具有梯度结构表层301不锈钢的压缩性能

利用表面机械研磨处理技术,在301奥氏体不锈钢中得到晶粒尺度呈梯度分布的变形表层,进行了压缩试验和微观组织观察。结果表明,变形表层中晶粒可细化至100nm。相比原始态的屈服强度236MPa,具有变形梯度表层后屈服强度增加到436MPa,变形后的加工硬化指数为0.31,经400和700℃的退火后分别增加到0.32和0.35。另外,随着应变速率的增加,流变应力增大而加工硬化能力降低.

脉冲激光导致不锈钢表层温度场演化的模拟

采用焓方法对Nd:YAG脉冲激光导致的不锈钢材料表面熔凝过程的温度场进行了数值模拟.在此基础上,结合材料的结晶动力学和快速凝固理论,对材料微结构演化的几个重要参数,包括凝固速率、冷却速度和界面温度梯度做了估算和讨论.

Performance of a small high-speed liquid jet apparatus

The performance of a small high-speed liquid jet apparatus is described. Water jets of 200m/s to 700m/s have been obtained by firing a deformable lead slug from an air rifle into a stainless steel nozzle containing water sealed with a rubber diaphragm. Nozzle devices of using the impact extrusion (IE) method and cumulation (CU) method are designed to generate jets. The injection sequences are visualized using schlieren photography. The difference between the IE and CU methods in the jet generation is found.

Measurement of small vibration amplitudes of a rough surface by an interferometer with a self-pumped phase-conjugate mirror

The application of a Michelson interferometer with a self-pumped phase-conjugate mirror to measure small vibration amplitudes of a rough surface is described. The distorted wave front of the light that is diffusely reflected from the rough surface is restored by phase conjugation to provide an interference signal with a high signal-to-noise ratio. The vibration amplitudes of a stainless-steel sample are measured with a precision of similar to 5 nm. (C) 2000 Optical Society of America OCIS codes: 120.3180, 190.5040, 120.7280.

Hydrogenated p-type nanocrystalline silicon in amorphous silicon solar cells

A wide bandgap and highly conductive p-type hydrogenated nanocrystalline silicon (nc-Si:H) window layer was prepared with a conventional RF-PECVD system under large H dilution condition, moderate power density, high pressure and low substrate temperature. The optoelectrical and structural properties of this novel material have been investigated by Raman and UV-VIS transmission spectroscopy measurements indicating that these films are composed of nanocrystallites embedded in amorphous SiHx matrix and with a widened bandgap. The observed downshift of the optical phonon Raman spectra (514.4 cm(-1)) from crystalline Si peak (521 cm(-1)) and the widening of the bandgap indicate a quantum confinement effect from the Si nanocrystallites. By using this kind of p-layer, a-Si:H solar cells on bare stainless steel foil in nip sequence have been successfully prepared with a V c of 0.90 V, a fill factor of 0.70 and an efficiency of 9.0%, respectively. (c) 2006 Elsevier B.V. All rights reserved.

Impact of wide bandgap p-type nc-Si on the performance of a-Si solar cells

This paper reports the impact of a wide bandgap p-type hydrogenated nanocrystalline silicon (nc-Si:H) on the performances of hydrogenated amorphous silicon (a-Si:H) based solar cells. The player consists of nanometer-sized Si crystallites and has a wide effective bandgap determined mainly by the quantum size-confinement effect (QSE). By incorporation of this p-layer into the devices we have obtained high performances of a-Si:H top solar cells with V-infinity=1.045 V and FF=70.3 %, and much improved mid and bottom a-SiGe:H cells, deposited on stainless steel (SS) substrate. The effects of the band-edge mismatch at the p/i-interface on the I-V characteristics of the solar cells arc discussed on the bases of the density-functional approach and the AMPS model.

Hydrogenated p-type nanocrystalline silicon in amorphous silicon solar cells

A wide bandgap and highly conductive p-type hydrogenated nanocrystalline silicon (nc-Si:H) window layer was prepared with a conventional RF-PECVD system under large H dilution condition, moderate power density, high pressure and low substrate temperature. The optoelectrical and structural properties of this novel material have been investigated by Raman and UV-VIS transmission spectroscopy measurements indicating that these films are composed of nanocrystallites embedded in amorphous SiHx matrix and with a widened bandgap. The observed downshift of the optical phonon Raman spectra (514.4 cm(-1)) from crystalline Si peak (521 cm(-1)) and the widening of the bandgap indicate a quantum confinement effect from the Si nanocrystallites. By using this kind of p-layer, a-Si:H solar cells on bare stainless steel foil in nip sequence have been successfully prepared with a V c of 0.90 V, a fill factor of 0.70 and an efficiency of 9.0%, respectively. (c) 2006 Elsevier B.V. All rights reserved.

Experimental investigation on TBAB clathrate hydrate slurry flows in a horizontal tube: Forced convective heat transfer behaviors

Tetra-n-butyl-ammonium bromide (TBAB) clathrate hydrate slurry (CHS) is one kind of secondary refrigerants, which is promising to be applied into air-conditioning or latent-heat transportation systems as a thermal storage or cold carrying medium for energy saving. It is a solid-liquid two phase mixture which is easy to produce and has high latent heat and good fluidity. In this paper, the heat transfer characteristics of TBAB slurry were investigated in a horizontal stainless steel tube under different solid mass fractions and flow velocities with constant heat flux. One velocity region of weakened heat transfer was found. Moreover, TBAB CHS was treated as a kind of Bingham fluids, and the influences of the solid particles, flow velocity and types of flow on the forced convective heat transfer coefficients of TBAB CHS were investigated. At last, criterial correlations of Nusselt number for laminar and turbulent flows in the form of power function were summarized, and the error with experimental results was within 20%.

Are the available boiling heat transfer coefficients suitable for silicon microchannel heat sinks?

The typical MEMS fabrication of micro evaporators ensures the perfect smooth wall surface that is lack of nucleation sites, significantly decreasing the heat transfer coefficients compared with miniature evaporators fabricated using copper or stainless steel. In the present paper, we performed the boiling heat transfer experiment in silicon triangular microchannel heat sink over a wide parameter range for 102 runs. Acetone was used as the working fluid. The measured boiling heat transfer coefficients versus the local vapor mass qualities are compared with the classical Chen’s correlation and other correlations for macro and miniature capillary tubes. It is found that most of these correlations significantly over-predict the measured heat transfer coefficients. New correlations are given. There are many reasons for such deviations. The major reason is coming from the perfect smooth silicon surface that lowers the heat transfer performances. New theory is recommended for the silicon microchannel heat sink that should be different from metallic capillary tubes.

Thermal performance of a micro-combustor for micro-gas turbine system

Premixed combustion of hydrogen gas and air was performed in a stainless steel based micro-annular combustor for a micro-gas turbine system. Micro-scale combustion has proved to be stable in the micro-combustor with a gap of 2 mm. The operating range of the micro-combustor was measured, and the maximum excess air ratio is up to 4.5. The distribution of the outer wall temperature and the temperature of exhaust gas of the micro-conbustor with excess air ratio were obtained, and the wall temperature of the micro-combustor reaches its maximum value at the excess air ratio of 0.9 instead of 1 (stoichiometric ratio). The heat loss of the micro-combustor to the environment was calculated and even exceeds 70% of the total thermal power computed from the consumed hydrogen mass flow rate. Moreover, radiant hunt transfer covers a large fraction of the total heat loss. Measures used to reduce the heat loss were proposed to improve the thermal performance of the micro-combustor. The optimal operating status of the micro-combustor and micro-gas turbine is analyzed and proposed by analyzing the relationship of the temperature of the exhaust gas of the micro-combustor with thermal power and excess air ratio. The investigation of the thermal performance of the micro-combustor is helpful to design an improved microcombustor.

Multi-exponentially photoelectric response of bacteriorhodopsin

A thin oriented bacteriorhodopsin (bR) him is deposited on a stainless steel slide by use of the electrophoretic sedimentation method. A junction is made with electrolyte gels having a counterelectrode to construct a bR-based photoelectric detector;. The photoelectric response signal to a 10 ns laser pulse is measured. A theory on the photoelectric kinetics of bR is developed based on the concept of the charge displacement current and the bR photocycle rate equations. Comparison between the theoretical and experimental results proves that the bR photoelectric response to a short laser pulse is a multi-exponential process. The decay time constants and amplitudes of each, exponential component are obtained by data fitting.

Impact of wide bandgap p-type nc-Si on the performance of a-Si solar cells

This paper reports the impact of a wide bandgap p-type hydrogenated nanocrystalline silicon (nc-Si:H) on the performances of hydrogenated amorphous silicon (a-Si:H) based solar cells. The player consists of nanometer-sized Si crystallites and has a wide effective bandgap determined mainly by the quantum size-confinement effect (QSE). By incorporation of this p-layer into the devices we have obtained high performances of a-Si:H top solar cells with V-infinity=1.045 V and FF=70.3 %, and much improved mid and bottom a-SiGe:H cells, deposited on stainless steel (SS) substrate. The effects of the band-edge mismatch at the p/i-interface on the I-V characteristics of the solar cells arc discussed on the bases of the density-functional approach and the AMPS model.

抗菌不锈钢抗菌性能和机理初步研究

由于近年来有害微生物的肆虐和人们防病抗菌意识的增强，社会对各种新型抗菌材料的需求越来越迫切。抗菌不锈钢是一种兼具良好机械和抗菌性能的新型功能材料，具有广泛的应用前景。开发和推广抗菌不锈钢，具有重要的经济和社会意义。 本文以中科院金属研究所研制的两种抗菌不锈钢为研究对象，对其抗菌性能和抗菌机理进行了研究，以期为抗菌不锈钢的深入研发和推广提供理论依据。 本文获得了如下主要结论： 1．采用覆膜法研究了抗菌不锈钢的抗菌广谱性，铁素体和奥氏体抗菌不锈钢对供试的17株菌（除产气肠杆菌外），均显示了较强的杀灭作用，证明其具有抗菌广谱性。两种材料对非孢子（或芽孢）产生菌的杀灭作用强于孢子（或芽孢）产生菌。但是，两种材料对产气肠杆菌均无杀灭作用。 2．考察了铁素体和奥氏体的杀菌率随时间和菌浓度的变化情况。两种材料分别在作用3h时和9h时，对菌体浓度为1×107CFU/mL的大肠杆菌（ATCC25922）的杀菌率均达到99.5%。对菌体浓度≤1×107CFU/mL的大肠杆菌在24h内均可全部杀灭。 3．随打磨次数的增加，抗菌率没有变化，表明打磨不影响铁素体和奥氏体抗菌不锈钢的抗菌性能；抗菌率不受温度的影响，0～37℃之间，未观察到抗菌率受温度变化的明显影响。 4．从抗菌不锈钢中溶出的铜在杀菌过程中可能起重要作用。铁素体和奥氏体抗菌不锈钢与添加了终浓度为1mmol/L的EDTA的菌液作用后，杀菌率分别降为46.8%和38.8%，因为EDTA络合了溶液中的金属离子，间接表明铜离子在杀菌过程中起重要作用。 5．两种抗菌不锈钢中O2-的产生速率分别为0.117 nmol•min-1•g-1和0.107nmol•min-1•g-1，显著高于普通不锈钢（0.062 nmol•min-1•g-1）。细胞膜不饱和脂肪酸过氧化的终产物丙二醛含量分别为1.96 nmol/g和1.93 nmol/g。显著高于普通对照的1.08 nmol/g，表明存在脂肪酸被氧化的现象。这些结果为抗菌过程中存在O2-的氧化杀菌作用提供了间接证据。 6．通过透射电镜和原子力显微镜观察，与抗菌不锈钢作用后的细胞外形多发生变化，细胞壁和细胞膜破裂，细胞内容物漏出，有的菌体完全溶解为碎片，显示两种不锈钢对细胞膜和细胞壁形态的显著影响。随作用时间延长，菌液中钾离子浓度亦显著升高，在3h时，分别达到2.57mg/L和2.79mg/L（普通对照为1.61mg/L）。 7．在巯基氧化实验中，添加终浓度为5 mmol/L的L-cys，作用8h，铁素体的抗菌率降为11.1%,薄层层析结果显示，半胱氨酸可能被氧化成胱氨酸，表明抗菌不锈钢可能对还原性酶具有氧化作用。 8．提取与抗菌不锈钢作用后菌的DNA，凝胶电泳观察并未出现smear现象。表明在本实验条件下尚不能检测到抗菌不锈钢对细菌遗传物质的氧化切割作用。 关键词： 抗菌材料 抗菌不锈钢 抗菌性能 抗菌机理 O2-

The main factor influencing the tensile properties of surface nano-crystallized graded materials

The improved mechanical properties of surface nano-crystallized graded materials produced by surface severe plastic deformation ((SPD)-P-2) are generally owing to the effects of the refined structure, work-hardened region and compressive residual stress. However, during the (SPD)-P-2 process, residual stress is produced simultaneously with work-hardened region, the individual contribution of these two factors to the improved mechanical properties remains unclear. Numerical simulations are carried out in order to answer this question. It is found that work hardening predominates in improving the yield strength and the ultimate tensile strength of the surface nano-crystallized graded materials, while the influence of the residual stress mainly emerges at the initial stage of deformation and decreases the apparent elastic modulus of the surface nano-crystallized graded materials, which agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.

不锈钢激光搭接焊接头温度场数值模拟及分析

温度场是影响激光焊接焊缝成形质量的关键因素. 针对非熔透型激光搭接焊接头焊缝成"钉头"状的特点,通过分析焊接时材料吸收激光能量的分布情况,提出了高斯面热源加线性递增式柱热源的复合体热源模型. 模型考虑板间接触热阻的影响,并将计算结果和试验结果进行了对比,发现模拟出的焊缝形状和试验吻合较好;此外基于本模型对焊缝各处的热循环与焊缝组织形貌及显微硬度的关系进行了分析. 结果表明,焊缝组织形貌及显微硬度除与加热和冷却速率有关外,峰值温度对其也有重要影响;在热循环基本一致的情况下焊缝的性能相似. 该模型较准确地模拟了薄板激光深熔焊接熔池温度场,对研究激光深熔焊接温度场问题和激光工艺参数的优化选择具有参考价值