Influence of mechanical treatment on thermophysical processes in illitic clay during firing

Csáki, Štefan; Štubňa, Igor; Dobroň, Patrik; Minárik, Peter; Záleská, Martina; Václavů, Tereza; Vozár, Libor

doi:10.1016/j.clay.2017.02.031

Cited by 7 publications

(4 citation statements)

References 23 publications

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“…The phase composition of the studied samples below 900 °C showed a gradual increase in the amorphous content with glass content in the mixtures. Above 900 °C, the mineral illite underwent a structural collapse, and a glassy phase formed in accordance with the results reported for a clay with high illite content in [8,[35][36][37]. Owing to this transition, the amorphous content increased further.…”

Section: Effect Of the Glass Concentration On The Sintering Processessupporting

confidence: 89%

“…After heating at 1000 °C (without glass addition), quartz (PDF#01-077-1060), muscovite (PDF#00-007-0025), illite (PDF#01-076-5970), diopside (PDF#01-071-3828), haematite (PDF#00-033-0664), and microcline (PDF#01-076-6582) were identified as mineral phases present in the sample (Figures 6 and The phase composition of the studied samples below 900 • C showed a gradual increase in the amorphous content with glass content in the mixtures. Above 900 • C, the mineral illite underwent a structural collapse, and a glassy phase formed in accordance with the results reported for a clay with high illite content in [8,[35][36][37]. Owing to this transition, the amorphous content increased further.…”

Section: Effect Of the Glass Concentration On The Sintering Processessupporting

confidence: 89%

“…More roughly grained (also called "stove") clay exhibits a lower shrinkage coefficient during drying [7]. However, a decrease in particle size reportedly led to an increase in the dimensional changes during the firing of an illitic clay [8]. Besides, the dimensional stability of shaped clay becomes challenging [7,9].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Glass Additions on Illitic Clay Ceramics

et al. 2020

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A mixture of an illitic clay and waste glass was prepared and studied during the sintering process. The illitic clay, from the Liepa deposit (Latvia), and green glass waste (GW) were disintegrated to obtain a homogeneous mixture. The addition of disintegrated GW (5–15 wt% in the mixture) led to a reduction in the intensive sintering temperature, from 900 to 860 °C, due to a significant decrease in the glass viscosity. The addition of GW slightly decreased the intensities of the endo- and exothermic reactions in the temperature range from 20 to 1000 °C due to the reduced concentration of clay minerals. GW reduced the plasticity of the clay and reduced the risk of structural breakage. The increase in sintering temperature from 700 to 1000 °C decreased the apparent porosity and water uptake capacity of the ceramics from 35% and 22%, down to 24% and 13%, respectively. The apparent porosities of all the sintered mixtures showed a decrease of between 6% to 9% after the addition of GW with concentrations from 5 up to 15 wt% respectively, while the water uptake capacities decreased from between 4% and 10%. The addition of GW led to an increase in the apparent density of the ceramic materials, up to 2.2 g/cm3. Furthermore, the compressive strength increased by more than two times, reaching a highest value of 240 MPa after the sintering of the 15 wt% GW-containing mixture at 1000 °C.

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Section: Effect Of the Glass Concentration On The Sintering Processessupporting

confidence: 89%

Section: Effect Of the Glass Concentration On The Sintering Processessupporting

confidence: 89%

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Influence of Glass Additions on Illitic Clay Ceramics

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“…3). 6)8),18), 36) The presence of the AE signals and decrease in Young's modulus showed that the cracks formation resumed below 500°C. The tensile radial stress on the grain and in its close vicinity reached 100180 MPa (Fig.…”

Section: 3mentioning

confidence: 99%

Development of stress on quartz grain in illite ceramics during cooling stage of firing

Štubňa

Mánik

Húlan

et al. 2020

J. Ceram. Soc. Japan

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If the volume fraction of quartz in traditional ceramics is higher than 10% then the use of Selsing's formula is questionable. A model of two concentric spheres, in which the inner sphere is a quartz grain and its spherical cladding is glassy phase, is proposed. The development of the stress on the grain surface during cooling stage of the firing and its influence on the microcracking is described. The tensile tangential stress which is developed between the glass transformation temperature and ¢ ¼ ¡ transition of quartz can be a source of the first microcracking. After this transition, the tangential stress becomes compressive. The radial stress on the grain surface, which is compressive before the ¢ ¼ ¡ transition of quartz, turns into tensile after this transition as a steep change of 4080 MPa (for 1050% of quartz content). These changes are in a narrow temperature interval around the ¢ ¼ ¡ transition of quartz passing through zero value and no cracks are expected. This is confirmed with acoustic emission (AE) and short recovery of Young's modulus. When the ¢ ¼ ¡ transition of quartz is finished and the temperature decreases, the creation of the cracks continues. The radial tensile stress on the grain and in its close vicinity reaches 100180 MPa, consequently, circumferential cracks can be formed. This is indirectly confirmed with a decrease of Young's modulus and weak AE activity.

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