Rearrangement During Liquid Phase Sintering of Ceramics

Huppmann, W. J.; Pejovnik, S.; Han, Seung-Gi

doi:10.1007/978-1-4684-3378-4_20

Cited by 11 publications

(28 citation statements)

References 2 publications

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“…A wetting liquid moves to occupy the lowest energy configuration, so it preferentially flows to the smaller grains and pores. This gives rise to rearrangement densification [32]. Rearrangement takes a few minutes, Fig.…”

Section: Contact Angle and Dihedral Anglementioning

confidence: 99%

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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: Contact Angle and Dihedral Anglementioning

confidence: 99%

“…Liquid completely wets the solid for S [ 0 and partially wets when S \ 0. It is convenient to classify [32,33]. The capillary force arises from the liquid-vapor surface tension as shown in Fig.…”

Section: Incipient Liquid Formationmentioning

confidence: 99%

Review: liquid phase sintering

2009

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“…Xu and Mehrabadi [24] confirmed the assumption that viscous flow within the liquid bridges and the relative sliding of particles, which is called grains rearrangement, bring about densification in the initial stage of the liquid phase sintering. Huppman and Riegger [25] also found that increased sintering time does not actually affect further rearrangement process, so significant shrinkage occurs only in the initial stage of liquid phase sintering until direct contact between solid grains occurs. But under conditions of poor wetting capillary forces may become repelling, which results in swelling [25].…”

Section: Capillary Forcesmentioning

confidence: 98%

“…Huppman and Riegger [25] also found that increased sintering time does not actually affect further rearrangement process, so significant shrinkage occurs only in the initial stage of liquid phase sintering until direct contact between solid grains occurs. But under conditions of poor wetting capillary forces may become repelling, which results in swelling [25]. Capillary forces could be strong only for small size of channels.…”

Section: Capillary Forcesmentioning

confidence: 98%

“…Therefore, it should be taken into consideration that the theoretical dissertations provide only a model for ideal rearrangement and almost continuous transition from bridge to direct contacts while sintering, which cannot be realized experimentally. Experimental approach to the rearrangement process in liquid phase sintering was presented by Huppman and Riegger [25] who used planar arrays of uniform size copper-coated tungsten in order to compare directly those liquid phase sintered samples with the pre-sintered one. The research focused on particle rearrangement for various liquid phase ratio, contact angle and packing density.…”

Section: Capillary Forcesmentioning

confidence: 99%

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Vaporization and Poor Wettability as the Main Challenges in Fabrication of TiB2-Cu Cermets Studied by SPS

Ziemnicka-Sylwester

2014

Metals

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TiB2-Cu cermets with various volume fractions of copper (from 3 to 30 vol. %) were produced via liquid phase sintering at the temperature range 1100-1200 °C in vacuum using spark plasma sintering (SPS) technique. Full densification could not be achieved as the consequence of poor wettability and vaporizing Cu. The quantitative Rietveld analysis indicated that insignificant reduction in Cu content occurred only in sample with initially 3 vol. % of Cu, but then densification was negligible. The relative density improved along with increasing volume content of Cu (10-20 vol. %), but then predominant amount of Cu introduced was reduced as the effect of vaporization or swelling, which caused that pellet with intended 20 or 30 vol. % of Cu contained respectively only 6 or 17 vol. % after sintering. Moreover, Cu droplets were released from the die at the temperature of 1000-1030 °C near the Cu melting point. The effect of vaporization was successfully reduced by increased heating rate and when isothermal annealing process was skipped, however, it could not be entirely eliminated. The experimental results on Cu vaporization are confronted with parameters that are commonly considered in the production of cermets, such as oxidation, wettability, contact angle and viscosity as well as their impact on densification.

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