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About the sintering technology of fine ceramics

About the sintering technology of fine ceramics

Pintejin Ceramics Factory is a professional manufacturer of precision ceramics machining, which can provide customized precision ceramics machining and production according to drawings. Below, Pintejin Ceramics Factory will introduce the sintering technology of precision ceramics to us.

Precision ceramic nozzle The sintering technology of precision ceramics mainly includes the following methods:

  1. Atmospheric pressure sintering of precision ceramics, also known as pressureless sintering. It belongs to the process of free sintering of the green body under atmospheric pressure. In the absence of external power, the sintering temperature of the material generally reaches the melting point of the material at 0.5-0.8. Solid-phase sintering at this temperature can induce sufficient atomic diffusion in liquid-phase sintering to promote the formation of a liquid phase or the generation of a liquid phase by chemical reactions to facilitate the occurrence of diffusion and viscous flow. It is very important to accurately formulate the firing curve in atmospheric sintering. A suitable heating system can ensure that the products reduce cracking and structural defects and improve the yield.
  2. Hot pressing sintering and hot isostatic pressing sintering of precision ceramics Hot pressing sintering refers to applying a certain pressure (10~40MPa) during the sintering process to accelerate the flow, rearrangement and densification of the material. The hot-pressing sintering method is generally about 100°C lower than the normal-pressure sintering temperature, which varies according to different products and whether or not a liquid phase is formed. Hot-pressing sintering is relatively simple to use pre-forming or directly load the powder into the mold. The sintering method has high density and theoretical density can reach 99. The product has excellent performance. However, this sintering method is not easy to produce products with complex shapes. The sintering production scale is small and the cost is high. Continuous hot pressing sintering has high production efficiency but high equipment and mold costs and is not conducive to the sintering of excessively thick products. Hot isostatic pressing sintering can overcome the above disadvantages and is suitable for the production of products with complex shapes. At present, some high-tech products such as ceramic shafts, mirrors, nuclear fuel and gun barrels for military industries can also use this sintering process.
  3. Reaction sintering of fine ceramics This is a method in which the material is sintered by reacting with the matrix material in the gas phase or liquid phase. The most typical representative products are reaction sintered silicon carbide and reaction sintered silicon nitride products. The advantage of this kind of sintering is that the products with simple process can be processed with little or no machining, and products with complex shapes can also be prepared. The disadvantage is that there are residual unreacted products in the product, and the structure is not easy to control. Too thick products are not easy to fully react and sinter. In addition to the reaction sintering of silicon carbide ceramics and silicon nitride ceramics, the reaction sintering Al2O3 method has recently emerged. Al2O3 and Al2O3-Al composite materials can be prepared by the oxidation reaction of Al powder.
  4. Liquid phase sintering of precision ceramics Many oxide ceramics use low melting point additives to promote material sintering. The addition of additives generally does not affect the performance of the material or instead has a good effect on a certain function. As an additive used in high temperature structures, it should be noted that grain boundary glass is the main factor causing the decline of high temperature mechanical properties. If the liquid phase has a high melting point or high viscosity by choice. Or select a suitable liquid phase composition and then perform high temperature heat treatment to precipitate some crystal phases on the grain boundaries to improve the creep resistance of the material.
  5. Microwave sintering method of precision ceramics It is a method of sintering by direct heating with microwave energy. At present, there are microwave sintering furnaces with an inner volume of 1 cubic meter whose sintering temperature can reach 1650 °C. If the controlled atmosphere graphite is used to assist, the temperature can be as high as 2000 ℃ or more. And appeared microwave continuous heating 15 meters long tunnel furnace device. The use of microwave ovens to sinter fine ceramics is superior to other kilns in terms of product quality and reduced energy consumption.
  6. Arc plasma sintering method of precision ceramics The heating method is different from hot pressing. It also applies a pulse power supply to the product to be toughened and densified while applying stress. Experiments have proved that this method can quickly sinter the material to form a fine-grained and high-density structure, which is expected to be more suitable for nanoscale material sintering. But so far still in the research and development stage, many issues still need to be further explored.
  7. The self-propagating sintering method of precision ceramics is to make precision ceramic material products through the rapid chemical exothermic reaction of the material itself. This method saves energy and reduces costs. It has been reported abroad that more than 200 compounds can be synthesized by this method, such as carbides, nitrides, oxides, intermetallic compounds and composite materials.
  8. The vapor deposition method of fine ceramics is divided into physical vapor phase method and chemical vapor phase method. There are two main physical methods, sputtering and evaporative deposition. In the sputtering method, electrons are bombarded on a flat target in a vacuum, and the atoms of the target are excited and then coated on the sample substrate.

Although the coating speed is slow and only used for thin coatings, purity can be controlled and the substrate does not require heating. The chemical vapor deposition method is that when the substrate is heated and the reaction gas or gas mixture is introduced to decompose or react at high temperature, the product is deposited on the substrate to form a dense material.

The advantage of this method is that it can produce highly dense and fine-grained materials with better light transmittance and mechanical properties than those obtained by other sintering processes. With the increasing demand for microelectronics, data storage, advanced display and optical coatings, the demand for precision ceramic films has grown significantly. Social demand and high-tech development are the driving force behind the continuous improvement and optimization of precision ceramic sintering. Precision ceramic sintering technology will continue to make new progress.

 


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