氢爆碎工艺中的吸氢和放氢现象

Behavior of hydrogen absorption and desorption in hydrogen decrepitation process

研究了氢爆碎 (hydrogen decrepitation,HD)过程中不同合金及合金表面状态的吸氢速率和吸氢量 ,并采用 X射线衍射、扫描电镜等手段研究 HD粉加热去氢过程中放氢规律和粉体微观形貌的变化。结果表明氢爆碎的吸氢速度和吸氢量与钕铁硼合金铸锭表面的活性有关 ,表面新鲜、活性大的合金铸锭氢爆碎的时间短、效率高。合金中存在足够的富 Nd相 ,是室温氢爆碎过程得以进行的前提条件。将 HD粉加热处理时 ,随加热温度的升高 ,氢不断释放出来 ,到10 73K时磁粉中氢的质量分数已降低到 1.5× 10 - 5,氢气基本释放。生产中可以将 HD粉经 5 2 3～ 72 3K加热放氢 1h后再进行磁场成型 ,以减少氢气对

The effect of alloy type and surface condition on the reactivity and the amount of hydrogen absorption in the hydrogen decrepitation (HD) process was investigated. The behavior of hydrogen desorption and morphology changes of degassing magnetic powders were also studied by Xray diffractometer and scanning electron microscope. The results show that the reactivity and the amount of hydrogen absorption in the HD process are related to the surface activity of the bulk alloy so that fresh active bulk has higher efficiency. The reactive nature of the NdFeB alloys with regard to hydrogen is ascribed to the presence of the Ndrich phase at the grain boundaries. During vacuum degassing, hydrogen was continuously released from the HD powders with increasing temperature and the residual hydrogen mass fraction reduced to 1.5×10 -5 at 1073K, which shows that the hydrogen was almost completely removed. It is feasible to dehydrogenate the HD powders by heating treatment at temperatures of 523～723K for 1h prior to the magnetic alignment and compaction procedure to decrease the effect of hydrogen on the easy axis alignment of a HD magnet.