Effects of Alumina on Cristobalite Crystallization and Properties of Silica-Based Ceramic Cores

Liang, Jingjing; Lin, Qian; Zhang, X.; Jin, Tongan; Zhou, Yihong; Sun, Xun; Choi, Baig-Gyu; Kim, I.S.; Do, Jeonghyeon; Jo, Chang-Yong

doi:10.1016/j.jmst.2016.02.012

Cited by 75 publications

(41 citation statements)

References 8 publications

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“…Conforme também observado na Fig. 3, a formulação F2 apresentou picos de cristobalita com maiores intensidades, provavelmente esta fase atuou como inclusões, que podem comprometer as propriedades mecânicas [48].…”

Section: Caracterização Das Amostras Tratadas Termicamenteunclassified

Influência da composição e das variáveis de processamento deformulações à base de argilas - uso em materiais refratários

Figueiredo¹,

Fernandes²,

Silva³

et al. 2018

Cerâmica

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ResumoAs argilas são componentes fundamentais das massas para produção de materiais cerâmicos tradicionais, pois garantem plasticidade na etapa de conformação e resistência mecânica após a queima; também podem ser utilizadas nas formulações de cerâmicas refratárias devido ao desenvolvimento da fase mulita em temperaturas elevadas. O objetivo deste trabalho foi avaliar o efeito da composição, tempo de maturação e temperatura de queima em formulações à base de argilas para uso na fabricação de materiais refratários. As argilas foram caracterizadas por análise granulométrica, análise química, refratariedade, difração de raios X, análise térmica diferencial e termogravimétrica. As formulações contendo caulim mais ball clay e caulim mais esmectita foram submetidas à maturação por um período de 1 a 4 semanas. Em seguida, as massas foram conformadas por prensagem uniaxial obtendo-se corpos de prova, que foram submetidos a tratamento térmico em 1200, 1300 e 1400 °C, e, posteriormente, analisados quanto às propriedades: absorção de água, retração linear de queima e resistência à flexão em três pontos. Os resultados obtidos evidenciaram que as formulações em estudo apresentaram após queima fases de quartzo, cristobalita e mulita como fase majoritária. A temperatura de queima foi o parâmetro que apresentou maior influência nas propriedades avaliadas, com maior efeito da temperatura mais alta (1400 °C). Palavras-chave: argilas, composição, refratário. AbstractClays are key components of mass for traditional ceramic materials production because they ensure plasticity in the shaping step and mechanical resistance after firing. They can also be used in refractory ceramic formulations due to the development of mullite phase at high temperatures. The objective of this study was to evaluate the effect of composition, maturation time, and firing temperature on clay formulations for use in manufacturing refractory materials. The clays were characterized by particle size analysis, chemical analysis, refractoriness, X-ray diffraction, as well as differential thermal and thermogravimetric analyses. Formulations containing kaolin with ball clay and kaolin with smectite were submitted to a maturation period of 1 to 4 weeks. Next, the masses were shaped by uniaxial pressing to obtain test specimens, which were then subjected to heat treatment at 1200, 1300 and 1400 °C, and the following properties were subsequently analyzed: water absorption, linear firing shrinkage, and three-point flexural strength. The results showed that after firing the samples had quartz, cristobalite and mullite phases, with the latter as the major phase. The firing temperature was the parameter that had the greatest influence on the evaluated properties, with the highest temperature (1400 °C) exerting the most influence.

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Section: Caracterização Das Amostras Tratadas Termicamenteunclassified

Influência da composição e das variáveis de processamento deformulações à base de argilas - uso em materiais refratários

Figueiredo¹,

Fernandes²,

Silva³

et al. 2018

Cerâmica

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“…The liquid phase formation temperature of fused silica can also be reduced by adding alumina additive. Liang and Kazemi reported that the addition of alumina promoted the crystallization of fused silica and increased the amount of cristobalite in silica‐based ceramic cores. They attributed the changes in flexural strength and sintering shrinkage to the increase in the amount of cristobalite.…”

Section: Introductionmentioning

confidence: 99%

Silica‐based ceramic core for aviation applications: Facile pore filling and flexural strength improvement

Chen

Han

Zhang

et al. 2019

Int J Applied Ceramic Tech

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The effect of alumina addition on the pore filling process, crystallization behavior and mechanical properties of silica-based ceramic cores was investigated. The sintered samples at 1250°C were treated at 1550°C for 0.5 hour in order to simulate a casting process condition. The microstructure analysis indicated that an appropriate alumina addition enhanced the pore filling process by supplying a substantial liquid viscous flow. With an increase in the liquid viscous flow, smaller pores were filled first, and larger pores were filled later. The results also indicated that the pore filling process could be enhanced by adding small powder additives to decrease the pore size between the particles in the ceramic material. However, an excessive alumina addition in the silica-based ceramic cores had a negative effect on the flexural strength and leaching rate. As the alumina content increased from 8 to 12 wt%, the flexural strength of the ceramic core decreased from 16.37 to 4.60 MPa, respectively, and the leaching rate also decreased obviously. These results were explained by an acceleration in crystallization trend of the fused silica particle surface and the merging of connected pores in the sintered body. K E Y W O R D Sliquid viscous flow, mechanical properties, pore filling process, silica-based ceramic core 2182 | CHEN Et al.

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“…1 Silica-based ceramic cores have been extensively used in investment casting in gas turbine blades for aviation engine due to their high mechanical strength, low thermal expansion coefficient (about 0.55 × 10 −6 /℃, 25-1100℃), excellent thermal shock resistance as well as superior chemical inertness with molten metal. 2,3 Additionally, they can be removed by some caustic solutions (e.g. NaOH and KOH) easily and no damage to the cast is created, 4 thereby forming the intricate internal cooling passages of the blades.…”

Section: Introductionmentioning

confidence: 99%

“…The cooling process of the inner blade passage plays a key role in the design of blades for gas turbine 1 . Silica‐based ceramic cores have been extensively used in investment casting in gas turbine blades for aviation engine due to their high mechanical strength, low thermal expansion coefficient (about 0.55 × 10 −6 /℃, 25–1100℃), excellent thermal shock resistance as well as superior chemical inertness with molten metal 2,3 . Additionally, they can be removed by some caustic solutions (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…However, alumina can break the silicon oxygen bonds and form large amounts of low melting point liquid phase at high temperatures 19 . This favors flexural strength but detrimental effect to deformation resistance of silica‐based ceramic cores could happen 2,20 . To find a kind of additive that could not only control cristobalite crystallization but also improve properties of silica‐based ceramic cores, the micro‐sized mullite was used in this study.…”

Section: Introductionmentioning

confidence: 99%

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Effects of micro‐sized mullite on cristobalite crystallization and properties of silica‐based ceramic cores

Zheng

Chen

Liu

et al. 2021

Int J Applied Ceramic Tech

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Silica-based ceramic cores are extensively used in investment casting process, during which they must exhibit sufficient flexural strength and deformation resistance.In this study, micro-sized mullite was used as an additive to silica-based ceramic cores to optimize their high temperature properties. To investigate the effects of micro-sized mullite on cristobalite crystallization, mechanical and thermal properties of silica-based ceramic cores, ceramic cores with different amounts of micro-sized mullite were fabricated. The XRD results showed that additional micro-sized mullite diminished the crystallization of cristobalite at high temperatures, primarily caused by the mullite related compressive stresses on the surface regions of fused silica particles. Three-point bending tests and SEM results showed that micro-sized mullite had a more significant effect on the flexural strength of ceramic cores compared with conventional additives. Particularly, the fracture mechanism of silica-based ceramic cores had been changed from intergranular fracture into a mixed fracture consisting of both intergranular and transgranular fracture. The mechanical and thermal properties of ceramic cores were all reduced slightly as the mullite content exceed 4.6 wt%.Hence, to optimize the properties of silica-based ceramic cores, the micro-sized mullite content should not exceed 4.6 wt%. K E Y W O R D Scristobalite, mechanical properties, mullite, silica-based ceramic core, thermal properties How to cite this article: Zheng W, Chen X, Liu C, Ren S, Zhang L. Effects of micro-sized mullite on cristobalite crystallization and properties of silica-based ceramic cores.

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Effects of Alumina on Cristobalite Crystallization and Properties of Silica-Based Ceramic Cores

Cited by 75 publications

References 8 publications

Influência da composição e das variáveis de processamento deformulações à base de argilas - uso em materiais refratários

Influência da composição e das variáveis de processamento deformulações à base de argilas - uso em materiais refratários

Silica‐based ceramic core for aviation applications: Facile pore filling and flexural strength improvement

Effects of micro‐sized mullite on cristobalite crystallization and properties of silica‐based ceramic cores

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