Metal/diamond composites for heat sink applications
L.Weber , R. Tavangar
This research activity is motivated by the need for highly efficient heat sink materials having a tailored coefficient of thermal expansion and a high thermal conductivity. To this end we investigate the parameters that allow successfully manufacturing of metals (e.g. Cu, Al, Mg and Ag and their alloys) containing large volume fractions of synthetic diamond particles.
Sound metal diamond composites are manufactured by gas-pressure assisted infiltration. Thermal conductivity reached so far goes up to 985 W/mK at 40°C in combination with a coefficient of thermal expansion of about 3-5 ppm/K for a composite containing 77 vol-pct of diamond in a Ag-Si matrix . Effects of the diamond size, volume fraction and quality on composite thermal conductivity have been investigated and thermodynamic conditions for efficient active elements in highly conductive matrix metals have been established . The latter allows rapid screening and selecting of effective active element additions. Based on this, one patent has been attributed and further patent applications are in preparation.
Apart from the practical interest in these materials, they are also appropriate to assess the predictive capacity of composite modelling schemes. In this view detailed studies of the influence of the phase contrast between matrix and inclusion have been conducted taking advantage of the fact that the matrix thermal conductivity in Ag-Si could significantly be varied by solution/precipitation heat treatment [3,4]. Other studies have focused on hybrid (diamond/SiC)/Al composites , the carbide formation in Al/diamond composites [6,7], and the influence of surface treatments of diamonds prior to infiltration .
 Weber L, Tavangar R: Advanced Materials Research, 59 (2009) 111-115
 Tavangar R, Molina JM, Weber L: Scripta Materialia, 57 (2007) 357-360
 Weber L: Metallurgical and Materials Transactions A, 33A (2002) 1145-1150
 Weber L, Tavangar R: Scripta Materialia, 57 (2007) 988-991
 Molina JM, Rhême M, Carron J, Weber L: Scripta Materialia, 58 (2008) 393-396
 Ruch PW, Beffort O, Kleiner S, Weber L, Uggowitzer PJ: Composite Science and Technology, 66 (2006) 2677-2685
 Beffort O, Khalid FA, Weber L, Ruch P, Klotz UE, Meier S, Kleiner S: Diamond and Related Materials, 15 (2006) 1250-1260
 Edtmaier C, Weber L, Tavangar R: Advanced Materials Research, 59 (2009) 125-130