Effect of UV irradiation on the densification behavior, microstructure, and microwave dielectric properties of low temperature sintering Al2O3 ceramics

In this paper, Al2O3 ceramics co-doped with 0.3 wt%CuO-0.6 wt%TiO2-0.1 wt%MnCO3 (CTM, the same below) were prepared. The effect of CTM and UV irradiation on the sintering behavior, microstructure, and microwave dielectric properties have been investigated systematically. The results indicate that the sintering temperature of Al2O3 ceramics could be effectively decreased to about 1200 °C by adding 1 wt% CTM. UV irradiation can further increase the density of the Al2O3 ceramics, improve its microstructure and microwave dielectric properties. By using the Al2O3 powders UV irradiated for 15 min as raw materials, CTM co-doped Al2O3 ceramics can sintered at 1200 °C with a high density of 3.93 g/cm3 and a very high Q × f value of 175,086 GHz.

Effects of Na2O additions to copper slag on iron recovery and the generation of ceramics from the non-magnetic residue

A novel process is proposed in this paper for a green and efficient utilization of copper slag. The basic premise involved the addition of different amounts of Na₂O into molten copper slag and evaluation of the effects on the magnetic fraction and the properties of ceramics generated from the non-magnetic residue, and mechanisms of the effects were further studied by XRD, SEM, EDS, viscosity test, hysteresis loop and FTIR. The results showed that Na₂O additions dropped the viscosity of the slag markedly, which promoted the growth of magnetite, but decrease quantity of magnetite due to oxidization of Fe²⁺ and precipitation of crystals containing Fe³⁺. With the addition of 4 % Na₂O, solidification temperature of slag decreased from 1790 K to 1530 K, optimum iron recovery rate of 81.08 % was achieved. Na₂O as flux in ceramics obviously reduced its sintering temperature and meantime decreased its bending strength because of insufficient crystallization of its main minerals. The non-magnetic residue from magnetic separation of slag with addition of 4% Na₂O was converted into ceramics with a much low sintering temperature of 1268 K (995 °C) and qualified bending strength of 64.5 MPa.