Articles de revues : « Carbonatic and metallic surface »

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Ben Yaacov, Adva, Roey Ben David, David C. Grinter, Georg Held et Baran Eren. « Identification of Adsorbed Species and Surface Chemical State on Ag(111) in the Presence of Ethylene and Oxygen Studied with Infrared and X-ray Spectroscopies ». Physchem 1, n^o 3 (12 novembre 2021) : 259–71. http://dx.doi.org/10.3390/physchem1030020.

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Using a combination of two surface-sensitive spectroscopy techniques, the chemical state of the Ag(111) surface and the nature of the adsorbed species in the presence of ethylene and oxygen gases are identified. In the 10 mbar pressure range and 25–200 °C studied here, Ag(111) remains largely metallic even in O2-rich conditions. The only adsorbed molecular species with a low but discernible coverage is surface carbonate, which forms due to further oxidation of produced CO2, in a similar manner to its formation in ambient air on Ag surfaces. Its formation is also pressure-dependent, for instance, it is not observed when the total pressure is in the 1 mbar pressure range. Production of carbonate, along with carbon dioxide and water vapor as the main gas-phase products, suggests that an unpromoted Ag(111) surface catalyzes mainly the undesired full oxidation reaction.

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Dutta, Abhijit, Kiran Kiran, Motiar Rahaman, Ivan Zelocualtecatl Montiel, Pavel Moreno-Garcí, Soma Vesztergom, Jakub Drnec, Mehtap Oezaslan et Peter Broekmann. « Insights from Operando and Identical Location (IL) Techniques on the Activation of Electrocatalysts for the Conversion of CO2 : A Mini-Review ». CHIMIA International Journal for Chemistry 75, n^o 9 (15 septembre 2021) : 733–43. http://dx.doi.org/10.2533/chimia.2021.733.

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In this mini-review we compare two prototypical metal foam electrocatalysts applied to the transformation of CO2 into value-added products (e.g. alcohols on Cu foams and formate on Bi foams). A substantial improvement in the catalyst performance is typically achieved through thermal annealing of the as-deposited foam materials, followed by the electro-reduction of the pre-formed oxidic precursors prior or during the actual CO2 electrolysis. Utilizing highly insightful and sensitive complementary operando analytical techniques (XAS, XRD, and Raman spectroscopy) we demonstrate that this catalyst pre-activation process is entirely accomplished in case of the oxidized Cu foams prior to the formation of hydrocarbons and alcohols from the CO2. The actually active catalyst is therefore the metallic Cu derived from the precursor by means of oxide electro-reduction. Conversely, in their oxidic form, the Cu-based foam catalysts are inactive towards the CO2 reduction reaction (denoted ec-CO2 RR). Oxidized Bi foams can be regarded as an excellent counter example to the above-mentioned Cu case as both metallic and the thermally derived oxidic Bi foams are highly active towards ec-CO2 RR (formate production). Indeed, operando Raman spectroscopy reveals that CO2 electrolysis occurs upon its embedment into the oxidic Bi2O3 foam precursor, which itself undergoes partial transformation into an active sub-carbonate phase. The potential-dependent transition of sub-carbonates/oxides into the corresponding metallic Bi foam dictates the characteristic changes of the ec-CO2 RR pathway. Identical location (IL) microscopic inspection of the catalyst materials, e.g. by means of scanning electron microscopy, demonstrates substantial morphological alterations on the nm length scale on the material surface as consequence of the sub-carbonate formation and the potential-driven oxide reduction into the metallic Bi foam. The foam morphology on a mesoscopic length scale (macroporosity) remains, by contrast, fully unaffected by these phase transitions.

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Sokol, Ella, Svetlana Kokh, Olga Kozmenko, Sofya Novikova, Pavel Khvorov, Elena Nigmatulina, Elena Belogub et Maxim Kirillov. « Mineralogy and Geochemistry of Mud Volcanic Ejecta : A New Look at Old Issues (A Case Study from the Bulganak Field, Northern Black Sea) ». Minerals 8, n^o 8 (8 août 2018) : 344. http://dx.doi.org/10.3390/min8080344.

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We characterise the mineralogy and geochemistry of Oligo-Miocene Maykopian shales that are currently extruded by onshore mud volcanoes of the Kerch-Taman Province (the Northern Black Sea) from the depths of ~2.5–3 km. The ejected muds are remarkable by highly diverse authigenic mineralogy that comprises glauconite, apatite, siderite, mixed Fe–Mg–Mn–(Ca) and Mn–Ca–Fe-carbonates, pyrite, marcasite, sphalerite, cinnabar, chalcopyrite, nukundamite, akantite, native Cu, Au and Au–Ag alloys. Precise geochemical techniques and high-resolution methods are applied to study the composition of bulk rocks, sulphide and carbonate fractions, as well as individual mineral species, including trace element and isotopic compositions of carbonates (C, O) and pyrite (S). Mineralogy of clastic and heavy fractions is used as a provenance tracer. Oxygen-deficient to weakly sulphuric deposition conditions are inferred for the parent sediments proceeding from trace element partitioning between carbonate, sulphide, and metallic phases. The main conclusion of the study is that onshore mud volcanoes of the region only transport buried sedimentary material and authigenic minerals they store to the ground surface.

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Rendek, Louis J., Gary S. Chottiner et Daniel A. Scherson. « Effects of Surface Impurities on the Reactivity of Metallic Lithium toward Propylene Carbonate ». Electrochemical and Solid-State Letters 5, n^o 4 (2002) : A77. http://dx.doi.org/10.1149/1.1459680.

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Branzei, Mihai, Mihai Ovidiu Cojocaru, Leontin Nicolae Druga et Mariana Ion. « Obtaining the Controlled Sulphonitrocarburized Layer Phase Compositions, by the Variation of the Solid Powdery Medium Components ». Revista de Chimie 71, n^o 7 (4 août 2020) : 225–33. http://dx.doi.org/10.37358/rc.20.7.8240.

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Simultaneous saturation of the metallic surface with sulphur, nitrogen and carbon � named sulphonitrocarburizing (SNC) process - may be carried out in a multitude of variants, differ in media state of aggregation which provide the elements in native state, or differ in phase composition. The most commonly used media in SNC process are liquid or gaseous and from standpoint of phase composition, there are media made of compounds generator of the cyanides, representing important source of carbon and nitrogen, and as a sulphur source, may be used iron sulphide, sodium sulphide, sodium thiocyanides or ammonium. Carbamide/urea (CON2H4) it is frequently used in the media composition met in nitro-carburizing or carbo-nitriding process, alongside being added carbonates (sodium or potassium carbonate), thus resulting in cyanides (primary sources of the elements helping superficial saturation of the metallic products), as a result of the reactions which take place at the operating temperature of process. The medium toxicity decreased, based on carbamide used in nitrocarburizing and in particular, SNC process, being possible by carbonates replacing with ammonium chloride. This paper quantify the possibility of using solid powder mixture constituted of carbamide, in order to achieve SNC process of the iron matrix and effects quantification varying the percentage of the solid powdery mixture, so that it becomes possible to control the layer phase composition, by modifying the phase composition of the powder mixture used in thermo chemical processing.

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Sirenko, H. O., M. B. Skladanyuk et L. M. Soltys. « Metallization of Carbon Fibers by Double and Triple Copper Composition ». Фізика і хімія твердого тіла 16, n^o 1 (15 mars 2015) : 185–92. http://dx.doi.org/10.15330/pcss.16.1.185-192.

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The theoretical foundations of physics and chemistry and application technology of single- and double-layer coating based on Cu0+Cu2O, Ni0+P, Pb0 on the surface of carbonated fibers have been reviewed. The changes of surface layers crystal structure of carbon fibres in the course of copper-plating have been investigated. The metallic coating process using modified formaldehyde and zinc technology was realized. It is established that copper content in copper – copper oxide increases when using two-layer alternately modified formaldehyde and zinc methods.

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Ion, Rodica-Mariana, Lorena Iancu, Gabriel Vasilievici, Madalina Grigore, Ramona Andrei, George-Ionut Radu, Ramona Grigorescu et al. « Ion-Substituted Carbonated Hydroxyapatite Coatings for Model Stone Samples ». Coatings 9, n^o 4 (2 avril 2019) : 231. http://dx.doi.org/10.3390/coatings9040231.

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Carbonated hydroxyapatite derivatives (CHAp) and its metallic derivatives (Ag, Sr, Ba, K, Zn) have been prepared and characterized in this paper and their coating capacity on some model stone samples have been evaluated and discussed. These compounds were characterized by using several analytical tools, including X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), to determine the purity of the CHAp sample. The XRD and FTIR results confirmed the presence of AB-carbonated type CHAp. The thermal analysis (TGA) established two stages of weight loss that occured during the heating process: The first weight loss between 30–225 °C corresponding to the partial carbonate release from OH-channel and the second one between 226–700 °C, corresponding to some thermal reactions, possibly to the generation of calcium phosphate. The efficiency and suitability of these products on model stone samples were evaluated by monitoring the resistance to artificial weather (freeze–thaw), and pore structure changes (surface area, pore volume, pore diameter). Meanwhile, optical microscopy (OM) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM–EDS) techniques showed the particles size and surface morphology of the samples, as well as information on its chemical composition. Also, the compressive strength of these new compounds as coatings revealed a homogeneity and strengthen of these model stone samples.

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Takahashi, H., Y. B. Tian, J. Sasaki, Jun Shimizu, Li Bo Zhou, Y. Tashiro, Hisao Iwase et Sumio Kamiya. « Effects of Sodium Carbonate and Ceria Concentration on Chemo-Mechanical Grinding of Single Crystal Si Wafer ». Advanced Materials Research 76-78 (juin 2009) : 428–33. http://dx.doi.org/10.4028/www.scientific.net/amr.76-78.428.

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Chemo-mechanical grinding (CMG) process is a promising process for large-sized Si substrate fabrication at low cost. An encountered issue in current CMG process of Silicon (Si) wafers is metallic contaminations on ground Si wafer surface, which is attributed to the existence of sodium carbonate in wheel compounds. In this paper, four different CMG wheels were developed and grinding experiments were conducted to study the effects of exclusion of sodium carbonate and concentration of ceria abrasive on grinding performance. The grinding characteristics of the four wheels were analysized and discussed to reveal the effects of different compositions.

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Kumar, H., A. K. Sharma et A. S. Rajawat. « APPLICATIONS OF IMAGING SPECTROSCOPY FOR NON-METALLIC MINERAL EXPLORATION ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-5 (27 novembre 2018) : 835–38. http://dx.doi.org/10.5194/isprs-archives-xlii-5-835-2018.

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Abstract. Imaging spectroscopy/hyperspectral remote sensing technique acquires images in a very narrow and contiguous spectral bands. High spectral resolution data provided by imaging spectrometers enables remote compositional mapping of earth surface. In the present study, we demonstrate the potentials of airborne AVIRIS-NG datasets for identification and mapping of non-metallic minerals. Several minerals such as carbonates, sulphates and phyllosilicate exhibit diagnostic absorption feature in Short Wave Infrared Region (SWIR) (2.0&ndash;2.5&mu;m). Therefore, mapping of wavelength of deepest absorption in SWIR is very useful for exploratory earth surface composition/mineral mapping. To map the mineralogical diversity in the parts of Banswara region, Rajasthan, wavelength of deepest absorption feature and absorption band depth in SWIR region was calculated at each pixel. It was found that majority of pixels showed absorption near &sim;2.31, 2.33 and 2.20&mu;m. Detailed analysis of spectra of image revealed dolomite as dominant mineral at pixels showing deepest absorption at 2.31&mu;m. Calcite and clays were found to be present at pixels showing deepest absorption feature near 2.33 and 2.20&mu;m respectively. It is noted that mapping wavelength position of deepest feature is a very fast and reliable indicator of mineralogy. The mineral map of calcite and dolomite shall be useful for locating new mining prospect in the region.

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Dwijaya, Made Subekti, Muhammad Satrio Utomo, Syafira Nur Ajeng Ramadhanti, Fendy Rokhmanto, Ibrahim Purawiardi, Galih Senopati, Aprilia Erryani et Inti Mulyati. « Deposisi Kalsium Karbonat pada Ti-6Al-6Mo[CALCIUM CARBONATE DEPOSITION ON TI-6AL-6MO] ». Metalurgi 36, n^o 1 (29 avril 2021) : 17. http://dx.doi.org/10.14203/metalurgi.v36i1.583.

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Osseointegration is one of important property in development of implant materials for orthopedic applications. While biocompatible metallic materials such as titanium alloys should already have adequate biocompatibility properties as implant materials, their osseointegration property could be further improved by bioceramic coating. Calcium carbonate (CaCO3) and hydroxyapatite are two major bioceramics in bones that can be utilized to improve the osseointegration property of metallic implant materials. Current challenge on bioceramic coating of metallic implant materials is to obtain coating method that is facile and economically feasible for implementation in the industry. Here we propose a simple and straightforward method to deposit calcium carbonate on Ti-6Al-6Mo. We utilize two common biomimetic solutions, the phosphate buffer saline (Dulbecco’s PBS) and supersaturated calcification solution (SCS) to induce the calcium carbonate formation on the Ti-6Al-6Mo surface. Microstructural and elemental observations by scanning electron microscope (SEM) – energy dispersive x-ray (EDX) has shown the presence of calcium carbonate on the surface of the Ti-6Al-6Mo immersed in SCS. Moreover, the crystallography analysis by x-ray diffraction (XRD) also confirmed the formation of calcium carbonate on the surface of Ti-6Al-6Mo. We also studied the proposed method on pure Ti (>95%) as comparison and similar outcomes were also observed. The effect on duration of immersion was also accounted in current setting. The outcomes of immersion duration for 7 and 10 days were not significantly different. ABSTRAKOsseointegrasi adalah salah satu properti penting dalam pengembangan material untuk aplikasi implan tulang. Meskipun material logam biokompatibel seperti paduan titanium sudah memiliki properti biokompatibel bawaan yang sudah mencukupi sebagai material implan tulang, sifat osseointegrasi -nya masih dapat ditingkatkan dengan pelapisan biokeramik. Kalsium karbonat (CaCO3) dan hidroksiapatit adalah dua biokeramik utama pada tulang yang dapat dimanfaatkan untuk meningkatkan sifat osseointegrasi pada material implan. Tantangan saat ini pada pelapisan biokeramik pada material implant adalah memperoleh metode pelapisan yang mudah diterapkan dan ekonomis untuk selanjutnya diterapkan di industri. Pada penelitian ini dilakukan sebuah metode yang sederhana untuk mendeposisi kalsium karbonat pada permukaan Ti-6Al-6Mo. Kami menggunakan dua larutan biomimetik yang sudah secara luas digunakan, yaitu Dulbecco’s PBS (phosphate buffer saline) dan SCS (supersaturated calcification solution) untuk membuat pembentukan kalsium karbonat pada permukaan Ti-6Al-6Mo. Pengamatan struktur mikro dan elemental dengan scanning electron microscope (SEM) - energy dispersive x-ray (EDX) menunjukkan keberadaan deposit kalsium karbonat pada permukaan Ti-6Al-6Mo. Lebih lanjut, analisa kristalografi dengan difraksi x-ray (XRD) juga menguatkan keberadaan deposit kalsium karbonat pada permukaan Ti-6Al-6Mo. Kami juga mempelajari metode yang diajukan pada Ti murni (>95%) sebagai perbandingan dan diperoleh hasil yang serupa. Pengaruh durasi perendaman juga diamati dalam penelitian ini. Hasil dari imersi dengan durasi 7 dan 10 hari tidak menunjukkan perbedaan yang signifikan

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Ielo, Ileana, Fausta Giacobello, Silvia Sfameni, Giulia Rando, Maurilio Galletta, Valentina Trovato, Giuseppe Rosace et Maria Rosaria Plutino. « Nanostructured Surface Finishing and Coatings : Functional Properties and Applications ». Materials 14, n^o 11 (22 mai 2021) : 2733. http://dx.doi.org/10.3390/ma14112733.

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This review presents current literature on different nanocomposite coatings and surface finishing for textiles, and in particular this study has focused on smart materials, drug-delivery systems, industrial, antifouling and nano/ultrafiltration membrane coatings. Each of these nanostructured coatings shows interesting properties for different fields of application. In this review, particular attention is paid to the synthesis and the consequent physico-chemical characteristics of each coating and, therefore, to the different parameters that influence the substrate deposition process. Several techniques used in the characterization of these surface finishing coatings were also described. In this review the sol–gel method for preparing stimuli-responsive coatings as smart sensor materials is described; polymers and nanoparticles sensitive to pH, temperature, phase, light and biomolecules are also treated; nanomaterials based on phosphorus, borates, hydroxy carbonates and silicones are used and described as flame-retardant coatings; organic/inorganic hybrid sol–gel coatings for industrial applications are illustrated; carbon nanotubes, metallic oxides and polymers are employed for nano/ultrafiltration membranes and antifouling coatings. Research institutes and industries have collaborated in the advancement of nanotechnology by optimizing conversion processes of conventional materials into coatings with new functionalities for intelligent applications.

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Li, Zihao, Xianhuai Chen, Jinghuan Chen, Huazhen Chang, Lei Ma et Naiqiang Yan. « Flower-like Co3O4 Catalysts for Efficient Catalytic Oxidation of Multi-Pollutants from Diesel Exhaust ». Catalysts 12, n^o 5 (7 mai 2022) : 527. http://dx.doi.org/10.3390/catal12050527.

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Nowadays, the oxidation activity at the low-temperature regime for Co3O4 catalysts needs to be improved to meet the stringent regulation of multi-pollutant diesel exhaust. Herein, nanoflower-like Co3O4 diesel oxide catalysts (DOCs) were fabricated with the addition of a low-content Pt to trigger better catalytic activities for oxidizing multi-pollutants (CO, C3H6, and NO) emissions by taking advantage of the strong-metal supporting interaction. Compared to the conventional DOCs based on Pt/Al2O3, the as-synthesized Pt/Co3O4 catalysts not only exhibited better multi-pollutants oxidation activities at the low temperature but also obtained better resistance toward NO inhibition. Moreover, Pt/Co3O4 catalysts showed exceptional hydrothermal durability throughout long-term tests in the presence of water vapor. According to the XPS and H2-TPR results, Pt promoted low-temperature catalytic activity by increasing the active surface oxygen species and reducibility due to the robust synergistic interaction between metallic Pt and supporting Co3O4. Meanwhile, TGA curves confirmed the Pt atoms that facilitated the desorption of surface-active oxygen and hydroxyl radicals in a low-temperature regime. Furthermore, instead of probing the intermediates during CO and C3H6 oxidation for Pt/Co3O4 catalysts, which included carbonates, formate, and acetate species, in situ DRIFTs experiments also revealed C3H6 oxidation mainly took place over metallic Pt sites.

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Kim, Sang Youl, Han-Seung Lee et Jin-Ho Park. « Deposition of Different Metallic Coatings as Repair Materials for Concrete by Using a Twin-Wire Arc Thermal Spray Process ». Applied Sciences 12, n^o 23 (22 novembre 2022) : 11874. http://dx.doi.org/10.3390/app122311874.

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Using a concrete surface, the ingress of aggressive ions and the initiation of the corrosion reaction of an embedded steel rebar were studied. To reduce the corrosion reaction of the embedded steel rebar, either a coating on the steel rebar or a repair material was used on the concrete surface. Therefore, in the present study, 200 µm thick Cu, Ti, and 85Zn-15Al were used as repair materials, and their coatings were deposited on the concrete surface using a twin-wire arc thermal spray process. Different experiments such as bond adhesion, water permeability, immersion in a 5 wt.% NaCl solution, and accelerated carbonation were performed to assess the durability of the coatings, and the characterization of the coatings was performed by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Cu and 85Zn-15Al coatings exhibited severe defects and porosity; therefore, these coatings exhibited very low bond adhesion, whereas the Ti coating showed a dense and compact morphology, and its bond adhesion value was 11 times greater than that of the Cu coating. The NaCl immersion results can be used to determine the extent of the deterioration of different coatings in coastal areas; based on these results, the Cu coating exhibited delamination, while 85Zn-15Al showed white rust deposition. By contrast, there was no detrimental effect of NaCl immersion on the Ti coating during the 28 days under study, and the coating exhibited characteristics identical to those observed after deposition. The Ti coating reduced the carbonation depth by 1.5–2 times that of the Cu and 85Zn-15Al coatings after four and eight weeks of exposure. The present study suggests that Ti can be the potential metal used as a repair material for concrete to enhance the durability of buildings and infrastructure.

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Duan, Ning, Yao Wen Gao, Teng Zhang, Ke Ming Wu et Yin Feng Zhang. « Study on Water-Based Paint Stripper for Tinplate ». Advanced Materials Research 690-693 (mai 2013) : 2071–75. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.2071.

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A novel water-based paint stripper was prepared for white, metallic ink and varnish coated on the tinplate steel surface. The effect of accelerator and surfactant on stripping efficiency was investigated with the types and dosage of the accelerator and surfactant, the stripping temperature and stirring up condition. The highest stripping efficiency was achieved with the stripper composited by (mass fraction) 35% benzyl alcohol, 6% propanediol carbonate, 10% formic acid, 2% cetyl tri-methyl ammonium bromide (CTMAB) and 47% distilled water, respectively. This paint stripper had low volatility, and was not easy to burn. Scanning electron microscopy (SEM) test indicated that the paint stripper had little corrosive effect on tinplates.

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Deng, Xiaoqing, Yu Ding, Xiaobing Wang, Xiaojing Jia, Shuo Zhang et Xiang Li. « Insight into the Properties of Plasmonic Au/TiO2 Activated by O2/Ar Plasma ». Nanomaterials 12, n^o 1 (29 décembre 2021) : 106. http://dx.doi.org/10.3390/nano12010106.

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The performance of CO oxidation over plasmonic Au/TiO2 photocatalysts is largely determined by the electric discharge characteristics and physicochemical properties of discharge gas. To explore the activation mechanism of Au/TiO2, an O2 and Ar mixture gas as a discharge gas was employed to activate Au/TiO2. The photocatalytic activity in CO oxidation over activated Au/TiO2 was obtained, and the electric discharge characteristics, Au nanoparticle size, surface chemical state, optical property and CO chemisorption were thoroughly characterized. As the O2 content increases from 10% to 50%, the amplitude of the current pulses increases, but the number of pulses and the discharge power decrease. The photocatalytic activity of Au/TiO2 rises rapidly at first and then remains constant at 75% when the O2 content is above 50%. Compared with the discharge gas of 10% and 30% O2/Ar, the sample activated by 50% O2/Ar plasma possesses less metallic Au and more surface oxygen species and carbonate species by X-ray photoelectron spectroscopy, which is consistent with UV-vis diffuse reflectance spectra and CO chemisorption. The CO chemisorption capacities of the activated samples are the same at a long exposure time due to the approximate Au nanoparticle size observed by transmission electron microscopy. An increase in carbonate species generated from the oxygen species on the surface of TiO2 is discovered.

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Raaen, Steinar. « Adsorption of Carbon Dioxide on Mono-Layer Thick Oxidized Samarium Films on Ni(100) ». Nanomaterials 11, n^o 8 (14 août 2021) : 2064. http://dx.doi.org/10.3390/nano11082064.

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Studies of adsorption of CO2 on nanoscopic surfaces are relevant for technological applications in heterogeneous catalysis as well as for sorption of this important greenhouse gas. Presently, adsorption of carbon dioxide on pure and oxidized thin samarium layers near mono-layer thickness on Ni(100) has been investigated by photoelectron spectroscopy and temperature programmed desorption. It is observed that very little CO2 adsorb on the metallic sample for exposures in the vacuum regime at room temperature. For the oxidized sample, a large enhancement in CO2 adsorption is observed in the desorption measurements. Indications of carbonate formation on the surface were found by C 1s and O 1s XPS. After annealing of the oxidized samples to 900 K very little CO2 was found to adsorb. Differences in desorption spectra before and after annealing of the oxidized samples are correlated with changes in XPS intensities, and with changes in sample work function which determines the energy difference between molecular orbitals and substrate Fermi level, and thus the probability of charge transfer between adsorbed molecule and substrate.

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Nguyen, Thuy Ha, Han Bom Kim et Eun Duck Park. « CO and CO2 Methanation over CeO2-Supported Cobalt Catalysts ». Catalysts 12, n^o 2 (11 février 2022) : 212. http://dx.doi.org/10.3390/catal12020212.

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CO2 methanation is a promising reaction for utilizing CO2 using hydrogen generated by renewable energy. In this study, CO and CO2 methanation were examined over ceria-supported cobalt catalysts with low cobalt contents. The catalysts were prepared using a wet impregnation and co-precipitation method and pretreated at different temperatures. These preparation variables affected the catalytic performance as well as the physicochemical properties. These properties were characterized using various techniques including N2 physisorption, X-ray diffraction, H2 chemisorption, temperature-programmed reduction with H2, and temperature-programmed desorption after CO2 chemisorption. Among the prepared catalysts, the ceria-supported cobalt catalyst that was prepared using a wet impregnation method calcined in air at 500 °C, and reduced in H2 at 500 °C, showed the best catalytic performance. It is closely related to the large catalytically active surface area, large surface area, and large number of basic sites. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study revealed the presence of carbonate, bicarbonate, formate, and CO on metallic cobalt.

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Li, Hao, Qing Lin Xie, Nan Chun Chen, Hui Xu et Li Li Ma. « Research Progress of Adsorption on Heavy Metals from Aqueous Solutions by Modified Diatomite ». Key Engineering Materials 697 (juillet 2016) : 766–70. http://dx.doi.org/10.4028/www.scientific.net/kem.697.766.

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Pollution of heavy metals has become a serious environmental problem and it needs to be solved as soon as possible. Diatomite is a kind of biogenic rock and it is siliceous and sedimentary. There is abundant diatomite resource in China. Diatomite has distinctive structure of diatom monoblock. It has strong adsorbability, its specific area is large and it has high porosity. Its surface adheres a lot of active groups and negative charge. Diatomite with proper modification would show outstanding absorption effect of heavy metal ions. This paper reviewed the absorption efficiency of heavy metal ions on diatomite modified by metallic oxide, acids and bases, acticarbon, calcium carbonate and organics, the results would offer references for related researches. At last, this paper takes the outlook for the modified methods and application prospects of diatomite in wastewater treatment of heavy metals.

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Huynh, Tuyên Thi Kim, Kha Minh Lê, Thịnh Gia Phùng, Hoàng Văn Nguyễn et Phụng Mỹ Loan Lê. « Synthesis and electrochemical properties of Na0:67Mn0:75Ni0:25O2 in carbonate-based electrolytes ». Science and Technology Development Journal - Natural Sciences 5, n^o 3 (10 mai 2021) : first. http://dx.doi.org/10.32508/stdjns.v5i3.1032.

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In this work, a single phase of P2-Na0:67Mn0:75Ni0:25O2 (NaMNO) material was successfully synthesized via a coprecipitation method with the size varying from 2 to 4 mm. According to the atomic absorption spectroscopy (AAS), all the metallic elements were uniformly distributed in the bulk material with the desired ratio Mn¸Ni = 3¸1. The electrochemical properties of P2-NaNMO were investigated in carbonate-based electrolytes using 1M NaClO4 or 1M NaPF6. Among these electrolytes, this cathode exhibited the best electrochemical performance with initial capacity up to 205.7 mAh/g and capacity retention reaches 63.2% during 60 cycles when using 1M NaClO4/PC + 2% (v/v) VC. Indeed, vinylene carbonate (VC) additive plays an important role in improving the performance of NaMNO cathode through the formation of a stable cathode electrolyte interphase layer (CEI). Electrochemical impedance spectroscopy (EIS) was performed to demonstrate CEI layer formation indicated by the elevation of the electrode surface film and double layer impedance in the initial cycle. During cycling, galvanostatic intermittent titration technique (GITT) helps to calculate the Na+ ion diffusion coefficient, which was increased clearly at the working voltages of Mn3+/Mn4+ and Ni3+/Ni4+ redox couples.

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Morales, Miguel, Sandra Gordon, Óscar Fernández-Arana, Fernando García-Marro, Antonio Mateo, Luis Llanes et Gemma Fargas. « Duplex Stainless Steels for Thermal Energy Storage : Characterization of Oxide Scales Formed in Carbonate Salts at 500 °C ». Metals 12, n^o 12 (15 décembre 2022) : 2156. http://dx.doi.org/10.3390/met12122156.

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Next generation concentrated solar power (CSP) plants promise a higher operating temperature and better efficiency. However, new issues related to the corrosion against protection of the construction alloys need to be solved. In this work, two different duplex stainless steels grades, namely 2205 (DS2205) and 2507 (DS2507), were evaluated for their compatibility with the eutectic molten salt mixture of Li2CO3-K2CO3-Na2CO3 at 500 °C in air for thermal energy storage applications. Corrosion tests combined with complementary microscopy, microanalysis and mechanical techniques were employed to study the oxide scales formed on the surface of the duplex steels. The corrosion tests evidenced that the attack morphology in both duplex steels was a uniform oxidative process without localized corrosion. DS2507 presented a better corrosion resistance than DS2205, due to the formation of thinner, compact and continuous oxide layers with higher compositional content in Cr, Ni and Mo than DS2205. The oxide scales of DS2507 showed more remarkable mechanical integrity and adhesion to the metallic substrate.

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Idriss, Hicham, et Jordi Llorca. « Low Temperature Infrared Study of Carbon Monoxide Adsorption on Rh/CeO2 ». Catalysts 9, n^o 7 (11 juillet 2019) : 598. http://dx.doi.org/10.3390/catal9070598.

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Fundamental studies of the interaction of adsorbates with metal oxides alone and on which a noble metal is deposited provide information needed for catalytic reactions. Rh/CeO2 is one of the textbook catalysts for many reactions including syngas conversion to ethanol, water gas shift reaction (WGSR), and ethanol steam reforming. In this work, the adsorption of CO is studied by infrared (IR) spectroscopy, over CeO2 and 0.6 at. % Rh/CeO2 at a temperature range of 90 to 300 K. CeO2 is in the form of nanoparticles with sizes between 5 and 10 nm and exposing predominantly {111} surface termination in addition to non-negligible fraction of the {100} termination, determined from high resolution transmission electron microscopy (HRTEM). The as prepared Rh/CeO2 contained metallic Rh as well Rh cations in higher oxidation states. At 90 K two IR bands were observed at 2183–2186 and 2161–2163 cm−1, with the former saturating first. The 2163 cm−1 peak was more sensitive to CO pressure than the 2186 cm−1. Heating resulted in the depopulation of the 2163 cm−1 before the 2186 cm−1 peak. The desorption energy computed, assuming a first-order desorption kinetic, was found to be 0.35 eV for the 2186 cm−1 and 0.30 for the 2163 cm−1 IR peak (+/−0.05 eV). The equilibrium constant at 90 K was computed equal to 1.83 and 1.33 Torr−1 for the 2183 and 2161 cm−1, respectively. CO adsorption at 90 K on Rh/CeO2 resulted (in addition to the bands on CeO2) in the appearance of a broad band in the 2110–2130 cm-1 region that contained two components at 2116 and 2126 cm−1. The high frequency of this species is most likely due to adsorption on Rh clusters with very small sizes. The desorption energy of this species was found to be equal to 0.55 eV (+/−0.05 eV). Heating the CO covered Rh/CeO2 surface accelerated the disappearance of CO species over CeO2 and resulted in the appearance of CO2 bands (at about 150 K) followed by carbonate species. At 300 K, the surface was mainly composed of carbonates.

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Wang, Yian, Jie Zhang, Junjian Zheng, Hua Lin, Gongning Chen, Chao Wang, Kong Chhuon, Zhonghua Wei, Chengfenghe Jin et Xuehong Zhang. « Thermal Preparation and Application of a Novel Silicon Fertilizer Using Talc and Calcium Carbonate as Starting Materials ». Molecules 26, n^o 15 (26 juillet 2021) : 4493. http://dx.doi.org/10.3390/molecules26154493.

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The deficiency of available silicon (Si) incurred by year-round agricultural and horticultural practices highlights the significance of Si fertilization for soil replenishment. This study focuses on a novel and economical route for the synthesis of Si fertilizer via the calcination method using talc and calcium carbonate (CaCO3) as starting materials. The molar ratio of talc to CaCO3 of 1:2.0, calcination temperature of 1150 °C and calcination time of 120 min were identified as the optimal conditions to maximize the available Si content of the prepared Si fertilizer. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) characterizations elucidate the principles of the calcination temperature-dependent microstructure evolution of Si fertilizers, and the akermanite Ca2Mg(Si2O7) and merwinite Ca3Mg(SiO4)2 were identified as the primary silicates products. The results of release and solubility experiments suggest the content of available metallic element and slow-release property of the Si fertilizer obtained at the optimum preparation condition (Si-OPC). The surface morphology and properties of Si-OPC were illuminated by the results of scanning electron microscope (SEM), surface area and nitrogen adsorption analysis. The acceleration action of CaCO3 in the decomposition process of talc was demonstrated by the thermogravimetry-differential scanning calorimetry (TG-DSC) test. The pot experiment corroborates that 5 g kg−1 soil Si-OPC application sufficed to facilitate the pakchoi growth by providing nutrient elements. This evidence indicates the prepared Si fertilizer as a promising candidate for Si-deficient soil replenishment.

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Brzezińska, Magdalena, Patricia García-Muñoz, Agnieszka Ruppert et Nicolas Keller. « Photoactive ZnO Materials for Solar Light-Induced CuxO-ZnO Catalyst Preparation ». Materials 11, n^o 11 (13 novembre 2018) : 2260. http://dx.doi.org/10.3390/ma11112260.

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In this work, the solar light-induced redox photoactivity of ZnO semiconductor material was used to prepare CuxO-ZnO composite catalysts at room temperature with a control of the chemical state of the copper oxide phase. Cu2(I)O-ZnO and Cu(II)O-ZnO composite catalysts were prepared by using Cu(acac)2 in tetrahydrofuran-water and Cu(NO3)2 in water as metallic precursor, respectively. Prior to the implementation of the photon-assisted synthesis method, the most efficient photoactive ZnO material was selected from among different ZnO materials prepared by the low temperature polyol and precipitation methods with carbonates and carbamates as precipitation agents. The photocatalytic degradation of the 4-chlorophenol compound in water under simulated solar light was taken as a model reaction. The ZnO support materials were characterized by X-ray diffraction (XRD), surface area and porosimetry measurements, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the synthesis method strongly influenced their photoactivity in terms of 4-chlorophenol degradation and of total organic carbon removal. The most photoactive ZnO material was prepared by precipitation with carbonates and calcined at 300 °C, benefitting from a high specific surface area and a small mean crystallite size for achieving a complete 4-chlorophenol mineralization within 70 min of reaction, with minimum Zn2+ released to the solution. Besides thermal catalysis applications, this work has opened a new route for the facile synthesis of Cu2O-ZnO heterojunction photocatalysts that could take place under solar light of the heterojunction built between the p-type semi-conductor Cu2O with direct visible light band gap and the ZnO semiconductor phase.

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Rebelo, Rita, Jorge Padrão, Margarida M. Fernandes, Sandra Carvalho, Mariana Henriques, Andrea Zille et Raul Fangueiro. « Aging Effect on Functionalized Silver-Based Nanocoating Braided Coronary Stents ». Coatings 10, n^o 12 (16 décembre 2020) : 1234. http://dx.doi.org/10.3390/coatings10121234.

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A previously developed fiber-based polyester (PES) stent, with mechanical properties comparable to commercial nitinol stents, was coated with metallic silver (Ag0) and silver oxides (AgxO) thin films through direct current (DC) magnetron sputtering. Ag0 and AgxO coatings provide antimicrobial properties to the stents to minimize the occurrence of coronary stent infections. Nevertheless, the stent interacts with the atmosphere and then with the biological fluids and may lead to the generation of silver species with diminished antimicrobial efficiency and/or prone to induce cytotoxicity. Therefore, stent coating nanostructures aged 3 months were thoroughly analyzed by X-ray photoelectron spectroscopy (XPS) and their antimicrobial and cytotoxicity properties were assessed. Aging led to the presence of silver carbonate and bicarbonate as well as chemisorbed oxygen species in Ag0 and AgxO coatings. Bactericidal efficacy was tested against an important nosocomial bacterium, particularly associated to indwelling devices: Staphylococcus epidermidis. Aged Ag0 and AgxO coating presented a Log reduction of 1 and 2 at their surface; respectively. However, aged stents were able to induce a Log reduction of 2 (Ag0) and 4 (AgxO) on the surrounding medium. Only aged AgxO stent was able to provide a mild reduction of the bacterium at its surface and a clear antimicrobial effect (Log reduction >3) within its vicinity. More importantly, both aged Ag0 and AgxO stents were shown to be compatible with fibroblasts cells indicating that they can be safely used as indwelling devices, despite the aging effect.

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Suárez-García, F., J. I. Paredes, M. Pérez-Mendoza, J. Nauroy, A. Martínez-Alonso et J. M. D. Tascón. « Porosity Development in Carbon Nanofibers by Physical and Chemical Activation ». Journal of Nano Research 17 (février 2012) : 211–27. http://dx.doi.org/10.4028/www.scientific.net/jnanor.17.211.

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In this Work we Have Compared the Effects of Physical Activation with CO2and Chemical Activation with KOH on Porosity Development in Vapor Grown Carbon Nanofibers (CNFs). both Physical and Chemical Activations Result in Micro- and Mesoporosity Development in the Studied Cnfs. under this Work’s Conditions, Chemical Activation with KOH Was More Efficient than Physical Activation with CO2in Terms of Surface Area Increase Regarding the Fresh Material (7.5-Fold versus 4-Fold, Respectively, under the Optimal Conditions Found for each Type of Activation). Atomic Force Microscopy Indicated that, although the CNF Samples Retained their Fibrous Morphology upon both Physical and Chemical Activation, the Latter Treatment Brought about Noticeable Changes in their Nanometer-Scale Structure. Likewise, an Appreciable Decrease in Nanofiber Diameter Following both Types of Activation Was Noticed. However, such Diameter Reduction Could Not Account for the Increase in Specific Surface Area of the Activated Materials, which Has to Be Attributed to Porosity Development. X-Ray Diffraction Studies Showed that both Physical as Chemical Activation Take Place Mainly on the Disordered Skin of the Cnfs but in a Different Way. Thus, Physical Activation Removes the More Amorphous Areas from the CNF Skin by Gasification (which Increases their Structural Order), while upon Chemical Activation with KOH, the Carbon Material Is Oxidized to a Carbonate, and the Alkali Hydroxide Is Reduced to Metallic Potassium, which Becomes Intercalated between the Graphene Layers of the Carbon Material, Leading to a Certain Expansion of the Structure.

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Huang, Junwei, Qiwu Zhang, Hongchao Li et Chao Wang. « Difficulties and Recent Achievements in Flotation Separation of Fluorite from Calcite—An Overview ». Minerals 12, n^o 8 (28 juillet 2022) : 957. http://dx.doi.org/10.3390/min12080957.

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As an important strategic non-metallic mineral resource, fluorite has been widely used in various industrial fields, such as metallurgy, optics and semiconductor manufacturing, as well as fluorine-related chemical engineering. Since the major gangue minerals of fluorite ore are silicate and carbonate ones, flotation is the main beneficiation method for the concentration. Compared with the relatively easy operation for silicate-type fluorite ore, fluorite concentration from calcite has always been the most difficult challenge in the field of mineral processing. In this review, analyses of the fundamental reasons for the difficulties of flotation separation of fluorite from calcite are performed, from the similar surface properties of both calcium minerals to the deterioration by the interference of dissolved ions in the pulp during grinding and flotation. Recent achievements in the flotation separation of fluorite from calcite as the main contents are comprehensively summarized, covering all aspects of flotation reagents of collectors, depressants and modifiers. Finally, successful examples of industrial practices forfluorite and calcite flotation separation are introduced. This overview provides a detailed and comprehensive reference source for the current research status of fluorite and calcite flotation separation, and some suggestions for future research are provided.

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Liu, Chenxu, Xiaosong Li, Xinxin Li, Weizi Li, Yu Tian et Yonggang Meng. « On-Line Feedback Control of Sliding Friction of Metals Lubricated by Adsorbed Boundary SDS Films ». Lubricants 10, n^o 7 (11 juillet 2022) : 148. http://dx.doi.org/10.3390/lubricants10070148.

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The on-line feedback control of sliding friction of metallic tribopairs lubricated by adsorbed sodium dodecyl sulfate (SDS) films was demonstrated on a customized tribosystem, in which the external electric field applied on the tribopair was modulated in feedback according to the electrical contact resistance signal. When a positive voltage was applied, the adsorption of SDS anions on the surface of tribopair was enhanced so that the boundary film was stable. When the contact resistance increased to a pre-set threshold (e.g., 6~10 Ω), which indicated the formation of a relatively complete boundary film, the external voltage was switched off for saving energy. For an aqueous solution with 160 mM SDS as the lubricant, the coefficient of friction (COF) was decreased by 24% for the 316 L plate/304 steel ball under 804 MPa by modulating the applied potential of +3.5 V. For the propylene carbonate lubricant with 5 mM SDS, the COF was decreased by 39% for the Cu plate/304 steel ball under 499 MPa and 54% for the Cu plate/bearing steel ball under 520 MPa by modulating the applied potential of +20 V. This novel approach could be effective to keep good boundary lubrication of machine components under variable work conditions by on-line sensing and actuation.

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Khadra, Mahdi, Elisabeth Marie-Victoire, Myriam Bouichou, Christian Crémona et Stéphanie Vildaer. « New warning sensors to detect corrosion risk in reinforced concrete ». MATEC Web of Conferences 289 (2019) : 06002. http://dx.doi.org/10.1051/matecconf/201928906002.

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Corrosion is the most frequent but also the most deleterious deterioration mechanism affecting reinforced concrete. In addition to the economic impact of the repair works, for historical concrete structures, corrosion can generate irreversible losses of original material of great cultural value. If the usual non-destructive electrochemical methods have highlighted their efficiency in evaluating on-going corrosion activity, they also have pointed out their drawbacks for accurate extrapolation and prevention. To prevent the corrosion phenomenon, by detecting the penetration of aggressive agents, a new warning sensor system has been developed. The principle of the technique is to embed thin metallic sheets (called orphan blades) in the concrete cover, at different distances from the surface to the reinforcing bars. Then the corrosion of those very reactive orphan blades is followed during the propagation of the carbonation front and/or the penetration of chloride ions using stimulated infrared thermography. The corrosion of the sensors at different depths is indicative of the ingress speed of the front and can alert about the risk of corrosion of reinforcing bars in the concrete. The purpose of this study is to present this new technique and the first results obtained in the laboratory on corroded and non-corroded sensors.

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Ahmad, Muhammad Ashfaq, Khalil Ahmad, Hu Li, Abdelaziz Gassoumi, Rizwan Raza, Muhammad Saleem, Syed Hassan Mujtaba Jafri et Ghazanfar Abbas. « Synergistic Electrochemical Properties of Graphene Incorporated LCZ-Oxide Cathode for Low Temperature Solid Oxide Fuel Cell ». Crystals 13, n^o 3 (2 mars 2023) : 434. http://dx.doi.org/10.3390/cryst13030434.

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Mixed metallic oxides are getting increasing attention as novel electrode materials for energy conversion devices. However, low mixed ionic-electronic conductivity and high operating temperature hamper the practical applications of these devices. This study reports an effective strategy to improve the conductivity and performance of the fuel cell at low temperature by partially incorporating graphene in the Li0.1Cu0.2Zn0.7-oxide (LCZ) composite. The proposed cathode material is synthesized via the cost effective conventional solid-state route. Graphene incorporated LCZ shows excellent performance, which is attributed to the favorable charge transport paths offering low area-specific resistance. An X-ray diffractometer (XRD) and scanning electron microscope (SEM) are employed for microstructural and surface morphological analyses, respectively. Electrical conductivities of all the materials are determined by the DC four probe method, and interestingly, LCZ-1.5% graphene exhibits an excellent conductivity of 3.5 S/cm in air atmosphere at a temperature of 450 °C with a minimum value of 0.057 Ωcm2 area-specific resistance (ASR) that demonstrates significantly good performance. Moreover, the three-layer fuel cell device is fabricated using sodium carbonated Sm0.2Ce0.8O (NSDC) as an electrolyte, which can operate at low temperatures exhibiting open circuit voltage 0.95 V and shows a peak power density, i.e., 267.5 mW/cm2 with hydrogen as the fuel.

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Tsiotsias, Anastasios I., Nikolaos D. Charisiou, Ioannis V. Yentekakis et Maria A. Goula. « Capture and Methanation of CO2 Using Dual-Function Materials (DFMs) ». Chemistry Proceedings 2, n^o 1 (9 novembre 2020) : 35. http://dx.doi.org/10.3390/eccs2020-07567.

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The conversion of CO2, captured from flue gases, into synthetic natural gas (SNG) aims to create a closed carbon cycle, where excess H2 produced from renewables is utilized to transform CO2 released from existing conventional power plants into a reliable and high energy density carrier, that is CH4. In the last five years, extensive research effort has been dedicated to the synthesis and optimization of composite materials for the realization of this process. These materials, also known as dual-function materials or DFMs, typically consist of an alkaline metal oxide or carbonate phase, along with a Ru or Ni metallic phase supported on a high surface area carrier. The DFMs incorporate both sorptive and catalytic capabilities, capturing the CO2 in the initial sorption step and then converting it into CH4 upon H2 inflow. The dispersion of the sorptive and catalytically active phases, the CO2 affinity of the alkaline phase, the reducibility of the supported metals, and the selectivity towards CH4 production are some of the parameters influencing their performance. Hereby, we aim to present the most recent works dedicated to the development and optimization of such dual-function materials to be used in the combined capture and methanation of CO2.

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Morales, Miguel, Laura Cabezas, Manuel Castro-Alloca, Gemma Fargas, Luis Llanes et Antonio Mateo. « Corrosion Evaluation of Austenitic and Duplex Stainless Steels in Molten Carbonate Salts at 600 °C for Thermal Energy Storage ». Metals 12, n^o 12 (19 décembre 2022) : 2190. http://dx.doi.org/10.3390/met12122190.

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Next-generation concentrated solar power (CSP) plants are required to operate at temperatures as high as possible to reach a better energy efficiency. This means significant challenges for the construction materials in terms of corrosion resistance, among others. In the present work, the corrosion behavior in a molten eutectic ternary Li2CO3-Na2CO3-K2CO3 mixture at 600 °C was studied for three stainless steels: an austenitic grade AISI 301LN (SS301) and two duplex grades, namely 2205 (DS2205) and 2507 (DS2507). Corrosion tests combined with complementary microscopy, microanalysis and mechanical characterization techniques were employed to determine the corrosion kinetics of the steels and the oxide scales formed on the surface. The results showed that all three materials exhibited a corrosion kinetics close to a parabolic law, and their corrosion rates increased in the following order: DS2507 < SS301 < DS2205. The analyses of the oxide scales evidenced an arranged multilayer system with LiFeO2, LiCrO2, FeCr2O4 and NiO as the main compounds. While the Ni-rich inner layer of the scales presented a good adhesion to the metallic substrate, the outer layer formed by LiFeO2 exhibited a higher concentration of porosity and voids. Both the Cr and Ni contents at the inner layer and the defects at the outer layer were crucial for the corrosion resistance for each steel. Among the studied materials, super duplex stainless steel 2507 is found to be the most promising alternative for thermal energy storage of those structural components for CSP plants.

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Meng, Yongtao, Xiao Zhang, Wei-Hsuan Hung, Junkai He, Yi-Sheng Tsai, Yun Kuang, Michael J. Kenney et al. « Highly active oxygen evolution integrated with efficient CO2 to CO electroreduction ». Proceedings of the National Academy of Sciences 116, n^o 48 (13 novembre 2019) : 23915–22. http://dx.doi.org/10.1073/pnas.1915319116.

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Electrochemical reduction of CO2 to useful chemicals has been actively pursued for closing the carbon cycle and preventing further deterioration of the environment/climate. Since CO2 reduction reaction (CO2RR) at a cathode is always paired with the oxygen evolution reaction (OER) at an anode, the overall efficiency of electrical energy to chemical fuel conversion must consider the large energy barrier and sluggish kinetics of OER, especially in widely used electrolytes, such as the pH-neutral CO2-saturated 0.5 M KHCO3. OER in such electrolytes mostly relies on noble metal (Ir- and Ru-based) electrocatalysts in the anode. Here, we discover that by anodizing a metallic Ni–Fe composite foam under a harsh condition (in a low-concentration 0.1 M KHCO3 solution at 85 °C under a high-current ∼250 mA/cm2), OER on the NiFe foam is accompanied by anodic etching, and the surface layer evolves into a nickel–iron hydroxide carbonate (NiFe-HC) material composed of porous, poorly crystalline flakes of flower-like NiFe layer-double hydroxide (LDH) intercalated with carbonate anions. The resulting NiFe-HC electrode in CO2-saturated 0.5 M KHCO3 exhibited OER activity superior to IrO2, with an overpotential of 450 and 590 mV to reach 10 and 250 mA/cm2, respectively, and high stability for >120 h without decay. We paired NiFe-HC with a CO2RR catalyst of cobalt phthalocyanine/carbon nanotube (CoPc/CNT) in a CO2 electrolyzer, achieving selective cathodic conversion of CO2 to CO with >97% Faradaic efficiency and simultaneous anodic water oxidation to O2. The device showed a low cell voltage of 2.13 V and high electricity-to-chemical fuel efficiency of 59% at a current density of 10 mA/cm2.

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Reale, Rita, Giovanni Battista Andreozzi, Maria Pia Sammartino et Anna Maria Salvi. « Analytical Investigation of Iron-Based Stains on Carbonate Stones : Rust Formation, Diffusion Mechanisms, and Speciation ». Molecules 28, n^o 4 (7 février 2023) : 1582. http://dx.doi.org/10.3390/molecules28041582.

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In cultural heritage, unaesthetic stains on carbonate stones due to their close contacts with metals are of concern for the preservation of sculptures, monumental facades and archeological finds of various origin and antiquities. Rust stains made up of various oxidized iron compounds are the most frequent forms of alteration. The presence of ferric iron on rust-stained marble surfaces was confirmed in previous studies and oriented the choice of the best cleaning method (based on complexing agents specific for ferric ions). However, the composition of rust stains may vary along their extension. As the corrosion of the metallic iron proceeds, if the oxygen levels in the surroundings are low and there are no conditions to favor the oxidation, ferrous ions can also diffuse within the carbonate structure and form a variety of intermediate compounds. In this study, the iron stains on archeological marbles were compared with those artificially produced on Carrara marbles and Travertine samples. The use of integrated techniques (optical and scanning electron microscopy as well as Mössbauer and XPS spectroscopy) with complementary analytical depths, has provided the overall information. Rust formation and diffusion mechanisms in carbonates were revealed together with the evolution of iron speciation and identification of phases such as ferrihydrite, goethite, maghemite, nanomagnetite, and hematite.

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Romio, Martina, Yuri Surace, Nicolas Eshraghi, Benedikt Herzog, Bruno Eckmann, Damian Marlon Cupid, Johannes Hoffmann et Marcus Jahn. « Advanced Investigation of the Electrolyte-Mg Anode Interphase for the Development of Mg-Ion Batteries ». ECS Meeting Abstracts MA2022-02, n^o 4 (9 octobre 2022) : 465. http://dx.doi.org/10.1149/ma2022-024465mtgabs.

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Magnesium-ion batteries (MIBs) represent a promising chemistry to potentially substitute lithium-ion technologies in the e-mobility and stationary energy storage applications. This is due to the favourable properties of metallic Mg, such as: abundancy, non-toxic nature, high recycling rate1, low redox potential (-2.37 vs SHE), safety (smooth Mg2+ electrodeposition), as well as divalent character of Mg2+ cations which leads to higher theoretical volumetric capacity (3833 mAh/cm3) than Li (2046 mAh/cm3) and commercial graphite (760 mAh/cm3).2 However, the major obstacle in the further development of MIBs is the incompatibility of Mg metal anode with conventional electrolyte solutions, which are formed by mixing simple Mg-based salts (e.g Mg(TFSI)2, Mg(ClO4)2, etc.) and polar aprotic solvents (e.g. acetonitrile, carbonates, etc.). These solutions decompose at the surface of metallic Mg forming an electronic and ionic insulating layer, leading to the passivation of the Mg anode and poor performance of the overall cell. Conversely, organoborate (Mg-tetrakis(hexafluorosisopropyloxy)borate in monoglyme, MgBOR)3 or organoaluminate (1:2 AlCl3:PhMgCl in THF, APC)4 ethereal solutions are known to prevent the passivation of the Mg metal anode, allowing the reversible electrochemical Mg2+ electrodeposition onto its surface. Despite a great effort has been done in the development of MIB,5 very little is known about the formation, evolution and degradation of the solid electrolyte interphase (SEI) formed at the interface between metallic Mg and electrolyte. This work, therefore, aims to investigate the interactions between Mg metal and passivating (Mg(TFSI)2 in monoglyme:diglyme) and non-passivating (MgBOR and APC) electrolytes combining ex-situ and in-situ spectroscopic and microscopic techniques with electrochemical testing. The properties of the SEIs will be evaluated at different states of charge (ex-situ) and during cell cycling (in-situ). Raman, Fourier transformed infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies are used to identify the composition of the electrolyte interphases, as well as monitor their changes upon cell discharge-charge cycles. Scanning electron microscopy (SEM) is performed to analyse the interphase morphologies, whereas scanning microwave microscopy (SMM)6,7 locally probes the impedance of the SEI layer. Atomic force microscopy (AFM) is also employed to evaluate the roughness of the Mg metal electrodes. Cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) are carried out in order to determine the electrochemical performance of bare Mg metal or covered with SEI layers. Furthermore, electrochemical impedance spectroscopy (EIS) is employed to probe the Mg2+ diffusion coefficients through the SEI layers at different state of charge (e.g. open circuit voltage, etc.) and determine charge transfer evolution with cycling time of the Mg metal anode. As the first step, a successful polishing method was developed to remove the native oxide layer form the surface of Mg discs allowing to expose a bare Mg metal to the electrolyte solutions and to evaluate their interactions. The polishing method also enabled to perform SMM imaging of the Mg metal since a roughness between 1-2.5 µm was achieved. The Mg discs were then immersed in the electrolyte solutions and an initial deposition of interfacial species (few nanometre thickness) was observed by SEM when Mg(TFSI)2 in monoglyme:diglyme was used, whereas a smooth surface was detected with MgBOR and APC electrolytes. This resulted in different electrochemical behaviours. In fact, symmetric cells (Mg||Mg) with MgBOR electrolyte showed a significantly higher cycling stability (> 250 h) than those with Mg(TFSI)2 in monoglyme:diglyme solution. In addition, when the latter electrolyte was used, fluorinated by-products were identified by XPS. In order to study the SEI formation and growth further, in-situ spectroscopic techniques (e.g. Raman and SMM) were employed to establish a correlation between the chemical composition of the electrolyte, the voltage range of the electrochemical tests and cycling time. In particular, the SMM method was applied to MIB technologies for the first time in this work. References I. R. P. United Nations Environment Programme, (available at https://wedocs.unep.org/20.500.11822/8702); J. Niu, Z. Zhang, D. Aurbach, Adv. Energy Mater., 2020, 10, 2000697; Z. Zhao-Karger, M. E. Gil Bardaji, O. Fuhr, M. Fichtner, J. Mater. Chem. A, 2017, 5, 10815–10820; D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407, 724; R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot, V. Di Noto, J. Power Sources, 2020, 478, 229027; A. Buchter, J. Hoffmann, A. Delvallée, E. Brinciotti, D. Hapiuk, C. Licitra, K. Louarn, A. Arnoult, G. Almuneau, F. Piquemal, M. Zeier, F. Kienberger, Rev. Sci. Instrum., 2018, 89, 23704; J. Hoffmann, M. Wollensack, M. Zeier, J. Niegemann, H. Huber, F. Kienberger, in 2012 12th IEEE International Conference on Nanotechnology (IEEE-NANO), pp. 1–4.

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Sugiyama, Sakuwa, Ogino, Sakamoto, Shimoda, Katoh et Kimura. « Gas-Phase Epoxidation of Propylene to Propylene Oxide on a Supported Catalyst Modified with Various Dopants ». Catalysts 9, n^o 8 (26 juillet 2019) : 638. http://dx.doi.org/10.3390/catal9080638.

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In the present study, the production of propylene oxide (PO) from propylene via gas-phase epoxidation was investigated using various catalysts. Although Ag is known to be a highly active catalyst for the epoxidation of ethylene, it was not active in the present reaction. Both Al and Ti showed high levels of activity, however, which resulted in confusion. The present study was conducted to solve such confusion. Although the employment of MCM-41 modified with Ti and/or Al was reported as an active catalyst for epoxidation, the combination resulted in the formation of PO at a less than 0.1% yield. Since this research revealed that the acidic catalyst seemed favorable for the formation of PO, versions of ZSM-5 that were both undoped and doped with Na, Ti, and Ag were used as catalysts. In these cases, small improvements of 0.67% and 0.57% were achieved in the PO yield on H‒ZSM-5 and Ti‒ZSM-5, respectively. Based on the results of the Ti-dopant and acidic catalysts, Ag metal doped on carbonate species with a smaller surface area was used as a catalyst. As reported, Ag‒Na/CaCO3 showed a greater yield of PO at 1.29%. Furthermore, the use of SrCO3 for CaCO3 resulted in a further improvement in the PO yield to 2.17%. An experiment using CO2 and NH3 pulse together with SEM and TEM examinations for Ag‒Na/CaCO3 revealed that the greatest activity was the result of the greater particle size of metallic Ag rather than the acid‒base properties of the catalysts.

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Dulski, Mateusz, Jacek Balcerzak, Wojciech Simka et Karolina Dudek. « Innovative Bioactive Ag-SiO2/TiO2 Coating on a NiTi Shape Memory Alloy : Structure and Mechanism of Its Formation ». Materials 14, n^o 1 (29 décembre 2020) : 99. http://dx.doi.org/10.3390/ma14010099.

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In recent years, more and more emphasis has been placed on the development and functionalization of metallic substrates for medical applications to improve their properties and increase their applicability. Today, there are many different types of approaches and materials that are used for this purpose. Our idea was based on a combination of a chemically synthesized Ag-SiO2 nanocomposite and the electrophoretic deposition approach on a NiTi shape memory substrate. As a result, silver-silica coating was developed on a previously passivated alloy, which was then subjected to sintering at 700 °C for 2 h. The micrometer-sized coat-forming material was composed of large agglomerates consisting of silica and a thin film of submicron- and nano- spherical-shaped particles built of silver, carbon, and oxygen. Structurally, the coatings consisted of a combination of nanometer-sized silver-carbonate that was embedded in thin amorphous silica and siloxy network. The temperature impact had forced morphological and structural changes such as the consolidation of the coat-forming material, and the partial coalescence of the silver and silica particles. As a result, a new continuous complex ceramic coating was formed and was analyzed in more detail using the XPS, XRD, and Raman methods. According to the structural and chemical analyses, the deposited Ag-SiO2 nanocomposite material’s reorganization was due to its reaction with a passivated TiO2 layer, which formed an atypical glass-like composite that consisted of SiO2-TiO2 with silver particles that stabilized the network. Finally, the functionalization of the NiTi surface did not block the shape memory effect.

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Zhang, Yu, Peilin Wang, Kaiyuan Zheng, Huayi Yin et Dihua Wang. « Corrosion Behaviors of SS310 and IN718 Alloys in Molten Carbonate ». Journal of The Electrochemical Society 168, n^o 12 (1 décembre 2021) : 121510. http://dx.doi.org/10.1149/1945-7111/ac436b.

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Abstract Long-lasting metallic materials are key to enabling a robust and reliable molten carbonate electrolyzer. In this paper, the corrosion behaviors of SS310 and IN718 in molten Li2CO3-K2CO3-Na2CO3 under CO2-O2 atmosphere were systematically studied. The results show that IN718 had a lower corrosion rate than that of SS310 because of the higher Ni concentration. In addition, increasing the temperature and decreasing the oxygen concentration can reduce the corrosion rate of both SS310 and IN718. As a result, IN718 is a suitable material to be used in molten salt electrolyzers. Overall, engineering the alloy and molten salt compositions as well as manipulating the gas atmosphere can suppress the corrosion of metallic materials, thereby screening durable metallic materials for high-temperature molten carbonate electrolyzers.

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Kuai, Dacheng, et Perla B. Balbuena. « Ab Initio Insights into the Solid Electrolyte Interphase Formation in Lithium Metal Batteries with Carbonate Electrolytes ». ECS Meeting Abstracts MA2022-02, n^o 4 (9 octobre 2022) : 498. http://dx.doi.org/10.1149/ma2022-024498mtgabs.

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As the research endeavors push the performance of widely used Li-ion battery to its theoretical limit, there are strong urges to develop next-generation energy storage devices. Li metal is a promising candidate battery anode material which can bring the energy density to a higher level. There are safety and cycling efficiency issues associated with the Li-metal battery (LMB), and the metal dendrite nucleation and lithium whisker formation are largely responsible for them. The solid electrolyte interphase (SEI) generated from the reactions between lithium metal and battery electrolyte components can regulate the lithium-ion diffusion and deposition which protects anode materials from undesired consumptions. According to the experimental evidence, the SEI from carbonate electrolytes may contain inorganic components including Li2O, Li2CO3, LiF, as well as organic structures such as polymers and oligomers with carbonate and carbonyl structures. However, the exact composition and ionic diffusion properties of SEI are challenging to be directly characterized via experimental techniques. In this work, we initiated the elucidation of the SEI composition by investigating plausible reaction pathways. The inorganic structures are mainly resulted from the degradation of electrolyte solvent and salt species upon contact with the anode material. Ab initio molecular dynamics (AIMD) simulation was implemented to track the interfacial reduction of ethylene carbonate (EC), vinylene carbonate (VC) and lithium hexafluorophosphate (LiPF6). Bader charge analysis demonstrated that the LiPF6 reduction requires consecutive uptake of outside electrons, no matter such reaction happens right on the metallic surface or in electrolyte phase. The final product of the LiPF6 degradation was determined to be Li3P, and the reaction thermochemistry was computed based on density functional theory (DFT). The experimentally measured battery electrochemical performance enhancement of the VC additive has been reported while the chemical mechanism behind such phenomenon was less discussed. We modeled the degradation and polymerization reactions of EC and VC molecules in the LMB environment. VC has significantly smaller energy barrier than EC to generate the lithium-carbonyl complexes and the oligomer/polymer species which takes longer time scale to form. In addition, the solvated lithium cation was found to have significant contribution to the polymerization reaction thermodynamics. The most kinetically favored pathways and products for EC and VC polymerization were identified via DFT calculations. Multiscale simulation based on the computed thermodynamic information was able to provide a glimpse of the microscopic morphology inside the SEI.

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Paterlini, Ambra, Joël Alexis, Yannick Balcaen et Ghislaine Bertrand. « Cold Spraying of Thick Biomimetic and Stoichiometric Apatite Coatings for Orthopaedic Implants ». Coatings 12, n^o 6 (24 mai 2022) : 722. http://dx.doi.org/10.3390/coatings12060722.

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Ceramic coatings have a long history in the orthopaedic field, with plasma sprayed coatings of hydroxyapatite as leading standard in the manufacturing process; however, these coatings can contain secondary phases resulting from the decomposition of hydroxyapatite at high temperatures, which limit the lifetime of implants and their osseointegration. This work aims to produce coatings that can maximize bone osseointegration of metallic implants. In order to preserve the raw characteristics of hydroxyapatite powders that are thermally unstable, coatings were deposited by cold spray onto Ti6Al4V alloy substrates. In contrast with other thermal spray technologies, this process presents the advantage of spraying particles through a supersonic gas jet at a low temperature. On top of hydroxyapatite, carbonated nanocrystalline apatite was synthesized and sprayed. This biomimetic apatite is similar to bone minerals due to the presence of carbonates and its poor crystallinity. FTIR and XRD analyses proved that the biomimetic characteristics and the non-stoichiometric of the apatite were preserved in the cold spray coatings. The cold spray process did not affect the chemistry of the raw material. The adhesion of the coatings as well as their thicknesses were evaluated, showing values comparable to conventional process. Cold spraying appears as a promising method to preserve the characteristics of calcium phosphate ceramics and to produce coatings that offer potentially improved osseointegration.

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Law, Kathleen A., Stephen Parry, Nicholas D. Bryan, Sarah L. Heath, Steven M. Heald, Darrell Knight, Luke O’Brien et al. « Plutonium Migration during the Leaching of Cemented Radioactive Waste Sludges ». Geosciences 9, n^o 1 (8 janvier 2019) : 31. http://dx.doi.org/10.3390/geosciences9010031.

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One of the most challenging components of the UK nuclear legacy is Magnox sludge, arising from the corrosion of Mg alloy-clad irradiated metallic U fuel that has been stored in high pH ponds. The sludges mainly comprise Mg hydroxide and carbonate phases, contaminated with fission products and actinides, including Pu. Cementation and deep geological disposal is one option for the long-term management of this material, but there is a need to understand how Pu may be leached from the waste, if it is exposed to groundwater. Here, we show that cemented Mg(OH)2 powder prepared with Pu(IV)aq is altered on contact with water to produce a visibly altered ‘leached zone’, which penetrates several hundred microns into the sample. In turn, this zone shows slow leaching of Pu, with long-term leaching rates between 1.8–4.4 × 10−5% of total Pu per day. Synchrotron micro-focus X-ray fluorescence mapping identified decreased Pu concentration within the ‘leached zone’. A comparison of micro-focus X-ray absorption spectroscopy (µ-XAS) spectra collected across both leached and unleached samples showed little variation, and indicated that Pu was present in a similar oxidation state and coordination environment. Fitting of the XANES spectra between single oxidation state standards and EXAFS modeling showed that Pu was present as a mixture of Pu(IV) and Pu(V). The change in Pu oxidation from the stock solution suggests that partial Pu oxidation occurred during sample ageing. Similarity in the XAS spectra from all samples, with different local chemistries, indicated that the Pu oxidation state was not perturbed by macro-scale variations in cement chemistry, surface oxidation, sample aging, or the leaching treatment. These experiments have demonstrated the potential for leaching of Pu from cementitious waste forms, and its underlying significance requires further investigation.

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Yi, Yuanbi, Min Xiao, Khan M. G. Mostofa, Sen Xu et Zhongliang Wang. « Spatial Variations of Trace Metals and Their Complexation Behavior with DOM in the Water of Dianchi Lake, China ». International Journal of Environmental Research and Public Health 16, n^o 24 (5 décembre 2019) : 4919. http://dx.doi.org/10.3390/ijerph16244919.

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The dynamics of trace metals and the complexation behavior related to organic matter in the interface between water and sediment would influence water quality and evolution in the lake system. This study characterized the distribution of trace metals and the optical properties of dissolved organic matter (DOM) on the surface, and the underlying and pore water of Dianchi Lake (DC) to understand the origin of metals and complexation mechanisms to DOM. Some species of trace metals were detected and Al, Ti, Fe, Zn, Sr and Ba were found to be the main types of metals in the aquatic environment of DC. Ti, Fe, Sr and Ba predominated in water above the depositional layer. Al, Ti, Fe and Sr were the most abundant metallic types in pore water. Mn and Zn were the main type found at the southern lake site, reflecting the contribution of pollution from an inflowing river. The correlations between DOM and metals suggested that both originated from the major source as particulate organic matter (POM), associated with weathering of Ca-, Mg-carbonate detritus and Fe- or Mn-bearing minerals. High dynamics of DOM and hydrochemical conditions would change most metal contents and speciation in different water compartments. Proportions of trace metals in dissolved organic carbon (DOC) in natural waters were correlated with both DOM molecular weight and structure, different metals were regulated by different organic properties, and the same metal also had specific binding characteristic with DOM in various water compartments. This study highlighted the interrelation of DOM and metals, as well as the pivotal role that organic matter and nutrients played during input, migrations and transformations of metals, thereby reflecting water quality evolution in the lake systems.

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Monetta, Tullio, et Annalisa Acquesta. « Metallic Biomaterials Surface Engineering ». Metals 11, n^o 9 (30 août 2021) : 1366. http://dx.doi.org/10.3390/met11091366.

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Bermudez, Victor M. « A metallic semiconductor surface ». Nature Materials 2, n^o 4 (avril 2003) : 218–19. http://dx.doi.org/10.1038/nmat861.

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Chandrasekaran, S., J. D. Brazzle et A. B. Frazier. « Surface micromachined metallic microneedles ». Journal of Microelectromechanical Systems 12, n^o 3 (juin 2003) : 281–88. http://dx.doi.org/10.1109/jmems.2003.809951.

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Goeppert, Nadine, Nico Goldscheider et Herbert Scholz. « Karst geomorphology of carbonatic conglomerates in the Folded Molasse zone of the Northern Alps (Austria/Germany) ». Geomorphology 130, n^o 3-4 (juillet 2011) : 289–98. http://dx.doi.org/10.1016/j.geomorph.2011.04.011.

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Rendek, Louis J., Gary S. Chottiner et Daniel A. Scherson. « The Reactivity of Linear Alkyl Carbonates toward Metallic Lithium ». Journal of The Electrochemical Society 149, n^o 10 (2002) : E408. http://dx.doi.org/10.1149/1.1507595.

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Satolli, Sara, Claudio Robustelli Test, Dorota Staneczek, Elena Zanella, Fernando Calamita et Evdokia Tema. « Magnetic fabric in carbonatic rocks from thrust shear zones : A study from the Northern Apennines (Italy) ». Tectonophysics 791 (septembre 2020) : 228573. http://dx.doi.org/10.1016/j.tecto.2020.228573.

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Jenkins, S. J., et D. A. King. « Minority metallic surface states of a half-metallic ferrimagnet ». Surface Science 494, n^o 3 (décembre 2001) : L793—L798. http://dx.doi.org/10.1016/s0039-6028(01)01547-3.

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Pavone, Michele, Francesca Fasulo et Ana Belen Munoz Garcia. « Reactivity of VC Electrolyte at Li-Metal Electrode : New Insights on SEI Initial Formation from Density Functional Embedding Theory ». ECS Meeting Abstracts MA2022-02, n^o 4 (9 octobre 2022) : 486. http://dx.doi.org/10.1149/ma2022-024486mtgabs.

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The metallic lithium (Li) represents the most promising anode material among the next generation of solid-state lithium batteries [1]. An efficient strategy to achieve durable and effective Li-anode batteries is by engineering the solid-electrolyte interphase (SEI) with purposely designed molecules. To this aim, the vinylene carbonate (VC) is one of the most used additives in conventional electrolytes. Some recent experiments proved that the VC promotes the formation of a stable and protective SEI layer between Li metal and electrolyte [2, 3]. Unless the well-known SEI composition, it is difficult to control the VC reactivity, that involves dissociation and polymerization at the electrode surface. Therefore, to dissect these tangled processes, here we present new atomistic insights on VC-Lithium SEI formation via first-principles calculations by Density Functional Embedding Theory (DFET) [4, 5]. Such approach has potentialities for modeling complex reactions at hybrid interfaces in electrocatalysis: it is well suited to combine the best feasible approaches for molecular species (in this case, hybrid HF-DFT for VC molecules and derivatives) and for Li metal electrode (semi-local GGA density functional). Our results highlight different VC dissociation pathways, with formation of reactive radical species and localized cluster of Li2O and Li2CO3. The use of hybrid-DFT-in-DFT embedding is crucial for obtaning energy barriers and qualtitative results in agreement with experiments [3]. Overall, the energetics and structural features of these intermediates improve the current understanding of SEI formation process and can be exploited to drive the reactions toward the desired interfacial properties. [1] J. Janek, W. G. Zeier, Nat Energy 1 (2016) 16141. [2] A. L. Michan et al. Chem. Mater. 28 (2016) 8149. [3] Y. Kamikawa, K. Amezawa, K. Terada, J. Phys. Chem. C 124 (2020) 19937 [4] C. Huang, M. Pavone, E. A. Carter, J. Chem. Phys. 134 (2011) 154110 [5] C. Huang, A.B. Muñoz-García, M. Pavone, J. Chem. Phys. 145 (2016) 244103

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Hanawa, Takao. « Surface Modification of Metallic Biomaterials. » Materia Japan 37, n^o 10 (1998) : 853–55. http://dx.doi.org/10.2320/materia.37.853.

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