• 한국전기전자재료학회논문지
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• 제17권10호
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• pp.1056-1060
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• 2004

In this study, 0.96B $i_{0.5}$($Na_{0.84}$ $K_{0.16}$)$_{0.5}$Ti $O_3$ + 0.04SrTi $O_3$ + 0.3 wt% N $b_2$ $O_{5}$+0.2 wt% L $a_2$ $O_3$ + xwt % Mn $O_2$ were investigated as a function of the amount of Mn $O_2$ addition in order to improve dielectric and piezoelectric properties of Lead-free piezoelectric ceramics. With increasing the amount of Mn $O_2$ addition, the density, electromechanical coupling factor( $k_{p}$), piezoelectric constant( $d_{33}$, $g_{33}$) and curie temperature (Tc) showed the maximum value of 5.7 g/㎤, 38 %, 219 pC/N, 26 mVㆍm/N and 32$0^{\circ}C$ at 0.1 wt% Mn $O_2$ addition, respectively, and mechanical quality factor( $Q_{m}$ ) showed the maximum value of 158 at 0.3 wt% Mn $O_2$ addition.ddition.ion.n.

• Tribology and Lubricants
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• 제23권6호
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• pp.261-265
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• 2007

Carbide-derived carbon coating has been synthesized by low temperature treatment of TiC disk with $H_2/Cl_2$ mixture gases. A variety of physical measurements indicated that Ti was extracted and carbon layer was formed by exposure of $Cl_2$ gas. The $I_D/I_G$ ratio increased with increasing $Cl_2$ gas concentration. Wear coefficient and frictional coefficient varied with $Cl_2$ gas concentration. When the $Cl_2$ gas concentration decreased to 3.3 vol%, the friction coefficient approach a minimum. The results showed that degree of graphite crystallinity and variation of porosity due to the $Cl_2$ gas content were responsible for different tribology performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1505-1506
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• 2011

염료감응형 태양전지(Dye-Sensitized Solar Cell, DSSC)의 FTO 표면에 compact layer를 형성시켜 직접적인 마찰에 의한 전자의 재결합을 줄일 수 있다. 따라서 광전극에서의 compact layer의 효과를 최대화하기 위하여 $TiCl_4$ 용액에 acetic acid를 첨가하여 특성변화를 측정하였다. UV-Vis 분광기, I-V 특성곡선, EIS 분석장비를 이용하여 검토한 결과, UV-Vis 분광분석을 통해서 acetic acid를 첨가한 compact layer의 투과도가 현저하게 높아진 것을 확인하였다. 이 결과는 $TiCl_4$ 처리에 의하여 compact layer를 구성하고 있는 $TiO_2$ 입자의 응집현상이 개선되므로 표면특성이 향상되었기 때문이다. Acetic acid를 첨가한 compact layer가 입자응집으로 인한 표면저항의 감소를 유발하여, 전자의 이동이 원활해진 것을 내부 임피던스 분석을 통하여 확인하였다. Compact layer에 의해 재결합이 감소하여 효율이 향상된 것을 I-V 특성곡선을 분석하여 확인하였다.

• 한국전기전자재료학회논문지
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• 제29권6호
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• pp.342-347
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• 2016

We investigated the effect of $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3$ (BNKT) modification on the ferroelectric and electric-field-induced strain (EFIS) properties of lead-free $0.97Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-0.03LaFeO_3$ (BNKTLF) ceramics as a function of BNKT content (x= 0, 0.1, 0.2, 0.3, 0.5, and 1). BNKT-modified BNKTLF powders were synthesized using a conventional solid-state reaction method. As the BNKT content x increased from 0 to 1 the normalized electric-field-induced strain ($S_{max}/E_{max}$) was observed to increase at relatively low fields, i.e., below the poling field. Moreover, BNKTLF-30BNKT showed about 460 pm/V as low as at 3 kV/mm, which is a considerably high value among the lead-free systems reported so far. Consequently, it was confirmed that ceramic-ceramic composite, a mixture of an ergodic relaxor matrix and embedded ferroelectric seeds, is a salient way to make lead-free piezoelectrics practical with enhanced EFIS at low field as well as less hysterical.

• 한국재료학회지
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• 제32권9호
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• pp.384-390
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• 2022

A spin coating process for RRAM, which is a TiN/TiO₂/FTO structure based on a PTC sol solution, was developed in this laboratory, a method which enables low-temperature and eco-friendly manufacturing. The RRAM corresponds to an OxRAM that operates through the formation and extinction of conductive filaments. Heat treatment was selected as a method of controlling oxygen vacancy (V_O), a major factor of the conductive filament. It was carried out at 100 ℃ under moisture removal conditions and at 300 ℃ and 500 ℃ for excellent phase stability. XRD analysis confirmed the anatase phase in the thin film increased as the heat treatment increased, and the Ti³⁺ and OH- groups were observed to decrease in the XPS analysis. In the I-V analysis, the device at 100 ℃ showed a low primary SET voltage of 5.1 V and a high ON/OFF ratio of 10⁴. The double-logarithmic plot of the I-V curve confirmed the device at 100 ℃ required a low operating voltage. As a result, the 100 ℃ heat treatment conditions were suitable for the low voltage driving and high ON/OFF ratio of TiN/TiO₂/FTO RRAM devices and these results suggest that the operating voltage and ON/OFF ratio required for OxRAM devices used in various fields under specific heat treatment conditions can be compromised.

• Membrane and Water Treatment
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• 제9권3호
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• pp.189-194
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• 2018

Electrochemical reduction of nitrate was studied using Zn, Cu and (Ir+Ru)-Ti cathodes and Pt/Ti anode in a cell divided by an ion exchange membrane. During electrolysis, effects of the different cathode types on operating parameters (i.e., voltage, temperature and pH), nitrate removal efficiency and by-products (i.e., nitrite and ammonia) formation were investigated. Ammonia oxidation rate in the presence of NaCl was also determined using the different ratios of hypochlorous acid to ammonia. The operating parameter values were similar for all types of cathode materials and were maintained relatively constant. Nitrate was well reduced and converted mostly to ammonia using Zn and Cu cathodes. Ammonia, produced as a by-product of nitrate reduction, was oxidized in the presence of NaCl in the electrochemical process and the oxidation performance was enhanced upon increasing the hypochlorous acid-to-ammonia ratio to 1.09:1. Zn and Cu cathodes promoted the nitrate reduction to ammonia and the produced ammonia was finally removed from solution by reacting with hypochlorite ions. Using Zn or Cu cathodes, instead of noble metal cathodes, in the electrochemical process can be an alternative technology for nitrate-containing wastewater treatment.

• 대한의생명과학회지
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• 제14권2호
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• pp.105-113
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• 2008

The objective of this study was to evaluate the influence of surface modifications on the bonding characteristics and cytotoxicity of specific titanium porcelain bonded to milling titanium and cast titanium. Milling titanium and cast titanium samples were divided into 8 test groups. These groups are as follow: i) sandblasted with particles of different size of $220{\mu}m\;and\;50{\mu}m$, ii) different sequences of sandblasting treatment and etching treatment, iii) etched with different etching solutions, and iv) preheated or not. The surface characteristics of specimens were characterized by the test of mean roughness of surface and SEM. The bond strength of titanium-ceramic systems was measured by using three-point bending test and SEM. The results show that the mean roughness of surface of sample sandblasted with $220{\mu}m$ aluminum oxide increased and bond strength were higher than sample sandblasted with $50{\mu}m$ aluminum oxide. The mean roughness of surface decreased, but the bond strength increased when the samples sandblasted with $220{\mu}m$ aluminum oxide were preheated. The sample sandblasted with $220{\mu}m$ aluminum oxide after oxidized with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF) showed higher bond strength than sample oxidized with 30% $HNO_3$ after sandblasted with $220{\mu}m$ aluminum oxide. Group NaCuNF220SP (milling Ti: 35.3985 MPa, casting Ti: 37.2306 MPa) which was treated with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF), followed by sandblasting with $220{\mu}m$ aluminum oxide and preheating at $750^{\circ}C$ for 1 hour showed the highest bond strength and significant differences (P<0.05). The method for modifying surface of titanium showed excellent stability of cells.

• 암석학회지
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• 제26권3호
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• pp.271-280
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• 2017

동천동 화강암은 경주 동천동 일대에 분포하는 알칼리장석화강암이다. 이는 주로 우백질의 조립질화강암이며 알칼리장석, 석영, 흑운모, 각섬석이 관찰된다. 경하관찰 결과, 알칼리장석은 퍼싸이트로 나타나며, 석영은 주로 파동소광을 보인다. 사장석은 주로 알바이트 쌍정을 보이며, 흑운모와 각섬석은 간극상으로 산출된다. 동천동 화강암은 $(Na_2O+K_2O)/Al_2O_3$ 비가 높고 (MgO+CaO)/FeOT가 낮은 전형적인 A-형 화강암 영역에 도시되며 경상분지 I-형 화강암류에 비해 $SiO_2$, $Na_2O$, $K_2O$, Rb, Ga, Zr이 부화되어 있는 반면 $TiO_2$, $Al_2O_3$, CaO, MgO, Sr, Ba, Sc 등은 결여되어 있다. 또한, 연구지역 화강암은 I-형 화강암에 비해 희토류원소의 함량이 높고 큰 Eu(-) 이상을 보여준다. 이러한 지화학적 특성은 기존에 보고된 경상분지 I-형 화강암류와 뚜렷이 구분된다. 동천동 A-형 화강암은 현재까지 제시된 A-형 화강암의 기원 중 지각 내의 토날라이트질(Tonalite) 내지 화강섬록암의 I-형 화강암의 부분용융으로 만들어졌을 가능성이 높은 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.462-469
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• 2018

The background spectrum of a $3^{{\prime}{\prime}}{\times}3^{{\prime}{\prime}}$ NaI(Tl) well-type scintillation SILENA detector was measured without shielding, in 6 cm thick lead shielding, and with 2 mm thick electrolytic copper covering the detector inside the lead shielding. The relative remaining background of the lead shield lined with copper was found to be ideal for low-level environmental radioactive spectroscopy. The background total count rate in the (20-2160 KeV) was reduced 28.7 times by the lead and 29 times by the Cu + Pb shielding. The effective reduction of background (1.04) by the copper mainly appeared in the energy range from X-ray up to 500 KeV, while for the total energy range the ratio is 1.01 relative to the lead only. In addition, a strong relation between the full-energy peak absolute efficiency and the detector well height was found using gamma-ray isotropic radiation point sources placed inside the detector well. The full-energy peak efficiency at a midpoint of the well (at 2.5 cm) is three times greater than that on the detector surface. The energy calibrations and the resolution of any single energy line are independent of the locations of the gamma source inside or outside of the well.

• 한국자원식물학회지
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• 제3권2호
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• pp.107-114
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• 1990

In view of the results to have measured metallic elements which is included in 45 sorts of herb medicines and surveyed their distribution, 8 kinds ofmetals including Co, Ge, Ga, TL, Cd, As, 8i, Pb, are never or little includedin almost herb medicines . Other twenty-five sorts of elements (Mo, Sc, Be, V,Ni, Sn, Se, Ba, Cr, Sb, Si, Ti, B, Li, Mg, Ca, Cr, Mn, Fe, Cu, Zn, p, Al, Na,K) are more or Less included in all herb Bedicines ana Na, Ca, p and K aremetals that are included in Large quentities in comrarison with others . Patri-uiae Radix Contains 7 kinds of metal lic elements more than other herb medicinesdoes .