High Deposition Efficiency Research Articles

Submicron Particles during Macro- and Micro-Weldings Procedures in Industrial Indoor Environments and Health Implications for Welding Operators

One of the emerging risks in the engineering and electronic industries is the exposure of workers to ultrafine particles during (micro-)welding operations, i.e., processes used for joining two metal parts heated locally, which constitute the base metal, with or without addition of another metal which is the filler metal, melted between the edges to be joined. The process is accompanied by formation of metallic fumes arising from the molten metal as well as by the emission of metal fumes of variable composition depending on the alloys welded and fused. The aim of this paper is to investigate the number, concentration and size distribution of submicron particles produced by (micro-)welding processes. Particle number size distribution is continuously measured during (micro-)welding operations by means of two instruments, i.e., Fast Mobility Particle Sizer and Nanoparticle Surface Area Monitor. The temporal variation of the particle number size distribution across the peaks evidences the strong and fast-evolving contribution of nucleation mode particles: peak values are maintained for less than 10 s. The implication of such contribution on human health is linked to the high deposition efficiency of submicronic particles in the alveolar interstitial region of the human respiratory system, where gas exchange occurs.

Low-temperature fabrication of protonic ceramic fuel cells with BaZr0.8Y0.2O3−δ electrolytes coated by aerosol deposition method

To overcome the difficulties of sintering yttrium (Y)-doped barium zirconate (BZY), an aerosol deposition (AD) method is suggested as an attractive alternative since it produces dense BZY films in commercially large areas with high deposition efficiency at low temperature. In this study, highly Y-doped BZY powder for use in AD method was synthesized successfully without use of sintering additives; the process involves a series of careful preparation processes including pre-doping of Y, high-energy milling, and calcination with an atmospheric powder which maintains controlled BaO vapour pressure. It is noted that Y-doping of BaZrO3 in starting powder is important in the AD method. The increased conductivity of BZY electrolyte film using this powder resulted in relatively small Ohmic resistance (∼0.5 Ω cm2 at 700 °C) and good cell performance (∼180 mW cm−2 at 700 °C). These are one of the best performance among the reported values of cells that employ BaZr0.8Y0.2O3−δ (or BZY20) as an electrolyte. The high performance is also remarkable although the firing temperature of this cell (1200 °C) is much lower than those (≥1400 °C) shown in literature studies. The performance can be further improved with appropriate choice of cathode and anode materials.

Effect of matrix/reinforcement combination on cold sprayed coating deposition behaviour

Cold sprayed composite coatings are usually composed of extensively deformed metal particles and undeformed hard reinforcements. Generally, there is a difference in the composition between the feedstock powder and the final coating. The reason was explored based on the deposition behaviour of cold sprayed composite coatings, which are composed of different combinations of matrix and reinforcement (Al5056+SiC, AZ91D+SiC and Al5056+In718). Experimental results show that a higher reinforcement content in the coating contributes from a higher deposition efficiency of the reinforcement. The great difference in the impact velocity between the matrix and the reinforcement mainly causes the difference in the reinforcement content between the starting powder and the resultant coating. Finally, when the particle velocity of the reinforcement is comparable to that of the matrix, the superior kinetic energy of the matrix or the reinforcement could benefit the incorporation of the reinforcement.

Development of Automatic GMAW Setup for Process Improvements: Experimental and Modeling Approach

Gas metal arc welding (GMAW) offers highly efficient and low-cost welding, but manual movement of torch affects the uniformity of bead geometry, penetration, and heat input. In the present work, an indigenous automatic movement setup is designed and fabricated for GMAW. System behaviors like drive motor response, carriage, and wheel movement are studied through bond graph modeling. Welding time and welding velocity obtained from simulation are used to obtain the deposition efficiency during weld bead deposition on low carbon steel and stainless steel workpieces. Spatter index is also calculated for both the materials. Welding performance of automatic welding is compared with manual movement welding, and automatic welding is found capable to offer high deposition efficiency, low spatter index, uniform depth of penetration, and lower distortion for both the materials. Variation in microhardness and metallurgical observations by scanning electron microscopy are carried out for microstructure analysis.

Controlling the surface nanostructure of ZnO and Al-doped ZnO thin films using electrostatic spraying for their application in 12% efficient perovskite solar cells.

In this paper, ZnO and Al-doped ZnO films were deposited using the electrospraying method and studied for the first time as photoanodes for efficient perovskite solar cells. Effects of substrate temperature, deposition time, applied voltage, substrate-to-nozzle distance and flow rate (droplet size) on the morphology of ZnO were studied with the help of FE-SEM images. The major factors such as the droplet size of the spray, substrate temperature and substrate-to-nozzle distance at deposition control the film morphology. Indeed, these factors determine the density of the film, its smoothness and the flow of solution over the substrate. The droplet size was controlled by the flow rate of the spray. The substrate-to-nozzle distance and flow rate will both regulate the solution amount deposited on the surface of the substrate. The most favorable conditions for a good quality ZnO thin film were a long substrate-to-nozzle distance and lower solution flow rates. In situ droplet size measurement shows that the size and dispersion of particles were narrowed. The method was shown to have a high deposition rate and efficiency relative to well-established thin film deposition techniques such as chemical and physical vapor deposition. In addition, it also allows easy control of the microstructure and stoichiometry of the deposits. The pure ZnO film produced under optimum conditions (440 nm thick) demonstrated a high power conversion efficiency (PCE) of 10.8% when used as a photoanode for perovskite solar cells, owing to its high porosity, uniform morphology and efficient electron transport. For thicker films a drastic decrease in PCE was observed due to their low porosity. We also observed that the open-circuit voltage increases from 1010 mV to 1045 mV and also the PCE increases from 10.8% to 12.0% when pure ZnO films were doped with aluminum (Al). Under atmospheric pressure, the electrospraying system produces the reasonably uniform-sized droplets of smaller size, so the films have a smooth surface and are highly suited for optoelectronic applications.

Analysis of single spray beads prepared using low-pressure cold spraying

Cold spraying is a coating deposition method for the production of high-quality metallic coatings. Copper, for instance, is widely used as a coating material due to its suitability for cold spray process. Cold-sprayed copper coatings are known to have interesting technical properties such as high electrical and thermal conductivity. Low-pressure cold spraying (LPCS) is a cold spray technique of preparing relatively dense and pure copper coatings. The deposition behaviour of low-pressure cold-sprayed spherical and dendritic copper particles impacting the substrate was evaluated in this study. The effect of powder type was clearly detected in the observations of single spray beads. Higher deposition efficiency and denser coatings were prepared by using the spherical copper powder.

Nanostructured Electrodes Via Electrostatic Spray Deposition for Energy Storage System

Energy storage system (such as Li-ion battery and supercapacitor) is an important technology in today’s society, and has been widely used as the power source for portable electronics, electrical vehicles and hybrid electrical vehicles. Lots of research has focused on improving its performance, however, many crucial challenges need to be addressed to obtain high performance for further applications. Recently, an electrostatic spray deposition (ESD) technique has attracted great interests to satisfy the goals. Due to its many advantages, such as simplicity, cost-effective setup, non-vacuum, low temperature deposition conditions, good control for tailoring film composition and morphology, and high deposition efficiency, the ESD technique shows very promising prospects compared to other conventional deposition techniques. It provides a simple but versatile strategy for generating single or multi-component materials with varied morphologies, such as sponge-like, dense, porous and fractal, etc. It is belived that controling structures is an effective way to optmize electrochemical performance in reagrding volume change buffering, short ion diffusion passway, etc.. In this talk, our recent research outcomes related to the ESD derived anodes for Li-ion batteries and supercapacitors, such as graphene, Li4Ti5O12, Sn, SnO2, NiO, Fe2O3, Co3O4, CoO, and Cu2O, etc. Will be summarized and discussed.

Pretreatment effect of Cu feedstock on cold-sprayed coatings

Powder properties of the feedstock used for spray coatings, especially cold-spray coatings, have an influence on the coating properties such as deposition efficiency, morphology and hardness. The effects of pretreatment on Cu feedstock with dendritic morphologies used for cold spraying were investigated. The Cu powders were pretreated into air and vacuum in the temperature range of 50–200°C at dwell times of 1 and 6h. The deposition efficiency of the air-annealed feedstock shows an initial increase due to the stress relaxation till the oxidation begins and prevails in bringing about drop in the efficiency. The coatings produced from the vacuum-annealed feedstock had much higher deposition efficiency than the air-annealed feedstock, resulting from the combined effect of stress relaxation and reduction of Cu. Therefore, it was confirmed that the feedstock properties modified by a pretreatment had a significant influence on the properties of cold-sprayed coatings.

Comparison of Surface Properties of TiN and TiAlN Coating Prepared by Arc Ion Plating for the Improvement of Life-Time Extension of Tool Steel

TiN and TiAlN films have been coated on the surface of tool materials by various methods for the life-time extension of tool. In this work, for the improvement of hardness and adhesion of coating to SKD61 substrate, radical nitriding (RN) of substrate was carried out at 450°C for 5 hours in ammonia gas pressure of 2.7×103 Pa. The results showed that TiN and TiAlN coatings were distributed uniformly on the SKD 61 substrate. And the film thickness was up to 4 μm, which showed so high deposition efficiency (~ 66.7 nm/min) of arc ion plating at this typical process condition. For both coatings, the TiN phases could be detected and the (111) was dominant crystallite grown orientation. The AlN crystallite structure could be detected as expected in TiAlN film. The critical load of TiN film (22.36 N) was slightly smaller than that of TiAlN film (23.88 N). With increasing the load during scratch test, the friction coefficient of TiN film rose quickly, but friction coefficient of TiAlN had a little change, even decreased slightly.

A Taguchi Design Study for Optimisation of Plasma Sprayed Hydroxyapatite Coatings

Plasma sprayed hydroxyapatite coatings were deposited onto mild steel substrates. A Taguchi L9 design of experiment protocol was used to optimise the coating process parameters. The effect of three factors: (i) power and secondary gas flow rate (X1), (ii) powder feed rate and carrier gas flow rate (X2), and (iii) stand-off distance (X3) on the coating responses was studied. The responses of the plasma sprayed hydroxyapatite coatings were evaluated in terms of porosity, deposition efficiency, microhardness, crystallinity, and surface roughness. A regression analysis established relationships between process parameters and responses. Higher power, lower powder feed rate and the middle stand-off distance of 11 cm lead to optimum attributes of low porosity, high deposition efficiency, high microhardness, high crystallinity, and high surface roughness.

Development and Characterization of B4C Reinforced Detonation-Sprayed Al Coatings

Because of their excellent properties aluminum and its alloys cover a wide range of applications especially in the lightweight construction sector. In order to reach a higher strength and wear resistance metal matrix composites (MMCs) are used. Typically Al MMCs are manufactured by casting or extrusion processes. The disadvantage of these production routes is a cost-intensive and time-consuming finishing in terms of grinding and milling. The technique of thermal spraying provides the possibility to coat aluminum parts with MMCs close to their final shape. In addition to the shape accuracy the ductility and toughness of the coated parts are generally higher compared to extruded or casted parts. This study describes the development of detonation-sprayed boron carbide reinforced aluminum coatings on aluminum (EN AW 5754) substrates. The optimization of the coatings was focused on a homogeneous coating structure, a low coating porosity, a high deposition efficiency, a high number of embedded carbides, and a small percentage of oxides. In continuous tensile tests the influence of the MMC coating on the tensile strength was determined. Furthermore, the tensile strength was investigated in a discontinuous tensile test step by step. The different stages of deformation were analyzed by using micro computed tomography. This method enables the observation of tensile specimens in 3D, and consequently the site and moment of crack formation.

MCrAlY Bondcoats by High-Velocity Atmospheric Plasma Spraying

MCrAlY bondcoats (M = Co, Ni) are used to protect metallic substrates from oxidation and to improve adhesion of ceramic thermal barrier coatings for high temperature applications, such as in land-based and aviation turbines. Since MCrAlYs are prone to take up oxygen during thermal spraying, bondcoats often are manufactured under inert gas conditions at low pressure. Plasma spraying at atmospheric conditions is a cost-effective alternative if it would be possible to limit the oxygen uptake as well as to obtain sufficiently dense microstructures. In the present work, high-velocity spray parameters were developed for the TriplexPro 210 three-cathode plasma torch using MCrAlY powders of different particle size fractions to achieve these objectives. The aims are conflictive since the former requires cold conditions, whereas the latter is obtained by more elevated particle temperatures. High particle velocities can solve this divergence as they imply shorter time for oxidation during flight and contribute to coating densification by kinetic rather than thermal energy. Further aims of the experimental work were high deposition efficiencies as well as sufficient surface roughness. The oxidation behavior of the sprayed coatings was characterized by thermal gravimetric analyses and isothermal heat treatments.

Study of stellite-6 deposition by cold gas spraying

Cold gas spraying (CGS) has been used to generate coatings using ductile materials which are easily deformed with the impact generated by the high kinetic energy of the process. The deposition of less ductile materials is being a challenge.The present work is intended to study the deposition behavior of a stellite alloy whose high mechanical strength hinders its plastic deformation. For this purpose, we evaluated the influence of spraying parameters such as distance and, gas temperature and pressure on the properties of cold sprayed stellite 6 coatings deposited onto steel substrates. Various sets of parameters were tested in order to optimize the porosity, thickness, and deposition efficiency of the stellite coatings and thereby achieve coatings with demonstrated hardness and corrosion and wear resistance.The results show that the two most important parameters for CGS are distance and gas pressure. These two parameters are correlated to coating quality in the way that higher distance and pressure produce lower deposition efficiencies (DEs) and increased porosity contents. Temperature, the third parameter in importance, is positively correlated to quality, thus an improved coating (i.e. dense and with higher DE) can be achieved by increasing this factor.

Mechanical properties of Cold Spray deposited NARloy-Z copper alloy

This work focuses on the properties of a Cu-3wt.% Ag-0.5wt.% Zr alloy deposited by a Cold Spray process. Helium was used as the carrier gas and main gas to obtain a high deposition efficiency, low porosity and high mechanical properties. The effect of deposition parameters and heat treating on the microstructure and mechanical properties was explored. An ultimate tensile strength higher than 650MPa, a yield strength of about 600MPa and a Vickers micro hardness HV0.2 higher than 220 were obtained, values which compare quite favorably with those corresponding to a classically forged material. The deposits microstructure and more particularly the plastic deformation of particles upon impact were observed by optical and electronical microscopy. The residual stress level was also investigated as a function of heat treating.

Numerical Simulation of Turbulent Mist Flows With Liquid Film Formation in Curved Pipes Using an Eulerian–Eulerian Method

Turbulent flows of air/water mixtures through curved pipes are modeled in this work using a Eulerian–Eulerian method. This is motivated by the possibility of using computational fluid dynamics (CFD) as a design tool applied to curved pipes feeding a gas/liquid separator. The question is to identify the curvature of such pipes that can promote film formation upstream of the separator and, thus, precondition the flow without creating a large pressure drop. The performance of the mixture theory with a drift flux model and the “realizable” k-ε closure was evaluated in the simulations. The enhanced wall treatment (EWT) was utilized to resolve the flow in the near-wall region. A qualitative study was first conducted to investigate the flow patterns and the liquid film formation in a 180 deg bend. The numerical results were validated by comparing the computed pressure drop with empirical correlations from the literature. Subsequently, the importance of droplet size and liquid volume fraction was investigated by studying their effect on the flow patterns of the continuous phase, as well as their impact on the secondary flow intensity, the pressure drop, and the liquid film formation on the wall. Various pipe geometries were studied to achieve a low pressure drop while maintaining a high droplet deposition. Results show that a combination of the drift flux model with the realizable k-ε closure and EWT for the near-wall treatment appears capable of capturing the complex secondary flow patterns such as those associated with film inversion. The pressure drop computed for various flows appear to be in good agreement with an empirical correlation. Finally, bends with a curvature ratio around 7 appear to be the optimal for providing a small pressure drop as well as a high droplet deposition efficiency in a U-bend.

J043024 低圧コールドスプレー法を用いた色素増感太陽電池用T102皮膜の開発([J043-02]厚膜形成技術と厚膜の機械特性評価(2))

In order to make a dye-sensitized solar (DSC) cell, a Low-pressure Cold Spray (LCS) technique is used to make Ti02 film in this study. In our previous study, it was successful that dense and more than 15μm thick TiO_2 film can be obtained by the LCS. However, in the case of the DSC, the dense film is not good for power generation. It is better to obtain films with pores, high cohesive force, and suitable thickness. Therefore, the aim of this study is to make the porous and thick film, which was controlled by mixture TiO_2 powder with large and small diameters. It was made that several mixture TiO_2 powders with different proportion of large and small powders, and then a film was coated by the LCS. Moreover, the influence on the deposition efficiency and the film thickness in repetition film coating were evaluated. As a result, it is successful to make porous TiO_2 films controlled by proportion of large and small powder contents. And, it was made clear that use of small particles indicated high deposition efficiency. On the other hand, use of large particles indicated low deposition efficiency. Finally, the battery properties of the film made by the LCS was evaluated. As a result, conversion efficiencies of the film made by the LCS were less than 1% in any mixture ratio, because of inhomogeneous porosity. However, the LCS becomes an effective tool for making films for the DSC.

Evaluation of the Airborne Particles Fraction Responsible for Adverse Health Effects

A new approach to evaluation of the fraction of airborne particles that is responsible for adverse health effects has been developed. In this approach a two-fraction concept for the adverse health effects is proposed. This concept considers aerosol particles in the air, the fraction of particles deposited in the respiratory system (captured by the system) and the fraction of particle accumulated in the body (captured by the body). The latter fraction of airborne particles actually causes the adverse health effects and associated with the health risk. The approach has been applied to workers in crystal glass industry exposed to lead. A size resolved sampling technique was employed to characterize nanoparticles at work places at several plants involved in lead processing. Lead aerosol size distributions were obtained across the entire aerosol particle size range from 1 nm to 30 μm (diameter). Size distributions were used to calculate the total lead intake due to particle deposition in the respiratory system of workers. A bio-kinetic model was employed to evaluate various size fraction contributions to the total blood lead level in workers. A comparison was made between calculated blood lead levels and actual measurements of blood lead levels of workers exposed to atmospheres containing lead. It was found that nanoparticles cause the major health risk due to high deposition efficiency and low clearance rate by the mucociliary escalator.

Electrochemical behavior of copper in 1-butyl-3-methylimidazolium bromide-copper(II) bromide binary ionic liquid

The methods of potentiometry, voltammetry, and gravimetry are used to study the electrochemical behavior of copper in the BMImBr-CuBr2 ionic liquid (0–30.5 mol % CuBr2). It is shown that electrochemical reduction of copper(II) occurs irreversibly, in two one-electron stages (transfer coefficient α of the cathodic process are 0.58 and 0.46, accordingly, for the first and second stages). Diffusion coefficients of copper-containing ions DCu(II) at 60°C are 1.3 × 10−7 and 1.6 × 10−7 cm2 s−1 in melts with the CuBr2 concentration of 0.1 and 1.5 mol kg−1 of BMImBr, accordingly. High (up to 98%) deposition efficiency and high-quality copper deposit can be obtained in the potential range of −2.0 to −1.8 V (vs. a platinum quasireference electrode). It is found that the copper corrosion rate grows at an increase in the CuBr2 concentration in the binary melt and is comparable with that in aqueous solutions of H2SO4-CuSO4.

Site-Specific Retention of Colloids at Rough Rock Surfaces

The spatial deposition of polystyrene latex colloids (d = 1 μm) at rough mineral and rock surfaces was investigated quantitatively as a function of Eu(III) concentration. Granodiorite samples from Grimsel test site (GTS), Switzerland, were used as collector surfaces for sorption experiments. At a scan area of 300 × 300 μm(2), the surface roughness (rms roughness, Rq) range was 100-2000 nm, including roughness contribution from asperities of several tens of nanometers in height to the sample topography. Although, an increase in both roughness and [Eu(III)] resulted in enhanced colloid deposition on granodiorite surfaces, surface roughness governs colloid deposition mainly at low Eu(III) concentrations (≤5 × 10(-7) M). Highest deposition efficiency on granodiorite has been found at walls of intergranular pores at surface sections with roughness Rq = 500-2000 nm. An about 2 orders of magnitude lower colloid deposition has been observed at granodiorite sections with low surface roughness (Rq < 500 nm), such as large and smooth feldspar or quartz crystal surface sections as well as intragranular pores. The site-specific deposition of colloids at intergranular pores is induced by small scale protrusions (mean height = 0.5 ± 0.3 μm). These protrusions diminish locally the overall DLVO interaction energy at the interface. The protrusions prevent further rolling over the surface by increasing the hydrodynamic drag required for detachment. Moreover, colloid sorption is favored at surface sections with high density of small protrusions (density (D) = 2.6 ± 0.55 μm(-1), asperity diameter (φ) = 0.6 ± 0.2 μm, height (h) = 0.4 ± 0.1 μm) in contrast to surface sections with larger asperities and lower asperity density (D = 1.2 ± 0.6 μm(-1), φ = 1.4 ± 0.4 μm, h = 0.6 ± 0.2 μm). The study elucidates the importance to include surface roughness parameters into predictive colloid-borne contaminant migration calculations.

Ion recognition properties of poly[Cu(3-MeOsalpd)] films

Poly[Cu(3-MeOsalpd)] films with good physical, chemical and electrochemical stability may be potentiodynamically electrodeposited with high deposition efficiency from acetonitrile solutions of the monomer. Comparative coulometric assays with the Ni-based analogue show that the metal in the salen motif does play a role in the electronic structure of the polymer, but that the electroactive response is ligand (not metal) based. The dynamics of redox switching are ultimately limited by coupled electron/counter ion diffusion, but this process is sufficiently rapid that it influences the voltammetric response only for thick films (Γ >420 nmol cm−2) at high scan rates. Redox cycling in monomer-free electrolyte shows a voltammetric signature that responds, via interaction with the pseudo-crown ether receptor sites, to the presence of Li+, K+, Mg2+ and Ba2+ ions in solution. The most prominent change is associated with the first anodic peak in the i-E signature. For each of the metal ions considered, this peak potential responds logarithmically to concentration in a manner that varies with individual complexed cation and film thickness and to an extent greater than predicted by the Nernst equation. The film characteristics offer some analytical promise, including a trade-off between sensitivity and dynamic range and signal amplification, possibly due to supramolecular effects.