A new shape-memory nanocomposite that exhibits rapid electrical actuation capabilities is fabricated by incorporating self-assembly multiwalled carbon nanotube (MWCNT) nanopaper and magnetic CNTs into a styrene-based shape-memory polymer (SMP). The MWCNT nanopaper was coated on the surface to give high electrical conductivity to SMP. Electromagnetic CNTs were blended with and, vertically aligned into the SMP resin upon a magnetic field, to facilitate the heat transfer from the nanopaper to the underlying SMP. This not only significantly enhances heat transfer but also gives high speed electrical actuation

Du, Shanyi

Gou, Jihua

Leng, Jinsong

Lu, Haibao

English

University of Central Florida (UCF): STARS (Showcase of Text, Archives, Research & Scholarship)

University of Central Florida STARS Faculty Bibliography 2010s Faculty Bibliography 1-1-2011 Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuation Haibao Lu Jihua Gou University of Central Florida Jinsong Leng Shanyi Du Find similar works at: https://stars.library.ucf.edu/facultybib2010 University of Central Florida Libraries http://library.ucf.edu This Article is brought to you for free and open access by the Faculty Bibliography at STARS. It has been accepted for inclusion in Faculty Bibliography 2010s by an authorized administrator of STARS. For more information, please contact STARS@ucf.edu. Recommended Citation Lu, Haibao; Gou, Jihua; Leng, Jinsong; and Du, Shanyi, "Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuation" (2011). Faculty Bibliography 2010s. 1590. https://stars.library.ucf.edu/facultybib2010/1590 Appl. Phys. Lett. 98, 174105 (2011); https://doi.org/10.1063/1.3585669 98, 174105© 2011 American Institute of Physics.Magnetically aligned carbon nanotubein nanopaper enabled shape-memorynanocomposite for high speed electricalactuationCite as: Appl. Phys. Lett. 98, 174105 (2011); https://doi.org/10.1063/1.3585669Submitted: 11 January 2011 . Accepted: 09 April 2011 . Published Online: 29 April 2011Haibao Lu, Jihua Gou, Jinsong Leng, and Shanyi DuARTICLES YOU MAY BE INTERESTED INSynergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymercompositeApplied Physics Letters 96, 084102 (2010); https://doi.org/10.1063/1.3323096Electroactivate shape-memory polymer filled with nanocarbon particles and short carbonfibersApplied Physics Letters 91, 144105 (2007); https://doi.org/10.1063/1.2790497Carbon nanotube chains in a shape memory polymer/carbon black composite: Tosignificantly reduce the electrical resistivityApplied Physics Letters 98, 074102 (2011); https://doi.org/10.1063/1.3556621Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuationHaibao Lu,1 Jihua Gou,2,a Jinsong Leng,1,a and Shanyi Du11National Key Laboratory of Science and Technology on Advanced Composites in Special Environments,Harbin Institute of Technology, Harbin 150080, People’s Republic of China2Department of Mechanical Engineering, University of Central Florida, Orlando 32816, USAReceived 11 January 2011; accepted 9 April 2011; published online 29 April 2011A new shape-memory nanocomposite that exhibits rapid electrical actuation capabilities isfabricated by incorporating self-assembly multiwalled carbon nanotube MWCNT nanopaper andmagnetic CNTs into a styrene-based shape-memory polymer SMP. The MWCNT nanopaper wascoated on the surface to give high electrical conductivity to SMP. Electromagnetic CNTs wereblended with and, vertically aligned into the SMP resin upon a magnetic field, to facilitate the heattransfer from the nanopaper to the underlying SMP. This not only significantly enhances heattransfer but also gives high speed electrical actuation. © 2011 American Institute of Physics.doi:10.1063/1.3585669To date, much attention has been directed to a variety offunctional materials including alloys, ceramics and poly-mers, which have all been found to exhibit shape memorybehavior.1 Shape-memory polymers SMPs are an excitingclass of materials that have the ability to store a temporaryshape, and then recover a predetermined permanent shapewhen subjected to an environmental stimulus.2 As comparedwith other available shape-memory alloys SMAs atpresent, SMPs have many advantages, namely, wider rangeof shape recovery temperature, better processing ability, bio-compatibility, etc.3 With these unique characteristics, SMPscurrently cover a broad application area ranging from self-deployable structure to medical implants for minimally inva-sive surgery.4Shape memory behavior of SMP is usually a thermalinduced process, which can be fixed and maintained untilshape recovery is triggered through an external heating. De-pending on the material used, stimuli can also be different.Fundamental shape-memory research is focusing on theimplementation of stimuli other than direct heating to actuateSMPs, or to actuate them remotely, such as infrared light,5water/solvent,6,7 or magnetic field.8The demand to identify alternative strategies in orderto heat SMPs above their transition temperature directedresearch to electrical sensitive SMPs filled with carbonnanotubes CNTs,9 carbon black,10 conductive hybridfibers,11 continuous conductive carbon fibers,12 conductivenanopaper13 and combination of nanopaper, randomly dis-persed particles,14 etc. Electrically induced actuation allowsthe convenient triggering of shape recovery by passing anelectrical current through a composite. However, either theexamples reported to date the conductivity is still relativelylow, due to the limited efficiency of discrete fillers to formpercolating conductive networks. Or the random dispersedconductive fillers slightly depressed the recovery behavior ofSMP.14 Here, we report the fabrication of a new shape-memory nanocomposite that exhibits rapid electrical actua-tion capabilities is fabricated by incorporating self-assemblymultiwalled CNT MWCNT nanopaper and magneticallyaligned CNT into a styrene-based SMP. The MWCNT nano-paper was coated on the surface to give high electrical con-ductivity to SMP nanocomposite. CNTs were blended withand, vertically aligned into the SMP resin upon a magneticfield, to facilitate the heat transfer from the nanopaper to theunderlying SMP. This not only significantly enhances heattransfer but also gives high speed electrical actuation.Before being able to manufacture the SMP nanocompos-ite, fabrication of MWCNT nanopaper was first needed. TheMWCNTs L-MWNT-1020 were received in powder fromShenzhen Nanometer Gang Co., Ltd, China. The nanotubehas an out diameter of 10 to 20 nm and 1–15 m in length.Each division of 0.6 g of MWCNT was added to 600 ml ofdistilled water. Twenty drops of Triton X-100 nonionic sur-factant were added to this mixture to ensure proper disper-sion of MWCNT within the distilled water. After mechanicalstirring for approximately 90 s, the suspension was then situ-ated in a Misonix S-4000 Sonicator and underwent twocycles of sonication at 60% amplitude for 15 min per cycle.That is, for every 0.6g of MWCNT mixture, 30 min of soni-cation was necessary to establish quality dispersion of theMWCNTs. After the sonication process was complete, thesuspension of MWCNTs and distilled water was run througha filtering system, aided by a high air pressure driver at ap-proximately 80 psi. At this point, the newly fabricatedMWCNT nanopaper was placed on a metal block. This as-sembly was then placed in a heating oven for 2 h at 120 °Cto rid of any excess water.The nickel coated CNTs are supplied from Chengdu Or-ganic Chemicals Co. Ltd., China. These products have a di-ameter of 8 to 15 nm, 50 m in length. In this study, themagnetic CNTs were dispersed into the distilled water. Anamount of drops of Triton X-100 surfactant were added tothis mixture to ensure proper dispersion of magnetic CNTswithin the distilled water. The suspension was then situatedin a Misonix S-4000 Sonicator at 60% amplitude for 15 min.This treatment helped the as-received magnetic CNTs toreach their nanosize.The SMP VeriflexS VF 62, supplied from Corner-stone Research Group, Inc., Dayton, Ohio, USA is aaAuthors to whom correspondence should be addressed. Electronic ad-dresses: lengjs@hit.edu.cn and Jihua.Gou@ucf.edu.APPLIED PHYSICS LETTERS 98, 174105 20110003-6951/2011/9817/174105/3/$30.00 © 2011 American Institute of Physics98, 174105-1styrene-based matrix. It was polymerized with the dibenzoylperoxide harder at a fixed weight ratio of 24:1. The as treatedmagnetic CNTs were blended into the SMP mixture withdifferent weight fraction of 2 wt %, 4 wt %, 6 wt %, and 8wt %, respectively. Two magnets were placed in a way formagnetic CNTs being aligned. Simultaneously, anothergroup of SMP nanocomposites was prepared in the same waybut without applying the magnetic field.The morphology and structure of the MWCNT nanopa-per and aligned CNTs were characterized using scanningelectron microscopy SEM, MX2600FE, Camscan Co.,U.K.. Figure 1a is a typical surface view of the rawMWCNT arrays at an accelerating voltage of 20.00 keV andmagnifications of 40 000 times. The nanopaper had a po-rous structure with MWCNTs entangled with each other. Thenetwork structure of the nanopaper was formed by molecularinteraction and mechanical inter-locking among individualnanotubes. Such a continuous network could provide con-ductive path for electrons, making the nanopaper electricallyconductive. Figures 1b reveals magnetic CNTs start toalign in presence of a magnetic field, and the morphologywas observed at an accelerating voltage of 20.00 keV andmagnifications of 5000 times. An amount of water contain-ing magnetic CNTs was allowed to dry. If a magnetic fieldwas applied to the solution as it dried, the CNTs were alignedalong the direction of the magnetic field.The electrical resistivity of the SMP nanocomposite wasmeasured with a four-terminal sensing method. The electricalresistivities of the SMP nanocomposites blending with vari-ous weight fractions of CNTs were plotted against differentlocations, as shown in Fig. 2. All the SMP nanocompositeswere coated with one layer of nanopaper containing 1.8 gMWCNTs. As the weight of magnetic CNTs blended into theSMP resin increased from 0 to 8 wt %, the average electricalresistivity of nanocomposite sample decreased from 2.076 to0.926  cm. The more magnetic CNTs were blended intothe SMP resin, the more conductive paths were formed in theSMP nanocomposite. Therefore, the electrical current ampli-tude and current-carrying capability increase as more elec-trons were forced to pass through the cross section of thebulk.SMP nanocomposite with 8 wt % vertically alignedCNTs was further utilized to demonstrate the electricallytriggered shape memory/actuation behavior. The electricalconductivity of SMP/nanopaper/CNT vertically alignedwas 1.080 S cm−1. This high electrical conductivity allowedfast activation of shape recovery by applying a constant dcvoltage. Experimentally, the recovery process was character-ized using a modified bending test method, with the recoveryratio calculated based on the change in deformation angle asfunction of time/temperature.12,15 A “” shaped geometrywas used to minimize the mechanical constraint imposed bythe electrodes. The flat permanent shape nanocompositespecimen was bent as “U”-like shape temporary shape at110 °C. This temporary shape was kept until the specimenwas cooled down to room temperature. No apparent recoverywas seen after the deformed specimen was kept in air for 2 h.Figure 3 shows the recovery of SMP nanocomposite speci-men blended with 8 wt % vertically aligned CNTs from afixed bent shape to its straight permanent shape under a con-stant dc voltage of 36V. The deformed nanocomposite speci-men started to return to its original shape when a constantelectrical current was applied for 10 s. The specimen showedvery little recovery ratio during the first 20 s. It then startedto exhibit a faster shape recovery behavior until 60 s. Duringthe last 15 s, a slight change in shape recovery was observed.Finally, the nanocomposite specimen showed a 100% recov-ery ratio. This fact can be attributed to the vertically alignedCNTs. These vertically aligned CNTs uniformly transferredthe electrically resistive heating from nanopaper to the un-derlying SMP part along the vertical direction, resulting inheat transfer and dispersion significantly improved. How-ever, they had no negative effect on the recovery ratio ofSMP nanocomposite.Meanwhile, each image was then analyzed to obtain thedeformation angle, where the deformation angle shown inFIG. 1. a Morphology and structure of MWCNT nanopaper. b Typicalsurface view of the raw MWCNT arrays at magnifications of 5000 times.FIG. 2. Color online Electrical resistivity of SMP nanocomposites withMWCNT nanopaper as function of contents of vertically aligned CNTs.FIG. 3. Color online Electroactive recovery of SMP nanocomposite with 8wt % vertically aligned CNTs under a 36 V voltage.174105-2 Lu et al. Appl. Phys. Lett. 98, 174105 2011the first image is considered as 0. Therefore, the recoveryratio is defined as,15R% =i − ti − e, 1where i, e are the initial deformation angle of the fixedsample, the deformation angle at a given time t, and thedeformation angle at the equilibrium state, respectively. Therecovery experiments were conducted under two different dcvoltages, for SMP nanocomposites with 8 wt % verticallyaligned CNTs and randomly dispersed CNTs, respectively.The resulting recovery profiles were shown in Fig. 4a.These curves revealed that the SMP nanocomposite with ver-tically aligned CNTs had the faster response behavior thanthat with randomly dispersed CNTs, against both two volt-ages. Obviously, the reduce in recovery time was the resultof aligned CNTs. This experimental result revealed that thevertically aligned CNTs facilitate the heat transfer from thenanopaper to the underlying SMP, and give the SMP highspeed electrical actuation.To reveal more detailed kinetics information, the recov-ery data were further analyzed using a standard Boltzmannfunction:Rt = A2 +A1 − A21 + et−t0/, 2where A1, A2, t0, and  are the four fitting parameters. Allthe four fitting parameters can be obtained from the experi-mental results. So, the data set for each curve is “A1=0.565 32, A2=179.056 62, t0=40.788 32 and =3.879 18,”“A1=−4.778 01, A2=178.670 36, t0=64.158 14, and =12.149 04” “A1=−4.498 47, A2=194.388 93, t0=128.184 74, and =22.292 09” and “A1=−0.687 03, A2=194.928 21, t0=179.340 18, and =22.382 64,” respec-tively. The fit curves had respective R2 values of 0.999 73,0.997 31, 0.997 56, and 0.999 27, and were shown as thesolid lines. The second derivatives of the fit curves were thencalculated and plotted in Fig. 4b. All the second derivativeplots showed a similar pattern consisting of two oppositepeaks with the same height. The induction time was definedas the time between “0” and the first positive peak on thesecond derivative plot. This corresponds to an induction pe-riod of the recovery profile, during which the nanocompositespecimens were heated from environmental temperature totheir switching temperature. It is found that the inductiontime of SMP nanocomposite with vertically aligned CNTswas 15.9 s shorter than that with randomly dispersed CNTsunder the 36 V triggering voltage.A series of experiments were conduct to study the syn-ergistic effect of MWCNT nanopaper and vertical alignedCNTs on the SMP nanocomposites. The actuation of theSMP nanocomposites was achieved by electrically resistiveheating of nanopaper. Electromagnetic CNTs were blendedwith and, vertically aligned into SMP resin upon a magneticfield, to facilitate the heat transfer from the nanopaper to theunderlying SMP. This not only improves electrical conduc-tivity and heat transfer but also gives high speed electricalactuation.1A. Lendlein and S. Kelch, Angew. Chem., Int. Ed. 41, 2034 2002.2P. T. Mather, X. F. Luo, and I. A. Rousseau, Annu. Rev. Mater. Res. 39,445 2009.3J. Van Humbeeck, Adv. Eng. Mater. 3, 837 2001.4J. S. Leng, H. B. Lu, W. M. Huang, and S. Y. Du, MRS Bull. 34, 8482009.5J. S. Leng, X. L. Wu, and Y. J. Liu, J. Appl. Polym. Sci. 114, 2455 2009.6B. Yang, W. M. Huang, C. Li, and J. H. Chor, Eur. Polym. J. 41, 11232005.7J. S. Leng, H. B. Lv, Y. J. Liu, and S. Y. Du, Appl. Phys. Lett. 92, 2061052008.8J. S. Leng, W. M. Huang, X. Lan, and S. Y. Du, Appl. Phys. Lett. 92,204101 2008.9Y. J. Liu, H. B. Lv, J. S. Leng, and S. Y. Du, Compos. Sci. Technol. 69,2064 2009.10H. B. Lu, K. Yu, Y. J. Liu, and J. S. Leng, Smart Mater. Struct. 19, 0650142010.11J. S. Leng, H. B. Lv, Y. J. Liu, and S. Y. Du, Appl. Phys. Lett. 91, 1441052007.12X. Lan, Y. J. Liu, J. S. Leng, and S. Y. Du, Smart Mater. Struct. 18,024002 2009.13H. B. Lu, J. Gou, J. S. Leng, and S. Y. Du, Smart Mater. Struct. 19,075021 2010.14H. B. Lu, J. Gou, J. S. Leng, and S. Y. Du, Appl. Phys. Lett. 96, 0841022010.15X. F. Luo and P. T. Mather, Soft Matter 6, 2146 2010.FIG. 4. Color online a shows the recovery profiles of SMP nanocomposites with, respectively, aligned and randomly dispersed 8 wt % magnetic CNTsunder 12 V and 36 V voltage, respectively. b plots the induction and recovery times of SMP nanocomposites for the two voltages studied.174105-3 Lu et al. Appl. Phys. Lett. 98, 174105 2011

Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuation

Haibao Lu

Jihua Gou

Jinsong Leng

Shanyi Du

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Applied Physics Letters

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Magnetically aligned carbon nanotube in nanopaper enabled shape-memory nanocomposite for high speed electrical actuation

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