Evaluation of the Influence of MgO and La2O3 on the Fast Sintering of Mullite

Souto, P. M.; Menezes, Romualdo Rodrigues; Kiminami, R. H. G. A.

doi:10.1590/1516-1439.264814

Cited by 10 publications

(10 citation statements)

References 35 publications

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“…Since the formation of cordierite phase (JCPDS 00‐012‐0303) takes place in the samples with 6 and 12 mass% of magnesite. In order to explain the cordierite mechanism formation, many authors 40‐43 have considered that it is related to the reaction between spinel and silica or mullite with magnesium oxide, obtained after the decarbonation of magnesite, as described by reactions .

2 ({Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) \to 2 {Al}_{2} {normalO}_{3} . 3 {SiO}_{2} + {SiO}_{2} (amorphous)

3 (2 {Al}_{2} {normalO}_{3} . 3 {SiO}_{2}) \to 2 (3 {Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) + 5 {SiO}_{2} (amorphous)

{MgCO}_{3} \to MgO + {CO}_{2} (gas)

2 (MgO . {Al}_{2} {normalO}_{3}) + 5 ({SiO}_{2}) \to (2 MgO . 2 {Al}_{2} {normalO}_{3} . 5 {SiO}_{2})

5 (3 {Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) + 15 MgO \to 2 (2 MgO . 2 {Al}_{2} {normalO}_{3} . {SiO}_{2}) + 11 (MgO . {Al}_{2} {normalO}_{3})

…”

Section: Resultsmentioning

confidence: 99%

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

Hammas

Lecomte‐Nana

Daou

et al. 2020

Int J Applied Ceramic Tech

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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.

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2 ({Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) \to 2 {Al}_{2} {normalO}_{3} . 3 {SiO}_{2} + {SiO}_{2} (amorphous)

3 (2 {Al}_{2} {normalO}_{3} . 3 {SiO}_{2}) \to 2 (3 {Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) + 5 {SiO}_{2} (amorphous)

{MgCO}_{3} \to MgO + {CO}_{2} (gas)

2 (MgO . {Al}_{2} {normalO}_{3}) + 5 ({SiO}_{2}) \to (2 MgO . 2 {Al}_{2} {normalO}_{3} . 5 {SiO}_{2})

5 (3 {Al}_{2} {normalO}_{3} . 2 {SiO}_{2}) + 15 MgO \to 2 (2 MgO . 2 {Al}_{2} {normalO}_{3} . {SiO}_{2}) + 11 (MgO . {Al}_{2} {normalO}_{3})

…”

Section: Resultsmentioning

confidence: 99%

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

Hammas

Lecomte‐Nana

Daou

et al. 2020

Int J Applied Ceramic Tech

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“…Mullite is a refractory ceramic of great industrial importance because of its variety of applications since it can be used in traditional applications such as dishes and refractory products as well as in advanced ones, including structural and functional applications [1][2][3][4][5]. Such versatility is because of its properties, namely: low thermal conductivity, low thermal expansion coefficient, hightemperature resistance, good chemical stability, low density (3.18 g/cm 3 ), excellent creep and thermal shock resistance, high melting point, and excellent electrical resistance [1,2,[5][6][7][8][9][10]. In the Al 2 O 3 -SiO 2 phase diagram, mullite is the only stable crystalline phase up to around 1800 ºC under atmospheric pressure [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

Olcoski

Chinelatto

2021

Cerâmica

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Mullite is a refractory material with singular properties, although high temperatures and long sintering times are required to obtain this material with good densification. In this study, aluminum hydroxide and colloidal silica were used to produce mullite through reactive sintering and MgO was employed as a sintering additive. The compositions were prepared with different amounts of MgO and sintered at 1350, 1450, and 1550 °C, and then analyzed using X-ray diffraction, scanning electron microscopy, and measurements of apparent porosity (AP) and flexural strength. The results showed that the raw materials used allowed the mullite formation at relatively low temperatures (1350 °C), regardless of the amount of MgO added but with the increase in MgO content, a spinel phase appeared, resulting in a fraction of residual α-alumina. The MgO addition lowered the densification temperature at around 50 °C. Furthermore, the higher the sintering temperature and the MgO content, the larger and more anisotropic the mullite grains were. At sintering temperatures above 1450 °C, AP was reduced to approximately 10%. The MgO addition and increase in sintering temperature improved the flexural strength of mullite materials.

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“…The mechanism of diffusion along the grain boundary and bulk diffusion becomes easier in the presence of the liquid phase. The role of sintering additive is to provide that liquid phase, or sometimes it reduces the viscosity of the glassy phase to enhance the mobility of the diffusing species and thereby help to sinter 16‐20 . In most of the cases, the additive effect was studied on the mullite precursor powder synthesized by sophisticated chemical routes.…”

Section: Introductionmentioning

confidence: 99%

“…The role of sintering additive is to provide that liquid phase, or sometimes it reduces the viscosity of the glassy phase to enhance the mobility of the diffusing species and thereby help to sinter. [16][17][18][19][20] In most of the cases, the additive effect was studied on the mullite precursor powder synthesized by sophisticated chemical routes. In clay alumina system also, some works covered on the effect of the additive on sintering.…”

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confidence: 99%

Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO₂

Behera

Bhattacharyya

2020

Int J Applied Ceramic Tech

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Mullite is the most important ceramic materials in the Al 2 O 3-SiO 2 binary system. It is a well-known refractory material and has several industrial applications. Some of the properties of mullite, which make it most useful as a structural and functional ceramic material are high mechanical strength, low thermal conductivity, excellent thermal shock resistance, stability to high temperature, and good creep resistance up to 1300°C. 1-2 The beneficial features of mullite ceramic are appropriate high-temperature strength for structural application and outstanding stability in severe chemical environments. These properties draw significant attention and made mullite useful as metal fillers, catalyst supports, radiant burner, heat exchanger, hot blast stove, and torpedo ladles. 3-5 Several techniques were applied to prepare mullite powder as it is not readily available in nature. 5,6 Some sophisticated methods used for mullite powder synthesis are solid-state reaction sintering, combustion, sol-gel, precipitation, hydrothermal, and chemical vapor deposition. 5,7-10 The high costs of the raw materials used in these methods make these processes unsuitable for large-scale production. Some readily available alumino-silicates such as sillimanite, andalusite, and kyanites are widely used for commercial mullite production. 11 Preparation of mullite from kaolinite is an economical way, due to the common occurrence, lower cost, and good availability of this clay mineral. 12-14 The alumina content in clay is much less than the requirement (72 wt%) for stoichiometric mullite formation. During heat treatment of kaolinite; mullite formed along with silica and impurity-containing

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Evaluation of the Influence of MgO and La2O3 on the Fast Sintering of Mullite

Cited by 10 publications

References 35 publications

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

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

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO₂

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Evaluation of the Influence of MgO and La2O3 on the Fast Sintering of Mullite

Cited by 10 publications

References 35 publications

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

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

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO2

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Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO₂