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CN-122010152-A - High-activity high-purity corundum micropowder and preparation method and application thereof

CN122010152ACN 122010152 ACN122010152 ACN 122010152ACN-122010152-A

Abstract

The invention relates to the technical field of special alumina or fine alumina, in particular to high-activity high-purity corundum micropowder and a preparation method and application thereof. The method comprises the following steps of S1, preparing aluminum hydroxide micro powder by taking sodium aluminate solution as a raw material through high-temperature seed precipitation, S2, calcining the aluminum hydroxide micro powder obtained in S1 at high temperature to prepare alpha-Al 2 O 3 corundum micro powder, S3, carrying out wet treatment on the alpha-Al 2 O 3 corundum micro powder obtained in S2 to generate boehmite on the surface of the corundum micro powder to form a corundum-boehmite mixture phase with a core-shell structure, and S4, carrying out high-temperature calcination or calcination on the corundum-boehmite mixture phase obtained in S3 to generate high-activity high-purity corundum micro powder. According to the invention, a layer of high-activity alpha-Al 2 O 3 is modified on the surface of high-density alpha-Al 2 O 3 to form alpha-Al 2 O 3 micro powder with the same phase and isomerization property, and alumina ceramic with the relative density of more than 98% and the Vickers hardness of more than 25 GPa is sintered at the temperature of less than 1500 ℃.

Inventors

  • LIU GUIHUA
  • QI TIANGUI
  • WANG YILIN
  • WEN JINQUAN
  • LIU NIANZI
  • GUO JIAN
  • SHEN LEITING
  • ZHOU QIUSHENG

Assignees

  • 中南大学

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. The preparation method of the high-activity high-purity corundum micro powder is characterized by comprising the following steps of: s1, preparing aluminum hydroxide micro powder by taking a sodium aluminate solution as a raw material and high-temperature seed precipitation; S2, calcining the aluminum hydroxide micro powder obtained in the step S1 at high temperature to prepare alpha-Al 2 O 3 corundum micro powder; S3, carrying out wet treatment on the alpha-Al 2 O 3 corundum micro powder obtained in the S2, and generating boehmite on the surface of the corundum micro powder to form a corundum-boehmite mixture phase with a core-shell structure, wherein the boehmite is in a shell structure, the thickness is less than 200nm, and the mass is less than 10 wt% of the total mass of the corundum-boehmite mixture phase; And S4, roasting or calcining the corundum-boehmite mixture obtained in the step S4 at high temperature to generate high-activity high-purity corundum micro powder.
  2. 2. The method according to claim 1, wherein in the high-temperature seed precipitation in S1, the concentration of Na 2 O k in sodium aluminate solution is 80-160 g/L, the caustic ratio alpha k is 1.35-1.60, the high-temperature seed precipitation specifically comprises adding active seed crystal according to 0.5-20 g/L, and preparing gibbsite phase aluminium hydroxide micropowder at initial temperature of 75-80 ℃ and final temperature of 60-65 ℃, wherein the particle size d50<4 μm, d90 is less than or equal to 11.7 μm, and the aluminium hydroxide purity is >99.6%, wherein in mass percent ,Na 2 O≤0.11%,Fe 2 O 3 <0.02%,SiO 2 <0.02%,CaO<0.002%, MgO<0.002%.
  3. 3. The method according to claim 1, wherein the high-temperature calcination temperature in S2 is 1150-1350 ℃ and the time is 1-6 hours, and the alpha-Al 2 O 3 corundum micropowder is prepared by the method, wherein the alpha-Al 2 O 3 is more than or equal to 90% by mass, the content of AlO 6 structural units is more than 90% by mass, the density of the alpha-Al 2 O 3 corundum micropowder is more than 3.90 g/cm 3 , the specific surface area is S BET <4 m 2 /g, and the mass percentage is ,Na 2 O≤0.16%, Fe 2 O 3 <0.02%,SiO 2 <0.02%,CaO<0.002%, MgO<0.002%.
  4. 4. The method of claim 1, wherein the wet treatment of the corundum fine powder in S3 comprises at least one of the following: In the scheme I, in a supersaturated sodium aluminate solution with Na 2 O k <20 g/L and a caustic ratio alpha k of 1.35-2.0, the temperature is controlled to be 80-130 ℃, and the time is 60 min-10 h; Adding pseudo-boehmite sol into alpha-Al 2 O 3 corundum micro powder according to the ratio of 0.5-5 g/L, and treating for 1-6 h at the temperature of 90-130 ℃; and thirdly, ball milling and dispersing the alpha-Al 2 O 3 corundum micro powder and the water wet method according to the proportion of 100-400 g/L, and treating for 2-6 hours at the temperature of 90-130 ℃.
  5. 5. The preparation method of claim 4, wherein in the wet treatment process in S3, a surfactant is added, the surfactant comprises one or more of glucose, stearic acid, oleic acid, tween 80 or polyethylene glycol 6000-20000, the addition amount is 0-30 ppm, and the particle size of the generated aluminum hydroxide micro powder is less than 1 μm, and the aluminum hydroxide micro powder has a uniformly-wrapped core-shell structure.
  6. 6. The method according to claim 4, wherein after the wet treatment in step S3, the wet cake obtained by the treatment is subjected to a hydrothermal treatment at 150-220 ℃ for a treatment time of not more than 2 h.
  7. 7. The method according to claim 1, wherein the high-temperature firing or calcining temperature in S4 is 900 to 1200 ℃ for 1 to 5 h.
  8. 8. The high-activity high-purity corundum micropowder is characterized in that the phase of the high-activity high-purity corundum micropowder is alpha-Al 2 O 3 , wherein the content of AlO 6 structural units is more than 89% and the content of AlO 4 structural units is not less than 4.5% in terms of atomic percentage, and the density of the high-activity high-purity corundum micropowder is more than 3.89 g/cm 3 and the specific surface area S BET <7 m 2 /g; The d50 and d90 of the high-activity high-purity corundum micro powder are less than 4 microns and less than 10 microns, and the micro powder comprises the following components in parts by mass ,Na 2 O ≤0.12%,Fe 2 O 3 <0.02%,SiO 2 <0.02%,CaO<0.002%, MgO<0.002%;α-Al 2 O 3 ≥91.7%.
  9. 9. Use of the highly active highly pure corundum micropowder according to any of claims 1 to 7 or according to claim 8 for the preparation of high density and high hardness alumina ceramics.
  10. 10. The method for preparing the high-hardness alumina ceramic according to claim 9, wherein the method for preparing the high-hardness alumina ceramic comprises the steps of forming and degreasing high-activity high-purity corundum micro powder, and then sintering the high-activity high-purity corundum micro powder at 1350-1500 ℃ for 2-5 hours to prepare the high-density high-hardness alumina ceramic.

Description

High-activity high-purity corundum micropowder and preparation method and application thereof Technical Field The invention relates to the technical field of special alumina or fine alumina, in particular to high-activity high-purity corundum micropowder and a preparation method and application thereof. Background The corundum micropowder is also called alpha-Al 2O3 micropowder, and is widely applied to the fields of ceramics, crucibles, refractory materials, biological materials and the like. However, the traditional corundum micropowder has low sintering activity, needs high temperature (> 1600 ℃) and long-time sintering, or is deeply ground, or is added with additives, or is molded and sintered by adopting specific equipment, so that the alumina-based material with high density can be prepared. The method has the advantages of high energy consumption, large investment, possibility of introducing impurities and difficult post-processing, so that the improvement of the sintering activity of the corundum micro powder has important significance for economically improving the performance of the alumina-based material. The corundum micropowder is prepared by calcining alumina powder obtained by seed precipitation of aluminum hydroxide micropowder of sodium aluminate solution or subsequent calcination at high temperature (> 1200 ℃). It is generally desirable that the micropowder be in the alpha-Al 2O3 phase and have an alpha-Al 2O3 content of greater than 90%. In order to improve the performance of alumina-based materials, the prior researches mainly focus on improving the refining, purifying, surface modifying, adding sintering aids and the like of alumina powder. The main method comprises 1) refining and purifying granularity, wherein nano alumina powder is generally adopted, or deep grinding alumina powder (CN 200910040429.2) is adopted; the powder can also be subjected to acid washing (CN202411018378. X) or water washing to remove impurities and purify corundum powder, and the refining and purifying processes can obviously increase the cost of powder preparation or introduce impurities in the grinding process; 2) surface modification by adding inorganic acid (CN 202011555880.0) or organic matter, strengthening particle dispersibility, such as adding alumina sol as adhesive or adding organic matter to change particle agglomeration, which can change interface property when sintering alumina-based material and affect material performance, 3) fire treatment of powder to improve purity and alpha-Al 2O3 content, often adding boric acid and other sodium removal agents, and adding NH 4Cl、NH4F、AlF3 and other mineralizer (CN200810109087. X, CN 01803230.3) can reduce phase transformation temperature and alpha-Al 2O3 content, and can improve sintering performance and alumina ceramic density, but introduce impurities, smoke is difficult to reach standard and affect product performance, 4) adding sintering additive, often adding MgO, siO 2、TiO2、ZrO2 or other rare metal oxide (CN 202511194204.8), improving interface, inhibiting grain size, increasing density and hardness of alumina-based material, but introducing impurities into physical property of alumina-based material, 5) adopting new sintering equipment or adopting new sintering process (Xie Zhipeng and the like, advanced ceramic material can improve sintering performance, and ceramic density of alumina-based material can be improved 821 and advanced research and development of new sintering technology (20138) (09-38), but also increases the manufacturing costs significantly. The powder post-treatment or the sintering new technology can be called as a terminal strengthening process in the preparation of the alumina-based material, which often leads to impurity introduction, complicated flow, limited application field, increased cost and the like, less concern is given to the influence of high-quality alpha-Al 2O3 micro powder on the sintering performance of the alumina-based material from the source, and the technology for improving the sintering performance of the alumina-based material through the high-quality alpha-Al 2O3 powder is provided based on the regulation and control of the microstructure and the reactivity of the alpha-Al 2O3. Disclosure of Invention The invention provides high-activity high-purity corundum micropowder and a preparation method and application thereof, and aims to provide a method for improving the quality performance of alpha-Al 2O3 micropowder on the premise of not increasing impurity introduction and simplifying process flow. In order to achieve the above purpose, the invention provides a preparation method of high-activity high-purity corundum micropowder, which comprises the following steps: s1, preparing aluminum hydroxide micro powder by taking a sodium aluminate solution as a raw material and high-temperature seed precipitation; S2, calcining the aluminum hydroxide micro powder obtained in the step S1 at high temperature to prepar