• 제목/요약/키워드: Nanosized $SiO_2$

검색결과 15건 처리시간 0.032초

Highly Porous Pillared Clay with Multistacked $SiO_2/TiO_2$ Nanosols

  • 조진호;박주형;윤주병
    • Bulletin of the Korean Chemical Society
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    • 제19권11호
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    • pp.1185-1188
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    • 1998
  • Layered nanocomposite, SiO2/TiO2 sol pillared clay, has been prepared by the ion exchange reaction of Na' ion in montmorillonite with positively charged mixed SiO2/TiO2 sol. The nanosized sol particles were synthesized by mixing SiO2 sol solution with TiO2 one, which is obtained by acidic hydrolysis of TEOS and TiCl4, respectively. From powder XRD, the basal spacing (d001) of the sample calcined at 400 ℃ was found to be ca. 60 Å, due to the multistacking of nanosized SiO2 and TiO2 sol particles, which was confirmed by the pore size analysis from 129Xe NMR and micropore analysis calculated from nitrogen adsorption. The BET specific surface area shows the value of 684 m2g-1 (Langmuir 1115 m2g-1), which is the highest among various pillared clays ever reported previously, and the total porosity is found to be 0.51 mlg-1, and the pores are mainly composed of micropore with a size of ca. 11.8 Å. This result agrees with the adsorption capacity obtained from water adsorption. According to diffuse reflectance ultraviolet-visible spectroscopy, it is found that the TiO2 particles stabilized in the interlayer space of montmorillonite are quantum-sized of ca. 20 Å.

다양한 SiO2 코팅 제어를 통한 화장품용 루타일형 TiO2의 색상 및 물성 연구 (A Study of Various SiO2 Coating Control on White TiO2 Pigment for Cosmetic Applications)

  • 박민솔;심우영;김유진
    • 한국분말재료학회지
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    • 제29권3호
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    • pp.207-212
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    • 2022
  • Nanosized rutile titanium dioxide (TiO2) is used in inorganic pigments and cosmetics because of its high whiteness and duality. The high quality of the white pigments depends on their surface coating technique via the solgel process. SiO2 coatings are required to improve the dispersibility, UV-blocking, and whiteness of TiO2. Tetraethyl orthosilicate (TEOS) is an important coating precursor owing to its ability to control various thicknesses and densities. In addition, we use Na2SiO3 (sodium silicate) as a precursor because of its low cost. Compared to TEOS, which controls the pH using a basic catalyst, Na2SiO3 controls the pH using an acid catalyst, giving a uniform coating. The coating thickness of TiO2 is controlled using a surface modifier, cetrimonium bromide, which is used in various applications. The shape and thickness of the nanosized coating layer on TiO2 are analyzed using transmission electron microscopy, and the SiO2 nanoparticle behavior in terms of the before-and-after size distribution is measured using a particle size analyzer. The color measurements of the SiO2 pigment are performed using UV-visible spectroscopy.

Epoxy/Annealing $SiO_2$ Composites의 충진함량에 대한 저 유전특성 (Low Dielectric Properties of Epoxy/Annealing $SiO_2$ Composites for Filler Contents Variation)

  • 박재준;안준오;윤종현
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2007년도 추계학술대회 논문집
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    • pp.224-225
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    • 2007
  • The Low dielectric properties of epoxy/Annealing $SiO_2$ composites using Annealing new material of nanosized amorphous particles were investigated as function frequency, temperature and filler contents composition. The dielectric constant decrease with increasing frequency and also increase with increasing ambient temperature. The dielectric constant decrease with increase annealing filler contents for epoxy base. The result of x-ray diffraction could obtained single crystal of annealing $SiO_2$ from 500nm amorphous $SiO_2$ powder.

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다양한 실리카 원과 결정화 촉진제를 이용한 나노크기의 TPA-Silicalite-1 제조 (Preparation Nanosized TPA-Silicalite-1 with Different Silica Sources and Promoters)

  • 정상진
    • 공업화학
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    • 제25권3호
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    • pp.286-291
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    • 2014
  • 본 연구에서는 기체 분리를 위한 제올라이트 세라믹 멤브레인 제조에 적합한 입자크기와 형상을 갖춘 나노크기의 제올라이트를 TPAOH : $SiO_2$ : $H_2O$의 적합한 조성으로 합성하였으며 그 특성을 분석하였다. 실리카 원으로는 TEOS, LUDOX AS-40, CAB-O-SIL을 사용하고, TPAOH와 함께 출발물질로 하여 특정 조성의 TPAOH, $SiO_2$, $H_2O$ gel을 합성하고, $NaH_2PO_4$ 및 다양한 산 염기를 결정화 촉진제로 사용하였다. 합성시간을 단축할 수 있는 방법의 일환으로 저온에서 2단계 온도 변화법을 적용한 수열합성법으로 TPA-Silicalite-1을 합성하였으며 XRD, SEM, BET, TGA 등을 사용하여 분석하였다. 그 결과, 2단계 온도 변화법을 사용하고, 결정화 촉진제로서 $NaH_2PO_4$를 사용하였을 때가 최적의 합성 조건으로 입자크기100 nm, 비표면적 $416m^2/g$의 TPA-Silicalite-1 분말을 제조할 수 있었다.

감마선 조사기술을 이용한 미량원소 비료 나노제제 제조 (Preparation of a Nanosized Micro Element Fertilizer Formulation by using Gamma-irradiation Technique)

  • 박해준;김화정
    • 방사선산업학회지
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    • 제4권4호
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    • pp.347-352
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    • 2010
  • In this study, we addressed a novel nanosized curdlan-silica complex, which is curdlan bound to silica, for the development of a sustain-releasing micro element fertilizer formulation. The complex was obtained as follow steps; First, Curdlan polymer, sodium silicate ($Na_2SiO_3$) and isopropyl alcohol were dissolved in DDW. Next the resultant solution was irradiated by $^{60}Co$ gamma-irradiator (150 TBq of capacity; ACEL, Canada). Then $MgSO_4$ was treated with the resultant solution. The obtained colloidal solution was dried by freeze dryer. Finally, we obtained a novel nanosized curdlan-silica formulation containing $MgSO_4$ from the colloidal solution. The morphology of the complex was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanosized curdlan-silica complex has a particle size ranging from 20 to 80 nm and high stability. Our results suggested that the nano-complex can be applicable to use in various sustain-releasing formulation for pesticide delivery system (PDS).

나노크기 TiO2의 제조에 미치는 첨가제 영향 (The Effect of Additives on the Preparation of Nanosized TiO2 Particles)

  • 김석현;나석은;김시영;김성수;주창식
    • Korean Chemical Engineering Research
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    • 제51권4호
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    • pp.426-431
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    • 2013
  • 비교적 낮은 온도와 상압에서 전구체 Titanium(IV) sulfate와 염기성 용액을 반응시키는 수열합성법을 이용하여 소성과정을 거치지 않고 $TiO_2$ 나노입자를 제조하였다. 염기성 용액의 종류(NaOH, $NH_4OH$, Monoethanolamine, Diethanolamine, Triethanolamine), 첨가되는 계면활성제의 종류(CTAB, Span 20, SDBS)와 농도, 제조 온도, pH 등을 변화시켜 $TiO_2$를 제조하였고, 생성되는 입자의 결정성, 입자크기 등과 같은 물리적 특성은 XRD, SEM, Zeta-potential 등을 사용하여 분석하였다. 또한, 광촉매적 특성을 확인하기 위하여 DRS를 통해 흡광면적을 측정, 비교하였다. 침전제로 사용된 염기성 물질 중 NaOH가 결정성이 우수하고 입자크기가 작은 $TiO_2$를 제조하는데 가장 효과적임을 확인할 수 있었다. 계면활성제는 양이온성 계면활성제인 CTAB를 첨가한 경우 다른 계면활성제보다 작은 크기의 $TiO_2$를 제조할 수 있었다. 그리고 동일한 조건에서 전구체인 $Ti(SO_4)_2$와 CTAB의 농도비를 10 : 1로 조절한 경우 CTAB를 첨가하지 않은 경우보다 제조되는 $TiO_2$ 입자의 크기는 약 1/10인 5.8 nm로 감소하였다.

Biguanide-Functionalized Fe3O4/SiO2 Magnetic Nanoparticles: An Efficient Heterogeneous Organosuperbase Catalyst for Various Organic Transformations in Aqueous Media

  • Alizadeh, Abdolhamid;Khodaei, Mohammad M.;Beygzadeh, Mojtaba;Kordestani, Davood;Feyzi, Mostafa
    • Bulletin of the Korean Chemical Society
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    • 제33권8호
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    • pp.2546-2552
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    • 2012
  • A novel biguanide-functionalized $Fe_3O_4/SiO_2$ magnetite nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperbase in chemical transformations. The structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental analyzer (EA), thermogravimetric analysis (TGA), $N_2$ adsorption-desorption (BET and BJH) and FT-IR. The biguanide-functionalized $Fe_3O_4/SiO_2$ nanoparticles showed a superpara-magnetic property with a saturation magnetization value of 46.7 emu/g, indicating great potential for application in magnetically separation technologies. In application point of view, the prepared catalyst was found to act as an efficient recoverable nanocatalyst in nitroaldol and domino Knoevenagel condensation/Michael addition/cyclization reactions in aqueous media under mild condition. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.

Ti-Al-N과 Ti-Al-Si-N 코팅막의 상 특성 및 내산화 거동 (Phase Characterization and Oxidation Behavior of Ti-Al-N and Ti-Al-Si-N Coatings)

  • 김정욱;전준하;조건;김광호
    • 한국표면공학회지
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    • 제37권3호
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    • pp.152-157
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    • 2004
  • Ti-Al-N ($Ti_{75}$ $Al_{25}$ N) and Ti-Al-Si-N ($Ti_{69}$ $Al_{23}$ $Si_{8}$N) coatings synthesized by a DC magnetron sputtering technique were studied comparatively with respect to phase characterization and high-temperature oxidation behavior. $Ti_{69}$ $Al_{23}$ $Si_{ 8}$N coating had a nanocomposite microstructure consisting of nanosized(Ti,Al,Si)N crystallites and amorphous $Si_3$$N_4$, with smooth surface morphology. Ti-Al-N coating of which surface $Al_2$$O_3$ layer formed during oxidation suppressed further oxidation. It was sufficiently stable against oxidation up to about $700^{\circ}C$. Ti-Al-Si-N coating showed better oxidation resistance because both surface Ab03 and near-surface $SiO_2$ layers suppressed further oxidation. XRD, GDOES, XPS, and scratch tests were performed.

구형 단분산 실리카 분말을 이용한 SiOx 음극활물질 제조 및 형상조절 기술 (Fabrication of SiOx Anode Active Materials Using Spherical Silica Powder and Shape Control Technology)

  • 권주찬;오복현;이상진
    • 한국재료학회지
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    • 제33권12호
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    • pp.530-536
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    • 2023
  • The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiOx materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO2) was synthesized using TEOS as a starting material for the fabrication of such SiOx through heating in a reduction atmosphere. SiOx powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiOx powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiOx.