Tribocorrosion on Mars

2020 ◽  
Author(s):  
Javier Martin-Torres ◽  
Maria-Paz  Zorzano ◽  
Erik Nyberg ◽  
Abhilash Vakkada Ramachandran ◽  
Anshuman Bhardwaj
Keyword(s):  
Chemical Species ◽  
Support Surface ◽  
Martian Surface ◽  
Steel Material ◽  
Stainless Steel Material ◽  
Combined Action ◽  
Series Of Experiments ◽  
Robotic Missions ◽  
Human Exploration

Abstract Tribocorrosion is a degradation phenomenon of material surfaces subjected to the combined action of mechanical loading and corrosion attack caused by the environment. Although corrosive chemical species such as materials like chloride atoms, chlorides and perchlorates have been detected on the Martian surface, there is a lack of studies of its impact on materials for landed spacecraft and structures that will support surface operations on Mars. Here we present a series of experiments on the stainless-steel material of the ExoMars 2020 Rosalind Franklin rover wheels. We show how tribocorrosion induced by brines accelerate wear on the materials of the wheels. Our results do not compromise the nominal ExoMars mission but have implications for future long-term surface operations in support of future human exploration or extended robotic missions on Mars.

scholarly journals Brine-Induced Tribocorrosion Accelerates Wear on Stainless Steel: Implications for Mars Exploration

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Javier Martín‐Torres ◽  
María‐Paz Zorzano‐Mier ◽  
Erik Nyberg ◽  
Abhilash Vakkada-Ramachandran ◽  
Anshuman Bhardwaj
Keyword(s):  
Stainless Steel ◽  
Chemical Species ◽  
Support Surface ◽  
Martian Surface ◽  
Steel Material ◽  
Stainless Steel Material ◽  
Combined Action ◽  
Series Of Experiments ◽  
Robotic Missions ◽  
Human Exploration

Tribocorrosion is a degradation phenomenon of material surfaces subjected to the combined action of mechanical loading and corrosion attack caused by the environment. Although corrosive chemical species such as materials like chloride atoms, chlorides, and perchlorates have been detected on the Martian surface, there is a lack of studies of its impact on materials for landed spacecraft and structures that will support surface operations on Mars. Here, we present a series of experiments on the stainless-steel material of the ExoMars 2020 Rosalind Franklin rover wheels. We show how tribocorrosion induced by brines accelerates wear on the materials of the wheels. Our results do not compromise the nominal ExoMars mission but have implications for future long-term surface operations in support of future human exploration or extended robotic missions on Mars.

The Effect of Stress and Warfarin on the Adrenal Gland in Relation to Spontaneous Hemorrhage, as Judged by Measurement of Adrenal Ascorbic Acid and Serum Corticosterone

1971 ◽  
Vol 26 (02) ◽  
pp. 275-288 ◽  
Author(s):  
S Chattopadhyay ◽  
D. D Johnson ◽  
G. J Millar ◽  
L. B Jaques
Keyword(s):  
Ascorbic Acid ◽  
Acid Concentration ◽  
Ascorbic Acid Concentration ◽  
Corticosterone Concentration ◽  
Serum Corticosterone ◽  
Spontaneous Hemorrhage ◽  
Combined Action ◽  
Series Of Experiments ◽  
Pituitary Adrenal Axis

SummaryRats were subjected to the following procedures: No treatment, Stressor (10% NaCl i.p.), Warfarin for 7 days, Stressor followed by Warfarin; and groups were sacrificed at intervals for assessment of spontaneous hemorrhage and of adrenal ascorbic acid concentration. There was no hemorrhage in the no treatment and stressor groups; some hemorrhage in the warfarin group; profound hemorrhage with Warfarin + Stressor. The adrenal ascorbic acid concentration was found to be lower, 8 h and again 5 days after stress, and remained lower in the warfarin + stress animals. Warfarin had no effect on adrenal ascorbic acid level.In another series of experiments in which the stress consisted of an electric current to the cage floor for 6 sec over 15 min, rats were sacrificed daily for determination of serum corticosterone concentration and occurrence of spontaneous hemorrhage. There was a statistically significant increase of serum corticosterone concentration with stress, warfarin and combined warfarin and stress treatments (P< 0.001 for all three variables). There was a significant correlation (r = 0.96 and 0.89, P< 0.01) for serum corticosterone concentration with hemorrhage score and incidence of hemorrhage in stressed rats receiving warfarin, but not in those receiving only warfarin. The results indicate an activation, rather than an exhaustion, of the pituitary-adrenal axis during the combined action of anticoagulant and stress, which results in the development of spontaneous hemorrhage.

scholarly journals CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

2021 ◽  
Author(s):  
Lovel Kukuljan ◽  
Franci Gabrovšek ◽  
Matthew D. Covington ◽  
Vanessa E. Johnston
Keyword(s):  
Temporal Variations ◽  
Observation Point ◽  
Spatially Distributed ◽  
Combined Action ◽  
Karst Systems ◽  
The Relationship ◽  
Co2 Dynamics ◽  
Global Carbon

AbstractUnderstanding the dynamics and distribution of CO2 in the subsurface atmosphere of carbonate karst massifs provides important insights into dissolution and precipitation processes, the role of karst systems in the global carbon cycle, and the use of speleothems for paleoclimate reconstructions. We discuss long-term microclimatic observations in a passage of Postojna Cave, Slovenia, focusing on high spatial and temporal variations of pCO2. We show (1) that the airflow through the massif is determined by the combined action of the chimney effect and external winds and (2) that the relationship between the direction of the airflow, the geometry of the airflow pathways, and the position of the observation point explains the observed variations of pCO2. Namely, in the terminal chamber of the passage, the pCO2 is low and uniform during updraft, when outside air flows to the site through a system of large open galleries. When the airflow reverses direction to downdraft, the chamber is fed by inlets with diverse flow rates and pCO2, which enter via small conduits and fractures embedded in a CO2-rich vadose zone. If the spatial distribution of inlets and outlets produces minimal mixing between low and high pCO2 inflows, high and persistent gradients in pCO2 are formed. Such is the case in the chamber, where vertical gradients of up to 1000 ppm/m are observed during downdraft. The results presented in this work provide new insights into the dynamics and composition of the subsurface atmosphere and demonstrate the importance of long-term and spatially distributed observations.

Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells

2007 ◽  
Vol 1041 ◽  
Author(s):  
Seon Hye Kim ◽  
Toshihiro Ohshima ◽  
Yusuke Shiratori ◽  
Kohei Itoh ◽  
Kazunari Sasaki
Keyword(s):  
Water Vapor ◽  
Solid Oxide Fuel Cells ◽  
Degradation Mechanism ◽  
Chemical Species ◽  
Cell Voltage ◽  
Ambient Air ◽  
Open Circuit ◽  
Constant Current ◽  
Constant Current Density

AbstractAmbient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.

scholarly journals Phytoremediation as a Prospective Method for Rehabilitation of Areas Contaminated by Long-Term Sewage Sludge Storage: The Greek Experience

2017 ◽  
pp. 836-853
Author(s):  
N. Suchkova ◽  
E. Darakas ◽  
J. Ganoulis ◽  
Y. Vergeles
Keyword(s):  
Sewage Sludge ◽  
Plant Species ◽  
Shoot Growth ◽  
The Other ◽  
Control Treatment ◽  
Distilled Water ◽  
Series Of Experiments ◽  
And Control ◽  
Control Samples

In this work the suitability of several plant species for phytoremediation under natural and artificially installed conditions was studied. Brassica napus, Medicago sativa, Zea mays, Triticum aestivum, and Hordeum vulgare were grown in pots with sewage sludge from Sindos Main WWTP in Thessaloniki and from Sindos Industrial WWTP in Thessaloniki, Greece. The first series of experiments included comparing measurements of various parameters for the above mentioned plants and the sludge to those for control samples (the same plants growing in compost). It was shown that shoot growth was less reduced in T. aestivum and H. vulgare than in the other plant species studied. B. napus had lower germination tax, followed by M. sativa with the lowest germination tax. Generally B. napus, giving less biomass production than Z. mays and T. aestivum, is characterised by a higher ability to accumulate heavy metals like Cd, Cu, Ni, Pb, Zn, Cr, As and Hg. The second series of experiments included comparing measurements of various parameters of B. napus grown in sludge and treated each 7 days with metal solutions of Ni, Zn and Pb containing 10-2mg/l, 10-4mg/l, 10-6mg/l of each metal, to those for control plants treated with double distilled water. Results showed that shoot growth of B. napus were increased at treatments with lower concentrations of metals (10-6 mg/l) and control (treatment with d-distilled water). At the same time uptake of metal ions was increased with the concentration of the solution, i.e. at higher concentrations (10-2 mg/l). It is truly for Pb and Zn, transfer coefficient TC of which (indicates a plant’s potential to concentrate a metal) was quite high 15 % and 7 % correspondingly. It was noticed that B. napus has high ability to accumulate Cr, from the other hand it did not accumulate Ni (at present case).

Application of the First Higher-Order (M21) Mode Rayleigh Wave to the Inspection of Stainless Steel Overlays

1990 ◽  
Vol 112 (3) ◽  
pp. 298-301 ◽  
Author(s):  
D. E. Bray
Keyword(s):  
Stainless Steel ◽  
Point Contact ◽  
Base Material ◽  
Higher Order ◽  
Inspection Method ◽  
High Frequencies ◽  
Steel Material ◽  
Welding Defects ◽  
Stainless Steel Material ◽  
Probe Placement

Efficient inspection of stainless steel overlays appears to present a particularly challenging problem due to the anisotropy that is characteristic of that material. An improved inspection technique may be available, however, when the dissimilar properties of the overlay and the base material are utilized. Higher order mode Rayleigh waves which at high frequencies remain confined to the upper layer of the stainless steel material are demonstrated to be able to detect welding defects in the overlay material in a field some distance away from the probe. With this technique, a larger area may be scanned with each probe placement rather than the point contact probe inspection method that is typically used.

Sign in / Sign up

Export Citation Format

Share Document