• Environmental Engineering Research
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• 제24권3호
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• pp.463-473
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• 2019

Nanoscale zero-valent iron (nZVI) has proved to be an effective tool in applied environmental nanotechnology, where the decreased particle diameter provides a drastic change in the properties and efficiency of nanomaterials used in water purification. However, the agglomeration and colloidal instability represent a problematic and a remarkable reduction in nZVI reactivity. In view of that, this study reports a simple and cost-effective new strategy for ultra-small (< 7.5%) distributed functionalized nZVI-EG (1-9 nm), with high colloidal stability and reduction capacity. These were obtained without inert conditions, using a simple, economical synthesis methodology employing two stabilization mechanisms based on the use of non-aqueous solvent (methanol) and ethylene glycol (EG) as a stabilizer. The information from UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy suggests iron ion coordination by interaction with methanol molecules. Subsequently, after nZVI formation, particle-surface modification occurs by the addition of the EG. Size distribution analysis shows an average diameter of 4.23 nm and the predominance (> 90%) of particles with sizes < 6.10 nm. Evaluation of the stability of functionalized nZVI by sedimentation test and a dynamic light-scattering technique, demonstrated very high colloidal stability. The ultra-small particles displayed a rapid and high nitrate removal capacity from water.

• 한국세라믹학회지
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• 제53권1호
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• pp.56-62
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• 2016

A heterogeneous $Bi_2S_3/TiO_2$ composite catalyst was synthesized via a green ultrasonic-assisted method and characterized by XRD, SEM, EDX, TEM analysis. The results clearly show that the $TiO_2$ particles were homogenously coated with $Bi_2S_3$ particles, indicating that $Bi_2S_3$ particle agglomeration was effectively inhibited after the introduction of anatase $TiO_2$. The Texbrite BA-L (TBA) degradation rate constant for $Bi_2S_3/TiO_2$ composites reached $8.27{\times}10^{-3}min^{-1}$ under visible light, much higher than the corresponding value of $1.04{\times}10^{-3}min^{-1}$ for $TiO_2$. The quantities of generated hydroxyl radicals can be analyzed by DPCI degradation, which shows that under visible light irradiation, more electron-hole pairs can be generated. Finally, the possible mechanism for the generation of reactive oxygen species under visible-light irradiation was proposed as well. Our result shows the significant potential of $Bi_2S_3$-semiconductor-based $TiO_2$ hybrid materials as catalysts under visible light for the degradation of industry dye effluent substances.

• 한국세라믹학회지
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• 제51권5호
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• pp.424-429
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• 2014

YAG:$Ce^{3+}$ phosphor powders were synthesized using $Al(OH)_3$ seeds by means of a PVA-polymer-solution route. Various types of PVA with different molecular weights (different polymerization) were used. All dried precursor gels were calcined at $500^{\circ}C$ and then heated at $1500^{\circ}C$ in a mix of nitrogen and hydrogen gases. The final powders were characterized via XRD, SEM, PSA, PL, and PKG analyses. The phosphor properties and morphologies of the synthesized powders were dependent on the PVA type. As the molecular weight of the PVA was increased, the particle size gradually decreased with agglomeration, and the luminous intensity of the phosphor increased. However, the phosphor powder prepared from the PVA exhibiting very high molecular weight, showed a 531 nm (blue) shift from the 541 nm (yellow) wavelength of the YAG:$Ce^{3+}$ phosphor. Finally, the synthesized YAG:$Ce^{3+}$ phosphor powder prepared from the PVA with 89,000 - 98,000 molecular weight showed phosphor properties similar to those of a commercial phosphor powder, but without a post-treatment process.

• 한국재료학회지
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• 제24권11호
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• pp.578-584
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• 2014

To synthesize Sn nanoparticles (NPs) less than 30 nm in diameter, a modified polyol process was conducted at room temperature using a reducing agent, and the effects of different pH values of the initial solutions on the morphology and size of the synthesized Sn NPs were analyzed. tin(II) 2-ethylhexanoate, diethylene glycol, sodium borohydride, polyvinyl pyrrolidone (PVP), and sodium hydroxide were used as a precursor, reaction medium, reducing agent, capping agent, and pH adjusting agent, respectively. It was found by transmission electron microscopy that the morphology of the synthesized Sn NPs varied according to the pH of the initial solution. Moreover, while the size decreased to 11.32 nm with an increase up to 11.66 of the pH value, the size increased rapidly to 39.25 nm with an increase to 12.69. The pH increase up to 11.66 dominantly promoted generation of electrons and increased the amount of initial nucleation in the solution, finally inducing the reduced-size of the Sn particles. However, the additional increase of pH dominantly induced a decrease of PVP by neutralization, which resulted in acceleration of the agglomeration by collisions between particles.

• 한국응용과학기술학회지
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• 제23권3호
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• pp.199-206
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• 2006

Direct decomposition of methane over three types of carbon black (N330-p, N330-f, and HI-900L) was carried out in a fluidized bed quartz reactor. Properties of carbon black before and after reaction were measured and found to be related with surface structure and weight gain. For N330-p and N330-f, some carbon deposit on the surface was considered to be the reason for the increase of BET surface area and pore volume with weight gain. Carbon deposits on the surface and the conglutination of some aggregates may explain the slight increase of particle size. Properties of HI-900L changed much more significantly with weight gain. It is supposed that the increase of aggregate size of HI-900L were due to some unknown oily components. The corresponding agglomeration might be the reason for the decrease of BET surface area with weight gain, as compared with the increase of that for the case of N330 black.

• 한국세라믹학회지
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• 제42권6호
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• pp.399-404
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• 2005

Anti-reflection film was coated by using spherical silica nano colloidal particles and fumed silica particles. Silica colloid sol was reserved between two inclined slide glasses by capillary force, and particles were stacked to form a film onto the substrate as the upper glass was sliding. The deposition processes were studied to enhance the wavelength dependency of the light transmittance and to control the effective refractive index of the film. Both of the spherical and fumed silica particles showed an enhancement of $4.0-4.4\%$ in light transmittance by one step coating. The dependence of the transmittance on wavelength was largely improved at the longer wavelength by partial coating of fumed particles on the film of spherical particles. The effective refractive index of the film was controlled by removing latex particles that were co-deposited with silica particles. Using this process the light reflectance from one side of the glass substrate could be reduced from $4.2\%$ to $0.6\%$ although zero reflectance was not achieved due to the agglomeration of the latex particles.

• 한국결정학회지
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• 제3권1호
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• pp.1-8
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• 1992

졸겔 및 공침법으로 제조된 티탄산 납 분말의 형태를 하소온도와 하소시간의 함수로 조사하였다. 질산 납과 사염화 티탄의 혼합용액을 사용하여 40-43℃ 및 9.0-9.7 pH에서 PbTiO3 전구체를 제조하였으며, 350-1000℃에서 1-10시간동안 공기중에서 이들을 히소시켰다. 하소온도와 시간의 증가에 따라 입자의 크기가 증가하고 응집이 심화되었다. 졸겔법으로 제조된 분말을 700℃에서 히소시킬 때, 초기에 형성된 침상형 혹은 각주 형의 입자들은 하소가 진행됨에 따라 다면체형으로 변한뒤, 모서리가 둥근 다면체형 입자로 성장하였다. 공침법으로 제조된 분말은 결정화 과정중에 형태가 변화되지 않았다.

• 한국세라믹학회지
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• 제30권4호
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• pp.299-308
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• 1993

Dispersant was used to avoid the agglomeration of aluminum hydrate precipitate and improve the sinterability of calcined alumina powder. The mean particle size of the aluminum hydrate precipitates was 0.26${\mu}{\textrm}{m}$ and 0.44${\mu}{\textrm}{m}$ when ball-milled with and without dispersant, respectively. After calcination at 110$0^{\circ}C$ for 5 hours, the size of the alumina powder without dispersant increased to 0.84${\mu}{\textrm}{m}$, while with dispersant slightly decreased to 0.22${\mu}{\textrm}{m}$. The most thermally active alumina powder was obtained from the sample calcined at 110$0^{\circ}C$ for 5 hours with the 1% dispersant concentration. Using the calcined alumina powder at the above optimized condition, the specimen showed fired density of 3.94g/㎤, 4-point MOR of 364MPa, and KIC of 3.26MPam1/2 after sintered at 155$0^{\circ}C$ for 3 hours.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 반도체재료
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• pp.30-33
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• 2001

Chemical mechanical polishing(CMP) process has been widely used to planarize dielectrics, which can apply to employed in integrated circuits for sub-micron technology. Despite the increased use of CMP process, it is difficult to accomplish the global planarization of free-defects in inter-level dielectrics (ILD). Especially, defects like micro-scratch lead to severe circuit failure, and affects yield. CMP slurries can contain particles exceeding $1{\mu}m$ size, which could cause micro-scratch on the wafer surface. The large particles in these slurries may be caused by particle agglomeration in slurry supply line. To reduce these defects, slurry filtration method has been recommended in oxide CMP. In this work, we have studied the effects of filtration and the defect trend as a function of polished wafer count using various filters in inter-metal dielectric(IMD)-CMP. The filter installation in CMP polisher could reduce defect after IMD-CMP. As a result of micro-scratches formation, it shows that slurry filter plays an important role in determining consumable pad lifetime.

• 한국재료학회지
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• 제27권5호
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• pp.270-275
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• 2017

Inorganic phosphors based on $ZrO_2:Eu^{3+}$ nanoparticles were synthesized by a salt-assisted ultrasonic spray pyrolysis process that is suitable for industrially-scalable production because of its continuous nature and because it does not require expensive precursors, long reaction time, physical templates or surfactant. This facile process results in the formation of tiny, highly crystalline spherical nanoparticles without hard agglomeration. The powder X-ray diffraction patterns of the $ZrO_2:Eu^{3+}$ (1-20 mol%) confirmed the body centered tetragonal phase. The average particle size, estimated from the Scherrer equation and from TEM images, was found to be approximately 11 nm. Photoluminescence (PL) emission was recorded under 266 nm excitation and shows an intense emission peak at 607 nm, along with other emission peaks at 580, 592 and 632 nm which are indicated in red.