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Slurry Development for Spray Granulation of Ceramic Multicomponent Batches
P. Höhne, B, Mieller, T. Rabe
BAM Federal Institute for Materials Research and Testing, Division 5.5 – Advanced Technical Ceramics, Unter den Eichen 44 – 46, D-12203 Berlin, Germany
received March 7, 2018, received in revised form May 16, 2018, accepted May 17, 2018
Vol. 9, No. 3, Pages 327-336 DOI: 10.4416/JCST2018-00022
Abstract
The granules commonly yielded by spray drying procedures exhibit a hard shell and an irregular, dimpled shape, which is often described as donut-like morphology. Sintered parts produced from such granules suffer from microstructural defects and reduced mechanical properties resulting from these disadvantageous granule properties.
Using the example of alumina, zirconia and zirconia-toughened alumina (ZTA) batches, this paper shows that the morphology of the granules can be tuned by adjusting slurry stability. High zeta potential is essential to optimally disperse the particles. But to achieve spherical and soft granules the electrostatic repulsion forces between the particles should be reduced before spray granulation. Electrostatic repulsion forces were changed with the addition of nitric acid. Measurements of zeta potential and viscosity, as well as sedimentation investigations with an optical centrifuge were used for precise slurry assessment as a major precondition for optimal and reproducible adjustment of slurries before spray drying. Sedimentation analysis using an optical centrifuge was performed to investigate different influences like that of additive composition, solids content or pH-value on the sedimentation behavior. Adequately flocculated slurries lead to homogeneous, soft granules that can be easily deformed and pressed. The fraction of donut-shaped particles and the rigidity of granules were reduced. Consequently, the sintered parts produced from these granulates show improvements regarding porosity, pore size distribution, sintered density and biaxial strength.
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Keywords
Slurry optimization, optical centrifugation, destabilization, spray drying, biaxial strength
References
1 German, R.M.: Particle Packing Characteristics, Metal Powder Industries Federation: Princeton New Jersey, (1989).
2 Zhang, Y., Binner, J., Rielly, C., Vaidhyanathan, B.: Comparison of spray freeze dried nanozirconia granules using ultrasonication and twin-fluid atomisation, J. Eur. Ceram. Soc., 34, [4], 1001 – 1008, (2014).
3 Rosenberger, N., Compson, C., Adria, J.: Comparative study on lab-scale granulation techniques, cfi Ber. DKG, 92, [4], E29 – E31, (2015).
4 Shinohara, N., Okumiya, M., Hotta, T., Nakahira, K., Naito, M., Uematsu, K.: Morphological changes in process-related large pores of granular compacted and sintered alumina, J. Am. Ceram. Soc., 83, [7], 1633 – 1640, (2000).
5 Vicente, J., Pinto, J., Menezes, J., Gaspar, F.: Fundamental analysis of particle formation in spray drying, Powder Technol., 247, 1 – 7, (2013).
6 Baklouti, S., Chartier, T., Baumard, J.F.: Binder distribution in spray-dried alumina agglomerates, J. Eur. Ceram. Soc., 18, [14], 2117 – 2121, (1998).
7 Tanaka, S., Pin, C.C., Uematsu, K.: Effect of organic binder segregation on sintered strength of dry-pressed alumina, J. Am. Ceram. Soc., 89, [6], 1903 – 1907, (2006).
8 Lee, H.-W., Song, G., and Suk, I.-S.: Effect of suspension property on granule morphology and compaction behavior, pp. 41 – 50 in 96. annual meeting of the American Ceramic Society (ACS). (1995).
9 Takahashi, H., Shinohara, N., Okumiya, M., Uematsu, K., Junichiro, T., Iwamoto, Y., Kamiya, H.: Influence of slurry flocculation on the character and compaction of spray-dried silicon-nitride granules, J. Am. Ceram. Soc., 78, [4], 903 – 908, (1995).
10 Bertrand, G., Filiatre, C., Mahdjoub, H., Foissy, A., and Coddet, C.: Influence of slurry characteristics on the morphology of spray-dried alumina powders, J. Eur. Ceram. Soc., 23, [2], 263 – 271, (2003).
11 Tsubaki, J., Yamakawa, H., Mori, T., Mori, H.: Optimization of granules and slurries for press forming, J. Ceram. Soc. Japan, 110, [10], 894 – 898, (2002).
12 Walker, W.J., Reed, J.S., Verma, S.K.: Influence of slurry parameters on the characteristics of spray-dried granules, J. Am. Ceram. Soc., 82, [7], 1711 – 1719, (1999).
13 Mahdjoub, H., Roy, P., Filiatre, C., Bertrand, G., Coddet, C.: The effect of the slurry formulation upon the morphology of spray-dried yttria stabilised zirconia particles, J. Eur. Ceram. Soc., 23, [10], 1637 – 1648, (2003).
14 Cao, X.Q., Vassen, R., Schwartz, S., Jungen, W., Tietz, F., Stoever, D.: Spray-drying of ceramics for plasma-spray coating, J. Eur. Ceram. Soc., 20, [14 – 15], 2433 – 2439, (2000).
15 Kim, D.J., Jung, I.Y.: Granule performance of zirconia/alumina composite powders spray-dried using polyvinyl pyrrolidone binder, J. Eur. Ceram. Soc., 27, [10], 3177 – 3182, (2007).
16 Naglieri, V., Gutknecht, D., Garnier, V., Palmero, P., Chevalier, J., Montanaro, L.: Optimized slurries for spray Drying: different approaches to obtain homogeneous and deformable alumina-zirconia granules, Materials, 6, [11], 5382 – 5397, (2013).
17 Greenwood, R.: Review of the measurement of zeta potentials in concentrated aqueous suspensions using electroacoustics, Adv. Colloid Interfac., 106, [1], 55 – 81, (2003).
18 Lerche, D., Sobisch, T.: Evaluation of particle interactions by in situ visualization of separation behaviour, Colloid Surface A, 440, 122 – 130, (2014).
19 EN ISO 14629:2016 (German version); Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of flowability of ceramic powders (ISO 14629:2012); in CEN, Brussels, 2016.
20 EN 725 – 9:2006 (German version); Advanced technical ceramics – Methods of test for ceramic powders - Part 9: Determination of untapped bulk density (EN 725 – 9:2006); in CEN, Brussels, 2006.
21 EN 623 – 2 Advanced technical ceramics - Monolithic ceramics - General and textural properties - Part 2: Determination of density and porosity. in CEN, Brussels, 1993.
22 Borger, A., Supancic, P., Danzer, R.: The ball on three balls test for strength testing of brittle discs: Part II: Analysis of possible errors in the strength determination, J. Eur. Ceram. Soc., 24, [10 – 11], 2917 – 2928, (2004).
23 Danzer, R., Harrer, W., Supancic, P., Lube, T., Wang, Z. H., Borger, A.: The ball on three balls test - strength and failure analysis of different materials, J. Eur. Ceram. Soc., 27, [2 – 3], 1481 – 1485, (2007).
24 Final Report of ZIM Project: Ultrasonic supported, energy-efficient spray granule synthesis, Support code KF2201088, BAM Berlin, (2016).
25 Aleš, D., Tomaž, K.: Weakly flocculated aqueous alumina suspensions prepared by the addition of Mg(II) ions, J. Am. Ceram. Soc., 83, [3], 666 – 668, (2000).
26 Hidber, P.C., Graule, T.J., Gauckler, L.J.: Competitive adsorption of citric acid and Poly(vinyl alcohol) onto alumina and its influence on the binder migration during drying, J. Am. Ceram. Soc., 78, [7], 1775 – 1780, (1995).
27 Shojai, F., Pettersson, A.B.A., Mäntylä, T., Rosenholm, J.B.: Electrostatic and electrosteric stabilization of aqueous slips of 3Y-ZrO2 powder, J. Eur. Ceram. Soc., 20, [3], 277 – 283, (2000).
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