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。     

热压烧结制备石墨/铜复合材料的热性能研究

以天然鳞片石墨粉和纯铜粉为原料,通过真空热压烧结制备高导热石墨/铜复合材料,研究了石墨在复合材料中的排列以及石墨含量对该复合材料热导率和热膨胀系数的影响.结果表明:该复合材料中石墨层片状结构定向排列,x-y向与z向性能有明显各向异性.在烧结温度为900℃,热压压力为80 MPa时,该复合材料热膨胀系数随石墨含量的增加而减小;当石墨含量质量分数在40％以内时,铜与石墨结合紧密,该复合材料致密度达98％以上,x-y向热导率变化不大,z向热导率逐渐减小;当石墨质量分数为40％时,该复合材料x-y向热导率最大,达378W/(m·K).     

孔隙率对Mo／Cu复合材料热物理性能的影响

采用添加不同含量造孔剂并结合固相烧结方法制备出4种不同孔隙率的Mo/Cu合金试样,测试了其热膨胀系数和热导率λ.结果表明,孔隙率对Mo-Cu合金λ值影响很大.随孔隙率的增加,材料的热导率急剧下降:在一定孔隙率范围内,钼铜合金的平均热膨胀系数随孔隙率的增加而增加,当孔隙率超过一定范围后,其热膨胀系数开始出现下降趋势.对孔隙率影响Mo-Cu合金热物理性能的机制进行了分析和探讨,并对热导率的理论计算作了一定推导计算.     

(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。     

金刚石混杂碳化硅/铝复合材料的组织与热物理性能(英文)

采用理论计算与实验相结合的方法对金刚石混杂SiC/Al复合材料的热物理性能进行研究,采用微分有效介质(DEM)理论和扩展的Turner模型分别计算金刚石混杂SiC/Al复合材料的热导率和热膨胀系数。从金刚石混杂SiC/Al复合材料的微观组织可以看到SiC颗粒与Al之间结合较紧密,金刚石颗粒与Al之间结合不紧密。金刚石混杂SiC/Al复合材料的热物理性能的实验结果与理论计算趋势一致。当金刚石颗粒与SiC颗粒的体积比为3:7时,混杂SiC/Al复合材料的热导率和热膨胀系数分别提高了39%和30%。因此,当在复合材料中加入少量金刚石颗粒时,其热物理性能得到显著提高,而复合材料的成本略有提高。     

3D-Si/LG5复合材料微观组织及热物理性能研究

采用压力浸渗技术制备Sip/LG5复合材料并对其进行高温扩散处理。组织观察表明:复合材料增强体形貌经过高温扩散处理后由不规则的尖角形状转变为三维网络结构(3D)。对3D-Si/LG5复合材料界面的研究表明,与高温扩散处理前复合材料的界面相比,三维网络结构3D-Si/LG5复合材料的界面更光滑,界面结合程度也更好。三维网络结构3D-Si/LG5复合材料界面处及基体合金内部有Si析出,基体合金中存在着孪晶;三维网络结构3D-Si/LG5复合材料的平均线膨胀系数与高温扩散处理前相比,降低了10.5%;增强体三维网络化减少界面及基体中大量细小弥散的Si析出,使得三维网络3D-Si/LG5复合材料的热导率变化不大。     

金刚石/铝导热复合材料的显微组织与热力学性能

以高温盐浴法对金刚石表面进行镀硅处理来改善金刚石和铝基之间的界面结合,镀硅后的金刚石颗粒表面略显粗糙,表面的镀层均匀;采用真空热压烧结法制备高导热镀硅金刚石/铝复合材料,研究了烧结温度和金刚石体积分数对复合材料相对密度和热导率的影响。随着金刚石体积分数的增加,复合材料的相对密度和热导均呈现先升后降的趋势,当金刚石体积分数为45%时,复合材料的热导率达到最大,为558 W/mK。     

放电等离子烧结法制备Cu/金刚石复合材料的性能与显微组织

由于具备较高的热导率,铜/金刚石复合材料已成为应用于电子封装领域的新一代热管理材料。采用放电等离子烧结工艺（SPS）成功制备含不同金刚石体积分数的Cu/金刚石复合材料,研究复合材料的相对密度、微观结构均匀性和热导率（TC）随金刚石体积分数（50%、60%和70%）和烧结温度的变化规律。结果表明：随着金刚石体积分数的降低,复合材料的相对密度、微观结构均匀性和热导率均升高;随着烧结温度的提高,复合材料的相对密度和热导率不断提高。复合材料的热导率受到金刚石体积分数、微观结构均匀性和复合材料相对密度的综合影响。     

Fe-Si-B-Cu体系中原位析出非晶/晶体复合粉末的制备与性能研究

本研究基于相图计算的CALPHAD方法和超音雾化技术,设计并制备了具有典型核/壳结构的(Fe0.75Si0.1B0.15)100-xCux(x=0,30,45,55,65,at%)非晶/晶体复合粉末。实验研究了该系列晶体/非晶复合粉体的显微组织,热稳定性,形成机理和磁性能。结果表明:本研究制备的复合粉体均由分布在核层的富FeSiB非晶相和壳层的富Cu相组成。磁滞回线结果表明,随着Cu含量的增加,饱和磁化强度呈线性关系逐渐降低,但对矫顽力的影响并不明显。该类非晶/晶体复合粉体的形成过程为:(1)高温下富Cu相和富FeSiB相的液相分离现象诱发形成核/壳组织;(2)由于富Cu相的玻璃形成能力远低于富FeSiB相,在超音雾化过程中,富FeSiB相从液态被冻结为非晶态,最终形成具有核/壳结构的非晶/晶体复合粉体。     

Cu-Fe64Ni32Co4合金显微组织及热物理性能研究

本研究利用相图计算的CALPHAD方法和真空电弧熔炼技术,设计并制备了Cu_x(Fe_0.64Ni_0.32Co_0.04)_100-x(x=30, 45, 60, wt. %)系列合金。实验研究了该系列合金在不同热处理工艺时的显微组织,热导率以及热膨胀系数。研究结果表明：Cu-Fe₆₄Ni₃₂Co₄系列合金在600 °C和800 °C时效处理后均为fcc富铜相和fcc富因瓦(铁镍钴)相组成的各向同性的多晶合金。该系列合金在1000 °C淬火并在600 °C时效处理50 h后,其热膨胀系数变化范围为6.88~12.36×10_-6 K_-1;热导率变化范围为22.91~56.13 W.m_-1.K_-1;其热导率明显高于因瓦合金,其中Cu₃₀(Fe_0.64Ni_0.32Co_0.04)₇₀与 Cu₄₅(Fe_0.64Ni_0.32Co_0.04)₅₅合金的热膨胀系数可以与电子封装中半导体材料的热膨胀系数相匹配。     

Influence of microstructure on the thermophysical properties of sintered SiC ceramics

The specific heat, thermal diffusivity and thermal conductivity of porous SiC ceramics sintered using two kinds of SiC powders (fine and coarse) have been investigated for sintering temperatures in the range 1700–2000 °C. Sintered SiC has a porous structure with approximately 30–40 vol.% porosity. Thermal diffusivity was measured by the laser flash method. The thermal diffusivities and thermal conductivities of sintered SiC ceramics increased with increasing sintering temperature. The specific heat decreased slightly with increasing sintering temperature. The thermal diffusivities and thermal conductivities of SiC sintered from coarse powder were higher than those of SiC sintered from fine powder. The thermal conductivity of samples increased markedly with increasing grain size.     

Low conductivity plasma sprayed thermal barrier coating using hollow psz spheres: Correlation between thermophysical properties and microstructure

Life and thermal properties of plasma sprayed TBCs - widely used in gas turbine engines - are closely related to the microstructure of the ceramic top coating. Especially, the thermal behaviour of this coating is induced by the void shapes and networks which are in turn determined by both the spraying conditions and the feedstock material.A specific hollow yttria partially stabilised zirconia powder was produced in a one-step process by spray drying and an experimental statistical design study was conducted to investigate the influence of spraying variables (primary and secondary gas flow rates, arc current, spraying distance, spraying angle and traverse speed) on structure and properties of resulting plasma sprayed coatings. The coatings were characterized with respect to deposition efficiency, roughness, porosity and thermal conductivity. A reduction of 25% of the thermal conductivity was achieved by improving the spray and powder parameters. A quantitative characterization of the porous structure using image analysis of polished cross-sections was implemented. The parameters that have relevant influence on the coating porous structure were identified, and their relative importance was determined. An attempt was made to identify morphological criteria of the porous network (coarse/fine porosity ratio, cracks total length, cracks orientation) correlating with the thermal conductivity values.     

Evolution of thermo-physical properties of diamond/Cu composite materials under thermal shock load

In this paper, the two-flume method was used to study the change laws of the thermal conductivity and thermal expansion coefficient of diamond/Cu composite materials with 100, 300, and 500 cycle numbers, under the action of thermal shock load between-196 and 85 °C; the X-ray diffraction method(XRD) was used to study the change of the residual stress in the thermal shock process of the diamond/Cu composite materials; and the evolution of the fracture microstructure with different thermal shock cycle numbers was observed through scanning electron microscopy(SEM). The results of the study show that the increase of the binder residue at the interface reduces the thermal shock stability of the diamond/Cu composite materials. In addition, under the thermal shock load between-196 and 85 °C, the residual stress of the diamond/Cu composite materials increases continuously with the increase of the cycle numbers, the increase of residual stress leads to a small amount of interface debonding, an increase of the interfacial thermal resistances, and a decrease of the constraints of low-expansion component on material deformation, thus the thermal conductivity decreases slightly and the thermal expansion coefficient increases slightly.     

Influence of extrusion temperature on deformation behavior of Csf/AZ91D composite during semi-solid extrusion

Deformation behavior and formability of C_sf/AZ91D magnesium composite were investigated by semi-solid extrusion between 695 K and 728 K, including temperatures below and above the partial melting temperature. A method of constructing kinematically admissible velocity fields for axisymmetric extrusion based on the theory of flow function was proposed. Flow lines were analyzed in C_sf/AZ91D composite after extrusion at elevated temperatures. Based on an analytic flow function, the deformation field was obtained. The results show that when the composite is extruded in a semi-solid state containing a small volume of liquid, the presence of the liquid reduces deformation resistance by relaxing the stress concentrations, and improves the formability of composites as lubricant. However, the gradient of velocity field is increased and deformation uniformity is aggravated at temperatures greater than partial melting point at 701.3 K. A more uniform deformation field was attained at the temperature close to or slightly below the partial melting temperature.     

Classical molecular dynamics simulation of UO2 to predict thermophysical properties

Interatomic potential parameters of UO₂, for a partially ionic potential model, were found out by a fitting method using isothermal compressibility data up to 1600 K. The inter-atomic potential used here is essentially a combined potential model comprising of Bushing–Ida and Morse-type potential to simulate UO₂ system using classical molecular dynamics. It has been shown that the deviation in the estimated lattice parameter from the experimental data as reported in literature is due to the inadequacy of the potential parameter. The calculated deviations in lattice parameter, due to the generation of point defects, with variation of temperature have been discussed. The calculated lattice parameters, thermal expansivity, isothermal compressibility of UO₂, using the current potential parameters are in close agreement with the experimental values. The model also successfully predicts Bredig transition.     

复合钙钛矿型Ba(Zn1/3Ta2/3)O3陶瓷作为热障涂层陶瓷层材料的性能评价

以BaCO₃、ZnO、Ta₂O₅为原料,采用固相反应法制备了Ba(Zn_1/3Ta_2/3)O₃(BZT)陶瓷材料。对BZT的物相结构、高温相稳定性、热导率、热膨胀系数和喷涂工艺适应性进行表征研究,并与同类Ba(Mg_1/3Ta_2/3)O₃(BMT)、Ba(Ni_1/3Ta_2/3)O₃(BNT)和Ba(Sr_1/3Ta_2/3)O₃(BST)对比,以评价BZT作为热障涂层陶瓷层材料的应用潜力。结果表明,BZT在室温至1500℃内无相变,且经1600℃长时处理48 h后不分解,表现出良好的高温相稳定性;在1200℃,BZT的热导率仅为1.65 W·m^-1·K^-1,明显低于BMT(2.57 W·m^-1·K     

Thermal properties of oxides with magnetoplumbite structure for advanced thermal barrier coatings

Oxides having magnetoplumbite structure are promising candidate materials for applications as high temperature thermal barrier coatings because of their high thermal stability, high thermal expansion, and low thermal conductivity. In this study, powders of LaMgAl₁₁O₁₉, GdMgAl₁₁O₁₉, SmMgAl₁₁O₁₉, and Gd_0.7Yb_0.3MgAl₁₁O₁₉ magnetoplumbite oxides were synthesized by citric acid sol-gel method and hot-pressed into disk specimens. The thermal expansion coefficients (CTE) of these oxide materials were measured from room temperature to 1500 °C. The average CTE value was found to be ∼ 9.6 × 10^− 6/C. Thermal conductivity of these magnetoplumbite-based oxide materials was also evaluated using steady-state laser heat flux test method. The effects of doping on thermal properties were also examined. Thermal conductivity of the doped Gd_0.7Yb_0.3MgAl₁₁O₁₉ composition was found to be lower than that of the undoped GdMgAl₁₁O₁₉. In contrast, thermal expansion coefficient was found to be independent of the oxide composition and appears to be controlled by the magnetoplumbite crystal structure. Preliminary results of thermal conductivity testing at 1600 °C for LaMgAl₁₁O₁₉ and LaMnAl₁₁O₁₉ magnetoplumbite oxide coatings plasma-sprayed on NiCrAlY/Rene N5 superalloy substrates are also presented. The plasma-sprayed coatings did not sinter even at temperatures as high as 1600 °C.