Liquid metal and application thereof, cathode material and micro cathode arc thruster

Abstract

The invention provides liquid metal and application thereof, a cathode material and a micro cathode arc thruster, and belongs to the technical field of alloy materials. The liquid metal provided by the invention comprises a liquid gallium alloy and metal particles, the mass ratio of the liquid gallium alloy to the metal particles is (3.78-4.62): (0.3-6); the metal particles comprise one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles. The surface tension of the liquid gallium alloy is reduced and the viscosity of the liquid gallium alloy is improved by adopting the metal particles, the metal particles can overcome slight vibration, are adsorbed on the surface of the metal feeding pipe and do not flow willfully, the metal particles serve as a cathode working medium of the micro-cathode arc thruster, stable work can be achieved, and the service life of the thruster is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and in particular relates to liquid metal and application thereof, cathode material and micro cathode arc thruster. Background Art

[0002] Micro cathode arc thrusters have become an ideal type of electric propulsion for micro-nano satellites due to their advantages such as micro power, miniaturization, low voltage, high efficiency, high specific impulse, wide range of controllability, low cost, long life and high reliability. They can be used for tasks such as orbit maintenance and formation flying of micro-nano satellites.

[0003] The power processing unit (PPU) of the micro-cathode arc thruster adopts an inductive energy storage method and controls the charging and discharging of the inductor through an insulated gate bipolar transistor (IGBT). During each discharge, the high voltage provided by the PPU breaks through the conductive carbon film on the insulating ceramic to produce a discharge channel between the anode and cathode. After that, an arc is formed between the anode and cathode, and the arc burns the metal cathode to produce a large amount of plasma.

[0004] In the prior art, solid metal (titanium, copper, tantalum, molybdenum) is used as cathode working fluid. During the discharge process of the micro cathode arc thruster, the thruster with solid metal as cathode working fluid relies on a spring to supply the cathode working fluid. However, due to the size of the thruster, the overall length of the cathode working fluid is generally less than 10 cm, and the effective working length is even lower. Therefore, there is a problem of insufficient cathode working fluid, and the morphology of the cathode working fluid will change, resulting in abnormal termination of the thruster operation. Therefore, the life of the thruster is often limited by the change of the cathode working fluid carried by it in a single space mission. Summary of the invention

[0005] The object of the present invention is to provide a liquid metal and its application, a cathode material and a micro-cathode arc thruster. The liquid metal provided by the present invention has lower surface tension and higher viscosity. As the cathode working fluid of the coaxial micro-cathode arc thruster, it can be adsorbed on the cathode feed pipe without flowing arbitrarily and deforming, thereby realizing stable operation of the thruster.

[0006] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0007] A liquid metal comprises a liquid gallium alloy and metal particles; the mass ratio of the liquid gallium alloy to the metal particles is 3.78-4.62:0.3-6; the metal particles comprise one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles.

[0008] Preferably, the liquid gallium alloy comprises, by mass percentage, 66-100% Ga, 0-25.0% In and 0-13.5% Sn.

[0009] Preferably, the particle size of the metal particles is ≤1 μm.

[0010] The present invention also provides the use of the liquid metal described in the above technical solution in cathode materials or heat-conducting materials.

[0011] The present invention also provides a cathode material, including a cathode feeding device and a cathode working fluid; the cathode working fluid is the liquid metal described in the above technical solution.

[0012] The present invention also provides a micro cathode arc thruster, comprising an anode, an insulating ceramic, a cathode and a magnet, characterized in that the cathode is the cathode material described in the above technical solution;

[0013] The anode, insulating ceramic, cathode and magnet are riveted to each other through screws and studs.

[0014] Preferably, the micro-cathode arc thruster is a coaxial micro-cathode arc thruster.

[0015] Preferably, the magnet is a neodymium iron boron magnet.

[0016] Preferably, the micro-cathode arc thruster further comprises a gasket arranged between the cathode and the magnet; the number of the gaskets is 1 to 3.

[0017] Preferably, it also includes an insulating bracket connected to the anode through a keyway relationship; and a magnet bracket connected to the insulating bracket through screws and bolts.

[0018] The present invention provides a liquid metal, including a liquid gallium alloy and metal particles; the mass ratio of the liquid gallium alloy to the metal particles is 3.78-4.62:0.3-6; the metal particles include one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles. In the present invention, the liquid gallium alloy will be adsorbed on the surface of the titanium particles, and the liquid gallium alloys will adsorb each other due to the greater attraction between their atoms, thereby forming a phenomenon in which the liquid gallium alloy is adsorbed on the surface of the metal particles, and the liquid gallium alloy acts as a "binder" to connect the metal particles together, and the metal particles with irregular appearance and the large particles with rough surfaces formed after the adsorption of the liquid gallium alloy form a mass of metal mixture with extremely rough surfaces, and this rough characteristic makes the mixture have strong adhesion to the metal wall (such as the cathode feeding device). And because of this bonding relationship, the liquid gallium alloy becomes an "adhesive" rather than a main body, which greatly destroys its surface tension and can overcome slight vibrations and adsorb on the surface of the metal feed tube without flowing arbitrarily. As the cathode working fluid of the micro-cathode arc thruster, it can achieve stable operation and increase the service life of the thruster. In addition, the low viscosity of pure liquid gallium alloy makes it impossible to adsorb on the solid surface, and there are small bubbles between the two, which will limit the thermal conductivity of pure liquid gallium alloy. The use of metal particles can increase the contact area between the liquid metal and the solid wall of the present invention, thereby increasing the thermal conductivity performance.

[0019] The present invention also provides a micro cathode arc thruster. The present invention controls the position and size of the magnetic field by controlling the number of gaskets and the number of magnets. Using more gaskets can make the strong magnetic field area farther away from the thruster outlet, which is beneficial to obtaining a plasma plume with a better focus. Using fewer gaskets can make the strong magnetic field area closer to the thruster outlet, which is beneficial to making the plasma plume more divergent. Using more magnets can enhance the strength of the magnetic field and further adjust the plasma plume, thereby effectively regulating the working performance of the thruster and the service life of the micro cathode arc thruster. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 This is a morphology diagram of the liquid metal obtained in Example 1 of the present invention;

[0022] Figure 2 This is the morphology of the gallium-indium-tin alloy;

[0023] Figure 3 An exploded view of the coaxial cathode micro-cathode arc thruster structure of the present invention;

[0024] Figure 4 It is an assembly diagram of the coaxial cathode micro-cathode arc thruster of the present invention;

[0025] Figure 5 The structural components of the coaxial cathode micro-cathode arc thruster of the present invention are shown in FIG. 1, wherein 1 is a nut, 2 and 3 are insulating ceramic brackets, 4 is a copper anode, 5 is insulating ceramic, 6 is a cathode feed pipe, 7 is a gasket, 8 is a magnet, and 9 is a magnet bracket;

[0026] Figure 6 This is the assembly diagram of the solid metal micro cathode arc thruster. DETAILED DESCRIPTION

[0027] The present invention provides a liquid metal, comprising a liquid gallium alloy and metal particles; the mass ratio of the liquid gallium alloy to the metal particles is 3.78-4.62:0.3-6; the metal particles comprise one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles.

[0028] In the present invention, unless otherwise specified, all raw materials are commercially available products well known to those skilled in the art.

[0029] In the present invention, the metal particles include one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles. In a specific embodiment, they can be titanium particles or copper particles. The mass ratio of the liquid gallium alloy and the metal particles is 3.78-4.62:0.3-6. In a specific embodiment, it can be 4.62:0.5, 3.78:2, 3.78:0.9, 4.2:1, 3.78:2, 4.0:3.0 or 4.5:0.5.

[0030] In the present invention, the liquid gallium alloy comprises, by mass percentage, Ga 66-100%, In 0-25.0% and Sn 0-13.5%. In a specific embodiment, it may be Ga 68.5%, In 21.5%, Sn 10%, or Ga 75%, In 25%.

[0031] In the present invention, the particle size of the metal particles is ≤1 μm, and in a specific embodiment, it can be 0.3 μm, 0.5 μm or 0.8 μm.

[0032] The present invention has no special limitation on the preparation method of the liquid metal. In a specific embodiment, the liquid metal is obtained by mixing liquid gallium alloy and metal particles.

[0033] In the present invention, the mixing temperature is room temperature, and in a specific embodiment, it can be 30°C, 33°C or 35°C; the air pressure is ≤1atm, and in a specific embodiment, it can be 1atm or 0.8atm; the speed is 60-100r / min, and in a specific embodiment, it can be 70r / min or 80r / min; the time is 30-60min, and in a specific embodiment, it can be 40min or 50min; the mixing instrument is a planetary mixer.

[0034] The present invention also provides the use of the liquid metal described in the above technical solution or the liquid metal prepared by the preparation method described in the above technical solution in cathode materials or thermal conductive materials.

[0035] In the present invention, the thermally conductive material may be a thermally conductive paste of an electronic device; the electronic device may be a CPU, a photovoltaic module, a solar panel or a household electronic device.

[0036] The present invention also provides a cathode material, including a cathode feeding device and a cathode working fluid; the cathode working fluid is the liquid metal described in the above technical solution.

[0037] In the present invention, the cathode feeding device may be tubular and made of stainless steel.

[0038] The present invention also provides a micro cathode arc thruster, comprising an anode, an insulating ceramic, a cathode and a magnet, wherein the cathode is the cathode material described in the above technical solution;

[0039] The anode, insulating ceramic, cathode and magnet are riveted to each other through screws and studs.

[0040] In the present invention, the micro cathode arc thruster is a coaxial micro cathode arc thruster.

[0041] In the present invention, the anode may be a copper anode; the conductivity of the anode is 15.5×10 6 S / m, thermal conductivity is 100~200W / (m·K).

[0042] In the present invention, the insulating ceramic may be a boron nitride ceramic; the resistivity of the insulating ceramic is 10 14 Ω·cm; density is 2.3g / cm 3 , Mohs hardness is 10, and surface roughness (Ra) is 0.05.

[0043] In the present invention, the surface of the insulating ceramic is coated with a conductive film; the conductive film is a conductive film formed by carbon particles; the thickness of the conductive film is 0.1 to 0.3 mm.

[0044] In the present invention, the magnet is a neodymium iron boron magnet (NdFeB52).

[0045] The present invention also includes an insulating bracket connected to the anode via a keyway relationship, and a magnet bracket connected to the insulating bracket via screws and bolts. The insulating bracket is made of ceramic or plastic, and the deformation temperature of the plastic is 200°C.

[0046] In the present invention, the coaxial micro-cathode arc thruster further comprises a magnet; the magnet is a neodymium iron boron magnet.

[0047] In the present invention, the micro cathode arc thruster further comprises a gasket arranged between the cathode and the magnet; the number of the gaskets is 1 to 3; the material of the gasket is high temperature resistant (300° C.) plastic.

[0048] The present invention controls the position and size of the magnetic field by controlling the number of gaskets and the number of magnets. When no gaskets are used, the strong magnetic area is flush with the thruster outlet; using more gaskets can make the strong magnetic field area farther away from the thruster outlet, which is beneficial to obtaining a plasma plume with a better focus; using fewer gaskets can make the strong magnetic field area closer to the thruster outlet, which is beneficial to making the plasma plume more divergent; using more magnets can enhance the strength of the magnetic field, thereby achieving adjustment of the plasma plume, thereby effectively regulating the performance of the thruster.

[0049] In order to further illustrate the present invention, the liquid metal and its application, cathode material and micro cathode arc thruster provided by the present invention are described in detail below in combination with the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] Gallium-indium-tin liquid metal with a mass ratio of 4.2:1 and Ti metal particles with a diameter of 1 μm were placed in a planetary mixer and stirred at 100 rpm / min for about 30 minutes to obtain liquid metal.

[0052] Figure 1 This is a morphology diagram of the liquid metal obtained in Example 1 of the present invention. Figure 2 is the morphology of the gallium-indium-tin alloy. Figures 1-2 It can be seen that compared with the gallium, indium, and tin liquid metal before mixing, the surface of the mixed liquid metal is extremely irregular, which means that its surface tension is lower, and it can be spread flat on the surface of the solid metal, which means that it has greater viscosity.

[0053] The properties of the liquid metal, gallium metal, gallium-indium alloy and gallium-indium-tin alloy obtained in Example 1 of the present invention were tested. The electrical conductivity and thermal conductivity of the liquid metal of the present invention were calculated based on the ratio of the raw materials used. The melting and boiling points of the liquid metal were based on the gallium-indium-tin liquid metal. After mixing, the solid particles inside the liquid metal did not affect its physical state. The surface tension and viscosity were measured by a Nayne cup. The test results are shown in Table 1.

[0054] Table 1 Performance test results of liquid metal, gallium metal, gallium-indium alloy and gallium-indium-tin alloy obtained in Example 1

[0055]

[0056] according to Figure 3 The exploded view shown, Figure 4 The assembly diagram shown and Figure 5 The structural components shown in the figure assemble a coaxial cathode micro-cathode arc thruster structure, wherein 1 is a nut, 2 and 3 are insulating ceramic brackets, 4 is a copper anode, 5 is insulating ceramic, 6 is a cathode feed pipe, 7 is a gasket, 8 is a NdFeB magnet, and 9 is a magnet bracket; the copper anode, insulating ceramic, cathode and magnet are riveted to each other through screws and studs, and the insulating ceramic bracket and the anode are connected to each other through a keyway relationship; the magnet bracket is connected to the insulating bracket through screws and bolts.

[0057] It can be seen from the results in Table 1 that the liquid metal provided by the present invention has lower surface tension and greater viscosity, and can be well adsorbed on the solid wall surface to achieve stable operation in aerospace missions.

[0058] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A liquid metal, characterized in that: It comprises liquid gallium alloy and metal particles; the mass ratio of the liquid gallium alloy to the metal particles is 3.78-4.62:0.3-6; the metal particles comprise one or more of titanium particles, silver particles, gold particles, copper particles and aluminum particles.

2. The liquid metal according to claim 1, characterized in that: Calculated by mass percentage, the liquid gallium alloy comprises: Ga 66-100%, In 0-25.0% and Sn 0-13.5%.

3. The liquid metal according to claim 1, characterized in that: The particle size of the metal particles is ≤1 μm.

4. Use of the liquid metal according to any one of claims 1 to 3 in cathode materials or thermal conductive materials.

5. A cathode material, characterized in that: It comprises a cathode feeding device and a cathode working medium; the cathode working medium is the liquid metal as described in any one of claims 1 to 3.

6. A micro cathode arc thruster, comprising an anode, an insulating ceramic, a cathode and a magnet, characterized in that: The cathode is the cathode material according to claim 5; The anode, insulating ceramic, cathode and magnet are riveted to each other through screws and studs.

7. The micro cathode arc thruster according to claim 6, characterized in that: The micro cathode arc thruster is a coaxial micro cathode arc thruster.

8. The micro cathode arc thruster according to claim 6, characterized in that: The magnet is a neodymium iron boron magnet.

9. The micro cathode arc thruster according to claim 6, characterized in that: The micro cathode arc thruster further comprises a gasket arranged between the cathode and the magnet; the number of the gaskets is 1 to 3.

10. The micro cathode arc thruster according to claim 6, characterized in that: It also includes an insulating bracket connected to the anode through a keyway relationship; and a magnet bracket connected to the insulating bracket through screws and bolts.

Images