Lasers processing of ultra-hard materials

Laser processing of ultra-hard materials is a relatively new field that have the potential to improve variety of products and different industries. This dissertation explores specific new development in this field through three main subjects: laser machining, laser deposition of thin film, and laser treatment. In laser machining of ultra-hard material, controlled crack propagation mechanism -as opposed to the typical ablation mechanism- was investigated, and micromachining of ultra-hard thin film was also observed. For the laser deposition of ultra-hard thin film, designing new microstructured materials was explored, and the utilization of the inherent particulate formation associated with the pulsed laser deposition process was proposed for the first time. After that, a novel laser/waterjet treatment process to increase the hardness of certain ceramic materials was studied. Also, laser shock processing was investigated. Analytical and experimental approaches was conducted through all of these studies, and different analysis techniques were applied. The results indicate the feasibility of these processes when applied on ultra-hard materials, and provide a better understanding of the governing mechanisms

Investigation of a novel manufacturing technique for two-dimensional machining of Polycrystalline Cubic Boron Nitride (PCBN) tools

The Laser/Water-Jet (LWJ) hybrid machining system, introduced and developed by the Iowa State University\u27s Laboratory for Lasers, MEMS, and Nanotechnology, was applied to overcome the major deficiencies associated with current EDM and laser machining techniques for shaping Polycrystalline Cubic Boron Nitride (PCBN) cutting tools from the blanks. For PCBN, the purpose of water in LWJ is twofold: phase transformation and thermal shock. Previously LWJ was used to perform straight line cuts on various materials including PCBN. In this work, a further investigation of an understanding of the action of water and two-dimensional contour cutting of PCBN was carried out. The role played by water in LWJ was compared with that of other fluids (argon, nitrogen, oxygen, and air) to illustrate the effectiveness of water in the controlled fracture mechanism of PCBN. In addition, a two-dimensional contour cutting of PCBN using LWJ was investigated by changing the crack direction to 60, 108, 120, 135 degrees and following a curve with 1 mm radius in accordance with the standard PCBN tool shapes. The phase transition and the cut quality were investigated using Raman spectroscopy, Scanning Electron Microscopy (SEM), and optical profilometer. Results indicated that water is the best medium to control the phase transition and apply the controlled fracture mechanism for PCBN. Also, it was shown that successful cuts were made with obtuse angles in contrast to acute angles. A preliminary qualitative model was presented to explain the observed experimental results

Development of Nanocoated Filaments for 3D Fused Deposition Modeling of Antibacterial and Antioxidant Materials

Three-dimensional (3D) printing is one of the most futuristic manufacturing technologies, allowing on-demand manufacturing of products with highly complex geometries and tunable material properties. Among the different 3D-printing technologies, fused deposition modeling (FDM) is the most popular one due to its affordability, adaptability, and pertinency in many areas, including the biomedical field. Yet, only limited amounts of materials are commercially available for FDM, which hampers their application potential. Polybutylene succinate (PBS) is one of the biocompatible and biodegradable thermoplastics that could be subjected to FDM printing for healthcare applications. However, microbial contamination and the formation of biofilms is a critical issue during direct usage of thermoplastics, including PBS. Herein, we developed a composite filament containing polybutylene succinate (PBS) and lignin for FDM printing. Compared to pure PBS, the PBS/lignin composite with 2.5~3.5% lignin showed better printability and antioxidant and antimicrobial properties. We further coated silver/zinc oxide on the printed graft to enhance their antimicrobial performance and obtain the strain-specific antimicrobial activity. We expect that the developed approach can be used in biomedical applications such as patient-specific orthoses