Problematic Waste Under Control Laser Welding Creates Safe Containers Made of Glass for Battery Waste

At the Laser Center Hannover (LZH) (Germany), it is well known that the increasing use of electric vehicles also raises the amount of battery materials to be disposed of. However, this can be managed using lasers...

With increasing electromobility, the need for safe and long-lasting storage of battery materials and chemical industrial waste is also growing, say the laser experts from Hanover. Certain waste also requires final storage in so-called Category IV landfills, as these meet particularly high requirements for containers. These must ensure environmental protection, safe handling, and long-term stability equally. Glass is a very promising material for this, they explain further. It is exceptionally chemically resistant and, as a thick-walled container, is particularly well-suited for safely storing hazardous substances. Glass containers are also of particular interest for potential new recycling methods in the future. Since the stored residues do not react with the container material, they can be easily retrieved and recovered, as emphasized.

Continuous Weld Seam Without Microcracks Achieved

So far, however, these glass containers are mainly produced using thermal gas processes. However, uncontrolled heat input, high internal stresses, and limited automation capability restrict the suitability of this common method. But laser welding offers high processing speeds and has excellent potential for automation. For this purpose, the researchers now used a CO₂ laser as the primary laser source. Normally, this has a wavelength of 10.6 micrometers, which results in a low optical penetration depth of just a few micrometers. Combined with the low thermal conductivity of silicate glass, this usually causes the glass piece to be incompletely welded through. However, as demonstrated, it is possible to use a single CO₂ laser source to heat both welding partners simultaneously to produce sealed glass containers. A continuous weld seam without micro-gaps or cavities was achieved across the entire thickness of the five-millimeter-thick (approx. 0.2-inch) flat glass.

Glass Container Production Without Complex Handling Systems

Moreover, despite the heat of the laser beam, the mechanical strength remains intact, as stress tests on the samples after two weeks of storage have proven. The process is unique because the container lid naturally sinks into the correct position during processing due to gravity. As a result, complex handling systems or clamping devices become unnecessary, the researchers emphasize. The scientists are now working on further adapting the edge geometries of the flat glass. For example, they aim to further reduce friction during the welding process and minimize the formation of bulges and notches at the joint, as noted in conclusion.

The underlying project titled "Innovative Manufacturing Technology for the Production of Laser-Welded Glass Hollow Bodies for Residue Storage" ("LasGlaReLa") was supported by the Federal Ministry for Economic Affairs and Energy under the funding code VN-KK5111715. Project partners were TU Bergakademie Freiberg (Germany) and Glasbiegerei Pfaltz e.K (Germany).