• Korean Journal of Materials Research
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• v.28 no.11
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• pp.611-614
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• 2018

Laminate composites composed of $0.95Pb(Zr_{0.52}Ti_{0.48})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3$ piezoelectric ceramic and Fe-Si-B based magnetostrictive amorphous alloy are fabricated, and the effect of control of the areal dimensions and the thickness of the piezoelectric layer on the magnetoelectric(ME) properties of the laminate composites is studied. As the aspect ratio of the piezoelectric layer and the magnetostrictive layer increases, the maximum value of the ME voltage coefficient(${\alpha}_{ME}$) increases and the intensity of the DC magnetic field at which the maximum ${\alpha}_{ME}$ value appears decreases. Moreover, as the thickness of the piezoelectric layer decreases, ${\alpha}_{ME}$ tends to increase. The ME composites exhibit ${\alpha}_{ME}$ values higher than $1Vcm^{-1}Oe^{-1}$ even at the non-resonance frequency of 1 kHz. This study shows that, apart from the inherent characteristics of the piezoelectric composition, small thicknesses and high aspect ratios of the piezoelectric layer are important dimensional determinants for achieving high ME performance of the piezoelectric-magnetostrictive laminate composite.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1929_1930
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• 2009

Fully embedded tunable bandpass filter (BPF) with inductive coupling circuits is newly designed and demonstrated for UHF TV tuner ranged from 500MHz to 900MHz receivers. Conventional RF tuning circuit with an electromagnetic coupled tunable filter has several problems such as large size, high volume, and high cost, since the electromagnetic coupled filter is comprised of several passive components and air core inductors to be assembled and controlled manually. To address these obstacles, compact tunable filter with inductive coupling circuit was embedded into low cost organic package substrate. The embedded filter was optimally designed to have high performance by using high Q spiral stacked inductors, high dielectric $BaTiO_3$ composite MIM capacitors, varactor diodes. It exhibited low insertion loss of approximately -2dB, high return loss of below -10dB, and large tuning range of 56.3%. It has an extremely compact size of $3.4{\times}4.4{\times}0.5mm^3$.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.6-13
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• 2011

In this study, we used activated carbon (AC) and charcoal (CH) as carbon sources with $TiO_2$ powder to prepare spherical carbons containing titania (SCCT) by using phenolic resin (PR) as a bonding agent. The physicochemical characteristics of the SCCT samples were examined by BET, XRD, SEM, EDX, iodine adsorption and compressive strength. The photocatalytic activity was evaluated by measuring the removal efficiency of three kinds of organic dyes: methylene blue (MB), methyl orange (MO) and rhodamine B (Rh.B) under a UV/SCCT system. In addition, evaluation of chemical oxygen demand (COD) of piggery waste was done at regular intervals and gave a good idea about the mineralization of wastewater.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.795-801
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• 1999

An experimental investigation has been conducted with the objective of studying the mixing mechanism near the nozzle exit in a tone-excited jet diffusion flame. The fuel jet was pulsed by means of a loudspeaker-driven cavity. The excitation frequencies were chosen for the two cases of the non-resonant and resonant frequency identified as a fuel tube resonance due to acoustic excitation. The effect of tone-excitations on mixing pattern near the nozzle exit and flame was visualized using various techniques, including schlieren photograph and laser light scattering photograph from $TiO_2$ seed particles. In order to clarify the details of the flame feature observed by visualization methods, hotwire measurements have been made. Excitation at the resonant frequency makes strong mixing near the nozzle. In this case, the fuel jet flow in the vicinity of nozzle exit breaks up into disturbed fuel parcels. This phenomena affects greatly the combustion characteristics of the tone excited jet and presumably occurs by flow separation from the wall inside the fuel nozzle. As a result, in the resonant frequency the flame length reduces greatly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.186-189
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• 2003

The role of excess Pb about the crystallization behavior and electrical properties in b(Zr$\sub$0.52/Ti$\sub$0.48/)O3(PZT) thin films has not been precisely defined. In this work, the effect of excess Pb content on the ferroelectric properties of these films was investigated. To analyze the effect, PZT films containing various amounts of excess Pb were Prepared. PZT thin films were deposited on the Pt/Ti bottom electrode by rf magnetron sputtering method and then they were crystallized by rapid thermal annealing (RTA). The experiment showed that all PZT films indicated perovskite polycrystalline structure with preferred orientation (111) and no pyrochlore phase was observed. As higher excess Pb was included, the films showed that value of leakage current shift from 2.03${\times}$10$\^$-6/ to 6.63 ${\times}$ 10$\^$-8/A/cm$^2$ at 100kV/cm, and value of remanent polarization shift from 8.587 ${\mu}$C /cm$^2$ to 4.256 ${\mu}$C/ cm$^2$. Electrical properties of PZT thin film affected by Pb excess content of target were explained to be caused of defect among space charges and defect grain boundaries.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.1
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• pp.75-92
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• 2015

This paper presents the application of the bond valence method to estimate the valence charge distribution in several perovskite systems: $La_{{\tilde{1}}x}Pb_xMnO_3$ (x=0.1-0.5), $La_{0.6}Sr_{0.{\tilde{4}}x}Ti_xMnO_3$ (x=0.0-0.25) and $La_{{\tilde{1}}x}Sr_xCoO_3$ (x=0.1-0.5); the reviewing of their crystal structures is also incorporated. The results showed the failure of the elastic bonding mechanism in all studied systems and revealed the general deficit of the valence charge in their unit cells. This valence deficit was not associated with the structural defects and was not equally localized in all coordination spheres. As the content of substitution increased, the charge deficit declined systematically from balanced level, signifying the transfer of valence charge from the ${\tilde{B}}O_6$ to ${\tilde{A}}O_{12}$ spheres. This transfer depended on the valence deviation of spheres and the average reached near 2 electron per unit cell. The possible impact of the limitted accuracy of the available structural data on the bond valence results has also been considered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.306-306
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• 2010

21 세기는 언제, 어디에서, 누구나가 정보를 자유롭게 염가에 이용할 수 있는 유비쿼터스 정보사회가 될 것으로 예상하고 있다. 이러한 유비쿼터스 사회가 실현되기 위해서는 필연적으로 대두되고 있는 과제가 에너지 공급원의 문제이다. 휴대용 전자제품이나 소형 에너지 공급원으로 지금까지 주로 전지가 사용되어 왔지만 이것들은 교환 및 충전이 불가피하다. 이러한 불편함을 개선하기위해 교환과 충전이 불필요하거나 아주 장시간동안 공급해주는 형태의 에너지 공급원의 필요성이 대두되고 있다. 이러한 에너지 공급원으로 최근에 많은 연구가 되고 있는 것이 주위의 환경으로부터 버려지는 에너지를 수확(harvesting)하여 전력으로 변환하는 에너지 하베스팅 (energy harvesting)기술이 연구 개발되고 있다. 에너지 하베스팅 응용을 위해서 사용되어지는 압전 세라믹스는 전압출력계수 ($g_{33}$)가 커야하는데 이것은 압전상수 ($d_{33}$)와 유전상수 (${\varepsilon}_{\tau}$)의 값에 영향을 받는 것으로 알려져있다. 그 중에서 우수한 전기적 특성 때문에 PZT를 기반으로 하는 압전 세라믹스가 사용되어져왔다. 그러나 Pb의 높은 유독성과 Pb를 포함하는 제품들의 처분문제들로 인해 제조에 관한 많은 문제점들을 지니고있다. 그리하여, Pb를 포함하지 않는 Pb-free계에 관한 연구가 전세계적으로 활발히 진행되고 있다. 다양한 Pb-free계 후보자들 가운데 $K_{0.5}Na_{0.5}NbO_3$ (KNN)는 높은 큐리온도와 좋은 강유전 특성 및 압전특성 때문에 PZT를 대체할 가장 장래성있는 대안들 중의 하나로 고려되고 있다. 그러나 고온에서 알칼라인 원소들의 높은 휘발성 때문에 보통의 소결공정으로는 소결이 잘되고 치밀한 세라믹스를 얻기가 어렵다. 많은 연구에서 KNN 세라믹스의 소결성을 개선하기 위하여 강유전 또는 반강유전체인 $SrTiP_3$와 $LiTaO_3$를 고용체 형성에 포함시키고 또한 $K_4CuNb_8O_{23}$, $MnO_2$, CuO등과 같은 소결조제를 첨가하여 압전 특성과 소결성을 개선시켰다. 따라서 본 연구에서는 비화학양론적 (1-X)[$[(K_{0.5}Na_{0.5}]_{0.97}(Nb_{0.96}Sb_{0.04})O_3]$ + 0.008CuO + 0.2wt% $Ag_2O$ + X $CeMnO_3$의 조성을 사용하여 A사이트와 B 사이트에 각각 Ce이온과 Mn 이온의 치환량을 변화하여 그에 따른 유전 및 압전특성을 조사하였다.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2923-2928
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• 2010

This study examined the synthesis of the crystal structure of bis(2,2'-bipyridine)nitrato zinc (II) nitrate, $[Zn(bipy)_2(NO_3)]^+NO_3^-$ using a microwave treatment at 300 W and 60 Hz for the application to dye-sensitized solar cells. The simulated complex structure of the complex was optimized with the density functional theory calculations for the UV-vis spectrum of the ground state using Gaussian 03 at the B3LYP/LANL2DZ level. The structure of the acquired complex was expected a penta-coordination with four nitrogen atoms of bipyridine and the oxygen bond of the $NO_3^-$ ion. The reflectance UV-vis absorption spectra exhibited two absorptions (L-L transfers) that were assigned to the transfers from the ligand ($\sigma$, $\pi$) of $NO_3$ to the ligand ($\sigma^*$, $\pi^*$) of pyridine at around 200 - 350 nm, and from the non-bonding orbital (n) of O in $NO_3$ to the p-orbital of pyridine at around 450 - 550 nm, respectively. The photoelectric efficiency was approximately 0.397% in the dye-sensitized solar cells with the nanometer-sized $TiO_2$ at an open-circuit voltage (Voc) of 0.39 V, a short-circuit current density (Jsc) of $1.79\;mA/cm^2$, and an incident light intensity of $100\;mW/cm^2$.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4246-4251
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• 2023

The optimized design of a Neutron Activation Analysis (NAA) system, including Delayed Gamma NAA (DGNAA) and Prompt Gamma NAA (PGNAA), has been proposed in this research based on Mevex Linac with 5 MeV electron energy and 50 kW power as a neutron source. Based on the MCNPX 2.6 simulation, the optimized configuration contains; tungsten as an electron-photon converter, BeO as a photoneutron target, BeD₂ and plexiglass as moderators, and graphite as a reflector and collimator, as well as lead as a gamma shield. The obtained thermal neutron flux at the beam port is equal to 2.06 × 10⁹ (# /cm².s). In addition, using the optimized neutron beam, the detection limit has been calculated for some elements such as H-1, B-10, Na-23, Al-27, and Ti-48. The HPGe Coaxial detector has been used to measure gamma rays emitted by nuclides in the sample. By the results, the proposed system can be an appropriate solution to measure the concentration and toxicity of elements in different samples such as food, soil, and plant samples.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.413-418
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• 2005

Perovskite $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3[PNN-PZT]$ ceramics were synthesized by conventional ceramic processing technique. In order to modify piezoelectric properties for sensor application in this system, NiO addition was considered to provide $Ni^{+2}$ as an acceptor, which was known to occupy with B site in the structure. The effect of NiO addition up to $8\;mol\%$ on the following piezoelectric properties as well as sintering properties was investigated. When NiO added more than $1\;mol\%$, average grain size was decreased and second phase was found to form. Moreover, the second phase caused decrease in relative dielectric constant $(\varepsilon_{33}T/\varepsilon0)$, electro-mechanical coupling factor $(k_p)$, and piezoelectric charge constant $(d_{33})$, while increasing mechanical quality factor $(Q_m)$. When $1\;mol\%$ NiO was added, density, dielectric properties and piezoelectric properties were abruptly increased.