Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures
In this work MnxCo1−xFe2O4 nanoparticles (NPs) were synthesized using a chemical co-precipitation method. Phase purity and structural analyses of synthesized NPs were performed by X-ray diffractometer (XRD). Transmission electron microscopy (TEM) reveals the presence of highly crystalline and narrowly-dispersed NPs with average diameter of 14 nm. The Fourier transform infrared (FTIR) spectrum was measured in the range of 400–4000 cm−1 which confirmed the formation of vibrational frequency bands associated with the entire spinel structure. Temperature-dependent magnetic properties in anti-ferromagnet (AFM) and ferromagnet (FM) structure were investigated with the aid of a physical property measurement system (PPMS). It was observed that magnetic interactions between the AFM (Mn) and FM (CoFe2O4) material arise below the Neel temperature of the dopant. Furthermore, hysteresis response was clearly pronounced for the enhancement in magnetic parameters by varying temperature towards absolute zero. It is shown that magnetic properties have been tuned as a function of temperature and an externally-applied field.
Role of water vapor in oxidative decomposition of calcium sulfide
Abstract CaS formed from the CaO sorbent during desulfurization in coal gasifiers has to be converted to CaSO 4 before disposal. CaS is mainly decomposed to CaO and SO 2 by O 2 and then CaO is converted to CaSO 4 by SO 2 and O 2 . The role of H 2 O in the oxidative decomposition of CaS with O 2 was studied using reagent grade CaS and H 2 18 O. The following results were obtained: (1) there is a synergistic effect of H 2 O and O 2 on the oxidative decomposition of CaS to CaO and SO 2 ; (2) H 2 O reacts with CaS to form CaO, SO 2 and H 2 in the absence of O 2 ; (3) the oxidative decomposition of CaS to CaO and SO 2 occurs stepwise; (4) H 2 O directly reacts with CaS in the presence of O 2 ; (5) H 2 O plays an important role in the oxidative decomposition of CaS even if the O 2 concentration is high.
Recovery of Calcium Carbonate and Hydrogen Sulfide from Waste Calcium Sulfide
The removal of H2S from hot coal gas using a limestone-based sorbent generates a large quantity of calcium sulfide waste (e.g., 67 tons/day from the gasification of 1000 tons/day of 3% S coal) that cannot be landfilled because of potential H2S evolution and sulfide leaching. In the process proposed here, the CaS is dissolved by reaction with H2S complexed with aqueous methyldiethanolamine (MDEA) or other alkanolamines. In the second step, the highly soluble Ca(HS)2 reacts readily with CO2, also complexed with aqueous MDEA, to precipitate pure CaCO3 of uniform crystal size and to form MDEA-complexed H2S in solution. The solution from step 2 is splithalf is recycled to step 1 and half is sent to a stripper to recover H2S and from there to a column where the needed CO2 is absorbed from a combustion gas.