Role of Al₄C₃ on the stability of the thermal conductivity of Al/diamond composites subjected to constant or oscillating temperature in a humid environment

Present technologies allow fabrication of aluminum/diamond particles composites with excellent thermal properties, in particular showing the by far highest Thermal Conductivity of any of the materials being evaluated for thermal management. Although there is a widespread consensus concerning the essential role that the interface plays, it is not yet fully clear how the aluminum carbide formed at the interface affects thermal properties. In particular, how it affects the stability of the thermal properties of composites subjected to thermal treatments under wetting conditions. This is precisely the objective of the present work. To this end, samples were fabricated by means of gas pressure infiltration of liquid Al into preforms of packed diamond particles. Infiltration was carried out at two temperatures and three contact times. Thermal fatigue with cooling phase in water and performance in moisture environments at temperatures close to 100 °C were evaluated. The results show that those samples having low amounts of carbide at the interface (shorter contact times) are more prone to a decrease of the thermal conductivity.