不同含量纳米羟基磷灰石/聚乳酸复合材料的性能

利用双螺杆挤出机制备了纳米羟基磷灰石(n-HA)质量分数分别为10%,20%,30%,40%的n-HA/PLA(聚乳酸)复合材料,研究了复合材料中n-HA的分散性以及n-HA含量对复合材料热学性能、黏度和弯曲强度的影响。结果表明:当n-HA质量分数在10%~40%时,n-HA在PLA基体中均具有较好的分散性;随着n-HA含量的增加,n-HA/PLA复合材料的冷结晶温度及特性黏度降低,而冷结晶焓和弯曲强度则均先升高后下降;当n-HA质量分数为10%时,n-HA/PLA复合材料的综合性能较好,其弯曲强度最大,为97.2 MPa,n-HA对PLA分子链的破坏程度最小。     

包覆镍CNTs/AM60复合材料铸态显微组织与力学性能

采用机械搅拌铸造法制备了包覆镍碳纳米管(CNTs)/AM60复合材料,研究了包覆镍CNTs加入量对铸态复合材料力学性能的影响规律,并用扫描电子显微镜观察了复合材料的拉伸断口形貌以及显微组织。结果表明:复合材料显微组织为等轴晶,包覆镍的CNTs主要分布在-αMg共晶相内和晶界处,不仅起到细化晶粒的作用,而且还起到搭接晶粒和强化晶界的作用;复合材料的力学性能随CNTs加入量的增多呈现先增大后减小的趋势,当其质量分数为1%时,抗拉强度、显微硬度、伸长率同时达到最大,比AM60镁合金分别提高了46.23%,41.82%,74.52%,弹性模量在其质量分数为1.2%时达到最大。     

碳纳米管增强镁基复合材料的组织与力学性能

在Mg-1.3Mn-1.0Ce-4.0Zn合金熔体中加入质量分数为0~1.5%的碳纳米管(CNTs),采用搅拌铸造法制备了碳纳米管增强镁基复合材料,研究了复合材料的组织和力学性能,并探讨了复合材料的强韧化机制。结果表明:CNTs能细化基体合金的晶粒尺寸,改变晶粒形貌及第二相的分布特征;随着CNTs添加量增大,复合材料的室温强度、断口伸长率和硬度均呈先增大后减小的趋势;当CNTs的质量分数为0.5%时,室温强度、断后伸长率和硬度最高,分别为212.2 MPa,21.1%和55.0HBW,较基体合金的分别增加了8.5%,37.5%和10%;复合材料的强韧化机制包括增强相强化、第二相强化和细晶强化,而晶粒细化、CNTs的润滑作用及对裂纹的阻碍作用是复合材料塑性提高的主要原因。     

碳纳米管增强PTFE复合材料摩擦磨损性能研究

以不同含量的CNTs(碳纳米管)为填料制备了PTFE基复合材料,测量其硬度,在M-2000型摩擦磨损试验机上研究其摩擦磨损行为。结果表明,CNTs能提高PTFE的硬度,CNTs/PTFE复合材料的耐磨性能明显优于纯PT-FE,当CNTs的质量分数为3%时,复合材料的耐磨性能大幅度提高。其摩擦因数随着CNTs含量的增加而加大,当CNTs的质量分数为1%时,摩擦因数随载荷的增加而减少,CNTs的质量分数为3%和5%时,摩擦因数随载荷的增加而增大。SEM观察发现:纯PTFE的断面上分布着大量的带状结构,而填充CNTs后,摩擦表面较平整光滑,表明CNTs作为填料可有效地抑制PTFE的犁削和粘着磨损。     

碳纳米管/ZM5复合材料的高温拉伸性能与显微组织

在氩气保护下,采用搅拌铸造法制备了碳纳米管(CNTs)/ZM5镁合金复合材料;测试了铸态下其高温拉伸性能,并对其显微组织和断口形貌进行了分析.结果表明:该复合材料具有良好的高温拉伸性能,在拉伸速率为1mm·min-1以及温度为473K时其抗拉强度可达117.65MPa,比基体提高了20%;当CNTs加入量为0.5%时,其最大伸长率达到8.32%,比基体提高了21.62%;在高温下该复合材料的断裂形貌主要由韧窝和撕裂棱所组成.     

碳纳米管/石墨烯-氧化铜复合粉体的制备及其光催化性能

采用喷雾干燥和煅烧的方法制备了碳纳米管/石墨烯-氧化铜(CNTs/rGO-CuO)复合粉体,对复合粉体进行了形貌观察和物相分析,讨论了分解温度、碳纳米管(CNTs)和氧化石墨烯(GO)的质量比、CNTs和GO的质量分数对复合粉体形貌和光催化性能的影响,并对制备工艺进行了优化。结果表明:当分解温度为210℃、CNTs与GO的质量比为1∶1、CNTs和GO的质量分数为10%时,制备的复合粉体性能最佳;CNTs与GO形成了一种球状结构,CuO颗粒均匀地分布在球体表面;在可见光照射20min后,该复合粉体对溶液中甲基橙(MO)的最大降解率能达到98.3%。     

CNTs/AZ91复合材料的摩擦磨损性能

采用粉末冶金法和热挤压工艺制备了碳纳米管增强AZ91镁合金(CNTs/AZ91)复合材料,研究了复合材料在干滑动条件下的摩擦磨损性能、磨损形貌及磨损机制,并与AZ91镁合金基体的进行了对比。结果表明:由于CNTs的自润滑和增强作用,复合材料的摩擦磨损性能明显优于基体合金的;随着载荷和CNTs质量分数增加,复合材料的摩擦因数逐渐降低;随着载荷增加,复合材料的磨损量增大;在相同的载荷下,复合材料的磨损量随CNTs质量分数的增大而减小;AZ91镁合金的磨损机制为疲劳磨损和磨粒磨损,复合材料的磨损机制以轻微的粘着磨损和磨粒磨损为主。     

短切碳纤维增强聚丙烯复合材料的制备与性能研究

通过双螺杆熔融共混法制备聚丙烯/短切碳纤维(PP/SCF)复合材料,研究了SCF和马来酸酐接枝聚丙烯相容剂(PP-g-MAH)的用量对复合材料力学性能、流动性能及热稳定性能的影响,并采用扫描电子显微镜观察了复合材料的断面形貌。结果表明：SCF用量对PP基体中的分散有显著影响,PP-g-MAH对界面结合特性起着重要作用,两者的结合显著影响SCF/PP复合材料的综合性能;当SCF质量分数为15%、相容剂质量分数为9%时,其综合性能最优。     

粉煤灰/聚丙烯复合材料的非等温结晶动力学行为

采用差示扫描量热仪研究了粉煤灰/聚丙烯(FA/PP)复合材料的非等温结晶行为,并探讨了基于Jeziorny法和莫志深法的结晶动力学,最后利用Flynn-Wall-Ozawa方程计算了纯PP和复合材料的结晶活化能。结果表明:在PP中加入FA后,复合材料的结晶起始温度To、结晶峰值温度Tp、Avrami指数n、半结晶时间t1/2和冷却速率F(T)均增大,结晶速率常数Zc降低;当FA的质量分数为15%时,复合材料的t1/2、活化能以及F(T)最小,Zc最大;FA/PP复合材料的结晶活化能均高于纯PP的。     

甘蔗渣微晶纤维素增强聚乳酸复合膜的性能

利用酸碱结合的方法提取出甘蔗渣纤维素,经酸水解制备甘蔗渣微晶纤维素(BCMC);以BCMC为增强材料,以生物可降解材料聚乳酸(PLA)作为基体,制备了BCMC/PLA复合膜,并对复合膜的结构、热稳定性和力学性能进行了研究。结果表明:BCMC均匀地分散于PLA基体中,没有发生明显的团聚现象;BCMC的加入增大了复合膜的结晶度;当BCMC的质量分数为5%时增强效果最佳,与纯的PLA膜相比,复合膜的起始分解温度提高了30.73℃,拉伸强度提高了50.98%,断裂伸长率提高了16.25%。     

纳米二氧化硅提高PTFE硬度的机制研究

采用溶剂蒸发法和固体纳米粉末混合法2种工艺制备了SiO2/PTFE复合材料。结果表明,随着SiO2含量的增加,复合材料的硬度增加,但采用溶剂蒸发法制备的复合材料具有更好的强化效果,在含量达到50%时,硬度达到最大,比固体粉末法制备的复合材料的硬度高6倍。XRD分析表明,随着SiO2含量增加,PTFE结晶度降低。SEM对其断口形貌进行观察表明,采用溶剂蒸发法制备的复合材料,纳米SiO2粒子可以较均匀分散在基体中,有效地阻碍了PT-FE分子链段的运动和规整排列。红外光谱分析表明,纳米SiO2粒子与PTFE分子之间存在着氢键作用力,因而硬度增加较大。     

Wear behaviour of carbon nanotube reinforced epoxy resin composites

This paper deals with the effect of a multi-walled carbon nanotube (MWCNT) reinforcement on the wear behaviour of Epoxy (EP) composites. Firstly, various dispersion methods were compared. Secondly, the optimum CNT amount was evaluated. In a third step, dry lubricants were added to the optimised EP/CNT composite. Finally, the influence of the steel counterpart (martensitic bearing steel 100Cr6 and austenitic stainless steel X5CrNi18-10) was studied. The preparation method was found to have a decisive effect on the wear behaviour of the composite. A pre-treatment of the CNTs in concentrated nitric acid proved beneficial. Even more important was the mixing method. A dual asymmetric centrifuge delivered so good wear results that the pre-treatment could be skipped. The optimum CNT content was at about 1 wt%, regardless of the preparation method. The lowest wear rates were found after addition of 10 wt% graphite. MoS₂ proved to be less effective and Polytetrafluorethylene (PTFE) even increased the wear. The wear rates against the unalloyed martensitic steel were far higher than against austenitic stainless steel.     

紫外光接枝丙烯酸改性废胶粉工艺优化及其复合材料的力学性能

以丙烯酸为接枝单体,二苯甲酮为光敏剂,在紫外光的引发下对废胶粉进行表面接枝,用正交方法对改性工艺进行了优化,制备了改性废胶粉/天然橡胶复合材料,表征了改性前后废胶粉的表面形貌和结构,考察了其加入量对复合材料力学性能的影响。结果表明:当丙烯酸和二苯甲酮与废胶粉的质量比分别为10%和9%,废胶粉粒径为150μm和光照时间为4min时,为最佳工艺条件,此时接枝率最高,达3.38%;接枝改性后的废胶粉表面粗糙度增加;随改性废胶粉含量的增加,复合材料的拉伸强度和邵氏A硬度先增大后降低,并在质量分数10%时达到最大值,分别为27.28MPa和69.2HSA。     

On dry sliding friction and wear behavior of PPESK filled with PTFE and graphite

Novel poly(phthalazinone ether sulfone ketone) (PPESK) resins have become of great interest in applications such as bearing and slider materials. In this paper, dry sliding wear of polytetrafluoroethylene (PTFE) and graphite-filled PPESK composites against polished steel counterparts were investigated on a block-on-ring apparatus at the same sliding velocities and different loads. The results indicated that the addition of 5–25 wt% PTFE and 5–30 wt% graphite contribute to an obvious improvement of tribological performance of PPESK at room temperature. Worn surfaces were investigated using a scanning electron microscope (SEM). As a result, the friction coefficient and wear rate of the PPESK composites decreased gradually with addition of fillers. A moderately low friction coefficient and specific wear rate were reached when the filler contents were above 20 wt%. The mechanical properties of PPESK composites were also investigated. The tensile and impact strength of PPESK composites decrease slightly as the addition of fillers contents were below 15 wt%.     

Tribological Behavior of Carbon Nanotube-Reinforced AZ91D Composites Processed by Cyclic Extrusion and Compression

Reciprocating wear tests were conducted to assess the wear resistance of CNT-reinforced AZ91D composites prepared by cyclic extrusion and compression (CEC). Effects of CEC, CNTs, and wear parameters on the tribological behavior of the composites were discussed. Results show that the matrix grain of the 0.5 wt% CNTs/AZ91D composites is largely refined from ~?112 µm to 126.6 nm after eight passes of CEC. Accordingly, the hardness of the composites is increased by more than 82.0%. The wear rate of the CNTs/AZ91D composites decreases with the implement of CEC and the addition of CNTs. The lubrication effect of CNTs diminishes after CEC. Besides the reinforcing effect, the incorporated CNTs help to liberate the friction heat of the CNTs/AZ91D composites and reduce the welding of the wear debris due to their extraordinary thermal conductivity.     

聚氨酯/碳纳米管复合材料的摩擦性能

采用溶液共混法制备聚氨酯/碳纳米管复合材料,探讨碳纳米管含量和超声分散时间对聚氨酯/碳纳米管复合材料摩擦性能的影响。结果表明:随着碳纳米管含量的增加,聚氨酯/碳纳米管复合材料的摩擦因数逐渐降低,随着载荷的增大,摩擦因数有所减小;超声分散时间对聚氨酯/碳纳米管复合材料摩擦性能影响不大;碳纳米管具有较好的润滑性质,可以降低聚氨酯/碳纳米管复合材料的摩擦因数,改善聚氨酯的摩擦性能。     

Tribological Studies of Nanoclay Filled Epoxy Hybrid Laminates

In this work, the tribological properties of a new class of hybrid composite material were examined. The hybrid composite consisting of glass fiber–reinforced epoxy polymer filled with nanoclay particles was prepared by vacuum-assisted resin infusion molding (VARIM). The effect of fiber content, fiber orientation, and nanoclay concentration on wear properties was examined. The results indicate that at higher fiber content (75 wt%), nanoclay addition in composites has less effect on the wear rate, whereas a significant positive effect was observed when nanoclay was filled in lower fiber content (25 and 50 wt%) composites. Microscopy examination reveals that nanoclay addition improves the wear properties of a matrix-rich phase at low fiber content with improved fiber matrix adhesion, whereas this effect was negligible in higher fiber content composites due to the reduced matrix concentration. The result also shows that the friction and wear of hybrids is a function of fiber orientation and epoxy–clay nanocomposite structure formation as studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis.     

聚乳酸/羟基磷灰石复合材料激光选区烧结工艺优化与性能研究

以生物可降解材料聚乳酸（PLA）和生物骨基质的主要无机成分羟基磷灰石（HA）为研究对象。为获得复合材料激光选区烧结(SLS)制件的最佳成形参数,首先对纯PLA的SLS工艺进行了优化,发现最优的激光能量密度范围为0.040~0.075 J/mm2,且制得的纯PLA试样的拉伸强度均超过23 MPa,最高可达27.28 MPa。为研究HA含量对PLA/HA复合材料微观结构与力学性能的影响,以激光能量密度为0.040 J/mm2（激光功率12 W,扫描速度1 500 mm/s）对不同HA含量的PLA/HA复合材料进行了成形。实验结果表明,当HA质量分数为10%时,PLA/HA复合材料的力学性能和微观形貌最优。水接触角测试显示材料的接触角从69.52°降至57.96°,表明材料的亲水性能得到了改善。     

The impact of the thermal annealing conditions on the structural properties of polylactic acid fibers

Polylactic acid (PLA) is a prominent biomaterial for plentiful applications in medicine and industry. The main goal of using this new material is replacing polymers based on petrochemical. Different thermal and structural properties of PLA fibers were studied after the thermal treatment using two different conditions (taut and free ends). Different techniques were used to study the effect of the thermal treatment conditions on the crystallinity and molecular orientations for PLA fibers such as differential scanning calorimetry technique, X-ray diffraction technique, and polarized light microscopy. The impact of the thermal annealing treatment on both the crystallinity and crystalline orientation was calculated. In case of taut ends thermal annealing treatment method, the measured parameters were higher than the case of free ends thermal annealing condition. The oriented segment relaxation due to the thermal annealing results an increase in the crystallinity values, but it does not indicate that the molecular orientation will be high. Results showed that the orientation of crystal and crystallinity was improved after thermal treatment. The taut conditions of annealing show significant improvement of crystallinity than free conditions.     

Tribological properties of carbon nanotube-doped carbon/carbon composites

Carbon nanotube (CNT)-doped carbon/carbon (C/C) composites were fabricated by the chemical vapor infiltration (CVI) method to investigate the effect of CNTs on tribological properties of C/C composites. CNTs, which had been synthesized by catalytic pyrolysis of hydrocarbons, were added to carbon fiber formed preforms before CVI process. Ring-on-block-type wear tests were performed to evaluate the frictional properties of CNT-doped C/C composites. Results show that CNTs can not only increase wear resistance of C/C composites but also maintain stable friction coefficients under different loads. Polarized light microscopy, X-ray diffraction, scanning electron microscopy and Raman spectroscopy analyses demonstrate that favorable effects of CNTs on tribological properties of C/C composites have been achieved indirectly by altering microstructure of pyrocarbons and directly by serving as high-strength lubricative frictional media at the same time. Electron dispersive spectroscopy (EDS) analyses verify the existence of adhesive wear mechanism in both pure C/C composites and CNT-doped C/C composites albeit the two-body abrasive mechanism dominates in pure C/C composites.