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TiWSixN films were deposited using a magnetron co-sputtering system on silicon (111), 316L stainless steel, and M2 high-speed steel substrates. The silicon target current density was varied from 0 mA/cm2 to 4.32 mA/cm2 in order to modify the Si content in the films. The microstructure and chemical composition were determined by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The surface of the films was explored via scanning electron microscopy (SEM) and atomic force microscopy (AFM). Mechanical, tribological, and thermal properties were investigated by means of the nanoindentation, ball-on-disc, and cyclic oxidation tests, respectively. Our results indicated that as the silicon target current density was increased, the microstructure changed from crystalline to amorphous, and the hardness and elastic modulus improved from initial values of 7.5 ± 0.3 GPa and 181 ± 8 GPa to 15 ± 1 GPa and 229 ± 9 GPa, respectively. Furthermore, films deposited at high silicon target current exhibited better resistance to thermal oxidation. The failure mechanism of the WTiSixN thin films under cyclic oxidation was attributed to the microstructure of the films, WO3 sublimation, and the thermal coefficient mismatch between the film and the substrate.

Poly(ethylene glycol) (PEG) chains were covalently grafted onto carbon black (CB) using a PEG-terminated trimethoxysilane, yielding PEGylated CB additives (CB-SiPEG) with different SiPEG contents. Unlike pristine CB, CB-SiPEG was readily dispersed in PEG200 base oil, with CB-SiPEG hydrodynamic particle sizes being considerably smaller than those of pristine CB. At optimal SiPEG content, friction coefficient and specific wear rate in ball-on-disk tribometer tests were reduced by 35% and 67% respectively, with 1% wt. CB-SiPEG compared to PEG200 alone. In contrast, pristine CB, alone or with unbound SiPEG, did not show friction-reducing or antiwear capacity. Disk analysis supports CB-SiPEG surface deposition forming a protective tribofilm. Hydrodynamic particle size and lubricating performance of CB-SiPEG/PEG200 blends were preserved after 6 months, indicating high dispersion stability.

Ruthenium oxide (RuO2) has received significant attention in recent years for its photocatalytic properties and photoelectrochemical (PEC) performance. In the present research, RuO2 nanolayers were grown on n-type porous silicon (PSi) by metal organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). The morphology, mechanical and optical properties of produced nanostructures were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, diffuse reflectance and photoluminescence (PL) spectroscopy. It was shown that that MOCVD gives non-uniform distribution of RuO2 along the pore and it is deposited mainly in the near-surface of PSi, while distribution of ruthenium obtained by ALD looks conformal over the entire pore. The mean size of RuO2 nanocrystallites and mechanical stresses were determined by TEM, XRD and Raman spectroscopy. It was demonstrated that samples obtained by ALD demonstrate a good crystallinity, while crystalline phase for samples produced by MOCVD improve with RuO2 layer thickness increasing. It was established the formation of hydrated RuO2 during ALD and MOCVD. It was shown that the samples produced by MOCVD have slightly higher electrical conductivity than ALD samples. The average value of energy gap (Eg) for samples prepared by MOCVD depended on the number of injections. RuO2 nanolayers quenched intrinsic PL from the PSi matrix. The correlation between structural, optical, and mechanical properties of samples produced by MOCVD and ALD was discussed.

The room temperature synthesis of copper (Cu) nanoparticles (NPs) supported within SiO2 mesoporous thin films (MTF) modified with either COOH or NH2 functional groups is reported. The functional groups present in the MTF surface acted as adsorption sites for Cu (II) ions, which were afterwards reduced to Cu NPs in presence of sodium borohydride at room temperature. The oxidation state of the copper NPs, corroborated by X-ray Photoelectron Spectroscopy and Electron Energy Loss Spectroscopy, was strongly dependent on the functional group present in the pores of the MTF and on the number of adsorption/reduction (A/R) cycles applied for NPs loading. Metallic Cu (0) NPs were obtained in MTFs displaying COOH groups applying 10 A/R cycles while NPs with higher oxidation state were as well present after 20 A/R cycles. For MTF functionalized with NH2 groups the copper is present as Cu (I) and Cu(II) in the NPs but no Cu (0) can be detected. The MTF-Cu(CuOx) composite materials were tested as catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. Catalytic activity of composite materials depends on the oxidation state of Cu NPs, being more active those samples containing Cu (0) NPs, synthesized from COOH functionalized MTFs. Fil: Coneo Rodríguez, Rusbel. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina Fil: Yate, Luis. No especifíca; Fil: Coy, Emerson. Adam Mickiewicz University; Polonia Fil: Martínez Villacorta, Ángel M.. No especifíca; Fil: Bordoni, Andrea Veronica. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina Fil: Moya, Sergio. No especifíca; Fil: Angelome, Paula Cecilia. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina

We investigate the deposition of TiWSiNx thin films by means of the method of reactive magnetron co-sputtering, setting the nitrogen flow ratios N2/(Ar + N2) at 4.8%, 9.1%,16.7 and 33.3%. The crystallographic structure of the films was established through X-ray diffraction (XRD), the morphology and topography were evaluated through scanning electron microscopy (SEM) and atomic force microscopy (AFM), the chemical composition was evaluated through X-ray diffraction and X-ray photoelectron spectroscopy, the mechanical properties were evaluated by nanoindentation, and the wear resistance was studied via nanowear and pin-on-disk. It was found that films deposited between 4.8% and 16.7% nitrogen flow ratio exhibited an amorphous phase. As the nitrogen was increased, the films evolved into a mixture of amorphous Si3N4 and crystalline TiWN phase. Moreover, the film morphology changed to fine columnar as the nitrogen flow ratio increased. As a general observation, the hardness, resistance to plastic deformation (H3/E2), and residual stress of the samples increased as the nitrogen flow ratio increased. The maximum hardness, resistance to plastic deformation, and residual stress were 22 ± 0.4 GPa, 213 ± 20 MPa, and 1.4 ± 0.01, respectively. The lowest nanowear volume (0.47 µm3) and wear rate (11 ± 8 10−9 mm3/N mm) were obtained for films deposited at high nitrogen flow ratios. The lowest friction coefficient (0.15) was recorded for films deposited at 16.7% nitrogen flow ratio.

Polymer brushes have a great potential for controlling surface wetting properties. In this work we study the surface wettability in respect to water of diblock copolymer brushes with an outer block of the thermoresponsive poly(N-isopropylacrylamide) (PNiPAM) polymer and an inner hydrophobic block of 1H 1H 2H 2H-perfluorodecyl Acrylate (PPFDA) and with variable block lengths. Block copolymer brushes are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The conditions of synthesis; polymerization time of NiPAM, grafting density of change transfer agent (CTA) on the surface, amount of initiator and monomers were varied to produce brushes with different ratios of PNiPAM and PPFDA. Diblock copolymer brushes are characterized by Raman, XPS and Atomic Force Microscopy. Brushes with contact angles from 28 to 85 degrees are produced. The brushes with longer PPFDA blocks are the more hydrophobic. Contact angle values increase when raising temperature from 20 °C to 40 °C as for PNiPAM but always to higher contact angles than for the PNiPAM brush.

International audience; Structural, electronic and mechanical properties of ZnO/Graphene (ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition (ALD) and chemical vapor deposition (CVD) were investigated. We performed scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), Raman spectroscopy, X-Ray photoelectron spectroscopy (XPS) and nanoindentation to characterize the ZnO/G nanolaminates. The main structural and mechanical parameters of ZnO/G nanolaminates were calculated. The obtained results were analyzed and interpreted taking into account mechanical interaction and charge effects occurring at the G-ZnO interface. The influence of graphene sublayers number on the mechanical behavior of the ZnO/G nanolaminates was studied. By reducing the bilayer thickness, the mechanical parameters of the films can be tuned (Young's modulus 100-200 GPa, hardness 3-9 GPa). The softer response of the multilayers as compared to the single layers of ZnO and graphene was attributed to the structural changes in the ZnO layer and the interfaces. This study shows the mechanical behavior of ZnO/G nanolaminates and their influence on the development of novel electro-optical devices based on these structures. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The use of silver nanoparticles (AgNPs) result in an inevitable contact with aquatic environments. Here we study the behavior of AgNPs and the developmental toxicity in zebrafish embryos exposed to these nanoparticles (0-10 mg/L) with and without the presence of HA (20 mg/L), using zebrafish facility water (ZFW) and zebrafish growing media (ZGM). The presence of cations and HA gave rise to a decrease in Ag ion release and ζ-potential, an increase in the hydrodynamic diameter and oxidation of the AgNP surface. The results show that the presence of HA and cations in the media, as well as the silver speciation, i.e., the unusual presence of Ag3+, decreases the toxicity of AgNPs (LC50AgNPs: 1.19 mg/L; LC50AgNPs + HA: 3.56 mg/L), as well as silver bioavailability and toxicity in zebrafish embryos. Developmental alterations and the LC50 (1.19 mg/L) of AgNPs in ZFW were more relevant (p ≤ 0.05) than for AgNPs in ZGM (LC50 ˃ 10 mg/L). It was demonstrated that the bioaccumulation and toxicity of AgNPs depends on several factors including AgNPs concentration, nanoparticle aggregation, dissolved silver ions, speciation of silver ions, the amount of salt in the environment, the presence of humic substances and others, and different combinations of all of these factors.

A study has been conducted based on the Mott-Schottky model acquisition by potentiodynamic electrochemical impedance spectroscopy, to determine the physical-chemical properties of binary TiO2, Nb2O5 and ternary Nb-Ti-O thin films (semiconductor type) based on Nb,Ti, O elements. The technique used for the study of optical properties was that of spectral transmittance, measurements were performed using a spectrophotometer. The consistency of the impedance data has been studied by calculating the Kramers-Kronig relations. The structural properties were analyzed by XRD patterns; the chemical composition measurements for all thin films were made by using XPS technique. So, in this research the transmittance values change from 72.74% for Nb2O5 to 59.68% for Ti-Nb-O with wavelength around 355 nm. The absorption coefficients for all films were analyzed from 31823.87 cm−1 for Nb2O5 to 91240.90 cm−1 for Nb-Ti-O with wavelength around 355 nm evidencing thus a 65% reduction. The direct band gap it was found that the photon energy (band gap Eg) changes in all films from 3.56 eV for Nb2O5 to 3.96 eV for Ti-Nb-O evidencing a 10% reduction. The extinction coefficient values change in all films from 0.038 cm−1 for Nb2O5 to 0.277 cm−1 for Ti-Nb-O films with wavelength around 355 nm, exhibiting an 86% increasing. Finally, it was observed by the Mott-Schottky analysis that the reference potential (Ag/AgCl) changes for all films from −2.09 V for Nb2O5 to −0.80 V for Ti-Nb-O material showing a 62% reduction. Keywords: Mott-Schottky, Thin films, Titanium oxide, Niobium oxide, Semiconductor properties

In this study, an osteogenic environment was constructed on Ti alloy implants by in-situ formation of nanosized fibrous titanate, Na2Ti6O13, loaded with bioactive ions, i.e. Sr, Mg and Zn, to enhance surface bioactivity. The bioactive ions were loaded by ion exchange with sodium located at inter-layer positions between the TiO6 slabs, and their release was not associated with the degradation of the structural unit of the titanate. In-vitro cell culture experiments using MC3T3-E1 cells proved that both bioactive ions and nanotopographic features are critical in promoting osteogenic differentiation of the cells. It was found that the osteogenic functions of the titanate can be modulated by the type and amount of ions incorporated. This study points out that nanosized fibrous titanate formed on the Ti alloy can be a promising reservoir for bioactive ions. The major advantage of this approach over other alternatives for bioactive ion delivery using degradable bioceramic coatings is its capacity of maintaining the structural integrity of the coating and thus avoiding structural deterioration and potential mechanical failure.

A Taguchi L16(45) orthogonal array design was selected to determine the influence of the deposition parameters on the mechanical properties, wear volume, and corrosion resistance of TiWSiN thin films. The power applied to the silicon-tungsten target, nitrogen to argon flow ratio (N2:Ar), substrate temperature, and bias voltage were set to four levels for depositing the films using co-sputtering equipment. The hardness, wear volume, and corrosion resistance were evaluated via nanoindentation, reciprocating-sliding, and potentiodynamic polarization, respectively. The microstructure, chemical composition, and morphology were also studied, by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The obtained results were transformed into signal-to-noise ratios (S/N), and an analysis of variance (ANOVA) was performed. It was found that the power applied to the silicon target was the factor that makes the greatest difference in the evaluated films’ properties. According to the combination of factors, nanocomposite structure and FCC and BCC crystalline structures were detected. Almost all of the films exhibited columnar growth; however, the columns’ width was affected as the deposition conditions were modified.

In this work, we report the first observation of novel nanocomposite thin films consisting of nanocrystalline chromium embedded in an amorphous chromium carbide matrix (nc-Cr/a-CrC) with relatively high hardness (∼22,3 GPa) and ultra low nanowear. The films were deposited onto silicon substrates using a magnetic filtered cathodic arc deposition system at various negative bias voltages, from 50 to 450 V. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) suggested the co-existence of chromium and chromium carbide phases, while high resolution transmission electron microscopy (HRTEM) confirmed the presence of the nc-Cr/a-CrC structure. The friction coefficient measured with the ball-on disk technique and the nanowear results showed a strong correlation between the macro and nano-tribological properties of the samples. These novel nanocomposite films show promising properties as solid lubricant and wear resistant coatings with relatively high hardness, low friction coefficient and ultra low nanowear.

In this study ZnPc@TiO2 hybrid nanostructures, both nanoparticles and nanotubes, as potential photosensitizers for the photodynamic therapy, fluorescent bioimaging agents, as well as anti-cancer drug nanocarriers, were prepared via zinc phthalocyanine (ZnPc) deposition on TiO2. In order to provide the selectivity of prepared hybrid nanostructures towards cancer cells they were modified with folic acid molecules (FA). The efficient attachment of both ZnPc and FA molecules was confirmed with dynamic light scattering (DLS), zeta potential measurements and X-ray photoelectron spectroscopy (XPS). It was presented that ZnPc and FA attachment has a strong effect on fluorescence emission properties of TiO2 nanostructures, which can be further used for their simultaneous visualization upon cellular uptake. ZnPc@TiO2 and FA/ZnPc@TiO2 hybrid nanotubes were then employed as doxorubicin nanocarriers. It was demonstrated that doxorubicin can be easily loaded on these hybrid nanostructures via an electrostatic interaction and then released. In vitro cytotoxicity and photo-cytotoxic activity studies showed that prepared hybrid nanostructures were selectively targeting to cancer cells. Doxorubicin loaded hybrid nanostructures were significantly more cytotoxic than un-loaded ones and their cytotoxic effect was even more severe upon irradiation. The cellular uptake of prepared hybrid nanostructures and their localization in cells was monitored in vitro in 2D cell culture and tumor-like 3D multicellular culture environment with fluorescent confocal microscopy. These hybrid nanostructures preferentially penetrated into human cervical cancer cells (HeLa) than into normal fibroblasts (MSU-1.1) and were mainly localized within the cell cytoplasm. HeLa cells spheroids were also efficiently labelled by prepared hybrid nanostructures. Fluorescent imaging of Hela cells treated with doxorubicin loaded hybrid nanostructures showed that doxorubicin was effectively delivered into cells, released and evenly distributed in the cytoplasm. In conclusion, prepared hybrid nanostructures exhibit high potential as selective bioimaging agents next to their photodynamic activity and drug delivery ability.

Portable screen-printed carbon electrodes (SPCE) were uniformly modified with TiO2 and Au nanoparticles (TiO2-AuNPs-SPCE). Synthetized AuNPs were characterized by TEM, showing an average diameter of 17.9 ± 2.3 nm. The doped electrodes were characterized using scanning electron microscopy, X-ray photoelectron and Raman spectroscopy. Cyclic voltammetry (CV) performed using as model analytes: an inorganic ([Fe(CN)6]3−/4−) and an organic (catechol) redox probe showed a drastic enhanced of the electrodes electrochemical surface activity and suggested a synergistic catalytic effect between Au NPs and TiO2. Additionally, the electrochemical performance was evaluated for other hydroxyphenols such as hydroquinone, pyrogallol and dopamine. In the case of hydroquinone, the electron transfer rate constant for TiO2-AuNPs-SPCE was estimated to be almost three times faster than for bare SPCE. The results for dopamine also demonstrated remarkably enhanced activity (up to 50%) respect to the non-modified SPCE, showing lower oxidation peak potentials and peak-to-peak separations, as well as, sharper peak current intensities at the TiO2-AuNPs modified SPCE.

The antioxidant activity of graphene quantum dots (GQD) with different chemical composition and sp 2 -hybridized carbon content has been evaluated and compared to that of a standard antioxidant, ascorbic acid. GQD were prepared by top down and bottom up synthetic approaches from three different precursors (carbon black, glucose and pyrene) in order to vary significantly the chemical composition, electron density and sp 2 -hybridized carbon content. For a given radical, the three types of GQD exhibited very different radical scavenging activity (RSA). Moreover, the RSA varied with the type of free radical and reactive oxygen species (ROS) tested, indicating different radical inhibition mechanisms. Overall, GQD with strong hydrogen donor behavior and large content of sp 2 –hybridized carbon domains were the most effective radical scavengers. Thus, highly graphitic GQD with abundant edge functional groups produced from pyrene exhibited an extraordinary high antioxidant activity, with inhibition effective concentrations much lower than those of ascorbic acid. The great potential of highly antioxidant GQD as protective films against organic dye decoloration by ROS was demonstrated with two model target molecules, methylene blue and rhodamine B.

Epitaxial thin films of double perovskite Y(Ni 0.5 Mn 0.5 )O 3 (001) and Y(Ni 0.5 Mn 0.5 )O 3 (101) grown on SrTiO 3 (001) and SrTiO 3 (111), respectively, were studied by XPS and SQUID magnetometer. Temperature dependent Ti diffusion was detected in the Y(Ni 0.5 Mn 0.5 )O 3 (101)/SrTiO 3 (111) samples, while no diffusion was observed in Y(Ni 0.5 Mn 0.5 )O 3 (001)/SrTiO 3 (001) samples. It was observed that the use of a low ablation rate promoted ionic migrations, mainly due to the associated annealing time that samples undergo when grown at lower rates. The migration speed was determined by XPS analysis and its influence on the magnetic properties of the Y(Ni 0.5 Mn 0.5 )O 3 (101) films was characterized and discussed.

A simple and versatile method to produce filtration membranes with graphene quantum dots (GQD) and their excellent performance as turn-off fluorescence sensing platforms for Cr (VI) detection in water is presented. Suitably functionalized GQD were immobilized on various types of membranes (nylon, cellulose and glass fiber) and the resulting GQD-modified membranes exhibited the characteristic fluorescence fingerprint of the GQD probes. The membrane fluorescence was quenched by highly toxic Cr (VI) ions due to selective coordination to GQD functional groups. The analytical performance of membranes was comparable to that of dispersed GQD fluorescent probes, displaying a fast and linear response to Cr (VI) concentration in the 1–500 μM range, a low detection limit of 190 nM, high sensitivity, reproducibility and selectivity. Moreover, the membranes can be regenerated by simple washing with deionized water and reused, preserving their good sensing response after several Cr (VI) detection-washing cycles. Membrane sensing performance was very stable after being immersed in water for several days and filtering water through them.

We report on the deposition and characterization of hard and wear resistant orthorhombic Cr3C2 thin films. Films are deposited using a novel linear filtered cathodic arc (LFCA) at high energetic conditions and relatively low substrate temperatures (

The positive electrodes based on nano- and micrometric carbon coated LiFePO 4 (LFP) powders are prepared via aqueous slurry processing using “normal” and “intensive” mixing procedures. The XRD, XPS, and electrochemical characterization reveal that the “intensive” mixing process improves the discharge C-rate capability of the n-LFP cathode however provokes formation of an undesirable thin surface layer enriched by Fe 3+ species. The waterborne graphite anodes and LiFePO 4 cathodes for the energy and power cells are being developed, upscaled and manufactured on a pilot plant. Energy LiFePO 4 /C pouch cells demonstrate outstanding durability maintaining 80% of initial discharge capacity (IDC) after 7450 and 2400 full cycles under 1D and 4D discharge currents, respectively. Moreover, further cycling of the energy cell working under 1C/4D protocol reveals its extra-long secondary life (70% of IDC on 9200 th cycle). Power LiFePO 4 /C pouch cell shows long lasting cycle life retaining 80% of IDC after 3350 cycles under harsh cycling conditions (3C/8D). The reported results are being achieved despite confirmed water release from lithium iron phosphate cathodes to the electrolyte. Finally, viability of aqueous processing of the electrodes without sacrificing electrochemical performance of LiFePO 4 /C batteries is clearly proven.

Normal micro-movements at the bone-implant interface originate fretting-corrosion processes, thus releasing wear debris from the bone and metallic devices and compromising the fixability of the implant. Titanium aluminum nitride (Ti 1− x Al x N) coatings have been considered to overcome these drawbacks and the effect of aluminum content on the fretting-corrosion resistance against bone in a simulated body fluid has been studied. Coatings were synthesized by magnetron co-sputtering by varying the power applied to the aluminum target. Morphology and chemical composition were studied by optical profilometry, SEM and XPS. Coatings with x =0.39, 0.47, 0.61 and 0.69 were obtained. Mechanical properties, adherence and corrosion behavior were assessed by nanoindentation, scratch test and potentiodynamic curves, respectively. The fretting-corrosion behavior was assessed at open circuit potential (OCP) using a tribo-electrochemical apparatus, bone-pins as the counterpart and Hank׳s solution as the simulated body fluid. It was found that the fretting-corrosion against bone in the simulated body fluid can damage the metal and coatings, thereby accelerating wear and increasing the current corrosion densities. Coatings with x =0.39, 0.47 and 0.61 are able to protect 304SS against fretting corrosion. The behavior of wear volume with aluminum content in coatings is related to the corrosion resistance and hardness to elastic modulus ratio.

Novel bioactive calcium titanate–tricalcium phosphate–tetracalcium phosphate composite coatings were developed. Powder mixtures of hydroxyapatite and 25, 50 and 75 vol% of calcium titanate were uniaxially pressed and sintered at 1100–1200 °C for 4 h. After heat treatment, the composites, which consisted of calcium titanate and oxyhydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2−2 x O x □ x ), were evaporated by magnetron sputtering to coat an AISI 304/Ti buffer layer substrate. Calcium phosphate (CP) and calcium titanate (CT) coatings were also produced for comparison. The surface topography of the composite coatings was observed by SEM and AFM. Their structure and composition were evaluated by XRD, FTIR and XPS, and the re-assembly process of the atoms from composite targets to the coatings was emphasized. Nanoindentation experiments were carried out to measure the hardness. Coated samples were immersed in a simulated body fluid (SBF) for 30 days under physiological conditions of pH and temperature for the in-vitro bioactivity assessment. Finally, because the coatings are proposed for orthopedic applications, the cytotoxicity of the coatings was examined with human osteoblasts. It was found that calcium titanate coating is harder than the calcium phosphate coating, the 75–25 composite coatings fit a rule of mixture of hardness, and the rougher coatings contained a larger amount of nano-scale precipitated apatite. Furthermore, all the coatings were not cytotoxic. The results indicate that 75%CP–25%CT coating is a potential material for bone tissue replacement and regeneration.

High temperature composite target AlN–TiB2–TiSi2 with heterogeneous distribution of compounds (AlN—50 wt.%; TiB2—35 wt.%; TiSi2—15 wt.%) is used for sputtering via combined reactive/non-reactive DC magnetron sputtering onto substrate materials either cylindrical polished steel (Fe, 18%—Ni, 12%—Cr, 10%—Ti) 3 mm diameter or monocrystalline silicon. The gradient coating has been produced by sequential non-reactive and reactive sputtering of the target. The structural and morphological properties of the deposited films are analyzed by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The tribo-mechanical properties are studied by means of nanoindentation and nanowear tests. The gradient film is composed of two layers with different microstructure and elemental composition. The first layer with thickness ~200 nm is mainly based on light B, C and N as well metal elements Al, Si and Ti. The presence of very well distributed nanocrystals embedded in an amorphous matrix, with crystal sizes ranging from 5 to 40 nm is observed in the second layer ~700 nm thickness and composed of Al, Ti, Si, B, and N. Films show very flat surfaces, with roughness around 0.35 nm. The hardness, elastic modulus, elastic recovery (We), H/E⁎ ratio and H3/E⁎2 ratio are determined as 17.55 GPa, 216.7 GPa, 60%, 0.08 and 0.12 GPa, respectively. Nanowear tests demonstrate relatively high wear resistance of the coatings. Samples show promising characteristics for hard protective adaptive coatings and diffusion barriers due to short propagation of dislocations in the amorphous matrix and the elastic and hard nature of the nanocomposite structure. Keywords: Hard coatings, Nanocomposite, Functionally graded film, Nanoindentation, Wear test

In this work Hf–C–N coatings were deposited on silicon substrates by reactive R.F. magnetron co-sputtering from two hafnium and carbon targets in a reactive nitrogen atmosphere at various negative bias voltages from 0 to 150 V. The effect of the bias voltage on the chemical composition, crystalline structure and mechanical properties was studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and nanoindentation. The results show that the obtained films have a Hf /( C + N ) ratio of around 1 and present an evolution with the bias voltage from a quasi-amorphous structure, with a low hardness (6 GPa) to crystalline Hf 2 CN films with a high hardness (23 GPa) and electrical resistivity values in the order of 10 4 Ω·cm − 1 . This study shows the potential for hard and electrically conductive Hf–C–N films in industrial applications.

An innovative electrochemical route is proposed to obtain CuI films. The approach is based on the electrochemical reduction of I2 in a solution of copper bis(trifluoromethanesulfonyl)imide salt in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide room temperature ionic liquid. The mechanisms involved in the deposition process are analyzed by cyclic voltammetry, pointing out that the CuI formation occurs from the chemical reaction between the Cu2+ and I- generated from the I2 reduction. Homogenous films constituted of open-packed primary CuI nanocrystals (~100 nm) are obtained. The electrodeposition from organic solvent-based media is also investigated, finding that the solvent nature affects strongly to the nanocrystal packing density. Compact CuI thin films are electrodeposited from the isopropanol-based electrolytes. The electrodeposition of ZnO/CuI heterostructures, with high transmittance in the visible range (i.e. > 75%), is also reported. The current density-voltage characteristic of the resulting device exhibits clear rectifying behavior, with a rectification of ~ 2x103 at V = ± 1.5 V. This result anticipates a significant potential of the present electrochemical route to obtain CuI films with competitive optoelectronic functionalities. Keywords: CuI, Electrodeposition, Ionic liquid, Halide semiconductor

Thin films of ferromagnetic Y(Ni0.5Mn0.5)O3 (YNMO) perovskite were grown on different SrTiO3 (STO) substrate orientations [i.e. (0 0 1), (1 1 0) and (1 1 1)] by means of pulsed laser deposition (PLD) and their morphological and functional properties were studied and characterized. Optimal deposition parameters were identified and their individual influence on the quality of the films was also addressed. Films showed a single out-of-plane orientation in all the substrate scenarios, while the in-plane texture in STO(0 0 1) and STO(1 1 1) show two and three in plane domains, respectively. Growth mechanism and morphology were studied by HRTEM and AFM. As a result, a clear 3D growth mechanism was identified and a direct correlation between the two in-plane crystalline domains on the surface morphology of the sample was observed. Magnetic response of the films was investigated as a function of their crystalline properties. The films were found to have a paramagnetic to ferromagnetic transition around 90 K consistent with their bulk counterparts. Finally, the discrepancies on the epitaxial growth between YMnO3 (YMO) and YMNO thin films were clarified and tabulated, giving a clear picture of the effect of Ni substitution in the epitaxial and crystalline properties of manganites of this family.

We demonstrate a method to modify the surface of graphene oxide (GO) by grafting polymer chains using nitroxide mediated radical polymerization (NMRP). Surface modification by NMRP was achieved using GO functionalized with 2,2,6,6-tetramethyl-piperidine 1-oxyl (TEMPO, T) to produce graphene oxide-TEMPO (GO-T). GO prepared from graphite by the Hummer's method was facilely functionalized in one step with T. Graft polymerization reactions of styrene and isoprene were carried out using nitroxide chemistry to control the polymerization and the ‘grafting from the surface’ polymerization technique. GO-T acts as a multifunctional macroalkoxyamine initiating and controlling the polymerization in the presence of monomer. The grafting reactions were performed by dispersing GO-T in dimethylformamide and heating at 130 °C in the presence of monomer to form graphene oxide-g-polystyrene-TEMPO (GO-g-PS-T) and graphene oxide-g-polyisoprene-TEMPO (GO-g-PI-T). FT-IR, Raman, XPS, XRD, TGA and TEM data are consistent with the attachment of the TEMPO group to the GO surface and with polystyrene and polyisoprene being grafted onto the GO surface. The amount of PS and PI grafted to GO-T was estimated from TGA data to be approximately 34% for a 7 h reaction time and 68% for a 144 h reaction time, respectively.

Nanocomposite coatings consisting of a hard nanocrystalline carbide phase and a-C:H amorphous matrix are the focus of many investigations because of their mechanical and tribological properties such as high hardness, low friction coefficient and high resistance to wear. In this work, nanocomposite coatings of nanocrystalline chromium carbide embedded in an amorphous matrix (nc-CrC/a-C:H) were deposited onto silicon substrates by cathodic vacuum arc deposition using a Cr target in an Ar/C2H2 gas mixture atmosphere. A linear magnetic shield was employed to reduce the macroparticle content in the films. A range of negative bias voltages from 50 to 450 V was applied to substrates during deposition. X-ray diffraction (XRD) analysis showed that amorphous or nanocrystalline thin films were formed in all cases. The hydrogen bonding in the material was studied by Fourier transform infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electron energy loss spectroscopy (EELS) were used to determine the carbon bonding and to study the presence of different forms of amorphous carbon. High resolution transmission electron microscopy (HRTEM) revealed a nanocomposite structure with chromium carbide nanocrystallites embedded in an amorphous hydrocarbon matrix. It was observed that the negative bias voltage significantly affected the carbon bonding and the hydrogen content.

The aim of this work is to improve the electrochemical behavior of AISI 4140 steel substrates by using a TiN[BCN/BN] n /c-BN multilayer system as a protective coating. We grew TiN[BCN/BN] n /c-BN multilayers via reactive r.f. magnetron sputtering technique, systematically varying the length period (Λ) and the bilayer number (n), maintaining constant the total thickness of the coating and all other growth parameters. The coatings were characterized by FTIR spectroscopy that showed bands associated to h-BN bonds, and c-BN stretching vibrations centered at 1385 cm − 1 and 1005 cm − 1 , respectively. Film composition was studied via X-ray photoelectron spectroscopy where typical signals for C1s, N1s and B1s are shown. The electrochemical properties were studied by electrochemical impedance spectroscopy and Tafel curves. In this work, the maximum corrosion resistance for the coating with (Λ) equal to 80 nm was obtained, corresponding to n = 25 bilayers. The polarization resistance and corrosion rate were around 10.1 kOhm cm 2 and 0.22 mm/year; these values were 83 and 15 times higher, respectively, than uncoated AISI 4140 steel substrate (0.66 kOhm cm 2 and 18.51 mm/year). Optical microscopy was used for surface analysis after corrosive attack. The improvement of the electrochemical behavior of the AISI 4140 coated with this TiN[BCN/BN] n /c-BN multilayer system can be attributed to the presence of several interfaces that offer resistance to diffusion of Cl − of the electrolyte toward the steel surface.

Enhancement of mechanical and tribological properties on AISI D3 steel surfaces coated with CrN/AlN multilayer systems deposited in various bilayer periods ( Λ ) via magnetron sputtering has been studied in this work exhaustively. The coatings were characterized in terms of structural, chemical, morphological, mechanical and tribological properties by X-ray diffraction (XRD), electron dispersive spectrograph, atomic force microscopy, scanning and transmission electron microscopy, nanoindentation, pin-on-disc and scratch tests. The failure mode mechanisms were observed via optical microscopy. Results from X-ray diffraction analysis revealed that the crystal structure of CrN/AlN multilayer coatings has a NaCl-type lattice structure and hexagonal structure (wurtzite-type) for CrN and AlN, respectively, i.e., made was non-isostructural multilayers. An enhancement of both hardness and elastic modulus up to 28 GPa and 280 GPa, respectively, was observed as the bilayer periods ( Λ ) in the coatings were decreased. The sample with a bilayer period ( Λ ) of 60 nm and bilayer number n = 50 showed the lowest friction coefficient (∼0.18) and the highest critical load (43 N), corresponding to 2.2 and 1.6 times better than those values for the coating deposited with n = 1, respectively. The best behavior was obtained when the bilayer period ( Λ ) is 60 nm ( n = 50), giving the highest hardness 28 GPa and elastic modulus of 280 GPa, the lowest friction coefficient (∼0.18) and the highest critical load of 43 N. These results indicate an enhancement of mechanical, tribological and adhesion properties, comparing to the CrN/AlN multilayer systems with 1 bilayer at 28%, 21%, 40%, and 30%, respectively. This enhancement in hardness and toughness for multilayer coatings could be attributed to the different mechanisms for layer formation with nanometric thickness such as the Hall–Petch effect and the number of interfaces that act as obstacles for the crack deflection and dissipation of crack energy.

Coatings of Ti-W-N on Si(100) and AISI D3 steel substrates have been deposited by an r.f. magnetron sputtering technique from a binary (50vol.% Ti, 50vol.% W) target. Their electrochemical characteristics have been studied by potentiodynamic and Electrochemical Impedance Spectroscopy (EIS) techniques and their mechanical properties were studied using depth-sensing nanoindentation. XRD was used to determine the phase composition, and a strong preferred orientation of the TiN(111), TiN(200), WN(107) and WN(220) planes was detected. Depth sensing nanoindentation measurements were used to investigate the elasto-plastic behavior of Ti-W-N coatings. Each group of samples was deposited under the same experimental conditions (power supply, Ar/N2 gas mixture and substrate temperature), except the d.c. negative bias voltages that varied (0 V, −50 V, −100 V) in order to study its effects on the mechanical and electrochemical properties of AISI D3 steel substrate with Ti-W-N coatings. The measurements showed that the hardness and elastic modulus increased from 19 GPa to 30 GPa and from 320 GPa to 390 GPa, respectively, as a function of the increasing negative bias voltages or bias current density. Coating indentation track and coating–substrate debonding have been observed with atomic force microscopy on the indentation sites (AFM-IS). Finally, the corrosion behavior obtained by Ti-W-N coatings was studied in relation to the increase of the bias voltage. The obtained results have shown that at the higher negative bias voltage or bias current density, the steel with Ti-W-N coatings presented the lowest corrosion resistance.

The aim of this work is to improve the mechanical properties of AISI 4140 steel substrates by using a TiN[BCN/BN] n /c-BN multilayer system as a protective coating. TiN[BCN/BN] n /c-BN multilayered coatings via reactive r.f. magnetron sputtering technique were grown, systematically varying the length period ( Λ ) and the number of bilayers ( n ) because one bilayer ( n = 1) represents two different layers ( t BCN + t BN ), thus the total thickness of the coating and all other growth parameters were maintained constant. The coatings were characterized by Fourier transform infrared spectroscopy showing bands associated with h-BN bonds and c-BN stretching vibrations centered at 1400 cm −1 and 1100 cm −1 , respectively. Coating composition and multilayer modulation were studied via secondary ion mass spectroscopy. Atomic force microscopy analysis revealed a reduction in grain size and roughness when the bilayer number ( n ) increased and the bilayer period decreased. Finally, enhancement of mechanical properties was determined via nanoindentation measurements. The best behavior was obtained when the bilayer period ( Λ ) was 80 nm ( n = 25), yielding the relative highest hardness (∼30 GPa) and elastic modulus (230 GPa). The values for the hardness and elastic modulus are 1.5 and 1.7 times greater than the coating with n = 1, respectively. The enhancement effects in multilayered coatings could be attributed to different mechanisms for layer formation with nanometric thickness due to the Hall–Petch effect; because this effect, originally used to explain increased hardness with decreasing grain size in bulk polycrystalline metals, has also been used to explain hardness enhancements in multilayered coatings taking into account the thickness reduction at individual single layers that make up the multilayered system. The Hall–Petch model based on dislocation motion within layered and across layer interfaces has been successfully applied to multilayered coatings to explain this hardness enhancement.

Enhancement of mechanical properties by using a TiCN/TiNbCN multilayered system with different bilayer periods (Λ) and bilayer numbers (n) via magnetron sputtering technique was studied in this work. The coatings were characterized in terms of structural, chemical, morphological and mechanical properties by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. Results of the X-ray analysis showed reflections associated to FCC (1 1 1) crystal structure for TiCN/TiNbCN films. AFM analysis revealed a reduction of grain size and roughness when the bilayer number is increased and the bilayer period is decreased. Finally, enhancement of mechanical properties was determined via nanoindentation measurements. The best behavior was obtained when the bilayer period (Λ) was 15 nm (n = 200), yielding the highest hardness (42 GPa) and elastic modulus (408 GPa). The values for the hardness and elastic modulus are 1.6 and 1.3 times greater than the coating with n = 1, respectively. The enhancement effects in multilayer coatings could be attributed to different mechanisms for layer formation with nanometric thickness due to the Hall-Petch effect; because this effect, originally used to explain the increase in hardness with decreasing grain size in bulk polycrystalline metals, has also been used to explain hardness enhancements in multilayers taking into account the thickness reduction at individual single layers that make the multilayered system. The Hall-Petch model based on dislocation motion within layers and across layer interfaces, has been successfully applied to multilayers to explain this hardness enhancement.

In plasma-PVD processes, ion bombardment during the growth of thin films has a strong influence on films properties such as morphology, composition, structure, stress, electrical conductivity, and others. Therefore, an accurate control of substrate bias voltage is needed in order to deposit films with the desired properties. For insulator substrates, dc biasing the substrate holder is useless, since the surface shall not follow the applied bias but it will be at the non-controlled floating potential. In this work we present a simple method for the effective control of the substrate bias in dc PVD processes with insulator substrates, based on placing a metallic grid at a certain distance from the nonconductive surfaces to be coated. The desired negative bias is applied to this metallic grid which accelerates ions from the plasma and directs them to the surface to cover. This method has been successfully applied to the deposition of TiN coatings on glass and decorative ceramics by Cathodic Arc Deposition. The deposited films showed good adhesion and gold color, in contrast with the bad adhered and brownish films deposited without the grid. The dependencies on the color and on the mechanical properties of our TiN films deposited on insulating substrates with the value of the bias voltage applied to the substrate are similar to those typically reported in the literature when conductive substrates are used.

article i nfo Aluminum carbide (Al-C), aluminum nitride (Al-N), and aluminum carbonitride (Al-C-N) thin films were grown onto Si (100) substrates by r.f. reactive magnetron sputtering at 400 °C. The Al-N coatings were obtained by sputtering of Al (99.9%) target in Ar/N2 atmosphere and the Al-C and Al-C-N by co-sputtering of a binary (50% Al, 50% C) target in argon and in Ar/N2 mixture, respectively. The d.c. bias voltage was varied between 0 and −150 V. The films were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transformed infrared spectroscopy (FTIR) and the mechanical properties by nanoindentation. The structure of the films has been determined by XRD, which shows that amorphous films are formed in all cases. The variation of polarization bias voltage produced chemical differences in the films. As the bias voltage is increased, the Al content is reduced in all three materials. The nitrogen content also varied between 10 and 14 at.% for Al-N coatings, remaining practically constant (21 at.%) for the Al-C-N films. The Berkovich hardness results were 7.0, 17.2 and 9.2 GPa for Al-C, Al-N, and Al-C-N films, respectively.