The present disclosure relates generally to nanoparticles and, more specifically, the formation of nanoparticles.
Nanoparticles exist in a variety of forms, including nanoparticles assembled on the surface of microparticles and nanoshells formed by coating nanoparticles on hollow microspheres. Additionally, nanoparticles are useful in a variety of applications, such as in coatings for combustion engines and exhaust systems or to activate sintering of bulk metallic parts. Nanoparticles are also useful in a variety of biological and medical applications.
Nanoparticles may be produced in a variety of methods, such as wire explosion, dry powder separation, and laser ablation. Wire explosion is a related art method that includes an instant capacitive discharge of a current through an electrically conductive wire, which explodes the wire to form the nanoparticles. However, in related art wire explosion methods, the wire is exploded in a nonflammable solvent, such as water, which reacts substantially with the nanoparticles upon their formation. This contamination from the reaction with the solvent reduces the quality and usefulness of the nanoparticles formed by this method. Similarly, related art femtosecond laser ablation methods are performed in a solvent, which results in contamination of the nanoparticles. Additionally, related art filtration methods, such as using air separators to filter particles by size, require the handling of dry powders, which presents a safety risk and a risk of contamination.
Many related art wire explosion methods also result in substantial downtime between wire explosion operations (i.e., a large off fraction of the duty cycle). For instance, some related art wire explosion methods include a limited number of discrete wire segments that are exploded successively in a stepwise manner. Furthermore, some related art wire explosion methods leave one end of the wire unconstrained during the explosion operation. Leaving one end of the wire unconstrained during explosion of the wire may cause reliability issues. For instance, nanoparticle size may vary between different wire explosion operations due to, for instance, variances in the length of the wire segment and/or variances in the tension applied to the wire segment during the wire explosion operation.
The present disclosure is directed to various embodiments of a wire explosion assembly configured to form nanoparticles by exploding at least a segment of an electrically conductive wire. In one embodiment, the wire explosion assembly includes a spool supporting the electrically conductive wire, a vessel defining a wire explosion chamber, means in the wire explosion chamber for pulling the electrically conductive wire off of the spool and applying tension on the segment of the electrically conductive wire, and a power source for delivering an electrical current to the segment of the electrically conductive wire. The electrical current is configured to explode the segment of the electrically conductive wire into the nanoparticles. The means for pulling and applying tension on the segment of the electrically conductive wire may include a wire clamping assembly rotatably housed in the wire explosion chamber. The wire clamping assembly may include a winding and tensioning member, at least first and second clamp assemblies coupled to the winding and tensioning member, and a wire guide coupled to the winding and tensioning member between the at least first and second clamp assemblies. The at least first and second clamp assemblies are each configured to move between a clamped position and a disengaged position. Rotation of the wire clamping assembly is configured to pull the segment of the electrically conductive wire into the wire explosion chamber and wind the segment of the electrically conductive wire around at least a portion of winding and tensioning member to apply the tension to the segment of the electrically conductive wire. When the at least first and second clamp assemblies are in the clamped position, the segment of the electrically conductive wire extends between the wire guide and one of the at least first and second clamp assemblies. The wire explosion assembly may also include a first electrical wire coupled to the first clamp assembly, a second electrical wire coupled to the second clamp assembly, and a third electrical wire coupled to the wire guide. The power source is coupled to the first and second electrical wires and the power source is configured to alternately deliver the current through the first and second clamp assemblies to the segment of the electrically conductive wire to explode the segment of the electrically conductive wire into the nanoparticles. The first and second electrical wires may each have a first polarity and the third electrical wire may have a second polarity opposite the first polarity. The wire explosion assembly may also include a motor coupled to the wire clamping assembly that is configured to rotate the wire clamping assembly in the wire explosion chamber. The vessel may include an inwardly-facing cam surface having at least one lobe and the first and second clamp assemblies may each include a roller engaging the cam surface. The engagement between the rollers and the at least one lobe on the cam surface of the vessel is configured to alternately move the first and second clamp assemblies into the disengaged position. The wire explosion assembly may include an inlet opening defined in the vessel and a wire feed guide housed in the wire explosion chamber. The inlet opening is configured to receive the electrically conductive wire extending into the wire explosion chamber. The wire feed guide is configured to align the electrically conductive wire with the wire clamping assembly. The at least one lobe on the inwardly-facing cam surface may be positioned proximate to the inlet opening and the wire feed guide. During the rotation of the wire clamping assembly, the first and second clamping assemblies may engage the at least one lobe before reaching the inlet opening. Each of the first and second clamp assemblies may also include a resilient member configured to bias the first and second clamp assemblies into the clamped position. The wire explosion assembly may include first and second wire guides coupled to the winding and tensioning member and located between the first and second clamp assemblies. The winding and tensioning member may include an electrically non-conductive material.
The present disclosure is also directed to various embodiments of a system configured to form a nanoparticle suspension. In one embodiment, the system includes a wire explosion assembly configured to form nanoparticles by exploding at least a segment of an electrically conductive wire and a gas flow system configured to introduce a first processing gas into a wire explosion chamber. The wire explosion assembly may include a spool supporting the electrically conductive wire, a vessel defining the wire explosion chamber, means in the wire explosion chamber for pulling the electrically conductive wire off of the spool and applying tension on the segment of the electrically conductive wire, and a power source for delivering an electrical current to the segment of the electrically conductive wire. The electrical current is configured to explode the segment of the electrically conductive wire into the nanoparticles. The first processing gas may be any suitable gas or combination or gases, such as oxygen, nitrogen, and/or argon. The system may include a liquid in the wire explosion chamber, and the means for pulling and applying tension on the segment of the electrically conductive wire may be submerged in the liquid such that the nanoparticles are formed in the liquid. The system may also include a bubbler system coupled to the wire explosion assembly that is configured to introduce a solvent to the nanoparticles to form the nanoparticle suspension. The system may also include a post-processing apparatus positioned between the wire explosion assembly and the bubbler system. The post-processing apparatus may be configured to introduce a second processing gas different than the first processing gas. The post-processing apparatus may be configured heat the nanoparticles, cool the nanoparticles, expose the nanoparticles to an electromagnetic field, expose the nanoparticles to radiation, increase a pressure on the nanoparticles, and/or decrease a pressure on the nanoparticles.
The present disclosure is also directed to various methods of forming nanoparticles. In one embodiment, the method includes pulling a segment of an electrically conductive wire into a wire explosion chamber, applying a substantially constant tension to the segment of the electrically conductive wire, and delivering an electrical current to the segment of the electrically conductive wire while applying the substantially constant tension to the segment of the electrically conductive wire to form the nanoparticles.
This summary is provided to introduce a selection of features and concepts of embodiments of the present disclosure that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter. One or more of the described features may be combined with one or more other described features to provide a workable device.
Embodiments of apparatuses for making nanoparticles and/or nanoparticle suspensions according to the present disclosure are described with reference to the following figures. The same reference numerals are used throughout the figures to reference like features and components. The figures are not necessarily drawn to scale.
The present disclosure is directed to various embodiments of an apparatus for forming nanoparticles and/or nanoparticle suspensions by a wire explosion technique. In one or more embodiments, the apparatus is configured to form uniform or substantially uniform nanoparticles. Additionally, in one or more embodiments, the apparatus is configured to form the nanoparticles and then directly introduce the nanoparticles into a desired solvent to produce a nanoparticle suspension. The direct introduction of the nanoparticles into the solvent is configured to form nanoparticle suspensions having a high degree of purity with minimal or no surface contamination. Furthermore, in one or more embodiments, the apparatus is configured to form nanoparticles in a continuous or substantially continuous manner with repeatability in the size and quality of the nanoparticles. Moreover, in one or more embodiments, the apparatus is configured to maintain the wire in constant or substantially constant tension throughout the wire explosion technique, which is configured to aid in the formation uniform or substantially uniform nanoparticles.
The gas flow system 102 and the at least one flow line 103a are configured to deliver the one or more process gases to the wire explosion assembly 101 with a flowrate suitable to maintain the proper stoichiometry of the nanoparticles. The process gas may be any suitable gas depending on the desired effect on the nanoparticles, such as, for instance, oxygen to form an oxide or nitrogen to form a nitride. Additionally, in one or more embodiments, the gas flow system 102 may be configured to deliver two or more gasses to the wire explosion assembly 101. In one or more embodiments, the gas flow system 102 may be configured to deliver one or more inert gases, such as argon, to assist in moving the nanoparticles through the system 100.
With continued reference to the embodiment illustrated in
Still referring to the embodiment illustrated in
Additionally, in one or more embodiments, the post-processing apparatus 105 may be configured to heat the nanoparticles to an elevated temperature, cool the nanoparticles to a reduced temperature, expose the nanoparticles to an electromagnetic field and/or radiation, and/or to increase or decrease the pressure of the nanoparticles. The post-processing apparatus 105 may include a single post-processing chamber or multiple post-processing chambers. Accordingly, the tasks described above may be performed sequentially in a single post-processing chamber or sequentially in multiple post-processing chambers. Additionally, in one or more embodiments, the post-processing apparatus 105 may be configured to process the nanoparticles in a closed-loop manner prior to introducing the nanoparticles into the bubbler 104. Furthermore, in one or more embodiments, the post-processing apparatus 105 may be under a vacuum (e.g., one or more of the post-processing chambers of the post-processing apparatus 105 may be a vacuum chamber) such that the post-processing apparatus 105 is configured to aid in drawing the nanoparticles from the wire explosion assembly 101. In one or more alternate embodiments, the system 100 may be provided without the post-processing apparatus 105.
Additionally, in one or more embodiments, the system 100 may be configured to form a dry nanoparticle powder rather than a nanoparticle suspension. In one or more embodiments, the system 100 may include one or more mechanisms configured to collect the dry nanoparticle powder, such as, for instance, a settling mechanism, a filtration mechanism, and/or a static attraction mechanism.
With reference now to
With continued reference to the embodiment illustrated in
With reference now to the embodiment illustrated in
In the illustrated embodiment, the wire guides 132, 133, 134, 135 are rollers, although in one or more embodiments the wire guides 132, 133, 134, 135 may have any other suitable configuration. In the illustrated embodiment, the wire guides 132, 133, 134, 135 are coupled to a lower surface 136 of the winding and tensioning member 129, although in one or more alternate embodiments, the wire guides 132, 133, 134, 135 may be coupled to any other portion of the winding and tensioning member 129, such as, for instance, one or more of sidewalls 137 or an upper surface 138 of the winding and tensioning member 129. Furthermore, in the illustrated embodiment, the wire guides 132, 133, 134, 135 are coupled to the winding and tensioning member 129 by fasteners extending down through the winding and tensioning member 129.
Additionally, in the illustrated embodiment, the winding and tensioning member 129 defines a central opening 139. In the illustrated embodiment, the wire clamping assembly 109 also includes a standoff 140 supporting the winding and tensioning member 129. The standoff 140 spaces the winding and tensioning member 129 apart from the base 116 of the wire explosion vessel 107. In the illustrated embodiment, the standoff 140 is a hollow member defining a central opening 141 aligned with the central opening 139 in the winding and tensioning member 129 and a central opening 142 defined in the base (or base plate) 116 of the wire explosion vessel 107. In the illustrated embodiment, the wire clamping assembly 109 also includes a lower cover 143 and a junction plate 144. The standoff 140 is supported on a portion of the lower cover 143 and extends upward from the lower cover 143. A portion of the lower cover 143 is supported on the junction plate 144 such that a portion of the lower cover 143 is between the standoff 140 and the junction plate 144. In the illustrated embodiment, the junction plate 144 is received in a recess 145 defined in the base plate 116 such that the lower cover 143 is flush or substantially flush with an upper surface 146 of the base plate 116. The lower cover 143 extends radially outward from the standoff 140 and the junction plate 144 and covers the recess 145 and the central opening 142 in the base plate 116. Accordingly, the lower cover 143 is configured to prevent nanoparticles formed in the wire explosion chamber 108 from escaping through the central opening 142 in the base plate 116.
With continued reference to the embodiment illustrated in
In the illustrated embodiment, each clamp assembly 130, 131 includes a horizontal pin 157 extending inward from the lever 151, a vertical pin 158 extending upward from the horizontal leg 148, and a resilient member 159 (e.g., a spring) extending between and coupled to the horizontal and vertical pins 157, 158. The lever 151 and the clamp 155 coupled to the lever 151 are configured to move (e.g., pivot or rotate) (arrow 160) between an engaged position and a disengaged position, the significance of which is described below. The resilient member 159 is configured to bias the lever 151 and the clamp 155 into the engaged position.
Still referring to the embodiment illustrated in
With continued reference to the embodiment illustrated in
In the illustrated embodiment, the transmission member 166 extends up into the central opening 142 of the base 116 of the wire explosion vessel 107 and an upper end 174 of the transmission member 166 is coupled to junction plate 144 of the wire clamping assembly 109. In the illustrated embodiment, the transmission member 166 is a hollow member defining a central axial opening 175. The central axial opening 175 extends from a lower end 176 to the upper end 174 of the transmission member 166. When the drive motor 163 is actuated, the drive motor 163 rotates (arrow 177) the drive shaft 164 and the drive gear 167. Additionally, because the drive gear 167 is engaged with the transmission gear 168, the rotation (arrow 177) of the drive gear 167 causes the transmission gear 168 and the transmission member 166 to rotate (arrow 178). The rotation (arrow 178) of the transmission member 166 causes the wire clamping assembly 109 to rotate (arrow 112) inside the wire explosion chamber 108. The relative sizes of the drive gear 167 and the transmission gear 168 may be selected based on the desired gear ratio and the desired rotation rate of the wire clamping assembly 109 in the wire explosion chamber 108.
Additionally, in the illustrated embodiment, the brush and slip ring assembly 111 is coupled to the lower end 176 of the transmission member 166. In the illustrated embodiment, the brush and slip ring assembly 111 includes a slip ring drum 179 having a stack of slip rings 180 and a cap plate 181 on top of the stack of slip rings 180. The brush and slip ring assembly 111 also includes a pair of brushes 182 (e.g., carbon brushes) contacting the slip rings 180. In the illustrated embodiment, the slip ring drum 179 is hollow and defines a central opening 183. Additionally, in the illustrated embodiment, the slip ring 180 that is contacted (e.g., engaged) by the brushes 182 is a split ring including two semi-annular components 180′, 180″, the significance of which is described below.
In the illustrated embodiment, the wire explosion assembly 101 includes a series of electrical wires 184, 185, 186 coupled to the slip rings 180. In the illustrated embodiment, the electrical wire 184 is coupled to the first semi-annular component 180′ of one of the slip rings 180 and the electrical wire 185 is coupled to the second semi-annular component 180″ of the slip ring 180. The electrical wires 184, 185, 186 extend up through the central opening 183 of the slip ring drum 179, through one or more openings 187 defined in the cap plate 181, up through the central axial opening 175 of the transmission member 166, through one or more openings 188 defined in the junction plate 144, and up through the central openings 141, 139 in the standoff 140 and the winding and tensioning member 129, respectively, of the wire clamping assembly 109. Additionally, upper ends of the electrical wires 184, 185, 186 are coupled to the wire clamping assembly 109. For instance, in the illustrated embodiment, the electrical wire 184 is coupled to the first clamp assembly 130, the electrical wire 185 is coupled to the second clamp assembly 131, and the electrical wire 186 is coupled to the wire guides 133, 135 that are located between the clamp assemblies 130, 131 (i.e., the electrical wire 186 is coupled to the wire guides 133, 135 that are not aligned with the clamp assemblies 130, 131). Additionally, in the illustrated embodiment, the electrical wire 186 coupled to the wire guides 133, 135 has the opposite polarity as the electrical wires 185, 186 coupled to the clamp assemblies 130, 131. For instance, in one or more embodiments, the electrical wires 184 and 185 may have a positive polarity (e.g., the electrical wires 184 and 185 may be anodes) and the electrical wire 186 may have a negative polarity (e.g., the electrical wire 186 may be a cathode). In one or more embodiments, the electrical wires 184 and 185 may have a negative polarity and the electrical wire 186 may have a positive polarity. Additionally, in the illustrated embodiment, the power source (supply) 113 (e.g., the capacitive discharge bank) is coupled to the brushes 182 of the brush and slip ring assembly 111. The brush and slip ring assembly 111 is configured to permit current to be transmitted to the electrical wires 184, 185, 186 housed within the transmission member 166 while the transmission member 166 and the electrical wires 184, 185, 186 housed therein are rotating (arrow 178). That is, as the slip ring drum 179, the transmission member 166, and the wire clamping assembly 109 rotate (arrows 178, 112), the brushes 182 maintain contact with an outer surface 189 of the stack of slip rings 180 to transmit current through the slip rings 180 and to the electrical wires 184, 185, 186 coupled to the slip rings 180.
Additionally, in the illustrated embodiment, the rotary drive assembly 110 includes a sealed rotary passthrough 190 coupled to the lower surface 172 of the base 116 of the wire explosion vessel 107. The transmission member 166 and the electrical wires 184, 185, 186 housed in the transmission member 166 extend up through the sealed rotary passthrough 190. The sealed rotary passthrough 190 is configured to create a hermetic seal to prevent or mitigate the risk of nanoparticles formed in the wire explosion chamber 108 from inadvertently escaping from the wire explosion chamber 108 through the central opening 142 in the base 116 of the wire explosion vessel 107. The sealed rotary passthrough 190 may include any suitable type or kind of sealing mechanism, such as, for instance, a magnetic liquid sealing mechanism using a ferrofluid.
As illustrated in
As illustrated in
Additionally, as the wire clamping assembly 109 is rotated (arrow 112) into the angular position illustrated in
When the second clamp assembly 131 is returned to the clamped position, as illustrated in
The explosion of the segment of the electrically conductive wire 115 between the first clamp assembly 130 and the second wire guide 133 forms a plurality of nanoparticles. In one or more embodiments, the nanoparticles formed by exploding the electrically conductive wire 115 may have a diameter from approximately (about) 5 nanometers (“nm”) to approximately (about) 1000 nm depending, for instance, on the processing conditions under which the electrically conductive wire 115 is exploded. Additionally, although in one or more embodiments the nanoparticles may be spherical or substantially spherical, in one or more embodiments, the nanoparticles may deviate from spherical in one or more dimensions by up to approximately (about) 10%. In one or more embodiments, the nanoparticles may have any suitable shape, such as, for instance, rod-like and/or an arbitrary shape. Additionally, in one or more embodiments, the composition of the nanoparticles may be the same or substantially the same as the composition of the electrically conductive wire 115 from which the nanoparticles were formed. In one or more embodiments, vaporization of lighter elements may occur during explosion of the electrically conductive wire 115 and therefore the composition of the nanoparticles may vary from the composition of the electrically conductive wire 115. Additionally, the composition of the nanoparticles may vary depending on the type of processing gas introduced. For instance, the composition of the nanoparticles may vary from the composition of the electrically conductive wire 115 due to the absorption and/or other reaction with one or more elements in the processing gas. For instance, in one or more embodiments, the processing gas may include oxygen to form oxide nanoparticles and/or nitrogen to form nitride nanoparticles.
Additionally, as illustrated in
In the illustrated embodiment, the conductive wire 115 is redundantly clamped between the clamps 155 of the clamp assemblies 130, 131. For instance, in the illustrated embodiment, the portion of the conductive wire 115 extending between one of the clamp assemblies 130 or 131 and one of the wire guide 133 or 135 is exploded during the wire explosion operation and the other portion of the conductive wire 115 extending between the wire guide 133 or 135 and the other clamp assembly 130 or 131 is not exploded during the wire explosion operation (e.g., only a portion of the segment of the conductive wire 115 extending between the two clamp assemblies 130, 131 is exploded during a single wire explosion operation). Accordingly, once a portion of the conductive wire 115 has been exploded into the nanoparticles, another portion of the conductive wire 115 remains clamped by one of the clamp assemblies 130, 131 (e.g., the end portion of the conductive wire 115 following a wire explosion operation remains secured by one of the clamp assemblies 130, 131). In one or more embodiments, the wire clamping assembly 109 may contain any other suitable number of clamp assemblies 130, 131, such as, for instance, three or more clamp assemblies.
While this invention has been described in detail with particular references to embodiments thereof, the embodiments described herein are not intended to be exhaustive or to limit the scope of the invention to the exact forms disclosed. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of assembly and operation can be practiced without meaningfully departing from the principles, spirit, and scope of this invention. Additionally, although relative terms such as “horizontal,” “vertical,” “upper,” “lower,” and similar terms have been used herein to describe a spatial relationship of one element to another, it is understood that these terms are intended to encompass different orientations of the various elements and components of the invention in addition to the orientation depicted in the figures. Additionally, as used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Furthermore, as used herein, when a component is referred to as being “on” or “coupled to” another component, it can be directly on or attached to the other component or intervening components may be present therebetween.
Also, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. Additionally, the system and/or any other relevant devices or components according to embodiments of the present invention described herein may be implemented utilizing any suitable hardware, firmware (e.g. an application-specific integrated circuit), software, or a combination of software, firmware, and hardware.
This application is a divisional of U.S. patent application Ser. No. 15/256,344, filed Sep. 2, 2016, which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/325,405, filed in the United States Patent and Trademark Office on Apr. 20, 2016, the entire contents of each of which are incorporated herein by reference.
Number | Date | Country | |
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62325405 | Apr 2016 | US |
Number | Date | Country | |
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Parent | 15256344 | Sep 2016 | US |
Child | 16203292 | US |