The object of the invention a method to produce foam silicates with admixtures having magnetic properties and foam silicate thus produced to be used for production of shields against electromagnetic waves and high energy ionizing radiation. Methods to produce foam silicates or other thermal insulation materials with admixtures having magnetic properties are known in the subject literature. From patent description CN102351496 (A) a method is known to produce decorative, antiseptic, inorganic, waterproof foam with composition containing silicates, aluminates, AI ₂ O ₃ , foaming agent, selected rare earth elements, and a mixture of Fe ₂ 0 ₃ / nO/Mn0 ₂ /Cr ₂ 0 ₃ . Furthermore, in document No. JP9148779A, a solution was disclosed, wherein concrete is mixed with short steel or carbon fibers and then with a powder (ferrite) having the property of absorbing electromagnetic waves of determined frequency. In JP2000143328 (Al), on the other hand, a method was presented, wherein waterglass is mixed with water solution of zinc borate, and the mixture is painted or sprayed upon the material (substrate) . International patent application No. WO2006083796 discloses that the matrix can be a silicate mineral containing halloysite, wherein particles of compounds containing atoms of lanthanides, actinides, cobalt, iron, manganese, chromium or mixtures thereof are dispersed. From patent description PL392889, a method is known to produce porous, insulating foam materials. In general, the method consists in mixing colloidal silica with a foaming agent being the waterglass, in appropriate proportions and then exposing the mixture to microwave radiation. In patent application No. PL399342, on the other hand, a description to produce porous silicate-gypsum materials was disclosed, consisnting in obtaining a silica sol by mixing waterglass and colloidal silica followed by adding a mixture of a bulk material from a group comprising metal sulfates with proper annealing.

The technological problem that the present invention is facing is to provide such method of producing foam silicates with admixtures having magnetic properties that will allow to obtain materials shielding against electromagnetic waves and high energy ionizing radiation whereby the method shall provide for using less active material, which shall directly translate into reduction of costs, and, concurrently, the material itself will be able to assume a number of various forms, allowing production of slabs, shields, panels, tiles, pipes, containers, irregular fillings, etc. Unexpectedly, the technical problems mentioned above have been solved by the present invention.

The first object of the invention is a method to produce foam silicates with admixtures having magnetic properties, comprising the following steps: a) mixing silica with waterglass until a homogeneous sol is obtained, b) drying the sol obtained in step a) to obtain a gel, c) crushing the obtained gel and filling it into a steel form, d) the closed form filled with the crushed gel is heated at the temperature form 300°C to 500°C for more than 1 hour, characterized in that in step a) or in step c) the admixture in the form of ferrite nanopowder is added, selected from a group comprising: Fe ₂ C>3, (Mn, Zn) Fe ₂ 0 ₄ , BaO* 6 Fe ₂ C>3; in step a) fumed silica is used, having bulk density of 150 g/dm ³ or with specific surface area ranging from 300 m ² /g to 380 m ² /g, and sodium waterglass with the density ranging from 1.37 g/ml to 1.45 g/ml and with the silicate modulus ranging from 2.5 to 3.5; in step b) , the drying takes place at the temperature ranging from 70°C to 90°C for 2 to 4 hours. Preferably, the weight ratio of ferrite in the solid part of substrates is from 1.5% to 20% for BaO*6Fe ₂ 0 ₃ and Fe ₂ 0 ₃ , and from 3% to 25% for (Mn, Zn) Fe ₂ 0 ₄ . More preferably, the weight ratio of ferrite in the solid part of substrates is 5% for BaO*6Fe ₂ C>3 and Fe ₂ C>3, and 6% for (Mn, Zn) Fe ₂ 0 ₄ . In another favorable embodiment of the invention, the form in step c) is secured from the inside with aluminum foil or with water solution of kaolin clay. In another favorable embodiment of the invention, heating in step d) comprises several steps, wherein in the first step, the temperature is increased from ambient temperature to 150 °C within 1 hour, in the second step, the temperature is increased up to 250°C within 100 min, and then the form is kept in 250°C for 1 hour, after which it is gradually cooled down to ambient temperature for 2 hours, and in the next step, the temperature is increased to the range of 300°C to 600°C during 3 to 5 hours, and the form is kept at this temperature for 1 hour, next slow cooling to ambient temperature takes place for 3 to 5 hours.

The second object of the invention is a foam silicate with admixtures having magnetic properties, characterized in that it has been produced according to the method defined in the first object of the invention. Favorably, the foam silicate assumes the form selected from the group comprising the following forms: slab, shield, panel, tile, pipe, container, filling openings, culverts, slits, fractures, recesses, and other difficult to access places.

The said method to produce foam silicate with admixtures having magnetic properties enables obtaining materials shielding electromagnetic waves as well as high energy ionizing radiation. The selected type of active materials (ferrite fillers) and their weight ratio in combination with the appropriately selected base matrix material and specific thermal processing conditions provide for obtaining foam silicates with effective attenuation of electromagnetic waves with minimum use of active materials. Furthermore, using the sol-gel technology allows to obtain a material that may assume a number of various forms, including slab, shield, panel, tile, pipe, container, filling openings, culverts, slits, fractures, recesses, and other difficult to access places.

Exemplary embodiments of the invention have been presented in the drawings, wherein fig. 1 represents the absorption chart for silicates with and without admixtures within the frequency range of 1 - 1000 MHz.

Example 1

150g of fumed silica with the bulk density of 150 g/cm ³ and 9.5 g of manganese- z inc ferrite, (Mn, Zn) Fe20 ₄ , nanopowder were added to 300 ml of sodium waterglass with the density of 1.4 g/cm ³ and 30 ml of distilled water, and mixed mechanically. The resulting sol was left for gelation for 2 hours at the temperature of 90°C. After drying, the obtained gel was crushed into pea-size pieces. The so crushed gel was filled into a steel form. The walls of the form were previously protected against material adhesion with water solution of kaolin clay. The form was closed and placed in the furnace. The material was heated in several stages. Stage one, temperature increase from ambient to 150°C, lasted for 1 hour. Stage two, temperature increase up to 250°C lasted for another 100 minutes. Next, the form was kept for 1 hour in 250°C, and within the next 2 hours, it was cooled down to ambient temperature. The following stages consisted in raising the temperature to 450°C within 4 hours and keeping the material in this temperature for another hour. The last stage was cooling down to ambient temperature, lasting 4 hours.

The material obtained that way demonstrates attenuation at the level from 5 to 35 dB/m for radio frequencies of 1-1000 MHz. The characteristics of frequency attenuation was illustrated in Fig. 1. High attenuation values for that kind of material originate from strong magnetic absorption by manganese-zinc ferrite in the 1-1000 MHz frequency range.

Example 2 150g of fumed silica with the bulk density of 150 g/cm ³ and 7.9 g of barium ferrite, BaO*6Fe ₂ C>3, nanopowder were added to 300 ml of sodium waterglass with the density of 1.4 g/cm ³ and 30 ml of distilled water, and mixed mechanically. The resulting sol was left for gelation for 2 hours at the temperature of 90°C. After drying, the obtained gel was crushed into pea-size pieces. The so crushed gel was filled into a steel form lined with thin aluminum foil. The form was closed and placed in the furnace. The material was heated in several stages. Stage one, temperature increase from ambient to 150°C, lasted for 1 hour. Stage two, temperature increase up to 250°C during another 100 minutes. Next, the form was kept for 1 hour in 250°C, and within the next 2 hours, it was cooled down to ambient temperature. The following stages consisted in raising the temperature to 450°C within 4 hours and keeping the material in this temperature for another hour. The last stage was cooling down to ambient temperature, lasting 4 hours. The material obtained that way demonstrates attenuation at the level from 3 to 18 dB/m for radio frequencies of 1-1000 MHz. The characteristics of frequency attenuation was illustrated in Fig. 1. High attenuation values for that kind of material originate from strong magnetic absorption by barium ferrite in the 1-1000 MHz frequency range. Example 3

150g of fumed silica with the bulk density of 150 g/cm ³ and 7.9 g of ferrite, Fe ₂ C>3, nanopowder were added to 300 ml of sodium waterglass with the density of 1.4 g/cm ³ , and mixed mechanically. The resulting sol was left for gelation for 2.5 hours at the temperature of 70 °C. After drying, the obtained gel was crushed into pea-size pieces. The so crushed gel was filled into a steel form lined with thin aluminum foil. The form was closed and placed in the furnace. The material was heated in several stages. The first stage, i.e. temperature increase from ambient to 150°C, lasted 1 hour. Stage two, temperature increase up to 250°C lasted for another 100 minutes. Next, the form was kept for 1 hour in 250°C, and within the next 2 hours, it was cooled down to ambient temperature. The following stage consisted in raising the temperature to 350°C within 200 minutes and keeping the material in this temperature for another hour. The last stage was cooling down to ambient temperature, lasting 3.5 hours.

The material obtained that way demonstrates attenuation at the level from 1 to 17 dB/m for radio frequencies of 1-1000 MHz. The character of the attenuation dependency on frequency was illustrated in Fig. 1. As can be seen from Fig. 1., admixing with ferrite does not amplify the attenuation of the obtained foam in the full frequency spectrum, except for general resonance close to 700 MHz. However, that increase in attenuation is connected with the average pore size in the foam .