阅读说明：本技术 一种梯度孔隙结构的多孔陶瓷的制备方法 (Preparation method of porous ceramic with gradient pore structure ) 是由 张军 于 2021-11-01 设计创作，主要内容包括：本发明公开一种具有梯度孔隙结构的多孔陶瓷的制备方法,包括步骤：将垃圾焚烧炉底灰、废玻璃、发泡剂(焦炭、木炭、活性炭、煤粉中的一种或任意几种的混合物)进行混合、磨细后,经干燥过筛处理,获得多孔陶瓷粉末原料；将所述多孔陶瓷粉末原料均匀平铺入外壁及底部具有透气性的坩埚中振实,在氮气气氛中进行高温加热并保温,在保温过程中通入一定量的空气,随炉冷却后,即可制得气孔尺寸从表面到内部呈现梯度减小的多孔陶瓷；本发明所述方法工艺过程简单,生产成本低且无需特殊处理手段,仅通过控制通入的空气量,即可制备出从表面到内部气孔尺寸呈梯度分布的多孔陶瓷。(The invention discloses a preparation method of porous ceramic with a gradient pore structure, which comprises the following steps: mixing and grinding waste incinerator bottom ash, waste glass and a foaming agent (one or a mixture of any of coke, charcoal, activated carbon and coal powder), and drying and sieving to obtain a porous ceramic powder raw material; uniformly spreading the porous ceramic powder raw material in a crucible with air permeability on the outer wall and the bottom, compacting, heating at high temperature in a nitrogen atmosphere, preserving heat, introducing a certain amount of air in the heat preservation process, and cooling along with a furnace to obtain the porous ceramic with the pore size gradually reduced from the surface to the inside; the method has simple process and low production cost, does not need special treatment means, and can prepare the porous ceramic with the pore size distributed in a gradient way from the surface to the inner part only by controlling the introduced air quantity.)

1. A preparation method of porous ceramics with a gradient pore structure is characterized by comprising the following steps:

s1, mixing the powder: mixing, grinding and drying the waste incinerator bottom ash, the waste glass and the foaming agent, and then sieving the mixture to obtain a porous ceramic raw material with the granularity of less than 90 meshes;

s2, die filling and foaming: uniformly spreading the porous ceramic powder raw material in a crucible with air permeability on the outer wall and the bottom, compacting, heating to a foaming temperature in a nitrogen atmosphere, and preserving heat; and introducing air during the temperature keeping period, and controlling the introduction volume of the air to obtain the porous ceramic with the pore size gradually reduced from the surface to the inside.

2. The method of claim 1, wherein in step S1, the foaming agent is one or a mixture of any of coke, charcoal, activated carbon, coal powder, and graphite.

3. The method of claim 1, wherein in step S1, the mass fraction of the bottom ash of the waste incinerator is 59.85 wt% to 79.95wt%, the mass fraction of the waste glass is 20 wt% to 40 wt%, and the mass fraction of the foaming agent is 0.05 wt% to 0.15 wt%.

4. The method of claim 1, wherein in step S2, the volume of the air is [ C content (g) of foaming agent in raw material x (0.1-10) ] (L).

5. The method for preparing porous ceramic with gradient pore structure according to claim 1, wherein in the high temperature foaming process in step S2, the temperature rise rate is 2-15 ℃/min before the target foaming temperature is reached, the foaming temperature is 900-1000 ℃, and the temperature is maintained for 10-90 minutes.

Technical Field

The invention relates to the technical field of porous ceramic preparation, in particular to a preparation method of porous ceramic with a gradient pore structure.

Background

The urban solid waste incineration is an efficient household waste management technology and has the advantages of small volume, light weight, energy recovery and the like. The bottom ash of the garbage incinerator is a dangerous waste containing a plurality of soluble salts and heavy metals generated in the using process of the municipal solid garbage incineration technology. The large stockpiling of the materials can cause immeasurable pollution to the surrounding environment. Heat treatment is considered to be one of the best methods for detoxifying the bottom ash of a garbage incinerator. Because the bottom ash of the waste incinerator contains a large amount of elements such as silicon, aluminum, calcium and the like which are needed by firing ceramics, the porous ceramics prepared by using the bottom ash not only can solve the problems of environmental pollution and the like caused by the accumulation of a large amount of the bottom ash, but also can reduce the production cost for preparing the porous ceramics.

Porous ceramics, as a novel functional material, has been widely used in many fields such as filters, catalyst carriers, heat converters, heat-insulating and sound-absorbing materials, etc. due to their high specific surface area, high specific strength, and good thermal shock resistance, sound insulation, and heat-insulating properties. The porous ceramic is generally prepared by a partial sintering method, an organic foam impregnation method, a pore-forming agent adding method, a direct foaming method, a gel filling method, a freeze drying method, a three-dimensional printing method and the like. Compared with other methods for producing porous ceramics, the direct foaming method has the advantages of simple process, high closed porosity of the prepared porous ceramics and the like, and can meet the heat preservation and insulation requirements of most application scenes.

Chinese patent (ZL 201310556866.6) discloses a method for preparing cordierite porous ceramic by using impurity-removed coal gangue as a raw material, wherein the method comprises the steps of removing impurities from the coal gangue, then using the impurity-removed coal gangue, talc, alumina and magnesium oxide as raw materials, using activated carbon as a pore-forming agent, performing compression molding, and performing high-temperature sintering to obtain the cordierite porous ceramic, wherein the prepared porous ceramic has good mechanical properties. However, the method needs impurity removal treatment on raw materials, the production process is complicated, the temperature required for firing the ceramic is high, energy consumption is high, and industrial production of the ceramic is limited.

The Chinese invention patent (ZL 201110252396.5) discloses a pore gradient silicon carbide porous ceramic and a preparation method thereof, wherein polycarbosilane and silicon carbide powder are used as main raw materials, carbon powder is used as a pore-forming agent, high-temperature sintering is carried out under the protection of inert atmosphere after ball milling and mixing, a porous ceramic intermediate is prepared after cooling to room temperature, and then secondary sintering is carried out to remove the carbon powder and the pore-forming agent, so that the silicon carbide porous ceramic with obvious pore gradient distribution can be obtained. However, the currently reported technology has the problems of complex production and treatment process and high cost of raw materials and foaming agents, and cannot meet the requirements of industrial production. A preparation method of the gradient structure porous ceramic with simple preparation process and low production cost needs to be searched.

In the above published schemes, carbon powder, activated carbon, etc. are used as pore-forming agents, and the pore-forming agents are oxidized at high temperature to obtain a porous structure. However, the structure of the obtained pores depends on the distribution and the shape of the pore-forming agent, so that the pore-forming agent is not uniformly mixed in the production process to cause uneven distribution of pores in the porous ceramic; and the pore-forming agent has uneven size, which also causes the pore size distribution to be larger.

In order to solve the problems, a novel preparation method of foamed ceramics is provided by deeply researching the foaming process and the foaming principle, taking one or a mixture of any more of carbon-containing coke, charcoal, activated carbon, coal powder and graphite as a foaming agent, and the foaming process is controlled by controlling the amount of air to be introduced so as to obtain a method for obtaining a gradient distribution pore structure. Through a large number of experiments, the method is proved to be feasible. The method avoids the oxidation loss of the foaming agent at low temperature, so the consumption of the foaming agent is less and the production cost of the porous ceramic is low.

Disclosure of Invention

In order to solve the technical defects, the technical scheme adopted by the invention is that the preparation method of the porous ceramic with the gradient pore structure comprises the following steps:

s1, mixing the powder: mixing, grinding and drying the waste incinerator bottom ash, the waste glass and the foaming agent, and then sieving the mixture to obtain a porous ceramic raw material with the granularity of less than 90 meshes;

s2, die filling and foaming: uniformly spreading the porous ceramic powder raw material in a crucible with air permeability on the outer wall and the bottom, compacting, heating to a foaming temperature in a nitrogen atmosphere, and preserving heat; and introducing air during the temperature keeping period, and controlling the introduction volume of the air to obtain the porous ceramic with the pore size gradually reduced from the surface to the inside.

2. Preferably, in step S1, the foaming agent is one or a mixture of any of coke, charcoal, activated carbon, coal powder and graphite.

3. Preferably, in the step S1, the mass fraction of the bottom ash of the waste incineration furnace is 59.85 wt% to 79.95wt%, the mass fraction of the waste glass is 20 wt% to 40 wt%, and the mass fraction of the foaming agent is 0.05 wt% to 0.15 wt%.

4. Preferably, in the step S2, the volume of the introduced air is [ carbon content (g) of the foaming agent in the raw material x (0.1-10) ] (liter).

5. Preferably, in the high-temperature foaming process in the step S2, the heating rate is 2 to 15 ℃/min before the target foaming temperature is reached, the foaming temperature is 900 to 1000 ℃, and the temperature is maintained for 10 to 90 minutes.

The invention has the following beneficial effects:

1. the materials used in the invention are solid wastes except the foaming agent, so that the waste of resources can be avoided, the production cost is greatly reduced, and the pollution to the environment can be avoided; 2. the foaming agent used in the invention is one or a mixture of any more of coke, charcoal, activated carbon, coal powder and graphite, so that the problem of high cost for producing the porous ceramic material due to overhigh price of the foaming agent is avoided; 3. the method has simple process and is beneficial to industrial production; 4. the temperature rise program is simple, the pore distribution of the prepared porous ceramic gradient structure is obviously different from that of the common porous ceramic, and the method can adapt to the requirements of different use environments on heat insulation materials.

Drawings

FIG. 1 is a schematic vertical sectional view of a porous ceramic prepared in the example.

Detailed Description

In order to show the essential features and the remarkable developments of the invention, the following non-limiting examples are used to further illustrate the embodiments and effects.

Example 1

(1) Prefabrication and batching of raw materials: 11.98 g of bottom ash of the garbage incinerator, 8 g of waste glass powder and 0.02 g of activated carbon are added, which respectively account for 59.90 wt%, 40 wt% and 0.10 wt% of the total mass of the sample, and the mixture is uniformly ground in a ball mill at high speed, and the grinding medium is distilled water. And drying the ground slurry at 110 ℃ for 4 hours, and then sieving the dried slurry by a 90-mesh sieve to obtain the porous ceramic powder raw material.

(2) Foaming procedure and temperature reduction: the porous ceramic powder raw material is flatly paved into a crucible with air permeability on the outer wall and the bottom, the crucible is scraped and compacted, the temperature is increased to 950 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, the heat preservation time is 30 minutes, air is introduced according to the quantity of [ carbon content (gram) x 1.5 (liter) of foaming agent in the raw material ] during the heat preservation period, then the nitrogen atmosphere is continuously maintained, the novel porous ceramic can be obtained, and the pore size distribution presents obvious gradient distribution from the surface to the inner part of the vertical section, and the real object is shown in figure 1. The porous ceramic obtained in example 1 gradually decreased in pore size from the surface to the inside, and exhibited a sharp gradient distribution, as compared with a general porous ceramic.

Example 2

(1) Prefabrication and batching of raw materials: 11.97 g of bottom ash of the garbage incinerator, 8 g of waste glass powder and 0.03 g of activated carbon are added, which respectively account for 59.85 wt%, 40 wt% and 0.15 wt% of the total mass of the sample, and the mixture is uniformly ground in a ball mill at high speed, wherein the grinding medium is distilled water. And drying the ground slurry at 110 ℃ for 4 hours, and then sieving the dried slurry by a 90-mesh sieve to obtain the porous ceramic powder raw material.

(2) Foaming procedure and temperature reduction: the porous ceramic powder raw material is spread in a crucible with air permeability on the outer wall and the bottom, the crucible is scraped and compacted, the temperature is raised to 900 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, the heat preservation time is 10 minutes, air is introduced according to the quantity of [ carbon content (gram) x 10 (liter) of foaming agent in the raw material ] during the heat preservation period, then the nitrogen atmosphere is continuously maintained, the novel porous ceramic can be obtained, and the pore size distribution presents obvious gradient distribution from the surface to the inner part of the vertical section.

Example 3

(1) Prefabrication and batching of raw materials: adding 15.99 g of bottom ash of the garbage incinerator, 4 g of waste glass powder and 0.01 g of activated carbon, which respectively account for 79.95wt%, 20 wt% and 0.05 wt% of the total mass of the sample, and uniformly grinding in a ball mill at high speed, wherein a grinding medium is distilled water. And drying the ground slurry at 110 ℃ for 4 hours, and then sieving the dried slurry by a 90-mesh sieve to obtain the porous ceramic powder raw material.

(2) Foaming procedure and temperature reduction: the porous ceramic powder raw material is spread in a crucible with air permeability on the outer wall and the bottom, the crucible is scraped and compacted, the temperature is raised to 1000 ℃ at the heating rate of 15 ℃/min in the nitrogen atmosphere, the heat preservation time is 90 minutes, air is introduced according to the quantity of [ carbon content (gram) x 0.1 (liter) of foaming agent in the raw material ] during the heat preservation period, then the nitrogen atmosphere is continuously maintained, the novel porous ceramic can be obtained, and the pore size distribution presents more obvious gradient distribution from the surface to the inner part of the vertical section.

The above examples are merely illustrative of the present invention and are not intended to limit the present invention. It will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined in the appended claims, and it is intended that all such embodiments be considered as examples herein. All obvious changes and modifications of the present invention are within the scope of the present invention.