Patent Application
20100285230
Nano technologies are widely recognized as enabling enhanced and new functionality to a wide range of applications and products. There have been many different ways developed to create and apply nanomaterials. One method for making dry nanocoatings is vapor deposition.
There is a continuing need for a non-vacuum deposition machine that can apply dry-deposited nanocoatings to a wide of range of surfaces in a wide range of locations. Embodiments of the present invention comprises such a machine that can apply dry-deposited nanocoatings to a wide range of surfaces in a wide range of locations and can do so using low electrical power.
There are many different vapor deposition processes. Most of these require a very low-pressure environment to function. Some chemical vapor deposition (CVD) techniques can operate at or near atmospheric pressure. One such technique is the combustion chemical vapor deposition (CCVD) process (U.S. Pat. No. 5,652,021). There is a continuing need for such a process that can be used in a wide variety of locations; embodiments of the present invention satisfy this need. In fact, an embodiment of the current invention comprises a machine that can be plugged into a standard electrical outlet, allowing a wide range of people to apply high-quality vapor-deposited nanocoatings on a wide range of surfaces in a wide range of locations, a capability which did not exist prior to the present innovation.
Embodiments of the present invention comprise a non-vacuum deposition machine that can apply dry-deposited nanocoatings to a wide of range of surfaces in a wide range of locations. An embodiment of the current invention comprises a machine that can be plugged into a standard electrical outlet, allowing a wide range of people to apply high-quality vapor-deposited nanocoatings on a wide range of surfaces in a wide range of locations.
One embodiment of the present invention is a low-power-consuming portable dry nanocoating machine that uses the principles of the CCVD process. A precursor in the correct concentration is fed into a flame, where it is burned, and the resulting chemically changed material then condenses onto a surface. It is important that the material is made small enough so that it adheres to the surface. If particles are made, these will not adhere well to the surface and can readily be wiped away. Thus, it is desirable that most of the material be deposited, so an adherent coating is made. This requires that the material in the gas stream be in the form of small clusters of atoms or vapors of the material to be deposited.
One familiar with the art might refer to these gas-borne materials as being “sub-critical sized” clusters (with larger-than-critical size materials being stable particles). A cluster is a grouping of atoms that are composed of elements with a combined bulk vaporization point above the temperature present in its exact location, and thus they can form stable condensates. A cluster remains in a vapor until it reaches the critical nucleus size at which a cluster will no longer combine with another similar composition and sized cluster, and the cluster then becomes a stable solid particle. Such particles also do not form strong bonds to surfaces that vapor clusters can bond to. Critical nucleus size varies with composition, and at 20° C. can be a small as 1 nm for some high melting point materials, such as Pt or refractory oxides, or over 100 nm for salts and low melting point metals or oxides. As the temperature is raised, the critical nucleus size increases continually to a point near the melting point, above which there exists only liquid and cluster bonding and growth is no longer size-limited. One skilled in condensed matter materials processing can determine the critical size relation to composition and temperature.
The current invention uses a series of largely off-the-shelf parts and assembles them into a practical machine that simplifies the production of nanocoatings, so that a wide range of people can make such coatings. Central to the nanocoating machine is a computer device, such as a PLC (programmable logic controller), that controls which components operate and when. Also important is that the machine not be too heavy and can be operated with a practical power input. Thus, all components run on low amounts of electricity and do not use difficult-to-obtain gases. It is also desired to have the parts be reliable and the machine certified for use in most locations; thus, parts having UL or other such listings are preferred.
The feedstock into the machine can be gas or liquid-based chemicals. To make a flame, as is required with CCVD, the mixture needs to be flammable. To be safe, an auto ignition system with a flame sensor is preferred to ensure that the materials are being burned, so that there will not be a build up of flammable material that could result in an uncontrolled fire or explosion. There are many suitable commercially available flame ignition and sensor devices. Also common in a wide range of burner applications for safe use is a pilot flame to ensure that the main flame continues to burn. To maintain sub-critical sized material clusters, it is important not to allow much time between reaction and deposition. Higher velocities help to reduce time. Higher velocity flames are more difficult to maintain in ignition, so a continuous operating pilot flame is preferred. The machine preferably uses air and does not need bottled oxygen or inert gases.
There are a number of small flame burners that can be used as a pilot. Most preferred are those that can operate with air. To reduce heat and the amount of fuel required, the pilot is preferably a small flame. A common type of pilot fuel is propane, from, e.g., cylinders used for camping gear or those used for plumbing and home improvement projects. These cylinders use the same connectors and thus allow connection to the machine. Different countries will have their types of common fuels and connectors, and the machine can be adapted for use in other countries by changing the input connector and pilot flame head to operate with these containers and the fuel. It is desired that the pilot fuel be a gas at STP and the source container is under pressure, so that no pump is required to enable flow to the pilot burner head. A pilot flame is desired over a glow plug to maintain the CCVD flame as the solid surface of a glow plug will be continuously exposed to the deposition material, causing a buildup of the material being deposited onto the glow plug and causing it to become dysfunctional over time.
Because electronics require electricity to run, a practical electrical input is an important part of the nanocoating machine. It is preferred that the machine simply plug into the local electrical service. The voltage, frequency, and current available differ around the world, and thus the machine must have the appropriate plug and electrical distribution to operate in the area in which it is to be used. This may mean that different components of the machine are used and/or an electrical converter be used so that the machine will operate in any area.
In the United States, the most common electrical outlets available provides 60 Hz electricity at about 110-120 V and is rated to either 15 or 20 amps, and thus a preferred embodiment of the invention is a machine able to operate with this electrical supply. Higher-powered machines can be used, but their ease of use will diminish. Higher power receptacles are fairly common, at 110 V and 20 A and more power can be obtained at about 220 V. There are a number of even higher power plugs available with more exotic plugs for multi-phase electricity. Portable power generators can also be a part of the machine or used with the nanocoating machine to supply the electricity needed. Overall, it is preferred that less than 2200 W of electricity is required, and more preferably, less than 1600 W is required. A portable generator or electrical storage and supply device can also be used to run the electronics and power various components, and these are smaller in size if the power level required is smaller.
A wide range of materials can be made with the portable coating machine, depending on the precursors inputted into the machine. It is widely understood in the CVD field how to alter the feed material to yield various coating compositions. Many gas CVD precursors are expensive, dangerous, limited to just a few elements, or sensitive. Many CVD practitioners use liquid or solid precursors with high vapor pressures. While there are more candidates than gas precursors, these are more expensive, sensitive to degradation, dangerous to use, or not available for all desired elements. Also, multiple feeders are needed when multiple elemental compositions are to be deposited, and these require high-precision components to ensure the proper feed amounts of each elemental precursor. Possible precursors with the lowest cost, most stability, most environmental friendliness and widest use in large-scale chemical applications, other than traditional CVD, are soluble chemicals such as nitrates and various metal organics. These can then be mixed in the right amount and dissolved in various liquids to form CCVD precursor solutions, as has been disclosed in a number of patents and articles with Andrew T. Hunt as an inventor or author, all of which are incorporated by reference (see, e.g., U.S. Pat. Nos. 5,652,021, 5,858,465, 5,863,604, 6,013,318, 6,368,665, 6,601,776, 6,793,975, 7,351,449; collectively “Hunt Information”). The liquids must be properly atomized and burned to yield an adherent coating, as provided for in the Hunt Information. Thus, using liquid solutions as feedstock provides a low cost and easy to handle form of precursors as the preferred source for the portable nanocoating machine.
To be portable, the machine should preferably be on wheels, more preferably lockable wheels, for safety. To be most ergonomic, it should have easy-to-handle parts that direct the deposition gases at the targeted surface. Because there are numerous devices that are required to make the system function, the portable coating machine has as many as possible components in a main apparatus and then a flexible connector to the coating device end. A connection to the hoses should be readily detachable if there are different heads for coating different surface types. A larger coating head for large areas or floors might have wheels and be readily moved across the surface. A smaller and lighter one for lifting to coat other surfaces is possible, as are more designs for going into crevasses, tubing, ducts, and on specifically shaped surfaces or equipment.
Various substrates can handle different amounts of heat. Flames can ignite other combustible materials. To coat the widest range of materials, the machine should have a coating head that does not allow the flame to touch the surface to be coated. It should also have a function to limit the temperature of the deposition gases to below that which might negatively affect the material to be coated. An air knife intersecting the flame near its end can be used to cool and direct the deposition gas at the substrate surface. This positions the flame so that it is not facing directly at the surface to be coated, and greatly improves the safety of the portable nanocoating machine. Hunt Information provides background on how to ensure an adherent coating can be made on low temperature surfaces.
The application head should contain safety devices that feed back to the system controller so that operating parameters can be changed to make it safe or to shut down the system. Previously mentioned auto igniters and flame sensors are part of this. There can also be thermocouples and IR sensors that monitor the coating head position so that the surface being coated does not get too hot. There can be initial limits where the system goes to a smaller flame or more air to make the deposition gasses cooler, and high temperature limits where the system shuts down automatically.
To make the system as widely useable to a range of people, it must be simple to operate and yield good results with no previous background knowledge of vapor deposition. The on-board controller takes the various components through a sequence to operate properly. This sequence is for pump priming, warming up of components that need this to function smoothly, such as mass flow controllers or atomizers, and when things are ready to start the pilot, gas flows and liquid flow. There are regular shutdown sequences that last minutes to remove all chemical precursors from the lines and then others for such times as emergency stops that are very fast, but do not leave the system in the best mode for extending on-off cycling and longer term operation. The machine is preferably simple enough for most active adults with at least a high school education to operate with training of less than 8 hours.
The electronic controller, along with the properly designed application heads, makes a functional system that most people can use with just basic equipment training. An operating procedure for the system should be simple, such as that written for the first portable coater built (see in the example section). The coating head is designed to provide the correct distance and temperature for the intended coating composition and substrate. Different application heads and solutions are to be used with different coating compositions and substrates. There will be a list for end users to reference that will provide necessary guidance for choices.
A surface does need to be clean to ensure adhesion and uniformity of the coating. It is widely understood there are many ways to prepare the surface prior to being coated, and any of these can be used if the surface is needs to be cleaned prior to using. The surface should be dry prior to coating, as it is difficult to vapor deposit onto out-gassing surfaces.
The deposition gases should be vented away as is generally recommended for all flame residual gases. To enable this, the machine has an application head with a center zone where such items as the pilot flame, CCVD flame and other items, if used, like an air knife, are all located, and surrounding this is an exhaust shroud with intake near the surface being coated. The shroud has an inner liner that extends to near the end of the coating device so that the deposition gases are not sucked in prior to reaching the surface. The outer shroud layer defines the distance to which the substrate should be located and directs the suction to the edge of the deposition area. The deposition gases strike the surface and flow towards the exhaust edge. The shroud is connected to a standard exhaust blower via a connecting hose. From the blower, the gases are directed away for the operator and other people so that no buildup of flame gases occurs where people are located. A filter is used prior to the gases going through the blower to catch debris sucked up along with any residual deposition materials.
When a NanoSpray of solution is combusted to form nanomaterials from a flame, we use the terminology “NanoSpray combustion processing.” A stable solution containing the elements to be deposited is formed and put into containers compatible with the nanocoating machine. The operator can then readily change out containers as the coating formulation is used. The machine has a warning system as the container level becomes low and the system goes into automatic shutdown if it empties. There is a second container of flushing solution that is used to remove and purge the lines of the deposition liquids prior to the full shutdown of the system. It is preferred that the machine should not turn on if there is not enough of the flushing solution for the warm up and shut down cycles.
Embodiments of the present invention include
An Example Nanocoating Machine
An initial nanocoating machine was built for the deposition of silver-based antimicrobial nanocoatings onto a wide range of materials and surfaces. As part of the design, many different conditions were run in an open flame system and then a functional application head around the end devices was built. The portable 15 A nano-spray combustion (P15ANSC) machine with rollers was operated from a standard 15 A outlet, a standard propane cylinder, flushing solvent, and deposition solution. All items were mounted on the main machine and a hand-held deposition device was connected to this by flexible connections of about 20 feet in length that enabled the coating head to be easily moved. It was operated on Jan. 23, 2009, by Andrew T. Hunt to make a silver-based nanocoating by passing the coating head, by hand, over some example materials, including Petri dishes for antimicrobial testing. The test results showed very strong antimicrobial action, as shown in Table 1.
Salmonella cell count at 2 h on samples coated with a silver-
The machine comprises a liquid delivery system. There are at least three containers for liquids, including the primary deposition liquid, a flushing liquid, and a waste liquid container. A fourth container can be attached for the primary deposition liquid so that the application can be continuous, by switching directly from one primary deposition liquid container as it empties to another full one. The machine has automatic valves that switch between these containers, as is required for proper operation. The lines allow for flow of the liquid to the pump that regulates the flow rate to either the waste container or the deposition head. There are filters before and after the pump to minimize clogging or wear for the wetted parts. There is also an inline pressure meter that indicates the line pressure downstream of the pump. If the pressure is too high then the system will go into shutdown as the right flow rate might not be produced by the pump. Also, if the pressure is too low, the system will go into shutdown as either the pump is not properly primed or there is a leak in a line that needs to be corrected, and either of these will not have enough of the deposition solution going to the flame making the dry nanocoating.
The pilot flame and air system consists of air supply and exhaust components. Compressed air is supplied to aid in the atomization and combustion of the liquid. The amount and pressure of the air can be controlled by a mass flow controller and the compressor settings. Having the minimum amount of air flow for proper operation keeps the flame from touching the atomizer, so that it does not overheat, causing chemicals to decompose and clog lines and coat other system surfaces. The air flow rate for best operation is usually so that the pilot light is required to maintain combustion of the deposition liquid spray. Too high an air flow rate does not allow for a full combustion of the deposition solution, even with the pilot flame operating properly. A second flame sensor or thermocouples can be used to determine whether the primary deposition flame is burning correctly. The compressed air source for the primary deposition flame should preferably be above 10 psi and more preferably above 30 psi. The exhaust system is designed to carry away much of the combustion byproducts. A blower sucks the gas away from the deposition zone to the potable coater and then out a flexible tube that can be attached to a building central exhaust systems or placed out a window or other exterior opening. If coating outdoors, then it is recommended that the outlet preferably be at least 15 feet from the operator or if closer than this, that it be downwind of the operator.
The flame components are the final components prior to forming the deposition gases. While compressed air could be supplied to the pilot, it is preferable to use a pilot light flame assembly that operates by entraining the appropriate amount of air. The use of a compressed fuel gas enables the fuel gas pilot assembly to use the Venturi effect to cause the proper air mixture to form a stable pilot flame. The pilot gas line has an electronic valve, which the electronic control system opens at the same time it turns on the electronic igniter, which operates at any time the pilot gas is open and the flame sensor does not indicate the presence of the pilot flame. The pilot flame is located just after the atomizing device. A number of atomizers can be used, but the preferred type is one supplied by nGimat Co., called the Nanomiser® device. The right control signals needs to be supplied to whatever atomizer is used. Some devices should not be energized when dry, so care needs to be made that liquid is flowing prior to powering the atomizer.
To help cool the deposition gasses and not have the primary flame directed at the surface to be coated, a gas flow is used to redirect the deposition gases to the surfaces to be coated. An air knife is capable of achieving this functionality, and is readily available to be incorporated into the deposition head assembly. The deposition system can have a mechanically or mass flow control capability to deliver the right amount of air. The air knife should be located about 4-10 cm from the initial burn point of the deposition flame, such that the material being deposited is dry and adherent.
The system has the capability to attach various deposition heads. To facilitate this, all the lines that go between the primary portable unit and the deposition head be attached by a simple attachment system and a flexible tubing and hose line joined together. The largest of these is the exhaust hose, which can be connected similarly to flexible exhaust lines used with vacuum cleaning systems, but designed to operate at least 100° C. Attached to this primary hose will be the lines for pilot flame gas, compressed air supplies, and the primary flame liquid, and well as electrical lines for flame starters, sensors, and controls on the deposition head assembly. On the handle of the deposition head assembly there should be an emergency off switch and a lever for idle or full deposition operation. The operator handle should be thermally isolated from the exhaust gas line and have a solid structure, connecting it to the deposition head so that the operator can continuously hold the handle and manipulate the deposition head over the surface to be coated by holding only the handle. There are a number of different quick-connect systems for industrial equipment that are able to make electrical gas and liquid connections, and these should be used for easy exchange of the dry nanocoating deposition head attachments.
The example system of this invention is designed to work indoors or outdoors near an electrical power source, which could be a generator. If operating only outdoors, some of the main power consuming items such as the blower and pump can be directly powered by internal combustion engines.
A list of components used to make the example system is provided in Table 2. These components make a functional system, but others of similar functionality can be used. These can be readily changed to other components that work with the electrical supply of country where the device is used.
indicates data missing or illegible when filed
The system does enable ease of operation as can be seen by the first operating procedure, which is as follows. There are five primary operating buttons, an emergency stop button, and a primary power switch, for a total of seven electronic interaction points. There is a connection for programming the electronic controls with an attached computer. On the system, there is a 16-key board for varying some of the flow rates and cycles, but this is for only advanced users and programmers, and should not be used by the daily operators. A touch screen could be used for operator interface, but the amount of user interface should be limited for people trained only as application operators.
Purpose
Scope
Solution Preparation
Pre-Deposition Setup
The small red LED located directly above the PRIME button will light up and stay lit until the prime sequence is complete. The STATUS screen above the display screen will turn from green to yellow while the prime sequence is running.
After about 60 s, the exhaust vacuum located on top of the control unit will turn on, and flushing solvent will begin to exit the Nanomiser device located inside the shroud. The flushing solvent may cause a small puddle to form; it is only methanol and will quickly evaporate. If air enters liquid lines after prime then perform leak check detailed in step 0 while exhaust vacuum is on DURING prime sequence.
When the prime cycle is complete the small LED light located directly above the PRIME button will turn off. The STATUS screen will also change from yellow to green. (Skip if no air in liquid lines) Perform leak check while exhaust vacuum is on during prime sequence.
While the exhaust vacuum on top of the control unit is on during the prime sequence, check the circled areas in
If the items circled in blue are leaking, the nuts need to be tightened or replaced.
If the in-line filter circled in red is leaking, try finger-tightening the beige plastic ends. If the leak persists, change the in-line filter. The system should be turned off when making any adjustments.
Repeat prime sequence in step 0 until no leaks are detected.
Starting Deposition
During Deposition
Shut Down
Emergency Shut Down
All documents, books, manuals, papers, patents, published patent applications, guides, abstracts, and other references cited herein are incorporated by reference in their entirety. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.
This application claims benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 61/151,358, filed Feb. 10, 2009, which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61151358 | Feb 2009 | US |
