Oscillating Cup Viscometer Research Articles

Melting, Solidification, and Viscosity Properties of Multicomponent Fe-Cu-Nb-Mo-Si-B Alloys with Low Aluminum Addition.

Melting, solidification, and viscosity properties of multicomponent Fe-Cu-Nb-Mo-Si-B alloys with low aluminum addition (up to 0.42 at.% Al) were studied using an oscillating cup viscometer. It is shown that melting and solidification are divided into two stages with a knee point at 1461 K. The temperature dependences of the liquid fraction between the liquidus and solidus temperatures during melting and solidification are calculated. It has been proven that aluminum accelerates the processes of melting and solidification and leads to an increase in liquidus and solidus temperatures. In the liquid state at temperatures above 1700 K in an alloy with a low aluminum content, the activation energy of viscous flow increases. This growth was associated with the liquid-liquid structure transition, caused by the formation of large clusters based on the metastable Fe23B6 phase. Aluminum atoms attract iron and boron atoms and contribute to the formation of clusters based on the Fe2AlB2 phase and metastable phases of a higher order.

Development of an oscillating cup viscometer for viscosity measurement of liquid metals at very high temperatures

The dynamic viscosity of molten metals is measured over a wide temperature range up to 2100 K using an oscillating cup viscometer. In order to further reduce the measurement uncertainties, a particular attention is paid to thermal effects, temperature measurement, acquisition and analysis of the mechanical response of the oscillating pendulum. Experiments are first conducted at low temperature with standard liquids, covering a wide range of viscosities from 1 mPa.s to 500 mPa.s. These preliminary tests helped to assess the accuracy and reliability of the Shvidkovskiy approach used to calculate viscosity. Further experiments were then performed at very high temperature using an induction furnace. As a result, the dynamic viscosity has been successfully measured over the temperature range 506–2135 K for liquid tin, and 710–1770 K for liquid lead, providing unpublished data. Additionally, this was achieved while maintaining a relatively low uncertainty of about 2.5% despite the very high temperature reached here.

On the secondary flows in oscillating-cup viscometer

Oscillating-cup viscometer is analysed numerically at high-amplitude regime. Full axi-symmetric Navier–Stokes equations are solved by a finite volume method. It is shown that the effect of the secondary flows on the decrement and period of the oscillations scales as square of the amplitude. The secondary flow consists of a stationary circulation and a periodic component whose period is a half of the period of the primary oscillations. A procedure allowing for determination of the linear decrement in a non-linear regime is proposed. It is shown that the constraints of “smallness” can be significantly relaxed and the experiments can be performed with higher amplitudes and higher decrements of the oscillations.

Oscillating-Cup Viscometer for Nonlinear Fluids in Forced Mode

Oscillating-Cup Viscometer for Nonlinear Fluids in Forced Mode

Theoretical foundation of electromagnetically-driven oscillating cup viscometer

The electromagnetically-driven oscillating cup viscometer (EOC viscometer) is a novel noncontact technique that has been used to simultaneously measure viscosity and electrical conductivity of liquid metals and molten semiconductors at high temperatures. Though there were already a few successful applications in the past, the theory of the EOC method has never been fully developed and examined in detail. This paper established an exact solution for the oscillatory flow that is coupled transient angular motion of the cylindrical cup in an EOC viscometer and provided options for different measurement methods based on EOC. The angular motion solution can be decomposed to three components, including the angular displacement at equilibrium state, fast decay, and damped oscillation, each of which is described by a series of motion parameters respectively. The dependences of these motion parameters on material properties of interest are quantitatively delineated with measurable experimental parameters for practical experimental conditions. Two practical methods are proposed, namely the rapid method, which mainly takes advantage of fast decay, and the quasi-steady state method, which uses only the information collected from the damped oscillation. The results of this study established a theoretical basis for EOC experimental design and clarified measurement methods based on different regimes of the working conditions of the EOC.

Viscosity of Ga-rich alloys in the Ga-In-Sn system

The viscosity of Ga-In-Sn liquid alloys has been measured from liquidus temperature to 1200 K in the Ga-rich corner (content of gallium above 71 at. %) using an oscillating cup viscometer. The temperature dependence of the viscosity of the investigated alloys is well described by the Arrhenius law. Isotherms of the viscosity for Ga-In-Sn liquid alloys in the Ga-rich corner can be represented as a linear dependence on the gallium content. The viscosity of the investigated alloys near the liquidus temperature has a positive deviation from the ideal value. These alloys behave as ideal solutions at higher temperatures. As the comparison of existing phenomenological models describing the viscosity as a function of composition to the experimental data is unsatisfactory, a new model for the viscosity has been developed in the present work using the concentration-concentration fluctuations structure factor in the long-wavelength limit. The agreement between the model calculation and experimental data for Ga-based alloys is excellent.

Viscosity of Industrially Important Zn–Al Alloys Part II: Alloys with Higher Contents of Al and Si

The viscosity of Zn–Al alloys melts, with industrial interest, was measured for temperatures between 693 K and 915 K, with an oscillating cup viscometer, and estimated expanded uncertainties between 3 and 5 %, depending on the alloy. The influence of minor components, such as Si, Mg and Ce + La, on the viscosity of the alloys is discussed. An increase in the amount of Mg triggers complex melt/solidification processes while the addition of Ce and La renders alloys viscosity almost temperature independent. Furthermore, increases in Al and Si contents decrease melts viscosity and lead to an Arrhenius type behavior. This paper complements a previous study describing the viscosity of Zn–Al alloys with quasi-eutectic compositions.

An oscillating cup viscometer based on Shvidkovskiy algorithm for molten metals

In this paper, an oscillating cup viscometer based on Shvidkovskiy algorithm and time-resolved reflection measurement was described for the molten metals over a broad temperature range up to 1800 K. The viscosity of molten metals was automatically calculated from Shvidkovskiy formulae by obtaining the time period and the logarithmic decrement of the oscillations. The representative viscosity measurements using our homemade viscometer were performed for water at a room temperature and pure aluminum in a temperature range from its melting point to 1300 K. It was found that the obtained viscosity results showed good agreement with the previous reports for both water and aluminum, indicating its reliable viscosity measurement. In addition, the experimental uncertainty of the viscometer was also estimated by analyzing the errors propagation of the input parameters of Shvidkovskiy equation. The results showed that a very low uncertainty of 2.1% for the dynamic viscosity measurement, which attributed from the small errors of the logarithmic decrement and time period with highly accurate time-resolved reflection measurement. Therefore, the developed oscillating cup viscometer would be an effective tool for high temperature viscosity measurement in both basic research and industrial applications.

Numerical analysis of an improved heating device for the electromagnetically driven oscillating cup viscometer

The electromagnetically driven oscillating cup viscometer is developed to accurately determine the conductivity and viscosity of molten semiconductors. To reduce the sample’s temperature gradient d...

Experimental and ab initio molecular dynamics study of the structure and physical properties of liquid GeTe

GeTe is a prototypical phase-change material employed in data storage devices. In this work, the atomic structure of liquid GeTe is studied by x-ray and neutron diffraction in the temperature range from 1197 to 998 K. The dynamic viscosity is measured from 1273 to 953 K, which is 55 K below the solidification point, using an oscillating-cup viscometer. The density of liquid GeTe between 1293 and 973 K is determined by the high-energy $\ensuremath{\gamma}$-ray attenuation method. The experiments are complemented with ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT). Compatibility of the AIMD-DFT models with the diffraction data is proven by simultaneous fitting of all data sets in the frame of the reverse Monte Carlo simulation technique. It is shown that octahedral order dominates in liquid GeTe, although tetrahedral structures are also present. The viscosity of the equilibrium and weakly undercooled liquid GeTe obeys the Arrhenius law with a small activation energy of the order of 0.3 eV, which is indicative of a highly fragile liquid. The calculated density of states and electronic wave functions point to the existence of a pseudogap and localized electron states within the gap in the equilibrium liquid near the melting point as well as in the undercooled liquid.

Measurements of the Viscosity of Molten Lithium Nitrate by the Oscillating-cup Method

New experimental data for the viscosity of molten lithium nitrate from its melting point up to about 700 K are reported. The measurements were taken, for the first time, with an oscillating-cup viscometer with an estimated uncertainty of 3 %. The obtained data were compared with previous works. It was concluded that there are still large discrepancies between different sets of data. Our data follow the Arrhenius behavior with an activation energy for viscous flow of $$E_{\eta } \hbox {= 19.3}$$ $$\hbox {kJ}{\cdot }\hbox {mol}^{-1}$$ , slightly higher than previous recommendations.

Sensitivity analysis of the transient torque viscosity measurement method

While a new type of oscillating-cup viscometer which uses a rotating magnetic field has been developed and tested, the uncertainty of such measurements has been considered to only a cursory level. This paper reports work in which the sensitivities of this new method’s output are studied for the measurement of mercury with a particular device. It is concluded from the analysis that while the new method requires dramatically shorter measurement times than previous methods, the resultant uncertainty seems to be nearly the same as the classical oscillating cup method. As such, since the results are just as precise as other oscillating-cup methods, the new method should be employed for its speed advantage, allowing the viscosity of materials as functions of temperature or pressure to be economically determined.

Viscosity of liquid binary Pb–Zn alloys in the miscibility gap region

The shear viscosity studies were performed for the liquid Pb–Zn monotectic system over a wide temperature range using an oscillating-cup viscometer, with special attention to the critical point (CP) region. The critical parameters describing the peculiarities of the viscosity behavior in the vicinity of CP are evaluated. The data analysis is based on the dynamic theory of phase transitions and the viscosity equation, which takes into account a spatial dispersion of the systems near their critical temperatures. The results are compared with available data for immiscible dielectric solutions.

Viscosity of liquid Co–Sn alloys: thermodynamic evaluation and experiment

Shear viscosity measurements were performed for liquid Co–Sn alloys over a wide temperature range above the respective liquidus temperatures. A high temperature oscillating-cup viscometer was used. It was found experimentally that viscosity as a function of temperature obeys an Arrhenius law. The data were compared with calculated values, obtained from different thermodynamic approaches. A good agreement was found between experimental results and calculated ones by the Budai–Benkö–Kaptay model.

Density and viscosity of ternary Al–Cu–Si liquid alloys

Densities and viscosities of ternary Al–Cu–Si liquid alloys have been investigated over a wide temperature and composition range. Density was measured using electromagnetic levitation as a container-less technique, while viscosity was measured by means of a high-temperature oscillating cup viscometer. In this ternary system, binary interaction parameters as well as a third (ternary) interaction parameter need to be taken into account for the excess volume to describe the liquid densities. The temperature dependences of the viscosities are well described by the Arrhenius law. A maximum of the activation energy of viscous flow is found in that compositional range in which intermetallic phases exist in the solid state.

Viscosity of Al–Cu liquid alloys: measurement and thermodynamic description

In the present work a high temperature oscillating cup viscometer has been used to measure the viscosities of liquid binary Al–Cu alloys. The dependence of viscosity on temperature is well described by the Arrhenius law. For constant temperature, the viscosity as a function of copper concentration exhibits a maximum at a mole fraction x Cu = 0.7. This might be due to a pronounced chemical short range order in the liquid phase at this composition. As the comparison of existing phenomenological models describing viscosity as a function of composition to the experimental data is unsatisfactory, a new model for the viscosity has been developed within this work based only on a few assumptions and using the enthalpy of mixing as input parameter which is easily accessible. The agreement between model calculation and experimental data is excellent.

Effect of Oils on Kinematic Viscosity of R134a

The kinematic viscosity defined as a ratio of viscosity to density is one of the key properties in making important dimensionless numbers such as Prandtl number and Reynolds number. The authors have measured both viscosity and density of R134a/POE and R134a/PAG mixtures in the range of relatively low oilconcentrations at saturated liquid state. The density measurements up to 50 mass% were conducted with a densimeter making use of glass buoys within overall uncertainty of ±1.0% and the viscosity measurements up to 16 mass% with an oscillating-cup viscometer making use of polarizer with overall uncertainty less than ±3.5%. The kinematic viscosity, which is obtained from the experimental viscosity and density data, is presented for both R134a/POE and R134a/PAG mixtures in the range of temperatures from 278 to 288 K for oil-concentrations up to 15 mass%. The oil-concentration dependence of the kinematic viscosity for both mixtures is also reported.

Viscosity of Industrially Important Al–Zn Alloys. I-Quasi-eutectic Alloys

Viscosity is a very important property in several fields of materials and metal processing. Many systems are still not fully characterized with regard to their thermophysical property data. In addition, as new alloys are developed or used, viscosity data are necessary to understand the best processing conditions. The data that are available frequently show large discrepancies. The effect of minor constituents is very difficult to model and can have a strong effect on the viscosity. Measurements of the viscosity of Zn–Al alloys, with a quasi-eutectic composition, were performed in the molten state, for temperatures between 690 K and 751 K. The measurements were performed with an oscillating cup viscometer, with an estimated uncertainty of 2 % to 5 %, depending on the alloy. The influence of other minor components, such as Pb, Mn, and Mg, on the viscosity of the alloys is discussed. It was concluded that Pb induces a decrease in viscosity, with Mg having the opposite effect, while the effect of Mn is not significant. All the alloys showed Newtonian behavior in the temperature range studied and a non-Arrhenius temperature dependence of viscosity, as usually found for pure molten metals.

Thermophysical properties of liquid Co–Cu–Ni alloys

Within the Coolcop project, funded by ESA, the thermophysical properties of selected liquid Cu–Co–Ni alloys were investigated. Using the new high-temperature oscillating cup viscometer at DLR, the viscosity of this alloy along two perpendicular cuts in the ternary phase diagram was measured as a function of temperature. Along the same cuts also surface tension and density were determined by using electromagnetic levitation and image processing.

The oscillating-cup viscometer placed in the magnetic field: the experiments under liquid gallium

Metal melts have such conductivity, that magneto-hydrodynamic effects can be easily observed even in moderate magnetic fields (around 0.01T) under conditions achieved in conventional physicochemical experiments. This fact gives an opportunity to create new methods of analyzing metal melts properties. Current work represents the experiments with the oscillating cup viscometer placed in the uniform steady longitudinal magnetic field. The oscillation' parameters dependencies on magnetic induction of the applied magnetic field have been measured. To record the motion of the viscometer the new optical scheme, which allows writing down quasi-continuously viscometer's angle position, has been implemented. Estimation of oscillation' parameters values (oscillation' decrement and period) has been evaluated with the aid of wavelet analysis and optimization methods. Field dependences of oscillation' parameters were being used for liquid gallium viscosity and electrical conductivity determination with the help of the viscosimetric theory, that was earlier suggested by us.