• 한국결정학회지
• /
• 제9권1호
• /
• pp.48-52
• /
• 1998

Nd2O3, BaCo3, Co3O4를 출발물질로 하여 새로운 Nd3Ba5Co4O15상을 고상반응법에 의하여 합성하였다. 반응 온도는 1200℃ 로 하였고 열처리 중 반복적인 혼합을 실시하였다. Nd3Ba5Co4O15상의 결정구조는 분말 X-선회절법에 의한 데이터를 Rietveld법을 이용하여 정밀화하였다. 출발 모델은 Nd3.43Ba4.42Co2.23Al1.77O15의 결정구조를 따랐고 공간군 P63mc(186), 격자상수 a=11.636(5) Å, c=6.846(3) Å. 최종 신뢰도 R값은 Rwp=0.097, Rp=0.068로 나타났다. 이 상의 결정구조는 CoVICoIV3O15 클러스터로 구성되어 있고 이 클러스터는 CoVI 육면체가 3개의 CoIV 사면체와 corner sharing하는 형태를 보인다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.215-216
• /
• 2002

This paper describes the wear characteristics of WC-Co cemented carbides machined with Wire-cut or Die-sinking EOM. We prepared the specimens with different grades of grinding to remove the affected layer after the EDM. These specimens were experimented by block-on-cylinder type tribometer. The result indicated that although the hardness of the affected layer was lower than that of the bulk, wear resistance was increased. In order to investigate the cause of the increase in wear resistance of the affected layer, the layer was observed and analyzed by SEM and ESCA. We also discussed the mean free path of Co phase.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제20권5호
• /
• pp.41-46
• /
• 2015

Three types of experiments, based on the physical properties of oily sludge landfilled soil, were conducted to recover total petroleum hydrocarbons (TPH) from the soil. These experiments included gravity separation, solvent extraction using water, and air floatation. The oil portion was not easily separated from the wet (raw) soil because water molecules aggregate the soil particles, despite the fact that the soil was sandy. However, the drying and grinding processes destroyed the aggregates, causing the TPH recovery to increase to approximately 60% when air floatation was used. The drying process decreased the specific gravity of the soil sample, thereby enhancing the overall recovery of TPH from the soil. Although thermal desorption and/or incineration are common choices for heavily dumped sites, physical separation can recover the oil portion instead of simply removing it.

• 열처리공학회지
• /
• 제10권3호
• /
• pp.165-171
• /
• 1997

Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.

• 한국결정학회지
• /
• 제13권1호
• /
• pp.31-35
• /
• 2002

카리장석을 여러 가지 가스 분위기 하에서 기계화학적으로 처리함으로써 안료의 합성 가능성을 연구하였다. 카리장석에 Cu 및 TiO₂ 분말을 첨가하고, 이를 N₂, O₂, He, CO₂, H₂ 및 공기 분위기에서 유성 볼밀을 이용하여 분쇄시간을 변경시키며 분쇄하였다. Cu를 1 wt% 첨가하고 24시간 분쇄한 분말을 1200℃에서 20분간 하소한 결과 분쇄 분위기에 따라서 다양한 색상이 나타남을 확인하였다. 즉 공기 중에서 분쇄한 소성산물은 녹색, O₂센서는 검은색, CO₂센서는 짙은 녹색, H₂에서는 갈색, He에서는 보라색 그리고 N₂ 가스 하에서는 엷은 푸른색의 안료원료를 얻을 수 있었다

• 자원리싸이클링
• /
• 제24권2호
• /
• pp.55-61
• /
• 2015

본 연구는 폐타이어 재활용을 위하여 수행된 전처리 공정이 재생 고무분말의 기계적 물성에 미치는 영향을 조사하는 것을 목적으로 하였다. 이를 위하여 분쇄 및 탈황공정을 통하여 생산된 폐타이어 고무분말을 재가황한 후 인장시험, 충격시험 및 파단면 관찰을 수행하였다. 분쇄 공정을 거쳐서 생산된 고무분말은 입자크기가 작아질수록 그 표면적이 증가되며 인장강도와 연신율이 모두 증가되었다. 반면에 탈황공정을 거친 고무분말은 내부에 존재하는 황과의 가교결합이 줄어들어서 이후의 가황처리 후에도 인장강도와 연신율이 모두 증가되었다. 따라서 폐타이어 재활용을 위한 전처리 공정은 재활용 분말을 일정크기로 분쇄한 후 탈황공정까지를 수행한 고무분말을 제조하는 것이 단순 분쇄공정만을 거친 재활용 고무분말에 비하여 가황 시에 연신율을 보다 효율적으로 증가시킬 수 있음을 확인하였다.

• Journal of Welding and Joining
• /
• 제31권3호
• /
• pp.84-88
• /
• 2013

These days embedded technology may be the most significant development in the electronics industry. The study focused on the development of active device embedding using flexible printed circuit in view of process and materials. The authors fabricated 30um thickness Si chip without any crack, chipping defects with a dicing before grinding process. In order to embed chips into flexible PCB, the chip pads on a chip are connected to bonding pad on flexible PCB using an ACF film. After packaging, all sample were tested by the O/S test and carried out the reliability test. All samples passed environmental reliability test. In the future, this technology will be applied to the wearable electronics and flexible display in the variety of electronics product.

• 한국세라믹학회지
• /
• 제40권7호
• /
• pp.620-624
• /
• 2003

LiCo$_{y}$Mn$_{2-y}$O$_4$ samples were synthesized by calcining a mixture of LiOH.$H_2O$, MnO$_2$ (CMD) and CoCO$_3$ calcining at 40$0^{\circ}C$ for 10 h and then calcining twice at 75$0^{\circ}C$ for 24 h in air with intermediate grinding. All the synthesized samples exhibited XRD patterns for the cubic spinel phase with a space group Fd(equation omitted)m. The electrochemical cells were charged and discharged for 30 cycles at a current density 600 $mutextrm{A}$/$\textrm{cm}^2$ between 3.5 and 4.3 V. As the value of y increases, the size of particles becomes more homogeneous. The first discharge capacity decreases as the value of y increases, its value for y=0.00 being 92.8 mAh/g. The LiMn$_2$O$_4$ exhibits much better cycling performance than that reported earlier. The cycling performance increases as the value of y increases. The efficiency of discharge capacity is 98.9％ for y=0.30. The larger lattice parameter for the smaller value of y is related to the larger discharge capacity. The more quantity of the intercalated and the deintercalated Li in the sample with the larger discharge capacity brings about the larger capacity fading rate.ate.

• 한국해양공학회지
• /
• 제29권1호
• /
• pp.56-61
• /
• 2015

To improve the accuracy of a machine, research needs to be conducted on the relationship between the output variables and design variables of a spindle-shaped part from the thermal and static viewpoints. Therefore, research was carried out by examining the correlation of each variable to find the optimum conditions. Moreover, DOE (design of experiments) was extensively used. The model used in this study was a grinding spindle to which a hydrostatic bearing was applied. This model was used in a preliminary analysis based on the experimental results of the previous studies. The influences of the output variables and design variables were compared through a main effect analysis. Generated response surfaces were applied to the Kriging model. To optimize the model, a screening method was selected. In comparison with the initial model, the deformation of the optimized model designed by DOE decreased by 4.1 μm, while the thermal deformation decreased by 1.2 μm. Therefore, it was efficient to design a spindle-shaped part through DOE to improve the accuracy of the machine.

• 한국산학기술학회논문지
• /
• 제15권9호
• /
• pp.5844-5853
• /
• 2014

본 논문에서는 고인성 섬유 시멘트 복합재료(DFRCC)를 이용한 철근콘크리트(RC) 보의 전단파괴거동에 대한 실험적 연구결과를 제시하였다. 이를 위해 $150{\times}300{\times}1,000mm$ 크기의 보를 총 10개 제작하여 변위제어에 의한 4점휨파괴실험을 실시하였다. 주요 실험변수로는 DFRCC에 의한 보강의 유무, 보강시 그라인딩을 통한 사전 표면처리 그리고 사전 균열발생 유무를 설정하였다. 실험으로부터 재하시작 후 파괴시까지 보의 하중-처짐곡선, 전단균열 및 휨균열 발생하중 그리고 파괴시 전단강도를 측정하였다. 실험결과, DFRCC에 의한 보강시 적절한 두께와 사전 표면처리를 적절히 시행할 경우 기존 RC보의 전단강도를 약 99% 이상 효과적으로 복원할 수 있는 것으로 나타났으며, 보다 신뢰성있는 연구를 위하여 실제 노후화된 구조물에서 채취한 부재에 대한 추가적인 실험과 이론적 연구가 필요한 것으로 판단된다.