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Porous thermal insulation materials (PTIMs) are a class of materials characterized by low thermal conductivity, low bulk density and high porosity. The low thermal conductivity of the gas enclosed in their pores allows them to achieve efficient thermal insulation, and are they among the most widely used and effective materials in thermal insulation material systems. Among the PTIMs, polyurethane foam (PUF) stands out as particularly promising. Its appeal comes from its multiple beneficial features, such as low density, low thermal conductivity and superior mechanical properties. Such attributes have propelled its broad application across domains encompassing construction, heterogeneous chemical equipment, water conservation and hydropower, and the aviation and aerospace fields. First, this article outlines the structure and properties of porous thermal insulation PUF materials. Next, it explores the methods of preparing porous thermal insulation PUF materials, evaluating the associated advantages and disadvantages of each technique. Following this, the mechanical properties, thermal conductivity, thermal stability, and flame-retardant characteristics of porous thermal insulation PUF materials are characterized. Lastly, the article provides insight into the prospective development trends pertaining to porous thermal insulation PUF materials.

Lightweight, high-temperature thermal insulation materials play a critical role in aerospace applications, where extreme temperature conditions necessitate lightweight, high-performance solutions. This paper explores advancements in lightweight, high-temperature insulation materials specifically designed for aerospace environments, focusing on innovative flexible ceramic fiber felts, thermal insulation tiles, nano-insulation materials (aerogels), and multilayer insulations (MLIs). These materials exhibit superior thermal resistance, low density, and durability under dynamic and harsh conditions. Key developments include the integration of nanostructures to enhance thermal conductivity control and improve mechanical stability. This paper also highlights applications in spacecraft thermal protection systems, providing insights into the challenges of future material design strategies. These advancements underscore the growing potential of thermal insulations to improve energy efficiency, safety, and performance in aerospace missions.

With the increasing depth of metal mines in China, heat injury due to high geothermal surrounding rock is a significant issue. This paper studies a new thermal insulation material for mines, a polyurethane foam (PUR) and expanded perlite (EP) composite, aiming to create a safe, comfortable working environment. The composite includes PUR and EP as the main insulation, ceramsite and fly ash as aggregates, and basalt fiber as an admixture. An orthogonal test with three factors—PUR-to-EP mass ratio, ceramsite amount, and basalt fiber amount—was conducted. Samples with varying ratios were tested for insulation efficiency, and results were verified using FLUENT software. The best insulation performance was observed at a PUR-to-EP mass ratio of 0.25:1. Simulation showed that thicker coatings (d = 0.2 m, d = 0.3 m, and d = 0.5 m) provided better insulation. Comparing tunnel temperatures before and after applying the coating at different wind speeds (v = 0.6 m s−1, v = 1.2 m s−1, v = 1.8 m s−1, and v = 2.4 m s−1), a 0.2-m-thick coating reduced outlet air temperatures by 6.8 K, 7.15 K, 7.02 K, and 6.73 K, respectively.

Ceramic membranes are attractive for thermal management applications due to its lightweight and ultralow thermal conductivity, while it is indispensable to address the long-standing obstacle of its poor mechanical stability and degradation under thermal shock. In this work, a series of the organic polymer template-modulated yttria doped zirconia (YDZ) nanofibrous membranes with lightweight, superior mechanical and thermal stability are developed through a cost-effective, scalable sol-gel electrospinning and subsequent calcination method. The YDZ membranes demonstrate excellent flexibility and foldability, which can be attributed to the tetragonal phase and small crystallite size of the YDZ fibers due to the presence of yttria. Besides, the fibrous size, grain size, mechanical and thermal stability of YDZ nanofibrous membranes could be tailored by varying the species and molecular weight of polymer template. The remarkable performances are obtained through the poly(vinyl pyrrolidone) (PVP) template YDZ nanofibrous membranes, featuring the superior tensile strength up to ∼ 4.82 MPa, excellent flexibility with bending rigidity ∼ 26 mN, robust thermal stability up to 1,200 °C, ultra-low thermal conductivity of 0.008–0.023 W·m −1 ·K −1 (25–1,000 °C), and excellent flame retardancy with tolerance of flame up to 1,000 °C. The remarkable properties can be attributed to the smaller fibrous size, and higher grain size resulting from PVP template. This robust material system is ideal for thermal superinsulation with a wide range of uses from energy saving building applications to spacecraft.

Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods.Graphic abstract

Ceramic nanofiber aerogels (CNFAs), built from ceramic fiber components, stand out for their multifunctional properties, including low density, low thermal conductivity, high porosity, compressibility, robust chemical stability, and resistance to high temperatures. The continuity of the building blocks overcomes the brittleness of ceramic aerogels and expands their applications, which makes them widely used in the fields of high-temperature thermal insulation, sound insulation, oil-water separation, seawater desalination, air filtration, and electromagnetic wave absorption. Among the current methods for preparing CNFAs, electrostatic spinning is a perfect method for producing reproducible micro-nanofibers. Direct electrostatic spinning combined with freeze casting makes it easy to prepare CNFAs with anisotropic properties, while chemical vapor deposition makes it easy to prepare aerogels with random structures. The method of solution blow spinning has advantages of high fiber productivity and low-voltage electric field relative to electrostatic spinning, and the atomic layer deposition depends on templates to produce films with formulated thickness. This review initially explores the fabrication methods of CNFAs, including electrostatic spinning, freeze casting, chemical vapor deposition, solution blow spinning, and atomic layer deposition. Subsequently, it delves into the novel applications of CNFAs in recent years in the fields of high-temperature thermal insulation, sound insulation, electromagnetic wave absorption, oil-water separation, seawater desalination, and air filtration. Moreover, the advancement of CNFAs with high-temperature thermal insulation, fire resistance, strong flexibility, and tensile properties opens up promising applications in aerospace, personal protective equipment, and flexible wearable devices in the future.

This study used pure silica fume nanoparticles (SF NPs) and 3-APTES-functionalized silica fume (F-SF) to improve the thermal properties of water-based acrylic paint. First, the NPs were synthesized and then their structural, chemical, and morphological studies were performed using infrared spectroscopy (FT-IR) to identify functional groups and confirm the functionalization reaction, X-ray diffraction (XRD) to determine the phase and crystal structural changes, scanning electron microscopy (SEM) to study the surface and overall morphology, energy dispersive X-ray spectroscopy/ elemental mapping (EDX/ Mapp), and transmission electron microscopy (TEM) to examine the particle size and dispersion. The addition of F-SF to water-based acrylic paint significantly improved the coating adhesion (up to 5B), hardness, and gloss, which is due to the higher dispersion of NPs and stronger interfacial interactions in the matrix. After confirming the above factors, NPs were added to water-based acrylic paint at 0.5–1.5 Wt.%. The thermal conductivity (K) properties of the samples were measured to investigate the thermal insulation performance. The K values ​​of the different samples as base coating, FS-0.5, FS-1, FS-1.5, F-FS-0.5, F-FS-1, and F-FS-1.5 were obtained as 0.420, 0.356, 0.326, 0.342, 0.337, 0.281, and 0.300 W/mK, respectively. The analysis showed that pure SF NPs reduced the paint’s K by 22% and F-SF NPs by 33%. This decrease in K is due to the creation of porosity and increased thermal circulation paths in the paint structure, which prevents easy energy transfer and helps increase thermal insulation properties. Also, functionalization with 3-APTES improves the adhesion and dispersion of NPs in the paint matrix due to the higher decrease in K compared to pure SF, the difference in surface structure, and its effect on heat transfer. Overall, the results indicate the high potential of these NPs to improve the thermal insulation performance of acrylic paints and industrial applications in thermal protective coatings.

Tree bark is a by-product of the timber industry available in large amounts, considering that approximately 10% of the volume of a tree stem is bark. Bark is used primarily for low-value applications such as heat generation or as mulch. To the best of our knowledge, this study is the first one that scrutinises thermal insulation panels made from spruce bark fibres with different densities and fibre lengths manufactured in a wet process. The insulation boards with densities between 160 and 300 kg/m3 were self-bonded. Internal bond, thermal conductivity, and dimensional stability (thickness swelling and water absorption), together with formaldehyde content, were analysed. The thermal properties of the boards were directly correlated with the density and reached about 0.044 W/m*K, while the internal bond was rather influenced by the fibre length and was relatively low (on average 0.07 N/mm2). The water absorption was high (from 55% to 380%), while the thickness swelling remained moderate (up to 23%). The results of this study have shown that widely available bark residues can be successfully utilised as an innovative raw material for efficient eco-friendly thermal insulation products.

The study is focused on ultra-light foam concrete (FC) aimed as a thermal insulation material. Two important properties of such material were investigated: compressive strength and thermal conductivity. In the conducted tests, the influence of the air-dry density (200–500 kg/m3), type of foaming agent (synthetic and protein) and binder type (ordinary Portland cement—OPC; calcium sulphoaluminate cement—CSA; metakaolin; siliceous fly ash—SFA; calcareous fly ash—CFA) on the mentioned properties were examined. The results confirmed the dependence of compressive strength and thermal conductivity on the FC density but also indicated the important effect of the nature of the foaming agent and the binder type. The best thermo-mechanical properties were obtained for the foam concrete made of protein-based foaming agent, OPC and metakaolin. Simultaneously, the use of CSA mixed with metakaolin and foam based on the synthetic foaming agent also shows satisfactory properties.

The unique structure of penguin feathers endows them with extremely high thermal insulation properties in extreme cold environments via sunlight absorption, heat insulation and infrared reflection. Herein, inspired by a thermal insulation strategy of the penguin feathers, the laminated wearable textile with coupled thermal insulation was fabricated for thermal management. The outermost layer, comprised of carbon nanotube-cellulose, simulates the black tip of the penguin's dorsal feather, exhibiting exceptional light-to-heat conversion as it can swiftly elevate its temperature by 5 ℃ upon exposure to simulated sunlight. The middle layer, constructed from polylactic acid, mimics the intermediate section of the penguin's feather, achieving effective heat insulation by trapping significant amounts of air. And the innermost layer MnO2-cellulose membrane is functionally similar to the fluff of the penguin closest to the skin, reflecting the infrared radiation of the body to reduce heat loss. Additionally, the textile underwent hydrophobic modification, endowing it with waterproof properties, resulting in an alteration of the exterior contact angle from 52.2 to 118.8°. Furthermore, the textile displayed anti-ultraviolet capabilities (with ultraviolet transmittance below 8%), excellent mechanical performance (with tensile strength is 3.22 MPa) and active deicing properties, enhancing the wearable comfort. This work represents a versatile and comprehensive textile learning from the bionic structure of penguin feathers for highly efficient thermal management applications, making it attractive for textiles to satisfy various wearable applications in cold environments and even extreme weather conditions.