This paper experimentally investigates the compressive and flexural strengths of cement-based grouting materials used in grouted sleeve connections at both room temperature and after exposure to high temperatures. The tests were conducted at three different temperatures (200°C, 400°C, and 600°C) using two cooling methods (natural-cooled and water-cooled), and various durations of constant temperature and dwell times after high-temperature exposure were considered. The mechanical properties of the grout after high temperature were comparatively analyzed, and the changes in the microstructure were observed and analyzed using a scanning electron microscope. The experimental results demonstrate a linear decrease in the dynamic elastic modulus as the temperature rises. Moreover, the sample tested at 200°C exhibits an upward trend in its mechanical properties due to the development of stable phases of calcium silicate hydrate (C-S-H) and the additional effects of secondary hydration. However, beyond 400°C, a substantial decomposition of C-S-H occurs, leading to severe internal structural damage and a sharp decline in mechanical performance.Furthermore, the cooling method employed also influences the mechanical properties of the grouting material after exposure to high temperatures. The sample cooled by water displays a slight increase (up to 10%) in the dynamic elastic modulus, attributed to the secondary hydration of surface hydration products, compared to the naturally cooled sample. Nevertheless, the water-cooled sample experiences an uneven temperature distribution caused by the temperature disparity between its interior and exterior, exacerbating internal damage. As a result, their flexural strength and compressive strength exhibited varying degrees of decline, up to 43.9% and 27.9%, respectively, compared to natural-cooled specimens. Microscopic observations revealed that exposure to high temperature induced significant physical and chemical changes in the cement-based grouting materials, which were closely correlated with their macro mechanical properties. Based on the experimental study, a calculation formula for the discount coefficient of flexural and compressive strengths of the cement-based grouting materials after exposure to high temperatures was established through data analysis. The computational results demonstrated good agreement with the experimental findings. Finally this study provides reliable and valuable test data for investigating the bonding properties between reinforcement and grouting materials in grouted sleeve connections.
Abstract The adaptive control of sunlight through photochromic smart windows could have a huge impact on the energy efficiency and daylight comfort in buildings. However, the fabrication of inorganic nanoparticle and polymer composite photochromic films with a high contrast ratio and high transparency/low haze remains a challenge. Here, a solution method is presented for the in situ growth of copper‐doped tungsten trioxide nanoparticles in polymethyl methacrylate, which allows a low‐cost preparation of photochromic films with a high luminous transparency (luminous transmittance T lum = 91%) and scalability (30 × 350 cm 2 ). High modulation of visible light (Δ T lum = 73%) and solar heat (modulation of solar transmittance Δ T sol = 73%, modulation of solar heat gain coefficient ΔSHGC = 0.5) of the film improves the indoor daylight comfort and energy efficiency. Simulation results show that low‐e windows with the photochromic film applied can greatly enhance the energy efficiency and daylight comfort. This photochromic film presents an attractive strategy for achieving more energy‐efficient buildings and carbon neutrality to combat global climate change.
Wrinkling phenomena has attracted wide attention owing to its applications in anticounterfeiting patterns, smart windows, flexible devices, and sensors, and the dynamic morphological transformations of wrinkle structure extend the application in dynamic displays, patterning, and surface wetting. However, developing simple and effective wrinkle morphology transformation strategies to design smart windows with good repeatability and stable properties presents ongoing challenges. In this paper, morphology transition of the wrinkle structure is presented to develop potential applications in smart window and pattern fabrication. At first, a nanoscale wrinkled structure was fabricated by immersing an ionic liquid mixed solution with poly(vinylidene fluoride)-hexafluoropropylene over a colloidal assembly based on the mismatch modulus between the surface layer and the interior during solvent evaporation. The wrinkle structure can be erased to form a pattern by inkjet printing based on the ink-induced dispersion of the ionic liquid. Interestingly, the wrinkled and erased structures have completely opposite optical reversible responsiveness to humidity changes, which forms the basis of a smart window. This wrinkled structure shows promising applications in anticounterfeit patterning, smart windows, and antiglare materials, which provides guidelines for the development of wrinkled-based optic materials and devices.
Abstract Azobenzene‐mesogen photo‐actuator is frequently utilized in diverse bionic motions due to their unparalleled advantages of wireless and reversible actuation. The realm of jumping behavior remains unexplored for azobenzene‐based actuators. Inspired by the Click‐beetles, here a Janus light‐driven jumping robot is achieved through the integration effect of an azobenzene molecule (with a short thermal relaxation time) and a splay alignment. The prepared Azobenzene liquid crystal films exhibit remarkable light‐driven continuous jumping capabilities, with jumping heights of 35 body lengths (BL) and takeoff speeds of 0.67 m s −1 (670 BL s −1 ), these data currently surpass the performance of small‐mass jumping robots. This research will be helpful for the design of novel actuators and broaden of the application scenarios of azobenzene actuators.
Abstract The emergence of smart windows has been a pivotal innovation in the field of energy efficiency and carbon emission reduction, sparking considerable interest worldwide. This review consolidates the latest research developments in inorganic‐based photochromic materials for smart windows applications, encompassing the design of device architectures, and their implementation in enhancing energy conservation, augmenting comfort levels, and optimizing indoor environmental control. Finally, this review culminates in an insightful analysis of the challenges and constraints in the existing research landscapes, which illuminates guidance for the directions and perspectives of future research.
Abstract Photochromic smart windows have drawn increasing attention as an approach to improve building energy efficiency and enhance indoor daylight comfort. However, existing photochromic smart windows still block sunlight from entering the room on sunny winter days, causing additional energy consumption for heating. Herein, a dual‐mode smart window is designed with decoupled photo and thermal functions by combining colorless Fe‐doped WO 3 photochromic film with window rotation. Based on this, selective heating and cooling of the room between winter and summer is achieved while maintaining the daylight comfort benefits during all seasons. As a proof of concept, the smart window reduces the temperature of a model house by up to 7.9 °C in summer mode, while in winter mode the temperature is only reduced by 0.7 °C. The proposed seasonally adaptive dual‐mode smart window obtains by window rotation overcomes the limitations of conventional photochromic smart windows, which not only achieves better energy efficiency but also retains improved daylight comfort. Furthermore, it demonstrates that the heat absorbed by the smart window can be harnessed to produce electricity through the integration of thermoelectric modules within the glazing, which enhances its impact on reducing energy consumption.
Photochromic or thermochromic liquid crystal (LC) smart windows have attracted wide attention due to their spontaneous transmittance modulation under different environments. There remains a challenge for the LC smart windows that can be modulated with light and temperature simultaneously owing to the difficulty in selecting photothermal molecules. Herein, we selected a photothermal molecule, isobutyl-substituted diimmonium borate (IDI), which shows excellent characteristics of a photothermal material used in smart windows, such as transparency in the visible light range with a slight brown color, good compatibility with the LC system, and excellent photothermal effect compared with common photothermal materials. Thus, a photothermal dual-driven smart window is developed by doping IDI into chiral LC mixtures, which can efficiently modulate the transmittance at different temperatures (or light intensities) by varying the phase state from the homeotropically oriented smectic phase (transparent) to the focal conic cholesteric phase (opaque). The transmittance is high (70%) when the ambient temperature is low and the light intensity is weak, allowing more sunlight to enter the room. The transmittance is low (20%) when the ambient temperature is high and the light intensity is strong, which prevents sunlight from entering the room. The proposed smart window will have a promising application in terms of energy saving and personalized privacy protection.
Butterfly coloration originated from the finely structured scales grown on the underlying wing cuticle. Most researchers who study butterfly scales are focused on the static optic properties of cover scales, with few works referring to dynamic optical properties of the scales. Here, the dynamic coloration effect of the multi-scales was studied based on the measurements of varying-angle reflection and the characterization of scale flexibility in two species of lycaenid, Plebejus argyrognomon with violet wings and Polyommatus erotides with blue wings. We explored the angle- dependent color changeability and the color-mediating efficiency of wing scales. It was found that the three main kinds of flexible scales (such as cover, ground and androconia situated under the ground scales) were considerably bent during wing rotation, which caused the color change effect. The three layers of composite scales broaden the light signal when compared to the single scale, which is of great significance to the recognition of insects. The androconia scales strongly contribute to the overall wing colouration. These findings are expected to explain the coloration change in flapping wings and to provide new inspirations for the fabrication of biomimetic flexible photonic materials.
The wettability of fiber membranes is very important in sewage treatment. This paper presents an interesting solvent-induced programable wettability/transparency transition of electrospun colloidal fibers from superhydrophilic to hydrophobic/highly hydrophobic depending on different solvent properties. There appeared three wettability transitions (from superhydrophilic to hydrophobic and then to hydrophilic and hydrophobic) during the solvent treatment process, accompanied by a program change of transparency from opaque to transparent and then to opaque states. This change can be attributed to the combined change in the surface chemical composition and the surface morphology during the solvent immersion process. These specific changes are due to the distinct dissolution effects of solvents toward poly(vinyl alcohol) (PVA) and poly(styrene–methyl methacrylate–acrylic acid) [P(St-MMA-AA)] latex, resulting in partial melting out of the hydrophobic latex particles, a residue of latex particles on the fiber surface, and a dynamic change of the intra-/intermolecular hydrogen bonding of the PVA surface, as could be confirmed from Fourier transform infrared and X-ray photoelectron spectroscopy data. The as-prepared porous fiber presents applications in oil absorption and catching plastic particles. This work is of significance for the development of advanced function porous fibers.
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