Spray Process Research Articles

Study on the influence of different factors on linear CCD online detection device for drug mixing concentration

In this experiment, the linear CCD mixing concentration online detection device was studied under five concentrations of carmine solution: 0.1 g/L, 0.3 g/L, 0.5 g/L, 0.7 g/L, and 0.9 g/L, for the factors that can affect the detection accuracy in the real spraying process (spray flow rate, spray pressure, liquid temperature, and light intensity). The results show the following results: different spray flow rates have less influence on the concentration detection results; the greater the concentration of the solution, the less the influence of the spray pressure on the detection; the smaller the concentration of the solution, the greater the influence of the spray pressure on the detection; the greater the concentration of the solution, the greater the influence of the liquid temperature on the detection; the smaller the concentration of the solution, the greater the influence of the liquid temperature on the detection; the smaller the concentration of the solution, the greater the influence of the liquid less.

Sensing Method for Wet Spraying Process of Tunnel Wall Based on the Laser LiDAR in Complex Environment.

In tunnel lining construction, the traditional manual wet spraying operation is labor-intensive and can be challenging to ensure consistent quality. To address this, this study proposes a LiDAR-based method for sensing the thickness of tunnel wet spray, which aims to improve efficiency and quality. The proposed method utilizes an adaptive point cloud standardization processing algorithm to address differing point cloud postures and missing data, and the segmented Lamé curve is employed to fit the tunnel design axis using the Gauss-Newton iteration method. This establishes a mathematical model of the tunnel section and enables the analysis and perception of the thickness of the tunnel to be wet sprayed through comparison with the actual inner contour line and the design line of the tunnel. Experimental results show that the proposed method is effective in sensing the thickness of tunnel wet spray, with important implications for promoting intelligent wet spraying operations, improving wet spraying quality, and reducing labor costs in tunnel lining construction.

Effects of the atomisation spray on heating transfer in evaporative condensers: A numerical study

Nowadays, due to the excellent performance of evaporative condenser, it has been widely applied in various industrial fields. Improving the heat transfer performance of evaporative condensers is of great importance to save water and energy. Spray features have a significant impact on the evaporative volume and efficiency of a heat-carrying agent (water) in an evaporative condenser, further dominating the condenser’s heat transfer performance. Therefore, it is important to improve the spray characteristics to enhance the heat transfer capacity of evaporative condensers. In this study, atomisation spray technology was introduced to an evaporative condensation system to optimise the spray process parameters. The objective is to elucidate the heat transfer capacity affected by the atomisation spray parameters, including spray density, spray distance, liquid particle size, air velocity, and air temperature. In addition, it is one of the aims of this paper to investigate the degree to which each parameter affects the heat transfer performance. This paper uses numerical simulations to investigate the relationship between the atomisation spray parameters and the heat transfer performance. A tube bundle model in an evaporative condenser was developed and Lagrangian method was used to treat the discrete phase. The results showed that a decrease in either liquid particle size or air temperature could improve the heat flux. In contrast, the heat flux exhibits a para-curve trend with an increase in any of the other three parameters. When other conditions are certain, the heat flux could reach up to 54.6 kW/m2 at an optimal atomisation spray density of 3.89 × 10−3 kg/(m·s). However, it could decrease by 53.23% with the increase in liquid particle size from 0.05 to 0.26 mm. What’s more, the atomisation spray density and liquid particle size are proven to be the two most critical factors; their grey relational coefficient exceeded 0.85. Moreover, the enhancements in the heat transfer capacity are found to be probably attributed to efficient liquid evaporation (removing substantial heat) and uniform liquid film distribution (avoiding dry zone and high thermal resistance). These findings can provide support information to enhance heat transfer via the atomisation spray technique for further research on evaporative condensers.

Spray‐Deposited, Virus‐Templated SnO2 Mesoporous Electron Transport Layer for High‐Efficiency, Sequential‐Deposited Perovskite Solar Cells

In recent years, researchers have developed spray deposition technology to fabricate tin oxide electron transport layer (ETL) with the aim of manufacturing high‐efficiency, large‐area perovskite solar cell (PSC). However, the power conversion efficiency (PCE) of PSC based on sprayed SnO2 ETL remains inferior to that of the spin‐coated SnO2 ETL. Herein, the combined use of spray deposition and genetically engineered M13 bacteriophages for the deposition of M13‐SnO2 biohybrid ETL over large‐area (62.5 cm2) substrates is demonstrated. The spray‐deposited M13‐SnO2 ETLs exhibit mesoporous morphologies with >85% transmittance in UV–vis region. Through the use of M13‐SnO2 ETL, the sequential‐deposited PSCs achieve a maximum PCE of ≈22.1%. The improved performance of the PSC is attributable to the mesoporous morphology of M13‐SnO2 ETL that facilitates the growth of larger perovskite grains. The PSCs based on M13‐SnO2 ETLs also display highly consistent photovoltaic performance which manifests the excellent scalability of the spraying process. Furthermore, M13‐SnO2‐based PSCs exhibit higher ambient stability compared to the SnO2‐based PSCs, showing that the use of M13 bacteriophage is incredibly beneficial to both the efficiency and stability of PSCs.

Localised surface modification of high-strength aluminium–alumina metal matrix composite coatings using cold spraying and friction stir processing

ABSTRACT This study presents a novel approach for surface repairs of high-strength, cold-worked aluminium (Al) alloys, without negatively affecting the base material strength. Low-pressure cold spraying was used to fabricate Al–Al2O3 metal matrix composite overlays, with varying concentrations of Al2O3 deposited on an Al alloy. Friction stir processing (FSP) was employed to disperse and consolidate the overlay coating on the base material. The FSP was found to improve the Al2O3 particle distribution in the coating and reduce the mean free path between Al2O3 particles. The coating hardness increased after FSP. The post-FSPed overlays also exhibited lower wear rates compared to the as-sprayed condition. Remarkable improvement was observed in the tensile properties of the coatings, which were attributed to the improved dispersion of Al2O3 particles in the matrix, while the enhanced ductility was attributed to the possible grain refinement that occurred due to the recrystallisation of Al during FSP.

Modeling and analysis of droplet deposition behavior: From the micro and macro perspectives

The variation of relevant parameters during the spraying process will affect the droplet deposition behavior (DDB) on the plant leaf surface. Hence, a comprehensive analysis and modeling are the basis for model-based control design and performance optimization of spraying efficiency. This paper adopted the method of computational fluid dynamics (CFD) to conduct real-time visualization analysis and numerical modeling establishment of the DDB from the micro and macro perspectives, aiming to obtain the quantitative deposition laws of relevant parameters in the deposition process. The micro results showed that the droplet had different degrees of deposition, bouncing, and diffusion at different blade inclination angles (IAs) and contact angles (CAs). The system’s total pressure presented a consistent trend, while there was a sharp increase of about 2–3 times at the moment of impact on the leaf surface. Numerically, the droplet diffusion speed was basically at 5–7 mm/ms. And it presented an exponential function between the diffusion time and the diffusion velocity of the droplets, whose coefficient of determination (R2) equaled 0.73. The DDB of macro analysis clearly explained the change laws of droplet size, residence time, shear stress, and spreading speed. And the mathematical models of the droplet deposition thickness (DDT) on the target surface about time, spraying speed, liquid density, and fluid viscosity were established, which showed a trend of string functions. The growth rate of DDT reached a maximum of 13331% at 40 ms, which could be considered as an economic spraying time. The study achieved a comprehensive dynamic visualization and model-building of relevant spraying parameters and provided an actual reference for the spraying deposition control design and the parameters selection.

Photoactive Ce-doped TiO2 and CeO2-TiO2 composite coatings deposited by suspension/solution plasma spray

In this work, Ce-doped TiO2 coatings were produced using a hybrid suspension (SPS) and solution precursor plasma spraying (SPPS) approach. CeO2-TiO2 composite coatings were also deposited by the SPS process. The photocatalytic activity of the coatings was evaluated by measuring the methylene blue degradation rate under visible light. Cerium doping and CeO2 composite coatings were characterized by X-ray diffractometer measurements and verified by energy dispersive spectroscopy mapping, Raman spectra, and X-ray photoelectron spectroscopy analysis. The hybrid SPS/SPPS technique presented a promising method to deposit doped ceramic coatings among thermal spray processes. According to the results, modifying TiO2 coatings decreased the bandgap of TiO2 from 3.25 to 2.3 eV using cerium dopant. However, a lower photocatalytic efficiency of TiO2 -CeO2 composite and Ce-doped TiO2 coatings compared to TiO2 could be related to the lower active surface area of TiO2 covered by submicron CeO2 particles and non-optimal dosage of cerium dopant, respectively.

Mechanism study on the influence of combustion models and spray gun geometric parameters on high-velocity oxygen-fuel (HVOF) thermal spraying

HVOF thermal spraying technology has unique advantages for spraying WC-12Co ceramic powder. The spraying process is complex, involving the gas-liquid-solid multiphase flow, chemistry, heat transfer and intelligent control. It is vital to quantitatively reveal the reaction mechanism of combustion components, which optimizes the thermal spraying process and improves the coating quality. A numerical model of HVOF thermal spraying was established, including the gas dynamics model, chemical thermodynamics model and discrete phase model for spraying particle. The difference between the eddy dissipation model (EDM) and EDC model in the traditional calculation was compared. The results show that the EDC model reveal the chemical reaction mechanism of the combustion in detail step by step, and quantitatively display the exothermic phenomenon during whole spraying. The exothermic reaction predicted by the EDC model continues into the air domain with the flame flow. The geometric structure of spray gun was analyzed based on the EDM model. The results show that the diameter of the combustion chamber is 30.2 mm, the diameter of the parallel nozzle is 10.5 mm, and the length from the particle inlet to the nozzle starting point is 13.3 mm, the flight temperature and velocity for particles are relatively high.

Effect of NiAl Bond Layer on the Wear Resistance of an Austenitic Stainless Steel Coating Obtained by Arc Spray Process

<div>The present investigation has been conducted to study the tribological and adhesion properties of X10CrNi18-8 austenitic stainless steel (ASTM 301) coatings deposited on aluminum alloys such as AU4G by using the arc-spraying process. These coatings were made with and without a bond-coat layer, which is constituted by NiAl. The structure of the phases that are present in coatings was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The measurements of microhardness and tribological behavior at different loads were also performed on the surface of the coatings. Adherence test was also carried out using four-point bending tests. The SEM showed that the dense microstructures of coatings have a homogeneous lamellar morphology with the presence of porosities and unmelted particles. The main phase of coating corresponds to a solid solution as a face-centered cubic (fcc). The microhardness of coatings is nearly four times that of the two substrates of aluminum alloys. The four-point bending test results showed that the NiAl bond layer increases the critical interfacial fracture energy <i>G</i> <sub>IC</sub>, the force to share the multilayer is more important.</div>

Thermal Spray Coating Technology – A Review

Thermal spray coating involves heating of coating materials (ceramic, carbide, and metal alloys) to a semi-molten or molten state and propels to substrate. The flame temperature is in the range of 3,000 to 16,000OC but the surface temperature of the substrate rarely exceeds 500 OC depending on the thermal spray processes being used. The coating materials are feed into the spray gun in the form of powders, rods or wires. Thermal spray coating is use for the following purposes; (i) increase corrosion and wear resistance, (ii) protection against electromagnetic, or electrostatic, (iii) protection against radio frequency interference, (iv) metal buildup and, (iv) cosmetic. Thermal spray coating can be categorized into five most common processes; (i) Flame arc spraying, (ii) Electric Arc spraying, (iii) Plasma arc spraying, (iv) High-velocity Oxy/Fuel (HVOF) and (v) Detonation Gun. In this paper, thermal spraying processes will be explained, along with the advantages and disadvantages of one another.

91 Isocyanates Aerosols Sampling for Occupational Exposures Assessment

Abstract Isocyanate compounds are potent sensitizers, in particular through the development of skin dermatitis and allergies. They are one of the main causes of occupational asthma. None no-adverse-effect level has been establishes for isocyanates, therefore, it is important to measure isocyanates level at workplaces. Most of the time, isocyanates are present in workplaces atmosphere both in gas and particle phase, which makes their quantitative sampling difficult. Actual sampling methods do not fit with individual sampling over 8 hours. The aim of this work was first to characterize the particles size distribution in workplaces, depending on the isocyanate and the process used. Then, we studied the effectiveness of CIP 10-I as a sampling device for four isocyanates, compared to impinger and impregnated filter. Particles size distribution was determined thank to different cascade impactors such as Andersen, DLPI+ and MiniMOUDI-8. The Mass Median Aerodynamic Diameter (MMAD) of 4,4’-MDI (4,4’-diphenylmethane diisocyanate) particles in polyurethane foam projection process was found to be higher than 4 µm. In paint spray process, HDI (hexamethylene diisocyanate) particles MMAD was between 1 and 2 µm. The aerosol generation system was designed to obtain particles sizes closed to those observed in workplaces. The CIP 10-I collection foam was impregnated with the same derivative agent as filters. HDI, 2,4-TDI and 2,6-TDI (Toluene diisocyanate) aerosols were generating at concentrations between 10 and 250 µg/m3 in dry air. Whatever the concentration, CIP 10-I collection efficiency is higher than that of filters. Further investigation are currently performed to investigate CIP 10-I performance for MDI sampling.

Investigation of sintering mechanism for novel composite structural thermal barrier coating

AbstractA micro‐agglomerated particle embedded–thermal barrier coating (TBC) structure was prepared by an improved plasma spray process to withstand the sintering‐induced degradation of TBCs during service. In this study, the sintering resistance and thermophysical and mechanical properties of conventional and novel‐structured TBCs were systematically characterized. The results suggested that the thermal conductivity and sintering shrinkage of the novel‐structured TBCs were approximately 30% lower than those of conventional air plasma spraying TBCs. The elastic modulus of the novel‐structured coating is only 32% of that of the conventional structure after thermal exposure at 1300°C for 100 h. The distinct structure of the coating is the main factor that influences its performance. The relationship between the structural evolution and residual strain of the coating was analyzed using electron backscatter diffraction and transmission electron microscopy. Significant differences were observed in the sintering behavior of the dense matrix and embedded particle regions in the coating. Some columnar grains near the intersplat pores in the dense matrix have similar lattice orientations, and they tend to connect and consequently heal the intersplat pores. The large pores between the agglomerated particles and non‐oriented submicron‐sized grains that constitute these particles are responsible for the sintering resistance of the coating.

Study of annular coaxial powder feeding effect on the characteristics of laminar plasma jet and atmospheric cluster deposition

In this paper, by means of numerical simulation and experimental analysis, the performance of the engulfment based annular coaxial powder feeding method and the particle behaviors were studied in the laminar plasma spraying process. First, numerical simulation methods are used to analyze the flow state of the laminar plasma jet and its interaction with the powder particles. Then, the laminar plasma spray was applied to deposit coatings based on the annular coaxial powder feeding method, and the performance of this method was evaluated by observing the coatings. The numerical simulation results show that the powder particles can be fed into the laminar plasma jet without affecting the flow state of the plasma jet, and can be sufficiently heated. The experimental results are consistent with the numerical simulation results. The surface morphologies of the coatings indicates that vapor phase deposition and liquid phase deposition occur simultaneously during the spraying process, and the laminar plasma spray - physical vapor deposition process has the potential to be applied in atmospheric environments.

Effect of Cr2O3 on the microstructure and wear resistance of coatings prepared from Cr2O3-SiC-Al composite powders

Introducing the in-situ reaction synthesis into the thermal spraying process, the content of each phase in the raw material will directly affect the phase and microstructure of the coating obtained by spraying. Therefore, composite powders with different Cr2O3–SiC–Al mass ratios were used as coating materials, and composite coatings were prepared using an atmospheric plasma spraying process. By analyzing the coatings' phase composition, microstructure, wear resistance, and other properties, the effect of the variation of Cr2O3 content in the composite powders on the performance of the coating was investigated. The results showed that with the decrease of Cr2O3 content in the composite powder, the coatings’ compactness, microstructure uniformity, and wear resistance decreased. The coating prepared by Cr2O3–SiC–Al composite powder with a mass ratio of 65:12:23 had good compactness and microstructure uniformity, the microhardness and toughness were also the best among the three groups of coatings, and it presented higher wear resistance.

Tensile Properties Enhancement Response of A413 and A356 Aluminum Casting Alloys to Direct Water Spray Processing

Tensile Properties Enhancement Response of A413 and A356 Aluminum Casting Alloys to Direct Water Spray Processing

Spray and Combustion Characteristics of CTL-Diesel Fuel Blends in a Constant-Volume Combustion Chamber.

Coal-to-liquid (CTL) fuel is considered a promising alternative fuel for diesel engine applications in China owing to its excellent fuel properties. However, little research on the spray and combustion processes of CTL fuel has been scarce. Therefore, in this study, the spray and combustion characteristics of diesel fuel blends with different CTL fuel blending ratios were investigated in a constant-volume combustion chamber. The results show that under non-evaporation conditions (300 K), a longer spray tip penetration (STP) and enlarged spray cone angle (SCA) were obtained with a higher injection pressure owing to the enhanced turbulent interaction. The SCA of CTL fuel blending was larger than that of diesel fuel owing to its lower viscosity and slightly shorter STP. Under the evaporation condition (700 K), with an increase in the CTL mixing ratio, both the STP and SCA of the fuel exhibited a decreasing trend owing to the higher volatility. Meanwhile, as the CTL mixing ratio increased, the ignition delay period was shortened, and the flame lift-off length decreased, whereas both the integrated natural flame luminosity and combustion duration increased. The cetane number of CTL fuel plays an important role in the occurrence of these results.

Mechanical properties optimization of Cr3C2-NiCr coatings produced by compact plasma spray process

Chromium carbides are widely used as functional coatings on steel structures in high-end applications, from energy to marine and aerospace sectors thanks to their corrosion and wear resistance at elevated temperatures. In the present work, a low-power compact plasma spray (CPS) equipment was used to deposit Cr3C2-based cermet coatings on carbon steel substrate. Design of experiment was applied to select and optimize the spraying parameters, namely current, stand-off distance, scanning speed, plasma gas rate and powder feeding rate. ANOVA analysis was conducted to estimate the effect of the spraying variables on morphology and mechanical properties of the coatings and evaluate the optimal spraying condition. Dense and compact coatings were fabricated by using the CPS. By optimizing the processing parameters, coating hardness equal to approximately 600 HV and average thickness ranging around 600 μm were obtained, while the adhesion strength was approximately equal to 14 MPa. Intermediate phases of Cr carbides were produced by the dissolution of the primary Cr3C2 induced by melting and re-solidification of the particles. The presence of weaker carbide phase, inter-lamellae different features and porosity also caused the scattered hardness values observed in the coatings.

An Evaluation of Bath Life Effects on Photoresist Removal for Wafer Level Packaging

With the emergence of 3D integration and wafer level packaging, the pillar bumping process has become a critical processing step. As the process has matured, significant efforts have been made for optimization in terms of both production and cost. This is especially true for photoresist stripping, since thick photoresists are needed to pattern high aspect ratios and must be removed in subsequent steps to expose underlying metal films. In this study, the removal of a thick negative tone photoresist with solder pillar plated wafers were investigated using a dimethyl sulfoxide blend with a quaternary ammonium hydroxide. Emphasis was placed on exploring the feasibility of an extended bath life beyond 7 days. Coupon level beaker tests were used to provide insight into the swelling and dissolution mechanisms with fresh and aged chemistry. Additionally, several chemistries were compared to examine the effect of the quaternary ammonium hydroxide. Based on these findings, chemical aging studies were performed on 300 mm wafers using a highly customizable single wafer processing tool that combined soaking and a high-pressure spray processing to potentially prolong the bath age even further. In addition to stripping efficiency at extended bath life, the compatibly with pillar structures and seed layers is investigated. Results from the study highlight potential methods to extend bath life while maintaining photoresist stripping efficiency.

Improving the Performance of PEM Fuel Cells: Form a Patterned Hydrophobic Catalyst Layer

In this study, we report a high-performance patterned hydrophobic catalyst layer suitable for efficient PEM fuel cells, thanks to alternating hydrophobic channels. Using the shadow mask spraying process, we produced a layer of dot-array and linear hydrophobic patterns on the ordinary cathode catalyst layer. The alternating hydrophobic channels enhance the transport of liquid water/air on the catalyst layer surface and improve the performance of the proton exchange membrane fuel cell. The performance of cells with dot-array hydrophobic catalyst layer (DHCL), linear hydrophobic catalyst layer (LHCL), and surface hydrophobic catalyst layer (SHCL) was compared with that of the ordinary catalyst layer (OCL). Their performance was characterized by in situ electrochemical methods such as electrochemical impedance spectroscopy and polarization curve. The results show that the output power of LHCL is 0.14 W higher than that of OCL, which is approximately 49% improvement. A stable water/gas channel is formed on the cathode catalyst layer surface, so that the mass transfer can be continuously and stably carried out. This work provides a new idea for the water management in fuel cells.

A review on preparation process and tribological performance of coatings for internal combustion engine piston ring

Reducing the energy consumption and exhaust emission, and improving the combustion efficiency of internal combustion engine are important for solving the problems of climate change and environmental pollution. The piston ring-liner system is one of the most serious friction pairs in internal combustion engine, accounting for 26% of the total friction loss. Depositing strengthened coatings on the surface of piston rings is an effective method to reduce the friction coefficient and wear rate. This paper reviews the research progress of several representative technologies for preparing coatings, such as electroplating, physical vapor deposition (PVD), thermal spraying and chemical vapor deposition (CVD), and so on. Various coatings, such as Cr-Al2O3 coating prepared by representative electroplating process, CrN and DLC coatings prepared by physical vapor deposition, and Mo-based and C-based coatings prepared by thermal spraying process, are briefly discussed. Furthermore, the positive and negative aspects of commonly used piston ring coatings are compared, and their development trends are summarized.