Near-infrared Shielding Properties Research Articles

Boosted near-infrared shielding properties of cesium-tungsten bronze based on solid state reaction with optimized precursor

Cesium doped tungsten bronze (CWO) nanoparticles can selectively keep high transmittance in the visible while presenting significant shielding rate in the near-infrared region. How to further improve the optical properties of CWO based on solid state method is crucial to the industry production. Based on changing the particle size and morphology of WO3 precursors, cesium-tungsten bronze powders with different dispersivity and concentrations of Cs+ doping were successfully prepared by solid-phase method. The characterization analysis reveals that the precursors with appropriated surface area and morphology are significant to improve the dispersivity of CWO nanocrystal and increase the density of free carriers, thereby improving the small polariton absorption performance and the local surface plasmon resonance effect. The result provides an effective strategy to boost the optical property of CWO nanocrystal synthesized by optimizing the morphology and size of precursor, which is important to the industry production and practical applications in the field of energy-saving window films.

Enhanced far infrared emissivity, UV protection and near-infrared shielding of polypropylene composites via incorporation of natural mineral for functional fabric development

Far infrared radiation in the range of 4–20 µm has been showed to have biological and health benefits to the human body. Therefore, incorporating far-infrared emissivity additives into polymers and/or fabrics hold promise for the development of functional textiles. In this study, we incorporated nine types of natural minerals into polypropylene (PP) film and examined their properties to identify potential candidates for functional textiles and apparels. The addition of 2% mineral powders into PP film increased the far-infrared emissivity (5–14 µm) by 7.65%-14.48%. The improvement in far-infrared emissivity within the range of 5–14 µm, which overlaps with the peak range of human skin radiation at 8–14 µm, results in increased absorption efficiency, and have the potential to enhance thermal and biological effects. Moreover, the incorporation of mineral powders in PP films exhibited favorable ultraviolet (UV) protection and near-infrared (NIR) shielding properties. Two films, specifically those containing red ochre and hematite, demonstrated excellent UV protection with a UPF rating of 50+ and blocked 99.92% and 98.73% of UV radiation, respectively. Additionally, they showed 95.2% and 93.2% NIR shielding properties, compared to 54.1% NIR shielding properties of PP blank films. The UV protection and NIR shielding properties offered additional advantages for the utilization of polymer composite with additives in the development of sportswear and other outdoor garments. The incorporation of minerals could absorb near-IR radiation and re-emit them at longer wavelength in the mid-IR region. Furthermore, the incorporation of minerals significantly improved the heat retention of PP films under same heat radiation treatment. Notably, films with red ochre and hematite exhibited a dramatic temperature increase, reaching 2.5 and 3.2 times the temperature increase of PP films under same heat radiation treatment, respectively (46.8 °C and 59.9 °C higher than the temperature increase of 20.9 °C in the PP film). Films with additives also demonstrated lower thermal effusivity than PP blank films, indicating superior heat insulation properties. Therefore, polypropylene films with mineral additives, particularly those containing red ochre and hematite, showed remarkable heat capacity, UV-protection, NIR-shielding properties and enhanced far infrared emissivity, making them promising candidates for the development of functional textiles.

Effect of substrate temperature on the near-infrared shielding properties of WO3-x thin films deposited by RF magnetron sputtering

Near-infrared (NIR) shielding materials emerge as potential candidates for energy conservation applications. In this work, tungsten oxide (WO3-x, 0 < x < 1) thin films were deposited on soda-lime glass substrate by RF magnetron sputtering at various substrate temperatures and NIR shielding properties of the films were studied. Structural, morphological and compositional properties of the films were also investigated. Optical constants, thickness and roughness of the films were extracted from spectroscopic ellipsometric (SE) measurements. The correlativity of SE with UV–Vis–NIR spectrophotometry, cross-sectional field emission scanning electron microscopy and atomic force microscopy was investigated. Of all the films, WO3-x thin films deposited at 500 °C showed the lowest NIR transmittance of about 23% with the highest visible transmittance of above 70% corresponding to a Tvis/Tsol ratio of 1.35 and NIR shielding value of 75%. WO3-x coated soda lime glass shows better NIR shielding performance compared to commercial soda lime glass in the thermal shielding test. The underlying reason for NIR absorption is the presence of oxygen vacancies which promote formation of W5+ ions and the resultant combined effects of polaron absorption and surface plasmon resonance. This work is significant in utilizing a facile technique for developing undoped WO3-x thin films for efficient NIR shielding applications.

Controlling the growth of hexagonal CsxWO3 nanorods by Li+-doping to further improve its near infrared shielding performance

In order to develop a novel high efficient energy-saving film, Li, Cs co-doped tungsten bronze (Li m Cs n WO 3 , m + n = 0.35) nanoparticles with excellent near-infrared (NIR) shielding properties were prepared by a facile solid state reaction method. It has been clarified that Li + -doping can control the crystal growth of Cs x WO 3 , resulting in formation of hexagonal nanorods with high aspect ratio, which is conducive to enhancing the local surface plasmon resonance (LSPR) and improving the NIR shielding performance. The as-prepared Li m Cs n WO 3 films from dispersion of nanoparticles with Li/Cs = 0.2:0.8 could exhibit excellent transparent heat shielding performance with the maximum visible light transmittance 75.18% and NIR shielding rate 97.65%. Moreover, the temperature difference between the outside surface and air in the box for the film glass during the thermal insulation test is 3 times that of ordinary glass. In addition, the regulation mechanism of Li + -doping on the crystal structure and NIR shielding properties were investigated. It is found that the mixed alkali effect in the Li m Cs n WO 3 nanoparticles is favorable for obtaining hexagonal Cs 0·32 WO 3 crystal grains with improved NIR shielding performance and stable crystal structure. This work has great significance for promoting industrial production and practical applications in the field of energy-saving window films. • Li m Cs n WO 3 nanorods were synthesized by a facile solid-state reaction method. • Li, Cs co-doping can lead to the growth of Li m Cs n WO 3 nanorods with high aspect ratio. • The mixed alkali effect is helpful for forming stable hexagonal nanorods. • The Li m Cs n WO 3 nanorods exhibit improved near infrared shielding performance.

Tm, Yb co-doped urchin-like CsxWO3 nanoclusters with dual functional properties: Transparent heat insulation performance and enhanced photocatalysis

In order to obtain ideal CsxWO3 powders that combine transparent thermal insulation and outstanding photocatalytic degradation of pollutants, Tm3+, Yb3+ co-doped CsxWO3 ((Tm, Yb)-CsxWO3) urchin-like nanoclusters were synthesized in situ by facile solvothermal reaction and subsequent heat treatment. The effects of Tm, Yb co-doping on the crystal structure, adsorption/photocatalysis, visible transmittance and near-infrared (NIR) absorption of CsxWO3 particles were investigated. The results indicate that the as-prepared (Tm, Yb)-CsxWO3 samples exhibit significantly improved photocatalytic activity while maintaining excellent visible transmittance and NIR shielding properties. In particular, sample 2T-10YC with 2 mol% Tm/10 mol% Yb co-doped CsxWO3 exhibited highest photocatalytic activity with the photocatalytic degradation efficiency of Rhodamine B attaining to 69.86%, and its films prepared from dispersion of powder samples exhibit high transparent heat shielding performance with visible transmittance 71.4% and NIR shielding rate 90.8%, respectively. The enhanced photocatalytic activity of the sample can be ascribed to the lattice distortion and decrease of band gap caused by Tm, Yb co-doping, and the increased light utilization due to the formation of impurity energy level and multiple light reflection caused by hierarchical structure can also enhance the photocatalytic activity. Moreover, the introduction of Tm and Yb elements can also refine the CsxWO3 grains, which is conducive to improving the visible transmittance. Thus, the as-prepared bifunctional (Tm, Yb)-CsxWO3 particles will have potential application prospects in the field of energy-saving and environmental purification.

Effect of Morphology on Near-Infrared Shielding Properties of Aluminum-Doped ZnO by Solvothermal Synthesis

In this work, aluminum-doped ZnO (AZO) is synthesized for heat-shielding applications. A family of ethanolamine (EA: monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine TEA)) is used to control the morphology of aluminum-doped ZnO (AZO) synthesized via a simple solvothermal method at the temperature of 120°C for 6 h. The samples were characterized by field-emission scanning electron microscopy (FE-SEM). The formation of primary ZnO nanoparticles (NPs) showed that TEA yielded highly packed-spherical aggregates not found when DEA and MEA were used. X-ray diffraction (XRD) found that all AZO samples have peaks of the ZnO hexagonal wurtzite structure. XRD patterns of aluminum were found for &gt;10 mol%. UV-Vis-NIR spectrophotometer was used to study the optical property and heat-shielding of the near-infrared region (NIR, the wavelength from 700 - 2500 nm). All AZO NPs of 0, 2, 4, and 10 mol% exhibited strong NIR shielding ability up to 80% insulation. From these results, the AZO NPs have potential use as NIR shielding materials of low-cost and simple processes to be coated on an energy-efficient window as smart window coating in buildings and automotive thus reducing energy consumption, especially in air conditioning usage.

Solvothermal Synthesis and Near-Infrared Shielding Properties of Cs0.3WO3/WO3 Composites

The Cs[Formula: see text]WO3/WO3 composite with near-infrared shielding properties was synthesized by the solvothermal method using tungstic acid and cesium salt as raw materials. The as-prepared composites were tested by X-ray powder diffraction, scanning electron microscopy, energy spectrum analysis, transmission electron microscopy, electron energy loss spectroscopy, and ultraviolet-visible near-infrared spectroscopy. The effects of different reaction conditions on the structure and near-infrared shielding properties of the synthesized composites were investigated. The best near-infrared light transmittance of as-prepared composites can reach up to 9%, which provides a feasible solution for the near-infrared shielding material. The new homogeneous composites of cesium tungsten bronze and tungsten oxide are good candidates for solar filters.

Synthesis of cesium tungsten bronze by a solution-based chemical route and the NIR shielding properties of cesium tungsten bronze thin films

In this study, hexagonal Cs0.32WO3 powders were synthesized by a simple solution-based chemical route. The experiment can be performed within a relatively short time and can easily produce large amounts of hexagonal Cs0.32WO3 powders. The CsxWO3 powders as synthesized and after heat treatment were characterized by X-ray diffraction, scanning electron microscopy, differential thermal and thermogravimetric analysis and Fourier transform infrared spectroscopy. CsxWO3 thin films were deposited by an electron beam evaporation method from sintered Cs0.32WO3 powders as the targets. The CsxWO3 films were annealed at different temperatures under Ar and Ar/H2 atmospheres. The effects of annealing on the microstructure, morphology and near-infrared (NIR) shielding properties of the Cs0.32WO3 films are discussed. The results show that the Cs0.32WO3 thin film specimen annealed for 500 °C in an Ar/H2 atmosphere has the highest transmittance (80%) in the visible light region and the lowest transmittance (42%) in the NIR region.

Effects of annealing on near-infrared shielding properties of Cs-doped tungsten oxide thin films deposited by electron beam evaporation

Abstract Near-infrared (NIR) shielding properties are important for solar films. In this study, Cs x WO 3 films prepared using electron beam evaporation were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometry. The effects of annealing on NIR shielding properties and film microstructure were investigated. The results show that the NIR shielding properties of Cs x WO 3 films can be improved by annealing at 300–450 °C under pure H 2 atmosphere, the amorphous thin films being transformed to crystalline films. The Cs x WO 3 films annealed at 450 °C in pure H 2 atmosphere showed high transmittance of visible light (70%) and high NIR shielding ratio (99%).

Dispersion of Cs0.33WO3 particles for preparing its coatings with higher near infrared shielding properties

Abstract In order to achieve good dispersion of Cs0.33WO3 particles and improve their near-infrared (NIR) shielding efficiency, the influences of ball-milling and dispersant on the dispersion stability of Cs0.33WO3 particles and its near infrared shielding properties were investigated. The microstructure, morphology, particle size distribution and Zeta potential of the particle samples were characterized by XRD, SEM and laser particle size analyzer. The results indicate that adding appropriate dispersant after ball-milling is conducive to dispersion of Cs0.33WO3 powders. Polyvinyl alcohol and titanate coupling agent have better effects on the dispersion of Cs0.33WO3 colloidal solution than poly-carboxylic salt dispersant. Particularly, the as-prepared Cs0.33WO3 coatings prepared from colloidal dispersion solution using titanate coupling agent at pH = 7 showed best visible light transmittance and near-infrared shielding properties, and have great potential applications as thermal insulation coatings for building and automotive glasses.

Hydrothermal Synthesis of CsxWO3 and the Effects of N2 Annealing on its Microstructure and Heat Shielding Properties

Cesium tungsten bronze (CsxWO3) powders were synthesized by hydrothermal reaction at 190 °C by using sodium tungstate and cesium carbonate as raw materials, and the effects of N2 annealing on the microstructure and near-infrared (NIR) shielding as well as heat insulation properties of CsxWO3 were investigated. The results indicated that the synthesized CsxWO3 powders exhibited hexagonal Cs0.32WO3 crystal structure, and subsequent N2 annealing could further improve the crystallinity of CsxWO3 particles. Moreover, the NIR shielding and heat insulation properties of CsxWO3 could be further improved after N2 annealing at appropriate temperature for a period of time. Particularly, the 500 °C-annealed CsxWO3 products in the N2 atmosphere showed the best NIR shielding and heat insulation properties. When the N2 annealing temperature was higher than 700 °C, the NIR shielding properties decreased again. The 800 °C-annealed samples in the N2 atmosphere showed higher visible light transmittance, however, the NIR shielding properties were lower than that of the non-annealed samples.

Nanocrystalline CsxWO3 particles: Effects of N2 annealing on microstructure and near-infrared shielding characteristics

In order to further improve the near-infrared shielding properties of cesium tungsten bronze (CsxWO3) for solar filter applications, CsxWO3 particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of CsxWO3 were investigated. The obtained CsxWO3 samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like CsxWO3 particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600°C. The near-infrared shielding properties of CsxWO3 particles could be further improved by N2 annealing at 500–700°C. Particularly, the 500°C-annealed CsxWO3 samples in the N2 atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500°C-annealed CsxWO3 samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies.

Effects of Annealing in Different Atmosphere on the Near-Infrared Shielding Properties of Cs&lt;sub&gt;x&lt;/sub&gt;WO&lt;sub&gt;3&lt;/sub&gt; Particles

Using sodium tungstate and cesium carbonate as raw materials, cesium tungsten bronze (CsxWO3) powders were synthesized by low temperature hydrothermal reaction with citric acid as the reducing agent. Effects of annealing in different atmosphere on the near-infrared shielding properties of CsxWO3 were investigated. The microstructure of CsxWO3 powders was characterized by X-ray diffraction. The CsxWO3 films were prepared on glass using polyvinyl alcohol solution as film-forming agent, and the optical transmission properties of CsxWO3 films were investigated. The results indicate that the near-infrared shielding ability of samples after annealed at 200°C in the air atmosphere did not deteriorate apparently, but the 400°C-annealed samples in the air atmosphere showed apparent decrease of near-infrared shielding properties. Annealing in the carbon powder atmosphere had no apparent effects on the properties of CsxWO3 particles. As for the N2 annealing, the 500°C-annealed samples showed best improved near-infrared shielding as well as high transparency in the visible light region.

Hydrothermal Synthesis of Cesium Tungsten Bronze and its Heat Insulation Properties

Using sodium tungstate and cesium carbonate as raw materials, cesium tungsten bronze (CsxWO3) powders were synthesized by low temperature hydrothermal reaction with citric acid as the reducing agent. The CsxWO3 films were prepared on glass using polyvinyl alcohol solution as dispersing agent. The microstructure and morphology of CsxWO3 powders were characterized by XRD and SEM, and the optical spectra and heat insulation properties of CsxWO3 powder and films were investigated. The results indicate that the synthesized cesium tungsten bronze powders have hexagonal Cs0.32WO3 crystal structure. The as-prepared CsxWO3 powder and films show strong near-infrared absorption and near-infrared shielding properties. Furthermore, the near-infrared shielding performance of glass coated with CsxWO3 film has been further improved after UV irradiation. Especially, the glasses coated with CsxWO3 films which was synthesized from the non-ethanol precursor solution exhibit most outstanding near-infrared shielding performance and best heat insulation effect. In comparison with the blank glass without CsxWO3 film, the heat insulation temperature difference can achieve 24.8°C.

Preparation and characterization of poly(styrene butylacrylate) latex/nano‐ZnO nanocomposites

AbstractPoly(styrene butylacrylate) latex/nano‐ZnO composites were prepared by blending poly(styrene butylacrylate) latex with a water slurry of nano‐ZnO particles, and the effects of certain parameters, such as particle size, dispersant type, dispersing time and others, on the dispersibility, mechanical properties, ultraviolet (UV) shielding and near infrared (NIR) shielding were investigated with transmission electron microscopy (TEM), an Instron testing machine, dynamic mechanical analysis and ultraviolet‐visible‐near infrared (UV‐VIS‐NIR) spectrophotometry. TEM observation showed that dispersants with long chains are better than those with short chains at enhancing the dispersibility of nano‐ZnO particles in a matrix; extending dispersing time also improves the dispersibility of nano‐ZnO particles in a matrix. Instron tests showed that the nanocomposite polymers embedded with nano‐ZnO particles had much higher tensile strength than the corresponding composite polymers with micro‐ZnO particles. As the nano‐ZnO content increased, the temperature of glass transition (Tg) of the nanocomposite polymer embedded with 60 nm ZnO particles first increased then decreased, but 100 nm ZnO and micro‐ZnO particles seemed to have no influence on the Tg of the composite polymers. The better dispersibility of nano‐ZnO particles resulted in higher Tg values. Increasing nano‐ZnO content or dispersibility could enhance the UV shielding properties of the nanocomposite polymers, and 60 nm ZnO particles could more effectively shield UV rays than 100 nm ZnO particles. Micro‐ZnO particles basically had no effect on the UV absorbance of the composite polymers. A blue‐shift phenomenon was observed at 365 nm when nano‐ZnO particles were present in the nanocomposite polymers. NIR analysis indicated that as nano‐ZnO content increased, the NIR shielding of the nanocomposite polymers increased, but the NIR shielding properties seemed to be more influenced by particle size than by the nano‐effect. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1923–1931, 2003