Silica aerogel/epoxy composites with preserved aerogel pores and low thermal conductivity

e-Polymers ◽  
2015 ◽  
Vol 15 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Hyung Min Kim ◽  
Hyun Su Kim ◽  
Seong Yun Kim ◽  
Jae Ryoun Youn
Keyword(s):  
Thermal Conductivity ◽  
Water Glass ◽  
Epoxy Composite ◽  
Physical Factor ◽  
Silica Aerogels ◽  
Processing Method ◽  
Ethanol Evaporation ◽  
New Processing ◽  
Drying Conditions ◽  
The Relationship

AbstractThe thermal conductivity of aerogel/epoxy composite based on the inexpensive powder form of silica aerogels by using water glass under ambient drying conditions was evaluated to investigate the relationship between the internal structure and the thermal conductivity of the composite. A high thermal conductivity was obtained for the composite fabricated by the typical liquid epoxy processing because the pores of the aerogels became filled with the epoxy resin during the processing of the composite. A new processing method for preserving the aerogel pores was then developed using ethanol evaporation, which lowered the thermal conductivity of the composite. The lowest thermal conductivity of 0.04 W/m K was obtained for the composite containing the as-received aerogel of 75 vol% with preserved pores. The preserved aerogel pores in the composite were the most significant physical factor in determining the thermal conductivity of the composite.

Thermal Conductivity of Polymer/Carbon Nanotube Composites

2012 ◽  
Vol 714 ◽  
pp. 99-113 ◽  
Author(s):  
Manel Haddadi ◽  
Boudjemaa Agoudjil ◽  
Abderrahim Boudenne
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Processing Method ◽  
Nanotube Composites ◽  
Important Field ◽  
Carbon Nanotube Composites ◽  
Equivalent Property ◽  
New Generation ◽  
The Relationship

As one of the most important field of current nanoscience, the polymer nanocomposites is a promising and efficient way for new generation materials with high performances and multifunctionalities. The incorporating of nanofillers in a polymer matrix may improve mechanical, thermal, electrical or dielectric properties of the composites. The current paper focuses on the thermal conductivity of polymer/carbon nanotube composites. These last, are considered to be ideal candidates for the development of nanocomposite materials. Clarifying the role of the factors, influencing the properties of the composites, enable us to choose the suitable processing method for obtaining the composites and to improve the different properties of these systems. This article reviews the dependence of thermal conductivity of carbon nanotubes on the tube size and the effect of interface on the equivalent property. The relationship between the thermal conductivity and the nanostructure of composites are discussed.

An Experimental Investigation on Thermal Conductivity and Viscosity of Graphene doped CNTs /TiO2 Nanofluid

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
A.M. Zetty Akhtar ◽  
M.M. Rahman ◽  
K. Kadirgama ◽  
M.A. Maleque
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Minimum Quantity Lubrication ◽  
Cutting Fluid ◽  
Cutting Zone ◽  
Observation Method ◽  
The Stability ◽  
The Relationship ◽  
Zeta Potential Analysis

This paper presents the findings of the stability, thermal conductivity and viscosity of CNTs (doped with 10 wt% graphene)- TiO2 hybrid nanofluids under various concentrations. While the usage of cutting fluid in machining operation is necessary for removing the heat generated at the cutting zone, the excessive use of it could lead to environmental and health issue to the operators. Therefore, the minimum quantity lubrication (MQL) to replace the conventional flooding was introduced. The MQL method minimises the usage of cutting fluid as a step to achieve a cleaner environment and sustainable machining. However, the low thermal conductivity of the base fluid in the MQL system caused the insufficient removal of heat generated in the cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. The ethylene glycol used as the base fluid, titanium dioxide (TiO2) and carbon nanotubes (CNTs) nanoparticle mixed to produce nanofluids with concentrations of 0.02 to 0.1 wt.% with an interval of 0.02 wt%. The mixing ratio of TiO2: CNTs was 90:10 and ratio of SDBS (surfactant): CNTs was 10:1. The stability of nanofluid checked using observation method and zeta potential analysis. The thermal conductivity and viscosity of suspension were measured at a temperature range between 30˚C to 70˚C (with increment of 10˚C) to determine the relationship between concentration and temperature on nanofluid’s thermal physical properties. Based on the results obtained, zeta potential value for nanofluid range from -50 to -70 mV indicates a good stability of the suspension. Thermal conductivity of nanofluid increases as an increase of temperature and enhancement ratio is within the range of 1.51 to 4.53 compared to the base fluid. Meanwhile, the viscosity of nanofluid shows decrements with an increase of the temperature remarks significant advantage in pumping power. The developed nanofluid in this study found to be stable with enhanced thermal conductivity and decrease in viscosity, which at once make it possible to be use as nanolubricant in machining operation.

scholarly journals Effect of microstructure on the properties of polystyrene microporous foaming material

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 103-110
Author(s):  
Anfu Guo ◽  
Hui Li ◽  
Jie Xu ◽  
Jianfeng Li ◽  
Fangyi Li
Keyword(s):  
Thermal Conductivity ◽  
Compression Modulus ◽  
Cell Diameter ◽  
Compressive Property ◽  
Strength Increase ◽  
Compression Performance ◽  
Negative Linear Correlation ◽  
Sample Density ◽  
Foaming Temperature ◽  
The Relationship

AbstractThe performance of Polystyrene microporous foaming (PS-MCF) materials is influenced by their microstructures. Therefore, it is essential for industrializing them to investigate the relationship between their microstructure and material properties. In this study, the relationship between the microstructure, compressive property, and thermal conductivity of the PS-MCF materials was studied systematically. The results show that the ideal foaming pressure of PS-MCF materials, obtaining compression performance, is around 20 MPa. In addition, the increase of temperature causes the decrease of sample density. It effects that the compression modulus and strength increase with the decrease of foaming temperature. Because the expansion rate and cell diameter of the PS-MCF materials reduce the thickness of cell wall, they are also negatively correlated with their mechanical properties. Moreover, there is a negative linear correlation between the thermal conductivity and cell rate, whereas the cell diameter is positively correlated with the thermal conductivity.

scholarly journals Improving the Actuation Speed and Multi-Cyclic Actuation Characteristics of Silicone/Ethanol Soft Actuators

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 62 ◽  
Author(s):  
Boxi Xia ◽  
Aslan Miriyev ◽  
Cesar Trujillo ◽  
Neil Chen ◽  
Mark Cartolano ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Short Term Memory ◽  
Conductive Filler ◽  
Thermally Driven ◽  
Thermally Conductive ◽  
Ethanol Evaporation ◽  
Long Short Term Memory ◽  
Soft Actuators ◽  
Robotic Applications ◽  
Soft Composite

The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.

Observation of Pressure Drop Behavior in an Operating Fuel Cell Stack

2005 ◽  
Author(s):  
Frano Barbir ◽  
Haluk Gorgun ◽  
Xinting Wang
Keyword(s):  
Fuel Cell ◽  
Pressure Drop ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Cathode Side ◽  
Fuel Cell Stack ◽  
Flow Through ◽  
Drying Conditions ◽  
Exchange Membrane ◽  
The Relationship

Pressure drop on the cathode side of a PEM (Proton Exchange Membrane) fuel cell stack has been studied and used as a diagnostic tool. Since the Reynolds number at the beginning of the flow field channel was <250, the flow through the channel is laminar, and the relationship between the pressure drop and the flow rate is linear. Some departure from linearity was observed when water was either introduced in the stack or produced inside the stack in the electrochemical reaction. By monitoring the pressure drop in conjunction with the cell resistance in an operational fuel cell stack, it was possible to diagnose either flooding or drying conditions inside the stack.

Thermal conductivity investigations of granular and powdered silica aerogels at different temperatures and pressures

2016 ◽  
Vol 118 ◽  
pp. 226-231 ◽  
Author(s):  
Gaosheng Wei ◽  
Lixin Wang ◽  
Chao Xu ◽  
Xiaoze Du ◽  
Yongping Yang
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogels ◽  
Different Temperatures

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.

Studies on Thermal Property of Silica Aerogel/Epoxy Composite

2007 ◽  
Vol 546-549 ◽  
pp. 1581-1584 ◽  
Author(s):  
Jiu Peng Zhao ◽  
Deng Teng Ge ◽  
Sai Lei Zhang ◽  
Xi Long Wei
Keyword(s):  
Thermal Conductivity ◽  
Thermal Property ◽  
Epoxy Resin ◽  
Silica Aerogel ◽  
Epoxy Composite ◽  
Transfer Model ◽  
Insulation Material ◽  
Thermal Transfer ◽  
Heat Distortion Temperature ◽  
Ft Ir

Silica aerogel/epoxy composite, a kind of efficient thermal insulation material, was prepared by doping silica aerogel of different sizes into epoxy resin through thermocuring process. The results of thermal experiments showed that silica aerogel/epoxy composite had a lower thermal conductivity (0.105W/(m·k) at 60 wt% silica aerogel) and higher serviceability temperature (Martens heat distortion temperature: 160°C at 20 wt% silica aerogel). In addition, the composite doping larger size (0.2-2mm) of silica aerogel particle had lower thermal conductivity and higher Martens heat distortion temperature. Based on the results of SEM and FT-IR, the thermal transfer model was established. Thermal transfer mechanism and the reasons of higher Martens heat distortion temperature have been discussed respectively.

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