Preparation of a B4C hollow microsphere through gel-casting for an inertial confinement fusion (ICF) target

B4C hollow microspheres have been proposed to be a promising target pellet for inertial confinement fusion (ICF). However, the preparation of a B4C hollow microsphere is challenging and has been rarely reported. In this study, we developed a gel-casting method followed by a calcining process to fabricate a core-shell structured B4C microsphere on a molybdenum core. The microstructure, stoichiometry, surface roughness, and wall thickness of the microsphere was characterized by Scanning Electron Microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray photography. The results indicated that a core-shell structured microsphere with uniform microstructure and high strength were obtained by gel-casting, accompanied by calcining at 1400 °C. The diameter of the molybdenum core was 2 mm, and the wall thickness was approximately 100-180 µm. It should be noted that the main phase of core-shell structured microsphere was B4C, with a small amount of residual carbon and B2O3. The core-shell structured B4C microsphere was subsequently processed by laser drilling and corrosion to obtain the B4C hollow microsphere. It was indicated that the B4C hollow microsphere has respectable corrosion resistance. Atomic Force Microscope (AFM) analysis demonstrates that the B4C hollow microsphere exhibits outer and inner surface roughness of 197 nm rms and 19.3 nm rms based on a 5 µm square scan, respectively. This study provides a new method for preparing a high quality B4C hollow microsphere, which have potential application as a target pellet for ICF.