Long-Term Stability of Aluminum Oxide Based Surface Passivation Schemes Under Illumination at Elevated Temperatures

2017 ◽  
Vol 7 (5) ◽  
pp. 1197-1202 ◽  
Author(s):  
Tim Niewelt ◽  
Wolfram Kwapil ◽  
Marisa Selinger ◽  
Armin Richter ◽  
Martin C. Schubert
Keyword(s):  
Aluminum Oxide ◽  
Elevated Temperatures ◽  
Surface Passivation ◽  
Term Stability ◽  
Long Term Stability

scholarly journals Long-Term Stability of Residual Stress Improvement by Water Jet Peening Considering Working Processes

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Tadafumi Hashimoto ◽  
Yusuke Osawa ◽  
Shinsuke Itoh ◽  
Masahito Mochizuki ◽  
Kazutoshi Nishimoto
Keyword(s):  
Stress Relaxation ◽  
Residual Stresses ◽  
Microstructure Evolution ◽  
Elevated Temperatures ◽  
Water Jet ◽  
Term Stability ◽  
Long Term Stability ◽  
Compressive Stresses ◽  
Compressive Residual Stresses

To prevent primary water stress corrosion cracking (PWSCC), water jet peening (WJP) has been used on the welds of Ni-based alloys in pressurized water reactors (PWRs). Before WJP, the welds are machined and buffed in order to conduct a penetrant test (PT) to verify the weld qualities to access, and microstructure evolution takes place in the target area due to the severe plastic deformation. The compressive residual stresses induced by WJP might be unstable under elevated temperatures because of the high dislocation density in the compressive stress layer. Therefore, the stability of the compressive residual stresses caused by WJP was investigated during long-term operation by considering the microstructure evolution due to the working processes. The following conclusions were made: The compressive residual stresses were slightly relaxed in the surface layers of the thermally aged specimens. There were no differences in the magnitude of the relaxation based on temperature or time. The compressive residual stresses induced by WJP were confirmed to remain stable under elevated temperatures. The stress relaxation at the surface followed the Johnson–Mehl equation, which states that stress relaxation can occur due to the recovery of severe plastic strain, since the estimated activation energy agrees very well with the self-diffusion energy for Ni. By utilizing the additivity rule, it was indicated that stress relaxation due to recovery is completed during the startup process. It was proposed that the long-term stability of WJP under elevated temperatures must be assessed based on compressive stresses with respect to the yield stress. Thermal elastic–plastic creep analysis was performed to predict the effect of creep strain. After 100 yr of simulated continuous operation at 80% capacity, there was little change in the WJP compressive stresses under an actual operating temperature of 623 K. Therefore, the long-term stability of WJP during actual operation was analytically predicted.

scholarly journals Long term stability of c-Si surface passivation using corona charged SiO 2

2017 ◽  
Vol 412 ◽  
pp. 657-667 ◽  
Author(s):  
Ruy S. Bonilla ◽  
Christian Reichel ◽  
Martin Hermle ◽  
Phillip Hamer ◽  
Peter R. Wilshaw
Keyword(s):  
Surface Passivation ◽  
Term Stability ◽  
Long Term Stability

Computational Design of Corrosion-Resistant Fe–Cr–Ni–Al Nanocoatings for Power Generation

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
K. S. Chan ◽  
W. Liang ◽  
N. S. Cheruvu ◽  
D. W. Gandy
Keyword(s):  
Grain Growth ◽  
Elevated Temperatures ◽  
Computational Design ◽  
Full Density ◽  
Corrosion Resistant ◽  
Term Stability ◽  
Long Term Stability ◽  
Interface Toughness ◽  
Thermo Calc Software

A computational approach has been undertaken to design and assess potential Fe–Cr–Ni–Al systems to produce stable nanostructured corrosion-resistant coatings that form a protective, continuous scale of alumina or chromia at elevated temperatures. The phase diagram computation was modeled using the THERMO-CALC® software and database (Thermo-Calc® Software, 2007, THERMO-CALC for Windows Version 4, Thermo-Calc Software AB, Stockholm, Sweden; Thermo-Calc® Software, 2007, TCFE5, Version 5, Thermo-Calc Software AB, Stockholm, Sweden) to generate pseudoternary Fe–Cr–Ni–Al phase diagrams to help identify compositional ranges without the undesirable brittle phases. The computational modeling of the grain growth process, sintering of voids and interface toughness determination by indentation, assessed microstructural stability, and durability of the nanocoatings fabricated by a magnetron-sputtering process. Interdiffusion of Al, Cr, and Ni was performed using the DICTRA® diffusion code (Thermo-Calc Software®, DICTRA, Version 24, 2007, Version 25, 2008, Thermo-Calc Software AB, Stockholm, Sweden) to maximize the long-term stability of the nanocoatings. The computational results identified a new series of Fe–Cr–Ni–Al coatings that maintain long-term stability and a fine-grained microstructure at elevated temperatures. The formation of brittle σ-phase in Fe–Cr–Ni–Al alloys is suppressed for Al contents in excess of 4 wt %. The grain growth modeling indicated that the columnar-grained structure with a high percentage of low-angle grain boundaries is resistant to grain growth. Sintering modeling indicated that the initial relative density of as-processed magnetron-sputtered coatings could achieve full density after a short thermal exposure or heat-treatment. The interface toughness computation indicated that the Fe–Cr–Ni–Al nanocoatings exhibit high interface toughness in the range of 52–366J/m2. The interdiffusion modeling using the DICTRA software package indicated that inward diffusion could result in substantial to moderate Al and Cr losses from the nanocoating to the substrate during long-term thermal exposures.

Shape control of silver nanoparticles and their stability on Al2O3

2020 ◽  
Vol 8 (31) ◽  
pp. 10755-10760 ◽  
Author(s):  
Graham C. Beaton ◽  
Adam J. Bottomley ◽  
Daniel Prezgot ◽  
Anatoli Ianoul ◽  
Kevin G. Stamplecoskie
Keyword(s):  
Silver Nanoparticles ◽  
Aluminum Oxide ◽  
Shape Control ◽  
Colloidal Suspensions ◽  
Term Stability ◽  
Long Term Stability

Colloidal suspensions and films of aluminum oxide afford long-term stability to silver nanoparticles and play an important role in their light driven shape conversion.

Computational Design of Corrosion-Resistant Fe-Cr-Ni-Al Nanocoatings for Power Generation

2009 ◽  
Author(s):  
K. S. Chan ◽  
W. Liang ◽  
N. S. Cheruvu ◽  
D. W. Gandy
Keyword(s):  
Grain Growth ◽  
Elevated Temperatures ◽  
Thermal Exposure ◽  
Computational Design ◽  
Full Density ◽  
Corrosion Resistant ◽  
Term Stability ◽  
Long Term Stability ◽  
Interface Toughness

A computational approach has been undertaken to design and assess potential Fe-Cr-Ni-Al systems to produce stable nanostructured corrosion-resistant coatings that form a protective, continuous scale of alumina or chromia at elevated temperatures. Phase diagram computation was modeled using the Thermo-Calc® software and database [1, 2] to generate pseudo-ternary Fe-Cr-Ni-Al phase diagrams to help identifying compositional ranges without undesirable brittle phases. Computational modeling of the grain growth process, sintering of voids, and interface toughness determination by indentation, assessed micro-structural stability and durability of the nanocoatings fabricated by a magnetron-sputtering process. Interdiffusion of Al, Cr, and Ni was performed using the DICTRA® diffusion code [3] to maximize the long-term stability of the nanocoatings. The computational results identified a new series of Fe-Cr-Ni-Al coatings that maintain long-term stability and a fine-grained microstructure at elevated temperatures. The formation of brittle sigma phase in Fe-Cr-Ni-Al alloys is suppressed for Al contents in excess of 4 wt.%. Grain growth modeling indicated that the columnar-grained structure with a high percentage of low-angle grain boundaries is resistant to grain growth. Sintering modeling indicated that the initial relative density of as-processed magnetron-sputtered coatings could achieve full density after a short thermal exposure or heat-treatment. Interface toughness computation indicated that Fe-Cr-Ni-Al nanocoatings exhibit high interface toughness in the range of 52–366 J/m2. Interdiffusion modeling using the DICTRA software package indicated that inward diffusion could result in substantial to moderate Al and Cr losses from the nanocoating to the substrate during long-term thermal exposures.

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