Researchers to optimise ceramic additive manufacturing
A group of researchers are looking to optimise the laser power and scanning speeds used in the additive manufacturing of complex ceramic structures.
The scientists, from the University of Nebraska-Lincoln (UNL), are using a technique known as neutron diffraction to observe the effects of the rapid heating and cooling that occurs during laser additive manufacturing (LAM) of ceramics.
Their work will reveal how to better manufacture and functionalise advanced products such as superconductors, fibre-optic components, precision sensors and porous microscopic spheres for drug delivery, which are often made from ceramics due to their superior thermal and mechanical properties.
‘To optimise the production of the ceramics for high-tech applications, we need to better understand how laser heating affects the materials at the atomic and molecular levels,’ said Xiang Zhang, a graduate researcher at UNL.
Specifically, the researchers are looking at how grain orientations, residual stress, and thermal stability in ceramics are related to common LAM processes, including laser scanning and layering direction.
Similar to firing clay in a kiln, above a laser is shown 'sintering' (strengthening) a ceramic object after the basic shape was produced layer by layer using laser-based melting and resolidification. (Credit: University of Nebraska-Lincoln/Xiang Zhang)
Lasers at the UNL Laser-Assisted Nano Engineering Lab, and the Nebraska Engineering Additive Technology Labs, were used to melt and print samples of advanced ceramics. The scientists then studied how the intense heat and rapid phase changes from laser melting and rapid re-solidification induced residual stress, chemical deviations, and defects such as pores and cracks in the ceramics, which can physically weaken the materials and reduce their mechanical properties.
Neutron diffraction was used to study the samples because neutrons are non-destructive, deeply penetrative and highly sensitive to light elements such as the oxygen and carbon found in ceramics. With it the scientists were able to successfully measure the grain orientation throughout the ceramic samples, allowing them to correlate texture development and other properties with the process parameters used.
Professor Bai Cui, the primary investigator on the project, explained that the results of the study are now being used to optimise the laser power and scanning speeds that can be used to additively manufacture complex ceramic structures. Once the team has done this, it plans to patent the process.
Top image caption: UNL researchers Xiang Zhang and Professor Bai Cui are studying the microstructure and residual stress characterisations of additively manufactured ceramic materials. (Credit: ORNL/Carlos Jones)