Spray Deposition Research Articles

Synthesis of high transparency of F doped NiO monocrystalline thin films by spray deposition

Synthesis of high transparency of F doped NiO monocrystalline thin films by spray deposition

Uncrewed Aerial Spray Systems For Mosquito Control: Efficacy Studies For Space Sprays.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

Evaluation of a hybrid cold spray and machining method for fabrication of parts with high surface integrity

Cold spray technology has been proven to have various engineering and manufacturing applications, including the capability to restore previously unrepairable parts. However, like most additively manufactured parts, it will likely require post-processing, such as machining, to improve surface finish and dimensional accuracy. In addition, cold spray deposits are typically porous. The porosity may be detrimental to the mechanical performance of the component. This paper presents a systematic evaluation of cold spray using readily available nitrogen as carrier gas, subsequent machining utilizing negative rake angle tools, and the effect of this novel hybrid fabrication method on subsurface porosity. The machining is optimized via finite element analysis (FEA) and the optimum is verified by experiments. The analysis informs the engineering of the proposed hybrid cold spray/machining method.

Ultrasonic Spray Deposition of a Passivating Agent for Spray‐Coated, Methylammonium‐Free Perovskite Solar Cells

Defect management in perovskite solar cells (PSCs) via surface passivation has become a cornerstone in maximizing both stability and solar‐to‐electrical power conversion efficiency (PCE) of devices by reducing defect densities and/or improving energetic alignment between the perovskite and charge‐transporting layers. Despite this, few reports explore the use of roll‐to‐roll compatible technologies to deposit such interfacial treatments, limiting the applicability of passivation in real‐world contexts. In this work, iso‐butylammonium bromide (i‐BABr) is spray‐coated onto a Cs0.15FA0.85PbI2.85Cl0.15 perovskite surface which is deposited using gas‐assisted ultrasonic spray coating. It is found that i‐BABr treatments result in the formation of a quasi‐2D perovskite layer. The spray‐coated surface treatment results in an impressive 80 mV improvement in the median open‐circuit voltage with respect to untreated devices. Importantly, the spray‐coated passivation results in very similar positive benefits to the application of spin‐coated treatments demonstrating the promise of the spray‐passivation methodology. It is shown that devices created in this manner demonstrate PCEs of up to 21.0% (19.4% stabilized), representing the highest reported efficiency for one‐step, spray‐coated methylammonium‐free PSCs. This work represents the first demonstration of a spray‐coated surface passivation treatment that is compatible with high‐throughput, roll‐to‐roll processing.

Design and Experiment of a Breakpoint Continuous Spraying System for Automatic-Guidance Boom Sprayers

Repeated and missed spraying are common problems during the working of boom sprayers, especially in the breakpoint continuous process. Therefore, the present study investigated a breakpoint continuous spraying system for automatic-guidance boom sprayers based on a hysteresis compensation algorithm for spraying. An operational breakpoint identification algorithm, which combines a real-time kinematic global navigation satellite system (RTK-GNSS) and wheel odometer, was proposed; a pre-adjusted proportional-integral-derivative (PID) control algorithm for the opening degree of the proportional control valve was designed in thus study. Tests were conducted to establish equations correlating the opening degree of the proportional control valve, pump output flow rate, and main pipeline flow rate, with an R2 ≥ 0.9525. The time to adjust to the target flow rate was experimentally tested. The breakpoint identification accuracy of the RTK-GNSS and RTK-GNSS + wheel odometer was experimentally assessed. A field spraying deposition variation experiment was conducted. According to the results, the system effectively eliminated missed spraying, with a maximum repeated spraying distance of ≤3.3 m, and it achieved a flow control error within 3%. This system also reduced the repeated spraying area and enhanced the pesticide spraying quality of breakpoint continuous spraying for automatic-guidance boom sprayers.

Lung toxicity, deposition, and clearance of thermal spray coating particles with different metal profiles after inhalation in rats

Thermal spray coating is a process in which molten metal is sprayed onto a surface. Little is known about the health effects associated with these aerosols. Sprague-Dawley rats were exposed to aerosols (25 mg/m3 × 4 hr/d × 4 d) generated during thermal spray coating using different consumables [i.e. stainless-steel wire (PMET731), Ni-based wire (PMET885), Zn-based wire (PMET540)]. Control animals received air. Bronchoalveolar lavage was performed at 4 and 30 d post-exposure to assess lung toxicity. The particles were chain-like agglomerates and similar in size (310–378 nm). Inhalation of PMET885 aerosol caused a significant increase in lung injury and inflammation at both time points. Inhalation of PMET540 aerosol caused a slight but significant increase in lung toxicity at 4 but not 30 d. Exposure to PMET731 aerosol had no effect on lung toxicity. Overall, the lung responses were in the order: PMET885≫PMET540 >PMT731. Following a shorter exposure (25 mg/m3 × 4 h/d × 1d), lung burdens of metals from the different aerosols were determined by ICP-AES at 0, 1, 4 and 30 d post-exposure. Zn was cleared from the lungs at the fastest rate with complete clearance by 4 d post-exposure. Ni, Cr, and Mn had similar rates of clearance as nearly half of the deposited metal was cleared by 4 d. A small but significant percentage of each of these metals persisted in the lungs at 30 d. The pulmonary clearance of Fe was difficult to assess because of inherently high levels of Fe in control lungs.

High temperature oxidation of cold spray Cr-coated accident tolerant zirconium-alloy cladding with Nb diffusion barrier layer

Cr-Nb bilayer coatings on Optimized ZIRLO™ light water reactor (LWR) fuel cladding tubes were developed using cold spray deposition technology to increase the limiting operational temperature (i.e., binary Cr-Zr eutectic temperature, 1332 °C) of Cr-coated Zr-alloy system. The properties of the dual-layered coatings were improved by varying the type of Cr powder and post-annealing of the cold sprayed Nb layer. High temperature oxidation behavior of Cr-Nb-coated cladding at 1200 °C and 1425 °C in flowing steam were compared with those of Cr-coated cladding and uncoated cladding. At 1200 °C, both Cr-coated cladding and Cr-Nb coated cladding exhibited outstanding oxidation resistance and a continuous intermetallic compound layer (1 – 3 μm thickness) of predominantly Zr-Cr and Cr2Nb formed at the Cr/Zr and Cr/Nb interface, respectively. At 1425 °C, the Cr-coated Zr-alloy cladding showed enhanced oxidation due to rapid consumption of Cr coating by interdiffusion and liquid phase formation, and consequent destabilization of the outer protective Cr-oxide layer. However, the Nb diffusion barrier layer between the Cr coating and Zr-alloy substrate prevented the melting and the outer Cr coating provided excellent oxidation resistance. For this bi-layered system, a diffusion layer devoid of intermetallic phases was observed at the Nb/Zr interface due to the miscibility of the two metals. Reaction pathways that include both surface oxidation and interdiffusion effects within the coating-substrate system have been proposed based on experimental results.

Leaf wettability is the main driver for foliar P uptake in P-deficient maize

Foliar fertilisation is an alternative form of nutrient application, which is of particular interest for phosphorus (P), where the efficiency of soil fertilisation is low. However, the uptake of foliar-applied nutrients is insufficiently characterised. The aim of this study was to investigate the individual and combined significance of wettability, foliar fertiliser properties and surfactant on foliar P uptake in P-deficient maize (Zea mays L.). Sorption and desorption properties of two P salts used as foliar fertilisers (KH2PO4, K2HPO4) were determined with dynamic vapor sorption isotherms. Leaf surfaces and foliar spray depositions of two differently wettable maize cultivars were investigated by scanning electron microscopy and contact angle measurement. Phosphorus uptake was then linked to leaf and fertiliser solution properties and its effect on cell ultrastructure was characterised by transmission electron microscopy. Wettability was the key factor for P absorption, as all foliar fertilisers were taken up reaching a tissue-P level of adequately nourished plants. For unwettable leaves, only solutions with surfactant, especially the combination of surfactant and hygroscopic P salt (K2HPO4) were taken up. This study provides novel insights into the significance of leaf surface and fertiliser properties, which can thus contribute to an improvement of P fertilisation strategies.

A hybrid computational approach for modeling cold spray deposition

Cold spray (CS) is a cold-state technology that uses high-velocity supersonic gas flow to propel and deposit powder particles onto a substrate surface. The design and optimization of the cold spray deposition process were recently achieved via the experimental trial-and-error approach, which is laborious and costly. The present study presents a computationally efficient hybrid method for simulating cold spray coating deposition, applied explicitly to Ni coating used for wear applications. The model effectively synergizes meshless and meshed computational schemes in predicting the thermo-mechanical deformation of the impacting Ni particles and SS304 steel substrate. During the simulations, the point cloud (PC) of deformed particle domains is converted into a high-quality finite element (FE) mesh with novel PC processing algorithms. The simulations are carried out for various particle characteristics and spraying conditions. The numerical predictions are validated by comparing them with other numerical schemes and previous experimental studies. The main results indicate that the kinetic energy and morphology of the impacting Ni particles strongly influence plastic deformation and temperature rise in the substrate and predeposited coating particles. Plastic deformation is more prominent at the particle edges and mating material interfaces. At the same time, the temperature rise does not reach the melting point but can allow for recrystallization near highly localized regions of the coating microstructure, even at lower deposition rates. Compressive residual stresses are also observed across the coating and substrate layers, with a non-uniform and nonlinear residual stress field due to complex interactions among neighboring particles. The study aims to provide a robust numerical framework for designing and optimizing cold spray deposition parameters for industrial coatings, bridging the knowledge gap and enabling efficient and cost-effective simulations for process optimization.

Uncovering the Electronic State Interplay at Metal Oxide Electron Transport Layer/Nonfullerene Acceptor Interfaces in Stable Organic Photovoltaic Devices.

The implementation of sputter-deposited TiOx as an electron transport layer in nonfullerene acceptor-based organic photovoltaics has been shown to significantly increase the long-term stability of devices compared to conventional solution-processed ZnO due to a decreased photocatalytic activity of the sputtered TiOx. In this work, we utilize synchrotron-based photoemission and absorption spectroscopies to investigate the interface between the electron transport layer, TiOx prepared by magnetron sputtering, and the nonfullerene acceptor, ITIC, prepared in situ by spray deposition to study the electronic state interplay and defect states at this interface. This is used to unveil the mechanisms behind the decreased photocatalytic activity of the sputter-deposited TiOx and thus also the increased stability of the organic solar cell devices. The results have been compared to similar measurements on anatase TiOx since anatase TiOx is known to have a strong photocatalytic activity. We show that the deposition of ITIC on top of the sputter-deposited TiOx results in an oxidation of Ti3+ species in the TiOx and leads to the emergence of a new O 1s peak that can be attributed to the oxygen in ITIC. In addition, increasing the thickness of ITIC on TiOx leads to a shift in the O 1s and C 1s core levels toward higher binding energies, which is consistent with electron transfer at the interface. Resonant photoemission at the Ti L-edge shows that oxygen vacancies in sputtered TiOx lie mostly in the surface region, which contrasts the anatase TiOx where an equal distribution between surface and subsurface oxygen vacancies is observed. Furthermore, it is shown that the subsurface oxygen vacancies in sputtered TiOx are strongly reduced after ITIC deposition, which can reduce the photocatalytic activity of the oxide, while the oxygen vacancies in model anatase TiOx are not affected upon ITIC deposition. This difference can explain the inferior photocatalytic activity of the sputter-deposited TiOx and thus also the increased stability of devices with sputter-deposited TiOx used as an electron transport layer.

Effect of cold spray processing parameters on the microstructure, wear, and corrosion behavior of Cu and Cu–Al2O3 coatings deposited on AZ31 alloy substrate

Cold spray coatings represent a newly emerging and recently implemented approach to enhance the poor wear and corrosion resistance of AZ31 magnesium alloy. In this study, the authors applied pure Cu and Cu-50 wt% Al2O3 composite coatings on an AZ31B substrate using the cold spray deposition method and investigated the effects of gas pressure (1, 2, and 3 MPa) and stand-off distance (1, 2, and 3 cm) on their microstructure characteristics. An increase in gas pressure from 1 MPa to 3 MPa resulted in a decrease in porosity, ranging from 33 % to 38 %, across varying stand-off distances. Increasing the stand-off distance from 1 to 3 cm resulted in a nearly four-fold rise in porosity for 2 and 3 MPa pressures and about 1.5 times for 1 MPa. The porosity increased with higher pressure due to the fragmentation of Al2O3 particles but decreased with greater spraying distance due to reduced Al2O3 retention. Additionally, the incorporation of Al2O3 particles into Cu coatings led to a significant improvement in sliding wear resistance, by up to 50 %, compared to the bare substrate. Abrasive wear and delamination were identified as the dominant wear mechanisms for the composite coatings based on friction coefficient values and micromorphology of wear tracks. Electrochemical results indicated a significant increase in the corrosion resistance of the Cu coating compared to both the bare Mg substrate and Cu–Al2O3 coating, attributed to improved resistance to galvanic corrosion.

Surface preparation of aluminum by atmospheric-pressure plasma jet for suspension plasma sprayed ceramic coatings

Surface preparation is a key step preceding the deposition of suspension plasma spray (SPS) coatings, a type of thermal spray coatings. This work evaluates the effect of surface preparation by atmospheric-pressure plasma jet (APPJ) treatment on the adhesion of SPS-deposited Al2O3 ceramic coatings on aluminum (Al-2024) substrates. For comparison, the substrate surfaces were also prepared by grit-blasting. Surface roughness (R) parameters and surface morphology of both grit-blasted and APPJ-treated substrates were characterized by confocal microscopy and scanning electron microscopy (SEM). In addition, surface chemistry was evaluated by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Based on morphological analyses, the grit-blasted surfaces exhibit typical random peaks and valleys, whereas those subjected to APPJ treatment show self-organized patterns with multilayered and multiscale features. ATR-FTIR spectroscopy analyses also demonstrated a significant difference in surface chemistry for both surface preparation types. After the characterization of both types of prepared substrates, SPS coating was deposited on the substrates under two spray conditions. One spray condition demonstrated poor adherence of the coatings for both types of the prepared substrates; the other spray condition produced coatings with good adherence. The microstructures of the coating were evaluated for both spray conditions. The Adhesion strength of the coating was evaluated for the condition, which produced a coating with good adhesion. ASTM-C-633 pull test protocol was followed for the adhesion evaluation, and the pull test revealed significant adhesion improvements when the surface was prepared by APPJ. Improved adhesion strength was linked to the surface morphology and also to the surface chemistry of the surface prepared by APPJ. In addition, splat morphology was investigated on both grit-blasted and APPJ-treated substrates to correlate the improved adhesion.

UNCREWED AERIAL SPRAY SYSTEMS FOR MOSQUITO CONTROL: EFFICACY STUDIES FOR SPACE SPRAYS.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

Cellulose acetate superhydrophobic coatings for efficient oil–water separation using a combination of electrostatic spraying and chemical vapor deposition

AbstractThe efficient and simple separation of oil–water mixtures has been a global challenge due to the growing problem of oily wastewater. To address this issue, various materials with special wetting properties and functionality have been developed in the past decades for oil–water separation. In this study, a superhydrophobic cellulose acetate (CA) functional coating was prepared by electrostatic spraying of CA and chemical vapor deposition of methyltrichlorosilane (MTCS) on a stainless steel mesh (SSM). Water contact angle in air (WCA) of the resulting coating is154° or more, and oil under water contact angle (UWOCA) is 0°. Simultaneously, the separation flux of the resulting coating for oil–water mixtures is as high as 23977.77 L·m−2·h−1, with separation efficiencies exceeding 99%. Due to its excellent water repellency, the CA functional coating can effectively separate oil and water, and can be easily dried for continuous use. Furthermore, the CA functional coating exhibits good stability in salt solutions and acidic environments, making it an ideal material for addressing oily wastewater challenges.Highlights The coating obtained by electrostatic spraying and CVD was superhydrophobic. The separation flux and separation efficiencies of coatings is 23977.77 L·m−2·h−1 and 99%. Coatings remain stable under polar environment conditions (pH = 2–12 and NaCl = 1–3 mol/L).

Investigation physical properties of sprayed Cr doped ZnO thin films

ZnO and ZnO:Cr films were grown by the chemical spray deposition (CSD). The effect of the Cr content on ZnO was studied. All ZnO films show polycrystalline, hexagonal wurtzite structure, with (002) dominant plane. AFM displayed that films have a compact surface, its root mean square roughness increased with Cr percentage. The average diameter was smaller than 64 nm. The optical bandgap was evaluated using Transmittance data. Their values were found to be decreases via increment in Cr doping.

Preparation of wettability-controlled surface by electrostatic spray deposition to improve performance uniformity of small molecule/polymer blend organic field-effect transistors

Preparation of wettability-controlled surface by electrostatic spray deposition to improve performance uniformity of small molecule/polymer blend organic field-effect transistors

Variable-rate spray system for unmanned aerial applications using lag compensation algorithm and pulse width modulation spray technology

To ensure that a variable-rate spray (VRS) system can perform unmanned aerial spray in accordance with a prescription map at different flight speeds, we examine in this paper such significant factors as the response time of the VRS system and the pressure fluctuation of the nozzle during the variable-rate spraying process. The VRS system uses a lag compensation algorithm (LCA) to counteract the droplet deposition position lag caused by the system response delay. In addition, pulse width modulated (PWM) solenoid valves are used for controlling the flowrates of the nozzles on the variable-rate spray system, and a mathematical model was constructed for the spray rate (L min-1) and the relative proportion of time (duty cycle) each solenoid valve is open. The pressure drop and solenoid valve response time at different duty cycles (50%~90%) were measured by indoor experiments. Meanwhile, the lag distance (LD), spray accuracy, and droplet deposition characteristics of the VRS system were tested by conducting outdoor experiments at different flight speeds (4m s-1, 5m s-1, 6m s-1). The results show that LCA can effectively reduce the lag distance. The lag distance (LD) values of the VRS system with LCA ranged from -0.27 to 0.78m with an average value of 0.32m, while without LCA, the LD values increased to 3.5~4.3m with an average value of 3.87m. The overall spray position accuracy was in the range of 91.56%~97.32%. Furthermore, the spray coverage and deposition density, determined using water sensitive paper (WSP), were used to evaluate the spray application performance taking into account the spray volume applied. The VRS system can provide the most suitable spray volumes for insecticide and fungicide plant protection products. Based on a prescription map, the optimized VRS system can achieve accurate pesticide spraying as well as desirable spray coverage and deposition density.

Adjusting Residual Stresses During Cold Spray Deposition of IN718

AbstractThe residual stress state in cold spray coatings, which is typically compressive in nature, can be crucial for the coating integrity at high levels or for thick coatings. As an alternative, the analysis using the curvature measurement was applied in this study. The stress measurement during cold spray deposition was made by using an in situ coating property sensor (ICP sensor), which is relatively widely used in thermal spray and enables a fast comparison of several process parameters. The results were then compared to post-deposition curvature measurements. It could be revealed that the usage of a very slow robot traverse speed can lead to tensile residual stresses in cold-sprayed coatings. This finding was explained by the high local temperature during deposition and the formation of tensile stresses during cooling of the deposited material to the average substrate temperature. The increase in the powder feed rate can increase this effect. Preheating did not influence the final stress state. An analytical model is presented which can at least semi-quantitatively explain the observed findings. As an outcome of the research work, it is now possible to adjust the residual stress state in cold spray coatings from tensile to compressive and vice versa with the opportunity of a zero stress state.

New generation unit for plasma-arc deposition of coatings and spraying of current-conducting wire materials

New generation unit for plasma-arc deposition of coatings and spraying of current-conducting wire materials

Application rate and hydraulic tips used in remotely piloted aircraft affect the phytosanitary products in coffee plant canopies

Most coffee (Coffea arabica) phytosanitary management techniques are performed using ground-based equipment, and remotely piloted aircraft are a recent alternative. Therefore, this study evaluates the effect of different application rates and hydraulic tips used for spreading phytosanitary products on coffee crops using a remotely piloted aircraft, assisted by artificial targets and dye tracing. The experiment was a 4 × 3 factorial randomized block design with four tips (XR 110-01, TT 110-01, AIXR 110-015, and TTJ60 110-02) and three application rates (8, 12, and 16 L ha-1). Hydrosensitive paper was used to analyze the droplet spectrum, and the Brilliant Blue tracer was used to detect spray deposition. The DJI Agras T20 remotely piloted aircraft was used to apply the phytosanitary product. Speed, flight height, and application range were maintained at 5.56 m s-1, 2 m, and 5 m, respectively. The flight direction was perpendicular to the crop planting lines. The application rate and hydraulic tip jointly controlled the accumulation of droplets on the target according to its position in the plant canopy. Therefore, remotely piloted aircraft can be used in coffee phytosanitary management, particularly to control targets that predominately occur in the upper third of the plant canopy.