Thermal Insulation Performance Research Articles

Carbon Nanofiber/Polyaniline Composite Aerogel with Excellent Electromagnetic Interference Shielding, Low Thermal Conductivity, and Extremely Low Heat Release

Abstract The rapid development of communication technology and high-frequency electronic devices has created a need for more advanced electromagnetic interference (EMI) shielding materials. In response to this demand, a study has been conducted to develop multifunctional carbon nanofibers (CNFs)/polyaniline (PANI) aerogels with excellent electromagnetic interference shielding, flame retardancy, and thermal insulation performance. The process involved freeze-drying of electrospun CNFs and PANI nanoparticles followed by in situ growth PANI to coat the CNFs, creating the core–shell structured CNFs/PANI composite fiber and its hybrid aerogels (CP-3@PANI). The interaction between PANI and aniline (ANI) provides attachment sites, allowing additional ANI adsorption into the aerogel for in situ polymerization. This results in PANI uniformly covering the surface of the CNFs, creating a core–shell composite fiber with a flexible CNF core and PANI shell. This process enhances the utilization rate of the ANI monomer and increases the PANI content loaded onto the aerogel. Additionally, effective connections are established between the CNFs, forming a stable, conductive three-dimensional network structure. The prepared CP-3@PANI aerogels exhibit excellent EMI shielding efficiency (SE) of 85.4 dB and specific EMI SE (SE d−1) of 791.2 dB cm3 g⁻1 in the X-band. Due to the synergistic flame-retardant effect of CNFs, PANI, and the dopant (phytic acid), the CP-3@PANI aerogels demonstrate outstanding flame-retardant and thermal insulation properties, with a peak heat release rate (PHRR) as low as 7.8 W g⁻1 and a total heat release of only 0.58 kJ g⁻1. This study provides an effective strategy for preparing multifunctional integrated EMI shielding materials.

High-temperature resistance and thermal insulation performance of continuous SiMOC ceramic fibers fabricated by the modified sol-gel method combined with dry spinning

High-temperature resistance and thermal insulation performance of continuous SiMOC ceramic fibers fabricated by the modified sol-gel method combined with dry spinning

Highly‐Buckled Nanofibrous Ceramic Aerogels with Ultra‐Large Stretchability and Tensile‐Insensitive Thermal Insulation

AbstractCeramic aerogels have exhibited many superior characteristics with promising applications. As an attractive material system for thermal insulation under extreme conditions, ceramic aerogels are required to withstand complex thermomechanical stress to retain their super‐insulating properties but, they often suffer from severe fracture damage that can lead to catastrophic failure. Herein, inspired by the tendrils of Parthenocissus, we report a design and synthesis of ultra‐stretchable ceramic aerogels constructed by highly buckled nanofibers. The buckling of nanofibers is formed by asymmetric deformation through two‐component off‐axial electrospinning method. The resulting aerogels feature an ultra‐large stretchability with a tensile strain of up to 150% and high restorability with a tensile strain of up to 80%. They also display a near‐zero Poisson's ratio (4.3 × 10−2) and a near‐zero thermal expansion coefficient (2.6 × 10−7 per °C), resulting in excellent thermomechanical stability. Benefiting from this ultra‐stretchability, the aerogels exhibit a unique tensile‐insensitive thermal insulation performance with thermal conductivities remaining only ≈106.7 mW m−1 K−1 at 1000 °C. This work promotes the development of ceramic aerogels for robust thermal insulation under extreme conditions and establishes a set of fundamental considerations in structural design of stretchable aerogels for a wide spectrum of applications.

Barrier materials integrated with gas regulation function are used to reduce the explosion risk of battery systems

Large-capacity lithium iron phosphate batteries are widely used in energy storage stations and electric vehicles due to their high cost-effectiveness and long lifespan. However, research shows that the gases generated during thermal runaway are mainly combustible, which may lead to fires or even explosions. Nevertheless, within the millimeter-scale confined space of a battery pack, effective solutions are scarce, making it challenging to simultaneously suppress kilowatt-level heat transfer and dilute the accumulated combustible gases. This research has developed a multifunctional fire shield with capabilities of “low-temperature heat conduction, medium-temperature heat absorption, high-temperature thermal insulation, and gas regulation.” The material is composed of hydrogel, aluminum hydroxide, ceramic fiber, and ammonium bicarbonate. In the low-temperature range, it exhibits an excellent thermal conductivity (0.58 W·m−1·K−1), capable of maintaining the battery module’s operating temperature within a reasonable range. In the medium to high-temperature range, its thermal conductivity rapidly decreases (0.04 W·m−1·K−1), and with its high phase change enthalpy (1727 J/g), the material can suppress the thermal propagation of a 100 Ah lithium iron phosphate battery module. This material starts to release CO2 at 90℃. In a confined space, the CO2 mixes uniformly with the gases generated during the thermal runaway process of the battery, reducing the risk of these gases (increasing the lower explosion limit by 44 % and reducing the maximum laminar flame speed by 58 %). Therefore, the multifunctional fire shield demonstrates exceptional heat conduction, heat absorption, thermal insulation, and gas regulation performance. This research provides new insights for the safety design of battery systems.

Development of a high-strength lightweight geopolymer concrete for structural and thermal insulation applications

Investigating the thermal insulation properties of lightweight geopolymer concrete is essential. This paper aims to develop a lightweight aggregate geopolymer concrete (LWAGC) with good density, compressive mechanical and thermal insulation properties. The dry density of LWAGC was adjusted by incorporating expanded perlite (EP). The variation in physical and mechanical properties of LWAGC with different EP content was discussed, including dry density, P-wave velocity, ultimate compression strength and elastic modulus. Based on infrared thermal imaging technology, a rapid measurement method was proposed to simulate the indoor temperature change of buildings at high ambient temperatures. The thermal insulation performance of the LWAGC with different EP contents was further evaluated. The findings show that as the EP content in LWAGC increases, there is a corresponding decrease in P-wave velocity, dry density, ultimate compressive stress, and elastic modulus. The lowest dry density of LWAGC reaches 1209kg/m3 while the ultimate compressive stress is still larger than 25.0MPa, which can used as LC25 building materials in load-bearing structures. The results also show that the addition of EP can improve the thermal insulation properties of LWAGC. The LWAGC with 50% EP content has the highest reduction rate of temperature and can maintain the indoor temperature lower than 35 °C under high ambient temperature, which have potential application prospects in the load-bearing structures and thermal insulation of tall buildings.

Thermo-Physical Properties of Hexavalent Tungsten W6+-Doped Ta-Based Ceramics for Thermal/Environmental Barrier Coating Materials

The CaTa0.8WO6 ceramic was fabricated by a solid-state reaction for thermal/environmental barrier coating (Thermal and Environmental Barrier Coating) applications, and the microstructures, mechanical and thermal properties were investigated. The result showed CaTa0.8WO6 has a lower thermal conductivity (1.05 W·m−1·K−1 at 900 °C) than 8 wt.% yttria-stabilized zirconia and the doped Ta-based ceramics with Mg2+, Yb3+, Zr4+ and Nb5+, indicating that hexavalent tungsten element W6+ doping effectively reduces thermal conductivity and improves thermal insulation performance of Ta-based ceramics. The thermal expansion rates curve without inflection points resulting from phase transition indicates that CaTa0.8WO6 has excellent high-temperature phase stability. Since the Young’s modulus and Pugh’s ratio of CaTa0.8WO6 ceramics were lower than those of various valence states doping Ta-based ceramics, which means that CaTa0.8WO6 has better damage tolerance.

Investigation on Mechanical Shock Wave Protective and Thermodynamic Properties of SiO2-Aerogel-Modified Polyurea

In recent years, industrial explosion accidents are frequent, causing serious negative influences on society. Mechanical shock waves, as a typical destructive factor in explosion accidents, can cause serious personal injury and building damage. In addition, actual explosion accidents usually involve heat sources, harming protective materials and personnel. In this study, we designed SiO2-aerogel-modified polyurea and studied the effects of manufacturing pressure process and the concentration of SiO2 aerogel on the mechanical shock wave mitigation and thermodynamic properties of the modified polyurea. The results show that the addition of SiO2 aerogel can improve the mechanical shock wave mitigation performance of polyurea. The maximum peak overpressure and acceleration mitigation rate of the material has reached 17.84% and 62.21%, respectively. The addition of SiO2 aerogel helps to reduce the thermal conductivity of materials and improve the thermal insulation performance, and the atmospheric pressure process is more conducive to improving the thermal insulation performance of materials. The minimum thermal conductivity of the material has reached 0.14174 W/m·K, which is 45.65% lower than that of pure polyurea. The addition of SiO2 aerogel has different effects on the limiting oxygen index (LOI) of polyurea. Using a vacuum process, the LOI value increased with the increase in the SiO2 aerogel concentration, while using atmospheric pressure, the LOI value increased but is always lower than 21% and lower than pure polyurea. Thermogravimetric analysis showed that the addition of SiO2 aerogel under the vacuum process was helpful to improve the thermal stability of materials. However, atmospheric pressure would disrupt the thermal stability, manifested in a decrease in peak degradation temperature, an increase in peak degradation rate, and a decrease in residual mass.

Boosting the efficiency of water-based intumescent coatings with fumed silica nanoparticles: A synergistic approach

This research looked into how well the water-based intumescent coating (WBIC) with fumed silica nanoparticles (FSNs) worked to keep steel parts safe from cellulose fire. The adhesion strength of the coatings was evaluated using the pull-off test according to ASTM D4541. Flame retardant performance was studied by a lab-scale simulated big panel test at 950 °C for 1 hour. Thermogravimetric analysis (TGA) and the UL94 test were used to study the thermal stability and burning characteristics of the WBIC. An FESEM, an X-ray diffraction (XRD), and a Fourier transform infrared spectroscopy (FTIR) analysis were used to fully characterize the residual chars of the optimized formulation and the control coating. Adhesion strength test results showed that adding 0.2 wt% of FSNs increased paint adhesion strength from 0 to 2 MPa and changed the failure mode from adhesive to cohesive. It was found that at the optimal FSNs content (0.2 wt% SiO2), the lowest steel backside temperature of 181℃ after 1 hour of fire testing was obtained. Adding fumed silica from 0.1 to 0.3 wt% has resulted in a reduction of the char layer's intumescent factor by 5.3–42.1 %. The SEM images indicated that fumed silica enhanced the formation of dense, crack-free char layers with small pore sizes. Thermogravimetric analysis revealed that intumescent coatings' thermal stability and residual weight increased with the addition of 0.2 wt% fumed silica. Additionally, the coating contained 0.2 wt% SiO2 passed the V0 rating in the UL94 vertical burning test. The XRD and FTIR tests also revealed that the leftover chars had rutile titanium oxide, aluminum metaphosphate, and titanium pyrophosphate in them. At high temperatures, these ceramic compounds exhibit thermal insulation performance, preventing heat and oxygen penetration into the char layer.

A Design Methodology Incorporating a Sound Insulation Prediction Model, Life Cycle Assessment (LCA), and Thermal Insulation: A Comparative Study of Various Cross-Laminated Timber (CLT) and Ribbed CLT-Based Floor Assemblies

Mass timber is increasingly being employed in constructing low- and mid-rise buildings. One of the primary reasons for using mass timber structures is their sustainability and ability to reduce environmental consequences in the building sector. One criticism of these structures is their lower subjective sound insulation quality. Therefore, acoustic treatments should be considered. However, acoustic solutions do not necessarily contribute to lower environmental impacts or improved thermal insulation performance. This paper discusses a design methodology that incorporates the development of a sound insulation prediction tool (using an artificial neural networks approach), life cycle assessment analysis, and thermal insulation study. A total of 112 sound insulation measurements (in one-third octave bands from 50 to 5000 Hz) are utilized to develop the network model and are also used for the LCA and thermal insulation study. They are lab-based measurements and are performed on 45 various CLT- and ribbed CLT-based assemblies. The acoustic model demonstrates satisfactory results with 1 dB differences in the prediction of airborne and impact sound indices (Rw and Ln,w). An acoustic sensitivity study and a statistical analysis are then conducted to validate the model’s results. Additionally, an LCA analysis is performed on the floor assemblies to calculate their environmental footprints. LCA categories are plotted against the acoustic performance of floors. No correlations are found, and the results emphasize that a wide range of sound insulation can be achieved with similar environmental impacts. Within each acoustic performance tier, the LCA results can be optimized for a floor assembly by selecting appropriate materials. The thermal insulation of floors is then calculated. Overall, a strong positive correlation is found between the total thermal resistance and heat loss against acoustic performance. Designers should be cognizant of the trade-offs between acoustic, thermal insulation, and environmental performance when choosing assemblies with favorable environmental impacts relative to acoustic and thermal insulation ratios.

Hierarchical Modeling of the Thermal Insulation Performance of Novel Plasters with Aerogel Inclusions

Silica aerogel possesses a significantly lower thermal conductivity compared to still air at room temperature, thanks to its high porosity and advanced thermal and physical properties. It is extensively investigated for its potential use as an insulation material, usually being incorporated into other matrix materials, such as cement plasters, to enhance the overall thermal performance with minimal weight load. The development of lightweight thermal insulation materials is a key step in reducing energy consumption in hot and cold environments during construction and in thermal equipment. The superior insulation capabilities of aerogels stem from their nanostructured SiO2 framework, which induces nanoscale rarefaction effects on the enclosed air near the SiO2 structure. This study reconstructed the nanostructured SiO2 network of modern aerogels using microscopy imaging and the literature data and integrated it into sophisticated heat transfer simulations at a microscopic level to predict its thermal performance. The simulation assumed conduction as the primary energy dissipation mechanism, incorporating local rarefaction effects based on kinetic theory approaches. SiO2 aggregates were modeled as interconnected strings of spherical beads, with variations in the aggregate size explored in a parametric study. Nanoscale rarefaction phenomena, such as slip wall and Knudsen diffusion, prevalent at these grain sizes and structures, were incorporated to refine the modeling approach. The degree of the aerogel content relative to the effective properties of the multiphasic material was then investigated systematically along the multilayered mortar thickness and on a representative multiphasic layer at the mesoscopic level. The results quantify the significant decrease in the thermal conductivity of the heterogeneous material as the porosity of the aerogel increased. The insulation performance of this aerogel incorporated into cement plasters was assessed with this hierarchical approach and validated against experimental data, providing insights for the optimization of the fabrication process and potential applications in construction.

A state-of-the-art review of novel aerogel insulation materials for building exterior walls

ABSTRACT The unique network-like framework and nanopore structure of aerogel endow it with excellent thermal insulation performance. The thermal conductivity is as low as 0.012 W/(m·K), far lower than 0.035-0.040 W/(m·K) of traditional thermal insulation materials. Research and industrialization of nanoaerogels as building insulation have gained increasing attention in recent years. This paper discusses the application status, existing challenges, and solutions in the field of building external wall energy conservation and insulation based on nanoaerogel materials. First, it reviews the research progress of nanoaerogels and the development status of traditional building exterior wall insulation materials. The external wall using nano aerogel can reduce the heat loss by about 40%. Second, it focuses on the characteristics and research status of several types of aerogel thermal insulation products for buildings. Some products show that the energy efficiency has been improved to 50% in practical applications. Finally, it analyzes existing challenges of nanoaerogels in the application of building external wall thermal insulation and summarizes the development direction of industrialization research. Building external wall thermal insulation and the application and development of aerogels in the field of building energy conservation are facilitated by this analysis.

Preparation and performance analysis of organic polyborosilazane-modified epoxy resin-based intumescent flame-retardant thermal insulation coatings

To improve the thermal insulation and flame retardancy properties of epoxy resin-based intumescent coatings, this study served epoxy resin (EP) as the base material, melamine (MEL), pentaerythritol (PER), and ammonium polyphosphate (APP) as the blowing agents, char-forming agents, and dehydration catalysts, palgorskite and sepiolite as fillers, and PSNB as the modifying agent to prepare the high-performance modified coatings by using the straightforward blending modification technique. With the introduction of PSNB, the coating achieves an in-situ vitrification/ceramisation effect in the char structure when exposed to fire, thus fully enhancing its fire protection capability Compared to the blank sample (EPC), the modified coating (EPC-PSNB-3) exhibited optimal performance when the PSNB content reached 30 wt%. In a 2 h thermal insulation performance test, the substrate backside temperature of EPC-PSNB-3 was only 165.99 °C. The Limiting Oxygen Index (LOI) value increased by 33.20 %. In cone calorimetry tests, EPC-PSNB-3 showed reductions of 63.56 %, 64.98 %, 21.37 %, and 24.35 % in peak heat release rate (PHRR), peak smoke production rate (PSPR), total heat release rate (THR), and total smoke production (TSP), respectively, compared to EPC. The residual char mass increased by 45.19 % with PSNB incorporation. The introduction of PSNB not only promotes the increase of residual char but also densifies its internal porous structure, enhancing its thermal barrier capability.

A Facile Strategy for In Situ Fabrication of Covalent Triazine Framework Aerogel with Thermal Insulation Property.

Covalent triazine frameworks (CTFs) have attracted tremendous attention with respect to their rich nitrogen content, functional triazine units, and high porosity. However, efficient and simple preparation of CTF monoliths is still a challenge. Here, we propose a novel and facile approach for the in situ preparation of CTF aerogels. Trifluoromethanesulfonic acid was used as the solvent and catalyst, which could not only promote the polymerization reaction to form a gel but also protonate the CTFs. By virtue of the simplicity and efficiency of the strategy, a series of macroscopic CTF aerogels with tunable density were obtained by adjusting the monomer concentration. Due to the porous and partially crystalline structure, the as-produced macroscopic CTF aerogels behaved with good mechanical and thermal insulation performances. This finding thus offers an effective and easily scalable approach toward fabricating macroscopic CTF aerogels and broadens the applications of CTFs in a variety of domains.

Hollow Structured‐Controllable Polyimide Nanofibers with Extreme Conditions Tolerance for Efficient Thermal Insulation

The rational use of efficient thermal insulation materials is one of the effective strategies for energy management. However, existing thermal insulation materials often exhibit poor stability, suboptimal thermal insulation performance, and weak mechanical properties in some extreme environments. Herein, this work develops an easy and scalable strategy for creating hollow polyimide (PI) nanofibers through coaxial electrospinning and high‐temperature template removal technology, in which the internal hollow structure is precisely controlled. A large amount of air is filled in the hollow structure within the nanofibers and the voids between the nanofibers, giving PI nanofibers low density (23.3 mg cm−3) and high porosity (98.2%). This characteristic also effectively suppresses the heat transfer of PI nanofibers, resulting in an ultralow thermal conductivity (20.6 mW m−1 K−1). Meanwhile, PI nanofibers also exhibit excellent mechanical properties with a stress and strain of 5.52 MPa and 62.7%, respectively. In addition, compared to other commercial thermal insulation materials, PI nanofibers demonstrate superior extreme temperature tolerance (from −196 to 350 °C) and flame retardancy (limit oxygen index of 30.8%). Given these advantages, this work provides inspiration for the structural design of nanofiber materials with efficient thermal insulation.

Lightweight, high-strength, thermal- and sound-insulating reed scraps/portland cement composite using extruded resin particles

The development of a lightweight composite made from reed scraps, Portland cement, and polystyrene particles can simultaneously address issues related to reed waste, environmental pollution, and carbon emissions produced by the construction industry. However, standard polystyrene particles have low bonding strength with Portland cement and reed scraps, giving the resulting composites inferior mechanical properties and thermal and acoustic insulation characteristics. To overcome these limitations, nano-silicon expanded resin particles (NSERP), composed of polyvinyl alcohol, polystyrene, nano-silicon, and various modifiers, were introduced to replace traditional polystyrene particles in the composite. These novel particles enhanced the interfacial bonding strength and improved the mechanical properties, as well as the thermal and acoustic insulation capabilities of the composites. This study investigated the effects of the water-cement ratio, reed scraps-to-cement ratio, and NSERP dosage on the composite's properties through single-factor experiments. The optimized composite had a density of 0.66 g/cm³ and a compressive strength of 2.5 MPa, and its sound absorption coefficient in the middle and high-frequency bands was 0.7, which was approximately 4.3 times higher than that of conventional silicate composites. Its thermal insulation performance surpassed that of standard composites. This lightweight, high-strength, thermally insulating, environmentally friendly, and energy-efficient multifunctional composite has potential applications in building energy conservation, traffic noise reduction, and new energy battery insulation.

Remarkable improvement in radiation shielding efficiency, thermal insulation performance and compressive strength of rigid polyurethane foam composites by synergetic effect of PbO and colemanite fillers

Developing radiation shielding materials is a critical phenomenon for protecting people and the environment with the increment in usage of nuclear technology in today's world. With this sense, PbO/colemanite-filled rigid polyurethane foams were fabricated by one-shut free rise method, and their performances were investigated via the advanced characterization techniques such as ATR-FTIR, SEM-EDS, TGA as well as thermal conductivity, universal mechanical and radiation shielding tests. The characteristic properties of the samples were evaluated in detail depending on the variation in the filler contents. The ATR-FTIR analysis illustrated that RPUF matrices exhibited good compatibility with the fillers by forming the secondary chemical bonds. Furthermore, SEM analysis revealed that the samples with low PbO/colemanite fillers exhibited fairly uniform and regular cellular morphology with anisotropic elliptical apparition thanks to synergetic catalytic effect of the filler particles, whereas, at high content, some local distortions with slightly chaotic appearance were observed accompanied by viewing the little ruptures and bursts in cell face and collapsed in cell plateau borders. TGA measurement indicated that the inclusion of the fillers into RPUF got worse the samples with comparison of neat RPUF due to the reduction in crosslinking density of the foam. Remarkable improvement (about 25 %) was also obtained in thermal insulation performance at the foam composites containing the fillers due to highly augmentation in number of closed cells and presence of more immobile CO2 gas inside the cells. Furthermore, high inclusion of the fillers in RPUF matrix improved compressive strength of the foams by nearly 15 % by enhancing the bending moment and rigidity of RPUF matrices via contributing to the overall stress dispersion. According to linear and mass attenuation coefficients results, the foam composites displayed excellent X-ray radiation shielding performance with increasing of PbO/colemanite content thanks to the density increment and presence of the atoms with high atomic number. Furthermore, at low photon energy levels, better shielding against X-ray radiation was obtained, while vice versa at high energy levels.

Ultra‐High Radial Elastic Aerogel Fibers for Thermal Insulation Textile

AbstractWhen nanoporous aerogels with excellent thermal insulation performance are processed into 1D fibers, they have great potential for application in the field of personal thermal management. However, coping with the impact of external forces, especially radial extrusion, and maintaining the macro morphology and microstructure of aerogels during use are remaining issues. To address these challenges, this study proposes a method that uses ultrafine and ultra‐highly entangled bacterial cellulose nanofibers as the basis to achieve high radial elasticity by forming an isomorphic coating of rigid silica on the soft gel skeleton of aerogel fibers. The obtained aerogel fibers can achieve an elastic recovery of 88% over 50 compression cycles under 90% strain, and they can be knotted, woven into textiles, and are washable. This strategy improves the radial compression resistance of aerogel fibers, providing rich possibilities for the development of aerogel fibers with excellent mechanical properties.

Novel ultralight carbon foam reinforced carbon aerogel composites with low volume shrinkage and excellent thermal insulation performance

Lightweight carbon aerogels are attractive for thermal insulation due to their low thermal conductivity and excellent high-temperature resistance under extreme environments. However, the preparation of monolithic carbon aerogels from phenolic resin precursor always faces the problem of large volumetric shrinkage during the drying and carbonization processes, thus resulting in the increasing density and thermal conductivity of aerogels. Here, to solve such issues, ultralight and rigid carbon foam was designed and synthesized as the reinforcement to fabricate carbon aerogel composites (CACs), which could significantly enhance the shrinkage resistance of monolithic carbon aerogels. The high rigidity of the carbon foam reinforcements (CFRs) was achieved through a pre-carbonization process, which also endowed the CFRs with a matched shrinkage with the monolithic carbon aerogels. As a result, the obtained CACs reinforced by the rigid CFRs showed not only crack-free structures, but also quite low shrinkage, which was about 5.9 % after carbonization. The low shrinkage of CACs then endowed them with quite low density (21.5 mg cm−3) and excellent thermal insulation performance (25.9 mW m−1 K−1). Furthermore, due to a highly rough nanostructure, the CACs also possessed outstanding hydrophobicity. These merits make the CACs a promising thermal insulation material even in humid environments.

Building Thermal Insulation Performance and economic benefits

Three different insulating scenarios were investigated using Energy-plus software, to study the effect of using expanded polystyrene boards on building energy consumption at the Libyan Center for Solar Energy Research and Studies. The three insulation scenarios with different polystyrene insulation thicknesses and densities were investigated. Polystyrene total cost, Payback period, total and net money saving using insulation, as well as the percentage gain were calculated for each case in the three investigated scenarios for 50 years. The most money saving scenarios after 50 years is by insulating the building roof and external walls with an average insulation thickness of 7 cm, reaching about 78000 L.D and a tariff of 0.9261 L.D /kWh. While the least money saving is the roof scenario with an insulation thickness of 2.5 cm, reaching more than 29000 L.D and the same tariff. The highest percentage gain values are 76 %, 103 % and1090 % at the roof scenario, 2.5 cm insulation thickness and energy tariffs of 0.15 L.D /kWh, 0.1732 L.D/kWh and 0.9261 L.D/kWh, respectively. While the lowest percentage gain values are about 17.5 %, 35.7 % and 725 % at the wall scenario 10 cm insulation thickness and energy tariffs of 0.15 L.D/kWh, 0.1732 L.D/kWh and 0.9261 L.D/kWh, respectively. the payback period of total insulation cost is significantly dependent on insulation thickness and energy tariff. These results show that low energy tariff (current energy tariff) values economically are not cost effective regarding the payback period. Consequently, prices do not motivate residents to save energy with the use of thermal insulation unless actual energy prices are considered.

Freezing‐Assisted Direct Ink Writing of Customized Polyimide Aerogels with Controllable Micro‐ and Macro‐ Structures for Thermal Insulation

AbstractPolyimide (PI) aerogels have attracted attention in thermal management due to their low thermal conductivity, high porosity, and robust mechanical properties. However, building PI aerogels with elaborately tailored micro‐ and macro‐ structures for optimized thermal insulation performance in specific scenarios remains a challenge. Here, a scalable approach is reported to prepare PI aerogels with controllable micro‐ and macro‐ structures by freezing‐assisted direct ink writing (FADIW) of poly(amic acid) (PAA) inks. This FADIW strategy can enable continuous ink deposition and transient low‐temperature‐induced gelation, contributing to the facile construction of spatially free geometries with structural complexity and shape fidelity. Importantly, controllable construction of microstructures of the aerogels is achieved by controlling the extrusion substrate temperature. The resulting customized PI aerogels show good thermal insulation owing to the porous microstructure and customized macrostructure, enabling good thermal management for portable electronics. In addition, this FADIW strategy is universal and allows for multi‐material integration, broadening the functionality of PI aerogels. Significantly, such FADIW approach can be promisingly applied to realize on‐demand design of PI aerogels and other polymer aerogels with targeted micro‐ and macro‐structures, offering an alternative avenue for the manufacture of customized aerogels toward widespread applications.