Sublimation Of Materials Research Articles

The effects of micro and macro structure on electronic properties of bismuth oxyiodide thin films

Bismuth oxyiodide (BiOI) thin film was deposited using successive ionic layer adsorption and reaction (SILAR) technique under the same molar ratio of bismuth (III) nitrate pentahydrate (Bi(NO3)5H2O) and potassium iodide (KI). The effects of micro and macro structures due to the post-annealing treatment has been studied towards the improved electronic properties of BiOI films. BiOI thin film was perfectly coated without any cracks or pinholes. The as-deposited BiOI film displayed small flakes with flower shape microstructure. The flakes size has increased from ∼0.8 μm to ∼3.2 μm upon annealing at 350 °C, thenceforth shattered with increasing annealing temperature. BiOI films annealed at 350 °C showed a sharper band edge slope with an energy bandgap ∼1.61 eV compared to others annealing temperatures. The single crystalline BiOI film has transformed from tetragonal to tetragonal-orthorhombic polycrystalline with mix Bi5O7I3 and Bi7O9I3 phases after being annealed ≥450 °C. Electronic properties of BiOI were studied in terms of average resistance and conductivity measured using four-probe hall effect measurement. The conductivity value has reached the maximum for sample annealed at 350 °C, owing to the formation of ordered phase in material structure, higher crystallinity, larger flakes sizes, as well as reduction of defects and grain boundaries resistance. When the annealing temperature exceeded 450 °C, the electrical conductivity decreased due to the particle aggregation, sublimation of materials, formation of mix-phase and polycrystalline structure that generated grain boundaries and provided more resistance for electrons flow. The work has demonstrated a better understanding of material issues and some clues on the effect of the thickness, microstructure and structural properties on the electronic properties of BiOI thin film.

Sublimation of organic-rich comet analog materials and their relevance in fracture formation

Aims.The morphology of cometary nuclei is the result of an ongoing evolution and can provide valuable information to constrain the composition of comets. In our laboratory experiments we investigated the morphological evolution of comet analog materials, which consist of volatile, dust, and organic components. The laboratory results are aimed to help understand the evolution of cometary surfaces.Methods.We used spherical particles of fly ash and mixtures of ice, glycine, and sodium acetate as analog materials in different mass ratios to reproduce observed cometary morphologies. The cohesive and gravitational properties in the laboratory are scaled to cometary conditions to draw meaningful conclusions from the experimental results. The samples were placed in a vacuum sublimation chamber, cooled down to below 150 K, and were insolated with an external light source. To analyze the morphology of the samples, a camera was used to monitor the alterations of the surface.Results.Organic components in volatile-rich samples can have a distinct adhesive effect after the volatiles sublimate. During the sublimation process the sample volume decreases and fractures form on the sample surface. Due to the stability of the remaining volatile-depleted material, significant cliff collapses or ejected particles were not observed in the laboratory.

Simultaneous sublimation activity of primitive asteroids including (24) Themis and (449) Hamburga: Spectral signs of an exosphere and the solar activity impact

We describe and analyze simultaneous sublimation activity of the main-belt primitive asteroids during their perihelion passages, which was detected by spectral methods. This phenomenon was observed for the first time in September 2012 for asteroids (145) Adeona, (704) Interamnia, (779) Nina, and Mars-crosser (1474) Beira (Busarev et al., 2015, 2016, 2018, 2019a). By our recent observations of (704) Interamnia, (24) Themis, and (449) Hamburga performed in March–April 2019, we confirmed the existence of this effect. (24) Themis and (449) Hamburga was detected as active for the first time. Never before, two or more asteroids have been observed active simultaneously. Activity on asteroids reveals itself by unusual spectral features (the maxima at approximately 0.40–0.50 and/or 0.60–0.70 μm), which appear in the reflectance spectra of the bodies when they approach perihelion. We explain them as manifestations of sublimation of ice materials and development of a subtle exosphere around the asteroids. Moreover, from numerical simulations of the light scattering in a medium containing ice and silicate/organic dust particles of complex structure, we found that some of these models fit well the reflectance spectra of active asteroids, which confirms the presence of a rarefied exosphere around these bodies. Our results show that the main conditions providing formation of a temporal sublimation-driven exosphere around primitive main-belt asteroids are: (1) the considerably higher content of H2O in their material than that previously believed from accounting for only the content of bound water in composition of carbonaceous chondrites, as possible components of asteroids; (2) frequent collisions of main-belt asteroids with smaller bodies and/or exposure to meteorite fluxes, which leads to excavation of ices and their subsequent sublimation; (3) the recurrent rise of the subsolar temperature on the surface of asteroids under proper orbital or dynamical parameters and the sublimation of subsurface ices (if present); and (4) the strengthening of solar activity (and the accompanying factors), which results in desiccation, destruction and/or dispersion of hydrated silicates and/or radiation damage of organic films isolating stocks of volatiles on or under the asteroid surface. According to our analysis, none of these factors produces a noticeable effect alone and can be marked as stronger or more frequent, but two or three of them working simultaneously may be effective.

Experimental researches of atmospheric sublimation drying and analysis of economic efficiency its applications

This article presents the results of experimental studies and economic analysis in the field of atmospheric freeze drying (AFD), analyzes the features of the processes of sublimation of polydisperse materials of animal and vegetable origin. Using the results of this work will reduce energy intensity and increase the efficiency of sublimation technologies in industrial production. An economic analysis of the feasibility of atmospheric freeze-drying technology is carried out according to discounted indicators. The values of the terms of the project implementation are obtained and practical recommendations on the modes and parameters of drying are given.

Organic matter in interstellar dust lost at the approach to the heliosphere

Aims. We tackle the conundrums of organic materials missing from interstellar dust when measured inside the Solar System, while undoubtedly existing in the local interstellar cloud (LIC), which surrounds the Solar System. Methods. We present a theoretical argument that organic compounds sublimate almost instantaneously by exothermic reactions, when solar insolation triggers the recombination of free radicals or the rearrangement of carbon bonds in the compounds. Results. It turns out that the triggering temperature lies in the range of 20–50 K by considering that sublimation of organic materials takes place beyond the so-called filtration region of interstellar neutral atoms. We find that in-situ measurements of LIC dust in the Solar System result in an overestimate for the gas-to-dust mass ratio of the LIC, unless the sublimation of organic materials is taken into account. We also find that previous measurements of interstellar pickup ions have determined the total elemental abundances of gas and organic materials, instead of interstellar gas alone. Conclusions. We conclude that LIC organic matter suffers from sublimation en route to the heliosphere, implying that our understanding of LIC dust from space missions is incomplete. Since space missions inside the orbit of Saturn cannot give any information on the organic substances of LIC dust, one must await a future exploration mission to the inner edge of the Oort cloud for a thorough understanding of organic substances in the LIC. Once our model for the sublimation of interstellar organic matter by exothermic chemical reactions of free radicals is confirmed, the hypothesis of panspermia from the diffuse interstellar medium is ruled out.

Rocklines as Cradles for Refractory Solids in the Protosolar Nebula

Abstract In our solar system, terrestrial planets and meteoritical matter exhibit various bulk compositions. To understand this variety of compositions, formation mechanisms of meteorites are usually investigated via a thermodynamic approach that neglects the processes of transport throughout the protosolar nebula. Here, we investigate the role played by rocklines (condensation/sublimation lines of refractory materials) in the innermost regions of the protosolar nebula to compute the composition of particles migrating inward toward the disk as a function of time. To do so, we utilize a one-dimensional accretion disk model with a prescription for dust and vapor transport, sublimation, and recondensation of refractory materials (ferrosilite, enstatite, fayalite, forsterite, iron sulfide, metal iron, and nickel). We find that the diversity of the bulk composition of cosmic spherules, chondrules, and chondrites can be explained by their formation close to rocklines, suggesting that solid matter is concentrated in the vicinity of these sublimation/condensation fronts. Although our model relies a lot on the number of considered species and the availability of thermodynamic data governing state changes, it suggests that rocklines played a major role in the formation of small and large bodies in the innermost regions of the protosolar nebula. Our model gives insights on the mechanisms that might have contributed to the formation of Mercury’s large core.

INHALATION OF TRANSURANIC ELEMENTS IN CASE OF EMERGENCIES IN THE EXCLUSION ZONE OF THE CHERNOBYL NPP

Relevance. In the radioactive contamination territory, any work must be carried out with mandatory individual dosimetric monitoring of participants using all the irradiation pathways. However, at present, the control of personnel exposure through the respiratory organs is not carried out due to the lack of methodological and technical support.Intention. To estimate the irradiation doses of personnel expected as a result of inhalation of transuranic elements during fires in the Belarusian sector of the Chernobyl exclusion zone.Methodology. The objects of research are aerosol particles containing137Cs,90Sr,238Pu,239Pu,240Pu,241Pu and241Am, formed as a result of high temperature sublimation and combustion of forest materials. The subject of research is the irradiation doses of personnel as a result of inhalation intake of137Cs,90Sr,241Am,238Pu,239Pu,240Pu and241Pu during fire fighting.Results and Discussion. The expected doses of internal irradiation in fire extinguishing participants in the Belarusian sector of the Chernobyl exclusion zone due to inhalation of transuranic elements were estimated. The assessments were carried out both by direct measurements of the volume activity of radionuclides in the breathing zone of fire fighting participants and via calculations. It is shown that the contribution of137Cs to the “inhalation” dose of personnel can be only 1 %. It is established that in the Belarusian sector of the Chernobyl exclusion zone the contribution of transuranic elements to the expected effective dose of internal radiation is about 60 %. Radiation doses of personnel expected as a result of inhalation of radionuclides did not exceed 0.1 mSv per year, which is significantly less than the control level established in the Polesye State Radiation Ecological Reserve for personnel (5 mSv per year).Conclusion. The proposed methods make it possible to conservatively assess the expected inhalation doses in personnel in case of fire fighting in the exclusion zone of the Chernobyl nuclear power plant, as well as to ensure their accounting for individual dosimetric control.

Thermal Energy Storage P(BeA-co-MMA) Microcapsules with Excellent Thermal Stability

Latent heat storage systems are a highly efficient and environmentally friendly way to use residual heat and store renewable energy. Phase change materials, which can absorb or release the enthalpy of phase changes in certain temperature ranges, are considered one of the most reliable latent heat storage and thermoregulation materials. Phase change materials have been successfully used in the fields of solar energy, aerospace and aviation, environmental control and textiles. Among phase change materials, paraffin and n-alkane are the most popular due to their characteristics of high phase change enthalpy, high energy storage density, relative low volume change ratio, good physical and chemical stability, and no super-cooling or phase segregation behavior. More importantly, there are wide selective working temperature ranges which greatly extend their operating conditions. Microcapsules are considered micro scale containers to prevent core from leaking, isolate from the surroundings and maintain chemical and functional stability in service. There are several methods to synthesize microcapsules: spray dying, complex coacervation, sol-gel, in-situ polymerization, suspension polymerization and emulsion polymerization. Among these, suspension polymerization has the advantages of being simple, cheap, stable, eco-friendly and being easily controlled, which makes it the most popular chemical method to synthesize microcapsules. The majority shell materials of traditional microcapsules are synthetic macromolecules. The properties of shell materials impact the application and processing conditions of the final energy storage composite materials greatly. Nevertheless, the low thermal stability and physical strength of polymers in nature strongly restrict application fields of microcapsules. What’s more, the evaporation or sublimation of core materials causes the low thermal stability. In order to overcome these shortages of shell fracture, core leakage, core evaporation or sublimation existing in traditional microcapsules, we design a copolymer microcapsule with strong interaction force between shell and core parts, which has an unseparated surface layer between shell and core. The strong interaction force between shell and core allows the extreme improvement of thermal stability of microcapsules. The copolymer microcapsule is synthesized by suspension polymerization of behenyl acrylate (BeA) and methyl methacrylate (MMA). In this paper, we report the synthesis, size control and structure analysis of P(BeA-co-MMA) microcapsules which have both excellent thermal stability and high thermal energy storage capacity.

Physical properties of ZnSe1-xTex,thin films prepared with a single three-chamber evaporation coaxial source

ZnSe1-xTex thin films were prepared using a single evaporation source specially designed to produce ternary material from the simultaneous sublimation of ZnSe and ZnTe precursor materials. A detailed description of the evaporation source and the procedure for depositing the thin films are given. The substrate temperature allows adequately controlling the Te concentration in the samples. The samples were studied using X-ray Diffraction, Energy Dispersive X-ray, transmittance, room temperature photoluminescence, and photoconductivity in the visible spectral region. The percentage of Te as a function of the substrate temperature was determined using Vegard's Law. Samples grew with the stable cubic structure and were oriented along plane [111]. The crystallite size and thickness of the samples were dependent on the substrate temperature. Absorption values on the order of 108 cm−1 and a gap change from 3,0 (x = 0,98) to 3,3 (x = 0,13) eV as the substrate temperature increased from 333 to 623 K were found. The photoluminescence and photoconductivity spectra have contributions of charge recombination through the band gap edge, with localized states below the band gap associated with Zn and Te vacancies in the material. The photoconductivity and photoluminescence signals changed according to the composition of the films.

Curvatures of smectic liquid crystals and their applications

ABSTRACTCurvature is an important concept for understanding layering structures in soft matters, ranging from complex macromolecular self-assembled structures to simple lipid bilayers. Among the various kinds of soft matters, smectic liquid crystal (LC) phases have been widely studied because of their periodic featured curvatures under various external forces. Generally, their curvatures are on the micron-scale due to the bulk elasticity of smectic LC materials. In this review, a combination of sublimation and recondensation of smectic LC materials generates a variety of curvatures at the nanometer scale, which cannot be achieved by self-assembly under thermal equilibrium conditions. In particular, we have focused on the change of curvatures in focal conic domains under non-equilibrium conditions, in which negative and zero Gaussian curvatures in the micron-scale transform to positive Gaussian curvatures in the micron- and nanometer scales. Finally, the review closes with applications using such non-equilibrium self-assembly of smectics.

The protective coatings for the multisectional thermoelements of the generators working at the temperatures up to 1200 K

To increase efficiency structure of multisectional thermoelectric generator working up to the temperature of 1200 K was developed. Compositions were proposed, and thermoelectric materials were obtained for the fabrication of each section of thermoelement. Investigations showed that these materials have high figure of merit. Sublimation of thermoelectric materials in the working temperature of multisectional thermoelement was investigated. To eliminate sublimation of thermoelectric material, Si3N4 and SiO2 protective layers were deposited by plasma-chemical method, which were effective up to the temperature of 1200 K.

Single Nanoparticle Mass Spectrometry as a High Temperature Kinetics Tool: Sublimation, Oxidation, and Emission Spectra of Hot Carbon Nanoparticles.

In single nanoparticle mass spectrometry, individual charged nanoparticles (NPs) are trapped in a quadrupole ion trap and detected optically, allowing their mass, charge, and optical properties to be monitored continuously. Previous experiments of this type probed NPs that were either fluorescent or large enough to detect by light scattering. Alternatively, small NPs can be heated to temperatures where thermally excited emission is strong enough to allow detection, and this approach should provide a new tool for measurements of sublimation and surface reaction kinetics of materials at high temperatures. As an initial test, we report a study of carbon NPs in the 20-50 nm range, heated by 10.6 μm, 532 nm, or 445 nm lasers. The kinetics for sublimation and oxidation of individual carbon NPs were studied, and a model is presented for the factors that control the NP temperature, including laser heating, and cooling by sublimation, buffer gas collisions, and radiation. The estimated NP temperatures were in the 1700-2000 K range, and the NP absorption cross sections ranged from ∼0.8 to 0.2% of the geometric cross sections for 532 nm and 10.6 μm excitation, respectively. Emission spectra of single NPs and small NP ensembles show a feature in the IR that appears to be the high energy tail of the thermal (blackbody-like) emission expected from hot particles but also a discrete feature peaking around 750 nm. Both the IR tail and 750 nm peak are observed for all particles and for both IR and visible laser excitation. No significant difference was observed between graphite and amorphous carbon NPs.

Estimating vapor enthalpies of sublimation by rising-temperature absorbance spectroscopy

Determining the enthalpies of sublimation of low volatile materials in the vapor phase is favored. Although benzoic acid, ferrocene, and naphthalene are used as reference materials in instrumentation calibration for indirect determination of vapor pressure of low volatile materials, the discrepancy of the values of their enthalpies of sublimation is considerably large (∼10–15 kJ mol−1). Time is a crucial factor in determining thermodynamic parameters for hazardous materials. In this article, we illustrate the use of UV–Vis absorbance spectroscopy in determining the enthalpies of sublimation of these materials in the vapor phase non-isothermally. The enthalpies of sublimation of benzoic acid, ferrocene, and naphthalene are found to be 86.11 ± 0.6, 72.40 ± 0.8, and 69.13 ± 0.3 kJ mol−1, respectively. The determined values of enthalpies of sublimation are in good agreement with the mean value of those reported in the literature and those recommended by the kinetic committee of ICTAC. The results suggest that UV absorbance spectroscopy is a reliable tool in non-isothermally measuring the thermodynamic properties of materials in the vapor phase.

Close-Spaced Sublimation of Organic Materials for Organic Light-Emitting Devices

We have demonstrated organic light-emitting devices (OLEDs) fabricated by using a close-spaced sublimation (CSS) method. We have deposited tris(8-hydroxyquinolinato)aluminum (Alq3) layer using a CSS process for the formation of electron transport layer of the PVK/Alq3 bilayer OLEDs. The distance between the sublimation source and substrate was fixed to be less than 5 mm. The substrate temperature was maintained less than 70°C while the sublimation source temperature was varied from 185 to 200°C during the deposition of Alq3 film. We investigated the photoluminescence characteristic of the CSS processed Alq3 film. We also investigated the emission and electro-optical properties of the PVK/Alq3 bilayer OLEDs with CSS deposited Alq3 film.

Shape, density, and geology of the nucleus of Comet 103P/Hartley 2

Data from the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission show Comet 103P/Hartley 2 is a bi-lobed, elongated, nearly axially symmetric comet 2.33km in length. Surface features are primarily small mounds <40m across, irregularly-shaped smooth areas on the two lobes, and a smooth but variegated region forming a “waist” between the two lobes. Assuming parts of the comet body approach the shape of an equipotential surface, the mean density of Hartley 2 is modeled to be 200–400kgm−3. Such a mean density suggests mass loss per orbit of >1%. The shape may be the evolutionary product of insolation, sublimation, and temporary deposition of materials controlled by the object’s complex rotation.

Martian Cratering 10. Progress in use of crater counts to interpret geological processes: Examples from two debris aprons

Recent controversies about systems of crater-count dating have been largely resolved, and with continuing refinements, crater counts will offer a fundamental geological tool to interpret not only ages, but also the nature of geological processes altering the surface of Mars. As an example of the latter technique, we present data on two debris aprons east of Hellas. The aprons show much shorter survival times of small craters than do the nearby contiguous plains. The order-of-magnitude depths of layers involved in the loss process can be judged from the depths of the affected craters. We infer that ice-rich layers in the top tens of meters of both aprons have lost crater topography within the last few 10 8 yr, probably due to flow or sublimation of ice-rich materials. Mantling by ice-rich deposits, associated with climate change cycles of obliquity change, has probably also affected both the aprons and the plains. The crater-count tool thus adds chronological and vertical dimensional information to purely morphological studies.

Theoretical Prediction of Heats of Sublimation of Energetic Materials Using Pseudo‐Atomic Orbital Density Functional Theory Calculations

AbstractWe present a predictive model for the heats of sublimation of the condensed phases of energetic materials that combine the empirical relations of Politzer with first‐principles density‐functional calculations of the electronic properties of the molecular surfaces. The distinct features of our methodology are the use of numerical pseudo‐atomic orbitals for the quantum mechanical calculation of the electronic charge density, as well as an improved technique for the molecular surface area determination. As applications, we used our model to predict heats of sublimation of energetic molecules CL‐20, HMX, RDX, TNT, FOX‐7, TATB, and LLM‐105, with the Politzer parameters fit based on a set of eight nitro‐aromatic molecules. In comparison with conventional quantum chemistry calculations, our approach is tremendously less computationally demanding, yet it still demonstrates competitive accuracy and predictive power.

A probe for moisture permeation using metal/organic composite films

Composite films made by simultaneous sublimation of metal and organic materials were used as sensors for moisture in overlying polymeric films, and polymer transport properties were obtained from a spatially resolved signal. In the probe film, the molecularly dispersed metal quenched the fluorescence of the organic dye. Upon exposure to water vapor, the metal was oxidized and the fluorescence of the dye recovered. The intensity profile development over time was modeled, and a diffusion coefficient for a ultraviolet-curable adhesive was obtained which compared well to other resins of its type. This technique offers several advantages in characterizing transport properties in confined geometries, such as those used for the passivation of light-emitting diodes or other electronic devices.

多様なPSI現象 4.核融合装置におけるプラズマ&amp;middot;表面相互作用 4.2 プラズマ対向材料と損耗過程

The erosion processes of plasma facing materials are reviewed. Chemical sputtering and radiation enhanced sublimation of graphite materials are explained including elementary processes and modeling. Several important phenomena affecting the erosion of plasma facing materials such as disruption, materials mixing, and prompt redeposion are briefly overviewed.

The impact of larger clusters formation C 5, C 6, C 7, C 8, C 9, and C 10 on the rates of carbon sublimation at elevated temperatures

To estimate the exact amount of the loss of material during the plasma disruption or during slow transients is critically important to design and component lifetime analysis. Over the years, a number of simulation experiments, using as heat sources electron beams, and laser beams on investigation of the influence of heat loads on the amount of sublimated carbon materials were carried out. In addition, computer programs and analytical techniques have been developed to estimate the loss of material from sublimation. For purpose of component life time assessment and comparison between theoretical calculation and experimental results, a detailed knowledge on sublimation behaviours of carbon materials at high temperature has therefore become indispensable. The sublimation behaviour of carbon at high temperature is a complex, because of the formation of stable carbon clusters. At present, in most of the literature, only the species C 1, C 2, C 3 and C 4 were taken into account to assess the sublimation rates. In this work, based on theoretical investigation, an analysis of the formation of larger clusters C 5, C 6, C 7, C 8, C 9 and C 10, as a function of temperature were performed and the total rate of sublimation of carbon materials was deduced. The consequence of this results on rates of carbon sublimation at elevated temperature is discussed.