Authors: Fan Li, Jing Zhe Pan
Abstract: The sintering of thin films is widely used for surface coatings and because of its
technological importance has generated extensive research interest. During the sintering process, the
thin film is constrained by the substrate, which generates considerably high levels of stresses.
Crackings are often observed and are considered as one of the major problems of the surface coating
technique. This paper has proposed a new numerical method in order to tackle the traditional
difficulties in simulating multi-crackings during constrained sintering. Main features of the present
method include: (i) the material data is represented by an anisotropic constitutive law, (ii) a new
numerical scheme is developed for the crack initialization and growth based on the material point
method, (iii) the 3D viscous film shrinkage model is solved by using a dynamic FE scheme, and (iv)
the random nature of the initial green body density is represented by statistical variabilities. It is
shown that the model proposed by the present paper is capable for the nucleation and propagation of
multi-cracks in a straightforward manner. Cracking patterns are shown to be consistent with
experimental understandings. The focus of the paper is on the numerical issues and demonstrating
the capacity of the model.
191
Authors: Ian P. Shapiro, Xiao Feng Zhao, Hui Xu, Ping Xiao
Abstract: The constrained sintering behavior of yttria stabilized zirconia coatings containing 1 wt. % alumina produced using electrophoretic deposition has been studied. Coatings have been characterized by scanning electron microscopy, micro-hardness and fluorescence spectroscopy after sintering in air at 1100°C and 1200°C. These coatings were compared with those that additionally contained 1 wt. % soda-lime glass. Micro-hardness and fluorescence spectroscopy are shown to accurately monitor the density of the coatings. Fluorescence spectroscopy showed that the density across the coating is even, as expected from modelling literature. The addition of 1 wt. % of soda-lime glass is shown to improve the sintered density of coatings.
177
Authors: Jason Nicholas, Lutgard C. De Jonghe, Craig P. Jacobson
Abstract: The synthesis of multilayer membranes for solid oxide fuel cells by means of co-firing
requires choice of compatible materials as well as a precise balance between densification rates of
the various layers throughout the densification process. One attractive practical objective is the
formation of dense electrolyte films on invariant, preformed electrode substrates, such as porous
electrodes of either ceramic or metal conductors. The formation of dense 10-20 micrometer thick
Ceria-based membranes on invariant substrates has been achieved by adjusting of the film sintering
properties trough selection of particle size, initial density, and novel sintering additives. The
accompanying theory pertaining to constrained sintering is examined, to determine the conditions
under which fully dense electrolyte layers can be produced on invariant or minimally variant
substrates.
549
Authors: Terry J. Garino, Jose G. Argüello
Abstract: When structures that consist of powders of two or more materials, such as low
temperature co-fired ceramic packages or a planar solid oxide fuel cells, are sintered, the mismatch
in the sintering shrinkage rates between the different materials produces stress, since the faster
shrinking materials are constrained by those that shrink at a slower rate. These stresses can lead to
the formation of defects such as cracks or shape distortion. Results of recent model experiments to
study the constrained sintering in multi-material systems will be discussed for two model
geometries. The first geometry is a simple bi-layer consisting of single layers of two different
materials bonded together. Results of in situ observation of sintering bi-layers will be presented and
discussed in relation to the properties of the individual layers such as their free sintering rates,
uniaxial viscosities and viscous Poisson’s ratio. The second geometry studied was that of a ring of
one material filled with a cylinder of a second, slower shrinking material. In this case, the results of
several variations of this geometry including filling the ring either fully or partly with a rigid, nonshrinking
cylinder or with rigid, non-cylindrical shapes will be presented and discussed.
501
Authors: Yoshiaki Kinemuchi, H. Morimitsu, H. Ishiguro, Shoji Uchimura, Koji Watari
Abstract: Co-firing of multiple materials results in the formation of internal stress due to the
difference in shrinkage behavior. This internal stress causes retardation of sintering, crack formation
and/or de-lamination at the interface. To reduce internal stress in layered structures, homogeneous
pressing via centrifuge has been attempted. The effect of centrifugal pressing was demonstrated by
film sintering, in which crack suppression and void removal by the present process were revealed.
Owing to the homogeneous microstructure, the thermal stability of the film was significantly
improved.
19
Authors: Yoshiaki Kinemuchi, Shoji Uchimura, Koji Watari
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