High-performance Thermal Insulation Materials Research Articles

High-Performance Thermal Insulation Material Based on Waste Glass

The article is devoted to the development technology of obtaining and properties of heat-insulating environmentally safe material production from waste glass. The subject of the study is a finely fraction of a mixture of window and container glass. Differential scanning calorimetry was used, the study of the gas release process was carried out on a specially designed and manufactured installation. Developed a foaming composition consisting of calcium carbonate and sodium nitrate, which allows you to combine the decomposition temperature of the main gas-forming agent (calcium carbonate) and the softening temperature of the glass, which is a necessary condition for obtaining a foam material with a minimum apparent density. The optimal mass ratio of sodium nitrate and calcium carbonate (100:35), the foaming temperature (700 ° C) and particle sizes (less than 60 microns) were determined, allowing to obtain a material with a density of 80-100 kg/m3. The dependence of the apparent density of the obtained material on the time of foaming and the content of the gas-forming agent is obtained by mathematical modeling, which allows determining the optimal time of foaming at different temperatures. During the development of the technology, factors affecting the properties of the resulting foam material were identified, and the dependence of the main technological parameters on these factors was established. For the production of thermal insulation material, a continuous powder method is proposed, including the processes of preparing a foaming composition and producing foam blocks. The developed material has a lower coefficient of thermal conductivity, higher strength and low density compared to existing analogues and does not emit hydrogen sulfide during operation. According to the developed technology, a pilot batch of foam glass was produced, which was used by a number of construction companies in various areas of construction.

Biomimetic structural cellulose nanofiber aerogels with exceptional mechanical, flame-retardant and thermal-insulating properties

With the rapid increase of energy consumption, thermal-insulating materials made from abundant renewable resources are in urgent need for energy-efficient buildings, which satisfies the sustainable development of society. Cellulose nanofiber aerogels exhibit a promising prospect in thermal-insulating application, whereas still confront the inherent weakness of high flammability as well as the improvement of mechanical stiffness and thermal insulation. In the present study, inserting the growth of two-dimensional zirconium phosphate within multilayer graphene results in the formation of hierarchical graphene-confined zirconium phosphate (ZrP/RGO) nanosheets through a spatial confinement strategy. Inspired by the porous lamella-bridge architecture of Thalia dealbata stem, a unidirectional freeze-casing technique is utilized to assemble the building blocks of cellulose nanofiber and ZrP/RGO nanosheet into a biomimetic-structural aerogel which has excellent thermal-insulating, mechanical and flame-retardant properties. Compared with state-of-the-art cellulose nanofiber-based aerogels, the resulting composite aerogel perpendicular to lamellar alignments shows an ultralow thermal conductivity (18 mW·m−1·K−1), the maximal specific Young’s modulus (104 kN·m·kg−1) and high limited oxygen index (33.5) as well as very low peak heat release rate (14.1 kW/m2). Nature provides renewable resources and structural inspirations to achieve high-performance thermal insulation materials through nanoscale engineering.

Flexible and thermal-stable SiZrOC nanofiber membranes with low thermal conductivity at high-temperature

Ceramic nanofibers with excellent thermal stability and low thermal conductivity are highly desired for high-temperature thermal insulation applications. However, the incompatibility of thermal stability and low thermal conductivity at high-temperatures largely limit the practical use of conventional single-phase ceramic nanofibers. Here, we report the preparation of multi-phase SiZrOC nanofiber membranes (NFMs) composed of amorphous SiOC and ZrO2 nanocrystals via electrospinning technique. The fabricated SiZrOC NFMs exhibited excellent high-temperature stability (∼1200 °C in Ar) and low thermal conductivity (∼0.1392 W m−1 K−1 at 1000 °C in N2). The decreased thermal conductivity is achieved through a synergistic mechanism, that the multi-phase interfaces and the ZrO2 nanocrystals create thermal transfer barriers to reduce the heat transfer, whilst the SiOC phase effectively suppresses radiative heat transfer. This unique combination of amorphous SiOC and ZrO2 nanocrystals provides a novel strategy to prepare high-performance thermal insulation materials, and the obtained SiZrOC NFMs are promising high-temperature thermal insulation materials.

Humidity control effect of vapor-permeable walls employing hygroscopic insulation material.

Airtight construction and high-performance thermal insulation materials are commonly considered important building features to enhance indoor thermal comfort while reducing thermal load. However, when water vapor is generated in such airtight indoor spaces, it cannot be discharged to the outside, causing interstitial condensation and subsequent intrusion of moisture into the walls. Hygroscopic building materials such as cellulose fiber insulation (CFI), characterized by high water capacity, are a potential countermeasure against such condensation. In this study, the humidity control performance of external walls containing CFI was evaluated using data measured inside a demonstration house and calculated by numerical simulations based on thermodynamic chemical potential theory. The changes in moisture adsorption and desorption were then evaluated for different wall constructions and different climate conditions using a parameter sensitivity analysis. Finally, the effective application of CFI to prevent interstitial condensation was confirmed by comparing different wall compositions.

Aerogel materials for heritage buildings: Materials, properties and case studies

Abstract Aerogels are open-porous, high-performance thermal insulation materials that can be used for very thin building insulation. So far, the application conditions of these materials and their potential in heritage buildings have not yet been described comprehensively. This review shows the technical properties of commercially available aerogel materials – such as blankets, boards and renders – and their use scenarios in heritage buildings, taking into account the heritage criteria of authenticity, integrity, reversibility and compatibility. Additionally, historic buildings that were refurbished using aerogels are presented. The study by theoretical evaluations and calculated U-values indicates that superinsulating aerogel materials have an exceptional potential in the refurbishment of heritage buildings. The presented examples show the feasibility of refurbishments with aerogel and the resulting improvements in terms of both comfort and thermal properties. Hence, aerogel materials are well suited to be used in preservation of heritage objects according to generally known rules and conditions of heritage preservation, thus contributing to the reduction of energy consumption in the building sector.

Aerogel Based High Performance Thermal Insulation Materials

In this paper, the thermal properties of polyester/polyethylene nonwoven thermal wraps of varying thicknesses treated with aerogel were analyzed and compared. The microscopic images were taken by confocal microscope and image analysis to compare the physical structure of the aerogel treated nonwoven fabrics. Thermal conductivity and thermal resistance were measured using FOX heat flow meter instrument. The water vapor resistance and thermal resistance were measured using sweating guarded hot plate (SGHP). These tests were conducted to understand and to compare the thermal properties and water vapor resistance of aerogel treated nonwoven fabrics. The results of the experiments were statistically analyzed and showed that the fabric density and the aerogel present in the fabric have a significant effect on thermal properties and water vapor resistance of the aerogel treated nonwoven fabrics.

Nano insulation materials exploiting the Knudsen effect

As the world’s focus is turned even stronger toward miscellaneous energy efficiency and saving aspects, the development of new high-performance thermal insulation materials for building applications will play an important role in this regard. The aim of the presented study is to develop an understanding for the governing thermal transport mechanisms and utilize the Knudsen effect in nanoporous insulation materials through theoretical concepts and experimental laboratory explorations, thus being able to synthesize nano insulation materials (NIM) with very low thermal conductivity values as a major goal. NIMs based on hollow silica nanospheres (HSNS) have been synthesized by a sacrificial template method, where the idea is that the heat transport by gas conductance and gas/solid state interactions decreases with decreasing pore diameters in the nano range as predicted by the Knudsen effect. HSNS with reduced thermal conductivity compared to their solid counterparts have been prepared where the hollow sphere cavities and voids between the spheres are filled with air at atmospheric pressure, i.e. eliminating the need for various measures like e.g. protective metallized foils to maintain a vacuum or expensive low-conducting gases in the cavities and voids. Hence, HSNS represent a promising stepping-stone toward the future high-performance thermal insulation materials.

Synthesis of white cement bonded porous fumed silica-based composite for thermal insulation with low thermal conductivity via a facile cast-in-place approach

Abstract High performance thermal insulation material was prepared by fumed silica as thermal insulation matrix, white cement as binder. SiC powder was incorporated as an opacifier. Short glass fibers were added to increase stiffness and minimize contraction. The samples were produced within 4 days under ambient pressure with no complicated equipment. The influences caused by white cement amount on the properties were investigated to achieve the optimal performance. A low thermal conductivity 0.033 W·m−1·K−1 at 25 °C and a low thermal conductivity 0.038 W·m−1·K−1 at 800 °C were achieved based on the experimental results. The linear shrinkage of the insulation up to 800 °C in air for 30 min was 7.54%. In addition, the insulation exhibited a compression stress above 0.15 MPa (3% strain). The relation between structure and performances was revealed. That we here publicly reported thermal insulation materials synthetized by nano-powder and inorganic binder might reveal a new method for synthesis high performance thermal insulation materials. Based on the simplicity of the manufacturing process, the optimized material properties and cheap cost of raw materials, we believe this technology can act as an effective thermal insulation material for buildings and myriad applications requiring improved thermal efficiency.

A generalized thermal conductivity model for nanoparticle packed bed considering particle deformation

Theoretically understanding the thermal conductivity of the nanoparticle packed beds (NPBs) is critical for designing high-performance thermal insulation materials. Currently, the classical effective medium assumption (EMA) model, Nan model, just show their good prediction at a high porosity of NPBs (≥0.75). Herein, we propose a generalized model of the thermal conductivity that almost covers the whole porosity range by considering the effect of the nanoparticle deformations on the thermal contact resistance (R). It has been demonstrated that our model matches the experimental results great well. It is also found that at high porosity R is dominated by the phonon diffusive scatterings (Rcd), while it is determined by the phonon ballistic scatterings (Rcb) at a low porosity. More interestingly, R can determine the porosity at which the lowest thermal conductivity of NPBs appears. This work opens a new way to design the desired thermal insulation materials.

Correlation between the Thermo-physical Properties and Core Material Structure of Vacuum Insulation Panel: Role of Fiber Types

Vacuum insulation panel (VIP), which is composed of an evacuated core material encapsulated in an envelope and supplemented with a desiccant, is a high performance thermal insulation material. In this paper, thermos-physical properties of chopped fiber, centrifugal-spinneret-blow (CSB) fiber, flame-spinneret-blow (FSB) fiber and hybrid (CSB: FSB=1:1) fiber as fillers of vacuum insulation panel are explored. The results show that the increase of pore size can improve thermal insulation property; fibers distribute in 2-D structure, which can reduce the heat conduction, leads to reduce the thermal conductivity. VIP with chopped fiber has the best thermal insulation, and thermal conductivity is 1.4 mW/m.K. Due to difference of core materials, thermal insulation characteristics of VIP can be divided into three distinct regions based on the internal pressure range, i.e., (I) ≥12000 Pa region, (II) 80-12000 Pa region, (III) ≤ 80 Pa region. It also finds that service life of VIP can be improved by the reducing the pore size of core materials. VIP with different core materials shows different degradation and the degradation rate of VIP with FSB core material is minimum.

Air-Filled Nanopore Based High-Performance Thermal Insulation Materials

State-of-the-art thermal insulation solutions like vacuum insulation panels (VIP) and aerogels have low thermal conductivity, but their drawbacks may make them unable to be the thermal insulation solutions that will revolutionize the building industry regarding energy-efficient building envelopes. Nevertheless, learning from these materials may be crucial to make new and novel high-performance thermal insulation products. This study presents a review on the state-of-the-art air-filled thermal insulation materials for building purposes, with respect to both commercial and novel laboratory developments. VIP, even if today’s solutions require a core with vacuum in the pores, are also treated briefly, as they bear the promise of developing high-performance thermal insulation materials without the need of vacuum. In addition, possible pathways for taking the step from today´s solutions to new ones for the future using existing knowledge and research are discussed. A special focus is made on the possible utilization of the Knudsen effect in air-filled nanopore thermal insulation materials.

Synthesis of Silica-Based Nano Insulation Materials for Potential Application in Low-Energy or Zero Emission Buildings

Sacrificial polystyrene (PS) templates have been used for synthesis of silica-based nano insulation materials (NIM). The PS was synthesized by a simple procedure where parameters as polyvinylpyrrolidone/styrene ratio and potassium persulfate amount were adjusted. Thereafter the PS templates were coated with silica by using tetraethyl orthosilicate (TEOS). The time used for adding TEOS was varied to investigate the effect on how the silica particles attached to the PS surface and the resulting silica spheres. By modifying the process, different PS templates were obtained. The thermal conductivity was measured for hollow silica spheres originating from the coating process of 198 nm PS templates, and the results showed thermal conductivities around 38 mW/(mK) for long-time measurements (160-640 s). Controlled synthesis of this silica-based NIM might be a stepping-stone on the path to a new generation of high-performance thermal insulation materials with low thermal conductivity, which can be used in the building envelope of low-energy or zero emission buildings in the future.

Comparative Analysis of High Performance Thermal Insulation Materials

Comparative Analysis of High Performance Thermal Insulation Materials

Thermal performance evaluation and comfort assessment of advanced aerogel as blown-in insulation for historic buildings

Research and development of cost-effective, high-performance thermal insulation materials for the construction sector has to be focused on their final application. In particular, solutions for refurbishing historic buildings, which represent 40% of the European building stock, have to offer a good compromise between environmental quality, energy efficiency and conservation aspects. In this paper, the experimental assessment of an insulation material based on aerogel technology, recently developed in the European project EFFESUS, is presented with regard to the material's thermal performance, compatibility with historic fabric and reversibility. The overall results obtained in laboratory testing on a real-size mock-up and in a real-world case application indicate that the new material is a promising solution for retrofitting historic buildings, thanks to its thermal properties, easy application, reversibility and material compatibility.

Improvement of thermal insulation performance of silica aerogels by Al2O3 powders doping

Abstract Silica aerogel is deemed as a kind of high-performance thermal insulation materials. However, the existence of macropores in the structure is always ignored in the research and application of aerogels. Thus the thermal insulation performance of silica aerogels could be further improved if the macropores are reduced. In this work, nano-sized Al2O3 powders are explored as nano fillers to reduce the macropore volume fraction in silica aerogels by filling the big voids among the silica aggregates, and further lower the thermal conductivity. The experimental results showed that the macropore volume fraction ( V MAC ) was dramatically reduced from 63.05% to 23.12% with the addition of Al2O3 powders ranging from 0.0 g to 1.0 g. This trend was also verified by the variation of (VT*-VBET) and (VBET/VT*). Accordingly, the thermal insulation performance was improved due to the reduction of macropores in aerogels. The lowest thermal conductivity of Al2O3-doped aerogels reached 7.41 mW/(m K) in contrast with that of pure silica aerogels (9.00 mW/(m K)), which was a significant decline for aerogel-based materials due to the gaseous heat transfer being further weakened. Moreover, the increment of thermal conductivity from 7.41 to 9.71 mW/(m K) with the Al2O3 powders increasing could be attributed to the enhancement of solid heat transfer in the system. The variation of experimental thermal conductivity was in good agreement with the result of theoretical calculation. This study proposed an innovative idea to improve the thermal insulation of aerogel under ambient conditions.

Temperature-induced microstructural changes of fiber-reinforced silica aerogel (FRAB) and rock wool thermal insulation materials: A comparative study

The strive for improved energy efficiency in the building sector has motivated extended research on high-performance thermal insulation materials, leading to new products available on the market. Fiber-reinforced aerogel is a state-of-the-art material suitable as a substitute for traditional ones such as rock wool, especially for retrofitting and refurbishment of historic buildings where interior insulation may be the only alternative. In view of fire safety, commercial products are already tested and classified according to European standards. However, these tests do not give information on microstructural changes which is important to gain full understanding of the material. Knowledge of the reaction dynamics leading to functional changes of the material is needed in order to take actions to improve product quality. Here, the thermally induced microstructure development of fiber-reinforced silica aerogel blankets and rock wool were investigated using in-situ techniques such as thermogravimetry and hot stage microscopy. In addition, X-ray powder diffraction and Scanning electron microscopy analyses were performed ex-situ on thermally treated materials. Flammability was evaluated using cone calorimetry. The results obtained for the two different materials were compared and discussed in view of relationship between microstructure development and fire performance.

Rapid thermal conductivity measurement of porous thermal insulation material by laser flash method

Measuring the thermal conductivity of a high performance thermal insulation material within a short time is challenging. In the present study, a laser flash method is adopted to measure the thermal diffusivity of porous thermal insulation material. Small sample size and short measuring time are major advantages of this method. The specific heat capacity was measured by a differential scanning calorimeter (DSC). With known density, the thermal conductivity was obtained. Applying a calibration routine, the measured thermal conductivity of the porous material is only 0.039W/(mK) at room temperature. This value is in good agreement with the data obtained using conventional method. It demonstrates that the laser flash method is a reliable technique to determine the performance of a very low thermal conductivity material.

NANO INSULATION MATERIALS FOR ENERGY EFFICIENT BUILDINGS

The advanced thermal insulation materials and solutions for improved thermal resistance have been receiving an ever increasing attention due to their significance for sustainable building. Reducing energy consumption and CO2 emissions by development and deployment of sustainable construction technologies, systems and materials in new and existing buildings will be key to addressing the challenge of a transition to nearly zero-energy buildings in Europe by 2020. Nanotechnology promises to make thermal insulation more efficient, less reliant on non-renewable resources as an important strategy on the pathway to green buildings. The application of nano insulation materials to limit the wall thickness is one of the greatest potential energy-saving characteristics for the existing buildings, as well as for the architectural heritage. This paper examines the potential advantages of using nanotechnology-based high-performance thermal insulation materials in reducing the life cycle energy, reduction of material usage and enhancing the life span of buildings.

Configured cavity-core matrix for vacuum insulation panel: Concept, preparation and thermophysical properties

Energy efficiency of buildings can be improved by implementing strategies to develop the building envelope components. Thermal insulation of buildings has become vital, to attenuate energy demands for space heating and cooling. Presently vacuum insulation panel (VIP) is regarded as a high performance thermal insulation material. VIP enables efficient insulation solutions in systems such as refrigerators, controlled thermal packages and buildings. For building applications, it is imperative to minimize material defects and to ensure thermal comfort. However, these panels typically use spacers that cause a significant thermal bridge and undesirable gas permeation through spacer hole seal area. This study introduces an unconventional VIP, labeled as cavity-core matrix VIP; solving the aforementioned technical issue related to VIP application in buildings. The cavity-core matrix VIP was composed of glass fiber core material, and laminated aluminum foil envelope material. Owing to interlocking surface topology, bond strength increased by nearly 50% magnitude; considering the limitations specified. The estimated equivalent thermal conductivity of the optimized cavity-core matrix VIP was about 4.8mW/(mK). The preparation processes, thermo-physical properties and challenges of cavity-core matrix VIP were discussed. The concept and exposition examined will enable building engineers and manufacturers to create thermally well performing and structurally adapted VIPs.

NANO INSULATION MATERIALS FOR ENERGY EFFICIENT BUILDINGS

The advanced thermal insulation materials and solutions for improved thermal resistance have been receiving an ever increasing attention due to their significance for sustainable building. Reducing energy consumption and CO2 emissions by development and deployment of sustainable construction technologies, systems and materials in new and existing buildings will be key to addressing the challenge of a transition to nearly zero-energy buildings in Europe by 2020. Nanotechnology promises to make thermal insulation more efficient, less reliant on non-renewable resources as an important strategy on the pathway to green buildings. The application of nano insulation materials to limit the wall thickness is one of the greatest potential energy-saving characteristics for the existing buildings, as well as for the architectural heritage.This paper examines the potential advantages of using nanotechnology-based high-performance thermal insulation materials in reducing the life cycle energy, reduction of material usage and enhancing the life span of buildings.