• Computers and Concrete
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• 제13권3호
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• pp.325-342
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• 2014

The use of lightweight aggregate (LWA) instead of ordinary aggregate may make lightweight aggregate concrete, which possesses many advantages such as lightweight, lower thermal conductivity, and better fire and seismic resistance. Recently the developments of LWA have been focused on using industrial wastes as raw materials to reduce the use of limited natural resources. In view of this, the intent of this study was to apply Taguchi optimization technique in determining process condition for producing synthetic LWA by incorporating waste thin film transition liquid crystal displays (TFT-LCD) glass powder with reservoir sediments. In the study the waste TFT-LCD glass cullet was used as an additive. It was incorporated with reservoir sediments to produce LWA. Taguchi method with an orthogonal array L16(45) and five controllable 4-level factors (i.e., cullet content, preheat temperature, preheat time, sintering temperature, and sintering time) was adopted. Then, in order to optimize the selected parameters, the analysis of variance method was used to explore the effects of the experimental factors on the performances (particle density, water absorption, bloating ratio, and loss of ignition) of the produced LWA. The results showed that it is possible to produce high performance LWA by incorporating waste TFT-LCD glass cullet with reservoir sediments. Moreover, Taguchi method is a promising approach for optimizing process condition of synthetic LWA using recycled glass cullet and reservoir sediments and it significantly reduces the number of tests.

• 한국분말재료학회지
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• 제22권3호
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• pp.203-207
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• 2015

This study investigated the microstructure and wear resistance property of HPHT(high pressure high temperature) sintered PDC(polycrystalline diamond compact) in accordance with initial molding pressure. After quantifying an identical amount of diamond powder, the powder was inserted in top of WC-Co sintered material, and molded under four different pressure conditions (50, 100, 150, $200kgf/cm^2$). The obtained diamond compact underwent sintering in high pressure, high temperature conditions. In the case of the $50kgf/cm^2$ initial molding pressure condition, cracks were formed on the surface of PDC. On the other hand, PDCs obtained from $100{\sim}200kgf/cm^2$ initial molding pressure conditions showed a meticulous structure. As molding pressure increased, low Co composition within PDC was detected. A wear resistance test was performed on the PDC, and the $200kgf/cm^2$ condition PDC showed the highest wear resistance property.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.185-189
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• 2000

ZnO varistor has many merits as compared with SiC varistor. But, because of leakage current and non-linear coefficient, it has unstable function properties. For the purpose of improvement of ZnO varistor properties, ZnO varistor is studied according to sintering condition and mixing condition. ZnO varistor, $ZnO-Bi_2O_2-Y_2O_3-MnO-Cr_2O_3-Sb_2O_3$ series, is fabricated with $Sb_2O_3$ mol ratio(0.5-4[mol%]) and sintered at $1250[^{\circ}C]$ In accordance with $Sb_2O_3$ mol ratio and sintering temperature, grain size and non-linear coefficient are measured. The specimen, $Sb_2O_3$ mol ratio is 1[mol%], has small grain size. It has best properties because of its liquid phase shape. When $Sb_2O_3$ mol ratio is 1[mol%], grain size is decreased.

• 한국분말재료학회지
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• 제21권6호
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• pp.407-414
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• 2014

The powder injection molding process having advantages in manufacturing three-dimensional precision parts essentially requires a debinding process before sintering to remove the binders used for preparing feedstock. In this study, powder injection molding of translucent alumina was performed, and carbon dioxide ($CO_2$) is used as a supercritical fluid that makes it possible to remove a large amount of binder, which is paraffin wax. The relationship between the optical property of translucent alumina and the debinding condition (temperature and pressure) of supercritical $CO_2$ was investigated. As temperature and pressure increased, extraction rate of the binder showed rising tendency and average grain size after sintering process was relatively fine. On the other hand, optical transmittance was reduced. As a result, the debinding condition at $50^{\circ}C$ and 20 MPa that represents the lowest extraction rate, $8.19{\times}10^{-3}m^2/sec$, corresponds to the largest grain size of $14.7{\mu}m$ and the highest optical transmittance of 45.2%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.319-320
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• 2006

In order to improve the ESD(Electrical Static Discharge) resistance of multilayer chip varistors, we have investigated ZnO-$Pr_6O_{11}$ based chip varistor by applying tape casting technology, whose fundamental component were ZnO : $Pr_6O_{11}$ :$Co_3O_4$: $Y_2O_3$: $Al_2O_3$=93.67: 2.53:2.53:1.25 : 0.015 (wt %). The effect of sintering condition on the multilayer chip varistors and electric properties was studied. The electrical properties and ESD resistance of multilayer chip varistor could be influenced the sintering temperature and condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1022-1024
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• 1995

In this study, $Pb(Zr_xTi_{1-x})O_3$(x=0.65, 0.52, 0.35) thin films were fabricated by Sol-Gel method. A stock solution with excess Pb 10[mol.%] of $Pb(Zr_xTi_{1-x})O_3$ was made and spin-coated on the Pt/$SiO_2$/Si substrate at 4000[rpm] for 30[sec.]. Coated specimens were dried on the hot-plate at $400[^{\circ}C]$ for 10[min.]. Sintering temperature and time were $500{\sim}800[^{\circ}C]$ and $1{\sim}60$[min.]. To investigate crystallization condition, PZT thin films were analyzed with sintering temperature, time and composition by the XRD. The microstructure of thin films were investigated by SEM. The ferroelectric perovskite phases precipitated under the sintering of $700[^{\circ}C]$ for 1 hour. In the PZT(52/48) composition, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively.

• 한국결정성장학회지
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• 제7권4호
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• pp.619-625
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• 1997

$Si_3N_4$에 2 wt% $Al_2O_3$와 6 wt% $Y_2O_3$을 첨가한 분말을 가스압소결 방법으로 시편을 제조하였다. 이때 소결시 조건(온도, 압력, 시간) 변화에 대한 기계적 특성 변화를 비교하였다. 이때 나타난 결과에 의하면 $1900^{\circ}C$, 3 MPa에서 1시간 동안 유지시켰을 때 최적의 조건을 갖는다는 것을 보여주었다. 이는 온도를 높여 주거나 유지 시간을 길게 하였을 때 입자 조대화에 의해 기계적 특성이 떨어지는 것을 볼 수 있었다. 그러나 압력을 증가시킬 때에는 미세한 조직을 가지므로 기계적 특성은 좋아짐을 나타내지만 파괴 인성이 떨어지는 것을 볼 수 있었다. 이로 인해 소결시 최적의 조건을 찾는 것이 중요함을 알 수 있었다.

• 한국분말재료학회지
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• 제24권3호
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.

• 한국세라믹학회지
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• 제32권6호
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• pp.748-760
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• 1995

Pyroelectric properties, figure of merits, and the other properties of the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, as expected to have excellent pyroelectric properties in the operating temperature range of pyroelectric type infrared sensor, were investigated. In the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, suppression of the pyrochlore phase depended on sintering condition, as like sintering temperature, holding time, sintering atmosphere. The specimen, sintered by the same composition atmosphere powder at 105$0^{\circ}C$ for 1.5h, possessed the best physical property. It was found that the piezoelectric parameters were mainly depended on the amount of spontaneous polarization and then the 0.2PZN-0.8PFN showed the best pyro- and piezoelectric properties. In terms of the experimental method, two pyroelectric-testing methods, i.e. static and dynamic methods, had a same tendency. Also the result of pyroelectric testing by the static method indicated that the diffuse phase transitiion resulted in the temperature difference of phase transition between dielectric constant and pyroelectric coefficient.

• 대한전기학회논문지
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• 제44권7호
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• pp.914-918
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• 1995

In this study, Pb(Zr$_{x}$ Ti$_{1-x}$ )O$_{3}$ (x=0.65, 0.52, 0.35) thin films were fabricated by Sol-Gel method. A stock solution with excess Pb 10[mol%] of Pb(Zr$_{x}$ Ti$_{1-x}$ )O$_{3}$ was made and spin-coated on the Pt/SiO$_{2}$/Si substrate at 4000[rpm] for 30[sec.]. Coated specimens were dried on the hot-plate at 400[.deg. C] for 10[min.]. Sintering temperature and time were 500~800[.deg. C] and 1~60[min.]. The coating process was repeated 6 times and the final thickness of the thin films were about 4800[A]. To investigate crystallization condition, PZT thin films were analyzed with sintering temperature, time and composition by the XRD. The microstructure of thin fulms were investigated by SEM. The ferroelectric perovskite phases precipitated under the sintering of 700[.deg. C] for 1 hours. In the PZT(52/48) composition, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively.ively.