System and corresponding production method

Abstract

The invention relates to a system (10), said system (10) comprising at least one insulation element (1) having a surface (2), wherein at least one region (3) of the surface (2) of the insulation element (1) is at least partially coated with a coating (4), the coating (4) contains an electrically conductive molten salt, and the coating (4) is liquid in a temperature range of -150°C to +350°C; the invention also relates to a corresponding production method.

Description

[0001] System and corresponding manufacturing process

[0002] The invention relates to a system and a corresponding manufacturing method.

[0003] Space-based satellites and probes are often powered by solar arrays. A solar array is typically constructed layer by layer, with several very sensitive solar cell layers covered by, for example, a glass plate.

[0004] Such a glass plate acts as an electrical insulator and is intended to protect the solar cells, especially from damage. For example, the glass plate stiffens the structure of the solar system and protects the solar cells from mechanical stress and damage.

[0005] Satellites and probes in space can be exposed to solar winds, whereby the electrically charged particles contained in the solar wind, such as electrons, accumulate on the upper side of the glass plate facing the solar wind, thus electrically charging the upper side. On the other hand, charge carriers, such as excess electrons, can be released from the glass plate by the effects of light from the sun, particularly the ultraviolet portion of the solar spectrum, as a result of the photoelectric effect. The accumulation and / or release of electrically charged particles can lead to a local excess or deficiency of electrons relative to the average charge density of the glass plate, particularly the upper side of the glass plate. In both cases, a dangerous potential difference can arise between a point of higher potential and a point of lower potential. The point of higher potential can, for example,the electrically charged surface of the glass plate, in particular a surface facing away from the sun. The point of lower potential can be another point on the glass plate, e.g. a side of the glass plate facing the sun, or it can be a point on the solar cells or on another part of the satellite. The glass plate acts like an electrical insulator, i.e. the glass plate is electrically non-conductive. In the worst case scenario, the potential difference can therefore lead to an electrical breakdown between the described points of different potential, e.g. the upper side of the glass plate and e.g. another point on the glass plate or the solar cells or the satellite. In the event of such an electrical breakdown, conductive plasma forms for a short time, e.g. in the material of the glass plate, which equalizes the potential difference, but the.

[0006] 1

[0007] REPLACEMENT BLADE (RULE 26) Glass plate, especially the solar cells or the satellite, may be irreversibly damaged.

[0008] US 2012 / 0 312 371 A1 relates to systems and methods for solar cells with Schottky junction, in particular a solar cell with a grid layer formed on a semiconductor layer and an ion layer formed on the grid layer.

[0009] WO 2014 / 178 254 A1 relates to a sealing film, a method for producing the sealing film and a functional element coated with the sealing film.

[0010] US 2012 / 0 052 395 A1 relates to polymer compositions, films, gels and foams containing electrically conductive polymers, as well as to electronic devices containing such polymer films, gels and foams.

[0011] Therefore, the technical problem arises of creating a system that reduces the risk of electrical breakdown.

[0012] The solution to the technical problem is achieved by the subject matter having the features of the independent claims. Further advantageous embodiments of the invention are set forth in the subclaims.

[0013] A system is therefore proposed, wherein the system comprises at least one insulating element with a surface, wherein at least one region of the surface of the insulating element is at least partially coated with a coating, wherein the coating comprises an electrically conductive molten salt.

[0014] The insulation element is a solid, i.e., the insulation element is in a solid state, particularly in the ambient pressure and / or temperature range defined in this disclosure. The electrical resistance or electrical conductivity of the insulation element is preferably direction-independent, i.e., isotropic, so that the specific resistance or electrical conductivity can be specified as a scalar value. The insulation element is preferably non-conductive. I.e., the insulation element preferably has, at least in one spatial direction, a specific resistance with a value in a range of 10 A 3 ohmmeters to 10 A 17 ohmmeters or an electrical conductivity with a corresponding reciprocal of the specific resistance. The insulating element can be made of a rock, a mineral, or similar material, in particular glass or strontium titanate.

[0015] The surface delimits an internal volume of the insulation element. The surface has one or more regions. One region of the surface is, for example, an upper side of the insulation element. Another region is, for example, an underside of the insulation element. Further regions can be, for example, side surfaces of the insulation element, wherein the upper side is opposite the underside and the upper and undersides delimit the internal volume of the insulation element via the side surfaces. Referring to the previously mentioned example of the solar system, the upper side of the insulation element is in particular the side of the insulation element which is oriented towards a direction of influence of the sun. As a result of solar wind, charge carriers can accumulate on the surface. Due to the low electrical conductivity of the insulation element, these charge carriers cannot move from the surface to a point of lower potential.In other words, the surface of the insulating element has an electrical chargeability, i.e. the charge carriers can create a dangerous potential difference.

[0016] The at least one region can be the previously described top side of the glass plate. This means that the region is, in particular, that part of the surface of the insulation element that can be electrically charged, for example, by the charge carriers of the solar wind.

[0017] The coating reduces the electrical chargeability of at least one region of the insulation element. For this purpose, the coating comprises a molten salt. The molten salt is an electrically conductive liquid, in particular an ionic liquid, particularly preferably an aprotic ionic liquid. In particular, the molten salt has a higher electrical conductivity than the insulation element. The molten salt comprises anions and cations, in particular molecular ones, which are freely mobile within the molten salt. As soon as charge carriers, in particular electrons, e.g. in connection with a solar wind, impact the system, in particular the coating or an outer side of the coating, they can be absorbed by the anions and / or cations contained in the molten salt. A local excess of electrons resulting from the impact of the charge carriers, e.g.on the outside of the coating, can be delocalized, i.e., compensated, by the anions and cations. A potential difference between a point on the outside and a point of lower potential can thus be balanced or at least weakened by the coating. The outside of the coating is, in particular, the side of the coating that is not adjacent to the insulation element, but rather to an environment of the system, such as space.

[0018] The orientation of the system in space and of the system's components relative to one another can be described by a Cartesian coordinate system, in particular a system-specific one. Thus, a vertical axis of the coordinate system can be oriented normal to the surface of the insulating element, in particular normal to the at least one surface region. The vertical axis can be oriented opposite a direction of solar radiation. The direction of radiation thus refers to the direction from which charge carriers can strike the coating. A transverse axis and / or longitudinal axis of the coordinate system can be oriented parallel to the surface of the insulating element, in particular parallel to the at least one surface region.

[0019] According to the invention, the coating is liquid in a temperature range from -150°C to +350°C, particularly preferably in a temperature range from -100°C to 100°C. Liquid means that the molten salt is in a liquid state. The temperature range here refers to a, in particular average, temperature of the coating. This can have the physical background, in particular, that the anions and cations in the molten salt are arranged in a correspondingly unstructured manner and / or the anions and cations have a corresponding size that hinders crystallization and / or evaporation in the stated temperature range. This has the technical effect that the coating can be used in high vacuum, ultra-high vacuum, in particular in space, as well as on Earth without evaporating or crystallizing. This is particularly advantageous for the use of the system in space-based solar systems or satellites.In addition, experiments have shown that a liquid state of aggregation has a particularly advantageous effect on achieving the technical effects of the invention mentioned in this disclosure.

[0020] The proposed system therefore has the advantage that the electrical chargeability of the surface of the insulating element, or of a region of the surface, is reduced or at least weakened by means of the coating and thus the risk of electrical breakdown is reduced, ie the insulating element is better protected by the coating against electrical breakdown, e.g. as a result of solar wind.

[0021] With regard to the proposed system, the inventors have also recognized that the electrically conductive coating of the insulating element can be used to draw conclusions about the surface properties of the insulating element, such as the shape and / or orientation of the area of ​​the surface coated with the coating. For example, a mineral such as strontium titanate can have a surface with different areas, each of which has a different shape and / or orientation. If the surface or an area of ​​the surface is coated with the coating, a conclusion about the shape and / or orientation of the coated area can be drawn, for example, via a current passed through the coating. Such a current can be introduced into the coating, for example, by targeted bombardment of the coated area with electrons, e.g. using an electron microscope.In this way, the surface quality of the insulation element can be measured extremely precisely, which represents a further technical effect of the invention.

[0022] In a further embodiment, the coating is transparent. In particular, a transmittance of the coating, in particular likewise a transmittance of the insulating element, for light, in particular for light in the visible range, in particular for light with wavelengths in a value range between 380 nanometers and 780 nanometers, has a transmittance value in a range of 0.9 to 1. This has the effect that light, in particular sunlight, penetrates the coating almost completely before striking the solar cells and the energy contained in the light is not significantly reduced by absorption in the coating or reflection at the coating. Such a solar cell, in particular a solar system, can be part of the system. In particular when the system is used in a solar system, the insulating element can also be transparent, so that light can penetrate the insulating element almost completely.

[0023] In a further embodiment, the molten salt is an aprotic ionic liquid. An example of an aprotic ionic liquid is 1-butyl-1-methylpyrrolidinium dicyanamide, also known as BMP DCA. Aprotic ionic liquids cannot form hydrogen anions and / or hydrogen cations. This has the advantage that no hydrogen bonds can form in the aprotic ionic liquid, which would reduce the electrical conductivity of the molten salt. Thus, aprotic liquids can exhibit increased electrical conductivity, e.g., compared to protic ionic liquids. Furthermore, aprotic ionic liquids have a lower vapor pressure, e.g., compared to protic ionic liquids. This makes the aprotic ionic liquid particularly suitable for use in high vacuums, in particular ultra-high vacuums, preferably in space.Aprotic ionic liquids such as BMP DCA are also characterized by their thermal and electrochemical stability, especially compared to protic ionic liquids.

[0024] In a particularly preferred embodiment, the molten salt is 1-butyl-1-methylpyrrolidinium dicyanamide. In particular, a coating formed in this way can have a layer thickness of less than one micrometer. Preferably, a coating formed in this way is transparent, with a transmittance between 0.9 and 1. BMP DCA is characterized by advantageous properties such as, for example, a particularly high resilience to chemical or electrochemical oxidation and reduction processes compared to other molten salts. Furthermore, BMP DCA is flame-resistant. In summary, BMP DCA has proven to be a particularly suitable molten salt in tests.

[0025] In a further embodiment, the coating has a layer thickness in a value range from 10 nanometers to 100 nanometers. The layer thickness is preferably measured along a straight line oriented normal to the surface of the insulating element. The layer thickness can be the value of the distance between a point on the surface of the insulating element and a point on an outer side of the coating, wherein the points are intersection points of the straight line with the surface and the outer side, respectively. The value of the layer thickness is preferably determined as the mean of several layer measurements. The value of the layer thickness can be determined, for example, using a reflectometric or ellipsometric layer measurement. Layer thicknesses from the specified value range have proven particularly advantageous in tests for achieving the aforementioned technical effects.By using a layer thickness within the specified range, a particularly low weight of the system can be achieved, which is particularly advantageous for the use of the system in space-based solar systems or satellites and limits the material costs accordingly.

[0026] In a further embodiment, the coating has a permittivity with a value in a range from 1 to 30, particularly preferably 10 to 30, extremely preferably 20 to 30. In other words, the coating is dielectric. An external electric field which, e.g. originating from external charge carriers, acts on the system, in particular the coating, is weakened by polarization of the dielectric coating. For this purpose, the anions and cations, for example, shift relative to one another as a result of such an electric field. The permittivity is a measure of the electrical polarizability of the coating, whereby the higher the permittivity, the better the coating is suited to compensating or weakening an external electric field. With the help of such a coating, the risk of electrical breakdown is therefore further reduced.The polarization of the coating can be divided into a temperature-independent displacement component of the anions and / or cations, e.g., as a result of an external electric field, and a temperature-dependent orientation component of the anions and / or cations, e.g., as a result of permanent electric dipoles of the anions and / or cations. The permittivity, which is particularly macroscopically measurable, can therefore be used to determine the electrical polarization, particularly microscopic molecular polarization, of the anions and / or cations, e.g., using the Debye equation or the Clausius-Mossotti equation. A molar mass, a permanent dipole moment, and a density of the coating, particularly of the molten salt or of the anions and / or cations, can be predetermined to evaluate the equations and determine the displacement and / or orientation component.

[0027] In a further embodiment, the coating is liquid in an ambient pressure range from 10 nanopascals to 5000 hectopascals. Preferably, the coating is liquid in all value combinations of the stated ambient pressure range and the aforementioned temperature ranges. Particularly preferably, a vapor pressure of the coating, in particular of the molten salt, is less than 10 picopascals, in particular at one or all temperature values ​​of the stated temperature ranges. The physical background corresponds to that disclosed for the temperature range. This has the technical effect that the coating can be used in high vacuum, ultra-high vacuum, in particular in space, as well as at ambient pressure on Earth without evaporating or crystallizing. This is particularly advantageous for the use of the system in space-based solar systems or satellites.

[0028] In a further embodiment, the coating has an electrical conductivity with a value that is greater than or equal to 0.05 S / m. Preferably, the coating has an electrical conductivity with a value from a value range of 0.05 S / m to 3 S / m, particularly preferably from a value range of 1 S / m to 3 S / m. The electrical resistance or the electrical conductivity of the coating is preferably direction-independent, i.e., isotropic, so that the conductivity or the specific resistance can be specified as a scalar value. Preferably, the coating has an electrical conductivity with a value of greater than or equal to 0.05 S / m or a specific resistance with a corresponding reciprocal value in at least one spatial direction. The spatial direction is preferably oriented normal or parallel to the surface of the insulating element, in particular along the straight line used to determine the layer thickness of the coating.Tests have shown that the coating with an electrical conductivity of greater than or equal to 0.05 S / m is particularly advantageous for achieving the effects mentioned in this disclosure.

[0029] In a further embodiment, the system further comprises at least one interface for potential equalization between a point on the coating and a point of lower potential. The interface for potential equalization can be an electrical conductor, e.g. a wire, between a point on the coating and a point of lower potential. The point on the coating can, for example, be a point on the outside of the coating. The point of lower potential can, for example, be a point of the reference potential to which the potential difference to be equalized refers. The point of lower potential can, for example, be arranged on or in a ground body. Such a ground body can, for example, be a base body, in particular a metallic housing, of a satellite. The ground body, in particular the satellite, can be part of the system.The interface thus electrically connects one point of the coating with the point of lower potential. This has the technical effect that charge carriers, especially electrons, that strike the coating can be discharged from the coating via the interface. This allows dangerous potential differences to be balanced out or even prevented from occurring altogether. This advantageously reduces the risk of electrical breakdown.

[0030] Further proposed is a manufacturing method for a system, wherein the system has at least one insulation element with a surface, wherein the manufacturing method comprises the steps:

[0031] - applying a molten salt in at least a partial area of ​​the surface area,

[0032] - Distribute the molten salt in the area so that the molten salt coats the area.

[0033] By means of the proposed manufacturing method, a system can be manufactured which can achieve one or all of the technical effects mentioned in this disclosure.

[0034] The application can be carried out, for example, using a pipette. The partial area of ​​the area particularly encompasses a center point of the area. By applying the molten salt near the center point, the molten salt can be distributed particularly evenly throughout the at least one area.

[0035] Distributing the molten salt preferably involves removing excess molten salt from the surface, particularly from the area to be coated, for example, using a laboratory wipe to remove excess droplets of the molten salt. This ensures that the light refraction at the coating is not negatively affected by droplets, for example. Furthermore, this removal ensures that, for example, during the launch of a satellite into space, no droplets detach from the surface and then cause unforeseen effects elsewhere, particularly on other electrical or electronic components.

[0036] Tests have shown that the previously discussed BMP DCA is a particularly suitable molten salt because it has a viscosity that facilitates spreading. In particular, the spreading step can involve removing excess molten salt until a desired layer thickness is achieved. The excess molten salt is removed, for example, using a laboratory wipe. This has the advantage of allowing a desired, particularly uniform, coating thickness to be achieved.

[0037] Preferably, the manufacturing process further comprises the step:

[0038] Treating at least one area of ​​the surface of the at least one insulation element with ozone,

[0039] Preferably, the treatment step precedes the application and distribution step. Treating at least one area of ​​the surface comprises at least partially surrounding the area with ozone molecules. Ozone decomposes substances or contaminants, particularly organic ones, and thus cleans the area. In particular, treatment with ozone increases the hydrophilicity of the surface, i.e., the ability of the molten salt to form droplets on the surface is reduced by lowering the interfacial energy. This allows a particularly advantageous production of a uniform coating. This simplifies the manufacturing process.

[0040] Ozone is preferably produced using ultraviolet light, i.e., light with wavelengths in the range from 100 nanometers to 380 nanometers, particularly from oxygen. The oxygen can be part of the ambient air, for example. This has the advantage that the ozone can be produced in close proximity to the area and at low cost.

[0041] Alternatively or cumulatively, chemical cleaning using ROA cleaning can also be used to clean the surface, especially prior to the other steps.

[0042] The invention is explained in more detail using exemplary embodiments. The figures show:

[0043] Fig. 1 is a schematic representation of an embodiment of a system according to the invention, and

[0044] Fig. 2 shows a schematic flow diagram of an embodiment of a manufacturing method according to the invention. In the following, like reference numerals designate elements with the same or similar technical features.

[0045] Fig. 1 shows a schematic representation of an embodiment of a system 10 according to the invention, which is suitable for use on a space-based satellite. The system 10 comprises a transparent insulating element 1 formed as a glass plate and a coating 4. The coating 4 comprises an electrically conductive, liquid molten salt, e.g., 1-butyl-1-methylpyrrolidinium dicyanamide.

[0046] An internal volume 11 of the insulation element 1 is delimited by a surface 2. In particular, the surface 2 delimits the internal volume 11 with respect to an environment 100 of the system 10. The surface 2 of the insulation element 1 is composed of at least an upper side 12, a lower side 13, and side surfaces 14, wherein the upper side 12 lies opposite the lower side 12 and the upper and lower sides 12, 13 form a closed surface 2 via the side surfaces 14. The upper side 12 forms the region 3 of the surface 2, which is coated with the coating 4.

[0047] A vertical axis Y of a system-fixed, Cartesian coordinate system is oriented normal to the top side 12. A longitudinal axis X is oriented parallel to the top side 12. A layer thickness 5 of the coating 4 is measured along a straight line parallel to the vertical axis Y between a point in the region 3 of the surface 2 and a point on an outer side 15 of the coating 4, with the points lying on the described straight line. In the embodiment shown in Fig. 1, the layer thickness 5 is, for example, 30 nanometers.

[0048] Furthermore, the system 10 comprises at least one solar cell 20, which is adjacent to the underside 13 of the insulation element 1 and enables a voltage supply for the electrical operation of a satellite when, for example, sunlight, in particular visible sunlight, hits the solar cell.

[0049] The direction of solar radiation is represented by seven parallel arrows. The direction of radiation is oriented opposite to the positive direction of the vertical axis Y. Furthermore, the embodiment shown in Fig. 1 illustrates that charge carriers from the environment 100, in particular electrons, strike the coating as a result of solar wind. This can lead to a local electron excess and / or a local electron deficiency, as explained in detail. In the embodiment shown, a local electron excess is represented by a circular symbol with a minus sign, and a local electron deficiency is represented by a circular symbol with a plus sign.

[0050] Fig. 1 shows, by way of example, a local electron excess on the outer side 15 of the coating 4. This local electron excess is compensated by the anions and cations contained in the molten salt, or the electric field created by the electron excess can be compensated by the anions and cations.

[0051] This is shown in more detail in an enlarged image section 30. Molecules, particularly the anions and cations, of the molten salt can be seen there. The anions NNN are marked with a minus symbol, and the cations N are marked with a plus symbol. As a result of the local electron excess, the molecules align themselves along the field lines of the electric field to be compensated. In particular, the anions NNN move away from the outer side 15 of the coating 4, i.e., from the local electron excess, and the cations N move toward the outer side 15. In this way, a potential difference between the outer side 15 and, for example, the area 3 of the surface 2 of the insulating element 1 can be compensated.

[0052] For this purpose, an interface 6 formed as a wire can electrically connect a point 7 of the coating 4 to a point 50 of lower potential. The point 50 of lower potential can, for example, be a ground body of a satellite that is supplied with power via the solar cells 20.

[0053] Furthermore, the local electron excess can also be (at least) partially compensated by a (molecular) polarization of the coating 4 or the cations N and / or anions NNN. Therefore, a potential difference does not necessarily have to be compensated via the interface 6.

[0054] Fig. 2 shows a schematic flow diagram of an embodiment of a manufacturing method according to the invention for a preferred embodiment of a system 10 according to the invention. The manufacturing method comprises at least the following three steps S1, S2, S3.

[0055] In a first step S1, at least one area 3 of the surface 2 of at least one insulation element 1 is treated with ozone. For this purpose, the insulation element 1 is placed in ambient air, and the area 3 is irradiated with ultraviolet light. This creates ozone, which reduces the ability of droplets to form on the surface, further decomposes contaminants, and thus prepares the area for the application of a molten salt.

[0056] In a further step S2, the molten salt, e.g., BMP DCA, is applied to at least a partial area of ​​area 3 of surface 2 using a pipette. This partial area is located centrally, i.e., around a center point, in area 3. The molten salt applied using the pipette can easily be distributed evenly throughout area 3 starting from this partial area.

[0057] In a further step S3, the molten salt is distributed in region 3. The molten salt can be distributed using, for example, a laboratory wipe. At the end of the manufacturing process, excess molten salt is removed using, for example, a laboratory wipe. This allows the previously explained coating thickness 5 to be achieved.

[0058] Thus, the insulation element 1 is coated with a coating 4, at least in the region 3. Thus, a system 10 according to the invention is produced by means of the manufacturing method.

[0059] List of reference symbols

[0060] 1 insulation element

[0061] 2 Surface

[0062] 3 Area

[0063] 4 Coating

[0064] 5 Layer thickness

[0065] 6 Interface

[0066] 7 point of coating

[0067] 10 systems

[0068] 20 solar cells

[0069] 30 enlarged image section

[0070] 50 point lower potential

[0071] 100 surroundings

[0072] NNN Anion

[0073] N cation

[0074] 51 first step

[0075] 52 further step

[0076] 53 further step

[0077] X Longitudinal axis

[0078] Y vertical axis

Claims

Patent claims System (10), wherein the system (10) has at least one insulation element (1) with a surface (2), wherein at least one region (3) of the surface (2) of the insulation element (1) is at least partially coated with a coating (4), wherein the coating (4) comprises an electrically conductive molten salt, characterized in that the coating (4) is liquid in a temperature range from -150 °C to +350 °C. System (10) according to claim 1, characterized in that the coating (4) is transparent. System (10) according to one of the preceding claims, characterized in that the molten salt is an aprotic ionic liquid. System (10) according to one of the preceding claims, characterized in that the coating (4) has a layer thickness (5) in a value range from 10 nanometers to 100 nanometers.System (10) according to one of the preceding claims, characterized in that the coating (4) has a permittivity with a value in a range from 1 to 30. System (10) according to one of the preceding claims, characterized in that the coating (4) is liquid in an ambient pressure range from 10 nanopascals to 5000 hectopascals. System (10) according to one of the preceding claims, characterized in that the coating (4) has an electrical conductivity with a value that is greater than or equal to 0.05 S / m. System (10) according to one of the preceding claims, characterized in that the system (10) further comprises at least one interface (6) for potential equalization between a point (7) of the coating (4) and a point (50) of lower potential. Manufacturing method for a system (10), wherein the system (10) has at least one insulation element (1) with a surface (2), wherein the manufacturing method comprises the steps: - applying (S2) a salt melt in at least a partial area of ​​the area (3) of the surface (2), - Distributing (S3) the molten salt in the region (3) so that the molten salt coats the region (3), wherein a coating (4) formed in this way is liquid in a temperature range of -150 °C to +350 °C.

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