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Spatially and angularly resolved diffuse reflectance measurement for in-line analysis of particle suspensions, a multi-sensor approach
Get PDFParticle size and shape are critical quality attributes for active pharmaceutical ingredients (API) as they have direct impact on downstream processing, as well as on the performance behaviour of the finished product. None of the current process analytical technologies (PAT), although capable of providing an indication on these key attributes, measures particle size directly. Obtaining a reliable and robust quantitative information of these particle attributes in real-time remains a great challenge across the multiple manufacturing steps and cannot be achieved by just using a single sensor. A Spatially and Angularly-Resolved Diffuse Reflectance Measurement (SAR-DRM) technology is for the first time applied to monitor micron size particles. SAR-DRM relies on multiple scattering of particles and collects multi-wavelength (UV-visibleNIR) diffuse reflectance spectra from optical fibres of multi-angle multi-space arrangements. Each SAR-DRM spectrum yields differences which correspond to the light travelling differently in the sample and to being differently affected by scattering and absorption effects. This technique is used alongside with Focus Beam Reflectance Measurement (FBRM) and Particle Vision and Measurement (PVM) which have been widely applied for in-line monitoring of particle attributes in crystallisation processes, in order to examine the SAR-DRM performance and investigate the possibility to broadening the size and concentration ranges of the applications.;The investigation was carried out on two model systems: polystyrene beads suspensions in water and alpha lactose monohydrate suspensions in acetone, for size (<38 to 800 µm) and concentration (0.5 to 25 wt.%) ranges, relevant to many pharmaceutical processes, e.g., during crystallisation and granulation. As particles scatter light differently depending on the size, shape and solid concentration, the spectral changes in SAR-DRM can be related to the sample's attributes. These properties can be either obtained by applying light propagation theory, which involves intensive computational calculations and are challenging to invert the information in real-time, or by multivariate regression analysis, an alternative and faster method. Characterisation of the particles attributes was performed by both in-line and off-line commercial technologies, and served as an input to validate SAR-DRM sensitivity, accuracy and capability to track the differences in size and solid loading in the model system. Robust calibration models were established to predict particle size and particle concentration for the individual technologies and for the combined measurement data, by applying multivariate regression analysis.;The results suggest that the accuracy of multivariate calibration models can be improved by combining key SAR-DRM configurations with FBRM data. This is due to the spectra captured by SAR-DRM containing more complete information about the light scattering properties of samples, which can be related to the particle size and concentration. As SAR-DRM prefers high turbidity samples, i.e., samples with higher solid content, the study shows that SARDRM technology can be a potential complementary to other PAT tools such as FBRM and PVM, which tend to perform better for low turbidity samples. Currently, solid concentration is not measured during pharmaceutical processes and particle size is not directly obtained. Our result suggests that combining the strengths of each technique can help to obtain reliable and quantitative information about particle attributes, allowing to achieve robust process monitoring and enable improved control and optimisation of manufacturing processes.Particle size and shape are critical quality attributes for active pharmaceutical ingredients (API) as they have direct impact on downstream processing, as well as on the performance behaviour of the finished product. None of the current process analytical technologies (PAT), although capable of providing an indication on these key attributes, measures particle size directly. Obtaining a reliable and robust quantitative information of these particle attributes in real-time remains a great challenge across the multiple manufacturing steps and cannot be achieved by just using a single sensor. A Spatially and Angularly-Resolved Diffuse Reflectance Measurement (SAR-DRM) technology is for the first time applied to monitor micron size particles. SAR-DRM relies on multiple scattering of particles and collects multi-wavelength (UV-visibleNIR) diffuse reflectance spectra from optical fibres of multi-angle multi-space arrangements. Each SAR-DRM spectrum yields differences which correspond to the light travelling differently in the sample and to being differently affected by scattering and absorption effects. This technique is used alongside with Focus Beam Reflectance Measurement (FBRM) and Particle Vision and Measurement (PVM) which have been widely applied for in-line monitoring of particle attributes in crystallisation processes, in order to examine the SAR-DRM performance and investigate the possibility to broadening the size and concentration ranges of the applications.;The investigation was carried out on two model systems: polystyrene beads suspensions in water and alpha lactose monohydrate suspensions in acetone, for size (<38 to 800 µm) and concentration (0.5 to 25 wt.%) ranges, relevant to many pharmaceutical processes, e.g., during crystallisation and granulation. As particles scatter light differently depending on the size, shape and solid concentration, the spectral changes in SAR-DRM can be related to the sample's attributes. These properties can be either obtained by applying light propagation theory, which involves intensive computational calculations and are challenging to invert the information in real-time, or by multivariate regression analysis, an alternative and faster method. Characterisation of the particles attributes was performed by both in-line and off-line commercial technologies, and served as an input to validate SAR-DRM sensitivity, accuracy and capability to track the differences in size and solid loading in the model system. Robust calibration models were established to predict particle size and particle concentration for the individual technologies and for the combined measurement data, by applying multivariate regression analysis.;The results suggest that the accuracy of multivariate calibration models can be improved by combining key SAR-DRM configurations with FBRM data. This is due to the spectra captured by SAR-DRM containing more complete information about the light scattering properties of samples, which can be related to the particle size and concentration. As SAR-DRM prefers high turbidity samples, i.e., samples with higher solid content, the study shows that SARDRM technology can be a potential complementary to other PAT tools such as FBRM and PVM, which tend to perform better for low turbidity samples. Currently, solid concentration is not measured during pharmaceutical processes and particle size is not directly obtained. Our result suggests that combining the strengths of each technique can help to obtain reliable and quantitative information about particle attributes, allowing to achieve robust process monitoring and enable improved control and optimisation of manufacturing processes
Measuring urban form and urban life four case studies in Baghdad, Iraq
No full textTraditional cities often demonstrated a capacity to adapt over time to the most remarkable economic, political, cultural and broadly environmental changes. From an Urban Morphology perspective, adaptation tends to accur through piecemeal 'spontaneous' physical changes, which directly relate to the individual and collective behaviours of inhabitants and city-users in general. Since adaptivity is increasingly regarded as a major asset of a city's ability to support a thriving urban life throughout time, this research explores how the form of historical cities and their enduring social and economic success are linked at the scale where urban life occurs, namely that of the street and the neighbourhood.;This thesis observes the relationship between urban form and urban life in the city of Baghdad, Iraq, by investigating four central neighbourhoods, which represent different historical periods in the development of the city. Here street life and the form of the built environment are quantified through an in-depth field study. A detailed observation on the ground is undertaken at four scales, namely plot, block street and neighbourhood, through indicators identified in the relevant literature. These are tested and, in some cases amended to better fit the research constraints and local conditions. Here ethnographic and analytical methods of data gathering are undertaken, including observations and interactive street-by-street surveys, mapping and historical studies.;The research findings cover the three fundamantal aspects of firstly, the urban form and secondly, urban life. The former considers two dimensions, namely the street centrality (MCA: betweenness/closeness) and consitutedness (permiability and intervisibility). The latter represents human activity and includes five patterns: movement, activities, gender, age and group pattern. A comparison of the four samples regarding the urban form elements revealed significant indicators that distinguish between the traditional pattern and the modern model of a neighbourhood.;In relating street life to both constitutedness and permeability, this helped determine the interrelationship between the street edge characteristics of people's activities. Street life and centrality (MCA) yielded a positive association between the movement volume and the betweenness centrality. Finaly, both constitutedness and permiability exhibited an essential relationship to the Multiple Central Assesment.Traditional cities often demonstrated a capacity to adapt over time to the most remarkable economic, political, cultural and broadly environmental changes. From an Urban Morphology perspective, adaptation tends to accur through piecemeal 'spontaneous' physical changes, which directly relate to the individual and collective behaviours of inhabitants and city-users in general. Since adaptivity is increasingly regarded as a major asset of a city's ability to support a thriving urban life throughout time, this research explores how the form of historical cities and their enduring social and economic success are linked at the scale where urban life occurs, namely that of the street and the neighbourhood.;This thesis observes the relationship between urban form and urban life in the city of Baghdad, Iraq, by investigating four central neighbourhoods, which represent different historical periods in the development of the city. Here street life and the form of the built environment are quantified through an in-depth field study. A detailed observation on the ground is undertaken at four scales, namely plot, block street and neighbourhood, through indicators identified in the relevant literature. These are tested and, in some cases amended to better fit the research constraints and local conditions. Here ethnographic and analytical methods of data gathering are undertaken, including observations and interactive street-by-street surveys, mapping and historical studies.;The research findings cover the three fundamantal aspects of firstly, the urban form and secondly, urban life. The former considers two dimensions, namely the street centrality (MCA: betweenness/closeness) and consitutedness (permiability and intervisibility). The latter represents human activity and includes five patterns: movement, activities, gender, age and group pattern. A comparison of the four samples regarding the urban form elements revealed significant indicators that distinguish between the traditional pattern and the modern model of a neighbourhood.;In relating street life to both constitutedness and permeability, this helped determine the interrelationship between the street edge characteristics of people's activities. Street life and centrality (MCA) yielded a positive association between the movement volume and the betweenness centrality. Finaly, both constitutedness and permiability exhibited an essential relationship to the Multiple Central Assesment
An investigtion into the ability of a kinetic particle-based solver for study of gas flows in micro-scale structures
No full textScientific enquiry has aligned itself, in recent times, to the understanding of the flow physics encountered in micro- and nano-scales. The prominence of this line of enquiryis due to its recurring influence in the fields of MEMS and porous media. These flows occur in pathways whose width is comparable to the mean free path and thus, are classified as rarefied gas flows. Assuming continuum and resorting to traditional CFD techniques leads to results with severe reservations while, deterministic kinetic theory based approaches, such as DVM, implement liberal approximations such as restricting the velocity space to a limited set determined through pre-cognizance or trials. Even stochastic particle approaches, such as the DSMC, usually adept at resolving such flows, proves to be prohibitively expensive owing to the small signal to-noise ratio necessitating a large number of samples to obtain appreciably accurate results. The present research is aimed at recovering the inherent advantages of particle methods through the development of parallel kinetic particle-based solver founded on the low variance ideologies. The solver is validated against classical fluid dynamics problems prior to application to simple, yet practical, MEMS applications such as isothermal flow through long ducts and past infinite arrays. The final objective of the current research is aimed at understanding and simulating the transport of unconventional gases in subterranean micro-porous networks which is of great significance in the oil and gas industry. To this end, the simulation of porescale flows for the entire rarefaction spectrum through idealized porous media such as Sierpinski carpets, Menger sponge etc. along with image-reconstructed porous media such as 2D Berea sandstone and 3D rock samples such as Gambier, Castlegate and Fayetteville shale are carried out and analysed. The unique approach enables the solver to obtain novel, substantial and reliable insights at the pore level while employing appropriate averaging to predict macroscopic properties such as apparent permeability and tortuosity with a previously unprecedented computational effciency.Scientific enquiry has aligned itself, in recent times, to the understanding of the flow physics encountered in micro- and nano-scales. The prominence of this line of enquiryis due to its recurring influence in the fields of MEMS and porous media. These flows occur in pathways whose width is comparable to the mean free path and thus, are classified as rarefied gas flows. Assuming continuum and resorting to traditional CFD techniques leads to results with severe reservations while, deterministic kinetic theory based approaches, such as DVM, implement liberal approximations such as restricting the velocity space to a limited set determined through pre-cognizance or trials. Even stochastic particle approaches, such as the DSMC, usually adept at resolving such flows, proves to be prohibitively expensive owing to the small signal to-noise ratio necessitating a large number of samples to obtain appreciably accurate results. The present research is aimed at recovering the inherent advantages of particle methods through the development of parallel kinetic particle-based solver founded on the low variance ideologies. The solver is validated against classical fluid dynamics problems prior to application to simple, yet practical, MEMS applications such as isothermal flow through long ducts and past infinite arrays. The final objective of the current research is aimed at understanding and simulating the transport of unconventional gases in subterranean micro-porous networks which is of great significance in the oil and gas industry. To this end, the simulation of porescale flows for the entire rarefaction spectrum through idealized porous media such as Sierpinski carpets, Menger sponge etc. along with image-reconstructed porous media such as 2D Berea sandstone and 3D rock samples such as Gambier, Castlegate and Fayetteville shale are carried out and analysed. The unique approach enables the solver to obtain novel, substantial and reliable insights at the pore level while employing appropriate averaging to predict macroscopic properties such as apparent permeability and tortuosity with a previously unprecedented computational effciency
Detection of multiple explosives by surface enhanced Raman scattering
Get PDFMilitary grade explosives such as 2,4,6-trinitroluene (TNT) are still a major worldwide concern in terms of terror threat and environmental impact. The most common methods currently employed for the detection of explosives involve colourimetric tests, which are known to be rapid and portable, however often display false positives and lack sensitivity. Other methods used include ion mobility mass spectrometry, gas chromatography - mass spectrometry (GC-MS) and liquid chromatography - mass spectrometry (LC-MS), which despite producing more reliable results; require large, expensive instrumentation and specially trained staff. This main aim of this research was to develop a novel method of explosives detection which had the capability of detecting multiple explosive compounds simultaneously in a robust, quick and sensitive assay format, which was easily translatable for use in the field. Initially, this research focussed on commercially available SERS substrates as a method of detection for the nitroaromatic explosives TNT, tetryl and HNS. The major disadvantage of this method of detection was the sensitivity, reproducibility and cost of the SERS substrates making them unsuitable for the detection of low levels of analyte. This led to the investigation of SERS detection using silver nanoparticles combined with modification of the explosives TNT, tetryl and HNS into SERRS active species for the development of a more selective and readily translatable solution based method of detection. Furthermore, TNT could be positively identified in samples which contained various interferents and contaminants which is representative of "real world" samples. Finally, the use of aptamers and molecular beacons was investigated as a means of qualitative detection of the illicit drug, methamphetamine and single stranded DNA sequences which code for disease. Methamphetamine was chosen as the target for proof-of-concept work in which aptamers could be used for the detection of small molecules, namely drugs and explosives using an "off" to "on" molecular beacon approach combined with SERS.Military grade explosives such as 2,4,6-trinitroluene (TNT) are still a major worldwide concern in terms of terror threat and environmental impact. The most common methods currently employed for the detection of explosives involve colourimetric tests, which are known to be rapid and portable, however often display false positives and lack sensitivity. Other methods used include ion mobility mass spectrometry, gas chromatography - mass spectrometry (GC-MS) and liquid chromatography - mass spectrometry (LC-MS), which despite producing more reliable results; require large, expensive instrumentation and specially trained staff. This main aim of this research was to develop a novel method of explosives detection which had the capability of detecting multiple explosive compounds simultaneously in a robust, quick and sensitive assay format, which was easily translatable for use in the field. Initially, this research focussed on commercially available SERS substrates as a method of detection for the nitroaromatic explosives TNT, tetryl and HNS. The major disadvantage of this method of detection was the sensitivity, reproducibility and cost of the SERS substrates making them unsuitable for the detection of low levels of analyte. This led to the investigation of SERS detection using silver nanoparticles combined with modification of the explosives TNT, tetryl and HNS into SERRS active species for the development of a more selective and readily translatable solution based method of detection. Furthermore, TNT could be positively identified in samples which contained various interferents and contaminants which is representative of "real world" samples. Finally, the use of aptamers and molecular beacons was investigated as a means of qualitative detection of the illicit drug, methamphetamine and single stranded DNA sequences which code for disease. Methamphetamine was chosen as the target for proof-of-concept work in which aptamers could be used for the detection of small molecules, namely drugs and explosives using an "off" to "on" molecular beacon approach combined with SERS
Ultrafast infrared spectroscopy investigation of DNA-ligand interactions
Get PDFTwo-dimensional infrared spectroscopy (2D-IR) is a label-free analysis method that can provide structural insight into biological processes by uncovering the coupling between the intrinsic, vibrational modes of a molecule. Technological advancements in the last decade have drastically reduced acquisition times for 2D-IR spectra from several hours down to seconds, enabling researches to perform 2D-IR experiments with unprecedented samples sizes and complexity. This thesis applies 2D-IR spectroscopy as a high-throughput analysis method to study non-covalent binding of small molecules to minor grooves of DNA duplex structures. Minor groove binding to DNA is relevant in the development of potential new therapeutics that target specific DNA sequences to influence a biological process. The conception of a 2D-IR screening experiment will therefore allow for an assessment of sequence-specific ligand interactions across multiple different binding sites. Minor groove binding of two different types of ligands are investigated in this thesis. Application of the 2D-IR method in the context of screening is first assessed in a proof of-concept by studying the interaction of a well-established DNA stain, Hoechst 33258, across a set of different dsDNA sequences. In the following chapter, 2D-IR spectroscopyis applied again to study the interaction of three new types of hairpin polyamide ligands, screened across a set of different minor grooves. The final chapter revisits the Hoechst 33258 system to investigate the impact of minor groove binding at non-equilibrium conditions using a laser-induced temperature jump. This chapter is part of preliminary work to develop a temperature-jump, 2D-IR experiment in the future.Two-dimensional infrared spectroscopy (2D-IR) is a label-free analysis method that can provide structural insight into biological processes by uncovering the coupling between the intrinsic, vibrational modes of a molecule. Technological advancements in the last decade have drastically reduced acquisition times for 2D-IR spectra from several hours down to seconds, enabling researches to perform 2D-IR experiments with unprecedented samples sizes and complexity. This thesis applies 2D-IR spectroscopy as a high-throughput analysis method to study non-covalent binding of small molecules to minor grooves of DNA duplex structures. Minor groove binding to DNA is relevant in the development of potential new therapeutics that target specific DNA sequences to influence a biological process. The conception of a 2D-IR screening experiment will therefore allow for an assessment of sequence-specific ligand interactions across multiple different binding sites. Minor groove binding of two different types of ligands are investigated in this thesis. Application of the 2D-IR method in the context of screening is first assessed in a proof of-concept by studying the interaction of a well-established DNA stain, Hoechst 33258, across a set of different dsDNA sequences. In the following chapter, 2D-IR spectroscopyis applied again to study the interaction of three new types of hairpin polyamide ligands, screened across a set of different minor grooves. The final chapter revisits the Hoechst 33258 system to investigate the impact of minor groove binding at non-equilibrium conditions using a laser-induced temperature jump. This chapter is part of preliminary work to develop a temperature-jump, 2D-IR experiment in the future
A comparison of Scottish and Norwegian hutting traditions, with particular reference to the communities of Carbeth and Lindøya 1905-2013
Get PDFThis thesis compares the origins and development of hutting as a leisure activity in Scotland and Norway through statistical comparison, examination of historical context, analysis of hitherto unpublished Scottish Government research and case studies of two hutting communities set up near Oslo and Glasgow in 1922. The evidence suggests hutting blossomed in Norway because a history of widespread and relatively uncontested landownership made Norwegians feel connected to nature and able to obtain individual hut sites in desirable, secluded, wooded settings with relative ease compared to the precarious and strictly-ordered hutting communities established by Scots. The enduring difficulty of buying or securely leasing a tiny strip of land in Scotland from private land or forest owners thwarted the expansion of hutting here beyond tightly packed, working class communities to the widely scattered, individually-sited cabins favoured by most Norwegians. This research suggests these different traditions are the result of similar political, economic and social forces coming to bear on fundamentally different democratic landscapes. Themes explored include the history of farming, forestry, landownership, urbanisation, industrialisation, housing, leisure and holiday provision for workers. Contemporary political and economic developments are examined along with the role of determined individuals in ignoring prevailing social norms. Early urbanisation seems less important in explaining the relative absence of huts in Scotland than the difficulty of accessing and retaining land which in turn, prompted the development of legislation, further embedding social outlooks that regarded huts as problematic and ideal landscapes as empty and "development-free."This thesis compares the origins and development of hutting as a leisure activity in Scotland and Norway through statistical comparison, examination of historical context, analysis of hitherto unpublished Scottish Government research and case studies of two hutting communities set up near Oslo and Glasgow in 1922. The evidence suggests hutting blossomed in Norway because a history of widespread and relatively uncontested landownership made Norwegians feel connected to nature and able to obtain individual hut sites in desirable, secluded, wooded settings with relative ease compared to the precarious and strictly-ordered hutting communities established by Scots. The enduring difficulty of buying or securely leasing a tiny strip of land in Scotland from private land or forest owners thwarted the expansion of hutting here beyond tightly packed, working class communities to the widely scattered, individually-sited cabins favoured by most Norwegians. This research suggests these different traditions are the result of similar political, economic and social forces coming to bear on fundamentally different democratic landscapes. Themes explored include the history of farming, forestry, landownership, urbanisation, industrialisation, housing, leisure and holiday provision for workers. Contemporary political and economic developments are examined along with the role of determined individuals in ignoring prevailing social norms. Early urbanisation seems less important in explaining the relative absence of huts in Scotland than the difficulty of accessing and retaining land which in turn, prompted the development of legislation, further embedding social outlooks that regarded huts as problematic and ideal landscapes as empty and "development-free.
Building skills for conserving seventeenth- and eighteenth-century Scottish built heritage : the initial assessment of timber roof structures
Get PDFThis thesis researches seventeenth- and eighteenth-century timber roof structures in Scotland,which had been largely forgotten up to now. Previous studies fail in characterizing the extent and nature of historic timber roofs in Scotland, especially post-1650, mainly because of the scarcity of measured surveys. This lack of knowledge, together with the lack of specific standards and training for the assessment of existing timber structures, hinders good conservation practice. Scottish professionals rely mainly on traditional methods and past experience, which makes it difficult for them to reach a confident structural assessment. The result is that many roofs are heavily altered or replaced.The thesis investigates the extent, nature and condition of seventeenth- and eighteenth-century timber roof structures in Scotland in order to raise awareness about their value and contribute in improving conservation practice. A database of 1500 Scottish buildings of the period has been created and a representative sample of 59 original timber roofs has been surveyed. Archival research has also been carried out. This has allowed tracing the historic development of seventeenth- and eighteenth-century timber roof structures in Scotland and demonstrating that they form a heritage of great extent and quality. For the first time overall structural arrangements, construction methods and details, the species and quality of the timber employed, the role of architects, wrights and patrons in the design process and foreign influences have been comprehensively described and classified. The data gathered during the surveys has also been used to identify typical pathologies and possible causes for each roof structural typology. Moreover, the assessment techniques used during the surveys have been evaluated in terms of effectiveness, reliability, costs and training needed, in order to inform specific training for conservation professionals.This thesis researches seventeenth- and eighteenth-century timber roof structures in Scotland,which had been largely forgotten up to now. Previous studies fail in characterizing the extent and nature of historic timber roofs in Scotland, especially post-1650, mainly because of the scarcity of measured surveys. This lack of knowledge, together with the lack of specific standards and training for the assessment of existing timber structures, hinders good conservation practice. Scottish professionals rely mainly on traditional methods and past experience, which makes it difficult for them to reach a confident structural assessment. The result is that many roofs are heavily altered or replaced.The thesis investigates the extent, nature and condition of seventeenth- and eighteenth-century timber roof structures in Scotland in order to raise awareness about their value and contribute in improving conservation practice. A database of 1500 Scottish buildings of the period has been created and a representative sample of 59 original timber roofs has been surveyed. Archival research has also been carried out. This has allowed tracing the historic development of seventeenth- and eighteenth-century timber roof structures in Scotland and demonstrating that they form a heritage of great extent and quality. For the first time overall structural arrangements, construction methods and details, the species and quality of the timber employed, the role of architects, wrights and patrons in the design process and foreign influences have been comprehensively described and classified. The data gathered during the surveys has also been used to identify typical pathologies and possible causes for each roof structural typology. Moreover, the assessment techniques used during the surveys have been evaluated in terms of effectiveness, reliability, costs and training needed, in order to inform specific training for conservation professionals
Wear assesment of superplastic forming ceramic dies : a study on protective coating performance
Get PDFSuperplastic forming (SPF) is an advanced manufacturing process, typically restricted to low volume and high value products, where metallic sheets are heated at the superplastic temperature and blow formed into a metallic die. Refractory ceramics are a low cost option to substitute the high temperature resistant steels and other alloys conventionally used in SPF dies, but their brittle nature is a limiting factor for most SPF applications. Suitable surface coatings have shown a significant effect on wear resistance in different applications and can be employed to improve the SPF ceramic performance in terms of tool life. This thesis addresses the lack of testing methods available to assess wear of dies under SPF conditions. A die-part interface (DPI) test method has been developed to assess wear of ceramic dies for sheet metal forming applications. In addition, the thesis discusses the employment of the DPI test to take strategic decisions in different material selection studies. A study is conducted on the comparison of two uncoated ceramic materials, Ceradyne ThermoSil ® 220 (ceramic CT) and Horizon Chrome infiltrated (ceramic HC), where DPI test results show that Ceradyne ceramic material has overall better performance under SPF conditions, thus its outcomes from the DPI test are considered the baseline to be compared with in further studies. Two deposition procedures of the same coating material, petalite, have been developed resulting in coating PET-A and PET-B. The resulting coatings are compared through DPI test, resulting in a better performance of the coating fired at higher temperature (PET-B). Three coating materials are assessed with the DPI test, which shows that two coatings soften under SPF conditions (F-50 and JK-N8), while another coating shows poor adhesion to the substrate (F-40). The thesis concludes presenting a DPI test protocol that proposes guidelines for die surface wear assessment under SPF conditions.Superplastic forming (SPF) is an advanced manufacturing process, typically restricted to low volume and high value products, where metallic sheets are heated at the superplastic temperature and blow formed into a metallic die. Refractory ceramics are a low cost option to substitute the high temperature resistant steels and other alloys conventionally used in SPF dies, but their brittle nature is a limiting factor for most SPF applications. Suitable surface coatings have shown a significant effect on wear resistance in different applications and can be employed to improve the SPF ceramic performance in terms of tool life. This thesis addresses the lack of testing methods available to assess wear of dies under SPF conditions. A die-part interface (DPI) test method has been developed to assess wear of ceramic dies for sheet metal forming applications. In addition, the thesis discusses the employment of the DPI test to take strategic decisions in different material selection studies. A study is conducted on the comparison of two uncoated ceramic materials, Ceradyne ThermoSil ® 220 (ceramic CT) and Horizon Chrome infiltrated (ceramic HC), where DPI test results show that Ceradyne ceramic material has overall better performance under SPF conditions, thus its outcomes from the DPI test are considered the baseline to be compared with in further studies. Two deposition procedures of the same coating material, petalite, have been developed resulting in coating PET-A and PET-B. The resulting coatings are compared through DPI test, resulting in a better performance of the coating fired at higher temperature (PET-B). Three coating materials are assessed with the DPI test, which shows that two coatings soften under SPF conditions (F-50 and JK-N8), while another coating shows poor adhesion to the substrate (F-40). The thesis concludes presenting a DPI test protocol that proposes guidelines for die surface wear assessment under SPF conditions
Enhanced ultrasonic techniques for inspection of pressure tubes
Get PDFPressure tube inspection within CANDU nuclear reactors is a critical maintenance operation to identify and track the growth of defects. Current inspection approaches utilising ultrasonic techniques are technically challenging due to transducer alignment caused by the tube dimensional changes. This Thesis focuses on enhancing ultrasonic techniques to improve the inspection accuracy by introducing signal processing algorithms and phased array technology. This work is motivated by the nuclear industry desire to reduce the time and cost consuming replica processes.;The Synthetic Aperture Focusing Technique (SAFT) has been applied to industrial inspection data where the ultrasonic image performance is poorly-focused. The transducer focal point operates as a virtual source to transmit ultrasound with a corresponding beam angle. Subsequently, the refocused image demonstrates a distinct improvement in the measurement of defect width.;Regarding to the defect depth measurement, this Thesis proposes a wavelet analysis method, which employs the Haar wavelet to decompose the original poorly-focused A-scan signal and reconstruct the defect information from selected frequency components within the transducer operational bandwidth. Compared to the original image characterisation, this method provides an improved estimate of defect depth within an acceptable error ±0.04 mm.;A hybrid simulation platform for ultrasonic phased array transducer inspection has been developed and experimentally validated, which combines the benefits of finite element modelling and analytical extrapolation. This approach has been used to study a range of phased array imaging solutions based on both the Total Focusing Method and array SAFT processing.;The phased array technique is predicted to improve the accuracy of characterising defects on the inner and outer surfaces of the pressure tube and a dual array system incorporating 32-element 5 and 10 MHz arrays is proposed as a potential future sensor head configuration. The results conclude there is significant potential to improve the quality of the inspection data.Pressure tube inspection within CANDU nuclear reactors is a critical maintenance operation to identify and track the growth of defects. Current inspection approaches utilising ultrasonic techniques are technically challenging due to transducer alignment caused by the tube dimensional changes. This Thesis focuses on enhancing ultrasonic techniques to improve the inspection accuracy by introducing signal processing algorithms and phased array technology. This work is motivated by the nuclear industry desire to reduce the time and cost consuming replica processes.;The Synthetic Aperture Focusing Technique (SAFT) has been applied to industrial inspection data where the ultrasonic image performance is poorly-focused. The transducer focal point operates as a virtual source to transmit ultrasound with a corresponding beam angle. Subsequently, the refocused image demonstrates a distinct improvement in the measurement of defect width.;Regarding to the defect depth measurement, this Thesis proposes a wavelet analysis method, which employs the Haar wavelet to decompose the original poorly-focused A-scan signal and reconstruct the defect information from selected frequency components within the transducer operational bandwidth. Compared to the original image characterisation, this method provides an improved estimate of defect depth within an acceptable error ±0.04 mm.;A hybrid simulation platform for ultrasonic phased array transducer inspection has been developed and experimentally validated, which combines the benefits of finite element modelling and analytical extrapolation. This approach has been used to study a range of phased array imaging solutions based on both the Total Focusing Method and array SAFT processing.;The phased array technique is predicted to improve the accuracy of characterising defects on the inner and outer surfaces of the pressure tube and a dual array system incorporating 32-element 5 and 10 MHz arrays is proposed as a potential future sensor head configuration. The results conclude there is significant potential to improve the quality of the inspection data
Design and fabrication of superhydrophobic and antimicrobial surfaces on AISI 316L stainless steel
Get PDFThis thesis was previously held under moratorium from 16/09/2019 to 21/05/2021.In a surgical procedure, the medical devices come into contact with blood, which increases the risk of the formation of blood clots, also known as thrombi. Antimicrobial resistance is another pressing issue in the healthcare field. With the increasing consumption of antimicrobial drugs, the threat of antimicrobial resistance is rising, and the global dimensions of this trend have been increasingly recognised. Some new strategies that utilise superhydrophobicity or antimicrobial properties to medical devices have garnered more attention and interest.;Superhydrophobic surfaces have attracted extensive attention over the past decade, primarily due to their self-cleaning, corrosion resistance, anti-icing and drag reduction abilities. The ability to reduce blood adhesion is one of the critical benefits of these types of surfaces. Nanosecond pulsed laser ablation is considered to be a promising technique for the industrial fabrication of superhydrophobic structures due to its high efficiency and low-cost. In this PhD thesis, nanosecond pulsed laser-based ablation technology was developed to manufacture functional surfaces that have superhydrophobicity or antimicrobial properties on AISI 316L stainless steel.;To achieve that goal, a deterministic design method was developed to design the dimensions of the microstructures to be fabricated by laser ablation in order to maximise superhydrophobicity. Then computational fluid dynamics (CFD) simulation was conducted to explore the underlying mechanism of superhydrophobicity and predict the hydrophobicity of the designed structures. The simulation results proved that the substrates trapped a large volume of air with high pressure at the bottom of the structures, which is critical to achieving stable superhydrophobicity.;Moreover, the superhydrophobic substrate has greater potential energy and kinetic energy in the water droplet's impacting process, which helps explain its self-cleaning and low-adhesion properties.;In the next step, the process and the product fingerprints are proposed for the first time to identify the correlations among the machining parameters, surface topography and functional performance (i.e. the contact angle of the laser ablated superhydrophobic surface on AISI 316L stainless steel) of the specimen. The dimensionless surface functional characterisation parameter Rhy (i.e. the average ratio of Rz to Rsm) has maximum values of Spearman and Kendall rank correlation coefficients with contact angle, which can be regarded as the product fingerprint.;The laser pulse energy per unit area on the specimen (Is) represents the combined effect of the laser power, exposure time and pitch of the structure on the surface topography, and it is the best process fingerprint that can be used to control the product fingerprint Rhy. The threshold values of Rhy and Is are 0.41 and 536 J/mm2, respectively, ensuring the specimen's superhydrophobicity (contact angle larger than 150°) in the laser ablation process.;Finally, two new hybrid processes based on laser ablation were developed to manufacture functional surfaces with anisotropic superhydrophobicity and antimicrobial properties. First, a sequential process of laser ablation and chemical etching (LA-CE) was proposed to produce ratchet-like microstructures on AISI 316L stainless steel. The experimental investigation concluded that the direction of the microstructures is the same as the direction of the laser beam feed. Moreover, the droplet easily rolls off the surface in the laser beam feed direction; however, it is pinned tightly in the opposite direction.;This study was the first to use a single-step fabrication approach (StruCoat) to develop the antimicrobial surfaces based on laser ablation technology in order to generate the antimicrobial microstructures coated with silver nanoparticles (AgNPs) on AISI 316L stainless steel.;Furthermore, StruCoat helped increase the cooling rate of the substrate in the laser ablation process, resulting in a significant decrease in the material grain size (by 81%). Furthermore, antimicrobial efficacy testing also demonstrated the enhanced antimicrobial properties of StruCoat, with an 86.2% antimicrobial rate against Staphylococcus aureus, in comparison to the unmodified specimens.In a surgical procedure, the medical devices come into contact with blood, which increases the risk of the formation of blood clots, also known as thrombi. Antimicrobial resistance is another pressing issue in the healthcare field. With the increasing consumption of antimicrobial drugs, the threat of antimicrobial resistance is rising, and the global dimensions of this trend have been increasingly recognised. Some new strategies that utilise superhydrophobicity or antimicrobial properties to medical devices have garnered more attention and interest.;Superhydrophobic surfaces have attracted extensive attention over the past decade, primarily due to their self-cleaning, corrosion resistance, anti-icing and drag reduction abilities. The ability to reduce blood adhesion is one of the critical benefits of these types of surfaces. Nanosecond pulsed laser ablation is considered to be a promising technique for the industrial fabrication of superhydrophobic structures due to its high efficiency and low-cost. In this PhD thesis, nanosecond pulsed laser-based ablation technology was developed to manufacture functional surfaces that have superhydrophobicity or antimicrobial properties on AISI 316L stainless steel.;To achieve that goal, a deterministic design method was developed to design the dimensions of the microstructures to be fabricated by laser ablation in order to maximise superhydrophobicity. Then computational fluid dynamics (CFD) simulation was conducted to explore the underlying mechanism of superhydrophobicity and predict the hydrophobicity of the designed structures. The simulation results proved that the substrates trapped a large volume of air with high pressure at the bottom of the structures, which is critical to achieving stable superhydrophobicity.;Moreover, the superhydrophobic substrate has greater potential energy and kinetic energy in the water droplet's impacting process, which helps explain its self-cleaning and low-adhesion properties.;In the next step, the process and the product fingerprints are proposed for the first time to identify the correlations among the machining parameters, surface topography and functional performance (i.e. the contact angle of the laser ablated superhydrophobic surface on AISI 316L stainless steel) of the specimen. The dimensionless surface functional characterisation parameter Rhy (i.e. the average ratio of Rz to Rsm) has maximum values of Spearman and Kendall rank correlation coefficients with contact angle, which can be regarded as the product fingerprint.;The laser pulse energy per unit area on the specimen (Is) represents the combined effect of the laser power, exposure time and pitch of the structure on the surface topography, and it is the best process fingerprint that can be used to control the product fingerprint Rhy. The threshold values of Rhy and Is are 0.41 and 536 J/mm2, respectively, ensuring the specimen's superhydrophobicity (contact angle larger than 150°) in the laser ablation process.;Finally, two new hybrid processes based on laser ablation were developed to manufacture functional surfaces with anisotropic superhydrophobicity and antimicrobial properties. First, a sequential process of laser ablation and chemical etching (LA-CE) was proposed to produce ratchet-like microstructures on AISI 316L stainless steel. The experimental investigation concluded that the direction of the microstructures is the same as the direction of the laser beam feed. Moreover, the droplet easily rolls off the surface in the laser beam feed direction; however, it is pinned tightly in the opposite direction.;This study was the first to use a single-step fabrication approach (StruCoat) to develop the antimicrobial surfaces based on laser ablation technology in order to generate the antimicrobial microstructures coated with silver nanoparticles (AgNPs) on AISI 316L stainless steel.;Furthermore, StruCoat helped increase the cooling rate of the substrate in the laser ablation process, resulting in a significant decrease in the material grain size (by 81%). Furthermore, antimicrobial efficacy testing also demonstrated the enhanced antimicrobial properties of StruCoat, with an 86.2% antimicrobial rate against Staphylococcus aureus, in comparison to the unmodified specimens
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