• Advances in concrete construction
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• 제11권1호
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• pp.73-80
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• 2021

Rice Husk Ash (RHA) geopolymer paste activated by sodium aluminate were characterized by X-ray diffractogram (XRD), scanning electron microscope (SEM), energy dispersion X-Ray analysis (EDAX)and fourier transform infrared spectroscopy (FTIR). Five series of RHA geopolymer specimens were prepared by varying the Si/Al ratio as 1.5, 2.0, 2.5, 3.0 and 3.5. The paper focuses on the correlation of microstructure with hardened state parameters like bulk density, apparent porosity, sorptivity, water absorption and compressive strength. XRD analysis peaks indicates quartz, cristobalite and gibbsite for raw RHA and new peaks corresponding to Zeolite A in geopolymer specimens. In general, SEM micrographs show interconnected pores and loosely packed geopolymer matrix except for specimens made with Si/Al of 2.0 which exhibited comparatively better matrix. Incorporation of Al from sodium aluminate were confirmed with the stretching and bending vibration of Si-O-Si and O-Si-O observations from the FTIR analysis of geopolymer specimen. The dense microstructure of SA2.0 correlate into better performance in terms of 28 days maximum compressive strength of 16.96 MPa and minimum for porosity, absorption and sorptivity among the specimens. However, due to the higher water demand to make the paste workable, the value of porosity, absorption and sorptivity were reportedly higher as compared with other geopolymer systems. Correlation regression equations were proposed to validate the interrelation between physical parameters and mechanical strength. RHA geopolymer shows comparatively lower compressive strength as compared to Fly ash geopolymer.

• 폴리머
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• 제36권6호
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• pp.822-830
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• 2012

본 연구에서는 실리카 나노입자를 우수한 내가수분해성을 가지는 dipodal 형태의 bis[3-(trimethoxysilyl)propyl]amine(BTMA) 실란 커플링제로 표면 개질한 후, 실리카에 도입된 BTMA의 2차 아미노기인 N-H기와 마이클 부가반응이 가능한 acrylate기를 1분자당 2개씩 가지는 poly(ethylene glycol)diacrylate(PEGDA)로 표면 처리하여 acrylate기를 실리카 입자 표면에 도입하는 연구를 수행하였다. PEGDA의 몰수 및 3가지 서로 다른 분자량의 PEGDA(M.W. 258, 575, 700) 처리가 실리카 표면에 도입되는 acrylate기의 구조에 미치는 영향을 fourier transform infrared spectroscopy(FTIR), elemental analysis(EA, 원소분석) 및 고체 상태 $^{13}C$ cross-polarization magic angle spinning(CP/MAS) nuclear magnetic resonance spectroscopy(NMR)법을 사용하여 분석하였다. 액체상태의 순수 PEGDA와 순수 BTMA를 같은 몰 비로 반응시키면 PEGDA 1분자당 2개씩 존재하는 acrylate기 중 1개 acrylate기는 순수 BTMA의 N-H기와 1:1의 비율로 마이클 부가반응이 일어나 ${\beta}$-amino acid ester를 형성하고, 나머지 1개의 acrylate기는 남아서 중합반응이 가능한 단량체 합성이 가능하다. 하지만, BTMA로 개질된 실리카 입자를 PEGDA와 반응시키면, PEGDA 1분자당 2개씩 결합있는 acrylate기 대부분이 실리카 입자에 결합되어 있는 BTMA의 N-H기와 마이클 부가반응으로 ${\beta}$-amino acid ester를 형성하여, acrylate기의 C=C기 대부분이 C-C로 변화함을 확인하였다.

• Journal of Photoscience
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• 제9권2호
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• pp.106-109
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• 2002

Archaeal rhodopsins possess retinal molecule as their chromophores, and their light-energy and light-signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of protein then leads to functional processes, proton pump in bacteriorhodopsin (bR) and transducer activation in phoborhodopsin (pR). It is known that sensory rhodopsins can pump protons in the absence of their transducers. Thus, there should be common and specific features in their protein structural changes for function. In this paper, our r ecent studies on pR from Natronobacterium pharaonis (ppR) by means of low-temperature Fourier-transform infrared (FTIR) spectroscopy are compared with those of bR. In particular, protein structural changes upon retinal photoisomerization are studied. Comparative investigation of ppR and bR revealed the similar structures of the polyene chain of the chromophore and water-containing hydrogen-bonding network, whereas the structural changes upon photoisomerization were more extended in ppR than in bR. Extended protein structural changes were clearly shown by the assignment of the C=O stretch of Asnl05. FTIR studies of a ppR mutant with the same retinal binding site as in bR revealed that the Schiff base region is important to determine their colors.

• 대한환경공학회지
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• 제39권7호
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• pp.426-439
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• 2017

이 총설은 근권에서 일어나는 유기산, 산화음이온, 그리고 금속 산화물 간의 상호작용을 이해하는데 활용하고 있는 적외선 분광학과 계산화학에 대한 기본적 원리, 역사, 적용 분야, 장점, 그리고 단점에 대해 최근 연구들을 바탕으로 요약하였다. 식물의 유기산과 금속 산화물은 토양 환경에서 산화음이온의 유효도와 이동성을 결정하기 때문에, 산화음이온의 환경 내 거동을 이해하기 위해서는 계면에서 이들의 상호작용을 이해하는 것이 중요하다. 적외선 분광학의 감쇠 전반사 기법은 계면에서 일어나는 화학적인 반응을 측정하는 강력한 도구이지만, 광학적 특성들이 실험 설계와 대상에 따라 매우 다르게 나타날 수 있으므로 이를 이용한 측정은 까다롭다. 전반사에 의해 발생하는 소멸파의 침투 깊이가 가장 중요한 매개 변수인데, 침투 깊이는 적외선의 입사각과 대상 파장, 그리고 매질의 굴절률에 따라 결정된다. 또한, 적외선을 이용하여 계면에서의 화학반응을 분석할 때 겹쳐서 발생하는 스펙트럼을 해석하는 것 역시 큰 문제이기 때문에, 겹쳐 나타나는 스펙트럼을 해석하여 밴드를 검출하고, 이 스펙트럼을 deconvolution하는 것이 필수적이다. 본 총설에서는 적외선스펙트럼을 처리하는 기본적인 절차와, 밴드 검출에 사용하는 네가지 방법인 도함수 분광학과 이차 상관 분광학, multivariate curve resolution, 계산 화학을 액체상에 존재하는 인산염 종분화로 설명하였다. 스펙트럼 처리와 계산 화학을 조합하였을 때 간단한 계에서 측정한 겹쳐진 스펙트럼 결과는 해석할 수 있었지만, 자연과 같은 복잡계에서 측정한 겹쳐진 스펙트럼을 해석하는 것은 여전히 불가능한 상황이다. 그러나 향후 분석 및 신호 처리 기술 발달에 따라 복잡계뿐만 아니라 자연계에서 일어나는 계면 반응을 해석할 수 있을 것으로 기대한다.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1638-1642
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• 2012

A series of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) tri and multiblock copolymers with relatively high molecular weights were synthesized through the coupling reaction between the bis(acyl chloride) of carboxylated PLA and mono or dihydroxy PEG. The coupling reaction and the copolymer structures were monitored by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The melting temperature (Tm) of PEG blocks decreased with the presence of PLA sequences attaching to PEG blocks. The CMC values were determined to be 10-145 mg/L depending on the length of PLA and PEG blocks and the structure of the block copolymers.

• 멤브레인
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• 제22권2호
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• pp.104-112
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• 2012

Chemically stable Polyvinylidene fluoride-hexa-fluoropropane (PVDF-HFP) copolymer asymmetric membranes were prepared by the conventional phase inversion process, using Dimethyacetamide (DMAc) as a solvent and water as a non-solvent. To control the pore size and porosity of the PVDF-HFP membranes, tetra-ethoxysilane (TEOS) was used as a pore-forming agent. The prepared membranes were characterized, using several analytical methods such as Fourier Transform Infrared spectroscopy (FTIR), Thermo-gravimetric analyzer (TGA), Field Emission Scanning Electronic Microscopy (FESEM). TEOS turned out to increase porosity and make homogeneous pores on the membranes. Depending on the composition of the dope solutions, the pore size was ranged from 0.1 to 1.0 ${\mu}m$. The flux of the PVDF-HFP membranes prepared by using TEOS as a pore forming agent was increased substantially without much decrease in the rejection. When 15 wt% PVDF-HFP solution was blended with 13 wt% TEOS solution at composition ratio of 70/30 in wt%, the water flux at 2 bars was about 2 $m^3/m^2day$.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2609-2612
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• 2012

A simple green method was developed for rapid synthesis of silver and gold nanoparticles (AgNPs and AuNPs) has been reported using Lonicera japonica flower extract as a reducing and a capping agent. AgNPs and AuNPs were carried out at $70^{\circ}C$. The successful formation of AgNPs and AuNPs have been confirmed by UV-Vis spectro photometer, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray Analysis (EDAX), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). To our knowledge, this is the first report where Lonicera japonica flower was found to be a suitable plant source for the green synthesis of AgNPs and AuNPs.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.134-137
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• 1995

Studies on the formulations of the additives such as antioxidants, crosslinking agent, and trans-stilbeneoxide (StO) with polypropylene (PP) have been carried out to improve the resistance of gamma radiation sterilization. The irradiated PP and ethylene-propylene copolymers samples with control and additives were characterized by mechanical tester, colorimetry, and Fourier transform infrared spectroscopy with total attenuated reflectance mode (FTIR-ATR). Crosslinking agent and StO formulated PP showed remarkable radiation resistance and minimum discoloration. Also, radiation resistance of ethylene propylene copolymers with 3% of ethylene contents was better than that of PP homopolymers in the case of no additives. The proposed mechanisms of radiation stabilization with additives are also discussed.

• 한국세라믹학회지
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• 제54권4호
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• pp.298-302
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• 2017

To investigate the influence of alkaline impurity K content on bubbles of quartz glass, samples were prepared based on $SiO_2$ sand with differing amounts of potassium hydroxide solution added by electric fusion. Bubble properties such as number, diameter and bubble fraction were determined using a stereoscopic microscope. The results of the observations indicated that an alkaline impurity content of 100 ppm had a good effect on bubble decline in quartz glass. The effect on OH was investigated by FTIR(Fourier transform infrared spectroscopy).

• Journal of Photoscience
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• 제12권3호
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• pp.171-174
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• 2005

The relationship between porous surfaces and photoluminescence (PL) behavior of porous silicon carbide (PSC) in various solvents has been studied. The porous surfaces of p-type silicon carbide can be fabricated by electrochemical anodization from the 6H, 15R, 4H-${\alpha}$-SiC substrates in dark-current mode (DCM) condition. We have been investigated the dependence of the PL spectra of PSC under the medium having the different dielectric constants. It has been found that PL depends sensitively on the environment surrounding the surface. The extent of chemically stability on the surface of PSC due to the various solvents was confirmed by reflectance Fourier transform infrared (FTIR) spectroscopy. Detailed IR experiments on the PSC samples were carried out before and after various solvents immersion. These results will be offered important information on the origin of PL in porous structure.