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Synthesis and characterization of a series of new green solar heat-reflective pigments: Cr-doped BiPO4 and its effect on the aging resistance of PMMA (Poly(methyl methacrylate))
摘要： A series of new green Cr-doped BiPO4 materials were synthesized by hydrothermal method and first used as solar heat-reflective pigments. XRD, FTIR, FE-SEM and HR-TEM analyses confirm that the phase structure was transformed from low-temperature monoclinic phase (LTMP) to hydrated hexagonal phase (HP), the particle size decreased and the morphology changed from irregular prism-shaped to rod-shaped, which all attributed to the incorporation of Cr3+ ions. Moreover, the valance of chromium ions was also confirmed by XPS. Color and ultraviolet-visible-near-infrared (UV–Vis–NIR) analysis indicate that different hues of green were obtained in these solid solutions and they possessed high NIR reflectance (> 83%) and solar reflectance (> 86%) in total NIR region. Meanwhile, the reason of decrease in NIR reflectance of doped samples was also analyzed, which mainly due to the decrease of free carrier concentration. TG-DTA and corrosion resistance tests prove that these pigments have excellent thermal and chemical stability. Compared with pure PMMA and the existing reports on pigmented PMMA, the NIR reflectance of PMMA pigmented with Cr-doped BiPO4 pigments have been greatly improved and have good coloring performance. The NIR solar reflectance of PMMA colored with Bi0.85Cr0.15PO4 in shortwave NIR region reaches up to 77.83%, an increase of nearly 52%. Heat aging test shows that Cr-doped BiPO4 pigments significantly improve the aging resistance of PMMA. In conclusion, these pigments have potential to become plastic colorants to increase the NIR reflectance and aging resistance of plastics.
关键词： Green pigments,Cr-doped BiPO4,Aging resistance,NIR reflectance,PMMA
更新于2025-09-23 15:23:52
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Spectroscopic Characterization of Emulsions Generated with a New Laser-Assisted Device
摘要： This paper presents a spectroscopic study of emulsions generated with a laser-assisted device. Fourier transform infrared (FTIR), Raman and UV–Vis–NIR reflectance spectra of emulsions, recorded before and after exposure to laser radiation were used to characterize the effect of laser irradiation. The paper also presents a comparison between the calculated IR spectra and the experimental FTIR spectra of an emulsion’s components. FTIR measurements allowed the identification of absorption bands specific to each of the emulsions’ components. Moreover, it enabled the observation of destabilization of the emulsion in real-time. Raman spectroscopy allowed the observation of the modifications at a molecular level, by identifying the vibrations of the representative functional groups and the polymerization of sodium tetradecyl sulfate (STS) molecules by analyzing the evolution of the carbonyl band. UV–Vis–NIR reflectance spectra of emulsions before and after exposure to laser radiation showed that the physical characteristics of the emulsions changed during irradiation—the dimensions of the droplets decreased, leading to an emulsion with a better time stability. These results proved that the employed spectroscopy techniques were powerful tools in emulsion analysis.
关键词： UV–Vis–NIR reflectance spectroscopy,FTIR spectroscopy,emulsion,Raman spectroscopy
更新于2025-09-23 15:19:57
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Synthesis of green cool pigments (CoxZn1-xO) for application in NIR radiation reflectance
摘要： Reconciling green synthesis, sustainability and production of pigments for protection of solar radiation is a continuous topic of search for unique, versatile and environmental compatible methods. In this perspective, we present the green synthesis of inorganic pigments with reflective properties of infrared radiation in the NIR region. Green powder pigments described by CoxZn1-xO, were obtained via the gelatinization method of starch colloidal suspension with inorganic salts (zinc and cobalt), calcined at different temperatures. Structural, morphological and spectroscopic characterization showed the pigments present Wurtzite crystalline phase with compact hexagonal structure, and monophasic when obtained at a calcination temperature above 800 °C. Colorimetric measurements obtained by the CIE-L*a*b* method presented values related to green pigments attributed to cobalt ions, which replace the zinc ions in the Wurtzite matrix and corroborate the composition estimated by X-ray fluorescence analysis for Co0.1Zn0.9O. The pigments' NIR reflectivity increased with the calcination temperature increasing, with R% > 35%; and when the pigment is dispersed in a white paint the increase is R% > 50%. Therefore, our green pigments present great potential to be used as an active material in cold coatings and in solar devices.
关键词： Colorimetry,NIR reflectance,Cool pigments,Green synthesis
更新于2025-09-10 09:29:36