CZ309482B6 - Plastic material for making glass-ceramic foam, glass-ceramic foam prepared from this material and preparing this glass-ceramic foam - Google Patents

Abstract

The solution relates to a plastic mass making open-cell glass-ceramic foam, which the mass consists of a homogeneous mixture of high-silica sand with an average grain size of 200 to 300 µm, sodium water glass with a silica modulus of 1.9 to 3.2 and a low molecular weight organic plasticizer in mass ratio 100 : (3 to 10) : (1 to 5). It also refers to the glass-ceramic foam with open pores created by sintering this plastic material, which is formed by a porous structure of sintered silica sand grains, has a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m3, a pore size (diameter) of 5 to 650 µm and also methods of preparing this glass-ceramic foam with open pores.

Description

Plastic material for the preparation of glass-ceramic foam, glass-ceramic foam prepared from this material and method of preparation of this glass-ceramic foam

Field of technology

The invention relates to plastic material for the preparation of glass-ceramic foam with open pores.

The invention also relates to glass-ceramic foam with open pores prepared by controlled sintering of this plastic material.

The invention also relates to the method of preparing this glass-ceramic foam.

Current state of the art

Currently, various glass foams with closed pores are known in the form of granules or plates, which are prepared mainly from waste glass and are used mainly as a material for thermal insulation. Several procedures using different materials are known for their preparation.

E.g. the publication by Durgaprasad d. Tamteke et al.: "Up-cycling of 'unrecyclable' glasses in glassbased foams by weak alkali-activation, gel casting and low-temperature sintering", Journal of Cleaner Production, Volume 278, 1 January 2021, 123985 describes method of production of glass foam from waste glass - glass fibers (55.2 SiO2, 4.3 AbO3, 22.8 CaO, 0.6 MgO, 4.4 B2O3, 0.4 Na2O, 0.7 K2O in wt.%) and opal glass (72 SiO2, 8 A2O3, 2 CaO, 2 BaO, 12 Na2O, 1.5 K2O, 5 F2 in % wt). The waste glass is first ground and the resulting fine glass dust is then dispersed in a weakly alkaline solution with the addition of a surfactant. Then this solution is foamed by intensive stirring and the foam formed is stabilized by gelation, subsequent drying and sintering in the liquid phase at a temperature of 700 to 800 °C, which takes place for 10 to 60 minutes. Thanks to the closed voids in its structure and partial crystallization, the glass foam created in this way has an excellent strength/density ratio. When using opal glass, a structure with open pores is formed. Thanks to rapid sintering at low temperatures, volatile and toxic fluorine is not excluded from the glass. The formability and final cohesion of the mass, i.e. the change in its viscosity, is solved by the addition of NaOH, and Triton X (polyoxyethylene octylphenyl ether) is used as a plasticizer. Different concentrations of NaOH (1 M, 2 M and 3 M) lead to different sizes of the resulting pores.

This procedure has a number of disadvantages for real use. Its biggest disadvantage is that it is primarily designed for low SiO2 glass. Although this allows sintering to be carried out at a relatively low temperature, the resulting product has, compared to silica glass, a lower chemical resistance to water and aqueous solutions (especially acidic), lower electrical and thermal insulation properties, a high loss coefficient and also less desirable optical properties (possible coloring and .). Another problem is working with NaOH as a strongly corrosive substance. The use of Triton X helps degassing (thus "foaming" the product), but at the same time, this substance is not an effective plasticizer to allow the prepared suspension to be plastically shaped/modeled as needed before sintering.

The publication by Daniel Heska et al.: "Water and waterglass mixtures for foam glass production", Ceramics International, Volume 41, Issue 10, Part A, December 2015, Pages 12604-12613 then describes the way in which for the production of fine foam glass with closed 4 nm to 800 μm pores use float glass powder (1 to 106 μm, soda-lime glass: 72.1 SiO2, 1.0 AbO3, 0.3 K2O, 0.1 Fe2O3, 3.8 MgO, 8 .8 CaO and 13.9 Na2O), water and sodium water glass as a foaming agent. The described experiments were based on different weight ratios of water glass. Melting took place at different temperatures, with a temperature of 800 °C determined to be optimal. A higher water glass content leads to a higher porosity of the sample, which is associated with higher strength and thermal insulation properties.

- 1 CZ 309482 B6

The disadvantage of this procedure is that it again uses a sodium-calcium glass system with a higher proportion of alkaline oxides. These are to blame for the lower chemical resistance of the created foam to water and aqueous solutions (especially acidic), lower electrical and thermal insulation properties, a high loss coefficient and also less desirable optical properties (possible discoloration, etc.). The given procedure uses the addition of water glass to foam the suspension (as opposed to commonly used and problematic substances such as CaCO3, MnO2, SiC, etc.). However, the resulting product is not moldable at all, plastic, and is intended only for casting into molds or free production of foam glass.

The publication by Yigit Attila et al.: Foam glass processing using a polishing glass powder residue", Ceramics International, Volume 39, Issue 5, July 2013, Pages 5869-5877 then describes the preparation of glass foam from waste glass. The foaming behavior of powder residue/waste from a soda-lime window polishing plant was investigated at temperatures between 700 and 950 °C. The results showed that the foaming of the glass powder started at a temperature between 670 and 680 °C. The maximum volume expansion of glass powder and foam density were between 600% and 750% and 0.206 and 0.378 g cm ^-3 , respectively. The expansion of the glass powder resulted from the decomposition of organic compounds on the surface of the glass powder particles originating from the oil-based coolant used in polishing. The stress at the collapse of the foams was between approx. 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 WK ^-1 m ^-1 . Both failure stress and thermal conductivity increased with increasing foam density.

The disadvantage of this procedure is again that it uses a sodium-calcium glass system with a higher proportion of alkaline oxides. These are to blame for lower chemical resistance to water and aqueous solutions (especially acidic), lower electrical and thermal insulation properties, a high loss coefficient and also less desirable optical properties (possible discoloration, etc.). Due to its composition, the resulting product is not malleable or plastic at all, and is intended only for casting into molds or free production of foam glass.

The aim of the invention is to propose a composition of plastic material for the preparation of glass-ceramic foam, which would not suffer from the above-mentioned disadvantages and would, above all, be easily moldable.

In addition, the object of the invention is also a glass-ceramic foam prepared from this plastic material, as well as a method of preparing this glass-ceramic foam from this plastic material.

The essence of the invention

The objective of the invention is achieved with a plastic material for the preparation of glass-ceramic foam with open pores, which is formed by a homogeneous mixture of high silica sand with an average grain size of 200 to 300 μm, sodium water glass with a silica modulus of 1.9 to 3.2 and a low-molecular organic plasticizer in mass of the ratio 100 : (3 to 10) : (1 to 5). Thanks to its composition, this material is easy to shape, cohesive, and at the same time non-sticky.

A suitable low-molecular organic plasticizer is polyethylene glycol 400 (PEG 400), but in addition to it, some of the classic agents commonly added to ceramic or concrete mixtures can be used.

The most suitable weight ratio of silica sand, sodium water glass with a silica modulus of 3.2 and polyethylene glycol 400 in the given mixture is 100 : 6 : 2.5.

By sintering this plastic, a glass-ceramic foam with open pores is prepared, consisting of a porous structure of sintered silica sand grains and a porosity of 20 to 80%, a bulk weight of 150 to 400 kg/m ³ , and a pore size (diameter) of 5 to 650 μm.

In the method of preparing glass-ceramic foam with open pores according to the invention, a homogeneous mixture of high-silica sand with an average grain size of 200 to 300 μm, sodium water glass with a silica modulus of 1.9 to 3.2 and a low molecular weight organic plasticizer is created

- 2 CZ 309482 B6 in the ratio 100 : (3 to 10) : (1 to 5), preferably 100 : 6 : 2.5. In this mixture, the surface of silica sand grains is etched spontaneously by the action of water glass. Then this mixture is heated at a rate of 2 to 15 °C/min, preferably 6 to 9 °C/min, to a temperature of 120 to 180 °C, preferably 150 °C, and remains there for 60 to 180 minutes, preferably 90 up to 180 minutes, during which free and bound water evaporates from it. Then this mixture is heated at a rate of 2 to 15 °C/min, preferably 6 to 9 °C/min, to a temperature of 270 to 330 °C, preferably 300 °C and remains there for another 60 to 180 minutes, preferably 90 up to 180 minutes, during which the low-molecular organic plasticizer is burned off. Then this mixture is heated at a rate of 2 to 10°C/min, preferably 3 to 5°C, to a temperature of 1100 to 1500°C, preferably 1150 to 1400°C, while the silica sand grains are further melted and joined, as a result of which their spatial arrangement is fixed, thereby creating a glass-ceramic foam formed by a porous structure of connected fused silica sand grains, with a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m ³ , a pore size (diameter) of 5 to 650 μm.

Clarification of drawings

In the attached drawings, Fig. 1 shows a photograph of samples made of plastic for the preparation of the glass-ceramic foam according to the invention, Fig. 2 shows a photograph of these samples after their sintering, when the plastic material was transformed into a glass-ceramic foam according to the invention. In Fig. 3 is an SEM image of the cut of one of the samples from Fig. 2 at a magnification of 19 times, in Fig. 4 an SEM image of the center of this cut at a magnification of 50 times, in Fig. 5 an SEM image of the center of this cut at a magnification of 120 times, in Fig. 6 SEM a picture of the edge of this cut at a magnification of 50 times, in Fig. 7 a SEM picture of the edge of this cut at a magnification of 120 times, and in Fig. 8 the EDS spectrum of this cut with the results of elemental analysis. In Fig. 9 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 10 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 11 an SEM image of the edge of this cutting edge at a magnification of 121 times, and in Fig. 12 the EDS spectrum of this cutting edge with results of elemental analysis. Fig. 13 shows an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 14 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 15 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 16 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 17 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 18 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 19 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 20 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 21 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 22 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 23 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 24 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 25 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 26 an SEM image of the center of this cutting edge at a magnification of 119 times, in Fig. 27 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 28 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 29 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 30 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 31 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 32 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 33 is an SEM image of the cut of another sample at a magnification of 19 times, in Fig. 34 an SEM image of the center of this cut at a magnification of 120 times, in Fig. 35 an SEM image of the edge of this cut at a magnification of 120 times, and in Fig. 36 the EDS spectrum of this cut with results of elemental analysis. In Fig. 37 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 38 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 39 an SEM image of the edge of this cutting edge at a magnification of 121 times, and in Fig. 40 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 41 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 42 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 43 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 44 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 45 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 46 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 47 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 48 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 49 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 50 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 51 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 52 the EDS spectrum of this cutting edge with results of elemental analysis. Fig. 53 is a SEM image

- 3 CZ 309482 B6 of the grinding of another sample at a magnification of 19 times, in Fig. 54 a SEM image of the center of this grinding at a magnification of 120 times, in Fig. 55 an SEM image of the edge of this grinding at a magnification of 120 times, and in Fig. 56 the EDS spectrum of this grinding with elemental results analysis. In Fig. 57 is an SEM image of the cutting edge of another sample at a magnification of 21 times, in Fig. 55 an SEM image of the center of this cutting edge at a magnification of 120 times, in Fig. 59 an SEM image of the edge of this cutting edge at a magnification of 120 times, and in Fig. 60 the EDS spectrum of this cutting edge with results of elemental analysis. In Fig. 61 is an SEM image of the cutting edge of another sample at a magnification of 19 times, in Fig. 62 an SEM image of the center of this cutting edge at a magnification of 80 times, in Fig. 63 an SEM image of the center of this cutting edge at a magnification of 123 times, and in Fig. 64 the EDS spectrum of this cutting edge with results of elemental analysis.

Examples of implementation of the invention

The plastic material for the preparation of glass-ceramic foam with open pores according to the invention is made up of a mixture of high-silica glass sand (with a SiO2 content of over 99% by weight and a Fe2O3 content of up to 0.008% by weight) with an average grain size (diameter) in the range of 200 to 300 pm, sodium water glass with a silicon modulus of 1.9 to 3.2 and a low-molecular organic plasticizer, such as one of the classic agents for ceramic or concrete mixtures, e.g. substances based on polycarboxylates (typically polyacrylates), melamine (typically sulfonated melamine formaldehyde resins), naphthalene (typically polynaphthalene sulfonates) or lignin (lignosulfonates), low-molecular nonionic surfactant, such as polyethylene glycols (typically PEG 400), polyglucosides (alkylglucosides, dextrins, etc.) or various ethoxylated fatty amines, amides or alcohol ethoxylates, etc. Mass ratio of these components is 100 (silica sand) : 3 to 10 (water glass) : 1 to 5 (plasticizer). By mixing these components and homogenizing the mixture, an easily shaped, cohesive, yet non-sticky plastic mass is created. Water glass binds the grains of silica sand and at the same time etches them, and the low-molecular organic plasticizer increases the plastic nature of the created mass, i.e. improves its formability. It is difficult to shape this mass into basically any shape/structure, e.g. even by hand.

Glass-ceramic foam with open pores is prepared from this plastic material by sintering it, during which the free and bound water is removed by evaporation and the low-molecular organic plasticizer is fired, and the silica sand grains are interconnected and connected into a solid porous structure.

In a suitable sintering procedure, the body of the plastic material described above is first heated at a rate of 2 to 15 °C/min, preferably 6 to 9 °C/min, to a temperature of 120 to 180 °C, preferably 150 °C, and remains there 60 to 180 minutes, preferably 90 to 180 minutes, and then heated at a rate of 2 to 15°C/min, preferably 6 to 9°C/min to a temperature of 270 to 330°C, preferably 300°C, and it remains on it for another 60 to 180 minutes, preferably 90 to 180 minutes. In the first phase, the free and bound water is mainly gradually removed from the internal structure of the plastic material, which prevents the subsequent uncontrolled increase in the volume of this material and the formation of cavities in its structure due to intensive water evaporation. In the second phase, the organic plasticizer is mainly removed - burnt. At the same time, water and plasticizer leave the structure of the material gradually in the form of small gas bubbles, thus creating a porous structure with typical open pores. The increase in mass volume is a maximum of 150%.

For the next phase, the mass treated in this way is heated at a rate of 2 to 10 °C/min, preferably 3 to 5 °C/min, to a temperature of 1100 to 1500 °C, preferably 1150 to 1400 °C. During this heating, the sintering of the melt and the interconnection and sintering of the sand grains (the formation of connecting necks between the grains) and the compaction and fixation of the mass occur under the desired action of other input raw materials. Alkaline water glass (i.e. colloidal solution of alkaline silicates) etches the surface of silica sand grains even before heating, thereby making it active for chemical interaction (this is the dissolution of the glass as a whole to form reactive silanol groups Si-OH/hydrogel, which polycondensate upon drying into a solid Si-O-Si siloxane bond connecting grain surfaces already at laboratory temperature). The grains are thus joined by a chemical bond already at low temperatures before sintering itself, so the water glass fulfills the function of a flux. Thanks to this, it is not necessary to heat the silica sand particles later

- 4 CZ 309482 B6 to high temperatures to cause their deformation and the formation of connecting necks (silica sands normally sinter at temperatures above 1700 °C). In addition, water glass in combination with an organic plasticizer also fulfills the function of a foaming agent, when its gaseous components (water, CO2) leave the mass during controlled heating ("two-plateau" method, i.e. with a double delay at a partial temperature) and cause it to foam and pore formation; however, they do not deform the shape of the structure created from this material. During the subsequent firing at a temperature of 1100 to 1500 °C, the grains are melted and the foamed shape is fixed with good mechanical stability. The given hardening process can be described by classic chemical reactions in the solid phase, which are analogous to glass products. These are modification transformations of SiO2. We can also talk about the beneficial effect of a small amount of Na2O from the addition of water glass. The mass remains at the given temperature for 0 to 180 minutes (remaining at this temperature is not necessary, as all reactions will already take place during heating and the grains of silica sand will coalesce).

This is followed by spontaneous or controlled cooling in the furnace, during which the internal stresses are relaxed. Depending on the size and volume of the plastic structure according to the invention, controlled cooling is not necessary, but it is possible to let the given product cool on its own, especially if it is not necessary to achieve the highest possible strength of the resulting product. For the needs of controlled cooling, it is recommended to relax the glass foam for a period of several minutes to 1 hour, depending on the size of the product, at an upper cooling temperature of around 580 °C.

Before the start of the sintering process, the plastic mass according to the invention is preferably left in an environment with a normal atmosphere and laboratory temperature, when free water is removed from it spontaneously by drainage and evaporation. This shutdown preferably lasts from 1 to 72 hours.

The created glass-ceramic foam is solid, shape- and chemically stable, light, absorbent, non-transparent, typically white porous structure with open pores - see e.g. Fig. 2 to 63. Its porosity is 20 to 80%, bulk density 150 to 400 kg/m ³ , pore size (diameter) from 5 to 650 μm. This foam has a number of applications - it can serve, for example, as a coarser filter for gaseous and liquid media (it is able to trap in its structure impurities with a particle size in the range of micrometers), as a base material for further functionalization (e.g. hydrophobization, sol-gel process, etc. .), as a sound and heat insulator, or as a material for the production of interior decorative objects - in combination with other elements, it creates novel decors and original lighting effects. Thanks to the excellent absorbency given by the high proportion of open pores, it can simultaneously serve, for example, as a hydroponic substrate, or a substrate for the creation of living walls for greenery (the so-called green wall), etc.

Below, several concrete examples of the preparation of plastic material and glass-ceramic foam according to the invention are given for illustration.

Example 1

By mixing and homogenizing a mixture of high-silica sand with an average grain size (diameter) of 210 μm (sand grains ranged in size from 63 to 315 μm), sodium water glass with a silica modulus of 3.2, and polyethylene glycol 400 (PEG 400) in a weight ratio of 100 : 6 : 2.5, a plastic mass was prepared for the preparation of glass-ceramic foam.

Samples in the shape of a cylinder with a diameter of 30 mm and a height of 4 mm, and with a diameter of 20 mm and a height of 4 mm were subsequently formed from this material by hand molding - see Fig. 1. These cylinders were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere . At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 7 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 4 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

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In the process, the plastic mass transformed into a porous glass-ceramic foam with a porosity of 34%, a bulk density of 350.5 kg/m ³ and a pore size (diameter) from 24 to 181 μm - see Fig. 2. The dimensions of the individual samples changed (increased) by 5 to 37.5%.

In Fig. 3 is an SEM image of the cut of one of the samples from Fig. 2 at a magnification of 19 times, in Fig. 4 an SEM image of the center of this cut at a magnification of 50 times, in Fig. 5 an SEM image of the center of this cut at a magnification of 120 times, in Fig. 6 SEM a picture of the edge of this cut at a magnification of 50 times, and in Fig. 7 a SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

In addition to measurements on an electron microscope, the glass-ceramic foam created in this way was also analyzed for elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 8, which shows the EDS spectrum with the results of the elemental analysis. The results of this analysis point to a complete burn-out of the PEG 400 polymer plasticizer, with the molten grain and the formed neck containing a majority of silicon, while there is a small, almost zero, sodium presence in the neck area. It can thus be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower Na2O content originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 2

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature (and atmosphere). At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 7 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 4 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass was transformed into a porous glass-ceramic foam with a porosity of 56.1%, a bulk density of 219.5 kg/m ³ and a pore size (diameter) from 37 to 642 μm. The dimensions of individual samples changed (increased) by 7 to 75%.

In Fig. 9 is a SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 10 a SEM image of the center of this cut at a magnification of 120 times and in Fig. 11 an SEM image of the edge of this cut at a magnification of 121 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 12, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

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Example 3

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a mass ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 6 °C/min to a temperature of 120 °C for 120 minutes, then heated at a rate of 10 °C/min to a temperature of 330 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 7 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 64.1%, a bulk density of 158 kg/m ³ and a pore size (diameter) from 25 to 385 μm. The dimensions of individual samples changed (increased) by 8 to 100%.

In Fig. 13 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 14 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 15 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 16, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain the majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 4

In the same manner as in Example 1, silica sand with a mean grain size (diameter) of 270 μm (the sand grains ranged in size from 250 to 310 μm), sodium water glass with a silica modulus of 3.2, and polyethylene glycol 400 (PEG 400) in a mass ratio of 100 : 6 : 2.5 formed a plastic mass.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 2 °C/min to a temperature of 120 °C for 180 minutes, then heated at a rate of 2 °C/min to a temperature of 270 °C for another 180 minutes and then were heated to a temperature of 1400 °C at a rate of 10 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 34%, a bulk density of 306.2 kg/m ³ and a pore size (diameter) from 30 to 165 μm. The dimensions of individual samples changed (increased) by 5 to 37.5%.

In Fig. 17 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 18 an SEM image of the center of this cut at a magnification of 120 times and in Fig. 19 an SEM image of the edge of this cut at a magnification of 120 times. From these images, it is evident that during sintering there was melting and mutual

- 7 CZ 309482 B6 sintering of silica sand grains - connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis by means of energy dispersive spectroscopy (EDS) - see Fig. 20, in which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 5

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 12 °C/min to a temperature of 180 °C for 60 minutes, then heated at a rate of 15 °C/min to a temperature of 330 °C for another 60 minutes and then were heated to a temperature of 1400 °C at a rate of 9 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass was transformed into a porous glass-ceramic foam with a porosity of 51.3%, a bulk density of 210.5 kg/m ³ and a pore size (diameter) from 23 to 184 pm. The dimensions of individual samples changed (increased) by 8 to 75%.

In Fig. 21 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 22 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 23 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 24, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates complete firing of the polymer plasticizer, while the molten grain and the formed neck contain the majority of silicon, while in the neck area there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 6

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a mass ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in the glass furnace at a rate of 15 °C/min to a temperature of 150 °C, where they remained for 100 minutes, then they were heated at a rate of 15 °C/min to a temperature of 300 °C, where they remained for another

- 8 CZ 309482 B6

100 minutes and then heated to 1400°C at a rate of 10°C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass was transformed into a porous glass-ceramic foam with a porosity of 58.6%, a bulk density of 192.7 kg/m ³ and a pore size (diameter) from 25 to 352 pm. The dimensions of individual samples changed (increased) by 7 to 100%.

In Fig. 25 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 26 an SEM image of the center of this cut at a magnification of 119 times, and in Fig. 27 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 28, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the neck area there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 7

In the same manner as in Example 1, a plastic mass was formed from silica sand with an average grain size (diameter) of 270 pm, sodium water glass with a silica modulus of 3.2, and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:6:2.5 .

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in the glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 120 minutes, then heated at a rate of 8 °C/min to a temperature of 310 °C for another 100 minutes and then were heated to a temperature of 1100 °C at a rate of 5 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 23.5%, a bulk density of 388 kg/m ³ and a pore size (diameter) from 6 to 192 pm. The dimensions of individual samples changed (increased) by 3 to 22.5%.

In Fig. 29 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 30 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 31 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 32, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates complete firing of the polymer plasticizer, while the molten grain and the formed neck contain the majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

- 9 CZ 309482 B6

Example 8

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 7 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1100 °C at a rate of 7 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass was transformed into a porous glass-ceramic foam with a porosity of 46.5%, a bulk density of 276.8 kg/m ³ and a pore size (diameter) from 26 to 254 pm. The dimensions of individual samples changed (increased) by 3 to 75%.

In Fig. 33 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 34 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 35 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 36, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates complete firing of the polymer plasticizer, while the molten grain and the formed neck contain the majority of silicon, while in the neck area there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 9

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a mass ratio of 100:6:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in the glass furnace at a rate of 9 °C/min to a temperature of 120 °C for 150 minutes, then heated at a rate of 9 °C/min to a temperature of 315 °C for another 90 minutes and then were heated to a temperature of 1100 °C at a rate of 2 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass was transformed into a porous glass-ceramic foam with a porosity of 51.6%, a bulk density of 218.6 kg/m ³ and a pore size (diameter) from 35 to 488 pm. The dimensions of individual samples changed (increased) by 5 to 87.5%.

In Fig. 37 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 38 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 39 an SEM image of the edge of this cut at a magnification of 121 times. From these images, it is evident that during sintering there was melting and mutual

- 10 CZ 309482 B6 sintering of silica sand grains - connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 40, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the neck area there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 10

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and alkyl polyglucoside (APG; D-glucopyranose/decyloctylglycoside, oligomeric) in a weight ratio of 100:3:2.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 72 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 6 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 6 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 5 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 65.2%, a bulk density of 229.5 kg/m ³ and a pore size (diameter) from 24 to 508 μm. The dimensions of individual samples changed (increased) by 10 to 112.5%.

In Fig. 41 is an SEM image of a cut of one of the samples at a magnification of 19 times, in Fig. 42 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 43 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 44, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 11

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and APG in a weight ratio of 100:3:1.5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 8 °C/min to a temperature of 160 °C for 90 minutes, then heated at a rate of 7 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 3 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

- 11 CZ 309482 B6

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 64.1%, a bulk density of 259.2 kg/m ³ and a pore size (diameter) from 26 to 262 pm. The dimensions of individual samples changed (increased) by 8 to 112.5%.

In Fig. 45 is an SEM image of a cut of one of the samples at a magnification of 19 times, in Fig. 46 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 47 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis by means of energy dispersive spectroscopy (EDS) - see Fig. 48, on which the EDS spectrum of the prepared glass-ceramic foam is shown, points to the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 12

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 2.3 and APG in a mass ratio of 100:3:1.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 5 °C/min to a temperature of 120 °C for 180 minutes, then heated at a rate of 9 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 8 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 57.4%, a bulk density of 282.1 kg/m ³ and a pore size (diameter) of 25 to 225 pm. The dimensions of individual samples changed (increased) by 8 to 100%.

In Fig. 49 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 50 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 51 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis by means of energy dispersive spectroscopy (EDS) - see Fig. 52, in which the EDS spectrum of the prepared glass-ceramic foam is shown, points to the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 13

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:3:1.5.

- 12 CZ 309482 B6

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 140 °C for 100 minutes, then heated at a rate of 7 °C/min to a temperature of 280 °C for another 120 minutes and then were heated to a temperature of 1300 °C at a rate of 5 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic material was transformed into a porous glass-ceramic foam with a porosity of 62.1%, a bulk density of 252.5 kg/m ³ and a pore size (diameter) from 26 to 193 μm. The dimensions of individual samples changed (increased) by 8 to 125%.

In Fig. 53 is an SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 54 an SEM image of the center of this cut at a magnification of 120 times and in Fig. 55 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 56, on which the EDS spectrum of the prepared glass-ceramic foam is shown, indicates the complete firing of the polymer plasticizer, while the molten grain and the formed neck contain the majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 14

In the same way as in example 1, a plastic mass was created from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:3:1.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 7 °C/min to a temperature of 300 °C for another 100 minutes and then were heated to a temperature of 1300 °C at a rate of 5 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass transformed into a porous glass-ceramic foam with a porosity of 57.4%, a bulk density of 303.6 kg/m ³ and a pore size (diameter) from 27 to 170 μm. The dimensions of individual samples changed (increased) by 8 to 100%.

In Fig. 57 is an SEM image of the cut of one of the samples at a magnification of 21 times, in Fig. 58 an SEM image of the center of this cut at a magnification of 120 times, and in Fig. 59 an SEM image of the edge of this cut at a magnification of 120 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis by means of energy dispersive spectroscopy (EDS) - see Fig. 60, on which the EDS spectrum of the prepared glass-ceramic foam indicates complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the region of the neck there is a slight, almost zero, sodium representation. So it can be concluded that

- 13 CZ 309482 B6 the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Example 15

In the same way as in example 1, a plastic mass was formed from silica sand, sodium water glass with a silica modulus of 1.9 and polyethylene glycol 400 (PEG 400) in a weight ratio of 100:10:5.

The same cylinder-shaped samples as in Example 1 were subsequently formed from this mass by hand molding. These samples were left to stand for 48 hours on a fireclay mat at laboratory temperature and atmosphere. At the same time, part of the free water was removed from them by spontaneous drainage and evaporation. After the shutdown, these samples were heated in a glass furnace at a rate of 7 °C/min to a temperature of 150 °C for 100 minutes, then heated at a rate of 6 °C/min to a temperature of 290 °C for another 120 minutes and then were heated to a temperature of 1300 °C at a rate of 4 °C/min. After reaching this temperature, the heating of the furnace was turned off and it cooled down to room temperature on its own within 48 hours.

In the process, the plastic mass transformed into a porous glass-ceramic foam with a porosity of 71.3%, a bulk density of 151.5 kg/m ³ and a pore size (diameter) from 70 to 300 μm. The dimensions of individual samples changed (increased) by 10 to 100%.

In Fig. 61 is a SEM image of the cut of one of the samples at a magnification of 19 times, in Fig. 62 an SEM image of the center of this cut at a magnification of 80 times and in Fig. 63 at a magnification of 123 times. It is evident from these images that during sintering, the silica sand grains melted and coalesced with each other - the connecting necks, the internal structure of the glass-ceramic foam and its high porosity are visible on them.

Elemental analysis using energy dispersive spectroscopy (EDS) - see Fig. 64, which shows the EDS spectrum of the prepared glass-ceramic foam, indicates complete firing of the polymer plasticizer, while the molten grain and the formed neck contain a majority of silicon, while in the neck area there is a slight, almost zero, sodium representation. It can therefore be stated that the result is a glass-ceramic foam with a majority of SiO2 and a lower content of Na2O originating from water glass. At the same time, it can be assumed that these two components are equally represented in the structure of this foam, similar to the structure of sodium silicate glass.

Claims (7)

PATENT CLAIMS 1. Plastic material for the preparation of open-pored glass-ceramic foam, characterized by the fact that it is formed by a homogeneous mixture of high-silica sand with an average grain size of 200 to 300 pm, sodium water glass with a silica modulus of 1.9 to 3.2 and a low-molecular organic plasticizer in a mass ratio of 100 : (3 to 10) : (1 to 5). 2. Plastic mass according to claim 1, characterized in that the low molecular weight organic plasticizer is polyethylene glycol 400. 3. Plastic material according to claim 1 or 2, characterized in that it is formed by a homogeneous mixture of high silica sand, sodium water glass with a silica modulus of 3.2 and polyethylene glycol 400 in a weight ratio of 100:6:2.5. 4. Glass-ceramic foam with open pores created by sintering plastic material according to any one of claims 1 to 3, characterized in that it is formed by a porous structure of sintered silica sand grains, has a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m ³ , pore size (diameter) 5 to 650 pm. 5. The method of preparing glass-ceramic foam with open pores according to claim 4, characterized in that a homogeneous mixture of high silica sand with an average grain size of 200 to 300 pm, sodium water glass with a silica modulus of 1.9 to 3.2 and low molecular organic plasticizer in a mass ratio of 100 : (3 to 10) : (1 to 5), while in this mixture the surface of silica sand grains is etched spontaneously by the action of water glass, then this mixture is heated at a rate of 2 to 15 °C/min to a temperature of 120 to 180 °C and remains there for 60 to 180 minutes, while free and bound water evaporates from it, and then this mixture is heated at a rate of 2 to 15 °C/min to a temperature of 270 to 330 °C and remains there for another 60 up to 180 minutes, burning out the low molecular weight organic plasticizer, and then this mixture is heated at a rate of 2 to 10 °C/min to a temperature of 1100 to 1500 °C, further fusing and bonding the grains of silica sand, as a result of which it is fixed their spatial arrangement, which creates glass ceramics á foam formed by a porous structure of connected fused silica sand grains, with a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m ³ , a pore size (diameter) of 5 to 650 pm. 6. The method of preparing glass-ceramic foam with open pores according to claim 4, characterized in that a homogeneous mixture of high silica sand with an average grain size of 200 to 300 pm, sodium water glass with a silica modulus of 1.9 to 3.2 and low molecular organic plasticizer in a mass ratio of 100 : (3 to 10) : (1 to 5), while in this mixture the surface of silica sand grains is etched spontaneously by the action of water glass, then this mixture is heated at a rate of 6 to 9 °C/min to a temperature of 120 up to 180 °C and held there for 90 to 180 minutes, while free and bound water evaporates from it, and then this mixture is heated at a rate of 6 to 9 °C/min to a temperature of 270 to 330 °C and held there for another 90 up to 180 minutes, burning out the low molecular weight organic plasticizer, and then this mixture is heated at a rate of 3 to 5 °C/min to a temperature of 1150 to 1400 °C, further fusing and bonding the grains of silica sand, as a result of which it is fixed their spatial arrangement, which creates a glass-ceramic p made up of a porous structure of connected fused silica sand grains, with a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m ³ , a pore size (diameter) of 5 to 650 pm. 7. The method of preparing glass-ceramic foam with open pores according to claim 4, characterized in that a homogeneous mixture of high silica sand with an average grain size of 200 to 300 pm, sodium water glass with a silica modulus of 1.9 to 3.2 and low molecular organic plasticizer in a mass ratio of 100 : 6 : 2.5, while in this mixture the surface of silica sand grains is etched spontaneously by the action of water glass, after which this mixture is heated to a temperature of 150 °C at a rate of 7 °C/min and remains there for 100 minutes , while free and bound water is evaporated from it, and then this mixture is heated at a rate of 7 °C/min to 300 °C and remains there for another 100 minutes, burning out the low molecular weight organic plasticizer, and then this mixture at a rate of 7 °C/min, it heats to a temperature of 1200 to 1400 °C, while the silica grains are further melted and joined - 15 CZ 309482 B6 sand, as a result of which their spatial arrangement is fixed, thereby creating a glass-ceramic foam formed by a porous structure of connected fused silica sand grains, with a porosity of 20 to 80%, a bulk density of 150 to 400 kg/m ³ , size (average ) of pores 5 to 650 pm.