PP/蒙脱土纳米复合材料的制备及剪切粘度

应用双螺杆挤出机熔融插层制备出PP／蒙脱土纳米复合材料，X射线衍射表明，PP高分子链已插层进入有机蒙脱土片层之间。应用两种不同缝隙厚度的窄缝流变仪对PP及PP／蒙脱土纳米复合材料的剪切粘度及影响因素进行了研究。结果表明，PP／蒙脱土纳米复合材料为剪切变稀性流体。在190℃和210℃温度下，PP／蒙脱土纳米复合材料呈现类固体的非牛顿流体行为，剪切粘度随着剪切速率的升高逐渐降低。在230℃和剪切速率小于80s^-1的情况下，PP／蒙脱土纳米复合材料呈现类牛顿性流体行为。温度较高时,蒙脱土的含量对复合材料的剪切粘度的影响较为明显。     

尼龙11/蒙脱土纳米复合材料的流变性能

使用XLY-Ⅱ型流变仪研究了尼龙11和尼龙11／蒙脱土纳米复合材料的流变行为,并对其1gηa～1／T、1gηa～1gγw、1gτw～1gγ,曲线进行了分析。实验结果表明,尼龙11和尼龙11／蒙脱土纳米复合材料均为假塑性流体,在215℃～245℃的非牛顿指数范围为0．35～0．69．其表现粘度随着蒙脱土含量的增加而升高．在高剪切速率下,蒙脱土对粘度的影响减小。荥脱土的加入使尼龙11的粘流活化能降低,故熔体流变特性受温度影响变小。     

OMMT共混改性HDPE/MH无卤阻燃体系研究

通过纳米有机蒙脱土（OMMT）改性高密度聚乙烯（HDPE）,纳米氢氧化镁（MH）无卤复合阻燃体系。研究了有机蒙脱土的用量对体系阻燃性能、力学性能及流变性能的影响。实验结果表明：OMMT单独对HDPE阻燃改性效果较差,它和MH复配可产生协同阻燃效果,但MH添加质量分数需在HDPE的60％以上方可有效阻燃。当m（HDPE）：m（MH）：m（OMMT）为100：60：6时,复合材料具有较好的阻燃性能和力学性能。HDPE／MH／OMMT熔体为假塑性流体,OMMT添加质量分数超过HDPE添加质量分数的6％时,会使体系在低剪切速率下的黏度大幅增加,流动性能降低。同时,0MMT的增加会导致熔体假塑性程度增加。     

聚氨酯/蒙脱土纳米复合弹性体材料--(Ⅰ)聚醚多元醇插层蒙脱土影响因素的研究

研究了研磨剪切作用对聚醚多元醇插层的蒙脱土片层结构的影响。研究发现，随着研磨时剪切应力强度和研磨次数的增加，有机蒙脱土的层间距从2．8nm逐渐扩大到5．6nm左右，直至(001)面衍射峰消失。聚醚种类对蒙脱土的片层结构也有一定影响。由此制备的聚醚多元醇／蒙脱土纳米复合物可用于本体法合成聚氨酯／蒙脱土纳米复合弹性体。     

聚苯胺/蒙脱土电流变液的稳定性

采用乳液共混插层法制备了高介电常数的聚苯胺／蒙脱土纳米复合材料微粒。聚苯胺／蒙脱土电流变液在外电场下的剪切强度达8.26kPa(3KV/mm DC,5s^-1)，并具有较好的温度稳定性，其剪切应力在10－100℃内随温度变化仅为6．5％（1.5kV/mm,DC,1.61s^-1)，静置60天沉降率仅为1％，IR及XRD分析表明，聚苯胺插入到蒙脱土层间，形成纳米复合颗粒，TEM标示颗粒的粒径约为100nm，在1000Hz，20℃时，聚苯胺／蒙脱土颗粒的介电常数比纯蒙脱土提高2．7倍，比纯聚苯胺提高5．5倍，电导率增加8．5倍。     

紫外光固化环氧丙烯酸酯/蒙脱土纳米复合材料的合成与表征

利用插层聚合合成了环氧丙烯酸酯／蒙脱土复合光固化树脂，并采用紫外光固化制备了环氧丙烯酸酯／蒙脱土纳米复合材料．用XRD、DSC对光固化过程中蒙脱土的插层和剥离行为进行了研究，并用FT-IR研究了蒙脱土对环氧-丙烯酸酯体系光固化速率的影响。力学试验证实，光固化后的环氧丙烯酸酯／蒙脱土纳米复合材料冲击与弯曲强度比原本体树脂分别提高了54％和10％．     

聚乳酸/蒙脱土纳米复合材料的冷结晶及熔融行为

采用熔融插层法制备了插层型的聚乳酸/蒙脱土纳米复合材料(PLA/MMTs)。利用差示扫描量热仪(DSC)和X射线衍射(XRD)对该纳米复合材料的结晶及熔融行为进行了研究。结果表明,PLA/MMTs复合体系不能从熔体冷却结晶,但可在较慢的升温过程中固态下冷结晶;蒙脱土不会改变PLA基体结晶的α晶型,但具有异相成核作用,促进了PLA基体的冷结晶在更低的温度下进行;复合体系在较慢升温速率下的双重熔融现象源于原始晶粒熔融重结晶行为。     

煤基聚乙烯/蒙脱土复合材料的阻燃特性

研究了以聚磷酸铵(APP)、季戊四醇(PER)和三聚氰胺(MEL)复配成的膨胀型阻燃荆、煤及蒙脱土阻燃协同作用及其对煤基聚乙烯／蒙脱土复合材料阻燃性能的影响。少量蒙脱土即可显著提高聚乙烯的极限氧指数。超细煤粉的含量在一定范围内可明显提高聚乙烯／蒙脱土复合材料的极限氧指数．煤、蒙脱土及膨胀型阻燃剂之间存在良好的协同阻燃效应．可使聚乙烯的极限氧指数得到一定的提高。热氧化分解及红外光谱分析表明，煤、蒙脱土及膨胀型阻燃荆之间的协同阻燃效应与煤基聚乙烯／蒙脱土阻燃材料具有良好的热稳定性和较高的残炭率有关。     

苯乙烯-丙烯酸丁酯/蒙脱土纳米复合材料的阻燃性

以乳液插层聚合法合成苯乙烯-丙烯酸丁酯／蒙脱土纳米复合材料。X射线衍射结果表明，聚合物能够有效地插层到经过有机化处理的蒙脱土层间，且蒙脱土片层可以均匀地分散在苯乙烯-丙烯酸丁酯共聚物中。TGA分析表明，苯乙烯-丙烯酸丁酯／有机蒙脱土纳米复合材料的热稳定性有所提高．锥形量热仪测试和研究表明。复合材料的燃烧性能，包括热释放速率和质量损失，在蒙脱土含量为2％时，效果最好。     

聚氨酯/蒙脱土纳米复合弹性体材料--(Ⅱ)结构及性能的表征

借助锥体磨的研磨剪切外力，将聚醚多元醇插层进入蒙脱土片层中，使其片层间距扩大并发生部分剥离，从而利用本体插层聚合法制备了综合性能优异的聚氨酯／蒙脱土纳米复合弹性体材料。当有机蒙脱土添加量仅为1％时，其拉伸强度比纯聚氨酯弹性体高30％．达到30．2MPa，断裂伸长率也略有增加。TGA及吸水实验分析表明聚氨酯／蒙脱土纳米复合材料有更高的热失重温度和更低的吸水率．研究了蒙脱土含量对聚氨酯／蒙脱土纳米复合材料各项性能的影响。     

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.     

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.     

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.     

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.