• 한국재료학회지
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• 제9권12호
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• pp.1188-1195
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• 1999

알루미노실리케이트 계 졸이 지르콘 쉘 몰드의 뮬라이트 층 생성에 미치는 영향을 고찰하였다. 알루미노실리케이트 졸은 콜로이달 실리카와 수용성 질산알루미늄을 혼합하여 제조하였으며 50$^{\circ}C$에서 48시간 조건에서 겔화 하였다. 이러한 겔은 깁사이트 및 알루미노실리케이트 복합 겔로 구성되어 있었으며, Si 이온과 결합하는 모든 Al 이온의 배위수가 4임을 확인하였다. 뮬라이트 상은 1300$^{\circ}C$ 이상에서 소결하였을 때 관찰되었으며 뮬라이트의 XRD 피크는 소결 온도와 질산알루미늄의 농도가 증가할수록 노실리케이트 졸 슬러리를 2차 층에 코팅하였다. 그 결과 1차 및 3차 층의 분리가 일어났으며, 이는 소결시 졸의 1차 및 3차 층으로 침윤 발생과 잔류 실리카와 뮬라이트 간의 열팽창계수 차이에 기인한 것으로 판단된다.

• 공업화학
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• 제9권7호
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• pp.1043-1046
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• 1998

국내에서 상수원중의 부유물질 및 용존 유기물질의 제거를 위하여 사용하는 알루미늄계 무기응집제들은 응집처리 과정에서 노인성 치매의 한 원인으로 알려져 있는 알루미늄 이온을 상수원수에 잔류시킬 수 있으며, 상수의 탁도가 일시적으로 매우 높아질 때 효과적인 응집에 한계가 있다. 따라서 이들을 대신한 epichlorohydrine-dimethylamine(EPI-DMA) poly(amine)계 고분자 응집제가 선진국을 중심으로 사용이 되어 왔으며, 우리나라에서도 이것을 도입하기 위한 준비가 필요한 상태에 있다. 본 연구에서는 먼저 EPI-DMA poly(amine)계 고분자 응집제의 국산화를 위해 EPI와 DMA의 조성비를 달리하거나 또는 반응시간, 반응온도 등의 합성조건을 변화시키면서 이들의 합성조건에 대한 최적화 연구를 수행하여 대량생산을 위한 최적합성 조건을 구하였다. 그리고 이 과정에서 조건을 달리하여 얻은 각각의 고분자 응집제들에 대한 점도를 측정하여 합성 방법에 따른 고분자 응집제의 효율을 조사하였으며, EPI, DCP, DCIPA, 그리고 CPDO 등 유해 잔류물의 양을 Gas Chromatography(GC)에 의해 정량하였다.

• 한국주조공학회지
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• 제11권4호
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• pp.303-313
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• 1991

The Purification mechanism of high purity aluminum was studied through the variation of stirring speed and coolant flow rate in the stirring method. In the stirring method the degree of purification was changed as the following factors;the variation of diffusion boundary layer thickness the variation of growth rate and the solute concentration of the residual melt. The concentration of Fe and Si was decreased as the stirring speed and the radial distance increased. In a high stirring speed of 2000rpm with unidirectional stirring mode, the uniformity of solutes was obtained. On the other hand, the purification of Si was done by the combinations of stirring method, fractional melting and acid leaching. In the case of Si purification, the centrifugal force developed in the melt acted as the significant purification factor. It was possible to obtain the purified 3N grade Si crystal after the complete elimination of residual aluminum by fractional melting and acid leaching.

• 대한기계학회논문집B
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• 제24권8호
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• pp.1062-1068
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• 2000

The effect of heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger is investigated experimentally. It is found that the hydrophilic surface mainly influences on the frosting behavior, however, the hydrophobic surface gives some influence on the defrosting behavior. In view of frosting performance, surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows a little improvement in the thermal performance than the aluminium heat exchanger with no surface treatment. The result reveals that the heat exchanger with hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amounts of residual water on the surface-treated heat exchangers are shown to be smaller than those of the bare heat exchanger, therefore further improvements on the performance of re-operations are expected.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.469-483
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• 2014

In an indentation approach, the smooth rigid spherical ball penetrated into a deformable flat is considered for the study based on contact mechanics approach. The elastic-plastic frictionless spherical indentation analysis has been under taken in the finite element analysis using "ABAQUS" and experimental study. The spherical indentation has been studied for the materials like steel, aluminium, copper and brass with an identical spherical indenter for diverse indentation depths. The springback analysis is executed for studying the actual indentation depth after the indenter is unloaded. In the springback simulation, the material recovers its elastic deformation after the indenter is unloaded. The residual diameter and depth of an indentation for various materials are measured and compared with simulation results. It shows a good agreement between the simulation and an experimental studies.

• 소성∙가공
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• 제12권5호
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• pp.457-464
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• 2003

In the powder compact melting technique, proper precursor fabrication is very important because density distribution after foaming and foamability are determined during precursor fabrication process. The fabrication of the precursor has to be performed very carefully because any residual porosity or other defects will lead to poor results in further processing. In order to evaluate the effect of the compaction parameters on the kinetics of the foaming process, a series of experiments were performed. In this study, aluminium foams with a closed cell structure were fabricated by using both the powder compact method and the induction heating process. A proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of precursor. To establish the foamable precursor fabrication conditions, effects of process parameters such as the titanium hydride content (0.3∼1.5 wt.%), pressing pressure of the foamable precursor (50∼150kN) on the pore morphology were investigated.

• 한국식품과학회지
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• 제29권6호
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• pp.1131-1137
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• 1997

팽창제 종류에 따른 시간별 가스 발생 속도 및 쿠키 텍스쳐에 대하여 살펴보았다. 본 실험에 사용된 가스 발생 장치에 의해서도 가스 발생 속도에 따라 크게 3타입으로 구분할 수 있었으며 이는 소암모늄명반을 제외하고는 문헌의 결과와 일치하였다. 속효성 평창제로는 주석산, 주석영, 후말산, 소암모늄명반이었고 이단 반응성 팽창제로는 산성피로인산나트륨, 무수모노인산칼슘, 소명반이었으며, 지효성 팽창제로는 중탄산암모늄, 중탄산나트륨, 글루코노-델타-락톤, 염화암모늄 등이었다. 제품 팽창률이 가장 높았던 것은 중탄산암모늄이었고 후미 면에서 가장 깨끗한 것은 글루코노-델타-락톤이었다. 팽창률이 높을수록 texture profile graph상에서 multi-peak를 나타내어 brittleness가 뛰어났으며 단순회귀분석에 의해, 팽창률과 brittleness간에 상관관계가 있음을 입증하였다$(r^2=0.8176)$. 중탄산암모늄을 사용한 쿠키 제품의 brittleness가 가장 높았다.

• Steel and Composite Structures
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• 제43권1호
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• pp.19-30
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• 2022

The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.

• 한국물환경학회지
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• 제24권4호
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• pp.415-422
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• 2008

Drinking water treatment is enhanced by coagulant dosages and chlorine injection because of pH increase in raw water in droughty seasons such as spring and fall. But water quality deterioration is occurred by increase in residual aluminium and disinfection by-products. Coagulation process can be used to control natural organic matter (NOM) during water treatment. The effect of coagulation process appeared to depend on the pH of water rather than coagulant dosages. In this study, for water treatment in high pH season $H_2SO_4$ was applied for pH adjustment at full scale. Before and after pH adjustment by $H_2SO_4$ injection, water quality of drinking water was evaluate. In the result of investigation of total organic carbon (TOC) removal in high pH season, TOC was removed approximately 30~40%, which showed decrease in water treatment efficiency. Also, it is increased both particle numbers and residual Al concentration in the water. After $H_2SO_4$ injection for adjustment to pH<7.5 in settled water, treated water turbidity decreased in 0.047 NTU from 0.059 NTU, and particle numbers of filtered water decreased in 20/mL from 90/mL. On the other side, TOC removal efficiency increased in approximately 10% after adjustment of pH. In the result of decrease in pH in raw water through more coagulants and prechlorine without $H_2SO_4$ injection, trihalomethanes (THMs) concentration increased in $16{\mu}g/L$ from $8{\mu}g/L$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.155.2-155.2
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• 2014

Plasma Enhanced Atomic Layer Deposition(PEALD)와 Atomic Layer Deposition(ALD) Techniques는 '정확한 두께 조절' 및 '우수한 균일도'를 가지는 신뢰할 수 있는 진공 기술이다. 본 연구에서는 다공성 구조를 가지는 기판을 대상으로 PEALD와 ALD Techniques을 이용한 $Al_2O_3$ 형성 공정의 증착 특성을 비교하였다. 각 공정은 공통적으로 Tris-Methyl-Aluminium(TMA)을 첫번째 전구체로 사용하였고 purge gas로는 Nitrogen를 사용하였다. 그리고 두번째 전구체로 PEALD 공정에서는 Oxygen Plasma를 사용하였고 ALD 공정에서는 Water를 사용하였다. 복잡한 다공성 구조를 가지는 기판은 $TiO_2$ Nano-Particle paste과 colloidal Silver paste를 소결시켜 제작하여 사용하였다. 각 공정의 차이점을 비교하기 위해서 배기단에 Capacitor Diaphram Gauge(CDG)와 Residual Gas Analyzer(RGA)를 통해서 압력과 잔류 가스를 모니터하였다. 그리고 각 공정을 통해서 porous한 Nano-Particles Network에 형성된 $Al_2O_3$막의 특성을 비교하기 위해서 FE-SEM과 EDX를 통해서 관찰하였다. 또한 좀 더 자세한 비교 분석을 위해서 $Al_2O_3$ 막이 형성된 porous한 Nano-Particles Networks의 각 각의 particles들을 분산시켜 TEM과 AFM를 통해서 관찰하였다. 나아가 전기적 물성의 차이점을 비교하기 위해서 IV 및 CV를 측정하였다. 위의 일련의 비교 실험을 통해서 'PEALD과 ALD을 이용한 다공성 기판의 증착 특성'에 대하여 고찰하였다.