Thermal conductivity behaviour of Al/diamond and Ag/diamond composites in the temperature range 4 K < T < 293 K

摘要

Two different systems, the non-reactive Ag-diamond and the reactive Al-diamond system, were assessed by their thermal conductivity behaviour, both were fabricated by gas pressure assisted infiltration of densely packed diamond bulks with aluminium or silver and different Si-concentration and diamonds of varying particle sizes. The effect of Si-concentration on the interface thermal conductance h between Al, Ag and diamonds was investigated in dependence of temperature by measuring thermal conductivity of composites with differently sized diamond particles in the temperature range from 4 K up to ambient. Composite thermal conductivities κ_c(T) can be as high as 860 W m~(-1) K~(-1) at roughly 100 K for Al/diamond and 1100 W m~(-1) K~(-1) for Ag-Si/diamond at approx. 150 K. Although the Si concentration in the matrix plays an eminent role for κ_c(T), i.e. the lower the Si concentration, the higher κ_c(T), interface thermal conductance h is almost unaffected in the reactive Al-diamond system. Furthermore, the h(T)-values in our findings on "real" composites are close to values determined on clean model systems, i.e. sputtered and evaporated metal layers on diamond monocrystals. For Ag-diamond composites, the matrix composition of Ag-1Si seems to reflect an optimal composition, as the highest thermal conductivity κ_c(T) and an extraordinarily higher interface conductance was achieved compared to Ag-3Si/diamond composites.