Surface properties of nanosize hollow silica particles on the molecular level

Fuji, Masayoshi; Takai, Chika; Tarutani, Yoshie; Takei, Takashi; Takahashi, Minoru

doi:10.1163/156855207779768124

Cited by 59 publications

(43 citation statements)

References 19 publications

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“…Hollow silica nanoparticles (HSNPs) with controlled shell density were prepared by adjusting reacting conditions based on an inorganic template method [12][13][14] as reported before. A microscopic image of HSNPs was shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Improved transparent thermal insulation using nano-spaces

Fuji

Takai

Watanabe

et al. 2015

Advanced Powder Technology

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a b s t r a c tFibrous materials and gas-foamed plastics provide some insulation due to the low thermal conductivity of air but are not transparent. Here we show for the first time that a nano-spaced polymer film consisting of hollow silica nanoparticles (HSNPs) dispersed in a polyurethane (PU) matrix provides good thermal insulation and is transparent. The HSNPs, having a silica shell and nano-sized hollow interior, are formed by removing the core from a core-shell structure prepared by sol-gel reaction of silicon alkoxide (TEOS). One advantage of using HSNPs is that a quasi-vacuum state in the nano-space is formed when the size of the space is close to the length of the mean free path of the air molecules in the space. Heat therefore tends to be transferred along the silica shells of HSNPs instead of through other materials in the film. Another advantage is that there are many defects in silica shells with low apparent density that are prepared using controlled sol-gel reaction conditions. The phonon-defect scattering in the silica shell suppresses heat conduction despite of high thermal conductivity of silica. Dispersed HSNP flocculation in the film is the key to both transparency and good thermal insulation.

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Section: Methodsmentioning

confidence: 99%

Improved transparent thermal insulation using nano-spaces

Fuji

Takai

Watanabe

et al. 2015

Advanced Powder Technology

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“…Our group has successfully reported this 35),36) via a template solgel process by utilizing and removing the nano-core CaCO 3 particles through dissolution by acid treatment followed by the formation of nanosize hollow silica particles. In this method, an aqueous ammonia solution was used as the catalyst and medium.…”

Section: Solid-core Template Methodsmentioning

confidence: 99%

“…It can be estimated from the water vapor adsorption that surface free silanol groups on the hollow particles have the same characteristics as on the dense particles. 35) Based on these results, definition of the shell microstructure as the apparent shell density has been proposed. Three typical types of hollow silica nanoparticles were selected using transmission electron microscopy (TEM) observations such as (A) the thickness of the silica shell is relatively thin and the spherical shape of the stacked particulates is clearly identified in the shell, (B) the thickness of the silica shell has the same thickness as the type A, but the shape of the stacked particulates is identified as halfround, and (C) the thickness of the silica shell is greater and the stacked particulates are not recognized in the shell as shown in the illustration of Fig.…”

Section: )mentioning

confidence: 99%

Hollow particles as controlled small space to functionalize materials

Fuji

2015

J. Ceram. Soc. Japan

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Molecules indicate a particular property by obeying a special characteristic in small space in some cases. It was discovered for a liquid phase such as decreasing the melting point in a nano-sized pore. A special phenomenon may also occur in the gas phase in a small space. To demonstrate this prediction, I have begun trying to fabricate a small space. A nano-sized hollow structure is very attractive for obtaining a small space. An inorganic template using inorganic particles is a facile technique to obtain hollow particles with various shapes, sizes, from nano to micron, and also different shell microstructures. This paper describes the solgel synthesis that is useful to form the shell structure of hollow particles and then how to control the particle structure using various templating routes. The hollow particles are used for the fabrication of air/solid composites with a controlled small space. These structure controls provide wide applications such as superior thermal insulation films, anti-corrosion films, and unexpected "easy-to-grip" volleyball coatings, etc. In addition to our achievements using hollow silica nanoparticles, the development of applications such as the lithium ion battery, biomedical products, catalysts, etc., will be outlined.

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“…Unique micro-scale anisotropic hollow silicate particles were synthesized based on the previous works done by our laboratory (CRL, NIT) using CaCO 3 as template [14]. Calcium carbonate (CaCO 3 ), ethanol (EtOH), tetraethoxysilane (TEOS) and ammonium aqueous solution (NH 4 OH) were mixed and stirred for (least) 2 h at ambient temperature with molar ratio of 1.…”

Section: Synthesis Of Anisotropic Micro-scale Hollow Silicate Particlesmentioning

confidence: 99%