WO2011020964A1

WO2011020964A1 - Method for ion implantation for producing an anti-icing surface

Info

Publication number: WO2011020964A1
Application number: PCT/FR2010/051608
Authority: WO
Inventors: Florent Bouillon; Thierry Jacques Albert Le Docte
Original assignee: Aircelle
Priority date: 2009-08-19
Filing date: 2010-07-29
Publication date: 2011-02-24
Also published as: FR2949236A1; FR2949236B1

Abstract

The present invention relates to the use of a method for ion implantation into the surface of a material so as to modify the surface properties of said material in order to produce an anti-icing surface, as well as to a method using this technique so as to manufacture a structure having anti-icing surface characteristics.

Description

Ion implantation process for producing an anti-ice surface

The present invention relates to an anti-ice material intended in particular for aeronautical equipment.

An aircraft is propelled by one or more propulsion units each comprising a turbojet engine housed in a tubular nacelle.

Each propulsion unit is attached to the aircraft by a mast located generally under a wing or at the fuselage.

A nacelle generally has a structure comprising an air inlet upstream of the engine, a median section intended to surround a fan of the turbojet, a downstream section optionally housing thrust reverser means and intended to surround the combustion chamber. of the turbojet, and is terminated by an ejection nozzle whose output is located downstream of the turbojet engine.

The air intake comprises, on the one hand, an inlet lip adapted to allow optimal capture to the turbojet of the air necessary to supply the blower and internal compressors of the turbojet, and other on the other hand, a downstream structure to which the lip is attached and intended to properly channel the air towards the blades of the fan.

The assembly is attached upstream of a blower housing belonging to the upstream section of the nacelle.

In flight, depending on the temperature and humidity conditions, ice may form on the nacelle at the outer surface of the air intake lip. The presence of ice or frost changes the aerodynamic properties of the air intake and disturbs the flow of air to the blower.

It should be noted in particular that the formation of ice causes among other things: modification of the mass of the propulsion unit, imbalance between the port and starboard parts and, in the particular case of engine air intakes, the formation of ice blocks susceptible to enter the engine and cause considerable damage.

To overcome the formation of ice or frost, a first solution is to prevent the ice can form on this external surface (anti-icing). A second solution is to leave ice or frost to form on the lip up to a certain thickness and to evacuate it by means making it possible to eliminate the ice or frost thus formed (defrosting).

Anti-icing is necessary especially in the case of engines comprising parts made of composite materials, such as the fan blades: in such a case, it is necessary to eliminate as much as possible any risk of ice entering the engine, the composite materials being sensitive to such shocks.

A first anti-icing solution consists of keeping the external surface exposed to frost at a temperature sufficient to prevent this formation of ice or frost.

This result can be achieved by drawing hot air at the compressor of the turbojet to bring it to the level of the air intake lip and warm the walls. Such a device, however, requires a system of hot air supply ducts between the turbojet engine and the air inlet and a hot air evacuation system at the level of the air intake lip. which increases the mass, drag and fuel consumption of the propulsion unit and is therefore not desirable.

The same result can also be achieved by equipping the external surface with electric heating means which may, for example, be integrated into said wall.

This solution, however, requires the presence of an electrical network at the air inlet and has a degree of control and significant maintenance of the electric heating elements. In addition, the electric heaters must be fed almost continuously during the flight.

In order to protect the heating resistors, it is generally necessary to provide an anti-erosion protection coating, this coating generally not being in adequacy with the required surface quality for the external wall of the air intake lip. In case of partial overlap of the lip, such a coating will cause a detrimental discontinuity to the aerodynamic line of the air inlet. In addition, such a coating contributes to increasing the total thickness of the lip which can lead to a degradation of the acoustic attenuation performance, these being related to the thickness of the air intake lip.

In order to at least partly solve the disadvantages mentioned below, the industrialists have sought to develop anti-corrosion coatings. ice, that is to say having intrinsic physicochemical properties making them unfavorable to the formation of ice, in particular by virtue of their hydrophobic properties.

Indeed, the materials used in aeronautical manufacturing, including composite materials of the carbon / epoxy type, metals and metal alloys including aluminum-based or titanium for example do not have special hydrophobic and anti-ice properties and it is appropriate therefore to cover them with a suitable coating having the desired properties.

The objectives of such coatings are mainly, on the one hand, to limit the thickness of the ice that can be formed and which must generally not exceed a thickness of 2 mm, and secondly, to have a low surface energy between said anti-ice coating and the ice layer so as to promote its detachment and evacuation.

Examples of such coatings are mentioned in particular in the application FR 2 922 522 in the name of the applicant.

The presence of such coatings is however not without drawbacks.

First, any additional layer represents an additional mass and is therefore not desirable.

Then, the application of these layers is difficult and must be performed so as to cause the least possible surface irregularities to maintain optimal aerodynamic properties.

It is also noted that an additional layer always has the risk of delamination and that it must be able to hook sufficiently to the material constituting the structure to be protected.

It should be noted in this connection that the US Aviation Authority (FAA) considers in its AC 20-73A, and in particular Chapter H, that existing products are being eroded and that processed must be certified as if there were no coating.

Indeed, currently, there is no anti-ice coating that meets the criteria of aeronautical certification, namely namely to be able to keep up with the speed of flight of the aircraft (about Mach 0.8) and withstand impacts of sand or other. Currently, it would be necessary to redo the ice layer after each flight. Moreover, the effectiveness of these layers is not constant and varies greatly depending on their erosion, which does not allow to consider them as a reliable equipment to ensure its own function, but only as additional equipment .

The present invention aims at proposing a solution making it possible to overcome the aforementioned drawbacks and consists for this purpose in using an ion implantation process in a surface of a material to modify the surface properties of said material in order to achieve a anti-ice surface.

Ion implantation is a material engineering process.

The ion implantation process is used to implant the ions of a material in another solid, which allows to modify the properties, including mechanical properties.

Among the documents describing ion implantation processes, reference may be made in particular to documents FR 2 876 391, FR 2 896 515, WO 2008/050071, WO 2008/047049, WO 2008/043964, WO 2008/037927, WO 2005 / 085491, FR 2 899 242.

Such a method is widely used to improve the hardness of the implanted material and more generally their resistance to surface aggression (mechanical and / or chemical).

Also known is US 4,948,760 which discloses an ion implantation process for the manufacture of an inorganic glass having strong hydrophobic properties. It should be noted that this document is not specifically oriented towards aeronautical applications. Furthermore, it should be noted that the term "hydrophobicity" refers to the non-wettability of liquid water on a surface, while the term "ice-free" (ice-phobic) is more specific and refers to the non-adherence of the ice, solid water, on said surface.

Document WO 2006/008153 is still known which aims at the manufacture of hydrophobic surfaces and more particularly at the manufacture of panes and aeronautical parts possessing such properties. To do this, the document WO 2006/008153 proposes above all to produce a surface having bumps and depressions according to a particular geometry. In addition, the targeted surfaces are mainly of polymer type and it does not disclose a composite material surface. In addition to the particular geometry provided for, document WO 2006/008153 discloses a complementary treatment by irradiation aimed at reinforcing the hydrophobic sprouts of the treated surface. The anti-ice properties are not affected.

Surprisingly, it has been found that such a process can also be used to modify finer physicochemical properties, and in particular to carry out a surface treatment aimed at rendering the surface treated anti-ice.

According to a first variant, the ion implantation process is used for the implantation of helium ions.

According to a second variant, the ion implantation process is used for the implantation of nitrogen ions.

According to a third variant, the ion implantation process is used for the implantation of oxygen ions.

Advantageously, the ion implantation process uses multi-energy ions. The use of multi-energy ions allows implantations at different depths from the same source and the same acceleration voltage, the energy of the implanted ion being proportional to its charge.

However, it is of course possible to change the implantation depth by varying the ion acceleration voltage without changing the charge of the ion.

The present invention also relates to a method of manufacturing a structure having an anti-ice surface, characterized in that it comprises the step of using an ion implantation process according to the invention.

Advantageously, the manufacturing process comprises several ion implantation steps according to the invention. The succession of implantation steps will make it possible to implant several different types of ions in the treated material and / or the same type of ions at different extraction energies.

Preferably, the ions are implanted in a surface layer of the material in an atomic concentration of between 20 and 40%.

Preferably, the ions are implanted with an energy of between 10 and 200 keV, preferably 10 to 100 keV. Indeed, more the implantation energy is important, plus this same implantation may cause structural damage in the treated surface.

More preferably, the ions are implanted to a depth of between 3 micrometers and 200 micrometers.

The present invention relates to a structure having an anti-ice surface, characterized in that said surface can be obtained by a method according to the invention.

Advantageously, the structure is a turbojet nacelle structure.

Advantageously, the structure is an air intake lip structure.

According to a first preferred embodiment, the structure is mainly made of composite material, in particular of the carbon / epoxy type.

According to a second preferred embodiment, the structure is mainly made from at least one metal alloy, in particular based on aluminum and / or titanium.

Preferably, the treated surface has a wettability such that the value of the contact angle of a water sample is greater than 80 degrees, preferably greater than 90 degrees.

The present invention finally relates to the use of an ion implantation device for the manufacture of a structure according to the invention.

The present invention will be better understood in the light of the following detailed description with reference to the appended drawing in which:

- Figure 1 is a picture of a drop on an epoxy carbon composite material not treated by ion implantation.

FIG. 2 is a photograph of a drop on the composition material of FIG. 1 treated by ion implantation.

As mentioned above, ion implantation is an engineering technique of materials used to implant ions of a material in a solid substrate, thereby changing the physicochemical properties of said substrate. The ion implantation technique is used in the usual way in the manufacture of semiconductor devices to improve the properties of resistance to oxidation, conductivity, hardness, etc. For more details on the technique, which is not specifically part of the present invention, reference may be made in particular to the documents cited above in FR 2 876 391, FR 2 896 515.

, WO 2008/050071, WO 2008/047049, WO 2008/043964, WO 2008/037927, WO 2005/085491, FR 2 899 242.

In general, ion implantation equipment consists of an ion source, a particle accelerator and a chamber for the target substrate.

The particle accelerator uses the electrostatic properties of the ion to increase its energy.

The amount of implanted material, called the dose, is the integral over time of the ionic current.

The electric currents involved in the implanters are of the order of the microampere and therefore allow to implant a relatively small amount of ions. This technique is therefore generally used for small-scale structural changes.

Ion acceleration typically reaches energies ranging from 10 to 500 keV. The acceleration energy will determine the depth of implantation of the ions. Ion implantation therefore generally remains a surface treatment.

It should be noted that an ion source generally produces ions of the atom to be implanted with several levels of ionization. In the case of helium, the ion source will produce He ⁺ and He ²⁺ ions. Consequently, for the same extraction voltage, for example 50 kV, the implantation energy of the He ⁺ ions will be 50 keV while the implantation energy of the He ²⁺ ions will be 100 keV.

The extraction voltage will of course be adjusted according to the desired ionization level and the desired implantation depths of the ions.

As stated, the present invention aims at implementing the ion implantation technique in order to perform an anti-ice treatment on an aeronautical part.

Tests have been carried out in particular on a piece of composite material of the carbon / epoxy type. More specifically, the implanted material bears the reference G803 / 914, that is to say a fabric of carbon fibers at 3000 filaments and satin type 5 (G803), impregnated with epoxy resin class 180 ⁰ C (914).

The material has been tested raw and in a version covered with an anti-UV polyurethane paint for the protection of composite materials type LBYH-142 sold by the company Bolloré-Jival.

Once the material has been processed by ion implantation, a wetting test consisting in measuring the contact angle of a drop of water on said material has been carried out.

The results are summarized in Table 1 below.

Table 1

Control: Composite material not pe int and not treated by implantation.

Painted indicator: Composite material painted but not treated by ion implantation.

Sample A: Unpainted composite material treated with ion implantation. Helium ion implantation, low dose.

Sample B: Unpainted composite material treated with ion implantation. Helium ion implantation, high dose.

Sample C: Composite material painted and treated by ion implantation. Helium ion implantation, low dose.

Sample D: Composite material painted and treated by ion implantation. Helium ion implantation, high dose.

These tests were carried out using an ion extraction voltage of around 50 kV.

It is recalled that the term "dose" refers to the amount of ions implanted in the material and is therefore related to the exposure time of the material in the accelerated ion beam.

The experiment conditions correspond to an ion density of substantially between 10 16 and 10 17 ions per square centimeter. The term "Low dose" therefore corresponds to a brief exposure of the material, namely a few seconds, while a "high dose" corresponds to a longer exposure of the material to the ion beam approaching ten seconds.

However, because of the unusual materials tested for ion implantation processes, the usual techniques (scanning electron microscope in particular) for measuring the concentration of ions implanted in the material have proved to be unsuitable.

The results clearly show an increase in the contact angle, which means an increase in hydrophobic properties.

Thus, it is found that for an unpainted composite surface, the contact angle value goes from about 55 degrees for an untreated surface about 80 degrees after treatment by ion implantation of helium ions.

Figures 1 and 2 are photos of a drop of water on a composite surface as tested, respectively raw and treated by ion implantation. The increase in the contact angle is striking.

However, it should also be noted that implantation with a low concentration of helium ions gives better results than implantation with a high concentration and that there is therefore optimum implantation.

Of course, this optimum depends on the implanted material, the ions implanted in the material, and the implantation energy.

It is also recalled that the implantation energy modifies the implantation depth of the ions. High implantation energy will allow ion implantation deeper into the material while low implantation energy will allow implantation closer to the surface. The optimum implantation depth may depend in particular on the natural hydrophobicity of the material as well as its surface structure.

It will therefore generally be necessary to find a balance between the implantation conditions (material, implanted ions, implantation energy, exposure time, etc.) and the desired hydrophobic anti-ice properties.

More particularly, it will be noted that the layers closest to the surface are naturally more fragile and susceptible to erosion, in particular. Implantation is therefore likely to have a shorter life. This is the reason why it may be interesting to implement ions with several energies so that in case of erosion, the eroded areas discover areas also implanted.

The improvement of the hydrophobic and anti-ice properties is also noted for a painted surface, even if the increase is less, in particular because of the already hydrophobic properties of the polyurethane paint. In addition, it is recalled that the ion implantation is a surface treatment, it is therefore necessary to take into account the thickness of the paint layer.

As for an unpainted material, it will be necessary to predict the erosion of the paint layer and to implant at several depths with several acceleration energies.

In the context of an aeronautical application, it will be possible to manufacture a part and then treat it according to the ion implantation process in order to improve its hydrophobic and anti-ice properties. This method is particularly advantageous for the air inlet lips and leading edges made in particular composite materials.

Although the tests described relate to the implantation of helium ions in a carbon / epoxy composite material possibly coated with polyurethane paint, the type of implanted material is not limited. Similarly, the type of implanted ions is not limited and will depend on the desired hydrophobicity properties as well as the implanted material (sizes of the implanted ion, held in the structure of the implanted material, hydrophobicity of the implanted ion

Those skilled in the art can determine combinations of implanted ion parameters / implanted material / implantation energy / exposure time, by experimentation.

In particular helium ions, nitrogen and oxygen ions may be used in particular.

As previously mentioned, the implantation may be multi-energy in order to implant ions at different depths. Multi-energy implantation can be carried out in one or more implementation steps.

In addition to composite carbon / epoxy materials, the ion implantation process can be implemented with other types of composite materials, but also with metallic and alloy materials, in particular in the aerospace industry, based on aluminum and / or titanium. Although the invention has been described with a particular embodiment, it is obvious that it is in no way limited and that it includes all the technical equivalents of the means described and their combinations if they enter into the scope of the invention.

Claims

1. Using an ion implantation process in a surface of a material to modify the surface properties of said material to provide an ice-free surface.

2. Use according to claim 1, characterized in that the ion implantation process is used for the implantation of helium ions.

3. Use according to claim 1, characterized in that the ion implantation process is used for the implantation of nitrogen ions.

4. Use according to claim 1, characterized in that the ion implantation process is used for the implantation of oxygen ions.

5. Use according to any one of claims 1 to 4, characterized in that the ion implantation process uses multi-energy ions.

6. A method of manufacturing a structure having an anti-ice surface, characterized in that it comprises the step of using an ion implantation process according to any one of claims 1 to 5.

7. Method according to claim 6, characterized in that it comprises several ion implantation steps according to any one of claims 1 to 5.

8. Method according to any one of claims 6 or 7, characterized in that the ions are implanted in a surface layer of the material in an atomic concentration of between 20 and 40%.

9. Method according to any one of claims 6 to 8, characterized in that the ions are implanted with an energy of between 10 and 200 keV, preferably 10 to 100 keV.

10. Method according to any one of claims 6 to 9, characterized in that the ions are implanted to a depth of between 3 micrometers and 200 micrometers.

11. Structure having an anti-ice surface, characterized in that said surface can be obtained by a process according to any one of claims 6 to 10.

12. Structure according to claim 11, characterized in that the structure is a turbojet engine nacelle structure.

13. Structure according to claim 12, characterized in that the structure is an air intake lip structure.

14. Structure according to any one of claims 11 to 13, characterized in that it is mainly made of composite material, in particular carbon / epoxy type.

15. Structure according to any one of claims 11 to 13, characterized in that it is mainly made from at least one metal alloy, in particular based on aluminum and / or titanium.

16. Use of an ion implantation device for the manufacture of a structure according to any one of claims 11 to 16.