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Trimby P, Al-Mosawi M, Al-Jawad M, Micklethwaite S, Aslam Z, Winkelmann A, Piazolo S. The characterisation of dental enamel using transmission Kikuchi diffraction in the scanning electron microscope combined with dynamic template matching. Ultramicroscopy 2024; 260:113940. [PMID: 38422822 DOI: 10.1016/j.ultramic.2024.113940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 02/11/2024] [Accepted: 02/18/2024] [Indexed: 03/02/2024]
Abstract
The remarkable physical properties of dental enamel can be largely attributed to the structure of the hydroxyapatite (HAp) crystallites on the sub-micrometre scale. Characterising the HAp microstructure is challenging, due to the nanoscale of individual crystallites and practical challenges associated with HAp examination using electron microscopy techniques. Conventional methods for enamel characterisation include imaging using transmission electron microscopy (TEM) or specialised beamline techniques, such as polarisation-dependent imaging contrast (PIC). These provide useful information at the necessary spatial resolution but are not able to measure the full crystallographic orientation of the HAp crystallites. Here we demonstrate the effectiveness of enamel analyses using transmission Kikuchi diffraction (TKD) in the scanning electron microscope, coupled with newly-developed pattern matching methods. The pattern matching approach, using dynamic template matching coupled with subsequent orientation refinement, enables robust indexing of even poor-quality TKD patterns, resulting in significantly improved data quality compared to conventional diffraction pattern indexing methods. The potential of this method for the analysis of nanocrystalline enamel structures is demonstrated by the characterisation of a human enamel TEM sample and the subsequent comparison of the results to high resolution TEM imaging. The TKD - pattern matching approach measures the full HAp crystallographic orientation enabling a quantitative measurement of not just the c-axis orientations, but also the extent of any rotation of the crystal lattice about the c-axis, between and within grains. Results presented here show how this additional information highlights potentially significant aspects of the HAp crystallite structure, including intra-crystallite distortion and the presence of multiple high angle boundaries between adjacent crystallites with rotations about the c-axis. These and other observations enable a more rigorous understanding of the relationship between HAp structures and the physical properties of dental enamel.
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Affiliation(s)
- Patrick Trimby
- Oxford Instruments Nanoanalysis, High Wycombe, Buckinghamshire, UK; Carl Zeiss Ltd., Cambourne, Cambridge, UK.
| | | | - Maisoon Al-Jawad
- School of Dentistry, University of Leeds, Leeds, West Yorkshire, UK
| | - Stuart Micklethwaite
- School of Chemical and Process Engineering, University of Leeds, Leeds, West Yorkshire, UK
| | - Zabeada Aslam
- School of Chemical and Process Engineering, University of Leeds, Leeds, West Yorkshire, UK
| | | | - Sandra Piazolo
- School of Earth and Environment, University of Leeds, Leeds, West Yorkshire, UK
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Yadav PC, Sarvesha R, Guruprasad TS. Microstructural evolution during short heat-treatment of constrained groove pressed Cu-5%Zn alloy. J Microsc 2022; 288:3-9. [PMID: 35917366 DOI: 10.1111/jmi.13136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/28/2022] [Accepted: 07/25/2022] [Indexed: 11/29/2022]
Abstract
Severe plastic deformation (SPD) is a widely used technique to obtain superior material properties specially mechanical properties. Constrained groove pressing (CGP) is found to be the most attractive SPD technique for the deformation of sheets and plates. However, this technique results in microstructural inhomogeneity during processing. The microstructural inhomogeneity can be alleviated by employing a thermal cycle, which assists in controlled recovery and recrystallization. The current work focuses on, the microstructure evolution of one pass as-deform CGP sample followed by a short heat-treated (SHT). A correlative imaging technique of transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM) showed the presence of dislocation cell structure in an as-deformed condition. The short heat-treatment resulted in the transformation of the dislocation cell wall to high angle boundaries, with a further increase in heat-treatment time resulting in grain growth. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Prabhat Chand Yadav
- Department of Mechanical Engineering, Thapar Institute of Engineering and Technology, Patiala, Punjab, 147004, India
| | - R Sarvesha
- Department of Materials Science and Engineering, Indian Institute of Technology-Kanpur, Kanpur, Uttar Pradesh, 208016, India.,Department of Mechanical and Materials Engineering, Florida International University, Miami, FL, 33174, USA
| | - T S Guruprasad
- Department of Materials Science and Engineering, Indian Institute of Technology-Kanpur, Kanpur, Uttar Pradesh, 208016, India.,Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
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Fanta ABS, Fuller A, Alimadadi H, Todeschini M, Goran D, Burrows A. Improving the imaging capability of an on-axis transmission Kikuchi detector. Ultramicroscopy 2019; 206:112812. [PMID: 31382231 DOI: 10.1016/j.ultramic.2019.112812] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 06/30/2019] [Accepted: 07/07/2019] [Indexed: 10/26/2022]
Abstract
Transmission Kikuchi Diffraction (TKD) in the scanning electron microscope has been developing at a fast pace since its introduction less than a decade ago. The recently presented on-axis detector configuration, with its optimized geometry, has significantly increased the signal yield and facilitated the acquisition of STEM images in bright field (BF) and dark field (DF) mode, in addition to the automated orientation mapping of nanocrystalline electron transparent samples. However, the physical position of the integrated imaging system, located outside the detector screen, requires its movement in order to combine high resolution STEM images with high resolution orientation measurements. The difference between the two positions makes it impossible to acquire optimal signals simultaneously, leading to challenges when investigating site-specific nanocrystalline microstructures. To eliminate this drawback, a new imaging capability was added at the centre of the on-axis TKD detector, thus enabling acquisition of optimal quality BF images and orientation maps without detector movement. The advantages brought about by this new configuration are presented and the associated limitations are discussed.
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Affiliation(s)
- Alice Bastos S Fanta
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, Fysikvej 307, 2800 Kgs. Lyngby, Denmark.
| | - Adam Fuller
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, Fysikvej 307, 2800 Kgs. Lyngby, Denmark.
| | - Hossein Alimadadi
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, Fysikvej 307, 2800 Kgs. Lyngby, Denmark; Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus C, Denmark.
| | - Matteo Todeschini
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, Fysikvej 307, 2800 Kgs. Lyngby, Denmark; Blue Scientific Ltd., St. John's Innovation Centre, Cowley Road, Cambridge CB4 0WS, UK
| | | | - Andrew Burrows
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, Fysikvej 307, 2800 Kgs. Lyngby, Denmark; ISS Group Services Ltd, Pellowe House, Francis Road, Withington, Manchester, Greater Manchester M20 4XP, UK
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