| The surface of SiCp was modified with electroless plating, and then SiCp/Alcomposites were prepared by pressureless-infiltration method. SiCp was modified withthree different ways, namely, the surface of SiCp was plated with Ni plating, Cu plating,and pre-oxidiaztion, respectively. The surface, interface morphology, elementalcomposition and phase composition of SiCp and SiCp/Al composites were analyzed by3D Video microscope, TG-DTA/DSC，SEM，EDS and XRD respectively. Thermalconductivity of SiCp/Al composites was measured by the laser thermal conductivitymeter.The results show that three main parameters as PH value, solution temperature andconcentration of main salt had important influence on SiCp. At the same time differenttypes of complexing agents were studied which have an important on chemical copperplating. It indicated that, when the PH value of chemical copper plating is12, solutiontemperature is45℃, and the main salt concentration is7.5g/l respectively, and thecomplexing agent was adopts double complexing agent which included sodiumpotassium tartrate (10g/l) and EDTA(5g/l), between copper plating layer and matrixgrain are combined closely, and the particle was covered completely. The coatingthickness is about4-5μm. After the coating was done by thermal shock experimentstest, it shows that coating of SiCp is close and tight. For electroless nickel plating, theresult shows that PH value is about4.8-5.2, plating solution temperature is80℃, themain salt concentration is7.5g/l respectively, nickel plating layer thickness is3.5-4μmand particle is covered completely. At last, thermal shock experiment shows that fewcoating is dropped off. There are two kinds of processes are adopted, one technology isdifferent pre-oxidization time, another technology is different pre-oxidizationtemperature, which obtained the different thickness of SiO2layer. SiCp initial oxidationtemperature is850℃, as the increase of oxidation temperature and time, the weight ofSiCp increases, meantime the thickness also increased. The surface of oxidation layerthickness is about0.31-0.8μm. When the pre-oxidation temperature is over1100℃, orpre-oxidation time is more than2h. There will be parts of SiCp ablation, at the sameoxide layer also can drop off.SiCp composite was also prepared by the surface of SiCp modified with copperplating and copper content is high in the interface, the copper only appear between thesilicon carbide and aluminum transition layer, its thickness is3-3.5μm, the thickness of copper in the composites can be thought as the thickness of the interface. The thermalconductivity of the composite is205W·M-1·K-1, thus, the thermal conductivity of thecomposite was obviously improved. The transition layer interface thickness ofcomposite with the SiCp modified by nickel plating is2.5-3μ m and thermalconductivity is155W·M-1·K-1.The formation of SiO2layer through the pre-oxidation of SiCp can provide certaininterface reaction with interface layer (3.1–6.36μm), and the thermal conductivity is179W·M-1·K-1, with the increase in the thickness of SiO2layer, and the thickness ofinterface layer in the composites are promoted, while the thickness of SiO2layerexceeds5.9μm and the thickness of interface layer becomes thin conversely. Variationof thermal conductivity of the composites is due to the difference of the thickness andcomponents of interface layer resulting from the pre-oxidation process of SiCp, with theincreasing in the thickness of interface layer, and thermal conductivity declines, but isnot linear. SiCp/Al composite was prepared by pressureless-infiltration before thesurface of SiCp was modified with Cu plating, which thermal conductivity is the highest;SiCp/Al composite with Ni plating is the lowest. |
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