CNTs含量对CNTs/Al微观组织及力学性能的影响

为增加碳纳米管(CNTs)在铝基体中的分散性,利用机械球磨-真空热压烧结工艺制备碳纳米管/铝(CNTs/Al)复合材料,采用扫描电子显微镜(SEM)、电子万能试验机和万能摩擦磨损实验机,研究了CNTs质量分数对CNTs/Al复合材料微观组织、力学性能及摩擦磨损性能的影响.结果表明:CNTs经超声波预先分散后分散性增加;当CNTs质量分数为2.0%时,复合材料中CNTs与Al粉之间表现出较好的相容性;随着CNTs含量进一步增加,CNTs团聚现象严重;热压烧结温度600℃时,随着CNTs添加量的增加,铝基复合材料的屈服强度和抗拉强度呈现出明显的先增大后降低的趋势,同时,CNTs/Al复合材料的摩擦因数和磨损率随CNTs含量的增大先减小后增加;CNTs质量分数为2.0%时,复合材料的屈服强度最大值为116 MPa,抗拉强度最大值为245 MPa,与纯Al基体相比,分别提高了78%和1.9倍.2.0%CNTs/Al复合材料可获得较好的摩擦磨损性能,其摩擦系数和磨损率呈现平缓趋势,复合材料的磨痕最浅.     

碳纤维增强TiC复合材料的制备与高温强度

采用热压烧结工艺制备了碳纤维增强 Ti C复合材料 (2 0 vol%碳纤维 ) ,研究了热压烧结温度对力学性能的影响和碳纤维对复合材料高温强度的增强作用。结果表明 :采用球磨湿混工艺将易于团聚的短碳纤维均匀地分散在 Ti C基体中 ,Cf/ Ti C复合材料最佳热压烧结温度为 2 10 0℃ ,Cf/ Ti C复合材料的室温抗弯强度为 5 93MPa,断裂韧性为 6 .87MPa· m1 / 2 ,140 0℃时的高温抗弯强度为 439MPa。定量分析了碳纤维对复合材料的增强和增韧效果     

纺织结构碳纤维增强聚醚醚酮基复合材料的制备及界面改性

采用热压成型法制备纺织结构碳纤维增强聚醚醚酮(CFF/PEEK)航空热塑性复合材料。通过对碳纤维(CF)进行去浆、活化,及采用磺化聚醚醚酮(SPEEK)进行表面涂层,显著提高了CFF/PEEK复合材料的层间剪切强度。讨论了热压温度、压力等工艺参数对材料综合力学性能的影响规律,确定优化工艺条件,制备的复合材料拉伸强度和弯曲强度分别达到714.29 MPa和955.84 MPa。借助扫描、金相显微镜等观察手段,发现经过界面改性处理后,复合材料断裂发生在基体内部而非界面处,基体与增强体浸润性和结合性良好。     

SiCw增强B4C陶瓷复合材料的制备与性能研究

以Si粉为烧结助剂,采用真空热压烧结工艺制备B4C-SiCw陶瓷复合材料.将不同含量的SiCw与B4C和Si混合,制得的复合粉体在1850℃、60MPa下真空热压烧结,研究了SiCw含量对复合材料力学性能的影响,并借助X射线衍射、扫描电镜分析了复合材料的物相组成和微观结构.研究结果表明:分散处理后的SiCw可以有效地提高复合材料的力学性能,当晶须含量为10％(质量分数)时,弯曲强度和断裂韧性达到最大值,分别为468 MPa和5.70 MPa·m1/2.复合材料中SiCw的拔出使复合材料的弯曲强度及断裂韧性得以提高.     

碳纳米管-Ti3AlC2/AZ91D复合材料的微观组织及力学性能

采用化学镀铜的方法对增强相碳纳米管(CNTs)和Ti₃AlC₂进行表面改性,热压烧结制备了CNTs-Ti₃AlC₂/AZ91D复合材料,研究了其微观组织和力学性能的变化及增强机制。结果表明:CNTs-Ti₃AlC₂/AZ91D复合材料内部主要物相为CNTs、Ti₃AlC₂、Mg和Al₁₂Mg₁₇,增强相均匀分布在基体内,在增强相与基体的界面处存在U相(MgAlCu),使二者界面结合良好。当增强相CNTs 和Ti₃AlC₂含量分别为1wt%和25wt%时,较镁合金AZ91D,CNTs-Ti₃AlC₂/AZ91D复合材料的弹性模量、拉伸强度、屈服强度和延伸率分别提高了120.30%、25.72%、126.50%和36.84%,弯曲强度和压缩强度分别为337.92 MPa和436.27 MPa。CNTs-Ti₃AlC₂/AZ91D复合材料的断裂方式表现为脆性断裂,其强化机制主要为热配错强化、Orowan强化和细晶强化机制。      

碳纤维织物增强聚苯硫醚复合材料的制备及性能

采用薄膜叠压法制备碳纤维织物增强聚苯硫醚(CFF/PPS)复合材料层压板,研究了热压温度、热压压力和热压时间对复合材料层压板力学性能的影响,确定了制备CFF/PPS复合材料的理想工艺参数为:热压温度320～330℃,热压压力0.15～0.20MPa,热压时间8～10min。在该参数下制得的层压板拉伸强度为652MPa,弯曲强度为711MPa,层间剪切强度为43MPa;在6.7J/mm的冲击能量下,层压板的冲击后压缩剩余强度为116MPa。     

模压工艺对玻璃纤维增强聚丙烯复合材料层合板力学性能的影响

利用热模压工艺制备玻璃纤维增强聚丙烯（GF/PP）复合材料层合板,通过差示扫描量热（DSC）法试验分析,确定相变参数,运用ANSYS有限元分析,将复合材料热力学参数与温度的非线性关系定义到材料特性中,研究模压成型过程中温度场变化情况,为模压成型工艺制度的确立提供理论指导和依据。以压缩强度、层间剪切强度和冲击韧性作为力学性能评价指标,采用响应曲面法探讨和分析制备工艺对GF/PP复合材料层合板力学性能的影响,得到最优模压工艺制备参数,获得最高复合材料层合板力学性能,为GF/PP复合材料自动铺放奠定铺放工艺基础。试验结果表明:模压加热工艺参数对复合材料层合板力学性能的影响度（从大到小）依次为:热压温度、热压时间、热压压力。较优的模压加热工艺参数为:热压温度228℃、热压时间6 min、热压压力1.1 MPa,在此工艺条件下制备的GF/PP复合材料层合板,层间剪切强度为31.12 MPa,压缩强度为100.96 MPa,冲击韧性为2.27 kJ/cm2。      

表面修饰碳纳米管对玻璃纤维及复合材料的性能影响

玻璃纤维因良好的力学性能被广泛应用于增强复合材料,而玻璃纤维与树脂基体的界面是影响复合材料性能的关键因素之一。实验中将碳纳米管(CNTs)改性后均匀地分散到浸润剂中,利用玻璃纤维在线成型工艺直接涂覆到玻璃纤维表面并制备复合材料。通过力学性能测试和显微形貌分析,结果表明CNTs能较好地分散于浸润剂和玻璃纤维表面,发现0.5%(质量分数)CNTs可以显著提高玻璃纤维的拉伸强度,并能显著改善纤维和基体的结合强度,从而提高复合材料的强度。     

ZnO及填料对磷酸铬铝基复合材料性能的影响

以磷酸铬铝(ACP)为基体,高硅氧纤维布为增强材料,Cr2O3和Al2O3为填料,通过热压成型制得磷酸铬铝基复合材料。采用TG-DSC和XRD等探讨了磷酸铬铝基体的固化特性和耐热性能,并研究了复合填料、纳米填料及热压工艺对材料力学性能的影响。结果表明,ZnO可以降低磷酸铬铝的固化温度并促进其晶型转变;复合填料Cr2O3和Al2O3可以提高材料的耐热性,当Cr2O3和Al2O3之比为7∶3且纳米Cr2O3加入量为5%时,复合材料的力学性能最好,其拉伸强度为95.2MPa,弯曲强度为190.02MPa。     

SiC晶须增强SiCf/SiC复合材料的力学性能

以连续SiC纤维为增强体,采用前驱体浸渍裂解工艺,在复合材料基体中引入SiC晶须制备出多级增强的SiCf/SiC-SiCw复合材料,并采用化学气相渗透工艺在SiC晶须表面制备BN界面层,研究了SiC晶须及其表面BN界面层对复合材料的性能影响.结果表明:在复合材料中引入SiC晶须后,由于晶须的拔出、桥连及裂纹偏转等作用增加了裂纹在基体中传递时的能量消耗,使SiCf/SiC复合材料的压缩强度有明显提高,当引入体积分数为20％的SiC晶须时,复合材料压缩强度提高了22.6％,可达673.9 MPa.通过化学气相渗透工艺在SiC晶须表面制备BN界面层后,复合材料的拉伸强度、弯曲强度和断裂韧度分别为414.0,800.3 MPa和22.2 MPa·m1/2,较SiC晶须表面无界面层时分别提高了13.9％,8.8％和19.0％.     

热交换器的分类及优缺点分析

热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考.     

聚苯胺及其复合物的制备和结构及形貌分析

通过化学氧化法分别制备盐酸,盐酸和十二烷基苯磺酸,碳纳米管(MWNTs-COOH)掺杂的聚苯胺,利用红外光谱,紫外光谱,扫描电子显微镜和透射电子显微镜对所制备聚苯胺的结构和形貌进行分析。分析不同掺杂物对聚苯胺的结构和形貌的影响;同时研究了超声波作用对聚苯胺形貌以及聚苯胺包裹MWNTs-COOH情况的影响。     

Modelling and computation of curing and damage of thermosets

The curing of thermosets is a complex process involving the transition from a fluid into a (visco-) elastic solid. This phase transition comes along with an increase in stiffness and a volume shrinkage of the polymer. The latter may lead to severe residual strains and stresses, which in turn can cause damage in the final, usually quasi-brittle material. In this contribution a constitutive model is developed which takes into account the curing of a thermosetting material together with the process-induced damage as resulting from curing shrinkage. The curing of the material is governed by a phenomenological hypoelastic constitutive equation which includes temporal evolutions for stiffness and volume shrinkage. Thermal and viscous effects are neglected in the present study. An isotropic gradient-enhanced damage model is adapted to describe the damage evolution. The curing-damage model is implemented into a finite element code and numerical examples for thermosetting materials demonstrate that the proposed model is capable to predict cure-induced damage in thermosets.     

Thermodynamic similarity and prediction of the properties and characteristics of substances and processes

Principles of the theory of thermodynamic similarity are considered in application to all aggregate states of a substance, including phase transitions, and to the change in dissipative structures in open systems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 709–716, November, 1987.     

Mechanisms of Corosion and Oxidation of Metals and Alloys

Selected topics in field of the study of the mechanisms of corrosion and of oxidation of metals or alloys are presented. The first part reports a new model for the mechanism of the breakaway oxidation of ferritic stainless steels in water vapour. The second part is devoted to the physico‐chemical aspects of oxidation and presents experimental methods useful in the kinetic modelling applied to two alloys, the zircalloy‐4 and an AlMg5 % in the liquid state. In the third part the physical and numerical modelling of the stress corrosion cracking behaviour in face‐centered cubic (fcc) alloys is detailed, which enables the study of the influence of macroscopic parameters (such as the temperature or hydrogen activity) on the fracture process.     

碳化硼陶瓷增韧补强和致密化研究现状及其展望

碳化硼陶瓷具有极高的硬度,然而其低韧性、低抗弯强度、难以致密化限制了它的广泛应用.已有一些研究集中于碳化硼陶瓷增韧补强和致密化,对这一方面国内外研究进展进行了归纳与评述,阐明各种增韧补强和致密化方法的优缺点,提出碳化硼陶瓷增韧补强和致密化研究值得发展的一些方向.     

Measurement and analysis of elastic and anelastic properties of alumina and silicon carbide

Measurements of dynamic Young's modulus, E, and damping as a function of temperature, T, were made for alumina and silicon carbide. The Young's modulus data were compared with some from the literature, and analysed in terms of a theoretical framework relating the Debye temperature, θD, with the elastic constants. For both materials this analysis yielded a ratio T₀/θ_D which was near 0.4, where T₀ is an empirical fitting constant for the plot of (E(0)−E)/T versus 1/T (E(0) is the value of E at 0 K). The analysis of the damping data in terms of an Arrhenius type dependence led to effective activation energies near kT, where k is Boltzmann's constant. This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation and characterization of phosphate and arsenate apatites of strontium and their solid solutions

Samples of phosphate and arsenate apatites of strontium and six of their solid solutions, spread over the entire compositional range, were prepared by a wet method. They were characterized by chemical, X-ray, electron microscopic and infrared analyses. The validity of Vegard's law established the homogeneity of the solid solutions.     

检定和校准证书的异同与应用

本文介绍了检定和校准以及证书的两点相同、五点不同之处,说明了对检定证书和校准证书的正确应用。