Display omitted
•By EIS the system API 5 L X52 steel / HCl was studied.•Under static conditions ƞ > 90 % for Fluconazole and <79 % for Afungyl, 20 ppm, were found.•For the fluconazole inhibitor ...follow a physisorption-chemisorption mechanism process.•Physisorption process is result of electrostatic interaction and electron pairs donation.•Reactivity indices indicate that the steel surface is effectively covered and passivated.
The corrosion inhibition of API 5 L X52 in 1 M HCl due to fluconazole as active substance 1 or drug (Afungil), and its fragments: 1,2,4-triazole 2 and 1-bromo-2,4-difluorobenzene 3 was evaluated through electrochemical techniques and DFT calculations. At 20 °C, 1 exhibited c.a. 90 % corrosion inhibition efficiency, IE, from 5–200 ppm. The fragment 2 displayed an IE of 83 % at 30 ppm, while the fragment 3 reached 80 % at all concentrations. However, the inhibition kinetics study of 1 demonstrated that it retained its IE properties up to 168 h of immersion with 84 % IE. 1 followed a Langmuir-type physisorption-chemisorption process while 2 and 3 a physisorption process. From SEM and AFM images it was directly verified the steel-protective capacity of 1 and from XPS analysis its presence onto the steel surfaces. Theoretical calculations, carried out at the dispersion corrected density functional theory BPW91-D2/6-311++G(2d,2p) level, are in full agreement with experimental observations, explaining that the physisorption-chemisorption process was provoked by the electrostatic interaction and electron pairs donation of fluconazole on the iron atoms. Similarly, the adsorption process of protonated fluconazole is due to electrostatic interactions and electrons shared from the metal cluster to the protonates species. Reactivity indices indicate that the steel surface is effectively covered and passivated.
•Elastic properties of surfaces by atomic force acoustic microscopy.•Influence of the lateral contact stiffness on the elastic measurements.•Regions on the flexural vibration curves independent of ...the kS/kN ratio.•Experimental study and finite element analysis of the dynamic behavior of AFM probes.•This analysis reduces uncertainties in the measurements of elastic properties.
Atomic force acoustic microscopy is a dynamic technique where the resonances of a cantilever, that has its tip in contact with the sample, are used to quantify local elastic properties of surfaces. Since the contact resonance frequencies (CRFs) monotonically increase with the tip-sample contact stiffness, they are used to evaluate the local elastic properties of the surfaces through a suitable contact mechanical model. The CRFs depends on both, normal and lateral contact stiffness, kN and kS respectively, where the last one is taken either as constant (kS<1), or as zero, leading to uncertainty in the estimation of the elastic properties of composite materials. In this work, resonance spectra for free and contact vibration were used in a finite element analysis of cantilevers to show the influence of kS in the resonance curves due to changes in the kS/kN ratio. These curves have regions for the different vibrational modes that are both, strongly and weakly dependent on kS, and they can be used in a selective manner to obtain a precise mapping of elastic properties.
•The Paraloid B-72 and organic compounds have a synergistic effect in protect the grey iron.•The best coating with paraloid are 50 mg/m2 theophylline and 200 mg/m2 for caffeine.•SEM-EDS revelated ...without Paraloid B-72 are effective in diminishing the corrosive process.
The effect of caffeine and theophylline concentrations as corrosion inhibitors for grey cast iron, in combination with a coating (Paraloid B-72) in a saline medium was evaluated through electrochemical impedance spectroscopy. Both compounds showed good results regarding to the inhibiting capability efficiency. Caffeine showed inhibition against corrosion in high concentrations and theophylline did so in low concentrations, thus exerting a synergic effect with the Paraloid B-72. The immersion time effect was also studied in both compounds. Results showed that 50 mg/m2 of theophylline + paraloid B-72, presented the most stable coating in the metal surface. By means of SEM-EDS, it was confirmed that the presence of the inhibitors on the metallic surface diminished the corrosive process as a result of the absence of chloride ions. Finally, Fourier transformed infrared spectroscopy (FT-IR) was employed to demonstrate the chemical interactions between the theophylline or caffeine and Paraloid B-72 functional groups.
The acrylonitrile-butadiene-styrene (ABS) is the most commonly used copolymer in industry for metallizing. The process in solution used for depositing metallic films on non-conductive substrates is ...known as electroless, which is an autocatalytic procedure. However, the sulfo-chromic admixture used to modify the ABS surface, in the first step of this process, is not environmentally suitable due to the use of Cr (VI), and its utilization implies a risk of severe damage to living beings. For this reason, a study of an alternative surface treatment with substantially lower levels concerning environmental impact is presented in this work, which is based on a photocatalytic reaction that is initiated on the copolymer surface by TiO
2 nanoparticles (30
nm), as a suspension, under UV exposure. After surface conditioning with the photocatalytic treatment was conducted, the substrates were metallized in two different ways: electroless process or dynamic chemical process (DCP), with a subsequent conventional electrolytic deposit. The DCP does not need a surface activation with palladium ions, unlike electroless process, which simplified the procedure by reducing directly both, the effluents and the costs. The prepared substrates were characterized using: scanning electron microscopy (SEM), atomic force microscopy (AFM), atomic force acoustic microscopy (AFAM), mechanic profilometry, optical interference profilometry, profilometry by AFM, and a cross cut tape test. The results obtained with the proposed pre-treatment stage are shown and compared with those obtained in the conventional electroless process.
► Photocatalytic alternative to sulfo-chromic chemical pre-treatment for electroless. ► TiO
2 nanoparticles suspension on ABS exposed to UV impart roughness and activation. ► AFM, mechanical and optical profilometry show the treatment effect on ABS surface. ► Electroless and electrolytic deposits show high adherence with TiO
2 pre-treatment.
•Friction coefficient (μ) of ferroelectric textured and polycrystalline YCrO3 films.•A simple method to evaluate μ from a single AFM image is presented.•The AFM-cantilever spring constant was ...determined from its dynamic response.•Polycrystalline and amorphous films have a lower μ than textured samples.
Differences in friction coefficients (μ) of ferroelectric YCrO3, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB® software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO3 film deposited on a Pt(150nm)/TiO2(30nm)/SiO2/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO3 (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO3 films seem to be the best candidates due to their lower μ.
Double-layer Pb(Zr
0.53
Ti
0.47
)O
3
films were fabricated by spin coating of a sol–gel acetic-acid-based precursor solution deposited onto commercial Pt–Si substrates. The structural properties of ...the samples were studied by several diffraction, spectroscopy and microscopy techniques. The annealed ferroelectric films were crystallized to a pure PZT perovskite phase. A significant monoclinic phase content was found together with a relatively large tetragonal c/a ratio, according to the diffraction pattern refinement results. No traces of organic material were observed. Good film densification with relatively large grain sizes and low surface roughness was achieved. Ferroelectric domain distribution and local piezoresponse hysteresis loops were investigated by piezoresponse force microscopy. The films showed good local ferroelectric properties and a relatively large d
33
piezoelectric coefficient was derived. A degree of self-polarization of the film was also found from the domain distribution-map analysis. Good macroscopic ferroelectric properties were also achieved, specially for the film with less rhombohedral content. An improved ferroelectric fatigue behavior was observed as the films proved to sustain down to 10
8
fatigue cycles with only a 10 % decrease of the initial remnant polarization.
•Single phase BNT-Mn and BNTBT-Mn epitaxial thin films were successfully grown on (00l)LSCO/LaAlO3 Mn incorporation was evidenced by Raman spectroscopy identifying the TiO6 vibrational modes.•High ...energy storage polarization density was found in the prepared Mn-doped thin films High Pr is associated to the combined effect of Mn addition and MPB composition in the BNTBT thin films.
The effects of Manganese doped (Bi1/2Na1/2)TiO3 and (Bi1/2Na1/2)TiO3–BaTiO3 epitaxial thin films on the structure, dielectric, ferroelectric and piezoelectric properties are reported. The thin films were grown by pulsed laser deposition on (Lao.5Sr0.5)CoO3 (LSCO) electrode LaAlO3 (LAO) substrates using homemade ceramic targets. The (La0.5Sr0.5)CoO3 (LSCO)/LaAlO3/system was chosen based on the adequate coupling conditions to grow high quality epitaxial films with desired properties. The dielectric and ferroelectric properties are all self-consistent to each other, despite the morphotropic phase boundary effect in Mn doped BNT-BT thin film. Even when remanent polarizations of 17 and 25μC/cm2 from BNT-Mn and BNT-BT-Mn thin films were respectively obtained from well-defined P–E hysteresis curves and the corresponding values of coercive field for BNT-Mn and BNT-BT-Mn thin films are 93 and 150kV/cm, respectively, no significant changes are observed suggesting that the effect of MPB composition is not fully activated due to Mn additions. In the ceramics, the vibrational modes associated to Mn interactions with the oxygen octahedral were identified with Raman spectroscopy. Finally, the local piezoelectric constants (d33) as measured by PFM are 60 and 124 pm/V for BNT-Mn and BNT-BT-Mn thin films, respectively. Thus, BNT-Mn and BNT-BT-Mn thin films are potential candidates to be used in lead-free piezoelectric devices.
Thermal Barrier Coatings (TBC) of 8% Yttria-Stabilized Zirconia (8YSZ) were deposited on AISI-304 substrates via r.f magnetron sputtering. A buffer layer of alumina, Al
2O
3, was deposited to improve ...the adhesion of the YSZ monolayer to the substrate. The influence of the Al
2O
3/8YSZ coating on the electrochemical conductance evolution,
C
t
T
, was examined by Electrochemical Impedance Spectroscopy measurements when the steels are exposed to temperatures of 700 and 500
°C for 2, 4, and 6
h. Results indicated that
C
t
T
diminished three orders of magnitude, in samples coated with Al
2O
3/8YSZ with respect to uncoated steel.
We report the mechanical and tribological properties of transparent conductive oxide CdO + SnO
2
coatings. The films were deposited on glass substrates by the sol–gel technique using, as precursor ...solution, a mixture of CdO and SnO
2
solutions obtained at room temperature. Depending on the Sn atomic concentration percentage values the X-ray diffraction patterns show three types of films constituted of (1) CdO + Cd
2
SnO
4
, (2) Cd
2
SnO
4
and (3) Cd
2
SnO
4
+ CdSnO
3
crystals. Reciprocal microfriction tests revealed that films with Cd
2
SnO
4
phase have friction values in the range 0.48–0.51 and a low wear rate of ~5 × 10
−5
mm
3
N
−1
m
−1
. Nanoindentation tests have shown an increment of the elastic modulus from 50 GPa for CdO + Cd
2
SnO
4
films to 90 GPa for Cd
2
SnO
4
films, while the hardest coating was the one constituted by Cd
2
SnO
4
crystals with H = 5.7 GPa, comparable to the hardness and elastic modulus reported for ITO films.
Bismuth titanate (BixTiyOz) thin films were grown using the r.f. magnetron sputtering technique on (100) silicon substrates. In the process, annealing was performed in both oxygen and dry air ...atmospheres at 600°C for 30 and 120min. The structure of the thin films was characterized through X-ray diffraction (XRD), and the ferroelectric response was determined with measurements of piezoelectric force microscopy (PFM). Bi4Ti3O12 with a predominant orthorhombic phase was obtained in the annealed thin films. All the annealed films exhibited the characteristic hysteresis and butterfly loops of ferroelectric materials. Thermal annealing of BixTiyOz films in an atmosphere of air for 30min resulted in the highest d33 value of 78±14pm/V, which decreased to 64±26pm/V for 120min. On the other hand, annealing in an oxygen atmosphere produced BixTiyOz films with more uniform d33 values, 54±3pm/V and 42±6pm/V for 30 and 120min, respectively. Ferroelectric coefficient values decreased with the increase of annealing time in an oxidant atmosphere, which can be explained by the vacancies present. These results are consistent with the experimental measurements carried out in other investigations.
PDF
