CN101113095A - Synthetic preparation method of A1N ceramic powder - Google Patents

Abstract

The invention belongs to the field of ceramic materials, and in particular relates to a method for synthesizing and preparing AlN ceramic powder. The material preparation process mainly includes: preparation of aluminum carbonate ammonia gel, wet mixing of batch materials, preparation of powder blocks and high temperature nitriding reaction synthesis. Prepare aluminum carbonate ammonia gel from Al(NO ₃ ) ₃ 9H ₂ O and (NH ₄ ) ₂ CO ₃ , wet mix it with carbon materials and additives and dry to obtain powder block A; Al(OH) ₃ or nano-Al ₂ O ₃ is wet mixed with carbon material and dried to obtain powder block B; powder block A or powder block B is subjected to carbon thermal reduction under high temperature nitrogen Synthesize AlN powder with nitriding reaction, the reaction synthesis temperature is 1400-1600°C, the holding time is 2h-6h, and AlN ceramic powder with AlN purity > 60% can be obtained. The invention relates to a method for preparing AlN ceramic powder by synthesizing nano particles.

Description

A kind of synthetic preparation method of AlN ceramic powder

【Technical field】

The invention belongs to the field of ceramic materials, and in particular relates to a synthesis preparation method of AlN ceramic powder.

【Background technique】

Because AlN ceramics have good properties such as high temperature resistance, corrosion resistance, high thermal conductivity, low thermal expansion coefficient, thermal shock resistance, and high electrical insulation, they have become excellent integrated circuit substrate materials developed in recent years. , packaging materials for electronic components and new high thermal shock resistance ceramic structural materials that can withstand high temperatures.

The key to preparing AlN ceramics is to synthesize and prepare aluminum nitride powder materials with high AlN content and good crystallization properties. At present, the main methods of synthesizing AlN include: direct nitriding method, carbothermal reduction method, arc melting method, gas phase reaction method, Plasma method, pyrolysis method, microwave synthesis method, self-propagating high-temperature synthesis method and high-energy ball milling method, etc. Among them, the methods that can realize industrial production mainly include direct nitriding method and carbothermal reduction method.

The direct nitriding method is based on aluminum powder as raw material, nitrogen gas is introduced at high temperature, and the method is directly combined to form AlN. The reaction temperature is generally 800-1200°C. Since the nitriding reaction is a strong exothermic reaction, the reaction process is difficult to control, and the product quality is unstable. The AlN powder produced often has a self-sintering phenomenon, and the AlN layer formed on the surface of the aluminum powder nitriding will hinder the progress of the reaction, which takes a long time. to fully respond. To prepare AlN powder by direct nitriding method, in order to obtain high-purity AlN, it is necessary to use high-purity raw materials, and the corresponding cost will increase, which is the main factor restricting the promotion of direct nitriding method.

Carbothermal reduction is another commercial method for producing AlN powder. Usually it is to mix α-Al ₂ O ₃ or γ-Al ₂ O ₃ with carbon black, and generally need 1600-1800°C for 12 hours under nitrogen conditions to synthesize and prepare AlN powder. This method can produce AlN powder with uniform size and almost no agglomeration. However, the preparation of AlN powder by α-Al ₂ O ₃ or γ-Al ₂ O ₃ carbothermal reduction requires relatively high reaction temperature and holding time.

In view of the shortcomings of the above-mentioned direct nitriding method or carbothermal reduction method for the synthesis and preparation of AlN powder, the problems to be solved are to stabilize the synthesis process of AlN, reduce the synthesis preparation temperature and reduce the holding time. The main feature of the invention is that it is used for synthesizing AlN ceramic powder with lower synthesis temperature and less heat preservation time.

【Content of invention】

The object of the present invention is to provide a method for the synthesis and preparation of AlN ceramic powder in order to overcome the deficiencies in the prior art.

Technical scheme of the present invention:

A synthesis and preparation method of AlN ceramic powder is characterized in that it comprises the following steps: preparation of aluminum carbonate ammonium gel, wet mixing of batch materials, preparation of powder block and high temperature nitriding reaction synthesis.

The preparation of aluminum carbonate ammonia gel is to prepare analytically pure Al(NO ₃ ) ₃ 9H ₂ O and (NH ₄ ) ₂ CO ₃ with deionized water to a concentration of 0.5mol.L ^-1 and 2.5mol.L ^{- 1} solution; under the condition of (35±4)℃ constant temperature and constant stirring, according to the molar ratio of (NH ₄ ) ₂ CO ₃ : Al(NO ₃ ) ₃ =2.5:1, Al(NO ₃ ) ₃ solution Add it dropwise to the (NH ₄ ) ₂ CO ₃ solution at a constant speed; after the dropwise addition, continue to stir for 30 minutes, and then wash with deionized water for 3 times to obtain the ammonium aluminum carbonate [NH ₄ AlO(OH)HCO ₃ ] glue.

One of the wet mixing methods of batch materials is to add an appropriate amount of deionized water to the prepared ammonium aluminum carbonate gel to dilute to make ammonium aluminum carbonate gel dilution slurry; then add carbon materials and additives to the ammonium aluminum carbonate gel Wet mixing is carried out in the gel dilution slurry, and the mixing time is 1 to 3 hours to obtain the mixed slurry A; the particle size of the carbon material and the additive is less than 5 μm; the carbon material is carbon black or coke or graphite, and the carbon material The added amount is 100-120% of the molar weight of the aluminum ammonium carbonate; the additive is SrCO ₃ or CaF ₂ -SrCO ₃ or CaF ₂ , and the added amount of the additive is 2.5-3.5% of the weight of the aluminum ammonium carbonate.

The second method of wet mixing of batch materials is to wet mix the batch materials of nano-Al(OH) ₃ or nano-Al ₂ O ₃ and carbon materials, and the mixing time is 1-3 hours to obtain the mixed slurry B; the carbon materials are Carbon black or coke or graphite, the particle size of the carbon material is less than 5 μm; the particle size of nano-Al(OH) ₃ or nano-Al ₂ O ₃ is less than 0.1 μm, and the amount of nano-Al(OH) ₃ added is the carbon material mole 75-80% of the molar weight of _{the carbon} material, and 145-160% of the molar weight of the carbon material.

The block preparation is to dry the above-mentioned mixed slurry A or mixed slurry B at 110° C. for 24 hours to obtain powder block A or powder block B for synthesizing AlN.

The above-mentioned powder block A or powder block B is subjected to high-temperature synthesis of AlN powder respectively. The atmosphere for synthesis of AlN powder by high-temperature carbothermal reduction and nitriding reaction is a nitrogen atmosphere, and the synthesis temperature is controlled at 1400-1600 ° C. The time is 2h-6h.

The main technical feature of the present invention is that nanomaterial technology is used for the synthesis of AlN powder. The raw material technical requirements for the synthesis of AlN powder in the present invention are shown in Table 1, and the physical performance test results of the synthesized AlN powder are shown in Table 2. The microstructure and phase of AlN powder are shown in Figure 1 and Figure 2 respectively. It can be seen from Table 1, Table 2, accompanying drawing 1, accompanying drawing 2 and the examples that the present invention is a practical preparation method for synthesizing AlN powder using nanoparticle technology.

Table 1 Technical requirements for raw materials used in the synthesis of AlN powder

raw material name chemical components Specification Aluminum nitrate Ammonium hydroxide Aluminum oxide Carbon black Graphite coke Strontium carbonate Calcium fluoride Al(NO ₃ ) ₃ 9H ₂ O > 99% (NH ₄ ) ₂ CO ₃ > 99% Al(OH) ₃ > 99% Al ₂ O ₃ > 99% C > 99% C > 98% C > 95% SrCO ₃ ＞99%CaF ₂ ＞99%  <5μm<5μm<0.1μm<0.1μm<5μm<5μm<5μm<5μm<5μm

Table 2 Physical performance test results of synthesized AlN powder

sample Aluminum source carbon source Additives temperature/℃ True density g/cm ³ AlN content% AN-1AN-2AN-3AN-4AN-5 NH ₄ AlO(OH)HCO ₃ Al ₂ O ₃ NH ₄ AlO(OH)HCO ₃ Al ₂ O ₃ Al(OH) ₃ carbon black carbon black graphite coke graphite SrCO ₃ SrCO ₃ CaF ₂ CaF ₂ , SrCO ₃ CaF ₂ 15001600150016001600 3.383.523.423.473.36 75.351.269.566.175.2

【Description of drawings】

Fig. 1 is the SEM photograph of the AlN crystal morphology of the AN-1 powder sample of the present invention

Fig. 2 is the XRD curve figure of AN-1 powder sample phase of the present invention

【Detailed ways】

Example 1

Prepare analytically pure Al(NO ₃ ) ₃ 9H ₂ O and (NH ₄ ) ₂ CO ₃ with deionized water to prepare solutions with concentrations of 0.5mol.L ^-1 and 2.5mol.L ^-1 respectively; at (35± 4) Under the condition of constant temperature and constant stirring at ℃, according to the molar ratio of (NH ₄ ) ₂ CO ₃ :Al(NO ₃ ) ₃ =2.5:1, add the Al(NO ₃ ) ₃ solution dropwise to the (NH ₄ ) ₂ CO ₃ solution; after the dropwise addition, continue to stir for 30 min, and then wash with deionized water three times to obtain ammonium aluminum carbonate [NH ₄ AlO(OH)HCO ₃ ] gel.

Dilute the ammonium aluminum carbonate gel by adding an appropriate amount of deionized water, then add carbon black with a particle size of <5 μm according to 100% of the molar weight of ammonium aluminum carbonate and SrCO ₃ with a particle size of <5 μm by 3.0% by weight of ammonium aluminum carbonate; Wet stirring and mixing for 1 hour to obtain a mixed slurry; dry the mixed slurry at 110°C for 24 hours to obtain a powder block for the synthesis of AlN; synthesize the powder block into AlN at a high temperature under a nitrogen atmosphere, and the synthesis temperature The temperature is 1500℃, and the holding time is 5h.

The AlN content in the AlN powder synthesized in this example is 75.3%

Example 2

Prepare analytically pure Al(NO ₃ ) ₃ 9H ₂ O and (NH ₄ ) ₂ CO ₃ with deionized water to prepare solutions with concentrations of 0.5mol.L ^-1 and 2.5mol.L ^-1 respectively; at (35± 4) Under the condition of constant temperature and constant stirring at ℃, according to the molar ratio of (NH ₄ ) ₂ CO ₃ :Al(NO ₃ ) ₃ =2.5:1, add the Al(NO ₃ ) ₃ solution dropwise to the (NH ₄ ) ₂ CO ₃ solution; after the dropwise addition, continue to stir for 30 min, and then wash with deionized water three times to obtain ammonium aluminum carbonate [NH ₄ AlO(OH)HCO ₃ ] gel.

Dilute the ammonium aluminum carbonate gel by adding an appropriate amount of deionized water, then add 120% of the graphite with a particle size of <5 μm according to the molar weight of the ammonium aluminum carbonate and CaF ₂ with a particle size of <5 μm at 3.0% by weight of the ammonium aluminum carbonate; Stir and mix for 2 hours to obtain a mixed slurry; dry the mixed slurry at 110°C for 24 hours to obtain a powder block for the synthesis of AlN; synthesize the powder block at a high temperature under a nitrogen atmosphere at a temperature of 1500°C, holding time is 6h.

The content of AlN in the AlN powder synthesized in this example is 69.5%

Example 3

coke with a particle diameter _of <5 μm, _Al2O3 with a particle diameter of <70 nm (150% of the molar weight of the coke), _SrCO3 with a particle diameter of <5 μm (1.0% of _the weight of _Al2O3 ) and CaF ₂ with a particle size of <5 μm (the amount added is 2.0% of the weight of Al ₂ O ₃ ) was wet-mixed for 3 hours to obtain a mixed slurry; the mixed slurry was dried at 110°C for 24 hours to obtain AlN powder block; the powder block is synthesized at high temperature under nitrogen atmosphere, the synthesis temperature is 1600°C, and the holding time is 6h.

The AlN content in the AlN powder synthesized in this example is 66.1%

Claims (10)

1. the synthesis preparation method of an AlN ceramic powder is characterized in that may further comprise the steps: the preparation of aluminium carbonate ammonia gel, admixtion wet-mixed, the preparation of powder material piece and high-temperature ammonolysis reaction are synthetic.

2. material preparation method as claimed in claim 1 is characterized in that the (NO with analytical pure Al ₃) ₃9H ₂O and (NH ₄) ₂CO ₃Being mixed with concentration respectively with deionized water is 0.5mol.L ^-1And 2.5mol.L ^-1Solution; Under (35 ± 4) ℃ constant temperature and continuous agitation condition, by (NH ₄) ₂CO ₃: Al (NO ₃) ₃The ratio of=2.5: 1 molar weight is with Al (NO ₃) ₃Solution at the uniform velocity is added drop-wise to (NH ₄) ₂CO ₃In the solution; After dropwising, continue to stir 30min, use deionized water wash again 3 times, can make aluminium carbonate ammonium (NH ₄AlO (OH) HCO ₃) gel.

3. material preparation method as claimed in claim 1 is characterized in that the aluminium carbonate ammonium gel that will make adds proper amount of deionized water and dilutes, and makes aluminium carbonate ammonium gel diluted slurry; Then carbon materials and additive are joined in the aluminium carbonate ammonia gel diluted slurry and carry out wet-mixed, mixing time 1～3h obtains mixed slurry A.

4. as carbon materials and additive in the mixed slurry preparation as described in the claim 3, the grain that it is characterized in that carbon materials and additive is through equal＜5 μ m, the add-on of carbon materials is the 100-120% of aluminium carbonate ammonium molar weight, and the add-on of additive is the 2.5-3.5% of aluminium carbonate ammonium weight.

5. material preparation method as claimed in claim 1 is characterized in that with nanometer Al (OH) ₃Or nanometer Al ₂O ₃Carry out wet-mixed with the admixtion of carbon materials, mixing time 1～3h obtains mixed slurry B.

6. as carbon materials and additive in the mixed slurry preparation as described in the claim 3, it is characterized in that carbon materials is carbon black or coke or graphite, additive is SrCO ₃Or CaF ₂-SrCO ₃Or CaF ₂

7. as carbon materials and nanometer Al (OH) in the mixed slurry preparation as described in the claim 5 ₃Or nanometer Al ₂O ₃, it is characterized in that carbon materials is carbon black or coke or graphite, the carbon materials particle diameter all＜5 μ m; Nanometer Al (OH) ₃Or nanometer Al ₂O ₃Particle diameter all＜0.1 μ m; Nanometer Al (OH) ₃Add-on be the 75-80% of carbon materials molar weight, nanometer Al ₂O ₃Add-on be the 145-160% of carbon materials molar weight.

8. material preparation method as claimed in claim 1 is characterized in that described mixed slurry A of claim 3 or the described mixed slurry B of claim 5 are placed dry 24h under 110 ℃ of conditions respectively, obtains to be used for powder material piece A or the powder material piece B of synthetic AlN.

9. material preparation method as claimed in claim 1 is characterized in that the atmosphere of the synthetic AlN powder of pyrocarbon thermal reduction and nitrogenizing reaction is nitrogen atmosphere.

10. material preparation method as claimed in claim 1 is characterized in that the temperature of synthetic AlN powder is controlled to be 1400-1600 ℃, and soaking time is 2h-6h.

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