Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

Michael P. SanSoucieJan R. Rogers

NASA Marshall Space Flight Center (MSFC), Huntsville, AL

Vijaya KumarJustin Rodriguez

Xiao XiaoDouglas M. Matson

Tufts University, Medford, MA

1

Nineteenth Symposium on Thermophysical PropertiesBoulder, C0

June 21-26, 2015

https://ntrs.nasa.gov/search.jsp?R=20150016448 2020-03-09T23:41:21+00:00Z

MSFC Electrostatic Levitation (ESL) Laboratory

• Michael SanSoucie (EM50)

• Jan Rogers (EM50)

• Paul Craven (EM50)

• Trudy Allen (METTS)

• Glenn Fountain (ESSSA)

• Curtis Bahr (ESSSA)

2

Glenn working on the ESL Lab’s Main Chamber

Tufts University, Dr. Matson’s Group

– Left to Right:

• Francesca Minervini

• Xiao Xiao

• Vijaya Kumar

• Erick Garcia

• Vadim Reytblat

• Nina Dytiuk

• Justin Rodriguez

• Gabrielle String

• Douglas Matson

3

Need for Oxygen Partial Pressure Control

• Supports microgravity principal investigators – An oxygen control system is planned

for the European Space Agency (ESA) Materials Science Laboratory Electromagnetic Levitator (MSL –EML) on the International Space Station (ISS)

– Japan Aerospace Exploration Agency (JAXA) Electrostatic Levitation Furnace (ELF) that is planned to fly on the ISS

• Surface tension of molten metals is affected by even a small amount of adsorption of oxygen– Oxidation may have an impact of 10-30% on surface

tension measurements3. – Causes a decrease in surface tension

• Oxidation can occur at very low 𝑝𝑂2– Has been observed in the MSFC ESL as low as ~ 1x10-25

bar 𝑝𝑂2

References: 1. Ozawa, S., et.al., Relationship of Surface Tension, Oxygen Partial Pressure,

and Temperature for Molten Iron, Japanese Journal of Applied Physics, 2011, 50, p. 11RD05

2. DebRoy, T. and S.A. David, Physical processes in fusion welding, Reviews of Modern Physics, 1995, 67(1), p. 85-112

3. Ozawa, S., et. al. , Influence of oxygen partial pressure on surface tension and its temperature coefficient of molten iron, Journal of Applied Physics, 2011, 109.

4

Measured relationship between surface tension, temperature, and 𝑝𝑂2for molten iron1

Calculated velocity and temperature fields for gas tungsten arc welding of pure iron and iron with 0.03 wt% oxygen2

Hardware

• Developed by AstriumNorth America

• Fabricated by ClausthalUniversity of Technology (TU Clausthal)

5

Oxygen Pump Oxygen Sensor

Controller

Oxygen Sensing

6

• Potentiometric sensor

– Determines the difference in oxygen activity in 2 gas compartments separated by an electrolyte

• Yttria-stabilized zirconia (YSZ)

• Activity of gaseous compounds corresponds closely with their partial pressures

• The cell generates an electromotive force

– Difference in pO2 between the process gas and air, which is the reference gas

• 𝑝𝑂2 is calculated by using the Nernst equation

– 𝐸 =𝑅𝑇

4𝐹𝑙𝑛

𝑝𝑂2

𝑝𝑂2𝑟𝑒𝑓

– E is the electromotive force

– R is the universal gas constant

– F is the Faraday constant

– 𝑝𝑂2𝑟𝑒𝑓

is the oxygen partial pressure of the reference

gas (the lab atmosphere, in this case)

– 𝑝𝑂2 is the oxygen partial pressure of the gas in

question

Ref: Schulz, M., et al., Oxygen partial pressure control for microgravity experiments, Solid State Ionics, 2012, 225, p. 332-336.

Oxygen Pumping

• Electric current is applied to the electrodes (Pt)– Charge moved across the

electrolyte in the form of oxygen ions, 𝑂2−

• Negative electrode– Oxygen is incorporated into

vacancies of the electrolyte, 𝑉𝑂00

• Positive electrode– Oxygen leaves crystal lattice

to form gaseous oxygen

• Must be operated above 500°C to enable sufficient ionic conductivity

7

Schematic of oxygen ion pump

Oxygen molecules move through the YSZ tube from inside to outside when a difference in electrical potential

is provided between the tube walls.

Ref: Ozawa, S., et al., Influence of oxygen partial pressure on surface tension of molten silver, Journal of Applied Physics, 2010, 107.

Example of 𝑝𝑂2vs. time

8

Oxygen partial pressure vs time Oxygen partial pressure during sample processing

Results

9

• Nickel samples were arc melted at MSFC

• Processed in the electrostatic levitator at MSFC

• Data was analyzed by Tufts University– Density– Surface Tension– Viscosity

• Chemical Analysis– Done by Luvak

Laboratories, Inc. (MA)

Oxygen Pump

Oxygen Sensor

Density

10

Surface Tension

11

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 1740

Surf

ace

Ten

sio

n (

N/m

)

T (K) Tm=1728K

pO2=1e-26

pO2=1e-18

pO2=1e-12

pO2=5e-8

Surface Tension

12

Surface Tension

13

Viscosity

14

0

2

4

6

8

10

12

14

16

1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 1740

Vis

cosi

ty(m

Pa*

s)

T (K) Tm=1728K

pO2=1e-26

pO2=1e-18

pO2=1e-12

pO2=5e-8

Viscosity

15

Viscosity

16

Oxygen Absorbed

17

• No correlation of oxygen absorbed with 𝑝𝑂2

• Samples were not yet internally equilibrated

• More work to be done

0

2

4

6

8

10

12

1.0E-281.0E-241.0E-201.0E-161.0E-121.0E-081.0E-041.0E+00

Vis

cosi

ty (

mP

a*s)

pO2 (bar)

ESL-688, 180ppm O

ESL-681, <40ppm O

ESL-676, 100ppm O

ESL-677, <30ppm O

ESL-693, 60ppm O

ESL-704, <40ppm O

ESL-679, 50ppm O

ESL-687, <40ppm O

ESL-700, 220ppm O

Conclusions

18

• Little effect on surface tension

– Need higher 𝑝𝑂2 levels

• The analysis showed the samples were not yet internally equilibrated

• The technique needs to evolve to include a thermal hold to equilibrate internal and external concentrations

Questions

19