Porous Ceramics (porous + ceramics)

Distribution by Scientific Domains


Selected Abstracts


The Manufacture of Porous Ceramics Using Supercritical Fluid Technology

ADVANCED ENGINEERING MATERIALS, Issue 3 2008
S. Matthews
Supercritical fluid-assisted technology has been combined with conventional polymer processing techniques, such as injection moulding and extrusion to manufacture porous ceramics components. This paper introduces the new process and highlights one of the key benefits of this technique; the ability to control the porous network formed. It was found that by altering the binder formulation and processing conditions the pore size, pore type and pore density could be controlled. [source]


Tomography-Based Multiscale Analyses of the 3D Geometrical Morphology of Reticulated Porous Ceramics

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008
Jrg Petrasch
X-ray microtomography with a digital resolution of 30 ,m and synchrotron submicrometer tomography with a digital resolution of 350/700 nm are performed on catalyst-coated reticulate porous ceramic foa, 22[2] 121,45ms. Porosity, specific surface, pore-size distribution, two-point correlation function, and minimum size of a representative elementary volume are computed by image processing of the tomographic reconstructions on the mm-scale- and ,m-scale-sized pores. Numerically determined porosities are experimentally validated by weighing, helium pycnometry, and mercury intrusion porosimetry. [source]


Flow Kinetics in Porous Ceramics: Understanding with Non-Uniform Capillary Models

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007
Debdutt Patro
The present work describes the development of a two-parameter non-uniform capillary model to describe kinetics of flow in porous solids with complex tortuous varying paths. Experimentally, the rate of fluid flow in such a non-uniform capillary is found to be orders of magnitude slower compared with a corresponding average uniform capillary. This slow rate is explained in terms of an extremely small ,effective' hydrodynamic radius. The origin of such an ,unphysical' radius is rationalized based on geometrical considerations and effective driving forces for flow through a stepped capillary. Infiltration rate parameters are derived from the geometry of the porous medium for both wetting and non-wetting conditions. [source]


Surface Treatment of Templates for Fabrication of Reticulated Porous Ceramics

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007
Xi-peng Pu
Before impregnation of the organic templates with an aqueous ceramic slurry, the templates were treated using silica sol. The surface morphology, elasticity of the templates, and the solid loading were studied. After the treatment, the coherence between the template and the slurry was significantly optimized, and the surfaces of the templates were uniformly covered by slurry. The elasticity of the templates was also increased. Consequently, the loading content increased considerably. [source]


Pressureless Sintering of ,-Si3N4 Porous Ceramics Using a H3PO4 Pore-Forming Agent

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007
Fei Chen
A new method for preparing high bending strength porous silicon nitride (Si3N4) ceramics with controlled porosity has been developed by using pressureless sintering techniques and phosphoric acid (H3PO4) as the pore-forming agent. The fabrication process is described in detail and the sintering mechanism of porous ceramics is analyzed by the X-ray diffraction method and thermal analysis. The microstructure and mechanical properties of the porous Si3N4 ceramics are investigated, as a function of the content of H3PO4. The resultant high porous Si3N4 ceramics sintered at 1000,1200C show a fine porous structure and a relative high bending strength. The porous structure is caused mainly by the volatilization of the H3PO4 and by the continous reaction of SiP2O7 binder, which could bond on to the Si3N4 grains. Porous Si3N4 ceramics with a porosity of 42%,63%, the bending strength of 50,120 MPa are obtained. [source]


Synthesis of Highly Porous Yttria-Stabilized Zirconia by Tape-Casting Methods

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2003
Martha Boaro
Porous ceramics of Y2O3 -stabilized ZrO2 (YSZ) were prepared by tape-casting methods using both pyrolyzable pore formers and NiO followed by acid leaching. The porosity of YSZ wafers increased in a regular manner with the mass of graphite or polymethyl methacrylate (PMMA) to between 60% and 75% porosity. SEM indicated that the shape of the pores in the final ceramic was related to the shape of the pore formers, so that the pore size and microstructure of YSZ wafers could be controlled by the choice of pore former. Dilatometry measurements showed that measurable shrinkage started at 1300 K, and a total shrinkage of 26% was observed, independent of the amount or type of pore former used. Temperature-programmed oxidation (TPO) measurements on the green tapes demonstrated that the binders and dispersants were combusted between 550 and 750 K, that PMMA decomposed to methyl methacrylate between 500 and 700 K, and that graphite combusted above 900 K. The porosity of YSZ ceramics prepared by acid leaching of nickel from NiO,YSZ, with 50 wt% NiO, was studied as a function of NiO and YSZ particle size. Significant changes in pore dimension were found when NiO particle size was changed. [source]


Wetting Behavior of Amorphous and Crystalline Silicon Dioxide in Contact with a Silicate Slag Based on Fayalite

ADVANCED ENGINEERING MATERIALS, Issue 4 2010
Christos G. Aneziris
In this work the wetting behaviour of amorphous and crystalline silicon dioxide in contact with a silicate slag based on fayalite is demonstrated as a function of contact angles, activation energies of the kinetic stages of wetting. In addition the dynamic adhesion work has been calculated as a function of the inclination angle. The amorphous silicon dioxide in contact with the slag presents lower contact angles accompanied also by higher dynamic adhesion works in comparison to crystalline porous ceramics with the same chemistry. [source]


Improvement in the Specific Strength by Arranging Closed Pores in Fully Densified Zirconia Ceramics,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009
Akira Kishimoto
Superplastic-foamed porous ceramics containing numerous closed pores were fabricated. The bending strength of the fabricated ceramics with the smallest pores was close to half that of fully dense ones, even with a porosity of 27%. The smaller pores were introduced selectively between top and bottom surfaces. The resultant dense/porous/dense layered ceramics had a specific mechanical strength greater than that of monolithic dense ceramics. [source]


Magnetic resonance microscopy analysis of transport in a novel Tape-Cast porous ceramic

AICHE JOURNAL, Issue 10 2009
Tyler R. Brosten
Abstract Freeze-tape-cast porous ceramics allow for tailored pore structures. The impact on transport dynamics of pore structures which vary as a function of spatial depth within a ceramic is an important consideration in designing pore structures for particular applications. In this article, the application of nuclear magnetic resonance microscopy and 1H NMR techniques to characterize the transport in a novel tape-cast ceramic is presented. 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Pressureless Sintering of ,-Si3N4 Porous Ceramics Using a H3PO4 Pore-Forming Agent

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007
Fei Chen
A new method for preparing high bending strength porous silicon nitride (Si3N4) ceramics with controlled porosity has been developed by using pressureless sintering techniques and phosphoric acid (H3PO4) as the pore-forming agent. The fabrication process is described in detail and the sintering mechanism of porous ceramics is analyzed by the X-ray diffraction method and thermal analysis. The microstructure and mechanical properties of the porous Si3N4 ceramics are investigated, as a function of the content of H3PO4. The resultant high porous Si3N4 ceramics sintered at 1000,1200C show a fine porous structure and a relative high bending strength. The porous structure is caused mainly by the volatilization of the H3PO4 and by the continous reaction of SiP2O7 binder, which could bond on to the Si3N4 grains. Porous Si3N4 ceramics with a porosity of 42%,63%, the bending strength of 50,120 MPa are obtained. [source]


Sintering Behavior of Gehlenite.

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007
Macro-/Mesoporous Gehlenite, Mechanical, Microstructure, Part I: Self-Forming, Physical Properties, Pore-Forming Mechanism
A novel kind of pore self-forming macro-/mesoporous gehlenite (2CaOAl2O3SiO2) ceramic (abbreviated C2AS) having a highest porosity of 80% corresponding to a volume expansion of 134% during sintering has been developed. The pore self-forming ability, microstructure, mechanical, and thermal physical properties of the porous ceramic are related to the sintering temperature. The gehlenite ceramic shows a very good pore self-forming ability over a very wide range of temperature from 900 to 1450C. No vesicant is required and no hydrothermal treatment is needed, as is generally the case for other kinds of porous ceramics or glasses. The pore self-forming ability of the C2AS porous ceramic can be attributed to the escape of the adsorbed water vapor during the sintering process, due to automatic hydration of the fine, amorphous, flakey-shaped starting C2AS powder particles synthesized by the organic steric entrapment (PVA) method, as well as to their fine, porous microstructure. The pores of the ceramics can be either open or closed, and the average pore size ranges from 0.6 to 1.1 ,m, corresponding to a porosity of 75%,80%, respectively. The porous ceramic can preserve nanometer-sized (26,50 nm) crystallites up to 1000C. Sintered or thermally treated under different conditions, the porous ceramics exhibit relatively high flexural strengths ranging from 9.1 to 15.4 MPa, with a standard deviation of 0.3 and 4.2 MPa, respectively. Thermal properties of the porous ceramic up to 1000C, including thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity, were investigated, and the stability of the porous ceramic in boiling water was also studied. [source]