인공경량골재의 표피층 구조가 흡수된 물의 방출속도에 미치는 영향

강승구,Kang, Seung-Gu 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.11

The artificial aggregates with dense surface layer (shell) was fabricated and the dependence of water emission rate upon the shell structures was studied. The EAF dust containing many flux components and waste white clay with ignition loss of above 48% were used as for liquid phase and gas forming agents during a sintering process respectively. In addition, the shell structure was modified with various processes and the modification effect on water emission rate was analyzed. The pores under $10{\mu}m$ were found in the sintered artificial light aggregates and disappeared by incorporating to a bigger pore during re-sintering. The water emission rate in an initial step depended on a void content of aggregates filled in a bottle rather than a shell structure. But, after 7 days where the water emission of the aggregate with a shell is above 40%, the shell of aggregates suppressed the water emission. The core of aggregates was exposed and most shell was lost when crushed to smaller size so, the ability for suppressing water emission of the crushed aggregates decreased. The activation energy for the water emission was $3.46{\pm}0.25{\times}10^{-1}$J/mol for the most specimens showing that the activation energy is irrelevant to the pore size distribution and shell structure.

수직로에서 부유 소성된 경량 세골재의 특성

강승구,Kang, Seung-Gu 한국결정성장학회 2008 韓國結晶成長學會誌 Vol.18 No.6

입자를 부유 상태에서 소성할 수 있는 수직로를 이용하여 2 mm 이하 크기의 경량 세골재를 제조하고 그 물리적 특성을 고찰하였다. $1200{\sim}1300^{\circ}C$에서 소성된 대부분 시편은 표면에 다량의 액상이 발달하였고 따라서 내부의 가스가 팽창하여 다공성의 중앙부와 상대적으로 치밀한 표피층이 형성되었다. 특히 압출 성형체를 파쇄시켜 얻은 부정형의 C 계열 시편은 $1300^{\circ}C$ 이상으로 소결하면 내부에 가스가 팽창하여 시편 전체가 부풀어져서 구형으로 되었다. 본 부유 수직로에서 소성된 시편의 겉보기 비중은 $0.68{\sim}1.08$ 범위로 대부분 물에 뜰 정도의 경량이었다. 제조된 경량 세골재의 흡수율은 기공율과 비례하였고, 따라서 내부 기공들이 완전 고립된 폐쇄기공은 아님을 나타내었다. 부유소성로에서 제조된 세골재는 전기 머플로에서 소성된 시편과 비슷한 물성을 나타내었으나, 전기로에서 나타나는 골재 간 융착 현상이 발생하지 않았다. 수직로에서 부유소성된 세골재의 내충격성은 자연골재보다 다소 낮았으나, 단위용적중량은 KS 규격 기준을 만족하였다. The fine aggregates of below 2 mm size was fabricated using by the vertical furnace in which the aggregates could be sintered at floating state and its physical properties were analyzed. The liquid formed at the surface of specimens sintered at $1200{\sim}l300^{\circ}C$ induced a gas in core to expand so the denser shell and porous core could be produced. The C series specimen fabricated by crushing an extruded body had an irregular shape and sharp edges but those became spheroidized by bloating due to gas expansion inside. The fine aggregates fabricated in this study was as light as floating in the water and had an apparent density of $0.68{\sim}1.08$. The absorption rate was proportioned to a porosity showing that the pores in core was not closed completely. The properties of fine aggregates fabricated in vertical furnace were similar with those of in an electric muffle furnace but the sticking-together phenomenon by surface fusion was not occurred in the vertical furnace. The aggregates fabricated in this study had a little lower impact resistance than that of natural aggregate but satisfied the unit volume weight standard specified in KS.

다양한 성형법으로 제조된 인공 골재의 특성

강승구,Kang, Seung-Gu 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.1

The physical properties of artificial aggregates made from clay and inorganic wastes with poor plasticity depends largely on forming method. The artificial aggregates composing of coal fly ash, stone sludge and clay were fabricated using 4 different forming methods and those physical properties were comparatively analyzed. The surface of aggregates made through the extrusion forming process was dense and smooth but was rough for the aggregates obtained by crushing a tile-shaped green body. The aggregates made by pelletizing process had a weak green strength and bumpy surface. The shell generated at surface during a high temperature sintering process induced the most aggregates to be bloated due to a dense shell. But the aggregates made through pelletizing process with dense surface layer showed no significant change in bulk density with sintering temperatures. The water absorption of aggregates decreased with sintering temperature, and that of pelletized specimen was standing $1.8{\sim}2.2$ times higher than that of made by other forming methods. It is concluded that the aggregates having various properties could be fabricated from one batch by using different forming methods.

EAF dust가 첨가된 결정화 유리의 물리적 특성

강승구,Kang, Seung-Gu 한국결정성장학회 2008 한국결정성장학회지 Vol.18 No.6

$Fe_2O_3$, ZnO 등이 주성분인 EAF dust를 $30{\sim}70\;wt%$ 첨가한 규산염계 유리 및 결정화유리를 제조하고, 시편내부에 생성된 상 및 미세구조와 물리적 특성과의 관계를 고찰하였다. 또한 제조된 유리와 결정화유리의 결정화 거동을 상분석 및 미세구조 관찰을 통하여 분석하였다. EAF dust가 30 wt% 첨가된 용융체의 경우 전형적인 비정질 XRD 패턴을 나타냈으며, 그 이상 첨가된 용융체에는 미용해 된 결정상이 일부 존재하였다. 모든 결정화유리에서는 franklinite, willemite 그리고 augite 결정상이 형성되었다. 결정화유리의 비중은 같은 조성의 유리에 비하여 높았고, EAF dust 함량에 따라 함께 증가하였다. 또한 결정화 유리의 열적 및 기계적 특성이 유리보다 우수하게 나타났다. 즉 유리는 EAF dust 첨가량과 함께 열팽창 계수가 증가하였으나 결정화유리에서는 반대로 감소하였다. 또한 EAF dust 첨가량에 따라 비커스 경도는 유리 및 결정화유리 모두 증가되었으며 같은 조성에서 결정화 유리의 경도값이 항상 더 높게 나타났다. The glass and glass-ceramics containing EAF dust $30{\sim}70\;wt%$ were fabricated and the dependance of physical properties upon crystal phases and microstructure formed was studied. The crystallization behavior of glass and glass-ceramics containing various contents of EAF dust composing of mainly $Fe_2O_3$ and ZnO was analyzed by crystal identification and microstructure observation. The glass specimen with EAF dust 30 wt% showed a typical amorphous pattern in XRD results and the specimen with above 30 wt% EAF dust had some un-dissolved crystals which was originated from EAF dust. The all glass-ceramics had franklinite, willemite and augite crystal phases. The density of glass-ceramics was higher than that of same composition glass, and it increased with EAF dust contents. In addition, the thermal and mechanical properties of glass-ceramics were always higher than those of glasses. In other words, the thermal expansion coefficient of glass increased with EAF dust contents while it decreased for the glass-ceramics. The vickers hardness for the glass and glass-ceramics increased with EAF dust content, the glass-ceramics always being higher those of glass of same composition.

화력발전소 바닥재로 제조된 결정화 유리의 미세구조

강승구,Kang, Seung-Gu 한국재료학회 2009 한국재료학회지 Vol.19 No.2

Glass ceramics were made from coal bottom ash by adding CaO and $Li_2O$ as glass modifiers and $TiO_2$ as a nucleating agent in a process of melting and quenching followed by a thermal treatment. The surface of the glass ceramics has 1.6 times more $Li_2O$ compared to the inner matrix. When $TiO_2$ was not added or when only 2 wt% was added, the surface parts of the glass ceramics were crystalline with a thickness close to $130{\mu}m$. In addition, the matrixes showed only the glass phase and not the crystalline phase. However, doping of $TiO_2$ from 4 wt% to 10 wt% began to create small crystalline phases in the matrix with an increase in the quantity of the crystalline. The matrix microstructure of glass ceramics containing $TiO_2$ in excess of 8 wt% was a mixture of dark-gray crystalline and white crystalline parts. These two parts had no considerable difference in terms of composition. It was thought that the crystallization mechanism affects the crystal growth, direction and shape and rather than the existence of two types of crystals.

인공경량골재 특성의 발포제 및 융제 첨가 의존성

강승구,Kang, Seung-Gu 한국결정성장학회 2009 韓國結晶成長學會誌 Vol.19 No.1

점토와 석분오니로 비중이 1 이하인 인공경량골재를 제조할 때 발포제와 융제의 종류 및 소성온도가 미세구조, 부피 비중 흐리고 흡수율에 미치는 영향을 분석하였다. 한 종류의 기포 발포제를 첨가한 경우 부피 비중 $0.5{\sim}1.0$, 흡수율 $41{\sim}110%$ 범위의 다공성 인공경량골재 제조가 가능하였으나 골재 외형이 거칠고 미세구조가 불균일하였다. 융제 된 발포제가 각각 한 종류씩만 첨가된 골재는 소성 중 시편이 폭발하여 표피층(shell)의 일부가 소실되었다. 발포제로서 진공오일외에 ${Fe_2}{O_3}$와 탄소를 복합 첨가할 경우 black core와 shell 구조가 잘 형성되어 균일한 미세구조론 나타내었다. 융제된 발포제가 복합적으로 첨가된 $1200^{\circ}C$ 소성체의 경우, 점토 및 석분오니로만 제조된 시편에 비해 부피비중이 67% 줄고 흡수율은 48배 증가하여 우수한 발포특성을 좌였다. 본 연구에서 제조된 복합 첨가 계열 시편은 부피비중 $0.5{\sim}1.0$, 흡수율 $50{\sim}125%$의 다양한 물성을 나타냈으며, 따라서 각종 분야에 적용할 수 있을 것으로 생각된다. The effect of bloating and fluxing agent on the microstructure and physical properties were studied in manufacturing the artificial lightweight aggregates of bulk density below] using clay and stone sludge. In case of the aggregates added only with bloating agent, the bulk density and water absorption were $0.5{\sim}1.0$ and $41{\sim}110%$ respectively but the microstucture was not uniform with a rough appearance. For the aggregates added with a fluxing agent and one bloating agent, a part of shell was lost due to explosion of specimen caused by over-bloating during a sintering. The mixed addition of bloating agents with vacuum oil, carbon and ${Fe_2}{O_3}$ made the microstructure homogeneous by generating an uniform black core and shell structure. The aggregates added with mixed agents and sintered at $1200^{\circ}C$ showed the bulk density 67 % lower and water absorption 48 times higher than those of the specimen with no additives. ]n this study, the artificial lightweight aggregates showing the bulk density of $0.5{\sim}1.0$ and water absorption of $50{\sim}125%$ could be fabricated to apply to various fields.

TiO₂ 하이브리드에 의한 바이오-폴리우레탄 멤브레인 필름의 투습성 향상에 관한 연구

강승구,강구,곽남호,진호진,홍성현,주일중,권오경,민병길,Kang, Seung-Gu,Kang, Goo,Kwak, Nam Ho,Jin, Hojin,Hong, Seong Hyun,Joo, Il Jung,Kwon, Oh Kyung,Min, Byung Gil 한국섬유공학회 2016 한국섬유공학회지 Vol.53 No.2

The aim of this work was to enhance the water vapor permeability of bio-polyurethane thin film, whose essential application is as a non-microporous type of film in breathable fabrics, by hybridizing it with nano- and micro-sized titania ($TiO_2$). The bio-polyurethanes were synthesized from 4,4-diphenylmethane diisocyanate (MDI) and a polyol mixture containing polyethylene glycol (PEG) and soybean oil-based polyol, that is, bio-glycols by the hydroxylation of soybean oils upto 25% by weight of bio-polyurethane. We studied the effect of hybridizing the bio-polyurethane films with hydrophilic nano- or micro-sized $TiO_2$ on their breathability by measuring the water contact angle and the water vapor permeability of the films; it was found to significantly enhance the permeability of the bio-polyurethane film. Further, nano-$TiO_2$ was more effective than micro-$TiO_2$ due to the higher surface area resulting from nano particles. On the other hand, it is expected that it would be possible to provide additive functionality to the bio-PU membranes due to photocatalytic effect of nano-$TiO_2$.

슬립 공정으로 제조된 비산재-점토 계 소결체의 물성 및 기반재로의 적용특성

강승구,이영생,Kang, Seung-Gu,Lee, Yeong-Saeng 한국결정성장학회 2008 한국결정성장학회지 Vol.18 No.6

The civil engineering properties for the coal fly ash produced from a power plant mixed with sintered powders made from the fly ash-clay slip system were measured and its applicability for the foundation soils was investigated. The F-slip whose dispersion state is 'not good' and C-slip which is re-flocculated by adding a flocculant to a well-dispersed slip were fabricated and then sintered. The sintered body made from C-slip had more uniform microstructure than that of F-slip, therefore, the bulk density and compressive strength were improved. The civil engineering properties such as compression index, compressive strength, permeability coefficient of fly ash were improved by mixing $0.84{\sim}2\;mm$ powders obtained by crushing a sintered body made from C-slip. Therefore, the applicability of mixed powders composing of fly ash and sintered body made from C-slip was confirmed to foundation soils due to its improved civil engineering properties. 비산재-점토 계 슬립으로부터 제조된 소결체 분쇄 분말을 화력발전소에서 배출되는 비산재와 혼합하여 그 토목공학적 특성을 측정하고 기반재로의 적용가능성을 조사하였다. 분산이 잘 되지 않은 비산재-점토 계 슬립(F-slip)과 이를 분산 시킨 후 재응집시킨 슬립(C-slip)을 제조하고 이로부터 소성체를 합성하였다. C-slip으로부터 제조된 소결체가 F-slip 경우 보다 더 균일한 미세구조를 나타냈으며 따라서 그 밀도 및 강도가 더 높았다. C-slip으로 부터 소성된 소결체를 파쇄한 뒤 $0.84{\sim}2\;mm$ 입자를 추출하여 순수 비산재에 섞은 혼합분말은 압축지수, 압축강도 그리고 투수계수 등 토목공학적 물성이 순수 비산재에 비하여 향상되었다. 따라서 슬립 공정으로 제조된 분말을 비산재에 혼합하게 되면 그 역학적 특성이 개선되어 기반재 또는 기층재로의 적용 가능성이 향상됨을 확인하였다.

표적물질 및 중성자 스펙트럼이 ⁹⁹Tc과 ¹²⁹I의 원자로 내부 핵변환에 미치는 영향

강승구,이현철,Kang, Seung-gu,Lee, Hyun-chul 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.2

As a rule, geological disposal is considered a safe method for final disposal of high-level radioactive waste. However, some long-lived fission products like $^{99}Tc$ and $^{129}I$ contained in spent nuclear fuel are highly mobile as less sorbing anionic species in the subsurface environment and can mainly cause exposure dose to the ecosystem by emission of beta rays in the hundreds of keV range. Therefore, if these two nuclides can be separated and converted with high efficiency into radioactively unharmful nuclides, this would have a positive effect on disposal safety. One candidate method is to transmute these two nuclides in nuclear reactors into short-lived nuclides or into stable nuclides. For this purpose, it is necessary to evaluate which reactor type is more efficient in burning these two nuclides. In this study, the simulation results of nuclear transmutation of $^{99}Tc$ and $^{129}I$ in light water reactor (PWR), heavy water reactor (CANDU) and fast neutron reactor (SFR, MET-1000) are compared and discussed.

수직형 유동층로에서 제조된 인공경량 세골재의 특성

강승구,Kang, Seung-Gu 한국결정성장학회 2009 한국결정성장학회지 Vol.19 No.1

기존의 로타리 킬른으로는 융착 현상 때문에 3 mm 이하 크기의 세골재를 제조하기 어려웠다. 이를 해결할 수 있는 수직형 유동층로를 설계, 제작하고 이로부터 점토 : 석분슬러지 :폐백토 =60 : 30 : 10(wt%)조성의 성형체를 소성하여 비중 $1.1{\sim}1.7$, 흡수율 $11{\sim}19%$의 다양한 특성을 갖는 경량 세골재를 제조하였다. 골재를 발포시키기 위한 최소 소성온도는 $1130^{\circ}C$이었다. $1140^{\circ}C$ 이상으로 소성된 시편은 전형적인 발포 경량골재 특성을 보였으며, 표면에 균열이 크게 벌어져서 내부 층이 드러나 보였다. 그러나 표면에 발생된 균열은 black core 내부로 진행되지 않았기 때문에 흡수율에 영향을 주지 않았다. 소성온도가 증가하면 골재의 shell 두께는 감소하고 black core 영역은 넓어졌으나 유지시간은 미세구조에 따른 영향을 주지 않았다. 소성온도가 증가되면 표면에 액상 발생량이 증가하여 골재의 흡수율은 감소하였다. 또한 소성시간도 골재 흡수율에 큰 영향을 주었는데, 이는 액상을 형성하고 또 생성된 액상이 표면의 개기공을 막아 폐기공으로 변화시키는데 시간이 필요하기 때문인 것으로 생각된다. It was difficult for the existing rotary kiln to fabricate the fine aggregates under 3 mm due to the sticking phenomenon between specimens. In this study, the vertical type fluidizing furnace was designed and manufactured by which the lightweight fine aggregates of specific gravity $1.1{\sim}1.7$, water absorption $11{\sim}19%$ could be fabricated from the green body of clay: stone sludge: spent bleaching clay = 60 : 30 : 10 (wt%) without sticking-together happening. The minimum sintering temperature for bloating of aggregates was $1130^{\circ}C$. The specimens sintered over $1140^{\circ}C$ showed the typical bloating characteristics of lightweight aggregates and an inner layer was discovered due to widened cracks on a surface. But the crack on a surface did not propagate into a black core area so had no effect on a water absorption of aggregates. The sintering temperature made the thickness of shell and the black core area thin and expanded respectively but the sintering time did not affect the microsturcture of aggregates. The water absorption of aggregates decreased with increasing temperature owing to increased amount of liquid formed on a surface. Also sintering time affected a lot on a water absorption because it takes a time to form a liquid, which change the open pores to closed pores by blocking.