Synthesis and processing of amorphous Si(Al)OC bulk ceramics [Elektronische Ressource] : high temperature properties and applications / by Rahul Ramesh Harshe

Informations

• Publié par: technischen_universitat_darmstadt
• Publié le: 01 janvier 2004
• Nombre de lectures: 15
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Synthesis and Processing of Amorphous Si(Al)OC
Bulk Ceramics: High Temperature Properties and
Applications
A dissertation submitted to the
Department of Materials Science
Darmstadt University of Technology
in partial fulfillment of the requirements for the degree
of
Doktor−Ingenieur
by
Rahul Ramesh Harshe
Master of Technology (M. Tech)
from
Kirloskarwadi, India
Referee: Prof. Dr. R. Riedel
Co-referee: Prof. Dr. H. Ortner
Date of submission: 19 August 2004
Date of oral examination: 07 September 2004
Darmstadt 2004
D 17Acknowledgments
Hardly-if-ever PhD is the sole achievement of one person. It rather is a journey
where the traveller is dependent on many aid on the path, has to ask for direc-
tions, and often needs a helping hand. It is only just to name my debts and
thank the people who helped me on my way−here is the right place for it as I
sincerely think that seldom is anything accomplished without the assistance or
encouragement of others.
First I would like to pay my sincere thanks to Prof. Dr. R. Riedel. He has
always been extremely generous with his time, knowledge and ideas and allowed
me great freedom in this research.
Likewise,IowemuchtotheadviceandintellectualsupportofProf. Dr. C.Balan.
His deep understanding in research helped me in understanding basic concepts. I
want to thank Prof. R. Raj for giving me the opportunity to work together with
his group in Boulder, USA.
My special thanks goes to Prof. Dr. H. M. Ortner, Chemical Analytic group in
TU-Darmstadt for his acceptance as a co-referee.
Further thanks to:
Dr. C. Konetschny for introduction to this project and kind help
C. Fasel for TGMS and discussion
Dr. I. Kinski for MAS-NMR characterization
Dr. Sandeep Shah for compression creep experiments and useful discussion
Dr. Stephan Flege for SIMS characterization
I appreciate the help from collogues and all those who have provided kind sup-
port, without which a great deal of this work would have been impossible.
I express my gratitude for the chance and financial support provided by the State
of Hessen, Germany to realize this research.
Much appreciation goes to my mother and father, and the rest of my family for
their support and belief in me which have always inspired me in my endeavors.
Thislistisfarfromexhaustive; IprayforforgivenessfromthoseIdidnotmention
by name and include them in my heart-felt gratitude.Contents
1 Abstract 1
2 Introduction & Motivation 3
3 Literature Review 7
3.1 Ceramics from Pyrolysis of Preceramic Polymers . . . . . . . . . . 7
3.2 Advantages over Conventional Fabrication Methods . . . . . . . . 10
3.3 Synthesis and Chemistry of Preceramic Polymers . . . . . . . . . 11
3.4 Silicon Oxycarbide: General . . . . . . . . . . . . . . . . . . . . . 18
3.4.1 Processing of Silicon Oxycarbide Glasses . . . . . . . . . . 21
3.4.1.1 ProcessingofSiliconOxycarbideGlasses: Sol-Gel
Method . . . . . . . . . . . . . . . . . . . . . . . 21
3.4.1.2 Processing of Silicon Oxycarbide Glasses: Sili-
cone Resins . . . . . . . . . . . . . . . . . . . . . 27
3.4.2 SiOCCeramicandPostTreatmentCharacterization: MAS-
NMR, TEM, EELS, Mechanical.. . . . . . . . . . . . . . . 34
3.5 Formation of Si(M)OC Ceramics; M = Modifiers (Elements or
Compounds) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5.1 Modifications with Fillers . . . . . . . . . . . . . . . . . . 39
3.5.1.1 InactiveFillerControlledPyrolysisofPreceramic
Polymers . . . . . . . . . . . . . . . . . . . . . . 39
3.5.1.2 Active Filler Controlled Pyrolysis of Preceramic
Polymers . . . . . . . . . . . . . . . . . . . . . . 43
3.5.2 Modification of Preceramic Polymers without Fillers . . . 45
3.5.2.1 Structural Characterization of Si-Al-O-C Polymers 46
iContents
3.5.2.2 PyrolysisProcesstoSi(Al)OCCeramicsandPost
Treatment Characterization . . . . . . . . . . . . 46
3.6 Kinetics of the Process . . . . . . . . . . . . . . . . . . . . . . . . 47
3.6.1 Basic Theories. . . . . . . . . . . . . . . . . . . . . . . . . 48
3.6.2 Rate of a Single Thermally Activated Process . . . . . . . 49
3.6.3 Rate Equations for Heterogeneous Reactions . . . . . . . . 51
3.7 Thermo-Mechanical Behavior . . . . . . . . . . . . . . . . . . . . 53
3.7.1 Developments in Thermo-Mechanical Behavior for Si(C)O
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.8 Oxidation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.8.1 Oxidation Review on Silicon Based Ceramics . . . . . . . . 55
3.8.1.1 Oxidation of Silicon . . . . . . . . . . . . . . . . 55
3.8.1.2 Oxidation of Silicon Carbide (SiC) . . . . . . . . 56
3.8.1.3 Additive Containing Materials. . . . . . . . . . . 60
3.8.2 Oxidation of SiOC Ceramics (Fibers and Powder) . . . . . 61
3.9 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.9.1 Polymer Derived Ceramic Fibers . . . . . . . . . . . . . . 65
3.9.2 Other Applications . . . . . . . . . . . . . . . . . . . . . . 66
4 Experimental Procedure 71
4.1 Unmodified Preceramic Polymer . . . . . . . . . . . . . . . . . . . 71
4.1.1 Basic Materials . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1.2 Mixing Procedure, Cross-linking and Shaping . . . . . . . 72
4.1.3 Pyrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2 Modified Preceramic Polymer . . . . . . . . . . . . . . . . . . . . 75
4.2.1 Basic Materials for Aluminum Modification . . . . . . . . 75
4.2.2 Modification Procedure: Sol-Gel Method . . . . . . . . . . 75
4.2.3 Shaping and Pyrolysis . . . . . . . . . . . . . . . . . . . . 75
4.3 Sample Designation . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.4 Post Pyrolysis Heat-treatments: Procedures . . . . . . . . . . . . 77
4.4.1 Inert Atmosphere (Crystallization Behavior): Powder and
Bulks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.4.2 Air Atmosphere (Oxidation): Bulks . . . . . . . . . . . . . 77
4.5 Mechanical Characterization of SiOC ceramic . . . . . . . . . . . 79
iiContents
4.5.1 Acoustic Method . . . . . . . . . . . . . . . . . . . . . . . 79
4.5.2 Indentation Method . . . . . . . . . . . . . . . . . . . . . 80
4.6 Thermo-Mechanical Behavior: Creep Test . . . . . . . . . . . . . 81
4.7 Methods for Material Characterization . . . . . . . . . . . . . . . 82
4.7.1 Rheology . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.7.2 Fourier Transform Infrared Spectroscopy (FTIR) . . . . . 83
4.7.3 Thermal Gravimetry and Mass Spectroscopy (TG/MS) . . 84
4.7.4 Thermo Mechanical Analysis (TMA) . . . . . . . . . . . . 84
4.7.5 Dimensional Changes (Dilatometry) . . . . . . . . . . . . . 85
4.7.6 Elemental Analysis . . . . . . . . . . . . . . . . . . . . . . 85
4.7.7 MAS-NMR Spectroscopy . . . . . . . . . . . . . . . . . . . 86
4.7.8 X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . 86
4.7.9 Scanning Electron Microscopy . . . . . . . . . . . . . . . . 87
4.7.10 Secondary Ion Mass Spectroscopy (SIMS) . . . . . . . . . 87
5 Results and Discussion 89
5.1 Material Selection: Identifying Ideal Polymer . . . . . . . . . . . . 89
5.2 Unmodified Siloxane System . . . . . . . . . . . . . . . . . . . . . 93
5.2.1 Investigating MK polymer: Chemical and Thermal Cross-
linking Behavior. . . . . . . . . . . . . . . . . . . . . . . . 94
5.2.2 Cross-linkingInvestigationbyRheology: OptimizingCross-
Linking-Agent Content . . . . . . . . . . . . . . . . . . . . 99
5.2.2.1 Rheology: Introduction . . . . . . . . . . . . . . 99
5.2.2.2 Theoretical Background and Definitions . . . . . 100
5.2.3 Rheology and its Advantage in Processing . . . . . . . . . 106
5.2.3.1 Rheology for Fiber Formation . . . . . . . . . . . 106
5.2.3.2 Rheology for Green-Bulk Formation . . . . . . . 112
5.2.4 Pyrolysis of Unmodified Polymer: Polymer-SiOC Ceramic
Conversion Process . . . . . . . . . . . . . . . . . . . . . . 112
5.3 Aluminum Modified Siloxane System . . . . . . . . . . . . . . . . 115
5.3.1 Gelation Process . . . . . . . . . . . . . . . . . . . . . . . 115
5.3.2 SiAlOC Polymer-Ceramic Transformation Process . . . . . 116
5.4 Chemical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.5 Presence of Residual Carbon in Si(Al)OC Pyrolyzed Products . . 121
iiiContents
5.6 MAS-NMR Investigation of Si(Al)OC System . . . . . . . . . . . 123
5.7 Bulk Formation: Physical Changes During Si(Al)OC Pyrolysis . . 128
5.7.1 Bulk SiOC Ceramics . . . . . . . . . . . . . . . . . . . . . 128
5.7.2 Bulk SiAlOC Ceramics . . . . . . . . . . . . . . . . . . . . 130
5.8 Mechanical Characterization of SiOC Ceramics . . . . . . . . . . 132
5.8.1 Acoustic Method . . . . . . . . . . . . . . . . . . . . . . . 132
5.8.2 Indentation Method . . . . . . . . . . . . . . . . . . . . . 134
5.9 High Temperature Behavior . . . . . . . . . . . . . . . . . . . . . 137
5.9.1 Crystallization, Phase Separation and High Temperature
Stability in Si(Al)OC Ceramics . . . . . . . . . . . . . . . 137
5.9.1.1 SiOC Ceramic . . . . . . . . . . . . . . . . . . . 137
5.9.1.2 SiAlOC Ceramic . . . . . . . . . . . . . . . . . . 140
5.10 Softening/Crystallization Kinetics of SiAlOC Ceramics . . . . . . 144
5.11 Creep in Bulk SiAlOC Ceramics . . . . . . . . . . . . . . . . . . . 154
5.12 Oxidation Behavior . . . . . . . . . . . . . . . . . . . . . . . .