氮掺杂二氧化钛纳米粉体的制备及光催化性能的研究

以钛酸正四丁酯为钛源、盐酸胍为氮源,用溶胶-凝胶法制备出了氮掺杂的TiO2纳米粉体,采用XRD、TEM、BET和UV-Vis对所制备的粉体进行了物相、形貌和结构表征,并分别在紫外光和可见光下进行了样品对甲基橙的光催化降解实验。结果表明,用该方法制备的N掺杂二氧化钛纳米粉体具有较单一的晶粒尺寸分布,分散性好,团聚少;掺杂样品在紫外光下对甲基橙的降解率比不掺杂样品有大幅度提高,并且在可见光下也具有较高的活性。     

基于溶胶-凝胶的两种旋涂方法制备PZT厚膜

采用溶胶-凝胶法,研究了两种在Au/Cr/SiO2/Si基底上沉积PZT(Pb(Zr0.52Ti0.48)O3)厚膜的方法.把与PZT澄清溶胶成分相同的PZT纳米粉混入澄清PZT溶胶,然后超声混合形成PZT浆料,PZT纳米粉的粒径为50～100nm.XRD分析表明两种方法得到的PZT厚膜都获得了单相钙钛矿结构.SEM结果显示两种厚膜厚度大约4μm,第一种旋涂方法制得的PZT厚膜表面粗糙,第二种旋涂方法制得的厚膜表面致密,无裂纹.在1 kHz的测试频率下,第一种和第二种厚膜的矫顽场分别为30 kV/cm和50 kV/cm,饱和极化分别为45 μC/cm2和54 μC/cm2,剩余极化分别为25μC/cm2 and 30μC/cm2.第二种厚膜有较高的直流耐压性能,在300 kV/cm的电场下,仍然保持较好的铁电性能.因而,第二种旋涂方法能够改善PZT厚膜的表面形貌和铁电性能.     

Growth of optical grade yttrium oxide single crystal via ceramic technology

To sinter neodymium doped yttrium oxide (NDY) singe crystal several successive technologies: laser synthesis of NDY nanopowder, pulsed magnetic compacting of the powder and two stage vacuum sintering were used. With the help of abnormal grain growth samples of NDY single crystal were produced. Conditions that are necessary for abnormal grain growth in yttrium oxide as well to grow the optical grade single crystal are discussed.     

Temperature-Independent Strain Sensor Based on a Hi-Bi Photonic Crystal Fiber Loop Mirror

This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 ) when compared with coated Hi-Bi PCF (1.21 ). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).     

基于正交试验的La_2O_3掺杂SnO_2气敏传感器的研究

以SnO2纳米粉和La2O3纳米粉为原料,采用高能球磨技术,结合正交试验设计,制备了经过高能球磨的纯SnO2纳米粉体和掺杂适量La2O3的SnO2纳米粉体。利用传统的厚膜气敏传感器制备工艺,制备了纯SnO2厚膜气敏传感器及掺杂一定量La2O3的SnO2厚膜气敏传感器。并对其本征电阻及其对乙醇、汽油、丙酮、氢气和CO等气体的敏感特性进行了测试。结果表明各因素对综合气敏性能影响的显著性水平由大到小依次为La2O3掺杂浓度〉烧结时间〉老化时间〉烧结温度。同时,通过分析还得到了最佳组合工艺。La2O3掺量为5%（质量分数）,烧结时间为2h,老化时间为7d,烧结温度为650℃条件下制备的气敏元件的综合气敏性能最好,其中对1.0×10-3乙醇蒸气的灵敏度达107.2,对相同浓度的干扰气体的选择性分别为S乙醇/S汽油=11.3,S乙醇/S丙酮=9.1。     

Use of hollow core fibers, fiber lasers, and photonic crystal fibers for spark delivery and laser ignition in gases

The fiber-optic delivery of sparks in gases is challenging as the output beam must be refocused to high intensity (approximately 200 GW/cm(2) for nanosecond pulses). Analysis suggests the use of coated hollow core fibers, fiber lasers, and photonic crystal fibers (PCFs). We study the effects of launch conditions and bending for 2 m long coated hollow fibers and find an optimum launch f# of approximately 55 allowing spark formation with approximately 98% reliability for bends up to a radius of curvature of 1.5 m in atmospheric pressure air. Spark formation using the output of a pulsed fiber laser is described, and delivery of 0.55 mJ pulses through PCFs is shown.     

Out-coupling efficiency enhancement of organic light emitting diode device by SiO2-UV hardener composite layer

The enhancement of out-coupling efficiency of organic light emitting diode (OLED) using SiO2-polymer composite layers was investigated. The SiO2-polymer composite was made from a SiO2 nanopowder and commercial UV-hardeners. The composite layer was coated on glass by dip-coating method in a SiO2 suspension, followed by spin-coating of 1 microm thick UV-hardener of was found that the optical properties were depend on the quantity of SiO2 nanopowder in the composite layer and dispersion of SiO2 suspension. 194/440 nm size of SiO2 nanopowders were added to the composite layer to enhance the light scattering effect. The OLED device which the SiO2-polymer composite layer was applied showed enhanced out-coupling efficiency around 30%.     

Nb NMR and Fe EPR study of local magnetic properties of magnetoelectric Pb(Fe1/2Nb1/2)O3

The ⁹³Nb NMR and Fe³⁺ EPR spectra of a magnetoelectric Pb(Fe_1/2Nb_1/2)O₃ (PFN) single crystal as well as of PFN ceramics and nanopowder have been measured. The relation between the chemical disorder and the local magnetic structure has been determined. The data show the occurrence of an antiferromagnetic (AFM) phase transition at 145 and 135 K in both single crystal and ceramic samples, respectively. The AFM phase transition is however essentially smeared out in the nanopowder. Two different Nb sites exist which have different local magnetic fields which are essentialy distributed in value. These two Nb sites correspond to different types of “chemical” order: Fe rich, Nb poor and Fe poor, Nb rich regions. The temperature dependences of the sublattice magnetizations and the values of the superhyperfine fields at the Nb ions are obtained. NMR data suggest that a spin-glass like state of PFN below T = 20 K arises from the Fe poor, Nb rich regions.     

碳纤维镀铜的研究

通过对碳纤维表面预处理,然后使用混合添加剂,以化学镀的方法在碳纤维表面镀铜,该方法有效地解决了对碳纤维镀铜时经常发生的碳纤维束"黑心"问题.在实验中观察到整束碳纤维被均匀连续地镀上了铜.通过扫描电镜观察镀铜碳纤维的断面,可以看到镀层和碳纤维结合得很紧密.     

Thermal stability of SiO2-coated SiC fiber (Hi-Nicalon) under argon atmosphere

Thermal stability of low-oxygen SiC fiber (Hi-Nicalon) coated with SiO₂ film was investigated. The SiO₂ film of same thickness but different crystal structure was formed by heating low-oxygen SiC fiber (Hi-Nicalon) under different oxidation conditions. The oxidation treatment and the subsequent exposure at 1773 K in argon caused very little loss of strength for unoxidized core. For as-oxidized fiber with SiO₂ film which containedimperfections, further loss of strength was caused after exposure in argon. There was little degradation of core strength on being exposed repeatedly at rapid heating and cooling rate in argon. The fiber oxidized at 1773 K kept high level of strength even after exposure at 1823 K. This is because the change in crystal structure of SiO₂ film before and after exposure in argon, which was the controlling factor in the degradation of strength, was diminished with increasing oxidation temperature.     

Highly Sensitive Fiber-Optic Faraday-Effect Magnetic Field Sensor Based on Yttrium Iron Garnet

1. IntroductionFaraday-effect sensors have been developed during the past 15 years to measure electric current andmagnetic fi.ldllL31. In these sensors) much attentionhas been given to enhance their sensitivity. Available optical materials providing a Faraday effect largeenough to be seriously considered for sensitive measuremellts of small magnetic field can be classified intwo groups. In one group are the paramagnetic anddiamagnetic doped glasses. In the other class are therare earth iron …     

银纳米粉的比表面积研究

采用阳极弧放电等离子体方法制备了高纯银纳米粉末.利用X射线衍射(XRD)、透射电子显微镜(TEM)对样品的形貌、晶体结构、粒度进行性能表征.利用静态表面吸附仪依据BET多层吸附原理,在液氮温度下(78K)和气体饱和蒸气压力范围内测试样品对N2的吸附-脱附等温线,用图解法根据吸附等温线求出单层吸附容量,由BET吸附公式计算出纳米粉末比表面积.结果表明:银纳米粉末的晶体结构为fcc结构,粒径范围在10～50nm,平均粒径为26nm,比表面积为23.81 m2/g.     

过氧化物的引发作用对玻璃纤维增强聚丙烯界面结合的影响

采用过氧化物溶液涂覆玻璃纤维,将处理过的玻璃纤维丙烯复合,采用单丝临界长度法测定了复合体系的界面剪切强度,研究了过氧化物的引发作用对玻璃纤维／聚丙烯复合体系界面结合的影响,探索了复合工艺条件对体系界面结合的影响,并考察了所形成界面的耐水性能,结果表明,涂覆于玻纤表面的过氧化物在复合过程中能引发聚丙烯与玻璃纤维表面含双键的偶联剂反应,在纤维与基体之间形成较界面结合,过氧化物的这种引发作用对界面的耐水     

聚多巴胺修饰聚对苯撑苯并双噁唑纤维增强其抗老化性与功能性

高性能纤维聚对苯撑苯并双噁唑(PBO)容易受紫外光照射而导致其性能显著下降。为了提高PBO材料的抗老化性能,文中通过简易方法在纤维表面直接修饰富含酚羟基的纳米厚度的聚多巴胺薄层,并比较研究了初始纤维与多巴胺修饰纤维在紫外光照射前后的力学性能、热稳定性能、结晶取向等性能的变化。结果表明,未经修饰的PBO纤维的力学等性能在紫外光照射后显著下降,如拉伸强度下降了67%;而表面经过修饰的PBO纤维在经过紫外光照射后,其性能变化显著减小,如拉伸强度仅下降了33%。并且,聚多巴胺修饰的PBO纤维对污染物罗丹明B染料等具有一定的吸附性能,吸附24 h的吸附容量达0.25 mg/g。因此,在材料表面修饰聚多巴胺层可有效改善PBO纤维的抗紫外光老化性能,提高了材料的功能性。     

Improved single mode property in elliptical air hole photonic crystal fiber

The single mode property of a holey, index-guided two-dimensional photonic crystal fiber (PCF) is investigated using the alternate direction implicit method. The modal analysis of a three-ring elliptical air hole photonic crystal fiber is performed and compared with the equivalent three-ring circular air hole photonic crystal fiber keeping the air-fill fraction the same for both cases. The fiber is investigated for single mode operation. The effect of the rotation of the ellipse axes on these characteristics is also considered. It is observed that a PCF with elliptical air holes exhibits a better single mode property over a wider wavelength range in the optical domain. Also when the diameter of the air hole is properly catered for, they can show an endlessly single mode property.     

尿素法制备纳米氮化锆粉体

利用尿素为固体氮源, 通过尿素分子与ZrCl₄、ZrOCl₂·8H₂O无机锆盐发生络合反应得到Z-U和ZO-U两种ZrN陶瓷的前驱体, 两种前驱体在较低温度下热裂解都可以得到ZrN陶瓷粉体。使用FT-IR对前驱体分子进行了结构分析, 采用TG-DTA跟踪了前驱体的热裂解过程, 并通过XRD和SEM对最终热裂解获得的ZrN产物进行了表征, 探讨了不同锆源制备前驱体的热裂解反应历程及其对产物ZrN的影响。结果显示: 结晶水的存在对络合反应有较大影响, 从而造成两种前驱体分子结构上存在较大差异; 尽管热裂解反应历程相似, 由于前驱体分子结构不同, 获得的ZrN粉体在纯度和形貌上存在较大差异; Z-U前驱体更容易得到纯度高的ZrN纳米粉体。     

Investigations on NiAl composites fabricated by matrix coated single crystalline AlO-fibers with and without hBN interlayer

The intermetallic compound NiAl has excellent potential for high temperature structural applications but suffers from low temperature brittleness and insufficient high temperature strength. One way to remove these deficiencies is the reinforcement by high strength ceramic fibers. Such intermetallic matrix composites can be conveniently fabricated by the hot pressing of matrix coated fibers. Al₂O₃ single crystal fibers show excellent chemical stability with the NiAl matrix, but the residual thermal compressive stresses during cool down dramatically degrades the fiber strength and thus, renders the composite useless for structural applications. We report on an experimental and computational study to mitigate this problem and to fabricate Al₂O₃/NiAl composites with sufficient high temperature strength. Analytical TEM, mechanical testing and push-out tests were employed to characterize chemistry, microstructure and mechanical properties of the composites. It will be shown that a processing window exists that allows producing intermetallic matrix composites with promising mechanical properties.     

INTERFACIAL MODIFICATION IN METAL MATRIX COMPOSITES BY THE SOL-GEL PROCESS

Detailed examination of thermodynamic and kinetic data suggest that it should be possible to develop an interfacial barrier coating which promotes wetting of metal matrix composite reinforcements, while simultaneously reducing deleterious interfacial chemical interactions. The current study has examined the feasibility of developing a procedure to coat graphite reinforcements with a thin, crack-free, protective oxide layer. Emphasis in this investigation being placed on sol-gel, TiO₂, coated PAN 650/42 graphite for inclusion in an aluminum metal matrix. Initially, the effect of the sol-gel composition and coating procedure on the coating uniformity, structure, and thickness were investigated. These procedures were then utilized for graphite fiber coating, with the coated fiber preforms being subsequently infiltrated by pure liquid aluminum. Energy dispersive x-ray analysis, optical and transmission electron microscopy confirmed that no reaction occurred at the TiO₂ -C interface, while chemical wetting and formation of a mixed (Al, Ti)O₂ oxide occurred at the TiO₂-Al interface.     

载药电纺丝素蛋白纤维毡的结晶含量对其药物释放的影响

以水溶液体系的再生丝素蛋白为原料,利用静电纺丝技术制备了载罗丹明B的丝素蛋白纤维毡。利用甲醇水溶液对其进行后处理,考察了不同处理时间下丝素蛋白的结晶含量对药物释放的影响。通过水溶性质量损失率、接触角、扫描电镜、傅里叶红外光谱、X射线衍射光谱及紫外光谱对处理前后的丝素蛋白纤维毡的表面形貌和结构以及药物释放行为进行了表征。结果表明,随着甲醇水溶液处理时间的延长,电纺丝纤维的质量损失率减小,亲水性减弱,丝纤维中的Silk II结晶(由β-折叠结构组成)含量增加,药物释放速率也增加。即通过控制处理时间,可以控制丝纤维中Silk II结晶的含量,从而控制药物的释放速率。     

Binary coherent beam combination with mirror pairs

A configuration of N coated mirrors or mirror pairs is described that has the potential to coherently combine 2N single-frequency phase-locked diffraction-limited polarized optical beams to form a single diffraction-limited beam. The application to beam combination of fiber amplifiers is discussed.