The effect of sintering atmosphere and C/U on UCO microspheres by internal gelation process with carbon black

Abstract UCO ceramic microspheres were fabricated by combination of internal gelation and carbothermic reduction process. The effects of the sintering atmosphere and C/U ratio on the UCO ceramic microspheres were studied. The composition, surface morphology, and microstructure of the sintered UCO ceramic microspheres were analyzed. The results indicated that increasing CO concentration in the sintering atmosphere could slow down the rate of the carbothermic reduction, and when the concentration of CO increased to 20% or above, CO could inhibit the reaction, and the microstructure of the sintered microspheres changed obviously and became loose. With the increase in C/U ratio in the broth, some residual carbon would exist in the sintered microspheres due to large size of the carbon particles. The increase in C/U did not cause the reduction in the crush strength and geometrical density of the microspheres. When the C/U was above 2.5, dense and strong UCO ceramic microspheres were produced in argon containing 5% CO at 1680°C.