纳米银/环氧树脂复合材料的制备及其介电性能的研究

采用紫外辐照还原的方法制备了纳米银粒子，研究了保护剂的添加、辐照强度和溶液配比等因素对纳米银粒子尺寸的影响。TEM反映出银粒子分散均匀，其粒度约为20nm。将制备出的纳米银与环氧树脂混合固化形成纳米复合电介质，研究了这种复合材料的介电性能：室温下复合材料的体积电阻率和工频击穿场强随着纳米银粒子的加入有所提高，介质损耗略有降低，而介电常数变化不大。结果表明，纳米银粒子能够提高基体聚合物的介电性能。这一现象可用库仑阻塞机制解释。     

n?SiO2的表面改性及其增强环氧树脂复合材料的性能

纳米粒子在聚合物中均匀、稳定分散,是纳米复合材料具有优良性能的前提。文中通过选择表面活性剂改性纳米SiO2,提高纳米粒子在环氧树脂中的分散性,制备出不同含量的n–SiO2/环氧树脂聚合物复合材料,探讨了纳米SiO2对复合材料强度的影响规律。研究结果表明:改性后的纳米SiO2粒子在聚合物体系中呈单分散状态,均匀分布的纳米粒子与基体结合紧密,其在基体中起到了物理交联点的作用,对剪切力的抵抗能力增强,提高了复合材料的综合性能。加入6%质量分数的纳米粒子,复合材料的拉伸剪切强度可提高35.1%。     

纳米Ag／PAM／EVA复合材料的制备及介电特性

利用γ射线辐照制备出均匀分布在PAM中的银粒子，直径约10nm。制备出的复合物再通过物理混合的方法与EVA复合，得到稳定的纳米Ag／PAM／EVA复合材料。结果表明：纳米银复合材料具有较高的电阻率和击穿场强，较低的tgδ和较高的介电常数。这种纳米粒子的新颖特性可以用库仑阻塞机理解释。     

载银纳米粒子聚乙烯醇(PVA)的一锅合成及其亚甲基蓝催化还原效率（英文）

用聚乙烯醇(PVA)作为还原剂和封端剂合成稳定的银纳米粒子,采用立体稳定法将银纳米粒子掺入聚合物基体中。用紫外-可见光谱、透射电子显微镜和傅里叶变换红外光谱等手段表征掺入聚合物基体中的银纳米粒子。紫外-可见光谱结果表明合成的银纳米粒子的特征峰为426 nm,透射电子显微镜表明银纳米粒子为球形,尺寸为10~13 nm,接着用紫外光照射还原,然后采用紫外-可见光谱分析其催化性能。结果表明,合成的银纳米粒子在亚甲基蓝还原中具有良好的催化性能。     

碘化多壁碳纳米管制备含有Ag/MWCNTs复合材料的银-环氧树脂浆料

提出一种将多壁碳纳米管碘化后制备银/多壁碳纳米管（Ag/MWCNTs）复合材料的方法。通过球磨对碘化多壁碳纳米管进行了功能化,并通过透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、拉曼光谱和热重分析（TG）对其进行了表征。结果表明,经碘化处理后,银纳米粒子（Ag-NPs）能更好地粘附在碳纳米管表面,改善了银纳米粒子与碳纳米管之间的连接。羟基（-OH）基团的伸缩振动明显增强,激活了碳纳米管的表面,增加了碳纳米管表面Ag⁺形核的数量。在260 ℃以下,Ag/MWCNTs复合材料的质量损失小于MWCNTs的质量损失。最后,制备了银-环氧树脂浆料,发现使用Ag/MWCNTs复合物制备的浆料具有最低的电阻率和最高的热导率。     

银纳米粒子熔化的尺寸效应研究

采用分子动力学方法对银纳米粒子进行了熔化过程的模拟,研究分析了银纳米粒子熔化的尺寸效应问题。仿真结果表明,银粒子固-液相变时,其系统势能在某一温度范围内具有明显的突变,熔化过程类似于非晶体,并且银纳米粒子的熔化温度明显低于块状材料,随着纳米粒子尺寸的减小,其熔点也随之降低,根据仿真结果及理论分析建立了纳米粒子熔点与粒径之间的数值关系,并分析了相关的主导机制。     

SiC颗粒尺寸对喷射沉积铝硅复合材料高温疲劳性能的影响

采用喷射沉积法制备SiCp/Al-7Si复合材料,研究SiC颗粒尺寸对复合材料低周疲劳性能的影响.结果表明:SiC颗粒尺寸对复合材料疲劳性能的影响显著.在相同体积分数下,小尺寸SiC颗粒复合材料的间距小、承载能力强,表现出较高的疲劳寿命,疲劳裂纹主要在SiC颗粒与基体脱粘处以及小尺寸颗粒团聚处形核并扩展.而在SiC颗粒...     

银纳米粒子的形状控制合成与应用

纳米金属颗粒由于小尺寸效应、表面效应、量子尺寸效应显示出与块体材料不同的热、光、电、磁、催化等性能。纳米金属材料的性能不仅与粒子尺寸有关，而且还受到粒子形貌的影响。近年来，金属纳米粒子的形状控制合成受到了特别的关注。本文着重评述近年来金属纳米粒子形状控制合成的方法并以银为例介绍了其形状控制合成的最新研究进展。     

Ormecon公司推出印刷线路板块构造学新型金属表面处理工艺

近日，Ormecon International公司向印刷电路板市场推出了纳米尺寸的全新表面处理新工艺。其表层由有机纳米金属和银（银10％以下）形成的纳米粒子复合材料组成，厚度仅为55nm。     

SiCp/Cu复合材料电性能研究

利用热压烧结工艺制备了含20%～65%SiC(体积分数,下同)颗粒的SiCp/Cu复合材料.在室温到600℃温度范围内测定了复合材料的电阻率.结果表明,随着SiC颗粒含量的增加,SiCp/Cu复合材料的电阻率提高,电阻率渗滤阈值发生在SiCp含量大约55%时;含有20%～35%SiC颗粒的SiCp/Cu复合材料的电阻率随温度的升高而线性增加,表现为铜的电导特征;而含有50%～65%SiC颗粒的SiCp/Cu复合材料的电阻率随温度的升高在225～500℃温度范围内明显偏离线性增加关系.     

原位一步法合成Ag/Fe2O3磁性核壳纳米粒子

采用原位法在低温下一步合成Ag/Fe2O3磁性核壳纳米粒子,并采用XRD,TEM和UV光谱研究了Ag-Fe2O3核壳纳米复合材料的结构。结果表明,纳米银粒子表面被Fe2O3层包覆,Ag核的平均粒径大约为35nm,Fe2O3壳层平均厚度约为7.5nm或15nm,形成了核壳结构的电磁复合纳米粒子。在室温下,饱和磁化强度达到0.98(A·m2)·kg-1,矫顽力8.48×103A/m;Ag/Fe2O3核壳粒子的导电率达到0.62S/cm。通过此法可以比较容易的控制核和壳的尺寸以及复合粒子的单分散性,并得到较高的产率,在催化剂、医药、光电等领域有着广阔的应用前景。     

Study on Properties of Conductive Adhesive Prepared with Silver Nanoparticles Modified by Silane Coupling Agent

采用经硅烷偶联剂KH-560表面改性的纳米银粉作为填料,环氧树脂为基体在180℃固化得到银导电胶。借助透射电子显微镜(TEM)、红外光谱(FTIR)、差示扫描量热法(DSC)等测试手段,对改性后纳米银粉和导电胶进行了表征。研究了银粉含量、固化时间对导电胶性能的影响。结果表明:KH-560改性后的纳米银粉平均粒径为20 nm,分散均匀;KH-560以化学键合的方式吸附在纳米银颗粒的表面。银粉含量、固化时间等均会影响导电胶的性能。当银粉含量为55%,固化时间为15 min时,导电胶的体积电阻率达最小值为2.5×10-3Ω·cm。与未做任何表面处理的纳米银粉填充的导电胶相比, KH-560改性后纳米银粉所得导电胶的电导率提高了3-5倍。     

纳米银对环氧树脂的增韧改性及其微波固化行为

在80℃双酚A型环氧树脂E-51中,通过还原原位构筑了超分散稳定纳米银(n-Ag);用冷冻蚀刻电镜、离心实验对其进行表征和分散稳定性评价;用间歇微波对分散系中n-Ag的微波吸收特性和环氧树脂的微波固化行为进行研究;通过拉伸试验和冲击试验考察n-Ag对环氧树脂的增韧改性行为。结果表明:银为30nm的粒状颗粒,大小均匀,有理想的分散稳定性;n-Ag对环氧树脂有显著地增韧作用,当其含量为2.0%～2.5%(质量分数)时,增韧改性效果最佳,复合材料的断裂伸长率可提高l10%～130%;原位合成n-Ag有良好的微波吸收特性,它的存在能明显减少环氧树脂的微波固化时间,当n-Ag含量超过2.5%时,微波固化时间可缩短38%;微波固化环氧树脂速度比传统加热固化速度快数倍,其抗拉伸强度和抗冲击强度也好于热固化,但拉伸断裂伸长率比热固化的小。     

The effect of gamma irradiation on electret properties of polyethylene

The paper describes the electret properties of low-density polyethylene and the effect of gamma irradiation on them. It is shown that the thicker polyethylene film the more stable the surface potential, electric field strength, and effective surface charge density values. The negative impact of gamma-radiation on the electret properties of the films that is caused by the release of the injected charge carriers from the traps due to clearing the energy barrier thanks to radiation energy is revealed. Irradiated polyethylene films, in turn, are polarized badly in a corona discharge because of the oxygen-containing groups on the surface formed during gamma-irradiation that act as charge carrier traps with low capture energy. It was found that the formation of cross bonds in the bulk of the polymer and carbonyl groups on its surface slightly raises the degree of crystallinity and the specific volume resistivity and decreases the specific surface resistivity.     

Easy and Large Scale Synthesis Silver Nanodendrites: Highly Effective Filler for Isotropic Conductive Adhesives

Dendritic silver (Ag) nanoparticles have been successfully prepared by an easy and large scale liquid-phase reduction method. Transmission electron microscope (TEM), scanning electron microscope (SEM), and x-ray diffraction (XRD) have shown that the Ag particles prepared by this method are pure and with uniform dendritic morphology. The bulk resistivity and bonding strength of isotropic conductive adhesives (ICAs) filled with Ag nanodendrite and micrometer-sized Ag have been measured. The results show that the dendritic morphology of Ag nanoparticles has a strong effect for improving the reinforcement of the composite electrical performance. ICA filled with small amounts of Ag nanodendrites exhibits lower bulk resistivity and higher bonding strength than ICA filled with micrometer-sized Ag. When ICA is filled with 50 wt.% micrometer-sized Ag and 10 wt.% Ag nanodendrites, the bulk resistivity is 1.3 × 10⁻⁴ Ω cm, and the bonding strength reaches 18.9 MPa.     

耐折高导电性银浆的制备

研究了银片粒径对折叠前后银浆电导率的影响。采用不同粒径的片状银制备了具有良好导电性能的低温固化耐折导电银浆料,将银浆网印在聚酰亚胺基板上,在140 ℃下烧结形成网印电路。用微欧姆计检测了印刷电路的电阻率,对印刷银电路折叠前后的电阻变化进行了检测,并用扫描电镜对其表面形貌进行了研究,分析了导电机理。结果表明,小片Ag作为未连接薄片之间的桥梁,在折叠后填补了空白,形成导电网络,提高了折叠后的银浆导电性能。     

氨基链修饰氧化石墨烯/环氧树脂界面性能的分子动力学模拟

目的 对氨基链修饰氧化石墨烯与DGEBA/3,3′-DDS环氧树脂复合材料界面的形成过程和性能进行理论研究,为环氧树脂涂层的性能改性提供理论依据.方法 利用Materials Studio 2019软件的Amorphous Cell模块建立了复合材料界面模型,采用分子动力学模拟方法对界面的结构、能量变化、界面处基团运动...     

Influence of Fe addition on microstructure and properties of Cu-Ag composite

We investigated the effects of Fe content on microstructure and properties in as-cast and as-drawn Cu-(5.1-x) vol%Ag-x vol%Fe alloys. In microscale, increasing Fe content first refined and then coarsened Cu dendrites. In nanoscale, the size and length of Ag precipitates in Fe-doped alloys were smaller than the size and length of Ag precipitates in Fe-free alloy, and the γ-Fe precipitates in Cu-2.9 vol%Ag-2.4 vol%Fe alloy were finer than the γ-Fe precipitates in Cu-5.1 vol%Fe alloy. The maximum hardness in as-cast Cu-Ag-Fe alloys was found in the Cu-2.9 vol%Ag-2.4 vol%Fe alloy. With increasing drawing strain, both ultimate tensile strength and hardness of Cu-Ag-Fe composites were increased. Simulation data among the relative volume fractions of Fe, hardness and electrical conductivity showed that, as the relative value approached 40%, the Cu-Ag-Fe composite displayed greater hardness than other samples. As a small amount of Ag was replaced by Fe, the electrical conductivity decreased significantly with a descending slope of approximately 3%IACS (International Annealed Copper Standard) per vol% Fe. As 47 vol%Ag was replaced by Fe, however, the electrical conductivity decreased by 51% and remained almost invariable with further increasing Fe content. After annealing at 450 °C for 4 h, the electrical conductivity of the Cu-2.9 vol%Ag-2.4 vol%Fe composite was elevated up to 68.3%IACS from 38.5%IACS.     

Thermal Expansion of Carbon Nanofiber-Reinforced Multiscale Polymer Composites

Improved dimensional stability of composites is desired in applications where they are exposed to varying temperature conditions. The current study aims at analyzing the effect of vapor-grown carbon nanofibers (CNFs) on the thermal expansion behavior of epoxy matrix composites and hollow particle-filled composites (syntactic foams). CNFs have a lower coefficient of thermal expansion (CTE) than epoxy resin, which results in composites with increased dimensional stability as the CNF content is increased. The experimental measurements show that with 10?wt.% CNF, the composite has about 11.6% lower CTE than the matrix resin. In CNF-reinforced syntactic foams, the CTE of the composite decreases with increasing wall thickness and volume fraction of hollow particle inclusions. With respect to neat epoxy resin, a maximum decrease of 38.4% is also observed in the CNF/syntactic foams with microballoon inclusions that range from 15?vol.% to 50?vol.% in all composite mixtures. The experimental results for CNF/syntactic foam are in agreement with a modified version of Kerner??s model. A combination of hollow microparticles and nanofibers has resulted in the ability to tailor the thermal expansion of the composite over a wide range.