研究目的
To investigate the structure, thermal stability, and chromaticity of TiB2 based high temperature solar selective absorbing coatings for improved solar thermal conversion efficiency.
研究成果
The SS/TiB2/Al2O3 coating demonstrates high solar absorptance (0.93) and low emittance (0.11), with good thermal stability up to 700°C for 2 hours and 600°C for 100 hours in vacuum. Degradation at higher temperatures is due to TiO2 formation, as confirmed by SEM and Raman analysis. The coating's color changes with annealing temperature, providing insights for applications in solar thermal systems. Future work could explore coatings in oxidative environments and under operational conditions.
研究不足
The study is limited to vacuum conditions; real-world applications may involve oxidative environments that could affect coating stability. The thermal stability tests are conducted up to 800°C, but higher temperatures or longer durations might reveal further degradation. The coating's performance under actual solar radiation and cycling conditions is not evaluated.
1：Experimental Design and Method Selection:
The study involves designing and fabricating a SS/TiB2/Al2O3 tandem solar absorber coating using magnetron sputtering, with systematic characterization using SEM, UV-vis-NIR spectrophotometer, FTIR, XPS, and Micro-Raman techniques to analyze structure, composition, and optical properties. Thermal stability is tested in vacuum at various temperatures and durations, and chromaticity is analyzed using CIE color coordinates.
2：Sample Selection and Data Sources:
Polished stainless steel (SS) substrates (50 mm × 50 mm × 2 mm) and Si substrates are used. Coatings are deposited on SS for reflectance and Raman measurements, and on Si for chemical and microstructural analysis.
3：List of Experimental Equipment and Materials:
Equipment includes a magnetron sputtering system (Kurt J. Lesker, USA), high-resolution SEM (SU8200, Tokyo, Japan), XPS (ESCALAB 250Xi, USA), Micro-Raman spectrometer (LabRAM HR Evolution, HORIBA Jobin Yvon S.A.S., French), UV/vis/NIR spectrometer (Perkin Elmer Lambda 950), FT-IR spectrometer (Bruker TENSOR 27), and a resistive tubular furnace. Materials include TiB2 and Al2O3 targets (99.99% purity), argon gas, and substrates.
4：99% purity), argon gas, and substrates.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Substrates are cleaned ultrasonically with ethanol. Coatings are deposited via DC magnetron sputtering for TiB2 and RF magnetron sputtering for Al2O3 in argon plasma. Thermal annealing is performed in vacuum at specified temperatures and times. Optical measurements are conducted using spectrometers, and data is analyzed to calculate absorptance and emittance.
5：Data Analysis Methods:
Reflectance spectra are used to compute solar absorptance and thermal emittance using standard equations. XPS and Raman data are analyzed for chemical bonding and structural changes. Chromaticity coordinates are calculated from reflectance data in the visible range.
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