Working principle of ceramic hot press sintering furnace

The working principle of ceramic hot press sintering furnace is as follows:

Loading: Ceramic powder or pre formed ceramic bodies are loaded into graphite molds of specific shapes, which must have high mechanical strength, high temperature oxidation resistance, and match the thermal expansion properties of ceramic materials to avoid interaction or bonding under high temperature and high pressure.
Vacuum pumping: The furnace is evacuated into a vacuum state through a vacuum system, with a typical vacuum degree of up to 6.67 × 10 ⁻ Pa level. The vacuum environment can remove gases and impurities inside the furnace, prevent oxygen and moisture in the air from oxidizing or contaminating ceramic materials, and ensure the high purity requirements of the sintering process.
Heating: Using graphite elements or domestic resistance wires and other heating elements to heat the furnace, a 30 segment temperature curve programming is achieved through an intelligent PID program temperature control system, with a temperature control accuracy of ± 1 ℃. When the temperature rises to the set value (the working temperature of conventional models is 1800-2000 ℃, and special models can be extended to 2200 ℃), the ceramic powder reaches a thermoplastic state at high temperature, providing an energy basis for the subsequent densification process.
Pressurization: Under high temperature conditions, pressure is applied to the powder inside the mold by driving the up and down bidirectional pressure heads and lateral multi pressure head modules (typically configured with 4) through an electric hydraulic cylinder. The standard pressure system can output 15-40 tons of pressure. During the pressure application process, ceramic powder particles undergo rearrangement, plastic flow, and volume diffusion in a thermoplastic state, gradually filling the gaps between the powders and forming a dense solid structure. At this stage, the synergistic effect of pressure and temperature significantly reduces the sintering temperature and shortens the time. For example, silicon nitride ceramics can achieve higher thermal conductivity than atmospheric sintering under hot pressing conditions.
Cooling: After sintering is completed, the furnace is cooled down through a cooling system. To avoid cracking of the product, the cooling rate should be adjusted according to the material’s thermal shock resistance and the size and shape of the product. For example, when the refractory compound changes from a plastic state to a brittle state at about 1000 ℃, a slow cooling process should be used. Some equipment is equipped with a cooling water under pressure alarm system to ensure the safety of the cooling process.

Technical advantages:
Densification effect: Through the synergistic effect of multidimensional pressure (coupling vertical pressure and lateral radial pressure), the density gradient caused by traditional uniaxial pressure is eliminated, resulting in a decrease in the standard deviation of sintered product density.
Material performance improvement: significantly improve the bending strength and fracture toughness of ceramic materials, while suppressing abnormal grain growth and obtaining a finer grain structure with better grain size.
Process adaptability: Supports vacuum sintering, atmosphere protected sintering, and hot pressing composite processes, which can be used to prepare structural ceramics such as silicon nitride and silicon carbide, as well as special functional materials such as transparent ceramics and piezoelectric ceramics.

Typical applications:
In the semiconductor field, it is used to manufacture precision ceramic components and solve the bottleneck problem of the domestic market being monopolized by the United States and Japan.
In the field of powder metallurgy, controlling the interfacial bonding strength of metal based composite materials such as tungsten copper alloys can improve the overall performance of the materials.
In terms of crystal growth research, the hot pressing sintering of artificial crystals can be completed in an inert atmosphere, expanding the boundaries of material research.