scholarly journals Computational prediction of electrical and thermal properties of graphene and BaTiO3 reinforced epoxy nanocomposites

2021 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
Raghvendra Kumar Mishra ◽  
Saurav Goel ◽  
Hamed Yazdani Nezhad
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Graphene Oxide ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Epoxy Matrix ◽  
Dc Conductivity ◽  
Neat Epoxy ◽  
Filler Materials ◽  
Volume Percentage

Graphene based materials e.g., graphene oxide (GO), reduced graphene oxide (RGO) and graphene nano platelets (GNP) as well as Barium titanate (BaTiO3) are emerging reinforcing agents which upon mixing with epoxy provides composite materials with superior mechanical, electrical and thermal properties as well as shielding against electromagnetic (EM) radiations. Inclusion of the aforementioned reinforcing agents has shown to improve the performance, however, the extent of improvement has remained uncertain. In this study, a computational modelling approach was adopted using COMSOL Multiphysics software in conjunction with Bayesian statistical analysis to investigate the effects of including various filler materials e.g. GO, RGO, GNP and BaTiO3 in influencing the direct current (DC) conductivity (σ), dielectric constant (ε) and thermal properties on the resulting epoxy polymer matrix composites. The simulation of epoxy composites were performed for different volume percentage of the filler materials by varying the geometry of the filler material. It was observed that the content of GO, RGO, GNPs and the thickness of graphene nanoplatelets can alter the DC conductivity, dielectric constant, and thermal properties of the epoxy matrix. The lower thickness of GNPs was found to offer the larger value of DC conductivity, thermal conductivity and thermal diffusivity than rest of the graphene nanocomposites, while, the RGO showed better dielectric constant value than neat epoxy, and GO, GNP nanocomposites. Similarly, BaTiO3 nanoparticles content and diameter were observed to alter the dielectric constant, DC conductivity and thermal properties of modified epoxy in several order magnitude than neat epoxy. In this way, the higher diameter particles of BaTiO3 showed better DC conductivity properties, dielectric constant value, thermal conductivity and thermal diffusivity. Moreover, this research provides guidance for further computational examination on the selection of GNP and BaTiO3 materials for the enhancement of the electrical and thermal properties of the epoxy matrix.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

scholarly journals Application of sonication and freezing as initial treatments before microwave-vacuum drying of cranberries

2019 ◽  
Vol 2 (22) ◽  
pp. 151-167 ◽  
Author(s):  
Izabela Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Physical Properties ◽  
Color Change ◽  
Vacuum Drying ◽  
Drying Time ◽  
Dried Fruits ◽  
Microwave Vacuum Drying ◽  
Drying Kinetic

The aim of study was to determine the influence of sonication and freezing on the kinetic of the microwave-vacuum drying, energy consumption and physical properties of whole cranberries as well as evaluate the applicability of sonication instead of freezing in order to change their physical properties and the drying kinetic of whole cranberries. Microwave-vacuum drying of whole cranberries with/without initial treatments took from 12 ± 1 to 14.5 ± 0.5 minutes. All of treatments did not significantly shorten the drying time of cranberries. However, they increased SMER values even by 31%. Despite of cryogenic freezing, all of treatments significantly increased the values of Dew. Sonication combined with drying allowed to obtain dried berries characterized by the lowest cohesiveness (0.19±0.02), springiness (0.62±0.02) and chewiness (3.4±0.8 N), while cryogenic freezing combined with drying allowed to obtain dried fruits characterized by highest springiness (0.75±0.03) and low chewiness (3.3±0.5 N). The highest lightness (32.2±0.7), redness (32.6±0.8), and yellowness (11.1±0.7) were found for fruits subjected to initial convective freezing before drying. The efficiency of sonication in color change was comparable to cryogenic freezing and much lower than convective freezing. All of initial treatments increased such thermal properties of dried cranberries as thermal conductivity and thermal diffusivity.

Exceptionally high thermal and electrical conductivity of three-dimensional graphene-foam-based polymer composites

RSC Advances ◽  
2016 ◽  
Vol 6 (27) ◽  
pp. 22364-22369 ◽  
Author(s):  
Zhiduo Liu ◽  
Dianyu Shen ◽  
Jinhong Yu ◽  
Wen Dai ◽  
Chaoyang Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Polymer Composites ◽  
Epoxy Matrix ◽  
Three Dimensional ◽  
Neat Epoxy ◽  
Graphene Foam

Three dimensional graphene foam incorporated into epoxy matrix greatly enhance its thermal conductivity (up to 1.52 W mK−1) at low graphene foam loading (5.0 wt%), over an eight-fold enhancement in comparison with that of neat epoxy.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Thermal Properties of Thin Metallic Layer Deposited on Insulators: Effect of the Interface on the Independent Determination of the Thermal Diffusivity and Conductivity of the Layer

2008 ◽  
Author(s):  
Danie`le Fournier ◽  
Jean Paul Roger ◽  
Christian Fretigny
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Thermal Resistance ◽  
Thermal Contact ◽  
Heat Diffusion ◽  
Metallic Layer ◽  
Good Thermal Contact ◽  
Lateral Heat

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.

scholarly journals Experimental investigations on graphene oxide/rubber composite thermal conductivity

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Joanna Wilk ◽  
Robert Smusz ◽  
Ryszard Filip ◽  
Grzegorz Chmiel ◽  
Tomasz Bednarczyk
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Thermal Properties ◽  
Reduced Graphene Oxide ◽  
Matrix Material ◽  
Oxide Content ◽  
Rubber Composites ◽  
Plate Method ◽  
Basic Matrix ◽  
Reduced Graphene

Abstract Graphene oxide/rubber composites were experimentally investigated for obtaining their thermal properties. Three kinds of the composite matrix material have been used: NBR, HNBR and FKM. The reduced graphene oxide in the form of crumped flakes has been applied as the filler influencing on thermal conductivity of the composites. Two values of graphene oxide weight concentration have been taken into account in the investigation. Thermal conductivity of the composites and basic matrix has been measured by the professional apparatus with the use of the guarded heat plate method. Before measurements the preliminary tests using the simplified comparative method have been performed. The results obtained, both from preliminary tests and using the guarded heat plate method, show an increase in thermal conductivity with increasing the reduced graphene oxide content in the composite. The experimental investigation allowed to determine not only the increase in thermal properties of graphene oxide/rubber composites compared to the basic matrix, but also the absolute values of thermal conductivities. Additionally, the SEM analysis showed that the tested composite samples contain agglomerates of the rGO nanoparticles. The occurrence of agglomerates could affect the composite thermal properties. This was noticed in the comparatively measurements of the temperature of different composites during the heating of samples tested. The maximum enhancement of thermal conductivity obtained was about 11% compared to the basis matrix of the composites tested.

scholarly journals Improved Performance of an Epoxy Matrix as a Result of Combining Graphene Oxide and Reduced Graphene

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
L. Ramos-Galicia ◽  
L. N. Mendez ◽  
Ana Laura Martínez-Hernández ◽  
A. Espindola-Gonzalez ◽  
I. R. Galindo-Esquivel ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Graphene Oxide ◽  
Modulus Of Elasticity ◽  
Epoxy Matrix ◽  
Neat Epoxy ◽  
Synergic Effect ◽  
Reduced Graphene ◽  
Improved Performance ◽  
Tensile Toughness

We present an easy and effective way to improve the mechanical properties of an epoxy matrix by reinforcing it with a combination of graphene oxide (GO) and reduced graphene oxide (RGO). These nanocomposites were prepared with different load of nanofillers: 0.1, 0.4, 0.7, 1.0 wt% and a neat epoxy. Ratios of graphene oxide and reduced graphene (GO : RGO) employed were: 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0. Results show that with only 0.4 wt% and a ratio 0.2 : 0.75 of GO : RGO, tensile strength and tensile toughness are 52% and 152% higher than neat epoxy while modulus of elasticity was improved~20%. The obtained results suggest that it is possible achieve advantageous properties by combining graphene in oxidized and reduced conditions as it shows a synergic effect by the presence of both nanofillers.

Thermal Properties of Tungsten SRM’S 730 and 799

1978 ◽  
Vol 100 (2) ◽  
pp. 330-333 ◽  
Author(s):  
R. E. Taylor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Thermal Properties ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Standard Material ◽  
International Program ◽  
Sintered Tungsten

Samples of sintered and arc-cast tungsten are available from NBS as thermal conductivity (SRM 730) and electrical resistivity (SRM 799) standards for the temperature range from 4 to 3000K. NBS recommended values for these properties above room temperature are based on results of various researchers during a previous international program which included arc-cast and sintered tungsten. The sintered tungsten used in this program was found to be unsuited for use as a standard material due to inhomogeneity and high temperature instability. The present paper gives results at high temperatures for thermal conductivity, electrical resistivity, specific heat, thermal diffusivity and Wiedemann-Franz-Lorenz ratio for a sample of the NBS sintered tungsten using the Properties Research Laboratory’s multiproperty apparatus. These results are compared to values recommended by the Thermophysical Properties Research Center, NBS, and an international program.

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