Multilayer radar absorbing materials containing metallurgical waste materials

Abstract

The invention relates to multi-layer radar absorbing materials containing metallurgical waste materials to be used to hide strategic military buildings such as hangars, warehouses and observation towers from satellite and air-based radar imaging systems.

Description

[0001] MULTILAYER RADAR ABSORBING MATERIALS CONTAINING METALLURGICAL WASTE MATERIALS

[0002] Field of the Invention

[0003] The invention relates to multi-layer radar absorbing materials containing metallurgical waste materials to be used to hide strategic military buildings such as hangars, warehouses and observation towers from satellite and air-based radar imaging systems.

[0004] State of the Art

[0005] Radar absorbing materials (RAM) are structures that aim to absorb the electromagnetic energy incident on them. RAMs are used for different military systems including land, sea and air. The absorption performance of RAMs is desirable for a wide frequency band. Multilayer radar absorbing material (MLRAM) structure is preferred to realize the absorption of electromagnetic (EM) waves in a wide frequency band. In MLRAM, the order of the materials, their thickness, and the electrical and magnetic properties of the materials are the parameters that affect the absorption ability. The design of MLRAM is generally carried out using carbon-containing materials such as graphite and carbon fiber, composite ferritic materials with magnetic properties, and conductive materials such as polymers or metals. However, synthesizing these materials and obtaining their electrical and magnetic properties in a wide frequency band and then obtaining the optimum structure is a challenging problem. In addition, since the isolation of areas such as hangars, ammunition depots, and shelters with anechoic room designs can only be achieved by using large-sized, radar-absorbing brick-shaped structures, more material is required. Therefore, using cost-effective materials is an important factor. A brick-shaped radar absorbing structure was designed by (Kharber et aL, 2017) using biomass material that absorbs in a part of the X band (8.2-12.4 GHz) frequency band.

[0006] However, there is no MLRAM study obtained from metallurgical wastes for the 2-18 GHz frequency band. 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.

[0007] Purpose of the Invention

[0008] The invention aims to solve the above-mentioned negativities and it is inspired by the current situation

[0009] The main purpose of the invention is to provide a new high value-added product, multilayer radar absorbing material (ML RAM), for the 2-18 GHz frequency band, by using metallurgical wastes containing precious metals.

[0010] One purpose of the invention is to provide a multi-layer radar absorbing material (MLRAM) that can be applied as a large-sized radar absorbing coating in the isolation of areas such as hangars, ammunition depots, shelters, and anechoic room designs used for military purposes.

[0011] In order to fulfil the above-described purposes, the invention is a multi layer radar absorbing material comprising metallurgical waste materials and comprises more than one layer selected from the following material layers;

[0012] (i) Zinc leach waste slip casting sintered-silica

[0013] (ii) Zinc leach waste dry sintered-silica with 40% iron additive

[0014] (iii) Iron-steel continuous casting scale dry sintered-silica

[0015] (iv) Copper converter slag, dry sintered-silica with 50% iron additive

[0016] (v) brass sawdust waste dry sintered with 50% iron additive

[0017] (vi) brass sawdust waste dry sintered with 40% iron additive

[0018] (vii) Copper converter slag dry sintered-silica with 20% iron addition.

[0019] According to an embodiment of the invention, the multi-layer radar absorbing material consists of the following layers, respectively:

[0020] (i) Zinc leach waste slip casting sintered-silica

[0021] (ii) Zinc leach waste dry sintered-silica with 40% iron additive (iii) Iron-steel continuous casting scale dry sintered-silica

[0022] (iv) Copper converter slag, dry sintered-silica with 50% iron additive

[0023] (v) brass sawdust waste Dry sintered with 50% iron additive.

[0024] According to an embodiment of the invention, the multi-layer radar absorbing material consists of the following layers, respectively:

[0025] (i) Zinc leach waste slip casting sintered-silica

[0026] (ii) Zinc leach waste dry sintered-silica with 40% iron additive

[0027] (iii) Iron-steel continuous casting scale dry sintered-silica

[0028] (iv) brass sawdust waste dry sintered with 40% iron additive

[0029] (v) Copper converter slag, dry sintered-silica with 50% iron additive.

[0030] According to an embodiment of the invention, the multi-layer radar absorbing material consists of the following layers, respectively:

[0031] (i) Zinc leach waste slip casting sintered-silica

[0032] (ii) Zinc leach waste dry sintered-silica with 40% iron additive

[0033] (iii) Iron-steel continuous casting scale dry sintered-silica

[0034] (iv) Copper converter slag, dry sintered-silica with 50% iron additive

[0035] (v) brass sawdust waste, dry sintered with 50% iron additive

[0036] (vi) Copper converter slag dry sintered-silica with 20% iron addition.

[0037] The multi-layer radar absorbing material which is the subject of the invention comprises a structure which provides at least 90% absorption of the reflected wave signal in both polarizations (TE and TM) at 2-18 GHz frequency and 0-60 incidence angle. The multi layer radar absorbing material in question is used to hide strategic military buildings such as warehouses and observation towers from satellite and air-based radar imaging systems.

[0038] 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.

[0039] Figures to Help Understanding the Invention

[0040] Figure 1 is the general view of the MLRAM (multi-layer radar absorbing material) structure which is the subject of the invention.

[0041] Figure 2(A-G) are the change graphs of the dielectric (g> ') and magnetic

[0042] ( properties of the layers (Materials 1 -7) used in the MLRAM structure which is the subject of the invention, corresponding to the 2-18 GHz frequency band.

[0043] Description of References

[0044] PEC: A perfect conductor that fully reflects electromagnetic waves

[0045] MLRAM: Multi-layer radar absorbing material (1 ,2,3... M layers)

[0046] Detailed Description of the Invention

[0047] In this detailed description, the preferred embodiments of the inventive multilayer radar absorbing material are described by means of examples only for clarifying the subject matter.

[0048] The invention relates to multi-layer radar absorbing materials containing metallurgical waste materials to be used to hide strategic military buildings such as hangars, warehouses and observation towers from satellite and air-based radar imaging systems. Within the scope of this invention, MLRAM has been introduced for the 2-18 GHz frequency band using metallurgical wastes containing precious metals. Recycling of industrial wastes containing precious metals has become very important and necessary for both economic and environmental reasons. In the proposed invention, MLRAM structures were designed by direct sintering of metallurgical wastes without using cost-effective and time-consuming procedures such as material synthesis. Firstly, plaster molds were manufactured in sizes suitable for electrical measurement kits and the shaping process was carried out using waste materials and two basic methods: slip casting and dry additive-free casting. Shaped and dried powder samples were baked (sintered) at appropriate temperatures (700 °C for 3 hours) to increase the strength of the materials and to maintain their shape for a long time. At this stage, iron powder was added to increase the absorption performance of some metallurgical wastes. Additionally, certain amounts of colloidal silica were added as a binder to ensure the materials adhere to each other. Since colloidal silica exhibits crystallization properties at high temperatures due to its structure, a more uniform structure can be obtained by ensuring that the materials between the layers in the multi-layered structure adhere to each other.

[0049] Seven different materials were used in the proposed invention. The first of these is zinc leach waste, a by-product of hydrometallurgical processes used in zinc production. Zinc ore is dissolved with sulfuric acid (leaching) to obtain zinc sulphate solution. Impurities in this solution are removed by precipitation with lime or other chemicals. The solid waste remaining after the leaching process is classified as zinc leach waste. The leach waste supplied by Qinkur enterprise, which produces zinc-lead; mainly consist of the following phases: Lead(ll) sulfate PbSO4, Calcium sulfate dihydrate CaSO4.2H2O, Zinc ferrite ZnFe2O4, Zinc sulfate heptahydrate ZnS04.7H2O, lron(ll,lll) oxide (Magnetite) Fe3O4. The major elements it contains are 10,7% zinc, 6,1% iron, 12,9% lead, 4,9% Si, 17,7% S, 1 ,2% Mg. Qinkur leach waste was used in this study in two different forms: slip casting sintered-silica and dry sintered-silica with 40% iron additive. The slip casting sintered-silica structure was obtained by shaping the suspension casting (silp casting) diluted Qinkur leach waste in a plaster mold, then adding 26% by weight silica (colloidal silica liquid) and sintering at 700 °C for 3 hours. The dry sintered-silica with 40% iron additive structure was obtained by adding 40% by weight iron powder to Qinkur leach waste and mixing it, then adding 15% by weight silica (colloidal silica liquid) in a plaster mold and sintering at 700 °C for 3 hours. Brass is an alloy of copper and zinc, and a significant amount of shavings and waste is produced during its processing. Chips are created during cutting, turning or milling of brass parts. These chips, which contain high amounts of copper (Cu) and zinc (Zn), were created from waste collected from metalworking machines and workplaces. The majority of brass sawdust waste consists of CuZn alloy, and it also contains some oxides, especially SiO2. The major elements in its structure are 40,4% Cu, 22,8% Zn, 9,29% Fe, 5,14% Si, 2,55% Na, and 0,89% Al. In this study, brass sawdust waste was mixed with 40% iron powder and 50% iron powder by weight and was used by sintering at 700 °C for 3 hours in a plaster mold, and no silica was added.

[0050] Another waste used in this study is copper converter slag. Copper converter slag, which is produced as a by-product in the conversion phase of pyrometallurgical copper production processes, is of the fayalite (Fe2SiO4) type and contains oxides such as FeO, Fe2O3, SiO2, CaO, AI2O3 and metals such as Cu, Co, Zn, Ni in different structures. The major chemical composition of converter slag is 44,3% Fe, 11 ,1% Si, 4,45% Cu, 3,39% Zn, 1 ,09% S, 0,87% Al, 0,65% Ca. The converter slag used in this study was supplied by Eti Bakir A.§., which produces copper from ore in our country, and was used as dry sintered-silica with 20% and 50% iron additions. Iron powder was added to the converter slag separately at 20% and 50% by weight, mixed and placed in a plaster mold. In the mold, 24,4% by weight of colloidal silica was added to the sample with 20% iron additive and 24,75% by weight of colloidal silica was added to the sample with 50% iron additive, and the samples were sintered at 700 °C for 3 hours and used.

[0051] Continuous casting scale, a waste of iron and steel production facilities, is formed during the continuous casting process of molten steel. During this process, iron oxides, calcium oxide, silica and magnesium oxide formed as molten steel is continuously poured from a mold form slag layers. This waste, whose composition generally depends on the chemical components of the steel and the casting conditions, mostly has a homogeneous structure and a glass-like appearance. This waste, which has a typical dense and hard structure, was obtained from Eregli Demir Qelik Fabrikalan T.A.§. and its chemical structure consists of the following elements: 54,6% Fe, 16,6% Ca, 5,54% Si, 2,2% Na, 0,44% Mg. Erdemir continuous casting scale was used in this study by mixing it with 33.4% colloidal silica liquid by weight and then sintering it in a plaster mold at 700 °C for 3 hours (dry sintered-silica). In the invention, multi-layer radar absorbing materials were obtained using the materials introduced in detail above. The two-stage Artificial Bee Algorithm (Yigit & Duysak, 2019) was used to determine the order of the materials used and to optimize the thickness of each material layer.

[0052] Multilayer radar absorbing material (MLRAM) samples with dimensions of 10cmx10cm were produced for the 2-18 GHz frequency band using metallurgical wastes. Commercial examples can be applied as large-scale radar absorber coatings in the insulation of areas such as hangars, ammunition depots, shelters, and anechoic room designs used for military purposes.

[0053] The basic view of the MLRAM structure is given in Figure 1 . The MLRAM consists of a layered material with a certain thickness and a perfect conductor (PEC). In this invention, metallurgical waste materials given in Table 1 were used for the design of the MLRAM. The changes in the dielectric (£ properties of the materials corresponding to the 2-18 GHz frequency band are given in Figure 2.

[0054] Table 1 . List of Materials Obtained from Metallurgical Wastes Since the reflection coefficient in MLRAM structures varies according to the incident angle and polarization of the EM wave, the design of the structure that can minimize the reflection coefficient of the targeted EM wave at all incident angles (0°> 6^” )and for all polarizations in the targeted 2-18 GHz frequency band can only be achieved by optimization algorithms. The optimum order and thickness of the materials in the MCRSM designs were determined by the two-stage artificial bee algorithm (Yigit & Duysak, 2019).

[0055] The highest reflection coefficient values according to the thickness and incident angle of each material in Example 1 obtained after optimization are given in Table 2. The first sample MLRAM consists of 5 layers and its total thickness is 18.22 mm. The reflection coefficient for TE polarization varies between -6.9205 and -13.177, while for TM it varies between -13.177 and -26.6214.

[0056] Table 2: Reflectance values obtained from sample 1

[0057] Sample 2 consists of materials numbered 1 , 2, 3, 6 and 5 (see Table 1) and has a total thickness of 17.27 mm. The highest reflection coefficient values for each material according to its thickness and incident angle are given in Table 3. The reflection coefficient for TE polarization varies between -6.9205 and -13.177, while for TM it varies between -13.177 and -26.6157. Table 3: Reflectance values obtained from sample 2

[0058] Sample 3 consists of materials numbered 1 , 2, 3, 4, 5 and 7 (see Table 1 ) and has a total thickness of 18.5 mm. The highest reflection coefficient values for each material according to its thickness and incident angle are given in Table 4. The reflection coefficient for TE polarization varies between -6.9205 and -13.177, while for TM it varies between -13.177 and -26.6641.

[0059] Table 4: Reflectance values obtained from sample 3

[0060] In Figure 1 , the incident electromagnetic wave hits the MLRAM and travels through the layers until it hits the perfect conductor PEC, resulting in complete reflection. The signal reflected back by the PEC travels through the layers and leaves the radar absorber. At 2-18 GHz frequency and 0-60sincidence angle, at least 90% absorption of the back- reflected wave signal is achieved in both polarizations (TE and TM). REFERENCES

[0061] Kharber, N. N., Damit, D. S. A., Abdullah, H., Ali, F. Z., Kasim, N. M., Razali, A. R., Rahim, N. A., Endut, M. Z., & Taib, M. N. (2017). Characteristic of biomass percentage in cement brick composites microwave absorber. 2017 International Conference on Electrical, Electronics and System Engineering (ICEESE), 21-26. https: / / doi.org / 10. 1109 / ICEESE.2017.8298390

[0062] 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(8), 3306-3317. https: / / doi.org / 10. 1109 / TMTT.2019.2919574

Claims

CLAIMS1. A multi layer radar absorbing material containing metallurgical waste materials, characterized by comprising; more than one layer selected from the following material layers:(i) Zinc leach waste slip casting sintered-silica(ii) Zinc leach waste dry sintered-silica with 40% iron additive(iii) Iron-steel continuous casting scale dry sintered-silica(iv) Copper converter slag, dry sintered-silica with 50% iron additive(v) Dry sintered brass sawdust waste with 50% iron additive(vi) Dry sintered brass sawdust waste with 40% iron additive(vii) Copper converter slag dry sintered-silica with 20% iron additive.

2. The multi layer radar absorbing material according to claim 1 , characterized by comprising the following layers, respectively:(i) Zinc leach waste slip casting sintered-silica(ii) Zinc leach waste dry sintered-silica with 40% iron additive(iii) Iron-steel continuous casting scale dry sintered-silica(iv) Copper converter slag dry sintered-silica with 50% iron additive,(v) Dry sintered brass sawdust waste with 50% iron additive.

3. The multi layer radar absorbing material according to claim 1 characterized by comprising the following layers, respectively:(i) Zinc leach waste slip casting sintered-silica(ii) Zinc leach waste dry sintered-silica with 40% iron additive(iii) Iron-steel continuous casting scale dry sintered-silica(iv) Dry sintered brass sawdust waste with 40% iron additive(v) Copper converter slag dry sintered-silica with 50% iron additive,.

4. The multi layer radar absorbing material according to claim 1 , characterized by comprising the following layers, respectively:(i) Zinc leach waste slip casting sintered-silica (ii) Zinc leach waste dry sintered-silica with 40% iron additive(iii) Iron-steel continuous casting scale dry sintered-silica(iv) Copper converter slag dry sintered-silica with 50% iron additive,(v) Dry sintered brass sawdust waste with 50% iron additive(vii) Copper converter slag dry sintered-silica with 20% iron addition.

5. The multi layer radar absorbing material according to claim 1 to 4, characterized by comprising a structure which provides at least 90% absorption of the reflected wave signal in both polarizations (TE and TM) at 2- 18 GHz frequency and 0-60'4incidence angle.

6. Use of multi layer radar absorbing material according to one of claims 1 to 5 to conceal strategic military buildings such as hangars, warehouses and observation towers from satellite and air-based radar imaging systems.

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