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Characterization of porous tungsten materials

  • Mosten
  • 13 Nov

Pore characteristics:The basic physical phenomenon of mercury intrusion method is to force non wetting and non reactive liquid mercury into porous samples under a given external pressure. According to the capillary phenomenon, if the liquid does not infiltrate the porous material, the surface tension will prevent the liquid from penetrating into the pore; however, when a constant pressure is applied to the liquid, the external force overcomes the resistance and drives the liquid to enter the pore. Therefore, the pressure required to fill a given pore can be used to measure the size of the pore or orifice. According to the national standard GB / T 21650.1, mercury porosimetry can be used to determine the through porosity, pore size and its distribution, and closed porosity of porous tungsten materials.

Small angle neutron scattering is the only method to characterize the porous system with closed pores. Atomic force microscopy (AFM) studies the surface structure and properties of materials by detecting the extremely weak interatomic interaction between the sample surface and a micro force sensor. It can quantitatively characterize the pore density of porous tungsten surface, and the length and width of the measurement area are generally 100 μm.

Mechanical properties: Firstly, the tungsten copper infiltrated bar was processed into tensile specimen, and then copper removal was carried out at high temperature and high vacuum to obtain the standard tensile sample of porous tungsten material. The mechanical properties at room temperature and high temperature were also tested according to GB / T 228.1 and GB / T 4338. Due to the brittleness of porous tungsten materials at room temperature, the tensile strength can only be obtained at room temperature. According to the porosity and the development state of sintering neck, the value is usually between 80 MPa and 300 MPa. It is recommended that the tensile strength should not be less than 150 MPa for high reliability and long service life applications. In addition, the structure uniformity and porosity of porous tungsten can be characterized by microhardness and its distribution.

The average microhardness of porous tungsten with 20% porosity is 220 ~ 250 MPa.