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Mechanical properties of metastable β-Ti alloys are highly dependent on the final microstructure, which is controlled by the thermomechanical processing. These alloys are used for biomedical applications and require a high mechanical strength as well as a low Young’s modulus to avoid stress shielding. Previous work on the development of cold swaged Ti-10Mo-20Nb alloy showed that the best compromise strength and Young’s modulus was obtained when the forming is followed by an aging heat treatment at 500 °C. In this work, Ti-10Mo-20Nb alloy was hot swaged and aged at 500 °C for 10 min, 4h and 24h. The microstructure was analyzed by X-ray diffraction, optical microscopy and transmission electron microscopy. Mechanical characterization was based on Vickers microhardness tests and Young’s modulus measurements. Aging at 500°C for 10 min after hot swaging resulted in a nearly 100% β phase microstructure while aging at 500°C for 4h or 24h led to a bimodal microstructure consisting on α precipitates dispersed in the β matrix. The higher hardness to Young’s modulus ratio was obtained for the sample aged at 500 °C for 4h. This value was higher than those obtained for the Ti-6Al-4V alloy and commercially pure Ti., SCOPUS: cp.k, info:eu-repo/semantics/published

Increased atmospheric CO2 concentration is leading to changes in the carbonate chemistry and the temperature of the ocean. The impact of these processes on marine organisms will depend on their ability to cope with those changes, particularly the maintenance of calcium carbonate structures. Both a laboratory experiment (long-term exposure to decreased pH and increased temperature) and collections of individuals from natural environments characterized by low pH levels (individuals from intertidal pools and around a CO2 seep) were here coupled to comprehensively study the impact of near-future conditions of pH and temperature on the mechanical properties of the skeleton of the euechinoid sea urchin Paracentrotus lividus. To assess skeletal mechanical properties, we characterized the fracture force, Young's modulus, second moment of area, material nanohardness, and specific Young's modulus of sea urchin test plates. None of these parameters were significantly affected by low pH and/or increased temperature in the laboratory experiment and by low pH only in the individuals chronically exposed to lowered pH from the CO2 seeps. In tidal pools, the fracture force was higher and the Young's modulus lower in ambital plates of individuals from the rock pool characterized by the largest pH variations but also a dominance of calcifying algae, which might explain some of the variation. Thus, decreases of pH to levels expected for 2100 did not directly alter the mechanical properties of the test of P. lividus. Since the maintenance of test integrity is a question of survival for sea urchins and since weakened tests would increase the sea urchins' risk of predation, our findings indicate that the decreasing seawater pH and increasing seawater temperature expected for the end of the century should not represent an immediate threat to sea urchins vulnerability., SCOPUS: ar.j, info:eu-repo/semantics/published

An alkaline bath, initially designed for electroless deposition of amorphous [Formula presented] coatings, is used for plating of [Formula presented] by introduction of Ce3 + within the range 0.001–0.006 mol·dm− 3. A decrease in both deposition rate and phosphorus content in the coating in comparison with the typical for [Formula presented] is observed. By means of TEM, SAED and XRD nanocrystalline and amorphous structure is revealed. Applying scanning Auger electron spectroscopy, sputter etch profiles of constituent elements are composed. X-ray photoelectron spectroscopy spectra, taken inside the coating, demonstrate the chemical status of coating components. The transformations during annealing are studied by differential scanning calorimetry and magnetic properties. Increased thermal stability of electroless deposited [Formula presented] coatings is observed., SCOPUS: ar.j, Electroless deposited Nisingle bondCesingle bondP coatings, info:eu-repo/semantics/published

β-metastable titanium alloys with high strength to Young's modulus ratio have been developed by different authors aiming their use as biomaterials for hard tissue replacement. However, it is not easy to combine low elastic modulus with high mechanical strength. In this work, a β-Ti alloy (Ti-10Mo-20Nb) was produced by arc-melting, then homogenized, cold swaged and aged in order to obtain fine α-Ti precipitates in a β-Ti matrix. The microstructures were characterized by transmission electron microscopy and X-ray diffraction. Mechanical properties characterization was based on Vickers microhardness tests and Young's modulus measurements. The cold swaged material subjected to an ageing treatment at 500 °C for 4 h showed the highest hardness/Young's modulus ratio, associated to very fine α phase precipitates in a β-Ti matrix., SCOPUS: cp.j, info:eu-repo/semantics/published

Beta titanium alloys were developed for biomedical applications due to the combination of its mechanical properties including low elasticity modulus, high strength, fatigue resistance, good ductility and with excellent corrosion resistance. With this perspective a metastable beta titanium alloy Ti-12Mo-13Nb was developed with the replacement of both vanadium and aluminum from the traditional alloy Ti-6Al-4V. This paper presents the microstructure, mechanical properties of the Ti-12Mo-13Nb hot swaged and aged at 500 °C for 24 h under high vacuum and then water quenched. The alloy structure was characterized by X-ray diffraction and transmission electron microscopy. Tensile tests were carried out at room temperature. The results show a microstructure consisting of a fine dispersed α phase in a β matrix and good mechanical properties including low elastic modulus. The results indicate that Ti-12Mo-13Nb alloy can be a promising alternative for biomedical application., SCOPUS: cp.j, info:eu-repo/semantics/published

It is well established that 718 superalloy exhibits brittle intergranular cracking when deformed under tension at temperatures above 600°C. This embrittlement effect is related with grain boundary penetration by oxygen (Oxygen Assisted Intergranular Cracking - OAIC). Simultaneously, impacting on its mechanical properties, the precipitation of coherent γ′ and γ″ phases occur above 650°C and Dynamic Strain Aging (DSA) occurs in the temperature range between 200 and 800°C. Although literature indicates that OAIC is the mechanism that controls mechanical properties at high temperatures, its interactions with DSA and precipitation are still under discussion. The objective of this work is to investigate the interactions between the embrittlement phenomena (OAIC and DSA) and the hardening mechanism of γ′ and γ″ precipitation on the mechanical properties of an annealed 718 superalloy. Tensile tests were performed at a strain rate of 3.2 × 10-4 s-1 under secondary vacuum, in temperatures ranging from 200 to 800°C. Fracture surfaces were observed by scanning electron microscopy (SEM) and precipitation by transmission electron microscopy (TEM). The effect of DSA and precipitation on the strength and of OAIC on the ductility was verified., SCOPUS: ar.j, info:eu-repo/semantics/published

Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial as encapsulation and/or as substrate insulator carrier for long term neural implants because of its remarkable properties. Femtosecond (λ = 263 and 527 nm) and nanosecond (266 and 532 nm) laser processing of PDMS-elastomer surface, in air, is investigated. The influence of different processing parameters, including laser wavelength, pulse duration, fluence, scanning speed and overlapping of the subsequent pulses, on the surface activation and the surface morphology are studied. High definition tracks and electrodes are produced. Remarkable alterations of the chemical composition and structural morphology of the ablated traces are observed in comparison with the native material. Raman spectra illustrate well-defined dependence of the chemical composition on the laser fluence, pulse duration, number of pulses and wavelength. An extra peak about ∼512-518 cm-1, assigned to crystalline silicon, is observed after ns- or visible fs-laser processing of the surface. In all cases, the intensities of SiOSi symmetric stretching at 488 cm-1, SiCH3 symmetric rocking at 685 cm-1, SiC symmetric stretching at 709 cm-1, CH3 asymmetric rocking + SiC asymmetric stretching at 787 cm-1, and CH3 symmetric rocking at 859 cm-1, modes strongly decrease. The laser processed areas are also analyzed by SEM and optical microscopy. Selective Pt or Ni metallization of the laser processed traces is produced successfully via electroless plating. The metallization process is not sensitive with respect to the time interval after the laser treatment. DC resistance is measured to be as low as 0.5 Ω mm-1. Our results show promising prospects with respect to use such a laser-based method for micro- or nano-fabrication of PDMS devices for MEMS and NEMS., SCOPUS: cp.j, info:eu-repo/semantics/published

Pt(Ni) catalysts were prepared by electroless deposition of Ni on TiO2 and mixed TiO2-C powder supports, followed by partial galvanic replacement of Ni by Pt in a chloroplatinate solution. Pt(Ni)/TiO2 and Pt(Ni)/TiO2-C catalysts were characterized by transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and anomalous small-angle X-ray scattering (ASAXS). XPS and ASAXS results showed no detectable alloying between Pt and Ni. In accordance with ASAXS analysis, the size of the Pt particles of the two samples is practically similar (2.1 and 1.5 nm). The electrocatalytic activity of the catalysts towards methanol oxidation and poisonous CO removal was assessed by cyclic voltammetry and chronoamperometry experiments and compared to commercial Pt/C catalysts. Despite the fact that the specific mass activity of the prepared catalysts is lower than that of the commercial material (as a result of their smaller surface area), both Pt(Ni)/TiO2 and Pt(Ni)/TiO2-C electrodes showed superior intrinsic catalytic activity (per Pt electroactive area) than the Pt/C catalyst. This is attributed to a synergistic effect of TiO2 on facile CO poison removal from Pt sites., SCOPUS: ar.j, info:eu-repo/semantics/published

In the current work, sheets of superalloy 718 were processed via thermomechanical route by hot and cold rolling, followed by annealing below the δ phase solvus temperature and precipitation hardening to optimum strength. Grain boundary character distribution throughout the processing was mapped via EBSD and its evolution discussed. The results show that it is possible to process the alloy to a fine grain size obtaining concomitantly a considerably high proportion of special boundaries Σ3, Σ9, and Σ27. The precipitation of δ phase presented a strong grain refining role, without significantly impairing the twinning mechanism and, consequently, the Σ3, Σ9, and Σ27 boundary formations., SCOPUS: ar.j, info:eu-repo/semantics/published

Two types of electroless Ni-W-P coatings: nanocrystalline with low P and amorphous with higher P content are investigated. Scanning probe microscopy is applied to study their morphology. Textured nanocrystalline coatings consist of coarse pyramids built of nanometer thick lamellas. The surface morphology of amorphous coatings is much finer and uniform. Nanohardness of all coatings depends on W content. Microhardness is increasing during the heat treatment up to 350 °C due to nickel phosphide precipitation affected by tungsten also. The wear resistance of nanocrystalline Ni-W-P coatings is much higher than that of amorphous in spite of the similar tungsten content in both. Lower corrosion resistance of amorphous Ni-W-P coatings is found by weight loss method during long-term immersion in 5 % NaCl. Electrochemical tests by potentiodynamic polarization curves in two model corrosion media - solutions of 0.5 M H 2SO4 and 5 % NaCl - are performed. The corrosion of bi-layered Ni-W-P/Ni-P and Ni-W-P/Ni-Cu-P deposits on mild steel is also investigated. The results prove that an electroless Ni-W-P coating on mild steel extremely improves its mechanical and corrosion behavior. It is demonstrated that in addition to deposit's structure and composition, the distribution and chemical state of alloy ingredients are also responsible for its properties. © 2014 Springer-Verlag Berlin Heidelberg., SCOPUS: ar.j, info:eu-repo/semantics/published

Bimetallic Pt-Cu carbon-supported catalysts (Pt(Cu)/C) were prepared by electroless deposition of Cu on a high surface area carbon powder support, followed by its partial exchange for Pt; the latter was achieved by a galvanic replacement process involving treatment of the Cu/C precursor with a chloroplatinate solution. X-ray diffraction characterization of the Pt(Cu)/C material showed the formation of Pt-rich Pt-Cu alloys. X-ray photoelectron spectroscopy revealed that the outer layers are mainly composed of Pt and residual Cu oxides, while metallic Cu is recessed into the core of the particles. Repetitive cyclic voltammetry in deaerated acid solutions in the potential range between hydrogen and oxygen evolution resulted in steady-state characteristics similar to those of pure Pt, indicating the removal of residual Cu compounds from the surface (due to electrochemical treatment) and the formation of a compact Pt outer shell. The electrocatalytic activity of the thus prepared Pt(Cu)/C material toward methanol oxidation was compared to that of a commercial Pt/C catalyst as well as of similar Pt(Cu)/C catalysts formed by simple Cu chemical reduction. The Pt(Cu)/C catalyst prepared using Cu electroless plating showed more pronounced intrinsic catalytic activity toward methanol oxidation than its counterparts and a similar mass activity when compared to the commercial catalyst. The observed trends were interpreted by interplay between mere surface area effects and modification of Pt electrocatalytic performance in the presence of Cu, both with respect to methanol oxidation and poisonous CO removal. © 2013 Springer Science+Business Media Dordrecht., SCOPUS: ar.j, info:eu-repo/semantics/published

The relationship between the δ phase content and the mechanical properties of Inconel 718 superalloy is still uncertain in the scientific literature. This study investigated the effects of the amount of δ phase and of the grain size on the mechanical properties of an aged γ-matrix with γ′ and γ′″ precipitates. The material in as-received condition in the form of a forged bar was solution-treated in different conditions and aged according to UNS7718 standard. The microstructures were characterized using optical, scanning, and transmission electron microscopy. Hardness and tensile tests were also conducted. After solution treatment, γ′ and γ′Prime; phases are dissolved and δ phase volume fraction is reduced to a minimum amount only observed by TEM, resulting in an increase of the grain size and a decrease of hardness and strength. After aging, the precipitation of γ′ and γ′″ occurs and the amount of δ phase increases. The volume fraction of d phase varying from 0.30 to 1.38% and the grain size varying from ASTM 7 to 5 do not have a significant effect on the tensile properties and hardness. © ASM International., SCOPUS: ar.j, info:eu-repo/semantics/published

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable β titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti-12Mo-13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000 C for 24 h, water quenching, cold forging to reduce 80% of the area, and ageing at 500 C for 24 h, where the final microstructure consisted of an α phase dispersed in a β matrix. The α phase appeared in two different forms: as fine lamellas (with 240 ± 100 nm length) and massive particles of 200-500 nm size. © 2013 Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

The influence of work hardening and aging on the mechanical properties of the X-750 nickel-based superalloy was investigated. The degree of cold working by wire drawing ranges from 0% to 30% and the aging heat treatment was performed at 1005. K for 16. h. The results have shown that the yield strength is proportional to the degree of area reduction, but the increase of yield strength becomes less important after aging. The static recovery plays an important role on the final properties of the alloy, reducing the contribution of γ' precipitates during aging. As a consequence of this recovery there is an increase of the ductility for the samples with area reduction superior to 20%. Empirical equations were proposed correlating the yield strength with the degree of cold working. © 2012 Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

Pt-Ni particles supported on Vulcan XC72R carbon powder have been prepared by a combination of crystalline Ni electroless deposition and its subsequent partial galvanic replacement by Pt upon treatment of the Ni/C precursor by a solution of chloroplatinate ions. The Pt-to-Ni atomic ratio of the prepared catalyst has been confirmed by EDS analysis to be ca. 1.5:1. No shift of Pt XPS peaks has been observed, indicating no significant modification of its electronic properties, whereas the small shift of the corresponding X-ray diffraction (XRD) peaks indicates the formation of a Pt-rich alloy. No Ni XRD peaks have been observed in the XRD pattern, suggesting the existence of very small pockets of Ni in the core of the particles. The surface electrochemistry of electrodes prepared from the catalyst material suggests the existence of a Pt shell. A moderate increase in intrinsic catalytic activity towards methanol oxidation in acid has been observed with respect to a commercial Pt catalyst, but significant mass specific activity has been recorded as a result of Pt preferential confinement to the outer layers of the catalyst nanoparticles. © 2012 Springer-Verlag Berlin Heidelberg., SCOPUS: ar.j, info:eu-repo/semantics/published

A bimetallic Pt-Cu carbon-supported catalyst (Pt(Cu)/C) has been prepared by a room temperature two-step procedure involving the chemical reduction of Cu ions by sodium borohydride in the presence of Vulcan XC72R carbon powder, followed by the partial galvanic replacement of Cu particle layers by Pt, upon immersion in a chloroplatinate solution. The characterization of the Pt(Cu)/C catalyst by XRD has proven the formation of a Pt-Cu alloy while cyclic voltammetry in deaerated acid revealed similar characteristics to those of pure Pt. These two findings point to the existence of Pt-rich outer layers and a Pt-Cu core. The electrocatalytic activity of the bimetallic Pt(Cu)/C catalyst towards methanol oxidation is comparable to or better than that of a commercial 20% Pt Vulcan XC72R catalyst (when assessed by voltammetric or prolonged chronoamperometric experiments respectively). This is attributed to the effect of Cu on CO poison adsorption and removal from Pt. Moreover, related to the same effect but also to the reduced Pt loading of the mixed Pt-Cu particles, the specific mass activity of the prepared catalyst is superior to that of the commercial catalyst. © 2013 Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

The structure of electroless nickel-boron with a boron content around 5. wt.% was investigated in the as deposited and heat treated states by X-ray diffraction and by transmission electron microscopy on thinned cross-sections prepared by focused ion beam technique.In the as-deposited state, the presence of areas with short range order has been observed. This shows that electroless nickel-boron coatings with high boron content are not fully amorphous, as is usually stated.After heat treatment, the structure of electroless nickel-boron appeared constituted of nanocrystalline nickel-boride Ni 3B. © 2012 Elsevier B.V.., SCOPUS: ar.j, info:eu-repo/semantics/published

Synthesis of nanosized particles with antibacterial properties is of great interest in the development of new pharmaceutical products. Silver nanoparticles (Ag NPs) are known to have inhibitory and bactericidal effects. In this article we present the synthesis of Ag NPs prepared by chemical reduction from aqueous solutions of silver nitrate, containing a mixture of hydrazine hydrate and sodium citrate as reductants and sodium dodecyl sulfate as a stabilizer. The results of the characterization of the Ag NPs show agglomerates of grains with a narrow size distribution (from 40 to 60 nm), whereas the radii of the individual particles are between 10 and 20 nm. Finally, the antibacterial activity was measured by the Kirby-Bauer method. The results showed reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The standard dilution micromethod, determining the minimum inhibitory concentration leading to inhibition of bacterial growth, is still under way. Preliminary results have been obtained. From the Clinical Editor: In this paper the synthesis of Ag NPs via chemical reduction from aqueous solutions is discussed. Reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus was demonstrated. © 2012 Elsevier Inc., SCOPUS: re.j, info:eu-repo/semantics/published

The main characteristic of cathodic copper is its concentration of impurities because this determines the mechanical properties, i.e. ductility, of the derived copper wires. However, the results of standard mechanical tests to evaluate ductility show that there is no clear correlation between the content of impurities in the cathodes and the ductility of the copper wires. In this study, from traction tests on copper wires and observation of their fracture surfaces by means of scanning electron microscopy and energy dispersive spectroscopy, it has been concluded that the principal impurity affecting the ductility of the copper wires is oxygen, which is mainly incorporated during the melting of the cathodes and casting of the rods. In addition, to discriminate the effect of oxygen concentration in copper ductility, the used probes or wires must have the same previous deformation and must not have been annealed. When copper wires are annealed, cuprous oxide particles are also more dispersed in the matrix, and not only segregated and concentrated as occurs in the non-annealed condition, thus diminishing the mechanical fragility effect of the oxide.©ASM International., SCOPUS: ar.j, info:eu-repo/semantics/published

info:eu-repo/semantics/published

Les alliages Cu-Al-Ni sont les seuls à posséder une température de transformation allant jusque 200°C. Ceci leur confère un avantage par rapport aux alliages Cu-Al-Zn ou Ti-Ni dont les températures de transformation ne dépassent pas 100°C.Néanmoins, un chauffage temporaire au dessus de 200°C peut provoquer une perte de l’effet mémoire des alliages Cu-Al-Ni.Nous avons étudié trois alliages aves des teneurs en nickel comprises entre 3 % et 5 %.L’objectif de notre étude est double :• Étudier la cinétique des transformations structurales au cours d’un vieillissement en phase β dans le domaine de températures 200°C-350°C ;• Quantifier la perte de l’effet mémoire au cours du vieillissement afin de déterminer les possibilités d’utilisation de ces alliages au dessus de 200°C.La caractérisation structurale a été effectuée par microscope optique, diffraction des rayons X, microscopie électronique à balayage et microscopie électronique en transmission. Les caractéristiques de la transformation martensitique ont été déterminées par analyse thermomécanique (TMA), par calorimétrie différentielle à balayage (DSC) et par des mesures de résistivité électrique. La perte de l’effet mémoire simple sens a été quantifiée à partir des courbes de transformations obtenues par analyse thermomécanique(TMA) sur des échantillons comprimés.Les résultats principaux sont :&61636; Au dessus de 300°C, la précipitation de la phase d’équilibre у&8322; se produit au cours du vieillissement. Elle entraîne une augmentation de la température Mѕ.Nous avons montré que cette augmentation de Ms peut être reliée à la fraction transformée par une loi de puissance.&61636; Il n’y a pas de relation directe, en revanche, entre la perte de l’effet mémoire et la fraction transformée. Cela indique que le nombre et la taille des précipités ont une influence sur la perte de l’effet mémoire.&61636; Pour un vieillissement de 256 minutes à 275°C, Doctorat en Sciences de l'ingénieur, info:eu-repo/semantics/nonPublished

Protective coatings for mild steel (MS) are prepared by combining two techniques: electroless (autocatalytic) deposition of a Ni-Cu-P layer and reactive DC sputtering of TiN/Ti atop. These hybrid coatings are designated to provide corrosion protection together with wear resistance and hardness. The corrosion behavior of the system Ni-Cu-P/MS is compared with the conventional Ni-P/MS and its superiority is demonstrated by the weight loss method. This justified the choice of the ternary coating as intermediate amorphous layer, aiming to improve the impermeability of the inherently porous TiN/Ti. The structure of the hybrid TiN/Ti/Ni-Cu-P/MS is studied by TEM of thinned cross-sections prepared by the focused ion beam (FIB) technique. Electrochemical characterization (via potentiodynamic polarization curves) of TiN/Ti/MS and hybrid TiN/Ti/Ni-Cu-P/MS in two model media: 5% NaCl and 0.5M H2SO4 shows the outperformance of the hybrid coatings. SEM-EDS study of the local corrosion areas is conducted on FIB prepared sections. The role of internal stress in corrosion destruction process is discussed. The importance of bias voltage applied to the substrate during sputtering is considered. The advantage and prospects are outlined of MS finishing with hybrid TiN/Ti/Ni-Cu-P coating to ensure reliable corrosion protection joint with the excellent mechanical properties of TiN. © 2010 Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

Repeated fast surface temperature transients can damage the materials and/or their surface treatments by thermal fatigue. This happens in aluminium diecasting devices. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multi-layer. In the last case, top coat is yttria stabilised zirconia (YSZ), followed by a nickel superalloy and then a borided layer (undercoat). The zirconia coating was applied with plasma spray. The multi-layer showed poor resistance during the thermal fatigue tests. Better understanding these tests and the resulting thermal fatigue observed on the treated materials was achieved by a lifetime model based on Coffin-Manson equations. © 2010 Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

The Cr-Mo steels are widely used in the power generation industry for equipment used at high temperatures and remaining in service for long periods of time. Under such conditions, creep is the main cause for premature failure. The evolution of the precipitate carbides and the reduction in Mo concentration in solid solution are the controlling mechanisms responsible for their properties. Estimating damage and the remaining life of power plants or high-temperature pressurized petrochemical equipment has become relatively common. As operating conditions vary considerably over time in such plants, inspection techniques are necessary to estimate the extent of damage, although these may not always provide clear evaluations of remaining life. An alternative assessment method is to use hardness measurements that can be correlated with creep damage and remaining life. In this study, using such a correlation, specimens of 2.25Cr-1Mo steel from accelerated creep tests performed under different conditions of temperature and stress have been examined. The results indicate that the Larson-Miller parameter can be used to correlate the recorded hardness values and so estimate the extent of damage and of remaining life, SCOPUS: cp.j, info:eu-repo/semantics/published

Silver nanoparticles were prepd. by chem. redn. method. Silver nitrate was taken as the metal precursor and hydrazine hydrate as a reducing agent. The formation of the silver nanoparticles was monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption maxima at 418-420 nm from the UV-Vis spectrum. Comparison of theor. (Mie light scattering theory) and exptl. results showed that diam. of silver nanoparticles in colloidal soln. is about 60 nm. We have used energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and, UV-Vis spectroscopy to characterize the nanoparticles obtained. The energy-dispersive spectroscopy (EDX) of the nanoparticles dispersion confirmed the presence of elemental silver signal no peaks of other impurity were detected. The av. size and morphol. of silver nanoparticles were detd. by transmission electron microscopy (TEM). TEM photographs indicate that the nanopowders consist of well dispersed agglomerates of grains with a narrow size distribution (40 and 60 nm), whereas the radius of the individual particles are between 10 and 20 nm. The synthesized nanoparticles have been structurally characterized by X-ray diffraction and transmission high-energy electron diffraction (HEED). The peaks in the XRD pattern are in good agreement with the std. values of the face-centered-cubic form of metallic silver and no peaks of other impurity cryst. phases were detected. Addnl. the antibacterial activity of the nanoparticles dispersion was measured by Kirby-Bauer method. The nanoparticles of silver showed high antimicrobial and bactericidal activity against gram pos. bacteria such as Escherichia Coli, Pseudimonas aeruginosa and Staphylococcus aureus which is a highly methicillin resistant strain., info:eu-repo/semantics/published

The biomimetic process of coating metals has been used to transform bioinert surfaces into bioactive ones. Simulated body fluid (SBF) has been classically used and has a composition similar to that of body fluid. The solution we used also has a composition closely similar to that of body fluid and is less complex than SBF. In this work, titanium surfaces were coated with a designed simplified solution whose chemical composition is based on the ions necessary to form calcium phosphates, e.g. calcium and phosphate ions in aqueous medium. This fluid was called solution for bioactivity evaluation (SBE). Besides the advantage of having a less complex composition, SBE presents fast deposition when compared with conventional SBF. We characterized the calcium phosphate layer by using grazing incidence X-ray diffraction, fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy and transmission electron microscopy. A uniform coating layer with 15 μm thickness was obtained after 7 days of soaking in this simplified solution. This coating exhibited low-dense morphology and a single-phase octacalcium phosphate (OCP) structure. © 2007 Elsevier B.V. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

A magnetic flux measurement technique was used to correlate the magnetic response of carburized cast austenitic steel tubes with the volumetric fraction of chromium carbides in the tube wall. Two different types of chromium carbides were identified by backscattered electron diffraction: Cr23C6 in the outer part and Cr7C3 in the inner part of the tubes. Magnetic force microscopy and energy-dispersive X-ray analysis reveal a correlation between the ferromagnetic behavior of the tubes and chromium depletion in the matrix. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A strategy is proposed to cope with combined thermal fatigue and hot corrosion resistance affecting industrial coatings. It allows comparing different materials, coatings and geometries with respect to thermal cracking and then properly selecting protective coatings. It uses a thermo-mechanical model combining the heat transfer conditions, thermal and mechanical properties of the materials and the system geometry. The model is applied to two cases: (i) borided steel, with experimental support; (ii) multilayer coating made of a thermal barrier layer, aimed at reducing thermal gradients in the system, and a corrosion layer., info:eu-repo/semantics/published

SCOPUS: cp.k, info:eu-repo/semantics/published

This work aimed to model the temperature distribution, phase transformation and residual stress induced during the heat treatment of grinding balls of 3 and 5 in. diameter. The temperature model considered factors such as the heating of the water and the formation of a steam layer that surrounds the balls at the start of the quenching. The model of the residual stress field considered: the temperature distribution, the force equilibrium equations and the constitutive thermo-elastic relationships, including the expansion due to the austenite-martensite transformation. A good agreement between the experimental and theoretical values for the temperature distribution was obtained with the differences at the end of the quenching being no higher than 0.5%. The experimental behavior of the balls in a mill simulator, as well as the residual stress measured by X-ray diffraction, agreed satisfactorily with the theoretical predictions. © 2008 Elsevier B.V. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

A magnetic flux measurement technique was used to correlate the magnetic response of carburized cast austenitic steel tubes with the volumetric fraction of chromium carbides in the tube wall. Two different types of chromium carbides were identified by backscattered electron diffraction: Cr23C6 in the outer part and Cr7C3 in the inner part of the tubes. Magnetic force microscopy and energy-dispersive X-ray analysis reveal a correlation between the ferromagnetic behavior of the tubes and chromium depletion in the matrix. © 2008 Acta Materialia Inc., SCOPUS: ar.j, info:eu-repo/semantics/published

info:eu-repo/semantics/published

Centrifugally cast heat-resistant HP stainless steels are particularly suitable for applications where service conditions comprise high temperatures and aggressive environments; thus, they are extensively used in reformer furnaces, in which hydrogen production takes place. The demand for better performance has motivated developments in these steels. The addition of Nb and Ti as microstructural modifiers has proved successful in providing a more stable microstructure. In this work yttrium was added to centrifugally cast NbTi-modified HP steels. It was observed that its presence increased the level of fragmentation of the chromium carbides, a positive aspect for creep resistance. The main cause of the fragmentation is the formation of yttrium carbides, which serve as heterogeneous nucleation sites for the other carbides. One of the tubes, with a lower titanium content, showed the best creep performance among those tubes studied owing to the presence of a smaller volume fraction of the deleterious G phase. © 2006 Elsevier Inc. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: cp.k, info:eu-repo/semantics/published

Yttrium addition to HP-type (where H stands for heat-resistant and P is related to the Ni content) heat-resistant cast stainless steel resulted in increased fragmentation of the primary chromium carbide network and improved high temperature mechanical properties. The improvement was caused by yttrium carbide particles acting as nucleation sites for other carbides, as indicated by transmission electron microscopy and energy dispersive X-ray spectroscopy analysis. Thermodynamic considerations support these conclusions. © 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

Extruded, flash welded and artificially aged 6061 and 6013 aluminum alloys were analyzed with the use of techniques such as transmission electron microscopy (TEM) imaging, selected area electron diffraction (SAD) and X-ray energy-dispersive spectroscopy (EDS) in order to identify the precipitates present in both alloys. Vickers microindentation hardness measurements were performed at different distances from the weld interface. The results show a small decrease in hardness near the 6013 alloy weld interface. On the other hand, there is an important hardness drop near the 6061 weld interface. This drop can be explained by a lack of fine structural precipitation during the aging treatment in the 6061 weld interface zone. © 2006 Elsevier Inc. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: cp.k, info:eu-repo/semantics/published

The initial phase arising at the interface with aluminum substrate during electroless deposition of amorphous high phosphorus (16-19 at.%) Ni-Cu-P alloy with alloyed copper 1.7-3.4 at.% is studied. Stripped deposit foils are inspected by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy coupled with energy dispersive X-ray analysis (TEM-EDX). Depending on the plating conditions, various particles, some of them crystalline, are revealed at the foils sides formerly adhering to the substrate. EDX analysis of the crystallites shows diverse copper contents of about 34-64 at.%, without any phosphorus. Electron diffraction analysis indicates a lattice structure very close to that of Cu. The presence of a phase without phosphorus and enriched in copper at the interface with the Al substrate is also confirmed by Auger electron spectroscopy. This initially arising crystalline phase might exert a limited effect on the main properties of bulk Ni-Cu-P deposits: the composition uniformity through the thickness, amorphous structure and paramagnetic behavior. A modification of the plating process is recommended, which is decreasing the probability of inhomogeneities formation. © 2004 Elsevier B.V. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published