The influence of two different additives, glycerol and polyvinyl alcohol (PVA), on the rheological behaviour and freeze casting performance of 35 vol.-% aqueous alumina suspensions is studied. Suspensions with PVA were prepared by either mixing all the components together or adding the PVA in a second step on the dispersed slurry. Although the slight increase in viscosity suggests that competitive adsorption occurs, the microstructure seems not to change depending on the order of addition of additives. Considering its lower molecular weight, glycerol provides lower viscosity, and as a consequence of its cryoprotective character, sintering leads to smaller pore size, being the porosity 35% for an added content of 10 wt-% with respect to solids. In the case of PVA, contents of 2 wt-% are enough to obtain solid firm bodies with a porosity of 48%. The porosity and the size of the pores decrease with increasing concentration of PVA.
ColomboP. and DegischerH. P.: ‘Highly porous metals and ceramics’, Mater. Sci. Technol., 2010, 26, 1145–1158.
2.
CormaA.: ‘From microporous to mesoporous molecular sieve materials and their use in catalysis’, Chem. Rev., 1997, 97, 2373–2419.
3.
OhjiT. and FukushimaM.: ‘Macro-porous ceramics: processing and properties’, Int. Mater. Rev., 2012, 57, 115–131.
4.
StudartA. R., GonzenbachU. T., TervoortE. and GaucklerL. J.: ‘Processing routes to macroporous ceramics: a review’, J. Am. Ceram. Soc., 2006, 89, 1771–1789.
5.
YangX. Y., LiY., LemaireA., YuJ. G. and SuB. L.: ‘Hierarchically structured functional materials: synthesis strategies for multimodal porous networks’, Pure Appl. Chem., 2009, 81, 2265–2307.
6.
FukasawaT., DengZ. Y., AndoM., OhjiT. and KanzakiS.: ‘Synthesis of porous silicon nitride with unidirectionally aligned channels using freeze-drying process’, J. Am. Ceram. Soc., 2002, 85, 2151–2155.
7.
SofieS. W.: ‘Fabrication of functionally graded and aligned porosity in thin ceramic substrates with the novel freeze-tape-casting process’, J. Am. Ceram. Soc., 2007, 90, 2024–2031.
8.
DevilleS.: ‘Freeze-casting of porous ceramics: a review of current achievements and issues’, Adv. Eng. Mater., 2008, 10, 155–169.
9.
KochD., AndresenL., SchmeddersT. and GrathwohlG.: ‘Evolution of porosity by freeze casting and sintering of sol–gel derived ceramics’, J. Sol–Gel Sci. Technol., 2003, 26, 149–152.
10.
MoonJ. W., HwangH. J., AwanoM. and MaedaK.: ‘Preparation of NiO–YSZ tubular support with radially aligned pore channels’, Mater. Lett., 2003, 57, 1428–1434.
11.
ChinoY. and DunandD. C.: ‘Directionally freeze-cast titanium foam with aligned elongated pores’, Acta Mater., 2010, 56, 105–113.
12.
ArakiK. and HalloranJ. W.: ‘Porous ceramic bodies with interconnected pore channels by a novel freeze casting technique’, J. Am. Ceram. Soc., 2005, 88, 1108–1114.
DevilleS., SaizE. and TomsiaA. P.: ‘Freeze casting of hydroxyapatite scaffolds for bone tissue engineering’, Biomaterials, 2006, 27, 5480–5489.
15.
PekorC., GrothB. and NettleshipI.: ‘The effect of polyvinyl alcohol on the microstructure and permeability of freeze-cast alumina’, J. Am. Ceram. Soc., 2010, 93, 115–120.
16.
ZuoK. H., ZengY. P. and JiangD.: ‘Properties of microstructure-controllable porous yttria-stabilized ziroconia ceramics fabricated by freeze casting’, Int. J. Appl. Ceram. Technol., 2008, 5, 198–203.
17.
ZuoK. H., ZengY. P. and JiangD.: ‘Effect of polyvinyl alcohol additive on the pore structure and morphology of the freeze-cast hydroxyapatite ceramics’, Mater. Sci. Eng., 2010, C30, 283–287.
18.
RenL., ZengY. P. and JiangD.: ‘Preparation of porous TiO2 by a novel freeze casting’, Ceram. Int., 2009, 35, 1267–1270.
19.
YoonH. J., KimU. C., KimJ. H., KohY. H., ChoiW. Y. and KimH. E.: ‘Macroporous alumina ceramics with aligned microporous walls by unidirectionally freezing foamed aqueous ceramic suspensions’, J. Am. Ceram. Soc., 2010, 93, 1580–1582.
20.
ZouJ., ZhangY. and LiR.: ‘Effect of suspension state on the pore structure of freeze-cast ceramics’, Int. J. Appl. Ceram. Technol., 2011, 8, 482–489.
21.
Rodriguez-ParraJ. M., MorenoR. and NietoM. I.: ‘Effect of cooling rate on the microstructure and porosity of alumina produced by freeze casting’, J. Serbian Chem. Soc., 2012, 77, 1775–1785.
22.
TallonC., MorenoR. and NietoM. I.: ‘Shaping of porous alumina bodies by freeze casting’, Adv. Appl. Ceram., 2009, 108, 307–313.
23.
SofieS. W. and DoganF.: ‘Freeze casting of aqueous alumina slurries with glycerol’, J. Am. Ceram. Soc., 2001, 84, 1459–1464.
24.
RahamannM. N. and FuQ.: ‘Manipulation of porous bioceramic microstructures by freezing of suspensions containing binary mixtures of solvents’, J. Am. Ceram. Soc., 2008, 91, 4137–4140.
25.
LuK.: ‘Microstructural evolution of nanoparticle aqueous colloidal suspensions during freeze casting’, J. Am. Ceram. Soc., 2007, 90, 3753–3758.
26.
MoritzT. and RichterH. J.: ‘Ice-mould freeze casting of porous ceramic components’, J. Eur. Ceram. Soc., 2007, 27, 4595–4601.
27.
MunchE., SaizE., TomsiaA. P. and DevilleS.: ‘Architectural control of freeze-cast ceramics through additives and templating’, J. Am. Ceram. Soc., 2009, 92, 1534–1539.
28.
WaschkiesT., OberackerR. and HoffmannM. J.: ‘Control of lamellae spacing during freeze casting of ceramics using double-side cooling as a novel processing route’, J. Am. Ceram. Soc., 2009, 92, S79–S84.
29.
LiuG. and ButtonT. W.: ‘The effect of particle size in freeze casting of porous alumina–zirconia composite’, Ceram. Int., 2013, 39, 8507–8512.
30.
HautcoeurD., LericheA., GononM., LardotV. and CambierF.: ‘Zirconia and alumina porous ceramics prepared by the ice templating method’, Proc. 5th Int. Conf. on ‘Shaping of advanced ceramics’. Mons, Belgium, January 2013.
31.
GutierrezC. A. and MorenoR.: ‘Preventing ageing on Al2O3 casting slips dispersed with polyelectrolytes’, J. Mater. Sci., 2000, 35, 5867–5872.
