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Steve D Sharples – One of the best experts on this subject based on the ideXlab platform.

  • Single Pixel Camera Methodologies for Spatially Resolved Acoustic Spectroscopy
    Applied Physics Letters, 2021
    Co-Authors: Rikesh Patel, Steve D Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    Spatially resolved Acoustic Spectroscopy (SRAS) is a laser ultrasound technique used to determine the crystallographic orientation (i.e. microstructure) of materials through the generation and measurement of surface Acoustic wave velocity on a sample. Previous implementations have used a grating pattern imaged onto the surface to control the frequency of the generated wave in a single direction-grain orientation can be computed by acquiring wave velocities in different directions on the surface (gathered by physically rotating the grating pattern). This paper reports an advance to this methodology, inspired by single pixel cameras, using a coded grating pattern, created using a spatial light modulator, to excite surface Acoustic waves in multiple directions simultaneously. This change to the optical arrangement can simplify the overall system alignment, remove mechanical complexities and is well suited for point-by-point full orientation imaging, potentially allowing for faster orientation imaging using SRAS microscopy. Improvements to the robustness of measurement may be expected to extend the applicability of SRAS in the material science field. To demonstrate this methodology, experiments were conducted on isotropic and anisotropic samples.

  • Spatially resolved Acoustic Spectroscopy (SRAS) microstructural imaging
    , 2019
    Co-Authors: Matt Clark, Steve D Sharples, Rikesh Patel, Adam T. Clare, Paul Dryburgh, Don Pieris, Richard J. Smith
    Abstract:

    Spatially resolved Acoustic Spectroscopy (SRAS) is an Acoustic microscopy technique that can image the microstructure and measure the crystallographic orientation of grains or crystals in the material.It works by measuring the velocity of surface Acoustic waves (SAWs) via the Acoustic spectrum. In the usual configuration, the SAWs are generated by laser using a pattern of lines and detected by laser at a point close to this grating-like source. The use of the Acoustic spectrum as a means of measuring the velocity has a number of practical advantages which makes the technique robust and fast and gives good spatial resolution. This makes the measurement suitable for imaging and gives it many advantages over traditional laser UT and microstructural measurement techniques.As SRAS is a laser ultrasound testing technique (LUT) which can be applied to a wide range of industrially relevant samples as a non-destructive evaluation technique. There are no size limitations on the samples that can be imaged and the surface preparation required is significantly more relaxed than many other techniques with the capability of operating on many as manufactured finishes. This permits the use of SRAS as an online inspection tool, for instance during additive or subtractive manufacturing, as a QA tool during manufacture or as an NDE/T tool in service.Spatially resolved Acoustic Spectroscopy (SRAS) is an Acoustic microscopy technique that can image the microstructure and measure the crystallographic orientation of grains or crystals in the material.It works by measuring the velocity of surface Acoustic waves (SAWs) via the Acoustic spectrum. In the usual configuration, the SAWs are generated by laser using a pattern of lines and detected by laser at a point close to this grating-like source. The use of the Acoustic spectrum as a means of measuring the velocity has a number of practical advantages which makes the technique robust and fast and gives good spatial resolution. This makes the measurement suitable for imaging and gives it many advantages over traditional laser UT and microstructural measurement techniques.As SRAS is a laser ultrasound testing technique (LUT) which can be applied to a wide range of industrially relevant samples as a non-destructive evaluation technique. There are no size limitations on the samples that can be imaged and the su…

  • Orientation imaging of macro-sized polysilicon grains on wafers using spatially resolved Acoustic Spectroscopy
    Scripta Materialia, 2017
    Co-Authors: Rikesh Patel, Richard J. Smith, Steve D Sharples, Wenqi Li, Matt Clark
    Abstract:

    Due to its economical production process polysilicon, or multicrystalline silicon, is widely used to produce solar cell wafers. However, the conversion efficiencies are often lower than equivalent monocrystalline or thin film cells, with the structure and orientation of the silicon grains strongly linked to the efficiency. We present a non-destructive laser ultrasonic inspection technique, capable of characterising large (52 × 76 mm2) photocell‘s microstructure – measurement times, sample surface preparation and system upgrades for silicon scanning are discussed. This system, known as spatially resolved Acoustic Spectroscopy (SRAS) could be used to optimise the polysilicon wafer production process and potentially improve efficiency.

Milan Timko – One of the best experts on this subject based on the ideXlab platform.

  • Acoustic Spectroscopy of functionalized carbon nanotubes in magnetic fluid
    Journal of Magnetism and Magnetic Materials, 2020
    Co-Authors: Jozef Kúdelčík, Milan Timko, Peter Bury, Peter Kopcansky, Stefan Hardoň, Zuzana Mitróová
    Abstract:

    Abstract Acoustic Spectroscopy is used to study the rearrangements of multi-walled carbon nanonanotubes (MWCNTs) functionalized by Fe3O4 magnetic nanoparticles dissolved in transformer oil under the influence of a magnetic field at various temperatures. Three methods for the application of the magnetic field are used: a jump change, a linear increase or decrease and a constant magnetic field with a change of its orientation to the Acoustic wave. The rearrangements of MWCNTs/Fe3O4 to new structures (chains) by the influence of a magnetic field is confirmed by changes in the Acoustic attenuation. From the measurement results, the lifetime of the chains after the switch-off of the magnetic field is less than 30 s. Such a rapid change is due to the fact that the nanotube chains are held by magnetic forces, resulting from the same direction of the magnetic moments of bound magnetic nanoparticles. A temperature-dependent hysteresis effect is observed with a linear change of the magnetic field. From our experiments, it follows that the reorientation of MWCNTs by magnetic nanoparticles with the magnetic field was gradual. The effect of the anisotropy of the Acoustic attenuation is observed at a magnetic flux density of 200 mT and at various temperatures. Three MWCNT/Fe3O4 concentrations diluted in the transformer oil are used for the measurements and their influences on the structural changes with various developments of the magnetic field are discussed.

  • Study of structural arrangement in ferrofluid by dielectric and Acoustic Spectroscopy
    2018 ELEKTRO, 2018
    Co-Authors: Stefan Hardon, Jozef Kúdelčík, Milan Timko, Peter Bury, Michal Rajnak, Peter Kopcansky
    Abstract:

    In the paper two methods of investigation of ferrofluid in magnetic and electric fields were used, namely the Acoustic and the dielectric Spectroscopy. The measurements were done at temperature 15 °C. The effect of structural changes in ferrofluid upon the effect of a magnetic field by the Acoustic Spectroscopy was studied. At jump change of the magnetic field to 100, 200 and 300 mT a continuous change of the Acoustic attenuation caused by an aggregation of magnetic nanoparticles to new structures was observed. The changes in dielectric parameters and structural arrangement of magnetic nanoparticles in ferrofluid upon the effect of magnetic and electric fields have been studied by the dielectric Spectroscopy, too. The frequency dependence of dissipation factor was measured by a capacitance method within the frequency range from 1 mHz to 10 kHz at the application of a magnetic and an electric fields. The magneto-dielectric effect was also observed.

  • Acoustic Spectroscopy of magnetic fluids based on transformer oil
    Journal of Intelligent Material Systems and Structures, 2016
    Co-Authors: Jozef Kúdelčík, Peter Bury, Peter Kopcansky, Stefan Hardoň, Milan Timko
    Abstract:

    The structural changes in a magnetic fluid (formation of clusters) upon the effect of an external magnetic field were studied by Acoustic Spectroscopy. The properties of magnetic fluid dispersed in inhibited transformer oil ITO 100 have been studied by the analysis of changes in the Acoustic wave absorption coefficient. The absorption coefficient of Acoustic waves was measured as a function of an external magnetic field in the range of 0-400 mT, parallel to the direction of Acoustic wave propagation. The magnetic fluids change their structure under the influence of an external magnetic field and do not return immediately to the initial state after the magnetic field switching off. It is supposed that the cluster of magnetic nanoparticles formed in the fluid subjected to a magnetic field remains after the field has been removed for the some time.

Jozef Kúdelčík – One of the best experts on this subject based on the ideXlab platform.

  • Acoustic Spectroscopy of functionalized carbon nanotubes in magnetic fluid
    Journal of Magnetism and Magnetic Materials, 2020
    Co-Authors: Jozef Kúdelčík, Milan Timko, Peter Bury, Peter Kopcansky, Stefan Hardoň, Zuzana Mitróová
    Abstract:

    Abstract Acoustic Spectroscopy is used to study the rearrangements of multi-walled carbon nanotubes (MWCNTs) functionalized by Fe3O4 magnetic nanoparticles dissolved in transformer oil under the influence of a magnetic field at various temperatures. Three methods for the application of the magnetic field are used: a jump change, a linear increase or decrease and a constant magnetic field with a change of its orientation to the Acoustic wave. The rearrangements of MWCNTs/Fe3O4 to new structures (chains) by the influence of a magnetic field is confirmed by changes in the Acoustic attenuation. From the measurement results, the lifetime of the chains after the switch-off of the magnetic field is less than 30 s. Such a rapid change is due to the fact that the nanotube chains are held by magnetic forces, resulting from the same direction of the magnetic moments of bound magnetic nanoparticles. A temperature-dependent hysteresis effect is observed with a linear change of the magnetic field. From our experiments, it follows that the reorientation of MWCNTs by magnetic nanoparticles with the magnetic field was gradual. The effect of the anisotropy of the Acoustic attenuation is observed at a magnetic flux density of 200 mT and at various temperatures. Three MWCNT/Fe3O4 concentrations diluted in the transformer oil are used for the measurements and their influences on the structural changes with various developments of the magnetic field are discussed.

  • Study of structural arrangement in ferrofluid by dielectric and Acoustic Spectroscopy
    2018 ELEKTRO, 2018
    Co-Authors: Stefan Hardon, Jozef Kúdelčík, Milan Timko, Peter Bury, Michal Rajnak, Peter Kopcansky
    Abstract:

    In the paper two methods of investigation of ferrofluid in magnetic and electric fields were used, namely the Acoustic and the dielectric Spectroscopy. The measurements were done at temperature 15 °C. The effect of structural changes in ferrofluid upon the effect of a magnetic field by the Acoustic Spectroscopy was studied. At jump change of the magnetic field to 100, 200 and 300 mT a continuous change of the Acoustic attenuation caused by an aggregation of magnetic nanoparticles to new structures was observed. The changes in dielectric parameters and structural arrangement of magnetic nanoparticles in ferrofluid upon the effect of magnetic and electric fields have been studied by the dielectric Spectroscopy, too. The frequency dependence of dissipation factor was measured by a capacitance method within the frequency range from 1 mHz to 10 kHz at the application of a magnetic and an electric fields. The magneto-dielectric effect was also observed.

  • Acoustic Spectroscopy of magnetic fluids based on transformer oil
    Journal of Intelligent Material Systems and Structures, 2016
    Co-Authors: Jozef Kúdelčík, Peter Bury, Peter Kopcansky, Stefan Hardoň, Milan Timko
    Abstract:

    The structural changes in a magnetic fluid (formation of clusters) upon the effect of an external magnetic field were studied by Acoustic Spectroscopy. The properties of magnetic fluid dispersed in inhibited transformer oil ITO 100 have been studied by the analysis of changes in the Acoustic wave absorption coefficient. The absorption coefficient of Acoustic waves was measured as a function of an external magnetic field in the range of 0-400 mT, parallel to the direction of Acoustic wave propagation. The magnetic fluids change their structure under the influence of an external magnetic field and do not return immediately to the initial state after the magnetic field switching off. It is supposed that the cluster of magnetic nanoparticles formed in the fluid subjected to a magnetic field remains after the field has been removed for the some time.

Matt Clark – One of the best experts on this subject based on the ideXlab platform.

  • Single Pixel Camera Methodologies for Spatially Resolved Acoustic Spectroscopy
    Applied Physics Letters, 2021
    Co-Authors: Rikesh Patel, Steve D Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    Spatially resolved Acoustic Spectroscopy (SRAS) is a laser ultrasound technique used to determine the crystallographic orientation (i.e. microstructure) of materials through the generation and measurement of surface Acoustic wave velocity on a sample. Previous implementations have used a grating pattern imaged onto the surface to control the frequency of the generated wave in a single direction-grain orientation can be computed by acquiring wave velocities in different directions on the surface (gathered by physically rotating the grating pattern). This paper reports an advance to this methodology, inspired by single pixel cameras, using a coded grating pattern, created using a spatial light modulator, to excite surface Acoustic waves in multiple directions simultaneously. This change to the optical arrangement can simplify the overall system alignment, remove mechanical complexities and is well suited for point-by-point full orientation imaging, potentially allowing for faster orientation imaging using SRAS microscopy. Improvements to the robustness of measurement may be expected to extend the applicability of SRAS in the material science field. To demonstrate this methodology, experiments were conducted on isotropic and anisotropic samples.

  • Spatially resolved Acoustic Spectroscopy (SRAS) microstructural imaging
    , 2019
    Co-Authors: Matt Clark, Steve D Sharples, Rikesh Patel, Adam T. Clare, Paul Dryburgh, Don Pieris, Richard J. Smith
    Abstract:

    Spatially resolved Acoustic Spectroscopy (SRAS) is an Acoustic microscopy technique that can image the microstructure and measure the crystallographic orientation of grains or crystals in the material.It works by measuring the velocity of surface Acoustic waves (SAWs) via the Acoustic spectrum. In the usual configuration, the SAWs are generated by laser using a pattern of lines and detected by laser at a point close to this grating-like source. The use of the Acoustic spectrum as a means of measuring the velocity has a number of practical advantages which makes the technique robust and fast and gives good spatial resolution. This makes the measurement suitable for imaging and gives it many advantages over traditional laser UT and microstructural measurement techniques.As SRAS is a laser ultrasound testing technique (LUT) which can be applied to a wide range of industrially relevant samples as a non-destructive evaluation technique. There are no size limitations on the samples that can be imaged and the surface preparation required is significantly more relaxed than many other techniques with the capability of operating on many as manufactured finishes. This permits the use of SRAS as an online inspection tool, for instance during additive or subtractive manufacturing, as a QA tool during manufacture or as an NDE/T tool in service.Spatially resolved Acoustic Spectroscopy (SRAS) is an Acoustic microscopy technique that can image the microstructure and measure the crystallographic orientation of grains or crystals in the material.It works by measuring the velocity of surface Acoustic waves (SAWs) via the Acoustic spectrum. In the usual configuration, the SAWs are generated by laser using a pattern of lines and detected by laser at a point close to this grating-like source. The use of the Acoustic spectrum as a means of measuring the velocity has a number of practical advantages which makes the technique robust and fast and gives good spatial resolution. This makes the measurement suitable for imaging and gives it many advantages over traditional laser UT and microstructural measurement techniques.As SRAS is a laser ultrasound testing technique (LUT) which can be applied to a wide range of industrially relevant samples as a non-destructive evaluation technique. There are no size limitations on the samples that can be imaged and the su…

  • Orientation imaging of macro-sized polysilicon grains on wafers using spatially resolved Acoustic Spectroscopy
    Scripta Materialia, 2017
    Co-Authors: Rikesh Patel, Richard J. Smith, Steve D Sharples, Wenqi Li, Matt Clark
    Abstract:

    Due to its economical production process polysilicon, or multicrystalline silicon, is widely used to produce solar cell wafers. However, the conversion efficiencies are often lower than equivalent monocrystalline or thin film cells, with the structure and orientation of the silicon grains strongly linked to the efficiency. We present a non-destructive laser ultrasonic inspection technique, capable of characterising large (52 × 76 mm2) photocell’s microstructure – measurement times, sample surface preparation and system upgrades for silicon scanning are discussed. This system, known as spatially resolved Acoustic Spectroscopy (SRAS) could be used to optimise the polysilicon wafer production process and potentially improve efficiency.

Michael G. Somekh – One of the best experts on this subject based on the ideXlab platform.

  • Single Pixel Camera Methodologies for Spatially Resolved Acoustic Spectroscopy
    Applied Physics Letters, 2021
    Co-Authors: Rikesh Patel, Steve D Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    Spatially resolved Acoustic Spectroscopy (SRAS) is a laser ultrasound technique used to determine the crystallographic orientation (i.e. microstructure) of materials through the generation and measurement of surface Acoustic wave velocity on a sample. Previous implementations have used a grating pattern imaged onto the surface to control the frequency of the generated wave in a single direction-grain orientation can be computed by acquiring wave velocities in different directions on the surface (gathered by physically rotating the grating pattern). This paper reports an advance to this methodology, inspired by single pixel cameras, using a coded grating pattern, created using a spatial light modulator, to excite surface Acoustic waves in multiple directions simultaneously. This change to the optical arrangement can simplify the overall system alignment, remove mechanical complexities and is well suited for point-by-point full orientation imaging, potentially allowing for faster orientation imaging using SRAS microscopy. Improvements to the robustness of measurement may be expected to extend the applicability of SRAS in the material science field. To demonstrate this methodology, experiments were conducted on isotropic and anisotropic samples.

  • Spatially resolved Acoustic Spectroscopy for rapid imaging of material microstructure and grain orientation
    Measurement Science and Technology, 2014
    Co-Authors: Richard J. Smith, Wenqi Li, Jethro Coulson, Matt Clark, Michael G. Somekh, Steve D Sharples
    Abstract:

    Measuring the grain structure of aerospace materials is very important to understand their mechanical properties and in-service performance. Spatially resolved Acoustic Spectroscopy is an Acoustic technique utilizing surface Acoustic waves to map the grain structure of a material. When combined with measurements in multiple Acoustic propagation directions, the grain orientation can be obtained by fitting the velocity surface to a model. The new instrument presented here can take thousands of Acoustic velocity measurements per second. The spatial and velocity resolution can be adjusted by simple modification to the system; this is discussed in detail by comparison of theoretical expectations with experimental data.

  • Frequency spectrum spatially resolved Acoustic Spectroscopy for microstructure imaging
    Journal of Physics: Conference Series, 2011
    Co-Authors: Steve D Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    The microstructure of a material influences the characteristics of a component such as its strength and stiffness. A previously described laser ultrasonic technique known as spatially resolved Acoustic Spectroscopy (SRAS) can image surface microstructure, using the local surface Acoustic wave (SAW) velocity as a contrast mechanism. The technique is robust and tolerant of Acoustic aberrations. Compared to other existing methods such as electron backscattered diffraction, SRAS is completely non-contact, non-destructive (as samples do not need to be polished and sectioned), fast, and is capable of inspecting very large components. The SAW velocity, propagating in multiple directions, can in theory be used to determine the crystallographic orientation of grains. SRAS can be implemented by using a fixed grating period with a broadband laser excitation source; the velocity is determined by analysing the measured frequency spectrum. Experimental results acquired using this “frequency spectrum SRAS” (f-SRAS) method are presented. The instrumentation has been improved such that velocity data can be acquired at 1000 points per second. The results are illustrated as velocity maps of material microstructure in two orthogonal directions. We compare velocities measured in multiple propagation direction with those predicted by the numerical model, for several cubic crystals of known orientations.