Application of Transmitted Kikuchi Diffraction in Studying Nano-oxide and Ultrafine Metallic Grains

Abbasi, Majid; Kim, Dong Ik; Guim, Hwanuk; Hosseini, Morteza; Daneshmanesh, Habib; Abbasi, Mehrdad

doi:10.1021/acsnano.5b04296

Cited by 39 publications

(27 citation statements)

References 67 publications

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“…The strong variation of the grain morphology between the three orientation maps comes from the instabilities and/or the drift of the electron beam. This has already been reported by Trimby et al (2014) and Abbasi et al (2015). These instabilities are less visible in EBSD because the step size is above a few dozen of nanometres, but it becomes particularly visible in TKD with a step size below 10 nm.…”

Section: -Reliability Of Orientation Mappingsupporting

confidence: 71%

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On‐axis versus off‐axis Transmission Kikuchi Diffraction technique: application to the characterisation of severe plastic deformation‐induced ultrafine‐grained microstructures

Yuan

Brodu

Chen

et al. 2017

Journal of Microscopy

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A new configuration for Transmission Kikuchi Diffraction (TKD) in a scanning electron microscope is presented; called 'on-axis TKD'. Compared to the usual off-axis configuration, the scintillator is placed perpendicular to the incident beam under the electron-transparent sample, not in vertical position. In this way, the setup benefits from intense forward scattered electrons enabling short acquisition times. At equivalent diffraction pattern quality, the electron dose needed on the sample is estimated to be 20 times lower in comparison to the off-axis configuration. The technique is particularly suited to the characterisation of severe plastic deformation induced ultrafine grained microstructures. The evolution of the microstructure of an Al-Mg alloy deformed by high pressure tube twisting was analysed. It is shown that the grain refinement was in the steady state stage for a shear strain of 24 with a mean grain size of 120 nm.

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Section: -Reliability Of Orientation Mappingsupporting

confidence: 71%

“…() and Abbasi et al . (). These instabilities are less visible in EBSD because the step size is above a few dozen of nanometres, but it becomes particularly visible in TKD with a step size below 10 nm.…”

Section: Resultsmentioning

confidence: 97%

On‐axis versus off‐axis Transmission Kikuchi Diffraction technique: application to the characterisation of severe plastic deformation‐induced ultrafine‐grained microstructures

Yuan

Brodu

Chen

et al. 2017

Journal of Microscopy

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“…Electron Backscattered Diffraction (EBSD) on cleavage fracture surfaces or in conjunction with serial-sectioning by Focused Ion Beam (FIB) has been previously utilized to locally study crack crystallography [1][2]. However, the depth of 3D analysis is restricted due to the imposed geometry by FIB serial-sectioning and EBSD 70° tilt.Recent developments in Transmission Kikuchi Diffraction (TKD) on electron-transparent samples in SEM offer higher spatial resolution and variable sample tilt [3][4][5][6][7]. Herein, a methodology based on TKD and FIB was explored to investigate crack crystallography by determining crack plane normal and comparing it to crystal orientations.…”

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confidence: 99%

Three-Dimensional Analysis of Cracks by Focused Ion Beam and Transmission Kikuchi Diffraction

et al. 2017

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Investigation of crystallography of crack planes has been a topic of interest for many decades. Understanding how cracks propagate is essential in improving fracture toughness by altering the microstructure and texture. This requires micro-/nano-analysis of grains along the crack path in three dimensions. Electron Backscattered Diffraction (EBSD) on cleavage fracture surfaces or in conjunction with serial-sectioning by Focused Ion Beam (FIB) has been previously utilized to locally study crack crystallography [1][2]. However, the depth of 3D analysis is restricted due to the imposed geometry by FIB serial-sectioning and EBSD 70° tilt.Recent developments in Transmission Kikuchi Diffraction (TKD) on electron-transparent samples in SEM offer higher spatial resolution and variable sample tilt [3][4][5][6][7]. Herein, a methodology based on TKD and FIB was explored to investigate crack crystallography by determining crack plane normal and comparing it to crystal orientations. This study was performed on a 2205 duplex stainless steel sample that experienced stress corrosion cracking in service. As presented in Fig. 1a, a FIB slice perpendicular to the crack trace (CT1) is removed. This slice would contain the second crack trace (CT2). The external product of these traces provides the crack plane normal (CPN=CT1×CT2) as schematically illustrated in Fig. 1b. It is assumed that crack trace (CT1) stays perpendicular to the slice throughout the entire depth.Maintaining the slice longitudinal direction (A2) perpendicular to the crack path (CT1) and its transverse direction (A1) aligned with the surface normal in Fig. 1a would facilitate the orientation interpretation (see Fig. 1). This way, crystallographic planes could be observed in pole figures with CT1 as normal since the slice normal is parallel to crack path (A3//CT1). An example is shown in Fig. 2. TKD orientation map of the area inside the white box in Fig. 1d is presented in Fig. 2a. Crack traces normal to the slice (CT1) and in the slice (CT2) are marked. Their external product provides CPN as presented with a black arrow in Fig. 2b.The <111> poles of highlighted red austenite and <011> poles of highlighted green ferrite grains along the crack in Fig. 2a are plotted in Fig. 2c and 2d, respectively. The calculated crack plane normal lies within 7° misorientation of <111> poles in austenite and 10° misorientation of <011> poles in ferrite (dotted circles in Fig. 2c and 2d). This is an indication of cracking along slip planes in ferrite and austenite. The implications of this observation in the context of stress corrosion cracking mechanism need to be determined. Careful considerations should be taken regarding EBSD/TKD sample coordinate system and FIB slice removal containing cracks [8][9][10][11][12]. A meaningful statistical crack analysis could be achieved by increasing the number of slices. Regarding nanocrystalline samples where many grains are present along cracks, orientation distribution could be utilized instead of discrete pole figures [13].

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“…However, on-axis TKD can reach a considerably better spatial resolution down to 2 nm and is, consequently, a technique well-suited for the investigation of nanocrystalline material including characterization of size and shape of NPs. This spatial improvement is gained by preparation of electron-transparent foils from the respective material leading to reduced background intensity, enhanced Kikuchi contrast and reduced beam broadening in comparison to conventional EBSD [4].Thus, TKD samples were prepared as thin as possible using conventional Focused Ion Beam technique (FIB) avoiding excessive amorphisation or Gallium ion implantation into the sample surface by thinning down with falling acceleration voltage beginning with 30 kV and finishing with 2 kV. To remove the very rest of amorphous skin and possible contamination from electron beam scanning, the FIB lamella was showered with low-kV Argon ions using the Fischione 1040 NanoMill® at Fischione instruments facility (Export, PA, USA).…”

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confidence: 99%

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Characterization of Porous, TiO2 Nanoparticle Films Using On-Axis TKD in SEM -a New Nano-Analysis Tool for a Large-Scale Application

et al. 2017

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Dye sensitized solar cells (DSSCs) attracted great attention as a low-cost alternative to fossil energy, but also to other photovoltaic energy conversion systems. The core of a DSSC mostly consists of a porous micrometer thick film such as titanium dioxide mostly in form of nanoparticles (NP) as electron carrier, easily screen-printed at industrial scale (Figure 1a and 1b). The performance of the cell is amongst others linked to the morphology and formation of the NPs within the layer [1]. Characterization of the NP network is a challenging task, since common techniques mainly work with isolated or dispersed particles rather than particle layers. The constituent NPs in our work are bipyramidal anatase crystals manufactured via a shape-controlled routine, of 50 nm mean length and 32 nm mean width measured by Transmission (Scanning) Electron Microscopy (T(S)EM) and, respectively, 67 nm by 44 nm as measured with atomic force microscopy (AFM) (dimensions are expressed as Feret max and Feret min, respectively [2]).The particulate layers were characterized using the new technique Transmission Kikuchi Diffraction (TKD) in a SEM [3]. In principle TKD works similar to the established Electron Backscatter Diffraction (EBSD) technique, which is a powerful method to identify grains/crystals via indexing Kikuchi pattern and determine their crystal orientation. However, on-axis TKD can reach a considerably better spatial resolution down to 2 nm and is, consequently, a technique well-suited for the investigation of nanocrystalline material including characterization of size and shape of NPs. This spatial improvement is gained by preparation of electron-transparent foils from the respective material leading to reduced background intensity, enhanced Kikuchi contrast and reduced beam broadening in comparison to conventional EBSD [4].Thus, TKD samples were prepared as thin as possible using conventional Focused Ion Beam technique (FIB) avoiding excessive amorphisation or Gallium ion implantation into the sample surface by thinning down with falling acceleration voltage beginning with 30 kV and finishing with 2 kV. To remove the very rest of amorphous skin and possible contamination from electron beam scanning, the FIB lamella was showered with low-kV Argon ions using the Fischione 1040 NanoMill® at Fischione instruments facility (Export, PA, USA). The on-axis TKD measurements were performed with the Bruker e-Flash FS retrofitted with the OPTIMUS® detector head (Bruker Nano GmbH, Berlin). Figure 1d shows a raw inverse pole figure map presenting the crystal orientation of a TiO2 NP layer obtained by on-axis TKD from which parameters like grain size and grain shape can be deduced. Some beam instabilities can be recognized in the acquired TKD orientation map caused by charging of the non-conductive, light and porous material. The drift areas were neglected (see black areas in Figure 1e) to avoid miscalculating the distributions of grain size in Figure 1f and aspect ratio in Figure 1g. For better statistics, incomplete grains at the fr...

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Application of Transmitted Kikuchi Diffraction in Studying Nano-oxide and Ultrafine Metallic Grains

Cited by 39 publications

References 67 publications

On‐axis versus off‐axis Transmission Kikuchi Diffraction technique: application to the characterisation of severe plastic deformation‐induced ultrafine‐grained microstructures

On‐axis versus off‐axis Transmission Kikuchi Diffraction technique: application to the characterisation of severe plastic deformation‐induced ultrafine‐grained microstructures

Three-Dimensional Analysis of Cracks by Focused Ion Beam and Transmission Kikuchi Diffraction

Characterization of Porous, TiO2 Nanoparticle Films Using On-Axis TKD in SEM -a New Nano-Analysis Tool for a Large-Scale Application

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