scholarly journals Novel Nanofluid Based on Water-Loaded Delafossite CuAlO2 Nanowires: Structural and Thermal Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
H. Alhummiany
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Power Systems ◽  
Nuclear Power ◽  
Industrial Applications ◽  
X Ray ◽  
Volume Fractions ◽  
Engine Cooling ◽  
Delafossite Cualo2

Ultra-high cooling performance is a crucial requirement of many thermomechanical systems, such as microelectronic devices, engine cooling systems, nuclear power systems, chemical reactors, and refrigeration systems. Recent experimental results reveal the potential thermal properties of suspended nanometallics in conventional fluids. In this study, the facile synthesis of one-dimensional delafossite CuAlO2 nanowires by microwave hydrothermal treatment was presented. A novel type of nanofluid consisting of CuAlO2 nanowires suspended in distilled water at various volume fractions (0.0, 0.2, 0.4, and 0.6 wt%) was successfully synthesized using an easily scalable sonication method. The microstructures of as-synthesized CuAlO2 were investigated by adopting X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FESEM). Furthermore, the thermal conductivity and specific heat capacity of water-loaded nanofluid were measured at different volume fractions and temperatures. The results reveal a significant increase in thermal conductivity with increasing CuAlO2 loading levels and temperatures. The obtained results propound the fact that water-loaded delafossite CuAlO2 nanowires-based nanofluid is a promising candidate for future industrial applications.

scholarly journals Structural and thermoelectric properties of the Pr2Zr2O7 compound

2019 ◽  
pp. 4-9
Author(s):  
Adolfo Quiroz-Rodríguez ◽  
Cesia Guarneros-Aguilar ◽  
Ricardo Agustin-Serrano
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Crystal Size ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Increasing Temperature ◽  
Thermal Stability Of ◽  
Scanning Electron

In this research, it is presented a detailed study of the structural and thermoelectric properties of the pyrochlore zirconium Pr2Zr2O7 compound prepared by solid-state reaction (SSR) in air at ambient pressure. The synthesized sample was characterized using powder X-ray diffraction. The thermal stability of the thermoelectric compound (TE) Pr2Zr2O7 was tested by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Scanning electron microscopy shows that the crystal size varies between 0.69 and 2.81μm. Electrical conductivity (\sigma) of the sample calcined at 1400 °C presented values increase irregularly with the increasing temperature from 0.001 to 0.018 S cm-1 as expected in a semiconductor material. The thermal conductivity is lower than 0.44 - 775 W m-1 K-1 which is quite anomalous in comparison with the thermal conductivity of other oxides.

Solution-Based Synthesis of Magnesium Oxide Nanorods

1999 ◽  
Vol 581 ◽  
Author(s):  
Q. Wei ◽  
C.M. Lieber
Keyword(s):  
Electron Microscopy ◽  
Magnesium Oxide ◽  
Magnesium Chloride ◽  
Low Cost ◽  
Industrial Applications ◽  
Transformation Process ◽  
Matrix Composites ◽  
X Ray ◽  
Transmission Electron ◽  
Oxide Nanorods

ABSTRACTA solution-based synthesis route was developed to produce large quantities of MgO nanorods. Hydrated basic magnesium chloride, which has needle-like crystal structure, was used as a precursor. A subsequent two-step transformation process with magnesium hydroxide as an intermediate product was used to preserve the morphology of the precursor to yield magnesium oxide nanorods. Scanning electron microscopy, powder X-ray diffraction and energy dispersive X-ray spectroscopy show that the products are very pure (>95%) crystalline MgO nanorods with diameters from 40 nm to 200 nm and lengths 10 microns or longer. High-resolution transmission electron microscopy and electron diffraction further reveal that these MgO nanorods are single crystals and that the rod axis is along the <110> crystal direction. A model for the structural transformation from hydrated basic magnesium chloride to magnesium oxide has been developed and compared to our experimental results. This solution-based process can be easily scaled-up, and is a low-cost source of pure magnesium oxide nanorods needed in many industrial applications, for example, as reinforcing agents in matrix composites and as flux-pinning centers in high-TC superconductors.

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%.

scholarly journals Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 38
Author(s):  
Wei Song ◽  
Bailing Jiang ◽  
Dongdong Ji
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Anodic Oxidation ◽  
Arc Discharge ◽  
Al2o3 Coating ◽  
Compact Structure ◽  
X Ray ◽  
Amorphous Al2o3 ◽  
Scanning Electron

Amorphous Al2O3 coating with a thickness of 143 μm was firstly prepared by anodic oxidation, then the amorphous Al2O3 was transformed into crystalline Al2O3 through applying micro arc discharge. The crystal structure of the Al2O3 coatings was analyzed with an X-ray diffractometer. Results indicated that the coating consisted of amorphous and crystalline Al2O3. The microstructure of the coating was characterized by scanning electron microscopy, which showed that the coating had a compact structure. The thermal conductivity of the coating was 23.7 W/m·K, which is significantly higher than that of amorphous Al2O3 coating. The total and specific breakdown voltages of the coating were 3.85 kV and 26.92 kV/mm, which is suitable to apply for high power LED heat sink substrate.

scholarly journals Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

Cerâmica ◽  
2016 ◽  
Vol 62 (361) ◽  
pp. 1-8 ◽  
Author(s):  
J. L. Alves ◽  
A. E. Zanini ◽  
M. E. de Souza ◽  
M. L. F. Nascimento
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Rietveld Method ◽  
Bentonite Clay ◽  
Rietveld Analysis ◽  
Industrial Applications ◽  
X Ray Diffraction ◽  
X Ray ◽  
Almost All ◽  
Scanning Electron

Abstract Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitória da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale.

Enhancement of styrene-butadiene rubber composites using kaolin covered with metal oxide pigments

2015 ◽  
Vol 44 (2) ◽  
pp. 57-73 ◽  
Author(s):  
Salwa H El-Sabbagh ◽  
Nivin M. Ahmed
Keyword(s):  
Electron Microscopy ◽  
Thermal Properties ◽  
Metal Oxide ◽  
Styrene Butadiene Rubber ◽  
Core Shell ◽  
Butadiene Rubber ◽  
Rubber Composites ◽  
Content Type ◽  
X Ray ◽  
Styrene Butadiene

Purpose – This paper aims to express in detail the rheological, morphological and thermal properties of unpigmented and pigmented styrene-butadiene rubber composites with new prepared inorganic pigment based on kaolin covered with a thin layer of calcium and magnesium oxides or mixed oxide of both together. These new pigments combine the properties of both their constituents (kaolin and metal oxides), which are a new trend in inorganic pigments called core-shell pigments. The pigments used for comparison are kaolin (K), CaO/kaolin (CaO/K), MgO/kaolin (MgO/K) and CaO.MgO/kaolin (CaO.MgO/K). Design/methodology/approach – The different pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray diffraction, scanning electron microscopy/energy dispersive X-ray and transmission electron microscopy, while rubber vulcanizates' rheological, morphological, swelling and thermal properties were examined using different standard and instrumental testing and methods. Findings – The study revealed that there is a significant effect of the new prepared pigments on SBR properties, where the optimum pigment loading was 40 phr for CaO/kaolin, while it was 2.5 phr for MgO/kaolin. Studying the effect of different ratios of oxides on kaolin (5, 10 and 20 per cent), different loadings of these pigments ranging between 2.5 and 40 phr were done for each pigment. These modified kaolin or core-shell metal oxide/kaolin pigments imparted new and improved reinforcing properties to SBR vulcanizates. Research limitations/implications – No research limitations were found. Practical implications – Core-shell MgO/kaolin pigments are eco-friendly and can replace other expensive pigments that are usually used as fillers in the rubber industry with less expenses and comparable efficiency. Originality/value – These new pigments are cheap and efficient and can be used in different fields other than rubber.

scholarly journals Synthesis and thermal conductivity of functionalized biocarbon-Fe3O4 nanocomposite-based green nanofluid for heat transfer applications

2021 ◽  
Vol 321 ◽  
pp. 01003
Author(s):  
Divya Barai ◽  
Sohan Parbat ◽  
Bharat Bhanvase
Keyword(s):  
Heat Transfer ◽  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Nanocomposite Particles ◽  
X Ray ◽  
Conductivity Enhancement ◽  
Water Based ◽  
One Step ◽  
Ultrasound Assisted ◽  
Scanning Electron

Bio-based graphitic carbon was synthesized in this work by one-step carbonization of bamboo waste at low temperature. This bio-based carbon was then functionalized in order to decorated it with Fe3O4 nanoparticles. The functionalized biocarbon-Fe3O4 (f-biocarbon-Fe3O4) nanocomposite was synthesized using ultrasound-assisted coprecipitation method which was then confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry. Water-based nanofluid was prepared using the synthesized f-biocarbon-Fe3O4 nanocomposite particles. Thermal conductivity of this nanofluid was analyzed at different concentrations and temperatures. A thermal conductivity enhancement of almost 80% was recorded at 35°C for nanofluid containing 0.1 vol.% of f-biocarbon-Fe3O4 nanocomposite particles compared to water. Also, empirical model is developed for prediction of thermal conductivity as a function of concentration and temperature of bamboo waste-derived f-biocarbon-Fe3O4 nanocomposite-based green nanofluid.

Thermoelectric Properties of InxCo4-yNiySb12 Skutterudite Compounds

2007 ◽  
Vol 1044 ◽  
Author(s):  
Veronique Da Ros ◽  
Juliusz Leszczynski ◽  
Bertrand Lenoir ◽  
Anne Dauscher ◽  
Christophe Candolfi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Thermal Properties ◽  
Chemical Composition ◽  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
X Ray Diffraction ◽  
X Ray

AbstractThe preparation of partially filled n-type InxCo4Sb12 skutterudite compounds has been recently reported. The results were particularly promising, the materials exhibiting a ZT value far higher than one at moderated temperature. In this paper, we propose to investigate another way to tune the electrical and thermal properties by substituting Co atoms by Ni atoms in InxCo4Sb12. InxCo4-yNiySb12 polycrystalline samples have been prepared by a conventional metallurgical route. Structural analyses have been carried out by X-ray diffraction. The chemical composition and micro-homogeneity have been checked by electron probe microanalysis. Measurements of the electrical resistivity, thermoelectric power and thermal conductivity have been performed between 300 and 800 K. The influence of the presence of Ni on the thermoelectric properties of InxCo4Sb12 compounds is presented and discussed.

Effect of Preparation on Standard Dry Density and Strength of Foamed Cement by Orthogonal Test

2014 ◽  
Vol 577 ◽  
pp. 1119-1122
Author(s):  
Na Li ◽  
Qi Wang ◽  
Peng Song
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
High Strength ◽  
Xrd Analysis ◽  
Orthogonal Test ◽  
Dry Density ◽  
Light Weight ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

In this paper, we studied the effect of preparation on standard dry density and strength of foamed cement by orthogonal test. The results indicate that the more excellent combination is A1B1C1, namely G1, the standard dry density is 376 kg/m3, the flexural and compressive strengths are 0.43 MPa and 0.8 MPa respectively, and the thermal conductivity is 0.074 W/(m·K), which conforms to the characteristics of light weight and high strength. Fewer Ca (OH)2 crystals and more C-S-H gel generated in G1 through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis is the reason for its high strength.

Effect of the Consolidation Technique on the Sintering Ability and Thermal Properties of AlN Processed from Aqueous Suspensions

2006 ◽  
Vol 514-516 ◽  
pp. 1531-1535
Author(s):  
Susana M.H. Olhero ◽  
José Maria F. Ferreira
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Scanning Electron Microscopy ◽  
Slip Casting ◽  
Inert Atmosphere ◽  
Sintering Aids ◽  
X Ray ◽  
Aqueous Suspensions ◽  
Dry Pressing ◽  
Scanning Electron

In this work, two different consolidation techniques were used to obtain AlN samples: slip casting and dry pressing of granules obtained from aqueous suspensions by freeze granulation. The green samples were sintered at a temperature (1750°C) lower than those usually used (>1800°C), using CaF2 and YF3 as sintering aids. The microstructural features were analysed by scanning electron microscopy (SEM) and the crystalline phases formed were identified by X-ray (XRD). Full dense AlN-based ceramics were obtained from both consolidation techniques; however the thermal conductivity values were quite different. The presence of carbon in the samples derived from the freeze granulated powder containing organic processing additives de-waxed in an inert atmosphere revealed to be helpful in the cleaning of oxygen present at the grain boundaries and consequently, for enhancing the thermal conductivity.

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