The Importance of Selective Laser Melting in Nanomaterials

Utilizing selective laser melting (SLM) to improve the performance and crystallographic properties of molybdenum disulfide (MoS2).

FREMONT, CA: Selective Laser Melting (SLM) is a 3D printing technique that uses a high power-density laser beam to completely melt and connect metal granules to produce near-net-shape objects with relatively maximal densities (up to 99.9 percent relative density). The vast majority of commercial SLM equipment use granules ranging from 20 to 50 m and a typical film thickness of 20–100 m.

Stay ahead of the industry with exclusive feature stories on the top companies, expert insights and the latest news delivered straight to your inbox. Subscribe today.

SLM is utilized in the aircraft, automotive, petrochemical, marine, architectural, food, and jewelry industries. Micro SLM has recently gained popularity in producing precise components and microstructures in numerous industries, such as microfluidic systems, MEMS, orthodontics, etc.

A 3D model must be translated into a format compatible with an SLM printer before it can be printed. Using so-called slicing software, the model is then sliced into layers, where each cross-section of the model represents the layers that the SLM machine will print.

After the model has been put into the printer, the powder stock is refilled with the proper metal powder via a hopper or automated cartridge. To prevent the metal from oxidizing in the presence of the high-powered laser beam, an inert gas (usually argon) is pumped into the build chamber. These lasers are primarily ytterbium fiber lasers with a high power, which are hot enough to melt powdered metal and generate enormous temperature differences. The enclosed chamber is heated to minimize temperature changes between the powder and laser to accommodate these discrepancies.

The printing process begins when the roller/re-coater spreads a thin layer of powder from the power stock onto the build platform. A controlled X-Y scanning mirror then focuses and directs the laser to selectively melt the powder into the shape of the first layer. After this layer has sufficiently cooled, the build platform decreases in the Z direction while the powder stock increases by the same amount in the Z direction. The printing procedure is repeated for each layer until the finished object is encased in unused powder on the build platform.

After printing, the part is removed from the build platform and post-processed in accordance with its intended use. In contrast to other powder-bed 3D printing processes, SLM requires significant support systems to prevent warping on minor angles and overhangs as the item cools. These supports also function as heat sinks, removing heat from the laser spot to prevent severe component defect growth. Supports must be removed from the component before any further processing.

Numerous post-printing processes, such as stress-relieving, CNC machining, heat treatments, smoothing or polishing, or any other technique generally used on metal parts, are required to bring the item to its final state. Although officially conducted after the SLM process, these stages are the most significant component of SLM and are responsible for the exceptional qualities of its prints.

The selective laser melting technology permits unrestricted sophistication and customization of biomedical equipment. In addition, SLM manufacture of biological devices does not demand additional expensive tooling or time-consuming installation processes.

SLM is Favored above Other Technologies

Compared to other 3D printing technologies, SLM is based on adaptive high-energy Nd: YAG laser technology, enabling the fabrication of objects with greater tensile strength and higher resolution. As SLM solves many of the disadvantages of conventional and other additive manufacturing technologies, it can be used to prototype prospective rechargeable batteries rapidly.

Molybdenum Disulfide: An Introduction

Molybdenum disulfide (MoS2) belongs to the class of sophisticated advanced, efficient materials known as transition metal dichalcogenides (TMDs), with a direct bandgap of 1.8 eV and a nonoxidizing melting temperature of 1185 degrees Celsius.

MoS2 nanoparticles dominate multilayer electroactive structures due to their strong S–Mo–S covalent bonds. Molybdenum disulfide is used as a dry lubricant in numerous applications, such as lubricating oils, colloids, friction compounds, and bonded films. Although complexes can be employed in suspension, they are often soluble in fats.