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Systematical experimental data on density, molar volume and the surface tension, measured in electromagnetic levitation, has been summarized for the liquid Ti-V system. The optical dilatometry method as well as the oscillating drop technique have been employed to investigate the temperature- and compositional dependence. A linear decrease in density and surface tension with increasing temperature has been observed for all investigated compositions. Pure Vanadium shows hereby the highest density and surface tension while pure titanium shows the lowest density and surface tension respectively. Therefore, the density and surface tension decrease with increasing titanium content, however not linear. Since no excess quantities were available, simple models could be employed to cover the complete liquid Ti-V system. Experimental data as well as the corresponding linear fits are presented.

The density of the liquid Ti–V system was systematically measured using the optical dilatometry method in electromagnetic levitation. Possible error sources have been discussed and minimized. A linear temperature dependency with negative slope of the density was found for all investigated alloys. Pure vanadium shows the highest density with$${\rho }_{V}\left(T\right)=5.55\pm 0.03{\mathrm{gcm}}^{-3}-6.01\pm 0.52 {10}^{-4}{\mathrm{gcm}}^{-3}{\mathrm{K}}^{-1}$$ρVT=5.55±0.03gcm-3-6.01±0.5210-4gcm-3K-1, pure titanium the lowest at$${\rho }_{Ti}\left(T\right)=4.21\pm 0.02{\mathrm{gcm}}^{-3}-3.46\pm 0.30 {10}^{-4}{\mathrm{gcm}}^{-3}{\mathrm{K}}^{-1}$$ρTiT=4.21±0.02gcm-3-3.46±0.3010-4gcm-3K-1with every measured alloy ranging between these two extrema. The molar volume was utilized in order to interpret the compositional density dependency. No significant excess volume was evident. It was therefore shown that the Ti–V system acts like an ideal solution regarding density, molar volume and temperature coefficient. This result allows to reliably calculate the density for the complete Ti–V system at any given temperature.

This paper presents the results of a comprehensive study of the pull-in phenomenon in the hybrid levitation microactuator (HLMA), in which square-shaped proof masses (PMs) of different sizes, namely, length sides of 2.8 and 3.2 mm and thicknesses of 25 and 10 μm were electromagnetically levitated. The pull-in actuation of the square-shaped PMs was performed by the electrostatic force generated by the set of energized electrodes and acting on the bottom surface of the PMs along the vertical direction. The pull-in parameters, such as pull-in displacements and the corresponding applied pull-in voltages, were measured with the developed setup. The experimental measurements showed that the pull-in actuation is nonlinearly dependent on the size and mass of the PMs and a levitation height. In particular, it was found that PMs levitated within a height range from 140 to 170 μm can be stably displaced within a range of 30 μm. The results of measurements were extensively simulated with the developed analytical model by means of the quasi-FEM method. The direct comparison of the results of simulation and measurements showed a very good agreement between the theory and experiments.

The surface tension of the liquid Ti-V system is systematically measured using the oscillating drop technique during electromagnetic levitation. Temperature- and compositional dependence are both investigated. The entire compositional range is covered. A linear decrease with increasing temperature is found for the pure elements as well as for all investigated alloys. The surface tension generally increases with increasing V-content. The obtained data are in good agreement with the Butler model for the ideal solution. Additionally, the Butler model for the regular solution was evaluated in the context of the obtained surface tension data. In contrast to many other Ti-based alloys, the Butler model for the regular solution yields no additional benefit for Ti-V, since there is only a neglectable small deviation between the calculations for the ideal and regular solution. Segregation effects are modeled using the Butler equation for an ideal solution. The findings are discussed considering already existing trends for the mixing behavior of liquid Ti-alloys. The results strongly suggest, that the Ti-V system obeys in general the ideal solution law.

Electromagnetic levitation (EML) was employed for studying the velocity and morphology of the solidification front as a function of undercooling of metallic materials. The limitation of the EML technique with respect to low melting alloys that emit outside the visible light spectrum was overcome by employing state-of-the-art high-speed mid-wavelength infrared cameras (MWIR cameras) with a photon detector. Due to the additional thermography contrast provided by the emission contrast of the solid and liquid phases, conductor, and semi-conductor, the pattern formation of Al-based alloys was studied in detail, revealing information on the nucleation, phase selection during solidification, and the influence of convection.

Recently, research on non-contact conveyance systems using electromagnetic levitation technology has accelerated. We have constructed an electromagnetic levitation control system that keeps the relative distance between the electromagnet and steel plate constant. To investigate the levitation stability of thin steel plates, we performed magnetic levitation experiments on a thin steel plate with curvature. A physical disturbance was applied to the electromagnet units by vibrators. The electromagnet units were vibrated up and down by a vibrator. We investigated whether the bending magnetic levitation improved the levitation performance even if the magnetic levitation system was in a vibrating environment. We determined that it was possible to realize stable levitation for a steel plate under external disturbances during levitation at the optimal bending angle.

Purpose. The purpose of this work is the formation of conceptual approaches to the construction of an effective integrated system of simultaneous synchronized control of the movement and suspension of a maglev vehicle – a magnetoplane. Methodology. The paper uses a technique for simultaneous control of the movement and suspension of a maglev vehicle with the mutually coordinated application of both levitation methods, electromagnetic and electrodynamic, through individual control of the energy supply of each track coil. Findings. The conceptual control principles of a traction-levitation system in a hybrid mode of its operation are substantiated. The interaction of a track structure with a vehicle on an electrodynamic suspension with a linear drive is disclosed and the features of the implementation of the power unit are highlighted. Originality. It is shown that a significant improvement in maglev technology can be achieved due to the mutually coordinated combination of electromagnetic and electrodynamic methods of magnetic levitation and the use of a fundamentally different architecture for constructing a MAGLEV track. It is constructed not from long sections with three-phase power windings, but from discrete ones, they are also linear engine traction coils, and a component (load) of a solar track power plant located along the overpass. The power plant includes a photovoltaic module (solar battery) that converts solar energy into electricity, a storage device and an inverter. This construction makes possible independent supply of each travel coil and its autonomous control with the ability to switch to traction or levitation mode. The control concept is that each track coil can participate both in the creation of a static suspension due to the interaction of the magnetic field of the onboard superconducting magnet and the magnetic field of the track coils when a certain amount of direct current is applied to them, as well as the dynamic suspension provided during the train movement as a result of the interaction of the magnetic field of the onboard superconducting magnet and the magnetic fields created in the track coils by currents induced in them when the magnetic fields of the onboard superconducting magnet intersect. Practical value. The results are of practical value, as the use of such complex control system of the suspension and the magnetic plane movement will significantly improve the quality of MAGLEV technology, increase the efficiency and reliability of high-speed land transport based on electrodynamics levitation using superconducting magnets., Мета. Основною метою цієї роботи є формування концептуальних підходів до побудови ефективної інтегрованої системи синхронізованого керування рухом та підвісом магнітолевітаційного транспортного засобу – магнітоплана. Методика. У ході дослідження використано метод одночасного керування рухом і підвісом магнітолевітаційного транспортного засобу, взаємоузгоджене застосування обох способів левітації – електромагнітного та електродинамічного – через індивідуальне керування енергопостачанням кожної шляхової котушки. Результати. Обґрунтовано концептуальні принципи керування тягово-левітаційною системою в гібридному режимі її роботи. Розкрито взаємодію шляхової структури та транспортного засобу на електродинамічному підвісі з лінійним приводом, висвітлено особливості реалізації силової частини. Наукова новизна. Показано, що значного поліпшення магнітолевітаційної технології можна досягнути завдяки взаємоузгодженій комбінації електромагнітного й електродинамічного способів левітації та використання принципово іншої побудови маглев-траси – не із довгих секцій з трифазними силовими обмотками, а з дискретних коротких котушок, які одночасно є і тяговими котушками лінійного двигуна, і складовим елементом (навантаженням) сонячної шляхової енергоустановки (СШЕУ), розміщеної уздовж шляхопроводу. До складу СШЕУ входять фотоелектричний модуль (сонячна батарея), що перетворює сонячну енергію в електроенергію, накопичувач та інвертор. Така будова робить можливим незалежне, автономне живлення кожної шляхової котушки та автономне керування нею з перемиканням або в тяговий режим, або в режим левітації. Концепція керування полягає в тому, щоб кожна шляхова котушка могла брати участь як у створенні статичного підвісу за рахунок взаємодії магнітного поля бортового надпровідного магніту та магнітного поля шляхових котушок під час подачі на них постійного струму певної величини, так і динамічного підвісу в процесі руху поїзда в результаті взаємодії магнітного поля бортового надпровідного магніту та магнітних полів, створюваних у шляхових котушках струмами, що надходять до них під час перетину магнітних полів бортового надпровідного магніту. Практична значимість. Використання такої комбінованої системи керування рухом та підвісом магнітоплана призведе до якісного поліпшення маглев-технології, збільшення ефективності та надійності високошвидкісного наземного транспорту на основі електродинамічної левітації з використанням надпровідних магнітів.

A new adaptive-like neural control strategy for motion reference trajectory tracking for a nonlinear electromagnetic suspension dynamic system is introduced. Artificial neural networks, differential flatness and sliding modes are strategically integrated in the presented adaptive neural network control design approach. The robustness and efficiency of the magnetic suspension control system on desired smooth position reference profile tracking can be improved in this fashion. A single levitation control parameter is tuned on-line from a neural adaptive perspective by using information of the reference trajectory tracking error signal only. The sliding mode discontinuous control action is approximated by a neural network-based adaptive continuous control function. Control design is firstly developed from theoretical modelling of the nonlinear physical system. Next, dependency on theoretical modelling of the nonlinear dynamic system is substantially reduced by integrating B-spline neural networks and sliding modes in the electromagnetic levitation control technique. On-line accurate estimation of uncertainty, unmeasured external disturbances and uncertain nonlinearities are conveniently evaded. The effective performance of the robust trajectory tracking levitation control approach is depicted for multiple simulation operating scenarios. The capability of active disturbance suppression is furthermore evidenced. The presented B-spline neural network trajectory tracking control design approach based on sliding modes and differential flatness can be extended to other controllable complex uncertain nonlinear dynamic systems where internal and external disturbances represent a relevant issue. Computer simulations and analytical results demonstrate the effective performance of the new adaptive neural control method.

The hybrid actuator presented in this article is meant to enable stationary and slow dynamic levitation in Maglev applications. The term ‘hybrid’ refers to the design of the actuator, which is a combination of permanent magnets (PM) and electromagnets. This paper presents an analytically computable control algorithm for the said hybrid actuator. The theory of magnetic circuits is summarized shortly and used to derive a cascaded control loop consisting of an inner current controller and an outer air gap controller. Since the uncontrolled hybrid actuator is inherently unstable, the system has to be stabilized. By introducing a PID-controller into the air gap control loop, the unstable behaviour of the uncontrolled system is changed into the system behaviour of a damped harmonic oscillator. The advantage of this approach is that the computed controller parameters of the PID-controller can easily be adjusted, so the system behaviour of damping and eigenfrequency can be selected within a certain range. For the execution of the control algorithm, a microcontroller (MCU) is used and for precise air gap measurement, an eddy current sensor is installed. Finally, the behaviour of the current- and air gap controller is discussed for different measurement results and the adjustable system behaviour of the damped harmonic oscillator is presented.

Surface tensions of electromagnetically levitated liquid Ti-samples were measured under the influence of oxygen. For this purpose, Ti-O samples were prepared by adding different amounts of TiO2 powder to pure Ti. The surface tension was found to strongly depend on the bulk oxygen mole fraction determined by chemical analysis. The results could be described by a simple model presented in the present work. In this model the Butler equation is applied and the formation of TiO2 – associates are taken into account. Non-ideal interactions ΔH≠0 between titanium and the associates also need to be taken into account. Good agreement with the experimental data is evident and also with a different model developed earlier by us.

One of the most important factors during Laser Powder Bed Fusion is a robust and stable process to generate reproducibly dense and crack-free components with the same homogenous and fine-grained microstructure. Among other factors, surface tension influences the robustness of this process. Three aluminum alloys were investigated by means of 3D laser printing with respect to their ability to form lightweight and high-performance structures. The alloys include two Al-Cr based alloys (Zicromal®: Al-Cr-Zr-Mn, Scancromal®: Al-Cr-Sc-Zr) and an Al-Mg based alloy (Scalmalloy®: Al-Mg-Sc-Mn-Zr). The surface tensions of their liquid melts were measured by means of the oscillating droplet method in electromagnetic levitation. Scalmalloy® exhibited a surface tension that was by 3-8% smaller than the other two alloys, over a temperature range of 500 K above their liquidus temperature; the evaporation analysis showed that Scancromal® exhibits significantly less evaporation compared to the other two alloys by an order of magnitude. During the Laser Powder Bed Fusion process, Scalmalloy® presented the most unstable melt dynamics, and Scancromal® appeared to be more robust and stable with less weld spatters and negligible dust deposition, as evidence from the high-speed video observations. The results support the idea that surface tension and evaporation are potentially crucial factors influencing the melt dynamics and also demonstrate the capability of additive manufacturing that produces customized aluminum alloys for aerospace applications.

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2022). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022, Solidification of metastable body-centered cubic 𝛿-phase and subsequent transformation into stable face-centered cubic 𝛾-phase in undercooled Fe-Co, Fe-Ni and Fe-Cr-Ni alloy melts have been investigated on electromagnetically levitated samples. Rapid solidification is recorded by a high-speed video camera, which enables the direct observation of the solidification front and the determination of growth velocity. Metastable phase formation is revealed by two-step recalescence event showing a primary solidification front of metastable bcc phase and nucleation and growth of secondary stable fcc phase within the solid-liquid region (mushy-zone) of the primary bcc phase. The data for phase selection, growth and transformation kinetics as obtained from the video records are analyzed in the frame of models for nucleation and dendritic growth of competing stable and metastable phases. A decisive parameter describing the kinetics of phase transformation is the delay time between nucleation of the metastable and the stable phase, which strongly decreases with undercooling prior to solidification. In the present work a model is proposed, which yields an explanation for the undercooling dependency of the delay time and a quantitative description of the measured data. It is based on the classical nucleation theory combined with an estimation of the evolution of the number of heterogeneous nucleation sites within the expanding mushy-zone during dendritic growth of primary metastable bcc phase. Thus, the delay time is not only determined by nucleation kinetics but it also depends on both growth velocity 𝑣 and the morphology of the dendritic network of the primary metastable phase, which are functions of undercooling Δ𝑇. Using the relation 𝑣(Δ𝑇) for the metastable bcc phase calculated by the model by Lipton, Kurz, Trivedi and verified by measured growth velocities, the experimental data as a function of undercooling Δ𝑇 for Fe-Co are well described by the calculated delay times in a wide range of compositions between 30 and 65 at.% Co. Furthermore, the phenomenon of metastable phase formation enabled to study growth kinetics and growth morphology of different crystallographic phases having the same composition. For all alloy systems investigated it is found that at the same undercooling the 𝛿-phase phase is growing at a slower velocity than the 𝛾-phase. The result can be explained by different kinetic growth coefficients 𝜇, which describes the atomic attachment rate to the crystal interface and which is larger for fcc crystals than for bcc structured phases. Moreover, the fcc phases undergo a morphological transition of the solidification front with rising undercooling. The front morphology is changed from an octahedral shape as expected for dendritic growth of cubic metals to a spherical shape. By contrast, the front of bcc phases remains octahedral-shaped in the entire undercooling range achieved. The origin of the spherical front for the 𝛾-phase is presumably due to a low crystalline anisotropy of the kinetic growth coefficient compared to that of the 𝛿-phase, by which dendritic growth is not stable at high solidification rates., Published by RWTH Aachen University, Aachen

Temperature dependent isobaric molar heat capacity cP was measured in a containerless way for liquid Ti and two AlTi binary liquid alloys. The technique of electromagnetic levitation was used in combination with laser modulation calorimetry. In all cases, linear temperature dependencies were found: At the corresponding liquidus temperatures, cP equals 49.75(±2.0) J∙K-1mol-1, 57.43(±2.9) J∙K-1mol-1, and 42.60(±2.2) J∙K-1mol-1, for Ti, Al20Ti80 and Al50Ti50, respectively. The respective temperature coefficients amount to -1.67∙10-2J∙K-2mol-1, -2.73∙10-2J∙K-2mol-1, and +7.83∙10-2J∙K-2mol-1. For liquid Ti, there is a good agreement with existing literature data. The results are discussed in relation to the Neumann-Kopp rule.

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022, Just recently Sulfur was considered as alloying element for bulk metallic glass production. It was found that the Sulfur addition extends the glass forming ability as well as the glass forming region in various alloys. In Titanium-based alloys without Beryllium, Sulfur addition allows the glass formation for the first time. These Titanium-based bulk metallic glasses are particular interesting for biomedical applications. This work aims to understand, why Sulfur improves the glass forming ability in these Titanium-based alloys as well as in Palladium-based alloys. Thus, the melt properties in ternary Pd-Ni-S and Ti-Ni-S melts were examined. In order to process these highly reactive Titanium-based melts, levitation methods were utilized, as electromagnetic levitation and electrostatic levitation. Thus, the structure-dynamics relation in Ti-Ni-S and Pd-Ni-S melts was examined. The levitation methods were supplemented by incoherent, quasielastic neutron scattering in order to examine the atomic motion in the melts. Furthermore, the levitation methods were supplemented by synchrotron X-ray diffraction and neutron diffraction in order to examine the atomic structure and the solidification behavior in the melts.Within the Ti-Ni-S system, the optimized composition with the best glass forming ability contains 8 at. % Sulfur. Here, it was found that the melt packing and the melt dynamics decreases upon Nickel substitution by Sulfur. Thus, there is no direct correlation between the melt packing and the melt dynamics. The decrease in packing fraction indicates chemical interactions, which may promote the glass formation in Ti-Ni-S melts. The melt structure in Ti-Ni melts reveals a preference to form heterogeneous atomic pairs, as well as a mean coordination number ⟨Z⟩ > 12, which implies a more complex short-range order than an icosahedral short-range order. Thus, the short-range order in Ti-Ni melts is composed of topological and chemical contributions. In contrast to binary Ti-Ni melts, ternary Ti-Ni-S melts reveal a primary Sulfur-rich phase upon solidification, which increases the liquidus temperature. This Sulfur-rich phase changes from Ti3S to Ti2S upon Nickel substitution by Sulfur. The microstructure in the quenched Ti-Ni-S alloys shows that the Ti3S phase is surround by metastable, quasicrystalline phases, while the Ti2S phase is surround by stable, crystalline phases. Thus, Ti3S promotes the glass formation in the quenched Ti-Ni-S alloys, while Ti2S promotes their crystallization. Within the Pd-Ni-S system, the optimized composition with the best glass forming ability contains 26 at. % Sulfur. Here, it was found that the melt dynamics barely change with composition. In comparison to Pd-Ni-P melts, the melt dynamics increase upon Phosphorous substitution by Sulfur, whereas the packing fraction decreases. Thus, similar to Pd-Ni-(Cu)-P melts, there is a direct correlation between the melt packing and the melt dynamics. However, in contrast to Pd-Ni-(Cu)-P melts, a dynamic decoupling was already observed above the liquidus temperature. Possibly, the small Nickel and Sulfur atoms diffuse through an immobile Palladium-matrix. Overall, these observations indicate different mechanisms responsible for the glass formation in Ti-Ni-S and Pd-Ni-S melts., Published by RWTH Aachen University, Aachen

A kinetic model was developed to study the dephosphorization of 600 MPa steel droplets under electromagnetic levitation conditions. The relationships which were derived from the model between dephosphorization and the influence of temperature and gas flow rate were in good agreement with experimental data. Both temperature and gas flow rate were conducive to the evaporation of phosphorus, with the effect of temperature having a greater influence than that of the gas velocity. The results show that the rate-controlling step for the dephosphorization process was diffusion within the gas phase. This work aims to provide a theoretical basis for process optimization during the dephosphorization of 600 MPa steel.

Vehicle seats have a significant impact on the comfort of passengers. The development of seats is a field in which scholars are widely concerned. In this study, we add an electromagnetic levitation structure and design a new active seat suspension based on the passive seat suspension. Then, simulation research is carried out based on a C-level road surface combined with integral sliding mode control and state feedback control. The results show that both state feedback control and integral sliding mode control positively affect vehicle seat vibration reduction, and integral sliding mode control has a better anti-interference effect than state feedback control. At the same time, it is proved that the seat suspension has good working characteristics and economy.

To accurately measure the surface tension of liquid titanium free of contamination from chemical reaction with the supporting materials and dissolution of atmospheric oxygen, the measurement was performed by using electromagnetic levitation (EML) and electrostatic levitation (ESL) in consideration of the influence of oxygen partial pressure of the measurement atmosphere, PO2. When liquid titanium was maintained at 2000 K under Ar–He gas with PO2 of 10 Pa flowing at 2 L·min−1 using EML, the surface tension decreased with time due to the dissolution of atmospheric oxygen into the sample. When the PO2 of the gas was decreased to 10−2 Pa, the oxygen content and the surface tension were confirmed to not vary, even after 120 min. Even though PO2 further decreased to 10−11 Pa under Ar–He–H2 gas, the surface tension slightly increased with time due to gas phase equilibrium between H2 and H2O that allowed for a continuous dissolution of atmospheric oxygen into the liquid titanium. The surface tension of liquid titanium measured by ESL, which prevents contamination of the sample from supporting materials and the high 10−5 Pa vacuum inhibits the dissolution of oxygen, showed almost the same value as that measured under Ar–He gas at PO2 of 10−2 Pa by EML. From the measurement results of EML and ESL, the surface tension of the 99.98 mass % pure liquid titanium, free from any contaminations from chemical reactions, with the supporting material and dissolved oxygen was expressed as σ99.98%=1613−0.2049T−1941 (10−3 N·m−1).

The quality and characteristics of a powder in powder bed fusion processes play a vital role in the quality of additively manufactured components. Its characteristics may influence the process in various ways. This paper presents an investigation highlighting the influence of powder deterioration on the stability of a molten pool in a laser beam powder bed fusion (LB-PBF, selective laser melting) process and its consequences to the physical properties of the alloy, porosity of 3D-printed components and their mechanical properties. The intention in this was to understand powder reuse as a factor playing a role in the formation of porosity in 3D-printed components. Ti6Al4V (15 μm–45 μm) was used as a base material in the form of a fresh powder and a degraded one (reused 12 times). Alloy degradation is described by possible changes in the shape of particles, particle size distribution, chemical composition, surface tension, density and viscosity of the melt. An approach of 3D printing singular lines was applied in order to study the behavior of a molten pool at varying powder bed depths. Single-track cross-sections (STCSs) were described with shape parameters and compared. Furthermore, the influence of the molten pool stability on the final density and mechanical properties of a material was discussed. Electromagnetic levitation (EML) was used to measure surface tension and the density of the melt using pieces of printed samples. It was found that the powder degradation influences the mechanical properties of a printed material by destabilizing the pool of molten metal during printing operation by facilitating the axial flow on the melt along the melt track axis. Additionally, the observed axial flow was found to facilitate a localized lack of fusion between concurrent layers. It was also found that the surface tension and density of the melt are only impacted marginally or not at all by increased oxygen content, yet a difference in the temperature dependence of the surface tension was observed.

第35回宇宙環境利用シンポジウム(2021年1月19日-20日. オンライン開催), Space Utilization Research (January 19-20, 2021. Online Meeting), 資料番号: SA6000156015, レポート番号: G-07

The electromagnetic levitation facility EML on board the ISS is a powerful tool for investigation of solidification phenomena of metallic melts and precise measurement of thermophysical properties of the liquid. Containerless processing enables deep undercoolings prior to solidification and the analysis of crystal nucleation and growth phenomena. The microgravity environment allows studying these processes under reduced fluid flow and moreover under different levels of melt convection by systematic variation of electromagnetic stirring. Materials properties like density, specific heat, surface tension, viscosity, thermal and electrical conductivity of liquid metals and semiconductors are determined in the absence of disturbances caused by container walls and gravity forces. Scientists are supported by facility and mission specialists for preparation and performance, which is decisive for successful operation on orbit. User support comprises the determination of materials data, development of experiment procedure, parameter sets and their validation in the ground model as well as the conduction of space experiments by real-time monitoring and control. The comprehensive support program for the entire life cycle of science project from experiment definition to its operation ensures high quality data and an optimum of scientific results.

Pure, low-oxygen zirconium samples have been observed to nucleate a solid phase under conditions during which the sample was expected to remain liquid. This phenomenon was first seen during Spacelab Mission MSL-1R (materials science laboratory) experiments and has since also been observed in the International Space Station (ISS) electromagnetic levitation (EML) facility on a different sample. Current work has been able to replicate these anomalous solidification events under a range of conditions in the ISS MSL-EML facility. The solidification events are not well explained by classical homogeneous or heterogeneous nucleation. The current theory is that collapsing voids in the melt create a local region of high pressure that results in local material being deeply undercooled and a strong driving force for solidification.

Electromagnetic levitation experiments in space are an essential tool for thermophysical property measurement and solidification studies. In light of the need for material properties as inputs to industrial process modeling, investigators need new tools for efficient experiment planning. MHD surrogate modeling is a parametric method for prediction of flow conditions during processing using the ISS-EML facility. Flow conditions in model Au, Zr, and Ti39.5Zr39.5Ni21 samples are predicted using the surrogate model. For Au, flow is shown be turbulent in nearly all experimental conditions, making property measurement difficult. For Zr, the flow is turbulent with the heater on and laminar with the heater off, allowing for property measurement during free-cooling experiments only. For TiZrNi, the flow is laminar under all experimental conditions, indicating that TiZrNi is an excellent candidate for EML experiments. This surrogate modeling approach can be easily applied to other materials of interest, enabling investigators to choose materials that will perform well in levitation and to tailor experiment parameters to achieve desirable flow conditions.

Loss of mass due to evaporation during molten metal levitation processing significantly influences the evaluation of density, viscosity and surface tension during thermophysical property measurement. Since there is no direct way to track the evaporation rate during the process, this paper describes a mathematical approach to track mass loss and quantify any changes in alloy composition as a function of time and temperature. The Ni-based super alloy CMSX-4 Plus (SLS) was investigated and a model was developed to predict the dynamic loss of mass with time and track the potential for composition shifts throughout each thermal cycle based on the Langmuir’s equation for ideal solution behavior. Results were verified by post-test chemical analysis of key elemental constituents including Al, Cr, Ti, and Co where the error in composition for each element was less than 1 % when the activity of aluminum in solution was fixed at zero - effectively eliminating evaporation of aluminum for ground-based electrostatic levitation (ESL) testing in vacuum. This model predicts the mass evaporation for Al and Co within +/- 6% errors for CMSX-4 plus samples processed in ESL. Application of this technique to the space tests using the ESA ISS-EML facility shows that by conducting experiments in an inert shielding-gas environment, composition shifts due to differential relative evaporation become negligible and the composition is maintained within the desired limits. By tracking overall mass loss during testing the influence of evaporation on density measurements is discussed.

The present study is an overview of the surface properties of liquid Al-Ni alloys, which are of great importance for the design and development of new Al-Ni and Ni-based industrial alloys, widely used as functional and structural materials. The solidification and thus, the microstructural evolution are directly dependent on the interface/surface properties of metallic melts. Therefore, numerical simulation of microstructure evolution requires reliable property data as input to such models. Taking into account the experimental difficulties related to a high reactivity of liquid Al-Ni alloys and the effects of impurities on their surface properties, the surface tension over the whole concentration range has been determined in the frameworks of three international research projects. Namely, the surface tension measurements have been carried out by both traditional container-based and as an alternative, containerless methods within the ESA-MAP ThermoProp and ESA-MAP Thermolab Projects and also under the EU FP6-IMPRESS Project. The obtained datasets were analysed and subsequently compared with the model predicted values as well as with the literature data. A strong exothermic mixing characterises the Al-Ni system and the presence of a few intermetallic compounds in the solid state leads to the formation of short range ordered elements or complexes in the liquid phase, at least near the melting temperature, which significantly affects the surface properties of alloy melts. Aiming to estimate the effects of short range ordering on these properties, the Compound Formation Model (CFM) and the Quasi Chemical Approximation (QCA) for regular solution were applied.

第33回宇宙環境利用シンポジウム (2019年1月24日-25日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県, Space Utilization Research (January 24-25, 2019. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000132003, レポート番号: G-02

The article presents the results of multivariate calculations for the levitation metal melting system. The research had two main goals. The first goal of the multivariate calculations was to find the relationship between the basic electrical and geometric parameters of the selected calculation model and the maximum electromagnetic buoyancy force and the maximum power dissipated in the charge. The second goal was to find quasi-optimal conditions for levitation. The choice of the model with the highest melting efficiency is very important because electromagnetic levitation is essentially a low-efficiency process. Despite the low efficiency of this method, it is worth dealing with it because is one of the few methods that allow melting and obtaining alloys of refractory reactive metals. The research was limited to the analysis of the electromagnetic field modeled three-dimensionally. From among of 245 variants considered in the article, the most promising one was selected characterized by the highest efficiency. This variant will be a starting point for further work with the use of optimization methods.

The drive train of a small scale magnetically levitated train reveals the principles of a mechatronic system and offers challenges related to design, construction and control. Therefore, it is used at the Institute of electrical Machines (IEM) of the RWTH Aachen University as a demonstrator for engineering solutions. Instead of being a part of a static predefined student laboratory, the small scale magnetically levitated train is part of dynamic individual student projects. This approach provides the advantage that the students are directly involved in the engineering process and gain motivation out of their personal ideas becoming reality.

When an ultrathin and flexible steel plate is to be levitated, levitation control becomes difficult because the ultrathin steel plate undergoes increased flexure. We herein propose a levitation method for an ultrathin steel plate that is bent to an extent that does not induce plastic deformation. In this study, to investigate the levitation stability of an ultrathin steel plate, we applied disturbance cancellation control in the bending levitation system. The object of electromagnetic levitation was a rectangular zinc-coated ultrathin steel plate (SS400) of length 800 mm, 600 mm, and thickness 0.19 mm. The vibrator was attached below the three frames, in which the electromagnet unit was installed so that the frames could be vibrated up and down. We conducted experiments on the levitation performance when the electromagnet was displaced by the frame vibration in the bending levitation system. The results showed that a stable levitation can be achieved even with an input of external disturbance when levitating at the optimum bending angle.

Today's machine tools for ultra-precision machining are generally characterised by low productivity. Above all, practical cutting parameters are limited due to uncontrollable disturbance forces. Therefore, it is necessary to pursue the qualification of new technologies to overcome current limitations in productivity. In this paper, an approach for the design of a novel electromagnetic levitation guide for use in ultra-precision milling centres is presented. Design and arrangement of the magnetic guide's components are considered with regard to requirements and design principles of precision machines. Deterministic methods are utilised throughout the engineering process to ensure high stiffness and high dynamics. As a result, a concept for the electromagnetic ultra-precision linear guide is derived. DFG/FOR/1845

A major reason to conduct solidification experiments in space is that the unique conditions accessible in reduced-gravity allow investigation of fundamental questions while limiting the influence of sedimentation or buoyancy-induced convection. When processing metallic alloys using containerless electromagnetic levitation, convection may be controlled over a wide range, spanning the laminar-turbulent transition, by proper selection of facility operating conditions. By measuring key thermophysical properties such as density, viscosity, and electrical resistivity on-orbit, the specific sample being processed may be characterized and the results used to update pre-mission magnetohydrodynamic model predictions of induced stirring within the droplet. Thus, convection becomes a controlled experimental parameter that can be applied to an investigation of how stirring influences the metastable-to-stable transformation during rapid solidification of FeCrNi alloys. For these alloys, the incubation or delay time is observed to be a weak function of undercooling and a strong function of applied convection.

The liquid-phase enthalpy of mixing for Al–Tb alloys is measured for 3, 5, 8, 10, and 20 at% Tb at selected temperatures in the range from 1364 to 1439 K. Methods include isothermal solution calorimetry and isoperibolic electromagnetic levitation drop calorimetry. Mixing enthalpy is determined relative to the unmixed pure (Al and Tb) components. The required formation enthalpy for the Al3Tb phase is computed from first-principles calculations. Based on our measurements, three different semi-empirical solution models are offered for the excess free energy of the liquid, including regular, subregular, and associate model formulations. These models are also compared with the Miedema model prediction of mixing enthalpy.

This paper investigates the magnetic saturation problem of self-sensing electromagnetic levitation system and presents a novel self-sensing scheme. The proposed approach employs a demodulation technique. By superimposing a high frequency voltage, the resulting electromagnet coil currents have ripples that can be used for gap sensing. This paper shows the effect of magnetic saturation on the gap sensing and the gap length is not uniquely determined when using the relation between the ripple, control current and the gap in simulations. The results imply that the constraint conditions are to be determined to solve the problem. The proposed approach utilizes the dynamical motion model of the electromagnetic levitation system to uniquely identify the gap. By using the system behavior information, the gap can be uniquely estimated. To incorporate the dynamical model with the gap sensing algorithm, the unscented Kalman filter is employed. The proposed estimator is demonstrated in simulations. The results show that it is possible to deal with magnetic saturation by using the proposed gap sensing scheme. The estimator has a good accuracy in wide gap range compared to the conventional method., The 6th International Conference on Positioning Technology (Mechatronics and Measurement in Precision Technology) ICPT 2014, November 18-21, 2014, Kitakyushu International Conference Center, Fukuoka, Japan

In this paper, the design of an electromagnetic levitation system and a technique for non-conductive silicon heating and conductive silicon levitation is described. The aim of the work is to describe the various parameters including coil design, applied power and specimen weight that govern the temperature of levitated silicon and silicon-iron alloy droplets.

In this Erratum, we present corrections of some of the formulas published in our article “Surface tension of liquid Ti with adsorbed oxygen” [J. Mol. Liquids 290 (2019) 111226]. Apart from a few typographic errors, this affects the way the energy barriers are calculated for adsorption and desorption. Fortunately, the impact on the figures is negligibly small, so that results, discussion, and conclusions remain unchanged.

Electromagnetic levitation melting is a containerless processing technique for liquid metals requiring non-contact diagnostic tools. In order to properly perform such experiments, a precise knowledge of the temperaturetime behaviour of the metal sample resulting from the heat Balance between its heating and cooling during the processing is a prerequisite. In two preceding papers we provided the necessary theoretical Background for the inductive heat input by the high frequency magnetic levitation field and the heat loss due to radiation and heat conduction through a surrounding process gas atmosphere and defined the set of experiments needed for obtaining the key parameters of the thermal model. In the present paper we extend the previous work by investigating experimentally the influence of the sample cooling by forced gas convection at high Péclet number in a surrounding Argon gas atmosphere at hand of tests under microgravity.

The nanoparticles of Ti and TiO2 have attracted extensive research interest because of their diverse applications in, for instance, catalysis, energy conversion, pigment and cosmetic manufacturing and biomedical engineering. Through this project, a one-step bulk synthesis method of electromagnetic levitational gas condensation (ELGC) was utilized for the synthesis of monodispersed and crystalline Ti and TiO2 nanoparticles. Within the process, the Ti vapours ascending from the high temperature levitated droplet were condensed by an argon gas stream under atmospheric pressure. The TiO2 nanoparticles were produced by simultaneous injection of argon and oxygen into the reactor. The effects of flow rate of the condensing and oxidizing gases on the size and the size distribution of the nanoparticles were investigated. The particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and image analysis. The process parameters for the synthesis of the crystalline Ti and TiO2 nanoparticles were determined.

Electromagnetic suspension system with a nonlinear and unstable behavior, is used in maglev trains. In this paper a linear mathematical model of system is achieved and the state feedback method is used to improve the system stability. The control coefficients are tuned by two different methods, Riccati and a new method based on Genetic algorithm. In this new proposed method, we use Genetic algorithm to achieve the optimum values of control coefficients. The results of the system simulation by Matlab indicate the effectiveness of new proposed system. When a new reference of air gap is needed or a new external force is added, the proposed system could omit the vibration and shake of the train coupe and so, passengers feel more comfortable.

第28回宇宙利用シンポジウム (2012年1月23-24日. 日本学術会議), 港区, 東京都, Space Utilization Research (January 23-24, 2012. Science Council of Japan), Minato-ku, Tokyo Japan, 資料番号: SA6000032028, レポート番号: M28

The Electromagnetic Levitational Gas Condensation (ELGC) method was used to synthesize ZnO nanorods. In this paper, the formation mechanism of the synthesized nanorods is discussed. The ELGC method involved vaporization of the levitated Zn specimen, with subsequent condensation and oxidation of nuclei formed under Ar or He–0.2Ar and O 2 atmospheres. The particles were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The presented results showed that the [0001]-oriented ZnO nanorods were directly produced by the ELGC process under different process conditions.