中文摘要：

研究了空气氛围中热处理天然菱铁矿在不同煅烧温度、时间的结构演化规律。结果表明：当煅烧温度达到约430℃时，矿石中的亚铁离子被轻微氧化，随即释放少量CO2，此时菱铁矿矿石表面逐渐出现多孔结构状态，孔径为几个纳米，呈现形态为不规则的串珠状；当煅烧温度达到460℃时，开始大量释放CO2并逐渐相转变为赤铁矿，并在595℃时完全相转变。400-600℃的煅烧产物比表面积和孔结构随着煅烧温度、时间的变化有较为明显的差异。其中470℃煅烧产物由于大量脱去CO2，菱铁矿颗粒内部出现大量1～5nm的介孔，最大比表面积为57．5m^2/g；随着煅烧温度增高、时间延长，赤铁矿晶粒逐渐变大，其晶粒间空隙孔径变大、数量减少，比表面积逐渐降低。天然菱铁矿可以在450-500℃空气氛围中快速热分解获得高比表面积纳米孔材料。

英文摘要：

The structure of natural siderite after annealing at different temperatures and durations was investigated. The results show that divalent iron in siderite is oxidized to ferric iron, forming a conjugate at 430 ℃ and releasing a small amount of CO2 simultaneously. As a results, the porous structure （beaded string） occurs on the surface of siderite, which the pore sizes are in nanoscale. When the temperature increases to 460℃, the conjugates release a great amount of CO2 and transforms into hematite. In addition, annealing temperature and time both affect the specific surface area and pore structure of the corresponding annealed product as the temperature changes from 400 to 600℃ and the time ranges from 10 to 60 rain. In particular, the specific surface area of annealed product increases to 57.5 m2/g at 470 ℃. The grain size of hematite increases with increasing the temperature and time. The decreased internal voids and the increased aperture increase with increasing the temperature and time, leading to the decreased specific surface area. The nano-porous material with the great specific surface area can be prepared through annealing siderite at 450-500℃.