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Elektrische, piezoresistive und thermische Charakterisierung der Kohlenstoffstruktur "Aerographit" und deren Epoxidkomposite
Citation Link: https://doi.org/10.15480/882.2001
Publikationstyp
Doctoral Thesis
Date Issued
2019
Sprache
German
Author(s)
Herausgeber*innen
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2018-03-29
TORE-DOI
First published in
Number in series
31
Citation
Technisch-wissenschaftliche Schriftenreihe / TUHH Polymer Composites 31: (2019)
Due to their great potential for applications in energy storage, sensor
technology or optics, three-dimensionally structured carbon materials
and their polymer composites are increasingly the subject of current research.
One of these carbon structures - Aerographite - is treated in this
dissertation. The aim of this thesis is a comprehensive characterization
of Aerographite with regard to mechanical, electrical and thermal properties.
These are discussed for the pristine Aerographite and for its
epoxy composites. The interpenetrating compound, which is formed by
infiltration of the Aerographite with epoxy resin, is a special feature compared
to particle-modified carbon nanocomposites.
Aerographite is first produced in different densities on the basis of highly
porous zinc oxide templates consisting of tetrapod-shaped particles by
means of chemical vapor deposition. The densities are in the range from
0.6 mg/cm³ to 13.9 mg/cm³. The samples produced are characterized
by means of scanning electron microscopy and transmission electron microscopy
with respect to their morphology. The graphite quality is evaluated
by means of thermogravimetric analysis and Raman spectroscopy.
A nanocrystalline structure of the graphitic walls could be identified. For
purposes of comparison, some of the samples are subjected to a thermal
post-treatment in which graphitization takes place. Prior to the production
of the Aerographite composite, mechanical, electrical and piezoresistive
properties of the pristine Aerographite are also determined.
Subsequently, the further processing of the Aerographite into a composite
is performed by filling it with epoxy resin in a vacuum-assisted infiltration
process. In addition to the electrical conductivity in the initial
state, piezoresistive properties under different load conditions are determined
and discussed depending on the filler content of the composite.
The electrical conductivity is by orders of magnitude higher than in particle-
modified polymer composites and assumes values of up to 13.6
S/m. The electrical response is evaluated under compressive load as well
as under quasi-static, cyclic and incremental tensile load. The obtainedresistance curves are explained by means of phenomenological models,
taking into account the unique morphology of Aerographite. By analyzing
the fracture surfaces after the quasi-static tensile test, the sliding off
of graphitic layers could be identified as the dominant failure mechanism
of the composite. The reasons for characteristic resistance responses under
stress are the time dependent deformation behavior of the Aerographite
network due to friction and Van der Waals forces, as well as a
possible the telescopic extension of individual tetrapods.
The thermal conductivity of the Aerographite composites was determined.
Unlike the electrical conductivity, the improvement is small. Finally,
the electrical and thermal conductivity of the composites are presented.
Post-graphitization has a considerable influence and leads to an
improvement in both conductivities.
technology or optics, three-dimensionally structured carbon materials
and their polymer composites are increasingly the subject of current research.
One of these carbon structures - Aerographite - is treated in this
dissertation. The aim of this thesis is a comprehensive characterization
of Aerographite with regard to mechanical, electrical and thermal properties.
These are discussed for the pristine Aerographite and for its
epoxy composites. The interpenetrating compound, which is formed by
infiltration of the Aerographite with epoxy resin, is a special feature compared
to particle-modified carbon nanocomposites.
Aerographite is first produced in different densities on the basis of highly
porous zinc oxide templates consisting of tetrapod-shaped particles by
means of chemical vapor deposition. The densities are in the range from
0.6 mg/cm³ to 13.9 mg/cm³. The samples produced are characterized
by means of scanning electron microscopy and transmission electron microscopy
with respect to their morphology. The graphite quality is evaluated
by means of thermogravimetric analysis and Raman spectroscopy.
A nanocrystalline structure of the graphitic walls could be identified. For
purposes of comparison, some of the samples are subjected to a thermal
post-treatment in which graphitization takes place. Prior to the production
of the Aerographite composite, mechanical, electrical and piezoresistive
properties of the pristine Aerographite are also determined.
Subsequently, the further processing of the Aerographite into a composite
is performed by filling it with epoxy resin in a vacuum-assisted infiltration
process. In addition to the electrical conductivity in the initial
state, piezoresistive properties under different load conditions are determined
and discussed depending on the filler content of the composite.
The electrical conductivity is by orders of magnitude higher than in particle-
modified polymer composites and assumes values of up to 13.6
S/m. The electrical response is evaluated under compressive load as well
as under quasi-static, cyclic and incremental tensile load. The obtainedresistance curves are explained by means of phenomenological models,
taking into account the unique morphology of Aerographite. By analyzing
the fracture surfaces after the quasi-static tensile test, the sliding off
of graphitic layers could be identified as the dominant failure mechanism
of the composite. The reasons for characteristic resistance responses under
stress are the time dependent deformation behavior of the Aerographite
network due to friction and Van der Waals forces, as well as a
possible the telescopic extension of individual tetrapods.
The thermal conductivity of the Aerographite composites was determined.
Unlike the electrical conductivity, the improvement is small. Finally,
the electrical and thermal conductivity of the composites are presented.
Post-graphitization has a considerable influence and leads to an
improvement in both conductivities.
Subjects
Aerogel
Epoxy resins
Electrical conductivity
Composite materials
DDC Class
620: Ingenieurwissenschaften
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