Pore filling process in liquid phase sintering

Park, Hyo-Hoon; Cho, Seong-Jai; Yoon, Duk N.

doi:10.1007/bf02644700

Cited by 73 publications

(16 citation statements)

References 4 publications

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“…For an isotropic surface energy, the excess energy associated with a nonspherical grain shape is termed the sphering force [123]. At full density, a low liquid content causes more grain shape accommodation, giving a larger sphering force.…”

Section: Grain Shape Accommodationmentioning

confidence: 99%

Review: liquid phase sintering

2009

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Liquid phase sintering (LPS) is a process for forming high performance, multiple-phase components from powders. It involves sintering under conditions where solid grains coexist with a wetting liquid. Many variants of LPS are applied to a wide range of engineering materials. Example applications for this technology are found in automobile engine connecting rods and high-speed metal cutting inserts. Scientific advances in understanding LPS began in the 1950s. The resulting quantitative process models are now embedded in computer simulations to enable predictions of the sintered component dimensions, microstructure, and properties. However, there are remaining areas in need of research attention. This LPS review, based on over 2,500 publications, outlines what happens when mixed powders are heated to the LPS temperature, with a focus on the densification and microstructure evolution events.

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Section: Grain Shape Accommodationmentioning

confidence: 99%

Review: liquid phase sintering

2009

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“…As the sintering proceeds and the grains grow, the liquid meniscus radius at the sample surface and the intact pore surface increases 9 . When the pore surface is completely wetted (the critical moment) with a radius increase of the liquid meniscus, the pore is filled with liquid 4,5,7 . Therefore, the pore filling is predicted to occur in temporal sequence: smaller pores earlier and larger pores later.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Densification of Liquid‐Phase‐Sintered WC–Co by Use of Coarse WC Powder: Experimental Support for the Pore‐Filling Theory

Kim

Jung

Kang

et al. 2005

Journal of the American Ceramic Society

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Densification during liquid‐phase sintering of WC–Co with various WC powder sizes has been measured in order to identify the densification mechanism. During heating of powder compacts in the solid state, densification was enhanced with a reduction of WC powder size. However, the behavior was reversed when the densification occurred in the presence of a liquid: enhanced densification with increasing WC powder size. This result is in contradiction to a prediction of the conventional theory of liquid‐phase sintering, the contact flattening theory, but in good agreement with a prediction of the pore‐filling theory. Microstructural analysis further confirmed that the densification at the liquid‐phase sintering temperature occurred by pore filling. The calculated densification kinetics based on the pore‐filling theory also fitted well with the measured data. The observed densification behavior thus demonstrates experimentally the prediction of the pore‐filling theory that the densification is enhanced with increasing average grain size for the same pore size distribution.

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“…The pressure difference between the load of the juvenile clasts (lithostatic pressure) and the pore pressure may induce rapid closing of the pores by the migration of remaining liquid melt under strong capillary and surface tension forces, and the rock becomes densely welded. This may be partly analogous to processes observed during the liquid phase sintering of metal alloys and ceramics (e.g., Park et al 1984;German 1985) and is enhanced when the particle size is small (Hwang et al 1987). Further investigation is required for volcanic systems.…”

Section: Discussionmentioning

confidence: 94%

On the Welding of Pyroclasts from Very Low-Viscosity Magmas: Examples from Kimberlite Volcanoes

Brown¹,

Buse²,

Sparks³

et al. 2008

The Journal of Geology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Geology. A B S T R A C TLithofacies in kimberlite pipes in southern Africa exhibit features consistent with welded pyroclastic rocks. These include flared conduit-filling geometries, abundant lithic clasts, lithic clast layers, subhorizontal clast fabrics, gradational contacts with volcaniclastic rocks and sintered and coalesced globular ash, and lapilli and melt-coated particles. The welding dynamics of kimberlite pyroclasts differ from those of glassy, vesiculated pyroclasts in silicic volcanic systems. Low melt viscosity (∼0:1 Pa s) results in the efficient separation of volatiles and melt and the breakup of magma into nonvesicular spherical droplets. The glassy state is difficult to form in silica-deficient magmas because the crystallization kinetics are fast in low-viscosity melts. Three pyroclastic lithofacies are recognized that primarily relate to the state of the initial melt phase in the pyroclasts on deposition: (1) densely welded kimberlite forms where the initial melt phase in pyroclasts remains as pure melt, coalescing almost immediately to form a degassed homogeneous melt that subsequently crystallizes and may be texturally indistinguishable from igneous kimberlite; (2) incipiently welded kimberlite forms where the melt phase in pyroclasts is mostly crystalline with some residual melt (pyroclasts are resistant to deformation but are sticky and can sinter together); and (3) nonwelded kimberlite forms where the melt phase in pyroclasts is fully crystalline on deposition. Transitions between these pyroclast conditions may be abrupt. Gradations to nonwelded deposits and overlaps in their textural features in several kimberlite pipes suggest that welded rocks may be deposited from large-scale fluidized systems. The presence of crystals and lithic clasts may inhibit compaction deformation-welding textures by the formation of hard-particle percolation networks. Similar rocks in other kimberlite pipes may turn out to be welded rocks. The processes outlined here may be generally applicable to other low-viscosity magmas.

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Pore filling process in liquid phase sintering

Cited by 73 publications

References 4 publications

Review: liquid phase sintering

Review: liquid phase sintering

Enhanced Densification of Liquid‐Phase‐Sintered WC–Co by Use of Coarse WC Powder: Experimental Support for the Pore‐Filling Theory

On the Welding of Pyroclasts from Very Low-Viscosity Magmas: Examples from Kimberlite Volcanoes

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