高导热SiO2@Al载体的制备及其在费托合成中的应用

通过在弱碱性条件下水解正硅酸乙酯(TEOS),以十六烷基三甲基溴化铵(CTAB)为模板剂成功制备了SiO2@Al核壳结构高导热载体,并采用过量浸渍法负载15％(质量分数)钴物种,进行了费托合成反应性能考察.结果表明,制备得到的核壳结构载体既保留了高金属铝含量,又具有高比表面积壳层,孔径较为均一,为2.6?2.8 nm....     

核壳结构NH2-UiO-66@TiO2的制备及其可见光下的甲苯降解性能研究

Metal-organic frameworks (MOFs) are of significant interest for photocatalysis using visible light, but they are typically limited by the instability and high recombination ratio of photoexcited pairs. Integrating MOFs into an inorganic semiconductor is one of the most widespread methods to promote their activity. In this study, a core-shell structured MOF@TiO₂ (NH₂-UiO-66@TiO₂) was synthesized as an efficient photocatalyst for the degradation of toluene. Pristine NH₂-UiO-66 was synthesized by a hydrothermal method as the core, which was then coated with an amorphous TiO₂ shell. Compared with pristine NH₂-UiO-66 and other samples prepared by the direct mixing of NH₂-UiO-66 and TiO₂, NH₂-UiO-66@TiO₂ exhibited a higher degradation rate of toluene. Using NH₂-UiO-66@TiO₂ as a catalyst, the degradation efficiency of toluene reached 76.7% within 3 h, which is 1.48 times higher than that of NH₂-UiO-66. The degradation performance was also stable in four repeated reuse experiments, and the slight deactivation was reactivated after washing with ethanol. A series of characterization methods were used to determine the physicochemical properties of NH₂-UiO-66@TiO₂, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Using the measured physicochemical properties, the photocatalytic mechanism of NH₂-UiO-66@TiO₂ was explored. NH₂-UiO-66 is an ideal photocatalyst, with visible-light response and a huge specific surface area (914.9 m²·g^-1), which is favorable for the utilization of sunlight as well as the absorption of pollutants in indoor air. In addition, a new interface formed between the two components (NH₂-UiO-66 and TiO₂), which efficiently broaden the light absorption area and enhanced the utilization of photogenerated species. The photogenerated holes and electrons could transfer through the interlayer as soon as they were formed. It is speculated that holes would transfer to the HOMO of NH₂-UiO-66, and then combine with H₂O molecules to form hydroxyl radicals (·OH). At the same time, more electrons tended to combine with oxygen molecules in the conduction band of TiO₂ rather than recombine with holes. Consequently, the recombination rate of electrons and holes decreased, while the quantity of oxygen radicals and hydroxyl radicals increased. Toluene was efficiently oxidized by these two types of radicals. Owing to the outstanding properties mentioned above, the strategy of constructing NH₂-UiO-66@TiO₂ is considered to be an effective approach. This work may provide new insights into the design of core-shell structured MOF@photocatalysts for the photocatalytic degradation of indoor air pollutants.      

ZSM-5@Mesoporous Silica核壳复合结构分子筛的制备及其甲苯甲醇烷基化择形催化性能的研究

采用阳离子表面活性剂模板法在ZSM-5晶体颗粒表面外延生长介孔氧化硅壳层来调变其外表面酸性, 制备了具有高择形催化性能的介孔氧化硅包裹ZSM-5分子筛的微孔-介孔核壳结构复合材料ZSM-5@mesosilica. 扫描电镜和高分辨透射电镜表征显示, 具有无序孔道结构的介孔壳层均匀包覆于ZSM-5晶粒的外表面, 而且壳层的厚度在一定范围内可调变; 另外, 壳层介孔的孔道走向垂直于分子筛核, N₂吸附曲线表明复合材料的微孔和介孔具有互通性. 吡啶吸附和氨吸脱附实验结果证明这些分子可以自由扩散进入分子筛的微孔道, 并且介孔壳层包覆以后ZSM-5分子筛内的酸性位和强度基本没有变化. 用固定床评价了该复合分子筛对甲苯甲醇烷基化反应的催化性能, 结果表明, 与常规ZSM-5相比, ZSM-5@mesosilica核壳材料表现出了较高的对位选择性. 核壳材料独特的择形催化性能归因于介孔氧化硅壳层将ZSM-5非择形性的外表面酸性位部分覆盖, 从而抑制了对二甲苯在外表面的二级异构化反应.     

核壳结构的Co3O4@δ-MnO2/Pt作为锂氧电池高效催化正极

通过简易、可控的水热方法在泡沫镍基体上直接生长了核壳结构的阵列型Co₃O₄@δ-MnO₂/Pt正极。阵列电极有利于电极的润湿、氧气的传输和Li₂O₂的负载。Co₃O₄@δ-MnO₂/Pt正极对氧还原和氧析出反应具有高的催化性能,可促使Li₂O₂依附Co₃O₄@δ-MnO₂/Pt阵列生长,从而保持阵列结构。该生长行为有利于Li₂O₂在充电时分解。以Co₃O₄@δ-MnO₂/Pt为催化正极的锂氧电池显示出高的容量（在电流密度100 mA·g^-1时容量为2 480 mAh·g^-1）,以及长的循环寿命（容量限定在500 mAh·g^-1时,在200 mA·g^-1电流密度下,可循环65次）,该性能超过了使用Co₃O₄或Co₃O₄@δ-MnO₂催化剂的电池。     

海胆状氧化锌/羰基铁粉核壳结构复合粒子的抗氧化及吸波性能

针对羰基铁粉吸收剂在温度较高时易被氧化的问题,采用水热法制备了氧化锌包覆羰基铁粉核壳结构复合粒子,并分别将羰基铁粉和氧化锌/羰基铁粉核壳粒子与石蜡混合,制备复合材料。结果表明,氧化锌纳米棒致密的包覆在羰基铁粉颗粒表面形成海胆状核壳结构复合粒子,正是这种结构将羰基铁粉颗粒与空气隔绝,使得复合粒子的抗氧化性能得到显著改善。与羰基铁粉复合吸波材料相比,氧化锌/羰基铁粉核壳粒子的复合材料吸收峰稍向低频移动,反射损耗小于-5dB的带宽几乎保持不变,在不改变电磁吸波性能的前提下,提高了羰基铁粉粒子的使用温度。     

具有红外反射膜的节能卤素灯

研究了节能卤素灯的技术和设计问题.给出了红外反射膜的厚度对近红外波段的反射率分布以及该涂层对2 850 K照明光源在可见光范围内的影响,讨论了灯丝和泡壳的几何形状,以及钨丝对红外反射能量的吸收.实验表明：1）当选用9层膜时,实验数据与计算值偏差很微小.当灯的管径为10 mm,而灯丝外径为1.5 mm时,节能可达12%到13%.2）对圆柱形灯外壳,在不考虑端面影响时,光源的灯丝若处于外壳的中心轴上,则反射的能量会有效地返回灯丝.3）螺旋结构的灯丝比表面光滑的直钨丝有更高的吸收率,灯丝绕成螺旋后在现行的螺距尺寸下吸收率能达到0.6~0.7.     

基于Shapley值的壳资源溢价影响因素的实证研究

本文选取了我国1997-2003年证券市场上符合买壳上市条件的63家目标企业作为样本,对影响买壳上市溢价因素进行了理论分析和实证检验。论文基于合作博弈理论Shapley值分担法建立了多元回归模型以解决多重共线性变量产生偏倚性和负的多重性问题。研究显示:上市公司"壳"资源的溢价比率与每股净资产、资产负债率、货币性资产占总资产比率、市净率、股权集中度、净资产收益率等变量之间存在着显著的相关性。     

Excel用于优化设计电容器尺寸

1 同轴柱形电容器的优化，设计两个同轴柱形导体构成了同轴柱形电容器．设电容器的内、外导体壳半径分别为r和R，长度为L(L≥R—r)，两导体壳层之间所填充电介质的介电常量为ε，其击穿场强为Emax(图1)．在外半径R一定的情况下，如何选择内圆筒导体半径r，使得设计出的电容器可以承受的电压最大?     

Zn-MOF模板法制备ZnO/C/SNTs及其药物缓释性能

采用超声法一步合成了SiO₂包覆金属-有机骨架[Zn₆(OH)₃(BTC)₃(H₂O)₃] ·7H₂O(Zn-MOF, BTC=1,3,5-均苯三羧酸根)纳米晶, 在N₂保护下, 热解Zn-MOF@SiO₂获得了ZnO/C/SNTs复合物, 进而与布洛芬(HIBU)反应合成药物组装体Zn(IBU)₂/C/SNTs. 通过透射电子显微镜(TEM)、 傅里叶变换红外光谱仪(FTIR)、 高分辨透射电子显微镜(HRTEM)和X射线衍射仪(XRD)对样品的结构和形貌进行表征. 结果显示, Zn-MOF@SiO₂呈棒状, 具有清晰的核/壳结构, 形貌单一, 分散性良好. 煅烧后SNTs结构稳定, 形貌基本不变. 载药实验表明, 药物组装体的载药量为752 mg/g, 并具有良好的pH响应性能.     

考虑弹性地基切向抗力的变截面圆弧壳梁分析

本文根据弹性薄壳理论,考虑了弹性地基径向和切向抗力的影响,解决了变截面圆弧壳地基梁的难题,作者所提出的近似解析法和加权余量法、传递矩阵法较有限单元法简便.