• Title/Summary/Keyword: Spray method

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Effects of Impact Velocity on Crystallization and Activation Energy of Cu-based Bulk Metallic Glasses in Kinetic Spray Coating (저온 분사 코팅 공정에서 충돌속도에 따른 CuNiTiZr 벌크 비정질 소재의 활성화 에너지와 결정화 거동 분석)

  • Yoon, Sang-Hoon;Bae, Gyu-Yeol;Kim, Jung-Hwan;Lee, Chang-Hee
    • Journal of Surface Science and Engineering
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    • 제41권6호
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    • pp.301-307
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    • 2008
  • In this paper, nanocrystallization of CuNiTiZr bulk metallic glass (BMG) subjecting to a kinetic spraying, dependent on impact velocity, was investigated by numerical and experimental approaches. The crystallization fraction and nucleation activation energy of initial feedstock and as-deposited coating were estimated by DSC and Kissinger method, respectively. The results of numerical modeling and experiment showed that the crystalline fraction and nucleation activation energy in BMG coatings were depended on kinetic energy of incident particle. Upon impact, the conversion of particle kinetic energy leads to not only decreasing free energy barrier but also increasing the driving force for an amorphous to crystalline phase transformation. The nanocrystallization of BMGs is associated with the strain energy delivered by a plastic deformation with a high strain rate.

Spray and Flame Characteristics of Waste Cooking Oil Biodiesel and Diesel in a Compression Ignition Diesel Engine Using In-cylinder Visualization (가시화 엔진을 이용한 직접 분사식 압축착화 디젤엔진에서 폐식용유 바이오디젤과 디젤의 분무 및 화염 특성 비교)

  • Hwang, Joonsik;Bae, Choongsik
    • Transactions of the Korean Society of Automotive Engineers
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    • 제22권3호
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    • pp.105-113
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    • 2014
  • Spray and combustion process with waste cooking oil (WCO) biodiesel and commercial diesel were analyzed in an optically-accessible single-cylinder compression ignition diesel engine equipped with a high pressure common-rail injection system. Direct imaging method was applied to investigate spray and combustion characteristics. From the mie-scattering results, it was verified that WCO biodiesel had a longer injection delay compared to diesel. Spray tip penetration length of WCO biodiesel was longer and spray angle was narrower than those of diesel due to poor atomization characteristics. In terms of combustion, WCO biodiesel showed later start of combustion, while flame was vanished more rapidly. Analysis of flame luminosity showed that WCO biodiesel combustion had lower intensity and lasted for shorter duration.

Numerical Study on the Effects of Spray Properties of Water Mist on the Fire Suppression Mechanism (미분무수 특성이 화재억제 메커니즘에 미치는 영향에 대한 수치해석적 연구)

  • Bae, Kang-Youl;Chung, Hee-Taeg;Kim, Hyoung-Bum
    • Journal of ILASS-Korea
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    • 제22권4호
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    • pp.175-184
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    • 2017
  • The numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of L×W×H=1.5×1.5×2.0m3 and a water mist nozzle that be installed 1.8 m from fire pool. In the present study, the parameters of nozzle for simulation are the droplet size and the spray velocity. The droplet size influences to fire flume on fire suppression more than the spray velocity because of the effect of the terminal velocity. The optimal condition for fire suppression is that the droplet size and the spray velocity are 100μm and 20 m/s respectively.

Fabrication of large scale Cu2S/CdS solar cells prepared by spray pyrolysis (Spray pyrolysis 방법에 의한 넓은 면적의 Cu2S/CdS 태양전지의 제작)

  • 차덕준;고정곤;정상조;남승재;김광윤;전용기
    • Journal of the Korean Vacuum Society
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    • 제5권4호
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    • pp.341-347
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    • 1996
  • We fabricated the effective Cu2S/CdS solar cells with large area by a spray pyrolysis method. In preparation process, we investigated the process parameters which directly influenced the efficiency of solar cell, such as the grid contact for electrodes, the temperature condition of CdS spray and the junction characteristics of Cu2S layer, by scanning electron microscope(SEM), x-ray diffraction(XRD) and temperature dependent optical absorption and photoconductivity. The Cu2S/CdS solar cell with area of 1cm2 showed the efficient of 3.15% under air mass 2(AM2) spectrum irradiation with 75mW/cm2.

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A Study of the Relation Between Nozzle Geometry, Internal flow and Sprays Characteristics in Diesel Fuel Injection Systems

  • Payri, Raul;Molina, S.;Salvador, F.J.;Gimeno, J.
    • Journal of Mechanical Science and Technology
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    • 제18권7호
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    • pp.1222-1235
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    • 2004
  • This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed: one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.

Effect of Process Parameters on the Morphology and Size of Spray-Dried Granule Powder for Fabrication of SiAlON Raw Material (SiAlON 원료분말제조를 위한 분무건조 과립분말의 형상과 크기에 미치는 공정변수효과)

  • Choi, Jae-Hyeong;Lee, Soyul;Han, Yoonsoo;Lee, Sung-Min;Nahm, Sahn;Kim, Seongwon
    • Korean Journal of Materials Research
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    • 제27권12호
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    • pp.716-721
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    • 2017
  • SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

Sliding Wear Characteristics of plasma Sprayed 8%Y2O3ZrO2 Coating for Post-spray Heat Treatment

  • Chae Young-Hun;Kim Seock-Sam
    • KSTLE International Journal
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    • 제6권2호
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    • pp.45-50
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    • 2005
  • Plasma ceramic spray that is applied on a machine part under severe work conditions has been investigated for tribological behavior. The application of ceramic coatings by plasma spray has become essential in tribosystems to produce wear resistance and long life in severe conditions. The purpose of this study was to investigate the wear characteristics of 8%Y2O3ZrO2 coating, in view of the effect of post-spay heat treatment. The plasma-sprayed 8%Y2O3ZrO2 coating was studied to know the relationship between phase transformations and wear behavior related to post-spray heat treatment. Wear test was carried out with ball on disk type on normal loads of 50N,70N and 90N under room temperature. The phase transformation of phase and the value of residual stress were measured by X-ray diffraction method(XRD). Tribological characteristics and wear mechanisms of coatings were observed by SEM. The tribological wear performance was discussed in the focusing of residual stress. Consequently, post-spray heat treatment plays an important role in decreasing residual stress. Residual stress in the coating system has a significant influence on the wear mechanism of coating.

A comparison of the effects of epinephrine and xylometazoline in decreasing nasal bleeding during nasotracheal intubation

  • Song, Jaegyok
    • Journal of Dental Anesthesia and Pain Medicine
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    • 제17권4호
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    • pp.281-287
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    • 2017
  • Background: Various techniques have been introduced to decrease complications during nasotracheal intubation. A common practice is to use nasal packing with a cotton stick and 0.01% epinephrine jelly. However, this procedure can be painful to patients and can damage the nasal mucosa. Xylometazoline spray can induce effective vasoconstriction of the nasal mucosa without direct nasal trauma. In this study, we aimed to compare the efficacy of these two methods. Methods: Patients were randomly allocated into two groups (n = 40 each): xylometazoline spray group or epinephrine packing group. After the induction of general anesthesia, patients allocated to the xylometazoline spray group were treated with xylometazoline spray to induce nasal cavity mucosa vasoconstriction, and the epinephrine packing group was treated with nasal packing with two cotton sticks and 0.01% epinephrine jelly. The number of attempts to insert the endotracheal tube into the nasopharynx, the degree of difficulty during insertion, and bleeding during bronchoscopy were recorded. An anesthesiologist, blinded to the intubation method, estimated the severity of epistaxis 5 min after intubation and postoperative complications. Results: No significant intergroup difference was observed in navigability (P = 0.465). The xylometazoline spray group showed significantly less epistaxis during intubation (P = 0.02). However, no differences were observed in epistaxis 5 min after intubation or postoperative epistaxis (P = 0.201). No inter-group differences were observed in complications related to nasal intubation and nasal pain. Conclusion: Xylometazoline spray is a good alternative to nasal packing for nasal preparation before nasotracheal intubation.

Effect of Sealing on the Corrosion Resistance of Plasma-Sprayed Alumina Coatings (실링이 플라즈마 스프레이 코팅된 알루미나 코팅재의 내부식성에 미치는 영향)

  • Kwon, Eui Pyo;Kim, Se Woong;Lee, Jong Kweon
    • Korean Journal of Materials Research
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    • 제32권10호
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    • pp.442-447
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    • 2022
  • Sealing treatment is a post-surface treatment of the plasma spray coating process to improve the corrosion resistance of the coating material. In this study, the effect of the sealing on the corrosion resistance and adhesive strength of the plasma spray-coated alumina coatings was analyzed. For sealing, an epoxy resin was applied to the surface of the coated specimen using a brush. The coated specimen was subjected to a salt spray test for up to 48 hours and microstructural analysis revealed that corrosion in the coating layer/base material interface was suppressed due to the resin sealing. Measurement of the adhesive strength of the specimens subjected to the salt spray test indicated that the adhesive strength of the sealed specimens remained higher than that of the unsealed specimens. In conclusion, the resin sealing treatment for the plasma spray-coated alumina coatings is an effective method for suppressing corrosion in the coating layer/base material interface and maintaining high adhesive strength.

Preparation of Nanocrystalline ZnO Ultrafine Powder Using Ultrasonic Spraying Combustion Method (초음파분무 연소법에 의한 나노결정 ZnO 초미분체 제조)

  • Kim, Kwang-Su;Hwang, Du-Sun;Ku, Suk-Kyeon;Lee, Kang;Jeon, Chi-Jung;Lee, Eun-Gu;Kim, Sun-Jae
    • Korean Journal of Materials Research
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    • 제12권10호
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    • pp.784-790
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    • 2002
  • For mass product of nanocrystalline ZnO ultrafine powders, self-sustaining combustion process(SCP) and ultrasonic spray combustion method(USCM) were applied at the same time. Ultrasonic spray gun was attached on top of the vertical type furnace. The droplet was sprayed into reaction zone of the furnace to form SCP which produces spherical shape with soft agglomerate crystalline ZnO particles. To characterize formed particles, fuel and oxidizing agent for SCP were used glycine and zinc nitrate or zinc hydroxide. Respectively, with changing combustion temperature and mixture ratio of oxidizing agent and fuel, the best ultrasonic spray conditions were obtained. To observe ultrasonic spray effect, two types of powder synthesis processes were compared. One was directly sprayed into furnace from the precursor solution (Type A), the other directly was heated on the hot plate without using spray gun (Type B). Powder obtained by type A was porous sponge shape with heavy agglomeration, but powder obtained using type B was finer primary particle size, spherical shape with weak agglomeration and bigger value of specific surface area. 9/ This can be due to much lower reaction temperature of type B at ignition time than type A. Synthesized nanocrystalline ZnO powders at the best ultrasonic spray conditions have primary particle size in range 20~30nm and specific surface area is about 20m2/g.