Lightweight Thermal Insulation Research Articles

Investigating the properties of sprayed insulating cementitious materials with corn cobs

As the mining depth increases, the underground space will face more serious thermal hazards. By using corn cobs, an agricultural waste, to prepare cementitious insulation materials, active insulation layers are constructed by injecting insulation materials into underground spaces using cementitious material spraying techniques. This article designed the ratios of corn cob sprayed cementitious materials and analyzed the changes in the properties of the materials obtained by adding 0–25% of corn cobs. The results of the study showed that the addition of different proportions of corn cobs improved the thermal insulation properties of the material by 6.9%-75.5% as compared to the ordinary mortar material. The mechanical properties became 25.9%-113.6% of the original. When the corn cob is wetted for more than 10 min, the fluidity of the material is sufficient to reach the minimum standard for spraying operations. Considering the comprehensive performance of the material, it is concluded that the wetting time of 30 min, the addition of corn cob 20%, the corn cob particle size of 200 mesh, and the amount of sand doping of 40% are the optimal ratios of the studied corn cob spraying cementitious materials. The study of corn cob lightweight thermal insulation spray cementitious material is of great significance for controlling the ambient temperature in deep underground space, promoting cleaner production and improving the use of environmental resources.

Characterization and performance evaluation of lightweight thermal insulation recycled concrete

To enhance forestry solid waste reuse, reduce building energy consumption, and increase building capacity, producing lightweight concrete with new materials has garnered recent attention. This study used waste wood and expanded perlite (EP) to design lightweight thermal insulation recycled concrete (LTIRC) with varying volume admixtures. Compared to mineral aggregate, wood aggregate (WA) and EP exhibit significant differences in water absorption, particle morphology, density, and crushing index. This study aimed to prepare LTIRC using two lightweight aggregates (WA & EP) and evaluate their dry density, mechanical properties, thermal properties, chloride ion permeability, and frost resistance. The results showed WA and EP introduction effectively reduced concrete bulk weight and met the dry density standard for lightweight concrete. In terms of thermal insulation performance, both WA and EP are characterized by porous, low–density, and low thermal conductivity. Consequently, LTIRC thermal conductivity was reduced by up to 76.5% versus conventional concrete, effectively increasing resistance to heat flow through concrete and providing potential for building energy savings. Additionally, WA and EP addition caused LTIRC to experience mechanical and durability property deterioration. However, some LTIRC achieved over 80% of the strength of natural aggregate concrete. Moreover, WA addition inhibited internal crack generation in LTIRC and slowed concrete damage from increased WA and EP dosage. The maximum mass loss of LTIPC was 2.72% after 100 freeze–thaw cycles. LTIPC precast panels are suitable for preparing low-carbon insulated building wall panels.

Scleroglucan-Based Foam Incorporating Recycled Rigid Polyurethane Waste for Novel Insulation Material Production.

This study details the synthesis and performance evaluation of a novel lightweight thermal and acoustic insulation material, resulting from the combination of a scleroglucan-based hydrogel and recycled rigid polyurethane waste powder. Through a sublimation-driven water-removal process, a porous three-dimensional network structure is formed, showcasing notable thermal and acoustic insulation properties. Experimental data are presented to highlight the material's performance, including comparisons with commercially available mineral wool and polymeric foams. This material versatility is demonstrated through tunable mechanical, thermal and acoustic characteristics, achieved by strategically adjusting the concentration of the biopolymer and additives. This adaptability positions the material as a promising candidate for different insulation applications. Addressing environmental concerns related to rigid polyurethane waste disposal, the study contributes to the circular economy.

Lightweight, hydrostatic pressure‐resistance, thermal insulating epoxy syntactic foam with a multiscale ternary structure for marine engineering application

AbstractThe study of lightweight epoxy syntactic foams is of great significance for the exploitation of marine resources. In this work, glass fibers reinforced epoxy hollow spheres (GFs‐EHS) were first prepared using a template method, and a lightweight three‐phase epoxy syntactic foam (LWTP‐ESF) with a multiscale ternary structure was prepared using a molding pressing method with epoxy resin as matrix, hollow glass microspheres (HGMs), and GF‐EHS as the lightweight fillers. The effect of HGMs content on the density, uniaxial compression properties, water absorption, and thermal conductivity of obtained LWTP‐ESF was evaluated. The results indicated that the density, uniaxial compression strength, and thermal conductivity of LWTP‐ESF were consistently decreased, while the water absorption was increased with the increase in HGMs content. The highest specific compression strength and lowest thermal conductivity of LWTP‐ESF could reach 52.77 ± 0.82 MPa·cm3/g and 0.113 ± 0.005 W/(m·K), respectively. Moreover, the effect of hydrostatic pressure on the water absorption and thermal conductivity of LWTP‐ESF were also systematically analyzed. This study provides a novel system and method to prepare lightweight epoxy syntactic foams, and the prepared composites have potential applications in the field of lightweight thermal insulation materials for marine.Highlights The composites with a multiscale ternary structure were designed. The composites possessed significantly lower density and thermal conductivity. The water absorption of composites under hydrostatic pressure was evaluated. The thermal conductivity of composites under hydrostatic pressure was evaluated. The water absorption mechanism and thermal insulation mechanism were proposed.

Effect of mPCMs on the properties of whisker-reinforced PG-based composites

Phase-change energy-storage building materials prepared by applying phase-change materials (PCMs) to building materials have the advantages of both common building materials and PCMs. The composites can help regulate the indoor temperature, while the introduction of phase-change microcapsule (mPCM) technology can make up for the shortcomings of traditional PCMs. Therefore, in this study, two different mPCMs were blended into whisker-reinforced β-hemihydrate phosphogypsum (β-HPG)-based composites to prepare a new lightweight thermal insulation and energy-storage building material, which improves the thermal performance of the building material while improving the utilization rate of phosphogypsum to a certain extent. In this study, the mechanical, thermal conductivity and energy-storage properties of the new building material were investigated through performance tests and compared with those of β-HPG-based composites without doped PCMs, The results showed that both PCMs could improve the mechanical strength of the materials. The incorporation of mPCMs increased the thermal conductivity and decreased the water absorption of the composites. In addition, the thermogravimetric–differential scanning calorimetry analysis showed that the addition of mPCMs improved the thermal storage properties of the composites, and the two mPCMs and their composites have good thermal stability and can be used in construction materials.

Ambient pressure dried polydicyclopentadiene based aerogels for low-cost lightweight thermal insulation materials

Ambient pressure dried polydicyclopentadiene based aerogels for low-cost lightweight thermal insulation materials

Foam concrete nanocomposites synergistic integration of ultrasonically exfoliated two-dimensional vermiculite nanoplatelets and expanded vermiculite: Mechanical and thermal performance optimisation

This study developed a novel two-dimensional nanoplatelet filler (thickness ≪ diameter in morphology), which significantly improved the mechanical performance of foam concrete. Expanded vermiculite (EV), characterized as a lightweight thermal insulator with porous three-dimensional multilayers microstructure, was exfoliated into two-dimensional vermiculite-based nanoplatelets (NV) filler. A scalable ultrasonic exfoliation methodology was proposed for the preparation of the NV filler by adopting ultrasound as the delamination force and water as the liquid phase. NV filler for the first time was introduced into foam concrete as nano-reinforcement. In this study, the ultrasonication times of 15 min, 30 min, 60 min, and 90 min were studied to determine the optimal delamination effectiveness. The scanning electron images and transmission electron microscopy identified that 60 min sonication effectively produced well-delaminated NV with a smooth surface and reduced wrinkling. The compressive strength, thermal conductivity, infra thermal observation, porosity, and microstructural morphology were systematically investigated on the nanocomposites containing different fractions of NV filler (0.5 % and 1 % under 15min–90min sonication, respectively), EV (10%–20 %) and various NV/EV combined proportions. The nanocomposite containing 1 %/90min of NV fillers exhibited the most significant enhancement in compressive strength by 27.6 %, corresponding to the improved microstructure and porosity. Of all co-existence NV/EV-derived nanocomposites, the sample containing 1 %/60min NV and 50 % EV suggested the lowest thermal conductivity of 0.304 W/(m K).

Fabrication, characterization, and application of light weight thermal insulation material from combined buffing dust and plaster of paris for construction industry

Buffing dust, generated from tannery industries, is a source of air pollution in Pakistan. Valorization of the waste into another useful material is important to deal with the environmental pollution, while reducing waste disposal costs in landfills. To demonstrate its technological strength, this work fabricates a thermal insulation material made of plaster of Paris and the buffing dust (from tanning waste) in the form of a composite with superior mechanical properties and low thermal conductivity. Buffing dust with concentrations ranging from 5 to 20% (w/w) were loaded in the composite. The samples synthesized were made slurry of plaster of Paris, buffing dust, and water at ambient temperature. The physico-mechanical properties of composite were analyzed. It was found that the composite had better thermal insulation properties than the panels of the plaster of Paris. Its thermal conductivity was reduced to 15% after adding buffing dust (20% w/w). All the materials had physico-chemical properties like tensile strength (0.02 MPa and 0.06 MPa), density (700-400 kg/m3), water absorption (5.2–8.6%) and thermal conductivity (0.17000–0.09218 W/m-K). Thermogravimetric analysis showed that the material was thermally stable at temperatures ranging from 145 to 177 °C, while FT-IR results revealed that the composite contained O–H, N–H, and CO functional groups. SEM analysis displayed that the composite's homogeneity was reduced with low voids due to buffing dust addition, while EDX analysis showed that the composite contained 23.62% of S, 26.76% of Ca, 49.2% of O and 0.42% of C. This implies that buffing dust could be recycled to manufacture heat insulation materials for construction sector to reduce air pollution, while minimizing energy consumption. By integrating the buffing dust from tanning waste and the plaster of Paris as a composite for construction sector, this work promotes the recycling of unused waste, while saving public funds. Instead of paying landfill fees and polluting soil, the waste may be recycled at lower cost, while reducing environmental damage.

Retracted: Application of Lightweight Thermal Insulation Building Materials for Green Building Design

Retracted: Application of Lightweight Thermal Insulation Building Materials for Green Building Design

Thermal properties of mullite based porous ceramics derived from high silica tailings obtained after extracting alumina from high alumina coal ash

In this study, to solve the problem of reducing the quantity and increasing the utilization of waste as resource for high silica tailings (HSTs) after extracting alumina from high alumina coal ash, lightweight thermal insulation materials for building were prepared by using the melt foaming method. The effects of the calcination temperature and holding time on the melting characteristics of ingredients with different melt indexes were investigated. The effects of the amount of foaming agent on the bulk density, total porosity, and thermal conductivity of porous ceramics were determined, and the thermal conductivity model structure was further elucidated by comparing the experimental data with the values predicted by a theoretical model. The results showed that porous ceramics with optimal performance were prepared by calcination at 1200 °C for 30–60 min with a melt index of 8 k, and the amount of added SiC foaming agent was 0.52 wt%. The bulk density, total porosity and thermal conductivity were determined for the prepared porous ceramics as 0.196 g cm−3, 93.8%, and 0.086 W m−1 K−1, respectively, where the added amount of HSTs reached 60 wt%. Comparison and verification of the thermal conductivity model confirmed that the prepared mullite based porous ceramics should be classified as materials with internal porosity, where the pores were dispersed in the mullite continuous phase to form isolated closed pores. The results obtained in this study are of economic significance for the reuse of HSTs at large dosages and with high added value.

Innovative Thermal and Acoustic Insulation Foams from Recycled Fiberglass Waste

AbstractThis study examines a lightweight thermal and acoustic insulation material, produced starting from a hydrogel‐based mixture composed by renewable biopolymer and fiberglass waste powders. The gel 3D porous network is preserved after water removal by sublimation, resulting in a lightweight thermal and acoustic insulation material with good overall performance. Mechanical, thermal, and acoustic properties can be tuned as a function of biopolymer and additives concentration. This material addresses environmental concerns both in terms of secondary raw sources use and fiberglass waste disposal. Moreover, contrary to mineral wools currently on the market, it can overcome the problem of fiber release, with significant human health benefits. Thanks to its good properties and its fabrication process based on a circular economy approach, it can be appealing for thermal and acoustic insulating applications in building and industrial sectors and also in terms of environmental footprint.

Thermal insulation properties of lightweight, self-healing, and mesoporous carrageenan/PMMA cryogels.

The development of new bio-based cryogel materials with low environmental impact and various properties such as self-healing, flame-retardancy, low thermal conductivity has emerged as a cutting-edge research topic in special-purpose materials and a significant challenge. Herein, we report a simple processing methodology for preparing new mesoporous light weight thermal insulation biomass hybrid cryogels based on natural and biocompatible polymers, including marine glycosaminoglycan carrageenan moss (CM) and polymethyl methacrylate (PMMA) abbreviated as CM/PMMA under cryo conditions. The mechanical, thermal, and physicochemical characterization of the obtained hybrid cryogel was studied. The effect of increasing thickness on thermal conductivity and compressive strength was investigated. The results show that the thermal conductivity increases from 0.068 W m-1 K-1 to 0.124 W m-1 K-1 with increasing thickness. Also, the compressive strength changed from 89.5% MPa to 95.4% MPa. The results revealed that cryogel has a wrinkled surface and interconnected pores and exhibits high flexibility, self-healing ability, flame retardancy, and low thermal conductivity.

Experimental and numerical study of prefabricated steel frame with integrated wall panels

The suitability of external integrated lightweight thermal insulation decorative wall panels as a fully bolted prefabricated steel frame enclosure system was studied. The test on the fully bolted prefabricated steel frame with the external integrated lightweight thermal insulation decorative wall panels was completed under quasi-static cyclic loading, and the impact of the beam-column joint types were investigated. The failure mode, lateral stiffness, bearing capacity, energy dissipation capacity, ductility, and strain distribution were analyzed, and the internal forces of the steel frame were calculated. Experimental results show that the external integrated wall has minimal effect on the stiffness and bearing capacity of the fully bolted prefabricated steel frame. Furthermore, the L-shaped angle joints can increase the bearing capacity, energy dissipation capacity, and lateral stiffness evidently and move the joint plastic hinge outwards. The differences between the experimental bearing capacity and the theoretical value of the steel frame were minimal. Significant buckling deformation was observed at the beam-end, and progressive full-field strain at the plastic hinge were distributed in a band shape. The corresponding improved design was proposed. In addition, the failure mode and hysteretic behavior of the structures were studied by finite element analysis, and the influence of the main parameters, such as the number of horizontal and vertical plate bolts, the types of L-shaped angle stiffeners, and the height-span ratio and axial compression ratio of steel frame were discussed. The finite element analysis results were consistent with those of the test. It provided theoretical evidence for the design and application of fully bolted prefabricated steel frame with external integrated lightweight wall panels.

Application of Lightweight Thermal Insulation Building Materials for Green Building Design

In order to focus on the application of green environmental protection lightweight thermal insulation materials, an in-depth study is carried out on the basis of joint architectural design. The application of green environmental protection materials in the construction industry was successfully analyzed through methods such as layout design method, optimization design method, and scientific optimization of material selection. In the process of urbanization development in our country, the number of urban population has increased sharply, and the demand for buildings has also increased. Therefore, it is necessary to rapidly promote green building design while the construction industry is developing rapidly and complete the upgrading and transformation of the building in terms of form design. We pay attention to the needs of buildings in terms of shading and lighting, and improve the conditions of building shading and lighting through green building technology. As a result, on the basis of maintaining the residual heat of the building, the diffuse radiation of the ultraviolet rays of the sun is realized, which effectively improves the utilization efficiency of natural energy and reduces the consumption of internal energy. Architectural design under the concept of green building design not only can it meet the current functional requirements of people for architecture but also imperceptibly promote the stable development of our country’s construction industry. After the research on the application of green environmental protection materials, the integration and application of green building design concepts in architectural design is of great significance not only to meet people's health and ecological needs of buildings but also to promote social stability and sustainable development.

The Aramid-Coating-on-Aramid Strategy toward Strong, Tough, and Foldable Polymer Aerogel Films.

Aerogel has been much highlighted as an emerging lightweight thermal insulation material, but problems such as fragility, low strength, liquid permeability, and lack of flexibility greatly limit further applications. In this work, a facile aramid-coating-on-aramid (ACoA) method is demonstrated to fabricate all-aramid aerogel composite films for thermal insulation. The method started from the bottom-up synthesis of polymerization-induced para-aramid nanofibers (PANF), which were easily transformed into aerogel films through the vacuum-assisted filtration followed by the freeze-drying techniques. Then, the heterocyclic aramid (HA) solution prepared through the low-temperature-solution polycondensation was used as the coating to be applied onto the PANF aerogel films, and composite films of HA/PANF aerogel were simply achieved with HA contributed to the dense and continuous surface layer. The bulk HA film is of superior mechanical and thermal properties to those of the PANF film. Moreover, reliable interfacial interlocking structures were developed beneath the outermost surface via the interpenetration of the infiltrated HA with PANF network. The comprehensive result was the 15 times enhanced tensile strength, 33 times enhanced fracture toughness, the high thermal decomposition temperature, and the additional flexibility for the foldable films of HA/PANF aerogel. The sealing of the surface macropores greatly suppressed the surface chalking and high water absorption. However, the survival of the tiny pores inside the composite maintained the low enough level of the thermal conductivity to provide effective protections against high temperature not only in air but also under wet or even liquid conditions, suggesting the broader applications for thermal insulation.

Printing Liquid Metal Elastomer Composites for High‐Performance Stretchable Thermoelectric Generators

AbstractContinuous powering of wearable electronics and personalized biomonitoring systems remains a great challenge. One promising solution is the use of thermoelectric generators (TEGs) that convert body heat to electricity. These energy harvesters must conform to curved surfaces and minimize thermal barriers to maintain efficiency while still exhibiting durability under large deformations. Here, highly efficient, stretchable thermoelectric generators made of inorganic semiconductors and printed multifunctional soft matter are introduced. Liquid metal elastomer composites with tailored microstructures are printed as highly conductive thermal interface materials and stretchable interconnects. Additionally, elastomer composites with hollow microspheres are formulated to print a deformable and lightweight thermal insulator within the device. These stretchable thermoelectric wearables show an excellent performance by generating an open‐circuit voltage of 392 mV and a power density of ≈650 µW cm−2 at ∆T = 60 °C and withstanding more than 15 000 stretching cycles at 30% strain. Furthermore, the additive manufacturing process is leveraged by direct writing of the TEGs on textiles to demonstrate their seamless integration and by 3D printing of stretchable heatsinks to maintain a large temperature gradient across the device and to study the effect of convective heat transfer on device performance.

Recycling of sewage sludge in clay-free thermal insulation brick: assessment of microstructure, performance, and environment impact.

Recycling municipal sewage sludge in fired bricks not only contributes to environmental protection, but is also an alternative to natural clay resource. The complex compositions of sludge have a great influence on the brick property. This work presents a systematical investigation on fired bricks made only with sludge and shale. The physicochemical properties of the raw mixtures, macroscopic performance, microstructure, and its evolution were quantitatively determined. The coordination between shale and sludge enables the blend of raw materials to achieve the desired gradation and plasticity. Although a reduction in compressive strength was observed, the open porosity was increased to 31.6% and thermal conductivity was reduced to 0.51W·(m·K)-1, indicating the benefit to the performance of lightweight thermal insulation bricks. The fitting results confirm the pore-forming effect induced by the organic matter in the sludge. The obtained bricks possess good performance, especially in thermal insulation properties, and environmental and economic benefits.

Preparation and properties of foamed cement for lightweight thermal insulation with Ti-extraction blast furnace slag and sulfoaluminate cement by chemical foaming

Ti-extraction blast furnace slag (TEBFS) is a chlorine-containing solid waste produced by the metallurgical industry in China. The accumulation of TEBFS is harmful to the environment and the sustainable development of industry. Herein, foamed cement was prepared as a load-bearing and insulation material using TEBFS and sulfoaluminate cement (SAC) by chemical foaming. The effects of TEBFS content, H2O2 content, and calcium stearate content on the properties, pore structure, and microstructure of the samples were explored. The results show that a stable foam system was obtained by mixing 20–40% TEBFS with SAC, and the most influential factor on the material properties of the samples was H2O2 content. The relationship between the average pore size and bulk density was y = 0.6219x − 0.7194 (R2 = 0.99). Based on an orthogonal experiment, the most influential factors for determining the bulk density, compressive strength, and thermal conductivity of the samples were the H2O2 content and the TEBFS content. The optimal foamed cement was produced with 40% TEBFS, 1% H2O2, and 1.0% calcium stearate. The water-cement ratio was 0.5. The bulk density, 28-day compressive strength, and thermal conductivity of this sample were 0.68 g/cm3, 1.86 MPa, and 0.17 W/(m·K), respectively. Morphological analysis demonstrated that the complete pore structure was helpful for improving the compressive strength of the foamed cement material. XRD showed that the main phases generated in this sample were ettringite, calcium silicate hydrate (C-S-H), and Friedel salt.

Carbothermal reduction synthesis of high porosity and low thermal conductivity ZrC-SiC ceramics via an one-step sintering technique

In this work, porous ZrC-SiC ceramics with high porosity and low thermal conductivity were successfully prepared using zircon (ZrSiO4) and carbon black as material precursors via a facile one-step sintering approach combining in-situ carbothermal reduction reaction (at 1600 °C for 2 h) and partial hot-pressing sintering technique (at 1900 °C for 1 h). Carbon black not only served as a reducing agent, but also performed as a pore-foaming agent for synthesizing porous ZrC-SiC ceramics. The prepared porous ZrC-SiC ceramics with homogeneous microstructure (with grain size in the 50–1000 nm range and pore size in the 0.2–4 µm range) possessed high porosity of 61.37–70.78%, relatively high compressive strength of 1.31–7.48 MPa, and low room temperature thermal conductivity of 1.48–4.90 W·m−1K−1. The fabricated porous ZrC-SiC ceramics with higher strength and lower thermal conductivity can be used as a promising light-weight thermal insulation material.

Carbon-bonded carbon fiber composites reinforced with SiOC-based polymer derived ceramics: Microstructure and properties

Carbon-bonded carbon fiber (CBCF) composites have been used extensively for lightweight thermal insulation applications. In this work, CBCF composites reinforced with SiOC, B-modified SiOC (SiBOC) or Zr-modified SiOC (SiZrOC) ceramics were investigated. The chemical modification of SiOC precursor has significant effects on the microstructure as well as the mechanical and thermal properties of the composites. The SiBOC and SiZrOC precursor exhibit higher impregnation efficiency than the SiOC precursor. The SiBOC/CBCF composites have the highest compressive strength and best oxidation resistance, which is attributed to its preferable microstructure, where the SiBOC ceramics wrap on the fibers and provide effective protection for carbon fibers from oxygen diffusion. The strength and modulus of SiBOC/CBCF composites along z direction is 4.5 and 148 MPa, respectively. The thermal conductivity and expansion coefficient of SiBOC/CBCF composites along z direction is 0.3 W/m⋅k and 1.75 × 10−6 K−1, respectively.