Assessment of Lubrication Property and Machining Performance of Nanofluid Composite Electrostatic Spraying(NCES)Using Different Types of Vegetable Oils as Base Fluids of External Fluid

The current study of minimum quantity lubrication(MQL)concentrates on its performance improvement.By contrast with nanofluid MQL and electrostatic atomization(EA),the proposed nanofluid composite electrostatic spraying(NCES)can enhance the performance of MQL more comprehensively.However,it is largely influenced by the base fluid of external fluid.In this paper,the lubrication property and machining performance of NCES with different types of vegetable oils(castor,palm,soybean,rapeseed,and LB2000 oil)as the base fluids of external fluid were compared and evaluated by friction and milling tests under different flow ratios of external and internal fluids.The spraying current and electrowetting angle were tested to analyze the influence of vegetable oil type as the base fluid of external fluid on NCES performances.The friction test results show that relative to NCES with other vegetable oils as the base fluids of external fluid,NCES with LB2000 as the base fluid of external fluid reduced the friction coefficient and wear loss by 9.4%-27.7%and 7.6%-26.5%,respectively.The milling test results display that the milling force and milling temperature for NCES with LB2000 as the base fluid of external fluid were 1.4%-13.2%and 3.6%-11.2%lower than those for NCES with other vegetable oils as the base fluids of external fluid,respectively.When LB2000/multi-walled carbon nanotube(MWCNT)water-based nanofluid was used as the external/internal fluid and the flow ratio of external and internal fluids was 2:1,NCES showed the best milling performance.This study provides theoretical and technical support for the selection of the base fluid of NCES external fluid.

Effect of steam spraying on a sintering bed on sinter quality and the emission of flue gas pollutants

The technology for spraying a sintering bed and thus improving sinter quality indicators while reducing the emission of flue gas pollutants has recently become an important research topic.The impacts on sinter quality and emissions when spraying the sintering surface with different amounts and flow rates of steam were investigated in this study.The sinter quality indicators were most effectively improved by spraying 180 g of steam flow continuously at a rate of 0.02 m^(3)/min for 15 min after ignition for 8 min.The optimal effect on emission reduction was obtained by spraying 90 g of steam flow continuously at a rate of 0.01 m^(3)/min for 15 min after ignition for 8 min.

Development of a PWM Precision Spraying Controller for Unmanned Aerial Vehicles

This paper presents a new Pulse Width Modulation (PWM) controller for Unmanned Aerial Vehicle (UAV) precisionsprayer for agriculture using a TL494 fixed-frequency pulse width modulator together with a data acquisition board and developedsoftware. An UAV can be remotely controlled or flown autonomously by pre-programmed flight plans. The PWMcontroller was implemented through the guidance system on the UAV with control commands sent between the UAV helicopterand the ground control station via a wireless telemetry system. The PWM controller was tested and validated using LabVIEW8.2. Several analyses were performed in a laboratory to test different control signals. The results show that the PWM controllerhas promise as a higher precision technique for spray applications, which will improve efficiency of pesticide application,especially in crop production areas.

Pre-harvest spraying of oxalic acid improves postharvest quality associated with increase in ascorbic acid and regulation of ethanol fermentation in kiwifruit cv. Bruno during storage

The kiwifruit trees(Actinidia deliciosa cv.Bruno)were sprayed with 5 mmol L-1 oxalic acid(OA)or water(as control)at 130,137 or 144 d after full-blossom,and then the fruit were harvested at commercial maturity and stored at room temperature(20±1)℃ for 13 d.The effect of pre-harvest spraying of OA on postharvest quality of kiwifruit was evaluated during storage.The OA spraying slowed the increase in soluble solids content(SSC)and decrease in titratable acid(TA),as well as increased contents of ascorbic acid(AsA)and total-AsA accompanied with higher AsA/DHA ratio in kiwifruit during storage.Moreover,the OA spraying significantly reduced the contents of acetaldehyde and ethanol in kiwifruit,along with significant decrease in activities of enzymes involved in ethanol fermentation metabolism during the later period of storage,which was beneficial to control off-flavor associated with over accumulation of ethanol during postharvest.It was suggested that pre-harvest spraying of OA might maintain the postharvest quality of kiwifruit in relation to delay in fruit ripening,AsA maintenance and regulation of ethanol fermentation.

Microstructure and corrosion resistance of Fe/Mo composite amorphous coatings prepared by air plasma spraying

Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were in- vestigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaC1 solutions, indicating supe- rior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion re- sistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.

Removal of adhesive dusts from flue gas using corona discharges with spraying water

Effective removal of adhesive and fine dusts from flue gas is very difficult. A new method of electrostatic precipitation of the corona discharges with spraying water(CDSW) was introduced. A new electrode configuration and the circulation spraying of water were employed in the method. The efficient electrostatic precipitation for adhesive and fine dusts can be accomplished without any drain water during a long operating period. The fundamental structure, discharge characteristics, mechanism of spraying and precipitation principle of the electrostatic precipitation using CDSW were described and analyzed. The V I characteristics, spraying state, supplying water quantity, influence of temperature and clean of the electrodes were researched in series experiments. The treating effects of circulating spraying using the corona plasma at the same time of electrostatic precipitation were investigated. The fundamental theories and experimental data were proposed, in order to effectively remove the adhesive dusts from flue gas using CDSW in practice.

Effect of Thermal Treatment on the Grain Growth of Nanostructured YSZ Thermal Barrier Coating Prepared by Air Plasma Spraying

A nanostructured thermal barrier coating is prepared by air plasma spraying using the 8wt% Y_2O_3 partially stabilized zirconia nano-powder with an average grain size of 40 nm. The microstructure and phase composition of feedstock nano-powder and coating are investigated using SEM, TEM and XRD. It is found that the as-sprayed zirconia coating has an average grain size of 67 nm and mainly consistes of metastable tetragonal phase, together with some monoclinic phase and tetragonal phase. Thermal treatment results show that the grains of the nanostructured coating grow slightly below 900℃, whereas over 1000℃ the gains grow rapidly and monoclinic phase noticeably appeares.

STUDY OF HOT CORROSION RESISTANCE MECHANISMS OF ARC SPRAYING COATINGS

According to the working condition of boiler tubes of power station, hot corrosion tests were carried out at two temperatures (650℃ and 800℃) to simulate the environment of coal fired boiler. The hot corrosion resistance and mechanism of three arc spraying coatings (SL30, 45CT and FeCrAl) have been studied. The result showed that coating SL30 and 45CT have a better protection ability against hot corrosion. It indicated that a protective Cr 2O 3 scale formed on the surface of coating SL30 and coating 45CT.

Deposition behavior of multi-particle impact in cold spraying process

In the practical cold-spraying process, a number of particles impact onto a substrate and then form a coating. To study the deformation behavior and multi-particle interactions, single-particle, two-particle, and three-particle impacts were simulated using the ANSYS/LS-DYNA version 970. A copper coating was prepared and scanning electron microscopy （SEM） was employed to analyze the microstructures of the powders and the coating. Numerical results reveal that the critical deposition velocity is 600 m/s for a copper particle/copper substrate. The particles deform more fully due to multi-particle interactions, such as tamping, interlocking, and extrusion effects. The compression ratio increases from 40% to 70% as a result of the tamping effect. This is beneficial for achieving the cold-sprayed coating. The multi-particle morphology and compression ratio in the experiment are consistent with those of simulation results. Based on these results, the coating of high performance can be prepared through selecting appropriate parameters and suitable pre-treatment processes.

One-step spraying method to construct superhydrophobic magnesium surface with extraordinary robustness and multi-functions

The robust magnesium surfaces with multi-functions are highly desirable,and the simple and scalable methods to construct such surfaces are urgently indispensable.Herein,we conducted a one-step spraying method to facilely fabricate the robust coating with multi-functions on magnesium alloys.The as-sprayed magnesium alloys surface is superhydrophobic with a static water contact angle(WCA)of 157.0°and a roll-off angle of 6.0°.Such surface has excellent mechanical,chemical and thermal stabilities,even undergoing various physical and chemical damages,including sand impact(10 gmin^(-1),≥20 min),water impact(2 impacts s^(-1),≥180 min),abrasion(1.00 kPa,≥25 cycles),peeling(≥2.15 kPa),high temperature(200°C,≥24 h),strong acidic/salty/basic media(p H=113)and organic-solvent immersion(ethanol and n-hexane,≥24 h),demonstrating brilliant robustness.Notably,the surface displays multi-functions of corrosion protection,anti-fouling and heat insulation,which will undoubtedly promote the much wider applications of magnesium alloys.

Preparation of Ni60-WC Coating by Plasma Spraying, Plasma Re-melting and Plasma Spray Welding on Surface of Hot Forging Die

In order to produce the hear-resistant inner layer of hot-forging die, the plasma spraying and plasma re-melting and plasma spray welding were adopted. Substrate material was W6Mo5Cr4V2, including 10%, 20%, 30% tungsten carbide （WC） ceramic powder used as coating material to obtain different Nickel-based WC alloys coating. Micro-structure and micro-hardness analysis of the coating layer are conducted, as well as thermophysical properties for the coating layer were measured. The experimental results show that the coating prepared with 70%Ni60, 30%WC powder has the best properties with plasma spray welding, in which the micro-hardness can achieve 900HV, meanwhile it can improve the thermal property of hot-forging die dramatically.

Preparation and characterization of nanostructured Al_2O_3-13wt.%TiO_2 ceramic coatings by plasma spraying

Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.

Configuration optimization of high velocity arc spraying gun

In order to improve the in-flight characteristics of the atomizing droplets during high velocity wire arc spraying (HVAS), some changes have been operated on the original design of the HVAS gun configuration. A comparative study was carried out to investigate the microstructure and properties of the coatings produced by the original design spraying gun and the modified one, using 3Cr13 wires of 3 mm in diameter. The characteristics of their jets were examined during spraying. The results indicate that, the included angle between the two wires and the distance from the nozzle to the meeting point of the two vires may have a strong influence on the characteristics of the in-flight droplets and then the coatings. The jet divergence is found to be lower than that of the original one (about 12° against 25°). By modified gun, the adhesion strength, the microhardness and porosity of the coating deposited by modified gun are increased by 39% and 9% respectively. And the porosity of the coatings is decreased by 57%.

High-temperature frictional wear behavior of MCrAlY-based coatings deposited by atmosphere plasma spraying

Al2O3-r2O03/NiCoCrAIYTa coatings were prepared via atmosphere plasma spraying （APS）. The microstructure and phase com- position of the coatings were analyzed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, laser confocal scanning microsco- py （LSCM）, and transmission electron microscopy （TEM）. The dry frictional wear behavior of the coatings at 500℃ in static air was inves- tigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approxi- mately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhe- sive wear.

Influence of TiCl_4 treatment on performance of dye-sensitized solar cell assembled with nano-TiO_2 coating deposited by vacuum cold spraying

Titanium tetrachloride (TiCl4) treatment was employed to TiO2 coating deposited on fluoride-doped tin oxide (FTO) conducting glass and indium oxide doped tin oxide (ITO) conducting glass, respectively. The nano-crystalline TiO2 coating was deposited using a composite powder composed of polyethylene glycol (PEG) and 25 nm TiO2 particles by vacuum cold spraying (VCS) process. A commercial N-719 dye was used to adsorb on the surface of TiO2 coating to prepare TiO2 electrode, which was applied to assemble dye-sensitized solar cell (DSC). The cell performance was measured under simulated solar light at an intensity of 100 mW·cm-2. Results show that with an FTO substrate the DSC composed of a VCS TiO2 electrode untreated by TiCl4 gives a short-circuit current density of 13.1 mA·cm-2 and an open circuit voltage of 0.60 V corresponding to an overall conversion efficiency of 4.4%. It is found that after TiCl4 treatment to the VCS TiO2 electrode with an FTO substrate, the short circuit current density of the cell increases by 31%, the open-circuit voltage increases by 60 mV and a higher conversion yield of 6.5% was obtained. However, when an ITO substrate is used to deposit TiO2 coating by VCS, after TiCl4 treatment, the conversion efficiency of the assembled cell reduces slightly due to corrosion of the conducting layer on the ITO glass by TiCl4.

Optimization of spray conditions in cold spraying based on numerical analysis of particle velocity

The effects of the parameters involved in cold spray on the acceleration of particles are systematically investigated by a CFD code in order to reveal the main factors influencing significantly particle velocity. The parameters involved include nozzle geometry parameters, processing parameters and properties of spray particles. It is found that driving gas type, operating pressure and temperature are main processing parameters which influence particle velocity. As for nozzle geometry, the expansion ratio and divergent section length of spray gun nozzle show significant effects. Moreover, the density, size and morphology of powder also have significant effects on particle velocity. The effects of those main parameters are summarized in a comprehensive equation obtained through nonlinear regression of the simulated results for the estimation of particle velocity. The interactions of the parameters on particle acceleration can be examined through the equation. Moreover, the optimization of the dimensions of spray gun nozzle and spray parameters can be realized based on the obtained results.

Study of Multi-Function Micro-Plasma Spraying Technology

A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT （Insulated Gate Bipolar Transistor） invert technique, micro-computer control technique, convergent-divergent nozzle structure and axial powder feeding techniques have been adopted in the design of the micro-arc plasma spraying system. It is not only characterized by a small volume, a light weight, highly accurate control, high deposition efficiency and high reliability, but also has multi-functions in plasma spraying, welding and quenching. The experimental results showed that the system can produce a supersonic flame at a low power, spray Al2O3 particles at an average speed up to 430 m/s, and make nanostructured AT13 coatings with an average bonding strength of 42.7 MPa. Compared to conventional 9M plasma spraying with a higher power, the coatings with almost the same properties as those by conventional plasma spray can be deposited by multi-functional micro-arc plasma spraying with a lower power plasma arc due to an improved power supply design, spray gun structure and powder feeding method. Moreover, this system is suitable for working with thin parts and undertaking on site repairs, and as a result, the application of plasma spraying will be greatly extended.

APPLICATION OF UNIFORM PRECRIPTION DESIGN IN STUDYING OF WEARREISTANT COATING IN PLASMA SPRAYING

Plasma spraying technics, a method of strengthening surfaces, shows advantages in wear-resistant, reducing friction, bearing corrosion and enduring higher temperature. While for the coating material, it is important to improve the ability of the functional coating. In this paper, a coating material of wear-resistant, bearing corrosion and enduring higher temperature in middle and low speed diesel is studied quantificationally with a uniform prescription design method, which reduced the test period as the test points distribute uniformly. An optimized combination is put forward of each part in the coating and a method to develop a new coating material is supplied.

Ni60-SiC Coating Prepared by Plasma Spraying, Plasma Re-melting and Plasma Spray Welding on Surface of Hot Forging Die

In order to produce the hear-resistant inner layer of hot-forging die, plasma spraying and plasma re-melting and plasma spray welding were adopted. Substrate material was W6Mo5Cr4V2, including 10%, 20%, 30% SiC ceramic powder used as coating material to obtain different Ni-based SiC alloys coating. Micro-structure and micro-hardness analysis of the coating layer were followed, as well as thermophysical properties for the coating layer were measured. The experimental results show that the coating prepared with 70% Ni60, 30% SiC powder has best properties with plasma spray welding, in which the micro-hardness can achieve 1100 HV, meanwhile can improve the thermal property of hot-forging die dramatically.

A new application field of plasma spraying technique to environmental depollution

To expand the application of plasma spraying technique, TiO2 coatings were prepared using agglomerated anatase TiO2 powder to solve the environmental problems. The composition and photocatalytic activity of plasma sprayed TiO2 coatings were investigated systematically. The content of anatase TiO2 in the sprayed coatings was approximate to 7%- 15%, which was influenced by the melting state of TiO2 powder in plasma spraying process. The surface of sprayed coating was very rough and the arithmetical mean deviation of the surface profiles (Ra) was in the range of 5.7 - 8.8 μm. Under lower arc current, the surface of the coating became rougher. The anatase to rutile phase transformation temperature of agglomerated anatase TiO2 powder was approximate to 1 173 K. The TiO2 coating sprayed under the arc current of 400 A had good photocatalytic activity for the relative high content of anatase phase in it. It is concluded that the application of plasma spraying technique to environmental field has been developed.