Stabilization of highly-loaded boron carbide aqueous suspensions

Injection molding of boron carbide (B4C) slurries affords the production of complex-shaped personal armor. To injection mold, however, requires preparation of a well dispersed, flowable suspension with >45 vol% B4C loadings to reduce porosity that must be removed during sintering. In the present study, the preparation of highly-loaded B4C suspensions is investigated using zeta potential and rheological measurements, varying dispersant type, molecular weight, and amount. Of those dispersants investigated, polyethylenimine (PEI) with a molecular weight of 25,000 g/mol was found to produce suspensions with up to 56 vol% B4C and the requisite rheological properties suitable for injection molding. A PEI concentration of 1.83 mg/m2 was established as the appropriate to produce highly-loaded B4C suspensions. The effect of a prior B4C powder treatment (ethanol washed or attrition milled) on rheological properties of the suspensions was also investigated. The PEI was completely burned out in argon, nitrogen, and air at 450 °C.