阅读说明：本技术 一种喷涂用球形高发射率粉体的制备方法 (Preparation method of spherical high-emissivity powder for spraying ) 是由 刘玲 马壮 柳彦博 张淑玉 于 2020-07-17 设计创作，主要内容包括：本发明涉及一种喷涂用球形高发射率粉体的制备方法,属于高发射率粉体制备技术领域。通过将干燥原料混均,然后以2～5℃/min升温至1300～1500℃,保温,得到钙钛矿型高发射率粉体；然后将钙钛矿型高发射率粉体、球磨分散剂和粘结剂放入搅拌球磨机中球磨,得到浆料；将浆料通过喷雾造粒得到球形团聚粉体；然后煅烧,随炉冷却后过筛,得到粒径30～80μm的团聚粉体,即为一种喷涂用球形高发射率粉体。所述方法制得的粉体几乎无杂相,适用于高温有氧环境,且所述粉体发射率较高,全波段发射率可达0.92以上；所述粉体球形度高、流动性好且粒径分布均匀；制备安全性高、工艺简便、成本低廉且可批量工业化生产。(The invention relates to a preparation method of spherical high-emissivity powder for spraying, belonging to the technical field of preparation of high-emissivity powder. Uniformly mixing dry raw materials, heating to 1300-1500 ℃ at a speed of 2-5 ℃/min, and preserving heat to obtain perovskite high-emissivity powder; then putting the perovskite high-emissivity powder, the ball-milling dispersing agent and the binder into a stirring ball mill for ball milling to obtain slurry; carrying out spray granulation on the slurry to obtain spherical agglomerated powder; then calcining, cooling along with the furnace, and sieving to obtain agglomerated powder with the particle size of 30-80 mu m, namely the spherical high-emissivity powder for spraying. The powder prepared by the method almost has no impure phase, is suitable for a high-temperature aerobic environment, and has high emissivity, and the emissivity of a full wave band can reach more than 0.92; the powder has high sphericity, good fluidity and uniform particle size distribution; the preparation safety is high, the process is simple and convenient, the cost is low, and the method can be used for batch industrial production.)

1. A preparation method of spherical high-emissivity powder for spraying is characterized by comprising the following steps: the chemical expression of the powder is La_1-xA_xCr_1-yB_yO₃(ii) a A is more than one of Ca and Sr, B is more than one of Mg, Co and Mn, x is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0.05 and less than or equal to 0.3;

the method comprises the following steps:

(1) the method comprises the following steps of uniformly mixing dry raw materials by adopting a dry powder mixer, wherein the raw materials are as follows: la₂O₃CaO and SrCO₃More than one of (1), (c) Cr₂O₃And MgO, Co₂O₃And MnO₂One or more of (1);

(2) heating the uniformly mixed raw materials to 1300-1500 ℃ at the heating rate of 2-5 ℃/min, and preserving the heat for 2-5 h to obtain the perovskite high-emissivity powder;

(3) putting the perovskite high-emissivity powder, the ball-milling dispersing agent and the binder into a stirring ball mill for ball milling to obtain slurry;

(4) feeding the slurry into an atomizer of a granulation tower through a peristaltic pump, wherein the upper opening temperature of the granulation tower is 250-310 ℃, the lower opening temperature is 100-130 ℃, the rotation speed of the peristaltic pump is 25-35 rpm, and the rotation speed of a spray head is 30-40 Hz, and performing spray granulation to obtain spherical agglomerated powder;

(5) calcining the spherical agglomerated powder: heating to 500-600 ℃ at the speed of 2-5 ℃/min, keeping the temperature for 3-5 h, continuing heating to 1100-1250 ℃ at the speed of 5-6 ℃/min, keeping the temperature for 2-3 h, cooling along with the furnace, and sieving to obtain the agglomerated powder with the particle size of 30-80 mu m, namely the spherical high-emissivity powder for spraying.

2. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (1): la₂O₃、CaO、SrCO₃、Cr₂O₃、MgO、Co₂O₃And MnO₂The purity of (A) is analytically pure.

3. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (1): heating up the La containing the crystal water at a heating rate of 3-5 ℃/min₂O₃Heating the powder to 1000 ℃, keeping the temperature for 2-3 h to remove the crystal water, heating other oxide powder containing the crystal water in the raw material to 400 ℃ at the heating rate of 3-5 ℃/min, and keeping the temperature for 1-3 h to remove the crystal water.

4. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (1): stirring the raw materials at the rotating speed of 1200 r/min-1600 r/min for 5 min-10 min, standing for 2 min-5 min, and uniformly mixing.

5. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (1): la₂O₃、CaO、SrCO₃、Cr₂O₃、MgO、Co₂O₃And MnO₂The purity of (A) is analytically pure;

heating up the La containing the crystal water at a heating rate of 3-5 ℃/min₂O₃Heating the powder to 1000 ℃, keeping the temperature for 2-3 h to remove the crystal water, and heating the powder at 3-5 ℃/minHeating other oxide powder containing crystal water in the raw material to 400 ℃ at a temperature rate, and keeping the temperature for 1-3 h to remove the crystal water;

stirring the raw materials at the rotating speed of 1200 r/min-1600 r/min for 5 min-10 min, standing for 2 min-5 min, and uniformly mixing.

6. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (3): the mass fraction of the perovskite high-emissivity powder is 40-50% based on 100% of the total mass of the perovskite high-emissivity powder and the ball-milling dispersing agent.

7. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (3): the mass fraction of the binder is 0.5 percent based on the total mass of the perovskite high-emissivity powder as 100 percent.

8. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (3): the ball milling dispersing agent is deionized water; the mass ratio of the ball material is 4: 1; zirconium oxide is used as a grinding ball; the ball milling speed is 150 r/min-180 r/min, and the ball milling time is 3 h-6 h.

9. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (3): the mass fraction of the perovskite high-emissivity powder is 40-50% calculated by the total mass of the perovskite high-emissivity powder and the ball-milling dispersing agent as 100%;

the mass fraction of the binder is 0.5 percent based on 100 percent of the total mass of the perovskite high-emissivity powder;

the ball milling dispersing agent is deionized water; the mass ratio of the ball material is 4: 1; zirconium oxide is used as a grinding ball; the ball milling speed is 150 r/min-180 r/min, and the ball milling time is 3 h-6 h.

10. The preparation method of the spherical high-emissivity powder for spraying according to claim 1, wherein the preparation method comprises the following steps: in the step (1):

La₂O₃、CaO、SrCO₃、Cr₂O₃、MgO、Co₂O₃and MnO₂The purity of (A) is analytically pure;

heating up the La containing the crystal water at a heating rate of 3-5 ℃/min₂O₃Heating the powder to 1000 ℃, keeping the temperature for 2-3 h to remove the crystal water, heating other oxide powder containing the crystal water in the raw material to 400 ℃ at the heating rate of 3-5 ℃/min, and keeping the temperature for 1-3 h to remove the crystal water;

stirring the raw materials at the rotating speed of 1200 r/min-1600 r/min for 5 min-10 min, standing for 2 min-5 min, and uniformly mixing;

in the step (3):

the mass fraction of the perovskite high-emissivity powder is 40-50% calculated by the total mass of the perovskite high-emissivity powder and the ball-milling dispersing agent as 100%;

the mass fraction of the binder is 0.5 percent based on 100 percent of the total mass of the perovskite high-emissivity powder;

the ball milling dispersing agent is deionized water; the mass ratio of the ball material is 4: 1; zirconium oxide is used as a grinding ball; the ball milling speed is 150 r/min-180 r/min, and the ball milling time is 3 h-6 h.

Technical Field

The invention relates to a preparation method of spherical high-emissivity powder for spraying, in particular to La with a perovskite structure_1-xA_xCr_1-yB_yO₃Belonging to the technical field of high-emissivity powder preparation.

Background

The high emissivity material is a thermal protection material which takes infrared radiation heat exchange as a main way. In the military field, high emissivity materials have become an effective way to reduce the surface temperature of the metallic skin of the hypersonic aircraft; in the civil field, high emissivity materials have been widely used in the fields of infrared radiation heating, kiln heat preservation, energy conservation and the like. However, the conventional non-oxide systems such as SiC have the defect of deterioration caused by oxidation, and cannot be efficiently used in a high-temperature aerobic environment, and a single material only has high emissivity in a limited waveband, and has low average emissivity in a full waveband, so that the problem of waveband expansion is urgently solved. Researches show that the composite oxide material of the perovskite system easily has high emissivity, and element doping is beneficial to further improving the emissivity of the perovskite system in the full-wave-band range.

Atmospheric plasma spraying is a very effective surface protection means, has a remarkable protection effect on inner layer materials, and is widely applied to the fields of aerospace, metallurgical industry and the like; the use of high emissivity materials is also common in the form of coatings. However, the powder prepared by sintering and crushing has irregular shape, poor fluidity and low deposition rate, and the granulation method commonly used in laboratories has complex process, low productivity, needs to use a large amount of absolute ethyl alcohol and has certain danger. Therefore, it is necessary to prepare a high emissivity powder with high sphericity and good fluidity, which can be mass produced.

Disclosure of Invention

The invention aims to provide a preparation method of spherical high-emissivity powder for spraying, which is simple in process, low in cost and suitable for mass production.

In order to achieve the purpose of the invention, the following technical scheme is provided.

A preparation method of spherical high-emissivity powder for spraying, wherein the chemical expression of the powder is La_1-xA_xCr_{1- y}B_yO₃(ii) a Wherein, A is more than one of Ca and Sr, B is more than one of Mg, Co and Mn, x is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0.05 and less than or equal to 0.3; the method isThe method comprises the following steps:

(1) uniformly mixing the dried raw materials by adopting a dry powder mixer;

(2) and (2) heating the uniformly mixed raw materials prepared in the step (1) to 1300-1500 ℃ at the heating rate of 2-5 ℃/min, and preserving the heat for 2-5 h to obtain the irregular brown black perovskite type high-emissivity powder.

(3) Putting the perovskite high-emissivity powder, the ball-milling dispersing agent and the binder into a stirring ball mill for ball milling to obtain stably suspended slurry;

(4) feeding the slurry obtained in the step (3) into an atomizer of a granulation tower through a peristaltic pump, wherein the upper opening temperature of the granulation tower is 250-310 ℃, the lower opening temperature is 100-130 ℃, the rotation speed of the peristaltic pump is 25-35 rpm, and the rotation speed of a spray head is 30-40 Hz, and performing spray granulation to obtain spherical agglomerated powder;

(5) calcining the spherical agglomerated powder obtained in the step (4): heating to 500-600 ℃ at the speed of 2-5 ℃/min, keeping the temperature for 3-5 h, continuing heating to 1100-1250 ℃ at the speed of 5-6 ℃/min, keeping the temperature for 2-3 h, cooling along with the furnace, and sieving to obtain the agglomerated powder with the particle size of 30-80 mu m, namely the spherical high-emissivity powder for spraying.

In the step (1):

the raw materials are as follows: la₂O₃CaO and SrCO₃More than one of (1), (c) Cr₂O₃And MgO, Co₂O₃And MnO₂More than one of them.

Preferably La₂O₃、CaO、SrCO₃、Cr₂O₃、MgO、Co₂O₃And MnO₂The purity of (A) is analytically pure.

Because the oxide is easy to react with water in the air to generate crystal water, the La containing the crystal water is preferably heated at a heating rate of 3-5 ℃/min₂O₃Heating the powder to 1000 ℃, keeping the temperature for 2-3 h to remove the crystal water, heating other oxide powder containing the crystal water in the raw material to 400 ℃ at the heating rate of 3-5 ℃/min, and keeping the temperature for 1-3 h to remove the crystal water.

Preferably, the raw materials are stirred for 5min to 10min at the rotating speed of 1200r/min to 1600r/min, then are kept stand for 2min to 5min and are mixed evenly.

In the step (3):

preferably, the mass fraction of the perovskite high-emissivity powder is 40-50% calculated by the total mass of the perovskite high-emissivity powder and the ball-milling dispersing agent being 100%; the mass fraction of the binder is 0.5 percent based on the total mass of the perovskite high-emissivity powder as 100 percent.

Preferably, the ball milling dispersant is deionized water.

Preferably, the mass ratio of the ball materials is 4: 1.

Preferably, the ball milling speed is 150 r/min-180 r/min, and the ball milling time is 3 h-6 h.

Zirconia is preferred as the grinding ball.

Advantageous effects

1. The invention provides a preparation method of spherical high-emissivity powder for spraying, the powder prepared by the method almost has no impure phase, is suitable for a high-temperature aerobic environment, has high emissivity, can reach the emissivity of more than 0.92 in all wave bands, and is an ideal high-emissivity material; the prepared material is spherical agglomerated powder, and has high sphericity, good fluidity and uniform particle size distribution; the preparation process does not need to introduce anhydrous ethanol and other flammable and explosive materials, has high safety, simple and convenient process and low cost, can be produced in batches, and is suitable for industrial popularization.

2. The invention provides a preparation method of spherical high-emissivity powder for spraying, which can remove residual binder by calcining and simultaneously ensure that the spherical agglomerated powder has a more compact structure and is not easy to break.

Drawings

FIG. 1 shows La of example 1_0.7Ca_0.3Cr_0.95Mn_0.05O₃X-ray diffraction (XRD) pattern of the powder.

FIG. 2 shows La in example 1_0.7Ca_0.3Cr_0.95Mn_0.05O₃And (3) locally scanning an electron microscope (SEM image) sheet before calcining the spherical agglomerated powder.

FIG. 3 shows La of example 1_0.7Ca_0.3Cr_0.95Mn_0.05O₃And (4) local SEM pictures of the calcined spherical agglomerated powder.

FIG. 4 shows La in example 2_0.95Sr_0.05Cr_0.7Co_0.1Mg_0.2O₃XRD pattern of powder.

FIG. 5 shows La in example 2_0.95Sr_0.05Cr_0.7Co_0.1Mg_0.2O₃SEM pictures of the powder.

Detailed Description

For a better understanding of the present invention, the following further illustrates the present disclosure with reference to the accompanying drawings and specific examples, but the present disclosure is not limited thereto.

The following tests were carried out on the products of the following examples:

(1) x-ray diffraction (XRD) testing

BRUKER Axs D2, BRUKER Axs ltd, germany;

(2) scanning Electron Microscope (SEM) Observation

Philips S-4800, Hitachi high and New technology Co, Japan;

(3) fluidity test

Funnel type Hall flow meter, Beijing iron and Steel research institute;

(4) emissivity test

IR-2, Shanghai Chengpo photoelectric technology, Inc.