Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and t... more Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and therefore requires reliable, accurate, and reproducible measurements with well-understood uncertainties. This is needed regardless of the production method or manufacturer because it is important for all GR2M products to be globally comparable. An international interlaboratory comparison on thickness measurements of graphene oxide flakes using atomic force microscopy has been completed in technical working area 41 of versailles project on advanced materials and standards. Twelve laboratories participated in the comparison project, led by NIM, China, to improve the equivalence of thickness measurement for two-dimensional flakes. The measurement methods, uncertainty evaluation and a comparison of the results and analysis are reported in this manuscript. The data and results of this project will be directly used to support the development of an ISO standard.
The estimation of nanoparticle number concentration in colloidal suspensions is a prerequisite in... more The estimation of nanoparticle number concentration in colloidal suspensions is a prerequisite in many procedures, and in particular in multi-stage, low-yield reactions. Here, we describe a rapid, non-destructive method based on optical extinction and dynamic light scattering (DLS), which combines measurements using common bench-top instrumentation with a numerical algorithm to calculate the particle size distribution (PSD) and concentration. These quantities were derived from Mie theory applied to measurements of the optical extinction spectrum of homogeneous, non-absorbing nanoparticles, and the relative PSD of a colloidal suspension. The work presents an approach to account for PSDs achieved by DLS which, due to the underlying model, may not be representative of the true sample PSD. The presented approach estimates the absolute particle number concentration of samples with mono-, bi-modal and broad size distributions with <50% precision. This provides a convenient and practical solution for number concentration estimation required during many applications of colloidal nanomaterials.
The rapid development of nanotechnology has led to concerns over their environmental risk. Curren... more The rapid development of nanotechnology has led to concerns over their environmental risk. Current analytical techniques are underdeveloped and lack the sensitivity and specificity to characterize these materials in complex environmental and biological matrices. To this end, single particle ICP-MS (spICP-MS) has been developed in the past decade, with the capability to detect and characterize nanomaterials at environmentally relevant concentrations in complex environmental and biological matrices. However, some nanomaterials are composed of elements inherently difficult to quantify by quadrupole ICP-MS due to abundant molecular interferences, such as dinitrogen ions interfering with the detection of silicon. Three approaches aimed at reducing the contribution of these background molecular interferences in the analysis of (28)Si are explored in an attempt to detect and characterize silica colloids. Helium collision cell gases and reactive ammonia gas are investigated for their conventional use in reducing the signal generated from the dinitrogen interference and background silicon ions leaching from glass components of the instrumentation. A new approach brought on by the advent of microsecond dwell times in single particle ICP-MS allows for the detection and characterization of silica colloids without the need for these cell gases, as at shorter dwell times the proportion of signal attributed to a nanoparticle event is greater relative to the constant dinitrogen signal. It is demonstrated that the accurate detection and characterization of these materials will be reliant on achieving a balance between reducing the contribution of the background interference, while still registering the maximum amount of signal generated by the particle event.
This thesis presents a study of the mechanical properties of thin films. The main aim was to dete... more This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work. The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out. The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films. It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings. In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H + ions at doses exceeding 3x10 16 ions/cm 2 , the mechanical properties closely resembled those of films that were conventionally fired to 450°C.
This thesis presents a study of the mechanical properties of thin films. The main aim was to dete... more This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work. The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out. The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films. It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings. In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H + ions at doses exceeding 3x10 16 ions/cm 2 , the mechanical properties closely resembled those of films that were conventionally fired to 450°C.
The mechanical properties of thin films of two allotropic modifications of alumina have been exam... more The mechanical properties of thin films of two allotropic modifications of alumina have been examined. These coatings were chemically vapour deposited onto cemented carbide substrates and the film ...
Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and t... more Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and therefore requires reliable, accurate, and reproducible measurements with well-understood uncertainties. This is needed regardless of the production method or manufacturer because it is important for all GR2M products to be globally comparable. An international interlaboratory comparison on thickness measurements of graphene oxide flakes using atomic force microscopy has been completed in technical working area 41 of versailles project on advanced materials and standards. Twelve laboratories participated in the comparison project, led by NIM, China, to improve the equivalence of thickness measurement for two-dimensional flakes. The measurement methods, uncertainty evaluation and a comparison of the results and analysis are reported in this manuscript. The data and results of this project will be directly used to support the development of an ISO standard.
The estimation of nanoparticle number concentration in colloidal suspensions is a prerequisite in... more The estimation of nanoparticle number concentration in colloidal suspensions is a prerequisite in many procedures, and in particular in multi-stage, low-yield reactions. Here, we describe a rapid, non-destructive method based on optical extinction and dynamic light scattering (DLS), which combines measurements using common bench-top instrumentation with a numerical algorithm to calculate the particle size distribution (PSD) and concentration. These quantities were derived from Mie theory applied to measurements of the optical extinction spectrum of homogeneous, non-absorbing nanoparticles, and the relative PSD of a colloidal suspension. The work presents an approach to account for PSDs achieved by DLS which, due to the underlying model, may not be representative of the true sample PSD. The presented approach estimates the absolute particle number concentration of samples with mono-, bi-modal and broad size distributions with <50% precision. This provides a convenient and practical solution for number concentration estimation required during many applications of colloidal nanomaterials.
The rapid development of nanotechnology has led to concerns over their environmental risk. Curren... more The rapid development of nanotechnology has led to concerns over their environmental risk. Current analytical techniques are underdeveloped and lack the sensitivity and specificity to characterize these materials in complex environmental and biological matrices. To this end, single particle ICP-MS (spICP-MS) has been developed in the past decade, with the capability to detect and characterize nanomaterials at environmentally relevant concentrations in complex environmental and biological matrices. However, some nanomaterials are composed of elements inherently difficult to quantify by quadrupole ICP-MS due to abundant molecular interferences, such as dinitrogen ions interfering with the detection of silicon. Three approaches aimed at reducing the contribution of these background molecular interferences in the analysis of (28)Si are explored in an attempt to detect and characterize silica colloids. Helium collision cell gases and reactive ammonia gas are investigated for their conventional use in reducing the signal generated from the dinitrogen interference and background silicon ions leaching from glass components of the instrumentation. A new approach brought on by the advent of microsecond dwell times in single particle ICP-MS allows for the detection and characterization of silica colloids without the need for these cell gases, as at shorter dwell times the proportion of signal attributed to a nanoparticle event is greater relative to the constant dinitrogen signal. It is demonstrated that the accurate detection and characterization of these materials will be reliant on achieving a balance between reducing the contribution of the background interference, while still registering the maximum amount of signal generated by the particle event.
This thesis presents a study of the mechanical properties of thin films. The main aim was to dete... more This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work. The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out. The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films. It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings. In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H + ions at doses exceeding 3x10 16 ions/cm 2 , the mechanical properties closely resembled those of films that were conventionally fired to 450°C.
This thesis presents a study of the mechanical properties of thin films. The main aim was to dete... more This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work. The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out. The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films. It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings. In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H + ions at doses exceeding 3x10 16 ions/cm 2 , the mechanical properties closely resembled those of films that were conventionally fired to 450°C.
The mechanical properties of thin films of two allotropic modifications of alumina have been exam... more The mechanical properties of thin films of two allotropic modifications of alumina have been examined. These coatings were chemically vapour deposited onto cemented carbide substrates and the film ...
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