Elektronen- und Ionenmikroskopie

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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.

AAC-Z0000174High 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. electron- and ion microscopy_1 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. electron- and ion microscopy_2electron- and ion microscopy_3

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.

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

electron- and ion microscopy_4Figure: 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

electron- and ion microscopy_5Figure: Rolled steel (grain and subgrain struc­ture; texture)