Graded transmitted wave structure in microwave sintering and method for preparing ceramic material using the same

A technology of microwave sintering and wave-transparent structure, which is applied in the field of microwave sintering ceramic materials, can solve the problems of increasing the heat-absorbing and heating of thermal insulation materials, realizing the importance of microwave reflection, affecting the heating rate and the limit value of heating, and reducing sintering The probability of cracking, the effect of improving the quality of sintered body, and increasing the temperature limit

Inactive Publication Date: 2008-12-17
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

No matter according to the US5,432,325 to make the container with the absorbing material, or according to the US5,736,092 proposed to use the absorbing material as the embedding powder, or let the absorbing sintered material directly contact with the microwave, the microwave directly hits the high dielectric constant When the material is on the surface, strong microwave reflections will occur on the surface, which will cause m...

Method used

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  • Graded transmitted wave structure in microwave sintering and method for preparing ceramic material using the same

Examples

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Effect test

Embodiment 1

[0033] Embodiment 1: the method for microwave sintering boron carbide ceramics, divided into three steps

[0034] The first step of preparation of boron carbide ceramic green body

[0035] Boron carbide powder 1kg, specific surface area 18m 2 / g, add 40g of carbon black, 800g of ethanol and 2000g of zirconia balls with a diameter of 2mm, place it in a 5L nylon tank and grind it with a planetary mill for 2h, spray dry and set aside (referred to as mix 1). Take the above-mentioned mixed powder raw materials and press them into a rod shape of Φ20×40mm.

[0036] The second step is boron carbide ceramic plus coating sintering

[0037]The boron carbide / carbon black mixed powder prepared in Example 1 was added to the boron nitride powder at a ratio of 90:10 and 50:50 (referred to as mix 2 and mix 3, respectively). Take Mix 2 and Mix 3 and add a small amount of water to make a paste, and apply it on the surface of the boron carbide blank prepared in Example 1, first apply Mix 3, an...

Embodiment 2

[0040] Example 2: Microwave sintered alumina ceramics

[0041] The outer layer is made of domestic alumina fiber material crucible (1800°C type), with an inner diameter of Φ70mm and a wall thickness of 15mm. Prepare a slurry of white corundum powder with d50 = 5 μm and silicon carbide powder with d50 = 0.9 μm (the weight ratio of corundum powder to silicon carbide powder is 85:15), pour it into a crucible made of alumina fiber material, and suck the slurry Finally, pour out the remaining slurry to form a layer of alumina / silicon carbide with a thickness of about 5mm. After it is half-dried, add pure alumina powder into the cavity for compaction and dry. Take out part of the alumina powder in the center, and put in a Φ20×30mm alumina biscuit doped with magnesia sintering aid. Put it in a 4kW microwave sintering furnace for sintering. After about 20 minutes, it reaches the lowest reading of 800°C on the thermometer, and after 15 minutes, it heats up to 1420°C, and keeps warm fo...

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Abstract

The invention relates to a gradient wave-transmitting structure used for microwave sintering and a method used for preparing ceramic materials, which are characterized in that: (1) when a material with high dielectric property is sintered, at least a transition layer is added into the exterior of the material and the transition layer is composed of high-efficient wave absorption material with certain concentration and a microwave transparent thinner; when a multilayered structure is used as the transition layer, the concentration of the high-efficient wave absorption material increases from exterior to interior in sequence; (2) when a material with low dielectric and relatively poor wave absorption properties is sintered, the multilayered structure is adopted for an exothermic material ora coat, wherein, the concentration of the high-efficient wave absorption material increases from exterior to interior in sequence and then decreases so as to be favorable for transmitting microwave. In the invention, energy consumption caused by a plurality of times of reflection and wave-absorbing and heat-emitting of a thermal insulating layer are reduced by improving the efficiency of being sintered and wave absorption, thus being capable of effectively realizing the purpose of increasing sintering temperature. In addition, the gradient thermal insulating structure can help materials sintered to obtain an even temperature field and better sintering quality.

Description

technical field [0001] The invention relates to a gradient wave-permeable structure in microwave sintering and a method for preparing ceramic materials, belonging to the field of microwave sintering ceramic materials. Background technique [0002] Compared with the traditional resistance heating method, the use of microwave sintering method can produce ceramic materials faster, better and save a lot of energy. However, the microwave field provided by the widely used multi-mode cavity sintering equipment is not uniform, and due to factors such as the size and shape of the material, it is easy to generate excessive temperature gradients, hot spots, thermal runaway and other problems at different positions of the material. resulting in sintering failure. In the microwave sintering process, there are other factors that also generate a temperature gradient in the sample. For example, when the sample is sintered in a microwave transparent crucible, the inner surface of the crucib...

Claims

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Application Information

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IPC IPC(8): C04B35/64C04B41/81
Inventor 张兆泉顾辉
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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