Microwave absorption properties of steelmaking dusts:effects of temperature on the dielectric constant (ε') and loss factor (ε'') at 1064 MHz and 2423 MHz

Abstract The microwave absorption properties of a material depend largely on the dielectric properties of the material being heated. Therefore, the influences of temperature on the dielectric constant (ε,) loss factor (ε,,) loss tangent (tan δd) and penetration depth (DP) of steelmaking dust at frequencies of 1064 MHz and 2423 MHz were measured. Three steelmaking dust samples were studied. The effects of temperature on the dielectric properties of the samples were insignificant at temperatures below 600 °C. However, above this temperature, a rapid rise in the values of the dielectric properties of the samples was observed. Comparing the thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) results and mass spectra (MS) of the dusts with their dielectric properties revealed that the changes in the dielectric values of the dusts were associated with the thermal decomposition of calcium carbonate and the release of CO/CO2 gases. Furthermore, the increase in the electrical conductivity of the samples at high temperature resulted in increased dielectric values. The behavior of the loss tangent of the samples with increasing temperature coincided with the behavior of the loss factor. The penetration depth decreased with an increase in temperature at both frequencies, while an increase in the dielectric properties caused a significant decrease in the penetration depth. The results indicated that steelmaking dusts have good microwave absorbing properties owing to their carbon and iron oxide contents

Simultaneous removal of Cr(III) and V(V) and enhanced synthesis of high-grade rutile TiO₂ based on sodium carbonate decomposition

Abstract Rutile TiO₂ is widely applied as the raw material to produce titanium dioxide and titanium sponge, whereas the Cr (III) and V (V) impurities in rutile TiO₂ significantly affect the performance of related products. In the present work, the sodium carbonate decomposition treatment on Panzhihua titanium slag was attempted, to improve the preparation process of rutile TiO₂ with high crystallinity and simultaneously reduce the chromium (Cr) and vanadium (V) content as hazardous elements. Effects of sodium carbonate decomposition treatment on the crystal composition, microstructure of rutile TiO₂ were determined using XRD, SEM and Raman characterization. The recovery of Cr(III) and V(V) was achieved through leaching the roasted titanium slag by dilute sulfuric acid, with the chromium and vanadium content in the residue decreasing up to 0.03 % and 0.04 %, respectively, followed by the final product rutile TiO₂ was produced by the leaching residue calcined at 1323.15 K with a duration time of 120 min, with 85.56 % of TiO₂ grade. The work highlights the feasibility of synchronously preparing rutile TiO₂ and removing hazardous Cr (III) and V (V) impurities from titanium slag using sodium carbonate decomposition