Microstructural evolution, phase transformation, and variations in physical properties of coal series kaolin powder compact during firing

Xu, Xin; Lao, Xinbin; Wu, Jianfeng; Zhang, Yaxiang; Xu, Xiaoyang; Li, Kun

doi:10.1016/j.clay.2015.07.031

Cited by 74 publications

(45 citation statements)

References 36 publications

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“…DTA plot shows the presence of an exothermic reaction also at~990°C, associated with the formation of Al-Si spinel/mullite and glass from metakaolin. 18,[24][25][26] Also, the dilatometric plot ( Figure 1B) is very similar to those reported for porcelain in many ceramics textbook 27 and it shows three fundamental shrinkage events. The first one, at about 590°C, is related to kaolin decomposition; the second one is very likely due to the formation of Al-Si spinel/mullite and glass from metakaolin; and the third event, which is associated to~10% shrinkage and which typically corresponds to real densification, reaches a maximum rate at 1190°C and it is associated to viscous flow sintering mechanisms.…”

Section: Resultssupporting

confidence: 82%

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Porcelain stoneware consolidation by flash sintering

Biesuz

Abate

2017

J Am Ceram Soc

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Porcelain stoneware was consolidated by flash sintering under DC polarization using current densities in the range 4-20 mA/mm 2 . The results show the applicability of this innovative sintering technology to a material whose densification occurs by vitrification, thus allowing to extend the possible application field of flash sintering to traditional ceramics. Using appropriate current density, the flashsintered samples are dense, homogeneous, and well-vitrified. XRD and microstructural analysis points out the formation of primary mullite while secondary mullite is only sporadically observed. In addition, comparison between flash sintering and fast firing shows that the densification obtained in the selected ceramic system via the former route cannot be reproduced just by a rapid heating process. K E Y W O R D Sfield-assisted sintering technology, porcelain, sinter/sintering

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Section: Resultssupporting

confidence: 82%

“…DTA plot shows the presence of an exothermic reaction also at ~990°C, associated with the formation of Al‐Si spinel/mullite and glass from metakaolin …”

Section: Resultsmentioning

confidence: 99%

Porcelain stoneware consolidation by flash sintering

Biesuz

Abate

2017

J Am Ceram Soc

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“…It deduced that kaolinite in coal gangue begins to decompose into amorphous meta-kaolinite at 450 °C and transforms to the crystallized mullite when the temperature reaches up to 1000 °C. The two thermal induced processes can be described by the following reactions [5,28]:…”

Section: Chemical and Physical Characteristicsmentioning

confidence: 99%

Investigation on Calcination Behaviors of Coal Gangue by Fluidized Calcination in Comparison with Static Calcination

Yuan

Han

et al. 2017

Minerals

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Abstract:In order to comprehensively utilize coal gangue, we present fluidized calcination as a new thermal technology for activating coal gangue and systematical study was conducted in comparison with static calcination. The calcined products obtained by different calcination methods under various temperatures were characterized by the means of X-ray diffraction (XRD), thermal gravimetry-differential scanning calorimeter (TG-DSC), Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). Chemical and physical characteristics such as aluminium leaching rate, chemical oxygen demand and whiteness of calcined products were also investigated. The results show that aluminium leaching rate could reach to the maximal value 74.42% at 500 • C by fluidized calcination, while the maximal value of 66.33% could be reached at 600 • C by static calcination. Products by fluidized calcination obtained higher whiteness and lower chemical oxygen demand (COD) under the same calcination temperature. The well-crystallized kaolinite transform to amorphous meta-kaolinite under 600 • C and mullite presence under 1000 • C according to phase transformation, chemical bond variation and microstructure evolution analysis. Fluidized calcination was more efficiently for combustion of carbon/organic matter and dehydroxylation of kaolinite, which might applied in coal gangue industry in future.

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“…In addition, for samples A and C, with the increase in sintering temperature, a significant reduction in the intensity of cristobalite and alumina peaks and an increase in the intensity of the mullite peaks were observed. The samples with higher amounts of flux oxides showed higher intensity mullite peaks, which may be related to the dissolution rate of Al 2 O 3 and lower viscosity [20]. The samples showed two mullite reflections at 2θ ~26°, which were attributed to the presence of orthorhombic mullite (secondary mullite), obtained from aluminosilicates [15].…”

Section: Methodsmentioning

confidence: 93%

Fabrication and characterization of dielectric ceramics using alumina and aluminosilicates

et al. 2020

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The aim was to study formulations containing aluminosilicate and alumina in order to obtain compositions with suitable properties to fabricate dielectric ceramic devices. Initially, the precursors were subjected to chemical, mineralogical and granulometric characterization. The formulations were defined and specimens were pressed (19.6 MPa) in shapes of disc and rectangular bar. Specimens were dried, heat-treated at 1400, 1450 and 1500 °C and the mineralogical, morphological, physical, dielectric and mechanical properties were evaluated. The relative dielectric constant (εr) and loss tangent (tanδ) were evaluated at 0.1, 1, 10 and 100 kHz at room temperature. The mullite was the major phase for the studied temperature range. Compositions with a higher content of fluxes showed lower porosity and better dielectric properties and flexural strength. Values of εr at 1 kHz (~3.5 to 4.5) were close to that of the mullite for the samples fired at 1400 °C.

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Microstructural evolution, phase transformation, and variations in physical properties of coal series kaolin powder compact during firing

Cited by 74 publications

References 36 publications

Porcelain stoneware consolidation by flash sintering

Porcelain stoneware consolidation by flash sintering

Investigation on Calcination Behaviors of Coal Gangue by Fluidized Calcination in Comparison with Static Calcination

Fabrication and characterization of dielectric ceramics using alumina and aluminosilicates

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