Lihong Bao

Effect of particle size on the polycrystalline CeB6 cathode prepared by spark plasma sintering

The full densification polycrystalline cerium hexaboride (CeB6) cathode material was prepared by using the spark plasma sintering (SPS) method in an oxygen free system. The starting precursor nanopowders with an average grain size of 50 nm were prepared by high-energy ball milling. The ball-milled nanopowder was fully densified at 1550 °C under 50 MPa, which was about 350 °C lower than the conventional hot-pressing method and it was also lower than that of coarse powder under the same sintering condition. The mechanical properties of nanopowder sintered samples were significantly better than that of coarse powder, e.g., the flexural strength and Vickers hardness were 211% and 51% higher than that of coarse powder, respectively. The electron backscattered diffraction (EBSD) result showed that the (100) fiber texture could be fabricated by the ball-milled nanopowder sintered at 1550 °C and the thermionic emission current density was measured to be 16.04 A/cm2 at a cathode temperature of 1873 K.

Synthesis, characterization and properties of nanostructured (La x Ba 1−x )B 6 cathode materials by liquid phase reactive spark plasma sintering

This paper studies the preparation procedure of nanostructured (LaxBa1-x)B6 cathode materials by liquid phase reactive spark plasma sintering. The phase identification and purity of the sintered samples is determined by X-ray diffraction (XRD) and X-ray fluorescence. The vibrational property is examined by using Raman spectroscopy. The SEM and electron back-scattered diffraction (EBSD) investigation is carried out for observation of the morphology of fracture surface and surface crystal orientation. The electrical resistivity and the pulse thermionic emission of the material is determined by using a four-probe dc technique.

Synthesis and properties of CeB 6 thermionic cathode with {001} fiber texture by reactive spark plasma sintering method

In this paper, a study on quick spark plasma sintering (SPS) method for synthesizing the polycrystalline CeB<;sub>6<;/sub> bulk is presented. CeB<;sub>6<;/sub> is the material of choice for high current density cathode. However, in fact, because of the long sintering time and high temperature, the traditional hot pressure sintering preparation of polycrystalline CeB<;sub>6<;/sub> bulk causes coarse grains and low density which decrease the emission property. The pulsed voltage method was used to test the electron emission of the CeB6. The pulse thermionic emission density was measured with increasing voltages up to 1000 V at various cathode temperatures from 1500 K to 1863 K, at pressure of 2x10-4 Pa, a pulse width of 20 μs and repetition frequency of 120 Hz.