Controllable provision of nanoparticle coatings on conveyed substrates

Abstract

A spray system and method for controllably applying a nanoparticle coating to a substrate is described. Specifically, the present invention describes a spray system device configured to meet the goal of depositing high quality nanoparticles on a substrate and minimizing the waste of expensive nanomaterials. More specifically, described herein is a nanoparticle spray system comprising: a spray nozzle configured to emit a spray stream loaded with nanoparticles; a conveyed substrate configured to be conveyed at a speed; and a controller configured to operate in the feedback loop such that the nanoparticles in the nanoparticle-loaded spray stream are controllably deposited on the surface of the conveyed substrate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a non-provisional application of U.S. Provisional Patent Application No. 63 / 400,485 filed on August 24, 2022, entitled "Controllably Providing a Nanoparticle Coating on a Conveyed Substrate," the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates generally to spraying ultrafine particles onto surfaces and, more particularly, to systems for depositing nanoparticles onto substrates. Background Art

[0004] Depositing ultrafine particles on substrates to form coatings presents a number of technical challenges that stem from the physical properties of such particles and the need to ensure minimal waste - as such particulate materials are very expensive. Ultrafine (nano) particles can be deposited on substrates to form coatings by either wet or dry spraying. In wet spraying, the nanoparticles are carried by a solvent liquid that evaporates before or after the particles reach the substrate. In dry spraying, a gas stream passes through a fluidized bed of nanoparticles, distributing the nanoparticles in space before they reach the substrate.

[0005] In both wet and dry spray setups, the fluid dynamics / physics of the system often work against the goal of achieving high deposition rates. In particular, the small droplets or particles carrying the nanoparticles themselves have low inertia and follow the gas phase flow field very well. Since the substrate at least partially blocks the flow, the streamlines of the gas phase tend to drive the nanoparticles around the surface rather than onto it. Droplets that follow these streamlines will not deposit on the target substrate, reducing the transfer efficiency of the nanomaterial.

[0006] For the purposes of the present invention, the following terminology will be used.

[0007] Substrate: A solid or partially solid surface (e.g., woven material) that is the target of deposition.

[0008] Spray system: A fluid mechanical system in which a fluid is atomized so that the bulk fluid is broken into smaller particles and distributed in space. The atomized fluid can be a liquid, a suspension or mixture of particles in a liquid, or a fluidized bed of particles. The spray process can be driven by the hydrodynamic effects of a single fluid or by the synergistic effects of two or more fluids (fluidized beds, liquids, or gases) to break the bulk fluid into smaller particles.

[0009] Particles: liquid droplets, microscopic solids, nanoparticles (in liquid, free-flying or attached to a substrate), and clusters of nanoparticles.

[0010] Fluid: A liquid, a gas, or a fluidized bed of solid particles maintained in a fluidized state by a liquid or a gas.

[0011] Bulk fluid: the environment into which the spray is introduced.

[0012] Spray flow: Sprays do not usually enter the bulk fluid at zero relative velocity. Therefore, the resistance between the fluids in the spray will tend to interact with the bulk fluid to equalize the velocity. The modified bulk fluid flow is called "induced" flow, and the velocity obtained is called the induced velocity to distinguish it from the bulk fluid in the absence of the spray. The induced bulk flow and the fluid motion from the spray fluid together constitute the spray flow.

[0013] Users of such systems are very concerned with ensuring that a particular nanoparticle spray application provides a particular desired coverage—eg, complete coverage and even distribution of a particular desired volume—with minimal waste (ie, high deposition rate). Summary of the invention

[0014] Embodiments of the present invention provide a spray system device configured to meet the above-mentioned goals of depositing high-quality nanoparticles on a substrate and minimizing the waste of expensive nanomaterials. More specifically, a nanoparticle spray system is described herein, comprising: a spray nozzle configured to emit a spray stream loaded with nanoparticles; a conveyed substrate configured to be conveyed at a certain speed; and a controller configured to operate in a feedback loop so that the nanoparticles in the spray stream loaded with nanoparticles are controllably deposited on the surface of the conveyed substrate.

[0015] In addition, the present invention describes a method for applying a nanoparticle coating to a substrate using a nanoparticle spray system. The method includes: using a spray nozzle to emit a spray stream loaded with nanoparticles; conveying the conveyed substrate at a certain speed; and controlling the nanoparticle spray system to operate in a feedback loop by a controller so that the nanoparticles in the spray stream loaded with nanoparticles are controllably deposited on the surface of the conveyed substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] While the appended claims set forth the features of the present invention with particularity, the present invention and its advantages will be best understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is an exemplary schematic diagram depicting a nanoparticle spray system apparatus according to the present invention, wherein output is emitted from a spray nozzle at an oblique angle relative to a substrate surface;

[0018] Figure 2is an exemplary schematic diagram depicting a nanoparticle spray system according to the present invention, the spray system further configured to effectively match nanoparticle velocity and substrate surface velocity within a deposition region of a moving substrate;

[0019] Figure 3 is another exemplary schematic diagram according to the present invention, wherein an air knife is added to any other examples provided by the present invention;

[0020] Figure 4 yes Figure 3 An exemplary improvement of the illustrative example of wherein the air knife is configured such that the air knife output has a flow velocity component parallel to and along the direction of motion of the substrate;

[0021] Figure 5 yes Figure 3 and / or Figure 5 An exemplary improvement of the illustrative example of wherein the air knife is configured to deliver heat to a spray stream emitted from a spray nozzle prior to deposition onto a substrate;

[0022] Figure 6 is an exemplary improvement of any of the apparatuses according to the present invention, with the addition of a radiant heater for delivering heat to the spray stream emitted from the spray nozzle prior to deposition onto the substrate;

[0023] Figure 7 is another exemplary apparatus according to the present invention, wherein a heated air knife is used in combination with radiant heat to control evaporation of a solvent in a wet spraying operation;

[0024] Figure 8 is another exemplary device according to the present invention, wherein the spray device is supplemented with a vacuum device having an inlet located below the non-continuous substrate to draw the spray stream to the deposition target area of ​​the substrate;

[0025] Fig. 9 is another exemplary apparatus according to the present invention, wherein a spray stream is emitted from a spray nozzle into a vacuum environment, which helps to direct the spray stream loaded with nanoparticles to a substrate surface;

[0026] Fig.10 is another exemplary apparatus according to the present invention, wherein a high pressure environment is created, wherein a high density bulk fluid can reduce the magnitude of the velocity;

[0027] Fig.11 is another exemplary device according to the present invention, wherein an electrostatic spray nozzle is incorporated into any of the devices described herein;

[0028] Fig.12 is another exemplary apparatus according to the present invention for in situ particle formation combined with electrostatic spraying;

[0029] Fig.13 is an exemplary apparatus according to the present invention, wherein an induction / RF field source is added to enhance drying of the particles; and

[0030] Fig.14 is another exemplary apparatus according to the present invention, wherein Fig.13 The device adds a camera to provide thermal (eg, infrared) images to ensure proper heating field coverage. DETAILED DESCRIPTION

[0031] Exemplary embodiments of nanoparticle spray systems are now described that address the need to provide satisfactory precise and accurate coverage of a substrate while minimizing waste of nanoparticle base material.

[0032] refer to Figure 1 , an exemplary schematic diagram of a nanoparticle spray system device is provided, wherein an output spray 120 is emitted from a spray nozzle 100 at an oblique angle relative to a substrate surface 110. In a device (not shown), the nozzle orifice is oriented to emit a spray stream so that the main velocity direction of the emitted nanoparticles is substantially perpendicular to the substrate surface 110, whereby the fluid stream formed creates a stagnation point at the surface. A relatively high pressure volume is established near the substrate surface 110, resulting in the spray stream 120 being redirected to a direction parallel to or even away from the substrate surface 110, rather than toward the substrate surface 110. Therefore, such a device tends to move particles away from the substrate surface 110, thereby possibly reducing the percentage of emitted nanoparticles actually deposited on the substrate surface 110.

[0033] Continue to refer Figure 1 , the spray nozzle 100 is physically configured to emit a nanoparticle spray stream 120 in a direction substantially oblique to a moving substrate surface 110, more specifically, in a direction substantially parallel to the surface, on which the nanoparticle coating is to be deposited. By emitting the spray stream 120 in a direction having a velocity component along the direction of motion of the conveyed substrate surface, viscous dissipation will have an opportunity to attenuate any velocity, thereby causing the particles to settle to the substrate surface 110 without generating a large flow field away from the surface. A controller 130 is provided to adjust the conveyor motor speed to move the conveyed substrate surface under the nanoparticle spray stream 120.

[0034] Go to Figure 2, the spray system is further configured to effectively match the nanoparticle velocity and the substrate surface velocity within the deposition region of the moving substrate surface 110. If there is a relative velocity between the substrate surface 110 and the output spray stream 120 adjacent thereto, a boundary layer will later exist in the fluid at the interface between the two. The eddies in this layer serve to push the particles of the output spray 120 away from the substrate surface 110. For a moving substrate (e.g., a conveying system), this effect can be minimized by matching or nearly matching the velocity of the spray stream 120 with the velocity of the substrate surface 110. By directing the spray stream 120 to the substrate surface 110, the spray system can be further configured to effectively match the velocity of the nanoparticles and the substrate surface velocity within the deposition region of the moving substrate surface 110. Figure 1 Such velocity matching can be achieved in the boundary layer by adding any one or more of the features of the boundary layer stripping device, the shroud and the fan to the device shown.

[0035] Figure 2 The system shown further adds a combination of sensors and real-time feedback loops (under the control of controller 130) to control either or both of the fan 200 speed and the conveyor 220 speed to substantially match the conveyor speed (V 传送带 ) and the gas / particle velocity of the spray 120 at the substrate surface 110. Thus, in an illustrative example, the system may include a controller 130 that processes the velocity measurement and matches the velocity of the controllable conveyor and the spray stream. In a specific example, a Doppler sensor (not shown) is provided to detect the particle velocity near the substrate surface. An acceptable velocity matching range is determined by observing the final coating quality and then by adjusting the conveyor speed (V 传送带 ) or blower air speed (V 空气 )—Ensure proper particle flow / substrate speed matching by modifying the speed of the fan 200. The feedback-based control loop operates based on the determined particle flow / substrate speed relationship to achieve the desired coating quality.

[0036] Go to Figure 3 In another embodiment, the air knife 300 is added to any other embodiment / device of the present invention. In particular, the air knife 300 is disposed downstream of the spray nozzle 100. In the absence of the air knife structure 300, the nanoparticles will tend to be distributed in space, but will not necessarily move toward the substrate at the desired speed. The addition of a downstream flow direction device in the form of an air knife 300 induces a flow velocity of the nanoparticle spray stream having a main velocity component perpendicular to the substrate, generating streamlines that direct the nanoparticle spray stream 120 to the substrate surface 110.

[0037] Go to Figure 4 , Figure 3 The apparatus is specifically configured so that the air knife 300 outputs a flow velocity component that is parallel to and along the direction of motion of the substrate (which is also moving).

[0038] Go to Figure 5 , Figure 3 (or Figure 4 ) is further configured to deliver heat to the spray stream 120 emitted from the spray nozzle 100 via the air knife 300 before being deposited onto the substrate surface 110.

[0039] Go to Figure 6 , any of the apparatuses of the present invention adds a radiant heater 600 for delivering heat to the spray stream 120 emitted from the spray nozzle 100 prior to deposition onto the substrate.

[0040] Go to Figure 7 , a combination of heating by the heated air knife 300 and radiant heat (via the radiant heater 600) can be controllably used to control the evaporation of the solvent in the wet spray operation. The radiant heater 600 helps to drive off the solvent in the spray 120, while the heated air flow from the heated air knife 300 also further drives the nanoparticles into the substrate. The combination of heating by the air knife 300 and the additional heat from the radiant heater 600 will allow for increased deposition rates. In a specific example, Figure 5 and Figure 6 The two heat sources are combined to drive off (via evaporation) the solvent in the spray stream, while the air knife 300 is also used to provide a heated air stream to further direct the remaining nanoparticles of the spray output 120 to the substrate surface 110. The combination of the two heat sources can control / increase the deposition rate. In a controlled / feedback-based device, measurements of temperature, humidity, etc. are used to set the heater operation to ensure the effectiveness of the spray deposition on the substrate.

[0041] Go to Figure 8 , Figure 1 The spray device of the embodiment of the present invention adds a vacuum device 800, whose inlet is located below the non-continuous substrate 810, to draw the spray stream 120 to the deposition target area of ​​the substrate 810, which is drawn above the inlet 820 of the vacuum device 800. If the substrate is not completely continuous (such as a woven fabric), the negative pressure applied by the vacuum device source 800 can draw the gas phase streamlines of the spray stream 120 into (and through) the substrate 810, and the inlet 820 of the vacuum device source 800 is located on the side of the substrate 810 that is opposite to the surface of the substrate 810 toward which the spray stream 120 flows. This flow will pass the particles through the fibers in the woven fabric, (for example) enhancing the deposition of particles on such woven fabrics (or any non-continuous substrate surface).

[0042] Go to Fig. 9, the spray stream 120 is emitted from the spray nozzle 100 into a vacuum environment 900, which helps to guide the spray stream loaded with nanoparticles to the substrate surface 810. The gas phase streamlines of the spray stream 120 may hinder the transfer of particles to the substrate 810. In this case, the solution is to reduce the density of the gas phase through which the nanoparticle spray passes before being deposited on the surface of the substrate 810 by creating a (partial) vacuum environment. This will also affect the distribution of the spray 120 by reducing the evaporation point of the solvent (due to the lower pressure environment), thereby increasing the evaporation rate of the solvent and improving the uniformity of the deposition of nanoparticles on the substrate 810.

[0043] Go to Fig.10 , as opposed to a reduction in ambient pressure, a high pressure environment 1000 is created in which a high density bulk fluid can reduce the magnitude of the velocity. This can be achieved by ejecting the spray 120 into a high density bulk fluid in the high pressure environment 1000. Higher pressures reduce the evaporation rate of the solvent in wet spray applications. Alternatively / additionally, evaporation can be slowed by reducing the bulk fluid temperature in the high pressure environment (through which the emitted spray stream passes before deposition) (e.g., reducing the spray field temperature above the substrate 110).

[0044] Go to Fig.11 , the electrostatic spray nozzle 1100 is incorporated into any of the devices described herein. Electrostatic spraying, wherein a charge is induced on the particles of the output spray 1120 emitted by the nozzle of the electrostatic spray nozzle 1100, enhances the distribution (spacing) of the emitted spray particles. In addition, by applying an opposite charge to the surface of the substrate 1110, the charged spray particles can be attracted to the substrate 1110.

[0045] In addition, by not providing a continuous charge, the distribution of the spray droplets can be carried out by enhancing control. In an exemplary device, during the spraying, the spray and the substrate will have the same charge, while certain parts of the rest of the device will maintain the opposite charge. Then the charged particles in the spray will begin to move toward this oppositely charged part of the system. After the spraying begins, the charge of the system is modulated so that the charge polarity of the substrate is opposite to the spray flow of the loaded nanoparticles. The charged part of the device may also change polarity to repel the particles of the spray flow. After this, the spray 1120 particles diffused in the flow field are attracted to the substrate 1110 with the opposite charge.

[0046] Go to Fig.12, depicts an apparatus for in situ particle formation combined with electrostatic spraying. In such an apparatus, two sprays 1120 of opposite polarity are sprayed so that their flows overlap. The oppositely charged particles will attract each other at the particle level, resulting in the merging of very small oppositely charged droplets. The fluids of each spray are selected so that they will react with solid particles that may be formed in liquid suspension. Since the droplets in which this reaction occurs are small, the particles will be small. This will allow the production of large quantities of small particles without agglomeration, the need for spray drying or grinding, etc.

[0047] Go to Fig.13 , depicts an RF / electromagnetic field enhancement device for heating a spray material, which includes a parallel plate RF heat source 1300.

[0048] Go to Fig.14 , is another exemplary apparatus according to the present invention, wherein Fig.13 The device adds a camera 1400 that is used to provide thermal (e.g., infrared) images to ensure proper heating field (provided by the RF heat source 1300) coverage.

[0049] Further enhancements / features of the device disclosed herein include:

[0050] 1. Detection of layer thickness (after multiple passes) by thermal imaging.

[0051] 2. Apply graphite doping and drying / curing equipment.

[0052] 3. Combined with radio frequency based heating device.

[0053] Additionally, an exemplary testing setup is contemplated where dye particles are used to configure / tune the operation of a system prior to actual operation using more expensive / valuable nanoparticle materials. Such a system would be able to build / prototype a system prior to actual mass production. Testing / configuration / tuning could incorporate an inductive feedback loop (e.g., RF response) and use machine learning and / or artificial intelligence to analyze test results and apply to further testing and / or configuration of an actual operating system.

[0054] It should be understood that the above description relates to examples showing preferred configurations of the system. However, it is conceivable that other embodiments of the present invention may differ in detail from the above examples. As previously stated, all references to the present invention are intended to reference the specific examples of the present invention being discussed at the time and do not imply any limitation on the scope of the present invention. All distinctions and derogatory language regarding certain features are intended to indicate a lack of preference for these features, but unless otherwise stated, they are not completely excluded from the scope of the present invention.

[0055] Unless otherwise specified herein or clearly contradictory to the context, the use of the terms "a", "an" and "The" and similar references in the context of describing the present invention (especially in the context of the following claims) should be interpreted as covering the singular and plural. Unless otherwise specified, the terms "include", "have", "include" and "include" should be interpreted as open terms (i.e., meaning "including but not limited to") unless otherwise specified. Unless otherwise specified herein, the reference to the numerical range herein is intended only as a shorthand method for individually citing each individual value falling within the range, and each individual value is incorporated into the specification as if it is individually quoted herein. Unless otherwise specified herein or clearly contradictory to the context, all methods described herein can be performed in any suitable order. The use of any and all examples or exemplary language (e.g., "for example") provided herein is intended only to better illustrate the present invention and will not limit the scope of the present invention unless otherwise required. Any language in the specification should not be interpreted as indicating that any unclaimed part is essential to the practice of the present invention.

[0056] Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Additionally, any combination of the above-described sections in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or clearly contradicted by context.

Claims

1. A nanoparticle spray system, comprising: a spray nozzle configured to emit a spray stream loaded with nanoparticles; a conveyed substrate configured to be conveyed at a speed; as well as A controller is configured to operate in a feedback loop so that nanoparticles in the nanoparticle-laden spray stream are controllably deposited on the surface of the conveyed substrate. 2 . The nanoparticle spray system of claim 1 , further comprising a fan, wherein the fan provides a controllable airflow to the nanoparticle-laden spray flow under the control of the controller. 3 . The nanoparticle spray system according to claim 1 , further comprising an air knife, which provides a controllable airflow in a downward direction to the nanoparticle-laden spray flow under the control of the controller.

4. The nanoparticle spray system of claim 3, wherein the air knife provides an air flow that includes a component that is at least partially parallel to a flow direction of the conveyed substrate.

5. The nanoparticle spray system of claim 3, wherein the air knife provides a heated air flow. 6 . The nanoparticle spray system of claim 1 , further comprising a radiation heater, wherein the radiation heater provides controllable heating energy to the nanoparticle-laden spray flow under the control of the controller.

7. The nanoparticle spray system of claim 3, further comprising a radiation heater, which cooperates with the controllable airflow provided by the air knife under the control of the controller to provide controllable heating energy to the nanoparticle-laden spray flow.

8. The nanoparticle spray system of claim 1 , further comprising a vacuum device having an inlet located below the surface of the conveyed substrate, wherein the conveyed substrate comprises an opening, an airflow passing through the opening in a path toward the inlet of the vacuum device according to a controlled suction flow provided by the vacuum device under the control of a controller, the airflow containing particles in the nanoparticle-laden spray flow. 9 . The nanoparticle spray system of claim 8 , further comprising a vacuum chamber environment, into which the nanoparticle-laden spray flow is provided through the spray nozzle.

10. The nanoparticle spray system of claim 1, further comprising a pressurized environment into which the nanoparticle-laden spray stream is provided through the spray nozzle.

11. The nanoparticle spray system of claim 1, wherein the spray nozzle is an electrostatic spray nozzle, wherein a net charge is induced on the nanoparticle-laden spray stream under the control of the controller.

12. The nanoparticle spray system of claim 11, wherein the polarity of the electrostatic field generated by the electrodes of the electrostatic spray nozzle remains unchanged during the spraying operation.

13. The nanoparticle spray system of claim 11, wherein the polarity of the electrostatic field generated by the electrodes of the electrostatic spray nozzle changes during the spraying operation.

14. The nanoparticle spray system of claim 11, wherein an electrical charge opposite to that of the nanoparticle-laden spray stream is induced on the conveyed substrate during a spraying operation.

15. The nanoparticle spray system of claim 1, further comprising a radio frequency induction heating element, the radio frequency induction heating element operating under the control of the controller to provide controlled heating to the nanoparticle-laden spray stream.

16. The nanoparticle spray system of claim 15, further comprising a camera configured to capture an image of a heating field generated by the RF induction heating element, wherein the image is used to control operation of the RF induction heating element according to a provided heating field target by the controller.

17. A method of applying a nanoparticle coating to a substrate using a nanoparticle spray system, comprising: Using a spray nozzle to emit a spray stream loaded with nanoparticles; conveying the conveyed substrate at a certain speed; as well as The nanoparticle spray system is controlled by a controller to operate in a feedback loop so that the nanoparticles in the nanoparticle-laden spray stream are controllably deposited on the surface of the transported substrate.

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