Chemie GmbH, Munich, Germany), zirconia (NZ-911, Lot: Z307317P, ABSCO Materials, Haverhill, Suffolk, U.K.), alumina (TM-DAR, Lot: 7553, Taimei Chemicals ...
J. Am. Ceram. Soc., 93 [9] 2574–2578 (2010) DOI: 10.1111/j.1551-2916.2010.03902.x r 2010 The American Ceramic Society
Journal Versatile Crack-Free Ceramic Micropatterns Made by a Modified Molding Technique Marzellus Grosse Holthaus,z Miron Kropp,y Laura Treccani,z Walter Lang,y and Kurosch Rezwanw,z z
Advanced Ceramics, University of Bremen, Bremen, Germany
y
Institute for Microsensors, -Actuators and -Systems (IMSAS), University of Bremen, Bremen, Germany
In addition, the shape, size, and thickness of the molded ceramic bodies are customizable to several requirements (Fig. 2), which emphasizes the versatility for large-area micropatterning of this technique. Moreover, this method has a high potential to get fully automatized.
Crack-free ceramic micropatterns made of oxidic ceramic powders, e.g. alumina, titania, zirconia, and nonoxidic calciumphosphate ceramic powders were fabricated by a novel, simple, and low-cost modified micromolding (m-lM) technique via polydimethylsiloxane stamps. By means of this m-lM technique it is possible to fabricate monolithic ceramic bodies with a micropatterned surface with very high accuracy on surface detail. Our produced micropatterns can feature various geometries, e.g. cylinders, holes, channels, and struts with diameters ranging from 8 to 140 lm in diameter or widths and from 8 to 30 lm in depth or height. The oxidic and nonoxidic ceramic micropatterns could be removed from the molds and dried without any cracks. Even after sintering, these micropatterned samples showed no cracks or fissures. The reported technique has a very high potential for fully automatized up-scale fabrication of micropatterned ceramic surfaces.
II. Experimental Procedure (1) Materials Seven commercially available ceramic powders were used to mix aqueous ceramic suspensions for filling the molds. Five of these powders, hydroxyapatite (04238, Lot: 8345A, Sigma-Aldrich Chemie GmbH, Munich, Germany), zirconia (NZ-911, Lot: Z307317P, ABSCO Materials, Haverhill, Suffolk, U.K.), alumina (TM-DAR, Lot: 7553, Taimei Chemicals Co. Ltd., Tokyo, Japan), titania (PT401L, Lot: 0/08, ISHIHARA SANGYO KAISHA, LTD., Osaka, Japan), and silica (SiO2PO1501, Lot: 090320-01, Fibre Optic Center, New Bedford, MA) had a particle size of approximately 150 nm. Additionally, two zirconia powders with particle sizes of approximately 26 nm (TZ3Y-E, Lot: Z309470P, Tosoh Corporation, Tokyo, Japan) and 360 nm (TZ-3YS-E, Lot: S-307752P, Tosoh) were used. The specific surface area (BET) of the used powders was measured using a Gemini 2375 (Micromeritics GmbH, Aachen, Germany). The zeta potentials in suspensions with a solid content of 2 vol% were measured using a DT1200 (Dispersant Technologies, Bedford Hills, NY).
I. Introduction
M
ICROPATTERNED surfaces are of great interest in a variety of research fields and are used in high-end technical applications such as electrical sensor devices, biochemical fluidic system reactors, abrasion-resistant antibacterial surfaces as well as in biological and medical applications.1–6 The advantages of ceramics as compared with metals or polymers are the chemical resistance and inertness, the high hardness, and the temperature resistance.7,8 However, especially in the micro range, advanced ceramics are often difficult to process without cracks and at the same time with a high accuracy on surface details. By our novel, simple, and low-cost modified micromolding (m-mM) technique via polydimethylsiloxane (PDMS) stamps, we obtained crack-free ceramic micropatterns made of oxidic ceramic powders, e.g. alumina, titania, zirconia, and nonoxidic calciumphosphate ceramic powders (Fig. 1). By means of this m-mM technique it is possible to fabricate monolithic ceramic bodies with a micropatterned surface with very high accuracy on surface detail (Fig. 2) instead of thinfilm micropatterns, which can be fabricated with well-known techniques such as microtransfer molding and capillary force lithography, conventional micromolding or replica molding, microcontact-printing, micropatterning via slip pressing, and especially micromolding in capillaries.2,9–15 In contrast to the thin-film techniques, it is feasible to fabricate large-area micropatterned three-dimensional (3D) solid ceramic devices by m-mM.
(2) Preparation of the Ceramic Suspensions Zeta potential measurements (DT1200, Dispersion Technologies) were carried out to characterize the behavior of the ceramic particles in aqueous surrounding (1 vol%) before preparing the suspensions for the molding processes. Suspensions with binder (12 mg/g ceramic) and without binder were applied. The binder s polyacrylic acid (Syntran 8220, Interpolymer GmbH, Hassloch, Germany) with a molecular weight of 4000 g/mol was used because it worked successfully as a binding polymer in preliminary tests. Thereby, the zeta potentials of hydroxyapatite suspensions with a solid content of 2 vol% andsvarious additions of binder ranging from 0 to 30 mg Syntran /g ceramic powder were measured. Results showed the lowest zeta potential of 17 s mV by an addition of 12 mg of Syntran /g ceramic powder as compared with no addition of binder withsa zeta potential of 12 mV. An addition of 30 mg of Syntran /g ceramic powder resulted in a zeta potential of 14 mV (Fig. S1, supporting information). In correlation with the preliminary tests, it was found that the isoelectric point (the pH value where the charge is zero) shifted to a smore acidic pH for each material after the addition of Syntran due to the RCOO groups of the polyacrylic acid. Furthermore, the results showed that all suspensions had negative charges in the alkaline range at pH 10–11 s s without the addition of Syntran . After addition of Syntran ,
A. Studart—contributing editor
Manuscript No. 27481. Received January 29, 2010; approved May 1, 2010. This work was supported by the University of Bremen (internal funding; ZF-Kennz.: 04/110/06). w Author to whom correspondence should be addressed. e-mail: krezwan@ uni-bremen.de
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humidity, the ceramic bodies were completely dry and were removed from their molds. After demolding, the presence of cracks due to shrinkage was evaluated visually using a microscope (Axio Imager M.1, Carl Zeiss AG, Go¨ttingen, Germany).
Fig. 1. Fabrication process of ceramic micropatterns. After sealing the micropatterned polydimethylsiloxane (PDMS) stamp with a plastic tube, the ceramic suspension is filled into this plastic tube for replicating the surface structure. The micropatterned ceramic bodies can be removed from the mold after 5 days of drying.
the charges have been even more negative in this alkaline range at pH 10–11. Each powder was stirred (RW20, IKA Werke GmbH, Staufen, Germany) separately into double deionized water (Synergy, Millipore, Schwalbach, Germany) to obtain suspensions of 10, 15, and 20 vol% solid loading. Dispersant polyacrylic acid (12 mg/g ceramic powder) was added to all suspensions. Each suspension was adjusted to pH 10–11 by adding ammonium (25 vol%) solution to achieve an electrosterical stability and prevent agglomeration of the particles. The ceramic suspensions were treated with an ultrasonic horn (Sonifier 450, Branson Ultraschall, Dietzenbach, Germany) for 3 min to destroy potential agglomerates after stirring.
(3) Fabrication of Nonstructured Ceramic Solid Bodies by Molding To find out the best solid contents, parameters for the fabrication of crack-free demolded ceramic bodies, cylindrical molds with a diameter of 6.6 mm (96-well microtiter plate, Nunc, Thermo Electron LED GmbH, Langenselbold, Germany) were filled with 100, 200, or 300 mL suspension with solid contents of 10, 15, or 20 vol%. Because of gravity, the particles settled down to the bottom of the mold and got densified, while the water in the supernatant evaporated slowly during the drying period. After a period of 5 days at 211–221C with 30%–43% relative air
(4) Fabrication of Micropatterned Ceramic Solid Bodies by Micromolding Via PDMS Stamps (m-lM) Cylindrically shaped molds with a diameter of 8 mm and micropatterning depths of 10, 20, and 30 mm were generated via PDMS s (Sylgard 184, Dow Corning GmbH, Wiesbaden, Germany) stamps from a structured silicon wafer. Before the molding process, the PDMS stamps were hydrophilized in oxygen plasma (Femto, Diener Electronic GmbH, Ebhausen, Germany) using low-pressure plasma with 50 W generator power for 2 min and an operating pressure of 0.3 mbar. After plasma treatment, the generated molds were sealed with cylindrical polyethylene tubes. Each mold was filled with 1 mL of ceramic suspension for casting the micropatterns on the PDMS stamps (Fig. 1). The particles settled down to the bottom of the microstructured mold due to gravity and got densified, while water evaporated from the supernatant. The samples were dried for 5 days at 211–221C with 30%–43% relative air humidity. Afterwards, the micropatterned samples were removed from their molds and densified in a furnace. With 20 kV, the micropatterns were visualized by SEM (Camscan Series 2, Cambridge Instruments Obducat CamScan Ltd., Cambridgeshire, U.K.) and 2D- and 3D-measurements were made by a 20-fold objective with a profilometer (Plm 2300, Sensofar Technology GmbH, Langen, Germany) to characterize the quality and shrinkage caused by the sintering process. III. Results and Discussion By applying this technique we achieved a maximum success rate of 88% crack-free dried samples for hydroxyapatite with a solid content of 10 vol%, 25% for zirconia (26 nm) with a solid content of 15 vol%, 100% for zirconia (150 nm) with a solid content of 10, 15, and 20 vol%, 100% for zirconia (360 nm) with a solid content of 10, 15, and 20 vol%, 100% for alumina with a solid content of 15 and 20 vol%, 71% for titania with a solid content of 15 vol% and 100% for silica with a solid content of 15 vol%. A correlation between the particle sizes and the achieved success rates for crackfree drying cannot be found by comparing the results of three different zirconia powders with particle sizes of 26, 150, and 360 nm. However, a correlation between the surface area (BET) ranging from 6.8 to 68.3 m2/g and the success rates for crack-free drying appears to be plausible (Table S1, supporting information16,17). We assume that a binder concentration of 12 mg/g ceramic is not high enough for hydroxyapatite with a specific surface area of 68.3 m2/g, silica with a specific surface area of 22.6 m2/g, zirconia (particles 26 nm) with a specific surface area of 15.1 m2/g,
Fig. 2. Left: SEM images of various fabricated ceramic micropatterns, e.g. channels, holes, struts, or cylinders. These geometries were applied to different ceramic materials such as alumina, zirconia, hydroxyapatite, silica, or titania. Right: Photographs of molded ceramic bodies made of alumina, zirconia, and hydroxyapatite with various diameters and thicknesses demonstrating the possibility of large surface area micropatterning.
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titania with a specific surface area of 13.1 m2/g, and alumina with a specific surface area of 12.8 m2/g to saturate the whole particle surface with binder molecules to avoid cracking during the drying process. These materials showed success rates o100% after drying. In contrast, success rates of 100% were achieved with zirconia powders with particle sizes of 150 and 360 nm, which exhibited the smallest surface areas of 9.7 and of 6.8 m2/g, respectively. These materials showed success rates of 100%. We assume that these particles have been fully coated by binder molecules by an addition of 12 mg/g which avoided cracking. An overview of exemplary results and particle and suspension characteristics such as zeta potential measurements, particle sizes, BET surface areas, the Hamaker constants, and achieved success rates for crack-free drying and demolding is given in Table S1 (supporting information). To check a difference in the packing density, further density measurements of the nonsintered zirconia powders (26, 150, and 360 nm) were taken. Therefore, 10 measurements per sample were taken with helium pycnometry (Accu Pyc 1330, Micromeritics). The density measurements of the nonsintered zirconia powder with particles of 26 nm showed an average density of 6.09 g/ cm370.04. For nonsintered zirconia powder with particles of 150 nm a density of 5.87 g/cm370.03 was measured, and for zirconia powder with particles of 360 nm a density of 5.98 g/ cm370.04 was measured. Thereby, the calculation of the total porosity of the molded zirconia samples, which were comparably made with 15 vol% in 200 mL fillings and 12 mg binder/g ceramic, resulted in 62.38% (26 nm), 57.19% (150 nm), and 58.45% (360 nm). The highest porosity of 62.38% gave rise to the assumption that the particles agglomerated stronger in the suspension before micromolding, which resulted in a lower final packaging density. The lower zeta potential of 12 mV as compared with zirconia with 150 nm particles (18 mV) and zirconia with 360 nm particles (25 mV) confirms the lower electrosterical stability of the suspension at the working pH of 9–10. Because of very high adhesion between the dried samples and the sidewalls of the cylindrical polyethylene plastic tube (not the micropatterned PDMS) it was not possible to remove any crackfree sample made of titania from the molds without destroying the sample. During the trial of demolding, the edges of the titania samples and the sample bodies were disconnected from each other. These disconnections were parallel to the sidewalls of the cylindrical plastic molds, thus circular throughout the entire sample. We assume that this effect occurred because of nonvisible damages before demolding, e.g. by defects or fine cracks inside the sample bodies. During the demolding process, the titania samples broke circular and titania material of the samples’ edges was partially sticking to the sidewalls of the plastic molds after demolding. The entire ceramic body itself did not break. This assumption was affirmed by the presence of circular cracks on clearly visible cracked titania samples after the drying process. We suppose that this unexpected effect can be minimized or completely avoided by the use of anti-sticking agents such as PTFE sprays, as these minimize the adhesion between PE mold and titania material or by the use of cylindrical molds of PTFE. A possible reason for this unexpected sticking effect could be a nonoptimal chosen concentration of binder which leads to higher forces between plastic and titania compared with the inner forces in the titania sample. The diameters and the heights of the samples were measured using a micrometer gauge before sintering to evaluate the shrinkage. Hydroxyapatite samples were densified at 12001C, zirconia samples at 13501C, alumina samples at 15001C, silica samples at 10001C, and titania samples at 12501C for 2 h with a heating rate of 50 K/h and a cooling rate of 100 K/h. Results showed shrinkages of 49% in volume for hydroxyapatite, 55% in volume for zirconia (26 nm), 53% in volume for zirconia (360 nm), and 40% in volume for silica. The zirconia powder (150 nm) could not be measured after sintering, because a monoclinic nonyttria-stabilized zirconia powder was used, which was not sinterable due to crystal phase changes.
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Fig. 3. SEM image of a sintered micropatterned zirconia surface of approximately 1 mm2 with over 6500 cylindrical holes. These holes have a diameter of about 10 mm and a depth of 8 mm. The graph inset shows a 2D profile measurement of a single cylinder.
Oxidic and nonoxidic ceramic micropatterns, e.g. holes and cylinders with diameters of 10 to 140 mm and depths or heights of 10 and 30 mm could be removed from the molds and dried without cracks. Even after sintering, these micropatterned samples showed no cracks and fissures (Figs. 2 and 3). It was also possible to fabricate areas of 1 mm2 with more than 6500 micropatterns with diameters of 10 mm and a depth of about 8 mm each without cracks and very high accuracy on surface details (Fig. 3). The excellent quality is on the one hand due to the chosen binder polyacrylic acid, and on the other due to the geometry of the molds effecting a favorable unidirectional and slow drying process (Fig. 4). Samples that did not dry crack-free showed two different kinds of cracking. Hydroxyapatite, alumina, silica, and zirconia samples showed a cracking throughout the entire structure and the entire sample body. The cracking did not occur only near the micropattern edges or along the micropattern direction, where the mechanical stresses appear to be most concentrated during the drying process (Fig. 5). Cracks were even visible throughout the center of the cylindrical sample. In contrast, cracking on titania samples occurred predominantly circular throughout the entire sample body (Fig. 6). Because the BET surface area measurements suggested a higher success rate for higher binder concentrations (412 mg/g ceramic), an additional test with 24 cylindrical samples of titania
Fig. 4. Drying process of ceramic micropatterns made by modified micromolding (m-mM): At the beginning, the ceramic particles are homogenously dispersed in the aqueous suspension. Because of gravity, the particles sink to the microstructured bottom of the mold (polydimethylsiloxane [PDMS] stamp), while water is continuously evaporating. The one-sided evaporation of water is completed within 5 days and the dried micropatterned ceramic body can be removed from the mold.
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Fig. 5. SEM micrograph of a micropatterned nonsintered hydroxyapatite surface that cracked during the drying process. The micropatterns were fabricated with a suspension with a solid content of 20 vol%. On samples made of alumina, hydroxyapatite, silica, and zirconia, the cracks were present throughout the entire sample and micropatterns.
With this simple and low-cost (m-mM) technique we can produce micropatterns featuring various geometries, e.g. cylinders, holes, channels, and struts with diameters ranging from 8 to 140 mm in diameter and widths from 8 to 30 mm in depth or height and very high accuracy on surface details. The molding process resulted in an outcome of 25%–100% crack-free, dried samples, whereas the mean shrinkage from dried ceramic body to the sintered ceramic body was ranging from 40% to 55% in volume, depending on the material. Because of shrinkage, it is even possible to fabricate ceramic microgeometries smaller than 10 mm without any cracks or fissures. No cracks occurred in the oxidic or in the nonoxidic ceramic samples during the sintering process. A relation between the used binder concentrations and their impact on the achieved success rates for crack-free drying could be shown in correlation with the measured BET surface area of the ceramic powders and their calculated porosity of the molded sample bodies. In addition, this method has a high potential to get fully automatized for the up-scale fabrication of micropatterned ceramic surfaces.
Supporting Information Additional Supporting Information may be found in the online version of this article: Table S1. Sintering shrinkages and success rates for crack-free drying and demoulding of various ceramic suspensions with three different solid contents filled into 200 mL moulds. Figure S1. Diagram shows the zetapotentials (pH 3 to 11) of hydroxyapatite suspensions with solid contents of 2 vol% and s various additions of polyacrylic acid based binder Syntran rangs ing from 0 to 30 mg Syntran /g ceramic powder. Lowest zetapos tential (17 mV) was achieved by an addition of 12 mg Syntran / g ceramic powder as compared to sno addition of PAA (12 mV) and an addition of 30 mg Syntran /g ceramic powder (14 mV). Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article.
References 1
Fig. 6. Photograph of the topview of four nonsintered titania samples (in their plastic molds) that cracked during the drying process. The samples were fabricated using a suspension with a solid content of 10 vol% s and the addition of 12 mg Syntran /g ceramic in 200 mL fillings. The disconnection between the sample bodies and the sample edges was parallel to the sidewalls of the cylindrical plastic molds, thus circular throughout the entire sample (black arrow bar). The dark gray dots in the center of the samples were made by a permanent marker.
suspension (10 vol%, 200 mL fillings) and the addition of 30 mg s Syntran /g ceramic was carried out to test the influence of binder concentration on the crack occurrence. Results showed a success rate for crack-free drying of 0%. All cracks occurred circular throughout the entire sample. Such a high concentration of binder does not increase the success rate for crack-free drying of titania. This does not mean that there are no concentrations between 12 mg and 30 mg/g ceramic which minimize the crack occurrence, but 30 mg is probably too much. Higher binder contents would lead to a higher porosity as well after sintering in the sample body, because more binder would be burned out during the sintering process.
Y. Zhang, K. Yu, S. Ouyang, and Z. Zhu, ‘‘Selective-Area Growth and Field Emission Properties of Zinc Oxide Nanowire Micropattern Arrays,’’ Physica, 382, 76–80 (2006). 2 J. Hu, R. G. Beck, T. Deng, R. M. Westervelt, K. D. Maranowski, A. C. Gossard, and G. M. Whitesides, ‘‘Using Soft Lithography to Fabricate GaAs/AlGaAs Heterostructure Field Effect Transistors,’’ Appl. Phys. Lett., 71 [14] 2020–2 (1997). 3 P. Kim, K. W. Kwon, M. C. Park, S. H. Lee, S. M. Kim, and K. Y. Suh, ‘‘Soft Lithography for Microfluidics: A Review,’’ Biochip J., 2 [1] 1–11 (2008). 4 L. Treccani, M. Maiwald, V. Zoellmer, M. Busse, G. Grathwohl, and K. Rezwan, ‘‘Antibacterial and Abrasion-Resistant Alumina Micropatterns,’’ Adv. Eng. Mater., 11, B61–6 (2009). 5 L. Wang, Z. Wu, B. Xu, Y. Zhao, and W. S. Kisaalita, ‘‘SU-8 Microstructure for Quasi-Three-Dimensional Cell-Based Biosensing,’’ Sens. Actuators B, 140, 349–55 (2009). 6 J. Y. Lee, S. S. Shah, J. Yan, M. C. Howland, A. N. Parikh, T. Pan, and A. Revzin, ‘‘Integrating Sensing Hydrogel Microstructures into Micropatterned Hepatocellular Cocultures,’’ Langmuir, 25, 3880–6 (2009). 7 J. E. Lemons, ‘‘Ceramics: Past, Present, and Future,’’ Bone, 19, 121S–8S (1996). 8 D. Munz and T. Fett, Ceramics—Mechanical Properties, Failure Behaviour, Materials Selection, Ch. 1, Vol. 26. Springer, Berlin, 1999. 9 S. U. Khan, O. F. Goebel, D. H. A. Blank, and J. E. ten Elshof, ‘‘Patterning Lead Zirconate Titanate Nanostructures at Sub-200-nm Resolution by Soft Confocal Imprint Lithography and Nanotransfer Molding,’’ Appl. Mater. Interfaces, 1, 2250–5 (2009). 10 K. Y. Suh, M. C. Park, and P. Kim, ‘‘Capillary Force Lithography: A Versatile Tool for Structured Biomaterials Interface Towards Cell and Tissue Engineering,’’ Adv. Funct. Mater., 19, 2699–712 (2009). 11 Y. Xia and G. M. Whitesides, ‘‘Soft Lithography,’’ Annu. Rev. Mater. Sci., 28, 153–84 (1998). 12 M. Heule, U. Scho¨nholzer, and L. J. Gauckler, ‘‘Patterning Colloidal Suspensions by Selective Wetting of Microcontact-Printed Surfaces,’’ J. Eur. Ceram. Soc., 24, 2733–9 (2004).
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U. P. Schonholzer, N. Stutzmann, T. A. Tervoort, P. Smith, and L. J. Gauckler, ‘‘Micropatterned Ceramics by Casting into Polymer Molds,’’ J. Am. Ceram. Soc., 85, 1885–7 (2002). 14 F. F. Lange, ‘‘Powder Processing Science and Technology for Increased Reliability,’’ J. Am. Soc., 72, 3–15 (1989). 15 W. Bauer, H.-J. Ritzhaupt-Kleissl, and J. Hausselt, ‘‘Micropatterning of Ceramics by Slip Pressing,’’ Ceram. Int., 25, 201–9 (1999).
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J. Tian, Y. Zhang, X. Guo, and L. Dong, ‘‘Preparation and Characterization of Hydroxyapatite Suspensions for Solid Freeform Fabrication,’’ Ceram. Int., 28, 299–302 (2002). 17 K. Rezwan, A. R. Studart, J. Voros, and L. J. Gauckler, ‘‘Change of z Potential of Biocompatible Colloidal Oxide Particles Upon Adsorption of Bovine Serum Albumin and Lysozyme,’’ J. Phys. Chem. B, 109, 14469–74 (2005). &
Supporting information: Table 1: Sintering shrinkages and success rates for crack-free drying and demoulding of various ceramic suspensions with three different solid contents filled into 200 µL moulds. material
particle
solid
BET
zetapotential
Hamaker-
success rate
success rate
size
content
surface area
of suspension
constant
for crack-free
for crack-free
of non-
+ 12 mg PAA/g
drying of
demoulding of
sintered
ceramic (at
200 µL fillings
200 µL fillings
powder
pH 9-10)
[m2/g]
[mV]
[%]
[%]
88
100
71
100
4
100
54
100
96
100
20
100
100
10
75
94
100
88
20
96
91
10
0
0
25
100
20
25
100
10
100
100
100
100
20
100
100
10
100
100
100
100
100
100
29
0 [a]
71
0 [a]
67
0 [a]
[nm]
[vol%]
[*10-20 J]
10 Hydroxyapatite
150
15
68.3
-16
6
[16]
20 10 Alumina
Silica
Zirconia
Zirconia
Zirconia
150
150
26
150
360
15
15
15
15
15
12.8
22.6
15.1
9.7
6.8
-16
-13
-12
-18
-25
6.7
[17]
1.6 [17]
13 [17]
13 [17]
13 [17]
20 10 Titania
150
15
13.1
-33
26
[17]
20 [a] demoulding of any crack-free dried sample was not possible without destroying the sample
Page 19 of 19
r Fo er
Pe Re
Diagramm shows the zetapotentials (pH 3 to 11) of hydroxyapatite suspensions with solid contents of 2 vol% and various additions of polyacrylic acid based binder Syntran® ranging from 0 to 30 mg Syntran®/g ceramic powder. Lowest zetapotential (-17 mV) was achieved by an addition of 12 mg Syntran®/ g ceramic powder as compared to no addition of PAA (-12 mV) and an addition of 30 mg Syntran® /g ceramic powder (-14 mV). 236x190mm (102 x 102 DPI)
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Journal of the American Ceramic Society
Journal of the American Ceramic Society
