0-3型γ-C_2S压电复合材料的制备及性能研究

以γ型硅酸二钙(以下简称γ-C_2S)为基体,以锆钛酸铅(PZT)为压电相,用压制成型、碳化养护方法制备出0-3型γ-C_2S压电复合材料。分析了压电相体积分数及粒径分布、成型压力、碳化时间和极化时间对复合材料压电性能的影响,结果表明:复合材料压电性能在一定范围内随着压电相体积分数、成型压力、极化时间的增加而提高。在压电相体积分数从40%增加到85%时,复合材料压电应变常数d_(33)从4.78 pC/N提升到67.8 pC/N;在压电相体积分数保持为60%,成型压力从50 MPa增加到200 MPa时,复合材料压电应变常数d_(33)从14.6 pC/N提升到17.8 pC/N;在保持体积分数、成型压力一定时,极化时间为30 min较15 min复合材料具有更高的压电应变常数。同时,合理的颗粒级配对复合材料的压电性能也有显著的提升,当压电相体积分数为60%时,压电相陶瓷颗粒采用大颗粒、小颗粒混掺时复合材料压电性能得到显著提升,压电应变常数较只有小颗粒提升了1倍,达到33.9 pC/N。     

压电相体积分数对1-3 型压电复合材料的性能影响

采用有限元软件仿真研究了不同的压电相体积分数对1-3 型压电复合材料性能的影响, 并进行了实验验证。结果表明: 当压电相体积分数按照47% 、52% 、68% 、74% 、100% 变化时, 串联谐振频率和并联谐振频率均随压电相体积分数增大而增大; 机电耦合系数在压电相体积分数为52% 时获得最优值0.698; 复合材料的频率常数、密度、纵波声速和声阻抗均随着压电相体积分数的增大而增大。有限元仿真与实验结果较为一致。该材料有望用于制备高性能的无损检测用超声换能器。     

铌酸钾钠基无铅压电陶瓷的研究进展

铌酸钾钠基无铅压电陶瓷的研究和开发是当前压电铁电材料领域的研究热点之一.本文结合近期国内外有关无铅压电陶瓷论文,综述了铌酸钾钠基无铅压电陶瓷的性能和改性方法,简介了几种最先进的制备方法,并分析了无铅压电陶瓷发展趋势.     

PMN/ CB/ IIR复合材料的阻尼性能研究

采用混炼-模压-极化工艺制备了压电陶瓷/碳黑/丁基橡胶聚合物基压电阻尼复合材料,研究了压电陶瓷和碳黑用量、外力及作用频率等因素对复合材料阻尼性能的影响.结果表明,当压电陶瓷体积分数为50%、碳黑质量分数为5%时复合材料的阻尼因子tanδ峰值达到最高,有效阻尼温域最宽;复合材料的阻尼性能随着外力的增加而增强;当外力作用频率f接近或等于橡胶分子运动单元松弛时间的倒数1/τ时,复合材料的损耗模量E″和阻尼因子tanδ均出现最大值.     

CNTs/PMN /EP压电阻尼复合材料的制备及其压电效应的作用机理

研究了铌镁锆钛酸铅(PMN)压电陶瓷含量的变化及其压电效应对碳纳米管(CNTs)/铌镁锆钛酸铅(PMN)/环氧树脂(EP)压电阻尼复合材料阻尼性能的影响,并用ZrO_2替代PMN添加到复合材料中探讨了压电效应的作用机理。研究表明,PMN/EP复合材料损耗因子峰值与ZrO_2/EP复合材料相近,没有明显体现出PMN的压电效应,主要通过异质界面效应促进能量损耗,增强阻尼性能。CNTs/PMN/EP复合材料相较于CNTs/ZrO_2/EP复合材料的损耗因子峰值明显增加,并在PMN质量含量为60%时达到最大值0.62,表明导电相CNTs与压电相PMN的协同作用,充分发挥了压电相的压电效应,将载荷振动能转化为电能,并通过CNTs形成的导电网络通路以热能形式耗散,进一步增强了复合材料的阻尼性能。     

AlFeCrCoNi/Mg复合材料的显微组织及力学性能分析

为了探究AlFeCrCoNi高熵合金增强相含量对金属基复合材料显微结构及力学性能的影响规律,文中采用放电等离子烧结法制备了AlFeCrCoNi/Mg,通过场发射扫描电镜对其宏观和微观形貌进行了观察,利用X射线衍射仪对其物相进行了表征,采用阿基米德排水法、显微硬度机和电子万能试验机分别研究了复合材料的密度、维氏硬度和压缩性能。研究结果表明:随着高熵合金体积分数的增加,复合材料的维氏硬度达到70.33N·mm-2,屈服强度ReHc、抗压强度Rmc分别从125 MPa和288 MPa增加到211 MPa和306 MPa,各自提高了68.80%和45.02%,其中复合材料增强相体积分数由0%增加到5%过程中,屈服强度、抗压强度增长最快,复合材料增强相体积分数大于5%后,其增长较为平缓。     

PMN／CB／IIR复合材料的阻尼性能研究

采用混炼-模压-极化工艺制备了压电陶瓷／碳黑／丁基橡胶聚合物基压电阻尼复合材料,研究了压电陶瓷和碳黑用量、外力及作用频率等因素对复合材料阻尼性能的影响．结果表明,当压电陶瓷体积分数为50％、碳黑质量分数为5％时复合材料的阻尼因子tanδ峰值达到最高,有效阻尼温域最宽;复合材料的阻尼性能随着外力的增加而增强;当外力作用频率f接近或等于橡胶分子运动单元松弛时间的倒数1／τ时,复合材料的损耗模量E＂和阻尼因子tanδ均出现最大值．     

Cu-Ti3SiC2复合材料真空热压法制备及性能研究

Ti3SiC2是一种具有MAX层状结构的先进材料,兼具金属与陶瓷的双重性能。将Ti3SiC2作为弥散强化相与Cu复合制备金属基复合材料,综合力学性能较好,有望在电接触材料中有较好的应用前景。采用热压烧结法制备Cu-Ti3SiC2复合材料,试验证明Cu-Ti3SiC2复合材料的最佳烧结工艺为:烧结温度750℃,压力30 MPa,保温30min,制得复合材料的组织均匀,团聚较少。其次研究了Ti3SiC2含量对复合材料硬度、电阻率等性能的影响,随着Ti3SiC2的体积分数的增加,硬度先增加后降低,相对密度和抗弯强度呈减小趋势,电阻率增加;通过微观显微分析,Cu-Ti3SiC2致密度随Ti3SiC2含量增加而下降。     

琼脂糖凝胶注模成型3Y-ZrO_2的制备及表征

经球磨且真空除泡后的3Y-ZrO_2浆料通过添加质量分数为4.5%的琼脂糖溶液,制备出了3Y-ZrO_2生坯.生坯于高温烧结炉中在1 550℃下烧结4 h制得3Y-ZrO_2陶瓷.研究了固相体积分数对3Y-ZrO_2生坯相对密度和抗弯强度的影响,固相体积分数对烧结体的密度、抗弯强度、显微结构和物相结构的影响.结果表明,当固相体积分数从47%升高到56%时,生坯的相对密度从47.8%提高到57.2%,其抗弯强度从0.31 MPa提高到0.76 MPa;3Y-ZrO_2陶瓷的密度从5.32 g/cm~3增加到5.81 g/cm~3,其抗弯强度从312.772 MPa提高到427.3 MPa;3Y-ZrO_2陶瓷以四方相为主,晶粒尺寸均匀,几乎没有气孔.     

放电等离子合成Ti3AlC2/TiB2复合材料的研究

采用放电等离子烧结工艺成功地制备了Ti3AlC2/TiB2复合材料.研究表明:在1 250 ℃,30 MPa压力和保温8 min下烧结,可以得到相对密度达98%以上的致密Ti3AlC2/TiB2块体材料;在Ti3AlC2中添加TiB2能大幅度提高材料性能,Ti3AlC2/TiB2复合材料Vickers硬度随TiB2掺量的增加而增大,最大可达到10.4 GPa;当TiB2体积含量为10%时,复合材料的最大的抗弯强度为696 MPa,断裂韧性为6.6 MPa·m1/2.     

TiB_2/SiC陶瓷复合材料制备工艺的研究

以TiO2、B4C和C为原料,基于原位合成法在SiC基体中生成TiB2颗粒,并采用无压烧结法制备出TiB2/SiC复合陶瓷.通过对复合材料制备工艺的研究,发现：高于1 300℃的预烧结能形成TiB2/SiC复合陶瓷坯体.C含量、烧结温度和保温时间对复合材料的相对密度均有影响.当C含量（质量分数）为4%时、在1 400℃×60 min＋2000℃×30 min的烧结工艺下能够制备出致密的TiB2/SiC陶瓷复合材料.微米级TiO2粉比纳米级TiO2粉更有利于形成较致密的烧结复合材料.随着生成TiB2体积分数的增加（5%～20%）,复合材料中TiB2颗粒逐渐粗化,间距逐渐变小.对复合材料的烧结机理还进行了分析.     

SiCp/Cu复合材料高温抗氧化性能研究

采用粉末冶金方法制备了SiCp/Cu复合材料,研究了复合材料在恒温氧化和循环氧化条件下的抗氧化性能。结果表明：在400—700℃时,SiCp/Cu复合材料具有比纯铜优良的抗氧化性能;在温度一定的条件下,SiC体积分数为20%时,复合材料的抗氧化性能最好;在循环氧化条件下,随着氧化时间延长,复合材料氧化增重率逐渐增大,而且呈现近抛物线变化规律;对相同SiC颗粒含量的SiCp/Cu复合材料,SiC颗粒越细,试样的抗氧化性能越好。     

TiC/Ti-Al基复合材料的燃烧合成

为了改善Ti-Al金属间化合物的脆性,利用SHS/PHIP工艺制备了TiC/Ti-Al基复合材料.理论分析表明,绝热温度随C质量分数的增加而呈升高趋势,当体系中碳的质量分数≥2%时,该体系能完成自蔓延过程.采用电子扫描显微镜,X射线衍射仪对合成产物进行了分析.结果表明,合成产物中除存在基体相Ti3Al和TiAl和增强相TiC外,还存在许多三元相Ti3AlC和Ti2AlC相;随着Al质量分数的增加,增强相的形貌由颗粒状逐渐变成棒状或片状;复合材料的硬度和压缩强度随C质量分数的增加逐渐增加,但密度及相对密度随C质量分数的增加呈先增加后降低的趋势.当C的质量分数达到4%时,其实际密度和相对密度均达到最大.     

Microstructure and thermal properties of SiCp/Cu composites with Mo coating on SiC particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/(m·K) and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.     

Tribological properties of SiC/Cu composite at high temperature

SiC/Cu composites were prepared by hot pressing. The high temperature tribological properties of the composites were investigated. XRD, SEM techniques were carried out to characterize the samples. It is found that the friction coefficient of SiC/Cu composites increases with the increasing SiC content. The SiC reinforcement particles are worn down other than removed by pulling out during the wear test. Oxidation of Cu debris leads to the smooth contacting surface. Ring crack is formed under the cyclic wear test. The crack propagates through the damaged matrix and along the brittle interface between SiC particles and Cu matrix.     

A novel technique for preparation of electrically conductive ABS/Cu polymeric gradient composites

A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes’ law. Acrylonitrilebutadiene-styrene/Cu (ABS/Cu) gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10₁₅ Ω at ABS rich side, while that declined to 10⁵ Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vol%–4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.     

Hierarchical Co_3O_4 Microstructures Decorated with Ag and Cu Oxides: Study of Photocatalytic and Electrochemical Properties

Three-dimensional hierarchical Co_3O_4 microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment.Photocatalytic properties measurements revealed that the photocatalystic activities of Cu O/Co_3O_4 composites(Co_3O_4 microstructures decorated with Cu O)were enhanced while those of Ag_2O/Co_3O_4 composites(Co_3O_4 microstructures decorated with Ag_2O)were reduced,when compared with those of pure hierarchical Co_3O_4 microstructures toward the degradation of methyl orange.In addition,Cu O/Co_3O_4 composites exhibited an excellent recyclability ability of photodegradation.The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability.With the increase of the loaded Ag_2O and Cu O dosages deposited on the Co_3O_4 microstructures surface,the specific capacitance values of the composites were increased.Ag_2O/Co_3O_4 composite electrodes showed higher specific capacitance values and better cycling stability than Cu O/Co_3O_4 composite ones.     

Microstructures and Properties of SiC／Al2O3 ／Al- Si Composites Prepared by Reactive Penetration

The composition, microstructures and properties of SiC/Al2O3/Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO2 and SiC were investigated. The composition of the composites was measured by X-ray diffraction ( XRD ). The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed. The experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers“ SiC gains“. The denser the SiC/Al2O3/Al-Si composites, the higher their bending strength. As the filler “SiC gains“ become fine, the bending strength of the composites increases.     

Effect of Cu-Ti-C Reaction Composition on Reinforcing Particles Size of TiC_x/Cu Composites

TiC_x/Cu composites were fabricated by combustion synthesis and hot press technology. Using XRD, SEM, EDS, FESEM analysis methods, the effects of various carbon sources and different Cu contents on the microstructures of TiC_x/Cu composites and the size of TiC_x particles were investigated. Results showed that TiC_x reinforcing particles size increases with decreasing Cu content in Cu-Ti-C reaction system. With carbon nanotubes(carbon black) serving as carbon source, the generated TiC_x particles size transits from nanometer to submicron when Cu content corresponding to the reaction system is reduced to 60 vol%(70 vol%); while graphite serves as carbon source, there is no clear limiting concentration. C particles with smaller size, larger specific surface area and better distribution result in finer TiC_x particles, which is more beneficial to generating nano-sized TiC_x/Cu composites.     

Physical, antioxidant and thermal shock properties of Cu/Ti2AlC conductive composites

Cu/Ti₂AlC composites were fabricated by vacuum hot-pressing technique. Phase composition was analyzed by XRD and morphology of fracture was observed by SEM. Physical performance such as density, resistivity, hardness and friction coefficient with different volume fraction of Cu/Ti₂AlC composites were studied. When the content of Ti₂AlC increased from 10% to 70%, the relative density reduced from 99.38% to 90.56% and the resistivity increased significantly. Hardness reached the maximum value when Ti₂AlC was at 60% and friction coefficient declined with the increasing of Ti₂AlC. Cu/Ti₂AlC composites, showing good conductivity properties and friction performance. Oxidation resistance enhanced obviously with the content of Ti₂AlC increasing. Cu-60%Ti₂AlC sample possessed optimum thermal shock resistance, and no cracking was found at 600 °C cycled for 10 times and 900 °C cycled for 1 time.