Mid Sweden University

Additive manufacturing is rapidly growing, where selective laser sintering technology dominates for industrial use. In the case of polymer selective laser sintering, polyamide is the standard material. However, polyamide is an electrical insulator, and for specific applications, it would be desirable to be able to manufacture polymer-based electrically conductive parts. Electromagnetic Compatibility is one of the most significant targeted applications, where the introduction of electric vehicles raises new electromagnetic compatibility demands. The goal is, therefore, to develop an electrically conductive composite material for selective laser sintering using graphene as the additive. Composites are prepared by mixing polyamide, graphene, and additives with varying graphene/polyamide ratios. The aim of this investigation is the laser-assisted processing of the resulting graphene/polyamide composites with various parameters to sinter the material, forming a solid conductive structure. The structure is characterized using SEM and resistance measurements. Results show sheet resistance values of about 700Ω/sq after laser-assisted processing with good powder flowability. 

Lithium-ion batteries are widely used today due to their high energy density, long life cycles, and low self-discharge rates. It commonly uses graphite as an anode material with a high theoretical capacity of 372mAh/g. At the same time, several research groups explore ways to further increase the energy storage capacity of lithium-ion batteries by, for example, adding silicon to the graphite anode material. Silicon is naturally abundant and inexpensive, with low environmental impact and a significantly higher theoretical specific capacity of ~4200mAh/g. A drawback is that graphite-silicon composite anode materials tend to degrade during the charge/discharge cycles, leading to decreased storage capacity over time. This degradation is associated with the size of the silicon particles, where large, micrometer-sized silicon particles are more susceptible to instability than smaller, nanometre-sized particles. To address this issue, we present an investigation using laser-assisted processing of nano-graphite-silicon composites. This process uses low-cost micrometer-sized silicon particles mixed with nano-graphite powder and a 1064 nm continuous wave laser to process the nano-graphite-silicon-coated anode material under various conditions and atmospheres (ambient and nitrogen). The performance of the lithium-ion battery is affected by different processing conditions. Specifically, the intensity of the 0.25V and 0.5V anodic peaks, which indicate the delithiation of silicon, is particularly affected, with the inclusion of an additional broader shoulder peak at around 0.3-0.35V. Our investigation suggests that laser-assisted processing of nano-graphite-silicon-composite materials is a scalable concept with the potential to improve the performance of nano-graphite-silicon anodes for lithium-ion batteries. 

Lithium-ion batteries are pivotal in modern energy storage, commonly utilizing graphite anodes for their high theoretical capacity and long cycle life. However, graphite anodes face inherent limitations, such as restricted lithium-ion storage capacity and slow diffusion rates. Enhancing the porosity of graphite and increasing d-spacing in expanded graphite anodes have been explored to improve lithium-ion diffusion and intercalation. Recent advancements suggest that nanoscale modifications, such as utilizing nano-graphite and graphene, can further enhance performance. Laser processing has emerged as a promising technique for synthesizing and modifying graphite and graphene-related materials, offering control over surface defects and microstructure. Here, we demonstrate an industrially compatible one-step laser processing method to transform a nano-graphite and graphene mixture into a nanoporous matrix, significantly improving lithium-ion battery performance. The laser-processed anodes demonstrated significantly enhanced specific capacities at all charge rates, with improved relative performance at higher charge rates. Additionally, long-term cycling at 1 C showed that laser-processed cells outperformed their non-processed counterparts, with specific capacities of 323 and 241 mAh/g, respectively.

Lasers, with their unparalleled precision and control, have become vital tools across numerous industries, offering transformative potential for the development of advanced materials. In this research, laser-assisted techniques were employed to develop and optimize functional materials for industrial and energy applications. By leveraging the unique properties of laser light, significant advancements were achieved in three key areas. First, selective laser sintering was employed to create electrically conductive polymer-graphene composites, demonstrating promising electrical conductivity, crucial for applications requiring electromagnetic compatibility. Second, rare-earth-doped nanocrystals were synthesized using ultrashort laser pulses, achieving precise control over nanoparticle size and morphology while maintaining consistent stoichiometry with the bulk material. This synthesis offers potential for applications in photonics due to the stability and tailored properties of the nanocrystal. Third, laser-assisted processing was applied to modify nanographite and nanographite-silicon composite anode materials for lithium-ion batteries. The laser-induced nanoporous structure in graphite-based anodes led to significant improvements in fast charging capabilities and specific capacity. Additionally, the optimization of silicon distribution within the nanographite matrix enhanced battery performance and cycling stability. These findings illustrate the versatility and efficacy of laser-assisted processing in tailoring material properties to meet the growing demands of advanced applications, offering a pathway to the development of next-generation materials with enhanced functionalities.

There is a growing demand for nanopowders and nanoparticles in fields like medicine, healthcare, optics, sensors, and environmental monitoring. To produce these particles, pulsed laser ablation in liquid is an emerging technology offering numerous benefits over more commonly used methods like chemical synthesis, despite its relatively low production rate. For photonics applications, the production of NPs via pulsed laser ablation in liquid of rare-earth doped crystals like YAG and YVO4 is of significant interest due to their high absorption and emission cross-section, as well as high thermal conductivity. There is an increasing interest in developing laser-active hybrid materials, such as nanoparticle-doped silica optical fibers, potentially offering new and unique optical properties in, e.g., fiber lasers. In this work, we present an investigation of using pulsed laser ablation in liquid to synthesize Yb:YVO4 nanoparticles using a 1030 nm femtosecond pulsed laser under various conditions. The size and structure of Yb:YVO4 nanoparticles were affected by the pulse repetition rate (frequency) and solvent parameters, producing ovoid-like and spherical structures in deionized water and ammonia solution, respectively, with increased colloidal stability utilizing ammonia. The produced NPs are in the 10 - 150 nm range, with smaller NPs formed using the ammonia solution. The NPs are characterized by dynamic light scattering, Raman spectroscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy.