$BaTiO_3/SiO_2$ 복합섬유의 제조와 미세구조 연구

김영운,이태상,김의화,이승구,Kim, Young-Un,Lee, Tae-Sang,Kim, Eui-Hwa,Joo, Yong-L.,Lee, Seung-Goo 한국섬유공학회 2007 한국섬유공학회지 Vol.44 No.5

In order to prepare neat barium titanate/silica ($BaTiO_3/SiO_2$) composite fibers, combined process of sol-gel synthesis and electrospinning was utilized. Electrospun composite fibers were subjected to the high temperature calcinations to fabricate the crystalline structure of $BaTiO_3$. The fraction of barium titanate to silica in fiber and the calcination temperature of fiber were varied. Prepared $BaTiO_3/SiO_2$ composite fibers have diameters of 500 nm to $3\;{\mu}m$ and show the neat surface morphology without any porous structure. Calcined composites fibers were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR).

지방산 칼륨 Cream Soaps 의 상거동 연구

노민주,여혜림,이지현,박명삼,이준배,윤명석 사단법인 대한화장품학회 2022 대한화장품학회지 Vol.48 No.1

The potassium cream soap with fatty acid called cleaning foam has a crystal gel structure, and unlike an emulsion system, it is weak to shear stress and shows characteristics that are easily separated under high temperature storage conditions. The crystal gel structure of cleansing foams is significantly influenced by the nature and proportion of fatty acids, degree of neutralization, and the nature and proportion of polyols. In order to investigate the effect of these parameters on the crystal gel structure, a ternary system consisting of water/KOH/fatty acid was investigated in this study. The investigation of differential scanning calorimeter (DSC) revealed that the eutectic point was found at the ratio of myristic acid (MA) : stearic acid (SA) = 3 : 1 and ternary systems were the most stable at the eutectic point. However, the increase in fatty acid content had little effect on stability. On the basis of viscosity and polarized optical microscopy (POM) measurements, the optimum degree of neutralization was found to be about 75%. The system was stable when the melting point (Tm) of the ternary system was higher than the storage temperature and the crystal phase was transferred to lamellar gel phase, but the increase in fatty acid content had little effect on stability. The addition of polyols to the ternary system played an important role in changing the Tm and causing phase transition. The structure of the cleansing foams were confirmed through cryogenic scanning electron microscope (Cryo-SEM), small and wide angle X-ray scattering (SAXS and WAXS) analysis. Since butylene glycol (BG), propylene glycol (PG), and dipropylene glycol (DPG) lowered the Tm and hindered the lamellar gel formation, they were unsuitable for the formation of stable cleansing foam. In contrast, glycerin, PEG-400, and sorbitol increased the Tm, and facilitated the formation of lamellar gel phase, which led to a stable ternary system. Glycerin was found to be the most optimal agent to prepare a cleansing foam with enhanced stability. Cleansing foam이라 불리는 지방산 칼륨 cream soap은 crystal gel 구조로 이루어져 있어 유화계와는달리 전단응력에 약하며 고온의 보관조건에서 쉽게 분리되는 특성을 보여준다. Crystal gel 구조는 지방산의종류 및 비율, 중화도, polyol의 종류와 사용량에 따라 크게 영향을 받는다. Crystal gel 구조에 미치는 이들의영향을 조사하기 위해 water/potassium hydroxide (KOH)/fatty acid ternary system에서 실험을 실시하였다. Differential scanning calorimeter (DSC) 측정 결과 myristic acid (MA) : stearic acid (SA) = 3 : 1 비율에서공융점(eutectic point)를 갖고 이 혼합비가 가장 안전한 삼성분계(ternary system)를 만든다는 것을 발견했다. 점도 측정과 편광현미경 (POM) 관찰 결과 중화도는 75% 부근이 최적이라고 판단된다. 삼성분계의 melting point (Tm)이 보관온도보다 높을 때, 그리고 crystal phase가 lamellar gel phase로 상 전이가 일어날 때 안정하나지방산 함량의 증가는 안정성에 거의 영향을 미치지 않는다. 삼성분계에 polyol의 첨가는 Tm을 변화시키고 상전이를 일으키는데 중요한 역할을 한다. 클렌징폼의 구조는 저온 주사전자현미경 (Cryo-SEM), 소각 및 광각X-선 산란 (SAXS, WAXS) 분석으로 규명하였다. Butylene glycol (BG), propylene glycol (PG), dipropylene glycol (DPG)은 Tm을 낮추어주며 lamellar gel phase 형성을 어렵게 하는 반면 glycerin, PEG-400, sorbitol은Tm을 상승시키고 lamellar gel phase 형성을 용이하게 하며 안정한 삼성분계를 만든다.

졸-겔 침지코팅법으로 제조된 TiO₂ 박막의 구조적.광학적 특설

김동진,이학준,한성홍,김의정 한국광학회 2002 한국광학회지 Vol.13 No.3

촉매로 사용한 HCl 농도를 달리하여 TiO$_2$ 졸(T1-0.7N, T2-2.ON)을 제조하고, 졸-겔 침지코팅법을 이용하여 TiO$_2$ 박막을 제작하였으며, 각 박막의 열처리 온도에 따른 박막의 구조적 및 광학적 특성을 측정.분석하였다. X-선 회절분석 결과 T1박막의 경우, 400-80$0^{\circ}C$의 열처리 온도에서는 아나타제 결정상을 나타내었고, 100$0^{\circ}C$에서는 루타일 결정상을 나타내었다. T2 박막의 경우, 루타일 결정상이 보다 낮은 열처리 온도인 80$0^{\circ}C$에서 나타났다. 그리고 박막의 결정성은 T2 박막이 T1 박막보다 우수하였다. 열처리 온도가 증가함에 따라 박막의 결정 크기는 증가하였으며, T2 박막의 경우 아나타제 결정의 크기는 T1 박막보다 크며 루타일 결정의 크기는 작은 것으로 측정되었다. 박막의 표면 상태는 루타일 결정상을 지닌 박막이 아나타제 결정상을 지닌 박막보다 치밀하게 형성되어졌고, 이러한 현상은 T2박막에서 보다 뚜렷하게 나타났다. 100$0^{\circ}C$에서 열처리한 박막은 300~700nm의 파장영역에서 결정상 전이에 의한 밴드갭 에너지의 변화와 박막의 조성변화로 인한 흡수의 발생, 그리고 입자의 크기 증가에 의한 산란효과로 투과율의 감소를 초래하였다. 제조된 박막의 굴절률은 열처리 온도가 증가할수록 증가하였으며, 두께와 porosity는 감소하였다. 또한 T2 박막의 굴절률은 T1 박막보다 높았고, porosity는 낮았다. The TiO$_2$ coating solutions were synthesized with different concentrations (T1-0.7N, T2-2.0N) of hydrochloric acid used as catalyst. and TiO$_2$ thin films were prepared by sol-gel dip coating. Their structural and optical properties were examined as a function of calcination temperature. XRD results showed that T1 thin films calcined at 400~80$0^{\circ}C$ had the anatase phase, while those calcined at 100$0^{\circ}C$ had the rutile phase. T2 thin films calcined at 40$0^{\circ}C$ and $600^{\circ}C$ had the anatase phase, with the rutile phase for calcination at 80$0^{\circ}C$. Crystallinity of T2 thin films was superior to that of T1 thin films. The crystallite size of TiO$_2$ thin films increased with increasing calcination temperature, and the crystallite size of anatase phase in T2 thin films was larger than that in T1 thin films, but the crystallite size of rutile phase in T2 thin films was smaller. The surface morphology of the films showed that the films were formed more densely in the rutile phase than in the anatase phase, this phenomenon appeared conspicuously in T2 thin films. The transmittance of the samples with thin films on quartz glass calcined at 100$0^{\circ}C$ was significantly reduced at wavelength range about 300-700 nm due to the increased absorption originating from the change of crystallite phase and composition of the films and the scattering effect originating from increasing crystallite size. The refractive index of TiO$_2$ thin films increased, and hence the film thickness as well as the porosity of TiO$_2$ thin films decreased with increasing calcination temperature. Furthermore, the refractive index of T2 thin films was higher than T1 thin films, and porosity of T2 films was lower.

Synthesis of Yttria Stabilized Zirconia by Sol-gel Precipitation Using PEG and PVA as Stabilizing Agent

Bramhe, Sachin N.,Lee, Young Pil,Nguyen, Tuan Dung,Kim, Taik-Nam Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.8

There is increasing interest in zirconia as a dental material due to its aesthetics, as well as the exceptionally high fracture toughness and high strength that are on offer when it is alloyed with certain oxides like yttria. In recent years, many solution based chemical synthesis methods have been reported for synthesis of zirconia, of which the sol-gel method is considered to be best. Here, we synthesize zirconia by a sol gel assisted precipitation method using either PEG or PVA as a stabilizing agent. Zirconia sol is first synthesized using the hydrothermal method. We used NaOH as the precipitating agent in this method because it is easy to remove from the final solution. Zirconium and yttrium salts are used as precursors and PEG or PVA are used as stabilizers to separate the metal ions. The resulting amorphous zirconia powder is calcined at $900^{\circ}C$ for 2 h to get crystallized zirconia. XRD analysis confirmed the partially stabilized zirconia synthesis in all the synthesized powders. SEM was taken to check the morphology of the powder synthesized using either PEG or PVA as a stabilizing agent and finally the transparency was calculated. The results confirmed that the powder synthesized with 10 % PVA as the stabilizing agent had highest percentage of transparency among all the synthesized powder.

Synthesis of basalt fiber@Zn_1-xMg_xO core/shell nanostructures for selective photoreduction of CO₂ to CO

Kwak, Byeong Sub,Kim, Kang Min,Park, Sun-Min,Kang, Misook Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.407 No.-

<P><B>Abstract</B></P> <P>This study focused on the development of a catalyst for converting carbon dioxide, the main cause of global warming, into a beneficial energy source. Core@shell structured particles, BF@ZnO and BF@Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O, are synthesized in order to selectively obtain CO gas from the photoreduction of CO<SUB>2</SUB>. A modified sol-gel process is used to synthesize the core@shell structures with a three-dimensional microstructure, which are subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDAX), ultraviolet (UV)–vis absorption, photoluminescence (PL), and photocurrent density analysis. The CO<SUB>2</SUB> adsorption abilities of the core@shell particles are estimated through CO<SUB>2</SUB>-temperature programmed desorption (TPD). The core@shell structured BF@Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O particles including the Mg ingredient significantly increased the adsorption of CO<SUB>2</SUB> gas at the microfiber/nanoparticle interface. Both the BF@ZnO and BF@Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O particles selectively reduce the carbon dioxide to carbon monoxide, with almost no other reduced products being observed. These results are attributed to the effective adsorption of CO<SUB>2</SUB> gas and inhibited recombination of the photogenerated electron–hole pairs. BF@Zn<SUB>0.75</SUB>Mg<SUB>0.25</SUB>O exhibited superior photocatalytic behavior and selectively produced 5.0μmolg<SUB>cat</SUB> <SUP>−1</SUP> L<SUP>−1</SUP> of CO gas after 8h of reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ZnO and Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O crystals were grown onto the BFs. </LI> <LI> The core@shell structured BF@Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O particles significantly increased the adsorption of CO<SUB>2</SUB> gas. </LI> <LI> The BF@ZnO or BF@Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O particles selectively reduce the carbon dioxide to carbon monoxide. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>