Thermographic Studies of Aerogel Composites

2020 ◽  
Vol 15 (2) ◽  
Author(s):  
K. Keerthi Sanghamitra ◽  
A. Yamini ◽  
A. Venu Vinod ◽  
Neha Hebalkar
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Cold Water ◽  
High Porosity ◽  
Fiber Mats ◽  
Aerospace Applications ◽  
Thermal Insulating ◽  
Wide Range ◽  
Composite Form ◽  
Insulation Performance

AbstractAerogels are regarded as the superior thermal insulating materials for wide range of temperatures, from cryogenic insulation, cold water diving garments to high temperature applications and even to defense and aerospace applications. For most of such applications, the aerogels are used in composite form rather than monolithic form as aerogels are fragile in nature due to its high porosity of up to 98%. These composites constitute aerogel infiltrated fiber mats to give flexibility, on the other hand, compromises on the insulation performance due to reinforcing aerogel with fibers that have comparatively higher thermal conductivity than silica aerogel. To increase the efficiency, density of the fiber mat needs to be reduced to incorporate higher loading of silica aerogel. Many techniques are being used to study the insulation performance of these composites. This paper presents about the study of insulation performance of fibre mats with different aerogel content and composition using a well-known thermography technique. The morphological, compositional, thermal and physical studies of the fiber mats and its composites using FESEM, EDAX, BET, thermal conductivity etc., are discussed.

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.

Thermal Insulative Performance of Bamboo Leaf Aerogel Opacified Using Activated Carbon Compared with Carbon Black

2014 ◽  
Vol 941-944 ◽  
pp. 2482-2485
Author(s):  
Kien Woh Kow ◽  
Rozita Yusoff ◽  
A. R. Abdul Aziz ◽  
E. C. Abdullah
Keyword(s):  
Thermal Conductivity ◽  
Activated Carbon ◽  
Carbon Black ◽  
Silica Aerogel ◽  
Radiative Heat ◽  
Radiative Heat Loss ◽  
Insulating Material ◽  
Thermal Insulating ◽  
Different Temperatures ◽  
Carbon Loading

Silica aerogel with extremely low thermal conductivity has great potential to be used as thermal insulating material. Opacification using carbon black is normally applied to reduce radiative heat loss in silica aerogel. This work attempted to replace carbon black with activated carbon as opacifer. Both the silica aerogel and activated carbon were synthesized via bamboo leaf. Effects of carbon loading and temperatures on the thermal conductivity of opacified aerogel were studied. The results show that an optimal carbon loading that minimized the thermal conductivity present at different temperatures. Such optimal loading increased as temperature applied to the opacified aerogel increased. Properties of aerogels opacified with activated carbon were also compared with aerogels opacified with carbon black.

scholarly journals Advanced Fabrication of Lightweight Aerogels from Fly Ash for Thermal Insulation

2021 ◽  
Vol 3 (4) ◽  
pp. first
Author(s):  
Nga Hoang Nguyen Do ◽  
Huy Gia Tran ◽  
Huong Ly Xuan Doan ◽  
Nghiep Quoc Pham ◽  
Kien Anh Le ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Mineral Wool ◽  
Expanded Polystyrene ◽  
Value Engineering ◽  
High Porosity ◽  
Thermal Insulating ◽  
Coffee Grounds ◽  
First Time ◽  
Good Heat

For the first time, an environmentally friendly and effective procedure to produce high-value engineering aerogels from fly ash (FA) has been developed by dispersing FA particles into a mixture of biodegradable polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC), followed by freezedrying. The effect of FA content on the physical properties, morphology, mechanical strength, and thermal conductivity of FA aerogels is also studied comprehensively. The lightweight FA aerogels show a low density of 0.072 – 0.093 g/cm3 with high porosity of 94.94 – 95.78%. The morphology of aerogels shows the uniform distribution of FA particles in PVA-CMC matrixes that creates a porous structure with a pore size of 2-5 mm. Therefore, the FA aerogels exhibit good heat insulation with extremely low thermal conductivity of 0.040 – 0.047 W/m.K at ambient temperature and pressure that is comparable to some commercial insulation materials such as mineral wool, fiberglass, expanded polystyrene, and other silica-based aerogels from waste. Moreover, the compressive modulus of FA aerogels is about 67.73 – 254.75 kPa indicating their excellent mechanical properties under 1 kN vertical compression. The experimental results indicate the significant better durability of FA aerogels than that of previous aerogels from other wastes such as sugarcane bagasse (88 kPa), pineapple leaf fibers (1.64 – 5.34 kPa), recycled polyethylene terephthalate (1.16 – 2.87 kPa), spent coffee grounds (5.41 – 15.62 kPa), and silica – cellulose (86 – 169 kPa). It is concluded that FA aerogels are a promising candidate as a lightweight thermal insulating material.

scholarly journals Aerogels as Promising Thermal Insulating Materials: An Overview

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Prakash C. Thapliyal ◽  
Kirti Singh
Keyword(s):  
Thermal Insulation ◽  
Energy Efficient ◽  
Structural Features ◽  
Primary Energy ◽  
Building Envelope ◽  
High Porosity ◽  
Thermal Insulating ◽  
Wide Range ◽  
Potential Applications ◽  
Insulation Systems

Aerogels are solids with high porosity (<100 nm) and hence possess extremely low density (∼0.003 g/cm3) and very low conductivity (∼10 mW/mK). In recent years, aerogels have attracted more and more attention due to their surprising properties and their existing and potential applications in wide range of technological areas. An overview of aerogels and their applications as the building envelope components and respective improvements from an energy efficiency perspective including performance is given here. This overview covers thermal insulation properties of aerogels and studies regarding structural features which will be helpful in buildings envelope. The improvements of thermal insulation systems have future prospects of large savings in primary energy consumption. It can be concluded that aerogels have great potential in a wide range of applications as energy efficient insulation, windows, acoustics, and so forth.

scholarly journals Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2198 ◽  
Author(s):  
Hu Zhang ◽  
Chao Zhang ◽  
Wentao Ji ◽  
Xian Wang ◽  
Yueming Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Silica Aerogel ◽  
Volume Fraction ◽  
Nitrogen Atmosphere ◽  
Nanoporous Structure ◽  
High Porosity ◽  
Low Thermal Conductivity ◽  
Pure Silica ◽  
Aerogel Composite

Due to their high-porosity, nanoporous structure and pores, aerogel materials possess extremely low thermal conductivity and have broad potential in the thermal insulation field. Silica aerogel materials are widely used because of their low thermal conductivity and high temperature resistance. Pure silica aerogel is very fragile and nearly transparent to the infrared spectrum within 3–8 μm. Doping fibers and opacifiers can overcome these drawbacks. In this paper, the influences of opacifier type and content on the thermal conductivity of silica fiber mat-aerogel composite are experimentally studied using the transient plane source method. The thermal insulation performances are compared from 100 to 750 °C at constant pressure in nitrogen atmosphere among pure fiber mat, fiber mat-aerogel, 20% SiC-fiber mat-aerogel, 30% ZrO2-fiber mat-aerogel and 20% SiC + 30% ZrO2-fiber mat-aerogel. Fiber mat-aerogel doped with 20% SiC has the lowest thermal conductivity, 0.0792 W/m·K at 750 °C, which proves that the proper type and moderate content of opacifier dominates the low thermal conductivity. The pore size distribution indicates that the volume fraction of the micropore and mesopore is also the key factor for reducing the thermal conductivity of porous materials.

Measurement of Thermal Conductivity of Carbon Foams

2003 ◽  
Author(s):  
M. K. Alam ◽  
A. M. Druma
Keyword(s):  
Thermal Conductivity ◽  
Carbon Foam ◽  
Lower Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Heat Spreaders ◽  
Carbon Foams ◽  
Interface Contact ◽  
Flash Diffusivity ◽  
Graphitic Foam

A number of carbon foam products are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. The application of carbon foams in aerospace applications is advantageous due to the high thermal conductivity and low density of the graphitic foam. However, the measurement of thermal conductivity has been difficult due the problems of interface contact and lower strength of the foam. The flash diffusivity method has been used to find thermal conductivity of a wide range of materials. Because of the porous nature of the foam, errors may be introduced with the flash diffusivity method. An analytical and experimental study has been carried out to determine the validity of the flash diffusivity method for foam specimen.

Fabrication of High Porosity Mullite Foams and their Thermal Properties

2016 ◽  
Vol 879 ◽  
pp. 1987-1991
Author(s):  
Toru Shimizu ◽  
Kunio Matsuzakaki
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Metal Foam ◽  
High Porosity ◽  
Refractory Brick ◽  
Thermal Insulating ◽  
Slurry Method ◽  
Mullite Refractory ◽  
Refractory Bricks ◽  
Insulating Properties

Already, we developed a high porosity alumina foam. However, alumina has high thermal conductivity about 36W/mK at room temperature, and it need to achieve to high porosity to decrease thermal conductivity to for application of refractory bricks. Therefore, high porosity mullite refractory brick is developed using GS (Gelation of Slurry) method that is already developed for production of high porosity metal foam. Appling this method to production of mullite foams, the ceramics foams from 93 to 97% porosity can be produced. Also, their thermal conductivities are proportional to densities and obey to Ashby-Glicksman model. Its thermal conductivity is about 0.07W/mK when density is 0.1 g/cm3. The high porosity mullite foams achieved enough thermal insulating properties for refractory brick.

scholarly journals Influence of Silica-Aerogel on Mechanical Characteristics of Polyurethane-Based Composites: Thermal Conductivity and Strength

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1790
Author(s):  
Jeong-Hyeon Kim ◽  
Jae-Hyeok Ahn ◽  
Jeong-Dae Kim ◽  
Dong-Ha Lee ◽  
Seul-Kee Kim ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Cell Morphology ◽  
Environmental Conditions ◽  
Silica Aerogel ◽  
Porous Silica ◽  
Mechanical And Thermal Properties ◽  
Insulation Material ◽  
Wide Range ◽  
Insulation Systems

Polyurethane foam (PUF) has generally been used in liquefied natural gas (LNG) carrier cargo containment systems (CCSs) owing to its excellent mechanical and thermal properties over a wide range of temperatures. An LNG CCS must be designed to withstand extreme environmental conditions. However, as the insulation material for LNGC CCSs, PUF has two major limitations: its strength and thermal conductivity. In the present study, PUFs were synthesized with various weight percentages of porous silica aerogel to reinforce the characteristics of PUF used in LNG carrier insulation systems. To evaluate the mechanical strength of the PUF-silica aerogel composites considering LNG loading/unloading environmental conditions, compressive tests were conducted at room temperature (20 °C) and a cryogenic temperature (−163 °C). In addition, the thermal insulation performance and cellular structure were identified to analyze the effects of silica aerogels on cell morphology. The cell morphology of PUF-silica aerogel composites was relatively homogeneous, and the cell shape remained closed at 1 wt.% in comparison to the other concentrations. As a result, the mechanical and thermal properties were significantly improved by the addition of 1 wt.% silica aerogel to the PUF. The mechanical properties were reduced by increasing the silica aerogel content to 3 wt.% and 5 wt.%, mainly because of the pores generated on the surface of the composites.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

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