静电纺醋酸纤维/PET复合过滤材料的制备及性能

采用静电纺丝技术将二醋酸纤维素纳米纤维直接沉积在聚对苯二甲酸乙二纯酯(PET)非织造布基材表面上,并在纳米纤维膜上覆1层PET无纺布,制备成三明治结构的复合滤材。研究了不同条件对复合过滤材料过滤性能的影响。结果表明:均匀纳米纤维有利于提高复合滤材的过滤效率而串珠纤维有利于降低复合滤材的过滤阻力;随着纺丝时间和电压的增大,复合滤材的过滤效率和过滤阻力都呈现增大的趋势;随着空气流量的增加,复合滤材的过滤效率几乎不变,但过滤阻力却呈现线性增大的趋势。当选择纺丝时间为60min,纺丝电压为18kV时所制备的串珠状复合纤维过滤材料,能对粒径0.5μm的颗粒达到99%以上的过滤效率。     

制成多尺寸量子点太阳能电池

近日,美国圣母大学（University of Notre Dame）～研究小组制备出世界上首例具有多种尺寸量子点的太阳能电池,在TiO2纳米薄膜表面以及纳米管上组装CdSe量子点,吸收光线以后,CdSe向TiO2放射电子,再在传导电极上收集,进而产生光电流。他们研究了2．3～3．7nm四种不同粒径的量子点,发现在505～580nm波段上具有不同的吸收峰。研究人员Prashant V．Kamat介绍说,TiO2纳米管上固定CdSe量子点能够形成规整的组装结构,不仅可以使电子有效地传输至电极表面,还能提高电池效率。长度为800nm的纳米管内外表面均可组装量子点,其传输电子的效率较薄膜高。研究发现,小的量子点能以更快的速度将光子转换为电子,而大的量子点     

不同Sol-Gel前躯体体系制备纳米ZnO粉体的研究

为研究不同溶胶前躯体体系对制备纳米ZnO粉体粒径大小的影响,采用溶胶-凝胶法分别研究了硬脂酸体系、草酸体系、高分子网络体系制备纳米ZnO粉体,并利用TG-DTA、XRD、TEM对其结构、形貌和粒径进行了表征.在3种体系中,高分子网络体系所得粉体粒径最小,粒径在30～40nm,粒径大小均匀,团聚较少.硬脂酸体系得到ZnO粉末粒径较小,范围分布在30～50nm,分散性较好.草酸体系制得ZnO粉末粒径相对较大,在40～60nm,有轻微团聚.     

金属橡胶组合滤材过滤性能实验研究

理想的液固相过滤材料应该是由多种不同过滤特性的材料组合而成,这种滤材能够最大程度地发挥滤材截留悬浮颗粒的能力,延长过滤材料的使用寿命。金属橡胶作为一种新型弹性多孔功能材料,自身诸多的性能优点使其适合制备各种过滤器。采用国际标准ISO16889-1999评定滤芯过滤性能的多次通过方法,详细研究和对比不同结构参数的金属橡胶组合滤材与整体式金属橡胶滤材的过滤性能。研究结果表明,由不同结构参数构成的金属橡胶组合滤材具有更加优异的过滤特性,在过滤效率相同的情况下,组合金属橡胶滤材过滤压降较低,流体的通过性能更好,在达到极限压降前能够容纳更多的污染物,滤材使用寿命大为延长,过滤性能得到充分的发挥。     

基于超细纳米纤维高效低阻复合滤材的制备及性能研究

以湿法无纺布为支撑层、纺粘无纺布为保护层，熔喷静电棉/纳米纤维/超细纳米纤维为核心过滤层，制备出一种具有多级梯度过滤的复合滤材，并讨论了不同选材和工艺参数对滤材性能的影响。SEM分析表明，该滤材呈现明显的梯度尺度结构。过滤测试结果表明，该滤材初始过滤效率达99.65%,且去除静电后仍能保持在90%以上，而滤阻仅有15.7Pa。与传统熔喷滤材相比，该产品显示出优异的高效低阻性能，而且不受静电衰减的影响，大大增加了滤材使用寿命，在空气过滤领域具有广阔的应用前景。     

采用比表面积和孔径分析仪测量纳米颗粒粒径

采用比表面积和孔径分析仪,利用颗粒堆积产生的孔隙大小与颗粒粒径之间存在的几何关系,通过测量纳米颗粒堆积产生的孔隙尺寸,实现了纳米颗粒粒径的测量。结果表明,对于粒径在30~70 nm的纳米颗粒,颗粒堆积产生的介孔尺寸与颗粒粒径之间存在良好的线性关系,通过工作曲线可快速获得粒径数值。尤其对于粒径小于100 nm的干燥颗粒,该方法具有良好的适用性,测量分辨率可达0.2 nm,测量结果具有统计意义。     

壁挂式空调器除尘净化功能设计

提出一种具有除尘净化功能的壁挂式空调器,通过对空气净化滤材的风阻特性进行分析,指出滤材应采用移动式安装方式,并对滤材移动机构进行结构优化和试验验证。结果表明:采用变轨道传动方案安装HEPA滤材,能够将空气净化滤材对空调器制冷/制热风量的影响控制在平均衰减2%～3%的水平,洁净空气量(CADR)达到200 m~3/h。     

单双室电解法合成纳米CeO2粉体及其表征

采用直流电解合成法,分别以CeCl3,Ce(NO3)3,CeCl3-KI溶液为电解液单室制备了纳米CeO2粉体.经高温焙烧后,TEM和XRD测试表明:粒子基本呈球形,所得产物均为立方晶系CeO2,粒径分别为20～50 nm,30～50 nm,20～100 nm.同时,使用阴离子交换膜的双室电解法电解CeCl3溶液,发现得到的CeO2粒径(7～20nm)比单室电解得到的小,分析了造成粒径不同的原因.本工作还对各溶液体系电解形成CeO2的机理进行了分析.     

Winsor-Ⅰ型多相微乳液中苯乙烯聚合

在烷基葡萄糖苷(APG)/苯乙烯/水三元体系形成的Winsor-Ⅰ型多相微乳液介质中,通过聚合制得了粒径在35～40nm的单分散聚苯乙烯小球,研究了温度、引发剂类型、引发剂浓度以及单体浓度对产物粒径和分子量的影响.结果表明温度在60～70℃,K2S2O8为引发剂的条件下单分散聚苯乙烯颗粒具有较小粒径(35～40nm),引发剂和单体浓度对粒径的影响很小.     

超声无皂BA/AM/纳米SiO2复合乳液的粒径及其分布

将超声波辐照技术引入到聚合物纳米材料的制备过程中,制备了丙烯酸丁酯(BA)／丙烯酰胺(AM)／纳米SiO2复合材料。粒径及粒径分布测试表明制备的乳胶粒粒径在400nm～500nm之间;反应过程中粒径经历了从小到大,然后又变小的过程;当超声输出功率为450W时,平均粒径最小,粒径分布也最窄;随着体系中丙烯酰胺(AM)含量的提高,粒径变小,粒径分布也变窄。     

Extreme-ultraviolet radiation filtering by freestanding transmission gratings

Measurement of energetic neutral atoms fluxes in space requires efficient suppression of exceptionally strong background extreme-ultraviolet (EUV) and UV radiation. Diffraction filters make it possible to separate (transmit) charged and neutral particles from the background radiation (which would be suppressed). Recently developed freestanding transmission gratings look especially promising for implementation in a new family of diffraction EUV/UV filters. The first results of our experimental study of filtering properties of freestanding transmission gratings with a period of 200 nm are presented. The grating transmission was measured in the 52-131-nm wavelength range, and grating polarization properties were determined at 58.4 nm. It is shown that transmission gratings can be used efficiently as filters and polarizers in the EUV/UV spectral range.     

GaN基热氧化物的XPS和椭偏光谱研究

采用X射线光谱R(XPS)和椭偏测试仪(SE)对GaN材料干氧氧化所得氧化物薄膜的组分、厚度、光学常数等物理特性进行了研究.当氧化温度为900℃、氧化时间为15～240min时,XPS测试结果表明,所得氧化物类型为Ga_2O_3,且由于大量O空位的存在,其表面Ga/O比率约为1.2.SE测试结果表明,GaN线性氧化速率约为40nm/h,呈抛物线生长,最终平均氧化速率约为25nm/h.在300～800nm测试范围内,Ga_2O_3折射率为1.9～2.2,与文献测试结果相符.但在300～400nm测试范围内存在反常色散现象,这与GaN在此波段的强吸收有关.     

Optimal design and performance evaluation of a metal fiber filter for capturing radioactive aerosols

ABSTRACT

Conventional high-efficiency particulate air (HEPA) filters made of glass fiber media are prone to recycling problem and restrictions in extreme environmental condition such as high flow rate, high temperature, and fire. Therefore, metal fiber filters with minimal maintenance can replace conventional HEPA filters. The objective of the study is to evaluate the theoretical and experimental characteristics of a SUS316L metal fiber filter made from the fiber diameter of 8 µm. Theoretical modeling for predicting the collection efficiency of the radioactive aerosol is performed on the metal fiber as a function of particle size, filter thickness, and flow rate. Comparison between the experimental and theoretical results demonstrates that they are in good agreement. Consequently, the model is later utilized for performance optimization of the metal fiber filter. Also the metal filter for collecting the radioactive aerosol is optimized at the particle collection efficiency of 99.97% in most penetrating particle size (MPPS) of region 0.3 µm which complies with the standards established for conventional glass fiber HEPA filters.     

Plasmonic Color Filters for CMOS Image Sensor Applications

We report on the optical properties of plasmonic hole arrays as they apply to requirements for plasmonic color filters designed for state-of-the-art Si CMOS image sensors. The hole arrays are composed of hexagonally packed subwavelength sized holes on a 150 nm Al film designed to operate at the primary colors of red, green, and blue. Hole array plasmonic filters show peak transmission in the 40-50% range for large (>5 × 5 μm(2)) size filters and maintain their filtering function for pixel sizes as small as ～1 × 1 μm(2), albeit at a cost in transmission efficiency. Hole array filters are found to robust with respect to spatial crosstalk between pixel within our detection limit and preserve their filtering function in arrays containing random defects. Analysis of hole array filter transmittance and crosstalk suggests that nearest neighbor hole-hole interactions rather than long-range interactions play the dominant role in the transmission properties of plasmonic hole array filters. We verify this via a simple nearest neighbor model that correctly predicts the hole array transmission efficiency as a function of the number of holes.     

Influence of leaks in surface filters on particulate emissions

Compliance with severe limit values of dust emissions is a main characteristic of surface filters. This characteristic is due to the high particle collection efficiency of surface filters. Beside regular operation it is necessary to consider phenomena such as a "pinhole" bypass through leaks in surface filters to ensure the above mentioned compliance with the limit values at all times. Experimental research has been carried out to observe and understand the "pinhole" bypass through leaks and the behaviour of pinholes over filtration time. To work out the influence of different filtration conditions the parameters pinhole diameter, filter face velocity and dust cake thickness were varied. The results can be explained by formulas usually used to calculate volumetric flow rates of orifice gauges. The experiments and the calculations lead to the conclusions that bigger pinholes decrease the collection efficiency and higher filter face velocities increase the collection efficiency of pinholed filter media.     

Temperature dependence properties of holographic gratings in phenanthrenquinone doped poly(methyl methacrylate) photopolymers

We examine the temperature dependence of edge-illuminated holographic filters formed in phenanthrenquinone doped poly(methyl methacrylate) (PQ/PMMA) operating at 1550 nm. It was found that the thermally induced change to the refractive index and volume can be used to select the wavelength filtered by the grating. The temperature can be varied over a range of 15 degrees C without introducing noticeable hysteresis effects. The wavelength can be tuned at a rate of 0.03 nm/degrees C over this temperature range. A model for the temperature tuning effect is presented and compared to experimental results.     

A windowless VUV excilamp

An open windowless excilamp capable of operating on argon (λ ～ 126 nm), krypton (～146 nm), and xenon (～172 nm) dimers is described. The lamp has a total radiating surface area of 23 × 23 = 529 cm². At a total power of ～0.8 W radiated through this area, the average output power density at λ ～ 126 nm is ～1.6 mW/cm² at a distance of 2 cm from the emitting surface. A pulsed discharge between insulator-coated anode and thin wire cathode ensures a high efficiency of the proposed radiation source operating in the vacuum ultraviolet spectral range.     

Efficient Single Photon Detection from 500 nm to 5 μm Wavelength

We report on superconducting nanowire single photon detectors (SNSPDs) based on 30 nm wide nanowires with detection efficiency η ～ 2.6-5.5% in the wavelength range λ = 0.5-5 μm. We compared the sensitivity of 30 nm wide SNSPDs with the sensitivity of SNSPDs based on wider (85 and 50 nm wide) nanowires for λ = 0.5-5 μm. The detection efficiency of the detectors based on the wider nanowires became negligible at shorter wavelengths than the 30 nm wide SNSPDs. Our 30 nm wide SNSPDs showed 2 orders of magnitude higher detection efficiency (η ～ 2%) up to longer wavelength (λ = 5 μm) than previously reported. On the basis of our simulations, we expect that by changing the optical coupling scheme and by integrating the detectors in an optical cavity, the detection efficiency of our detectors could be increased by a factor of ～6.     

Photoanode Activity of ZnO Nanotube Based Dye-Sensitized Solar Cells

Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a largearea. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffractionpeak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements ofthe ZNT layer showed an average thickness of ～7 μm. Diameter size distribution (DSD) analysis showedthat ZNTs exhibited a narrow diameter size distribution in the range of 65–120 nm and centered at ～75nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks thatwere centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV)spectroscopy showed major absorbance peak at ～348 nm, exhibiting an increase in energy gap value of 3.4 eV.By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximumof incident photon-to-electron conversion efficiency in a visible region located at 520–550 nm range.     

DETERMINATION OF FIBER CHARGE DENSITY OF ELECTRET FILTERS

Particle collection in electret filters is enhanced by electrostatic forces resulting from the embedded charge on the fibers of the filters. Currently, there is no simple method available for determining the charge density on the electret fibers. Since charge on the fibers can degrade with loading or during storage, a simple evaluation technique is desirable. Aerosol consisting of organic oil mist generally used for testing HEPA filters should not be used for evaluating electret filters since organic aerosol droplets rapidly degrade the electrostatic charge effect. In this study experimental measurements of penetration were made on electret filters challenged with monodisperse, polystyrene latex spheres, PLS, of known size and charge. The experimental data on penetration were used to separate the contributions of the individual collection parameters and to determine the effective density of charge on the fibers. Collection efficiency due to mechanical filtration mechanisms was measured using filters in which the electret charge had been effectively neutralized by loading the filters with an oil aerosol. Collection due to dielectrophoretic force was obtained using aerosol with zero charge. The effective charge density on the fibers was determined by comparing measurements of penetration for particles having known size and charge with the predictions of available theoretical equations. Details of this method of determining the density of charge on the fibers are described here. Experimental determinations of charge density showed reasonable agreement with the charge densities given by the manufacturers of the tested filters.