Ternary Ru/Al-based reactive multilayers

金属间化合物B2 RuAl具有良好的高温性能和较高的室温延展性。-62 kJ/mol（原子）的高负生成热使Ru和Al的亚微米复合材料能够自传播放热反应形成B2化合物RuAl。这使得Ru/Al体系类似于其他金属间反应体系，如Ni/Al、Pt/Al、Pd/Al和Co/Al。然而，Ru/Al体系特别令人感兴趣，因为它是一种延展性反应产物的组合，其组成范围为4.1% at。（室温下）和良好的能量密度（可与市售的Ni/Al箔相媲美）。这使得Ru/Al在反应键合领域成为一个有趣的体系，局部加热仅限于连接区域。二元反应多层体系的特征参数是决定体系基本性质（反应速度、着火温度、反应产物的微观结构和形貌）的双层厚度，不能独立变化。该项目的目的是开发一种新的方法，通过从二元转移到三元Ru/Al/X层（X=Ni, Pt, Hf, Ti）来操纵Ru/Al基反应性多层膜的性质。重点是将Ru/Al多层材料相对较高的着火温度（400-575°C）降低到约300°C，与Ni/Al多层材料相当，从而改善存在散热器（例如在接头间隙内）的反应。由于据申请人所知，目前还没有对三元金属间反应体系进行系统的研究，因此本项目的一个重要组成部分是研究化学成分和堆叠顺序对反应多层的基本性质（反应速度、形貌和微观结构）的影响。因此，应该更好地理解潜在的机制。为了能够研究大范围的成分，采用组合溅射。该技术允许通过连续溅射具有厚度梯度的层在单个衬底上沉积材料库。采用x射线衍射和高通量电阻率测量方法对三元多层材料热处理后的钌基B2结构的存在范围进行了研究。在这些成分范围内，金属间相的形成作为温度的函数进行了原位四点电阻率测量，得出了点火温度的结论。在深入研究组分和堆叠顺序影响的基础上，结合Ru/Al的优点和较低的着火温度，开发了三元Ru/Al基反应性多层材料。

The intermetallic B2 compound RuAl combines good high-temperature properties with high room-temperature ductility. The high negative heat of formation of -62 kJ/mol(atoms) enables sub-µm composites of Ru and Al to self-propagating exothermic reactions forming the B2 compound RuAl. This makes the system Ru/Al similar to other intermetallic reactive systems like Ni/Al, Pt/Al, Pd/Al and Co/Al. However, the system Ru/Al is of particular interest due to the combination of a ductile reaction product, a compositional range of existence of 4.1 % at. (at room temperature) and a good energy density (comparable to that of commercially available Ni/Al foils). This makes Ru/Al an interesting system in the field of reactive bonding with local heating limited to the region of joining. The characteristic parameter of binary reactive multilayer systems is the bilayer thickness by which the basic properties of the system (speed of reaction, ignition temperature, microstructure and morphology of the reaction product) are determined and cannot be varied independently. Aim of this project is to develop a new way to manipulate the properties of Ru/Al-based reactive multilayers by moving from binary to ternary Ru/Al/X layers (X=Ni, Pt, Hf, Ti). The focus is on lowering the relatively high ignition temperature of Ru/Al multilayers (400-575°C) to values of approximately 300°C, comparable to that of Ni/Al multilayers, thus improving the reaction in the presence of a heat sink (e.g. inside a joint gap). Because there are, to the best knowledge of the applicants, no systematic studies on ternary intermetallic reactive systems, an essential part of this project is to investigate the influence of chemical composition and stacking sequence on the basic properties of a reactive multilayer (speed of reaction, morphology and microstructure). Thereby, a better understanding of the underlying mechanisms shall be gained. To enable the investigation of large ranges of composition, combinatorial sputtering is employed. This technique allows deposition of materials libraries on a single substrate by sequential sputtering of layers with thickness gradients. The compositional range of existence of the RuAl-based B2 structure is investigated by X-ray diffraction and high-throughput electrical resistivity measurements after a thermal treatment of the ternary multilayers. Within these compositional ranges, intermetallic phase formation as a function of temperature is investigated by in-situ four point measurements of the electrical resistivity to draw conclusions on the ignition temperature. Based on the insights into the influence of composition and stacking sequence, ternary Ru/Al based reactive multilayers are developed combining the benefits of Ru/Al with a reduced ignition temperature.