Meso- and Macroporous Ceramics by Phase Separation and Reactive Sintering Methods

Suzuki, Yoshikazu; Morgan, Peter E. D.

doi:10.1557/mrs2009.158

Cited by 13 publications

(5 citation statements)

References 50 publications

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“…A number of innovative techniques which have been developed recently for critical control of pores are introduced, divided into these four categories, together with some important properties of porous ceramics obtained in these processes. It should be noted however, that a lot of new approaches for macroporous ceramics such as phase separations [26][27][28][29][30] have been developed other than the processes shown here. Figure 2 shows schematic illustrations of these processes, each of which will be interpreted in its section.…”

Section: Introductionmentioning

confidence: 99%

Macro-porous ceramics: processing and properties

Ohji

Fukushima

2012

International Materials Reviews

612

319

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Porous ceramics are now expected to be used for a wide variety of industrial applications from filtration, absorption, catalysts and catalyst supports to lightweight structural components. During the last decade, tremendous efforts have been devoted for the researches on innovative processing technologies of porous ceramics, resulting in better control of the porous structures and substantial improvements of the properties. This article intends to review these recent progresses of porous ceramics. Because of a vast amount of research works reported in this field these days, the review mainly focuses on macro-porous ceramics whose pore size is larger than 50 nm. Followed by giving a general classification of porous ceramics, a number of innovative processing routes developed for critical control of pores are described, along with some important properties. The processes are divided into four categories including (i) partial sintering, (ii) sacrificial fugitives, (iii) replica templates and (iv) direct foaming. The partial sintering, the most conventional technique for making porous ceramics, has been substantially sophisticated in recent years. Very homogeneous porous ceramics with extremely narrow size distribution have been successfully prepared through sintering combined with in situ chemical synthesis. Carefully tailored micro-structure (size, morphology and orientation of grains and pores, etc.) of porous ceramics has led to unique mechanical properties, which cannot be attained even in the dense materials. Various types of the sacrificial fugitives have been examined for obtaining well-tuned shape and size of pores. The freeze-drying techniques using water or liquid as fugitive materials have been most frequently studied in recent years. Controlling growth of ice during freezing has led to unique porous structures and excellent performances of porous ceramics, e.g. excellent mechanical behaviour for highly porous lamellar hydroxyl-apatite scaffolds. Numerous approaches on the replica templates have been developed in order to produce highly porous ceramics having interconnected large pores and sufficiently strong struts without cracks. Natural template approaches using wood, for example, as positive replica, have been intensively studied in these years and have realised highly oriented porous open-porous structure with a wide range of porosity. As for the direct foaming technique, a variety of novel techniques which stabilise the bubbles in ceramic suspension have been developed to suppress large pore formation, e.g. evaporation of emulsified alkane droplets and use of surface-modified particles. We also briefly review porous ceramics with hierarchical porosity (incorporation of macro-, meso-and micropores), which have attracted much attention in both academic and industrial fields. Finally the article gives the summary and discusses the issues to be solved for further activating the potential of porous ceramics and for expanding their applicability.

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Section: Introductionmentioning

confidence: 99%

Macro-porous ceramics: processing and properties

Ohji

Fukushima

2012

International Materials Reviews

612

319

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“…Though several reports discussed from experimental results that porosity has no obvious effect on the CTE value of porous ceramics [25,26], traditional synthetic methods for the generation of three dimensional pores in ceramics, such as gelate freezing, pyrolytic reactive sintering, addition of porogen (inert gas or polymers) and self-assembly, find their difficulty to maintain nanometer scale pores in the ceramic body after calcination at high temperature [27], where the drastic crystal growth commonly leads to densified skeletons. Hence, the effect of porosity at nanometer scales on CTE of bulky ceramics has yet to be thoroughly studied.…”

Section: Thermal Expansion and Mechanical Propertiesmentioning

confidence: 99%

Metal zirconium phosphate macroporous monoliths: Versatile synthesis, thermal expansion and mechanical properties

Zhu

Kanamori

Moitra

et al. 2016

Microporous and Mesoporous Materials

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A versatile synthetic method has been developed for the fabrication of metal zirconium phosphate (MZP) macroporous monoliths via a sol-gel process accompanied by phase separation. More than 30 kinds of MZP monolithic polycrystalline monoliths with co-continuous macroporous structure have been synthesized by simply adding the target metal salt in the starting solution with optimized compositions. Glycerol, due to its high boiling point, plays the key role as the solvent to prevent metal salt from recrystallization, allowing a homogeneous distribution of metal salts over the polymerizing zirconium phosphate network. Hierarchically porous polycrystalline strontium zirconium phosphate (SrZrP) monolith has been obtained when the dried gel was calcined at 800 °C. Very low thermal expansion (coefficient of thermal expansion (CTE) as 1.4 × 10 −6 K −1) over a wide temperature range (38 °C to 1000 °C) together with good mechanical properties (flexural modulus as 8.0 GPa from 3 point bending test and Young's modulus as 1.9 GPa from uniaxial compression test) has been demonstrated, while high porosity (43 %) due to the presence of macropores reduces bulk density. As compared with dense ceramics of the same composition, the CTE value is lower and can be attributed to the presence of nanometer-sized small pores, which absorbs the anisotropic thermal expansion of each crystallite in the macropore skeletons at elevated temperatures.

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“…Well-ordered microstructures consisting of a unidirectionally separated cylindrical phase in a surrounding matrix can be obtained by unidirectional solidification of eutectic melts in the ZrO 2 /MgO and MgAl 2 O 4 /Al 2 O 3 systems [59]. The possibility of obtaining a wood-like porous microstructure from such a unidirectionally separated microstructure by selectively leaching one phase was suggested by Suzuki and Morgan [59] but the realization of such a process has not yet been reported.…”

Section: Unidirectional Solidification Of Molten Meltsmentioning

confidence: 99%

“…The possibility of obtaining a wood-like porous microstructure from such a unidirectionally separated microstructure by selectively leaching one phase was suggested by Suzuki and Morgan [59] but the realization of such a process has not yet been reported.…”

Section: Unidirectional Solidification Of Molten Meltsmentioning

confidence: 99%

Porous ceramics mimicking nature—preparation and properties of microstructures with unidirectionally oriented pores

Okada

Isobe

Katsumata

et al. 2011

Science and Technology of Advanced Materials

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Porous ceramics with unidirectionally oriented pores have been prepared by various methods such as anodic oxidation, templating using wood, unidirectional solidification, extrusion, etc. The templating method directly replicates the porous microstructure of wood to prepare porous ceramics, whereas the extrusion method mimics the microstructures of tracheids and xylems in trees. These two methods are therefore the main focus of this review as they provide good examples of the preparation of functional porous ceramics with properties replicating nature. The well-oriented cylindrical through-hole pores prepared by the extrusion method using fibers as the pore formers provide excellent permeability together with high mechanical strength. Examples of applications of these porous ceramics are given, including their excellent capillary lift of over 1 m height which could be used to counteract urban heat island phenomena, and other interesting properties arising from anisotropic unidirectional porous structures.

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Meso- and Macroporous Ceramics by Phase Separation and Reactive Sintering Methods

Cited by 13 publications

References 50 publications

Macro-porous ceramics: processing and properties

Macro-porous ceramics: processing and properties

Metal zirconium phosphate macroporous monoliths: Versatile synthesis, thermal expansion and mechanical properties

Porous ceramics mimicking nature—preparation and properties of microstructures with unidirectionally oriented pores

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