The Technical Principle And Advantages Of Ultrasonic Spraying

Ultrasonic spraying, also known as ultrasonic spraying, is a spraying process using ultrasonic atomization technology. The material to be sprayed is first in a liquid state, and the liquid can be solution, sol, suspension, etc. The liquid coating is first atomized into fine particles by an ultrasonic atomizing device, and then uniformly coated on the surface of the substrate by a certain amount of carrier gas. , thereby forming a coating or film. The biggest difference between ultrasonic spraying and traditional single-fluid or two-fluid spraying is that the atomizing device or atomizing nozzle adopts an ultrasonic atomizing device, that is, an ultrasonic nozzle.

Ultrasonic nozzle, also known as ultrasonic atomizing nozzle, is an ultrasonic atomizing device based on the principle of horn transducer. It atomizes the liquid through the amplified high-frequency ultrasonic oscillation, and sends the liquid mist to the object to be sprayed or a specific space through a certain amount of carrier gas. In the case of not exceeding the limit, the amount of liquid atomization is only determined by the amount of liquid delivered and the operating frequency of the spray head. A wide variety of coatings, chemicals, lubricants, particle suspensions, etc. can be atomized. However, the viscosity, miscibility, solids content, etc. of the liquid all need to be considered. For the best atomization effect, the liquid viscosity should be below 30cps and the solid content should be below 30%. Because the atomization process is affected by the motion effect produced by the liquid film, the high viscosity will inevitably result in a low atomization amount, which brings difficulties to the application. Due to the high cohesion of polymer molecules, atomization of liquids containing polymer molecules, even in dilute conditions, is problematic. Most of the time, the solid particle mixture can be atomized. Because the solid particles will be dispersed in the atomized particles. Even coarse mud can be atomized at low speed to the sprinkler.

Compared with traditional two-fluid spraying, ultrasonic spraying has the advantages of high coating uniformity, high raw material utilization, high coating thickness control accuracy, thinner coating thickness, less splashing, no nozzle blockage, and low maintenance cost. Compared with coating processes such as vacuum evaporation and CVD, ultrasonic spraying is a more economical film coating process. Especially in the preparation of large-area films, the equipment cost of ultrasonic spraying is significantly lower than that of vacuum coating equipment. Below we briefly describe the main advantages of ultrasonic spraying.

1. High uniformity of coating

The uniformity of the liquid particle distribution after atomization by the ultrasonic nozzle is significantly higher than that of the two-fluid nozzle, which is commonly known as the air spray gun, so the uniformity of the coating after spraying by the ultrasonic nozzle is also significantly improved. Usually, the coating uniformity of ultrasonic spraying can reach more than 95%.

2. High utilization rate of raw materials and less splash

Since ultrasonic spraying is liquid atomization by ultrasonic oscillation, the process of coating is atomized does not require any gas, that is, the atomization process does not require pressure, and only a very low carrier gas pressure is applied after atomization to transport the liquid mist, so The liquid rebound and splash caused by the high-pressure air of the two-fluid spraying are greatly reduced, thereby greatly improving the utilization rate of the paint. The raw material utilization rate of ultrasonic spraying is more than 4 times that of ordinary air spraying, and the utilization rate can reach more than 90%.

3. High precision of coating thickness control

The main factor that affects the accuracy of coating thickness is the spray flow of the coating, that is, the amount of material loaded on the substrate per unit time. The ultrasonic nozzle does not have any pressure effect on the liquid, so the flow rate of the sprayed paint liquid can be completely controlled by the high-precision metering pump, thus realizing the high-precision spraying flow control. For example, a high-precision syringe pump, its flow control accuracy can reach the level of picoliters per second, and the micro-channel design of the ultrasonic nozzle can also achieve the overall control accuracy of nanoliters per second.

4. The thickness of the coating is thin, which can reach tens of nanometers

Since the spray volume of the ultrasonic nozzle can achieve a very low steady flow (0.001ml/min), it can achieve very little load on the substrate, resulting in a very thin dry film. For some nanomaterials, the dry film thickness can be as low as tens of nanometers. It can be used to prepare glass films such as transparent conductive films, antireflection and antireflection films, heat insulation films, hydrophilic and hydrophobic films, etc.

5. The nozzle is not blocked and the maintenance cost is low

Because the ultrasonic nozzle realizes liquid atomization through ultrasonic oscillation, and the atomized particles are determined by the ultrasonic oscillation frequency, so it is different from the two-fluid nozzle. risk of nozzle clogging.