• 청정기술
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• 제24권4호
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• pp.315-322
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• 2018

탄산칼슘($CaCO_3$) 형태의 천연 굴패각을 포졸란 반응 물질인 생석회(CaO)로 전환하기 위해서는 고온(> $800^{\circ}C$)의 소성 공정이 필요하다. 이로 인한 과도한 에너지 비용 투입이 굴패각의 산업적 이용에 큰 걸림돌로 작용하였다. 본 연구의 목적은 소성과정 없이 굴패각을 뒷채움용 고화재 소재로 개발하는 것이다. 본 연구팀은 굴패각을 황산칼슘 형태로 전환하고, 이를 수산화나트륨 및 황토와 혼합하여 고화물을 생성시키는 방법을 제안하였다. 굴패각을 황산칼슘으로 전환시키기 위한 황산용액과 황산칼슘을 소석회($Ca(OH)_2$)로 전환하는 데 필요한 수산화나트륨 용액의 최적 농도를 결정하였다. 신규 고화재, 천연 굴패각, 석탄회 비율을 변화시켜 뒷채움재를 제조하고 양생한 후 공시체의 일축압축강도를 비교하였다. 고화재 함량 비율이 증가할수록 공시체의 일축압축강도는 증가한 반면 동일한 고화재 함량에서 석탄회 대비 천연 굴패각 함량이 증가할수록 공시체의 일축압축강도가 증가하였다. 본 결과는 천연 굴패각과 석탄회를 이용한 뒷채움재 제조에 있어서 황산처리 굴패각, 황토, 수산화나트륨 용액으로 구성된 고화재가 효과적으로 사용될 수 있음을 보여준다. 황산처리 굴패각 기반 고화재는 기존에 개발된 바 없고, 굴패각을 활용한 경제성 있는 뒷채움용 소재 개발과 굴패각의 산업적 활용도를 높이는데 커다란 기여를 할 것이다.

• Advances in nano research
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• 제3권3호
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• pp.169-176
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• 2015

Iron nanoparticles were made by using the modified coprecipitation technique. Usually the characteristics of synthesised particles depend upon the process parameters such as the ratio of the iron ions, the pH of the solution, the molar concentration of base used, type of reactants and temperature. A modified coprecipitation method was adopted in this study. A magnetic stirrer was used for mixing and the morphology and nature of particles were observed after synthesis. Nanoparticles were characterised through XRD. Obtained nanoparticles showed the formation of magnetite and maghemite under citric acid and oxalic acid as stabilisers respectively. The size of nanoparticle was greatly affected by the use of different types of stabilisers. Results show that citric acid greatly reduced the obtained particle size. Particle size as small as 13 nm was obtained in this study. The effects of different kinds of nucleating agents were also observed and two different types of nucleating agents were used i.e. potassium hydroxide (KOH) and copper chloride ($CuCl_2$). Results show that the use of nucleating agent in general pushes the growth phase of nanoparticles towards the end of coprecipitation reaction. The particles obtained after addition of nucleating agent were greater in size than particles obtained by not utilising any nucleating agent. These particles have found widespread use in medical sciences, energy conservation and electronic sensing technology.

• 한국분말재료학회지
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• 제18권3호
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• pp.277-282
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• 2011

[ $LiCoO_2$ ] a cathode material for lithium rechargeable batteries, was prepared using recycled $Co_3O_4$. First, the cobalt hydroxide powders were separated from waste WC-Co hard metal with acid-base chemical treatment, and then the impurities were eliminated by centrifuge method. Subsequently, $Co_3O_4$ powders were prepared by thermal treatment of resulting $Co(OH)_2$. By adding a certain amount of $Li_2CO_3$ and $LiOH{\cdot}H_2O$, the $LiCoO_2$ was obtained by sintering for 10 h in air at $800^{\circ}C$. The synthesized $LiCoO_2$ particles were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analysis.

• Applied Science and Convergence Technology
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• 제23권4호
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• pp.187-191
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• 2014

Indium oxide ($In_2O_3$) nanorods (NRs) which can be expected to increase the device performance in various electronic and electrochemical applications were prepared on carbon fibers via an electrochemical deposition (ED) method. During the ED, the indium hydroxide ($In(OH)_3$) NRs were well grown and firmly attached onto the carbon fibers. After that, they were changed into $In_2O_3$ by dehydration through a thermal annealing. The morphological and structural properties were investigated using field-emission scanning electron microscope images. The crystallinity of as-prepared sample was evaluated by X-ray diffraction. The Fourier transform infrared results confirm that the functional groups are present in the $In_2O_3$ NRs. This facile process of metal oxide nanostructures on carbon fiber can be utilized for flexible electronic and energy related applications.

• 한국입자에어로졸학회지
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• 제10권4호
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• pp.177-182
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• 2014

In this study, nickel-coated aluminum (Ni/Al) powders were synthesized for the utilization of energetic applications. Oxide materials present at the surface of Al powders of $45{\mu}m$ in averaged size were removed by using sodium hydroxide(NaOH) solution which is used for controlling pH. Nickel material is coated into the surface of oxide-removed Al powders by electroless-plating process. The microstructure of fabricated Ni/Al powders shows that nickel layers with a few hundreds nm were very homogeneously formed onto the surface of Al powders. The oxidation behavior of Ni/Al exihibit somewhat faster oxidation rate than that of pure Al with surface oxidation. Also, the higher exothermic reaction was observed from the Ni/Al powders. From the result of this, nickel coating is very promising method to obtain highly reactive and safe Al powders for energetic applications.

• 한국지반공학회지:지반
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• 제2권3호
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• pp.5-14
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• 1986

점성토인 실트질점토(CL)와 사질토인 사질실트(SM)의 시료토에 Ca계의 소석회, Al계의 황산알미늄 첨가제로 안정처리한 결과 Ca계에 있어서는 실트질점토의 경우 알민산칼슘수화물과 탄산칼슘이 반응생성 되었으며 사질실트의 경우에는 탄산화알민산칼슘수화물과 탄산칼슘이 반응생성 (반도생성)되었고 Al계의 첨가 처리 경우에서는 실트질점토와 사질실트 모두에서 산화암미늄이 생성되어 있음을 X-선 회절분석에 의한 구조적 특성을 비교함으로써 확인되었고 이들 안정처리 효과로서 일축압축강도가 Ca계의 경우는 크게 증가하였으나 Al계의 경우에서는 거의 증가가 없었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.93-94
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• 2022

The presence of chloride (Cl-) ions in environments causes localized corrosion resulting decrease the durability of the structures. In this study, 5% Mg containing Al alloys (Al-5Mg) wire used vis-à-vis compared its corrosion resistance with pure Al in 3.5wt.% NaCl solution with exposure periods. Initially both wires exhibited identical open circuit potential (OCP) attributed to the presence of native oxide film on the surface but with the exposure periods it shifted towards active direction owing to the dissolution of oxide film. The pure Al continuously shifted the OCP towards active direction while Al-5Mg shows stabilization of OCP after 8 days of exposure. The OCP of Al-5Mg is slightly higher compared to pure Al wire owing to the activeness of Mg. The total impedance of the Al-5Mg alloy is almost three times greater than pure Al with exposure periods in 3.5 wt.% NaCl solution. It might be formation of Al-Mg LDH (layered double hydroxide) thin film onto the surface.

• 한국응용과학기술학회지
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• 제34권4호
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• pp.705-716
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• 2017

본 연구에서는 0.5, 1.0, 1.5 wt%의 $TiO_2$를 함유하는 인듐-티타늄 수산화물을 졸 및 염기 첨가에 의해 얻었고, $200^{\circ}C$와 $500^{\circ}C$에서 겔화 과정을 통해 ITiO(Indium Titanate Oxide)를 얻었다. $200^{\circ}C$에서 겔화 과정 후 얻어지는 ITiO 입자가 작아서 조밀성이 있는 ITiO 타겟을 제조하였다. 0.5, 1.0, 1.5 wt%의 $TiO_2$를 함유하는 ITiO 타겟을 스퍼터링하여 ITiO 박막을 유리판위에 제작하여 비저항, 전하 이동도, 캐리어 농도를 조사하였다. 이들 박막 중에서 산소 조성이 0.4 %인 조건에서 0.5 wt% 중량% $TiO_2$를 함유하는 ITiO 타겟으로부터 제작된 ITiO 박막이 가장 낮은 비저항, 가장 큰 전하이동도 및 가장 낮은 캐리어 농도를 보임을 알 수 있었고, 얻어진 ITiO 박막의 광투과율을 측정하여 적외선 영역에서 광투과율이 ITO(Indium Tin Oxide) 박막에 비해 현저히 증가함을 발견하였다.

• 대한치과의사협회지
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• 제21권7호통권170호
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• pp.573-577
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• 1983

The antimicrobial action of various dental cements evaluated against common micro-organisms most frequenty found within the components of the normal bacterial flora of oral cavity. They include Streptococcus mutans (2 strains), Lactobacillus acidophilus, Actinomyces viscosus, and Streptococcus sanguis. The test was done by the use of brain heart infusion (BHI) agar plates. A standard mix of each cement was made and placed on the plates which were seeded with a standard culture of microorganisms. After incubation, the halo of bacterial growth inhibition around the cement was identified and its size was measured. Some of the cements tested had obvious antibacterial effect. The cements listed in decreasing order of effectiveness are 1) zinc phosphate and oxyphosphate, 2) silicate, 3) zinc oxide-eugenol, 4) calcium hydroxide, and 5) carboxylate.

• 한국임상수의학회지
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• 제17권1호
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• pp.298-298
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• 2000

Seven years old male lion in Everland Zoo has three fractured canine tooth. To avoid the risk of a possible fracture with pulp exposure after restroration of largest abration defects, endodontic therapy was performed. The pulp chamber was filled with calcium hydroxide, zinc oxide cement and gutta percha. We also installed the Crown prosthesis was installed in fractured canine tooth to protect the tooth and to improve the cosmetics and function of the tooth. The lion could eat in one day and there were no any signs of dental problem. It is the obvious prophylactic procedure for wild animal is the inclusion of an oral examination at every opportunity to handle the animal. It is considered that crown prosthesis after endodontic therapy was useful for maintaining normal physiological function and for provention of additional fracture or complication.