Electrocrystallisation of CoFe alloys under the influence of external homogeneous magnetic fields [Elektronische Ressource] / Koza, Jakub Adam

Jak1

Informations

• Publié par: technische_universitat_dresden
• Publié le: 01 janvier 2010
• Nombre de lectures: 33
• Langue: English
• Poids de l'ouvrage: 56 Mo

Extrait

Electrocrystallisation of CoFe Alloys
Under the Influence of
External Homogeneous Magnetic Fields





An der Fakultät Maschinenwesen
der
Technischen Universität Dresden
zur
Erlangung des akademischen Grades
Doktoringenieur (Dr.-Ing.)
eingereichte Dissertation




Dipl.-Ing. Koza, Jakub Adam
geb. am: 02.12.1979 in Stalowa Wola, Polen


Tag der Einreichung: 27.01.2010
Tag der Verteidigung: 24.06.2010



































To my beloved wife Kasia
and daughter Ola TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................. 1
2. STATE OF REASEARCH ............................................................................................... 4
2.1. FUNDAMENTALS OF ELECTRODEPOSITION............................................................ 4
2.1.1. Electrocrystallization.............................................................................................. 4
2.1.2. Mass Transport of Ions to the Electrode Surface ................................................... 5
2.1.3. Nucleation, Growth and Phase Formation of Electrodeposited Layers................. 7
2.2. INFLUENCE OF AN EXTERNAL MAGNETIC FIELD ON THE
ELECTRODEPOSITION PROCESS ............................................................................... 15
2.2.1. Magnetically Induced Forces ............................................................................... 15
2.2.2. Classical Magnetohydrodynamic Effect ............................................................... 17
2.2.3. Micro- MHD Effect ............................................................................................... 18
2.2.4. Nucleation, Growth and Phase Formation in the Presence of an External
Magnetic Field ...................................................................................................... 19
2.3. ELECTRODEPOSITION OF Co, Fe AND CoFe ALLOYS............................................ 21
2.3.1. Electrode Kinetics................................................................................................. 21
2.3.2. Properties of the Electrodeposited CoFe Alloy .................................................... 22
3. EXPERIMENTAL SETUP AND PROCEDURES ...................................................... 25
3.1. CELL DESIGN AND ELECTRODES ............................................................................. 25
3.2. ELECTROCHEMICAL METHODS................................................................................ 27
3.3. DEPOSIT CHARACTERISATION ................................................................................. 32
4. RESULTS......................................................................................................................... 34
4.1. INFLUENCE OF AN EXTERNAL HOMOGENEOUS MAGNETIC FIELD ON THE
MASS TRANSPORT DURING ELECTRODEPOSITION............................................. 34
4.1.1. Influence of a Magnetic Field on the Metal Deposition ....................................... 34
4.1.1.1. Cobalt............................................................................................................. 34
4.1.1.2. Iron................................................................................................................. 39
4.1.1.3. Cobalt-Iron Alloys ......................................................................................... 46
4.1.1.4. Summary........................................................................................................ 57
4.1.2. Influence of a Magnetic Field on the Hydrogen Evolution Reaction (HER) and the
pH Value at the Interface...................................................................................... 60
4.1.3. Conclusions regarding the Influence of a Magnetic Field on the Mass Transport
............................................................................................................................... 75
i TABLE OF CONTENTS

4.2. INFLUENCE OF A MAGNETIC FIELD ON THE NUCLEATION AND GROWTH
PROCESSES..................................................................................................................... 76
4.2.1. Cobalt ................................................................................................................... 79
4.2.2. Iron ....................................................................................................................... 82
4.2.3. Cobalt-Iron Alloys ................................................................................................ 88
4.2.4. Summary and Conclusions Regarding the Influence of a Magnetic Field on the
Nucleation and Growth Processes........................................................................ 95
4.3. INFLUENCE OF A MAGNETIC FIELD ON THE PROPERTIES OF DEPOSITED
LAYERS ........................................................................................................................... 99
4.3.1. Chemical Composition of Cobalt-Iron Alloys ...................................................... 99
4.3.2. Morphology......................................................................................................... 102
4.3.2.1. Cobalt and Iron ............................................................................................ 102
4.3.2.2. Cobalt-Iron Alloys....................................................................................... 107
4.3.2.3. Summary...................................................................................................... 111
4.3.3. Structure and Texture ......................................................................................... 114
4.3.4. Magnetic properties............................................................................................ 121
4.3.5. Conclusions Regarding the Influence of a Magnetic Field on the Deposited Layer
Properties ........................................................................................................... 128
5. CONCLUSIONS AND REMARKS ............................................................................ 130
References: ................................................................................................................................. 135



ii LIST OF SYMBOLS

The meaning of symbols used in text:
a – crystal lattice constant
a – activity
a – constant
A – electrode surface area
A – nucleation rate constant
– constant
– roughness (Hurst) exponent
B – magnetic flux density
B – saturation magnetic flux density S
– symmetry parameter (Butler-Volmer)
– width of the peak at half maximum intensity at angle
– growth exponent
c – concentration
c – constant
– molar magnetic susceptibility m
d – diameter
d – interplanar distance hkl
D – diffusion coefficient
D – weighted crystallite size K
– diffusion layer thickness D
– hydrodynamic layer thickness H
e – electron
E – potential
o E – standard potential
f – frequency
f – resonance frequency of quartz oscillator 0
-1
F – Faraday’s constant (96500 Cmol )
F – diffusion driving force D
F – gravity force G
F – Lorentz force L
iii
dbadacbbqLIST OF SYMBOLS

F – paramagnetic concentration gradient force P
F – magnetic field gradient force ? B
H – coercivity c
– overpotential
i – current density
i – exchange current density 0
i – limiting current density lim
I – current
J – magnetic polarisation
J – remanence magnetic polarisation r
J – saturation magnetic polarisation s
k – constant
k – electrochemical equivalent of M M
l – spatial size (length)
l – critical length c
– wave length
m – constant
m – mass
M – molar mass
-6 -1 -1– magnetic permability of a free space (1.26·10 VsA m ) 0
11 -1 -2
– quartz shear modulus (2.947·10 g cm s ) q
n – Overstone number
n – order of reflection
n – Néel’s exponent
N – number of nuclei at saturation (saturation nucleus density) 0
N(t) – number of nuclei at time t
– kinematic viscosity
– incident angle
– fraction of the surface area
– extended are fraction ex
r – radius
iv
mlqhqqmnLIST OF SYMBOLS

-1 -1R – universal gas constant (8.314 JK mol )
Rms – root mean square roughness
– density
t – time
T – temperature
u – time at which nucleus has been born
w(l,t) – surface width
x – atomic (molar) fraction
interaction nergy
z – number of charges taking part in the electrochemical reaction

Abbreviations:
AES – Auger electron spectroscopy
AFM – atomic force microscope
bcc – body centred cubic
BOS – background oriented schlieren
CA – chronoamperogram
CE – counter electrode
CV – cyclic voltamogram
DL – electrochemical double layer
EDX – energy dispersive X-ray spectroscopy
EQCM – electrochemical quartz crystal microbalance