Study On The Preparation Of Transparent Alumina Hollow Spheres By Multiphasic Emulsion Method

The development of perfect implosion target is a main task in the research of ICF target preparation. The requirement of suitable target is that having a single hollow structure and reaching to millimeter scale. Thus transparent alumina hollow spheres with excellent physical and chemical properties have a huge potential application value for ICF target. This paper discusses the preparation of millimeter-scale alumina hollow spheres by self-made double channel co-flow micro-emulsion device via the precursor of com-droplets which paraffin liquid as inner core and alumina sol as outer shell through the processes of curing and sintering. The morphology and structure of samples were tested and characterized by fourier transform infrared spectroscopy(FTIR), X-ray diffraetion(XRD), scanning electron microscopy(SEM) and atomic force microscopy(AFM) et al. related methods. And the various factors influencing the morphology of spheres were analyzed contrastively including geometric structure, curing conditions, sintering temperature and atmosphere.As seen from research results, under the condition that the density and viscosity of the aqueous phase are close to or slightly larger than the oil phase,the com-droplets had homogeneous and complete core-shell structure by the specially geometric device. After curing and rotating in horizontal at 90?,when the rotation speed is controlled between 20r/min and 60r/min, the semisolid spheres kept hollow structure and spherical greatly. After calcining at 1200 ? for 4 h, the prepared hollow ceramic spheres had the complete hollow structure and the sphericity of spheres is above 98%. The thickness and diameter of spheres could be adjusted in the range of 30~80 ?m and 800~2000?m by controlling the flow rate of oil phase in 1~10m L·h-1. The surface of sphere was relatively smooth with the roughness of about 22 nm which displayed by AFM. The XRD pattern showed that the main crystal of theprepared ceramic hollow spheres was alpha alumina. With 0.1 wt.% La2O3 and0.1 wt.% Mg O doped, under the effect of vacuum environment at 1700?, the grains of spherical shell grown regularly. The pores dissipated gradually which can promote sample more densifying. Then the transparency of sample at 532 nm laser light was improve further which reach above 30 %.