Development of micro / nano-size hollow silicate particles for thermal energy saving application
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Development of micro / nano-size hollow silicate particles for thermal energy saving application Raymond V.Rivera-Virtudazo1, Rudder T. Wu2, and Takao Mori2 1 Global Research Center for Environment and Energy Based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Namiki, Tsukuba, Ibaraki 305-0044 Japan 2 Atomic Network Materials Group, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 Japan ABSTRACT Design and fabrication of hollow silicate micro-/ nanoparticles (HSMNP) with varied sizes and morphologies are of great interest especially in developing new generation of thermal insulation materials for building applications. Efficient energy use, simply called energy-saving, involves efforts to reduce the amount of energy required and recover wasted energy. This is important since building constitutes a substantial part in the total global energy consumption. Therefore, the current study is aimed at developing new HSMNP for thermal insulation application. INTRODUCTION There have been extensive studies in developing hollow silicate micro-/ nanoparticles (HSMNP) with hierarchically porous core-shell composite materials, which are expected to produce novel and desired performances [1, 2]. HSMNP also known as nano/microcapsules(size particles ranging from 10 nm to1000 µm), have been studied and developed as a special class of materials [2, 3]. These materials have been playing an important part in improving the micro/nano-materials science application, which can improve vital characteristics (such as strength, durability and thermal related properties) especially as fillers for energy efficiency on building materials [2, 4]. Previous studies have shown that hollow silica particles with a typical wall thickness of 10-15 nm and a pore diameter of about 150 nm can significantly reduce thermal conductivity of about 0.02 W/(mK), compared to 1.4 W/(mK) of the bulk silica materials [5-8]. This is one indication that size dependency in thermal transport at nanometer scale. This is also partly due to the hollow spacing inside the particle with intricate nanostructured shell wall [1, 2]. These make them an ideal for various applications such as sorption of CO2 gas [2, 5, 6] and thermal insulation [7] especially for the building part. There have been various synthetic strategies reported for the fabrication of HSMNP, such as soft (emulsion and vesicles) and hard template methods as the most common approaches [4]. However, most HSMNP inherit substantial drawbacks such as having large diameters, inconsistency in size and poor dispersion. Thus, facile and large-scale production of HSMNP with well-controlled structure geometry and stable hollow cavity is still a significant challenge. With respect to the fabrication of a thermal insulating material with the presence of HSMNP, it mostly improves the thermal energy efficiency (e.g. insulating properties). HSMNP is usually used as fillers or additives to materials inorde
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