Temperature dependence of electrical conductivity of a green porcelain mixture

Lerdprom, Wirat; Li, C.; Jayaseelan, Daniel Doni; Skinner, Stephen J.; Lee, William

doi:10.1016/j.jeurceramsoc.2016.08.019

Cited by 13 publications

(4 citation statements)

References 22 publications

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“…Fig.6a presents the calculated loss tangent of the porcelain powder from room temperature to 900 °C using , where is overall electrical conductivity, f is frequency of alternating electric field, and is permittivity of free space (ε 0 = 8.85x10 −12 F·m −1 ). The electrical conductivity of the porcelain sample was obtained elsewhere [30] . Generally, microwave energy is effectively absorbed at 0.01-5 [4] of loss tangent.…”

Section: Methodsmentioning

confidence: 99%

Impact of microwave processing on porcelain microstructure

Lerdprom

Zapata-Solvas

Jayaseelan

et al. 2017

Ceramics International

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Microstructural evolution on sintering of porcelain powder compacts using microwave radiation was compared with that in conventionally sintered samples. Using microwaves sintering temperature was reduced by ~ 75 °C and dwell time from 15 min to 5 min while retaining comparable physical properties i.e. apparent bulk density, water absorption to conventionally sintered porcelain. Porcelain powder absorbed microwave energy above 600 °C due to a rapid increase in its loss tangent. Mullite and glass were used as indicators of the microwave effect: mullite produced using microwaves had a nanofibre morphology with high aspect ratio (~32±3:1) believed associated with a vapour-liquid-solid (VLS) formation mechanism not previously reported. Microwaves also produced mullite with different chemistry having ~63 mol% alumina content compared to ~60 mol% alumina in conventional sintered porcelain. This was likely due to accelerated Al +3 diffusion in mullite under microwave radiation. Liquid glass was observed to form at relatively low temperature (~900-1000°C) using microwaves when compared to conventional sintering which promoted the porcelains ability to absorb them.

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Section: Methodsmentioning

confidence: 99%

Impact of microwave processing on porcelain microstructure

Lerdprom

Zapata-Solvas

Jayaseelan

et al. 2017

Ceramics International

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“…34,35 The top pyrometer was also calibrated using iron Curie temperature in a previous work. 36 A finite element modeling (FEM) study described the differences between the temperatures in the external wall of graphite die and alumina sample (alumina has a similar behavior to porcelain in terms of thermal and electrical insulation 37,38 ), and the temperature in the alumina sample was found to be higher by~150°C than the external surface of the die for a wall thickness of 22 mm in a radial direction. 38 However, there was a temperature difference <20°C in the radial direction at a distance from the sample of 5 mm.…”

Section: Sample Preparationmentioning

confidence: 99%

Impact of spark plasma sintering (SPS) on mullite formation in porcelains

et al. 2017

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The effect of the spark plasma sintering (SPS) process on mullite formation in porcelains was studied using X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. SPS affected the kinetics and morphology of formed mullite. After sintering at 1100°C, unlike conventional sintering, SPS promoted the formation of mullite due to the combination of vacuum and applied pressure. Mullite crystal growth was altered by the atmosphere (vacuum), dwell time (0‐15 minutes), and temperature (1000‐1200°C). The applied pressure caused the mullite needles to orient perpendicular to the direction of the applied load. Depending on SPS dwell time, the mullite formed after sintering at 1100°C also had different crystal structure (tetragonal for short dwell time of 0‐5 minutes and orthorhombic for a long dwell time of 10‐15 minutes). Dissolution of mullite was observed at 1100°C by extending the dwell time by up to 15 minutes and the dissolved mullite reprecipitated on the small needles (~40 nm) and coarsened via Oswald ripening resulting in larger mullite needles (~60 nm).

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“…This is unlike some alumosilicate and silicate minerals such as clay, feldspar, and quartz that are electrical insulators at room temperature, but due to ionic conduction they can behave like semiconductors and conductors when temperature is increased [4]. Generally, the electrical conductivity of these kinds of minerals increases exponentially with increasing temperature, because the mobility of the charge carrier is a thermally activated process [4][5][6]. Aluminosilicates are quasi solid electrolytes [7,8] in which protons move along the net of hydrogen bonds.…”

Section: Introductionmentioning

confidence: 95%

“…Cui et al [2] and Novais et al [3] reported that the synthesized geopolymer possessed a high electrical conductivity at room temperature. This is unlike some alumosilicate and silicate minerals such as clay, feldspar, and quartz that are electrical insulators at room temperature, but due to ionic conduction they can behave like semiconductors and conductors when temperature is increased [4]. Generally, the electrical conductivity of these kinds of minerals increases exponentially with increasing temperature, because the mobility of the charge carrier is a thermally activated process [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Structural and electrical properties of geopolymer materials based on different precursors (kaolin, bentonite and diatomite)

Kljajević

Melichová

Stojmenović

et al. 2019

Maced. J. Chem. Chem. Eng.

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Geopolymers (GP) were successfully synthesized from metabentonite (MB), metadiatomite (MD) and metakaolinite (MK). Characterization of their phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. A SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel, and it is significantly different from the micrographs of the other two geopolymer samples, GPMB and GPMK. A considerable amount of unreacted particles, as well as the presence of pores in the geopolymer matrix of GPMK and GPMD, indicate an incomplete reaction in the system. Aluminosilicate inorganic polymers, geopolymers, are quasi solid electrolytes which possess a high electrical conductivity at room temperature in relation to materials of similar chemical composition. The highest conductivity was found for the sample obtained from GPMK, amounting to 2.14 × 10 -2 Ω -1 cm -1 at 700 ºC. The corresponding activation energies of conductivity for this sample amounted to 0.33 eV in the temperature range of 500-700 ºC. The geopolymer synthesized from metakaolin has good ionic conductivity values, which recommends it for use as an alternative material for an SOFC (Solid Oxide Fuel Cell). СТРУКТУРНИ И ЕЛЕКТРИЧНИ СВОЈСТВА НА ГЕОПОЛИМЕРНИ МАТЕРИЈАЛИ БАЗИРАНИ НА РАЗЛИЧНИ ПРЕКУРЗОРИ (КАЛОЛИН, БЕНТОНИТ И ДИАТОМИТ)Успешно беа синтетизирани геополимери (GP) од метабентонит (MB), метадиатомит (MD) и метакаолинит (MK). Карактеризацијата на нивните фазни структури беше определена со методите на XRD, FTIR и SEM/EDX. Mикрографот SEM на GPMD покажува хомогена површина со лонгитудинални празнини во гелот и значајно се разликува од микрографите на двата други примероци на геополимери, GPMB и GPMK. Значителна количина на неизреагирани честички, како и присуство на пори во геополимерната матрица на GPMK и GPMD укажуваат на нецелосна реакција на системите. Алумосиликатните неоргански полимери, геополимери, се квазицврсти електролити што имаат висока електрична спроводливост на собна температура во однос на материјалите со сличен хемиски состав. Највисока спроводливост е најдена кај примерокот од GPMK и изнесува 2,14 × 10 -2 Ω -1 cm -1 на 700 ºC. Соодветните активациони енергии на кондуктивноста за овој примерок изнесуваат до 0,33 eV во температурниот опсег од 500-700 ºC. 284Геополимерот синтетизиран од метакаолин има добри вредности на јонска спроводливост, што го прави погоден за употреба како алтернативен материјал на SOFC (Горивна ќелија од цврст оксид).

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Temperature dependence of electrical conductivity of a green porcelain mixture

Cited by 13 publications

References 22 publications

Impact of microwave processing on porcelain microstructure

Impact of microwave processing on porcelain microstructure

Impact of spark plasma sintering (SPS) on mullite formation in porcelains

Structural and electrical properties of geopolymer materials based on different precursors (kaolin, bentonite and diatomite)

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