Abstract Both H2S and CO2, ubiquitous in hydrocarbon production, can severely compromise asset integrity. While both are corrosive, H2S-containing environments tend to be more aggressive, causing faster and more severe corrosion than CO2—especially in high-temperature oil and gas systems. Research on H2S corrosion at elevated temperatures has been limited, leading to an incomplete understanding of the mechanisms behind observed phenomena. As a result, corrosion in the presence of H2S remains a key concern for the oil and gas industry. This experimental work aimed to examine the effects of varying CO2 and H2S concentrations at high temperatures. Data for autoclave experiments conducted at pHinitial 5.0, 0.00385-0.0385 M [H2S]aq (0.13-1.65 bar pH2S), 0.009-0.093 M [CO2]aq (1-13 bar pCO2) contrasting corrosion product layers at 120 and 160 °C are reported. The corrosion specimens were machined from X65 steel. Experimental results demonstrate that corrosion rates at 120 and 160 °C for different concentrations of CO2 and H2S were essentially the same, within error, with a combination of various iron sulfides (pyrrhotite, mackinawite, pyrite, troilite) and magnetite found as corrosion products. Also, localized corrosion appeared on the X65 steel specimens in select cases, with no clear pattern identified yet.

We have conducted a comprehensive investigation into the magnetic properties of the chiral multiferroic material CoTeMoO6. In contrast with the previous claim of canted antiferromagnetic order with ferromagnetic netic ground state with compensated moments, providing an interesting platform for exploring exotic material properties. Through careful measurements of magnetization under a series of applied fields, we demonstrate that there exist two sequential field-induced magnetic transitions in CoTeMoO6, with one occurring at Hc1 = 460 Oe along the a axis, and the other at Hc2 = 1.16 T with the field along the b axis. The values of Hc1 and Hc2 exhibit strong angular dependence and diverge with different rates as the applied field is rotated 90 degrees within the ab plane. This reflects the distinct nature of these transitions, which is further supported by the different critical behavior of Hc1 and Hc2, characterized by the values of gamma , in the function of Hc = H0(1-T/Tc)gamma . Furthermore, we have demonstrated that there exist structural and magnetic twin domains in CoTeMoO6 that strongly affect the experimental measurement of their macroscopic properties. Intriguingly, these twin domains can be related to the orthorhombicity/chirality of the crystal structure with the space group P21212. We further explored the magnetic and structural domains with uniaxial pressure and polarized light microscopy. Our results suggest that CoTeMoO6 could be used as a unique platform for investigating the intriguing physics involving intertwined degrees of freedom. The tunability of the underlying domain distribution and its strong anisotropy could also be useful for developing functional devices and applications.

Questions about temperature-dependent structural and compositional stability persist as new alloys are developed for additive manufacturing (AM) applications. The accuracy of phase diagram predictions using CALPHAD was evaluated with energy-dispersive X-ray diffraction (ED-XRD) on electrostatically levitated samples at high temperatures, concurrently measuring composition through X-ray fluorescence (XRF) emissions. A set of AMrelevant alloys comprising 3d transition metals was tested, including NiCu, Ni51Cu44Cr5, Ni38Co33Cu29, Ni29Co33Cu38, Ni38Co33Cr29, and CoCrFeNi. While it was found that experimental results partially aligned with CALPHAD predictions for many binary and ternary alloys, they proved inaccurate for more complex alloys, such as the CoCrFeNi quaternary. Additionally, XRF measurements indicated that among the tested alloys, those containing Cu became Cu deficient in the near-surface at high temperatures, raising questions about the viability of these alloys for specific AM processes.

Correction for ‘Cellulose derived magnetic mesoporous carbon nanocomposites with enhanced hexavalent chromium removal’ by Bin Qiu et al., J. Mater. Chem. A, 2014, 2, 17454–17462, https://doi.org/10.1039/C4TA04040F.

The phase transitions of a series of Co-doped Heusler alloys, Ni2Mn1-xCoxGa ( 0 <= x <= 0.2), were investigated experimentally using the magnetization measurements, x-ray diffraction, and calorimetric measurements up to their respective melting points. With increasing Co concentration, the structural transition temperatures, Curie temperatures, and melting points, were observed to increase, while the order-disorder transition temperatures decreased. Temperature-dependent x-ray diffraction experiments revealed two different crystal structures in the low-temperature martensite phase for different Co concentrations. However, above their respective structural transitions, both low-temperature crystal structures transformed into the L2( 1) cubic structure. These findings enabled the construction of a complete magnetic and structural phase diagram for Ni2Mn1-xCoxGa, spanning from cryogenic temperatures to the melting points. The temperature-dependent XRD results revealed the abrupt changes in interatomic Mn-Mn distances, which validates the crucial role of Mn-Mn interatomic distance and the effect of the magnetic coupling competition in the structural stability between the martensite phase and austenite phase.

In monocrystalline Si (c-Si) solar cells, identification and mitigation of bulk defects are crucial to achieving a high photoconversion efficiency. To spectroscopically detect defects in the c-Si bulk, it is desirable to passivate the surface defects. Passivation of the c-Si surface with dielectrics such as Al2O3 and SiNx requires deposition at elevated temperatures, which can influence defects in the bulk. Herein, we report on the passivation of different Czochralski (Cz) Si wafer surfaces by an organic copolymer, Nafion. We test the efficacy of the surface passivation at temperatures ranging from 6 to 473 K to detect bulk defects using electron paramagnetic resonance (EPR) spectroscopy. By comparing with state-of-the-art passivation layers, including Al2O3 and liquid HF/HCl, we found that at room temperature, Nafion can provide comparable passivation of n-type Cz Si with an implied open-circuit voltage (iVoc) of 713 mV and a recombination current prefactor J0 of 5 fA/cm2. For p-type Cz Si, we obtained an iVoc of 682 mV with a J0 of 22.4 fA/cm2. Scanning electron microscopy and photoluminescence reveal that Nafion can also be used to passivate the surface of c-Si solar cell fragments scribed from a solar cell module by using a laser. Consistent with previous studies, analysis of the EPR spectroscopy data confirms that the H-terminated surface is necessary, and fixed negative charge in Nafion is responsible for the field-effect passivation. While the surface passivation quality was maintained for almost 24 h, which is sufficient for spectroscopic measurements, the passivation degraded over longer durations, which can be attributed to surface SiOx growth. These results show that Nafion is a promising room-temperature surface passivation technique to study bulk defects in c-Si.

Volatile corrosion inhibitors (VCIs), specifically formulations based on thiols and amines, can be used to mitigate top-of-the-line corrosion (TLC) that arises during the transportation of wet gas through transmission pipelines. Nevertheless, the VCI inhibition efficiency (IE) can be compromised by the presence of condensable hydrocarbon phases. In this research, the IE of two thiol compounds (decanethiol and hexanethiol) and three combinations of VCIs for TLC scenarios, both in the presence and absence of n-heptane, representing a condensing hydrocarbon phase were studied. The results proved the IE of thiols in a water-only condensing environment, with effectiveness increasing with the alkyl tail length. Conversely, in a water/n-heptane co-condensing environment, a reversed trend was observed, where hexanethiol exhibited higher corrosion IE compared to decanethiol. Molecular simulation results indicated a synergistic adsorption behavior when the alkane was of a similar length as the alkyl tails of the inhibitors, leading to the incorporation of alkane molecules with the inhibitor molecules. A mixture of thiols (decanethiol and hexanethiol) and two mixtures of thiol and amines (decanethiol and diethylamine/t-butylamine) were also considered in both water-only and water/n-heptane co-condensing environments. In the presence of n-heptane, only the thiol mixture, featuring molecules with different tail lengths, demonstrated high IE. This behavior was attributed to the superior IE provided by thiol-based molecules with a shorter alkyl tail (hexanethiol) in the presence of n-heptane. Additionally, the results revealed that the mixtures of decanethiol and amines did not enhance corrosion inhibition in the presence of n-heptane within the system.

This article explores the use of femtosecond (fs) lasers to form glass-to-glass welds for hermetically sealed, polymer-free solar modules. Low-iron solar glass coupons were welded together without the use of glass filler using a fs laser with dedicated optics to elongate the focal plane parallel to the incident beam. The resulting welds were then stress tested to failure to reveal the critical stress intensity factor, K-Ic. These values were used in a structural mechanics model of a 1 m x 2 m glass/glass module under a simulated static load test. The results show that the fs laser welds are strong enough for a suitably framed module to pass the IEC 61215 static load test with a load of 5400 Pa. Key to this finding is that the module must be framed and braced, and the glass must be ribbed to allow pockets for the cells and welds inside the border of the module. The result is a module design that is completely polymer free, hermetically sealed, has improved thermal properties, and is easily recycled.

In this study, phase transitions (structural and magnetic) and associated magnetocaloric properties of stoichiometric MnCoGe have been investigated as a function of annealing pressure. Metastable phases were generated by annealing at 800 °C followed by rapid cooling under pressures up to 6.0 GPa. The x-ray diffraction results reveal that the crystal cell volume of the metastable phases continuously decreases with increasing thermal processing pressure, leading to a decrease in the structural transition temperature. The magnetic and structural transitions merge and form a first-order magnetostructural transition between the ferromagnetic orthorhombic and paramagnetic hexagonal phases over a broad temperature range (>80 K) spanning room temperature, yielding considerable magnetic entropy changes. These findings demonstrate the utility of thermal processing under high pressure, i.e., high-pressure annealing, to control the magnetostructural transitions and associated magnetocaloric properties of MnCoGe without altering its chemical composition.

The phase transitions in MnNiGe compounds were explored by manipulating the heat treatment conditions and through hydrostatic pressure application. As the quenching temperature increased, both the first-order martensitic structural transition temperatures and magnetic transition temperatures decreased relative to those in the slowly-cooled samples. When the samples were quenched from 1200 circle C, the first-order martensitic structural transition temperature lowered by more than 200 K. The structural transitions also shifted to lower temperature with the application of hydrostatic pressure during measurement. Temperature-dependent x-ray diffraction results reveal that the changes of the cell parameters resulting from the structural transitions are nearly identical for all samples regardless of the extensive variation in their structural transition temperatures. In addition, neutron scattering measurements confirm the magnetic structure transition between simple and cycloidal spiral magnetic structures.

Intermittent oil-water wetting can have a significant effect on the internal corrosion of steel pipelines. This paper presents a combined experimental and molecular modeling study of several influential factors on the surface properties and corrosion behavior of mild steel in CO2 environments. The influence of different model oils (LVT-200 and Aromatic-200) and select surface-active compounds (myristic acid, cyclohexane butyric acid, and oleic acid) on the corrosion behavior of carbon steel during intermittent oil-water wetting was determined by measuring the corrosion rate after intermittent wetting cycles. The interfacial tension measurements were performed to study the incorporation of the oil phase along with surface-active molecules in the protective layer formed on the specimen surface. Results showed that the interfacial tension for an aromatic oil-water interface is lower than that for an aliphatic oil-water interface. To understand this result, molecular dynamics simulations of oil-water interfaces were performed in the presence of surface-active molecules and different oils to analyze the structure of the layer formed at the interface. The simulations supported the hypothesis that aromatic molecules are less structured at the interface, which results in the incorporation of more water molecules into the protective layer formed at the steel surface, causing a higher corrosion rate. On the other hand, the simulations revealed that myristic acid in an aliphatic oil forms a well-aligned structure at the interface, devoid of any water molecules. This is in agreement with the hypothesis that the linear molecular structure of myristic acid favors the alignment of molecules at an aliphatic oil-water interface, resulting in a lower interfacial tension and more effective corrosion mitigation as compared to the other two nonlinear compounds tested. It is concluded that an important factor controlling the corrosion behavior is the molecular structure of the oil-water interface, which is adopted by the steel surface layer through the Langmuir-Blodgett process.

A novel methodology and experimental apparatus were developed to address the limitations of previous studies and investigate corrosion inhibitor persistency under batch treatment conditions. This approach effectively removed all residues after inhibitor application and prevented O-2 2 ingress during film formation and subsequent steps. A model compound corrosion inhibitor (CI) was utilized to validate the methodology and investigate the effects of solvent on CI persistency. In all experiments, CI was applied in situ on the prepared API 5L X65 steel rotating cylinder electrode inside the empty deoxygenated glass cell using a holder and vial. The setup used a reservoir of CO2-sparged 2-sparged uninhibited brine to continuously dilute the test electrolyte at a constant flow rate. Electrochemical measurements were performed at 20-min intervals to characterize the inhibition behavior over time.

In this contribution we demonstrate how symmetric poly-Si/SiOx test structures can be used to measure the total contact resistivity on n- and p-type passivating contacts. We also show how these test structures illustrate the difference between total contact resistance and specific contact resistivity. The specific contact resistivity as measured by traditional methods such as TLM may be misleading in some cases, and current spreading in the polysilicon layer must be considered. We demonstrate how this area may be estimated and show current spreading can be visualized by simulation in Quokka3.

The effect of a paraffinic model oil (LVT-200)-containing select surface-active compounds (myristic acid and acridine) on CO2 corrosion with and without intermittent wetting has been studied. Observations have shown that the presence of myristic acid in the oil phase does not affect the corrosion behavior due to its lack of partitioning in the water phase. However, after direct contact between the oil phase-containing myristic acid and the metal surface, there was a significant decrease in the corrosion rate. This phenomenon gradually diminished at pH 4.0 but was more persistent at pH 6.5. The presence of acridine in the oil phase was shown to have a strong inhibitive effect at pH 4.0, even during the partitioning step. The partitioning of acridine from the oil phase to the water phase at pH 4.0 was confirmed by ultraviolet-visible spectroscopy results. However, there was no inhibitive effect conferred by the presence of acridine on the corrosion rate at pH 6.5. An experimental methodology was developed that facilitated improved simulation of the effect of intermittent oil/water wetting on CO2 corrosion. The electrochemical current response during the oil/water intermittent wetting cycles showed that the persistency of model oil (without surface-active compounds) on the mild steel surface is only a matter of seconds. Corrosion rate measurements showed that the presence of myristic acid renders the oil layer more persistent after intermittent wetting compared to one-time direct contact.

This study presents unique data on top-of-the-line corrosion (TLC) occurring in high-pressure environments where CO2 was in the gaseous, liquid, or supercritical state. While CO2 is traditionally in a gaseous phase, this form of degradation is referred to as TLC. In this study, similar phenomena with different mechanisms were observed in liquid CO2 and supercritical states all of which are referred to as TLC due to the location of specimens and ease of comprehension. Experiments were conducted to investigate the effect of CO2 partial pressure (ranging from 20 bar to 100 bar) with temperatures (30 degrees C to 50 degrees C) relating to different water condensation rates (0.001 mL/m(2)/s to 0.1 mL/m(2)/s). Uniform and localized TLC rates increased with a higher water condensation rate and surface temperature. As long as CO2 remained gaseous, its partial pressure (pCO(2)) showed a negligible influence on both uniform and localized TLC rates. At the highest gaseous CO2 content tested, the formation of a protective iron carbonate (FeCO3) layer decreased the TLC rate, with this effect being more pronounced at lower water condensation rates. The risk of localized corrosion for specimens exposed to this environment at high and medium water condensation rates remained an issue. In the dense phase CO2 environment, the difference in temperature between the bulk environment and the specimen's surface caused a similar phenomenon to water condensation, termed water drop-out, which resulted in corrosion. The rate of water drop-out could not be measured experimentally or estimated theoretically but is a complex function of temperature, pCO(2), and CO2 physical state. The interplay between high pCO(2) and low pH of the dropped-out water led to elevated uniform and localized corrosion rates. The depth of localized corrosion, at the high and medium water drop-out conditions, reached its maximum at the surface temperature of ca. 45 degrees C. At a lower surface temperature of ca. 25 degrees C and a higher surface temperature of ca. 65 degrees C, the maximum penetration rate was decreased due to slower kinetics of reactions and the formation of a more protective FeCO3 layer, respectively. The results presented in this study highlight the significant difference between corrosion rates, especially in the form of localized damage, in gaseous and dense-phase CO2 environments.

We have conducted a comprehensive investigation into the magnetic properties of the chiral multiferroic material CoTeMoO_6. In contrast with the previous claim of canted antiferromagnetic order with ferromagnetic components, our investigation reveals an antiferromagnetic ground state with compensated moments, providing an interesting platform for exploring exotic material properties. Through careful measurements of magnetization under a series of applied field, we demonstrate that there exist two sequential field-induced magnetic transitions in CoTeMoO_6, with one occurring at H_c1=460 Oe along the a-axis, and the other at H_c2=1.16 T with the field along the b-axis. The values of H_c1 and H_c2 exhibit strong angular dependence and diverge with different rates as the applied field is rotated 90 degrees within the ab plane. This reflects the distinct nature of these transitions, which is further supported by the different critical behavior of H_c1 and H_c2, characterized by the values of γ,in the function of H_c=H_0×(1-T/T_c)^n. Furthermore, we have demonstrated that there exist structural and magnetic twin domains in CoTeMoO_6 that strongly affect the experimental measurement of their macroscopic properties. Intriguingly, these twin domains can be related to the orthorhombicity/chirality of the crystal structure with the space group P2_1 2_1 2. We further explored the magnetic and structural domains with uniaxial pressure and polarized light microscopy. Our results suggest that CoTeMoO_6 could be used as a unique platform for investigating the intriguing physics involving intertwined degrees of freedom. The tunability of the underlying domain distribution and its strong anisotropy could also be useful for developing functional devices and applications.

Light-induced degradation of Si solar cells when deployed in warmer climates can cause up to a ∼10% relative degradation in efficiency, but the atomic structure of the defect responsible for this degradation remains elusive. Herein, using electron paramagnetic resonance, we show that the defect responsible for light- and elevated-temperature-induced degradation (LeTID) is likely an Si dangling bond within an extended defect such as a vacancy agglomerate, with H atoms in its vicinity and likely O nearby. Our atomistic-level insights suggest that the defect responsible for LeTID can be mitigated by targeted engineering of the intrinsic defect populations by optimizing annealing routines prior to or during device fabrication and by controlling the amount of H injected in the Si bulk during cell processing. Mitigating LeTID through detailed knowledge of its atomic structure can help preserve the long-term efficiency of gigawatts of future worldwide installations of solar based on crystalline Si.

In this contribution, we examine Ga hyper-doped poly-Si/SiOx contacts realized by pulsed laser melting (PLM). Here, we use Ga as a novel p-type dopant and B as a conventional dopant to induce non-equilibrium doping using an excimer laser. We perform simulations to visualize the maximum melt depth profiles within the poly-Si, with a goal of distributing dopants close to the tunneling oxide, but at the same time preserving the passivation. Hall measurements show that sheet resistance for B is lower than Ga due to its higher solid solubility limit in Si. After comparing the Hall active dopant concentration with the chemical concentration obtained by SIMS measurement, we show nearly 100% activation B activation reaching 10(21) cm(-3), while only similar to 20% activation for Ga. Nevertheless, we achieve active doping concentrations of Ga in poly-Si six times higher than its solid solubility limit in Si (similar to 10(19) cm(-3)). We compare our Hall mobilities with values in the literature for c-Si and show that B mobilities in laser-treated poly-Si are close to that of the literature value for B, while Ga mobilities are lower, possibly due to additional scattering channels within grain boundaries and deformed lattice. We also compare our results on PLM samples with conventional furnace annealed samples, and we show much higher percent activation and mobilities. Previously, we showed a low contact resistivity of 35.5 +/- 2.4 m Omega.cm(2). Here, we further confirm this result by scanning spreading resistance microscopy and Kelvin force nanoprobe microscopy. We demonstrate that our poly-Si: Ga/nCz contact exhibits large drift and diffusion currents under normal cell operating voltage, which widens the laser processing window for a good metal/poly-Si/c-Si contact.

A thick cementite skeleton exposed on a ferritic-pearlitic C1018 steel surface after pre-corrosion significantly compromised inhibition efficiency. However, this detrimental effect was insignificant for a lower carbon X65 steel with dispersed cementite microstructure, due to the insignificant amount of cementite that remained on its surface after pre-corrosion. After normalizing the increased cathodic area in the presence of residual cementite back to original area, both anodic and cathodic reactions were inhibited to the same extent as on bare steel with a sufficient inhibitor concentration. However, the detrimental effect of cementite cannot be completely eliminated due to its galvanic coupling effect.