Key Engineering Materials Vol. 826

Abstract: Amorphous magnetoelastic alloys show outstanding magnetic and magnetoelastic properties that make them excellent candidates for simple detection and actuation devices. The coupling between elastic and magnetic properties reflects in the dependence of the Young’s modulus with the applied magnetic field. We present a study of the change of the Young’s modulus with the applied magnetic field in ribbons of Fe-Ni-Co-Si-B composition. Strips of different lengths (L = 35, 30, 25, 20 mm) and widths (w = 5, 3.3, 2.5, 1.7 mm) have been measured and obtained results analyzed in terms of the different length-to-width ratios (4 < R < 21). From our observations, depth of the ΔE effect reduces and needed applied magnetic bias field for minimum Young’s modulus value increases as the strips shortens. In order to test the applicability of these materials in a situation of open/close simple designed gas valve, FEM simulations have been performed by using the experimentally measured Young’s modulus values, searching to estimate the maximum deflection of such a strip when working under applied constant pressure. Obtained useful deflection ranges from 1 mm to 10 mm, telling us about the feasibility of this amorphous magnetoelastic ribbons for simple gas valve applications.

Abstract: The structure, magnetic properties, ferromagnetic resonance and giant magnetoimpedance effect (GMI) were studied in Fe_xNi_100-x thin films and multilayered systems having compositions with small deviation from zero magnetostriction in order to find the best conditions for possible applications in the area of small pressure sensors. A comparative analysis of the effective magnetization and g-factor was carried out for the thin films of Fe_xNi_100-x (x = 19.8, 17.5, 15.0, 11.9) alloys. Comparison of the concentration dependences for static 4πM_s and dynamic 4πM_eff magnetization values allows to select a narrow interval of concentrations around Fe₁₅Ni₈₅ for the development of a microfluidic small pressure sensitive elements based on GMI effect. The maximum value of GMI ratio (ΔZ/Z) ratio shows linear dependence on the iron content in the Fe_xNi_100-x alloy for the concentration range under consideration.

Abstract: Operation on the principle of the giant magnetoimpedace (GMI) magnetic field sensor was designed and tested for the case of CoFeSiB amorphous wire of 6 mm length. We considered magnetic field displacement of the order of 10 Oe. Piece of amorphous wire was placed as a central conductor of a coaxial cable. The maximum slope of the sensor GMI characteristic was observed at the terminator resistance R_T = 50 Ohm, while the maximum of the GMI ratio variation was observed in the not “matched” (R_T = 75 Ohm) but closer to the “short” mode. Amorphous wire placed as a central conductor of a coaxial cable serves as a sensitive element with high sensitivity with respect to applied field making possible to use a simple design with a miniature coil for magnetic field biasing.

Abstract: In recent decades the application of magnetic iron oxide micro-and nanoparticles has been established in various technological fields, such as magnetic separation of biomolecules and ions, biosensors, biofuel production and others [1-4]. Working with iron oxide particles is becoming main stream subject thanks to the facility that this kind of materials can be functionalized with a variety of chemical groups which confer them specific selective or catalytic properties [5]. Furthermore, iron oxide nanoparticles present magnetic properties, and in particular super-paramagnetism, which allows to remotely control them making their manipulation easy and cost-effective [6]. In addition, a new method of synthesis has been recently proposed, which can guarantee a cost-effective production of magnetic particles that may further reduce the running cost of separation methods based on magnetism [7]. Nevertheless, biotechnological applications of iron oxide particles are still confined to research level (lab scale devices) or for low throughput clinical applications [8,9]. Indeed, most systems based on the use of magnetic elements are design to work with microfluid dynamic or are able to process samples in bath-based fashion, therefore discontinuously. The need of robust and high-productive methods is demanded especially in bioscience where, independently from the reaction or process involving magnetic particles, once such composite materials are mixed or added to a given solution, inevitably at the end of workflow they must be separated/harvested from the reaction vessel. Therefore, it is vital for a good productivity and processivity of reactions involving magnetic particles to ensure that large volumes of solution can be treated, and magnetic particles withdrew in the most fast and accurate way. The purpose of this paper is to compare an open and a closed type magnetic trapping system regarding their efficiency using two different types of magnetic sources.

Abstract: The present study deals with the optimal design of a Graphene reinforced composite. The Graphene was prepared by chemical exfoliation process and was chemically blended with matrix material in acetone. Further chemically mixed solution was exposed to air for acetone vaporization. Next, this Graphene composite was extruded through twin screw extrusion (TSE) for preparation of feedstock filament with 1.75±0.05mm diameter via fused deposition modelling (FDM). The presented results suggest that statistically controlled Graphene reinforced functional prototypes can be usefully employed as sensors for bio-medical and engineering applications.

Abstract: In the present work an effort has been made to prepare Al matrix composite by 3D printing assisted rapid investment casting (RIC). The RIC has been performed by using patterns prepared by fused deposition modelling (FDM). For preparation of 3D parts, a composite material reinforced with ceramic particles (SiC and Al₂O₃) has been used as filament wire. The main motive of this research work is to prepare metal matrix composites as functionally graded innovative materials (FGIM), via investment casting as functional prototypes which will have wear resistance properties of SiC and Al₂O₃ (especially in rapid tooling (RT) applications. The reinforcements in the RT (as functional prototype) have been ensured by SEM analysis. The potential of the analysed materials for the fabrication of novel sensor devices is highlighted. Also the functional prototypes were checked for process capability analysis for batch production

Abstract: The purpose of this work was to determine whether novel hybrid nanomaterials obtained in mild synthesis conditions between a Pt (II) metalloporphyrin, namely: Pt (II) 5,10,15,20-tetra (4-methoxy-phenyl)-porphyrin (PtTMeOPP) and nanoGold (n-Au) offer better recognition or detection properties toward hydrocortisone than the solely uncombined compounds. The Pt-porphyrin, gold-colloid and the hybrid nanomaterials were synthesized and characterized by UV-vis, FT-IR, ¹H-NMR, AFM and TEM microscopy. For the concentrations of hydrocortisone that have relevance for medical field, covering the range of 10^-8 to 10^-7 M, an excellent correlation of 0.99 was obtained between the intensity of absorption of the n-Au-PtTMeOPP hybrid plasmon and the hydrocortisone concentration, measured in THF-water system. So, this n-Au-PtTMeOPP conjugate system can be further developed to implement an accurate hydrocortisone optical sensor.

Abstract: The detection of volatile organic compounds (VOCs), humidity and toxic industrial chemicals is important for various environmental and industrial applications. The design of interdigital capacitor (IDCs) sensor is carried out in such a way that it would be suitable for microelectronic technology. The basic geometry of IDCs is defined by some parameters such as: number of electrodes N, electrode width W, electrode length L and the separation between electrodes G. The interactions between IDCs sensitive coating and analyte induced a change in the sensors capacitance due to the permittivity variation of the sensitive layer and to the change in polymer thickness (swelling). In this work, a fairly new approach of IDCs based sensor in terms of capacitance calculation has been presented. The results have been obtained from the modeling of the sensors geometry 2D and 3D using multi-physics simulation software COMSOL. The effects of some geometry parameters coupled with swelling measurements for polymeric films have been studied.

Abstract: This paper highlights the detailed procedure for preparation of biocompatible sensors and transducers by CAD-CAM assisted investment casting (IC). Along with the properties such as biocompatibility and bioactivity, the presented materials possess good surface finish (required for aesthetic sense), acceptable dimensional accuracy (required for assembly purposes) and good surface hardness (required while chewing). In this paper efforts were made for improving surface hardness, finish, and dimensional accuracy of biocompatible materials by controlling composition/proportion of Ni and Cr in IC process. In this case study stir casting (SC) assisted Ni and Cr based metal matrix composites (MMC) has been prepared and composite prepared were poured in the investment mould. The result of study reveals that different material composition influenced the microstructure and the hardness of the MMC prepared. Further with change in weight percentage of Ni and Cr, different microstructures with particle clustering was observed. The employment of nickel and chromium composites for the fabrication of novel sensors and transducers is discussed.