OF A FUEL CELL

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent

Application No. 62/466,849 filed on March 3, 2017, the entire disclosure of which is incorporated by reference herein.

BACKGROUND

[0002] The present disclosure relates to an anode of a fuel cell. In particular, the present disclosure relates to an electrolyte barrier formed of a low-wetting or non-wetting material and a method for manufacturing the electrolyte barrier for eliminating electrolyte creep from the anode of a fuel cell to a direct internal reforming catalyst.

[0003] A fuel cell is a device, which directly converts chemical energy stored in hydrocarbon fuel into electrical energy by an electrochemical reaction. Generally, a fuel cell includes an anode and a cathode separated by an electrolyte that conducts electrically charged ions. Fuel cells operate by passing a reactant fuel gas through the anode, while passing oxidizing gas through the cathode. In order to produce a desired power level, a number of individual fuel cells may be stacked in series with an electrically-conductive separator plate between each cell.

[0004] Before undergoing the electrochemical reaction in the fuel cell, hydrocarbon fuels such as methane, coal gas, etc. are typically reformed to produce hydrogen for use in the anode of the fuel cell. In internally reforming fuel cells, a steam reforming catalyst is placed within the fuel cell stack to allow direct use of hydrocarbon fuels without the need for expensive and complex reforming equipment. In addition, the endothermic reforming reaction can be used

advantageously to help cool the fuel cell stack.

[0005] In internally reforming fuel cells such as the internally reforming fuel cell, a reforming catalyst is placed within the fuel cell stack to allow direct use of hydrocarbon fuels such as pipe line natural gas, liquefied natural gas (LNG), liquefied petroleum gas (LPG), bio-gas, methane containing coal gas, etc. without the need for expensive and complex external reforming equipment. In an internal reformer, water and heat produced by the fuel cell are used by the reforming reaction, and hydrogen produced by the reforming reaction is used in the fuel cell. The heat produced by the fuel cell reaction supplies heat for the endothermic reforming reaction. Thus, internal reforming is used to cool the fuel cell stack.

[0006] Two different types of internally reforming fuel cell designs have been developed and used. The first reforming technique, direct internal reforming ("DIR") is accomplished by placing a reforming catalyst ("DIR catalyst") within the active anode compartment. This catalyst is exposed to the electrolyte of the fuel cell. The second reforming technique, indirect internal reforming ("IIR"), is accomplished by placing the reforming catalyst ("IIR catalyst") in an isolated chamber within the fuel cell stack and routing the reformed gas from this chamber into the anode compartment of the fuel cell. Internal reforming fuel cells have a simpler, more efficient and cost-effective energy conversion system, as compared to external reforming fuel cells. In addition, the internal reforming approach improves cell/stack efficiency and enables better control of cell temperature and stack thermal management

[0007] The DIR catalyst may be a nickel-based DIR catalyst in the form of pellets, extruded paste, and/or coated thin film. A well-known DIR catalyst decay mechanism in a MCFC is electrolyte creep from the anode that results in catalyst aging and deactivation. During operation of the MCFC, the anode is filled (e.g., 5% to 50% of its void volume) with liquid carbonate electrolyte. The electrolyte tends to wet an associated anode support and an anode current collector during operation and/or during conditioning. The electrolyte is then able to reach the DIR catalyst, which is stored in the anode current collector. Electrolyte pickup by the DIR catalyst leads to poisoning and reduced reforming activity. This results in lower hydrogen generation and in reduced cooling, which may accelerate MCFC degradation. Long-term exposure of the DIR catalyst to electrolyte creep through the anode support and the anode current collector accelerates the coarsening and sintering of the catalyst nickel particles, as well as a surface area reduction of the anode support, resulting in incomplete

reforming(approximately less than 99% reforming).

[0008] Previous approaches to preventing DIR catalyst poisoning from electrolyte creep involved using nickel-based supports, such as nickel screen, nickel mesh or nickel foam, as a barrier for electrolyte creep. For example, nickel supports with 5 mm to 20 mm thickness were laminated or attached to green anode tapes and/or sintered anodes to mitigate electrolyte movement from the anode to the reforming catalyst stored in the anode current collector.

Another approach involved cladding the base materials, such as stainless steel, with nickel to eliminate electrolyte creep. Although a nickel clad having a thickness, for example, of 25 μιη to 50 μπι provides a barrier to prevent electrolyte creep, the addition of the nickel clad increases cost and may promote the carburization of the anode current collector, leading to an increased brittleness.

[0009] A need exists for improved technology, including an improved anode current collector and anode support having an electrolyte barrier capable of preventing electrolyte creep from the anode to the DIR catalyst during cell operation and transient conditions. By preventing electrolyte creep into the DIR catalyst, electrolyte poisoning can be reduced or eliminated from a fuel cell.

SUMMARY

[0010] In some embodiments, an anode component of a fuel cell comprises a porous anode, an anode support, an anode current collector in contact with the anode support, a direct internal reforming catalyst on the anode current collector, and an electrolyte barrier configured to prevent electrolyte poisoning of the direct internal reforming catalyst. The electrolyte barrier comprises graphite, high surface area carbon, carbon black, graphene, boron nitride, or a combination thereof.

[0011] In one aspect, the electrolyte barrier has a low wettability, where a contact angle Θ between an electrolyte droplet and the electrolyte barrier satisfies the condition 90° < Θ < 180°.

[0012] In one aspect, the electrolyte barrier has a low wettability, where a contact angle Θ between an electrolyte droplet and the electrolyte barrier satisfies the condition 110° < Θ < 180°.

[0013] In one aspect, the electrolyte barrier is a layer on a surface of the anode support, a surface of the anode current collector, a surface of the direct internal reforming catalyst or a combination thereof, and the electrolyte barrier does not include nickel. [0014] In one aspect, the electrolyte barrier has a communicating surface configured to communicate with an electrolyte, and the communicating surface does not include nickel.

[0015] In one aspect, the electrolyte barrier further comprises nickel embedded therein, and the electrolyte barrier is a layer on a surface of the anode support, a surface of the anode current collector, a surface of the direct internal reforming catalyst, or a combination thereof.

[0016] In one aspect, the electrolyte barrier has a communicating surface configured to communicate with an electrolyte, and the embedded nickel is not present in the communicating surface.

[0017] In one aspect, the anode current collector comprises a nickel cladding on a surface thereof, and the electrolyte barrier is a layer on a surface of the anode support, a surface of the nickel cladding, a surface of the direct internal reforming catalyst, or a combination thereof.

[0018] In one aspect, the electrolyte barrier is on a surface of the anode support.

[0019] In one aspect, the electrolyte barrier is on a surface of the anode current collector.

[0020] In one aspect, the electrolyte barrier is on a surface of the direct internal reforming catalyst.

[0021] In one aspect, an average thickness of the electrolyte barrier is between Ιμπι and 50μπι.

[0022] In one aspect, the average thickness of the electrolyte barrier is between 25μπι and

[0023] In one aspect, the anode support and the anode current collector comprise stainless steel.

[0024] In one aspect, the anode support and the anode current collector comprise a nickel- based material.

[0025] In one aspect, the direct internal reforming catalyst is a nickel-based catalyst.

[0026] In one aspect, the direct internal reforming catalyst comprises at least one of Ni/Ce- Zr0 ₂ , Ni/Zr0 ₂ , Ni/MgAl ₂ 0 ₄ , Ni/Ce0 ₂ , Ni/Al ₂ 0 ₃ , or Ni/Al ₂ 0 ₃ -Zr0 ₂ .

[0027] In some embodiments, a molten carbonate fuel cell comprises a cathode component; an anode component according to any of the embodiments/aspects above; and an electrolyte matrix between the cathode component and the anode component.

[0028] In one aspect, the electrolyte matrix comprises a molten alkali carbonate electrolyte contained within a porous ceramic matrix.

[0029] In one aspect, the molten alkali carbonate electrolyte comprises lithium carbonate, sodium carbonate, potassium carbonate, or combinations thereof. The porous ceramic matrix comprises lithium aluminate. The direct internal reforming catalyst of the anode component is a nickel-based catalyst. The electrolyte barrier comprises graphite, high surface area carbon, carbon black, graphene, boron nitride, or a combination thereof

[0030] In some embodiments, a method of manufacturing an electrolyte barrier for an anode component of a fuel cell including a porous anode, an anode support, an anode current collector in contact with the anode support, and a direct internal reforming catalyst on the anode current collector is provided. The method comprises coating a surface of the anode support, a surface of the anode current collector, a surface of the direct internal reforming catalyst (DIR) or a combination thereof with an electrolyte barrier comprising graphite, high surface area carbon, carbon black, graphene, boron nitride, or a combination thereof.

[0031] In one aspect, the electrolyte barrier has a low wettability, where a contact angle Θ between an electrolyte droplet and the electrolyte barrier satisfies the condition 90° < Θ < 180°.

[0032] In one aspect, the coating step comprises mixing graphite, high surface area carbon, carbon black, graphene, boron nitride, or a combination thereof and a solvent, and spray coating, dip coating or PVD coating a resulting mixture from the mixing step in an average thickness between Ιμπι and 50μπι to form the electrolyte barrier.

[0033] In one aspect, the electrolyte barrier is coated on the surface of the anode support, the surface of the anode current collector or a combination thereof, and the anode support and the anode current collector comprise stainless steel. [0034] In one aspect, the electrolyte barrier is coated on the surface of the anode support, the surface of the anode current collector or a combination thereof, and the anode support and the anode current collector are comprised of a nickel-based material.

[0035] In some embodiments, an anode component of a fuel cell comprises a porous anode; an anode support; an anode current collector in contact with the anode support; a direct internal reforming catalyst on the anode current collector; and an electrolyte barrier configured to prevent electrolyte poisoning of the direct internal reforming catalyst. The electrolyte barrier comprises a material having a low wettability, where a contact angle Θ between an electrolyte droplet and the electrolyte barrier satisfies the condition 90° < Θ < 180°. The electrolyte barrier has a communicating surface configured to communicate with an electrolyte, and the

communicating surface does not include nickel.

[0036] In one aspect, the electrolyte barrier comprises graphite, high surface area carbon, carbon black, graphene, boron nitride, or a combination thereof.

[0037] In one aspect, the electrolyte barrier further comprises nickel embedded therein, and the embedded nickel is not present in the communicating surface.

[0038] In one aspect, the anode current collector comprises a nickel cladding on a surface thereof, and the electrolyte barrier is a layer on a surface of the anode support, a surface of the nickel cladding, a surface of the direct internal reforming catalyst, or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures in which:

[0040] FIG. 1 is a schematic illustration of an internal reforming and cell package with a direct internal reforming catalyst in a fuel cell assembly.

[0041] FIG. 2 is a schematic illustration of a fuel cell in the fuel cell assembly of FIG. 1. [0042] FIG. 3 is a schematic illustration of an electrolyte barrier formed on a surface of an anode current collector of FIG. 2.

[0043] FIG. 4 is a schematic illustration of an electrolyte barrier formed on a surface of an anode support of FIG. 2.

[0044] FIG. 5 is a schematic illustration of an electrolyte barrier formed on a surface of a direct internal reforming catalyst of FIG. 2.

[0045] FIG. 6 is a schematic illustration of an electrolyte barrier formed on a surface of a nickel cladding on the anode current collector of FIG. 2.

[0046] FIG. 7 is a schematic illustration of an electrolyte barrier including nickel embedded within graphite, high surface area carbon, carbon black, graphene, boron nitride, or

combinations thereof.

[0047] FIG. 8 is a graph illustrating lithium carbonate (i.e., electrolyte) pickup in a direct internal reforming catalyst of a conventional anode current collector and graphite-coated anode current collector.

DETAILED DESCRIPTION

[0048] Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

[0049] Referring generally to the figures, aspects of the concepts described herein are directed to an improved electrolyte barrier for a molten carbonate fuel cell and a method of

manufacturing an improved electrolyte barrier.

[0050] An example of an internally reforming fuel cell is shown in FIG. 1. Fuel (in this example, natural gas) flows into an indirect internal reformer where it is partially reformed and follows a U-shaped path and exits the indirect internal reformer on the same side of the fuel cell stack at which it entered the indirect internal reformer. That partially reformed fuel then enters the fuel cells of the fuel cell stack on the same side of the fuel cell stack at which the fuel enters the indirect internal reformer, where it is further reformed by a direct internal reforming catalyst (DIR catalyst). Oxidant gas flows through the fuel cells in a direction transverse to the flow of fuel.

[0051] Referring to FIG. 2, a cathode side of a fuel cell 10 includes a bipolar plate 1 adjacent to a cathode current collector 2 which is in contact with a cathode 3. An anode side of the fuel cell 10 includes another bipolar plate 1 adjacent to an anode current collector 4 which is in contact with an anode support 5. The anode support 5 supports a porous anode 6. The anode current collector 4 includes a DIR catalyst 8, which may be a nickel-based DIR catalyst in the form of pellets, extruded paste, and/or coated thin film. For example, the DIR catalyst may be comprised of Ni/Ce-Zr0 ₂ , Ni/Zr0 ₂ , Ni/MgAl ₂ 0 ₄ , Ni/Ce0 ₂ , Ni/Al ₂ 0 ₃ , or Ni/Al ₂ 0 ₃ -Zr0 ₂ . The DIR catalyst 8 is not limited to these compositions. An electrolyte matrix 9 is disposed between the cathode side and the anode side of the fuel cell 10. Wet seals 1 1 may be provided at an active area perimeter of the electrolyte matrix 9 to prevent gas leakage from the electrode compartments.

[0052] In one example, the fuel cell 10 may be a molten carbonate fuel cell. Generally molten carbonate fuel cells operate at intermediate temperatures (575°C-650°C) and employ

carbonaceous fuels containing carbon dioxide and carbon monoxide. A typical molten carbonate fuel cell assembly may include a porous Ni anode 6 stabilized against sintering by Cr and/or Al additives and a porous in-situ oxidized and lithiated NiO cathode 3. The anode 6 and the cathode 3 may be separated by a molten alkali carbonate electrolyte, such as Li ₂ C0 ₃ /K ₂ C0 ₃ or Li ₂ C0 ₃ /Na ₂ C0 ₃ , contained within a porous ceramic matrix (i.e., an electrolyte matrix 9), such as LiA10 ₂ . A molten carbonate fuel cell generates electric power by passing a reactant fuel gas through the anode 6 while oxidizing gas is passed through the cathode 3.

[0053] In order to prevent electrolyte creep from the anode 6 to the DIR catalyst 8 during cell operation and transient conditions, an electrolyte barrier 20 may be provided on any substrate. For example, the electrolyte barrier 20 may be provided on at least one of a surface of the anode current collector 4 (see FIG. 3), a surface of the anode support 5 (see FIG. 4), a surface of the DIR catalyst 8 (see FIG. 5), a cladding on a surface of the anode current collector 4 (see FIG. 6), a cladding on a surface of the anode support 5, or combinations thereof. In examples in which the DIR catalyst 8 is provided in the form of a pellet, the electrolyte barrier 20 covers an entire surface area of the pellet. The anode current collector 4 and the anode support 5 may be made of any suitable material, for example, stainless steel (e.g., stainless steel 310 or 316L) or a nickel-based material.

[0054] The surface of the anode current collector 4 may be clad with a nickel cladding. In examples in which the surface of the anode current collector 4 is clad with a nickel cladding 4A, the electrolyte barrier 20 may be provided on at least one of a surface of the nickel cladding 4A (see FIG. 6), a surface of the anode support 5 (see FIG. 4), a surface of the DIR catalyst 8 (see FIG. 5) or combinations thereof.

[0055] The electrolyte barrier 20 is made of a material having a low wettability (i.e., a contact angle of 90° < Θ < 180°) or a non-wetting material (i.e., a contact angle of Θ = 180°), where the contact angle Θ is an angle at which the electrolyte 21 meets the electrolyte barrier 20. For example, the electrolyte barrier 20 may be made of a material having a contact angle of 110° < Θ < 180°. As used herein, the term "low wettability" refers to the electrolyte barrier 20 having a very low electrolyte pick up (<0.1 wt%), and the electrolyte barrier 20 does not spread the liquid electrolyte. Because the electrolyte barrier 20 is made of a material having a low wettability or a non-wetting material, it is possible to reduce or eliminate electrolyte contact with the DIR catalyst 8.

[0056] The electrolyte barrier 20 may be comprised, for example, of graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof. In some examples, the electrolyte barrier 20 does not include nickel. In other examples, the electrolyte barrier 20 includes nickel embedded within graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof. The electrolyte barrier 20 has a communicating surface 22 configured to communicate with the electrolyte 21. In the examples in which the nickel is embedded within the electrolyte barrier 20, the communicating surface 22 of the electrolyte barrier 20 does not include nickel (i.e., the nickel is entirely embedded within or entirely coated with the graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof). See FIG. 7. Forming the electrolyte barrier 20 from graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof, or nickel embedded within graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof, allows for the use of low-cost materials, such as stainless steel, as the anode current collector 4 and/or the anode support 5 and eliminates the need for cladding the anode current collector 4 and/or the anode support 5 with nickel.

[0057] The electrolyte barrier 20 is formed by mixing an appropriate amount (e.g., 15-20 wt%) of graphite, high surface area carbon, carbon black, graphene, boron nitride, or combinations thereof in isopropanol (e.g., 60-70wt%) or an equivalent solvent (e.g., propanol, methanol, MEK, a MEK/cyclohexane mixture, etc.) in the presence of a small amount of a dispersant such as fish oil or Hypermer (KD-1) (e.g., 0.5-2wt%). An acryloid binder and/or plasticizer may be added to the mixture. For example, the plasticizer may be benzyl butyl phthalate. The mixture may be applied to a surface of the anode current collector 4, a surface of the anode support 5, a surface of the DIR catalyst 8 or combinations thereof using any known coating technique, for example, spray coating, dip coating, or PVD coating to form the electrolyte barrier 20. A thickness of the electrolyte barrier 20 may be from 1 μπι to 100 μπι (e.g., from 25 μπι to 50 μπι, from 25 μπι to 30 μπι, or from 20 μπι and 25 μπι). Spray coating may be used to achieve electrolyte barrier thicknesses, for example, from 1 μπι to 50 μπι. PVD coating may be used to achieve smaller electrolyte barrier thicknesses for example, about 1 μπι to 2 μπι.

[0058] In one example, the electrolyte barrier 20 is made of graphite, which exhibits a high surface tension, poor wetting in molten carbonate, and excellent stability under anode atmosphere. Compared to nickel, graphite demonstrates improved stability in air up to a temperature of about 550°C to 600°C, which is within the operating temperatures of molten carbonate fuel cell. Compared to nickel, graphite exhibits a higher contact angle, and is therefore less wettable than nickel in molten carbonate electrolyte. Graphite is also resistant to oxidization (combustion) under anode atmosphere and during initial conditioning of the molten carbonate fuel cell to remove binders and other organic additives. Therefore, an electrolyte barrier 20 made of graphite offers improved protection against electrolyte creep, as compared to conventional barriers made of nickel-based materials.

[0059] Experiment

[0060] In order to evaluate the effectiveness of an electrolyte barrier made of graphite, a plurality of anode current collectors were prepared, coated with different electrolyte barrier materials, and tested in a single fuel cell to measure DIR catalyst electrolyte pickup. Graphite ink solutions were prepared by mixing or milling graphite powder (KS15, 15-20 wt%) in isopropanol (60-70wt%) in the presence of a small amount of fish oil (i.e., a dispersant). An attrition milling technique using yttrium stabilized zirconia grinding beads (e.g., YTZ® grinding media) having a diameter of 0.3 mm to 3 mm was used to disperse the graphite powder and achieve a required particle size distribution of approximately less than 0.5μπι. The grinding media content in the attrition mill chamber varied between 55% and 70%, and the grinding speed varied between 1000 and 3000 rpm. After achieving the required particle size, 0.5wt% to 6wt% acryloid binder and Santicizer 160 plasticizer were added to complete the graphite ink formulation. In the next step, graphite ink was spray coated on both flat and corrugated sides of the anode current collector. The spray coating was dried at room temperature for between 5 and 15 minutes and then heat treated at 100°C to 150°C to form the electrolyte barrier comprised of graphite. The resultant electrolyte barrier had an average thickness between 5μπι to 50μπι.

[0061] The anode current collectors coated with a graphite electrolyte barrier were loaded with an appropriate amount of DIR catalyst (e.g., 10-14g of DIR catalyst for a 7"x7" anode current collector and subjected to single cell endurance tests to quantify the electrolyte creep in the DIR catalyst.

[0062] Several bench-scale, single fuel cells (250 cm ² ) were tested to compare the

performance of the DIR catalyst loaded on anode current collectors with and without graphite electrolyte barriers. Each single fuel cell assembly included a porous nickel aluminum alloy and/or nickel chromium alloy anode with a conventional or graphite coated anode current collector and a porous in-situ oxidized and lithiated nickel oxide cathode, separated by a porous ceramic matrix made of lithium aluminate. In this example, the cathode (250 cm ² ) was filled with an appropriate amount of lithium / potassium or lithium / sodium electrolyte, and an appropriate amount of lithium / potassium or lithium / sodium electrolyte was also stored in the cathode current collector to achieve the desired electrolyte balance.

[0063] At the beginning of the experiment, the cells were operated with an anode gas composed of 72.8%H ₂ -18.2%C0 ₂ -9%H ₂ 0 and a cathode gas composed of 18.5%C0 ₂ -12.1%0 ₂ - 66.4%N ₂ -3%H ₂ 0 to check the performance and gas sealing efficiency. Next, a simulated reforming gas composed of 17%CH ₄ -17%CC) ₂ -66%H ₂ humidified at 66°C was used to evaluate the DIR reforming conversion. Single cell tests in this example were performed at 650°C and 160mA/cm ² and 75% fuel utilization. Post-test analysis of endurance cells using conventional and graphite coated anode current collectors were conducted to determine the amount of electrolyte present in the DIR catalyst. Lithium carbonate content in the catalyst was measured to quantify electrolyte creep. The baseline or conventional anode current collector used for comparison in this experiment consisted of a stainless steel (310 S) anode current collector with no nickel cladding or electrolyte barrier.

[0064] FIG. 8 is a graph summarizing results of the quantification of electrolyte creep. Results show that the graphite-coated anode current collector offers >60-65% reduction of lithium carbonate pickup in the DIR catalyst. These results indicate that using graphite electrolyte barriers on a stainless steel anode current collector offers improvement in terms of reducing electrolyte creep compared to uncoated conventional anode currently collectors. PVD coated samples with an average electrolyte barrier thickness of about Ιμπι to 2μπι were also tested. See FIG. 8.

[0065] The construction and arrangements of the electrolyte barrier and the methods of manufacturing the electrolyte, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, image processing and segmentation algorithms, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

[0066] As utilized herein, the terms "approximately," "about," "substantially", and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0067] References herein to the positions of elements (e.g., "top," "bottom," "above,"

"below," etc.) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0068] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for the sake of clarity.