Spray Technology Research Articles

Understanding dilution effects on particle-containing pesticide droplets deposition on rice leaf via developing CFD-VOF-DPM model.

Pesticide dilution is one of the essential aspects of plant protection. However, the effect of dilution on the deposition characteristics of pesticide droplets containing particulate additives on crop leaf surfaces remains unclear and warrants further research. Herein, a validated computational fluid dynamics (CFD)-volume of fluid (VOF)-discrete phase model (DPM) numerical model was developed to analyze the influence of particle content on the deposition behavior of droplets on the leaf surface comparatively, taking into account the particle content of different diluted thifluzamide solutions. Additionally, the study aimed to analyze further the kinetic behavior of pesticide droplets landing on rice leaves across different dilution conditions. Pesticide droplets diluted 100-fold had a lower retraction rate during spreading than particle-free droplets, so the solution is more easily deposited in the leaves. Moreover, the low dilution (high concentration) increased the critical adhesion rate between droplets and rice leaves, inhibiting the bouncing of droplets on the leaf surface, thus promoting their effective deposition on the surface. In addition, low dilution (high concentration) is not conducive to spreading droplets when the impact velocity is high, and it also results in a large amount of pesticide use. The actual application process can be through understanding the dilution factor of the configured pesticide solution, and reasonable adjustment of the nozzle pressure can effectively improve the utilization rate of pesticides and reduce the pollution brought by pesticides to the environment. These results provide an essential reference for studying pesticide droplet deposition characteristics, including rice plant protection and spraying technology. © 2024 Society of Chemical Industry.

Microstructure and tribological properties of Al-30Si-5Cu composite coating reinforced with ceramic phases synthesized in situ by plasma spraying

For improving the wear resistance of Al-30Si-5Cu coating, in this study, the composite coating in-situ synthesized TiC-TiN-TiN0.8C0.2/Al-30Si-5Cu (TiCN/Al-30Si-5Cu) was prepared used TiH2-graphite aggregates as raw materials and plasma spraying technology. The effect of in-situ synthesized ceramic reinforcements on the coating was researched in detail. The results showed that during the plasma spraying process, TiH2 decomposed and chemically reacted with graphite to form TiC. Additionally, some Ti also reacted with N2 and O2 in the air to form TiN and TiO2. The phases composition of TiCN/Al-30Si-5Cu composite coating were α-Al, β-Si, θ-Al2Cu, β-Ti, TiC, TiN, TiN0.8C0.2, TiO2, as well as amorphous CNX and residual graphite. The TiC-dominated ceramic phases and β-Si were uniformly distributed in the coating, which were tightly bound to the α-Al matrix. Because of the exceptionally rapid cooling rate during the coating preparation, a minor amount of submicron Si particles were also generated. The microhardness, elasticity modulus, and fracture toughness of TiCN/Al-30Si-5Cu composite coating appeared improvements compared to those of Al-30Si-5Cu coating. The TiCN/Al-30Si-5Cu composite coating exhibited smoother friction coefficient curve, along with lower friction coefficient and wear volume in comparison to the Al-30Si-5Cu coating. This suggested that the ceramic reinforcing phases in-situ synthesized led to a notable advancement in the wear resistance of the TiCN/Al-30Si-5Cu composite coating. The wear resistance of TiCN/Al-30Si-5Cu composite coating demonstrated an increasement of 78.3 % over the substrate and 28.2 % over the Al-30Si-5Cu coating. Under the dry friction test conditions outlined in this study, the wear mechanism of the TiCN/Al-30Si-5Cu composite coating included abrasive wear and fatigue wear, coupling with a minimal amount of oxidative wear.

Thermal Spray Technology in Automotive Industry Applications

Thermal Spray Technology in Automotive Industry Applications

A feasibility study on femtosecond laser texturing of sprayed nanocellulose coatings

Nanocelluloses are emerging as natural materials with favourable properties for coating industry and can be applied by state-of-the-art spraying technology. While additional functionalities are commonly introduced through chemical modification, the surface microstructuring of nanocellulose coatings with high throughput methods remains unexplored. Here, a femtosecond laser is used for texturing spray-coated coatings made of cellulose nanofibrils (CNF) or cellulose nanocrystals (CNC). For coating thickness of 1.5 to 8 μm, processing limits were determined with maximum ablation energy linearly increasing with coating thickness and minimum ablation energy decreasing or increasing depending on the apparent coating density. Within applicable processing window of pulse rate and power setting, the operational ranges were determined for creating one-dimensional and two-dimensional surface patterns, requiring a higher laser energy for CNC compared to CNF coatings and yielding thinnest possible resolved patterns of 17 μm as determined by the laser spot diameter. The laser ablation under low energy corresponds to an increase in surface roughness and intensifies surface hydrophilicity, while the line patterns are able to pin water droplets with rising water contact angles up to 90°. Present feasibility study opens future possibilities for managing surface properties of nanocellulose coatings in applications where tuning of surface hydrophilicity is required.

Prediction of HVAF thermal spraying parameters and coating properties based on improved WOA-ANN method

In this study, high-velocity air fuel (HVAF) thermal spray technology was utilized to deposit Hastelloy C276 powder onto 316 L stainless steel substrates. The effects of various spray process parameters such as propane pressure, air pressure, spray distance, and powder feeding rate on the microstructure, microhardness, and corrosion resistance of the coatings were investigated. In addition, the coupling effects among multiple spray parameters were considered by employing a combined approach with the Improved Whale Optimization Algorithm (IWOA) and Artificial Neural Network (ANN) model, and the mapping relationships between the spray process parameters and coating porosity, microhardness, and corrosion current density was established. The results revealed that the prepared C276 coating exhibits lower porosity, higher microhardness, and exceptional corrosion resistance. And the IWOA-ANN model outperforms the ANN model and WOA-ANN model in the prediction accuracy and stability for all three performance measures, particularly for porosity and microhardness. Furthermore, the comparison between experimental results and predicted results validates the reliability and accuracy of the trained IWOA-ANN model, demonstrating its efficacy in predicting HVAF spray parameters and coating properties.

Micropatternable Ink Composed of MAX Phase ZIF-8 for Gas Sensing Applications

This work provides a detailed introduction to the preparation methods, structural characteristics, and various performance tests of the Ti3C2/ZIF-8 composite material. Initially, the composite material is obtained through the synthesis, mixing, and subsequent processing of MXene solution and ZIF-8 nanoparticles. The coating structure and properties were comprehensively characterized using SEM, TEM, and XRD. These analyses revealed the material's layered structure, high crystallinity, and surface activity. BET analysis of Ti3C2/ZIF-8 also shows excellent gas adsorption-desorption performance, having an especially high-efficiency adsorption capacity for VOCs. TGA further demonstrates the thermal stability and chemical stability of Ti3C2/ZIF-8 and its printability was tested indicating widespread application potential in coating preparation through ultrasonic spray technology. Finally, we show methods to regulate and control coating thickness and roughness for precision manufacturing. These analyses together emphasize the application value of Ti3C2/ZIF-8 in fields such as gas-storage, gas-separation, and environmental monitoring.

Study on droplet deposition characteristics and application of small and medium crown garden plants sprayed by UAV sprayer.

The Unmanned Aerial Vehicle (UAV) sprayer has the advantages of high work efficiency, simple operation, and high safety factor, and has broad application prospects UAV sprayer are widely used in the agricultural field, and the application of UAV sprayer spraying technology in agriculture has provided convenience and increased profits for farmers, and has also become a research hotspot in the field of agriculture. In recent years, although research has been conducted on the feasibility and application effects of UAV sprayer spraying crown shaped plants, there have been no experiments or studies in the field of garden plants. This experiment conducted a droplet deposition experiment of UAV sprayer spraying garden plants, exploring the droplet deposition effect of UAV sprayer in the field of garden plants, and conducting experiments on the influence of spray volume and nozzle type on droplet deposition. The experimental results showed that the canopy performance of small and medium-sized garden plants was better at a flight altitude of 1.5m, a spray volume of 180L/hm2, and a flight speed of 2m/s. Reducing flight altitude, increasing spray volume, and reducing flight speed can improve the distribution of droplets in the canopy. This experiment lays the foundation for the application of UAV sprayer for the prevention and control of pests and diseases in garden plants, as well as for the application of growth regulators, and provides a basis for further innovative research in the field of garden plant application technology.

Cooled Spray Technology for Particulate Reduction in a Heavy-Duty Engine

Abstract Cooled spray (CS) technology passively reduces particulate matter (PM) emissions from diesel engines compared to non-CS-equipped diesel engines. CS inserts are mounted near the injector nozzle and control mixing so that the fuel and air can premix while limiting combustion near fuel-rich zones, thereby reducing the formation of particulate matter. CS components contain no moving parts and could be installed as a retrofit or built into new engines. However, CS technology is early in its development, and further investigations are needed to understand the overall performance implications and practicality of the technology. In this paper, we investigate several important aspects of CS, providing a clearer picture of some challenges and potential benefits of CS. Two alignment techniques are used to characterize measurement ease and bias, namely, an optical alignment and spray-plug impact alignment. While the optical technique facilitates alignment more easily, a bias was measured between the optical and spray-plug techniques, suggesting the optical technique may have insufficient accuracy without additional corrections. We also evaluate the engine performance of a well-aligned and poorly aligned CS insert, compared to the baseline configuration. The poorly aligned insert shows slower combustion than the baseline and mixed overall performance. However, the well-aligned insert shows faster combustion than the baseline and PM emission reduction at most operating conditions, with some conditions showing PM reduction up to 80%. The results of this paper highlight the alignment challenges of CS technology as well as the potential PM reduction benefit of the technology.

REVIEW: MATERIALS FOR IMPREGNATION OF POROUS METALLIZATION THERMAL SPRAYED ANTICORROSIVE COATINGS OF SUBMERSIBLEOILFIELD EQUIPMENT. Part 1

Submersible oilfield equipment undergoes aggressive corrosive effects of petroleum fluid, abrasive effects of mechanical impurities during operation, and also operates at elevated temperatures in the bottom. The most effective way to protect the outer surface of oilfield equipment is the use of metallization thermal sprayed coatings, and therefore the application of thermal spraying technology is becoming more and more in demand.However, the formation of a coating structure from many particles of molten material, due to their spraying, incomplete melting and loose packaging, leads to the formation of porosity, and porosity is one of the main disadvantages of thermal sprayed coatings. To eliminate this disadvantage, it is possible to use impregnation of porous coatings with various compositions, in which case the coating becomes composite. Depending on the operating environment, temperature conditions and operating conditions, metal, organic and inorganic impregnating compositions are used,but their use in the oil environment has been little studied, therefore the development of composite impregnated coatings is relevant for the protection of submersible oilfield equipment. The article highlights the influence of technological modes of its application on the porosity of thermal sprayed coating and the quality of substrate surface preparation. The main methods of sealing the porosity of thermal sprayed coatings by impregnation are described. The mechanism of impregnation (infiltration) of porous coatings, used methods of application and their classification are described, the determining role of wetting the coating with an impregnating material is emphasized. The effect of the rough surface of a thermal sprayed coating is shown, which consists in enhancing the wetting properties of the impregnating composition, the influence of roughness on the formation of adhesive bonds between the coating and the impregnating composition.The review presents traditional impregnating materials used in industry and their application modes.The application of metal and non-polymer inorganic impregnating compounds, represented mainly by salts of inorganic acids (nitrates, phosphates, silicates), is described. Specific test results are presented, including for the corrosion and abrasive resistance of thermal sprayed coatings after the application of impregnating compounds.

Orifice section velocity fitting method and its application in flash spray research

Although spray technology is widely used, research on spray flow is limited by the complexity of its flow field. To simplify the spray simulation, this work proposed an orifice section velocity fitting method, which can simplify the calculation of the flow field inside the nozzle by using a set of special velocity fitting equations as boundary conditions. For the application and verification of the method, the characteristics of methyl nonafluorobutyl ether (HFE7100) flash spray under temperature influence were experimentally studied in this paper using phase Doppler particle analyzer equipment and compared the results of simulation and experiment. The comparison results show that the simulation and experimental results of the spray axial velocity distribution have good consistency at different temperatures. The simulation results show that the swirling flow in the orifice is stronger when the temperature is lower than the boiling point and the spray velocity isosurface is conical. The swirling flow in the nozzle is attenuated by flash evaporation when the temperature increases above the boiling point, while the spray velocity isosurface changes to a bell shape. The experimental results show that the spray velocity increases with increasing evaporation caused by increasing temperature and that the spray axial velocity distribution also changes from a saddle shape to a single peak shape. The spray droplet size increased significantly under the influence of flash evaporation, but the spatial distribution maintained a saddle shape. This study can provide a reference for spray simulation analysis and the study of flash spray characteristics.

Application of cold spray technology in design and manufacturing of complex geometries

Application of cold spray technology in design and manufacturing of complex geometries

Research on Thermocouple Integration Method of Hollow Thin-Walled Turbine Rotor Blade Surface

The hollow thin-walled structure is increasingly used in advanced aero-engine turbine rotor blades, and the traditional surface temperature measurement method based on groove buried couple is no longer applicable. In this paper, a new thermocouple integration method is proposed. The laser additive manufacturing process is used to generate thermocouple embedding channels on the surface of turbine blades. After the thermocouple is embedded, it is pre-fixed, and the thermocouple protection is realized by supersonic flame spraying technology. The strength of the thermocouple integrated structure of the turbine blade is verified by finite element analysis. Based on CFD analysis, the influence of thermocouple integration on the efficiency, pressure ratio and temperature distribution of the turbine blade is studied. The high-speed rotation test shows that the thermocouple integrated structure has high strength and reliability and meets the measurement requirements. This method can provide technical support for the surface temperature measurement of hollow thin-walled turbine rotor blades.

Study on the Corrosion Resistance Of Thermal Sprayed Aerospace Coatings Under The Action Of High Current Pulsed Electron Beam

Aluminum-based amorphous alloys have excellent mechanical properties and corrosion resistance and are currently used in the form of coating materials for the protection of aircraft surfaces. In this study, AlCoCe alloy and powder are prepared, and then AlCoCe alloy coating is prepared on Q235 substrate by supersonic flame thermal spraying technology, and finally, the surface remelting modification treatment is carried out on the coating by current pulsed electron beam, and the transformation behavior of microstructure of the coating and the change of the corrosion resistance in this process are analyzed by structural characterization and corrosion experiment, to make clear the relationship between the structure of the coating and its corrosion resistance performance. After 15 current pulsed electron beam pulses, the coating surface formed a layer of dense and homogeneous composition of the amorphous structure of the treatment layer, when the number of pulses is higher, due to the heat of the substrate leads to a decrease in the cooling rate, which in turn will lead to the emergence of a crystalline structure of the surface treatment layer.

A novel plasma-sprayed Cr/FeCrAl dual-layer coating on Zr alloy for potential high‐temperature applications

To better meet the requirements in loss-of-coolant accidents (LOCA) and conventional operating conditions in nuclear applications, this work prepared Cr, FeCrAl, and Cr/FeCrAl composite coatings on Zr alloys using plasma spraying technology. The microstructures, hardness, and high-temperature oxidation resistance of coatings are examined. The high-temperature oxidation of coatings was conducted at 1200 °C in air for 20, 40, and 60 min. All coatings exhibited characteristic lamellar microstructures accompanied by small pores. The inner layers of the coatings, benefiting from the “compacting effect” of subsequently deposited particles, displayed lower porosity and higher hardness. The order of high-temperature oxidation resistance among the coatings was determined as follows: Cr/FeCrAl coating > Cr coating > FeCrAl coating. Notably, the Cr/FeCrAl composite coating demonstrated exceptional durability even after a 60-min exposure, with no ZrO2 formation and negligible Fe and Cr diffusion. However, oxygen could still reach the Zr substrate due to inherent pores and the lamellar structure in the as-sprayed coatings. Therefore, post-treatments are suggested to mitigate or eliminate these pores, thereby improving high-temperature oxidation resistance.

Bioinspired melt-blown fiber felt with flame retardancy for efficient oil spill remediation by solar-driven oil evaporation and adsorption

Confronted with rapid-spread river oil leaks and marine oil spills containing toxic and light fractions, conventional emergency response measures often fall short. This study proposes a solar-driven oil evaporation and adsorption (SOEA) strategy that efficiently addresses the challenges posed by toxic and light oils in rivers and oceans. Inspired by the self-protection and anti-fouling effects of fish scales, a photothermal oil-adsorbing felt with a biomimetic scale structure for efficient SEOA is constructed by decorating functional components onto the melt-blown fiber felt using scalable spraying technology. The rational integration of a dual-layer scale structure and functional constituents imparts stable superhydrophobicity, self-cleaning, flame retardancy, enhanced mechanical strength, and a higher oil adsorption capacity. Benefiting from the superior photothermal conversion, the solar-vapor conversion efficiency of the resulting P-EG/MXene@PP reaches 85.6 % under 1 sunlight, with an evaporation rate for light oil of 13.17 kg/m2/h, 8 times higher than natural volatilization. For crude oil floating on water, it achieves a 98 % oil removal efficiency in 6 h, with 41 wt% of the light fraction evaporated. This research provides distinctive insights into solar-driven oil spill remediation behavior and pioneers the SOEA strategy, offering rapid, efficient, and safe solutions for intricate oil spill scenarios.

Insight into the Hot Corrosion Behavior of FeMnCrSi/TiC Coatings at 900 °C

This study explores the deposition of an Fe-MnCrSi/TiC coating on 45 steel surfaces using high-velocity arc spraying technology, examining the microstructure and hot corrosion behavior of the resultant layer. The microstructure of the FeMnCrSi/TiC coating primarily consists of an α-Fe (BCC) solid solution, composed of Fe, Mn, Cr, Si, C, and other elements, with a minor presence of β-Fe (FCC) solid-solution phase and unmelted TiC particles. Following 100 h of cyclic 900 °C hot corrosion, Mn on the coating surface preferentially oxidizes, forming a manganese-rich oxide layer. This process reduces the oxygen partial pressure (O2) within the coating, prompting the formation of a dense Cr2O3 layer on the inner side of the oxide layer. Concurrently, the rapid diffusion of Mn and Cr elements triggers the generation of Mn- and Cr-deficient regions at the metal/oxide layer interface, inducing the transformation of the coated metal primary matrix from an FCC + BCC dual phase to an α-Fe (BCC) single phase. After the reaction, the hot corrosion weight gain of the coating reached 12.43 mg/cm2, approximately one-fourteenth of the weight gain of the 45 steel substrates. This weight gain adheres to the parabolic law, suggesting that the FeMnCrSi/TiC coating exhibits excellent corrosion resistance under the given conditions.

Hybrid decision-making in atmospheric plasma spraying enables human–machine teaming

With the development of human-cyber-physical-production systems in intelligent manufacturing, cyber-supported production based on artificial intelligence is becoming an increasingly powerful means of controlling machines and collaborating with human users. Semi-autonomous systems with a medium degree of automation enable human-centered, flexible, and sustainable production, for instance, in hybrid decision-making. Especially in applications that do not meet the requirements for full automation and when humans are to be involved in their role as qualified decision-makers, teaming-capable systems are desirable and offer considerable advantages. This paper outlines the transdisciplinary concept of human–machine teaming and the role of human cognition in engineering tasks with multi-criteria decision-making. An illustrative real-life example from thermal spray technology is used to show how explainable artificial intelligence models offer targeted, hybrid cyber decision support. This new approach based on fuzzy pattern classifiers combines expert knowledge- and data-based modeling and enables a transparent interpretation of the results by the human user, as shown here using the example of test data from atmospheric plasma spraying. The method outlined can potentially be used to provide hybrid decision support for a variety of manufacturing processes and form the basis for advanced automation or teaming of humans and cyber-physical-production systems.

Effect of La2O3 on hardness, wear resistance and corrosion resistance of WC/Fe90 iron-based composite coatings

In this paper, WC/Fe90 iron-based composite coatings were prepared using plasma spraying technology. The influence of rare earth oxide La2O3 on the microstructure and properties of the composite coatings was studied through microstructural characterization, phase identification, microhardness, wear resistance, and corrosion resistance. The results showed that the composite coatings were mainly composed of α-Fe, M7C3, Fe-Cr, FexCy, and other reinforcing phases. The addition of La2O3 promoted the decomposition of WC particles and improved the uniformity of the coatings. When the La2O3 content reached 1.0 wt%, the hardness was the highest, reaching 885.481 HV, which was 10% higher than that of the untreated coatings. The addition of La2O3 increased the friction coefficient but still improved the wear resistance. Compared to the coatings without La2O3, the mass loss due to wear was reduced by approximately 40%. Moreover, the addition of La2O3 formed a passive film on the surface of the coatings, effectively preventing the penetration of Cl- ions and refining the grain structure of the coatings, significantly enhancing the corrosion resistance. When the La2O3 content was 1.0 wt%, the corrosion resistance of the coatings was the best.

The effect of AlCrN, TiN and Ni-Cr-Nb coatings on the wear and corrosion performance of 45 # steel in 3.5 % sodium chloride solution

The press bar of the oil press is prone to corrosion and abrasion in the high-temperature and high-pressure environment, which reduces the quality of oil and the efficiency of agricultural production. In this paper, Ni-Cr-Nb, TiN and AlCrN coatings were prepared on the surface of press bar substrate by thermal spraying and multi-arc ion plating technology. The tests were analyzed by modern analytical methods such as HV-1000Z micro Vickers hardness tester, SEM, XRD and electrochemical corrosion. The results show that: Vickers hardness tester analysis shows that the surface hardness of AlCrN coating is 3.6 times higher than that of the base material, which is higher than that of several other coatings; SEM shows that the surfaces of the Ni-Cr-Nb, TiN and AlCrN coatings are smooth and even, the film structure is compact and uniform, and the thickness of the coating film is 5.67μm, 6.31 μm and 6.55 μm, respectively; XRD shows the elemental content of each coating, and the Al atoms in the AlCrN coating have good corrosion resistance; Electrochemical corrosion experiment shows that AlCrN coating has the biggest and most important advantages. It shows that AlCrN coating has the maximum potential and minimum corrosion current density, which indicates that its corrosion resistance is the best, followed by TiN coating, Ni-Cr-Nb layer of the corrosion resistance of the first two coatings, but better than the press bar substrate.

Tribological behaviour of Fe-based amorphous coating at elevated temperatures

Fe-based amorphous coatings (AMCs) were deposited using detonation spraying technology to investigate its performance in high-temperature wear conditions. The results indicate that the detonation-sprayed Fe-based AMC possesses a dense structure, low porosity, high amorphous phase content. At 300 °C, the coating has a maximum wear rate of 6.53 × 10−6 mm3 N−1 m−1, which is almost three times that at room temperature. The main wear mechanisms are oxidative wear, accompanied by fatigue stripping wear and adhesive wear. At 500 °C, the wear scar surface demonstrates increased toughness, resisting plastic deformation due to high-temperature softening. Additionally, partial crystallisation occurs, leading to an overall increase in the hardness of coating. Combined, these factors reduce the wear rate of the coating.