• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.611-615
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• 2003

The crystalline and dielectric properties on $Al_2O_3$ filled glass frit ($CaO-Al_2O_3-SiO_2-MgO-B_2O_3$) with admixtures of $TiO_2$ have been investigated. The dielectric constant value of $7.5{\sim}7.8$, quality factor value of 700 were obtained for glass frit : $Al_2O_3$ (50 : 50 wt%) ceramics. As the amount of $TiO_2$ increased, temperature coefficient of dielectric constant were decreased.

• Nuclear Engineering and Technology
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• 제34권6호
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• pp.574-585
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• 2002

The microstructural characteristics and its related mechanical properties of RPV cladding have been investigated using small punch (SP) tests. SA508 Cl.3 RPV steel plates were overlay cladded with the type ER309L welding consumables by submerged arc welding process. Although the RPV clad material had a small portion of 5 ferrite phase, it still showed the ductile to brittle transition behavior The transition temperature was determined by the SP test and it depended on the content of $\sigma$ phase, specimen size, and determination methods. The fracture appearance of SP specimen was changed from circumferential to radial cracking as test temperature became low, and below the transition temperature region, ER309L cladding usually fractured along the 6 ferrite by the low temperature failure of ferrite phase.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.290-291
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• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, sensers, transducers, PMN-PNN-PZT ceramics were manufacrtured with the sintering temperature, and their piezoelectric and dielectric properties were investigated. At the composition ceramics sintered at $900^{\circ}C$, desity, dielectric constant$({\varepsilon}_r)$, electromechanical coupling factor(kp), piezoelectric constant$(d_{33})$ and mechanical quality factor(Qm) showed the optimal value of $7.86g/cm^3$, 1417, 0.634, 410pC/N and 1138, respectively.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.454-457
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• 2010

The influence of CuO addition on what of the $(Ba,Sr)TiO_3$ ceramics was studied. The sintering temperature of $(Ba,Sr)TiO_3$ ceramics was lowered by the addition of CuO additives. The 1 - 5 wt% CuO were selected and employed as the sintering aids. Low-Temperature Co-fired Ceramic technologies are popular technologies used in the manufacture of microwave devices. In this study, crystalline and electrical properties of CuO doped $(Ba,Sr)TiO_3$ ceramics were investigated to determine the low temperature sintering properties. The addition of CuO to $(Ba,Sr)TiO_3$ lowered the sintering temperature from $1350^{\circ}C$ to $1150^{\circ}C$. The dependence of the sintering temperature shrinkage rate and mechanism of CuO doped $(Ba,Sr)TiO_3$ ceramics are investigated and discussed. Also, the crystalline structure of CuO - doped $(Ba,Sr)TiO_3$ ceramics is discussed by the X-ray diffraction (XRD) method.

• 한국도로학회논문집
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• 제6권4호
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• pp.1-12
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• 2004

본 논문은 상온상태의 폐아스팔트 포장재료를 가열재활용하여 기층용뿐만 아니라 표층용으로 활용함에 있어 재생 아스팔트 바인더의 특성을 연구한 것이다. 4종류의 RAP을 가지고 RAP 자체의 기본 물성을 시험하였다. 배합설계는 표층에는 RAP을 10, 20%를 첨가하였고, 기층에는 10. 20, 30%를 첨가하였다. 재생혼합물의 신규바인더로는 AC 60-80을 선정하였다. 침입도, 점도, GPC, TFO. 저온균열 저항성을 평가하기 위한 BBR 실험을 수행하였다. 절대점도와 GPC에서의 대형입도분자(LMS)를 지수함수 회귀분석을 통해 $R^2$이 0.95 이상이었고 이것은 절대점도 추정에 GPC 결과가 상당히 정확함을 시사해주고 있다. RAP을 첨가한 재생 아스팔트 바인더의 PG 저온 등급은 일반 신규 바인더에 비해 한 단계 높은 등급을 나타내므로 저온균열에 대한 저항성은 약간 약한 것으로 나타났다.

• 한국건축시공학회지
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• 제17권5호
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• pp.419-427
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• 2017

동절기에 콘크리트를 시공할 경우 초기동해와 강도발현이 지연되는 문제가 있으며, 이를 방지하기 위해서는 콘크리트가 동결하기 이전에 시멘트의 수화반응이 일정수준 이하 진행되는 것이 중요하다. 이에 본 연구는 저온에서도 수화열이 높게 발생되는 $Al_2O_3$성분이 함량이 높은 CSA, 알루미나시멘트를 OPC에 치환하여 물성평가를 수행하였다. 그 결과 CSA, 알루미나시멘트를 사용하여 $-5^{\circ}C$의 저온환경에서 초기에 수화반응이 빠르게 진행되며, 급결현상 및 유동성저하현상이 발생되었고, 석고를 사용하여 응결시간을 지연하며 유동성을 확보하여 작업성을 개선하였다. 또한 단열양생공법을 적용하여 모르타르의 동결시간을 지연하였으며 수축보상효과를 증진시켰고 3일, 7일 강도가 증진되었다. 따라서 본 연구 결과 저온환경에서 CSA, 알루미나시멘트 및 석고를 사용하여 조기에 강도발현 증진효과가 우수하였으며, 석고 및 단열양생공법을 적용하여 작업성, 동결저항성, 조기강도 발현 성능이 개선되어 초기동해를 방지하는데 효과가 있을 것으로 판단된다.

• 한국표면공학회지
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• 제51권4호
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• pp.249-255
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• 2018

High temperature and low temperature gaseous nitriding was performed in order to study of the surface hardening and wear properties of the nitrided AISI 410 Martensitic stainless steels. High temperature gaseous nitiridng (HTGN) was carried out using partial pressure $N_2$ gas at $1,100^{\circ}C$ for 10 hour, and Low temperature gaseous nitiridng (LTGN) was conducted in a gas mixture of NH3 and N2 at $470^{\circ}C$ for 10 hour. The nitrided samples were characterized by microhardness measurements, optical microscopy and scanning electron microscopy. The phases were identified by X-ray diffraction and nitrogen concentration was analyzed by GD-OES. The HTGN specimen had a surface hardness of about $700HV_{0.1}$, $350{\mu}m$ of case depth. A ${\sim}50{\mu}m$ thick, $1,250HV_{0.1}$ hard nitrided case formed at the surface of the AISI 410 steel by LTGN, composed nitrogen supersaturated expanded martensite and ${\varepsilon}-Fe_{24}N_{10}$ iron nitrides. Additionally, the results of the wear tests, carried out LTGN specimen was low friction coefficient and high worn mass loss of ball. The increase in wear resistance can be mainly attributed to the increase in hardness and to the lattice distortion caused by higher nitrogen concentration.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.41-44
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• 2001

Mechanical test of the Carbon Fiber Reinforced Plastics (CFRP) composite specimen was performed based on the ASTM code at the ambient and low temperature. Tension, compression in-plane shear, and inter-laminar shear properties of the composite laminates were evaluated experimentally using the Universal Testing Machine(UTM) system at the temperature of $24^{\circ}C$,$-76^{\circ}C$ , and $-196^{\circ}C$. From the test results it was found that the CFRP chosen for the Korea Superconducting Tokamak Advanced Research(KSTAR) magnet supporting post had smaller tensile strength and larger compressive strength at the low temperature than those of the ambient temperature because of material ductility.

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.29-34
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• 2006

The effects of $B_2O_3$ addition on the low-temperature sintering behavior and microwave dielectric properties of $(Zn_{0.8}Mg_{0.2})TiO_3$ ceramic system were investigated. Highly dense samples were obtained at the sintering temperatures below $900^{\circ}C$. The $Q{\times}f_o$ values were determined by the microstructures and sintering shrinkages which are affected by the amount of $B_2O_3$ and sintering temperature. Temperature coefficient of resonance frequency($T_f$) changes to a positive value with increasing the amount of $B_2O_3$ due to the increased amount of rutile phase which is one of the reaction products between $(Zn_{0.8}Mg_{0.2})TiO_3$ and $B_2O_3$. For $6.19 moi.{\%}B_2O_3$-added $(Zn_{0.8}Mg_{0.2})TiO_3$ system, it exhibits ${\epsilon}_r$ = 23.5, $Q{\times}f_o$ = 53,000 GHz, and $T_f$ = 0 ppm/$^{\circ}C$ when sintered at $900^{\circ}C$ for 5 h.

• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.906-910
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• 2008

$(K_{0.5}Na_{0.5})NbO_3$ (NKN) ceramics doped with $Li_{2}CO_3$ as sintering aids were manufactured in order to develop the low temperature sintering ceramics for piezoelectric device. The sintering aids were proved to lower the sintering temperature of doped NKN ceramics due to the effect of $Na_{2}CO_{3}-Li_{2}CO_3$ liquid phase. All the specimens showed the orthorhombic phase without secondary phase. And also, the piezoelectric properties of specimens were improved with increasing $Li_{2}CO_3$ contents. At sintering temperature of $930^{\circ}C$, the density, electromechanical coupling factor (kp), mechanical quality factor (Qm) and dielectric constant(${\epsilon}_{\gamma}$), piezoelectric constant of 0.3 wt.% $Li_{2}CO_3$ added specimen showed the optimum values of $4.255 g/cm^3$, 0.37, 234, 309, 136 pC/N, respectively.