Photoacoustic thermal characterization of kaolinite clays (original) (raw)
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Applied Clay Science, 2008
Values of some thermal properties and the crystalline phases of red ceramic samples from the Northern region of Rio de Janeiro state in Brazil are reported as a function of firing temperature (900, 950, 980, 1020, 1060 and 1100°C). The open photoacoustic cell (OPC) technique and a continuous light illumination photothermal method were employed in order to obtain the thermophysical characteristics: thermal diffusivity (α) and specific heat capacity (ρc), respectively. Indirectly, using simple mathematical relations, the thermal conductivity (k) and the thermal effusivity (ε) were obtained. Crystalline phases were identified by X-ray diffraction (XRD). The intrinsic relationship between the structure and the thermal diffusivity was analysed.
The influence of ultrasound on the thermal behaviour of clay minerals
Journal of The European Ceramic Society, 2006
The aim of this work is to compare the influence of sonication on the thermal behaviour of kaolinites (KGa-1, KGa-2), pyrophyllite, talc and muscovite. Sonication produces a significant increase of the specific surface area due to particle size reduction. As sonication time increases and the particle size decreases, the thermal behaviour of these clay minerals is strongly modified. Thus, there is a significant increase of the weight loss at low temperature which is related to the loss of some outer hydroxyl groups and protonated hydroxyls whose proportion in the minerals increase as the new surface generated increases. Additionally, the original endothermic dehydroxylation effects of all these minerals shift to lower temperatures. Disordered kaolinite shows the smallest shift (9 • C) while muscovite presents the largest (184 • C). A linear relation has been established between the temperature shift of the dehydroxylation and the percentage of increase in the specific surface area. The influence of sonication on the high temperature DTA effects of kaolinite, pyrophyllite, and muscovite is also studied.
Thermal behaviour of ceramics obtained from the kaolinitic clays of Terra Alta, Catalonia, Spain
Journal of Thermal Analysis and Calorimetry, 2021
The thermal properties and evolution of mineralogy and colour of kaolinitic clay from the Terra Alta region were studied. The mineralogy of these materials consists mainly of kaolinite (13-27 mass%) and quartz (48-86 mass%). Minor illite, hematite, K-feldspar and calcite also occur. The linear expansion and absorption curves were used to predict the optimal firing temperature of the raw clays. During firing, from 1100 °C the water absorption decreases steeply, due to an increase in liquid phase, which penetrates into the pores and close the porosity. At this temperature, the firing shrinkage increases progressively. The fired clays are mainly composed of quartz, cristobalite and mullite, with minor hematite and rutile. Mullite starts to appear at 1050-1100 °C. SEM observations show that porosity decreases with the firing temperature. The colour properties were measured in the raw clays and in the fired bricks at different temperatures. The lightness, L*, is lower in the fired test pieces respect to the natural clays. This colour varies according to the hematite content, being from white to reddish in the fired samples.
Advanced Materials Research, 2014
The kaolin is an important component of a wide variety of industrial products, therefore kaolin samples of region mines Huayacocotla, Veracruz and Alumbres, Hidalgo were collected, these were treated to reduce the size particle employment an agate mortar and part of each one were analyzed using analytical techniques such as: absorption and emission atomic spectroscopy (AEAS), optical microscopy of polarization (OMP); X-rays diffraction (XRD); scanning electron microscopy (SEM); refractory test under ASTM standard C-24-79 using a pyrometric cone mold designed on ASTM standard C-24 and thermal test at different temperatures up to 1600 °C with heating and cooling rate of 2.5 °C·min-1; thermogravimetric analysis (TGA) was carried out in a thermogravimetric analyzer with sample placed in alumina crucibles of high purity and the temperature was increased from room temperature up to 1000 °C with a heating rate of 10 oC·min-1. Dates from elemental analysis were converted to percentage in ox...
The influence of ultrasound on the thermal behaviour of a well ordered kaolinite
Thermochimica Acta, 2003
The aim of this work is to compare the influence of sonication on the thermal behaviour of kaolinites (KGa-1, KGa-2), pyrophyllite, talc and muscovite. Sonication produces a significant increase of the specific surface area due to particle size reduction. As sonication time increases and the particle size decreases, the thermal behaviour of these clay minerals is strongly modified. Thus, there is a significant increase of the weight loss at low temperature which is related to the loss of some outer hydroxyl groups and protonated hydroxyls whose proportion in the minerals increase as the new surface generated increases. Additionally, the original endothermic dehydroxylation effects of all these minerals shift to lower temperatures. Disordered kaolinite shows the smallest shift (9 • C) while muscovite presents the largest (184 • C). A linear relation has been established between the temperature shift of the dehydroxylation and the percentage of increase in the specific surface area. The influence of sonication on the high temperature DTA effects of kaolinite, pyrophyllite, and muscovite is also studied.
Thermal Characterization of Sintered Clay-Petroleum Waste Mix by the Photoacoustic Technique
Materials Science Forum, 2005
In Campos oil Basin (Brazil), which is responsible for more than 80 % of the national petroleum production, it is generated a great amount of wastes from deep crude oil extraction related activities. Particularly, the oil sludge waste has been intensely studied in order to search alternatives for the reuse of the waste in treated form in the ceramic industry. the present work focuses on the photoacoustic thermal characterization of sintered ceramic bodies containing up to 5 wt.% added waste. Specimens were uniaxially pressed at 25 MPa, and sintered between 850 ºC and 1000 ºC. The results of thermal diffusivity indicate that the use of petroleum waste in structural ceramic up to 5 wt.% does not cause significant changes in the structure or composition of the clay/waste system, resulting in great advantages in waste minimization.
Thermal Diffusivity of Sandstone Using Photoacoustics
An open photoacoustic cell was used to investigate the thermal diffusivity of sandstone taken from the Paraná Basin, in Brazil. Although the organic-rich sedimentary rocks represent an important energy source in the Paraná Basin, only limited data are reported concerning their thermophysical properties. A sandstone rock sample, from the Botucatu Formation, was investigated. The thermal diffusivity values were determined with uncertainties around 12 %, comparable to other methods. These values consider not only the experimental errors but also take into account the heterogeneity of thematerials. Itwas possible to verify the behavior of the thermal diffusivity of the sandstone under heat treatment. The variation of the thermal diffusivity followed an expected trend, based on the possible variation of porosity which is related to the decomposition of some constituents. The results presented in this work identify the photoacoustic technique as a useful tool for thermal characterization of sedimentary rocks.
Applied Clay Science, 2009
Soil clay used as ceramic raw material under heat treatment was investigated using X-ray diffraction, X-ray fluorescence, photoacoustic spectroscopy -PAS and electron spin resonance -ESR. The results indicated the presence of at least three different sites for the Fe 3+ ions, one of them representative of a set of distorted cubic sites. The optical absorption spectra obtained with the photoacoustic technique showed bands associated with d-d transitions of Fe 3+ ions. Mullite and hematite were detected in the 1100°C heated samples. Crystalline-amorphous-crystalline transformations were detected between 110°C and 1100°C. The conclusion drawn from photoacoustic and magnetic resonance measurements agreed very well with that obtained by X-ray diffraction.
6th Eeigm International Conference on Advanced Materials Research, 2012
The aim of this study was to compare the thermal behaviour of clays containing illite and kaolinite in various proportions. The clays contained small amounts of K and Fe, which act as fluxing agents. In order to investigate the phase formations during heating, the samples were examined in a differential scanning calorimeter at temperatures up to 1300ºC. The thermal expansion of the samples was determined by dilatometer measurements from room temperature up to 1150ºC. Phases were identified using x-ray diffraction and scanning electron microscopy. In all samples, most of the kaolinite was transformed into metakaolinite during heating up to 650ºC, while illite remained unchanged up to 950ºC. There was no influence of K and Fe on dehydroxylation. Metakaolinite formed at temperatures above 950ºC leading to a Si-Al spinel. Furthermore, mullite was formed in the temperature interval 1050-1150ºC. In this temperature range, the mechanism of mullite formation depended on the amount of K and Fe in the samples, changing the temperature of formation of mullite. It was observed by x-ray diffraction that most of the illite was transformed into a Si-Al spinel phase at 1050ºC, and during further heating transformed into mullite. An increased amount of illite in the clays slightly decreased the melting temperature. The dilatometer measurements showed expansion and shrinkage for the dehydroxylation and spinel-phase formation, respectively.