High Partial Pressure Research Articles

Evolution of Ti2O3 and mullite in Si-Al2O3-fused mullite containing Ti2O3 composite at 1600 °C

Si-Al2O3-fused mullite containing Ti2O3 composite was sintered at 1600 °C in N2. Changes in the structure and activity of fused mullite containing Ti2O3 raw material during the coupled reaction of metallic silicon and Ti2O3 are explored. The mechanism of regulating the phase composition and microstructure of the composite with the changes of Ti2O3 and fused mullite is also revealed. At high temperatures and low oxygen partial pressures, the stability of fused mullite decreases and decomposes to form SiO(g) and alumina-rich mullite. SiO(g) reacts with N2 to form Si3N4, which solidifies with mullite to form X-Sialon, further optimizing the phase composition. With the transformation of Ti2O3 to Ti(C,N)ss, the inhibitory effect of Ti3+ on the growth and development of fused mullite disappears, and the morphology of the fused mullite is gradually transformed from a dense structure to a classical elongated columnar morphology. A model for the mechanism of non-oxide formation and the regulation of micro-morphology is developed.

Reverse water gas-shift reaction product driven dynamic activation of molybdenum nitride catalyst surface

In heterogeneous catalysis catalyst activation is often observed during the reaction process, which is mostly attributed to the induction by reactants. In this work we report that surface structure of molybdenum nitride (MoNx) catalyst exhibits a high dependency on the partial pressure or concentration of reaction products i.e., CO and H2O in reverse water gas-shift reaction (RWGS) (CO2:H2 = 1:3) but not reactants of CO2 and H2. Molybdenum oxide (MoOx) overlayers formed by oxidation with H2O are observed at reaction pressure below 10 mbar or with low partial pressure of CO/H2O products, while CO-induced surface carbonization happens at reaction pressure above 100 mbar and with high partial pressure of CO/H2O products. The reaction products induce restructuring of MoNx surface into more active molybdenum carbide (MoCx) to increase the reaction rate and make for higher partial pressure CO, which in turn promote further surface carbonization of MoNx. We refer to this as the positive feedback between catalytic activity and catalyst activation in RWGS, which should be widely present in heterogeneous catalysis.

Boosting the electrocatalytic activity of NdBaCo2O5+δ via calcium co-doping as bifunctional oxygen electrodes for reversible solid oxide cells

The oxygen electrode of the solid oxide cells (SOCs) operates under an oxidizing atmosphere. Lattice shrinkage in a high oxygen partial pressure environment results in cation misalignment, leading to a decline in performance. Addressing the drawbacks associated with A-site cation mismatch in LnBaCo2O5+δ double perovskite oxides for reversible solid oxide cells (RSOCs) oxygen electrodes, a novel calcium ion co-doping strategy is proposed. This approach effectively mitigates A-site cation segregation and enhances stability. The glycine-nitrate method was employed to synthesize Nd0.8Ca0.2Ba1−xCaxCo2O5+δ (x = 0–0.2) layered double perovskites oxides co-doped with calcium ions, denoted as NCBCC. NCBCC exhibits excellent compatibility with commonly used electrolytes. The doping of calcium co-doped in NdBaCo2O5+δ decreases the thermal expansion coefficient and improves the electron transfer characteristics. The sample with x = 0.1 exhibited an area-specific resistance (ASR) of 0.024 Ω cm2 when operated at a temperature of 800 °C in air. In the solid oxide fuel cell mode, employing x = 0.1 as an oxygen electrode, the maximum power density achieved was 766 mW cm−2 at 800 °C. In the solid oxide electrolysis cell mode, operating with CO2 and steam at an electrolysis voltage of 1.5 V and a temperature of 800 °C, the corresponding current densities were −1.51 and −1.85 A cm−2, respectively. The incorporation of calcium ions into layered perovskite oxides offers a promising strategy to enhance the performance of oxygen electrodes in RSOCs.

Abstract 237: Establishment of an ex vivo tissue culture model as a potential preclinical drug testing platform for hepatocellular carcinoma

Abstract Background: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide, and there is a critical need for more effective treatments. The development of new therapies, especially those aiming to modulate the tumor microenvironment (TME), is limited by the lack of in vitro and in vivo models that recapitulate the complexity of the TME and spatial architecture of HCC. Here, we aimed to establish an HCC model to assess the treatment response and hepatotoxicity of selected drugs by ex vivo culturing fresh human liver tumor tissue and adjacent normal tissue, respectively. Materials and Methods: Fresh human liver tissues, including 5 malignant and 20 adjacent-normal, were obtained from surgical resections. PDX tumors were generated from patient-derived organoids. Tissue resections were cut into ultra-thin slices (from 150µm to 350µm) using a vibratome. Related culture conditions such as high oxygen partial pressure, air-liquid interface (ALI) culture, artificial extracellular matrix (AEM), and delay duration were evaluated to optimize the protocol. As a readout, cell viability was quantified by an expert pathologist using Hematoxylin/Eosin staining. The preservation and complexity of the TME were evaluated by immunohistochemistry or flow cytometry using specific antibodies for each cell population (T cells, anti-CD3; stroma cells, a-SMA; endothelial cells, CD34; Kupffer cells, CD68). Liver cell function was tested by measuring ALT/AST activity, albumin release, and CYP340 activity. Results: The highest tissue viability was observed in normal and tumor tissue with a thickness of 150µm and 250µm, respectively. Compared to standard conditions, the combination of ALI and high-oxygen partial pressure conditions dramatically improved tissue viability, with most of the samples having 70% and 50% cell viability at days 3 and 5 of ex vivo culture, respectively (p<0.05). AEM could prevent the efflux of cellular components (p=0.016). The impact of the time delay between the liver resection and the start of slicing was minimal when the slicing occurred within two hours after hepatectomy (p<0.05). Key cellular components including hepatocytes, T cells, fibroblasts, and Kupffer cells also remained better preserved throughout the 5-day culture period in optimized conditions. Conclusion: Our study has successfully optimized the ex vivo tissue culture model of liver tissue, capable of maintaining the tissue for several days while preserving the unique TME. These results highlight the potential of using the ex vivo tissue culture model in the preclinical setting to further investigate and evaluate TME-related treatments and their hepatotoxicity in HCC tissues. Citation Format: Huiche Feng, Miriam Cieri, Cinzia Esposito, Karolina Guja-Jarosz, Daniela Liberati, Lukas Bubendorf, Savas Deniz Soysal, Mairene Coto-Llerena, Luigi Maria Terracciano, Otto Kollmar, Salvatore Piscuoglio. Establishment of an ex vivo tissue culture model as a potential preclinical drug testing platform for hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 237.

Electrical conductivity, luminescence, and deep acceptor levels in β-Ga2O3-In2O3 polycrystalline solid solution doped with Zr4+ or Ca2+ ions

Photoluminescence, luminescence excitation spectra, and electrical conductivity of β-Ga2O3-In2O3 solid solutions were studied. For this purpose, polycrystalline samples of unintentionally doped (UID) and doped with Ca or Zr β-Ga2O3-In2O3 solid solution with 20% In were synthesized and characterized. All samples were obtained by the high-temperature solid-phase method from appropriate oxides at 1300 °C at low and high oxygen partial pressure. It was established that UID and doped with Ca2+ or Zr4+ samples synthesized in an oxygen atmosphere were highly resistive, while the samples synthesized in an argon atmosphere had high conductivity. The conductivity was the lowest in the samples doped with Ca2+ and was 10−13 Ω−1 cm−1, while in the samples doped with Zr4+, the electrical conductivity was the highest and reached 10−3 Ω−1 cm−1. The broadband luminescence of β-Ga2O3-In2O3 solid solution is a superposition of three elementary bands with maxima in the violet 3.08 eV, blue 2.73 eV, and green 2.45 eV regions of the spectrum. Doping with Ca2+ or Zr4+ impurities and varying the synthesis atmosphere led mainly to a redistribution of intensities between the elementary luminescence bands. The luminescence arises from the radiative recombination of charge carriers through donor–acceptor pairs and self-localized holes. Donors and acceptors are formed by native defects such as (Gai, VGa, VGaVo) or doping impurities (Zr4+, Ca2+). Unlike the luminescence spectra, the luminescence excitation spectra change significantly when the synthesis conditions vary or when doping with divalent impurities. The excitation band at 4.46 eV is due to electron transitions from the VGa or VGaVO acceptor levels to the conduction band. Electron transitions from acceptor levels of Ca2+ impurities are manifested in the intense excitation band at 4.1 eV.

Advances in fast 4H–SiC crystal growth and defect reduction by high-temperature gas-source method

This paper reviews recent progress in the development of high-speed 4H–SiC bulk crystal growth technology using the high-temperature gas-source method (high-temperature chemical vapor deposition). Vertical-type reactors capable of growing SiC bulk crystals of 50–75 and 100–150 mm in diameter have been developed, as have reactor configurations and growth conditions to achieve a high growth rate and material quality. Using the reactors, high growth rates up to or exceeding 3 mm/h have been achieved by employing an H2–SiH4–C3H8 gas system with high partial pressures of source gases and high growth temperature of 2500–2550 °C. It is also confirmed that the dislocation densities decline significantly in the direction of growth under proper growth conditions. Key factors for enhancing growth rate and improving crystal quality in the growth process are discussed.

Understanding the Reverse Water Gas Shift Reaction over Mo2C MXene Catalyst: A Holistic Computational Analysis

AbstractPristine Mo2C MXene has been proposed as an heterogeneous catalysis of the reverse water gas shift (RWGS) reaction. The present computational study aims at understanding its catalytic performance and reaction mechanisms tackling its thermodynamics, kinetics, and surface dynamic effects, combining Gibbs free energy profiles gained by density functional theory (DFT), mean‐field kinetics by microkinetic modeling, and rare‐event steps by kinetic Monte Carlo (kMC). The RWGS endergonicity goes for the use of high temperatures and reactants partial pressures to make the reaction exergonic. Gibbs free energy profiles show a preference for redox mechanism, whereas microkinetic simulations favor a low‐temperature preference of formate mechanism. The kMC reveals simultaneous operating redox and formate pathways, where surface coverage disfavors redox favoring the formate pathway. A peak performance is found at 700 K, in line with reported experiments, where the formation of surface O2* is found to be key, acting as a reservoir for O* adatoms while freeing surface sites upon O2* formation. Even though high turnover frequencies are predicted, the system could benefit from swing operando conditions, alternating CO production steps with H2 reduction regeneration steps, and/or ways to reduce the surface O2* and so to have more active catalytic sites.

Short-term salt stress reduces photosynthetic oscillations under triose phosphate utilization limitation in tomato.

Triose phosphate utilization (TPU) limitation is one of the three biochemical limitations of photosynthetic CO2 assimilation rate in C3 plants. Under TPU limitation, abrupt and large transitions in light intensity cause damped oscillations in photosynthesis. When plants are salt-stressed, photosynthesis is often down-regulated particularly under dynamic light intensity, but how salt stress affects TPU-related dynamic photosynthesis is still unknown. To elucidate this, tomato (Solanum lycopersicum) was grown with and without sodium chloride (NaCl, 100 mM) stress for 13 d. Under high CO2 partial pressure, rapid increases in light intensity caused profound photosynthetic oscillations. Salt stress reduced photosynthetic oscillations in leaves initially under both low- and high-light conditions and reduced the duration of oscillations by about 2 min. Besides, salt stress increased the threshold for CO2 partial pressure at which oscillations occurred. Salt stress increased TPU capacity without affecting Rubisco carboxylation and electron transport capacity, indicating the up-regulation of end-product synthesis capacity in photosynthesis. Thus salt stress may reduce photosynthetic oscillations by decreasing leaf internal CO2 partial pressure and/or increasing TPU capacity. Our results provide new insights into how salt stress modulates dynamic photosynthesis as controlled by CO2 availability and end-product synthesis.

Transitioning from Methanol to Olefins (MTO) toward a Tandem CO2 Hydrogenation Process: On the Role and Fate of Heteroatoms (Mg, Si) in MAPO-18 Zeotypes.

The tandem CO2 hydrogenation to hydrocarbons over mixed metal oxide/zeolite catalysts (OXZEO) is an efficient way of producing value-added hydrocarbons (platform chemicals and fuels) directly from CO2via methanol intermediate in a single reactor. In this contribution, two MAPO-18 zeotypes (M = Mg, Si) were tested and their performance was compared under methanol-to-olefins (MTO) conditions (350 °C, PCH3OH = 0.04 bar, 6.5 gCH3OH h-1 g-1), methanol/CO/H2 cofeed conditions (350 °C, PCH3OH/PCO/PH2 = 1:7.3:21.7 bar, 2.5 gCH3OH h-1 g-1), and tandem CO2 hydrogenation-to-olefin conditions (350 °C, PCO2/PH2 = 7.5:22.5 bar, 1.4-12.0 gMAPO-18 h molCO2-1). In the latter case, the zeotypes were mixed with a fixed amount of ZnO:ZrO2 catalyst, well-known for the conversion of CO2/H2 to methanol. Focus was set on the methanol conversion activity, product selectivity, and performance stability with time-on-stream. In situ and ex situ Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), sorption experiments, and ab initio molecular dynamics (AIMD) calculations were performed to correlate material performance with material characteristics. The catalytic tests demonstrated the better performance of MgAPO-18 versus SAPO-18 at MTO conditions, the much superior performance of MgAPO-18 under methanol/CO/H2 cofeeds, and yet the increasingly similar performance of the two materials under tandem conditions upon increasing the zeotype-to-oxide ratio in the tandem catalyst bed. In situ FT-IR measurements coupled with AIMD calculations revealed differences in the MTO initiation mechanism between the two materials. SAPO-18 promoted initial CO2 formation, indicative of a formaldehyde-based decarboxylation mechanism, while CO and ketene were the main constituents of the initiation pool in MgAPO-18, suggesting a decarbonylation mechanism. Under tandem CO2 hydrogenation conditions, the presence of high water concentrations and low methanol partial pressure in the reaction medium led to lower, and increasingly similar, methanol turnover frequencies for the zeotypes. Despite both MAPO-18 zeotypes showing signs of activity loss upon storage due to the interaction of the sites with ambient humidity, they presented a remarkable stability after reaching steady state under tandem reaction conditions and after steaming and regeneration cycles at high temperatures. Water adsorption experiments at room temperature confirmed this observation. The faster activity loss observed in the Mg version is assigned to its harder Mg2+-ion character and the higher concentration of CHA defects in the AEI structure, identified by solid-state NMR and XRD. The low stability of a MgAPO-34 zeotype (CHA structure) upon storage corroborated the relationship between CHA defects and instability.

Anaerobic dihydrogen consumption of nutrient-limited aquifer sediment microbial communities examined by stable isotope analysis

ABSTRACT The biogeochemical consequences of dihydrogen (H2) underground storage in porous aquifers are poorly understood. Here, the effects of nutrient limitations on anaerobic H2 oxidation of an aquifer microbial community in sediment microcosms were determined in order to evaluate possible responses to high H2 partial pressures. Hydrogen isotope analyses of H2 yielded isotope depletion in all biotic setups indicating microbial H2 consumption. Carbon isotope analyses of carbon dioxide (CO2) showed isotope enrichment in all H2-supplemented biotic setups indicating H2-dependent consumption of CO2 by methanogens or homoacetogens. Homoacetogenesis was indicated by the detection of acetate and formate. Consumption of CO2 and H2 varied along the differently nutrient-amended setups, as did the onset of methane production. Plotting carbon against hydrogen isotope signatures of CH4 indicated that CH4 was produced hydrogenotrophically and fermentatively. The putative hydrogenotrophic Methanobacterium sp. was the dominant methanogen. Most abundant phylotypes belonged to typical ferric iron reducers, indicating that besides CO2, Fe(III) was an important electron acceptor. In summary, our study provides evidence for the adaptability of subsurface microbial communities under different nutrient-deficient conditions to elevated H2 partial pressures.

Re-evaluating the impact of feeding shock on anaerobic co-digestion of food waste and waste activated sludge: Trade-off between efficiency and stability

To optimize the feeding strategy of anaerobic digestion (AD) treating food waste and waste activated sludge, the impact of relative feeding shock (RFS) on the trade-off between efficiency and stability was re-evaluated at six feeding conditions from 1/96 (approximate continuous feeding) to 1. The results showed that increasing the RFS from 1/96 to 1/3 increased the CH4 yield from 293.23 mL CH4/g-total solid (TS) to the maximum value of 345.11 mL CH4/g-TS, which was due to the highest specific microbial growth rates (μmax) of acetate (1.05d-1) and propionate (0.48d-1) and a balanced reaction rate between acidogenesis and methanogenesis. However, when the RFS increased to 1, the total volatile fatty acids (TVFA) concentration increased from 0.51 to 5.90 g-COD/L, with the predominant VFAs changing from acetate to propionate, limiting methanogenesis. Meanwhile, the stability coefficient decreased to 0.37, leading to decreased CH4 yield and μmax. In addition, the high hydrogen partial pressure caused by high RFS increased the Gibbs free energy by 17 %, aggravating the thermodynamic disadvantages. The abundant methanogens shifted from Methanosaeta to Methanosarcina, which cooperated with a syntrophic partner-Syntrophomonas to ensure the smooth VFAs degradation at RFS of 1/3. These findings provide prima facie insights into the optimization of operational conditions for AD treating organic wastes.

Anti-corrosion study of tungsten alloy coating on tube column under high CO2 partial pressure

In order to address the low-cost corrosion prevention of wellbore tubing in high-temperature and high-pressure gas injection development environments, tungsten alloy-coated tubing specimens were selected for corrosion experiments. Microscopic characterization techniques such as SEM/EDS were used to analyze the corrosion product composition, phase structure, and three-dimensional morphology of the specimens. Uniform corrosion rates and localized pitting corrosion rates of the specimens were tested separately. Based on the uniform corrosion rate, residual strength verification and service life prediction of the tubing after corrosion were conducted. The study revealed that in a simulated gas injection development corrosion environment at a high temperature of 190 °C, as the CO2 partial pressure increased, both the uniform corrosion rate and pitting corrosion rate of the tungsten alloy-coated specimens gradually increased. When the CO2 content reached 100%, the uniform corrosion rate was 0.4300 mm/a, and the pitting corrosion rate was 0.4684 mm/a. The main substances causing material corrosion were O, Cl, and S in the environment. Furthermore, with the increasing CO2 partial pressure, the damage to the tungsten alloy coating on the specimen's surface deepened. By verifying the residual strength of the tubing after corrosion, it was found that at a temperature of 190 °C and a CO2 content of 38%, the tensile safety factor of the production tubing exceeded the critical value in the 10th year, and the casing's tensile safety factor exceeded the critical value in the 36th year. This research can provide reference insights for the selection of tungsten alloy coatings for corrosion prevention in gas injection wellbore tubing.

The Effect of Bismuth and Tin on Methane and Acetate Production in a Microbial Electrosynthesis Cell Fed with Carbon Dioxide.

This study investigates the impacts of bismuth and tin on the production of CH4 and volatile fatty acids in a microbial electrosynthesis cell with a continuous CO2 supply. First, the impact of several transition metal ions (Ni2+, Fe2+, Cu2+, Sn2+, Mn2+, MoO42-, and Bi3+) on hydrogenotrophic and acetoclastic methanogenic microbial activity was evaluated in a series of batch bottle tests incubated with anaerobic sludge and a pre-defined concentration of dissolved transition metals. While Cu is considered a promising catalyst for the electrocatalytic conversion of CO2 to short chain fatty acids such as acetate, its presence as a Cu2+ ion was demonstrated to significantly inhibit the microbial production of CH4 and acetate. At the same time, CH4 production increased in the presence of Bi3+ (0.1 g L-1) and remained unchanged at the same concentration of Sn2+. Since Sn is of interest due to its catalytic properties in the electrochemical CO2 conversion, Bi and Sn were added to the cathode compartment of a laboratory-scale microbial electrosynthesis cell (MESC) to achieve an initial concentration of 0.1 g L-1. While an initial increase in CH4 (and acetate for Sn2+) production was observed after the first injection of the metal ions, after the second injection, CH4 production declined. Acetate accumulation was indicative of the reduced activity of acetoclastic methanogens, likely due to the high partial pressure of H2. The modification of a carbon-felt electrode by the electrodeposition of Sn metal on its surface prior to cathode inoculation with anaerobic sludge showed a doubling of CH4 production in the MESC and a lower concentration of acetate, while the electrodeposition of Bi resulted in a decreased CH4 production.

Development of a genetic engineering toolbox for syngas-utilizing acetogen Clostridium sp. AWRP

BackgroundClostridium sp. AWRP (AWRP) is a novel acetogenic bacterium isolated under high partial pressure of carbon monoxide (CO) and can be one of promising candidates for alcohol production from carbon oxides. Compared to model strains such as C. ljungdahlii and C. autoethanogenum, however, genetic manipulation of AWRP has not been established, preventing studies on its physiological characteristics and metabolic engineering.ResultsWe were able to demonstrate the genetic domestication of AWRP, including transformation of shuttle plasmids, promoter characterization, and genome editing. From the conjugation experiment with E. coli S17-1, among the four replicons tested (pCB102, pAMβ1, pIP404, and pIM13), three replicated in AWRP but pCB102 was the only one that could be transferred by electroporation. DNA methylation in E. coli significantly influenced transformation efficiencies in AWRP: the highest transformation efficiencies (102–103 CFU/µg) were achieved with unmethylated plasmid DNA. Determination of strengths of several clostridial promoters enabled the establishment of a CRISPR/Cas12a genome editing system based on Acidaminococcus sp. BV3L6 cas12a gene; interestingly, the commonly used CRISPR/Cas9 system did not work in AWRP, although it expressed the weakest promoter (C. acetobutylicum Pptb) tested. This system was successfully employed for the single gene deletion (xylB and pyrE) and double deletion of two prophage gene clusters.ConclusionsThe presented genome editing system allowed us to achieve several genome manipulations, including double deletion of two large prophage groups. The genetic toolbox developed in this study will offer a chance for deeper studies on Clostridium sp. AWRP for syngas fermentation and carbon dioxide (CO2) sequestration.

Oxygen Toxicity

In a broad sense, if the oxygen partial pressure is higher than the oxygen partial pressure at atmospheric pressure (21kPa), they can be called high partial pressure oxygen or hyperoxia. Hyperoxia is often used in diving operations, underwater special operations and clinic treatment. When in diving operations. Hyperoxia can shorten the decompression time after diving and avoid decompression sickness. In underwater special operations, a fully closed breathing apparatus is used to breathe high partial pressure. Oxygen can also improve its concealment. Hyperoxia can also improve the function of ischemic and hypoxic tissues in clinic treatment. However, if the oxygen pressure exceeds a certain threshold, or the breathing oxygen exceeds a certain time, it will cause adverse effects on the body, that is, oxygen toxicity. Currently, oxygen toxicity is a major factor that limited oxygen use in diving operations, underwater special operations, and clinical treatment. Oxygen toxicity is divided into lung type, brain type and eye type. When the oxygen partial pressure is between at 60 ~ 200 kPa, the damage to the body is mainly manifested in the lungs. It is called pulmonary oxygen toxicity. When the oxygen partial pressure exceeds 300 kpa, the damage caused by oxygen toxicity is mainly manifested in the central nervous system, which is called central nervous system oxygen toxicity or brain-type oxygen toxicity.

Reoxidation Phenomena of Liquid Steel in Secondary Refining and Continuous Casting Processes: A Review

This review article reports the critical issue of reoxidation in clean steel production during secondary refining and continuous casting processes. Reoxidation presents substantial challenges to process stability and final product quality. Various sources of reoxidation, including exposure to oxidizing gases, reducible oxides in slag and refractories, and the presence of ferroalloys are explored. Fundamental reactions and their consequences, such as changes in steel composition, inclusion composition/morphology, and the formation of reaction products at the interface between liquid steel and refractory materials, are reviewed. High oxygen partial pressure on the refractory side is identified as a significant factor, particularly in tundish and continuous casting processes. To address reoxidation effectively, the review discusses modeling approaches like computational fluid dynamics and thermodynamic/kinetic modeling. In the industrial context, reoxidation in the tundish is mainly attributed to open‐eye formation in the tundish flux and reducible oxides like SiO2 in an insulating cover powder, for example, rice hust ash. Maintaining precise tundish flux control is crucial for steel cleanliness. In conclusion, this review highlights the multifaceted nature of reoxidation challenges in clean steel production. A comprehensive understanding of reoxidation mechanisms and the implementation of effective strategies are essential for achieving cleaner steel production.

Comparative investigation on high-pressure flow accelerated corrosion at gradual contraction and gradual expansion pipes

In current study, the flow accelerated corrosion behaviors of X65 steel gradual contraction and gradual expansion pipes under high-pressure conditions were comparatively investigated by establishing dynamic in situ electrochemical tests under high CO2 partial pressure conditions in a loop apparatus. The findings indicate that the corrosion rate is reduced along the flowing direction of gradual contraction pipe. Nevertheless, the corrosion rate firstly descends and subsequently ascends along the flowing direction of gradual expansion pipe, and the lowest corrosion rate is presented in inclination segment close to the straight pipe with large diameter. The corrosion rate at the top wall of gradual contraction pipe is symmetrical to that at the bottom wall, while it is asymmetrically distributed at the top wall and the bottom wall of inclination segment in gradual expansion pipe. The distribution of corrosion rate is correlated with the flow fields at gradual contraction and gradual expansion pipes. Furthermore, the special corrosion rate distribution at inclination segment of gradual expansion pipe is ascribed to the formation of secondary flow and vortexes.

Atomic Layer Depostion within Polymers Templates for Spatially Controlled Growth and Doped Materials

Today’s nanofabrication techniques require multistep and costly processes in order to fabricate complex, multi-materials nanostructures. Performing atomic layer deposition (ALD) within polymeric templates can offer a simple solution for nanostructure fabrication. In this process, named sequential infiltration synthesis (SIS), high partial pressures and long exposures times lead to inorganic materials growth within polymers. Sequential polymer removal results in polymer-templated inorganic nanostructure. While SIS shows great potential in fabricating large variety of structures, it is currently limited to a single material growth process.In our research, we utilized SIS properties to achieve two different objectives: selective spatial growth and homogenous growth for doped materials. We demonstrated, for the first time, multi-material SIS process with control over the spatial location of each material and fabricate heterostructure nanorods and nanowires. Doping materials were fabricated using simultaneously growth of two precursors.We studied SIS within self-assembled block copolymer (BCP) films and electrospun polymer fibers and developed multi-material SIS, where two metal oxides are grown together in a single process, with precise control over their location within the polymer template. We used cylinder forming poly (styrene-block-methyl methacrylate) (PS-b-PMMA) films and electrospun PMMA as the polymeric template and DEZ (diethyl zinc), TMA (trimethyl aluminum) as the organometallic precursors. We achieved control over the growth location of each metal oxide by tuning the organometallic precursors diffusion time, forming heterostructures after polymer removal. A short exposure of the first precursor resulted in a limited growth only at the outer part of the polymer, while a long exposure of the second precursor enabled it to reach the full depth of the polymer besides the section which was already occupied by the first precursor. An exposure to water completed the cycle. We demonstrated this process on BCP films to achieve AlOx-ZnO nanorods arrays (Figure 1A-B) and on polymer fibers to achieve AlOx-ZnO fibers (Figure 1C-D). We performed structural characterization using scanning and transmission electron microscopy (SEM and TEM, respectively) to characterize the nanowires and nanorods as well as three-dimensional characterization scanning TEM (STEM) tomography and energy-dispersive X-ray spectroscopy (EDS) STEM tomography in order to probe the structure and the chemical composition in 3D. To fabricate doped materials, we applied SIS process with TMA and DEZ in the same exposure within homopolymer film. We preformed SEM-EDS to quantify each element and evaluate the doping percentage. This research opens new pathways for multi-materials nano scale structure fabrication through ALD-based growth within polymers.Figure 1 caption: AlOx-ZnO nanorods array: cross-sectional views using A) EsB detector and B) secondary electron in-lens detector. AlOx-ZnO fibers C) EDS map D) HAADF image [1] R. Azoulay et al., Small, 15, 1904657 (2019).[2] R. Azoulay et al., ACS Appl. Nano Mater., 5, 7228 (2022). Figure 1

Highly Conducting Sc and Y co-doped Zirconia Solid Electrolyte Thin Films Prepared via Pulsed Laser Deposition for Solid Oxide Electrochemical Cells Applications

Scandium (Sc) and yttrium (Y) co-doped ZrO2 thin films were fabricated via pulsed laser deposition (PLD). The target material, 4 mol% Sc2O3 and 4 mol% Y2O3 co-doped ZrO2 (ScYSZ), was first synthesized via a solid-state reaction. The ScYSZ thin film was deposited on SiO2-Si substrate by laser ablation, using a Q-switched Nd3+:YAG laser (λ = 266 nm) and substrate temperatures of 600 and 800 oC. Micro-structural and conductivity properties of the resulting as-deposited thin films were investigated. X-ray diffraction (XRD) sample patterns revealed that the as-deposited polycrystalline films can be indexed to a cubic structure. In addition, varying the oxygen partial pressures during the deposition was studied. FE-SEM images revealed dense and crack-free surface morphologies achieved at lower oxygen partial pressures (0.01 Pa and 0.1 Pa) and rough surface with porous morphology at high oxygen partial pressures (1.0 Pa and 10 Pa). The thickness of the film is about 120 nm for the thin film deposited at 800 oC substrate temperature (TS). The total conductivity of the thin film was measured using electrochemical impedance spectroscopy (EIS). Interestingly, the calculated total conductivity of the deposited ScYSZ thin film, 0.1 Pa and TS at 800 oC, revealed about 2.8x10-1 S/cmat 700 oC and with activation energy (Ea) of 0.78 eV from 500 oC to 700 oC. The fabricated as-deposited ScYSZ thin film is one of the highest reported highly conducting solid electrolytes that is a promising material for fuel cell or electrolysis cell applications.

Degradation Issues in Solid Oxide Electrolysers

One of the crucial aspects to achieving long lifetime and high-efficient SOCs (Solid oxide cells) is to enhance durability of the current devices.Degradation issues are typically associated with problems in both electrodes. For example, nickel-yttria stabilized zirconia (Ni-YSZ) hydrogen electrodes present under extreme conditions of high steam partial pressures, a low durability due to Ni oxidation resulting in lowered electronic conductivity and catalytic activity of the electrode. Ni agglomeration, depleting and micro crack in Ni-containing hydrogen electrode can also occur leading to a lower activity of the Ni-based electrodes as an SOEC fuel electrode. Furthermore, carbon deposition and sulfur poisoning on the Ni surface are also lead to cell performance degradation and poor durability.In addition, the performance of the oxygen electrode is also particularly more important in electrolysis mode than in fuel cell mode, as it is well established that electrochemically induced oxygen pressure increase at the electrolyte-oxygen electrode interface and subsequent membrane failure have been theoretically predicted and experimentally observed in SOEC mode. For example, several examples in the literature reported the presence on voids at the YSZ electrolyte, leading to delamination of the oxygen electrode. In this sense, lanthanide nickelates (Ln = La, Nd, Pr) have received considerable interest as materials for IT-SOFC electrodes and oxygen separation membranes, and they seem to be very attractive for electrolysis applications. The hyperstoichiometry of some oxygen electrode materials such as these Ruddlesden-Popper phases is believed to be favourable for effective oxygen evolution, as performance of these electrodes is enhanced in SOEC mode.Different strategies to develop optimized electrode structures as well as controlled operating conditions will be discussed in order to improve the durability of SOCs.