• 공업화학
• /
• 제30권4호
• /
• pp.460-465
• /
• 2019

본 연구에서는 각종 산업시설에서 발생하는 $H_2S$를 처리하기 위하여 금속산화물 기반의 흡착제의 활성물질 최적화 및 입상형 흡착제 제조에 관한 연구를 진행하였다. 적용되는 흡착제는 금속산화물 중 높은 물리화학적 안정성과 비교적 큰 비표면적을 가지는 $TiO_2$를 이용하여 활성물질의 종류와 함량을 다르게 제조하였다. 이러한 흡착제의 물리화학적 특성과 흡착성능과의 상관관계를 확인한 결과 활성금속 중 대표적인 알칼리 물질인 KI를 첨착한 흡착제의 흡착성능이 가장 우수하였으며, 함량과 흡착성능의 관계는 비례하지 않고 volcano plot을 나타냈다. XRD, SEM, BET 분석을 통해 특정 함량 이상부터 활성물질이 표면에 노출됨을 확인하였으며, 비표면적은 $40{\sim}100m^2/g$, 기공의 부피는 $0.1{\sim}0.3cm^3/g$의 기공 특성을 가질 때 흡착성능이 가장 우수한 것으로 판단하였다. 실 공정 적용을 위해 흡착제를 입상형으로 성형 또는 세라믹 지지체에 코팅을 진행하였으며, 성형보다는 세라믹 지지체에 흡착제를 코팅하였을 때 우수한 흡착성능을 나타내는 것으로 확인하였다.

• 대한치과기공학회지
• /
• 제45권3호
• /
• pp.67-73
• /
• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.397-400
• /
• 2007

For mapping the distribution of heavy metals in the mining area, field spectroscopy and hyperspectral remote sensing were used in this study. Although heavy metals are spectrally featureless from the visible to the short wave infrared range, possible variations in spectral signal due to heavy metals bound onto minerals can be explained with the metal binding reaction onto the mineral surface. Variations in the spectral absorption shapes of lattice OH and oxygen on the mineral surface due to the combination of heavy metals were surveyed over the range from 420 to 2400 nm. Spectral parameters such as peak ratio and peak area were derived and statistically linked to metal concentration levels in the streambed samples collected from the dry stream channels. The spatial relationships between spectral parameters and concentrations of heavy metals were yielded as well. Based on the observation at a ground level for the relationship between spectral signal and metal concentration levels, the spectral parameters were classified in a hyperspectral image and the spatial distribution patterns of classified pixels were compared with the product of analysis at the ground level. The degree of similarity between ground dataset and image dataset was statistically validated. These techniques are expected to support assessment of dispersion of heavy metal contamination and decision on optimal sampling point.

• 대한치과보철학회지
• /
• 제58권3호
• /
• pp.251-256
• /
• 2020

최근 치과 분야에서 디지털 기술의 발전으로 DMLS (Direct Metal Laser Sintering) 기술을 사용하여 의치의 금속구조물 제작이 가능하다. 이 방법에서 인상은 구강 스캔이나 모델 스캔으로 대체 할 수 있으며, 기존 주조 소환 방법에서 왁스 패턴은 CAD 소프트웨어에서 설계되고, 설계된 STL (standard template library) 파일을 DMLS 기법을 통해 국소의치의 최종 구성 요소를 제작할 수 있다. 치과 분야에서 디지털 기술 이용의 장점은 적합도와 정확성에 있다. 본 증례에서 지지 및 간접 유지 역할을 하는 교합면 레스트의 파절이 발생한 환자에서 DMLS 기술과 레이저 용접 기술을 사용하여 국소의치를 수리하였으며, 기능적, 심미적으로 만족스러운 결과를 보였다.

• 세라미스트
• /
• 제23권2호
• /
• pp.211-230
• /
• 2020

Perovskite-type oxides with the nominal composition of ABO₃ can exsolve the B-site transition metal upon the controlled reduction. In this exsolution process, the transition metal emerges from the oxide lattice and migrates to the surface at which it forms catalytically active nanoparticles. The exsolved nanoparticles can recover back to the bulk lattice under oxidation treatment. This unique regeneration character by the redox treatment provides uniformly dispersed noble metal nanoparticles. Therefore, the conventional problem of traditional impregnated metal/support, i.e., sintering during reaction, can be effectively avoided by using the exsolution phenomenon. In this regard, the catalysts using the exsolution strategy have been well studied for a wide range of applications in energy conversion and storage devices such as solid oxide fuel cells and electrolysis cells (SOFCs and SOECs) because of its high thermal and chemical stability. On the other hand, although this exsolution strategy can also be applied to gas phase reaction catalysts, it has seldomly been reviewed. Here, we thus review recent applications of the exsolution catalysts to the gas phase reactions from the aspects of experimental measurements, where various functions of the exsolved particles were utilized. We also review non-perovskite type metal oxides that might have exolution phenomenon to provide more possibilities to develop higher efficient catalysts.

• Macromolecular Research
• /
• 제15권3호
• /
• pp.221-224
• /
• 2007

A silica-magnesium bisupport (SMB) was prepared by a sol-gel method for use as a support for a metal-locene/Ziegler-Natta hybrid catalyst. The prepared $rac-Et(Ind)_2ZrCl_2/TiCl_4$/MAO(methylaluminoxane)/SMB catalyst was applied to the copolymerization of ethylene with l-hexene using a variable triethylaluminum (TEA)/transition-metal (Ti) ratio and fixed MAO/transition-metal (Zr) ratio. The effect of the Al(TEA)/Ti ratio on the physical properties and chemical composition distributions (CCDs) of the ethylene-hexene copolymers produced by the hybrid catalyst was investigated. In the ethylene-hexene copolymers, two melting temperatures attributed to the metal-locene and Ziegler-Natta catalysts were clearly observed. The number of CCD peaks was increased from six to seven and the temperature region in which the peaks for the short chain branches of the ethylene-hexene copolymer were distributed became lower as the Al(TEA)/Ti ratio was increased from 300 to 400. Furthermore, the temperature regions corresponding to the lamellas in the copolymer became lower and those corresponding to the small lamellas in the copolymer became higher as the Al(TEA)/Ti ratio was increased from 300 to 400. In the copolymer produced with Al(TEA)/Ti = 500, however, only four CCD peaks were observed and the short chain branches were poorly distributed.

• Korean Chemical Engineering Research
• /
• 제59권4호
• /
• pp.481-486
• /
• 2021

극초음속 비행체의 비행 중에 발생되는 열 문제를 해결하기 위해 탑재된 연료의 분해반응 시 나타나는 흡열효과를 이용하는 냉각기술이 개발되고 있다. 본 연구에서는 HZSM-5를 촉매로 사용하여 n-dodecane 연료의 분해반응을 수행하였으며, 촉매 분해반응의 흡열효과를 극대화하고 코크생성을 억제하기 위해 촉매를 메탈폼에 코팅하였다. 반응기는 외경 1.27 cm의 스테인리스 스틸 흐름형 반응기를 사용하였다. HZSM-5를 메탈폼에 코팅한 촉매를 사용한 촉매 분해반응 결과 흡열량은 최대 2887 kJ/kg, 기상전환율은 34% 이었으며, 메탈폼의 코크생성량은 촉매를 코팅함에 따라 촉매를 코팅하지 않은 것에 비해 약 56% 감소하였다.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1996년도 춘계 총회 및 학술발표회
• /
• pp.62-64
• /
• 1996

Chitin, which is obtained mainly from the cuticle of a marine crustacean, has recently aroused great interest in its industrial and biomedical applications. Chitosan, deacetylated form of chitin, appears to be more useful for biomedical application and dehydration of aqueous solutions than chitin, since it has both hydroxyl and amino groups that can be modified easily. Amino groups on chitosan reacts with dialdehyde to form a Schiff base and then crosslinked, and can be easily neutralized with sulfuric acid and metal ions. Polyfunctional metal ions can form a metal-polyelectrolyte complexes with chitosan. Membranes used in modules so far working in industrial pervaporation plants are generally of composite type. This composite membrane was prepared by coating a porous polysulfone ultrafiltration membrane support of definite structure with a thin, dense layer of permselective chitosan. To apply industrial scale pervaporation process for dehydration of aqueous ethanol and isopropanol, chitosan composite membranes were prepared and tested at various conditions.

• Nuclear Engineering and Technology
• /
• 제41권5호
• /
• pp.709-714
• /
• 2009

An ion implanter, which can serve as a metal-ion supply, has been constructed and performance tested. Copper ions are generated and extracted from a Bernas ion source with a heating crucible that provides feed gases to sustain the plasma. Sable arc plasmas can be sustained in the ion source for a crucible temperature in excess of $350^{\circ}C$. Stable extraction of the ions is possible for arc Currents less than 0.3 A. Arc currents increase with the induced power of a block cathode and the transverse field in the ion source. $Cu^+$ ions in the extracted beam are separated using a dipole magnet. A $20{\mu}A$ $Cu^+$ ion current can be extracted with a 0.2 A arc current. The ion current can support a dose of $10^{16}ions/cm^2$ over an area of $15\;cm^2$ within a few hours.

• 한국항공우주학회지
• /
• 제34권10호
• /
• pp.40-47
• /
• 2006

반사경 지지부의 접착 특성은 인공위성카메라 반사경의 광학적 성능에 지대한 영향을 미치므로 이에 대한 연구가 필수적이다. 이를 위해 본 연구에서는 세 종류의 우주용 접착제의 접착 특성에 관한 연구를 수행하였다. 반사경의 재료인 제로더(Zerodur)와 금속이 접착된 시편을 사용하여 중첩 전단(lap shear) 시험을 수행하였고 금속과 금속이 접착된 시편에 대해서도 시험을 수행하였다. 또한 다양한 온도 환경을 겪더라도 안정적인 접착력이 보장되는지의 여부를 확인하였으며 세 접착제의 접착력을 비교하였다.