• Journal of the Korean Wood Science and Technology
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• 제28권4호
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• pp.41-50
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• 2000

Cement-bonded particleboard is being used as outdoor siding material all over the world, because this composite particularly bears a light weight, high resistance against fire, decay, and crack by cyclic freezing and thawing, anti-shock property, and strength enhancement. Construction systems are currently changing into a frame-building style and wooden houses are being constructed with prefabrication type. Therefore, they require a more durability at outdoor-exposed sides. In this study, the cement hydration property for Korean pine particle, Japanese larch particle and face- and middle layer particles (designated as PB particle below) used in Korean particleboard-manufacturing company was investigated, and the rapid manufacturing characteristics of cement-bonded particleboard by supercritical $CO_2$ curing was evaluated. Korean pine flour showed a good hydration property, however, larch flour showed a bad one. PB particle had a better hydration property than larch flour. The addition of $Na_2SiO_3$ indicated a negative effect on hydration, however, $MgCl_2$ had a positive one. Curing by supercritical $CO_2$ fluid gave a conspicuous enhancement in the performances of cement-bonded particleboards compared to conventional curing. $MgCl_2$ 3%-added PB particle had the highest properties, and $MgCl_2$ 1%-added Korean pine particle had the second class with the conditions of cement/wood ratio of 2.7, a small fraction-screened particle and supercritical curing. On the contrary, the composition of non-hammermilled or large fraction-screened particle at cement/wood ratio of 2.2 was poorer. Also, the feasibility for actual use of 3%-added, small PB particle-screened fraction was greatest of all the conventional curing treatments. Relative superiority of supercritical curing vs. conventional curing at dimensional stability was not so apparent as in strength properties. Through the thermogravimetric analysis, it was ascertained that the peak of a component $CaCO_3$ was highest, and the two weak peaks of calcium silicate hydrate and ettringite and $Ca(OH)_2$ were present in supercritical treatment. Accordingly, it was inferred that the increased formation of carbonates in board contributes to strength enhancement.

• 공업화학
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• 제7권3호
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• pp.597-604
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• 1996

사용후핵연료 수송용기 등에 사용되는 수지계 중성자 차폐재, KNS-115A, 115B 및 115C를 제조하였다. 기본물질은 에폭시수지이며, 첨가제로는 폴리프로필렌, 수산화알루미늄 및 탄화붕소이다. 이들 중성자 차폐재들은 유동성이 좋아 수송용기와 같은 복잡한 구조에 사용할 수 있다. 개발된 중성자 차폐재들의 차폐능, 연소특성, 난연성, 열적 및 역학적 성질 등을 평가하기 위해 여러 특성시험을 행하였다. 개발된 중성자 차폐재(수소원자 밀도, $6.1{\sim}6.2{\times}10^{22}atoms/cm^3$)들은 외국산 중성자 차폐재(NS-4-FR, $6.0{\times}10^{22}atoms/cm^3$)보다 수소원자 밀도가 높아 차폐능이 우수할 것으로 예측되며, 조사된 제반 특성들은 열분해온도; $267{\sim}270^{\circ}C$, 열전도도; $0.62{\sim}0.72W/m{\cdot}K$, 연소특성; $800^{\circ}C$ 이하, 평균연소시간; 5초 이하, 평균연소길이; 5mm 이하, 인장강도; $2.3{\sim}3.0kg/mm^2$, 압축강도; $5.3{\sim}13.3kg/mm^2$, 굴곡강도; $4.4{\sim}5.4kg/mm^2$ 등을 나타냈다.

• 한국건축시공학회지
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• 제15권3호
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• pp.265-271
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• 2015

본 연구는 재령 6시간에 압축강도 10MPa 이상을 만족하는 조강형 콘크리트를 개발함에 스팀양생 공정을 생략한 PC(Precast Concrete)부재를 생산하고자 하였으며, 거푸집의 회전율을 높임에 경제성을 확보하는데 목적이 있다. 이에, $C_3S$의 함유량이 높은 조강시멘트와 $C_3S$의 수화작용을 촉진시키는 분말형 경화촉진제를 사용하였으며, 경화촉진제 혼입율 0%, 1.2%, 1.6%, 2.0%에 따른 콘크리트의 특성을 평가하였다. 경화촉진제 혼입율에 따라 슬럼프 및 공기량 시험에는 큰 차이를 나타내지 않았으며, 1.6%이상을 혼입하였을 때, 재령 6시간에 10MPa를 만족하였다. 자기(건조)수축 길이변화 시험 및 소성수축 시험결과, 경화촉진제의 혼입으로 수화반응 속도에 따른 차이는 있지만, 균열 및 내구성에 대한 문제가 발생되지 않을 것으로 나타났으며, 동결융해 및 탄산화 침투에 대한 저항성도 우수한 것으로 나타났다.

• 자원리싸이클링
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• 제13권2호
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• pp.16-23
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• 2004

무연탄 석탄회의 재활용 향상을 위하여, 무연탄 석탄회의 특성을 유연탄 석탄회의 특성과 비교하였다. 특히, 무연탄 석탄회를 소성블릭의 원료로 활용하기 위하여, 무연탄 석탄회의 고온 특성이 열분석, 고온현미경 및 X선 회절 분석에 의해 조사되었다. 무연탄석탄회의 $A1_2$$O_3$/SiO$_2$ 비는 평균 0.62이고 유연탄 석탄회는 $A1_2$$O_3$/$SiO_2$ 비가 0.34로 무연탄 석탄회 중 A1$_2$$O_3$ 성분의 조성이 높았다. 무연탄 석탄회 중 $SiO_2$는 석탄회 중의 $A1_2$$O_3$와 반응하여 $1000^{\circ}C$의 고온에서 새로운 뮬라이트 결정을 형성하였고, 그 결과 우수한 내화도를 나타내었다. 또한, 무연탄 석탄회의 첨가량 변화에 따른 혼합시료의 압출 성형 특성을 평가하기 위하여 고령토와의 혼합시료가 제조되었고, 무연탄 석탄회 첨가 성형 벽돌의 압출속도는 혼합시료 중 석탄회의 첨가량이 증가할수록 감소하였으며, 압출 성형가능한 무연탄 석탄회의 최대 첨가량은 60wt%이었다.

• 한국가스학회지
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• 제11권1호
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• pp.29-33
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• 2007

[ $TiO_{2},\;Pd,\;Pt$ ]와 In을 사용하여 trimethylamine gas에 대한 감도를 향상시키는 $SnO_{2}$ 가스센서에 대하여 연구하였다. 금속-$SnO_{2}$ 후막은 백금전극이 내장된 알루미나 지지체에 스크린 법으로 제작하였다. 센서의 특성은 검출가스 농도의 함수로서 반응기내 각 센서의 전기적 저항을 측정하여 조사하였으며, $100{\sim}1000ppm$범위의 trimethylamine, dimethylamine과 암모니아가스에 대하여 측정하였다. 그 결과, 금속-$SnO_{2}$의 가스 검출특성은 금속의 종류와 양에 따라 결정되었으며, $250^{\circ}C$에서 trimethylamine에 대한 센서의 감도와 선택성은 1 wt%, Pd와 10 wt%, $TiO_{2}$를 첨가하였을 때 감도가 가장 우수한 것으로 나타났다.

• 한국산업보건학회지
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• 제24권2호
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• pp.122-129
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• 2014

Objectives: Because of its properties such as resistance to heat, chemicals and corrosion; tensile strength; sound absorption; and affordable price, asbestos has been widely used as a building material, fire resistant and retardant, thermal and heat insulator, soundproofing material, and electrical insulation. Since the prolonged inhalation of asbestos can cause serious illnesses such as lung cancer, mesothelioma, and asbestosis after an incubation period of 20 to 40 years, the mineral was classified as a Group 1 carcinogen by the International Agency for Research on Cancer, an intergovernmental agency forming part of the World Health Organization. Children and infants are more at risk than are adults if they are exposed to carcinogens, due to aweaker immunity that has not yet been fully developed. Most childcare centers are operated all day and children tend to spend a great amount of time in the centers. This is why it is important for them to be systematically isolated from environments that may expose them to asbestos. Materials: In order to understand both indoor and outdoor hazards to which children may have been exposed, the study focused on actual surveys of asbestos used in childcare centers, paying special attention to slate-roofed buildings in the vicinity of the centers. Results: A survey of a total of 211 childcare centers showed that the buildings of 18.1% of the centers contained asbestos, with 60.53% of the material being found in classroom ceilings. "Tex" was the most used material for ceilings, making up 89.47% of all ceilings. An outdoor survey showed that childcare centers in Daegu Metropolitan City had an average of 143 slate-roof buildings within a distance of 1km. Conclusions: Buildings housing mainly toddlers, children, teenagers and others more vulnerable to the toxicity of asbestos are not subject to asbestos investigation by law. A legal and practical basis for asbestos control is required for such buildings. In particular, housing materials which contain asbestos in day care centers require asbestos control. GIS should be used to identify the location of buildings with slate roofing materials in the vicinity of daycare centers in order to gauge toxicity of exposure to asbestos caused by potential asbestos friability possibility in outdoor conditions.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.102-110
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• 2005

Piezoelectric transformers(PT) are expected to be small, thin and highly efficient, and which are attractive as a transformer with high power density for step down voltage. For these reasons, we have attempted to develop a step-down PT for the miniaturized adaptor. We propose a PT, operating in thickness extensional vibration mode for step-down voltage. This PT consists of a multi-layered construction in the thickness direction. In order to develop the step-down PT of 10 W class and turn ratio of 0.1 with high efficiency and miniaturization, the piezoelectric ceramics and PT designs are estimated with a variety of characteristics. The basic composition of piezoelectric ceramics consists of ternary yPb(Zr$_{x}$Ti$_{1-x}$)O$_{3}$-(1-y)Pb(Mn$_{1/3}$Nb1$_{1/3}$Sb$_{1/3}$)O$_{3}$. In the piezoelectric characteristics evaluations, at y=0.95 and x=0.505, the electromechanical coupling factor(K$_{p}$) is 58$\%$, piezoelectric strain constant(d$_{33}$) is 270 pC/N, mechanical quality factor(Qr$_{m}$) is 1520, permittivity($\varepsilon$/ 0) is 1500, and Curie temperature is 350 $^{\circ}C$. At y = 0.90 and x = 0.500, kp is 56$\%$, d33 is 250 pC/N, Q$_{m}$ is 1820, $\varepsilon$$_{33}$$^{T}$/$\varepsilon$$_{0}$ is 1120, and Curie temperature is 290 $^{\circ}C$. It shows the excellent properties at morphotropic phase boundary regions. PZT-PMNS ceramic may be available for high power piezoelectric devices such as PTs. The design of step-down PTs for adaptor proposes a multi-layer structure to overcome some structural defects of conventional PTs. In order to design PTs and analyze their performances, the finite element analysis and equivalent circuit analysis method are applied. The maximum peak of gain G as a first mode for thickness extensional vibration occurs near 0.85 MHz at load resistance of 10 .The peak of second mode at 1.7 MHz is 0.12 and the efficiency is 92$\%$.