Metal-covered photonic bandgap multilayer for infrared hollow waveguides

Infrared hollow waveguides utilizing a dielectric multilayer are examined by use of a photonic bandgap theory. It is shown that, in the waveguide consisting of quarter-wave film stack, the act of covering the dielectric films with a metal layer is effective in the reduction of the number of film layers. To verify the effect of this design, we fabricated a prototype waveguide with three dielectric layers of SiO2/Ta2O5/SiO2 and a silver layer by using a liquid-phase coating technique. From the loss spectrum of the fabricated waveguide, it is confirmed that, as designed, the waveguide shows wideband low-loss property at the wavelength of Nd:YAG laser light 1.06 microm.     

Cyclic olefin polymer-coated silver hollow glass waveguides for the infrared

Cyclic olefin polymer (COP) is newly used as the inner dielectric of infrared, hollow glass waveguides because of its low extinction coefficient in the mid-infrared region. A liquid-flow coating and dry-cure process are employed to form the COP layer on the inside of a silver-coated hollow glass tube. In the coating process, cyclohexane is chosen as the solvent of COP to form a smooth and uniform COP layer. It is shown that COP-coated silver hollow glass waveguides show low loss properties for CO(2), CO, and Er:YAG laser light when the thickness of the COP layer is properly chosen.     

Gradually tapered hollow glass waveguides for the transmission of CO2 laser radiation

Hollow glass waveguides with bores tapered from 1000 to 500 microm and from 700 to 500 microm over a length of 2 m were coated with silver and silver iodide inner films. These waveguides were designed for low attenuation at the 10.6-microm CO2 laser wavelength. The straight losses, which were measured to be 0.8 and 1.6 dB/m, respectively, decreased when the guides were bent. A simple ray-trajectory model is presented to explain this unexpected behavior.     

Development of a stainless steel check valve for cryogenic applications

This paper describes the development of a check valve for use in a sorption compressor that will drive a 10 mW 4.5 K Joule-Thomson cryocooler. For the check valve extremely low backflow rates are tolerable at an operating temperature of the valve of 50 K. To fulfill these requirements, the sealing mechanism of the valve is based on a full metal to metal contact. In order to obtain sufficiently low leak rates, both parts were machined to a surface flatness in the order of 100 nm. In addition, the closing plate (boss) of the valve deforms (bends) slightly under pressure, forming itself to the opposite valve seat and thus reducing the gap between these parts. The measured leak flow at 50 K was 1.6 μg/s helium @ 16 bar pressure difference, which is well below the aim of 3 μg/s.The valve was subjected to an accelerated lifetime test of 300,000 cycles. It was observed that the leak flow through the valve during this test steadily decreased to a level of 0.15 μg/s after 100,000 cycles.     

Development of new templating approach for hollow nanoparticles and their applications

This review mainly focuses on simple template routes for hollow particles and introduces their applications. An inorganic template using inorganic particles is a facile technique to obtain hollow particles with various shapes, sizes, from nano to micron, and also different shell microstructures. These structure controls provide wide applications such as superior thermal insulation films, anti-corrosion films, and unexpected “easy-to-grip” volley ball coatings, etc. This technique is also an environmentally friendly route that only requires a mild condition to remove the template, and the generated byproducts can be reused for synthesis of the template. This paper describes the sol–gel synthesis which is useful to form the shell structure of the hollow particle and then how to control the particle structure using various templating routes. In addition to our achievements using hollow silica nanoparticles, the development of applications such as the lithium ion battery, biomedical products, and catalysts, will be outlined.     

Fabrication and properties of Lotus-type porous nickel-free stainless steel for biomedical applications

Lotus-type porous Fe–25 wt.%Cr, Fe–23 wt.%Cr–2 wt.%Mo alloys and type AISI 446 stainless steel were fabricated by continuous zone melting technique in pressurized hydrogen and helium gas. The porosity of the samples varied in the range 44–48% and the mean pore size values obtained (145–374 μm) are in the biomedical field desired range. The fabricated Lotus-type porous nickel-free stainless steel was nitrided at high temperature up to the nitrogen concentration of 1.0 wt.% and this amount resulted to be sufficient for maintaining almost single-phase austenitic structure at room temperature. The combination of very small magnetic susceptibility, light weight, mechanical properties close to the human cortical bone, together with the known good enough corrosion resistance of high nitrogen nickel-free stainless steel, makes this Lotus-type porous Fe–Cr–N alloys very attractive for bone implant applications.     

A new constitutive model of austenitic stainless steel for cryogenic applications

A series of uniaxial tensile test under cryogenic temperature was carried out for AISI 304 and 316 austenitic stainless steels (ASS) in this study. Typical non-linear hardening phenomena under the cryogenic environment, such as transformation induced strain hardening and threshold strain for the 2nd hardening, has been observed in a quantitative manner.The important factors affecting the non linear material behavior of austenitic stainless steel including phase transformation, discontinuous yielding and micro-damage are modeled using constitutive equations system based on strain decomposition at the small strain formulation. A strong nonlinearity of strain hardening is described using the coupling of modified Bodner’s plasticity model and phase transformation induced strain model. The strain (threshold strain for onset of 2nd hardening) dependent plasticity model was proposed in the hardening function of Bodner’s model. In order to explicitly express the phase transformation induced strain, TI model (Tomita and Iwamoto model [Y. Tomita, T. Iwamoto, Constitutive modeling of TRIP steel and its application to the improvement of mechanical properties, International Journal of Mechanical Sciences 37 (1995) 1295–1305.]), which is a function of accumulated plastic strain and volume fraction factor of martensite, is selected in this study.Also the unified damage model, which can be connected with elasto-plastic constitutive equation developed in this study, is suggested, and the utility of proposed model was validated by the comparison between experiments and numerical evaluations.     

镂空不锈钢超材料的双频段类电磁诱导反射研究

目的:研究镂空不锈钢超材料的双频段类电磁诱导反射(Electromagnetic-like induced reflection, EIR-like)。方法:采用有限积分法CST软件数值仿真镂空不锈钢超材料的反射率与磁场分布,利用聚焦激光束对不锈钢进行微米量级激光切割来加工出镂空不锈钢超材料并进行实验测试。结果:在太赫兹波的激励下,镂空不锈钢超材料与太赫兹波发生近场耦合,镂空不锈钢超材料三个独立的镂空结构谐振器激发出三个明模,线槽阵列结构谐振器分别和两个边长不等的开口环(SRRs)槽阵列结构谐振器共振产生两个类EIR现象。结论:镂空不锈钢超材料在反射域获得两个大的群指数,数值分别为11.2和11.8,其产生的类EIR现象也可以称为慢光现象,这种现象将用于慢光器件的设计及生物传感应用。     

Mechanical properties of cellular solids produced from hollow stainless steel spheres

Mechanical properties of cellular hollow sphere structures are studied in this work. The material was fabricated by coating the metallic powder slurry on expanded polystyrol (EPS) spheres, drying, forming under compression, debinding, and final sintering of the spheres to each other. Longitudinal elastic wave velocities were measured using ultrasound phase spectroscopy while compression tests were carried out up to a homologous temperature of 0.6. Dependence of the relative Young’s modulus on the relative density is similar to conventional open-cell foams. Compression stress–strain plots show the three stages of elastic deformation, plateau, and densification. With increasing temperature the overall level of the compressive stress–strain plots shifts to lower stresses. The hollow sphere solids show slightly better high temperature strength in comparison to the base metal. However, due to the considerable scatter in the experimental data points, this improvement seems to be insignificant. Structural observations on samples deformed to within the plateau region clearly show the heterogeneous progress of deformation.     

Mechanical,electrochemical and magnetic behaviour of duplex stainless steel for biomedical applications

Mechanical, electrochemical and magnetic properties of duplex stainless steel were analysed to evaluate its use as biomaterial, comparing the results with those obtained for austenitic stainless steel. Yield and ultimate tensile strengths are almost twice in duplex stainless steel, being the values 870?MPa and 564?MPa, respectively. The electrochemical test revealed that this material has lower susceptibility to localised corrosion because of its greater passive range, 1?V from the open circuit potential, while the austenitic stainless steel exhibited a passive region of 0.370?V. Both steels behave as soft magnetic materials, however, duplex stainless steel has higher magnetic saturation and remanence, while austenitic stainless steel is more prone to heating when exposed to a magnetic field.     

空芯光纤硅太阳能电池制备及光捕获研究

本文提出一种空芯光纤结构硅基太阳能电池,并探讨其制备方法和光捕获性能.依据平面电池受光原理和空芯波导的限光机制提出了空芯光纤硅基太阳能电池结构,采用卷曲柔性平面非晶硅薄膜电池制备出圆筒形空芯光纤硅电池.通过对比研究入射光量一定的条件下平面电池和空芯光纤电池的光生电流和电压值,评估空芯光纤电池的光捕获效果.通过测量不同光入射角度和光照强度下空芯光纤电池的光生电流和电压值,揭示光入射角度和光照强度对空芯光纤电池光捕获性能的影响关系.研究表明,空芯光纤硅基电池能将入射光线限制在波导结构内反复吸收和反射,从而在光捕获性能方面较平面电池有所提升(~19.8%).光线入射角度对空芯光纤电池的光捕获性能有较大影响,在30°~50°入射时可以获得较大的光生电压和电流值.在0~100 000 lux的光照强度范围内,光生电压先随光照度增加而增大,而后逐渐趋于恒定值.通过卷曲柔性平面硅电池获得光捕获效率较高的空芯光纤硅电池是可行的,采用结构简单、光线单次入射吸收较低的单节薄膜电池制备空芯光纤电池有望获得更好的光捕获效率提升效果.     

Ag/Zn双元离子注入不锈钢的研制与抗菌性能研究

在单一金属离子抗菌性能和作用范围存在不足的基础上,提出了Ag/Zn双元抗菌金属离子注入制备抗菌不锈钢的方法。该方法将有助于抗菌广谱性和抗菌性能的提高,迄今未有双元抗菌金属离子不锈钢的报道。平板菌落计数法表明,Ag/Zn双元离子注入试样对革兰氏阴性大肠杆菌(E.coil)和革兰氏阳性金黄色葡萄球菌(S.aureus)都具有优良的抗菌效果(抗菌率99%);电化学极化曲线表明,注入试样的耐腐蚀性能较未注入试样略有提高;X射线光电子能谱(XPS)、原子力显微镜(AFM)等对离子注入层离子化学状态及微观形貌进行了表征,并初步讨论了注入层性质与抗菌性能之间的关系。     

Oral microbiota accelerates corrosion of 316L stainless steel for orthodontic applications

In this work,microbiologically influenced corrosion(MIC) of 316 L stainless steel(SS) caused by oral microbiota was investigated with HOMINGS 16 S rRNA gene sequencing technology,and electrochemical and surface analysis techniques.The results showed that oral microbiota from different subjects developed multi-species biofilms with significant differences in structure and composition of bacteria strains on the316 L SS coupons.In the presence of oral microbiota,more severe pitting corrosion and fa...     

Efficient fabrication of ultrafine-grained 316L stainless steel surfaces for orthopaedic applications

Commonly used severe plastic deformation (SPD) methods are suitable for fabrication of bulk nano and ultrafine-grained metals. Drawbacks of these methods include durability of dies, geometrical restrictions and reduced ductility of the products. In this study, two common machining techniques used in manufacturing of orthopaedic components, turning and milling, were applied on 316L stainless steel as surface SPD to refine the surface microstructures of the workpiece. Machining with optimised parameters resulted in substantial grain refinement down to 98?nm on the surfaces. Biological experiments showed up to ～70% and ～280% increased bone cell density on milled and turned samples compared to conventionally machined 316L stainless steel at 5 days, which was correlated with nanocrystallisation and nanoroughness of the samples.     

Fabrication of hollow waveguides for CO2 lasers

Germanium-coated metal (silver, gold, and copper) hollow waveguides for CO(2) laser energy delivery have been fabricated by electron-beam evaporation and plating techniques in which an acid-soluble glass mandrel with small surface roughness was used. The transmission characteristics of Ge-coated metal hollow waveguides were studied. Ge-coated Ag hollow waveguides showed smaller loss, 0.2 dBm, for CO(2) laser light than Ge-coated Au and Cu waveguides. The transmission characteristics of Ge-coated Ag hollow waveguides were measured in relation to a core diameter and a bending radius.     

Ray optics model for triangular hollow silicon waveguides

Closed silicon V grooves are proposed as new hollow waveguides suitable for optical microelectromechanical systems applications. These easily fabricated guides with large index contrast could be designed to work with very low loss for the fundamental mode. A ray optics model is developed for the loss analysis of such guides. The model is tested using the beam propagation method. The model allows one to obtain approximate design equations for the fundamental mode losses in equilateral triangles as well as the practical waveguide and thus greatly simplifies the design effort.     

中空玻璃微球近期技术发展和应用

综述了国内外人造中空玻璃微球的制造技术及发展趋势,着重叙述了中空玻璃微球制备吸波材料、中空玻璃微球制备高强度浮力材料的技术发展状况,并介绍了国内外主要生产厂家及产品应用情况.     

Effect of sintering atmosphere on properties of porous stainless steel for biomedical applications

This study discusses manufacturing of metallic biomaterials by means of powder metallurgy with consideration for their unquestionable advantages, i.e. opportunities of obtaining materials with controllable porosity. The paper focuses on properties of 316L stainless steel obtained using the method of powder metallurgy with respect to compacting pressure and sintering atmosphere. All the specimens were compacted at 700, 400 and 225 MPa, and sintered at 1250 °C. In order to analyze the sintering atmosphere, three different media were used: dissociated ammonia, hydrogen and vacuum. The study covered sintering density, porosity, microstructure analysis and corrosion resistance. The proposed method of powder metallurgy allowed for obtaining materials with predictable size and distribution of pores, depending on the parameters of sinter preparation (compaction force, sinter atmosphere). High corrosion resistance of the materials (sintering in the atmosphere of hydrogen and in vacuum) and high porosity in the sinters studied offer opportunities for using them for medical purposes.