Excellent Thermal Insulation Properties Research Articles

An optimal design of battery thermal management system with advanced heating and cooling control mechanism for lithium-ion storage packs in electric vehicles

Battery thermal management is crucial for the efficiency and longevity of energy storage systems. Thermoelectric coolers (TECs) offer a compact, reliable, and precise solution for this challenge. This study proposes a system that leverages TECs to actively regulate temperature and dissipate heat using transformer oil, known for its excellent thermal conductivity and electrical insulation properties. A thermal management system utilizing liquid immersion cooling was developed, providing both cooling and heating functionalities. The system was tested on a 48 V 26 Ah NMC Li-ion battery pack at charging rates of 0.5C and discharging rates of 0.5C and 1C. Maximum temperatures recorded were: natural convection (NC) at 42.8 °C and 54.9 °C, forced convection (FC) at 33.2 °C and 45.2 °C, and liquid immersion cooling (LIC) at 29.3 °C and 37.7 °C. LIC significantly lowered temperatures compared to NC and FC, while maintaining acceptable misbalance and capacity levels. Additionally, the liquid immersion heating setup effectively heated the battery from −25 °C to 0 °C before charging, demonstrating the system's capability to maintain optimal battery performance.

Polymerization-induced aramid nanofiber in-situ loaded poly-pyrrole for construction of ultra-strong microwave absorption aerogel

Increasing electromagnetic (EM) radiation and EM pollution have driven extensive attention for high efficiency EM wave absorbing materials, especially aerogel-based composite absorbing materials, which are lightweight, flexible, and heat-insulating. Here, highly efficient absorbing poly-pyrrole@aramid nanofibers (Ppy@ANF) aerogels were assembled using Ppy@ANF nanofibers with core-shell structure. Ppy@ANF nanofibers were constructed for the first time by introducing a Ppy capping layer on the surface of ANF induced by ambient polymerization through a simple redox reaction. Benefit from the macroscopic porous structure of the aerogel and the microscopic core-shell structure design. The Ppy@ANF aerogels achieved an ultra-broadband absorption of 8.27 GHz at 3.43 mm, amd strong absorption characteristic with a reflection loss of −59.63 dB. Meanwhile, it had excellent thermal insulation and mechanical properties. Ppy@ANF aerogels are looked bright to be applied as flexible, lightweight, heat-insulating, and highly efficient absorbing material in wearable electronics, artificial intelligence and other high-tech fields.

A coral-like skeleton carbon aerogel achieves good mechanical and thermal insulation properties

A coral-like network carbon aerogel was synthesized by introducing acid-modified carbon nanofibers (a-CNF) into phenolic (PR) aerogel through chemical grafting, followed by high-temperature carbonization. The bonding interaction between a-CNF and PR was analyzed by FT-IR spectroscopy. The microstructure of a-CNF/PR composite aerogel (a-CNF/PRA) was studied by SEM and pore structure analysis. The results showed that introducing 5 wt% of a-CNF was most favorable for forming a porous network of a-CNF/PRA. SEM photographs and pore structure analysis indicated that a-CNF/C composite aerogel (a-CNF/CA) developed a stable porous skeletal structure during carbonization. TEM images revealed that the complete porous skeleton consisted of a-CNF encapsulated by carbon layers. The carbonization shrinkage of a-CNF/CA was only 26.53% due to the presence of a-CNF as the skeleton support. Compared to carbon aerogel, a-CNF/CA exhibited lower density (0.072 g cm−3), thermal conductivity (0.0452 W m−1 K−1), and higher compressive strength (up to 3.26 MPa) up to 3.26 MPa than that of carbon aerogel (1.21 MPa). These findings confirmed the excellent mechanical and thermal insulation properties of a-CNF/CA.

Advancing reinforcement of sustainable gypsum composites: High-performance design by reusing waste materials

This study tends to optimize and develop an innovative gypsum material by incorporating hybrid waste compounds. Using a Doehlert design, this work explores the effects of introducing paper (X1), polystyrene (X2), and polyester fibers (X3), as well as their interactions, on gypsum's thermophysical and mechanical behavior. Bulk density, thermal conductivity, flexural strength, compressive strength, and the fire resistance test were performed on the developed formulations. Statistical analysis emphasizes the significant influence of all process variables on gypsum properties. Polyester fibers notably enhance flexural strength when combined with the cooperative effect of paper and polystyrene wastes, which strike a balance between physical and mechanical characteristics. The optimum formulation parameters lead to a significant 33% decrease in bulk density, a 43% reduction in thermal conductivity, a notable 42% increase in flexural strength, and a significant reduction in compressive strength of around 50%, but still meet the 2 MPa standard. The new samples show ductile behavior, highlighting gypsum's potential as a load-bearing material with excellent thermal insulation properties and impressive fire resistance. This research significantly improves our understanding of the effectiveness of a gypsum compound incorporating waste in a hybrid manner, bringing this approach into line with sustainable development objectives.

The effect of pore morphology on thermal insulation properties of thermal barrier coatings

The inhomogeneous-geometry microstructures caused by pores make thermal barrier coatings (TBCs) to have excellent thermal insulation properties, thus ensuring that the superalloy matrix is stable in its service at higher temperatures. Consequently, significant attention has been paid to understand the relationship between pore morphology and thermal conductivity. However, unclear the influence mechanisms of pore morphology-thermal insulation properties leads to a poor guide to the structural tailoring for better thermal insulation for TBC. In this study, a finite element method was used to simulate the thermal transport behavior of porous structures, and the influence mechanism of pore morphology on the thermal transport behavior of coatings was clarified. It indicated that thermal conductivity has a significant dependence on the pore aspect ratio, orientation angle, and porosity. The thermal insulation properties would be enhanced when large aspect ratio prolate spheroids are inserted with a pillar at the center. Further, the results shed light on the heat transport process across highly porous structures and provide a guide to design the coating with high thermal insulation properties.

Cost-effective preparation of pre-oxygenated PAN fiber composite SiO2 aerogel felt with excellent mechanical and thermal insulation properties

Silica aerogel is an attractive thermal insulation material due to its low thermal conductivity, light weight and non-combustible inorganic properties, but its inherent brittleness and high production cost hinder its practical application on a large scale. Herein, the high-performance pre-oxidized polyacrylonitrile fiber composite silica aerogel felt (PPAF-SiO2) was successfully prepared by a cost-effective combustion drying technique for the first time. The results show that the PPAF-SiO2 has the feature of lightweight, good flexibility, and its heat resistance, hydrophobicity, and specific surface area are significantly improved. Due to the further polymerization of fiber structure molecules caused by combustion, the tensile strength of the PPAF-SiO2 is increased by 81.9 % to 1.71 MPa. More importantly, due to the high proportion of silica aerogel in felt, its thermal conductivity can be reduced to 0.02 W/(m·K), which is lower than most aerogel composite materials. Moreover, the thermal insulation performance of the PPAF-SiO2 was further confirmed by the infrared thermal imager from room temperature to 300 ℃. In addition, the innovative drying mechanism based on the combustion flame model was proposed. Finally, compared with traditional physical drying technologies in terms of drying time and drying conditions, the combustion drying technology shows great advantages in drying efficiency, energy consumption and equipment investment, which greatly reduces production costs. The combustion drying technology opens up a promisingly method for high efficiency, low energy consumption, and low cost preparation of silica aerogel composites.

Construction of chitosan/alginate aerogels with three-dimensional hierarchical pore network structure via hydrogen bonding dissolution and covalent crosslinking synergistic strategy for thermal management systems

To replace traditional petrochemical-based thermal insulation materials, in this work, the chitosan (CHI)/alginate (ALG) (CA) aerogels with three-dimensional hierarchical pore network structure were constructed by compositing CHI and ALG using a synergistic strategy of hydrogen bonding dissolution and covalent crosslinking. The structure and properties were further regulated by crosslinking the CA aerogels with epichlorohydrin (ECH). The CA aerogels exhibited various forms of covalent crosslinking, hydrogen bonding and electrostatic interactions, with hydrogen bonding content reaching 79.12 %. The CA aerogels showed an excellent three-dimensional hierarchical pore network structure, with an average pore size minimum of 15.92 nm. The structure regulation of CA aerogels obtained excellent compressive properties, with an increase of stress and strain by 137.61 % and 45.05 %, which can support a heavy object 5000 times its weight. Additionally, CA aerogels demonstrate excellent thermal insulation properties and low thermal conductivity, comparable to commercially available insulation materials. More importantly, CA aerogels have good cyclic insulation stability and thermal properties, and they have a flame retardancy rating of V-0, which shows the stability of insulation properties and excellent safety. CA aerogels provide new ideas for the development of biomass thermal insulation materials and are expected to be candidates for thermal management applications.

Hollow engineering of Co/N-doped C@carbon aerogel with hierarchical structure boosting interfacial polarization for ultra-thin microwave absorption and thermal insulation

Rational manipulation of the composition and microstructure design of aerogel materials is considered to be an effective method for achieving the dual functions of microwave absorption and thermal insulation. Herein, hollow Co/N-doped C@carbon aerogel with hierarchical structures was designed and constructed via a synergistic strategy including directed freeze-drying, ZIF-67 in situ growth, chemical etching and calcination treatment. Co/N-doped hollow carbon nanocages derived from ZIF-67 with uniform heterojunctions and layered micro-mesopores were constructed using tannic acid and heat treatment process. After that, abundant macroporous structure from the carbon aerogel itself was further introduced to upgrade the impedance matching property, light weight and interfacial polarization loss capability. Remarkably, as-fabricated Co/N-doped C@carbon aerogel (ZTA@A-900) displays optimal MA performance with a minimum reflection loss (RLmin) value of −54.0 dB at 15.32 GHz and a broad effective absorption bandwidth (EAB) of 4.04 GHz (13.44–17.48 GHz) at a thickness of only 1.4 mm. Furthermore, the ideal CST simulation results and excellent thermal insulation property of ZTA@A-900 make it an outstanding candidate for microwave absorbers under extreme conditions. Thus, our work opens up a new avenue for the design and fabrication of multifunctional lightweight microwave absorbers.

Microphase separation regulation of polyurethane modified phenolic resin aerogel to enhance mechanical properties and thermal insulation

Applications of aerogels are commonly restricted by their complicated preparation route, high energy cost, brittleness and poor mechanical properties. Herein, a facile synthesis route for mechanical robust polyurethane (PU) modified phenolic resin (PF) aerogel was developed. The aerogel was prepared via polymerization of PU and phenolic resin (PF) followed by direct ambient pressure drying, sub-10 nm scale co-continuous phase structure was realized via control of kinetics of sol–gel reaction. The regulation of phase structure significantly enhanced mechanical properties of aerogels, which showed compressive strength and modulus of 29 MPa and 112 MPa, respectively, at 60 % strain without notable collapse. Furthermore, these aerogels showed excellent thermal insulation properties at both room temperature and high temperature. They exhibited superior dynamic ablative thermal protection at 1200℃ in oxygen-acetylene ablation test. This facile, inexpensive, environment-friendly methodology for aerogel preparation expands the application scope of aerogels in the field of thermal insulation under harsh environments.

Preparation of multifunctional polypyrrole hydrogel/Fe3O4/calcium alginate composite aerogel with electromagnetic shielding and fire warning performance

Purpose This study aims to fabricate a novel electromagnetic interference (EMI) shielding composite aerogel with both thermal insulation and high temperature warning functions. Design/methodology/approach An emerging bio-based polypyrrole (PPy) gel/Fe3O4/calcium alginate (PFC) EMI shielding composite aerogel was prepared by freeze-drying and in situ polymerization method. First, Fe3O4/calcium alginate (CA) aerogel was obtained by freeze-drying the Fe3O4/CA mixture. Then, PPy/Fe3O4/CA was obtained by synthesizing PPy on the surface of CA/Fe3O4 aerogel through in situ polymerization. Finally, PPy/Fe3O4/CA was immersed in porphyrin solution (cross-linking agent) to get the final PFC EMI shielding composite aerogel. Findings Due to the matched impedance between Fe3O4 and PPy, the EMI shielding performance of PFC composite aerogel can reach up to −8 dB. In addition, the PFC EMI shielding composite aerogel also shows excellent self-extinguishing and thermal insulation properties. After leaving the flame, the burning PFC aerogel is quickly extinguished. When the PFC aerogel is placed on the heating plate at 230 °C, the temperature on the side of the aerogel away from the heating plate is only 90.3 °C after 5 min of heating. The electrical resistance of the PFC composite aerogel can be reduced from 3.62 × 104 O to 5 × 102 O to trigger the warning light after 3 s of exposure to the alcohol lamp flame. This reversible thermal resistance response characteristic can be used to give an early warning signal when the PFC encounters high temperature or flame. Originality/value This work provides a novel strategy for designing a multifunctional EMI shielding composite aerogel with repeatable high temperature warning performance. This PFC composite aerogel shows potential applications in the prevention of material combustion in high temperature electromagnetic environments.

Broadband sound absorption cellulose/basalt fiber composite paper with excellent thermal insulation and hydrophobic properties

Cellulose-based materials find extensive applications in sound absorption due to their high porosity, biodegradability, and cost-effectiveness. However, these materials also suffer from some limitations such as hydrophilicity and low thermal stability that restrict their applicability and lifespan. Herein, we report a cellulose/basalt fiber (CBF) broadband sound absorption composite paper with excellent thermal insulation and hydrophobic properties fabricated by wet forming and silane vapor treatment. Benefiting from the introduction of eco-friendly basalt fibers, the composite paper has an adjusted pore structure and thermal conduction pathway, leading to enhanced sound absorption and thermal insulation performance. Particularly, the composite paper with 50 wt% basalt fiber shows remarkable sound absorption coefficient (0.71 on average) and ultralow thermal conductivity (0.034 W/m·K). As a novel application of eco-friendly materials for sound absorption, the CBF composite paper is an ideal candidate for indoor architectural decoration.

A novel thermal insulation material with excellent mechanical properties: Carbon fiber-modified aerogel /cement-based composite material

The demand for thermal insulation materials in construction with excellent mechanical properties is increasingly growing. A pivotal challenge in the application of aerogels in construction revolves around the comparatively lower mechanical strength of composites formed. This study aims to develop a novel carbon fiber-modified aerogel/cement-based composite thermal insulation material (CFAC) to considerably enhance both the heat retention capability and structural strength of construction insulation materials. Composite materials incorporating different proportions of carbon fibers were evaluated experimentally in terms of microstructure, thermal insulation performance, and mechanical properties. The experimental findings indicate that the addition of 1 wt% carbon fibers exhibits superior dispersion within the CFAC composite material, refining the pore size distribution of pores above 1 μm. Furthermore, these samples maintain the advantages of lightweight and excellent thermal insulation while increasing compressive strength by over 90 % compared to materials without carbon fibers. CFAC composite materials exhibit excellent thermal insulation and mechanical properties that can effectively reduce energy consumption and enhance material durability. As a result, CFAC composites hold significant potential for various applications in the construction and industrial sectors.

Research on effective thermal conductivity of hollow glass microspheres under vacuum at low temperature

As insulation materials with excellent thermal insulation properties, high robustness, and low maintenance costs, hollow glass microspheres (HGM) are gradually being applied in large liquid hydrogen storage tanks. However, the low-temperature insulation mechanism of HGMs is still unknown, and the insulation effect of HGMs of different types under various conditions has been neglected in recent decades. In this study, an existing theoretical model was improved by considering the gas thermal conductivity equations under various pressure intervals, and an experimental platform was built based on the steady vertical heat flux method to measure the effective thermal conductivities of three commercially available HGM models. The effective thermal conductivities of HGM models K1, T15, and HL20 at 0.1 Pa were 10, 8.9, and 7.6 mW/(m·K), respectively. The values decreased to 2.5, 2.9, and 2.0 mW/(m·K), respectively, when the cold boundary temperature was 90 K. To analyse the effect of the HGM physical parameters and environment on the HGM insulation, the thermal conductivities were calculated using the derived theoretical model. It was found that continuing to reduce the pressure after the ambient pressure reached 10 Pa hardly improved the insulation performances of the HGMs. The radiative heat transfer was very sensitive to temperature changes and jointly dominated the heat transfer with integrated thermal conductivity in the low-temperature region. In summary, HGMs are advanced vacuum-insensitive insulation materials, which have great potential in the field of cryogenic liquid storage and transportation.

Hygrothermal performance of timber-framed walls in Turkey – Long-term monitoring

The increasing energy consumption emphasizes the urgency of sustainable building practices. Worldwide, there is a tendency towards local, natural, durable, and recyclable materials like timber. Furthermore, timber's excellent thermal insulation and natural hygroscopic properties enable it to efficiently regulate indoor humidity levels, ensuring stability and comfort. In Turkey, timber construction declined significantly in the 20th century due to the shift towards vertical reinforced concrete, however, recent years have witnessed a renewed interest driven by earthquake concerns and global inclination. Despite this resurgence, timber construction practices are still limited, and the hygrothermal performance of exterior walls in both restoring traditional timber buildings and constructing new ones is often disregarded. Furthermore, there is a lack of scientific research in this area. Understanding the hygrothermal behaviour of these structures is essential for meeting modern energy efficiency standards. This study evaluates the hygrothermal performance of prevalent practices in timber-framed constructions in Turkey. Long-term monitoring in a full-scale test cabin exposed to real climatic effects provides insights. Findings indicate the exterior plywood sheathing on the North-west facing walls being more susceptible to moisture, particularly when the indoor relative humidity is elevated. South-east facing walls are better at drying, but air barrier membrane slows down drying. Timber cladding with ventilated cavity offers improved protection but its high exposure to rainfall in North-west, and solar radiation in South-east, implies potential performance degradation over time. Installing suitable vapour retarders and additional exterior thermal insulation particularly to the North-west facing walls could possibly reduce risks associated with moisture, as well as preventing thermal bridges.

Feasibility of natural bamboo branches aggregate applied to the thermal insulation layer of rock walls in roadways

The high-temperature heat damage is mainly caused by heat dissipation of surrounding rock in deep mining of mine, so spraying thermal insulation layer (TIL) on mine roadway can be used to actively heat insulation. As a kind of green material, bamboo branches have excellent thermal insulation and mechanical properties. In this paper, gravel and ceramsite were used as aggregate, bamboo branches and glass hollow bead were used as main thermal insulation materials, and the effects of different content, diameter, and length of bamboo branches on mechanical properties, thermal insulation properties, and microstructure were studied through orthogonal experiments. A group of specimens with the best comprehensive performance was selected through the analysis of the efficiency coefficient, and the optimal ratio was determined. This ratio ensures the perfect balance between insulation and strength for TIL, which is essential for the preparation of TIL. At the same time, the numerical simulation software Fluent was used to establish the roadway model, and the cooling effect of the TIL on the airflow temperature in the roadway under different working conditions was studied based on the parameters of the selected specimens. These parameters are based on the actual characteristics of the specimen, and their accuracy ensures the reliability and validity of the research results. The results show that under the optimal mixing ratio, the thermal conductivity (TC) of the specimen is 0.224 W/(m·K), the thermal insulation performance of the prepared coating is increased by 25∼65 %, and the mechanical strength is also improved. The optimal mix ratio obtained in this study can be applied to the field of mine thermal damage control, and the feasibility of natural bamboo branches for preparing roadway thermal insulation material is demonstrated. Bamboo branches grow rapidly, and their use as thermal insulation materials will not only not cause a burden on the environment, but help to promote ecological recycling and achieve sustainable use of resources.

Integration of N- and P- elements in sodium alginate aerogels for efficient flame retardant and thermal insulating properties

In the field of building energy conservation, the development of biodegradable biomass aerogels with excellent mechanical performance, flame retardancy and thermal insulation properties is of particular importance. Here, a directional freeze-drying method was used for fabricating composite sodium alginate (SA) aerogels containing functionalized ammonium polyphosphate (APP) flame retardant. In particular, APP was coated with melamine (MEL) and phytic acid (PA) by a supramolecular assembly process. Through optimizing the flame retardant addition, the SA-20 AMP sample exhibited excellent flame retardant and thermal insulation properties, with the limiting oxygen index of 38.2 % and the UL-94 rating of V-0. Such aerogels with anisotropic morphology demonstrated a low thermal conductivity of 0.0288 (W/m·K) in the radial direction (perpendicular to the lamellar structure). In addition, as-obtained aerogels displayed remarkable water stability and mechanical properties, indicating significant potential for practical applications.

Study on the thermal insulation property of lanthanum–cerium oxide coatings

Functional fillers with low thermal conductivity and high near-infrared reflectance play a vital role in high temperature thermal insulation coatings and make an outstanding contribution to achieving efficient comprehensive thermal insulation. In this work, the thermal insulation and bonding properties of lanthanum–cerium oxide (LCO) coatings were regulated by composition design. The effects of the La/Ce mole ratio on phase composition, the thermal conductivity and near-infrared reflectivity of LCO coatings were investigated systematically. The results showed that coating with a La/Ce mole ratio of 1:1 possess the excellent thermal insulation properties (ΔT ≈ 115°C) due to the formation of a LCO solid solution and a lanthanum phosphate mesophase with low thermal conductivity and high near-infrared reflectivity. In addition, the mortise and tenon structure was formed between the coating and the substrate, which led to the remarkable bonding properties. The LCO coating offers excellent thermal insulation properties and broad application prospects in the fields of high temperature and energy conservation.

Core–Shell Bacterial Cellulose/Graphene Oxide@Polydopamine Aerogel Fibers for Personal Thermal Management Textiles

AbstractThe porous nature and gel network of aerogel fibers make them ideal options for personal thermal management because they can significantly cut down on energy waste. However, aerogel fibers generally suffer from poor mechanical properties and single function. Herein, the porous continuous bacterial cellulose/graphene oxide@polydopamine core–shell aerogel fibers with high strength, excellent photothermal properties, and thermal insulation are investigated by wet spinning and freeze‐drying. The bacterial cellulose/graphene oxide@polydopamine aerogel fiber prepared by wet spinning method has a porous structure, which can prevent heat convection, reduce heat conduction, and suppress heat radiation, making the aerogel fiber have excellent thermal insulation properties. More crucially, graphene oxide may considerably enhance infrared radiation's capacity for heating, while polydopamine can enhance ultraviolet light absorption and boost photothermal conversion capability.

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.

Development of polyamide foam by supercritical CO2: Low density, anti-shrinkage and thermal insulation

Saving energy and reducing environmental harmful emissions have become a global concern, so the foam thermal insulation materials are of great significance for saving energy, reducing greenhouse effect and ensuring the comfort and safety requirements of buildings. Polyamide12 (PA12) has outstanding weather resistance, mechanical stability and termite resistance, which is a promising building material. Herein, we prepared a series of PA12 foams by using supercritical carbon dioxide (Sc-CO2) as foaming agent, polymethyl methacrylate (PMMA) as a blend modification material, tridehydroglycerol isocyanurate (TGIC) as chain extender improved the cells wall strength and stability. When the PA12 and PMMA blending ratio was 70:30 and TGIC content was 0.2 phr, the foam density was 0.02 g/cm3, and the thermal conductivity of the foam was as low as 0.0302 W/m·K. Moreover, the influence of viscosity gradually increased with the increase of PMMA as shown by tanδ; at the same time, as an amorphous material, PMMA enlarged the melting range of the blends and reduced the enthalpy of melting. Therefore, the introduction of PMMA increased the temperature range of the foaming window to170–190 °C. This study provided an effective method for the design of foams with low density, low shrinkage, excellent mechanical properties and high thermal insulation properties, which has broad PA12 foam application prospects in the fields of buildings, such as wall or roof insulation.