【作者】 巴志新；

【导师】 李李泉；

【作者基本信息】 南京工业大学 ， 材料物理化学， 2003， 硕士

【摘要】 随着石油危机和环境污染的日益严重，氢能利用及其燃料电池被认为是本世纪新能源开发主要方向之一。其中高性能镁基储氢合金的研究和开发，则又被认为是氢能利用和燃料电池研发的重要课题之一。新的合成技术——氢化燃烧合成（Hydriding Combustion Synthesis）—HCS法，不仅在省能、省时、设备简单等方面具有显著的优越性，其合成产物也表现出了优良的性能。HCS法在镁基储氢合金开发中具有的重要应用价值，已引起国内外的足够关注，而我国在此方面的研究刚刚起步。 为了引进国外先进的合成技术，在我国开展镁基储氢合金HCS法研究建立基本条件，本课题围绕镁基合金HCS高压设备的研制和HCS产物—Mg₂NiH₄的制备开展了一系列初步的研究。 高压合成设备是开展HCS研究的基础，根据HCS镁基储氢合金研究的实验要求（氢气气氛6MPa，工作温度600℃以及反应器内合成样品温度的直接测量和控制）和日本同类反应设备的第一手资料，结合国内实际情况，在大量调研的基础上完成了简易HCS高压合成设备的设计、选材、制作和测试，设备达到了合成实验要求，并已投入使用。 使用自制反应设备，在较低的合成压力下（≤1.5MPa）制备纯的HCS产物—Mg₂NiH₄，对产物成分进行X射线衍射分析。同时研究了主要工艺参数：压力、合成温度、Mg₂Ni氢化时间对合成产物纯度的影响。并通过HCS制备Mg₂NiH₄过程的DSC曲线、产物Mg₂NiH₄的SEM照片及EPMA图谱，初步探讨了燃烧合成Mg₂Ni的反应机制，对所得结论进行解释。发现在初始压力为1.5MPa下，产物的纯度提高比较明显；合成温度及其保温时间的延长可以促进燃烧合成Mg₂Ni反应的进行，而氢化时间的延长为氢在Mg₂Ni中的扩散提供了足够的时间，从而提高了Mg₂Ni的氢化程度；但高温下长时间保温又不利于Mg₂Ni的氢化，导致产物中不完全氢化物—Mg₂NiH_0.3含量增加，主要是因为长时间的保温使Mg₂Ni经历长时间的烧结过程导致其致密化，阻碍了氢在其中的扩散。因此提高产物纯度的重点是：控制合适的合成条件，在促使燃烧合成Mg₂Ni反应完全的同时使Mg₂Ni具有易于氢化的高活性。分别在合成条件为：合成温度850K，合成保温60min， 摘 要MgzNi氢化保温90min及合成温度808K，合成保温120min，MgzNi氢化保温60min下制得了纯的MgZNIH4。 通过改变镁吸脱氢循环数及在镁氢化反应温度的保温时间，研究了不同合成压力、温度下，镁的氢化反应对产物纯度的影响。产物的成分及微观形貌的变化分别使用x射线衍射仪及扫描电镜SEM进行分析：通过产物纯度及其微观形貌的变化首次探讨了中间反应低的氢化反应与燃烧合成MgZNi反应及其氢化反应的内在联系。研究发现：镁的充分氢化可以促进Mg－Ni燃烧合成反应，主要是因为镁的膨胀开裂及部分粉化促进了燃烧合成 MgZNi过程中的液固反应和固相扩散反应。同时镁的膨胀导致了产物颗粒间孔隙的增大，从而明显提高Mg。Ni的氢化程度；主要表现在低压0．SMPa，镁氢化时间为120min时，产物MgZNifu纯度有了明显提高，这一结果为低压①．SMPa)合成纯MgzNifu提供了一种可能；在燃烧合成温度较低时，仅延长镁的氢化时间很难消除未燃烧合成完全的Ni。更多还原

【Abstract】 With the oil crisis and air pollution coming worse and worse, the using of clean energy of hydrogen, as well as, hydrogen fuel cell has become one of the main orientation of new energy in this age, in which the development of the Mg-based hydrogen storage alloy with excellent properties is a very important research subject. Hydriding Combustion Synthesis (HCS), a new materials processing technology proposed to produce hydrogen storage alloys recently, offers many advantages, such as short processing time, simple equipment and low energy requirements. In addition, its product also shows excellent performance, such as high activity, high purity and no activation process. Owing to its potential important values in preparing of hydrogen storage alloy, HCS has drawn great attention internationally recently. But the research of HCS is just at the beginning in our country now.In order to introduce the advanced synthesis technology and set up basal conditions for the research of HCS of Mg-based hydrogen storage alloy in our country, in this study, a series of primary research on the development of HCS reaction apparatus and the preparation of pure Mg-based hydrogen storage alloy-Mg2NiH4 by HCS were carried out and some conclusions on the process parameters of HCS have been also obtained.A simple HCS reaction apparatus was developed to meet the experimental requirements of hydrogen pressure of 6MPa, working temperature of 600℃ and direct measurement and control of the sample temperature. It involved the design of apparatus, selection of material, manufacture and testing according to the practical situation and a great deal of investigation.Pure Mg2NiH4 has been obtained by the simple HCS reaction apparatus developed under the lower pressure (≤1.5MPa). The purity of products was analyzed by X-ray diffraction (XRD). Meanwhile, the effects of main parameters such as hydrogen pressure, synthesis temperature, and the holding time at hydriding temperature on product purity were studied. Some results were obtained as follows: Comparing with the hydrogen pressures of l.0MPa and 0.5MPa, the purity of Mg2NiH4 obtained in the initial pressure of 1.5MPa increased obviously. Under this pressure, with the increasingof synthesis temperature and its holding time, the synthesis of Mg2Ni was promoted. Those results were explained by the mechanism of the combustion synthesis of Mg2Ni including solid-solid diffusion reaction between magnesium and nickel and the liquid-trigger of reaction mechanism. The increasing of the holding time at 653 K, the temperature of hydriding reaction from Mg2Ni to Mg2NiH4, can promote the hydriding reaction. However, long holding time at high synthesis temperature is disadvantageous to the hydriding of Mg2Ni because of the compaction of Mg2Ni during a long course of sintering accompanied. It is very significant and important to balance the two aspects: the high activity of product of Mg2Ni for hydriding reaction and the completion of the reaction of combustion synthesis Mg2Ni. In the initial pressure of 1.5MPa, pure Mg2NiH4 was obtained under different conditions, such as, holding 120min at synthesis temperature of 808K and 60min at Mg2Ni hydriding temperature of 653K; holding 60min at synthesis temperature of 850K and 90min at 653K.The effect of hydriding reaction of Mg on the purity of products of HCS was also studied under different pressures and different synthesis temperatures with changing cycles of hydriding and dehydriding and the holding time at the hydriding reaction of Mg. The relationships of hydriding reactions of Mg, synthesis of Mg2Ni and hydriding reaction from Mg2Ni to Mg2NiH4 were investigated firstly by means of XRD and SEM. It was found that with the hydriding reaction of Mg processed, the synthesis of Mg2Ni was accelerated and the hydriding activity of Mg2Ni increased obviously. The main reason is that the volume expansion of Mg during hydriding introduced not only crack and the pulverizing particles that accelerate the synthesis reaction of Mg2Ni, but also larger pores,更多还原