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Nanoporous BiVO4 thin films were deposited using reactive magnetronsputtering in Ar and O2 atmosphere, on various substrates,employing pulsed direct-current (DC) power supplies applied tometallic Bi and V targets for rapid deposition. The procedure wasfollowed by a post-annealing treatment in air to crystallize thephotoactive monoclinic scheelite structure. The influence of totalpressure and substrate on the crystal structure, morphology,microstructure, optical and photocatalytic properties of the filmswas investigated. The crystallization of monoclinic scheelitestructure deposited on fused silica substrate starts at 250 °C andthe films are stable up to 600 °C. The morphology of the films israther dense, despite at the high sputtering pressure (>2 Pa),with embedded nanopores. Among the thin films deposited on fusedsilica, the one deposited at 4.5 Pa exhibits the highest porosity(52%), with the lowest bandgap (2.44 eV) and it shows the highestphotocatalytic activity in the degradation of Rhodamine-B (26%after 7 h) under visible light irradiation. The film deposited onthe silicon substrate exhibits the highest photoactivity (53% after7 h). Lack of hypsochromic shift in the UV−Vis temporal absorptionspectra shows the dominance of the chromophore cleavage pathway inthe photodecomposition.

International audience; The p-type Ge-doped (0, 1, 4 and 7 at.%) Mg

To study the effect of the laser energy density (LED) on surface morphology, microstructural evolution, and magnetic properties of Fe-3wt.% Si alloy, the alloy was manufactured via selective laser melting (SLM) technology. The SLM Fe-3wt.% Si parts were characterized by a series of advanced material methods including a 3D profilometer, optical microscope, scanning electron microscopy, and vibrating sample magnetometer, etc. The results show that no obvious microcracks exist in the SLM Fe-3wt.% Si parts. With the LED increases, the porosity rate and the surface roughness of the SLM Fe-3wt.% Si parts decrease. Furthermore, the cross-sectional microstructure of the SLM Fe-3wt.% Si parts is a typical columnar structure with an orientation growth building direction. The microhardness of each SLM Fe-3wt.% Si sample is higher than 200 HV0.1. Besides, the coercivity of SLM Fe-3wt.% Si parts decreases first and then increases with the increase in the LED. The specimen with a LED at 300 J/m exhibits better comprehensive magnetic properties than others. It could be concluded that the magnetic properties of SLM Fe-3wt.% Si alloys are affected by the synergistic effects of manufacturing defects and internal stress.

Fully dense and thick Ni/FeSiAl soft magnetic composite deposits were successfully fabricated by cold spraying (CS) using the Ni-coated FeSiAl composite powder. To improve magnetic properties, the post-annealing treatments were conducted on CS deposits to eliminate the undesired internal defects, like strain stress and dislocations, and fine grains. Characterization of the composite coating was carried out in terms of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) analyses. XRD patterns displayed that no newly formed phases were observed at different annealing temperatures, even though EDS analysis showed obvious element diffusion between Ni matrix and FeSiAl particles at the temperature of 800 °C for 2 h. Grain growth and stress relief after annealing treatment were proved by both XRD and EBSD analyses. The magnetic property measurements showed that the coercivity was decreased by around two times (from 62 to 30 Oe) and the magnetization saturation was increased by 15% (from 68 to 80 emu/g). The relevant mechanisms were discussed in terms of microstructural evolution. This work shows that the post heat treatment can be a potential method to improve the soft magnetic properties of CS coating.

International audience; Gadolinia doped ceria coatings were elaborated by cathodic arc evaporation from a metallic Ce–Gd (90–10 at.%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon–oxygen gas mixture. The structural and chemical features of these films were determined by x-ray diffraction and scanning electron microscopy. Their electrical properties were characterized using impedance spectroscopy measurements. It was shown that the as-deposited coatings crystallize in the fluorite type fcc structure of ceria and that their composition is the same as that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation and the activation energy was slightly higher than that given in the literature data for the bulk material.

International audience; Delafossite CuFeO2 films have been synthesized by reactive magnetron sputtering at different substrate temperatures from 380 up to 550 °C. The films adopt the rhombohedral structure from 380 to 550 °C. At the highest temperature, the delafossite phase partially dissociates in FCC Cu and Fe3O4 magnetite phases. In addition to the average crystallite size increase, a change of the preferential orientation in the out-of-plane direction from the [012] to [006] directions occurs between 460 and 510 °C. Modelling of the optical properties shows the presence of 2 interband transitions in the visible range. The 1st main transition at 1.5 eV is ascribed to the absorption component parallel to the c-axis whereas the 2nd transition (2.10 – 2.26 eV) is related to the absorption component in the (a, b) plane. Both evolutions with temperature of the refractive index (~ 2.5) and absorption coefficient (~ 10-3 cm-1) in the infrared suggest the formation of secondary phases. The electronic conductivity, dominated by positive charge carrier, varied from 0.01 to 10 S m-1 according to the preferential orientation and to the presence of secondary phases. A very small amount of a short-range ferromagnetic component (magnetization ~ 10 kA m-1 at 1.5 T) is clearly observed at room temperature thanks to magnetometry confirming the formation of secondary phases undetected by X-ray diffraction. In addition to depend on the film orientation, the presence of secondary phases in weak proportion alters the optical and electrical behaviours such as the transmittance in the visible range..

International audience; Currently, soft magnetic composites (SMCs) have attracted increasing attention due to their outstanding magnetic properties, and various methods have been developed and applied for their fabrication. As an emerging additive manufacturing technique, cold spraying (CS) can fabricate bulk material via solid-state deposition by avoiding oxidation and phase change. In this work, SMCs coating was first fabricated by Ni-coated FeSiAl composite powder via CS. Two groups of Ni-coated FeSiAl composite particles (40 μm and 57 μm) were used as feedstocks for deposition under different processing parameters. No phase transformation can be detected from XRD analysis. The coating thickness increased with the increasing of propelling gas temperature and pressure. Higher deformation of FeSiAl particles and higher micro-hardness of the composites fabricated from the powders with larger size were obtained due to the enhanced in-situ peening effect of the rebounded particles during deposition. The magnetic property of cold sprayed SMCs showed a soft ferromagnetic characteristic with a coercivity of about 60 Oe. The investigation on the coating formation mechanism was carried out by single particle deposition, and the results showed that the Ni bonding layer with sufficient plastic deformation plays a significant role during the deposition of the composite coating.

In this study, nanoporous BiVO4 thin films were deposited using reactive direct-current (DC) magnetron sputtering. The effects of thickness on the film morphology, crystal structure, microstructure, composition, optical and photocatalytic properties under visible light were investigated. The film porosity and refractive index were also determined via the UV-Vis spectrophotometric technique using transmittance and reflectance spectra and Cauchy dispersion law as the fitting model. The nanoporous morphology was observed using field-emission scanning electron microscopy (FESEM) with average pore sizes in the 20–40 nm range. The X-ray diffraction (XRD) results showed different texture grades corresponding to the (040) crystallographic plane, establishing the film thickness influence on the preferential orientation. The X-ray photoelectron spectroscopy (XPS) was also implemented to investigate the chemical state of the film surface, as well as to determine the valence band position. The film 715 nm in thickness showed the highest porosity (52%), narrowest bandgap (2.44 eV), highest exposed (040) crystallographic plane and highest visible-light-driven photodegradation towards Rhodamine-B (RhB) solution. The pH of the solution also impacted the RhB photodegradation which was optimum at pH 3 with chromophore cleavage pathway dominance, whereas at neutral pH it had distinctively slow kinetics probably due to poor electrostatic interactions and the N-deethylation kinetics bottleneck. The photocatalytic cycle experiments exhibited high stability and recyclability of BiVO4 thin-film photocatalysts after four cycles (4 × 7 h) of exploitation. The photocatalytic mechanism was determined using scavengers and the significance of hydroxyl radicals and photogenerated holes were established. The photocatalytic activity reached 97% after 7 h of illumination with a 400 W light source.

Nowadays, the researchers that are working on the SOFC technology, are agree that it is necessary to decrease the operating temperature at 700°C(650-750 °C) of IT-SOFC technology, which currently is around 850-900°C for electrolyte supported cell used by the three main operators –Bloom, Hexis and Sun Fire. At this temperature the reactivity and the component cost of the cell decrease. Nevertheless, some interactions between the conventional electrolyte material (YSZ) and the cathode material (lanthanum based) are still present and it is necessary to include a ceria buffer layer to avoid the possible formation of an insulating pyrochlore structure La2Zr2O7 layer at the electrolyte-cathode interface. In ceria family, the best material regarding the ionic conductivity is the samaria doped ceria. However, the gadolinia doped ceria is the most employed from the cost point of view and the availability of gadolinium in comparison with samarium. This buffer layer avoids the reactivity between electrolyte and cathode, and presents a good anionic conductivity. It must be dense, thin and adherent on electrolyte, in order to be suitable for the surface treatment process. In this paper, we present some recent results obtained on the gadolinia doped ceria coatings deposited by magnetron sputtering from metallic targets in argon-oxygen reactive gas mixtures with different substrate bias voltage. After a description of the experimental device, a first part will be dedicated to their chemical, microstructural and structural characterization (SEM, XRD,…) in relation with the magnetron sputtering deposition parameters. In a second part, the ionic transport characteristics of the half cell (Ni-YSZ/YSZ/GDC) will be investigated via impedance spectroscopy measurements performed at various temperatures up to 800°C under Ar-H2 gas mixtures. Finally, a complete cell test ((Ni-YSZ/YSZ/GDC/LSC) was performed with the Fiaxell Open Flanges test bench. This study is carried out within the framework of the European territorial cooperation program INTERREG V A France-Switzerland. It has benefited from financial support from the EU through the European Regional Development Fund (ERDF- € 139,176) and the Swiss Confederation's contribution of CHF 134,173

In this work, the techniques of cold spray (CS) and high velocity oxygen-fuel (HVOF) were employed to fabricate Ni/FeSiAl soft magnetic composite (SMC) coatings by using Ni-coated FeSiAl composite powder. The microstructural features were characterized in terms of scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses. The tribological and magnetic properties of the Ni/FeSiAl SMC coatings were also comparatively studied. Results showed that the CS coating exhibited higher particle deformation and much higher density, whereas the HVOF coating showed more visible defects and slightly higher oxide content. Both CS coating and HVOF coating resulted some loss of FeSiAl particles during deposition, while a higher content of FeSiAl particles was achieved in the HVOF composite coating, indicated a higher deposition efficiency of FeSiAl particles during HVOF deposition. According to the XRD analysis, both SMC coatings had no obvious oxidation and phase transformation during deposition processes. The EDS analysis proved partially melted particles during HVOF deposition. Tribological tests revealed a better wear performance of the CS coating as a result of the enhanced plastic deformation and microhardness. The HVOF coating showed a better magnetic performance, with a lower coercivity and a higher saturation magnetization compared to those of CS coating. This can be explained by a higher retainability of FeSiAl particles and a smaller strain stress generation during HVOF deposition.

International audience; • FeO films were synthesized by pulsed-DC magnetron sputtering from metallic target. • The film oxidation was controlled with a plasma emission monitoring system. • Special attention was paid to the sample position relative to the target axis. • Structural features depend on the oxidation rate of the growing films. • FeO behaviors are tuned from hematite semiconductor to magnetite semimetal properties. A R T I C L E I N F O Keywords: FeO Reactive sputtering Plasma emission monitoring Hematite Magnetite A B S T R A C T Iron oxide films were synthesized by pulsed-DC magnetron sputtering from a metallic target in Ar and O 2 gas mixtures. Plasma emission monitoring was implemented to accurately control the metal-to-oxygen ratio in the coating through the chemical state of the iron target. The intensity of the Fe* emission line was maintained at a given value (setpoint) by regulating the introduced oxygen flow rate. In addition, the oxidation rate of the growing film was adjusted by controlling the oxidation-to-deposition rate ratio as a function of the position of the substrates relative to the magnetron axis. The iron oxide films were characterized by X-ray diffraction, UV-VIS spectrophotometry, electrical measurement and vibrating sample magnetometry. In addition to the crys-tallization of pure hematite and magnetite phases, both phases coexist in a transition domain for a short range of setpoint depending on the oxidation-to-deposition rate ratio. The electrical, optical and magnetic behaviors of the FeO x films suggest that the relative proportion of phases can be tailored in this range. The FeO x film behaviors can then be tuned from the hematite semiconductor properties to the semi-metallic magnetite properties .

To investigate the microstructure and magnetic properties, FeSiBCrC bulk soft magnetic alloy was prepared by selective laser melting (SLM) technology using amorphous feedstock powder in this work. The results show that amorphous structures and crystalline phases occur in the alloy. And this alloy is mainly composed of α-Fe(Si), Fe3Si, FeB and Fe2B. It is mainly composed of metastable grains, equiaxed grains and amorphous matrix. This alloy has high microhardness (nearly 900 HV0.1). The SLMed alloy exhibits good soft magnetic properties. The coercivity of the direction X and direction Z is almost the same, which is 78.8 Oe. And it has great saturation magnetization with 162 emu/g in both directions. This work reveals the potential of fabricating bulk Fe-Si based amorphous soft magnetic alloys via SLM.

In this work, the influences of the temperature and the air residual pressure during post-annealing treatment on the structural, optical and electrical properties of copper iron oxide thin films were investigated. The films were co-sputtered from metallic Cu and Fe targets in the presence of argon and oxygen gas mixture. The powers dissipated on the metallic targets were adjusted to fix the Cu/Fe metallic ratio close to 1 in the films. The as-deposited thin films were initially amorphous, and they were annealed under different oxidizing conditions as a function of the temperatures (380, 450 and 550°C) and of the air residual pressures (secondary vacuum, primary vacuum, and air atmosphere corresponding to the air residual pressures of 10−4, 10−1 and 105 Pa respectively). Spinel CuFe2O4 were clearly detected by X-ray diffraction analysis after air-annealing. With the diminishing of the air residual pressure, the films are reduced. It was shown that the delafossite CuFeO2 phase growth is possible in a limited range of temperature and pressure and is accompanied by the crystallization of phase mixture in which the nature of secondary phases depends on the air residual pressure. The optical and electrical properties of Cu-Fe-O thin films were then detailed and discussed according to the structural evolution with the treatment conditions.

International audience; The crystalline and magnetic properties of micron thick magnetron sputtered Co1−x Crx and Co1−x Nix alloy films are analyzed in the view of their implementation as semi-hard magnets. All of the tested films crystallize in an hcp lattice, at least up to 35 at% of alloying elements (Cr or Ni). The structural study shows that the ratio of hcp phase with [0001] axis orientated perpendicular to the film as compared with in-plane orientation increases (resp. decreases), when Ni (resp. Cr) concentration increases independently of the post-annealing temperature. The orientation of the magnetization results from the competition between the demagnetization field which tends to align the magnetization in plane and the crystalline anisotropy which tends to maintain the magnetization along the [0001] axis. Interestingly, we find that, although Co and Ni are very similar atoms, Co1−x Nix alloys crystalline anisotropy can be strongly increased and reach up to twice the anisotropy of the best Co1−x Crx alloy, while maintaining a magnetization at saturation above 1200 kA/m. The thermal stability of the structural and magnetic properties of both alloys is demonstrated for an annealing temperature up to 300 °C.

The direct synthesis of chalcopyrite Cu2MnSnS4 (CMTS) thin films by a spray pyrolysis technique on glass substrates under oxidative conditions (ambient atmosphere and using compressed air as a carrier gas instead of nitrogen) was studied. The effect of the deposition temperature on the structural, chemical composition, and optical and electrical properties of thin films has been assessed. X-ray diffraction study reveals that the tetragonal stannite structure crystallizes with a [112] preferential orientation from 280 up to 360 &deg, C, with its crystallinity correlated with the substrate temperature. However, in addition to its crystallization, traces of secondary phases are observed: a mixture of SnO and CuO at 360 &deg, C prevails on the formation of CuS at 320 &deg, C. Above 360 &deg, C, the oxidant conditions combined with the loss in sulfur lead to the crystallization of only the tenorite CuO. The crystallization of sulfides by spray pyrolysis under air is possible only at relatively low deposition temperature for which the oxidation rate is inefficient compared to the sulfidation rate. Further optical studies of stannite films indicate a high absorption coefficient toward the visible range (&gt, 104 cm&minus, 1) and an optical band gap of about 1.64&ndash, 1.85 eV, also depending on the substrate temperature. The CMTS thin films deposited below 360 &deg, C exhibit a moderate electrical resistivity of about Ω&middot, cm at room temperature. The properties of the stannite films synthesized using a spray pyrolysis technique in ambient air are comparable to those of films obtained by spray pyrolysis with nitrogen carrier gas despite the presence of oxides traces, an increase in the deposition temperature improving the microstructure, and its related optical and electrical properties.

International audience; Fe-Ni-Si soft magnetic parts, using Ni coated high silicon steel powder, were manufactured by selective laser melting process. The type of defect changes from porosity to cracks and the relative density increases, from 50% to 99%, with the decreasing laser scanning speed. The microstructural analyses indicate that the low laser scanning speed fully melted the nickel coating and high-silicon steel core. The EBSD study showed that the separated island and lamellar mesostructures appeared on the top and side view respectively. Moreover, no apparent texture were observed. The magnetization saturation of SLM processed sample decreased, as the laser scanning speed was increased. Consequently, the magnetic properties of SLM processed Fe-Ni-Si alloy also showed anisotropic feature in building and scanning directions, which can be attributed to their different mesostructure.

The ultimate goal of diversion applications is to enhance contact of the stimulation fluid with the reservoir rock in such a way to maximize the conductive reservoir volume. Unfortunately, intentions to simplify diversions with rule of thumbs, trial and error, and pump and hope have generated uncertainties and slowed the impact in stimulation efficiency and production enhancement that this technique is capable of generating. Fluids introduced into a reservoir for stimulation typically take the path of least resistance and therefore frequently go into areas where there are open flow paths. In many cases, those existing flow paths are neither the areas you would want to stimulate for increased production, nor areas from which formation damage will need to be removed. The success of a hydraulic fracturing or acidizing operation depends on maximizing the contact between the stimulation fluid and the intact rocks. To achieve this goal, existing fluid paths must be efficiently plugged to divert the fluid towards intact or under- stimulated rock for efficient application, which in turn maximizes the BOE (barrels of oil equivalent) returned from the stimulation treatment relative to unit cost. Although industry has been deploying this technology on a more widespread basis recently, they have not been as focused on the underlying mechanisms, physics and controlling parameters which ultimately govern the success of the stimulation event. This paper will present a comprehensive discussion around missing factors associated with jamming and plugging efficiency, particle size, particle shape, frictional parameters, particle concentration, opening geometry, rate during placement, and particles ratio. It will clearly highlight the importance of understanding the physics and mechanisms associated with a complex diversion process requiring a rigorously engineered approach. Multiple experiments were reviewed to quantify and understand the effect and importance of the different key factors that dictate the overall goal of a successful diversion treatment. In fact, an analytical model has been developed, verified with advanced numerical simulations and calibrated with experimental results to optimize the operational parameters required for efficient diverter displacement; including adjusting the displacement rate during diverter injection and also determining and adding the required volume of spacer to minimize particle dispersion, which ensures that the diverter pill arrives at the required site intact and as designed. The proposed numerical and analytical engines are presented within the design engineering process to better enable and achieve the necessary pressure buildup required for efficient fluid diversion.

International audience; A radial injection experimental setup is presented in this paper, which allows one to study the transport and deposition of suspended particles and permeability impairment in porous media. This setup allows one to simulate the conditions of the injection of produced water in oil reservoirs from an injection well. This is achieved by a radial injection of water containing suspended particles of a few microns in size from a central well including a sand screen, through a confined cylindrical sand pack (diameter 52 cm, height 40 cm). A peripheral drainage system permits the recovery of the fluid at the outlet of the sand pack by a collector equipped with a turbidimeter for measuring the concentration of suspended particles. The injection pressure is measured at the inlet, and six pore pressure probes have been installed at different locations inside the sand pack. First experimental results presented show a significant heterogeneity of deposited particle profiles in both radial and axial directions.

CuCr 0.93 Mg 0.07 O 2 thin films were successfully deposited by DC reactive magnetron sputtering at 1123 K from metallic targets. The influence of film thickness on the structural and optoelectronic properties of the films was investigated. X-ray diffraction (XRD) results revealed that all the films had a delafossite structure with no other phases. The optical and electrical properties were investigated by UV–VIS spectrophotometer and Hall measurement, respectively. It was found that the optoelectronic properties exhibited a thickness-dependent behavior. The optical band gap and the average transmittance of the films showed a monotonous decrease with respect to the increase in thickness. The average transmittance in the visible region decreased from 67% to 47% as the thickness increased from ~70 nm to ~280 nm. Simultaneously, the conductivity of the films fell from 1.40 S∙cm −1 to 0.27 S∙cm −1 . According to Haacke's figure of merit (FOM), a film with a maximum FOM value of about 1.72×10 −7 Ω −1 can be achieved when the thickness is about 70 nm (σ≈ 1.40 S·cm −1 and T av. ≈67%).

Silicon oxynitride thin films were sputter deposited by the reactive gas pulsing process. Pure silicon target was sputtered in Ar, N 2 and O 2 mixture atmosphere. Oxygen gas was periodically and solely introduced using exponential signals. In order to vary the injected O 2 quantity in the deposition chamber during one pulse at constant injection time ( T ON ), the tau mounting time τ mou of the exponential signals was systematically changed for each deposition. Taking into account the real-time measurements of the discharge voltage and the I(O * )/I(Ar * ) emission lines ratio, it is shown that the oscillations of the discharge voltage during the T ON and T OFF times (injection of O 2 stopped) are attributed to the preferential adsorption of the oxygen compared to that of the nitrogen. The sputtering mode alternates from a fully nitrided mode ( T OFF time) to a mixed mode (nitrided and oxidized mode) during the T ON time. For the highest injected O 2 quantities, the mixed mode tends toward a fully oxidized mode due to an increase of the trapped oxygen on the target. The oxygen (nitrogen) concentration in the SiO x N y films similarly (inversely) varies as the oxygen is trapped. Moreover, measurements of the contamination speed of the Si target surface are connected to different behaviors of the process. At low injected O 2 quantities, the nitrided mode predominates over the oxidized one during the T ON time. It leads to the formation of Si 3 N 4− y O y -like films. Inversely, the mixed mode takes place for high injected O 2 quantities and the oxidized mode prevails against the nitrided one producing SiO 2− x N x -like films.

Fe–Ni thin films were co-sputter deposited from Ni and Fe metallic targets on different substrates. The evolution of the coating composition as a function of the discharge current dissipated on each target is studied and the targeted composition for Ni 3 Fe is obtained by fixing the discharge current applied on Fe target at 0.5 A and adjusting the discharge current applied on Ni target at 0.45 A. The as deposited coating with convenient composition presents a disordered solid solution FCC structure. Finally, the magnetic properties of the films are investigated as a function of their thickness. We have observed that coercivity decreases slightly and magnetic moment increases which increasing film thickness.

An accurate description of reactive transport phenomenon in porous media has major applications for many processes such as, contamination in groundwater resources, carbon capture and storage, enhanced oil recovery, and acid stimulation. These processes, involve surface reaction coupled with flow that result in dynamic alteration of the porous media structure. More particularly, in well acidizing, an accurate understanding and control of the stimulation operations outcomes still represents a major challenge in heterogeneous carbonates. The objective of this paper is to describe how an integrated experimental and numerical approach is adopted to develop a core-scale reactive transport simulator that could be used to investigate acidizing efficiency in carbonates. A series of core flooding experiments were performed on Richemont carbonate blocks from queries at reservoir temperature. A back pressure valve system is used to eliminate the effect of free gaseous CO2 on the flow dynamics of acid. Moreover, mathematically, a continuum-scale model was used to describe the reactive transport phenomenon. This model consists of fluid transport, continuity, species balance, and porosity evolution equations at a continuum scale. The porous media characteristics such as permeability and pore radius are obtained as a function of local porosity using closure relations. The rock properties required as input to the model come from numerous experimental techniques such as computed tomography (CT), Mercury injection capillary pressure (MICP), and X-ray diffraction (XRD) The numerical results obtained using the model, show a close match with the experimental observations, in terms of pore volume to breakthrough (PVBT). Additionally, the developed model was able to reproduce the different dissolution regimes along with the transient pressure response, as observed experimentally.

A simple and inexpensive procedure based on the bleaching of orange II (acid orange 7) solution has been developed in order to quantitatively assess the photocatalytic activity of titanium dioxide thin films. The influence of experimental parameters including, pH and light flux density on the reaction rate has been investigated. The results of this study suggest that at natural pH (7.2) and low dye concentration, the mechanism responsible for the degradation of orange II is mainly photooxidation via the formation of radicals. The procedure was used to compare the photoefficiency of TiO2 films poisoned with variable amounts of sodium. The obtained results are in good agreement with the previously reported effect of sodium on the photoactivity of titanium dioxide thin films.

Summary Gas-well productivity in tight reservoirs is greatly impeded by fracturing-fluid interactions with the formation. New simulators introduce formation-damage mechanisms to calculate gas-well productivity. However, equations describing formation damage must be supported by experimental data obtained in conditions representative of fracturing operations. The purpose of this work is to derive absolute-permeability and multiphase-flow damages upon return gas permeability after core invasion by a fracturing fluid by methods used in the Special Core Analysis Laboratory (SCAL). The core permeability is in the microdarcy range with significant illitic content. Absolute-permeability damages caused by fracturing-fluid filtration and water sensitivity are measured. Water-saturation profiles recorded by X-ray in two-phase-flow experiments are interpreted. The methodology of interpretation provides the petrophysical data specific to the rock/fluid system: absolute permeability, relative permeability damage caused by hysteresis, and capillary pressure. In addition, simulations are presented for the evaluation of the effect of various operational parameters, such as pressure drawdown, on gas productivity. It is shown that permeability hysteresis is the determinant factor to explain low gas recoveries at short term. In the long term, the natural cleanup is very slow. The results, derived from a real rock/fluid system, are used to provide recommendations for improving backflow procedures. This methodology can be applied to any case of damage caused by the alteration of rock/fluid properties.

Summary Invasion of aqueous drilling, completion, or fracturing fluids can reduce the relative permeability to gas and thereby causes a water block. In the case of low-permeability formations, the capillary pressure tends to be high because of the small pore size. Cleanup of water blocks requires high drawdown unless water vaporization by the flowing gas is improved by using specific additives such as alcohols. The purpose of this work is to investigate fracture-face damage by measuring relevant petrophysical parameters: absolute-permeability damage and gas return permeabilities. Measurements are performed in representative conditions of a fracturing operation in a tight gas formation: cores with an absolute permeability of 10 μd set at Swi and experimental pressure of 200 bars for the fracturing-fluid invasion. Water and gas saturations during the fracturing-fluid invasion and during gas backflow are monitored by X-ray equipment. Adding alcohol in the fracturing fluid has a striking effect on resolving water blocks. Cake formation on the simulated fracture face is also discussed. Numerical simulations are performed to assess relative permeabilities from the experimental results. It is shown that hysteresis of gas and water relative permeabilities has a strong impact on the rate of water removal. Sufficiently high pressure drawdown is crucial to overcome capillary forces and initiate the alcohol- assisted vaporization process. Water removal by water vaporization is assessed and compared to the experimental results.

The aim of this paper is an investigation of the photocatalytic efficiency of TiOx thin films deposited by DC reactive magnetron sputtering at low temperature and doped by Ag noble metal. Crystallographic structure and chemical composition of as-deposited films were examined by XRD and RBS, respectively. Ag/TiOx films morphology was studied by SEM analysis. The photocatalytic activity was evaluated from the decomposition speed of an aqueous solution of the Acid Orange 7, exposed to UV/VIS light. A systematic change of Ag concentration in TiOx films led to a maximum activity. Such a maximum is discussed taking into account composition, morphology and structure of the films.

WxZr1−x thin films were deposited at room temperature on glass substrates by co-sputtering tungsten and zirconium targets in argon. The composition was found in the range 0 ≤ x ≤ 0.81. The grain size deduced from X-ray diffraction analysis ranged from 1.3 nm to 16 nm depending on the composition. The events in the resistivity, optical reflectivity and thickness evolutions were correlated with the X-ray diffraction analysis. Depending on the composition, the local organization can be attributed to a nanocrystalline solid solution of W in Zr, to a nanocomposite structure involving ZrW2 nanograins embedded in an amorphous matrix, to ZrW2 Laves phase nanograins and to a nanocrystalline solid solution of Zr in W. For 0

Photocatalyst TiO 2 coatings have been reactively sputtered at high pressure on cold glass substrates pre-coated by a SiN x sodium diffusion barrier. The as-deposited coatings were amorphous and the TiO 2 /SiN x /glass samples were subsequently heated at different temperatures under air. The TiO 2 films crystallise in the anatase structure above temperatures of 250 °C with a [001] preferential orientation. The structural analyses have demonstrated that the crystallites are elongated following the c axis direction, perpendicularly to the surface. No modifications of grain size and texture have been observed over the complete temperature range studied (250–550 °C). However, the lattice parameters evolution shows a decrease of the tensile stress with a rise in annealing temperature. The microstructure is then completely relaxed around 400 °C and finally compressive stress is observed at higher temperature. The study of the photo-induced (photocatalytic and hydrophilic) properties shows an activity maximum at 400 °C. These results suggest that the photo-induced properties would be favoured by a relaxed microstructural state of titanium dioxide.

Amorphous and porous TiO 2 coatings were deposited by reactive magnetron sputtering at high pressure (3.4 Pa) on cold soda-lime glass placed at different positions relatively to the magnetron target, which corresponds to different impingement angles and target-to-substrate distances. The as-deposited coatings were heated at 450 °C under ambient air to crystallise into the photoactive anatase phase. The structural analyses combined with AFM experiments have shown a reduction of the crystallites and the lateral grain size with the removal of the substrate from the target axis inducing a specific area rise. Moreover, the stress state is all the less as compressive as the substrates are far away from the target. As a result, the photocatalytic properties are improved with the decrease of the incidence angle and with the target-to-substrate distance rise.

Amorphous titanium dioxide coatings were deposited at high pressure (about 5 Pa) on cold soda-lime glass by reactive magnetron sputtering. In order to obtain anatase form known for its photocatalytic properties, an annealing at 450 °C was required. The morphology of the photocatalyst coating, examined by scanning and transmission electron microscopy, exhibits a columnar structure with closed intercolumnar porosity. The concentration profile obtained by means of sputtered neutral mass spectrometry revealed the presence of sodium into the TiO 2 coating due to the Na diffusion from the soda-lime glass during the annealing step. This level of contamination reaches 5.5 at.% in the whole film thickness. Since the presence of Na in TiO 2 coatings is harmful to the photocatalytic properties, a silicon nitride (SiN x ) coating, acting as a Na diffusion barrier, was intercalated between the glass substrate and the TiO 2 coating. The concentration profiles showed that the TiO 2 coating deposited on SiN x /glass substrate is sodium-free. Furthermore, photocatalytic tests revealed that TiO 2 /SiN x /glass system is about threefold more efficient than TiO 2 /glass, showing both the poisoning effect of Na and the superior efficiency of SiN x as a diffusion barrier. To illustrate this, diffusion barriers made of silicon dioxide have also been grown and compared to SiN x .

A well-designed acid stimulation treatment is a rapid well intervention operation that can lead to long-trim economical benefits. In carbonates, the main challenge is to better design acid stimulation treatments in order to meet the two main characteristics of carbonate reservoirs which are high water production and a wide range of heterogeneities. Acid diversion is one of the key factors for a proper distribution of acid which determines the success of these treatments, especially in heterogeneous carbonate formations. In this study, we aim at producing novel solutions in order to reduce water production and enhance zonal coverage through effective diversion. The ultimate goal is to validate a single pumping sequence that combines water mitigation, diversion and acid injection. In order to achieve this, we rely on an integrated R&D approach combining single core and dual core experimental setups. The advantage of the dual core setup is to investigate different permeability contrasts, different saturations configurations and to experimentally validate wormholing in heterogeneous carbonates. In fact, in carbonate effective diversion happens when acid is flowing in the low permeability area at sufficient velocity. An easy way to validate this is through parallel core flooding. We performed a series of high pressure and temperature single and dual core flooding experiments over a range of different carbonate samples having different permeability and porosities. The injection took place at 90 °C and 250 bars. We assessed the efficiency of polymer adsorption by measuring permeability during, before and after polymer injection. Computed Tomography scans were used in order to validate our conclusions. We showed that, adsorption of polymer in carbonates is possible but needs careful design. We experimentally investigated acid diversion in high permeability contrasts (matrix-fissures) through core flooding. This is another novelty in this study. Finally, the combined pumping sequences were experimentally assessed. We validated diversion in carbonates and identified the optimum injection rates required for such applications. An optimum configuration of permeability contrasts and saturations exists for a combined pumping sequence. The experimental results and observations are translated into a series of guidelines and procedures which are directly applicable to acid stimulation field operations. The areas of future required research in applied fluid-rock interactions will be highlighted.

In a high number of deepwater fields, water injector and producer wells are being drilled with synthetic or oil-based drilling fluid (SBM or OBM). The filter cake and drilling fluids residue left on all of the well surfaces after the drilling phase is a water-impermeable layer. If not removed, they will compromise project objectives. To avoid excessive operating costs and to remove near-wellbore damage, a quick and efficient removal of SBM or OBM with properly-designed clean-up fluids, such as microemulsion fluids, is required. Properly designed microemulsion spacer fluid formulations can be used to displace the SBM or OBM to a water-based fluid and completely water-wet all the surfaces in less than one circulation. The displacement fluids are formulated with customized surfactant blends (CSB) that exhibit equal affinity for the oil and water phases. They promote a very thorough microemulsification of the oil residue from the SBM or OBM during the displacement operation resulting in an aqueous external phase at the end of the process. The microemulsion displacement fluids are formulated to: (a) prevent viscous sludge at the fluids interface; (b) remove all of the oil from the surfaces; and (c) make the wellbore surfaces and near- wellbore region water-wet. In addition to spacer fluid formulations, customized microemulsion fluids can remediate wells and increase water injectivity and well productivity. These fluids contain a customized surfactant blend (CSB), a small amount of acid, and an optional co-surfactant. They form an in-situ microemulsion and produce a uniform wellbore cleanup in horizontal and highly-deviated open-hole wells. Customized microemulsion fluids are able to cleanup in a broad range of temperature, density, and salinity. They restore the water-wet condition of the rock and increase injectivity or productivity of the wells. This paper presents laboratory evaluations and field data of treatment fluids for wellbore displacement and near-wellbore cleanup based on the microemulsification mechanism. Data from systematic evaluation tests performed prior to field application (e.g. interfacial tension, detergency tests, fluids compatibility, filter cake removal and regain permeability) demonstrates performance results that were beyond the capabilities of conventional treatments. Based on the key performance indicators (turbidity of completion brine, volume used and resulting cleanliness of tools), displacement of SBM or OBM with microemulsion cleaners in deepwater applications was achieved in one circulation during the wellbore displacement process. Successful removal of SBM or OBM in the near wellbore region is evidenced by comparing predicted and achieved injection and production rates.

International audience; Damage and clogging of the granular structure of reservoirs are commonly observed during the re-injection of produced water containing solid particles and oil droplets. These phenomena can lead to a significant decrease of the reservoir permeability around the injectors and affect the injectivity of these wells. In this paper an experimental study on the transport and deposition of silica particles in a porous medium subjected to flow is presented. The study is performed on two different devices; the first one is an injection column 1 m long in which a sand pack with controlled density using the pluviation technique has been placed and the second one is an injection cell in which a cylindrical sand specimen (height 80 mm, diameter 80 mm) is put under isotropic stress. Water containing a low concentration of fine particles (diameter of few microns) is injected at a constant flow rate. The evolutions of the sample mass and of the injection pressure are recorded. The experimental results show an increase of particles mass retained inside the sample during the injection and an increase of the injection pressure attributed to a decrease of the permeability of the sample. They also show that despite the low concentration of particles of the injected fluid, a clogged area of a few centimetres forms at the column inlet. The analysis of this area by mercury porosimetry showed a significant decrease of the porosity and of the pore size and the formation of a new family of pores by the agglomerated particles. This study focuses on the impact of various parameters (diameter of the injected particles, pore size distribution of the porous medium, concentration of particles in the injected water, injection flow rate and surface roughness of the grains) on the reduction of the permeability.

Historically, leak-off analyses of stimulation fluids have been performed using in-house laboratory procedures. The lack of industry standard procedures to perform leak-off and wall building coefficient analyses of stimulation fluids has introduced inconsistency in both results and reporting for many years. A technical standard adopted in 2006 by both API and ISO for static conditions has provided the oil and gas industry with the first standardized procedure to measure and report leak-off1. However, the more complex testing under dynamic conditions was not addressed. As a result, a group of industry experts have compiled their years of experiences in developing a new technical standard to measure the leak-off characteristics of stimulation and gravel-pack fluids under dynamic flow conditions. Stimulation and gravel-pack fluids are defined, for the purpose of this technical standard, as fluids used to enhance production from oil and gas wells by fracturing and fluids used to place filtration media to control formation sand production from oil and gas wells. Leak-off is the amount of fluid lost to porous media during these operations. The leak-off procedure was developed through the collaboration of several industry companies by evaluating numerous in-house laboratory techniques and conducting round robin testing to ensure that any modifications to these procedures were reliable and repeatable. The new standard provides a step-by-step procedure that includes fluid preparation, experimental equipment design, testing procedure and data analyses for fluids exhibiting viscosity controlled leak-off or wall building characteristics. Example calculations are reviewed within this paper.

International audience; Amorphous and nanocrystalline materials have attracted much interest in the field of new materials design because of their excellent mechanical and physical properties as well as their magnetic properties. In this work, Fe-40Al coatings were prepared from nanostructured feedstock with a very low degree of order using atmospheric plasma spraying. Scanning electron microscopy, X-ray diffraction, and magnetic measurements were used to investigate microstructure, phase structure, and magnetic properties of the coatings. The results showed that Fe-40Al coating presented a ferromagnetic character due to partial structure with a low degree of order and unmelted nanostructured particles retained from the feedstock. Moreover, the heterogeneous magnetic properties were found in the parallel and vertical direction of the coating.

Stand alone screens is a sand control technique that has been widely used in the industry for many years. However, some failures have been experienced, raising some concerns about the validity of design and operating procedures. Contrary to gravel pack for which Saucier criteria is well accepted, design criteria for a sand screen only has always been subject to discussion. As it is a simple and cost effective sand control solution, there is still an incentive to develop more robust design and installation rules. Within Total, a large experience was built in running stand alone screens that allowed optimizing installation practices. In addition, a multi-year laboratory experiments program was run to establish the key parameters in designing stand alone screens. Results of this work are discussed in this paper. First, an experimental work flow was developed and made reliable after evaluating consistence and repeatability of results. Then, a sizing criteria based on the retention of the largest sand grains was confirmed to be pertinent. At last, it was demonstrated the sand size distribution does not have any impact on the sand retention performance of a screen. It cannot be the origin of screen plugging. This work will set new standards in stand alone screen design in Total.

International audience; Amorphous columnar TiO2 films were synthesised by reactive sputtering on cold sodaâ€"lime glass substrates (TiO2/glass films). The films were subsequently heated in order to crystallise the photoactive anatase phase. The surface chemical composition assessment demonstrates the occurrence of metallic Na, the amount of which increases with the annealing temperature. The evolution of the structural, microstructural and photocatalytic properties of the films with the annealing temperature was investigated and compared to that of TiO2 films deposited in same conditions, but on glass pre-coated with a SiNx diffusion barrier (TiO2/SiNx/glass films). Once crystallised, both series of TiO2 films exhibit [001] preferential orientation corresponding to the columnar growth. Grain coalescence associated to a modification of the grain shape is only observed in TiO2/glass films for annealing temperatures higher than 450 °C, whereas neither microstructural nor structural change is observed in TiO2/SiNx/glass films. The Na-contaminated TiO2 films exhibit different photocatalytic behaviour with the annealing temperature compared to the Na-free TiO2 films. A discussion is finally based on these differences.

Silicon oxynitride thin films were synthesised by the reactive gas pulsing process using an argon, oxygen and nitrogen gas mixture from a semiconductor Si target. Argon and nitrogen were introduced at a constant mass flow rate, whereas oxygen gas was periodically supplied using a rectangular pulsed flow rate. The O 2 injection time T ON (or duty cycle α ) was the only varied parameter. The influences of this parameter on the discharge behaviour, on the Si target voltage, and on the resulting chemical composition of the films were investigated. The temporal evolution of the total pressure exhibits exponential shape differing from the rectangular oxygen pulse shape, due to the response time of the gas flowmeter and to the progressive oxidation of the target and the chamber walls. During the T ON time, the preferential adsorption of the introduced O 2 induces a decay in Si target voltage. Reversion to the nitrided mode is still possible as soon as the O 2 injection is stopped. The elemental analyses assessed by secondary neutral mass spectrometry (SNMS) showed that the O/N ratio within silicon oxynitride films linearly depends on the T ON time. Increasing the duty cycle α over a certain value results in an oxidised steady state formation during the T ON time. This formation was observed by real time measurements of the emission lines ratio I (O * )/ I (Ar * ) indicative of the O 2 partial pressure and confirmed by the time derivative of the target voltage. During the T OFF time, the alternation with the nitrided mode becomes impossible, leading to the specific synthesis of stoichiometric SiO 2 films.

Invasion of aqueous drilling, completion or fracturing fluids can reduce the relative permeability to gas and thereby causes a waterblock. In the case of low permeability formations, the capillary pressure tends to be high because of the small pore size. Clean up of water blocks requires high draw down unless water vaporization by the flowing gas is improved by using specific additives like alcohols. The purpose of this work is to investigate fracture face damage by measuring relevant petrophysical parameters: absolute permeability damage and gas return permeabilities. Measurements are performed in representative conditions of a fracturing operation in a tight gas formation: cores with an absolute permeability of 10 microDarcy set at Swi, experimental pressure of 200 bars for the fracturing fluid invasion. Water and gas saturations during the invasion of the fracturing fluid as well as during the gas back flow are monitored thanks to a XRay equipment. Adding alcohol in the fracturing fluid has a striking effect on resolving the water block. Cake formation on the simulated fracture face is also discussed. Numerical simulations are performed to assess relative permeabilities from the experimental results. It is shown that the hysteresis of gas and water relative permeabilities has a strong impact on the rate of water removal. Sufficiently high pressure draw down is crucial to overcome capillary forces and initiate alcohol assisted vaporization process. Water removal by water vaporization is assessed and compared to the experimental results.

Gas well productivity in tight reservoirs is greatly impeded by the fracturing fluid interactions with the formation. New simulators introduce formation damage mechanisms to calculate gas well productivity. However, equations describing formation damage must be supported by experimental data obtained in conditions representative of fracturing operations.The purpose of this work is to derive the absolute permeability damage and multiphase flow upon return gas permeability after core invasion by a fracturing fluid by methods used in Special Core Analysis Laboratory (SCAL). The core permeability is in the microDarcy range. Experimental data of absolute permeability damage due to the fracturing fluid filtration and water sensitivity of this illitic sandstone as well as water saturation profiles measured by X-Ray in two phase flow experiments are interpreted. The methodology of interpretation provides the petrophysical data specific to the rock-fluid system: the absolute permeability, the relative permeability damage due to hysteresis, and the capillary pressure curve.In addition, simulations are presented for the evaluation of the impact of various operational parameters like pressure draw-down on the gas productivity. It is shown that permeability hysteresis must be considered to explain the low gas recoveries at short term. On the long term, the natural clean-up is very slow. The results, derived from a real rock-fluid system, are used to provide recommendations for improving back flow procedures. This methodology can be applied to any case of damage due to the alteration of rock-fluid properties.