S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Mechanical Aerospace Engineering (기계항공공학부) Theses (Ph.D. / Sc.D._기계항공공학부)
Development of hybrid process using lase and dry particle deposition system
레이저와 건식 분말 적층 장치를 사용한 하이브리드 공정 개발
- 공과대학 기계항공공학부
- Issue Date
- 서울대학교 대학원
- 학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 8. 안성훈.
- A nanoparticle deposition system (NPDS) was developed as an alternative to aerosol deposition, with advantages including cold spray (room temperature) processing, the use of various materials (metal and ceramic), high deposition rates (versus molecular and atomic deposition), and a green manufacturing process with no wet chemical processing, binder, or post-processing step. This NPDS was shown to be useful in the deposition of particles on soft matter for flexible substrate applications.
With the aim of enhancing adhesion between the film and the fabricated substrate in NPDS, a laser was used initially on flying nanoparticles, referred to as laser-assisted NPDS (LaNPDS). In other fabrication methods, the laser has been used to shape objects by sintering and melting target materials. In contrast, a coherent laser can transfer thermal energy inside the tube to flying nanoparticles and deposited nanoparticles, without thermal damage, for the fusion and dissolution of substrates. This indicates that thermal energy transfer plays a role in preheating, with an increase in the diffusion rate at the interface between nanoparticles, resulting in enhanced necking phenomena over the mechanism of solid-state sintering. Given this, LaNPDS was expected to improve not only surface integrity, but also adhesion among nanoparticles in the film, as well as the interfaces between the film and substrate. However, the intrinsic role of the laser in relation to surface integrity and adhesion has not been reported previously, so the effect of laser irradiation was examined in this study.
In this study, Al2O3 and TiO2 ceramic particles were deposited on ceramic (sapphire) and polymer substrates (PET and ITO-PET) by LaNPDS. The surface morphology, hardness, elastic modulus, and interface were characterized by field emission scanning electron microscopy (FE-SEM), surface profile, nano indentation, and X-ray diffraction (XRD). To demonstrate the heating effect and changes in the mechanical properties of ceramic films, as influenced by the laser, a finite-element method was used.
Using LaNPDS, applications of this research include fabricated dye-sensitized solar cells (DSSCs) and electrochromic windows (ECWs). As the intensity of the laser was increased, the efficiencies of the DSSCs and ECWs increased.
Flying particle velocity was analyzed by a computational fluid dynamics (CFD) method and a microparticle image velocimetry (micro-PIV) method. Through these measurements, the effects of the laser on flying particles were analyzed. The flying particle kinetic energy and laser activation energy were calculated and compared with a CFD analysis. The laser activation energy added to the kinetic energy, so the total impact energy increased. From these results, the LaNPDS process can deposit ceramic materials on various substrates more effectively, because the laser energy is transferred to the flying nanoparticles.