Optical properties of hollow calcium aluminate glass waveguides

Calcium aluminate glass has a refractive index less than 1 at 10.6 μ, and therefore it is a good candidate for a hollow fiber for the transmission of CO(2) laser energy. We have drawn hollow calcium aluminate glass fibers with inner diameters ranging from 380 to 500 μ. The loss for our 500-μm inner-diameter hollow glass fibers measured at 10.6 μm is 8.6 dB/m.     

Bundled hollow optical fibers for transmission of high-peak-power Q-switched Nd:YAG laser pulses

A hollow-fiber bundle was designed and used to deliver high-peak-power pulses from a Q-switched Nd:YAG laser. An 80 cm long bundle with a total diameter of 5.5 mm was composed of 37 glass capillaries with bore diameters of 0.7 mm. Beam-resizing optics with two lenses were used to couple the laser beam into the bundle. The measured coupling loss due to the limited aperture ratio of the bundle was 2.3 dB, and the transmission loss at wavelengths of 1064 and 532 nm was 0.3 dB. When an inert gas flowed through the bores of the capillaries, the maximum output pulse energy was 200 mJ, which was the limit of the laser used in the experiment. Hollow-fiber bundles withstand irradiation better than single hollow fibers and silica-glass optical fibers do. They are suitable for many dermatological applications because they can be used to irradiate a large area.     

Lensed-taper launching coupler for small-bore, infrared hollow fibers

A new type of launching coupler for small-bore, hollow fibers, consisting of a lens and a tapered hollow waveguide, is proposed to increase the alignment tolerance between an input laser beam and small bore fibers. First, we designed the structural dimensions of the coupler by using a ray-tracing method. Then, a series of experiments employing tapered hollow waveguides made of Pyrex glass was performed to investigate the effectiveness of the new coupler. It is shown that the coupler has a high efficiency with attenuation of around 0.5 dB, especially when the inside of the taper section is coated with a polymer and silver film. In addition, we also show that the coupler has great tolerance for the transverse displacement of a waveguide axis, which gives a 0.1-dB loss increase for a 300-mum displacement.     

Optical properties of dual-core hollow waveguides

A new type of hollow glass waveguide has been fabricated that transmits radiation from visible to infrared wavelengths with low loss. The broadband transmission is achieved with a structure consisting of two distinct core regions; a silica annulus for transmission of wavelengths from 0.3 to 2.0 μm and a hollow core for transmission from 2.0 to 12.0 μm. Losses in the silica core at 633 nm are 0.3 dB/m. Losses in the 575-μm bore hollow core at 10.6 μm are 0.6 dB/m. Bending loss is negligible for radiation transmitted in the solid silica core, whereas the hollow guide loss exhibits a 1/R dependence. The dual-core waveguide can transmit broadband radiation, is rugged and flexible, and therefore, is a good candidate for medical or sensor applications.     

Erbium:YAG laser lithotripsy by use of a flexible hollow waveguide with an end-scaling cap

An Er:YAG laser light delivery system composed of a polymer-coated silver hollow waveguide and a quartz sealing cap has been developed for calculus fragmentation. Sealing caps with various distal-end geometries were fabricated, and the focusing effects of these caps for Er:YAG laser light were measured both in air and in water. Owing to the high power capability of the quartz a beam of sealing caps, Er:YAG laser light with an output energy of 200 mJ and a repetition rate of 10 Hz was successfully transmitted in saline solution by use of the system. Calculus fragmentation experiments conducted in vitro showed that the delivery system is suitable for medical applications in lithotripsy. We also found that the cap with a focusing effect is more effective in cutting calculi. The deterioration of the sealing caps after calculus fragmentation is also discussed.     

Fabrication of copper oxide-coated hollow waveguides for CO2 laser radiation

Hollow fibers for transmitting CO(2) laser light were fabricated by the chemical vapor deposition (CVD) method. A dielectric film of copper oxide (Cu(2)O) was deposited upon the inside of a Ag-coated glass capillary by use of a metal acetylacetonate as the precursor. The waveguide, which was coated with Cu(2)O and had a bore diameter of 700 mum, showed a loss of 0.9 dB/m for CO(2) laser light. The Cu(2)O film deposited by CVD had high chemical and heat resistivity. Therefore a hollow fiber coated with copper oxide is suitable for high-power laser applications in a severe environment.     

6种铝阳极氧化无铬封孔膜的性能比较

为了消除铝阳极氧化膜高耐蚀封孔液中六价铬对环境的污染,对LY12铝合金阳极氧化膜分别进行勃姆石溶胶封孔、硝酸铈溶液封孔、Ni2+-Co2+盐高温水解封孔、Co2+-三乙醇胺常温封孔和Ni2+-F--Zn2+盐常温封孔,测试无铬封孔膜的膜重,磷铬酸酸浸失重,酸性点滴液变色时间,并进行染色试验,然后与沸水封孔、重铬酸钠封孔工艺做对比.结果表明,无铬封孔方法中勃姆石溶胶法制得的封孔膜的点滴液变色时间最长为36 min,酸浸失重量最小为2.45 g/m2,且封孔膜染色后膜颜色最浅;极化曲线和电化学阻抗谱显示封孔膜的耐3.5%NaCl腐蚀性由强到弱依次为:勃姆石溶胶封孔膜>重铬酸钠封孔膜>Ni2+-F--Zn2+封孔膜>沸水封孔膜>Ni2+-Co2+封孔膜>硝酸铈封孔膜>Co2+-三乙醇胺封孔膜,且盐水中溶胶封孔膜的腐蚀电流密度比重铬酸钠封孔膜的低2个数量级.     

铝合金阳极化二重封闭工艺的研究EI

本文论述了铝合金阳极氧化二重封闭工艺及封闭膜层的性能，并对二重封闭膜层比重铬酸钾膜层抗蚀能力有明显提高进行了分析。     

High-peak-power, pulsed CO(2) laser light delivery by hollow glass waveguides

Flexible hollow glass waveguides with internal metallic and dielectric coatings have been used to deliver high-peak-power transversely excited atmosphere CO(2) laser energy. The straight guide loss is as low as 0.17 dB/m for 1000-mum-bore guides and 0.46 dB/m for 530-mum-bore guides propagating the HE(11) mode. The loss increases to 0.93 and 1.36 dB/m, respectively, when guides are bent to a radius of 0.25 m. The hollow glass waveguides have been used to deliver pulsed CO(2) laser energy successfully with a peak power of 0.7 MW and an energy of 350 mJ per pulse with a gas purge through the hollow core. The delivered average power is as high as 27 W. It is concluded that these waveguides are promising candidates for pulsed CO(2) laser delivery in medical and surgical applications.     

Zn-Al-Mg-RE涂层在含SRB海水中的耐腐蚀性与机理

利用高速电弧喷涂技术在Q235钢基体上制备Zn-Al-Mg-RE涂层,采用环氧改性有机硅树脂对涂层进行封孔,在含硫酸盐还原菌(SRB)海水中浸泡后,采用EIS,PC等方法研究Zn-Al-Mg-RE涂层在SRB一个生长周期内的腐蚀行为,并对涂层进行表面微观形貌和化学成分分析,探讨其腐蚀机理。结果表明:封孔和未封孔的Zn-Al-Mg-RE涂层在含SRB海水中的腐蚀速率均呈先增大后减小的趋势;封孔后Zn-Al-Mg-RE涂层的耐腐蚀性得到较大提高。经过浸泡后的Zn-Al-Mg-RE涂层表面覆盖了一层微生物和腐蚀产物组成的混合物层和钝化膜层,避免了涂层进一步遭受损坏。     

Optical properties of small-bore hollow glass waveguides

Hollow glass waveguides with a 250-μm i.d. have been fabricated with a liquid-phase deposition technique that uses silica tubing as a base material. The losses of the 250-μm-bore guide measured at CO(2) laser wavelengths are as low as 2.0 dB/m. The straight losses for the hollow guides are in good agreement with theoretically predicted losses as a result of the nearly ideal structure of the guides. It is also shown that the guides have low bending losses, a nearly pure-mode delivery, and good high-power laser transmission. By proper design of the dielectric thickness, the guide is also able to deliver Er:YAG laser energy with a low loss of 1.2 dB/m for the 320-μm-bore waveguide. Because the hollow glass waveguide is very flexible and robust, it is quite suitable for medical applications.     

Effect of carbonization temperature on microwave absorbing properties of polyacrylonitrile-based carbon fibers

The pre-oxidized fibers were carbonized at the temperature ranging from 400 to 1300 °C for 1 h. The microwave absorption properties of carbon fibers (CFs) were examined in the frequency range of 2–18 GHz. It is found that the reflection loss characteristics are highly sensitive to the carbonization temperature. At a thickness of 2 mm, the CFs obtained at 710 °C exhibit the best microwave absorbing ability with a maximum reflection loss of ?22.9 dB at 15 GHz, and a bandwidth exceeding ?10 dB in the range 12.4–18 GHz. Results indicate that dielectric loss in cooperation with better matched characteristic impedance results in the excellent microwave absorption of CFs. Low temperature makes ?′ and ?″ too small to consume the energy of microwave, while over high temperature makes ?′ and ?″ too large to transmit the microwave into the CFs.     

Hollow fibers for delivery of harmonic pulses of Q-switched Nd:YAG lasers

Flexible hollow fibers for delivery of the second, third, and fourth harmonic pulses of Q-switched Nd:YAG lasers are introduced. For the doubled (532-nm) wavelength, we fabricated a hollow fiber with an internal metal and polymer film by using a silver-mirror plating and a liquid-phase-coating method. For tripled (355-nm) and quadrupled (266-nm) Nd:YAG in the ultraviolet region, we fabricated aluminum hollow fibers with or without an internal polymer layer by using the metal-organic chemical-vapor deposition method. Both types of fiber show high stability for the transmission of high-peak power laser pulses with low transmission losses.     

Cavitation erosion behavior of nitinol coating sealed by epoxy resin

The nitinol coating against cavitation erosion was prepared by air plasma spraying and sealed with epoxy resin successfully. After the coating sealed with epoxy resin, the pores and cracks of the coating were filled with the epoxy resin and then the cohesiveness between the lamellae was improved, the hardness increased from 3.68 GPa to 7.49 GPa, the energy recovery ratio (superelasticity) was improved from 41.9 % to 49.0 % and the toughness was enhanced from 0.011 GPa to 0.045 GPa. During the cavitation erosion test, the epoxy resin reduced the cavitation resources and absorbed the impact energy from the micro-jet or shock waves. Meanwhile, the high hardness and superelasticity can help the coating to resist cavitation erosion and the high toughness can delay the expansion of cracks during the cavitation erosion test. As a result, after cavitation erosion for 300 min the cumulative mass loss of the coating sealed by epoxy resin was 1/5 times as much as that of the nitinol coating without sealing. Therefore, the cavitation erosion resistance of the nitinol coating can be improved by sealed with epoxy resin.     

汽车车门密封结构的传声实验研究

汽车高速行驶时气流导致的车身内外压差和密封件局部压力变化,会使车门密封传声加剧,目前针对车门密封传声的相关研究较少.通过小型气动-声学风洞实验测试手段,参考汽车实车门结构密封和气动力作用特点,建立门单道密封和门板四周密封结构实验研究环境和试验件,研究其密封结构的传声特性.研究表明:竖向和横向密封对门板中高频传声影响较大...     

传输紫外激光用空芯光纤结构设计

对传输紫外激光用空芯光纤结构进行了研究.铝膜是从紫外到红外都有很高反射率的理想材料,用它来研制的空芯光纤的直线损耗和弯曲损耗均较小.在铝膜上涂覆设计厚度的低折射率膜可进一步提高系统的反射率,增加传输效率,并保护铝膜免受大气侵蚀.     

硬脂酸封闭工艺参数对铝阳极氧化膜耐蚀性的影响

通过电化学极化和扫描电镜（SEM）形貌观察，研究了硬脂酸封孔工艺中封闭液浓度、温度和时间等参数对铝阳极氧化膜在NaCl溶液中耐蚀性的影响，提出了提高耐蚀性的最佳封孔工艺参数为：90－95℃，100％硬脂酸封闭30min,6%N-甲基烷络丙酮50℃，2min去油膜。结果表明，经硬脂酸封孔后的铝阳极氧化膜表面平整无缺陷，膜的耐蚀性显著提高，在中性NaCl溶液中耐蚀性优于经沸水法和重铬酸钾法封闭的氧化膜。     

短切中空多孔碳纤维复合材料的吸波性能

以中空多孔聚丙烯腈(PAN)原丝为原料, 通过预氧化处理和碳化处理工艺制备了中空多孔碳纤维, 采用SEM和XRD对其微观结构和晶体结构进行了表征, 并对其吸波性能进行了分析. 研究结果表明, 中空多孔碳纤维是一种非石墨结构的电损耗型雷达波吸收剂; 随着短切中空多孔碳纤维体积分数的提高, 随机分布的纤维/石蜡复合吸波材料的介电常数随之增大; 用所得的电磁参数结果计算了不同厚度材料的反射率, 在2～18GHz频率范围内, 当体积分数为33.30%, 厚度为2mm时, 最低反射率为-21.36dB, 其中<-5dB的反射率带宽为5.17GHz, <-10dB的反射率带宽为2.88GHz.     

Preparation of silica hollow fibers by surface-initiated atom transfer radical polymerization from electrospun fiber templates

Silica hollow fibers were produced by surface-initiated atom transfer radical polymerization (ATRP) from poly(methyl methacrylate-co-vinylbenzyl chloride) (P(MMA-co-VBC)) electrospun fibers combined with sol-gel process and subsequent calcination. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to characterize the intermediate products and the silica hollow fibers. The resulting silica hollow fibers are of high purity with amorphous morphology. The thickness of the hollow fibers is approximately 0.25 µm.     

玻璃浆料低温气密封装MEMS器件研究

系统地研究了玻璃浆料在低温下气密封装MEMS器件的过程。采用该工艺（预烧结温度400℃,烧结温度500℃,外加压强3kPa）形成的封装结构具有较高的封接强度（剪切力〉15kg）及良好的气密性（气密检测合格率达到85％）,测得的漏率符合相关标准。