不同工艺对SiC／Cu复合材料界面结合的影响

采用包裹法和机械合金法制备了SiC：Cu为20：80（体积比）的SiC／Cu复合材料。采用XRD，SEM及EDAX能谱对粉体和烧成样品的物相、断口显微形貌及断口物质成分进行了表征。结果表明：采用包裹法在制备复合粉体过程中出现Cu2O，其含量在烧结过程中减少，包裹法制备的烧成样品SiC颗粒和Cu结合成“核．壳”结构，两相分布比机械合金法更均匀，界面结合更好，强度更高。     

不同工艺对SiC/Cu复合材料界面结合的影响

采用包裹法和机械合金法制备了SiC∶Cu为20∶80(体积比)的SiC/Cu复合材料.采用XRD,SEM及EDAX能谱对粉体和烧成样品的物相、断口显微形貌及断口物质成分进行了表征.结果表明:采用包裹法在制备复合粉体过程中出现Cu2O,其含量在烧结过程中减少,包裹法制备的烧成样品SiC颗粒和Cu结合成"核-壳"结构,两相分布比机械合金法更均匀,界面结合更好,强度更高.     

造孔剂含量对无压浸渗法制备SiC/Al复合材料性能的影响

采用无压浸渗法制备了SiC/Al复合材料,研究了造孔剂含量对SiC/Al复合材料性能的影响。实验结果表明:不同含量的造孔剂对残余气孔率的影响不同,随着造孔剂加入量的增加,残余气孔率先减小后增大,但试样抗弯强度呈先增加后减小。在SiC/Al复合材料中加入质量分数为20%的造孔剂时,SiC/Al复合材料的抗弯强度出现最大值,其残余气孔率达到最小值0.9%左右。     

碳纤维增强Cu-Ti3SiC2复合材料的研究

采用电镀Cu碳纤维（Cf）与化学镀Cu的Ti3SiC2粉及Cu粉进行湿混,通过真空热压烧结法制备Cf增强的Cu-Ti3SiC2复合材料。研究了其致密度、电阻率、维氏硬度随Cf,Ti3SiC2含量变化的规律。实验结果表明,Ti3SiC2体积含量为20％,Cf体积含量为8％时,制备的Cf增强Cu-Ti3SiC2复合材料综合性能最好。Cf镀Cu和Ti3SiC2镀Cu改善了它们和Cu的润湿性,从而提高了相互之间的结合强度是复合材料获得良好综合性能的基本原因。     

SiC（Cu）／Fe复合材料制备工艺研究

采用非均相沉淀法制得Cu包裹SiC复合粉体，利用粉末冶金和常压烧结制备SiC（Cu）／Fe复合材料。利用Zeta电位仪、XRD，EDS以及SEM等手段对包裹粉体和烧结样品进行了分析。结果表明，采用非均相沉淀法可以得到Cu／SiC复合粉体。包裹后的粉体与原始SiC粉体的表面电位不同，达到了对SiC颗粒表面改性的目的。Cu作为过渡层改善了SiC／Fe的界面相容性，在1050℃烧结的样品只有微量的FeSi或Fe2Si生成，界面反应得到有效控制，获得化学结合的界面，温度过低不能烧结致密，温度过高出现大量缺陷。     

粉末注射成形SiCp/Cu复合材料的显微组织与力学性能

通过粉末注射成形技术制备了SiC颗粒增强Cu基复合材料,并采用溶剂脱脂和热脱脂工艺对注射坯料进行脱脂,再对脱脂坯料进行了烧结,获得了致密烧结件.观察了不同SiC含量的SiCp/Cu复合材料的断口形貌,研究了不同SiC含量SiCp/Cu复合材料的硬度、抗拉强度和磨损性能.结果表明:随着SiC含量的提高,SiCp/Cu复合材料的断口韧窝减少,撕裂棱增多,材料趋向于脆性断裂;随着SiC含量的提高,该复合材料的硬度升高,但强度在SiC含量为10vol％时最高,SiC含量进一步提高则强度下降;随着SiC含量的提高,SiCp/Cu复合材料由粘着磨损向颗粒磨损转变,磨损率下降.     

P-G法制备纳米金刚石低温陶瓷结合剂复合烧结体

使用高分子网络凝胶法（polyacrylamide-gel method,简称P-G法）制备纳米金刚石（nano-diamond,ND）-低温陶瓷结合剂复合烧结体,并设计4种不同金刚石添加量来制备试样条,然后考察二氧化硅包覆纳米金刚石（ND@SiO₂）在陶瓷结合剂中分散的均匀性,并对比分析试样的物相、抗弯强度和显气孔率。实验结果表明:利用P-G法制备的试样中的金刚石浓度从25%增加到100%时,ND@SiO₂在凝胶体中分散均匀,无明显团聚现象;其烧结温度范围为670~720℃,抗折强度达到66.4~87.6 MPa,气孔率为10.2%~22.4%。      

CNTs/SiC/Cu复合材料制备及性能

以碳纳米管(CNTs)、碳化硅(SiC)粉体、锌(Zn)粉和CuSO_4·5H_2O为主要原料,用化学镀的方法制备CNTs /Cu复合粉体,再采用非均相沉淀法制备CNTs/SiC/Cu复合粉体.在750 ℃、100 MPa的制度下进行真空热压烧结后制得CNTs/SiC/Cu复合材料,其中Cu的含量(体积分数,下同)为70%,CNTs的含量(体积分数, 下同)分别为0,3%,5%,8%,12%.利用XRD、SEM分析样品的物相组成和显微结构;利用阿基米德排水法、显微硬度计、三点弯曲法测试了复合材料的密度、显微硬度和抗弯强度.结果表明,随着碳纳米管含量的增加,CNTs/SiC/Cu复合材料的密度、显微硬度和抗弯强度等性能发生相应变化,其中,抗弯强度呈现逐渐升高趋势.与未添加碳纳米管的30SiC/70Cu复合材料相比,添加12%CNTs的12CNTs/18SiC/70Cu 样品,抗弯强度提高了21.45 MPa.     

凝胶-发泡法制备多孔氧化铝隔热材料的研究

结合凝胶注模和发泡法制备了多孔氧化铝隔热材料,研究了发泡剂用量、固相含量和烧结温度等对氧化铝陶瓷气孔率的影响.结果表明,当发泡剂用量为1 wt％、固相含量为45vol％、烧结温度为1500℃时,可制备出总气孔率和闭气孔率高、孔径较小且分布均匀、强度高和热导率低的多孔氧化铝陶瓷.     

C／C-SiC材料的快速制备及显微结构研究

分别以碳毡和二维碳纤维为预制体，采用化学液相气化渗入法结合熔融渗硅反应法快速制备了C／C-SiC陶瓷复合材料。对这种材料的密度和气孔率进行了表征，并通过XRD，OM和SEM等方法对其相组成、显微结构和反应机理进行了研究。结果表明：不同预制体制备的C／C—SiC材料密度和气孔率分别为～2．0g／cm^3和～1．0％。其相组成包括反应生成β-SiC以及未反应的游离Si和C。C／C—SiC中纤维被环状的沉积碳包裹，生成SiC的反应只发生在Si与沉积碳之间，纤维没有损伤。Si，C和SiC各相分布和含量因预制体的不同而有明显差异。     

热压反应烧结制备ZrB2-SiC复合材料的工艺及性能研究

以二硼化锆、正硅酸乙酯、蔗糖为原料,采用溶胶-凝胶法制备ZrB2-SiC前躯体,然后利用热压反应烧结方法,在1800℃,30MPa压力,流动的Ar气氛条件下,制备出高致密的ZrB2-SiC复合材料。其最大相对密度达到99.6%。ZrB2-SiC复合材料的抗弯强度和断裂韧性都随着SiC含量的增加先增加后降低。当SiC含量为20%时,ZrB2-SiC复合材料断裂韧性最大达到5.1MPa·m1/2。ZrB2-SiC复合材料的最大弯曲强度为272MPa,比报道出的值要低,这可能与过大的ZrB2晶粒有关。但当SiC含量为30%时,由于出现大量气孔而使材料不致密,从而导致其力学性能下降。     

Effect of SiC particle size on flexural strength of porous self-bonded SiC ceramics

Porous self-bonded silicon carbide (SBSC) ceramics were fabricated from SiC powders with various particle sizes (0.7 μm, 25 μm, 50 μm, 65 μm), plus Si, C and boron (as a sintering additive). The effects of submicron (0.7 μm) SiC particle incorporation into the SBSC and the SiC particle size (25 μm, 50 μm, 65 μm) on the flexural strength and porosity of the ceramics were investigated as a function of sintering temperature. Incorporating 0.7 μm SiC particles into the ceramic material containing 25 μm SiC particles increased the flexural strength by 3 times, from 11.7 MPa up to 35.5 MPa after sintering at 1800 °C. Simultaneously, the porosity was reduced by ∼5 %. Furthermore, the flexural strength of ceramic with 25 μm SiC particles was superior to that with 65 μm SiC particles. Generally, the flexural strength of the SBSC increased as, both, a function of submicron SiC particle incorporation along with relatively small micron-sized particles (25 μm) in the microstructure of the ceramic plus increased sintering temperature.     

Production and characterization of a three-dimensional cellular metal-filled ceramic composite

Silicon carbide in the form of a foam network was vacuum infiltrated with aluminum alloy A356 to produce a new Interpenetrating Composite material. The foam, once infiltrated with a second phase transforms into a composite where two distinct, continuous, three-dimensional network structures are formed. The advantage of this metal matrix composite is its high strength-to-weight ratio for use in lightweight applications such as electronic packaging materials. The electroless nickel coating and vacuum infiltration procedures are developed. Materials characterization of the composite is evaluated by microstructural and compositional analysis, and density, porosity, and nano-indentation measurements. Selected experimental mechanical and thermal property measurements are performed to understand its properties and compare against theoretical models. Results show the final composite to have lower density than conventional electronic base plate packaging materials with low porosity. The composite has an increased Young's modulus and flexural strength to that of the unreinforced alloy and comparable impact toughness to composites with 50–70 vol% SiC particles but with only 12 vol% SiC. The fracture surface of the matrix illustrates conventional fibrous fracture and brittle cleavage whilst the reinforcement struts show signs of layer de-bonding from their SiC layered structure.     

Fabrication of protective-coated SiC reinforced tungsten matrix composites with reduced reaction phases by spark plasma sintering

SiC reinforced tungsten matrix composites were fabricated via the spark plasma sintering process. In order to prevent an interfacial reaction between the SiC and tungsten during sintering, TiOx coated SiC particles were synthesized by a solution-based process. TiOx layer coated SiC particles were treated in high temperature nitriding conditions or annealed in a high temperature vacuum to form TiN or TiC coated SiC particles, respectively. The TiC layers coated on SiC particles successfully prevented tungsten from reacting with SiC; hence the proposed process resulted in successful fabrication of the SiC/W composites. The mechanical properties such as compressive strength and flexural strength of the composites were measured. Additionally, the effect of SiC on the high temperature oxidative ablation of tungsten was also investigated. The addition of SiC resulted in an improved oxidative ablation resistance of the tungsten-based composites.     

Thermal shock resistance of ZrC matrix ceramics

A ZrC-20 vol% SiC based ceramic matrix composite containing 10 vol% graphite flake was fabricated by hot press sintering. The thermal shock resistance of the materials was investigated through the water-quench method and subsequent three-point bend testing of flexural strength diminution. The ZrC-20 vol% SiC composite containing 10 vol% graphite flake exhibited higher critical temperature difference and higher residual ratio of strength compared with that of ZrC-20 vol% SiC composite. It is the main reason that addition of the graphite flake provides a weak interface into the material which acts to deflect propagating cracks, and the bridging of the cracks occurred. Meanwhile, a laminar structure of the graphite flake would relax the interface stress by sliding of interlayers and provide favorable sites for the dissipation of energy associated with crack growth during fracture.     

Ti3AlC2／Cu复合材料的制备及其性能研究

采用粉末冶金的方法在1000℃和30MPa的热压条件下，烧结制备了以Ti3AlC2为增强相的Ti3AlC2／Cu复合材料，研究了增强相含量（10％～40％）对复合材料的显微结构、抗弯强度、硬度和电阻率的影响。结果表明：Ti3AlC2能够有效增强铜，当Ti3AlC2含量为30％时，增强效果最佳，复合材料的抗弯强度达1033MPa，最大形变为2．5％，增强相含量继续增加时，复合材料的强度反而降低；随着增强相含量的增加，复合材料渐趋脆性断裂，同时复合材料的电阻率基本呈线性升高。     

无压反应烧结MOSi2—SiCp复相材料的制备与性能

采用无压反应烧结方法制备了MOSi2-SiCp复相材料。结果表明：直接采用元素粉Mo，Si与Si，C粉或SiC粉反应，较难制得致密的MOSi2-SiCp复相材料；而采用MoSi2合金粉同Si，C反应可获得致密的MOSi2-SiCp复相材料。同时对不同SiC含量的MOSi2-SiCp复相材料的强度和电阻率进行了测定分析，得到强度最高值为157MPa，电阻率随SiC含量的增加而增加。     

热压烧结纳米晶铜粉性能的研究

利用置换反应制得平均粒径47nm的纳米晶铜粉并将其进行真空热压烧结。作为对比,将市售电解铜粉在相同条件下制得烧结试样。对试样的微观结构和性能进行了研究和分析。研究发现,由纳米晶铜粉制得的烧结试样,与电解铜粉的具有相同的致密度,弯曲强度提高21％,维氏硬度提高83％,电阻率提高50％。     

Oxy-Acetylene Flame Thermal Spray of Al/SiCp Composites with High Fraction of Reinforcements

Aluminum matrix composites reinforced with more that 50 vol.% of SiC particles were fabricated using oxyacetylene thermal spraying. The sprayed material consisted of mixtures of aluminum powder with 60-85 vol.% of SiC particles. To favor the processing of the composite, in some cases, the SiC particles were coated with silica following a sol-gel route. This allowed obtaining as-sprayed samples with thickness above 2 mm and with porosity values below 2%. Post-processing of the samples by hot pressing allowed to reduce further the porosity of the composites and to enhance their microstructural homogeneity. The whole process of spraying and hot pressing has been optimized and the role played by the different spraying parameters and by time length and temperature of hot pressing has been also studied.