【作者】 许前丰；

【导师】 严有为；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2006， 硕士

【摘要】 纳米MgO是一种重要的高功能精细无机材料,在化工、轻工、食品、医药、涂料、橡胶、电子等行业具有广阔的应用前景。我国具有丰富且品位好的镁矿物资源, MgO也是我国西部盐湖镁资源开发的重要产品之一。因此,为了充分利用我国的镁资源,进一步提高MgO的品位和扩大MgO的应用范围,开展纳米MgO材料制备技术的研究具有十分重要的意义。本文将溶胶-凝胶湿化学法和燃烧合成技术结合起来,开展了凝胶-燃烧合成技术制备纳米MgO的研究。研究结果表明,柠檬酸对Mg2+离子的络合性强,易于制备凝胶,而尿素对Mg2+离子的络合性弱,不易凝胶化,且采用柠檬酸为燃料时制备的纳米MgO更细小;硝酸镁与柠檬酸的比例对燃烧合成反应有较大影响,当比例为2/1,燃烧合成反应能进行到底,燃烧剧烈,燃烧波推进速度快,合成产物颗粒最小,无团聚;前驱体溶液的pH值和水浴温度对凝胶的形成及燃烧产物有重大影响,当pH值为7时,水浴温度为80℃时,凝胶时间最短,制得干凝胶为有利于燃烧的多孔隙状态,且燃烧合成的MgO颗粒最小。此外,本文还研究了点火温度和煅烧温度对合成产物的影响。研究表明,点火温度和煅烧温度对合成MgO颗粒的形貌、团聚程度有一定的影响。点火温度为500℃时,一次燃烧合成产物的颗粒大小适中,团聚程度轻;将合成产物在600℃下煅烧1小时能有效去除残留有机物,且MgO颗粒无明显长大。在优化合成工艺的条件下,成功制备出了平均晶粒尺寸为10nm、比表面积为34.8234m2·g-1的高纯纳米MgO颗粒。所制备的纳米MgO颗粒表现出与块体MgO不同的红外特性,其A峰表现出明显的红移。因此,凝胶—燃烧合成法为制备纳米MgO颗粒提供了一条简单的新途径。更多还原

【Abstract】 Nanocrystalline MgO is an important inorganic material, and has potential applications in chemistry, light industry, food, medication, paint, rubber, electron industry and so on. There are abundant and good magnesium mineral resources in our China, and MgO is also one of the important products of west saline of China. Therefore, in order to make full use of our magnesium resources, to advance MgO quality and to extend its application range, it is of great meaning to study the fabrication technology of nanocrystalline MgO powders.In this paper, nanocrystalline MgO powders were prepared by a gel-combustion synthesis technology. The results show that, the link of citric acid with Mg2+ is strong and it is easy to prepare gel by citric acid, whereas the link of urea with Mg2+ is weak and it is difficult to prepare gel. So, citric acid is in favor of preparing fine nanocrystalline MgO. In addition, the radio of Mg(NO3)2 to citric acid has remarkable effects on the process of combustion synthesis, when the radio is 2/1, the dry gel can completely burn. Moreover, the combustion speed is fast, and the synthesized powders are pure MgO with a fine grain size. The effects of both the pH value of precursors and the temperature of the bathtub on the gel formation, morphology, combustion behavior and the crystalline size of the synthesized powders are systematically investigated. When the pH value is 7 and the temperature of the bathtub is 80℃, the time of the formation of gel is the shortest and the prepared dry gel has lots of small openings which was in favor of burning.Besides, the effects of ignition temperature and calcining temperature on the synthesized powders were also investigated in this paper. The results show that both of the two parameters have some effects on the size, shape and conglomeration of the synthesized powders. When igniting temperature is 500℃and calcining process is 600℃for 1 hour, nanocrystalline MgO powders with none organic compound left and low conglomeration can be obtained.In condition of the optimized parameters, pure nanocrystalline MgO powders with a average diameter of 10nm and BET value of 34.8234m2·g-1 were obtained; the nanocrystalline MgO powders produced put up infrared characteristic different with nubbly MgO, the A apex of which put up obvious Einstein shift. Therefore, it is proved that nanocrystalline MgO powders can be prepared by this simple gel-combustion synthesis method.更多还原