• 한국재료학회지
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• 제21권8호
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• pp.468-475
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• 2011

[ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

• 한국건축시공학회지
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• 제23권2호
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• pp.153-164
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• 2023

이 연구의 목적은 황산화물(SO_x) 및 질소산화물(NO_x)을 제거할 수 있는 소재를 코팅한 제올라이트 비드를 이용하여 제조된 콘크리트 투수블록의 대기전구물질의 제거율을 평가하는데에 있다. 대기전구물질인 SO_x와 NO_x를 제거하기 위해서 사용된 소재는 이산화티타늄(TiO₂) 분말과 야자각 분말이며, 이 두 소재를 제올라이트 비드에 코팅하였다. 시편은 실제 공장생산라인을 이용하여 제올라이트 비드가 임베디드된 콘크리트 투수블록을 제작하였다. 실험결과 표층에서 야자각 분말로 코팅된 제올라이트 비드가 첨가된 콘크리트 투수블록의 SO_x와 NO_x 제거율은 각각 12.5% 및 99%로서 다른 블록보다도 우수한 성능을 발휘하였다. 또한, 휨 강도 및 미끄럼저항성은 각각 5.3MPa 및 65BPN 이상으로 KS F 4419 및 KS F 4561에서 제시된 값을 만족하였다. 반면, 투수계수는 서울특별시의 투수블록 포장 설계, 시공 및 유지관리 기준으로 협잡물 오염 전후에 각각 3 및 4등급으로 낮은 투수성을 보였다. 결과적으로 표층에서 야자각 분말로 코팅된 제올라이트 비드의 첨가는 충분한 휨강도 및 미끄럼저항성을 확보하면서 자외선에 관계없이 SO_x와 NO_x를 동시에 제거할 수 있지만, 투수성이 낮으므로 이에 대한 보완이 필요하다.

• International Journal of Precision Engineering and Manufacturing
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• 제9권1호
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• pp.51-53
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• 2008

A new nano-particle deposition system (NPDS) was developed for a ceramic and metal coating process. Nano- and micro-sized powders were sprayed through a supersonic nozzle at room temperature and low vacuum conditions to create ceramic and metal thin films on metal and polymer substrates without thermal damage. Ceramic titanium dioxide ($TiO_2$) powder was deposited on polyethylene terephthalate substrates and metal tin (Sn) powder was deposited on SUS substrates. Deposition images were obtained and the resulting chemical composition was measured using X-ray photoelectron spectroscopy. The test results demonstrated that the new NPDS provides a noble coating method for ceramic and metal materials.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.466-467
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• 2006

The anatase particle was facetted at the free surface and a neck formation between the anatase particles prior to the phase transformation occured. This resulted in the severe lattice distortion at the region of the interface near the neck and this can act as the nucleation sites for the phase transformation. The grain growth of rutile particles after the phase transformation grew very fast by the sweeping phenomena of grain boundary. Therfore, It leaded to the microstructure without the rutile phase located in anatase particle.

• 한국세라믹학회지
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• 제39권6호
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• pp.558-565
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• 2002

국내화력발전소의 비산재를 재활용하고자 결정화유리를 제조하여 그 물리적 특성을 평가하였다. 용융석탄재의 융점을 낮게 하기 위하여 CaO와 유리의 결정화를 유도하기 위하여 TiO$_2$를 첨가하였다. 저융점의 유리를 제조 후, 일단계 열처리 (950~105$0^{\circ}C$에서 30~240분)에 의하여 결정화유리를 제조하였다. 그 결과로, 제조된 결정화유리는 새로운 미세한 결정상(a=7.4480, b=10.2381, c=4.3940 A, $\alpha$=94.9, $\beta$=98.6, ${\gamma}$=108.5$^{\circ}$)을 갖고, 높은 경도(7.1~7.6 GPa)와 고 내마모성을 나타냈다. 이처럼 화력발전소의 비산재와 CaO의 공급원인 조개껍질로 제조된 결정화유리는 자원 재활용, 건축자재로 사용될 수 있는 새로운 응용성을 보여주었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.656-658
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• 2004

Pb$(Zr_{0.8}Ti_{0.2})TiO_3$ powder were prepared by the sol-gel method using a solution of Pb-acetate, Zr n-propoxide and Ti iso-propoxide. PZT thick film were fabricated by the screen printing method, and the structural and ferroelectric properties asafunting of the sintering temperature were studied. PZT film thickness, obtained by four screen printing, was approximately $70\sim90{\mu}m$. The relative dielectric constant and the dielectric loss of the PZT thick film sintered at $1050^{\circ}C$t were approximately 676 and 1.4%, respectively. The remanent polarization and the coercive field of the PZT thick film sintered at $1050^{\circ}C$ were $21.15{\mu}C/cm^2$ and 10.1 kV/cm, mapetively

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.527-530
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• 2009

$(Ba_{0.57}Sr_{0.33}Ca_{0.10})TiO_3$(=BSCT) powders, prepared by the sol-gel method, were doped using $MnCO_3$ as the acceptor and $Dy_2O_3$ as the donor. This powder was mixed with an organic vehicle. BSCT thick films were fabricated by the screen-printing techniques on the alumina substrate. The structural and dielectric properties of BSCT thick films were investigated with variation of the $Dy_2O_3$ amount. As a result of the differential thermal analysis (DTA), the exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films showed the XRD patterns of a typical polycrystalline perovskite structure. The average grain size of BSCT thick films decreased with an increasing amount of $Dy_2O_3$. The relative dielectric constant and dielectric loss of the BSCT thick film doped $Dy_2O_3$ 0.1mol% were 4637.4 and 1.6% at 1kHz, respectively.

• 한국재료학회지
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• 제25권8호
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• pp.386-390
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• 2015

Fe-base superalloy powders with $Y_2O_3$ dispersion were prepared by high energy ball milling, followed by spark plasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50 mm were used for the preparation of $Fe-20Cr-4.5Al-0.5Ti-O.5Y_2O_3$ powder mixtures (wt%). The milling process of the powders was carried out in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation (350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) were applied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclic operation and was about 15 nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constant milling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at $1100^{\circ}C$ for 30 min in vacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, a homogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.181-184
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• 2017

Multilayer ceramics in which piezoelectric layers of $0.90Pb(Zr_{0.48}Ti_{0.52})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3-0.05Pb(Zn_{1/3}Nb_{2/3})O_3$ (0.90PZT-0.05PMS-0.05PZN) stack alternately with silver electrode layers were prepared by an advanced low-temperature co-fired ceramic (LTCC) method. The electrical properties and bonding strength of the multilayers were associated with the interface morphologies between the piezoelectric and silver-electrode layers. Usually, the inner silver electrodes are fabricated by sintering silver paste in multi-layer stacks. To improve the interface bonding strength, piezoelectric powders of 0.90PZT-0.05PMS-0.05PZN with an average particle size of $23{\mu}m$ were added to silver paste to form a gradient interface. SEM observation indicated clear interfaces in multilayer ceramics without powder addition. With the increase of piezoelectric powder addition in the silver paste, gradient interfaces were successfully obtained. The multilayer ceramics with gradient interfaces present greater bonding strength as well as excellent piezoelectric properties for 30~40 wt% of added powder. On the other hand, over addition greatly increased the resistance of the inner silver electrodes, leading to a piezoelectric behavior like that of bulk ceramics in multilayers.

• 한국포장학회지
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• 제27권2호
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• pp.55-62
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• 2021

This study aims to reduce the rancid odor generated during the fermentation process of kimchi by inserting zinc oxide (ZnO) into an inorganic porous material with a high surface area to decompose or adsorb the fermentation odor. ZnO activated by the presence of moisture exhibits decomposition of rancid odors. Mixed with Titanium dioxide (TiO₂), a photocatalyst. To manufacture the packaging liner used in this study, NaOH, ZnCl₂, and TiO₂ powder were placed in a tank with diatomite and water. The sludge obtained via a hydrothermal ultrasonication synthesis was sintered in an oven. After being pin-milled and melt-blended, the powders were mixed with linear low-density polyethylene (L-LDPE) to make a masterbatch (M/B), which was further used to manufacture liners. A gas detector (GasTiger 2000) was used to investigate the total amount of sulfur compounds during fermentation and determine the reduction rate of the odor-causing compounds. The packaging liner cross-section and surface were investigated using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to observe the adsorption of sulfur compounds. A variety of sulfur compounds associated with the perceived unpleasant odor of kimchi were analyzed using gas chromatography-mass spectrometry (GC-MS). For the analyses, kimchi was homogenized at room temperature and divided into several sample dishes. The performance of the liner was evaluated by comparing the total area of the GC-MS signals of major off-flavor sulfur compounds during the five days of fermentation at 20℃. As a result, Nano-grade inorganic compound liners reduced the sulfur content by 67 % on average, compared to ordinary polyethylene (PE) foam liners. Afterwards SEM-EDS was used to analyze the sulfur content adsorbed by the liners. The findings of this study strongly suggest that decomposition and adsorption of the odor-generating compounds occur more effectively in the newly-developed inorganic nanocomposite liners.