scholarly journals Anisotropic and hierarchical SiC@SiO2 nanowire aerogel with exceptional stiffness and stability for thermal superinsulation

2020 ◽  
Vol 6 (26) ◽  
pp. eaay6689 ◽  
Author(s):  
Lei Su ◽  
Hongjie Wang ◽  
Min Niu ◽  
Sheng Dai ◽  
Zhixin Cai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
High Temperatures ◽  
Thermal Insulation ◽  
Extreme Conditions ◽  
Aerospace Vehicles ◽  
Hierarchical Microstructure ◽  
High Efficient ◽  
Low Stiffness ◽  
Insulation Performance

Ceramic aerogels are promising lightweight and high-efficient thermal insulators for applications in buildings, industry, and aerospace vehicles but are usually limited by their brittleness and structural collapse at high temperatures. In recent years, fabricating nanostructure-based ultralight materials has been proved to be an effective way to realize the resilience of ceramic aerogels. However, the randomly distributed macroscale pores in these architectures usually lead to low stiffness and reduced thermal insulation performance. Here, to overcome these obstacles, a SiC@SiO2 nanowire aerogel with a nanowire-assembled anisotropic and hierarchical microstructure was prepared by using directional freeze casting and subsequent heat treatment. The aerogel exhibits an ultralow thermal conductivity of ~14 mW/m·K, an exceptional high stiffness (a specific modulus of ~24.7 kN·m/kg), and excellent thermal and chemical stabilities even under heating at 1200°C by a butane blow torch, which makes it an ideal thermally superinsulating material for applications under extreme conditions.

scholarly journals Industrial Thermal Insulation Properties above Sintering Temperatures

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4721
Author(s):  
Amalie Gunnarshaug ◽  
Maria-Monika Metallinou ◽  
Torgrim Log
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Insulation ◽  
Fire Protection ◽  
Thermal Transport ◽  
Amorphous Materials ◽  
Transport Theory ◽  
Treatment Temperature ◽  
Dimensional Changes ◽  
Passive Fire Protection

Processing highly flammable products, the oil and gas (O&G) industry can experience major explosions and fires, which may expose pressurized equipment to high thermal loads. In 2020, oil fires occurred at two Norwegian O&G processing plants. To reduce the escalation risk, passive fire protection may serve as a consequence-reducing barrier. For heat or cold conservation, equipment and piping often require thermal insulation, which may offer some fire protection. In the present study, a representative thermal insulation (certified up to 700 °C) was examined with respect to dimensional changes and thermal transport properties after heat treatment to temperatures in the range of 700 °C to 1200 °C. Post heat treatment, the thermal conductivity of each test specimen was recorded at ambient temperature and up to 700 °C, which was the upper limit for the applied measurement method. Based on thermal transport theory for porous and/or amorphous materials, the thermal conductivity at the heat treatment temperature above 700 °C was estimated by extrapolation. The dimensional changes due to, e.g., sintering, were also analyzed. Empirical equations describing the thermal conductivity, the dimensional changes and possible crack formation were developed. It should be noted that the thermal insulation degradation, especially at temperatures approaching 1200 °C, is massive. Thus, future numerical modeling may be difficult above 1150 °C, due to abrupt changes in properties as well as crack development and crack tortuosity. However, if the thermal insulation is protected by a thin layer of more robust material, e.g., passive fire protection to keep the thermal insulation at temperatures below 1100 °C, future modeling seems promising.

scholarly journals The effect of heat treatment on thermal conductivity of paulownia wood

2019 ◽  
Vol 78 (1) ◽  
pp. 205-207
Author(s):  
Z. Pásztory ◽  
S. Fehér ◽  
Z. Börcsök
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Treatment ◽  
Thermal Insulation ◽  
Insulation Materials ◽  
Heat Treated ◽  
Paulownia Wood

AbstractThe thermal conductivity properties of wood of Paulownia Clones in Vitro 112 were investigated after heat treatment at temperatures of 180 °C, 200 °C and 220 °C. After the treatment, the density decreased by 5.6, 8.9, and 14.1% for the samples heat-treated at 180 °C, 200 °C and 220 °C, respectively. The decrease in the thermal conductivity was 0, 2.6 and 15.7%, respectively. The thermal conductivity of kiri wood after thermal treatment at 220 °C was 0.064 W/mK, which is almost the same as that of thermal insulation materials.

Study on the Thermal Insulation Performance of PAN Pre-Oxidised Fibre Felts

2020 ◽  
Vol 28 (3(141)) ◽  
pp. 27-37
Author(s):  
Xiaoming Zhao ◽  
Yuanjun Liu ◽  
Tenglong Liang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Tensile Strength ◽  
Tensile Properties ◽  
Thermal Insulation ◽  
Silica Aerogel ◽  
Orthogonal Experiment ◽  
Excellent Thermal Stability ◽  
Coefficient Of Thermal Conductivity ◽  
Insulation Performance

In this paper, an orthogonal experiment of 3 factors and 3 levels was firstly designed to prepare PAN pre-oxidised fibre felts with good thermal insulation properties; the range method was used to analyse the result of the orthogonal experiment, and finally the tensile properties and thermal stability were tested. Finally, pre-oxidised fibre felt composites for the coating of silica aerogel were prepared using the coating process to compound silica aerogel on re-oxidised fibre felts. Firstly, the influence of the content of silica aerogel on the heat insulation performance of the coated composite materials was analysed, and then a test of the coefficient of thermal conductivity, an experiment on the back temperature, and characterisations of the tensile properties and thermal stability of the composite coating of pre-oxidised fibre felt composites of the coating of silica aerogel were carried out. Results showed that through analysis of the orthogonal experiment, we can state that the best preparation process of pre-oxidised fibre needled felts was as follows: needle number – 2, needle depth – 8 mm, and needle frequency – 140 times/min. The transverse tensile strength of PAN pre-oxidised fibre needled felts prepared by crossly webbing of PAN pre-oxidised fibres was superior to the longitudinal tensile strength; thermogravimetric analysis showed that the pre-oxidised fibre needled felts had excellent thermal stability. The coefficient of thermal conductivity of the aerogel coating of the composites firstly decreased and then increased with an increase in the content of aerogel. Coated composites had the lowest coefficient of thermal conductivity when the aerogel content was 4% wt. At temperatures of 100 °C, 150 °C and 200 °C, the heating rate of the transient-state back temperature and the steady-state average temperature were both the lowest when the aerogel content was 6% wt.

Fabrication and properties of carbon/carbon-carbon foam composites

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4452-4460
Author(s):  
Bin Wang ◽  
Bugao Xu ◽  
Hejun Li
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Bonding Strength ◽  
Carbon Foam ◽  
Shear Load ◽  
Foam Composite ◽  
Final Failure ◽  
Carbon Foams ◽  
Insulation Performance

This paper was focused on the development of a new composite for high thermal insulation applications with carbon/carbon (C/C) composites, carbon foams and an interlayer of phenolic-based carbon. The microstructure, mechanical properties, fracture mechanism and thermal insulation performance of the composite was investigated. The experiment results showed that the bonding strength of the C/C-carbon foam composite was 4.31 MPa, and that the fracture occurred and propagated near the interface of the carbon foam and the phenolic-based carbon interlayer due to the relatively weak bonding. The shear load-displacement curves were characterized by alternated linear slopes and serrated plateaus before a final failure. he experiment revealed that the thermal conductivity of the C/C-carbon foam composite was 1.55 W·m−1ċK−1 in 800℃, which was 95.8% lower than that of C/C composites, proving that the thermal insulation of the new foam composite was greatly enhanced by the carbon foam with its porous hollow microstructure.

scholarly journals Effect of density, phonon scattering and nanoporosity on the thermal conductivity of anisotropic cellulose nanocrystal foams

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Varvara Apostolopoulou-Kalkavoura ◽  
Pierre Munier ◽  
Lukasz Dlugozima ◽  
Veit-Lorenz Heuthe ◽  
Lennart Bergström
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Phonon Scattering ◽  
Cellulose Nanocrystal ◽  
Foam Density ◽  
Aqueous Dispersions ◽  
Gas Conduction ◽  
Insulation Performance ◽  
Ice Templating

AbstractAnisotropic cellulose nanocrystal (CNC) foams with densities between 25 and 130 kg m−3 (CNC25 –CNC130) were prepared by directional ice-templating of aqueous dispersions. Estimates of the solid and gas conduction contributions to the thermal conductivity of the foams using a parallel resistor model showed that the relatively small increase of the radial thermal conductivity with increasing foam density can be attributed to interfacial phonon scattering. The foam wall nanoporosity and, to a lesser extent, the orientation of the CNC particles and alignment of the columnar macropores, also influence the insulation performance of the foams. The insight on the importance of phonon scattering for the thermal insulation properties of nanocellulose foams provides useful guidelines for tailoring nanofibrillar foams for super-insulating applications.

Research on the Pass Optimization Design of Sintered Shale Porous Brick

2014 ◽  
Vol 672-674 ◽  
pp. 1879-1884
Author(s):  
Jian Long Liu ◽  
Jie Nan Xie ◽  
Peng Liu ◽  
Mu Ye Huang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Optimization Design ◽  
Void Ratio ◽  
Thermal Conductivity Coefficient ◽  
Time Factors ◽  
Structure Design ◽  
3D Numerical Simulation ◽  
Equivalent Thermal Conductivity ◽  
Insulation Performance

The equivalent thermal conductivity coefficient of 10 kinds of sintered shale porous brick with different void number, void ratio, and arrangement (size: 240mm x 190mm x 90mm) are studied through 3D numerical simulation. An optimal structure design of the shale perforated brick design has been obtained. At the same time, factors such as void ratio, void number and arrangement of porous brick affected thermal insulation performance are systematically analyzed, which provides a reference to further improving the thermal insulation performance of insulation sintered shale porous brick model.

Fabrication of Infrared Opacifiers Loaded Al2O3 Aerogel-SiO2 Fiber Mat Composites with High Thermal Resistance

2020 ◽  
Vol 19 (03) ◽  
pp. 1950021
Author(s):  
Shangyan Wen ◽  
Jiayi Zhu ◽  
Qiang Yin ◽  
Yutie Bi ◽  
Hongbo Ren ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Sol Gel ◽  
Doping Content ◽  
Low Thermal Conductivity ◽  
Sic Particles ◽  
Sol Gel Process ◽  
High Thermal Resistance ◽  
Insulation Performance

The infrared opacifiers loaded Al2O3 aerogel-SiO2 fiber mat composites were fabricated by the sol–gel process. The effects of the content of the TiO2 and SiC particles on thermal insulation performance of the Al2O3 aerogel-SiO2 fiber mat composites were studied. The results showed that the optimum doping content of TiO2 and SiC for Al2O3 aerogel-SiO2 fiber mat composites were 10[Formula: see text]mol.% and 0.5[Formula: see text]mol.%, respectively. The optimum TiO2-Al2O3 aerogel-SiO2 fiber mat composite had the low thermal conductivity of 0.021[Formula: see text]W/(m[Formula: see text][Formula: see text][Formula: see text]K) at 35∘C and 0.031[Formula: see text]W/(m[Formula: see text][Formula: see text][Formula: see text]K) at 600∘C. Meanwhile, the SiC-Al2O3 aerogel-SiO2 fiber mat composite also had the low thermal conductivity of 0.022[Formula: see text]W/(m[Formula: see text][Formula: see text][Formula: see text]K) at 35∘C and 0.025[Formula: see text]W/(m[Formula: see text][Formula: see text][Formula: see text]K) at 600∘C.

Analysis of Thermal Insulation Material on Building Exterior Wall

2017 ◽  
Vol 873 ◽  
pp. 153-157 ◽  
Author(s):  
Jia Jiu Diao ◽  
Xin Qin Liao ◽  
Can Fa Diao
Keyword(s):  
Thermal Conductivity ◽  
Flame Retardant ◽  
Thermal Insulation ◽  
Insulation Material ◽  
Low Thermal Conductivity ◽  
Insulation Materials ◽  
Existing Problems ◽  
Comprehensive Properties ◽  
First Choice ◽  
Insulation Performance

The use of performance, application status and existing problems of organic and inorganic thermal insulation materials, which are commonly used in the external walls of the building, are described in detail in this paper. Organic thermal insulation materials with low thermal conductivity, good thermal insulation performance, but with the flammable, low fire rating, poor safety, then it needing for flame retardant treatment. However, Inorganic thermal insulation materials with flame retardant, high fire rating, good safety performance, but poor thermal insulation properties than the organic insulation materials, so it needs to develop a low thermal conductivity of inorganic insulation materials.In the end, we pointed out that the inorganic insulation materials with low thermal conductivity and excellent comprehensive properties are expected to be the first choice for building thermal insulation materials.

scholarly journals Enhanced Thermal Insulation of the Hollow Glass Microsphere/Glass Fiber Fabric Textile Composite Material

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 505
Author(s):  
Jintao Sun ◽  
Fei Cai ◽  
Dongzhi Tao ◽  
Qingqing Ni ◽  
Yaqin Fu
Keyword(s):  
Thermal Conductivity ◽  
Glass Fiber ◽  
Thermal Insulation ◽  
Thermal Constant ◽  
Hollow Glass Microsphere ◽  
Glass Microspheres ◽  
Textile Composite ◽  
Hollow Glass Microspheres ◽  
Hollow Glass ◽  
Insulation Performance

Glass fiber fabrics/hollow glass microspheres (HGM)–waterborne polyurethane (WPU) textile composites were prepared using glass fiber, WPU, and HGM as skeleton material, binder, and insulation filler, respectively, to study the effect of HGM on the thermal insulation performance of glass fiber fabrics. Scanning electron microscopy, Instron 3367 tensile test instrument, thermal constant analysis, and infrared thermal imaging were used to determine the cross-sectional morphology, mechanical property, thermal conductivity, and thermal insulation property, respectively, of the developed materials. The results show that the addition of HGM mixed in WPU significantly enhanced thermal insulation performance of the textile composite with the reduction of thermal conductivity of 45.2% when the volume ratio of HGM to WPU is 0.8 compared with that of material without HGM. The composite can achieve the thermal insulation effect with a temperature difference of 17.74 °C at the temperature field of 70 °C. Meanwhile, the tensile strength of the composite is improved from 14.16 to 22.14 MPa. With these results, it is confirmed that designing hollow glass microspheres (HGM) is an effective way to develop and enhance the high performance of insulation materials with an obvious lightweight of the bulk density reaching about 50%.

scholarly journals Effects of the Heat Treatment in the Properties of Fibrous Aerogel Thermal Insulation

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 2001 ◽  
Author(s):  
Ákos Lakatos ◽  
Attila Csík ◽  
Anton Trník ◽  
István Budai
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Annealing ◽  
Thermal Insulation ◽  
Structural Changes ◽  
Glass Fibers ◽  
Material Structure ◽  
Scanning Calorimetry ◽  
Plastic Foams ◽  
Isothermal Heat Treatments

Nowadays, besides the use of conventional insulations (plastic foams and wool materials), aerogels are one of the most promising thermal insulation materials. As one of the lightest solid materials available today, aerogels are manufactured through the combination of a polymer with a solvent, forming a gel. For buildings, the fiber-reinforced types are mainly used. In this paper, the changes both in the thermal performance and the material structure of the aerogel blanket are followed after thermal annealing. The samples are put under isothermal heat treatments at 70 °C for weeks, as well as at higher temperatures (up to 210 °C) for one day. The changes in the sorption properties that result from the annealing are presented. Furthermore, the changes in the thermal conductivity are followed by a Holometrix Lambda heat flow meter. The changes in the structure and surface of the material due to the heat treatment are investigated by X-ray diffraction and with scanning electron microscopy. Besides, the above-mentioned measurement results of differential scanning calorimetry experiments are also presented. As a result of using equipment from different laboratories that support each other, we found that the samples go through structural changes after undergoing thermal annealing. We manifested that the aerogel granules separate down from the glass fibers and grow up. This phenomenon might be responsible for the change in the thermal conductivity of the samples.

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