The Impact of Surface Finish and Organic Additives on the Shear Behavior of Extruded Ceramic Pastes
Date
2015-04
Authors
Journal Title
Journal ISSN
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Publisher
New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Abstract
The contribution of die-wall friction in ceramic extrusion systems is a variable that
has been studied to only a limited degree. The introduction of abrasion-resistant surface
coatings, now a common practice in industry, and their associated roughness, is an
important area that requires study. To determine the contribution of surface roughness,
and the potential to understand that factor in extrusion processes, simple alumina extrusion
batches with two levels of a surfactant (a fatty acid), were evaluated.
The goal was to use wall pressure as a function of temperature (°C) and linear
extrusion velocity (mm/second) to derive the constants for wall shear behavior constant (β)
as well as rate dependent constant (n). Constraints included: four capillary die surface
finishes, temperature testing capability ranging from 10°C to 60°C, extrusion noodle
velocity up to 50.8 mm per second, and two alumina based extrusion batches designed to
elicit a low and high wall pressure response, with which substrate surface finish and
capillary wall pressure relationships were developed.
Through minor changes in batch composition, two stable wall pressure regions
were achievable without concern of temperature sensitivity. On a high wall pressure batch,
varying roughness of the capillary wall surface yields mean pressure differences with little
difference in slip behavior. Addition of 0.8% total fatty acid reduced wall pressure to a
level where varying roughness of the capillary wall surface yields differences in wall slip
behavior. The above modifications were able to produce a range of shear rate behavior
constants allowing for the understanding of the interaction of surface finishes when
combined with high and low wall pressure extrusion batch.
Description
Advisory committee members: Daniel McCauley, Matthew Hall. Dissertation completed in partial fulfillment of the requirements for the degree of Masters of Science in Materials Science and Engineering at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis