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There is an increasing demand for highly efficient thermal insulating materials in buildings. This study presents a novel solution incorporating nanomaterials, such as silica aerogel, which can achieve low thermal conductivity values (below 0.030 W m−1 K−1) in renders. A key challenge of using aerogels is their low mechanical strength and high capillary water absorption. Here we describe a novel approach employing fibres which mitigates against some key properties which are decreased as a consequence of using aerogel. The incorporation of aramid (0.50%), sisal (0.10%), and biomass (0.10%) fibres (by total volume) was evaluated experimentally in terms of physical, mechanical, and microstructural properties. A synergistic effect between the fibres and aerogel increased mechanical resistance and a reduction in the capillary water absorption, when compared to the reference render (without fibres), whilst maintaining the low thermal conductivity. However, these properties depended significantly on whether the fibres were synthetic or organic. This study is important as it demonstrates that aerogel-based fibre-enhanced thermal renders can contribute to higher energy efficiency in both new construction and retrofitting. The use of these materials will have a direct positive impact on addressing the climate crisis. [ABSTRACT FROM AUTHOR]

• Long-term heat exposure above critical temperature can induce continuous degeneration of thermal insulation property for Fe-based amorphous coating, revealing an importance of kinetic effect. • The coupling effect of microstructure transformation and structural sintering is disclosed, leading to a particular insight into the degeneration mechanism. • The low atomic diffusivity of amorphous phase retards the progress including crystallization transition, grain growth and pore healing, resulting in a sluggish degeneration of thermal insulation property. Fe-based amorphous coatings have been proposed to perform a promising thermal barrier application, however, the uncertain degeneration of properties induced by thermal stimulation is significantly concerned owing to their metastable nature. Herein, Fe 57 Cr 15 Nb 4 B 20 Si 4 amorphous coating with a low thermal conductivity was employed to investigate the degeneration of thermal insulation property and related mechanisms during long-term heat exposure. Excellent stability can be defined for the amorphous coating when annealed below glass transition temperature, despite a slight increase of thermal conductivity induced by structural relaxation. Extraordinary increase of thermal conductivity is found when prolonged annealing time at a critical temperature of 600 °C. The sluggish structural sintering dominates thermal conductivity to increase, whereas the effect of precipitated ultrafine nanocrystals is little. The cooperation of grain coarsening and structural sintering leads to a dramatical increase of thermal conductivity at the initial stage of 850 °C annealing, while the relatively low increase of thermal conductivity with prolonged duration is ascribed to the further grain growth. The obtained results demonstrate a comprehensive understanding on the thermal evolution of Fe-based amorphous coatings and form a basis for future works aiming to shed further light on the degeneration of related metallic coatings at high temperatures. [ABSTRACT FROM AUTHOR]

• Fully bio-sourced building insulation materials from rice straw and natural binders are developed. • A crosslinking method is proposed to prevent the water solubility issue. • The effect of fiber size, binder type and binder ratio on the hygrothermal properties is investigated. • Alginate-based composites shows more serious mold growth than chitosan-based composites. Conversion agricultural straws to building insulation materials has attracted great interest due to their good hygrothermal properties and low carbon footprint. In this study, fully bio-sourced composite materials were designed based on rice straw and natural binders. Sodium alginate and chitosan were used as the binders. A crosslinking method was proposed to prevent the water-soluble issue of the composites using sodium alginate as the binder. The influence of fiber size, binder type and binder ratio on the hygrothermal properties of the composite materials made of rice straw were investigated. It was found that all the materials are insulating with their thermal conductivity values between 0.038 and 0.047 W/(m⋅K). The alginate-based composites had the higher water vapor permeability and moisture sorption capacity than the chitosan-based composites. Larger fiber size and lower binder ratio resulted in lower thermal conductivity and higher water vapor permeability. However, fiber size and binder ratio had a negligible effect on moisture sorption capacity of the composite materials. Additionally, the mold growth was investigated by exposing the composite materials to severe conditions, i.e., 93% RH and 97% RH at 20 °C. Mold proliferation was found to be easier and quicker in the surface of alginate-based composites compared to the chitosan-based composites. [ABSTRACT FROM AUTHOR]

The correlation between the thermal transport properties and microstructure features of amorphous coatings is crucial for reliable thermal insulation applications. In this work, an Fe 48 Cr 15 Mo 14 C 15 B 6 Y 2 amorphous coating prepared by high-velocity oxygen-fuel spraying (HVOF) was employed to reveal this relationship under long-term heating. From the combined effects of the amorphous phase and unique coating structure, the proposed coating exhibits an extremely low thermal conductivity of 1.92 W/(m∙K), granting a significant potential for being as metal-based thermal barrier coatings. Isothermal annealing experiments below the glass transition temperature demonstrate that the thermal insulation property can maintain stability with prolonged annealing time, despite a slight degradation relative to the as-sprayed coating which is ascribed to structural relaxation. Although nearly full crystallization can be slowly induced by annealing at the critical temperature of 600 °C, the thermal conductivity displays a distinct two-stage variation with annealing time, which is primarily attributed to the sluggish sintering of the coating structure. Moreover, grain growth and rapid structural sintering result in a drastic degradation of thermal insulation in the early stage of annealing at 850 °C, whereas grain growth upon prolonged annealing governs further variation of thermal conductivity. The results of this study not only provide important insights into the degeneration mechanism of thermal insulation of Fe-based amorphous coating, but also present an inspiration for exploring the degeneration mechanism of the most metallic coatings serving at high temperatures. • The Fe-based amorphous coating exhibits an extremely low thermal conductivity of κ = 1.92 W/(m∙K). • The degeneration mechanism of thermal insulation property of Fe-based amorphous coating is disclosed. • The low atomic diffusivity retards the bridge-connection of interlamellar pores, resulting in a sluggish sintering kinetics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Expanded lightweight plates were prepared by combining expanded glass, expanded vermiculite, and expanded perlite particles with an innovative TEOS/MTMS sol-gel binder. • Expanded glass based plate exhibited the greatest compressive strength (7.04 ± 0.44 MPa) and the highest direct tensile strength (0.486 ± 0.04 MPa). • The long term water absorbency values of expanded perlite based plate was found to be 1.76 ± 0.1 v% in the 1st day and increased slightly to 9.96 ± 0.04 v% in the 28th day. • Thermal conductivity coefficient of expanded glass based plate performed the best result which was measured as 0.125 W/m.K at 25 °C. • NIR-reflective property of expanded glass based plate was recorded as 83.2 ± 0.5 %. • All inorganic-based plates exhibited high fire resistance performance (withstand temperatures of up to ∼900 °C for 30 min). Thermal insulation materials are a great solution to minimize energy consumption for construction applications. Especially, expanded inorganic lightweights are excellent candidates in terms of their low thermal conductivity and high fire resistance properties. Sol-gel type inorganic based binders are also useful chemical substances to combine lightweight particles. In current study, inorganic-based plates were developed by using expanded glass, expanded vermiculite, and expanded perlite particles with a novel tetraethoxysilan (TEOS)/methyltrimethoxysilane (MTMS) sol-gel binder. The chemical, physical, mechanical and thermal properties of the plates were examined comparatively to reveal the effect of expanded lightweight particle types in the plates. According to the experimental results, the compressive strength of the developed plates was between 7.04 ± 0.44 MPa and 3.15 ± 0.17 MPa whilst the direct tensile strength ranged from 0.486 ± 0.04 MPa and 0.079 ± 0.04 MPa, respectively. Furthermore, the long term water absorbency values of the plates on the 28th day varied between 9.96 ± 0.04 v% and 49.8 ± 0.8 v%. On the other hand, while the thermal conductivity coefficient of the plates at 25 °C ranged from 0.125 to 0.254 W/m.K, infrared reflectance properties were determined between 83.2 ± 0.5 % and 64.1 1.8 %. Besides, all inorganic-based plates exhibited high fire resistance performance (withstand temperatures of up to ∼900 °C for 30 min). The results demonstrated that utilizing expanded inorganic lightweight particles with TEOS/MTMS sol-gel binder could be a promising combination to construct energy saving insulating plates to overcome poor fire resistance properties of conventional organic materials. [ABSTRACT FROM AUTHOR]

• Part of water was pre-located in the lightweight aggregates (LWA) for producing HPLC. • The increasing amount of LWA decreased the density of HPLC significantly. • The water penetration and ion permeability of HPLC were very low. • The HPLC exhibited high structural efficiency and low thermal conductivity; • The dislocation of mixing water method enhanced the microhardness of the paste matrix. To prepare high-performance concrete, the mixing water was normally blended with the dry constituents directly, whereas in this study part of water was pre-located in the lightweight aggregates (LWA) for producing a high-performance lightweight concrete (HPLC). With the pre-location of water in the LWA, an extremely low w / b ratio paste (ultra high-performance composite) was resulted for producing HPLC. High-performance cement mortar (HPCM) was prepared with similar volumes of natural aggregates for comparison. Based on the initial spatial dislocation of mixing water in two systems, the physical, thermal and durability properties of high-performance cementitious composites were evaluated and compared. The results showed that the HPLC experienced delayed heat evolution when compared with that of the HPCM, while the cumulative heat output and degree of cement hydration of the two systems were similar. With the use of an increasing amount of LWA, the density of HPLC decreased significantly while the water penetration and ion permeability of HPLC were comparable to those of HPCM. More importantly, the HPLC exhibited a higher structural efficiency and much lower thermal conductivity than the HPCM. In addition to the pozzolanic reactivity and internal curing provided by the water-entrained LWA, the dislocation of mixing water method also enhanced the microhardness of the paste matrix, which contributed to the excellent performance of HPLC. [ABSTRACT FROM AUTHOR]

[Display omitted] • This research investigates the composites obtained from EP and camelina stalks. • Thermal, physical and mechanical properties of the new bio-composites were studied. • The thermal conductivity of the composites decreased with the addition of expanded perlite. • The water absorption, UPV and compressive strengths of the composites to which expanded perlite was added increased. • C45 and C45P5 composites can be used as an alternative to thermal insulation materials. • Thermal conductivity, unit weight, compressive strength and UPV decreased as the camelina ratio increased. Increasing urbanization has made lightweight construction materials with low thermal conductivity important. One of these materials, which has gained importance recently, is bio-composite materials consisting of agricultural wastes. The usability of camelina stalks, an agricultural waste, in the production of bio-composite has not been studied. The aim of this research is to develop new lightweight bio-composites with camelina stalks filled. For this, 11 composite mixtures using unsaturated polyester resin as the binder were created. Camelina stalks at 25, 30, 35, 40 and 45 % substitution ratios were used in half of 10 mixtures outside reference. Later, five more different mixtures by adding expanded perlite (EP) up to 5 % of the amount of camelina stalks in each mixture were produced. The physical, mechanical and thermal properties of the bio-composites produced with polyester binder were examined and the microstructure analysis was performed by SEM. The results showed that thermal conductivity, unit weight, compressive strength and ultrasonic pulse velocity (UPV) decreased as the ratio of the camelina stalks increased. The lowest thermal conductivity value was determined as 0.0842 W/(mK) in the 45 % camelina + 5 % EP filled specimen. The highest compressive strength value of the mixtures excluding the reference specimen was found to be 35.78 MPa in the 25 % camelina + 5 % EP-filled specimen. The addition of EP to the composites increased the water absorption, UPV and compressive strengths, but decreased the thermal conductivity. The results showed that camelina stalks can be used to produce sustainable bio-composites. [ABSTRACT FROM AUTHOR]

Hospitals consume large quantities of energy to produce hot water and offset the distribution and recirculation thermal losses. This paper analyses a solar thermal system combined with gas boilers for domestic hot water production in a medium-size hospital. The solar contribution to the total demand (27%) is below design expectations (75%), resulting in significant gas consumption. The energy audit conducted in the first part of the paper highlights the vast thermal loss through poorly insulated pipes as the primary cause of the poor solar fraction. This issue is endemic to hot water-intensive buildings. The second part of the paper addresses the techno-economic evaluation of energy retrofit measures to reach a solar fraction of 60%. The simulation results indicate that cost-optimised solutions generally expand the solar caption area by 43–57% and improve insulations to reduce thermal losses by 70%. Depending on carbon taxes, the cost of hot water production would be 31–41 cent-€/kWh, which represents a 15–45% reduction from the current costs. Under stringent climate policies, installing heat pumps may further enhance economic competitiveness. The indicators and charts developed in this work are helpful decision-making tools concerning the energy refurbishment of solar domestic hot water systems. • Solar thermal system combined with gas boilers to supply hot water in a hospital. • Solar fraction below design expectations (28% vs. 75%) due to huge thermal losses. • Enhanced thermal insulation and extra collectors to reach 60% solar fraction. • Refurbished system with hot water production cost estimated at 31–41 cent-€/kWh. • A heat pump would minimise carbon taxes in ambitious climate policy scenarios. [ABSTRACT FROM AUTHOR]

• Laminated CMPFA membranes were fabricated via electrospinning, vacuum filtration, and magnetron sputtering. • Waster polyester clothes were used to fabricate substrate membranes. • The asymmetrically wettable improve sweat transportation properties of CMPFA membranes. • Laminated CMPFA membranes can reflect thermal radiation and absorb solar energy to achieve dual thermal insulation. • The obtained CMPFA membranes have potential application in human thermal management. Wearable polyester fiber materials with excellent sweat transportation and enhanced thermal management properties have received increasing attention in functional materials and energy saving fields because of not only for wearing comfort but also for developing advanced energy-saving materials. Herein, this work presents an effective and sustainable strategy for fabrication of laminated CNTs-MnO 2 nanowires/PET fibers@Ag (CMPFA) membranes using waste polyethylene terephthalate (PET) fabric, manganese dioxide (MnO 2) nanowires, carbon nanotubes (CNTs) and silver nanoparticles as building blocks through electrospinning, vacuum filtration and subsequent magnetron sputtering processes, as well as its application in personal thermal management. The results indicated that simulated sweat on the PET fibers@Ag side can penetrate quickly into the CNTs-MnO 2 nanowires side within 2.4 s, implying the excellent sweat transport properties of laminated CMPFA membranes. More importantly, the synergistic thermal management properties can be obtained via infrared radiation and absorb sunlight. Compared with bare PET fibers membranes, the laminated CMPFA membranes exhibited excellent thermal insulation properties. The surface temperature of laminated CMPFA membranes is 11.9 °C higher than that of bare PET fibers membranes after 50 s of simulate sunlight exposure. In addition, the laminated CMPFA membranes show antibacterial properties, breathability, and water vapor permeability, which is beneficial to improving the comfort of wearer. This study shows that the fabrication of flexible wearable laminated membranes for personal thermal management application can be extended for the fabricated of other waste plastic based-materials with controlled structures and desired functions for various applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Millimetric hollow glass microspheres/epoxy(HGMs/EP) hollow spheres were prepared. • HGMs/EP hollow spheres showed low density and excellent mechanical properties. • A lightweight, thermal insulated EP composite with lattice structure was designed. • EP composites showed good thermal insulation properties. • Thermal insulation mechanism of the EP composites was proposed. In this study, a novel, lightweight, thermally insulated epoxy resin (EP) composite was designed and fabricated by arranging hollow glass microspheres/epoxy resin (HGMs/EP) hollow spheres and EP matrices using a combination of templates and a simple casting method. The designed HGMs/EP exhibited low density and excellent thermal insulation properties, and their size was of the order of millimeters. HGMs/EP hollow sphere–reinforced EP composites exhibit considerably lower density (0.73 ± 0.06 g/cm3; 39.16 % lower) and thermal conductivity (0.121 ± 0.016 W/(m·K); 37.31 % lower) than the traditional HGMs/EP composites with the same HGM content. Overall, the designed HGMs/EP hollow sphere–reinforced EP composites are excellent candidates for providing thermal insulation in construction materials. [ABSTRACT FROM AUTHOR]

For the first time, a multiphase closed cell SiC-based composite nanofiber integrating efficient electromagnetic (EM) wave absorption, thermal insulation and high temperature resistance was designed and fabricated through electrospinning technique with zirconium as sintering aid and hollow C/SiO 2 spheres (HCSSs) as pore-forming materials. The unique multi-phase and closed cell structure not only improves the dielectric loss and facilitates the multiple reflection and absorption of EM waves, but also hinders the solid-phase heat transfer and increases the interfacial thermal resistance. Given their 10 % HCSSs content, the nanofibers exhibited a minimum reflection loss of − 48.6 dB at 3.5 mm thickness. Meanwhile, the samples showed ultra-low thermal conductivity (∼ 0.026 W/m K) and excellent thermal stability (∼ 1400 ℃). These superior properties make our nanofibers are expected to be applied for EM wave absorption and high-temperature thermal insulation under extreme conditions. [Display omitted] • A novel strategy for developing porous absorbing material is reported. • Multiphase and closed cell structure improve the microwave absorption and thermal insulation performance simultaneously. • Close cell ZrO 2 /SiC nanofibers show great potential as microwave wave absorption devices in high-temperature. [ABSTRACT FROM AUTHOR]

In this paper, triangular hollow porous polyacrylonitrile (PAN) fibers were prepared by coaxial wet spinning inspired by silver ant hair. These PAN fibers with ideal triangular hollow cross section structure were obtained by adding inorganic salts into the cortex and core spinning solution combined with proper drawing ratio. Its strength increases to 4.3 times compared with that of the nascent fiber without inorganic salt. Subsequently, the light reflection as well as thermal insulation properties of triangular and circular hollow porous fibrous mats were compared and analyzed. The results show that the triangular hollow porous fibers have higher light reflectance and heat insulation performance than the circular fibers, which endows the fabric a shimmering gloss. This research further expands the application of hollow porous fiber in both thermal insulation field and optical field, which is conducive to the design of "heat stealth" materials and flash materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• Polyimide aerogels with nano-porous structure were prepared by ambient drying. • SiO 2 nanoparticles were used as skeleton enhancers and shrinkage inhibitors. • The aerogels exhibit robust mechanical properties and efficient thermal insulation. Ambient drying of polyimide (PI) aerogel is rarely reported due to the strong cross-linking network leading to large shrinkage. In this work, the hydrophobic SiO 2 nanoparticles are used as skeleton enhancers and shrinkage inhibitors to maintain the nano-porous network structure and achieve ambient drying of PI/SiO 2 aerogels. The results show that the PI/SiO 2 aerogel prepared by ambient drying has similar thermal insulation and mechanical properties as the PI aerogel prepared by supercritical drying. The PI/SiO 2 aerogel prepared by ambient drying is low-cost and simple to operate, which is expected to realize the industrialization and wide engineering application. [ABSTRACT FROM AUTHOR]

Phenolic-based composites are the most promising ablative thermal protection materials for space applications, but optimizing their thermal insulation performance while maintaining high strength remains extremely challenging. Herein, phenolic-based composites with co-optimized thermal insulation and mechanical properties are prepared via 2.5D quartz fabric reinforcing nanoporous phenolic. The pore size of phenolic matrix is efficiently refined to ∼35 nm by adjusting resin concentration, enabling composites to exhibit high density but low thermal conductivity by enhancing Knudsen diffusion. Finite element analysis shows that low braiding angle of 2.5D fabric can further weakening heat transfer of composites due to anisotropic thermal conductivity of fiber yarns. In-situ X-ray micro-CT results indicate that 2.5D fabrics can reinforce composites through interwoven yarns, and straighter weft yarns result in higher strength along weft direction than that along warp direction. Compared with dense quartz/phenolic composite, the resulting composites exhibit 16.5% lower density (1.32 g/cm3), 58.8% lower thermal conductivity (0.21 W/(m·K), ≥372.7% higher tensile strength (≥182.0 ± 9.6 MPa) and comparable ablation resistance. The present results will further advance the application of phenolic-based composites in more extreme re-entry environments. [Display omitted] [ABSTRACT FROM AUTHOR]

A stitched integrated thermal protection system (SITPS) has thermal protection/insulation and load-bearing capacity. According to the thermal protection/insulation, loading-bearing, and lightweight requirements, the SITPS has multiple characterizations and optimization parameters. So, it is essential to calculate its thermal and mechanical performance indexes in specific working environments to evaluate its structural efficiency. SITPS contains different components and spans multiple dimensions; therefore, multiscale models and hierarchical statistical methods are tailored to calculate the thermal and mechanical properties of the SITPS. This approach investigates the influences of the two critical structural parameters, stitching density and thermal insulation core thickness, on four key performance indicators of the SITPS. A structural efficiency indicator for the SITPS is proposed, which quantitatively characterizes the thermal insulation, load-bearing, and lightweight performance of the SITPS. It provides new insights into the structural design and optimization of the SITPS in its engineering applications. [ABSTRACT FROM AUTHOR]

Controlling thermal conductivity of nanostructures is a key element in manufacturing tailor-made nanodevices for thermoelectric applications. Moreover, superlattice nanostructures have been demonstrated to be useful in achieving minimal thermal conductivity for the employed nanomaterials. In this work, we model two-dimensional biphenylene, a recently-synthesized sp2-hybridized allotrope of carbon atoms, for the implementation of a biphenylene/hexagonal Boron-Nitride (biphenylene/ h -BN) superlattice nanoribbons. The effects of the length of ribbon and its superlattice period (l p) on the thermal conductivity are explored using molecular dynamics simulations. We calculated the length-independent intrinsic thermal conductivity (K α) of the superlattice nanostructure, which was approximately 68% and 55% lower than the thermal conductivity of pristine h -BN and biphenylene nanosheets, respectively. The superlattice period largely determines the minimum thermal conductivity, which was at 64.1 W m−1k−1 for a period value of l p = 2.51 nm. This work opens a new window to tune and/or minimize thermal conductivity in nanoribbons when designing thermoelectric and thermal insulation materials for favorable applications. • Biphenylene/h-BN superlattice was theoretically born using dynamic MD computation. • Thermal fingerprint of biphenylene/h-BN superlattice microstructure was precisely taken. • Thermal properties of biphenylene sp2-hybridized allotrope of carbon atoms were visualized. • Thermal conductivity of biphenylene/h-BN superlattice in minimal condition was 64.1 W m−1k−1. • Overall, thermal conductivity of this superlattice was 68 and 55% lower than pristine BN and biphenylene, respectively. [ABSTRACT FROM AUTHOR]

• Phenolic resin aerogel is synthesized from linear and boron phenolic resin. • The ultralow shrinkage attributes to the strong B-O bond in boron phenolic resin. • Thermal conductivity of aerogel with a density of 0.105 g/cm3 is 0.0352 W/(m·K). • Aerogel shows excellent mechanical stability and resilience capacity. Lightweight phenolic resin aerogel with excellent thermal insulation and mechanical properties is an attractive material for thermal engineering applications. However, to synthesize such material, generally, a significant volume shrinkage would occur during the aerogel formation and the processing time is long. To conquer such issues, the lightweight phenolic resin aerogel with excellent thermal insulation and mechanical properties was synthesized by an elaborately designed process, where linear thermoplastic phenolic resin (LPR) and boron-modified thermosetting phenolic resin (BPR) were used as the raw materials. It was found that the shrinkage rate and the processing time of the phenolic resin aerogel were significantly reduced. By optimizing the synthesis process, the aerogel with a density of 0.105 g/cm3 and a thermal conductivity of 0.0352 W/(m·K) was achieved. [ABSTRACT FROM AUTHOR]

• Lightweight, flexible aerogels using renewable curdlan and wood waste chips as raw materials. • Low thermal conductivity (30.1 × 10−3 W/(m·K)) and high thermal stability up to 300 °C. • Hydrophobic and good compression-resilience behavior. Developing flexible and lightweight materials with elevated thermal insulation performance from renewable biomass is significant for green and sustainable energy. In this work, a multifunctional biomass aerogel using wood waste as a raw material is proposed. The composite aerogel consists of curdlan as a structural framework, wood fibers and nano-hydroxyapatite as reinforcing phases. By employing thermogravimetry (TG), infrared thermal imager and thermal conductivity tester, the thermal stability and thermal insulation performance of the aerogel were evaluated. The consequent thermal conductivity reaches 30.1 × 10−3 W/(m·K). As the strength and toughness of the aerogel is improved by introducing cellulose into the matrix, it shows a maximum compressive modulus of 1.65 MPa. The hydrophobicity of the aerogel is achieved by an alkylation method and the contact angle is over 120°. This nontoxic aerogel composite with high thermal and mechanical performance indicates a potential utilization in the thermal management of food and electronic industry. [Display omitted] [ABSTRACT FROM AUTHOR]

• Elaborate and characterize new ecological acoustic absorbers/sound insulation panels and thermal insulation panels. • Acoustic and thermal properties were measured experimentally using standardized methods. • Morphological analysis of the different fibers was carried out using scanning electron microscopy. • Bulk density, air flow resistivity and water absorption were measured experimentally. • The new panels are good candidates for the development of local materials with the required acoustic and thermal properties. This work aims to elaborate and characterize new ecological composite materials from cardboard waste and abandoned natural fibers for the manufacture of local acoustic absorbers/sound insulation panels and thermal insulation panels. For this purpose, twenty-eight samples were prepared by mixing a mass fraction of 60 % of cardboard waste and 40 % of natural fibers available in the south-east region of Morocco, i.e. Doum, Wheat straw, Reed, Esparto, Bagasse, Fig, and Olive. Firstly, the morphological analysis of the different fibers was carried out by scanning electron microscopy (SEM). Secondly, the acoustic and thermal properties were measured experimentally using standardized methods. In addition, bulk density, air flow resistivity and water absorption were measured. The experimental results showed that the studied panels have good acoustic and thermal performances. The sound absorption coefficient, sound transmission loss, bulk density, thermal conductivity, and heat capacity were in the range of 0.4–0.8; 20–45 dB; 278.6–343.8 kg/m3; 0.072–0.10 W/m.K; 1254.5–1807.5 J/kg.K, respectively. Consequently, the new panels developed in this study are good candidates for the development of local materials with the required acoustic and thermal insulation properties for applications in buildings. Their main advantages are: low environmental impact, low cost, and they can even compete with commercialized synthetic materials. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by thermal foaming of active cross-linkable units terminated polyester ammonium salts (PEAS) precursor powders. The active cross-linking strategy was realized by breaking C C bonds in maleic anhydride under heating treatment. Results showed that the formation of cross-linked structure before complete imidization effectively resisted matrix shrinkage and endowed PIFs with outstanding mechanical properties. The room temperature compressive strength and modulus of PIFs with four repeating units reached as high as 2.34 and 56.1 MPa, respectively. Moreover, the PIFs exhibited excellent thermal properties with onset decomposition temperatures ranging from 490 to 550 °C and the glass transition temperatures exceeding 290 °C. The PIFs displayed better thermal insulation, and the values of thermal conductivity fell within a range of 0.056–0.090 W m−1 K−1, which demonstrates potential application as high temperature resistant structural materials in aerospace and energy sectors. [Display omitted] • Rigid PIFs were fabricated by thermal foaming of active cross-linkable units terminated PEAS precursor powders. • Cross-linking structure was formed before complete imidization which endowed PIFs with outstanding mechanical properties. • Relationship between chain structure and properties of rigid PIFs were investigated. [ABSTRACT FROM AUTHOR]

• Preparation of Casein based zinc oxide nanocolloids using the two-step approach. • Thermal diffusivity studies of prepared samples using dual-beam thermal lens techniques. • Tunable behavior of thermal diffusivity depending on volume fraction and morphology. Nanofluids with suitable heat transfer properties were found to be applied in thermal insulators, transport, nanodevices, medicine, etc. Their heat transfer properties are influenced by the particle size, morphology, and concentration of the nanoparticles present in the nanofluids. Nanofluids of different morphologies of zinc oxide such as nanospheres, nanoflowers, and nanorods were synthesized and their thermal properties were evaluated using a dual-beam thermal lens technique. All these nanofluids were found to exhibit tunable thermal diffusivity depending on concentration. The nanofluids with flower-like morphology show maximum deviation in diffusivity due to the layered structure and the increased surface area. As compared to pristine zinc oxide nanofluids, casein-capped zinc oxide nanofluids show excellent thermal insulation properties at 60 μg/ml. The findings suggest that biofunctionalized zinc oxide nanofluid is a promising candidate for a variety of thermal applications. [ABSTRACT FROM AUTHOR]

Rape straw as a waste product of the oilseed industry is available abundantly in the European Union. In this paper, the utilization of rape straw-based fibers for the preparation of binderless thermal insulation materials is investigated. The effect of steaming temperature, which can be considered as one of the most important parameters of the production process, on microstructure and mechanical, hygric and thermal properties of the insulation boards is analyzed. The experimental results show that the designed binderless rape straw fiberboards achieve the most suitable combinations of mechanical, hygric and thermal properties for the steaming temperatures of 180 °C and higher, which indicates 180 °C as the most promising solution. • Binderless rape straw fiberboards with a bulk density of 100 kg/m3 were designed. • The effect of steaming temperature is analyzed. • Thickness swelling decreased substantially with increasing steaming temperature. • The most suitable properties achieved fiberboards produced at 180 °C and 200 °C. • The thermal conductivity was within the range of 0.045–0.052 W/mK. [ABSTRACT FROM AUTHOR]

Epoxy (EP) resin insulations are widely used in electronic devices and power systems. They are gradually finding their way as winding insulation material for medium frequency transformers (MFT) due to their attractive insulating and adhesive properties along with low cost and easy processing. However, their dielectric insulation properties are compromised at high frequencies and high temperatures due to poor thermal properties. In this context, the surface-treated hexagonal boron nitride (h-BN) micro fillers and core-shell TiO 2 @SiO 2 nanofillers are doped in epoxy (EP) to enhance their thermal and electrical insulation properties under high frequencies and high temperatures. Results reveal that the thermal conductivity of the EP increases continually, whereas the electrical breakdown strength is reduced above the threshold content of micro/nano fillers. Particularly, the micro h-BN addition is beneficial for thermal conductivity enhancement, whereas the core-shell structure of TiO 2 @SiO 2 improves the electrical insulation properties of the EP. The multi-layer core model is used to explain the dynamics of the fillers. The homogeneous dispersion and optimal content of suitable micro-nano fillers can produce efficient EP composites as the electrical insulation for medium frequency transformers. [Display omitted] [ABSTRACT FROM AUTHOR]

• The chemical grafting of ammonium polyphosphate onto the surface of HGM was reported for the first time. • Composites aerogel have excellent thermal insulation properties. • Composites aerogel have excellent flame retardancy, and the LOI value is as high as 100. • Composites aerogel have good mechanical properties. The development of high-performance flame-retardant materials with better thermal insulation properties is of great significance to modern building energy conservation. In this study, we report the facile and scalable fabrication of novel aerogels (SA-HGM-APP) based on the building blocks of ammonium polyphosphate (APP) coated hollow glass microspheres (HGM) and matrix material sodium alginate (SA) by freeze drying method. The as-prepared composite aerogel exhibits better thermal stability (decomposition temperature over 210°C). In addition, SA-HGM-APP composite aerogels have good thermal insulation properties and low thermal conductivity, which is 0.035 W m−1 K−1. More importantly, the peak heat release rate (pHRR) is 14.14 kW m−2, the limiting oxygen index (LOI) value is as high as 100%, and the aerogel composite material can reach UL-94 V-0 grade, so it shows excellent flame retardancy. These results attributed to a synergistic effect, which combines the rich porous structure derived from HGM, so that SA and APP have better thermal insulation and excellent non flammability, thus providing excellent flame retardancy. SA-HGM-APP aerogel composite has many advantages, such as simple preparation method and high mechanical strength. It has great potential in future thermal insulation and flame retardancy applications. [ABSTRACT FROM AUTHOR]

Geopolymers have been a frequently studied topic during the last decades due to waste materials utilization, low energy demands, and low carbon dioxide emissions related to their production, which makes them very attractive within the current environmental trends. However, the original idea to use them as a concrete replacement showed to be unattainable in the nearest future, so other alternatives of geopolymers applications are being sought that could exploit the efforts spent and research progress made so far. This review paper summarizes the recent progress in the field of directly foamed geopolymers, as one of the alternatives, focusing on the material base, foaming and stabilization processes, and assessments of selected material parameters, as related to raw materials used and treatment techniques applied. As the main result, several gaps and challenges are identified that deserve more attention and deeper investigations, which can help to move the geopolymer foams closer towards their regular application in civil engineering. A detailed knowledge of hygric parameters and their influence on thermal properties, long-term performance analyses in real-world applications, or extension of the material base to achieve environmental more friendly solutions represent the most topical issues that are supposed to be addressed. • Recent progress in the field of directly foamed geopolymers is reviewed. • Foaming and stabilization processes are analyzed. • Material parameters are assessed and linked to raw materials and treatment techniques. • An overview of durability of geopolymer foams is given. • Several gaps in the current knowledge are identified that require deeper investigations. [ABSTRACT FROM AUTHOR]

The novel multifunctional lightweight composites (MLCs) reinforced with integrated preform were prepared for thermal protection system (TPS) of hypersonic vehicles in extreme aerothermodynamic environment. The high-temperature behavior including thermal physical properties decomposition performance, and the ablation resistance were tested by the oxy-acetylene torch system, as well as the micro-morphologies of MLCs from non-destructive testing were investigated. An integration factor was proposed to evaluate the comprehensive performance of MLCs. The results show that MLCs had high structural efficiency without delamination and defelting, excellent thermal insulation performance, and superior ablation resistance ability. The comprehensive performance of MLCs had obvious advantages to polymer-matrix composites (PMCs). The novel MLC reinforced with integrated preform can help for the development of thermal protection materials of hypersonic aircrafts. [ABSTRACT FROM AUTHOR]

• Graphene/Fe3O4 hybrid aerogel were prepared by self-assembly synthesis. • The effects of concentration of nano-Fe3O4 in the aerogel were studied. • Mechanical and thermal properties of the hybrid aerogels were investigated. [Display omitted] Graphene aerogel and graphene-magnetite hybrid aerogel were prepared using hydrothermal method followed by a freeze-drying process. Magnetite nanoparticles were encapsulated by graphene sheets in an electrostatic self-assembly process. The morphology and properties of aerogels were characterized by several techniques including UV-Vis spectroscopy, Raman spectroscopy, FESEM, TEM and XRD. The mechanical and thermal behavior of the aerogels were evaluated at different concentration levels of Fe 3 O 4 nanoparticles (0, 10, 20 and 30 wt%). The compressive strengths of the hybrid aerogels at the strain of 80% for graphene aerogels containing 0, 10, 20 and 30 wt% Fe 3 O 4 nanoparticles were determined to be 5.93, 12.96, 6.85, and 6.15 kPa, respectively. The highest mechanical properties were achieved for the sample containing 10 wt% Fe 3 O 4 nanoparticles (FGA10). Thermal analysis revealed that FGA10 sample had a 15% less weight loss when heated up to 600 °C compared with that for the bare graphene aerogel, indicating the formation of a more thermally stable structure. Furthermore, adding Fe 3 O 4 nanoparticles improved the thermal insulation performance of the graphene aerogel, since the dynamic heat transfer rate and heat dissipation rate of FGA10 were lower than those for the bare graphene aerogel. [ABSTRACT FROM AUTHOR]

• A new method to obtain hierarchical material microstructures is proposed. • The weight coefficients can be adaptively adjusted during the optimization. • Good connectivity and clear interfaces between two materials are always maintained. • This method is universal, high efficiency, program easiness and good connectivity. Composite materials with multiple properties are important for a range of engineering applications. Hence, this study focuses on topological design of hierarchical materials with multiple performance in both thermal insulation and mechanics. First, a novel multi-objective optimization function is defined to find a solution from the Pareto frontier, where the weight coefficients can be adjusted adaptively, to keep all the individual objective functions and their sensitivities stabilized at the same level during the optimization. Second, a new design strategy is proposed to achieve the hierarchical designs of biphasic material microstructures, they are periodically arranged by the porous base materials that are known in advance and independent of topology optimization. Third, sensitivity information and algorithm implementation are given in detail, and the bi-directional evolutionary structural optimization method is adopted to iteratively update the micro-structural topologies, by combining with the homogenization method. Last, numerical examples are provided to illustrate the benefits of the proposed design method, such as high efficiency, implementation easiness, good connectivity and clear interface between adjacent phases, etc. [ABSTRACT FROM AUTHOR]

A novel naturally grown mycelium-composite insulation brick was bio-produced by cultivating a biocompatible and fast-growing fungus, Pleurotus ostreatus , in the rye berries feedstocks. The resultant mycelium composites consisted of a core of colonized substrate, encased by a layer of water-repellent fungal skin. The microstructure of mycelium composites shows that fungal fibers grow from feedstocks and bonded adjacent feedstocks. The impact of density and moisture on the mechanical properties of mycelium composites were studied, finding that composites with increased density presented an improvement of flexural strength under both low and middle levels of Relative Humidity (RH). However, under high level of RH, composites have a lower flexural strength but a greater deformation. The mechanical strength of mycelium composites, however, meets the existing transportation and construction requirements. Based on the measured thermal properties of mycelium composites, EnergyPlus analyses were conducted to evaluate their performance in buildings' operational energy in comparison with conventional natural insulation materials, i.e., lightweight expanded clay aggregate (LECA) and expanded vermiculite (EV). Compared with LECA and EV, the use of mycelium-composite for building insulation reduced the indoor temperature fluctuations. Compared with LECA and EV, mycelium-composite insulation reduced the total annual heating and cooling energies as well as the total annual CO 2 emissions for buildings located in US Climate Zone 2–8, with the only exception being in Zone 1 or the very hot climate zone. Therefore, naturally grown mycelium-composite, as demonstrated in this study, is promising to provide sustainable building insulation materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low cost and high performance. • Silica aerogel fabricated from incineration bottom ash. • Thermal insulation paint with silica aerogel additive. • 12 °C surface temperature reduction improvement on the heated plate at 60 °C. • 1 °C in-chamber temperature reduction with external temperature of 44.6 °C. In this work, silica aerogel (SA) powder is fabricated through a sustainable method from incineration bottom ash. The fabricated SA has a low thermal conductivity of 0.025 W/mK, high surface area of 786 m2/g, and high porosity of 96.36%. The thermal analysis of SA powder shows it has a stable hydrophobicity up to 418 °C. The SA powder has been mixed into water-based paints to develop a high efficient thermal insulation paint with inproved thermal insulaton properties. Different percentage of SA were mixed into the paint samples to prepare the silica aerogel thermal insulation paint (SATIP) and their physical properties were studied. The SATIP samples were then coated on cement board substrates. The thermal conductivity, water resistance, durability and insulation performance of the samples were investigated and evaluated systematically. The scrub resistance of SATIP can be improved significantly by 219% after adding 5 vol% SA powder. And by adding 20 vol% of SA into the SATIP, it achieves up to 12 °C surface temperature reduction improvement compare to the one without SA on the heated plate at 60 °C, and 1 °C in-chamber temperature reduction with external temperature of 44.6 °C. The spectral reflectance analysis demonstrates that the improvement of the thermal insulation performance of the SATIP is attributed to the thermal insulation property of SA and proves that the developed SATIP is color insensitive and has wider applications. The results demonstrated a low-cost and scalable process fabricates SA with superor properties. The developed SATIP has a great potential for application in sustainable and green buildings for energy saving. [ABSTRACT FROM AUTHOR]

• To achieve the desired printability, the optimal replacement range for silica sand by aerogel in a cementitious mixture is 0–20% by volume. • The thermal conductivities of the SC and 3D printed specimens ranked in the order of 3DCP-X > SC > 3DCP-Y > 3DCP-Z, irrespective of aerogel content. • The weak bonding interfaces between adjacent filaments produce gaps, providing channels for heat to transfer in specimens 3DCP-X. • Under the same thermal and mechanical requirements, walls fabricated by AG-incorporated concrete are 7-cm thinner than traditional concrete walls. This study investigated the properties of fresh and hardened aerogel (AG)-incorporated concrete suitable for 3D concrete printing. After trial and error, it was found, that to achieve the desired printability, the optimal replacement range for silica sand by aerogel in a cementitious mixture is 0–20% by volume. The physical, mechanical, and thermal insulation properties of hardened concrete in three directions were studied, and the influence of anisotropy on these properties was investigated. The results showed that irrespective of the aerogel content, the compressive strength of the cast specimens (avg. 24.90 MPa in A20) was slightly higher than those of the 3D printed specimens, 3DCP-X (avg. 23.63 MPa in A20), 3DCP-Y (avg. 20.77 MPa in A20), and 3DCP-Z (avg. 20.40 MPa in A20). The thermal conductivity of the cast and printed specimens decreased gradually with an increase in the aerogel content. Relative to that of the cast specimens (0.330 W/(m·K) in A20), the thermal conductivity of specimens 3DCP-X (0.405 W/(m·K) in A20) was slightly higher, while those of 3DCP-Y (0.320 W/(m·K) in A20) and 3DCP-Z (0.306 W/(m·K) in A20) were lower. A thermal insulation wall (400 mm × 200 mm × 600 mm) with hollow structures was printed using the AG-incorporated concrete. To satisfy the same thermal and mechanical requirements, walls fabricated using AG-incorporated concrete can be 7 cm thinner than traditional concrete walls. The mechanism for the heat transfer of AG-incorporated concrete in three directions was examined as well. [ABSTRACT FROM AUTHOR]

• Unidirectional anisotropic PIAs have been prepared by freeze-drying. • The PIA shows excellent thermal stability and stable mechanical behavior. • The u -PIA-6 exhibits great strength, which is over twice as high as that of the TEEK-HH at 177 °C with a similar density. • The u -PIA shows great thermal insulation properties in anisotropic. Polyimide aerogels (PIAs) are the new type of high-performance lightweight material that combines the excellent thermal and mechanical behavior of polyimides with the highly porous and lightweight properties of aerogels. PIAs can meet the increasing material requirements of high-tech fields such as the aerospace and transportation industries. This study reports a series of all-aromatic anisotropic polyimide aerogels (p-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA)) with unprecedented behavior. These PIAs were synthesized using a random or unidirectional freeze-drying method followed by thermal imidization of the precursor solution. Their mechanical and thermal conductivity performance were anisotropic (u -PIA-8 strength: 1.86 and 0.14 MPa, thermal conductivity: 62.9 and 50.1 mW·m−1·K−1 along the axial and radial direction, respectively). Furthermore, the PIAs possessed excellent compression behavior in a wide temperature range from 25 °C to 316 °C, with a compressive strength over twice that of the commercial polyimide foam TEEK-HH (u -PIA-6 strength: 0.83 and 0.32 MPa at 177 and 316 °C, TEEK-HH strength: 0.31 MPa at 177 °C). These aerogels also demonstrated good thermal insulation performance after being held at 300 °C for 20 min (u -PIA-8: 76.3 °C at 25 mm). These highly anisotropic aerogels exhibit flexible thermal protection properties that extend the potential use of PIAs to applications such as high-temperature-resistant rocket fairings, sandwich structures, and arc-shaped structures for aerobats or the automobile industry. [ABSTRACT FROM AUTHOR]

The development of eco-friendly thermal insulation material composed of recyclable wastes contributes to enhancing environmental sustainability with less pollution. In this study, polysaccharide-based aerogels with improved thermal insulation property were obtained by using konjac glucomannan, starch, and office waste paper cellulose fiber (WPCF) via sol-gel and freeze-drying method. The obtained aerogels had a bulk density of 30.1–44.9 mg/cm3, a porosity of 95.1–97.0%. Results revealed that increased WPCF addition did not impact the thermal stability, but improved the sol stability, reduced the pore size, strengthened the mechanical property, and lowered the hygroscopicity of the aerogels, benefiting practical application. Although WPCF solids showed a high thermal conductivity, increased WPCF addition at 0.1–0.5 wt% reduced the aerogel thermal conductivity, which was explained by the longer heat path and less heat convention. Further higher WPCF addition at 0.5–1.5 wt% increased the aerogel thermal conductivity as the heat conduction of solid matrix was increased and the heat convection was strengthened. Therefore, the lowest thermal conductivity (0.0335 Wm−1 K−1) of the aerogel was reached at the optimized WPCF addition of 0.5 wt%. This work showed the high potential of the WPCF to be used to strengthen the thermal insulation property of polysaccharide-based aerogels. • Fully bio-based aerogel was prepared with recyclable cellulose fiber addition. • WPCF addition changed the aerogel structure including pore shape and pore size. • The optimum thermal insulation property was achieved at WPCF addition of 0.5 wt%. • The thermal insulation mechanism was interpreted through the pore structure changes. [ABSTRACT FROM AUTHOR]

The highly thermally conductive yet electrically insulating polymeric materials are exhibiting tremendous potential for thermal management materials. However, the practical application of these materials is restrained by the limited thermal conductivity (TC) and deterioration of mechanical properties. In this work, an ultraflexible polyamide-imide (PAI) film with a sandwich-like structure composed with assembled well-oriented functionalized boron nitride nanosheets (FBN) by facile layer-by-layer solution-coating strategy is constructed. The design of the layered structure and highly oriented arrangement of interconnected FBN (Herman's orientation parameter ƒ up to 0.847) endows the obtained PAI composite film with super-flexibility, ultrahigh in-plane thermal conductivity (λ //), superior thermal transfer capability (ΔT max = 24.4 °C) and excellent electrical insulation performance. The PBP composite film reaches an ultrahigh λ // of 45.7 W m−1 K−1 with only 23 wt% FBN loading and exhibits a remarkable TC enhancement factor over 23 because of the more continuous phonon transfer networks that constructed by interconnected well-oriented FBN which could effectively suppress the phonon scattering. Furthermore, the mechanical properties of the layered composite film (PB4P) exhibit noteworthy enhancement compared with uniform PBN composite film, in which the tensile strength is increased by 110% and toughness enhancement is 329%. Meaningfully, our fabrication strategy has the advantage of simplicity and adaptability for commercial amplification. The composite film developed in this work provides a promising prospect for the thermal management system of modern power electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• Raw and treated doum fibers were used to produce compressed earth brick (CEB). • The mechanical and thermophysical properties of CEB are investigated. • The reinforcement by doum fibers decreases density and increases water absorption. • The addition of fibers decreases thermal conductivity and compressive strength. • The use of doum fibers promises the production of an ecological building material. This work investigates the physical and mechanical properties of compressed earth brick (CEB) reinforced with raw doum fibers (RDF) and treated doum fibers (TDF). Firstly, the raw materials were characterized. Then CEB reinforced by fibers varying from 0 to 2% by mass were elaborated. The addition of RDF and TDF reduces the compressive strength by 25% and 35% respectively. However, the inclusion of fibers improves the thermal insulation of CEB and decreases its density of about 16%. The research finding indicates also that the capillarity absorption increases with the increase of fiber content. These results indicated that the use of doum fibers to produce ecological building materials has a promising future. [ABSTRACT FROM AUTHOR]

Thermal insulation materials play an important role in energy conservation and the sustainable development of natural resources. Herein, novel silica composite nanofibers (SiO 2 NFs) with closed cell structure and excellent thermal insulation performance were designed and prepared via electrospinning technique using hollow SiO 2 /TiO 2 spheres (HSTSs) as pore-forming agent and infrared shielding agent. The addition of HSTSs broke the continuity of heat transfer pathways inside the NFs and enhanced the infrared thermal radiation shielding performance of SiO 2 NFs, endowed it with ultra-low thermal conductivity and low infrared transmittance. Meanwhile, the materials exhibited good flexibility, high tensile strength, low density and excellent thermal stability, indicating promising application as insulation materials. This research not only provides a novel strategy to prepare porous nanocomposite fibers for thermal insulation, but also offers a new insight for the development of porous materials with multiple functions. [Display omitted] • A novel strategy for constructing porous thermal insulators is reported. • Hollow SiO 2 /TiO 2 spheres broke the heat transfer pathways of the fiber and enhanced its infrared shielding performance. • The obtained SiO 2 composite nanofibers show great potential as thermal insulators in high-temperature. [ABSTRACT FROM AUTHOR]

• We develop a slim double-skin window with a 20-mm-thick air cavity and single frame. • Heating and cooling energy use was analyzed through a 15-month testbed experiment. • The proposed window exhibits comparable energy efficiency to double-skin façades. • The life-cycle costs are 47% lower than those of double-skin façades. We developed a slim double-skin window (SDSW) with the aim of reducing building energy consumption for cooling and heating, thereby reducing the impact of buildings on climate change. The developed SDSW is a slim structure with an air cavity thickness of 20 mm, i.e., thinner than that of a traditional double-skin façade (DSF). We analyzed changes in the thermal properties and cooling and heating energy consumption of the SDSW as well as the effects of the thin air cavity on window performance. A testbed was constructed to analyze the seasonal temperature properties of the glass and the cooling and heating energy consumption. We also compared the long-term effects of the air cavity on the difference between outdoor and indoor glass surface temperatures under similar conditions for the SDSW and traditional DSF. The SDSW temperature was 3 °C lower than that of the traditional DSF, and the cooling and heating energy consumption dropped by 6.5%. Although the performance of the developed SDSW was comparable to that of traditional DSF, the life-cycle cost was reduced by 47%. [ABSTRACT FROM AUTHOR]

In this paper, large-sized covalent organic framework (COF) aerogels were prepared using high-efficiency catalysis under room temperature combined with rapid gel and freeze-drying methods for the first time. Two kinds of COF aerogels with rigid and semi-rigid building blocks were prepared using this method, having good mechanical strength (126 and 106 kPa), elasticity (aerogels structure remains intact after 10 cycles), thermal insulation properties (low thermal conductivity of 0.03 wm−1K−1), low dielectric constant (1 kHz of 1.21 and 1.51), thermal stability and solvent stability, and ultra-light characteristics (densities of 0.029 and 0.040 g cm−3). Compared to the traditional COF methods that generally result in small particles, the high-efficiency catalysis method developed in this paper can be used to prepare large-sized COF aerogels under mild reaction temperatures and within less time conducive to industrial production. This method is expected to greatly broaden the application field and application scope of COF materials. [Display omitted] • Two COF aerogels were prepared combined with rapid gel and freeze-drying methods for the first time. • The COF aerogels behave good mechanical properties, thermal insulation properties, and ultra-light characteristics. • The method in this paper can be used to prepare large-sized COF aerogels under mild reaction temperatures and less time. [ABSTRACT FROM AUTHOR]

• WMGFs were successfully prepared via chemical foaming method. • Wollastonite significantly improved mechanical strength of geopolymer foams. • WMGFs exhibited effective thermal insulation under high temperature exposure. This paper aims to investigate the physical properties and fire resistance of wollastonite-metakaolin-based geopolymer foams (WMGFs). Both compressive and flexure strengths of WMGFs are significantly improved since wollastonite fibers possess inherent stiffness and provide effective crack control. Meanwhile, wollastonite addition promotes viscosity of geopolymer slurry to some extent and then determines pores formation in foaming process, which is also crucial for mechanical strength development. The thermal conductivity of the specimens rises triflingly with elevated wollastonite addition corresponding to slightly decrease in porosity. Owing to the steady skeleton structure of WMGFs, the highest reverse-side temperature of sliced blocks is merely 202.7 °C after exposed to fire for 3 h, showing that the reduction in thermal conductivity has no negative impact on fire resistance of specimens. Physicochemical stability of wollastonite under high temperature and alkaline environment is confirmed to be vital for sustaining integrated porous skeleton structure of geopolymer foams. Therefore, geopolymer foams reinforced by wollastonite possess extraordinary mechanical strength and fire resistance, revealing strong possibility for fire protection. [ABSTRACT FROM AUTHOR]

Fe-based amorphous and nanocrystalline alloys offer application prospects in the field of coating materials, and their thermal transport property is crucial for their application in thermal insulation coating. However, the mechanism of thermal conductivity in the process of isothermal annealing preparation of Fe-based nanocrystalline alloys are still unclear. In this work, the thermal conductivity of Fe 76 Si 13 B 8 Nb 2 Cu 1 amorphous alloy isochronal annealed at different temperature was examined. It was found that the thermal conductivity of the amorphous alloy is as low as 7.06 W/mK, whereas significantly increases to 10.38 W/mK after annealing at 693 K for 1800s. The result of the limited increase in thermal conductivity at annealing temperatures below the 693 K can be ascribed to the conflicting variations of electronic and phonon contributions with increasing temperature. At annealing temperature above 693 K, the two contributors start to cooperate, leading to abrupt enhancement of thermal conductivity. This work provides an insight into the thermal transport mechanisms for amorphous alloys. [ABSTRACT FROM AUTHOR]

• Layered samples of thermal mortars have lower A w than standard prism samples. • The s d of paints can depend on the substrate (singular mortar VS composite sample). • Recommended in technical sheets: s d of complete systems, and also A w for external ones. • Thermal mortars with cork/EPS: lower λ than declared, still of interest in temperate climates. • Thermal mortars: strong dependency of λ on water content. Among thermal insulation solutions for historic walls, thermal renders and plasters appear to be a very feasible option. Thus, this work analyses commercially available thermal mortars suitable for the scope. An extensive experimental campaign showed that testing single materials only, which is the standard requirement for thermal mortar-based systems, is in fact not sufficient for understanding the potential impact of the intervention on walls: whole-systems should also be examined. This study provides a detailedcharacterization of materials and systems, useful as a database for forthcoming investigations on compatibility and efficacy for application on historic walls, via numerical hygrothermal simulations. [ABSTRACT FROM AUTHOR]

Lightweight and multiscale nanocomposites are considered to be the most promising materials applied in the field of advanced aerospace and modern building industry, owing to their outstanding mechanical, thermal and flame-resistant properties served in high-temperature oxidizing environments. Herein, a novel siliconoxycarbide (SiOC) modified needle quartz fiber felt reinforced phenolic resin nanocomposite (SiQF/PR) with a hierarchical macro-/micro-/nano-scaled structure is reported. The as-prepared highly porous SiQF/PR nanocomposite exhibits a multiscale three-dimensional network and the micro-sized SiOC particles, derived from the hydrolysis of methyltrimethoxysilane (MTMS) and dimethyldiethoxysilane (DDS), are uniformly incorporated into the phenolic aerogel. The resultant nanocomposite has a bulk density of 0.30–0.35 g/cm3, and the maximum compressive strength reaches 4.20 MPa and 3.34 MPa in xy and z directions, respectively. Thermal stability and oxidation resistance experiments show that the SiQF/PR multiscale composite has a good ablation and heat insulation performance under oxyacetylene test condition, and the backside temperature of SiQF/PR is only 55.5 °C under 1.8mw/m2 for 120 s, and line ablation rate of SiQF/PR multiscale nanocomposite decreases by 20.1% at 1.8 MW/m2 and 59.5% at 0.4 MW/m2 compared to non-SiOC modified composite. These results indicate that the lightweight SiQF/PR nanocomposite fabricated by this method is very suitable for architectural or aerospace applications as high-performance insulation material. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Used thin profiled steel cladding as a lightweight cladding replacement for combustible ACPs in LSF buildings. • Standard fire tests of two external LSF walls showed significant fire resistance improvement due to steel cladding. • Conducted accompanying thermal property tests of two types of Earthwool insulation (glass fibre). • Evaluated total R -values of external LSF walls using THERM to understand the implication of insulation location. • Replacing cavity insulation with external insulation enhanced both fire and energy performance. This paper presents the details of full-scale standard fire tests of external light-gauge steel-framed (LSF) walls with corrugated steel cladding exposed to fire on the external side. Corrugated steel cladding of 0.42 mm thickness is generally used in roof and wall systems of buildings. In this study, it is used as the wall cladding of external LSF walls and as a lightweight cladding replacement to the combustible aluminium composite panels. A detailed investigation was undertaken to evaluate and understand the fire and energy performance of corrugated steel clad external LSF walls, which included (a) thermal property tests of two different types of Earthwool insulation (glass fibre insulation) used in wall systems, (b) full-scale (3 m × 3 m) load bearing standard fire tests of two external LSF wall systems – first with cavity insulation and the second with external insulation and (c) THERM modelling of the tested walls. Steel cladding prevented direct exposure of fire on plasterboards and hence delayed the temperature rise and increased the failure time. Overlaps along the vertical edges of steel cladding played a critical role as gaps formed during the tests. The two external LSF wall systems achieved fire resistance levels (FRLs) in excess of two hours (122 min and 158 min) with improvements greater than 40% due to the addition of thin steel cladding. Replacing cavity insulation with external insulation improved the FRL by about 30% and also its effectiveness in terms of energy efficiency. [ABSTRACT FROM AUTHOR]

Polyimide (PI) foams possess excellent mechanical properties, high-temperature resistance, and other unique properties, which facilitate impact in aerospace, automotive, and microelectronics industries. However, when they are used as lightweight insulation structural layers for high-temperature carbon fiber reinforced composites, improvement in thermal-insulating properties and temperature resistance of PI foams without compromising the flexibility in extreme environments is a challenging task. In this study, the flexible blocks were linked into rigid polymeric structures to fabricate a thermoplastic structure through a simple aqueous strategy to construct hydrogen-bonding networks. Thus, with a low shrinkage of 8.42%, an ultrahigh compressive modulus of 11.17 MPa, and a specific modulus of 81.03 MPa cm3 g−1 was successfully achieved. Benefitting from the formation of ultra-strong network backbones, foams showed excellent thermal-insulating properties and temperature resistance. The robust porous material with thermal-insulating properties (0.0481 W m−1 K−1) exhibited a compression modulus of 4.21 MPa after heat treatment at 300 °C and maintained 91% strength retention, thus it can be used as lightweight heat-insulation composite sandwich structures up to 300 °C. The copolymer foam obtained by using 30 mol% flexible blocks reserves its high flexibility undergoing only 10% dimensional changes after 40,000 compression-release cycles. The lightweight thermoplastic PI foams with flexibility, thermal-insulating properties, and temperature resistance can be used for high-temperature lightweight composite sandwich structures in aeronautics and space exploration. Preparing flexible thermoplastic polyimide foams with exceptional mechanical, thermal insulating properties, and temperature resistance through a simple aqueous strategy. [Display omitted] [ABSTRACT FROM AUTHOR]

Owing to the rapid development of advanced power system and modern micro-electronic devices, exploiting composites with excellent thermal conductivity and dielectric properties has become increasingly important. In this work, a double-layer surface modification method of grafting dopamine (DA) at the end of 3-glycidoxypropyl-trimethoxysilane (KH560) is firstly proposed to modify the surface of boron nitride nanosheet (BNNS), for improving the thermal conductivity and dielectric properties of epoxy resin (EP). Besides, the thermal conductivity of EP composites with double-layer surface-modified BNNSs and its improvement mechanism is explored with molecular dynamics (MD) simulation from micro level. The results illustrate that thermal conductivity of EP composites doped with double-layer modified BNNSs by grafting DA at the end of KH560 (DKBP) is 0.252 W/(m·K), 129% higher than EP. Moreover, this double-layer surface modification method of DKBP is beneficial to enhance the heat transfer effect and reduce scattering effect at the interface, which is the essential reasons for improving thermal conductivity of composites. Meanwhile, DKBP composite also presents superior dielectric properties. This work provides a promising idea to develop new insulating materials with high thermal conductivity. [Display omitted] • Grafting DA at the end of KH560 is firstly proposed to functionalize BNNSs. • Thermal conductivity and electrical properties of DKBP are enhanced significantly. • Improvement mechanism is explored by molecular dynamics simulation. • This method improves transfer effect and reduces scattering effect at the interface. [ABSTRACT FROM AUTHOR]

In order to study the effect of zirconia on the properties of laser deposited Ni15 coating on Q345 steel, laser deposition experiments were carried out with LSJG-GQ-6000M3 laser equipment with rated power of 6000 watts. The effects of adding zirconia on the microstructure, wear resistance and thermal insulation of the coating were studied by electron microscope, energy dispersive spectrometer, hardness tester, friction and wear tester and thermocouple. Study found that the addition of zirconia can refine the microstructure, improve the hardness and reduce the friction coefficient. The wear pattern has changed, and the high temperature resistance of the coating is improved. [ABSTRACT FROM AUTHOR]

Low density, high strength, together with good thermal insulation are desirable but hard to achieve simultaneously for lightweight cementitious composites. This work addresses the preparation of a novel lightweight cementitious composite (HP-LWCC) by employing the hot-pressing method and optimizing the insulating particles packing. The main raw materials are glass microspheres (GB), fly ash cenospheres (FAC), white Portland cement (PW), aluminum cement (AC), and silica fume (SF). Results showed that HP-LWCC specimens with density of 800–1200 kg/m3 exhibited superior mechanical properties and thermal insulation. Their flexural strength, compressive strength, and thermal conductivity achieved 7.5–10 MPa, 30–51 MPa, and 0.16–0.29 W/(mK), respectively. The microstructure results show that the packing of glass microspheres, which are tightly bridged by the hydration products, significantly refines the pore morphology, forming a denser cementitious matrix. The hot-pressing method benefits the reaction of aluminum cement and the alignment of fibers, resulting in high strength and flexural toughness. Based on the Compressible Packing Model, it is found that the optimized particles packing of HP-LWCC can decrease the porosity of specimens and improve the strength. Such HP-LWCC material provides a potentially solution in developing thermal insulated construction applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel high-entropy oxide (YYHEO) was engineered with significant mass disorder. • YYHEO exhibited glass-like low thermal conductivity (1.27 W/m∙K). • YYHEO exceeded typical substitutional solid solubility limit even with a significant atomic size difference (>50%). • YYHEO shows thermal stability even at elevated temperature (1500 ° C) without any phase degradation. • Thermophysical properties were compatible with YSZ (CTE: 10.08 × 10−6 K−1, E : 218.21 ± 3.64 GPa and H : 14.42 ± 0.5 GPa). An entropy-stabilization strategy was applied to engineer a novel thermal insulating material by establishing a single-phase solid solution with the formula of (Y 1/2 Yb 1/2) 2 (Ti 1/3 Zr 1/3 Hf 1/3) 2 O 7 (YYHEO). Structural analysis revealed that this material exceeded the typical substitutional solubility limit, even with a significant atomic size difference, where the conventional determination rule was defied. YYHEO exhibited a lower glass-like thermal conductivity due to its highly disordered crystal structure and the specific design strategy. The coefficient of thermal expansion and mechanical properties (e.g. elastic modulus and hardness) were comparable to conventional materials, suggesting that YYHEO is a promising candidate for application as a new thermal insulating material. [ABSTRACT FROM AUTHOR]

Biomass-derived aerogels have received extensive attention as potential thermal management materials for energy-efficient buildings. However, it remains a huge challenge to fabricate a fully bio-based aerogel with excellent mechanical property, flame retardancy, and low thermal conductivity. Herein, we demonstrate a novel and facile strategy to manufacture a fully biomass-based aerogel from naturally abundant ammonium alginate (AL) and phytic acid (PA), in which PA acting as both flame retardant and cross-linking components constructs a strong network with AL matrix. Consequently, the resultant biomass aerogel with a low density of 0.052 g/cm3 exhibits ultrahigh mechanical modulus (25.1 ± 3.1 MPa) and specific modulus (440.4 ± 54.4 MPa cm3·g−1), much superior to those of biomass aerogels ever reported. Due to the existence of the uniform three-dimensional porous network, the biomass aerogels exhibit low thermal conductivity (34–38 mW/m·K) and excellent thermal insulation performances. Further, the introduction of PA endows the aerogel with high flame retardancy (limiting oxygen index value of 57%, UL-94 V-0 rating, and extremely low heat release), while the biodegradability of the materials keeps at a high level with a biodegradation rate of 91.43%. Combining with the advantages of mechanically strong property, high flame retardancy, excellent thermal insulation, and biodegradation, the aerogel of this work provides a new strategy to fabricate thermal insulation materials with high environmental safety. [Display omitted] [ABSTRACT FROM AUTHOR]

• Lignocellulosic bio-wastes from forest management and agro-industry as building materials are reviewed. • Some bio-wastes produced in Euro-Mediterranean countries are selected. • Studies on eco-efficient boards made of natural fibers and other bio-wastes are analysed. • Further studies on properties of bio-wastes and eco-efficient boards are needed. This study investigates the possibility of using agro-industrial wastes for building products, mainly focusing on their insulation properties. A classification of bio-wastes is provided, namely of the lignocellulosic ones and their features and properties are described. Information about three main topics is collected: world production and consumption of some crops already used as building materials, their chemical composition and their most studied properties. Since the considered materials are lignocellulosic and they have many common features, a comparison is made. The aim is to have comparable information to support future research related to the production of eco-efficient indoor insulation boards. The result of this research is the choice of four different agro-industrial wastes produced in the Euro-Mediterranean Countries. This area was chosen as buildings typically have little or no insulation due to the regional mild climate; however, particularly with climate change, indoor hygrothermal comfort is poor. The collection of information allows some conclusions to be reached about the different bio-wastes already studied and identify gaps in the literature. [ABSTRACT FROM AUTHOR]