Interfacial engineering of solution-processed Ni nanochain-SiO_x (x< 2) cermets towards thermodynamically stable, anti-oxidation solar selective absorbers

Journal Article · Fri Apr 01 00:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4945035· OSTI ID:1249356

Yu, Xiaobai ^[1]; Wang, Xiaoxin ^[1]; Zhang, Qinglin ^[2]; Liu, Jifeng ^[1]

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1. Dartmouth College, Hanover, NH (United States)
2. Univ. of Kentucky, Lexington, KY (United States)

Here, cermet solar thermal selective absorber coatings are an important component of high-efficiency concentrated solar power (CSP) receivers. The oxidation of the metal nanoparticles in cermet solar absorbers is a great challenge for vacuum-free operation. Recently, we have demonstrated that oxidation is kinetically retarded in solution processed, high-optical-performance Ni nanochain-SiO_x cermet system compared to conventional Ni-Al₂O₃ system when annealed in air at 450–600 °C for several hours. However, for long-term, high-temperature applications in CSP systems, thermodynamically stable antioxidation behavior is highly desirable, which requires new mechanisms beyond kinetically reducing the oxidation rate. Towards this goal, in this paper, we demonstrate that pre-operation annealing of Ni nanochain-SiO_x cermets at 900 °C in N₂ forms the thermodynamically stable orthorhombic phase of NiSi at the Ni/SiO_x interfaces, leading to self-terminated oxidation at 550 °C in air due to this interfacial engineering. In contrast, pre-operation annealing at a lower temperature of 750 °C in N₂ (as conducted in our previous work) cannot achieve interfacial NiSi formation directly, and further annealing in air at 450–600 °C for >4 h only leads to the formation of the less stable (metastable) hexagonal phase of NiSi. Therefore, the high-temperature pre-operation annealing is critical to form the desirable orthorhombic phase of NiSi at Ni/SiO_x interfaces towards thermodynamically stable antioxidation behavior. Remarkably, with this improved interfacial engineering, the oxidation of 80-nm-diameter Ni nanochain-SiO_x saturates after annealing at 550 °C in air for 12 h. Additional annealing at 550 °C in air for as long as 20 h (i.e., 32 h air annealing at >550 °C in total) has almost no further impact on the structural or optical properties of the coatings, the latter being very sensitive to any interfacial changes due to the localized surface plasmon resonances of the metal nanostructures. This phenomenon holds true for Ni nanoparticle diameter down to 40 nm in Ni-SiO_x system, where the optical response remains stable for 53 h at 550 °C in air. The oxidation vs. time curve also shows saturation behavior deviating from the kinetic Deal-Grove oxidation model. These results strongly suggest a promising approach to thermodynamically stable, anti-oxidation Ni/SiO_x cermet absorbers via interfacial engineering.

• Research Organization: Dartmouth College, Hanover, NH (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0007112
• OSTI ID: 1249356
• Alternate ID(s): OSTI ID: 1245034
• Journal Information: Journal of Applied Physics, Vol. 119, Issue 13; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
nickel
oxidation
cermets
surface oxidation
Gibbs free energy