Antifouling coatings containing biocidal agents can be used to prevent the accumulation of biotic deposits on submerged surfaces; however, several commercial biocides can negatively affect the ...ecosystem. In this study, various formulations of a potential biocide product comprising copper nanoparticles and capsaicin supported on zeolite ZSM-5 were analyzed to determine the influence of the concentration of each component. The incorporation of copper was evidenced by scanning electron microscopy and energy dispersive spectroscopy. Similarly, Fourier-transform infrared spectroscopy confirmed that capsaicin was supported on the zeolite surface. The presence of capsaicin on the external zeolite surface significantly reduced the surface area of the zeolite. Finally, bacterial growth inhibition analysis showed that copper nanoparticles inhibited the growth of strains Idiomarina loihiensis UCO25, Pseudoalteromonas sp. UCO92, and Halomonas boliviensis UCO24 while the organic component acted as a reinforcing biocide.
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The precipitation kinetics of secondary phases in a 10.5%Cr heat resistant steel, designed by the authors, was studied experimentally and theoretically. Experimental data of nucleation, growth and ...coarsening stages for M23C6 carbides, V-MX, Nb-MX and Laves phase were obtained by HRTEM-characterization on samples after tempering (780°C/2 h) and isothermally aging for 1440 h and 8760 h at 650 °C. Theoretical studies of precipitation behavior of M23C6 and Laves phase were carried out by TC-PRISMA and complemented with DICTRA. A good fit between TC-PRISMA simulation and experimental results was obtained for M23C6 carbides considering a heterogeneous nucleation in grain boundaries, a semi-coherent interfacial energy of 0.3 J/m2, and decreasing the atomic mobility along grain boundary in order to include the effect of B. Experiments and simulation indicate a low coarsening rate for M23C6 carbides. Furthermore, precipitation of Laves phase at 650 °C was simulated by TC-PRISMA considering the effect of W and Si segregation at grain boundary, prior to the beginning of the nucleation and growth processes. Therefore, thermodynamic and kinetic boundary conditions were changed purposely in TC-PRISMA. Best agreement with the experimental results was obtained for an interfacial energy of 0.6 J/m2 and heterogeneous nucleation in grain boundary.
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•Design, production and characterization of 10%Cr steel assisted by ThermoCalc.•Long term aging (8760 h) and TEM characterization of M23C6, MX and Laves phase.•Simulation of nucleation-growth-coarsening of M23C6 and Laves by PRISMA and DICTRA.•The effect of Boron on M23C6 carbides was satisfactory simulated by PRISMA.•PRISMA simulation of Laves Phase considering micrograin segregation of Si and W.
With the purpose of improving the protection of steel ASTM A36 from corrosion, in this paper the use of tannin as an inhibitor was studied by incorporating it in an epoxy resin along with zinc oxide ...nanoparticles functionalized with 3-aminopropyltriethoxysilane (APTES) in concentrations of 1, 3, and 5%w/w. Electrochemical techniques such as polarization curves and EIS for the characterization of the anticorrosive properties, SKP for the study of coating delamination with the substrate, contact angle measurement and other standardized methods were used for the evaluation of the properties of the film. The results of the polarization curves revealed that the corrosion current density of the steel (icorr) decreases markedly with the addition of the tannin extract by changing the cathodic behavior without affecting the active anodic behavior. Likewise, the EIS analysis showed that the coatings with surface modified nanoparticles provide an excellent protection against corrosion that is complemented by the protective layer of the tannin-iron complex formed and the same was confirmed by FTIR spectroscopy after exposing the plates to accelerated corrosion tests in salt spray and weathering chamber. Finally, it could be demonstrated that the incorporation of zinc oxide nanoparticles in the coating formulation subtly improves the film properties and likewise, partially increases the hydrophobicity.
Abstract
In this study, were extensively reviewed the hardening and self-healing properties of Laves-phase in Fe-based alloys. First, the microstructural features of different polytypes of the ...Laves-phase, focusing on the thermodynamics and kinetics of formation in ferritic and martensitic steels were revised. C14 was identified as the dominant polytype in steels, providing strengthening by precipitation, anchoring of dislocation, and interphase boundaries, thereby increasing the creep resistance. Although the Laves phase is widely known as a reinforcement particle (or even a detrimental phase in some systems) in martensitic/ferritic and ferritic steels, recent findings have uncovered a promising property. Particles with self-healing characteristics provide creep resistance by delaying creep cavities formation. In this regard, different elements such as tungsten and molybdenum are known to provide this feature to binary and tertiary ferrous alloys due to their ability to diffuse into the creep cavities and form Laves-phase Fe(Mo,W)
2
. To date, self-healing by precipitation has only been reported in commercial stainless steel AISI 312, 347, and 304 modified with boron, nevertheless with a little contribution to creep rupture life. Although, commercial computational tools with thermodynamic and kinetic databases are available for researchers, to tackle the self-healing process with exactitude, genetic algorithms arise as a new tool for computational design. The two properties of Laves phase reported in the literature, precipitation hardening and self-healing agent, is a mix that can bring out a new research field. Therefore, it is not unreasonable to think of tailor-made high chromium creep-resistant steels reinforced by Laves-phase coupled with self-healing properties. However, owing to the characteristic of Laves-phase seems to be a complex challenge, mainly due to the crystallographic features of this phase in comparison with the host matrix, available computational tools, and databases.
In this study, three martensitic creep-resistant steels with 100, 90, and 70 ppm of boron were investigated. The experimental data obtained from isothermal aging and creep test at 650 °C were ...compared with the results of simulation conducted using TC-PRISMA software. Tungsten was found to be the rate-controlling element in the coarsening of (Cr, Fe, W)
23
C
6
carbides; however, this result differed in terms of boron-containing steel. Several studies indicate that the low solubility of boron in ferrite promotes boron enrichment in (Cr, Fe, W)
23
C
6
carbide, thereby reducing its coarsening rate. However, this mechanism is not universally agreed upon. In the present study, a comparison between experimental and theoretical results revealed that in boron-containing steels, the coarsening of (Cr, Fe, W)
23
C
6
carbide is controlled probably by boron volume diffusion or by trans-interface diffusion.
Graphic Abstract
A 12 pct Cr martensitic/ferritic steel was designed and produced to study Laves and Z-phase as precipitation hardening particles under creep conditions (650 °C). According to thermodynamic ...calculations, W and Cu additions were selected to ensure the precipitation of Laves after tempering. It is known that Z-phase formation does not follow the classical nucleation theory. Indeed, MX particles are transformed into Z-phase by Cr diffusion from the matrix to the precipitate. Therefore, to promote fast Z-phase formation, Ta, Co, and N additions were used to produce Ta-MX, which will be transformed into Z-phase. The main result achieved was the precipitation of Laves after tempering, with a particle size of 196 nm. As regards to Z-phase, the transformation of Ta-MX into Z-phase after tempering was confirmed by the formation of hybrid nanoparticles of 30 nm. Although W and Ta have a low diffusion in the martensitic/ferritic matrix, characterization of the precipitates after isothermal aging revealed that Laves and Z-phase have fast growth kinetics, reaching 400 and 143 nm, respectively, at 8760 hours. Consequently, creep test at 650 °C showed premature failures after few thousand hours. Therefore, it is expected that future research in the field of martensitic/ferritic steels will focus on the growth and coarsening behavior of Laves and Z-phase.
The corrosion behavior of a new Nb-doped stainless steel (SDSS-Nb) designed by the CALPHAD method, produced using an open atmosphere process based on recycled materials, was investigated to improve ...the circular economy. Three heat-treatment conditions were evaluated to assess the sensitization effects of the precipitates and inclusions. XRD and SEM-EDS were used for phase identification, and sensitization was analyzed by cyclic polarization and Scanning Kelvin Probe Force Microscopy (SKPFM). The thermodynamic stability predicted by Thermo-Calc agrees with that observed by SEM-EDS. It was observed by cyclic polarization that the corrosion sensitization was mainly provided by the σ phase, which was deduced from the results obtained by SEM-EDS, XRD, and Thermo-Calc simulations. Furthermore, it was obtained that the sensitization due to Cr2N precipitates and nonmetallic inclusions was low, and the mechanical response is comparable to commercial UNS32750 super duplex stainless steel, which allows a good performance in severe environments and an efficient industrial application. Additionally, it has been obtained by SKPFM that the shear potential between the σ phase and the austenite is between 210 mV and 241 mV and that its value depends on the stability and equilibrium reached by the σ phase during thermal cycling.
Nucleation, growth and coarsening of three different precipitates (NbC, M23C6 and V(C,N)) in a novel 9%Cr heat resistant steel designed by the authors were investigated. The microstructure evolution ...after tempering (780 °C/2 h) and after creep (650 °C/100 MPa) was characterized using transmission electron microscopy in the scanning mode (STEM). Thermodynamic and kinetic modeling was carried out using the softwares Thermo-Calc, DICTRA and TC-PRISMA. The Thermo-Calc software predicted formation of NbC, V(C,N) and M23C6 carbides at the tempering temperature of 780 °C. STEM investigations revealed that M23C6 precipitated on prior austenite grain boundaries and lath or block boundaries whereas NbC and V(C,N) were located within sub-grains. Simulations by TC-PRISMA showed that M23C6, NbC and V(C,N) particles nucleation begins as soon as the tempering treatment starts and it is completed in a very short time, reaching the equilibrium volume fraction after 40 s for M23C6, 100 s for NbC and 80 s for V(C,N). Best agreement between simulations and experimental investigations was found for low interfacial energy values of 0.1 J m−2. Both STEM measurements as well as DICTRA simulations indicate very low coarsening rate for both kind of precipitates. Creep tests up to 4000–5000 h suggest that this special combination of NbC, V(C,N) and M23C6 may provide increased pinning of dislocations reducing boundary migration therefore enhancing creep strength.
•Nucleation, growth and coarsening of NbC and M23C6 precipitates were investigated.•The microstructure was characterized using transmission electron microscopy (STEM).•Modeling was carried out using the softwares Thermo-Calc, DICTRA and TC-PRISMA.•M23C6 and NbC nucleation begins as soon as the solution treatmentinitiates.•Best agreement modeling/experiments was found for low interfacial energy values of 0.1 J m−2.
ABSTRACT We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The ...continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0 075 (10 AU) to 0 025 (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analog HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination ( ) and position angle We obtain a high-fidelity image of the 1.0 mm spectral index ( ), which ranges from in the optically thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, and we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km s−1 consistent with Keplerian motion around a ∼1.3 star, although complicated by absorption at low blueshifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkH 358 at 2.9 mm.
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