scholarly journals Constructing Cellulose Diacetate Aerogels with Pearl-Necklace-Like Skeleton Networking Structure

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 210
Author(s):  
Shixian Xiong ◽  
Yangbiao Hu ◽  
Sizhao Zhang ◽  
Yunyun Xiao ◽  
Zhengquan Li
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Property ◽  
Supercritical Drying ◽  
Drying Process ◽  
Ambient Conditions ◽  
Cellulose Diacetate ◽  
Insulation Property ◽  
Radial Shrinkage ◽  
New Strategy ◽  
Thermal Insulation Property

Cellulose and its derivative aerogels have attracted much attention due to their renewable and biodegradable properties. However, the significant shrinkage in the supercritical drying process causes the relatively high thermal conductivity and low mechanical property of cellulose and its derivatives aerogels. Considering the pearl-necklace-like skeleton network of silica aerogels, which can improve thermal insulation property and mechanical property. Herein, we propose a new strategy for fabricating cellulose diacetate aerogels (CDAAs) with pearl-necklace-like skeletons by using tert-butanol (TBA) as exchange solvent after experiencing the freezing-drying course. CDAAs obtained have the low density of 0.09 g cm−3, the nanopore size in the range of 10–40 nm, the low thermal conductivity of 0.024 W m−1 K−1 at ambient conditions, and the excellent mechanical properties (0.18 MPa at 3% strain, 0.38 MPa at 5% strain). Ultimately, CDAAs with moderate mechanical property paralleled to cellulose-derived aerogels obtained from supercritical drying process are produced, only simultaneously owning the radial shrinkage of 6.2%. The facile method for fabricating CDAAs could provide a new reference for constructing cellulose/cellulose-derived aerogels and other biomass aerogels.

scholarly journals Thermal Conductivity Performance of Silica Aerogel after Exposition on Different Heating under Ambient Pressure

2019 ◽  
Vol 16 (3(Suppl.)) ◽  
pp. 0770 ◽  
Author(s):  
Israa F. Al-sharuee
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Ambient Pressure ◽  
Ambient Pressure Drying ◽  
Drying Method ◽  
Insulation Property ◽  
M 10 ◽  
Basic Characteristics ◽  
Thermal Insulation Property ◽  
Quality Material

         The varied thermal conductivity (insulation) of silica aerogel with heating for different pH has been investigated, it has been depended on ambient pressure drying method in the preparing silica aerogel samples, also six different pH of samples (1, 2, 3, 7, 8 and 9) were treated under five degree of heating with (50,100,150,200 and 250) ᴼC. This technique is important to test the carry-outs hydrophobic silica to temperature without high-quality material changes in the basic characteristics. The hot-wire technique is used in this work to examine the thermal conductivity, Fourier Transform Infrared Spectroscopy (FTIR) depended to characterize the bonds and their artificial by heating. Results show that the samples affected by heating through decreasing the density leading to obtaining more insulation metal, moreover varied pH is an important role in thermal conductivity. The average thermal conductivity of all aerogel samples in this work is (0.01- 0.0061 mW m-10 C-1) this means that it is still below thermal conductivity for air equals to (0.02257) mW m-10 C-1 . Meanwhile, we concluded that the insulation property of silica aerogel is affected by heat treatment and gives it more thermal insulation property.

Thermal properties of organic and inorganic aerogels

1994 ◽  
Vol 9 (3) ◽  
pp. 731-738 ◽  
Author(s):  
Lawrence W. Hrubesh ◽  
Richard W. Pekala
Keyword(s):  
Thermal Conductivity ◽  
Pore Size ◽  
Average Pore Size ◽  
Sol Gel ◽  
Total Thermal Conductivity ◽  
Insulation Property ◽  
Average Pore ◽  
Thermal Insulating ◽  
Thermal Insulation Property ◽  
Infrared Extinction

Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. This paper examines the three major contributions to thermal transport through porous materials, solid, gaseous, and radiative, to identify how to reduce the thermal conductivity of air-filled aerogels. We found that significant improvements in the thermal insulation property of aerogels are possible by (i) employing materials with a low intrinsic solid conductivity, (ii) reducing the average pore size within aerogels, and (iii) affecting an increase of the infrared extinction in aerogels. Theoretically, polystyrene is the best of the organic materials and zirconia is the best inorganic material to use for the lowest achievable conductivity. Significant reduction of the thermal conductivity for all aerogel varieties is predicted with only a modest decrease of the average pore size. This might be achieved by modifying the sol-gel chemistry leading to aerogels. For example, a thermal resistance value of R = 20 per inch would be possible for an air-filled resorcinol-formaldehyde aerogel at a density of 156 kg/m3, if the average pore size was less than 35 nm. An equation is included which facilitates the calculation of the optimum density for the minimum total thermal conductivity, for all varieties of aerogels.

scholarly journals Incorporation of Polymers into Calcined Clays as Improved Thermal Insulating Materials for Construction

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Serina Ng ◽  
Bjørn Petter Jelle
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Insulation Property ◽  
One Pot ◽  
Calcined Clay ◽  
Thermal Insulating ◽  
Thermal Insulation Property ◽  
Clay Layers ◽  
Thermally Conducting ◽  
Cementing Material

Calcined clay is a Type Q supplementary cementing material according to EN197-1:2000. It possesses lower thermal conductivity than cement. To further improve its thermal insulation property, polymer-calcined clay complexes (PCCs) were produced in a one-pot synthesis. Two contrasting polymers, polystyrene (PS) and polyethylene glycol (PEG), were employed. The hydrophilicity of the polymers influenced the thermal conductivity of PCC. Hydrophilic PEG entrapped more water molecules on clay layers than the hydrophobic PS, making PEG-PCC more thermally conducting than PS-PCC. Contaminants in calcined clays played a role in affecting the overall thermal conductivity. PCC can improve thermal insulation properties for future construction applications.

An Experimental Study on Thermal Insulation Performance of Straw Wire Aircraft Sandwich Panel

2013 ◽  
Vol 639-640 ◽  
pp. 1307-1312
Author(s):  
Qun Yi Huang ◽  
Feng Xiong ◽  
Kui Fan ◽  
Yu Chuan He
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Sandwich Panel ◽  
Cement Content ◽  
Insulation Property ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Shear Connectors ◽  
Thermal Insulation Property ◽  
Wire Meshes

Straw wire aircraft sandwich panel is a new type of composite slab which consist of straw insulation core lamped between two welded wire meshes. Diagonal shear connectors connect two wire meshes to form an integrated frame. The straw insulation core (also known as straw board) is prepared from cut straw agglutinated by magnesium oxychloride cement (MOC). In order to study thermal conductivity of straw board, multi-group models were quantitatively investigated by the CD－DR3030A thermal conductivity meter. Five parameters, including the water－cement ratio, cement content, straw gradation, straw length, wettability were considered in the test. The results show that the thermal conductivity of straw board samples is in the range of 0.08~0.12 w/m•k, which indicates that the straw board has a good thermal insulation property. And the water－cement ratio, cement content, straw gradation, straw length, wettability has remarkable effects on the thermal conductivity of straw board.

Thermal Conductivity of Akar Bamboo (Dendracalamus pendulus) and Semantan Bamboo (Gigantochloa scortechinii)

2013 ◽  
Vol 748 ◽  
pp. 160-164
Author(s):  
Noor Zuraida Jusoh ◽  
Abdul Muhaimin Zakaria ◽  
Mansur Ahmad ◽  
Ibrahim Azmi
Keyword(s):  
Thermal Conductivity ◽  
Heat Source ◽  
Wood Adhesive ◽  
Insulation Property ◽  
Environmental Friendly ◽  
Laminated Bamboo ◽  
Mechanical And Physical Properties ◽  
Parallel Direction ◽  
Thermal Insulation Property ◽  
Common Application

Bamboo is known as economically and environmental friendly plant. The most common application of bamboos is furniture and traditional handcrafts. Many studies on mechanical and physical properties of bamboo have been conducted. However the thermal insulation property of these abundance species has never been recognized and commercially utilized which results in the reason why thermal properties of bamboo have never been studied. In this experiment, two species of bamboo which are Akar bamboo (Dendracalamus pendulus) and Semantan bamboo (Gigantochloa scortechinii) has been tested to determine their thermal conductivity. The test samples were prepared to conduct this experiment in parallel and perpendicular grain direction towards the heat source. Wood adhesive was used as the binder for cylindrical laminated bamboo. The result shows that thermal conductivity of bamboo is low in perpendicular direction towards the heat source compared to the parallel direction. Different species of bamboo also give significant result on thermal conductivity hence improved the insulation properties of the bamboo.

scholarly journals Temperature Effect on the Thermal Conductivity of Expanded Polystyrene Foamed Concrete: Experimental Investigation and Model Correction

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Jinyan Shi ◽  
Yuanchun Liu ◽  
Baoju Liu ◽  
Dan Han
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Expanded Polystyrene ◽  
Effect Of Temperature ◽  
Dry Density ◽  
Insulation Property ◽  
Different Temperatures ◽  
Foamed Concrete ◽  
Thermal Insulation Property ◽  
The Impact

In this research, ultralightweight expanded polystyrene foamed concrete (EFC) was made by the chemical foaming method, and its thermal insulation property was measured by the transient method at different environment temperatures (from −10 to 40°C). Then, the effect of temperature and EPS volume fraction on the thermal conductivity and dry density of EFC were observed. Ultimately, the Cheng–Vachon equation was modified by introducing the temperature parameter. The results indicated that EFC thermal conductivity decreases with increasing temperature. It was also demonstrated that the suitable volume of EPS particles can not only decrease the EFC thermal conductivity but also reduce the impact of temperature on the thermal conductivity. The thermal conductivity of EFC at different temperatures was accurately predicted in this study using the proposed model.

Test Research of Thermal Insulation Property of Straw-Based Board

2013 ◽  
Vol 671-674 ◽  
pp. 1848-1851
Author(s):  
Yan Liu ◽  
Juan Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Thermal Insulation ◽  
Green Building ◽  
Insulation Property ◽  
Minimum Thickness ◽  
Thermal Insulation Property ◽  
Different Thickness ◽  
Heat Flow Meter

A new green building material has been studied through investigating the thermal insulation properties of board produced from crop straw in this paper. Three straw-based boards with different thicknesses (8mm, 16mm and 32mm) were selected to detect heat transfer coefficient of the wall using JW-III heat-flow meter type thermal conductivity tester. Based on the standard specified in [1], we obtained the minimum thickness for the straw-based board for thermal insulation of different thickness brick walls.

Polyimide-Silica Hybrid Aerogels with High Mechanical Strength for Thermal Insulation Applications

2011 ◽  
Vol 1306 ◽  
Author(s):  
Wenting Dong ◽  
Wendell Rhine ◽  
Shannon White
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Ambient Conditions ◽  
Separation Membranes ◽  
Low Dielectric ◽  
Aging Conditions ◽  
Hybrid Aerogels ◽  
Mechanical Strengths ◽  
The Relationship ◽  
Silica Hybrid

ABSTRACTHigh performance polyimides have been widely investigated as materials with excellent thermal, mechanical, and electronic properties due to their highly rigid structures. Aspen has developed an approach to prepare polyimide aerogels which have applications as low dielectric constant materials, separation membranes, catalyst supports and insulation materials. In this paper, we will discuss the preparation of polyimide-silica hybrid aerogel materials with good mechanical strengths and low thermal conductivities. The polyimide-silica hybrid aerogels were made by a two-step process and the materials were characterized to determine thermal conductivity and compressive strength. Results show that compressive moduli of the polyimide-silica hybrid aerogels increase dramatically with density (power law relationship). Thermal conductivity of the aerogels is dependent on the aging conditions and density, with the lowest value achieved so far being ~12 mW/m-K at ambient conditions. The relationship between aerogel density and surface area, thermal stability, porosity and morphology of the nanostructure of the polyimide-silica hybrid aerogels are also described in this paper.

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