**3.2 Measurement of surface tension and melt viscosity during levitation in zero gravity in parabolic flights and ISS**

Volumetric metal glasses or amorphous alloys are a new phenomenon in materials science. The main advantage of these materials is their superior mechanical properties compared to conventional crystalline materials. Amorphous alloys are solid metal materials with a disordered glass-like structure of an atomic scale. They are formed when their cooling from a liquid state occurs much faster than the critical cooling rate. During supercooling of the melt, the increasing thermodynamic driving force of crystallization and amorphous atomic kinetics compete with each other. A strong increase in viscosity during cooling and a high probability of amorphization of the melt also establish boundary conditions for the correct choice of parameters of the process. To justify superplasticity, it is important to know the temperature-dependent viscosity of the alloy. Thus, in order to create technology

#### **Figure 13.**

*Temperature of liquid iron in the process of electromagnetic levitation; red—a "zig-zag" at the moment of melting the iron sample.*

and theoretical models, it is necessary to know the basic thermophysical properties in a wide temperature range. Electromagnetic levitation is clearly a powerful technique for the noncontact manipulation of electrically conductive samples. This method allows to correctly measure the surface tension and viscosity of metal melts. However, under conditions of gravity of the earth, the melt in natural geometry or raised by an electromagnetic field will be significantly deformed. The simultaneous control of temperature and levitation is limited under normal gravitational conditions of 1 G, since the electromagnetic field needed to lift the samples can heat the sample to significant temperatures, even above the melting point. Flows in a heated, deformed melt drop under terrestrial conditions are poorly controlled (laminar transition to turbulent), which makes it necessary to conduct experiments in zero gravity (microgravity) conditions. One of the possibilities to achieve microgravity in a short period of time (10–20 s) is parabolic flights, for example, performed using the Airbus A310 or International Space Station. The experimental results were obtained during several parabolic flight campaigns in 2016 and 2017 using the TEMPUS EML setup. The surface tension and viscosity of the Pd43Cu27Ni10P20 melt were measured, and it was shown that the temperature dependence of the viscosity of this alloy can be well described by the free volume model. In addition, in [23–33], using X-ray diffraction, it was confirmed the absence of the long-range order characteristic of amorphous samples. The morphology of the samples was analyzed using X-ray computed tomography before and after flights.

The noncontact of a liquid sample is the essence of electromagnetic levitation, combined with an ultra-clean environment. In addition, electromagnetic levitation is one of the oldest noncontact methods of levitation used for materials science experiments for decades. Electromagnetic levitation is the most mature of all noncontact melting methods and has been used for decades in ground-based experiments, as well as in microgravity experiments with a wide range of alloys. Electromagnetic levitation in terrestrial conditions has some problems associated with gravitational forces, so if levitation is performed under microgravity conditions, then only small levitation forces are required to compensate for residual

**181**

[20–22].

*Electromagnetic Levitation of Metal Melts DOI: http://dx.doi.org/10.5772/intechopen.92230*

**3.3 Atomization of liquid metals in levitation**

with higher accuracy.

possible.

accelerations. With an inductor optimized for microgravity, heating and positioning of the samples can be carried out almost independently. Since positioning requires minimal effort, the low temperature mode is more accessible, convection is reduced and the deformation of the samples is eliminated. As a result, many additional samples can be processed, and their thermophysical properties can be determined

Other factors are the length of periods of microgravity and the ability of the experimenter to interactively control the experiment during a parabolic flight. Electromagnetic levitators have been developed for a wide range of carriers and tasks. Due to the flight duration, which was on the order of 1–2 weeks, it was possible to conduct several experiments lasting several hours each, where each experiment with this sample included several melting cycles with this sample. The experiments were preprogrammed, so interactive access via telemetry is possible. The ISS missions are essentially a continuation of previous Spacelab missions and provide long-term access to a good microgravity environment. Several batches of samples can be loaded onto an object, processed and returned to the ground. The experiments are preprogrammed; interactive access via telemetry is

The advent of 3D metal printing and other additive technologies has stimulated an increase in demand for spherical metal powders with high rheological flow characteristics. The spraying process consists of feeding a vertical sacrificial rod into a conical inductor, where the end of the rod is melted by eddy currents of an electromagnetic field, resulting in the formation of a stream or droplets of liquid metal that are sprayed with a powerful flow of inert gas. In fact, one of the functions of classical electromagnetic levitation is involved in the process-the melting of the metal, without holding it by a magnetic field. The spraying unit is very simple and consists of a feeder with a sacrificial rod, a melting chamber with an inductor, a spraying chamber with nozzles for supplying an inert gas, a powder storage device and a generator. The proposed method is noncontact and ideal for producing high-purity, reactive and refractory metal powders. All process parameters are known and easily adjusted, which allow full control of the size of the powders. The process is simple, manageable and flexible. Perhaps, this process stands out among analogues for its simplicity and reliability, especially in the production of high-quality pure spherical powders from refractory and rare metals such as titanium, zirconium, niobium and precious metals, which are in great demand in additive technologies in aerospace, medical and other industries

**3.4 Chemical equilibrium in the system metal-slag-gas during EML**

Heating, melting and crystallizing a metal melt with slag occur in a controlled gas atmosphere or in vacuum. The exposure time to the onset of chemical equilibrium in the "iron melt-slag melt-gas" system is usually short and does not exceed several minutes. Slag melting occurs due to levitation and heating of iron, liquid slag initially covers a metal drop with a thin film, which can be observed visually, and then it collects in the lower part of the drop and is held in liquid state by interfacial tension. It is this joint behavior of the molten metal and slag plus convection in liquid iron that ensures the rapid achievement of chemical equilibrium in the distribution of sulfur (the usual or radiochemical sulfur isotope 35S). The initial sample for levitation was a capsule of a specially prepared alloy of iron with carbon weighing

### *Electromagnetic Levitation of Metal Melts DOI: http://dx.doi.org/10.5772/intechopen.92230*

*Magnetic Materials and Magnetic Levitation*

and theoretical models, it is necessary to know the basic thermophysical properties in a wide temperature range. Electromagnetic levitation is clearly a powerful technique for the noncontact manipulation of electrically conductive samples. This method allows to correctly measure the surface tension and viscosity of metal melts. However, under conditions of gravity of the earth, the melt in natural geometry or raised by an electromagnetic field will be significantly deformed. The simultaneous control of temperature and levitation is limited under normal gravitational conditions of 1 G, since the electromagnetic field needed to lift the samples can heat the sample to significant temperatures, even above the melting point. Flows in a heated, deformed melt drop under terrestrial conditions are poorly controlled (laminar transition to turbulent), which makes it necessary to conduct experiments in zero gravity (microgravity) conditions. One of the possibilities to achieve microgravity in a short period of time (10–20 s) is parabolic flights, for example, performed using the Airbus A310 or International Space Station. The experimental results were obtained during several parabolic flight campaigns in 2016 and 2017 using the TEMPUS EML setup. The surface tension and viscosity of the Pd43Cu27Ni10P20 melt were measured, and it was shown that the temperature dependence of the viscosity of this alloy can be well described by the free volume model. In addition, in [23–33], using X-ray diffraction, it was confirmed the absence of the long-range order characteristic of amorphous samples. The morphology of the samples was

*Temperature of liquid iron in the process of electromagnetic levitation; red—a "zig-zag" at the moment of* 

analyzed using X-ray computed tomography before and after flights.

The noncontact of a liquid sample is the essence of electromagnetic levitation, combined with an ultra-clean environment. In addition, electromagnetic levitation is one of the oldest noncontact methods of levitation used for materials science experiments for decades. Electromagnetic levitation is the most mature of all noncontact melting methods and has been used for decades in ground-based experiments, as well as in microgravity experiments with a wide range of alloys. Electromagnetic levitation in terrestrial conditions has some problems associated with gravitational forces, so if levitation is performed under microgravity conditions, then only small levitation forces are required to compensate for residual

**180**

**Figure 13.**

*melting the iron sample.*

accelerations. With an inductor optimized for microgravity, heating and positioning of the samples can be carried out almost independently. Since positioning requires minimal effort, the low temperature mode is more accessible, convection is reduced and the deformation of the samples is eliminated. As a result, many additional samples can be processed, and their thermophysical properties can be determined with higher accuracy.

Other factors are the length of periods of microgravity and the ability of the experimenter to interactively control the experiment during a parabolic flight. Electromagnetic levitators have been developed for a wide range of carriers and tasks. Due to the flight duration, which was on the order of 1–2 weeks, it was possible to conduct several experiments lasting several hours each, where each experiment with this sample included several melting cycles with this sample. The experiments were preprogrammed, so interactive access via telemetry is possible. The ISS missions are essentially a continuation of previous Spacelab missions and provide long-term access to a good microgravity environment. Several batches of samples can be loaded onto an object, processed and returned to the ground. The experiments are preprogrammed; interactive access via telemetry is possible.
