SPS, also known as Plasma Activated Sintering (PAS) or Pulse Current Pressure Sintering, It is a new process of rapid sintering that has been studied abroad since 1990s. Because it combines plasma activation, hot pressing, ohmic heating is an organic whole, have short sintering time, temperature control accurate, easy automation, sintered sample uniform particles, high density, etc. In a few minutes alone makes the relative theory of sintering product density close to 100%, and can restrain the sample particles to grow up, improve the properties of the material, Therefore, the advantages are fully demonstrated in the material treatment process.
Will instantly, intermittent, high-energy pulse current factory is equipped with powder mold, can produce plasma discharge between the powder particles, because of the plasma is a kind of highly ionized conductance gas, therefore, plasma can rapidly eliminate the powder particle surface adsorption of impurities and gas, and accelerate the proliferation and migration of material of high speed, lead to the purification of the powder, activation, such as homogenization effect. Switching DC pulse power supply is used in the third generation of SPS equipment. Under the power supply of 50 Hz, the time of a pulse is 312 ms. Due to the strong pulse current added between powder particles, it can produce many effects conducive to rapid sintering. First of all, due to the discharge impact 3 waves generated by pulse discharge and the high speed flow of electrons and ions in the opposite direction in the electric field, the powder adsorbed gas can escape, and the initial oxide film on the powder surface can be broken down to a certain extent, so that the powder can be purified and activated; Second, due to the pulse is instant, intermittent, high frequency, the powder particles did not contact parts of electric heating, and the powder particles contact parts of joule heat, have greatly promoted the powder particles atom diffusion, the diffusion coefficient of hot-pressing condition is much larger than usual, so as to achieve the rapidness of powder sintering; Finally, the addition of the switch rapid pulse, either the
discharge site within the powder or the site producing joule heat, will move quickly, so that the sintering of the powder can be homogenized.
