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Ultrahigh-pressure low-temperature sintering preparation method of transparent aluminium nitride ceramic

A low-temperature sintering technology for aluminum nitride ceramics, which is applied in the field of non-oxide transparent ceramics, can solve the problems of expensive plasma sintering equipment, low repetition rate of mold use, uneven temperature distribution, etc., and achieves fine grain size, low cost, The effect of short production cycles

Inactive Publication Date: 2013-04-03
HENAN POLYTECHNIC UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] Chinese patent CN 1199036A reports a method for preparing aluminum nitride transparent ceramics, which uses pressureless sintering, hot pressing sintering and low temperature hot pressing The heat treatment process after sintering produces transparent aluminum nitride ceramics. This method uses industrial grade calcium carbide or a mixture of industrial grade calcium carbide and rare earth oxides (Y2O3, Sm2O3, etc.) are sintering aids, under the protection of flowing gas such as N2, after several hours or even dozens of After hours of sintering or heat treatment, transparent AlN ceramics with a light transmittance greater than 62% have been obtained. The disadvantages of this method are high sintering temperature, long sintering time, and high energy consumption.
The disadvantage of this method is that the plasma sintering equipment is expensive, and the temperature distribution is extremely uneven during SPS sintering, especially for large-sized products, which reduces the quality of the product
In addition, the repetition rate of mold use is low, which increases the cost of the product

Method used

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Examples

Experimental program
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Effect test

Embodiment 1

[0031] Select the AlN powder with a particle size of 40 μm prepared by Japan Soda Company, heat-treat at 720°C for 50 minutes under vacuum conditions, add 3.5% calcium carbide as a sintering aid, and mix evenly; use graphite paper to dry the mixed powder Coating, put into pyrophyllite synthetic block, use six-sided top press to carry out dry pressing molding, the molding pressure is at 1Gpa; wrap the formed sample with molybdenum foil, put the coated sample into zirconia and oxidation In the insulating tube made of magnesium, put the insulating tube into the graphite tube, then put the graphite tube into the pyrophyllite composite block, use the pyrophyllite as the pressure transmission medium for ultra-high pressure sintering, after assembly, carry out the process on the six-sided top press High-pressure sintering, the high-pressure sintering temperature is 1600 °C, the pressure is 4.0 GPa, and the heat preservation is 30 min. The sample is naturally cooled with the six-sided ...

Embodiment 2

[0041] The AlN powder with a particle size of 40 μm prepared by Japan Soda Co., Ltd. was selected, and a mixture of 3.0% calcium carbide and 1.0% yttrium oxide was used as a sintering aid. The top press is naturally cooled, and other operations are the same as in Embodiment 1. The properties of the prepared transparent aluminum nitride ceramics are as follows:

[0042] Density (g / cm 3 ): 3.26;

[0043] Main crystal phase (X-ray): AlN;

[0044] Strength (MPa): 500;

[0045] Dielectric constant (1MHz, 25°C): 8.0;

[0046] Thermal conductivity (W·m -1 ·K -1 ): 190;

[0047] Such as figure 2 As shown, the maximum transmittance (%) in the 2.5-25 μm infrared band: >63, and the SEM fracture morphology analysis is the same as that in Example 1.

Embodiment 3

[0049] The AlN powder with a particle size of 40 μm prepared by the domestic self-propagating method is selected, and a mixture of 2% calcium carbide and 2% samarium oxide is used as a sintering aid, and it is pressed by a high-pressure molding method. After the synthetic block is assembled, it is placed on a six-sided top press Ultra-high pressure sintering was carried out, the high pressure temperature was 1650 °C, the pressure was 5.2 GPa, and the temperature was kept for 35 minutes. The sample was naturally cooled with the six-sided top press to obtain transparent aluminum nitride ceramics. Other operations are the same as in Embodiment 1. The properties of the prepared transparent aluminum nitride ceramics are as follows:

[0050] Density (g / cm 3 ): 3.24;

[0051] Main crystal phase (X-ray): AlN;

[0052] Strength (MPa): 490;

[0053] Dielectric constant (1MHz, 25°C): 8.0;

[0054] Thermal conductivity (W·m -1 ·K -1 ): 170;

[0055] The maximum transmittance (%) o...

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Abstract

The invention relates to an ultrahigh-pressure low-temperature sintering preparation method of transparent aluminium nitride ceramic. The preparation method comprises the following steps of: (1) selecting materials by selecting AlN (aluminium nitride) micron powder with an average grain diameter of 40 mu m as a raw material; (2) pre-processing the AlN powder; (3) adding a sintering accessory ingredient which is selected from calcium carbide and / or rare earth oxide in an addition amount of 2.0-5.0wt%; (4) high-pressure forming with a forming pressure of 1Gpa; and (5) high-pressure low-temperature sintering with a high-pressure temperature of 1500-1700 DGE C, a pressure of 4.0-5.5Gpa; and insulating for 20-60 minutes, naturally cooling samples to obtain the transparent aluminium nitride ceramic. The transparent aluminium nitride ceramic prepared by the invention has the advantages of small grains, regular shape, even and compact structure, pore-free property, high density and small grains. The preparation method has no need of the atmosphere control and also has the advantages of simple process flow, convenience in operation and short production period.

Description

technical field [0001] The invention belongs to the field of non-oxide transparent ceramics, in particular to a method for preparing transparent aluminum nitride ceramics by ultra-high pressure and low-temperature sintering. Background technique [0002] Aluminum nitride (AlN) ceramics have excellent thermal conductivity (theoretical value of thermal conductivity is 320 W / (m K)), reliable electrical insulation (volume resistivity greater than 1012Ω m), low dielectric constant (about 8 at 1MHz) and dielectric loss, non-toxic, and a linear expansion coefficient that matches silicon (Si) and gallium arsenide (GaAs) (at 293-773K, 4.8×10 -6 K -1 ) and a series of excellent properties, it is considered to be a new generation of ideal large-scale integrated circuits, semiconductor module circuits and heat dissipation materials and packaging materials for high-power devices. Aluminum nitride transparent ceramics not only have the above-mentioned advantages of aluminum nitride cera...

Claims

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Application Information

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IPC IPC(8): C04B35/581C04B35/64
Inventor 李小雷王红亮王利英胡美华胡强李尚升宿太超曹新鑫何小芳
Owner HENAN POLYTECHNIC UNIV