Numerical investigation on the phase change of water-saturated porous media with thermosyphon

Numerical investigations were carried out to determine the coupled heat transfer of water-saturated porous media with a two-phase closed thermosyphon for soil freezing, and to examine the characteristics of the freezing heat transfer in the water-saturated porous media. The whole control volume includes the thermosyphon and the porous media. The two-dimensional governing equations for the water-saturated porous media are used. The conjugation of heat transfer between the thermosyphon and porous media is reflected through thermal balance between the thermosyphon and the porous media. The finite-difference method was used to solve the two-dimensional goverming equation, for the water-saturated porous media and the heat transfer characteristics of the thermosyphon, obtain the flow fields and the temperature distributions in the soil. This paper deals mainly with the effect of some factors (such as soil properties, climate and thermosyphon dimensions) on the heat transfer rate of the thermosyphon and the growth of the freezing front. The predictions of the present study agree well with the measured data.     

石墨型氮化碳纳米管的模板方法制备

利用二次阳极氧化方法制备了高度有序的多孔氧化铝（AAO）模板,利用这些模板,并通过溶胶-凝胶过程和高温后处理制备了氮化碳纳米管。分别用SEM、XRD和XPS表征了AAO模板以及氮化碳纳米管的形貌、物相结构和表面元素组成,发现所制备的氮化碳纳米管彼此平行、表面光洁,而且氮化碳纳米管的直径与所用AAO模板的孔径基本一致。     

N-heterocyclic carbene-stabilized metal nanoparticles within porous organic cages for catalytic applicationOA

Tuning the surface-embellishing ligands of metal nanoparticles(NPs) is a powerful strategy to modulate their morphology and surface electronic and functional features, impacting their catalytic activity and selectivity. In this work, we report the design and synthesis of a polytriazolium organic cage PIC-T, capable of stabilizing Pd NPs within its discrete cavity. The obtained material(denoted Pd@PCC-T) is highly durable and monodispersed with narrow particle-size distribution of 2.06 ± 0.02 nm,...     

Light-driven directional ion transport for enhanced osmotic energy harvesting

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe use of a TiO₂/C₃N₄ semiconductor heterojunction nanotube membrane to realize similar light-driven directional ion transport performance to that of biological systems. This heterojunction system can be fabricated by two simple deposition steps. Under unilateral illumination, the TiO₂/C₃N₄ heterojunction nanotube membrane can generate a photocurrent of about 9 μA/cm², corresponding to a pumping stream of ∼5500 ions per second per nanotube. By changing the position of TiO₂ and C₃N₄, a reverse equivalent ionic current can also be realized. Directional transport of photogenerated electrons and holes results in a transmembrane potential, which is the basis of the light-driven ion transport phenomenon. As a proof of concept, we also show that this system can be used for enhanced osmotic energy generation. The artificial light-driven ion transport system proposed here offers a further step forward on the roadmap for development of ionic photoelectric conversion and integration into other applications, for example water desalination.     

Hierarchically porous monoliths based on low-valence transition metal (Cu,Co, Mn) oxides: gelation and phase separation

Hierarchically porous monoliths based on copper (Cu), cobalt (Co) and manganese (Mn) oxides with three-dimensionally (3D) interconnected macropores and open nanopores were prepared using metal bromides as precursors via a sol–gel process accompanied by phase separation. The difficulty of gelation for low-valence metal cation was overcome by introducing a highly electronegative Br atom near to the metal atom to control the rates of hydrolysis and polycondensation. The 3D interconnected macropores were obtained using appropriate polymers to induce phase separation. The domain sizes of macropores and skeletons can be controlled by reaction parameters such as concentration and/or average molecular weight of polymers, and the amount of hydrochloric acid. The crystalline metal oxide monoliths with their 3D interconnected macroporous structure preserved were obtained after heat treatment in air.     

袁荣鑫教授功能配合物研究工作评述

主要从光致发光、生物功能、磁性功能和类分子筛配合物的合成、结构调控和性质研究等方面评述袁荣鑫教授在功能配合物研究领域开展的相关研究工作.     

冷冻干燥法制备多孔生物活性玻璃陶瓷

以纳米级45S5生物玻璃粉体为原料,采用冷冻干燥法,以丙三醇(甘油)、聚乙二醇为分散剂,制备多孔生物陶瓷材料。实验结果表明:通过冷冻铸造法制备的复合陶瓷呈薄层状结构,在950℃下烧结的材料能保持多孔形貌,但是孔隙分布不均匀,大多为2-10μm的微孔,由阿基米德排水法测得的孔隙率知道孔隙在60%以上,孔径内部连通性良好;1 050℃下生物玻璃粉体出现玻璃软化,冻干胚体经烧结出现塌陷,微孔消失,孔径的连通性较差,大多数孔隙为不连通的半开孔。高温烧结定向多孔结构陶瓷胚体,温度高于1 000℃生物玻璃发生软化难以保持材料的定向多孔结构。生物玻璃粉体烧结多孔陶瓷的温度为950℃。     

以滇蔗茅为模板合成的Co/SiO_2在环己烷氧化反应中催化性能的影响

考察以滇蔗茅为模板合成的Co/SiO2催化剂对环己烷催化氧化的性能,探讨了反应时间、反应温度、催化剂用量、溶剂、氧化剂用量等对该催化反应的影响。实验表明,在催化剂用量为50m g;环己烷750m g;以冰醋酸为溶剂,5.0m L 30%的H2O2;反应温度373K;反应时间10h的条件下,环己烷转化率为71.0%,环己酮的选择性为76.7%,环己醇选择性为21.2%。     

溶胶-凝胶法制备多孔TiO2薄膜的研究

采用溶胶一凝胶法在玻璃基片上制备了TiO：多孔薄膜,主要研究了pH值、模板剂以及乙醇添加量对溶胶和多孔膜性能的影响．研究结果表明：溶胶一凝胶制备过程中,pH一3时和以聚乙二醇～1000为模板剂可得到稳定的溶胶,且n（PEO-1000）／n（Ti）为0．050时所得到的溶胶颗粒最小,团聚最轻,由其可制备出结构均一性好、无开裂的多孔膜;n（CH3CH2OH）／n（Ti）为24：1时,溶胶可在玻璃基体上形成完整的膜,烧结过程中随着聚乙二醇分解的CO2和H2O的逸出形成了许多微孔,得到完整的有序多孔TiO2薄膜。     

全过程课题式教学与考核方法的理论与实践

基于《多孔介质流体动力学》研究生课程,提出了全过程课题式教学方法。在课堂教学中,首先建立基础知识的概念框架,然后让同学们自行寻找应用领域和科学问题,撰写并提交课题申请,完成课题工作,提交研究报告,通过演讲对课题进行总结和汇报,最终采用多指标体系对成绩进行评定。该方法教学效果良好,可为类似课程教改提供参考。