Net-shape production of graphite parts via powder injection moulding of carbon mesophase

Abstract

In the present study the feasibility of the net-shape production of graphite components via powder injection moulding (PIM) of carbon mesophase is demonstrated. The difficulty in the PIM process lies in the selection of an appropriate binder system. If conventional binders are used, problems arise because the sintering temperature of carbon mesophase is below the thermal degradation temperature of most organic binders. One promising alternative is the use of partially water-soluble binder systems. These can be easily removed by solvent debinding in water. Binder selection and debinding process were adapted to avoid crack formation. Special attention has been paid to the influence of thermal treatment. The elastic modulus improved from 2.1 to 7.2 GPa while the open porosity was reduced from 32.6 to 23.7% by an adjusted temperature ramp in the thermal-debinding step. The second approach is to use a water-based binder system. This has the advantage that the water can be removed by drying at room temperature. Under optimized drying conditions, crack-free parts were produced with a very homogeneous distribution of small pores which has a positive influence on the mechanical properties. An average pore diameter of 0.32 μm was obtained with this binder system compared to 1.03 and 0.69 μm of the samples produced with the water-soluble binder system. With the water-based binder system an elastic modulus of 9.0 GPa was achieved.