Thermophysical properties and microstructure of short carbon fibre reinforced Cu-matrix composites made by electroless copper coating or powder metallurgical route respectively

Abstract

Carbon fibre reinforced copper ma& composites possess interesting properties of copper, i.e., excellent thermal and electrical conductivities, but the properties of carbon fibre, i.e., a small thermal expansion coefficient dominate the mechanical behaviour. Since the desirable properties of the composite can be obtained by selecting the amount and type of the carbon fibres, it is considered to be suitable for use as electric and electronic materials like special heat sinks. It is a competitive material which is able to overcome some of the disadvantages of e.g. CopperMolybdenum, Copper-Invar or Aluminium-Silicon Carbide.Copper matrix composites with high conducting endless carbon have been investigated in different research groups for several years, but copper matrix composites with high conducting short fibres are a new and promising field of research. Short carbon fibre reinforced copper composites have been made by hot-pressing of copper coated carbon fibres chopped into different lengths (60 pm -2 mm). Due to a special production route -electroless copper coating -a good distribution of the fibres in the matrix and a good interfacial contact is obtained. The fibre length distribution influences strongly the properties of the composite. During hot pressing, the carbon fibres take on a preferred orientation in a plane perpendicular to the hot pressing direction. Within this plane the fibre orientation is random. Samples using PITCH-and PAN-type fibres have been produced. The volume content of carbon fibres has been varied in a range of 38 -64 vol.%.The microstructure of the composites has been investigated using SEM and optical microscope. Measured properties, i.e., thermal conductivity and coefficient of thermal expansion have been compared with microstructural results and results obtained from mathematical models. Up to now these composites provide a thermal conductivity of about 250-300 W/mK in two dimensions and about 140 W/mK in the third dimension. The coefficient of thermal expansion (CTE) can be tailored in a range of 4-10 ppm/K by changing the content of carbon fibres. The relatively low density of about 4-6 g/cm3 is also of importance wherever weight reduction is desired. The results are compared with composites produced by powder metallurgical route and composites made with low conducting short carbon fibres respectively.

Thermal conductivity improvement of copper–carbon fiber composite by addition of an insulator: calcium hydroxide

“…The composite without Ca(OH) 2 , sintered with the same conditions as the composite with Ca(OH) 2 , exhibited a parallel TC of 303 W m -1 K -1 , a perpendicular TC of 202 W m -1 K -1 , and a parallel CTE of 11.6910 -6 K -1 . These values are slightly higher than the ones from the literature and will be used as reference values in this paper [15][16][17]. For the samples with a low content of Ca(OH) 2 (i.e., B1 %), the parallel TC did not change; but the perpendicular TC decreased about 5 % for x = 1 % of Ca(OH) 2 .…”

Preparation by tape casting and hot pressing of copper carbon composites films

“…2 Their advantages are (i) lower density than copper, (ii) very good thermal conductivity, (iii) low coefficient of thermal expansion, and (iv) good machinability ( are adaptive thermal properties which can be adjusted with the nature and the volume ratio of carbon fibres. During last decades, several processes have been developed to elaborate copper carbon composites through hot pressing or squeeze casting.…”

Research and Application of CNT Composite Electroplating

“…Their advantages are :(i) lower density than copper, (ii) excellent thermal conductivity, (iii) low coefficient of thermal expansion and (iv) good machinability. Other advantages of Cu/CNT composites are adaptive thermal properties, which can be adjusted [68][69][70]. However, it is difficult to make CNTs disperse uniformly and combine well in the metal matrix [71], traditional techniques such as the powder metallurgic process would bring for midable technical hurdles to prepare highquality metal-matrix CNT composites, which is ascribed to the low-strength interfacial adhesion [72].…”