单层和三层结构的PVDF基复合材料介电与储能特性

通过水热合成法制备CaCu₃Ti₄O₁₂球型颗粒填料,以PVDF为基底,采用溶液逐层涂覆法制备单层和三层结构的PVDF基复合材料。利用X-射线衍射仪和扫描电镜表征材料的微观组织结构,LRC测试仪和铁电综合测试工作站测试其电学性能,研究低填充浓度和多层结构对PVDF基复合材料微观结构、介电特性、极化强度、耐电压特性和储能特性的影响规律。结果表明,CaCu₃Ti₄O₁₂填料的尺寸约为200 nm,增加其填充浓度,可以提高单层PVDF/CaCu₃Ti₄O₁₂复合材料的介电特性与极化强度；在3.0vol.%填充量下,复合材料达到最大的介电常数13.2、介电损耗0.074和电位移极化强度4.04 μC/cm²；而在0.5vol.%的超低填充量下,复合材料达到最大的释放能量密度3.51 J/cm³。三层结构的PVDF基复合材料体系中,在上下层复合材料的高介电极化特性与中间层材料的击穿阻挡特性的协同作用下,获得了综合储能特性优化的PVDF基复合材料,使其在300 kV/mm的低电场强度下,达到最高的释放能量密度4.36 J/cm³。     

B4C包覆ZTA颗粒增强铁基复合材料制备与性能

ZTA (ZrO₂增韧Al₂O₃)陶瓷颗粒表面包覆B₄C微粉,将其制备成蜂窝状结构陶瓷预制体。采用传统重力浇注工艺将陶瓷预制体与熔融的高铬铸铁(HCCI)金属溶液进行复合,获得ZTA陶瓷颗粒增强高铬铸铁基复合材料。对复合材料中ZTA陶瓷颗粒增强相与高铬铸铁基体之间的界面及复合材料的耐磨料磨损性能进行了研究。结果表明,ZTA陶瓷颗粒与高铬铸铁界面结合处形成了明显的过渡区域,界面过渡区域的存在提高了陶瓷颗粒与金属基体的结合,从而提升了复合材料的整体稳定性能。同时,三体磨料磨损试验表明该复合材料的耐磨料磨损性能是高铬铸铁的3.5倍左右。     

界面层对复合材料强度的影响

本文对氧化铝(Al₂O₃),氟化钙(CaF₂)和玻璃微珠颗粒填充环氧基(双酚A类E-51-胺固化体系)复合材料的断裂和抗拉强度进行了研究,并考察了复合材科抗拉强度与填料体积分数的关系。复合材料中,从填料固体表面开始形成了有一定厚度的密界面层。界面层的强度性质对复合材料的强度有重要作用。得到了三种复合材料界面层的抗拉强度。并提出了颗粒填充复合材料抗拉强度的计算公式:σ_o=〔σ_mS_m+σ₁S₁a₁〕η计算结果和实验数据有较好的一致性。      

碳纤维/TiO2改性树脂复合材料的制备及力学性能

针对环氧树脂脆性大、与碳纤维形成的界面性能较差等问题,本文选用纳米TiO₂对5284环氧树脂进行改性,并以角联锁机织物为增强体制备了碳纤维/环氧树脂复合材料。使用FT-IR、旋转流变仪、表面张力仪等设备对TiO₂/环氧树脂进行表征,并研究了树脂改性对复合材料压缩与层间剪切性能的影响。研究表明:TiO₂的羟基与环氧树脂的环氧基和羟基发生了反应;经1wt.%TiO₂改性的树脂复数黏度为0.066 Pa·s,纤维与树脂间接触角为28.85°,浸润效果较好;相较于未改性复合材料,树脂改性的复合材料纵向压缩强度与模量分别提高了7.46%和11.03%,横向压缩强度与模量分别提高了6.99%和4.96%,纵向、横向的剪切强度分别提高了6.88%和4.65%。TiO₂改性环氧树脂提高了复合材料的承载能力,改善了界面结合强度。     

原始SiC颗粒表面及SiCP/Al复合材料界面化学状态的研究

本文采用X射线光电子谱(XPS)和俄歇能谱技术(AES)对原始SiC颗粒表面和粉末冶金法制备的SiC_P/Al复合材料界面的化学状态进行了研究.结果表明:原始SiC颗粒表面主要存在SiC、SiO₂、游离C、吸附氧、Fe₂O₃等;SiC_P/Al复合材料界面存在Mg偏聚和氧元素.由热力学分析可知,Mg元素能够向界面偏聚,并可能与界面处的氧反应生成MgO.     

填充HDPE复合材料基体结晶形态的控制因素

本文以HDPE/玻璃微珠和HDPE/CaCO₃体系为研究模型,通过扫描电镜、红外光谱、偏光显微、小角激光散射和材料力学性能实验等方法考察了这两种体系的界面粘结性、填料含量、粒径及试样成型冷却速率等与其材料性能及基体结晶形态变化间的关系。实验结果表明;在复合材料试样成型过程中,因基体树脂冷却收缩而产生的界面应力可干扰基体中球晶的生长环境,应变诱导填料颗粒周围基体树脂的结晶,促使其表面伸展链晶体结构的形成,并由此而明显改变了复合材料的耐热性;复合材料的界面粘结性是产生这种应变诱导作用,并控制异相结晶的关键。     

SiCP/ZA22 复合材料界面反应层形成机制

通过电镜观察和扫描能谱分析, 发现在SiC_P/ ZA 22复合材料中,SiC 颗粒和ZA 22合金富铝相α-A l 两相界面上存在着层状反应物MgAl₂O₄, 并对其产生条件进行了分析。结果表明: 在该复合材料制备温度范围内满足产生MgAl₂O₄的热力学条件, 反应层厚度符合S = A t 规律, 最终反应物量主要与合金中的M g 含量以及SiC 颗粒表面的SiO₂层厚度有关。     

纳米填料改性丁基橡胶复合材料的力学性能、芥子气防护性能和燃烧性能

以有机蒙脱土、纳米级SiO₂气凝胶和沉淀法白炭黑等具有不同粒子形状和结构特性的纳米粒子为增强填料,采用熔体共混法制备了丁基橡胶复合材料。采用SEM和XRD对复合材料的微观结构进行了表征,并研究了不同纳米填料对复合材料的力学性能、芥子气防护性能和燃烧性能的影响。结果显示：纳米级SiO₂气凝胶/丁基橡胶复合材料的力学性能最优,填充15 wt% SiO₂气凝胶的复合材料的拉伸强度和撕裂强度分别比丁基橡胶硫化胶提高了9倍和2.2倍。复合材料的芥子气防护性能与纳米填料的粒子形状有密切的关系,填充15 wt%层片状结构有机蒙脱土的复合材料的芥子气防护时间达到了21h以上,明显优于填充近似球形粒子的纳米级SiO₂气凝胶和白炭黑的复合材料的防护性能。然而纳米填料使复合材料的氧指数和氧化分解温度只有少量提高,阻燃性能改善有限。     

表面修饰纳米SiO2增强增韧聚氯乙烯

用过量的2 , 4-甲苯二异氰酸酯(TDI)对纳米SiO₂表面进行修饰合成含—NCO 的功能化SiO_2,再用丙烯酸羟丙酯(HPA)对其表面进行修饰合成出HPA修饰纳米SiO₂(SiO₂-HPA)。用共混法制备了SiO₂-HPA/PVC纳米复合材料,研究了不同 SiO₂含量及不同界面特性时复合材料的力学性能。结果表明: SiO₂-HPA/PVC复合材料的力学性能和加工性能等方面均优于未修饰的样品。在纳米SiO₂质量分数为0%～5%时,SiO₂-HPA/PVC的拉伸强度和冲击强度随着填充量的增加呈先上升后下降的趋势并在3%～4%达到最大值。表面修饰纳米SiO₂与PVC基体之间具有很强的界面结合作用,其相容性得到大大改善,填充表面修饰纳米SiO₂达到了增强增韧双重效果。此外,对纳米粒子增强增韧机制进行了深入的探讨。     

EPDM/Al(OH)3 复合材料界面结构参数表征研究

采用动态力学分析(DMA ) 研究了EPDM/Al(OH)₃ 复合材料的界面结构参数, 提出了用DMA 分析估算复合材料界面层厚度的新方法, 讨论了Al(OH)₃ 粒子表面状态对EPDM/Al(OH)₃ 复合材料界面结构参数的影响。     

BN表面改性对BN/环氧树脂复合材料导热性能的影响

采用十八烷基三甲基溴化铵（OTAB）阳离子表面活性剂对BN微米片进行有机化改性,研究了BN表面改性对BN/环氧树脂复合材料导热性能的影响。当OTAB浓度为0.6 g · L^-1时,BN表面的OTAB吸附量接近饱和。BN表面改性提高了环氧树脂对BN的浸润性,降低了BN的导热系数。SEM观察及黏度测试结果表明：BN表面改性改善了BN/环氧树脂复合材料的界面性能及体系相容性。由于界面热阻的降低,改性BN/环氧树脂复合材料的导热系数高于未改性BN/环氧树脂复合材料,当BN填充量为30%（填料与树脂基体的质量比）时,改性BN/环氧树脂复合材料的导热系数为1.03 W （m · K）^-1,是未改性BN/环氧树脂导热系数（0.48 W （m · K）^-1）的2.15倍。     

Development and characterization of epoxy nanocomposites based on nano-structured oil palm ash

The aim of this study is to utilize the bio-agricultural waste as filler material for composite production which are abundantly available and low cost compared to the silica, alumina etc. The lacks of sufficient scientific information about the utilization of the oil palm ash (OPA) on composites production were the driving force for the choice of this work. Furthermore, the effect of filler loading percentage on physical, mechanical, thermal and morphology properties of the epoxy nanocomposites were studied. It was concluded that the size of the OPA had been successfully reduced from macromolecular to the nano-size range by high energy ball milling and was confirmed by TEM analysis. The density of the nano-structured OPA filled epoxy composites revealed that increasing filler loading will eventually increase the density. The tensile and flexural strength attained maximum value when the filler loading was 3%. Also, increase in the thermal stability was observed in case of 3% filler loading and was attributed to the increase in cross-linking of the epoxy resin in the presence of nano-stuctured OPA and having minimum particle to particle interaction and well dispersed nanoparticles.     

三维网状石墨烯/环氧树脂热界面复合材料的制备和热性能

三维网状石墨烯/环氧树脂热界面复合材料由于具有良好的热导性能和力学性能,而被广泛应用于微电子器件领域。但是通过化学剥离-还原法制备石墨烯,在填加石墨烯质量分数相同的条件下,石墨烯/环氧树脂热界面复合材料的热导率差别仍然很大。研究发现这主要是由于石墨烯表面官能团含量不同所导致的,因此很难建立统一的标准评估石墨烯作为导热填料的作用效果。为了避免表面官能团对石墨烯/环氧树脂复合物热导率的影响,本研究小组采用化学气相沉积法制备的三维网状石墨烯作为导热填料,对环氧树脂进行修饰,制备了一系列石墨烯/环氧树脂材料。通过研究三维网状石墨烯含量对石墨烯/环氧树脂材料热导率、力学性能及热导率在高温条件下稳定性的影响,有助于完善石墨烯修饰的环氧树脂热界面复合材料的研究,并建立石墨烯作为导热填料的评价体系。     

玻璃鳞片／环氧树脂复合材料的界面优化研究

采用ＥＳＣＡ，ＩＲ等研究了玻璃鳞片表面改性前后表面的变化，分别用ＳＥＭ，盐水浸泡实验和电子万能测试机研究了复合材料的界面，抗渗透性和力学性能。结果表明；玻璃鳞片表面经改性后形成了一层有机物分子层，优化了玻璃鳞片与环氧树脂的界面结合提高敢复合材料的抗渗透性和力学性能。     

聚合物涂层对高模量碳纤维表面性能的影响

为改善碳纤维表面性能以及碳纤维/树脂复合材料的界面性能,对PAN基高模量碳纤维（HMCF）表面进行聚合物涂层处理。研究了不同潜伏性固化剂含量的聚合物涂层对HMCF表面以及碳纤维/树脂复合材料的界面性能的影响。IR分析表明,聚合物涂层与纤维或树脂基体发生了化学反应。扫描电镜和动态机械热分析的结果也说明,聚合物涂层能够提高...     

Influence of glass microspheres on selected properties of polylactide composites

Comparison of some changes occurring in polylactide (PLA) due to its modification by glass filler being in the form of microspheres (GM) was the objective of the present study. Mechanical and thermal properties, density, mass flow rate, and were determined. In addition, there were examined surface free energy and changes in the surface geometrical structure of sample fractures. It was found that PLA as modified with GM exhibited the enhanced longitudinal modulus of elasticity, flexural modulus, and mass flow rate. The impact strength and flexural strength did not change. The tensile strength and tensile strain at break decreased. The used glass filler did not affect essentially the thermal properties of PLA. The prepared composites exhibited uniform distribution of the dispersed phase in the polymer matrix and adequate adhesion at the interface between the two components. Substantial changes in the properties of the surface layer were observed, mainly in surface free energy.     

A new method of reinforcing graphene nanoplatelets in glass/epoxy composites

This research aims to develop a method for the amalgamation of graphene nanoplatelets in glass/epoxy composites. The poor interface bonding between the fiber and matrix is critical and hinders the full performance of the composites. Glass fabric and epoxy were used as reinforcement and matrix in the composite, respectively. Graphene nanoplatelets were utilized as an additional nano-materials filler for the composites. Glass/graphene/epoxy and glass/epoxy composites were fabricated via vacuum infusion molding. The new method of applying graphene nanoplatelets as secondary reinforcement in the composite was developed based on proper functionalization in the sonication process. The physical, tensile, flexural, and short beam interlaminar properties of fabricated composites were examined to analyze the method's effectiveness. The results showed that density decreased by around 5 %; however, thickness increased by around 34 % after introducing graphene nanoplatelets into the composites. The tensile strength and modulus of the composites declined by approximately 19 %, on the other hand, flexural strength and modulus increased by around 63.3 % and 8.3 %, respectively, after the addition of graphene nanoplatelets into the composites. Moreover, interlaminar shear strength of the composite was enhanced by approximately 50 %.     

Free-volume properties of epoxy composites and its relation to macrostructure properties

Some characteristics of epoxy composites are discussed based on the results of positron annihilation lifetime spectroscopy (PALS), electrical and mechanical measurements. The effect of different types and wt% of fillers such as aluminium oxide (Al₂O₃), titanium oxide (TiO₂) and silicon carbide (SiC) on the epoxy structure and hence free volume, physical, electrical, and mechanical properties is presented. The results showed that the electrical properties are improved at high wt% of filler, while mechanical properties are improved at low wt% of filler. Furthermore, a similar trend is observed for all fillers but with a systematic shift to high influence when Sic added to cured epoxy. On the other hand, adding SiC as a filler on epoxy improved the resistance to water absorption.The role of PALS as a sensitive probe for changes in microstructure of epoxy composites is confirmed during the correlation between the free-volume parameters and the other measurements.     

Tribological properties of surface modified nano-alumina/epoxy composites

Nano-sized Al₂O₃ particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites. Curing habit, mechanical properties and tribological performance revealed by sliding wear tests of the composites were investigated. The experimental results indicated that the nanoparticles accelerate curing of epoxy, increase composites' impact strength and decrease wear rate and frictional coefficient of the composites. The surface modification by means of grafting polymerization can further enhance the properties improvement of epoxy due to the increased filler/matrix interfacial interaction. Compared to frictional coefficient, wear rate of epoxy can be decreased more remarkably by the addition of nano-alumina when rubbing against steel. The wear mode changes from severe peeling off of unfilled epoxy to mild micro-ploughing in the case of nano-alumina filled composites.