Alumina bodies with near-to-theoretical density by aqueous gelcasting using concentrated agarose solutions

Santacruz, Isabel; Nieto, Ma I.; Moreno, Rodrigo

doi:10.1016/j.ceramint.2004.06.007

Cited by 74 publications

(54 citation statements)

References 9 publications

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“…~40 o C for the 6 wt% solution [14,15]. The agar solution was then added to the nanosuspension at a concentration of 0.5 wt% with respect to the dry solids content whilst maintaining a temperature of >50ºC.…”

Section: Methodsmentioning

confidence: 99%

“…Solutions of agar were prepared at concentrations of 6 wt% by heating in a pressure vessel [14,15] in order to achieve the 110ºC required for its full dissolution without the water boiling.…”

Section: Methodsmentioning

confidence: 99%

“…Thermogelling polysaccharides such as agar, agarose and carrageenan have demonstrated a high efficiency at low concentration when they are dissolved and incorporated into a hot slurry and cast or injected into a mould cavity where they cool to below their glass transition temperature, T g ]13,14]. Gel casting with polysaccharides appears to be a good technique for consolidating ceramics with complex shapes and different sizes in a period that can be as short as a few seconds [15].…”

Section: Introductionmentioning

confidence: 99%

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Gel casting of aqueous suspensions of BaTiO3 nanopowders

Santacruz¹,

Nieto²,

Binner³

et al. 2009

Ceramics International

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Commercial nano BaTiO 3 powders have been formed into green bodies using colloidal forming routes. A study of the rheological behaviour of the suspensions as a function of dispersant concentration and homogenisation time was made in order to prepare stable concentrated suspensions of the nanopowders. Bulk components were then manufactured using aqueous slip and gel casting involving polysaccharides that gel on cooling, i.e. agar. The performance of theses consolidation techniques for obtaining dense green bodies from the BaTiO 3 nanopowders was studied. It was possible to prepare relatively big gel cast samples with a similar density and microstructure and in a shorter time compared to those obtained by slip casting. Another difficulty found in nanoceramics manufacturing is the shaping of homogeneous green bodies. In general, colloidal processing allows the production of complex-shaped parts with a decreased number and size of pores and hence higher reliability 6 . In colloidal systems the interfaces play a key role in the surface properties, such as adsorption, surface charge, electric double layer, etc [6,7]. In the case of 3 nanosized particles, their massive surface areas and hence substantial interaction forces between the particles make it more difficult to prepare stable nano-particle suspensions and study their colloidal properties.Over the last few years, significant effort has been devoted to developing new forming methods for manufacturing complex-shaped ceramic products with minimal number of detrimental defects [8][9][10] This work aims to study the preparation and rheological characterisation of concentrated aqueous suspensions of commercial nanosized powders of barium titanate (nanoBT) for shape forming by slip and gel casting, the latter using thermogelling polysaccharides. The performance of these consolidation techniques for obtaining dense green bodies from the BT nanopowder is discussed. ExperimentalThe starting material was a commercial nanoBT powder (HPB-1000, TPL Inc., was added as a deflocculant to the solution [20,27] prior to the addition of sufficient of the nanoBT powder to generate suspensions with solids loadings of 70, 75 and 80 wt% (28, 33 and 40 vol%, respectively). The suspensions were mixed using by mechanical agitation with helices and further homogenised using ultrasound (a 400 W sonication probe, UP400S, Hielscher Ultrasonics GmbH, Stuttgart, Germany) for up to 10 min.Suspensions were cooled in an ice-water bath during ultrasonication in order to avoid heating.A commercially available agar (Grand Agar, Hispanagar S.A., Burgos, Spain) was used as the gelling agent. Solutions of agar were prepared at concentrations of 6 wt% by heating in a pressure vessel [14,15] in order to achieve the 110ºC required for its full dissolution without the water boiling.The rheological behaviour of the suspensions was studied using a rheometer (Haake RS50, Karlsruhe, Germany) with a double-cone and plate measuring system, provided with a solvent trap to reduce evaporation. Flow curves...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gel casting of aqueous suspensions of BaTiO3 nanopowders

Santacruz¹,

Nieto²,

Binner³

et al. 2009

Ceramics International

Self Cite

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“…Aqueous gelcasting allows obtaining complex-shaped parts with high density, low cost, machinable property and higher reliability of the formed green bodies [9][10][11]. Many studies have been done to promote the gelcasting process, however, it is still difficult to obtain concentrated Si 3 N 4 based suspensions with a solids loading above 50 vol% [10,11].…”

Section: Introductionmentioning

confidence: 99%

Characterization of porous silicon nitride/silicon oxynitride composite ceramics produced by sol infiltration

Jia

Shao

Liu

et al. 2010

Materials Chemistry and Physics

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a b s t r a c tPorous silicon nitride/silicon oxynitride composite ceramics were fabricated by silica sol infiltration of aqueous gelcasting prefabricated Si 3 N 4 green compact. Silica was introduced by infiltration to increase the green density of specimens, so suitable properties with low shrinkage of ceramics were achieved during sintering at low temperature. Si 2 N 2 O was formed through reaction between Si 3 N 4 and silica sol at a temperature above 1550 • C. Si 3 N 4 /Si 2 N 2 O composite ceramics with a low linear shrinkage of 1.3-5.7%, a superior strength of 95-180 MPa and a moderate dielectric constant of 4.0-5.0 (at 21-39 GHz) were obtained by varying infiltration cycle and sintering temperature.

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“…18) So far, preparing suspensions with high solid loading and low viscosity has always been the priority focus when the gelcasting system is of concern in sintering of ceramics. 14), 16) Because of the difficulty to obtain the near-net-shape products, less attention has been paid to the study of the gelcasting system through the suspension with low solid loadings. One of the important factors responsible for homogeneous gel structure is the distribution of the solidification agent in the suspensions.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of translucent tetragonal zirconia by gelcasting of thin zirconia nano-slurry

Yoshida

Takeno

Sakurada

2016

J. Ceram. Soc. Japan

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Microstructural evolution during the sintering of nanoceramics was investigated in the compacts prepared by gelcasting of tetragonal zirconia nano-slurry with the solid loading of 7 vol %. The initial compact prepared by the gelcasting in this study had the densely packed structure with a narrow pore-size distribution and high connectivity in the particle network. Special attentions were paid to the evolutions of pore structures in the initial and intermediate stage sintering. It was found that the coarsening of the pores, which is thought to be the important obstacle of the densification in nanoceramics, was not remarkable in the sintering of the densely packed compact. The suppression of the pore coarsening resulted in the lowering the sintering temperature. Almost fully dense sample with 99.5% of theoretical density was successfully obtained at the sintering temperature of 1373 K for 2 h. The sample sintered at 1373 K maintained the nanometric structure with the grain size of 79 nm and exhibited the optical translucency.

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Alumina bodies with near-to-theoretical density by aqueous gelcasting using concentrated agarose solutions

Cited by 74 publications

References 9 publications

Gel casting of aqueous suspensions of BaTiO3 nanopowders

Gel casting of aqueous suspensions of BaTiO3 nanopowders

Characterization of porous silicon nitride/silicon oxynitride composite ceramics produced by sol infiltration

Fabrication of translucent tetragonal zirconia by gelcasting of thin zirconia nano-slurry

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