气相二氧化硅的异氰酸酯改性及其对浇注型聚氨酯弹性体力学性能的影响

为了改善气相二氧化硅(FS)/浇注型聚氨酯(PU)体系成型流动性,在制备预聚体的过程中,采用2, 4-甲苯二异氰酸酯(TDI)进行改性获得异氰酸酯改性的二氧化硅(NCO@FS),通过原位聚合法制备了NCO@FS/PU弹性体复合材料。采用FTIR、XPS及动态接触角对NCO@FS及FS进行了表征。结果表明：FS的表面羟基与TDI的-NCO基团发生反应生成了氨酯基(-NHCOO),改善了FS与PU间的界面相容性及界面结合。复合材料中NCO@FS质量分数为1.5wt%时,NCO@FS/PU复合材料的拉伸和撕裂强度分别为57 MPa和110.5 kN/m,比纯浇注型PU分别提高了31.6%和23.6%;玻璃化转变温度由3.4℃下降到-11.2℃,损耗因子tanδ由0.59下降到0.46。异氰酸酯改性FS适合制备FS增强浇注型聚氨酯复合材料。     

Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al_2O_3 composite coatings

In this study, three kinds of A380/Al_2O_3 composite coatings were prepared by cold spray(CS) using spherical, irregular and spherical + irregular shaped Al_2O_3 particulates separately mixed in the original A380 alloy powders. The influence of Al_2O_3 particulates' morphology on the microstructural characteristics(i.e.retention of Al_2O_3 content in coatings, coating/matrix interfacial bonding, pore size distribution and morphology etc.) and wear performance of the coatings was investigated by scanning electron microscopy(SEM), X-ray computed tomography(XCT) and 3-D optical profilometry. Results indicated that the spherical Al_2O_3 shows obvious tamping effect during deposition process. As a result, the interface showed a wavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion. In addition, the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions. The irregular Al_2O_3 particles predominantly displayed the embedding effect together with fragmentation of Al_2O_3 particulates. Consequently, poor coating/matrix interfacial bonding, high porosity and the formation of angular-shaped pores were resulted in the coating. Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al_2O_3 in the coating. The coating containing irregular Al_2O_3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating. The coating containing both kinds of Al_2O_3 particulates showed mixed characteristics of above two kinds of Al_2O_3 composite coatings.     

Preparations and tribological properties of soft-metal/DLC composite coatings by RF magnetron sputter using composite targets

This work reports the characteristics and tribological properties of both Ag/DLC nanocomposite coatings (RF-Ag-DLC) and Cu/DLC nanocomposite coatings (RF-Cu-DLC) with hydrogen-free DLC matrix deposited by RF magnetron sputtering using a concentric composite target (CCT). The CCT consisted of a C base target and metal tablet, and the tablet was located on the center of the base target concentrically where the etching rate by Ar ions is extremely low. By changing the diameter of Ag or Cu tablets in CCT, RF-Ag-DLC with an Ag concentration ranging from 6 to 65 at.% and RF-Cu-DLC with Cu concentration ranging from 7 to 75 at.% can be prepared. These coatings show a granular structure having Ag or Cu nano-crystals with a diameter ranging from 5 to 10 nm dispersed homogeneously in the hydrogen-free DLC matrix. The friction coefficient of DLC varied depending on the species and content of metal. The transition of the friction coefficient became stable when metal-rich tribofilms formed on the counterfaces.     

Nanostructural, electrical, and tribological properties of composite Au-MoS2 coatings

Considerable research has been done on the tribological properties of cosputtered metal/MoS₂ solid lubricant films with low metal content (< 20 at.%) because of their usefulness in applications at high Hertzian contact stress (around 1 GPa). However, cosputtered Au-MoS₂ coatings with a much higher range of metal contents up to (95 at.%) have shown surprisingly good performance at low contact stresses (as low as 0.1 MPa). In the present study, transmission electron microscopy, X-ray diffraction and electrical resistance measurements of cosputtered Au-MoS₂ coatings reveal them to be composites of nanocrystalline Au particles within an amorphous MoS₂ matrix. Electrical conductivity images of the coatings displayed metallic (Au) and semi-conducting (MoS₂) domains of nanometer dimensions. Auger Nanoprobe analyses confirmed that sliding on the coatings causes the formation of a pure MoS₂ layer about a nanometer thick on top of the bulk of the coatings. Lattice resolution atomic force microscopy revealed that this nanometer-thick MoS₂ layer is crystalline, and oriented with the basal plane (0001) parallel to the coating surface. Electrical resistance obtained during sliding and pull-off force measurements was consistent with the structure of the coatings. Sliding friction data on the coatings support previous results showing that performance at different Hertzian contact stresses correlated strongly with Au content.     

Mechanical,thermal and tribological properties of electro- and chemodeposited composite coatings

By means of chemical (autocatalytic) and electrolytic codeposition of nickel and silicon carbide particles it is possible to produce coatings with enhanced wear and corrosion resistance on metallic and plastic substrates.In the first part of the paper the basic plating technique in relation to the type, form, grain size and activation of the SiC particles will be described.The mechanical properties of the coatings depend on the amount of incorporated particles in the nickel matrix. By activation of the SiC powder the content of particles in the coating can be increased significantly. Mechanical properties such as hardness, strength and elastic modulus improve with increasing content of particles. It will be further shown that the negative influence of a pure nickel coating on fatigue is reduced with a coating of NiSiC. This result can be explained by the behaviour of the internal stresses in the coating as a function of the SiC content. The tribological properties of the coatings were tested by an abrasive wear mechanism under lubricated conditions combined with corrosion. The corrosive wear tests were performed under potentiostatically controlled conditions.The high temperature application of these coatings is limited by the thermal decomposition of the SiC particles in the nickel matrix at about 500 °C. The coatings were examined by various techniques such as differential thermal analysis, X-ray diffraction and secondary ion mass spectrometry. The influence of different temperatures on the mechanical and tribological properties of the coatings will be described.     

Effect of CNTs on morphology and electromagnetic properties of non-firing CNTs/silica composite ceramics

Carbon composite ceramics have much attention for industry because of their excellent properties such as strong toughness, high electrical conductivity as well as low percolation threshold. Therefore, carbon nanotubes (CNTs) were used to incorporate with silica ceramics in order to improve their electromagnetic properties. The amount of CNTs in CNTs/silica composite ceramics was varied in order to investigate its effect on morphologies and electromagnetic properties of those. The composites were successfully fabricated by non-firing process. The results revealed that the obtained CNTs/silica composite ceramic have an electrical resistivity of 66.6?Ω·cm with a bending strength of 13.8?MPa. At the same time, the electromagnetic wave absorption ability achieved 70% over a wild frequency. This indicates that the CNTs in CNTs/silica composite ceramics may be potentially applied for an electromagnetic wave reflective material.     

纳米石墨/聚氨酯复合涂层的制备及耐腐蚀性能

为研制高性能电力金具防护涂层,首先,以羟基丙烯酸树脂和异氰酸酯为主要成膜物质,纳米石墨为填料,制备了不同纳米石墨含量的纳米石墨/聚氨酯复合涂料;然后,将涂料喷涂在电力热镀锌钢上,固化干燥后得到纳米石墨/聚氨酯复合涂层;最后,测试了纳米石墨/聚氨酯复合涂层的力学性能和耐磨性,并采用模拟酸雨试验、中性盐雾试验及电化学阻抗谱（EIS）研究了纳米石墨/聚氨酯复合涂层的耐腐蚀性能。结果表明:添加纳米石墨后,涂层与热镀锌钢的附着力有所提高,纳米石墨含量为2.0wt%的纳米石墨/聚氨酯复合涂层的耐磨性比未添加纳米石墨的空白涂层提高了92%,并且涂层中纳米石墨的分布较均匀,表现出良好的耐腐蚀性能。 所得结论表明在涂层中添加适量的纳米石墨可以提高涂层的耐磨性和耐腐蚀性能,进而可将涂层用于电力金具的表面防护。      

Tensile properties of fumed silica filled polydimethylsiloxane networks

Tensile properties of fumed silica filled hydroxylated polydimethylsiloxane (PDMS) networks were investigated in the current work. Similar to unfilled bimodal networks, unimodal networks filled with concentrated fumed silica exhibit non-Gaussian effect and improved ultimate tensile properties. The concept of “hierarchical network” was proposed to depict the networks exhibiting non-Gaussian effect at sufficiently high strains. It was found that the reinforcing effect originates from both the effective volume effect from filler volume and polymer–filler interaction and the synergistic effect between network chains within the “hierarchical network”. Experimental results showed that filler’s dispersion, concentration, specific surface area and surface chemistry have a great influence on the tensile properties, which could be interpreted by analyzing the variation of both effective volume effect and synergistic effect.     

The running-in tribological behavior of nano-SiO2/Ni composite coatings

The running-in tribological behavior of the electrodeposited nano-SiO₂/Ni composite coatings is investigated using an M-200 block-on-wheel friction and wear tester. The results show that the electrodeposited nano-SiO₂/Ni composite coatings exhibit good wear resistance in the running-in period. With increasing nano-SiO₂ particle content in the electrodeposition plating solution, the wear resistance of the composite coatings are first improved and then decreased slightly, and the friction coefficient decreases first and then increased. If the nano-SiO₂ particle content in electrodeposition plating solution is 10 g/L, the composite coatings show the best wear resistance.     

气相二氧化硅聚集体的网络结构对硅橡胶性能的影响

采用RPA橡胶加工分析仪,在一定的温度和频率下,分析不同性质结构的气相二氧化硅在高温硅橡胶中的聚集体网络结构差异及聚集体网络对填充胶Payne效应的影响。研究发现,高分支结构聚集体的填充胶具有明显的Payne效应,补强效果好。原子力显微镜（AFM）表明,高分支结构的聚集体在高温胶基体中分散均匀,呈三维链网结构,聚集体橡胶约为100-200nm。示差扫描量热（DSC）分析表明,在-42℃左右,填充胶结晶而失去弹性。     

钡铁氧体/石墨烯/二氧化硅柔性复合材料吸波性能的研究

随着信息化时代的快速发展,各种各样的电子产品也被广泛地应用到生活与工作中,伴随其而来的电磁污染也成为日益严重的问题,具有“薄、轻、宽、强”的吸波材料得到了广泛的关注。采用机械混合法将钡铁氧体(BaFe₁₂O₁₉)、石墨烯（graphene）、二氧化硅（SiO₂）进行混合,制备多元复合吸波剂,以水性聚氨酯为粘结剂,使用流延工艺制备多元复合吸收剂涂层织物,并分析其结构、形貌、机械以及吸波性能。结果表明,所制备的柔性吸波涂层织物在吸波剂配比为0.4(BaFe₁₂O₁₉-graphene)-0.6SiO₂、吸波涂层厚度为1.2 mm时,最小反射损耗达到-14.58 dB,有效吸波带宽为0.94 GHz（12.91～13.58 GHz）,具备涂层薄、吸波强度高、吸收频带宽、质量轻的潜质。     

自润滑Cr/C复合镀层的制备和机械性能研究

采用闭合场非平衡磁控溅射技术,固定碳靶电流参数,调节铬靶电流参数,在GCr15轴承钢球、45#钢和单晶硅基体上制备出自润滑Cr/C复合镀层。用XRD对镀层相结构进行分析,测试了镀层的摩擦系数、磨损率、结合强度、硬度和韧性,用光学显微镜观察镀层磨损形貌。结果表明,镀层相结构为非晶态,随铬靶电流变大逐渐向晶态转变;与未镀层的基体相比,镀层有良好的摩擦磨损性能和载荷承载能力;镀层随铬靶电流增加,硬度逐渐降低,韧性逐渐提高。所获铬电流为0.1和0.3A镀层有很好的自润滑性能,且后者有良好的综合机械性能。     

纳米TiO2/有机-无机杂化丙烯酸复合涂层机械及耐腐蚀性能的研究

在采用溶胶-凝胶法合成有机-无机杂化丙烯酸树脂的基础上,研究了纳米TiO2添加量对有机-无机杂化丙烯酸复合涂层机械和耐腐蚀等性能的影响。研究表明,当纳米TiO2添加量为15%时,涂层的性能有了较大的提高,其硬度由3H提高至6H,涂层的耐盐雾时间由100h提高到500h,涂层的阻抗值也由104Ω.cm2提高至106Ω.cm2。另外,通过扫描电镜观察了复合涂层的断面,发现涂层中纳米粒子分散均匀,并且粘接紧密,形成了较为致密的复合涂层。     

氟树脂/硅溶胶复合涂层的制备和超疏水性能研究

在醇溶性氟树脂(FR)溶液中,以正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为前驱体,并掺杂聚四氟乙烯(PTFE),以两步催化溶胶-凝胶法,在通常条件下,制备了有机-无机复合涂层.较低的表面张力、较大的润湿角和较大网络模数,有效地防止了通常条件下含凝胶材料干燥过程所引起的网络结构的破坏.表面气相氨催化法使涂层具有良好的机械性能.该涂层对水的接触角可高达155°.扫描电镜观察到,涂层表面的形貌为具有与天然荷叶表面极其相似的微米与纳米相结合的阶层结构.该方法扩大了现有超疏水性涂层的应用范围,可根据不同需要,制备出不同力学性能的超疏水性涂层.     

Corrosion and tribological properties of a composite based on aluminum with graphite particles

We study the corrosion resistance and tribological characteristics of composite materials based on an aluminum-silicon alloy with dispersed metallized graphite particles. Graphite decreases the friction coefficient and makes the wear resistance of materials 3–5 times higher as compared with the matrix alloy without decreasing its corrosion resistance. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 119–121, November–December, 2007.     

Influence of Egyptian nanoilmenite/amorphous silica composite particles on the electrochemical and mechanical properties of cold galvanizing formulation coatings

In the present work, Egyptian ilmenite nanoparticles (FeTiO₃ NPs) were obtained with the average diameters of 20?nm by a direct solid-phase milling process and synthesized amorphous silica powder grains were processed to prepare a novel fabricated Egyptian nanoilmenite/amorphous silica composite (ENI/AS) particles. Flaky-like nature of ENI/AS and the spherical shape of Zn-dust particles were emphasized by scanning electron microscopic (SEM) micrographs. The nano features of ENI/AS particles were confirmed by transmission electron microscope (TEM) investigation. Various alkyd-based cold galvanizing coating formulations were modified using different uniformly dispersing amounts of the processed ENI/AS particles as a modifier to form some nanocomposite coatings. The electrochemical behavior of nanocomposite modified coated steel films in oil-wells formation water solution have been studied by both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The mechanical properties of the coated films were studied through some coating tests as cross-cut adhesion, bend and impact to assert their application efficiency. Scanning electron microscope (SEM) technique was utilized to survey the protective film formed on the carbon steel surface by these modified coatings in formation water solution. The results of this study reinforced remarkable corrosion protection properties of ENI/AS modified cold galvanizing coating.     

Mechanical and tribological properties of gradient a-C:H/Ti coatings

The unusual combination of high hardness and very low friction coefficient are the most attractive tribological parameters of DLC (diamond-like carbon) layers. However, their usability is strongly restricted by the limited thickness due to high residual stress. The main goal of the presented work was to obtain thick, wear resistant and well adherent DLC layers while keeping their perfect friction parameters. As a proposed solution a Ti-Ti _x C _y gradient layer was manufactured as the adhesion improving interlayer followed by a thick diamond-like carbon film. This kind of combination seems to be very promising for many applications, where dry friction conditions for highly loaded elements can be observed. Both layers were obtained in one process using a hybrid deposition system combining PVD and CVD techniques in one reaction chamber. The investigation was performed on nitrided samples made from X53CrMnNiN21-9 valve steel. Structural features, surface topography, tribological and mechanical properties of manufactured layers were evaluated. The results of the investigation confirmed that the presented deposition technique makes it possible to manufacture thick and well adherent carbon layers with high hardness and very good tribological parameters. Preliminary investigation results prove the possibility of application of presented technology in automotive industry.     

TiAlSiN-Ti(Mo)N/MoS2复合涂层微观结构及摩擦学性能的研究

采用磁控溅射技术在AISI-304不锈钢上制备了TiAlSiN-Ti(Mo)N/MoS2复合涂层。采用电子显微镜(SEM)、X射线衍射仪(XRD)、显微硬度计、球盘摩擦磨损试验机、表面形貌仪等对涂层的表面形貌、显微组织、硬度和摩擦学性能进行了系统的研究。结果表明TiAlSiN-Ti(Mo)N/MoS2复合涂层的硬度为27.56 GPa,相比于TiAlSiN涂层的硬度(29.1 GPa)有所下降,但是涂层的耐磨性能得到明显提高。在室温至600℃条件下TiAlSiN-Ti(Mo)N/MoS2复合涂层的主要磨损机理为黏着磨损,200和400℃时的磨损率分别为0.0339×10^-3和0.1122×10^-3mm^3/(Nm),相较于TiAlSiN涂层分别降低了38%和57%,600℃时的磨损率接近TiAlSiN涂层。总体来说TiAlSiN-Ti(Mo)N/MoS2复合涂层的性能高于单一的TiAlSiN涂层。