阅读说明：本技术 利用粉煤灰制备复合微波吸收材料的方法 (Method for preparing composite microwave absorbing material by using fly ash ) 是由 梁丽萍 王亚珂 力国民 王凯悦 周毅 武雅乔 张克维 田玉明 柴跃生 白频波 于 2019-10-11 设计创作，主要内容包括：本发明提供了利用粉煤灰制备复合微波吸收材料的方法,属于微波吸收材料技术领域。技术方案为：首先对粉煤灰进行球磨、筛分处理,得到粉煤灰粉,通过添加络合剂、粘结剂和金属盐离子溶液形成均匀稳定的料浆,接着将料浆经过喷雾干燥工艺得到粉煤灰基微粉,然后经还原处理获得负载磁性金属单质或者合金的莫来石基复合微波吸收材料。本发明方法以固体废弃物粉煤灰为原料,实现了粉煤灰的有效回收利用,节约资源和成本；同时,本发明所述的原位喷雾干燥-负载工艺可以保证负载物均匀地分散于粉煤灰颗粒载体上,且操作过程简便,易于实施,适合于规模化工业生产应用。(The invention provides a method for preparing a composite microwave absorbing material by using fly ash, belonging to the technical field of microwave absorbing materials. The technical scheme is as follows: firstly, performing ball milling and screening treatment on the fly ash to obtain fly ash powder, adding a complexing agent, a binder and a metal salt ion solution to form uniform and stable slurry, then performing spray drying on the slurry to obtain fly ash-based micro powder, and then performing reduction treatment to obtain the mullite-based composite microwave absorbing material loaded with a magnetic metal simple substance or alloy. The method takes the solid waste fly ash as the raw material, realizes the effective recycling of the fly ash, and saves resources and cost; meanwhile, the in-situ spray drying-loading process can ensure that the loading substance is uniformly dispersed on the fly ash particle carrier, has simple and convenient operation process and easy implementation, and is suitable for large-scale industrial production application.)

1. The method for preparing the composite microwave absorbing material by using the fly ash is characterized by comprising the following steps of:

s1, ball-milling the fly ash, screening the ball-milled fly ash by a 100 ~ 240-mesh standard sieve, drying the screened fly ash for 2 ~ 3 hours at the temperature of 90 ~ 100 ℃, and reserving the fly ash powder prepared after drying for later use;

s2, preparing a solution A, namely preparing a sodium carboxymethylcellulose aqueous solution with the concentration of 0.1 ~ 6 wt% as the solution A for later use;

s3, preparing a solution B, namely preparing a salt solution with the concentration of 0.5 ~ 2 mol/L as the solution B for later use, wherein the solution B contains Fe³⁺、Co²⁺、Ni²⁺One or two of the salt solutions;

s4, adding the fly ash powder prepared in the step S1 and sodium hexametaphosphate into distilled water and stirring for 1 ~ 2 hours to prepare a solution C, respectively adding the solution C into the solution A prepared in the step S2 and the solution B prepared in the step S3, and continuously stirring for 2 ~ 3 hours at room temperature to prepare slurry for the next step, wherein the mass ratio of the fly ash powder, the sodium hexametaphosphate, the distilled water, the solution A and the solution B in the slurry is 2: 0.15: 3: 2 ~ 3: 4 ~ 6;

s5, performing spray drying treatment on the slurry obtained in the step S4 through a spray dryer to obtain the fly ash-based composite powder, wherein the working parameters of the spray dryer are as follows: the inlet temperature is 200 ℃, the air outlet temperature is 100 ℃, the feeding speed is 60 mL/h, and the pressure of the atomizer is 10 MPa;

s6, placing the fly ash-based composite powder prepared in the step S5 into a tube furnace, sintering at the constant temperature of 600 ~ 1000 ℃ for 2 ~ 3 hours in a reducing atmosphere, and cooling to the room temperature along with the furnace to prepare the composite microwave absorbing material.

2. The method for preparing a composite microwave absorbing material by using fly ash as claimed in claim 1, wherein: the main phase of the prepared composite microwave absorbing material is a mullite phase, and the magnetic component loaded on the main phase is one of simple substance Fe, simple substance Co, simple substance Ni, FeCo alloy, FeNi alloy and CoNi alloy.

Technical Field

The invention belongs to the technical field of microwave absorbing material preparation processes, and particularly relates to a method for preparing a composite microwave absorbing material by utilizing fly ash.

Background

With the rapid development of modern electronic information technology, more and more electronic devices become important tools essential for our lives and works, and are widely applied to the military field (radar) and the civil field (computer, navigation, communication and electrical equipment), thereby making great contribution to the progress and development of society. At the same time, people are also faced with the increasingly serious problem of electronic equipment radiation. In the modern society, electromagnetic wave radiation is a new pollution source following water pollution, air pollution and noise pollution, and not only can interfere communication, but also seriously harms human health.

The fly ash is mainly a solid waste and is mainly discharged by thermal power plants and industrial and mining enterprises. A large amount of land resources are occupied by solid waste coal ash, and the atmosphere, soil and water are seriously polluted. Along with the rapid development of domestic industry, the emission amount of the fly ash is continuously increased, and the emission amount of the fly ash in China reaches 1/5 which is close to the global emission amount at present, but the average utilization rate of the fly ash is relatively low. Therefore, the contradiction that the supply is more than the demand in the link of comprehensive utilization of the fly ash is urgently needed to be solved, so that the effective reutilization of solid waste resources is realized. It is worth noting that the fly ash has a porous cellular structure and a large number of unique hollow microbeads with stable performance, so that the fly ash is widely used as a good light matrix.

In view of the above, if the fly ash can be recycled to prepare the microwave absorbing material, not only can the pollution caused by the emission and accumulation of the fly ash be eliminated, but also the economic benefit and the social benefit are remarkable, and more importantly, reference is provided for the effective comprehensive utilization of the solid waste. The Chinese patent 201811250634.7 discloses that magnetic metal and organic polymer are coated on hollow micro-beads in fly ash by chemical plating and in-situ polymerization respectively to obtain a light microwave absorbing material; bora and the like adopt a chemical precipitation and thermal reduction method to coat NiO on the fly ash hollow microsphere to prepare a polyvinyl butyraldehyde-NiO-fly ash hollow microsphere composite wave-absorbing material (composite Part B-Eng, 2018, 134, 151-containing 163.); the Chinese patent 201811258205.4 discloses that a series of barium ferrite magnetic components are coated on glass beads by a sol-gel process to prepare the fly ash glass bead-ferrite composite wave-absorbing material.

The common idea of the above patent methods is to separate the cenospheres in the fly ash, perform hydrophilization treatment on the cenospheres, then coat the magnetic component on the surface of the cenospheres by adopting various chemical synthesis processes, including a precipitation method, a sol-gel method, a solvothermal method and a chemical vapor deposition method, and finally form the composite microwave absorbing material after high-temperature heat treatment. However, the above studies only selectively utilize the hollow microspheres in the fly ash, and the remaining components are discarded therewith, which is very likely to cause the problem of secondary pollution, and actually does not completely improve the current situation of comprehensive utilization of fly ash.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a method for preparing a composite microwave absorbing material by using fly ash, which solves the technical problem that the preparation process of the composite microwave absorbing material in the prior art is complicated on one hand, and solves the problem of secondary pollution caused by excess materials after the composite microwave absorbing material is prepared in the prior art on the other hand.

The invention is realized by the following technical scheme:

the method for preparing the composite microwave absorbing material by utilizing the fly ash comprises the following steps:

s1, ball-milling the fly ash, screening the ball-milled fly ash by a 100 ~ 240-mesh standard sieve, drying the screened fly ash for 2 ~ 3 hours at the temperature of 90 ~ 100 ℃, and reserving the fly ash powder prepared after drying for later use;

s2, preparing a solution A, namely preparing a sodium carboxymethylcellulose aqueous solution with the concentration of 0.1 ~ 6 wt% as the solution A for later use;

s3, preparing a solution B, namely preparing a salt solution with the concentration of 0.5 ~ 2 mol/L as the solution B for later use, wherein the solution B contains Fe³⁺、Co²⁺、Ni²⁺One or two of the salt solutions;

s4, adding the fly ash powder prepared in the step S1 and sodium hexametaphosphate into distilled water and stirring for 1 ~ 2 hours to prepare a solution C, respectively adding the solution C into the solution A prepared in the step S2 and the solution B prepared in the step S3, and continuously stirring for 2 ~ 3 hours at room temperature to prepare slurry for the next step, wherein the mass ratio of the fly ash powder, the sodium hexametaphosphate, the distilled water, the solution A and the solution B in the slurry is 2: 0.15: 3: 2 ~ 3: 4 ~ 6;

the fly ash micro powder in the prepared slurry is uniformly dispersed in the slurry, and the sodium hexametaphosphate is a stable complex ion compound formed by the sodium hexametaphosphate and metal salt ions and is attached to the surface of the fly ash particles, so that the hydrolysis of the metal ions is prevented; meanwhile, the sodium carboxymethyl cellulose plays a role in dispersing and binding, so that the slurry has certain viscosity, namely, the uniformity and stability of each component in the slurry are ensured;

s5, performing spray drying treatment on the slurry obtained in the step S4 through a spray dryer to obtain the fly ash-based composite powder, wherein the working parameters of the spray dryer are as follows: the inlet temperature is 200 ℃, the air outlet temperature is 100 ℃, the feeding speed is 60 mL/h, and the pressure of the atomizer is 10 MPa;

s6, placing the fly ash-based composite powder prepared in the step S5 into a tube furnace, sintering at the constant temperature of 600 ~ 1000 ℃ for 2 ~ 3 hours in a reducing atmosphere, and cooling to room temperature along with the furnace to prepare the composite microwave absorbing material;

through a spray drying process, moisture in the slurry is fully removed to obtain composite powder, a matrix of the composite powder is fly ash particles, a metal salt ion precursor is uniformly deposited on the surfaces of the fly ash particles and in the pores after being subjected to spray drying and primary decomposition, and then various magnetic components can be obtained through reduction treatment, wherein the magnetic components are generated through in-situ reduction reaction on the fly ash particles. Meanwhile, SiO in the carrier fly ash component₂And Al₂O₃The mullite (3 Al) is generated by reaction in the sintering process₂O₃·2SiO₂) Therefore, the obtained mullite-based composite wave-absorbing material is uniform in composition and structure, and finally the material is ensured to have good wave-absorbing performance.

Furthermore, the main phase of the prepared composite microwave absorbing material is a mullite phase, and the magnetic component loaded on the main phase is one of simple substance Fe, simple substance Co, simple substance Ni, FeCo alloy, FeNi alloy and CoNi alloy.

Compared with the prior art, the invention has the beneficial effects that:

(1) the in-situ spray drying-loading process used by the invention realizes that the loading substance is uniformly dispersed on the fly ash particle carrier, and compared with the traditional chemical synthesis process comprising a precipitation method, a hydrothermal method, chemical plating and a chemical vapor deposition method, the method has simple process steps and better loading effect of the magnetic component.

(2) The raw material fly ash used by the invention is solid waste, and has wide source and low cost; the fly ash is not subjected to separation and purification and subsequent series of modification treatment, is directly used after being crushed, is not limited by regions and production places, and really realizes high-efficiency recycling of the fly ash.

Drawings

FIG. 1 is an X-ray diffraction spectrum of the wave-absorbing material prepared in example 1.

Fig. 2 is a microwave absorption curve of the wave-absorbing material prepared in example 4 at different coating thicknesses.

Detailed Description

To explain technical solutions, structural features, and technical effects of the present invention in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the detailed description. The following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention.