Researchers in Germany have developed a laser-based process for permanently sealing thick-walled glass containers used to store hazardous chemical waste, including materials from electric vehicle batteries. The work was carried out at Laser Zentrum Hannover e.V. as part of a project called LasGlaReLa, and the results were published in the Journal of Laser Applications.
As reported by Phys.org, the process addresses a growing problem tied to the expansion of electric vehicles. Battery materials and other industrial chemical waste streams must sometimes be disposed of in Category IV landfills, which impose strict requirements on the containers used. Those containers must protect the environment, allow safe handling, and maintain structural integrity over the long term.
Glass is considered a strong candidate material for this application because it is chemically inert, meaning it reacts with almost no other substances. Thick-walled glass containers can hold hazardous materials without the contents degrading the container itself. Glass also offers a potential advantage for future recycling: stored materials do not bond with the glass and could be recovered later.
Until now, the standard method for manufacturing these sealed containers involved thermal gas processes. Those methods come with drawbacks including uncontrolled heat input, high residual stresses in the finished product, and limited potential for automation. Laser welding offers a faster processing speed and is better suited to automated production.
The Hannover team used a CO2 laser operating at a wavelength of 10.6 micrometers as the primary energy source. This laser type normally has a very low optical penetration depth of just a few micrometers in glass, and combined with the low thermal conductivity of silicate glass, it typically cannot produce a complete weld through thick material. The researchers developed an approach that overcame this limitation.
Using a single CO2 laser source, they heated both pieces of glass simultaneously and produced a continuous weld seam through the full 5 millimeter thickness of flat borosilicate glass. The seam contained no micro-gaps or voids. Mechanical strength was also preserved after welding, confirmed through stress tests conducted on samples after two weeks of storage.
One of the more unusual features of the process is how the two glass pieces are held together during welding. Rather than using clamps or complex handling equipment, the team let gravity do the work. The lid sinks onto the base piece during processing due to its own weight, automatically positioning the two surfaces against each other. This simplifies the production setup considerably.
Researchers are now working on refining the geometry of the glass edges to reduce friction during welding and minimize the formation of protrusions and notches at the joint. Further optimization work is ongoing at Laser Zentrum Hannover.
