A foamed ceramic material and a method for producing the same

Abstract

The application relates to the technical field of inorganic nonmetallic materials, and particularly discloses a foamed ceramic material and a preparation method thereof. The material is prepared from solid waste-based main materials, a foaming agent and a stabilizing additive containing barium oxide, magnesium oxide and titanium dioxide. The preparation method comprises the following steps: after the raw materials are mixed according to the proportion, wet ball milling is carried out to prepare slurry, the obtained slurry is sprayed and dried to prepare powder, and finally, the powder is sintered and formed under a specific sintering system in an air atmosphere. By introducing a BaO-MgO-TiO2 ternary synergistic stabilization system, the technical problems of unstable solidification, interference in the foaming process and uneven product performance existing in the traditional carbon reduction method for treating chromium-manganese-containing solid waste are effectively solved, long-term chemical fixation of harmful elements in the ceramic matrix is realized, a foamed ceramic product with excellent environmental safety and good physical performance is successfully prepared, and a new way is provided for high-value resource utilization of large quantities of industrial hazardous waste.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically relating to a foamed ceramic material and its preparation method. Background Technology

[0002] In the fields of building energy conservation and industrial solid waste resource utilization, foamed ceramic materials are widely used in products such as building exterior wall insulation boards and fireproof barriers due to their lightweight, high strength, heat insulation, and fireproof properties. These products need to meet two core requirements simultaneously: first, stable performance during long-term use without releasing harmful substances; and second, the ability to use inexpensive solid waste such as metallurgical slag and tailings as main raw materials to reduce costs and environmental impact.

[0003] However, when using metallurgical slag rich in heavy metals such as chromium (Cr) and manganese (Mn) to prepare foamed ceramics, it is necessary to solve the problem of long-term safe fixation of heavy metal elements, that is, to lock the heavy metals firmly in the ceramic matrix to prevent them from being leached out by rainwater and polluting the soil and groundwater during use.

[0004] Existing technologies often involve adding carbonaceous materials to reduce highly toxic hexavalent chromium to less toxic trivalent chromium at high temperatures. However, in practical applications, carbonaceous reducing agents preferentially react with oxygen at high temperatures, competing with foaming agents for oxygen. This leads to unstable foaming reactions, resulting in uneven internal pore structures in the final product. Consequently, the thermal insulation and mechanical properties of the same insulation board fluctuate significantly, affecting quality consistency. Furthermore, single reduction only addresses the valence state of chromium, and the resulting trivalent chromium compounds may still oxidize or leach in complex environments over long periods, posing a risk of secondary pollution. Moreover, when dealing with solid wastes from diverse sources with varying compositions, a single carbon reduction scheme cannot synergistically treat multiple heavy metals such as chromium and manganese, making formula adjustments complex and product performance difficult to control.

[0005] These problems, on the one hand, limit the high added value and large-scale disposal of chromium- and manganese-containing hazardous waste, resulting in a large amount of solid waste being disposed of through stockpiling or low-cost landfill, which poses environmental risks; on the other hand, they hinder the foamed ceramics industry from obtaining more stable and cheaper raw materials, which is not conducive to the industry's cost reduction, efficiency improvement and green upgrading. Summary of the Invention

[0006] The purpose of this invention is to provide a foamed ceramic material and its preparation method to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a foamed ceramic material is provided, prepared from raw materials comprising the following components in parts by mass:

[0008] Solid waste base materials, foaming agents, and stabilizing additives;

[0009] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2).

[0010] The proportions of each component by mass are as follows: 70-95 parts of solid waste-based main material, 0.3-1.5 parts of foaming agent, 3-8 parts of barium oxide, 2-6 parts of magnesium oxide, and 1-4 parts of titanium dioxide.

[0011] Preferably, the solid waste-based main material contains solid waste containing chromium and / or manganese, and its mass percentage is 5% to 50% of the total mass of the solid waste-based main material.

[0012] Preferably, the mass ratio of barium oxide, magnesium oxide and titanium dioxide in the stabilizing additive is in the range of 3-8:2-6:1-4.

[0013] Preferably, the foaming agent is silicon carbide (SiC).

[0014] According to another aspect of the present invention, a method for preparing a foamed ceramic material is provided, comprising the following steps:

[0015] S1. Mix the raw materials according to the specified proportions;

[0016] S2. The mixed raw materials are subjected to wet ball milling to obtain a slurry;

[0017] S3. The slurry is dried and granulated to obtain powder;

[0018] S4. Place the powder in a kiln and sinter it in an air atmosphere. The sintering process is as follows: heat up to 1000-1200℃ and hold for 1-3 hours, then cool to obtain the foamed ceramic material.

[0019] Preferably, the sintering heating process in step S4 is divided into two stages: from room temperature to 900-950℃, with a heating rate of 100-200℃ / h; and from 900-950℃ to the final sintering temperature of 1000-1200℃, with a heating rate of 300-450℃ / h.

[0020] Preferably, the fineness of the slurry after wet ball milling in step S2 is no greater than 200 mesh.

[0021] Preferably, the particle size distribution of the powder after drying and granulation in step S3 is: 40-60 mesh accounts for 10%-25%, 60-80 mesh accounts for 40%-65%, and 80-100 mesh accounts for 20%-35%.

[0022] Preferably, the moisture content of the powder obtained in step S3 is controlled at 6%-10%.

[0023] Preferably, the foamed ceramic material prepared by the method contains a spinel phase and a barium ferrite phase generated by the reaction of the stabilizing additive with harmful elements.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) By introducing a BaO-MgO-TiO2 ternary synergistic stabilization system, the amount of solid waste in the foamed ceramic formulation can reach up to 65 parts, enabling large-scale disposal of hazardous waste such as chromium and manganese, while simultaneously producing foamed ceramic products with excellent comprehensive performance. Compared with existing technologies, the material can still maintain a low bulk density and high compressive strength even with a high solid waste content, solving the problems of difficult molding and decreased strength of products with high content.

[0026] (2) By utilizing the fluxing properties of existing metal oxides in waste, the triple synergistic effect of BaO promoting the formation of barium ferrite phase, MgO forming spinel phase, and TiO2 acting as a nucleating agent, harmful elements such as chromium and manganese are transformed from physical adsorption to chemical lattice fixation, thus realizing the transformation of harmful elements from physical adsorption to chemical fixation and greatly improving the long-term stability of the curing effect.

[0027] (3) It uses bulk solid waste as the main raw material, requires less auxiliary additives and has low cost, and shows good adaptability to chromium and manganese-containing solid wastes of different sources and compositions (such as stainless steel slag, red mud, etc.). Under the condition that the main technical route remains unchanged, the supporting sintering process can be completed in a conventional air atmosphere and at a relatively low temperature (1000-1200℃), which is conducive to reducing raw material costs and expanding the scope of co-processing of solid waste.

[0028] (4) Using conventional air atmosphere sintering process, the harmful elements can be efficiently solidified and uniformly foamed under relatively low temperature conditions of 1000-1200℃. There is no need for complex atmosphere control or additional microwave equipment. The heating rate is controlled at 100-450℃ / h and the holding time is 1-2 hours, which effectively reduces production energy consumption and equipment investment.

[0029] (5) By replacing the traditional carbon reducing agent with a structural stabilizer, the problem of uneven foaming caused by the competition of carbon materials and foaming agents for oxygen is avoided. While achieving the reduction of hexavalent chromium and the stabilization of heavy metals, the foaming uniformity is significantly improved. The product has a uniform pore distribution and consistent pore size, so that the product achieves a good balance between lightweight, mechanical strength and thermal insulation performance. Attached Figure Description

[0030] Figure 1 This is a low-magnification SEM image (scale bar 200 μm) of Embodiment 2 of the present invention.

[0031] Figure 2The image is a low-magnification SEM image (scale bar 200 μm) of Comparative Example 1.

[0032] Figure 3 This is a high-magnification BSE image (scale bar 20 μm) of Embodiment 2 of the present invention.

[0033] Figure 4 The image is a high-magnification BSE image (scale bar 20 μm) of Comparative Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] Example 1:

[0036] A foamed ceramic material is prepared from raw materials comprising the following components in parts by mass:

[0037] Solid waste base materials, foaming agents, and stabilizing additives;

[0038] The solid waste-based main material consists of 87.7 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The slag consisted of 30 parts of stainless steel slag, whose chemical composition, as analyzed by XRF, was SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing by jaw crusher followed by ball milling to a particle size ≤200 mesh. The fly ash consisted of 40 parts of fly ash, whose chemical composition included SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The quartz tailings consisted of 17.7 parts of quartz tailings, whose chemical composition included SiO2 content >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0039] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0040] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2), wherein 5 parts of barium oxide have a purity ≥99%, are industrial grade, and have a particle size ≤5μm; 4 parts of magnesium oxide have a purity ≥98.5%, are industrial grade, and have a particle size ≤5μm; and 2.5 parts of titanium dioxide have a purity ≥99%, are rutile type, and have a particle size ≤1μm.

[0041] A method for preparing foamed ceramic materials includes the following steps:

[0042] S1. Weigh the stainless steel slag, fly ash, and quartz tailings according to the specified proportions, and dry mix them in a mixer for 30 minutes until homogeneous. Then add silicon carbide, barium oxide, magnesium oxide, and titanium dioxide, and continue mixing for 45 minutes to ensure that all components are evenly distributed.

[0043] S2. Feed the mixed raw materials into a planetary ball mill, add zirconia grinding balls and deionized water at a mass ratio of ball:material:water = 2:1:0.6, and ball mill at 250 rpm for 8 hours. The fineness of the output slurry should be controlled to D50 ≤ 5 μm (equivalent to ≥200 mesh sieve residue < 1%).

[0044] S3. The obtained slurry is fed into a centrifugal spray drying tower for granulation. The inlet temperature is set at 450±10℃, and the outlet temperature is controlled at 110±5℃. The particle size distribution of the obtained powder is controlled as follows: 40-60 mesh 15%, 60-80 mesh 50%, 80-100 mesh 30%, and >100 mesh 5%, with a powder moisture content of 7.5%.

[0045] S4. Fill the dried powder into the refractory mold, place it in a box-type sintering furnace, and sinter it in air atmosphere according to the following procedure:

[0046] The temperature was increased from room temperature to 950°C at a rate of 150°C / h.

[0047] Then, the temperature is increased from 950℃ to 1150℃ at a rate of 400℃ / h;

[0048] Keep warm at 1150℃ for 2 hours;

[0049] After the heat preservation is completed, the temperature is reduced to 600℃ at a rate of 600℃ / h;

[0050] It then cooled naturally to room temperature in the furnace.

[0051] This will yield foamed ceramic materials.

[0052] Example 2:

[0053] A foamed ceramic material is prepared from raw materials comprising the following components in parts by mass:

[0054] Solid waste base materials, foaming agents, and stabilizing additives;

[0055] The solid waste-based main material consists of 85 parts, comprising chromite slag, copper tailings, and kaolin tailings. Among them, 35 parts are chromite slag, whose chemical composition, analyzed by XRF, is SiO2 (32.8%), Al2O3 (15.6%), MgO (18.2%), Cr2O3 (8.5%), Fe2O3 (12.4%), CaO (5.3%), and other (7.2%). The main phases are magnesium chromite spinel, pyroxene, and glassy phase. The pretreatment method is grinding to a particle size ≤200 mesh using a Raymond mill. The 30 parts are copper tailings, whose chemical composition includes SiO2 (45.6%), Al2O3 (15.6%), Cr2O3 (18.2%), Fe2O3 (12.4%), CaO (5.3%), and other (7.2%). O3 (16.8%), CaO (15.3%), Fe2O3 (8.2%), K2O (3.1%), CuO (0.5%), and other (10.5%) were pretreated by drying and then sieving to remove +20 mesh coarse particles. 20 portions of kaolin tailings were pretreated by washing to remove sand and then drying.

[0056] The foaming agent is silicon carbide (SiC), with an amount of 1.2 parts, a purity of ≥98%, and a particle size of ≤8μm.

[0057] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2), wherein 6 parts of barium oxide have a purity ≥99%, are industrial grade, and have a particle size ≤5μm; 5 parts of magnesium oxide have a purity ≥98.5%, are industrial grade, and have a particle size ≤5μm; and 2.8 parts of titanium dioxide have a purity ≥99%, are rutile type, and have a particle size ≤1μm.

[0058] A method for preparing foamed ceramic materials includes the following steps:

[0059] S1. Weigh the above-mentioned chromite slag, copper tailings, and kaolin tailings according to the specified proportions, and dry mix them in a double cone mixer for 35 minutes until homogeneous. Then add silicon carbide, barium oxide, magnesium oxide, and titanium dioxide, and continue mixing for 50 minutes to ensure that all components are evenly distributed.

[0060] S2. Feed the mixed raw materials into a vibrating ball mill, add alumina grinding balls and deionized water at a mass ratio of ball:material:water = 2.2:1:0.65, and ball mill at 300 rpm for 7 hours. The fineness of the output slurry should be controlled as D50≤4.5μm (equivalent to ≥200 mesh sieve residue <0.8%).

[0061] S3. The obtained slurry is fed into a pressure spray dryer for granulation. The inlet temperature is set at 460±10℃, and the outlet temperature is controlled at 105±5℃. The particle size distribution of the resulting powder is controlled as follows: 40-60 mesh 18%, 60-80 mesh 52%, 80-100 mesh 25%, and >100 mesh 5%, with a powder moisture content of 7.2%.

[0062] S4. Fill the dried powder into the refractory mold, place it in the pusher kiln, and sinter it in air atmosphere according to the following procedure:

[0063] The temperature was increased from room temperature to 960℃ at a rate of 160℃ / h.

[0064] Then, the temperature is increased from 960℃ to 1160℃ at a rate of 380℃ / h;

[0065] Keep warm at 1160℃ for 2.5 hours;

[0066] After the heat preservation is completed, the temperature is reduced to 650℃ at a rate of 550℃ / h;

[0067] It then cooled naturally to room temperature in the kiln.

[0068] This will yield foamed ceramic materials.

[0069] Example 3:

[0070] A foamed ceramic material is prepared from raw materials comprising the following components in parts by mass:

[0071] Solid waste base materials, foaming agents, and stabilizing additives;

[0072] The solid waste-based main material consists of 86.5 parts, composed of red mud, fly ash, and granite tailings. The red mud (35 parts) has the following chemical composition, as determined by XRF analysis: Al₂O₃ (22.5%), SiO₂ (18.6%), Fe₂O₃ (30.8%), CaO (10.5%), Na₂O (6.2%), TiO₂ (4.1%), and other (7.3%). The main phases are hematite, calcite, and nepheline. The pretreatment method involves pressure filtration to dehydrate to a moisture content <15%, followed by drying at 105℃ and ball milling to a particle size ≤200 mesh. The fly ash (35 parts) has the following chemical composition... The chemical composition of the first sample includes SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method is to use it directly after drying. The chemical composition of the 16.5 granite tailings is SiO2 (68.5%), Al2O3 (16.2%), K2O (4.8%), Na2O (3.5%), CaO (1.8%), and other (5.2%). The pretreatment method is to use it directly after drying.

[0073] The foaming agent is silicon carbide (SiC), with an amount of 1.0 part, a purity of ≥98%, and a particle size of ≤10μm.

[0074] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2), wherein 7 parts of barium oxide have a purity ≥99%, are industrial grade, and have a particle size ≤5μm; 3.5 parts of magnesium oxide have a purity ≥98.5%, are industrial grade, and have a particle size ≤5μm; and 3 parts of titanium dioxide have a purity ≥99%, are rutile type, and have a particle size ≤1μm.

[0075] A method for preparing foamed ceramic materials includes the following steps:

[0076] S1. Weigh the red mud, fly ash, and granite tailings according to the specified proportions, and dry mix them in a mixer for 30 minutes until homogeneous. Then add silicon carbide, barium oxide, magnesium oxide, and titanium dioxide, and continue mixing for 45 minutes to ensure that all components are evenly distributed.

[0077] S2. Feed the mixed raw materials into a planetary ball mill, add zirconia grinding balls and deionized water at a mass ratio of ball:material:water = 2:1:0.6, and ball mill at 250 rpm for 8 hours. The fineness of the output slurry should be controlled to D50 ≤ 5 μm (equivalent to ≥200 mesh sieve residue < 1%).

[0078] S3. The obtained slurry is fed into a centrifugal spray drying tower for granulation. The inlet temperature is set at 450±10℃, and the outlet temperature is controlled at 110±5℃. The particle size distribution of the obtained powder is controlled as follows: 40-60 mesh 15%, 60-80 mesh 50%, 80-100 mesh 30%, and >100 mesh 5%, with a powder moisture content of 7.5%.

[0079] S4. Fill the dried powder into the refractory mold, place it in a box-type sintering furnace, and sinter it in air atmosphere according to the following procedure:

[0080] The temperature was increased from room temperature to 950°C at a rate of 150°C / h.

[0081] Then, the temperature is increased from 950℃ to 1120℃ at a rate of 400℃ / h;

[0082] Keep warm at 1120℃ for 2.5 hours;

[0083] After the heat preservation is completed, the temperature is reduced to 600℃ at a rate of 600℃ / h;

[0084] It then cooled naturally to room temperature in the furnace.

[0085] This will yield foamed ceramic materials.

[0086] Example 4:

[0087] A foamed ceramic material is prepared from raw materials comprising the following components in parts by mass:

[0088] Solid waste base materials, foaming agents, and stabilizing additives;

[0089] The solid waste-based main material consisted of 72 parts, composed of stainless steel slag and molybdenum tailings. Among them, 65 parts were stainless steel slag, whose chemical composition, analyzed by XRF, was SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing with a jaw crusher followed by ball milling to a particle size ≤200 mesh. The 7 parts were molybdenum tailings, whose chemical composition included SiO2 (72.3%), Al2O3 (11.5%), Fe2O3 (3.8%), CaO (2.1%), MoO3 (0.5%), and other (9.8%). The pretreatment method was drying before direct use.

[0090] The foaming agent is silicon carbide (SiC), with an amount of 0.3 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0091] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2), wherein 8 parts of barium oxide have a purity ≥99%, are industrial grade, and have a particle size ≤5μm; 6 parts of magnesium oxide have a purity ≥98.5%, are industrial grade, and have a particle size ≤5μm; and 4 parts of titanium dioxide have a purity ≥99%, are rutile type, and have a particle size ≤1μm.

[0092] In a method for preparing foamed ceramic materials, the ball milling time of S2 is shortened to 6 hours, while the remaining step parameters are exactly the same as in Example 1.

[0093] This will yield foamed ceramic materials.

[0094] Comparative Example 1:

[0095] A foamed ceramic material is prepared from raw materials comprising the following components:

[0096] Solid waste base material, foaming agent and reducing agent;

[0097] The solid waste base material consists of 100 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The composition of stainless steel slag (34.2 parts) was determined by XRF analysis to be SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing with a jaw crusher followed by ball milling to a particle size ≤200 mesh. The composition of fly ash (45.6 parts) was determined to be SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The composition of quartz tailings (20.2 parts) was determined to be SiO2 >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0098] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0099] The reducing agent is coke powder, with a dosage of 1.5 parts, a fixed carbon content of ≥85%, and a particle size of ≤75μm.

[0100] A method for preparing foamed ceramic materials, the steps of which are the same as those in Example 1.

[0101] Comparative Example 2:

[0102] A foamed ceramic material is prepared from raw materials comprising the following components:

[0103] Solid waste base materials, foaming agents, and stabilizing additives;

[0104] The solid waste-based main material consists of 91.5 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The slag consisted of 30 parts of stainless steel slag, whose chemical composition, as analyzed by XRF, was SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing by jaw crusher followed by ball milling to a particle size ≤200 mesh. The fly ash consisted of 40 parts of fly ash, whose chemical composition included SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The quartz tailings consisted of 21.5 parts of quartz tailings, whose chemical composition included SiO2 content >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0105] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0106] The stabilizing additives include barium oxide (BaO) and magnesium oxide (MgO), wherein 5 parts of barium oxide have a purity ≥99%, are industrial grade and have a particle size ≤5μm; and 4 parts of magnesium oxide have a purity ≥98.5%, are industrial grade and have a particle size ≤5μm.

[0107] A method for preparing foamed ceramic materials, the steps of which are the same as those in Example 1.

[0108] Comparative Example 3:

[0109] A foamed ceramic material is prepared from raw materials comprising the following components:

[0110] Solid waste base materials, foaming agents, and stabilizing additives;

[0111] The solid waste-based main material consists of 90.5 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The slag consisted of 30 parts of stainless steel slag, whose chemical composition, as analyzed by XRF, was SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing by jaw crusher followed by ball milling to a particle size ≤200 mesh. The fly ash consisted of 40 parts of fly ash, whose chemical composition included SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The quartz tailings consisted of 20.5 parts of quartz tailings, whose chemical composition included SiO2 content >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0112] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0113] The stabilizing additives include magnesium oxide (MgO) and titanium dioxide (TiO2), wherein 4 parts of magnesium oxide have a purity ≥98.5%, are industrial grade and have a particle size ≤5μm; and 2.5 parts of titanium dioxide have a purity ≥99%, are rutile type and have a particle size ≤1μm.

[0114] A method for preparing foamed ceramic materials, the steps of which are the same as those in Example 1.

[0115] Comparative Example 4:

[0116] A foamed ceramic material is prepared from raw materials comprising the following components:

[0117] Solid waste base materials, foaming agents, and stabilizing additives;

[0118] The solid waste-based main material consists of 71.5 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The composition of stainless steel slag (30 parts) was determined by XRF analysis to be SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing with a jaw crusher followed by ball milling to a particle size ≤200 mesh. The composition of fly ash (40 parts) included SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The composition of quartz tailings (1.5 parts) included SiO2 content >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0119] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0120] The stabilizing additives include barium oxide (BaO), magnesium oxide (MgO), and titanium dioxide (TiO2), wherein 12 parts of barium oxide have a purity ≥99%, are industrial grade, and have a particle size ≤5μm; 10 parts of magnesium oxide have a purity ≥98.5%, are industrial grade, and have a particle size ≤5μm; and 6 parts of titanium dioxide have a purity ≥99%, are rutile type, and have a particle size ≤1μm.

[0121] A method for preparing foamed ceramic materials, the steps of which are the same as those in Example 1.

[0122] Comparative Example 5:

[0123] A foamed ceramic material is prepared from raw materials comprising the following components:

[0124] Solid waste base materials, foaming agents, and stabilizers;

[0125] The solid waste base material consists of 100 parts, which are composed of stainless steel slag, fly ash and quartz tailings. The slag consisted of 30 parts of stainless steel slag, whose chemical composition, as analyzed by XRF, was SiO2 (38.5%), CaO (22.1%), Al2O3 (9.8%), MgO (7.2%), Cr2O3 (4.2%), Fe2O3 (6.5%), and other (11.7%). The main phases were dicalcium silicate, iron-magnesium spinel, and chromite. The pretreatment method was coarse crushing by jaw crusher followed by ball milling to a particle size ≤200 mesh. The fly ash consisted of 40 parts of fly ash, whose chemical composition included SiO2 (51.2%), Al2O3 (27.6%), Fe2O3 (6.8%), CaO (3.5%), and K2O (1.8%). The pretreatment method was drying before direct use. The quartz tailings consisted of 30 parts of quartz tailings, whose chemical composition included SiO2 content >92%, Al2O3 (3.5%), and K2O (1.2%). The pretreatment method was washing to remove mud and then drying.

[0126] The foaming agent is silicon carbide (SiC), with an amount of 0.8 parts, a purity of ≥98%, and a particle size of ≤10μm.

[0127] The stabilizers include aluminum dihydrogen phosphate and ammonium metavanadate, wherein 5 parts of aluminum dihydrogen phosphate have a purity ≥95% and 5 parts of ammonium metavanadate have a purity ≥99%.

[0128] A method for preparing foamed ceramic materials, the steps of which are the same as those in Example 1.

[0129] Comparative Example 6:

[0130] A foamed ceramic material, the raw material composition of which is exactly the same as that in Example 1.

[0131] A method for preparing foamed ceramic materials includes the following steps:

[0132] S1. Weigh the stainless steel slag, fly ash, and quartz tailings according to the specified proportions, and dry mix them in a mixer for 30 minutes until homogeneous. Then add silicon carbide, barium oxide, magnesium oxide, and titanium dioxide, and continue mixing for 45 minutes to ensure that all components are evenly distributed.

[0133] S2. Feed the mixed raw materials into a planetary ball mill, add zirconia grinding balls and deionized water at a mass ratio of ball:material:water = 2:1:0.6, and ball mill at 250 rpm for 8 hours. The fineness of the output slurry should be controlled to D50 ≤ 5 μm (equivalent to ≥200 mesh sieve residue < 1%).

[0134] S3. The obtained slurry is fed into a centrifugal spray drying tower for granulation. The inlet temperature is set at 450±10℃, and the outlet temperature is controlled at 110±5℃. The particle size distribution of the obtained powder is controlled as follows: 40-60 mesh 15%, 60-80 mesh 50%, 80-100 mesh 30%, and >100 mesh 5%, with a powder moisture content of 7.5%.

[0135] S4. Fill the dried powder into the refractory mold, place it in a box-type sintering furnace, and sinter it in air atmosphere according to the following procedure:

[0136] The temperature was raised directly from room temperature to 1150℃ at a rate of 300℃ / h.

[0137] Keep warm at 1150℃ for 0.5 hours;

[0138] After the heat preservation is completed, the furnace will naturally cool to room temperature.

[0139] This will yield foamed ceramic materials.

[0140] The foamed ceramic materials obtained in the examples and comparative examples were subjected to performance tests, and the results are as follows.

[0141] I. Environmental Safety Testing

[0142] This refers to the Total Chlorination Toxicity Test (TCLP).

[0143] Test Objective: To quantitatively evaluate the leaching potential of heavy metals and other toxic components in solid waste under simulated acidic landfill conditions. This test simulates the ease with which hazardous substances migrate into the environment when waste is leached by rainwater. Lower leaching concentration values ​​indicate better solidification / stabilization of hazardous elements in the material, higher long-term environmental safety, and a lower risk of secondary pollution.

[0144] Quantitative indicators: Leaching concentration of each target heavy metal element, in milligrams per liter (mg / L). Key indicators include, but are not limited to: chromium (Cr), manganese (Mn), vanadium (V), molybdenum (Mo), etc. (determined based on the actual composition of the solid waste used).

[0145] Test standard: HJ / T300-2007 - Solid waste leaching toxicity leaching method acetic acid buffer solution method.

[0146] Test method: After crushing and grinding the foamed ceramic sample, pass it through a φ9.5mm sieve, and take the sample that passes through the sieve as the test sample. Weigh a certain mass (accurate to 0.1g) of dry sample and place it in an extraction bottle. Add the extraction solvent (acetic acid buffer solution with pH 2.64 or 4.93, depending on the alkalinity of the sample) at a specified liquid-to-solid ratio (20:1L / kg). Fix the extraction bottle on a tilting shaker and shake it at a speed of (30±2)r / min for (18±2)h at a temperature of (23±2)℃.

[0147] After shaking, the leachate was pressure filtered (using a 0.6 μm or 0.8 μm glass fiber membrane). The filtrate was collected and acidified with nitric acid to pH < 2 for storage. Finally, the acidified leachate was quantitatively analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentration of each target heavy metal element. The test results were compared with the concentration limits in GB5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification".

[0148] II. Physical Performance Testing

[0149] This demonstrates that the material of this invention still possesses excellent performance while ensuring safety.

[0150] 1) Bulk density

[0151] Test objective: To quantitatively evaluate the degree of lightweighting of foamed ceramic materials. This indicator is directly related to the product's weight, thermal conductivity, and final application cost. The lower the bulk density value, the higher the degree of foaming, the lighter the material, and generally the better the thermal insulation performance, but a balance must be struck with mechanical properties.

[0152] Quantitative indicator: Bulk density, measured in kilograms per cubic meter (kg / m³). The bulk density of high-quality foamed ceramics is typically in the range of 200-400 kg / m³.

[0153] Test standard: GB / T5486-2008 - Test methods for inorganic rigid thermal insulation products.

[0154] Test method: Samples of regular geometric shapes (usually cubes or cylinders) are cut from finished foamed ceramic. The sample size should be greater than 100 mm and the volume should be not less than 100 cm³. The length, width, and height, or diameter and height, of the sample are measured using a dimensional measuring instrument with an accuracy of not less than 0.1 mm (such as a vernier caliper), and its volume (V) is calculated. The dry mass (m) of the sample is weighed using a balance with an accuracy of 0.01 g. The bulk density (ρ) is calculated using the formula ρ = m / V.

[0155] 2) Compressive strength

[0156] Test Purpose: To quantitatively evaluate the ability of foamed ceramic materials to resist compressive failure. This indicator is a core mechanical property for determining whether a material can be used as a load-bearing or non-load-bearing structural material such as walls and floors. A higher compressive strength value indicates a stronger mechanical load-bearing capacity and higher reliability during use.

[0157] Quantitative indicator: compressive strength, measured in megapascals (MPa). The compressive strength of foamed ceramics typically ranges from 3.0 to 10.0 MPa.

[0158] Test standard: GB / T5486-2008 - Test methods for inorganic rigid thermal insulation products.

[0159] Test method: The regular specimen prepared in the above bulk density test was used. The specimen was placed in the center of the pressure plate of the universal testing machine, and pressure was applied uniformly at a loading rate of (1±0.5) mm / min until the specimen failed. The maximum load (F) at specimen failure was recorded. The compressive strength (σ) was calculated according to the formula σ=F / A, where A is the area of ​​the specimen subjected to pressure.

[0160] 3) Thermal conductivity

[0161] Test Objective: To quantitatively evaluate the heat conduction capacity and thermal insulation performance of foamed ceramic materials. This indicator is a key parameter for measuring the energy-saving efficiency of materials as building insulation boards. The lower the thermal conductivity value, the better the material's thermal insulation performance, the stronger its ability to prevent heat transfer, and the more significant the energy-saving effect.

[0162] Quantitative indicator: thermal conductivity, measured in watts per meter Kelvin [W / (m·K)]. The thermal conductivity of foamed ceramics is typically in the range of 0.06-0.10 W / (m·K).

[0163] Test standard: GB / T10295-2008 - Determination of steady-state thermal resistance and related properties of thermal insulation materials by heat flow meter method.

[0164] Test method: Cut a flat, plate-shaped sample of specified dimensions (e.g., 300mm × 300mm) from the finished product, with a thickness equal to the actual thickness of the product. Place the sample in a thermal conductivity meter using the heat flux method, ensuring that the two parallel planes of the sample are in close contact with the hot and cold plates of the instrument. Under the set average temperature (e.g., 25℃) and temperature difference (e.g., 10-20℃), after the system reaches thermal stability, measure the heat flux density through the sample and the temperature difference between the two sides. The instrument then calculates and outputs the thermal conductivity value of the material.

[0165] 4) Water absorption rate

[0166] Test Objective: To quantitatively evaluate the tendency and ability of foamed ceramic materials to absorb moisture. This indicator not only reflects the open-cell porosity of the material, but is also closely related to its durability, frost resistance, weathering resistance, and long-term stability. The lower the water absorption rate, the higher the closed-cell rate of the material, the denser the structure, the less likely moisture is to penetrate, the more stable its physical properties are in humid environments, and the longer its service life.

[0167] Quantitative indicators: volumetric water absorption rate or mass water absorption rate, usually expressed as a percentage (%). The volumetric water absorption rate of high-quality foamed ceramics is typically less than 1%.

[0168] Test standard: GB / T3810.3-2016 - Test methods for ceramic tiles - Part 3: Determination of water absorption, apparent porosity, apparent relative density and bulk density (applicable to wet and dry weight method).

[0169] Test method: Cut a dry sample with a mass of not less than 50g from the finished product, place it in a drying oven at (110±5)℃ until constant weight (m_d), and cool it to room temperature in a desiccator. Immerse the cooled dry sample completely in distilled or deionized water and soak it at normal pressure and room temperature for (24±0.5)h. Remove the sample, wipe off all excess moisture with a damp gauze, and immediately weigh its saturated surface-dry mass (m_s). The water absorption rate (W_v) is calculated using the formula W_v=[(m_s-m_d) / m_d]×100% (mass water absorption rate).

[0170] III. Microstructure Testing

[0171] That is, observation by scanning electron microscopy (SEM).

[0172] Test Objective: To visually characterize the microstructure, pore structure, and phase distribution of foamed ceramic materials. This test aims to reveal the root causes of macroscopic performance differences at the microscopic level, specifically including: assessing the uniformity, size, shape (open / closed pores), and pore wall integrity of pores; and observing the morphology, size, and distribution of stabilized solidified phases (such as compounds containing Ba and Cr) within the glass matrix. By comparing the microstructures of the embodiments of this invention with those of comparative examples, direct morphological evidence is provided for their excellent leaching toxicity and physical properties.

[0173] Test Method: The foamed ceramic sample was cut into small pieces using a diamond cutter, and then vacuum-mounted and cured to protect the pore structure. The observation surface was then ground and polished to obtain a smooth surface. To enhance conductivity, the polished sample surface was sputtered with gold (Au) or carbon (C). Field emission scanning electron microscopy (FE-SEM) was used for observation. For accurate analysis of elemental distribution, backscattered electron (BSE) imaging was necessary (areas with higher atomic numbers in the BSE image are brighter). Finally, the imaging was analyzed. First, the overall pore structure was observed at low magnification, and then the micro-phase distribution was observed at high magnification using BSE mode. Energy dispersive spectroscopy (EDS) can be used to perform point or area scanning compositional analysis on the bright white areas in the BSE image to confirm that they are stable cured phases rich in elements such as Ba and Cr.

[0174] Table 1: Environmental Safety Testing

[0175]

[0176] Comparative Example 1 uses a conventional carbon reduction process without introducing the Ba-Mg-Ti stabilization system. Its Cr and Mn leaching concentrations are 2.10 mg / L and 3.50 mg / L, respectively, which are within the limits of GB5085.3-2007, but close to the critical value. It is comparable to the data of similar carbon reduction foamed ceramics in published literature, objectively reflecting the starting level of the existing technology.

[0177] In Examples 1 to 4, after the simultaneous introduction of BaO-MgO-TiO2, the Cr leaching concentration decreased from 2.10 mg / L to 0.08-0.40 mg / L, and the Mn leaching concentration decreased from 3.50 mg / L to 0.10-0.60 mg / L, with reductions of 81-96% and 83-91%, respectively. When BaO ≥ 5 parts, the Cr and Mn leaching concentrations decreased by another order of magnitude compared to the baseline, indicating that the fixation effect obtained after the three groups were combined was better than the sum of the effects when each group was used alone.

[0178] While pursuing extremely low leaching values, the examples still maintain a bulk density of 280-320 kg / m³ and a compressive strength of 8.0-8.4 MPa, which is at the same mechanical level as Comparative Example 1. This avoids the imbalance of "high curing" accompanied by "high density" or "low strength", showing a good balance of comprehensive performance.

[0179] Comparative Examples 2 and 3 showed Cr leaching levels rebounded to 1.05 mg / L and 0.85 mg / L, respectively, representing a 5-10 fold increase compared to the complete formulation; Comparative Example 4 showed Mn leaching levels rebounded to 0.15 mg / L, an order of magnitude increase. The data directly demonstrate that the absence of any single member prevents the formation of a complete crystal lattice network, disrupting the synergistic effect and leading to a significant decrease in curing efficiency.

[0180] Examples 1 to 4 all achieved Cr and Mn levels of <0.4 mg / L within the range of 1100-1150℃ and 2-2.5h holding time, demonstrating that the present invention has a practical tolerance of ≥50℃ for kiln temperature fluctuations, providing operability for industrial-scale production.

[0181] Table 2: Physical Performance Tests

[0182]

[0183] Comparative Example 1 uses the most common "carbon reduction + Ba-Mg-Ti-free" formula in existing technology. Its bulk density is 310 kg / m³, compressive strength is 7.1 MPa, thermal conductivity is 0.070 W / (m·K), and water absorption is 0.9%. These physical indicators are consistent with the range of similar foamed ceramics in published literature, objectively reflecting the current market performance starting point without being artificially suppressed, thus ensuring the comparability of subsequent comparisons.

[0184] In Examples 1 to 4, after introducing the BaO-MgO-TiO2 ternary stabilization system, the compressive strength continuously increased from 7.1 MPa to 8.4-8.9 MPa, an increase of 18-25%; the thermal conductivity decreased from 0.070 W / (m·K) to 0.063-0.068 W / (m·K), a decrease of 4-10%; and the bulk density and water absorption remained at 295-305 kg / m³ and 0.6-0.8%, respectively, on the same order of magnitude as the baseline. The data show that the ternary additive, while achieving crystal phase strengthening, did not bring about a significant increase in weight or porosity, achieving a comprehensive positive benefit of "increased strength, decreased thermal conductivity, and unchanged weight." Its overall performance improvement is greater than the range that can be explained by the superposition of single components, demonstrating synergistic enhancement characteristics.

[0185] The volume density and water absorption rate of the embodiment are within ±5% of the benchmark, avoiding the common trade-off of "high curing" accompanied by "high density" or "high water absorption". At the same time, the thermal conductivity decreases simultaneously, enabling the material to achieve better thermal insulation while maintaining its lightweight properties, successfully balancing mechanical, thermal and wet durability.

[0186] Compared with Comparative Examples 2 to 4, the compressive strength rapidly dropped to 7.0-7.3 MPa, the thermal conductivity rose to 0.069-0.071 W / (m·K), and the water absorption increased to 0.9-1.0%. All properties returned to near the baseline level, directly proving that the absence of any member would interrupt the crystalline phase synergistic network, leading to the failure of the reinforcement effect.

[0187] As the BaO content increased from 4% to 8%, the compressive strength increased by an average of 0.2-0.3 MPa for every 2 parts increase, while the thermal conductivity decreased by 0.002-0.003 W / (m·K). The changes were continuous without jumps, which is consistent with the gradual modification law. Moreover, when the BaO content was greater than 6%, the strength increase tended to level off, indicating that 6% was close to the optimal economic dosage, providing a data anchor for subsequent process optimization.

[0188] Microstructure testing

[0189] according to Figure 2 As can be seen, the 200x image of Comparative Example 1 shows that the pore size distribution is dispersed, with some through-holes >500μm appearing, and microcracks visible on the pore walls, indicating a high overall connectivity. This structure corresponds to the "carbon reduction + Ba-Mg-Ti-free" formulation in the prior art, which is consistent with the starting point of this invention and has not been artificially deteriorated, ensuring an objective comparison.

[0190] pass Figure 1 As can be seen, in Example 2 at the same magnification, the pores are circular or elliptical, with diameters concentrated in the range of 200-300 μm, uniformly distributed, and with smooth and uniform pore walls. The Ba-Mg-Ti system precipitates high-melting-point crystalline phases in advance at 1100-1150℃, and the melt viscosity window is precisely controlled, so that the bubble growth and solidification rate are matched during the SiC foaming stage, resulting in an ideal structure with high closed-pore ratio and low connectivity. The pore uniformity is improved by about 40% compared to the comparative example.

[0191] In the 3000x BSE image of Comparative Example 1, the matrix has uniform grayscale, with only sporadic bright white particles (Cr / Mn rich phase) and particle size >5μm, exhibiting an aggregated state and a number density <50 particles / mm², which corresponds to the typical characteristics of insufficient glass phase encapsulation and incomplete crystal phase analysis.

[0192] pass Figure 3 As can be seen from Example 2, under the same conditions, a large number of 1-2μm bright white particles are diffusely distributed in the matrix, with a number density ≥400 particles / mm², which are confirmed by EDS to be mainly Ba(Cr,Mn). 12 O 19 It is in the MgCr2O4 crystal phase. The grains are small and uniformly embedded, indicating that TiO2 nucleation enables the rapid precipitation of barium ferrite and spinel at low temperatures, achieving chemical fixation of heavy metals. The density of bright white particles is more than 8 times higher than that of the control group.

[0193] Figure 1 In Example 2, the uniform closed-cell structure of the sample reduced the thermal conductivity by 4-10% compared to the comparative example. Figure 3 The high-density crystalline network did not significantly increase the pore wall thickness, and the bulk density and water absorption rate remained on the same order of magnitude (±5%), successfully meeting the dual requirements of "lightweight thermal insulation" and "high strength and high curing".

[0194] Figure 3 and Figure 4 The comparison directly proves that: when BaO is missing, the bright white particles almost disappear; when TiO2 is missing, the particles are large and agglomerated; and when MgO is missing, the Mn-rich region is sparse. The absence of any member leads to a simultaneous decrease in the number and dispersion of crystal phases, reverting to the level of the comparative example, confirming that ternary synergy is a necessary condition for the formation of a dispersed solidified phase.

[0195] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A foamed ceramic material, characterized in that, Prepared from raw materials comprising the following components by mass parts: Solid waste-based main material, foaming agent and stabilizing additive; The stabilizing additive comprises barium oxide, magnesium oxide and titanium dioxide; The ratio of the components is 70-95 parts by mass of solid waste-based main material, 0.3-1.5 parts of foaming agent, 3-8 parts of barium oxide, 2-6 parts of magnesium oxide and 1-4 parts of titanium dioxide; The foamed ceramic material is prepared by the following steps: S1. Mix the raw materials according to the ratio; S2. Wet ball mill the mixed raw materials to obtain a slurry; S3. Dry granulate the slurry to obtain a powder; S4. Place the powder in a kiln and sinter in an air atmosphere, with a sintering schedule of heating to 1000-1200℃ and holding for 1-3 hours, and then cooling, to obtain the foamed ceramic material; The solid waste-based main material comprises chromium and / or manganese solid waste, with a mass ratio of 5% to 50% of the total mass of the solid waste-based main material; The phase thereof comprises spinel phase and barium ferrite phase generated by the reaction of the stabilizing additive with harmful elements.

2. A foamed ceramic material according to claim 1, characterised in that The mass ratio of barium oxide, magnesium oxide and titanium dioxide in the stabilizing additive is 3-8:2-6:1-4.

3. A foamed ceramic material according to claim 1, wherein The foaming agent is silicon carbide.

4. A method of producing a foamed ceramic material as claimed in any one of claims 1 to 3, characterised in that, Comprising the following steps: S1. Mix the raw materials according to the ratio; S2. Wet ball mill the mixed raw materials to obtain a slurry; S3. Dry granulate the slurry to obtain a powder; S4. Place the powder in a kiln and sinter in an air atmosphere, with a sintering schedule of heating to 1000-1200℃ and holding for 1-3 hours, and then cooling, to obtain the foamed ceramic material.

5. The method of claim 4, wherein, The heating process of sintering in step S4 is divided into two stages: from room temperature to 900-950℃ at a rate of 100-200℃ / h; from 900-950℃ to the final sintering temperature of 1000-1200℃ at a rate of 300-450℃ / h.

6. The method of claim 4, wherein, The fineness of the slurry after wet ball milling in step S2 is not greater than 200 mesh.

7. The method of claim 4, wherein, The particle size distribution of the powder after dry granulation in step S3 is: 40-60 mesh accounts for 10%-25%, 60-80 mesh accounts for 40%-65%, and 80-100 mesh accounts for 20%-35%.

8. The method of claim 4, wherein, The water content of the powder obtained in step S3 is controlled at 6%-10%.

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