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Thermophysical properties of the γ-TiAl alloy Ti-48Al-2Cr-2Ni in the liquid phase were investigated with a containerless electromagnetic processing device on board the International Space Station. Containerless processing is warranted by the high liquidus temperature T liq = 1 776 K and the high dissolution reactivity in the liquid phase. Thermophysical properties investigated include the surface tension and viscosity, density, specific heat capacity and the electrical resistivity. The experiments were supported by magnetohydrodynamic fluid flow calculations. The Ti-48Al-2Cr-2Ni alloy could be stably processed over extended times in the stable and undercooled liquid phase and exhibited an exceptional degree of undercooling before solidification. Experimental processes and thermophysical properties so obtained will be described. The experiments demonstrate the broad experimental capabilities of the electromagnetic processing facility on the International Space Station for thermophysical investigations in the liquid phase of metallic alloys not achievable by other methods.

The contribution of non-linear fluid flow effects to the damping of surface oscillations in the oscillation drop method was investigated in a series of experiments in an electromagnetic levitation device installed on the International Space station, ISS-EML. In order to correctly evaluate the damping time constant from measured surface oscillation decays the effect of a modulated signal response on measured surface oscillation decay curves was investigated. It could be shown that various experimentally observed signal patterns could be well represented by a modulated response. The physical origin of such modulations is seen in rotation and precession. Over a temperature range of 220 K covered by different surface oscillation excitation pulses with an initial sample shape deformation of 5 – 10% the amplitude of surface oscillations as a function of time could be very well represented by a Lamb type damping with a temperature dependent viscosity. A direct comparison of surface oscillation decay times measured in the same temperature range but for different oscillation amplitudes showed no non-linear contribution to the damping time constant with a confidence level better 10%.

High Entropy Alloys (HEA) can be classified in three domains according to their e/a and r values, with e/a, the number of itinerant valence electrons and r the average radius for a 12 nearest atoms neighborhood. The phase composition, thermal stability and possible phase transformations of a series of HEA alloys, CoCrzFeNi-XY (with X and Y = Al, Cu, Pd, Ru, Ti and z = 0 or 1), selected according to their e/a ratio were investigated in cast conditions (T0), after 3 h homogenization at 1100 °C (T1) and after 3 h annealing at 700 °C (T3). When observing the behavior of the different Domains of HEAs as classified by electronic structure it is observed that for the alloys from Domain I which contain fcc structures, the microstructure transforms from multi-to almost single-phase under homogenization (T1). In Domain III alloys containing cubic (bcc and/or B2) structures, very small multi-structural changes are observed. Alloys in Domain II have a mixed structure, i.e. several different structures in the diffraction pattern, which changes during heat treatments.

Materials science, as an interdisciplinary field with significant attention paid to nanoscience and nanotechnology in recent years, is generally concerned with the synthesis, atomic structure, chemical element distribution and various favorable properties of solid materials and structures. While solid-state processing conditions are generally insensitive to gravity effects, liquid-state processing depends considerably on gravity, leading to strong impact of interfacial phenomena (liquid/solid, liquid/liquid), momentum, heat and mass transport on solidification patterns, as well as further consequences regarding phase selection during solidification and growth conditions, segregation, etc. In this regard, it is interesting to note that almost 100% of all metallic products are, at some stage, produced through solidification and casting processes. Experiments on metallic liquids excluding the effects of gravity—which is achievable through processing in space, thus reducing gravity effects to micro-levels—allow benchmark experiments and the opening of a new realm of experimental possibilities to investigate basic features of the liquid state. The basics and several experimental results are discussed including recent experiments on long time scales under high temperature and containerless processing conditions on board the International Space Station.

Thermophysical properties of metallic alloys in the liquid phase are important for modeling of manufacturing processes, such as casting or additive manufacturing. Herein, the thermophysical properties of three advanced Ni‐based superalloys are measured on board the International Space Station. Advanced nickel‐based superalloys combine excellent high‐temperature mechanical strength, creep resistance, and toughness, and therefore find applications in next‐generation aircraft engines and turbines for land‐based power generators. The related fabrication processes are complex, time consuming, and costly, making it necessary to perform supporting computer simulations of the heat and material flow in the melt before and during crystallization. Such models are based on reliable thermophysical property data in the solid and liquid phase. However, measurements of surface‐ and volume‐dependent properties, such as liquid surface tension, viscosity, and specific heat of these complex liquid metal alloys, are very challenging, due to the melts high chemical reactivity at temperatures of interest. The method of choice is electromagnetic levitation, a containerless method. The measurements of surface tension, viscosity, mass density, and specific heat capacity, performed in the electromagnetic levitator (EML) on board the Space Laboratory Columbus in the International Space Station (ISS), are presented and discussed., publishedVersion

Bulk metallic glasses are of critical interest for a wide range of applications, including their use in spacecraft gearboxes and mechanisms due to their excellent low-temperature, unlubricated wear resistance. Also of interest, is the potential for in-space manufacturing of metal alloys and the use of microgravity to determine fundamental thermophysical properties to inform ground-based modeling and experimentation. In this work, a Zr-based bulk metallic glass was processed in the electromagnetic levitator ISS-EML to determine undercooling, electrical resistivity, specific heat capacity, surface tension, and viscosity. A 6.5 mm sphere was vitrified during the processing, resulting in the first bulk metallic glass manufactured on board the international space station (ISS).

Here we present measurements of surface tension and viscosity of the bulk glass-forming alloy Pd43Cu27Ni10P20 performed during containerless processing under reduced gravity. We applied the oscillating drop method in an electromagnetic levitation facility on board of parabolic flights. The measured viscosity exhibits a pronounced temperature dependence following an Arrhenius law over a temperature range from 1100 K to 1450 K. Together with literature values of viscosity at lower temperatures, the viscosity of Pd43Cu27Ni10P20 can be well described by a free volume model. X-ray diffraction analysis on the material retrieved after the parabolic flights confirm the glassy nature after vitrification of the bulk samples and thus the absence of crystallization during processing over a wide temperature range.

The effect of severe plastic deformation by high-pressure torsion (HPT) on the structure and plastic tensile properties of two Zr-based bulk metallic glasses, Zr55.7Ni10Al7Cu19Co8.3 and Zr64Ni10Al7Cu19, was investigated. The compositions were chosen because, in TEM investigation, Zr55.7Ni10Al7Cu19Co8.3 exhibited nanoscale inhomogeneity, while Zr64Ni10Al7Cu19 appeared homogeneous on that length scale. The nanoscale inhomogeneity was expected to result in an increased plastic strain limit, as compared to the homogeneous material, which may be further increased by severe mechanical work. The as-cast materials exhibited 0.1% tensile plasticity for Zr64Ni10Al7Cu19 and Zr55.7Ni10Al7Cu19Co8.3. Following two rotations of HPT treatment, the tensile plastic strain was increased to 0.5% and 0.9%, respectively. Further testing was performed by X-ray diffraction and by differential scanning calorimetry. Following two rotations of HPT treatment, the initially fully amorphous Zr55.7Ni10Al7Cu19Co8.3 exhibited significantly increased free volume and a small volume fraction of nanocrystallites. A further increase in HPT rotation number did not result in an increase in plastic ductility of both alloys. Possible reasons for the different mechanical behavior of nanoscale heterogeneous Zr55.7Ni10Al7Cu19Co8.3 and homogeneous Zr64Ni10Al7Cu19 are presented., publishedVersion

The temperature dependent viscosities of stable and undercooled liquid zirconium (Zr) have been studied by the electromagnetic levitation (EML) experiments on the International Space Station ISS together with molecular dynamics (MD) simulations. Oxygen additions of about 1.2 ± 0.5 at.% in EML experiments increases the viscosity of undercooled liquid Zr. MD simulations reveal a Vogel-Fulcher-Tammann-type temperature dependent viscosity for pure Zr in the temperature range of 1600–2700 K. The evolution of the internal energy and the nearest neighboring coordination numbers show crossovers at about 2000 K, indicating a local structural change when stable liquid Zr is cooled into undercooled liquid state. This local structural change is reflected by a slight drop of fraction of the cluster, and the nonlinear temperature dependent evolution of icosahedral-like, bcc-like and tetrahedral-like short-range order. The temperature dependent fraction of mobile atoms with high potential energy exhibits a strong anti-correlation with the temperature dependent viscosity. The decrease of these mobile atoms reduces the potential energy and increases the high-coordinated clusters with strong spatial correlations upon cooling, resulting in an increase of the local stability and viscosity of stable and undercooled liquid Zr. All results obtained here will promote the research activities of the thermophysical properties and structural evolution of metallic liquids.

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 effects of annealing and cobalt content on relaxation and the crystallization process of Zr 64 Ni 10 Al 7 Cu 19 bulk metallic glasses were investigated. β-relaxation occurs during annealing, leading to increased endotherm before crystallization. α-relaxation during high temperature annealing (higher than Tg) affects the crystallization process. The introduction of cobalt leads to an inhomogeneous amorphous structure and two-step crystallization due to the positive mixing enthalpy between cobalt and copper. Non-affine thermal strain arising from low temperature annealing of heterogeneous structure leads to a reduced endotherm phenomenon during relaxation on the DSC curves and a reduction in hardness.

The viscosities of Cu50Zr50 melt from 1250 K to 1435 K were measured in a containerless electromagnetic levitator under microgravity. The viscosity in the investigated temperature range can be expressed by an Arrhenius temperature dependence η(T) = η0 exp(EA/kBT), with η0 = (0.08 ± 0.02) mPa·s and EA = (0.58 ± 0.03) eV. We find a correlation between the fraction of closer neighboring atoms, f, and viscosity, which is described by η = expn f m, where n = 1.746/Δpec-4.478, m = −0.374/Δpec + 0.440, and Δpec is the excess potential energy, indicating that the temperature dependent viscosity during cooling is controlled by the fraction of closer neighboring atoms.

Results of a thermophysical characterization of a Fe-Cr-Mo alloy in the solid and liquid phases are reported. Methods applied include calorimetry, dilatometry; the laser flash technique for thermal diffusivity measurement and ultrasound pulse echo for the measurement of the room temperature sound velocities and elastic constants. Density in the liquid phase and surface tension were measured by optical dilatometry and by the oscillating drop method on electromagnetic levitated specimen. In addition, surface tension and viscosity were measured by the oscillating drop method on board parabolic flights under reduced gravity conditions. The methods applied and results obtained are presented. This work represents a collaborative effort, including round robin measurements in different laboratories for a characterization of the basic thermophysical properties needed for process simulation.

Mechanical properties of the two-phase TiAl(Nb) alloys have been studied after being subjected to mechanical as well as electrolytic polishing. Indentation tests at different maximum loads using different instrumentation allow probing the overall mechanical behavior of the alloys. Nanoindentation experiments have been carried out to study the local hardening of each phase during mechanical polishing. Since the deformation of γ-TiAl is facilitated by twin formation, the mechanical polishing associated with considerable frictional forces causes a significant work hardening of the γ-TiAl phase resulting in an enhancement of the overall surface hardness of the alloy. A similar hardening effect has been observed during a scratch test. The influence of local hardening owing to different crystal structures on the overall mechanical behavior in the mechanically polished alloys has also been investigated.

The Poisson’s ratio of Zr-based bulk metallic glasses in the system Zr63−xCu24AlxNi10Co3 was found to exhibit a non-monotonous behavior as a function of x when measured with ultrasound by the pulse–echo technique. In addition, from wave propagation velocity measurements at different frequencies, i.e. f = 2.25 MHz and f = 10 MHz, a composition-dependent anelastic behavior as a function of x is found, exhibiting a similar non-monotonous behavior. In this work we further investigated the plastic deformation and the creep properties of this glass system in compression tests and by nanoindentation. The plastic strain and the measured creep deformation show correlations with the Poisson’s ratio. We then discuss the anelastic behavior observed while measuring the sound-wave propagation velocity in the frame of the thermoelastic damping and the bond reorientation as proposed by Egami. Finally we discuss these effects with regard to X-ray diffraction analysis.

We report composition optimization, thermal and physical properties of new La-based bulk metallic glasses with high glass forming ability (GFA) based on a ternary La62Al14Cu24 alloy. By refining the (Cu, Ag)/(Ni, Co) and La/(Cu, Ag) ratios in the La–Al–(Cu,Ag)–(Ni, Co) pseudo-quaternary alloy, the formation of 30 mm diameter of La65Al14(Cu5/6Ag1/6)11(Ni1/2Co1/2)10 bulk metallic glass (BMG) alloy is achieved using water quenching. The origin of the high GFA was investigated from the kinetic, structural and thermodynamic points of view, and was found to be due to the smaller difference in Gibbs free-energy between the amorphous and crystalline phases in the pseudo-quaternary alloy. These alloys exhibit low glass transition temperatures, below 430 K, and relatively wide supercooled liquid regions of 40–60 K. Mechanical tests on these alloys show a fracture strength of 650 GPa, Vicker’s hardness 200 kg mm−2, Young’s modulus 35 GPa, shear modulus 13 GPa and Poisson ratio 0.356. The La-based BMGs are useful for both scientific and engineering applications.

In this report, a survey is presented about state-of-the-art thermophysical property measurements of liquid metallic: alloys at high temperatures. Methods for measuring both caloric quantities, like specific heat and thermal conductivity, and thermophysical properties, like density, surface tension and viscosity, are described in detail. Measurement techniques discussed include container-based as well as containerless techniques. Strengths and potential pitfalls in applying these methods are pointed out and recommendations for best-practice are given.

Thermodynamic properties, enthalpy relaxation and fragility of a Pd43Ni10Cu27P20 bulk metallic glass-forming liquid have been investigated and the thermodynamic functions been calculated. The enthalpy relaxation from the amorphous state into the equilibrium supercooled liquid state was found to follow a stretched exponential function with the relaxation time obeying an Arrhenius law. The fragility index, calculated from the heating rate dependence of Tg, yields a value of 65. The excellent glass-forming ability of this alloy is attributed to a smaller thermodynamic driving force and larger diffusion length for crystallization than in other bulk metallic glass-forming alloys.

The results of an investigation of the thermophysical properties in the stable and undercooled liquid state of the glass forming metallic alloys Zr 64 Ni 36 , Zr 65 Al 7.5 5 Cu 17.5 5 Ni 10 and Zr 60 Al 10 Cu 18 Ni 9 Co 3 is described. In order to make accessible a large range of liquid undercooling and to provide for extended experimentation in the liquid phase the experiments have been performed under the condition of reduced gravity with an electromagnetic levitation device onboard spacelab. Aspects of the experimental method as well as results regarding the thermophysical properties investigated shall be described. Properties investigated included the specific heat and enthalpy of fusion allowing evaluation of the thermodynamic functions, and as such a comparison of the thermodynamic contribution to glass forming ability among different metallic glass forming alloys. Furthermore, transport properties such as the effective thermal conductivity and total hemispherical emissivity as well as the electrical resitivity have been investigated. The temperature dependence of the specific heat capacity and that of the electrical resistivity indicate a temperature dependent chemical short range order.

Isotope selective effects in resonance ionization mass spectrometry (RIMS) pose a potentially serious limitation to the application of this technique to the precise and reproducible measurement of isotope ratios. In order to identify some of the underlying causes of isotope selectivity in RIMS and to establish procedures for minimizing these effects, we investigated laser-induced isotope selectivity in the resonance ionization of Os. A single-color, one-photon resonant ionization scheme was used for several different transitions to produce Os photoions from a thermal atomization source. Variations in Os isotope ratios were studied as a function of laser parameters such as wavelength, bandwidth, power and polarization state. Isotope selectivity is strongly dependent on laser power and wavelength, even when the bandwidth of the laser radiation is much larger than the optical isotope shift. Variations in the ^(190)Os/^(188)Os ratio of ≈20% for a detuning of 0.8 cm^(−1) were observed on a transition with a small oscillator strength. Large even—odd isotope selectivity with a 13% depletion of ^(189)Os was observed on a ΔJ = +1 transition at low laser intensity; the odd mass Os isotopes are systematically depleted. For ΔJ = −1 and 0 transitions the isotope selectivity was reduced by polarization scrambling and for strongly saturating conditions. A technique employing the wavelength dependence of even—even isotope selectivity as an internal wavelength standard was developed to permit accurate and reproducible wavelength adjustment of the laser radiation. This technique provides control over laser-induced isotope selectivity for single-color ionization and enabled us to obtain reproducible measurements of ^(192)Os/^(188)Os and ^(189)Os/^(190)Os ratios in the saturation regime for a ΔJ = +1 transition with a precision of better than 0.5%. The application of this wavelength-tuning procedure should significantly improve the quality of RIMS isotope ratio data for many elements.

Reversible formation and disappearance of vacant spaces (vacancy-type defects) in bulk Zr 57 Cu 15.4 Ni 12.6 Nb 5 Al 10 glass are directly evidenced by high-resolution, time-differential dilatometry studies. The vacancy kinetics are strongly temperature-dependent, with an effective migration enthalpy of H V M = 3.34 eV. This may explain the strong temperature dependence of glass properties such as viscosity. The results presented here are of general importance for understanding amorphous condensed matter and biomaterials and for the technical development of amorphous steels.

The synthesis of a multicomponent Zr60Al10Ni9Cu18Co3 glass by mechanical alloying has been investigated using thermal and structural analysis and compared with a metallic glass produced by liquid undercooling. The solid-state amorphization reaction is preceded by rapid solution of smaller solute atoms in the Zr matrix with a concomitant reduction in grain size to 10 nm at the amorphization onset. A fully amorphous mechanically alloyed sample shows relaxation compared to a sample synthesized by liquid cooling probably due to removal of residual inhomogeneities on the scale of the nanocrystal size at amorphization. While the kinetic pathways for the two synthesis methods differ, the relaxed amorphous phases from each method exhibit identical thermodynamic properties.

Thermophysical properties of the Ni-based superalloys CMSX-4, IN738LC, and MM247LC have been measured in the liquid and high-temperature solid phase. Properties included calorimetric, thermal transport, the surface tension, and the viscosity. Experiments have been performed in ground-based laboratory using classical calorimetry and rheometry as well as under reduced gravity conditions in an electromagnetic levitation device on board parabolic flights. In this contribution, an overview of the various properties of three Ni-based superalloys is given with emphasis on the surface tension and viscosity as obtained from the parabolic flight experiments. The measurements were performed within a program called ThermoLab dedicated to the measurement of thermophysical properties of industrial alloys.

In this study, the importance of the accuracy of the thermophysical property to a simulation of an investment cast directionally solidified nickel-based superalloy turbine blade was investigated. CMSX-4 was chosen as the base alloy. The effect of the thermophysical properties on the thermal field and solidification microstructure was studied using a coupled macromesoscale model. Relevant thermophysical properties examined include density, specific heat (enthalpy) and thermal conductivity in both the liquid and the solid phases. Commercial finite-element analysis software, ProCAST, was used as the macroscale model to solve the heat and mass transportation equations. An in-house mesoscale code was used to simulate the dendritic solidification structure including microsegregation. During the macroscale analysis, the simulation results were compared to an idealized turbine blade previously cast under industrial conditions. In the mesoscale simulation, the response of primary arm spacing and segregation range was examined. The temperature prediction and the thermal gradient in the liquid show the greatest sensitivity to density and solid state thermal conductivity. Primary arm spacing is most sensitive to density and specific heat. Segregation range shows greatest sensitivity to density and thermal diffusivity in the solid.

The differences in the thermodynamic functions between the liquid and the crystalline states of three bulk metallic glass forming alloys, Cu_(47)Ti_(34)Zr_(11)Ni_8, Zr_(52.5_Cu_(17.9)Ni_(14.6)Al_(10)Ti_5, and Zr_(57)Cu_(15.4)Ni_(12.6)Al_(10)Nb_5, were calculated. The heat capacity was measured in the crystalline solid, the amorphous solid, the supercooled liquid, and the equilibrium liquid. Using these heat capacity data and the heats of fusion of the alloys, the differences in the thermodynamic functions between the liquid and the crystalline states were determined. The Gibbs free energy difference between the liquid and the crystalline states gives a qualitative measure of the glass forming ability of these alloys. Using the derived entropy difference, the Kauzmann temperatures for these alloys were determined.

Noncontact modulation calorimetry using electromagnetic heating and radiative heat loss under ultrahigh-vacuum conditions has been applied to levitated solid, liquid, and metastable liquid samples. This experiment requires a reduced gravity environment over an extended period of time and allows the measurement of several thermophysical properties, such as the enthalpy of fusion and crystallization, specific heat, total hemispherical emissivity, and effective thermal conductivity with high precision as a function of temperature. From the results on eutectic glass forming Zr-based alloys thermodynamic functions are obtained which describe the glass-forming ability of these alloys.

Titanium isotope ratios have been measured by resonance ionization mass spectrometry (RIMS) with special emphasis on the nature of laser-induced isotopic selectivity. A pronounced wavelength dependence of even mass isotope ratios is caused by large nuclear volume effects near the magic neutron number 28 in ^(50)Ti . Optical isotope shifts, ranging from 0.07 to 0.21 cm^(-l), between ^(50)Ti and ^(46)Ti were measured for several transitions. The ^(50)Ti/^(46)Ti and ^(48)Ti/^(46)Ti ratios, nevertheless, exhibited only mass-dependent fractionation, in which the lighter Ti isotopes were enriched by ~2.5%/amu, when the laser operating parameters were properly controlled. Odd-even mass isotopic selectivity in the resonant ionization process was also examined for several transitions as a function of the laser polarization state and intensity. Under saturating conditions for a ΔJ= +1 transition and a high degree of laser depolarization for a ΔJ = 0 transition, the odd-even isotopic enhancement was reduced below the 2% level. The Ti isotope data agree with our previous results for Os and indicate that, by a careful choice of resonance transitions and laser operating parameters, isotope ratios can be measured accurately and reliably with RIMS.

Sources of laser-induced even-even and odd-even isotopic selectivity in the resonance ionization mass spectroscopy of Os and Ti have been investigated experimentally for various types of transitions. A set of conditions with regard to laser bandwidth and frequency tuning, polarization state and intensity was obtained for which isotopic selectivity is either absent or reduced below the 2 % level.

Strong pumping of “extended” alkali metal vapors near two-photon resonances produces copious stimulated emissions by amplified spontaneous emission (ASE) or stimulated electronic hyper-Raman scattering (SEHRS), and by phase matched parametric four-wave mixing (PFWM). The new electromagnetic fields that are generated within the near-resonant nonlinear medium can strongly influence the total atomic response through processes including interferences, level shifting, and population transfer mechanisms. The internally generated fields can, e.g., suppress transition probabilities for processes involving excitations (SEHRS and two-photon excitations) and produce gain saturation for PFWM processes. Recent experiments have demonstrated that in two-photon resonant pumping of S → D and S → S transitions in Na, the excitation rate is strongly reduced through a two-photon interference effect involving PFWM.1-5 In this process, two-photon pumping from the ground state, ∣0 >, to a two-photon level, ∣2 >, by laser photonsω1 andω2 with two-photon Rabi frequency \(\Omega _{02}^2\) produces two new frequencies ω3 and ω4 through PFWM. These generated fields create a second two-photon Rabi rate \(\tilde \Omega _{02}^{(2)}\) between the same two states. Under phase matched PFWM generation, the second pathway destructively interferes with the first;1’2,6,7 that is, in the equations of motion the two-photon pumping rate by the laser field, \(\Omega _{02}^2\), is cancelled off by the two-photon rate \(\tilde \Omega _{02}^{(2)}\) due to PFWM which becomes equal in magnitude but opposite in sign $$\Omega _{02}^{(2)} = - \tilde \Omega _{02}^{(2)}$$ (1)

The surface tension and viscosity of the Ni-based superalloys LEK94 and CMSX-10 were measured by the oscillating drop method in a containerless electromagnetic processing device on board a parabolic flight airplane. Surface oscillations were recorded by 150 and 200 Hz frame rate digital cameras positioned in two perpendicular directions and by the inductive coupling between the oscillating sample surface and the oscillating circuit of the radio frequency heating and positioning generator. The surface tension as a function of temperature of LEK94 and CMSX-10 was obtained as σ(T) = 1.73 − 4.51 × 10−4 [T—1656 K (1383 °C)] Nm−1 and σ(T) = 1.71 − 5.80 × 10−4 [(T—1683 K (1410 °C)] Nm−1, respectively. The viscosity at the liquidus temperatures as 9.8 and 7.8 mPa.s, respectively. In addition, some basic thermophysical properties such as solidus and liquidus temperatures, densities at room temperature, and thermal expansion in the solid phase are reported.

On the basis of combined experimental and theoretical studies of nonlinear processes associated with two‐photon excitations near 3d and 4d states in Na, we show how resonantly enhanced stimulated hyper‐Raman emission, parametric four‐wave mixing processes and total resonant two‐photon absorption can become severely suppressed through the actions of internally generated fields on the total atomic response in extended media.