The core of the special ceramic sintering furnace is divided into three major sections: the basic physical densification principle, the furnace body heating and temperature control principle, and the exclusive process principle for different furnace types. It covers oxide/non oxide special ceramics such as alumina, zirconia, aluminum nitride, silicon carbide, and silicon nitride.
1、 Principle of densification of ceramic sintering core material at the bottom layer (applicable to all sintering furnaces)
      Sintering essence: High temperature activates the diffusion of ceramic powder atoms, eliminates internal pores in the body, and transforms loose green bodies into high-strength and dense ceramic parts, with the entire process below the melting point of the material (melting point 0.5-0.8 times the temperature range).
1. Solid phase sintering device (no liquid phase, commonly used for high-purity alumina and SiC)
      Three stage atomic diffusion mass transfer:
Initial sintering stage (heating stage)
      As the temperature rises, the atomic kinetic energy on the surface of the particles increases, forming a "sintering neck" at the contact point of the particles. The particles are bonded by surface diffusion, causing slight shrinkage of the body and opening of the pores.
      Mid sintering stage (insulation dense section)
      Grain boundary diffusion is dominant, the sintering neck continues to grow, the connected pores gradually shrink and penetrate, the billet shrinks significantly, the density increases to about 90%, and the strength significantly increases.
      Post sintering stage (insulation finishing)
      Pores become isolated and closed, atoms continue to fill the pores, and the pores disappear continuously; The grains grow slowly, forming a dense and continuous ceramic matrix.
2. Liquid phase sintering device (silicon nitride, multiphase ceramics)
      Add a little amount of sintering aid, and the aid melts to form a liquid phase at high temperature:
      Liquid phase capillary force pulls particles to rearrange tightly;
      Solid particles dissolve in the liquid phase and precipitate at low-energy grain boundaries;
      Fill residual pores with liquid phase, form grain boundary phase after cooling, significantly reduce sintering temperature and increase density.
3. Reaction sintering device (SiC, nitride ceramics)
      The raw material powder inside the billet undergoes in-situ chemical reactions at high temperatures, generating the target ceramic phase while simultaneously densifying; If silicon powder+carbon powder reacts at high temperature to generate silicon carbide, it does not require a large amount of additives and has low residual stress.
2、 Working principle of heating and temperature control system for sintering furnace body
1. Principle of Heating Energy Transfer
      Mainstream heating methods:
      Resistance radiation heating (most commonly used in industry)
      Silicon carbon rod, silicon molybdenum rod, and molybdenum wire generate heat through electrical resistance, and evenly transfer the heat to the ceramic body through thermal radiation and conduction; The furnace adopts mullite/alumina fiber insulation to reduce heat loss.
      Induction heating (hot pressing/hot isostatic pressing furnace)
      The alternating magnetic field causes eddy current heating in graphite molds and metal crucibles, resulting in a fast heating rate and uniform temperature field.
Microwave assisted heating (new type of rapid sintering furnace)
      Ceramic media absorb microwave energy and generate overall heat, synchronously heating both inside and outside, shortening sintering time and preventing grain coarsening.
2. Principle of closed-loop temperature control
      Thermocouples collect furnace temperature in real-time and convey the signal to the PLC intelligent temperature controller; By using PID algorithm to automatically adjust heating power, segmented control of heating rate, high temperature insulation duration, and cooling curve, the temperature control accuracy can reach ± 1~± 5 ℃, avoiding cracking of the billet and uneven grain size.
3. Principle of degreasing integrated matching
      Slowly raise the temperature in the low-temperature range (200~600 ℃), discharge the binder and dispersant from the body, and equip it with a waste gas combustion treatment system to prevent organic residue from causing ceramic blackening and porosity defects.