• Journal of Powder Materials
• /
• v.19 no.5
• /
• pp.348-355
• /
• 2012

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at $500^{\circ}C$) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at $500^{\circ}C$. It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

• Journal of The Korea Institute of Healthcare Architecture
• /
• v.24 no.2
• /
• pp.37-44
• /
• 2018

Purpose: This study investigates the influences of coughing direction and healthcare worker's location on the transport characteristics of coughed particles in airborne infection isolation room (AIIR), which is commonly called negative pressure isolation room, with a downward ventilation system. Methods: Computational Fluid Dynamics (CFD) was used to simulate the airflow and for tracing the behavior of particles. Results: The results show that the airflow pattern and coughing direction have a significant influence on the characteristics of particle dispersion and deposition. When healthcare workers are in the isolation room with the patient who is lying on the bed, it is recommended to be located far from the anteroom to reduce the exposures from infectious particles. And when the patient is lying, it is more effective in removing particles than when the patient is in Fowler's position. Although it is an isolation room that produces unidirectional flow, coughing particles can spread to the whole room and a large number of particles can be deposited onto patient, bed, side rails, healthcare worker, ceiling, floor, and sidewall. Implications: Following the patients' discharge or transfer, terminal cleaning of the vacated room, furniture, and all clinical equipment is essential. Also, it is necessary to establish detailed standard operating procedure (SOP) in order to reduce the risk of cross-contamination.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.1
• /
• pp.25-32
• /
• 2020

Generally, high-temperature, high-pressure, high-priced sintering equipment is used for diamond sintering, and conductivity is a problem for improving the surface modification of the sintered body. In this study, to improve the efficiency of diamond sintering, we identified a new process and material that can be sintered at low temperature, and attempted to develop a composite thin film that can be discharged by doping boron gas to improve the surface modification of the sintered body. Sintered bodies were sintered by mixing Si and two diamonds in different particle sizes based on CIP molding and HIP molding. In CVD deposition, CVD was performed using WC-Co cemented carbide using CH₄ and H₂ gas, and the specimen was made conductive using boron gas. According to the experimental results of the sintered body, as the Si content is increased, the Vickers hardness decreases drastically, and the values of tensile strength, Young's modulus and fracture toughness greatly increase. Conductive CVD deposited diamond was boron deposited and discharged. As the amount of boron added increased, the strength of diamond peaks decreased and crystallinity improved. In addition, considering the release processability, tool life and adhesion of the deposition surface according to the amount of boron added, the appropriate amount of boron can be confirmed. Therefore, by solving the method of low temperature sintering and conductivity problem, the possibility of solving the existing sintering and deposition problem is presented.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2005.09a
• /
• pp.193-196
• /
• 2005

Low resistance Ni thin films for using NiSi formation and metallization by atomic layer deposition (ALD) method have been studied. ALD temperature window is formed between $200^{\circ}C\;and\;250^{\circ}C$ with deposition rate of $1.25{\AA}$/cycle. The minimum resistance of deposited Ni films shows $4.333\;{\Omega}/\square$ on the $SiO_2/Si$ substrate by $H_2$ direct purging process. The reason of showing the low resistance is believed to be due to format ion of the $Ni_3C$ phase by residual carbon in Bis-Ni The deposited film exhibits excellent step coverage in the trench having 1(100 nm) : 16 (1.6 um) aspect ratio.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.319-319
• /
• 2023

Flows of water in the environment (e.g. in a river or estuary) generally occur in complex conditions. This complexity can hinder a general understanding of flows and their related sedimentary processes, such as erosion and deposition. To gain insight in simplified, controlled conditions, hydraulic flumes are a popular type of laboratory research equipment. Linear flumes use pumps to recirculation water. This isn't appropriate for the investigation of cohesive sediments as pumps can break fragile cohesive sediment flocs. To overcome this limitation, the rotating annular flume (RAF) was developed. While not having pumps, a side-effect is that unwanted secondary circulations can occur. To counteract this, the top and bottom lid rotate in opposite directions. Furthermore, a larger flume is considered better as it has less curvature and secondary circulation. While only a few RAFs exist, they are important for theoretical research which often underlies numerical models. Many of the first-generation of RAFs have come into disrepair. As new measurement techniques and models become available, there is still a need to research cohesive sediment erosion and deposition in facilities such as a RAF. New RAFs also can have the advantage of being automatic instead of manually operated, thus improving data quality. To further advance our understanding of cohesive sediment erosion and deposition processes, a large, automatic RAF (1.72 m radius, 0.495 m channel depth, 0.275 m channel width) has been constructed at the Hydraulic Laboratory at Chungnam National University (CNU), Korea. The RAF has the ability to simulate both unidirectional (river) and bidirectional (tide) flows with supporting instrumentation for measuring turbulence, bed shear stress, suspended sediment concentraiton, floc size, bed level, and bed density. Here we present the current status and future prospect of the CNU RAF. In the future, calibration of the rotation rate with bed shear stress and experiments with unidirectional and bidirectional flow using cohesive kaolinite are expected. Preliminary results indicate that the CNU RAF is a valuable tool for fundamental cohesive sediment transport research.

• Elastomers and Composites
• /
• v.58 no.1
• /
• pp.44-56
• /
• 2023

Additive manufacturing (AM) or three-dimensional (3D) printing of metals has been drawing significant attention due to its reliability, usefulness, and low cost with rapid prototyping. Among the various AM technologies, fused deposition modeling (FDM) or fused filament fabrication is receiving much interest because of its simple manufacturing processing, low material waste, and cost-effective equipment. FDM technology uses metal-filled polymer filaments for 3D printing, followed by debinding and sintering to fabricate complex metal parts. An efficient binder is essential for producing polymer filaments and the thermal post-processing of printed objects. This study involved an in-depth investigation of and a fabrication route for a novel multi-component binder system with steel alloy powder (45 vol.%) ranging from filament fabrication and 3D printing to debinding and sintering. The binder system consisted of polyvinyl pyrrolidone (PVP) as a binder and thermoplastic polyurethane (TPU) and polylactic acid (PLA) as a carrier. The PVP binder held the metal components tightly by maintaining their stoichiometry, and the TPU and PLA in the ratio of 9:1 provided flexibility, stiffness, and strength to the filament for 3D printing. The efficacy of the binder system was examined by fabricating 3D-printed cubic structures. The results revealed that the thermal debinding and sintering processes effectively removed the binder/carrier from the cubic structures, resulting in isotropic shrinkage of approximately 15.8% in all directions. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) patterns displayed the microstructure behavior, phase transition, and elemental composition of the 3D cubic structure.

• Journal of Ceramic Processing Research
• /
• v.21
• /
• pp.47-52
• /
• 2020

Graphene was synthesized using rapid thermal chemical vapor deposition (RT-CVD) equipment designed to produce largearea graphene at high speed. The effects of methane (CH₄), argon (Ar), and hydrogen (H₂) gases were investigated between 800 ℃ and 1,000 ℃ during heating and cooling in the graphene synthesis process. The findings reveal that multilayer domains increased due to hydrogen pretreatment with increase in temperature. Furthermore, when pretreated with the same gas, it was confirmed that the post-argon-treated sample cooled from 1,000 ℃ to 800 ℃ had a higher I_D/I_G value than that of the other samples. This result was consistent with the sheet resistance properties of graphene. The sample prepared in methane atmosphere maintained during both the pre-treatment and post-treatment demonstrated the lowest sheet resistance of 787.49 Ω/sq. Maintaining the methane gas atmosphere in the high-temperature region during graphene synthesis by RT-CVD reduced the defects and improved the electrical property.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.8
• /
• pp.6-14
• /
• 2006

This paper is a study about a proper method of plasma generation to cleaning method and a high frequency power equipment circuit to generation of plasma that used cleaning of chamber for TFT-LCD PECVD. The high density plasma required for cleaning causes a possibility of high density plasma more than $1{\times}10^{11}[EA/cm^3]$. It apply a ferrite core of ferromagnetic body to a existing ICP form. In case of power transfer equipment on 400[kHz] high frequency to generation of plasma it makes certain a stable switching operation in condition of plasma through using a inverter form for general purpose HB. And it demonstrates the performance of power transfer equipment using methods of measurement which use a transformer of series combination the density of plasma and the rate of dissolution of $NF_3$ in condition of $A_r\;and\;NF_3$.

• Journal of the Semiconductor & Display Technology
• /
• v.4 no.2 s.11
• /
• pp.39-43
• /
• 2005

In the study, in order to deposit TaN thin film for diffusion barrier and bottom electrode we made the Plasma Assisted ALD equipment and confirmed the electrical characteristics of TaN thin films grown PAALD method. Plasma Assisted ALD equipment depositing TaN thin film using PEMAT(pentakis(ethylmethlyamino) tantalum) precursor and NH3 reaction gas is shown that TaN thin film deposited high density and amorphous phase with XRD measurement. The degree of diffusion and reaction taking place in Cu/TaN (deposited using 150W PAALD)/$SiO_{2}$/Si systems with increasing annealing temperature was estimated for MOS capacitor property and the $SiO_{2}$, (600${\AA}$)/Si system surface analysis by C-V measurement and secondary ion material spectrometer (SIMS) after Cu/TaN/$SiO_{2}$ (400 ${\AA}$) layer etching. TaN thin film deposited PAALD method diffusion barrier have a good diffusion barrier property up to 500$^{\circ}C$.

• Journal of Surface Science and Engineering
• /
• v.29 no.4
• /
• pp.219-228
• /
• 1996

Neutral Zinc Electroplating(NZE) utilizing the electrolyte of pH 6 to 8 has advantages in waste treatment and the protection of equipment. NZE is beneficially used in chromating treatment, but the limiting current density and the current efficiency are low. Therefore this study is investigated to analyse the characteristics of NZE and to obtain high current density and current efficiency. The deposition potential of zinc in the NZE bath is about 110mV, which is lower than acidic bath. The current density possibily increases up to 60A/d$\m^2$ in lower complexing agent content and pH 6. More than 90% of cathodic current efficiency was obtained in NZE bath. The NZE morphology shows smaller grains than acidic bath. The addition of 4$m\ell$/1 second brightener gives finer morphology. As pH becomes higher, (002) plan decreases and (100), (101) and (110) planes increase in the no additives solution.