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Sökning: WFRF:(Leygraf Christopher)

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1.
  • Bender, R., et al. (författare)
  • Corrosion challenges towards a sustainable society
  • 2022
  • Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 73:11, s. 1730-1751
  • Tidskriftsartikel (refereegranskat)abstract
    • A global transition towards more sustainable, affordable and reliable energy systems is being stimulated by the Paris Agreement and the United Nation's 2030 Agenda for Sustainable Development. This poses a challenge for the corrosion industry, as building climate-resilient energy systems and infrastructures brings with it a long-term direction, so as a result the long-term behaviour of structural materials (mainly metals and alloys) becomes a major prospect. With this in mind “Corrosion Challenges Towards a Sustainable Society” presents a series of cases showing the importance of corrosion protection of metals and alloys in the development of energy production to further understand the science of corrosion, and bring the need for research and the consequences of corrosion into public and political focus. This includes emphasis on the limitation of greenhouse gas emissions, on the lifetime of infrastructures, implants, cultural heritage artefacts, and a variety of other topics. 
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3.
  • Chang, Tingru, et al. (författare)
  • A mechanistic study of stratified patina evolution on Sn-bronze in chloride-rich atmospheres
  • 2020
  • Ingår i: Corrosion Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0010-938X .- 1879-0496. ; 166
  • Tidskriftsartikel (refereegranskat)abstract
    • The complex stratified patina formed on Sn-bronze in chloride-rich atmospheres has been explored through long-term field exposures and short-term laboratory investigations using a multi-analytical approach. The stratified patina is composed of Cu2O- and Cu-2(OH)(3)Cl-rich sublayers intercalated by Sn-oxides, mainly SnO2. The stratification is triggered by events of high chloride deposition, resulting in repeated dissolution and solidification of sublayers, whereby redox reactions between the intermediate products of Sn- and Cu-chlorides play a crucial role. Sn-induced patina stratification is a major reason for enhanced patina flaking on Sn-bronze and its accelerated corrosion rate compared to Cu metal in marine environments.
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4.
  • Chang, Tingru, et al. (författare)
  • A novel methodology to study antimicrobial properties of high-touch surfaces used for indoor hygiene applications-A study on Cu metal
  • 2021
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 16:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Metal-based high-touch surfaces used for indoor applications such as doorknobs, light switches, handles and desks need to remain their antimicrobial properties even when tarnished or degraded. A novel laboratory methodology of relevance for indoor atmospheric conditions and fingerprint contact has therefore been elaborated for combined studies of both tarnishing/corrosion and antimicrobial properties of such high-touch surfaces. Cu metal was used as a benchmark material. The protocol includes pre-tarnishing/corrosion of the high touch surface for different time periods in a climatic chamber at repeated dry/wet conditions and artificial sweat deposition followed by the introduction of bacteria onto the surfaces via artificial sweat droplets. This methodology provides a more realistic and reproducible approach compared with other reported procedures to determine the antimicrobial efficiency of high-touch surfaces. It provides further a possibility to link the antimicrobial characteristics to physical and chemical properties such as surface composition, chemical reactivity, tarnishing/corrosion, surface roughness and surface wettability. The results elucidate that bacteria interactions as well as differences in extent of tarnishing can alter the physical properties (e.g. surface wettability, surface roughness) as well as the extent of metal release. The results clearly elucidate the importance to consider changes in chemical and physical properties of indoor hygiene surfaces when assessing their antimicrobial properties.
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5.
  • Chang, Tingru, et al. (författare)
  • Analysis of historic copper patinas. Influence of inclusions on patina uniformity
  • 2017
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 10:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The morphology and elemental composition of cross sections of eight historic copper materials have been explored. The materials were taken from copper roofs installed in different middle and northern European environments from the 16th to the 19th century. All copper substrates contain inclusions of varying size, number and composition, reflecting different copper ores and production methods. The largest inclusions have a size of up to 40 μm, with most inclusions in the size ranging between 2 and 10 μm. The most common element in the inclusions is O, followed by Pb, Sb and As. Minor elements include Ni, Sn and Fe. All historic patinas exhibit quite fragmentized bilayer structures, with a thin inner layer of cuprite (Cu2O) and a thicker outer one consisting mainly of brochantite (Cu4SO4(OH)6). The extent of patina fragmentation seems to depend on the size of the inclusions, rather than on their number and elemental composition. The larger inclusions are electrochemically nobler than the surrounding copper matrix. This creates micro-galvanic effects resulting both in a profound influence on the homogeneity and morphology of historic copper patinas and in a significantly increased ratio of the thicknesses of the brochantite and cuprite layers. The results suggest that copper patinas formed during different centuries exhibit variations in uniformity and corrosion protection ability.
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6.
  • Chang, Tingru, et al. (författare)
  • Effect of blue light illumination on atmospheric corrosion and bacterial adhesion on copper
  • 2024
  • Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 230
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of blue light on atmospheric corrosion of Cu and on the antimicrobial properties was explored upon exposure mimicking the condition of hygienic surface disinfection. The results show that blue light illumination enhanced the formation of Cu2O, resulting in a slightly increased corrosion resistance of Cu without pre-deposited NaCl, whereas the enhanced formation of Cu2O, CuCl and/or Cu(OH)3Cl on copper with pre-deposited NaCl caused concomitant corrosion product flaking and a reduced corrosion resistance. The blue light induced enhancement of Cu corrosion led to increased surface roughness and more pronounced integration of bacteria within the corrosion products.
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7.
  • Chang, Tingru, et al. (författare)
  • The role of Sn on the long-term atmospheric corrosion of binary Cu-Sn bronze alloys in architecture
  • 2019
  • Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 149, s. 54-67
  • Tidskriftsartikel (refereegranskat)abstract
    • The role of Sn on the atmospheric corrosion performance of binary Cu-Sn bronze alloys (4–6 wt.% Sn) compared with Cu metal used in outdoor architecture is elucidated in terms of microstructure, native surface oxide composition, patina evolution, corrosion rates, appearance and metal release. Results are presented for non-exposed surfaces and surfaces exposed at different urban and marine sites in Europe up to 5 years and based on multi-analytical findings from microscopic, spectroscopic, electrochemical and chemical investigations. Alloying influenced the corrosion, aesthetic appearance and patina evolution, differently for urban and marine sites, whereas no effects were observed on the release pattern. © 2019 The Authors
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8.
  • Chang, Tingru, et al. (författare)
  • Understanding the Barrier Layer Formed via Adding BTAH in Copper Film Electrodeposition
  • 2019
  • Ingår i: Journal of the Electrochemical Society. - : ELECTROCHEMICAL SOC INC. - 0013-4651 .- 1945-7111. ; 166:2, s. D10-D20
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of surface adsorption of benzotriazole (BTAH) and of chloride ions (Cl-) on the kinetics of copper electrodeposition/dissolution in copper sulfate solutions and on copper deposit characteristics have been investigated using electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry (CV). The addition of BTAH alone increases the overpotential of copper deposition, whereas a Cu(I)BTA complex forms at potentials higher than 0.08 V (vs. SCE) accompanied with the occurrence of copper anodic dissolution. With simultaneous addition of BTAH and Cl-, surface adsorption of Cl- competes with that of BTAH during the initial stage of copper nucleation. Different cuprous reaction intermediates form in the examined potential range -0.4 to 0.3 V (vs. SCE), which partly eliminate the favorable effect of BTAH on the deposited copper. A BTAH-containing adsorbed layer formed on the matte side of electrodeposited copper film in the presence of BTAH with or without Cl-, exhibiting a barrier surface property and an improved corrosion resistance compared with the copper film electrodeposited in the electrolyte without addition of BTAH.
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9.
  • Chen, Shuhui, et al. (författare)
  • First-principles analysis of the stability and hydrogen adsorption properties of the α-Ti/α2-Ti3Al interface towards clarified hydrogen embrittlement mechanism of titanium alloys
  • 2024
  • Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 72, s. 338-348
  • Tidskriftsartikel (refereegranskat)abstract
    • First-principles calculations were employed to investigate the adsorption and diffusion energy of hydrogen (H) in the Ti/Ti3Al binary system, along with the evolution of the interfacial stability induced by the presence of H. The penetration energy barrier indicates that H can more easily penetrate the substrate through the Ti/Ti3Al interface. The formation energy of H increases with distance from the interface and the Ti/Ti3Al interface acts as a sink for trapping hydrogen interstitials. When all interstitial sites are completely occupied by H, the cleavage energy along the interface decreases from 1.935 to 1.094 J/m2, suggesting that H doping significantly reduces the strength of the Ti-Ti3Al (01–10) interface. When the area density of H-doping at the interface exceeds 0.37 atoms/Å2, the α-Ti lattice expands. Consistent with experimental observations, this triggers atomic migration and the generation of Ti-hydrides. Further analysis of the atomic structure and Bader charge transfers indicate that the interaction of Ti and H can alter the localized electronic structure of Al, leading to a weakened interface due to loss of interface bond strength. In summary, the theoretical calculations have provided new insights into possible hydrogen embrittlement (HE) mechanism in titanium alloys.
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10.
  • Chico, B., et al. (författare)
  • Analysis of historic copper patinas 2 : Characterization of 400 year old patina from Royal Summer Palace in Prague
  • 2017
  • Ingår i: EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017. - : Asociace koroznich inzenyru z.s.- AKI - Czech Association of Corrosion Engineers.
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents an in-depth characterisation study of the patina formed on a copper tile taken from the roof of Queen Anne's Summer Palace in Prague after close to 400 years of exposure to the action of the atmosphere. A wide variety of techniques have been performed, including metallographic and chemical analysis (electrogravimetry, AAS, XRF) of the copper matrix, and spectroscopic and microscopic investigations (GIXRD, TEM/EDS and SEM/EDS) to determine the composition and structure of the patina. The major conclusions of the study are: (a) the base copper contains abundant inclusions mainly of rosiaite (PbSb2O6); (b) the patina is formed by an inner sublayer of cuprite (Cu2O) and an outer sublayer of brochantite [Cu4SO4(OH)6] and antlerite [Cu3SO4(OH)4] and traces of azurite [Cu3(CO3)2(OH)2]; and (c) the brochantite/antlerite crystals are randomly doped with Fe and C.
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