In recent years,bamboo,as a green building material,has attracted more and more attention worldwide.Inspired by the investigation of cross-laminated timber in structural systems,a new engineered cross-laminated bamboo...In recent years,bamboo,as a green building material,has attracted more and more attention worldwide.Inspired by the investigation of cross-laminated timber in structural systems,a new engineered cross-laminated bamboo(CLB)consisting of the cross lamination of bamboo scrimber plates is proposed in this paper.To evaluate its potential in structural applications,the thermal insulation performances of the CLB walls and CLB walls with the EPS foam plate were studied and evaluated by the temperature-controlled box-heat flow meter method.Test results indicated that the thermal insulation performance improved with the increase of thickness,but different wall configurations had little effect on the thermal insulation performance under the same thickness of the CLB wall.The thermal insulation performance of EPS-CLB composite wall was much better than that of CLB wall.In addition,a relatively acceptable accuracy of the theoretical calculations was proved.Finally,the influence of different locations of the EPS foam plate on heat transfer coefficient can be neglected as it was studied based on the validated numerical models.展开更多
In order to solve the problem of poor thermal insulation in the current wood-plastic building,two kinds of structural wood wall integrated with wood plastic composite(WPC)are designed,and the thermal insulation perfor...In order to solve the problem of poor thermal insulation in the current wood-plastic building,two kinds of structural wood wall integrated with wood plastic composite(WPC)are designed,and the thermal insulation performances of the walls are studied.The results show that the WPC integrated wall with frame-shear structure has a good stability,and the excellent performance of the WPC can be fully realized.Wall studs and wall panels are important factors affecting the thermal performance of the walls.Wood plastic materials can meet the thermal performance requirements of the walls.The single-layer frame walls and double-layer frame walls integrated with the WPC both have a good thermal performance.According to‘Design Standard for Energy Efficiency of Public Buildings(GB 50189-2015)’,the heat transfer coefficient of the single-layer frame wall integrated with 20 mm thick WPC wall boards and WPC wall studs is 0.414 W/(m^(2)•K),which can meet the standard of wall thermal levelⅡt and is suitable for cold areas.The heat transfer coefficient of the double-layer frame wall integrated with 50 mm thick WPC wall panel and WPC wall studs is 0.207 W/(m^(2)•K),which can meet the standard of wall thermal levelⅠt and is suitable for severe cold areas.展开更多
Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TB...Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.展开更多
As a heat-resistant wave-absorbing material,silicon carbide(SiC)aerogel has become a research hotspot at present.However,the most common silicon sources are organosilanes,which are costly and toxic.In this work,SiC ae...As a heat-resistant wave-absorbing material,silicon carbide(SiC)aerogel has become a research hotspot at present.However,the most common silicon sources are organosilanes,which are costly and toxic.In this work,SiC aerogels were successfully prepared by using water glass as the silicon source.Specifically,the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process,and the effect on SiC aerogel microwave absorption properties was investigated.The SiC aerogels prepared with Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity,with a minimum reflection loss value of-46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz.They also have good physical properties,such as the density of0.0444 g/cm^(3),the thermal conductivity of 0.0621 W/(m·K),and the specific surface area of 1099 m^(2)/g.These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.展开更多
The low thermal conductivity and light mass of castables for tundish permanent linings are crucial for minimizing the heat loss of molten steel.In consideration of the low bulk density and thermal conductivity of pear...The low thermal conductivity and light mass of castables for tundish permanent linings are crucial for minimizing the heat loss of molten steel.In consideration of the low bulk density and thermal conductivity of pearlescent sand,the thermal insulation performance of castables was attempted to be improved by adding pearlescent sand.Pearlescent sand was modified to prevent the strength of its porous structure from deteriorating.The modification mechanism of pearlescent sand and the effect of pearlescent sand on the performance of bauxite castables were studied.The results suggested that the addition of the modified pearlescent sand significantly raised the apparent porosity and decreased the bulk density of bauxite castable.At 1000℃,the bulk density of more than 60%of the modified pearlescent sand-bauxite castable was only 2.03 g/cm^(3).The mechanical properties and thermal shock resistance of the modified pearlescent sand-bauxite castable were inferior to those of conventional bauxite castable but were adequate to meet the use conditions of casta-bles for tundish permanent linings.At high temperatures of 200-800℃,the thermal conductivity of more than 60%of the modified pearlescent sand-bauxite castable was smaller than that of conventional bauxite castable.The addition of the modified pearlescent sand can greatly reduce the thermal conductivity and bulk density of bauxite castable.展开更多
We synthesized tungsten-doped vanadium dioxide(W-VO_(2))particles via a one-step hydrothermal method,followed by their integration with antimony-doped tin oxide(ATO)nanoparticles to formulate a composite coating.Subse...We synthesized tungsten-doped vanadium dioxide(W-VO_(2))particles via a one-step hydrothermal method,followed by their integration with antimony-doped tin oxide(ATO)nanoparticles to formulate a composite coating.Subsequently,the VO_(2)/ATO composite coating was fabricated through a spin-coating process.The impact of varying W-VO_(2) content and coating thickness on the performance of the composite coatings was systematically investigated by employing X-ray diffraction,particle size distribution analysis,spectrometry,and other pertinent test methodologies.Our findings revealed that an escalation in both W-VO_(2) content and coating thickness retained high transmittance in the near-infrared band at lower temperatures.However,as the temperature increased,a notable reduction in transmittance in the near-infrared band was observed,alongside a slight decrease in transmittance within the visible band.Remarkably,when the W-VO_(2) content reached 5%and the coating thickness was 1253 nm,the transmittance of the composite coating surpassed 80%.Furthermore,the heat insulation effect achieved a remarkable 10.0℃increase.Consequently,the synthesized composite coating demonstrates significant potential for smart glass applications,particularly in the realm of heat-insulating glass.展开更多
A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was...A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was facilitated by the atomic rearrangement of Al_(2)O_(3) and SiO_(2) catalyzed with MoO_(3).The effects of the molar ratio of Al_(2)O_(3) to SiO_(2),MoO_(3) content,sintering time,and sintering temperature on the structure and properties of(xAl_(2)O_(3)·ySiO_(2))m(MoO_(3))n-T-t(T=sintering temperature,and t=sintering duration)ceramics were comprehensively studied.The molar ratio of Al_(2)O_(3) to SiO_(2) had a more significant effect on the morphology of the whiskers,while the other three conditions generally promote whisker growth.Under conditions of x:y=3:1.8,m:n=9:1,T=1300℃,and t=3 h,(3Al_(2)O_(3)·1.8SiO_(2))9(MoO_(3))1-1300℃-3 h ceramics exhibited a satisfactory compressive strength of 4.81 MPa at a density of 0.76 g/cm3.Microstructural analysis revealed that a multi-level reinforcement structure was obtained by the interlaced distribution of tiny and large whiskers,significantly increasing the crack deflection area and enhancing the crack deflection resistance when resisting external forces.After 100 thermal shock cycles between room temperature and 1300℃,the compressive strength retention rate was 77.13%.In addition,the multi-scale whisker-overlapping structure also has a high specific surface area(1.83 m^(2)/g),high porosity(74.18%),and small pore size(7.44μm).The thermal conductivity was as low as 0.260 W/(m·K),and the ceramic maintained a rear-side temperature below 200℃ when subjected to a 1300℃ butane flame.In addition,the regulatory mechanism between parameters,structure,and properties was analyzed in detail,providing data support for research on porous materials.展开更多
基金from the National Natural Research and Development Fund(9Z05000049D0)Integrated Key Precast Components and New Wood-bamboo Composite Structure(2017YFC0703502).
文摘In recent years,bamboo,as a green building material,has attracted more and more attention worldwide.Inspired by the investigation of cross-laminated timber in structural systems,a new engineered cross-laminated bamboo(CLB)consisting of the cross lamination of bamboo scrimber plates is proposed in this paper.To evaluate its potential in structural applications,the thermal insulation performances of the CLB walls and CLB walls with the EPS foam plate were studied and evaluated by the temperature-controlled box-heat flow meter method.Test results indicated that the thermal insulation performance improved with the increase of thickness,but different wall configurations had little effect on the thermal insulation performance under the same thickness of the CLB wall.The thermal insulation performance of EPS-CLB composite wall was much better than that of CLB wall.In addition,a relatively acceptable accuracy of the theoretical calculations was proved.Finally,the influence of different locations of the EPS foam plate on heat transfer coefficient can be neglected as it was studied based on the validated numerical models.
文摘In order to solve the problem of poor thermal insulation in the current wood-plastic building,two kinds of structural wood wall integrated with wood plastic composite(WPC)are designed,and the thermal insulation performances of the walls are studied.The results show that the WPC integrated wall with frame-shear structure has a good stability,and the excellent performance of the WPC can be fully realized.Wall studs and wall panels are important factors affecting the thermal performance of the walls.Wood plastic materials can meet the thermal performance requirements of the walls.The single-layer frame walls and double-layer frame walls integrated with the WPC both have a good thermal performance.According to‘Design Standard for Energy Efficiency of Public Buildings(GB 50189-2015)’,the heat transfer coefficient of the single-layer frame wall integrated with 20 mm thick WPC wall boards and WPC wall studs is 0.414 W/(m^(2)•K),which can meet the standard of wall thermal levelⅡt and is suitable for cold areas.The heat transfer coefficient of the double-layer frame wall integrated with 50 mm thick WPC wall panel and WPC wall studs is 0.207 W/(m^(2)•K),which can meet the standard of wall thermal levelⅠt and is suitable for severe cold areas.
基金Supported by Scientific and Technological Innovation of Shaanxi Provincial State-Owned Capital Operation Budget(2022-056)Institute's Self-Developed Technology Program(0801YK2317)+4 种基金Qin Chuangyuan Cites High-Level Innovation and Entrepreneurship Talent Program(QCYRCXM-2023-120)Qin Chuangyuan Industry Cluster Zone“Four Chains”Integration Program(2024CY-JJQ-46)National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.
基金supported by the Program of Applied Basic Research Program of Shanxi Province,China (No.202103021223055)the Shanxi Scholarship Council of Chinathe Key R&D program of Shanxi Province,China (No.202102030201006)。
文摘As a heat-resistant wave-absorbing material,silicon carbide(SiC)aerogel has become a research hotspot at present.However,the most common silicon sources are organosilanes,which are costly and toxic.In this work,SiC aerogels were successfully prepared by using water glass as the silicon source.Specifically,the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process,and the effect on SiC aerogel microwave absorption properties was investigated.The SiC aerogels prepared with Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity,with a minimum reflection loss value of-46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz.They also have good physical properties,such as the density of0.0444 g/cm^(3),the thermal conductivity of 0.0621 W/(m·K),and the specific surface area of 1099 m^(2)/g.These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.
基金support provided by the National Natural Science Foundation of China(U21A20317).
文摘The low thermal conductivity and light mass of castables for tundish permanent linings are crucial for minimizing the heat loss of molten steel.In consideration of the low bulk density and thermal conductivity of pearlescent sand,the thermal insulation performance of castables was attempted to be improved by adding pearlescent sand.Pearlescent sand was modified to prevent the strength of its porous structure from deteriorating.The modification mechanism of pearlescent sand and the effect of pearlescent sand on the performance of bauxite castables were studied.The results suggested that the addition of the modified pearlescent sand significantly raised the apparent porosity and decreased the bulk density of bauxite castable.At 1000℃,the bulk density of more than 60%of the modified pearlescent sand-bauxite castable was only 2.03 g/cm^(3).The mechanical properties and thermal shock resistance of the modified pearlescent sand-bauxite castable were inferior to those of conventional bauxite castable but were adequate to meet the use conditions of casta-bles for tundish permanent linings.At high temperatures of 200-800℃,the thermal conductivity of more than 60%of the modified pearlescent sand-bauxite castable was smaller than that of conventional bauxite castable.The addition of the modified pearlescent sand can greatly reduce the thermal conductivity and bulk density of bauxite castable.
基金Funded by Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park(No.Z221100006722022)。
文摘We synthesized tungsten-doped vanadium dioxide(W-VO_(2))particles via a one-step hydrothermal method,followed by their integration with antimony-doped tin oxide(ATO)nanoparticles to formulate a composite coating.Subsequently,the VO_(2)/ATO composite coating was fabricated through a spin-coating process.The impact of varying W-VO_(2) content and coating thickness on the performance of the composite coatings was systematically investigated by employing X-ray diffraction,particle size distribution analysis,spectrometry,and other pertinent test methodologies.Our findings revealed that an escalation in both W-VO_(2) content and coating thickness retained high transmittance in the near-infrared band at lower temperatures.However,as the temperature increased,a notable reduction in transmittance in the near-infrared band was observed,alongside a slight decrease in transmittance within the visible band.Remarkably,when the W-VO_(2) content reached 5%and the coating thickness was 1253 nm,the transmittance of the composite coating surpassed 80%.Furthermore,the heat insulation effect achieved a remarkable 10.0℃increase.Consequently,the synthesized composite coating demonstrates significant potential for smart glass applications,particularly in the realm of heat-insulating glass.
基金supported by the Fundamental Research Funds for the Central Universities of Civil Aviation University of China(No.3122024050)the Undergraduate Innovation Project of Civil Aviation University of China(Nos.202410059049 and IECAUC2025043).
文摘A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was facilitated by the atomic rearrangement of Al_(2)O_(3) and SiO_(2) catalyzed with MoO_(3).The effects of the molar ratio of Al_(2)O_(3) to SiO_(2),MoO_(3) content,sintering time,and sintering temperature on the structure and properties of(xAl_(2)O_(3)·ySiO_(2))m(MoO_(3))n-T-t(T=sintering temperature,and t=sintering duration)ceramics were comprehensively studied.The molar ratio of Al_(2)O_(3) to SiO_(2) had a more significant effect on the morphology of the whiskers,while the other three conditions generally promote whisker growth.Under conditions of x:y=3:1.8,m:n=9:1,T=1300℃,and t=3 h,(3Al_(2)O_(3)·1.8SiO_(2))9(MoO_(3))1-1300℃-3 h ceramics exhibited a satisfactory compressive strength of 4.81 MPa at a density of 0.76 g/cm3.Microstructural analysis revealed that a multi-level reinforcement structure was obtained by the interlaced distribution of tiny and large whiskers,significantly increasing the crack deflection area and enhancing the crack deflection resistance when resisting external forces.After 100 thermal shock cycles between room temperature and 1300℃,the compressive strength retention rate was 77.13%.In addition,the multi-scale whisker-overlapping structure also has a high specific surface area(1.83 m^(2)/g),high porosity(74.18%),and small pore size(7.44μm).The thermal conductivity was as low as 0.260 W/(m·K),and the ceramic maintained a rear-side temperature below 200℃ when subjected to a 1300℃ butane flame.In addition,the regulatory mechanism between parameters,structure,and properties was analyzed in detail,providing data support for research on porous materials.
