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Borrajo-Pelaez, Rafael
Publications (3 of 3) Show all publications
Borrajo-Pelaez, R. & Hedström, P. (2018). Recent Developments of Crystallographic Analysis Methods in the Scanning Electron Microscope for Applications in Metallurgy. Critical reviews in solid state and materials sciences, 43(6), 455-474
Open this publication in new window or tab >>Recent Developments of Crystallographic Analysis Methods in the Scanning Electron Microscope for Applications in Metallurgy
2018 (English)In: Critical reviews in solid state and materials sciences, ISSN 1040-8436, E-ISSN 1547-6561, Vol. 43, no 6, p. 455-474Article, review/survey (Refereed) Published
Abstract [en]

The field of metallurgy has greatly benefited from the development of electron microscopy over the last two decades. Scanning electron microscopy (SEM) has become a powerful tool for the investigation of nano- and microstructures. This article reviews the complete set of tools for crystallographic analysis in the SEM, i.e., electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD), and electron channeling contrast imaging (ECCI). We describe recent relevant developments in electron microscopy, and discuss the state-of-the-art of the techniques and their use for analyses in metallurgy. EBSD orientation measurements provide better angular resolution than spot diffraction in TEM but slightly lower than Kikuchi diffraction in TEM, however, its statistical significance is superior to TEM techniques. Although spatial resolution is slightly lower than in TEM/STEM techniques, EBSD is often a preferred tool for quantitative phase characterization in bulk metals. Moreover, EBSD enables the measurement of lattice strain/rotation at the sub-micron scale, and dislocation density. TKD enables the transmitted electron diffraction analysis of thin-foil specimens. The small interaction volume between the sample and the electron beam enhances considerably the spatial resolution as compared to EBSD, allowing the characterization of ultra-fine-grained metals in the SEM. ECCI is a useful technique to image near-surface lattice defects without the necessity to expose two free surfaces as in TEM. Its relevant contributions to metallography include deformation characterization of metals, including defect visualization, and dislocation density measurements. EBSD and ECCI are mature techniques, still undergoing a continuous expansion in research and industry. Upcoming technical developments in electron sources and optics, as well as detector instrumentation and software, will likely push the border of performance in terms of spatial resolution and acquisition speed. The potential of TKD, combined with EDS, to provide crystallographic, chemical, and morphologic characterizations of nano-structured metals will surely be a valuable asset in metallurgy.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS INC, 2018
Keywords
Electron microscopy, steels, metals, EBSD, TKD, ECCI
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-231642 (URN)10.1080/10408436.2017.1370576 (DOI)000435672700001 ()2-s2.0-85042031269 (Scopus ID)
Note

QC 20180904

Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2018-09-04Bibliographically approved
Nosko, O., Borrajo-Pelaez, R., Hedström, P. & Olofsson, U. (2017). Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron. Journal of Aerosol Science, 113, 130-140
Open this publication in new window or tab >>Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron
2017 (English)In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 113, p. 130-140Article in journal (Refereed) Published
Abstract [en]

The wear of brakes in transport vehicles is one of the main anthropogenic sources of airborne particulate matter in urban environments. The present study deals with the characterisation of airborne wear microparticles from a low-metallic friction material / cast iron pair used in car brakes. Particles were generated by a pin-on-disc machine in a sealed chamber at sliding velocity of 1.3 m/s and contact pressure of 1.5 MPa. They were collected on filters in an electrical low pressure impactor, and an investigation was conducted to quantify their shape and porosity. Scanning electron microscopy revealed that most of the 0.1−0.9 µm particles are flakes and have a breadth-to-length aspect ratio of 0.7 ± 0.2. Particle porosity was determined by milling particles with a focused ion beam and subsequent analysis of the exposed particle cross-sections. Most of the 0.3–6.2 µm particles were revealed to have porosity of 9 ± 6%. Analysis of the relationship between effective particle density, particle material density, dynamic shape factor and porosity showed that the shape factor has a stronger influence on the effective density of airborne wear particles than the porosity factor. The obtained results are useful for accurate prediction of particle behaviour in the atmosphere and in the human respiratory system.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Aerosol measurement, Airborne wear particles, Dynamic shape factor, Particle porosity, Particle shape, Pin-on-disc, Aspect ratio, Cast iron, Characterization, Friction, Friction materials, Ion beams, Respiratory system, Scanning electron microscopy, Urban transportation, Airborne wears, Pin on disc, Shape factor, Porosity
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-218639 (URN)10.1016/j.jaerosci.2017.07.015 (DOI)000413664700013 ()2-s2.0-85028439645 (Scopus ID)
Note

QC 20171129

Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2019-10-18Bibliographically approved
Ma, T., Borrajo-Pelaez, R., Hedström, P., Borgh, I., Blomqvist, A., Norgren, S. & Odqvist, J. (2016). Microstructure evolution during phase separation in Ti-Zr-C. International Journal of Refractory Metals and Hard Materials, 61, 238-248
Open this publication in new window or tab >>Microstructure evolution during phase separation in Ti-Zr-C
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2016 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 61, p. 238-248Article in journal (Refereed) Published
Abstract [en]

(Ti,Zr)C powder was synthesized by carbothermal reduction and subsequently aged at 1150–2000 °C. The phase composition and microstructure was investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction. It was found that the as-synthesized (Ti,Zr)C particles have a concentration gradient with a higher concentration of Ti at the surface of the particles. Furthermore, during aging the (Ti,Zr)C decomposes into Ti-rich and Zr-rich lamellae. During aging at 1400 and 1800 °C for 10 h, most Zr-rich and Ti-rich domains precipitate at grain boundaries, inheriting the crystal orientation of the parent grain behind the growth front. When the precipitate grows into another (Ti,Zr)C grain, that grain adopts the same crystal orientation as the parent grain. The crystallographic misorientation between adjacent lamellae is 0–5°. Based on these microstructural observations it is hypothesized that the mechanism of decomposition is discontinuous precipitation.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Carbides, Discontinuous precipitation, Electron backscatter diffraction, Energy-dispersive X-ray spectroscopy, Phase separation, Backscattering, Carbothermal reduction, Electron diffraction, Energy dispersive spectroscopy, Grain boundaries, Grain growth, Microstructure, Precipitation (chemical), Scanning electron microscopy, X ray diffraction, X ray spectroscopy, Concentration gradients, Electron back scatter diffraction, Energy dispersive X ray spectroscopy, Mechanism of decomposition, Micro-structural observations, Micro-structure evolutions, Mis-orientation, Crystal orientation
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-195185 (URN)10.1016/j.ijrmhm.2016.09.019 (DOI)000388048300032 ()2-s2.0-84989814061 (Scopus ID)
Funder
VINNOVA, 2014-03392
Note

QC 20161208

Available from: 2016-12-08 Created: 2016-11-02 Last updated: 2017-06-28Bibliographically approved
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