The effects of substitution of Sn for Co on the microstructure, hydrogen storage and electrochemical discharge capacity of La0.7Mg0.3Al0.3Mn0.4Co0.5-xSnxNi3.8 （x=0, 0.1, 0.2, 0.3 and 0.5） alloys were investigated us...The effects of substitution of Sn for Co on the microstructure, hydrogen storage and electrochemical discharge capacity of La0.7Mg0.3Al0.3Mn0.4Co0.5-xSnxNi3.8 （x=0, 0.1, 0.2, 0.3 and 0.5） alloys were investigated using X-ray diffraction （XRD）, pressure composition isotherm （PCT） and electrochemical discharge cycle. XRD, scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） tests showed that all of alloys are mainly composed of LaNi5 and MgNi2 phases, but when increasing the content of Sn in alloys, the LaNiSn phase appears and microstructure is refined. The PCT showed that increasing substitution of Sn for Co results in decrease of the maximum hydrogen storage capacity from 1.48% （x=0） to 0.85% （x=0.5）. The electrochemical tests indicated that the maximum discharge capacity decreases from 337.1 mA-h/g （x=0） to 239.8 mA.h/g （x=0.5）; however, the discharge capacity retention at the 100th cycle increases from 70.2% （x=0） to 78.0% （x=0.5）.展开更多
Thorium is nearly three times more abundant than uranium in the Earth＇s crust. Some papers evaluate the thorium resourcesin Brazil over 1,200,000 metric t. These figures mean that the country is probably the biggest ...Thorium is nearly three times more abundant than uranium in the Earth＇s crust. Some papers evaluate the thorium resourcesin Brazil over 1,200,000 metric t. These figures mean that the country is probably the biggest thorium resource in the world, with onlypart of the territory prospected. Nevertheless, Brazil has not a research program for use of thorium in nuclear reactors, even havingdedicated special attention to the subject in the beginning of its nuclear activities, in the fifties and sixties. From 1985 until 2003 IPENoperated a pilot plant for thorium nitrate production and purification, used by Brazilian industry for production of gas mantles. Thisfacility produced over 170 metric t of thorium nitrate. Despite the non-nuclear application, the pilot plant was unique in the southernhemisphere. On the other hand, Brazil has the biggest world niobium resources. The Brazilian thorium and niobium resources added tothe predictable future importance of alternative fissile materials have motivated this research, since uranium is a finite resource if usedin the present thermal nuclear reactors. Besides this, thorium oxide is an important nuclear reactor material. It is a refractory oxide andits ceramic fabrication process involves a very high temperature sintering treatment considering that thoria melting point is very high（3,650 K）. Cations of elements of the group VB （V, Nb and Ta） have a known effect in the reduction of thoria sintering temperature.IPEN has initiated an investigation about the use of niobium as a dopant for thoria sintering temperature reduction. The thoria used inthe research was produced in the IPEN＇s pilot plant and different amounts of niobium oxide （Nb2Os） will be added to thoria by differentroutes. The powders will be compressed and the compacted pellets will be sintered at different temperatures. The influence of thedifferent parameters in the density of sintered pellets is being investigated. This paper presents the chemical and physicalcharacterization for the thoria used in the investigation.展开更多
基金Institute for Superconducting and Electronic Materials (ISEM)University of Wollongong and Institute Nuclear and Energy Research (IPEN)+2 种基金University of Sao Paulo for the financial supportNational Council for Scientific and Technological Development – CNPQ – Brazil for the scholarshipsfinancial support (CNPQ 472504/2010-0) granted to Julio Cesar Serafim CASINI
文摘The effects of substitution of Sn for Co on the microstructure, hydrogen storage and electrochemical discharge capacity of La0.7Mg0.3Al0.3Mn0.4Co0.5-xSnxNi3.8 （x=0, 0.1, 0.2, 0.3 and 0.5） alloys were investigated using X-ray diffraction （XRD）, pressure composition isotherm （PCT） and electrochemical discharge cycle. XRD, scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） tests showed that all of alloys are mainly composed of LaNi5 and MgNi2 phases, but when increasing the content of Sn in alloys, the LaNiSn phase appears and microstructure is refined. The PCT showed that increasing substitution of Sn for Co results in decrease of the maximum hydrogen storage capacity from 1.48% （x=0） to 0.85% （x=0.5）. The electrochemical tests indicated that the maximum discharge capacity decreases from 337.1 mA-h/g （x=0） to 239.8 mA.h/g （x=0.5）; however, the discharge capacity retention at the 100th cycle increases from 70.2% （x=0） to 78.0% （x=0.5）.
文摘Thorium is nearly three times more abundant than uranium in the Earth＇s crust. Some papers evaluate the thorium resourcesin Brazil over 1,200,000 metric t. These figures mean that the country is probably the biggest thorium resource in the world, with onlypart of the territory prospected. Nevertheless, Brazil has not a research program for use of thorium in nuclear reactors, even havingdedicated special attention to the subject in the beginning of its nuclear activities, in the fifties and sixties. From 1985 until 2003 IPENoperated a pilot plant for thorium nitrate production and purification, used by Brazilian industry for production of gas mantles. Thisfacility produced over 170 metric t of thorium nitrate. Despite the non-nuclear application, the pilot plant was unique in the southernhemisphere. On the other hand, Brazil has the biggest world niobium resources. The Brazilian thorium and niobium resources added tothe predictable future importance of alternative fissile materials have motivated this research, since uranium is a finite resource if usedin the present thermal nuclear reactors. Besides this, thorium oxide is an important nuclear reactor material. It is a refractory oxide andits ceramic fabrication process involves a very high temperature sintering treatment considering that thoria melting point is very high（3,650 K）. Cations of elements of the group VB （V, Nb and Ta） have a known effect in the reduction of thoria sintering temperature.IPEN has initiated an investigation about the use of niobium as a dopant for thoria sintering temperature reduction. The thoria used inthe research was produced in the IPEN＇s pilot plant and different amounts of niobium oxide （Nb2Os） will be added to thoria by differentroutes. The powders will be compressed and the compacted pellets will be sintered at different temperatures. The influence of thedifferent parameters in the density of sintered pellets is being investigated. This paper presents the chemical and physicalcharacterization for the thoria used in the investigation.
