• Journal of Institute of Convergence Technology
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• v.6 no.2
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• pp.35-40
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• 2016

Ignitor tip is a component of burner to start the burning process in power plant. This is used to ignite the coal to a constant operating state by fuel mixed with air and kerosene. This component is composed of three components so that air and kerosene are mixed in the proper ratio and injected uniformly. Because the parts with the designed shape are manufactured in the machining process, they have to be made of three parts. These parts are designed to have various functions in each part. The mixing part mixes the supplied air and kerosene through the six holes and sends it to the injecting part at the proper ratio. The inject part injects mixed fuel, which is led to have a constant rotational direction in the connecting part, to the burner. And the connecting plate that the mixed fuel could rotate and spray is assembled so that the flame can be injected uniformly. But this part causes problems that are worn by vibration and rotation because it is mechanically assembled between the mixing part and the inject part. In this study, 3D printing method is used to integrate a connecting plate and an inject part to solve this wear problem. The 3D printing method could make this integrated part because the process is carried out layer by layer using a metal powder material. The part manufactured by 3D printing process should perform the post process such as support removal and surface treatment. However, while performing the 3D printing process, the material properties of the metal powders are changed by the laser sintering process. This change in material properties makes the post process difficult. In consideration of these variables, we have studied the optimization of manufacturing process using 3D printing method.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.620-626
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• 2015

$Ho^{3+}$ doped $SrAl_2O_4$ upconversion phosphor powders were synthesized by spray pyrolysis, and the crystallographic properties and luminescence characteristics were examined by varying activator concentrations and heattreatment temperatures. The effect of organic additives on the crystal structure and luminescent properties was also investigated. $SrAl_2O_4:Ho^{3+}$ powders showed intensive green emission due to the $^5F_4/^5S_2{\rightarrow}^5I_8$ transition of $Ho^{3+}$. The optimal $Ho^{3+}$ concentration in order to achieve the highest luminescence was 0.1%. Over this concentration, emission intensities were largely diminished via a concentration quenching due to dipole-dipole interaction between activator ions. According to the dependence of emission intensity on the pumping power of a laser diode, it was clear that the upconversion of $SrAl_2O_4:Ho^{3+}$ occurred via the ground state absorption-excited state absorption processes involving two near-IR photons. Synthesized powders were monoclinic as a major phase, having some hexagonal phase. The increase of heat-treatment temperatures from $1000^{\circ}C$ to $1350^{\circ}C$ led to crystallinity enhancement of monoclinic phase, reducing hexagonal phase. The hexagonal phase, however, did not disappear even at $1350^{\circ}C$. When both citric acid (CA) and ethylene glycol (EG) were added to the spray solution, the resulting powders had pure monoclinic phase without forming hexagonal phase, and led to largely enhancement of crystallinity. Also, N,N-Dimethylformamide (DMF) addition to the spray solution containing both CA and EG made it possible to effectively reduce the surface area of $SrAl_2O_4:Ho^{3+}$ powders. Consequently, the $SrAl_2O_4:Ho^{3+}$ powders prepared by using the spray solution containing CA/EG/DMF mixture as the organic additives showed about 168% improved luminescence compared to the phosphor prepared without organic additives. It was concluded that both the increased crystallinity of high-purity monoclinic phase and the decrease of surface area were attributed to the large enhancement of upconversion luminescence.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.