MWCNTs/hydroxypropyl cellulose/polyethylene glycol-based shape-stabilized phase change materials

Journal of Thermal Analysis and Calorimetry - Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its...     

One‐Pot Synthesis of Pomegranate‐Structured Fe3O4/Carbon Nanospheres‐Doped Graphene Aerogel for High‐Rate Lithium Ion Batteries

A unique hierarchically nanostructured composite of iron oxide/carbon (Fe₃O₄/C) nanospheres‐doped three‐dimensional (3D) graphene aerogel has been fabricated by a one‐pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe₃O₄ nanocrystals (5–10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate‐like structure. The carbon matrix suppresses the aggregation of Fe₃O₄ nanocrystals, avoids direct exposure of the encapsulated Fe₃O₄ to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe₃O₄/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe₃O₄ nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long‐term stability of 634 mA h g^?1 over 1000 cycles at a high current density of 6 A g^?1 (7 C), and an excellent rate capability of 413 mA h g^?1 at 10 A g^?1 (11 C), thus exhibiting great potential as an anode composite structure for durable high‐rate lithium‐ion batteries.     

Numerical study of buoyancy- and thermocapillary-driven flows in a cavity

Thermocapillary- and buoyancy-driven convection in open cavities with differentially heated endwalls is investigated by numerical solutions of the two-dimensional Navier-Stokes equations coupled with the energy equation. We studied the thermocapillary and buoyancy convection in the cavities, filled with low-Prandtl-number fluids, with two aspect-ratiosA=1 and 4, Grashof number up to 10⁵ and Reynolds number ⋎Re⋎≤10⁴. Our results show that thermocapillary can have a quite significant effect on the stability of a primarily buoyancy-driven flow, as well as on the flow structures and dynamic behavior for both additive effect (i.e., positiveRe) and opposing effect (i.e., negativeRe).     

有应力史差非匀质截面轴心受压杆的性能研究

对有应力史差、非匀质、非线弹性的轴心受压构件进行了理论分析和试验研究，初步揭示了此类构件的受力特点．理论分析和试验表明：此类构件截面承载力不是各部分材料承载力的简单叠加；承载力和截面破坏控制点因截面上材料的本构关系的变化和应力史差而发生改变．     

数值研究激波与旋涡的相互作用

从非定常形式的Euler方程出发,数值模拟了运动激波与旋涡相互作用的非定常流动过程。为保证激波具有较高的分辨率,采用对称型TVD格式进行了数值计算。结果表明。这样可以有效地模拟流场中一些复杂的流动现象,如激波变形、激波分叉和三波点的形成,以及旋涡结构的变化过程等,并与已有的实验流动显示相符良好。同时,也是对TVD格式求解这类问题的一次初步尝试。     

Effect of surface oxidation on the surface condition and deuterium permeability of a palladium membrane

Oxidation and deoxidation of a Pd membrane was conducted in a quartz tube oven in a temperature range of 23-500 °C. The micromorphology and chemical composition of the Pd membrane surface was characterized using scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Micropores and PdO began to form on the Pd membrane surface after oxidation at 240 °C for 1 h and their quantity increased gradually with increasing temperature. A rough Pd membrane surface was obtained when the temperature rose to 500 °C. The PdO on the Pd membrane surface was completely deoxidized once more using H₂ at room temperature, but the rough surface morphology caused by oxidation remained. The deuterium permeability of the Pd membrane was tested using special equipment in the China National Key Laboratory and the results indicated that the rough Pd membrane surface had higher deuterium permeability than the original membrane. The improved deuterium permeability could be attributed to the higher Pd membrane surface area, which provided deuterium atoms with more adsorption sites and dissociation sites.     

常温下 MnO2/Al2O3催化剂催化臭氧氧化甲苯反应

采用浸渍法制备了Al2O3负载的5种过渡金属氧化物催化剂,考察了它们在常温下催化臭氧氧化甲苯的性能,并运用程序升温还原、程序升温氧化、N2吸附-脱附和X射线光电子能谱对催化剂进行了表征.结果表明,NiO/Al2O3,CoO/Al2O3和MnO2/Al2O3催化剂上活性氧中心数量较少,臭氧与甲苯转化率较高;而Fe2O3/...     

固相萃取-高效液相色谱法测定环境水样中的三嗪类化合物

建立了固相萃取-高效液相色谱法(SPE-HPLC)测定地表水中三嗪类化合物的方法。考察了4种不同固相萃取柱对三嗪类化合物的吸附效果,最终选择ENVI-18固相萃取柱用于萃取地表水中的三嗪类化合物;系统研究了环境水样中三嗪类化合物的最佳固相萃取条件,选择洗脱溶剂为甲醇,洗脱溶剂用量5 mL,水样在萃取前不需要添加甲醇,不调节pH值。测定了方法的检测限,结果表明,扑草净、莠去津、西玛津、脱乙基莠去津、羟基化莠去津和脱异丙基莠去津的最低检测限依次为0.14 μg/L,0.12 μg/L,0.08 μg/L,0.08 μg/L,0.10 μg/L和0.18 μg/L。将该法应用于实际环境水样的分析测定,结果表明某湖水中扑草净的含量为（9.33±0.27） μg/L,某江水中莠去津和扑草净的含量分别为（5.28±0.43） μg/L和（7.12±0.54） μg/L。     

金属-氮-氢体系储氢材料

氢能作为未来理想的清洁能源之一,已经成为全球研究的重要领域,而在氢能的应用中最关键的问题是氢气的存储.近年来,人们的研究集中在固态储氢材料上,许多新型储氢材料不断出现,其中由轻元素组成的金属-氮-氢体系拥有储氢容量高、可逆性好等优点,被认为是最有前景的储氢材料之一.目前金属-氮-氢体系已经发展出许多体系,而研究最多的是Li-N-H和Li-Mg-N-H两种体系.本文重点综述了两者作为可逆储氢材料的研究现状,主要从制备方法、储氢性能、反应机理、理论计算和存在的问题等方面进行了讨论,同时指出了金属-氮-氢储氢体系的发展趋势.     

Systematic investigation on morphologies, forming mechanism, photocatalytic and photoluminescent properties of ZnO nanostructures constructed in ionic liquids

In this contribution, a series of shape-controllable ZnO nanostructures were synthesized in ionic liquids by a simpler, only one-step, low-temperature route, and characterized by XRD, XPS, TEM, HRTEM, SAED, EDXA, SEM, FTIR, surface area measurement and photoluminescence. We mainly investigate the effect of cations of ionic liquids on the shape of ZnO nanostructures and the forming mechanism of ZnO nanostructures in ionic liquids, as well as the luminescent property and photocatalytic activity for the degradation of Rhodamine B. The results show that the longer alkyl chain at position-1 of the imidazole ring of the ionic liquid will hinder the ZnO nanostructures from growing longer, and the hydrogen bonds may play a crucial role for the directional growth of the 1D nanocrystals. The photoluminescent study shows that the as-obtained ZnO nanostructures exhibit a unique green emission, indicating the existence of oxygen vacancies in the ZnO nanostructures. Importantly, the as-obtained ZnO nanostructures prepared in different ionic liquids show strong size/shape-dependent photocatalysis activity for degradation of Rhodamine B, and the well-dispersed homogeneous ZnO nanoparticles and nanowires display high photocatalytic activity. The investigation of photodegradation kinetics of Rhodamine B indicates that the photodegradation process obeys the rule of a first-order kinetic equation ln( C(0)/ C) = kt. This is the first systematic investigation on the relationship between the structure of ionic liquids and the morphology of ZnO nanostructures.