Inflight Particle Behavior in the Vacuum Kinetic Spray Process
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Inflight Particle Behavior in the Vacuum Kinetic Spray Process Hyungkwon Park1 • Hansol Kwon1 • Changhee Lee1
Submitted: 13 February 2017 / in revised form: 16 July 2017 Ó ASM International 2017
Abstract The vacuum kinetic spray (VKS) process, alsocalled aerosol deposition, is a promising spray technology by which a thin or thick film can be fabricated at room temperature. Although a number of relevant studies have been performed, almost all have focused on the development of various applications, and unfortunately, the deposition mechanism has not yet been clarified. In this respect, the particle velocity in the flow field in VKS is investigated as a first stage of research into the VKS deposition mechanism. In this research, after a simulation prototype was derived based on the experimental results, the particle average and impact velocities were estimated. In addition, the change in particle velocities with gas flow rates, particle size, and working distance was analyzed based on simulation analyses and microstructural evidence. As a result, the gas flow rate, particle size, and working distance affect the particle impact velocity and further deposition behavior and film microstructure. Keywords acceleration mechanism computational fluid dynamics (CFD) deposition behavior particle velocity vacuum kinetic spraying (VKS) process List qF pop ps R
of symbols Gas density (kg/m3) Operating pressure (Pa) Local static pressure (Pa) Universal gas constant
& Changhee Lee [email protected] 1
Kinetic Spray Coating Laboratory (NRL), Division of Materials Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, South Korea
Mw T t ~ vF Sm p s ~ g ~ Fe E h J Sh ~ vP qF ~ Fa FD l dp CD Re Kn k Dt
Molecular weight (kg/kmol) Temperature (K) Time (s) Fluid velocity (m/s) Mass source (kg) Pressure (Pa) Stress tensor (Pa) Gravitational acceleration (m/s2) External body force vector (N) Total energy (J) Species enthalpy (energy/mass) Mass flux (kg/m2-s) Volumetric heat source (W/m3) Particle velocity (m/s) Fluid density (kg/m3) Additional acceleration term (N) Drag force (N) Molecular viscosity of the fluid (Pa-s) Particle diameter (m) Drag coefficient Reynolds number Knudsen number Mean free path (m) Diameter of the nozzle throat (m)
Introduction The vacuum kinetic spraying (VKS) process, also-called aerosol deposition (AD), is a novel and promising spray technology by which a thin or thick film can be fabricated (Ref 1). Above all, because the process is performed at room temperature, various kinds of materials, such as metal, ceramic, polymer, can be used without oxidation or
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J Therm Spray Tech
thermal degradation (Ref 1-3). In addition, the deposition rate is relatively high, the film thickness can be readily controlled, and the process cost is relatively low (Ref 1). Therefore, a number of studies have focused on the development of applications in a wide range of industrial fields, including electronic devices, solid oxide fuel cells (SOFC), dye-sensitized
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