Surface Deposition Rate Research Articles

DeNOxing the air in urban spaces by building and construction photocatalytic coverings

A variety of air depolluting TiO2-based marketed products were applied on bituminous mixtures, sidewalk pavements and facades, giving NOx oxidation ratios under ISO 22197–1:2007 in the 35–9%, 56–2% and 28–2% ranges, respectively. Correspondingly, DeNOx toxicity indexes varied from −0.8 to 5.6, 0 to 14 and −4 to 1.The three most efficient photocatalytic products were selected: two TiO2-water emulsions, for road and sidewalk, and a TiO2-paint, for facade. NOx purifying ability of these materials were evaluated when key physical parameters were modified. The observed NOx conversion is positively correlated with UV-A irradiance up to 10 W/m−2(−|-), reaching a plateau, and negatively correlated with relative humidity, with a more pronounced decrease above 35 %. Inversely, no dependence with inlet NOx concentration is observed in the range of 0.14–1 ppmv.Further, two first-order kinetic approximations were followed to calculate NO surface deposition rates, giving 2 to 8 10−3 m/s on the selected photocatalytic urban surfaces. Subsequently, the potential NOx sink effect induced in a photocatalytic urban canyon and a NOx-purifier was modelled taking NOx surface deposition rates from 10−3 to 10−1 m/s. Purifying devices could be utilised as a preferred option to help alleviate local atmospheric NOx in high-polluted areas.

Formation of SiO2 thin films through plasma- enhanced chemical vapor deposition using SiH4/Ar/N2O

SiO2 films and their formation technologies are critical for the fabrication of Si-based integrated circuits (ICs). SiO2 films fabricated using plasma-enhanced chemical vapor deposition (PECVD) have become increasingly important because of the increasing trend of three-dimensional (3D) architectures in ICs. SiO2 films formed by PECVD have been widely studied for over 40 years; however, owing to the complex plasma reactions and the differences in system conditions, the relationship between the experimental parameters and film characteristics are disputed. In this study, focusing on the two important characteristics (surface morphology and deposition rate) of SiO2 films for 3 D ICs manufacturing, SiO2 film growth was systematically investigated via SiH4/Ar/N2O in PECVD; a theoretical reaction process model (including gas-phase reaction, chemical adsorption, and surface reaction) bridging the experimental parameters (chamber pressure, gas ratio, radio frequency power, and substrate temperature) and characteristics (surface morphology and deposition rate) of SiO2 films was established. This study contributes to the precise formation of sub-100 nanometer SiO2 films using PECVD for manufacturing 3 D ICs.

Effects of NaH2PO2 concentration and deposition potential on microstructural characteristics and corrosion properties of electrodeposited amorphous Fe–P coatings

ABSTRACT This study reports the influence of NaH2PO2 concentration and deposition potential on the microstructural characteristics and corrosion properties of fully amorphous electrodeposited Fe–P coatings. The morphology and P content of the coatings were observed and the effect of the processing parameters on the surface roughness, deposition rate, and current efficiency were investigated. The morphology and P content of the coating varied significantly with the NaH2PO2 concentration, but the deposition potential did not significantly influence these properties. As the P content and morphology determine electrochemical corrosion properties, the deposited Fe–P film with the best anti-corrosion properties was determined by analysing the corrosion properties of the coatings in 3.5 wt.% NaCl solution through potentiodynamic polarisation and electrochemical impedance spectroscopy; the corrosion morphology and corrosion products were also characterised. This study can provide new insights into the corrosion behaviour of amorphous Fe–P coatings and provide guidelines for industrial production.

Experiment and modeling of stochastic ignition and combustion of fuel droplets impacting a hot surface

The ignition dynamic of liquid fuel droplets impacting hot surfaces is critical for fire-safety analysis in engineering systems, as well as for controlling wall-filming effects in IC engines. The scenario of slow fuel-leakage rates poses challenges associated with the stochastic processes of droplet splashing, break-up, turbulent mixing, and combustion. To address this, we conduct controlled experiments of liquid n-heptane droplets impacting a heated surface in the Leidenfrost regime, targeting the individual-droplet-deposition conditions. The experiment encompasses a range of surface temperatures and droplet-deposition rates. The experiments are complemented by theoretical analysis, where we developed a stochastic low-order numerical model, demonstrating good accuracy for predicting ignition probability and overall combustion dynamics. Notably, we observe a broad region of intermittent combustion behavior, with ignition probability varying based on surface temperature and droplet deposition rate. Additionally, we find that the transition to consistent ignition relies heavily on both surface temperature and deposition rate. Experimental and numerical model results shed light on the roles of the complex interplay between droplet breakup, chemical kinetics, and evaporation and mixing time scales, as well as the interaction among subsequent droplet combustion events, in governing the ignition and combustion of impacting droplet trains. The revealed dynamic of droplet/hot-surface ignition and the proposed stochastic model hold promise for advancing predictive capabilities of hot-surface-induced ignition and combustion arising from accidental leaks in flammable-liquid piping and wall-filming, particularly in the stochasticity-dominated individual-droplet-deposition regime.

Bronze-on-steel deposition with blue light high-speed Laser Cladding and IR Laser Cladding, properties and differences

Laser cladding could replace casting as a productive and efficient way to deposit lead-free bronze on steel. Bronzes, however, mostly reflect IR wavelength, usually used in LC. Therefore, bronze melting requires high powers, which can excessively heat the substrate, potentially leading to quality issues. Using blue light high-speed laser cladding (B-HSLC) can improve bronze light absorption and lower the heat input to the substrate, as most of the energy is coupled directly into the powder which is melted in flight. This work compares bronze-on-steel coatings made by IR laser cladding (IR-LC) and B-HSLC. B-HSLC coatings were produced with a higher single-layer surface deposition rate and a lower power input than IR-LC coatings. Microstructural appearance was assessed through optical and electronic microscopy. The B-HSLC samples displayed better quality, comparable dilution, and extremely reduced heat impact on the substrate. B-HSLC represents an effective alternative for lead-free bronze depositions on dissimilar substrates.

Effect of bias voltage on the erosion performance of TiAlSiN coatings on TC6 substrate by high power impulse magnetron sputtering

TiAlSiN coatings were deposited on TC6 substrates by high power impulse magnetron sputtering at various bias voltages for the improvement of titanium alloy anti-sand erosion performance. The effect of bias voltage on the composition, microstructure and mechanical properties were investigated by X-ray photoelectron spectroscopy, X-ray diffractometer, transmission electron microscopy, scanning electron microscopy, Rockwell-C indentation, scratch testing and nano nanoindentation. The erosion performance was evaluated at the impingent angles of 30° and 90° respectively in a sand blasting tester. With the application and increase in bias voltage, the discharge current increases from ∼87 A to ∼210 A. The coatings exhibit face center cubic structure, mainly composed of the (Ti,Al)N nanocrystallites and Si3N4 matrix. The preferred orientation shifts from (200) to (220) in the range of 0∼−150 V, but goes back to (200) at −200 V. The surface nodular defects and deposition rate are gradually reduced, yet the sectional structure becomes much denser. The residual stress is compressive and continually grows, whereas the adhesion strength, hardness (H), Young's modulus (E) and H/E ratio gradually increase before decreasing, arriving at maximum values of ∼68 N, ∼37.53 GPa, ∼339.9 GPa and 0.11 respectively at −150 V. The erosion resistance of the TiAlSiN coatings is consistent with these mechanical changes at various bias voltages and is also optimal at −150 V, which is ∼14 times that of TC6 substrate. The failure mechanism comes from coating brittleness nature, fractured chips and microcracks, regardless sand erosion angles, yet the driving forces are different.

Study on the dynamic characteristics of thermal oxidation deposition of aviation kerosene under supercritical pressure

Thermal oxidation deposition of aviation kerosene has a significant impact on the long-term operation of aircraft. In this study, a two-dimensional axisymmetric numerical model incorporating a pseudo-detailed chemical kinetic model of thermal oxidation deposition was developed based on dynamic mesh technology, and a 30-hour transient simulation of the thermal oxidation deposition process of supercritical aviation kerosene was conducted. The dynamic characteristics of the thermal oxidation deposition are examined and the effect of dissolved oxygen concentration is analyzed. According to the results, the large temperature gradient at the inlet and the higher temperatures in the second half of the channel encourage the thermal oxidation and surface deposition reactions to proceed rapidly. And it is found that the surface deposition rate decreases with increasing heating time. Both temperature and concentration determine the rate of dissolved oxygen consumption. The surface deposition rate increased by 195.33 % as the dissolved oxygen concentration increased from 10 to 40 ppm. In addition, the entry of aviation kerosene into the pseudo-critical region can indirectly reduce the rate of thermal oxidation surface deposition. This study is a guide to predict and inhibit the thermal oxidation deposition of aviation kerosene, improving the structural design of the regenerative cooling channel, and ensuring aircraft safety.

Computational Fluid Dynamics Insights into Chemical Vapor Deposition of Homogeneous MoS2 Film with Solid Precursors

AbstractIn this work, a comprehensive computational fluid dynamics (CFD) investigation to develop an in‐depth understanding on the fluid flow to obtain a homogenous deposition of MoS2 thin film is reported. First, the effect of substrate orientations (0, 20, 45, 70, and 90°) was simulated using ANSYS Fluent. The horizontal substrate (0°) showed a non‐uniform surface deposition rate (SDR) with relative standard deviation (RSD) of 44.1 %. The non‐uniformity gradually reduces with the increase of substrate angles and reaches the lowest for 90° with RSD of 13.1 %. The transient state analysis showed that no growth occurred for the first 8 s, followed by an SDR overshoot and finally reached a steady state >200 s. Next, the effect of horizontal separation distance (d = 1 to 6 cm) between MoO3 and the substrate is investigated. It is find that the Mo/S ratio reduces with the increase of separation distance. For d between 5 and 6 cm, the Mo/S drops by >1000 times and causes the growth environment to switch from Mo to S‐rich. This work offers a fast and cost‐effective approach to understand the fluid flow and to obtain a homogeneous deposition of MoS2 and other 2D TMD thin films.

Numerical Simulation of a Simplified Reaction Model for the Growth of Graphene via Chemical Vapor Deposition in Vertical Rotating Disk Reactor

The process of graphene growth by CVD involves a series of complex gas-phase surface chemical reactions, which generally go through three processes, including gas phase decomposition, surface chemical reaction, and gas phase diffusion. The complexity of the CVD process for growing graphene is that it involves not only chemical reactions but also mass, momentum, and energy transfer. To solve these problems, the method of numerical simulation combined with the reactor structure optimization model provides a good tool for industrial production and theoretical research to explore the influencing factors of the CVD growth of graphene. The objective of this study was to establish a simplified reaction model for the growth of graphene by chemical vapor deposition(CVD) in a vertical rotating disk reactor (VRD). From a macroscopic modeling perspective, computational fluid dynamics (CFD) was used to investigate the conditions for the growth of graphene by chemical vapor deposition in a high-speed rotating vertical disk reactor on a copper substrate surface at atmospheric pressure (101,325 Pa). The effects of gas temperature, air inlet velocity, base rotation speed, and material ratio on the surface deposition rate of graphene in a VRD reactor were studied, and the technological conditions for the preparation of graphene via the CVD method in a VRD reactor based on a special structure were explored. Compared with existing models, the numerical results showed the following: the ideal growth conditions of graphene prepared using a CVD method in a VRD reactor involve a growth temperature of 1310 K, an intake speed of 470 mL/min, a base speed of 300 rpm, and an H2 flow rate of 75 sccm; thus, more uniform graphene with a better surface density and higher quality can be obtained. The effect of the carbon surface deposition rate on the growth behavior of graphene was studied using molecular dynamics (MD) from a microscopic perspective. The simulation showed that the graphene surface deposition rate could control the nucleation density of graphene. The combination of macro- and microsimulation methods was used to provide a theoretical reference for the production of graphene.

Numerical Simulation of Graphene Growth by Chemical Vapor Deposition Based on Tesla Valve Structure

Chemical vapor deposition (CVD) has become an important method for growing graphene on copper substrates in order to obtain graphene samples of high quality and density. This paper mainly focuses on the fluid flow and transmission phenomenon in the reactor under different process operating conditions and reactor structures. Two macroscopic physical parameters that are established as important for CVD growth are temperature and pressure. Based on the special structure of a miniature T45-R Tesla valve acting as a CVD reactor structure, this study uses numerical simulation to determine the effect of the pressure field inside a Tesla valve on graphene synthesis and temperature variation on the graphene surface deposition rate. This macroscopic numerical modeling was compared to the existing straight tube model and found to improve the graphene surface deposition rate by two orders of magnitude when the 1290–1310 K reaction temperature range inside the Tesla valve was maintained and verified through the experiment. This study provides a reference basis for optimizing the reactor geometry design and the effects of changing the operating parameters on carbon deposition rates during a CVD reaction, and will furthermore benefit future research on the preparation of high-quality, large-area, and high-density graphene by CVD.

Extruded 3D Printing Assisted Electrochemical Additive Manufacturing

This essay investigates an additive manufacturing technique of an extruded 3D printing-assisted electrochemical deposition. The effects of solutions with different additive (Cl− and brightener) concentrations on the surface micromorphology and deposition rate of the formed films were investigated by using characterization data from test tools such as an electrochemical workstation, X-ray diffractometer, and scanning electron microscope, as well as discussing the laws of interaction between these two additives during the electrodeposition process. The experimental results show that when the concentration of Cl− in the copper plating solution is 2×10−3 mol/L and the brightener concentration is 10 ml/L, the electrodeposition experiments yielded deposited copper films with a significantly preferred orientation on the (111) crystal plane, and the prepared copper film has thicker deposited film and better surface quality. To validate the additive manufacturing method for extruded 3D printing-assisted electrochemical deposition, deposition experiments of 25-layer copper samples were carried out utilizing the best process parameters.

Effects of applied potential, initial gap, and megasonic vibrations on the localized electrochemical deposition of Ni-Co microcolumns

This study demonstrates the localized electrochemical deposition (LECD) of nickel–cobalt (Ni-Co) alloy microcolumns and investigates the effects of the experimental parameters on the deposition process. The results revealed that the applied potential significantly affected the surface morphology, deposition rate, and compositions of the Ni-Co microcolumns. Although a high potential significantly improved the deposition rate of the microcolumns, the deterioration of the surface morphologies of the microcolumns was observed. The microcolumns were also deposited at different initial gaps, and smoother surface morphologies were achieved with a relatively larger initial gap. The addition of megasonic vibrations was shown to significantly increase the deposition rate, due to the accelerated ion mass transfer and bubble elimination. Furthermore, the compositions of deposited samples confirmed the anomalous co-deposition behavior of Ni-Co alloys. This study lays the experimental groundwork for potential applications such as micro actuators and magnetic helical microrobots.

Magnetic field exposure on electroplating process of ferromagnetic nickel ion on copper substrate

In this research, nickel electroplating was carried out under a magnetic field. A constant magnetic field was used to influence the electroplating process. Its effects on surface morphology, deposition rate, current efficiency, crystal structure, hardness, and corrosion properties of nickel films were investigated. Inhomogeneous pyramidal-type structures without crevices were formed on all samples. Ni films electrodeposited under exposure of 0.14T of the magnetic field revealed the highest deposition rate, current efficiency, and hardness. Less crystallite size would produce higher hardness. Three major peaks of X-ray diffraction are observed, and the (111) crystal plane is the most affected by the magnetic field during the electroplating process. The presence of 0.14T of magnetic field on the electrodeposition process also decreases (111) plane, crystallite size, and microstrain. A magnetic field could improve the corrosion and hardness properties of Ni films.

Simulating indoor inorganic aerosols of outdoor origin with the inorganic aerosol thermodynamic equilibrium model ISORROPIA.

Outdoor aerosols can transform and have their composition altered upon transport indoors. Herein, IMAGES, a platform that simulates indoor organic aerosol with the 2-dimensional volatility basis set (2D-VBS), was extended to incorporate the inorganic aerosol thermodynamic equilibrium model, ISORROPIA. The model performance was evaluated by comparing aerosol component predictions to indoor measurements from an aerosol mass spectrometer taken during the summer and winter seasons. Since ammonia was not measured in the validation dataset, outdoor ammonia was estimated from aerosol measurements using a novel pH-based algorithm, while nitric acid was held constant. Modeled indoor ammonia sources included temperature-based occupant and surface emissions. Sensitivity to the nitric acid indoor surface deposition rate was explored by varying it in model runs, which did not affect modeled sulfate due to its non-volatile nature, though the fitting of a filter efficiency was required for good correlations of modeled sulfate with measurements in both seasons. Modeled summertime nitrate well-matched measured observations when , but wintertime comparisons were poor, possibly due to missing thermodynamic processes within the heating, ventilating, and air-conditioning (HVAC) system. Ammonium was consistently overpredicted, potentially due to neglecting thirdhand smoke impacts observed in the field campaign, as well as HVAC impacts.

A numerical approach on the selection of the purge flow rate in an atomic layer deposition (ALD) process

The variation of the purge flow rate is investigated in a reactor scale simulation of a typical atomic layer deposition (ALD) process. The investigation in its context addresses the possible issues of inadequate deposition rates with regard to the purge flow rate. A three-dimensional reactor is numerically implemented to simulate the physical and chemical processes to fabricate aluminum oxide (Al2O3) thin films. The purge flow rate disparity is focused to examine the effects within the fluid flow, mass transport, along with the chemical kinetics of the ALD process. The fabrication process employs trimethyl-aluminum and ozone (O3) as the metal and oxidant precursors, respectively, and inert argon as the purge gas. The reactor operation is set up to operate at a pressure of 10 torrs, with a substrate temperature of 200 °C. Three purge flow rates of 20, 10, and 5 sccm, respectively, have been examined. It was discovered that the slower flow rate showed, superior mass fraction distribution, reached unity surface coverage, and a time extensive surface deposition rate. A prolonged ozone exposure was crucial in providing an adequately oxidized substrate. The 20, 10, and 5 sccm purge flow rate growth obtained a 0.58, 0.85, and 1.6 Å/cycle, respectively. These findings revealing close similarities to experimental behaviors and recorded growths.

Influence of cationic epoxy resin type on electrophoretic deposition effect on repair of rust-cracked reinforced concrete

This study proposed an electrophoretic deposition repair method to effectively repair and improve the durability of rust-cracked reinforced concrete structures, exploring the influence of cationic epoxy resin types on the repair process. After electrophoretic deposition repair, the carbonation resistance and waterproofing performance of the specimens improved significantly; as the repair in the solution of cationic epoxy resin molecular weight increased, the specimen surface crack healing rate and deposition rate increased; the larger the molecular weight of the cationic epoxy resin in the repair solution, the poorer the compactness of the repaired specimen, and the smaller the filling depth of epoxy resin.

Effect of process parameters on growth pattern of micro-nickel column in mask-less localized electrodeposition

The additive manufacturing of mask-less localized electrodeposition technology is a new technology that combines the principle of electrochemical deposition with additive manufacturing. Micro-nickel columns were prepared by this technique under low voltage/small duty cycle, high voltage/large duty cycle, and high voltage/small duty cycle. The surface morphology, deposition rate, cross-section structure, and growth pattern of micro-nickel columns were studied to understand the formation process of micro-nickel columns and obtain high-quality micronickel columns. The research found that the diameter of the deposited micro-nickel column is uniform, the grain is fine and smooth under low voltage/small duty cycle (4.2V/0.3). The micro-nickel columns deposited under high voltage/large duty cycle conditions (4.8V/0.7) were thickerin diameter, but the particles were irregularly stacked. The volume deposition rate increases with the increase of voltage and duty cycle. The volume deposition rate is the highest when the duty cycle is 0.5. Three growth patterns are proposed: the layer-by-layer deposition in the initial deposition phase, accumulation deposition in the middle phase, and mixed deposition in the final phase. These three growth patterns are based on the surface morphology and cross-section microstructure of the micro-nickel column deposited under a high voltage/small duty cycle

Computational synthesis of 2D materials grown by chemical vapor deposition

The exotic properties of 2D materials made them ideal candidates for applications in quantum computing, flexible electronics, and energy technologies. A major barrier to their adaptation for industrial applications is their controllable and reproducible growth at a large scale. A significant effort has been devoted to the chemical vapor deposition (CVD) growth of wafer-scale highly crystalline monolayer materials through exhaustive trial-and-error experimentations. However, major challenges remain as the final morphology and growth quality of the 2D materials may significantly change upon subtle variation in growth conditions. Here, we introduced a multiscale/multiphysics model based on coupling continuum fluid mechanics and phase-field models for CVD growth of 2D materials. It connects the macroscale experimentally controllable parameters, such as inlet velocity and temperature, and mesoscale growth parameters such as surface diffusion and deposition rates, to morphology of the as-grown 2D materials. We considered WSe2 as our model material and established a relationship between the macroscale growth parameters and the growth coverage. Our model can guide the CVD growth of monolayer materials and paves the way to their synthesis-by-design.Graphic abstract

Surface deposition of marine fog and its treatment in the Weather Research and Forecasting (WRF) model

Abstract. There have been many studies of marine fog, some using Weather Research and Forecasting (WRF) and other models. Several model studies report overpredictions of near-surface liquid water content (Qc), leading to visibility estimates that are too low. This study has found the same. One possible cause of this overestimation could be the treatment of a surface deposition rate of fog droplets at the underlying water surface. Most models, including the Advanced Research Weather Research and Forecasting (WRF-ARW) Model, available from the National Center for Atmospheric Research (NCAR), take account of gravitational settling of cloud droplets throughout the domain and at the surface. However, there should be an additional deposition as turbulence causes fog droplets to collide and coalesce with the water surface. A water surface, or any wet surface, can then be an effective sink for fog water droplets. This process can be parameterized as an additional deposition velocity with a model that could be based on a roughness length for water droplets, z0c, that may be significantly larger than the roughness length for water vapour, z0q. This can be implemented in WRF either as a variant of the Katata scheme for deposition to vegetation or via direct modifications in boundary-layer modules.

The gap between atmospheric nitrogen deposition experiments and reality

Anthropogenic activities have dramatically altered the global nitrogen (N) cycle. Atmospheric N deposition, primarily from combustion of biomass and fossil fuels, has caused acidification of precipitation and freshwater, and triggered intense research into ecosystem responses to this pollutant. Experimental simulations of N deposition have been the main scientific tool to understand ecosystem responses, revealing dramatic impacts on soil microbes, plants, and higher trophic levels. However, comparison of the experimental treatments applied in the vast majority of studies with observational and modelled N deposition reveals a wide gulf between research and reality. While the majority of experimental treatments exceed 100 kg N ha−1 y−1, global median land surface deposition rates are around 1 kg N ha−1 y−1 and only exceed 10 kg N ha−1 y−1 in certain regions, primarily in industrialized areas of Europe and Asia and particularly in forests. Experimental N deposition treatments are in fact similar to mineral fertilizer application rates in agriculture. Some ecological guilds, such as saprotrophic fungi, are highly sensitive to N and respond differently to low and high N availability. In addition, very high levels of N application cause changes in soil chemistry, such as acidification, meaning that unrealistic experimental treatments are unlikely to reveal true ecosystem responses to N. Hence, despite decades of research, past experiments can tell us little about how the biosphere has responded to anthropogenic N deposition. A new approach is required to improve our understanding of this important phenomenon. First, characterization of N response functions using observed N deposition gradients. Second, application of experimental N addition gradients at realistic levels over long periods to detect cumulative effects. Third, application of non-linear meta-regressions to detect non-linear responses in meta-analyses of experimental studies.