With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and ...With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and high sunlight reflection are developed for energy-efficient buildings.A solvent-assisted freeze-casting strategy is used to produce boron nitride nanosheet/polyvinyl alcohol(BNNS/PVA)composite aerogels with a tailored alignment channel structure.The effects of acetone and BNNS fillers on microstructures and multifunctional properties of aerogels are investigated.The acetone in the PVA suspension enlarges the cell walls to suppress the shrinkage,giving rise to a lower density and a higher porosity,accompanied with much diminished heat conduction throughout the whole product.The addition of BNNS fillers creates whiskers in place of disconnected transverse ligaments between adjacent cell walls,further ameliorating the thermal insulation transverse to the cell wall direction.The resultant BNNS/PVA aerogel delivers an ultralow thermal conductivity of 23.5 mW m^(−1) K^(−1) in the transverse direction.The superinsulating aerogel presents both an infrared stealthy capability and a high solar reflectance of 93.8%over the whole sunlight wave-length,far outperforming commercial expanded polystyrene foams with reflective coatings.The anisotropic BNNS/PVA composite aerogel presents great potential for application in energy-saving buildings.展开更多
The optical properties of coatings pigmented with different black colorants were systematically investigated and their surface temperatures and cooling energy savings were estimated. The black coatings pigmented with ...The optical properties of coatings pigmented with different black colorants were systematically investigated and their surface temperatures and cooling energy savings were estimated. The black coatings pigmented with chromite iron nickel black and manganese ferrite black spinel colorants are not cool enough to be energy efficient cool black coatings. The cool black coatings pigmented with NIR-transmitting perylene black and dioxazine purple colorants possess a green shade and a violet shade, respectively. The estimated surface temperature reduction values and annual cooling energy savings in Beijing range from 3.0°C and 1.21 kWhm-2yr-1 for the black coating pigmented with chromite iron nickel colorant to 13.8°C and 5.52 kWhm-2yr-1 for the black coating pigmented with dioxazine purple colorant, respectively.展开更多
基金supported by the Research Grants Council(GRF Projects:16205517,16209917,and 16200720)and Innovation and Technology Commission(ITS/012/19)of Hong Kong SAR.Technical assistance from the Materials Characterization and Preparation Facility(MCPF)the Advanced Engineering Material Facility(AEMF)the Environmental Central Facility(ENVF)at HKUST are also appreciated.
文摘With the mandate of worldwide carbon neutralization,pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice.Novel composite aerogels with super thermal insulation and high sunlight reflection are developed for energy-efficient buildings.A solvent-assisted freeze-casting strategy is used to produce boron nitride nanosheet/polyvinyl alcohol(BNNS/PVA)composite aerogels with a tailored alignment channel structure.The effects of acetone and BNNS fillers on microstructures and multifunctional properties of aerogels are investigated.The acetone in the PVA suspension enlarges the cell walls to suppress the shrinkage,giving rise to a lower density and a higher porosity,accompanied with much diminished heat conduction throughout the whole product.The addition of BNNS fillers creates whiskers in place of disconnected transverse ligaments between adjacent cell walls,further ameliorating the thermal insulation transverse to the cell wall direction.The resultant BNNS/PVA aerogel delivers an ultralow thermal conductivity of 23.5 mW m^(−1) K^(−1) in the transverse direction.The superinsulating aerogel presents both an infrared stealthy capability and a high solar reflectance of 93.8%over the whole sunlight wave-length,far outperforming commercial expanded polystyrene foams with reflective coatings.The anisotropic BNNS/PVA composite aerogel presents great potential for application in energy-saving buildings.
文摘The optical properties of coatings pigmented with different black colorants were systematically investigated and their surface temperatures and cooling energy savings were estimated. The black coatings pigmented with chromite iron nickel black and manganese ferrite black spinel colorants are not cool enough to be energy efficient cool black coatings. The cool black coatings pigmented with NIR-transmitting perylene black and dioxazine purple colorants possess a green shade and a violet shade, respectively. The estimated surface temperature reduction values and annual cooling energy savings in Beijing range from 3.0°C and 1.21 kWhm-2yr-1 for the black coating pigmented with chromite iron nickel colorant to 13.8°C and 5.52 kWhm-2yr-1 for the black coating pigmented with dioxazine purple colorant, respectively.
