• Title/Summary/Keyword: 소성환경

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Piezoelectric and Dielectric Characteristics of (Na,K)$NbO_3$ Ceramics System According to Variations of Sintering Time (소결시간변화에 따른 (Na,K)$NbO_3$계 세라믹스의 유전 및 압전특성)

  • Kim, Do-Hyung;Yoo, Ju-Hyun;Jeong, Young-Ho;Hong, Jae-Il
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.48-48
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    • 2008
  • 현재 압전재료로써 사용되고 있는 PZT계 세라믹스는 우수한 압전 및 유전특성으로 초음파 센서, 압전변압기, 액츄에이터, 필터, 레조네이터와 같은 여러 응용분야에 널리 사용되어지고 있다. 그러나 납을 60%이상 포함하므로 환경오염에 의하여 그 사용에 대한 규제가 강화되고 있어 최근에는 납을 함유하지 않은 무연 환경친화형 압전세라믹스가 주목받고 있다. 현재 무연 조성 세라믹스에는 텅스텐-브론즈 형, 비스머스 레이어형, 페로브스카이트 형 등이 이으며, 그 중 페로보스카이트 혈을 제외하고는 보통 소성법 조제시 낮은 압전특성을 갖는다. 그러므로 압전특성을 증가시키기 위하여 Hot pressing, Hot forging, RTGG(Reactive Template Grain Growth), SPS(Spark Plasma Sintering), 그러나 이는 무연 세라믹스의 대량생산 과정에서 어려운 문제를 가지고 있고, 저가격 관점에서 볼 때 보통소성법이 보다 바람직하다. 그래서 보통소성법으로 NKN세라믹스의 소결성을 향상 시키고 비교적 높은 압전특성을 얻기 위해서 $LiSbO_3$, $LiNbO_3$, $LiTaO_3$, alkaline-earth(Mg, Ca, Sr, Ba) 등을 첨가한 논문들이 보고되고 있으며, 이러한 재료들의 kp는 대략 0.3-0.4를 나타내고 있다. 따라서, 본 연구에서는 소결온도를 낮추고자 $Ag_2O$를 소결조제로 사용하였고 유전 및 압전특성을 높이고자 소결시간 변화시켜 시편을 제작하여 NKN 세라믹스의 유전 및 압전특성을 조사하였다.

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Optimization of Gold Leaching from the Refractory Sulfide Concentrate by HCl-NaClO-FeCl3 Solution (HCl-NaClO-FeCl3 용액을 이용한 저항성 황화광물 정광으로부터 금 용출 최적화)

  • Kim, Bong-Ju;Cho, Kang-Hee;Lee, Jong-Ju;Choi, Nag-Choul;Park, Cheon-Young
    • Economic and Environmental Geology
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    • v.46 no.1
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    • pp.21-28
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    • 2013
  • In order to optimize gold leaching from refractory sulfide concentrate, a HCl-NaClO-$FeCl_3$ solution with varying attributes was applied to the roasted concentrate from Uil mine. The gold from Uil mine occurs in the form of invisible gold that is difficult to leach. The results of the gold leaching experiments showed that the best gold leaching parameters were $550^{\circ}C$ of roasting temperature, 2.0 M of concentration, 1.0% of pulp density, and $70^{\circ}C$ of leaching temperature. It is confirmed that the HCl-NaClO-$FeCl_3$ solution was an environmentally friendly method to leach gold and silver from the refractory sulfide concentrate as an alternative lixiviant to cyanide.

The Effects on the Atterberg Limits of Clays with Heat Treatment (열처리에 따른 점토의 애터버그 한계 영향)

  • Min, Tuk-Ki;Hwang, Kwang-Mo;Lee, Sung-Ho
    • Journal of the Korean Geotechnical Society
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    • v.23 no.2
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    • pp.29-34
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    • 2007
  • This study examines the effects of heat treatment under laboratory conditions for mixtures of two types of clay (kaolinite and montmorillonite). Clay samples were burned with different temperatures ranging from $100^{\circ}C\;to\;500^{\circ}C$. The Atterberg limits such as liquid and plastic limits were influenced with heat treatment. According to the experimental results, the liquid limits slightly decreased between $100^{\circ}C\;to\;300^{\circ}C$, whereas rapid decreases were observed after $300^{\circ}C$. The plastic limits did not show noticeable differences in the interval $100^{\circ}C\;to\;400^{\circ}C$. But the clay samples showed non plastic behavior at $500^{\circ}C$. The amount of NaCl was getting decreased with temperature. It also revealed that the pH values were also influenced with heat treatment, and the cation exchange capacity (C.E.C) values decreased with temperature.

A Study on the Behaviour of Jacket Anchor (자켓앵커 거동특성에 관한 연구)

  • Kim, Dong-Hee;Kim, In-Chul;Kong, Hyun-Seok;Lee, Woo-Jin
    • Journal of the Korean Geotechnical Society
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    • v.24 no.8
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    • pp.89-97
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    • 2008
  • A series of field tests were performed to investigate the behavior of jacket anchor and to evaluate the ultimate bond stress of jacket anchor. From twelve sets of field tests on the jacket anchor and general type ground anchor, it was observed that the pullout resistance of jacket anchor is significantly larger than that of the ground anchor and that the plastic deformation of jacket anchor is significantly smaller than that of general ground anchor at the same loading cycle. Especially in gravel layers, the jacket anchor provides more than 250% increase in ultimate resistance and more than 600% reduction in plastic deformation, compared with the general ground anchor. Finally, the relationship between the injection pressure and overburden pressure is proposed to determine the optimum injection pressure, based on additional field test results.

Performance Evaluation of Asphalt Concrete Pavements at Korea Expressway Corporation Test Road (시험도로 아스팔트 포장의 공용성 변화 분석)

  • Seo, Youngguk;Kwon, Soon-Min
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1D
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    • pp.35-43
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    • 2008
  • This paper mainly deals with the performance evaluation of 33 asphalt sections of Korea Expressway Corporation Test Road (KECTR) during the past four years. Since the construction of the KECTR in December 2002, key performance indicators of asphalt pavements have been collected five times with an Automatic Road Analyzer (ARAN), and have been analyzed for permanent deformation, surface distress, and road roughness. Linear viscoelastic characteristics of four dense graded HMAs used in KECTR were investigated with a series of complex modulus test. The effect of air void in HMAs on dynamic modulus was investigate at two air void contents for a surface course HMA (19 mm Nominal Maximum Size of Aggregate). Layer densification due to traffic was estimated from air void contents of field cored samples, and was correlated with pavement distresses and performances. One of findings of this study was that both permanent deformation and cracking were suspectible to pavement temperatures, rather than traffic. However, it was found that road roughness was mostly affected by traffic loading.

A Case Study about Problem EPS Plastic Displacement on High Embankment (고성토 지반의 EPS 소성변형 문제점에 대한 사례연구)

  • Shin, Chang Gun;Seo, Jeong You;Lee, Jong keyn;Chae, Min Lee
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.11
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    • pp.5-12
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    • 2011
  • Numerous studies on the improvement of low strength for soft ground have been performed. EPS, light weight filling material, is used at the study site for stability on consolidation settlement. However, several problems such as settlement of pavement layer and damage of curb occurs. The elevation is lower 1 m than that of designed value by consolidation. It is caused by excessive load during construction. In this study, problems due to overloading on the soft ground where the EPS is used were analyzed and some cases for reasonable improvement method were described. From the results, instructions for design and construction are suggested.

An Evaluation of Field Performance of Environmentally Friendly Asphalt Pavement (친환경 아스팔트 도로포장의 현장 공용성 분석)

  • Kim, Nakseok
    • Journal of the Society of Disaster Information
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    • v.9 no.1
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    • pp.22-29
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    • 2013
  • Warm mix asphalt(WMA), which is produced at lower temperatures than hot mix asphalt, has advantages in reductions of fuel consumption and greenhouse-gas emission. In this study, field tests such as skid resistance, rutting(permanent deformation), and roughness were conducted for analysis of long-term field performance of modified warm mix asphalt pavement. Skid resistance after 20 months represents the result similar to initial performance results but rutting and roughness decreased somewhat depending on the period of performance. Measurement results of permanent deformation and roughness could be acceptable because measured pavement location is bus lane that a lot of buses pass and stop. There were no cracks after 11 months, but some minor cracks were observed after 20 months. These results were influenced by increased crack resistance due to fiber addition.

Formulation of Dynamic Cyclic Plasticity Model for SM490 and Its Application to 3-Dimensional Elastic-Plastic Finite Element Analysis (SM490강재의 동적반복소성모델의 정식화 및 3차원 탄소성 유한요소해석의 적용)

  • Chang, Kyong Ho;Jang, Gab Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.3A
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    • pp.465-471
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    • 2006
  • To describe hysteretic behavior of steel structures under dynamic loading such as earthquake, the dynamic cyclic plasticity model considering stress-strain relationship and characteristics of used steel materials under static-dynamic deforming is required. In this paper, mechanical characteristics and stress-strain relationship of SM490 was clarified by carrying out static-dynamic monotonic and cyclic loading test. A dynamic cyclic plasticity model of SM490 was proposed based on the test results and applied 3-dimensional finite element analysis using finite deformation theory. An analytical method developed by the authors was verified validity and accuracy by comparing both analysis and test results. The comparison result shows that the analytical method developed by the authors can predict static-dynamic hysteretic behavior of steel structures with accuracy.

Effect of Ball End Mill Cutting Environments on Machinability of Hardened Tool Steel (볼 엔드밀 가공환경 조건이 고경도 강재의 절삭 특성에 미치는 영향)

  • 이영주;원시태;허장회;박동순
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10a
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    • pp.245-250
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    • 2003
  • This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL (Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.

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