Solid State Phenomena Vol. 154

Abstract: This paper investigates the rapid prototyping of components from ceramics. Selective laser sintering of barium titanate powder has been investigated as a potential route to manufacturing freeform electro-ceramic based components. Raman spectroscopy has been used to investigate the effect of laser power and oxygen partial pressure on the phase and composition of the sintered material. It is shown that the sintering laser power strongly influences the composition. As the laser power is increased during sintering, the Eg mode of anatase becomes evident at 640 cm-1. When the oxygen partial pressure in the sintering atmosphere is reduced from 19% to 0.2% the whole depth of the powder bed sampled by Raman spectroscopy resembles bulk anatase.

Abstract: The preliminary results of gel swelling experiments are reported, and then compared to predictions made by a recently-developed finite element model (FEM). This model utilises energy transport between different energy domains, and is being used to simulate gel swelling dynamics. Initial experiments have revealed the model does capture the general behaviour of polymer hydrogel swelling dynamics and further improvements are necessary for better accuracy.

Abstract: Stimuli responsive hydrogels are very attractive for applications in sustained and/or targeted drug delivery systems. As the release of drugs is related to the swelling behavior of hydrogels, the swelling kinetic studies become of great importance to appreciate the release kinetics from hydrogel matrices. Hydrogels with high performance properties have been prepared from N-isopropylacryl amide (NIPAAm) and sodium alginate, crosslinked with N,N`-methylene-bis-(acrylamide) (MBAAm). This study is focused on the investigation of swelling and drug release kinetics, coupled by morphological studies. The kinetic parameters of the swelling at different temperatures for hydrogels samples have been evaluated and confirmed their temperature-responsive behavior. The swelling rate constant (ksw) decreases of with increasing temperature and slight increases with the alginate content in the samples. The drug release kinetic study from the prepared hydrogel matrices was performed in twice-distilled water and ethanol for bioactive agents as vanillin and ketoprofen, respectively. An increase of alginate content results in a slower rate and smaller percentage of vanillin and ketoprofen released. It has been established that the ketoprofen occurs according with case II of transport and vanillin release behavior occurs by an anomalous transport mechanism. The values of the release rate constant (kr) decreased by increasing swelling degree in case of 75/25 NIPAAm/alginate hydrogels and decreased also by increasing content of alginate in hydrogels with various compositions. Morphological studies performed by environmental scanning electron microscopy (ESEM) evidenced a relaxed network at high relative humidity, which explain both swelling and release profiles.

Abstract: Paper presents the results of investigation on functional characteristics of magnetoelastic compressive force sensor utilizing two Fe81Si4B15 amorphous alloy ring-shaped cores. Uniform distribution of stresses in one of two cores was achieved owing to special non-magnetic backings. Signal from sensing coils of cores was connected to differential amplifier, whereas sine wave voltage signal was applied to magnetizing circuit. High stress sensitivity of developed sensor was indicated together with expected reduction of temperature sensitivity of magnetoelastic sensor. These results confirm, that differential configuration of magnetoelastic sensor is suitable for practical application in sensors development.

Abstract: Paper presents a novel application of magnetostrictive delay lines, which give a possibility of real time monitoring of strain in ceramic components. Magnetostrictive delay line was based on highly magnetostrictive Fe-Si-B amorphous alloy ribbon, mounted outside of ceramic component, what is a new solution for increasing sensor’s sensitivity. Developed specially for this sensor, hybrid digital-analog signal processing unit covers the sample-and-hold integrated circuit. The achived sensitivity and repeatability of the sensor confirms, that such solution is suitable for ceramic machine tool monitoring.

Abstract: In this work the methodology of determining mechanical and magnetomechanical properties (mainly magnetostriction) of original composite material on epoxy resin matrix and powdered Giant Magnetostrictive Material (Terfenol-D) has been presented. Researches were carried out in order to differentiate properties of the GMM composite with two different volume fraction of Terfenol-D powder (35% and 45%) in comparison with bulk Terfenol-D. Results show that composites magnetostriction highly depends on volume fraction of Terfenol-D powder, and it is few times lower than in monolithic material. Moreover a possible ways of application were indicated.

Abstract: Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D (Tb0.3Dy0.7Fe1.9) possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency. These are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed which included magnetostrictive material Terfenol-D as the actuator material. A 2D cross-sectional geometry of the injector assembly, which incorporated both linear and non-linear magnetic properties of the corresponding materials, was modeled in ANSYS for 2D axisymmetric magnetic simulation. Subsequently, a 3D replica of the CNG flow conduit was modeled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with the Standard k  , the Realizable k   and RSM turbulence models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rate was verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle.

Abstract: If a shape-memory alloy (SMA) thin strip is applied as an element subjected to torsion, a rotary driving element with a simple mechanism can be developed. The torsion tests were carried out for the SMA thin strip. Torque and recovery torque, both increase in proportion to the angle of twist and temperature. The recoverable strain energy increases in proportion to temperature. The dissipated work decreases slightly with an increase in temperature. A means of opening and closing a door with an element driven by an SMA thin strip is demonstrated.

Abstract: The nearly-equiatomic NiTi (50.6 at.%Ni, Af = 10°C) alloy was nitrided at 1073 K using glow discharge technique. Additionally, at the end of the nitriding some amount of oxygen was added. Phase identification and thickness of the nitrided/oxided layer was done using electron microscopy method and the X-ray reflectivity measurements. The chemical composition of the layers was determined using energy dispersive spectrometer. Combination of nitriding and oxidation of the NiTi surface produces nitride/oxide complex layer of a nanocrystalline structure. The average thickness of the obtained layer was about 0,5 μm. The potentiodynamical studies in Tyrod’s solution reveal good corrosion resistance of obtained nitrided/oxidized NiTi surface proving its high quality.