Water Vapor Environment Research Articles

Atomic mechanisms of oxidative behavior of ferrochromium alloys by water-oxygen environment

The formation of chromium-rich oxide layers on the surface of Fe-Cr alloys significantly impacts their performance at elevated temperatures. Understanding the formation process of these oxide layers at the atomic scale is crucial for further elucidating oxidation behavior, though it presents substantial challenges. In this study, ReaxFF molecular dynamics simulations were used to investigate the oxidation behavior of Fe-Cr alloys in high temperature water vapor and oxygen environments. The results demonstrate that chromium atoms are the primary contributors to the oxidation process, with Cr atoms diffusing to the surface more readily than iron atoms, leading to uneven stress distribution and creating high-stress regions near the Cr atoms. Additionally, hydrogen atoms generated from the breakdown of water molecules infiltrate the alloy matrix, promoting the creation, movement, and clustering of cation and anion vacancies, thereby enhancing oxidation reactions in high-temperature, humid conditions. The study further analyzes electron transfer during single-atom chemical reactions and explores the linear relationship between varying Cr content (10 %–30 %) and oxidation behavior under identical environmental conditions. These findings provide an important theoretical basis for optimizing the performance of Fe-Cr alloys for applications in high temperature environments.

Properties of Si/Yb2SiO5/LaMgAl11O19 tri-layered EBCs in high-temperature water vapor environment

SiCf/SiC with fully wrapped Si/Yb2SiO5/LaMgAl11O19 tri-layered environmental barrier coatings (EBCs) were subjected to high-temperature water vapor corrosion tests for 40, 100, and 200 h at 1200 °C. The flexural strength of the specimens was then evaluated. These results demonstrate that the EBCs exhibit excellent resistance to water vapor corrosion. After 40 h of exposure, the flexural strength retention rate of the specimens with EBCs was greater than 96 %, which was more than three times higher than that of the specimens without EBCs. Conversely, the flexural strength of the SiCf/SiC without EBCs decreased significantly following the water corrosion test. Within 100 h of exposure, the SiCf/SiC specimens without EBCs still showed “pseudo-plastic” fractures, while after 200 h, the entire specimens became loose and deformed due to severe corrosion.

Unveiling the Structural and Chemical Evolution of Layered Oxide Cathode for Na‐Ion Batteries Induced by Water Vapor

AbstractNa‐ion batteries (NIBs) have received considerable attention as promising alternatives to lithium‐ion batteries, particularly for low‐speed electric vehicles and large‐scale energy storage applications. Currently, layered oxide compounds are considered the most important cathode materials for NIBs. However, they suffer from reduced capacity and a shortened lifespan when exposed to water vapor during storage or battery assembly. This article elaborates on the structural and chemical evolution of NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode at the atomic scale in a pure water vapor environment. The Na+/H+ exchange induces the formation of a spinel‐like phase via a multi‐site nucleation mechanism. This transition preferentially occurs either at the cathode surface or along planar defects such as twin boundaries and grain boundaries. Additionally, numerous microcracks perpendicular to <003> direction appear inside NFM grains, further exacerbating the structural deterioration. Upon prolonged exposure to water vapor, NFM grains decompose into a mixture of Na2O and transition metal oxide nanoparticles (FeO, NiO, and MnO), accompanied by the generation of oxygen gas. This research provides a comprehensive atomic‐scale insight into the water vapor instability mechanism of layered oxide cathodes, offering guidance for the design and manufacture of the next generation of water vapor‐tolerant layered oxide cathodes in NIBs.

Promoting fine particle removal in cyclone by spray agglomeration and heterogeneous condensation

By adding a spray chamber in front of the cyclone separator, spray agglomeration and heterogeneous vapor condensation were combined to improve the removal effect of the cyclone separator on fine particles, which is used for the deep treatment of high-humidity industrial flue gas and fine particles. Fine particles can form agglomerates through the capture effect of micron droplets, and can also grow in size through heterogeneous vapor condensation in supersaturated water vapor environment, thus being effectively removed by cyclone separators. Supersaturated water vapor environment was a necessary condition for heterogeneous vapor condensation. Numerical simulation results showed that supersaturated water vapor environment can be formed in the spray chamber when the relative humidity of the original flue gas was high, and the higher the relative humidity, the higher the supersaturation and the larger the supersaturation area. The experimental results indicated that spray agglomeration and spray coupling heterogeneous condensation increased the particle removal efficiency of the cyclone separator by 11.6 % and 22.6 %, and the removal efficiency in the 2–4 μm “fish-hook” range was increased by 21.6 % and 41.7 %, respectively. This technology was successfully applied for the first time in the deep treatment of the tail gas in Fluid Catalytic Cracking (FCC) catalyst production industry, which can ensure that the particle emission concentration was within 20 mg/Nm3.

Improving the removal of fine particles in cyclone using heterogeneous vapor condensation enhanced by atomization

Using a heat exchanger to cool high humidity flue gas can create a supersaturated water vapor environment, allowing fine particles to grow into large droplets by heterogeneous vapor condensation, which is conductive to the removal of fine particles by traditional equipment. However, due to the limited condensable vapor obtained by cooling, this technology can only be used in the flue gas with low particle concentration. In this study, atomization droplets were added before the heat exchanger to improve the effect of heterogeneous vapor condensation at high particle concentration, and then coupled with a cyclone separator, which was used for the deep treatment of the flue gas after the wet dedusting system. The particle removal characteristics were investigated through laboratory experiments and bypass experiments in a metallurgical company. The experimental results show that the application of atomization-heterogeneous condensation reduced the particles concentration after cyclone by 74.2 % compared with that of single heterogeneous condensation. Temperature-drop and atomized volume affected the removal of particles with size < 2 μm and > 2 μm, respectively. The industrial flue gas bypass experiment indicated that the system had strong adaptability to fluctuating conditions. When the inlet particle concentration did not exceed 2000 mg/Nm3, the outlet particle concentration can be maintained within 20 mg/Nm3.

Influence mechanism of further hydration on the compressive strength of ultra-high performance concrete with coarse aggregates

A further hydration test was conducted to study the effects of temperature and humidity conditions on the compressive strength and microstructure of ultra-high performance concrete with coarse aggregates (UHPC-CA), while analyzing the mechanisms influencing its compressive strength. The results indicated that the higher temperatures resulted in more significant strength and pore structure variations, with strength and pore structure changes being greater in liquid water environments compared to water vapor environments. The hardness of interfacial transition zone (ITZ) increased initially and then declined. The influence of further hydration on the strength of UHPC-CA was primarily divided into three stages: enhancement, damage and filling. These findings provide a theoretical foundation for the evaluation and design of UHPC materials for long-term service in aquatic environments.

Study on the modification and mechanism of N-Mo co-doping for U-2.0Nb alloy surface by pulsed laser

The surface of a U-2.0Nb alloy pre-coated with a Mo layer was successfully modified by pulsed laser in N2 gas, resulting in an N-Mo co-doped layer. Evaluation of this layer at 363 K in a water vapor environment demonstrated its exceptional corrosion resistance for the U-2.0Nb substrate. Analysis using XRD and XPS revealed that the layer comprises uranium nitrides (UN and UO2-xNy) and uranium alloys (U, Nb, Mo), whose chemical stability and distribution are crucial for significantly enhancing corrosion resistance. This study also confirms that high-energy pulsed laser modification induces the sequential formation of reactants, favoring those with higher melting points. This technology shows promise for developing high melting point, ablation-resistant layers and enhancing the corrosion resistance of advanced nuclear fuels like UN/UC/UC1-xNx, thereby broadening the application scope of pulsed laser modifications.

Positive and Negative Impacts of Interfacial Hydrogen Bonds on Photocatalytic Hydrogen Evolution.

Understanding the behavior of water molecules at solid-liquid interfaces is crucial for various applications such as photocatalytic water splitting, a key technology for sustainable fuel production and chemical transformations. Despite extensive studies conducted in the past, the impact of the microscopic structure of interfacial water molecules on photocatalytic reactivity has not been directly examined. In this study, using real-time mass spectrometry and Fourier-transform infrared spectroscopy, we demonstrated the crucial role of hydrogen bond (H-bond) networks on the photocatalytic hydrogen evolution in thickness-controlled water adsorption layers on various TiO2 photocatalysts. Under controlled water vapor environments with relative humidity (RH) below 70%, we observed a monotonic increase in the H2 formation rate with increasing RH, indicating that reactive water molecules were present not only in the first adsorbed layer but also in several overlying layers. In contrast, at RH > 70%, when more than three water layers covered the catalyst surface, the H2 formation rate turned to decrease dramatically because of the structural rearrangement and hardening of the interfacial H-bond network induced during further water adsorption. This unique many-body effect of interfacial water was consistently observed for various TiO2 particles with different crystalline structures, including brookite, anatase, and a mixture of anatase and rutile. Our results demonstrated that depositing several water layers in a water vapor environment with RH ∼ 70% is optimal for photocatalytic hydrogen evolution rather than liquid-phase reaction conditions in aqueous solutions. This study provides molecular-level insights into designing interfacial water conditions to enhance photocatalytic performance.

24-h continuous non-invasive multiparameter home monitoring of vitals in patients with Rett syndrome by an innovative wearable technology: evidence of an overlooked chronic fatigue status.

Sleep is disturbed in Rett syndrome (RTT), a rare and progressive neurodevelopmental disorder primarily affecting female patients (prevalence 7.1/100,000 female patients) linked to pathogenic variations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Autonomic nervous system dysfunction with a predominance of the sympathetic nervous system (SNS) over the parasympathetic nervous system (PSNS) is reported in RTT, along with exercise fatigue and increased sudden death risk. The aim of the present study was to test the feasibility of a continuous 24 h non-invasive home monitoring of the biological vitals (biovitals) by an innovative wearable sensor device in pediatric and adolescent/adult RTT patients. A total of 10 female patients (mean age 18.3 ± 9.4 years, range 4.7-35.5 years) with typical RTT and MECP2 pathogenic variations were enrolled. Clinical severity was assessed by validated scales. Heart rate (HR), respiratory rate (RR), and skin temperature (SkT) were monitored by the YouCare Wearable Medical Device (Accyourate Group SpA, L'Aquila, Italy). The average percentage of maximum HR (HRmax%) was calculated. Heart rate variability (HRV) was expressed by consolidated time-domain and frequency-domain parameters. The HR/LF (low frequency) ratio, indicating SNS activation under dynamic exercise, was calculated. Simultaneous continuous measurement of indoor air quality variables was performed and the patients' contributions to the surrounding water vapor partial pressure [PH2O (pt)] and carbon dioxide [PCO2 (pt)] were indirectly estimated. Of the 6,559.79 h of biovital recordings, 5051.03 h (77%) were valid for data interpretation. Sleep and wake hours were 9.0 ± 1.1 h and 14.9 ± 1.1 h, respectively. HRmax % [median: 71.86% (interquartile range 61.03-82%)] and HR/LF [median: 3.75 (interquartile range 3.19-5.05)] were elevated, independent from the wake-sleep cycle. The majority of HRV time- and frequency-domain parameters were significantly higher in the pediatric patients (p ≤ 0.031). The HRV HR/LF ratio was associated with phenotype severity, disease progression, clinical sleep disorder, subclinical hypoxia, and electroencephalographic observations of multifocal epileptic activity and general background slowing. Our findings indicate the feasibility of a continuous 24-h non-invasive home monitoring of biovital parameters in RTT. Moreover, for the first time, HRmax% and the HR/LF ratio were identified as potential objective markers of fatigue, illness severity, and disease progression.

Stressed oxidation behaviour of 3D C/SiC in water/oxygen/Na2SO4 coupled environment

Present work compared the stressed oxidation behavior of thin interlayer 3D C/SiC composites (3DCSC-A) and normal 3D C/SiC composites (3DCSC-B) under coupled environment, founding 3DCSC-A had better anti-fatigue property in the water vapor environment. Oxygen is the primary cause of stressed oxidation damage, and water vapor and Na2SO4 vapor accelerate the stressed oxidation damage of 3DCSC-A composites. The reaction rate of oxygen with the carbon phase is higher than that with the SiC phase. The oxidation of the carbon phase promotes the expansion of cracks within interfaces and cross-sections, leading to damage failure in the load-bearing areas.

Predictive model for the ignition and combustion behaviors of micron-sized aluminum particles in a water vapor environment

Predictive model for the ignition and combustion behaviors of micron-sized aluminum particles in a water vapor environment

Kinetic Analysis of the Reaction of Micrometer-Sized Al-Mg Alloy Particles in a Water Vapor Atmosphere.

This study investigated the reaction mechanism of aluminum-magnesium (Al-Mg) alloy particles with water (Al-Mg/H2O) through thermogravimetric analysis-differential scanning calorimetry experiments and kinetic analysis using isoconversional methods and the master plot technique to determine the reaction mechanism function, with the aim of providing insights to support metal powder/water ramjet engine design and combustion characteristics. The results showed that the Al-Mg/H2O reaction occurred in two distinct stages, with stage 1 primarily involving the reaction of Mg elements in the L(Al-Mg) alloy with water while Al played a leading role in stage 2. Notably, the reaction temperatures of Al-Mg particles were significantly lower than those for either Al or Mg particles alone in a water vapor environment. Additionally, the activation energy of stage 1 was lower than that for the individual Al and Mg particles and decreased with increasing Mg content in stage 2. Furthermore, the concentration of Mg in the alloy was found to have a major influence on the reaction mechanism, which followed a random nucleation and growth model. Overall, this work elucidated an alternating endothermic and exothermic staged reaction process for Al-Mg/H2O dominated first by Mg and then Al with kinetic insights providing theoretical support for optimizing Al-Mg alloy compositions for improved ignition and combustion performance in metal powder/water ramjet engines.

Effect of Sc and Gd co-doping on the oxidation behavior of FeCrAl alloys in water vapor environment at 1000°C

Rare earth Sc, Gd double doped alloys FeCrAl-xScxGd with different compositions (x=0.25, 0.5, 1.0, 2.0) were prepared by vacuum hot press sintering, and their microstructures were investigated. The double-doped alloy FeCrAl-xScxGd was also oxidized with the single-doped alloys FeCrAl-xSc and FeCrAl-xGd (as a control variable) at high temperature water vapor oxidation at 1000 ℃ for 100 h, and the oxidation kinetic curves were investigated. It is concluded that they have positive effects on the enhancement of the oxidation resistance of FeCrAl alloys in different aspects, while there is no "synergistic effect" of Sc and Gd rare earth elements on the oxidation kinetics of FeCrAl alloys. In FeCrAl alloys, the element Gd not only exists as Gd monomer, but also forms two intermetallic compounds of Gd and Fe, Fe5Gd and Fe9Gd, and the oxide Gd3Fe2Al3O12, which hinders the outward diffusion of Al and reduces its oxidation rate. The element Sc, on the other hand, undergoes longitudinal segregation at the oxide grain boundaries and produces a pinning effect on the alumina scale, which enhances the bonding at the oxide scale/alloy interface, thus preventing the growth of new oxide grains and the generation of new nucleation sites at the alumina scale/alloy interface, thus having a positive effect on the alloy.

Yb2SiO5-Yb2Si2O7 gradient environment barrier coating: Rational design and corrosion behavior in water vapor environment at 1300 ℃

Gradient environmental barrier coatings (EBCs) were fabricated via atmospheric plasma spraying to deposit Yb2Si2O7-Yb2SiO5 onto a laser-sculpted SiC substrate, with varying mass ratios. Experimental results reveal that the gradient coating exhibited remarkable integrity, showing no signs of cracking even after exposure to 90% H2O-10% O2 (g) water vapor corrosion at 1300 ℃ for 100 h. Besides, the thickness of the thermally grown oxide (TGO) layer was minimal (18.53 ± 1.08 μm) compared to 75Yb2Si2O7-25Yb2SiO5 single layer EBCs (24.93 ± 1.62 μm) with similar integrity under water vapor environment for 100 h. The superior performance of the gradient coating against water vapor corrosion can be attributed to the outmost layer containing more Yb2SiO5 with excellent vapor corrosion resistance, while the innermost layer primarily comprises Yb2Si2O7, providing significant damage resistance and resilience to thermal shock. These favorable attributes make the gradient coating a promising candidate for EBC application in aerospace.

Study on condensation of oily particles under the influence of water vapor phase transition

To address the problem that oily fine particles are too small to be easily captured by traditional dust removal equipment, which hinders improving the purification efficiency, this paper proposes using the technical principle of water vapor phase transition to conduct experiments and simulations. A set of water vapor experimental devices for fine particles of oil mist is designed, and the data are analyzed by a Grimm spectrometer. The experimental results show the phase change of water vapor has a remarkable effect on the agglomeration of oily fine particles. Phase change condensation makes the particle size of fine particles increase by 5–10 times in a truly brief time, and the polymerization and removal efficiency are greatly improved. To analyze the changes of the coalescence characteristics in a larger range of parameter changes, the Euler multiphase flow model is adopted, the particle condensation growth rate function is introduced by a user-defined function to establish a coalescence model and the heterogeneous condensation growth characteristics of oily particles are analyzed in a supersaturated water vapor environment. The simulation results show that the condensing chamber temperature of the condensing chamber is 283 K, and the lower the air flow rate of the condensing chamber, the more favorable the heterogeneous condensation growth of oil particles. The change rule of agglomeration characteristics of oily particles obtained by experiment and simulation proves the feasibility of improving the removal efficiency of oily fine particles.

Effect of strain rate on the stress corrosion cracking of TP439 stainless steel in water vapor environment at 500 ℃

The effect of water vapor on the stress corrosion cracking (SCC) behavior of TP439 stainless steel at 500 °C was investigated using slow strain rate tensile tests at three strain rates of 2 × 10–5/s, 2 × 10–6/s, and 2 × 10–7/s. Air was selected as a comparative blank test environment for the water vapor environment. The results showed that the tensile strength of the specimens increased significantly in air when the strain rate was decreased from 2 × 10–5/s to 2 × 10–7/s, while it decreased in water vapor. Dynamic strain aging (DSA) and SCC are the main factors contributing to the difference in tensile strength of the specimens in air and water vapor. The SCC of TP439 stainless steel in water vapor at 500 °C occurs at a strain rate of 2 × 10–7/s or even lower. Based on the SCC susceptibility index and SEM observation of specimen fracture, TP439 stainless steel exhibits a slight transgranular SCC in water vapor with low SCC susceptibility.

Secondary droplet activation during condensational growth in convective clouds and its detection from satellites

By acting as cloud condensation nuclei (CCN), aerosol particles play a key role in the climate system. The CCN can be activated into cloud droplets at the cloud base (i.e., primary activation), or above it (i.e., secondary activation). This study shows the conditions required for secondary activation during the condensational growth phase in convective clouds. It also proposes a methodology for detecting this secondary activation from satellites. Using a spectral bin adiabatic parcel model, we simulate the vertical profile of cloud microphysical properties and demonstrate how different aerosol size distributions and updraft velocities greatly affect the secondary activation initiation and the cloud properties. The secondary activation slows down the cloud drop effective radius (re) growth rate with increasing height, and decreasing temperature (T), due to the relatively larger population of smaller droplets in the cloud parcel. Therefore, the vertical profile of re growth with height is slower than the adiabatic rate when the secondary activation occurs.The proposed physical principle was verified by satellite-retrieved T-re profiles and adiabatic cloud drop number concentrations (Nd) over the Amazon region. The results obtained from this study can be utilized to identify the secondary droplet activation during the condensational growth phase, which can lead to an overestimation of the retrieved Nd as well as suppression of warm rain. This improves our knowledge and observational capabilities of the role of aerosol particles in the microphysics, dynamics, and precipitation behavior of convective clouds. Plain text summarySmall particles serve as sites for cloud droplets' condensation at the cloud base (primary droplet activation) or above it (secondary activation). Once a droplet is activated at the cloud base, the surrounding water vapor condenses on it and the droplet grows - this is called condensational growth. The cloud droplet number concentrations (Nd) can be obtained by the satellite-retrieved vertical growth rate of droplet size in the condensational growth phase. However, new small droplets formed during this phase (i.e., secondary activation), might cause an overestimate in the retrieved Nd. This study presents the physical principle of secondary activation during condensational growth. Using a model, we simulate the condensational growth of aerosol particles, which act as cloud condensation nuclei (CCN), for different particle size distributions and thermodynamic conditions (i.e., vertical velocities). Our simulations show that secondary activation slows the cloud droplet growth rate with height due to the larger competition for the available water vapor promoted by the new drops. Comparisons between satellite-retrieved Nd of convective clouds and in-situ measurements show that the satellite retrievals overestimate Nd when the secondary activation of droplets is neglected. Our findings improve the understanding of aerosols' role in the condensational growth of droplets in convective clouds.

The Diagnostics of Power Boilers in Terms of Their Sustainability

Diagnosing steam pipelines is crucial because they are subjected to a water vapor environment and exhaust gases. Layers of oxides/deposits formed on steel utilized at elevated temperatures for long time periods have a significant impact on elements operating in power plants as well as in combined heat and power plants. Currently, these devices are an important topic of sustainable energy development. The aim of this work was to characterize the structure of the steel and of the oxides/deposit layer formed on the steam superheaters of power boilers and its impact on the durability of power equipment. The tests were carried out on 13CrMo4-5 steel utilized at various temperature and time parameters. In order to assess the degradation of the material, the following research methods were used: light microscopy, X-ray structural analysis, and infrared spectroscopy with Fourier transform. The use of the FTIR method in this type of diagnostics has deepened the existing analysis of oxide/sediment layers. The obtained test results showed that the kinetics of the corrosion process on steel being used for long periods at elevated temperatures is complex and depends, among others, on the element’s operating temperature, the operating time, and the flow medium.

Synthesis, crystal structure and proton conductive properties of one stable cobalt(II) coordination polymer from thiourea carboxylate

To search for more high-performance crystalline proton conducting materials and to accelerate the related research progress, in this paper, a one-dimensional coordination polymer (CP), [Co(BBOT)2(H2O)3·2H2O]n (1) (H2BBOT = N-benzoyl-N′-(4-benzoxy)thiourea) was firstly prepared by solvent volatilization approach. Subsequently, the thermal, H2O and chemical stabilities of the CP were tested and its high structural stability was confirmed. Furthermore, in 1, a stable solid three-dimensional framework can be constructed by intermolecular H-bonds and stacking interactions between phenyl units. Then, utilizing the AC impedance determination, the dependence of the proton conductivity of this CP on temperature and humidity in the water vapor environment was explored and the positive correlation was verified. Excitingly, the optimized proton conductivity of this compound under specific test conditions (100 °C/98 % relative humidity) can be as high as 10−4 S/cm, being in the forefront of similar crystalline solid materials. Finally, according to the value of activation energy and the characteristics of crystal structure, we speculate on the proton conduction mechanism.

A Self-Assemble Supramolecular Film with Humidity Visualization Enabled by Clusteroluminescence.

Clusteroluminescence (CL) has recently gained significant attention due to its unique through-space interactions associated with a high dependence on the aggregation of subgroups. These distinct features could easily transform the stimuli into visual fluorescence and monitor the fluctuation of the environment but have not received sufficient attention before. In this work, supramolecular films are designed based on the neutralization reaction of anhydride groups and the self-assembly of dynamic covalent disulfide bonds in NaOH aqueous solution. The self-assembly of hydrophilic carboxylate chromophores and hydrophobic disulfide-containing five-membered rings could be observed by the variation of the aggregation state of carboxylate in CL. Furthermore, the dynamic cross-linking films obtained with water-sensitive carboxylate chromophores could alter the aggregation distance stimulated by surrounding water vapor, causing the emission wavelength to change from 534 to 508nm by varying the relative humidity. This work not only provides an approach to monitor the self-assembly of clusteroluminogens but also offers new strategies for designing stimuli-responsive materials that utilize the intrinsic features of CL.