Decomposition and Densification Study of Zircon with

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R. Sarkar*, A. Baskey*

Decomposition and Densification Study of Zircon with Additives The corresponding author, Dr. Ritwik Sarkar, Associate Professor, National Institute of Technology, Rourkela, ­India, has more than 15 years of experience in Ceramics and Refractories. He worked with IFGL Bioceramics Ltd, IFGL Refractories Ltd, CG & CRI, R&D of ACC Ltd, and H&R Johnson Ltd, all in India, and at the IKKM, RWTH Aachen, Germany (DAAD Fellowship). Dr Sarkar has re­ ceived many awards for academic excellence and contri­ butions to Ceramics and Materials Science, including the Young Scientist Award. A life member of the Indian Ceramic Society & Indian Institute of Ceramics, Dr Sarkar has more than 80 research publications and 9 patents to his credit. E-Mail: [email protected]

1 Introduction Zircon (ZrSiO4) has a wide range of applications as a ceramic and refractory material [1–4], including: •• a refractory for construction of glass tank furnaces and nozzles in iron and steel making •• various uses in energy technology •• as moulds and cores in precision investment casting •• protective coatings of steel-moulding tools. The wide range of applications of zircon is due to its excellent thermo-physical properties such as: low thermal expansion, low thermal conductivity and good corrosion resistance, for example, against glass melts, slag and liquid metal alloys [5–6]. Zircon is important as an opacifier in the decorative ceramic industries due to its high refractive index. It is also used as the principal precursor for metallic zirconium and many other zirconium compounds [7]. Zircon is one of the most chemically stable compounds with DG1400K = 1489.1 kJ/mol) [8]. This is a consequence of the high coor-

* Department of Ceramic Engineering, National Insti­ tute of Technology, Rourkela, India

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Abstract

Keywords

Decomposition and densification of fine zircon sand was studied in the presence of different additives, namely alumina, iron oxide, magne­ sium oxide, and titanium oxide. The zircon sand was mixed, pressed and sintered be­ tween1500–1600 °C. Additives were found to have a strong effect on densification behavior but minimal impact on decomposition.

dination of bisdisphenoid ZrO8 in a tetra­ gonal structure with SiO4 tetrahedra [9]. Mineral acids other than HF cannot attack zircon and very aggressive reaction conditions are required to break down the strong binding between the zirconium and silicon parts of the compound. Several industrial methods are used to decompose zircon, ­including: •• fusion of zircon with caustic soda (at 600– 650 °C) or with soda ash (at 900 °C) [10] •• thermal dissociation by plasma [11] •• sintering with a source of alkaline earth oxides [12–13] •• chlorination of sand by mixing it with coal at 900–1000 °C in a blast furnace or chlorination of zirconium carbide at 350–450 °C after carburization of zircon in a mixture of coal in an electric arc furnace at 2000–2200 °C [14–15] •• mechano-chemical treatment of zircon followed by acid attack [16]. All the high-temperature applications mentioned above strongly depend on accurate knowledge of the thermal stability of zircon, but the information available about this topic differs enormously concerning both dissociation mechanisms and temperature. Although most publications agree that zircon decomposes by a solid-state reaction, the stated dissociation temperatures vary

zircon fines, decom­ position, densification, additives Interceram 60 (2011) [5]

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Intensity (u.a.)

The author

between 1285 and 1700 °C, resulting in different phase diagrams (17–20). This information is, however, critical for prediction of the expected life-time of zircon and zirconia-based refractories and parts in contact with silica-containing melts. At the present time it is well established that chemically pure zircon decomposes in solid state at a temperature of 1676 ±7 °C giving a mixture of tetragonal zirconia and cristobalite [18]. At this temperature, zircon dissociation is expressed by the following reaction: ZrSiO4 = ZrO2 + SiO2

(1)

which forms zirconia (ZrO2) and silica (SiO2). Above about 1173 °C, zirconia takes a tetragonal form and below this temperature zirconia is present in monoclinic phase [21]. Zircon dissociation behaviour has been studied widely in the literature and is reported to be greatly influenced by its impurity content. Specifically, the more impurities present in zircon, the lower the onset temperature of dissociation [22–24]. To reduce the degree of zircon degradation, a reduction in iron, titanium, aluminum, and alkali content is required [3, 23, 25]. This study measured the effect of different additives on the densification and decomposition characteristics of “zirflor” (fine milled zircon sand, from beach sand miner-

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Fig. 2 • and m

als). M at a The r sity, a X-ray

2 Exp Zirflo ­Indian used chem given (XRD was m nesia, at 1 m M, T was p

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Table 1 • Physico-chemical properties of zirflor High-Performance Ceramics

Chemical properties ZrO2(+HfO2) / mass-% SiO2 / mass-%

Intensity (u.a.)

Fe2O3 / mass-% U1_U4_IC_2_10.indd 2

n difinforion of zircoontact resent mically e at a ixture [18]. ion is (1)

silica takes mperaphase r has and is ts immpuonset To re, a rem, and

ferent ecom(fine miner-

34.35

TILE & BRICK The Use of Residues in the Manufacture of Ceramic Tile Bodies Hot-Pressed Gres Porcellanato Body Effect of Calcite on the Brick Body Closing Glossiness and Slipperiness of Polished Porcelain Stoneware Tiles Effect of Diaspore Addition on Microwave-Assisted Sintering of Floor Tile

0.16

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0.63

Particle size

96 % finer than 45 mm

Bulk density

1.84 g / cm3

Fig. 1 • XRD plot of the raw unfired zircon sample (zirflor)

2θ / °

3

Intensity (u.a.)

2

2θ / °

2θ / °

Fig. 2 • XRD plot of different batches sintered at 1500 °C (where z = zircon and m = monoclinic ­zirconia phase)

als). Mixed and pressed compacts were fired at a temperature range of 1500–1600 °C. The resulting products were tested for density, and for decomposition behaviour by X-ray diffraction. 2 Experimental Zirflor, milled zircon sand, supplied by ­Indian Rare Earths Ltd (IREL, India), was used as the starting material. The physicochemical properties of the raw material are given in Table 1 and an X-ray diffraction (XRD) plot is provided in Fig. 1. Zirflor was mixed separately with alumina, magnesia, titania and iron oxide additives, each at 1 mass-%. The batches were labeled as A, M, T and F, respectively. Another Z batch was prepared without additives. All the

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Physical properties

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11) [5]

Ceramic Bricks Filling – Energy Saving

Al2O3 / mass-%

s

m­ ation,

TiO2 / mass-%

Composition Modifications on the Properties of Some Bioactive Glasses and Glass Ceramics Titanium Nitride Coating of Cobalt Chromium Coronary Stents: a SEM-EDS Analysis Ceramic Based Bio-Medical Implants Preparation of Ca-_/`Sialon Powders by Microwave Reaction Nitridation

Fig. 3 • XRD plot of different batches sintered at 1550 °C (where z = zircon and m = monoclinic z­ irconia phase)

batches were mixed thoroughly for proper distribution of the additives and then the batches were formed into pellet shapes by hydraulic pressing using 6 mass-% PVA ­solution (4 % concentration). The pellets were dried at 110 °C and then sintered at 1500, 1550 and 1600 °C with 2 h soaking time at the peak temperatures. The sintered products were characterized for phase analysis study by XRD (for decomposition) and tested for bulk density, apparent porosity and water absorption (for densification). All results were based on an average of five individual measurements. Phase analysis was performed in a X-ray diffractometer (PW-1830, Philips, Netherlands) using Cu-Kα radiation in the range of 20–60 °C with a scanning speed of 2 °/min.

The densification study employed the ­liquid displacement method with boiling water, by Archimedes’ principle (as per ­Bureau of Indian Standard (BIS) specifications, IS 1528–1974, Part XII and Part ­VIII, reaffirmed in 2002). The firings were conducted in a programmable electric ­furnace (Bysakh & Co., India). 3 Results and discussion 3.1 Phase analysis study Figure 1 is a phase analysis of the raw zircon sand. Figure 2 shows that zircon starts dissociating even at a temperature of 1500 °C and forms free zirconia phase. The presence of free zirconia is very weak for the Z batch, but with added iron oxide and titania (the F and T batches), free zirconia peaks are com-

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zircon er pea the sin Increa increa the ap tion v Addit fect o oxide benef

5

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Ceramic Bricks Filling – Energy Saving

Building Materials Effect of Bi2O3 on Cordierite Formation in Cordierite Based Bodies

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The Use of Residues in the Manufacture of Ceramic Tile Bodies Hot-Pressed Gres Porcellanato Body Effect of Calcite on the Brick Body Closing Glossiness and Slipperiness of Polished Porcelain Stoneware Tiles Effect of Diaspore Addition on Microwave-Assisted Sintering of Floor Tile

Tile surface

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BD / g · cm–3

Intensity (u.a.)

TILE & BRICK

Refere

  [1] Ur Gla   [2] Mo Mi ter Jpn   [3] Co Zir (19   [4] Lo tre Sc   [5] Bo Bo (19

Temperature / °C

2θ / ° Fig. 4 • XRD plot of different batches sintered at 1600 °C (where z = zircon and m = monoclinic ­zirconia phase)

7

AP / %

WA / mass-%

6

Fig. 5 • Variation of bulk density (BD) against ­temperature

Temperature / °C

Temperature / °C

Fig. 6 • Variation of apparent porosity (AP) against temperature

P

Fig. 7 • Variation of water absorption (WA) against temperature

Pl KP paratively stronger. Higher temperatures caused greater decomposition (Figs. 3–4) as is indicated by increased strength of the monoclinic zirconia phase. But at higher temperatures there was negligible difference in the peak strength of free zirconia phase for all the different batches. Also the batches showed similar phase distribution and intensities. Only zircon and monoclinic zirconia phases were observed in the phase analysis of the sintered products [21] and no free silica phase was found, which may be due to the presence of free silica as glassy phase. The study indicates that additives have negligible effect on the dissociation and phase content of sintered zircon at the 1 mass-% level.

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3.2 Densification study Density values for all batches were found to increase with higher sintering temperature due to greater extent of sintering (Fig. 5). All the additives were found to have beneficial effect on densification at all the tested temperatures. This may be due to more liquid phase in the presence of additives. The batch without additives can have only free silica, but the additive-containing batches can form silicates, increasing the extent of liquid phase, which results in greater sintering and higher density values. Among the different additives studied, iron oxide showed the maximum beneficial effect. Variation of apparent porosity plotted against temperature (Fig. 6) reinforces the results of the density

plot. Increase in temperature reduces porosity and the maximum porosity was reached in the batch containing zero additives. The iron oxide-containing batch showed minimum porosity values for all tested temper­ atures. Water absorption measurement (Fig. 7) also shows results similar to the graph of apparent porosity. 4 Conclusions The fired pellets showed only zircon and ­zirconia phases and no free silica phase. Increase in firing temperature was found to enhance the dissociation of zircon and boost zirconia phase intensity in the sintered pellet. The additives showed little beneficial ­effect on the decomposition behaviour of

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zircon sand and showed marginally stronger peaks of zirconia phase, especially for the sintering temperature of 1500 °C. Increase in temperature was also found to increase the sintered density and decrease the apparent porosity and water absorption values for all the sintered products. Additives were found to have beneficial effect on densification behaviour and iron oxide was found to have the maximum beneficial effect on the sintered properties. References   [1] Urffer, D.: The Use of Zircon in Refractories for Glass Making. Ind. Miner. 344 (1996) 49–53   [2] Mori, T., Yamada, Y., Yamamura, H., Kobayashi, H., Mitamura, T.: Reactivity of High-Purity ZrSiO4 Sin­ tered Bodies for Alkaline Glass Melts. J. Ceram. Soc. Jpn. 100 (1992) [3] 250–258   [3] Comstock, G.F.: Some Experiments with Zircon and Zirconia Refractories. J. Amer. Ceram. Soc. 16 (1933) [1] 12–35   [4] Lowe, l.A., Wosinski, J., Davis, G.: Stabilizing Dis­ tressed Glass Furnace Melter Crowns. Ceram. Eng. Sci. Proc. 18 (1997) [1] 164–179   [5] Boggum, P., Schulte, K., Glaser, W.: Sicherheit im Boden von Glasschmelzwannen. Sprechsaal 116 (1983) [5] 386–392

  [6] Schulle, W.: Feuerfeste Werkstoffe-Feuerfest­kera­mik –Eigenschaften, prüftechnische Be­ur­tei­lung, Werk­ stofftypen, Feuerfeste Werkstoffe. 1st ed., Deut­ scher Verlag für Grundstoffindustrie, Leipzig, Germa­ ny (1990)   [7] Banerjee, G.: Beach sand minerals: A new material resource for glassand ceramics. Bulletin of Materials Science 21 [4] 349–354 (1998)   [8] Brain, I., Knacke, O.: Thermochemical Properties of Inorganic Substances, Springer-Verlag, Berlin (1973)   [9] Hyde, B.G., Andersson, S.. Inorganic Crystal Struc­ ture. Wiley–Interscience, New York (1989) [10] El-Barawy, K.A., El Tawil, S.Z., Francis, A.A.: Alkali Fusion of Zircon Sand. Transaction of the Institute of Mining and Metallurgical Sect. C 109 (2000) C49–C56 [11] Ananthapadmanabhan, P.V., Sreekumar, K.P., Iyer, K.V., Venkatramani, N.: J. Alloys Compd. 196 (1/2) (1993) 251–254. [12] Jeong-Gu, Y., Sung-Churl, C., Jae-Won, K., Jae-Ean, L., Je-Hyun, L., Yeon-Gil, J.: Mater. Sci. Eng. A 368 (2004) [1/2] 94–102 [13] Rodr´ıguez, J.L., Rodr´ıguez, M.A., De Aza, S., ­Pena, P.: J. Europ. Ceram. Soc. 21 (2001) [3] 343–354 [14] Gupta, C.K., Venkatachalam, S., Bidaye, A.C.: Met­ all. Mater. Trans. 30B (1999) 205–213 [15] Stephens, WW. in: Franklin, G.D., Adamson, R.B. (Eds.): Extractive Metallurgy of Zirconium-1945 to the Present Paper Published in “Zirconium in the Nuclear Industry: Sixth International Symposium “ASTM STP 824, Amer. Soc. for Testing and Materials (1984) 5–36 [16] Puclin, T., Kaczmarek, W.A., Ninham, B.W.: Mater. Chem. Phys. 40 (1995) [2] 73–81

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[17] Washburn, E.W., Libman, E.E.: Approximate determi­ Ceramic diagram Bricks Filling nation of melting point of zirconia–­silica. J. – Energy Saving Amer. Ceram. Soc. 3 (1920) 634–640 [18] Butterman, W.C., Foster, W.R.: Zircon stability and the ZrO2–SiO2 phase diagram. Amer. Mineralogist 52 (1967) 880–885 [19] Curtis, C.E., Sowman, H.G.: Investigation of the ther­ mal dissociation, re-association, and synthesis of Polished Porcelain zircon. J. Amer. Ceram.Stoneware Soc. Tiles 36 (1953) [6] 190–195 [20] Toropov, N.A., Galakhov, F.Yu.: Liquidation in the sys­ tem ZrO2–SiO2. Izv. Akad. Nauk. USSR, Ser. Khim. 2 (1956) 158–161 [21] Pavlik Jr., R.S., Holland, H.J., Payzant, E.A.: Thermal Decomposition of Zircon Refractories, J. Amer. Cer­ am. Soc. 84 (2001) [12] 2930–2936 [22] Curtis, C.E., Sowman, H.G.: Investigation of the Ther­ mal Dissociation, Reassociation, and Synthesis of Zircon. J. Amer. Ceram. Soc. 36 (1953) [6] 190–198 [23] Pena, P., DeAza, S.: The Zircon Thermal Behaviour: Effect of Impurities. J. Mater. Sci. 19 (1984) 135–142 [24] Pena, P., Guitian, F., DeAza.: The Zircon Thermal ­Behaviour: Effect of Impurities. J. Mater. Sci. 19 (1984) 143–149 [25] Sempolinski, D.R., Swaroop, L.I.: U.S. Pat. No. 5 332 702, (1994) July 26 The Glass Industry in the EU Today – a Survey

High-Performance Ceramics Composition Modifications on the Properties of Some Bioactive Glasses and Glass Ceramics Titanium Nitride Coating of Cobalt Chromium Coronary Stents: a SEM-EDS Analysis Ceramic Based Bio-Medical Implants Preparation of Ca-_/`Sialon Powders by Microwave Reaction Nitridation

Building Materials

Effect of Bi2O3 on Cordierite Formation in Cordierite Based Bodies

TILE & BRICK

The Use of Residues in the Manufacture of Ceramic Tile Bodies Hot-Pressed Gres Porcellanato Body Effect of Calcite on the Brick Body Closing Glossiness and Slipperiness of Polished Porcelain Stoneware Tiles Effect of Diaspore Addition on Microwave-Assisted Sintering of Floor Tile

Tile surface

12.04.10 13:54

Received: 12.06.2011

Hosted by

TARJ The Technical Association of Refractories, Japan

OfficialHome HomePage: Page: http://www.unitecr2011.org/ http://www.unitecr2011.org/ Official Official Home Page: http://www.unitecr2011.org Place of Conference: Place of Conference: Session Session Topics; Topics; Kyoto International Conference Center Kyoto International Conference Center 1.Refractories for 1.Refractories for Iron Iron && Steel, Steel,Non-ferrous Non-ferrous Place of Conference: Metallurgy, Glass, Ceramics, Cement & &Lime, President of UNITECR 2011 Kyoto International Conference Center Metallurgy, Glass, Ceramics, Cement Lime, President of UNITECR 2011 Session Topics: Petrochemical, Waste Incineration and Others Mr. Tsuneo Kayama Petrochemical, Waste Incineration and Others Mr. Tsuneo Kayama President of UNITECR 2011: 1. Refractories for Iron &and Steel, Non-ferrous 2. Environmental Environmental Sustainability Recycling Chair of Technical Program Committee 2. Sustainability and Recycling Chair of Technical Mr. Tsuneo Kayama Program Committee Metallurgy, Glass, Ceramics, 3. Advances in Refractory ScienceCement & Lime， Mr. Eizo Maeda 3. Advances in Petrochemical, Refractory Basic Basic Science Mr. Eizo Maeda Waste Incineration and Others 4. Nano-Engineered Refractories E-mail: [email protected] Chair of Technical Program Committee: 4. Nano-Engineered Refractories Environmental Sustainability E-mail: [email protected] 5. Refractory2. Applications of Ceramicsand Recycling Mr. Eizo Maeda 5. Refractory3. Applications of Ceramics Advances in Refractory Basic Science 6. Raw Material Selection and Application Contact Information: E-Mail: [email protected] 4. Nano-Engineered Refractories 6. Raw Material Selection and Application Contact Information: 7. Refractory Engineering Systems and Design Secretary General of UNITECR 2011 5. Engineering Refractory Applications ofand Ceramics 7. Systems Design Contact Information: Secretary General of UNITECR 2011 8. Refractory Advances in Manufacturing, Installation and Dr. Masanori Ueki 6. Raw Material Selection and Application 8. Advances in Manufacturing, Installation and Secretary General of UNITECR 2011 Dr. Masanori Ueki Equipment Secretariat 7. Refractory Engineering Systems and Design Equipment Dr. Masanori Ueki Secretariat 9. Process Control, Quality Control and 8. Advances in Manufacturing, Installation and Ms. Yoko Yoshii 9. Process Control, Quality Control and Ms. Yoko Yoshii Quality Assurance Equipment The Technical Association of Refractories, Japan Secretariat: Assurance 10.Quality New Tests Testing Development TheNew Technical Association of Refractories, Japan 9. and Process Control, Quality Control and Quality Ginza Ms. Yoko YoshiiBldg., 10. New Tests and Testing Development Assurance 11. Education and Training New Ginza Bldg., 7-3-13 Ginza, Chuo-ku, Tokyo 104-0061, Japan The Technical Association ofFax:+81-3-3572-0175 Refractories, Japan 10. and NewTraining Tests and Testing Development 11. Education 7-3-13 Ginza, Chuo-ku, Tokyo 104-0061, Japan Tel: +81-3-3572-0705 11. Education and Training New Ginza Bldg., 7-3-13 Ginza, Chuo-ku, Tokyo 104-0061, Japan Tel:E-mail: +81-3-3572-0705 Fax:+81-3-3572-0175 [email protected] Tel: +81-3-3572-0705, Fax: +81-3-3572-0175 E-mail: [email protected] Abstract (100-word) submission was closed at the end of December, 2010 E-Mail: [email protected] Deadline for the proceedings paper pages) page) for2010 conference book: (100-word) submission was (4 closed atand the abstract(1 end of December, Abstract 2011 May 31,for Abstract submission was closedand at the end of December, 2010 Deadline the proceedings paper (4 pages) abstract(1 page) for conference book: May 31, 2011

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