Coating method for energetic material and coating system for coating energetic material using said type of coating method

Abstract

The invention relates to a coating method for energetic material (12), in particular in a vacuum. The energetic material (12) is coated by chemical or physical vapor deposition. The coating material (16) is electrically conductive and/or hydrophobic or hydrophilic. The energetic material (12) is shaped as grains and/or pellets and/or is in the form of a powder.

Claims

1-11. (canceled)

12. A coating method for energetic material (12), which is in the form of grains, pellets and/or a powder, with a coating material (16), characterized in that the coating material (16) a) is hydrophobic or hydrophilic and/or b) is electrically conductive, wherein the coating is carried out by plasma-enhanced chemical vapor deposition, wherein the energetic material is coated in a vacuum chamber (28) which is rotated about an axis of rotation running in the horizontal direction during vapor deposition.

13. The coating method according to claim 12, characterized in that the energetic material (12) comprises an explosive, a pyrotechnic composition and/or a propellant.

14. The coating method according to claim 12, characterized in that the energetic material (12) has an explosion heat of more than 2500 kJ/kg, a burn rate of more than 30 m/s and/or a Trauzl number of more than 30 cm.sup.3.

15. The coating method according to claim 12, characterized in that the energetic material (12) comprises black powder, nitroglycerin and/or nitrocellulose.

16. The coating method according to claim 12, characterized in that the coating material (16) contains halogens; monomers containing at least one halogen; silicon; monomers containing silicon; silazanes, in particular hexamethyldisilazane; siloxanes; silanes; fluorine; hydrocarbon; in particular saturated and/or unsaturated hydrocarbon; aliphatic hydrocarbon; aromatic hydrocarbon; derivatives of aliphatic hydrocarbon and/or aromatic hydrocarbon, in particular containing heteroatoms; oxygen; conductive polymers; alkanes, in particular fluoroalkanes; cycloalkanes; mixtures containing alkanes and halogens, alkenes, mixtures containing alkenes and halogens; hexamethyldisiloxane; fluoroacrylates; octafluorocyclobutane; ethine; parylene; paraffin; octene; hexafluoroethane; acrylic acid and/or combinations of the aforementioned substances.

17. The coating method according to claim 12, characterized in that the coating takes place at a pressure of a maximum of 10 millibars and/or a temperature of a maximum of 130° Celsius.

18. The coating method according to claim 12, characterized in that the plasma is ignited by an electrode (40) in the vacuum chamber (28) which is coated in particular with an electrical insulator (38), preferably glass or ceramics.

19. The coating method according to claim 17, characterized in that the coating is applied with a thickness of more than 0.1 nanometers, in particular a maximum thickness of two micrometers.

20. The coating system (10) for coating energetic material (12) according to claim 19 with a vacuum chamber (28) which has an inlet (30) for gas, characterized in that the vacuum chamber (28) is rotatable by a shaft (24) arranged on the vacuum chamber (28) and running in the horizontal direction and in that there is coated energetic material in the vacuum chamber (28).

21. The coating system according to claim 19, characterized in that the chamber comprises an electrode (40) coated with an electrically insulating material (38), in particular glass or ceramics.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further features and advantages of the invention are apparent from the following detailed description of embodiments of the invention with reference to the accompanying drawings, which show details essential to the invention. The various features can each be implemented individually for themselves or for a plurality of combinations of any kind in variants of the invention. The features shown in the drawings are shown in such a way that the special features according to the invention can be made dearly visible.

[0041] In the drawings:

[0042] FIG. 1 shows a coating system for coating energetic material:

[0043] FIG. 2 shows a parylene system for coating energetic material.

EMBODIMENTS OF THE INVENTION

[0044] In a first embodiment of the invention, black powder in the form of pellets was chosen as the hygroscopic propellant. Before coating, a water drop of one microliter of pure water has a water contact angle of 23.2° five seconds after being placed on the surface of the pellet. The water drop is completely absorbed in 15 seconds.

[0045] After being coated with hexamethyldisiloxane for ten minutes, a water drop of one microliter of pure water has a water contact angle of 118.4° five seconds after being placed on the surface of the pellet. Four minutes after placement, the water contact angle is 105.7°.

[0046] In a second embodiment of the invention, black powder in the form of pellets is coated with 1-octene for 10 minutes. A water drop of one microliter of pure water has a water contact angle of 122.7° five seconds after being placed on the surface of the pellet. Four minutes after placement, the water contact angle is 91.2°.

[0047] In a third embodiment of the invention, black powder in the form of pellets is coated with perfluoroacrylate (PFAC 8) for 20 minutes. A drop of one microliter of pure water has an almost superhydrophobic water contact angle of 135.5° five seconds after being placed on the surface of the pellet. Four minutes after placement, the water contact angle is 111.0°.

[0048] In a fourth embodiment of the invention, a propellant with nitrocellulose in smokeless powder in a 9×19 mm cartridge is coated twice with hexamethyldisiloxane for 20 minutes each time.

[0049] In a fifth embodiment of the invention, a propellant with nitrocellulose in smokeless powder in a 9×19 mm cartridge is coated twice with 1-octene for 20 minutes each time.

[0050] In a sixth embodiment of the invention, a propellant with nitrocellulose in smokeless powder in a 9×19 mm cartridge is coated twice with perfluoromonomer 8 or perfluoroacrylate 8 (PFAC 8) for 20 minutes each time.

[0051] In a seventh embodiment of the invention, a propellant with nitrocellulose in smokeless powder in a 9×19 mm cartridge is coated twice with nitrogen trifluoride (NF.sub.3) for 20 minutes each time.

[0052] In FIG. 1, a coating system 10 for coating energetic material 12 is shown. The coating system 10 comprises a gas container 14 in which there is a coating material 16 that is evaporated into a coating gas, in particular by a heating element 18 outside the gas container 14. A first fluidic connection 20a leads from the gas container 14 to a fluidically conductive first rotary vacuum feedthrough 22a. The first rotary vacuum feedthrough 22a engages around a shaft 24 which is rotatable about an axis of rotation running in the horizontal direction 23. The shaft 24 is attached to opposite sides of a vacuum chamber 28 which can be rotated by the shaft 24. The coating gas flows in the form of a gas flow 29 through the fluidically conductive shaft 24 and enters the vacuum chamber 28 through a coating gas inlet 30.

[0053] The vacuum chamber 28 is closed by a cover 32. The energetic material 12 that is to be coated, for example black powder, as well as plasma (not shown) are located in the vacuum chamber 28. To generate the plasma, a voltage source as a plasma generator 34 is connected via a first slip ring 36a on the shaft 24 to an electrode 40 in the vacuum chamber 28, which electrode is provided with an insulating layer 38, here in the form of ceramics. A pressure measuring device 42 measures the pressure in the vacuum chamber 28.

[0054] The molecules of the coating gas are dissociated by the plasma. The energetic material 12 is coated with components of the dissociated coating gas. As a result of the rotation of the vacuum chamber 28 with the horizontally running shaft 24, the energetic material 12 is moved up and down in the vacuum chamber 28 in the vertical direction 44. The energetic material 12 is in particular in the form of grains. By moving the grains in the vertical direction 44, the grains do not collect in one place (“at the bottom” of the vacuum chamber) for a long time and can all be coated.

[0055] The shaft 24 is rotated by a motor 46 connected to a gear 48. The gear 48 transmits the rotary movement of the motor 46 through a chain 50 to a second slip ring 36b which engages around the shaft 24.

[0056] The remaining components of the coating gas that are not used in the coating flow through a coating gas outlet 52 which is opposite the coating gas inlet 30. The coating gas then flows through a second rotary vacuum feedthrough 22b. The remaining components of the coating gas then exit the coating system 10 through a second fluid connection 20b and a vacuum pump 54. The coating system 10 is controlled by a controller 56. The vacuum pump 54 and the controller 56 are preferably located at a distance di of more than 1 meter, preferably more than three meters, from the other components of the coating system 10.

[0057] In FIG. 2, a parylene system 58 for coating energetic material 12 is shown as the coating system 10. The parylene system 58 comprises a parylene vaporizer 60 for vaporizing parylenes 62 at approximately 250° C. A tubular fluidic connection 64 leads from the parylene vaporizer 60 through a pyrolysis tube 66 to a rotating drum 68. The parylene emerges as a parylene gas flow 70 from the parylene vaporizer 60 and flows through the pyrolysis tube 66, which is designed in particular as a resistance heater.

[0058] When flowing through the pyrolysis tube 66, the parylene is broken down into monomers at about 650° C. The parylene then flows through the fluidic connection 64 into the rotating drum 68, in which energetic material 12 is located. The energetic material 12 is circulated by rotating the rotating drum and coated with the parylene at about 20° C. The remaining parylene monomers are conveyed out of the rotating drum through a second fluidic connection 72 and polymerized in a cold trap 74 of the parylene system at about −196° C. For this purpose, the cold trap 74 comprises liquid nitrogen (LN.sub.2) 76. The parylene is then conveyed out of the cold trap 74 by a vacuum pump 78 of the parylene system 58.

[0059] Taking into account the drawings, the invention relates in summary to a coating method for energetic material 12, in particular in a vacuum. The energetic material 12 is coated by chemical or physical vapor deposition. The coating material 16 is electrically conductive and/or hydrophobic or hydrophilic. The energetic material 16 is shaped as grains and/or pellets and/or is in the form of a powder. The coating is particularly preferably carried out in a plasma. The coating is more preferably carried out in the form of a plasma polymerization. Energetic materials are understood to mean in particular explosives and pyrotechnic compositions, propellants, fuels and/or battery materials. It must be taken into account that a coating is understood to mean not only the accumulation of a layer, but also the transformation of a layer. For example, in the case of a plasma treatment of smokeless powder with NF.sub.3, there is no NO deposition, but a corridor addition of the surface. The aim of the treatment is to increase or decrease the burn rate of the energetic material, to increase the conductivity of the electrical material to protect against electrical discharges, to minimize nitrogen oxides to protect against corrosion, to achieve protection against plagiarism and/or to improve lubrication, to make the energetic material hydrophobic to protect against corrosion or to achieve better miscibility of the energetic material with water by hydrophilizing.