纳米薄层SAPO-5分子筛的离子热合成及催化性能

以小剂量的丁二酸、氯化胆碱和四乙基溴化铵复配形成的低共熔混合物为溶剂和模板,以水热法合成的纳米薄层SAPO-5分子筛作为晶种,使用离子热法在微波加热功率为400 W、温度为180℃和晶化时间为20 min的条件下,高效合成了具有六角花瓣状的纳米薄层SAPO-5分子筛。采用XRD、SEM、N2物理吸/脱附和NH3-TPD对合成样品的物相、形貌、孔结构和酸性进行了分析。结果表明,所合成的样品SC2-T180-t20-P400是一种同时含有微孔-介孔-大孔结构的多级孔SAPO-5分子筛,其外表面积高达85m2/g。分子筛产物中无机物的原子利用率达到88%。该样品在苯与苯甲醇的烷基化反应中,苯甲醇转化率和二苯甲烷选择性分别达到99.9%和94.0%,表现出比传统水热法合成的纳米薄层SAPO-5催化剂更为优异的催化性能。     

Hollow tremella-like graphene sphere/SnO2 composite for high performance Li-ion battery anodes

A hollow tremella-like graphene sphere/tin dioxide (HTGS/SnO₂) composite was successfully prepared by simple emulsification and impregnation followed by calcination. In this material, tin dioxide adheres to the folds on the surface of the hollow tremella-like graphene spheres. Hollow tremella-like graphene spheres as the matrix of SnO₂ not only provide a space of volumetric expansion for the tin oxide particles, relieve the internal stress of the tin dioxide, but also effectively avoid aggregation of the tin dioxide and increase the electrical conductivity. As an anode electrode material for batteries, the initial discharge/charge capacities of HTGS/SnO₂ are 1762.4 mAh g^-1 and 1169.4 mAh g^-1, and the Coulomb efficiency is 96.9%. After 50 cycles, capacity remains 80.4% of reversible capacity. The excellent electrochemical stability is attributed to the extraordinary structure of HTGS/SnO₂. The hollow structure of graphene sphere allows simultaneous insertion of lithium ions from the inner and outer surfaces. Meanwhile, the tin dioxide particles are uniformly dispersed by the wrinkles on the surface of the graphene, thereby enlarging the space for the volume expansion of tin dioxide in order to avoid contact with the electrolyte.     

基于低速预处理的风力机翼型外形优化设计

针对经典的S809翼型,耦合基于低速预处理的流场求解方法和序列二次规划方法,开展针对翼型升阻比的翼型气动外形优化设计研究。优化结果显示优化翼型具有较大的翼型前缘半径和较平坦的上表面。数值计算结果表明,优化翼型在设计点1的状态下升阻比提高43.3%,在设计点2的状态下升阻比提高48.9%。进一步数值验证表明,优化翼型在雷诺数为5.0×10⁵状态下的最大升力系数从S809翼型的1.140增大到1.297,在雷诺数为1.0×10⁶状态下的最大升力系数从1.236增大到1.418。在优化翼型的基础上,开展翼型气动外形人工修型研究,数值模拟表明修型翼型能更好地消除气流分离,从而进一步增大翼型升力系数、减小翼型阻力系数。     

Facile synthesis of MoS2/N-doped macro-mesoporous carbon hybrid as efficient electrocatalyst for hydrogen evolution reaction

A novel three-dimensional (3D) hybrid consisting of molybdenum disulfide nanosheets (MoS₂) uniformly bound at N-doped macro-mesoporous carbon (N-MMC) surface was fabricated by the solvothermal method. The resulting MoS₂/N-MMC hybrid possesses few-layer MoS₂ nanosheets structure with abundant edges of MoS₂ exposed as active sites for hydrogen evolution reaction (HER), in sharp contrast to large aggregated MoS₂ nanoflowers without N-MMC. The high electric conductivity of N-MMC and an abundance of exposed edges on the MoS₂ nanosheets make the hybrid excellent electrocatalytic performance with a low onset potential of 98 mV, a small Tafel slope of 52 mV/decade, and a current density of 10 mA cm^?2 at the overpotential of 150 mV. Moreover, the MoS₂/N-MMC hybrid exhibits outstanding electrochemical stability and structural integrity owing to the strong bonding between MoS₂ nanosheets and N-MMC.     

半干旱地区黑碳气溶胶变化特征及来源分析

利用兰州大学半干旱气候与环境观测站（SACOL）多角度吸收分光光度计（MAAP-5012）黑碳浓度观测数据,分析了榆中地区黑碳气溶胶的变化特征,以及黑碳气溶胶的来源。     

Morphology and electrochemistry of LiMn2O4 optimized by using different Mn-sources

Spinel-typed LiMn₂O₄ cathode active materials have been prepared for different microstructures by the melt-impregnation method using different forms of manganese. The effect of the starting materials on the microstructure and electrochemical properties of LiMn₂O₄ is investigated by X-ray diffraction, scanning electron microscopy, and electrochemical measurements. The powder prepared from nanostructured γ-MnOOH, with good crystallinity and a regular cubic spinel shape, provided an initial discharge capacity of 114 mAh g⁻¹ with excellent rate and high capacity retention. These advantages render LiMn₂O₄ attractive for practical and large-scale applications in mobile equipment.     

固液两相流对离心泵压力脉动特性的影响

为了研究含沙水流下径向式导叶离心泵内的压力脉动变化规律,采用大涡模拟和Mixture多相流模型相结合的数值模拟方法,并结合SIMPLEC算法,对输送固液两相流介质的径向式导叶离心泵进行了全流道三维非定常数值计算,并在叶轮与导叶交接面及蜗壳出口段处,将固液两相介质与清水介质时的计算结果进行对比分析。数值计算结果表明,离旋转轴越远处压力脉动幅值越小;导叶与蜗壳内叶频是压力脉动主要频率,且在1倍叶频处最大;导叶内压力脉动幅值均大于蜗壳内,且随着颗粒粒径的增大,压力脉动幅值逐渐减小;蜗壳隔舌处的压力脉动幅值大于蜗壳其他部位;在叶轮与导叶交接面处,清水介质时压力脉动幅值大于固液两相介质时,固液两相介质时脉动波形滞后于清水介质时0.003 5 s;蜗壳出口段,固液两相时压力脉动幅值均大于清水时。     

混凝土抗硫酸盐腐蚀性的试件尺寸选取

采用2种不同尺寸的混凝土试件进行室内混凝土抗硫酸盐腐蚀性快速破坏试验,寻求适用于室内混凝土抗硫酸盐腐蚀性快速破坏试验的最合理的混凝土试件尺寸。结果表明:采用尺寸为100mm×100mm×400mm的混凝土试件比采用尺寸为40mm×40mm×160mm的混凝土试件进行抗硫酸盐腐蚀性快速破坏试验的试验结果具有较好的准确性。     

Synthesis and magnetic properties of Zr doped ZnO Nanoparticles

Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies.     

含全氟异丙基的呋喃酰基硫脲类化合物的合成及生物活性

[目的]寻找具有高生物活性的农药先导化合物。[方法]以呋喃甲酸和全氟异丙基苯胺为起始原料,合成了12个未见文献报道的新型含全氟异丙基的呋喃酰基硫脲类化合物。[结果]通过1H NMR和MS确定了化合物的结构,并进行了生物活性测试。其中化合物4c、4k在500 mg/L质量浓度下对黏虫的死亡率大于80%;化合物4a、4d、4g在500 mg/L质量浓度下对黄瓜灰霉病的抑制率分别为34.78%、43.48%和23.08%。[结论]化合物具有一定的杀虫活性和杀菌活性。