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Sensor Technology for Non Destructive Assessment of Materials Degradation J. Ernesto Indacochea & Ming L. Wang, Civil & Materials Engineering National.

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Presentation on theme: "Sensor Technology for Non Destructive Assessment of Materials Degradation J. Ernesto Indacochea & Ming L. Wang, Civil & Materials Engineering National."— Presentation transcript:

1 Sensor Technology for Non Destructive Assessment of Materials Degradation J. Ernesto Indacochea & Ming L. Wang, Civil & Materials Engineering National Science Foundation Problem Statement and Motivation Technical Approach Key Achievements and Future Goals Corrosion and creep damage of materials are among the most important challenges for engineers in selecting materials for operation in extreme environments. Corrosion stands for loses of about 300 billion dollars per year only in the USA. Creep assessment is a major concern for repair and life extension of infrastructure equipment in power plants. Early detection and close monitoring of corrosion and creep by non-destructive examination (NDE) is most effective to extend the life of structures and insure the continuous operation of power plants. The material is a key part of the sensor. A magnetic field is applied to the component being assessed and its magnetic response is monitored. The hysteresis loop and magnetic saturation depend on the microstructure and cross section of the exposed material. Corrosion is a surface phenomenon that reduces the cross section of materials due to mass loss. During the different stages of creep, materials suffer changes in grain size, phases, crystallographic lattice, and voids appear. The magnetoelastic response of metals due to corrosion or creep gradually changes and it is used to estimate the degradation level due to creep or corrosion. Corrosion damage with 0.5% mass loss of ferromagnetic materials can be detected with a 95% confidence limit. Microstructural changes are also detected during the sensing of corrosion and creep. In the third stage of creep damage the material becomes magnetically harder and the hysteresis curve shifts. Future Goals Improve sensor sensitivity to detect less than 0.5% mass loss due corrosion and subtle microstructure changes during creep. Extend our studies to development of nanostructured hydrogen sensing MOS devices. Full creepFull creep Intermediate creep As-received

2 Development of ultrafast AAO nanowell/Pd nanoparticle structures for hydrogen detection at low temperature Investigators: J.E. Indacochea, M.L. Wang, Department of Civil and Materials Engineering, UIC H.H. Wang, Materials Science Division, Argonne National Laboratory Primary Grant Support: National Science Foundation Problem Statement and Motivation Technical ApproachKey Achievements and Future Goals Hydrogen has been envisioned as a futuristic energy system. Gas detectors will be key components to ensure safety and reliability in hydrogen infrastructure. Limitations of current hydrogen sensing devices include long response time, low sensitivity, and poor performance at room temperature. Very large active surface and nanoscale dimensions make nanostructures a promising alternative to overcome current limitations in hydrogen detectors. Anodic aluminum oxide (AAO) nanowell array has been selected as substrate because it provides a robust, insulating, and ordered structure for catalyst deposition. Pd nanoparticles have been selected as catalyst due to their high sensitivity and selectivity to react with hydrogen. The nanostructure is being characterized and tested for hydrogen detection. Dimensions and configuration are being systematically studied to achieve optimal performance. The electrical resistance of the nanostructure increases with hydrogen concentration due to the formation of a non conductive Pd hydride phase. Response time is greatly faster compared to that for other nanostructured and micro sensing devices. Very low hydrogen concentrations can be detected at room temperature without compromising sensitivity. The main goal is to achieve optimal performance and integrate the nanostructure into modern sensors. Pd nanoparticle AAO nanowell Al substrate Change in resistance in presence of hydrogen at different concentrations H on H off

3 Joining Yttria Stabilized Zirconia (YSZ) to Crofer22-APU ® for Applications in Solid Oxide Fuel Cells Investigator: J.E. Indacochea, Department of Civil and Materials Engineering, UIC Problem Statement and Motivation Technical ApproachKey Achievements and Future Goals Develop a filler material and brazing procedure that provides a high quality hermetic seal to enhance the performance of Solid Oxide Fuel Cells (SOFCs). Reactive brazing has proved to be the most effective and efficient method for joining ceramics–to-metals. The addition of reactive elements to filler metals improve wetting in ceramics by the formation of a reaction layer that insures bonding. The thickness of the reaction layer on the interface YSZ/filer metal will have an important effect on the mechanical properties of the joint. YSZ was brazed to itself and to Crofer22-APU ® using Ag- Cu-Ti alloys. Commercial alloys: Ticusil ® (4.5%Ti) and Cusil-ABA ® (1.5%Ti) were evaluated for joining efficiency at 900°C for 15, 30, and 60 minutes in vacuum (~6 x torr.). Optical microscopy, electron microscopy, dispersive energy spectroscopy (SEM-EDS), and X-ray diffraction (XRD) were carried out in order to study the interface YSZ/Ag-Cu-Ti. YSZ reacted with the active filler metals (Ag-Cu-Ti) to form a reaction layer at the interface. This reaction layer was rich in Ti and the presence of  - TiO was confirmed using XRD analysis and SEM-EDS. The thickness of the reaction layers was a function of the Ti content in the filer metal. Reaction layers for Ticusil ® as a filler metal were larger than Cusil-ABA ®. The main goal is to develop a sound seal between the interconnect and the electrolyte that withstand operating temperatures up to 1000°C, using novel materials. YSZ Ticusil ® Interface2.0 mm XRD spectra of interface YSZ/Ticusil ®, 900°C, 60’. (a). Pure YSZ, (b). HNO 3 etched interface YSZ/Ticusil ®, (c). Ground interfaceYSZ/Ticusil ®. 2θ (a) (b) (c) 1: Monoclinic ZrO 2 2: Tetragonal ZrO 2 3: γ -AgTi 3 4: δ -TiO YSZTicusil ® YSZ Ti Ag Cu Zr 2.0 μm Braze metal YSZ Reaction layer

4 Advanced Sensor Development for Life Assessment of Power Plants J. Ernesto Indacochea & Ming L. Wang, Civil & Materials Engineering National Science Foundation Problem Statement and Motivation Technical Approach Key Achievements and Future Goals The societal needs for greater energy, demand larger power outputs. Higher yields are possible by exposing plant components to higher temperatures; this will hasten materials degradation or creep and their end life. Accurate damage appraisal is needed for effective plant maintenance and repair, as well as for remaining life assessment of components for safe operation. The electromagnetic response of the material is affected by the microstructural changes due to damage and this is assessed by means of advanced sensors. Systematic creep microstructural changes are induced and assessed in conjunction with their magnetic properties. The magnetic responses are measured with hysteresis curves. The material creep damage is measured by changes in grain size, dislocations density, micro particle precipitation and coarsening, void formation, and coalescence The microstructure changes affect the pinning factor of the magnetic domain walls (k) during magnetization; this is reflected in variations of the magnetic hysteresis curves, which is then use to estimate the creep degradation level. Accurate identification of the stages allows for better component maintenance and remaining life prediction. An extension of the Jiles-Atherton model of magnetic hysteresis to evaluate creep changes was attained to closely check the progress of the pinning domain factor. In the final creep stage, void coalescence cuses the most significant changes in the magnetic hysteresis of steel. Extend the validity of the sensor to similar failure mechanisms such as like radiation damage in nuclear power plants. Spent Life: 18 % : 33% 63% 76%

5 Nanocrystalline Carbide Derived Carbon for Tribological Applications Investigators: Michael McNallan, Civil and Materials Engineering, UIC; Ali Erdemir, Argonne National Laboratory Prime Grant Support: U.S. Department of Energy Problem Statement and Motivation Technical Approach Key Achievements and Future Goals Mechanical Seals and bearings fail due to frictional heating and wear Materials used are hard ceramics, such as SiC or WC Friction can be reduced by coating with carbon as graphite or diamond Graphitic coatings are not wear resistant Diamond coatings are wear resistant, but fail by spallation or delamination from the underlying ceramic Produce a low friction carbon layer by chemical conversion of the surface of the carbide SiC(s) + 2C l2 (g)  SiCl 4 (g) + C(s) At temperatures < 1000 o C, carbon cannot relax into equilibrium graphitic state and remains as Carbide Derived Carbon (CDC) CDC coating contains nano-porous amorphous C, fullerenes, and nanocrystalline diamond CDC is low friction, wear resistant, and resistant to spallation and delamination CDC has been produced in the laboratory It’s structure and conversion kinetics have been characterized Tribological performance was verified in laboratory and industrial scale pump tests with water CDC was patented and selected for an R&D 100 Award in 2003 CDC was Licensed to Carbide Derivative Technologies, Inc.in 2006 Scale up to industrial production rates, characterization of process reliability and testing in specific industrial environments is the next goal. max. safe temperature SiC-CDC SiC-SiC Pump seal face temperature during dry running at 4000 rpm With and without CDC coating


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