High Resolution Scanning Electron Microscope (HRSEM) and Focused Ion Beam (FIB) based Methods
The department offers a wide range of modern facilities for the evaluation of the micro- and nanostructure. There is large experience available in the examination of spacecraft materials both, for the characterisation of the microstructure and for failure investigations by correlation to macroscopic properties. Numerous ceramic, metallic and organic spacecraft materials were investigated.
High Resolution Scanning Electron Microscope - HRSEM
Investigations in high resolution SEM of nano structured composites and alloys e.g. distribution, size, morphology of nano-particle and CNT, interactions with matrix, precipitation behaviour. HRSEM with unique GEMINI-field emission (Zeiss – Supra VP40) offers outstanding options for characterisation of complex structures and phenomena down to nano scale:
- Inspection of material quality – inclusions, pores, cracks
- Grains, grain boundaries, phases and precipitates characteristics
- Distribution of reinforcement particles / fibres in composites – enrichment and depletion effects
- Analysis of interfaces between the matrix and reinforcement - interface reactions and evaluation of bonding / de-bonding processes
- Coating analysis – thickness, interface architecture, adhesion quality
- Surface analysis including surface topography and contaminations
- Investigation of surface and sub-surface phenomena due to tribological stress
- Fracture surface analysis
- Investigation of corrosion and stress corrosion cracking (SCC) processes
- Advanced failure analysis
The integrated system provides an ability to create, modify and characterise complex structures even in nano-scale. Using a focused Ga2+ ion beam, it can precisely remove or deposit material at the sample surface as well as image the sample surface producing high quality contrast images with high magnifications.
In this connection our lab offers analysis on the following topics:
- Cleaning of the surfaces by Ga2+ ions sputtering for removing of contaminations like oxide layers, hydrocarbons, dirt particles and etc. and getting pristine surface structure
- Cross sections preparations
- for study of coatings, multi-layers, composites with respect to thickness, adhesion, formation of intermetallic compounds, interface contaminations
- for evaluation of material behavior exposed to tribological forces – breaking, deformation and delamination processes, material transfer, phase transformation in the deformed areas.
- for determination of precipitates, inclusions and fibres distribution in nano-composed materials.
- for investigation of early stage of corrosion processes
- Grains and subgrains analysis using “channeling contrast”
- 3 D reconstructions applying automatic serial sections (FIB – Tomography)
- Preparation of Atom Probe Spectrosopy slim needles with tip radii in the nm – range using patterned FIB milling.
- Micromachining – preparing and providing of specimens for micro – mechanical tests.
EDS / EBSD
The integrated system EDS/EBSD (Pegasus) implemented in the HRSEM enables simultaneous collection of EDS (chemistry) and EBSD (crystallography) data, allowing direct correlation between the elemental content and microstructural aspects of the material being studied.
EDS ( Energy Dispersive Spectrum) - Detector
The Sapphire Si(Li) LN (Liquid Nitrogen) Cooled EDS detector offers the highest peak to background ratio and the best resolution (@ Mn K) available. Following analyses by EDS are offered:
- detection and quantifications of elements - including light elements B, C, N, O
- point and area spectra – qualitative and semi quantitative analysis of phases present
- elements distribution according to predefined lines (line-scans) and areas (mappings) – qualitative and semi quantitative analysis
Figure: EDS line-scan showing elements distribution along a coating system.
EBSD (Electron Backscattered Diffraction) - Detector
EBSD is a technique which allows crystallographic information to be obtained from crystalline bulk materials and coating in the SEM. To obtain the crystallographic data Electron Back-Scattered Patterns (EBSP or Kikuchi-Line) are collected and computed. Our customers benefit from our wide experience and knowledge on EBSD analysis such as:
- grains, subgrains size and morphology ‚…
- recovery and recrystalisation processes
- grains and subgrains boundary charcteristic
- texture (global, local)
- crystal orientations
- phase identification and phase distribution
Figure: Rolled steel (grain and subgrain structure; texture)