Browsing by Author "Luo, Jen-Tsung"

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Mechanical Research of Carbon Nanotubes/PMMA Composite Films
(2008-12-01)
Luo, Jen-Tsung
;
Wen, Hua-Chiang
;
Wu, Wen-Fa
;
Chou, Chang-Pin
;
機械工程學系
Carbon nanotubes (CNTs) are one of the best candidates for reinforcing the next generation of high-performance nanocomposites owing to their excellent mechanical properties. In this study, CNTs were dispersed in poly-methymethacrylate (PMMA) gel to enhance its mechanical strength. CNTs/PMMA composite films were fabricated using direct mixing and sonication. FTIR was utilized to observe the chemical structure and functional groups of the material components. The morphological feature and phase structure were observed via scanning electron microscope. A nanoindenter system was also applied to investigate the mechanical properties of composite films by a conventional method. CNTs were chemically treated by immersing them in acidic solutions to ensure extensive dispersion in the surrounding matrix. Most of the CNTs were dispersed uniformly therein. The effective dispersion of CNTs improves the mechanical performance of the composite film, wheras the poor dispersion reduces the performance. The solvent, solubility and attractive intermolecular forces, such as hydrogen bonds and Van Der Waal forces affect the dispersion of the CNTs. The carbonyl group, which was found on the composite film, contributed to the formation of a covalent bond between PMMA and the CNTs. The mechanical interaction between CNTs and the polymer was very complex. It was also governed by the interface interaction. The mechanical properties of the composite films improved as the concentration of CNTs increased. POLYM. COMPOS., 29:1285-1290, 2008. (C) 2008 Society of Plastics Engineers
Mesoporous silica reinforced by silica nanoparticles to enhance mechanical performance
(2007-01-15)
Luo, Jen-Tsung
;
Wen, Hua-Chiang
;
Chang, Yu-Ming
;
Wu, Wen-Fa
;
Chou, Chang-Pin
Silica nanoparticle/mesoporous silica composite films were prepared by direct mixing with mechanical stirring and thermal imidization. The structural morphology was elucidated by scanning electron microscopy and the surface of the film was imaged by atomic force microscopy. The functional groups and desorption process of the films were elucidated by Fourier transform infrared spectroscopy and thermal desorption spectroscopy. The mechanical properties were investigated using a nanoindenter system. The gel matrix and the filler are very compatible because they have similar molecular content. The composite films had a higher mechanical strength than pure porous silica film. Their strength is related to the silica nanoparticle content. The interfacial compatibility, dispersion effect, and interfacial strength also affect the mechanical strength of composite films. (c) 2006 Elsevier Inc. All rights reserved.
Reinforcing porous silica with carbon nanotubes to enhance mechanical performance
(2007-04-01)
Luo, Jen-Tsung
;
Wen, Hua-Chiang
;
Chou, Chang-Pin
;
Wu, Wen-Fa
;
Wan, Ben-Zu
In this study, porous silica NOD film is reinforced with carbon nanotubes (CNTs), which gets homogeneously dispersed in porous SiO2 gel by ultrasonic stirring. The SiZC of SiO2 molecules is the same as that of nanotubes, so a fine CNTs/SiO2 network is formed. Nanoindenters used to test the mechanical properties of the resulting specimens show a marked enhancement in the properties as a function of filler content. Interfacial bonding and the distribution of CNTs also strongly affected the mechanical performance. Although a high concentration of CNTs improves the mechanical characteristics of the matrix, it also causes agglomeration such that the mechanical performance at the surface was disproportionate. Fourier transform infrared spectroscopy (FTIR) analysis indicates that there is little chemical reaction occurring between CNTs and SiO2. The results suggest that CNTs are ineffective reinforcements.
The roles of hydrophobic group on the surface of ultra low dielectric constant porous silica film during thermal treatment
(2007-06-25)
Luo, Jen-Tsung
;
Wu, Wen-Fa
;
Wen, Hua-Chiang
;
Wan, Ben-Zu
;
Chang, Yu-Ming
Porous silica films with ultra low-k (below 2) and low leakage current densities (10(-8) A/cm(2) or lower at an electric field of 1.8 MV/cm) were prepared by the surfactant-template method. Hexamethyldisilazane (HMDS), a surface modification agent, was utilized to yield hydrophobic groups on the surface of porous silica film to prevent the absorption of moisture. It effectively retained the low permittivity properties of the films. Thermal treatment at high temperature (> 350 degrees C) destroyed surface hydrophobic groups and generated hydrophilic groups (Si-OH), which replaced the surface Si(CH3)(3) groups, and resulted in the absorption of moisture. However, Si-OH not only resulted in the absorption of moisture but also initiated the formation of trimethylsilyl groups on the surface by HMDS. When the damaged film is repaired by HMDS again, the k value falls to its initial value (which may be below 1.6). A denser hydrophobic low-k film is formed and the electrical properties are improved. (C) 2007 Elsevier B.V. All rights reserved.