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Disclosure of Double Exchange Bias Effect in Chromium (III) Oxide Nanoparticles
Not provided.
Formation of Nanosized Surface Layers of 03Kh17N12M2 Stainless Steel by Implantation of N{sup +} Ions
Accumulation of nitrogen in nanosized surface layers of 03Kh17N12M2 stainless steel has been detected upon N{sup +} ion implantation up to 14 at % together with metal nitrides, mainly of chromium nitride CrN and interstitial solid solution. It has been demonstrated that N{sup +} ion implantation accompanied by preliminary irradiation by Ar{sup +} and O{sup +} ions decreases maximum nitrogen concentration by at least two times. It is assumed that this is stipulated by segregation to surface layers of iron atoms upon irradiation by Ar{sup +} ions as well as formation of chromium oxide Cr{sub 2}O{sub 3} and chromium hydroxide CrOOH upon irradiation by O{sup +} ions.
H 2 O Absorption Assisted Sr-Segregation in Strontium Nickel Oxide Based Chromium Getter and Encapsulation with SrCO 3
Not Available
Auger electron spectroscopy study of oxidation of a PdCr alloy used for high-temperature sensors
A Pd-13 wt. percent Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical resistance versus temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy was used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13 wt. percent Cr.
Contact Sensor Attachment to Titanium Metal Composites
A Pd-13wt%Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical-resistance-versus-temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy has been used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13wt%Cr.
NASA PS400: A New Temperature Solid Lubricant Coating for High Temperature Wear Applications
A new solid lubricant coating, NASA PS400, has been developed for high temperature tribological applications. This plasma sprayed coating is a variant of the patented PS304 coating and has been formulated to provide higher density, smoother surface finish and better dimensional stability than PS304. PS400 is comprised of a nickel-molybdenum binder that provides strength, creep resistance and extreme oxidative and dimensional stability. Chromium oxide, silver and barium-calcium fluoride eutectic are added to the binder to form PS400.Tribological properties were evaluated with a pin-on-disk test rig in sliding contact to 650 C. Coating material samples were exposed to air, argon and vacuum at 760 C followed by cross section microscopic analysis to assess microstructure stability. Oil-Free microturbine engine hot section foil bearing tests were undertaken to assess PS400 s suitability for hot foil gas bearing applications. The preliminary results indicate that PS400 exhibits tribological characteristics comparable to the PS304 coating but with enhanced creep resistance and dimensional stability suitable for demanding, dynamic applications.
Characterizing Radiation-Induced Chromium Redox Chemistry
The redox behavior of Cr(III) and Cr(VI) in nuclear environments were studied by analyzing aqueous irradiated chromium ions using UV-Visible spectroscopy. The formation of different chromium oxidation states can occur through gamma radiolysis of chromium solutions. Characterization of radiation-induced chromium is not well understood, and yet important as chromium can make its way into the primary coolant of reactors because of the corrosion of stainless steel reactor components. Furthermore, Cr(VI) is toxic and not suitable for environmental release, therefore Cr speciation is important. Fricke dosimetry was performed to collect doses rates, specific extinction coefficients were obtained from various analytical methods for the two oxidation states of chromium. Chromium samples--conditioned at various pH's and concentration to understand the effects--were then irradiated using a Coblat-60 gamma irradiator. Three optical spectroscopy analytical methods were used , including direct oxidation state measurements and complexation by either EDTA or DPC. Complexation by EDTA was found to not be a reliable method. Radiolytic oxidation of Cr(III) to Cr(VI), and reduction of Cr(VI) to Cr(III) were clearly seen, except for Cr(III) samples were a pH less than or equal to 2, where no change occurred.
Chromium evaporation and oxidation characteristics of alumina-forming austenitic stainless steels for balance of plant applications in solid oxide fuel cells
The chromium (Cr) evaporation behavior of several different types of iron (Fe)-based AFA alloys and benchmark Cr 2 O 3 -forming Fe-based 310 and Ni-based 625 alloys was investigated for 500 h exposures at 800 °C to 900 °C in air with 10% H 2 O. The Cr evaporation rates from alumina-forming austenitic (AFA) alloys were ~5 to 35 times lower than that of the Cr 2 O 3 -forming alloys depending on alloy and temperature. The Cr evaporation behavior was correlated with extensive characterization of the chemistry and microstructure of the oxide scales, which also revealed a degree of quartz tube Si contamination during the test. As a result, long-term oxidation kinetics were also assessed at 800 to 1000 °C for up to 10,000 h in air with 10% H 2 O to provide further guidance for SOFC BOP component alloy selection.
Electrochemical cleaning: An in-Situ method to reverse chromium poisoning in solid oxide fuel cell cathodes
Chromium poisoning is one of the primary factors that affect solid oxide fuel cell (SOFC) durability. In this study, an electrochemical cleaning method has been employed to reverse the effects of chromium poisoning. Two cells were fabricated and poisoned under identical conditions by operating them at 800°C in the presence of a Cr source. Both poisoned cells exhibited a significant reduction in maximum power density and an increase in polarization resistance. One of the poisoned cells, designated as the baseline cell, was cooled to room temperature after poisoning. Microstructural observation of the baseline cell showed significant contamination of the cathode active layer by chromium oxide and (Cr,Mn) spinel deposits. The other poisoned cell was electrochemically cleaned for two hours under a mild electrolytic condition. As a result of the electrochemical cleaning process, the chromium oxide deposits were substantially removed leading to a significant reduction of Cr concentration in the cathode, especially at the cathode/electrolyte interface. Furthermore, a substantial fraction of the cell performance loss was also reversed. To the best of our knowledge, this is a first demonstration of reversing the effects of chromium poisoning using a rapid in-situ process.
Co-electrocatalytic CO 2 reduction mediated by a dibenzophosphole oxide and a chromium complex
A dibenzophosphole oxide is intrinsically inactive for electrocatalytic CO 2 reduction, however, when combined with a Cr complex it can coordinate in a reduced state, facilitating electron transfer and improving activity.
Structural, Vibrational, and Magnetic Properties of MoS{sub 2}/Cr{sub 2}O{sub 3} Composites Synthesized by the Solid-State Technique
(1− x) Cr{sub 2}O{sub 3}/x MoS{sub 2} (x = 0.25, 0.5, 0.75) were synthesized using the powder solid-state route. The structural, morphological, vibrational, and magnetic properties of the as-prepared MoS{sub 2}/Cr{sub 2}O{sub 3} samples with different Cr{sub 2}O{sub 3} contents have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy, Raman spectroscopy, and vibrating sample magnetometry (VSM), respectively. The X-ray diffraction results show the presence of the parent compounds (molybdenum disulfide (MoS{sub 2}) and chromium oxide (Cr{sub 2}O{sub 3})) in addition to a secondary phase corresponding to chromium molybdenite Cr{sub 2}Mo{sub 3}O{sub 12}. Raman and IR spectra were recorded, and the observed modes were analyzed and assigned to different normal modes of vibration. Magnetic characterizations revealed that all the series MoS{sub 2}/Cr{sub 2}O{sub 3} composites possess paramagnetic characteristics both at room temperature and at 30 K. Further, the maximum of magnetization increased with the increase of Cr{sub 2}O{sub 3} content.
Enhancement of Hot Corrosion Resistance of Modified 9Cr-1Mo Steel Through Surface Nanostructuring and Pre-oxidation
Nanosize grains of ~ 65 nm were developed with large misorientation angles of grain boundaries in surface region of normalized and tempered modified 9Cr-1Mo steel by ultrasonic shot peening (USSP) with hard steel balls of 3 mm diameter. The surface roughness and the depth of nanostructured surface region were found to increase with the duration of USSP from 0.5 to 5 min. Hot corrosion tests were performed for the Un-USSP and the samples USSPed for the durations of 0.25 and 1.5 min and also for the samples subjected to USSP and subsequently pre-oxidation at 600 °C for 4 h. The hot corrosion resistance at 600 °C under 100% NaCl coating was significantly improved by USSP for 1.5 min and subsequent pre-oxidation at 600 °C for 4 h. The results are discussed in terms of the formation of more uniform and effective protective iron–chromium oxide layer on the USSPed surface from the subsequent pre-oxidation treatment, prior to hot corrosion of the specimens under 100% NaCl coating at 600 °C.
The oxidation of Ni-20 wt. percent Cr-2ThO2
Oxidation kinetics and scale morphology of chromium oxide forming thoriated and unthoriated Ni alloys, discussing rate controlling processes effects
Preliminary Evaluation of PS300: A New Self-Lubricating High Temperature Composite Coating for Use to 800 C
This paper introduces PS300, a plasma sprayed, self-lubricating composite coating for use in sliding contacts at temperatures to 800 C. PS300 is a metal bonded chrome oxide coating with silver and BaF2/CaF2 eutectic solid lubricant additives. PS300 is similar to PS200, a chromium carbide based coating, which is currently being investigated for a variety of tribological applications. In pin-on-disk testing up to 650 C, PS300 exhibited comparable friction and wear properties to PS200. The PS300 matrix, which is predominantly chromium oxide rather than chromium carbide, does not require diamond grinding and polishes readily with silicon carbide abrasives greatly reducing manufacturing costs compared to PS200. It is anticipated that PS300 has potential for sliding bearing and seal applications in both aerospace and general industry.
INVESTIGATION OF MECHANICAL PROPERTIES AND METALLURGICAL CHARACTERISTICS OF A METALLIC CHROMIUM AND MAGNESIUM OXIDE COMPOSITE
Mechanical properties and metallurgical characteristics of chromium and magnesium oxide composite
Cr{sub 2}O{sub 5} as new cathode for rechargeable sodium ion batteries
Chromium oxide, Cr{sub 2}O{sub 5}, was synthesized by pyrolyzing CrO{sub 3} at 350 °C and employed as a new cathode in rechargeable sodium ion batteries. Cr{sub 2}O{sub 5}/Na rechargeable batteries delivered high specific capacities up to 310 mAh/g at a current density of C/16 (or 20 mA/g). High-resolution solid-state {sup 23}Na NMR both qualitatively and quantitatively revealed the reversible intercalation of Na ions into the bulk electrode and participation of Na ions in the formation of the solid-electrolyte interphase largely at low potentials. Amorphization of the electrode structure occurred during the first discharge revealed by both NMR and X-ray diffraction data. CrO{sub 3}-catalyzed electrolyte degradation and loss in electronic conductivity led to gradual capacity fading. The specific capacity stabilized at >120 mAh/g after 50 charge-discharge cycles. Further improvement in electrochemical performance is possible via electrode surface modification, polymer binder incorporation, or designs of new morphologies. - Graphical abstract: Electrochemical profile of a Cr{sub 2}O{sub 5}/Na battery cell and high-resolution solid-state {sup 23}Na MAS NMR spectrum of a Cr{sub 2}O{sub 5} electrode discharged to 2 V. - Highlights: • Cr{sub 2}O{sub 5} was synthesized and used as a new cathode in rechargeable Na ion batteries. • A high capacity of 310 mAh/g and an energy density of 564 Wh/kg were achieved. • High-resolution solid-state {sup 23}Na NMR was employed to follow the reaction mechanisms.