Probing the Effects of Alloying, Grain Size, and Turbostratic Disorder on Thermal Conductivity

2011 ◽  
Vol 3 (4) ◽  
pp. 639-645 ◽  
Author(s):  
Clay Mortensen ◽  
Matt Beekman ◽  
David C. Johnson
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Turbostratic Disorder

High thermal conductivity of pure dense SiC ceramics prepared via HTPVT

2019 ◽  
Vol 12 (03) ◽  
pp. 1950032 ◽  
Author(s):  
Yuchen Deng ◽  
Yaming Zhang ◽  
Nanlong Zhang ◽  
Qiang Zhi ◽  
Bo Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Carbide ◽  
Grain Size ◽  
Phase Composition ◽  
Room Temperature ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Growth Substrate ◽  
Sic Ceramics ◽  
Evolution Of Microstructure

Pure dense silicon carbide (SiC) ceramics were obtained via the high-temperature physical vapor transport (HTPVT) method using graphite paper as the growth substrate. The phase composition, the evolution of microstructure, the thermal diffusivity and thermal conductivity at RT to 200∘C were investigated. The obtained samples had a relative density of higher than 98.7% and a large grain size of 1[Formula: see text]mm, the samples also had a room-temperature thermal conductivity of [Formula: see text] and with the temperature increased to 200∘C, the thermal conductivity still maintained at [Formula: see text].

scholarly journals THE EFFECT GRAIN-SIZE COMPOSITION ON THERMAL CONDUCTIVITY OF SANDY SOILS

2020 ◽  
Vol 11 (2) ◽  
pp. 19-27
Author(s):  
A. V Zakharov ◽  
S. E Makhover
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Sandy Soil ◽  
Alternative Energy ◽  
Radiant Energy ◽  
Sandy Soils ◽  
Size Composition ◽  
Experiment Planning ◽  
Pore Filling ◽  
Grain Size Composition

Today the issue of energy saving is acute. The main sources of energy are radiant energy of the Sun, wind energy, energy of moving water. Therefore, the issue of solving alternative energy sources is relevant. The article aims to solve the problem by using low-potential heat of the soil mass by means of energy-efficient building constructions - foundations. It is necessary to know the thermal characteristics of soils for this. At the moment, methods for determining the thermophysical properties of inert materials with subsequent practical application in the field of construction have been widely studied, but no one of these methods takes into account the grain-size composition. Thus, the study of the connection between the thermal conductivity and the grain-size composition of the soil is important. The aim of the work is to Estimation of thermal conductivity of sandy soils based on grain-size composition. This article presents an analysis of the dependence of the thermal conductivity of the sandy soil of its grain-size composition. The matrix of experiment planning is made; the methodology and technological sequence of the experiment were tested. Statistical processing of the obtained experimental data was carried out. Based on a series of test experiments, it was concluded that there are two factors competing in its thermal conductivity: an increase in λ due to an increase in the degree of pore filling and a decrease in total heat conductivity due to a decrease in the degree of pore filling. These results suggest that grain-size composition has an impact on the thermal conductivity of the sandy soil. During the experiment, the dependence of the thermal conductivity of sandy soils on their grain-size composition was experimentally established.

Thermal Diffusivity and Conductivity of La0.7Ca0.3-xSrxMnO3 (x=0 to 0.10)

2012 ◽  
Vol 501 ◽  
pp. 319-323
Author(s):  
Hasan A. Alwi ◽  
Lay S. Ewe ◽  
Zahari Ibrahim ◽  
Noor B. Ibrahim ◽  
Roslan Abd-Shukor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Electronic Contribution ◽  
Insulator Metal Transition ◽  
Thermal And Electrical Properties

We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.

Effect of grain size on low-temperature electrical resistivity and thermal conductivity of pure magnesium

2018 ◽  
Vol 229 ◽  
pp. 261-264 ◽  
Author(s):  
Xin Tong ◽  
Guoqiang You ◽  
Yuhan Ding ◽  
Hansong Xue ◽  
Yichang Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Electrical Resistivity ◽  
Low Temperature ◽  
Pure Magnesium

Thermal Conductivity of Si₃N₄ Ceramics Fabricated From Carbothermal-reduction-derived Powder

2021 ◽  
Author(s):  
Yuelong Wang ◽  
Xingyu Li ◽  
Haoyang Wu ◽  
Baorui Jia ◽  
Deyin Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Fracture Toughness ◽  
Grain Size ◽  
Flexural Strength ◽  
Grain Boundaries ◽  
Carbothermal Reduction ◽  
Secondary Phase ◽  
Gas Pressure ◽  
Gas Pressure Sintering

Abstract Si3N4-based ceramic (Si3N4-5wt%Y2O3-3wt%MgO) was obtained from carbothermal-reduction-derived powder combined with gas pressure sintering. The phase, microstructure, thermal conductivity and mechanical properties of Si3N4 ceramics were comprehensively analyzed. Dense Si3N4 ceramic with uniform grain size was obtained after sintering at 1900°C for 7 h under a N2 pressure of 1.2 MPa. The secondary phase consisted of Y4Si2O7N2 and Y2Si3O3N4 was found to gather around triangular grain boundaries. The thermal conductivity, flexural strength, hardness and fracture toughness of the Si3N4 ceramics were 95.7 W·m-1·k-1, 715 MPa, 17.2 GPa and 7.2 MPa·m1/2, respectively. The results were compared with product derived from commercial powder, the improvement of thermal conductivity (~8.3%) and fracture toughness (~4.3%) demonstrating the superiority of Si3N4 ceramics prepared from carbothermal-reduction-derived powder.

scholarly journals Effect of Grain Size and Film Thickness on the Thermoelectric Properties of Flexible Sb2Te3 Thin Films

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Pornsiri Wanarattikan ◽  
Piya Jitthammapirom ◽  
Rachsak Sakdanuphab ◽  
Aparporn Sakulkalavek
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Film Thickness ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Flexible Substrate ◽  
Rf Magnetron Sputtering ◽  
Mean Free Path

In this work, stoichiometric Sb2Te3 thin films with various thicknesses were deposited on a flexible substrate using RF magnetron sputtering. The grain size and thickness effects on the thermoelectric properties, such as the Seebeck coefficient (S), electrical conductivity (σ), power factor (PF), and thermal conductivity (k), were investigated. The results show that the grain size was directly related to film thickness. As the film thickness increased, the grain size also increased. The Seebeck coefficient and electrical conductivity corresponded to the grain size of the films. The mean free path of carriers increases as the grain size increases, resulting in a decrease in the Seebeck coefficient and increase in electrical conductivity. Electrical conductivity strongly affects the temperature dependence of PF which results in the highest value of 7.5 × 10−4 W/m·K2 at 250°C for film thickness thicker than 1 µm. In the thermal conductivity mechanism, film thickness affects the dominance of phonons or carriers. For film thicknesses less than 1 µm, the behaviour of the phonons is dominant, while both are dominant for film thicknesses greater than 1 µm. Control of the grain size and film thickness is thus critical for controlling the performance of Sb2Te3 thin films.

Microwave Processing of Ceramics

2006 ◽  
Vol 45 ◽  
pp. 857-862 ◽  
Author(s):  
Isabel K. Lloyd ◽  
Yuval Carmel ◽  
Otto C. Wilson Jr. ◽  
Geng Fu Xu
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Heating Rate ◽  
Thermal Gradients ◽  
Heating Rates ◽  
Volumetric Heating ◽  
Wide Range ◽  
Conventional Sintering ◽  
Atmosphere Control ◽  
Very High

Microwave (MW) processing is advantageous for processing ceramics with tailored microstructures. Its combination of volumetric heating, a wide range of controlled heating rates, atmosphere control and the ability to reach very high temperatures allows processing of 'difficult' materials like high thermal conductivity AlN and AlN composites and microstructure control in more readily sintered ceramics such as ZnO. MW sintering promotes development of thermal conductivity in AlN (225 W/mK) and its composites (up to 150W/mK inAlN-TiB2 and up to 129 W/mK in AlN-SiC when solid solution is avoided). In ZnO, heating rate controls sintered grain size. Increasing the heating rate from 5°C/min. to 4900°C decreases grain size from ~10 μm (comparable to conventional sintering of the same powder) to nearly the starting particle size (~ 1μm). Microstructural uniformity increases with sintering rate since ultra-rapid MW sintering minimizes the development of thermal gradients due to heat loss.

scholarly journals Synthesis of AG Nanocrystal/Few-Layer Graphite Nanoplatelet Composites

2018 ◽  
Vol 27 (2) ◽  
pp. 096369351802700
Author(s):  
Shasha li ◽  
Nailiang Liu ◽  
Changqing Fang
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Electroless Plating ◽  
Organic Materials ◽  
Treatment Results ◽  
Plating Method ◽  
Distinct Boundary ◽  
Electroless Plating Method

The present study focuses on improving the combination of graphite nanoplatelet (GNP) with other organic materials without reducing its properties. An Ag nanocrystal was synthesized by electroless plating method under sonication at 40 °C, which was coated densely onto few-layer GNP and hexagon-slice GNP that was found during GNP treatment. Results illustrated that the Ag nanocrystal had uniform grain size and distinct boundary covered onto GNP. The thermal conductivity of the Ag nanocrystal /few-layer GNP (Ag/GNP) composite was superior to that of the GNP material. In addition, the Ag/GNP composite exhibited excellent electrical conductivity.

scholarly journals Grain-size effects on the thermal conductivity of nanosolids

2016 ◽  
Vol 10 (3) ◽  
pp. 375-380 ◽  
Author(s):  
Madan Singh ◽  
Kopang Khotso Hlabana ◽  
Sanjay Singhal ◽  
Kamal Devlal
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Size Effects ◽  
Grain Size Effects

Effects of grain size of AISI 304 on the machining performances in micro electrical discharge machining

2016 ◽  
Vol 231 (2) ◽  
pp. 359-366 ◽  
Author(s):  
Qingyu Liu ◽  
Qinhe Zhang ◽  
Min Zhang ◽  
Jianhua Zhang
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Melting Point ◽  
Grain Boundary ◽  
Electrical Discharge ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
Aisi 304 ◽  
Micro Electrical Discharge Machining

The material removal process of micro electrical discharge machining is based on the instantaneous ultra-high temperature generated by a series of repetitive discharge pulses. Due to the size effects, the polycrystal cannot be considered as continuous and homogeneous material when machining is in micron scale, and the effects of material microstructure should not be neglected. In this article, the thermoelectric characteristics of grain and grain boundary are discussed, and the influence of grain size on the machining performances in micro electrical discharge machining is researched. Two kinds of austenitic stainless steels (AISI 304) which are different in grain size are chosen as the workpieces in experiments. It is verified by both theory models and experimental results that the smaller the grain size, the higher the material removal rate, under the same discharge conditions. Both thermal conductivity and melting point of the grain boundary are lower than those of the grain because of the grain boundary segregation. The effective thermal conductivity and local effective melting point of polycrystalline materials vary with their grain sizes since the grain boundary volume fractions change. As a consequence, the material removal rate of micro electrical discharge machining has direct relationship with grain size of the workpiece.

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