Thermal Insulation Performance Research Articles

Thermal insulation and energy performance's assessment of a mycelium-based composite wall for sustainable buildings

Bio-composite insulation materials play a crucial role in reducing the environmental impact of buildings. This paper numerically investigates the eco-friendly application of mycelium in south-facing walls in Marrakech, Morocco, using 2D CFD simulations. In this context, the thermal efficiency of bio-sourced insulating materials was assessed and compared to that of conventional insulating materials. The study basically aims at the time lag and the decrement factor analysis to evaluate the dynamic thermal performance of a multilayer wall insulated with mycelium. A life cycle cost analysis (LCCA) is performed to establish the optimal thickness of the mycelium insulation, which was turned out to be 0.08m. This optimization leads to a substantial improvement in energy efficiency, resulting in energy savings increasing by 87.4% in winter and 55.9% in summer. Besides, during the last 72hours of the simulation, the indoor surface temperature drops by approximately 4 °C on summer days and raises by approximately 1 °C on winter days. The thickness of mycelium insulation was found to have a significant impact on energy savings, increasing them from 56% to 93%, and representing nearly a 1.7-fold improvement. The study has also targeted annual CO2 emissions to reveal a potential reduction of around 72% using optimal mycelium composite insulation. Finally, a comparative analysis with the guidelines of Moroccan thermal regulations was achieved. The obtained findings exhibit that the examined configuration excels in terms of thermal performance, economic feasibility, and environmental benefits.

One-step preparation of macropore phase change materials enabled exceptional thermal insulation, thermal energy storage and long-term stability

Phase change materials (PCMs) capable of reversibly storing and releasing thermal energy have been widely used in our daily life to reduce energy consumption. However, traditional PCMs are mainly focused on the promotion of their enthalpy and thermal conductivity yet are rarely noticed on incorporating their thermal energy storage capacity with thermal insulation performance. Herein, a kind of macropore PCMs (MPCMs) was synthesized by directly adding expanded microspheres into polyethylene glycol-based PCMs, in which the microspheres can form an internal closed porous structure in matrix for realizing thermal insulation and polyethylene glycol is used as the phase change component for achieving thermal energy storage. Amazingly, the designed MPCMs have significant latent heat storage capacity reached up to130.2 J g−1 and simultaneously possess extremely low thermal conductivity of 0.08577 W m−1 K−1. The thermal power generation system test further revealed the thermal insulation capability of these MPCMs was eleven times more than that of the commercial wood. Especially, these MPCMs with relatively low density of 0.492 g cm−3 can still maintain the remarkable tensile strength of 11.74 MPa and can also exhibit good toughness via multiple cyclic shape memory analysis. The focus of this work that is to combine the thermal insulation ability of porous materials with the thermal energy storage ability of PCMs, can effectively reduce the heat conduction meanwhile can maintain the stability of internal temperature contributed to reducing energy consumption, applying in food transportation, building energy conservation and other fields.

2D Tantalum Disulfide Reduction Strategy Customized Ta2O5/rGO Heterointerface Aerogel Toward Boosting Electromagnetic Wave Absorption and Flame Retardancy.

The exceptional and substantial electron affinity, as well as the excellent chemical and thermal stability of transition metal oxides (TMOs), infuse infinite vitality into multifunctional applications, especially in the field of electromagnetic wave (EMW) absorption. Nonetheless, the suboptimal structural mechanical properties and absence of structural regulation continue to hinder the advancement of TMOs-based aerogels. Herein, a novel 2D tantalum disulfide (2H-TaS2) reduction strategy is demonstrated to synthesize Ta2O5/reduced graphene oxide (rGO) heterointerface aerogels with unique characters. As the prerequisite, the defects, interfaces, and configurations of aerogels are regulated by varying the concentration of 2H-TaS2 to ensure the Ta2O5/rGO heterointerface aerogels with appealing EMW absorption properties such as a minimum reflection loss (RLmin) of -61.93dB and an effective absorption bandwidth (EAB) of 8.54GHz (7.80-16.34GHz). This strategy provides valuable insights for designing advanced EMW absorbers. Meanwhile, the aerogel exhibits favorable thermal insulation performance with a value of 36mW m-1 K-1, outstanding fire resistance capability, and exceptional mechanical energy dissipation performance, making it promising for applications in the aerospace industry and consumer electronics devices.

Morphological, TGA, and FTIR on Rigid Polyurethane Composite Laminated with Untreated and Treated Bamboo Fiber Roof Insulation

The performance of roof insulation such as polyurethane decreased due to problems such as insufficient absorption and poor thermal insulation performance, especially during rainstorms. The aims of this study are to investigate the physical property and its potential reinforced material such as rigid polyurethane doped with treated and untreated bamboo fiber composite (RPU-BF) at different ratios of 0, 25, 30, 35, and 40% of bamboo fibers as an insulation material for roof applications. The bamboo fibers were treated by using silane coupling agent treatment. The rigid polyurethane composite samples were prepared and then laminated bamboo fiber to overcome the sound problem in roofs. The physical characterization was investigated by Water Contact Angle (WCA), the morphological by Scanning Electron Microscopy (SEM), Thermo-gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) Analysis. The results showed that the treated bamboo fiber had a 192.5° water contact angle as a super hydrophobic property due to the presence of the chemical bonds Si-O-Si and Si-O-C in the silane coupling agent treatment. The morphology showed that 30% ratios of RPU-BF-T30 give the smallest pore diameter size. The peak of thermal degradation temperature of untreated and treated bamboo fiber was increased from 320°C to 350 °C with a weight loss of 80% to 50%. The treated bamboo fiber exhibited peaks at 3010–3040 cm-1 were associated with stronger Si-O-Si bonding, indicating the formation of new chemical bonds between bamboo fiber and silane coupling agent due to the ester bond from the cellulose, lignin, and hemicellulose. Thus, there was a similar trend peak in the functional chemical group in the FTIR spectrum of the RPU-BF composite. This result shows that RPU-BF composite had the potential of the optimum ratio of bamboo fiber as an insulation material for local communities and beneficial to the bamboo industry.

Superior performance foamed concrete fabricated with amphiphilic and hydrophilic particles stabilized ultra-stable foam

Materials possessing sufficient strength, exceptional thermal insulation, and energy-efficient characteristics are in short supply within the construction industry. Foamed concrete, known for its cost-effectiveness, ultralight composition, and prominent thermal insulation characteristics, has displayed significant potential in applications geared towards enhancing energy efficiency. Nevertheless, its widespread adoption is hindered because, at present, the strength and thermal insulation properties of foamed concrete fail to meet engineering requirements due to inadequate foam stability. In response to this challenge, an ultra-stable foam with a multi-walled core-shell structure is successfully synthesized by modifying the gas-liquid interface through coupling the synergistic effects of surfactant, Janus-ZrO2 nanoparticles, and hydrophilic homogeneous SiO2. Utilizing the innovative approach, we incorporate the ultra-stable foam, containing 5 wt% Janus-ZrO2 nanoparticles, in the fabrication of foamed concrete with a resultant density of 500 kg m−3. Notably, this foamed concrete exhibits remarkable mechanical properties (compressive strength of 5.1 MPa) and outstanding thermal insulation performance (thermal conductivity of 0.091 W/(m·K)). These enhancements can be attributed to the refining of the pore structure and an increased proportion of closed pores within the foamed concrete, both facilitated by the utilization of the ultra-stable foam. The introduction of this unique ultra-stable foam is poised to expand the applications of foamed concrete in the construction sector.

Nickel-Fe3O4@Graphene coated lightweight carbonized wood for efficient electromagnetic interference shielding

The miniaturization and integration of electronic equipment promote electromagnetic effect radiation pollution more and more serious. The lightweight, renewable electromagnetic interference (EMI) shielding materials is urgently needed. This study developed a high temperature carbonization, Fe3O4@Graphene impregnation, and electroless Ni technique to construct a carbonized wood composite with strong EMI shielding performance using sustainable natural wood as the raw material. The Fe3O4@Graphene is distributed throughout the carbonized wood to provide the conductivity and magnetism of the reinforced composite material, and provide more interfaces to increase the dielectric loss and magnetic loss, thereby exhibiting excellent EMI shielding performance. The results show that at low thickness (2 mm) and ultra-low density (0.284 g/cm3), the CWN-7 composite exhibits excellent EMI shielding effectiveness of up to 84.2 dB in the whole X-band (8.2–12.4 GHz). At the same time, it has extraordinary compressive strength and good thermal insulation performance. This study offers a different method for creating composite multifunctional electromagnetic shields out of carbonized green wood.

Porous high-entropy rare-earth phosphate (REPO4, RE = La, Sm, Eu, Ce, Pr and Gd) ceramics with excellent thermal insulation performance via pore structure tailoring

Porous high-entropy rare-earth phosphate (REPO4, RE = La, Sm, Eu, Ce, Pr and Gd) ceramics with excellent thermal insulation performance via pore structure tailoring

Ultralight air-filled hollow yarn fabrics for efficient thermal insulation and its heat and mass transfer mechanism

Fibrous thermal insulating materials rely on retaining stationary air in their porous structure for effective insulation. However, hollow fibers lose their insulation when turned into textiles due to compression. In this study, we developed connected knitted loop sheaths to create stable hollow yarns. This direct formation allowed immediate use in fabric weaving, avoiding flattening during spinning. Comprehensive experimental analyses examined hollowness, porosity, mass density, and thermal resistance of air-filled hollow (AFH11AFH: air-filled hollow.) yarn fabrics. Results showed remarkable hollowness (41.62%) and porosity (87.509%), effectively trapping stagnant air and enhancing insulation while maintaining a lightweight structure. Computational Fluid Dynamics (CFD) revealed that minor temperature gradients and negligible airflow within the hollow structure minimized heat transfer, resulting in superior thermal insulation performance. These insights aid in designing textiles with hollow yarns for desired insulation and thermal comfort.

Surface Modification of Polyimide Aerogel by Thermoplastic Polyurethane for Enhanced Mechanical Strength and Thermal Insulation Performance.

Polyimide (PI) aerogel is a good thermal insulation material with the highest temperature resistance in practical application. But the mechanical strength of PI aerogels prepared by freeze-drying or thermoimide methods is weak. In this research, TPU was selected as an aging solution to solve the problem of the low mechanical strength of PI aerogel prepared by the freeze-drying method. Previous work has certified that the coupling of PI and thermoplastic polyurethane (TPU) can enhance the mechanical strength of PI aerogel to a certain extent due to the flexibility of TPU. But excessive TPU will change the PI structure in the cross-linking process and decrease the mechanical strength of the aerogel. Thus, a new kind of PI gel modification method was provided by using TPU as an aging solution, and the mechanical strength of PI aerogel is improved to 3.06 MPa. Furthermore, the shrinkage, specific surface area, waterproof angle, and thermal conductivity all show good performance, thus enabling PI aerogel to be used in many aspects. Specially, the method is simple and can be used to prepare some other high-strength aerogels.

Multifunctional Integrated Organic–Inorganic-Metal Hybrid Aerogel for Excellent Thermal Insulation and Electromagnetic Shielding Performance

HighlightsThe homogeneous hybridization of organic–inorganic-metal elements in 3D aerogel was achieved by an expeditious method.The aerogel tightly integrates excellent thermal insulation (49.6 mW m−1 K−1), ablative resistance, mechanical strength, and superhydrophobic properties.The ablated carbon aerogel combines notable electromagnetic interference shielding properties (31.6 dB) and load-carrying properties (272.8 kN·m kg−1).

Evaluation of heterogeneous core sandwich panels for energy efficiency and fire safety in warehouse buildings

Sandwich panels are extensively used in the construction industry because of their superior thermal insulation performance and ease of installation. However, panels with combustible cores are prone to fire, whereas those with mineral-based cores exhibit lower thermal insulation capabilities. Therefore, to address these limitations, this study proposed a composite core approach to enhance both fire resistance and thermal insulation performance. A surface layer incorporated phenolic foam (PF), which fulfilled the fire resistance requirements and delivered excellent thermal insulation properties, and 30–40 mm of glass wool (GW) and mineral wool (MW) with exceptional fire resistance were applied. The heterogeneous core sandwich panels exhibited excellent flame-retardant performance, with a maximum peak heat release rate of 0.712 kW/m2 and a total heat release of 0.18 MJ/m2. This satisfied the semi-non-combustible flame retardancy level and ensured sufficient time for residents to evacuate safely. Moreover, based on its low thermal transmittance of 0.114–0.125 W/m2·K, when applied to warehouse-type buildings, heating energy consumption was reduced by approximately 10 % compared to sandwich panels based on inorganic core GW and MW. Heterogeneous core sandwich panels can exhibit excellent flame retardancy and thermal performance owing to the use of inorganic materials and PF, respectively.

Preparation and heat-insulating properties of hollow mullite fibers achieved via template impregnation method to replicate the structure of metaplexis fibers

Mullite fibers possess low thermal conductivity, excellent high-temperature stability, and thermal shock resistance, making them extensively utilized in high-temperature heat-insulating components. However, the majority of current mullite fibers have solid structures, limiting the potential for further enhancement of their heat-insulating properties. Metaplexis fiber, a plant fiber with a hollow structure, effectively obstructs heat transfer, and therefore exhibits excellent heat-insulating properties. In this study, we employed metaplexis fibers as templates to fabricate mullite fibers with hollow structures. First, a precursor solution was prepared using Al(NO3)3·9H2O and ethyl orthosilicate as the solute and anhydrous ethanol as the solvent. The metaplexis fibers were immersed in the solution, removed, and dried to obtain precursor fibers. Finally, the precursor fibers were heated to the target temperature to obtain hollow mullite fibers. The investigation focused on the impact of preparation parameters such as sintering temperature, precursor solution concentration, and aluminum–silicon molar ratio on the morphologies, phases, pore-size distributions, and thermal conductivities of the resulting hollow mullite fibers. The results demonstrated that the prepared mullite fibers inherited the hollow structure of metaplexis fibers, with the cavity diameter in the range of 3–6 μm and porosity of 91 %. Compared to traditional solid mullite fibers, the thermal insulation performance was improved by more than 59 %. These findings highlight the significant potential of hollow ceramic fibers for the development of heat-insulating materials. Using the unique characteristics of their hollow structure, these fibers offer improved heat-insulating properties compared to their solid counterparts.

Rapid and efficient synthesis of energy-saving cool pigments and environmental restoration materials using rare earth secondary resources

This paper proposes a method for the short-process recovery and reuse of rare earth secondary resources. Low-value rare earth polishing powder waste (WP), trichromatic phosphor waste (WT), NdFeB permanent magnetic waste (WN), and SmCo permanent magnetic waste (WS) were used as the raw materials. Based on the concept of combinatorial chemistry, energy-efficient cool pigments and environmental remediation materials were synthesized by a solid-phase method. The results showed that the synthesized materials had fluorite-type and garnet-type structures. In terms of cool pigments, doping with different rare earth permanent magnets can enrich the color (including yellow, green, brown, gray, and blue) and cause fluctuations in the near-infrared (NIR) reflectance (59.05–99.54 %) and NIR solar reflectance (55.32–95.64 %). Yellow fluorite-type pigments (WP: WT = 1:1) have the highest NIR reflectance (R = 99.54 %), while brown fluorite-type pigments (WP: WN = 1:0.1) and blue garnet-type pigments (WP:WS = 1:0.1) have relatively high NIR reflectance, 88.18 % and 59.30 %, respectively. The synthesized pigments possessed better chemical stabilities and thermal insulation performance. In terms of environmental remediation materials, the adsorption capacities of fluorite-type materials for F− and PO43− can reach 84.03 mg/g and 85.3 mg/g, respectively. In summary, materials synthesized from rare earth waste exhibit excellent potential for use in energy-efficient wastewater treatment and promote the sustainable utilization of secondary rare earth resources.

Energy-saving benefits of thermal insulation and glazing in code-compliant office building in cooling-dominated climates

Thermal insulation of wall and roof and high-performance glazing have potential to save energy in cooling-dominated climates. However, lack of careful selection of these options based on the climatic location can adversely affect their energy performance. The local building codes need to be revisited to ensure that the thermal insulation and glazing options fulfil their intended purpose in a given climate. In this context, this study was aimed at assessing the energy performance of thermal insulation (polystyrene) and glazing for different climatic locations. A multistory office building was simulated by using Ecotect software for typical climatic locations of Saudi Arabia. Considering uninsulated wall and roof with single-glazed windows as the baseline, three different cases were studied: insulated wall and roof with single-glazed windows, uninsulated wall and roof with double-glazed windows, and insulated wall and roof with double-glazed windows. In general, the energy-saving benefit of glazing was significantly higher than that of thermal insulation. Also, the collective application of double-glazing and thermal insulation according to the local building code could significantly save the cooling energy demand (ranging from 18 % to 28 %). Conversely, this code-compliance caused an increase of cooling energy demand by 55 % in Abha and by 20 % in Khamis Mushait. However, a sensitivity analysis of these two regions showed that the energy-saving benefit could be positive by proper choice of the heating and cooling setpoints. Besides research interest, the findings of this study will guide for necessary amendments in the building code, eventually contributing to substantial savings in cost and energy and reduction in CO2 emission.

A high-entropy carbonitride aerogel thermal insulator: Theoretical and experimental investigations

A resilient, flame-retardant and high-temperature resistant high-entropy carbonitride aerogel (HECNA), (Ti1/5Cr1/5Mo1/5Nb1/5Ta1/5)(C0.56N0.44), was successfully synthesized and thoroughly characterized. It exhibited a porosity of 93.9 %, a compressive strength of 1.1 MPa and a remarkable stability at temperatures up to 1673 K, which, along with its outstanding fire-retardancy, and low thermal conductivity (as low as 0.149 W·m−1·K−1 at 298 K), made it a good candidate material for thermal insulation applications in demanding environments. Density functional theory (DFT) calculations indicate that the [N]/([C]+[N]) ratio in HECNA affects its lattice thermal conductivity, with a potential 83 % reduction achievable by increasing the ratio from 0 to 1/2. This aligns with experimental findings, underscoring the substantial impact of elemental composition of HECNA on its thermal insulation performance.

Study on damaged expanded water-repellent perlite insulation integrating neural network and simulation on temperature field and Boil-off Rate in a Liquefied Natural Gas Cargo Containment

The temperature field and Boil-off Rate (BOR) of the cargo containment system (CCs) in the LNG (Liquefied Natural Gas) carrier are directly impacted by the thermal performance of insulation, which has an adverse effect on the structural safety and commercial feasibility of LNG transportation. However, the potential damage to hydrophobic layer of expanded perlite during the processes of filling, storage, and transportation can lead to undesirable increases in water absorption, thermal conductivity, even the risk of insulation failure. To investigate the variations in the thermal conductivity of damaged expanded water-repellent perlite used in CCs of LNG carrier, The variations in the thermal conductivity of expanded water-repellent perlite are tested using a guarded hot plate apparatus extending down to liquid nitrogen temperatures under the combined influence of moisture content and damage rates. Furthermore, heat transfer models are established, and the accuracy of the mathematical models is validated using experimental data collected from LNG carrier CCs. A Back-propagation Neural Network is used to conduct sensitivity analysis and predictions based on the experimental results. The results show that both the breakage rate and water content have detrimental effects on insulation performance. Specifically, under equatorial sailing conditions, 450 mm-thick expanded water-repellent perlite show respective BOR increases of 22.8% and 116.4%. With 530 mm-thick expanded water-repellent perlite, BOR increased by 20.7% and 112.1%, respectively, even exceeding the daily BOR limit for LNG cargo. Analyzing temperature field and BOR provides essential insight for evaluating the thermal insulation performance of the structural system in the NO 96 LNG carrier.

MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

HighlightsThe SiO2 nanofiber membranes and MXene@c-MWCNT6:4 as one unit layer (SMC1) were bonded together with 5 wt% PVA solution.When the structural unit is increased to three layers, the resulting SMC3 has an average electromagnetic interference SET of 55.4 dB and a low thermal conductivity of 0.062 W m−1 K−1.SMCx exhibit stable electromagnetic interference shielding and excellent thermal insulation even in extreme heat and cold environment.

Natural fiber-based multifunctional aerogel with advanced oil absorption property and high thermal insulation performance

Designing an ultra-light and controllable structure for multifunctionality of low-cost aerogels is of great significance but remains a huge challenge because of the limitations of structural processability and mechanical vulnerability. Herein, we demonstrated a facile approach to synthesize a low-cost, ultralight, elastic, and highly recyclable superabsorbent from renewable fibers via environmentally friendly physical bonding and freeze-drying. Our approach introduces skin-core structure polyester (SPFs) into natural agriculture plant kapok, through which fibers entanglement and bonding to construct aerogel with adjustable hierarchical structure and desirable shapes. The resultant composite aerogel can be easily modified by organosilane, demonstrating durable superhydrophobicity (158.5°), advanced absorption capacity (128.4 g/g), good mechanical performance, self-cleaning, and thermal insulating (0.020 W/(m·K)). Therefore, the sustainable and multifunctional composite fibrous porous aerogels are potential materials for oil absorption applications and thermal management.

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

This research intends to examine the potential of incorporating waste materials in place of coarse aggregates to augment the mechanical characteristics and thermal insulation of lightweight foamed concrete (LWFC), along with the inclusion of polypropylene (PP) fibres. The PP fibre exhibits excellent tensile strength and enhancement on thermal insulation properties of cementitious materials. In this study, eco-friendly bio-based oil palm shell (OPS) and robust solid polyurethane (SPU) aggregates derived from industrial waste were utilized as substitutes for conventional aggregates. Additionally, silica fume was partially incorporated as supplementary cementitious materials. The addition of PP fibre impacted the workability of the LWFC with the inverted slump value decreased by 1.7 %–17.5 %. The inclusion of PP fibre proportion increased from 0 % to 0.5 % revealed a positive result in mechanical properties and thermal insulation performance. The OPSSPU/0.5 showed the significantly increment of 40.4 % compressive strength, 102.9 % of splitting tensile strength, and 70.8 % flexural strength, respectively. The optimum result was obtained in the OPSSPU/0.5 mixture, which exhibited 3.74 MPa residual compressive strength. Furthermore, utilizing PP fibres brought about a significant reduction in thermal conductivity in the environmentally sustainable LWFC, leading to improvements ranging from 0.2 % to 16.3 % when compared to the control composition. Thus, these findings are essential for encouraging the adoption of such practices in the construction industry and contributing to the reduction of environmental impacts associated with sustainable concrete production.

Advancements in Thermal Insulation through Ceramic Micro-Nanofiber Materials.

Ceramic fibers have the advantages of high temperature resistance, light weight, favorable chemical stability and superior mechanical vibration resistance, which make them widely used in aerospace, energy, metallurgy, construction, personal protection and other thermal protection fields. Further refinement of the diameter of conventional ceramic fibers to microns or nanometers could further improve their thermal insulation performance and realize the transition from brittleness to flexibility. Processing traditional two-dimensional (2D) ceramic fiber membranes into three-dimensional (3D) ceramic fiber aerogels could further increase porosity, reduce bulk density, and reduce solid heat conduction, thereby improving thermal insulation performance and expanding application areas. Here, a comprehensive review of the newly emerging 2D ceramic micro-nanofiber membranes and 3D ceramic micro-nanofiber aerogels is demonstrated, starting from the presentation of the thermal insulation mechanism of ceramic fibers, followed by the summary of 2D ceramic micro-nanofiber membranes according to different types, and then the generalization of the construction strategies for 3D ceramic micro-nanofiber aerogels. Finally, the current challenges, possible solutions, and future prospects of ceramic micro-nanofiber materials are comprehensively discussed. We anticipate that this review could provide some valuable insights for the future development of ceramic micro-nanofiber materials for high temperature thermal insulation.