Low temperature solid-phase sintering of sintered metal fibrous media with high specific surface area

A procedure of low temperature solid-phase sintering（LTSS） was carried out to fabricate sintered metal fibrous media（SMFM） with high specific surface area.Stainless steel fibers which were produced by cutting process were first plated with a coarse copper coating layer by electroless plating process.A low-temperature sintering process was then completed at about 800 °C for 1 h under the protection of hydrogen atmosphere.The results show that a novel SMFM with complex surface morphology and high specific surface area（0.2 m2/g） can be obtained in this way.The effect of sintering temperature on the surface morphology and specific surface area of SMFM was studied by means of scanning electron microscopy and Brunauer-Emmett-Teller.The damage of micro-structure during the sintering process mainly contributed to the loss of specific surface area of SMFM and the optimal sintering temperature was 800 °C.

Analysis of the Machining Characteristics on Surface Roughness of a Hybrid Aluminium Metal Matrix Composite (Al6061-SiC-Al₂O₃)

Aluminium metal matrix composites are finding increased applications in many areas. Adding of the third element to the metal matrix make the composite hybrid. This paper presents the study on the surface roughness characteristics of a hybrid aluminium metal matrix (Al6061-SiC-Al2O3) composites. The experimental studies were carried out on a lathe. The composites were prepared using the liquid metallurgy technique, in which 3, 6 and 9 wt % of particulates SiC and Al2O3 were dispersed in the base matrix. The obtained cast composites were carefully machined. The characteristics that influence the surface roughness such as feed rate, depth of cut and cutting speed were studied, which made the analysis come to a conclusion that the surface roughness is increases with the increase of feed rate and it reduces the surface roughness with the increase of cutting speed.

Machining of the Flat Surfaces with Abrasive-metallic Lapping Tools

The constructional principle of abrasion metal disc is that abrasive insertions are spread uniformly on the working surface of a metal base. During lapping by means of such tools only the machining fluid is dosed and that by drop. Abrasive elements of circular shape pellets are produced by mixing boron carbide BC400 micrograins with electrographite components, the pellets were pressed with a load of about 12 kN. Next they were heated in furnace at about 520K for hours, then cooled together with the furnace. Tests were carried out on the making of circular abrasive insertions of which the main components were born carbide and micrograins of electric copper mixed the epoxide resins.

Surface Modification with Carbon Fiber for the Metallization of Polyether-ether-ketone

The poly-ether-ether-ketone(PEEK)polymer is a semi-crystalline aromatic thermoplastic with outstanding features,such as superior mechanical properties,thermal stability,radiation resistance and excellent chemical and hydrolysis resistance.However,PEEK exhibits a high volume resistivity(1014Ω·m)and surface resistance(1015Ω).This limits its use in the electronics and electromagnetic field.To decrease the resistivity and reduce the thermal expansion of composite materials,this paper modified the PEEK with carbon fiber(CF)and metalized the composites with the electroless Ni-P alloy plating through self-catalyzed deposition,which brings about high conductivity,thermal conductivity,high-temperature weldability resistance and high-low temperature resistance property.The composites and metal coatings were characterized by metallurgical microscope,SEM,and resistance tester.The metal coatings have a uniform surface and low surface resistance less than 10 mΩ~20 mΩ.The thermal shock test at 250°C and the-70°C^100°C high-low temperature environment test were measured.Compared with the electroless plating on unmodified peek,there is no bump and crack,etc.after testing,which shows a good adhesion between the metal coatings and PEEK-CF,high-low temperature resistance as well as high temperature weldability.The researches on the modification of PEEK by carbon fiber and its surface metallization provide technical support for the application of PEEK Composites in radar antenna and other electronic fields.

MACHINING OF METAL MATRIX COMPOSITES

Two types of aluminium-based composites reinforced respectively with 20 vol short fibre alumina and with a hybrid of 15 vol SiC particle and 5 vol short alumina fibre are machined with different tool materials:cemented carbide,ceramic,cubic boron nitride(CBN)and polycrystalline diamond(PCD).The analysis on tool wear shows that the various tool materials exhibite different tool wear behaviours,and the tool wear mechanisma are discussed.Apparently,PCD tools do not necessarily guarantee dimensional stability but they can provide the most economic means for machining all sorts of composites.Consequently,a suitable tool material is suggested for machining each metal matrix composite(MMC) from the standpoints of tool wear and machined surface finish.

Modelling Anti-Corrosion Coating Performance of Metallic Bipolar Plates for PEM Fuel Cells:A Machine Learning Approach

Proton exchange membrane(PEM)fuel cells have significant potential for clean power generation,yet challenges remain in enhancing their performance,durability,and cost-effectiveness,particularly concerning metallic bipolar plates,which are pivotal for lightweight compact fuel cell stacks.Protective coatings are commonly employed to combat metallic bipolar plate corrosion and enhance water management within stacks.Conventional methods for predicting coating performance in terms of corrosion resistance involve complex physical-electrochemical modelling and extensive experimentation,with significant time and cost.In this study machine learning techniques are employed to model metallic bipolar plate coating performance,diamond-like-carbon coatings of varying thicknesses deposited on SS316L are considered,and coating performance is evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy.The obtained experimental data is split into two datasets for machine learning modelling:one predicting corrosion current density and another predicting impedance parameters.Machine learning models,including extreme gradient boosting(XGB)and artificial neural networks(ANN),are developed,and optimized to predict coating performance attributes.Data preprocessing and hyperparameter tuning are carried out to enhance model accuracy.Results show that ANN outperforms XGB in predicting corrosion current density,achieving an R2>0.98,and accurately predicting impedance parameters with an R2>0.99,indicating that the models developed are very promising for accurate prediction of the corrosion performance of coated metallic bipolar plates for PEM fuel cells.

Surface tension of liquid metal： role, mechanism and application

Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal （RTLM） mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measure- ment methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fimdamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self- actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.

Stable Li metal anode by crystallographically oriented plating through in-situ surface doping

Lithium(Li)metal is regarded as the holy grail anode material for high-energy-density batteries owing to its ultrahigh theoretical specific capacity.However,its practical application is severely hindered by the high reactivity of metallic Li against the commonly used electrolytes and uncontrolled growth of mossy/dendritic Li.Different from widely-used approaches of optimization of the electrolyte and/or interfacial engineering,here,we report a strategy of in-situ cerium(Ce)doping of Li metal to promote the preferential plating along the[200]direction and remarkably decreased surface energy of metallic Li.The in-situ Ce-doped Li shows a significantly reduced reactivity towards a standard electrolyte and,uniform and dendrite-free morphology after plating/stripping,as demonstrated by spectroscopic,morphological and electrochemical characterizations.In symmetric half cells,the in-situ Ce-doped Li shows a low corrosion current density against the electrolyte and drastically improved cycling even at a lean electrolyte condition.Furthermore,we show that the stable Li|LiCoO2 full cells with improved coulombic efficiency and cycle life are also achieved using the Ce-doped Li metal anode.This work provides an inspiring approach to bring Li metal towards practical application in high energy-density batteries.

Parametric optimization of electrochemical machining of Al/15% SiC_p composites using NSGA-Ⅱ

Electrochemical machining（ECM） is one of the important non-traditional machining processes,which is used for machining of difficult-to-machine materials and intricate profiles.Being a complex process,it is very difficult to determine optimal parameters for improving cutting performance.Metal removal rate and surface roughness are the most important output parameters,which decide the cutting performance.There is no single optimal combination of cutting parameters,as their influences on the metal removal rate and the surface roughness are quite opposite.A multiple regression model was used to represent relationship between input and output variables and a multi-objective optimization method based on a non-dominated sorting genetic algorithm-Ⅱ（NSGA-Ⅱ） was used to optimize ECM process.A non-dominated solution set was obtained.

面向表面质量的镍基高温合金铣削参数多目标优化研究

针对镍基高温合金材料在铣削过程中存在表面加工质量低的问题,提出一种基于神经网络及NSGA-Ⅱ算法的工艺参数多目标优化方法。采用不同工艺参数进行数控铣削镍基高温合金Inconel 718加工并获取数据集,以表面粗糙度为输出,不同工艺参数组合为输入,利用麻雀搜索算法建立SSA-BP神经网络模型用于预测Inconel 718铣削表面粗糙度;以最大材料去除率、最小表面粗糙度为优化目标,构建NSGA-Ⅱ工艺参数多目标优化主体模型,调用构建好的预测模型作为主体模型的目标函数并优化求解得到Pareto最优解集。使用TOPSIS法对Pareto最优解集进行最优解决策,得出最佳的工艺参数组合。优化结果表明:该方法不仅可用于高温合金材料数控铣削表面粗糙度预测,还可用于工艺参数优化,为进一步提高数控铣削材料加工质量和效率提供参考。

考虑回弹的水平上调式三辊卷板机卷圆精度研究

为提高卷圆成形精度,建立了不考虑回弹与考虑回弹时水平位移量与卷圆半径之间的理论模型。采用ABAQUS软件建立了卷圆成形有限元模型,并通过实验验证了理论模型及有限元模型的可靠性。基于可靠的有限元模型,研究了材料、摩擦力和板厚对卷圆成形精度的影响规律。研究结果表明,不考虑回弹时实验和仿真的成形半径与目标半径之间的误差分别为31.3%和20.7%。考虑回弹后的误差分别降低至2.2%和1.2%;在相同水平位移量下,材料的屈服强度越高,成形半径越大;摩擦力对成形半径的影响较小;板料越厚,成形半径越小。针对不同材料与不同厚度的板料卷圆成形,考虑回弹时的理论模型能够获得更精确的水平位移量,从而提升卷圆精度。

基于深度学习的金属表面缺陷检测

由于金属产品生产过程中各种因素的影响,金属工件可能会存在一些表面缺陷.这会降低材料强度,缩短工件寿命,并且增加安全风险.因此,需要对金属产品表面进行质量检测,这也是保证工业生产质量的关键环节.与传统人工检测相比,基于机器视觉的表面缺陷检测方法具有速度快、精度高等优点.提出了一种改进的YOLOv5算法,用于金属表面缺陷检测研究,在原YOLOv5算法的基础上将空间金字塔池化结构SPP替换成SPPCSPC,提高模型对金属表面缺陷的检测能力.为了验证算法的有效性,分别采用YOLOv3,YOLOv4,YOLOv5及改进的YOLOv5算法对1 800张金属表面缺陷样本图像进行对比测试.结果表明,与YOLOv3,YOLOv4,YOLOv5原算法相比,改进的YOLOv5算法平均目标检测精度均值分别提高了4.3%,3.3%,2%.通过大量图片的学习,可以获得更好的精确率.

镀镍磷金属片表面处理对电镀铜生长状态影响的研究

对镀镍磷金属片进行了微蚀,化学镀铜,微蚀后化学镀铜这三种表面处理,对比了表面处理方法对镀镍磷金属片表面形貌、电镀铜平整性和可靠性的影响。结果表明,化学镀铜处理能够有效提升镀镍磷金属片表面的平整性,提升导电性,得到平整可靠的电镀铜层。化学镀铜处理方法有效解决了在化学镀镍表面直接电镀铜的平整性和可靠性问题,为提升电镀铜平整性和可靠性提供有效手段。

质子交换膜燃料电池金属双极板表面改性研究进展

质子交换膜燃料电池(PEMFC)在缓解全球能源危机和解决环保难题方面提供了创新性的解决方案。在PEMFC中,双极板作为关键组件备受关注。其中,金属双极板因其成本低廉、材料容易获取、导电性能卓越以及易于机械加工而备受关注。然而,金属双极板目前仍然面临耐久性和导电性方面的挑战。为解决这些问题,通常采用表面改性涂层的方法对金属双极板进行处理。综述了近年来关于金属双极板表面改性涂层的研究进展,涵盖了材料设计、沉积工艺和涂层性能等多个方面。在此基础上,基于导电性、耐蚀性、膜基结合力以及疏水性等测试结果,分析了不同涂层对金属双极板表面改性效果的影响。同时,展望了各种类型改性涂层未来的研究趋势。这些研究成果为改善金属双极板的性能、进一步推动PEMFC表面改性技术的发展提供了有益的指导和启示。

表面热扩渗技术在金属双极板表面改性中的研究进展

燃料电池因其环保和资源利用率高等优点近年来备受关注,对改善全球环境具有重要意义。双极板是燃料电池的重要组成部分,目前燃料电池中大多数的双极板为石墨双极板,其厚度大、加工成本高、柔韧性较差,而金属双极板是替代石墨双极板的最佳材料,其易于加工、成本较低。目前对金属双极板表面制备涂层的研究最为广泛,然而大多数涂层方法工艺复杂,容易形成缺陷,且对燃料电池商业化来说过于昂贵,因此可以通过对金属双极板进行热扩渗改性以满足其服役性能。介绍了不同金属双极板的表面改性技术,列出了不同种类的热扩渗改性技术,重点概况了热扩渗工艺以及耐蚀、导电性能。分析结果表明,对于热扩渗工艺,在制备双极板时应选用合适的温度,以减小或消除形变对双极板的影响;制备出均匀、致密且组织单一的热扩渗层可以明显提高金属双极板的性能;在空气和模拟燃料电池溶液环境中形成的氧化膜和钝化膜同样对金属双极板的性能具有重要影响。在金属双极板表面进行热扩渗改性研究,以提高其耐蚀性、导电性及服役稳定性,同时开发出新型复合工艺,对推动金属双极板在燃料电池的应用至关重要。

圆柱金属管件外表面图像在线采集装置构建及关键参数控制优化

提出一种针对圆柱形金属管件的外表面图像在线采集方案,实现高质量成像信息采集。首先,通过获取单个相机所摄二维图像,建立与柱面所覆盖曲面的对应关系,计算二维图像对应的实际管件表面覆盖角度,判断获取管件外表面信息所需的相机数量,采用多相机协同配合圆盘顺时针方向实时采集图像。其次,基于响应曲面设计方法建立多因素实验方案评估镜头的光圈值、相机的曝光时间和增益对图像质量的影响。在可接受最大转速的情况下,确定动态采图时柱面相机和端面相机的最优相机参数,以减小运动模糊影响并提高拍摄效率。最后,在最优参数的基础上,对金属管件图像进行在线实时采集和评估,保留较好质量的管件图像。实验结果满足高质量、细微缺陷清晰的金属表面缺陷检测数据要求,可为后续研究圆柱形金属管件的实时缺陷检测奠定一定的基础。

PEMFC铝合金双极板表面改性研究现状与发展

质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell,PEMFC)作为第五代燃料电池,是最具发展前景的新能源电池,其中双极板作为PEMFC的核心元件,不仅能将单一电池链接起来形成电池堆,起到支撑作用,还具有提供气体流道、隔绝阴阳极两端等作用,对燃料电池工作性能、寿命起到关键作用。其中铝合金作为一种具有良好导电性能、成本低、轻质的材料,在PEMFC双极板材料方面应用潜力巨大。但铝合金双极板耐腐性不佳,在PEMFC工作环境下极易被腐蚀,且其表面生成的钝化膜,增大了电池的接触电阻,从而对电池性能和寿命产生不利影响,而通过铝合金表面改性是解决该问题的主流方法。首先概述了PEMFC原理、双极板材料类型及内部环境,然后阐述了PEMFC中铝合金双极板的服役问题,并对近年来铝合金双极板的表面改性进行分类。重点概括了铝合金表面金属及其化合物涂层(贵金属、金属氮/碳化物、镍磷金属涂层)与非金属涂层(碳基涂层、高分子聚合物涂层)的结构设计、成分优化、服役性能特点。分析结果表明,选用低成本、具有良好耐蚀性和导电性的金属惨杂的无定型碳、金属碳/氮化物涂层,能降低双极板生产成本,提高双极板工作性能,并对涂层设计出多层复合涂层,能打断涂层中的细长针孔缺陷,提高涂层的完整性和致密性。在铝合金表面进行改性研究,以提高其耐蚀性、导电性及服役稳定性,对推动铝合金双极板在PEMFC电堆中的应用至关重要。

金属板材近表面缺陷远聚焦像素成像方法研究

针对超声成像方法在金属板材近表面缺陷检测中存在的伪像过多、缺陷定量不准确的问题,开展基于远聚焦像素成像算法的金属板材近表面缺陷成像研究。首先分析了远聚焦算法在近表面缺陷成像中的局限性,然后采用自适应噪声抵消的方法提取近表面缺陷波。对于噪声抵消过程中的参考信号获取问题,结合远聚焦算法的采集特征,提出一种以平均回波信号计算参考信号的方法,信号处理的结果表明,该方法能够正确提取淹没于盲区中的近表面缺陷波。最后,采用优化后的远聚焦算法对铝合金板进行缺陷检测,成像结果表明,自适应噪声抵消后图像的信噪比提升了4.31 dB,缺陷定量的最大误差为0.51 mm^(2),以半峰值宽度为指标对成像分辨率进行测试,成像分辨率可达0.66 mm。

基于多视图融合的微弱缺陷检测增强方法

电池金属表面浅划伤、浅凹陷等微弱缺陷在传统二维图像中对比度低、与背景纹理难区分等问题,降低了缺陷的检出率;为解决以上问题,提出了一种基于多视图融合的微弱缺陷检测增强方法;针对微弱缺陷在不同光源方向下合成的三维信息存在缺失问题,提出通过多方向光源装置采集八张不同光源角度图像增加金属表面的光度信息;通过改进的八方向光度立体简化模型获取金属表面三维信息,凸显缺陷的三维特征;针对微弱缺陷在深度图像中存在的图像模糊、对比度低下等问题,通过分析微弱缺陷高度特征呈现角度敏感性特点,拆分抽取深度相关性高的三维信息分量图,由融合系数融合得到增强图像,提高了微弱缺陷的对比度;实验结果表明,该方法应用于实际金属表面缺陷图像检测中,检测精确率提升了19.8%,召回率提升了18.9%,能够较好地解决金属表面微弱缺陷图像检测对比度低下的问题。

金属型板铸造工艺在浮选机过流部件铸造生产中的应用

以XJM-S45浮选机为例,通过对其过流部件铸件质量缺陷及加工工艺的分析,提出了采用金属型板模具代替木质模具的铸造方案,同时改进机加工工艺,有效降低铸件重量,提升铸件质量,减少加工工艺步骤,实现全面提质增效。