Flash pyrolysis, which combines conventional pyrolysis with flash sintering, was first conducted to produce polymer derived SiC‐TiC nanocomposites. Pre‐pyrolysis at 800℃ allows the conversion from titanium isopropoxide (TTIP) modified polysiloxane to an amorphous SiTiOC ceramic. The subsequent application of an electric field gives rise to the formation of turbostratic carbon and creates Joule heating to obtain a sample internal temperature of ~1400℃. The precipitation of β‐SiC, TiC, as well as titanium oxides is realized upon carbothermal reduction of extensively phase separated SiO2and TiO2with carbon. Increasing TTIP content embodies the nanocomposites with prominent electrical percolation behaviors. The electrical transport of the synthesized ceramics follows an amorphous semiconductor mechanism. High thermal stability in air is guaranteed, thanks to the in‐situ formed TiC nanocrystals and preferentially reduced amorphous carbon. Flash pyrolyzed nanocomposite with a Ti:Si molar ratio of 0.20 exhibits the highest electrical conductivity (0.696 S/cm) and minimum mass change (~2%) at 1000℃, serving as a competitive candidate for electro‐discharge machining (EDM) applications or self‐standing conducting devices that must withstand high temperature conditions.
Thermal stability of self-assembled ordered three-phase Au–BaTiO 3 –ZnO nanocomposite thin films via in situ heating in TEM
Thermal stability of oxide–metal nanocomposites is important for designing practical devices for high temperature applications. Here, we study the thermal stability of the self-assembled ordered three-phase Au–BaTiO 3 –ZnO nanocomposite by both ex situ annealing under air and vacuum conditions, and by in situ heating in TEM in a vacuum. The study reveals that the variation of the annealing conditions greatly affects the resulting microstructure and the associated dominant diffusion mechanism. Specifically, Au nanoparticles show coarsening upon air annealing, while Au and Zn either form a solid solution, with Zn atomic percentage less than 10%, or undergo a reverse Vapor–Liquid–Solid (VLS) mechanism upon vacuum annealing. The distinct microstructures obtained also show different permittivity response in the visible and near-infrared region, while retaining their hyperbolic dispersion characteristics enabled by their highly anisotropic structures. Such in situ heating study in TEM provides critical information about microstructure evolution, growth mechanisms at the nanoscale, and thermal stability of the multi-phase nanocomposites for future electronic device applications.
- Publication Date:
- NSF-PAR ID:
- 10226867
- Journal Name:
- Nanoscale
- Volume:
- 12
- Issue:
- 46
- Page Range or eLocation-ID:
- 23673 to 23681
- ISSN:
- 2040-3364
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1039/d0nr06115h
