Diamond based Composites for Collimators Contribution to EuCard L. Weber Laboratory for Mechanical Metallurgy Ecole Polytechnique Fédérale de Lausanne (EPFL) CH-1015, Lausanne, Switzerland

Liquid metal infiltration process Alternative routes: hot pressing of powder mixtures hot pressing of coated particles

Pressure infiltration apparatus Cold wall vessel (250 bar, 200°C) Inner side of the wall in contact with a water cooled heat shield Induction heating (using a graphite susceptor) primary vacuum pump (0.1 mbar) Crucible can be lowered on quench (directional solidification) 100 mm

Selected diamond grit Mono-crystalline diamond Low nitrogen level Relatively large size (>100µm)

Critical issues Diamond particle size: the larger the better the TC Limited machinability => Need for net-shape solutions Size of the net-shape parts Radiation damage in Diamonds CTE varies strongly with temperature Electrical conductivity rather low (5-10 MS/m)

Materials & parts Diamond composites: 60-75 vol-% diamond + Al, Ag, Cu Parts: fabrication capacity established for plates in Ag-Si diamond and Al-diamond size: 80*300*10 mm3 Expected thermal conductivity (@RT): >800 W/mK for Ag-Si composites >600 W/mK for Al based composites

First results: CTE Cu-B composites:

First results: CTE Ag-3Si composites:

Other tasks Brazing of SiC on diamond composites Thermal fatigue of SiC brazed on substrate Mechanical tests Thermal conductivity measurement: 3 setups: 0-40°C, 4-300 K, 100-500 K