CONSTRUCTION MATERIAL MIXTURE FOR SHIELDING AGAINST ELECTROMAGNETIC RADIATION

Abstract

A construction material mixture contains a dry mass of 10 to 98 wt. % carbon and 2 to 70 wt. % binding agent. The construction material mixture further comprises 1 to 80 wt. % loose particles, wherein the surface of the loose particles is at least partially coated with an electrically conductive material.

Claims

1-14. (canceled)

15: A construction material mixture, comprising: a dry mass, comprising the following components 10 to 95 wt. % carbon, and 2 to 70 wt. % binding agent, 1 to 80 wt. % of loose particles, wherein the wt. % is based on the weight of the dry mass, wherein a total weight of components in the construction material mixture adds up to 100 wt. %, wherein the surfaces of the loose particles are at least partially coated with an electrically conductive material, and wherein a coated part of the surfaces of the loose particles is advantageously on average between 50 and 90%.

16: The construction material mixture according to claim 15, wherein the loose particles comprise a glass or a ceramic material.

17: The construction material mixture according to claim 15, wherein the loose particles comprise spheres.

18: The construction material mixture according to claim 15, wherein the size of the loose particles is in a range between 0.01 mm and 10 mm.

19: The construction material mixture according to claim 15, wherein the carbon of the dry mass comprises graphite.

20: The construction material mixture according to claim 15, wherein the electrically conductive material is at least one material selected from the group consisting of magnetite, graphite, and graphene.

21: The construction material mixture according to claim 19, wherein the graphite is present as at least one form selected from the group consisting of a graphite powder, expanded graphite flakes, film graphite, natural graphite, and synthetic graphite.

22: The construction material mixture according to claim 15, wherein the binding agent is at least one element selected from the group consisting of lime, cement, gypsum, synthetic materials, organic binding agents, water glass, water-soluble adhesives, and glues.

23: The construction material mixture according to claim 15, further comprising up to 50 wt. % of a functional additive.

24: The construction material mixture according to claim 23, wherein the functional additive is at least one element selected from the group consisting of trass powder, microglass hollow spheres, aluminum oxide, defoamers, magnetite, heavy spar, thickening agents, cellulose, synthetic additives, metallic nanoparticles, and fibers.

25: A plaster compound, comprising: the construction material mixture in accordance with claim 15.

26: A construction element produced by a process comprising: manufacturing the construction element from the construction material mixture in accordance with claim 15.

27: The construction material mixture according to claim 17, wherein the loose particles comprise hollow spheres.

28: The construction material mixture according to claim 22, wherein said construction material mixture comprises at least one synthetic material selected from the group consisting of acrylates and polyurea silicates.

29: The construction material mixture according to claim 24, wherein said construction material mixture comprises at least the metallic nanoparticles, wherein the metallic nanoparticles are silver nanoparticles.

30: The construction material mixture according to claim 20, wherein the electrically conductive material is at least the graphite, wherein the graphite is present as at least one form selected from the group consisting of a graphite powder, expanded graphite flakes, film graphite, natural graphite, and synthetic graphite.

Description

[0075] The figures show:

[0076] FIG. 1 a schematic representation of a section through a construction element in accordance with the invention;

[0077] FIG. 2 a schematic representation of the course of radiation when partly coated glass spheres are used in the construction material mixture in accordance with the invention;

[0078] FIG. 3 a schematic representation of measuring equipment for the analysis of the construction elements according to the invention;

[0079] FIG. 4 a schematic representation of the absorption characteristics of a construction element made from the construction material mixture according to the invention;

[0080] The functional principle of the construction material mixture according to the invention is exemplified in the FIGS. 1 and 2. A construction element 10, which is manufactured from a construction material mixture according to the invention, comprises a binding agent 11, graphite parts 12 in the binding agent and graphite-coated spheres 13. The graphite parts 12 in the binding agent essentially cause a partial reflection of the impinging radiation at the surface and reflections and absorption in the underlying layers. The additional graphite-coated spheres 13 additionally provide for numerous reflections of the radiation, which lengthens the path of the radiation through the construction element 10, which increases the absorbed part of the radiation. The radiation part reflected at the surface of the construction element can be further minimized when the graphite content in the binding agent is not homogeneous, but rather decreases towards the surface of the construction element.

[0081] When the graphite-coated spheres 13 are not completely coated with a graphite layer 14, but rather exhibit uncoated areas 15, as shown illustratively on the sphere 13, a larger portion of the radiation 16 can enter the interior 17 of the partially coated spheres 13 and effectively fizzle out by repeated reflections on the coated adjacent surfaces in the interior 17 of the spheres 13, which further increases the absorbed part of the radiation.

[0082] FIG. 3 depicts a typical test set-up with which the construction material mixtures according to the invention, which were processed into panel-shaped test objects, were analyzed. FIG. 3 shows a vector network analyzer 20 of the type ZVRC from the company Rohde and Schwarz, with which electromagnetic waves in a frequency range of 30 kHz to 8 GHz are generated and can be measured. Line 21, 22 lead or can be led to two coaxial TEM measuring heads 23, 24 between which the test object 25 is arranged (TEM measuring probes for the frequency range 1 MHz-4 GHz from the company Wandel & Goltermann). The generated initial radiation to the test object 25 and the radiation reflected by the test object 25 are measured via the line 21. Via the line 22, the radiation transmitted through the test object 25 is fed to the network analyzer. The absorbed power can then also be determined from the emitted, transmitted and reflected power.

[0083] In this measurement, the electric field strengths in the TEM arrangementas is common with coaxial linesimpinge on the test object in all polarization orientations. One is thus unable to make any discrete statements about the behaviour of the test object in the face of a given linear polarization, yet one gets an impression of how the test object will behave when faced with polarizations of an arbitrary orientation. If a test object shields particularly well in these measurements, it will shield at least correspondingly well vis--vis both linear vertical and horizontal polarizations.

[0084] Generally, the shielding against electromagnetic waves can occur either by reflection of the waves on a shielding surface and/or by absorption of the power in the shielding material. The shielding part of the reflection depends on the good conductivity of the shielding surface, which can also be described by its surface resistance. The shielding of most materials is based on this principle. If the materials have a very good conductivity, even very thin objects can result in excellent shielding values from 80 dB up to over 100 dB.

[0085] The absorption occurs within the shielding material when the latter is lossy. Here, the thickness of the material also plays an essential role. It can be determined that all materials that heat up quickly, for instance in a microwave oven, absorb electromagnetic energy in the high-frequency wave range well and are thus also suitable for use in shielding products.

[0086] In order to isolate the parts brought about by reflection from those caused by absorption in the characteristics of a test object, it is necessary to conduct, in addition to the transmission (S.sub.21), a reflection measurement (S.sub.11) with the same measurement set-up in a closed system. If one converts the measured dB values of the transmission and reflection into percentage values, it is possible to use the following equation to represent the power balance:

P.sub.transmtted=P.sub.irradiated(P.sub.reflected+P.sub.absorbed)

[0087] This means: Of the power (100%) irradiated onto the test specimen, only the part of the power that is not reflected or absorbed makes it through the test specimen (P.sub.transmitted).

Example 1

[0088] In a test mixture GKB 1, a base of gypsum was used (800 g gypsum anhydrite and 130 g lime, quenched). By adding 500 g ground natural graphite (graphite 99.5) and 120 g graphite-coated glass bubbles (diameter 1-2 mm), 100 g magnetite 10 and functional additives (250 g sand 0.2-1.5 mm, 85 g calcium carbonate, 0.14 g Pangel FF rheology optimizer, 0.03 g Lumiten surfactant, 0.20 g ELOTEX MP2100 redispersible polymer powder) and by adding water, a compound ready for processing was manufactured, which exhibited an excellent adhesion to a vertical Regips surface when applied manually (thrown). A compound approx. 3 cm thick continued to adhere to the wall without sinking. The setting compound could be felted after a waiting period. After setting and drying completely, a 2 cm thick panel was measured in accordance with ASTM D4935-2010.

[0089] The measurement of the shielding effect against electromagnetic waves in the frequency range of 10 MHz to 4.5 GHz and for the determination of the absorption occurred with a device as shown in FIG. 3.

[0090] The respective measurement values relating to the test object GKB1 are depicted in FIG. 4 (at 2450 MHz in the example).

[0091] One can see that 100% power was irradiated onto the test object 25 as symbolized by the arrow 26. The measured reflection resulted in a return loss in dB of 5.7 dB.

[0092] The resulting power reflection on the front side constituted a reflected power percentage of 27%, which is symbolized by the arrow 27. 73% of the power thus penetrates the test object 25 (arrow 28). As symbolized by the arrow 29, 1% of the power is transmitted. The losses by absorption in the test object thus constitute 73%1%=72% of the power.

[0093] In the case of this test object, a shielding effect of 20 dB was measured. Unlike conventional shielding products, the product in accordance with the invention thus exhibits a particularly high quality, as an essentially greater portion of the power is absorbed rather than reflected or transmitted.

[0094] The tested panels have the following measurements 200 mm*200 mm*20 mm. As the shielding effect in the case of absorption occurs within the shielding material, the thickness of the material also plays an essential role. By increasing the layer thickness and modifying the reflection values, the absorption within the shield can be changed, i.e. increased.

Example 2

[0095] In the test mixture KZ 1, a base of lime cement was used (800 g white cement, 120 g lime, quenched). By adding 500 g ground natural graphite (graphite 99.5) and 100 g glass bubbles (perlites 0-1 mm), and functional additives (500 g sand 0.2-1.5 mm, 0.2 g Pangel FF rheology optimizer, 0.02 g Lumiten surfactant, 0.4 g ELOTEX MP2100 and 0.5 g ELOTEX FL2280 redispersible polymer powder) and by adding water, a compound ready for processing was manufactured, which exhibited an excellent adhesion to a vertical Rigips surface when applied manually (thrown). A compound approx. 3 cm thick continued to adhere to the wall without sinking. The setting compound could be felted after a waiting period. After setting and drying completely, a 2 cm thick panel was measured in accordance with ASTM D4935-2010. Here, an absorption of 69.5% could be determined. A further gain in absorption can also attained here by increasing the material thickness. A virtual 100% neutralization of the radiation can also be attained here with a material thickness as of approx. 3 cm. A material thickness of 3 cm was attainable in one production step by means of injection with machine technology.

Example 3

[0096] In the test mixture AP 2, a base of lime cement was used (400 g cement, 400 g lime, quenched). By adding 500 g ground natural graphite (graphite 99.5) and 400 g glass bubbles (perlites 0-1 mm) and functional additives (200 g sand 0.2-1.5 mm, 0.02 g Lumiten surfactant, 0.6 g ELOTEX MP2100 and 0.5 g ELOTEX FL2280 redispersible polymer powder) and by adding water, a compound ready for processing was manufactured, which exhibited an excellent adhesion to a vertical Regips surface when applied manually (thrown). A compound approx. 3 cm thick continued to adhere to the wall without sinking. The setting compound could be felted after a waiting period. After setting and drying completely, a 2 cm thick panel was measured in accordance with ASTM D4935-2010. Here, an absorption of 67.4% could be determined. A further gain in absorption is again attainable by increasing the material thickness so that a virtual 100% neutralization of the radiation could be attained with a material thickness of approx. 3 cm. A material thickness of 3 cm was also attainable here in one production step by means of injection with machine technology.

[0097] The conducted measurements are to be regarded as illustrative. It was generally possible to determine that the adhesion of the plaster to other substrates common in construction such as brickwork, artificial stone or porous concrete could be considered very good from a technical point of view.