Complex shaped boron carbides from negative additive manufacturing

Complex shaped boron carbide with carbon (B4C/C) at near-full densities were achieved for the first time using negative additive manufacturing techniques via gelcasting. Negative additive manufacturing involves 3D printing of sacrificial molds used for casting negative copies. B4C powder distributions and rheology of suspensions were optimized to successfully cast complex shapes. In addition to demonstrating scalability of these complex geometries, hierarchically meso-porous structures were also shown to be possible from this technique. Resorcinol Formaldehyde (RF) polymer was selected as the gelling agent and can also pyrolyze into a carbon aerogel network to act as the sintering aid for B4C. Due to the highly effective distribution of in situ carbon for the B4C matrix, near-full sintered density of 97-98% of theoretical maximum density was achieved. (C) 2018 Elsevier Ltd. All rights reserved.