Freeze-drying preparation of porous diatomite ceramics with high porosity and low thermal conductivity

2020 ◽  
Vol 119 (4) ◽  
pp. 195-203
Author(s):  
Lei Han ◽  
Faliang Li ◽  
Haijun Zhang ◽  
Yuantao Pei ◽  
Longhao Dong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Freeze Drying ◽  
High Porosity ◽  
Low Thermal Conductivity

Rigid Polyurethane Foam: A Versatile Energy Efficient Material

2016 ◽  
Vol 678 ◽  
pp. 88-98 ◽  
Author(s):  
Harpal Singh
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Weight Ratio ◽  
Building Envelope ◽  
Polymerization Reaction ◽  
Low Density ◽  
High Porosity ◽  
Rigid Polyurethane Foam ◽  
Low Thermal Conductivity ◽  
Moisture Permeability

Rigid polyurethane foam (RPUF) is typically prepared by the reaction of an isocyanate, such as methyl diphenyl diisocyanate (MDI) with a polyol blend. During the polymerization reaction, a blowing agent expands the reacting mixture. The finished product is a solid, cellular polymer with a high thermal resistance. RPUF is an outstanding material for different applications. It has many desirable properties such as low thermal conductivity, low density, low water absorption, low moisture permeability, excellent dimensional stability, high strength to weight ratio. So, it is the best insulating material for industrial buildings, cold storages, telecom and defense shelters due to low thermal conductivity, low density, low moisture permeability and high porosity. It works to reduce heating and cooling loss, improving the efficiency of the building envelope. Thus, RPUF insulation in building envelopes brings additional benefits in energy savings, resulting in lower energy bills and protecting the environment by cutting CO2 emissions.

Low thermal-conductivity and high thermal stable silica aerogel based on MTMS/Water-glass co-precursor prepared by freeze drying

2017 ◽  
Vol 113 ◽  
pp. 246-253 ◽  
Author(s):  
Yuelei Pan ◽  
Song He ◽  
Lunlun Gong ◽  
Xudong Cheng ◽  
Congcong Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Water Glass ◽  
Freeze Drying ◽  
Low Thermal Conductivity ◽  
Thermal Stable

scholarly journals Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu

2019 ◽  
Vol 3 (11) ◽  
pp. 971-976 ◽  
Author(s):  
M. Grott ◽  
J. Knollenberg ◽  
M. Hamm ◽  
K. Ogawa ◽  
R. Jaumann ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Porosity ◽  
Low Thermal Conductivity

scholarly journals Development of Porous Tungsten Mud Waste-based Alkali-activated Foams with Low Thermal Conductivity

2020 ◽  
Author(s):  
Imed Beghoura ◽  
Joao Castro-Gomes
Keyword(s):  
Thermal Conductivity ◽  
Mining Waste ◽  
Foaming Properties ◽  
Original Material ◽  
Insulation Material ◽  
High Porosity ◽  
Low Thermal Conductivity ◽  
Aluminium Powder ◽  
Blowing Agent ◽  
Alkali Activated

Aim of this study was to produce alkali-activated foams with low thermal conductivity. Different precursors’ maximum particles sizes of 150μm, 300μm, and 500μm using a blend of 70% tungsten mining waste mud (TWM), 20% grounded waste glass (WG) and 10 % metakaolin (MK) with sodium silicate (SS) and sodium hydroxide (SH) as original material. Aluminium powder (Al) was used as a blowing agent and added first to the dry mix by changing content from 0.1g to 0.5g. Precursors and activators were mixed together to produce a homogeneous mixture, which was placed into a mould (100x200x60 mm3), and cured in the oven at 60∘C for 24 hours. The effect on foaming properties of different precursors maximum particles sizes were studied. The AAFs exhibited 28 day compressive strengths ranging from 2.28 to 16.1 MPa with the different densities from 913 to 1647 kg/m3 achieved through alteration of the foaming content. The thermal conductivity of AAFs was in the range 0.21– 0.33 W/m*K. Open celled hardened of the AAFs with 0.5g Al shows a high porosity of 58% with the mix made with 500μm. Therefore, tungsten mining waste-based alkali-activated foams shows a promise as thermal insulation material in some situations.

scholarly journals Thermal conductivity and thermoelectric properties in 3D macroscopic pure carbon nanotube materials

2021 ◽  
Vol 10 (1) ◽  
pp. 178-186
Author(s):  
Xueming Yang ◽  
Jixiang Cui ◽  
Ke Xue ◽  
Yao Fu ◽  
Hanling Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermoelectric Properties ◽  
Room Temperature ◽  
High Porosity ◽  
Single Walled Carbon Nanotube ◽  
Low Thermal Conductivity ◽  
Multi Walled Carbon Nanotube ◽  
Interconnected Structure ◽  
Sintered Carbon

Abstract Sintered carbon nanotube (CNT) blocks and porous CNT sponges were prepared, and their thermoelectric properties were measured. The maximum dimensionless thermoelectric figure-of-merit, ZT, at room temperature of the sintered single-walled carbon nanotube (SWCNT) block is 9.34 × 10−5, which is twice higher than that of the sintered multi-walled carbon nanotube (MWCNT) block in this work and also higher than that of other sintered MWCNT blocks reported previously. In addition, the porous MWCNT sponge showed an ultra-low thermal conductivity of 0.021 W/(m K) and significantly enhanced ZT value of 5.72 × 10−4 at room temperature and 1 atm. This ZT value is higher than that of other 3D macroscopic pure CNT materials reported. The pronounced enhancement of the ZT in the porous MWCNT sponge is attributed to the ultra-low density, ultra-high porosity, and interconnected structure of the material, which lead to a fairly low thermal conductivity and better Seebeck coefficient. The finding of this work provides an understanding for exploring potential enhancement mechanisms and improving the thermoelectric properties of CNT-based thermoelectric composites.

scholarly journals RICE STRAW CELLULOSE AEROGELS

2018 ◽  
Vol 56 (2A) ◽  
pp. 118-125 ◽  
Author(s):  
Nguyen Truong Son
Keyword(s):  
Thermal Conductivity ◽  
Rice Straw ◽  
Freeze Drying ◽  
Soxhlet Extraction ◽  
High Porosity ◽  
Specific Density ◽  
Water Contact ◽  
X Ray ◽  
Oil Adsorption ◽  
Scanning Electron

In this study, cellulose was obtained from rice straw by dewaxing with Soxhlet extraction and treating with sodium hydroxide and hydrogen peroxide. The obtained cellulose was used to successfully fabricate cellulose aerogels with a binder by freeze drying technique. The materials were then functionalized with methyltrimethoxysilane (MTMS) to achieve hydrophobicity. The morphology, pore structure and other properties of the aerogels were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetrical analysis (TGA), thermal conductivity and water contact angle (WCA) measurements. The rice straw cellulose aerogels exhibited very low specific density (0.0412-0.0470 g/cm3), high porosity (> 96 %), superhydrophobicity (WCA > 137o) and low thermal conductivity (0.034-0.036 W/(m.K)). The aerogels showed good oil adsorption capacity of 15.66-16.09 g/g. 

scholarly journals Short-Chain Modified SiO2 with High Absorption of Organic PCM for Thermal Protection

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 657 ◽  
Author(s):  
Fuxian Wang ◽  
Shiyuan Gao ◽  
Jiachuan Pan ◽  
Xiaomei Li ◽  
Jian Liu
Keyword(s):  
Thermal Conductivity ◽  
Phase Change Materials ◽  
Thermal Protection ◽  
Short Chain ◽  
High Porosity ◽  
Step Method ◽  
Hydrophobic Property ◽  
Low Thermal Conductivity ◽  
Hydrophobic Sio2 ◽  
High Absorption

Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require “leak-proof” packaging materials with low thermal conductivity. Herein, we successfully modify SiO2 through a simple 2-step method consisting of n-hexane activation followed by short-chain alkane silanization. The modified SiO2 (M-SiO2) exhibits superior hydrophobic property while maintaining the intrinsic high porosity of SiO2. The surface modification significantly improves the absorption rate of RT60 in SiO2 by 38%. The M-SiO2/RT60 composite shows high latent heat of 180 J·g−1, low thermal conductivity of 0.178 W·m−1·K−1, and great heat capacity behavior in a high-power thermal circuit with low penetrated heating flow. Our results provide a simple approach for preparing hydrophobic SiO2 with high absorption of organic PCM for thermal protection applications.

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