• Title/Summary/Keyword: Drop-casting

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Effect of InGaZnO Solution Concentration on the Electrical Properties of Drop-Cast Oxide Thin-Film Transistors (InGaZnO 용액의 농도가 Drop-casting으로 제작된 산화물 박막 트랜지스터의 전기적 특성에 미치는 영향)

  • Noh, Eun-Kyung;Yu, Kyeong Min;Kim, Min-Hoi
    • Journal of Sensor Science and Technology
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    • v.29 no.5
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    • pp.332-335
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    • 2020
  • Drop casting, a solution process, is a simple low-cost fabrication technique that does not waste material. In this study, we elucidate the effect of the concentration of a InGaZnO solution on the electrical properties of drop-cast oxide thin-film transistors. The higher the concentration the larger the amount of remnant InGaZnO solutes, which yields a thicker thin film. Accordingly, the electrical properties were strongly dependent on the concentration. At a high concentration of 0.3 M (or higher), a large current flowed but did not lead to switching characteristics. At a concentration lower than 0.01 M, switching characteristics were observed, but the mobility was small. In addition to a high mobility, sufficient switching characteristics were obtained at a concentration of 0.1 M owing to the appropriate thickness of the semiconductor layer. This study provides a technical basis for the low-cost fabrication of switching devices capable of driving a sensor array.

Effect of Shrinkage Defect on Fracture Impact Energy of A356 Cast Aluminum Alloy (A356 알루미늄 합금의 파단 충격에너지에 대한 수축공결함의 영향)

  • Chul, Hwang-Seong;Kwak, Si-Young
    • Journal of Korea Foundry Society
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    • v.34 no.1
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    • pp.22-26
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    • 2014
  • Internal defects, such as shrinkage during casting, cause stress concentrations and initiate cracking. Therefore, it is important to understand the effects of internal defects on the mechanical properties including the impact behavior. This study evaluates the effects of internal casting defects on the impact performance of A356 Al-alloy castings. The internal shrinkage defects in the casting impact specimen are scanned using an industrial Computed Tomography (CT) scanner, and drop impact tests are performed with varing impact velocities on the A356 casting aluminium specimen ($10mm{\times}10mm$ section area) in order to locate the fracture energy under an impact load. The specimens with defects with a diameter less than 0.35 mm exhibit equivalent fracture impact energies of approximately 32 J and those with a 1.7 mm diameter defect reduced the fracture impact energy by 35%.

A Study on Terminology of Metal Handles in Traditional Korean Furniture - Focusing on Korean and Western Furniture - (한국전통가구의 금속 손잡이 영문표기 연구 - 한국 및 서구를 중심으로 -)

  • Moon, Sun-Ok
    • Journal of the Korea Furniture Society
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    • v.23 no.4
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    • pp.449-459
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    • 2012
  • The article aims to making a comparison between traditional Korean and Western furniture metal handles to give the detail information of the handle terms by analyzing the related literature including internet and interviews. In terms of that, the Korean and Western metal handles are compared in the types, components, materials, methods, and terms affecting the development made by the craftsmen before the Industrial Revolution about the mid or late 18th century. As a result, first, ring and drop pull handles were mostly and wooden knobs were a little used to open the furniture doors and drawers. The Korean drop pulls, Deulswae, came out after the ring pulls, Gori, while the Western drops called loop or bail handles as well, came out before the ring pulls. Second, the components were composed by ring, Gori, loop or bail, Deulswae, Post, Baemok, washer, Baemokbatchim, and backplate, Deulswaebatchim. Most of the Western handles were fastened by the bolt and nut, while the post of two strips, Baemok, fastened the Korean metal handles. Third, the metal handles were created of brass and iron mostly, gilded gold and silver. Forth, the method were largely used by casting, engraving, forging, plating, and hammering in the Korean handles, and by casting, molding, engraving, and stamped in the Western handles. Finally, the terms such as "knobs, pulls, drops, ring and drop pulls, loop or bail handles, posts, washers, backplate, casting, molding, engraving, forging, plating, and stamped" were clarified by the two comparison in Korean and English.

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Capillary Assembly of Silicon Nanowires Using the Removable Topographical Patterns

  • Hong, Juree;Lee, Seulah;Lee, Sanggeun;Seo, Jungmok;Lee, Taeyoon
    • Korean Journal of Materials Research
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    • v.24 no.10
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    • pp.509-514
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    • 2014
  • We demonstrate a simple and effective method to accurately position silicon nanowires (Si NWs) at desirable locations using drop-casting of Si NW inks; this process is suitable for applications in nanoelectronics or nanophotonics. Si NWs were assembled into a lithographically patterned sacrificial photoresist (PR) template by means of capillary interactions at the solution interface. In this process, we varied the type of solvent of the SiNW-containing solution to investigate different assembly behaviors of Si NWs in different solvents. It was found that the assembly of Si NWs was strongly dependent on the surface energy of the solvents, which leads to different evaporation modes of the Si NW solution. After Si NW assembly, the PR template was cleanly removed by thermal decomposition or chemical dissolution and the Si NWs were transferred onto the underlying substrate, preserving its position without any damage. This method enables the precise control necessary to produce highly integrated NW assemblies on all length scales since assembly template is easily fabricated with top-down lithography and removed in a simple process after bottom-up drop-casting of NWs.

Highly Sensitive Colorimetric Formaldehyde Gas Sensors using Nylon Sheet and Dye (나일론 시트와 염료를 이용한 고감도 색변환 포름알데히드 가스 센서)

  • Jung, Suenghwa;Cho, Yeong Beom;Kim, Yong Shin
    • Journal of Sensor Science and Technology
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    • v.26 no.6
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    • pp.420-426
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    • 2017
  • A colorimetric sensor was investigated to achieve a low-cost warning device for harmful gaseous formaldehyde (HCHO). The sensor is based on selective reactions between hydroxylamine sulfate and HCHO, leading to the production of sulfuric acid. The produced acid results in color-changing response through the acid-base reaction with dye molecules impregnated on a solid membrane substrate. For attaining this purpose, sensors were fabricated by drop-casting a dye solution prepared using different pH indicators on various commercially available polymer sheets, and their colorimetric responses were evaluated in terms of sensitivity and reliability. The colorimetric sensor using bromophenol blue (BPB) and nylon sheet was found to exhibit the best performance in HCHO detection. An initial bluish green of a sensor was changed to yellow when exposed to gaseous formaldehyde. The color change was recorded using an office scanner and further analyzed in term of RGB distance for quantifying sensor's response at different HCHO(g) concentrations. It exhibited a recognizable colorimetric response even at 50 ppb, being lower than WHO's standard of 80 ppb. In addition, the sensor was found to have quite good selectivity in HCHO detection under the presence of common volatile organic compounds such as ethanol, toluene, and hexane.

Preparation of Porous Separators for Zn Air Batteries Through Phase Inversions of Polyethersulfone-PVP Solutions (Polyethersulfone-PVP 용액의 상전이를 통한 아연공기전지의 다공성 분리막 제조)

  • Cho, Yu Song;Koo, Ja-Kyung
    • Membrane Journal
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    • v.24 no.1
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    • pp.10-19
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    • 2014
  • Porous flat sheet membranes for separators in Zn air batteries were prepared with polyethersulfone (PES) solutions by immersion precipitation phase inversion method. PES/polyvinylpyrrolidone(PVP)/N-methylpyrrolidone(NMP) mixtures were used for casting solutions and water was used for coagulant. With the separators, Zn air batteries were fabricated. The separators were characterized by means of stress-strain test, impedance test and SEM. The Zn air batteries were tested by current interrupt method (CIM) and galvanostatic discharge method. The tensile strength increased with increasing PES content in the casting solution while the ionic conductivity decreased. On the other hand, the ionic conductivity increased while the tensile strength decreased with increasing PVP content. The effect of ionic conductivity trend of the separator in the Zn air battery was confirmed through current interrupt method and galvanostatic discharge method experiments. The battery with the separator from casting solution with higher PES content showed higher IR drop and lower discharge capacity. And the battery with the separator from casting solution with higher PVP content showed lower IR drop and higher discharge capacity.

A Study on the Process for Improving Mechanical Property of Sand Casting by Using the Binder Jetting Method (사형 주조에서 바인더 젯 3D 프린터를 이용한 기계적 물성 향상을 위한 공정 연구)

  • Jung-Chul Hwang;Tae-Sung Kim
    • Journal of the Korea Safety Management & Science
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    • v.25 no.1
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    • pp.23-29
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    • 2023
  • Among the Additive Manufacturing (AM) technologies, the Binder-Jetting printing technology is a method of spraying an adhesive on the surface of powder and laminate layer by layer. Recently, this technique has become a major issue in the production of large casting products such as ship-building, custom vehicles and so on. In this study, we performed research to make actual mold castings and increase mechanical property by using special sand and water-based binders. For use as a mold, it has a strength of more than 3MPa and permeability. Various experiments were carried out to obtain suitable them. The major process parameters were binder jetting volume, binder types, layer thickness and heat treatment condition. As a result of this study, the binder drop quantity was measured to be about 60 pico-liter, layer thickness was 100㎛ and the heat treatment condition was measured about 1,000℃ and compressive strength were measured to be more than 5MPa. The optimum condition of this experiment was established through actual casting of aluminum. The equipment used in this study was a Freeforms T400 model (SFS Co., Ltd.), and the printing area of 420 * 300 * 250mm and resolution of 600dpi can be realized.

Lightweight Porcelain using GHM(Glass Hollow Microsphere) (유리질 중공체 GHM(Glass Hollow Microsphere)을 활용한 자기의 경량화)

  • Kim, Geun-Hee;Choi, Hyo-Sung;Pee, Jae-Hwan;Cho, Woo-Seok;Kim, Kyeong-Ja
    • Journal of the Korean Ceramic Society
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    • v.48 no.1
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    • pp.74-79
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    • 2011
  • The pore generation technology using GHM (Glass Hollow Microsphere) was studied in order to reduce the weights of porcelain. In this study, we verify the property of modified slurry by adding GHM. The modified slurry was prepared by adding 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM to the slurry for porcelain. The slurry viscosity were stable inside a content range of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37). However, the viscosity of modified slurry increased more than 3.0 wt%(K1) and 6.5 wt%(K37). The formed specimen by slip casting was fired at $1229^{\circ}C$, $1254^{\circ}C$. As the amount of GHM content increased, the weight decreased and the addition of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM resulted in a weight drop of 30%(K1) and 25(K37). However, when the GHM content increased, the strength decreases over 70%. This is caused by the presence of a large volume of surface defects (pores) and defects from the agglomeration of GHM.

Thermal Shock Behavior of Porous Nozzles with Various Pore Sizes for Continuous Casting Process

  • Kim, Ju-Young;Yoon, Sang-Hyeon;Kim, Yoon-Ho;Lee, Hee-Soo
    • Journal of the Korean Ceramic Society
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    • v.48 no.6
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    • pp.617-620
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    • 2011
  • Thermal shock behavior of porous ceramic nozzles with various pore sizes for continuous casting process of steel was investigated in terms of physical properties and microstucture. Porous nozzle samples with a composition of $Al_2O_3$-$SiO_2$-$ZrO_2$ were fabricatedby adding various sizes of graphite as the pore forming agent. As the graphite size increased from 45~75 to 150~180 ${\mu}m$, both the resulting pore size and the flexural strength also increased. A thermal shock test was carried out at temperatures (${\Delta}$T) of 600, 700, 800, and 900$^{\circ}C$. Microstructure analysis revealed a small number of cracks on the sample with the largest mean pore size of 22.32 ${\mu}m$. In addition, increasing the pore size led to a smaller decrease in both pressure drop and elastic modulus. In conclusion, controlling the pore size can enhance thermal shock behavior.

Analysis on Nasal Airflow by PIV

  • Kim Sung Kyun
    • 한국가시화정보학회:학술대회논문집
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    • 2001.12a
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    • pp.138-150
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    • 2001
  • Researchers have investigated nasal flow both numerically and experimentally for centuries. Experimental studies most have suffered from various limitations necessary to allow the measurements to be obtained with available equipment. Nasal airflow can be subdivided into two interrelated categories; nasal airflow resistance and heat and mass transfer between the air stream and the walls of the nasal cavity. In this study, thanks to a new method for model casting by a combination of Rapid prototyping and curing of clear silicone, a transparent rectangular box containing the complex nasal cavity is made for PIV experiments. The CBC PIV algorithm is used for analysis. Average and RMS distributions are obtained for inspirational and expiration nasal airflows. Comparison between western and Korean nasal air flows are appreciated. Flow fields for Korean model shows some differences from western's. Flow resistances for breathing are measured with varying flow rates.

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