High-temperature Phase Research Articles

Effects of a nanobiofilm-covered echelon oxygen-controlled composting process on carbon and nitrogen conversion and emission reduction efficiency

To address the defects of traditional composting products, such as slow fertilizer efficiency, high dosage and high emissions of gas pollutants, we propose a new composting process from the perspective of increasing the dissolved organic carbon (DOC) content in compost. The results showed that nanobiofilm-covered echelon oxygen-controlled composting could effectively reduce the emissions of CH4, CO2 and NH3 and increase the DOC content in the composting products. Among the methods, using nanobiofilm covering and applying moderate ventilation during the warming phase and high ventilation during the high-temperature phase, along with low ventilation during the cooling and maturation phases (T3), proved to be the most effective in promoting the conversion of carbon to dissolved organic carbon and in reducing carbon and nitrogen losses. Compared to the control, this treatment resulted in a 36.16% reduction in total carbon loss, a 21.14% reduction in total nitrogen loss, and a 57.22% reduction in greenhouse gas emissions while also increasing the DOC content by 82.64%. This is because treatment T3 initially maintained the composting process in an aerobic state, followed by a semianaerobic state, which is conducive to the accumulation of DOC. The research results provide a new technical path for improving the quality, efficiency and emission reduction of organic fertilizer.

Electropulsing of Low-Density Duplex Steel for Strengthening and Ductilization by Microstructural Refinement

The present investigation finds the effect of electropulsing treatment on the mechanisms of refining and reprecipitation of ordered L20 structure (B2) and its impact on tensile properties of low-density duplex steel of Fe-18Mn-10.5Al-1C-6Ni composition. The selected composition without manganese is melted at 1600°C by induction heating in a vacuum but Mn is added into the melt at 1560°C, in the argon atmosphere to reduce the loss. The melt is cast into a plate form in a copper mold. The cast steel is homogenized, hot rolled, and annealed (PD1-A sample) to get elongated bands, spheroids, and platelets of B2 phase with an austenitic matrix which results in a yield strength of 1015MPa, and tensile strength of 1285MPa with a plastic elongation of 16.3%. Electropulsing partially dissolves the B2 phase at a temperature much lower than the equilibrium solvus by reducing barrier energy because of electron wind. As a result, the sizes of bands and spheroids are reduced, and platelets are disintegrated. Electron wind force deforms coarse precipitates, and fragments as well as spheroidized it. Electropulsing of annealed steel (PD1-AE) mobilizes dislocations, and recovers it in B2, but induces localized recrystallization of austenite. At a later time of the signal, the temperature rapidly falls and the matrix becomes supersaturated but electropulsing accelerates low-temperature precipitation of the B2 phase. Therefore, electropulsing can be adopted as a fast manufacturing process to dissolve, deform, fragment, spheroidize and reprecipitate high temperature phase at much lower temperature by dominant athermal effect of electron wind energy over thermal effect. Electropulsing also induces recovery and recrystallization at a relatively low temperature and reduces defect density. Reduction in the overall size of B2 and its distribution towards better uniformity provided an increased yield strength of 1077MPa, tensile strength of 1355MPa, and a plastic elongation of 21.6%. The selected duplex low-density steel follows two-stage work hardening of Ludwigson model with an additional stage of dynamic recovery. Fractography analysis confirms that both samples show mixed modes of ductile and brittle fracture, with an increase in size and area percentage of dimples.

Ghost states and surface structures of the charge density wave kagome metal ScV[formula omitted]Sn[formula omitted]

We investigate the high-temperature phase of the kagome metal ScV6Sn6 using scanning tunneling microscopy/spectroscopy (STM/S) and density functional theory calculations. STM topographic images of the cleaved sample reveal two distinct surface terminations: flat islands with Sn termination and trenches terminated by kagome layers with Sn as the outermost atomic layer. STS measurements on the Sn-terminated and kagome-terminated surfaces show significant differences, in particular the presence of large density of states near the Fermi level in the former case. Our first-principles calculations reveal that the charge density on the kagome-terminated surface gives rise to “ghost states” which show intensity away from surface atoms, arising due to hybridization of orbitals above the surface. These states can obscure the intrinsic properties of the surface, potentially leading to misattribution of the surface termination. This underscores the need for careful interpretation in STM studies, especially when discerning surface states of localized states. Understanding the surface structure of this versatile quantum material provides essential information for interpreting surface-sensitive experiments, tailoring material properties, engineering interfaces, and controlling stability and reactivity. This knowledge paves the way for further exploration and potential applications of kagome lattice materials in various fields, including quantum computing, topological physics, and advanced electronic devices.

Thermal Oxidation Reaction between NH3 and O3: Low-temperature Formation of an NH4+ -bearing Salt

NH3 has long been predicted to be an important component of outer solar system bodies, yet detection of this compound suggests a low abundance or absence on many objects where it would be expected. Here, we demonstrate that a thermally driven oxidation reaction between ammonia (NH3) and ozone (O3) in a H2O + NH3 + O3 mixture may contribute to the low abundance of NH3 on some of these objects, as this reaction efficiently occurs at temperatures as low as 70 K. We determined the overall activation energy for this reaction to be 17 ± 2 kJ mol−1, which is consistent with other chemical systems that react at cryogenic temperatures. The loss of these two compounds coincides with the formation of NH4+ and NO3− at low temperatures, both of which are observable with infrared spectroscopy. Warming our H2O + NH3 + O3 mixtures through sublimation, we find a number of higher-temperature phases, such as ammonia hemihydrate, nitric acid, and ammonium nitrate (NH4NO3). The most stable of these is NH4NO3, which remains on the substrate until temperatures near 270 K. The salt product within this sample contains near-infrared spectral features between 2.0 and 2.22 μm, which is a spectral region of interest for several outer solar system objects, including the Uranian satellites Miranda, Ariel and Umbriel, and Pluto's satellite Charon.

Magnetic Bistability in the Crystaline Fullerene Radical Salt

Comprehensive SummaryCompounds with magnetic bistability is highly attractive for the construction of switches, thermal sensors, information‐storage media and memory devices. Herein, we report a crystalline fullerene radical anion salt [Na(THF)5]C60 (1), obtained by the reduction of C60 with Na in solution, which exhibits magnetic bistability accompanied with one magnetostructural transition, giving low temperature (LT), high temperature (HT) phases and a metastable phase. Fullerene radical anions (C60•‐) in the structure were found arranged into a three‐dimensional close‐packed honeycomb subnetwork with hollow channels occupied by complex cations [Na(THF)5]+ as spacers. The magnetic bistability is attributed to structural transitions as the LT−IT phase transition was associated with the orientational disorder of fullerene anions and the distortion of the complex cations [Na(THF)5]+ in the 3D packing of fullerene anions.

High Potential Electrochemical Synthesis of Thermally Reduced Graphene Nanomaterial

In this study, we provide electrochemical techniques for synthesizing thermally reduced graphene nanomaterial that have high potential, low defects, cost-effectiveness, and ecological sustainability. The electrochemical exfoliation is carried out by employing a 195 W DC (voltage = 60[Formula: see text]V and current = 3.25 A) power source at a maximum electrolyte temperature of about 92.5∘C within the aqueous suspension of 2[Formula: see text]M of sulfuric acid (H2SO[Formula: see text]. Thereafter, the synthesized nanomaterial was treated in the weak piranha [combination of sulfuric acid and hydrogen peroxide (H2O[Formula: see text]] solution using an electrochemical technique inside the water bath sonicator at 80∘C. X-ray diffraction (XRD) analysis shows the peak of diffraction to the (002) plane of the reduced graphene oxide (RGO) samples emerges at around 2[Formula: see text] and 26.56∘ with an interplanar distance of 3.40 Å and 3.54 Å. According to the XRD data, after the high-temperature thermal reduction phase, the structure of the crystals and interplanar separation were recovered. The size of the crystallite of RGO produced under H2SO4 conditions was discovered to be greater than the crystallite size of graphene oxide produced under piranha solution conditions. The Raman analysis results show that the degree of disorder of the graphene synthesized within the H2O2 was higher than in comparison to the graphene synthesized in H2SO4. Field emission scanning electron microscopy (FE-SEM) results show that graphene synthesized in the presence of H2O2 has a thin and porous microstructure in comparison to H2SO4 with no significant effect on the presence of the availability of the C/O ratio. The atomic force microscopy (AFM) analysis indicates that the surface roughness of the graphene synthesized in the H2O2 was higher than that of the H2SO4. The Fourier transform infrared spectroscopy (FT-IR spectroscopy) analytical results show that the majority of the functional groups have been eliminated within the samples.

Spectroscopy of Magnesium Sulfate Double Salts and Their Implications for Mars Exploration

Magnesium sulfate has been widely detected on the surface of Mars. The occurrence of magnesium sulfate and mixed cationic sulfates preserves clues regarding the sedimentary environment, hydrological processes, and climate history of ancient Mars. In this study, seven magnesium sulfate double salts were synthesized in the laboratory using a high-temperature solid phase reaction or slow evaporation of aqueous solutions. The samples were analyzed using X-ray diffraction to confirm their phase and homogeneity. Subsequently, the Raman, mid-infrared spectra, and visible near-infrared spectra of these samples were collected and analyzed. Our results showed that the spectra of the analyzed magnesium sulfate double salts exhibited distinctive spectral features. These laboratory results may provide new insights for the identification of various magnesium sulfate double salts on Mars during the interpretation of in situ data collected by Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC), SuperCam, and the ExoMars Raman Laser Spectrometer (RLS). In addition, the MIR and VNIR spectra features obtained in this study provide an improved reference and spectra library for decipherment of data sourced from the Thermal Emission Spectrometer (TES), Thermal Emission Imaging System (THEMIS), and Mars Mineralogical Spectrometer (MMS).

Selective Separation of Rare Earth Ions from Mine Wastewater Using Synthetic Hematite Nanoparticles from Natural Pyrite

The separation of rare earth ions (RE3+) from aqueous solutions poses a significant challenge due to their similar chemical and physical characteristics. This study presents a method for synthesizing hematite nanoparticles (Fe2O3 NPs) through the high-temperature phase transition of natural pyrite for adsorbing RE3+ from mine wastewater. The characteristics of Fe2O3 NPs were studied using XRD, SEM, BET, XPS, FTIR, and Zeta potential. The optimal condition for RE3+ adsorption by Fe2O3 NPs was determined to be at pH 6.0 with an adsorption time of 60 min. The maximum adsorption capacities of Fe2O3 NPs for La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, and Y3+ were 12.80, 14.02, 14.67, 15.52, 17.66, 19.16, 19.94, and 11.82 mg·g−1, respectively. The experimental data fitted well with the Langmuir isotherm and pseudo-second-order models, suggesting that the adsorption process was dominated by monolayer chemisorption. Thermodynamic analysis revealed the endothermic nature of the adsorption process. At room temperature, the adsorption of RE3+ in most cases (La3+, Ce3+, Pr3+, Nd3+, Sm3+, and Y3+) onto Fe2O3 NPs was non-spontaneous, except for the adsorption of Gd3+ and Dy3+, which was spontaneous. The higher separation selectivity of Fe2O3 NPs for Gd3+ and Dy3+ was confirmed by the separation factor. Moreover, Fe2O3 NPs exhibited excellent stability, with an RE3+ removal efficiency exceeding 94.70% after five adsorption–desorption cycles, demonstrating its potential for the recovery of RE3+ from mine wastewater.

Tracing the phase formation and stability of the clathrate phase BaGe5

Thermal stability and phase formation of the clathrate phase BaGe5 and its formation from the clathrate-I phase Ba8Ge43□3 (□ = vacancy in the crystal structure) have been investigated by microstructure analysis, differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD). The experiments confirm the peritectic formation of the high-temperature phase Ba8Ge43□3 from α-Ge and liquid at 810 °C, and the eutectic temperature of Ba8Ge43□3 and Ba6Ge25 at 808 °C. At T = 770 °C, Ba8Ge43□3 decomposes by a eutectoid reaction to Ba6Ge25 and α-Ge, and at T = 520 °C, the low-temperature phase BaGe5 forms in a peritectoid reaction from these two phases. BaGe5 was synthesized by decomposition of the high-temperature clathrate-I phase Ba8Ge43□3 at temperatures between 350 °C and 520 °C. Annealing and DSC experiments verify that BaGe5 is an equilibrium phase at ambient pressure. The formation of BaGe5 from Ba8Ge43□3 was traced through microstructure analysis, revealing microdomains with pleochroic behavior in polarized light.

Hydrogen bonds and elastic anisotropy of nitrile molecular crystals: an investigation from first-principles

ABSTRACT Atomistic calculations based on semi-classical dispersion-corrected density functional theory were performed to investigate bonding and elastic properties of low temperature polymorphs of three nitrile molecular crystals. For that purpose, the DFT-PBE-D3ijk method, which account for both pair and three-body interactions, was applied. The analysis of Hirshfeld surfaces demonstrated that the (C-N…H) hydrogen bonds are the strongest and the dominant ones in the three nitrile molecular crystals. The latter were found to share a common structural feature, consisting of an antiparallel orientation of the terminal nitrile groups at their constituent molecules. Our prediction of the elastic properties demonstrated that malonitrile has the highest Young modulus and succinonitrile has the lower one. The three nitrile crystals are expected to have similar resistance to volume variation while succinonitrle is predicted to exhibit the lowest resistance to shape change. Otherwise, succinonitrile was found to be ductile while malononitrile and acetonitrile were shown to be brittle. Elasticity anisotropy analysis demonstrated that the directions of maximum Young’s modulus are always nearly parallel to the direction of alignment of strong (C-H…N) hydrogen bonds in the three nitrile crystals. The present analyses are relevant for understanding the structure and the properties of more complex high temperature phases.

Anchored Cobalt Nanoparticles on Layered Perovskites for Rapid Peroxymonosulfate Activation in Antibiotic Degradation.

In the Fenton-like reaction, revealing the dynamic evolution of the active sites is crucial to achieve the activity improvement and stability of the catalyst. This study reports a perovskite oxide in which atomic (Co0) in situ embedded exsolution occurs during the high-temperature phase transition. This unique anchoring strategy significantly improves the Co3+/Co2+ cycling efficiency at the interface and inhibits metal leaching during peroxymonosulfate (PMS) activation. The Co@L-PBMC catalyst exhibits superior PMS activation ability and could achieve 99% degradation of tetracycline within 5min. The combination of experimental characterization and density functional theory (DFT) calculations elucidates that the electron-deficient oxygen vacancy accepts an electron from the Co 3d-orbital, resulting in a significant electron delocalization of the Co site, thereby facilitating the adsorption of the *HSO5/*OH intermediate onto the "metal-VO bridge" structure. This work provides insights into the PMS activation mechanism at the atomic level, which will guide the rational design of next-generation catalysts for environmental remediation.

Growth and impact of intrinsic interlayers in high temperature vapor phase epitaxy of GaN

Structural quality of GaN layers grown on foreign substrates is usually improved by applying masks or interlayers, which interact with the crystal structure defects, mainly with threading dislocations, and consequently reduce their density. In this work, GaN interlayers with intrinsic defect structures were employed as barriers impeding the propagation of threading dislocations. The GaN samples were produced in a multistage deposition process by high-temperature vapor phase epitaxy (HTVPE). They consisted of GaN seed layers deposited on 15 × 15 mm2 (001)-oriented sapphire substrates, structured GaN interlayers and GaN top layers. The structuring of the interlayers was facilitated by changing the substrate temperature and the V/III ratio during the growth. The optical and scanning electron microscopies revealed that the structured interlayers contain pyramidal facets, vertical trenches and elongated voids. The results of X-ray diffraction and Raman spectroscopy have shown that these microstructure features are able to reduce the density of threading dislocations in the top layer and the tensile residual stress that develops in the top layer during the deposition process. These results demonstrate the potential of the intrinsic interlayer concept for the in-line defect and stress engineering in HTVPE GaN layer stacks.

Effect of B2O3 and Basic Oxides on Network Structure and Chemical Stability of Borosilicate Glass

Glass properties play crucial roles in ensuring the safety and reliability of electronic packaging. However, challenges, such as thermal expansion and resistance to acid corrosion, pose long-term service difficulties. This study investigated the impact of the microstructure on acid resistance by adjusting the glass composition. A glass material with excellent acid resistance was obtained by achieving a similar coefficient of thermal expansion to tantalum; it exhibited a weight loss rate of less than 0.03% when submerged in 38% sulfuric acid at 85 °C for 200 h. Theoretically, this glass can be used to seal wet Ta electrolytic capacitors. Differential scanning calorimetry (DSC) was used to analyze the glass transition temperature and thermal stability of borosilicate glasses. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and Raman spectroscopy were used to study the microstructure of the amorphous phase of the borosilicate glass, which revealed a close relationship between the degree of network phase separation in the borosilicate glass and the degree of polymerization (isomorphic polyhedron value, IP) of the glass matrix. The IP value decreased from 3.82 to 1.98 with an increasing degree of phase separation. Boron transitions from [BO4] to [BO3] within the glass network structure with increasing boron oxide content, which diminishes the availability of free oxygen provided by alkaline oxide, resulting in a lower acid resistance. Notably, the glass exhibited optimal acid resistance at boron trioxide and mixed alkaline oxide contents of 15% and 6%, respectively. Raman experiments revealed how the distributions of various bridging oxygen atoms (Qn) affect the structural phase separation of the glass network. Additionally, Raman spectroscopy revealed the depolymerization of Q4 into Q3, thereby promoting high-temperature phase separation and highlighting the unique advantages of Raman spectroscopy for phase recognition.

Viscosity and structure studies of iron-based quaternary melts: The effect of P

This study systematically investigates the underlying principles and mechanisms governing viscosity across the entire range for the Fe-4.5C-0.1Ti-xP (in wt.%) melts. The viscosity profile exhibits distinct variations in different phases. In the solid–liquid transition region, the primary determinant of viscosity is the presence of solid phase particles, while in the region characterized by liquid phase, the primary influencing factor is the number of clusters. Notably, the impact of P content demonstrates a contrasting effect on low-temperature solid phase precipitation and high-temperature liquid phase structure. During the low-temperature solid phase precipitation stage, an increase in P content serves as a catalyst for graphite precipitation, resulting in an increase in system viscosity and, by extension, impacting an increase in system viscosity. In contrast, within the high-temperature liquid phase, the interaction of P with iron (Fe) results in the breakdown of mid-range clusters in the original system, leading to the formation of smaller clusters with a reduced overall cluster volume. Consequently, an increase in P content is associated with a decrease in viscosity. These findings provide a nuanced understanding of the interplay between P content and viscosity throughout different phases of the melt.

Unusual photoinduced crystal structure dynamics in TaTe2 with double zigzag chain superstructure

Transition metal dichalcogenides with superperiodic lattice distortions have been widely investigated as the platform of ultrafast structural phase manipulations. Here we performed ultrafast electron diffraction on RT TaTe2, which exhibits a peculiar double zigzag chain pattern of Ta atoms. From the time-dependent electron diffraction pattern, we revealed a photoinduced change in the crystal structure occurring within <0.5 ps, although there is no corresponding high-temperature equilibrium phase. We further clarified the slower response (∼1.5 ps) reflecting the lattice thermalization. Our result suggests the unusual ultrafast crystal structure dynamics specific to the non-equilibrium transient process in TaTe2.

Am-241 in the urban air – monitoring and simulation results.

Concentration of 241Am was identified and analyzed during seven weeks between April and June 2021 in central Poland, using ASS500 monitoring station. The results changed from 0.305 to 4.241 µBq/m3. The lack of other, associate artificial isotopes on filters and no presence of isotope on other stations in Poland indicate on local emission. Processing of electrical waste, especially isotopic smoke detectors, has been investigated as a possible reason of the 241Am release into the atmosphere, probably in high temperature phase of metal separation. The possible circumstances of distribution of the radioactive 241Am isotope in the urban air in central Poland have been investigated and described.

(Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 and (Sc0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 high-entropy rare-earth disilicates as promising materials for environmental barrier coatings

The novel potential environmental barrier coating materials, two high-entropy rare earth disilicates (HEDs) (Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 and (Sc0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 were prepared by the solid-phase method. Both the HEDs showed remarkable high-temperature phase stability and an appropriate thermal expansion coefficient (CTE) that matched that of SiCf/SiC. In addition, both the HEDs possessed above 20% lower thermal conductivity at 1000 °C (1.37 and 1.42 W·m-1·K-1, respectively) compared to traditional single-component rare earth disilicate material YbDS, and they also exhibited higher mechanical properties and good resistance to water vapour corrosion at 1300 °C. Moreover, the corresponding free-standing coatings obtained after deposition by atmospheric plasma spraying (APS) showed excellent resistance to CMAS corrosion, primarily because of the formation of an apatite layer.

The transformation behaviour of ZnFe2O4 spinel particles in the CaO-FexO-SiO2-ZnO slag system

Treating zinc hydrometallurgical residues and other Zn-bearing solid waste in direct lead smelting processes has been recognized as the preferred solution for the sustainable development of the lead and zinc industry. However, new technical problems occurred when changing the starting material of lead-making processes, the pyrometallurgical process for treating zinc hydrometallurgical residues and zinc bearing solid waste usually had the CaO-FexO-SiO2-ZnO slag. Along with the increasing of Zn content in the raw material, high ZnO slag formed, and the ZnFe2O4 spinel particles intended to precipitate from the molten slag. The understanding of the particle behaviour of ZnFe2O4 spinel was the core part of monitoring the slag properties. This study investigated the transformation behaviour of zinc ferrite spinel particles and the changes in glassy slag phase through the high-temperature phase equilibrium experimental technique, and the temperature was 1100 °C-1300 °C and the oxygen potential was 10−8 atm – 10−4 atm. It is found that the particle size of ZnFe2O4 spinel in the molten slag increased along with the increasing of the oxygen potential. The Zn/Fe mass ratio in spinel particles decreased when increasing of temperature and it increased when increasing of oxygen potential. The Fe/SiO2 mass ratio and the Zn content in glassy slag phase gradually increased along with increasing temperature and they decreased along with increasing oxygen potential. The growing and decomposition of ZnFe2O4 spinel was essentially a process of material exchange with the glassy slag phase.

Fate of Chiral Symmetries in the Quark-Gluon Plasma from an Instanton-Based Random Matrix Model of QCD.

We propose a new way of understanding how chiral symmetry is realized in the high temperature phase of QCD. Based on the finding that a simple free instanton gas precisely describes the details of the lowest part of the spectrum of the lattice overlap Dirac operator, we propose an instanton-based random matrix model of QCD with dynamical quarks. Simulations of this model reveal that even for small quark mass the Dirac spectral density has a singularity at the origin, caused by a dilute gas of free instantons. Even though the interaction, mediated by light dynamical quarks, creates small instanton-anti-instanton molecules, those do not influence the singular part of the spectrum, and this singular part is shown to dominate Banks-Casher type sums in the chiral limit. By generalizing the Banks-Casher formula for the singular spectrum, we show that in the chiral limit the chiral condensate vanishes if there are at least two massless flavors. Our model also indicates a possible way of resolving a long-standing debate, as it suggests that for two massless quark flavors the U(1)_{A} symmetry is likely to remain broken up to arbitrarily high finite temperatures.

High-pressure–high-temperature phase diagram of tin

High-pressure–high-temperature phase diagram of tin