Tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced PTFE-PPS composites in sliding system

Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.

Influence of current density on nano-Al_2O_3/Ni+Co bionic gradient composite coatings by electrodeposition

Metal and nano-ceramic nanocomposite coatings were prepared on the gray cast iron surface by the electrodeposition method. The Ni-Co was used as the metal matrix,and nano-Al2O3 was chosen as the second-phase particulates. To avoid poor inter-face bonding and stress distribution,the gradient structure of biology materials was found as the model and therefore the gradient composite coating was prepared. The morphology of the composite coatings was flatter and the microstructure was denser than that of pure Ni-Co coatings. The composite coatings were prepared by different current densities,and the 2-D and 3-D morphologies of the surface coatings were observed. The result indicated that the 2-D structure became rougher and the 3-D surface density of apices became less when the current density was increased. The content of nanoparticulates reached a maximum value at the current density of 40mA·cm^-2,at the same time the properties including microhardness and wear-resistance were analyzed. The microhardness reached a maximum value and the wear volume was also less at the current density of 40mA·cm^-2. The reason was that nano-Al2O3 particles caused dispersive strengthening and grain refining.

Ni-P/nano-Al_2O_3复合镀层的制备及性能

以汽车模具配件—导柱常用的20Cr钢为基材,在其表面制备Ni-P/nano-Al_2O_3复合镀层及普通Ni-P镀层。对Ni-P/nano-Al_2O_3复合镀层的微观形貌、晶相结构、显微硬度和摩擦磨损性能进行了测试与分析,并与Ni-P镀层和基材进行了对比。结果表明,Ni-P/nano-Al_2O_3复合镀层的晶粒细小,结构更加致密,显微硬度平均值可达到436.4 HV,高于Ni-P镀层的357.3 HV和基材的190HV;与Ni-P镀层相比,Ni-P/nano-Al_2O_3复合镀层能更有效地改善基材的摩擦磨损性能。NanoAl_2O_3颗粒复合量对Ni-P/nano-Al_2O_3复合镀层的显微硬度和摩擦磨损质量损失率有一定影响,增加颗粒复合量可以提高复合镀层的显微硬度,改善其摩擦磨损性能。

纳米Al_2O_3改性变压器绝缘纸性能的研究

为了研究纳米Al2O3改性绝缘纸的绝缘性能,实验室制备了含不同质量分数的纳米Al2O3绝缘纸手抄片,并对真空浸油后的绝缘纸性能进行了测试。结果表明在一定的质量分数内纳米Al2O3改性后的绝缘纸的工频击穿场强得到较大的提高,在质量分数为1%时,工频击穿场强提高了12.75%,绝缘纸的抗张强度增加了14.13%;在1%的添加量内绝缘纸的介电常数、介电损耗都随纳米Al2O3含量的增加而减小。

Morphology and Mechanical Properties of PS/Al_2O_3 Nanocomposites Based on Selective Laser Sintering

Selective laser sintering （SLS） is a new process to prepare the polystyrene （PS）/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density and mechanical properties of the sintered specimens were investigated. It was found that nano-sized inorganic particles are uniformly located in the PS matrix and the maximum density of the sintered specimens with pure PS powder reaches 1.07 g/cm^3, higher than 1.04 g/cm^3 that of the sintered specimens with mixture powder. Due to strengthening and toughness of the nano-sized Al2O3 inorganic particles, the maximum notched impact strength and tensile strength of the sintered part mixed with nano-sized inorganic particles are improved greatly from 7.5 to 12.1 kJ/m^2 and from 6.5 to 31.2 MPa, respectively, under the same sintering condition.

Effect of Al2O3np on the Properties and Microstructure of B4Cp/Al Composites

Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.

Characteristics and properties of SiO_2-Al_2O_3/EP-PU composite

SiO2-Al2O3/EP-PU nanocomposites, which contained polyurethane(PU) flexible chain, were prepared via epoxy resin, PU and modified silica and alumina particles. Silica and alumina particles were modified by coupling agents KH-560 and KH550, respectively. EP-PU was used as matrix, PU as toughening agent, Si O2-Al2O3 as filled and MTHPA as curing agent. The mass ratio of PU was 30% in this system. The chemical structure of the products was confirmed by FT-IR measurements, the morphological structure of fracture surface and the surface of the hybrid materials were observed by scanning electron microscope(SEM) and transmission electron microscope(TEM), and shearing strength and breakdown field were measured, respectively. When the mass fraction of inorganic component was 10% and the mass ratio of Si O2 to Al2O3 was 4.5:5.5, shearing strength of Si O2-Al2O3/EP-PU was 28.5 MPa and breakdown field was 15 k V/mm, the data could meet the property requirement of insulating material.

Hydrolyzed Al(Ⅲ) clusters:Speciation stability of nano-Al_(13)

Pure nano-All3 and aggregates at various concentrations were prepared to examine the particle size effect of coagulation with inorganic polymer flocculant. The property and stability of various species formed were characterized using Infrared, 27Al-NMR, photo correlation spectroscopy （PCS）, and Ferron assay. Results showed that concentration and temperature exhibited different roles on the stability of Al13. The quantity of Alb species analyzed by ferron assay in the initial aging period corresponded well with that of Al13, which has been confirmed in a dimension range of 1-2 nm by PCS. Al13 solutions at high concentrations （0.5-2.11 tool/L） were observed to undergo further aggregation with aging. The aggregates with a wide particle size distribution would contribute to the disappeared/decreased Al13 basis on the eTA1-NMR spectrum, whereas a part of Al13 would still remain as Alb. At low concentrations, All3 solution was quite stable at normal temperature, but lost its stability quickly when heating to 90~C.