scholarly journals Electrolytic superconducting niobium coatings for a cryogyroscope rotor: creation and properties

2021 ◽  
Vol 2144 (1) ◽  
pp. 012037
Author(s):  
M A Okunev ◽  
A R Dubrovskiy ◽  
O V Makarova ◽  
S A Kuznetsov
Keyword(s):  
Electron Microscopy ◽  
Gas Chromatography ◽  
Quantitative Analysis ◽  
Current Density ◽  
Xrd Analysis ◽  
Cathodic Current Density ◽  
Electrolysis Time ◽  
Special Design ◽  
Cathodic Current ◽  
Metallic Impurities

Abstract Electrodeposition of niobium coatings on spherical substrates for a cryogyroscope rotor made of carbopyroceram was considered. A special design of the installation for obtaining coatings on spherical samples was created. The coatings were applied at a temperature of 750°C with the cathodic current density of 5·10−3 - 2–10−2 A·cm−2 and the electrolysis time of 8-12 h. It was found that the use of a cathodic current density of 2·10−2 A·cm−2 and higher is impractical, because there is a roughening of the coatings surface. The composition of electrolytic coatings was identified by XRD analysis. The macrostructure of niobium coatings was studied using electron microscopy. The concentration of metallic impurities in the niobium coatings was defined by spectral quantitative analysis. The content of gas impurities was determined by gas chromatography. The roughness, nonsphericity, and superconductive properties of niobium coatings were investigated.

Comparative Cathodic Behavior of ~9% Cr and Plain Steel Reinforcement in Concrete

CORROSION ◽  
2012 ◽  
Vol 68 (4) ◽  
pp. 045003-1-045003-10 ◽  
Author(s):  
M. Akhoondan ◽  
A.A. Sagüés
Keyword(s):  
Carbon Steel ◽  
Oxygen Reduction ◽  
Current Density ◽  
Surface Condition ◽  
Corrosion Current ◽  
Reduction Reaction ◽  
Cathodic Current Density ◽  
Cathodic Current ◽  
Steel Rebar ◽  
Cathodic Region

The extent of the oxygen reduction reaction in concrete was evaluated for ~9% Cr rebar approaching the ASTM A1035 specification and compared to that of conventional carbon steel rebar, at ages of up to ~1 year. Cathodic strength was measured by the cathodic current density developed at −0.35 V vs. copper/copper sulfate (Cu/CuSO4 [CSE]) and −0.40 VCSE in cyclic cathodic potentiodynamic polarization tests, both in the as-received condition with mill scale and with scale removed by glass bead surface blasting. In both conditions the ~9% Cr alloy was a substantially weaker cathode, by a factor of several fold, than carbon steel. Within each material, the surface-blasted condition yielded also much lower cathodic current density than the as-received condition. For a small anode-large cathode system with a given anode polarization function, and no important oxygen reduction concentration polarization, the corrosion current was projected to be significantly lower if the cathodic region were ~9% Cr instead of plain steel rebar with comparable surface condition. There was strong correlation between the charge storage capability of the interface and the extent of cathodic reaction of oxygen. The result cannot be ascribed solely to differences in effective surface area between the different materials and conditions.

Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte

2015 ◽  
Vol 180 ◽  
pp. 313-330 ◽  
Author(s):  
Geraint Williams ◽  
Nick Birbilis ◽  
H. Neil McMurray
Keyword(s):  
Current Density ◽  
Radial Growth ◽  
Cathodic Current Density ◽  
Nacl Solution ◽  
High Concentration ◽  
Cathodic Current ◽  
Density Distributions ◽  
Filiform Corrosion ◽  
Density Values ◽  
Current Densities

The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally “pure” Mg, these dark areas can either take the form of discs which expand radially with time, or filiform-like tracks which lengthen with time. For Mg surfaces which display disc-form corrosion features in concentrated NaCl electrolyte, a transition to filiform corrosion (FFC) is observed as the concentration is decreased, indicating ohmic constraints on radial propagation. A similar effect is observed when Mg specimens of different iron impurity are immersed in a fixed, high concentration NaCl solution, where disc-form corrosion is observed on samples having ≥280 ppm Fe, but FFC predominates at ≤80 ppm Fe. An in situ scanning vibrating electrode technique (SVET) is used to determine current density distributions within the propagating corrosion features. Cathodic current density values of between −100 and −150 A m−2 measured in central areas of disc-like features are sufficient to sustain the radial growth of a local anode at the perimeter of the discs. However, for high purity Mg specimens (≤80 ppm Fe), cathodic current densities of −10 A m−2 or less are measured over FFC affected regions, indicating that linear propagation arises when there is insufficient cathodic current produced on the corroded surface to sustain radial growth. The results are consistent with surface control of localised corrosion propagation in concentrated electrolyte, but ohmic control in dilute, lower conductivity NaCl solution.

scholarly journals Hydrogen Absorption and Desorption in Steel by Electrolytic Charging

2006 ◽  
Vol 15-17 ◽  
pp. 816-821 ◽  
Author(s):  
Geert Mertens ◽  
Lode Duprez ◽  
Bruno C. De Cooman ◽  
Marc Verhaege
Keyword(s):  
Current Density ◽  
Hydrogen Absorption ◽  
Failure Mechanisms ◽  
Great Influence ◽  
Hydrogen Desorption ◽  
Cathodic Current Density ◽  
Cathodic Current ◽  
Charging Current ◽  
Current Densities ◽  
Profound Insight

The presence of hydrogen in steel decreases its toughness and formability leading to hydrogen embrittlement. To understand the failure mechanisms of steel due to the presence of hydrogen, a profound insight in the hydrogen household of the steel is needed. This includes a study of the solubility, the diffusion and the trapping of hydrogen. Next, the absorption and desorption behavior during and after electrolytic charging must be well determined. This was investigated in this research for steels with various types of traps, e.g. dislocations, microcracks, grain boundaries and precipitates such as TiC and Ti4C2S2. The samples were cathodically charged at three different current densities: 0.8mA/cm2; 8.3mA/cm2 and 62.5mA/cm2. It was noticed that the cathodic current density used for hydrogen loading had a great influence on the results. Observation of the samples by scanning electron microscopy (SEM) showed that at the highest current density major damage of the surface had occurred. Hence it was decided to study more systematically the influence of charging current density on the resulting surface aspect and on hydrogen absorption and desorption. The hydrogen charging kinetics, maximum hydrogen solubility and hydrogen desorption behavior have also been evaluated for the different current densities during charging.

Experimental Research on Electroforming Nano-ZrO2 Reinforced Cu-Matrix Composite Aided by Pulse Power

2018 ◽  
Vol 764 ◽  
pp. 95-105
Author(s):  
Zhong Wen Sima ◽  
Zhi Yong Li ◽  
Hong Bin Cui ◽  
Hun Guo
Keyword(s):  
Surface Morphology ◽  
Matrix Composite ◽  
Current Density ◽  
Duty Cycle ◽  
Pulse Frequency ◽  
Cathodic Current Density ◽  
Ultrasonic Power ◽  
Cathodic Current ◽  
Maximum Content ◽  
Cycle Pulse

Prepared the nanoZrO2 reinforced Cu-matrix composite by pulse electroforming. The effects of the content of nanoZrO2 particle in the casting solution, average cathodic current density, duty cycle, pulse frequency and ultrasonic power on the content of nanoZrO2 in the electroforming Cu-matrix composite have been studied. The microhardness and surface morphology of Cu-ZrO2 composite were analyzed. The experimental results demonstrate that the maximum content of nanoZrO2 in the electroforming Cu-ZrO2 composite is 2.94%, microhardness is 492 HV, which is significantly improved compared with pulse pure copper’s 337 HV, when the content of nanoZrO2 is 40 g/L, average cathodic current density is 4A/dm2, duty cycle is 0.2 , pulse frequency is 1100 Hz and ultrasonic power is 20w .The surface of composite prepared by pulse electroforming is more smooth, organization is denser, grain is finer and agglomeration of nanoZrO2 particles is fewer compared with Direct-current electroforming nanoZrO2 reinforced Cu-ZrO2 composite.

Electrochemical Behaviour and Electrorefining of Cobalt in NaCl-KCl-K2TiF6 Melt

2009 ◽  
Vol 64 (7-8) ◽  
pp. 485-491 ◽  
Author(s):  
Sergey A. Kuznetsov ◽  
Olga S. Kazakova ◽  
Olga V. Makarova
Keyword(s):  
Current Density ◽  
Electrochemical Behaviour ◽  
Linear Sweep Voltammetry ◽  
Cathodic Current Density ◽  
Argon Atmosphere ◽  
Limiting Current ◽  
Linear Sweep ◽  
Cathodic Current ◽  
Limiting Current Density ◽  
The Right

AbstractThe electrorefining of cobalt in NaCl-KCl-K2TiF6 (20 wt%) melt has been investigated. It was shown that complexes of Ti(III) and Co(II) appeared in the melt due to the reaction 2Ti(IV) + Co → 2Ti(III) + Co(II) and this reaction was entirely shifted to the right hand side. On the base of linear sweep voltammetry diagnostic criteria it was found that the discharge of Co(II) to Co metal is controlled by diffusion. The limiting current density of discharge Co(II) to metal in NaCl-KCl-K2TiF6 (20 wt%) melt was determined by steady-state voltammetry. The electrorefining of cobalt was carried out in hermetic electrolyser under argon atmosphere. Initial cathodic current density was changed from 0.2 Acm−2 up to 0.7 Acm−2, the electrolysis temperature varied within 973 - 1123 K. Behaviour of impurities during cobalt electrorefining was discussed. It was shown that electrorefining led to the elimination of most of the interstitial impurities (H2, N2, O2, C), with the result that the remaining impurity levels below 10 ppm impart high ductility to cobalt.

Cathodic Protection of Iron In the Temperature Range 25 C-92 C★

CORROSION ◽  
1958 ◽  
Vol 14 (4) ◽  
pp. 54-56 ◽  
Author(s):  
G. R. HOEY ◽  
M. COHEN
Keyword(s):  
Current Density ◽  
Cathodic Protection ◽  
Cathodic Polarization ◽  
Open Circuit ◽  
Cathodic Current Density ◽  
Oxygen Solubility ◽  
Nacl Solution ◽  
Cathodic Current ◽  
Temperature Range ◽  
Higher Temperature

Abstract The cathodic protection of iron was studied in the temperature range 25 C to 92 C. The limiting protective current density and the open circuit cathodic current density for iron in dilute NaCl solution goes through a temperature maximum at roughly 75 C. This is explained in terms of the effect of decreasing oxygen solubility at the higher temperature on the local cathodic reaction, 2H+ + O2 + 4e = 20H- Iron corrodes under cathodic control at room temperature, whereas at the higher temperatures there is a mixed cathodic-anodic control. Cathodic polarization curves for iron in dilute NaCl solution were obtained in the temperature range 25 C to 92 C. Unsteady potentials were observed in the vicinity of the limiting protective current, whereas at higher and lower currents, steady potentials were observed. The current density at which the potential of the iron reaches —0.5 volt on the hydrogen scale gives satisfactory protection. The nature of the corrosion products of iron is unaffected by temperature in the range studied. 5.2.2

Porous Co–P foam as an efficient bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

2016 ◽  
Vol 4 (47) ◽  
pp. 18272-18277 ◽  
Author(s):  
SeKwon Oh ◽  
HyoWon Kim ◽  
YongKuen Kwon ◽  
MinJoong Kim ◽  
EunAe Cho ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Current Density ◽  
High Performance ◽  
Cathodic Current Density ◽  
Cathodic Current ◽  
Bifunctional Electrocatalyst ◽  
One Step

A high-performance bifunctional Co–P foam catalyst was successfully synthesized by facile one-step electrodeposition at a high cathodic current density.

Metal–organic framework-derived nickel phosphides as efficient electrocatalysts toward sustainable hydrogen generation from water splitting

RSC Advances ◽  
2015 ◽  
Vol 5 (14) ◽  
pp. 10290-10295 ◽  
Author(s):  
Tian Tian ◽  
Lunhong Ai ◽  
Jing Jiang
Keyword(s):  
Water Splitting ◽  
Current Density ◽  
High Performance ◽  
Hydrogen Generation ◽  
Metal Organic Framework ◽  
Cathodic Current Density ◽  
Cathodic Current ◽  
Nickel Phosphides ◽  
Metal Organic ◽  
Organic Framework

Ni-based metal–organic framework (MOF)-derived Ni2P nanoparticles exhibited high-performance for electrochemical HER, as manifested by a low overpotential and a large cathodic current density.

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