IIW White Paper

9 Needs and challenges of major industry sectors for future applications

nano effects is not new in technology (e.g. in the glass industry), but has generally never been known by this name.

While developments in nanotechnology can be utilised in joining technology, joining technology itself on the other hand is an essential step in manufacturing and assembly of nanodevices and nanosystems, to provide mechanical support and integration, electrical connection, optical coupling, environmental protection, etc. just like welding and joining at macro- and microscales. At the moment, there are two fields that are on the forefront: The utilization of nano effects for joining technology, such as the application of nanomaterials in joining technology. Joining of nanomaterials, or nano-scale building blocks, for applications in nanodevices and nanosystems. 9.17.1 Nanotechnology for joining One example in this field is nanoparticle-alloyed filler metals for welding that can lead to nano-structurised solidification of the weld pool and hence to a structure with the same base metal properties. This can be combined with no or low heat input welding processes as well for the joining of nano alloyed materials, e.g. nanoalloyed steels for conventional use. Additionally the expected energy saving can be a sustainability aspect. Similarly, nanoparticle-based pastes are suited as a filler material, with the right composition, for joining with low heat input, in particular of electronic components, e.g. to replace lead-free solders. Up to now, the nanoparticles in the pastes, as a rule, are wrapped up in organic substances. When submitted to temperature, these organic coatings evaporate and thus the nanoparticles are released. Under low pressure, they bond, via a sintering-like process, with each other and with the material surfaces to be joined, in a firmly bonded manner by diffusion. The current developments go in the direction of substituting the organic coating substances with others in order to avoid the bothersome vaporization products and to further reduce the joining temperatures as well as to reduce the required pressure. Another option for the use of nano effects for joining is the use of Nanofoils®. These multi-layer bands, made up of layers that are 25 to 90 nm thick and comprise different materials, when laid between the surfaces to be joined, lead to a self-progressing exothermic reaction after ignition as a result of their negative binding energy. The heat required for welding is thereby generated directly in the joining zone. The very costly production of the tapes is disadvantageous.

Nanoparticle-based adhesives with good adhesion, and electrical and other properties are also being developed and are used in the field of microelectronics.

9.17.2 Joining of nanomaterials Nanomaterials are materials comprising nanoparticles (nanotubes, nanofoams, nanofibers, nanowire) which are made of equivalent or different materials of the same kind and have the respective properties. The technical use of such materials requires bonding them with each other and with other materials to be assembled into nanodevices and nanosystems. In doing so, of course, the special properties of the nanomaterials are meant to be preserved as much as possible. Respective technologies and processes are currently being developed. For example, femto-second lasers are high performance pulse lasers with pulse durations in the femtosecond area (1 femtosecond = 10 -15 seconds). By the use of such extremely short-pulsed lasers, new options arise for material machining

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Through Optimum Use and Innovation of Welding and Joining Technologies

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