• Title/Summary/Keyword: Nanosized $SiO_2$

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

  • 조진호;박주형;윤주병
    • Bulletin of the Korean Chemical Society
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    • v.19 no.11
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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.

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

  • Park, Minsol;Shim, Wooyoung;Kim, YooJin
    • Journal of Powder Materials
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    • v.29 no.3
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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.

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

  • Park, Jae-Jun;Ahn, Zu-No;Yun, Jong-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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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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Preparation Nanosized TPA-Silicalite-1 with Different Silica Sources and Promoters (다양한 실리카 원과 결정화 촉진제를 이용한 나노크기의 TPA-Silicalite-1 제조)

  • Jung, Sang-Jin
    • Applied Chemistry for Engineering
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    • v.25 no.3
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    • pp.286-291
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    • 2014
  • In this study, nanosized TPA-silicalite-1 was synthesized with a suitable molar composition of TPAOH: $SiO_2$: $H_2O$ for the development of zeolite ceramic membranes to utilize as gas separation. As silica sources, TEOS, LUDOX AS-40 and CAB-O-SIL were used with the starting material of TPAOH. $NaH_2PO_4$, and a variety of acids and bases were used as promoters after TPAOH, $SiO_2$, $H_2O$ gel synthesis. To decrease synthesis time, a two step temperature change method was applied to the synthesis of TPA-silicalite-1 at a low temperature. TPA-silicalite-1 synthesized was analyzed with XRD, SEM, BET and TGA. As a result, TPA-silicalite-1 powders with a particle size of 100 nm and a specific surface area of $416m^2/g$ were obtained as optimum synthesis conditions when the two stage temperature change method was used with $NaH_2PO_4$ as promoter.

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

  • Park, Hae-Jun;Kim, Hwa-Jung
    • Journal of Radiation Industry
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    • v.4 no.4
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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).

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

  • Kim, Seok-Hyeon;Na, Seok-En;Kim, Si-Young;Kim, Seong-Soo;Ju, Chang-Sik
    • Korean Chemical Engineering Research
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    • v.51 no.4
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    • pp.426-431
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    • 2013
  • Nanosized $TiO_2$ particles were prepared from titanium (IV) sulfate solution using base solutions at low reaction temperature ($95^{\circ}C$) and atmospheric pressure by hydrothermal precipitation method without calcination. The effects of preparation conditions, such as kind of base solutions (NaOH, $NH_4OH$, Monoethanolamine, Diethanolamine, Triethanolamine) and surfactants (CTAB, Span 20, SDBS), concentration of surfactants, temperature and pH, on the physical properties of $TiO_2$ particles have been investigated by XRD, SEM and Zeta-potential meter. Absorption area was also investigated by DRS in order to confirm the photocatalytic activity of the nanosized $TiO_2$ particles. It was turned out that, among base solutions, NaOH provides the smallest $TiO_2$ particles with excellent crystallinity. And cationic surfactant (CTAB) prepared smaller $TiO_2$ particles than any other surfactants. When CTAB is added in the concentration ratio of $Ti(SO_4)_2$:CTAB=10:1, $TiO_2$ particles with particle diameter of 5.8 nm were prepared. This is approximately 1/10 of that prepared without CTAB.

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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    • v.33 no.8
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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.

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

  • Kim, Jung-Wook;Jeon, Jun-Ha;Cho, Gun;Kim, Kwang-Ho
    • Journal of the Korean institute of surface engineering
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    • v.37 no.3
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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.

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

  • Ju-Chan Kwon;Bok-Hyun Oh;Sang-Jin Lee
    • Korean Journal of Materials Research
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    • v.33 no.12
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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.