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Author Van Tendeloo, M.
Title Resource-efficient nitrogen removal from sewage : kinetic, physical and chemical tools for mainstream partial nitritation/anammox Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages iv, 204 p.
Keywords Doctoral thesis; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Abstract Adequate removal of pollutants from sewage is important to protect the environment and public health. Today, sewage treatment plants are operational in many parts of the world, and although the used technologies are effective in removing pollutants from wastewater, they are energy- and resource-intensive. Reshaping sewage treatment into a two-stage system, with separated organic carbon and nitrogen removal, facilitates the transformation towards energy-positive sewage treatment. This thesis will focus on resource-efficient nitrogen removal from sewage via partial nitritation/anammox (PN/A), with reduced organic carbon and oxygen consumption compared to conventional techniques. PN/A relies on the teamwork between two microbial groups to convert ammonium into nitrogen gas. Several other groups of microbes however can proliferate in the sludge, competing for substrate with the key players, lowering the nitrogen removal efficiency and increasing the energy demand. To obtain the desired microbial community, control tools should be applied to selectively promote the desired microbes while suppressing the unwanted competitors. In this thesis, multiple control tools were studied to establish a workable framework for successful implementation of PN/A in the main stream of a sewage treatment plant. These tools can be divided into three categories: i) kinetic tools, regulating substrate availability (e.g., oxygen availability control and residual ammonium concentration), ii) physical tools, revolving around sludge retention and selection (e.g., sludge age control and sludge aggregation form), and iii) chemical tools, exposing the sludge to stress conditions for which the unwanted microbes are vulnerable (e.g., sludge treatments with a single stressor such as free ammonia). The first research chapter focussed on oxygen availability control and single-stressor sludge treatments. The following two chapters covered the development of a novel multi-stressor concept combining substrate starvation and exposure to sulphide and free ammonia. In the final research chapter, the previously obtained knowledge was combined into a demonstration study on pilot-scale. The combination of these control tools was found effective in achieving nitrogen removal via PN/A, both on lab- and pilot-scale. Consequently, the obtained results in this thesis can catalyse the implementation of mainstream PN/A by providing a toolbox with multiple control tools and clever reactor design, thus advancing the concept of energy neutrality and resource efficiency in sewage treatment plants.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:187665 Serial 7204
Permanent link to this record
 

 
Author Schelles, W.; Van Grieken, R.
Title Direct current glow discharge mass spectrometry for elemental characterization of polymers Type A1 Journal article
Year 1997 Publication Analytical chemistry Abbreviated Journal
Volume 69 Issue Pages 2931-2934
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1997XN42400017 Publication Date 2002-07-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-2700; 5206-882x ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18773 Serial 7809
Permanent link to this record
 

 
Author Schelles, W.; Van Grieken, R.
Title Quantitative analysis of zirconium oxide by direct glow discharge mass spectrometry using a secondary cathode Type A1 Journal article
Year 1997 Publication Journal of analytical atomic spectrometry Abbreviated Journal
Volume 12 Issue Pages 49-52
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0267-9477 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18774 Serial 8439
Permanent link to this record
 

 
Author Jambers, W.; Van Grieken, R.
Title Single particle characterisation of inorganic suspension in Lake Baikal Type A1 Journal article
Year 1997 Publication Environmental science and technology Abbreviated Journal
Volume 31 Issue Pages 1525-1533
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0013-936x; 1520-5851 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18776 Serial 8538
Permanent link to this record
 

 
Author Parrilla, M.; Slosse, A.; Van Echelpoel, R.; Montiel, F.N.; Langley, A.R.; Van Durme, F.; De Wael, K.
Title Rapid on-site detection of illicit drugs in smuggled samples with a portable electrochemical device Type A1 Journal article
Year 2022 Publication Chemosensors Abbreviated Journal
Volume 10 Issue 3 Pages 108-116
Keywords A1 Journal article; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract The smuggling of illicit drugs urges the development of new tools for rapid on-site identification in cargos. Current methods rely on presumptive color tests and portable spectroscopic techniques. However, these methods sometimes exhibit inaccurate results due to commonly used cutting agents, the colorful nature of the sample or because the drugs are smuggled in common goods. Interestingly, electrochemical sensors can deal with these specific problems. Herein, an electrochemical device is presented that uses affordable screen-printed electrodes for the electrochemical profiling of several illicit drugs by square-wave voltammetry (SWV). The identification of the illicit compound is based on the oxidation potential of the analyte. Hence, a library of electrochemical profiles is built upon the analysis of illicit drugs and common cutting agents. This library allows the design of a tailor-made script that enables the identification of each drug through a user-friendly interface (laptop or mobile phone). Importantly, the electrochemical test is compared by analyzing 48 confiscated samples with other portable devices based on Raman and FTIR spectroscopy as well as a laboratory standard method (i.e., gas chromatography-mass spectrometry). Overall, the electrochemical results, obtained through the analysis of different samples from confiscated cargos at an end-user site, present a promising alternative to current methods, offering low-cost and rapid testing in the field.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000775813500001 Publication Date 2022-03-11
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2227-9040 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access OpenAccess
Notes Approved no
Call Number (up) UA @ admin @ c:irua:187766 Serial 8920
Permanent link to this record
 

 
Author de Jong, M.; Van Echelpoel, R.; Langley, A.R.; Eliaerts, J.; van den Berg, J.; De Wilde, M.; Somers, N.; Samyn, N.; De Wael, K.
Title Real-time electrochemical screening of cocaine in lab and field settings with automatic result generation Type A1 Journal article
Year 2022 Publication Drug testing and analysis Abbreviated Journal
Volume 14 Issue 8 Pages 1471-1481
Keywords A1 Journal article; Pharmacology. Therapy; Engineering sciences. Technology; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract This work presents the results of a novel application for the fast on-site screening of cocaine and its main cutting agents in suspicious and confiscated samples. The methodology behind the novel application consists of portable electrochemical detection coupled with a peak-recognition algorithm for automated result output generation, validated both in laboratory and field settings. Currently used field tests, predominantly colorimetric tests, are lacking accuracy, often giving false positive or negative results. This presses the need for alternative approaches to field testing. By combining portable electrochemical approaches with peak-recognition algorithms, an accuracy of 98.4% concerning the detection of cocaine was achieved on a set of 374 powder samples. In addition, the approach was tested on multiple 'smuggled', colored cocaine powders and cocaine mixtures in solid and liquid states, typically in matrices such as charcoal, syrup and clothing. Despite these attempts to hide cocaine, our approach succeeded in detecting cocaine during on-site screening scenarios. This feature presents an advantage over colorimetric and optical detection techniques, which can fail with colored sample matrices. This enhanced accuracy on smuggled samples will lead to increased efficiency in confiscation procedures in the field, thus significantly reducing societal economic and safety concerns and highlighting the potential for electrochemical approaches in on-the-spot identification of drugs of abuse.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000790965700001 Publication Date 2022-04-23
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1942-7603; 1942-7611 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access OpenAccess
Notes Approved no
Call Number (up) UA @ admin @ c:irua:187767 Serial 8921
Permanent link to this record
 

 
Author Torfs, K.; Van Grieken, R.
Title Chemical relations between atmospheric aerosols, deposition and stone decay layers on historic buildings at the Mediterranean coast Type A1 Journal article
Year 1997 Publication Atmospheric environment : an international journal Abbreviated Journal
Volume 31 Issue Pages 2179-2192
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1352-2310 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18777 Serial 7660
Permanent link to this record
 

 
Author Wegrzynek, D.; Jambers, W.; Van Grieken, R.; Eisma, D.
Title Individual particle analysis of Western Mediterranean sediment cores, Rhône suspended matter and Sahara aerosols: investigation of inputs to the sediments Type A1 Journal article
Year 1997 Publication Marine chemistry Abbreviated Journal
Volume 57 Issue Pages 25-40
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-4203; 1872-7581 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18778 Serial 8079
Permanent link to this record
 

 
Author Injuk, J.; Van Grieken, R.; Klockenkämper, R.; von Bohlen, A.; Kump, P.
Title Performance and characteristics of two total-reflection X-ray fluorescence and a particle induced X-ray emission setup for aerosol analysis Type A1 Journal article
Year 1997 Publication Spectrochimica acta: part B : atomic spectroscopy Abbreviated Journal
Volume 52 Issue Pages 977-984
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1997XH53500023 Publication Date 2002-07-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0584-8547; 1873-3565 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18779 Serial 8370
Permanent link to this record
 

 
Author Claes, M.; de Bokx, P.; Willard, N.; Veny, P.; Van Grieken, R.
Title Optimization of sample preparation for grazing emission X-ray fluorescence in micro- and trace analysis applications Type A1 Journal article
Year 1997 Publication Spectrochimica acta: part B : atomic spectroscopy Abbreviated Journal
Volume 52 Issue Pages 1063-1070
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1997XH53500035 Publication Date 2002-07-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0584-8547; 1873-3565 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18780 Serial 8340
Permanent link to this record
 

 
Author Dekov, V.M.; Komy, Z.; Araujo, F.; van Put, A.; Van Grieken, R.
Title Chemical composition of sediments, suspended matter, river and ground water of the Nile (Aswan-Sohag transvers) Type A1 Journal article
Year 1997 Publication The science of the total environment Abbreviated Journal
Volume 201 Issue Pages 195-210
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1997XL69100003 Publication Date 2002-07-25
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0048-9697; 1879-1026 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18781 Serial 7658
Permanent link to this record
 

 
Author Civici, N.; Van Grieken, R.
Title Energy-dispersive X-ray fluorescence in geochemical mapping Type A1 Journal article
Year 1997 Publication X-ray spectrometry Abbreviated Journal
Volume 26 Issue Pages 147-152
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1997XM14500003 Publication Date 2002-08-25
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0049-8246 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18782 Serial 7906
Permanent link to this record
 

 
Author Torfs, K.M.; Van Grieken, R.E.; Buzek, F.
Title Use of stable isotope measurements to evaluate the origin of suphur in gypsum layers on limestone buildings Type A1 Journal article
Year 1997 Publication Environmental science and technology Abbreviated Journal
Volume 31 Issue Pages 2650-2655
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0013-936x; 1520-5851 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18784 Serial 8724
Permanent link to this record
 

 
Author Torfs, K.; Van Grieken, R.; Zezza, F.; Garcia, N.; Macri, F.
Title The cathedral of Bari, Italy: evaluation of environmental effects on stone decay phenomena Type A1 Journal article
Year 1997 Publication Studies in conservation = Études de conservation Abbreviated Journal
Volume 42 Issue Pages 193-206
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000071198200001 Publication Date 2006-04-23
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18785 Serial 7585
Permanent link to this record
 

 
Author Dekov, V.M.; Araujo, F.; Van Grieken, R.; Subramanian, V.
Title Chemical composition of sediments and suspended matter from the Cauvery and Brahmaputra rivers (India) Type A1 Journal article
Year 1997 Publication The science of the total environment Abbreviated Journal
Volume 203 Issue Pages 51-53
Keywords A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0048-9697; 1879-1026 ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18787 Serial 7657
Permanent link to this record
 

 
Author Broos, W.; Wittner, N.; Geerts, J.; Dries, J.; Vlaeminck, S.E.; Gunde-Cimerman, N.; Richel, A.; Cornet, I.
Title Evaluation of lignocellulosic wastewater valorization with the oleaginous yeasts R. kratochvilovae EXF7516 and C. oleaginosum ATCC 20509 Type A1 Journal article
Year 2022 Publication Fermentation Abbreviated Journal
Volume 8 Issue 5 Pages 204-221
Keywords A1 Journal article; Pharmacology. Therapy; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL); Biochemical Wastewater Valorization & Engineering (BioWaVE)
Abstract During the conversion of lignocellulose, phenolic wastewaters are generated. Therefore, researchers have investigated wastewater valorization processes in which these pollutants are converted to chemicals, i.e., lipids. However, wastewaters are lean feedstocks, so these valorization processes in research typically require the addition of large quantities of sugars and sterilization, which increase costs. This paper investigates a repeated batch fermentation strategy with Rhodotorula kratochvilovae EXF7516 and Cutaneotrichosporon oleaginosum ATCC 20509, without these requirements. The pollutant removal and its conversion to microbial oil were evaluated. Because of the presence of non-monomeric substrates, the ligninolytic enzyme activity was also investigated. The repeated batch fermentation strategy was successful, as more lipids accumulated every cycle, up to a total of 5.4 g/L (23% cell dry weight). In addition, the yeasts consumed up to 87% of monomeric substrates, i.e., sugars, aromatics, and organics acids, and up to 23% of non-monomeric substrates, i.e., partially degraded xylan, lignin, cellulose. Interestingly, lipid production was only observed during the harvest phase of each cycle, as the cells experienced stress, possibly due to oxygen limitation. This work presents the first results on the feasibility of valorizing non-sterilized lignocellulosic wastewater with R. kratochvilovae and C. oleaginosum using a cost-effective repeated batch strategy.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000801796000001 Publication Date 2022-05-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2311-5637 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access OpenAccess
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:187883 Serial 7157
Permanent link to this record
 

 
Author Jambers, W.; Van Grieken, R.E.
Title Environmental problems Type H3 Book chapter
Year 1997 Publication Abbreviated Journal
Volume Issue Pages 803-819 T2 - Handbook of microscopy: applications
Keywords H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18789 Serial 7929
Permanent link to this record
 

 
Author Delalieux, F.; Sweevers, H.; Van Grieken, R.
Title Weathering mechanism of Pentelic marble under ambient atmospheric conditions derived from runoff studies Type P3 Proceeding
Year 1997 Publication Abbreviated Journal
Volume Issue Pages
Keywords P3 Proceeding; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:18791 Serial 8751
Permanent link to this record
 

 
Author Spanoghe, J.
Title Purple bacteria cultivation on light, carbon dioxide and hydrogen gas : exploring and tuning the potential for microbial food production Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages vi, 207 p.
Keywords Doctoral thesis; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Abstract The human population is projected to grow to 9.7 billion by 2050, resulting in an estimated increase in protein demand of 50%. From an environmental perspective, the current and future demand of protein cannot be sustainably met as the conventional food production chain is severely altering biogeochemical cycles of nitrogen and phosphorus, biodiversity and land-use, with flows towards the biosphere and oceans that are exceeding the planetary boundaries. Microbial protein (protein derived from microorganisms) has been suggested as an excellent sustainable protein source, a fortiori when produced in a land- and fossil free manner. The photoautohydrogenotrophic cultivation (i.e. with light, CO2 and H2) of purple bacteria links up perfectly with the upcoming green electrification of industry (green H2) and the need for carbon capture and utilization. However, this metabolism represented a gap in literature, and thus this thesis aimed to establish a basic knowledge platform on its kinetic, stoichiometric and nutritional performance. At first, three originally photoheterotrophically enriched purple bacteria were studied of which Rhodobacter capsulatus reached the highest protein productivity of 0.16 g protein/L/d, which aligned well with the commonly-known photoautotrophic microalgae. Moreover, a full dietary essential amino acid match was found for human food, while the fatty acid content was dominated by the health-stimulating vaccenic acid (82-86%). Lastly, the achieved protein yield in photoautohydrogenotrophic purple bacteria was 2.3 times higher compared to hydrogen oxidizing bacteria, indicating a resource-efficient use of H2. Next, a photoautohydrogenotrophic enrichment of wastewater treatment microbiomes was performed in search for specialist species. While the isolates of this enrichment showed improvements in their performance during acclimation, the kinetic and nutritional performance of Rhodobacter capsulatus still excelled. Subsequently, the influence of nutrient limitations (C or N) and nitrogen gas fixation was studied on the nutritional tuning potential. Both the limitations as well as the N2 fixation resulted in the shift of the essential amino acid profiles. Additionally, the limitations significantly decreased the pigment content, while an increase in the storage of poly-P was seen in case of carbon limitations. The next major challenge was the production intensification in a photobioreactor of which the design was linked to minimizing both H2 and light limitations. The chosen bubble-column photobioreactor already resulted in a doubled biomass productivity. Finally, the remaining technological and non-technological challenges ahead for the production of a high-value, cost-efficient, environment-friendly microbial protein that complies with legislative requirements and appeals to future consumers were discussed.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN 978-90-5728-741-1 Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188233 Serial 7198
Permanent link to this record
 

 
Author van 't Veer, K.C.
Title Plasma kinetics modelling of nitrogen fixation : ammonia synthesis in dielectric barrier discharges with catalysts Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages 241 p.
Keywords Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract Ammonia (NH3) synthesis is crucial for the production of artificial fertilizer and is carried out through the Haber-Bosch process. With an energy consumption of 30 GJ/t-NH3 and the emission of 2 kg-CO2/kg-NH3, ammonia is the chemical with the largest environmental footprint. Haber-Bosch operates under high pressure and high temperature conditions. Plasma technology potentially allows greener ammonia production. Dielectric barrier discharges are a popular plasma source in which a catalyst is easily incorporated. The combination of plasma and catalyst can circumvent the harsh reaction conditions of the Haber-Bosch process. Plasma kinetics modelling is used to gain insight into the mechanisms of such plasma-catalytic systems. Special attention is given to the instantaneous power absorbed by the electrons, the relevant fraction of the microdischarges and the discharge volumes. The importance of vibrational excitation is investigated. Depending on the exact discharge conditions, it was found that both the strong microdischarges and vibrational excitation can be simultaneously important for the ammonia yield. The temporal behavior of filamentary dielectric barrier discharges was explicitly taken into account. Ammonia was found to decompose during the microdischarges due to electron impact dissociation. At the same time atomic nitrogen and other excited species are created. Those reactive species recombine to ammonia in the afterglow through various elementary Eley-Rideal and Langmuir-Hinshelwood surface reaction steps with a net ammonia gain. Finally, the concept of the fraction of microdischarges was generalized. It directly represents the efficiency with which the applied electric power is transferred to each individual particle in the plasma reactor. It is argued that any type of spatial or temporal non-uniformity of the plasma will cause unequal treatment of the gas molecules in the reactor, corresponding to a lower efficiency at which the power is transferred to the gas molecules. All of those insights aid in an increased understanding of plasma-catalytic ammonia synthesis as a potential green chemistry solution to the synthesis of ammonia on small scale.  
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188246 Serial 7193
Permanent link to this record
 

 
Author Arslan Irmak, E.
Title Modelling three-dimensional nanoparticle transformations based on quantitative transmission electron microscopy Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages 169 p.
Keywords Doctoral thesis; Electron microscopy for materials research (EMAT)
Abstract Nanomaterials are materials that have at least one dimension in the nanometer length scale, which corresponds to a billionth of a meter. When three dimensions are confined to the nanometer scale, these materials are referred to as nanoparticles. These materials are of great interest since they exhibit unique physical and chemical properties that cannot be observed for bulk systems. Due to their unique and often superior properties, nanomaterials have become central in the field of electronics, catalysis, and medicine. Moreover, they are expected to be one of the most promising systems to tackle many challenges that our society is facing, such as reducing the emission of greenhouse gases and finding effective treatments for cancer. The unique properties of nanomaterials are linked to their size, shape, structure, and composition. If one is able to measure the positions of the atoms, their chemical nature, and the bonding between them, it becomes possible to predict the physicochemical properties of nanomaterials. In this manner, the development of novel nanostructures can be triggered. However, the morphology and structure of nanomaterials are highly sensitive to the conditions for relevant applications, such as elevated temperatures or intense light illumination. Furthermore, any small change in the local structure at higher temperatures or pressures may significantly modify their performance. Hence, three-dimensional (3D) characterization of nanomaterials under application-relevant conditions is important in designing them with desired functional properties for specific applications. Among different structural characterization approaches, transmission electron microscopy (TEM) is one of the most efficient and versatile tools to investigate the structure and composition of nanomaterials since it can provide atomically resolved images, which are sensitive to the local 3D structure of the investigated sample. However, TEM only provides two-dimensional (2D) images of the 3D nanoparticle, which may lead to an incomplete understanding of their structure-property relationship. The most known and powerful technique for the 3D characterization of nanomaterials is electron tomography, where the images of a nanostructured material taken from different directions are mathematically combined to retrieve its 3D structure. Although these experiments are already state-of-the-art, 3D characterization by TEM is typically performed under ultra-high vacuum conditions and at room temperature. Such conditions are unfortunately not sufficient to understand transformations during synthesis or applications of nanomaterials. This limitation can be overcome by in situ TEM where external stimuli, such as heat, gas, and liquids, can be controllably introduced inside the TEM using specialized holders. However, there are some technical limitations to successful perform 3D in situ electron tomography experiments. For example, the long acquisition time required to collect a tilt series limits this technique when one wants to observe 3D dynamic changes with atomic resolution. A solution for this problem is the estimation of the 3D structure of nanomaterials from 2D projection images acquired along a single viewing direction. For this purpose, annular dark field scanning TEM (ADF STEM) imaging mode provides a valuable tool for quantitative structural investigation of nanomaterials from single 2D images due to its thickness and mass sensitivity. For quantitative analysis, an ADF STEM image is considered as a 2D array of pixels where relative variation of pixel intensity values is proportional to the total number of atoms and the atomic number of the elements in the sample. By applying advanced statistical approaches to these images, structural information, such as the number or types of atoms, can be retrieved with high accuracy and precision. The outcome can then be used to build a 3D starting model for energy minimization by atomistic simulations, for example, molecular dynamics simulations or the Monte Carlo method. However, this methodology needs to be further evaluated for in situ experiments. This thesis is devoted to presenting robust approaches to accurately define the 3D atomic structure of nanoparticles under application-relevant conditions and understand the mechanism behind the atomic-scale dynamics in nanoparticles in response to environmental stimuli.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188295 Serial 7063
Permanent link to this record
 

 
Author Schram, J.; Parrilla, M.; Slosse, A.; Van Durme, F.; Åberg, J.; Björk, K.; Bijvoets, S.M.; Sap, S.; Heerschop, M.W.J.; De Wael, K.
Title Paraformaldehyde-coated electrochemical sensor for improved on-site detection of amphetamine in street samples Type A1 Journal article
Year 2022 Publication Microchemical journal Abbreviated Journal
Volume 179 Issue Pages 107518-107519
Keywords A1 Journal article; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract The increasing illicit production, distribution and abuse of amphetamine (AMP) poses a challenge for law enforcement worldwide. To effectively combat this issue, fast and portable tools for the on-site screening of suspicious samples are required. Electrochemical profile (EP)-based sensing of illicit drugs has proven to be a viable option for this purpose as it allows rapid voltammetric measurements via the use of disposable and low-cost graphite screen-printed electrodes (SPEs). In this work, a highly practical paraformaldehyde (PFA)-coated sensor, which unlocks the detectability of primary amines through derivatization, is developed for the on-site detection of AMP in seized drug samples. A potential interval was defined at the sole AMP peak (which is used for identification of the target analyte) to account for potential shifts due to fluctuations in concentration and temperature, which are relevant factors for on-site use. Importantly, it was found that AMP detection was not hindered by the presence of common diluents and adulterants such as caffeine, even when present in high amounts. When inter-drug differentiation is desired, a simultaneous second test with the same solution on an unmodified electrode is introduced to provide the required additional electrochemical information. Finally, the concept was validated by analyzing 30 seized AMP samples (reaching a sensitivity of 96.7 %) and comparing its performance to that of commercially available Raman and Fourier Transform Infrared (FTIR) devices.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000809675500010 Publication Date 2022-04-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0026-265x; 0026-265x ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access OpenAccess
Notes Approved no
Call Number (up) UA @ admin @ c:irua:188454 Serial 8910
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Author Nicolau, F.; Gielis, J.; Simeone, A.L.; Simoes Lopes, D.
Title Exploring and selecting supershapes in virtual reality with line, quad, and cube shaped widgets Type P1 Proceeding
Year 2022 Publication Abbreviated Journal
Volume Issue Pages 21-28
Keywords P1 Proceeding; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Abstract Supershapes are used in Parametric Design to model, literally, thou-sands of natural and man-made shapes with a single 6 parameter formula. However, users are left to probe such a rich yet dense collection of supershapes using a set of independent 1-D sliders. Some of the formula’s parameters are non-linear in nature, making them particularly difficult to grasp with conventional 1-D sliders alone. VR appears as a promising setting for Parametric Design with supershapes since it empowers users with more natural visual inspection and shape browsing techniques, with multiple solutions being displayed at once and the possibility to design more interesting forms of slider interaction. In this work, we propose VR shape widgets that allow users to probe and select supershapes from a multitude of solutions. Our designs take leverage on thumbnails, mini-maps, haptic feedback and spatial interaction, while supporting 1-D, 2-D and 3-D supershape parameter spaces. We conducted a user study (N = 18) and found that VR shape widgets are effective, more efficient, and natural than conventional VR 1-D sliders while also usable for users without prior knowledge on supershapes. We also found that the proposed VR widgets provide a quick overview of the main supershapes, and users can easily reach the desired solution without having to perform fine-grain handle manipulations.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000828657500003 Publication Date 2022-04-20
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 978-1-6654-9617-9 ISBN Additional Links UA library record; WoS full record
Impact Factor Times cited Open Access OpenAccess
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188471 Serial 7161
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Author Van Echelpoel, R.; Schram, J.; Parrilla, M.; Daems, D.; Slosse, A.; Van Durme, F.; De Wael, K.
Title Electrochemical methods for on-site multidrug detection at festivals Type A1 Journal article
Year 2022 Publication Sensors & Diagnostics Abbreviated Journal
Volume 1 Issue 1 Pages 793-802
Keywords A1 Journal article; Engineering sciences. Technology; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract Two electrochemical methodologies, i.e. flowchart and dual-sensor, were developed to aid law enforcement present at festivals to obtain a rapid indication of the presence of four illicit drugs in suspicious samples encountered.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date 2022-06-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access OpenAccess
Notes Approved no
Call Number (up) UA @ admin @ c:irua:188521 Serial 8856
Permanent link to this record
 

 
Author Jiang, J.
Title Ginzburg-Landau dynamical simulations on the nonreciprocal transport properties of two-dimensional superconductors Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages XII, 79 p.
Keywords Doctoral thesis; Condensed Matter Theory (CMT)
Abstract The nonreciprocal charge transport property which depends on the polarity of the applied current, such as the diode effect and the rectification effect, is of great importance for both theoretical research and engineering application. The nonreciprocal transport property in superconductors generally requires to break both the spatial inversion symmetry and the time-reversal symmetry, and therefore becomes one of the fundamental issues in superconductivity. Of particular interest, the superconducting diode effect, which exhibits one-way superconductivity, can potentially be applied to dissipationless diode devices, as a consequence has received extensive attention in recent years. In this Ph. D thesis, we simulate vortex dynamics with heat dissipation by numerically solving time-dependent Ginzburg-Landau equations and heat transfer equation. The nonreciprocal transport properties of the following three superconducting systems are studied. We study a superconducting film patterned with a conformal pinning array and find a giant rectification effect which is consistent with the experimental observation. In presence of the funneling effect due to the geometry of the conformal pinning array, Joule heating of the accumulating vortices creates hot spots and drives the sample to the normal state. Meanwhile, the density gradient of vortex does not match the gradient of pinning. The two mechanisms together lead to the giant rectification effect. We study the nonreciprocal charge transport property in a pinning-free superconducting nano-ring. We systematically calculate the response of the ratchet signal to various parameters in both D.C. and A.C. currents. By analyzing the vortex potential, we find that the nonreciprocal transport property is caused by the asymmetry potential barriers for vortex entry and exit. We study a superconductor/nanoscale-magnetic-dot hybrid structure. It takes advantage of the external current to control the nucleation of vortex-antivortex pairs, and can produce superconducting diode effect without applied magnetic fields. Our vortex dynamics simulation details the progress of the superconducting-normal phase transition due to motion of vortex pairs and heat dissipation. The nonreciprocal transport properties of the above three systems are all based on the broken symmetry of spatial inversion, which is caused by the anisotropic pinning array, the asymmetric geometry, and the nonuniform distribution of the magnetic field, respectively. The mechanisms we discuss in this thesis do not require special property of the materials and thus can be applied to any kinds of conventional superconductors. The present studies would provide solid theoretical basis for the future design and application of the dissipationless superconducting devices.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188525 Serial 7168
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Author Moro, G.; Foumthuim, C.J.D.; Spinaci, M.; Martini, E.; Cimino, D.; Balliana, E.; Lieberzeit, P.; Romano, F.; Giacometti, A.; Campos, R.; De Wael, K.; Moretto, L.M.
Title How perfluoroalkyl substances modify fluorinated self-assembled monolayer architectures : an electrochemical and computational study Type A1 Journal article
Year 2022 Publication Analytica chimica acta Abbreviated Journal
Volume 1204 Issue Pages 339740-12
Keywords A1 Journal article; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract There is an urgent need for sensing strategies to screen perfluoroalkyl substances (PFAS) in aqueous matrices. These strategies must be applicable in large-scale monitoring plans to face the ubiquitous use of PFAS, their wide global spread, and their fast evolution towards short-chain, branched molecules. To this aim, the changes in fluorinated self-assembled monolayers (SAM) with different architectures (pinholes/defects-free and with randomized pinholes/defects) were studied upon exposure to both long and short-chain PFAS. The applicability of fluorinated SAM in PFAS sensing was evaluated. Changes in the SAM structures were characterised combining electrochemical impedance spectroscopy and voltam-metric techniques. The experimental data interpretation was supported by molecular dynamics simu-lations to gain a more in-depth understanding of the interaction mechanisms involved. Pinhole/defect-free fluorinated SAM were found to be applicable to long-chain PFAS screening within switch-on sensing strategy, while a switch-off sensing strategy was reported for screening of both short/long-chain PFAS. These strategies confirmed the possibility to play on fluorophilic interactions when designing PFAS screening methods.(c) 2022 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000789493000010 Publication Date 2022-03-17
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-2670; 1873-4324 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access Not_Open_Access
Notes Approved no
Call Number (up) UA @ admin @ c:irua:188658 Serial 8880
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Author Vanschoenwinkel, J.; Vancauteren, M.; Van Passel, S.
Title How do western European farms behave and respond to climate change? A simultaneous irrigation-crop decision model Type A1 Journal article
Year 2022 Publication Climate change economics Abbreviated Journal
Volume 13 Issue 4 Pages 2250009-2250038
Keywords A1 Journal article; Economics; Engineering Management (ENM)
Abstract Most farm adaptations are reactive actions that run the risk of locking farm systems into suboptimal long-term trajectories. This is especially the case with regard to water management as water scarcity will be aggravated by climate change. This paper looks into farm irrigation choices in combination with crop choices because a proper crop choice has the potential to reduce water requirements. It proposes an extended Ricardian model to capture multiple adaptation decisions explicitly. The new simultaneous irrigation-crop farm decision model uses spatially detailed farm-level data of over 18,000 European farms on irrigation and seven different crop choices. The analysis shows that larger farmers and farmers in less water-scarce regions that use irrigation are more sensitive to temperature increases than rain-fed agriculture. This might be explained by the fact that these farmers do not experience the real cost of water scarcity because of which they take less efficient decisions.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000791485900001 Publication Date 2022-03-09
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2010-0086 ISBN Additional Links UA library record; WoS full record
Impact Factor Times cited Open Access OpenAccess
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188680 Serial 7359
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Author Parrilla, M.; Detamornrat, U.; Domínguez-Robles, J.; Donnelly, R.F.; De Wael, K.
Title Wearable hollow microneedle sensing patches for the transdermal electrochemical monitoring of glucose Type A1 Journal article
Year 2022 Publication Talanta : the international journal of pure and applied analytical chemistry Abbreviated Journal
Volume 249 Issue Pages 123695-123699
Keywords A1 Journal article; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Abstract According to the World Health Organization, about 422 million people worldwide have diabetes, with 1.5 million deaths directly attributed each year. Therefore, there is still a need to effectively monitor glucose in diabetic patients for proper management. Recently, wearable patches based on microneedle (MN) sensors provide minimally invasive analysis of glucose through the interstitial fluid (ISF) while exhibiting excellent correlation with blood glucose. Despite many advances in wearable electrochemical sensors, long-term stability and continuous monitoring remain unsolved challenges. Herein, we present a highly stable electrochemical biosensor based on a redox mediator bilayer consisting of Prussian blue and iron-nickel hexacyanoferrate to increase the long-term stability of the readout coupled with a hollow MN array as a sampling unit for ISF uptake. First, the enzymatic biosensor is developed by using affordable screen-printed electrodes (SPE) and optimized for long-term stability fitting the physiological range of glucose in ISF (i.e., 2.5–22.5 mM). In parallel, the MN array is assessed for minimally invasive piercing of the skin. Subsequently, the biosensor is integrated with the MN array leaving a microfluidic spacer that works as the electrochemical cell. Interestingly, a microfluidic channel connects the cell with an external syringe to actively and rapidly withdraw ISF toward the cell. Finally, the robust MN sensing patch is characterized during in vitro and ex vivo tests. Overall, affordable wearable MN-based patches for the continuous monitoring of glucose in ISF are providing an advent in wearable devices for rapid and life-threatening decision-making processes.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000826441800002 Publication Date 2022-06-16
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0039-9140; 1873-3573 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access OpenAccess
Notes Approved no
Call Number (up) UA @ admin @ c:irua:188955 Serial 8955
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Author Tschulkow, M.
Title A techno-environmental economic assessment of a lignin-first biorefinery : a dynamic and prospective framework for emerging technologies Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages 175 p.
Keywords Doctoral thesis; Engineering sciences. Technology; Engineering Management (ENM)
Abstract Novel emerging biorefinery technologies have gained interest and have the potential to tackle several sustainability challenges in our society. A lignin-first biorefinery process – reductive catalytic fractionation (RCF) – is currently under development with the aim to process wood into high-value end-products that replace highly polluting fossil oil-based products. However, such emerging technologies are not matured yet, holding a certain degree of technological, economic, and environmental uncertainty. Hence, an appropriate assessment method is required to assess techno-economic feasibility and environmental impacts of emerging uncertain technologies (e.g lignin-first RCF process). This dissertation aims to develop an integrated techno-environmental economic assessment framework to assess emerging technologies dynamically and prospectively from economic and environmental points of view. First, a techno-economic assessment (TEA) is performed to assess the economic feasibility and the most influential economic and technological parameters of the lignin-first RCF biorefinery taking the whole wood value chain into account. By making the relations across the wood value chain, the scale of the biorefinery, wood species, and output prices highly determine the economic feasibility. The economic feasibility can be reached by a sufficient capacity level which depends on wood species-specific conditions. Also, waste wood proves to be the most profitable feedstock in comparison to virgin wood. Second, an analytical real options analysis (ROA) is performed taking two correlated market uncertainties and the value of flexibility into account to identify the optimal investment decision in an RCF biorefinery. Two different investment options, separated and united investments in harvesting equipment and RCF biorefinery, are analyzed. In both scenarios, market uncertainty postpones the investment. When both investment decisions are united, the probability of investment increases in comparison to separated investments. The study reveals that RCF has the potential to stimulate investments within the wood value chain. Third, a consequential life cycle assessment (LCA) is performed to assess the carbon emissions and the environmental consequences of the lignin-first RCF process and its products. The study reveals that at the current stage RCF products have higher carbon emissions than their alternative counterparts. Several options to improve the environmental performance are discussed such as different RCF technology configurations, targeting different RCF products with the ability to replace higher polluting alternative counterparts on the markets. Other discussion points such as transportation type and the distance, (in-)direct land-use change, the use stage and disposal stages implications, and a more comprehensive environmental view of the RCF products, show the potential to improve the environmental performance of the RCF technology. Overall, the study shows that the RCF process can be environmentally desirable if the appropriate RCF configuration and products are chosen. Finally, the above-mentioned methods – techno-economic assessment, analytical real options analysis, and consequential life cycle assessment – are uniquely integrated within the newly developed integrated assessment framework. The framework has the aim to complement the shortcomings and combine the advantages of all three methods. The framework assesses emerging technologies to give predictive insights about the time-specific economic and environmental performance under the newly developed three threshold conditions: technological readiness, economic feasibility, and environmental desirability. The developed integrated assessment framework assesses dynamically and prospectively the RCF biorefinery implementation under Belgian conditions. It reveals that the economic feasibility increases and carbon emissions decrease over time. The RCF biorefinery fulfills all three threshold conditions – technological readiness, economic feasibility, and environmental desirability – consecutively. The newly developed integrated assessment framework offers decision support to several stakeholders of emerging technologies starting from low technology readiness level (TRL). Practitioners such as the technology developers, researchers, and policymakers can use the framework to evaluate emerging technologies that deal with high levels of technological, economic, and environmental uncertainties. The framework assesses emerging technologies on a detailed level to give decision-makers in-depth insights into the intertwined nature of the technological, economic, and environmental dimensions. It offers insights into the expected time-specific economic and environmental performances, potential, and challenges of the emerging technology to further improve the technology and direct R&Ds along the right path.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:188968 Serial 7369
Permanent link to this record
 

 
Author Kashiwar, A.
Title TEM investigations of deformation mechanisms in nanocrystalline metals and multilayered composites Type Doctoral thesis
Year 2022 Publication Abbreviated Journal
Volume Issue Pages xvi, 129 p.
Keywords Doctoral thesis; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Abstract In the last few decades, nanostructuring has driven significant attention towards the development of novel metallic materials with advanced mechanical properties. Nanocrystalline (nc) metals are a class of nanostructured materials with grain sizes smaller than about 100 nm. These exhibit outstanding mechanical strength and fatigue properties compared to their coarse-grained (cg) counterparts. These are promising candidates for application as structural or functional materials. Nc metals in the form of thin films are employed as hard coatings on bulk components, structural components, and conductive layers in various micro-/nanoscale devices. These structural components and devices are often subjected to cyclic stresses or fatigue loading. Under these cyclic stresses, nc metals tend to exhibit the Bauschinger effect (BE). The strength loss during the BE is of great importance concerning the strength-ductility trade-off in nc metals. Furthermore, contact surfaces of the engineering components in service often undergo relative motion and are subject to both friction and wear. These extreme loading conditions demand nc metals with tailored interfacial characteristics for improved tribological performance. Aiming at ensuring high reliability and mechanical robustness for optimum performance of these components, there has been a strong motivation for understanding the mechanical properties and governing deformation mechanisms in nc metallic materials. This thesis aimed at in-depth investigation of microstructures at micro-/nanoscales using state-of-the-art in situ and ex situ transmission electron microscopy (TEM) to develop a closer link between the deformation structure and underlying deformation mechanisms in some nc metallic materials. The thesis has primarily focused on the in situ TEM nanomechanics of the BE and rotational deformation of grains in nc palladium thin films. A sputtered thin film of nc Pd was deformed inside TEM by cyclic loading-unloading experiments and the evolving microstructure was studied in real-time under different TEM imaging modes. The stress-strain response of the film exhibited a characteristic non-linear unloading behavior confirming the BE in the film. The corresponding bright-field TEM imaging revealed evidence of partially reversible dislocation activity. Towards a quantitative understanding of the deformation structure in real-time, in situ nanomechanical testing was coupled with precession-assisted automated crystal orientation mapping in scanning TEM (ACOM-STEM). Global ACOM-STEM analysis offered crystal orientation of a large number of grains at different states of deformation and confirmed partially reversible rotations of nanosized grains fitting to the observed BE during loading and unloading. Analysis of intragranular rotations showed substantial changes in the sub-structure within most of these grains indicating a dominant role of dislocation-based processes in driving these rotations. Globally, an unusually random evolution of texture was seen that demonstrated the influence of deformation heterogeneity and grain interactions on the resulting texture characteristics in nc metals. In the quest of understanding the grain interactions, local investigations based on annular dark-field STEM imaging during loading-unloading showed reversible changes in the contrast of grains with sets of adjoining grains exhibiting a unique cooperative rotation. Local analysis of the density of geometrically necessary dislocations (GNDs) showed the formation of dislocation pile-up at grain boundaries due to the generation of back-stresses during unloading. Critical observations of the evolution of GND density offered greater insights into the mechanism of cooperative grain rotations and these rotations were related to grain structure and grain boundary characteristics. In addition to understanding the influence of grain structure and grain boundaries, the thesis has further investigated the role of heterointerfaces in sputtered Au-Cu and Cu-Cr nanocrystalline multilayered composites (NMCs) deformed under cyclic sliding contact. The microstructural evolution in the NMCs was investigated at different deformation states by classical TEM imaging, ACOM-STEM as well as energy-filtered TEM (EFTEM). Au-Cu NMC with an initial high density of twin boundaries deformed by stress-driven detwinning with a concurrent change in grain structure in both Au and Cu. The formation of a vortex structure was observed due to plastic flow instabilities at Au-Cu interfaces that led to codeformation and mechanical intermixing. Cu-Cr NMC showed a preferential grain growth in Cu layers whereas no noticeable change in the grain sizes was seen in Cr layers. The phase maps revealed sharp interfaces between Cu and Cr layers indicating no intermixing between the immiscible phases. EFTEM results exposed the cracking processes in Cr layers with a concurrent migration of Cu in the cracks. Overall, the thesis has attempted to analyze the competing deformation processes and relate these with the microstructural heterogeneity in terms of grain structure and GB and interfacial characteristics in nc metallic materials.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access OpenAccess
Notes Approved Most recent IF: NA
Call Number (up) UA @ admin @ c:irua:189013 Serial 7343
Permanent link to this record