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<ul><li><p>Nan</p><p>omaterials</p><p>Nanocomposites</p><p>Guest Editor: Chunxiang Cui</p><p>Journal of Nanomaterials</p></li><li><p>Nanocomposites</p></li><li><p>Journal of Nanomaterials</p><p>Nanocomposites</p><p>Guest Editor: Chunxiang Cui</p></li><li><p>Copyright 2006 Hindawi Publishing Corporation. All rights reserved.</p><p>This is a special issue published in volume 2006 of Journal of Nanomaterials. All articles are open access articles distributed under theCreative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided theoriginal work is properly cited.</p></li><li><p>Editor-in-ChiefMichael Z. Hu, Oak Ridge National Laboratory, USA</p><p>Advisory BoardJames Adair, USAJe Brinker, USATaeghwan Hyeon, South Korea</p><p>Nathan Lewis, USAAlon Mccormick, USAGary Messing, USA</p><p>Z. L. Wang, USAAlan Weimer, USAJackie Ying, USA</p><p>Associate EditorsJohn Bartlett, AustraliaMichael Harris, USADo Kyung Kim, South Korea</p><p>S. J. Liao, ChinaJun Liu, USASanjay Mathur, Germany</p><p>Michael S. Wong, USAM. Yoshimura, Japan</p><p>Editorial BoardDonald A. Bansleben, USASiu Wai Chan, USAGang Chen, USASang-Hee Cho, South KoreaChunxiang Cui, ChinaAli Eftekhari, IranClaude Estournes, FranceAlan Fuchs, USALian Gao, ChinaHongchen Gu, ChinaJustin Holmes, Ireland</p><p>David Hui, USAAlan Lau, Hong KongButrand I., Lee USAJ. Li, SingaporeJ. -Y. Liu, USASongwei Lu, USAEd Ma, USAPierre Panine, FranceDonglu Shi, USABohua Sun, South AfricaXiaogong Wang, China</p><p>Y. Wang, USAE. G. Wang, ChinaC. P. Wong, USAZhili Xiao, USAPing Xiao, UKNanping Xu, ChinaDoron Yadlovker, IsraelZhenzhong Yang, ChinaPeidong Yang, USAKui Yu, Canada</p></li><li><p>Contents</p><p>Damping Augmentation of Nanocomposites Using Carbon Nanofiber Paper, Jihua Gou, Scott OBraint,Haichang Gu, and Gangbing SongVolume 2006, Article ID 32803, 7 pages</p><p>Control Eect of Nanometer SiO2 Hydrosol on Alloy Impurity in CMP Process of ULSI, Liu Yuling,Li Weiwei, Zhang Xihui, and Liu ChangyuVolume 2006, Article ID 29139, 2 pages</p><p>Silica-Polystyrene Nanocomposite Particles Synthesized by Nitroxide-Mediated Polymerization andTheir Encapsulation through Miniemulsion Polymerization, Berange`re Bailly, Anne-Carole Donnenwirth,Christe`le Bartholome, Emmanuel Beyou, and Elodie Bourgeat-LamiVolume 2006, Article ID 76371, 10 pages</p><p>Preparation and Properties of Polyester-Based Nanocomposite Gel Coat System, P. Jawaharand M. BalasubramanianVolume 2006, Article ID 21656, 7 pages</p><p>Study on the Eect of Nano-SiO2 in ULSI Silicon Substrate Chemical Mechanical Polishing Process,Liu Yuling, Wang Juan, Sun Ming, and Liu ChenglinVolume 2006, Article ID 25467, 4 pages</p><p>Microstructure and Thermomechanical Properties of Polyimide-Silica Nanocomposites, A. Al Arbash,Z. Ahmad, F. Al-Sagheer, and A. A. M. AliVolume 2006, Article ID 58648, 9 pages</p><p>Nonlinear Optical Study of Nano-Sized Eects in a-Si : H Thin Films Deposited by RF-Glow Discharge,J. Ebothe, K. J. Plucinski, K. Nouneh, P. Roca i Cabarrocas, and I. V. KitykVolume 2006, Article ID 63608, 5 pages</p></li><li><p>Hindawi Publishing CorporationJournal of NanomaterialsVolume 2006, Article ID 32803, Pages 17DOI 10.1155/JNM/2006/32803</p><p>Damping Augmentation of Nanocomposites UsingCarbon Nanofiber Paper</p><p>Jihua Gou,1 Scott OBraint,1 Haichang Gu,2 and Gangbing Song2</p><p>1 Department of Mechanical Engineering, University of South Alabama, Mobile, AL 36688-0002, USA2 Department of Mechanical Engineering, University of Houston, Houston, TX 77204-4006, USA</p><p>Received 11 January 2006; Accepted 4 May 2006</p><p>Vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the nanocomposites through integrating carbonnanofiber paper into traditional glass fiber reinforced composites. The carbon nanofiber paper had a porous structure with highlyentangled carbon nanofibers and short glass fibers. In this study, the carbon nanofiber paper was employed as an interlayer andsurface layer of composite laminates to enhance the damping properties. Experiments conducted using the nanocomposite beamindicated up to 200700% increase of the damping ratios at higher frequencies. The scanning electron microscopy (SEM) charac-terization of the carbon nanofiber paper and the nanocomposites was also conducted to investigate the impregnation of carbonnanofiber paper by the resin during the VARTM process and the mechanics of damping augmentation. The study showed a com-plete penetration of the resin through the carbon nanofiber paper. The connectivities between carbon nanofibers and short glassfibers within the carbon nanofiber paper were responsible for the significant energy dissipation in the nanocomposites during thedamping tests.</p><p>Copyright 2006 Jihua Gou et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p><p>1. INTRODUCTION</p><p>In recent years, nanoparticles have been attracting increas-ing attention in the composite community as they are ca-pable of improving the mechanical and physical proper-ties of traditional fiber reinforced composites [14]. Theirnanometer size, leading to high specific surface areas of upto more than 1000m2/g and extraordinary mechanical, elec-trical, and thermal properties make them unique nano-fillersfor structural and multifunctional composites. Commonlyused nanoparticles in nanocomposites include multiwallednanotubes (MWNTs), single-walled nanotubes (SWNTs),carbon nanofibers (CNFs), montmorillonite (MMT) nan-oclays, and polyhedral oligomeric silsesquioxanes (POSS).Other nanoparticles, such as SiO2, Al2O3, TiO2, and nanosil-ica are also used in the nanocomposites. Compared toother particulate additives, carbon nanotubes and carbonnanofibers oer more advantages. The addition of small sizeand low loading of carbon nanotubes and carbon nanofiberscan enhance the matrix-dominated properties of compos-ites, such as stiness, fracture toughness, and interlaminarshear strength [59]. They have proven to be excellent ad-ditives to impart electrical conductivity in nanocompositesat lower loadings due to their high electrical conductiv-ity and aspect ratio [1012]. In addition, they have better</p><p>performance as flame retardant by reducing the heat releaserate of polymer and conducting heat away from the flamezone [13, 14].</p><p>While there are many reported benefits of carbon nan-otubes and carbon nanofibers in composites, the potentialof carbon nanotubes and carbon nanofibers to enhance thedamping properties of composites has been less explored.Traditional damping enhancements of composites are basedon viscoelastic polymer materials [15], carbon fiber prepregs[16], and magnetostrictive particles [17]. The major limi-tations of the viscoelastic polymer materials are the struc-tural integrity issue, the sacrifice of stiness and strengthof the composite system due to the resin penetration, andpoor thermal stability. Kishi et al. [16] evaluated the damp-ing properties of composite laminates with/without the in-terleaved films. The eects of the lay-up arrangements ofcarbon fiber prepregs on the damping properties of the in-terleaved laminates were examined. The viscoelastic proper-ties of interleaved polymer films were reflected in the damp-ing properties of the corresponding interleaved laminates.Magnetostrictive particles have been used in a polymer ma-trix as active transducer and passive damper, providing sti-ness and strength while incorporating damping capabilities.Pulliam et al. [17] developed a novel manufacturing tech-nique based onmagnetic fields to distribute magnetostrictive</p></li><li><p>2 Journal of Nanomaterials</p><p>particles in polymer resins and applied them in thin-layer onthe surfaces for vibration damping. Recently, carbon nan-otubes have been used in the composite system for struc-tural damping and stiness augmentation. Suhr et al. [18]conducted direct shear testing of epoxy thin films contain-ing multiwalled carbon nanotubes and reported strong vis-coelastic behavior with up to 1400% increase in loss factor(damping ratio) of the baseline epoxy resin. The great im-provement in damping was achieved without sacrificing themechanical strength and stiness of the polymer, and withminimal weight penalty. Koratkar et al. [19, 20] fabricatedmultiwalled nanotube thin films by using catalytic chemi-cal vapor deposition of xylene-ferrocene mixture precursor.The nanotube films were employed as interlayers to rein-force the interfaces between composite plies, enhancing lam-inate stiness and structural damping. The flatwise bend-ing tests of a piezosilica composite beam with an embed-ded nano-film sublayer indicated up to 200% increase in thedamping level and 30% increase in the baseline bending sti-ness.</p><p>Traditionally, researchers fabricated composites by di-rectly mixing carbon nanotubes and carbon nanofibers intopolymers and then using casting and injection techniquesto make nanocomposites. Gou et al. [21, 22] have de-veloped a new technique approach to fabricate nanocom-posites using single-walled carbon nanotube bucky papers.The experimental details of fabrication of single-walledcarbon nanotube bucky paper can be found in reference[23]. The dynamic mechanical analysis (DMA) results in-dicated an enhancement of the thermomechanical proper-ties of single-walled carbon nanotube bucky paper/epoxyresin nanocomposites. The present work describes the inte-gration of carbon nanofiber paper as damping material intolarge structural level laminates-glass fiber reinforced com-posites. The very first time an example of carbon nanofiberpaper-enabled nanocomposites in the dimension of a struc-tural element is presented. The manufacturing via VARTMand the investigation of the damping properties and ten-sile properties of the fabricated nanocomposites are de-scribed.</p><p>2. EXPERIMENTAL DETAILS</p><p>2.1. Materials</p><p>The carbon nanofiber paper used in this study was ob-tained from Applied Sciences, Inc. The carbon nanofiber pa-per had good strength and flexibility to allow for handlinglike traditional glass fiber mat. The carbon nanofiber paperwas composed of short glass fibers and vapor grown car-bon nanofibers (Polygraf III) with diameter of 100150 nmand length of 30100 m. The short glass fiber and carbonnanofibers appeared in an entangled and porous formwithinthe paper. The unsaturated polyester resin (product code:7126117, Eastman Chemical Company) was used as matrixmaterial for glass fiber reinforced composites. The polyesterresin was used with the MEK peroxide hardener at a weightratio of 100 : 1.</p><p>2.2. Manufacturing of carbon nanofiberpaper-enabled nanocomposites</p><p>The VARTM process has been widely used to produce low-cost, high-quality, and geometrically complicated compos-ite parts. In this study, the VARTM process was used to fab-ricate the carbon nanofiber paper-enabled nanocomposites,which was carried out in three steps. In the first step, glassfiber mats carbon nanofiber paper were placed on the bot-tom half of a mold. After the lay-up operation was com-pleted, a peel ply, resin distribution media, and vacuum bagfilm were placed on the top of fiber mats. The vacuum filmbag was then sealed around the perimeter of the mold and avacuum pump was used to draw a vacuum within the moldcavity. The next step was the mold filling during which resinwas sucked into the mold under atmospheric pressure. In theVARTM process, the distribution media provided a high per-meability region in the mold cavity, which allowed the resinto quickly flow across the surface of the laminate and thenwet the thickness of the laminate. Therefore, the dominantimpregnation mechanism in the VARTM process was thethrough-thickness flow of resin. In the final step, the com-posite part was cured at room temperature for 24 hours andpost-cured in the oven for another 2 hours at 100C.</p><p>In this study, the test laminates consisted of six plies offiberglass with a single layer of carbon nanofiber paper em-bedded at the surface or the midplane. In the manufactur-ing of composite laminates with carbon nanofiber as an in-terlayer, one layer of carbon nanofiber paper was placed be-tween the fiber mats. The peel ply and resin distribution me-dia were used on both top and bottom sides to facilitate theresin flow through the thickness.</p><p>2.3. Damping test of carbon nanofiber paper-enablednanocomposites</p><p>The regular composite beam without carbon nanofiber pa-per and the nanocomposite beam with carbon nanofiber pa-per were used as the specimens for damping test. For eachbeam, a PZT (lead zirconate titanate, a type of piezoce-ramic material) patch (20mm 20mm) was attached onone side as an actuator to excite the beam and a smaller PZTpatch (10mm 8mm) was attached on the other side of thebeam as a sensor to detect the beams vibration, as shown inFigure 1. A micro laser sensor (NAIS-LM10-ANR12151) wasalso used to detect the beams tip displacement. The microlaser sensor had a resolution of 20 m(0.0008 inch). The test-ing specimen was clamped on an aluminum stand as shownin Figure 2.</p><p>2.4. Tensile test of carbon nanofiber paper-enablednanocomposites</p><p>The tensile tests were performed using the VARTM man-ufactured composite laminates with and without carbonnanofiber paper. The tensile tests on the composite beamswere conducted according to ASTM test standards. All thesetests were performed on a Qualitest testing machine.</p></li><li><p>Jihua Gou et al. 3</p><p>PZT actuators</p><p>Nanocomposite beam</p><p>Regular composite beam</p><p>Figure 1: Regular composite beam and nanocomposite beam fordamping test.</p><p>2.5. Electron microscopy</p><p>The SEM images were taken to study the porous structureof carbon nanofiber paper and the impregnation of carbonnanofiber paper by the resin. The interface between the car-bon nanofiber paper and the resin was examined. The SEMspecimens of the nanocomposites were obtained by the ultramicrotome cutting.</p><p>3. RESULTS AND DISCUSSION</p><p>3.1. SEM observations of carbon nanofiber paperand nanocomposites</p><p>Figure 3(a) shows the carbon nanofiber paper used in this re-search, which can be handled like traditional glass fiber mats.The SEM images of carbon nanofiber paper are shown in Fig-ures 3(b) and 3(c). These images show the multiscale porousstructure of carbon nanofiber paper formed by short glassfibers and carbon nanofibers. The pore size formed by shortglass fibers was in the range of 100200 m and the poresformed by carbon nanofibers had an average opening around1 m. The carbon nanofibers within the paper have an aver-age diameter about 100150 nm. Figure 3(d) shows the SEMimage of the fracture surface of the nanocomposites embed-ded with carbon nanofiber paper. This sample was fracturedunder tensile force. It can be clearly seen that the resin hadcompletely penetrated the carbon nanofiber paper throughthe thickness direction during the VARTM process.</p><p>3.2. Damping properties of carbon nanofiber-enabledcomposite laminates</p><p>The damping test was conducted on the composite lami-nates with carbon nanofiber paper as midlayer and surfacelayer. During the damping test, the sweep sinusoidal signalswere used as excitation source for the PZT actuator to get</p><p>Laser sensor</p><p>Beam</p><p>Fi...</p></li></ul>