Characterization and properties of cordierite – mullite refractories from raw materials and Narathiwat clay (in Thailand)

Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 5 (2018) 13948–13953

www.materialstoday.com/proceedings

SACT 2016

Characterization and properties of cordierite – mullite refractories from raw materials and Narathiwat clay (in Thailand) N. Ariyajinnoa,b,* and S. Thiansemc a, b

Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Department of Ceramics Technology, Industrial Faculty of Technology, Loei Rajabhat University, Loei 42000, Thailand c Department of Industrial Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand

Abstract In the present study, the relationship between characterization and properties of mullite-cordierite refractory were investigated. Talc, alumina oxide and kaolin (Narathiwat clay, Thailand: NRT) were mixed by varying the ratio of MgO+Al2O3+SiO2 as NRT1 (31:66:3), NRT2 (45:54:1), NRT3 (13:86:1) and NRT4 (50:49:1). The mixture was pressed into rectangular shape by a hydraulic press under a pressure of 150 kg/cm2 and sintered at 1300 °C with a heating rate of 5 °C/min for 1 hour of soaking time and cooled down to room temperature in a furnace chamber. Sample dimensions, density, water absorption, porosity, shrinkage, and mechanical properties were measured as a function of firing temperature. The chemical composition and loss on ignition (LOI) of the raw materials were performed using X-ray fluorescence spectrometer (XRF). Effects on the phases formation and morphology that capable to improve mullite and cordierite in samples were performed using X-ray diffractometer (XRD). The results revealed that mullite was the major phase in sintered samples and cordierite was also found which formed during expense of the other phases with talc. SEM pictures exhibited the role of talc in the grain growth of mullite and also showed the formation of pseudohexagonal cordierite which was observed by Scanning electron microscope (SEM). © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of SACT 2016. Keywords: Mullite; Cordierite; Refractory; Narathiwat Clay

1. Introduction There are many raw materials to be used as refractories such as magnesite, silica, cordierite, mullite, zirconia, silicon carbide, silicon nitride and alumina, etc [1]. In accordance with use conditions, a suitable material must be

* Corresponding author. Tel.: +66 94-2625444; fax: +66 42-835232. E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of SACT 2016.

N. Ariyajinno et al./ Materials Today: Proceedings 5 (2018) 13948–13953

13949

selected in due consideration of the characteristics stated above. It is also possible to use them in combination by blending more than 2 kinds of raw materials in accordance with use purpose and features and make high efficient kiln furniture equipped with the respective material feature [2]. Natural cordierite having a chemical composition of (Mg, Fe) 2Al4Si5O18 is a magnesium aluminosilicate mineral, occurring very rare in nature [3]. The cordierite ceramics due to its low thermal expansion coefficient, high chemical durability, low dielectric constant, high resistance to thermal shock and high refractoriness are a promising candidate for many applications. The principal raw materials used in the production of refractories were: the oxides of silicon, aluminum, magnesium, calcium and zirconium and some non-oxide refractories like carbides, nitrides, borides, silicates, and graphite. Mullite refractory was about 72% alumina with 28% silica [4].Mullite was an essential phase in conventional ceramics and also in advanced high-temperature structural materials, applied for aircraft gas turbine engine and heat shield materials for space vehicle [5] Mullite is a promising material for advanced ceramics application [6] due to its properties such as high melting point (> 18OO °C), low thermal expansion, good thermal shock fracture resistance, low true density, high creep resistance and good chemical stability can be compared with the properties of Si3N4 and SiC in terms of being a candidate for high-temperature structural materials applications [7]. Industrial clays of Thailand comprise white kaolin, white illite, ball clays, plastic clays, dickite bentonite, and talc. They are of residual (altered granite, altered rhyolite) and hydrothermal origin. The white kaolin of Narathiwat is derived from the altered granite and can be found in the plains of the south, Thailand. Its produced from Amphoe Range and Amphoe Sungai Padi is composed of kaolinite (75 %) and quartz, with sporadic illite [8]. Kaolin is a commercial term used to describe white clay composed essentially of kaolinite, Al4Si4O10 (OH). This research aims to investigations the Characterization and Properties of Cordierite – Mullite Refractories from Raw Materials and Kaolin Narathiwat, Thailand. 2. Experimental details The starting materials used to prepare cordierite-mullite ceramics were natural kaolin from Narathiwat (South Thailand). Quartz and Talc from Bangkok province (Commercial grade). The chemical composition of natural raw materials from Narathiwat Thailand (4 Sample of natural kaolin from Narathiwat), the presented were mixed by varying the ratio of MgO+Al2O3+SiO2 as NRT1 (31:66:3), NRT2 (45:54:1), NRT3 (13:86:1) and NRT4 (50:49:1). The mixture was pressed into rectangular shape with a hydraulic press under a pressure of 150 kg/cm2 and sintered at 1300 °C with a heating rate of 5 °C/min for 1 hour of soaking time and cooled down to room temperature in a furnace chamber. Using an X-ray diffractometer technique (XRD: X’ Pert PROMPT, Philips Netherland). The microstructures of the raw materials were observed by a scanning electron microscope (SEM: JEOL JSE-5410 LV). Chemical analysis of the raw materials was carried out prior to characterization by an X-ray fluorescence technique (XRF: Horiba Mesa-500w). [9] Physical properties the Samples were measured following ASTM C 373-88. Threepoint bending strength was determined using a universal testing machine, (UTM: Instron 5566 USA) Table 1. The chemical composition of raw materials. Oxide SiO2 Al2O3 K2O Na2O TiO2 CaO MgO Fe2O3 Mn2O3 LOI

Kaolin (NRT) 52.69 32.29 1.05 1.07 0.05 0.70 12.15

Talc 39.11 1.23 35.36 0.69 0.03 23.58

Quartz 99.38 0.23 0.05 0. 03 0.5 0.05 0.2

Alumina 0.02 99.50 0. 30 0.02 0.01 0.15

The chemical composition of the used raw materials summarized in Table 1. Natural of high purity is from Narathiwat (South Thailand). The composite cordierite-mullite ceramics were obtained by high-temperature solid-

13950

N. Ariyajinno et al./ Materials Today: Proceedings 5 (2018) 13948–13953

state reaction of mixtures, in which natural kaolin Narathiwat (South Thailand), quartz, talc, and commercial grade aluminum hydroxide were used as raw materials for the synthesis. Preparation of cordierite – mullite composites. Four mixtures were prepared to obtain cordierite-mullite with different. Firstly, the mixtures of raw materials were prepared in MgO·Al2O3·SiO2 molar ratio of 31:66:3 for pure cordierite-mullite in MgO·Al2O3·SiO2 molar ratio of 45:54:1 for pure cordierite-mullite in MgO·Al2O3·SiO2 molar ratio of 13:86:1 for pure cordierite-mullite and MgO·Al2O3·SiO2 molar ratio of 50:49:1 for pure cordierite Then, a series of different mixtures corresponding to different ratio of cordierite-mullite ceramics have been set as shown in Table 2. After mixing and homogenizing process, 50 g of powder of different mixtures was mixed with water to form a paste and pressed into rectangular shape with a hydraulic press under a pressure of 150 kg/cm2. After drying, the samples were sintered in an electrical furnace at different temperatures at 1300 °C with a heating rate of 5 °C /min for 1 hour of soaking time and cooled down to room temperature in a furnace chamber. Characterization Procedure and Techniques. Samples were submitted to the thermal shock resistance measurement test was conducted according to an adapted experimental procedure of international standards ASTM C 117-91 [10]. by quenching method. The Sample was dried at 110 °C and then heated in an electric furnace at 1100 °C for 1 hour. Then the samples were dropped into the water bath having a temperature of 2 °C, left there for a few seconds and dried again at 110 °C before returning to the furnace. This procedure was repeated until apparition of first cracks or defects on the surface of the first sample. Table 2. The composition of cordierite-mullite ceramics, sintering temperatures and detected phases. Temperatures at 1300 C MgO·Al2O3·SiO2

Identified phases

Sample1

31:66:3

Indialite

Sample 2

45:54:1

Indialite

Sample 3

13:86:1

Indialite, Mullite

Sample 4

50:49:1

Indialite

C - Cordierite (2MgO·2Al2O3·5SiO2), M - Mullite (3Al2O3·2SiO2), I - Indialite (Mg2Al4Si5O18), Q - Quartz (SiO2).

The crystal phases of the samples were identified by XRD analysis (XRD: X’ Pert PROMPT, Philips Netherland). Microstructural characterization of the sintered samples before and after the thermal shock test was carried out using scanning electron microscope SEM (JEOL JSE-5410 LV). The pore structure (particle size distribution-PSD) was measured using a particle size analyzer (Mastersizer 2000+Hydro 2000 MU, Malvern Instruments Limited, UK). Chemical analysis of the raw materials was carried out prior to characterization by an Xray fluorescence technique (XRF: Horiba Mesa-500w). 3. Results and discussion XRD Analysis the formation of cordierite-mullite and other crystalline phases in samples sintered at different temperatures through 1300 °C and submitted to heating-quenching cycles were analyzed by XRD analyses. The results are summarized in Table 2. I detected phases are found in almost all samples sintered at lower temperatures. This is due to difficulties of solid state reaction in general, but the main reason can be explained by the mineralogical and chemical composition of natural raw materials. Indeed, natural raw materials, apart from the main oxides (Al2O3, SiO2, and MgO), contain also some minor oxides (CaO, alkalis, TiO2, Fe2O3) which can greatly influence the course of the reaction. Fig. 1 to Fig. 4 depicts the XRD patterns of pure cordierite and pure mullite, before and after cycling. The formation of cordierite phases relates to the starting raw materials.

N. Ariyajinno et al./ Materials Today: Proceedings 5 (2018) 13948–13953

Fig. 1. Pattern of sample before NRT1.

Fig. 2. Pattern of sample before NRT 2.

Fig. 3. Pattern of the sample before NRT 3.

Fig. 4. Patterns of the sample before NRT 4.

13951

In Fig. 1, Fig. 2 and Fig. 4 shows that only Indialite phase, while as Fig. 3 shows Indialite and Mullite phase indicating that NRT 3 is melt after sintering process. The first peak characterizing the presence of cordierite (maximum intensity peak (110) corresponds to 2θ =12. 46) appears at 1300 °C. This peak increased after 35 heatingquenching cycles (Fig. 3). It is clear that cordierite is mostly in the crystalline phase, as it can be observed on microstructure. The solid state reaction of mixtures consists of step reaction starting with the formation of a spinel at about 1040 °C (Naskar and Chatterjee 2004). The fact that the dominant phase is cordierite proves the reliability of the preparation of refractory cordierite ceramics from natural raw materials and confirms the accuracy of mixture calculation. Cordierite is well crystallized, but mullite and quartz still remain. Cordierite content increases with increasing temperature, while SiO2 decreases and it is transformed into cristobalite. The presence of quartz at lower temperature and cristobalite at higher ones results from the kinetics of solid state reaction due to factors like fi nesses of the powder including its particle distribution, nonhomogeneity and reactivity of quartz. The XRD pattern of sintered mixture for the preparation of pure mullite ceramics before and after cycling is reported in Fig. 3. The first peak characterizing mullite has been found at 1300 °C. The compositions sintered at 1300 °C for 1 h exhibit the XRD pattern corresponding to mullite supplemented by sillimanite that is another form of alumina-silicate Table 3. Physical properties of the samples after sintered at 1300 C. Properties Shrinkage (%) Water absorption (%) Bulk density (g/cm3) Apparent porosity (%) Bending strength (kg/cm3)

NRT 12.36 4.16 2.27 9.2 240.08

Physical property evaluation. According to Table 3, shows compositions, physical and mechanical NRT 3 sample as a function of only firing temperatures. NRT 3 sample showed 4.12 % water absorption with 2.25 g/cm3 bulk density after firing at 1300 °C. At this firing temperature, the flexural strength in NRT clay reached the highest

13952

N. Ariyajinno et al./ Materials Today: Proceedings 5 (2018) 13948–13953

value of 330.82 kg/cm3 after firing at 1300 °C. The evidence indicated the complete vitrification in NRT clay after firing at 1300 °C. The microstructure of NRT specimens is shown in Fig. 5. It was found that the crystalline size of mullite in NRT fired clay was larger than that flexural strength. The compositions NRT because of better homogeneity attained during sintering gave acceptable values of shrinkage, apparent porosity, and bulk density

(NRT 1)

(NRT 3)

(NRT 2)

(NRT 4)

Fig. 5. Microstructures of NRT 1 - NRT 4 clays fired at 1300 °C (M: mullite).

Mechanical property evaluation. The bending strength measurements of conventionally prepared cordierite samples have been carried out as per ASTM standards. Compositions NRT showed poor strength values because of the inhomogeneity in the microstructure of sintered samples as shown in Table 2. The result indicated that the sample strength greatly depended on the amount of Al2O3: SiO2 ratio. Additionally, it also showed that the highest bending strength of the samples NRT value was 240.08 Kg/cm3 and bulk density was 2.27 g/cm3. While the lowest values were water adsorption and apparent porosity. 4. Conclusion Cordierite – Mullite was successfully synthesized by using raw materials, including talc, quartz, and kaolin (NRT) and the different molar ratio of MgO, Al2O3 and SiO2 sintered at the 1300 °C for 1 hour. The beneficial effects of firing temperature on sintering of Cordierite – Mullite Refractories from Raw Materials and Narathiwat Clay (In Thailand) on the mechanical and physical properties have been analyzed. The XRD results showed that the synthesized from raw materials different molar ratio NRT (33:5:62) was formed of only indialite or α-cordierite (2MgO.2Al2O3.5SiO2) phase. Sample led to the best physical and mechanical properties. Further work for cordierite may include testing, thermal properties. Mechanical properties of synthesized cordierite ceramics may be studied. Ground cordierite mixtures can be extruded into honeycomb substrates and

N. Ariyajinno et al./ Materials Today: Proceedings 5 (2018) 13948–13953

13953

firing temperature, porosity, thermal shock resistance and mechanical strength of these substrates can be investigated. Acknowledgments The author would thank the Office of the Higher Education Commission for financial support, Department of Industrial Chemistry, Faculty of Science, Chiang Mai University and Department of Ceramics Technology, Industrial Faculty of Technology Loei Rajabhat University, Loei. References [1] Hayase, M. And Nagai, H, Handbook of Refractories, The Technical Association of Refractories, Tokyo, Japan. (1998) 1-577. [2] Information on http://www.jcilant.or.jp/projec_planning/pdf/64_kiln_furniture manufacturing plan.pdf [3] Goren, R., Ozgur, C., and Gocmez, H, The preparation of cordierite from talc, fly ash, fused silica, and alumina mixtures. Ceramics International. (2006) 32, 53-56. [4] A. Bhatia, B.E., Overview of Refractory Materials, PDH Course M158. www.PDHonline.org. [5] Schneider J, Hildman B, and Scneider H J. Am. Ceram. Soc 891624 - 31S. (2006) [6] Sainz, M. A., Serrano, F. J., Amigo, J. M., Bastida, J. and Caballero, A., XRD microstructural analysis of mullites obtained from kaolinitealumina mixtures. J. Eur. Ceram. Soc. (2000) 20, 403 - 412. [7] Montanaro, L., Tulliani, J. M., Perrot, C. And Negro, A., Sintering of industrial mullites. J. Eur. Ceram. Soc. (1997) 17, 1715-1723. [8] J. S. JUNG, H. C. PARK, R. STEVENS.J. OF MATERIALS SCIENCE LETTERS 20, (2001) 1089 – 1091. [9] R. Griffiths and C. Radford, Calculations in Ceramics (1965) 116-119. [10] American society for testing of materials, Designation C177-91 Standard test method for Quantitatively measuring the effect of thermal cycling on refractories. In: Annual Book of ASTM Standard 04.06, West Conshohocken, Pennsylvania: ASTM (2000).