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Process for preparing alumina powder with high sinter activity

A technology of alumina powder and sintering activity, applied in the field of fine chemical industry, can solve the problems of affecting the microstructure and mechanical properties of sintered porcelain, reducing the sinterability of powder, unfavorable to environmental protection, etc., achieving good market prospects and improving sinterability. , the effect of low cost of raw materials

Inactive Publication Date: 2002-09-18
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In the Bayer method and chemical precipitation method, the intermediate product is usually colloidal aluminum hydroxide precipitation, which contains a large amount of water and hydroxyl groups, and is easily affected by interparticle capillary force and hydroxyl condensation in the subsequent drying and calcination process. It leads to hard agglomeration of the obtained alumina powder, reduces the sinterability of the powder, and seriously affects the microstructure and mechanical properties of the sintered ceramic body
In addition, although it is possible to obtain alumina powder with less hard agglomeration and higher sintering activity through the ammonothermal decomposition of aluminum sulfate, because this method usually releases a large amount of SO 2 Harmful gas, not conducive to environmental protection

Method used

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  • Process for preparing alumina powder with high sinter activity
  • Process for preparing alumina powder with high sinter activity
  • Process for preparing alumina powder with high sinter activity

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] Add 0.4M aluminum nitrate solution (1000ml) dropwise to 4M ammonium bicarbonate solution (1500ml) while stirring at room temperature, and the white precipitate obtained is aged for 12 hours and washed 5 times with deionized water to remove free inorganic ion. The resulting precipitate was semi-dry after long-term suction filtration and dehydration, and then transferred to an oven for drying at 50°C. The obtained dry powder was subjected to XRD characterization before and after calcination at 1200°C for 1 hour, and it was found that the uncalcined powder had completely generated NH 4 Al(OH) 2 CO 3 ( figure 1 A), NH after high temperature calcination 4 Al(OH) 2 CO 3 Decompose into α-Al 2 o 3 ( figure 2 A). generated α-Al 2 o 3 The particle size is around 300nm ( image 3 A), has good sinterability. 96% of the theoretical density can be achieved by pressureless sintering at 1500°C for 2 hours, and it can be completely densified by sintering at 1525°C for 2 h...

Embodiment 2

[0030] Using 2M ammonium bicarbonate and 0.2M aluminum nitrate as raw materials, alumina powder was prepared by aging for 24 hours and calcining at 1200° C. for 1 hour, and the others were the same as in Example 1. figure 1 B and figure 2 B are the resulting NH 4 Al(OH) 2 CO 3 Precipitation and α-Al 2 o 3 XRD pattern of the powder. image 3 B is the resulting α-Al 2 o 3 SEM photo of the powder. The powder exhibits good sinterability, 98% of the theoretical density can be achieved by pressureless sintering at 1500°C for 1 hour, and complete densification can be achieved by sintering at 1525°C for 1 hour ( Figure 4 Curve B).

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Abstract

A process for preparing alumine powder with high sinter activity includes reaction of Al-contained inorganic salt chosen from aluminium nitrate, aluminium chloride and aluminium ammonium sulfate on ammonium bicarbonate at 5-50 deg.C to generate NH4Al(OH)2CO3, depositing and ageing for 2-24 hrs, washing with deionized water, baking at 50-150 deg.C and sintering at 1100-1200 deg.C to obtain alpha-Al2O3 particles less than 400 nm.

Description

technical field [0001] The invention relates to a method for preparing highly sintered active alumina powder, which belongs to the field of fine chemical industry. Background technique [0002] Alumina ceramics have the characteristics of high hardness, wear resistance, high mechanical strength, high resistivity and good chemical stability. They are widely used as integrated circuit substrates, spark plugs, friction plates and tool materials in chemical industry, electronics, textile, machinery It is a ceramic material with the widest application fields. Under ideal conditions, the strength of single-phase alumina ceramics is as high as about 700MPa. When alumina is combined with zirconia and silicon carbide nanoparticles (or whiskers), the mechanical properties of the material can be further improved to above 1-1.5GPa. [0003] At present, alumina powder is produced in large quantities in industry mainly through Bayer method, chemical precipitation method and aluminum salt...

Claims

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Application Information

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IPC IPC(8): C01F7/34
Inventor 高濂靳喜海
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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