E. Williams, J. Putman, P. Willis
Keywords: mass spectrometry, chemical characterization, chemical mapping, elemental analysis
Summary:Understanding the chemical composition of any manufactured material is essential to predicting a part’s performance. Despite its importance, however, executing chemical characterization on solid materials is expensive, difficult, and time consuming. Currently, the results required by highly regulated industries like aerospace, energy, and medicine involve multiple analytical instruments, complicated operational and calibration procedures, and trained chemistry experts. As a result, materials engineers in the advanced manufacturing industry typically choose to outsource chemical characterization, paying hundreds of dollars per analysis and waiting weeks for results. This work describes a new analytical technique for rapid chemical characterization of solid materials that addresses the challenges associated with existing techniques. Combining a patented ionization system with industry leading time of flight mass spectrometry, it is the first commercial instrument using Laser Ablation Laser Ionization Time of Flight Mass Spectrometry (LALI-TOF-MS). LALI uses one laser to remove material from a solid sample and a second laser to subsequently ionize neutrals. Traditional mass spectrometry and spectroscopy instruments require liquid sample introduction, which involves complex dilution/digestion and correction/calibration procedures. By directly analyzing solid materials, LALI significantly reduces sample preparation time and complexity. By targeting neutral particles, the ionization technique removes many of the matrix effects and interferences that plague traditional plasma-ionizing methods. After ionization, the TOF mass analyzer creates a full mass spectrum at each laser spot. The entire process is performed under vacuum, greatly improving ion transmission efficiency compared to other techniques. Additionally, this system does not require an inert gas, and it is fully contained within a compact package that fits on a desktop. LALI-TOF-MS provides versatility, high-throughput, broad elemental coverage, and low detection limits and has potential to meet the growing characterization of needs of the advanced manufacturing industry. Mass spectrometry is used in a variety of industries from pharmaceuticals to environmental testing. These established markets are already dominated by traditional instruments and the experts trained to operate them. Instead, the entrepreneurs developing LALI-TOF-MS are focused on industries that currently lack in-house analytical capabilities and choose to outsource chemical testing to external laboratories, like advanced manufacturing. Specifically, additive manufacturing has progressed from being mainly a tool for low-cost prototyping to a manufacturing activity that can produce large volumes of high-value metallic components. Now, the industry’s priority is stable, repeatable, and standardized processes to ensure predictable performance across the ecosystem. LALI-TOF-MS can quantify the metallic, trace, and low-mass elemental constituents of any additive manufacturing powder or build in a single analytical session. As a result, materials engineers can avoid the costs and time associated with sending samples to external laboratories. In addition to bulk chemical characterization, LALI-TOF-MS can perform chemical mapping with a spatial resolution ranging from 5-200 microns. Revealing localized chemical heterogeneity can identify poorly distributed feedstock particles and diagnose failed builds. By providing chemical data at the same scale as feedstock particles and the melt pool in many additive manufacturing techniques, it is an ideal tool for quality control, failure analysis, and new material development.