Ceramics are one of the most tolerant materials when it comes to dealing with heat. To produce ceramics, its raw materials are subjected to very high temperatures that would cause them to bond in an atomic level via ionic or covalent bonds. With the same principle, when ceramics need to be joined together-like in instances when they get broken and need repair-they again need to be subjected to very high temperatures. And even if that is to be considered a procedural technique, it still puts the integrity of the material into question as after heating, a great temperature difference across it would be present. This would cause the material to eventually crack or break.
In a recent development by engineers at the University of California San Diego and at the University of California Riverside, a new ceramic welding technique is described in an issue of Science. Senior author and UC San Diego mechanical engineering professor Javier Garay collaborated with UC Riverside professor and chair of mechanical engineering Guillermo Aguilar to work on the project.
The researchers used an ultrafast laser pulse to weld ceramic materials together. Compared to the heating the ceramic to very high temperatures in a furnace, this development would only use a laser with rated power at less than 50 Watts. On top of that, it can be used in ambient conditions, increasing its practicability.
The ultrafast pulsed laser works by first sending a series of short laser pulses to the material interface, where heat is allowed to build up. This promotes localized melting at the interface of two ceramic parts so that they are joined together. The engineers who worked on the research had to consider a number of factors including the exposure time of the laser, number of pulses, the length of pulses, and the transparency of the ceramic.
To prove its effectiveness, the team welded a transparent cylindrical cap to the inner surface of a ceramic tube. The welded material was so strong that it was able to hold a vacuum.
The team plans to use their technology in manufacturing medical and electronic devices. Ceramics are biocompatible, hard, and shatter-resistant. Ideally, these properties make ceramics great materials for biomedical implants and encasing electronic devices. But because there is no practical procedure yet to incorporate them in the devices, such devices do not exist yet. Garay explained this in a statement. "Right now there is no way to encase or seal electronic components inside ceramics because you would have to put the entire assembly in a furnace, which would end up burning the electronics," he said.
Currently, however, the laser was only used to weld together ceramic parts that are less than two centimeters small. Further research on this will involve scaling it up and using the laser for other type of materials and various shapes.
