• Resources Recycling
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• v.17 no.4
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• pp.47-56
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• 2008

The aim of this study is to produce cokes which can be used for the production of ferroalloy, for this purpose, domestic anthracite mixed with plastic was sintered at various condition. The combustion and physical properties of anthracite and plastic, coal separation, and the influence of factors on the strength of coke were investigated. The results of this study are as follows: 1. The three kinds of anthracite from the Samcheok region contained 25 to 30% ash of $100{\mu}m$ over size, and have the caloric value of 5,205 cal/g(TaeAn), 4,893 cal/g(JangSung), 4,873cal/g(KyongDong). 2. The recommendable conditions for heavy-fluid separation of the Samcheok coal are to set the specific gravity of heavy fluid to 2.4 and control the size of coal to $35{\sim}140mesh$. 3. It is concluded that phenolic resin powder, liquefied phenolic resin, SAN, and melamine resin can be used as a binder for the anthracite cokes, from the thermal analysis of various plastics. Especially, the liquefied phenolic resin was considered as the most suitable binder as it would simplify the process.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.145-149
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• 2015

The electrochemical behavior of $Nd_2O_3-La_2O_3-NiO$ mixed oxide including rare earth resources has been studied to synthesize $La_{0.5}Nd_{0.5}Ni_5$ alloy in a LiCl molten salt. The $Nd_2O_3-La_2O_3-NiO$ mixed oxide was converted to $NiNd_2O_4$ (spinel) and $LaNiO_3$ (perovskite) structures at a sintering temperature of $1100^{\circ}C$. The spinel and perovskite structures led a speed-up in the electrolytic reduction of the mixed oxide. Various reaction intermediates such as Ni, $NiLa_2O_4$ were observed during the electrochemical reduction by XRD analysis. A possible reaction route to $La_{0.5}Nd_{0.5}Ni_5$ in the LiCl molten salt was proposed based on the analysis result.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.182-186
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• 2003

A new axial pressing method using pulse magnetizing field was studied to improve the remanence of Nd-Fe-B sintered magnets. In order to make near-net shape green compacts of butterfly, disk, or coin magnets, conventional axial-type pressing has been normally used. However, compared to the transverse-type pressing, it is not possible to obtain higher remanence by this method because the magnetic alignment of powder begins to deteriorate when the density of green compacts increases over a critical value. On the other hand, we found that an axial pressing under pulse magnetizing field was very effective to increase the degree of magnetic alignment of powder, yielding remanences even higher than those obtained by the transverse pressing. In this study, it was revealed that appropriate tapping density and how to apply pulse magnetic held were important to improve the grain alignment and thus remanence of Nd-Fe-B sintered magnet.

• Analytical Science and Technology
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• v.16 no.2
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• pp.117-124
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• 2003

Oxygen to metal ratio has been measured by wet and dry chemical analysis to study the properties of sintered $UO_2$ pellets and $U_3O_8$ in the lithium reduction process of spent pressurized water reactor fuels. Uranium dioxide pellets simulated for the spent PWR fuels with burnup values of 20,000~60,000 MWd/MtU were prepared by mixing $UO_2$ powder and oxides of fission product elements, pelleting the powder mixture and sintering it at $1,700^{\circ}C$ under a hydrogen atmosphere. For wet chemical analysis, the simulated spent fuels were dissolved with mixed acid (10 M HCl : 8 M $HNO_3$, 2.5 : 1, v/v) using acid digestion bomb technique. The total amount of uranium and fission products added in the simulated spent fuels were measured using inductively coupled plasma atomic emission spectrometry. Weight change of the simulated fuel during its oxydation was measured by thermogravimetry and then the O/M ratio result was compared to that obtained by wet chemical analysis. Influence of $Mo_{0.4}-Ru_{0.4}-Rh_{0.1}-Pd_{0.1}$, quaternary alloy, on the determination of O/M ratio was investigated.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.58-65
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• 2005

The $LaCrO_3$-dispersed Cr alloys for metallic interconnect of solid oxide fuel cell were prepared as a function of $LaCrO_3$ content in the range of 5 to 25 vol.% and were sintered at 1500$^{\circ}C$ under an Ar atmosphere with 5 vol.% $H_2$. The sintering and oxidation behaviors of these alloys were examined. The alloys indicated a good sinterability above 95% relative density at a given sintering condition, and their sintering densities is independent on $LaCrO_3$ content. The $LaCrO_3$ particles of the sintered alloys were concentrated on interfaces of Cr particles, and the size of the Cr particles increased with decreasing $LaCrO_3$ content, which is caused by inhibited grain growth of Cr particle by $LaCrO_3$ particle. The oxidation test showed all $LaCrO_3$-dispersed Cr alloys have good oxidation resistance as compared with pure Cr, which is attributed to presence of $LaCrO_3$ at the interface at which the oxidation reaction occurs rapidly. The Cr alloys with about 15 vol.% $LaCrO_3$ are very resistant to oxidation.

• Journal of Powder Materials
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• v.21 no.4
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• pp.277-285
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• 2014

The effects of processing parameters on the flow behavior and microstructures were investigated in hot compression of powder metallurgy (P/M) Ti-6Al-4V alloy. The alloy was fabricated by a blended elemental (B/E) approach and it exhibited lamellar ${\alpha}+{\beta}$ microstructure. The hot compression tests were performed in the range of temperature $800-1000^{\circ}C$ with $50^{\circ}C$ intervals, strain rate $10^{-4}-10s^{-1}$, and strain up to 0.5. At $800-950^{\circ}C$, continuous flow softening after a peak stress was observed with strain rates lower than $0.1s^{-1}$. At strain rates higher than $1s^{-1}$, rapid drop in flow stress with strain hardening or broad oscillations was recorded. The processing map of P/M Ti-6Al-4V was designed based on the compression test and revealed the peak efficiency at $850^{\circ}C$ and $0.001s^{-1}$. As the processing temperature increased, the volume fraction of ${\beta}$ phase was increased. In addition, below $950^{\circ}C$, the globularization of phase at the slower strain rate and kinking microstructures were found. Based on these data, the preferred working condition of the alloy may be in the range of $850-950^{\circ}C$ and strain rate of $0.001-0.01s^{-1}$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.33-55
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• 2016

PVD(Physical Vapour Deposition)코팅은 70년대 미국의 Multi-arc이란 기업에 의해 질화물계나 탄화물계 피막 증착이 가능한 아크이온플레팅(Arc Ion Plating) 기술이 산업에 소개되어, 주로 내마모나 내구성을 요구하는 금형, 절삭공구, 산업용 부품 분야 등에 적용되면서 꾸준한 성장세를 거듭해 왔다. 최근 들어 PVD기술은 그 수요의 급증과 더불어 보다 진화된 형태의 코팅장치 및 코팅피막들이 산업에 소개 되고 있다. 먼저 절삭가공분야에는 new composition, nano composite, multi-element composition, multi-layer, SML(Self Modification Layer)등의 코팅피막들이 단독 또는 조합된 형태로 개발되어 철계 소재를 대상으로 고경도 소재의 고속가공, 저경도~중경도 소재의 중속~고속 광범위영역에서 동시 절삭을 가능케 하였고, 비철.비금속 소재 절삭용으로 종전의 가스방식의 DLC(a-C:H)코팅을 훨씬 능가하는 ta-C Plus(Ultra super DLC) 코팅이 개발되어 고 Si함량의 Al-Si계 합금, Cu-W계, 고 섬유 CFRP, CFRM 및 반소결 상태의 세라믹 소재들을 황삭에서 정삭까지 단일 공정으로 절삭이 가능한 고성능 공구들이 개발보급되고 있다. 금속 성형분야에는 고장력 강판을 냉간에서 성형 가능한 Lubricative multi-layer coating, 열간 또는 고온에서 성형이 가능한 functional multi layer과 이형성이 더한층 개선된 dimpled(or embossed) functional multi layer 코팅들이 개발되어 산업현장에 빠르게 확산되고 있다. PVD 코팅의 또 다른 주요 적용분야로 의료분야를 들 수 있는데, 이는 코팅의 대다수가 고경도의 생체친화적인 특성을 가진데 착안되었으며, 흔히 현대성 질환이라 일컫는 과민성 체질, 과체중 및 허약체질 환자의 증가와 각종 재해 및 사고의 증가 및 인간 수명 증가에 따른 인공적인 시술의 요구증가에 편승하여 이 분야의 시장 또한 가파르게 성장하고 있다. 또한 대량으로 양산 적용단계에 접어든 자동차 핵심부품들을 비롯해서 각종 산업용, 방산용 기계 부품에도 성능 향상, 내구성 향상, 환경친화성 등 다양한 목적으로 확대 적용되고 있는 사례들을 본 발표를 통해 간략하게나마 소개하고자 한다.

• Journal of Powder Materials
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• v.15 no.3
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• pp.239-243
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• 2008

Ni-W(1-5 at.%) alloy rods were made by powder metallurgy process including powder mixing, compacting and subsequent sintering. Ni and W powder of appropriate compositions were mixed by a ball milling and isostatically pressed in a rubber mold into a rod. The compacted rods were sintered at $1000^{\circ}C-1150^{\circ}C$ at a reduced atmosphere for densification. The lattice parameters of Ni-W alloys were estimated by a high resolution neutron powder diffractometer. All sintered rods were found to have a face centered cubic structure without any impurity phase, but the diffraction peak locations were linearly shifted with increasing W content. The lattice parameter of a pure Ni rod was $3.5238{\AA}$ which is consistent with the value reported in JCPDS data. The lattice parameter of N-W alloy rods increased by $0.004{\AA}$ for 1 atomic % of W, which indicates the formation of a Ni-W solid solution due to the substitution of nickel atoms by tungsten atoms of larger size.

• Journal of Powder Materials
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• v.23 no.5
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• pp.397-401
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• 2016

A lean alloy is defined as a low alloy steel with a minimum amount of the alloying element that maintains the characteristics of the sintered alloy. It is well known that the addition of elements such as Cr, P, Si, or Mn improves the mechanical characteristics of the alloy, but decreases the sinterability. The mother alloy is used to avoid an oxidation reaction with the alloying elements of Cr, P, Si or Mn. The purpose of this study is to determine the change in the mechanical properties of Fe-P-Mo and Fe-P-Mn alloys as a result of the addition of Si. In this article, the Fe-P-Mo and Fe-P-Mn alloys to which Si is added are compacted at $7.0g/cm^3$ and then sintered in $H_2-N_2$ at $1120^{\circ}C$. The P around the macropores and large grains reduces due to the formation of $SiO_2$ as the Si content increases. This is caused by the increase in strength owing to reducing intergranular fracture by suppressing the reaction with oxygen.