• 대한금속재료학회지
• /
• 제48권4호
• /
• pp.369-375
• /
• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• 대한금속재료학회지
• /
• 제47권8호
• /
• pp.508-515
• /
• 2009

Ti-6Al-4V biomaterial is widely used as a bone alternative. However, Ti-6Al-4V ELI alloy suffers from numerous problems such as a high elastic modulus and high toxicity. Therefore, non-toxic biomaterials with low elastic moduli need to be developed. Ti-HA(hydroxyapatite) composites were fabricated in the present work by pulsed current activated sintering (PCAS) at $1000^{\circ}C$ under 60 MPa using mixed Ti and HA powders. The effects of HA content on the physical and mechanical properties of the sintered Ti-HA composites have been investigated. X-ray diffraction(XRD) analysis of the Ti-HA composites, including Ti-40 wt%HA in particular, revealed new phases, $Ti_{2}O$, CaO, $CaTiO_3$, and TixPy, formed by chemical reactions between Ti and HA during sintering. The hardness of the Ti-HA composites decreased with an increase in HA content. The corrosion resistance of these composites was observed to be an excellent candidate as a commercial Ti-6Al-4 V ELI alloy. A Ti-5 wt%HA composite fabricated by PCAS is recommended as a new biomaterial, because it offers good corrosion resistance, compressive strength, wear resistance, and biocompatibility, and a low Young's modulus.

• 한국결정성장학회지
• /
• 제31권1호
• /
• pp.16-23
• /
• 2021

리튬이차전지 제조 공정 중 발생한 폐액으로부터 회수된 탄산리튬의 경우, 이차전지 양극재의 원료인 코발트, 니켈 및 망간의 중금속이 함유되어 있다. 본 연구에서는 탄산리튬의 재결정화를 통하여 순도 98.28 %의 저급 탄산리튬 분말에 함유된 중금속을 제거하고 탄산리튬의 순도를 높이고자 하였다. 먼저 염산 수용액을 이용하여 탄산리튬의 침출 효율을 살펴보았으며, pH 5 조건으로 침출 후 탄산나트륨의 당량 및 농도의 탄산리튬 재결정에 대한 영향을 확인하였다. 리튬의 함량 기준 대비 탄산나트륨 1 당량에서 1.5로 증가할수록, 농도 1.4 M에서 2.8 M로 증가할수록 회수율은 향상되었으며, 탄산나트륨의 투입 조건이 달라짐에 따라 결정 형상이 달라지는 것을 SEM 분석을 통해 확인할 수 있었다. 재결정된 탄산리튬 분말은 수세하여 순도 99.9 % 이상의 고순도 탄산리튬을 회수할 수 있었다.

• 한국산업융합학회 논문집
• /
• 제25권5호
• /
• pp.899-908
• /
• 2022

In this study, a study was conducted to localize a large aluminum turbo fan used for tank powerpack. The turbo fan was scanned with a 3D scanner and then 3D modeling was performed. Computational fluid dynamics (CFD) were performed from the performance conditions of the fan, and structural analysis was performed using the pressure data obtained from CFD. The fan was reduced to 1/5 size by applying the geometric similarity. A 1/5 size fan has a honeycomb structure inserted into the front shroud and back shroud to reduce the weight by 5.3%. A 1/5 size fan was printed using a PBF 3D printer, and a 1/5 size fan with honeycombs was also printed. The pressure drop of 8.67 kPa and the required power of 138.19 kW, which satisfies the performance conditions of the fan, were confirmed from the results of CFD. The values of the maximum deformation amount of 0.000788 mm and the maximum effective stress of 0.241 MPa were confirmed from the structural analysis results. The fan printed by the PBF 3D printer had the same shape as the modeling, and the shape was perfect. There are no defects anywhere in appearance. However, the condition of the outer surface of the fan's back shroud is rough compared to other locations. The fan in which the honeycomb was inserted was also perfectly output, and the shape of the honeycomb was the same as the modeling.

• 센서학회지
• /
• 제32권3호
• /
• pp.140-146
• /
• 2023

Water quality is crucial for human health and the environment. Accurate measurement of the quantity of organic carbon in water is essential for water quality evaluation, identification of water pollution sources, and appropriate implementation of water treatment measures. Total organic carbon (TOC) analysis is an important tool for this purpose. Although other methods, such as chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are also used to measure organic carbon in water, they have limitations that make TOC analysis a more favorable option in certain situations. For example, COD requires the use of toxic chemicals, and BOD is time-consuming and can produce inconsistent and unreliable results. In contrast, TOC analysis is rapid and reliable, providing accurate measurements of organic carbon content in water. However, common methods for TOC analysis can be complex and energy-intensive because of the use of high-temperature heaters for liquid-to-gas phase transitions and the use of acid, which present safety risks. This study focuses on a TOC analysis method using TiO₂ photocatalysis, which has several advantages over conventional TOC analysis methods, including its low cost and easy maintenance. For TiO₂, rutile and anatase powders are mixed with an inorganic binder and spray-coated onto a glass fiber substrate. The TiO₂ powder and inorganic binder solutions are adjusted to optimize the photocatalytic reaction performance. The TiO₂ photocatalysis method is a simple and low-power approach to TOC analysis, making it a promising alternative to commonly used TOC analysis methods. This study aims to contribute to the development of more efficient and cost-effective approaches for water quality analysis and management by exploring the effectiveness and reliability of the developed equipment.

• 한국재료학회지
• /
• 제33권7호
• /
• pp.285-294
• /
• 2023

Porous ceramics are used in various industrial applications based on their physical properties, including isolation, storage, and thermal barrier properties. However, traditional manufacturing environments require additional steps to control artificial pores and limit deformities, because they rely on limited molding methods. To overcome this drawback, many studies have recently focused on fabricating porous structures using additive manufacturing techniques. In particular, the binder jet technology enables high porosity and various types of designs, and avoids the limitations of existing manufacturing processes. In this study, we investigated process optimization for manufacturing porous ceramic filters using the binder jet technology. In binder jet technology, the flowability of the powder used as the base material is an important factor, as well as compatibility with the binder in the process and for the final print. Flow agents and secondary binders were used to optimize the flowability and compatibility of the powders. In addition, the effects of the amount of added glass frit, and changes in sintering temperature on the microstructure, porosity and mechanical properties of the final printed product were investigated.

• 한국초전도ㆍ저온공학회논문지
• /
• 제6권1호
• /
• pp.12-17
• /
• 2004

High critical current density. $J_c$ over $1MA/cm^2$ at 77 K in a self field was successfully achieved from the YBCO film prepared on (100) $SrTiO_3$ single-crystal substrates by the TFA-MOD process. Unlike a normal TFA-MOD process, we prepared the TFA precursor solution by dissolving YBCO powder into the trifluoroacetic acid. A significant amount of the second phases, including $BaF_2$, was observed in the films fired at $700-725^{\circ}C$ for 2 h under $P(O_2)=10^{-3}$ atm and $P(H_2O)=4.2%$, most probably due to an insufficient reaction time, and hence $T_c$ was greatly degraded. However the films fired at $750-800^{\circ}C$ for 2 h were composed of strongly c-axis oriented YBCO grams without any second phases. and exhibited the $T_c$ values of 89.5 ~ 91 K with a sharp transition. With increasing the firing temperature from 750 to $800^{\circ}C$ average grain size of YBCO was increased and grain connectivity was enhanced. The highest $J_c$ value of $1.1MA/cm^2$ was obtained from the YBCO film fired at $800^{\circ}C$.

• 마이크로전자및패키징학회지
• /
• 제6권1호
• /
• pp.51-58
• /
• 1999

지르코니아에 접합과 반응성이 정합되며 고온에서 물리화학적으로 안정성을 갖는 접합재를 제조하기 위하여 silicate계 유리의 조성에 따른 적심특성, 결정화 및 반응성등 제반 특성을 고찰하였다. 지르코니아와의 열팽창계수가 정합 될 수 있는 유리계에 대한 조성 실험하였다. Alkaline earth silicate 유리는 적심성이 우수하였으며 적심각이 낮으며 $B_2O_3$의 첨가함로써 유리의 점도를 조절 및 결정화를 억제할 수가 있었다. $900^{\circ}C$ 이하에서 적심공정에 일어났으며 $800^{\circ}C$에서 10시간동안 유지한 후에 결정화와 계면 반응을 조사한 결과 기공이 많이 발생하였으며 $B_2O_3$를 15mo1% 첨가한 경우 흐름성이 증가하였으며 기판과의 반응성이 높아졌다. 기공을 없애기 위해서는 공정변수를 조절하여 유리의 소결을 촉진할 필요가 있으며 유리점도와 반응성에 관한 최적화가 요구된다. 본 연구에서는 유리-세라믹필러 복합체의 고온적심성에 대하여 조사하였다. Filler로서 $ZrO_2$분말을 여러 조건으로 열처리하여 분말종류와 첨가량에 따라 기공, $ZrO_2$ filler의 형상 및 계면반응 등을 고찰하였다.

• 한국세라믹학회지
• /
• 제39권11호
• /
• pp.1035-1041
• /
• 2002

세라믹섬유지에 VOC 흡착특성이 우수한 제올라이트-Y와 ZSM-5를 담지시키기 위하여 바인더로 사용된 실리카 졸의 첨가량 변화에 따른 흡착제의 표면고착특성을 고찰하였다. 세라믹섬유지에 담지된 제올라이트는 입자가 고르게 분산되어 31 wt% 정도가 고착되었으며, X-ray 회절분석결과 담지 후 열처리와 바인더의 사용에도 불구하고 제올라이트는 원래의 결정구조를 유지하였다. 담지된 제올라이트의 비표면적 감소는 메조포어의 감소에 따른 것으로, VOC 흡착에 가장 유효한 $20{\AA}$ 미만의 마이크로포어에는 영향을 미치지 않음을 알 수 있었다. 세라믹섬유지로 제조한 직경 10cm, 길이 40cm의 허니컴에 제올라이트를 담지시켜 톨루엔, MEK, Cyclohexanone에 대한 흡착실험결과 흡착제거효율이 모두 97% 이상으로 나타났으며, 회전식 흡착농축장치에 적용할 경우 VOC 농도 300 ppmv의 오염공기를 $42 Nm^3/h$ 정도 연속적으로 처리할 수 있는 흡착특성을 나타내었다.

• 구강회복응용과학지
• /
• 제20권2호
• /
• pp.109-120
• /
• 2004

덴틴, 에나멜, 투명 일반도재를 페이스트화 하여 치아의 색상, 투명도 및 구조를 고려한 복합층구성물을 미리 제조하여 심미수복물을 용이하게 제작하는 공정을 개발하였다. 페이스트 상태에서 성형성과 유동특성이 확보되고, 소성 후 색도, 및 강도 등의 제특성들을 만족시킬 수 있는 결합제 시스템으로서 UV (creation universal liquid)를 선정하였고 조성 및 최적화가 이루어졌다. 페이스트는 24시간까지도 점성 및 작업성이 유지되었고, 이를 이용하여 복합층 구성물의 용이한 성형이 가능하였다. 소성수축률은 15.2%로 기존의 방법으로 제조한 시편에 비해 0.8% 낮았으나 유의차는 없었다. spectrophotometer에 의한 색도특성 관찰결과 덴틴재를 기존 제조방식으로 제조한 시편과 페이스트형 도재 시스템으로 제조한 시편에서 $L^*$, $a^*$, $b^*$가 각각 60~80, -1.5~+1.5, 5~20 사이의 값을 나타냄을 확인하였다. 측정값으로부터 구해진 제조방식에 따른 시편 간의 색차(${\Delta}E^*$)는 0.156으로 극히 근소한 차이를 나타냄을 확인하였다. 유기물 첨가에 따른 소성 후 잔류물 함량은 검출오차범위 내에 있었으며, 기존의 제조방식으로 제조한 소성체와 페이스트형 도재 시스템을 이용한 소성체의 강도는 각각 $70{\pm}4MPa$, $74{\pm}3MPa$으로 유의차가 없이 근사한 물성을 나타내었다. 페이스트형 도재를 이용한 도재축성법을 기존방법과 비교분석한 결과, 기계적 또는 광학적 특성의 변화없이 적용이 가능하였다.