Silica Aerogel Insulation Research Articles

Research on Forging Dimension Online Measuring System Based on Vibration Point Cloud Compensation

Mechanical vibration in the high-temperature forging production line often causes large forging thermal dimensional measurement error in the detection task, so a vibration point cloud compensation method based on an acceleration sensor is proposed in this study. First, the vibration signal is obtained through the built-in acceleration sensor in the laser camera. After the acceleration of the camera vibration is detected, the displacement of the camera in three directions is solved by secondary integration. Subsequently, the coordinate value of the corresponding point is obtained by the rotation matrix transformation so as to compensate and correct the point cloud deviation caused by the camera vibration. Finally, the forging point cloud is matched using the surface matching algorithm in Halcon. An automatic forging production line for wheel hubs has been built, and the key dimensions of high-temperature forging products have been measured online using the developed method. After the forging point cloud is compensated, the average measurement error of dimensions is reduced from ±0.9 mm to ±0.1 mm, and the standard deviation is reduced from 0.52 mm to 0.056 mm. Using the vibration point cloud compensation method based on the acceleration sensor, as well as using silica aerogel insulation, vibration structural parts, heat insulation and constant temperature, a blue-violet 3D laser camera, and other measures, the dimensional detection accuracy of high-temperature forgings in the forging production line can be improved, and the instability of dimensional detection can be reduced.

A novel combustion drying technology for in-situ preparation of glass fiber composite SiO2 aerogel thin felt with excellent thermal insulation performance

Glass fiber reinforced composite aerogel felt is an important thermal insulation material, but its thermal insulation performance is often compromised due to the limitation of preparation methods. In this study, the high performance glass fiber composite silica aerogel insulation thin felt was successfully prepared by in-situ sol-gel impregnation and combustion drying process for the first time. Especially, the drying time for the whole procedure is extremely quick, only taking a few minutes. The composite felt shows the characteristics of light weight, porous, hydrophobic, and has good mechanical properties. More importantly, due to the unique composite structure of the prepared felt, it has extremely low thermal conductivity (0.016 W/(m·K)) and thermal stability. The infrared thermal imager further confirmed that glass fiber composite silica aerogel thin felt has excellent thermal insulation ability, and has promising application potential in the thermal management system of power battery. Finally, the preparation process and drying mechanism based on sol-gel impregnation combined with combustion drying technology were discussed. Compared with the common technology, the preparation method has significant advantages of high efficiency and low cost, which offer an innovative technical approach for producing composite aerogel felt.

Performance analysis of solar drying system with sunlight transparent thermally insulating aerogels

Solar drying can solve the problems of product quality caused by open sun drying and high energy consumption caused by conventional energy drying. However, due to the low solar heat collection efficiency of conventional flat-plate solar collectors, the maximum drying temperature of the existing solar drying system is typically <70 °C, making them difficult to be used in cold regions. Herein, we proposed a new solar drying system with high solar heat collection efficiency, high hot air outlet temperature, and high drying efficiency based on silica aerogels that are transparent to sunlight and have ultra-low thermal conductivity. The results show that the optimum thickness of the silica aerogel insulation layer is 10 mm. At ambient temperatures of −10 to 30 °C, the air outlet temperatures of the designed solar collector are 52–97 °C, increasing the air outlet temperature by 23 °C and 28 °C, respectively, compared to conventional solar collectors. The proposed solar drying system incorporating a 10-mm-thick silica aerogel insulation layer can meet the drying requirements of most agricultural products without an additional heat source and shorten the drying time by 58%.

Study of Energy Saving Using Silica Aerogel Insulation in a Residential Building

Energy consumption, specifically in the building sector, is expected to rise. One potential way to reduce energy consumption, or to slow this increase, is to reduce the heat loss in residential homes. Silica aerogels have grown in popularity as an insulating material due to their extremely low thermal conductivity. However, the benefits of using silica aerogels as an insulator in residential buildings have not been thoroughly studied. To understand the benefits of using silica aerogels as a thermal insulator in residential homes, experimentally validated simulations were performed. The simulations were performed on a model of a full-scale residential house using the multiphysics software ANSYS FLUENT 2019 R2. The simulations helped predict the actual saving benefits of using aerogels as an insulator. Aerogels have the potential to be used as an insulator in both the walls and windows due to its semitransparency. The results showed that the average kWh savings using one half-inch layer of wall aerogel insulation coupled with window aerogel insulation was 20.9% for the single-family house compared to traditional insulation. On average, the energy lost through the windows was 39.1% lower when using aerogel insulation compared to standard insulating materials. The energy lost through the house walls was 13.3% lower on average when using a thin layer of aerogel insulation. While a thin layer of aerogel insulation provided a benefit when used in the house walls, the potential for savings per quantity used was greater in the windows.

Acoustical and thermal properties of different insulation layers for glass fibre/epoxy composites

In the present study, novel insulation materials, such as nonwoven blankets with nanofibre webs, along with the conventional materials, such as stone wool blankets and nonwoven blankets containing silica aerogel for glass fibre fabric/epoxy composites, have been investigated experimentally. The results reveal that the nonwoven blankets containing nanofibres may replace the conventional stone wool insulation layers or nonwovens with silica aerogel insulation layer especially in the vibrational working conditions due to the brittle nature of both of these conventional materials.

The economics of thermal superinsulation in buildings

In comparison to conventional thermal insulators, superinsulation materials (SIMs), such as silica aerogel or vacuum insulation panels, provide a similar insulation performance at half to a quarter of the material thickness but this superior thermal insulation performance typically comes at a significantly higher material cost. However, under certain conditions, the use of superinsulation materials in building walls allows for the creation of additional floor space.Here, we derive a simple equation to quantify the cost to create such additional space using superinsulation materials as opposed to conventional thermal insulators. The equation has six independent variables, namely the thermal conductivity and cost of the superinsulation and conventional insulation materials, as well as two building geometry parameters. Notably, the cost to create additional floor space is independent of the heat transfer coefficient (U-value) of the wall.The real estate price distributions within major cities around the world are presented in order to compare the cost to create additional space with the potential financial benefit.The analysis of typical construction types, combined with the real estate data, shows that, from a financial perspective, the use of superinsulation such as silica aerogel or vacuum insulation panels (VIPs) is already clearly profitable in several major cities globally. Improvements of the production processes of superinsulation materials and the associated reduction in costs will be key drivers to make superinsulation materials economically feasible for many other locations in the future.

Three-Dimensional-Printed Silica Aerogels for Thermal Insulation by Directly Writing Temperature-Induced Solidifiable Inks.

Silica aerogels are attractive materials for various applications due to their exceptional performances and open porous structure. Especially in thermal management, silica aerogels with low thermal conductivity need to be processed into customized structures and shapes for accurate installation on protected parts, which plays an important role in high-efficiency insulation. However, traditional subtractive manufacturing of silica aerogels with complex geometric architectures and high-precision shapes has remained challenging since the intrinsic ceramic brittleness of silica aerogels. Comparatively, additive manufacturing (3D printing) provides an alternative route to obtain custom-designed silica aerogels. Herein, we demonstrate a thermal-solidifying 3D printing strategy to fabricate silica aerogels with complex architectures via directly writing a temperature-induced solidifiable silica ink in an ambient environment. The solidification of silica inks is facilely realized, coupling with the continuous ammonia catalysis by the thermolysis of urea. Based on our proposed thermal-solidifying 3D printing strategy, printed objects show excellent shape retention and have a capacity to subsequently undergo the processes of in situ hydrophobic modification, solvent replacement, and supercritical drying. 3D-printed silica aerogels with hydrophobic modification show a super-high water contact angle of 157°. Benefiting from the low density (0.25 g·cm-3) and mesoporous silica network, optimized 3D-printed specimens with a high specific surface area of 272 m2·g-1 possess a low thermal conductivity of 32.43 mW·m-1·K-1. These outstanding performances of 3D-printed silica aerogels are comparable to those of traditional aerogels. More importantly, the thermal-solidifying 3D printing strategy brings hope to the custom design and industrial production of silica aerogel insulation materials.

Preparation of Fiber Reinforced Silica Aerogel Block

Silica aerogels are lightweight, highly porous nanomaterial with extremely large internal surface area but fragile and brittleness. To enhance the applicability of aerogels, fiber reinforced silica aerogel insulation blocks are prepared by frothing method. Polyurethane emulsion acts as binder whereas polyethylene (PE) fiber and polyurethane (PU) fiber is used as reinforcing phase. The effect of polyethylene fiber and polyurethane fiber on the performance of composites were characterized by material's chemical microscopic morphology, compression performance, recovery performance, surface area, thermal conductivity and hydrophobicity. The research results show that the prepared PU fiber reinforced silica aerogel insulation block has excellent comprehensive performance. The water absorption rate of decreased from 19.35% (0 phr, PU fiber) to 6% (20 phr, PU fiber), and comprehensive rebound rate was increased by 97.83% at 20 phr PU fiber compared with pure insulation block (83.88%). Meanwhile, the dimensional stability of the composite aerogel block is above 96%. PU fiber reinforced silica aerogel insulation block has light weight, good hydrophobicity and good thermal and mechanical properties, so it has a wide range of application prospects in the field of insulation.

Cost-Effective Additive Manufacturing of Ambient Pressure-Dried Silica Aerogel

Abstract The conventional manufacturing processes for aerogel insulation materials mostly rely on the supercritical drying, which suffers from issues of massive energy consumption, high-cost equipment, and prolonged processing time. Considering the large market demand for the aerogel insulation material in the next decade, a cost-effective and scalable fabrication technique is highly desired. In this paper, a direct ink writing (DIW) method is used to three-dimensionally fabricate the silica aerogel insulation material, followed by room-temperature and ambient pressure drying. Compared with the supercritical drying and freeze-drying techniques, the reported method significantly reduces the fabrication time and costs. The cost-effective DIW technique offers the capability to print complex hollow internal structures, coupled with the porous aerogel structure, it is found to be beneficial for the thermal insulation property. The addition of fiber to the ink assures the durability of the fabricated product, without sacrificing the thermal insulation performance. The foam ink preparation methods and the printability are demonstrated in this paper, along with the printing of complex three-dimensional geometries. The thermal insulation performance of the printed objects is characterized, and the mechanical properties were also examined. The proposed approach is found to have a 56% reduction in the processing time. The printed silica aerogels exhibit a low thermal conductivity of 0.053 W m−1 K−1.

The Model and Experiment for Heat Transfer Characteristics of Nanoporous Silica Aerogel

Nanoporous silica aerogel insulation material is both lightweight and efficient; it has important value in the fields of aerospace, petrochemicals, electric metallurgy, shipbuilding, precision instruments, and so on. A theoretical calculation model and experimental measurement of equivalent thermal conductivity for nanoporous silica aerogel insulation material are introduced in this paper. The heat transfer characteristics and thermal insulation principle of aerogel nano are analyzed. The methods of SiO2 aerogel production are compared. The pressure range of SiO2 aerogel is 1Pa-atmospheric pressure; the temperature range is room temperature-900K. The pore diameter range of particle SiO2 aerogel is about 5 to 100 nm, and the average pore diameter range of about 20 ~ 40 nm. These results show that experimental measurements are in good agreement with theoretical calculation values. For nanoporous silica aerogel insulation material, the heat transfer calculation method suitable for nanotechnology can precisely calculate the equivalent thermal conductivity of aerogel nano insulation materials. The network structure is the reason why the thermal conductivity of the aerogel is very low. Heat transfer of materials is mainly realized by convection, radiation, and heat transfer. Therefore, the thermal conductivity of the heat transfer path in aerogel can be reduced by nanotechnology.

Thermal performance evaluation of glass window combining silica aerogels and phase change materials for cold climate of China

This paper investigates the thermal performance of glass window composed of glass, silica aerogel and phase change material (PCM), which concurrently provides storage and restitution of heat, super thermal insulation and daylighting to the interior environment. To assess the glass window thermal behavior, a numerical model describing the heat transfer mechanisms occurring in the PCM layer in combination with the other transparent wall layers was established and verified. Then, the influence of factors such as thermal conductivity, density, specific heat and thickness of silica aerogel on the thermal performance of the glass window was analyzed. The results show that the most significant controlling parameters are the thermal conductivity and thickness of silica aerogel, while the impact of density and specific heat of silica aerogel on the thermal performance of glazing unit is marginal. A proper thickness of aerogel that maximizes the exploitation of latent heat of PCM should be identified, which is between20 and 30 mm for the studied climatic conditions. It was concluded that integrating silica aerogel insulation into PCM-glass window system is an effective technology in cold regions, solving the problem that PCM cannot effectively exploit latent heat, while retaining the advantages of PCM in winter.

Microstructure and Thermal Insulation Property of Silica Composite Aerogel.

Tetraethyl orthosilicate was selected as a matrix of heat insulating materials among three silanes, and an anti-infrared radiation fiber was chosen as a reinforcement for silica aerogel insulation composite. The silica aerogel was combined well and evenly distributed in the anti-infrared radiation fiber. The heat insulation effect was improved with the increase in thickness of the aerogel insulation material, as determined by the self-made aerospace insulation material insulation performance test equipment. The 15 mm and 30 mm thick thermal insulation material heated at 250 °C for 3 h, the temperatures at the cold surface were about 80 °C and 60 °C, respectively, and the temperatures at 150 mm above the cold surface were less than 60 °C and 50 °C, respectively. The silica aerogel composites with various thicknesses showed good thermal insulation stability. The silica insulation composite with a thickness of 15 mm exhibited good heat insulation performance, meets the thermal insulation requirements of general equipment compartments under low-temperature and long-term environmental conditions. The thermal conductivity of prepared silica aerogel composite was 0.0191 W·m−1·k−1 at room temperature and 0.0489 W·m−1·k−1 at 500 °C.

Density effects of silica aerogel insulation on the performance of a graphite probe calorimeter.

With the introduction of a novel graphite probe calorimeter, called the Aerrow, various thermal insulating materials are being explored to further improve the device. Silica-based aerogels are proving to be an optimal material due to their low densities, small thermal conductivities, rigidity, and machinability. The aim of this work is to determine how various silica aerogel densities affect the Aerrow's performance. Performance concerns three areas: heat transfer from the core, the Aerrow's beam quality dependence, and the effects of an applied magnetic field on its measurement of absorbed dose to water. A numerical heat transfer study was done to determine heat transfer time constants. The EGSnrc radiation transport toolkit was used to determine absorbed dose conversion factors which are used to quantify the Aerrow's beam quality dependence. Dose conversion factors for Cobalt-60 and two clinical photon beams (6 and 10MV) were determined. Magnetic field perturbation factors are used to characterize the Aerrow's performance under an applied magnetic field. EGSnrc with the magnetic field transport algorithm was used to determine these perturbations for a 1.5T MR-linac. Several aerogel densities (0.01-0.55g ) were examined for each performance area. Heat transfer time constants were found to vary from 52±2 to 117.4±0.4s. The time constants decreased with increasing aerogel density. The Aerrow's beam quality dependence varied between 0.5% and 1%, decreasing with increasing aerogel density. Beam quality dependence was determined in the range of Co to 10MV (58.4% ≤ ≤73.5%). Under an applied magnetic field, perturbations were smallest when the Aerrow was parallel to the field. Perturbations varied more so when the Aerrow was perpendicular to the magnetic field and increased with increasing aerogel density. In all cases, perturbations were less than 0.6% from unity with a relative uncertainty of 0.1%. Silica-based aerogels demonstrate an improved performance over thermal insulation used in previous iterations of the Aerrow. With it, the Aerrow has shown to be robust in several areas. If heat transfer can be properly corrected for in the dose determination and the parallel orientation is used under a magnetic field, then the high density aerogel is possibly more preferable.

Simulation of energy- efficient building prototype using different insulating materials

The objective of this work is to analyze the energetic efficiency of an individual building including an area of 130 m2 multi-zone, located in the region of FEZ which is characterized by a very hot and dry climate in summer and a quite cold one in winter, by incorporating insulating materials. This study was performed using TRNSYS V16 simulation software during a typical year of the FEZ region. Our simulation consists in developing a comparative study of two types of polystyrene and silica-aerogel insulation materials, in order to determine the best thermal performance. The results show that the thermal insulation of the building envelope is among the most effective solutions that give a significant reduction in energy requirements. Similarly, the use of silica-aerogels gives a good thermal performance, and therefore a good energy gain.

Study on the Corrosion Behavior of Aqueous Extract of Thermal Insulation Materials to A3 Steel

The pH, conductivity and ions contents of aqueous extract of thermal insulation materials and deionized water were tested. Their corrosion behavior to A3 steel was investigated by static weight loss method. The results showed that the corrosion rate of glass wool was the lowest and performed local corrosion. The danger was the largest. Silica aerogel insulation blankets performed homogeneous corrosion and the corrosion rate was lower than that of deionized water. Aqueous extract of polyurethane foams expanded with HCFC-141b and CO₂ were homogeneous corrosion. The corrosion rate of the former was slightly lower than that of the latter，but both were larger than deionized water.

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.

Multi-layer graded doping in silica aerogel insulation with temperature gradient

Radiative heat transfer at high temperature deteriorates the insulating capability of silica aerogel due to its poor extinction characteristics for wavelength below 8μm. Both the infrared opacifier doping and fiber doping can reduce the heat transfer and improve insulating capability of silica aerogel efficiently at high temperature. We determine the optimal temperature-dependent size for typical opacifiers and silica fibers by combining the spectral extinction coefficient with blackbody radiation. The optimal temperature-dependent doping amount is obtained by minimizing the effective thermal conductivity. Based on the obtained temperature-dependent optimal parameters and the graded temperature distribution in silica aerogel, four solutions of multi-layer graded doping are presented and the insulating capability is improved effectively. The measured back temperature curves of doped silica aerogel in the experiment qualitatively verify the optimization predictions.

A review of heat transfer models of nanoporous silica aerogel insulation material

In this paper, the development of effective thermal conductivity models for nanoporous silica aerogel insulation materials is summarized. In the first part, heat transfer characteristics of nanoscale gaseous/solid/radiative heat transfer inside aerogel insulation material are introduced. Then, the existing theoretical models, empirical models, and numerical methods for the thermal conductivity of each heat transfer mode are reviewed and analyzed. After that, the advances in effective thermal conductivity models for the nanoporous silica aerogel materials as well as their composite insulation materials after the addition of opacifiers and reinforced fibers are presented. Next, the authors previous work is taken as an illustration of a procedure for establishing an effective thermal conductivity model of an aerogel insulation material from nano- to macro-scale. A brief introduction to the application of molecular dynamics in the simulation of aerogel materials is also given. In the end, further researchneeds are indicatedfor the nanoporous silica aerogel insulation materials. These include: the coupled heat transfer behavior at the gas–solid contact interface, the influence of scale/interfacial effects on the thermal conductivity of nanoscale solid particles, and the effect of different influencing factors on the total heat transfer performance. Such studies could provide help in accurately predicting the thermal conductivity as well as optimizing the insulation performance for the aerogel material and could provide guide for the design of new type aerogel insulation material which can be used in industry such as aeronautics and astronautics, thermal insulation, building, chemical industry and so on.

Mechanical and Adiabatic Properties of Silica Aerogel Doped with TiO&lt;sub&gt;2&lt;/sub&gt; Nanowire

A novel silica aerogel insulation composite was prepared by using TiO2 nanowires as modifier via sol-gel processing and supercritical drying methods in order to address issues of the poor mechanical and the infrared shading performance of silica aerogel. The effects of TiO2 nanowire content on the mechanical and adiabatic performance were investigated by X-Ray diffraction (XRD), nitrogen adsorption (BET), field emission scanning electron microscopy (FESEM), static compression test and thermal analysis. The results show that TiO2 nanowire reinforced aerogels had great thermal insulation properties, while high surface area, low density and mechanical strength were retained.

Gaseous Conductivity Study on Silica Aerogel and Its Composite Insulation Materials

This paper presents a theoretical and experimental study on gaseous conductivity of silica aerogel and composite insulation materials. First, the insulation material samples (including silica aerogel, xonotlite-type calcium silicate, xonotlite-aerogel composite, and ceramic fiber-aerogel composite) were prepared. Next, the gaseous conductivities of the prepared samples were measured from 0.045 Pa to atmospheric pressure using the transient hot-strip (THS) method. The gaseous conductivity expressions obtained based on the kinetic theory were then compared with the experimental results. It is shown that the gaseous conductivity of both xonotlite-type calcium silicate and silica aerogel decreases significantly with decreasing pressure. The gaseous conductivities of xonotlite-type calcium silicate and silica aerogel reach zero at about 100 Pa and 104 Pa, respectively. The theoretical gaseous conductivity expressions match well with the experimental results of xonotlite-type calcium silicate and silica aerogel but not with the experimental results for the composite insulation materials. This mismatch indicates that the aerogel does not totally fill the original interspace of the xonotlite-type calcium silicate and ceramic fiber in the two kinds of composite insulation materials.