The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.T...The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.展开更多
The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during t...The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during the long-term operation process.Moreover,the correction of the insulation failure model of polypropylene media is implemented.Some conclusions are drawn from a series of experiments.The breakdown strength of the insulation dielectrics decreases as the withstand time rises,with amaximum decrease of 37.91%compared to the polypropylene sample without withstand voltage.As the electric field increases from−20 to−100 kV/mm,the total amount of space charge,the trap energy level and the trap density inside the polypropylene increase by 524.15%,18.99%and 773.36%,respectively.In the capacitor simulation model,the electric field in the capacitor increases by 19.62%after presetting space charge relative to the nonspace charge.The experimental data are substituted into the inverse power model,and the trap parameters are used to modify the model.The results show that the ageing state of the polypropylene has a negative exponential relationship with the trap parameters.This paper provides an important reference for the study of the failure mechanism of polypropylene in high-voltage capacitors and the assessment of polypropylene ageing state.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
Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crossl...Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.展开更多
BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation intervention...BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation interventions in maintaining normothermia and reducing postoperative risks in this vulnerable group.AIM To evaluate the efficacy of perioperative composite insulation in older patients undergoing colorectal cancer surgery.METHODS We selected 100 older patients who underwent laparoscopic surgery for colorectal cancer at Huzhou Central Hospital from September 2023 to April 2024.Using a random number table,patients were divided into a control group and inter-vention group of 50 patients each.After returning to the regular ward,the con-ventional group received traditional insulation intervention measures,while the intervention group received composite insulation nursing intervention.We ob-served and recorded postoperative blood pressure and heart rate changes,as well as postoperative anesthesia recovery time and incidence of complications.RESULTS The statistical results showed significant differences(P<0.05)in heart rate changes and systolic blood pressure between the two groups.There was a sig-nificant change in heart rate between the groups immediately after surgery and at 15 and 30 minutes after surgery(P<0.05).The heart rate and systolic blood pressure of the intervention group were significantly lower than those of the control group at 15 and 30 minutes after surgery(P<0.05).The rewarming time of the intervention group was shorter than that of the control group,and the overall incidence of postoperative complications was significantly lower than that of the control group(P<0.05).CONCLUSION For elderly patients undergoing laparoscopic colorectal cancer surgery,a composite insulation intervention during the perioperative period can maintain body temperature,reduce postoperative stress,and significantly reduce the incidence of hypothermia and related complications.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
Hygroscopic hydrogel is a promising evaporativecooling material for high-power passive daytime cooling with water self-regeneration.However,undesired solar and environmental heating makes it a challenge to maintain su...Hygroscopic hydrogel is a promising evaporativecooling material for high-power passive daytime cooling with water self-regeneration.However,undesired solar and environmental heating makes it a challenge to maintain sub-ambient daytime cooling.While different strategies have been developed to mitigate heat gains,they inevitably sacrifice the evaporation and water regeneration due to highly coupled thermal and vapor transport.Here,an anisotropic synergistically performed insulation-radiation-evaporation(ASPIRE)cooler is developed by leveraging a dual-alignment structure both internal and external to the hydrogel for coordinated thermal and water transport.The ASPIRE cooler achieves an impressive average sub-ambient cooling temperature of~8.2℃ and a remarkable peak cooling power of 311 W m^(-2)under direct sunlight.Further examining the cooling mechanism reveals that the ASPIRE cooler reduces the solar and environmental heat gains without comprising the evaporation.Moreover,self-sustained multi-day cooling is possible with water self-regeneration at night under both clear and cloudy days.The synergistic design provides new insights toward high-power,sustainable,and all-weather passive cooling applications.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
This applied research seeks to explore feasible plant design for manufacturing insulation materials for construction projects using waste sheep fleece to address environmental issues related to wasted sheep wool and e...This applied research seeks to explore feasible plant design for manufacturing insulation materials for construction projects using waste sheep fleece to address environmental issues related to wasted sheep wool and enhance the gross national product. The process starts by collecting low-cost sheep fleece from farms and processed via a production line, including scouring, plucking, carding, thermal bonding, and packing. The design process involves determining an optimal location, infrastructure, staffing, machinery, environmental impact, and utilities. A final economic analysis is undertaken to estimate the product’s cost, selling price, and break-even point based on the anticipated capital and operational costs. The plant is intended to process 6778 tons of sheep wool annually. The study suggests that Mafraq Industrial City is a perfect location for the plant, and purchasing land and structures is the optimal option. The projected capital cost is 1,416,679 USD, while the anticipated operational costs amount to 3,206,275 USD. Insulation material production is estimated to be 114,756 m3 annually. The material may be manufactured into 1 m wide, 0.05 m thick sheets for 2.02 USD per square meter. Thus, for a 10-year plant, a 2.47 USD/m2 selling price breaks even in one year.展开更多
This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-bas...This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.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
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
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
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
This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-laye...This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-layered flat samples and cylindrical samples are prepared to imitate the interface in the PP-insulated EMJ.The DC conductivity,space charge,and breakdown strength are tested.The results demonstrate that in the EMJ manufacturing process,the lower wielding temperature leads to microdefects at the insulation interface.As shallow traps,the microdefects exacerbate hetero charge accumulation,thereby intensifying the electric field distortion and increasing the conductivity.Meanwhile,the interfacial microdefects lead to a reduction in the insulation breakdown strength.At 90°C,the normal and tangential breakdown strengths decrease by a maximum of 20.6%and 54.5%,respectively.Notably,the space charges and microdefects lead to a rapid decline in the breakdown strength after hetero polarity pre-stressing.Especially for the tangential breakdown strength,the maximum decrease rate reaches 22.9%.Therefore,the interfacial microdefects caused by the drop in the welding temperature are the primary factors leading to a serious decrease in the electrical properties of EMJ insulation,making the EMJ insulation weaker than PP cable insulation.展开更多
In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion s...In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion source.Through the finite element analysis method,the electrostatic analyses of insulators and grid plates were carried out,the material and structure parameters of insulators were determined.The maximum electric field around each insulator is about 4 kV/mm,and the maximum electric field between grids is about 14 kV/mm,which can meet the 120 keV withstand voltage holding.The insulation system for the positive ion source accelerator with 120 keV is designed,and the connection and basic parameters of insulators and support flanges are analyzed and determined.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
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
Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powde...Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powders were self-assembled and anchored onto the aerogel framework,followed by the deposition of carbon nanotubes(CNTs)via catalytic chemical vapor deposition,yielding MIL-88C/CuCo_(2)S_(4)-derived bamboo-like CNTs/carbon nanofiber aerogels(FCC@CC series).By modulating component loading ratios,the formation of a three-dimensional conduction network,the presence of heterogeneous interfaces,enhanced magnetic loss,and engineered defects synergistically optimized dielectric and magnetic loss.This adjustment improved the impedance matching of the composite carbon aerogel,resulting in exceptional EMW absorption performance.The FCC@CC2 sample achieved a minimum reflection loss of−71.15 dB and an effective absorption bandwidth of 6.10 GHz.CST simulations further demonstrated the practical applicability,showing a maximum radar cross-section reduction of 34.92 dB·m2.Power loss density and electric field distribution analyses corroborated the superior electromagnetic attenuation capabilities of the FCC@CC.This work establishes a methodology for developing lightweight multifunctional aerogels with pressure resistance,thermal insulation,and infrared stealth properties,providing a novel strategy for the fabrication of microwave absorbers for use under complex conditions.展开更多
Materials with a low thermal emittance surface have been used for many years to create reflective insulations that reduce the rate of heat flow across building envelopes. Reflective insulation technology is now being ...Materials with a low thermal emittance surface have been used for many years to create reflective insulations that reduce the rate of heat flow across building envelopes. Reflective insulation technology is now being combined with other energy conserving technologies to optimize overall thermal performance. The basis for the performance of reflective insulations and radiant barriers will be discussed along with the combination of these materials with cellular plastic or mineral fiber insulations to form hybrid insulation assemblies. Calculations of thermal resistance for enclosed reflective air spaces and current field data from Southeast Asia will be presented. These data show that reductions in heat transfer across the building enclosure can be effectively reduced by the use of enclosed reflective air spaces and attic radiant barriers. Reflective technology increases the overall thermal resistance of the building enclosure when used to insulate poured concrete structures.展开更多
基金supported by the Science and Technology Project of State Grid Corporation of China(Grant 5500-202455120A-1-1-ZN).
文摘The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.
基金supported in part by the National Natural Science Foundation of China(Grant 52277153).
文摘The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during the long-term operation process.Moreover,the correction of the insulation failure model of polypropylene media is implemented.Some conclusions are drawn from a series of experiments.The breakdown strength of the insulation dielectrics decreases as the withstand time rises,with amaximum decrease of 37.91%compared to the polypropylene sample without withstand voltage.As the electric field increases from−20 to−100 kV/mm,the total amount of space charge,the trap energy level and the trap density inside the polypropylene increase by 524.15%,18.99%and 773.36%,respectively.In the capacitor simulation model,the electric field in the capacitor increases by 19.62%after presetting space charge relative to the nonspace charge.The experimental data are substituted into the inverse power model,and the trap parameters are used to modify the model.The results show that the ageing state of the polypropylene has a negative exponential relationship with the trap parameters.This paper provides an important reference for the study of the failure mechanism of polypropylene in high-voltage capacitors and the assessment of polypropylene ageing state.
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 Basic Science Program(No.2022R1A2C2009700)through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICTthe Basic Science Research Capacity Enhancement Project(National Research Facilities and Equipment Center)through the Korea Ba-sic Science Institute funded by the Ministry of Education(No.2019R1A6C1010047)the Industrial Strategic Technology Development Program(No.20013248)through Korea Evaluation In-stitute of Industrial Technology funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.
文摘BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation interventions in maintaining normothermia and reducing postoperative risks in this vulnerable group.AIM To evaluate the efficacy of perioperative composite insulation in older patients undergoing colorectal cancer surgery.METHODS We selected 100 older patients who underwent laparoscopic surgery for colorectal cancer at Huzhou Central Hospital from September 2023 to April 2024.Using a random number table,patients were divided into a control group and inter-vention group of 50 patients each.After returning to the regular ward,the con-ventional group received traditional insulation intervention measures,while the intervention group received composite insulation nursing intervention.We ob-served and recorded postoperative blood pressure and heart rate changes,as well as postoperative anesthesia recovery time and incidence of complications.RESULTS The statistical results showed significant differences(P<0.05)in heart rate changes and systolic blood pressure between the two groups.There was a sig-nificant change in heart rate between the groups immediately after surgery and at 15 and 30 minutes after surgery(P<0.05).The heart rate and systolic blood pressure of the intervention group were significantly lower than those of the control group at 15 and 30 minutes after surgery(P<0.05).The rewarming time of the intervention group was shorter than that of the control group,and the overall incidence of postoperative complications was significantly lower than that of the control group(P<0.05).CONCLUSION For elderly patients undergoing laparoscopic colorectal cancer surgery,a composite insulation intervention during the perioperative period can maintain body temperature,reduce postoperative stress,and significantly reduce the incidence of hypothermia and related complications.
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 Young Scientists Fund of National Natural Science Foundation of China(Grant No.52303106)Research Grants Council of Hong Kong SAR(16200720)+3 种基金Environment and Conservation Fund of Hong Kong SAR(Project No.21/2022)Research Institute of Sports Science and Technology(Project No.P0043535)Research Institute of Advanced Manufacturing(Project No.P0046125)the start-up fund for new recruits of Poly U(Project No.P0038855 and P0038858)。
文摘Hygroscopic hydrogel is a promising evaporativecooling material for high-power passive daytime cooling with water self-regeneration.However,undesired solar and environmental heating makes it a challenge to maintain sub-ambient daytime cooling.While different strategies have been developed to mitigate heat gains,they inevitably sacrifice the evaporation and water regeneration due to highly coupled thermal and vapor transport.Here,an anisotropic synergistically performed insulation-radiation-evaporation(ASPIRE)cooler is developed by leveraging a dual-alignment structure both internal and external to the hydrogel for coordinated thermal and water transport.The ASPIRE cooler achieves an impressive average sub-ambient cooling temperature of~8.2℃ and a remarkable peak cooling power of 311 W m^(-2)under direct sunlight.Further examining the cooling mechanism reveals that the ASPIRE cooler reduces the solar and environmental heat gains without comprising the evaporation.Moreover,self-sustained multi-day cooling is possible with water self-regeneration at night under both clear and cloudy days.The synergistic design provides new insights toward high-power,sustainable,and all-weather passive cooling applications.
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This applied research seeks to explore feasible plant design for manufacturing insulation materials for construction projects using waste sheep fleece to address environmental issues related to wasted sheep wool and enhance the gross national product. The process starts by collecting low-cost sheep fleece from farms and processed via a production line, including scouring, plucking, carding, thermal bonding, and packing. The design process involves determining an optimal location, infrastructure, staffing, machinery, environmental impact, and utilities. A final economic analysis is undertaken to estimate the product’s cost, selling price, and break-even point based on the anticipated capital and operational costs. The plant is intended to process 6778 tons of sheep wool annually. The study suggests that Mafraq Industrial City is a perfect location for the plant, and purchasing land and structures is the optimal option. The projected capital cost is 1,416,679 USD, while the anticipated operational costs amount to 3,206,275 USD. Insulation material production is estimated to be 114,756 m3 annually. The material may be manufactured into 1 m wide, 0.05 m thick sheets for 2.02 USD per square meter. Thus, for a 10-year plant, a 2.47 USD/m2 selling price breaks even in one year.
基金supported by the National Natural Science Foundation of China(No.52077151)the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23208)the Key Laboratory of Engineering Dielectrics and Its Application,Ministry of Education(No.KFM202203).
文摘This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.
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.
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 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 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National Natural Science Foundation of China under the Grant 52477151 and 52077148Key Science and Technology Programme of Yunnan Province,China under Grant 202202AC080002.
文摘This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-layered flat samples and cylindrical samples are prepared to imitate the interface in the PP-insulated EMJ.The DC conductivity,space charge,and breakdown strength are tested.The results demonstrate that in the EMJ manufacturing process,the lower wielding temperature leads to microdefects at the insulation interface.As shallow traps,the microdefects exacerbate hetero charge accumulation,thereby intensifying the electric field distortion and increasing the conductivity.Meanwhile,the interfacial microdefects lead to a reduction in the insulation breakdown strength.At 90°C,the normal and tangential breakdown strengths decrease by a maximum of 20.6%and 54.5%,respectively.Notably,the space charges and microdefects lead to a rapid decline in the breakdown strength after hetero polarity pre-stressing.Especially for the tangential breakdown strength,the maximum decrease rate reaches 22.9%.Therefore,the interfacial microdefects caused by the drop in the welding temperature are the primary factors leading to a serious decrease in the electrical properties of EMJ insulation,making the EMJ insulation weaker than PP cable insulation.
基金supported by National Natural Science Foundation of China(No.11975261)。
文摘In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion source.Through the finite element analysis method,the electrostatic analyses of insulators and grid plates were carried out,the material and structure parameters of insulators were determined.The maximum electric field around each insulator is about 4 kV/mm,and the maximum electric field between grids is about 14 kV/mm,which can meet the 120 keV withstand voltage holding.The insulation system for the positive ion source accelerator with 120 keV is designed,and the connection and basic parameters of insulators and support flanges are analyzed and determined.
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 Natural Science Foundation of Shandong Province(Nos.2024TSGC0550,2023TSGC0545,and 2023TATSGC025)Key Technology Research and Development Program of Shandong Province(No.2021ZLGX01)The authors would like to thank Conghua Qi from Shiyanjia Lab(www.shiyanjia.com)for TEM test.The scientific calculations in this paper have been done on the HPC Cloud Platform of Shandong University.
文摘Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powders were self-assembled and anchored onto the aerogel framework,followed by the deposition of carbon nanotubes(CNTs)via catalytic chemical vapor deposition,yielding MIL-88C/CuCo_(2)S_(4)-derived bamboo-like CNTs/carbon nanofiber aerogels(FCC@CC series).By modulating component loading ratios,the formation of a three-dimensional conduction network,the presence of heterogeneous interfaces,enhanced magnetic loss,and engineered defects synergistically optimized dielectric and magnetic loss.This adjustment improved the impedance matching of the composite carbon aerogel,resulting in exceptional EMW absorption performance.The FCC@CC2 sample achieved a minimum reflection loss of−71.15 dB and an effective absorption bandwidth of 6.10 GHz.CST simulations further demonstrated the practical applicability,showing a maximum radar cross-section reduction of 34.92 dB·m2.Power loss density and electric field distribution analyses corroborated the superior electromagnetic attenuation capabilities of the FCC@CC.This work establishes a methodology for developing lightweight multifunctional aerogels with pressure resistance,thermal insulation,and infrared stealth properties,providing a novel strategy for the fabrication of microwave absorbers for use under complex conditions.
文摘Materials with a low thermal emittance surface have been used for many years to create reflective insulations that reduce the rate of heat flow across building envelopes. Reflective insulation technology is now being combined with other energy conserving technologies to optimize overall thermal performance. The basis for the performance of reflective insulations and radiant barriers will be discussed along with the combination of these materials with cellular plastic or mineral fiber insulations to form hybrid insulation assemblies. Calculations of thermal resistance for enclosed reflective air spaces and current field data from Southeast Asia will be presented. These data show that reductions in heat transfer across the building enclosure can be effectively reduced by the use of enclosed reflective air spaces and attic radiant barriers. Reflective technology increases the overall thermal resistance of the building enclosure when used to insulate poured concrete structures.
