搅拌铸造法制备短碳纤维/AZ91复合材料的组织与性能

采用搅拌铸造法制备了不同体积分数（10vol%、15vol%、20vol%）的短碳纤维增强镁基（CF_s/AZ91）复合材料,并选取了三个挤压比和两个挤压温度对其进行热挤压变形,采用光学显微镜（OM）、SEM和TEM对CF_s/AZ91复合材料的显微组织进行了观察,并测试其室温力学性能及阻尼性能。研究结果表明,热挤压能够有效降低CF_s/AZ91复合材料气孔率;在热挤压过程中,纤维沿挤压方向定向排列,同时基体发生动态再结晶。随着挤压温度及挤压比的增大,晶粒呈现等轴状,组织更加均匀。CF_s/AZ91复合材料经过挤压后,其力学性能得到提高,屈服强度和抗拉强度随挤压比和CF_s体积分数的增大而增大,然而CF_s纤维在热挤压后发生明显断裂,限制了挤压态复合材料强度的进一步提升。低温低挤压比条件下,CF_s/AZ91复合材料具有较好的阻尼性能,随着挤压比及挤压温度的升高,CF_s/AZ91复合材料室温及高温阻尼性能均有所降低。      

Ca0.7La0.2TiO3陶瓷填充氰酸酯树脂高频介电复合材料的制备与性能

将具有优异介电性能的Ca_0.7La_0.2TiO₃陶瓷填充到氰酸酯(CE)树脂中,通过熔融浇铸技术成功制备了Ca_0.7La_0.2TiO₃/CE复合材料。结果表明,不同Ca_0.7La_0.2TiO₃填料体积分数的复合材料微观结构致密。填料体积分数为40vol%时,获得了高介电常数(ε)和低介电损耗(tanδ) (ε=25.7,tanδ=0.0055, 10 GHz)的复合材料, 且弯曲强度达到130 MPa,同时材料的导热系数提高到0.8601 W/(m·K),可有效进行散热。TGA结果表明,相比于CE树脂,复合材料具有更高的热稳定性,在高频通信、集成电路等领域具有良好的应用前景。      

复合区体积分数对氧化锆增韧氧化铝颗粒/40Cr空间结构复合材料冲击磨损性能的影响

为研究空间结构复合材料中复合区体积分数对复合材料冲击磨损性能的影响,采用挤压铸造法制备了不同复合区体积分数(35vol%、50vol%、65vol%)的氧化锆增韧氧化铝颗粒(ZTA_P)三维网络增强40Cr钢基复合材料(ZTA_P/40Cr空间结构复合材料),经过850℃淬火和460℃回火,在冲击功为1.5 J下进行无磨料冲击磨损实验。结果表明:复合区体积分数为35vol%、50vol%、65vol%的ZTA_P/40Cr空间结构复合材料磨损率分别为4.68×10?3 cm3/h、3.40×10?3 cm3/h、1.04×10?3 cm3/h,ZTA_P/40Cr复合材料和40Cr钢的磨损率分别为13.41×10?3 cm3/h和79.87×10?3 cm3/h。ZTA_P/40Cr空间结构复合材料的耐磨性随复合区体积分数增加而提高。进一步分析表明,ZTA_P/40Cr空间结构复合材料的冲击磨损机制包含表面发生的磨粒磨损和黏着磨损,主要是基体黏着和整个表面被犁削及亚表层萌生的疲劳磨损,是由反复冲击过程中产生的ZTA_P破碎和ZTA_P与40Cr界面开裂导致的材料块状脱落。      

镀Ag玻璃微珠-膨胀石墨/聚氯乙烯导电复合材料的制备与表征

采用一种无Pd无SnCl₂化学镀Ag新工艺对空心玻璃微珠（HGB）表面进行化学镀Ag,然后通过熔融共混方法制备镀Ag玻璃微珠（Ag-GB）-膨胀石墨（EG）/聚氯乙烯（PVC）复合材料。借助SEM、EDS和XRD测试手段对Ag-GB镀层的表面形貌与结构进行了表征,研究了Ag-GB和EG作为复合填料对Ag-GB-EG/PVC复合材料导电和力学性能的影响。结果表明:预处理的HGB的表面更易于Ag层的沉积,镀覆的镀层更为均匀、致密;Ag-GB表面的Ag层质量分数为81.15%;固定Ag-GB的质量分数为15%,随着EG质量分数的增加,Ag-GB（15%）-EG/PVC复合材料的体积电阻率呈非线性降低趋势,当EG的质量分数达到逾渗阈值12%时,Ag-GB（15%）-EG/PVC复合材料的体积电阻率为2.18×103 Ω·cm,满足抗静电PVC材料的应用要求。添加质量分数为12%的EG,Ag-GB（15%）-EG/PVC复合材料的体积电阻率与单独填充质量分数为50%的Ag-GB时Ag-GB/PVC复合材料的体积电阻率相当,此时其拉伸强度达到最大值。      

石墨/环氧树脂高填充复合材料的制备和性能研究

通过溶液共混法和“真空处理-预固化-破碎-模压-加热固化”的方式制备了石墨/环氧树脂高填充复合材料.使用光学显微镜对其形貌进行了分析,研究了石墨含量对复合材料导电性能和力学性能的影响规律,确定了一种制备石墨/环氧树脂高填充复合材料可行的方法.结果表明,所制备的复合材料中石墨含量达80％,体积电阻率为10-2Ω·cm.逾...     

添加铜网对片层石墨/Al复合材料热物理性能的影响

使用盐浴法对片层石墨（GFs）进行表面镀Si处理,采用真空热压法制备片层石墨/Al复合材料（Si-GFs/Al）。向Si-GFs/Al复合材料中添加10vol%的铜网,研究了铜网对Si-GFs/Al复合材料热导率和力学性能的影响。使用SEM、聚焦离子束（FIB）和TEM对Si-GFs/Al复合材料的微观结构和微观界面进行表征,并分析了复合材料的断裂机制。结果表明,添加铜网使Si-GFs/Al复合材料内部出现了高聚集定向GFs带,形成高导热通道。当GFs体积分数为30vol%~40vol%时,Si-GFs/Al复合材料的热导率提升了约20%,弯曲强度提升了40%以上。当GFs体积分数为40vol%时,Si-GFs/Al复合材料热导率和弯曲强度同时达到一个优值,分别为512 W/（mK）和127 MPa。      

EG/SSF/ABS复合材料的导电性能与力学性能

采用硅烷偶联剂（KH550）改性膨胀石墨（EG）和不锈钢纤维（SSF）,将表面处理前后的EG和SSF与丙烯晴-丁二烯-苯乙烯（ABS）树脂通过混炼挤出制备了复合材料,分析了EG、SSF含量及改性处理EG、SSF对复合材料导电性能和力学性能的影响。结果表明,随着EG含量增加,复合材料的体积电阻率逐渐下降,且变化规律符合＂渗滤效应＂;EG改性后,复合材料的体积电阻率减小,拉伸强度增大,冲击强度减小。改性EG含量保持20%不变,加入SSF后,复合材料的导电性能有较大提高;SSF改性后,复合材料的体积电阻率变大,拉伸强度和抗冲击强度均提高,当改性后SSF含量为16%时,体积电阻率为5190Ω.cm,拉伸强度和抗冲击强度分别为50.11MPa和2.1kJ/m2。     

SiO2粉体粒径对STF/Kevlar复合材料防刺性能的影响

采用自制的不同粒径的SiO₂粉体, 利用球磨分散技术配制具有剪切增稠特性的SiO₂/PEG200悬浮液流体(STF), 并利用静态浸渍方法制备STF/Kevlar复合材料, 研究了粉体粒径对流体体系流变性能和复合材料防刺性能的影响。结果表明, 不同粒径SiO₂粉体配制的悬浮液均具有明显的剪切增稠性能, 当SiO₂粉体质量分数相同时, 流体体系的起始黏度、 临界剪切速率、 最大黏度均随着粒径的增大而减小。16层STF/Kevlar试样能承受24.0 J锥体冲击, 远远优于相同面密度的纯Kevlar试样, 随着粒径的增加, 试样的防锥刺性能提高。刀体冲击能量为13.0 J时, STF/Kevlar试样的防刀刺性能优于相同面密度的纯Kevlar试样, 随着粒径的增大, 试样的被刺穿深度减小, 主要表现为剪切断裂破坏。      

石墨在固相剪切碾磨力场下的片层剥离及与PVC的纳米复合

采用固相剪切复合技术成功制备石墨-聚氯乙烯(PVC)复合粉体, 实现了石墨的片层剥离和在PVC基体中的纳米分散及对PVC的抗静电改性。通过XRD、 SEM、 TEM等表征了石墨-PVC/PVC复合材料的结构, 研究了其抗静电性能。结果表明, 石墨的片层厚度约20 nm, 径厚比超过10。固相剪切碾磨技术制备的石墨-PVC/PVC复合材料的导电性能有较大提高。在石墨质量分数为2%时, 表面电阻率为4.6×10⁷ Ω·cm, 已达到了抗静电材料的要求, 实现了低填充。在石墨质量分数为10%时, 表面电阻率达到最低的4.1×10⁴ Ω·cm。     

石墨在固相剪切碾磨力场下的片层剥离及与PVC的纳米复合

采用固相剪切复合技术成功制备石墨-聚氯乙烯(PVC)复合粉体,实现了石墨的片层剥离和在PVC基体中的纳米分散及对PVC的抗静电改性.通过XRD、SEM、TEM等表征了石墨-PVC/PVC复合材料的结构,研究了其抗静电性能.结果表明,石墨的片层厚度约20 nm,径厚比超过10.固相剪切碾磨技术制备的石墨-PVC/PVC复合材料的导电性能有较大提高.在石墨质量分数为2％时,表面电阻率为4.6×107 Ω·cm,已达到了抗静电材料的要求,实现了低填充.在石墨质量分数为10％时,表面电阻率达到最低的4.1×104 Ω·cm.     

A comparative study of the coated filler method and the admixture method of powder metallurgy for making metal–matrix composites

Copper–matrix composites were made by powder metallurgy (PM). The reinforcements were molybdenum particles, silicon carbide whiskers and titanium diboride platelets. The coated filler method, which involves a reinforcement coated with the matrix metal, was used. In contrast, conventional PM uses the admixture method, which involves a mixture of matrix powder and reinforcement. For all the composite systems, the coated filler method was found to be superior to the admixture method in providing composites with lower porosity, greater hardness, higher compressive yield strength, lower coefficient of thermal expansion (CTE), higher thermal conductivity and lower electrical resistivity, though the degree of superiority was greater for high than low reinforcement contents. In the coated filler method, the coating on the reinforcement separated reinforcement units from one another and provided a cleaner interface and stronger bond between reinforcement and matrix than the admixture method could provide. The highest reinforcement content attained in dense composites (<5% porosity) made by the coated filler method was 70 vol% Mo, 60 vol% TiB2 and 54 vol% SiC. The critical reinforcement volume fraction above which the porosity of composites made by the admixture method increases abruptly is 60% Mo, 42% TiB2 and 33% SiC. This fraction increases with decreasing aspect ratio of the reinforcement. Among Cu/Mo, Cu/TiB2 and Cu/SiC at the same reinforcement volume fraction (50%), Cu/Mo gave the lowest CTE, highest thermal conductivity and lowest electrical resistivity, while Cu/SiC gave the greatest hardness and Cu/TiB2 and Cu/SiC gave the highest compressive yield strength. Compared to Cu/SiC, Cu/TiB2 exhibited much higher thermal conductivity and much lower electrical resistivity. This revised version was published online in November 2006 with corrections to the Cover Date.     

BN表面沉积纳米Sn对BN/环氧树脂复合材料导热绝缘性能的影响

采用液相还原法,制备了BN表面沉积纳米Sn粒子(BN-Sn NPs)杂化材料,用于环氧树脂(EP)的导热绝缘填料。BN-Sn NPs表面纳米Sn的粒径和熔点分别为10~30 nm 和166.5~195.3℃。BN表面沉积纳米Sn后,粉体Zeta电位及压片的导热系数增加,EP滴在压片表面的接触角降低。在BN-Sn NPs/EP复合材料固化过程中,BN-Sn NPs表面纳米Sn熔融烧结,有利于填料相互桥联在一起,降低接触热阻,并改善界面性能,从而提高BN-Sn NPs/EP复合材料的导热系数。当填料体积含量为30vol%时,BN-Sn NPs/EP复合材料的导热系数达1.61 W(m·K)?1,比未改性BN/EP复合材料的导热系数(1.08 W(m·K)?1)提高了近50%。Monte Carlo法模拟表明,BN和BN-Sn NPs在EP基体中的接触热阻(R_c)分别为6.1×106 K·W?1和3.7×106 K·W?1。与未改性BN/EP复合材料相比,BN-Sn NPs/EP复合材料的介质损耗增加,介电强度及体积电阻率降低,但仍具有良好电绝缘性能。      

Increasing the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation

The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer-matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (?1.5 vol.%) at the interlaminar interface. The 7-μm-diameter 7-W/m K-thermal-conductivity continuous fiber volume fraction is increased by the curing pressure increase, but is essentially unaffected by filler incorporation. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber-fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber-fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. The curing pressure increase does not affect the effectiveness of 1-mm-long 10-μm-diameter 900-1000-W/m K-thermal-conductivity K-1100 carbon fiber or single-walled carbon nanotube (SWCNT) as fillers for enhancing the conductivity, but hinders the effectiveness of carbon black (CB, low-cost), which is less effective than K-1100 or SWCNT at the higher curing pressure, but is almost as effective as K-1100 and SWCNT at the lower curing pressure. The effectiveness for enhancing the flexural modulus/strength/ductility decreases in the order: SWCNT, CB, K-1100.     

Thermal conductivity of liquid crystalline epoxy/BN filler composites having ordered network structure

BN filler was added to a liquid crystalline (LC) epoxy resin to obtain a high thermal conductive material. The LC epoxy/BN composites, which were cured at different temperatures, formed an isotropic or LC polydomain phase structure. The relationship between the network orientation containing mesogenic groups and the dispersibility of the BN filler was discussed. As a result, the thermal conductivity of the LC polydomain system was drastically enhanced even at a relatively low volume fraction of BN (30 vol%), regardless of the fact that both the LC and isotropic phase systems consisted of the same resin and filler content combination. This result is due to the formation of thermal conductive paths by the BN filler by exclusion of the BN filler from the LC domain formed during the curing process in the composite having the LC polydomain matrix.     

Brass-matrix silicon carbide whisker composites prepared by powder metallurgy

Brass (Cu-18Zn)-matrix and copper-matrix composites containing 0–50 vol% silicon carbide whiskers were fabricated by powder metallurgy using both the admixture method and the coated filler method, such that the fabrication of the copper-matrix composites did not involve a liquid phase whereas that of the brass-matrix composites did during the sintering process. The coated filler method gave composites with lower porosity, greater hardness, higher compressive yield strength, lower coefficient of thermal expansion (CTE), higher thermal conductivity and lower electrical resistivity than the admixture method, though the differences were much larger for copper-matrix composites than brass-matrix composites due to the liquid phase present during the fabrication of the brass-matrix composites. The mechanical properties of the brass-matrix composites were similar to those of the copper-matrix composites (also made by the coated filler method) at >35 vol% SiC, but were superior to those of the copper-matrix composites at <35 vol% SiC. The CTE was lower for brass-matrix composites than copper-matrix composites at >35 vol% SiC. The thermal conductivity was lower and the electrical resistivity was higher in brass-matrix composites than copper-matrix composites at <50 vol% SiC.     

MWCNTs改善WS2/三元乙丙橡胶复合材料的非线性电导特性与热导性能

通过在一定量的纳米WS₂中添加极少量的多壁碳纳米管（MWCNTs）,形成MWCNTs-WS₂复配填料,采用双辊开炼机将三元乙丙橡胶（EPDM）与不同配比的复配填料混合制备了不同MWCNTs含量的MWCNTs-WS₂/EPDM复合材料。并研究了极少量的MWCNTs添加对MWCNTs-WS₂/EPDM复合材料非线性电导性能、直流击穿性能和导热性能的影响。结果表明,极少量的MWCNTs对MWCNTs-WS₂/EPDM复合材料在25℃时的非线性电导特性起到明显的增强作用,且随着MWCNTs含量的增加,复合材料非线性电导特征有明显的规律性变化;由于MWCNTs自身的高电导率和电导正温度系数效应,MWCNTs-WS₂/EPDM复合材料电导率随电场强度的变化趋势在80℃时不再表现非线性特征。另外,极少量的MWCNTs对MWCNTs-WS₂/EPDM复合材料的热导率有明显地改善。      

Fabrication and characterization of aluminum nitride polymer matrix composites with high thermal conductivity and low dielectric constant for electronic packaging

Polymethyl methacrylate (PMMA) composites filled with Aluminum Nitride (AlN) were prepared by powder processing technique. The microstructures of the composites were investigated by scanning electron microscopy techniques. The effect of AlN filler content (0.1–0.7 volume fraction (vf)) on the thermal conductivity, relative permittivity, and dielectric loss were investigated. As the vf of AlN filler increased, the thermal conductivity of the specimens increased. The thermal conductivity and relative permittivity of AlN/PMMA composites with 0.7 vf AlN filler were improved to 1.87 W/(m K) and 4.4 (at 1 MHz), respectively. The experimental thermal conductivity and relative permittivity were compared with that from simulation model.     

固相剪切碾磨对Al/低密度聚乙烯导热复合材料结构与性能的影响

采用固相剪切碾磨预处理结合熔融再加工技术制备了高性能铝粉(Al)/线性低密度聚乙烯(LLDPE)导热复合材料,并与常规熔融共混法对比,系统研究了固相剪切碾磨对复合材料微观形态、结晶性能、热稳定性、流变特性、热导率和力学性能等的影响。结果表明:通过固相剪切碾磨实现了球形Al颗粒应力诱导变形为具有较大径厚比的片状,在基体中均匀分散且与其界面结合得以增强,同时这种大片状的铝粉在Al/LLDPE复合材料成型时更易有效接触形成导热网链并形成一定取向分布,特别是在高填充量下。因此Al/LLDPE复合材料拥有更好的结晶性能和热稳定性、更低的流变逾渗阈值、更高的热导率和力学性能。固相剪切碾磨预处理制备的Al/LLDPE复合材料在铝粉含量超过15%就出现流变逾渗现象,且当Al填充质量分数80%时,复合材料的热导率高达8.86 W/(m·K),拉伸强度和弯曲强度分别为33.0 MPa和31.2 MPa,都明显优于常规熔融共混复合体系,同时其初始分解温度也提高了近13℃。