The effect of processing parameters on the tensile properties of alumina fiber reinforced magnesium

The effect of processing variables on the tensile properties of commercially pure (CP) magnesium reinforced with FP alumina fibers has been studied. Composite plates were cast at 698°C, 755°C, and 810°C, with a five-minute hold period prior to solidification. The properties of the composites were compared to those of both conventionally cast CP magnesium and ZE41A (Mg-4.25Zn-0.5Zr-1.25RE) composites. The tensile properties were found to be independent of casting temperature in the range 698 to 810°C, although the five-minute hold period significantly decreased the axial properties of the CP magnesium. The results indicated that, during processing, the time at temperature has a more pronounced effect on tensile strength than the actual casting temperature. Increasing casting temperature was found to increase the MgO fiber-matrix reaction zone to a size comparable to that observed in conventionally processed ZE41A material. However, the strengths of the CP magnesium composites cast at the three different temperatures were significantly lower than that of ZE41A, indicating that the interfacial strengthening observed in ZE41A is not due to larger MgO reaction zone particles. A possible explanation for the interfacial strengthening in ZE41A is the presence of zinc and aluminum in low concentrations, which act to enhance the bonding between the reaction zone and the metallic matrix.     

宏观颗粒增强铁基复合材料的制备与性能

颗粒与基体之间难以均匀稳定的混合以及二者的界面结合强度较差是限制颗粒增强金属基复合材料制备以及推广应用的共性关键问题,而目前的主要解决措施\     

Tribological properties of thermally expanded graphite reinforced with knitted metal nets

Production of thermally expanded graphite composites reinforced with knitted copper net is developed and their tribological properties are determined. Wear resistance under reciprocating and rotary movement can be improved by the reinforcement. Reinforced thermally expanded graphite seals may be a substitute for asbestos-containing materials. Institute of Materials Science Problems, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 33–37, July–August, 1997.     

碳纳米管增强环氧树脂基复合材料的制备及其力学性能

通过对多壁碳纳米管进行表面处理,用超声分散和模具浇注成型法制备了碳纳米管/环氧树脂纳米复合材料.研究了碳纳米管含量和表面处理对碳纳米管/环氧树脂复合材料力学性能和断面形貌的影响,分析了碳纳米管对环氧树脂的增强机理.结果表明,随着碳纳米管含量的增加,碳纳米管/环氧树脂复合材料的拉伸强度和弯曲强度及模量先增加后减小;当碳纳米管的质量分数为0.5%时,复合材料的拉伸强度、弯曲强度和弯曲模量分别达到最大值69.8MPa、136.9MPa和3.72GPa,比纯环氧树脂提高了33.9%、29.3%和4.8%;当碳纳米管的质量分数为1.5%时,拉伸模量达到最大值2050.5 MPa,比纯环氧树脂提高了7.3%.     

混杂短纤维增强无石棉摩擦材料的制备及摩擦磨损性能

采用热压成型结合180℃/8 h固化热处理工艺制备混杂短纤维增强无石棉摩擦材料,通过正交实验优化热压工艺参数。在JF150D定速式摩擦实验机上测试材料的摩擦磨损性能。结果表明:实验制备的混杂短纤维增强无石棉摩擦材料的密度为2.1~2.21 g/cm3,洛氏硬度为62.2~68.0,摩擦过程中摩擦因数在0.37~0.43之间变化,随温度升高先增大后减小,磨损率为0.1~0.54×10 7cm3/(N.m)。制备摩擦材料的最优热压工艺参数是:热压温度为155℃,压力为18 MPa,热压时间为15 min。摩擦材料的摩擦磨损机理以粘着磨损和磨粒磨损为主。     

镀钨碳纳米管增强铜基复合材料的制备及性能

采用羰基热分解法对多壁碳纳米管表面进行镀钨处理,并以镀钨碳纳米管和电解铜粉为原料,进行机械球磨混粉和放电等离子体烧结,制备了镀钨碳纳米管/铜基复合材料.采用场发射扫描电镜观察了粉体和复合材料的组织形貌,并对复合材料物相进行了X射线衍射分析.探讨了镀钨碳纳米管含量和放电等离子体烧结温度对复合材料致密度、抗拉强度、延伸率和电导率的影响.结果表明,镀钨碳纳米管质量分数为1%和烧结温度为850℃时,复合材料的致密度、抗拉强度和电导率最高.与烧结纯铜相比,复合材料的抗拉强度提高了103.6%,电导率仅降低15.9%.     

镀钨碳纳米管增强镁基复合材料的摩擦磨损性能研究

以羰基钨为前驱体, 采用金属有机化学气相沉积在碳纳米管表面镀覆了金属钨, 利用磁力搅拌混粉和放电等离子体烧结制备了镀钨碳纳米管增强镁基复合材料((W-CNTs) /Mg), 研究了W-CNTs质量分数对复合材料摩擦磨损性能的影响。结果表明: W-CNTs的加入可对镁基体起到降低摩擦系数、减少磨损量的作用; 当W-CNTs质量分数为0.75%时, 复合材料的摩擦系数和磨损量均最小, 分别较纯镁降低了43.7%和71.4%;增加或降低复合材料中的W-CNTs质量分数, 材料的摩擦系数、磨损量均将增大。(W-CNTs) /Mg复合材料的摩擦磨损性能高于CNTs/Mg复合材料。     

Carbon fiber reinforced root canal posts. Mechanical and cytotoxic properties

The aim of this study was to compare the mechanical properties of a prefabricated root canal post made of carbon fiber reinforced composites (CFRC) with metal posts and to assess the cytotoxic effects elicited. Flexural modulus and ultimate flexural strength was determined by 3 point loading after CRFC posts had been stored either dry or in water. The bending test was carried out with and without preceding thermocycling of the CFRC posts. The cytotoxicity was evaluated by an agar overlay method after dry and wet storage. The values of flexural modulus and ultimate flexural strength were for dry stored CFRC post 82 +/- 6 GPa and 1154 +/- 65 MPa respectively. The flexural values decreased significantly after water storage and after thermocycling. No cytotoxic effects were observed adjacent to any CFRC post. Although fiber reinforced composites may have the potential to replace metals in many clinical situations, additional research is needed to ensure a satisfying life-span.     

热解碳沉积温度对增强石墨力学性能的影响

采用化学气相沉积增密技术制备热解碳增强普通石墨材料。研究沉积温度对增强石墨力学性能的影响,并探讨热解碳增强普通石墨材料的沉积机理。结果表明:随沉积温度升高,增强石墨的抗弯强度提高,在1 600℃沉积时达到最大值39.33 MPa,比石墨基体提高21.7%。其主要原因是随沉积温度升高,热解沉积由CVI过程变为CVD过程。当温度低于1 600℃时,化学气相渗透过程占主导;温度高于1 600℃后热解碳极易沉积在基体表面,形成热解碳膜,化学气相沉积过程占主导。在1 600℃温度下,其抗弯强度随沉积时间的变化不大,这证明高温下(1 600℃)化学气相沉积主要发生在石墨块体表面。     

The transverse tensile properties of boron fiber reinforced aluminum matrix composites

The transverse tensile properties of boron fiber reinforced aluminum have been determined as a function of fabrication parameters, matrix alloy and fiber types, fiber content, specimen geometry, and thermal environment. Matrix alloys investigated include 2024, 6061, 5052, 5056, 2219, 1100, and Al-7 pct Si. The fibers investigated include 4.0 mil boron, 4.2 mil BORSIC, R.F. boron, 5.6 mil boron, 5.7 mil BORSIC, and 4.0 mil silicon carbide. It was shown that the composite transverse tensile performance is a function of all of these variables and that transverse strengths of up to 45,000 psi can be achieved by the choice of the proper combination of matrix, fiber type and fabrication procedures.     

镀W碳纳米管增强Mg基复合材料的力学和电学性能

以羰基钨为前驱体,采用金属有机化学气相沉积在碳纳米管表面镀覆了金属W。利用磁力搅拌混粉和放电等离子体烧结制备了镀W碳纳米管(W-CNTs)/Mg复合材料,并研究了W-CNTs含量对材料力学性能和电导率的影响。结果表明:W-CNTs含量为0.75%(质量分数,下同)时,复合材料抗拉强度和维氏硬度最大,较纯Mg增加了40.1%和35.1%;基体中添加W-CNTs虽然使复合材料电导率下降,但0.75%W-CNTs/Mg复合材料电导率仍可达到纯Mg的94.8%;W-CNTs/Mg复合材料的力学性能和电导率均高于CNTs/Mg复合材料。     

碳纤维电镀Cu/Ni双镀层及其性能表征

碳纤维经过脱胶和活化预处理后,表面活性大大增加,碳纤维表面由疏水性转变为亲水性,电镀过程中能很好地在镀液中润湿、分散,可解决碳纤维电镀常易出现的"黑心"问题。通过对照实验,确定最佳电镀工艺:镀Cu温度为45℃,电流密度为0.7 A/dm2;镀Ni温度为25℃,电流密度为0.8 A/dm2。碳纤维经连续电镀后得到Cu/Ni双镀层。测试结果表明:双镀层均匀致密,界面结合良好,镀层纯度高,结合力强。电镀前后单丝拉伸性能基本无改变,可很好地保持碳纤维的力学性能。电镀后碳纤维电阻率急剧下降,导电能力显著增加。     

苎麻纤维增强聚乳酸复合材料性能研究

通过密炼?注塑成型工艺制备了不同苎麻纤维含量的聚乳酸基复合材料,研究了纤维含量对复合材料性能的影响规律,并揭示了纤维增强机理。研究表明,苎麻纤维的添加提高了复合材料的耐热性能,尤其是当纤维质量分数为40%时,复合材料的热变形温度提高了10.5%。此外,苎麻纤维均匀地分散在基体中,由于纤维与聚乳酸的界面强度较弱,断面上有大量的纤维拔出和纤维孔洞;差示扫描量热仪测试表明高含量的纤维限制了聚乳酸分子链的运动,促进复合材料形成更加致密完善的晶核;同时,流变行为也表明苎麻纤维含量的增加有助于提高复合材料的黏弹响应和复合黏度;最后,苎麻纤维的加入提高了复合材料的拉伸和弯曲强度,且随纤维含量的增加而增大。与聚乳酸相比,当纤维质量分数为40%时复合材料的拉伸和弯曲强度分别提高了30%和21.9%。      

凝胶注模法制备碳纤维/氮化硅复合材料的微观结构与力学性能

通过化学气相沉积在短碳纤维表面制备C/Si C复合涂层,然后采用凝胶注模法制备纤维体积分数分别为2%和4%的Cf/Si3N4复合材料,利用X射线衍射与扫描电镜对该材料的物相与组织结构进行分析,研究短碳纤维对Si3N4陶瓷力学性能的影响。结果表明:随碳纤维体积分数增加,Cf/Si3N4复合材料的密度和抗弯强度降低,但断裂韧性明显提高。当纤维体积分数为4%时,材料的断裂韧性达到8.91 MPa·m1/2,比氮化硅陶瓷提高1.6倍,材料主要由长柱状的β-Si3N4基体、C/Si C涂层及碳纤维组成,碳纤维表面的C/Si C双涂层可防止高温下碳纤维与氮化硅基体发生反应,使碳纤维与氮化硅基体界面结合良好,以提高材料韧性并保证有合适的强度,满足功能材料在一定条件下的使用要求。     

粉末冶金制备碳纤维增强铁-铜基摩擦材料的组织与性能

以铁-铜为主组元,以石墨和MoS2为润滑组元,以Al2O3、SiC、锆英砂为摩擦组元,并添加不同质量分数的碳纤维,将原料混合均匀后经600 MPa冷压成形,然后在氢气气氛下热压烧结2 h(980℃,2~3 MPa),制备得到碳纤维增强铁-铜基摩擦材料,并对其硬度、相对密度、显微组织、摩擦磨损性能进行研究。结果表明:铁-铜基体上均匀分布着耐磨的陶瓷相及润滑组元,铁-铜基体有部分固溶,碳纤维掩埋在基体和摩擦组元间。当碳纤维质量分数为2%~4%时,所制备的摩擦材料硬度为HV 102.2~118.6,相对密度为90.4%~92.6%,摩擦系数为0.56~0.60,磨损失重量最小。该摩擦材料的磨损主要为磨粒磨损,伴随少量粘着磨损。碳纤维可以强化基体,钉扎摩擦组元,在摩擦磨损过程中隔断犁沟,降低材料磨损。