纳米二氧化钛对质子辐照下MQ增强硅橡胶力学性能的影响

采用空间综合辐照模拟设备研究了纳米二氧化钛对100 keV和150 keV能量质子辐照下MQ增强加成型硅橡胶力学性能的影响。试验结果表明,质子辐照后,未添加纳米粒子的硅橡胶表面颜色明显加深,同时出现不同程度的老化龟裂裂纹,裂纹数量和深度随辐照能量和剂量的增加而增加;硅橡胶的硬度和拉伸强度随辐照剂量的增加先增加而后降低。添加纳米二氧化钛的硅橡胶与未改性硅橡胶相比,经过相同能量、剂量的质子辐照后,表面颜色加深和表面裂纹损伤的程度均减小,硬度和力学性能的损伤程度下降,表现出明显的抗质子辐照性能。     

纳米二氧化钛对质子辐照下MQ增强硅橡胶热性能的影响

采用空间综合辐照模拟设备研究了纳米二氧化钛对100keV和150keV能量质子辐照下MQ增强加成型硅橡胶损伤及热性能的影响.试验结果表明,质子辐照后,未添加纳米粒子的硅橡胶表面颜色明显加深,同时出现不同程度的老化裂纹,裂纹数量随辐照能量和剂量的增加而增加;辐照后硅橡胶的质损率增加,耐热性能下降;辐照后硅橡胶在玻璃态和玻璃转变区的温度区间内收缩率降低,而在高弹态的温度区间内膨胀率增加.添加纳米二氧化钛的硅橡胶与未改性硅橡胶相比,经过相同能量、剂量的质子辐照后,表面颜色加深和表面裂纹损伤的程度减小;质损率增加、耐热性能下降以及收缩膨胀率变化的程度均降低,表现出明显的抗辐照性能.     

热处理温度对β-NaYF4:Yb3+、Er3+纳/微米颗粒上转换发光性能的影响

采用溶剂热法和热分解法分别制备纳/微米的β-NaYF4:20%Yb3+,2%Er3+晶体.根据两种不同粒径颗粒的TG-DTA测试分析,对其进行不同温度的热处理。通过XRD、SEM、FT-IR以及PL等手段研究不同热处理温度对两种粒径的颗粒的尺寸、形貌以及上转换发光性能的影响.研究结果表明,随着热处理温度的升高,纳/微米颗粒的发光性能主要呈现出先升高后下降的趋势。与未作热处理样品对比发现,适当的热处理(580℃)可以提高纳米颗粒的发光强度,却不利于改善微米颗粒发光性能。分析认为,结晶质量的提高、缺陷浓度的降低以及有机配体的去除,导致了纳/微米颗粒的发光性能的逐步提高。而过高处理温度(>580℃)引起的相转变(β→α)和表面Na2CO3的生成又大大降低了稀土离子的发光效率。热处理过程中颗粒之间的不同团聚程度是造成纳/微米颗粒发光性能差异变化的主要原因。     

聚乙烯醇/氧化淀粉/二氧化钛复合纳米纤维膜的制备

采用静电纺丝技术制备聚乙烯醇/氧化淀粉/二氧化钛复合纳米纤维膜。采用场发射扫描电子显微镜、差示扫描量热仪及热重分析仪研究组分对材料表面形貌、纤维直径、结晶度和热性能的影响。结果表明,复合纳米纤维表面粗糙程度随二氧化钛含量增加而增大,纤维平均直径在183~222 nm之间且随氧化淀粉含量增加而减小,材料结晶度在30.73%~16.78%之间且随氧化淀粉含量增加而下降,热稳定性随氧化淀粉含量增加而增强。     

杜仲翅果壳粉/PVC复合材料力学性能研究

本论文通过采用超微粉碎的方法对杜仲翅果壳进行粉碎、筛选、烘干后与聚氯乙烯(PVC)共混制得PVC木塑复合材料(WPC)。研究了杜仲翅果壳粉的用量及粒径对(未添加DOP及添加DOP)WPC性能的影响。结果表明:经过对添加DOP与未添加DOP的性能对比,发现DOP的加入能够明显改善材料的加工性能,拉伸强度与弯曲强度有明显的降低,而冲击强度则有增加的趋势;随着杜仲翅果壳粉的用量的增加,杜仲翅果壳粉/PVC复合材料的拉伸强度、冲击强度呈现下降趋势,弯曲强度呈现先上升后下降的趋势,硬度基本保持不变,杜仲翅果壳粉的粒径对杜仲翅果壳粉/PVC复合材料的性能影响不大。     

纳米Al2O3/尼龙复合材料的制备及性能表征

为了提高单体浇铸尼龙6的高温性能,用纳米Al2O3对单体浇铸尼龙尼龙进行填充增强,采用原位聚合技术制备了纳米Al2O3/尼龙复合材料(简称NA/MCN),用万能材料试验机测试了复合材料的拉伸强度,用扫描电镜观察了断口形貌特征,通过动态热机械分析仪对材料的热机械性能进行了表征,并与微米Al2O3增强铸型尼龙复合材料进行了对比分析,研究了粒子的粒径、粒子含量对复合材料拉伸强度和热力学性能的影响.采用傅里叶红外光谱研究了复合材料的结构.结果表明,复合材料的拉伸强度和玻璃化温度比尼龙基体明显提高,而储能模量的变化不大,纳米粒子增强尼龙复合材料的拉伸强度和玻璃化转变温度明显高于微米粒子增强尼龙复合材料;并且纳米氧化铝与尼龙基体之间存在化学相互作用.     

纳米Al2O3/尼龙复合材料的制备及性能表征EI

为了提高单体浇铸尼龙6的高温性能,用纳米Al2O3对单体浇铸尼龙尼龙进行填充增强,采用原位聚合技术制备了纳米Al2O3/尼龙复合材料(简称NA/MCN),用万能材料试验机测试了复合材料的拉伸强度,用扫描电镜观察了断口形貌特征,通过动态热机械分析仪对材料的热机械性能进行了表征,并与微米Al2O3增强铸型尼龙复合材料进行了对比分析,研究了粒子的粒径、粒子含量对复合材料拉伸强度和热力学性能的影响.采用傅里叶红外光谱研究了复合材料的结构.结果表明,复合材料的拉伸强度和玻璃化温度比尼龙基体明显提高,而储能模量的变化不大,纳米粒子增强尼龙复合材料的拉伸强度和玻璃化转变温度明显高于微米粒子增强尼龙复合材料;并且纳米氧化铝与尼龙基体之间存在化学相互作用.     

麦秸/木材均质复合无机碎料板的阻燃性能研究

以镁系无机胶粘剂和均匀混合的麦秸和木材碎料为原料,采用热压工艺,制备麦秸/木材均质复合无机碎料板。利用导热系数测定仪、锥形量热仪对比研究了普通有机胶粘剂胶合麦秸板、麦秸无机碎料板、木材无机碎料板以及麦秸/木材均质复合无机碎料板的阻燃抑烟性能。结果表明,与普通有机胶粘剂胶合麦秸板相比,无机胶粘剂能显著降低板材的热释放和烟释放;麦秸/木材均质复合无机碎料板的热释放速率(HRR)、总热释放量(THR)、烟生成速率(SPR)、总烟生成量(TSP)和质量损失均高于麦秸无机碎料板而低于木材无机碎料板,点燃时间(TTI)小于麦秸无机碎料板而大于木材无机碎料板,麦秸/木材均质复合无机碎料板具有良好的阻燃抑烟性能。     

改性纳米或微米SiO_2的分散方法对木粉-SiO_2/聚丙烯复合材料力学性能的影响

未改性和乙烯基三甲氧基硅烷(VTS)改性的纳米SiO_2和微米SiO_2作为增强相,采用直接分散(干分散)和溶液分散(湿分散)两种方法将SiO_2添加到聚丙烯(PP)基体中。将木粉(WF)作为改性相添加到SiO_2改性的PP中制备WF-SiO_2/PP复合材料,探索SiO_2粒径、分散度及界面改性对复合材料增强效果的影响。红外光谱显示改性后的SiO_2已经成功接枝到PP基体上;与未填充SiO_2的WF/PP复合材料相比,干分散模式添加质量比为9%的微米SiO_2或9%的纳米SiO_2,WF-SiO_2/PP复合材料的弯曲强度分别降低了21%和18%;然而,湿分散模式以VTS改性微米SiO_2和纳米SiO_2,WF-SiO_2/PP复合材料弯曲模量分别提高了17%和22%,且抗蠕变性能也明显改善;通过干分散和湿分散模式添加微米SiO_2,均使WF-SiO_2/PP复合材料冲击强度提高了17%。研究表明,在SiO_2粒子分散均匀且与基体界面结合良好的前提下,加入适量微米SiO_2或纳米SiO_2使WF-SiO_2/PP复合材料的冲击强度提高了15%～25%。     

耐蒸煮软包装用聚氨酯胶粘剂的研究

目的以聚酯二元醇(PBA)、异佛尔酮二异氰酸酯(IPDI)、植物油多元醇蓖麻油和硅烷偶联剂为原料,制备一种耐蒸煮的无溶剂聚氨酯胶粘剂。方法采用红外光谱(FT-IR)、热重分析(TG)等手段对胶粘剂的结构和性能进行了分析表征,同时考察了不同有机硅烷偶联剂的添加量对胶粘剂固化时间、粘结强度、固化膜吸水率等的影响。结果适量添加硅烷偶联剂可以有效提高胶粘剂的粘结强度、热稳定性和耐蒸煮性,但是硅烷偶联剂添加量过多会导致胶粘剂分层,固化困难。结论硅烷偶联剂添加量在1%~2%为最佳。     

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.