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The oxygen dissociation and the oxidized structure on the pristine C3N monolayer in exposure to air are the inevitably critical issues for the C3N engineering and surface functionalization yet have not been revealed in detail. Using the first-principles calculations, we have systematically investigated the possible O2 adsorption sites, various O2 dissociation pathways and the oxidized structures. It is demonstrated that the pristine C3N monolayer shows more O2 physisorption sites and exhibits stronger O2 adsorption than the pristine graphene. Among various dissociation pathways, the most preferable one is a two-step process involving an intermediate state with the chemisorbed O2 and the barrier is lower than that on the pristine graphene, indicating that the pristine C3N monolayer is more susceptible to oxidation than the pristine graphene. Furthermore, we found that the most stable oxidized structure is not produced by the most preferable dissociation pathway but generated from a direct dissociation process. These results can be generalized into a wide range of temperatures and pressures using ab initio atomistic thermodynamics. Our findings deepen the understanding of the chemical stability of 2D crystalline carbon nitrides under ambient conditions, and could provide insights into the tailoring of the surface chemical structures via doping and oxidation., Comment: 23 pages,8 figures

A series of AuPt nanoparticles supported on multi-walled carbon nanotubes (AuxPt/MWNTs) catalysts with ultrafine distribution (d ≈ 3.0 nm) were synthesized for Al-air battery cathode to enhance the oxygen reduction reaction. Among them, Au0.67Pt/MWNTs catalyst with metal loading of 10.2 wt% (Au:4.1 wt%, Pt:6.1 wt%) exhibited a superior ORR catalytic activity and competitive durability to 20 wt% Pt/C catalyst. When applied as Al-air battery, appropriate increasing Au loading encourage better battery performance. Au1.68Pt/MWNTs with 8.95 wt% of Au and as little as 5.3 wt% Pt content exhibit larger specific capacity (921 mAh g−1) and power density (146.8 mW cm−2) as well as better durability than 20 wt% Pt/C catalyst when it is assembled as cathode in Al-air battery.

Proper morphology, surface and interface structure designing are required to obtain efficient gas sensing and photocatalytic materials. In the present work, ultra-thin NiO single-crystalline porous nanosheets with dominant {1 1 1} crystal facets (denoted as SP-NiO) and hierarchical NiO porous microspheres (denoted as HP-NiO) supported highly dispersed Pt nanoparticles with controllable sizes were designed and synthesized. Their gas sensing and photocatalytic performance were investigated. It was found that both the formaldehyde sensing and methyl orange photocatalytic degradation performance were greatly enhanced by decorating Pt nanoparticles on SP-NiO, while Pt nanoparticles decoration contributed little to the improved photocatalytic performance of HP-NiO. The results indicated that surface structure of the NiO support could also produce significant impact on the activity of Pt/NiO heterojunctions. Moreover, Pt decorated SP-NiO with stable structure showed a marked long-term stability with negligible attenuation of gas sensitivity (less than 5%) for 45 days, while Pt decorated HP-NiO exhibited obvious attenuation of gas sensitivity (more than 30%) due to the structural collapse. The work not only offers promising materials for gas sensing and photocatalytic application, but also brings new dawn for the designing of efficient p-type metal oxides gas sensing and photocatalytic materials through the synergistic effect of single-crystalline porous structures modulation, crystal facets engineering and facet-selective deposition of highly-dispersed Pt nanoparticles.

To get insight into nano-scale deformation behavior and material removal mechanism of RB-SiC ceramic, nanoscratch experiments were performed using a Berkovich indenter. Structure changes in chips and subsurface deformation were characterized by means of Raman spectroscopy. The result shows that the SiC phase underwent amorphization in ductile chips, while no amorphous feature can be observed in brittle chips and substrate within scratch groove. The following estimated stress surround the indenter reveals that amorphous deformation in ductile chips is governed by tangential stress (above 95 GPa), whereas the dislocations-based substrate deformation mechanism was dominated by normal stress. In the end, the effects of normal load and scratching velocity on the scratch behavior including scratch residual depth, elastic recovery and friction coefficient that related to RB-SiC ceramic deformation mechanism were also analyzed. With the increase of normal load, the deformation mechanism transfers from ductile to brittle fracture mode and cause the decrease of elastic recovery and the increase of residual depth and friction coefficient. Furthermore, the increased high density of dislocations as a result of the increased scratching velocity give rise to the increase of scratch hardness, which finally result in the increase of elastic recovery and decrease of residual depth and friction coefficients. This study contributes a new understanding of the brittle material deformation mechanism during a nano-scale scratching process.

Developing efficient and cost-effective oxygen reduction reaction (ORR) catalysts for fuel cells is quite necessary but still full of challenges. In this study, tungsten nitride nanosheets (WN NSs) decorated with nitrogen-containing carbon dots hybrid materials are developed using a facile two-step route. Specifically, a sandwich-like porous electrode, which contains a N-doped carbon layer encapsulated with uniform carbon dots (N-CDs) and a sheet-like WN for both-side formation of N-CDs, is obtained and designed as a novel type of ORR catalysts (denoted as N-CDs@WN). The N-CDs@WN hybrid shows superior catalytic activity via a four-electron pathway and demonstrates excellent stability over long periods of time and resistance to methanol. The excellent electrocatalytic properties of N-CDs@WN hybrids benefited from a hierarchical structure with large specific area, numerous active sites, and synergistic effect between CDs and WN that can facilitate the conductivity and mass transfer during the ORR process. Compared to other carbon dots-based nanocomposites, our facile synthetic route for N-CDs@WN not only presents the advantages of being relatively green, simple, and cost-effective but also is an attractive alternative for the electrocatalyst in the non-precious ORR.

When an asphalt mixture cracks, adhesive debonding occurs along bitumen-mineral interfaces and cohesive debonding occurs within bitumen films. At microscale, the two debonding processes can happen simultaneously but it is unknown for their percentages. This study aims to determine the percentages for cohesive and adhesive debonding and investigate how the material and external factors can affect these percentages using molecular dynamics (MD) modeling. The pull-off simulations of bitumen-calcite interfaces were performed at different bitumen film thicknesses, pull-off velocities and temperatures. The percentages of cohesive debonding were calculated as the area ratio of the remained bitumen molecules over the total interface. Results show that the percentage of cohesive debonding increases from 29% to 65% with thicker bitumen films, and decreases from 86% to 59% with higher loading velocities. When temperature rises, the percentage of cohesive debonding increases from 61.3% to 88.2%. Quartz presents a weak adhesion to bitumen, and thus a complete (100%) adhesive debonding occurs regardless of bitumen thickness. Microcline shows a very strong adhesion to bitumen due to its high polarity. The modeled cohesive debonding percentage with different variables were verified and found consistent with the laboratory pull-off testing results available from the existing studies.

Two-dimensional (2D) materials with robust magnetism have drawn immense attention for their promising applications in spintronics. Recently, intrinsic ferromagnetic vanadium triiodide (VI3) has been synthesized experimentally. To enhance its spintronic property, we modified VI3 by interstitial doping with 3d transition metals (TM) and used first-principles calculations to investigate the geometric structure, formation energy, electronic property, and magnetism of pristine VI3 and 3d TM-doped VI3 monolayer. Among eight transition metal (Sc-, Ti-, V-, Cr-, Mn-, Fe-, Co-, and Ni-) doped VI3 materials, four of them (Ti-, V-, Mn-, and Ni-doped VI3) show robust magnetism with full spin polarization near the Fermi energy. Our research demonstrates that Ti-doped VI3 results in half-metallic semiconductor properties (HMS), while V-doped VI3 and Ni-doped VI3 result in half-semiconductor properties (HSC). Surprisingly, Mn-doped VI3 exhibits an unusual bipolar magnetic semiconductor property (BMS). This unique combination of strong ferromagnetism and 100% spin polarization with a half-metallic, half-semiconductor, or bipolar semiconductor property renders 3d TM-doped VI3 as potential candidates for next generation semiconductor spintronic applications. These spin-polarized materials will be extremely useful for spin-current generation and other spintronic applications.

The synthesis of one-dimensional nanocrystals on flexible substrates has attracted a great attention in the last decade. We here report an integrated approach using a sequential sol-gel and hydrothermal synthesis method to successfully assemble well-aligned single-crystalline wurtzite ZnO nanorod arrays (ZnO NRAs) on activated carbon fibers (ACFs). The ZnO NRAs, with high rod surface area (up to 20 m2 g−1), high aspect ratio (rod length/rod diameter, ca. 20:1) and high defect level (indicated by an extremely sharp blue emission, strong green and yellow emissions), were shown to grow nearly perpendicularly on the ACFs surface. The pre-coating of ZnO seed layers on ACFs surface during sol-gel synthesis is vital for the growth of the ordered ZnO nanorod arrays. The structural and optical properties of ZnO NRAs/ACFs can be adjusted by tuning the synthesis parameters for sol-gel and hydrothermal steps. As compared to the ZnO NRAs grown on the stiff substrates (e.g., silicon wafer, fluorine-doped tin oxide glass, GaN and metal sheets), ZnO NRAs grown on ACFs have very high surface area and intensive blue, green and yellow emissions. The novel ZnO NRAs/ACFs show excellent photocatalytic degradation of methylene blue and robust recyclability as compared to the individual ZnO nano particles (powder, NRs and NRAs).

A simple two-step microwave-assisted method was developed for the preparation of adenine-modified graphene quantum dots (A-GQDs) with striking fluorescence properties. The prepared A-GQDs with the lateral size of 3–5 nm and single- to few-layer thickness exhibit intense fluorescence with a quantum yield of 21.63% (excited at 350 nm) and an average lifetime of 4.47 ns. The A-GQDs are biocompatible and present two-photon green fluorescence, which render them suitable for two-photon fluorescent cell imaging. More interestingly, we demonstrate for the first time that the A-GQDs also possess white light-activated antibacterial property. Due to their excellent photoluminescence performance and ease of biological conjugation, A-GQDs can be envisioned as an emerging role for many multifunctional biomedical applications.

Three novel polydiacetylenes (PDAs) are synthesized through the self-assembly followed by the topochemical polymerization via controllable electrophoretic deposition. All the samples could undergo a multi-step thermochromic process, turning purple and red successively over a wide range from room temperature to above 250 °C. Resulting PDAs are studied by UV–vis, IR, Raman spectroscopies, and chromoisomerism by naked eye visualization; their stabilities by thermogravimetric method, and emission behavior by fluorescence spectroscopy. To study the mechanism of the thermochromic response, temperature-dependent UV–vis spectra, the results of which successfully highlighted the close relationship between chromatic transitions and the conformational changes.

Three-dimensional Bi2O3/TiO2 hierarchical composites have been successfully prepared by a two-step hydrothermal method and subsequent calcination. The samples were characterized using XRD, SEM, TEM, EDS, BET and DRS. The measurement results signified that heterojunctions of various morphologies β-Bi2O3 growing on the three-dimensional hierarchical anatase TiO2 nanorods arrays on FTO glass were apparently formed. The morphology of Bi2O3 changed from three-dimension flower-like microstructures to the sphere-like nanoparticles as the Li(OH) dosage increased. The photocatalytic results showed that all samples exhibited much higher photocatalytic activities than that of pure Bi2O3 and TiO2 (P25) in photocatalytic degradation of methyl blue (MB) under visible-light irradiation. Whereas BTL4 sample exhibited the highest photoactivity with increasing the dosage of Li(OH) to 2 mmol. Furthermore, the absorption edge of the Bi2O3/TiO2 series composites displayed a broad-spectrum photoabsorption from UV to visible-light compared with the individual component. The as-synthesized Bi2O3/TiO2 composites possessed excellent photocatalytic activity and outstanding recyclability. The enhanced photocatalytic efficiency was mainly attributed to the Bi2O3/TiO2 p-n heterojunctions and hierarchical nanostructure. The recombination of photogenerated electron–hole pairs was efficiently suppressed by the Bi2O3/TiO2 p-n heterojunctions.

As for the application of CH4 dry reforming (DRM), primary concern was focused on solving the deactivation of supported Ni catalysts caused by particle sintering and coke accumulation, while little attention has been paid to negative effect resulted from sulfur poisoning. The present work gave an account of the effect of H2S on the DRM over MoOx decorated Ni/SiO2 catalyst. It showed that Mo modified samples presented better sulfur resistance performance. Moreover, the interesting discovery was that different forms of Mo species were worked as special roles during H2S-induced DRM. The suitable amount of Mo, involved as the inhibitor and/or the co-catalyst, could increase the competitive adsorption capacity for H2S, thus slowing down sulfuration rate of the active Ni sites. Meanwhile, as for the specially pre-reduced catalysts, the formed intermetallic metal of Ni-Mo component contributed to a continuous sulfur-adsorption behavior for H2S, thus protecting the active Ni sites from sulfuration. Consequently, probing the sulfur-tolerance of MoOx surface decoration on Ni/SiO2 could elucidate some useful keys for the development of high sulfur-resistance catalysts, which, as a consequence, would be adequate catalysts for the H2S-induced DRM process.

International audience; Lithium-sulfur (Li-S) batteries using hybrid electrolytes, which are composed of solid-electrolyte separator and liquid-electrolyte wetting agent, can effectively eliminate the polysulfide shuttling issue. The cycling performance of these hybrid batteries is mainly limited by the interfacial stability between the solid and liquid electrolytes. This work detailly discusses the influence of the composition on the stability of a highly ionic conductive sulfide solid electrolyte, lithium thiophosphate xLi2S·(100–x)P2S5 (70 ≤ x ≤ 75, SSEs), in hybrid Li-S batteries. It reveals that the solid electrolyte with low Li2S content favors the formation of a SEI layer containing Li3PS4 and therefore improves the interfacial stability with Li anode, while the one with high Li2S content behaves more stable with the cathode. Using 75Li2S·25P2S5 as the separator, a hybrid battery runs more than 400 cycles with a low capacity fading rate of 0.14%/cycle. This is benefited from the elimination of polysulfide shutting and especially the excellent compatibility of the sulfide solid electrolyte with both anode and cathode.

In this work, a novel label free photoelectrochemical (PEC) immunosensor has been developed for the detection of α-fetoprotein (AFP). The immunosensor was based on Au-ZnO flower-rods (FRs) heterostructure, where Au nanoparticles (NPs) were firstly electrodeposited by cyclic voltammetry methods. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Mott-Schottky plot (MS), UV–vis diffuse reflectance spectrum and fluorescence emission spectrum were used for the characterizations of Au-ZnO FRs. The results demonstrated that Au NPs not only obviously enhanced the visible light absorption of ZnO FRs due to surface plasmon resonance (SPR) but also improved the separation of photo-generated electron-hole pairs. Therefore, the photocurrent of Au-ZnO FRs was increased under simulated sunlight. The photocurrent was reduced after the specific antibody-antigen immune reaction. And the photocurrent decrement was linear with the logarithm of AFP antigen concentration in the range from 0.005 ng mL−1 to 50 ng mL−1 with a low detection limit of 0.56 pg mL−1 (S/N = 3). The PEC immunosensor also exhibited high anti-interference property and acceptable stability. This work would provide a promising photoelectrochemical strategy for the detection of other proteins in clinical diagnosis.

Electrospun LaCoO 3 and Ce(NO 3 ) 3 ·6H 2 O were used as precursors to synthesize CeO 2 /LaCoO 3 (SSI-LaCoCe) with high oxygen mobility by solid state impregnation. Besides, electrospinning and ball milling technologies were also adopted to prepare the other two La-Co-Ce oxides, which are denoted as ES-LaCoCe and BM-LaCoCe, respectively. The catalysts were evaluated for total benzene oxidation in comparison with bare electrospun LaCoO 3 and CeO 2 , and characterized by means of O 2 -TPSR, XRD, BET, TEM, H 2 -TPR, O 2 -TPD, and XPS. Relative to LaCoO 3 , an enhanced catalytic performance can be obtained for La-Co-Ce oxides. Importantly, the concentration of surface adsorbed oxygen species from the highest to the lowest is SSI-LaCoCe > BM-LaCoCe > ES-LaCoCe, which is in good agreement with the order of catalytic activity in terms of T 50 . The high oxygen mobility in SSI-LaCoCe can be connected with sufficient interaction between active LaCoO 3 and CeO 2 . On the other hand, O 2 -TPSR analysis match well with the catalytic behaviors of La-Co-Ce oxides. Moreover, the catalyst with the best performance, SSI-LaCoCe, also represents good thermal stability during the long-term continuous test.

Precise transportation of liquid microdroplets is a great challenge in the microfluidic field. A sticky superhydrophobic surface with a high static contact angle (CA) and a large contact angle hysteresis (CAH) is recognized as the favorable tool to deal with the challenging job. Some approaches have been proposed to fabricate such surface, such as mimicing the dual-scale hierarchical structure of a natural material, like rose petal. However, the available approaches normally require multiple processing steps or are carried out with great expense. In this study, we report a straightforward and inexpensive method for fabricating the sticky superhydrophobic surfaces. The fabrication relies on electroless galvanic deposition to coat the copper substrates with a textured layer of silver. The whole fabrication process is carried out under ambient conditions by using conventional laboratory materials and equipments, and generally take less than 15 min. Despite the simplicity of this fabrication method, the rose petal-like hierarchical structures and the corresponding sticky superhydrophobic wetting properties were well achieved on the artificial surfaces. For instance, the surface with a deposition time of 10 s exhibits the superhydrophobity with a CA of 151.5°, and the effective stickiness with a CAH of 56.5°. The prepared sticky superhydrophobic surfaces are finally shown in the application of droplet transportation, in which the surface acts as a mechanical hand to grasp and transport the water droplet.

In this work, we investigate the droplet bouncing on the hierarchical branched nanotube (BNT) arrays surface above and below 0 °C. By anodization, we fabricate large-area arrays of BNT with the BNT spacing controlled from adjacent to sparse. We evaluate the influence of the BNT spacing on the droplet bouncing. The adjacently distributed BNT (A-BNT) outperforms the sparsely distributed BNT (S-BNT). We find that the A-BNT can repel up to 3.1 m/s droplet at 20 °C and 2.3 m/s droplet at −18 °C, while the maximum bouncing velocity on the S-BNT is below 2.3 m/s at 20 °C and below 0.9 m/s at −10 °C. For the bouncing on the supercooled A-BNT surface, the droplet bouncing contact time increases as the substrate temperature decreases for the same droplet velocity, while the bouncing contact time decreases as the droplet velocity increases for the same substrate temperature. We discuss the influence of the nanosized air cushion entrapped amid the branched-arms of the BNT on the three-phase contact line on the BNT walls and bouncing performance under supercooled conditions.

In this study, a series of porous graphitic carbon nitride (g-C3N4) materials were fabricated through a direct pyrolysis of protonated melamine by nitric acid solution. These as-prepared porous samples were characterized by a collection of analytical techniques. It was found that a proper concentration of nitric acid solution involved facilitated to generate samples in tube-like morphology with numerous pores, identified with X-ray diffraction patterns, FT-IR spectra, SEM, TEM, and BET measurements. These g-C3N4 samples were subjected to photocatalytic degradation of dye Rhodamine B (RhB) in aqueous under visible-light irradiation. Under identical conditions, those porous g-C3N4 samples showed significantly improved catalytic performance in comparison with the sample prepared without the introduction of nitric acid. In particularly, the best candidate, sample M1:1, showed an apparent reaction rate nearly 6.2 times that of the unmodified counterpart. The enhancement of photocatalytic performance could be attributed to the favorable porous structure with the enlarged specific surface area and the suitable electronic structure as well. In addition, ESR measurements were conducted for the sake of proposing a photocatalytic degradation mechanism. (C) 2015 Elsevier B.V. All rights reserved.

a b s t r a c t Formation of oxygen vacancies by introducing various mixed-valent cation dopants is a common practice to improve the cathode performance in solid oxide fuel cells. A computational procedure is developed in this work to predict the equilibrium oxygen vacancy non-stoichiometric concentrations at experimen- tally relevant temperatures and oxygen partial pressures for both bulk and surface oxide phases. The calculations are based on the first-principles density functional theory and a constrained free-energy functional. Quantitative agreements are found by direct comparisons to the thermogravimetry and solid electrolyte coulometry measurements for the strontium-doped lanthanum cobalt iron oxides at different compositions. Our results indicate that the oxygen vacancies are energetically stabilized at surfaces for all temperatures and all oxygen partial pressures, while such surface stabilization effects become stronger at higher temperatures and lower oxygen partial pressures.

A series of TiO2 hybrids composited with exfoliated g-C3N4 nanosheets (CNs) were successfully synthesized through a facile sal-gel method and fully characterized by X-ray diffraction patterns (XRD), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-vis diffuse reflectance spectra (UV-vis DRS). The CNs-TiO2 hybrids were exposed to visible light irradiation and showed much higher catalytic capability toward degrading dye rhodamine B (RhB) comparing with bare TiO2 and N-TiO2. The sample CNs-TiO2-0.05 exhibited the largest apparent reaction rate constant among all CNs-TiO2 hybrids, which was 2.4 times and 7.0 times as high as bare TiO2 and N-TiO2, respectively. The enhanced catalytic efficiency could be mainly attributed to the well-matched band gap structure with heterojunction interface, suitable specific surface area, and favorable optical property. In addition, active species trapping experiments were conducted, revealing that photoinduced holes (hi) had a severe influence on catalytic outcome, through which a possible catalytic mechanism was finally realized and proposed. (C) 2014 Elsevier B.V. All rights reserved.

The nano/ultrafine grain (NUG) with an average grain size of 230 nm was obtained by cold rolling down to 94% reduction in thickness and reversion annealing at 800 °C for 200 s. The NUG sample exhibited a lower corrosion resistance than coarse grain (CG) sample in 0.1 M NaCl solution at room temperature, indicating that the passive film formed on the surface of the NUG austenite did not improve corrosion resistance in the solution. However, the corrosion resistance of the former was higher than that of the latter in 0.5 M H 2 SO 4 solution at room temperature, which was proved by electrochemical impedance spectroscopy and Mott–Schottky plots in conjunction with the point defect model. Comparing slightly difference of acceptor density (i.e. cation vacancies) between CG and NUG samples, higher corrosion resistance of NUG sample was probably attributed to significant decreased donor density (i.e. oxygen vacancies and cation interstitials) in 0.5 M H 2 SO 4 solution. Moreover, the corrosion resistance of the passive films formed on CG and NUG samples in borate buffer solution at room temperature showed little difference.

In this investigation, a facile modification of g-C3N4 through co-pyrolysis of melamine and sodium nitrate or potassium nitrate was reported and the as-synthesized samples were characterized by a collection of techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, nitrogen adsorption-desorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and elemental analysis. Based upon the analysis, we speculated that the g-C3N4 framework was partially destroyed to produce cyano-containing fragments, which resulted into the variation of physical and optical properties, further affecting the adsorption and photocatalytic performance of g-C3N4 on the dye methylene blue. Furthermore, we found that nitrate anions rather than sodium or potassium ions had important effect on the structure and photocatalytic performance of g-C3N4. In addition, the photocatalysis mechanism and reusability test were also investigated and discussed in the study. (C) 2013 Elsevier B.V. All rights reserved.

Electronic structure modeling is carried out for bulk Pd–H system with implications for certain surface effects and hydrogen transport. The calculation is performed under the framework of density functional theory. The results provide new insight into the charge state of H inside Pd. The H is slightly negatively charged over the composition range studied, and the negative charge around the proton increases with an increasing loading of hydrogen. By studying the behavior of H at the “bridging” site, which is important to surface and transport phenomena, this paper helps to explain why the effective charge observed in H drift experiments is different from the static charge state.

We present the results of an AES, XPS, LEED and photoluminescence study of the reaction of oxide and contaminant overlayers on CdTe(100) and (110) surfaces with atomic hydrogen. For both surfaces exposure of an oxide overlayer to a flux of atomic hydrogen produced by ‘cracking’ ambient molecular hydrogen on a hot tungsten filament results, in contrast to the case of GaAs substrates, in a rapid, quantitative removal of the oxide overlayer at substrate temperatures as low as 300 K. This process results in surfaces free of contaminants which have sufficient surface order to produce clear LEED patterns characteristic of well known reconstructions of these surfaces. Additionally in situ photoluminescence spectroscopy allows direct correlation of surface cleaning with reduced nonradiative carrier recombination.

The influence of the temperature and reaction time on the sulfation process of a dolomite is investigated in this paper. The sulfation effectiveness was evaluated and correlated with changes in the physical characteristics of a Brazilian dolomite during the reactive process. Calcination and sulfation experiments were performed under isothermal conditions for dolomite samples with average particle sizes of 545 ?m at temperatures of 750 °C, 850 °C and 950 °C at different times of sulfation. Thermogravimetric tests were applied to establish the reactivity variation of the dolomite in function of the time in the sulfation reaction and evaluate the methodology of the samples preparation. Porosimetry tests were performed to study the pore blockage of dolomite during the sulfation reaction. The highest values of BET surface area were 25.55 m2/g, 29.55 m2/g and 12.62 m2/g for calcined samples and after their sulfation processes, conversions of 51.5%, 61.9% and 42.8% were obtained at 750 °C, 850 °C and 950 °C, respectively. Considering the process as a whole, the best fit was provided by a first-order exponential decay equation. Moreover, the results have shown that it is possible to quantify the decreasing in the dolomite reactivity for sulfur dioxide sorption and understand the changes in the behavior of the sulfation process of limestones when applied to technologies, as fluidized bed combustor, in which sulfur dioxide is present

Co–Cr–Mo alloys are one of the most widely used metallic biomaterials for metal-on-metal joint prostheses. However, concerns over increased revision rates mainly due to nano-sized wear debris have been raised. This study was aimed at enhancing the friction, wear and load-bearing properties of Co–Cr–Mo alloys by developing a new duplex surface system combining super hard and wear-resistant S-phase layer with self-lubricating, low-friction carbon-based coating. To this end, ASTM F1537 Co–Cr–Mo alloy surface was plasma carburised (PC) at 450°C and then coated with a carbon-based GiC coating. The microstructures of the duplex and single treated (PC or GiC coating) Co–Cr–Mo surface systems were characterized and their mechanical, tribological and corrosion properties were evaluated. The results showed that the new duplex surface system exhibited a high load bearing capacity, a low friction coefficient, excellent wear resistance and good corrosion behaviour.