Modified nanopastes for pressureless nanojoining in the field of structural applications

与纳米颗粒连接(纳米连接)是一种很有前途的替代传统的铜焊和焊接工艺。与相应的块体材料相比，纳米颗粒的烧结和熔化温度较低，因此可以降低连接温度，因此纳米连接具有很大的优势。然而，这一加入过程也带来了新的挑战。例如，在连接过程中，必须对要连接的表面施加高压，以获得足够的连接强度，这限制了纳米连接的灵活性和适用性。为了抵消施加连接压力的缺点，本项目的目标是在完全不受连接压力的情况下或至少在连接压力显著降低的情况下实现所需的纳米接头的性能。这将使连接几何结构的设计具有更大的灵活性，简化系统技术和工艺步骤，并使机械敏感部件结构能够连接。研究的起点是纳米镍，可用于结构应用领域的连接。在拟议的项目中，提出了一个概念，即通过在连接温度下存在于液相中的组分来扩大纳米棒的金属含量。这样做的主要目的是减少接头中的孔隙率，并改善纳米颗粒与基材之间的结合。在液态的帮助下，试图获得一种在理想情况下不需要连接压力就能获得足够高的连接强度的微观结构。通过根据与镍的混合行为仔细选择这种成分，可以通过原位合金形成来保证较高的重熔温度，从而保证连接组件的较高工作温度。在我们前期工作的基础上，论证了这一概念的基本可行性。此外，还计划进行基础研究，以创建一个模型，以便更好地了解连接压力对微观结构和连接强度的影响。

Joining with nanoparticles (nanojoining) is a promising alternative to conventional brazing and soldering processes. The lower sintering and melting temperature of the nanoparticles compared to corresponding bulk material enables reduced joining temperatures, so that nanojoining offers great advantages. However, new challenges also arise with this joining process. For example, high pressures must be applied to the surfaces to be joined during the process in order to achieve sufficient joint strengths, which limits the flexibility and applicability of nanojoining. In order to counteract the disadvantages of applying joining pressure, the aim of this project is to achieve the desired properties of a nanojoint entirely without or at least with significantly reduced joining pressure. This would allow greater flexibility in the design of the joining geometry, simplify system technology and process steps, and also enable mechanically sensitive component structures to be joined.The starting point of the investigations are Ni nanopastes, which can be used for joining in the field of structural applications. In the proposed project, a concept is presented in which the metal content of the nanopastes is expanded by a component which is present in the liquid phase at the joining temperature. The main aim of this is to reduce the porosity in the joint and to improve the bonding between the nanoparticles and the base material. With the help of the liquid phase, it is attempted to achieve a microstructure which leads to sufficiently high joining strengths without the need for joining pressure in the ideal case. By carefully selecting this component according to the mixing behavior with nickel, a high remelting temperature and thus a high operating temperature of the joined assembly can be guaranteed through in situ alloy formation. The basic feasibility of this concept is demonstrated on the basis of our own preliminary work. In addition, fundamental investigations are also planned to create a model that allows a better understanding of the influence of the joining pressure on the microstructure and the joint strength.