Materials Characterization

Quenching- and Deformation Dilatometer

A quenching dilatometer can be applied for the study of phase transformations under industrially relevant heating or cooling conditions. There are two dilatometers available at our department (TA Instruments DIL 805 A/D and DIL805 A). The former one is additionally equipped with a device for uniaxial compression testing which can be applied for the study of the deformation behavior of materials. In both dilatometers the specimens are inductively heated in a special water-cooled double wound coil which also allows controlled gas-quenching. During heating, deformation and cooling the dilatation of the specimen is recorded as a function of temperature, time and true strain. With this technique it is possible to determine continuous as well as isothermal time-temperature-transformation- (TTT-) diagrams or TTT-diagrams after deformation.

Applications: determination of thermal expansion coefficients, kinetics of phase transformations, TTT-diagrams, TTT-diagrams after deformation, TTA- (time-temperature-austenitization)- diagrams, determination of flow curves

 

Technical data:

  • Temperature range: 20°C - 1600°C or 2000°C (DIL 805A)
  • Heating: induction
  • Atmosphere: inert gas, vacuum, air
  • Heating rate: max. 4000 K/s (quenching dilatometer)
  • Quenching rate: max. 2500 K/s (quenching dilatometer)
  • Strain rate: 0,01 – 125 mm/s
  • True strain: max. 1,2
  • Force: max. 25 kN

Atom probe tomography

For the characterization of materials with near-atomic resolution, Atom Probe Tomography (APT) is of special interest. For such examinations are an atom probe 3DAP type of Oxford Nanoscience Ltd. as well as a LEAP 3000X HR Imago are available. A very sharp tip is subjected to a high DC voltage (5-20kV), applied via an ultra-fast voltage pulse or an ultra-fast laser pulse. Due to the electrostatic field at the tip, surface atoms or ions are evaporated. Afterwards these atoms/ions are projected onto a position sensitive detector. The detector measures simultaneously the time to flight and the positions of the atoms in the tip. A reconstruction can be done, obtaining a 3D image of the analysed tip with information of the entire chemical composition. Almost the entire periodic system can be analyzed by this technique. By the use of a laser pulse, materials with poor electrical conductivity can also be analyzed.

Main applications: precipitation reactions, grain boundary segregation, phase analysis, Principal applications are: chemical analysis of materials at the atomic level, ion implantation, chemical clustering, 3D reconstruction of atoms.

 

Technical data:

LEAP 3000x HR:

  • Temperature range: 20K to 120K
  • Image gas: Helium, Neon
  • Field of View: < 200 nm
  • Mass Resolution: FWHM=1100

3DAP:

  • Temperature range: 20K to 120K
  • Image gas: Argon, Helium, Neon
  • Field of View: < 100 nm
  • Mass Resolution: FWHM=800

Differential Scanning Calorimetry and Thermogravimetry

Dynamic methods are particularly applicable for the study of phase transformations in materials. Two thermal analysis devices are available at our department (Setaram Setsys Evo 2400 und Setaram Labys) for this means. Both are combinations of differential scanning calorimeters (DSC) with thermogravimeters (TGA). In case of DSC a sample and a reference material are subjected to a well-defined temperature program. Due to the heat generated or consumed during transformations in the sample material, temperature differences between the sample and the reference occur. These differences are recorded. With this technique it is possible to determine the temperature range and kinetics of phase transformations, reaction enthalpies or the specific heat capacity of a material. During thermogravimetry mass differences are additionally recorded which allows the study of e.g. oxidation or decomposition reactions.

 

Technical data:

Setsys Evo 2400:

  • Temperature range: room temperature to 2400°C
  • Heating- and Cooling rate: 1 K/min  - 50 K/min
  • Atmosphere: vacuum, air, inert gas,reactive gas up to 1100°C

Labsys:

  • Temperature range: room temperature to 1600°C
  • Heating- and Cooling rate: 1 K/min  - 99 K/min
  • Atmosphere: vacuum, air, inert gas

Focused Ion Beam

Site-specific sample preparation for transmission electron microscopy (TEM), and atom probe tomography (APT) requires specific preparation methods. At the Department is available the Dual Beam Focused Ion Beam Versa 3D device manufactured by FEI. This microscope incorporates a focused ion beam column (FIB) and a scanning electron microscope column (SEM). This duality offers the possibility of cross-section imaging during the ion beam does material milling/etching and/or deposition. In combination with Energy Dispersive Spectroscopy (EDS) enables elemental mapping, and in combination with Electron Backscatter Diffraction (EBSD) offers the possibility of crystallographic analysis.  

Principal applications are: sample preparation for Transmission Electron Microscopy (TEM) investigations, sample preparation for Atom Probe Tomography (APT) and low-damage surface finishing  
 

Technical data:  

  • Electron column: High-resolution field emission SEM column optimized for high-brightness / high-current
  • Acceleration voltage (Electron column): 200V – 30kV
  • Ion Column: High-current ion column with Ga liquid-metal ion source
  • Acceleration voltage (Ion column): 0,5 – 30kV
  • Detectors: SE, SI, BSE, STEM
  • Gas Injektion System (GIS): Platin
  • In situ Sample Lift-Out System: Omniprobe 100.7

Ion milling systems Hitachi IM5000

Ion milling systems are widely used as instruments for preparing surfaces as well as cross-section samples for scanning electron microscopy (SEM), with applications to fields such as materials science and semiconductor research. The two types of ion-milling methods commonly used for SEM samples are flat milling and cross-section milling1)

Cross-section Milling

Used to produce wider, undistorted cross-sections without applying mechanical stress to the sample

Flat Milling

Used for removing surface layer artifacts and final polish after traditional mechanical polishing techniques.

 

Technical data:

  • Ar ion gun, max. 8KV accelerating voltage
  • Max. milling rate >1mm/hr for Si
  • Cross-section and flat milling sample holder
  • Max. sample size 20mm (cross-section), 50mm (flat milling)

Scanning electron microscope (SEM) Tescan Clara

SEM is widely used to study the microstructure and the chemical composition of a wide range of organic and inorganic materials. The electron beam, focused by an electromagnetic lens system, is scanning across the sample’s surface, which is located in an evacuated specimen chamber. Due to the interaction between electron beam and sample several signals are generated, which can be measured by various detectors. These signals provide information from the topography, the chemical composition and the microstructure.

Technical Data:
Field Emitter SEM
Resolution: 0.9 nm with 15 kV, 1.6 nm with 1 kV
Acceleration voltage: 200 V to 30 kV
Detector: SE, BSE, InBeamSE, InBeam BSE with energy filtering Beam Deceleration, Plasmacleaner
EDX and WDX system by Oxford Instrument