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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]

In this study, mullite thermal insulation materials with in-situ synthesized mullite hollow whiskers were prepared by a solid-state reaction method using industrial alumina and silica as raw materials and tungsten-containing compounds as catalysts. The phase transition, microstructures, and effects of in-situ formed hollow whiskers on morphologies and properties of mullite thermal insulation materials were investigated by TG-DTA, XRD, SEM, TEM, thermal conductivity and compressive strength tests. The formation mechanism of mullite hollow whiskers was also studied. The results show that Al–Si–O agglomerations adsorbed on the surface of Al 2 (WO 4) 3 columnar particles which were formed at about 900 °C, then the decomposition of Al 2 (WO 4) 3 columnar particles and mullitization of Al–Si–O agglomerations led to the formation of mullite hollow whiskers at about 1200 °C. The mullite thermal insulation materials (prepared at 1500 °C) with in-situ formed hollow whiskers exhibit a low thermal conductivity of 0.329 W/(m∙K) to 0.396 W/(m∙K) and a sufficient cold compressive strength of 5.22 MPa. The physical and mechanical properties were controlled by the width and aspect ratio of mullite hollow whiskers. The research of this work provides a new insight into the development of mullite thermal insulation materials used at high temperatures. [ABSTRACT FROM AUTHOR]

Crystalline silica nanoparticles exhibit superior physical properties to amorphous phase when incorporated in nanocomposites. In this paper, we introduce the crystalline silica nanoparticles–embedded nanocomposites (CSN–nanocomposite) as a high-performance insulation material, and discuss their improved macro/microscopic properties according to the CSN contents. Monodisperse CSN particles (50 nm in size) are produced via facile and cost-effective top-down grinding methods, and their surfaces are modified with organic ligands to endure homogeneous dispersion and chemical crosslinking with epoxy matrix. With the aid of optimal hybridization of the CSN and the matrix, the CSN–nanocomposite exhibits high optical transparency, enhanced mechanical strength, increased thermal conductivity, and improved electrical insulating property. [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]

This paper presents a new model of the transient temperature at a point situated at a distance d of the heating wire, in a parallel hot wire measurement device. A preliminary theoretical study shows the limits of the estimation method proposed by the standard ISO8894-2. First, we proposed an optimal processing method, based on the model used in the standard, to improve the estimation of the thermal conductivity. Then, a new model based on the quadrupolar formalism is developed, it takes into account: the mass and the radius of the heating wire, the thermal contact resistance between the heating wire and the sample and the mass of the thermocouple. A theoretical study shows that this model enables a precise estimation of the thermal conductivity of a large range of materials and that it makes also possible to obtain an estimation of the volume heat capacity. An experimental study has been realized using a very low density material (polystyrene with ρ = 15 kg m − 3 ) at ambient temperature and a reference material (Silcal 1100) at temperatures varying from 200 °C to 1000 °C to validate the results of the theoretical study. Compared to known thermal properties of these two materials, the thermal conductivity was estimated with a deviation lower than 3.4% and the volume heat capacity was estimated with a deviation lower than 10%. [ABSTRACT FROM AUTHOR]

The performance of light timber frame wall and floor assemblies in fire depends on their composition. The assemblies' ability to form fire-separations between building compartments (separating function) can be assessed by full-scale fire testing or calculation methods. Calculations are the low cost and more flexible alternative. The component additive method is a commonly used calculation method for fire design of timber structures. The method considers the insulation ability of the material layers present in the assembly. The component additive method described in this article is developed to be flexible to implement different materials and products of different dimensions. However, the amount of different materials currently included in this method is rather limited and there is no generally accepted procedure to implement new materials. This paper presents a common agreement of the procedure to implement new materials which comprises of: (1) the design and execution of model-scale fire tests; (2) determination of the modified thermal properties needed for simulations; (3) thermal simulations of assemblies in fire conditions; (4) development of design equations and; (5) verification by one or more full-scale fire test(s). The abovementioned steps have been clearly presented in this paper and supported by examples. • The paper focuses on improving the component additive method. • The procedure for implementing new materials to the method has been presented. • Claddings and insulations are considered differently. • All necessary steps have been covered comprehensively. [ABSTRACT FROM AUTHOR]

Highlights • Specific heat determined for four corn stover fractions. • The thermal properties of corn stover fractions should be determined separately. • All corn stover fractions are useful for insulating materials production. • The applied method ensured high accuracy of measurements of corn stover specific heat. Abstract The properties of agriculture by-products make them applicable for insulating materials production. One of the potential source of natural insulating material is corn stover, especially the stalks. In the present study the density, specific heat and volumetric specific heat capacity of individual fractions of corn stover were determined. The separation of the corn fractions allowed to identify the most suitable fractions for insulating panels production. Four separated fractions, i.e. stalks, leaves, husks and cobs, were in focus of the study. The specific heat measurements of selected corn factions were carried out with a water calorimeter. The measurements were made for the oven dry materials which were placed in a heat shrinkable membrane to prepare samples of a cylindrical shape. The obtained values of specific heat and volumetric specific heat capacity confirmed that the thermal properties of corn stover fractions should be determined separately. Only leaves and stalks were characterized by similar values of specific heat and volumetric specific heat capacity. The highest value of specific heat equal to 1723 J/(kg·K) was determined for husks. The observed high values of volumetric specific heat capacity determined for all corn stover fractions confirmed their ability of heat accumulation. [ABSTRACT FROM AUTHOR]

Abstract A comprehensive concept for coal conversion is proposed in this work, from which a series of products generated including light volatiles, liquid oils, and pyrolysis chars. The result indicates the optimal temperature for the pyrolysis from organic solvent extraction residue is between 700 °C to 900 °C, producing largest amount of liquid oils and giving rise to a chemically stable pyrolysis char sample with considerable BET specific surface area. The pyrolysis chars are then utilized as an alternative material for the fabrication of heat-insulating building material (char clay plaster-CCP, char brick-CB and foam glass-FA). Due to the inherent large specific surface area and ample pore channels, the water could be absorbed and stored in these pores, resulting in the effects of regulating indoor humidity and also low thermal conductivity. The char-based building material makes the exterior walls good breathing properties, able to maintain a proper humidity level. The building energy saving will be benefited from the excellent insulation property of these building products. Graphical abstract Schematic illustration of pyrolysis char derived building materials. Image 1004 Highlights • A clean production technique of coal conversion into building material is investigated. • Optimal pyrolysis temperature when producing chars for better performance is determined. • The enhanced property is attributed to the inherent porosity nature of pyrolysis chars. [ABSTRACT FROM AUTHOR]

Abstract The work deals with the thermal characterization of low conductivity millimeter-sized samples. Regarding the increasing of the technical problems when the sample sizes decrease and become millimetric, an analytical solution obtained from the fin model and adapted from previous work is developed to estimate the thermal diffusivity and a modified Biot number by least-squares method. Then separated calorimetric and density measurements enable the calculation of the thermal conductivity. During experiment, the sample is heated from one side for a few seconds. An infrared thermography is used to measure the temperature field of the sample surface. At first, the method is tested with polycarbonate and balsa samples, which thermal properties are well-known. Then, the thermal diffusivity and conductivity of the hemp shiv are estimated, which values are of the same order of magnitude as those encountered in the literature for cellulosic materials of same density. If the estimation of the thermal diffusivity of the samples is in good agreement with a low uncertainty, the uncertainty on the thermal conductivity is about 10% due to the difficulty to consider the heat exchange coefficient when the tested material becomes a better insulator. Nevertheless, this method seems relevant to characterize millimeter samples of low thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract Owing to the integration of power electronic devices and the development of flexible devices, demands for high quality thermal conductive composites have substantially increased. Thus highly flexible poly (vinylidene fluoride)/boron nitride (i.e. PVDF/BN-x) composite films were prepared in this work, and a low quantity of graphite nanoplatelets (GNP) was added to simultaneously improve the thermal and mechanical properties of the film (i.e. PVDF/BN-30/GNP-y). The synergistic effect of the two fillers has been discussed, and results show that the thermal conductivity of PVDF/BN-30/GNP-2.5 reaches up to 0.720 Wm−1K−1 compared with 0.634 Wm−1K−1 of PVDF/BN-30. And the tensile strength is also increased from 12.43 MPa to 20.21 MPa, which has been improved by 63%. In addition, the experiment results validate that the films possess high electrical insulation and satisfactory breakdown strength, which proves its applicability to high-voltage environment. Besides, the thermal conductivity of films can be preserved after 300 thermal shocks with extreme temperature changes. This study provides a kind of flexible thermal interface material with excellent comprehensive properties for application in field of power electronics. [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]

An innovative powder-foaming process able to produce thermal and acoustic insulating foams obtained by sol-gel and a subsequent freeze-drying process was developed. Gel containing glass powder was formed using alginate, a polysaccharide composed of 1-4linked α-L-guluronic acid and β-D-mannuronic acid, capable to form stable gels in presence of calcium cations. In order to obtain a porous foam, gels were frozen and then freeze-dried. Foam properties strongly depend on production parameters, particle dimension and different binder concentrations, their influence was investigated. The resulting glass foams were characterized in order to evaluate structure, density, mechanical and acoustic properties. The results pointed out an improved acoustic insulating performance respect to rock wool. Foams were also subjected to a thermal process to better fix powders into the final glass structure. [ABSTRACT FROM AUTHOR]

There are approximately 10 million suspended timber ground floor constructions in the UK and millions more globally. However, it is unknown how many of these floors are insulated and their performance has not been widely investigated. This study investigates the impact of retrofitting insulation on the thermal performance of suspended timber ground floors through the detailed investigation of a UK case study dwelling. Practical and buildable interventions were undertaken: fully-filling the floor void with EPS beads, and 100 mm woodfibre insulation between the joists. The performance of both interventions was monitored by high-resolution in-situ heat-flow monitoring in 27 floor locations, allowing for comparison with the uninsulated floor and with modelled results. While floors often remain uninsulated due to the disruption of retrospective works, this study highlighted potentially significant heat loss reductions: the mean whole floor U-value dropped by 65% for woodfibre insulation and 92% for bead-insulation which also benefited from sealed airbricks. A disparity between the in-situ measured and modelled performance was observed; this gap reduced the better insulated the floor was. The findings have implications for policy, retrofit decision-making and carbon emission reduction stock models, especially given the modelled underestimation of floor heat loss, impact of interventions and assumed financial payback for this study. [ABSTRACT FROM AUTHOR]

Liquid paraffin microcapsules (LPMs) were incorporated into epoxy resin to prepare fluid-filler/polymer composite materials in this work, with the objective of introducing fluid heat convection into thermally conductive and electrically insulting materials. The LPMs were fabricated by coating urea resin onto liquid paraffin via in-situ polymerization, enabling the as-prepared LPMs to experience no weight loss below 240 °C. The heat dissipation efficiency of the LPM/epoxy-resin composite with 25 vol% LPM content was remarkably improved above 50 °C, although its thermal conductivity was only 0.25 W/(m·K) at room temperature. The enhancement of heat dissipation efficiency above 50 °C could be ascribed to the effect of fluid heat convection in the LPM filler increased with increasing temperature. The LPM/epoxy composites containing 20 vol% of LPM filler exhibited tensile strengths, bending strengths, and breaking elongations that were 14.3%, 12.5%, and 30.5% higher, respectively, than those of the pure epoxy resin. The results of this study indicate that fluid heat convention is of great significance in the development of thermally conductive and electrically insulting materials. [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]

This work aims to contribute to the long term objective of developing in situ thermal characterization of building insulation material. Cylindrical hot probe can be considered the most adapted instrument but the heat flux is radial then unreliable results can be obtained if samples are not homogeneous or radially symmetric like common layered insulation materials. To avoid this difficulty, we have studied glass wool which has been performed by a “crimping” process in order to obtain a more isotropic structure. The main problem treated in this work concerns the identification procedure to determine thermal characteristics of insulation materials. The standard procedure to determine thermal conductivity requires linear thermogram representing temperature rise against the logarithm of the time. Sigmoid curve (not linear curve) has been obtained for insulation material. So we suggest to develop identification procedure applied from the whole thermogram and not only from the linear part. The interest of this procedure is also to determine simultaneously thermal conductivity and thermal capacity of the surrounding material. Analytical solution based on Jaeger model has been employed to resolve the time dependant problem of heat transfer. The mathematical approach of the model of Blackwell [22], Jaeger [23] and Devries [24] are very similar. However, none of these models described a proper way to calculate the thermal conductivity and thermal capacity simultaneously from thermogram. This work is referred to the work of van Haneghem [17] and Hutter [31] for granular materials which developed or applied revised model based on that of Jaeger. Inverse technique with optimization routines from Matlab has been used to minimize the difference between measured and estimated temperature thermograms. [ABSTRACT FROM AUTHOR]

A new lightweight and thermal insulating material was successfully prepared by impregnating Al 2 O 3 –SiO 2 aerogel into a porous mullite–zirconia fiber network with a quasi-layered microstructure. The microstructures, thermal and mechanical properties of the porous mullite–zirconia ceramics were investigated before and after the impregnating of Al 2 O 3 –SiO 2 aerogel. It was observed that the mullite and zirconia fibers combined well with aerogels. Compared with fibrous porous mullite-zirconia ceramics, the Al 2 O 3 –SiO 2 aerogel/porous mullite–zirconia composite exhibited higher compressive strength (i.e. 1.36 MPa in the z direction) and lower thermal conductivity (i.e. 0.052 W/(m·K)). The present work provides an efficient way to fabricate highly porous ceramics with high strength and ultra-low thermal conductivity, which find potential use in high-temperature thermal insulation 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]

Electrically insulating polymeric nanocomposites with high thermal conductivity have great potential for use as thermal-management materials in increasingly high-power-density electronics and optoelectronics. Conventional composite materials require a large amount, over 70 vol%, of electrically conducting fillers such as carbon allotropes to attain thermal conductivities of 1–5 W/mK, [Balandin, 2011] [1] which restricts the utility of these materials to applications that require both electrical and thermal conductivities. Here, we introduce a strategy to achieve the strongest enhancement of thermal conductivity to date at a low level of filler loading (≤15 vol%) in insulating polymer nanocomposites with hexagonal boron nitride (BN) nanosheets. The combination of electric-field switching and the application of fillers with various aspect ratios enables the rearrangement of the BN nanofillers into linear densely packed BN structures (LDPBNs). Flexible nanocomposite films with LDPBNs exhibit electrical resistivity greater than 1.50 × 10 −6 MΩ cm and a thermal conductivity of 1.56 W/mK, a dramatic enhancement over that of pristine polysiloxane with the same BN loading (0.4 W/mK). Our strategy of electric-field-induced BN nanosheet assembly offers insight into the possibility of solving thermal-management problems using ideal thermal interface materials, thus enabling improved next-generation integrated circuits and nanoelectronics. [ABSTRACT FROM AUTHOR]

Improvement in the thermal performance of the historic building stock has the potential to reduce building operational energy and its associated negative impact on the environment. Currently, there is a lack of knowledge on the performance of traditional solid walls and the impact of internal insulation on their hygrothermal behaviour. This paper investigates the in-situ thermal performance of seven internal insulation options, on a historic brick wall, using heat flux sensors (U-value measurement), thermal imaging survey and internal wall temperature. The insulations include thermal paint, aerogel, cork lime, hemp lime, calcium silicate board, timber fibre board and PIR board. Their performance is compared to a traditional lime plaster finish. Additionally, their density and specific heat capacity is measured in the laboratory. The brick wall with lime plaster (c.840 mm) has a higher U-value of 1.32 W/m 2 K than expected. All the internal insulations were found to reduce the U-value of the wall (between 34 and 61%) with the exception of a thermal paint which had no effect. The thermal imaging survey corroborated the U-value results, and insulations with low wall U-values also had high wall surface temperatures. Internal wall temperatures showed a similar trend; a reduced temperature at the wall/insulation interface for low thermal conductivity insulations. Lastly, the in-situ insulations underperformed when compared to their manufacturer's specified properties (wall U-value higher by 13–25% with the exception of cork lime). This is attributed to real in-situ environments compared to ideal testing laboratory conditions. [ABSTRACT FROM AUTHOR]

Nowadays, energy dissipation of buildings has caused serious problems to the environment for leading to overuse of resources in China. To reduce energy consumption and protect the environment, shale that widely distributed in China and the waste, including both building waste and industrial waste are used as raw materials to manufacture fired hollow blocks with 29-row holes which ensure the insulation properties and reduction of weight. As samples, 365 mm × 248 mm × 249 mm rectangular fire hollow blocks with density of 850 kg/m 3 were produced to study the mechanical and thermal properties of this wall material. The results satisfied the relevant Chinese Standard, and the block has a high compressive strength and reliable insulation performance comparing with fired common brick or other hollow blocks. Because of the excellent self-insulation characteristics, the blocks could be used directly as wall materials without requiring the usage of special insulation measures in masonry structures, which mean that this new-type material could reduce the cost of housing construction and had broad application prospect in masonry structures. Therefore, using this block could not only cut down the consumption of energy, but also could ease the pressure applied on the environment. [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]

Highlights: [•] We studied the processing properties of various epoxy matrices. [•] We studied the radiation resistance of TGPAP-based and DGEBF-based composites. [•] TGPAP-based systems are more suitable for VPI process than DGEBF-based systems. [•] TGPAP systems present more radiation resistant than DGEBF systems. [Copyright &y& Elsevier]

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]

Abstract: The hot-disk technique is a very practicable transient method of measurement of the thermal properties of solid materials. It has been applied successfully to a wide variety of materials. However, it is based on several approximations regarding the nature of the heat transfer. Notably, the probe is considered thermally neutral, and the heat transfer is assumed purely conductive. These two assumptions are questionable when dealing with low-density thermal insulators. In order to evaluate the accuracy of the method, we have generated numerically noised thermograms reproducing the thermal response that would be recorded when measurements are applied to those type of materials. Thereafter, the best-fitting procedure of the classical hot-disk technique was applied to these thermograms. The analysis of the identification results show that the presence of a radiative contribution do not affect the accuracy of the thermal properties identified. The conductivity measured actually corresponds to the equivalent conductivity. On the other hand, when the method is applied to materials with thermal inertia strongly different from the probe (≈2 order of magnitude lower or more), the accuracy of the method becomes questionable. This is notably the case for common insulators used in the building industry like polymer foam or mineral wools. The preceding conclusions have been validated by experimental measurements on a standard low-density XPS foam sample and a superinsulating silica areogel. [Copyright &y& Elsevier]

Abstract: An efficient solar reflective thermal insulating coatings (SRCs) based on Y-stabilized Sb2O3 nanoparticles has been prepared via a facile one-pot ball-milling route. Y-stabilized Sb2O3 have smaller particle size (about 5nm), disperse more evenly in coating films and exhibit higher solar reflectance compared with pure Sb2O3. Y-stabilized Sb2O3 SRCs have the reflectance of more than 90% in the region 450–1600nm and more than 80% in the region 1600–2200nm and excellent thermal insulating properties. The observed solar reflectance properties of Y-stabilized Sb2O3 SRCs were explained on the basis of the electronic structure of the material and physical parameters such as mean particle size (crystallite size) and refractive index. Due to its high solar reflectance and excellent thermal insulation properties, as-prepared Y-stabilized Sb2O3 SRCs maybe a promising candidate for the energy saving applications in the constructions and industry furnishment. [Copyright &y& Elsevier]

Abstract: In this paper, experiments to investigate fibrous insulating materials used in buildings have been performed. Two kinds of glass fibers based products were studied. Scanning electron microscopy (SEM) coupled with an EDX detector, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction diagnostic method were used to assess materials properties. Through the coupling of thermal analyses with morphological and structural characterization techniques, a fast and safer comparison between the insulators becomes possible. So, after being tested at various rates of humidities, it is shown that the aim cause of ageing in the glass wools studied is mainly due to their binders. In fact, the alteration of glass constituting fibers comes much later. Besides, there is no preferential orientation for the vapor transfer inside glass wools. [Copyright &y& Elsevier]

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]