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Materials Science in Additive Manufacturing Alumina platelets additive manufacturing

A E F

B

G H

C

I J
D

Figure 1. Initial study on the effects of powder type on platelet slurry properties. (A–D) Scanning electron microscope (SEM) images of alumina platelets
(PL), nanopowder (NS), regular micron-sized powder (MR), and irregular micron-sized powder (MI). (E) The viscosity of each slurry. (F) Sedimentation
behavior of the slurry containing platelets with NS, MI, or MR. (H–J) SEM images of the sintered sample in (G).

dispersed. Alumina platelets were subsequently added and rheometer (HAAKE Mars III) with a parallel plate set-up
mixed to obtain a 35 vol.% slurry. The proportion of each of a gap of 0.4 mm from shear rates of 0 – 200 s at an
−1
additive was measured based on the total solid loading ambient temperature of 25°C. Each slurry was prepared
of 35 vol.% in this study. Photo-initiator was added last and left untouched over a period of 7 days to observe the
and before fabrication to prevent premature curing of sedimentation of the powder.
the slurry. All of the mixing steps were carried out on a The porosity (P) of sintered ceramic samples was
planetary mixer at 2000 rpm for 5 min each. As a result, calculated by:
the total time needed to prepare the slurry takes <40 min.
Additive manufacturing of this composite was p 1 (I)
conducted on a vat polymerization system (Cerafab 8500, s
Lithoz, Austria). The printer equipped with a coating
blade provided additional aid to align the platelets in an Where ρ is the density of samples, and ρ is the density
s
3
orientation that mimics the nacre structure. The wavelength of alumina (3.97 g/cm ). Three-point bending test was
®
of the projector is approximately 450 nm, and the build performed on an Instron 8874 system (Instron , US).
volume of the printer is 115 mm × 64 mm × 200 mm. The support span for the test setup was 40 mm, and the
sample was loaded at a rate of 0.1 mm/min until failure.
ImageJ was used to measure the particle sizes. The fracture surface was then examined under a scanning
Rheological properties were characterized by measuring electron microscope (SEM; Hitachi S-4300, Hitachi High-
the viscosity and observing the stability of the slurry over Tech Corporation, Japan) after gold coating at 20 mA for
7 days. The viscosity of each slurry was measured on a 60 seconds.

Volume 3 Issue 1 (2024) 3 https://doi.org/10.36922/msam.2711