用正交设计研究PVDF印VC／PMMA共混中空纤维膜

制备了PVDF（聚偏氟乙烯）／PVC（聚氯乙烯）／PMMA（聚甲基丙烯酸甲酯）三元共混中空纤维膜，讨论了影响膜性能的主要因素．正交实验结果表明：在PVDF／PVC／PMMA体系中，聚合物总浓度是影响膜的水通量的主要因素；PVDF浓度对膜强度影响最大；PMMA对膜的亲水性有较大的贡献．得到优化的制膜条件为：铸膜液中PVDF：PVC：PMMA=7：1．2：1．8（质量比），聚合物溶质的总质量分数为17％；添加剂吐温-80的质量分数为6％．     

PVC/PVDF/PMMA共混膜的研制

采用剪切黏度法对聚氯乙烯(PVC)/聚偏氟乙烯(PVDF)/聚甲基丙烯酸甲酯(PMMA)体系的相容性进行研究,结果表明,该体系为部分相容体系,在此基础上采用稀溶液黏度法对各共混配比的相容性进行预测.对相容性较好的PVC/PVDF/PMMA共混体系由相转化法制备共混膜,并用扫描电镜对共混膜的形态结构进行了观察.对共混膜的...     

PVDF/PMMA/PEG型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方法制备PVDF/PMMA/PEG型聚合物隔膜。通过对制备的聚合物隔膜的孔隙率、吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物占溶剂质量百分比为8%,PVDF∶PMMA=7∶3,增塑剂含量为30%,非溶剂含量为3%,反应温度为45℃,在此最佳工艺条件下制备的PVDF/PMMA/PEG隔膜的离子电导率可达2.848 m S/cm,对电解液体系的亲和性和导电性得到显著提高。     

PVDF/PMMA/TiO_2型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜的导电性和降低PVDF基聚合物隔膜的结晶度,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,掺杂无机纳米材料TiO_2,采用相转化方法制备PVDF/PMMA/TiO_2型聚合物隔膜。通过对制备的PVDF/PMMA/TiO2型多孔膜吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物浓度为5%,PVDF∶PMMA为72∶28,纳米TiO_2添加量为5%,非溶剂添加量为3%,水浴温度为55℃。该方案下制备的多孔膜结晶度较纯PVDF薄膜结晶度降低,吸液率达到109.76%,离子电导率为2.64mS/cm,电化学稳定窗口为4.86V,高于4.5V,能够满足锂离子电池正常工作需要。     

静电纺丝制备PMMA/PVDF锂离子电池隔膜

利用电纺法制备了聚偏氟乙烯(PVDF)以及PVDF/聚甲基丙烯酸甲酯(PMMA)纳米纤维膜,用扫描电镜、红外光谱和热重等手段对纤维膜进行结构和性能表征,并测定了膜的孔隙率和吸液率。结果表明:当电压为20kV,接受距离为16cm,纺丝速率为0.001mm/s时,纺丝浓度为12%(质量分数),得到的纤维形貌较好。混合纺时PMMA加入没有改变PVDF原有的结构,复合隔膜的耐热温度达到470℃。PMMA/PVDF复合隔膜的吸液率和孔隙率整体提高且远远大于商业隔膜,其中PMMA/PVDF(4∶6)隔膜的吸液率和孔隙率分别达637%、67%,为最优。     

PVDF/PMMA/CA共混膜的制备及性能研究

主要讨论了PVDF(聚偏氟乙烯)／PMMA(聚甲基丙烯酸甲酯)／CA(醋酸纤维素)三元共混膜的制备及性能，并研究了影响膜性能的主要因素．正交实验结果表明：在PVDF／PMMA／CA体系中，PVDF同亲水性物质PMMA和CA的共混比是影响共混膜的水通量的首要因素；而PMMA与CA的共混比则对共混膜强度影响最大，当PMMA与CA的质量共混比为1：1时，膜强度最大；PMMA对膜的亲水性有较大的贡献，共混膜中只要有PMMA加入，其润湿角就变得同纯PMMA膜的润湿角相接近，通过采用红外衰减全反射法和干膜撕裂法，分别从微观和宏观上证明了PVDF／PMMA/CA气制膜体系在自来水中将会发生分层凝胶现象；综合考虑膜的各种性能，针对PVDF／PMMA／CA体系，较佳的制膜条件定为A883C2D12，也就是PVDF/CA/PMMA的质量共混比为12：2：1，以质量溶剂比为8：2的二甲基甲酰胺(DMF)／冰乙酸混合溶剂溶解，制得的膜的性能较好．     

PVDF/PMMA/PEG/TiO_2型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜的导电性和降低PVDF基聚合物隔膜的结晶度,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,掺杂有机添加剂PEG和无机纳米材料TiO_2,采用相转化方法制备PVDF/PMMA/PEG/TiO_2型聚合物隔膜。通过对制备的PVDF/PMMA/PEG/TiO_2型多孔膜吸液率、离子电导率、微观形貌和电化学性能等的分析研究,确定制膜的最佳工艺条件为聚合物浓度为8%,PMMA占聚合物质量百分比为30%,PEG含量为30%,纳米TiO_2含量为5%,C2H5OH含量为3%,反应温度为45℃。该最优方案下制备的多孔膜结晶度较纯PVDF薄膜结晶度降低,多孔膜吸液率达345%,离子电导率达5.2mS/cm,拉伸强度为1 183kg/cm~2,电化学稳定窗口为4.68V,高于4.5V,能够满足锂离子电池正常工作需要。     

相分离方式对PVC/PVDF/PMMA共混膜性能的影响

在PVC/PVDF/PMMA共混比为6∶1∶3,聚合物质量分数为16％的条件下,考察了该体系相分离方式随添加剂PEG200,400,600的加入,溶剂二甲基乙酰胺(DMAc)减少而变化的情况.并通过电镜扫描(SEM)、水通量及孔隙率的测试和拉伸试验,探讨了相分离方式(扩散诱导相分离DIPS、热致相分离TIPS、扩散诱导相分离DIPS与热致相分离TIPS相结合)及PEG分子量对PVC/PVDF/PMMA共混膜断面形态结构、水通量、孔隙率、拉伸强度等性能的影响.结果表明,PEG分子量为200,400,600,加入量分别达到15％,18％,20％时,在常温下共混体系的相分离方式将由DIPS变为DIPS与TIPS相结合或单纯的TIPS;通过TIPS得到的PVC/PVDF/PMMA共混膜断面形态结构为海绵状,表面比较粗糙,水通量较DIPS和DIPS与TIPS结合得到的膜稍低,截留率和拉伸强度有一定程度的提高;PEG分子量对TIPS得到的膜的微观结构有明显的影响;由DIPS得到的膜,由致密皮层与指状大孔构成,由DIPS与TIPS相结合得到的膜,除了皮层与指状大孔外,还有海绵状结构.     

PVDF/PMMA共混挤出流延膜结构与性能研究

探讨了聚偏氟乙烯(PVDF)/聚甲基丙烯酸甲酯(PMMA)共混挤出流延膜的结构和性能.研究结果表明:PMMA的加入能够大大改善其微观结构,不但使结晶度降低,而且红外分析(IR)和广角x射线衍射(WXRD)证实,其中部分α晶型能明显地转变成β晶型;TGA研究表明,共混体系的稳定性比纯粹的PMMA稳定性提高,但PVDF的热稳定性只有很少降低;流变性能研究显示,PMMA含量在很宽的范围内体系扭矩变化不大,为选择加工条件提供了依据;力学性能测试显示出共混膜具有很好的力学性能.PVDF/PMMA共混挤出膜被证明是一种很有前途的薄膜材料.     

阳离子季铵型表面活性剂对PVDF/PHEMA共混微滤膜的成膜性能研究

采用凝胶相转化法,以聚偏二氟乙烯(PVDF)/聚甲基丙烯酸-2-羟基乙酯(PHE-MA)共混合金为膜材料,N,N-二甲基乙酰胺(DMAc)为溶剂,阳离子季铵型表面活性剂(TM)为添加剂制备微滤膜.考察了添加剂浓度对铸膜液相容性、铸膜液黏度、铸膜液凝胶速度、膜结构和性能的影响.对PVDF/PHEMA/DMAc铸膜液体系中TM添加剂的作用规律进行了研究.实验发现:TM添加质量分数小于5.0%时,铸膜液中组分的相容性得到很大改善,制备出的微滤膜表面孔径均一、孔密度高.随着TM添加浓度的增大,铸膜液黏度先减小后增大,凝胶速度逐渐增大,膜的纯水通量先增大后减小,截留率则始终上升.     

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.     

Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

n-PbTep+−Pb1−xSnxTe heterojunctions prepared by a modified hot wall technique

$\text{n-PbTe}\text{p}{}^{\mathrm{+}}\text{?}\text{Pb}{}_{\mathrm{1?x}}\text{Sn}{}_{\mathrm{x}}\text{Te}$ heterojunctions with a long wavelength spectral cutoff (λ_c ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with R_oA equal to 170 Ω cm² and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.     

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.