Deploying energy storage and carbon capture at scale is hindered by the substantial endothermic penalty of decomposing CaCO3to CaO and CO2, and the rapid loss of CO2absorption capacity by CaO sorbent particles due to sintering at the high requisite decomposition temperatures. The decomposition reaction mechanism underlying sorbent deactivation remains unclear at the atomic level and nanoscale due to past reliance on postmortem characterization methods with insufficient spatial and temporal resolution. Thus, elucidating the important CaCO3decomposition reaction pathway requires direct observation by time‐resolved (sub‐)nanoscale methods. Here, chemical and structural dynamics during the decomposition of CaCO3nanoparticles to nanoporous CaO particles comprising high‐surface‐area CaO nanocrystallites are examined. Comparing in situ transmission electron microscopy (TEM) and synchrotron X‐ray diffraction experiments gives key insights into the dynamics of nanoparticle calcination, involving anisotropic CaCO3thermal distortion before conversion to thermally dilated energetically stable CaO crystallites. Time‐resolved TEM uncovered a novel CaO formation mechanism involving heterogeneous nucleation at extended CaCO3defects followed by sweeping reaction front motion across the initial CaCO3particle. These observations clarify longstanding, yet incomplete, reaction mechanisms and kinetic models lacking accurate information about (sub‐)nanoscale dynamics, while also demonstrating calcination of CaCO3without sintering through rapid heating and precise temperature control.
Electronic properties of silicon, the most important semiconductor material, are controlled through doping. The range of achievable properties can be extended by hyperdoping, i.e., doping to concentrations beyond the nominal equilibrium solubility of the dopant. Here, hyperdoping is achieved in a laser pyrolysis reactor capable of providing nonequilibrium conditions, where doping is governed by kinetics rather than thermodynamics. High resolution scanning transmission electron microscopy (TEM) with energy‐dispersive X‐ray spectroscopy shows that the boron atom distribution in the hyperdoped nanoparticles is relatively uniform. The hyperdoped nanoparticles demonstrate tunable localized surface plasmon resonance (LSPR) and are stable in air for periods of at least one year. The hyperdoped nanoparticles are also stable upon annealing at temperatures up to 600 °C. Furthermore, boron hyperdoping does not change the diamond cubic crystal structure of silicon, as demonstrated in detail by high flux synchrotron X‐ray diffraction and pair distribution function (PDF) analysis, supported by high‐resolution TEM analysis.
more » « less- Award ID(s):
- 1809439
- NSF-PAR ID:
- 10435595
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 29
- Issue:
- 8
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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