The present invention relates to nano-multilayered coatings. More specifically, but not exclusively, the present invention relates to fabrication of layers of nanoparticles and amorphous oxides or amorphous nitrides, which superhydrophobic, icephobic properties, as well as resistance to removal environments (e.g., hot acid and abrasion with hard particles) of interest for anti-tamper protection of electronic components.
Effective superhydrophobic and icephobic coatings that also offer superior anti-tamper protection for electronics and electronic materials preventing, for example, reverse engineering are easily manufactured. Therefore, there is a need to address the present deficiencies in these arts.
Therefore, it is a primary object, feature, or advantage of the present invention to improve over the state of the art.
It is a further object, feature, or advantage of the present invention to provide layers of discrete nanoparticles contained between layers of continuous oxide or nitride materials that provide unique properties not-available by either material alone.
It is a still further object, feature, or advantage of the present invention to provide applications for use of these nanolayered materials such as coatings for water-repellent (superhydrophobic) and ice-repellent (icephobic) surfaces on engineering materials.
Another object, feature, or advantage is to provide nano-multilayered coatings for anti-tamper protection of electronic materials to retard or prevent reverse engineering.
Yet another object, feature, or advantage is to provide nano-multilayered coatings that include alternating layers of amorphous oxide and discrete nanoparticles. The amorphous oxide nanolayer can be made continuous, while the nanolayer of nanoparticles can be made discontinuous and the nanoparticles contact the amorphous oxide materials in the nano-multilayer architecture.
In at least one embodiment, a method of fabrication can include use of an atmospheric-plasma (AP) chemical-vapor-deposition (CVD) plasma with a vapor precursor to form a continuous amorphous oxide nanolayer, while nanoparticles are sprayed onto the continuous oxide nanolayer using, for example, an ultrasonically-agitated, air-atomized spray nozzle (UAS) of the nanoparticles in a suitable carrier solvent.
In one aspect, an alternating fabrication method of AP-CVD and UAS can be repeated a large number of times, providing a coating that has x-layers of amorphous oxides by AP-CVD and x−1 layers of ceramic or oxide nanoparticles.
According to another aspect and prior to fabrication of the coating, an AP-CVD plasma, consisting of helium (He) and oxygen (O2) or Argon (Ar) and O2, can be used to functionalize and etch the engineering material substrate surface.
In at least one other embodiment, the AP-CVD amorphous oxide layer can be deposited first onto the engineering material substrate, followed by the UAS deposition of the nanoparticle materials, which constitutes a bilayer, and if repeated a large number of times results in a tailored set of material properties, e.g., a larger number of bilayers produce a larger WCA value.
Illustrated embodiments are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein, and where:
Throughout the disclosure, the terms coating, nanolayer, nanolayered coating, multilayered coating, and nano-multilayered coating(s) are used in reference to the coatings of the present invention. In accordance with an exemplary embodiment of the present invention and prior to fabrication of the a-oxide/hard nanoparticle multilayered coating, an engineering material substrate can be cleaned using, for example, but not limited to the following chemical procedure: 1) ultrasonic agitation in acetone solvent for 5-10 minutes, 2) rinse with methanol solvent, 3) blow-dry in hot air, 4) ultrasonic agitation in hot (≤100° C.) degreaser solution (1 part/7 parts deionized (DI) water) for 5-10 minutes, 5) rinse in DI water, 6) rinse in methanol solvent, 7) blow dry in hot air. Although a method for preparing an engineering material of interest is set forth, the present invention contemplates additional/other steps whether proprietary or conventional for chemically preparing the surface of an engineering material to receive a nanolayered coating of the present invention.
After chemical cleaning, an etch or functionalization of the upper surface of substrate 1 shown in
Although the proceeding and proceeding processes provide for functionalization of the substrate 1 surface, the present invention contemplates other functionalization steps, processes and plasma agents. Process parameters that can be employed, for example, during the AP-CVD functionalization include, but are not limited to, configuring: 1) AP-CVD shower-head to substrate 1 surface separation distance generally between a range of 5-10 mm, 2) radio frequency (RF) power to AP-CVD shower head generally between 60-100 W, 3) He or Ar gas flow rate generally between 15-30 standard liters per minute (SLM), 4) O2 gas flow rate generally between 0.3-0.6 SLM, 5) AP-CVD shower head translation rate generally between 10-20 millimeters (mm)/second (s) using a robot, 6) robot program horizontal translation step change generally between 0.5-1.0 mm, and 2) number of AP-CVD passes generally between 1-2.
The AP-CVD fabrication method can be used to deposit amorphous oxides 2 shown by way of example in
Suitable precursors can have a relatively high (e.g., ≥20 mm Hg (torr)) vapor pressure at room temperature, which enables the easy formation of a vapor which can be carried into the AP shower head plasma by an inert gas (e.g., He or Ar) stream. Of the listed precursors above, precursors 1, 2, 4, 6, and 7 all have by way of example acceptable vapor pressures, suggesting their use to form silicon-dioxide. The elements (e.g., silicon (Si)) of the precursor vapor, can react with the O2 gas in the plasma to form silicon dioxide (or silica; SiO2). The silica coating can be amorphous, not exhibiting a long-range crystalline structure.
Other amorphous material coatings formed by the AP-CVD method can include, for example, silicon nitride (Si3N4) by injection of the HMDSO or HMDS precursor vapors into a He and N2 or Ar and N2 plasma. Similarly, amorphous aluminum oxide (Al2O3) can be formed by the AP-CVD method by injection of an aluminum (Al) containing vapor precursor, (e.g., Alumatrane; C6H12NO4Al) into the He and O2 or Ar and O2 plasma.
The present invention contemplates varying process parameters that can be used to deposit the amorphous oxide material 2 shown in
After the AP-CVD process is used to deposit the first amorphous oxide layer, then a ultrasonically-agitated, atomized spray system UAS system shown in
A bilayer of amorphous oxide and nanoparticles 3 shown in
The present invention is described below by way of examples. However the present invention is not limited thereto the examples described below.
An aluminum alloy (6061 Al) coupon of selected size 50.8 mm (2 in) wide×101.6 mm (4 in) long×6.35 mm (0.25 in) thick was cleaned according to the chemical-cleaning and He & O2 ionized-gas plasma-etch/functionalization procedure described below.
In at least one of the examples of the present invention, a chemical cleaning procedure can consist of, but is not limited to: 1) ultrasonic agitation in acetone solvent for ˜5-minutes, 2) rinse with methanol solvent, 3) blow-dry in hot air, 4) ultrasonic agitation in hot (generally ≤100° C.) degreaser solution (1 part/7 parts deionized (DI) water) for ˜5-minutes, 5) rinse in DI water, 6) rinse in methanol solvent, 7) blow dry in hot air.
After chemical cleaning and before AP-CVD etch/functionalization, SS substrates are mechanically-attached to a hot-plate to heat the substrate material to a temperature of 100° C., to remove or otherwise evaporate water from the surface.
Stainless steel coupons mounted on the hot-plate can be plasma-etched/functionalized by treating the substrate surface with the AP-CVD plasma, consisting of, for example, He (99.5% purity) and O2 (99.995% purity) or Ar (99.5% purity) and O2 ions, in a raster-scanning method to ensure complete processing of the substrate surface. Process parameters that can be employed during the AP-CVD functionalization include, but are to limited to, configuring: 1) AP-CVD shower-head to substrate surface separation distance of 5 mm, 2) radio frequency (RF) power to AP-CVD shower head of 100 W, 3) He gas flow rate of 25 standard liters per minute (SLM), 4) O2 gas flow rate of 0.3 SLM, 5) AP-CVD shower head translation rate of 20 millimeters (mm)/second (s) using robot, 6) robot program horizontal translation step change of 0.5 mm, and 2) number of AP-CVD passes of 2.
In accordance with at least one exemplary aspect of the present invention, the AP-CVD fabrication method was used to deposit amorphous oxides by introduction of a vapor from a hexamethyldisilazane (C6H19NSi2) (or HMDS) liquid precursor heated to 30° C., while contained in a SS container housed in a heated-water bath. The vapor from the HMDS precursor was swept by He gas, maintained at a flow rate of 0.4 SLM, into the AP shower head which emits a He and O2 plasma. The element (e.g., silicon (Si)) of the HMDS precursor vapor reacted with the O2 gas ions in the plasma to form silicon dioxide (or silica; SiO2). The silica coating is amorphous, as confirmed by x-ray diffraction (XRD), and therefore does not exhibit a long-range crystalline structure.
At least some specific process parameters used to deposit the amorphous oxide material by AP-CVD can include, but are not limited to, configuring: 1) AP-CVD shower-head to substrate surface separation distance of 5 mm, 2) radio frequency (RF) power to AP-CVD shower head of 100 W, 3) He or Ar gas flow rate of 25 standard liters per minute (SLM), 4) O2 gas flow rate of 0.3 SLM, 5) HMDS liquid precursor held in a stainless steel (SS) container inside a DI-water bath which can be heated to a temperature of 30° C. by a heating-rod immersed in the DI water bath, 6) He gas sweep-flow to the SS container with the precursor liquid at a rate of 0.4 SLM, 7) AP-CVD shower head translation rate of 20 millimeters (mm)/second (s) using robot, and 8) robot program horizontal translation step change of 0.5 mm.
In accordance with at least one method of the present invention, ultrasonic atomized spray (UAS) is used to spray-deposit a layer of nanoparticles in a solvent carrier. Process parameters used to deposit the nanoparticle layer UAS can include, but are not limited to, configuring: 1) RF power to the ultrasonic transducer in the syringe pump plunger and spray nozzle of 3 W, 2) number of turns on the focus mechanism for the spray nozzle of 4, 3) a weight percent loading of 0.1% of nanoparticles (e.g., 35 nm boron carbide (B4C)) in a suitable solvent (isopropanol (IPA)), 4) a syringe pump flow rate of 0.8 millimeter (ml)/minute (m) to inject the nanoparticle/solvent mixture into the tubing that feeds the ultrasonic spray nozzle, 5) number of opening turns on the air-nozzle in the nozzle to promote atomization of the spray mixture of 6.25, 6) robot translation speed for the spray nozzle translation of 10 mm/s, 7) number of passes for the spray nozzle of 1, 8) spray-nozzle to substrate surface separation distance of 18 mm (0.71 in), 9) robot program horizontal translation step change of 6.25 mm (0.25 in.).
The above two (2) deposition processes were performed sequentially to produce a bilayer of material: 1) AP-CVD of a-silica and 2) UAS of B4C nanoparticles. This sequence was performed a total of six (6) times with a final cap layer of a-silica by AP-CVD, resulting in a total number of 7 individual layers.
Scanning electron microscope (SEM) images of the surface of the fabricated nanolayered material showed the uniform distribution of the B4C nanoparticles, as shown in both images of
Water contact angles were measured using a conventional digital camera and the software program (i.e., Simages).
Another exemplary aspect of the present invention includes fabricating one or more nano-multilayered coatings. For example, a second a-SiO2/B4C nano-multilayered coating, fabricated with a greater number of bilayers (e.g., 11 a-silica and 11 B4C nanoparticles) capped with a final a-silica layer (total of 23 layers) exhibited a larger WCA as shown in
The same nano-multilayered coating as above while on 6061-Al was subjected to an icing exposure using the following test conditions: 1) impact angle of air/water stream: 30°, 2) air flow rate: 151.2 gm/second (20 lbs/min), 3) inlet temperature: 20° C., 4) inlet pressure: 137.9 kPa (20 psia), and 5) water flow rate: 0.166 gm/second (0.022 lbs/min).
It is desirable to protect electronic components from intrusion and tampering which can be used to remove program sensitive information. Contextually speaking, “anti-tamper resistant” generally refers to a surface that either: 1) cannot be easily removed by conventional removal methods (e.g., hot acid etch or hard-particle abrasion that occurs during sanding) or 2) one that if removed would result in the underlying electronic components being damaged beyond use/repair. The nano-multilayered coating described in
The same nano-multilayered coating described above can provide resistance to hot (e.g., 260° C.) sulfuric-acid jet-etch for a 15-minute duration, without coating damage or removal (
The illustrative embodiments are not to be limited to the particular embodiments described herein. In particular, the illustrative embodiments contemplate numerous variations in the type of ways in which embodiments may be applied. The foregoing description has been presented for purposes of illustration and description. It is not intended to be an exhaustive list or limit any of the disclosure to the precise forms disclosed. It is contemplated that other alternatives or exemplary aspects are considered included in the disclosure. The description is merely examples of embodiments, processes or methods of the invention. It is understood that any other modifications, substitutions, and/or additions may be made, which are within the intended spirit and scope of the disclosure. For the foregoing, it can be seen that the disclosure accomplishes at least all of the intended objectives.
The previous detailed description is of a small number of embodiments for implementing the invention and is not intended to be limiting in scope. The following claims set forth a number of the embodiments of the invention disclosed with greater particularity.
This application claims priority to U.S. Provisional Patent Application 62/559,994, filed on Sep. 18, 2017, and entitled Fabrication of Superhydrophobic and Icephobic Coatings by Nanolayered Coating Method, hereby incorporated by reference in its entirety.
This invention was made with government support under Contract W9113M-08-C-0133, awarded by the U.S. Army/ARSTRAT, Huntsville Ala. The government may have certain rights in this invention.
Number | Date | Country | |
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62559994 | Sep 2017 | US |