Vapor-phase Material Research Articles

Будова груп атомів пари системи Аs-S для створення перспективних матеріалів для автомобільної промисловості

Quantum mechanical simulation methods was found two kinds of different isomorphic forms of two- and three-atom clusters of As-S system vapor phase materials: chain and triangular. Nature of their structure was analyzed within the first two coordination spheres as central atoms for sulfur and arsenic. It is shown the possibility of realization in small clusters of a broader spectrum of different short-range order atomic configurations, compared with the condensed phase materials As-S. The calculated length of the different chemical bonds, their energy and bond angles for the clusters are in good agreement with the experimental data. The results of the research can be useful for improving the process of manufacturing fuel for cars. With the help of mathematical modeling, the values of the spatial structure were specified and the energy states of the formation of various phases of di- and triatomic formations of the pair of As-S compound materials were calculated. Such states can be differentiated into two structures: row-like and triangular-like. Analysis of the close-order structure of similar formations indicates the probability of formation of different structures of the 1st and 2nd coordination spheres: ten types of close proximity of central sulfur atoms, fourteen types of close proximity of central arsenic atoms, and nine types of configuration of the location of other particles. The 1st coordination sphere of groups is formed by covalent chemical compounds of all kinds of relations from one-dimensional to three-dimensional with lengths correlating with experimental ones. In base-like compounds, the angles between sulfur chains are 120 or 160 degrees, in arsenic chains - within 90-110 degrees. All bond angles of three-dimensional bonds are close to 60 degrees. In small associations of this system, a more diverse set of atomic configurations is formed in the boundaries of the close neighborhood, in contrast to the condensed formations of the studied compound. At the same time, calculated compounds of small groups, energy states of differentiated chemical compounds correlate with experiment.

Transport and deposition behaviors of vapor coating materials in plasma spray-physical vapor deposition

The plasma spray-physical vapor deposition (PS-PVD) technology offers great potential to support the development of non-line-of-sight deposition. However, many researches indicated that the shadowing effect is a significant mechanism of PS-PVD for the coating growth and formation of the micro-structure. There seems to be an irreconcilable contradiction between the two theories. In this study, both the transport and deposition behavior of PS-PVD processes are researched from a macroscopic and microscopic perspective, respectively. The deposition processes of vapor coating materials are separated by the last collision position. The process before reaching the last collision position is defined as transport behavior, and the process after the last collision position is defined as deposition behavior. The results of simulation and experiment indicated that the flow behavior of plasma jet and the frequent collisions between plasma gas and vapor coating material provide opportunities for the vapor coating material to deposit in shadowed surfaces or non-line-of-sight positions. The shadowing effect under micro line-of-sight deposition is a major factor in the growth of columnar structures, and it accompanies the entire process of coating growth. This study divides the deposition process of vapor coating materials into the macro non-line-of-sight transport and micro line-of-sight deposition, illuminates the macro-non-line-of-sight transport behavior of vapor-phase materials, and sheds light upon the micro-line-of-sight deposition mechanism of the PS-PVD process.

Three-dimensional electroactive ZnO nanomesh directly derived from hierarchically self-assembled block copolymer thin films.

Three-dimensional (3D) nanoarchitectures can offer enhanced material properties, such as large surface areas that amplify the structures' interaction with environments making them useful for various sensing applications. Self-assembled block copolymers (BCPs) can readily generate various 3D nanomorphologies, but their conversion to useful inorganic materials remains one of the critical challenges against the practical application of self-assembled BCPs. This work reports the vapor-phase infiltration synthesis of optoelectrically active, 3D ZnO nanomesh architectures by combining hierarchical successive stacking of self-assembled, lamellar-phase polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCP thin films and a modified block-selective vapor-phase material infiltration protocol. The 3D ZnO nanomesh exhibits optoelectrical functionality, featuring stack-layer-number-dependent electrical conductance resembling the percolative transport originating from the intrinsic morphological network connectivity of the lamellar BCP pattern with symmetric block ratio. The results not only illustrate the first demonstration of electrical functionality based on the ZnO nanoarchitecture directly generated by the infiltration synthesis in self-assembled BCP thin films but also present a new, large-area scalable, metal oxide thin film nanoarchitecture fabrication method utilizing industry-compatible polymer solution coating and atomic layer deposition. Given the large surface area, three-dimensional porosity, and readily scalable fabrication procedures, the generated ZnO nanomesh promises potential applications as an efficient active medium in chemical and optical sensors.

Review of Recent Advances in Applications of Vapor-Phase Material Infiltration Based on Atomic Layer Deposition

Polymer–inorganic hybrid nanocomposites exhibit enhanced material properties, combining the advantages of both their organic and inorganic subcomponents. Extensive research is being carried out to functionalize polymers towards various improved physicochemical characteristics such as electrical, optical, and mechanical properties for various applications. Vapor-phase material infiltration is an emerging hybridization route, derived from atomic layer deposition, which facilitates uniform incorporation of inorganic entities into a polymer matrix, leading to novel applications in fields such as microelectronics, energy storage, smart coatings, and smart fabrics. In this article, recent advances in employing vapor-phase material infiltration as a hybridization and nanopatterning technique for various application avenues are reviewed.

Effects of Residual Solvent Molecules Facilitating the Infiltration Synthesis of ZnO in a Nonreactive Polymer

Infiltration synthesis, the atomic-layer-deposition-based organic–inorganic material hybridization technique that enables unique hybrid composites with improved material properties and inorganic nanostructures replicated from polymer templates, is shown to be driven by the binding reaction between reactive chemical groups of polymers and perfusing vapor-phase material precursors. Here, we discover that residual solvent molecules from polymer processing can react with infiltrating material precursors to enable the infiltration synthesis of metal oxides in a nonreactive polymer. The systematic study, which combines in situ quartz crystal microgravimetry, polarization-modulated infrared reflection–absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, shows that the ZnO infiltration synthesis in nominally nonreactive SU-8 polymer is mediated by residual processing solvent cyclopentanone, a cyclic ketone whose Lewis-basic terminal carbonyl group can react with the inf...

Construction and control of 3D porous structure based on vapor deposition on sublimation solids

Three-dimensional porous structures are constructed via vapor deposition onto a sublimating solid template. Construction upon deposition of vapor-phase material occurs at a dynamic vapor–solid interface and is directed by the solid surface vanishing by sublimation. A proof-of-concept demonstration showed vapor depositions of poly-para-xylylenes (PPXs) on sublimating templates, including ice and mixtures with ethanol and hexane. The material construction macroscopically produces a replica architecture of the parent template. Characteristics of the pore structures are formed during the construction process as a result of the gas vapor and the space that is vacated by sublimation, thus enabling control of the porosity through regulation of the sublimation speed and/or the thermodynamic properties of the templates. The technology introduced herein provides a novel approach for 3D porous material manufacturing and overturns the notion that vapor deposition necessarily forms dense thin films on substrates.

Enhanced Evaporation of Microscale Droplets With an Infrared Laser

Enhancement of water droplet evaporation by added infrared radiation was modeled and studied experimentally in a vertical laminar flow channel. Experiments were conducted on droplets with nominal initial diameters of 50 μm in air with relative humidities ranging from 0% to 90% RH. A 2800 nm laser was used with radiant flux densities as high as 4 × 105 W/m2. Droplet size as a function of time was measured by a shadowgraph technique. The model assumed quasi-steady behavior, a low Biot number liquid phase, and constant gas–vapor phase material properties, while the experimental results were required for model validation and calibration. For radiant flux densities less than 104 W/m2, droplet evaporation rates remained essentially constant over their full evaporation, but at rates up to 10% higher than for the no radiation case. At higher radiant flux density, the surface-area change with time became progressively more nonlinear, indicating that the radiation had diminished effects on evaporation as the size of the droplets decreased. The drying time for a 50 μm water droplet was an order of magnitude faster when comparing the 106 W/m2 case to the no radiation case. The model was used to estimate the droplet temperature. Between 104 and 5 × 105 W/m2, the droplet temperature changed from being below to above the environment temperature. Thus, the direction of conduction between the droplet and the environment also changed. The proposed model was able to predict the changing evaporation rates for droplets exposed to radiation for ambient conditions varying from dry air to 90% relative humidity.

Direct fabrication of high aspect-ratio metal oxide nanopatterns via sequential infiltration synthesis in lithographically defined SU-8 templates

Nanopatterning high aspect-ratio metal oxide structures remains challenging for conventional nanofabrication methods based on reactive ion etching due to marginal etch selectivity between target oxides and typical mask materials. Here, the authors report the application of sequential infiltration synthesis (SIS) on lithographically defined SU-8 polymer templates for patterning arbitrarily designed, high aspect-ratio metal oxide nanostructures with sub-50 nm linewidths, smooth vertical profiles, and three-dimensional (3D) morphologies difficult to achieve by the conventional fabrication methods. As examples, various AlOx nanostructures with ∼40 nm linewidths and up to 16 aspect ratios were demonstrated, along with TiOx in-plane nanowire arrays of controlled positional registrations. Detailed scanning and transmission electron microscopy studies revealed nanocrystalline and amorphous internal structures of respective AlOx and TiOx, as well as the swelling and contraction behaviors of polymer templates during the SIS process, which allowed the facile fabrication of high aspect-ratio, sub-50 nm-featured oxide nanopatterns with 3D morphologies. These results confirm the potential of vapor-phase material infiltration in directly nanopatterning complexly structured metal oxides.

Fabrication and characterization of SnO2 nanospheres for hydrogen detection

This article demonstrates a novel chemical vapor deposition strategy of tin oxide (SnO2) by vapor phase material reaction at room temperature and presents the applications to hydrogen detection using this material. Tin chloride anhydrate was used as the precursor, and it reacted with NH3 to form Sn(OH)4 nanospheres. The samples with Sn(OH)4 nanospheres were subject to drying up at 80 °C, and then they transformed to polycrystalline SnO2 nanospheres. The X-ray diffraction measurement was carried out to investigate the structural properties of the SnO2 films annealed at various temperatures. The morphology of the samples was investigated by field-emission scanning electron microscopy. Micropellistor was fabricated based on the SnO2 catalyst for hydrogen detection. Compared with the traditional method to make SnO2 sensing material (hydrolysis of SnCl4·5H2O in basic solutions), the SnO2 nanospheres prepared by this method have a higher relative sensitivity and a good linearity for the concentration of H2 ranging from 0% v/v to 4% v/v. A short response time about 6 s was achieved.

A study of fine particulate emissions from combustion of treated pulverized municipal sewage sludge.

Municipal sewage sludge (MSS) is formed during wastewater treatment and its processing and disposal represent one of the most environmentally challenging aspects of the wastewater treating process. One disposal option currently being considered is a process involving heat treatment (to render the sludge biologically inactive) followed by dewatering, drying, pulverizing, and combustion. This research focuses on fine particle emissions from the combustion of dried, treated, MSS, cofired with either natural gas or pulverized Ohio bituminous coal as a supplemental fuel. These fuels were burned at 13 kW in a downflow laboratory combustor designed to replicate time/temperature histories and particle concentrations typical of practical combustion units yet also sufficiently well defined aerodynamically to allow elucidation of mechanisms. Size-segregated particle size distributions were obtained by isokinetic sampling followed by dilution/quenching and passage into a Berner Low-Pressure Impactor. Major and trace elements were analyzed by flame and graphite furnace atomic absorption spectroscopy. Four particle size regions were identified: furnace vapor-phase material that formed ultrafine particles either in or just before the sampling probe, submicron-sized particles formed during the combustion process, micron-sized fine particles, and larger supermicron sized bulk fly ash particles. The fuel mix appears to influence trace metal partitioning routes and the composition of fine particulate matter in the exhaust. Cofiring of MSS with coal increases the ultrafine/submicron particle emission compared to firing coal alone. This increase in ultrafine/submicron particles is most likely due to an interaction between species derived from MSS (possibly alkali metals) and those from coal (possibly sulfur and/or chlorine). Vapor-to-solid phase partitioning of arsenic and selenium is controlled by surface reaction with active surface sites during MSS combustion with either gas or coal. Co-combustion of MSS with the Ohio bituminous coal allows the arsenic and selenium to be reactively scavenged by calcium, thus changing the speciation of the trace metal emitted. Ohio bituminous coal alone contained insufficient calcium to accomplish this same scavenging effect.

A comparison of phase change phenomena in CTH with experimental data

An estimate of the current state of the predictive capabilities of hydrocodes for impacts where phase changes may be important was made by simulating a series of experiments where zinc spheres impact thin zinc plates at 4 velocities. The experimental data was taken from Mullin, et al. [1] and consisted of radiographs of the debris cloud and estimates of the momentum in the debris cloud along the velocity vector. The velocities ranged from 3.30 to 6.79 km/s indicating that the debris consists of solid/molten fragments to predominately vapor phase material as the velocity increases. The simulations reveal that the CTH hydro can accurately predict the debris structure and momentum transfer for this class of impacts.

Mesoscale structural studies of thin films of YBa 2Cu 3O 7

The surface morphology and growth mechanism of thin films of YBa 2Cu 3O 7 on a variety of single crystal substrates has been investigated using scanning tunneling microscopy. Over a wide range of deposition conditions c-axis films nucleate as islands and grow by a dislocation-mediated mechanism (spiral growth). a-axis films, on the other hand, grow by edge addition of vapor phase material to the component layers, giving a very different morphology. Many defect features associated with these growth patterns have been been observed and their dependence on deposition conditions and substrate material, as well as their importance for some superconducting properties is discussed.

Genetic toxicology studies comparing the activity of sidestream smoke from cigarettes which burn or only heat tobacco

The results of in vitro genetic toxicology studies of sidestream cigarette smoke (SSCS) from cigarettes which heat but do not burn tobacco were compared to those of sidestream smoke from cigarettes which burn tobacco. SSCSs from 5 cigarettes were compared. Three of the cigarettes, the Kentucky reference research cigarette (1R4F), a commercially available ultra-low-tar brand (ULT) and a commercially available ultra-low-tar menthol brand (ULT-menthol) burn tobacco while two of the cigarettes, a regular (TEST) and a menthol (TEST-menthol) heat tobacco. SSCSs from all cigarettes were prepared by identical techniques, which involved collecting sidestream smoke particulate matter on Cambridge filter pads and combining the particulate matter with the vapor-phase materials collected by bubbling the smoke exiting the Cambridge pad through DMSO. The SSCSs obtained (equivalent to 0.4 cigarettes/ml DMSO) were evaluated at identical concentrations in an in vitro genetic toxicology test battery. SSCS from 1R4F, ULT and ULT-menthol cigarettes produced positive results in Ames bacterial strains TA98, TA100, TA1537 and TA1538 in the presence of metabolic activation (S9 from Aroclor-induced rat liver) but negative results in strain TA1535. In the absence of metabolic activation. 1R4F, ULT and ULT-menthol SSCSs were not significantly mutagenic. TEST and TEST-menthol SSCSs produced negative results in all 5 bacterial strains, both with and without metabolic activation. SSCS from 1R4F, ULT and ULT-menthol cigarettes produced positive results in the CHO chromosomal aberration assay and in the CHO sister-chromatid exchange assay both with and without metabolic activation while TEST and TEST-menthol SSCSs produced negative results in both assays, either with or without metabolic activation. The SSCSs from 1R4F, ULT and ULT-menthol cigarettes were weakly positive in inducing DNA repair in cultured rat hepatocytes while TEST and TEST-menthol SSCSs were negative in this assay. All 5 SSCSs were nonmutagenic in the CHO-HGPRT assay both with and without metabolic activation. SSCSs from the 1R4F, ULT and ULT-menthol cigarettes were cytotoxic in the CHO-HGPRT assay, both with and without metabolic activation, while TEST and TEST-menthol SSCSs were not cytotoxic under either condition. These results demonstrate that sidestream smoke from cigarettes which heat but do not burn tobacco (TEST and TEST-menthol) was neither genotoxic nor cytotoxic under conditions where sidestream smoke from cigarettes which burn tobacco (1R4F, ULT and ULT-menthol) was genotoxic and/or cytotoxic in a concentration-dependent manner.