Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always...Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.展开更多
Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectiv...Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.展开更多
In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica a...Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.展开更多
As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties...As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties such as high-temperature resistance,hydrophobicity,and chemical stability.However,the PTFE aerogels are difficult to be molded due to the weak interaction between resin particles.In this work,poly(ethylene oxide)(PEO)was selected as the carrier to assist the PTFE aerogels molding.The pure PTFE aerogels were prepared by homogeneously mixing PTFE aqueous dispersion and PEO,freeze-drying,and high-temperature sintering.When the mass fraction of PTFE and PEO were appropriate,the porosity of PTFE aerogels exceeded 90%and had a hierarchical honeycomb structure.Results showed that the PTFE aerogels not only had excellent hydrophobicity but also possessed superior acoustic insulation,mechanical strength,thermal insulation,and heat resistance properties.Specifically,the water contact angle is about 140°.The noise reduction coefficient is 0.34 and the average sound absorption coefficient is greater than 88%in the frequency range of 2000-6400 Hz.Meanwhile,the thermal conductivity in the air is about 0.045 W/(m·K),and the initial thermal decomposition temperature is 450℃.More importantly,the PTFE aerogels had excellent temperature and corrosion resistance.Even after extremely thermal and chemical treatment,they remained unchanged porous structure as well as acoustic and thermal insulation properties,which exhibits great potential for application in many harsh environments.展开更多
Three-dimensional(3D)carbon aerogel with high porosity and lightweight merit has emerged as an important high-performance electromagnetic(EM)absorption material.Despite great progress has been made,most reported 3D ca...Three-dimensional(3D)carbon aerogel with high porosity and lightweight merit has emerged as an important high-performance electromagnetic(EM)absorption material.Despite great progress has been made,most reported 3D carbon aerogels suffer from non-renewability and high cost.Moreover,the randomly distributed porous structure restricts the effective regulation of microwave absorption.Herein,the sustainable shaddock peel cellulose(SPC)was adopted to construct an ultralight and orientated carbon aerogel through a facile bidirectional freezing technique and subsequently thermal treatment process.The resultant carbon aerogel is composed of ordered lamellar layers interconnected by supported bridges,forming a continuous 3D conductive network.Addition of a small amount of graphene oxides(GO)nanosheets in biomass aerogel enhances the interaction of SPC and promotes electron transmission along 3D conductive network.Through tuning the lamellar spacing of aerogel,the as-prepared carbon aerogel achieves a remarkable microwave absorption property with a strong reflection loss(RL)of−63.0 dB and broad effective absorption bandwidth(EAB)of 7.0 GHz under ultralow filler content of 4 wt.%.Moreover,this carbon aerogel also demonstrates excellent thermal insulation property,and is even comparable to commercial products.The present work paves the way for designing low-cost and sustainable biomass-derived carbon aerogel for lightweight and high-performance microwave absorption and infrared stealth function.展开更多
Due to the global energy shortage,it has become essential to reduce energy consumption in the steelmaking process in order to promote the sustainable development of the metallurgical industry.The limitations of tradit...Due to the global energy shortage,it has become essential to reduce energy consumption in the steelmaking process in order to promote the sustainable development of the metallurgical industry.The limitations of traditional ladle insulation materials were addressed by using kaolin as the main raw material in combination with foam-gelcasting technique for in-situ synthesis of porous anorthite thermal insulation materials.Concurrently,the effects of sintering temperature and time on the composition of the physical phases,microstructure and physical properties were elucidated.The results showed that anorthite was the main phase obtained in sintering temperature range of 1200-1450℃,and edges of anorthite grains were well defined and well developed,presenting a plate-like morphology,which significantly improved mechanical strength of sample.The best overall performance was achieved at a firing temperature of 1400℃ and a holding time of 3 h.Compared to conventional ladle thermal insulation materials,samples developed herein showed excellent performance with a porosity of 63.3%,a compressive strength of 14.51 MPa,and an ultra-low thermal conductivity of only 0.29 W/(m K).展开更多
Objective:This study primarily analyzes the effectiveness of thermal insulation nursing(empowered by temperature intervention)in urological stone patients during the general anesthesia recovery period.Methods:A total ...Objective:This study primarily analyzes the effectiveness of thermal insulation nursing(empowered by temperature intervention)in urological stone patients during the general anesthesia recovery period.Methods:A total of 76 urological stone patients who underwent surgical treatment as the preferred option were selected as the research subjects.The earliest consultation time was May 2024,and the latest was May 2025.The patients were randomly divided into two groups using the random number table method,namely the observation group and the control group,with 38 patients in each group.The intervention indicators of the patients were compared.Results:The overall satisfaction rate in the observation group was higher than that in the control group,and the incidence of adverse reactions was lower,with p<0.05.At 0.5 hours,1 hour after surgery,and at the end of surgery,the body temperature in the observation group was significantly different from that in the control group,with p<0.05.Postoperatively,various hemodynamic indicators in the observation group were significantly different from those in the control group,with p<0.05.The time to clench the first upon verbal command,the time to open the eyes upon verbal command,the extubating time,and the recovery retention time in the observation group were all shorter than those in the control group,with p<0.05.Postoperative stress indicators and agitation scores at different time points in the observation group were significantly different from those in the control group,with p<0.05.Conclusion:For urological stone patients during the general anesthesia recovery period,actively implementing thermal insulation nursing combined with temperature intervention not only enhances hemodynamic stability but also effectively reduces the risk of adverse reactions such as hypothermia and shivering.It optimizes the recovery condition,significantly improves the stress state,and increases nursing satisfaction.展开更多
Poly(vinylidene fluoride)(PVDF)foam has received widespread attention due to its high strength,and excellent combination of flame-retardancy,antibacterial performance,and chemical stability.However,the foaming ability...Poly(vinylidene fluoride)(PVDF)foam has received widespread attention due to its high strength,and excellent combination of flame-retardancy,antibacterial performance,and chemical stability.However,the foaming ability of conventional PvDF is severely limited by its rapid crystallization kinetics and poor melt strength.Although ultra-high molecular weight PVDF(H-PVDF)theoretically offers prolonged melt elasticity favorable for foaming,the extremely high melt viscosity poses substantial processing challenges,and its foaming behavior has remained largely unexplored.To address these issues,this study proposes a novel fabrication strategy combining solvent casting with microcellular foaming to prepare H-PVDF foams.Dynamic mechanical analysis and differential scanning calorimetry reveal that extensive chain entanglements in H-PVDF impose constraints on crystallization and significantly enhance melt strength.By tuning the processing parameters,the distinctive foaming be-havior of H-PVDF under various conditions is systematically elucidated.Remarkably,a record-high expansion ratio of 55.6-fold is achieved,ac-companied by a highly uniform and fine cellular structure.The resulting H-PVDF foams exhibit a low thermal conductivity of 31.8 mW·m^(-1).K^(-1),while retaining excellent compressive strength,flame-retardancy,and hydrophobicity.These outstanding properties highlight the great potential of H-PVDF foams as the thermal insulation materials for applications in aerospace,energy infrastructure,and other extreme environments.展开更多
This study examines the development of loose-fill thermal insulation materials derived from annual plant residues,such as wheat straw,water reeds,and corn stalks,processed using the chemimechanical pulping(CMP)techniq...This study examines the development of loose-fill thermal insulation materials derived from annual plant residues,such as wheat straw,water reeds,and corn stalks,processed using the chemimechanical pulping(CMP)technique.The chopped plants were soda-cooked for 30 min,varying NaOH concentration(2%–8%on a dry basis of biomass),and mechanically refined using different disc types.The CMPprocess enhances the homogeneity and stability of defibratedmaterial,yielding improved insulation properties compared to untreated chopped rawmaterials.Chemical analysis revealed that CMP increases cellulose content and reduces lignin levels,enhancing water retention and vapor diffusion properties.Settlement tests confirmed that CMP materials are more resistant to compaction under vibration,maintaining long-term performance.Additionally,the CMP enables the production of lightweight materials that require less resource consumption while achieving comparable thermal insulation performance.The investigated biobased materials offer a sustainable alternative to conventional insulation,with competing thermal conductivity values(0.041-0.046 W/mK)at the settlement-resistant bulk density level of 60 kg/m^(3).The thermal conductivity of CMP materials remains minimally affected.However,the resulting fibers demonstrate significant advantages in stability and material efficiency.This highlights its suitability for loose-fill applications to improve the sustainability of the construction.Using renewable plant residues,CMP-based insulation materials align with circular economy principles and contribute to environmental sustainability.This research underscores the potential of CMP materials to reduce greenhouse gas emissions,optimize resource use,and promote eco-friendly building practices.展开更多
The demand for anisotropic aerogels with excellent comprehensive properties in cutting-edge fields such as aerospace is growing.Based on the above background,a novel heterocyclic para-aramid nanofiber/reduced graphene...The demand for anisotropic aerogels with excellent comprehensive properties in cutting-edge fields such as aerospace is growing.Based on the above background,a novel heterocyclic para-aramid nanofiber/reduced graphene oxide(HPAN/rGO)composite aerogel was prepared by combining electrospinning and unidirectional freeze-drying.The anisotropic HPAN/rGO composite aerogel exhibited a honeycomb morphology in the direction perpendicular to the growth of ice crystals,and a through-well structure of directed microchannels in the direction parallel to the temperature gradient.By varying the mass ratio of HPAN/rGO,a composite aerogel with an ultra-low density of 5.34-7.81 mg·cm^(-3) and an ultra-high porosity of 98%-99%was obtained.Benefiting from the anisotropic structure,the radial and axial thermal conductivities of HPAN/rGO-3 composite aerogel were 29.37 and 44.35 mW·m^(-1)·K^(-1),respectively.A combination of software simulation and experiments was used to analyze the effect of anisotropic structures on the thermal insulation properties of aerogels.Moreover,due to the intrinsic self-extinguishing properties of heterocyclic para-aramid and the protection of the graphene carbon layer,the composite aerogel also exhibits excellent flame retardancy properties,and its total heat release rate(THR)was only 5.8 kJ·g^(-1),which is far superior to many reported aerogels.Therefore,ultralight anisotropic HPAN/rGO composite aerogels with excellent high-temperature thermal insulation and flame retardancy properties have broad application prospects in complex environments such as aerospace.展开更多
Integrating phase change materials(PCM)into thermal insulation materials offers a novel approach to aerospace thermal protection.Herein,we used waste biomass as a template;by selecting the appropriate carbonization te...Integrating phase change materials(PCM)into thermal insulation materials offers a novel approach to aerospace thermal protection.Herein,we used waste biomass as a template;by selecting the appropriate carbonization temperature,we obtained carbon aerogels(CCA)with extremely high porosity(95.8%)and high pore volume.After encapsulating PEG2000,we achieved high enthalpy(137.79 J g^(−1),91%of pure PEG2000)and low thermal conductivity(0.137 W(m·K)^(–1),45% of pure PEG2000).Thanks to the rich hierarchical nano-micro porous structure of CCA and the high latent heat of PEG2000,CCA/PEG exhibits excellent thermal insulation properties(under a heating temperature of 131℃,the material takes 1400 s to reach its maximum temperature and can be maintained below 65℃)and cycle performance.Additionally,irradiation destroyed the structure of CCA/PEG,leading to the degradation of PEG and the formation of other carbonyl-containing compounds,which decreased its latent heat(4.2%)and thermal conductivity(16.1%).However,the irradiation-resistant CCA,acting as a protective layer,minimizes the impact of irradiation on PEG2000.Instead,irradiation enhances the hierarchical porous structure of the material,ultimately improving its thermal insulation performance.CCA/PEG has potential application prospects in thermal protection and aerospace and is a strong competitor for high-efficiency thermal insulation materials.展开更多
The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock ...The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock properties in deep reservoirs.High-performance thermal insulation materials are crucial for supporting ITP-Coring during deep oil and gas exploration.This study explores the impact of high-temperature and high-pressure(HTHP)conditions on hollow glass microsphere/epoxy(HGM/EP)thermal insulation materials,focusing on the interphase.Investigations of HGM/EP materials with varying hollow glass microsphere(HGM)strengths and volume fractions reveal that elevated temperatures cause the molecular chains of the epoxy resin matrix to relax,leading to matrix softening and a decline in mechanical properties.Additionally,high-pressure water infiltrates the material,damaging the interphase and HGMs,further compromising material performance.The combined HTHP environment accelerates this degradation.Dynamic mechanical analysis(DMA)shows that S60HS HGMs,which possess higher strength,interact more strongly with the matrix and exhibit higher entanglement density,resulting in superior interphase adhesion.This enhances stress transfer efficiency and reduces the loss of storage modulus at the interphase.Theoretical analysis indicates that the interphase thickness and modulus of S-f40 remain mostly unaffected after HTHP treatment,with values higher than the epoxy matrix.This correlates with DMA results,demonstrating that S-f40 has the smallest adhesion factor(A),indicating the highest interfacial stress transfer efficiency.S-f40 also exhibits optimal thermal conductivity and mechanical properties,making it ideal for ITP-Coring in deep reservoirs.These findings provide insights for optimizing materials in HTHP environments for deep reservoir exploration.展开更多
The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal prote...The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal protection systems. The inverse problem of heat transfer is solved by the genetic algorithm and data from the steady heat transfer experiment of fibrous thermal insulations. The density radiation attenuation coefficient, the albedo of fibrous thermal insulations and the surface emissivity of reflective screens are optimized. Finally, the one-dimensional steady heat transfer model of MTIs with optimized thermal physical parameters is verified by experimental data of the effective MTI conductivity.展开更多
Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-s...Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-stacking tendency,and high density.To tackle these challenges,MXene nanosheets were incorporated into polyacrylonitrile(PAN)nanofibers and subsequently assembled into a three-dimensional(3D)network structure through PAN carbonization,yielding MXene/C aerogels.The 3D network effectively extends the path of microcurrent transmission,leading to enhanced conductive loss of electromagnetic(EM)waves.Moreover,the aerogel’s rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXenebased absorbers.EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss(RL_(min))value of−53.02 dB(f=4.44 GHz,t=3.8 mm),and an effective absorption bandwidth(EAB)of 5.3 GHz(t=2.4 mm,7.44–12.72 GHz).Radar cross-sectional(RCS)simulations were employed to assess the radar stealth effect of the aerogels,revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m^(2).In addition to the MA performance,the MXene/C aerogel also demonstrates good thermal insulation performance,and a 5-mm-thick aerogel can generate a temperature gradient of over 30℃ at 82℃.This study provides a feasible design approach for creating lightweight,efficient,and multifunctional MXene-based MA materials.展开更多
The materials with thermal insulating and fre-retardant properties are highly demanded for architectures to improve the energy efficiency.The applications of conventional inorganic insulating materials such as silica ...The materials with thermal insulating and fre-retardant properties are highly demanded for architectures to improve the energy efficiency.The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance.Here,we report an organic/inorganic composite aerogel with integrated double network structure,in which silica constituent homogeneously distribute in the anisotropic polyimide nanofber aerogel matrix and strong interfacial effect is formed between two components.The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%,which can withstand 500 cyclic fatigue tests at a compressive strain of 50%in the radial direction.The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity(21.2 mW m^(-1)K^(-1))and excellent resistance to a 1200℃flame without disintegration.The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fre,demonstrating great potential as efficient building materials.展开更多
The present work introduces a novel concurrent optimization formulation to meet the requirements of lightweight design and various constraints simultaneously.Nodal displacement of macrostructure and effective thermal ...The present work introduces a novel concurrent optimization formulation to meet the requirements of lightweight design and various constraints simultaneously.Nodal displacement of macrostructure and effective thermal conductivity of microstructure are regarded as the constraint functions, which means taking into account both the loadcarrying capabilities and the thermal insulation properties.The effective properties of porous material derived from numerical homogenization are used for macrostructural analysis. Meanwhile, displacement vectors of macrostructures from original and adjoint load cases are used for sensitivity analysis of the microstructure. Design variables in the form of reciprocal functions of relative densities are introduced and used for linearization of the constraint function. The objective function of total mass is approximately expressed by the second order Taylor series expansion. Then, the proposed concurrent optimization problem is solved using a sequential quadratic programming algorithm, by splitting into a series of sub-problems in the form of the quadratic program. Finally, several numerical examples are presented to validate the effectiveness of the proposed optimization method. The various effects including initial designs, prescribed limits of nodal displacement, and effective thermal conductivity on optimized designs are also investigated. An amount of optimized macrostructures and their corresponding microstructures are achieved.展开更多
Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have ...Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have largely hampered their applications in these areas.This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers(CNFs)with continuous nanolayers of MOFs.The cross-linking gives the aerogels high mechanical strength but superelasticity(80%maximum recoverable strain,high specific compression modulus of^200 MPa cm3 g−1,and specific stress of^100 MPa cm3 g−1).The resultant lightweight aerogels have a cellular network structure and hierarchical porosity,which render the aerogels with relatively low thermal conductivity of^40 mW m−1 K−1.The hydrophobic,thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy.This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials.It presents a pathway for the design of thermally insulating,superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.展开更多
In recent years, solar desalination and water evaporation/purification with various artificial architectures have drawn significant attention. Herein, we introduce a rational design structure for efficient solar water...In recent years, solar desalination and water evaporation/purification with various artificial architectures have drawn significant attention. Herein, we introduce a rational design structure for efficient solar water evaporation and purification, focusing on the balance between water transportation and thermal insulation.Natural wood after a simple flame treatment on the surface was utilized as the solar absorber, with a high solar absorbance(~90 %), good hydrophilicity, and excellent heat localization abilities. Besides,a thermal insulator(polystyrene foam) was used to further reduce the thermal loss, and the optimized ratio between the water path and thermal insulator was obtained. A set of floating foam-flamed-wood(F-F-wood) devices were fabricated with a high evaporation rate of 3.92 kgm-2 h-1, exhibiting photothermal purification abilities from seawater and wastewater containing organic dyes and heavy metals. This study sheds light on the rational design of scalable and low-cost devices for solar water evaporation and purification.展开更多
Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitan...Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitant precursors as well as cumbrous multi-step hydrophobization process has often narrowed the field of applications. In this work, granular silica aerogel materials were synthesized by extracting Si O2 from recycled rich silicon coal gangue, followed by one-step hydrophobization and ambient pressure drying. Lightweight(about 0.16 g/cm3) and nanostructural aerogels were obtained through this route. They exhibit a 3D open porous microstructure with around 600 cm2/g surface area and 20 nm of the average pore diameter, thermal conductivity of 4-5 mm packed granules is 20-25 m W/(m·K), which was proved by both guarded hot plate and hot-wire transient methods. This study offers a new facile route for the synthesis of silica aerogel from recycled solid waste coal gangue and suggests a method, which may lead to a cost reduction in terms of industrial production.展开更多
基金supported by Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the National Natural Science Foundation of China(No.52273053)the Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA41)。
文摘Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.
文摘Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
基金supported by the National Natural Science Foun-dation of China(Grant No.U2167214).
文摘Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.
基金supported by the National Natural Science Foundation of China(No.52233003)the Department of Sichuan Province(No.2022JDJQ0023)。
文摘As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties such as high-temperature resistance,hydrophobicity,and chemical stability.However,the PTFE aerogels are difficult to be molded due to the weak interaction between resin particles.In this work,poly(ethylene oxide)(PEO)was selected as the carrier to assist the PTFE aerogels molding.The pure PTFE aerogels were prepared by homogeneously mixing PTFE aqueous dispersion and PEO,freeze-drying,and high-temperature sintering.When the mass fraction of PTFE and PEO were appropriate,the porosity of PTFE aerogels exceeded 90%and had a hierarchical honeycomb structure.Results showed that the PTFE aerogels not only had excellent hydrophobicity but also possessed superior acoustic insulation,mechanical strength,thermal insulation,and heat resistance properties.Specifically,the water contact angle is about 140°.The noise reduction coefficient is 0.34 and the average sound absorption coefficient is greater than 88%in the frequency range of 2000-6400 Hz.Meanwhile,the thermal conductivity in the air is about 0.045 W/(m·K),and the initial thermal decomposition temperature is 450℃.More importantly,the PTFE aerogels had excellent temperature and corrosion resistance.Even after extremely thermal and chemical treatment,they remained unchanged porous structure as well as acoustic and thermal insulation properties,which exhibits great potential for application in many harsh environments.
基金financially supported by the National Natural Science Foundation of China(Nos.52302110,52231007,52301236,12327804,T2321003,and 22088101)the Shanghai Pujiang Pro-gram(No.22PJ1401000)the“Start-up Fund”provided by Xi’an Technological University(No.0853/302020646).
文摘Three-dimensional(3D)carbon aerogel with high porosity and lightweight merit has emerged as an important high-performance electromagnetic(EM)absorption material.Despite great progress has been made,most reported 3D carbon aerogels suffer from non-renewability and high cost.Moreover,the randomly distributed porous structure restricts the effective regulation of microwave absorption.Herein,the sustainable shaddock peel cellulose(SPC)was adopted to construct an ultralight and orientated carbon aerogel through a facile bidirectional freezing technique and subsequently thermal treatment process.The resultant carbon aerogel is composed of ordered lamellar layers interconnected by supported bridges,forming a continuous 3D conductive network.Addition of a small amount of graphene oxides(GO)nanosheets in biomass aerogel enhances the interaction of SPC and promotes electron transmission along 3D conductive network.Through tuning the lamellar spacing of aerogel,the as-prepared carbon aerogel achieves a remarkable microwave absorption property with a strong reflection loss(RL)of−63.0 dB and broad effective absorption bandwidth(EAB)of 7.0 GHz under ultralow filler content of 4 wt.%.Moreover,this carbon aerogel also demonstrates excellent thermal insulation property,and is even comparable to commercial products.The present work paves the way for designing low-cost and sustainable biomass-derived carbon aerogel for lightweight and high-performance microwave absorption and infrared stealth function.
基金supported by the National Natural Science Foundation of China(Nos.51472220 and 51872265)Collaborative Innovation Major Special Project of Zhengzhou(No.20XTZX12025)+1 种基金Program for Leading Talents of Science and Technology in the Central Plain of China 2022(No.234200510002)Key Scientific Research Projects of Henan Higher Education Institutions(No.25A150016).
文摘Due to the global energy shortage,it has become essential to reduce energy consumption in the steelmaking process in order to promote the sustainable development of the metallurgical industry.The limitations of traditional ladle insulation materials were addressed by using kaolin as the main raw material in combination with foam-gelcasting technique for in-situ synthesis of porous anorthite thermal insulation materials.Concurrently,the effects of sintering temperature and time on the composition of the physical phases,microstructure and physical properties were elucidated.The results showed that anorthite was the main phase obtained in sintering temperature range of 1200-1450℃,and edges of anorthite grains were well defined and well developed,presenting a plate-like morphology,which significantly improved mechanical strength of sample.The best overall performance was achieved at a firing temperature of 1400℃ and a holding time of 3 h.Compared to conventional ladle thermal insulation materials,samples developed herein showed excellent performance with a porosity of 63.3%,a compressive strength of 14.51 MPa,and an ultra-low thermal conductivity of only 0.29 W/(m K).
文摘Objective:This study primarily analyzes the effectiveness of thermal insulation nursing(empowered by temperature intervention)in urological stone patients during the general anesthesia recovery period.Methods:A total of 76 urological stone patients who underwent surgical treatment as the preferred option were selected as the research subjects.The earliest consultation time was May 2024,and the latest was May 2025.The patients were randomly divided into two groups using the random number table method,namely the observation group and the control group,with 38 patients in each group.The intervention indicators of the patients were compared.Results:The overall satisfaction rate in the observation group was higher than that in the control group,and the incidence of adverse reactions was lower,with p<0.05.At 0.5 hours,1 hour after surgery,and at the end of surgery,the body temperature in the observation group was significantly different from that in the control group,with p<0.05.Postoperatively,various hemodynamic indicators in the observation group were significantly different from those in the control group,with p<0.05.The time to clench the first upon verbal command,the time to open the eyes upon verbal command,the extubating time,and the recovery retention time in the observation group were all shorter than those in the control group,with p<0.05.Postoperative stress indicators and agitation scores at different time points in the observation group were significantly different from those in the control group,with p<0.05.Conclusion:For urological stone patients during the general anesthesia recovery period,actively implementing thermal insulation nursing combined with temperature intervention not only enhances hemodynamic stability but also effectively reduces the risk of adverse reactions such as hypothermia and shivering.It optimizes the recovery condition,significantly improves the stress state,and increases nursing satisfaction.
基金supported by the National Natural Science Foundation of China(No.52175341)Shandong Provincial Natural Science Foundation(No.ZR2022JQ24)+2 种基金Funding Project of Jinan City's New Twenty Items for Colleges and Universities(No.202333038)Excellent Young Team Project of Central Universities(No.2023QNTD002)Qingdao Key Technology Research and Industrialization Demonstration Project(No.24-1-2-qljh-10-gx).
文摘Poly(vinylidene fluoride)(PVDF)foam has received widespread attention due to its high strength,and excellent combination of flame-retardancy,antibacterial performance,and chemical stability.However,the foaming ability of conventional PvDF is severely limited by its rapid crystallization kinetics and poor melt strength.Although ultra-high molecular weight PVDF(H-PVDF)theoretically offers prolonged melt elasticity favorable for foaming,the extremely high melt viscosity poses substantial processing challenges,and its foaming behavior has remained largely unexplored.To address these issues,this study proposes a novel fabrication strategy combining solvent casting with microcellular foaming to prepare H-PVDF foams.Dynamic mechanical analysis and differential scanning calorimetry reveal that extensive chain entanglements in H-PVDF impose constraints on crystallization and significantly enhance melt strength.By tuning the processing parameters,the distinctive foaming be-havior of H-PVDF under various conditions is systematically elucidated.Remarkably,a record-high expansion ratio of 55.6-fold is achieved,ac-companied by a highly uniform and fine cellular structure.The resulting H-PVDF foams exhibit a low thermal conductivity of 31.8 mW·m^(-1).K^(-1),while retaining excellent compressive strength,flame-retardancy,and hydrophobicity.These outstanding properties highlight the great potential of H-PVDF foams as the thermal insulation materials for applications in aerospace,energy infrastructure,and other extreme environments.
基金funded by the LatvianCouncil of Science,the project“Investigation of Eco-Friendly Thermal Insulation Materials from Sustainable and Renewable Industrial Crops Residuals,”number lzp-2021/1-0599.
文摘This study examines the development of loose-fill thermal insulation materials derived from annual plant residues,such as wheat straw,water reeds,and corn stalks,processed using the chemimechanical pulping(CMP)technique.The chopped plants were soda-cooked for 30 min,varying NaOH concentration(2%–8%on a dry basis of biomass),and mechanically refined using different disc types.The CMPprocess enhances the homogeneity and stability of defibratedmaterial,yielding improved insulation properties compared to untreated chopped rawmaterials.Chemical analysis revealed that CMP increases cellulose content and reduces lignin levels,enhancing water retention and vapor diffusion properties.Settlement tests confirmed that CMP materials are more resistant to compaction under vibration,maintaining long-term performance.Additionally,the CMP enables the production of lightweight materials that require less resource consumption while achieving comparable thermal insulation performance.The investigated biobased materials offer a sustainable alternative to conventional insulation,with competing thermal conductivity values(0.041-0.046 W/mK)at the settlement-resistant bulk density level of 60 kg/m^(3).The thermal conductivity of CMP materials remains minimally affected.However,the resulting fibers demonstrate significant advantages in stability and material efficiency.This highlights its suitability for loose-fill applications to improve the sustainability of the construction.Using renewable plant residues,CMP-based insulation materials align with circular economy principles and contribute to environmental sustainability.This research underscores the potential of CMP materials to reduce greenhouse gas emissions,optimize resource use,and promote eco-friendly building practices.
基金supported by the National Key R&D Program of China(No.2021YFB3700103).
文摘The demand for anisotropic aerogels with excellent comprehensive properties in cutting-edge fields such as aerospace is growing.Based on the above background,a novel heterocyclic para-aramid nanofiber/reduced graphene oxide(HPAN/rGO)composite aerogel was prepared by combining electrospinning and unidirectional freeze-drying.The anisotropic HPAN/rGO composite aerogel exhibited a honeycomb morphology in the direction perpendicular to the growth of ice crystals,and a through-well structure of directed microchannels in the direction parallel to the temperature gradient.By varying the mass ratio of HPAN/rGO,a composite aerogel with an ultra-low density of 5.34-7.81 mg·cm^(-3) and an ultra-high porosity of 98%-99%was obtained.Benefiting from the anisotropic structure,the radial and axial thermal conductivities of HPAN/rGO-3 composite aerogel were 29.37 and 44.35 mW·m^(-1)·K^(-1),respectively.A combination of software simulation and experiments was used to analyze the effect of anisotropic structures on the thermal insulation properties of aerogels.Moreover,due to the intrinsic self-extinguishing properties of heterocyclic para-aramid and the protection of the graphene carbon layer,the composite aerogel also exhibits excellent flame retardancy properties,and its total heat release rate(THR)was only 5.8 kJ·g^(-1),which is far superior to many reported aerogels.Therefore,ultralight anisotropic HPAN/rGO composite aerogels with excellent high-temperature thermal insulation and flame retardancy properties have broad application prospects in complex environments such as aerospace.
基金funded by the National Natural Science Foundation of China(No.52236006,No.52176054)the Natural Science Foundation of Guangdong province(2024A1515012033).
文摘Integrating phase change materials(PCM)into thermal insulation materials offers a novel approach to aerospace thermal protection.Herein,we used waste biomass as a template;by selecting the appropriate carbonization temperature,we obtained carbon aerogels(CCA)with extremely high porosity(95.8%)and high pore volume.After encapsulating PEG2000,we achieved high enthalpy(137.79 J g^(−1),91%of pure PEG2000)and low thermal conductivity(0.137 W(m·K)^(–1),45% of pure PEG2000).Thanks to the rich hierarchical nano-micro porous structure of CCA and the high latent heat of PEG2000,CCA/PEG exhibits excellent thermal insulation properties(under a heating temperature of 131℃,the material takes 1400 s to reach its maximum temperature and can be maintained below 65℃)and cycle performance.Additionally,irradiation destroyed the structure of CCA/PEG,leading to the degradation of PEG and the formation of other carbonyl-containing compounds,which decreased its latent heat(4.2%)and thermal conductivity(16.1%).However,the irradiation-resistant CCA,acting as a protective layer,minimizes the impact of irradiation on PEG2000.Instead,irradiation enhances the hierarchical porous structure of the material,ultimately improving its thermal insulation performance.CCA/PEG has potential application prospects in thermal protection and aerospace and is a strong competitor for high-efficiency thermal insulation materials.
基金This work was funded by the National Natural Science Foun-dation of China(No.52304033)the National Key Research and Development Program of China(No.2023YFB2390200)Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization(No.DESGEEU-2023-10).
文摘The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock properties in deep reservoirs.High-performance thermal insulation materials are crucial for supporting ITP-Coring during deep oil and gas exploration.This study explores the impact of high-temperature and high-pressure(HTHP)conditions on hollow glass microsphere/epoxy(HGM/EP)thermal insulation materials,focusing on the interphase.Investigations of HGM/EP materials with varying hollow glass microsphere(HGM)strengths and volume fractions reveal that elevated temperatures cause the molecular chains of the epoxy resin matrix to relax,leading to matrix softening and a decline in mechanical properties.Additionally,high-pressure water infiltrates the material,damaging the interphase and HGMs,further compromising material performance.The combined HTHP environment accelerates this degradation.Dynamic mechanical analysis(DMA)shows that S60HS HGMs,which possess higher strength,interact more strongly with the matrix and exhibit higher entanglement density,resulting in superior interphase adhesion.This enhances stress transfer efficiency and reduces the loss of storage modulus at the interphase.Theoretical analysis indicates that the interphase thickness and modulus of S-f40 remain mostly unaffected after HTHP treatment,with values higher than the epoxy matrix.This correlates with DMA results,demonstrating that S-f40 has the smallest adhesion factor(A),indicating the highest interfacial stress transfer efficiency.S-f40 also exhibits optimal thermal conductivity and mechanical properties,making it ideal for ITP-Coring in deep reservoirs.These findings provide insights for optimizing materials in HTHP environments for deep reservoir exploration.
文摘The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal protection systems. The inverse problem of heat transfer is solved by the genetic algorithm and data from the steady heat transfer experiment of fibrous thermal insulations. The density radiation attenuation coefficient, the albedo of fibrous thermal insulations and the surface emissivity of reflective screens are optimized. Finally, the one-dimensional steady heat transfer model of MTIs with optimized thermal physical parameters is verified by experimental data of the effective MTI conductivity.
基金supported by the National Natural Science Foundation of China(52171033)the Natural Science Foundation of Jiangsu Province(No.BK20201283).
文摘Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-stacking tendency,and high density.To tackle these challenges,MXene nanosheets were incorporated into polyacrylonitrile(PAN)nanofibers and subsequently assembled into a three-dimensional(3D)network structure through PAN carbonization,yielding MXene/C aerogels.The 3D network effectively extends the path of microcurrent transmission,leading to enhanced conductive loss of electromagnetic(EM)waves.Moreover,the aerogel’s rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXenebased absorbers.EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss(RL_(min))value of−53.02 dB(f=4.44 GHz,t=3.8 mm),and an effective absorption bandwidth(EAB)of 5.3 GHz(t=2.4 mm,7.44–12.72 GHz).Radar cross-sectional(RCS)simulations were employed to assess the radar stealth effect of the aerogels,revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m^(2).In addition to the MA performance,the MXene/C aerogel also demonstrates good thermal insulation performance,and a 5-mm-thick aerogel can generate a temperature gradient of over 30℃ at 82℃.This study provides a feasible design approach for creating lightweight,efficient,and multifunctional MXene-based MA materials.
基金supported by the Fundamental Research Funds for the Central Universities(2232019A3-03)the National Natural Science Foundation of China(52073053,21674019)+3 种基金Shanghai Rising-Star Program(21QA1400300)Shanghai Municipal Education Commission(17CG33)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-03-E00108)Science and Technology Commission of Shanghai Municipality(20520741100)。
文摘The materials with thermal insulating and fre-retardant properties are highly demanded for architectures to improve the energy efficiency.The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance.Here,we report an organic/inorganic composite aerogel with integrated double network structure,in which silica constituent homogeneously distribute in the anisotropic polyimide nanofber aerogel matrix and strong interfacial effect is formed between two components.The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%,which can withstand 500 cyclic fatigue tests at a compressive strain of 50%in the radial direction.The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity(21.2 mW m^(-1)K^(-1))and excellent resistance to a 1200℃flame without disintegration.The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fre,demonstrating great potential as efficient building materials.
基金supported by the National Natural Science Foundation of China (Grants 11202078, 51405123)the Fundamental Research Funds for the Central Universities (Grant 2017MS077)
文摘The present work introduces a novel concurrent optimization formulation to meet the requirements of lightweight design and various constraints simultaneously.Nodal displacement of macrostructure and effective thermal conductivity of microstructure are regarded as the constraint functions, which means taking into account both the loadcarrying capabilities and the thermal insulation properties.The effective properties of porous material derived from numerical homogenization are used for macrostructural analysis. Meanwhile, displacement vectors of macrostructures from original and adjoint load cases are used for sensitivity analysis of the microstructure. Design variables in the form of reciprocal functions of relative densities are introduced and used for linearization of the constraint function. The objective function of total mass is approximately expressed by the second order Taylor series expansion. Then, the proposed concurrent optimization problem is solved using a sequential quadratic programming algorithm, by splitting into a series of sub-problems in the form of the quadratic program. Finally, several numerical examples are presented to validate the effectiveness of the proposed optimization method. The various effects including initial designs, prescribed limits of nodal displacement, and effective thermal conductivity on optimized designs are also investigated. An amount of optimized macrostructures and their corresponding microstructures are achieved.
文摘Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have largely hampered their applications in these areas.This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers(CNFs)with continuous nanolayers of MOFs.The cross-linking gives the aerogels high mechanical strength but superelasticity(80%maximum recoverable strain,high specific compression modulus of^200 MPa cm3 g−1,and specific stress of^100 MPa cm3 g−1).The resultant lightweight aerogels have a cellular network structure and hierarchical porosity,which render the aerogels with relatively low thermal conductivity of^40 mW m−1 K−1.The hydrophobic,thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy.This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials.It presents a pathway for the design of thermally insulating,superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.
基金financially supported by the National R&D Program of China (No. 2017YFA0207400)the National Key Research and Development Plan (No. 2016YFA0300801)+1 种基金Program for Innovative and Entrepreneurial Leading Talents of DongguanFundamental Research Funds for the Central Universities (No. ZYGX2018J030)。
文摘In recent years, solar desalination and water evaporation/purification with various artificial architectures have drawn significant attention. Herein, we introduce a rational design structure for efficient solar water evaporation and purification, focusing on the balance between water transportation and thermal insulation.Natural wood after a simple flame treatment on the surface was utilized as the solar absorber, with a high solar absorbance(~90 %), good hydrophilicity, and excellent heat localization abilities. Besides,a thermal insulator(polystyrene foam) was used to further reduce the thermal loss, and the optimized ratio between the water path and thermal insulator was obtained. A set of floating foam-flamed-wood(F-F-wood) devices were fabricated with a high evaporation rate of 3.92 kgm-2 h-1, exhibiting photothermal purification abilities from seawater and wastewater containing organic dyes and heavy metals. This study sheds light on the rational design of scalable and low-cost devices for solar water evaporation and purification.
基金Funded by the National Natural Science Foundation of China(Nos.51308079,51408073 and 51278073)
文摘Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitant precursors as well as cumbrous multi-step hydrophobization process has often narrowed the field of applications. In this work, granular silica aerogel materials were synthesized by extracting Si O2 from recycled rich silicon coal gangue, followed by one-step hydrophobization and ambient pressure drying. Lightweight(about 0.16 g/cm3) and nanostructural aerogels were obtained through this route. They exhibit a 3D open porous microstructure with around 600 cm2/g surface area and 20 nm of the average pore diameter, thermal conductivity of 4-5 mm packed granules is 20-25 m W/(m·K), which was proved by both guarded hot plate and hot-wire transient methods. This study offers a new facile route for the synthesis of silica aerogel from recycled solid waste coal gangue and suggests a method, which may lead to a cost reduction in terms of industrial production.
