Thin film coated multilayer radar absorbent textile material

Abstract

The invention relates to a thin-film coated multilayer radar absorbing textile material for use in the military defence industry, electronic device technology and wearable technology, which is lightweight, thin, relatively flexible and mobility independent of polarisation in a wide bandwidth range.

Description

[0001] DESCRIPTION

[0002] THIN FILM COATED MULTILAYER RADAR ABSORBENT TEXTILE MATERIAL

[0003] Field of the Invention

[0004] The invention relates to radar absorber materials.

[0005] In particular, the invention relates to ALD thin film coated multilayer radar absorber textile materials designed for use in the military defence industry, electronic device technology and wearable technology, etc.

[0006] State of the Art

[0007] Radar absorbing materials are metamaterials specially designed to suppress reflected electromagnetic energy by converting the electric and / or magnetic fields of the incident wave into heat. Along with artificially engineered metamaterials, which have been widely used in the design of radar absorbing materials in the past (Tirkey & Gupta, 2019) a large number of nanomaterials (magnetic materials, carbon materials, magnetic carbon composites) have recently emerged and used in radar absorbers by controlling their size, shape, internal structure and composition

[0008] For example, the radar absorbing material described in patent application TR2020 / 19524 consists of a resin-soaked layer of graphene and / or carbon nanotubes between layers containing carbon fibre-based fibres.

[0009] Despite the great progress made in conventional electromagnetic wave absorber nanomaterials (Fe, FesO4, graphene, graphite, carbonnanotube) in terms of magnetic loss or dielectric loss, high density and poor absorption, as well as other disadvantages such as complex synthesis, difficulties in the processes and mass production of nanostructures have severely hampered their development and large-scale utilisation.

[0010] The fabrics obtained in the study titled ‘Graphene Based Wideband Electromagnetic Absorbing Textiles at Microwave Bands’ are light, flexible and washable with 5-10% reflection loss (D'Aloia, Bidsorkhi, De Bellis, & Sarto, 2022) In the article ‘Broadband and Tunable High- Performance Microwave Absorption of an Ultralight and Highly Compressible Graphene Foam’ published by Huang et al. (2015), the design of RSM in the form of an ultralight and highly compressible graphene foam with a bandwidth of 60.5 GHz, covering 93.8% of the overall bandwidth, is described. Although the foam form generally provides high performance, the fact that its shape cannot be changed and is not suitable for flexible areas of use is a disadvantage.

[0011] In another study, a Nacre-Inspired layered radar absorber was designed by combining 2D MXene (d-Ti 3 C 2 T x ) with 1-D cellulose nanofibre composite paper (Cao, et al., 2018). The developed layered structure causes multiple internal reflections, absorption of EM waves and energy dissipation (Xiaojun, Xiaoyu, Ronghai, & D., 2020).

[0012] In another study, hollow Mxene spheres were formed in graphene foam and a core-shell structure was designed (Li, et al., 2018). Mxene, one of the commonly used 2D materials, is produced as a result of a number of difficult processes and is costly.

[0013] The absorption capability of the structures designed in the core-shell structure is high, but it is possible to provide the performance increased by these methods through internal reflections in the multilayer structure.

[0014] In general, the mechanical properties of conventional radar absorbers, such as their large size, heavy weight, inability to stretch and limited mobility, are not useful; while the difficulty in production processes and high cost of newly developed nanomaterial-based composite materials are the obstacles to their widespread use.

[0015] In the literature, there is no microwave absorber study with Atomic Layer Deposition (ALD) thin film technique. ALD has a controlled layer deposition mechanism at nanometre scale at low temperatures and has advantages over other thin film coating methods in terms of this sensitivity (Akyildiz et al., 2021).

[0016] Due to ALD, thin fabrics can be coated with different dielectric materials in the desired thickness and the thickness of these coatings can be in the desired dimensions with the desired precision. When any fabric is coated with ALD, for example zinc oxide, titanium dioxide or any other material, the electrical and magnetic permeability of the fabric varies depending on the coating material and thickness. Thus, materials with different electrical permeability are obtained with different configurations. While these materials mostly show the ability to absorb at a single frequency, their performance in polarization and angle of incidence of the electromagnetic wave is low. However, a multilayer radar absorber (MRA) can be designed by combining different textile materials with different electrical permeability in an optimal order and this MRA can provide an effective absorption capability in a very wide band, at different polarisations and at different incidence angles.

[0017] There are many studies in the literature on MRA design with different materials. While the majority of these studies are based on designing with virtual materials that are not actually produced, some studies are based on MRA materials designed with chemical powder or resin type materials in the literature (Yigit and Duysak 2019, Yigit and Duysak 2021). However, these studies are always aimed at designing MRA with hard and rigid materials, and there are no studies on MRA design with flexible and light materials such as fabric.

[0018] For example, the MRA developed by Aselsan in the utility model numbered TR2015 / 07628 consists of glass fabric, fiber-reinforced frequency selective surface and resin and foam filled filling layers. Since the proposed structure does not consist entirely of fabrics, the flexibility capability is not at a sufficient level, the frequencies at which it is effective are not specified, and the bandwidth and polarisation efficiency are also not given.

[0019] In the utility model numbered CN212555299U, a radiation protective structure is presented by combining different fabrics with a multi-layered structure. However, since the utility model is not an electromagnetic absorber, it has a radiation-blocking structure and contains conductive layers, it has the ability to reflect electromagnetic energy back and does not have the ability to absorb it.

[0020] As a result due to the abovementioned disadvantages and the insufficiency of the current solutions regarding the subject matter, a development is required to be made in the relevant technical field.

[0021] Purpose of the Invention

[0022] The present invention aims to solve the abovementioned disadvantages by being inspired from the current conditions. The main purpose of the present invention is to produce an ALD thin film coated multilayer radar absorbing textile material that is light, thin, relatively flexible and has the ability to move, independent of polarization and angle of incidence in a wide band range. Being able to hide from electromagnetic waves is very important today, both in civilian and military areas. With the invention, it will be possible to hide military vehicles and ammunition, which are critical in military warfare strategies, from radar waves. The increase in the use of electronic devices and the inclusion of 5G technology in our lives in the future will cause the exposure to electromagnetic waves in daily life to reach the highest levels. The developed radar absorbing textile materials can be used for a wide range of applications such as military radar camouflage, wearable technologies, protective clothing of health personnel, protective clothing of personnel working under intense electromagnetic fields such as high voltage lines, and protection of patients and babies in sensitive conditions from electromagnetic fields. In addition, electronic devices can be protected from electromagnetic interference. As a result, the invention will be used in the fields of military defence industry, electronic device technology and wearable technology etc.

[0023] In order to fulfil the abovementioned purposes, the present invention is a thin-film coated multilayer radar absorbing textile material for use in the military defence industry, electronic device technology and wearable technology, which is lightweight, thin, relatively flexible and mobility independent of polarisation in a wide bandwidth range.

[0024] Preferred embodiments of the invention comprise at least one fabric layer coated with dielectric material using the ALD thin film technique. Preferred embodiments of the invention further comprise at least one pure fabric layer.

[0025] The fabric mentioned here is preferably at least one fabric selected from cotton fabric, polyester fabric, glass fabric, and said dielectric material is preferably zinc oxide and / or titanium dioxide.

[0026] Preferred embodiments of the invention comprise at least one pure cotton fabric layer and / or at least one pure polyester fabric layer and at least one glass fabric layer coated with zinc oxide by ALD thin film technique and / or at least one glass fabric layer coated with titanium dioxide by ALD thin film technique. In preferred embodiments of the invention, the total textile material thickness is below 40 mm, preferably below 35 mm.

[0027] In preferred embodiments of the invention, the thickness of the coating made with the Atomic layer deposition thin film technique is between 1-100 nm and preferably below 90 nm.

[0028] Preferred embodiments of the invention provide at least 90% absorption in the frequency band between 2-8 GHz, regardless of polarization and angle between 0 and 40 degrees.

[0029] Preferred embodiments of the invention are between 0 and 40 degrees, the maximum reflection coefficient in TM polarization is less than -10 dB, and the maximum reflection coefficient in TE polarization is less than -8 dB.

[0030] In preferred embodiments of the invention, the glass fabric layer coated with zinc oxide by ALD thin film technique has a coating thickness of 88.9 nm, obtained with ALD recipe 0.1 / 60 / 0.1 / 60 and ALD cycle number 500.

[0031] In preferred embodiments of the invention, the glass fabric layer coated with zinc oxide with the ALD thin film technique contains a coating thickness of 54,11 nm, obtained with ALD recipe 0.2 / 60 / 0.2 / 60 and ALD cycle number 250.

[0032] In preferred embodiments of the invention, the glass fabric layer coated with titanium dioxide with the ALD thin film technique contains a coating thickness of 9,75 nm, obtained with ALD recipe 00.05 / 60 / 0.03 / 60 and ALD cycle number 200.

[0033] A preferred embodiment of the invention comprises at least one pure cotton fabric layer, at least one glass fabric layer coated with titanium dioxide by ALD thin film technique, at least one glass fabric layer coated with zinc oxide by ALD thin film technique, respectively.

[0034] A preferred embodiment of the invention comprises at least one pure cotton fabric layer, at least one glass fabric layer coated with titanium dioxide by ALD thin film technique, at least one glass fabric layer coated with zinc oxide by ALD thin film technique, at least one glass fabric layer coated with titanium dioxide by ALD thin film technique, respectively. A preferred embodiment of the invention comprises at least one pure cotton fabric layer, at least one pure polyester fabric layer, at least one glass fabric layer coated with titanium dioxide by ALD thin film technique, respectively.

[0035] The structural and characteristic features of the present invention will be understood clearly by the following figures and the detailed description made with reference to these figures and therefore the evaluation shall be made by taking these figures and the detailed description into consideration.

[0036] Figures to Help Understand the Invention

[0037] Figure 1 : Graphs showing the electrical and magnetic permeability values of the fabric layers (a-e: fabric numbers 10-50) used in the invention against frequency.

[0038] Figure 2: A general representation of the multilayer radar absorber structure.

[0039] Description of the References

[0040] 10 Cotton fabric layer

[0041] 20 Polyester fabric layer

[0042] 30 Glass fabric layer coated with zinc oxide by ALD thin film technique

[0043] 40 Glass fabric layer coated with titanium dioxide by ALD thin film technique

[0044] 50 Glass fabric layer coated with zinc oxide by ALD thin film technique (different thickness)

[0045] Detailed Description of the Invention

[0046] In this detailed description, the preferred embodiments of the inventive multilayer radar absorbing textile material are described by means of examples only for clarifying the subject matter.

[0047] The invention relates to a thin-film coated multilayer radar absorbing textile material for use in the military defence industry, electronic device technology and wearable technology, which is lightweight, thin, relatively flexible and mobility independent of polarisation in a wide bandwidth range.

[0048] In this invention, for the first time, multilayer radar absorbing (MRA) textile materials have been produced by combining dielectric materials and thin film coated fabric materials in the appropriate order by ALD technique. MRA designs can consist of different number of layers. Each layer can contain any of the fabric types such as pure cotton, polyester, glass fabric, etc., as well as fabrics coated with ALD in different thicknesses.

[0049] In the present invention, textile fabrics have been selected as the main material in order to provide instantaneous radar protection and to ensure that a radar absorber can be used repeatedly for different purposes in different environments and times, and also because they are relatively flexible and mobile. In this way, wearable and flexible designs will be realized.

[0050] In the present invention, coatings of different thicknesses were produced with ALD and these materials were optimized with the artificial bee colony algorithm. Thus, three different radar absorber textile samples that are light, thin, relatively flexible and capable of movement at an angle of incidence of 0-40*, independent of polarization in a wide band range, have been presented.

[0051] The fabrics forming the layers of Designs 1 , 2 and 3, which are the preferred examples of the invention, are listed in Table 1 and the coated fabrics are explained and numbered.

[0052] As shown in Figure 2, in the designed multilayer absorber structure, the first layer corresponds to the air surface, that is, the outer surface, while the last layer corresponds to the conductive surface (PEC). For example, the glass fabric layer coated with zinc oxide by ALD thin film technique (30), which is the third layer in Design 1 , corresponds to the conductive surface, while the glass fabric layer coated with titanium dioxide by ALD thin film technique (40), which is the fourth layer in Design 2, corresponds to the conductive surface.

[0053] In creating composite structures, stitching or binder / adhesive joining methods can be used to hold the fabrics together. ALD method is a vapour coating method and a film is formed by the reaction of chemical vapors with the surface of the substrate material. This results in the coating of all fibers and all surfaces in the material when textile underlays are used. For this reason, both surfaces of the fabric coated with a dielectric thin film with the ALD used in the invention perform the same.

[0054] The fabric structures of the layers belonging to Design 1 consist of three layers, respectively; pure cotton fabric layer (10) that has not undergone any chemical treatment and has a plain weave knitting structure, ALD titanium dioxide coated glass fabric (40) in plain weave knitting structure, ALD zinc oxide coated glass fabric (30) in plain weave knitting structure and its total thickness is 24.5 mm.

[0055] The fabric structures of the layers belonging to Design 2 consist of four layers, respectively; pure cotton fabric layer (10) that has not undergone any chemical treatment and has a plain weave knitting structure, ALD titanium dioxide coated glass fabric (40) in plain weave knitting structure, ALD zinc oxide coated glass fabric (50) in plain weave knitting structure and ALD titanium dioxide coated glass fabric (40) in plain weave weave structure and its total thickness is 23,8 mm.

[0056] The fabric structures of the layers belonging to Design 3 consist of three layers, respectively; pure cotton fabric layer (10) that has not undergone any chemical treatment and has a plain weave knitting structure, Pure polyester fabric (20) without any chemical treatment with 2 / 1 twill weave structure, ALD titanium dioxide-coated glass fabric (40) in plain weave structure and its total thickness is 35.0 mm.

[0057] For the ALD cycle, the feeding time of the gases to the reactor for dosage and cleaning is also important. An ALD process basically consists of the steps “Precursor 1 / Cleaning 1 / Precursor 2 / Cleaning 2”. Zinc oxide and titanium dioxide coatings of glass fabrics were made with the ALD device described in detail in the article ‘Antibacterial Activity of Photodeposited Ag Nanoparticles on Cotton Fibres Enabled by Atomic Layer Deposition’ published by Akyildiz et al. (2022) is used in this study (Akyildiz, Aydemir Yilmaz, & Diler, 2022). The recipes for different doses and cleaning times (s) at different times with a reactor temperature 150°C are given in Table 1 .

[0058] In Table 1 , the ALD recipe and ALD cycle of fabrics coated with ALD and the resulting total thickness are given. Accordingly, each item given between four different / in the ALD prescription corresponds to the Precursor 1 / Cleaning 1 / Precursor 2 / Cleaning 2 steps, while the number of ALD cycles indicates how many times this recipe is applied consecutively. For example, for the glass fabric layer coated with zinc oxide by ALD thin film technique (30), zinc oxide gas was first introduced into the reactor for 0.1 seconds and then nitrogen was pumped into the environment for 60 seconds and vacuum cleaning was performed at the same time, as presented in Table 1 . Then, 0.1 pure water vapor (H2O) was released into the environment and a 60-second cleaning procedure was followed. Since this process corresponds to a single cycle, this cycle was repeated 500 times in the production of the said fabric, and at the end, a fabric with a thin film coating of 88.9 nm thickness was obtained. The complex electrical (s) and magnetic (p) permeability values of 5 different fabrics obtained according to Table 1 are plotted in Figure 1 .

[0059] Table 1 : List of fabric types and ALD process characteristics used for a sample design Table 2: Reflectance values obtained from sample designs

[0060] The general MRA structure of the designs created within the scope of the invention is given in Figure 2. As shown in the figure, the structure, which can consist of M layers, is mostly designed to be covered on a conductor. In the M-layer structure, the thickness and electrical conductivity of each layer can be different from each other and can come together in different orders. Since the reflection coefficient will vary according to the angle of incidence and polarisation of the incident electromagnetic wave, the design of the structure that can minimise the reflection coefficient in all targeted frequency bands, at all targeted angles and for all polarisations can only be achieved by optimisation algorithms. The MRA designs described here were optimised with the optimisation method published by Yigit and Duysak (Yigit & Duysak, Determination of Optimal Layer Sequence and Thickness for Broadband Multilayer Absorber Design Using Double-Stage Artificial Bee Colony Algorithm, 2019) and three different multilayer radar absorbers were presented.

[0061] As can be seen from the tables and graphs, 3 different designs were realised with only five different fabrics, two of which were untreated pure fabrics. Two of the designs have 3 layers and one has four layers and the thinnest design is 23.8 mm while the thickest is 35 mm.

[0062] Three different multilayer radar absorbing textile designs produced with ALD have been tested to minize the reflected wave by providing at least 90% absorption in the frequency band between 2-8 GHz, regardless of polarisation and angle between 0 and 40 degrees.

[0063] In an application as shown in Figure 2, the electromagnetic wave to which the inventive multilayer radar absorber textile material is exposed interacts with the multilayer structure and travels between the layers coated with ALD and dielectric material and is fully reflected by the perfect electrical conductor (PEC). In real applications, materials that do not provide full reflection can also be coated with radar absorbers, but the preferred embodiments of the invention are designed for extreme cases. The signal reflected back by the PEC bounces back through the layers and leaves the radar absorber. At 2-8 GHz frequency and 0-40 incidence angle, at least 90% absorption of the back-reflected wave signal is achieved in both polarizations (TE and TM).

[0064] REFERENCES

[0065] Akyildiz, H. I., Aydemir Yilmaz, B., & Diler, S. (2022). Antibacterial Activity of Photodeposited Ag Nanoparticles on Cotton Fibers Enabled by Atomic Layer Deposition. Fibers and Polymers, 2769-2779.

[0066] Akyildiz, H. I., Diler, S., & Islam, S. (2021). Evaluation of TiO 2 and ZnO atomic layer deposition coated polyamide 66 fabrics for photocatalytic activity and antibacterial applications. Journal of Vacuum Science & Technology A, 39(2), 022405. https: / / doi.Org / 10.1116 / 6.0000761

[0067] Cao, W.-T., Chen, F.-F., Zhu, Y.-J., Zhang, Y.-G., Jiang, Y.-Y., Ma, M.-G., & Chen, F. (2018). Binary Strengthening and Toughening of MXene / Cellulose Nanofiber Composite Paper with Nacre-Inspired Structure and Superior Electromagnetic Interference Shielding Properties. ACS-Nano, 4583-4593.

[0068] D’Aloia, A. G., Bidsorkhi, H., De Bellis, G., & Sarto, M. (2022). Graphene Based Wideband Electromagnetic Absorbing Textiles at Microwave Bands. IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, 710-719.

[0069] Diler, S. (2021 , February 5). ALD FILM KAPLI POLiAMiD KUMA§LARIN ANTiBAKTERiYEL ETKiNLiKLERiNiN ARA§TIRILMASI. Bursa, Turkiye.

[0070] Li, X., Yin, X., Song, C., Han, M., Xu, H., Duan, W., . . . Zhang, L. (2018). Self-Assembly Core-Shell Graphene-Bridged Hollow MXenes Spheres 3D Foam with Ultrahigh Specific EM Absorption Performance. Advanced Functional Materials.

[0071] Tirkey, M. M., & Gupta, N. (2019). Electromagnetic absorber design challenges. IEEE Electromagnetic Compatibility Magazine, 59-65.

[0072] Xiaojun, Z., Xiaoyu, C., Ronghai, Y., & D., S. G. (2020). Electromagnetic microwave absorption theory and recent achievements in microwave absorbers. Carbon, 606-623.

[0073] Yigit, E., & Duysak, H. (2019). Determination of Optimal Layer Sequence and Thickness for Broadband Multilayer Absorber Design Using Double-Stage Artificial Bee Colony Algorithm. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, 67.

[0074] Yigit, E., & Duysak, H. (2021). Fully optimized multilayer radar absorber design using multi-objective abc algorithm. International Journal of Engineering and Geosciences, 136-145.

Claims

CLAIMS1. A thin-film coated multilayer radar absorbing textile material for use in the military defence industry, electronic device technology and wearable technology, which is lightweight, thin, relatively flexible and mobility independent of polarisation in a wide bandwidth range.

2. The textile material according to Claim 1 , characterized by comprising; at least one fabric layer coated with a dielectric material using the ALD thin film technique.

3. The textile material according to Claim 1 , characterized by comprising; at least one pure fabric layer.

4. The textile material according to Claim 1 , characterized by comprising the following; at least one pure cotton fabric layer (10), at least one pure polyester fabric layer (20), and at least one glass fabric layer coated with zinc oxide by ALD thin film technique (30, 50), at least one glass fabric layer coated with titanium dioxide by ALD thin film technique (40).

5. The textile material according to Claim 1 , characterized in that, it provides at least 90% absorption in the frequency band between 2-8 GHz, regardless of polarization and angle between 0 and 40 degrees.

6. The textile material according to Claim 1 , characterized in that, the total textile material thickness is less than 40 mm, preferably less than 35 mm.

7. The textile material according to Claim 1 , characterized in that, the thickness of the coating made with the ALD thin film technique is between 1-100 nm, preferably below 90 nm.

8. The textile material according to Claim 1 , characterized in that, between 0-40 degrees, the maximum reflection coefficient is less than -10 dB In TM polarization, and the maximum reflection coefficient is less than -8 dB in TE polarization.

9. The textile material according to Claim 4, characterized in that, the glass fabric layer coated with zinc oxide by ALD thin film technique (30) comprises a coating thickness of 88,9 nm, obtained with ALD recipe 0.1 / 60 / 0.1 / 60 and ALD cycle number 500.

10. The textile material according to Claim 4, characterized in that, the glass fabric layer coated with zinc oxide with the ALD thin film technique (50) comprises a coating thickness of 54,11 nm, obtained with ALD recipe 0.2 / 60 / 0.2 / 60 and ALD cycle number 250.

11. The textile material according to Claim 4, characterized in that, the glass fabric layer coated with titanium dioxide by atomic layer deposition thin film technique (40) comprises a coating thickness of 9.75 nm, obtained with ALD recipe 00.05 / 60 / 0.03 / 60, ALD cycle number 200.

12. The textile material according to Claim 4, characterized by comprising; the following layers respectively:■ at least one pure cotton fabric layer (10), at least one glass fabric layer coated with titanium dioxide by ALD thin film technique (40), at least one glass fabric layer coated with zinc oxide by ALD thin film technique (30),13. The textile material according to Claim 4, characterized by comprising the following layers respectively:- at least one pure cotton fabric layer (10), at least one glass fabric layer coated with titanium dioxide by ALD thin film technique (40), at least one glass fabric layer coated with zinc oxide by ALD thin film technique (50), at least one glass fabric layer coated with titanium dioxide by ALD thin film technique (40),14. The textile material according to Claim 4, characterized by comprising the following layers respectively: at least one pure cotton fabric layer (10),- at least one pure polyester fabric layer (20), at least one glass fabric layer coated with titanium dioxide by ALD thin film technique (40).

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