Magnetic field microscopy of rock samples using a giant magnetoresistance–based scanning magnetometer

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95412/1/ggge1634.pd

Designing a Giant Stress Impedance (GSI) Strain Sensor for Monitoring Intermediate Level Nuclear Waste (ILW) Packages

In this thesis the practicality and viability of a giant stress impedance (GSI) sensor was studied on three amorphous magnetic ribbons. The GMI effect between the three amorphous magnetic ribbons was investigated, initially, to understand the influence of the GMI behaviour between materials of varying magnetic properties, especially the different chemical structure and, their respective, magnetostriction coefficients (a variable that describes a magnetic material's magnetoelastic properties) (λS); Co66Si15B14Fe4Ni1 (λS = < 1x10^-6), Fe81Si13.5B13C2 (λS = 30x10^-6) and Ni40Fe40Si+B19Mo1-2 (λS = 8x10^-6). Initial characterisation of the GMI effect was difficult due to the dimensions of the samples being larger compared to previous studies investigating the GMI effect of their studied samples. It used a trial-and-error approach to improve the characterisation technique to the point it could repeatably measure a consistent GMI response of the samples. The characterisation technique for measuring the GSI effect followed a similar procedure but with little time remaining it was incomplete to achieve the desired reliability. The influence of the geometry, λS and fabrication process of the samples on their GMI behaviour was explored. It was observed that the Co-rich sample had a higher GMI response compared to Fe- and Ni-rich ribbon samples. This was related to the difference in domain structures where a negative (near zero) λS domain structure promotes transverse permeability (µT), thus having a higher GMI response. A critical aspect ratio (l/w = 20) was observed for all three samples where at the critical aspect ratio all samples exhibited their highest GMI response. In addition, it was observed the GMI response of the three samples would be impeded by the presence of permanent damages (such as plastic deformation) caused by the fabrication process. The varying GMI behaviour between the ribbon samples was discussed using the competing effects between the shape anisotropy and demagnetisation factors, influencing the ribbon sample’s transverse permeability (µT). The suitability of using the GSI effect to detect the expansion of intermediate-level nuclear waste (ILW) packages was investigated by applying stress/strain on the sensing material directly. The influence of the magnetostriction coefficients (λS) to the GSI effect of the three samples displayed similar responses to their GMI behaviours; where the Co-rich ribbon sample exhibited the highest magnitude in GSI ratio compared to the Fe- and Ni-rich ribbon samples. This implies the lower the magnetoelastic effects the higher GSI response. Although, the data suggests a more complicated interaction between the transverse permeability (µT) to the shape and stress anisotropies (magnetoelastic effects). The GSI performance between all three samples was explored at stresses/ strains up to 400 MPa/ 10x10^-3 at frequencies between 0.1 – 10 MHz. Finally, the demonstration of the feasibility of the selected material (Co-rich) as a strain sensor on monitoring globally expanding ILW nuclear waste packages was investigated. Simulating the strains that were comparable to a globally expanding ILW waste package (referenced from Sellafield Ltd) the strain sensor observed a clear noticeable trend when undergoing strain at 0.4 Ω decrease at 0.25% strain. This demonstrated a proof-of-concept of using a GSI strain sensor to monitor the expansion of a nuclear waste package using the change in the stress impedance of the sensor – where high and low impedance values signify the early and late stages of the waste package expansion. This is under the assumption the sensor will be used to monitor the waste package within an approximate time period of a decade. The experimental results and the existing literature on using the GSI effect for strain sensing applications suggest the technology is applicable for structural health monitoring for detecting very small changes of strain that are not (typically) noticeable by the naked eye. This is possible from their high sensitivity to detecting minor external changes in the material, which includes minor changes of strain. In addition, it is possible to adjust the strain-sensing capability of the material by either adjusting its magnetic or mechanical properties, such as heat treatments or Young’s modulus. As a result, this is considered a viable solution for the current application of monitoring the expansion of intermediate-level nuclear waste (ILW) packages since it has been reported by the staff at Sellafield, the expansion becomes noticeable after decades of observation [1]

Miniature Magnetic Sensors

Magnetic sensors are widely used in nearly all engineering and industrial sectors, including high-density magnetic recording, navigation, target detection, anti-theft systems, non-destructive testing, magnetic labeling, space research, and bio-magnetic measurements in the human body. Miniature magnetic sensors with high sensitivity are particularly advantageous in biomedical and specialized industrial applications. Amongst the various extant magnetic sensors, Micro-Electro-Mechanical System (MEMS) and Giant Magneto impedance (GMI) sensors have the ability to sense low levels of magnetic field in the order of 10 millitesla as well as the space to be further miniaturized. In this thesis, MEMS and GMI sensors are studied in detail both theoretically and experimentally. Multiphysics analyses have been developed to provide a path to further investigate these two types of sensors for various sensor configurations. Several prototype units are successfully developed, fabricated and tested to verify the validity of these models. MEMS reed sensors consist of tri-layer beams of Au/Ni/Au. The actuation of these sensors is initiated by the magnetic force to maintain the continuity of magnetic field streamlines. The Ni layer is deployed as the main magnetic core, and the gold layers are used to enhance the contact quality of the switches. In this work, a unique fabrication process is developed that significantly reduces the number of masking and lithography steps. As well, a detailed finite element method is presented to study the behavior of these sensors and to optimize the device performance. The FEM study considers various magnetic environments, providing a performance map for the sensors. Having a performance map is essential for a system's operation and for tracking its operational behavior. The study also considers the effects of various device formations and packaging for these types of sensors. The generated magnetic force is observed to be much higher than the required mechanical force for device actuation. The GMI sensors exhibit many advantages over their conventional counterparts. In particular, thermal stability and high sensitivity make GMI sensors attractive candidates for a wide range of applications. The GMI sensors are based on concepts different from those for conventional giant magneto resistance (GMR) sensors. GMI sensors have been under active research only in the past decade. In this thesis, thin film multilayer GMI sensors are realized using microfabrication technology. The fabricated sensors are tri-layers of Co73Si12B15 /Au./ Co73Si12B15 The thin film GMI sensors are studied in detail using FEM simulation, and several sensors are developed, fabricated and tested to work in the millitesla range. A post-processing step is proposed to optimize the performance of GMI sensors and to enhance their magnetic sensitivity. The post-processing characterization shows that annealing the devices with a specific annealing cycle has the optimal effect of enhancing the magnetic characteristics of CoSiB. The sensors are treated with this post-processing recipe, demonstrating a considerable increase in their magneto impedance (MI) ratio. The research has made a contribution to establishing the engineering foundation toward the development of low-cost miniature GMI magnetic sensors for low field intensity applications

Magnetars: the physics behind observations

Magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. Magnetars are observed as peculiar, burst--active X-ray pulsars, the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma Repeaters (SGRs); the latter emitted also three "giant flares," extremely powerful events during which luminosities can reach up to 10^47 erg/s for about one second. The last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or "outbursting," and "low-field" magnetars. Substantial progress has been made also on the theoretical side. Quite detailed models for explaining the magnetars' persistent X-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. New insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. The long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. The aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. This addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources.Comment: 81 pages, 24 figures, This is an author-created, un-copyedited version of an article submitted to Reports on Progress in Physic

Ferromagnetic Composite Wire Inductors

Ph.DDOCTOR OF PHILOSOPH

Low-cost technologies used in corrosion monitoring

Globally, corrosion is the costliest cause of the deterioration of metallic and concrete structures, leading to significant financial losses and unexpected loss of life. Therefore, corrosion monitoring is vital to the assessment of structures’ residual performance and for the identification of pathologies in early stages for the predictive maintenance of facilities. However, the high price tag on available corrosion monitoring systems leads to their exclusive use for structural health monitoring applications, especially for atmospheric corrosion detection in civil structures. In this paper a systematic literature review is provided on the state-of-the-art electrochemical methods and physical methods used so far for corrosion monitoring compatible with low-cost sensors and data acquisition devices for metallic and concrete structures. In addition, special attention is paid to the use of these devices for corrosion monitoring and detection for in situ applications in different industries. This analysis demonstrates the possible applications of low-cost sensors in the corrosion monitoring sector. In addition, this study provides scholars with preferred techniques and the most common microcontrollers, such as Arduino, to overcome the corrosion monitoring difficulties in the construction industry.The authors are indebted to the projects PID2021‐126405OB‐C31 and PID2021‐126405OB‐C32 funded by FEDER funds—A Way to Make Europe and Spanish Ministry of Economy and Com‐petitiveness MICIN/AEI/10.13039/501100011033/, project PID2019‐106555RB‐I00 and project IDEAS 2.14 from Ports 4.0. It should also be noted that funding for this research was provided for Seyed‐milad Komarizadehasl by the European Social Fund and the Spanish Agencia Estatal de Investi‐gación del Ministerio de Ciencia Innovación y Universidades, grant (PRE2018‐083238).Peer ReviewedPostprint (published version

Quantum Sensors for Electromagnetic Induction Imaging: from Atomic Vapours to Bose-Einstein Condensates

In this thesis, two sensors for electromagnetic induction imaging (EMI) are presented based on radio-frequency atomic magnetometry (RF-AM) in alkali atoms. The first sensor addresses portability and real-world use of EMI with AMs, by housing the major components of the RF-AM within a lightweight, minaturised system that can be mechanically translated. The atomic source was provided by a thermal vapour of 87Rb and was pumped/probed on the D1 line. The performance of the sensor is detailed and an RF sensitivity of dBAC = 19pT/√Hz was achieved. Stability of the device was investigated and potential improvements to the design are discussed. EMI with the sensor is then tested by application to two real-world industrial problems. Through-skin pilot-hole detection in Al strut-skin arrangements and corrosion detection under thermal/electrical insulation. The mechanically translatable RF-AM was able to detect and localise pilot-holes of diameter 16 mm concealed by an Al skin of thickness 0.41 mm with sub-mm precision. For corrosion detection, localisation and depth detection of recesses in an Al plate was achieved when concealed with a 1.5 mm thick piece of rubber acting as an electrical/thermal insulator. The sensor demonstrates key advantages over existing solutions to these challenges in a package that is within the reach of real-world deployment. The second sensor addresses the spatial resolution limitations of thermal vapours, by instead utilising ultra-cold atoms trapped in a tight optical potential, as the atomic source for the RF-AM. Initially an existing 87Rb BEC setup is optimised and characterised. A BEC of 65k atoms is produced via optical evaporation with a final volume of 3.2×10^−8 cm^−3. The BEC RF sensitivity is measured to be 268pT/√Hz with a volumetric sensitivity of 50.2fT/(cm3/Hz). The BEC RF-AM is found not to be limited by the atomic projection noise and a strategy for further improvements is discussed

Recent advances in non-optical microfluidic platforms for bioparticle detection

The effective analysis of the basic structure and functional information of bioparticles are of great significance for the early diagnosis of diseases. The synergism between microfluidics and particle manipulation/detection technologies offers enhanced system integration capability and test accuracy for the detection of various bioparticles. Most microfluidic detection platforms are based on optical strategies such as fluorescence, absorbance, and image recognition. Although optical microfluidic platforms have proven their capabilities in the practical clinical detection of bioparticles, shortcomings such as expensive components and whole bulky devices have limited their practicality in the development of point-of-care testing (POCT) systems to be used in remote and underdeveloped areas. Therefore, there is an urgent need to develop cost-effective non-optical microfluidic platforms for bioparticle detection that can act as alternatives to optical counterparts. In this review, we first briefly summarise passive and active methods for bioparticle manipulation in microfluidics. Then, we survey the latest progress in non-optical microfluidic strategies based on electrical, magnetic, and acoustic techniques for bioparticle detection. Finally, a perspective is offered, clarifying challenges faced by current non-optical platforms in developing practical POCT devices and clinical applications.</p