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Nano-structured Alumina-ZrO2 ceramic laminates

ABSTRACT

In the last years many efforts have been expended to develop colloidal process that uses water instead of organic solvents in the tape casting process. In present work, alumina/zirconia laminated nanocomposites were fabricated by layer-by-layer method and using water-based tape casting process. Physical and mechanical properties as well as the fracture mode were investigated. The laminates consisted of stacked alumina and zirconia green sheets produced by thermopressing. The ceramic laminates were first heated at 450°C (organic elimination) and subsequently sintered in air at 1500°C during 1 h. The ceramic laminates showed a mechanical strength of approximately 103 MPa (AZAZA) and 44 MPa (ZAZAZ), respectively and an intergranular-transgranular mixed fracture mode.

Keywords
nanocomposites; laminates; tape casting

1. INTRODUCTION

Nanostructured materials have received much attention in last decades, which can be attributed to the unusual physical and mechanical properties, such magneto resistance, unusual dielectric properties and high temperature mechanical properties [11 RAMASESHAN, R., SUNDARRAJAN, S., JOSE, R., “Nanostructured ceramics by eletrospinning”, J. Applied Physics, v.102, pp.1101-10,2012.

2 HAN, H., AVERBACK, R.S., “High temperature mechanical propertiesof nanostructured Ceramics”, Nanostructured Materials, v.1, pp.95-100, 1992.

3 THOSTENSON, E.T., LI, C., CHOU, T.W., “Nanocomposites in Context”, Composites Science and Technology, v.65, pp. 491-516, 2005.
-44 DEY, A., DEY, P., DATTA, S., et al., “A new model for multilayer ceramic Composites”, Mater and Manufacturing Processes., v.23, pp. 513-527, 2008.]. The ability to sinter the powders into dense bodies and retain the grain size in the nano scale has attracted many researches in various fields from materials science to biotechnology, solar cells and in biology for tissue engineering. Tape casting is an effectively technique for making thin sheets and flat ceramic substrates and multilayer structures mainly for the electronic industry [55 REED, J.S., Principles of Ceramics Processing, second ed., Wiley, New York, 1995.

6 PORTU G., MICELE L., PEZZOTTI G., “Laminated ceramic structures from oxide systems”, Comp., v.37, pp. 556–567, 2006.
-77 CLEGG, J., KENDALL, K., BUTTON, T.J., et al., “A simple way to make tough ceramic”, Nature, v.347, pp. 455-457, 1990.]. The characteristic uses for tape cast products were solid electrolytes for sensors and solid oxide fuel cells. Tape casting is a well-stablished method that consists in the preparation of a suspension of the ceramic powder in a solvent, with addition of a dispersant, binder and plasticizer [88 MORENO, R., “The role of slip additives in tape casting technology: Part 1-Solvents and dispersants”, Am. Ceram. Soc. Bull., v.71, pp.1521–1531, 1992.

9 ARAUJO, M.R., ACCHAR, W., “ Fabrication and characterization of nano-zirconia produced by aqueousbased tape casting” , Mater. Today. Proc., v.4, pp.11506-511, 2017.
-1010 FENG, J.H., DOGAN, F., “Aqueous processing and mechanical properties of PLZR green Tapes”, Mater. Sci.Eng. A, v.283, pp. 56–64, 2000.].

The mainly factor is the control the rheological behavior of the slips, which will produce an adequate strength and flexibility to the green tapes, respectively. Recently water based tape casting process has been used, in order to avoid the toxic effects produced by organic solvents [1111 MORENO, V., AGUILLAR, J.L., HOTZA, D., “ 8YSZ tapes produced by aqueous tape casting”, Mater. Sci. Forum, v.727-728, pp. 752–757, 2012.-1212 ALBANO, M.P., GARRID, L.B., “Aqueous tape casting of yttria stabilized zirconia”, Mater. Sci. Eng. A, v. 420 , pp.171-178, 2006.]. The use of alumina and zirconia as the constituent materials of ceramic laminates can be related to the excellent bonding between the layers in the absence of excessive diffusion between components, their good thermo-mechanical properties and their relatively ease of processing [1313 CORREA, M.A., ARAUJO, M.R., ACCHAR, W., et al., “ ZrO2 tape as flexible substrate to artificially nanostructured materials”, Mater.Lett., v.196, pp.69-73, 2017.-1414 GUGLIELMI, P., BLAESA, D., HABLITZEL, M.P., et al., “Microstructure and flexural properties of multilayered fiber reinforced oxiddes composites fabricated by a novel lamination route”, Ceram.Inter, v. 41, pp. 7836-46, 2015.]. These characteristics make the two materials interesting candidates for the manufacture of ceramic laminates.

The literature about the fabrication and characterization of alumina-zirconia and other nanocomposites laminates are still scarce. Some recent works published in the literature reports some results obtained for composite ceramic laminates [1515 MINATTO, F.D., MILAK, P., NONI, A., et al., “Multilayered ceramic composites – a review”, Adv. Applied. Ceram., v.114, pp.127-138, 2015.

16 ARAUJO, M.R., HOTZA, D., ACCHAR, W., “Processing and properties of Tape-Cast alumina-zirconia laminates”, submitted to J. Alloy & Componds in 2017.

17 SONG, J., ZHANG, Y., FAN, H., et al., “Design of structure parameters and corrugated interfaces for optimal mechanical properties in alumina-graphite laminated Nanocomposites” , Mat. Design, v.65, pp.1205-1213, 2015.

18 HU, T.C., ZHANG, Y.S., HU, L.T., “Mechanical and wear characteristic of Y-TZP-Al2O3 Nanocomposites”, Ind. Lubr. Tribol., v. 66, pp. 209-14, 2014.

19 FANG, Y., ZHANG, Y.S., SONG, J.J., et al., “Design and fabrication of laminated graded zirconia selflubricating composites”, Mater.Des. v. 49, pp.421-425, 2013.
-2020 HU, T., ZHANG, Y., HU, L., “Mechanical and wear characteristic of Y-TZP/Al2O3 nanocomposites”, Industrial Lubrication and Tribology, v.66, pp. 209-214, 2014.]. The laminated structure shows an improvement of the mechanical properties as compared to monolithic material and indicated that the physical, mechanical and electric properties are very sensitive to process variations. [2020 HU, T., ZHANG, Y., HU, L., “Mechanical and wear characteristic of Y-TZP/Al2O3 nanocomposites”, Industrial Lubrication and Tribology, v.66, pp. 209-214, 2014.

21 CLEGG, W.J., “Design of ceramic laminates for structural applications”, Mater Science and Technology, v.14, pp. 483-494, 1998.

22 FANG, Y., ZHANG, Y., SONG, J., et al., “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.
-2323 KRSTIC, Z., KRSTIC, V.D., “Crack propagation and residual stress in laminated Si3N4/BN composite structures”, J.European Ceram Soc., v.31, pp. 1841-1847, 2011.].

This increase is associated to the energy dissipation and also the crack propagating path that depends strongly on the interface property of the laminated composite material [2222 FANG, Y., ZHANG, Y., SONG, J., et al., “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.

23 KRSTIC, Z., KRSTIC, V.D., “Crack propagation and residual stress in laminated Si3N4/BN composite structures”, J.European Ceram Soc., v.31, pp. 1841-1847, 2011.
-2424 YAE, Q., YONSHENG, Z., LITIAN, H.U., “Microstructure and bending strength of Al2O3/ Al2O3ZrO2(3Y) laminated nanocomposites”, J.Chinese Ceram Soc., v.39, pp. 228-32, 2011.]. This study uses water instead of organic solvents in the tape casting process to produce a nanostructured laminate constituted by alumina and zirconia sheets. Physical and mechanical properties as well as the fracture mode of the laminates were investigated.

2. MATERIALS AND METHODS

Commercial yttria-stabilized zirconia powder (TZ-3YE, 3 mol% Y2O3 stabilized ZrO2, Tosoh, Japan) and alumina powder (α–Al2O3 Taimei, Japan) were used in this study. Two different tapes using both the powders were separately produced by aqueous tape casting. The powder was deagglomerated in deionized water in a ball mill for 24 h with addition of a dispersant, respectively Darvan 821A in zirconia and alumina slurry. After deagglomeration, an acrylic emulsion binder (Mowilith LDM 6138, Clariant), a defoaming agent (Antifoamer A, Sigma-Aldrich), a surfactant (coconut diethanolamide, Stepan) and a plasticizer were added.

Table 1
Slurry composition (in wt%).

The slurry was mixed by ball milling for 120 min, and then cast at 25°C by a tape cast machine (CC1200, Mistler) with moving polyethylene terephthalate carrier film coated with a fine silicon layer (Mylar G10JRM, Mistler). A casting speed of 200 mm/min was set. The gap between the blade and the carrier was adjusted manually to obtain a final tape thickness of 150 to 200 µm. The stability of the two slurries was analyzed by means of rheological characterization using a Haake Viscotester-Thermo Fischer Scientific viscosimeter with cone and plate geometry, at room temperature, and with shear stress between 0 and 800 s1.The green tapes were dried at 25°C for 24h. Composition of alumina and zirconia slurries is showed in Table 1. The laminar composites were arranged as follows; five layers in the cast direction for each combination, where ceramic A is alumina Z is zirconia. Lamination was carried in a warm pressing between two metal plates at 60 °C, 19 MPa for 5 min. Details about the fabrication of both tapes can be founded elsewhere [99 ARAUJO, M.R., ACCHAR, W., “ Fabrication and characterization of nano-zirconia produced by aqueousbased tape casting” , Mater. Today. Proc., v.4, pp.11506-511, 2017.,1616 ARAUJO, M.R., HOTZA, D., ACCHAR, W., “Processing and properties of Tape-Cast alumina-zirconia laminates”, submitted to J. Alloy & Componds in 2017.]. Debinding of the green laminates tapes was carried out by slow heating (0.5°C/min) up to 600°C with a dwell time of 1h. Then, the laminates were sintered with a heating rate of 5°C/min up to 1500°C with a dwell time of 1h. The microstructure of green laminates was analyzed using a high-resolution field-emission gun scanning electron microscopy FEG-SEM (Supra 35-VP, Carl Zeiss, Germany). Density of the sintered tapes was measured by Archimedes method. A mechanical testing machine (BZ 2.5/TS1T, Zwick/Roell) was used to measure the mechanical properties of the laminates with a crosshead speed of 5 mm min−1 based on the ISO 527-3 norm. For those mechanical tests, 7 rectangular laminar composites specimens (50 × 20 mm) were cut using a blade.

3. RESULTS AND DISCUSSION

3.1 Rheological charactertization

Figure 1 shows the typical rheological behavior of alumina and zirconia slurries. Both materials have shown a decrease of viscosity with the increasing shear rate, which is characteristic of a pseudoplastic behavior. At high shear rates the flakes are destroyed, causing a decrease of the viscosity, leading to a production of a homogeneous tape with smooth surface.

Figure 1
Viscosity as a function of the shear rate for the ZrO2 and Al2O3 suspensions.

3.2 Microstructure and physical properties

Fig. 2 shows a dense ceramic laminate with strong joining and a visible interface. The laminate shows also some cracks that are characteristic of the tape process. Delamination effects can be also observed along the sample (figure 3) and is a consequence of the warm processing. Table 2 show the porosity and density values of the laminates. The Z-A-Z-A-Z laminate shows better values of porosity (13.67 %) and density (4.15 gcm-3) as compared to the A-Z-A-Z-A material, which can be associated to the better sinterability of the zirconia nanopowder.

Figure 2
Schematic representation of the alumina (A) and zirconia (Z) layers in the respective AZAZA laminates.
Figure 3
Typical micrograph showing delamination.
Table 2
Density and porosity mean values of the laminated samples with 5 layers after pressing and sintering.

3.3 Mechanical behavior

Figure 4 shows a representative stress-strain curve of the laminates tested in 3-point bending. Both samples presented the typical behavior of laminated composites, where the material deforms elastically until crack growth begins. The nanocomposites materials show several falls in loading that occur due to failure of the individual layers until a chain disruption. Each step of the load-displacement curve of the both laminated composite represents the break of one or several adjacent layers, according to other works [2020 HU, T., ZHANG, Y., HU, L., “Mechanical and wear characteristic of Y-TZP/Al2O3 nanocomposites”, Industrial Lubrication and Tribology, v.66, pp. 209-214, 2014.

21 CLEGG, W.J., “Design of ceramic laminates for structural applications”, Mater Science and Technology, v.14, pp. 483-494, 1998.

22 FANG, Y., ZHANG, Y., SONG, J., et al., “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.

23 KRSTIC, Z., KRSTIC, V.D., “Crack propagation and residual stress in laminated Si3N4/BN composite structures”, J.European Ceram Soc., v.31, pp. 1841-1847, 2011.
-2424 YAE, Q., YONSHENG, Z., LITIAN, H.U., “Microstructure and bending strength of Al2O3/ Al2O3ZrO2(3Y) laminated nanocomposites”, J.Chinese Ceram Soc., v.39, pp. 228-32, 2011.]. The A-Z-A-Z-A laminate present a better strength value (103 MPa) as compared to ZAZAZ composite (44 MPa) and may be attributed to the higher density value and lower porosity value founded in this laminate (table 2). Large stresses are developed on cooling the laminate from the sintering temperature, due the higher coefficient of thermal expansion of the zirconia (10.5 x 10-6 C-1) as compared to alumina (7.2 x 10-6 C-1), at 40-400 °C. The existence of such stresses may be large enough to lead to failure of individual layers in the laminate contributing to the laminates strength values. This difference on expansion coefficient of zirconia may cause on cooling a tension state in zirconia and a compression state in alumina, also contributing to the strength results in the nanocomposites laminates. These results are in agreement with other works [1616 ARAUJO, M.R., HOTZA, D., ACCHAR, W., “Processing and properties of Tape-Cast alumina-zirconia laminates”, submitted to J. Alloy & Componds in 2017., 2020 HU, T., ZHANG, Y., HU, L., “Mechanical and wear characteristic of Y-TZP/Al2O3 nanocomposites”, Industrial Lubrication and Tribology, v.66, pp. 209-214, 2014.

21 CLEGG, W.J., “Design of ceramic laminates for structural applications”, Mater Science and Technology, v.14, pp. 483-494, 1998.
-2222 FANG, Y., ZHANG, Y., SONG, J., et al., “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.]. It may be concluded that the resistance of the laminates depends strongly on the level of residual stress on its surface. The laminate with alumina layers on the surface reached higher values of mechanical strength, which can be associated to the compressive residual tension in this material and higher density values. The A-Z-A-Z-A nanocomposites laminate shows a strength value of approximately 100 MPa that is comparable with recent results reported in the literature for laminated-graded zirconia composites [2222 FANG, Y., ZHANG, Y., SONG, J., et al., “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.]. Studies about the use of higher temperatures and pressures during the warm pressing of the laminates are still under way in order to decrease the presence of laminate defects such as microcracks in order to improve the strength vales of the laminates.

Figure 4
Stress-strain curves for the two conditions of laminates after 3-point flexural tests (a) A-Z-A-Z-A; (b) Z-A-Z-A-Z.

Figure 5 shows the fracture surface of the laminates after 3-point flexural testing. It is clear to see that the crack propagation develops differently in the components of the laminate. The alumina layer shows a predominant intergranular fracture mode, while the zirconia presents mainly a transgranular fracture mode.

Figure 5
Crack propagation in Z-A-Z-A-Z and A-Z-A-Z-A laminates.

4. CONCLUSIONS

Alumina/zirconia laminated nanocomposites were fabricated by aqueous tape casting process. The results indicate a better mechanical performance of the AZAZA-nanostructured material, showing the nanocomposite laminate a strength value of 103 MPa. The lower strength in the Z-A-Z-A-Z laminates is caused by the presence of microcraks due the large stresses during the cooling from the sintering process. The propagation of the crack develops differently in the components of the laminate. In the zirconia layer, the crack develops mainly in a transgranular form, while in the alumina layer the predominant mechanism is the intergranular mode.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the financial support of CNPq and CAPES.

BIBLIOGRAPHY

  • 1
    RAMASESHAN, R., SUNDARRAJAN, S., JOSE, R., “Nanostructured ceramics by eletrospinning”, J. Applied Physics, v.102, pp.1101-10,2012.
  • 2
    HAN, H., AVERBACK, R.S., “High temperature mechanical propertiesof nanostructured Ceramics”, Nanostructured Materials, v.1, pp.95-100, 1992.
  • 3
    THOSTENSON, E.T., LI, C., CHOU, T.W., “Nanocomposites in Context”, Composites Science and Technology, v.65, pp. 491-516, 2005.
  • 4
    DEY, A., DEY, P., DATTA, S., et al, “A new model for multilayer ceramic Composites”, Mater and Manufacturing Processes, v.23, pp. 513-527, 2008.
  • 5
    REED, J.S., Principles of Ceramics Processing, second ed., Wiley, New York, 1995.
  • 6
    PORTU G., MICELE L., PEZZOTTI G., “Laminated ceramic structures from oxide systems”, Comp, v.37, pp. 556–567, 2006.
  • 7
    CLEGG, J., KENDALL, K., BUTTON, T.J., et al, “A simple way to make tough ceramic”, Nature, v.347, pp. 455-457, 1990.
  • 8
    MORENO, R., “The role of slip additives in tape casting technology: Part 1-Solvents and dispersants”, Am. Ceram. Soc. Bull, v.71, pp.1521–1531, 1992.
  • 9
    ARAUJO, M.R., ACCHAR, W., “ Fabrication and characterization of nano-zirconia produced by aqueousbased tape casting” , Mater. Today. Proc, v.4, pp.11506-511, 2017.
  • 10
    FENG, J.H., DOGAN, F., “Aqueous processing and mechanical properties of PLZR green Tapes”, Mater. Sci.Eng. A, v.283, pp. 56–64, 2000.
  • 11
    MORENO, V., AGUILLAR, J.L., HOTZA, D., “ 8YSZ tapes produced by aqueous tape casting”, Mater. Sci. Forum, v.727-728, pp. 752–757, 2012.
  • 12
    ALBANO, M.P., GARRID, L.B., “Aqueous tape casting of yttria stabilized zirconia”, Mater. Sci. Eng. A, v. 420 , pp.171-178, 2006.
  • 13
    CORREA, M.A., ARAUJO, M.R., ACCHAR, W., et al, “ ZrO2 tape as flexible substrate to artificially nanostructured materials”, Mater.Lett, v.196, pp.69-73, 2017.
  • 14
    GUGLIELMI, P., BLAESA, D., HABLITZEL, M.P., et al, “Microstructure and flexural properties of multilayered fiber reinforced oxiddes composites fabricated by a novel lamination route”, Ceram.Inter, v. 41, pp. 7836-46, 2015.
  • 15
    MINATTO, F.D., MILAK, P., NONI, A., et al, “Multilayered ceramic composites – a review”, Adv. Applied. Ceram, v.114, pp.127-138, 2015.
  • 16
    ARAUJO, M.R., HOTZA, D., ACCHAR, W., “Processing and properties of Tape-Cast alumina-zirconia laminates”, submitted to J. Alloy & Componds in 2017.
  • 17
    SONG, J., ZHANG, Y., FAN, H., et al, “Design of structure parameters and corrugated interfaces for optimal mechanical properties in alumina-graphite laminated Nanocomposites” , Mat. Design, v.65, pp.1205-1213, 2015.
  • 18
    HU, T.C., ZHANG, Y.S., HU, L.T., “Mechanical and wear characteristic of Y-TZP-Al2O3 Nanocomposites”, Ind. Lubr. Tribol, v. 66, pp. 209-14, 2014.
  • 19
    FANG, Y., ZHANG, Y.S., SONG, J.J., et al, “Design and fabrication of laminated graded zirconia selflubricating composites”, Mater.Des v. 49, pp.421-425, 2013.
  • 20
    HU, T., ZHANG, Y., HU, L., “Mechanical and wear characteristic of Y-TZP/Al2O3 nanocomposites”, Industrial Lubrication and Tribology, v.66, pp. 209-214, 2014.
  • 21
    CLEGG, W.J., “Design of ceramic laminates for structural applications”, Mater Science and Technology, v14, pp. 483-494, 1998.
  • 22
    FANG, Y., ZHANG, Y., SONG, J., et al, “Design and fabrication of laminated-graded zirconia selflubricating composites”, Mater Design, v.49, pp. 421-425, 2013.
  • 23
    KRSTIC, Z., KRSTIC, V.D., “Crack propagation and residual stress in laminated Si3N4/BN composite structures”, J.European Ceram Soc., v.31, pp. 1841-1847, 2011.
  • 24
    YAE, Q., YONSHENG, Z., LITIAN, H.U., “Microstructure and bending strength of Al2O3/ Al2O3ZrO2(3Y) laminated nanocomposites”, J.Chinese Ceram Soc, v.39, pp. 228-32, 2011.

Publication Dates

  • Publication in this collection
    20 May 2019
  • Date of issue
    2019

History

  • Received
    31 Jan 2018
  • Accepted
    09 July 2018
Laboratório de Hidrogênio, Coppe - Universidade Federal do Rio de Janeiro, em cooperação com a Associação Brasileira do Hidrogênio, ABH2 Av. Moniz Aragão, 207, 21941-594, Rio de Janeiro, RJ, Brasil, Tel: +55 (21) 3938-8791 - Rio de Janeiro - RJ - Brazil
E-mail: revmateria@gmail.com