With increasing of thermal cycle times, the crystalline size of sisal became smaller gradually, but the change was not obvious when sisal fiber was treated thermally in air and in argon before five times. The change trend of crystalline index of sisal after cycle process in air and in argon was similar. However, it is different in composites. From once to 10 times cycle process, the crystalline index of sisal fiber was degressive. When the cycle times was close to 15, crystalline index increased gradually. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Effect of Tempering on the Texture and Polymorphic Behaviour of Margarine Fats

Separated fats from commercial soft (soft fat) and stick (stick fat) margarines and mixtures of hydrogenated super olein (H-olein) and canola oil, were temperature cycled between 4°C and 15,20 and 25°C. The polymorphic form, SFC and texture of the fats were evaluated. Temperature cycling of soft fats between 4 and 20°C resulted in the crystals being either in the β polymorphic form or mixtures of β′ and β. When temperature cycled between 4 and 15°C the presence of β′ crystals was improved, but there were soft fats that after the fourth cycle contained only β crystals. When stick fats were temperature cycled between 4 and 20°C, the crystals after the fourth cycle were either in the β′ form or contained mixtures of β′ and β. Mixtures of H-olein-canola showed superior β′ stability throughout. A mixture of 20% H-olein/canola oil compared well with the SFC and texture of soft margarines while a mixture of 40% H-olein/canola oil with those of stick margarines. Texture was evaluated by constant speed penetration. Texture of fats is very dependent on temperature history. DSC-crystallization curves of the fats showed a variety of patterns.     

拉伸聚丙烯的相转变

用广角X射线衍射考察了不同晶型的IPP单轴拉伸时的相转变情况。发现提高拉伸速率和减小拉伸比不利于α晶相向近晶相的转化,β晶型IPP拉伸后仍含有β晶相,而近晶型IPP拉伸后仅能得到近晶相。由此表明,拉伸样品对起始形态有"记忆"效应,该结果符合拉伸中结晶结构的转化是含片层的倾斜及沿分子链方向的剪切形变模型而不符合熔融重结晶形变机理。     

熔盐法制备λ-MnO_2及其超级电容性能

在600℃的m(NaC l)∶m(L iC l)=1∶3的熔盐体系中,将KMnO4反应5 h制备了MnO2。X射线衍射分析其结构表明,所制样品为λ-MnO2;扫描电镜对其形貌研究表明,样品为微米级片状结构。按m(MnO2)∶m(石墨)∶m(乙炔黑)∶m(羧甲基纤维素)∶m(聚四氟乙烯)=75∶10∶10∶3∶2制备电极材料,在电解液为c〔(NH4)2SO4〕=2mol/L的三电极体系中,通过循环伏安、交流阻抗和恒流充放电对其超级电容性能进行了考察。不同扫速循环伏安曲线表明,该材料具有典型的超级电容特性;交流阻抗测试结果表明,溶液电阻RL为0.69Ω,电极电阻RE为2.5Ω;用恒流充放电测得在1 mA恒流充放电条件下,放电比容量可达306.92 F.g-1。经5 mA恒电流循环100次,充放电效率接近100%。     

High-performance Sn–Ni alloy nanorod electrodes prepared by electrodeposition for lithium ion rechargeable batteries

To reduce irreversible capacity and improve cycle performance of tin used in lithium ion batteries, Sn–Ni alloy nanorod electrodes with different Sn/Ni ratios were prepared by an anodic aluminum oxide template-assisted electrodeposition method. The structural and electrochemical performance of the electrode were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic charge–discharge cycling measurement. The results showed that the copper substrate is covered with uniformly distributed Sn–Ni alloy nanorods with an average diameter of 250 nm. Different phases (Sn, Ni₃Sn₄ and metastable phases) of alloy nanorod formed in the electrodeposition baths with different compositions of Sn²⁺ and Ni²⁺ ions. Sn–Ni alloy nanorod electrode delivered excellent capacity retention and rate performance.     

Improvement of acid resistance of calcium silicate hydrate by thermal treatment

The following conclusions were obtained from the examinations of the acid resistance of calcium silicate hydrate.

(1)

The 1.1-nm tobermorite was formed from the batch mixture with a Ca/Si molar ratio of 0.6. Xonotlite was formed from the batch mixture with a Ca/Si molar ratio of 1.0.

(2)

For the sample prepared from a Ca/Si molar ratio of 1.0 in a batch mixture, β-wollastonite was formed by thermal treatment as the transition phase, and it was significantly dissolved in a hydrochloric acid solution.

(3)

For the sample prepared from a Ca/Si molar ratio of 0.6 in a batch mixture, β-wollastonite was formed by thermal treatment above 1000 °C, but the dissolved amount of this sample by acid treatment was small and left the original morphology. It was suggested that excess silica content was deposited on surface during the thermal transition from the 1.1-nm tobermorite to β-wollastonite. The deposited silica content significantly improved the acid resistance of β-wollastonite due to the surface coating with a silica layer.

     

Electric fatigue of ceramic–polymer composite film under cyclic electric field

Electric fatigue under cyclic electric loading was characterized for 0–3 composite film with particles of barium titanate dispersed in poly(vinylidene fluoride‐trifluoroethylene) copolymer matrix. The data reveal that both remanant polarization and coercive field decrease as the cycle number increases. Scanning electron microscope observation and X‐ray diffraction analysis were carried out to examine the morphology and microstructure change during the electric field cycling. On cyclic electric field, large quantities of flaw‐like defects occur and the crystallites grow in size, leading to reduction of interfacial layers between the crystalline and amorphous regions. The relationship between the microstructure evolution and the polarization behavior is discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

纳米复合结构二氧化钛薄膜的制备及其光降解水中若丹明B的能力

用双氧水低温氧化金属钛片的方法制备了TiO2纳米棒阵列,并以该阵列为基体,用浸渍渗透溶胶-凝胶技术制备了TiO2纳米颗粒嵌入TiO2纳米棒阵列基体的复合结构薄膜.用X射线衍射、场发射扫描电镜及光致发光光谱研究制得薄膜的结构和发光性能.结果表明:纳米棒阵列为金红石与锐钛矿的混晶结构,而溶胶-凝胶获得的TiO2为纯锐钛矿结构.在复合构造薄膜中TiO2纳米颗粒嵌入到纳米棒阵列间隙中,其光生电子-空穴对的空间分离效果得到明显改善.用制得的薄膜进行光催化降解水中若丹明B的实验结果显示:复合结构薄膜的光催化效率高于相应的纳米棒阵列,其表观反应常数是相同质量的溶胶-凝胶法制备薄膜的3倍,这是因为第二相TiO2纳米颗粒嵌入TiO2纳米棒阵列中促进了光生电子-空穴对的空间分离,从而提高了复合结构薄膜的光催化活性.     

Investigation of a high stable β-cristobalite ceramic powder from CaO–Al2O3–SiO2 system

The room temperature stabilized β-cristobalite ceramic powder has great potential for use in production of engineering ceramic materials due to its high resistance to thermal shock, low expansion coefficient, high chemical resistance and low density. However, the use of this material is not common in ceramic industries. The problem is shown to be the instability of β-phase during milling. The applied external force leads to phase transformation to α-cristobalite and thus the material shows poor thermal stability and so on. In this study, a reliable β-cristobalite ceramic powder from CaO–Al₂O₃–SiO₂ ternary system was investigated at different compositions and under various sintering temperatures and sintering times. The phase stability of the powder sample was investigated by milling for 50 h using a planetary mill. The crystalline phases were examined by X-ray and FTIR analysis and the results were discussed with respect to the phase homogeneity through the particle mass.