Non-destructive characterization of materials by single-sided NMR [Elektronische Ressource] / vorgelegt von Nicolae-Octavian Goga

Lzumakulowa

Sujets

• Physik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2007
• Nombre de lectures: 4
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Non-destructive Characterization of
Materials by Single-sided NMR








Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der
Rheinisch-Westfälischen Technischen Hochschule Aachen
zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften
genehmigte Dissertation





vorgelegt von
M.Sc. Nicolae-Octavian Goga
aus Satu Mare, Romania





Berichter: Universitätsprofessor Dr. Dr. h.c. Bernhard Blümich
Universitätsprofessor Dr. Dan E. Demco



Tag der mündlichen Prüfung: 20. August 2007
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.



































































“I am not aware of any other field of science outside of magnetic resonance that offers so
much freedom and opportunities for a creative mind to invent and explore new
experimental schemes that can be fruitfully applied in a variety of disciplines.”


~ Richard R. Ernst ~







































Contents



1 Introduction...................................................................................................................1
2 Nuclear Magnetic Resonance.......................................................................................7
2.1 Basic NMR...............................................................................................................7
2.1.1 Magnetic resonance phenomenon.....................................................................7
2.1.2 Magnetic and electric spin interactions...........................................................11
2.1.3 Magnetization relaxation.................................................................................15
2.1.4 Spin coherences...............................................................................................18
2.1.5 Spin echoes .....................................................................................................21
2.2 NMR imaging ........................................................................................................25
2.2.1 Principles of NMR imaging ............................................................................26
2.2.2 Spin system response in heterogeneous samples ............................................28
2.2.3 Frequency encoding ........................................................................................29
2.2.4 Phase encoding................................................................................................31
2.2.5 Sampling k-space ............................................................................................32
2.2.6 Contrast in NMR imaging...............................................................................33
3 Single-Sided NMR.......................................................................................................37
3.1 Introduction............................................................................................................37
3.2 Inhomogeneous magnetic fields.............................................................................38
3.3 Unilateral sensors – the NMR-MOUSE.................................................................40
3.3.1 Field profiles ...................................................................................................41
3.3.2 Signal-to-noise ratio........................................................................................43

4 Characterization of Materials by Single-Sided NMR..............................................49
4.1 NMR of polymers ..................................................................................................49
4.1.1 Cross-linked polymers ....................................................................................50
4.1.2 Network properties by transverse magnetization relaxation...........................52
4.1.3 Heterogeneities in rubbery materials ..............................................................53
4.2 Unilateral NMR relaxometry .................................................................................55
4.2.1 Method ............................................................................................................56
4.2.2 Non-invasive quality control in the tire production........................................58
4.2.3 Relaxometry on aged PE pipes .......................................................................63
4.2.4 In situ NMR at a stress-strain device ..............................................................66
4.2.5 Mechanical testing versus NMR.....................................................................69
4.3 Single-sided NMR imaging ...................................................................................77
4.3.1 Method ............................................................................................................77
4.3.2 Imaging of polymers and biological materials................................................81
4.4 High resolution NMR profiling..............................................................................89
4.4.1 Method ............................................................................................................90
4.4.2 Single-sided NMR profiling of multi-layer objects ........................................92
4.4.3 Surface UV aging of elastomers investigated with microscopic resolution by
single-sided NMR ....................................................................................................98
5 Conclusions................................................................................................................107
Appendix.......................................................................................................................113
References .....................................................................................................................115
Publications by the Author..........................................................................................128





Chapter 1


Introduction

There is a question I asked myself many times: What is our Universe made of? The
simplest answer which inherently comes into my mind is: particles in motion and their
fields. For the sake of simplicity, one might answer this question based on the
“macroscopic” information available to human senses, eventually pointing to atoms and
molecules, though, without thinking of those many interactions between them about
which Einstein said: “All actions would cease if those powerful elemental forces were to
cease stirring within us”. Talking about the delicate motion of a magnetic particle in an
external field, the Nobel Prize awarded Edward M. Purcell noticed: “It should reside in
all the ordinary things around us, revealing itself only to him who looks for it”; and
remembering the winter of his first successful NMR experiments while he started
looking even on snow with new eyes: “There the snow lay around my doorstep - great
heaps of protons quietly precessing in the earth’s magnetic field. To see the world for a
moment as something rich and strange is the private reward of many a discovery.”
What can we learn from all these about the structure of matter? Let us begin with
the most direct application of nuclear induction methods, the measurement of nuclear
magnetic moments. The basis for this is the resonance condition

μH0ν = , (1.1)
Ih
in which ν is the frequency of precession of the axis of the nuclear spin in a magnetic
field of strength H , and μ is the magnetic moment of the nucleus. The number I, is the 0

Chapter 1: Introduction 2
nuclear spin quantum number, an integer or half-integer, and h is Planck’s constant.
Now H except for a certain slight correction, is simply the field of the magnet in which 0,
the substance has been put, and it can be measured. The frequency of precession, is
easily measured with high accuracy, and thus one can determine the quantityμ/Ih .
Regarding the motion of atomic nuclei in a magnetic field one finds in Nuclear
Magnetic Resonance (NMR) a powerful tool to investigate structure and motion, and
though not all nuclei possess a magnetic moment, one can hardly find an element
without at least one isotope sensitive to magnetic fields. Thus, the world of the nuclear
spins is a true paradise for theoretical and experimental physicists. It supplies, for
ex