碳纤维和纳米氮化硼增强聚醚醚酮/聚四氟乙烯复合材料的摩擦学性能研究

以碳纤维（CF）为增强相,添加不同含量的纳米氮化硼（h-BN）,通过注塑成型的方式,制备了聚醚醚酮/聚四氟乙烯（PEEK/PTFE）复合材料样条,使用力学试验机进行拉伸试验,利用摩擦试验机进行表面摩擦试验,并利用白光仪对磨痕数据和三维形貌进行观测,使用SEM对磨痕进行观测与分析。结果表明：随着h-BN含量的增加,PEEK/PTFE复合材料样条最大应力先增加后减小;当h-BN含量分别为3%、6%时,PEEK/PTFE复合材料样条的最大应力分别为174 MPa、165 MPa。与PEEK/PTFE相比,单独添加CF的样品摩擦系数降至0.23。同时添加CF、h-BN时,复合材料样条的摩擦系数均降低;h-BN含量分别为3%、6%时,复合材料样条的摩擦系数分别为0.06、0.09。随着h-BN含量的升高,PEEK/PTFE/CF/h-BN复合材料的磨损率先降低后升高。h-BN含量为3%时,复合材料样条的磨损率最低。     

ZTA纳米复相陶瓷的研究

综述了近年国内外对ZTA纳米复相陶瓷材料力学性能及影响因素、内部结构、制备工艺及强韧化机理等方面的研究结果.     

复凝聚法制备壳聚糖/海藻酸钠纳米香精胶囊

以壳聚糖和海藻酸钠为壁材,古龙香精为芯材,在高速乳化条件下,通过复凝聚方法制备了纳米香精胶囊。研究了助凝聚剂种类、交联剂种类以及交联固化温度对香精胶囊的形状、尺寸及分布的影响。应用TEM和激光粒度分析仪对香精胶囊的粒子尺寸、形态及分布进行了表征。结果表明,以TPP和CaCl2为助凝聚剂、以戊二醛为交联剂、在35℃条件下能制备出球型规整、粒径均匀、干态尺寸约为80nm、湿态尺寸约为160nm的纳米级香精胶囊。热重分析表明纳米香精胶囊的热分解起始温度大于200℃,具有良好的热稳定性。UV-Vis测试表明,纳米香精胶囊的装载量为34.3%,包埋率为87.2%。     

湿法/干法共混制备石墨烯/炭黑/丁腈橡胶纳米复 合材料

采用湿法/干法两步共混的方法制备了石墨烯/炭黑/丁腈橡胶纳米复合材料。将二维纳米片层状石墨烯与炭黑形成共增强体系,提高丁腈橡胶的力学性能及耐磨性。选用质量比分别为1/39、2/38、3/37、4/36和5/35石墨烯/炭黑对丁腈橡胶进行增强,采用橡胶加工分析仪研究了复合材料的动态力学性能。结果表明,石墨烯和炭黑与橡胶基体之间形成二次网络结构,使得橡胶的储能模量呈增加趋势。当石墨烯/炭黑的质量比为4/36时,储能模量显著提高,拉伸强度为26.59 MPa,Arkon耐磨指数达到319.1%,综合性能优异,增强效果最佳。     

聚乙烯醇/水杨酸/纳米二氧化钛复合水凝胶膜的制备及性能

用纳米二氧化钛(nano-TiO_2)对聚乙烯醇/水杨酸(PVA/SA)水凝胶膜进行改性,考查了不同nano-TiO_2用量的PVA/SA/nano-TiO_2复合水凝胶膜的结构与性能。结果表明:复合膜的透明度随nano-TiO_2用量的增加而降低,而其抗菌性、抗紫外线性及透气性均随nano-TiO_2用量的增加而提高;复合膜的力学性能随nano-TiO_2用量的增加呈先上升后下降的趋势,而其溶胀性却恰好与之相反;当nano-TiO_2用量为5.0%时,复合水凝胶膜的透气系数为0.737 9 m~2/(s·kPa),拉伸强度为8.44 MPa,最大紫外线透过率仅为71.12%,透光率达69.08%,对大肠杆菌与霉菌均具有较好的抑制作用,15℃时溶胀度达19.41%。     

复凝聚法制备壳聚糖/海藻酸钠纳米香精胶囊

以壳聚糖和海藻酸钠为壁材,古龙香精为芯材,在高速乳化条件下,通过复凝聚方法制备了纳米香精胶囊。研究了预交联剂种类、交联剂种类以及交联固化温度对香精胶囊的形状、尺寸及分布的影响。应用TEM和激光粒度分析仪对香精胶囊的粒子尺寸、形态及分布进行了表征。结果表明,以TPP和CaCl2为预交联剂、以戊二醛为交联剂、在35℃下能制备出球形规整、粒径均匀、干态尺寸约为80 nm、湿态尺寸为160 nm的纳米级香精胶囊。热重分析表明,纳米香精胶囊的热分解起始温度大于200℃,具有良好的热稳定性。UV-Vis测试表明,纳米香精胶囊的装载量为34.3%,包埋率为87.2%。     

基于缺陷MoS2构筑高强度、自修复纳米复合水凝胶的研究

通过巯基修饰表面富含缺陷的花状MoS₂纳米微球,设计出多功能纳米复合交联剂。在单体、多功能的纳米复合交联剂、引发剂和催化剂等条件下,通过自由基原位聚合制备出高强度、自修复纳米复合水凝胶。结果表明,该水凝胶断裂应变为2 297%,断裂强度达到2.87 MPa,是传统化学交联水凝胶的664.35%和1 001.16%,是不含巯基修饰的MBA-MoS₂-PAM纳米复合水凝胶的99.1%和212.64%;该材料可以在近红外光诱导下实现96%的自修复效率。     

热压温度和时间对Fe3Al/Al2O3纳米复相陶瓷结构和性能的影响

以自制的纳米晶Fe3Al(有序DO3结构)为增强相,纳米粉Al2O3为基体相,采用热压烧结制备了Fe3Al/Al2O3纳米复相陶瓷,研究了热压温度和时间对复相陶瓷显微结构和力学性能的影响。结果表明:复相陶瓷的相组成为Fe3Al和Al2O3。热压温度为1400℃时,部分晶粒尺寸从0.5μm增大到1μm,板片状Al2O3晶粒消失;热压时间为60min时,晶粒尺寸趋于一致,为1μm左右,呈现出较致密的准球形堆积状态。随着热压温度的升高或热压时间的延长,复相陶瓷的相对密度、Vickers硬度和断裂韧性均有不同程度的提高,最大值分别为93.31%,975MPa和8.30MPa·m1/2。对显微硬度压痕裂纹进行扫描电镜观察和分析表明:材料断裂韧性的提高,是通过对裂纹的偏转和吸收、超细晶韧化和Fe3Al的补强和增韧等方式进行的。     

Si3N4-TiN纳米复相陶瓷的制备与性能研究

采用热压烧结方法制备了Si3N4-TiN纳米复相陶瓷,研究了纳米TiN颗粒的添加对Si3N4陶瓷组织、力学性能和抗热震性能的影响.研究结果表明:Si3N4-TiN纳米复相陶瓷的显微组织由粒径为100 nm左右的晶粒构成,TiN以独立颗粒的形式存在;纳米TiN颗粒的添加可以提高纳米Si3N4陶瓷的断裂韧性和抗弯强度,但对硬度影响不大;适量TiN颗粒的添加能改善纳米Si3N4陶瓷的抗热震性.     

由酚醛树脂基板CO2活化法制备高性能活性炭

采用CO2活化法以阻燃的FR-1型酚醛树脂基板为原料制备出性能优良的活性炭。研究了活化温度、活化时间和气体流量对产品性能的影响。所得产品BET比表面积达到1 198 m2/g,总孔体积达到0.703 cm3/g。在最佳条件,即活化温度910℃,活化时间140 min和CO2流量350 cm3/min时,亚甲基蓝值和碘值分别达到292.0 mg/g和1 113.05 mg/g,均达到国家一级品标准。     

由酚醛树脂基板C02活化法制备高性能活性炭

采用CO2活化法以阻燃的FR-1型酚醛树脂基板为原料制备出性能优良的活性炭。研究了活化温度、活化时间和气体流量对产品性能的影响。所得产品BET比表面积达到1198m^2／g,总孔体积达到0．703cm^3／g。在最佳条件,即活化温度910℃,活化时间140rain和CO2流量350cm。／min时,亚甲基蓝值和碘值分别达到292．0mg／g和1113．05mg／g,均达到国家一级品标准。     

Fatigue fracture behaviour of PEEK: 2. Effects of thickness and temperature

Experimental results on the effects of specimen thickness and environmental temperatures on fatigue fracture behaviour of poly(ether ether ketone) (PEEK) are reported. Low cycle fatigue experiments are conducted on injection moulded single-edge notched specimens of 1.57, 2.70 and 5.42 mm in thickness at ambient temperatures, and on specimens 2.70 mm thick at environmental temperatures of 39, 50, 63, 75 and 100°C. In all the thickness experiments and in the experiments with temperatures of 39 and 50°C, the crack tip profile is initially round. At long crack lengths the crack tip profile changes to a triangular shape. When the test temperature is 63, 75 and 100°C, the crack tip remains round throughout the fracture process. The crack tip angle is primarily dependent upon the test temperature. Examinations of the fracture surfaces and transverse sections indicate that in the thickest specimen, relatively rough fracture surfaces are observed and a few discontinuities (crazes or cracks) underneath the main crack path. Thus, crack propagates in a ‘brittle’ manner. In all other experiments both ‘brittle’ and ‘ductile’ modes of fracture are observed. The point of transition from ‘brittle’ to ‘ductile’ fracture is dependent upon the specimen thickness and test temperature. Fatigue striations are seen throughout the fracture surfaces. Correlation of the striations and the number of cycles indicates a one-cycle crack growth mode. Hysteretic losses during fatigue crack growth are negligible until a few cycles prior to unstable fracture. Crack opening displacements are independent of the specimen thickness and increase with rise in temperature. When crack growth rates are correlated with the elastic energy release rate, they are independent of specimen thickness and increase with increase in temperature.     

低温环境下PEEK/CF复合材料结构和性能研究进展

分析了碳纤维(CF)增强聚合物(CFRP)复合材料特别是CF增强聚醚醚酮(PEEK/CF)复合材料在新一代可重复使用航天运载器(RSLVs)低温燃料贮箱上应用的优势,并根据RSLVs低温燃料贮箱对材料的要求,介绍了低温环境及低温-室温热循环处理对PEEK/CF复合材料内部结构、气体渗透性能和力学性能影响的研究进展.在此...     

Static and Cyclic Fatigue of Alumina at High Temperatures

Fatigue behavior of alumina at 1200°C was investigated. Uniaxial tensile tests were conducted in both static and cyclic loading. A variety of loading wave forms were applied during the cyclic tests. Cyclic lifetime is found to be cycle shape dependent and controlled by the duration of the hold time at the maximum tensile stress in a cycle. Cyclic loading with a higher strain rate and a short duration of maximum stress during each cycle provides a beneficial effect on lifetime in comparison to static loading at the same maximum stress. The time to failure for cyclic loading with a longer hold time at maximum stress is very close to the static loading lifetime. Viscous boundary phase may be the primary contributor to the improved cyclic fatigue resistance for cyclic loading with a short duration of maximum stress.     

热封温度对PET/Al/PE包装膜热封性能的影响

设计多种实验工况研究热封工艺参数对聚对苯二甲酸乙二酯(PET)/Al/聚乙烯(PE)复合薄膜热封强度的影响.结果表明,热封温度对热封强度的影响最为显著.在此基础上,采用扫描电子显微镜和拉伸破坏模式对热封区域表观判定,采用差示扫描量热法分析热封材料PE的热性能,并结合工程实际,确定PET/Al/PE有效热封温度为110～160℃.     

16MnR钢高温疲劳裂纹扩展行为试验研究

对16MnR钢在常温、150℃、300℃和425℃下的疲劳裂纹扩展速率进行了测试和分析,得到了四种温度下的疲劳裂纹扩展规律。结果表明：该材料在150℃和300℃的疲劳裂纹扩展速率比常温和425℃时低,425℃时疲劳裂纹扩展速率最高。     

大丝束CF/EP汽车地板VARTM模拟与高温力学性能

汽车轻量化是全球面临的共同问题,采用更具成本优势的大丝束碳纤维（CF）增强复合材料是实现汽车轻量化结构化的重要途径。然而,大丝束碳纤维在液体成型时,单束过多的纤维丝易导致纤维束内微观浸润困难,易产生干斑、气泡等缺陷。同时,传统的汽车电泳烘干工艺对复合材料的高温性能提出了挑战。鉴于此,本文采用0°/90°双轴向缝编大丝束碳纤布和耐高温环氧树脂（EP）,开展了纤维渗透率测试和汽车地板真空辅助树脂传递成型（VARTM）模拟优化研究,设计、制造了成型模具,成功试制出汽车地板样件,超景深显微镜观测显示纤维束内和层间浸润良好,无明显缺陷。高温在线拉伸和应变测试显示,温度对材料拉伸模量影响显著而对强度影响不大,180℃高温下应变恢复能力良好,表明该材料在高温下仍具备较好的强度和抗蠕变性能,该结果对指导复合材料能否通过传统汽车的电泳烘干工艺具有重要意义。     

Static and Cyclic Fatigue of Alumina at High Temperatures: II, Failure Analysis

Failure mechanisms of an alumina, tested at 1200°C under static and various cyclic loading conditions, were examined. Slow crack growth of a single crack is the dominant mechanism for the failure in specimens under cyclic loading with a short duration of maximum stress at all applied stress levels, as well as at high applied loads for static loading and cyclic loading with a longer hold time at maximum stress. At low stress levels, failure of static loading and cyclic loading with a longer hold time at maximum stress might occur by formation and/or growth of multiple macrocracks. More importantly, for all the given loading conditions. The viscous glassy phase behind the crack tip could have a bridging effect on the crack surfaces. A simplified model for calculating effective stress intensity factor at the crack tip under static and various cyclic loading demonstrated a trend consistent with the stress–life data.     

Fatigue of three advanced SiC/SiC ceramic matrix composites at 1200°C in air and in steam

High‐temperature mechanical properties and tension‐tension fatigue behavior of three advanced SiC/SiC composites are discussed. The effects of steam on high‐temperature fatigue performance of the ceramic‐matrix composites are evaluated. The three composites consist of a SiC matrix reinforced with laminated, woven SiC (Hi‐Nicalon?) fibers. Composite 1 was processed by chemical vapor infiltration (CVI) of SiC into the Hi‐Nicalon? fiber preforms coated with boron nitride (BN) fiber coating. Composite 2 had an oxidation inhibited matrix consisting of alternating layers of silicon carbide and boron carbide and was also processed by CVI. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Composite 3 had a melt‐infiltrated (MI) matrix consolidated by combining CVI‐SiC with SiC particulate slurry and molten silicon infiltration. Fiber preforms had a CVI BN fiber coating applied. Tensile stress‐strain behavior of the three composites was investigated and the tensile properties measured at 1200°C. Tension‐tension fatigue behavior was studied for fatigue stresses ranging from 80 to 160 MPa in air and from 60 to 140 MPa in steam. Fatigue run‐out was defined as 2 × 10⁵ cycles. Presence of steam significantly degraded the fatigue performance of the CVI SiC/SiC composite 1 and of the MI SiC/SiC composite 3, but had little influence on the fatigue performance of the SiC/SiC composite 2 with the oxidation inhibited matrix. The retained tensile properties of all specimens that achieved fatigue run‐out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.