One-Pot Coating of Ceramic Powders by Exfoliated Boron Nitride Layers with a Dense CO2 Medium and Ultrasound-Aided Mixing
The coating or doping of substrates by two-dimensional materials to impart superior functional properties (such as improved thermal conductivity, bacterial resistance, reduced friction) is receiving increased attention. Environmentally benign, rapid and scalable coating techniques are desirable for this purpose. Here, we report a novel process for coating alumina, silicon carbide and boron carbide substrates with hexagonal boron nitride (h-BN) layers. The process consists of two sequential steps. First, h-BN layers are exfoliated from bulk h-BN in supercritical carbon dioxide (scCO2) using ultrasound-aided mixing. This step is followed by self-assembly (i.e., coating) of the exfoliated h-BN on the substrates in liquid CO2 also aided by ultrasound. The liquid CO2 state is achieved by simply lowering the pressure and temperature of the first step below the critical point of CO2 (Pc = 72.8 atm; Tc = 31.1 °C). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) micrographs clearly reveal the exfoliation of h-BN under scCO2 conditions as well as the h-BN assembly on various substrates under liquid CO2 conditions. X-ray diffraction patterns confirm the structural integrity of the coated h-BN layers. It was also confirmed that without a transition to the liquid CO2 phase following exfoliation in scCO2, there was negligible coating of h-BN on the substrates. Researchers in the field could consider this benign process to rapidly coat or dope materials with h-BN and other 2D materials to impart improved functional properties in myriad applications.
- Research Organization:
- Kansas City Nuclear Security Campus (KCNSC), Kansas City, MO (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- NA0002839
- OSTI ID:
- 2461592
- Report Number(s):
- NSC--614-6270
- Journal Information:
- Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 41 Vol. 63; ISSN 0888-5885
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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