聚氨酯/纳米SiO2原位复合互贯网络材料研究

用原位聚合的方法制备了聚氨酯(PUR)／纳米SiO2复合物，研究了各因素对复合材料性能的影响。结果表明：当纳米SiO2的质量分数为2％时，PUR／SiO2纳米复合材料的综合力学性能最佳，与纯PUR相比，抗拉强度和伸长率分别提高了160%和10％。加入分散剂CH-10B，纳米复合材料的抗拉强度和伸长率分别比未加分散剂时提高了50％和5％。复合材料的玻璃化温度向高温方向偏移了7℃。复合材料中团聚的纳米SiO2粒子被部分分散，但分散状况随着其含量的增大而变差。PU和PS的二组分互贯聚合物网络(IPNs)材料通过同时聚合反应被制备，当苯乙烯含量为40%时，该IPNs材料力学性能有进一步的提高。     

纳米TiO2改性塑料的抗菌及分解内毒素特性研究

研究了纳米TiO2的制备、相结构及抑菌作用，含0．7％TiO2的纳米TiO2／PS复合材料的分解内毒素及抑菌作用。结果表明：锐钛矿型纳米TiO2对常见的菌种具有良好的抑制作用。纳米TiO2／PS复合材料具有明显的分解细菌内毒素的作用和良好的抑菌效果；对内毒素的分解率可达90％以上，对常见细菌的杀菌率达到999／5以上。     

纳米Ti02改性塑料的抗菌及分解内毒素特性研究

研究了纳米TiO2的制备、相结构及抑菌作用,含0.7%TiO2的纳米TiO2/PS复合材料的分解内毒素及抑菌作用.结果表明锐钛矿型纳米TiO2对常见的菌种具有良好的抑制作用.纳米TiO2/PS复合材料具有明显的分解细菌内毒素的作用和良好的抑菌效果;对内毒素的分解率可达90%以上,对常见细菌的杀菌率达到99%以上.     

聚合物/层状粘土纳米复合材料及其应用

有机/无机纳米复合材料将在宇航、机械、生物、热学、电学、磁学、光学等领域表现出广阔的应用前景,是探索高性能复合材料的一条重要途径.本文综述了聚合物/粘土纳米复合材料制备中粘土的有机化处理、插层复合工艺以及复合材料优异性能及其应用.     

纳米碳管增强纯铝基复合材料的制备及性能

将采用电孤放电法制备的未纯化和纯化的CNTs作为增强体与纯铝粉混合，用粉末冶金法成功制备了1％纳米碳管增强铝基复合材料。力学性能测试表明，未经纯化的纳米碳管对基体增强效果甚小；而纯化的纳米碳管增强效果较为明显，1％纯化纳米碳管增强铝基复合材料力学性能高于10％微米碳化硅强化铝基复合材料，证实添加的纯化纳米碳管对铝基体有良好的强化效果。     

选区激光烧结聚苯乙烯/Al2O3纳米复合材料研究

在采用选区激光烧结法成功地制备出纳米粒子较均匀分散于基体中的聚苯乙烯／Al2O3纳米块体复合材料的基础上,通过试验观察和微观结构分析,着重就激光功率和扫描速度两种关键参数对烧结成形性的影响进行了研究,同时对相同工艺条件下的纳米复合材料与纯聚苯乙烯烧结件的力学性能进行了比较。结果表明：纳米复合材料的缺口冲击强度提高了20％～50％,其最大值达到10．1kJ／m^2;而洛氏硬度值仅增加约5％。     

溶液共混母胶法制备纳米石墨/氢化丁腈橡胶复合材料的性能

采用溶液共混母胶法制备了纳米石墨/氢化丁腈橡胶(HNBR)复合材料,研究了其微观结构、硫化性能、力学性能、耐磨性能等,并将其与采用传统机械共混法制备得到的复合材料进行对比.结果表明:溶液共混母胶法可使纳米石墨更加均匀地分散在HNBR基体中;与传统机械共混法相比,用溶液共混母胶法制备的复合材料的硫化性能和力学性能更优,最...     

尼龙66/蒙脱土纳米复合材料的绿色阻燃和力学性能

对蒙脱土进行有机化处理后，使用熔融插层法制备了绿色阻燃尼龙66／有机蒙脱土（OM-MT）纳米复合材料，表征了复合材料的力学性能及其阻燃性能。结果表明，少量纳米二氧化硅的加入能够在一定程度上改善力学性能，其冲击性能相对提高了38．9％。当OMMT：SiO2为3：1，APP：MA为1.2：1，ZnO：APP为1／12-1／1O时材料的极限氧指数提高了33．3％。     

原位聚合法制备环氧树脂／纳米炭黑复合导电材料的性能研究

采用原位聚合法制备了环氧树脂／纳米炭黑复合导电材料,并对其力学性能、电阻率和抗弯断面形貌进行了分析。结果表明,环氧树脂／纳米炭黑复合导电材料的邵氏硬度和抗弯强度随纳米炭黑含量而变化,当其含量为3％（质量分数）附近时两者出现最大值,抗弯强度可达到43．86MPa,邵氏硬度可达到5．34HD;纳米炭黑的加入使复合材料的电性能得到较大的提高。     

聚四氟乙烯纳米复合材料的制备及其力学和摩擦学性能

以添加表面活性剂的水为溶剂,采用溶剂混合法制备纳米 Al2 O3填充聚四氟乙烯（PTFE）复合材料,研究其力学性能和摩擦学性能,并与乙醇中分别制备纳米 Al2 O3填充 PTFE 复合材料进行比较。结果表明：在相同 Al2 O3填充比例下,水中制备的复合材料的拉伸强度和硬度要低于乙醇中制备的复合材料,而断裂伸长率却要高于乙醇中制备的复合材料。在200 N 和干摩擦条件下,当纳米 Al2 O3质量分数为1％～5％时,水中制备的复合材料的磨耗量要低于乙醇中制备的复合材料,并较纯 PTFE 磨耗量下降了1～2个数量级;且水中制备的复合材料的摩擦因数也要低于乙醇中制备的复合材料。复合材料磨痕处 SEM显示复合材料的磨损机制为黏着磨损和磨粒磨损。     

Micromechanical scribing and indentation behavior of injection-molded polymeric carbon nanotube (CNT) nanocomposites

Polymeric carbon nanotube (CNT) nanocomposites have unique mechanical, electrical, and thermal properties. Anisotropy can be induced depending on the alignment of the CNT fillers within polymeric composites, which is known to affect material properties. In order to investigate the effects of CNT alignments in micromechanical scribing using a single crystal diamond tool, a microindenter–scriber system was developed. Multiwalled carbon nanotube–polystyrene (MWCNT–PS) samples with varying CNT concentrations were prepared through a microinjection molding process, where the injection enables the partial alignment of CNTs in the flow direction through high shear stress. A mechanistic scribing force model was proposed based on the material properties that could be obtained using the microindentation techniques. Scribing experiments were performed in the parallel and perpendicular directions to the CNT alignment. Forces in three axes were measured and analyzed to identify three unknown parameters—the shearing, plowing, and adhesion friction coefficients. The resulting coefficients for scribing perpendicular to the CNT alignment showed distinguishable trends from scribing parallel to the CNT alignment as the CNT loadings increased. Their linear trends in relation to the material properties identified from indentation techniques can be used to predict microscribing parameters and resulting cutting forces, in combination with the proposed mechanistic model.     

Investigation into the selective laser sintering of styrene–acrylonitrile copolymer and postprocessing

The amorphous polymer of polystyrene (PS) has been widely used in the selective laser sintering (SLS) process. However, PS is not suitable to make parts with thin-wall or delicate structures because of the poor mechanical properties of its SLS parts. Therefore, styrene–acrylonitrile copolymer (SAN), another kind of amorphous polymers, was investigated as an SLS material. The effects of laser energy density on the relative density, mechanical properties, and dimensional accuracy of the SLS parts were studied, and the properties of PS and SAN SLS parts were compared. The postprocessing method of infiltrating with epoxy resin was used to reinforce the green SAN SLS parts. The results show that there is little difference in the relative density between the SAN and PS SLS parts, while the flexural strength of the SAN SLS specimens is obviously higher than that of the PS SLS specimens at the same energy density. After the postprocessing, the flexural strength, flexural modulus, and impact strength of the SAN SLS specimens increase by 133%, 4394%, and 254%, respectively, and the SLS parts maintain relatively high-dimensional accuracy although slight shrinkage occurs due to epoxy resin cure. SAN can be used to fabricate SLS parts with more complex and delicate structures.     

Investigation of the tribological properties: Core-shell structured magnetic Ni@NiO nanoparticles reinforced epoxy nanocomposites

Epoxy resin (EP) nanocomposites reinforced with core-shell structured magnetic Ni@NiO nanoparticles (NPs) were fabricated by using a surface wetting method. The mechanical and tribological properties of the varied EP nanocomposites were comparatively investigated. Results revealed that 5 wt.% Ni@NiO NPs was the optimal content for Ni@NiO/EP nanocomposites to achieve the best mechanical and tribological properties. The 5 wt.% Ni@NiO/EP nanocomposites exhibited 37.8%, 16.3% and a 22.2-fold increase in hardness, elastic modulus and wear resistance, respectively. Meanwhile, the effect of Ni@NiO NPs on the tribological properties of Ni@NiO/EP nanocomposites were also investigated by the observations of scanning electron microscopy (SEM).     

Visualization of single-wall carbon nanotube (SWNT) networks in conductive polystyrene nanocomposites by charge contrast imaging

The morphology of conductive nanocomposites consisting of low concentration of single-wall carbon nanotubes (SWNT) and polystyrene (PS) has been studied using atomic force microscopy (AFM), transmission electron microscopy (TEM) and, in particular, scanning electron microscopy (SEM). Application of charge contrast imaging in SEM allows visualization of the overall SWNT dispersion within the polymer matrix as well as the identification of individual or bundled SWNTs at high resolution. The contrast mechanism involved will be discussed. In conductive nanocomposites the SWNTs are homogeneously dispersed within the polymer matrix and form a network. Beside fairly straight SWNTs, strongly bended SWNTs have been observed. However, for samples with SWNT concentrations below the percolation threshold, the common overall charging behavior of an insulating material is observed preventing the detailed morphological investigation of the sample.     

Microscopy and formation of polymer/metal composites

A new class of materials, formed by dispersion of low-melting-point metal alloys in a polymer matrix, has been studied from the point of view of microstructure, interfacial interaction and mechanical properties. The phases in these composites were formed in the same way as for polymer blends and were thus dependent on viscosity ratio, concentration, surface tension and interfacial interactions. Metal alloys of tin and bismuth (Sn/Bi) were mixed with high-density polyethylene (HDPE) and polystyrene (PS) at elevated temperatures. Some preliminary investigations of lead and tin (Pb/Sn) alloys blended with HDPE, PS, polypropylene (PP), polyoxymethylene (POM), polyethylene-terephtalate (PET), polymethylmethacrylate (PMMA), polycarbonate (PC), polyvinylidenefluoride (PVDF) and Polyvinylchloride (PVC) were also undertaken. The composites were characterized by light and electron microscopy, image analysis, electrical conductivity measurements and impact testing. It is shown that the low-melting-point metal alloys can be dispersed in polymers to a submicrometre level by blending. The particle size distribution follows an exponential function, which means that very fine as well as large particles are present. The equilibrium between dispersion and coalescence is very rapidly established during mixing. The average particle size can be controlled by the properties of the matrix, concentration of the metal and processing conditions. An investigation of interfaces revealed that in some cases a chemical interaction between the metal and the polymer can occur. This is apparent by observation of degradation, fluorescence and changes in mechanical properties.     

Effect of nanoclay concentration level on the electrical properties of polypropylene under electron irradiation in a SEM

For studying the electrical properties (charge trapping, transport and secondary electron emission) of the polypropylene‐based nanocomposites with different contents of natural clay, the specimens were submitted to electron irradiation of a scanning electron microscope. A device, suitably mounted on the sample holder of the scanning electron microscope, was used to measure two currents (i.e. leakage and displacement currents) induced in the polypropylene‐based nanocomposites (polymer nanocomposites) under electron irradiation. The evolution of trapped charge during irradiation for each type of studied polymer nanocomposites is deduced. The amount of trapped charge at the steady state is also determined by measuring the change of secondary electron image size associated to the electron trajectory simulation. It is found, surprisingly, that not only the leakage current increases as a function of clay loading level but also trapped charge. However, this could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighbouring materials on the other hand. These two processes play crucial role in controlling the carrier transport (through polymer nanocomposites or/and along its surface) closely related to the charge storage and leakage current. Additional experiment using dielectric spectroscopy were performed to show the effect of clay concentration in changing the dielectric relaxation behaviour and to evidence the existence of interfaces between nanoparticles and polymer. The secondary electron emission during electron irradiation is also studied through the total electron yield that is deduced by correlating the measured leakage and displacement currents.     

Scratch Resistance of New Polystyrene Nanocomposites with Ionic Liquid-Modified Multi-walled Carbon Nanotubes

Multi-walled carbon nanotubes, both neat (MWCNT) and modified (MWCNTm) by the room-temperature ionic liquid (IL) 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIM]BF₄), were added in a 1 wt% to polystyrene (PS) to obtain the new nanocomposites (PS + MWCNT and PS + MWCNTm). Friction coefficients and abrasive wear from instantaneous penetration depth, residual depth and viscoelastic recovery were determined for compression-moulded materials as a function of applied normal load and of the number of successive scratches. The new nanocomposites improve the abrasion resistance of neat PS and of the analogous PS nanocomposites containing neat and IL-modified single-walled carbon nanotubes. The lowest friction coefficient and residual depth values, after 15 scratches, under the whole range of applied loads are obtained for PS + MWCNTm, with maximum reduction under the most severe conditions. The influence of sliding direction with respect to flow was studied for injection-moulded PS + MWCNTm under multiple scratching. The most severe surface damage is observed in the transverse direction to injection flow, while the lowest friction coefficient and the highest abrasion resistance and viscoelastic recovery values are obtained in the direction parallel to injection flow, due to the higher mobility of the polymer chains and the additives. Thermal analysis (DSC and TGA), Raman spectroscopy, transmission electron microscopy, X-ray diffraction and XPS surface analysis have been used as characterization techniques. XPS shows that the IL molecules are present on the nanotube surface. According to TGA, the IL content in MWCNTm can be estimated to be of a 12 wt%. Mechanisms of surface damage are discussed upon scanning electron microscopy, 3-D surface topography, surface roughness and profilometry observations.     

Effect of Molecular Structure on Friction and Wear of Polymer Thin Films Deposited on Si Surface

In this study, the influence of the molecular structure (linear or with bulky side groups) of polymer films covalently attached to Si surface on tribological properties is investigated. Two polymers, PE (polyethylene) and PS (polystyrene), are selected where PE has simple linear molecular structure whereas PS has linear molecular structure but contains bulky benzene groups located at the sides of the linear chain. PE and PS molecules, both with reactive maleic anhydride groups, are chemisorbed onto Si via an intermediate APTMS SAM (3-aminopropyltrimethoxysilane self-assembled monolayer). Water contact angle measurements, AFM (atomic force microscopy), ellipsometry, and XPS (X-ray photoelectron spectroscopy) are used to identify and characterize the polymer films. Tribological properties are studied using a microtribometer where a 4 mm diameter Si₃N₄ ball is used as the counterface. Among the two polymer films investigated, Si/APTMS/PE has shown very low coefficient of friction (0.08) and high wear life (∼4,400 cycles) than those of Si/APTMS/PS. Surprisingly, Si/APTMS/PS did not show any improvement in tribological properties when compared to that of bare Si. The present study proves that the polymer with linear molecular structure without the bulky side groups show good tribological properties even when it is coated as a thin film and hence such polymers can be used as thin-films for reducing friction and wear of substrates such as Si or other materials.     

烧结温度对Al_2O_3/SiC(n)纳米复相陶瓷性能的影响

采用极性分散剂 ,在微米Al2 O3 基体中加入SiC纳米颗粒 ,用真空热压烧结法制备出Al2 O3 /SiC(n)纳米复相陶瓷 ;研究了烧结温度对氧化铝纳米复相陶瓷性能的影响。研究结果表明 :烧结温度的不同使得烧结后Al2 O3 /SiC(n)纳米复相陶瓷的所得相和力学性能都有较大差异     

UHMWPE Hybrid Nanocomposites for Improved Tribological Performance Under Dry and Water-Lubricated Sliding Conditions

To tap the full potential of polymers to be used as tribo-materials under water lubrication, it is very important to improve their resistance to water uptake on the one hand and improve their strength and load bearing capacity on the other so that their performance under these conditions is not deteriorated. Hence, a unique approach of fabricating a hybrid polymer nanocomposite reinforced with nanoclay for improving the resistance to water uptake and carbon nanotubes (CNTs) to improve the mechanical/tribological properties is undertaken. Ultrahigh molecular weight polyethylene (UHMWPE) hybrid nanocomposites were fabricated via ball milling followed by hot pressing method. Functionalized multi-wall CNTs and C15A organoclay were used as nanofillers in UHMWPE matrix. Hybrid nanocomposites were developed with CNT loadings of 0.5, 1.5 and 3.0 wt% while keeping C15A organoclay content fixed at an optimized value of 1.5 wt%. Initially, the hybrid nanocomposites were optimized under dry sliding conditions whereby a loading of 1.5 wt% of CNTs and 1.5 wt% C15A organoclay resulted in the maximum reduction in the specific wear rate by about 64% as compared to pristine UHMWPE. Later, tribological performance of the optimized hybrid nanocomposite was compared with pristine UHMWPE and its UHMWPE nanocomposites under water-lubricated conditions sliding against a 440C stainless steel ball for 150,000 cycles. The specific wear rate showed a reduction by ~46% for the 1.5 wt% CNTs hybrid nanocomposites as compared to pristine UHMWPE under water lubrication. The improved resistance to wear was attributed to the uniform dispersion of both the nanofillers, namely CNTs and C15A organoclay which effectively increased the load bearing capacity of UHMWPE. Moreover, the excellent barrier properties of the platelet-like structure of C15A clay which presented a torturous path for the diffusion of the water molecule in UHMWPE reduced the softening of the surface layer leading to better resistance to wear under water lubrication.