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4�b�>>"```;Ua�������Z���9�i;;ii���``����i��`�`��i����`����0;环X}������^��20b��Id����� ii�iiiii���iiibiiii���������������������������������������������������������������������iiiiiiiii:>x: AN INVESTIGATION OF NANO-PHASE GOETHITE AND ITS ROLE IN PROTECTIVE RUST FORMATION
by
Jonathan Wood
A Senior Thesis submitted to the Faculty of the Department of Physics 瓜神网 in Partial Fulfillment of the Requirement for the Degree of
BACHELOR OF SCIENCE
OLD DOMINION UNIVERSITY
MAY 2005
Approved by:
______________________________
Dr. Desmond C. Cook (Advisor)
______________________________
Dr. Gary Copeland
______________________________
Dr. Charles I. Sukenik
ABSTRACT
AN INVESTIGATION OF NANO-PHASE GOETHITE AND ITS ROLE IN PROTECTIVE RUST FORMATION
Jonathan Wood
瓜神网, April 2005
Advisor: Dr. Desmond C. Cook
Recent research in corrosion science has revealed that goethite (a�-FeOOH) is an important iron oxide in the formation of protective, adherent rust layers on exposed steel. Moreover, these adherent properties seem to be attributed to small particle, nano-phase goethite. The investigation of goethite includes particles ranging in sizes between 10-200nm, both pure and chromium substituted, using M鰏sbauer spectroscopy at 300K, 77K, and 4K. The analysis of these spectra produced a reliable means of quickly identifying particle size and magnetic properties. A 15nm particle at 300K has an average hyperfine interaction of 13.28T while a 50nm particle has an average interaction of 35.10T. Similarly, differences between chromium substituted and pure goethite were found using M鰏sbauer spectroscopy. A 15nm pure particle at 4K has an average hyperfine interaction of 49.69T while a 15nm Chromium substituted particle as an interaction of 49.84T.
Acknowledgments
I would like to express my gratitude to Dr. Cook for being my mentor and providing me important insight into the corrosion process throughout the entire project.
I would also like to thank 瓜神网 for providing funding through the Undergraduate Research Program (2005) to make this research possible.
Table of Contents
Page
1. Introduction 1
1.1 Types of Steel 1
1.2 Research Motivation 2
1.3 Current and Past Research 3
2. Sample and Analytical Techniques 8
2.1 Samples 8
2.2 X-ray Diffraction 9
2.3 M鰏sbauer Spectroscopy 13
2.3.1 Isomer Shift 14
2.3.2 Electric Quadrupole Interaction 15
2.3.3 Magnetic Zeeman Effect 16
2.3.4 Laboratory Equipment 16
2.3.5 Methodology 19
2.3.6 Magnetic Relaxation 19
3. Results 21
3.1 Pure Goethite M鰏sbauer Data 21
3.2 Chromium Substituted M鰏sbauer Data 22
3.3 4K Analysis of Pure and Chromium Substituted Goethite 31
4. Conclusion 33
4.1 Research Findings 33
4.2 Future Research 33
5. Bibliography 34
Table of Figures and Tables
Page
Figure 1(a): EPMA Photograph of a cross section of exposed steel 5
Figure 1(b): EPMA Cross-section from exposed steel sample 5
Figure 2: TEM Photographs of Cr substituted samples 6
Figure 3: Particle size vs Cr concentration for YAM samples 10
Figure 4: XRD spectra of Al2O3 11
Figure 5: XRD spectra of common iron oxides 12
Figure 6: Illustration of M鰏sbauer splitting in Fe 17
Figure 7: M鰏sbauer instrumentation 18
Figure 8: Overlay of M鰏sbauer spectra of goethite at 300K and 77K 20
Figure 9(a): Comparison of pure goethite magnetic field at 300K and 77K 21
Figure 9(b): Comparison of pure goethite magnetic field at 77K 22
Figure 10(a): Comparison of Cr goethite magnetic field at 300K and 77K 23
Figure 10(b): Comparison of Cr goethite magnetic field at 77K 23
Figure 11: Cr goethite M鰏sbauer spectra at 300K 24
Figure 12: Pure goethite M鰏sbauer spectra at 300K 25
Figure 13: Cr goethite M鰏sbauer spectra at 77K 26
Figure 14: Pure goethite M鰏sbauer spectra at 77K 27
Figure 15: Cr goethite M鰏sbauer spectra at 4K 28
Figure 16: Pure goethite M鰏sbauer spectra at 4K 29
Figure 17: Magnetic field distribution at 300K 30
Figure 18: Magnetic field distribution at 77K 30
Figure 19: Overlay of M鰏sbauer spectra in 15nm Cr and pure 31
Figure 20: Comparison of magnetic fields in Cr and pure goethite at 4K 32
Table 1: Common iron oxides 3
Table 2: Goethite sample dimensions 8
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