研究目的
To examine the near infrared (NIR) reflectivity of Cr-doped ZnO nanopigments prepared by thermal decomposition for potential use in cool paint applications.
研究成果
Cr-doped ZnO nanorods were successfully synthesized with a wurtzite hexagonal structure, showing substitution of Zn2? by Cr3? ions. The optical energy gap decreased slightly with Cr doping, and the sample with 0.5 wt% Cr exhibited the highest NIR reflectance among doped samples (53.1%), making it suitable for cool-colored nanopigments. The thermal decomposition technique is cost-effective and high-yield, with nanoscale particles improving reflectivity for aesthetic applications.
研究不足
The study is limited to Cr-doped ZnO nanopigments synthesized via thermal decomposition; other dopants or synthesis methods were not explored. The inhomogeneity in color due to agglomeration and potential crystal defects at high Cr concentrations may affect performance. Scalability and long-term stability in real-world applications were not tested.
1：Experimental Design and Method Selection:
The study used a thermal decomposition technique to synthesize Cr-doped ZnO nanorods, chosen for its simplicity, cost-effectiveness, and ability to produce high-purity nanocrystals. Theoretical models included XRD for structural analysis, FTIR for vibrational modes, SEM for morphology, and diffuse reflectance with Kubelka-Munk theory for optical properties.
2：Sample Selection and Data Sources:
Samples were prepared with varying weight percentages of chromium(III) acetate hydroxide to zinc acetate dihydrate (0%, 0.5%, 1%, 3%, 5%), named ZC0 to ZC4. Data sources included synthesized nanopigments and standard solar spectral irradiance from ASTM G173-
3：5%, 1%, 3%, 5%), named ZC0 to ZCData sources included synthesized nanopigments and standard solar spectral irradiance from ASTM G173-List of Experimental Equipment and Materials:
03.
3. List of Experimental Equipment and Materials: Equipment included a ball miller (agate mortar and ball), oven, X-ray diffractometer (Philips X'pert MPD 3040 with CuKα radiation), FTIR spectrometer (JASCO FT/IR-4100), FE-SEM (Quanta FEJ20), and spectrophotometer (JASCO UV/Vis/NIR V570 with integrating sphere). Materials were zinc acetate dihydrate (Winlab, 99.999% purity) and chromium(III) acetate hydroxide (Aldrich).
4：999% purity) and chromium(III) acetate hydroxide (Aldrich).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Zinc acetate dihydrate was ground for 2 hours, mixed with chromium precursor in a ball mill for 2 hours, then thermally decomposed in an alumina crucible at 350°C for 4 hours. Characterization involved XRD (2θ range 20° to 80°), FTIR (400-4000 cm?1), SEM imaging, and diffuse reflectance (200-2500 nm).
5：Data Analysis Methods:
XRD data analyzed for crystal structure and lattice parameters; FTIR for functional groups; SEM for morphology; diffuse reflectance data used to calculate NIR solar reflectance (R*) using ASTM standard and optical energy gap (Eg) via Kubelka-Munk function.
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