Effect of Abrasives on Three-Body Abrasive Wear Behaviour of Particulate-Filled Polyamide66/Polypropylene Nanocomposites

Polyamide66/polypropylene (PA66/PP) blend, graphite (Gr)-filled PA66/PP composite and nanoclay (NC)-filled PA66/PP nanocomposites were prepared by twin screw extrusion and injection molding. Three-body abrasive wear behaviour of the injection moulded composites was carried out using a rubber wheel abrasion wear tester. In this study, angular silica sand and quartz particles of size ranging from 200 to 250 μm were used as dry and loose abrasives. The tests were carried out for 150, 300, 450 and 600 m abrading distances at a constant load of 36 N. It was observed that inclusion of particulate fillers in PA66/PP have significant influence on wear under varied abrading distances for different abrasive particles. Further, it was found that NC-filled PA66/PP nanocomposite exhibited lower wear rate compared to Gr filled ones for different abrasive particles. In addition, the worn surfaces of the samples were examined by scanning electron microscopy (SEM) and the morphology was also discussed.     

Effects of the Synergy of Hardness and Resilience on the Akron Abrasion Properties of SBR Vulcanizates

The hardness (H) and resilience (R) of rubber vulcanizates were combined together in this paper, named as hardness–resilience product (H⁴R), and its relationship with the Akron abrasion loss was investigated using various styrene-butadiene rubber (SBR) vulcanizates possessing specific hardness and resilience characteristics as samples. For the unfilled SBR vulcanizates with different chain microstructure, possessing high elastic resilience and low hardness, the results showed that their Akron abrasion loss had a good linear relationship with the log(H⁴100R). This linear relationship also occurred when these SBRs were filled with 50 phr carbon black. For two particular types of SBR, after being filled with different fractions of carbon black and aged for different times, all their Akron abrasion losses (including unaged, aged for 24 h, and aged for 48 h) also had a good linear relationship with the log(H⁴100R). However, this linear relationship weakened for one of the SBRs after being aged for 48 h. In the high H⁴R region (the carbon black fractions being 60 and 70 phr), the data obviously deviated from the fitting curve due to the high hardness of the aged vulcanizates. However, after being filled with 50 phr of various kinds of carbon blacks, the relationships between abrasion loss and log(H⁴100R) were also approximately linear, with the correlation coefficient of the fitting curves being 0.99966 and 0.99878, respectively, for the two types of SBR.     

Effect of montmorillonite on abrasion resistance of SiO2-filled polybutadiene

The effect of organically modified montmorillonite (OMMT) and silane coupling agent on the abrasion resistance of SiO₂-filled butadiene rubber (BR) vulcanizates has been investigated. Various amounts of OMMT are added into SiO₂-filled BR vulcanizates. A silane coupling agent, bis-(3-triethoxysilyl propyl) tetrasulfide (Si69), is used to modify OMMT during the masterbatch preparation for evaluating the influence of surface treatment on the abrasion resistance. Incorporation of OMMT into BR results in deterioration of the abrasion resistance as compared to unfilled BR vulcanizate due to poor dispersion of OMMT and insufficient interfacial adhesion between OMMT and BR matrix. The use of Si69 improves dispersion of OMMT particles and rubber/OMMT adhesion, resulting in abrasion resistance enhancement of BR/OMMT vulcanizates. By using similar compounding conditions as those for BR/OMMT vulcanizate, nanodispersion of OMMT in BR/SiO₂/OMMT vulcanizate has been achieved as judged by the high viscosity of the SiO₂-filled BR compound. This improved dispersion leads to better abrasion resistance of the BR/SiO₂/OMMT than that of the BR/SiO₂ composite. Utilization of Si69 slightly affects the DIN volume loss of BR/SiO₂/OMMT vulcanizates and the abrasion pattern.     

单点金刚石车削加工切削距离的计算

讨论了大型金属反射镜在金刚石车削中,金刚石刀具的磨损对加工精度的影响;详细介绍了超精密加工中几种典型零件形状单点金刚石车削加工的切削距离计算方法,经计算在加工直径为1000mm的圆盘工件时,当刀具的进给量为2μm/r,切削距离达到近400km。通过计算为加工大型光学元件刀具磨损规律的研究提供分析基础。     

Styrene Butadiene Rubber/Epoxidized Natural Rubber (SBR/ENR50) Nanocomposites Containing Nanoclay and Carbon Black as Fillers for Application in Tire-Tread Compounds

Nanocomposite vulcunizates based on a SBR/ENR50 (50/50%wt) rubber blend containing nanoclay (5 or 10 phr) with and without carbon black (CB 20 phr) were prepared by melt blending in an internal mixer. The compound containing 35 phr carbon black (only) was prepared as a reference sample. Microstructure of nanocomposite samples was investigated by using X-ray diffraction (XRD), melt rheo-mechanical spectroscopy (RMS), and scanning electron microscopy (SEM). The XRD patterns revealed that the distance between the clay layers were increased by adding CB to the nanocomposite samples; they caused better diffusion of chains between the layers and resulted in an intercalated structure. The RMS results also indicated the formation of the filler-filler networks. SEM images of fracture surfaces showed the presence of much roughness in the samples containing both nanoclay and CB compared to the other samples. The results obtained from application of the Flory–Rhener equation showed a high crosslink density for the sample with 10 phr nanoclay and 20 phr CB. Dynamic mechanical behavior, mechanical properties, and abrasion resistance of the nanocomposites were evaluated. The results indicated that the sample containing 10 phr nanoclay and 20 phr CB had an increased dynamic elastic modulus, reduced maximum loss factor (tanδ)_max,, and an improved tensile strength and abrasion resistance compared to the reference sample. Also, this sample showed the lowest maximum loss factor, at 50–60°C, so it can be a candidate for tire-tread application.     

The Abrasion Behavior and Mechanisms of a Superhydrophobic Surface Comprising Styrene Butadiene Rubber

The microprotuberances of superhydrophobic surfaces are easily destroyed during a friction cycle, resulting in invalidation of superhydrophobicity, because they are then loaded with pressure and shearing stress. Thus, the abrasion-resistance of superhydrophobic surfaces is the main barrier preventing their wide application. Elastic microprotuberances will be compressed and collapsed by elastic deformation to avoid being broken during a friction cycle, and the deformation will rebound to renew the original surface structure when the load is withdrawn. A superhydrophobic surface comprising styrene butadiene rubber (SBR) was fabricated via template replication in the research described here, with a water contact angle up to 160°. Friction testing was then used to characterize the abrasion resistance of the surface; the contact angle remained more than 139° even after being loaded with 4.4 KPa or 6.87 KPa and rubbed by a smooth metal surface at 18 cm/s for 10,000 times. Scanning electron microscopy was used to characterize the change of morphology before and after the friction testing and to explain the abrasion mechanism.     

Taguchi approach for characterization of three-body abrasive wear of carbon-epoxy composite with and without SiC filler

Fiber–matrix interfacial bonding plays a critical role in controlling performance properties of polymer composites. Carbon fibers have major constraints of chemical inertness with the matrix and need the surface treatment to improve the adhesion with the matrix. In this work, parametric appraisal of three-body abrasive wear behavior was presented for silane treated carbon fabric reinforced epoxy (C-E) composites with and without silane treated silicon carbide (SiC) as filler. The fiber content was fixed at 60?wt.%, while the weight fraction of SiC was varied (5 and 10?wt.%) to obtain three different compositions. Three-body abrasive wear tests were conducted using design of experiments approach based on Taguchi’s orthogonal arrays. The findings of experiments indicate that the wear loss is greatly influenced by load and grain size of abrasive. An optimal parameter combination was determined, which leads to maximization of abrasion resistance. Inclusion of SiC filler reasonably increased the abrasion resistance of C-E composite. Analysis of variance results showed that the load significantly influenced the abrasion of SiC filled C-E composites. Efforts were also made to correlate the abrasive wear performance of SiC filled C-E composites using artificial neural network (ANN). The wear behavior of composite by ANN prediction closely matched the experimental results and finally, optimal wear settings for minimum wear were identified.     

Carbon Black–Filled Styrene Butadiene Rubber Masterbatch Based on Simple Mixing of Latex and Carbon Black Suspension: Preparation and Mechanical Properties

An improved process was developed for the production of carbon black (CB)–filled styrene butadiene rubber masterbatch (SBR-CB-MB) using a simple latex/CB mixing technology; the improvement comprised processing the CB as an emulsifier-free aqueous suspension by high-rate shearing. Tensile and tear strength, dynamic compression behaviors, the Payne effect, equilibrium swelling and bound rubber of the SBR-CB-MB and dry mixing CB filled SBR (SBR-CB-DM), covering a wide range of CB loading (45–70 phr), were investigated and compared. It was found that the tensile and tear strength, heat buildup and compression set, abrasion volume loss, and the Payne effect of the SBR-CB-MB were lower than those of the SBR-CB-DM, while the bound rubber content were higher, indicating good CB/rubber interaction in the SBR-CB-MB. SEM analysis showed that no free CB could be found on the surface or inside of the granular SBR-CB-MB particles, indicating good CB dispersion in the rubber matrix.     

Preparation and Properties of Organically Modified Montmorillonite/Nitrile Rubber Nanocomposites

A series of organically modified montmorillonite (OMMT)/nitrile rubber (NBR) nanocomposites were prepared by a simple mechanical-mixing method. The structures of OMMT and the dispersion of OMMT in the rubber matrix were detected by X-ray diffraction (XRD). The mechanical properties of the NBR/OMMT nanocomposites were characterized, and the tribological behaviors of the nanocomposites were evaluated on a ring-block (MRH-3) wear tester. The results showed that the OMMT was homogeneously dispersed in the NBR matrix. The tensile strength of the OMMT/NBR nanocomposites increased with increasing OMMT contents. Both the coefficient of friction (COF) and wear of the nanocomposites decreased remarkably with increasing OMMT content. In addition, the influence of the applied load on the tribological properties of the nanocomposites is discussed. It is expected that the research may be of aid in the rational design and use of solid, self-lubricating nanocomposites under different loading states.     

损耗对串联双微环谐振器滤波特性的影响

对存在光损耗的串联双微环谐振器的滤波特性进行了研究.在理想耦合条件下,当环间耦合系数确定时,分析了光损耗的大小对主谐振峰的透过率、带宽、形状因子,以及伪模峰值透射率的影响,揭示了光损耗对滤波特性影响的规律.分析结果表明:主谐振峰和伪模的透射率随损耗的增大而下降,环与直波导间的耦合系数随损耗的增大而变小,而带宽和形状因子无明显变化|有损耗时环与直波导间的耦合系数不能过大也不能过小.     

Interactions Between an Ionic Liquid and Silica,Silica and Silica,and Rubber and Silica and Their Effects on the Properties of Styrene-Butadiene Rubber Composites

An investigation of the effect of an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (BMI), on the properties of silica reinforced styrene-butadiene rubber (SBR), aimed to correlate the interactions between the ionic liquid and silica, silica and silica, and silica and rubber with the macro-properties and microstructure of SBR and SBR/silica vulcanizates is described. The interaction between the ionic liquid and silica was characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), the interaction between silica and silica was characterized by a rubber processing analyzer (RPA), and the interaction between rubber and silica was characterized by the bound rubber content. The FTIR analysis revealed that BMI can react with the hydroxyl groups on the surface of silica, improving the compatibility between the rubber and silica. The RPA and bound rubber testing indicated that the interactions between silica and silica particles were weakened and the interaction between silica and rubber increased with the incorporation of BMI into the SBR rubber. The bound rubber content showed a maximum with a BMI content of 3 phr. At the same time, the dispersion of silica in SBR was improved with the incorporation of BMI. With the increase of BMI content, the curing rate was greatly improved and the crosslink density increased. BMI also increased the tensile strength and abrasion resistance of the SBR vulcanizates. Most important, the BMI significantly improved the dynamic properties of the rubber composites, especially the wet-skid resistance and rolling resistance. However, excessive BMI (beyond 3 phr) acted as a plasticizer and was detrimental to the mechanical properties, resulting in a decrease of tensile strength and abrasion resistance.     

基于CRDS系统对北京夜间大气边界层NO_3自由基观测与分析

夜间大气NO3自由基的氧化能力相当于白天OH自由基,鉴于NO3自由基在大气反应过程中的关键作用,准确测量其浓度及研究其夜间大气化学过程具有重大意义。采用以二极管激光器为光源(中心波长为662nm,半高宽0.3nm),两块高反射率镜片(R≥99.998 5%)形成的腔体为光学共振腔,有效光程达到约20km的腔衰荡光谱系统(CRDS)对夜间大气NO3自由基进行测量,并且针对秋冬季交通繁忙区域夜间大气边界层NO3自由基化学过程进行研究。采用该系统于2014年10月29日—11月15日在北京市中国科学院大学校园开展了NO3自由基连续外场观测实验,观测期间NO3自由基浓度相对较低,最大浓度约为50pptv,平均值为10pptv。并结合NO2,NO和O3等相关辅助数据对测量结果进行分析,分析表明在观测期间NO3自由基产率为0.04~1.03pptv·s-1,平均寿命约为68s。并且近一步分析了观测期间大气NO3自由基损耗途径,探讨了不同湿度及颗粒物浓度对其损耗的影响。即观测期间当大气中RH≥60%,PM2.5浓度大部分大于60μg·m-3时,ln(τss(NO3))与ln(NO2)的相关性达到0.79,大气中NO3自由基损耗主要以间接为主;然而在RH≤40%,PM2.5浓度大部分小于60μg·m-3时,因测量点靠近国道受局地污染源影响,直接损耗较显著;当大气中40%RH60%时,直接损耗与间接损耗途径都存在且不可忽视。     

Dielectric permittivity of nickel ferrites at microwave frequencies 1 MHz to 1.8 GHz

NiFe₂O₄ prepared via the sol–gel technique were pre-sintered at 900 °C and synthesized at different sintering temperatures from 1,000 °C to 1,200 °C at 100 °C intervals. The samples were characterized for microwave dielectric properties. These samples were measured using Agilent Impedance/Material Analyzer at frequencies 1 MHz to 1.8 GHz. Results showed a decrease in the dielectric constant and loss factor with frequency except at the turning point, around 150 MHz, where the loss factor showed a gradual increase. However, both the dielectric constant and loss factor increase with increasing sintering temperature. The grain size and density also increased with increasing sintering temperature, but the porosity and grain boundary density showed a decrease. This paper was presented at the International Conference on Solid State Science and Technology 2006, Kuala Terengganu, Malaysia, Sept. 4–6, 2006.     

Abrasive wear on the atomic scale

A scanning force microscope in ultrahigh vacuum has been used to realize and detect atomic-scale abrasion on KBr(001). The continuous time evolution of the lateral force under scratching reveals that the wear mechanism is due to the removal and the rearrangement of single ion pairs. The debris is reorganized in regular terraces with the same periodicity and orientation as the unscratched surface, as in local epitaxial growth. The applied load has a strong influence on the abrasive process, whereas the scan velocity is less relevant.     

Influence of Carbon Black on Crosslink Density of Natural Rubber

Vulcanization and reinforcement are two important factors contributing to the properties of vulcanized rubber. In order to investigate the influence of carbon black (CB) on chemical crosslinking, three groups of samples with different crosslink densities were prepared. In each group with the same crosslink density, different amounts of CB were introduced. Data fitting showed that delta torque (ΔM = M _H–M _L, the difference between the highest and lowest torques during curing) in the cure curves of each group had a good linear relationship with CB load and extrapolation of the fitting lines almost intercepted the x coordinate at the same value, which indicated that CB had no influence on the chemical crosslinking of the rubber. To verify the above result, a series of nonfilled natural rubber (NR) vulcanizates with different crosslink densities were studied using equilibrium swelling and the swelling ratios were compared with those of corresponding CB filled rubbers with the same sulfur and accelerator amount. The results of both the equilibrium swelling and NMR relaxation parameter measurements showed that CB filled vulcanizates had higher apparent crosslink densities than those of unfilled ones due to the strong interaction between rubber molecules and the surface of the CB particles. The swelling ratios of filled rubbers had a parallel relationship with those of the unfilled ones which indicated that CB had little influence on chemical crosslink density introduced by chemical vulcanization.     

负载回路电感对低阻抗脉冲形成线输出波形的影响

 介绍了一个基于带状脉冲形成线的低阻抗实验平台,针对该平台设计了两种不同类型结构的匹配负载,并分别进行了实验研究,得到了不同的输出脉冲波形,发现轨道结构的水负载具有很低的负载回路电感,适于作为低阻抗脉冲形成线的匹配负载。实验结果表明：在开关电感一定的情况下,负载回路电感是影响低阻抗形成线输出波形的决定性因素。对于0.5 Ω的带状脉冲形成线,只有将负载回路电感控制在30 nH以内,才能获得波形较好的输出脉冲,高压实验结果也验证了此结论。利用数值模拟的方法,分析了负载回路电感对不同阻抗形成线输出波形的影响,结果表明：随着形成线阻抗的增加,负载回路电感对波形的影响越来越小。     

Ⅰ层厚度对限幅器热损伤效应的影响

基于器件物理模拟分析法研究PIN限幅器二极管的微波脉冲热效应,利用Sentaurus-TCAD仿真器建立了PIN二极管二维多物理场仿真模型,研究了在5.3,7.5,9.4 GHz的微波脉冲作用下,不同Ⅰ层厚度的二极管模型的峰值温度变化。仿真结果表明：Ⅰ层厚度对PIN二极管微波脉冲热效应的影响分两个阶段,拐点前厚度增加,峰值温度提高,拐点后厚度增加峰值温度降低;一定范围内微波脉冲频率的变化对拐点影响不明显。     

负载回路电感对低阻抗脉冲形成线输出波形的影响

介绍了一个基于带状脉冲形成线的低阻抗实验平台,针对该平台设计了两种不同类型结构的匹配负载,并分别进行了实验研究,得到了不同的输出脉冲波形,发现轨道结构的水负载具有很低的负载回路电感,适于作为低阻抗脉冲形成线的匹配负载。实验结果表明：在开关电感一定的情况下,负载回路电感是影响低阻抗形成线输出波形的决定性因素。对于0.5 Ω的带状脉冲形成线,只有将负载回路电感控制在30 nH以内,才能获得波形较好的输出脉冲,高压实验结果也验证了此结论。利用数值模拟的方法,分析了负载回路电感对不同阻抗形成线输出波形的影响,结果表明：随着形成线阻抗的增加,负载回路电感对波形的影响越来越小。     

负载不匹配对大功率速调管输出特性的影响

采用微波等效电路和3维电磁场计算软件研究了负载不匹配对大功率速调管输出腔的谐振频率、间隙阻抗和外观品质因数的影响。并采用1维大信号计算软件研究了负载不匹配对速调管效率的影响。对C波段速调管的研究表明：对于单间隙输出腔,负载不匹配对谐振频率影响较小,对间隙阻抗和等效外观品质因子影响较大,当负载驻波比为1.5时,谐振腔的谐振频率变化约35 MHz,间隙阻抗实部最大值变化为3 660~7 998 Ω,等效外观品质因子变化为36.9~93.5,中心频率处的效率下降4.6%。对于滤波器加载输出电路,负载不匹配对阻抗-频率特性和效率-频率特性有较大影响,当负载驻波比为1.5时,中心频率处的效率下降11.2%。当负载驻波比小于1.2时,负载失配对速调管性能的影响较小。     

深海不完整声道下反转点会聚区研究

近期南海远程声传播实验数据的处理分析表明在深海不完整声道中声道轴以下存在一种会聚区,该会聚区相比于海面附近的上反转点会聚区在远距离处具有更高的会聚增益.本文利用射线简正波理论确定了水中反转型焦散线和海面反射型焦散线位置,对比发现实验中观测到的深海大深度会聚区位置与水中反转型焦散线位置一致,证明该会聚区是由大量简正波同相...