孔隙率与界面结构对高体积分数SiC_p/Al复合材料热学和力学性能的影响（英文）

采用放电等离子烧结技术成功制备具有高热学和力学性能的50vol.%SiC_p/Al复合材料,研究烧结温度对复合材料热导率、热膨胀系数和抗弯强度的影响。结果表明,在520℃下烧结获得的复合材料,导热系数为189W/(m·K),热膨胀系数(50～200℃)为10.03×10~(-6)K~(-1),抗弯强度为649 MPa。Al合金基体与SiC颗粒之间的界面结合良好,复合材料接近完全致密,因而具有较高的热学性能和力学性能。为满足高性能电子封装材料的制备提供一种新的可行方法。     

热等静压制备铜金刚石复合材料

利用包套热等静压(HIP)烧结在温度900℃和压力110 MPa下烧结1 h实现了铜金刚石复合材料的制备,并对复合材料的显微结构和热学性能进行了研究。结果表明:该材料中金刚石分布均匀且未发生石墨化。随着金刚石体积分数的增大,复合材料的致密度、热导率与热膨胀系数下降。制得样品中的最高致密度和热导率分别为98.5%和305W/(m·K)~(-1)。和热压烧结(HP)及放电等离子体烧结(SPS)相比,热等静压制得的铜金刚石复合材料的热导率达到相同水平甚至更高。可见,热等静压在制备铜金刚石复合材料上具有很大潜力。     

SiC颗粒级配对SiC_p/Al复合材料微观结构和性能的影响

采用放电等离子烧结技术制备高体积分数SiC_p/Al复合材料,研究SiC颗粒级配对复合材料微观结构、热和力学性能的影响。结果表明:放电等离子烧结制备的SiC_p/Al复合材料由SiC和Al两相组成,SiC颗粒基本呈均匀随机分布、层次明显,SiC颗粒与Al基体界面结合强度高且无Al_4C_3等脆性相生成。在双粒径级配的SiC_p/Al复合材料中,SiC体积分数从50%增加到65%时,其相对密度从99.93%下降到96.40%;其中,当SiC体积分数为60%时,复合材料的相对密度、热导率、平均热膨胀系数(50～400℃)和抗弯强度分别为99.19%、227.5W/(m·K)、9.77×10~(-6) K~(-1)和364.7MPa。     

电子封装用diamond/Al复合材料研究进展

Diamond/Al复合材料作为第四代电子封装材料,具有高热导率、低热膨胀系数和低密度等优良性能,成为研究重点。论述diamond/Al复合材料研究概况,分析挤压铸造、浸渗法和放电等离子烧结制备方法的优点和缺点,讨论热导率和热膨胀系数等热物理性能的影响因素,并对其发展前景进行展望。     

SiC粒径比及体积比对SiCp/Al-5Si-2.5Mg复合材料组织及性能影响

采用放电等离子烧结技术制备60 vol%SiCp/Al-5Si-2.5Mg复合材料,研究SiC粒径比及粗/细体积比对复合材料微观组织、热导率和抗弯强度的影响。结果表明:随着细SiC粒径减小,其抗弯强度增加、热导率降低;同时,随着细SiC体积分数增加,其抗弯强度增加、热导率先升高后下降;当复合材料中SiC粒径比为76/16、体积比为3∶1时,热导率、平均热膨胀系数(100~400℃)、抗弯强度分别为214 W/(m·K)、9.8×10~(-6)K~(-1)和309 MPa,其断裂方式以SiC解理断裂和基体的韧性断裂为主。     

热处理对金刚石/2024Al复合材料微观组织和热物理性能的影响

采用挤压铸造法制备粒径为5μm、体积分数为50%的金刚石/2024Al 复合材料。退火处理后对其金相组织界面反应、界面结合情况以及金刚石颗粒的内部缺陷进行观察与分析,并对其热物理性能进行测试与研究。结果表明,金刚石/2024Al 复合材料的组织致密,无明显的气孔、夹杂等缺陷;颗粒为不规则多边形,有棱角,分布比较均匀。透射电镜观察表明,部分金刚石颗粒内部有位错和层错存在,而2024Al 基体中的位错密度较大,金刚石/2024Al界面处有较多的界面反应物生成,可能为Al2Cu。复合材料在20~100°C温度区间内的平均热膨胀系数为8.5×10-6°C-1,退火处理的复合材料其热膨胀系数有一定程度的降低;随着温度的升高,复合材料的平均热膨胀系数也呈现增加的趋势。复合材料的热导率约为100 W/（m·K）,退火处理能够提高复合材料的热导率。     

Si含量对Si/Al复合材料组织及性能的影响(英文)

采用放电等离子烧结(SPS)技术制备不同Si含量的电子封装用Si/Al复合材料,测试复合材料的性能,包括密度、热导率、热膨胀系数及弯曲强度;进行成分及断口分析,研究Si含量对Si/Al复合材料微观组织及热、力学性能的影响规律。结果表明:Si/Al复合材料由Si、Al组成,Al均匀分布于Si晶粒之间;随着Si含量的降低,Si/Al复合材料的相对密度不断增大,当Si含量为50%(体积分数)时,复合材料的相对密度达到98.0%;复合材料的热导率、热膨胀系数及弯曲强度均随着Si含量的增加而减小,当Si含量为60%(体积分数)时,复合材料具有最佳的热导率、热膨胀系数及强度匹配。     

放电等离子烧结制备Ti/TiC/C层状复合材料的研究

以Ti和C片状材料为原料,利用放电等离子烧结(SPS)技术制备了具有层状结构特征的Ti/TiC/C复合材料,研究反应界面的性质和状况,讨论了烧结温度对界面反应层的影响。结果表明:采用放电等离子烧结技术可制备出Ti/C叠层复合材料;材料的界面反应程度与烧结温度有关。随着烧结温度的升高,反应层的厚度增大,烧结温度达到1500℃时界面反应程度较好,反应层的厚度达到32.6μm;进一步提高烧结温度,将会使Ti发生熔化,无法得到Ti/C叠层复合材料。     

热压烧结制备Cu/FeCoCr复合材料的显微组织及热物理性能（英文）

利用相图计算的CALPHAD方法和超音雾化制粉技术,在CuFeCoCr体系中设计并制备了一系列微米级复合粉体。通过热压烧结方法在烧结温度为950℃,烧结压力为45 MPa的工艺条件下成功获得块体复合材料。研究了块体复合材料中Cu含量对显微组织,热导率,热膨胀系数以及显微硬度的影响。结果表明:CuFeCoCr块体复合材料均由fcc富铜相和fcc富铁钴铬相组成。该系列复合材料经600℃时效处理8 h后,其热膨胀系数变化范围为5.83×10~(-6)～10.61×10~(-6) K~(-1),热导率变化范围为42.17～107.53 W·m~(-1)·K~(-1)。其中Cu_(55)(Fe_(0.37)Cr_(0.09)Co_(0.54))_(45)复合材料表现出良好的综合性能,即其热膨胀系数和热导率分别为9.08×10~(-6)K~(-1)和91.09 W·m~(-1)·K~(-1),与电子封装半导体材料的热膨胀系数相匹配。     

(SiC)TiN/Cu复合材料的热物理性能和焊接性能

以醇盐水解-氨气氮化法在SiC颗粒表面包覆TiN,然后采用放电等离子体烧结进行致密化,重点分析所制备的(SiC)TiN/Cu复合材料的热物理性能和焊接性能。结果表明:醇盐水解-氨气氮化法能够制备出TiN包覆SiC复合粉末,TiN包覆层均匀连续,能够提高材料的致密度并改善界面结合。(SiC)TiN/Cu复合材料的热膨胀系数介于8.1×10-6～11.9×10-6K-1之间,并且随着SiC体积分数的增加而降低。(SiC)TiC/Cu复合材料经过8次热循环以后的残余塑性应变为4.0×10-4。当SiC的体积分数为30%时,复合材料的热导率达到270W·m-1·K-1。Ag-Cu-Ti钎料在900℃时能在(SiC)TiN/Cu复合材料上完全铺展,具有良好的润湿性。(SiC)TiN/Cu复合材料与Ag-Cu-Ti钎料焊接接头的剪切强度高达56MPa。     

高分数GNFs/6061Al基复合材料的放电等离子体烧结制备及其显微组织与性能

采用放电等离子体烧结(SPS)工艺在610℃制备30％～50％(质量分数)纳米石墨片(GNF)/6061Al基复合材料,研究烧结压力及GNF含量对复合材料显微组织和力学、热学性能的影响.结果表明,SPS有效抑制GNFs/6061Al基复合材料中Al4C3等界面反应产物的生成.随着GNF含量的增加,GNFs团聚程度增加,...     

Thermal properties of diamond/Al composites by pressure infiltration: comparison between methods of coating Ti onto diamond surfaces and adding Si into Al matrix

This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity(TC) and the coefficient of thermal expansion(CTE) of diamond/Al composites by pressure infiltration.The fracture surfaces,interface microstructures by metal electro-etching and interfacial thermal conductance of the composites prepared by two methods were compared.The results reveal that Ti coating on diamond surfaces and only12.2 wt% Si addition into Al matrix could both improve the interfacial bonding and increase the TCs of the composites.But the Ti coating layer introduces more interfacial thermal barrier at the diamond/Al interface compared to adding 12.2 wt% Si into Al matrix.The diamond/Al composite with 12.2 wt% Si addition exhibits maximum TC of 534 W·m~(-1)·K~(-1)and a very low CTE of 8.9×10~(-6)K~(-1),while the coating Ti-diamond/Al composite has a TC of 514 W·m~(-1)·K~(-1)and a CTE of 11.0×10~(-6)K~(-1).     

Thermal properties of pressureless melt infiltrated AlN–Si–Al composites

Thermal properties of AlN-Si-Al composites produced by pressureless melt infiltration of Al/Al alloys into porous α-Si₃N₄ preforms were investigated in a temperature range of 50-300 °C. SEM and TEM investigations revealed that the grain size of AlN particles was less than 1 μm. In spite of sub-micron grain size, composites showed relatively high thermal conductivity (TC), 55-107 W/(m.K). The thermal expansion coefficient (CTE) of the composite produced with commercial Al source, which has the highest TC of 107 W/(m.K), was 6.5×10^?6 K^?1. Despite the high CTE of Al (23.6×10^?6 K^?1), composites revealed significantly low CTE through the formation of Si and AlN phases during the infiltration process.     

电子封装用Al/Si/SiC复合材料的显微组织与性能(英文)

采用气压浸渗法制备中体积分数电子封装用 Al/Si/SiC 复合材料。在保证加工性能的前提下,用与 Si 颗粒相同尺寸(13 μm)的 SiC 替代相同体积分数的硅颗粒制得复合材料,并研究其显微组织与性能。结果显示,颗粒分布均匀,未发现明显的孔洞。随着 SiC 的加入,强度和热导率将得到明显提高,但热膨胀系数变化较小,对使用影响也不大。讨论几种用于预测材料热学性能的模型。新的当量有效热导被引入后,H-J 模型将适用于混杂和多颗粒尺寸分布的情况。     

Interfacial microstructure and properties of diamond/Cu-<Emphasis Type="Italic">x</Emphasis>Cr composites for electronic packaging applications

Diamond/Cu-xCr composites were fabricated by pressure infiltration process.The thermal conductivities of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were above 650 W/mK,higher than that of diamond/Cu composites.The tensile strengths ranged from 186 to 225 MPa,and the bonding strengths ranged from 400 to 525 MPa.Influences of Cr element on the thermo-physical properties and interface structures were analyzed.The intermediate layer was confirmed as Cr3C2 and the amount of Cr3C2 increased with the increase of Cr concentration in Cu-xCr alloys.When the Cr concentration was up to 0.5 wt.%,the content of the Cr3C2 layer was constant.As the thickness of the Cr3C2 layer became larger,the composites showed a lower thermal conductivity but higher mechanical properties.The coefficients of thermal expansion(CTE) of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were in good agreement with the predictions of the Kerner’ model.     

Investigation of thermoelectric properties of Cu2GaxSn1 − xSe3 diamond-like compounds by hot pressing and spark plasma sintering

P-type compounds Cu₂Ga_xSn_1 ? xSe₃ (x = 0.025, 0.05, 0.075) with a diamond-like structure were consolidated using hot pressing sintering (HP) and spark plasma sintering (SPS) techniques. High-temperature thermoelectric properties as well as low-temperature Hall data are reported. Microstructural analysis shows that the distribution of Ga is homogeneous in the samples sintered by HP but inhomogeneous in the samples sintered by SPS, even with an electrically isolating and thermally conducting BN layer during the sintering. The Seebeck coefficients of the samples sintered by HP and SPS show similar dependence on the carrier concentration and are insensitive to the composition inhomogeneity. In contrast, the composition inhomogeneity results in lower carrier mobility and thus lower electrical conductivity in the samples sintered by SPS than those sintered by HP. Lattice thermal conductivity is further reduced through Ga doping; however, this effect is weakened by the inhomogeneous distribution of Ga. Due to their larger carrier mobility and lower lattice thermal conductivity, the samples sintered by HP exhibit 15–35% higher thermoelectric figure of merits (ZT) than those SPS samples with a high Ga doping level and without the coated BN layer, in which the composition homogeneity is worse. A ZT value of 0.43 is obtained for the HP Cu₂Ga_0.075Sn_0.925Se₃ sample at 700 K.     

Interface and thermal expansion of carbon fiber reinforced aluminum matrix composites

Two kinds of unidirectional PAN M40 carbon fiber(55%,volume fraction) reinforced 6061Al and 5A06Al composites were fabricated by the squeeze-casting technology and their interface structure and thermal expansion properties were investigated.Results showed that the combination between aluminum alloy and fibers was well in two composites and interface reaction in M40/5A06Al composite was weaker than that in M40/6061Al composite.Coefficients of thermal expansion(CTE) of M40/Al composites varied approximately from(1.45-2.68)×10-6 K-1 to(0.35-1.44)×10-6 K-1 between 20 °C and 450 °C,and decreased slowly with the increase of temperature.In addition,the CTE of M40/6061Al composite was lower than that of M40/5A06Al composite.It was observed that fibers were protruded significantly from the matrix after thermal expansion,which demonstrated the existence of interface sliding between fiber and matrix during the thermal expansion.It was believed that weak interfacial reaction resulted in a higher CTE.It was found that the experimental CTEs were closer to the predicted values by Schapery model.     

Microstructure and thermoelectric properties of β-FeSi2 ceramics fabricated by hot-pressing and spark plasma sintering

The microstructure and thermoelectric properties of β-FeSi₂ ceramics by hot pressing (HP) and spark plasma sintering (SPS) are investigated. With increasing hot-pressing temperature, the density, electronic conductivity and thermal conductivity of the samples increase significantly, the thermoelectric figure of merit is improved slightly. The microstructure study indicates that the sizes of the β-FeSi₂ and ?-FeSi phases in the sample sintered by the SPS process are smaller than that by the HP process. The SPS sample shows excellent thermoelectric performance due to the low thermal conductivity.     

Thermal residual stresses in co-continuous composites

The thermal residual stresses in two types of co-continuous composites copper/aluminum oxide (Cu/Al₂O₃) and aluminum/aluminum oxide (Al/Al₂O₃) were measured by neutron diffraction experiments. These stresses were generated during the cooling after high processing temperature. The coefficient of thermal expansion (CTE) mismatch of metal and ceramic phases led to significant amount of thermal stresses. In both the composites, the metallic phase was found to be under tension and aluminum-oxide phase under compression. Even though the magnitude of compressive stress in both the composites was similar; the two metal-phases had very different magnitude of tensile stresses. The difference in volume fraction, CTE, elastic stiffness and plastic flow properties led to this difference. The hydrostatic stresses were found to be predominant in both the phases. Finite element simulations were used to predict the stress distributions inside each phase and at the interfaces. A representative unit cell approach was considered to represent the composite. Concept of effective ΔT was utilized to simulate the thermal stress distribution inside the two phases in the unit cell. This model utilized the neutron diffraction measurements to predict the stress distribution inside each phase and at the interface. The simulations showed that significant amount of tensile stresses develop at the metal–ceramic interfaces.     

New environmental barrier coating system on carbon-fiber reinforced silicon carbide composites

Carbon-fiber-reinforced silicon carbide composites (C/SiC) are promising materials for high-temperature, light weight structural components. However, a protective coating and environmental barrier coating (EBC) are necessary to prevent the oxidation of the carbon and the reaction of the formed silica scale with water vapor. Current EBC systems use multiple layers, each serving unique requirements. However, any mismatch in the coefficients of thermal expansion (CTE) creates internal stresses and might lead to crack formation. In this case, oxygen and water vapor penetrate through the EBC, reducing the lifetime of the component. Mullite (Al₆Si₂O₁₃) is used in many known EBC systems on silicon-based ceramics either as an EBC itself or as a bondcoat. Due to its low CTE and its sufficient thermal cycling behavior, mullite was chosen in this investigation as a first layer. As mullite suffers loss of SiO₂ when exposed to water vapor at high temperatures, an additional protective top coat is needed to complete the EBC system. Different oxides were evaluated to serve as top coat, especially high-temperature oxides with low coefficients of thermal expansion (LCTE). An EBC containing mullite as bondcoat and the LCTE oxide La₂Hf₂O₇ as a top coat is proposed. Both layers were applied via atmospheric plasma spraying. In this paper, results of the influence of processing conditions on the microstructure of single mullite and LCTE oxide layers as well as mullite/LCTE oxide systems are presented. Special emphasis was directed toward the crystallinity of the mullite layer and, in the top layer, toward low porosity and reduced crack density.