FABRICATION OF TRANSPARENT MgAl2O4 SPINEL CERAMICS BY PECS PROCESSING OF COMBUSTION - SYTHESIZED NANOPOWDERS

Abstract

Transparent MgAl<sub>2</sub>O<sub>4 </sub>ceramic could be found in a wide range of applications for both military and civil sector due to its high melting point, good mechanical properties, small refractive index (1.71) and its ability to allow light in range from UV to mid-IR to pass through. In the present work, transparent MgAl<sub>2</sub>O<sub>4</sub> was fabricated from metal nitrates via two steps. Firstly, the MgAl<sub>2</sub>O<sub>4</sub> nanopowder was synthesized via solution combustion synthesis from the metal nitrates. Secondly, the powder was then consolidated by Pulsed Electric Current Sintering (PECS) technique to fabricate transparent ceramic. XRD patterns of the obtained powder showed the peaks of only MgAl<sub>2</sub>O<sub>4</sub> phase. Besides, the atomic compositions of magnesium, aluminium and oxygen determined by EDX analysis were approximately corresponded to 1:2:4 of the molecular formula of MgAl<sub>2</sub>O<sub>4</sub>. After deagglomerating for 48 hours using soft ball-milling, the powder had the average particle of 27 nm. Transparent MgAl<sub>2</sub>O<sub>4</sub> samples, which were sintered with two-step sintering mode of 1050<sup>o</sup>C/60 minutes-1400<sup>o</sup>C/20 minutes, permitted the transmission of visible and infrared light with the transmittance up to 80%, Vickers hardness of 14.2 GPa, and fracture toughness of 1.1 MPa.m<sup>1/2</sup>. The results are a critical step toward fabrication of high-quality transparent ceramics from metal nitrates.

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