Excellent Thermal Insulation Properties Research Articles

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.

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.

The uniqueness of flexible and mouldable thermal insulation materials in thermal protection systems—A comprehensive review

AbstractIn thermal control and safety systems, thermal insulation materials which are lightweight and flexible with hierarchical microstructures are commonly used nowadays. Flexible thermal insulation materials are designed to prevent heat transfer between two surfaces. These materials have various applications, from building insulation to automotive components, aerospace, and industrial processes. This review aims to provide an overview of flexible thermal insulation materials, their properties, and their applications. The most commonly used materials used for flexible thermal insulation are aerogels, ceramic fibres, and polymers. These materials are lightweight, durable, and have excellent thermal insulation properties and are also gaining popularity due to their unique characteristics. The insulation performance of flexible thermal insulation materials is influenced by thickness, density, porosity, and thermal conductivity factors. The choice of insulation material and its properties depend on the application site and the desired thermal insulation. The literature shows that nanofibrils‐based insulating materials have low thermal conductivity values and can be excellent flexible thermal insulating materials. Using flexible thermal insulation materials is crucial in reducing energy consumption and dissipation, enhancing thermal efficiency, and improving sustainability in various industries.

Lightweight and robust cellulose/MXene/polyurethane composite aerogels as personal protective wearable devices for electromagnetic interference shielding

The increasing electromagnetic pollution is urgently needed as an electromagnetic interference shielding protection device for wearable devices. Two-dimensional transition metal carbides and nitrides (MXene), due to their interesting layered structure and high electrical conductivity, are ideal candidates for constructing efficient conductive networks in electromagnetic interference shielding materials. In this work, lightweight and robust cellulose/MXene/polyurethane composite aerogels were prepared by mixing cellulose nanofiber (CNF) suspensions with MXene, followed by freeze-drying and coating with polyurethane. In this process, CNF effectively assembled MXene nanosheets into a conductive network by enhancing the interactions between MXene nanosheets. The prepared aerogel exhibited the shielding effectiveness of 48.59 dB in the X-band and an electrical conductivity of 0.34 S·cm−1. Meanwhile, the composite aerogel also possessed excellent thermal insulation, infrared stealth, mechanical and hydrophobic properties, and can be used as a wearable protective device to protect the human body from injuries in different scenarios while providing electromagnetic interference shielding protection.

Composite aerogel with oriented structure of polyimide@ polypyrrole /MXene for effective shielding against electromagnetic waves and insulation

Although the rapid evolution of electromagnetic wave technology make much progress to society, but has also caused electromagnetic pollution, which poses risks to health, information security, and disrupts communication and device operation. The development of new Electromagnetic Interference (EMI) shielding materials, especially those that are lightweight, easy to process and high shielding efficiency, has become the key to overcoming this challenge. In this study, MXene nanosheets with few layers were fabricated by chemical etching with lithium fluoride (LiF) and hydrochloric acid (HCl). Subsequently, the unidirectional freeze-drying method and vacuum-assisted impregnation method were applied to fabricate polyimide@ polypyrrole/MXene (PI@PPy/MXene) composite aerogel with oriented structure. The electromagnetic shielding properties of the oriented PI@PPy composite aerogel were modulated by changing the polymerization time of PPy to control its conductivity. When the polymerization time was set as 7 h, the oriented PI@PPy composite aerogel showed the highest EMI efficiency, the value of EMI SE was 19.36 dB. With the introduction of MXene, the EMI SE of the PI@PPy/MXene composite aerogel was increased compared to PI@PPy and reached to 32.64 dB. The improvement in electromagnetic shielding performance was attributed to the co-enhancement among the PI aerogel with oriented structure, PPy and MXene, which is the result of the synergisic effect of Multiple reflection losses and polarization losses within the aerogel. The infrared thermography at 200°C showed that with increasing PPy polymerization time, the external temperatures of the samples are 40.3°C, 44.8°C, 51.4°C, 55.4°C and 48.6°C, demonstrating the excellent thermal insulation properties.

Effects of carboxymethyl cellulose concentration on mechanical, viscoelastic properties, and thermal properties of starch/plant fiber foaming tableware materials with foam structure

In this study, a novel bio-based composite of starch/plant fiber foaming tableware material was prepared by the hot-pressing foaming method. The influence of the content of carboxymethyl cellulos (CMC) as a new type of film-forming agent filler on the properties of foam materials was systematically investigated. The results showed that the foam material with 10 wt% CMC had excellent cell morphology and uniform cell size (the average cell size reached the minimum value of 465.7 μm), relatively high porosity (57.01%), and excellent thermal insulation properties (thermal conductivity: 0.0541 W/m·K). The tensile strength of foam increased from 4.289 MPa for 0 wt% CMC to 5.714 MPa for 10 wt% CMC loading. Similarly, the flexural strength also increased from 11.609 MPa to 15.719 MPa for the foam material with 10 wt% CMC. The thermal stability and viscoelastic properties of the foam material reached the highest after adding 10 wt% CMC. In addition, the increase of CMC content is beneficial to improve the oil resistance and biodegradability of the material. The research shows that CMC is an effective filler to improve the properties of starch/plant fiber foaming tableware materials, which can greatly promote the development of bio-based polymer foam materials.

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.

Experimental study on the preparation of wood aggregate recycled concrete using waste wood and recycled fine aggregate from construction and demolition wastes

As a renewable resource, wood has the advantages of a high strength-weight ratio, high yield and excellent thermal insulation. Meanwhile, the resource utilization of large quantities of waste wood, waste furniture and mixed wood generated by the demolition of old houses and the removal of building formwork are basically in a blank state. Therefore, in this study, construction solid waste—waste wood and recycled fine aggregate were used as coarse and fine aggregates to replace natural sand and gravel, respectively, and synergized with three cementitious materials (sulfoaluminate cement, portland cement and geopolymer cement) to prepare wood aggregate recycled concrete (WARC). Focus on the evolution law of basic property, thermal insulation property, mechanical property, shrinkage property, environmental and economic benefits of WARC. The results showed that the mechanical and shrinkage properties of WARC were deteriorated by using WA and recycled fine aggregate (RFA) instead of natural aggregates. The dry density of WARC was as low as 1770 kg/m3. The 28 d maximum compressive and flexural strength were 34.8 and 5.69 MPa, which were better than traditional C30 concrete. Compared with conventional concrete, WARC has excellent thermal insulation properties. The thermal conductivity was reduced by up to 81.9 % compared to traditional concrete, which would make WARC very promising for non-structural components (green insulated wall materials and precast wall panels, etc.). By calculating CO2 emissions and compressive strength-cost efficiency values, it was found that the WARC prepared with geopolymer cement could reduce CO2 emissions by 31.3 % while possessing good mechanical properties and economic benefits, making it the optimal cement-based material for preparing WARC.

Photothermal performance of vitreous products from high-temperature melting of hazardous waste

High-temperature molten vitreous (HTMV), as the primary means of hazardous waste disposal, was produced in large quantities. Exploring its potential in photothermal applications could extend its high-value. Herein, the HTMV was used to explore the photothermal performance potential. It indicates that the HTMV possesses significant photothermal conversion capability, capable of increasing the tested water temperature by 6.65 °C. The HTMV mass and water volume are critical factors affecting the water temperature outcomes. The HTMV exhibits distinct conversion capabilities when applied at different application scenarios on the test object. Application on the bottom primarily focuses on photothermal conversion with high heat production efficiency, while side application additionally demonstrates excellent thermal insulation properties. Based on heat balance and backpropagation neural network predictions, optimal scheme of HTMV on both inside and outside bottom application scenarios of the heated object can achieve a maximum heat input of 660.6 kJ m−2 and 570.1 kJ m−2, respectively, and reduce carbon emissions by 0.062 kg CO2 m−2 and 0.054 kg CO2 m−2. This study not only provides a foundation for the further application of HTMV but also opens a new direction for the development of photothermal conversion materials, which is of great significance in advancing sustainable energy technology.

Synthesis of micro/nano multi-scale polyimide aerogels via confinement-controlled freeze-casting

The freeze-casting is widely utilized as a tool for regulating micro-scale pore structures in the fabrication of flexible polyimide (PI) aerogels for applications in adsorption, filtration, and fire-retardant. Herein, a confinement-controlled freeze-casting method is developed to fabricate PI aerogels with excellent thermal insulation properties by designing multi-scale structural adaptability. In a confinement-controlled system, the enhanced solid/solid and solid/liquid interface interactions in the solution dispersion system induce dendritic evolution of ice crystals. Under the directional freezing, grown dendritic ice crystals squeeze the loaded particles to form polyamic acid salt (PAAs) cryogels. Followed by template removal and thermal imidization, PI aerogels with a micro/nano-scale slit-like porous structure were obtained. The PI aerogels are characterized by ultra-low density (as low as 9.82 mg/cm3) and exceptional thermal insulation performance (25.0 mW/(m·K) at 25 °C).

CO2 adsorption properties of aerogel and application prospects in low-carbon building materials: A review

The applications and researches of the aerogel in the field of building materials and building energy conservation had been widely concerned due to its excellent thermal insulation properties. However, it has not been paid attention that the potential application values for excellent CO2 adsorption properties of aerogel in building materials. The CO2 adsorption properties of aerogel and the research progress on utilizing SiO2 aerogel in building materials had been reviewed. And the application prospect of the technologies that exploit the CO2 adsorption properties of aerogel and the carbonization technology to prepare SiO2 aerogel-based low-carbon building materials was discussed. It was shown that the type, morphology, and pore structure of aerogel significantly affect the resulting carbon adsorption performance. Amino modification was an effective method for improving the carbon adsorption capacity of aerogel. The performance of aerogel-incorporated cement-based composites could be optimized by improving the performance of binder materials, modifying the aerogel, or preparing new aggregates by loading aerogel into porous materials with higher strength. In addition, it was feasible to prepare new green low-carbon building materials by using aerogel as thermal insulating aggregate and carbon adsorption material, industrial solid wastes rich in alkali metal ions as cementitious materials, and carbonation curing technology. The purpose of this review was to promote the application of CO2 adsorption properties of aerogel in building materials, and enhance the development of low-carbon (or zero-carbon, or negative-carbon) building materials. This is of great significance for reducing carbon emissions in the construction sector and promoting the "carbon neutrality" of global.

Investigating the Emissions and Performance of Ethanol and Biodiesel Blends on Al2O3 Thermal Barrier Coated Piston Engine Using Response Surface Methodology Design - Multiparametric Optimization

The Response Surface Methodology (RSM) optimization technique to examine the effect of load, Tomato Methyl Ester (TOME), and Ethanol injection enhanced diesel on engine performance and exhaust gas emissions with normal piston and Al2O3 coated piston. TOME biodiesel (10, 20, and 30%) and Ethanol (10, 20, and 30%) were chosen to increase BTE while minimizing BSFC, NOx, CO, smoke, and HC. The RSM technique was used to operate the engine by load (0-100%). The results revealed that engine load, TOME, and ethanol concentration all exhibited a considerable effect on the response variables. The (ANOVA) results for the established quadratic models specified that each model, furthermore, an ideal was discovered by optimizing an experiment's user-defined historical design. The present research efforts to improve the performance of a diesel engine by using a thermal barrier-coated piston that runs on biodiesel blends. Al2O3 is the chosen material for TBC due to its excellent thermal insulation properties. B20E30 has a 4% higher brake thermal efficiency than diesel, but B10E20 and B30E20 mixes have a 3.6% and 12% reduction in (BSFC). The B20 blends lowered CO and HC emissions by 6% to 8% respectively. In terms of performance and emissions, biodiesel blends performed similarly to pure diesel, and the combination was optimized through a design of experiment tool.

Robust, thermally insulating, and high-temperature resistant phosphate-enhanced mullite fiber porous ceramic composites

Porous mullite ceramics with high porosity and low thermal conductivity are urgently required as high-temperature thermal insulators in harsh environments. How to improve the strength of Porous mullite ceramics dramatically under the premise of no sacrificing its thermal insulating properties has remained an extremely challenging. Inspired by the freezing rain phenomenon in nature, high-strength and high-temperature resistant phosphate coatings were applied to the surface of mullite fibers, which significantly improved the mechanical properties of porous mullite ceramics without significantly increasing their thermal conductivity. The Al(H2PO4)3 solution concentration significantly affected the mechanical and thermal properties of the composite material, where the mechanical performance improved with an increasing Al(H2PO4)3 solution concentration. The phosphate coating phase stabilized with an increasing calcination temperature. The mechanical properties of the ceramics were improved by the excellent interfacial bonding strength between the coating and mullite fiber, and the forms of phosphate in the porous ceramics. The optimum composite preparation process increased its compressive strength by approximately nine-fold to 4.1 MPa and resulted in a thermal conductivity of only approximately 0.09 W/(m·K), demonstrating that the composite exhibited a significantly higher comprehensive performance than other previously reported porous ceramics and aerogels. Such new composites with excellent mechanical and thermal insulation properties exhibit excellent potential for high-strength thermal insulation in the chemical, metallurgical, pharmaceutical, aerospace, and other fields.

Mechanical properties and discrete element simulation of KH-560 modified polystyrene concrete

Polystyrene foam (EPS) concrete is a composite concrete material commonly used in construction, which has excellent thermal insulation and thermal insulation properties, but also has defects of weak bonding interface.KH-560 can significantly improve the characteristics of EPS particles and concrete matrix, which have different physical and chemical properties and are difficult to combine. In this study, the effects of different levels of KH-560 on the enhanced mechanical properties of EPS concrete were studied from the aspects of macroscopic mechanical properties, microstructure characteristics, chemical composition and discrete element simulation, and the mechanism of action was discussed. The results of mechanical experiments show that the compressive strength and flexural strength of EPS concrete mixed with KH-560 are higher than those of ordinary EPS concrete, and its mechanical properties gradually increase with the increase of KH-560 content. XRD, FT-IR and SEM observations showed that more C-S-H gels would be produced under the action of KH-560, which made the structure of the weak interface transition zone of EPS concrete more compact. The results of discrete element simulation show that the peak strength of EPS concrete increases with the increase of friction coefficient, but has little effect on its elastic modulus.

A study on aramid nano-aerogel fiber and its fabric thermal conductivity

Aramid nano-aerogel represents an ideal structure for the fabrication of next-generation high-performance thermal insulation fibers and textiles. Single aramid nano-aerogel fiber can be achieved via wet spinning. The thermal conductivity of these fibers, a crucial determinant of textile insulation performance, remains under-explored in terms of numerical modeling. This research aims to establish a numerical inversion model to determine the thermal conductivity of single aramid nano-aerogel fiber. By simulating the three-dimensional geometry of plain fabric, the volume fraction of gas and solid within the fabrics are computed. Drawing from the law of energy conservation and Fourier's law of heat conduction, a relationship model is proposed between the thermal conductivity of single aramid nano-aerogel fiber and the overall thermal conductivity of the fabric. The finite difference method is employed to ascertain the thermal conductivity of single aramid nano-aerogel fiber. Furthermore, the influence of the geometric structure and the fiber diameter on the thermal insulation performance of the single-layer fabric is analyzed, which provides a feasible approach for the subsequent design of fabric structures with excellent thermal insulation properties.

Interface stress analysis and bonding strengthening exploration of metal layer on the laser-activated copper-clad AlN

Aluminum nitride ceramics has excellent thermal conductivity and insulation property, making it a kind of excellent electronic packaging material. But enhancing the bonding strength between the metal layer and aluminum nitride (AlN) ceramic is a challenging problem. Especially regarding the lack of accurate data analysis on the stress between interfaces, enhancing adhesive strength still relies on blind attempts. By using the finite element method, this study reveals that the shear stress generated between the metal/ceramic interface is concentrated at the interface edge. Based on this finding, a method of inserting micro-pore arrays at the edge is proposed to enhance the interfacial bonding strength. The simulation results show that by inserting micro-pores with an appropriate density, the interface shear stress between metal and ceramic can be reduced obviously by 36 %. Finally, vertical peel-off verification experiments were designed. After inserting micro-pores to the interface, the bonding strength of the interface increased from 8.75 MPa to 11.69 MPa, and the performance was improved by 33.6 %. The experimental results were consist with the simulation results and indicated that the micro-pores had a significant effect on improving the bonding strength.

High porosity and low thermal conductivity lanthanum zirconate porous ceramics via replica method

ABSTRACT Low thermal conductivity and excellent high-temperature stability make lanthanum zirconate (La2Zr2O7, LZO) a very promising material for high-temperature insulation applications. In this study, LZO porous ceramics with ultra-high porosity and an open-pore structure were prepared by the replica method using a polyurethane template. The flowability and coating quality of the ceramic slurry were optimized. When the dispersant content of the slurry was 0.6 wt% and the alcohol to water ratio was 1:1, the slurry had low surface tension and low viscosity, leading to good coating quality of the ceramic slurry on the sponge template. The pore size between hollow skeletons was 100–500 μm with the hollow structure of the skeletons forming secondary pores. LZO porous ceramics showed high porosity of 87.6%-96.0%, low thermal conductivity of 0.048–0.126 W/(m·K), and compressive strength of 0.13–0.74 MPa by adjusting the ceramic content. A high temperature insulation performance test showed that the temperature difference between the cold side and the hot side of the sample was over 1000°C, indicating the excellent thermal insulation properties of LZO porous ceramics. LZO porous ceramics had good high-temperature stability without sintering shrinkage at heat treatment temperatures below 1500°C.

Sound-Absorbing, Thermal-Insulating Material Based on Poly(methylsiloxane) Xerogel and Cellulose Nanofibers

The automotive industry needs to improve energy efficiency rapidly to achieve carbon neutrality while creating a safe, secure, and comfortable driving environment for customers. Porous sound-absorbing materials and porous thermal insulators are typically used to satisfy these requirements despite limitations in mass and space. While these porous materials are similar, the microstructures they offer for high performance differ in the size and connectivity of their fluid phases, which enhances the difficulty of achieving excellent sound absorption and thermal insulation in the same material. In this study, a hydrophobic cellulose nanofiber–poly(methylsiloxane) xerogel composite was developed using computational microstructure modeling. This porous material has high porosity and excellent thermal insulation and sound absorption properties.

Thermal Performance Assessment of Aerogel Application in Additive Construction of Energy-Efficient Buildings

The main development direction of energy efficiency technologies in construction is the creation of various materials with complex structures and unique strength, thermal properties, and other properties. The aerogel is a material with high porosity and excellent thermal insulation properties. This paper provides state-of-the-art aerogel applications for the additive manufacturing of energy-efficient buildings. This work provides the experimental and numerical assessment results of the thermal conductivity of aerogel-enhanced blanket, the experimental assessment results of thermal performance of aerogel-enhanced building structure, the experimental assessment results of the aerogel application as a mixture powder component of the concrete mixture to printing buildings, and the experimental assessment results of the aerogel application as a parget powder component. Experimental results show the effect of aerogel powder component application: thermal conductivity decreased by 25%.