海藻酸钠/聚乙烯醇纳米纤维的制备与表征

以水为溶剂通过静电纺丝手段制备了海藻酸钠/聚乙烯醇(SA/PVA)纳米纤维膜,研究了溶液混合比例、纺丝参数、氯化钠(NaCl)和曲拉通X-100对其静电纺丝的影响,并对SA/PVA纳米纤维膜进行了XRD、FT-IR表征和力学性能测试。结果表明,溶液混配合比和纺丝参数对静电纺丝性能有着重要影响;添加0.5%(wt,质量分数,下同)的NaCl和1.5%的曲拉通X-100后能显著改善SA/PVA的静电纺丝性能。XRD和FT-IR分析表明,PVA能够破坏SA分子间作用力并形成了新的氢键。SA溶液∶PVA溶液的配合比为3∶7时,SA/PVA纳米纤维膜拉伸强度最优,达11.36MPa。     

羽毛角蛋白/PVA复合纳米纤维膜的制备及表征

以羽毛角蛋白(FK)和聚乙烯醇(PVA)为原料,水为溶剂,通过静电纺丝技术制备了FK/PVA复合纳米纤维膜。探讨了复合纳米纤维中FK与PVA的相容性,研究了FK的添加对纤维膜微观形貌、结晶度、热稳定性、亲水性等性能的影响。SEM结果表明,在聚合物总质量分数为14%的条件下制备的FK/PVA复合纳米纤维,表面平整光滑,平均直径为250~320nm,FK含量越大,直径越小。FTIR结果表明,FK与PVA具有良好的相容性,分子间存在氢键作用力。XRD结果表明,FK的加入破坏了PVA分子的规整排列,复合纳米纤维膜的结晶度下降。TG分析与接触角测试结果表明,随着体系中FK配比的增大,复合纳米纤维膜的热稳定性和亲水性均得到提高。     

羽毛角蛋白/PVA复合纳米纤维膜的制备及表征

以羽毛角蛋白(FK)和聚乙烯醇(PVA)为原料,水为溶剂,通过静电纺丝技术制备了FK/PVA复合纳米纤维膜.探讨了复合纳米纤维中FK与PVA的相容性,研究了FK的添加对纤维膜微观形貌、结晶度、热稳定性、亲水性等性能的影响.SEM结果表明,在聚合物总质量分数为14％的条件下制备的FK/PVA复合纳米纤维,表面平整光滑,平均直径为250～320 nm,FK含量越大,直径越小.FTIR结果表明,FK与PVA具有良好的相容性,分子间存在氢键作用力.XRD结果表明,FK的加入破坏了PVA分子的规整排列,复合纳米纤维膜的结晶度下降.TG分析与接触角测试结果表明,随着体系中FK配比的增大,复合纳米纤维膜的热稳定性和亲水性均得到提高.     

壳聚糖/聚乙烯醇复合纳米导电纤维的制备及性能表征

以壳聚糖(CS)、聚乙烯醇(PVA)和纳米石墨粉(G)为原料,利用静电纺丝技术分别制备了壳聚糖/聚乙烯醇共混纳米纤维及壳聚糖/聚乙烯醇/纳米石墨粉复合纳米纤维,采用原位聚合法在纤维表面聚合导电聚合物聚苯胺,得到具有优良导电性能的聚合CS/PVA和聚合CS/PVA/G复合纳米纤维。通过扫描镜、X射线衍射、红外光谱等测试手段对纤维的形貌和结构进行表征。结果表明,聚苯胺均匀包覆在经原位聚合的复合纳米纤维表面,提高了纤维的导电性能,纳米石墨粉与聚苯胺形成插入化合物进一步提高了纤维的导电性能。     

静电纺丝制备聚乙烯醇/再生柞蚕丝素蛋白复合纳米纤维

将聚乙烯醇(PVA)与再生柞蚕丝素蛋白(RWSF)共混,通过静电纺丝技术制备了PVA/RWSF复合纳米纤维,在保持材料降解性能和力学强度不变的前提下,获得了具有生物活性的表面。应用正交法优选出PVA/RWSF复合纳米纤维的最佳制备工艺参数。扫描电镜观察到,各组电纺膜中纤维的形貌较好,不同参数条件下纤维的直径和均匀程度有较大差别;方差分析表明,静电纺丝过程中纺丝液浓度、PVA/RWSF质量比和纺丝电压对纤维均匀性的影响显著;结合后期验证性实验确定PVA/RWSF复合纳米纤维最佳电纺参数为电纺液浓度0.09 g/mL、PVA/RWSF质量比90/10、纺丝电压18kV、推进速度1.5mL/h、接收距离14cm,此时制备的纤维均一、纤细,重复性好。     

海藻酸钠/羽毛角蛋白复合纤维的制备与性能

采用酸碱法在鸭毛中提取羽毛角蛋白（FK）,通过正交实验研究了FK提取的最佳条件。将FK与海藻酸钠（SA）进行共混,制备SA/FK复合溶液,测试了复合溶液的流变性。通过湿法纺丝制备SA/FK复合纤维,研究了复合纤维的基本性能并表征了复合纤维分子间氢键作用。结果表明:在最佳提取条件下（提取温度为60.0℃,提取时间为120.00 min,碱浓度为2.00wt%）,FK产率最高为45.75%。SA/FK复合溶液的表观黏度随剪切速率的增加而减小,随FK含量的增加呈现先增后减的趋势。FK的加入使分子间氢键作用增强。SA/FK复合纤维的力学断裂强度能够达到1.96 cN/dtex。SA与FK的复合破坏了原有分子的晶体结构,SA/FK复合纤维分子结构是以非晶态存在。SA/FK复合纤维的表面具有均匀的沟槽结构。      

动态线纺聚乙烯醇/海藻酸钠纳米纤维膜的制备

为了实现静电纺纳米纤维产量化的制备,使用自主设计的无针式动态线性电极静电纺丝机制备聚乙烯醇(PVA)/海藻酸钠(SA)(AP)纳米纤维膜。采用扫描电子显微镜(SEM)研究PVA/SA配比、收集距离和纺丝电压对纤维形貌及直径分布的影响。结果表明,PVA/SA配比对纤维形貌影响最大,随着SA含量降低,溶液牵伸顺利;在此基础上随着距离增加,纤维形貌逐渐改善但不匀率有所增加。当7.5%PVA与2%SA按体积比9∶1共混时,所得纤维形貌及直径分布最佳,最佳纺丝电压和距离分别为75 kV和25 cm,纤维平均直径为(187±44) nm,产量可达2.5 g/h。为AP纳米纤维膜的规模化制备提供了参考。     

海藻酸钠-聚乙烯醇复合纤维的研制及性能表征

海藻(SA)与聚乙烯醇(PVA)溶液共混得到不同配比的纺丝原液,通过粘度法从热动力学角度对2种高分子材料的相客性及分子间作用力进行了表征,结果表明,当m(SA)∶m(PVA)=4:1时最优,分子间作用力最强,通过长时间的静置观察,验证了该比例共混液表现出的良好相容性,并辅以红外光谱分析,再对各比例条件的共混液膜材料进行了力学性能的检测,结果表明,在该比例时膜材料具有最强的抗张强度和断裂伸长率.对SA-PVA复合纤维的湿法纺丝工艺条件进行优化,结果显示,在现有条件下,当选用30℃、pH=6.0的Ca2+凝固浴时,SA-PVA共混纺丝原液成纤性最强,并对复合纤维的吸湿性能进行了测定.     

静电纺丝制备PEI/PVA纳米纤维膜负载甘草酸的研究

通过静电纺丝技术制备了聚乙烯亚胺/聚乙烯醇(PEI/PVA)复合纳米纤维,并用戊二醛作为交联剂使其疏水化,然后在交联后的PEI/PVA复合纤维膜上修饰了甘草酸。利用傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)对PEI/PVA交联前后的复合纤维膜以及甘草酸修饰的PEI/PVA复合纳米纤维膜分别进行了表征。SEM结果表明,交联后的纳米纤维形貌均匀且有明显的结节,而交联前和甘草酸修饰后的纳米纤维,表面光滑均匀,形貌没有发生明显的变化,且甘草酸修饰后的纤维直径在400~600nm之间。FT-IR表明利用静电纺丝技术可以制备甘草酸修饰的PEI/PVA复合纳米材料,利用此纤维材料,可以进一步的应用于肝癌的早期诊断和检测。     

基于氧化-还原胺化反应改性海藻酸盐制备载药性电纺纳米复合纤维

以辛胺为疏水改性剂,采用氧化-还原胺化反应制得具有两亲性的海藻酸衍生物(RAOA)。通过FTIR、~1H NMR、荧光光谱和光学接触角测量仪对RAOA的结构和性能进行表征。进而,以聚乙烯醇(PVA)为助纺剂,对疏水改性的RAOA进行电纺性能的研究。通过光学接触角测量仪、电导率仪、流变仪和扫描电子显微镜对RAOA/PVA纺丝液的物理性能和与之相应的RAOA/PVA纳米复合纤维的形貌进行了测试,考察了该电纺纳米复合纤维对疏水性布洛芬的负载和释药性能。结果表明,辛胺成功接枝到海藻酸钠(SA)分子链上,RAOA的临界聚集浓度为0.43 g/L,说明RAOA具有良好的两亲性。氧化-还原胺化反应改性RAOA不能从根本上改变单一RAOA溶液的可纺性,但是它可以改善RAOA/PVA纺丝液的电纺性能,提高RAOA在RAOA/PVA电纺纳米复合纤维中的含量。载药后的SA/PVA电纺纳米复合纤维在释药初期有突释行为,但改性后的RAOA可以有效地减缓布洛芬的释放速度,提高其缓释性能。     

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.     

Anomalous Hall Effect in Sn1?x?yMnxEuyTe and Sn1?x?yMnxEryTe Mixed Crystals

The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn_1–x Mn _x Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R _s depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R _s changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R _s , particularly change of the sign.     

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.     

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.     

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.