• 한국추진공학회지
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• 제8권1호
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• pp.1-7
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• 2004

과염소산암모늄(AP)의 N-메틸피롤리돈(NMP) 용액으로부터 초미세 크기를 갖는 과염소산암모늄(UFAP) 결정의 결정화 연구를 수행하였고, 침전된 결정들의 특성들을 scanning electron micrograph(SEM)와 X-ray diffraction(XRD) 그리고 thermogravimetric analysis(TGA)를 사용하여 분석하였다. 침전용매로 클로로포름, 염화메틸렌 그리고 톨루엔이 사용되었을 경우, 2$\mu\textrm{m}$ 이하의 크기를 갖는 결정들이 제조되었다. 제조된 UFAP의 결정학적 특성과 열분해 거동은 상용으로 사용되는 AP와 거의 유사하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.733-734
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• 2006

Granulated powders, prepared from PF-5F($D_{50}=4(\mu}m$), PF-10F($D_{50}=6{\mu}m$) and PF-20F($D_{50}=10{\mu}m$) water atomized powder, were compacted, debound and sintered to evaluate the properties of sintered parts. As a result, the relative sintered density of about 97% at sintering temperature of 1423K was obtained. It can be considered that by using granulated finer particle size powder, mechanical properties of sintered parts were also improved.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.523-532
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• 1999

This study is aimed to obtain fundamental knowledge of pulse laser welding phenomena the authors investigated the structure and composition of evaporated particles of Al alloys in air and in the Ar atmosphere during pulsed laser welding. The ultra-fine particles of 5 to 100nm diameter in a globular or irregular shape were formed in laser-induced plasma and the main structure was $MgAl_2O_4$ The composition of particles was ifferent depending on the power density of a laser beam; namely under the low power density conditions magnesium was predominant in the parti-cles while aluminium content increased with an increase in the power density. These results were attributed to evaporation phenomena of metals with different boiling points and latent heats of vaporization. On the other hand the number density of laser-induced plasma species was obtained by Saha's equation. it was confirmed that the number density depends upon the plasma tempera-ture and total pressures.

• 한국분말재료학회지
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• 제26권6호
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• pp.493-501
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• 2019

In this work, ultra-fine calcium oxide (CaO) powder derived from eggshells is used as the starting material to synthesize mineral trioxide aggregate (MTA). The prepared CaO powder is confirmed to have an average particle size of 500 nm. MTAs are synthesized with three types of fine CaO-based powders, namely, tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate (C3A). The synthesis behavior of C3S, C2S and C3A with ultra-fine CaO powder and the effects of C₃A content and curing time on the properties of MTA are investigated. The characteristics of the synthesized MTA powders are examined by X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), and a universal testing machine (UTM). The microstructure and compressive strength characteristics of the synthesized MTA powders are strongly dependent on the C3A wt.% and curing time. Furthermore, MTA with 5 wt.% C3A is found to increase the compressive strength and shorten the curing time.

• 한국자기학회지
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• 제6권1호
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• pp.21-27
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• 1996

초미립 자성 입자를 이용한 MP(metal particle) 테이프의 특성을 개선하기 위하여, 제조 공정상의 여러가지 인자의 영향을 조사하였다. kneading 조건, milling 고형분, coating 두께, 배향조건, calender 조건, 경화 조건 등 주요 제조 조건에 따른 MP 테이프의 휘도(luminance) S/N, RF 재생 출력등의 전자 변환 특성과 광택, 점도, 강성 (stiffness)등의 물리특성이 조사하였으며, 이로부터 각 공정의 최적 제조 조건을 결정하였다. 이상의 제조 공정 조건으로 제조된 테이프는 High Band 8 mm 비디오 테이프에서 요구되는 전자변환특성, 툴리특성 및 내구성 등의 기본특성을 모두 만족하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.36-37
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• 2006

This study aims to investigate the usage of nano-scale particles in a micro metal injection molding ($\mu$-MIM) process. Nanoscale particle is effective to improve transcription and surface roughness in small structure. Moreover, the effects of hybrid micro/nano particles, Cu/Cu and SUS/Cu were investigated. Small dumbbell specimens were produced using various feedstocks prepared by changing binder content and fraction of nano-scale Cu particle (0.3 and $0.13{\mu}m$ in particle size). The effects of adding the fraction of nano-scale Cu powder on the melt viscosity of the feedstock, microstructure, density and tensile strength of sintered parts were discussed.

• 한국분말재료학회지
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• 제19권1호
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• pp.19-24
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• 2012

The consolidation results of fine tungsten powders, W-Cu composite and W/Cu FGM by using a novel method combining resistance sintering with ultra high pressure have been reviewed. The densification effects of the consolidation parameters, including pressure, input power and sintering time, have been investigated. The sintering mechanism of this method was quite different from other sintering methods. Particle rearrangement, sliding, distortion and crushing due to the ultra high pressure are the dominant mehanisms at the initial stage, then the dominant sintering mechanisms are transient arc-fused processes controlled by the input power.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.441-444
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• 2008

본 연구에서의 초고성능 콘크리트(Ultra High Performance Concrete, UHPC)는 모래, 시멘트, 실리카퓸, 석영미분말, 강섬유 및 고성능감수제 등으로 구성되며, 평균입경 약 0.5mm이하의 아주 작은 입자들로 구성된다. 일반적으로 석영미분말는 일정크기 이상의 공극을 메움으로써 물리적 성능개선의 효과가 있으며 또한 높은 $SiO_2$함량을 가지므로 고온 또는 고압의 양생조건에서 시멘트 수화물과의 화학반응을 통해서도 성능 향상효과가 있는 것으로 알려져 있다. 본 연구에서는 상압, $90^{\circ}C$ 증기양생 조건에서 석영미분말의 입자크기가 초고성능 콘크리트의 역학적 특성에 어떠한 영향을 미치는지에 대해 알아보고자 하였으며, 평가항목으로는 굳지 않은 상태에서의 유동성과 굳은 상태에서의 압축강도, 극한변형률, 탄성계수 및 휨강도를 평가하였다. 석영미분말의 입경크기의 영향은 약 $2{\mu}m$에서 $26{\mu}m$까지의 범위에서 고려하였으며, 입경 크기가 작을수록 유동성 및 강도특성이 모두 향상되는 것으로 나타났다.

• Advances in concrete construction
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• 제16권3호
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• pp.169-176
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• 2023

The aim of the study was to establish the influence of particle size, chemical and phase composition of fine microspherical high-calcium fly ash (HCFA), as well as superplasticizer content on the strength of cementless composite materials based on 100% HCFA and mixtures of HCFA with Portland cement (PC). For the initial HCFA fractions, the particle size distribution, chemical and quantitative phase composition were determined. The compressive strength of cured composite materials obtained at W/B 0.4 and 0.25 was determined at a curing time of 3-300 days. For cementless materials, it was found that a change in the particle size d90 from 30 ㎛ (fraction 3) to 10 ㎛ (fraction 4) leads to an increase in compressive strength by more than 2 times. Compressive strength increases by at least another 2.2 times with the addition of Melflux 5581F superplasticizer (0.12%) and at W/B 0.25. The HCFA-PC blends were investigated in the range of 60-90% HCFA and the maximum compressive strength was found at 80% HCFA. On the basis of 80% HCFA-20% PC blend, the samples of ultra-high strength (108 and 150 MPa at 28 and 100 days of hardening) were obtained with the addition of 0.3% Melflux 5581F and 5% silica fume. The quantitative phase composition was determined for composite materials with a curing age of 28 days. It has been established that in a sample with ultra-high strength, a more complete transformation of the initial phases of both HCFA and PC occurs as compared to their transformation separately.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.109-116
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• 2011

To measure the traffic pollutants with high temporal and spatial resolution under real conditions a mobile emission laboratory (MEL) was designed and built in KIST with close-cooperation with KIMM and Yonsei university. The equipment of the mini-van provides gas phase measurements of CO, NOx, $CO_2$, THC (Total hydrocarbon) and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and a condensation particle counter (CPC). The inlet sampling port above the bumper enables the chasing of different type of vehicles. This paper introduces the construction and technical details of the MEL and presents data from the car chasing experiment of diesel and CNG city bus. The dilution ratio was increased rapidly according to the chasing distance. Most particles from the diesel city bus were counted under 300 nm and the peak concentration of the particles was located between 40-60 nm. However, the most particles from the CNG city bus were nano particle counted under 50 nm.