PVDF/ZIF-8复合滤材的制备及其过滤性能研究

以聚酯纤维无纺布为接收基材,通过静电纺丝技术制备了包覆2-甲基咪唑锌盐(ZIF-8)纳米颗粒的聚偏氟乙烯(PVDF)/ZIF-8超细纤维过滤材料,系统研究了纺丝液浓度对PVDF纤维形貌的影响和不同纳米纤维复合膜克重的PVDF/ZIF-8复合滤材的过滤性能。研究表明:ZIF-8可显著降低PVDF/ZIF-8复合纤维的直径,最小平均直径可达(83±11) nm。在最佳纺丝条件下,随着纳米纤维复合膜克重的增加,纤维毡的过滤效率与阻力均增加。对于质量中值直径为0. 26μm的Na Cl气溶胶,PVDF/ZIF-8复合纤维毡的过滤效率为95. 910%时,阻力为47. 6 Pa;过滤效率为99. 534%时,阻力为111. 1 Pa。ZIF-8与纳米纤维结合形成的超细纤维复合毡,为低克重节能滤材的研制提供了新的思路。     

静电纺PVDF/O-MMT膜对水面浮油吸附性能研究

采用静电纺丝法制备了添加不同比例[1%(wt,质量分数,下同),2%,3%]的有机改性蒙脱土(O-MMT)聚偏氟乙烯(PVDF)复合纳米纤维膜。利用扫描电子显微镜(SEM)研究O-MMT的添加比例对所制备的复合纳米纤维形貌结构的影响;借助傅里叶变换红外光谱(FT-IR)分析了PVDF及PVDF/O-MMT复合纳米纤维膜的化学结构;并应用DCAT21表面张力仪对比分析了PVDF及PVDF/O-MMT复合纳米纤维膜的吸油速率、单位面积吸油量。结果表明:加入O-MMT后,复合纳米纤维表面变得粗糙且珠节增加;复合纳米纤维膜的疏水性提高,并且纤维膜的单位面积吸油量和吸油速率提高。     

PVDF-g-PVP及PVDF/PVP微滤膜的制备与表征

选取经辐射接枝的PVDF(聚偏氯乙烯)-g-PVP(聚乙烯基吡咯烷酮)接枝物粉体及相同PVP含量的PVDF/PVP共混物粉体,利用浸没-沉淀相转化法制备微滤膜,并通过元素分析、红外光谱(FT-IR)、热重分析(TG)、差示扫描量热(DSC)、扫描电镜(SEM)对PVDF膜、PVDF-g-PVP及PVDF/PVP微滤膜的结构和性能进行表征,同时对膜的接触角和水通量进行测试.实验结果表明,PVDF-g-PVP及PVDF/PVP微滤膜的亲水性随PVP含量的增加而增强,但二者的热稳定性与PVDF膜相比略有降低.由于PVDF/PVP微滤膜中的PVP在成膜过程中主要作致孔剂,大部分会流失,因此与PVDF-g-PVP微滤膜相比,相同PVP含量的铸膜液在成膜后PVDF/PVP膜中的N含量较低,膜表面孔数较多,水通量较大,但亲水性略低.     

ZnMn2O4微/纳米纤维的制备及其性能的研究

以聚乙烯吡咯烷酮(PVP)为络合剂与醋酸锌〔Zn(CH3COO)2〕和乙酸锰(Mn(CH3COO)2)反应制得前驱体溶液,用静电纺丝法制备了PVP/Zn(CH3COO)2/Mn(CH3COO)2复合纳米纤维,经煅烧得到具有微孔结构的Mn掺杂ZnO微/纳米纤维。对所制备纤维分别采用差热-热重分析(TG-DTA)、红外光谱(IR)、X射线衍射(XRD)、扫描电镜(SEM)等手段进行了表征。结果表明:PVP/Zn(CH3COO)2/Mn(CH3COO)2纤维表面光滑,直径约300～700nm,经煅烧后,可得到Mn掺杂ZnO微/纳米纤维,XRD测试表明煅烧后的无机纳米纤维呈ZnMn2O4晶相。     

超细PAN/PVP复合纳米纤维的制备及其性能研究

采用五因素五水平正交实验研究了溶液浓度、PAN/PVP比例、电压、接收距离和LiCl含量对聚丙烯腈(PAN)/聚乙烯吡咯烷酮(PVP)复合纳米纤维形貌的影响,成功的制备出了直径在100nm以下形貌优良的PAN/PVP复合纳米纤维,并通过XRD进行表征;并对PAN/PVP复合纤维在400℃下进行了低温碳化处理,采用四探针电导仪对纤维的电导率进行了研究。结果表明:制备PAN/PVP复合纤维最优参数组合为:浓度10wt%、PAN/PVP为5/5、电压10kV、接收距离20cm、LiCl含量0.5wt%;随溶液浓度增大,PAN/PVP复合纤维的结晶性能增大;PAN/PVP比例为5/5时,纤维的电导率最高,能达到1.2×10-2S/m。     

极端湿热环境下隔热的超疏水聚偏氟乙烯/聚酰亚胺纳米纤维复合气凝胶

优异的隔热材料在建筑、航空航天和体育设备等领域有着广泛的应用需求.然而,在实际应用中,隔热材料在不同温度和湿度条件下,其性能往往会恶化.因此,构建在极端湿热环境下仍具有出色的隔热性能的块状材料是非常重要的.在本工作中,我们构思了一种绿色制备策略,即通过静电纺丝和冷冻干燥技术来制备超疏水且可压缩的聚偏氟乙烯/聚酰亚胺(PVDF/PI)纳米纤维复合气凝胶. PVDF纳米纤维和PI纳米纤维分别充当疏水性纤维骨架和机械支撑骨架,形成具有良好机械柔韧性的坚固的三维框架. PVDF/PI气凝胶在室温下具有出色的超疏水特性(水接触角为152°)和低导热性(31.0 m W m^-1K^-1).同时,在100%湿度(80℃)下, PVDF/PI气凝胶仅显示出48.6 m W m^-1K^-1的低热导率,其性能优于大多数商业绝热材料.因此,新型的PVDF/PI复合气凝胶有望成为高温和高湿环境中应用的优良隔热材料.     

含氟聚合物纳米多孔纳米纤维膜的制备

采用"电纺-相分离-沥滤"方法制备了聚(偏氟乙烯-co-六氟丙烯)(PVDF-HFP)以及聚偏氟乙烯(PVDF)纳米多孔纳米纤维膜.首先,将PVDF-HFP或PVDF和致孔剂聚乙烯吡咯烷酮(PVP)混合电纺,得到共混物纳米纤维膜.然后,将纳米纤维膜在水中沥洗出共混物中的PVP,获得纳米多孔纳米纤维膜.用场发射扫描电子显微镜(FESEM)观察水洗前后纤维表面精细结构.结果表明,纳米多孔纳米纤维表面呈多孔结构,孔径数10 nm.PVP的分子量对水洗后纤维表面结构有明显影响.致孔剂含量不同获得的PVDF-HFP纳米多孔纤维膜力学性能相近.     

TiO2/WO3微纳米纤维复合材料的制备及光催化性能

通过溶胶-凝胶和静电纺丝技术相结合的方法, 成功制备不同复合浓度聚乙烯吡咯烷酮(PVP)/钛酸四正丁酯(Ti(OC₄H₉)₄)/钨酸铵(N₅H₃₇W₆O₂₄·H₂O)前驱体。通过控温煅烧获得不同煅烧温度、不同复合浓度的TiO₂/WO₃微纳米纤维复合材料。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、场发射扫描电子显微镜(FE-SEM)和紫外-可见漫反射光谱(UV-Vis )技术对样品进行表征。以亚甲基蓝(MB)的光降解为模型反应, 研究TiO₂/WO₃微纳米纤维复合材料在紫外光照射下的光催化活性。结果表明, 煅烧温度500℃时, n(Ti):n(W) = 12:1形成WO₃掺杂的TiO₂微纳米纤维及n(Ti):n(W) = 4:1形成的TiO₂/WO₃复合微纳米纤维的光催化活性均高于纯TiO₂。     

静电纺载银PVDF纳米纤维膜的制备及其在层压织物中的应用

采用静电纺丝技术制备了载银PVDF复合纳米纤维膜,以PVP为还原剂,探索了不同的PVDF与PVP质量比对所得纤维形貌的影响。加入AgNO3后,研究了反应温度、AgNO3添加量对纳米银生成情况的影响。还考察了纺丝时间对复合纳米纤维膜的水接触角、阻气性、保暖率、防雨性能的影响。研究结果表明,PVDF与PVP质量比为7∶3时纤维具有较好形貌,Ag+的最佳还原温度为60℃、添加量为0.09g/g。随纺丝时间的增加,复合纳米纤维膜的水接触角逐渐增大,层压织物的阻气值、保暖率也随之增大。     

静电纺丝制备超疏水/超亲油空心微球状PVDF纳米纤维及其在油水分离中的应用

采用静电纺丝技术制备了超疏水超亲油具有空心微球结构的聚偏二氟乙烯(PVDF)纳米纤维。通过扫描电镜(SEM)对样品的表面形貌及纤维直径的变化进行了表征。通过视频显微镜对纳米纤维表面与水的接触角和水滴照片进行测量与拍照。研究了不同结构的PVDF纳米纤维对润滑油的吸附性能。结果表明:PVDF/N,N-二甲基甲酰胺/H_2O静电纺丝溶液中水含量达到2.5%时得到具有空心微球结构的纳米纤维,纤维表面的水接触角为153.55°,其吸油率达到21.48g/g。     

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.     

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.     

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.     

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 $\text{0.10 ?}\text{x}\text{? 0.14}$.     

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.     

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.     

Reactive plasma deposited SixCyHz films

Si_xC_yH_z films have been prepared at 200°C by reactive plasma deposition from SiH₄ and CH₄ diluted in helium in a tubular reactor. These films have a ratio s (equal to $\text{Si}\text{(}\text{Si+C}\text{))}$ ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH₄-CH₄-He plasma have been performed and the results are related to the composition of the deposited layers.     

Core-current-enhanced domain-wall pinning in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon

We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results.     

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.