微结构光纤预制棒拉制过程的温度场分布

根据非稳态傅里叶热传导方程及微结构光纤(MSF)预制棒的初始条件和边界条件，建立圆柱形坐标系，推导出MSF预制棒的温度场分布方程.计算结果表明：当MSF预制棒在高温炉内的温度场分布接近热传导稳态分布时的下棒速度为制备MSF的最佳速度，此时高温炉的加热温度可降低到MSF预制棒的软化温度，另外，随着MSF空气填充率的增加，MSF预制棒的下棒速度也应加快. 关键词： 微结构光纤 光纤预制棒 温度场分布 热传导     

纳米银修饰的微结构聚合物光纤作为化学-光学传感材料的初步研究

通过调节在微结构聚合物纤维(Microtubes Polymer Opeical Fibers,MPOF)孔道中进行的动态化学反应——银镜反应的条件,可以得到管状或岛状纳米Ag修饰的MPOF.扫描电镜分析显示：在高反应物浓度下,在孔洞阵列中进行反应得到管状银修饰的MPOF;该Ag微管-MPOF复合纤维是导电性的,可以直接作为阵列电极制造电化学传感器.研究结果显示,MPOF复合纤维对治癌物质硝酸根或亚硝酸根有高的可逆氧化还原活性;在低反应物浓度下,在孔洞阵列中进行反应得到岛状银修饰MPOF;当把岛状银修饰MPOF插入有机荧光物质的水溶液中时,观察到荧光有明显的增强效应.     

微结构光纤制备过程中不同位置空气孔的形变量分析

根据热传导原理，在拉制微结构光纤(MSF)时，在高温区中，MSF预制棒的包层内不同位置加热的温度也不一样，且由表面往中心方向温度逐渐下降，温度梯度随MSF预制棒下棒速度的加快或包层空气填充率的减少而增大.由于材料的表面张力和黏度系数都是温度的函数，因此将MSF预制棒拉细成MSF时，实际所得到的MSF结构，并非是预制棒等比例的缩小，而是温度越高的空气孔形变量越大.为得到符合设计要求的MSF，就必须将MSF预制棒包层空气孔尺寸按温度变化规律设计，从而消除由于加热温度的非均匀性对拉制的MSF包层空气孔所产生的影响.     

Ag微米管阵列修饰的聚合物光子晶体光纤制备工艺研究

以聚合物光子晶体光纤空气孔阵列为模板,制备了Ag微米管阵列修饰的聚合物光子晶体光纤.讨论了银氨溶液和葡萄糖溶液浓度以及反应时间和温度对银微米管形貌的影响.在Ag(NH3)+2与C6H6O浓度比为2,反应时间为20 min,温度为65℃条件下光纤孔洞表面获得了规则的Ag微米管状结构,并对Ag的生长机理进行了讨论.     

负载型二氧化钛光催化材料的制备及其光催化性能研究

以球形氧化铝为载体,采用溶胶-凝胶法和浸渍涂覆过程制备了负载型二氧化钛光催化材料。以扫描电子显微镜(SEM)和X-射线衍射仪(XRD)等手段对所合成的样品形貌及晶型进行了表征。结果表明,氧化铝载体经负载二氧化钛后,在球形氧化铝表面沉积了一层粒径为10~20nm的锐钛型二氧化钛纳米颗粒。通过能量色散X射线光谱(EDX)对氧化铝载体和所合成的样品进行进一步分析,表明样品中明显存在Ti元素。另外,提高氧化铝载体在二氧化钛溶胶中的浸渍次数能够有效提高二氧化钛的负载量。当浸渍次数增加到5次时,Ti元素的含量由3.8Wt.%提高至15.7Wt.%。另外,以亚甲基蓝为目标降解物,详细研究了不同浸渍次数获得的负载型二氧化钛催化材料的催化性能。结果表明:随着浸渍次数的增加,负载型二氧化钛催化材料的表面形貌不仅得到明显改善,而且显著提高了样品的光催化活性。当浸渍次数由1次提高至4次时,亚甲基蓝的降解率由40%上升至83.1%。然而,当二氧化钛负载量达到一定程度时,由于不断浸渍导致下层的二氧化钛受光照机会和光照强度减弱,导致其光催化活性提高缓慢。当浸渍次数提高至5次时,亚甲基蓝降解率仅为85.6%。所制备的负载型二氧化钛光催化材料重复使用5次,其光催化活性保持相对稳定。     

掺镱石英光纤预制棒的制备与表征

采用改进化学汽相沉积结合溶液掺杂法制备了掺镱石英光纤预制棒,并研究了不同镱掺杂浓度下的吸收光谱和发光光谱.吸收光谱和发光光谱的强度随着YbCl3溶液浓度的增大而增强.在不产生失透的前提下,得到预制棒芯层能够掺杂的YbCl3溶液最大浓度为0.057mol/L.     

掺镱石英光纤预制棒的制备与表征

采用改进化学汽相沉积结合溶液掺杂法制备了掺镱石英光纤预制棒,并研究了不同镱掺杂浓度下的吸收光谱和发光光谱.吸收光谱和发光光谱的强度随着YbCl₃溶液浓度的增大而增强.在不产生失透的前提下,得到预制棒芯层能够掺杂的YbCl₃溶液最大浓度为0.057 mol/L.     

使用MCVD设备制取62.5μm大芯径、大数值孔径光纤预制棒的新工艺探索

总结了使用ＭＣＶＤ设备制备大芯径、大数值孔径光纤预制棒的新工艺。探索在不掺硼的情况下,在预制棒芯层逐层增加ＧｅＣｌ４的流量。在内包层掺氟以降低内包层折射率。解决了为达到较高折射率差Δｎ,在芯层掺锗过多而引起光纤预制棒在沉积后期和缩棒过程中由材料的热膨胀系数而导致的炸裂问题。并通过改变火焰平移速度,提高了沉积速率,缩短了制棒时间。所拉制的光纤、数值孔径ＮＡ高达０．３０。     

聚合物PVP表面修饰CdS纳米棒的制备及其光谱特性

用水热合成方法制备了PVP表面修饰CdS纳米棒,用XRD,TEM,TG-DTA,IR,UV-Vis,PL等光谱技术进行了表征。与未修饰的CdS纳米棒相比,PVP修饰后的CdS纳米棒具有更均匀的尺寸分布,吸收光谱具有结构峰特征,其荧光发射谱增强。     

聚合物光子晶体光纤作为新型传像光纤应用的初步探索

制备了两种具有传像功能的聚合物光子晶体光纤.该光纤分别由525个空气孔按四方排列和由547个空气孔按六方排列的二维光子晶体聚合物光纤组成.实验结果表明：在短距离内,这两种光纤可以以抗传导的机理传送图像,且制备工艺简单,单根光纤就带有数百个像素,可用于制造集成光学器件.     

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO₂⁻) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF. It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution. The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 × 10^− 4 g/ml-5.0 × 10^− 3 g/ml. The method possesses ease of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results.     

The enhanced photocatalytic activity of CdS/TiO2 nanocomposites by controlling CdS dispersion on TiO2 nanotubes

CdS/TiO₂ nanocomposites were prepared via a simple wet chemical method, and characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their ability to degrade Acid Rhodamine B was investigated under visible light irradiation. The results indicate that CdS/TiO₂ nanocomposite with a mass ratio of 4:1(TiO₂:CdS) showed high photocatalytic activity and the CdS loaded on TiO₂ nanotube surface exhibited a hexagonal phase. The dispersion of CdS on TiO₂ nanotube surface had an important effect on the degradation efficiency of pollutant, which provides a strategy for practical industry application.     

Tunable photocatalytic selectivity of fluoropolymer PVDF modified TiO2

Fluoropolymer poly-vinylidene-fluoride modified TiO₂ (PVDF/TiO₂) were prepared via a simple chemisorption approach and characterized by thermo gravimetric analyse, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence spectra. The modified mechanism and the photocatalytic selectivity of the PVDF/TiO₂ were studied. The existence of Ti-F coordination bond on the interface between TiO₂ and PVDF was confirmed. For the PVDF modification, the photocatalytic degradation (PCD) of cationic dye was greatly enhanced, and the PCD of anionic dye was obviously inhibited. PVDF/TiO₂ shows high photocatalytic selectivity than that of TiO₂ by degrading mixed solution of cationic dyes MB and anionic dyes MO. The selectivity can be tuned by changing the PVDF modification amount.     

Microstructural, optical and photocatalytic properties of CdS doped TiO2 thin films

CdS doped TiO₂ thin films (with CdS content=0, 3, 6, 9 and 12 at%) were grown on glass substrates. The X-ray diffraction analysis revealed that the films are polycrystalline of monoclinic TiO₂ structure. The microstructure parameters of the films such as crystallite size (D_ν) and microstrain (e) are calculated. Both the crystallites size and the microstrain are decreased with increasing CdS content. The optical constants have been determined in terms of Murmann's exact equations. The refractive index and extinction coefficient are increased with increasing CdS content. The optical band gap is calculated in the strong absorption region. The possible optical transition in these films is found to be an allowed direct transition. The values of E_g^opt are found to decrease as the CdS content increased. The films with 3 at% CdS content have better decomposition efficiency than undoped TiO₂. The films with 6 at% and 9 at% CdS content have decomposition efficiency comparable to that of undoped TiO₂, although they have lower band gap. The CdS doped TiO₂ could have a better impact on the decomposing of organic wastes.     

Oxygen gas optrode based on microstructured polymer optical fiber segment

In this article, we first propose a novel type of oxygen gas optrode by forming fluorophore doped sensing film in the array microholes with the characteristics of microstructured optical fiber (MOF) segment. Comparing with the conventional O₂ detecting method, this slender shaped optrode shows potential in trace amount of O₂ sensing and online O₂ monitoring. Organical silicate gel or plastified cellulose acetate are chosen as sensing films and tris (4,7-diphenyl-1,10-phenathroline) ruthenium(II) dichloride ([Ru(dpp)₃]Cl₂) or meso-tetraphenylporphyin (TPP) as quenching fluorophores. From the experimental results, we find [Ru(dpp)₃]²⁺-Gel-MOF optrode has favorable sensing characteristics, and the Stern-Volmer plots are linear in the full concentration range of O₂ (0-100% v/v). The ratio of I₀/I₁₀₀, where I₀ and I₁₀₀ respectively represents the fluorescence intensities of the optrode exposed to 100% N₂ and 100% O₂, as a sensitivity of the optrode is 10.8. Simultaneously, the optrode can make a quick response within 50 ms.     

Comparison of photocatalytic performance of anatase TiO2 prepared by low and high temperature route

Anatase TiO₂ was prepared by a facile sol-gel method at low temperature through tailoring the pH of sol-gel without calcination. As a control, anatase TiO₂ was also synthesized by the conventional sol-gel process, in which calcination at 500 °C was required to transform the amorphous oxide into highly crystalline anatase. As-prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). Their photocatalytic activities were evaluated by degradation of methyl orange under UV light irradiation. On the basis of experiment results, it could be concluded that TiO₂ prepared by low temperature route showed more advantages in small particle size, highly dispersion nature, abundance of surface hydroxyl groups, strong PL signal, and high photocatalytic activity over TiO₂ obtained by the conventional sol-gel process. Furthermore, the reason of the former possessing higher photocatalytic activity was discussed.     

Structural, photochemical and photocatalytic properties of zirconium oxide doped TiO2 nanocrystallites

Composite photocatalysts composed of TiO₂ and ZrO₂ have been prepared via the sol-gel method. The as-prepared nanocomposites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectrometry and fluorescence emission spectra. The results shows that TiO₂/ZrO₂ nanocomposites are composed of mainly anatase titania and tetragonal ZrO₂. Incorporating TiO₂ particles with ZrO₂ plays an important role in promoting the formation of nanoparticles with an anatase structure and leads to decreased fluorescence emission intensity. Most of the TiO₂/ZrO₂ nanocomposites exhibited comparable photocatalytic activity compared with commercial TiO₂ for the degradation aqueous methyl orange (MO) under ultraviolet irradiation, while the composite with Zr/Ti mass ratio of 15.2% shows the highest photocatalytic performances. Furthermore, the as-prepared nanocomposites can be reused with little photocatalytic activity loss. Without any further treatment besides rinsing, the photocatalytic activity of TiO₂/ZrO₂ (15.2%) composites is still higher than after five-cycle utilization.     

Effect of post heat treatment on microstructure and photocatalytic activities of TiO2 nanoribbons

Low-dimensional TiO₂ nanoribbons were synthesized by a simple one-step hydrothermal method. The TiO₂ nanoribbons were calcined over the temperature range 200-800 °C in order to enhance their photocatalytic properties by altering their crystal phase and increasing crystallization. Effects of hydrothermal temperature, calcinated temperature and calcination time on the formation of nanostructures have been observed and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The (BET) specific surface area of the samples which with different post treatments were determined by N₂ absorption-desorption experiment. In addition, photocatalytic activities of the nanoribbons were evaluated by photodegradation of organic dyes methyl orange under the radiation of UV light. The results reveal that the post-treatments have great effects on the microstructures and the photocatalytic activities of TiO₂ nanoribbons.     

Preparation and characterization of Fe-doped TiO2 on fly ash cenospheres for photocatalytic application

Fe³⁺-doped TiO₂ film deposited on fly ash cenosphere (Fe-TiO₂/FAC) was successfully synthesized by the sol-gel method. These fresh photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). The XRD results showed that Fe element can maintain metastable anatase phase of TiO₂, and effect of temperature showed rutile phase appears in 650 °C for 0.01% Fe-TiO₂/FAC. The SEM analysis revealed the Fe-TiO₂ films on the surface of a fly ash cenosphere with a thickness of 2 μm. The absorption threshold of Fe-TiO₂/FACs shifted to a longer wavelength compared to the photocatalyst without Fe³⁺-doping in the UV-vis absorption spectra. The photocatalytic activity and kinetics of Fe-TiO₂/FAC with varying the iron content and the calcination temperatures were investigated by measuring the photodegradation of methyl blue (MB) during visible light irradiation. Compared with TiO₂/FAC and Fe³⁺-doped TiO₂ powder (Fe-TiO₂), the degradation ratio using Fe-TiO₂/FAC increased by 33% and 30%, respectively, and the best calcined temperature was 450 °C and the optimum doping of Fe/Ti molar ratio was 0.01%. The Fe-TiO₂/FAC particles can float in water due to the low density of FAC in favor of phase separation to recover these photocatalyst after the reaction, and the recovery test shows that calcination contributes to regaining photocatalytic activity of Fe-TiO₂/FAC photocatalyst.     

Enhancement of photocatalytic degradation of polyethylene plastic with CuPc modified TiO2 photocatalyst under solar light irradiation

Solid-phase photocatalytic degradation of polyethylene (PE) plastic, one of the most common commercial plastic, over copper phthalocyanine (CuPc) modified TiO₂ (TiO₂/CuPc) photocatalyst was investigated in the ambient air under solar light irradiation. Higher PE weight loss rate, greater texture change; more amount of generated CO₂, which is the main product of the photocatalytic degradation of the composite PEC plastic can be achieved in the system of PE-(TiO₂/CuPc) in comparison with PE-TiO₂ system. The CuPc promoted charge separation of TiO₂ and enhanced the photocatalytic degradation of PE based on the analysis of surface photovoltage spectroscopy (SPS). During the photodegradation of PE plastic, the reactive oxygen species generated on TiO₂ or TiO₂/CuPc particle surfaces play important roles. The present study demonstrates that the combination of polymer plastic with TiO₂/CuPc composite photocatalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants under solar light irradiation.