Zhaojin Wu

Growth of phosphorus concentrating phase in modified steelmaking slags

Abstract Recycling steel slag to metallurgical process requires removing phosphorus from slag. In this paper, solidification experiments of converter slag modified by SiO2 at three isothermal temperatures with several durations were performed at air conditions from superheating temperature (1520°C). Grain size evolution of P concentrating phase (C2S, dicalcium silicate) was investigated. Results show that crystal size distributions of C2S can be fitted by lognormal distributions, the average size of C2S increases with increasing dwelling time and grows faster at higher holding temperature, and the relationship between average size of C2S and holding time can be best described by equation D = ktm. It is concluded that the growth mechanism of C2S is diffusion controlled, and higher isothermal temperature promotes the growth of C2S. Le recyclage de la scorie de l’acier par un procédé métallurgique nécessite l’enlèvement du phosphore de la scorie. Dans cet article, on discute d’expériences de solidification de scorie de convertisseur modifiée par du SiO4 à trois températures isothermes avec durées variées, effectuées à l’air à partir d’une température de surchauffage (1520°C). On a examiné l’évolution de la taille de grain de la phase de concentration du P (C2S, silicate dicalcique). Les résultats montrent que l’on peut ajuster les distributions de la taille de cristal (CSD) du C2S à une distribution log-normale, que la taille moyenne du C2S augmente avec l’augmentation du temps de résidence et croît plus vite à une température plus élevée de rétention et que la relation entre la taille moyenne du C2S et la durée de rétention est bien décrite par l’équation D = ktm. On conclut que le mécanisme de croissance du C2S est contrôlé par la diffusion et que la température isotherme la plus élevée favorise la croissance du C2S.

Effect of Cu substitution on structures and electrochemical properties of Li[NiCo1−xCuxMn]1/3O2 as cathode materials for lithium ion batteries

Copper ions are one of the major associated metal ions present in the precursors of the synthesis of Li[NiCoMn]1/3O2 from the recovery of spent Li-ion batteries by wet chemical processes. To evaluate the feasibility of reusing Cu(2+) as a favourable dopant in Li[NiCoMn]1/3O2 instead of as usual removing it as an undesirable impurity, the effect of Cu-doping on the electrochemical behaviour of Li[NiCoMn]1/3O2 is investigated in this work. Li[NiCo1-xCuxMn]1/3O2 (x = 0, 0.02, 0.04, 0.06 and 0.08) is synthesized through two steps, roasting the precursors obtained from carbonate co-precipitation, and their structures and electrochemical performances are systemically investigated. The results indicate that substitution of Co with Cu was successfully achieved without any detectable second phases. The initial discharge capacity of Li[NiCo1-xCuxMn]1/3O2 gradually dropped with an increase of x but the rate property and capacity retention were remarkably enhanced. In particular, the capacity retention of the Li[NiCo0.94Cu0.06Mn]1/3O2 sample reached 95.87% within 50 cycles at a current density of 160 mA g(-1). CV and EIS revealed that such improvements are ascribed to a higher Li(+) diffusion coefficient and lower charge-transfer resistance derived from Cu(2+) doping. The results suggest that Cu can be used as a beneficial dopant to partially substitute Co in synthesizing Li[NiCoMn]1/3O2 from spent LIBs instead of having to remove it as an impurity.