Preparation of α-alumina powder and binder For 3D printer

Abstract

Alpha-alumina is a ceramic with excellent chemical stability, mechanical property, high melting point, and insulating property; however, it shows poor workability due to its low fracture toughness. There are a lot of molding processes for α-alumina, such as press molding and extrusion methods. 3D printing is rapidly growing technology to make complex and precious moldings. However, there are still only a few descriptions on 3D ink-jet powder laminating printings for α-alumina due to no self-hydration hardening property. To achieve α-alumina moldings with the 3D ink-jet printers, powder fluidity of α-alumina powders and binders for bonding the powders should be investigated. The powders mixed with α-alumina at 20, 3.4 and 0.4 μm in sizes were adjusted to improve powder fluidity and packing density. Polyvinyl alcohol (PVA) or polyallylamine (PAA) including other additives was used as an ink. The addition of PVA on the adjusted powders made no chemical interaction of powders and no retention of shapes, but that of PAA formed the printed moldings. The relative packing density and compressive strength of the printed moldings were 40 % and 8.2 kPa, which was clearly depended on the printed directions due to the nozzle structure of printer head. Sintering the moldings at 1500°C caused near-net zero shrinkage and improved the maximum compressive strength at 3.6 MPa.

Ceramic Binder Jetting Additive Manufacturing: A Literature Review on Density

“…Generally, the manual granulation method, comprising manual mixing in a crucible, oven drying, Fig. 9 Achieved values of relative green densities and porosities by various special treatment techniques (N stands for no special treatment, G for powder granulation, L for using slurry feedstock, and S for mixing powders of different sizes) [23][24][25]27,37,54,55,57,58,63,64,67,68,73,74,81,82,[86][87][88][89]92,110,156,161] Fig. 10 Achieved values of relative sintered densities and porosities by various special treatment techniques (N stands for no special treatment, C for chemical reaction, G for powder granulation, I for infiltration, L for using slurry feedstock, M for mixing different materials, P for pressing, and S for mixing powders of different sizes) [24,27,37,53,55,[63][64][65][68][69][70][71]77,83,85,86,[88][89]…”

“…[37,54,68,71,80,82,85,86,88,96,99,102,107,108,115,144,145,148,149,155,156,158,162,163,166,167] Phosphoric acid[85,101,104,[111][112][113]116,[118][119][120][121][122][123]125,126,133,138,140,141,168] Polymers (polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, etc. )[23][24][25]27,37,57,58,64,65,67,69,73,80,94,95,109,110,114,134,142,143,153,157]…”