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Sol-gel Synthesis and Properties of Phosphate Ceramics
Lee, Burtrand I.,Cao, Zhicheng,Samuels, Willam D.,Exarhos, Gregory J. The Korean Ceramic Society 2000 The Korean journal of ceramics Vol.6 No.4
Silicon, titanium, zirconium phosphates were synthesized by starting with appropriate chemical precursors in a solution. The synthetic procedure, chemical and physical structures were examined by FT-IR, liquid and solid state NMR, TGA, SEM, XRD, etc. The phosphates were examined for thermal and electrical properties. Advantages of the synthesis technique and the data on unique structures and thermal properties are reported.
폴리머 함침 탄소섬유보강 시멘트 복합체의 역학적 특성에 관한 연구
박승범,윤의식,Lee, Burtrand. I. 한국콘크리트학회 1992 콘크리트학회지 Vol.4 No.1
본 연구는 고강도 고내구성이면서 신뢰성이 높은 폴리머 함침 탄소섬유보강 시멘트복합에의 개발 응용을 위한 여러 가지 특성을 검토하기 위하여, 복합체는 PAN계 및 Pitch계 탄소섬유, 조강포틀랜드 시멘트, Silica Powder 및 폴리머 함침재를 사용하여 제조하였고, 배합조건별, 재령별, 그리고 양생조건별로 역학적특성, 동결융해저항성 및 장기변형특성에 관한 실험연구를 행하였다. 연구결과, CFRC의 Flow값은 CF혼입율 증가에 따라 거의 직선적으로 저하하였고, 폴리머 함침 CFRC의 압축 인장 휨강도는 CF혼입율 증대에 따라 오토클래브 양생 및 기건양생의 경우에 비하여 현저히 증대하였으며, 또한 월등히 높은 강도를 나타내었다. 그리고, 인자응력-변형관계 및 휨응력-처짐관계는 기건양생 및 오토클래브 양생의 경우 연성적인 비선형을 나타낸 데 비하여 폴리머함침의 경우는 거의 직선적 으로 변화하였고, 동결융해저항성, 건조수촉변형특성 및 내크리프 특성도 다른 양생 방법의 경우에 비하여 크게 개선됨을 확인하였다. In order to examine the mechanical properties of carbon fiber reinforced cement composites with silica powder PAN - based carbon fiber and Pitch- based carbon fiber, and polymer impregnators experimental studies on CFRC impregnated in polymer were carried out. The effects of types, length, and content~i of carbon fibers and matrices of fresh and hardened CFRC impregnated in polymer were examined. The test results show that compressive, tensile, and flexural strength of CFRC impregnated in polymer were much more iriCreased than those of air cured and autodaved CFIIC CFRC impregnated in polymer was also considerably effective in improving toughness, freeze thaw resistance, loss of shrinkage, and creep resist ance, compared with air cured and autoclaved CFRC.
Hydrogen adsorption on nitrogen-doped carbon xerogels
Kang, Kyung Yeon,Lee, Burtrand I.,Lee, Jae Sung Elsevier 2009 Carbon Vol.47 No.4
<P><B>Abstract</B></P><P>Nitrogen-doped (1.2–4.5wt%) carbon xerogels were synthesized from carbonization of resorcinol-formaldehyde polymer in an ammonia atmosphere at various temperatures. The textural properties and the chemical nature of nitrogen in the nitrogen-doped carbon xerogels were analyzed by Ar adsorption/desorption isotherms and X-ray photoelectron spectroscopy, respectively. The maximum hydrogen uptakes were measured to be 3.2wt% at −196°C and 0.28wt% at 35°C. Hydrogen adsorption had a stronger correlation with specific surface area than nitrogen content at the low temperature of −196°C. At the higher temperature of 35°C, optimal nitrogen doping enhanced hydrogen adsorption by electronic modification of carbon in agreement with previous theoretical predictions.</P>