Temperature Variation in Energy Absorption System Functionalized by Nanomaterials
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Temperature Variation in Energy Absorption System Functionalized by Nanomaterials 1
Yu Qiao,1 Zhongyuan Sun,2 Weiyi Lu,1 and Aijie Han2, * Department of Structural Engineering, University of California-San Diego, La Jolla, California 92093, USA 2 Department of Chemistry, University of Texas-Pan American, Edinburg, Texas 78539, USA
ABSTRACT The thermal effect on the nanofluidic behaviors in a nanoporous silica gel is investigated experimentally. When a nanoporous silica gel is modified by silyl groups, its surface becomes hydrophobic. A sufficiently high external pressure must be applied to overcome the capillary effect; otherwise liquid infiltration could not occur. The formation and the disappearance of a solid–liquid interface are employed for energy storage or dissipation. When the hydrophobic surface of nanoporous silica gel is decomposed at various temperatures, the organic surface layers can be deactivated. As a result, the degree of hydrophobicity, which can be measured by the liquid infiltration pressure, is lowered. The infiltration and defiltration behaviors of liquid are dependent on the controlled by the decomposition-treatment temperature. INTRODUCTION Porous materials have been widely applied in chemistry, biology, and energy-related areas [1]. Depending on their synthesis and treatment process, the nanopores inside of the structures can be either close-end or open-end, and the pore shape can be either ordered or disordered. Besides the pore diameter and shape, the component of the nanoporous materials can also affect their property and application. Recently, a system consisting of lyophobic nanoporous materials in liquid phases to produce the colloidal suspension has attracted the interest of experts in terms of their applications as mechanical actuators, thermal machines, or dampers [2-3]. The smart systems are developed by dispersing lyophobic nanoporous materials in liquid phases. Applying an external pressure, the liquids overcome the capillary effect and enter the nanopores. During this process, a significant amount of external work is converted to the excess solid/liquid interfacial tension, Δγ. One way to calculate the specific absorbed energy is E= Δγ A, where A is the specific surface area of the nanoporous material. Typically, Δγ is 10-50 mJ/m2 [4]. Since the surface area of nanoporous materials is as large as ranging from 100 to 1000 m2/g, E can be 1-50 J/g, attractive for developing lightweight and small-sized protective and damping devices, e.g. soldier armors and vehicle bumpers [5]. During the past a few decades, a number of nanoporous materials have been developed [6-7], among which nanoporous silica gel is another good candidate for the energy absorption system. Their nanopore size can be controlled in the range of 2-100 nm and their specific surface areas are around 100-1000 m2/g [8]. Furthermore, the nanoporous structure of silica gel is quite stable even under a high pressure of around 500 MPa. Usually, nanoporous silica gel is obtained through the aggregation of na
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