Outstanding Thermal Stability Research Articles

Fabrication of high-flux PTFE hollow fiber membranes through nonionic surfactant infiltration coupled with mussel-inspired chemistry coating

Polytetrafluoroethylene (PTFE) hollow fiber membrane holds tremendous potential for the treatment of complex wastewater due to its outstanding chemical and thermal stability. However, its treatment efficiency is often hindered by the low water permeate flux arising from the inherent hydrophobicity of PTFE. Here, we present a gentle and convenient hydrophilic modification method that involves immersion in a nonionic surfactant aqueous solution, followed by dopamine self-polymerization. The nonionic surfactant facilitated the penetration of the dopamine solution into the membrane, where dopamine self-polymerized to form a hydrophilic layer on the surface and inner pores of the membrane. The hydrophilicity-modified PTFE hollow fiber membranes demonstrated an impressive increase in water permeate flux, reaching 10231.4 L m−2 h−1, nearly ten times that of the original membrane. Even after prolonged exposure to a strong acid solution (pH = 1) or an oxidant solution (1000 mg L−1 NaClO) for two weeks, this membrane still maintained its favorable water permeability. Furthermore, the modified PTFE membranes also exhibited remarkable resistance to fouling by humic acid. These results showcased a straightforward method for designing a hydrophilic layer on PTFE hollow fiber membranes, underscoring their significant potential for real wastewater treatment applications.

Synthesis and application of environmental plasticizers based on benzene polyacid ester

AbstractUsing benzene‐1,3,5‐tricarboxylic acid, trimellitic anhydride, 2‐propylheptanol and 2‐ethylhexanol as raw materials, four kinds of environmental plasticizers were prepared, which were used as additives for polyvinyl chloride (PVC) products. Compared with commercially available di (2‐ethylhexyl) phthalate (DOP), di (2‐ethylhexyl) terephthalate (DOTP), and tributyl citrate (TBC), the application performance and plasticizing performance were compared. The structure of the target product was analyzed by fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy to verify the fingerprint region of the molecular structure of the product. The properties of plasticized PVC films were tested by thermal weight loss analysis, oven thermal aging test, migration and volatility resistance test, DMA analysis, and scanning electron microscopy. The plasticizing mechanism was confirmed through quantum chemical calculations, and the results of the calculations were in line with the migration outcomes. The results showed that compared with commercially available plasticizers, benzene polyacid ester plasticizers had better thermal stability, and better cold resistance in the polar environments, suitable for high‐temperature and water‐based environments.Highlights The four plasticizers prepared in this study were compared with reference plasticizers, and the plasticizing mechanism was validated through quantum chemical calculations. The PVC film plasticized with benzene polyacid ester prepared in this study demonstrates outstanding thermal stability, surpassing certain plasticizers reported in current literature. Benzene polyacid esters plasticized PVC film has migration stability under various conditions, it has great potential in packaging and other applications.

Preparation of a bio-based PU/EP IPN concrete adhesive with optimized performance and decent adhesion

An adhesive serves as a vital tool in construction, repair, and rehabilitation projects. Typically crafted from polymer materials such as epoxies or polyurethane latex, it facilitates the creation of resilient bonds between a variety of surfaces, ranging from concrete-concrete and metal-concrete to concrete-composites. However, employing epoxy or polyurethane individually as adhesives often demonstrate insufficient performance and weak interfacial adhesion during service. In this study, an adhesive combining polyurethane and epoxy was synthesized, featuring an interpenetrating polymer network (IPN) structure. This innovative agent was created using polyols sourced from soybean oil and a commercial epoxy resin. By tuning the infusion of polyurethane content, the resultant resin exhibited favorable flowability in civil applications, simultaneously improved strength and toughness due to the IPN structure, and outstanding thermal stability. Notably, the incorporation of 20 wt% polyurethane yielded a polymer with a remarkable tensile strength of 35.9 MPa. Additionally, the bonding adhesion of the prepared resins on concrete specimens was investigated through splitting tensile test and shear strength test. The study explored the influences of polyurethane content, concrete strength, and adhesive layer thickness on interfacial bonding strength. The introduction of an IPN structure within the PU-20 agent proved advantageous for enhancing the bonding adhesion of the concrete, resulting in remarkable interfacial tensile and shear strengths of 4.56 MPa and 21.73 MPa, respectively.

Generation of protective ceramic coatings on magnesium by laser treatment of Al2O3/ZrO2 filled organosilazane

Protective ceramic coatings are frequently the most common solutions for problems like corrosion and wear. Polymer derived ceramics technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace but requires high temperatures for the ceramization. To overcome this restriction a Nd:YVO4 laser (λ = 1064 nm) as energy source was used to process a novel ceramic coating system composed of an organosilazane with zirconia and alumina particles specially to protect magnesium. The resulting dense ceramic coating with a thickness up to 20 µm exhibits very good adhesion (25.9 ± 2.7 MPa) to the magnesium substrate, exceptionally high hardness (19.79 ± 1.90 GPa), an outstanding thermal shock stability but also a low coefficient of friction (0.21 ± 0.02) and a very good wear protection towards a SiC counter body. Furthermore, the coating protects the magnesium substrate effectively against corrosion (5 wt% aqueous NaCl solution).

Synthesis of ZnO nanorods decorating with Ag nanoparticles on flexible polyimide substrate for visible photodetector application

Polyimide (PI), which have many remarkable features such as excellent mechanical strength, outstanding thermal stability, exceptional electric properties, etc, is a potential carrier for optoelectronic devices due to its abundant applications. However, because of chemical inertness and smooth surface that led to the growth of materials on this substrate being more complex than that on rigid substrate, thus, this report aims to emphasise the synthesis of ZnO NRs decorated with the Ag NPs on flexible substrate for photodetector application. In this study, we successfully synthesise ZnO NRs/Ag NPs on a flexible PI substrate by the hydrothermal method. The performance of our photodetector in visible region (395 nm) exhibits via the responsivity of the device, which recorded value of ca. 40.16 mA W−1 at 1.66 mW cm−2. With obtained results, our research can pave the way for future studies based on flexible optoelectronic devices.

Sustainable production of biodiesel enabled by acid-base bifunctional ZnF2 via one-pot transformation of Koelreuteria integrifoliola oil: Process optimization, kinetics study and cost analysis

Against the backdrop of energy crisis and quest for carbon neutrality, efficient utilization of heterogeneous catalysts to facilitate one-pot conversion of low-quality nonedible oils into biodiesel, shows enormous promise for the reduction of carbon footprints and environmental pollution. In this study, an effective heterogeneous catalyst, acid-base bifunctional mesoporous ZnF2 (MP-ZnF2) was successfully fabricated for biodiesel synthesis from Koelreuteria integrifoliola oil (KIO, acid values of 8.26 mg KOH/g) via facile one-pot process. Meanwhile, systematic characterization showed the large specific surface area (62.9 m2/g), abundant mesoporous (12.15 nm), outstanding thermal stability, and plentiful stable acid-base sites (1.22 and 0.56 mmol/g) of MP-ZnF2. Consequently, MP-ZnF2 achieved a high biodiesel yield of 97.15% under moderate conditions (103 °C, 6.2 h, 10.2 wt% catalyst dosages, 29:1 MeOH/KIO molar ratio) optimized by response surface methodology (RSM). More importantly, through the kinetic investigation, a low activation energy of 49.24 kJ/mol explained the reason for its high activity, and the possible reaction mechanism of (trans)esterification was also proposed. In addition, MP-ZnF2 demonstrated satisfactory reusability (6th cycle, >90%), water resistance (8 wt% water content, 89.25%), and versatility (all yields >90%). According to cost analysis, the price of biodiesel in this work was about 0.64 $/kg. Notably, the as-prepared biodiesel conformed to ASTM D6751 and EN 14,214 standards, indicating great application prospects. It was demonstrated that one-pot transformation of KIO into biodiesel using acid-base bifunctional MP-ZnF2 contributes to the sustainable development of clean energy.

Highly thermally conductive composite films by the rational assembly of aramid nanofibers with low-dimensional nanofillers

Highly efficient thermal management of electronic devices has grown in significance with the burgeoning of semiconductor technology and 5th generation communication. It is urgently desired to rationally construct highly thermally conductive composite films for enhancing the performance, service life and operation reliability of electronic equipment. Aramid nanofibers (ANFs), as one of the most promising building blocks to fabricate high-performance and multifunctional composite films, have attracted wide attention of researchers over the past few years due to its impressive mechanical performances, excellent electric insulation, and outstanding thermal stability. Especially, the rational assembly of ANFs with low-dimensional thermally conductive nanofillers exhibits significant opportunity for developing highly thermally conductive flexible composite films. However, there is no specialized review to systematically summarize the research advances and prospective challenges of this area until now. Herein, the preparation strategies, structure and properties, as well as the potential applications of various ANFs-based thermally conductive composite films with different low-dimensional nanofillers are highlighted. Finally, possible challenges and opportunities for ANFs-based thermally conductive composite films are envisioned. This brief review delivers the readers an in-depth understanding of the thermal conduction performances of ANFs-based composite films, which may give meaningful enlightenment for designing advanced thermal management materials and ANFs-based functional composites.

A wide-angle broadband dual-polarization electromagnetic absorbing structure based on the carbonyl iron powder/polydimethylsiloxane composites

Electromagnetic absorbing structure with wide-angle and broadband absorption plays a vital role in radar stealth. Hence, a novel gradient composite multilayer absorbing structure (GCMAS) is designed and fabricated by a simple and low-cost direct ink writing (DIW) 3D printing technology. The GCMAS consists of the CIP/PDMS composites composed of carbonyl iron powder (CIP) and polydimethylsiloxane (PDMS), which have outstanding flexibility, chemical and thermal stability. By metastructure design of gradient composites, a material-structure–function integrated absorbing structure with 50 wt% CIP/PDMS in the top layer, 60 wt% CIP/PDMS in the middle two layers, and 70 wt% CIP/PDMS in the bottom two layers is obtained. Simulations demonstrate that the designed GCMAS with the thickness of 13 mm can achieve the −10 dB absorbing bandwidth in the frequency range from 2.88 to 38.24 GHz, and the absorbing bandwidth corresponding to −15 dB in 2.97–36.17 GHz. The maximum reflection loss is −42.17 dB at 22.96 GHz. Experiments demonstrate that the GCMAS can achieve the −10 dB absorbing bandwidth in 3.6–40 GHz. Moreover, the GCMAS also can maintain the broadband and strong absorbing performance with incident angle from 0° to 50° for transverse electric (TE) polarization and 0° to 60° for transverse magnetic (TM) polarization. This work provides a promising strategy for the fabrication of functional gradient composites and flexible or bendable absorbing structure, which have great potential in satellite communications and radar stealth.

New frontiers in thermal energy storage: An experimental analysis of thermophysical properties and thermal stability of a novel ternary chloride molten salt

It has been always a daunting task to develop thermal systems with a wide range of thermochemical properties and high stability. It presents a significant challenge, especially when aiming to utilize them for heat storage and transfer applications. In this regard, the thermal characteristics and thermal stability behaviour of molten salt mixture as a heat transfer fluid (HTF) at high temperatures were explored. A novel ternary eutectic salt mixture (base mixture) made of cuprous chloride (CuCl), potassium chloride (KCl) and sodium chloride (NaCl) was investigated as HTF for thermal energy storage (TES) system with a range up to 653 °C in a concentrated solar power (CSP) plant. To extend the temperature span and stability, the effect of an additive was investigated. Different compositions were studied in detail concerning the properties and stability regarding the additive. The molten salt with 7 % CaCl2 additive improved thermal stability and operating temperature from 653 °C to 700 °C. The transport characteristics and thermal stability of the eutectic mixture with and without the additive were measured by high-temperature thermal analyzers. The results indicated that the melting temperature decreased and the average specific heat capacity considerably increased with the addition of CaCl2 additive compared to the ternary chloride base mixture. As the temperature increased, the eutectic salt mixture exhibited a reduction in viscosity and density. The viscosity and density of the salt mixture with and without the additive were almost uniform at 700 °C. The average thermal conductivity of the ternary salt mixture with and without additives was 0.72 W/(m°C) which is much more than that of Solar and Hitec salts. In a 100 h experiment of long-period isothermal stability, the eutectic salt mixture showed less than 4 % weight loss at 700 °C. It was defined as the highest operating temperature at which the eutectic salt mixture remained stable. The stability and recyclability of the salt mixture were confirmed through the short-period stability test. The effect of the CaCl2 additive on thermal stability of base salt mixture was analyzed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) techniques. According to the results, this novel eutectic salt mixture had outstanding thermal stability up to 700 °C and could be employed as a viable TES material in CSP plants.

Promising improved mechanical, wear, corrosive properties by the impact of CNTs on Al alloy by FSP – A review

The monolithic alloys of aluminium have the qualities of less density, elevated strength and high resistance to corrosion. Generally, alloys of aluminium are most comprehensively used in the fields of aerospace sectors such as skeleton parts of aircraft, fuselages, bulk heads, wing ribs, wing spars, automobile and transportation industries, architectural parts, electrical and electronic applications, etc.The evolution of microstructure, and mechanical characteristics such aselongation, hardness, tensile strength, tribological property, and corrosion resistance are examined in this paper for the composites of aluminium-carbon nano-tubes (CNTs). With the use of a surface composite processing method known as friction stir processing, CNTs are added as reinforcements to improve the various properties of the base metal. The CNTs provide a wide variety of characteristics, such as outstanding electrical conductivity, thermal stability, high strength, and superior elastic properties.Numerous collections of published literature have been thoroughly studied, and it discusses a few of the essential underlying assumptions needed to achieve the optimal combination of CNTs with the aluminium under friction processing technique. From the comprehensive review, the statements are summarized that will assist future research work involving the accumulation of CNTs reinforced with aluminium alloy and utilized in various applications of aerospace and aircraft sectors.

Ultrastability and color-tunability of CsPbI3 nanocrystals glass via doping CoBr2 and application in WLED

Extensive research has been conducted on all-inorganic CsPbI3 nanocrystals (NCs) due to their exceptional optical properties. In this study, we successfully prepared CoBr2-doped CsPbI3 NCs in Lithium-borosilicate using the conventional melting quenching approach. We investigated the optical characteristics of CsPbI3 NCs glass doped with varying amounts of CoBr2. Remarkably, the samples exhibited outstanding water and thermal stability and tunable emission ranging from 702 to 652 nm. Interestingly, the CsPbI3 NCs glasses doped with CoBr2 demonstrated significantly enhanced photoluminescence quantum yields (PLQYs), which increased from 8 % to 32 %. Furthermore, by mixing a red CsPbI3 NCs glass doped with 0.5 mol CoBr2 and a green CsPbBr3 under a blue LED chip, we effectively generated a WLED which achieved (0.3341, 0.3360) of chromaticity coordinate (CIE), 5775.35 K of a correlated color temperature (CCT) that close to positive white light (0.330, 0.330) and the color rendering index (CRI) 79.4. This study provides a new technique in the field of metal ion-doped perovskite NCs, providing a valuable reference for future research and demonstrating possible applications in LEDs.

Hierarchical Polyimide Microparticles with Controllable Morphology.

Hierarchical polyimides (PIs) not only show outstanding thermal stability and high mechanical strength but also have great advantages in terms of microstructure and surface area, which makes them highly valuable in various fields such as aerospace, microelectronics, adsorption, catalysis, and energy storage. However, great challenges still remain in the synthesis of hierarchical PIs with well-defined microstructure. Herein, polyamide acid salts (PAAS) with tunable ionization degree are synthesized first via the polymerization of dianhydride and diamine monomers in deionized water with 1,2-dimethylimidazole (DMIZ). Then cationic cetyltrimethylammonium chloride (CTAC) is added to the PAAS aqueous solution to induce the formation of polyelectrolyte-surfactant complexes based on electrostatic interaction. After a typical hydrothermal reaction (HTR) procedure, hierarchical PIs with different microstructures such as urchin-like PI microparticles, flower-like PI microparticles, and lamellar PI petals can be fabricated simply by changing the additive amount of DMIZ and CTAC. The nanostructure self-assemblies of PAAS are dominated by the charges on macromolecular chains and the formation of hierarchical structures of polymers is ascribed to a geometrical selection process during crystal growth. This work provides valuable insights into the self-assembly behaviors of polyelectrolyte systems for synthesizing well-defined hierarchical polymers.

Unveiling the physical properties of RbCu3MSe4 (M = Si, Ge) direct band gap semiconductors: A systematic first-principles study

The Silicon and Germanium-based quaternary chalcogenides have remarkable features including their adjustable optical properties and outstanding thermal stability. We explored the complex interplay among the structural, electronic, optical, and thermoelectric characteristics of direct band gap novel RbCu3MSe4 (M = Si, Ge) quaternary chalcogenides by employing the well-known density functional theory. Direct type of band gap at high symmetry Г-point was noticed for both materials. The predicted band gaps of RbCu3SiSe4 and RbCu3GeSe4 are 1.32 eV and 0.73 eV, respectively. Due to the large size of germanium ions compared to silicon, the Ge–Se bonds in RbCu3GeSe4 are more wide-ranging than the Si–Se bonds in RbCu3SiSe4. The complex dielectric function along with other significant optical parameters are investigated and analyzed for their probable employment for optoelectronic applications. These examined materials are suitable to be employed in thermoelectric devices as observed from substantial and outstanding thermoelectric features. The present work could establish the potential employment of these complex systems and would open the way for advanced applications in various fields and technologies.

Bovine serum albumin-liposome stabilized high oil-phase emulsion: Effect of liposome ratio on interface properties and stability

This study aimed to solve the issue of poor lipophilicity of natural bovine serum albumin (BSA) by combining with liposomes (Lips) to stabilize high oil-phase emulsions (HOPEs). The interaction between BSA and Lips was mainly driven by hydrophobic forces, followed by hydrogen bonding. The secondary structure and tertiary structure of BSA were characterized and indicated that the addition of Lips promoted the structural expansion of BSA exposing the hydrophobic groups inside. Interfacial adsorption behaviours were assessed through dynamic interfacial tension, three-phase contact angle, and quartz crystal microbalance with dissipation. These results indicated that BSA-Lips crosslinking improved wettability, promoting adsorption and rearrangement at the oil-water interface, thereby resulting in a dense interfacial layer. The emulsifying efficacy of BSA-stabilized HOPEs also displayed a distinct Lips dependency. Varying the BSA-to-Lips ratio transformed their consistency from flowing to semi-solid, reinforcing the gel network. Under optimal conditions (BSA: Lips = 1:1), the droplet size of BSA-Lips stabilized HOPEs reached a minimum with a highly uniform distribution. Moreover, a 1:1 BSA to Lips ensured outstanding storage, thermal, and centrifugal stability for the HOPEs. This work provides valuable references for the interaction between protein and Lips, guiding the development of highly stable HOPEs stabilizers.

Highly efficient molybdenum nanostructures for solar thermophotovoltaic systems: One-step fabrication of absorber and design of selective emitter

Efficient solar energy harvesting materials or structures have become a topic of great interest in response to the ever-increasing energy demand. Refractory transition metals have been found to exhibit attractive properties in broadband absorptance, making them highly effective in solar thermophotovoltaic (STPV) systems that aim to surpass the Shockley-Queisser limit. Typically, broadband absorbers are made from hybrid materials or complex geometrical structures, which require multi-step fabrication technologies. In this study, we successfully developed a highly efficient broadband absorber based on molybdenum (Mo) nanosheets using a one-step physical vapor deposition process. The nanosheets result in the high absorber efficiencies of 96.1 % for blackbody radiation (BBR) at 5778 K and of 96.4 % for air mass (AM) 1.5 spectrum, and are insensitive to polarization and incident angle. After annealing at 1650 K for 24 h, the Mo nanosheets absorber demonstrates outstanding thermal stability without compromising the efficiency of the STPV system. To complete the STPV system, a selective narrowband Mo-based gratings emitter was further designed with a high emissivity of 96 % at a wavelength of 2.17 μm, resulting in a high PV cell efficiency of 41.8 % around 1723 K. Through a series of theoretical calculations, the proposed STPV system can achieve an overall conversion efficiency of 40.2 % by a trade-off between the structure temperature and the sun concentration. Furthermore, an efficiency of 35.5 % can be achieved at a low temperature of 1073 K with a low solar concentration of 500 suns.The results provide tremendous opportunities for widespread applications of high-performance STPV systems.

Top-down approach making anisotropic, stable and flexible wood-based ionogels for wearable sensors

Ionogels exhibit outstanding ionic conductivity, thermal stability, and non-volatility, positioning them as highly promising for sensor devices rivaling hydrogels. However, the inherent limitation of most existing ionogels is that their strength and toughness are not ideal, which significantly hinders their widespread application. One possible method is using natural wood with anisotropic properties to reinforce ionogels. Herein, we reported a top-down approach to obtain a semi-dissolved wood template, in which the delignified balsa wood was heated and impregnated in an ionic liquid to partially dissolve the cellulose in the wood skeleton. Finally, acrylic acid was infiltrated into the wood template, and the wood-based ionogels with a dual network were successfully synthesized by in-situ polymerization. The prepared wood-based ionogels were significantly anisotropic with longitudinal strength up to 9.0 MPa and radial strength of 0.97 MPa. These wood ionogels also have translucency (53.9 %), anti-drying (remain stable at room temperature for more than 30 days), fatigue resistance (>500 loading cycles), and flexibility. In addition, they have excellent electrical conductivity (3.8 μS cm−1) with high sensitivity (GF = 8.6), making them ideal candidates for strain sensors capable of detecting a wide range of human activities. The preparation of gel using semi-dissolved wood as a template provides an advanced strategy for producing biomass-based flexible gel materials.

A Tb(III) Complex Based on 3‐Pyridylacetic Showing Luminescent Detection for Fe3+ Ion

AbstractA new Tb(III) complex based on 3‐pyridylacetic acid, [Tb(H(3‐PAA)2)(NO3)2] (1, 3‐PAA=3‐pyridylacetic acid), has been triumphantly prepared and structurally characterized. Complex 1 is a 1D chained structure linked by carboxylate groups of the 3‐PAA ligand, and its 2D supramolecular packing is controlled mainly by hydrogen‐bonds. The compound exhibits outstanding thermal stability and excellent stability under ethanol solutions. Moreover, compound 1 shows a strong solid‐state green‐emitting emission at room temperature, which demonstrates that the ligand can effectively sensitize the emission of the Tb(III) ion, and it can serve as a responsive sensing material for detecting the Fe3+ ion in ethanol solutions.

Study on microstructure, tensile performance and creep resistance of Al–Mg–Si-Sc-Zr alloy strengthened by Al3(Sc, Zr) nanoprecipitates

In this work, a newly designed Al–Mg–Si-Sc-Zr alloy with both excellent room-temperature tensile performances and high-temperature creep resistance was prepared. The microstructure of Al–Mg–Si matrix alloy was significantly modified by Sc, Zr micro-alloying. The average grain size of Al–Mg–Si-Sc-Zr alloy in as-cast and as-rolled states was 68.3 μm and 7.33 μm respectively, which was far smaller than those of Al–Mg–Si alloy. Numerous Ll2-ordered Al3(Sc, Zr) nanoprecipitates ranging from 20 to 60 nm were generated during heat treatment, and they had a strong coherent interface relation with α-Al matrix. During rolling deformation, a further DRX (dynamic recrystallization) progress happened in Al–Mg–Si-Sc-Zr alloy due to the severe dislocations pile-up caused by Al3(Sc, Zr) nanoprecipitates. The YS (yield strength), UTS (ultimate tensile strength) and EL (elongation) of as-rolled Al–Mg–Si-Sc-Zr alloy at room temperature were 315.2 MPa, 372.3 MPa and 20.1 % respectively, which were increased by 21.9 %, 17.1 % and 41.5 % compared to tensile performances of Al–Mg–Si matrix alloy. An enhanced high-temperature creep resistance was obtained by Al–Mg–Si-Sc-Zr alloy, which was mainly attributed to the outstanding thermal stability possessed by Al3(Sc, Zr) nanoprecipitates. The strengthening mechanisms including grain refinement strengthening and Orowan strengthening were also discussed.

Pressure induced thermal conduction paths in liquid metal-boron nitride fillered thermal interface materials with high thermal conductivity

With the continuous evolution of wearable and mobile devices, flexible electronics, and intelligent thermal management, there is a growing interest in thermal interface materials (TIMs) that combine high thermal conductivity with low modulus for stretchability. However, materials with high thermal conductivity often come with elevated Young's modulus. Here, we have developed a TIMs by combining liquid metal and BN with polydimethylsiloxane (PDMS), achieving a blend of low modulus and high thermal conductivity. To enhance thermal conductivity, we introduced boron nitride sheets as “scalpel”, puncturing the oxide layer of the liquid metal under pressure to establish a continuous thermal path. After pressure induction, the LM-BN/PDMS composite exhibits a thermal conductivity of 4.3 W/(m K), with a Young's modulus of only 193 kPa and a fracture strain of 483%. Furthermore, it demonstrates outstanding thermal stability under multiple thermal shock cycles, indicating significant potential for applications in future thermal management for flexible electronic devices, wearable devices, and beyond.

Preparation of anisotropic polyimide aerogels for thermal protection with outstanding flexible resilience using the freeze-drying method.

Polyimide aerogels (PIAs) not only possess excellent thermodynamic properties but also have a high porosity structure, making them an exceptional protective and thermal insulation material, and further broadening their application scope in aerospace and other cutting-edge fields. In this work, a series of anisotropic polyimide aerogels (3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA), p-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA)) with excellent properties were prepared. These PIAs were obtained by unidirectional freeze-drying and thermal amination of two different precursor solutions mixed in proportion. These PIAs possess an irregularly oval tubular structure, exhibiting pronounced anisotropy. (PIA-2 exhibits outstanding flexible resilience in the radial direction. It can still regain its original form after half an hour of compression by a universal testing machine, yet it cannot do so in the axial direction. The thermal diffusivity of PIA-5 in the radial direction at room temperature is as low as 0.067 mm2 s-1, and even at 200 °C, the thermal diffusivity is as low as 0.057 mm2 s-1. Meanwhile, the thermal diffusivity in the axial direction at room temperature is 0.11 mm2 s-1, surpassing the value of 0.106 mm2 s-1 of aerogels prepared from monomeric raw materials and dried under supercritical conditions). PIAs exhibit outstanding thermal stability (the axial strength and modulus retention of PIA-8 at 200 °C are as high as 52.63% and 44.82%), and its weight loss temperature of 5% is as high as 603 °C and it has a glass softening temperature of 387 °C. PIAs also demonstrate exceptional flame retardancy in imitation flame retardant experiments and exhibit outstanding thermal insulation performance when heated on a 150 °C heating plate for 10 minutes (the radial surface temperature of PIA-5 was only 49.9 °C). These anisotropic PIAs materials exhibit outstanding flexible resilience, and thermal protection performance, holding significant importance for their widespread adoption as thermal insulation materials in aerospace, high-precision electronic components, and other domains.