【作者】 孙景文；

【导师】 李长生；

【作者基本信息】 江苏大学 ， 机械设计及理论， 2007， 硕士

【摘要】 铁磁形状记忆合金Ni-Mn-Ga是一种新型的智能材料，最突出的应用功能在于它的马氏体变体可以由外加磁场驱动重新排列而显示出类似于磁致伸缩效应的宏观应变。由于Ni-Mn-Ga合金块体材料的高脆性，很难切割成较小的块，这限制了其在微机电系统中的应用，而薄膜则很好的解决了这个问题。本文采用微波ECR射频磁控溅射技术在Si(100)基片、铜箔和Ni-Mn-Ga基片上分别制备Ni-Mn-Ga薄膜，研究了各种制备参数对薄膜成分和性能的影响，以期对这种新型的薄膜材料的制备及特性进行初步探索。结果如下：1．射频功率和工作气压对薄膜的成分有较大影响。当溅射功率处于175W与200W之间时，所沉积的薄膜的成分与靶的成分较为接近。随着工作气压的增加，Mn的含量基本上变化不大，Ni的含量先是有所增加，0.6Pa之后又有回复趋势，Ga的变化过程正好与Ni相反。2．随后，对薄膜进行了真空热处理，随着热处理时间的增加，薄膜中Ni的含量稍有下降，Mn的含量呈线性增加，而Ga的含量则是先有所下降，后又稍微上升。热处理时间为60分钟时，在400℃到600℃的温度范围内，Ni的含量受温度的影响较小，而Ga的含量减少，Mn的含量相对增加。随着温度的进一步升高，三种元素的变化趋于缓和。3．沉积于硅片上的薄膜表面比较光滑，同时膜上存在颗粒状物质，最大颗粒直径约为2μm。在400℃保温60分钟后，薄膜并没有明显的结晶现象，在450℃保温60分钟后，薄膜出现了结晶现象，并且随着热处理温度的升高，结晶现象愈来愈明显。由于硅片和Ni-Mn-Ga薄膜的热膨胀系数并不相同，导致部分薄膜出现裂纹。4．沉积后的薄膜并没有完全晶化，热处理后的薄膜呈多晶态，晶粒呈多种取向，分别为(022)(400)(214)，同时还存在Manganosite相。晶粒尺寸随着热处理温度的增加几乎呈线性增加趋势。5．热处理对薄膜的铁磁特性有明显的影响，当热处理温度较低时，薄膜并未完全晶化，铁磁特性亦不明显。当温度达到500℃之上才显示明显的磁性。6．对薄膜应变进行测试结果表明，随着磁场强度的增加，各个样品的应变值都增大。在磁场强度为4.0KOe时，铜箔上的薄膜的应变值为-98ppm，热处理后的硅片上薄膜的应变值-85ppm，未热处理的硅片上的薄膜的应变值为-82ppm，Ni-Mn-Ga块体上的薄膜的应变值为-142ppm。更多还原

【Abstract】 Ferromagnetic Shape Memory Alloys (FSMAs) is a new type of intelligent material. Their notable character is shape memory effect which can be induced by magnetic field, and their martensite has large reversible magnetic-field-induced strain. However, the bulk has very high brittleness and is difficult to be machined to small parts. In order to be applied in MEMS such as micro actuators and micro sensors, Ni-Mn-Ga alloys have to be in the form of thin films.In this text, Ni-Mn-Ga thin films were prepared by MW-ECR RF magnetron sputtering on Ni-Mn-Ga bulks, Cu foils and Si wafers. And then the effect of preparation parameters to the films’ composition and appearance were discussed. The results are given as below:1. Two main factors that affect films composition are sputtering power and deposition pressure. When the target and substrate distance is 60mm and the air pressure was 0.4Pa, the composition of Ni and Mn increase with the power grows, and Ga decreases. The composition of Ni and Ga are affected clearly by air pressure.2. Subsequently films were annealed in vacuum heat treatment device. Following the increasing of the heating time at 600℃, the Ni content decreases slowly, Mn increases in line with the aging time, and the Ga decreases first then increases little. While the heating time is 60min and the heating temperature between 400℃and 600℃, the Ni content isn’t affected as much as Ga and Mn. As the temperature further increases, three elements change slowly.3. The surfaces of the films deposited on silicon wafer are much smoother than others, and in some images can see large grains with the largest diameter about 2μm. After annealed in 400℃about 60min, the film crystallized. With the increasing of the heating temperature, crystal grains grow larger.4. By XRD analyze, the annealed films are polycrystal with main grain orientation (022) (400) (214). The Manganosite phase was found at one time.5. Heating treatment affects the film ferromagnetism greatly. Films have no ferromagnetism until the heating time above 500℃.6. The strain and magnetic field intensity curve shows that the strain grows with the increasing of magnetic field intensity. The largest strain of heated films on copper foil, Si wafer and Ni-Mn-Ga bulk are -98ppm,-85ppm and -142ppm respectively with the field about 4.0KOe.更多还原