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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

The Feasibility of Using a Galvanic Cell Array for Corrosion Detection and Solution Monitoring

An initial investigation into the response of the individual galvanic couples was conducted using potentiodynamic polarization measurements of solutions under conditions of varying corrosivity. It is hypothesized that the differing electrodes may provide a means to further investigate the corrosive nature of the analyte through genetic algorithms and pattern recognition techniques. The robust design of the electrochemical sensor makes its utilization in space exploration particularly attractive. Since the electrodes are fired on a ceramic substrate at 900 C, they may be one of the most rugged sensors available for the anticipated usage.

Kolody, Mark↗
NASA NTRS1990

A simple demonstration of corrosion cells

The objective is to reinforce and enhance the understanding of galvanic cells, anode cathode reactions and polarization phenomena. Complete instructions are given for laboratory demonstration to be performed by students.

Guichelaar, Philip J.↗
NASA NTRS1973

Electromotive force measurements on cells involving beta-alumina solid electrolyte

Open circuit emf measurements have been made to demonstrate that a two-phase, polycrystalline mixture of beta- alumina and alpha-alumina could be used as a solid electrolyte in galvanic cells with reversible electrodes fixing oxygen or aluminum chemical potentials. These measurements indicate that such a two phase solid electrolyte can be used to monitor oxygen chemical potentials as low as that corresponding to Al, Al2O3 coexistence. The activity of Na2O in beta-alumina in coexistence with alpha-alumina was also determined by emf measurements.

Choudhury, N.↗
NASA NTRS1973

Electromotive force measurements on cells involving beta-alumina solid electrolyte

Open-circuit emf measurements have been made to demonstrate that a two-phase, polycrystalline mixture of beta-alumina and alpha-alumina could be used as a solid electrolyte in galvanic cells with reversible electrodes fixing oxygen or aluminum chemical potentials. These measurements indicate that such a two-phase solid electrolyte may be used to monitor oxygen chemical potentials as low as that corresponding to Al and Al2O3 coexistence (potentials of about 10 to the minus 47th power atm at 1000 K). The activity of Na2O in beta-alumina in coexistence with alpha-alumina was also determined by emf measurements.

Choudhury, N. S.↗
NASA NTRS1978

Some studies on a solid-state sulfur probe for coal gasification systems

As a part of a program for the development of a sulfur probe for monitoring the sulfur potential in coal gasification reactors, an investigation was conducted regarding the efficiency of the solid electrolyte cell Ar+H2+H2S/CaS+CaF2+(Pt)//CaF2//Pt)+CaF2+CaS/H2S+H2+Ar. A demonstration is provided of the theory, design, and operation of a solid-state sulfur probe based on CaF2 electrolyte. It was found that the cell responds to changes in sulfur potential in a manner predicted by the Nernst equation. The response time of the cell at 1225 K, after a small change in temperature or gas composition, was 2.5 Hr, while at a lower temperature of 990 K the response time was approximately 9 hr. The cell emf was insensitive to a moderate increase in the flow rate of the test gas and/or the reference gas. The exact factors affecting the slow response time of galvanic cells based on a CaF2 electrolyte have not yet been determined. The rate-limiting steps may be either the kinetics of electrode reactions or the rate of transport through the electrolyte.

Jacob, K. T.↗
NASA NTRS1999

Electrochemical Measurement of Atmospheric Corrosion

Corrosion of Shuttle thruster components in atmospheres containing high concentrations of nitrogen tetroxide (NTO) and water is an important issue in ground operations of bipropellant systems in humid locations. Measurements of the corrosivities of NTO-containing atmospheres and the responses of different materials to these atmospheres have been accomplished using an electrochemical sensor. The sensor is composed of alternating aluminum/titanium strips separated by thin insulating layers. Under high humidity conditions a thin film of water covers the surface of the sensor. Added NTO vapor reacts with the water film to form a conductive medium and establishes a galvanic cell. The current from this cell can be integrated with respect to time and related to the corrosion activity. The surface layer formed from humid air/NTO reacts in the same way as an aqueous solution of nitric acid. Nitric acid is generally considered an important agent in NTO corrosion situations. The aluminum/titanium sensor is unresponsive to dry air, responds slightly to humid air (> 75% RH), and responds strongly to the combination of humid air and NTO. The sensor response is a power function (n = 2) of the NTO concentration. The sensor does not respond to NTO in dry air. The response of other materials in this type of sensor is related to position of the material in a galvanic series in aqueous nitric acid. The concept and operation of this electrochemical corrosion measurement is being applied to other corrosive atmospheric contaminants such as hydrogen chloride, hydrogen fluoride, sulfur dioxide, and acidic aerosols.

DeArmond, Anna H.↗
NASA NTRS2001

Thermodynamic Activity Measurements with Knudsen Cell Mass Spectrometry

Coupling the Knudsen effusion method with mass spectrometry has proven to be one of the most useful experimental techniques for studying the equilibrium between condensed phases and complex vapors. The Knudsen effusion method involves placing a condensed sample in a Knudsen cell, a small "enclosure", that is uniformly heated and held until equilibrium is attained between the condensed and vapor phases. The vapor is continuously sampled by effusion through a small orifice in the cell. A molecular beam is formed from the effusing vapor and directed into a mass spectrometer for identification and pressure measurement of the species in the vapor phase. Knudsen cell mass spectrometry (KCMS) has been used for nearly fifty years now and continues to be a leading technique for obtaining thermodynamic data. Indeed, much of the well-established vapor specie data in the JANAF tables has been obtained from this technique. This is due to the extreme versatility of the technique. All classes of materials can be studied and all constituents of the vapor phase can be measured over a wide range of pressures (approximately 10(exp -4) to 10(exp -11) bar) and temperatures (500-2800 K). The ability to selectively measure different vapor species makes KCMS a very powerful tool for the measurement of component activities in metallic and ceramic solutions. Today several groups are applying KCMS to measure thermodynamic functions in multicomponent metallic and ceramic systems. Thermodynamic functions, especially component activities, are extremely important in the development of CALPHAD (Calculation of Phase Diagrams) type thermodynamic descriptions. These descriptions, in turn, are useful for modeling materials processing and predicting reactions such as oxide formation and fiber/matrix interactions. The leading experimental methods for measuring activities are the Galvanic cell or electro-motive force (EMF) technique and the KCMS technique. Each has specific advantages, depending on material and conditions. The EMF technique is suitable for lower temperature measurements, provided a suitable cell can be constructed. KCMS is useful for higher temperature measurements in a system with volatile components. In this paper, we briefly review the KCMS technique and identify the major experimental issues that must be addressed for precise measurements. These issues include temperature measurements, cell material and cell design and absolute pressure calibration. The resolution of these issues are discussed together with some recent examples of measured thermodynamic data.

Copland, Evan H.↗
NASA NTRS1966

Device removes hydrogen gas from enclosed spaces

Hydrogen-oxidant galvanic cell removes small amounts of hydrogen gas continually released from equipment, such as vented silver-zinc batteries, in enclosed compartments where air venting is not feasible. These cells are used in satellite compartments.

Carson, W. N.↗
NASA NTRS1983

Standard free energy of formation of iron iodide

An experiment is reported where silver iodide is used to determine the standard free energy of formation of iron iodide. By using silver iodide as a solid electrolyte, a galvanic cell, Ag/AgI/Fe-FeI2, is formulated. The standard free energy of formation of AgI is known, and hence it is possible to estimate the standard free energy of formation of FeI2 by measuring the open-circuit emf of the above cell as a function of temperature. The free standard energy of formation of FeI2 determined by this method is -38784 + 24.165T cal/mol. It is estimated that the maximum error associated with this method is plus or minus 2500 cal/mol.

Khandkar, A.↗
NASA NTRS1983

Friction and wear of iron in sulfuric acid

Elemental iron sliding on aluminum oxide in aerated sulfuric acid concentrations ranging from very dilute (0.000007 N; i.e., 4 ppm) to very concentrated (96 percent acid) was studied. Load and reciprocating sliding speeds were kept constant. With the most dilute acid of 0.7 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent, the high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid, and decreased somewhat at 50 percent in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It is apparent that the normal passivating film was being worn away and a galvanic cell established which rapidly attached to the wear area.

Rengstorff, G. W. P.↗
NASA NTRS1984

Interaction of sulfuric acid corrosion and mechanical wear of iron

Friction and wear experiments were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

Rengstorff, G. W. P.↗
NASA NTRS1986

Interaction of sulfuric acid corrosion and mechanical wear of iron

Friction and wear experiment were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

Rengstorff, G. W. P.↗
NASA NTRS2002

E-tongue 2 REDOX response to heavy metals

E-Tongue 2 an array of electrochemical sensors including REDOX electrodes for Cylic Voltammetry and Anodic Stripping Voltammetry measurements, Galvanic cells for corrosion measurements, and Ion Selective Electrodes.

electromechanical sensors↗