Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling

The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 μm were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%

In Situ FTIR Studies of CO Adsorption on Palladium Loading Zeolite Elec trode

制备载Pd的分子筛电极 ,以CO吸附为探针结合电化学原位FTIR反射光谱 ,首次发现限定在分子筛超笼中的纳米Pd微粒对CO的吸附具有增强红外吸收效应。Adsorption of CO on palladium loading zeolite el ectrode supported on Pt or GC substrate was studied by in situ MSFTIR spectrosco py.The results demonstrated that the geometry of faujasite supercages favors the formation of bridge-bonded CO species.The enhanced IR adsorption of CO adsorbe d on Pd clusters located in the supercages of zeolite has been observed for the first time,which is a new phenomenon and differs from the abnormal infrared effe cts discovered by our group and the surface enhanced infrared absorption phenome non reported in the literature.国家自然科学基金资助项目!(2 99730 35

化学模拟生物固氮——Ⅸ 铁钼辅基模型化合物的合成和性能表征

本文曾在全国化学摸拟生物固氮协作组领导小组扩大会议(昆明,1980,8)上宣读。[中文文摘]采用乙二醇基阴离子作为活插头(可通过水解除去的双配位螯形配位体),对前文提出的合成方法作了重要改进,以期所合成的铁钼辅基模型化合物中Mo~(Ⅳ(Ⅲ))第一配位界内两个不稳定的配位体处于相邻的位置,如厦门模型Ⅲ(或厦门模型Ⅱ)所要求。合成和重组活性评价结果,重组活性比使用乙腈等为活插头的提高2个数量级,化学催化活性和选择性接近于天然FeMo-co水平。[英文文摘]A significant improvement has been made to the method previously proposed[3] for synthesizing FeMo-co modeling compounds. With the use of ethylene glycolate anion as labilizable blocking agent (hydrolyzable bidentatc chelating ligand)to protect two neighboring coordination sites in the first coordination sphere of MoIV(III) of the synthesized FeMo-co modeling compound, an increase in reconstituted-nitrogenase activity of 2 orders of magnitude of the sample synthesized (as compared with the use of acetoni-trile or other monodentare ligands as bloeking agents)has been obtained.Catalytic activity and selectivity assays as well as preliminary characterization by EPR method have also been made

Influences of refrigerant-based nanofluid composition and heating condition on the migration of nanoparticles during pool boiling. Part II: Model development and validation

The objective of this study is to propose a model for predicting the migration characteristics of nanoparticles during the refrigerant-based nanofluid pool boiling. In establishing the present model, the departure and rising processes of bubble, as well as the movement of nanoparticles in the liquid-phase are firstly simulated; then the capture of nanoparticles by bubble and the escape of nanoparticles from the liquid-vapor interface are simulated; finally, the migration ratio of nanoparticles is obtained by flotation theory combining the analysis on the boiling process. The proposed model can predict the influences of nanoparticle type, nanoparticle size, refrigerant type, mass fraction of lubricating oil, heat flux and initial liquid-level height on the migration of nanoparticles. The migration ratio of nanoparticles predicted by the model can agree with 90% of the experimental data of within a deviation of +/- 20%, and the mean deviation is 12.1%. (C) 2011 Elsevier Ltd and IIR. All rights reserved

In situ FTIR studies of CO adsorption on palladium loading zeolite electrode

Adsorption of CO on palladium loading zeolite electrode supported on Pt or GC substrate was studied by in situ MSFTIR spectroscopy. The results demonstrated that the geometry of faujasite supercages favors the formation of bridge-bonded CO species. The enhanced IR adsorption of CO adsorbed on Pd clusters located in the supercages of zeolite has been observed for the first time, which is a new phenomenon and differs from the abnormal infrared effects discovered by our group and the surface enhanced infrared absorption phenomenon reported in the literature

Study on the Synthesis of Copoly(lactic acid-co-glycolic acid)by Solid-state Polymerization

为了制备安全、经济且能满足生物医学工程材料要求的聚乳酸乙醇酸(PlgA),以乙醇酸(gA)和外消旋乳酸(lA)为原料,在无催化剂条件下熔融聚合制备低聚物,而后引入固相聚合合成PlgA.采用红外光谱、黏度法、X射线衍射、差示扫描量热对产物进行表征,探讨了固相聚合条件对PlgA结构的影响.结果表明,固相聚合明显提高了聚合物的分子质量,分段控温聚合更有利于聚合物分子质量的提高,可使PlgA的分子质量提高到固相聚合反应前的2.46倍.低聚物在压力0.001MPA条件下,先后经过135℃/4H,160℃/8H,165℃/20H固相聚合后,其分子质量可达到9.34x104 u.在一定时间内,随着反应的进行,聚合物的分子质量不断提高,其熔点也随着固相时间的延长而增大.The object of this study is to synthesize poly(lactic acid-co-glycolic acid)(PLGA)which is safe,economical and can meet the requirements of biomedical engineering material.Starting from a mixture of glycolic acid(GA)and lactic acid(LA),PLGA was synthesized through direct melt polycondensation without catalysts,the condition of solid-state polymerization were especially studied.The products were characterized by FTIR,Ubbelohde viscosity method,X-ray diffraction(XRD)and differential scanning calorimetry(DSC).Effects of the conditions of solid-state polymerization on structure of product were discussed.The results showed that the viscosity-average molecular weight(Mη)of PLGA was significantly improved,and the Mηof PLGA with different temperature controlling was much higher,the result demonstrated that the Mηof PLGA could be 2.46times as large as that of PLGA without the solid-sate polycondensation.When PLGA was synthesized at the reaction for 4hat 135℃,8hat 160℃,finally 20hat 165 ℃,the Mηof PLGA could reach to 9.34×104 u.In a certain period of time,the Mηand melting point of PLGA increased as the reaction time increased

Migration Characteristic of Spherical Nanoparticles from Liquid to Vapor Phase during Refrigerant/Nanolubricant Mixture Boiling

为了评估纳米制冷剂的沸腾传热效果以及球形纳米颗粒在制冷系统中的循环能力,采用称重法实验研究了纳米制冷剂沸腾中气/液相间球形纳米颗粒的迁移特性,重点考察球形纳米颗粒种类和粒径、制冷剂种类、润滑油浓度、热流密度和初始液位高度对球形纳米颗粒迁移特性的影响.结果表明:球形纳米颗粒迁移率随球形纳米颗粒密度或粒径的减小而增大;制冷剂的动力学黏度越小、密度越大,其在完全蒸发时的球形纳米颗粒的迁移率越大;球形纳米颗粒的迁移率随润滑油浓度的增大而减小,随热流密度的增大而减小,随初始液位高度的增加而增大