James Joseph Noël

The corrosion resistance of alpha and near‐alpha titanium alloys has resulted in their widespread application in extreme environments. Their corrosion behavior is often influenced by their microstructure, particularly intermetallic particles (IMPs), and even slight compositional variations can produce significant differences in microstructure and corrosion performance. This study examines the microstructure of two different source materials for each of ASTM Grade‐2 titanium (Ti‐2), ASTM Grade‐7 titanium (Ti‐7), and ASTM Grade‐12 titanium (Ti‐12). Field emission scanning electron microscopy coupled to energy‐dispersive X‐ray spectroscopy (FESEM/EDX) and a field emission scanning Auger microprobe (FESAM) were used to investigate the relationship between the nominal composition and microstructure of each material. The IMPs on Ti‐2 were found to be enriched in Fe, with average compositions of Ti _4.6 Fe and Ti _5.5 Fe in the two Ti‐2 materials, respectively. For Ti‐7, no IMPs formed in the lower‐iron material, and Pd was distributed evenly through the Ti matrix. In the alloy with higher Fe content, the IMPs were predominantly composed of Fe and were only slightly enriched in Pd relative to the matrix. Pd was detected but could not be accurately quantified by AES due to low enrichment levels. The average IMP composition was Ti _4.8 FePd _x . For Ti‐12, Ni, Mo, and Fe were present in the IMPs. The average IMP compositions for the Ti‐12 materials were Ti _5.2 NiMo _0.17 and Ti _3.4 NiFe _0.16 Mo _0.11 . Across all materials, an increase in Fe content was associated with an increase in average IMP size; Fe played a unique role that was not shared by other elements in driving IMP formation.

Thorium-based fuels are anticipated to play a pivotal role in the future energy supply due to their natural abundance. Therefore, it’s essential to understand their properties and corrosion behaviour, especially in the context of waste management.The reactivity of UO2 and its susceptibility to dissolution rely significantly on the degree of non-stoichiometry (x in UO2+x), but, in the case of mixed urania-thoria specimens, Th has the advantages of being stable in the +4 oxidation state and having extremely low solubility; unlike U, Th has no higher, more soluble oxidation states available. In this work, three mixed urania-thoria specimens containing various thoria concentrations were studied. This study investigated the effect of Th on U dissolution and whether corrosion can be sustained if U dissolves and Th becomes enriched in the specimen surface. The reactivity of the mixed urania-thoria specimens with H2O2 was determined by performing chemical dissolution and spectroscopic analysis (ultraviolet-visible spectroscopy (UV-Vis) and inductively coupled plasma-mass spectroscopy (ICP-MS)) to measure the amount of H2O2 consumed and uranium dissolved. The results suggested the H2O2 decomposition was the dominant reaction for all the three specimens. X-ray photoelectron spectroscopy was used to understand the changes in the uranium oxidation state after dissolution studies and exhibited the dominance of U(V) after the dissolution studies, which revealed that the consumption of H2O2 is predominantly through H2O2 decomposition rather than oxidation of U. XPS also confirmed the formation of a thorium-rich layer on the mixed specimen surface.

TRi-structural ISOtropic (TRISO) particle fuel is an attractive advanced fuel type due to its improved fissionproduct retention and mechanical and thermal stability. Several investigations have confirmed the high performance of TRISO fuel under reactor operation and safety-testing conditions; however, the fuel’s degradation mechanisms and pathways under disposal repository conditions are poorly understood. Particularly underexplored is the possibility of galvanic corrosion of the uranium ceramic fuel kernel coupled to the significant amounts of graphite within the fuel layers and matrices. Herein, we report the first approach to evaluating galvanic corrosion of TRISO fuel by studying the macroscale electrochemical behaviour of UO2 and nuclear-grade graphite. The macroscale electrochemistry of nuclear-grade graphite was found to be somewhat complex, complicating electrochemical analysis; however, we show that glassy carbon is a reasonable proxy. Of the relevant radiolysis oxidants explored—O2, H2O2, NaClO, NaNO3, and NaNO2—only O2, H2O2, and NaClO may drive galvanic corrosion.

Polymeric N -heterocyclic carbene (NHC) films offer a promising strategy for generating durable protective coatings on metals.

Sulfide corrosion of Cu is rapid, and hydrogen atoms produced by its cathodic half-reaction could adsorb on the Cu surface and diffuse into the Cu, potentially leading to hydrogen embrittlement. However, in solutions with low concentrations of SH⁻, absorption of hydrogen into Cu is not observed by ex-situ hydrogen analysis, although it is unclear whether this is due to the lack of absorption, the outgassing of hydrogen from the Cu before it can be measured, or another mitigation mechanism. Herein, hydrogen uptake into Cu and the development of Cu2S layers during corrosion by SH⁻ were studied by in situ neutron reflectometry and electrochemical impedance spectroscopy. The method relies on a 4 nm Ti layer beneath 50 nm of Cu to trap hydrogen that may penetrate the Cu. Additionally, elastic recoil detection analysis and Rutherford backscattering spectrometry were used to measure hydrogen. While no increase in hydrogen was detected in either the Ti or Cu layers, a higher concentration of hydrogen was observed in the outer Cu2S layer (2560 ppm) than in the underlying Cu (244 ppm), demonstrating that bisulfide-driven corrosion does not lead to hydrogen absorption into the Cu. These results have implications for deep geological repositories utilizing Cu corrosion barriers

ASTM grade-2 titanium (Ti-2) is widely used in industrial applications due to its excellent corrosion resistance. However, in these applications, crevice corrosion or galvanic coupling can cause the formation of titanium hydride (TiHx), potentially resulting in material failure through hydrogen-induced cracking (HIC). During the metal fabrication process, Fe impurities in Ti-2 can form TixFe intermetallic particles (IMPs) that can significantly alter the corrosion behavior of the material. This study investigates the relationship between TiHx formation and TixFe IMPs in 0.5 M HCl at 60 °C by forming TiHx galvanostatically for varying durations and subsequently analyzing the surface. We determined that TiHx formation initiates at TixFe IMPs, causing swelling and creating a protrusion at these sites. Initially, the hydride grows in an arc profile around the TixFe IMP, reaching a thickness of ∼5 μm before beginning to form on the Ti matrix surface. Hydride growth into the metal occurred in preferential directions, attributed to favored H diffusion pathways. The dissolution of the Ti matrix and TixFe IMPs in the acidic solution increased with polarization time, presumably because of oxidation and/or chemical dissolution of the TiHx formed. The potential measurements during galvanostatic polarization, XRD analysis, and electron microscopy observations all indicated that TiHx grew rapidly over the first 4 h, followed by slower growth that increased the surface coverage.

This research investigates the impact of incorporating montmorillonite-based nanoclay additives on the anti-corrosive properties of a polyester/triglycidyl isocyanurate (polyester/TGIC) powder coating on phosphated steel. The self-repairing capability facilitated by the swelling and expansion of nanoclay was demonstrated to enhance the corrosion resistance of the coatings significantly. A statistical Mixture Design methodology was employed to establish the optimal combination of nanoclay dosage and coating film thickness. Nineteen experiments were conducted using Design of Experiments, and two regression models were developed using the measured polarization resistance (R_p) and specular gloss values as responses. The mathematical maximization of the R_p value predicted an optimal nanoclay dosage of 4.1% with a corresponding film thickness of 80 µm. Statistical and experimental verification validated the results obtained from the regression models. Notably, the optimized coating demonstrated an R_p value one order of magnitude higher than the coating with 4% nanoclay and a standard film thickness of 60 µm. The behavior of the newly developed coatings was analyzed and compared through measurements of open circuit potential, polarization resistance, and electrochemical impedance spectroscopy. The findings confirm the substantial improvement in the anti-corrosive and self-repairing properties of the polyester/TGIC powder coating with the incorporation of montmorillonite-based nanoclay additives.

Nuclear energy is a proven technology with a low carbon footprint. Thorium-based fuel is anticipated to play a pivotal role in the future energy supply due to its natural abundance. Therefore, it’s important to understand their properties as well as their corrosion behaviour, especially in the context of waste management. Nuclear Waste Management Organization (NWMO) is responsible for the safe long-term management of used nuclear fuel in a deep geological repository (DGR). In this approach, the spent nuclear fuel will be sealed within a carbon steel container coated with copper for corrosion protection. While the container will provide long-term containment, it is necessary to consider the consequences of its failure, which could lead to exposure of the fuel to groundwater. Although groundwater entering the failed waste container will be anoxic, H₂O radiolysis will provide oxidants capable of driving fuel corrosion/dissolution and radionuclide release. Assuming a reasonable container containment period prior to groundwater ingress, α-radiolysis will be the dominant source of oxidants, of which H₂O₂ will be the most important. The reactivity of UO₂ and its susceptibility to dissolution rely significantly on the degree of non-stoichiometry (x in UO_2+x) but, in the case of mixed urania-thoria fuel specimens, Th has the advantages of being stable in the +4 oxidation state and having extremely low solubility; unlike U, Th has no higher, more soluble oxidation states available. Therefore, this project aims to investigate whether fuel corrosion can be sustained if U dissolves and Th becomes enriched in the specimen surface. In this work, a series of mixed thoria-urania fuel specimens containing 0% to 100% thoria fabricated by various sintering techniques was characterized using several surface analysis techniques, including scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. The morphology of the surface of the mixed fuel specimens was explored using scanning electron microscopy. Raman spectroscopy observed the nearly stoichiometric structure of specimens composed of 100% thoria. With higher proportions of UO₂ in the material, peak shifts and the emergence of new peaks were observed. X-ray diffraction analysis was employed to investigate differences in the crystalline structure of the specimens with different thoria: urania ratios. Additionally, electrical impedance studies were performed on the mixed fuel specimens to understand the resistance values and determine whether the samples were suitable for electrochemical studies. All these surface characterizations can be used to compare the structural and morphological properties of the mixed fuel specimens across a range of thoria concentrations.