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Investigation of the role of impurities and sintering parameters on the microstructure and properties of dense titanium diboride ceramics and boron carbide–titanium diboride composites

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Title
Investigation of the role of impurities and sintering parameters on the microstructure and properties of dense titanium diboride ceramics and boron carbide–titanium diboride composites
Name (type = personal)
NamePart (type = family)
Celik
NamePart (type = given)
Azmi
NamePart (type = date)
1990
DisplayForm
Azmi Celik
Role
RoleTerm (authority = RULIB); (type = text)
author
Name (type = personal)
NamePart (type = family)
Haber
NamePart (type = given)
Richard A
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Richard A Haber
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
chair
Name (type = personal)
NamePart (type = family)
Mann
NamePart (type = given)
Adrian B
DisplayForm
Adrian B Mann
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
internal member
Name (type = personal)
NamePart (type = family)
Matthewson
NamePart (type = given)
Michael J
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Michael J Matthewson
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
internal member
Name (type = personal)
NamePart (type = family)
Lehman
NamePart (type = given)
Richard
DisplayForm
Richard Lehman
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
internal member
Name (type = personal)
NamePart (type = family)
Rafaniello
NamePart (type = given)
William
DisplayForm
William Rafaniello
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
outside member
Name (type = corporate)
NamePart
Rutgers University
Role
RoleTerm (authority = RULIB)
degree grantor
Name (type = corporate)
NamePart
School of Graduate Studies
Role
RoleTerm (authority = RULIB)
school
TypeOfResource
Text
Genre (authority = marcgt)
theses
Genre (authority = ExL-Esploro)
External ETD doctoral
OriginInfo
DateCreated (qualifier = exact); (encoding = w3cdtf); (keyDate = yes)
2020
DateOther (type = degree); (qualifier = exact); (encoding = w3cdtf)
2020-10
Language
LanguageTerm (authority = ISO 639-3:2007); (type = text)
English
Abstract
Titanium diboride (TiB2) is an important ultra-high temperature ceramic material due to its excellent mechanical, elastic, thermal, and chemical properties. It has received great attention for a variety of industrial and technological applications including refractory, cutting tools and aerospace applications. Boron carbide (B4C) is another significant non-oxide ceramic with favorable physical and chemical properties such as high hardness, high strength and good chemical stability. B4C is one of the most used ceramic materials as personal body armor plates, abrasives, wear-resistant components for grinding and cutting, and neutron absorbent material for nuclear reactors.
Both TiB2 and B4C are strongly covalent and sintering of these ceramics is often challenging either with or without additives. Impurities in the starting powders such as TiO2 and B2O3 inhibit densification and the use of high temperatures cause exaggerated grain growth and spontaneous microcracking.

The goals of this thesis were to synthesize phase-pure TiB2 powders, and process and characterize dense TiB2 ceramics as well as utilization of in-house synthesized powders in B4C–TiB2 composite samples. Densification experiments were carried out mainly using spark plasma sintering (SPS) method and hot pressing (HP) was used to fabricate industry-scale composite samples. This thesis examines the effects of starting powder quality and sintering parameters on the microstructure and mechanical properties of dense TiB2 ceramics and B4C–TiB2 composites. X-ray diffraction (XRD) was used to identify phases present in the powders and densified samples. Archimedes’ method was used to determine bulk density values of sintered monolithic and composite materials. The observations in the changes of microstructures were made using field-emission scanning electron microscopy (FESEM) equipped with an electron backscatter diffraction (EBSD) detector. Non-destructive ultrasonic evaluation (NDE) techniques were employed to measure elastic properties of the dense samples. Transmission electron microscopy (TEM) was utilized to reveal atomic structure of the grain boundaries of TiB2 specimens. Vickers micro-hardness testing and Berkovich nano-indentation experiments were performed on mechanically polished sample surfaces to measure hardness values.

The results showed that synthesis of titanium diboride powders containing small amount of surface oxide impurity layers is of vital importance for good sinterability of the powders into dense monolithic TiB2 ceramics. The presence of residual surface oxide impurities (≥1.6 wt%) in commercial boride powders inhibited densification, therefore degraded the material properties. In-house synthesized TiB2 powders contained much lower oxygen content (≤0.5 wt%) and monolithic TiB2 ceramics with fine-grained microstructure (g = 4.6 ± 0.6 µm) were spark plasma sintered successfully up to relative density of 99.4% ρth using those powders. TEM observations revealed the existence, for the first time, of an amorphous BC-Si intergranular film (IGF) along the grain boundaries of monolithic TiB2 ceramics.

B4C–TiB2 composite samples with up to 15 wt% TiB2 content were densified via spark plasma sintering (SPS) and hot pressing (HP) to investigate the effects of the TiB2 second phase addition on the microstructure and mechanical properties of boron carbide ceramics. Addition of 10 wt% TiB2 improved the Vickers hardness and fracture toughness of B4C by 15% and 25%, respectively. Microstructure evaluation through FESEM on hot pressed samples revealed that the rapid grain growth of boron carbide was inhibited as the average grain size of hot pressed B4C decreased from 16.99 ± 2.1 µm to 1.59 ± 0.5 µm and the number of planar defects was greatly decreased by TiB2 addition.
Subject (authority = local)
Topic
Titanium diboride
Subject (authority = RUETD)
Topic
Materials Science and Engineering
RelatedItem (type = host)
TitleInfo
Title
Rutgers University Electronic Theses and Dissertations
Identifier (type = RULIB)
ETD
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ETD_11133
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application/pdf
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text/xml
Extent
1 online resource (xxvii, 173 pages)
Note (type = degree)
Ph.D.
Note (type = bibliography)
Includes bibliographical references
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School of Graduate Studies Electronic Theses and Dissertations
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rucore10001600001
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NjNbRU
Identifier (type = doi)
doi:10.7282/t3-y1e7-xd66
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The author owns the copyright to this work.
RightsHolder (type = personal)
Name
FamilyName
Celik
GivenName
Azmi
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Copyright Holder
RightsEvent
Type
Permission or license
DateTime (encoding = w3cdtf); (qualifier = exact); (point = start)
2020-09-09 16:32:35
AssociatedEntity
Name
Azmi Celik
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Affiliation
Rutgers University. School of Graduate Studies
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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DateTime (encoding = w3cdtf); (qualifier = exact); (point = start)
2020-10-31
DateTime (encoding = w3cdtf); (qualifier = exact); (point = end)
2022-10-31
Detail
Access to this PDF has been restricted at the author's request. It will be publicly available after October 31st, 2022.
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Copyright protected
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Permission or license
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