热喷涂纳米结构涂层的研究

纳米材料具有许多优异的特性,利用热喷涂技术制备纳米结构涂层是一种应用纳米材料的有效办法.文中介绍了纳米结构涂层喷涂材料的制备,包括液体喂料制备纳米材料、纳米粉末材料和纳米药芯丝材的制备,以及热喷涂制备纳米结构涂层的种类,纳米结构涂层的种类包括纳米结构陶瓷涂层、金属-陶瓷纳米复合涂层和金属纳米结构涂层.简要介绍了制备这些涂层所采用的工艺方法,以及涂层的结构和性能.指出了目前热喷涂制备纳米结构涂层存在的问题,并对其应用和发展前景作了展望.     

一般问题/焊接科学和技术的发展及前景

纳米材料具有许多优异的特性，利用热喷涂技术制备纳米结构涂层是一种应用纳米材料的有效办法。介绍了纳米结构涂层喷涂材料的制备，包括液体喂料制备纳米材料、纳米粉末材料和纳米药芯丝材的制备，以及热喷涂制备纳米结构涂层的种类，其中包括纳米结构陶瓷涂层、金属一陶瓷纳米复合涂层和金属纳米结构涂层。[第一段]     

刀具和磨具用的纳米结构涂层

纳米结构涂层定义为晶粒尺寸或膜层厚度小于 10 0nm的功能材料。纳米结构涂层包括金属 -金属、金属 -陶瓷、陶瓷 -陶瓷以及附着有固体润滑剂的材料。纳米结构涂层分为纳米晶薄膜结构、膜厚为纳米多层膜结构以及纳米混合相薄膜结构。纳米晶涂层　纳米晶金属或涂层显示出较低的磨损率 ,这种耐磨性能的提高归因于纳米尺寸效应引起的高硬度、高韧性及特殊的裂纹变化和移动机理。例如 ,电沉积制备涂层的晶粒尺寸降到 10nm ,维氏硬度增大3倍。制备纳米晶涂层的关键是保证粒子的纳米尺寸 ,在高温时控制晶粒生长 ,方法包括把纳米粒子首先制成微米粒…     

纳米多孔金属孔结构粗化方法研究进展

纳米多孔金属具有特殊的力学、热学、光学、电学和化学性能,尤其是其特殊的结构已经受到越来越多科研工作者的广泛关注。纳米多孔金属的结构决定了其性能,因此研究纳米多孔金属孔结构的粗化方法非常有意义。综述了纳米多孔金属孔结构的粗化方法,包括制备过程中的粗化、热退火粗化、酸溶液处理粗化、碱溶液处理粗化、盐溶液处理粗化及其他粗化方法。最后对纳米多孔金属的粗化中存在的问题进行了探讨。     

纳米颗粒复合电刷镀镀层的微/纳观结构特征

在45钢表面制备了n-Al2O3/Ni和n-SiO2/Ni纳米颗粒复合电刷镀层,借助SEM、TEM、HREM等分析手段,在微观和纳观尺度上研究了纳米颗粒复合电刷镀层微观组织特征,分析了纳米颗粒分布、纳米颗粒/基质Ni金属界面结合等微/纳观现象.结果发现:纳米颗粒在基质Ni金属中均匀弥散分布,纳米颗粒与基质Ni金属之间达到了原子尺度的良好结合;基质Ni金属晶格发生了畸变,存在大量原子空位和位错等结构缺陷.这使得纳米颗粒复合电刷镀层具有优良的力学性能.     

纳米孔结构金属多孔材料研究进展

纳米孔结构金属多孔材料(以下简称金属纳米多孔材料)是近年来纳米技术及多孔材料科学领域引人注目的研究对象.本文综述了近年来金属纳米多孔材料的制备方法(粉末烧结法、脱合金法、胶晶模板法、斜入射沉积法等)、表征技术、应用现状以及最新的研究成果.指出了金属纳米多孔材料研究进程中存在的主要问题、发展前景及今后的研究方向.     

蝶翅精细分级结构金属纳米复合材料的研究进展

具有精细分级结构的金属纳米复合材料耦合了多组分和结构功能化的综合优势,展现出优良的光学及催化性能,这对于材料结构功能的一体化设计及其在环境能源等领域的应用有着重要意义。本文以蝶翅模板为例,系统介绍了精细分级结构金属纳米复合材料的制备、性能和应用探索研究,并对该领域的未来发展进行展望。     

金属纳米复合材料的界面和尺度效应

在宏观尺度上制造出具有纳米结构和纳米效应的高性能金属材料,并揭示这些材料的组织演化特征以实现功能调控,是金属材料学科面临的重大科学问题和需要解决的核心关键技术。阐述金属纳米材料界面、尺度与材料塑变、强化关系的主要研究进展,重点介绍宏观尺寸制备金属纳米复合材料、纳米尺度下经典Hall-Petch关系和复合材料混合定律的适用性、界面特征和尺度效应对材料微观结构、力学性能以及物理特性等的影响,指出面向应用的高性能金属纳米复合材料的发展趋势。     

金属含量对Co-TiO2纳米颗粒复合薄膜微观结构及其性能的影响

目的使Co-TiO_2纳米颗粒复合薄膜同时具备高的磁化强度及电阻率,从而实现更好的高频软磁特性。方法通过磁控共溅射的方法,在不同金属靶功率下制备了Co-TiO_2纳米颗粒复合薄膜,并探究金属含量对薄膜的微观结构、表面形貌、电学和静态磁学性能的影响。结果薄膜中的金属颗粒被非晶态的TiO_2分散。金属含量的增加可以显著提高纳米颗粒薄膜中金属颗粒的结晶性,降低薄膜电阻率,并且通过改变金属含量,可使薄膜逐渐从超顺磁态向铁磁态转变,达到精确调控纳米颗粒复合薄膜的磁学和电学性能的目的。结论在金属含量达到54%时,实现了高电阻率和高饱和磁化强度共存,有望得到具有高频软磁特性的纳米颗粒复合薄膜。     

Ag-Cu纳米合金MIM结构的制备及其光学性质

采用微电极电化学沉积的方法,在氧化铟锡(ITO)玻璃衬底上制备了Ag-Cu纳米合金.实验发现,Ag-Cu纳米合金在紫外-可见光波长范围内有2个吸收峰.通过在Ag-Cu纳米合金薄膜表面涂覆一定厚度的聚乙烯醇(PVA)作为绝缘层,然后与另外一层Ag-Cu纳米合金薄膜叠合组装成Ag-Cu纳米合金/PVA/Ag-Cu纳米合金的金属-绝缘体-金属(MIM)结构.首次测试到该MIM结构的透过率和吸收率在1000 ～ 2600 nm波长范围内出现多重响应峰,这些多重响应峰是由MIM结构中不同尺寸的纳米粒子表面等离子耦合导致的交替电磁共振引起的.     

Atomic simulation on evolution of nano-crystallizaion in amorphous metals

The deformation-induced nano-crystallization behavior of amorphous pure Ni was investigated by using a molecular dynamics simulation. The microevolution mechanism of the nano-crystallization, the crystallization process in the multicomponent amorphous Ni-Pd alloys and the temperature effect on the nano-crystallization behavior in amorphous metals were studied. The results show that the small nano-crystalline grain will nucleate and grow during the compression deformation. The deformation induces the growth of the ordered clusters in the amorphous metals and the nano-crystalline grain grows under the shearing combination and sheafing deposition. The nano-crystalline grain will nucleate in a lower strain under a higher temperature. The combining severe plastic deformation with thermal annealing treatments presents a new opportunity for developing bulk nano-crystalline materials with controlled microstructures.     

压力及稀释剂对块体纳米晶Fe3Al组织和性能的影响

采用透射电镜(TEM)、X射线衍射(XRD)和压缩试验,研究了氩气压力和稀释剂对铝热法制备的块体纳米晶Fe3Al材料组织和性能的影响。结果表明,在氩气压力分别为3、6、9MPa和稀释剂含量分别为0、20%、40%条件下制备的Fe3Al块体材料均为DO3有序结构,晶粒尺寸≤30nm;随氩气压力增加,材料晶粒尺寸无明显变化,但随稀释剂含量增加,材料晶粒尺寸明显减小。屈服强度随压力增加而提高,但与晶粒尺寸间无明显对应关系。当稀释剂含量不同时,材料晶粒尺寸与屈服强度呈反Hall-Petch关系。     

摩擦辅助喷射电沉积纳米晶镍的电化学腐蚀行为

采用摩擦辅助喷射电沉积工艺和传统喷射电沉积工艺制备纳米晶镍,用TEM对比分析了二者的组织结构,用电化学极化法研究了2种纳米晶镍层在3.5%NaCl(质量分数)溶液及1 mol/L H2SO4溶液中的腐蚀行为。结果表明,摩擦辅助喷射电沉积结晶过程更加均匀,制备的纳米晶镍层组织致密,晶粒细小,平均晶粒达到9.77 nm;在2种腐蚀溶液中,摩擦辅助喷射电沉积制备的纳米晶镍的电化学腐蚀性能均优于传统喷射电沉积;在NaCl溶液中,摩擦辅助喷射电沉积所制纳米晶镍在腐蚀过程中有钝化膜产生。并指出晶粒大小与微观缺陷是影响纳米晶镍耐腐蚀性能的2个重要因素     

Preparing nano-crystalline rare earth doped WC/Co powder by high energy ball milling

The nano-crystalline rare earth doped WC/Co powder was prepared by high energy ball milling. The nano-crystalline powders were characterized by means of XRD (X-ray diffraction), SEM (scanning electron microscope) and DTA (differential thermal analysis). The results show that adding trace rare earth elements into carbides is effective to minish the grain size of WC/Co powder. The grain size of rare earth doped powder became two times smaller as compared with the undoped powder within ball milling times of 25–45 h. The XRD peak of Co phase disappeared after 25 h ball milling. A sharp peak of heat release at the temperature of 597 °C was emerged in DTA curve within the range of heating temperature. After consolidated the rare earth doped WC/Co alloy by high energy ball milling exhibits ultra-fine grain sizes and better mechanical properties.     

纳米面心立方金属的变形机制及影响其力学性能的因素

综述了纳米面心立方金属的变形机制随晶粒尺寸的减小而发生的变化,即变形机制由晶界处发射不全位错、形成孪晶转变为晶界滑移、晶粒转动.当变形机制为晶界处发射不全位错、形成孪晶时,存在最佳孪晶形成晶粒尺寸范围,此时的孪晶形核应力最小.另一方面,随着晶粒尺寸的减小,在变形机制发生转变的临界晶粒尺寸附近存在韧-脆断裂方式的转变.提高孪晶密度、在纳米晶材料中加入微米晶相形成双峰晶粒材料可以提高纳米晶材料的塑性,得到更好的综合机械性能.     

纳米氧化锆粉体包碳修饰研究

对共沉淀-凝胶法制备的氧化锆纳米陶瓷粉体,采用有机物液相悬浮法、弧光放电法、气相沉积法及粉体制备过程中直接包裹等方法对纳米氧化锆粉体进行表面包碳修饰,成功制备了包裹层厚度均匀、颗粒分散性好的碳包纳米氧化锆粉体,通过形貌观察、粒度测定、粉体烧结性能测试,探讨包裹层形成机理,为防止纳米陶瓷粉体的团聚长大探索有效途径。     

Effects of ternary alloying on mechano-synthesis and nano-crystal stability of an iron-silicon alloy

This paper reports the effects of ternary alloying additions Al, Cu and Nb to Fe₇₅Si₂₅ in high energy ball milling to produce nano-crystalline alloy powder, and its microstructural stability during subsequent high temperature annealing. It is shown that all additions generally retard grain growth up to some temperature. Nb appears to amorphise the alloy. The binary base alloy and Al containing alloy forms the DO₃ ordered structure at high temperatures accompanied by rapid grain growth. The Cu and Nb containing alloys precipitate Cu and Nb₂Fe at high temperatures but do not become ordered.     

脉冲放电烧结纳米WC-10%Co粉

以喷雾转化工艺(SCP)制备的纳米WC-10％Co(质量分数)粉为原料，应用脉冲放电烧结方法(EDC)制备出平均晶粒尺寸为120am左右的超细晶WC-Co硬质合金，并对样品的微观组织结构与力学性能进行了分析．结果表明，EDC方法极短的烧结时间是抑制晶粒长大的重要原因．除裂纹桥联机制外，弥散分布的小孔隙对提高WC-Co硬质合金的断裂韧性也起到重要作用。     

Improving the properties of cryomilled light alloys Using Spark plasma Sintering and hot isostatic pressing

Ultrafine grained materials consolidated using spark plasma sintering and hot isostatic pressing show great potential for applications in aerospace, energy, and a vast range of other industries. The Hall-Petch relationship cites the strengthening of materials by reducing the average crystallite (grain) size. A study is proposed to investigate the increase in mechanical properties provided by fine-grained, near-nano- and nano-crystalline powders produced from cryomilling and consolidation using spark plasma sintering (SPS) and hot isostatic pressing (HIPing). Initial testing indicates an increase in hardness and shear in commercially pure aluminum by 2–3 times from use of fine-grained, near-nano-, nano-crystalline materials. Cryomilled powders and consolidated forms of these powders will be examined using field emission scanning electron microscopy. Macrohardness, microhardness, tensile testing and shear testing will be performed to examine the mechanical properties.     

Sintering of a nano-crystalline tungsten heavy alloy powder

A nano-crystalline Tungsten heavy alloy powder was obtained by mechanical alloying of elemental powders in a jar mill with a high ball to powder ratio. The chemical composition of the primary powder was 93 W-4.9Ni-2.1Fe (wt%). The mechanically alloyed powder had 22 nm sized tungsten crystallites distributed in an amorphous nickel base phase. Mechanical alloying reduced particle size of powders and also yielded to more uniform particles size distribution. Sintering behavior and microstructural development of that powder were studied and compared with a conventionally mixed powder. Mechanically stored energy and better distribution of primary elements in Nano-crystalline powder had decreased motivation energy of sintering and that powders showed more densification at relatively lower sintering temperatures. Sintering at low temperatures can depress grain growth during sintering and provide desirable properties. A transient intermetallic phase was formed in the nano-crystalline powder during sintering that has not been seen in conventionally mixed powders.