H2O Gas Research Articles

Computational Study on Sensing Properties of Pd‐Decorated Phosphorene for Detecting Acetone, Ethanol, Methanol, and Toluene—A Density Functional Theory Investigation

AbstractLate reports on the application of black phosphorene for gas sensing have raised great attention to this remarkable 2D material. In this regard, the sensing behavior of phosphorene toward a group of volatile organic compounds (VOCs) is scrutinized. The studied gas molecules are acetone, ethanol, methanol, and toluene as main members of VOCs, along with CO2and H2O gas molecules. The adsorption of the gases on the pristine and Pd‐decorated phosphorene is studied by employing first‐principles density functional theory (DFT) combined with non‐equilibrium Green's function (NEGF). It is divulged that the selected molecules are weakly adsorbed upon the pristine phosphorene, but after decoration with Pd atom, the adsorption energy, and net charge transfer are improved. It is discovered based on the moderate adsorption energy and large charge transfer for acetone on the Pd‐decorated phosphorene that it can be a suitable sensor for acetone detection. Additionally, recovery time of 2.57 s at the temperature of 350 K, and under ultraviolet (UV) light is achieved after decoration for detection of acetone. Therefore, the authors' theoretical investigations help to better understand the adsorption mechanism of Pd‐decorated phosphorene as a gas sensor and provide a facile approach to broaden its application in industrial, medical, and environmental monitoring.

SO2 Poisoning Mechanism of the Multi-active Center Catalyst for Chlorobenzene and NOx Synergistic Degradation at Dry and Humid Environments.

The performance of fresh (PdV/TiO2), sulfur poisoned (Used-S and Used-H), and regenerated (Used-RS and Used-RH) multi-active center catalysts for chlorobenzene catalytic oxidation and selective catalytic reduction (CBCO + SCR) reaction is investigated. The reaction on the catalyst surface is blocked after sulfur poisoning owing to the occupation and deposition of catalyst active centers (mainly Pd centers) by PdSO4 (and/or PdS in a dry environment) and NH4HSO4 species, especially the CBCO process. Sulfates (mainly NH4HSO4) on the sulfur poisoned catalyst surface are partially decomposed after 400 °C thermal regeneration, while the deactivation caused by the formation of PdSO4 species is irreversible. Density functional theory calculation results show that in the PdSO4 and NH4HSO4 generation paths, each step of the elementary reaction has just a small energy barrier to overcome, and the stability of the product for each elementary reaction increases gradually. Even worse, SO2 is easily combined with H2O gas molecules to form H2SO3 in a humid environment, and the energy barrier for conversion of SO32- to SO42- is just 0.041 eV. The two oxygen vacancies (VOx-1 or TiOx-1) provide adsorption sites for CBCO + SCR reaction gas molecules but do not exhibit adsorption properties for SO2, which gives a possible idea for optimization of sulfur resistance. The present work is favorable for further synergistic removal of CB/NOx by the catalyst for anti-SO2 poisoning modification and application in the manufacture industry.

The color change analysis of historic wooden remains after fire-suppression by fluorinated chemical gases

Many wooden Chinese historic buildings are destroyed due to the ravages of frequent fire disasters. The fire risk of historic buildings are highly enlarged since a long-time weathered wooden structures in the natural environment. The clean fire-extinguishing technology using fluorinated chemical gases to put out a historic building fire rapidly at the initial stage is highly recommended and widely used. However, the gaseous hydrogen fluoride (HF) yielded during the fire suppression process could be a potential method to result in secondary damage due to its corrosiveness. Nowadays, experiments were employed to clarify the effect of fire suppression on the surface of historic wooden buildings. Five traditional fluorinated chemical gases, H-37, FK-5-1-12, H-1323, H-2402, and H-1301, are used to suppress a fixed flame. The wooden samples, including a Dao Talisman board, a painting paper, and wooden chips, are placed in a chamber. Wooden chips consist of traditional and weathered samples (acting as the Chinese historic buildings). The concentration of gaseous products yielded from fire suppression are monitored by a gas-FTIR from ABB, and the surface analysis is conducted by a Quanta FEG SEM–EDX from FEI. It is observed that flame enhancement happens at the early stage of fire suppression and varies with fire agents. The amount of F-deposited on the wooden surface is positively correlated with a total amount of gaseous HF. The color change mechanism of the wooden surface is comprehensive, although the amount of HF is a leading factor. The influence of HF on color change depends on the amount of both gaseous H2O and HF. It is concluded that the value of L* of the traditional chip is much easier to be reduced comparing with weathered samples with the same wood grain. The reduction of {mathrm{b}}^{*} value of weathered samples is much larger than the traditional ones. It suggests the weathered chips show a color shift toward blue because of fire suppression. The present study hopes to provide a basic acknowledgment for the comprehensive understanding of secondary damage caused by fire suppression.

Role of hydrogen species in promoting photoluminescence from Eu3+-doped ZnO thin films via bandgap excitation

We studied the role of hydrogen-containing species (OH and/or H) in promoting photoluminescence (PL) from 1 at. % Eu3+ ions doped in ZnO thin films. The hydrogen concentration in the films was systematically changed by varying the substrate temperature and the vapor pressure of H2O gas supplied during sputter deposition. The correlation between the PL spectra via bandgap excitation and the degree of oxidization/hydrogenation was investigated by x-ray diffraction and Fourier-transform infrared spectroscopy. Films deposited at room temperature under H2O partial pressures higher than 10−2 Pa were sufficiently hydroxylated, as confirmed by the appearance of diffractions peaks from Zn(OH)2 coexisting with ZnO(002). Eu3+ emissions were observed after post-annealing in a vacuum or O2 atmosphere. When the H2O pressure was lower than 10−2 Pa, the ZnO:Eu films were so oxygen-deficient as to exhibit a metallic character, which deactivated the Eu3+ emission. Deposition at temperatures above 200 °C reduced the OH and/or H species incorporated in the ZnO films and only a faint Eu3+ emission was observed. The H2O pressure under which a sharp Eu3+ emission could be obtained was between 1.0 and 2.5 × 10−2 Pa if subsequent post-annealing was done in a vacuum. For more oxidized films deposited at 3.5 × 10−2 Pa, reduction by post-annealing in an H2 atmosphere was effective to generate a sharp and intense Eu3+ emission signal through reduction and hydrogenation, confirming that a moderate oxidization/hydrogenation state is a necessary condition. Codoped hydrogen species will facilitate substituting Zn2+ sites with emission-active Eu3+ ions and stabilize them.

The Influence of Instrumental Line Shape Degradation on Gas Retrievals and Observation of Greenhouse Gases in Maoming, China

The instrument line shape (ILS), as a very important parameter, has a significant influence on the inversion of trace gas concentration. Different levels of ILS degradation for H2O, CO2, CH4, and CO gases were investigated, and the influence of ILS on the inversion of column-averaged dry air mole fractions (DMFs) was assessed. Our results indicate that the averages of XH2O, XCH4, and XCO with modulation efficiency (ME) amplitude values have a positive correlation, the correlation coefficients are 0.9925, 0.9968, and 0.9981 respectively, whereas the relationship between the average of XCO2 and ME is a negative correlation with 0.986 correlation coefficient. For a typical ILS degradation, a decrease of 5% in the modulation efficiency amplitude value results in the average of XCO2 changing by 0.744%, XCH4 and XH2O are less sensitive species, with average values of −0.206% and −0.464%, whereas XCO shows the strongest intraday variability with an average value of −0.238%. However, with a decrease of 2‰ in the phase error (PE) value, the average of XCO changed by −0.150%, XCO2 and XH2O almost coincided with the same average value of −0.141%, whereas XCH4 was the least sensitive species with an average value of −0.133%. At the same time, we measured the ILS for EM27/SUN spectrometers—the mean values of modulation efficiency amplitudes and phase errors were 0.9611 and 0.00593. Compared with standard values, the modulation efficiency amplitudes and the phase error deviations were 2.450% and 0.433%. During the observation period, the daily average of XCO2 ranged from 415.09 to 421.78 ppm. XCH4 ranged from 1.96 to 2.02 ppm with a mean of 1.982 ppm, and the daily average of XCO ranged from 0.118 to 0.157 ppm with a mean of 0.137 ppm. For the relationship between XCO2 and XCH4, the linear regression line shows a good correlation with the correlation coefficient R2 ≥ 0.5. Especially, for the correlation coefficient R2 = 0.82 on 8 October, our studies found a weak correlation in the variation of CO2 and CO during the observations. The correlation coefficient R2 ≥ 0.5 was only found on 30 September and 3 October. The trajectories dram at a height of 10 km give a hint of trace gas transport from the bay of western India, Bengal, and the Arabian Sea, whereas for the trajectories dram boundary layer height, trace gases were transported from southwest and east of China. These results provide a theoretical basis to understand the time and space distribution and the changes of greenhouse gas in the atmosphere as well as providing a theoretical basis for calculations of atmospheric radiation transmission.

ALMA 870 μm continuum observations of HD 100546

This paper reports on a new analysis of archival ALMA 870 μm dust continuum observations. Along with the previously observed bright inner ring (r ~ 20–40 au), two addition substructures are evident in the new continuum image: a wide dust gap, r ~ 40–150 au, and a faint outer ring ranging from r ~ 150 au to r ~ 250 au and whose presence was formerly postulated in low-angular-resolution ALMA cycle 0 observations but never before observed. Notably, the dust emission of the outer ring is not homogeneous, and it shows two prominent azimuthal asymmetries that resemble an eccentric ring with eccentricity e = 0.07. The characteristic double-ring dust structure of HD 100546 is likely produced by the interaction of the disk with multiple giant protoplanets. This paper includes new smoothed-particle-hydrodynamic simulations with two giant protoplanets, one inside of the inner dust cavity and one in the dust gap. The simulations qualitatively reproduce the observations, and the final masses and orbital distances of the two planets in the simulations are 3.1 MJ at 15 au and 8.5 MJ at 110 au, respectively. The massive outer protoplanet substantially perturbs the disk surface density distribution and gas dynamics, producing multiple spiral arms both inward and outward of its orbit. This can explain the observed perturbed gas dynamics inward of 100 au as revealed by ALMA observations of CO. Finally, the reduced dust surface density in the ~40–150 au dust gap can nicely clarify the origin of the previously detected H2O gas and ice emission.

A low-cost automated growth chamber system for continuous measurements of gas exchange at canopy scale in dynamic conditions

BackgroundObtaining instantaneous gas exchanges data is fundamental to gain information on photosynthesis. Leaf level data are reliable, but their scaling up to canopy scale is difficult as they are acquired in standard and/or controlled conditions, while natural environments are extremely dynamic. Responses to dynamic environmental conditions need to be considered, as measurements at steady state and their related models may overestimate total carbon (C) plant uptake.ResultsIn this paper, we describe an automatic, low-cost measuring system composed of 12 open chambers (60 × 60 × 150 cm; around 400 euros per chamber) able to measure instantaneous CO2 and H2O gas exchanges, as well as environmental parameters, at canopy level. We tested the system’s performance by simulating different CO2 uptake and respiration levels using a tube filled with soda lime or pure CO2, respectively, and quantified its response time and measurement accuracy. We have been also able to evaluate the delayed response due to the dimension of the chambers, proposing a method to correct the data by taking into account the response time ({t}_{0}) and the residence time (τ). Finally, we tested the system by growing a commercial soybean variety in fluctuating and non-fluctuating light, showing the system to be fast enough to capture fast dynamic conditions. At the end of the experiment, we compared cumulative fluxes with total plant dry biomass.ConclusionsThe system slightly over-estimated (+ 7.6%) the total C uptake, even though not significantly, confirming its ability in measuring the overall CO2 fluxes at canopy scale. Furthermore, the system resulted to be accurate and stable, allowing to estimate the response time and to determine steady state fluxes from unsteady state measured values. Thanks to the flexibility in the software and to the dimensions of the chambers, even if only tested in dynamic light conditions, the system is thought to be used for several applications and with different plant canopies by mimicking different environmental conditions.

Adsorption of gas molecules on Co-doped SnO2 (110): First-principles investigation

First-principles calculations based on density functional theory were employed to study the adsorption of gas molecules (CH4, CO, H2O) on various SnO2 (110) surfaces. We found that CO and CH4 molecules are weakly adsorbed on intrinsic SnO2 (110) surfaces, and intrinsic SnO2 is sensitive only to the H2O molecule. Compared with the gas molecules adsorbed on the intrinsic SnO2 surfaces, the significantly increased adsorption energy indicates that there is an improvement in the gas sensitivity properties of Co-doped SnO2 (Co/SnO2) and oxygen vacancy modified Co-doped SnO2 (Co/VO/SnO2) to CO, CH4, and H2O gas. The CO adsorbed on the Co/VO/SnO2 surface has the strongest adsorption energy (−1.402 eV). We also studied the optical properties of the Co/SnO2 and Co/VO/SnO2 surfaces influenced by the three gas molecules. We found that the three gas molecules cause an enhancement of the adsorption peaks of Co/SnO2 configuration in the visible light range. Our study benefits research on the potential application of SnO2 sensor materials.

In situ observation of the deterioration process of sulfide-based solid electrolytes using airtight and air-flow TEM systems.

Sulfide-based solid electrolytes (SEs) exhibiting high ionic conductivity are indispensable battery materials for next-generation all-solid-state batteries. However, sulfide-based SEs have a major drawback in their low chemical stability in air. When exposed to H2O or O2 gas, toxic H2S is generated, and their ionic conductivity considerably declines. However, their degradation mechanism caused by air exposure has not been understood yet. To clarify the degradation process, in this study, we developed a transmission electron microscope (TEM) system to evaluate the air stability of battery materials. Using a vacuum transfer double-tilt TEM holder with a gas-flow system, the in situ observation of the degradation process was conducted for a sulfide-based Li4SnS4 glass ceramic under an air-flow environment. Consequently, electron diffraction (ED) patterns and TEM images could clearly capture morphological changes and the amorphization process caused by air exposure. Moreover, based on the analysis of ED patterns, it is observed that Li4SnS4 is likely to decompose because of the reaction with H2O in air. Therefore, this airtight and air-flow TEM system should be effective in clarifying the process of the deterioration of sulfur-based SEs during exposure to air.

Comparison of the expansion behavior of atoms and droplets ablated from a β-tricalcium phosphate target under low-pressure ambient H2O gas for hydroxyapatite coating

Visualizing the expansion of particles of different size in a laser-ablated plume is useful for understanding the mechanism of the pulsed-laser deposition process. In our previous work that the crystalline hydroxyapatite content in a coating layer decreased with increasing H2O gas pressure. We concluded that ablated atoms and ions, which were immediately changed into crystalline hydroxyapatite, were stopped before reaching the substrate in the H2O pressure range. In the present study, the expansion behavior of ablated droplets and atoms in H2O gas was measured independently. Droplets were also measured via Mie scattering images using a second probe laser beam and were found to not be affected by the ambient gas pressure. However, the excited Ca atoms and ions in this H2O pressure range were effectively prevented from reaching the substrate. These confirm that the decrease in the crystalline hydroxyapatite content was caused by the increase in the ambient gas pressure.

Selective Preparation of Mo2N and MoN with High Surface Area for Flexible SERS Sensing.

γ-Mo2N and δ-MoN are the two most important molybdenum nitrides, but controllable preparation of them with high surface area has not been achieved. Herein, we achieved selective preparation of γ-Mo2N and δ-MoN. The key factor for the selective preparation of γ-Mo2N and δ-MoN is to control the crystal phase of the precursor MoO3. In H2O and NH3 mixed gas, the α-MoO3 nanoribbons are nitridated to obtain γ-Mo2N single-crystal porous nanobelts, while the h-MoO3 prisms are nitrided to obtain δ-MoN hierarchical porous columns. The corrosion effect of H2O plays a key role in the formation of single-crystal porous structure. The γ-Mo2N flexible membrane composed of the single-crystal porous nanobelts exhibits strong localized surface plasmon resonance and surface enhanced Raman scattering effect, which show highly sensitive response to polychlorinated phenol.

Unraveling the Dynamic Evolution of Pd Species on Pd-Loaded ZnO Nanorods for Different Hydrogen Sensing Behaviors

Probing the dynamic evolution of active species under different sensing conditions is achieved to the rational design of sensing materials for outstanding sensing performance. In this study, a palladium (Pd)-loaded ZnO sensing material was approached via the impregnation method. The Pd-loaded ZnO100 gas sensor has a better H2 sensing performance than a pure ZnO gas sensor at an operating temperature of 190 to 360 °C. The in situ Raman and H2 temperature-programmed surface reaction characterization technologies confirmed that the synergistic effect of metal Pd (Pd0) and Pd oxide (PdOx) played a decisive role in improving the sensing capability for H2 in low concentrations (less than 100 ppm). The proportion of Pd0 in the Pd/PdOx dynamically increased with the elevation of operating temperature. The small size Pd/PdOx dispersed on the ZnO surface enhanced the dissociation of H2 by Pd0 and the charge transfer between PdOx and ZnO, boosting the sensing performance of the gas sensor to H2. With the increase of the operating temperature to more than 360 °C, H2 was directly oxidized to gaseous H2O on the Pd/PdOx active sites, resulting in a relatively low H2 sensing capacity. In addition, the change of the appropriate Pd/PdOx ratio could effectively improve the H2 sensing performance of the gas sensor.

Effect of H2O Molecules on the CO2 Replacement in CH4 Hydrate Behavior by Molecular Simulation

CH₄–CO₂ replacement technology has broad application prospects in reducing CO₂ emission and developing natural gas hydrate (NGH) resources. It is of great significance to study the mechanism of CH₄–CO₂ replacement. In this paper, the effect of H₂O on CH₄–CO₂ displacement behavior is studied by molecular dynamics (MD) simulation and quantum mechanics calculation. The interactions between the host and guest in cages of CH₄ hydrate are calculated using the symmetry-adapted perturbation theory method. The contribution of physical components of binding energy can be determined. The result indicates that the electrostatic interaction of H₂O–H₂O and H₂O–gas is a key factor of the CH₄–CO₂ replacement mechanism. Additionally, the microconfigurations and microstructure properties are analyzed by MD simulation in the systems containing a gas layer (CO₂ or CH₄) and a CH₄ hydrate layer. The results showed that the movement and the arrangement of H₂O molecules influence the hydrate structure due to the interaction of H₂O–gas during the replacement process. The molecular simulation suggests that the change of electrostatic interaction with H₂O molecules could improve the CH₄–CO₂ replacement efficiency, which can be favorable for the investigation of CH₄ replacement technology in NGH with CO₂ injection.

Gas terminal velocity from MIRO/Rosetta data using neural network approach

Context. The Microwave Instrument on the Rosetta Orbiter (MIRO) on board the Rosetta spacecraft was designed to investigate the surface and gas activity of the comet 67P/Churyumov-Gerasimenko. The MIRO spectroscopic measurements carry information about the velocity of gas emanating from the nucleus surface. Knowledge of the terminal velocity of the H2O gas is valuable for interpretation of in situ measurements, calibrating 3D coma simulations, and studying the physics of gas acceleration. Aims. Using a neural network technique, we aim to estimate the gas terminal velocity from the entire MIRO dataset of nadir geometry pointings. The velocity of the gas is encoded in the Doppler shift of the measured rotational transitions of o-H216O and o-H218O even when the spectral lines are optically thick with quasi or fully saturated line cores. Methods. Neural networks are robust nonlinear algorithms that can be trained to recognize underlying input to output functional relationships. A training set of about 2200 non-LTE simulated spectra for the two transitions is computed for known input cometary atmospheres, varying column density, temperature, and expansion velocity profiles. Two four-layer networks are used to learn and then predict the gas terminal velocity from the MIRO nadir measured o-H216O and o-H218O spectra lines, respectively. We also quantify the accuracy, stability, and uncertainty of the estimated parameter. Results. Once trained, the neural network is very effective in inverting the measured spectra. We process the entire dataset of MIRO measurements from August 2014 to July 2016, and investigate correlations and temporal evolution of terminal velocities derived from the two spectral lines. The highest terminal velocities obtained from H218O are higher than those from H216O with differences that evolve in time and reach about 150 m s−1 on average around perihelion. A discussion is provided on how to explain this peculiar behavior.

Effect of ALD- and PEALD- Grown Al2O3 Gate Insulators on Electrical and Stability Properties for a-IGZO Thin-Film Transistor

This study investigated the electrical and stability characteristics of Al2O3 as a gate insulator, which was deposited by various atomic layer deposition methods in top-gate staggered amorphous InGaZnO (a-IGZO) thin film transistors. A trimethylaluminum precursor was used as an Al source, and H2O gas (H2O device) and O2 plasma with a long plasma time (O2 LP device) and a short plasma time (O2 SP device) were used as oxidants. The initial electrical characteristics, including the hysteresis, on–off current ratio, and subthreshold swing, were superior in the H2O device compared to the O2 LP and O2 SP devices. In the positive bias stress (PBS) results, the degradation characteristics showed a tendency similar to the transfer properties. However, under the negative bias illumination stress (NBIS), the stability of the H2O device was significantly reduced compared to the O2 LP and O2 SP devices. In this paper, the mechanism of instability, which has opposite results in terms of the PBS and NBIS for the three devices, was identified using capacitance–voltage, three-terminal charge pumping as electrical analysis techniques and secondary ion mass spectroscopy (SIMS) as a physical analysis technique. It was confirmed that the surface oxidation of a-IGZO deteriorates the interfacial properties, causing the transfer characteristics to degrade. The carbon of the Al2O3 film identified via SIMS analysis acts as a trap layer, causing deterioration in the PBS. Alternatively, in the NBIS, it was observed that the carbon acts as a capture site for photo-excited holes, thereby promoting device stability.

Correlation between ferroelectricity and ferroelectric orthorhombic phase of HfxZr1−xO2 thin films using synchrotron x-ray analysis

The change in the interplanar spacing (d-spacing) including the ferroelectric orthorhombic (O) phase in the low-temperature fabricated HfxZr1−xO2 (HZO) films was studied using synchrotron grazing-incidence wide-angle x-ray scattering analysis. The 10-nm-thick HZO films were fabricated by thermal and plasma-enhanced atomic layer deposition (TH- and PE-ALD) methods using H2O gas and O2 plasma as oxidants, respectively, and a post-metallization annealing (PMA) was performed at 300–400 °C. The d-spacing of the mixture of (111)-, (101)-, and (111)-planes of O, tetragonal (T), and cubic (C) phases, respectively, for the TH- and PE-ALD HZO films increased up to 2.99 Å with an increase in PMA temperature, while the d-spacing estimated by conventional x-ray diffraction was 2.92 Å regardless of the PMA temperature. The remanent polarization (2Pr = Pr+ − Pr−) of the HZO films increased as the PMA temperature increased. It is clear that the 2Pr value satisfied a linear relationship as a function of the d-spacing of O(111)/T(101)/C(111) phases. Furthermore, the wake-up effect was found to depend on the ferroelectric O phase formation. The wake-up effect was significantly reduced in both the TH- and PE-ALD HZO films after the PMA at 400 °C due to the increase in the ferroelectric O phase formation. The leakage current density (J)–electric field properties of the PE-ALD HZO film with the lowest d-spacing were divided into three steps, such as low, middle, and large J values, in the wake-up (103 cycles), pristine (100 cycle), and fatigue (107 cycles) states, respectively. Therefore, an analysis of the ferroelectric O phase is very important for understanding the ferroelectricity including endurance.

The usage of water conditioning sludge from heat power industry enterprises in wall ceramics production

The paper considers the ecological problems of water conditioning systems at heat power industry facilities. It is noted that the stable operation of water-heating equipment is provided with the quality of feed water. Various water-soluble salts, which can incrust the inner walls of boilers or pipelines, are removed from the natural water. For desalination of natural water the physical-chemical methods are mostly used. The by-product of desalination or chemical water-conditioning systems is the sludge waste. This work presents the results of using chemical water conditioning sludge from JSC Verofarm in the raw charge for wall ceramics production. The sludge is a finely-divided powder, the mineral composition of which is presented with calcium and magnesium carbonates, brucite and iron compounds, which make the sludge pink. It has been determined that the baking of sludge-containing ceramic samples at temperature 1000°C results in dissociation of calcium and magnesium carbonates with the formation of gaseous products H2O and CO2, which make the structure of ceramic materials porous. The presence of iron compounds in the raw charge promotes the formation of low-temperature silicate melt, which intensifies the baking process of ceramic samples. The optimal sludge content in the charge that doesn’t reduce the strength characteristics of wall ceramics is 10%. Such sludge content forms the liquid phase on the surface of the raw mix’s particles, which solidifies the forming pores. The increase of sludge content up to 20% intensifies gas generation; the amount of the formed liquid phase is not sufficient, which increases porosity and reduces the density and strength of ceramic materials. At that, the engobe layer is formed on the surface of the obtained wall ceramics samples. The wall ceramics products, obtained with the use of chemical water conditioning sludge, can be used as structural heat-insulation materials in making building envelopes or interior partitions.

Solid-Phase Quasi-Intramolecular Redox Reaction of [Ag(NH3)2]MnO4: An Easy Way to Prepare Pure AgMnO2.

Two monoclinic polymorphs of [Ag(NH3)2]MnO4 containing a unique coordination mode of permanganate ions were prepared, and the high-temperature polymorph was used as a precursor to synthesize pure AgMnO2. The hydrogen bonds between the permanganate ions and the hydrogen atoms of ammonia were detected by IR spectroscopy and single-crystal X-ray diffraction. Under thermal decomposition, these hydrogen bonds induced a solid-phase quasi-intramolecular redox reaction between the [Ag(NH3)2]+ cation and MnO4– anion even before losing the ammonia ligand or permanganate oxygen atom. The polymorphs decomposed into finely dispersed elementary silver, amorphous MnOx compounds, and H2O, N2 and NO gases. Annealing the primary decomposition product at 573 K, the metallic silver reacted with the manganese oxides and resulted in the formation of amorphous silver manganese oxides, which started to crystallize only at 773 K and completely transformed into AgMnO2 at 873 K.

High temperature Zircaloy-4 oxidation in water vapour-containing environments examined with Raman imaging and labelled oxygen

High Temperature oxidation of Zircaloy-4 was studied in N2–O2–H2O gas mixtures using labelled 18O2, thermogravimetry, Raman imaging and mass spectrometry. Samples were either exposed to N2–18O2–H2O gas mixtures, or two-stage oxidised first in 18O2, then in H216O - N2 or 16O2 - N2 atmospheres. In the pre-transition, diffusion-controlled regime, mostly steam contributes to the zirconia formation, while in the nitrogen-catalysed post transition regime both oxygen and steam contribute to the oxidation. These results were tentatively explained by competitive adsorption of oxygen and steam at the gas/solid interfaces, and the formation of porosity in the oxide layers.

Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy

Abstract We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1 m s−1 speeds with a ∼1′ jet pointing in the southwest direction. LD2 experienced a total dust mass loss of ∼108 kg at a loss rate of ∼6 kg s−1 with Afρ/cross section varying between ∼85 cm/125 km2 and ∼200 cm/310 km2 from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD2's activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of ≲1027 mol s−1/≲1026 mol s−1 from our 4.5 μm Spitzer observations; g–r = 0.59 ± 0.03, r–i = 0.18 ± 0.05, and i–z = 0.01 ± 0.07 from GROWTH observations; and H2O gas production of ≲80 kg s−1 scaling from our estimated C 2 production of mol s−1 from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 × 106 yr, having a dynamical half-life of 3.4 × 105 yr.