Blar i NTNU Open på forfatter "Walmsley, John"
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Active sites for the oxygen reduction reaction in nitrogen-doped carbon nanofibers
Buan, Marthe Emelie Melandsø; Cognigni, Andrea; Walmsley, John; Muthuswamy, Navaneethan; Rønning, Magnus (Journal article; Peer reviewed, 2019)Understanding the role of iron and the nature of the active sites in nitrogen-doped carbon nanomaterials is vital for their future application as oxygen reduction electrocatalysts in fuel cells. In this paper, porphyrin-like ... -
Characterization of Non-Metallic Inclusions in Ferritic Weld Metals for Arctic Applications
Hjeltereie, Isabella Juul (Master thesis, 2015)In Arctic applications, structural steel weldments will be subjected to low temperatures, in the worst cases approaching -60 °C. This may be a major challenge, due to the ductile to brittle transition taking place at certain ... -
Copper enriched by dealloying as external cathode in intergranular corrosion of aluminium alloy AA6005
Kumari, Shilpa; Wenner, Sigurd; Walmsley, John; Lunder, Otto; Nisancioglu, Kemal (Journal article; Peer reviewed, 2019)The purpose of this work is to understand the role of Cu in the propagation mechanism of IGC on extruded alloy AA6005-T5. The constituent Cu segregates as a Cu-rich nanolayer, together with the formation of a solute depleted ... -
Decoding atomic-level structures of the interface between Pt sub-nanocrystals and nanostructured carbon
Cheng, Hongye; Kvande, Ingvar; Zhu, Yi-An; Hammer, Nina; Rønning, Magnus; Walmsley, John; Li, Ping; Qi, Zhiwen; Zhou, Xing-Gui; Chen, De (Journal article; Peer reviewed, 2018)Gaining an insight into the interface structure resulting from the interaction between metal nanoparticles and their supports, particularly under relevant reaction conditions, has been an important topic in heterogeneous ... -
Effects of metal dusting relevant exposures of alloy 601 surfaces on carbon formation and oxide development
Guo, Xiaoyang; Vanhaecke, Estelle Marie M.; Vullum, Per Erik; Ma, Jianyu; Panditha Vidana, Daham Sanjaya Gunawardana; Walmsley, John; Chen, De; Venvik, Hilde Johnsen (Peer reviewed; Journal article, 2020)Ni and Fe are excellent catalysts for carbon formation, and industrial alloys are therefore susceptible to metal dusting corrosion; a costly issue in e.g. synthesis gas manufacture. The objective of this work is to better ... -
Effects of sulphur on a Co/Mn-based catalyst for Fischer-Tropsch reactions
Enger, Bjørn Christian; Walmsley, John; Svenum, Ingeborg-Helene; Tolchard, Julian R; Yang, Jia; Myrstad, Rune; Gjervan, Torbjørn; Khan, Asad Ahmad; Mutairi-Al, Abdulkarim; Karim, Khalid (Journal article; Peer reviewed, 2018)The long term effect of up to 10 ppm H2S was studied for Fischer–Tropsch conversion of syngas by catalytic testing at 240 °C, 5 bar, H2/CO = 2.1 and GHSV = 2400 Nml/gcat h. Sulphur was dosed after ~ 300 or ~ 1000 h time ... -
Evaluation of ORR active sites in nitrogen-doped carbon nanofibers by KOH post treatment
Muthuswamy, Navaneethan; Buan, Marthe Emelie Melandsø; Walmsley, John; Rønning, Magnus (Journal article; Peer reviewed, 2018)Oxygen reduction on N-doped carbon nanomaterials is believed to take place at either N-centered active sites (C-Nx) or Fe-centered active sites (Fe-Nx). In this work the origin of the oxygen reduction on nitrogen-doped ... -
Evaluation of Reoxidation Thresholds for γ-Al2O3-Supported Cobalt Catalysts under Fischer - Tropsch Synthesis Conditions
Tsakoumis, Nikolaos; Walmsley, John; Rønning, Magnus; van Beek, Wouter; Rytter, Erling; Holmen, Anders (Journal article; Peer reviewed, 2017)Size-dependent phenomena at the nanoscale influence many applications, notably in the science of heterogeneous catalysis. In cobalt-based Fischer–Tropsch synthesis (FTS), the size of Co nanoparticles (NPs) dictates to a ... -
High Temperature Decomposition of Methane on Quartz Pellets
Lindgaard, Henrik (Master thesis, 2015)This work has shown that pure methane, when exposed to quartz at a temperatures of 900°C and 1000°C, cracks and deposits carbon at a near constant rate. The deposition rates for the individual temperature levels were shown ... -
Investigation of Co2AlO4/CeO2 Catalyst for N2O Abatement using Electron Microscopy Techniques
Berntsen, Ørjan Uteng (Master thesis, 2014)A N2O abatement catalyst of a Co2AlO4 active phase and CeO2 support phase has been investigated using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and scanning electron microscopy ... -
Investigation of metal dusting corrosion process over UNS N08800 alloy
Guo, Xiaoyang; Panditha Vidana, Daham Sanjaya Gunawardana; Chen, De; Vanhaecke, Estelle Marie M.; Venvik, Hilde Johnsen; Walmsley, John (Journal article; Peer reviewed, 2017)Metal dusting corrosion is a catastrophic degradation phenomenon that initiates on metallic surfaces of chemical process equipment at elevated temperature and under carburizing atmospheres. It proceeds by a gradual breakdown ... -
Methane activation on bimetallic catalysts: properties and functions of surface Ni-Ag alloy
Dam, Anh Hoang; Wang, Hongmin; Dehghan-Niri, Roya; Yu, Xiaofeng; Walmsley, John; Holmen, Anders; Yang, Jia; Chen, De (Peer reviewed; Journal article, 2019)The paper presents a fundamental study of the properties and functions of well‐defined Ni−Ag surface alloys in methane decomposition and steam reforming, aiming at providing a better understanding of the principle for ... -
Microstructural heterogeneity in hexagonal close-packed pure Ti processed by high-pressure torsion
Chen, Yongjun; Li, Yanjun; Walmsley, John; Gao, N; Roven, Hans Jørgen; Starink, MJ; Langdon, TG (Journal article; Peer reviewed, 2012)Microstructural evolution was studied quantitatively by electron backscattering diffraction in commercial purity Ti processed by high-pressure torsion (HPT) at room temperature. The results show that a heterogeneous ... -
Nanostructural Analysis of Co-Re/γ-Al2O3 Fischer-Tropsch Catalyst by TEM and XRD
Dehghan-Niri, Roya; Tsakoumis, Nikolaos E.; Voronov, Alexey; Holmen, Anders; Holmestad, Randi; Vullum, Per Erik; Borg, Øyvind; Rytter, Erling; Rønning, Magnus; Walmsley, John (Journal article; Peer reviewed, 2022)A rhenium promoted Fischer-Tropsch (FT) cobalt catalyst supported on γ-Al2O3 has been investigated by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD), before and after reduction. Electron diffraction, ... -
Nitrogen-doped Carbon Nanofibers for the Oxygen Reduction Reaction: Importance of the Iron Growth Catalyst Phase
Buan, Marthe Emelie Melandsø; Muthuswamy, Navaneethan; Walmsley, John; Chen, De; Rønning, Magnus (Journal article; Peer reviewed, 2017)A systematic evaluation of the oxygen reduction reaction (ORR) on nitrogen-doped carbon nanofibers (N-CNFs) has been performed by tuning the properties of the N-CNFs by using chemical vapor deposition. Analysis of the ... -
Nitrogen-doped carbon nanofibers on expanded graphite as oxygen reduction electrocatalysts
Buan, Marthe Emelie Melandsø; Muthuswamy, Navaneethan; Walmsley, John; Chen, De; Rønning, Magnus (Journal article; Peer reviewed, 2016)A single-step chemical vapor deposition method using simple gaseous precursors was employed to grow nitrogen-doped carbon nanofibers from Fe and Ni particles on the surface of expanded graphite (N-CNF/EG). Due to the high ... -
Optical response of rectangular array of elliptical plasmonic particles on glass revealed by Mueller matrix ellipsometry and finite element modeling
Walmsness, Per Magnus; Brakstad, Thomas Vågenes; Svendsen, Brage Bøe; Banon, Jean-Philippe Armand; Walmsley, John; Kildemo, Morten (Peer reviewed; Journal article, 2019)We report here on the optical response of elliptical gold particles arranged in a rectangular lattice on glass and probed at non-normal incidence in reflection using spectroscopic Mueller matrix ellipsometry in the energy ... -
Photoemission spectroscopies and their application in solid state and material physics
Mazzola, Federico (Doctoral thesis at NTNU;2016:97, Doctoral thesis, 2016)Understanding the electronic properties of solid state systems is of fundamental importance to all matter. In particular, understanding and tailoring the properties of bound electrons in materials is an indispensable step ... -
Precipitation in an extruded AA7003 aluminium alloy: Observations of 6xxx-type hardening phases
Lervik, Adrian; Marioara, Calin Daniel; Kadanik, Maria; Walmsley, John; Milkereit, Benjamin; Holmestad, Randi (Journal article; Peer reviewed, 2019)Precipitation behaviour in an industrially extruded AA7003 alloy has been studied using Transmission Electron Microscopy (TEM) together with Differential Scanning Calorimetry (DSC). Air Cooling (AC) after solution heat ... -
Progress in Understanding Initiation of Intergranular Corrosion on AA6005 Aluminum Alloy with Low Copper Content
Kumari, Shilpa; Wenner, Sigurd; Walmsley, John; Lunder, Otto; Nisancioglu, Kemal (Journal article; Peer reviewed, 2019)As part of an extensive research program to study recent, unexpected intergranular corrosion (IGC) on 6xxx series aluminum alloys (AlMgSi), this paper investigates the mechanism of initiation and early propagation of IGC ...