CERAMICS INTERNATIONAL SEVIER Ceramics International 30(2004)813-815 www.elsevier.com/locate/ceramint Short communication SiC/TiC laminated structure shaped by electrophoretic deposition Ch. You*, D.L. Jiang, S.H. Tan hanghai Institute of Ceramics, Chinese Academy of sciences, Shanghai 200050, PR China Received I September 2003; received in revised form 17 September 2003; accepted 2 October 2003 Available online April 2004 Abstract A SiC/TiC laminated structure was fabricated by electrophoretic deposition(EPD)from acetone-based suspensions. The formation rate of Sic is almost twice of that of TiC at the same deposition voltage and solid loading. The laminated material was then pressureless sintered Without sintering additives, the composites cannot be densified by pressureless sintering even at 2000"C o 2003 Elsevier Ltd and Techna Group S r l. All rights reserved Keywords: A Shaping; A Sintering: D. SiC 1. Introduction 2. Experimental Laminar ceramic composites are synthesized by tape cast- The following starting powders were used: (1)TiC pow- ing [1, 2], slip casting 31, centrifugal casting [4], dough der(zhuzhou, PR China) with a density of 4.93 g/cm,spe- rolling [5] and self-propagating high temperature synthesis cific surface area of 4. 8m-/g, and a mean particle size of [6]. In the nineties of last century electrophoretic deposi- 0.6 um; (2) SiC powder(Norton, USA) with a density of tion(EPD) has gained interest in the production of laminar 3. 1 g/cm, specific surface area of 6.8 m/g, and a mean par- ticle size of 0.6 um. A suspension of 50 g/l TiC (or SiC)in EPD is a colloidal processing technique for ceramics [7]. acetone was prepared in an airtight glass container. It was It has been employed to fabricate coatings, thin films [8, 9]. placed in an ultrasonic bath for 15 min. The electrolytic cell Laminar materials can also be produced via EPD. When the is a glass beaker containing the counterelectrode stainless desired thickness of the first layer is reached, the deposition steel and the working carbon paper electrode. The effective electrode can be moved to a second suspension for deposi- surface areas of both cathode and anode were 6 cm- each tion of a layer of different composition. By changing back The distance between the anode and the cathode was con and forth, a layered material is readily obtained. Sarkar and stantly 3 cm. The schematic diagram of the cell and the cir- Nicholson [7 have produced Zro2/Al2O3 laminates with cuit used for the electrical measurements are presented in alumina layers as thin as 12 um and zirconia layers of 2 um Fig. 1. Layered composites were obtained by sequential de- from ethanol-based suspensions. Ferrari et al. [10] and Fis- position experiments alternatively changing both slurries to cher et al. [11] produced alumina/zirconia laminates from form deposits with different numbers of layers, up to 20 aqueous suspensions. Vandeperre and co-workers made a Each layer was formed after I min deposition. The layered range of Sic-based laminates with graphite [ 12], and porous deposits were left in a cabinet drier more than 5 h for drying iC interlayers [13]. In this study, the fabrication via EPd of Sic/TiC laminar ceramics was investigated using an acetone base suspension. The material was pressureless sintered at 3. Result and discussion 2000° for i h The voltage evolution along the 10 min EPD experiment for both slurries is plotted in Fig. 2. The voltage increases nding author. Tel. +86-21-5241-1034 rapidly during the first minute of the deposition process and fax:+86-21-5241-3903 remains constant for longer deposition times. The measured E-mail address: youchang mail sic ac cn(Ch. You) voltage is always higher for the Tic slurry because of 0272-8842/$30.00 0 2003 Elsevier Ltd and Techna Group S r l. All rights reserved doi:10.1016/ ceramist2003.10.002
Ceramics International 30 (2004) 813–815 Short communication SiC/TiC laminated structure shaped by electrophoretic deposition Ch. You∗, D.L. Jiang, S.H. Tan Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China Received 1 September 2003; received in revised form 17 September 2003; accepted 2 October 2003 Available online 9 April 2004 Abstract A SiC/TiC laminated structure was fabricated by electrophoretic deposition (EPD) from acetone-based suspensions. The formation rate of SiC is almost twice of that of TiC at the same deposition voltage and solid loading. The laminated material was then pressureless sintered. Without sintering additives, the composites cannot be densified by pressureless sintering even at 2000 ◦C. © 2003 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Shaping; A. Sintering; D. SiC 1. Introduction Laminar ceramic composites are synthesized by tape casting [1,2], slip casting [3], centrifugal casting [4], dough rolling [5] and self-propagating high temperature synthesis [6]. In the nineties of last century electrophoretic deposition (EPD) has gained interest in the production of laminar ceramic composites. EPD is a colloidal processing technique for ceramics [7]. It has been employed to fabricate coatings, thin films [8,9]. Laminar materials can also be produced via EPD. When the desired thickness of the first layer is reached, the deposition electrode can be moved to a second suspension for deposition of a layer of different composition. By changing back and forth, a layered material is readily obtained. Sarkar and Nicholson [7] have produced ZrO2/Al2O3 laminates with alumina layers as thin as 12m and zirconia layers of 2m from ethanol-based suspensions. Ferrari et al. [10] and Fischer et al. [11] produced alumina/zirconia laminates from aqueous suspensions. Vandeperre and co-workers made a range of SiC-based laminates with graphite [12], and porous SiC interlayers [13]. In this study, the fabrication via EPD of SiC/TiC laminar ceramics was investigated using an acetone base suspension. The material was pressureless sintered at 2000 ◦C for 1 h. ∗ Corresponding author. Tel.: +86-21-5241-1034; fax: +86-21-5241-3903. E-mail address: youchang@mail.sic.ac.cn (Ch. You). 2. Experimental The following starting powders were used: (1) TiC powder (Zhuzhou, PR China) with a density of 4.93 g/cm3, specific surface area of 4.8 m2/g, and a mean particle size of 0.6m; (2) SiC powder (Norton, USA) with a density of 3.1 g/cm3, specific surface area of 6.8 m2/g, and a mean particle size of 0.6m. A suspension of 50 g/l TiC (or SiC) in acetone was prepared in an airtight glass container. It was placed in an ultrasonic bath for 15 min. The electrolytic cell is a glass beaker containing the counterelectrode stainless steel and the working carbon paper electrode. The effective surface areas of both cathode and anode were 6 cm2 each. The distance between the anode and the cathode was constantly 3 cm. The schematic diagram of the cell and the circuit used for the electrical measurements are presented in Fig. 1. Layered composites were obtained by sequential deposition experiments alternatively changing both slurries to form deposits with different numbers of layers, up to 20. Each layer was formed after 1 min deposition. The layered deposits were left in a cabinet drier more than 5 h for drying. 3. Result and discussion The voltage evolution along the 10 min EPD experiment for both slurries is plotted in Fig. 2. The voltage increases rapidly during the first minute of the deposition process and remains constant for longer deposition times. The measured voltage is always higher for the TiC slurry because of its 0272-8842/$30.00 © 2003 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2003.10.002
814 Ch. You et al. /Ceramics International 30(2004) I Cathode 5 DC power ⊙⊙⊙ EP 口-Tc △-SiC 0.01 Time(min) Time(min) Fig. 2. Voltage variation of TiC and SiC suspensions during 10 min Fig 3. Growth rates of Sic and TiC vs. time in same current density and deposition experiments. suspension concentration. lower conductivity. Deposits of both materials were pre- only to the electrical conductivity of the slips. The origin pared at different deposition times under similar conditions of this effect must be found in the nature of the electrode to evaluate the growth rates. The results can be seen in Fig. 3. consisting of an easily oxidizable substance, as Zn. During As observed, a linear growth with time is obtained for both the EpD tests in aqueous media, Zn-t cations are formed materials. The formation rate of Sic is almost twice of that in the substrate, which can easily move through the deposit of TiC at same condition. However, from Fig. 2 the volt- by either diffusion or migration phenomena [14] age does not increase any more after the first minute of the Fig. 4 shows the scan electron micrographs of the pres- deposition. This means that the resistance of the formed de- sureless sintering of the laminated structure. It is obvious posit is very low and the registered voltages must be related that the silicon carbide was not sintered for there were no Fig. 4. The SEM morphology of the pressureless sintered SiC/TiC laminated structure
814 Ch. You et al. / Ceramics International 30 (2004) 813–815 Fig. 1. Setup of EPD experiment. Fig. 2. Voltage variation of TiC and SiC suspensions during 10 min deposition experiments. lower conductivity. Deposits of both materials were prepared at different deposition times under similar conditions to evaluate the growth rates. The results can be seen in Fig. 3. As observed, a linear growth with time is obtained for both materials. The formation rate of SiC is almost twice of that of TiC at same condition. However, from Fig. 2 the voltage does not increase any more after the first minute of the deposition. This means that the resistance of the formed deposit is very low and the registered voltages must be related Fig. 4. The SEM morphology of the pressureless sintered SiC/TiC laminated structure. Fig. 3. Growth rates of SiC and TiC vs. time in same current density and suspension concentration. only to the electrical conductivity of the slips. The origin of this effect must be found in the nature of the electrode, consisting of an easily oxidizable substance, as Zn. During the EPD tests in aqueous media, Zn2+ cations are formed in the substrate, which can easily move through the deposit by either diffusion or migration phenomena [14]. Fig. 4 shows the scan electron micrographs of the pressureless sintering of the laminated structure. It is obvious that the silicon carbide was not sintered for there were no
Ch. You et al. /Ceramics International 30(2004)813-815 815 Sic Tic 30 40 50 70 Fig. 5. XRD analysis of the SPS SiC/TiC laminated structure [2]T. Chartiful, J. L. Bess The densities of the green deposits and sintered composites ZrO2-AlO3 laminates composites, in: Advances in Ceram Samples Green sic issueless ics, vol. 24B, Science and Technology of Zirconia deposit sintered SiCTIC p.1l31 3]J. Requena, R Moreno, J.S. Moya, Alumina and alumina/zirconia Relative density (% 60.1 multilayer composites obtained by slip casting, J. Am. Ceram Soc 72(1989)1511 additives. The pressureless sintering of pure silicon carbide [4] D.B. Marshall, J.J. Ratto, F.E. Lange, Enhanced fracture toughness is very difficult. The sintering of TiC is easier relatively in layered microcomposites of Ce-ZrO2 and Al2O3, J. Am. Ceram. Soc.74(1991)2979 More denser TiC can be observed in Fig. 4 5]wJ. Clegg, K. Kendall, N. McN. Alford, T.W. Botton, J D. Birchall, The densities of the green deposits and sintered compos- A simple way to make tough ceramics, Nature( London)347(1990) ites were measured by Archimedes method are shown in Table 1. The green density of the SiC and TiC deposits were [6]M. Koizumi, Recent progress of functionally gradient materials in pan, Ceram. Eng. Sci. Proc. 13(1992)333 measured respectively. Without sintering additives, pressure- [7 P Sarkar, P.S. Nicholson, Electrophoretic deposition(EPD): mecha less sintered sample has a very low density. Further research nisms kinetics and application to ceramics, J. Am. Ceram. Soc. 79 on the densification of the material should be carried out later. The XRD analysis of the sample is shown in Fig. 5 [8]L. Gal-Or, S.R. Chaim, Electrolytic Zro2 coatings, J. Electrochem. There are only SiC and TiC phase in the So.138(1991)1939-1946 [9J Mizuguchi, sions for the electrophoretic deposition of powdered substances, J 4. Conclusions lectrochem Soc. 130(1983)1819-182 lOJ B. Ferrari, A.J. SaI EPD was demonstrated to be an effective technique in syn- trophoretic deposition of Al2 O3/ZrO2 layered ceramics, Mater. Lett. 35(1998)370-374 thesizing laminated structure ceramics. SiC particles have [11]R. Fischer, E. Fischer, G. De Portu, E. Roncari, Preparation of bigger formation rate than TiC particles at the same deposi- ceramic micro-laminates by electrophoresis in aqueous system, J tion voltage and solid loading. Pressureless sintering cannot Mater:.sci.Let.14(1995)25-27 densify the Sic/TiC laminated structure without sintering [12]L. Vandeperre, O. Van der Biest, w.J. Clegg, Silicon carbide lami- additives Mater.127(1997)567-574 [13]L. Vandeperre, O. Van der Biest, SiC laminates with porous inter References American Ceramic Society, Cincinnati, OH, 1998 [14]B. Ferrari, R. Moreno, Zirconia thick films deposited on nickel by 11]P Boch, T. Chartier, M. Huttepain, Tape casting of Al2O3/Zro2 queous electrophoretic deposition, J Electrochem. Soc. 147(2000) laminated composites, J. Am. Ceram. Soc. 69(1986)C-191 2987-2992
Ch. You et al. / Ceramics International 30 (2004) 813–815 815 Fig. 5. XRD analysis of the SPS SiC/TiC laminated structure. Table 1 The densities of the green deposits and sintered composites Samples Green SiC deposit Green TiC deposit Pressureless sintered SiC/TiC Relative density (%) 60.1 59.6 90.2 additives. The pressureless sintering of pure silicon carbide is very difficult. The sintering of TiC is easier relatively. More denser TiC can be observed in Fig. 4. The densities of the green deposits and sintered composites were measured by Archimedes’ method are shown in Table 1. The green density of the SiC and TiC deposits were measured respectively. Without sintering additives, pressureless sintered sample has a very low density. Further research on the densification of the material should be carried out later. The XRD analysis of the sample is shown in Fig. 5. There are only SiC and TiC phase in the composites. 4. Conclusions EPD was demonstrated to be an effective technique in synthesizing laminated structure ceramics. SiC particles have bigger formation rate than TiC particles at the same deposition voltage and solid loading. Pressureless sintering cannot densify the SiC/TiC laminated structure without sintering additives. References [1] P. Boch, T. Chartier, M. Huttepain, Tape casting of Al2O3/ZrO2 laminated composites, J. Am. Ceram. Soc. 69 (1986) C-191. [2] T. Chartiful, J.L. Besson, P. Boch, Mechanical properties of ZrO2–Al2O3 laminates composites, in: Advances in Ceramics, vol. 24B, Science and Technology of Zirconia III, 1988, p. 1131. [3] J. Requena, R. Moreno, J.S. Moya, Alumina and alumina/zirconia multilayer composites obtained by slip casting, J. Am. Ceram. Soc. 72 (1989) 1511. [4] D.B. Marshall, J.J. Ratto, F.F. Lange, Enhanced fracture toughness in layered microcomposites of Ce-ZrO2 and Al2O3, J. Am. Ceram. Soc. 74 (1991) 2979. [5] W.J. Clegg, K. Kendall, N. McN. Alford, T.W. Botton, J.D. Birchall, A simple way to make tough ceramics, Nature (London) 347 (1990) 455. [6] M. Koizumi, Recent progress of functionally gradient materials in Japan, Ceram. Eng. Sci. Proc. 13 (1992) 333. [7] P. Sarkar, P.S. Nicholson, Electrophoretic deposition (EPD): mechanisms kinetics and application to ceramics, J. Am. Ceram. Soc. 79 (1996) 1987–2002. [8] L. Gal-Or, S.R. Chaim, Electrolytic ZrO2 coatings, J. Electrochem. Soc. 138 (1991) 1939–1946. [9] J. Mizuguchi, K. Sumi, T. Muchi, Highly stable nonaqueous suspensions for the electrophoretic deposition of powdered substances, J. Electrochem. Soc. 130 (1983) 1819–1825. [10] B. Ferrari, A.J. Sanchez-Herencia, R. Moreno, Aqueous electrophoretic deposition of Al2O3/ZrO2 layered ceramics, Mater. Lett. 35 (1998) 370–374. [11] R. Fischer, E. Fischer, G. De Portu, E. Roncari, Preparation of ceramic micro-laminates by electrophoresis in aqueous system, J. Mater. Sci. Lett. 14 (1995) 25–27. [12] L. Vandeperre, O. Van der Biest, W.J. Clegg, Silicon carbide laminates with carbon interlayers by electrophoretic deposition, Key Eng. Mater. 127 (1997) 567–574. [13] L. Vandeperre, O. Van der Biest, SiC laminates with porous interlayers produced by EPD, Presented at 100th Annual Meeting of the American Ceramic Society, Cincinnati, OH, 1998. [14] B. Ferrari, R. Moreno, Zirconia thick films deposited on nickel by aqueous electrophoretic deposition, J. Electrochem. Soc. 147 (2000) 2987–2992