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Mullite fiber-based porous ceramics is one of the most commonly used high-temperature insulation materials. However, how to further reduce the thermal conductivity and improve the strength of such materials has been a challenge in the field of high-temperature insulation. In this paper, mullite micro/nano fiber-based porous ceramic was prepared by introducing mullite nanofibers into mullite microfiber-based porous ceramics and the effect of microfiber/nanofiber weight ratio on the samples properties were characterized and analyzed. Results showed that the compressive strength and high-temperature thermal insulation properties of the porous ceramics increased significantly with an increase in the nanofiber content. For the porous ceramics with similar density (about 0.50 g/cm3), the compressive strength of the sample with a microfibers/nanofibers weight ratio of 1:2 was 1.43 MPa, which was much higher than that of the porous ceramics prepared with only microfibers (0.26 MPa). Meanwhile, the backside thermal equilibrium temperature of the sample with a microfiber/nanofiber weight ratio of 1:2 at 900 °C environment was 355.8 °C, which was much lower than that of the porous ceramic prepared with only microfibers (476.5 °C). In addition, in order to investigate the temperature resistance of mullite micro/nano fiber-based porous ceramics, the sintering temperatures was increased from 1400 °C to 1500 °C. Results shows that the high-temperature thermal insulation performance of mullite micro/nano fiber-based porous ceramics with high mullite nanofiber content decays more seriously. The back-temperature test showed that the thermal equilibrium temperature of the samples with a mullite micron/nanofiber weight ratio of 1:1 in 900 °C environment increased rapidly from 386.3 °C to 454.2 °C when the sintering temperature was increased from 1400 °C to 1500 °C. The preparation of mullite micro/nanofiber-based porous ceramics provides a new strategy to improve the performance of fiber-based porous ceramics. [ABSTRACT FROM AUTHOR]

Layered materials exhibit competitively low thermal conductivity along the out-of-plane direction. The solution process is a promising method for preparing stacked structures. However, the thermal stability of the layered materials is poor after processing in solution, thus hindering their applications at high temperatures. One of the solutions to improve the thermal stability of layered structures is to expand the interlayer distance by inserting large-size metal ions. In this work, we studied the thermal properties of Cs+ intercalated layered niobate obtained by the ion-exchanged process. The layered structure of the Cs+ intercalated layered niobate survives after thermal treatment even at 1200 °C. The room temperature thermal conductivity of as prepared stacked Cs–HCa 2 Nb 3 O 10 is as low as 0.11 W m−1 k−1. Upon thermal annealing, the thermal conductivity increases. After annealing at 1200 °C, the value is 0.90 W m−1 k−1. The finding suggests Cs+ intercalated layered niobate is a promising material for high-temperature insulation applications. [ABSTRACT FROM AUTHOR]

An accurate estimation of the effective thermal conductivity of various insulation materials is essential in the evaluation of heat leak and boil-off rate from liquid hydrogen storage tanks. In this work, we review the existing experimental data and various proposed correlations for predicting the effective conductivity of insulation systems consisting of powders, foams, fibrous materials, and multilayer systems. We also propose a first principles-based correlation that may be used to estimate the dependence of the effective conductivity as a function of temperature, interstitial gas composition, pressure, and structural properties of the material. We validate the proposed correlation using available experimental data for some common insulation materials. Further improvements and testing of the proposed correlation using laboratory scale data obtained using potential LH 2 tank insulation materials are also discussed. [Display omitted] • We develop physics-based insulation property models for cryogenic LH 2 storage tank • Model captures the micro- and macro-features of the insulation system with any gas • We demonstrate the applicability of model to several typical insulation materials • Model performs well against experiment even at extended pressure/temperature range • Model parameters can be evaluated from either physics or experimental measurements [ABSTRACT FROM AUTHOR]

Thermal protection has always been an important issue in the energy, environment and aerospace fields. Porous ceramics produced by the particle-stabilized foaming method have become a competitive material for thermal protection because of their low density and low thermal conductivity. However, the study of porous ceramics for composite systems using particle-stabilized foaming method was relatively rare. Here, silica-alumina composite porous ceramics were prepared by particle-stabilized foaming method, which was achieved by tailoring the surface charges of silica and alumina through adjustment of the pH. Porous ceramics exhibited porosity as high as 97.49% and thermal conductivity (25 °C) as low as 0.063 W m−1 K−1. The compressive strength of porous ceramics sintered at 1500 °C with a solid content of 30 wt% could reach 0.765 MPa. Based on the light weight and excellent thermal insulation properties, the composite porous ceramic could be used as a potential thermal insulation material in the spacecraft industry. [ABSTRACT FROM AUTHOR]

Despite the increasing attention on two-dimensional (2D) metal iodides in recent years for their appropriate bandgaps and exceptional optical properties, there is limited understanding of their intriguing thermal transport properties. Here, the strain-tunable mechanic, electronic, and transport properties of the monolayer CaI 2 are calculated in detail by combining first-principles calculations with Boltzmann transport theory. We have checked its thermal, dynamic, and mechanical stability by computing ab -initio molecular dynamics, phonon spectra and elastic constants, respectively. The calculation results from the PBE-GGA and HSE06 methods indicate that the monolayer CaI 2 is an indirect semiconductor, with band gaps of 3.92 eV and 5.12 eV, respectively. Additionally, the effective masses and Fermi velocities for both holes and electrons are also obtained, which indicates that the monolayer CaI 2 owns the excellent electronic transport property. These mechanical constants and electronic parameters are also highly sensitive to the external strain. The calculated real lattice thermal conductivity of the monolayer CaI 2 at 300 K is about 1.01 W/mK, which is rather low among 2D materials, implying its potential application in heat insulation materials or thermal insulation material. With the biaxial tensile strain increasing, its lattice thermal conductivity would further decrease. The difference in lattice thermal conductivities between 0 % and 2 % strain, as well as between 4 % and 6 % strain, is much smaller than that between 2 % and 4 % strains. Subsequently, the group velocities, phonon scattering rates, and cumulative lattice thermal conductivities of the monolayer CaI 2 are discussed under the different strains. [ABSTRACT FROM AUTHOR]

Most of the thermal characterization methods using a uniform heating of a surface (Guarded Hot Plate, Transient Hot Plate, Fluxmeter Method) assume 1D transfer in the measurement area and neglect the in-plane heat transfer in the heating element. This results in limitations regarding the time interval for estimation, the thickness of samples or the possibility of simultaneously measuring thermal conductivity and capacity. To overcome these limits, a new 3D transient analytical model suited to isotropic materials and taking into account the convective lateral heat losses on the periphery of the samples as well as the 3D heat transfers in the heating element has been developed. It is first presented and then validated by comparison with 3D numerical simulations carried out with COMSOL. A study of the reduced sensitivities of the measured temperature to the various parameters and parameters estimations carried out on simulations obtained with the 3D model enable us to define an optimal estimation process. Finally, transient hot plate experiments were carried out on five extruded polystyrene samples with thickness ranging from 9.1 mm to 49.8 mm and on samples of PVC foam, PVC and of the reference anisotropic material IRMM-440. The results validate the theoretical study with a deviation lower than 5% compared to the known values of the thermal conductivity for the isotropic materials when using the 3D model, while the deviation may reach 77% using the1D model for the thickest sample of extruded polystyrene. The deviation reaches 11% for the thermal conductivity of IRMM-440 showing the need for a model taking into account the anisotropy for this type of materials. • 1D heat transfer is most often assumed in thermal characterization methods using plane source. • Experimental devices to ensure a 1D heat transfer are complex. • A 3D analytical model is developed for transient plane source methods. • The accuracy of thermal properties estimation using this 3D model is demonstrated. [ABSTRACT FROM AUTHOR]

Heat consumption is a serious energy waste, especially in an extremely cold environment. In view of their excellent advantages, several kinds of aerogels with different functions were emerged successively and served as critical materials in various areas. In this contribution, a simple strategy was developed to fabricate a high-fidelity and high-performance organic/inorganic composite aerogel by integrating dianhydrid-end capped polyamide acid (PAA) precursor and multi-amino functionalized hydroxyapatite (m-AmHA; used as the inorganic cross-linkers) in different feed ratios. Followed by the freeze-drying and thermal imidization treatments, the chemical cross-linked polyimide (PI) and HA based aerogels (HA x @PI, in which x represents the percentage of HA content) were obtained. The synergistic effect of inorganic filler and microporous structure of aerogel led to a great improvement of mechanical and thermal properties. Most importantly, the resultant HA x @PI aerogels could maintain their excellent physicochemical properties in several extreme environments such as ultra hot (300 °C), extreme cold (-196 °C; liquid nitrogen), water soaking (2 h, 40 °C), acid (pH 2.0; 1 h, 40 °C) and alkali (pH 12.0; 1 h, 40 °C) conditions. Based on these outstanding properties, we believe that such HA x @PI composite aerogels with low cost and high performances endowed them to be an ideal candidate to be employed in several harsh environments in addition to the conventional insulation and flame-retardant materials. • Uniformity dispersed HA contained polyimide-based aerogels were fabricated. • The mechanical properties, flame resistance, and thermal insulation properties were enhanced with the doping of HA. • Such aerogels could withstand several harsh environments, including ultra hot, extreme cold, water soaking, acid and alkali conditions, without influence on their physicochemical properties. [ABSTRACT FROM AUTHOR]

Aerogels are excellent thermal insulation materials with extremely low thermal conductivity. However, the practical applications of traditional oxide aerogels, such as SiO 2 and Al 2 O 3 aerogels, are limited by the disadvantages of easy sintering and intrinsic brittleness. SiC is a good candidate for new aerogel due to its superior stability and good properties from room to high temperatures. However, it is generally supposed that SiC cannot be employed as thermal insulation material because of its high intrinsic thermal conductivity. We herein developed SiC nanowire aerogel with quite low thermal conductivity using freeze-drying method. The fabricated SiC nanowire aerogel exhibits ultra-high porosity (∼99.5%), excellent high-temperature stability (∼1700 °C), extremely low thermal conductivity (0.035 W/(m⋅K)) and good compressive flexibility. The low thermal conductivity is resulted from ultra-high porosity and multi-level nanostructures. Flexible compression behavior is attributed to the capability of moving and buckling of SiC nanowires, originating from both ultra-high porosity and strong connection between nanowires. This exploration highlights the flexible SiC nanowire aerogel as a promising high temperature thermal insulation material. [ABSTRACT FROM AUTHOR]

Ultra-lightweight foam concrete (ULFC) is a relatively new construction material that has gained attention recently due to its unique properties. This material is not very heavy and low-density, making it easy to form into different shapes and sizes. Its excellent thermal insulation makes it popular for building walls, roofs, and floors. This review paper provides an in-depth examination of the properties and characteristics of ULFC. Its composition typically consists of cement, water, foam, additives, and the various manufacturing methods used to produce it—the mechanical properties of ULFC, including its compressive strength. The density of ULFC can vary greatly, usually falling between 100 and 600 kg/m3. The diversity of this can be affected by different factors, such as the kind and number of additives applied and the methods of foaming and thickening employed. The paper highlights the various applications of ULFC in the construction industry. Its use is as a TC material, which can help reduce heating and cooling costs; as a structural material, it can help reduce dead loads of structures. The review paper also discusses the challenges associated with ULFC production, including foam stability. Foam insulation concrete emits 302–508 kg CO 2 per cubic meter, primarily due to Portland cement, but enhances building energy efficiency, reducing household CO 2 emissions, while advanced recycled insulation materials offer superior thermal and acoustic properties with lower environmental impact. Additionally, we examine the current research on ULFC and suggest potential avenues for future investigation. This paper aims to introduce and put forward a range of cutting-edge and original recommendations and informative guidelines, with the ultimate objective of directing and shaping future research endeavors that focus on effectively exploiting and utilizing ultra-light foamed concrete. • Utilisation of Ultra-light foamed concrete for sustainable construction. • Mechanical properties and thermal insulation perspective incorporating Ultra-light foamed concrete. • The density of ULFC materials compared with normal concrete. • Microstructures properties of concrete incorporated with ULFC. • Recommendations and observations are advanced for future research in ULFC. [ABSTRACT FROM AUTHOR]

• Substitution of OPC cement with geopolymer for wood wool boards. • Formulate precursor and activator compositions in geopolymer and fibre treatment. • Light composite, low thermal conductivity, and meet minimum strength requirements. • Natural fibres influences the optimal Na 2 O concentration and modulus for strength. • Treated fibres recommended for higher modulus applications and improved strengths. This study investigates the substitution of ordinary Portland cement (OPC) with geopolymer in the production of wood wool geopolymer boards (WWGB), offering insights into manufacturing methods, design parameters, and performance characteristics. The composite formulation involves fibre pre-treatment, adjustment of precursor components, and control of activator compositions. The optimized formulation results in a lightweight composite with a density of 392 kg m−3 and porosity of 76 %, meeting prescribed minimum compressive (20 kPa) and bending strength (1700 kPa) requirements. The inclusion of natural fibres influences the optimal Na 2 O concentration and modulus for strength, with treated fibres recommended for higher modulus applications and improved strengths. Furthermore, it exhibits low thermal conductivity at 77 mW m−1 K−1, minimal moisture sorption, and low vapour resistance, offering a sustainable alternative in the field of insulation materials. [Display omitted] [ABSTRACT FROM AUTHOR]

High-strength thermal insulation mortar, with its excellent mechanical properties and thermal insulation performance, is commonly used in building structure insulation and reinforcement renovations. In this study, vitrified microbeads and expanded perlite (EP) were used as thermal insulation materials to create high-strength thermal insulation mortar. The effects of the replacement percentage of these materials (50%, 65%, 75%, and 80%) on the density, water absorption, porosity, compressive and flexural strength, and thermal conductivity of the mortar were studied. The results show that increased replacement percentages of vitrified microbead (EP) led to a decrease in the density of the mortar and an increase in the water absorption rate and porosity. Furthermore, when the replacement percentages were increased, the compressive and flexural strength and the thermal conductivity of the mortar were reduced. Comparative analysis of the pore structure of high-strength thermal insulation mortar using scanning electron microscopy and digital microscope revealed the influence of vitrified microbead (EP) on the internal pore structure of high-strength thermal insulation mortar. The influence coefficient (η s) of volume replacement percentage of insulation materials was introduced using the Hamilton and Crosser models. Furthermore, the prediction model of thermal conductivity of high-strength thermal insulation mortar was established under different volume replacement percentages of vitrified microbead (EP). The calculated values of the model matched well with the measured values, with the ratios of the calculated values of the model to the experimental ones ranging from 0.85 to 1.15. • The physical, mechanical, and thermal conductive properties of mortar are found to be influenced by the amount of insulation. • The prediction model of thermal conductivity of high-strength thermal insulation mortar is established. [ABSTRACT FROM AUTHOR]

• The fabrication process of Ni-P-Al 2 O 3 hollow microlattice is proposed. • The high-temperature antioxidant property of hollow microlattice is improved. • The heat insulation performance can be enhanced up to 13.9%. Hollow microlattice material is a kind of excellent heat insulation material due to its special microstructural characteristics and ultra-low relative density. However, the possibility of oxidation at the temperature higher than 500℃ limits its application in the high-temperature insulation fields, such as rockets and aircraft engines. In order to overcome this obstacle, this study successfully prepared nano-Al 2 O 3 reinforced metallic hollow microlattice materials with an equivalent density of 26.5 mg/cm3. Heat insulation tests and thermogravimetric (TG) experiments were also carried out to investigate the thermal performances of the Al 2 O 3 reinforced metallic hollow microlattice materials, while the effect of the concentration of the Al 2 O 3 was also investigated in accordance with the comparative tests. The results indicate that the Al 2 O 3 plays a significant role in hindering the high-temperature oxidation of hollow microlattice material, especially with Al 2 O 3 concentration in the range of 2 g/L to 4 g/L, and the heat insulation performance can be improved by 13.9%. [ABSTRACT FROM AUTHOR]

This study demonstrates scalable mechanochemical synthesis of rhodostannite Cu 2 FeSn 3 S 8 nanocrystals. On the contrary to the previous reports focused on the synthesis of stannite Cu 2 FeSnS 4 reporting the rhodostannite impurity, we succeeded in preparing stannite-free product after milling. Pure elements were used for a solvent-free production in a batch of 100 g using an eccentric vibratory mill. The progress of the synthesis was monitored by X-ray diffraction and magnetometry, which both confirmed a successful reaction progress until 6 h of milling. However, further treatment (until 10 h) did not result in an improvement, as quite a high saturation magnetization (7.8 emu/g) and clearly evident diffraction at around 44° in the XRD pattern of the product due to the presence of ferromagnetic un-reacted iron with content slightly above 5% was evidenced. The product is sulfur- and tin-deficient, with crystallite size of around 12 nm. In-depth SEM/EDS analysis has shown the inhomogeneity of Fe distribution due to unfinished reaction. The bandgap of the produced material was 1.29 eV. The spark plasma sintering treatment resulted in complete consumption of non-reacted iron, but partial decomposition to stannite Cu 2 FeSnS 4 was observed. The product is an intrinsic semiconductor with high electrical resistivity, and is therefore unsuitable for thermoelectric application. However, its thermal conductivity is low, thus it could be used as an electrically and thermally insulating material. [Display omitted] • Rhodostannite Cu 2 FeSn 3 S 8 nanocrystals have been successfully produced. • Environmentally friendly solid-state mechanochemical approach has been used. • Scalability of the synthesis up to 100 g per batch was demonstrated. • The product showed interesting electrical and thermal insulating properties. [ABSTRACT FROM AUTHOR]

Recycled concrete powder (RCP) is a promising supplementary cementitious material, its application in thermal insulation materials is however very limited. In this study, the influence of RCP substitution on the properties of insulation mortars was investigated. The results showed that as the RCP content increased, the compressive strength and thermal conductivity of insulation mortars decreased by 39.8% and 16.8%, owing to the increasing volumes of porous paste and internal air voids. Note that the mortar containing a high content (50 wt%) of RCP struggled to meet the strength requirements of the specification. Therefore, CO 2 curing was further employed here to alleviate the strength loss and successfully increased the compressive strength by 11%∼38%. It was found that since the CaCO 3 particles formed and densified the microstructure (confirmed by the porosity test), the strength reduction derived from the RCP substitution was compensated for. Consequently, insulation mortars incorporating 50% RCP after CO 2 curing for 7 days exhibited satisfactory compressive strength (∼ 0.22 MPa) and relatively low thermal conductivity (∼ 0.048 W/(m∙K)). The mortars showed improved aesthetic appearance and excellent thermal insulation capacity in both hot and cold environments. This study proposed a successful approach to combining reutilization of RCP and CO 2 curing in insulation mortar generation, which effectively improved the sustainability of materials. • A novel and sustainable EPS insulation mortar is developed for energy-efficient buildings. • The synergistic influence of the RCP substitution and CO 2 curing duration is studied. • Remarkably low thermal conductivity is attained through the incorporation of RCP. • Excellent aesthetic appearance and thermal performance are achieved simultaneously. [ABSTRACT FROM AUTHOR]

• Rigid polyurethane foam as the preferred thermal insulation. • Analysis of the influence of fly ash on material thermal conductivity. • Calculation of the heat balance for a wall with polyurethane insulation. • Study of the temperature field in the cross-section of the wall. Limitations in natural resource availability have a significant impact on prices of thermal energy. As a result, a growth of interest in the technology of insulation materials is observed. The paper presents a comparative analysis of rigid polyurethane foams, which are widely used as insulation materials. Rigid polyurethane foam with 10 wt.% addition of coal fly ash is compared to a reference foam, without any addition. The thermal conductivity coefficient of polyurethane materials was determined by the Hot Disk device. Heat transfer for both types of foams was modelled. As a result of the numerical modelling, the temperature field for the wall was obtained. The results of the computations have shown differences in energy losses. Conducted analyses demonstrate that the modified polyurethane foam (with the addition of coal fly ash) performs better as an insulation material. The reduction of heat requirement is 2.9 %. An environmental analysis of the insulation materials was also carried out. Using the SUBRAW index method it was calculated that embodied energy and the carbon footprint are lower in the case of the modified polyurethane compared to the unmodified foam. [ABSTRACT FROM AUTHOR]

• Cyclic loads applied on foam glass aggregates (FGA) at different compaction ratios. • FGA response under deviatoric stresses 25 kPa, 100 kPa, and 200 kPa was investigated. • Resilient modulus (M r) and accumulated plastic strain (ɛ acc) were measured. • Increasing the compaction ratio led to a significant decrease in ɛ acc values. • Revealed that FGA at 40% can be used in infrastructure base layer material. Foam glass aggregate (FGA) is considered as a lightweight and thermal insulation material. It has a wide granular size distribution nature that can influence the material's dynamic response when subjected to moving loads. Therefore, it is crucial to investigate the impact of different compaction ratios on the material's dynamic behavior. This study focused on examining the effects of varying compaction ratios (10%, 20%, 30%, and 40%) on dynamic parameters such as resilient stiffness (M r) and accumulated plastic strains (ɛ acc) of FGA. Uniaxial deviatoric stresses were applied to the material samples in a series to assess their influence on the material's behavior over multiple cycles. The results revealed the significant influence of increasing the compaction ratio to 40% on the material's behavior. At this compaction ratio, the ɛ acc decreased to approximately 71%, 69%, and 86% for deviatoric stresses of 25 kPa, 100 kPa, and 200 kPa, respectively, after subjecting the material to 40,000 cycles. The increase in recoverable strains resulting from the material's fragile property under higher compaction energy led to a decrease in the M r values of FGA samples as the compaction ratios increased. The lower boundary of M r values for FGA ranged from 102 MPa to 189 MPa, while the upper boundary ranged from 150 MPa to 219 MPa under the selected deviatoric stresses. Although the interpretation of the shakedown criterion limitations yielded varying ranges for the colocation of FGA samples, it was found that FGA samples compacted at 40% exhibited robust characteristics suitable for constructing road embankments. This can be beneficial for infrastructure applications due to their excellent lightweight and thermal insulation properties. [ABSTRACT FROM AUTHOR]

With the development of alternate electrical power system and the improvement of voltage level, the operation conditions faced by epoxy resin (ER) insulation materials are becoming more and more complex. The traditional ER materials have been difficult to meet the increasingly stringent requirements. In this paper, the thermal and mechanical properties of DGEBA/TDE-85/MTHPA blend system were studied by molecular dynamics (MD) simulation and experiment. The results show that the addition of TDE-85 can significantly improve the thermal and mechanical properties, and the comprehensive improvement effect is the best when the molar ratio of DGEBA and TDE-85 is about 8:2. The experimental results are consistent with the simulation results. Further analysis of the micro-parameters of the monomer and the cross-linking network found that the torsional energy barrier of TDE-85 is higher than DGEBA. And the compatibility of the two ER is better when the ratio is 8:2. In addition, TDE-85 can introduce high-stability Y-nodes into the system, making the cross-linked network more stable, which has a significant effect on improving the thermal and mechanical properties. The research provide a reference for the blending modification of high-performance ER for high-voltage insulation. [Display omitted] • TDE-85 can introduce the Y-nodes of elevated stability into the epoxy resin crosslinking system. • TDE-85 has the potential to substantially enhance the thermal and mechanical characteristics of epoxy resin. • The most optimal improvement effect was observed when the molar ratio of DGEBA to TDE-85 was 8:2. [ABSTRACT FROM AUTHOR]

• Pumice aggregates were coated with polyester to obtain polymer-coated pumice aggregates (PCPA). • Lightweight concretes were produced with different cement dosages (200, 250 and 300) and PCPAs at different ratios (0%, 50% and 100%). • Physical properties, mechanical strength, thermal properties and internal structure analysis (SEM-EDS) of the produced concrete samples were performed. • REF D300 and REF D250 dosage series are in the semi-load-bearing lightweight concrete class, and the other all series are in the insulation concrete class. With the technological advances in the field of building materials, there has been an increasing focus on the research of lightweight concrete made with coated aggregates for improving the durability of concrete. In this study, pumice aggregates were coated with cast-based polyester to obtain polymer-coated pumice aggregates (PCPA). Lightweight concretes were produced with different cement dosages (200, 250 and 300) and PCPAs at different ratios (0%, 50% and 100%). Physical properties, mechanical strength, thermal properties and internal structure analysis (SEM-EDS) of the produced concrete samples were performed. According to the RILEM functional classification of lightweight concrete, the test results showed that REF D300 and REF D250 dosage series are in the semi-load-bearing lightweight concrete class, and the other all series are in the insulation concrete class, and the produced concretes can be classified as lightweight insulation materials. It can also be used in non-load-bearing walls or as an alternative lightweight insulation material. [ABSTRACT FROM AUTHOR]

Naturally-derived aerogels have attracted considerable attention owing to their good biocompatibility, biodegradability and sustainability, but their weak mechanical properties largely limit their applications in various fields. Herein, we proposed the use of a directional freeze-drying method to prepare an anisotropic honeycomb three-dimensional porous aerogel with water-soluble chitosan (CS) as a rigid skeleton and water-soluble biobased epoxy resin as cross-linked hard segments, which had low volume shrinkage and density of 13.9 % and 34.3 mg/cm3, respectively. The resultant aerogel had anisotropic mechanical properties, such as rigidity in the axial direction with a maximum axial modulus of 6.71 MPa, which was 51.6 times larger than that of the pure chitosan aerogel, demonstrating a good compressive elasticity in the radial direction. It also had anisotropic thermal management properties, with a lower thermal conductivity in the radial direction than in the axial direction, down to 0.029 W/mK. The introduction of biobased epoxy resin improved the overall thermal stability, flame retardancy, and increased the biomass content in the aerogel, reducing the carbon footprint of the material. This study paves the way for the construction of a special graded porous, structurally and functionally integrated thermal insulation aerogel, which is of great significance for the development of new thermal insulation materials. [Display omitted] • Anisotropic honeycomb bio-based aerogels have been prepared by directional freeze-drying. • The introducing of bio-based epoxy resin improves the comprehensive properties of aerogel. • The aerogel exhibits low thermal conductivity of 0.029 W/mK in the radical direction. • The aerogel shows low volume shrinkage (13.9 %) and density (34.3 mg/cm3). [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]

[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]

[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]

• Effect of diss fibers rate on mechanical and thermal properties of cementitious composite. • The incorporation of diss fibers in cement matrix makes the composite lighter and improves its insulating capacity. • Enhancement of Toughness of diss fibers based composites under flexion and compression. • The composites could be classified as structural and insulating material according to RILEM classification. This study investigates the performances of a new material composed of cement binder and natural vegetal diss fibers. The main goal is to use a locally abundant plant (diss) as a substitute for aggregates, in order to produce a lightweight material with excellent thermal insulation. Three composites with diss fiber content of 20%, 25% and 30% by weight of cement were produced, and their thermal and mechanical performances were experimentally investigated. At first, the flexural strength, toughness index, compressive strength and toughness energy of the composites were examined. Then, thermal properties in terms of conductivity, diffusivity and effusivity were evaluated for the three composites. The results show that incorporating a large amount of diss fibers in the cement matrix causes an increase in the porosity of the composite and consequently a reduction in density. The high porosity of the composites causes a significant reduction in compressive strength. However, the toughness of the composites in the post-cracking stage is significantly enhanced. Under three-point loading, the diss-fiber-reinforced composites exhibit pseudo-ductile post-peak behavior with high values of toughness index (I5). The low density is accompanied by an improvement in the composites' thermal performance, with a significant decrease in thermal conductivity, thermal diffusivity and thermal effusivity. According to RILEM, the developed composites could be classified as lightweight insulating materials and can be used in non-load bearing walls and insulating fillers. [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]

• CP is used to adjust the properties of foamed geopolymers. • The geopolymer foam with 50% CP exhibits excellent performance. • The incorporation of CP is beneficial for the pore structure in foamed concrete. In this study, cenospheres (CP, a lightweight component) was used to replace part of fly ash (FA) to prepare ultra-lightweight foamed geopolymer concrete (UFGC), and the fresh properties of the geopolymer paste was used to control the hardening performance of the UFGC sample. The results show that incorporating CP to the slag-FA system can effectively reduce the reaction rate of the geopolymer paste and increase its fluidity and setting time. Meanwhile, as the CP content increases, the density of the geopolymer foams decreases, and it exhibits better mechanical properties and thermal insulation performance when the substitution ratio of CP is 50%. In addition, a proper amount of CP improves the pore structure of the UFGC sample, reduces its sorptivity coefficient and drying shrinkage deformation. Therefore, a novel building exterior wall insulation material is prepared through CP to optimize the UFGC system, and its (C50) thermal conductivity is reduced by 37.86% compared to the control group, which is beneficial to the development of green and sustainable buildings. [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]

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]

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]

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]

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]

• The density of composites is higher with stabilized clay for the same hemp content. • The hemp to binder ratio impacts density, thermal conductivity and sorption curve. • Hemp clay composites are excellent hygric regulators and good insulation materials. • A correlation between hemp to binder ratio and water content is identified. • Innovative analysis of hemp and binder contribution to water sorption is performed. The objective of this paper is to investigate the effect of clay stabilization and hemp content on hygric and thermal performances. This experimental study is based on the measurement of sorption isotherm, moisture buffer value and thermal properties. The effect of water content on thermal conductivity is also investigated. The results show that Hemp Clay Composites (HCC) and Hemp Stabilized Clay Composites (HSCC) are hygroscopic and moisture buffering materials. The correlations between hemp content and water content are identified for sorption curves. An innovative analysis of the contribution of hemp and binder to water sorption is performed. The moisture buffer values classify the designed composites as excellent hygric regulators according to the Nordtest classification. The thermal conductivity ranges from 0.089 to 0.120 W/(m.K) at dry state, making them suitable for distributed insulation. The thermal conductivity increases linearly with density, for the two binders investigated in this study. Besides, the thermal conductivity increases linearly with water content too. Finally, this study underlines that the designed composites show high hygrothermal qualities. [ABSTRACT FROM AUTHOR]