管道连接装配型ITER增强热负荷第一壁的热工水力分析

对管道连接装配型ITER增强热负荷第一壁(EHF FW)的标准手指对、边缘手指对及中心梁(CB)开展了热工水力分析.分析结果显示流速分布合理,低于1m·s-1或高于10m·s-1的区域非常小;手指对间的流量分配较合理;整个第一壁的压降为0.351MPa,小于0.4MPa的限定值;在8个循环周期内CB最高温度为409.2...     

TEM characterization of a nitrogen implanted austenitic stainless steel

Pure austenitic stainless-steel samples (18% Cr, 10% Ni) were implanted at room temperature with nitrogen ions at an energy of 40 keV with fluences from 10¹⁷ to 6X10¹⁷ ions cm^-2. Microstructures obtained after implantation were studied by transmission electron microscopy and selected-area diffraction. The observations show the formation of ε martensite (hexagonal), of α' martensite (tetragonal) and the appearance of nitrides (Fe, Cr, Ni)₂N_1-x hexagonal or orthorhombic.     

Tin oxide nanocrystals embedded in nanopore arrays on stainless steel surface for photocatalytic applications

The immobilization of SnO₂ nanocrystals on solid substrates for practical photocatalytic applications suffers from poor adhesion that will lead to loss of photocatalytic activity and short service life. An efficient hydrothermal synthesis of SnO₂ nanocrystals embedded in nanopore arrays on stainless steel surface was presented in this paper. The morphology, chemical composition and microstructure of the embedded tin oxide nanocrystals were investigated by X-ray diffraction, field-emission scanning electron microscope, X-ray photoelectron spectroscopy and UV-visible diffuse reflectance spectroscopy. The photocatalytic activity and stability of SnO₂ nanocrystals was evaluated by photodegradation of methylene blue. SnO₂ nanocrystals embedded in nanopore arrays on stainless steel surface existed in a tetragonal rutile structure. The increasing of the hydrothermal temperature will lead to the improvement in photocatalytic activity of SnO₂ nanocrystals. The SnO₂ nanocrystals prepared at 220 °C performed the highest photocatalytic activity and good photocatalytic stability, indicating the effective immobilization of SnO₂ nanocrystals on anodized stainless steel.     

Process mapping of laser surface modification of AISI 316L stainless steel for biomedical applications

A 1.5-kW CO₂ laser in pulsed mode at 3 kHz was used to investigate the effects of varied laser process parameters and resulting morphology of AISI 316L stainless steel. Irradiance and residence time were varied between 7.9 to 23.6 MW/cm² and 50 to 167 μs, respectively. A strong correlation between irradiance, residence time, depth of processing and roughness of processed steel was established. The high depth of altered microstructure and increased roughness were linked to higher levels of both irradiance and residence times. Energy fluence and surface temperature models were used to predict levels of melting occurring on the surface through the analysis of roughness and depth of the region processed. Microstructural images captured by the SEM revealed significant grain structure changes at higher irradiances, but due to increased residence times, limited to the laser in use, the hardness values were not improved.     

CXMS and XRD analyses of heat treated A533B stainless steel

Heat induced surface changes on A533B stainless steel were followed by XRD and CXMS techniques. Whereas the XRD patterns of the studied A533B samples were characteristic of α-Fe phase only, the surface Mössbauer spectrum showed a broad sextet, being fitted with two magnetic patterns whose hyperfine magnetic fields were 33 and 31 T associated with a pure and perturbed α-Fe phase, respectively and a broad singlet with an isomer shift δ _A533B = ?0.115(4) mms $^{-1}/\alpha $ -Fe, characteristic of the γ-Fe phase. This singlet, probably, arising from the samples’ surface only was further analyzed by using a singlet and a quadrupole doublet. From hyperfine distribution and discrete value calculations of their corresponding hyperfine parameters, the quadrupole interaction was the most affected by thermal treatments ranging from 300° to 700 °C showing a slight decrease at 600 °C. The average values of the hyperfine parameters were δ ₁ = ? 0.110(6) mms $^{-1}/\alpha $ -Fe for the singlet, and δ ₂ = ?0.081 (6) mms $^{-1}/\alpha $ -Fe and Δ₂ = 0.143(7) mm/s) for the quadrupole doublet, respectively. In spite of the temperature dependence of the quadrupole splitting on the doublet, which was higher than that of the isomer shifts of both patterns, only a single defect type was suggested, being associated with monovacancias near the ⁵⁷Fe sites.     

直流磁控溅射法在管道内壁镀TiZrV薄膜

用氩气作为放电气体,采用直流磁控溅射法,成功地在不锈钢管道内壁获得了TiZrV薄膜。分别利用能量弥散X射线谱和X射线光电子能谱测量薄膜的成分组成,应用扫描电子显微镜和X射线衍射仪对薄膜进行了测试,并对TiZrV的二次电子产额进行了测量。测试结果表明:TiZrV的成分基本保持在Ti原子分数为30%,Zr原子分数为30%,V原子分数为40%左右,位于“低激活温度区”内;薄膜具有无定形的结构,由微小的纳米晶粒组成;加热激活后TiZrV的二次电子产额有所下降,其峰值由2.03降到1.55,低于不锈钢和无氧铜。     

直流磁控溅射法在管道内壁镀TiZrV薄膜

用氩气作为放电气体,采用直流磁控溅射法,成功地在不锈钢管道内壁获得了TiZrV薄膜。分别利用能量弥散X射线谱和X射线光电子能谱测量薄膜的成分组成,应用扫描电子显微镜和X射线衍射仪对薄膜进行了测试,并对TiZrV的二次电子产额进行了测量。测试结果表明:TiZrV的成分基本保持在Ti原子分数为30%,Zr原子分数为30%,V原子分数为40%左右,位于"低激活温度区"内;薄膜具有无定形的结构,由微小的纳米晶粒组成;加热激活后TiZrV的二次电子产额有所下降,其峰值由2.03降到1.55,低于不锈钢和无氧铜。     

芯片冷却用热管散热器的数值模拟研究

随着计算机性能的提高,CPU散热量也持续增大,并导致了能量分布不均匀,所以高热流密度热控制或大型服务器的冷却处理方式已受到广泛关注。文中对大型计算机服务器CPU的耗能量、冷却效果等进行了实验研究,提出通过采用导热板扩大CPU散热面积的同时,采用高导热相变方法来解决高热流密度器件冷却的处理办法。研究结果证实,对高热流密度器件,依靠增大外界气流的速度来改善散热器的冷却性能并不明显,采用高效热管散热器来强化芯片传热,可满足计算机服务器CPU的冷却要求。     

Surface characterisation and electrochemical behaviour of porous titanium dioxide coated 316L stainless steel for orthopaedic applications

Porous titanium dioxide was coated on surgical grade 316L stainless steel (SS) and its role on the corrosion protection and enhanced biocompatibility of the materials was studied. X-ray diffraction analysis (XRD), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) were carried out to characterise the surface morphology and also to understand the structure of the as synthesised coating on the substrates. The corrosion behaviour of titanium dioxide coated samples in simulated body fluid was evaluated using polarisation and impedance spectroscopy studies. The results reveal that the titanium dioxide coated 316L SS exhibit a higher corrosion resistance than the uncoated 316L SS. The titanium dioxide coated surface is porous, uniform and also it acts as a barrier layer to metallic substrate and the porous titanium dioxide coating induces the formation of hydroxyapatite layer on the metal surface.     

In situ characterization of localized corrosion of stainless steel by scanning electrochemical microscope

Scanning electrochemical microscopy (SECM) area scan measurements have been performed to investigate the localized corrosion of type 304 stainless steel in neutral chloride solution. Variations in the Faradaic current measured at selected tip potential values can be related to changes in the local concentration and electrochemical activities of electroactive species involved in corrosion reactions occurring at the substrate as a function of immersion times of the substrate and polarized currents or potentials applied on the substrate. To further verify the results acquired from cyclic voltammetric experiments, SECM measurements were employed to in situ study the compositions and electrochemical activity distribution profile of the pitting corrosion products of stainless steel. It has been demonstrated that the combination of feedback current mode with generation-collection (G-C) mode of SECM is suitable to elucidate the possible reaction mechanisms and paths involved in the localize corrosion of stainless steel in neutral chloride solution.     

不锈钢管道低温溅射镀TiN薄膜技术

 设计了一套适用于加速器细长管道真空室的低温溅射镀TiN薄膜装置。利用该装置，对86 mm×2 000 mm的不锈钢管道真空室进行溅射镀TiN膜实验，并对镀膜实验结果进行分析，得到了适用于加速器管道真空室内壁溅射镀TiN膜的表面处理参数。样品测试结果表明：在压强为80～90 Pa、基体温度为160~180 ℃的镀膜参数下，不锈钢管道内壁获得的TiN薄膜最佳，薄膜沉积速率为0.145 nm/s。镀膜后真空室的二次电子产额明显降低。     

不锈钢管道低温溅射镀TiN薄膜技术

设计了一套适用于加速器细长管道真空室的低温溅射镀TiN薄膜装置。利用该装置,对86 mm×2 000 mm的不锈钢管道真空室进行溅射镀TiN膜实验,并对镀膜实验结果进行分析,得到了适用于加速器管道真空室内壁溅射镀TiN膜的表面处理参数。样品测试结果表明：在压强为80～90 Pa、基体温度为160~180 ℃的镀膜参数下,不锈钢管道内壁获得的TiN薄膜最佳,薄膜沉积速率为0.145 nm/s。镀膜后真空室的二次电子产额明显降低。     

Optical and electrical characterization of well-aligned ZnO rods electrodeposited on stainless steel foil

Aligned ZnO nanorods grown on polycrystalline substrates have promising optoelectronic applications. Novel samples with such structures were electrodeposited on stainless steel foil from a ZnCl₂ route. Well-aligned and free-standing hexagonal nanorods with 100-nm diameter and closely packed microrods with a diameter above 1 μm could be grown normal to the substrate. The optical transition energies (absorption and emission) of samples were determined by transmittance and photoluminescence spectroscopy. We report, for the first time, the fabrication of high-quality Ag Schottky diodes formed on the oxygen-treated (002) facets of electrodeposited microrods. Diodes with a large barrier height (1.2 eV), low saturation current density (1.3 pA/cm²) and high rectification factor (5×10⁶ at ± 3 V) were achieved. The concentration and mobility of free electrons in oxygen-treated microrods were measured as 1.4×10¹⁴ cm^-3 and 1.2 cm² V^-1 s^-1, respectively. PACS  81.15.Pq; 81.16.-c; 85.30.Kk; 81.05.Dz; 78.55.Et     

多蒸发器CPL热管及纳米流体应用于热管的研究进展

毛细泵回路热管(CPL)具有较高的传热能力,控温能力强,在航空和电子元器件的冷却方面具有广泛的应用背景,采用纳米流体强化热管内部的传热性能获得了越来越多的关注.文中首先介绍了多蒸发器CPL热管的工作原理、特点及研究现状;其次分析纳米流体应用于各种热管强化传热的研究现状,指出以纳米流体为工质的多蒸发器CPL的特点及其优势...     

The effect of ultrasonic processing on solidification microstructure and heat transfer in stainless steel melt

The heat transfer in the ultrasonic processing of stainless steel melt is studied in this thesis. The temperature field is simulated when the metal melt is treated with and without ultrasound. In order to avoid the erosion of high temperature melt, ultrasound was introduced from the bottom of melt. It is found that the temperature of melt apparently increases when processed with ultrasound, and the greater the ultrasonic power is, the higher the melt temperature will be; ultrasonic processing can reduce the temperature gradient, leading to more uniform temperature distribution in the melt. The solidification speed is obviously brought down due to the introduction of ultrasound during solidification, with the increasing of ultrasonic power, the melt temperature rises and the solidification speed decreases; as without ultrasound, the interface of solid and mushy zone is arc-shaped, so is the interface of liquid and mushy zone, with ultrasound, the interface of solid and mushy zone is still arc-shaped, but the interface of liquid and mushy zone is almost flat. The simulation results of temperature field are verified in experiment, which also indicates that the dendrite growth direction is in accord with thermal flux direction. The effect of ultrasonic treatment, which improves with the increase of treating power, is in a limited area due to the attenuation of ultrasound.     

焊后热处理对聚变堆用奥氏体不锈钢MAG焊焊缝金属冲击韧性的影响

对聚变堆用316LN奥氏体不锈钢熔化极活性气体保护电弧焊(MAG焊)接接头进行不同温度的热处理,并在液氮温度下进行夏比冲击试验。利用光学显微镜、扫描电镜、EDS分析等研究了热处理温度对接头微观组织、断口形貌及析出物的影响。结果表明,873K热处理可以显著提高焊缝金属冲击韧性,但随着热处理温度的上升,焊缝金属逐渐出现沿着晶界分布的析出物,韧性逐渐下降。断口均为延性断裂,但随着热处理温度的升高,韧窝变浅、数量变少。韧窝底部存在球状析出和不规则状析出,球状析出在焊接过程中产生,不因热处理温度而变化,不规则析出随着热处理温度的升高逐渐增多。焊材中的Mo含量过高导致焊缝金属中Mo在晶界大量偏聚,促进了σ相的析出,当σ相在晶界形成连续分布后,焊缝金属冲击韧性显著下降。     

Low-temperature liquid phase deposited TiO2 films on stainless steel for photogenerated cathodic protection applications

The low-temperature synthesis of anatase TiO₂ films was an imperative requirement for their application to corrosion prevention of metals. In this paper, a liquid phase deposition (LPD) technique was developed to prepare TiO₂ films on SUS304 stainless steel (304SS) at a relatively low temperature (80 °C). The as-prepared films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photon spectroscopy (XPS). It was observed that a dense and crack-free anatase TiO₂ film with a thickness about 300 nm was obtained. The film contained some fluorine and nitrogen elements, and the amounts of these impurities were greatly decreased upon calcination. Under the white light illumination, the electrode potential of TiO₂ coated 304SS rapidly shifted to a more negative direction. Moreover, the photopotential of TiO₂/304SS electrode showed more negative values with increased film thickness. In conclusion, the photogenerated cathodic protection of 304SS was achieved by the low-temperature LPD-derived TiO₂ film.     

Initial oxidation of duplex stainless steel

Three different techniques were used to produce thin oxide layers on polished and sputter-cleaned duplex stainless-steel samples. These samples were exposed to 10⁻⁵ mbar of pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 h, and plasma oxidized. The oxide layers thus produced were analysed using XPS depth profiling in order to determine the oxide layers’ compositions with depth. We found that all the techniques produce oxide layers with different traces of metallic components and with the maximum concentration of chromium oxide shifted towards the oxide-layer-bulk-metal interface. A common characteristic of all the oxide layers investigated is a double-oxide stratification, with regions closer to the surface exhibiting higher concentrations of iron oxide and those more in-depth exhibiting higher concentrations of chromium oxide. A simple non-destructive Thickogram procedure was used to corroborate the thickness estimates for the thinnest oxide layers.