Bottom‐up vs reactive sintering of Al₂O₃–YAG–YSZ composites via one or three‐phase nanoparticles (NPs). Bottom‐up processing wins this time

Abstract

The bottom‐up approach describes the synthesis of bulk materials from the finest possible length scales to obtain the best global properties. This approach was adapted to the synthesis of multi‐phase ceramic composites produced from metal oxides produced by liquid‐feed flame spray pyrolysis (LF‐FSP). The effect of length scale of mixing was tested through two processing schemes, mixed single metal‐oxide nanopowders (NPs) and nanocomposite NPs having the desired composition within single particles. For the Al2O3–Y2O3–ZrO2 ternary system, composites prepared from nanostructured nanoparticles sinter to finer grain sizes (<410 nm) at equivalent densities of 95%TD than those prepared from mixed nanoparticle processing. These contrast with our previous studies in this area where mixed NP processing gave the best or equivalent results. The nanocomposite NPs produced in this study exhibit novel nanostructures with three phases contained within single particles <26 nm average particle size (APS). This nanostructure may directly explain the enhanced sintering of the nanocomposite NPs and may provide an impetus for future synthesis of similarly structured NPs.

Processing YAG/α‐Al2O3 composites via reactive sintering Y2O3/Al2O3 NP mixtures. A superior alternative to bottom up processing using atomically mixed YAlOx NPs

“…To reduce the grain size into the nanometer range, we explored the addition of a third phase to both further pin grain boundary movement and provide lower temperature sintering. These studies are described elsewhere, where we add a Y 2 O 3 stabilized ZrO 2 phase to YAG/α‐Al 2 O 3 composites.…”

Chemical modification in and on single phase [NiO]0.5[Al2O3]0.5 nanopowders produces “chocolate chip‐like” Nix@[NiO]0.5‐x[Al2O3]0.5 nanocomposite nanopowders

“…As a very effective method of generating a wide variety of single and mixed metal oxide NPs from metalloorganic precursors, liquid feed flame spray pyrolysis (LF-FSP) has been employed by many groups. [43][44][45][46][47][48][49][50][51][52][53][54] Our group typically uses 1-10 wt. % ceramic yield ethanol solutions of metal carboxylates, alkoxides, beta-diketonates, and/or related metalloorganic precursors to prepare a wide variety of single and mixed-metal oxide NPs that provide novel catalyst.…”

“…The as‐prepared nickel aluminate spinels still suffer from serious powder agglomeration, uneven particle size distributions, and oversized particles, which affect seriously the application of nickel aluminate spinels in many fields. As a very effective method of generating a wide variety of single and mixed metal oxide NPs from metalloorganic precursors, liquid feed flame spray pyrolysis (LF‐FSP) has been employed by many groups . Our group typically uses 1‐10 wt.…”