Thermal expansion of Cu-graphite composites: effect of copper coating

Abstract

Cu/graphite composites with 30 and 50 vol.% of graphite were prepared. Copper coated graphite particles enabled to prepare more homogeneous structure at 50 vol.% of graphite as simple powder mixture. In the case of 30 vol.% of graphite, composite prepared from mixture of coated graphite and copper powders is more heterogeneous as simple powder mixture. Measured CTE of coated composites was significantly smaller at both compositions. It is the result of the different area of copper-graphite interface that is established only by mechanical clamping. For coated composites the area of interface increases significantly due to avoiding graphite clustering. Simple model was proposed to predict this behaviour on the basis of anisotropy of graphite CTE. Further, the model can be used for calculation of the thermal expansion coefficient of the graphite reinforcement. K e y w o r d s : metal matrix composites, thermal expansion, coating

An Overview of Metal Matrix Nanocomposites Reinforced with Graphene Nanoplatelets; Mechanical, Electrical and Thermophysical Properties

“…However, it should be mentioned that c a + c c = 1 and V a + V c = V G . These are the main assumption used in this modeling and by inserting these assumptions in the previous equation; the model could be as follow [78]:…”

“…According to literature, the thermal expansion of graphene is anisotropic so that in-plane thermal expansion coefficient of graphene is −1 × 10 −6 K −1 , while its out-of-plane CTE is 26 × 10 −6 K −1 . Thus the average CTE of polycrystalline graphene should lie in the range of 0~5 × 10 −6 K −1 [78].…”

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“…Table 2. Parameters used in this model [8]. As shown earlier, by increasing the GNPs content from 4.0 vol % to 8.0 vol %, the graphene started to agglomerate, and these clusters resulted in the lower interface area.…”

“…However, it should be mentioned that c i + c o = 1 and V i + V o = V G . These are the main assumptions used in this model, and by inserting these assumptions in the previous equation the model could be as follows [8]:…”

“…Heat sinks, which are the cooling systems for electronic devices, have been developed to solve this issue. It has been indicated that materials with a thermal conductivity higher than 150 W/(m·K) and coefficient of thermal expansion (CTE) between 4 × 10 −6 K −1 and 9 × 10 −6 K −1 are desirable materials for use in this application [8].…”