Foamed ceramic with low loss and high flatness and preparation process thereof

Abstract

The application discloses a foamed ceramic with low loss and high flatness, which is prepared by high-temperature sintering with silicon carbide as a foaming agent, and raw materials for preparing the foamed ceramic include, in terms of mass percentage of oxides, SiO2 64-70.5%, Al2O3 16-19%, Fe2O3 0-3.5%, TiO2 0-1%, CaO 0.5-3%, MgO 1.5-3.5%, K2O 3-5%, and Na2O 2-4%. The foamed ceramic can be uniformly expanded in a foaming process by the above-mentioned raw material formula, the viscosity and surface tension of a high-temperature melt of the foamed ceramic are improved, the flatness problem in the sintering process of the foamed ceramic is improved, the product after sintering only needs a small amount of cutting or no cutting to reach the use standard, the utilization rate of the foamed ceramic material is greatly improved, and the cost of the foamed ceramic is reduced.

Description

Technical Field

[0001] This invention relates to the field of building ceramics, and in particular to a low-loss, high-flatness foamed ceramic and its preparation process. Background Technology

[0002] Foamed ceramic panels, a commonly used wall material in the field of building decoration, are high-porosity ceramic materials made from solid waste such as polishing ceramic slag, waste stone tailings, and stone sawdust as the main raw materials and fired using high-temperature foaming technology. They have the properties of being lightweight and high-strength, heat-insulating and sound-insulating, fire-resistant and moisture-proof. However, their high production cost limits their widespread application in the construction field.

[0003] Currently, the production of foamed ceramics generally involves granulating the foamed ceramics into powder, spreading it evenly within a mold made of refractory material, and then sintering it after high-temperature foaming. Under existing manufacturing processes, both the top and bottom layers of the slabs exhibit some unevenness and deformation after exiting the kiln. To ensure flatness, approximately 15-20mm of excess material needs to be removed from the top layer and approximately 10-15mm from the bottom layer during the cutting process. This results in a significant amount of scrap material, and the yield rate of foamed ceramics is only around 70%. Therefore, the production cost of foamed ceramics remains consistently high.

[0004] To solve the above-mentioned technical problems, there is an urgent need for a low-loss, high-flatness foamed ceramic and its production process. Summary of the Invention

[0005] The main objective of this invention is to propose a low-loss, high-flatness foamed ceramic and its preparation process.

[0006] To achieve the above objectives, on the one hand, the present invention proposes a low-loss, high-flatness foamed ceramic, which is formed by high-temperature sintering using silicon carbide as a foaming agent. The raw materials for preparing the foamed ceramic, by mass percentage of oxides, include: SiO2 64-70.5%, Al2O3 16-19%, Fe2O3 0-3.5%, TiO2 0-1%, CaO 0.5-3%, MgO 1.5-3.5%, K2O 3-5%, and Na2O 2-4%.

[0007] This invention improves the viscosity and surface tension of the high-temperature melt of foamed ceramics by controlling the amount of each component in the raw materials. This allows the foamed ceramics to expand uniformly during the foaming process, improving the flatness problem during the firing process. The foaming powder can foam steadily during firing, resulting in a product with relatively flat upper and lower surfaces and four sides. The fired blanks only need a small amount of cutting or no cutting at all to meet the usage standards, which can greatly improve the utilization rate of the finished foamed ceramic materials and reduce the cost of foamed ceramics.

[0008] Preferably, in the raw materials for preparing the foamed ceramic, the mass ratio of K to Na is 0.95 to 1.5. Further controlling the high-temperature viscosity of the powder during high-temperature foaming ensures uniform pore size in the fired product and further improves the surface smoothness.

[0009] Preferably, the raw materials used to prepare the foamed ceramic also include known ceramic colorants. This allows for the formation of different colors at a uniform firing temperature, and the resulting colored products achieve a decorative effect through powder or slurry mixing.

[0010] On the other hand, the present invention also proposes a preparation process for low-loss, high-flatness foamed ceramics, comprising the following steps: ball milling the raw materials of the foamed ceramics into powder by mass percentage; then spreading the powder into a refractory kiln furniture to form a powder layer; scraping it flat and sending it into a kiln for firing at a firing temperature of 1160-1170℃ for a firing cycle of 8-13.5h; and after cooling and removing the refractory kiln furniture, the low-loss, high-flatness foamed ceramics are obtained.

[0011] The particle size and moisture content of the powder can be controlled within the required range through spray granulation. The aging process of ball mill slurry can improve the performance of the powder. The longer aging time can fully decompose the organic matter in the slurry, reduce the impact of organic matter on the green body during firing, and also help improve the uniformity of powder moisture, making it easier to form.

[0012] According to the above preparation method, the thickness of the powder layer is ≥80mm, and the linear thermal expansion coefficient of the foamed ceramic raw material meets the following conditions: 30~200℃: 5.7×10 -6 K -1 ≤α≤6.4×10 -6 K -1 30~600℃: 6.7×10 -6 K -1 ≤α≤7.6×10 -6 K -1 The greater the thickness of the powder, the more difficult it is to guarantee the flatness after firing. Therefore, by controlling the linear thermal expansion coefficient of the foamed ceramic raw material, stress deformation can be reduced, further improving the flatness and avoiding cracking.

[0013] According to the above preparation method, the powder layer includes at least two materials: a first powder layer and a second powder layer. The first powder layer and the second powder layer are respectively coated with ceramic pigments of different colors, and a preset pattern is formed using a known fabric application method. This results in a decorative panel with a patterned color.

[0014] The preparation process also includes the steps of edge grinding and / or cutting the low-loss, high-flatness foamed ceramic, wherein the cutting process includes the step of transversely slicing the foamed ceramic blank from the middle. After one firing, two types of slabs with different decorative effects can be obtained by transverse slicing, thereby improving the utilization rate of the foamed ceramic material and the kiln.

[0015] According to the above preparation method, the process parameters of the powder are: bulk density ≥ 0.87 g / ml, powder moisture content 5.5-6.0%, 1-2% above 20 mesh sieve, 45-70% above 20-40 mesh sieve, 80-97% above 20-60 mesh sieve, ≤1.5% below 100 mesh sieve, and the green body strength of the foamed ceramic layer powder is higher than 1.3 MPa. By adjusting the process parameters of the powder, the uniformity and flowability of the powder are controlled, preventing the problem of reduced flatness caused by fluctuations in powder performance.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0017] 1. Strictly limit the chemical composition of the foamed ceramic raw materials and the potassium-sodium ratio in the raw material components to ensure that the obtained foamed ceramic blank itself has good flatness, reduce loss, and improve material utilization.

[0018] 2. By limiting the range of linear thermal expansion coefficient of the foamed ceramic raw material, when the material thickness is ≥80mm, the powder layer can also expand uniformly and foam steadily, resulting in high flatness after firing and no cracking.

[0019] 3. By adding different colorants, two foamed ceramic slabs with different decorative effects can be obtained in one firing, which greatly improves the utilization rate of foamed ceramic materials and kilns and reduces energy consumption. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The diagram shows (a) of the foamed ceramic structure obtained in Example 9 and (b) after cutting.

[0022] In the attached diagram, 1 represents the first foamed ceramic layer and 2 represents the second foamed ceramic layer.

[0023] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] A process for preparing low-loss, high-flatness foamed ceramics includes the following steps: The raw materials for the foamed ceramics are ball-milled into powder according to a mass percentage; the powder is then spread into a refractory kiln furniture to form a powder layer; after leveling, it is fed into a kiln for firing at a temperature of 1160-1170℃ for a firing cycle of 8-13.5 hours; after cooling and removing from the kiln, the refractory kiln furniture is dismantled, thus obtaining the low-loss, high-flatness foamed ceramics. The process parameters of the powder are: bulk density ≥ 0.87 g / ml, powder moisture content 5.5-6.0%, 1-2% above 20 mesh sieve, 45-70% of 20-40 mesh, 80-97% of 20-60 mesh, and ≤1.5% below 100 mesh sieve. Controlling these conditions allows the green strength of the foamed ceramic layer to exceed 1.3 MPa.

[0027] The raw materials of the foamed ceramic, by mass percentage of oxides, include: SiO2 64-70.5%, Al2O3 16-19%, Fe2O3 0-3.5%, TiO2 0-1%, CaO 0.5-3%, MgO 1.5-3.5%, K2O 3-5%, and Na2O 2-4%.

[0028] It should be noted that during the firing process of foamed ceramics, due to the action of foaming agents such as silicon carbide, the size of the foamed ceramic powder tends to expand as the temperature rises, with an overall expansion of 150-300%. Therefore, the resulting foamed ceramic blank generally exhibits an uneven surface, requiring the upper and lower surfaces and four sides to be cut flat to meet usage standards. This invention, by strictly limiting the chemical composition of the foamed ceramic raw materials and controlling the viscosity and surface tension of the high-temperature melt, ensures uniform expansion and stable foaming during firing, thereby obtaining foamed ceramics with excellent flatness.

[0029] Furthermore, by mass percentage, the mass ratio of K to Na in the chemical composition of the foamed ceramic is 0.95 to 1.5.

[0030] Furthermore, when the thickness of the powder layer is ≥80mm, the linear thermal expansion coefficient of the foamed ceramic raw material satisfies the following condition: 30~200℃: 5.7×10 -6 K -1 ≤α≤6.4×10 -6 K -1 30~600℃: 6.7×10 -6 K -1 ≤α≤7.6×10 -6 K -1 Due to the expansion characteristics during the firing process of foamed ceramics, the greater the thickness of the fabric, the more difficult it is to control the surface smoothness of the foamed ceramics after firing. Therefore, by adjusting the linear thermal expansion coefficient of the raw materials, it is possible to ensure that the high-temperature expansion and cooling contraction of the foamed ceramics are controlled within a suitable range, and to avoid cracking and deformation caused by excessive stress.

[0031] Specifically, the decorative function of this invention is mainly achieved by adding ceramic colorants to the foamed ceramic raw materials.

[0032] Specifically, the raw materials used to prepare foamed ceramics are mixed with ceramic pigments, then ball-milled into a slurry and spray-granulated to obtain powder. This powder is then spread and sintered. Single-tube spreading can be used to prepare foamed ceramics of a single color; alternatively, multi-tube spreading can be used, mixing the foamed ceramic powder with different ceramic pigments and spreading it through multiple tubes according to a preset pattern to prepare foamed ceramics with decorative patterns. It can produce effects such as multi-colored imitation sandstone, natural stone textures, three-dimensional stone textures, solid colors, and intricate carvings, but is not limited to these.

[0033] Specifically, in this invention, two types of foamed ceramics with different decorative effects can be fired in one step using fabric.

[0034] Preferably, in one embodiment of the present invention, after mixing the foamed ceramic raw material according to the present invention with ceramic pigments of different colors, two foamed ceramic powders with different colors are prepared. These powders are then sprinkled into the refractory kiln furniture to form a first powder layer and a second powder layer. After sintering, the powders are cut horizontally from the middle to obtain two foamed ceramic slabs with different decorative effects.

[0035] The test standard for the linear thermal expansion coefficient of ceramic raw materials and foamed ceramic raw materials is the national standard GB / T7320-2018, and the test method is the push rod method known in the field.

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0037] The specific chemical composition of each ceramic preparation raw material in the following embodiments is provided in the table below (in mass percentage, unit is %):

[0038] Raw material name <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> LOI <![CDATA[ZrO2]]> ZnO Zirconium white frit 61.02 6.18 0.17 0.37 10.94 3.58 4.09 0.01 0.34 6.3 6.16

[0039] Note: If the chemical composition of the raw materials in the table above is less than 100%, it is mainly due to the presence of other undetected impurities.

[0040] The green silicon CF-25 used in the examples is silicon carbide with a purity of over 98.5%, purchased from Foshan Changyuan New Materials Co., Ltd., manganese oxide purchased from Foshan Yuhui Trading Co., Ltd., green body reinforcing agent purchased from Foshan Xinjinhui Economic and Trade Co., Ltd., liquid degumming agent purchased from Jiangxi Keben New Materials Technology Co., Ltd., sodium tripolyphosphate purchased from Jingdezhen Jiatao Ceramic Materials Co., Ltd., and sodium carboxymethyl cellulose purchased from Foshan Chancheng Yingyuan Trading Co., Ltd.

[0041] The liquid degumming agents used in the examples mainly consist of inorganic salts and polyelectrolytes. Among them, the inorganic salt liquid degumming agents mainly include water glass, sodium carbonate, sodium tripolyphosphate, sodium hexametaphosphate, etc.

[0042] The green body reinforcing agents used in the examples are divided into organic and inorganic green body reinforcing agents. Organic green body reinforcing agents typically include polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), modified starch, sodium polyacrylate, modified polysaccharides, polyacrylates, and lignin, etc. Organic green body reinforcing agents can improve the plasticity, flowability, and suspension properties of the green body, and increase its drying strength and abrasion resistance. Inorganic green body reinforcing agents include water glass, phosphates, bentonite, sodium humate, lignin sulfonate, and alkali lignin, etc. Inorganic green body reinforcing agents can enhance the density and abrasion resistance of the green body, while improving its plasticity and rheological properties.

[0043] Refer to the embodiment

[0044] Here, we select polishing slag, waste brick powder, feldspar tailings, pressed mud, talc mud, and silicon carbide as raw materials for foamed ceramics. In this formula system, the raw materials used are recycled waste, resulting in low cost and environmental friendliness. Foamed ceramic production has low requirements for the grade of raw materials and allows for some deviation in the composition of the raw materials each time.

[0045] First, a raw material formulation system for producing conventional foamed ceramics is provided, comprising, by mass parts: 6 parts river sand processing tailings, 35 parts water slag, 3 parts diopside, 56 parts construction waste, 1.5 parts liquid deflocculant, 0.25 parts manganese oxide, 0.4 parts green silicon CF-25, and 0.25 parts body reinforcing agent. The above formulation components are converted into oxides by chemical analysis as shown in Table 1 (by mass percentage, in %).

[0046] Table 1

[0047] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> LOI Refer to the embodiment 63.18 14.06 1.13 0.32 8.4 3.35 2.67 1.33 5.56

[0048] The preparation of foamed ceramics based on the above raw material composition includes the following steps:

[0049] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.87 g / ml, powder moisture content 6.0%, 2% above 20 mesh, 70% of 20-40 mesh, 85% of 20-60 mesh, and 1.5% below 100 mesh. By controlling the above conditions, the green strength of the powder of the foamed ceramic layer is higher than 1.3 MPa.

[0050] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0051] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0052] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0053] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0054] Its performance was tested, as shown in Table 2.

[0055] Table 2

[0056]

[0057] Note: Surface flatness is measured by the difference in surface height.

[0058] As shown in Table 2, conventional foamed ceramics have an uneven surface and poor flatness after firing due to foaming expansion. The height difference of the surface can reach 15mm. Therefore, a lot of cutting is required in the later processing, resulting in waste of raw materials.

[0059] Examples 1-6

[0060] The raw material formulations used in Examples 1-6 are shown in Table 3 by mass parts (unit: parts):

[0061] Table 3

[0062]

[0063]

[0064] The above formulation components were converted into oxides based on chemical analysis, as shown in Table 4 (by mass percentage, in %):

[0065] Table 4

[0066] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> LOI <![CDATA[K2O / Na2O]]> Example 1 70.13 16.49 1.17 0.19 1.02 1.98 3.03 3.41 2.58 0.89 Example 2 65.39 18.59 2.11 0.24 1.03 3.11 3.38 2.71 3.44 1.24 Example 3 69.22 16.65 1.13 0.1 1.11 2.75 3.31 3.42 2.31 0.96 Example 4 64.52 18.06 3.24 0.51 2.64 1.61 3.48 2.45 3.49 1.42 Example 5 67.11 18 2.15 0.25 2.29 1.74 3.04 2.93 2.49 1.04 Example 6 69.38 16.66 1.09 0.02 1.13 2.8 4.26 2.32 2.34 1.83

[0067] In addition to the exemplary formulations given above, those skilled in the art can adjust and combine them according to the actual situation of the raw materials used, such as bentonite, feldspar, sand, talc, etc., which will not be elaborated here. It is only necessary to ensure that the chemical composition of the raw material components is within the scope described in this application.

[0068] Foamed ceramics were prepared according to the above raw material composition.

[0069] The method for preparing foamed ceramics in Example 1 specifically includes the following steps:

[0070] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.87 g / ml, powder moisture content 5.5%, 1% above 20 mesh, 70% of 20-40 mesh, 85% of 20-60 mesh, and 1.5% below 100 mesh. By controlling the above conditions, the green strength of the powder of the foamed ceramic layer is higher than 1.3 MPa.

[0071] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0072] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0073] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0074] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0075] The method for preparing foamed ceramics in Example 2 specifically includes the following steps:

[0076] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.88 g / ml, powder moisture content 5.8%, 2% above 20 mesh, 45% of 20-40 mesh, 80% of 20-60 mesh, and 1.2% below 100 mesh. By controlling the above conditions, the green strength of the powder of the foamed ceramic layer is higher than 1.3 MPa.

[0077] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0078] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0079] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0080] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0081] The method for preparing foamed ceramics in Example 3 specifically includes the following steps:

[0082] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.87 g / ml, powder moisture content 6.0%, 1% above 20 mesh, 65% of 20-40 mesh, 95% of 20-60 mesh, and 1.5% below 100 mesh. By controlling the above conditions, the green strength of the powder of the foamed ceramic layer is higher than 1.3 MPa.

[0083] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0084] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0085] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0086] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0087] The method for preparing foamed ceramics in Example 4 specifically includes the following steps:

[0088] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.88 g / ml, powder moisture content 5.5%, 2% above 20 mesh, 55% of 20-40 mesh, 90% of 20-60 mesh, and 1.5% below 100 mesh. By controlling the above conditions, the green strength of the foamed ceramic layer powder is higher than 1.3 MPa.

[0089] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0090] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0091] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0092] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0093] The method for preparing foamed ceramics in Example 5 specifically includes the following steps:

[0094] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.87 g / ml, powder moisture content 6.0%, 1% above 20 mesh, 70% of 20-40 mesh, 97% of 20-60 mesh, and 1.2% below 100 mesh. By controlling the above conditions, the green strength of the foamed ceramic layer powder is higher than 1.3 MPa.

[0095] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0096] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0097] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0098] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0099] The method for preparing foamed ceramics in Example 6 specifically includes the following steps:

[0100] (1) First, the foamed ceramic raw material is ball-milled and granulated to form powder. The process parameters of the powder are: bulk density 0.87 g / ml, powder moisture content 5.9%, 1% above 20 mesh, 50% of 20-40 mesh, 85% of 20-60 mesh, and 1.3% below 100 mesh. By controlling the above conditions, the green strength of the foamed ceramic layer powder is higher than 1.3 MPa.

[0101] (2) Then the powder cloth is sprinkled into the refractory kiln furniture to form a powder layer with a thickness of 67mm, and then leveled.

[0102] (3) The kiln is fired at a temperature of 1165℃ for a period of 13 hours.

[0103] (4) After cooling and exiting the kiln, the refractory kiln furniture is removed to obtain foamed ceramic blanks;

[0104] (5) After cooling for 24 hours, the product is processed to obtain foamed ceramic products.

[0105] The properties of the foamed ceramics prepared in Examples 1-6 were tested, and the results are shown in Table 5.

[0106] Table 5

[0107]

[0108] As shown in Tables 2 and 5, the surface flatness deviation of the foamed ceramics prepared in Examples 1 to 6 is within the range of 2–6 mm, which is significantly better than the 15 mm surface flatness deviation of the foamed ceramics prepared in the reference example, eliminating the need for extensive cutting. The surface flatness deviation of the foamed ceramics prepared in Examples 1 and 6 is within the range of 5–6 mm, exhibiting good flatness, requiring only minimal cutting to meet usage requirements. Furthermore, the potassium-to-sodium ratio of the compounds in the raw material components of Examples 2 to 5 is within the range of 0.95–1.5, further improving the surface flatness of the foamed ceramics, with the deviation controlled within 2–3 mm, requiring only edge grinding to meet usage requirements. Therefore, the formulation described in this scheme improves the viscosity and surface tension of the high-temperature melt of the foamed ceramic, enabling uniform expansion and improving the flatness problem during the firing process. In particular, when the mass ratio of K to Na in the chemical composition of the raw material formulation is 0.95 to 1.5 based on the mass percentage of oxides, the powder foaming process is controlled to have a suitable high-temperature viscosity, resulting in a more stable foaming process. This further improves the flatness of the foamed ceramic, resulting in better surface smoothness, greatly reducing raw material loss, and increasing output value.

[0109] Example 7

[0110] Example 7 uses the same parameters and preparation steps as Example 3. The only difference is that the thickness of the powder layer in preparation step (2) is 85 mm. At the same time, the raw material formula of the foamed ceramic is adjusted to adjust the linear thermal expansion coefficient of the foamed ceramic raw material at 30-200℃ and 30-600℃. The raw material formula is shown in Table 6 by mass parts (unit: parts), and the corresponding linear thermal expansion coefficient is shown in Table 8.

[0111] Table 6

[0112]

[0113]

[0114] The above formulation components were converted into oxides based on chemical analysis, as shown in Table 7 (by mass percentage, in %):

[0115] Table 7

[0116] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> LOI Example 8-1 67.28 16.61 0.65 0.22 1.51 2.82 4.29 3.77 2.85 Example 8-2 65.91 17.34 2.83 0.43 1.74 2.09 3.45 3.04 3.17 Example 8-3 68.14 17.43 1.19 0.03 0.94 2.79 3.2 3.23 3.05 Example 8-4 68.12 17.06 1.27 0.17 0.98 2.58 3.68 3.34 2.8 Example 8-5 67.8 16.83 0.24 0.08 2.6 2.59 3.94 3.61 2.31

[0117] Table 8

[0118]

[0119]

[0120] The performance of the foamed ceramic prepared in Example 8 was examined, and the test results are shown in Table 9:

[0121] Table 9

[0122]

[0123] Note: A small amount of delamination cracking is permissible in industrial production; generally, a cracking rate below 10% is considered to indicate good industrialization characteristics.

[0124] As shown in Table 9, the surface smoothness decreases with increasing powder layer thickness. This invention addresses this by strictly controlling the raw material composition and adjusting the linear thermal expansion coefficient of the raw materials to meet the following conditions: 30–200℃: 5.7 × 10⁻⁶ -6 K -1 ≤α≤6.4×10 -6 K -1 30~600℃: 6.7×10 -6 K -1 ≤α≤7.6×10 -6 K -1 It can control the expansion and contraction of foamed ceramics within a suitable range, reduce stress deformation, and maintain good flatness without cracking or deformation when the fabric thickness is ≥80mm.

[0125] The results of Examples 8-1 and 8-5 show that when the linear thermal expansion coefficient is not within the above range, a small amount of delamination and cracking occurs in the surface layer during the cooling process.

[0126] Comparative Example 1

[0127] The same parameters and preparation steps as in Example 3 were used, except that the process parameters of the powder in step (1) were adjusted as follows: bulk density 0.87 g / ml, powder moisture content 7.0%, 2% above 20 mesh, 70% of 20-40 mesh, 85% of 20-60 mesh, 2% below 100 mesh, and green strength of the powder for the foamed ceramic layer 0.5 MPa.

[0128] The performance of the foamed ceramics prepared in Example 3 and Comparative Example 1 was examined, and the test results are shown in Table 10:

[0129] Table 10

[0130]

[0131]

[0132] As shown in Table 10, after adjusting the powder process parameters, the difference in powder particle size and moisture content led to a decrease in the smoothness after firing. Therefore, this scheme adjusts the powder process parameters to: bulk density ≥ 0.87 g / ml, powder moisture content 5.5-6.0%, 1-2% above 20 mesh sieve, 45-70% of 20-40 mesh, 80-97% of 20-60 mesh, and ≤1.5% below 100 mesh sieve. The green strength of the foamed ceramic layer powder is higher than 1.3 MPa. This can effectively control the uniformity and flowability of the powder, prevent smoothness problems caused by fluctuations in powder performance, and further improve the surface smoothness of the foamed ceramic.

[0133] Example 9

[0134] The decorative function of this invention is mainly achieved by adding colorants to the foamed ceramic powder. Specifically, different proportions of colorants can be added to the ceramic powder, such as inorganic colorants like YD2201 (encapsulated orange-red), YD1254 (encapsulated red), YD3671 (encapsulated yellow), and YD-513 (high-speed iron red) purchased from Foshan Yuanda Glaze Technology Co., Ltd. The mass ratio of the added inorganic colorant to the foamed ceramic powder is 0-10:100. After adding inorganic colorants, foamed ceramics with different decorative colors such as beige, earth yellow, brick red, and brick yellow can be obtained. Specific addition ratios are shown in Table 11 (by mass parts).

[0135] Table 11

[0136] A B C D beige earthy yellow brick red brick yellow Package in orange-red YD2201 0.35 0.25 1 2 Package red YD1254 0.05 0.15 1 - Package Yellow YD3671 0.15 0.35 - - YD-513 Zirconium Iron Red - - 1.5 1.5 Foamed ceramic powder 100 100 100 100

[0137] Example 9 is based on the raw material formula of Example 3. The foamed ceramic raw material of Example 3 is used as the first foamed ceramic layer, and the second foamed ceramic layer raw material is sprinkled on the first foamed ceramic layer to form the second foamed ceramic layer. Different colorants are added to the first foamed ceramic layer and the second foamed ceramic layer.

[0138] The raw material composition of the second foamed ceramic layer, in parts by mass, is shown in Table 12.

[0139] Table 12

[0140]

[0141]

[0142] In the preparation steps, firstly, a first foamed ceramic layer powder, containing three pigments—YD2201 (encapsulated orange-red), YD1254 (encapsulated red), and YD3671 (encapsulated yellow)—is applied according to the proportions in Scheme A of Table 11, with a thickness of 20 mm. Then, a second foamed ceramic layer powder, containing the same three pigments—YD2201 (encapsulated orange-red), YD1254 (encapsulated red), and YD-513 (high-speed iron red)—is applied according to the proportions in Scheme C of Table 11, with a thickness of 45 mm. All other parameters and preparation steps are the same as in Example 3. The resulting foamed ceramic brick is as follows: Figure 1 As shown in Figure a, it has a two-layer structure, namely a first foamed ceramic layer 1 and a second foamed ceramic layer 2.

[0143] The foamed ceramic produced using the formula described in this invention has high flatness, and decorative effects can be achieved by adding different colored pigments, such as... Figure 1 As shown, by cutting the prepared foamed ceramic blank along the cutting line F, two foamed ceramic slabs with different decorative effects can be obtained: ceramic slab I with only the second foamed ceramic layer 2, and ceramic slab II which is a composite of the first foamed ceramic layer 1 and the second foamed ceramic layer 2, which greatly improves the kiln utilization rate and increases production capacity.

[0144] The above-mentioned proportions of ceramic pigments are merely exemplary formulations. Those skilled in the art can use known pigments to prepare powders of different colors and apply them according to the pattern design using known application methods to achieve the desired decorative effect.

[0145] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-loss, high-flatness foamed ceramic, which is formed by high-temperature sintering using silicon carbide as a foaming agent, characterized in that... The raw materials for preparing the foamed ceramic, by mass percentage of oxides, include: SiO2 64-70.5%, Al2O3 16-19%, Fe2O3 0-3.5%, TiO2 0-1%, CaO 0.5-3%, MgO 1.5-3.5%, K2O 3-5%, and Na2O 2-4%. The preparation process of the low-loss, high-flatness foamed ceramic includes the following steps: the raw materials of the foamed ceramic are ball-milled and granulated into powder according to the mass percentage; the powder is then spread into the refractory kiln furniture to form a powder layer; after being leveled, it is sent into the kiln for firing at a firing temperature of 1160-1170℃ for a firing cycle of 8-13.5h; after cooling and exiting the kiln, the refractory kiln furniture is removed, thus obtaining the low-loss, high-flatness foamed ceramic. The thickness of the powder layer is ≥80mm, and the linear thermal expansion coefficient α of the foamed ceramic raw material satisfies the following condition: 30~200℃: 5.7×10 -6 K -1 ≤α≤6.4×10 -6 K -1 30~600℃: 6.7×10 -6 K -1 ≤α≤7.6×10 -6 K -1 .

2. The low-loss, high-flatness foamed ceramic as described in claim 1, characterized in that, In the raw materials for preparing the foamed ceramic, the mass ratio of K to Na is 0.95 to 1.

5.

3. The low-loss, high-flatness foamed ceramic as described in claim 1, characterized in that, The raw materials used to prepare the foamed ceramics also include known ceramic colorants.

4. A preparation process for low-loss, high-flatness foamed ceramics as described in any one of claims 1-3, characterized in that, The process includes the following steps: the raw materials of the foamed ceramic are ball-milled and granulated into powder according to a mass percentage; the powder is then spread into a refractory kiln furniture to form a powder layer; after being leveled, the powder is sent into a kiln for firing at a temperature of 1160-1170℃ for a firing cycle of 8-13.5 hours; after cooling and removing the refractory kiln furniture, the low-loss and high-flatness foamed ceramic is obtained. The thickness of the powder layer is ≥80mm, and the linear thermal expansion coefficient α of the foamed ceramic raw material satisfies the following condition: 30~200℃: 5.7×10 -6 K -1 ≤α≤6.4×10 -6 K -1 30~600℃: 6.7×10 -6 K -1 ≤α≤7.6×10 -6 K -1 .

5. The preparation process of low-loss, high-flatness foamed ceramic as described in claim 4, characterized in that, The powder layer comprises at least two materials: a first powder layer and a second powder layer. The first powder layer and the second powder layer are respectively coated with ceramic pigments of different colors, and a preset pattern is formed by a known fabric application method.

6. The preparation process of low-loss, high-flatness foamed ceramic as described in claim 4, characterized in that, The preparation process also includes the steps of grinding and / or cutting the low-loss, high-flatness foamed ceramic, wherein the cutting process includes the step of horizontally splitting the foamed ceramic blank from the middle.

7. The preparation process of low-loss, high-flatness foamed ceramic as described in claim 4, characterized in that, The process parameters of the powder are: bulk density ≥ 0.87 g / ml, powder moisture content 5.5~6.0%, 1~2% above 20 mesh sieve, 45~70% of 20~40 mesh, 80~97% of 20~60 mesh, ≤1.5% below 100 mesh sieve, and the green body strength of the powder for the foamed ceramic layer is higher than 1.3 MPa.

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