• 한국전기전자재료학회논문지
• /
• 제31권4호
• /
• pp.212-215
• /
• 2018

The phase evolution, microstructure, and microwave dielectric properties of $Ba(Mg_{0.5-2x}Y_{2x}W_{0.5-x}Ti_x)O_3$ (x = 0.005~0.05) ceramics sintered at $1,700^{\circ}C$ for 1h were investigated. All compositions exhibited a 1:1 ordered cubic perovskite structure. The field emission scanning electron microscopy image revealed a dense microstructure in all the compositions. As the value of x increased, the lattice parameter, dielectric constant, and quality factor increased. The temperature coefficient of resonant frequency changed from $-19.6ppm/^{\circ}C$ to $-5.9ppm/^{\circ}C$ with increasing x value. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of $Ba(Mg_{0.40}Y_{0.10}W_{0.45}Ti_{0.05})O_3$ were 21.7, 132,685 GHz, and $-5.9ppm/^{\circ}C$, respectively.

• 한국환경과학회지
• /
• 제13권6호
• /
• pp.599-603
• /
• 2004

In a batch reactor, the characteristics of photocatalytic degradation of brilliant blue FCF in titanium dioxide suspension was studied under the irradiation of ultra-violet ray. Photocatalytic degradation in anatase type of TiO$_2$ was more effective than in rutile type of $TiO_2$ below the dosage of 5g. The degradation rate was slightly increased with decreasing initial pH of brilliant blue FCF aqueous solution, but rapidly increased with the addition of oxidant. Potassium bromate acted as more effective oxidant than ammonium persulfate. The photocatalytic degradation rate of brilliant blue FCF was pseudo-first order with rate constants of 0.012, 0.006 and $0.003min^{-1}$ at initial pH 3.1, 5.2 and 7.1 of brilliant blue FCF solution, respectively.

• Transactions on Electrical and Electronic Materials
• /
• 제11권5호
• /
• pp.212-215
• /
• 2010

$BiFeO_3/Pb(Zr_{0.95}Ti_{0.05})O_3$ (BFO/PZT) heterolayered thin films were fabricated by the spin coating method on a Pt/Ti/$SiO_2$/Si substrate using metal alkoxide solutions. The coating and heating procedure was repeated 6 times to form the heterolayered films. The thickness of the BFO/PZT films after one cycle of drying/sintering is about 30-40 nm. All BFO/PZT films show a void free uniform grain structure without the presence of rosette structures. It can be assumed that the crystal growth of the upper BFO layers can be influenced by the lower PZT layers. As the number of coatings increased, the dielectric constant increased, so that the value for the 6-layer film was 1360 at 1 KHz.

• 공업화학
• /
• 제2권4호
• /
• pp.411-420
• /
• 1991

$Pt-Sn/{\gamma}-Al/_2O_3$ 촉매에서 조촉매 주석의 함량을 달리하여 n-heptane을 반응물로 사용하여 탈수소 고리화 반응을 고정층 연속 흐름 반응기에서 행하였다. 조작 조건의 범위는 온도 $450-550^{\circ}C$, 압력 $20{\times}10^5-50{\times}10^5Pa$, 접촉 시간 0.09-0.27 hr, $H_2/H.C$. 몰비는 10이었다. 온도는 증가함에 따라 탈수소고리화반응의 전화율과 선택도가 증가했으며 압력의 증가에 대해서는 그 반대의 결과를 나타냈다. 조촉매 주석을 사용하였을 때 탈수소고리화반응의 선택도는 큰 변화를 보이지 않았지만 전화율이 증가했으며 이성화반응의 선택도는 커다란 증가를 보였다. 0.6 wt % Pt-0.6 wt % $Sn/{\gamma}-Al_2O_3$ 촉매에서 n-heptane의 탈수소 고리화 반응의 활성화에너지는 34.5 kcal/mole 이었다.

• 한국전기전자재료학회논문지
• /
• 제16권6호
• /
• pp.532-537
• /
• 2003

Crystallographic, electric, magnetic and heat transition properties of $\alpha$-Fe$_2$O$_3$ have been studied with a small addition of Eu impurities. Hematite($\alpha$-Fe$_2$O$_3$) is a basic ferromagnetic material having rhombohedral structure, which is similar to perovskites structure. Eu is a rare earth element that has an electric configuration of 4f$^{7}$ 6s$^2$. X-ray diffraction pattern of Fe$_{1-x}$ Eu$_{x}$O$_3$ (x = 0.00, 0.04, 0.06) shows an increament of a value when the amount of Eu impurities increased. The VSM data show an increment of magnetization by increasing the amount of Eu impurity. The one with x=0.06 shows the largest increment of magnetic remanence. The magnetic remanence varied from 0.49$\times$10$^{-3}$ emu/g to 0.62$\times$10$^{-3}$ emu/g when Eu impurity is increased by 2 %. Coercivity is decreased as Eu impurity is increased. Resistances is reduced significantly by Eu impurity. There is a clear difference in temperature-dependent resistance depending on the amount of Eu impurities. Especially, there are cusps between 150 K to 175 K. It indicates the change of electronic quantum states inside the atoms by rare earth impurities in rhombohedral structure. Temperature-dependent heat capacity shows that the most effective amount of Eu impurities is 6 %. %.

• 한국전기전자재료학회논문지
• /
• 제16권12S호
• /
• pp.1195-1199
• /
• 2003

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, dielectric and piezoelectric properties of PSN-PZT[0.91Pb(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$0.03/(Zr$\sub$0.495/Ti$\sub$0.505/)$\sub$0.97/O$_3$-0.04Pb(Ni$\sub$1/2/W$\sub$1/2/)O$_3$+0.05BiFeO$_3$+0.3wt％MnO$_2$+0.6wt％CuO〕 ceramics were investigated according to Zr/Ti ratio. As Zr/Ti ratio is increased, electromechanical coupling factor(k$\sub$p/) and dielectric constant increased and then decreased after the ratio of Zr/Ti=50/50. Also, mechanical qualify factor(Q$\sub$m/) decreased and then increased after the ratio of Zr/Ti=50/50.

• 공업화학
• /
• 제32권6호
• /
• pp.690-694
• /
• 2021

본 연구에서는 글루코스를 전구체로 사용하여 수열합성방법을 통해 구형탄소입자(carbon sphere, CS)를 제조하였다. 200 nm, 500 nm, 1,200 nm 크기의 중공형 TiO₂ (H-TiO₂)는 CS/TiO₂ core-shell 구조를 졸-겔 법과 열처리 방법으로 합성하였다. FE-SEM, HR-TEM, XRD 분석을 통하여 H-TiO₂의 물리적 특성을 측정하였다. H-TiO₂/polyacrylate (PA) 복합체의 UV-Vis-NIR 분석을 통해 색상변화와 일사반사율을 얻었으며, 실험실에서 제작한 차열온도 측정기를 통해 차열온도를 측정하였다. H-TiO₂/PA 복합체는 열전도도가 낮은 건조공기로 채워진 중공구조에 의한 우수한 차열 특성과 근적외선 반사율을 보였다. H-TiO₂/PA 복합체에서 중공구의 크기가 증가함에 따라 열차단 특성이 증가하였다. 1,200 nm 중공 크기의 H-TiO₂를 혼합한 PA 필름에서 측정된 차열온도가 투명 유리판의 차열온도보다 26 ℃ 감소하였다.

• 한국재료학회지
• /
• 제34권6호
• /
• pp.283-290
• /
• 2024

The aggressive scaling of dynamic random-access memory capacitors has increased the need to maintain high capacitance despite the limited physical thickness of electrodes and dielectrics. This makes it essential to use high-k dielectric materials. TiO₂ has a large dielectric constant, ranging from 30~75 in the anatase phase to 90~170 in rutile phase. However, it has significant leakage current due to low energy barriers for electron conduction, which is a critical drawback. Suppressing the leakage current while scaling to achieve an equivalent oxide thickness (EOT) below 0.5 nm is necessary to control the influence of interlayers on capacitor performance. For this, Pt and Ru, with their high work function, can be used instead of a conventional TiN substrate to increase the Schottky barrier height. Additionally, forming rutile-TiO₂ on RuO₂ with excellent lattice compatibility by epitaxial growth can minimize leakage current. Furthermore, plasma-enhanced atomic layer deposition (PEALD) can be used to deposit a uniform thin film with high density and low defects at low temperatures, to reduce the impact of interfacial reactions on electrical properties at high temperatures. In this study, TiO₂ was deposited using PEALD, using substrates of Pt and Ru treated with rapid thermal annealing at 500 and 600 ℃, to compare structural, chemical, and electrical characteristics with reference to a TiN substrate. As a result, leakage current was suppressed to around 10^-6 A/cm² at 1 V, and an EOT at the 0.5 nm level was achieved.

• 한국세라믹학회지
• /
• 제50권6호
• /
• pp.510-517
• /
• 2013

In this study, the properties of blue inorganic nano-pigments with a spinel structure were systematically investigated. We report the preparation of a blue ceramic nano-pigment and the Co and Ni substitutional effects on the blue color. $MgAl_2O_4$ was selected as the crystalline host network for the synthesis of cobalt and nickel-based blue ceramic nano-pigments. Various compositions of $Co_xMg_{1-x}Al_2O_4$ and $Ni_xMg_{1-x}Al_2O_4$ ($0{\leq}x{\leq}1$) powders were prepared using apolymerized complex method. The obtained powder was preheated at $400^{\circ}C$ for 5 h and then calcined at $1000^{\circ}C$ for 5 h. XRD patterns of the (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ samples showed a single phase of the spinel structure in all compositions. TEM results indicated nano-sized pigments for (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ with a particle size ranging from 20 to 50 nm. The characteristics of the color tones of (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ were analyzed by CIE $L^*a^*b^*$ measurements. In addition, the thermal stability and the binding characteristics of (Co,Mg)$Al_2O_4$, (Ni,Mg)$Al_2O_4$ are discussed in terms of the TG-DSC and FT-IR results, respectively.

• 한국산학기술학회논문지
• /
• 제20권6호
• /
• pp.95-103
• /
• 2019

대표적인 치주질환인 치주염은 출혈, 통증 및 치아 손실을 초래하며, 산화적 스트레스는 치주염의 주요 원인으로 알려져 있다. 본 연구는 지방조직 유래 무막줄기세포추출물의 $H_2O_2$ 유도 산화적 손상에 대한 치주염 보호 효과를 확인하고자, 치주인대 섬유모세포(human periodontal ligament fibroblasts; HPLF)를 이용하여 세포 생존율, 염증 및 세포 사멸 관련 단백질 발현을 측정하였다. $H_2O_2$로 산화적 스트레스를 유도한 HPLF 세포에 무막줄기세포추출물 처리 시, $H_2O_2$만을 처리한 control군에 비해 유의적으로 세포 생존율이 증가함을 통해 산화적 손상에 대한 세포 보호 효과를 확인하였다. 또한, 무막줄기세포추출물은 nuclear factor kappa light chain enhancer of activated B cells, inducible nitric oxide synthase 및 interleukin-6와 같은 염증 관련 단백질 발현을 감소시켜 $H_2O_2$로 유도된 염증반응 보호 효과를 확인할 수 있었다. 뿐만 아니라, 무막줄기세포추출물 처리 군은 caspase-9, -3, poly (ADP-ribose) polymerase 단백질 발현 감소와 B-cell lymphoma 2 (Bcl-2)-associated X protein/Bcl-2 비율을 저하시켜 $H_2O_2$ 유도 산화적 손상에 대한 세포사멸 보호 효과를 보였다. 따라서 지방조직 유래 무막줄기세포추출물은 $H_2O_2$ 유도 산화적 손상에 대한 HPLF 세포의 염증반응 및 세포사멸을 저해함으로써 치주염으로부터 보호 효과가 있어, 치주질환 치료용 소재로써의 활용 가능성이 있을 것으로 기대된다.