Low Thermal Coefficient Research Articles

Aluminium-SiC-B4C Hybrid Composites- An Overview on the Mechanical Properties

Abstract: Modern growth necessitates the use of modern engineering materials for a variety of engineering applications, and demand for these materials is continually rising. Metal matrix composite is a dependable supply of the material that has been shown to be advantageous in every part of advancement for meeting such demands.With composites, materials are blended in a way that allows us to maximize the benefits of their parent material while somewhat reducing the consequences of any shortcomings. The word "Composites" simply refers to materials that have been combined to increase their qualities.Due to their low density and good mechanical properties, improved corrosion resistance and wear, and low thermal coefficient of expansion when compared to conventional metals and alloys, aluminium composites, among the available composite materials, are in higher demand and are therefore frequently used in the aerospace and automotive industries. However, the properties of the materials can he further enhanced with addition of the reinforcement materials like SiC, Al2O3 and B4C. Hence in the present investigation an attempt is made to process a composite material with a combination of SiC and B4C as reinforcement materials followed by the evaluation of the mechanical properties. The results of the study indicate a progressive strength in the processed materials.

Sustainable Transformation of Cellulose-Containing Textile Waste into Multifunctional Panels with Tailored FR-Lignocellulosic Fibres.

The fashion industry significantly impacts the environment, mainly through the substantial generation of waste textiles fostered by fast fashion business models. This study introduces an innovative approach to textile waste management by recycling waste textiles without the use of chemical or mechanical treatments. Herein, we developed a method adhering to the principles of circular economy to transform these textile wastes into high-quality construction panels using a papermaking process. This method not only provides a sustainable solution to reduce landfill dependency but also enhances resource efficiency in the construction industry. The fabricated panels, composed of a blend of 45% textile waste microfibres and 55% fire-retardant fibres, exhibit several advantageous properties. They feature a low apparent density ranging between 170-180 kg/m3 and a low thermal conductivity coefficient of 0.047 W/m∗K at 50 kPa. It revealed that phosphorylated fibres not only provide flame-retardant properties, but they also significantly improve the mechanical properties of the panels. For example, load at break increases from 12.4 to 81.1 N, stress at break from 0.44 to 3.59 MPa, and E-modulus from 29.2 to 198.8 MPa after the addition of these 55% fibres. Moreover, these panels successfully met the criteria set by international standards for construction products satisfying the fire test, EN ISO 11925-2. These characteristics make the panels superior options for sustainable construction materials, offering enhanced fire resistance and insulation properties, which are critical to meet modern building standards. They mark a pivotal step towards sustainable construction and waste reduction in the fashion industry.

Enhanced Thermal Conductivity of Thermoplastic Polyimide Nanocomposites: Effect of Using Hexagonal Nanoparticles.

Thermoplastic polyimides have garnered significant interest in the electronic and electrical industries owing to their performance characteristics. However, their relatively low thermal conductivity coefficients pose a challenge. To address this issue, this study focused on the properties of nanocomposites comprising two thermoplastic semicrystalline polyimides R-BAPB and BPDA-P3, one amorphous polyimide ULTEMTM, and hexagonal nanoparticles. Polyimide R-BAPB was synthesized based on 1,3-bis-(3',4-dicarboxyphenoxy)benzene (dianhydride R) and 4,4'-bis-(4'-aminophenoxy)biphenyl (BAPB diamine); polyimide BPDA-P3 was synthesized based on 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and diamine 1,4-bis[4-(4-aminophenoxy)phenoxy]benzene (P3); and amorphous polyimide ULTEMTM was commercially produced by Sabic Innovative Plastics. Using microsecond-scale all-atom molecular dynamics simulations, the effects of incorporating hexagonal nanoparticles with enhanced thermal conductivity, such as graphene, graphene oxide, and boron nitride, on the structural and thermophysical characteristics of these materials were examined. The formation of stacked aggregates was found for graphene and hexagonal boron nitride nanoparticles. It was observed that graphene oxide nanoparticles exhibited a dispersion in polyimide binders that was higher than those in graphene and hexagonal boron nitride nanoparticles, leading to reduced translational mobility of polymer chains. Consequently, the decrease in polyimide chain mobility correlated with an increase in the glass transition temperature of the nanocomposites. Aggregates of nanoparticles formed a pathway for phonon transport, resulting in improved thermal conductivity in polyimide nanocomposites. An increase in the thermal conductivity coefficient of polyimide nanocomposites was observed when the concentration of graphene, graphene oxide, and hexagonal boron nitride nanofillers increased. The enhancement in thermal conductivity was found to be strongest when graphene nanoparticles were added.

Regulating the thermophysical properties of rare earth cerates through high entropy design and substitute

Cerate ceramics are considered promising candidates for the new generation of thermal barrier coatings. However, in the middle temperature area (473–673 K), the CTE mismatch due to the thermal contraction often results in coating failure. The aim of this work is to develop an innovative component regulation method that significantly reduces the thermal conductivity and alleviates the thermal contraction. Cerates exhibit a low thermal diffusion coefficient, primarily attributed to the impact of extrinsic phonon scattering mechanisms. Our comprehensive analysis encompassed various factors such as point defects, the degree of size and mass disorder, grain interfaces, and lattice distortion. By employing high entropy design and doping strategies, we have successfully alleviated the thermal contraction phenomenon in cerates, while maintaining their high CTE. Furthermore, an in-depth investigation of the valence states of elements and lattice energy was conducted to elucidate the thermal contraction mechanism of cerates in the middle temperature area.

Microstructural, thermal characterization and CMAS corrosion resistance of novel quaternary (Y0,25Er0,25Tm0,25Yb0,25)2Si2O7 high entropy disilicate material

A novel (Y0,25Er0,25Tm0,25Yb0,25)2Si2O7 high entropy disilicate quaternary composition was synthesized from commercial oxide powders using ball milling and sintering processes as a candidate material for environmental barrier coatings (EBC). As-synthesized high entropy disilicate powders were sintered at different durations (12, 18, and 24 h) at 1600 °C in a muffle furnace before characterization. The XRD and SEM analyses revealed the single-phase monoclinic structure (β-type) with homogeneous elemental distribution for the sintered samples. The (Y0,25Er0,25Tm0,25Yb0,25)2Si2O7 samples exhibited low thermal diffusivity coefficient, low thermal conductivity, a close coefficient of thermal expansion (CTE) to SiC and a high temperature stability. The (Y0,25Er0,25Tm0,25Yb0,25)2Si2O7 samples were subjected to CMAS corrosion tests at 1300 °C with different durations (2, 12, and 24 h) to evaluate CMAS corrosion resistance. Additionally, Yb2Si2O7 samples were prepared and subjected to molten CMAS in the same way for comparison. Based on the results, the CMAS corrosion resistance was improved with (Y0,25Er0,25Tm0,25Yb0,25)2Si2O7 composition.

Sustainable chitosan derived 3D hierarchically porous carbon aerogel toward advanced infrared-radar compatibility

Simultaneously achieving infrared-radar compatibility in one material is an important challenge for multi-spectral compatible stealth technology. Chitosan-derived three-dimensional (3D) hierarchically porous carbon aerogel can effectively solve the problem. Inspired by floors-pillars concept, this work elaborately designed and successfully fabricated 3D skeletons consisted of two-dimensional (2D) sheets and one-dimensional (1D) struts. Benefiting from esterification and directional freeze drying method, the entire network could provide sufficient space for reducing thermal conductivity and motivating dipole polarization sites. Thanks to the facile calcination process, conductive components could be obtained, which guarantee low infrared (IR) emissivity and high conduction loss performance. In this work, the as-prepared carbon aerogel with ultra-low density of 0.005 g cm−3 exhibits superb infrared stealth property. It shows a low thermal conductivity coefficient of only 0.0933 W m−1 K−1. In addition, the heating rate of the upper surface is slow when placed on a heating platform of 60 °C. The relevant IR emissivity value is as low as 0.563 in 3–5 μm band and 0.432 in 8–14 μm band. Under relatively thin thicknesses, the prominent radar stealth performance including the optimum reflection loss value of −75.90 dB, the maximum effective bandwidth of 3.93 GHz, and the simulated radar cross section reduction value of 27.66 dB m2, can be obtained. This study not only introduces innovative design ideas but also offers technical approaches, facilitating further development in the realm of infrared-radar compatible stealth.

Low shrinkage polyimide aerogel cross-linked with amino-functionalized hollow glass microbeads for thermal and acoustic insulation

As a nanoporous material, polyimide (PI) aerogels have excellent thermal and acoustic properties. However, their high air flow resistance is detrimental to the development of their acoustic properties. To enhance the thermal and acoustic insulation properties of PI aerogels, we have selected hollow glass microbeads (HGM) with a low thermal conductivity coefficient to be combined with the PI aerogel, leading to the fabrication of PI/HGM aerogel composite materials. In this study, there are two preprocessing methods for HGM: untreated and aminized (HGM-NH2). These were then individually combined with PI aerogel to fabricate two distinct PI/HGM composite aerogels: a physically blended variant (PIHGM) and a chemically bonded one (PHN). The thermal insulation and acoustic properties of these two composite aerogels were compared. The results show that HGM-NH2 not only functions as a cross-linking agent but also plays a key role in forming the three-dimensional network structure, which effectively reduces the shrinkage rate and density of the composite aerogel. Moreover, the thermal conductivity of PHN reached a low of 27.92 mW m⁻1 K⁻1, which is a reduction compared to PIHGM's thermal conductivity of 29.83 mW m⁻1 K⁻1. Moreover, the PHN composite aerogel with 10% HGM addition exhibited an average sound insulation level that was 120% higher than that of PIHGM. The method of incorporating pore structures with different scales also offers valuable insights for enhancing the sound insulation performance of other materials.

Experimental investigation of pressure drop and heat transfer in porous media based on 3D printed triple periodic minimum surfaces

ABSTRACT Porous media are widely preferred for heat transfer applications because of complex structure and high porosity. It is relatively easy to produce complex structures with the additive manufacturing method. In this study, Gyroid-based triple periodic minimal surface is produced ABS (Acrylonitrile butadiene styrene) and PLA (polylactic acid) materials using 3D printers. The pressure drops and heat transfer in the porous structure with the gyroid model are investigated experimentally. Permeability and Forchheimer coefficients are determined for each gyroid porous channel. While the permeability and Forchheimer coefficient of the porous medium of PLA were calculated as 2.97 × 10−8 m2 and 0.07, respectively, the permeability and Forchheimer coefficient of the porous medium of ABS were calculated as 5.52 × 10−8 m2 and 0.09. The correlation between the Reynolds number and pressure drop per length is given. The gyroid structure-filled channel is heated by an asymmetric heat flux on the bottom side. The convection heat transfer in polymer-based porous media was investigated. Also, the correlation between the Nusselt number and the Reynolds number based on permeability is presented. While the Nusselt correlation of the PLA porous medium was obtained as N u K = 0.08 R e K 0.57 , the Nusselt correlation of the ABS porous medium was found to be N u K = 0.09 R e K 0.61 . There are improvements in heat transfer due to the flow mixing effect of the porous medium. The study aims to broaden the current knowledge of heat transfer in polymer porous structures. Especially, this study investigates heat transfer and flow in polymer-based porous structures with a low thermal conductivity coefficient produced by 3D printers.

Effect of Ferric Catalyst on Chemical Decomposition of Polyimide-Film-Surface for Enhancing Chemical–Mechanical-Planarization Polishing-Rate

In semiconductor devices, flexible displays and microelectromechanical systems (MEMS), polyimide has been utilized as a protecting layer, interlayer dielectric polymer for thin-film metallization and low-stress polymer for wafer-level packaging. Since, it has low stress, low thermal coefficient of expansion, low moisture, high modulus, good ductility, thermal stability, high glass transition temperature, and low process cost. However, the applications of polyimide required estentially chemical-mechanical-planarization (CMP) of the polyimide-film-surface. that can be challenging to enhance the polishing rate of the polyimide-film-surface because of the hard and covalently bonded nature of the polyimide-film surface.In this study, to enhance chemical dominant CMP, the chemical decomposition of the polyimide-film-surface was performed by hydrolysis reaction between ferric ions and oxygen atoms covalently bonded with pyromellitimide on the polyimide-film-surface during CMP, as shown in Fig. 1. The polyimide-film polishing rate was estimated as a function of ferric catanylst concentration in the CMP slurry;surprisingly, the polyimide film polishing rate(i.e., 1465A/min) peaked at a specific(i.e., 0.05wt%) ferric catalyst concentration, as shown in Fig. 2. This result indicates that the degree of chemical decomposition during CMP could be principally determined by ferric nitrate concentration. The details of both chemical and mechanical dominant polishing mechanisms will be presented. In addition, the evidence of the chemical composition of the polyimide-film-surface will be demonstrated, depending on the ferric catalyst concentation in the CMP slurry. Figure 1

Cascading latent heat thermal energy storage in parabolic trough solar collector as a promising solution: An experimental investigation

Solar energy system can be considered as a reliable energy source if it connects to a latent heat thermal energy storage (LHTES) system using phase change materials (PCMs). To tackle the low thermal conductivity coefficient of PCMs, the cascaded latent heat storage (CLHS) configuration is a promising solution. This study aims to illustrate the improvement of CLHS setup comparing with non-cascaded arrangement, performing a whole-scale experimental investigation. A compact parabolic trough collector (PTC) unit equipped with a LHTES module is designed and constructed for a residential purpose. Experimental results reveal that the average thermal efficiency of PTC is 73.5 %. Three paraffin waxes with melting ranges of (64–68 ℃), (57–60 ℃) and (46–48 ℃) are injected in three same series of shell-tube heat exchangers. For comparing cascaded and non-cascaded PCM performance, three experimental series, namely (Exp.1, Exp.2 and Exp.3) are performed. The experimental findings show that the deployment of the CLHS configuration improves the latent heat storage of non-CLHS-Exps.1, 2, and 3 by more than 10, 47, and 5 %, respectively. In addition, CLHS system has a potential to increase the exergy storage of non-CLHS setup by up to 27.4 %. Furthermore, impact of increasing heat transfer fluid (HTF) flow rate is examined and it is observed that the melting process is shortened by almost 39 %. Accordingly, increasing flow rate improves energy stored in PCMs1, 2, and 3 by 60 %, 59.62 %, and 72.04 %, respectively. Consequently, the latent thermal exergy storage of the PCM experiences a twofold increase. Conducting an experimental evaluation of thermal performance of the storage module integrated with PTC setup can be valuable, particularly in the realm of residential applications.

Low dielectric constant and highly intrinsic thermal conductivity fluorine‐containing epoxy resins with ordered liquid crystal structures

AbstractEpoxy resins with a high dielectric constant and low intrinsic thermal conductivity coefficient cannot meet the current application requirements of advanced electronic and electrical equipment. Therefore, novel fluorine‐containing liquid crystal epoxy compounds (TFSAEy) with fluorinated groups, biphenyl units, and flexible alkyl chains are first synthesized via amidation and esterification reactions. Then, 4,4′‐diaminodiphenylmethane (DDM) is used as a curing agent to prepare the corresponding fluorine‐containing liquid crystal epoxy resins. The obtained dielectric constant (ε) and dielectric loss (tan δ) values of TFSAEy/DDM at 1 MHz are 2.54 and 0.025, respectively, which are significantly lower than those of conventional epoxy resins (E‐51/DDM, 3.52 and 0.038). Additionally, the intrinsic thermal conductivity coefficient (λ) of TFSAEy/DDM is 0.36 W/(m·K), 71.4% higher than that of E‐51/DDM (0.21 W/(m·K)). Meanwhile, the corresponding elastic modulus, hardness, glass transition temperature, and heat resistance index of TFSAEy/DDM are 5.73 GPa, 0.35 GPa, 213.5°C, and 188.7°C, respectively, all superior to those of E‐51/DDM (3.68 GPa, 0.27 GPa, 107.2°C, and 174.8°C), presenting potential application in high‐heating electronic component packaging and printed circuit boards.

Highly efficient adiabatic and flame-retardant SiO2 aerogel and its fibrous composite for high-temperature applications within underground chambers

In the present scenario, the underground chambers of deep metal mines are plagued by excessively high temperatures, and the existing adiabatic materials have proven to be inadequate in addressing this challenge. Considering these issues, this study introduces an innovative adiabatic and flame-retardant SiO2 aerogel-based fibrous composite designed specifically for underground applications. The optimal preparation method for SiO2 aerogel preparation was identified through monomer and orthogonal experiments, ultimately achieving a low thermal conductivity coefficient of 0.028 W/(m·K). Subsequently, through integral moulding, a composite material was developed, incorporating the optimal SiO2 aerogel as a precursor along with ceramic fibres. The resulting ceramic fibre/SiO2 aerogel exhibited an increased thermal conductivity coefficient of 0.061 W/(m·K). When subjected to a high-temperature combustion source of approximately 700 °C, the temperature of the upper surface of the sample was maintained at 131.9 °C and its mass loss rate was a mere 1.2%, exhibiting strong adiabatic and flame-retardant capabilities of the composite material. Moreover, the composite material exhibited good hydrophobic, adsorbent, and mechanical properties, making it well-suited for underground chamber applications. The research conducted on SiO2 aerogel and its adiabatic ceramic fibre composite not only holds theoretical significance by guiding the development of improved adiabatic materials but also provides practical engineering solutions for mitigating heat transfer through raw rock and reducing chamber temperatures in underground mining environments.

Green recycling of waste poly(ethylene terephthalate) into Ni‐MOF nanorod for simultaneous interfacial solar evaporation and photocatalytic degradation of organic pollutants

AbstractInterfacial solar evaporation is regarded as the promising technology to mitigate freshwater scarcity. However, when polluted water is used, toxic pollutants might accumulate in the bulk water. Herein, we report the production of Ni‐MOF nanorod from waste poly(ethylene terephthalate) and fabricate bifunctional Ni‐MOF‐based evaporators. Owing to high light absorption and photothermal conversion, low thermal coefficient, and vaporization enthalpy, it shows an exciting evaporation rate (2.25 kg m−2 h−1) with good flexibility/durability, rated as one of most advanced evaporators. Density functional theory and COMSOL results show that the combination of nickel‐sites in Ni‐MOF and local heat plays a crucial role in peroxymonosulfate activation to produce reactive species. Thereby, it exhibits the high degradation activity of tetracycline. In outdoor, the freshwater production reaches 5.54 kg m−2 per day, and the tetracycline removal efficiency is 91%. This work provides a sustainable approach to produce solar evaporators capable of freshwater production and contaminant degradation.image

Construction of walnut protein/tea polyphenol/alginate complex for enhancing heat and gastrointestinal tolerance of lactic acid bacteria

The presence of live cells in the intestinal tract is crucial for the beneficial effects of probiotic products containing lactic acid bacteria. However, many bacterial cells lose viability during production, storage, and gastric passage. Protein-based hydrogels and polysaccharide-based capsules effectively enhance the viability of live probiotic cells in products, but the underlying mechanisms and in vivo effectiveness are unclear. In this study, a complex was developed by self-aggregating walnut protein, tea polyphenol, and Lactobacillus rhamnosus cells under acidic conditions, followed by alginate coating. Complex formation was facilitated by hydrogen bonding and hydrophobic interactions. The complex had a low thermal diffusion coefficient of 4.9 × 10−7 m2/s, making the bacterial cells resistant to temperature fluctuation. Cell survival rate was 75.5% after 12 h at 55 °C and 92.8% after freeze-drying. Shelf-life predictions were 14 years at 4 °C. and 2.3 months at 25 °C, with a live cell count exceeding 106 CFU/g. The product demonstrated a 60% increase in live bacterial cells compared to free cells in simulated gastric fluid, and achieved complete release in simulated intestinal fluid within 120 min. This method was successfully applied to L. rhamnosus, L. casei and L. plantarum. Oral administration of the L. rhamnosus product significantly increased the abundance of Lactobacillus and L. rhamnosus in the colon and cecum of mice. These findings present a new method for producing highly active probiotic products using plant materials and provide insights into the underlying mechanisms from a thermodynamic perspective, contributing to the industrialization and advancement of probiotics.

Improved thermal properties and CMAS corrosion resistance of rare-earth monosilicates by adjusting the configuration entropy with RE-doping

The novel rare earth monosilicates (xRE1/x)2SiO5 (RE=Yb, Tm, Er, Y, Dy and Tb, x = 2–6) were prepared in order to establish the relationship between configurational entropy and lattice distortion, and the effect of configurational entropy on their properties was investigated. The results showed that the lattice distortion of (xRE1/x)2SiO5 increased gradually with the increase of configurational entropy, but the multi-principal component solid solution tended to form a highly symmetrical crystal structure when the configurational entropy was large enough, thus inhibiting the lattice distortion. (5RE1/5)2SiO5 had a maximum lattice distortion, which leaded to a relatively low thermal conductivity and coefficient of thermal expansion, and good CMAS corrosion resistance.

Optimization of microclimate parameters in sports frame and tent facilities

The paper considers measures to optimize energy costs in the heating of frame and tent facilities designed for sports events. Data on the available heating systems of temporarily used tent facilities are presented. It is shown that climatic conditions for athletes and the audience in these facilities do not meet the existing standards in the vast majority of cases. The combination of two factors affecting the microclimate parameters, i.e., the usage frequency and the low thermal resistance coefficient of the enclosing structures, requires the application of new practices not only in the form of climate control equipment operation mode, but also in the form of new monitoring techniques. The paper presents the results of a study of microclimate parameters in a frame and tent facility when using new techniques and approaches to climate control systems and to the process of forming climatic conditions depending on the clothing and the type of work performed. The results show that the introduction of new control algorithms and the implementation of new ways of monitoring microclimate parameters can save up to 30% of thermal energy while providing favorable microclimate parameters throughout the entire room, with the room reaching steady-state heating mode more than twice as fast. For the development of physical education and sports, it is necessary to use structures that can be quickly assembled and put into operation. For these purposes, frame and tent facilities are the best option.

Novel Cr–Mn–Fe–Co–Ni oxide composites fabricated by in situ spark plasma sintering for high-temperature applications

Spinel composite is being considered for electrode materials in molten salt electrolysis, aiming to improve high-temperature stability and conductivity. Multi-phase composites with the general formula of (Fe1-3x-y Niy Cox Crx Mnx)3 O4 (x = 0.03, 0.06, 0.09, y = [1-2x]/3) were prepared via in situ SPS method. The composites were confirmed to consist of spinel and rock-salt phases through XRD and SEM analysis. Compared to the Ni–Fe–O system, the doping of Cr, Mn and Co improved the phase stability of the spinel during SPS, but hindered the shrinkage process. These composite exhibited low thermal diffusivity (1.236–2.481 m2/s, room temperature) and low coefficient of thermal expansion (9.8 - 14.4 × 10−6 K−1, 400–800 °C). Moreover, the composite with x = 0.06 and y = 0.29 exhibit 94.4 % lower permittivity, 7 times higher dielectric loss (at 40 Hz) and 26.6 % lower high-temperature conductivity (at 800 °C) than that of Ni–Fe–O system. This work demonstrates the enhanced thermal and electrical properties of spinel-based composites, which can provide inspiration to researchers and promote the development of high-temperature electrodes.

A computational insight into the Zintl SZr2N2 and BaAg2S2 phases for optoelectronic thermoelectric applications

The physical characteristics of SZr2N2 and BaAg2S2 Zintl phases have been explored by utilizing the full-potential augmented plane wave (FP-LAPW) method with the combination of modified Becke-Johnson (mBJ) approximation. The negative formation energies and phonon modes with positive frequencies endorsed the stability of both compounds. The electronic band profile reveals a bandgap of 1.18 eV for SZr2N2 and 2.15 eV for BaAg2S2. The optical characteristics are also calculated. The absorption of light for the studied compounds falls in the ultra-violet region, which shows their possibility to be employed as UV-rays absorbers. A large optical conductivity and low energy loss is also seen for both materials on UV region. The efficiency of temperature-dependent thermoelectric properties increases with the temperature rise, as calculated with the BoltzTraP code. The high electrical with low thermal conductivities and maximum Seebeck coefficient is witnessed for both materials. The large ZT values of 0.75 and 0.80 are achieved for SZr2N2 and BaAg2S2, respectively. All calculated transport parameters indicate the opportunity of using the studied compounds for thermoelectric applications.

High-entropy engineering promotes the thermal properties of monosilicates

It is difficult to obtain X2-type rare-earth monosilicates that have the advantages of low thermal conductivity and a thermal expansion coefficient that matches that of ceramic matrix composites, and thus, the efficient use of these materials in extreme environments is challenging. In this study, we developed a novel component regulation method, which significantly reduced thermal conductivity and helped achieve a suitable thermal expansion coefficient for monosilicates. Monosilicates have low thermal diffusion coefficients mainly due to the effect of extrinsic phonon scattering mechanisms. We analyzed different extrinsic phonon scattering mechanisms associated with point defect, disorder, grain boundary, lattice distortion, dislocation, and symmetry.

Functional upcycling of waste polyester into Cr-MOF towards synergistic interfacial solar evaporation and organic pollutant degradation

The development of hybrid photothermal materials coupling interfacial solar-driven water evaporation with advanced oxidation process has recently aroused extensive attention to simultaneously realize freshwater production and wastewater purification. However, designing advanced hybrid photothermal materials with high specific surface areas and robust active sites remains challenging to meet the distinct requirements of photothermal conversion and photocatalysis. Herein, we report the waste-to-metal-organic framework (MOF) strategy for converting waste poly(ethylene terephthalate) [PET] into Cr-MOF hexahedron with abundant active sites and large specific surface area (896.1 m2/g), and subsequently fabricate multifunctional chromium-based metal-organic frameworks (Cr-MOF)/carbon nanotube (CNT) composite solar evaporators in a cost-effective, scalable manner towards simultaneous interfacial solar-driven steam generation and stubborn contaminant removal. First, the composite evaporator presents high light absorption (98%), high photothermal conversion efficiency, super-hydrophilicity, low thermal coefficient (0.087 W/(m/K)) and low vaporization enthalpy. Accordingly, the composite evaporator not only holds a high evaporation rate (2.46 kg/(m2/h)), superior to most of advanced solar evaporators, but also owns good flexibility and long-term stability. Subsequently, according to density functional theory (DFT) calculation and COMSOL results, chromium sites of Cr-MOF and local solar heat contribute to the peroxymonosulfate (PMS) activation to produce various reactive species. Thereupon, the composite evaporator exhibits good tetracycline (TC) degradation activity. Finally, in the practical freshwater production and photocatalytic degradation, the freshwater production amount is 7.3 kg/m2 per day, along with the tetracycline degradation efficiency of 92.4%. This work provides an ingenious strategy to massively synthesize hybrid evaporators and concurrently advances freshwater production and pollutant elimination.