纳米Al2O3增强PA6复合材料的摩擦磨损性能研究

利用MMW-1型摩擦磨损试验机考察了纳米Al2O3增强PA6复合材料同45#钢对摩时的摩擦磨损性能,采用扫描电子显微镜观察分析了试样磨损表面形貌.结果表明:纳米Al2O3可以提高PA6的耐磨性能;在小于100 N低载荷下纳米Al2O3填充PA6复合材料的滑动摩擦系数符合粘弹性材料的变化规律;只有当填充量适当时,纳米Al2O3微粒才能有效地增强聚合物基体的抗磨粒磨损性能,并阻碍聚合物基体向偶件磨损表面的粘着转移;纳米Al2O3质量分数为10%的PA6复合材料的抗磨性能最佳.     

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO4 nanoparticles were synthesized in the presence of sodium polyacrylate （PAAS） by a simple precipitation method, with BaCl2 and （NH4）2SO4 as reactants. The different roles performed by PAAS in the synthesis of BaSO4 nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the assynthesized BaSO4 nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl2 to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO4 nuclei. During formation of the BaSO4 nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO4 seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO4 nanoparticles.     

Conductive hydrogels incorporating carbon nanoparticles: A review of synthesis,performance and applications

As one of the most rapidly expanding materials, hydrogels have gained increasing attention in a variety of fields due to their biocompatibility, degradability and hydrophilic properties, as well as their remarkable adhesion and stretchability to adapt to different surfaces. Hydrogels combined with carbon-based materials possess enhanced properties and new functionalities, in particular, conductive hydrogels have become a new area of research in the field of materials science. This review aims to provide a comprehensive overview and up-to-date examination of recent developments in the synthesis, properties and applications of conductive hydrogels incorporating several typical carbon nanoparticles such as carbon nanotubes, graphene, carbon dots and carbon nanofibers. We summarize key techniques and mechanisms for synthesizing various composite hydrogels with exceptional properties, and represented applications such as wearable sensors, temperature sensors, supercapacitors and human-computer interaction reported recently. The mechanical, electrical and sensing properties of carbon nanoparticles conductive hydrogels are thoroughly analyzed to disclose the role of carbon nanoparticles in these hydrogels and key factors in the microstructure. Finally, future development of conductive hydrogels based on carbon nanoparticles is discussed including the challenges and possible solutions in terms of microstructure optimization, mechanical and other properties, and promising applications in wearable electronics and multifunctional materials.     

The structure of colloidal polyethylenimine–silica nanocomposite microparticles

Deposition of silica from an organosilane tetraethoxysilane (TEOS) onto parent polyethylenimine (PEI) microgel particles produces a novel PEI–silica nanocomposite, which possesses greater adsorption capacity for copper ions than either parent material. This study explores factors governing interactions of silica with the PEI matrix, along with structural features of resulting PEI–silica composite particles, to explain their properties and determine their application potential. The influence of initial TEOS/PEI mass ratio and the duration of silica deposition on the final silica content and distribution in the composite are studied. A comparative analysis of the structural architecture of chemically etched silica remnants, original PEI–silica composite particles and the parent PEI-microgel is carried out using X-ray photoelectron spectroscopy, small-angle X-ray scattering, and electron microscopy techniques. It is found that silica sol nanoparticles are evenly distributed throughout the PEI-microgel framework and interlinked with it via electrostatic interactions, enabling a structural model of the PEI–silica nanocomposite to be proposed. The chemical stability of resulting nanocomposite particles in parallel with the parent PEI-microgel is tested and shown to be robust for more than 100 days of storage in aqueous dispersions across a range of pH conditions, highlighting the application potential for these particles in copper capture.     

聚合物／无机纳米复合材料润滑油添加剂的摩擦学功能设计

选择3种具有不同抗磨性能的纳米组分,制备了具有不同界面特性的聚合物／无机纳米复合材料;考察了纳米复合材料的减摩抗磨性能和机理,探讨了关于纳米复合材料润滑油添加剂的摩擦学功能设计准则。结果表明：对聚合物与无机纳米组分界面进行设计优化后能明显提高纳米复合材料的摩擦学性能。实现聚合物与无机纳米组分界面的优化设计后,聚合物与无机纳米组分之间具有更好的相容性,无机纳米组分在聚合物基体中分布更均匀;当聚合物基体在摩擦热和剪切作用下熔融分解后,裸露出来的具有高活性的无机纳米组分可在摩擦副接触表面形成具有良好摩擦学性能的表面膜。     

电解质吸附对水基带电表面黏着的影响

为研究界面黏着,利用表面力仪在高离子强度电解质水溶液中测量负电云母表面之间的法向力. 在纯水中,因范德华吸引,两表面跳跃至直接接触(间距0 ?),分离两表面时测得界面黏着力为?46.7 mN/m. 在0.1 mol/L K₂SO₄中,因K+离子牢固吸附于云母,表面间距稳定于5 ?,黏着力仅?2.9 mN/m;在0.1 mol/L Ca(NO₃)₂中,云母表面吸附的Ca2+离子产生显著短程水合排斥,但在较低载荷下解吸附,导致两表面直接接触,黏着力高达?40.7 mN/m. 加入Ca(OH)₂于0.1 mol/L K₂SO₄仅产生微弱短程排斥,黏着状态几乎与纯K₂SO₄水溶液中相同. 聚电解质PCE从0.1 mol/L K₂SO₄中吸附于云母表面且诱导远程空间位阻排斥,但在中等载荷下解吸附,导致两表面轻度黏着(间距5 ?);牢固吸附于云母表面的PNS高分子薄膜之间的空间位阻完全阻止云母界面黏着. 牢固吸附是电解质吸附层稳定阻止界面黏着的必要条件.      

Fe及SiO2对铜基刹车材料摩擦磨损性能的影响机制

通过加压烧结法制备出铜基粉末冶金航空刹车材料,采用模拟刹车制动试验方法考察了不同转速条件下Fe含量和添加SiO2对材料摩擦磨损性能的影响,利用光学显微镜和扫描电子显微镜观察材料的显微组织结构及其磨损表面形貌,分析了Fe和SiO2对材料磨损性能的影响机制.结果表明:由于高硬度及耐磨的Fe弥散分布于铜基体中,使得刹车材料的摩擦系数和耐磨性能有所提高;SiO2虽然能够更有效地增加材料的摩擦系数和提高高速条件下的耐磨性,但对低速下材料磨损性能的提高不利.这是由于在低速下,SiO2易凸出摩擦表面而增加材料的磨损,而在高速下由于硬质SiO2颗粒对摩擦膜起到很好的钉扎作用而使其摩擦系数增加,磨损率降低.     

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO₄ nanoparticles were synthesized in the presence of sodium polyacrylate (PAAS) by a simple precipitation method, with BaCl₂ and (NH₄)₂SO₄ as reactants. The different roles performed by PAAS in the synthesis of BaSO₄ nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the as-synthesized BaSO₄ nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl₂ to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO₄ nuclei. During formation of the BaSO₄ nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO₄ seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO₄ nanoparticles.     

铜表面高疏水薄膜的制备及摩擦学性能的研究

通过简单两步法在金属铜表面构筑高疏水薄膜,首先金属铜经氢氧化钠化学刻蚀处理后在表面构筑微纳结构薄膜,然后覆盖硬脂酸薄膜以实现高疏水.采用扫描电子显微镜、X-射线光电子谱、傅里叶红外光谱仪和接触角测量仪等手段表征了金属铜表面高疏水薄膜的形成机制和表面形貌,并利用微纳米摩擦磨损试验机研究了高疏水薄膜的减摩耐磨特性.研究结果发现:在氢氧化钠处理导致的表面微织构化效应以及脂肪酸自组装薄膜的纳米润滑效应的联合作用下,金属铜表面形成的高疏水薄膜具有明显的减摩和耐磨特性.     

聚四氟乙烯和二硫化钼填充聚酰亚胺复合材料的摩擦磨损性能研究

采用MM-200型摩擦磨损试验机考察了聚四氟乙烯(PTFE)和MoS2填充聚酰亚胺(PI)复合材料在干摩擦下与GCr15轴承钢对摩时的摩擦磨损性能，并利用扫描电子显微镜和X射线能量色散谱仪分析了PI复合材料及其偶件磨损表面形貌和元素面分布．结果表明，PTFE和MoS2均可降低PI的摩擦系数，其中PI 30％MoS2复合材料的减摩性能最佳，其摩擦系数同纯PI的相比降低了约50％．除PI 10％PTFE 20％MoS2外，其它几种复合材料的抗磨性能均明显优于纯PI，其中PI 20％PTFE 10％MoS2复合材料的抗磨性能最佳，其磨损率比纯PI的低1个数量级．PI复合材料的摩擦磨损性能同其在偶件磨损表面形成的转移膜的性质密切相关，当转移膜厚度适当且分布较均匀时，PI复合材料的减摩抗磨性能良好．     

粘结剂特性对填充树脂复合材料摩擦学性能的影响

采用酚醛树脂、丁腈橡胶改性酚醛树脂和聚四氟乙烯（PTFE）作为粘结相,通过填充一定配比的石墨、焦炭及碳黑制备了3种树脂基复合材料电刷试样,并在MM-200型摩擦磨损试验机上对比考察了复合材料试样与铜对摩时的摩擦磨损性能,结果表明,与未改性的酚醛树脂基复合材料相比,改性酚醛树脂基复合材料由于韧性提高和硬度降低,因而磨损加剧;但相应的偶件铜环的磨损有所减轻,PTFE基复合材料具有良好的综合性能,偶件铜环的磨损亦较小,因此是一种潜在的高性能电刷复合材料。     

Experimental study of enhanced heat transfer by addition of CuO nanoparticle

An energy storage system has been designed to study the thermal characteristics of paraffin wax with an embedded nano size copper oxide (CuO) particle. This paper presents studies conducted on phase transition times, heat fraction as well as heat transfer characteristics of paraffin wax as phase change material (PCM) embedded with CuO nanoparticles. 40?nm mean size CuO particles of 2, 5 and 10% by weight were dispersed in PCM for this study. Experiments were performed on a heat exchanger with 1.5–10?l/min of heat transfer fluid (HTF) flow. Time-based variations of the temperature distributions are revealed from the results of observations of melting and solidification curves. The results strongly suggested that the thermal conductivity enhances 6, 6.7 and 7.8% in liquid state and in dynamic viscosity it enhances by 5, 14 and 30% with increasing mass fraction of the CNEPs. The thermal conductivity ratio of the composites can be augmented by a factor up to 1.3. The heat transfer coefficient during solidification increased about 78% for the maximum flow rate. The analysis of experimental results reveals that the addition of copper oxide nanoparticles to the paraffin wax enhances both the conduction and natural convection very effectively in composites and in paraffin wax. The paraffin wax-based composites have great potential for energy storage applications like industrial waste heat recovery, solar thermal applications and solar based dynamic space power generation with optimal fraction of copper oxide nanoparticles.     

常用摩擦副材料与抗磨添加剂配伍性研究

本文对传统的润滑油抗磨添加剂(S型、P型、S-P型)和自制的有机硼抗磨剂与常用摩擦副材料(钢、铜、铸铁)在Falex-6型多功能摩擦磨损试验机上进行了配伍性研究,测得了4种抗磨剂与6对摩擦副配合时的P-V图。作者指出,二烷基二硫代磷酸锌(ZDDP)和有机硼抗磨剂对摩擦副材料的选择性不大,特别是有机硼对铜-钢摩擦副显示出较好的减摩抗磨性能;P剂有利于铜-钢和铸铁-钢摩擦副的润滑;S剂和ZDDP更适合于钢-钢摩擦副的润滑。本文还应用X-射线光电子能谱仪(XPS)相扫描俄歇微探针仪(AES)表面分析技术对典型试件表面膜的化学结构进行了分析。     

FROST RESISTANCE OF POLYVINYL ALCOHOL FIBER REINFORCED CEMENTITIOUS COMPOSITES

This article studies the frost resistance of polyvinyl alcohol (PVA) fiber reinforced cementitious composites. The test samples contain different PVA fiber volume fractions such as 0, 0.5%, 1% and 2%. The freeze-thaw test is carried on in TDR type apparatus. The outward appearance, the weight loss factor and the relative dynamic elastic modulus are analyzed, and conclusions are drawn that PVA fibers can significantly improve the frost resistance of cementitious composites and frost resistance of PVA fiber reinforced cementitious composites with fiber volumetric fraction of 1% is better.     

聚四氟蜡和二硫化钼填充凯夫拉纤维织物复合材料的摩擦磨损性能研究

采用玄武三号栓-盘式摩擦磨损试验机研究凯夫拉(Kevlar)纤维织物材料及聚四氟蜡(PFW)和MoS2填充Kevlar纤维织物复合材料的摩擦磨损性能,采用扫描电子显微镜观察其磨损表面形貌.结果表明,PFW和MoS2均可以改善Kevlar纤维织物材料的摩擦磨损性能,其中PFW的改善效果尤为显著.当PFW质量分数为20%时,Kevlar纤维织物复合材料的摩擦系数减小75%、磨损率降低82%,Kevlar纤维织物复合材料的减摩抗磨性能最佳.     

Transport of Lead (Pb<Superscript>2+</Superscript>) Ions Through Silty-Clayey Soils Under Acidic Conditions

This study aimed to identify effects of pH on the transport of Pb²⁺ ions through a saturated silty-clayey soil layer by using advection–dispersion equation (ADE). The predictive accuracy of the solution of ADE depends on the proper determination of the retardation by adsorption and, therefore, the adsorption mechanism of lead onto silty-clayey soil was investigated first by performing batch equilibrium experiments. These results showed that the sorption mechanism of lead onto silty-clayey soil depended on pH and could be best described by the Langmuir isotherm. Based on the results of the sequential experiments, it was also concluded that the pH dependent charges in silty-clayey soil were mainly associated with the surfaces of carbonates and the specific adsorption of lead ions. The numerical solutions of the combined form of ADE with the Langmuir isotherm indicated that the migration profiles of lead in silty-clayey soil were a strong function of the parameters of the Langmuir isotherm rather than the infiltration velocity.     

Templating core–shell particles using metal ion-chelating biosurfactants

Designer biosurfactants can be used to stabilise and functionalise interfaces. One particularly promising use is the stabilisation of oil-in-water emulsions, enabling fine tuning physical, chemical and biological surface properties. The ability of emulsion systems to carry high payloads makes them attractive for applications in medicine, food and fragrances, and cosmetics. However, they have limited long-term stability. Here we sought to use the metal ion-chelating ability of the biosurfactant peptide, AM1, to precipitate the formation of a gold metal shell on AM1-stabilised emulsions by electroless plating. We found that replacing the commonly used zinc(II) with palladium(II) for coordination by histidine residues of adjacent AM1 peptides produced interfacial films that maintained elasticity at acidic pH. Proton NMR suggested a coordination mechanism independent of the imidazole ring of the histidines. Nevertheless. stabilisation of emulsions at low pH enabled the deposition of a gold shell, albeit by an unexpected mechanism. We propose that gold nanoparticles forming in bulk are adsorbed onto the peptide-stabilised interface, accumulating into a particulate coating. The resulting one-step method for nanoparticle precipitation and shell formation will be useful for the creation of biocompatible core–shell particles for applications where large payloads of hydrophobic active compounds require stability over long time periods.     

纳米及微米颗粒改性玻璃纤维织物复合材料的摩擦磨损性能研究

用玄武三号栓-盘式摩擦磨损试验机研究了纯玻璃纤维织物以及辐照聚四氟乙烯(PTFE)粉末、MoS2粉末、纳米TiO2和纳米CaCO3填充改性玻璃纤维织物复合材料的摩擦磨损性能；采用扫描电子显微镜观察分析了其磨损表面形貌．结果表明，辐照PTFE粉末和纳米TiO2可以明显提高玻璃纤维织物复合材料的减摩抗磨性能，且辐照PTFE粉末的减摩抗磨效果明显优于纳米TiO2；当PTFE的质量分数为10％时，PTFE改性玻璃纤维织物复合材料的综合摩擦磨损性能最好．MoS2和纳米CaCO3则使得玻璃纤维织物复合材料的摩擦系数和磨损率明显增大，其中纳米CaCO3填充玻璃纤维织物的摩擦磨损性能最差。     

两种UHMWPE／Kaolin复合材料在干摩擦条件下的滑动摩擦磨损性能研究

在ＭＭ－２００型磨损试验机上分别对以釜内聚合和熔融机械混合方法制备的高岭土填充超高分子量聚乙烯基复合材料（ＵＨＭＷＰＥ／Ｋａｏｌｉｎ）在干摩擦条件下与４５＾＃钢对摩时的摩擦磨损性能进行了研究,并用扫描电子显微镜和立体光学显微镜对其磨损表面进行了观察与分析,对材料的磨损机理进行了探讨。结果表明：引入适量的高岭土能明显降低ＵＨＭＷＰＥ的摩擦系数和磨损率,用釜内聚合方法制备的ＵＨＭＷＰＥ／Ｋａｏｌｉｎ复     

Design of three dimensional isotropic microstructures for maximized stiffness and conductivity

The level-set method of topology optimization is used to design isotropic two-phase periodic multifunctional composites in three dimensions. One phase is stiff and insulating whereas the other is conductive and mechanically compliant. The optimization objective is to maximize a linear combination of the effective bulk modulus and conductivity of the composite. Composites with the Schwartz primitive and diamond minimal surfaces as the phase interface have been shown to have maximal bulk modulus and conductivity. Since these composites are not elastically isotropic their stiffness under uniaxial loading varies with the direction of the load. An isotropic composite is presented with similar conductivity which is at least 23% stiffer under uniaxial loading than the Schwartz structures when loaded uniaxially along their weakest direction. Other new near-optimal isotropic composites are presented, proving the capablities of the level-set method for microstructure design.