聚乙烯醇/壳聚糖共混膜渗透汽化性能研究

制备了聚乙烯醇(PVA)/壳聚糖(CS)共混膜,用渗透汽化膜技术实现了甲醇/碳酸二甲酯二元共沸物的有效分离,研究了共混组成、操作温度、原料组成对膜分离性能的影响,结果表明,随着共混膜中CS含量的增加,膜的渗透通量增大,分离系数先增大后减小,当共混膜中CS含量为66%时,该膜具有优异的渗透汽化性能,有较大渗透汽化分离指数PSI值=660.8g/(m2.h).操作温度升高,膜的渗透通量增大,分离系数略微减小;随着原料中甲醇含量的增大,膜的渗透通量增大,分离系数减小.该共混膜在分离甲醇/碳酸二甲酯二元共沸物时得到的渗透侧甲醇的浓度远大于对应饱和蒸汽的浓度,表明用膜法渗透汽化分离是优于精馏分离的.     

聚二甲基硅氧烷膜分离甲醇/碳酸二甲酯混合物的渗透汽化研究

制备了一系列聚二甲基硅氧烷(PDMS)均质膜,用于渗透汽化法分离甲醇/碳酸二甲酯混合物,此系列PDMS均质膜优先脱除碳酸二甲酯.考查了PDMS均质膜在甲醇和碳酸二甲酯液体中的溶胀性能,并研究了PDMS预聚体的黏度、交联剂浓度、操作温度及料液浓度对渗透汽化分离性能的影响.结果表明,对于不同黏度的PDMS预聚体均表现出随交联剂浓度增加分离因子先增加后减小,而渗透通量则逐渐减小;随操作温度增加分离因子减小而渗透通量增大;随料液中碳酸二甲酯浓度增加分离因子先增加后减小,而渗透通量则逐渐增大.对于碳酸二甲酯浓度为30%的甲醇/碳酸二甲酯混合物,40℃时渗透侧碳酸二甲酯浓度为59.7%,分离因子为3.46,渗透通量为1.41 kg/(m2·h).     

交联PEG/PVDF复合膜分离环己醇/环己烷混合物的渗透汽化研究

以PVDF超滤膜为支撑层,PEG为分离层,制备了交联PEG/PVDF复合膜,用于环己醇/环己烷的渗透汽化分离,此复合膜优先脱除环己醇.通过傅立叶红外光谱仪对PEG/PVDF复合膜表面进行结构分析,证实交联后PEG复合膜在1 104.63 cm-1有典型的饱和醚键C—O—C的特征吸收峰;从扫描电镜图看出,PEG在PVDF多孔膜表面形成均匀致密的分离层.将PEG/PVDF复合膜应用于环己醇/环己烷体系,考察了料液浓度和操作温度对膜分离性能的影响以及膜的溶胀性和长时间操作下的稳定性.实验结果表明:随操作温度或料液中环己醇浓度的增加膜的分离因子逐渐减小而渗透通量增大.膜在环己醇中的溶胀度小于6%.在环己醇浓度为2.5%,操作温度80℃,72 h长时间操作下PEG/PVDF复合膜的渗透通量为0.46 kg/(m2.h),分离因子为7.30.     

PVA-PAA共混／CA复合膜制备及其分离碳酸二甲酯的性能

研究了聚乙烯醇(PVA)、聚丙烯酸(PAA)共混膜的交联以及铸膜液配方和膜的热处理条件对PVA-PAA共混/CA复合膜渗透汽化(PV)分离碳酸二甲酯(DMC)/水混合物性能的影响.结果表明:交联的PvA-PAA膜在纯水中的溶解率小,改善了膜在长期运行中的稳定性;随着PAA含量、混合交联剂戊二醛和乙二醇的浓度以及热处理条件的变化,水渗透通量JH2O和渗透液的含水量CP-H2O呈规律性变化.在优化条件下制备的PVA-PAA共混/CA复合膜,PV分离DMC/水二元混合物的JH2O为100 g/(m2·h),CP-H2O接近100%,分离DMC/甲醇/水三元混合物时,可同时脱除甲醇和水,当操作温度升高,JH2O和JCH3OH分别增加,CP-DMC始终小于3.6%.     

PVA膜渗透汽化分离低浓度乙醇/水溶液的实验研究

将聚乙烯醇(PVA)复合膜用于乙醇/水溶液的渗透汽化过程,考察了料液浓度、操作温度、膜后真空度等操作条件对复合膜渗透通量和分离因子的影响。实验结果表明,复合膜的渗透通量随着操作温度和膜后真空度的升高而增加,分离因子随着料液浓度、操作温度和膜后真空度的升高而减小,在料液浓度低于70%时显优先透醇性,在料液浓度高于70%时显优先透水性。温度对PVA膜渗透通量的影响符合Arrhenius方程。由Arrhenius公式计算得到乙醇组分的渗透活化能Ep=42.88kJ/mol。     

离子液体复合膜用于渗透汽化分离乙醇水溶液

将离子液体[bmim]PF6引入制膜过程,制备了PDMS膜以及离子液体支撑液膜和PDMS-IL共混膜.用所制的膜进行渗透汽化实验分离乙醇水溶液,研究料液温度、浓度和真空度等对膜渗透通量和分离因子的影响,并比较了3种膜的分离效果.实验结果表明,在分离乙醇水溶液时,PDMS-IL共混膜的综合分离效果优于普通的PDMS膜,而离子液体支撑液膜分离性能不理想.此外膜渗透通量都随料液温度、浓度的增大而增大,随透过侧压力的增大而减小;分离因子随料液温度、浓度和透过侧压力的增大而减小.     

高通量ZSM-5填充硅橡胶复合膜渗透汽化性能研究

以硅铝比为360的ZSM-5型沸石对聚二甲基硅氧烷(PDMS)进行填充,以聚偏氟乙烯(PVSF)为支撑层,制备了ZSM-5填充PDMS/PVDF复合膜,用于渗透汽化乙醇/水混合物的分离.研究了沸石填充量、操作温度、进料液浓度对乙醇/水的渗透汽化分离性能的影响,发现该复合膜较文献报道中的沸石填充膜,其渗透通量有了明显的提高,在50℃沸石填充量为40%时,对乙醇的分离因子为11.7,其渗透通量达到749.8 g/(m2·h).随着操作温度的升高或料液中乙醇浓度升高,渗透通量增大,分离因子下降.     

溴化聚苯醚渗透汽化非对称膜的制备及其乙醇/水分离性能

对聚苯醚(PPO)进行了溴代反应,采用凝胶相转化法制备溴代聚苯醚(BPPO)非对称膜.通过扫描电镜(SEM)观察膜表面及断面形貌,并以低浓度乙醇/水体系为研究对象,考察了添加剂含量、BPPO浓度、料液组成及料液温度对BPPO膜渗透汽化分离性能的影响.结果表明,该非对称膜较文献报道中的PPO膜,其分离因子有了明显的提高,在60℃添加剂浓度9.9％,BPPO浓度10％,进料液乙醇浓度5％时,膜的渗透通量236.4 g/(m2·h),其对乙醇的分离因子达到16.74.随着料液中乙醇浓度的增大,BPPO膜的分离因子减小,渗透通量增大；而随料液温度的升高,BPPO膜的分离因子及渗透通量均增大.     

高选择性PDMSP/VDF复合膜渗透汽化分离乙醇/水混合物

以聚偏氟乙烯( PVDF)为基膜、聚二甲基硅氧烷(PDMS)为选择层制备了PDMS/PVDF复合膜,应用于渗透汽化分离乙醇/水混合物.系统研究了膜交联温度、操作温度、物料浓度和膜下侧压力对乙醇/水混合物的渗透汽化分离性能的影响,发现经130℃交联的复合膜在温度为60℃时,对乙醇的分离因子为8.23,可将乙醇浓度从体积分...     

陶瓷中空纤维担载有机共混渗透汽化脱水膜的制备及表征

在多孔陶瓷中空纤维支撑体表面用浸渍提拉法制备了致密、无缺陷的有机分离层,其中有机分离层是以马来酸酐交联的对水具有分离选择性的壳聚糖(CS)-聚乙烯醇(PVA)共混复合材料.采用扫描电子显微镜、溶胀度分析与渗透汽化性能测试等手段,系统地考察了支撑体孔径和不同CS和PVA共混比例对膜性能的影响.同时研究了进料液水含量和操作温度对乙酸乙酯脱水渗透汽化性能的影响.实验结果表明,该复合膜在乙酸乙酯渗透汽化脱水过程中表现出优异的分离性能,在操作温度50℃,料液水质量分数为3％时,CS共混比(质量分数)为60％的PVA-CS共混复合膜的渗透通量高达1 195 g/(m2·h),对水的分离因子大于10 000.所制备的陶瓷中空纤维担载有机共混渗透汽化脱水膜将具备良好的商业应用前景.     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.     

Properties of CdxPb1−xTe thin films

Thin films of Cd_xPb_1?xTe have been grown on mica substrates using a flash evaporation technique and isothermal substrate heaters. The Cd concentration of the films was found to increase with decreasing substrate temperature and increasing deposition rates. The Hall coefficient changed from positive to negative with increasing substrate temperature, as did the Seebeck coefficient. Both these changes were associated with an increase in the rate of re-evaporation of Te and an improvement in the crystallinity of the films. Carrier mobilities less than bulk values were obtained; scattering mechanisms are discussed.     

Bibliography of high-Tcsuperconductivity

Bibliography of high-T _c superconductivity     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Optical and electrical H/sub 2/- and NO/sub 2/-sensing properties of Au/In/sub x/O/sub y/N/sub z/ films

In this paper, we describe the optical and electrical gas-sensing properties of In/sub x/O/sub y/N/sub z/ films with an ultrathin gold promoter overlayer. We have fabricated In/sub x/O/sub y/N/sub z/ films with a nanocrystalline porous structure by RF-sputtering in Ar/N/sub 2/ followed by an annealing process. Gold particles with 20-30-nm diameter have been formed on top of the In/sub x/O/sub y/N/sub z/ films by dc sputtering and an annealing process. We have investigated the optical H/sub 2/and NO/sub 2/-sensing properties (change of absorbance) and also the electrical sensing effect (change of electrical resistance) for these two gases. A combined optical/electrical sensor for H/sub 2//NO/sub 2/ is proposed.     

Effect of pressure onTc in La2-xBaxCuO4 withx=0.125

The superconducting transition temperature,T _c , of La_2–x Ba _x CuO₄ has been measured under high pressure up to 8 GPa.T _c is found to change drastically at the pressure where the structural phase transition takes place. This finding clearly indicates that there exists an intimate relation between the crystal structure and superconductivity.     

t-Model mechanism of high-Tc cuprates

A doublon formalism ofd-p model Hubbard Hamiltonian is studied only with transfer integrals, and without the superexchange term. This gives excellent doping-dependent features ofT _c in high-T _c cuprates.