• 한국세라믹학회지
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• 제27권5호
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• pp.583-588
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• 1990

Glass films in the binary system B2O3-SiO2 and Al2O3-SiO2 were prepared on soda-lime-silica slide glass by the dip-coating technique from TEOS and boric acid or aluminum nitrate. Thickness of the films varying with viscosity and withdrawal speed were measured and effect of composition and firing temperature on the properties such as transmittance and refractive index were investigated. nM2O3.(100-n)SiO2(M=B or Al) films containing up to 20mol% B2O3 and 40mol% Al2O3 were transparent. Maximum transmittance at visible range were obtained for the sample containing 15mol% Ba2O3 and 32.5mol% Al2O3 and heat-treated at 50$0^{\circ}C$, respectively. Refractive index of the film containing 15mol% B2O3 was mininum in the B2O3-SiO2 binary system and minimal refractive index was appeared at the film containing 32.5mol% Al2O3. In IP spectra, addition of B2O3 were increased absorption peak intensity of B-O and Si-O-B bond and addition of Al2O3 were decreased absorption peak intensity of Si-O bond, respectively.

• Tribology and Lubricants
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• 제5권1호
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• pp.21-27
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• 1989

A paper facirig, used for clutch disc or brake lining of the vehicles, is consisted of a combination of cellulose fiber of pulp with assorted filler and friction imparting particles, impregnated with a thermo-setting resin. In this study, as a substitution for the paper-production method, the molding-production method was attempted to produce the paper facings, and their frictional characteristics were investigated. According to the experimental results, it was estimated that the paper facings added with silica (SiO$_2$) have superior frictional characteristics, which is mused by the porosity and Mobs' hardness of the silica (SiO$_2$).

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.159.1-159
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• 2003

• 한국세라믹학회지
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• 제41권7호
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• pp.528-533
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• 2004

입자크기가 20∼700nm인 구형 실리카입자의 자연침강 혹은 원심분리법으로 제조한 주형체에 탄화규소 전구체 polymethyl-silane (PMS) 혹은 polycarbosilane (PCS) 고분자 용액을 함침한다음, 가교 및 1000∼140$0^{\circ}C$ 열분해하고 마지막으로 불산 (HF)으로 실리카를 식각하여 84∼658nm 기공이 3차원으로 정렬된 메크로다공성(macroporous) 탄화규소 세라믹과 불규칙적인 15∼65nm 기공을 가진 메조다공성(mesoporous) 탄화규소 세라믹을 제조하였다. 전자는 112nm 실리카 입자 주형체를 사용하여 140$0^{\circ}C$로 처리했을 때, 표면적 584.64$m^2$g$^{-1}$을 나타낸 반면, 후자는 20-30nm 실리카 주형체를 사용하여 100$0^{\circ}C$로 처리하였을때, 최대의 표면적 619.4$m^2$g$^{-1}$를 나타내었다, 이와 같이 사용된 실리카 입자, 고분자 전구체, 그리고 열처리 조건에 따른 기공특성을 SEM. TEM 및 BET으로 분석 설명하였다.

• 한국세라믹학회지
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• 제32권9호
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• pp.977-988
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• 1995

Several oxide (ZrO2, Al2TiO5, reactive Al2O3) and nonoxide (SiC, Si3N4, "ALON" (5AlN.9Al2O3)) additives were used as a microfiller for alumina based LCC (Low-Cement-Castable). High temperature prooperties (HMOR, softening under load) and the phase changes of developed LCC on various sintering temperatures were examined. In addition, thermal shock test and corrosion test were accomplished. Based on these data the effects of each microfiller on the properties of LCC were established comparing to those of the commercial LCC with amorphous silica as a microfiller. The castables, containing reactive alumina, ZrO2 and "ALON" (5AlN.9Al2O3) as a first portion, exhibited considerably higher HMOR-values over 100$0^{\circ}C$, better creep behavior, and thermal shock resistance than those of castables with amorphous silica. The LCC with 5% Al2TiO5 showed no corrosion against molten aluminum.nst molten aluminum.

• 한국세라믹학회지
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• 제47권2호
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• pp.113-116
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• 2010

The silica coated $Fe_3O_4$ nanoparticles have been synthesized using a micro-emulsion method. The $Fe_3O_4$ nanoparticles with the sizes 6 nm in diameter were synthesized by thermal decomposition method. Hydrophobic $Fe_3O_4$ nanoparticles were coated silica using surfactant and tetraethyl orthosilicated (TEOS) as a $SiO_2$ precursor. Shell thickness of silica coated $Fe_3O_4$ can be controlled (11~20 nm) through our synthetic conditions. The $Fe_3O_4$ and silica coated $Fe_3O_4$ nano powders were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and vortex magnetic separation (VMS).

• Biomolecules & Therapeutics
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• 제19권2호
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• pp.261-266
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• 2011

As recent reports suggest that nanoparticles may penetrate into cell membrane and effect DNA condition, it is necessary to assay possible cytotoxic and genotoxic risk. Three different sizes of magnetic nanoparticle silica (MNP@$SiO_2$) (50, 100 and 200 nm diameter) were tested for cytotoxicity and DNA damage using L5178Y cell. MNP@$SiO_2$ had constant physicochemical characteristics confirmed by transmission electron microscope, electron spin resonance spectrometer and inductively coupled plasma-atomic emission spectrometer for 48 h. Treatment of MNP@$SiO_2$ induced dose and time dependent cytotoxicity. At 6 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$ compared to vehicle control (p<0.05 or p<0.01). Moreover, at 24 h, 50 or 100 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$(p<0.01). And treatment of 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Furthermore, at 48 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Cellular location detected by confocal microscope represented they were existed in cytoplasm, mainly around cell membrane at 2 h after treatment of MNP@$SiO_2$. Treatment of 50 nm MNP@$SiO_2$ significantly increased DNA damage at middle and high dose (p<0.01), and treatment of 100 nm or 200 nm significantly increased DNA damage in all dose compared to control (p<0.01). Taken together, treatment of MNP@$SiO_2$ induced cytotoxicity and enhanced DNA damage in L5178Y cell.

• Macromolecular Research
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• 제17권5호
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• pp.346-351
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• 2009

$TiCl(O-i-Pr)_3/SiO_2$ and $Ti(O-i-Pr)_4/SiO_2$ were prepared by immobilizing chlorotitanium (IV) isopropoxide ($TiCl(O-i-Pr)_3$) and titanium (IV) isopropoxide ($Ti(O-i-Pr)_4$), to pretreated silica. The effect of the polymerization reaction conditions on the catalytic activity and characteristics of the resulting PLA were investigated. The catalytic conversion, molecular weight and polydispersity index (PDI) of the PLA produced on the titanium alkoxide supported catalysts increased proportionally with the reaction temperature. When the PLA was synthesized in bulk polymerization, the PLA produced with the supported catalysts had higher molecular weight than those with homogeneous catalysts. The melting temperature of the polymer produced with silica supported alkoxide catalysts was approximately $170-180^{\circ}C$.

• Advances in nano research
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• 제14권4호
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• pp.355-362
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• 2023

Physical exercise, especially intense exercise and high intensity interval training (HIIT) by trampoline, can lead to muscle injuries. These effects can be reduced with intelligent products made of nanocomposite materials. Most of these nanocomposites are polymers reinforced with silicon dioxide, alumina, and titanium dioxide nanoparticles. This study presents a polymer nanocomposite reinforced with silica. As a result of the rapid reaction between tetraethyl orthosilicate and ammonia in the presence of citric acid and other agents, silica nanostructures were synthesized. By substituting bis (4-amino phenoxy) phenyl-triptycene in N, N-dimethylformamide with potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C, the diamine monomer bis (4-amino phenoxy) phenyl-triptycene is prepared. We synthesized a new polyaromatic (imide) with triptycene unit by sol-gel method from aromatic diamines and dianhydride using pyridine as a condensation reagent in NMP. PI readily dissolves in solvents and forms robust and tough polymer films in situ. The FTIR and NMR techniques were used to determine the effects of SiO₂ on the sol-gel process and the structure of the synthesized nanocomposites. By using a simultaneous thermal analysis (DTA-TG) method, the appropriate thermal operation temperature was also determined. Through SEM analysis, the structure, shape, size, and specific surface area of pores were determined. Analysis of XRD results is used to determine how SiO₂ affects the crystallization of phases and the activation energy of crystallization.

• 한국세라믹학회지
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• 제42권3호
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• pp.205-210
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• 2005

Tetraethyl Orthosilicate(TEOS)를 $SiO_2$ 전구체 용액으로 사용하여 Polyacrlamide gel 방법으로 나노 실리카 분말을 합성하였다. 이 gel 공정법은 비교적 간단한 중합법이며, 고분자 망상구조가 $SiO_2$의 응집을 억제하므로 비교적 낮은 하소온도에서 나노입자를 합성할수 있었다. $SiO_2$ 분말입자의 크기는 gel 전구체중의 ammonium persulphate와 N,N'-methylene-bis-acryamide(BIS)의 농도에 영향을 받았다. 실리카 입자의 크기는 ammonium persulphate의 농도가 증가할수록 작아졌으며 그 농도가 0.01M일때 가장 작은 10nm크기의 입자를 얻었다. 또한 그 입자의 크기는 BIS의 농도가 증가할수록 작아졌으며 그 높도가 0.05M일때 입자의 크기는 5nm였다.