Thermal Conductivity: I, Concepts of Measurement and Factors Affecting Thermal Conductivity of Ceramic Materials

1954 ◽  
Vol 37 (2) ◽  
pp. 67-72 ◽  
Author(s):  
W. D. KINGERY ◽  
M. C. McQUARRIE
Keyword(s):  
Thermal Conductivity ◽  
Ceramic Materials ◽  
Factors Affecting

scholarly journals SYNTHESIS AND CHARACTERIZATION OF GREENER CERAMIC MATERIALS WITH LOWER THERMAL CONDUCTIVITY USING OLIVE MILL SOLID BYPRODUCT

2020 ◽  
Vol 1 ◽  
pp. 96-106 ◽  
Author(s):  
Xenofon Spiliotis ◽  
Vayos Karayannis ◽  
Stylianos Lamprakopoulos ◽  
Konstantinos Ntampegliotis ◽  
George Papapolymerou
Keyword(s):  
Thermal Conductivity ◽  
Solid Waste ◽  
Energy Savings ◽  
Sintering Temperature ◽  
Ceramic Body ◽  
Ceramic Materials ◽  
Raw Material ◽  
Gravimetric Analysis ◽  
Olive Mill Solid Waste ◽  
Olive Mill

In the current research, the valorization of olive mill solid waste as beneficial admixture into clay bodies for developing greener ceramic materials with lower thermal conductivity, thus with increased thermal insulation capacity towards energy savings, is investigated. Various clay/waste mixtures were prepared. The raw material mixtures were characterized and subjected to thermal gravimetric analysis, in order to optimize the mineral composition and maintain calcium and magnesium oxides content to a minimum. Test specimens were formed employing extrusion and then sintering procedure at different peak temperatures. Apparent density, water absorption capability, mechanical strength, porosity and thermal conductivity were determined on sintered specimens and examined in relation to the waste percentage and sintering temperature. The experimental results showed that ceramic production from clay/olive-mill solid waste mixtures is feasible. In fact, the mechanical properties are not significantly impacted with the incorporation of the waste in the ceramic body. However, the thermal conductivity decreases significantly, which can be of particular interest for thermal insulating materials development. Furthermore, the shape of the produced ceramics does not appear to change with the sintering temperature increase.

scholarly journals Thermal Conductive Networks Constructed by Sialon Fibers in-Situ Synthesized in Barium Aluminosilicate Glass-Ceramic

2021 ◽  
Author(s):  
Shaojie Sun ◽  
Xinyu Wang ◽  
Junjie Zhou ◽  
Siqi Zhang ◽  
Kongyu Ge ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Glass Ceramic ◽  
Ceramic Matrix Composite ◽  
Theoretical Models ◽  
Ceramic Materials ◽  
Aluminosilicate Glass ◽  
Complex Shapes ◽  
Barium Aluminosilicate ◽  
Enhanced Thermal Conductivity

Abstract The application of ceramic materials is limited due to the complicated preparation process and intrinsic brittleness. In this work, a pressureless manufacturing route that enables the formation of barium aluminosilicate (BAS) glass-ceramic consisting of internal β-Sialon fibers with enhanced thermal conductivity is developed. By adjusting the carbon source content, composites with different Sialon contents can be easily fabricated. The thermal conductivity of the sample with 3.5 wt.% is improved to 5.845 W/m ∙ K with the Sialon content of 26 wt.% in the composite, which is 112.64 % higher than that of the pure BAS matrix. The theoretical models suggest that the enhanced thermal conductivity is mainly ascribed to the thermal conduction network constructed by Sialon fibers. This work provides a method with industrial application prosperity to fabricate the high temperature ceramic matrix composite of different sizes and complex shapes.

scholarly journals Thermoelectric Study of La2Ti2-xNbxO7 (0≤x≤0.25) Ceramic Materials

2020 ◽  
pp. 38-47
Author(s):  
A. C. Iyasara ◽  
F. U. Idu ◽  
E. O. Nwabineli ◽  
T. C. Azubuike ◽  
C. V. Arinze
Keyword(s):  
Crystal Structure ◽  
Thermal Conductivity ◽  
Solid State ◽  
Single Phase ◽  
Ceramic Materials ◽  
Solid State Reaction Method ◽  
Reaction Method ◽  
Reducing Atmosphere ◽  
High Seebeck Coefficient ◽  
Porous Microstructures

La2Ti2-xNbxO7 (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) powders were synthesised via solid state reaction method, followed by sintering at 1673 K in a reducing atmosphere of 5% H2/N2 gas. The crystal structure, microstructure and thermoelectric (TE) properties of the pure and Nb-doped La2Ti2O7 ceramics were investigated. All compositions were single phase with porous microstructures consistent with their low experimental densities. Thermoelectric results of Nb-doped compositions showed improved properties in comparison to pure La2Ti2O7, suggesting that cation doping has the potential to improve the thermoelectric properties. Generally, the TE results obtained are not suitable for thermoelectric applications. However, the high Seebeck coefficient (≥190 μV/K) and glass-like thermal conductivity ( ≤2.26 w / m.k )  values achieved have opened a new window for exploring the thermoelectric potentials of La2Ti2O7 and other related oxides.

Stable, highly concentrated suspensions for electronic and ceramic materials applications

1991 ◽  
Vol 6 (5) ◽  
pp. 1082-1093 ◽  
Author(s):  
I. Sushumna ◽  
R.K. Gupta ◽  
E. Ruckenstein
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Ceramic Materials ◽  
Rheological Characteristics ◽  
Concentrated Suspensions ◽  
Thermal Paste ◽  
Electrical Conductivities ◽  
Liquid Suspensions ◽  
Very High ◽  
Highly Loaded

Highly concentrated solid-in-liquid suspensions find applications in a number of areas such as electronics, ceramics, paints, coatings, etc. Highly loaded, stable suspensions which exhibit desirable rheological characteristics (moderate viscosity, shear thinning behavior, thixotropy, and a small yield stress, for example), and which have high thermal or electrical conductivities are frequently sought after. We describe here some techniques which can be used to obtain such highly concentrated suspensions. These involve employing mixed size grades of particles and effective dispersants. For thermal paste applications, for example, compliant pastes of up to 78 vol. % solids with thermal conductivity values as high as 6 W/mK (hence, a few times greater than the values reported previously by others), low electrical conductivity, and moderate viscosity have been prepared by mixing different particle size grades of materials such as Al2O3, SiC, AlN, Al, and diamond. Effective dispersants, both commercial as well as those synthesized in our laboratory as novel variations of previously known molecular architectures, have been used to facilitate the achievement of these very high loading and stable suspensions.

The Machining Characteristics of Insulating AlN Ceramics by EDM

2012 ◽  
Vol 523-524 ◽  
pp. 328-331
Author(s):  
Kensei Kaneko ◽  
Ken Yamashita ◽  
Yasushi Fukuzawa
Keyword(s):  
Thermal Conductivity ◽  
Removal Rate ◽  
Ceramic Materials ◽  
High Thermal Conductivity ◽  
Electrode Wear ◽  
Machining Time ◽  
Laser Method ◽  
Wear Ratio ◽  
Machining Properties ◽  
Machining Characteristics

AlN ceramic materials have high thermal conductivity and electrical insulation, prompting consideration of their use as a semiconducting material. Although AlN should be machined with a high accuracy of form and dimension to achieve products and components with requisite precision, mechanical and other machining methods such as the micro blasting technology or laser method cannot be used because of the brittleness and high thermal conductivity of AIN. Recently, we have succeeded in machining many insulating ceramics by EDM with the assisting electrode method. We have already machined many insulating ceramic materials such as Si3N4, ZrO2 and Al2O3. However, inferior machining characteristics were obtained with AlN than with other materials. In this study, the effects of several electrical discharge conditions were examined to obtain better machining properties, such as high material removal rate and a low electrode wear ratio. It was found that machining time decreased with an increase in capacitance, while the electrode wear ratio increased. In addition, the machining hole profiles were straight along the depth direction, and the shape of holes was non-tapered

Enhanced Thermal Conductivity for Graphene Nanoplatelets/Epoxy Resin Composites

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Dahai Zhu ◽  
Yu Qi ◽  
Wei Yu ◽  
Lifei Chen ◽  
Mingzhu Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Epoxy Resin ◽  
Mass Fraction ◽  
Great Influence ◽  
Graphene Nanoplatelets ◽  
Resin Matrix ◽  
Heat Conducting ◽  
Factors Affecting ◽  
Molding Method ◽  
Ep Matrix

Graphene nanoplatelets (GNPs) have excellent thermal conductivity. It can significantly improve the heat-conducting property of epoxy resin (EP) matrix. In this paper, the GNPs/EP composites were successfully prepared by using ultrasonication and the cast molding method. The prepared GNPs/EP composites were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal conductivity analyzer. Some factors affecting the thermal transfer performance of the composites were discussed. The defoamation has great influence on the thermal conductivity of composite. There is a nearly linear relationship between the mass fraction and the thermal conductivity of composite when the mass fraction of GNPs is below 4.3%. The results show that when the mass fraction of GNPs is 4.3% with crushing time of 2 s, the thermal conductivity of GNPs/EP composite is up to 0.99 W/m K. The thermal conductivity is increased by 9.0% compared with that without pulverization treatment (0.91 W/m K). When it is ground three times, the thermal conductivity of composite reaches the maximum (1.06 W/m K) and it is increased by 307.7% compared with that of epoxy resin matrix.

A review of factors affecting minimum temperature reached on clear, windless nights.

1991 ◽  
Vol 42 (1) ◽  
pp. 191 ◽  
Author(s):  
WK Gardner ◽  
GK McDonald ◽  
SE Ellis ◽  
M Platt ◽  
RG Flood
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Water Content ◽  
Temperature Profiles ◽  
Surface Emissivity ◽  
Factors Affecting ◽  
Surface Temperatures ◽  
Net Flux ◽  
Soil Heat Capacity ◽  
Initial Starting

A mathematical model of heat flux in which net flux was assumed to be proportional to the surface temperature was used to examine the effects of important environmental variables on minimum surface temperatures reached during cloudless nights. Variables considered were altitude, atmospheric water content, surface emissivity, soil heat capacity and conductivity, length of night, and initial starting temperature. Final temperatures reached were especially sensitive to changes in soil thermal conductivity and heat capacity. Both these parameters are affected by moisture content (particularly when low), making this the single most important factor affecting the severity of frost. Lower initial starting temperatures and longer nights increase the severity of frosting, as does any decrease in the depth of the atmosphere (as happens with changes in altitude) or reductions in the water content of the atmosphere. Emissivity of the radiating surface is relatively unimportant. Temperature profiles in the soil were similar, but extended to greater depths as heat capacitance declined, whereas lower thermal conductivity resulted in cooler surface temperatures while the decline in temperature did not extend as deep. The model was shown to be an improvement on one in which net flux was assumed to remain constant, and allows for a more instructive sensitivity analysis.

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