• 한국결정성장학회지
• /
• 제3권1호
• /
• pp.31-36
• /
• 1993

FZ법을 이용하여 Tourmaline ($NaFe_3Al_6B_3Si_6O_{27}F_4$) 단결정을 성장하였다. 성장조건으로 회전수 상호 역방향으로 20~30rpm, 성장속도 2~5mm/hr로 조절하였다. 성분 원소 중 전이금속 원소가 존재하여 dopant는 첨가하지 않았다. 원료봉은 $1000~1100^{\circ}C$에서 소결하였고 이 온도보다 고온의 영역에서는 F등의 휘발원소의 휘발로 인해 원료봉을 제작하기가 어려웠다. 성장된 결정은 어두운 색을 띄고 있었고 길이 60~50mm, 직경 5~6mm였다. 결정의 원료에 대하여 XRD 분석을 통하여 Tourmaline 조성을 확인하였고 FTIR로 성분의 결합상을 보았다.

• 한국세라믹학회지
• /
• 제46권4호
• /
• pp.413-418
• /
• 2009

Glass systems based on Ca, Sr, Ba, and Zn modified alumino-boro silicates were investigated in order to improve the dielectric and mechanical properties of a typical LTCC (low temperature co-fired ceramic) which was developed for high frequency highly-integrated modules. The glass was prepared by a typical melting procedure and then mixed with cordierite fillers to fabricate glass/ceramic composite-type LTCC materials. The amount of cordierite filler was fixed at 50 volumetric%. For an optimal glass composition of 7.5% CaO, 7.5% BaO, 5% ZnO, 10% $Al_2O_3$, 30% $B_2O_3$, and 40% $SiO_2$ in mole ratio, the resultant LTCC composite showed a dielectric constant of 5.8 and a dielectric loss ($tan{\delta}$) of 0.0009 after firing at $900^{\circ}C$. An average bending strength of 160MPa was obtained for the optimal composition.

• 한국수소및신에너지학회논문집
• /
• 제35권2호
• /
• pp.152-161
• /
• 2024

In this study, a fuel cell system for future defense unmanned vehicles was designed and validated. A Co/Al₂O₃-Ni foam catalyst for NaBH₄ hydrolysis was characterized using several analytical methods. A NaBH₄ hydrogen generation system with the Co/Al₂O₃-Ni foam catalyst continuously generated hydrogen at elevated reaction temperatures. The fuel cell system with the NaBH₄ hydrogen generation system was designed and tested. The performance of the fuel cell system was comparable to that of the fuel cell system using pure hydrogen. Therefore, the fuel cell system with the NaBH₄ hydrogen generation system is a suitable power source for future defense unmanned vehicles owing to its easy refueling and simple system.

• 한국재료학회지
• /
• 제3권2호
• /
• pp.175-184
• /
• 1993

Nd-Fe-B계에 Co와 Al을 첨가한 자석합금을 진공유도용해로에서 제조하여 이들 합금을 단롤법으로 melt-spun시켜 급냉리본을 얻었다. 제작된 급냉리본의 냉각속도에 따른 자기적 성질의 변화를 조사하였고, 최적의 급냉속도에서 제작된 리본을 파쇄하여 resin bond 자석을 제조하였으며, 이들 급냉리본 및 bond자석의 자기적 성질, 미세구조, 결정구조에 관하여 연구, 조사하였다. 이들 급냉리본의 자기적 성질은 급냉속도에 따라 크게 변하였으며 20m/sec전후에서 최적의 자기적 성질을 보였다. 이때의 급냉리본의 미세조직은 Nd-rich의 입계상이 미세한 N$d_2$F$e_14$B결정립을 둘러싼 cell 형의 구조였으며, 특히 Al이 2.1at%첨가된 리본시료에서는 iHc=15.5KOe, Br=7.8KG, (BH)max=8.5MGOe의 자기적 성질을 나타내었다. 최적의 급냉속도에서 제작된 리본을 polyamide resin과 2.5wt%의 비율로 혼합하여 상온에서 성형, 결합시켜 제작한 bond자석에서 보다 현저히 향상되었으며 유지시간이 8분인 경우 iHc=10.8KOe, Br=7.3KG, (BH)max=8.0MGOe의 값을 가졌다. 한편, 자구구조는 maze pattern이 주로 관찰되어 자화용이축인 C축이 배열되었으며 bond자석에서보다 hot-press 자석에서 자구폭이 보다 작았다.

• 한국의류학회지
• /
• 제27권3_4호
• /
• pp.364-372
• /
• 2003

In this study, the characteristics of catechol tannin and pyrogallol tannin contained in Pteridium aquilinum were analysed by It spectrum. Silk fabrics were dyed with Pteridium aquilinum extracts using various mordants, and their dyeing properties were discussed. Additionally the fastness the water digestion, perspiration liquid digestion and light irradiation were investigated. IR spectrum of catechol tannin showed bands of O-H at $3417cm^{-1}$, C-H at $2930cm^{-1}$, C=0 at $1722cm^{-1}$, C=C at $1644cm^{-1},\;CH_2\;at\;1402cm^{-1}$. And IR spectrum of pyrogallol tannin showed bands of O-H at $3409cm^{-1}$, C-H at $3003cm^{-1}\;and\;2933cm^{-11}$, C=0 at $1701cm^{-1}$, C=C at $1582cm^{-11},\;CH_2\;at\;1410cm^{-1}$, CO at carboxylic acid and carboxylic acid ester at $1287cm^{-1}\;and\;1135cm^{-1}$. The maximum absorption wavelength of the extracts appeared at 270.0nm and 311.5nm. The optimum conditions for dyeing silk fabric with Pteridium aquilinum extracts were $80^{\circ}C$, 60min. Surface color of the silk fabric dyed with Pteridium aquilinum extracts was 2.7Y Surface color of the pre-mordanted fabrics with Al, Cu and Fe were 4.3Y, 2.5Y and 4.7Y, respectively. And Surface color of the post-mordanted fabrics with Al, Cu and Fe were 3.7Y, 2.8Y and 0.2GY. The water fastness and the alkaline perspiration fastness were improved in the Al-mordanted silk fabrics. By acidic and alkaline perspiration treatment, ${\Delta}E of the unmordanted fabrics was lower than hat of pre- and post- mordanted fabrics. Also after 40hour irradiation, ${\Delta}E of the unmordanted fabrics was lower than that of pre- and post- mordanted fabrics.

• 공업화학
• /
• 제9권1호
• /
• pp.115-120
• /
• 1998

메타세시스에 높은 활성을 나타내는 고분산 레늄촉매을 제조하기 위한 레늄카보닐 침착의 표면화학 및 활성점 생성에 관하여 연구하였다. 알루미나는 773K(PDA)와 1223K(DA)에서 각각 처리하여 담체로 사용하였고, 메타세시스 활성은 순수한 프로펜을 사용하여 상압하의 298K에서 조사하였다. PDA상의 레늄 산화가는 상당히 높았으나, DA에서는 저산화가의 레늄으로 담지되어 있었다. 제조한 Re/DA촉매를 고온에서 열분해시킨 다음 저온에서 산소로 처리하면 메타세시스 활성이 나타났고, 그 활성은 극히 낮은 담지율에서도 Re/PDA이나 통상의 $Re_2O_7/Al_2O_3$촉매에 비해 높은 활성을 보여, 레늄 카보닐을 출발물질로 하고 DA를 사용하는 것이 효과적이었다. 열분해하여 얻은 Re/DA촉매상의 레늄이온은 알루미나의 산소원자 2개와 결합하여 2가를 가지고, 산소처리에 의하여 4가만큼 증가한 6가의 레늄이온이 되며, 메타세시스는 그 6가이온에 의해 생성된 카르벤착체를 통하여 진행됨을 알았다.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
• /
• pp.179-180
• /
• 2012

Aluminum alloys are widely known as non-ferrous metal with light weight and high strength. Consequently, these materials take center stage in the aircraft and automobile industry. The Al7075 aluminum alloy is based on the Al-Zn-Mg-Cu and one of the strongest wrought aluminum alloys. Aluminum nitride has ten times higher thermal conductivity($319W/m{\cdot}K$) than Al2O3 and also has outstanding electric insulation($1{\times}1014{\Omega}{\cdot}cm$). Furthermore, it has high mechanical property (430 MPa) even though its co-efficient of thermal expansion is less than alumina For these reasons, it has great possibilities to be used for not only the field which needs high strength lightweight but also electronic material field because of its suitability to be applied to the insulator film of PCB or wafer of ceramic with high heat conduction. This paper investigates the mechanical properties and corrosion behavior of aluminum alloy Al7075 deposited with aluminum nitride thin films To improve the surface properties of Al7075 with respect to hardness, and resistance to corrosion, aluminum nitride thin films have been deposited by pulsed DC reactive magnetron sputtering. The pulsed DC power provides arc-free deposition of insulating films.

• Asian Journal of Atmospheric Environment
• /
• 제9권2호
• /
• pp.165-172
• /
• 2015

Under a very tough situation that there has been increasing concern to the air quality in underground subway spaces, this study set sights on the thorough estimation of the chemical properties and source apportionment of particulate matter (PM) collected on an underground subway platform by a cooperative approach of semi-bulk and single particle analyses. The size-resolved PMs were intensively collected on the platform of Miasageori station on the Seoul Subway Line-4, and then, they were semibulkily analyzed by a PIXE and the TOR$^{(R)}$ method, and individually analyzed by a SEM-EDX. Overwhelmingly enriched iron was a notable feature of elemental concentration of $PM_{2.5}$. Source classification of iron in $PM_{10-2.5}$ and $PM_{2.5}$ performed along with their elemental concentrations, indicates that the railway originated iron accounts for 95.71% and 66.39% of total iron in $PM_{10-2.5}$ and $PM_{2.5}$, respectively. Via a stoichiometric categorization, $Fe_2O_3$, $CaAl_2Si_2O_8$, $Al_2O_3$, and $CaCO_3$ show more than 85% abundance ratio in individual coarse particles. The result of theoretical estimation of the subway derived organic carbon ($OC_{Subway}$) suggests that $OC_{Subway}$ in $PM_1$ and $PM_{2.5-1}$ account for 75.86% and 51.88% of total organic carbon, respectively.

• 한국세라믹학회지
• /
• 제47권6호
• /
• pp.529-533
• /
• 2010

Porous frit-bonded alumina ceramics were fabricated using alumina and frit as raw materials. The effects of frit content and sintering temperature on microstructure, porosity, and flexural strength were investigated at low temperature of $750{\sim}850^{\circ}C$. Increased addition of frit content or higher sintering temperature resulted in improved flexural strength of porous frit-bonded alumina ceramics. It was possible to produce frit-bonded alumina ceramics with porosities ranging from 35% to 40%. A maximum strength of 52MPa was obtained at a porosity of ~38% when 90 wt% alumina and 10 wt% frit powders were used.

• Archives of Pharmacal Research
• /
• 제28권5호
• /
• pp.550-556
• /
• 2005

The flower of Campsis grandiflora K. Schum. Was extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH and H$_2$O. From the EtO Ac fraction, seven triterpenoids were isolated through the repeated silica gel, ODS column chromatographies and preparative HPLC. From the result of physico- chemical data including NMR, MS and IR, the chemical structures of the compounds were determined as 3${\beta}$-hydroxyolean-12-en-28-oic acid (oleanolic acid, 1), 3${\beta}$-hydroxyurs-12-en-28-oic acid (ursolic acid, 2), 3${\beta}$-hydroxyurs-12-en-28-al (ursolic aldehyde, 3), 2${\alpha}$,3${\beta}$-dihydroxyolean-12-en-28-oic acid (maslinic acid, 4), 2${\alpha}$,3${\beta}$-dihydroxyurs-12-en-28-oic acid (corosolic acid, 5), 3${\beta}$,23-dihydroxyurs-12- en-28-oic acid (23-hydroxyursolic acid ,6) and 2${\alpha}$,3${\beta}$,23-trihydroxyolean-12-en-28- oic acid (arjunolic acid, 7). These teriterpenoids were isolated for the first time from this plant. Also, compounds 4, 5, 6, and 7 revealed relatively high hACAT-1 inhibitory activity with the value of 46.2${\pm}$1.1, 46.7${\pm}$0.9, 41.5${\pm}$1.3 and 60.8${\pm}$1.1% at the concentration of 100${\mu}$g/mL, respectively.