Rapid Sublimation Research Articles

Research of the family associations of active asteroids in the main belt

ABSTRACT We apply the Hierarchical Clustering method (HCM) and Selective Backward Integration method (BIM) to search for associated families and young families for all main-belt active asteroids (MBAAs) known to date. We find four newly candidate sub-groups of known families, which include the candidate Brueghel family associated with 176P/LINEAR, the candidate 324P group associated with 324P/La Sagra, the candidate G1 group associated with P/2016 G1, and the candidate Tutenchamun family associated with (62412) 2000 SY178. Additionally, we identify three entirely new candidate families, the Interamnia family associated with P/2021 A5, the candidate 457P group associated with 457P/Lemmon-PANSTARRS, and the candidate Scheila family associated with (596) Scheila. We also reveal two newly identified family associations with known families between 259P/Garradd and the Adeona family, P/2019 A4 and the Jones family. All main-belt comets (MBCs) are likely associated with young and primitive families. Some unstable MBCs, which cannot be identified using HCM, may still originate from young and primitive families. However, due to dynamic diffusion, they cannot be conclusively linked to current families. Impact-disrupted asteroids could be linked with young families and they may change their original spectrum under the impact activity. Rotational fission of young and primitive asteroids might be a useful mechanism for facilitating the exposure of subsurface ice, and therefore triggering sublimation-driven activity. Rapid rotation and sublimation activity mechanisms are likely coupled. Therefore, further research should be made on such fast rotational asteroids that are located in primitive families.

An analytical study of coupled convective heat and mass transfer with volumetric heating describing sublimation of a porous body under most sensitive temperature inputs: Application of freeze-drying

Sublimation heat-mass transfer has great applications in the pharmaceutical and food industries, such as the preservation of biological products, accelerated freeze-drying (AFD), energy storage systems, microwave freeze-drying, and enabling long-time active covid like vaccines. The current technological demand encourages investigators to provide new knowledge for freeze-drying so that it reduces the high economic cost, prevents materials from being denatured, and remains stable for a long time. In connection with this, it is of key interest to analyze the impact of convective heat and mass transfer, the rate of water vaporization, and the volumetric heating source under the most realistic temperature inputs. Despite the available works on sublimation, there is still a lack of mathematical modeling that accounts for these informations together and is presently being considered. This paper presents a heat and mass transfer problem describing sublimation in a half-porous space. The mathematical model accounts for convective heat/mass transfer and a volumetric heat source within dried and frozen regions. In addition, convection driven by the mass transfer of ice crystals within the dried region is also considered. Three different types of temperature input are placed at the surface x=0 to obtain the rapid sublimation process without harming the material properties. The exact solution to the problem is obtained successfully by using similarity transformation. The impact of various problem parameters on sublimation is comprehensively studied. In this study, it is found that with a volumetric heating source term G0, material sublimates faster than without one. Furthermore, convective heat transfer in terms of Pe1 and Pe2, enhances the temperature within the porous medium, and as a result, material sublimates faster than usual. As the value of the convective term β goes up, a reduction in the temperature field is observed. The temperature of the medium rises as the value of the Kirpichev-like number Ki increases. Similar observation is found in the case of Biot like number Bi. The concentration profile decreases as the value of the Luikov number Lu increases. It is also found that Newton-type temperature input offers a faster sublimation rate in comparison to constant and flux-type temperature input. The analytical results obtained in this study show excellent agreement with previous available results. These results provide a comprehensive theoretical and mathematical understanding of sublimation heat/mass transfer and are expected to be useful in energy storage systems, food technology, and accelerated freeze drying.

Optimum energy efficiency in lunar in-situ water ice utilization

Lunar in-situ water ice utilization is considered an essential part of the future construction of Lunar Bases. However, the thermal conductivity of lunar regolith without water ice is extremely low, which seriously hinders the thermal mining of lunar water ice. In this study, we proposed a novel approach to optimize the energy efficiency of water ice thermal mining. In this method, a constant temperature heat source with a heating temperature selected according to the particle size of water ice was used to slow down the reduction rate of the thermal conductivity of icy soil. Our simulation results showed that the relatively high mining temperature led to the rapid sublimation of water ice near the heat source, reducing the thermal conductivity of the icy soil and the energy efficiency.A relatively low mining temperature decreases the sublimation speed of water ice and reduces energy efficiency. The particle size of water ice determined the decreasing rate of thermal conductivity of icy soil, thus affecting its optimum heating temperature. Using a constant temperature heat source at the optimal heating temperature, the energy efficiency of water ice mining could be increased by several orders of magnitude compared with constant power heating.

Fast and Reproducible Matrix Deposition for MALDI Mass Spectrometry Imaging with Improved Glass Sublimation Setup

Sublimation is one of the preferred methods of choice for matrix deposition in high spatial resolution MALDI mass spectrometry imaging (MALDI-MSI) experiments. However, reproducibility and time are the major concerns for this setup. Here we present a lab-made glass sublimator with significant improvements in fine control of the vacuum with real-time monitoring and a rapid sublimation process of only 22 min. This method yielded reproducible homogeneous matrix crystals of <1 μm on the sample surface. MALDI-MSI was performed in tissue sections of barley inflorescence meristems at 15 μm spatial resolution, thus demonstrating its efficiency. Overall, we believe these simple yet effective new modifications can be easily adapted to the standard glass sublimation devices to achieve highly reproducible matrix deposition for high spatial resolution MALDI-MSI.

Enhanced performance of GeSe thin-film solar cells via bifacial charge transport materials design

Owing to non-toxic, earth abundant and stable properties, GeSe has become a promising photovoltaic absorber material in thin-film solar cells (TFSCs). Currently GeSe film is mainly prepared by rapid thermal sublimation (also called one-step method), where the evaporation source and substrate are heated together, thus it is difficult to regulate their temperatures independently, leading to the re-sublimation of GeSe film and diffusion of Cd element. In this work, a two-step method is introduced to prepare the GeSe film. Moreover, a synergic interface design is applied to enhance the performance of GeSe TFSCs. On one hand, the conductivity of CdS buffer layer is increased by post-annealing to reduce the series resistance and promote the electron transfer from GeSe to CdS, validated via linear sweep voltammetry curves. On the other hand, Cu2O is inserted as a hole transport layer for the first time. The Cu2O layer has sufficiently improved the hole extraction efficiency and suppressed the charge recombination, demonstrated by transient photovoltage spectroscopy and electrochemical impedance spectroscopy. By incorporating these bifacial modifications, the power-conversion efficiency (PCE) of the device has been improved by about four times (0.16%–0.63%), comparable to the highest PCE among all the reported GeSe TFSCs fabricated via a two-step method.

Precise positioning and inert processing of the high-temperature zone in a longwall gob during a mining-stopped period: an application case

ABSTRACT During a mining-stopped period, coal spontaneous combustion (CSC) may occur in a gob area, which not only causes huge economic losses but also poses a serious threat to the mine’s production safety. To address this situation, a working face in the Chinese Silaogou Coal Mine was considered as an example. With a combination of numerical simulation and field temperature measurements, the spatiotemporal distribution of the temperature in a longwall gob was determined, and the area of potential spontaneous combustion was identified. Furthermore, a dry-ice rapid sublimation unit used for underground fire prevention was developed. The device was successfully applied underground to exert the effect of low-temperature carbon dioxide gas to reduce the coal temperature. The results show that the temperature of the mined-out area near the air intake side of the working face is significantly higher than that of the return side, and the longer the stopping time is, the more obvious the temperature difference is. Within 12 hours of using the generator to inject carbon dioxide, the observed temperatures of the two hot spots dropped from 26.1°C and 26.6°C to 19.1°C and 19.8°C, respectively, and the temperatures hardly rebounded after stopping the gas injection, effectively suppressing the heat storage and oxidation of the coal.

Problems in pore property testing of lignite: Analysis and correction

Due to the low coalification degree of lignite, the colloid-like properties and loose characteristics lead to low energy utilization efficiency and seriously hinder the correct understanding of the original pore structure and its mechanical behavior. As a standard process for physical property test, removing the moisture in the pores by drying will cause the lignite to shrink sharply, destroying its original pore structure. Also, for test methods that need to be performed under high pressure, such as mercury intrusion porosimetry (MIP), the soft and loose texture of lignite will cause it to be significantly compressed, making the test results inaccurate. Aiming at the conventional lignite testing process problems, an optimized scheme suitable for lignite was proposed. By rapid freezing and sublimation at low temperatures, freeze-drying can effectively prevent the collapse of lignite. The solid-state of water protects the lignite's primary structure and shape and minimizes volume shrinkage. The average shrinkage rate of lignite sample after freeze-drying is only 9.72%, while that after hot air-drying is 34.8%. Therefore, dehydration by freeze-drying can be an effective method to protect the pore structure of lignite. Based on correcting the syneresis problem, the piecewise linear interpolation method is used to correct the compression effect of lignite. The corrected result excludes the increased pore volume due to the compression of the lignite skeleton. Also, it avoids the under-correction of the low-pressure part and overcorrection of the high-pressure part in the conventional correction method. Based on the corrected nitrogen adsorption and MIP results, the nuclear magnetic resonance (NMR) surface relaxivity of lignite is calculated. The average surface relaxivity value of the samples is 42.8 μm/s, which is significantly greater than that of medium and high-rank coals. The corrected NMR pore size distribution is closer to the actual pore size distribution of lignite. Finally, based on the analysis and correction of the problems in pore property testing of lignite, the improved workflow suitable for lignite is proposed, which provides some referential significance for the correct understanding of its actual physical property.

Study on Dry-Ice Particle Jet Polishing Process of 316L Stainless Steel Electrode

Dry-ice particle jet technique has the advantages of rapid sublimation, easy drying, and without residues after striking onto the surface, which has been applied in the field of optical coating and the polishing and cleaning of integrated circuit. However, the process mechanism of this technique on stainless steel is not clear and the application research is not in-depth, which restricts the development and application of dry-ice particle jet technique in electrode polishing. In this work, the influence of the processing parameters such as spraying pressure, spraying angle, spraying distance, and spraying time on the micro-morphology and roughness of the stainless steel electrode surface was studied by single factor experiments. In addition, the characterization methods for the surface roughness, surface defects, surface micro-morphology, surface micro-unevenness, and surface chemical composition of the stainless steel electrodes were developed. Comprehensive characterization technology of the electrode surface was established.

Impact of Convectively Detrained Ice Crystals on the Humidity of the Tropical Tropopause Layer in Boreal Winter

AbstractDeep convection detraining in the uppermost tropical troposphere is capable of transporting water vapor and ice into the tropical tropopause layer (TTL), but the impact of deep convection on the global and regional TTL water vapor budget remains uncertain. In particular, the role of convectively detrained ice crystals that remain suspended after active convection has subsided is not well understood. These ice crystals represent aging cirrus anvils detached from the convective core. We use a cloud microphysical model that tracks individual ice crystals throughout their lifetimes to quantify the impact of detrained ice on the humidity of the TTL during boreal winter. Convective influence of air parcels near the wintertime cold point tropical tropopause is determined by tracing thousands of backward trajectories through satellite‐derived, global, 3‐hourly convective cloud‐top altitude fields. Detrained ice, most of which is found over the tropical western Pacific, experiences cooling on the order of 1 K day−1 downstream of convection. Downstream cooling increases relative humidity and explains the observed supersaturated TTL over this region. Vapor in excess of saturation condenses onto the detrained ice, which ultimately brings the relative humidity down to saturation. Thus, convectively detrained ice crystals in aging anvils predominantly dehydrate the TTL, but the effect is small (0.01 ppmv). Moistening by active convection (0.30 ppmv), including the rapid sublimation of convectively lofted ice crystals near the tops of core anvils, overwhelms the dehydration by aging anvil ice crystals detrained from the core. The net effect is moistening by convective core anvils during boreal winter.

Thermomechanical Nanocutting of 2D Materials.

Atomically thin materials, such as graphene and transition metal dichalcogenides, are promising candidates for future applications in micro/nanodevices and systems. For most applications, functional nanostructures have to be patterned by lithography. Developing lithography techniques for 2D materials is essential for system integration and wafer-scale manufacturing. Here, a thermomechanical indentation technique is demonstrated, which allows for the direct cutting of 2D materials using a heated scanning nanotip. Arbitrarily shaped cuts with a resolution of 20 nm are obtained in monolayer 2D materials, i.e., molybdenum ditelluride (MoTe2 ), molybdenum disulfide (MoS2 ), and molybdenum diselenide (MoSe2 ), by thermomechanically cleaving the chemical bonds and by rapid sublimation of the polymer layer underneath the 2D material layer. Several micro/nanoribbon structures are fabricated and electrically characterized to demonstrate the process for device fabrication. The proposed direct nanocutting technique allows for precisely tailoring nanostructures of 2D materials with foreseen applications in the fabrication of electronic and photonic nanodevices.

Promising GeSe Nanosheet-Based Thin-Film Photocathode for Efficient and Stable Overall Solar Water Splitting

Compound semiconductor GeSe nanosheet-based thin films were systematically researched for application in solar water splitting. p-type GeSe films obtained from the rapid thermal sublimation method ...

In Situ Atomic-Scale Oscillation Sublimation of Magnesium under CO2 Conditions.

Understanding the interactive role between Mg and CO2 is crucial for many technological applications, including CO2 storage, melting protection, corrosion resistance, and ceramic welding. Here we report observations of rapid oscillation sublimation of Mg at room temperature in the presence of both CO2 gas and electron irradiation using environmental transmission electron microscopy. The sublimation is mainly related to phase transformation of amorphous MgCO3. Differing from the direct formation of gas-state MgCO3, which attributes to the sublimation of pure Mg under a mild electron beam dose, a unique oscillation process is detected during the process of Mg sublimation under a harsh electron beam dose. The main reason stems from the first-order reaction of a reversible decomposition-formation of amorphous MgCO3. These atomic-level results provide some interesting insights into the interactive role between Mg and CO2 under electron beam irradiation.

Insights into incipient soot formation by atomic force microscopy

Combustion-generated soot particles can have significant impact on climate, environment and human health. Thus, understanding the processes governing the formation of soot particles in combustion is a topic of ongoing research. In this study, high-resolution atomic force microscopy (AFM) was used for direct imaging of the building blocks forming the particles in the early stages of soot formation. Incipient soot particles were collected right after the particle nucleation zone of a slightly sooting ethylene/air laminar premixed flame at atmospheric pressure and analyzed by AFM after a rapid sublimation procedure. Our data shed light on one of the most complex and still debated aspect on soot formation, i.e., the nucleation process. The molecular constituents of the initial particles have been individually analyzed in detail in their chemical/structural characteristics. Our data demonstrate the large complexity/variety of the aromatic compounds which are the building blocks of the initial soot particles. Nevertheless, some fundamental and specific characteristics have been clearly ascertained. These include a significant presence of penta-rings as opposed to the purely benzenoid aromatic compounds and the noticeable presence of aliphatic side-chains. In addition, there were indications for the presence of persistent π radicals. Incipient soot was also investigated by Raman spectroscopy, the results of which agreed in terms of chemical and structural composition of the particles with those obtained by AFM.

Early extinguishment of spontaneous combustion of coal underground by using dry-ice’s rapid sublimation: A case study of application

Carbon dioxide injection is an ideal approach to prevent and control spontaneous combustion of coal in coal mines, which has higher purity, wider coverage and stronger inerting effect, but its application is limited by how to produce considerable gaseous carbon dioxide underground. Liquid carbon dioxide has high risks to be used underground due to its phase-state instability. Dry-ice has stable properties, but its sublimation in normally is too slow to extinguish the fire. To address this issue, a new type of apparatus for efficiently sublimating dry-ice has been developed independently, which would yield more than 205 times as much carbon dioxide as dry-ice under normal condition. There is no external power supply during its working, but the heat for dry-ice’s rapid sublimation originates from continuously running water in a copper pipe inside the apparatus, thereby greatly improving the security of the use underground. This apparatus has been successfully applied to extinguish several early spontaneous combustion in Yangmeiwu Coal Mine in China. This paper describes the apparatus and its application.

Compatibility studies on Mo–coating systems for nuclear fuel cladding applications

To improve the safety factor of nuclear power plants in accident scenarios, molybdenum (Mo), with its high-temperature strength, is proposed as a potential fuel-cladding candidate. However, Mo undergoes rapid oxidation and sublimation at elevated temperatures in oxygen-rich environments. Thus, it is necessary to coat Mo with a protective layer. The diffusional interactions in two systems, namely, Zircaloy-2 (Zr2) on a Mo tube, and iron-chromium-aluminum (FeCrAl) on a Mo rod, were studied by aging coated Mo substrates in high vacuum at temperatures ranging from 650 °C to 1000° for 1000 h. The specimens were characterized using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and nanoindentation. In both systems, pores in the coating increased in size and number with increasing temperature over time, and cracks were also observed; intermetallic phases formed between the Mo and its coatings.

Investigation of Physical and Electronic Properties of GeSe for Photovoltaic Applications

AbstractGeSe is a promising absorber material for photovoltaic applications due to its attractive material, optical, and electrical properties as well as its low toxicity and earth abundance. The first GeSe‐based solar cell with 1.48% efficiency has been recently reported through self‐regulated rapid thermal sublimation. However, most of the fundamental physical and electronic properties of GeSe such as refractive index, dielectric constant, carrier mobility, lifetime, and diffusion length remain unclear, despite the necessity of this for the design of high‐performance GeSe solar cells. In this work, the above basic properties of GeSe are systematically studied by using spectroscopic ellipsometry, space charge limited current measurements, and transient absorption spectroscopy. These comprehensive results provide a solid foundation for the further development of GeSe solar cells.

Temperature‐ and pressure‐dependent structural transformation of methane hydrates in salt environments

AbstractUnderstanding the stability of volatile species and their compounds under various surface and subsurface conditions is of great importance in gaining insights into the formation and evolution of planetary and satellite bodies. We report the experimental results of the temperature‐ and pressure‐dependent structural transformation of methane hydrates in salt environments using in situ synchrotron X‐ray powder diffraction, solid‐state nuclear magnetic resonance, and Raman spectroscopy. We find that under pressurized and concentrated brine solutions methane hydrate forms a mixture of type I clathrate hydrate, ice, and hydrated salts. Under a low‐pressure condition, however, the methane hydrates are decomposed through a rapid sublimation of water molecules from the surface of hydrate crystals, while NaCl · 2H2O undergoes a phase transition into a crystal growth of NaCl via the migration of salt ions. In ambient pressure conditions, the methane hydrate is fully decomposed in brine solutions at temperatures above 252 K, the eutectic point of NaCl · 2H2O.

Slow Release of Menthol Using Sorbents Developed from Microwave Graphene Oxide

Menthol is a key ingredient in many of the traditional Thai aroma products such as potpourri and herbal air freshener. However, it suffers from the rapid evaporation and sublimation loss. In this work, microwave graphene oxide (mGO) has been prepared as sorbent and tested for the slow release of menthol. Menthol was loaded into microwave graphene oxide at loading ratios of 1:0.5 and 1:1. The release performance of the mGO as compared to traditional essential oil reed diffuser and the pure menthol was studied by monitoring the menthol weight loss at the temperature of 80°C until all of the menthol evaporated using thermogravimetric analysis. It was found that mGO can significantly slow down the menthol release rate compared to that of the pure menthol by up to eight times slower. The interaction and adsorption mechanism of the menthol-loaded microwave graphene oxide was also studied using Fourier Transform Infrared Spectroscopy (FTIR) which indicates that menthol adsorbs strongly onto the mGO leading to the slow release rate.

GeSe Thin-Film Solar Cells Fabricated by Self-Regulated Rapid Thermal Sublimation.

GeSe has recently emerged as a promising photovoltaic absorber material due to its attractive optical and electrical properties as well as earth-abundant and low-toxic constituent elements. However, no photovoltaic device has been reported based on this material so far, which could be attributed to the inevitable coexistence of phase impurities Ge and GeSe2, leading to detrimental recombination-center defects and seriously degrading the device performance. Here we overcome this issue by introducing a simple and fast (4.8 μm min-1) rapid thermal sublimation (RTS) process designed according to the sublimation feature of the layered structured GeSe. This new method offers a compelling combination of assisting raw material purification to suppress deleterious phase impurities and preventing the formation of detrimental point defects through congruent sublimation of GeSe, thus providing an in situ self-regulated process to fabricate high quality polycrystalline GeSe films. Solar cells fabricated following this process show a power conversion efficiency of 1.48% with good stability. This preliminary efficiency and high stability, combined with the self-regulated RTS process (also extended to the fabrication of other binary IV-VI chalcogenide films, i.e., GeS), demonstrates the great potential of GeSe for thin-film photovoltaic applications.

Sublimation as a landform-shaping process on Pluto

Fields of pits, both large and small, in Tombaugh Regio (Sputnik Planitia, and the Pitted Uplands to the east), and along the scarp of Piri Rupes, are examples of landscapes on Pluto where we conclude that sublimation drives their formation and evolution. Our heuristic modeling closely mimics the form, spacing, and arrangement of a variety of Tombaugh Regio's pits. Pluto's sublimation modified landforms appear to require a significant role for (diffusive) mass wasting as suggested by our modeling. In our models, the temporal evolution of pitted surfaces is such that initially lots of time passes with little happening, then eventually, very rapid development of relief and rapid sublimation. Small pits on Sputnik Planitia are consistent with their formation in N2-dominated materials. As N2-ice readily flows, some other ``stiffer'' volatile ice may play a role in supporting the relief of sublimation degraded landforms that exhibit several hundred meters of relief. A strong candidate is CH4, which is spectroscopically observed to be associated with these features, but the current state of rheological knowledge for CH4 ice at Pluto conditions is insufficient for a firm assessment.