聚合物基复合材料摩擦学改性研究新进展

总结了国内外近几十年来聚合物基复合材料摩擦学改性方面的研究新进展情况.通过介绍聚合物摩擦学改性方法包括聚合物共混改性、纤维增强改性,以及纳米材料改性和多元复合改性等,讨论了其对聚合物摩擦学性能的影响,分析了其摩擦磨损机理.分析认为功能性纳米材料及多元复合填料的协同效应能更加有效地改善聚合物基复合材料的摩擦磨损性能,并且在聚合物摩擦学改性方面起着越来越重要的作用.     

微纳米尺度下材料性能多尺度模拟方法进展

微纳米材料的力学行为正日益引起研究者的关注.微纳米材料的性能取决于从微观、细观到宏观多个空间、时间尺度上不同物理过程非线性耦合演化的结果,发展相应的多尺度数值模拟方法已成为该领域研究工作的一个热点.本文对微纳米材料模拟中比较典型的几种协同多空间尺度和协同多时间尺度方法进行了介绍,着重介绍这些方法的的基本思想、应用情况, 以及各自的优缺点,并对微纳米材料多尺度方法的发展趋势进行总结和评述.      

纳米材料力学行为的原子尺度模拟研究

对几何尺寸极小的纳米材料而言,数值模拟是与实验测试同样有效的研究手段, 而且,当材料特征尺寸更小、缺乏可用的测试系统时,数值模拟可能是唯一的方法.介绍了近年来纳米材料力学行为的原子尺度数值模拟研究方面的若干新进展,重点综述了采用分子动力学模拟与第一原理计算对纳米材料的晶格不稳定性、理想强度、界面断裂、碳纳米管的力电特性和铁电纳米材料的力电特性等问题的研究结果.总结介绍了纳米材料原子尺度模拟中一些实用的计算策略和方法,并提出了若干需要进一步研究的问题.      

纳米材料力学行为的原子尺度模拟研究

对几何尺寸极小的纳米材料而言, 数值模拟是与实验测试同样有效的研究手段, 而且, 当材料特征尺寸更小、缺乏可用的测试系统时, 数值模拟可能是唯一的方法. 介绍了近年来纳米材料力学行为的原子尺度数值模拟研究方面的若干新进展, 重点综述了采用分子动力学模拟与第一原理计算对纳米材料的晶格不稳定性、理想强度、界面断裂、碳纳米管的力电特性和铁电纳米材料的力电特性等问题的研究结果. 总结介绍了纳米材料原子尺度模拟中一些实用的计算策略和方法, 并提出了若干需要进一步研究的问题.     

石墨烯摩擦学及石墨烯基复合润滑材料的研究进展

本综述详细介绍了二维碳纳米材料-石墨烯的纳米摩擦学性能,以及作为纳米润滑薄膜、润滑添加剂和润滑填料的研究进展.总结了石墨烯的各种纳米摩擦机理,阐述了通过自组装、多层构筑、表面化学改性等技术改善石墨烯与基底的结合性、润滑剂中的分散性,与基体材料的界面结合强度以及石墨烯提高材料减摩抗磨性能的机制,并指出石墨烯作为高性能润滑材料仍需解决的问题及未来的研究趋势.     

磷酸酯阴离子插层水滑石作为纳米润滑添加剂的研究

利用尿素分解法制备了镍铝基水滑石(LDH)纳米材料,然后采用离子交换法对其进行了磷酸酯插层修饰,成功合成了二丁基磷酸酯阴离子插层水滑石(LDH-DBP)和二异辛基磷酸酯阴离子插层水滑石(LDH-OBP)纳米材料.通过傅立叶变换红外光谱仪、X射线衍射仪、热重和透射电子显微镜对所制备纳米材料的化学组成、晶体结构及颗粒形貌进行了分析表征.采用SRV-IV摩擦试验机研究其作为PAO-4的润滑添加剂的摩擦学性能,试验结果表明:磷酸酯阴离子插层修饰的水滑石纳米添加剂可显著提高PAO-4在高载荷(200 N))条件下的摩擦学性能,其减摩抗磨机理可归于水滑石纳米材料的片状吸附和磷酸酯摩擦化学反应的协同作用.     

陶瓷摩擦学研究的发展现状

本文综述了陶瓷摩擦学研究的发展现状,从干摩擦和润滑两个方面总结了氧化物陶瓷(Al_2O_3、ZrO_2)和非氧化物陶瓷(Si_3N_4、SiC)的摩擦磨损性能、磨损机理以及影响摩擦磨损性能的若干因素,并且提出了今后需要重点研究的几个课题。     

二维纳米材料异质结构的原子间相互作用模型

近些年二维纳米材料得到了大量的研究,其中一个热点研究方向是将不同的二维纳米材料堆垛成纳米异质结构,从而实现多功能的纳米器件.这些二维纳米材料可以从面外和面内两个方向上进行堆垛从而形成两类不同的异质结构.在关于这类二维纳米材料及其异质结构的理论研究中,原子间的相互作用起到类似于连续介质力学中本构关系的作用.因此学者提出了多种方案用于描写原子间相互作用,主要包括第一性原理计算和经验势能模型等.本文主要是对比和分析各种描写二维纳米材料及其异质结构的常见经验势能模型,从而为研究人员选择相互作用模型提供一些参考.      

头盔用复合材料抗侵彻性能研究进展

对头盔用复合材料抗冲击性能的研究及其主要成果进行了总结和评述,包括所用材料的冲击动力学性能、头盔结构在冲击下的损伤和破坏特点、其能量吸收机制的理论分析和数值模拟等几方面,提出了一些亟待深入的研究方向．     

复合圆柱管撞击吸能特性实验研究

本文研究了外部缠有玻璃纤维增强环氧的金属圆柱管（简称为“复合管”）在轴向撞击载荷下的能量吸收特性。总结了复合管撞击渐进破坏压缩历程的瞬时速度、位移、载荷等的变化规律。从破坏模式、压缩速率（与准静态实验比较）、金属材料的性能、复合材料层的厚度、纤维的缠绕角这几个角度研究了复合管的吸能性能的影响因素。     

SPD纳米材料制备方法及其力学特性

剧烈塑性变形(severe plastic deformation, SPD)纳米化技术是近年来发展的一种力致材料纳米化方法.该方法克服了由粉体压合法带来的残余空隙、球磨法带来的杂质等不足,并且适用于不同形状尺寸的金属、合金、金属间化合物等,因此受到了越来越多的关注.介绍了SPD纳米材料的制备方法及相关纳米材料力学性能研究的现状,并展望了对SPD力致纳米材料的研究趋势.      

Micromechanical simulation on strength and ductility of two kinds of Al-based nanostructural materials

The nanostructured Al-based composites possess the combination of high yield strength and good ductility. In this paper, a micromechanical model is presented to simulate the mechanical response of bimodal nanostructured Al and the particle-reinforced aluminum matrix composite(PAMC). The constitutive relations for different phases are addressed in the model, as well as the contribution of microcracks. Numerical results show that the model can successfully describe the enhanced strength and ductility of the bimodal nanostructured Al, and the predictions of the PAMC are in good agreement with the experimental data. It is worth noting that the strength and ductility are sensitive to the volume fraction of constituents and the distribution of microcracks in both bimodal nanostructured Al and PAMC. Therefore, the present theoretical results can be used to optimize the microstructure for improving the mechanical properties of nanostructured Al-based composites.     

梯度纳米结构金属力学性能、变形机理和多尺度计算研究进展

近年来，梯度纳米结构金属因其优越的力学性能和独特的塑性变形机理受到广泛关注，已成为材料与力学学科的热点和前沿。本文首先介绍梯度纳米结构金属的强度、塑性、加工硬化和抗疲劳等核心力学性能，以及晶粒长大、塑性应变梯度和几何必需位错等塑性变形机理及其力学研究。其次介绍梯度纳米结构金属的多尺度计算与模拟研究。最后讨论梯度纳米结构金属研究领域存在的挑战。     

SURFACE STRESS EFFECT IN MECHANICS OF NANOSTRUCTURED MATERIALS

This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements,including nanoparticles,nanowires,nanobeams,and nanofilms,and heterogeneous materials containing nanoscale inhomogeneities.It begins with the fundamental formulations of surface mechanics of solids,including the definition of surface stress as a surface excess quantity,the surface constitutive relations,and the surface equilibrium equations.Then,it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements,as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption.Afterwards,the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing.The effect of surface elasticity on the diffraction of elastic waves is elucidated.Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations,finite element approaches have been developed for heterogeneous materials with the surface stress.Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips.The solutions of crack problems taking into account surface stress effects are also included.Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention.The advances in this topic are inevitably delineated.Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications.Some most recent work is reviewed.Finally,some challenges are pointed out.They include the characterization of surfaces and interfaces of real nanomaterials,experimental measurements and verification of mechanical parameters of complex surfaces,and the effects of the physical and chemical processes on the surface properties,etc.     

NANOSCALE PROCESS ENGINEERING

The research of nanoscale process engineering (NPE) is based on the interdisciplinary nature of nanoscale science and technology. It mainly deals with transformation of materials and energy into nanostructured materials and nanodevices, and synergizes the multidisciplinary convergence between materials science and technology, biotechnology, and information technology. The core technologies of NPE concern all aspects of nanodevice construction and operation, such as manufacture of nanomaterials “by design“, concepts and design of nanoarchitectures, and manufacture and control of customizable nanodevices. Two main targets of NPE at present are focused on nanoscale manufacture and concept design of nanodevices. The research progress of nanoscale manufacturing processes focused on creating nanostructures and assembling them into nanosystems and larger scale architectures has built the interdiscipline of NPE. The concepts and design of smart, multi-functional, environmentally compatible and customizable nanodevice prototypes built from the nanostructured systems of nanocrystalline, nanoporous and microemulsion systems are most challenging tasks of NPE. The development of NPE may also impel us to consider the curriculum and educational reform of chemical engineering in universities.     

含能材料装药的损伤及力学性能研究进展

研究含能材料的损伤和力学性能对于指导含能材料配方和结构件设计,以及对含能材料进行安全性评估和寿命预测等都具有重要的意义.损伤一方面使含能材料的力学性能劣化,另一方面还影响含能材料的感度、燃烧甚至爆炸性能.本文对含能材料损伤和力学性能的研究现状进行了综述和归纳.对含能材料损伤的产生、实验模拟、主要损伤模式,损伤对含能材料的感度和燃烧性能等的影响,炸药单相材料的性质,影响含能材料力学性能的因素以及损伤本构关系等进行了介绍.对其中的一些关键问题和热点问题进行了分析,并对今后需要开展的工作发表了一些看法.      

Hierarchical structure observation and nanoindentation size effect characterization for a limnetic shell

In the present research, hierarchical structure observation and mechanical property characterization for a type of biomaterial are carried out. The investigated biomaterial is Hyriopsis cumingii, a typical limnetic shell, which consists of two different structural layers, a prismatic "pillar"structure and a nacreous "brick and mortar" structure. The prismatic layer looks like a "pillar forest" with variationsection pillars sized on the order of several tens of microns.The nacreous material looks like a "brick wall" with bricks sized on the order of several microns. Both pillars and bricks are composed of nanoparticles. The mechanical properties of the hierarchical biomaterial are measured by using the nanoindentation test. Hardness and modulus are measured for both the nacre layer and the prismatic layer, respectively.The nanoindentation size effects for the hierarchical structural materials are investigated experimentally. The results show that the prismatic nanostructured material has a higher stiffness and hardness than the nacre nanostructured material.In addition, the nanoindentation size effects for the hierarchical structural materials are described theoretically, by using the trans-scale mechanics theory considering both strain gradient effect and the surface/interface effect. The modeling results are consistent with experimental ones.     

电弧喷涂纳米结构涂层的组织与磨损性能

基于机器人自动化高速电弧喷涂技术在45#钢基体上制备了铁基纳米结构涂层.研究了纳米结构涂层在不同磨损速度?不同载荷下的磨损行为,并利用3Cr13涂层进行对比试验.采用扫描电镜?能谱分析仪,透射电镜和X射线衍射仪等设备对涂层的组织结构进行了表征,利用纳米压痕仪对涂层的力学性能进行了分析.结果表明:涂层的组织主要由非晶相和α(Fe,Cr)相纳米晶组成;平均尺寸为46nm的α(Fe,Cr)相纳米晶均匀分布于非晶基体内.涂层的组织均匀,结构致密,平均孔隙率含量为1.7%.纳米结构涂层具有较高的显微硬度;随着磨损速度升高,载荷增加,纳米结构涂层的磨损量也随之增加.纳米结构涂层具有良好的耐磨性,同一磨损条件下,其相对耐磨性为3Cr13涂层的2.6倍.纳米结构涂层主要磨损机制为脆性断裂机制.     

Effect of surface/interface stress on the plastic deformation of nanoporous materials and nanocomposites

Surface and interface play an important role on the overall mechanical behaviors of nanostructured materials. We investigate the effect of surface/interface stress on the macroscopic plastic behaviors of nanoporous materials and nanocomposites, where both the surface/interface residual stress and surface/interface elasticity are taken into account. A new second-order moment nonlinear micromechanics theory is developed and then reduced to macroscopically isotropic materials. It is found that the effect of surface/interface residual stress is much more prominent than that of the surface/interface elasticity, causing strong size effect as well as asymmetric plastic deformation for tension and compression. The variation of yield strength is more prominent with smaller pore/inclusion size or higher pore/inclusion volume fraction. For a representative nanoporous aluminum, the surface effect becomes significant when the pore radius is smaller than about 50 nm. When hard inclusions are embedded in a ductile metal matrix, the interface effect and resulting size effect are much smaller than that of nanoporous materials. The results may be useful for evaluating the mechanical integrity of nanostructured materials.     

Nickel doped zinc oxide nanoparticles produced by hydrothermal decomposition of nickel-doped zinc hydroxide nitrate

Zinc hydroxide nitrate, an anionic exchanger layered material, undoped as well as doped with 2–10% nickel, was synthesized by using a pH-controlled precipitation method. The layered materials were then used to produce the undoped and nickel-doped zinc oxides by hydrothermal-treatment. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the formation of pure phase undoped and nickel-doped layered materials, as well as the products of the hydrothermal-treated materials, nanostructured zinc oxides. Optical studies of the nanostructured zinc oxides showed a decrease in band gap with increasing content of the doping agent, nickel.