Research

I investigate diffusion kinetics of different elements and species in various geological and few commercial materials. Through experiments I determine diffusion rates as a function of different parameters (e.g., temperature). I operate a variety of experimental techniques (e.g., cold seal pressure vessels ,gas-mixing, ion implantation, thin film deposition) and analytical techniques (EPMA, SEM, RBS, NRRA) to approach previously inaccessible conditions and diffusion settings. These results can be used in numerous applications for example the determination of duration of geological processes. Other projects I am involved in are for example the study of hydrogen implantation into solids, the investigation of sulfide melt properties at mantle pressures, or multicomponent diffusion studies

Projects

Diffusion of H-bearing species in silicate glasses and melts

It affects various applications covering
- Earth Sciences (e.g., seafloor alteration, volcanic explosivity, cosmic weathering)
- Material Sciences (e.g., nuclear waste glass corrosion)
- Archaeoemtry (obsidian hydration dating)
Diffusion of H in glasses/melts is complicated by:
- H exists in glasses and melts as different species, molecular H2O and hydroxyl (OH)
- Diffusion across the glass transition (i.e., a change in the diffusion environment)
Challenges in studying H diffusion in glasses especially at low temperatures are:
- Experimentally - Classical experimental design do not work (e.g., diffusion couple)
- Analytically - diffusion is slow at low temperatures. Changes that can be modelled are therefore difficult to resolve.
I developed a novel method to overcome previous difficulties by combining:
- Pusled Laser Deposition (PLD)
- Nuclear Resonance Reaction Analysis (NRRA) ...more details on these techniques below

Diffusion of hydrogen in Nominally Anyhdrous Minerals (NAMs)

Nominally Anhydrous Minerals (NAMs)
- contain only trace to minor amounts of hydrogen
- major part of upper mantle
- Traces of hydrogen present a large contribution to the deep water cycle in Earth
- Mineral properties are strongly affected by hydrogen
How much are initial H contents in NAMs affected by diffusional modification at low temperatures?
- diffusion rates at LT need to be quantified
- challenges are similar to studies in silicate glasses (above)
Application of an exotic experimental design
- Implantation of H into gem-quality clinopyroxene (diopside) crystals
- Production of an artifical H concentration gradient
- Analysis of the modification of concentration gradients by NRRA

Solar wind implantation

Airless planetary bodies are exposed to solar wind implantation
- Ions get implanted into minerals and amorphous materials
- Source of hydrogen by hydration of near-surface regions of materials
- possible contribution to water on Earth
Experiments on hydrogen implantation in olivine
- How does H implantation in silicates work?
- How much H can be retained in silicates?
- Implantation of H in San Carlos Olivine at low energies (< 20 keV)
- Alternating H implantation with analysis using NRRA

Phase relations in the Fe-Ni-Cu-S system at mantle conditions

Base metal sulfides are the most abundant inclusions in diamonds
Sulfides strongly influence the behaviour of chalkophile elements (e.g., Ag, Cu...)
Performance of High-Pressure High-Temperature experiments that simulate mantle conditions
Use of mantle-relevant compositions with varying Ni contents and metal/sulfur ratios
Evaluation of phase relations (solidi and liquidi) as a function of pressure and temperature

NRRA analysis of H in garnet to calibrate IR-spectroscopy

NRRA provides an absolute measure of H in solids
Meausurement of H depth profiles in garnet crystals
These will be used as a calibration for IR-spectroscopy

Corner Brook Collisional Complex (CBCC), Newfoundland

Metapelitic rocks from a former collision zone between Laurentia and a microcontinent (Dashwoods)
Combination of petrographic observations with thermodynamic calculations to reconstruct the rock's metmamorphic history
Calculation of mineral isopleths (e.g., garnet) to obtain PT paths
Exposure of a complex metmamorphic scenario with interrelating PT paths
Localities of collected samples constitute a Barrovian-type zoning
Signs of high pressure metamorphism (Taconic?) that has been partly overprinted by Barrovian-type metamorphism
Signs of significant fluid-rock interaction in some samples

Methods

Nuclear Resonance Reaction Analysis (NRRA)

Nanometer-scale depth profiles of elements (e.g., H) in near-surface regions in solids
Ionbeam of 15N ions at energies > 6.4 MeV
Nuclear Reaction 1H(15N,ay)12C is induced that emitts y-rays
Y-rays have a characteristic energy of 4.4 MeV
Counting the y-rays using a NaI borehole detector (picture) give an absolute measure of total hydrogen
Increasing the beam energy shifts the reaction deeper into the sample as 15N ions need to reduce their energy by ion-matter interaction to introduce the nuclear reaction
Analysis with increasing energies consitutes H depth profiles (max. 2 - 3 um) with a depth resolution of few nm.
The technique is non-destructive
No further calibration or use of standards

Rutherford Backscattering Spectroscopy (RBS)

Nanometer distribution of elements in near-surface regions of solids
Analysis of absolute number of atoms
Insensitive to bondings
Preferably used for heavy elements
Maximum depth is about 2 um
Backscattering of 2 MeV He ions
Short measurement times of about 5 - 20 min

Pulsed Laser Deposition (PLD)

Deposition of thin films onto solids
Pulsed excimer laser produces a plasma from a target (desired thin film material, e.g., hydrated glass)
Plasma condenses on substrate (e.g., anhydrous glass)
Final sample is a couple of two compositional different materials with a well-defined and tight interface
Samples (concentration gradients between both parts) can be used in diffusion studies

Ion implantation

Implantation of different ions in solids at the accelerators of the Dynamitron Tandem Laboratory at the RUBION (Ruhr-University Bochum)
Deposition of elements at specific depths in the sample material as a function of ion energy
Production of concentration gradients (and defects) at depths (e.g., 400 nm)
Concentration profile can be described by an asymmetric Gauss distribution
Suitable for diffusion studies

Cold Seal Pressure Vessel (CSPV)

Used for synthesis and petrological experiments at high temperatures (max. 800 °C) and high pressures (max. 400 MPa)
External furnaces for heating
Pressure medium is water
Temperature measurements using K-type thermocouples
Very stable temperature and pressure conditions over long experimental durations
Large sample volumes compared to other high pressure methods (Piston Cylinder)
5 CSPV stations supplied by a pressure line allow the simultaneous performance of 5 experiments

Multi Anvil Press (630 ton)

Pressures up to 18 GPa and temperatures up to 2000 °C
14/8 assemblies and 10/4 assemblies
Use of resistive heater (e.g., graphite or Re)
Computer controlled pressure generation
Very small sample volumes
Combination of ZrO2 (insulator), MgO, pyrophyllite as solid pressure media
Temperature measurements by D-type (W/Re) thermocouples

...and more:

optical microscopy
gas mixing furnaces
Electron microprobe analyis (EPMA)
Scanning electron microscopy (SEM)

Research

Projects

Diffusion of H-bearing species in silicate glasses and melts

​​

It affects various applications covering

Earth Sciences (e.g., seafloor alteration, volcanic explosivity, cosmic weathering)

Material Sciences (e.g., nuclear waste glass corrosion)

Archaeoemtry (obsidian hydration dating)

Diffusion of H in glasses/melts is complicated by:

H exists in glasses and melts as different species, molecular H2O and hydroxyl (OH)​

Diffusion across the glass transition (i.e., a change in the diffusion environment)

Challenges in studying H diffusion in glasses especially at low temperatures are:​

Experimentally - Classical experimental design do not work (e.g., diffusion couple)​

Analytically - diffusion is slow at low temperatures. Changes that can be modelled are therefore difficult to resolve.

I developed a novel method to overcome previous difficulties by combining:​

Pusled Laser Deposition (PLD) ​

Nuclear Resonance Reaction Analysis (NRRA)​ ...more details on these techniques below

Diffusion of hydrogen in Nominally Anyhdrous Minerals (NAMs)​​​

​​

Nominally Anhydrous Minerals (NAMs)

contain only trace to minor amounts of hydrogen

major part of upper mantle

Traces of hydrogen present a large contribution to the deep water cycle in Earth

Mineral properties are strongly affected by hydrogen

How much are initial H contents in NAMs affected by diffusional modification at low temperatures?

diffusion rates at LT need to be quantified​

challenges are similar to studies in silicate glasses (above)

Application of an exotic experimental design

Implantation of H into gem-quality clinopyroxene (diopside) crystals

Production of an artifical H concentration gradient

Analysis of the modification of concentration gradients by NRRA

​

Solar wind implantation​​​

​​

Airless planetary bodies are exposed to solar wind implantation

Ions get implanted into minerals and amorphous materials

Source of hydrogen by hydration of near-surface regions of materials

possible contribution to water on Earth

Experiments on hydrogen implantation in olivine ​

How does H implantation in silicates work?

How much H can be retained in silicates?

Implantation of H in San Carlos Olivine at low energies (< 20 keV)​

Alternating H implantation with analysis using NRRA

Phase relations in the Fe-Ni-Cu-S system at mantle conditions​​​

​​

Base metal sulfides are the most abundant inclusions in diamonds

Sulfides strongly influence the behaviour of chalkophile elements (e.g., Ag, Cu...)

Performance of High-Pressure High-Temperature experiments that simulate mantle conditions

Use of mantle-relevant compositions with varying Ni contents and metal/sulfur ratios

Evaluation of phase relations (solidi and liquidi) as a function of pressure and temperature

NRRA analysis of H in garnet to calibrate IR-spectroscopy​​​

​​

NRRA provides an absolute measure of H in solids

Meausurement of H depth profiles in garnet crystals

These will be used as a calibration for IR-spectroscopy

Corner Brook Collisional Complex (CBCC), Newfoundland

Metapelitic rocks from a former collision zone between Laurentia and a microcontinent (Dashwoods)

Combination of petrographic observations with thermodynamic calculations to reconstruct the rock's metmamorphic history

Calculation of mineral isopleths (e.g., garnet) to obtain PT paths

Exposure of a complex metmamorphic scenario with interrelating PT paths

Localities of collected samples constitute a Barrovian-type zoning

Signs of high pressure metamorphism (Taconic?) that has been partly overprinted by Barrovian-type metamorphism

Signs of significant fluid-rock interaction in some samples

​

Methods

Nuclear Resonance Reaction Analysis (NRRA)

​

Nanometer-scale depth profiles of elements (e.g., H) in near-surface regions in solids

Ionbeam of 15N ions at energies > 6.4 MeV

Nuclear Reaction 1H(15N,ay)12C is induced that emitts y-rays

Y-rays have a characteristic energy of 4.4 MeV

Counting the y-rays using a NaI borehole detector (picture) give an absolute measure of total hydrogen

Increasing the beam energy shifts the reaction deeper into the sample as 15N ions need to reduce their energy by ion-matter interaction to introduce the nuclear reaction

Analysis with increasing energies consitutes H depth profiles (max. 2 - 3 um) with a depth resolution of few nm.

The technique is non-destructive

No further calibration or use of standards

Rutherford Backscattering Spectroscopy (RBS)

​

Nanometer distribution of elements in near-surface regions of solids

Analysis of absolute number of atoms

H exists in glasses and melts as different species, molecular H2O and hydroxyl (OH)

Challenges in studying H diffusion in glasses especially at low temperatures are:

Experimentally - Classical experimental design do not work (e.g., diffusion couple)

I developed a novel method to overcome previous difficulties by combining:

Pusled Laser Deposition (PLD)

Nuclear Resonance Reaction Analysis (NRRA) ...more details on these techniques below

Diffusion of hydrogen in Nominally Anyhdrous Minerals (NAMs)

diffusion rates at LT need to be quantified

Solar wind implantation

Experiments on hydrogen implantation in olivine

Implantation of H in San Carlos Olivine at low energies (< 20 keV)

Phase relations in the Fe-Ni-Cu-S system at mantle conditions

NRRA analysis of H in garnet to calibrate IR-spectroscopy

Electron microprobe analyis (EPMA)