Sintering and final properties of kaolinite‐magnesite tapes for the manufacture of cordierite‐mullite ceramics

Abstract

The present work aims at studying the effect of the sintering temperature and magnesite addition on the structure and final properties of silicate ceramics tapes. A kaolinitic clay from Algeria was selected and mixed with different magnesite contents (≤12 mass%). Tape casting process was used to produce the green tapes in an aqueous system with optimized amount of surfactants. The green tapes were fired from 1000°C to 1200°C using a dwelling time of 30 minutes. The effect of the dwelling time was investigated for a firing temperature of 1200°C namely: 30 minutes, 1 hour 30 minutes and 3 hours for samples with 6 and 12 mass% of magnesite. Regarding firing conditions, crystalline phases, thermal conductivity, porosity, and flexural strength were analyzed. The results showed that increasing the sintering temperature to 1200°C tended to significantly decrease the total porosity of samples, which led to the improvement of the stress to rupture values. Specimens with 6 and 12 mass% sintered during 3 hours exhibited highest stress to rupture values (≈117 MPa) and lowest thermal conductivity (<0.2 W.m−1.K−1) and moderate open porosity (27%). The as‐obtained ceramics appeared promising for further utilization in refractory industry, thanks to the presence of both cordierite and mullite phases.

Kaolinite-Magnesite or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes

“…This behavior seemed to be related to the higher plasticity of the kaolin used in this study compared to the talc material or to the magnesite. However, according to our previous study [1], it was indicated that the mechanical properties of K94M6 tapes were strongly affected by their microstructure, and as a result, biaxial flexural strength increased when porosity decreased [26]. Consequently, it appears in Figure 8 that…”

“…This behavior seemed to be related to the higher plasticity of the kaolin used in this study compared to the talc material or to the magnesite. However, according to our previous study [1], it was indicated that the mechanical properties of K94M6 tapes were strongly affected by their microstructure, and as a result, biaxial flexural strength increased when porosity decreased [26]. Consequently, it appears in Figure 8 that the stress to rupture values decreased while sintering at 1000 or 1100 • C. Moreover, the decarbonation of magnesite contributed to increasing the apparent porosity of K94M6 samples after sintering up to 1100 • C, thus to observed decrease the biaxial flexural strength down to 10 MPa.…”

“…Many traditional and advanced ceramic materials are made from clay (or clay mixed with other materials) [1][2][3][4]. Indeed, the mixture of two or more clays of different composition and texture to form a paste is performed to improve the workability and firing behavior in comparison to the behavior of each single clay.…”

“…The crystalline structure of talc has a 2:1 or TOT layer type with one octahedral (O) magnesium layer sandwiched between two tetrahedral silica layers ( Figure 2) [21]. In our previous work [1,17], the effect of magnesite amount on the different properties of kaolinitic clay ceramics was studied. However, in this study, we aimed to compare the final characteristics of the kaolinitic clay from Algeria (KT2) mixed with 6 mass% of magnesite, with those resulting from the use of a commercial kaolin (kaolin BIP) mixed with talc (as the source of magnesium oxide).…”