Development of Magnetostrictive Transducer Prototype for Blockage Detection on Molten Salt Pipes

In solar thermal power plants molten salt is often used to store and transport the energy that is collected during the day. The external pipe temperature is measured to activate an electric heating system if the temperature approaches the melting point. However, salt solidification cannot be completely excluded from the plant management. Once occurred, the location of a salt blockage is very complex due to the high temperature of the pipe. Therefore, when this problem arises, power plants have to stop production with the consequences in time and cost that this entails. Electro-magnetic acoustic transducers can be used as non-destructive testing systems for this application. A method for salt blockage detection is proposed that is applicable in straight sections of pipes by employing torsional guided waves that are generated with magnetostrictive transducers. The present paper deals with the transducer conception and the design of the power supply to activate it. Two alternatives are proposed and compared to determine the improvement in the amplitude/noise ratio. Finally, the experimental results show the performance of the equipment in a small prototype, thus validating the technique presented

ΔE-Effect Magnetic Field Sensors

Many conceivable biomedical and diagnostic applications require the detection of small-amplitude and low-frequency magnetic fields. Against this background, a magnetometer concept is investigated in this work based on the magnetoelastic ΔE effect. The ΔE effect causes the resonance frequency of a magnetoelastic resonator to detune in the presence of a magnetic field, which can be read-out electrically with an additional piezoelectric phase. Various microelectromechanical resonators are experimentally analyzed in terms of the ΔE effect and signal-and-noise response. This response is highly complex because of the anisotropic and nonlinear coupled magnetic, mechanical, and electrical properties. Models are developed and extended where necessary to gain insights into the potentials and limits accompanying sensor design and operating parameters. Beyond the material and geometry parameters, we analyze the effect of different resonance modes, spatial property variations, and operating frequencies on sensitivity. Although a large ΔE effect is confirmed in the shear modulus, the sensitivity of classical cantilever resonators does not benefit from this effect. An approach utilizing surface acoustic shear-waves provides a solution and can detect small signals over a large bandwidth. Comprehensive analyses of the quality factor and piezoelectric material parameters indicate methods to increase sensitivity and signal-to-noise ratio significantly. First exchange-biased ΔE-effect sensors pave the way for compact setups and arrays with a large number of sensor elements. With an extended signal-and-noise model, specific requirements are identified that could improve the signal-to-noise ratio. The insights gained lead to a new concept that can circumvent previous limitations. With the results and models, important contributions are made to the understanding and development of ΔE-effect sensors with prospects for improvements in the future

Magnetic and magnetoelastic properties of FeGa epitaxial thin films for low-power Magnetoelectronics

Esta tesis aborda la fabricación y caracterización de películas delgadas de la aleación hierro-galio (FeGa). El interés de esta aleación reside en su alto valor de magnetostricción tetragonal, la cual puede ser 100 veces superior a la del Fe puro. Se han fabricado películas epitaxiales delgadas de FeGa en un rango de 10-50 nm mediante MBE sobre dos tipos de sustratos: MgO y PMN-PT. Estas muestras han sido caracterizadas estructural (RHEED, TEM, XRD, XRR) y magnéticamente (VSM, MOKE, MFM, magnetometría de placa en voladizo).Sobre sustratos MgO se ha estudiado la dependencia magnética y estructural con la temperatura de depósito y contenido de Ga en la aleación. Los resultados indican que al aumentar la temperatura de depósito su superficie se vuelve rugosa. El aumento en contenido de Ga implica la observación de fases cristalinas ordenadas y la aparición de estructuras de dominios magnéticos corrugados atribuibles a una anisotropía magnética aleatoria débil.Además, se han medido a temperatura ambiente los coeficientes magnetoelásticos irreducibles B1 y B2 para aleaciones FeGa y FeGaTb, sin observarse cambios significativos al dopar con Tb. En cambio, para la aleación FeGaCu los valores de dichas tensiones magnetoelásticas disminuyen, debido a la presencia de una fase omega observada mediante TEM.Sobre sustratos ferroeléctricos PMN-PT se han buscado aplicaciones en el campo denominado "Straintronics". Las películas crecidas sobre PMN-PT(011) muestran anisotropía uniaxial, que no varía al aplicar campo eléctrico perpendicular. En cambio, las películas crecidas sobre PMN-PT(001) muestran un giro de anisotropía uniaxial y de la imanación de 90º al aplicar campo eléctrico sin presencia de campo magnético, con un elevado valor del coeficiente magnetoeléctrico inverso de 15 E-6 s/m. Se ha probado con éxito que estas heteroestructuras pueden integrarse en memorias no volátiles.<br /

Integrated torque sensor for e-bike motors

Hoganas AB develops and build motors for e-bikes and with the current legislation the e-bikes must be equipped with a torque sensor to measure the torque applied by the rider. The motor may only assist when the rider pedals and there is no throttle on e-bikes. Hoganas want to develop a torque sensor that is integrated in the e-bike motor. Physical sensing principles for measuring torque on e-bikes are evaluated and the currently used sensors and the competitors' solutions are analyzed. Two types of torque sensor concepts are developed and evaluated with FEA (Finite Element Analysis). One of the concepts is realized in a prototype for evaluation. To further evaluate if the prototype concept is feasible the noise levels in Hoganas e-bike motor was measured to estimate how the sensor will be affected. The specifications for a torque sensor is established with demands and desirable properties for an integrated torque measurement system

Demonstration of a quantile system for compression of data from deep space probes

Quantile system of data compression for space telemetr