What makes a good construction material? There are many requirements, but one is the ability to efficiently connect different parts. Steel is almost the perfect example: you can join steel with fasteners (like nuts and bolts), by brazing, or by welding. The last of these is especially important. If we couldn’t weld metals, life would be quite different.
You don’t see this with ceramics. Ceramic parts are the hard-wearing miracle of modern life, but unlike steel and aluminum, you won’t find ceramics everywhere. This is because ceramics, though very useful, are difficult to work with. Joining two ceramics, or even connecting a ceramic to a metal, is a difficult and energy-consuming process because ceramics cannot be welded. That has changed, thanks to a team of researchers that is developing a ceramic welding laser.
Welding is riveting
Welding is a really special process. At one level, it is very simple: heat two materials until they melt and flow together. However, the melting is only local, so there is only minimal deformation to the rest of the part. The joint needs to be strong, which means that changes to the structure of the metal should not be too dramatic. Melting metals tend to oxidize vigorously, complicating the process.
Ceramic welding should be similar. The ceramic parts would be heated locally so that they melt and pool together. On cooling, the liquid recrystallizes to recreate the ceramic. Since ceramics are oxidized already, you don’t even have to worry too much about setting yourself on fire—a relief to me, as I have a bit of a flaming track record.
The problem is delivering heat to the right location. Since ceramics don’t conduct much heat, lasers are the weapon of choice for precision heating. Unfortunately, ceramics don’t efficiently absorb light; instead, they’re actually really good at scattering light. That means that the laser does not form a nice focus at the weld location and ends up gently heating a wide area of ceramic.