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A review: controlled synthesis of vertically aligned carbon nanotubes
Myung-Gwan Hahm,Daniel P. Hashim,Robert Vajtai,Pulickel M. Ajayan 한국탄소학회 2011 Carbon Letters Vol.12 No.4
Carbon nanotubes (CNTs) have developed into one of the most competitively researched nano-materials of this decade because of their structural uniqueness and excellent physical properties such as nanoscale one dimensionality, high aspect ratio, high mechanical strength, thermal conductivity and excellent electrical conductivity. Mass production and structure control of CNTs are key factors for a feasible CNT industry. Water and ethanol vapor enhance the catalytic activity for massive growth of vertically aligned CNTs. A shower system for gas flow improves the growth of vertically aligned single walled CNTs (SWCNTs) by controlling the gas flow direction. Delivery of gases from the top of the nanotubes enables direct and precise supply of carbon source and water vapor to the catalysts. High quality vertically aligned SWCNTs synthesized using plasma enhance the chemical vapor deposition technique on substrate with suitable metal catalyst particles. This review provides an introduction to the concept of the growth of vertically aligned SWCNTs and covers advanced topics on the controlled synthesis of vertically aligned SWCNTs.
Composites with carbon nanotubes and graphene: An outlook
Kinloch, Ian A.,Suhr, Jonghwan,Lou, Jun,Young, Robert J.,Ajayan, Pulickel M. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6414
<P>Composite materials with carbon nanotube and graphene additives have long been considered as exciting prospects among nanotechnology applications. However, after nearly two decades of work in the area, questions remain about the practical impact of nanotube and graphene composites. This uncertainty stems from factors that include poor load transfer, interfacial engineering, dispersion, and viscosity-related issues that lead to processing challenges in such nanocomposites. Moreover, there has been little effort to identify selection rules for the use of nanotubes or graphene in composite matrices for specific applications. This review is a critical look at the status of composites for developing high-strength, low-density, high-conductivity materials with nanotubes or graphene. An outlook of the different approaches that can lead to practically useful nanotube and graphene composites is presented, pointing out the challenges and opportunities that exist in the field.</P>
Satish, Tejus,Balakrishnan, Kaushik,Gullapalli, Hemtej,Nagarajaiah, Satish,Vajtai, Robert,Ajayan, Pulickel M. Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.2
In this paper, we present a strain-sensitive composite skin-like film made up of piezoresistive zinc oxide (ZnO) nanorods embedded in a flexible poly(dimethylsiloxane) substrate, with added reduced graphene oxide (rGO) to facilitate connections between the nanorod clusters and increase strain sensitivity. Preparation of the composite is described in detail. Cyclic strain sensing tests are conducted. Experiments indicate that the resulting ZnO-PDMS/rGO composite film is strain-sensitive and thus capable of sensing cycling strain accurately. As such, it has the potential to be molded on to a structure (civil, mechanical, aerospace, or biological) in order to provide a strain sensing skin.
Functionalized Multilayered Graphene Platform for Urea Sensor
Srivastava, Rajesh K.,Srivastava, Saurabh,Narayanan, Tharangattu N.,Mahlotra, Bansi D.,Vajtai, Robert,Ajayan, Pulickel M.,Srivastava, Anchal American Chemical Society 2012 ACS NANO Vol.6 No.1
<P>Multilayered graphene (MLG) is an interesting material for electrochemical sensing and biosensing because of its very large 2D electrical conductivity and large surface area. We propose a less toxic, reproducible, and easy method for producing functionalized multilayer graphene from multiwalled carbon nanotubes (MWCNTs) in mass scale using only concentrated H<SUB>2</SUB>SO<SUB>4</SUB>/HNO<SUB>3</SUB>. Electron microscopy results show the MLG formation, whereas FTIR and XPS data suggest its carboxylic and hydroxyl-functionalized nature. We utilize this functionalized MLG for the fabrication of a novel amperometric urea biosensor. This biosensor shows linearity of 10–100 mg dL<SUP>–1</SUP>, sensitivity of 5.43 μA mg<SUP>–1</SUP> dL cm<SUP>–2</SUP>, lower detection limit of 3.9 mg dL<SUP>–1</SUP>, and response time of 10 s. Our results suggest that MLG is a promising material for electrochemical biosensing applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-1/nn203210s/production/images/medium/nn-2011-03210s_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203210s'>ACS Electronic Supporting Info</A></P>
In Situ Synthesis of ThermochemicallyReduced Graphene Oxide Conducting Nanocomposites
Park, Ok-Kyung,Hahm, Myung Gwan,Lee, Sungho,Joh, Han-Ik,Na, Seok-In,Vajtai, Robert,Lee, Joong Hee,Ku, Bon-Cheol,Ajayan, Pulickel M. American ChemicalSociety 2012 NANO LETTERS Vol.12 No.4
<P>Highly conductive reduced graphene oxide (GO) polymer nano composites are synthesized by a well-organized in situ thermochemical synthesis technique. The surface functionalization of GO was carried out with aryl diazonium salt including 4-iodoaniline to form phenyl functionalized GO (I-Ph-GO). The thermochemically developed reduced, GO (R-I-Ph-GO) has five times higher electrical conductivity (42 000 S/m) than typical reduced GO (R-GO). We also demonstrate a R-I-Ph-GO/polyimide (PI) composites having more than 10(4) times higher conductivity (similar to 1 S/m) compared to a R-GO/PI composites. The electrical resistances of PI composites with R-I-Ph-GO were dramatically dropped under similar to 3% tensile strain. The R-I-Ph-GO/PI composites with electrically sensitive response caused by mechanical strain are expected to have broad implications for nanoelectromechanical systems.</P>
Experimental investigation of mechanical properties of UV-Curable 3D printing materials
Hong, Sung Yong,Kim, Ye Chan,Wang, Mei,Kim, Hyung-Ick,Byun, Do-Young,Nam, Jae-Do,Chou, Tsu-Wei,Ajayan, Pulickel M.,Ci, Lijie,Suhr, Jonghwan Elsevier 2018 Polymer Vol.145 No.-
<P><B>Abstract</B></P> <P>More recently, three dimensional printing (3D Printing), also known as an additive manufacturing (AM), has been highlighted since it shows a great promise to realize almost any three dimensional parts or structures with computer aided design (CAD). Several different processes are available for 3D printing, which includes fused deposition modeling, selective laser sintering, stereolithography, photopolymerization, and etc. In particular, considerable attention is paid to the 3D printing technique with photopolymerization due to their high resolutions. Unfortunately, the 3D printed products with photopolymerization however possess poor mechanical properties. Understanding of this should be necessary for the advantages of the 3D printing to be fully realized. Here, this study experimentally investigates the mechanical properties of the 3D printed photopolymer through thermomechanical analysis and tensile testing. In this study, it is found that the printed specimens are not fully cured after the 3D printing with photopolymerization. DiBenedetto equation is employed to better understand the relationship between the curing status and tensile properties. In addition to the poor mechanical properties, anisotropic and size dependent tensile properties of the 3D printed photopolymers are also observed. Electron beam treatment is used to ensure the cure of the 3D printed photopolymer and the corresponding tensile properties are characterized and investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The interesting mechanical behaviors of 3D printed photopolymer were investigated. </LI> <LI> Anisotropic and size dependent tensile properties are studied by thermal analysis. </LI> <LI> Modeling with DiBenedetto equation was employed to understand curing degree. </LI> <LI> Electron beam treatment was chosen to ensure full cure of 3D printed photopolymer. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ultrathin Planar Graphene Supercapacitors
Yoo, Jung Joon,Balakrishnan, Kaushik,Huang, Jingsong,Meunier, Vincent,Sumpter, Bobby G.,Srivastava, Anchal,Conway, Michelle,Mohana Reddy, Arava Leela,Yu, Jin,Vajtai, Robert,Ajayan, Pulickel M. American Chemical Society 2011 Nano letters Vol.11 No.4
<P>With the advent of atomically thin and flat layers of conducting materials such as graphene, new designs for thin film energy storage devices with good performance have become possible. Here, we report an “in-plane” fabrication approach for ultrathin supercapacitors based on electrodes comprised of pristine graphene and multilayer reduced graphene oxide. The in-plane design is straightforward to implement and exploits efficiently the surface of each graphene layer for energy storage. The open architecture and the effect of graphene edges enable even the thinnest of devices, made from as grown 1−2 graphene layers, to reach specific capacities up to 80 μFcm<SUP>−2</SUP>, while much higher (394 μFcm<SUP>−2</SUP>) specific capacities are observed multilayer reduced graphene oxide electrodes. The performances of devices with pristine as well as thicker graphene-based structures are examined using a combination of experiments and model calculations. The demonstrated all solid-state supercapacitors provide a prototype for a broad range of thin-film based energy storage devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-4/nl200225j/production/images/medium/nl-2011-00225j_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl200225j'>ACS Electronic Supporting Info</A></P>