金属基磷酸钙陶瓷涂层的界面研究进展

论述了金属基磷酸钙陶瓷涂层的界面力学环境及界面物理化学特性,并为改善涂层与基体的界面结合强度及材料稳定性,对金属基磷酸钙涂层的设计进行了综合评述,提出涂层与基体界面优化设计的要点是合理设计过渡层,注重多种改善途径的结合及预先评定材料界面设计的可行性.     

碳/金属复合材料界面结构优化及界面作用机制的研究进展

依赖于增强相的界面效应和尺寸效应,金属基复合材料不断向综合性能优异的方向发展。由于界面结构对金属基复合材料最终的综合性能起决定性作用,故通过工艺设计实现界面结构的优化成为金属基复合材料的重要研究方向。碳材料(金刚石、碳纳米管和石墨烯等)由于具有优异的本征力学与功能特性,作为金属基复合材料的增强相近年来受到研究者的广泛关注。本文总结了近年来碳/金属复合材料界面结构的不同优化手段,讨论了不同界面结构对碳/金属复合材料结构和功能性能的作用机制,并对未来碳/金属复合材料的界面研究方向进行了展望。     

电子辐照诱导Mo/Si纳米多层膜向非晶态转变

纳米级的轻重元素交替形成的多层膜材料用于制作物理学和天文学中软X射线光学元件 ,尤其Mo Si界面层因稳定性差而降低了膜的反射性能 ,因此研究纳米结构材料的稳定性显得更为重要。与块材相比 ,多层膜受到高能粒子辐照时 ,原子扩散能力较强 ,因此 ,纳米多层膜的稳定性可通过热处理或高能粒子辐照来研究。在Mo Si系中 ,3种各具不同晶体结构和化学成分的MoSi2 ,Mo5 Si3 和Mo3 Si经典化合物已为人们所了解 ,但在电子辐照下 ,其纳米结构相的稳定性还没有人研究 ,日本学者借助高分辨电子显微镜研究了其多层膜中非平衡相的形成和原子扩散过程…     

电子显微术在原位金属基复合材料界面研究中的应用

原位金属基复合材料的增强颗粒是在基体中原位生成,因而增强颗粒和基体间不存在界面反应,两者间为直接的原子结合.界面对原位金属基复合材料的性能有着重要的影响.本文综述了扫描电子显微镜、普通透射电子显微镜、高分辨电子显微镜和电子能量损伤谱仪等现代电子显微技术在原位金属基复合材料界面研究中的应用及部分研究结果.利用现代电子显微技术和先进的实验方法在原子尺度上对界面的精细结构、结合方式、界面缺陷、界面稳定性及其影响因素等进行研究,从而在较深的层次上认识原位金属基复合材料的界面,对在该领域做进一步研究探讨起到促进作用.     

高能球磨中纳米亚稳相的合成

高能球磨是合成纳米亚稳相的一种重要方法。利用高能球磨可以合成纳米晶、金属间化合物、非晶相及过饱和固溶相等多种纳米亚稳相。在球磨过程中,被研磨物质晶粒尺寸逐步细化,并产生大量的界面、位错等结构缺陷。这磐结构缺陷在动力学上为原子的集聚和扩散的一条低能通道,为新相的形核提供了基础。     

梯度多孔金属基复合材料的制备综述

梯度多孔金属基复合材料是孔径或者孔隙率沿厚度方向呈连续或准连续变化的一类金属基复合材料,具备多孔材料高比表面积、高比强度及梯度材料稳定性好、环境适应性好等优点。梯度多孔金属基复合材料可应用于催化、传感、生物、燃料电池、吸声、食品及环境等领域,近年来得到国内外学者的广泛研究,为符合不同领域的应用要求,不同的梯度结构、不同的制备方法及不同的梯度层间界面设计都有不同的影响,本文综述了近年来三种有代表性的梯度多孔金属基复合材料的制备及梯度层间界面设计方法。指出在梯度多孔金属基复合材料的研究中,梯度层间界面设计以及界面对特殊性能的影响将是今后的重点研究方向。     

金属基复合材料界面反应控制研究进展

金属基复合材料可以通过基体合金成分改变、增强体的形态和种类选择及工艺控制等要素获得不同的材料特性,因而具有很强的可设计性。在金属基复合材料性能设计中,界面状态的控制是核心内容。归纳了作者近几年在金属基复合材料界面控制研究方面的研究工作,包括利用工艺技术方法控制Cf／Al有害界面反应,获得TiB2／Al自润滑界面;利用基体合金化方法控制SiC／Al和Cf／Al有害界面反应,获得W／Cu固溶体界面等方面的理论与实践。研究表明,采用材料制备工艺和基体合金化等方法控制界面反应热力学和动力学过程可以实现抑制有害界面产生及获得有益界面,而且是十分简捷、有效和低成本的方法。     

离子辐照对钼金属损伤行为研究进展

钼作为一种难熔金属,因其良好的高温强度、抗蠕变性能、导热性能、耐蚀性能和低溅射率等特性,是满足新一代核能技术发展的重要候选材料。离子辐照会改变钼金属的微观结构,使其产生位错环、空洞、气泡等多种缺陷,导致钼的性质发生改变,服役性能大大降低,最终使得钼金属不能长期有效应用于核反应堆中。本文综述了近年来国内外学者基于辐照对钼损伤行为方面的研究,分析了不同离子辐照下钼的微观结构、表面形貌、力学性能及光学特性等方面的影响,并在现有研究基础上对未来离子辐照对钼金属的损伤行为的研究方向进行了展望,以期望对钼金属的研发和核反应堆方面的应用提供参考。     

316奥氏体不锈钢离子辐照损伤中的温度效应研究

采用7MeV的Xe26+和1 MeV的Xe20+在室温和600℃下分别对316SS块体和TEM试样进行了辐照实验.利用纳米压痕仪测试材料辐照损伤前后的显微硬度,利用TEM观察辐照损伤前后的微观结构演变,并将室温和600℃的实验结果进行了比对.结果表明,室温离子辐照造成316SS中形成大量尺寸在3~8 nm之间的位错环缺陷,它们会阻碍材料内位错线的自由移动,进而导致材料的硬化.在600℃辐照下,316SS内形成了尺寸介于4~12 nm之间的溶质原子团簇缺陷.尽管其尺寸较室温辐照下形成的位错环有轻微的增大,但是其体积密度较前者显著地降低,辐照硬化现象发生了明显的回复,材料辐照损伤行为存在温度效应.     

金属氧化物表面与界面的第一性原理热力学:一个研究实例

通过第一性原理计算研究,能够揭示和阐明材料相关表面与界面热力学性质,这是通向纳米和界面材料设计自由的重要一步,即以理想性能为目标,科学设计制备工艺参数,针对性地调控材料微观结构.以SnO2纳米颗粒表面和原位内氧化制备获得的Ag-SnO2界面计算研究为例,系统介绍这一计算研究策略.基于缺陷热力学模型,构建不同环境温度和氧分压条件下所对应的热力学平衡状态的表面和界面结构模型,计算评估其相应性能.通过一系列的第一性原理能量学计算,进一步构建出平衡状态的表面与界面相图.这些相图能够充分描述制备和服役过程中,工况对材料表面和界面微观结构和相应性能的影响和作用关系.介绍和讨论如何应用这些相图理解和科学设计相应材料的制备工艺.     

Nanostructured metals under irradiation

Particle irradiation has a pronounced influence on the mechanical and thermal properties of materials, largely due to the generation of point defects. Owing to their large free surface to volume ratio, nanostructured metals show improved irradiation resistance. This nanostructuring can negatively impact the creep resistance of these materials, but by introducing fine precipitates this effect can be balanced.     

Structure–Property–Functionality of Bimetal Interfaces

Interfaces, such as grain boundaries, phase boundaries, and surfaces, are important in materials of any microstructural size scale, whether the microstructure is coarse-grained, ultrafine-grained, or nano-grained. In nanostructured materials, however, they dominate material response and as we have seen many times over, can lead to extraordinary and unusual properties that far exceed those of their coarse-grained counterparts. In this article, we focus on bimetal interfaces. To best elucidate interface structure?Cproperty?Cfunctionality relationships, we focus our studies on simple layered composites composed of an alternating stack of two metals with bimetal interfaces spaced less than 100?nm. We fabricate these nanocomposites by either a bottom?Cup method (physical vapor deposition) or a top?Cdown method (accumulative roll bonding) to produce two distinct interface types. Atomic-scale differences in interface structure are shown to result in profound effects on bulk-scale properties.     

Al-C复合材料中Al/C界面的高分辨观察

通过等通道挤压（ECAP）制备了Al-C复合材料，并使用HRTEM、EDS和XRD研究了Al／C界面。结果表明，界面上并未出现不稳定的Al4C3，界面结合较好。Al／C界面分两类：一类为由非晶C和Al形成的界面；另一类为由石墨C和Al形成的界面。在石墨C和Al形成的界面处由于界面应力的作用晶格出现部分扭曲，此处的石墨C有向非晶C转变的趋势。     

The Influence of Grain Boundaries on Radiation-Induced Point Defect Production in Materials: A Review of Atomistic Studies

Radiation-induced defects cause severe degradation of materials properties during irradiation that can ultimately cause the material to fail. Consequences of these defects include swelling, embrittlement, and undesirable phase transformations. Nanocrystalline materials, which contain a high density of grain boundaries, have demonstrated enhanced radiation tolerance compared to large grain counterparts under certain conditions. This is because, as has long been recognized, grain boundaries can serve as defect sinks for absorbing and annihilating radiation-induced defects. Increasingly, researchers have examined how grain boundaries influence the direct production of defects during collision cascade, the origin of the radiation-induced defects. In this review article, we analyze the computational studies in this area that have been performed during the past two decades. These studies examine defect production near grain boundaries in metallic, ionic, and covalent systems. It is found that, in most systems, grain boundaries absorb more interstitials than vacancies during the defect production stage. While this is generically true of most boundaries, the detailed interaction between defects and grain boundaries does depend on boundary atomic structure, the stress state near the boundary, cascade-boundary separation, and materials properties. Furthermore, the defect distribution near boundaries is qualitatively different from that in single crystals, with the former often exhibiting larger vacancy clusters and smaller interstitial clusters than the latter. Finally, grain boundaries that are damaged after cascades have occurred exhibit different interaction behavior with defects than their pristine counterparts. Together, these atomistic simulation results provide useful insight for both developing higher-level modeling of defect evolution at long timescales and how interfaces influence radiation damage evolution.     

Ti-Mo合金的缺陷结构对材料性能的影响

采用真空烧结方法,分别在870℃、890℃制备Ti-Mo（9：1）多孔合金,对材料的微观结构及吸气性能进行研究。结果表明,高温样品中存在大量的α/β界面和β1/β2界面,α/β界面附近存在大量各种类型的缺陷。结合吸气性能测试结果,表明α/β界面及其附近的大量缺陷有利于提高Ti-Mo样品的吸气性能。     

基于弥散强化钨基面向等离子体材料研究进展

重点综述了国内外关于氧化物或碳化物作为强化相的钨基面向等离子体材料的力学性能、氢滞留特性以及辐照损伤,发现制备工艺和强化相含量是影响钨基面向等离子体材料力学性能的主要方面,而均匀分散的强化相颗粒所致使的组织致密化程度更高是钨基材料力学性能提高的主要因素。其次,阐述了晶界和晶内的强化相颗粒分散不均表现出的位移损伤、气泡、绒毛、微裂纹等缺陷都将增加材料对氢同位素的捕获几率,以及等离子体辐照造成的脆化硬化将降低材料的抗热冲击性能。最后分析了近些年弥散强化钨基面向等离子体材料存在的关键基础问题,展望了未来弥散强化钨基材料的主要发展趋势,期望为开发优异的抗高热负荷和辐照损伤的钨基材料方面提供重要参考。     

Atomic-Scale Interfacial Structure in Rock Salt and Tetradymite Chalcogenide Thermoelectric Materials

Interfaces play important roles in the performance of nanostructured thermoelectric materials. However, our understanding of the atomic-scale structure of these interfaces is only beginning to emerge. In this overview article, we highlight and review several examples illustrating aspects of interfacial structure in the rock salt and tetradymite classes of chalcogenide materials. The chalcogenide compounds encompass some of the most successful and well-understood thermoelectric materials employed in actual application and are also relevant more broadly in diverse fields including phase-change memory materials, infrared radiation detection, and topological insulators. The examples we consider here focus in three areas: the influence of weak interlayer bonding on grain boundary structure in Bi₂Te₃, crystallographic alignment and interfacial coherency in rock salt and related cubic chalcogenides, and the structure of interfaces at tetradymite precipitates in a rock salt chalcogenide matrix. The complex interfaces in these systems can be understood and generalized by considering the similarities between the rock salt, tetradymite, and related structures and by analyzing of the relevant interfacial defects.     

冷轧钢板中弱界面对拉伸行为的影响

Q235钢经冷轧－时效－再结晶处理后，钢中存在大量弱界面。应用TEM和SEM观察钢的微观组织结构及拉伸断口。结果表明，弱界面有阻碍位错运动、偏转主裂纹扩展方向的作用，可形成分层断口。这种断裂方式使断口表面积增加，显著提高了材料的力学性能。     

空位扩散诱导点缺陷环与富Cu相的相互作用

辐照诱导产生的点缺陷会加速核电站材料微观组织的演变,在很大程度上影响反应堆的寿命。本文基于相场法的四元连续相场模型,耦合了空位和间隙原子,利用该模型模拟了Fe-15at.%Cu-1at.%Ni-1at.%Mn合金在空位扩散机制下的相分离,研究了点缺陷与富Cu相的相互作用机理。结果表明,空位和间隙原子会促进富Cu相的长大和粗化,点缺陷初始浓度的升高会促进相分离,加快析出相的失稳分解速率,并且升高温度会延缓Cu原子和空位环的生长和粗化,点缺陷也可以增加一定的屈服强度,为探究空位扩散机制影响抗辐照材料性能方面提供了新的思路。     

Atom Probe Tomography Study of Fe Segregation at Phase Interface in Zr–2.5Nb Alloy

β-Nb is a typical second phase in Zr–Nb-based alloys used as fuel claddings in water-cooled nuclear reactors. The segregation of alloying element Fe may affect the corrosion resistance of Zr–Nb-based alloys. In this work, the Fe segregation at the interface between β-Nb phase and α-Zr matrix in Zr–2.5 Nb alloy was studied using atom probe tomography and focused ion beam. The results suggested that the Fe concentration was much lower than Nb concentration in α-Zr matrix, while Fe selectively segregated at the β-Nb/α-Zr phase interface, leading to a Fe concentration peak at some interfaces. The peak Fe concentration varied from 0.4 to 1.2 at.% and appeared at the position where Zr concentration was approximately equal to Nb concentration. The selective segregation of Fe should be affected by the heat treatment and structure defects induced by cold rolling.