Search Results (226)

The reaction of the bulky ligand 1,2-bis-(di-tert-butylphosphinomethyl)benzene, 1 with [Ni(DME)Cl₂], 3, DME = 1,2-dimethoxyethane, at room temperature over extended periods, affords the new blue Zwitterionic complex [2-(C₆H₄-CH₂P(H)^tBu₂-1-(CH₂P^tBu₂NiCl₃)], 4, which contains a phosphonium group and an anionic nickel trichloride. This complex decomposes in alcohols such as methanol and the solution turns yellow. A discussion of the possible mechanism leading to the observed product is presented. Key to this is identification of the source of the phosphonium proton, which we speculated to arise from trace water in the initial nickel complex. To prove that trace water was present in [Ni(DME)Cl₂], a sample of this precursor was reacted under similar condition with anhydrous DMF alone. In addition to the known complex [Ni(DMF)₆)]²⁺[NiCl₄]²⁻, 5, we identified the trans-diaqua complex [Ni(Cl)₂(H₂O)₂(DMF)₂], 6, which proved the presence of trace water. Interestingly in dimethylformamide, [2-(C₆H₄-CH₂P(H)^tBu₂-1-(CH₂P^tBu₂NiCl₃)] exhibits thermochromic properties: an solution that is pale blue at ambient temperature reversibly changes colour to yellow upon cooling. This behaviour is specific to DMF and is related to the solvato-chromic behaviour exhibited by related DMF–nickel complexes. A discussion of the NMR spectra of compound 4 in a range of solvents is presented. The structures of the previously prepared molybdenum complex, [1,2-(C₆H₄-CH₂P^tBu₂)₂Mo(CO)₄] and the bis-(phosphine sulphide) of the ligand, [1,2-(C₆H₄-H₂P(S)^tBu₂)₂], 5, are described for structural comparative purposes. Full article

Nanocomposites, which combine various nanomaterials, offer immense potential in the design of advanced materials for energy-related applications. These materials, engineered at the nanoscale, exhibit enhanced properties compared to their bulk counterparts, such as improved electrical conductivity, mechanical strength, and thermal stability. Nanocomposites have emerged as promising candidates for use in energy storage systems, including batteries and supercapacitors, by improving energy density, cycle life, and charge–discharge rates. In renewable energy technologies such as fuel cells, nanocomposites play a crucial role in enhancing efficiency and stability, which are vital for reducing costs and promoting the adoption of clean energy solutions. The unique properties of nanocomposites, such as high surface area and tunable composition, allow for the integration of multiple functionalities, making them ideal for multifunctional catalysts in energy conversion and environmental remediation. Additionally, nanocomposites enable the development of energy harvesting systems with improved performance and durability. These materials can be tailored by adjusting the composition of the nanomaterials, opening new opportunities for energy applications. The increasing research into nanocomposites continues to drive innovation in energy-related technologies, positioning them as a key enabler for sustainable energy solutions and future advancements in renewable energy systems. Full article

To meet the growing demand for intelligent surfaces in furniture and interior design, this study developed thermochromic UV coatings for bleached poplar. While conventional UV coatings are valued for their ecofriendliness and rapid curing, their functionality remains limited; integrating thermochromic capability offers a highly promising solution. We examined how the combination of two microcapsule systems (UF@TS and UF@TS-R) influenced the performance of UV coatings on bleached poplar by applying a two-primer/two-topcoat protocol with varied microcapsule loadings to impart color-changing behavior. The effects were then analyzed from multiple perspectives—type, application layer, and concentration gradient—covering optical and mechanical properties as well as thermochromic response. Results indicated that the optimum performance was achieved when UF@TS was incorporated into the UV topcoat and UF@TS-R into the UV primer at specific mass concentrations. The resulting coating delivered temperature-responsive color variation, providing both theoretical and technical support for developing high-value-added UV finishes for wooden furniture and advancing the use of fast-growing timber in high-end applications. Full article

In this study, poplar boards were bleached and treated with two types of urea–formaldehyde-coated ternary system thermochromic microcapsules (UF@TS), which were mixed with UV primer. The bleached poplar boards were manually painted with two layers of primer and topcoat. Coating samples with varying microcapsule contents were prepared and evaluated based on factors such as glossiness, reflectivity, and other surface properties. The experimental results showed that bleaching treatment significantly increased the whiteness of poplar wood, with an improvement rate of up to 17%. Among the two microcapsule types, the coating containing #2 microcapsules exhibited superior surface quality compared to #1 microcapsules. As the microcapsule content increased, the coating glossiness showed an overall decreasing trend and a certain degree of fluctuation, and the #2 microcapsule showed lower reflectivity values. The addition of UF@TS microcapsules negatively affected the coating adhesion but had little effect on hardness. The #2 microcapsule enhanced the impact resistance of the coating to a certain extent and increased surface roughness. Regarding thermochromic performance, the #1 microcapsule exhibited higher color-changing temperature and larger color difference, while the #2 microcapsule showed color-changing temperature closer to room temperature. Despite a decline in thermochromic performance and glossiness during aging, the 1# microcapsule showed slightly better stability. The coating containing 10% #2 microcapsules demonstrated the best comprehensive performance on bleached poplar wood, with glossiness of 2.1 GU, reflectivity of 67.95%, adhesion grade of 1, hardness of 6 H, impact resistance grade of 4, and surface roughness of 0.681 μm. The ΔE in the range of −20 °C to 50 °C was 7.434. After aging, ΔE was 5.846, and the light loss rate was 9%, with excellent comprehensive performance. Full article

A thermochromic cholesteric liquid crystal (CLC) mixture was prepared using epoxies. The structural color of the CLCN film was tuned by changing the concentration of a chiral dopant and the polymerization temperature. It was found the yellow CLCN film can be used as a sensor for the discrimination of methanol and ethanol which was proposed to be driven by the difference between the solubility parameters. Moreover, a colorful pattern was prepared based on the thermochromic property of the CLC mixture, which could be applied for decoration and as a sensor for chloroform. Full article

Vanadium dioxide (VO₂) is a phase-change material of great importance due to its thermochromic properties, which make it a potential candidate for energy-saving applications. In this work, a comparative study between VO₂ thermochromic films prepared from powders synthesized by either a lab-scale hydrothermal autoclave or a large-scale hydrothermal reactor is presented. In both cases, the as-obtained material, after the hydrothermal step, was subsequently annealed at 700 °C under a nitrogen atmosphere, in order to obtain the monoclinic VO₂(M) thermochromic phase. The VO₂ powder prepared in the large-scale hydrothermal reactor exhibited a critical transition temperature of 54 °C with a hysteresis width of 9 °C, while for the one prepared in the lab-scale autoclave, the respective values were 62 °C and 5 °C. Despite these differences, the prepared films showed similar thermochromic performance with the lab-scale material displaying a 17% IR (InfraRed), switching at 2000 nm upon heating, and a transmittance solar modulation of 11%, compared to 17% and 9%, respectively, for the large-scale material. Moreover, both films appeared to have similar luminous transmittance of 44% and 46%, respectively, at room temperature (25 °C). These results showcase the potential for scaling up the hydrothermal synthesis of VO₂, resulting in films with similar thermochromic performance to those from lab-scale fabrication. Full article

Tungsten-doped vanadium dioxide (W-VO₂) shows semiconductor-to-metal phase transition properties at room temperature, which is an ideal thermo-chromic smart window material. However, low visual transmittance and solar modulation limit its application in building energy saving. In this paper, a W-VO_2−x@AA core-shell nanoparticle is proposed to improve the thermo-chromic performance of W-VO₂. Oxygen vacancies were used to promote the connection of W-VO_2−x nanoparticles with L-ascorbic acid (AA) molecules. Oxygen vacancies were tuned in W-VO₂ nanoparticles by thermal annealing temperatures in vacuum, and W-VO_2−x@AA nanoparticles were synthesized by the hydrothermal method. A smart window was formed by dispersing W-VO_2−x@AA core-shell nanoparticles into PVP evenly and spin-coating them on the surface of glass. The visual transmittance of this smart window reaches up to 67%, and the solar modulation reaches up to 12.1%. This enhanced thermo-chromic performance is related to the electron density enhanced by the AA surface molecular coordination effect through W dopant and oxygen vacancies. This work provides a new strategy to enhance the thermo-chromic performance of W-VO₂ and its application in the building energy-saving field. Full article

To improve the convective heat transfer in internal cooling channels of heavy-duty gas turbine blades, this study experimentally and numerically investigates the thermal performance of rectangular channels with hybrid pin-fins and micro V-ribs turbulators. The transient thermochromic liquid crystal (TLC) technique and ANSYS 2019 R3 (ICEM CFD 2019 R3, Fluent 2019 R3, CFD-Post 2019 R3) were employed under Reynolds numbers ranging from 10,000 to 50,000, with the numerical model rigorously validated against experimental data (the maximum RMSE is 2.5%). It is found that hybrid pin-fins and continuous V-ribs configuration exhibits the maximum heat transfer enhancement of 27.6%, with an average friction factor increase of 13.3% and 21.9% improvement in thermal performance factor (TPF) compared to the baseline pin-fin channel. In addition, compared to the baseline pin-fin channel, hybrid pin-fins and broken V-ribs configuration exhibits average heat transfer enhancement (Nu/Nu0) of 24.4%, an average friction factor increase of 7.2% and 22.5% improvement across the investigated Reynolds number range (10,000~50,000) based on computational results. The synergistic effects of hybrid pin-fin and micro V-rib structures demonstrate superior coolant flow control, offering a promising solution for next-generation turbine blade cooling designs. This work provides actionable insights for high-efficiency gas turbine thermal management. Full article

Thermochromic materials have attracted interest in textile applications, particularly in printing and dyeing processes. However, their thermochromic properties and impact on fabric comfort remain underexplored. This study aimed to investigate the thermochromic properties of printed fabrics with green-to-brown transitions and evaluates their comfort attributes. In the present study, a thermochromic dye paste was applied to nylon/cotton medium-weight fabric via screen printing process. The brown pigment paste was applied first, followed by the thermochromic olive green dye. The printed fabrics were tested for thermochromism, morphology, Fourier Transform Infrared Spectroscopy (FTIR), and comfort properties. Comfort properties were assessed via air permeability, water vapour permeability, and moisture management tests. The results show reversible colour changes from green (25 °C) to brown (40 °C), with increasing lightness (L*) and shifting green–red coordinates (−a*). The scanning electron microscopy (SEM) confirmed uniform dye dispersion, and the FTIR validated the presence of thermochromic pigments. The printed fabrics showed a reduction in air permeability from 40.2 mm/s to 0 mm/s, while water vapour permeability decreased by 62.50% compared to the pristine fabric due to the coating layers. The overall moisture management properties of the printed fabric remained similar to those of the unprinted fabric, with a grade of 1. These findings highlight the potential of thermochromic textiles for adaptive camouflage, particularly in military uniforms, contributing to the advancement of intelligent textiles with enhanced thermal responsiveness. Full article

Cholesteric liquid crystal polymer network (CLCN) films with composite structural colors have potential applications in decoration and anti-counterfeiting. Herein, a thermochromic acrylate-based cholesteric liquid crystal mixture was prepared. The structural color of CLCN films can be controlled by the photopolymerization temperature. Based on the oxygen inhibition of the acrylate group, CLCN films with double reflection bands were prepared using a two-step photopolymerization method. The distance between these two reflection bands was controlled by the polymerization temperatures of these two steps. Since golden colors are the most attractive for decoration, herein, colorful patterns with a golden structural color were prepared by controlling the polymerization temperatures. Full article

Food contact polymers require thermochromic pigments to provide temperature-sensitive visual cues for consumer safety and product integrity. However, their susceptibility to ultraviolet (UV) degradation limits long-term application. This study investigates the UV resistance of food-grade thermochromic polypropylene blends under simulated indoor and outdoor UV exposure for 500 and 1000 h. Visual properties, colorimetric (CIE L*a*b*) measurements, mechanical testing (tensile and impact), and mass variation analysis were performed to assess photostability and material integrity. Exposure to UV led to progressive discoloration (ΔE*_ab up to 34.07) and significant mechanical deterioration. Tensile strain at break decreased by 48.67%, and notched impact strength dropped by 44.15% after 1000 h of UV exposure. No measurable mass loss occurred, indicating degradation was confined to surface-level oxidation rather than bulk material erosion or leaching. These findings highlight the need for optimal pigment loading and UV stabilization to extend the shelf life of thermochromic food packaging materials in light-exposed storage and retail environments. The study offers a framework for improving the long-term reliability of smart packaging in the food industry. This work uniquely integrates optical, mechanical, and mass loss analyses to evaluate thermochromic packaging degradation under extended UVA exposure. Full article

The transition toward sustainable construction practices has intensified the demand for intelligent and energy-efficient building components, particularly smart window technologies. While numerous innovations exist, the selection of the most optimal smart window solution is difficult due to the trade-offs among conflicting criteria such as energy performance, economic feasibility, environmental impact, and user comfort. This study proposes an integrated Fuzzy Multi-Criteria Decision-Making (FMCDM) framework for selecting smart window technologies. The methodology combines the Fuzzy Analytic Hierarchy Process (FAHP) to determine criterion weights and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to rank alternatives. Nine sustainability-related criteria across the environmental, economic, and social dimensions were evaluated using expert input. The results identify thermochromic smart windows as the optimal choice. This research contributes a structured, adaptable, and scalable FMCDM framework for sustainable technology selection, with broader applicability to green product design and decision-making in the construction and energy sectors. Full article

The adhesion of printing inks to printing substrates is a complex process influenced by both the physical and chemical properties of the printing substrate and of the printing ink. Synthetic paper, being a polymer with no absorption capability, limits the interaction between the ink and substrate, leading to lower adhesion values. On synthetic paper, the thicker polymer resin layer covering the microcapsules results in a more stable ink film and lighter print coloration. In contrast, UV-curable ink applied to bulky and recycled papers, which have porous structures, exhibits more dynamic interactions. The polymer resin in the ink penetrates the paper’s pores, forming a stronger bond with the paper fibers and improving adhesion quality. Surface roughness also plays a significant role in ink adhesion. Rough surfaces increase contact between ink and paper, enhancing mechanical adhesion by allowing the ink to “lock” into the surface’s irregularities. The surface energy (SFE) at the interphase between paper and ink is also a key factor. Low SFE promotes better wetting and ink absorption, improving adhesion. Ink penetration into the printing substrate is crucial for achieving high-quality adhesion. Full article

The use of thermochromic pigments in food packaging offers several advantages, including improved food safety, waste reduction, and temperature change monitoring. However, little is known about how chemically resilient these materials are, especially regarding optical stability, thermochromic activation, and mechanical integrity following exposure to acidic, alkaline, oil-based, and neutral food-contact environments. This study evaluates the chemical resistance, thermal cycling effects, and mechanical durability of thermochromic pigment–polymer blends. Thermochromic polymer samples were subjected to multiple chemical environments, repeated thermal cycling, and mechanical analysis to assess degradation behavior. The findings show that virgin food-grade polymer with no thermochromic pigment sustains its performance stability throughout chemical exposure with little degradation. However, thermochromic polymer blends experienced reduced thermochromic functionality. This study offers insight into how well thermochromic pigment can be incorporated into intelligent food packaging despite the limitations associated with chemical exposure. Full article

This study focused on developing a color-changing fabric face mask for fever detection. Reversible Thermochromic Leuco dye (RTL) was applied as an indicator to alert wearers of elevated body temperatures, with the color change occurring at 37.5 °C. Five fabric types Polyethylene (PE), cotton (CO), a cotton–polyester blend (TC), polyester (PL), and Polyamide (PA) were coated with blue RTL to evaluate their color change responsiveness. The results showed that fabrics with higher thermal conductivity (λ), thermal absorptivity (b), and heat flow (q) exhibited faster color transitions. RTL-coated PE fabric demonstrated the best performance, with a thermal absorptivity of 312.8 Ws^0.5m⁻²K⁻¹ and a heat flow of 2.11 Wm⁻², leading to a rapid color-change time of approximately 4.20 s. Although PE fabric had a lower thermal conductivity (57.6 × 10⁻³ Wm⁻¹K⁻¹) compared to PA fabric 84.56 (10⁻³ Wm⁻¹K⁻¹), the highest thickness 0.65 mm of PA fabric slowed its color-change reaction to 11.8 s. When selecting fabrics for optimal heat transfer, relying solely on fiber type or thermal conductivity (λ) is insufficient. The fabric’s structural properties, particularly thickness, significantly impact thermal resistance (γ). Experimental results suggest that thermal absorptivity and heat flow are more effective criteria for fabric selection, as they directly correlate with color-change performance. Full article