Diamagnetism is a property of substance where magnetization M opposes an applied magnetic field H, (i.e., M=χH, where the susceptibility χ<0). Diamagnetism occurs as a result of microscopic electric currents of quantum nature and is a universal property of substances. However in many substances, diamagnetism is partially or completely masked off by paramagnetism or ferromagnetism—where χ>0. Typically, diamagnetism is a weak effect, so that |χ|<<1, (e.g., χ˜10−5). However, in superconductors, if an applied field is small enough, χ=−1. This phenomenon is called ideal diamagnetism. Currently, only superconductors reveal properties of ideal diamagnetism.
The system, method, and apparatus disclosed herein provide an ideal diamagnetism composition at room temperature. The disclosed system includes single-layer (or multi-layer) graphene on a substrate, which is immersed in n-heptane (a straight-chain alkane liquid). The system also includes a thin permalloy (nickel-iron magnetic alloy) foil that is placed in parallel to the graphene layer. The disclosed system potentially enables either room temperature superconductivity or represents a novel quantum effect in condensed matter physics. Room temperature superconductivity is more efficient compared to known superconductors, which require extremely low temperatures (and the corresponding cooling resources such as liquid nitrogen) to operate. The disclosed system may lead to applications for magnetic levitation. Additionally, the disclosed system may serve as a basis for superconducting quantum interference devices for the detection of extremely weak magnetic fields (e.g., can be used for applications such as land mine detection) and/or very fast computing electronics.
The disclosed system, method, and apparatus may exhibit the Meissner effect for superconductivity applications. Additionally or alternatively, the disclosed system, method, and apparatus may exhibit quantum effects for magnetic screening applications, levitation applications, and/or energy storage applications. Regardless of the end-use application, the example system, method, and apparatus have properties of diamagnetism at room temperature rather than at cryogenic temperatures, thereby enabling efficient and wide-spread commercial applicability.
In an example embodiment, a diamagnetism system includes a first substrate having a surface that is coated by a metallic layer and a second substrate having a surface that is coated by graphene. The first substrate may be separated from the second substrate by a distance between zero and some finite distance which enables diamagnetic properties. The first substrate may instead be a metallic foil such as permalloy, nickel, or cobalt. The second substrate may include a metallic layer (e.g., copper) to enable graphene to be grown thereon. Alternatively, the graphene may be grown on a temporary substrate and transferred to the second substrate.
The system also includes a coating of an alkane placed on the first substrate (or metallic foil) and the second substrate. In some embodiments, the alkane includes n-heptane, n-hexane, n-octane, etc. Instead of being coated, the substrates (or metallic foil) may be immersed into the alkane.
It is accordingly an advantage of the system, method, and apparatus to provide a composition that has properties of diamagnetism at room temperature.
Additional features and advantages are described in, and will be apparent from, the following Detailed Description and the Figures. The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the figures and description. Also, any particular embodiment does not have to have all of the advantages listed herein and it is expressly contemplated to claim individual advantageous embodiments separately. Moreover, it should be noted that the language used in the specification has been selected principally for readability and instructional purposes, and not to limit the scope of the inventive subject matter.
The system, method, and apparatus disclosed herein constitute an ideal diamagnetic composition at room temperature. The disclosed system includes single-layer (or multi-layer) graphene on a substrate, which is immersed in (or coated with) n-heptane (a straight-chain alkane liquid). The system also includes a thin permalloy (nickel-iron magnetic alloy) foil that is placed parallel to the graphene layer. The disclosed system potentially enables either room temperature superconductivity or represents a novel quantum effect in condensed matter physics. Room temperature superconductivity is more efficient compared to known superconductors, which require extremely low temperatures (and the corresponding cooling resources such as liquid nitrogen) to operate. The disclosed system may lead to applications for magnetic levitation. Additionally, the disclosed system may serve as a basis for superconducting quantum interference devices for the detection of extremely weak magnetic fields (e.g., can be used for applications such as land mine detection) and/or very fast computing electronics.
The disclosed system exhibits perfect screening of milligauss magnetic field (e.g., ideal diamagnetism) at room temperature. As disclosed herein, the system demonstrates ideal diamagnetism (no magnetic field inside the system) after injection of n-heptane, where the magnetic flux (B) drops down to a value of 0. The screening effect disappears if any of the disclosed components are absent, including n-heptane. This reproducible ideal diamagnetism may yield superconductivity at room temperatures and/or be indicative of a yet unknown effect in condensed matter physics.
While the disclosure refers to the system containing a thin permalloy foil, it should be appreciated that another substance (e.g. cobalt or nickel), that has very similar electrochemical potential as the permalloy, can also enable the system to achieve ideal diamagnetism. For example, the electrochemical potential of the permalloy foil is about −0.26 eV. Accordingly, the permalloy foil may be replaced by other metallic foils or metal layers with similar electrochemical potential, such as cobalt with an electrochemical potential of −0.28 eV or nickel with an electrochemical potential of −0.257 eV.
In some embodiments, the thin permalloy foil (or similar metallic foil) does not touch or have direct electrical contact with the graphene layer. Instead, n-heptane is provided between the permalloy foil and the graphene layer. In some examples, the foil and the graphene layer are immersed in n-heptane. In some examples, the n-heptane may be replaced by another alkane including n-hexane, n-octane, etc.
In an example embodiment, the disclosed system includes a silicon substrate instead of a metallic foil. In this embodiment, the silicon substrate has at least one surface that is coated by permalloy, cobalt, nickel, or similar metal via deposition. The disclosed system also includes a second substrate having at least one surface that is coated by a copper film. The silicon substrate surface is parallel to the second substrate. In some instances, a perfect (or near perfect) layer of graphene is grown on the copper film of the second substrate via chemical vapor deposition or a similar deposition method. In other instances, the copper film of the second substrate is omitted and the graphene is instead transferred to the second substrate. The first and second substrates are then placed into n-heptane. In some instances, both the first and second substrates are immersed in the n-heptane.
Graphene, since the time of its isolation, has proven to be a very fertile material for the exploration of novel features otherwise unattainable in solid-state objects. For example, graphite has long been recognized as an object with situation-dependent diamagnetic properties, exhibiting features that can be associated with superconductivity (even at room temperatures). The composite or apparatus disclosed herein includes single layer (or multiple layer) graphene that is wetted by n-heptane in the presence of at least one permalloy foil. The disclosed apparatus is a mixed solid-liquid system within the scope of condensed matter physics, rather than a traditional solid-state substance. The disclosed system has a diamagnetic response on the order of a weak, milligauss range magnetic field.
The example apparatus 100 also includes a housing or container 104. The example housing 104 may include glass or other inert material that does not react with the alkane and does not produce, attenuate, or otherwise affect a magnetic field. In some embodiments, the housing 104 may have an open top end. The housing 104 is configured to enclose a substrate 106 having at least one surface that is coated by a metallic layer or a freestanding metallic layer. The housing also encloses a second substrate 108 having at least one surface that is coated by graphene 110.
The first substrate 106 may include a silicon/silicon dioxide or quartz base. At least one surface of the first substrate 106 includes a metallic layer such as permalloy, cobalt, nickel, or another similar metal. The metallic layer may be grown on the substrate or be attached via a chemical or mechanical adhesive. Alternatively, the first substrate 106 may include a free standing metallic foil of permalloy, cobalt, nickel, or another similar metal. In these alternative embodiments, the first substrate 106 may comprise only the metallic foil.
The second substrate 108 may include silicon/silicon dioxide or quartz. In some embodiments, a layer of graphene 110 is grown on a temporary substrate and transferred to the second substrate 108. Alternatively, the second substrate 108 includes at least one surface that is coated with a metallic layer 111, such as copper. In this alternative embodiment, the graphene 110 is grown on the metallic layer 111. As shown in
In the illustrated embodiment, the first substrate 106 is separated from the second substrate 108 by a distance between zero millimeters (or at least 1 micron) and a distance sufficient to cause diamagnetism between the first substrate 106 and the second substrate 108. Further, while the first substrate 106 is positioned above the second substrate 108, in other embodiments the second substrate 108 maybe positioned above the first substrate 106.
In some embodiments, a single substrate may be used. In this example, the substrate may include a silicon or quartz base (or another other dielectric base) with at least one metallic layer comprised of permalloy, nickel, or cobalt. An opposite side of the substrate includes graphene 110. If the graphene is grown on the substrate, the substrate may include a copper layer to enable the graphene growth.
The example housing 104 also includes an alkane 112 placed on both the first substrate 106 and the second substrate 108. In the illustrated example, the first substrate 106 and the second substrate 108 are immersed in the alkane 112. As discussed below, the addition of the alkane 112 reduces a magnetic permeability ,u of the apparatus 100 to a value of zero. In some embodiments, the alkane 112 may include n-heptane or a similar liquid such as n-hexane or n-octane.
It should be appreciated that the example housing 104 is configured to retain the substrates 106 and 108 and the alkane 112 in place. Movement of the substrates 106 and 108 relative to each other or relative to the alkane 112 may cause reduction or elimination of diamagnetic properties. The substrates 106 and 108 may be secured to a side of the housing 104. Alternatively, the substrates 106 and 108 may be connected to a bracket or other mechanical fastener within the housing 104.
As shown in
The example current source 202 (e.g., a (Keithley-220®) is configured to use the messages and/or signals from the controller 204 to generate a corresponding current. The current source 202 is electrically connected to the wire coil 206 via a wire pair. The current source 202 provides a current to the wire coil 206 via the wire pair to generate a direct current (“DC”) magnetic field. An intensity of the DC magnetic field is defined by an amount of current applied to the wire coil 206 via the current source 202. In some instances, the wire coil 206 may be replaced by another component for creating the DC magnetic field. While
In the applied DC magnetic field, the diamagnetic apparatus 100 exhibits diamagnetism as soon as n-heptane is added. As described above, the substrates 106 and 108 in addition to the alkane 112 are kept at room temperature. As such, the diamagnetic apparatus 100 exhibits diamagnetism properties at room temperature.
The example sensor 302 is communicatively coupled to a computer 304. The sensor 302 transmits data indicative of a measured magnetic field to the computer 304 for analysis and visualization. The computer 304 includes any processor, workstation, laptop, server, etc. for processing data indicative of a measured magnetic field. In the current embodiment, LabVIEW® software and a General Purpose Interface Bus (“GPIB”) connection were used.
The example sensor 302 may be used in an experimental setup discussed below to measure magnetic properties of the diamagnetic apparatus 100. Additionally or alternatively, the sensor 302 may be used in a commercial application to provide feedback control to the controller 304. For example, detection of a magnetic field (in the absence of DC current through the wire coil 206) may indicate that the apparatus 100 is not properly configured to provide diamagnetic properties or that an adjustment is needed to an applied DC magnetic field.
The housing 104 included a Pyrex® glass beaker. Glassblowing work was done to make the bottom of the housing 104 flat or sagging a bit for easier access of liquid 112 to the central part of the graphene layer 110.
In the initial experiments, the permalloy foil of the first substrate 106 was used with the intention of reducing the amplitude of the external magnetic flux at the location of the graphene 110. There is also a question of magnetic field direction. Modeling of the magnetic field revealed that in the disclosed configuration where the graphene 110 and the permalloy of the first substrate 106 are separated by the second substrate 108, the normal component of the field is prevailing (see graph 500 of
It should be appreciated that this reported effect shown in
To understand the effect of graphene layer 112 inhomogeneity, additional modeling was performed on an ideal diamagnet (relative permeability μ=0) with a spatial defect (where μ˜1). The ideal diamagnet with spatial defects can amplify locally the magnetic flux. The results are shown in
However, the situation shown in
These experimental observations confirm and further extend the initial results on magnetic response. Until now, perfect screening (μ=0) was attributed only to superconductivity. Either the disclosed apparatus 100 is a superconductor (with extremely small values of the first critical field Hc1), or possibly the apparatus 100 comprises an ideal diamagnetic substance of unknown physical origin. One of the most interesting aspects of this research is the role of the permalloy of the first substrate 106. The thickness of permalloy does not have a significant effect on the results. Instead, the thickness only reduces the value of B-field. Working with thinner foil is easier, since it almost does not change the field value. One can think of permalloy as affecting the results not magnetically, but rather electrochemically.
As provided above, the disclosed apparatus 100 reproducibly provides observations regarding the screening of milligauss-range magnetic fields by a condensed matter system consisting of pristine graphene, n-heptane and permalloy. The screening is ideal such that it corresponds to χ=−1, i.e., χ=−1/(4π) in Gaussian units. This indicates a presence of either a room temperature, ambient pressure superconductor or a yet unknown type of ideal diamagnetic complex material.
The example procedure 1000 begins when a first substrate 106 is formed (block 1002). The first substrate 106 may be formed from silicon/silicon dioxide or quartz. Alternatively, the first substrate 106 comprises a metallic foil such as permalloy, cobalt, nickel, or another similar metal.
If the first substrate 106 is a dielectric, a metallic layer is coated on at least one surface of the first substrate 106 (block 1004). The metallic layer may include at least one of permalloy, cobalt, nickel, or another similar metal and be deposited via deposition or sputtering. The permalloy may have a composition of 79% Ni, 16% Fe, and 5% Mo at thicknesses between 1 micron to 100 micron. Alternatively, the permalloy may have a composition of 77-78% Ni, 5% Mo, 4% Cu, and the remainder Fe at thickness of about 12 micron. If the first substrate is a foil, this step is omitted.
The example procedure 1000 continues by forming a second substrate 108 (block 1006). The second substrate 108 may include silicon/silicon dioxide or quartz. A layer of graphene 110 may be grown on a temporary substrate and transferred to the second substrate (block 1008). The graphene 110 may be grown via chemical vapor deposition or a similar deposition method. Alternatively, a metallic layer (e.g., a copper layer) may be deposited on at least one surface of the second substrate 108. The graphene 110 may be grown on the metallic layer of the second substrate 108 instead of being transferred.
The first and second substrates 106 and 108 are then connected or otherwise placed into a housing 104 (block 1010). The substrates 106 and 108 may be parallel with each other and separated by a distance of at least 1 micron. An alkane 112 is then placed on the first and second substrates 106 and 108 (e.g., a composition) (block 1012). Alternatively, the alkane 112 is added to the housing 104 to immerse the first and second substrates 106 and 108. The example procedure 1000 concludes when the housing 104 is secured. In some embodiments, the housing 104 may be installed into a commercial application. Additionally, a DC magnetic field is applied to induce the diamagnetic property with the addition of n-heptane (block 1014). Further, a sensor 302 may detect zeroing of a magnetic response that is indicative of diamagnetism (block 1016).
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
This application claims priority to and the benefit as a non-provisional application of U.S. Provisional Patent Application No. 62/992,391, filed Mar. 20, 2020, the entire content of which is hereby incorporated by reference and relied upon.
This invention was made with government support under Grant/Contract Numbers N00014-16-2269, N00014-17-1-2972, N00014-18-1-2636, N00014-19-1-2265, and N00014-20-1-2442 awarded by the United States Office of Naval Research. The government has certain rights in the invention.
Number | Date | Country | |
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62992391 | Mar 2020 | US |