Ceramic membranes offer more advantageous performances than conventional polymeric membranes. However, membrane fouling caused by Natural Organic Matters (NOM) contained in the feed water is still become a major problem for operational efficiency. A new method of ceramic membrane pre-coating with Powdered Activated Carbon (PAC), which allows extremely contact time for adsorbing aquatic contaminants, has been studied as a pre-treatment prior to ceramic microfiltration membrane. This bench scale study evaluated five different types of PAC (SA Super, G 60, KCU 6, KCU 8 and KCU 12,). The results showed that KCU 6 with larger pore size was performed better compared to other PAC when pre-coated on membrane surface. PAC pre-coating on the ceramic membrane with KCU 6 was significantly enhance NOM removal, reduced membrane fouling and improved membrane performance. Increase of total membrane resistance was suppressed to 96%. The removal of NOM components up to 92%, 58% and 56% for biopolymers, humic substances and building blocks, respectively was achieved at pre-coating dose of 30 mg/l. Adsorption was found to be the major removal mechanism of NOM. Results obtained showed that biopolymers removal are potentially correlated with enhanced membrane performance.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18277号 / 工博第3869号 / 新制||工||1593(附属図書館) / 31135 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 松原 英一郎, 教授 杉村 博之, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In recent years, there has been an increase in the use of press hardened steel (PHS) in the body-in-white of automobiles, namely in parts such as side impact beams, roof rails, engine firewalls, and the floor area. As these parts are expected to possess corrosion resistance, Al-Si coatings are utilized on them. The implementation of Zn coatings is limited, despite possessing improved corrosion resistance attributed to cathodic corrosion protection, due to the detrimental effects of liquid metal embrittlement (LME) and microcracking. LME can be mitigated if stamping occurs at a temperature lower than the Fe-Zn peritectic temperature of 782 °C, as this ensures that the conditions of LME are not met and the cathodically-protective Γ-Fe3Zn10 phase is formed. The objective of this work was to determine a process window for stamping at lower temperatures for a GA80-coated prototype steel (steel K) with the composition of 0.19C-1.92Mn-0.20Si-0.003B-0.03Ti (wt.%). The target mechanical properties in this process window were UTS ≥ 1400 MPa, and YS ≥ 1000 MPa. To achieve robust cathodic corrosion protection, more than 15 vol% of Γ-Fe3Zn10 in the coating was desired. Furthermore, it was aimed to determine the robustness of this process and the industrial feasibility of it through pilot-scale trials for the GA80-coated prototype steel. To this end, a bare prototype steel (steel I) with the composition of 0.20C-1.96Mn-0.25Si-0.003B-0.01Ti was compared to GA-coated steel K. It was found that stamping a direct hot press forming (DHPF) temperature of 650 °C produced similar mechanical properties such as tensile strengths and ductilities. Microstructural analysis of laboratory-scale DHPF for steel K showed that both the coating and the substrate microstructures were not a strong function of the DHPF temperatures of 550 – 700 °C. The substrate predominantly consisted of martensite with small amounts of ferrite and the coating consisted of α-Fe(Zn) and ≥ 15 vol.% Γ-Fe3Zn10. Based on the fraction of Γ-Fe3Zn10 and the coating thickness, robust cathodic corrosion protection is expected from GA80-coated steel K. Furthermore, no evidence of LME or severe microcracking was observed in the microstructure for DHPF temperatures of 550–700 °C for steel K and ductile fracture was observed in tensile coupons. Tensile testing for laboratory-scale DHPF for steel K showed that the mechanical properties such as YS, UE and PUE were not significantly affected by DHPF temperatures of 550-700 °C. Moreover, the targets of UTS ≥ 1400 MPa, and YS ≥ 1000 MPa were met for all DHPF temperatures of 550 – 700 °C. Through pilot-scale tensile testing of steel K, it was determined that the targets for tensile strengths (UTS and YS), were achieved across various conditions involving austenitization at 890 °C for 60 – 240 s and DHPF temperatures ranging from 550 – 700 °C. These findings strongly suggest that industrial feasibility is attainable for DHPF of GA-coated steel K at lower temperatures, enabling the attainment of desirable mechanical properties and robust corrosion protection. Thus, it can be concluded that the process window yielding desirable properties for steel K was determined to be austenitization at 890 °C for 60 – 240 s and DHPF temperatures between 550 – 700 °C. / Thesis / Master of Applied Science (MASc) / The forming process of the steels used in the automotive industry is not suitable for zinc coatings because it requires pressing at high temperatures to ensure obtaining strong steels. Thus, zinc coatings cannot be utilized despite the desirable cathodic corrosion protection properties they can provide. This study aimed to determine a suitable process window for a zinc-coated prototype steel that would have both high strength and desirable corrosion protection. The zinc-coated prototype steel was pressed at lower temperatures. It was observed that the target mechanical properties were met for all the temperatures tested. Moreover, robust cathodic corrosion protection is expected for all the temperatures. Furthermore, pilot-scale tests yielded comparable results to those obtained in the laboratory, indicating that this process can be successfully applied in the industry as it possesses a sufficiently large process window.

Dry-cured hams often become infested with ham mites (Tyrophagus putrescentiae) during the aging process. Methyl bromide has been used to fumigate dry cured ham processing plants and is the only known fumigant that is effective at controlling ham mite infestations. However, methyl bromide will be phased out of all industries by 2015. This research was designed to 1) determine the efficacy of phosphine fumigation at controlling ham mites and red-legged beetles and its impact on the sensory quality and safety of dry cured hams, and 2) to develop and evaluate the potential of using food-grade film coatings to control mite infestations without affecting the aging process or sensory properties of dry-cured hams. Fumigation trials were conducted in simulated ham aging houses and commercial ham aging houses. Mite postembryonic mortality was 99.8% in the simulated aging houses and >99.9% in commercial aging houses two weeks post fumigation. Sensory tests with trained panelists indicated that there were no detectable differences (P>0.05) between phosphine fumigated and control hams. An analytical method was developed to determine phosphine concentration in ham. In addition, residual phosphine concentration was below the legal limit of 0.01 ppm in ham slices taken from phosphine fumigated hams. Coating trials were conducted on ham cubes and slices. Cubes coated with xanthan gum+20% propylene glycol and carrageenan/propylene glycol alginate+10% propylene glycol were effective at controlling mite infestations under laboratory conditions. Barrier properties (water vapor permeability and oxygen permeability) were measured to estimate the impact of coatings during the aging process. It was evident that carrageenan/propylene glycol alginate were permeable to moisture and therefore could potentially be applied to the hams during the aging process.

A seven-element Modified Embedded Atom Method (MEAM) potential comprising Fe, Mn, Si, C, Al, Zn, and O is developed by employing a hierarchical multiscale modeling paradigm to simulate low-alloy steels, inhibition layer, and galvanized coatings. Experimental information alongside first-principles calculations based on Density Functional Theory served as calibration data to upscale and develop the MEAM potential. For calibrating the single element potentials, the cohesive energy, lattice parameters, elastic constants, and vacancy and interstitial formation energies are used as target data. The heat of formation and elastic constants of binary compounds along with substitutional and interstitial formation energies serve as binary potential calibration data, while substitutional and interstitial pair binding energies aid in developing the ternary potential. Molecular dynamics simulations employing the developed potentials predict the thermal expansion coefficient, heat capacity, self-diffusion coefficients, thermomechanical stress-strain behavior, and solid-solution strengthening mechanisms for steel alloys comparable to those reported in the literature. Interfacial energies between the steel substrate, inhibition layer, and surface oxides shed light on the interfacial nanostructures observed in the galvanizing process.

Increasing tool life is a significant objective in production. Achieving this objective in a machining process poses a significant challenge, especially during cutting hard-to-cut materials such as superalloys, due to the severe tool chipping/failure at the beginning of the cut. Although numerous attempts have been carried out to improve tool performance and prolong tool life during the machining of difficult-to-cut materials over the past several years, researchers have not obtained sufficient control over sudden tool failure/chipping. The focus of this study is to prolong tool life and control tool chipping by developing an ultra-soft deposited layer on the cutting tool that can protect it during the machining of difficult-to-cut materials such as Inconel 718. In the current study, an ultra-soft layer of material is deposited on the tool through two different techniques; a typical physical vapor deposition (PVD) technique and a novel developed method called “pre-machining”. In the PVD method, the soft layer is deposited under a high vacuum environment using a PVD coater. In the novel pre-machining method, the soft layer is deposited through a very short machining process involving Al-Si. It should be mentioned that soft coatings have never been used before for machining applications of difficult-to-cut materials including Inconel 718. This study shows that in contrast to what is expected, depositing an ultra-soft layer on the cutting tool significantly improves tool performance, by reducing chipping, and improving the machined surface integrity during cutting of Inconel 718. The obtained results show up to a 500% ± 10% improvement in tool life and around a 150% ± 10% reduction in cutting forces. Significant reductions in work hardening, residual stress, and surface roughness on the machined surface were other main achievements of the current study. / Thesis / Doctor of Philosophy (PhD) / Inconel 718 is considered to be a difficult-to-cut material due to its poor machinability. Significant tool failure at the early stage of cutting is the main challenge of machining this material and is the most significant contributing factor to its high manufacturing costs. Studies show that the common methods used to tackle this issue have not been completely successful. The goal of the present study is to tackle the machining challenges of Inconel 718 by developing tool coatings that meet the specific needs of the material to eliminate tool failure and thereby improve overall machining performance. For this purpose, a new tool coating material and a novel deposition technique that can be used as an alternative for commonly used coatings were developed in this study to improve the tool performance during the machining of Inconel 718. In addition, thorough studies have been carried out to gain a better understanding of the dominant wear phenomena and tool surface treatments that result in an improvement in the machinability of Inconel 718.

In metal cutting applications, development of coatings to reduce friction between tool and chip and also enhance wear resistance of the tool is an important objective. The effectiveness of such coatings is ultimately evaluated through metal cutting trials; however, bench-scale tests can play a role in predicting some aspects of a candidate coating’s performance. This dissertation further develops the concept of an on-axis rotation pin-on-disc tribometer for the evaluation of friction coefficient between tool and work material pairs under temperature and stress conditions similar to those experienced between tool and chip in metal cutting. Firstly, the characteristics of the imprint formed by the spherical-tipped pin in the disc during tribometer tests are studied. Specific focus is given to the growth of the imprint during the rotating stage of the test; the severity of pile-up of work material around the periphery of the imprint; different zones of contact at the imprint surface; and evidence of (or lack thereof) of bulk shear in the surrounding work material below the surface of the disc. The importance of estimating the actual temperature at the pin-disc interface (inaccessible for direct measurement) is also raised. Evidence is presented that suggests the pin-disc interface is higher for tests involving coatings with higher electrical resistivity, despite exhibiting similar temperatures 2 mm above the interface (accessible for direct measurement). A numerical model is developed in an effort to estimate the pin-disc interface during stationary specimen tests for specific pin and disc materials under controlled conditions. An empirical relationship is also established to express the variation of electrical resistivity with temperature for cemented tungsten carbide (6% cobalt content). Finally, coefficient of friction results for coated and uncoated cemented carbide pins in contact with AISI 1045 steel discs are related to short duration turning trials involving the same material pairs. Coatings exhibiting low friction coefficient result in appreciably lower cutting forces, reduced built-up edge intensity and more tightly curled chips. The possibility that the low thermal conductivity of such coatings could be producing similar effects by forcing more heat into the chips is also explored. / Dissertation / Doctor of Philosophy (PhD) / This dissertation further develops the concept of a pin-on-disc apparatus for evaluating the friction coefficient between materials under temperature and stress conditions similar to those experienced in metal cutting. Firstly, characteristics of the imprint formed by the pin in the disc during tests with the apparatus are studied. Specific focus is given to the growth of the imprint during the rotating stage of the test and different zones of contact at the imprint surface. Secondly, the importance of estimating the actual temperature at the pin-disc interface, inaccessible for direct measurement, is raised and a numerical model developed to aid in its estimation. Finally, coefficient of friction results generated on the apparatus are correlated to the magnitude of forces measured and other observations made during metal cutting trials involving the same material pairs.

Tesis por compendio / [ES] En esta Tesis, se han analizado diferentes estrategias para adaptar las formulaciones de almidón con el fin de obtener recubrimientos útiles en la conservación poscosecha de frutas. El almidón se sustituyó parcialmente por gomas de origen microbiano (xantano, gelano y pululano) para mejorar las propiedades funcionales de las películas. La adición de gelano a la matriz de almidón, redujo su capacidad de adsorción de agua y la permeabilidad al vapor de agua y oxígeno. Tuvo un efecto positivo en las propiedades mecánicas, mejorando su resistencia a la rotura y previniendo la retrogradación. La goma xantana aumentó la resistencia a la rotura de las películas de almidón, pero no redujo su capacidad de adsorción de agua y la permeabilidad al vapor de agua. La sustitución del almidón por un 10 o 20% de gelano, podría ser una buena estrategia para obtener películas con propiedades más adecuadas con fines de envasado/recubrimiento de alimentos. Se analizaron películas mezcla de almidón-gelano con aceite esencial de tomillo (EO), con el objetivo de proporcionar actividad antifúngica a las formulaciones. El aceite se incorporó mediante emulsificación directa o encapsulado en liposomas de lecitina. Las películas mostraron un efecto antifúngico en las pruebas in vitro contra A. alternata y B. cinerea. La encapsulación del EO promovió una mayor retención del aceite, mejorando su actividad antifúngica, siendo éstas más efectivas contra B. cinerea que contra A. alternata. Una mayor proporción de almidón en el film dio lugar a mayor crecimiento fúngico a baja concentración del compuesto activo. Todas las películas exhibieron alta capacidad de barrera al oxígeno. La lecitina mejoró la capacidad de barrera al vapor de agua y redujo la rigidez, la resistencia a la rotura y la extensibilidad. Las películas con EO encapsulado, con una proporción de almidón-gelano de 8:2, fueron las más efectivas para controlar el crecimiento fúngico. Para aplicar las formulaciones de almidón-gelano como recubrimientos, se analizaron las propiedades superficiales de distintas frutas (manzana, tomate y caqui), y el coeficiente extensibilidad de las formulaciones sobre la superficie de la frutas, en función de la concentración de Tween 85. Las pieles de las frutas evaluadas se comportaron como superficies de baja energía. La adición de Tween 85 a las muestras sin EO, tuvo un efecto positivo en el ángulo de contacto y la tensión superficial. Sin embargo, cuando contenían EO, emulsionado o encapsulado en lecitina, el surfactante ejerció un efecto negativo en estas propiedades, dependiendo de su concentración. Las formulaciones con EO, emulsionado o encapsulado, no requirieron surfactante para mejorar su extensibilidad, mientras que la adición de Tween 85 a una concentración de 5x104 mg/L, mejoró notablemente esta propiedad en formulaciones S:G sin EO. Recubrimientos a base de almidón-gelano, con o sin EO emulsionado o encapsulado en liposomas de lecitina, fueron aplicados en manzanas y caquis. Los recubrimientos no redujeron la pérdida de peso en las manzanas, pero evitaron la pérdida de agua en los caquis. No se observó un efecto significativo de los recubrimientos en las tasas de respiración y el cociente de respiración de los caquis, mientras que estos parámetros aumentaron en manzanas. En los ensayos in vivo, los recubrimientos sin lecitina redujeron la incidencia y severidad de la mancha negra por A. alternata en caquis, y la severidad del moho gris por B. cinerea en manzanas. A pesar de su acción antifúngica in vitro, el EO no ejerció un efecto antifúngico adicional en la fruta. Esto podría explicarse por las interacciones particulares entre los componentes del recubrimiento, la superficie de la fruta y el patógeno. Los recubrimientos a base de almidón-gelano sin lecitina ni EO podrían aplicarse en caquis para controlar la pérdida de peso y reducir la incidencia de A. alternata. / [CA] En esta Tesi, s'han analitzat diferents estratègies per a adaptar les formulacions de midó a fi d'obtenir recobriments útils per a la conservació postcollita de fruites. El midó es va substituir parcialment per gomes d'origen microbià (xantano, gelano i pululano) per a millorar les propietats funcionals de les pel¿lícules. L'addició de gelano a les pel¿lícules de midó, va reduir la seua capacitat d'adsorció d'aigua. També va tindre un efecte positiu en les propietats mecàniques, i va millorar la seua resistència a la ruptura i va prevenir els fenòmens de retrogradació. La goma de xantano també va augmentar la resistència a la ruptura de les pel¿lícules de midó, però no va reduir la seua capacitat d'adsorció d'aigua i la permeabilitat al vapor d'aigua. La substitució del midó per un 10 o 20% de gelano, podria ser una bona estratègia per a obtenir pel¿lícules amb propietats més adequades per al envasat/recobriment d'aliments. S'analitzaren les pel¿lícules mescla de midó-gelano amb oli essencial de timó (EO), amb l'objectiu de proporcionar activitat antifúngica a les formulacions. L'oli es va incorporar mitjançant emulsificació directa o encapsulat en liposomes de lecitina. Estes pel¿lícules van mostrar un efecte antifúngic en les proves in vitro contra A. alternata i B. cinerea. L'encapsulació de l'EO en els liposomes de lecitina va promoure una major retenció de l'oli i va millorar la seua activitat antifúngica, sent estes més efectives contra B. cinerea que contra A. alternata. En les formulacions amb una major proporció de midó amb baix contingut en compost actiu va haver un major creixement fúngic. Totes les pel¿lícules van exhibir alta capacitat de barrera a l'oxigen. La presència de lecitina va millorar la capacitat de barrera al vapor d'aigua i va reduir la rigidesa, la resistència a la ruptura i l'extensibilitat. Les pel¿lícules amb EO encapsulat, amb una proporció de midó-gelano 8: 2, van ser les més efectives per a controlar el creixement fúngic. Amb l'objectiu d'aplicar les formulacions de midó-gelano com a recobriments, es van analitzar les propietats superficials de distintes fruites (poma, tomaca i caqui), i el coeficient d'extensibilitat d'estes formulacions sobre la superfície de la fruita, en funció de la concentració de Tween 85. Les pells de les fruites avaluades es van comportar com a superfícies de baixa energia. L'addició de Tween 85 a les formulacions sense EO, va tenir un efecte positiu en els angles de contacte i la tensió superficial. En presència de l'EO, emulsionat o encapsulat en liposomes de lecitina, el tensioactiu va exercir un efecte negatiu en estos valors, depenent de la seua concentració. Els recobriments amb EO, emulsionat o encapsulat, no van requerir tensioactiu per a millorar la seua extensibilitat, mentre que l'addició de Tween 85 a una concentració de 5x104 mg/L, va millorar notablement esta propietat en les formulacions sense EO. Recobriments a base de midó-gelano, amb o sense l'agregat d'EO emulsionat o encapsulat en liposomes, van ser aplicats en pomes i caquis.. Els recobriments no van reduir la pèrdua de pes en les pomes, però van evitar la pèrdua d'aigua en els caquis. No es va observar un efecte significatiu dels recobriments en les taxes de respiració i el quocient de respiració dels caquis, mentre que les taxes i el quocient de respiració van augmentar en les pomes. En els assajos in vivo, els recobriments sense lecitina van reduir la incidència i severitat de la taca negra per A. alternata en els caquis, i la severitat de la floridura grisa per B. cinerea en les pomes. No obstant això, la incorporació de l'EO no va exercir un efecte antifúngic addicional en la fruita. Açò podria explicar-se per les interaccions particulars entre els components del recobriment, la superfície de la fruita i el patogen. Els recobriments a base de midó-gelano sense lecitina o EO de timó podrien aplicar-se en caqui / [EN] In this Thesis, different strategies have been analysed to tailor starch formulations for the purposes of obtaining useful coatings in postharvest fruit preservation. Starch was partially substituted by microbial gums (xanthan, gellan, and pullulan) in order to improve film functional properties. Moisture sorption capacity and water vapour and oxygen permeability were reduced by the presence of gellan gum in the starch films. It also had a positive effect on the tensile properties, enhancing the films' strength and resistance to break and preventing retrogradation phenomena. Xanthan gum increased the tensile strength of the starch films, but did not reduce their water sorption capacity and water vapour permeability. Functional properties were not notably improved by the addition of pullulan. Then, 10 and 20 % starch could be substituted by gellan gum to obtain films with more adequate properties for food packaging/coating purposes. Starch-gellan blend films containing thyme essential oil (EO) were also studied in order to provide antifungal activity to the formulations. This was incorporated either by direct emulsification or encapsulated in lecithin liposomes. These films exhibited antifungal effect in in vitro tests against A. alternata and B. cinerea. The encapsulation of the EO in lecithin liposomes allowed for greater EO retention in the films, enhancing their antifungal activity, which were more effective against B. cinerea than against A. alternata. The antifungal action was slightly affected by the polymer matrix composition. Thus, the greatest starch ratio enhanced the fungal growth when the content of the active compound was low. All the films exhibited high oxygen barrier capacity. The presence of lecithin enhanced their water vapour barrier capacity and reduced the film stiffness, resistance to break and extensibility. The films with lecithin-encapsulated EO, with a starch-gellan ratio of 8:2, were the most effective at controlling fungal growth. In order to apply these starch-gellan formulations as fruit coatings, the surface properties of apple, tomato and persimmon, and the spreadability coefficient of these liquid formulations on the fruit surface, were analysed as a function of the concentration of Tween 85, as surfactant. The fruit skins behaved as low-energy surfaces. The values of the contact angles and surface tension of EO-free formulations were positively influenced by the addition of Tween 85. However, in the presence of emulsified or lecithin-encapsulated thyme EO, the surfactant exerted a negative effect, depending on its concentration. Coating-forming systems containing emulsified or encapsulated EO did not require surfactant to improve their already good spreadability, while Tween 85 at 5x104 mg/L notably improved this property in EO-free formulations. Starch-gellan coatings, containing or not emulsified or lecithin-encapsulated EO, were applied on apples and persimmons. Coatings did not reduce the weight loss in apples, but they prevented water loss in persimmons. In contrast, no significant effect of the coatings was observed on respiration rates and respiration quotient of persimmons, whereas they increased the respiration rates and quotient in apples. Coatings did not affect the changes in fruit firmness either in apples or persimmons. In the in vivo assays, the coatings without lecithin reduced the incidence and severity of black spot caused by A. alternata in persimmons, and the severity of grey mould caused by B. cinerea in apples. The incorporation of EO did not exert an additional antifungal effect on the fruit and seemed to exert a negative effect on some other fruit quality attributes. This could be explained by the particular interactions of the coating components, fruit surface and pathogen. Starch-gellan coatings without lecithin or thyme EO could be used in persimmons to control weight loss and reduce the incidence of infections caused by A. alternata. / This work has been founded by the “Ministerio de Economía y Competitividad” of Spain, through the Project AGL2016-76699-R and the “Conselleria de Educación, Investigación, Cultura y Deporte de la Generalitat Valenciana” trough the Santiago Grisolía grant GRISOLIA/2015/001. / Sapper, MI. (2019). Starch based coatings with thyme essential oil for fruit preservation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124342 / TESIS / Compendio

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The use of aluminiferous coatings profoundly improves the service life of superalloys but leads to the microstructural degradation of superalloys and thus the loss of mechanical properties. To solve this trade-off, two strategies were employed in this research. At first, we modified MCrAlY coatings by inducing Ta to reduce the interdiffusion effect on substrate alloys. This strategy was verified by 2000 h/1100 °C oxidation tests in two Ta-containing MCrAlY-IN792 systems. The system with 3.3 wt.% Ta MCrAlY displays an outstanding resistance to γ′ depletion in the substrate and comparable oxidation property in comparison with a reference system of Ta-free MCrAlY-IN792. Increasing Ta to 7.4 wt.% results in reduced oxidation resistance. Thermodynamic simulations revealed the phase-transformation mechanism induced by initial interdiffusion, uncovering the cause of γ′ depletion in the substrate and the mechanism behind improving resistance to γ′ depletion by Ta addition. In addition, we developed novel Y-doped AlCoCrFeNi high-entropy alloys by tuning Al/Cr ratio ACR. After a long-term isothermal test in air at 1100 °C up to 1000 h, the higher ACR alloy displayed a stronger oxidation resistance at the early oxidation stage, whereas a contrary result could be detected in the later stage. The microstructural analysis confirmed that the fast growth of spinel dominated the early oxidation process, leading to higher oxidation rate of the lower ACR alloys. The later stage was governed by the growth of Al2O3. Lager size Al2O3 gain formed on the lower ACR alloy impeded the inward diffusion of oxygen and thus reduced the oxidation rate, which was further verified by our thermodynamic calculations.