Novel Processing of MgO-Y2O3 Nanocomposites for IR Window Applications
Date
2012-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Abstract
Polycrystalline ceramics used for infrared transparent windows have a great
advantage over their single crystal counterparts. In these materials, grain size plays an
important role on the transparency and mechanical durability of the windows. Through
the use of unique nanomaterial processing techniques, a magnesium oxide - yttrium oxide
nanocomposite material has been studied.
The main purpose of this study was to establish a correlation between powder
characteristics and the final grain size of a sintered compact. Powders synthesized by
two methods were studied. First, a common hydroxide precipitation method was used to
synthesize the MgO-Y2O3 nanocomposite powders. Second, a reverse micelle synthesis
method was used to prepare the MgO-Y2O3 nanocomposite powders. The stability of the
reverse micellar system was explored and correlations were established between the
solution molarities and successful powder synthesis. It was discovered that a molarity of
0.3 M in the AOT-isooctane-water system was within stable parameters. Both methods
were successful in the synthesis of powders with mean particle sizes less than 100 nm.
After synthesis, the powders were characterized by X-ray diffraction (XRD) for
phase, purity, and crystallite size; dynamic light scattering (DLS) for particle size;
transmission electron microscopy (TEM) for powder morphology; and BET for surface
area. The powders were then consolidated.
The sintering of the powders was accomplished by spark plasma sintering (SPS),
using high pressures, between 300 and 500 MPa. Densities were measured by using an
immersion technique. High resolution scanning electron microscopy (SEM) was
performed on fracture surfaces to analyze grain size. The high pressure SPS method
resulted in densities of approximately 90% of theoretical and final grain sizes of about 60
nm.
Description
Advisory committee members: William Carty, Scott Nordahi. Dissertation completed in partial fulfillment of the requirements for the degree of Masters of Science in Ceramic Engineering at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis