• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1999년도 춘계학술대회 및 발표대회 강연 및 발표논문 초록집
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• pp.5-5
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• 1999

The Principal deficiency of the existing notion about the sintering-mixtures consists in the fact that almost no attention is focused on the Phenomenon of alloy formation during sintering, its connection with dimensional changes of powder bodies, and no correct ideas on the driving force for the sintering process in the stage of establishing chemical equilibrium in a system are available as well. Another disadvantage of the classical sintering theory is an erroneous conception on the dissolution mechanism of solid in liquid. The two-particle model widely used in the literature to describe the sintering phenomenon in solid state disregards the nature of the neighbouring surrounding particles, the presence of pores between them, and the rise of so called arch effect. In this presentation, new basic scientific principles of the driving forces for the sintering process of a two-component powder body, of a diffusion mechanism of the interaction between solid and liquid phases, of stresses and deformation arising in the diffusion zone have been developed. The major driving force for sintering the mixture from components capable of forming solid solutions and intermetallic compounds is attributed to the alloy formation rather than the reduction of the free surface area until the chemical equilibrium is achieved in a system. The lecture considers a multiparticle model of the mixed powder-body and the nature of its volume changes during solid-state and liquid-phase sintering. It explains the discovered S-and V-type concentration dependencies of the change in the compact volume during solid-state sintering. It is supposed in the literature that the dissolution of solid in liquid is realised due to the removal of atoms from the surface of the solid phase into the melt and then their diffusicn transfer from the solid-liquid interface into the bulk of liquid. It has been shown in our experimental studies that the mechanism of the interaction between two components, one of them being liquid, consist in diffusion of the solvent atoms from the liquid into the solid phase until the concentration of solid solutions or an intermetallic compound in the surface layer enables them to pass into the liquid by means of melting. The lecture discusses peculimities of liquid phase formation in systems with intermediate compounds and the role of the liquid phase in bringing about the exothermic effect. At the frist stage of liquid phase sintering the diffusion of atoms from the melt into the solid causes the powder body to grow. At the second stage the diminution of particles in size as a result of their dissolution in the liquid draws their centres closer to each other and makes the compact to shrink Analytical equations were derived to describe quantitatively the porosity and volume changes of compacts as a result of alloy formation during liquid phase sinteIing. Selection criteria for an additive, its concentration and the temperature regime of sintering to control the density the structure of sintered alloys are given.

• 대한원격탐사학회지
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• 제37권6_2호
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• pp.1849-1858
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• 2021

본 연구에서는 2011년부터 2020년까지 수원시 내에서 측정한 기상과 미세먼지 농도 자료를 이용하여 월별, 연별 기상과 미세먼지 농도의 변화 경향을 분석하였고, 수원시 미세먼지 농도(PM₁₀, PM_2.5)와 기상 인자(풍속, 기온), 도시공간정보(건물부피비, 도로면적비) 간의 연관성을 조사하였다. 도시대기측정소의 도시공간정보를 산출하기 위해 국토지리정보원과 환경공간정보서비스에서 제공하는 수치지형도의 건물 고도 정보와 세분류 토지피복자료의 도로 정보를 이용하였고, 도시대기측정소를 중심으로 2 km×2 km 영역의 건물 부피와 도로면적을 계산하였다. 기상측정자료를 분석한 결과, 수원시는 주로 서풍과 서북서풍이 우세하게 나타났고, 평균풍속은 봄철에 높았다. 미세먼지 농도는 여름철(7월~9월)에 낮았고 봄철과 겨울철에 비교적 높았다. 연별 추이를 분석한 결과, 대부분의 지점에서 2020년에 미세먼지 농도가 가장 낮았다. 측정 미세먼지 농도는 풍속과 기온과 약한 음의 상관관계를 보였는데, 기온과 PM_2.5 농도의 상관성이 상대적으로 높았다. 6개 도시대기측정소의 PM₁₀, PM_2.5 평균 농도와 도시매개수의 상관성을 조사한 결과, PM₁₀ 농도는 도로 배출이나 건물에 의한 지상 풍속 감소의 영향보다는 외부로부터의 유입 영향을 더 크게 받았고, PM_2.5 농도는 국지적 배출이나 건물에 의한 풍속 감소 영향을 더 크게 받는 것으로 분석된다.

• 한국재료학회지
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• 제22권1호
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• pp.54-60
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• 2012

The particle size of MgO was examined as a function of the Na content in $Mg(OH)_2$ powders and the calcination temperature. $Mg(OH)_2$ suspension was obtained by dropwise precipitation of $Mg(NO_3)_2{\cdot}6H_2O$ and NaOH solutions. The suspension was diluted by varying the dilution volume ratio of distilled water to $Mg(OH)_2$ suspension to change the Na salt concentration in the suspension. $Mg(OH)_2$ slurry was filtered and dried at $60^{\circ}C$ under vacuum, and then its $Mg(OH)_2$ powder was calcined to produce MgO with different amount of Na content at $500\sim900^{\circ}C$ under air. Investigation of the physical and chemical properties of the various MgO powders with dilution ratio and calcination temperature variation was done by X-ray diffraction, transmission electron microscopy, BET specific surface area and thermal gravimetric analysis. It was observed that MgO particle size could depend on the condition of calcination temperature and dilution ratio of the $Mg(OH)_2$ suspension. The particle size of the MgO depends on the Na content remaining in the $Mg(OH)_2$ powder, which powder was prepared by changing the dilution ratio of the $Mg(OH)_2$ suspension. This change increased as the calcination temperature increased and decreased as the dilution ratio increased. The growth of MgO particle size according to the increase of temperature was more effective when there was a relatively high content of Na. The increase of Na content lowered the temperature at which decomposition of $Mg(OH)_2$ to MgO took place, thereby promoting the crystal growth of MgO.

• 한국대기환경학회지
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• 제5권1호
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• pp.68-78
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• 1989

The heavy metal of suspended particulates with human health has long been studied in environmental interest concerned. This study was intended to identify harmful heavy metals of the ambient air borne dusts which were related with the respirable sizes in the aerodynamics. Two sampling sites were selected comparatively; one was in the Shinchon area, which is the commercial district with heavy traffic and the other site was in the Bulgwang area which is residential area. The supended particulates were sampled by high volume air sample with 6 cascade impactor stages. The heavy metals in terms of As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn were determined by stomic absorption spectrometry or inductively coupled plasma emission spectrometry. The samples weretaken bimothly for seven consecutive days from May 1987 to March 1988. The annual average concentration of the respirable suspended dust of which diameter is less than 10$\mum$ was 152.59 $\mug/m^3$ of the Shinchon air samples; the respirable dust was equivalent to approximately 85% of the total suspended particulates. The annual average concentration of the respirable suspended dust of the Bulgwang air samples was 112.56 $\mug/m^3$; that was approximately 86% of the total suspended particulates. The concentration of heavy metals was investigated in relation to the particle size. The concentration of Cr, Fe, Mn and V were tended to be much more in the coarse particles than in the fine particles. Cd and Pb in the fine particles were more than in the coarse particles. In the partial correlation coefficients; in the Shinchon area, high correlations among Fe, Se and Mn were determined; it is assumed that those sources would be originated from coal, gasolineand diesel. In Bulgwang area, would be high correlation among Fe, Se, Hg and Mn considered to be originated from coal, Bunker-C and heavy oil as well. From the above results, the hazardous heavy merals in air should be measured and controlled in originally their sources.

• 한국대기환경학회지
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• 제17권2호
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• pp.133-145
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• 2001

The receptor modeling is one of the statistical methods to achieve reasonable air pollution strategies. The pur-pose of this study was to survey the concentration variability oi inorganic elements and ionic species in the PM-10 particles, to qualitatively characterize emission sources by an advanced algorithm called positive matrix factoriza-tion(PMF) as a receptor model that can strictly provide results in every loading matrix. A total of 254 samples was collected by a PM-10 high volume air sampler from Mar. 1997 to Feb. 1998 in Kyung Hee University at Suwon Campus. Fourteen chemical species(Zn, Cu, Fe, Pb, Al, Mn, $Na^{+}$, NH$_4$+, $K^{+}$, $Mg^{2+}$, $Ca^{2+}$, $SO_4^{2-}$, $NO_{3}^{-}$, and $Cl^{-}$) were determined by AAS and IC methods. The study results showed that the average monthly concentration of PM-10 particles were 86.3$\mu\textrm{g}$/$\textrm{m}^3$ in March (maximum) and 28.5$\mu\textrm{g}$/$\textrm{m}^3$ in August(minimum), respectively. The concentrations of Na+, NH$_4$+, $K^{+}$ and $Cl^{-}$ in winter, $Mg^{2+}$, $Ca^{2+}$ and $NO_{3}^{-}$, in spring, and $SO_4^{2-}$ in summer showed the largest peak concentration for the respective season. Through and app-lication of a PMF program of Pm-10 concentration data of Suwon, 9 sources were qualitatively identified , such as incineration source, oil burning source, soil related source, open burning source automobile source, coal burning sources, secondary sulfate related source, and secondary nitrate related source.

• Journal of Advanced Marine Engineering and Technology
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• 제30권3호
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• pp.403-412
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• 2006

The effect of a wall temperature on the soot deposition process from a diffusion flame to a solid wall was investigated in a microgravity environment to attain in-situ observations of the process. The fuel for the flames was an ethylene ($C_2H_4$). The surrounding oxygen concentration was 35% with surrounding air temperatures of $T_a=600K$. In the study, three different wall temperatures. $T_w$=300, 600, 800K, were selected as major test conditions. Laser extinction was adopted to determine the soot volume fraction distribution between the flame and burner wall. The experimental results showed that the maximum soot volume fractions at $T_w$=300, 800 K were $8.8{\times}10^{-6},\;9.2{\times}10^{-6}$, respectively. However, amount of soot deposition on wall surface was decreased because of lower temperature gradient near the wall with increasing wall temperature. A numerical simulation was also performed to understand the motion of soot particles in the flame and the characteristics of the soot deposition to the wall. The results from the numerical simulation successfully predicted the differences in the motion of soot particles by different wall temperature near the burner surface and are in good agreement with observed soot behavior that is, the 'soot line', in microgravity.

• 대한환경공학회지
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• 제38권8호
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• pp.459-467
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• 2016

본 연구는 기기중성자방사화분석법을 이용하여 다중이용시설 중 지하철 객차 내 실내공기 중 미세먼지(PM10)의 미량원소 분포특성과 실내공기질을 평가하고, 향후 실내공기질의 효율적인 제어를 위한 객차 내 PM10의 오염원을 평가하고자 하였다. 대전광역시에서 운행 중인 지하철 객차 내에서 채취한 PM10의 평균농도는 $59.3{\pm}14.5{\mu}g/m^3$이었고, 지하철 객차 내 PM10 중 24종의 원소성분을 정량분석한 결과, 농도는 $10^{-3}{\sim}10^5ng/m^3$ 범위에 걸쳐 넓게 분포하였으며, Fe ($12.5{\mu}g/m^3$)의 농도가 특히 높았다. 이는 지하철 브레이크 시스템과 철로 및 차륜 마찰과 같은 지하철 운행에 의하여 Fe가 상당히 부유되기 때문인 것으로 판단된다. 분석된 미량원소 농도를 바탕으로 오염원을 평가한 결과, brake-nonferrous metal particle, resuspended rail dust, fuel combustion, vehicle exhaust, black carbon, Cr-related가 주요 오염원인 것으로 나타났다.

• Korean Chemical Engineering Research
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• 제47권6호
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• pp.727-733
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• 2009

슬러리 기포탑에서 침강성 탄산칼슘의 평균입도와 모폴로지의 변화에 대한 수산화칼슘의 농도(0.16~0.64 wt%), 총 부피유량(3~6 L/min) 및 이산화탄소의 부피분율(0.3~0.6)의 영향을 나타내었다. 실험에 사용한 반응기는 높이가 1.0 m, 직경이 0.11 m이고 중앙에는 직경 4 cm인 튜브가 들어있는 슬러리 기포탑이다. 반응 시간에 따른 수산화칼슘의 전화율을 구하기 위해 FT-IR을 이용하여 수산화칼슘과 탄산칼슘 함량비에 따른 검량곡선을 구하였다. 수산칼슘의 포화농도인 0.16 wt%에서 이산화탄소의 유량에 따른 침강성 탄산칼슘의 모폴로지를 살펴보면 반응 속도가 증가할수록 결정 크기는 증가하는 경향을 보이며 결정의 형태는 단일 결정으로 존재하는 입자들이 많아졌다. 또한 수산화칼슘의 농도가 증가할수록 결정 크기는 감소하지만 입자들간의 응집에 의해 탄산칼슘의 평균 입도는 증가하는 것을 확인하였다.

• 약학회지
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• 제34권1호
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• pp.1-10
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• 1990

Total suspended particulate (TSP) in the atmosphere was collected and size-fractionated by Andersen high volume air sampler for the past two years (Mar. 1987-Feb. 1989) in Seoul. The concentrations of several polycyclic aromatic hydrocarbons and heavy metals were determined to investigate the atmospheric concentrations, seasonal variations and its relationship with the size distribution of suspended particulate matter. The arithmetic mean concentration of total suspended particulate was $229.48\;{\mu}g/m^3$. The concentrations of heavy metals were $2971.94\;ng/m^3$ for Fe, $767.75\;ng/m^3$ for Zn, $765.80\;ng/m^3$ for Pb, $218.40\;ng/m^3$ for Cu, $129.91\;ng/m^3$ for Mn, respectively. And the concentration of PAHs were $3.23\;ng/m^3$ for benzo(a)pyrene, $2.71\;ng/m^3$ for benzo(k)fluoranthene, $4.53\;ng/m^3$ for benzo(ghi)perylene, respectively. The mass-size distribution of TSP was lowest in the particle size range $1.1-3.3\;{\mu}m$ increased as the particle size increased or decreased. But PAHs, Pb and Zn abounded in particles below $2.0\;{\mu}m$, while Fe and Mn abouned in particles above $2.0\;{\mu}m$. TSP and its chemical compositions showed the seasonal variations. The concentrations of anthrophogenic origin like TSP, PAH and heavy metals in the fine particles were highest in winter and lowest in summer. PAH and Ph analyzed showed significant correlations with each other and with TSP concentration in fine particles, indicating that the particles in which they are contained have a similar behavior in the atmosphere.

• 공업화학
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• 제17권2호
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• pp.188-193
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• 2006

용액의 pH, 주입방법, 온도, 유량의 변화를 주면서 질산알루미늄($Al_{3}(NO_{3})_3{\cdot}9H_{2}O$)을 암모니아수($NH_{4}OH$)로 침전시켜 베마이트(Boehmite)를 합성하였다. 베마이트 상이 형성되는 pH 범위와 입자의 형상과 기공특성에 미치는 합성 조건의 영향을 조사하였다. 베마이트는 반응 용액의 pH가 7.5~9일 때 형성되었고, P2jet 주입방법은 침전이 일어나는 동안 pH를 일정하게 유지할 수 있어 용액내의 반응에 참여하는 이온의 농도가 일정하게 유지되어 균일한 크기의 입자와 기공을 형성할 수 있게 하였다. 따라서 비표면적과 기공부피 두 가지 동시에 향상되었다. 온도가 올라갈수록, 유량이 감소할수록 비표면적과 기공부피가 증가함을 보이고, $60^{\circ}C$ 이상에서는 미세섬유모양의 입자를 얻을 수 있었다. 최적의 조건은 pH 9에서 P2jet 방법으로 주입하고 반응온도 $90^{\circ}C$와 유량 2.5 mL/min을 유지하였을 경우로 비표면적은 $385.46m^2/g$이고 기공 부피는 1.0252 mL/g을 가지는 평균 10 nm의 기공이 형성된 다공성 베마이트를 얻을 수 있었다.