Permeability of Green Ceramic Tapes as a Function of Binder Loading

Abstract

The permeability of green ceramic tapes was determined as a function of binder content for binder removed by air oxidation. The tapes were comprised of barium titanate as the dielectric, and polyvinyl butyral and dioctyl phthalate were the main components of the binder mixture. The flow in porous media through the tapes was analyzed in terms of models for describing Knudsen, slip, and Poiseuille flow mechanisms. The characteristic pore size was determined to be 1–2 μm, and thus Poiseuille flow was the dominant transport mechanism contributing to the flux. The permeability was then determined from Darcy's law for flow in porous media. The permeability was also determined from microstructural attributes in terms of the specific surface, the pore fraction, and a term to account for tortuosity and constrictions.

Pressure Distribution and Defect Formation in Green Ceramic Bodies During Supercritical Extraction of Binder

“…For both compositions, two properties in the green state were determined, both before and after SCE. The porosity was determined by Archimedes' method, and the permeability was determined from flux measurements using a procedure described in more detail elsewhere 18,19 . Both the porosity and permeability measurements were made on five laminated tapes.…”

Scaling Analysis of the Effect of Binder Content and Binder Distribution on the Gas Permeability of Porous Green Ceramics

“…The tape samples used in this study have been described in more detail elsewhere, 9 so we simply summarize the procedure here. Barium titanate powder (Tamtron X7R 412H, Ferro Electronic Materials, Niagara Falls, NY) at 55.4 wt% with a mean particle diameter of 1.2 μm and specific surface area of 3.3 m 2 /g was mixed with 44.6 wt% of binder solution (B73305 Ferro Corp., San Marcos, CA).…”

“…The binder, although only a fugitive phase, influences the properties of the green body, and thus its presence has important ramifications on processing steps subsequent to forming of the green ceramic component. One property influenced by the binder content and binder distribution is the gas‐phase permeability 1–6 of the green ceramic body 7–10 . The permeability, which plays an important role in determining the build up of pressure in the green body during thermal heating cycles for binder removal, 11,12 does not have a constant value, however, but varies as binder is degraded.…”

“…The permeability of a porous medium is often expressed in terms of at least two independent microstructural attributes, namely a parameter related to the amount of porosity and one or more characteristic dimensions related to the pore size 1–10 . For example, if the permeability is represented with the Kozeny–Carman model, both the porosity and the specific surface appear therein; the latter quantity can further be related to either the pore size or the particle size.…”

“…In earlier work, we have used measurements of the gas flux through porous green ceramic tapes to determine the permeability as a function of binder content 9,10 . For the flow conditions examined therein, the ratio of the mean free path to the pore size was such that the dominant transport mechanism was laminar flow, and thus Darcy's law was valid.…”