Research

The research of the group focuses on interdisciplinary fundamental, basic experimental and theoretical investigations to reveal the link between the physical properties such as hardness or electrical/ magnetic behavior of a material and the arrangements of its constitutional different species at the atomic scale.  The specific interest is directed towards topics including thermodynamics and phase separation in constitutional alloys and compounds, such as steels and super-alloys; segregation effects along grain and interface boundaries particularly in nano-crystalline materials and thin film layers; internal oxidation and exploration of the metallic/non metallic (oxide, semiconductor) interface. The main topics can be further specified as in the following foci:
 
1)     Thermodynamics and phase separation in constitutional alloys and compounds with specific focus on ordering effects in ternary
        intermetallics.
  
2)     Nano-crystalline Materials and Functional thin layers: in particular the fundamental understanding of intermixing of Mechanically alloyed
        metallic powders such as Fe-Cu are of our interest, besides investigation of the inter-diffusion reactions in metallic and non metallic  Multi-
        layers. Thereby analyzing their life time stability under service conditions and evaluating their possible application in the microelectronics.
 
3)     Numerical Modeling and Computational Material Physics. This focus includes both specific calculations to develop a realistic Reconstruction
        Algorithms and appropriate Data Analysis Tools for the Atom Probe Tomograph (APT), which includes the simulation of the field evaporation
        behaviour of a tip. Particularly, the lattice site occupation of atoms in some ordered inter-metallic phases are studied as model systems.
 
 
A compilation of the different research areas can be downloaded here: research_alkassab_1.pdfResearch_Al-Kassab.pdf
 
 

Current Research

The degree of order in intermetallic compounds such TiAl and Fe3Al can be evaluated utilizing a special tool named AtomVicinity algorithm, which was first developed in our group and designed to trace the sequence of occupation of the single atomic planes in different directions. Additionally, a computer simulation model was generated to explain the formation of an image in the field ion microscope and subsequently the field assisted evaporation of the upper most surface atoms from the atomic layers as originated in the atom probe. A comparison between simulated and measured data finally allows us to estimate the binding energies of atoms in the respective ordered unit cell. The systems studied so far include ternary FeAlX and TiAlX.  
TEM-image of the multi layer stacking of a TMR-device
Nano-structured Materials and Thin Layers are currently of considerable interest for various industrial applications, e.g. for new magnetic and or electronic devices and as coating layers to protect the surface of specific functional materials against corrosion. The macroscopic physical properties of these nano-structured materials are largely controlled by their numerous internal interfaces, which make these materials promising candidates for future applications. This change in their physical properties is often closely related to the stability of their interfaces, and hence an investigation of the chemical reactions at these interfaces is of a great importance to understand and optimize their properties. The relevant systems are currently Ni-W, Co-P, Cu-Bi and Cu-Al, Fe-Ni-Cu, Co-Al, Cu-Co-FeNi, Co-Al2O3-FeNi.
Ti-precipitates in Cu-0.7at%Ti
Phase Transformations play a significant role in human daily life, as they represent the most applied technical process to improve macroscopic properties of functional materials such as mechanical hardness, electrical conductivity and magnetic behavior.