Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

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Carbon Nanotubes: Present and Future Commercial Applications

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.

Dispersion and functionalization of carbon nanotubes for polymer-based nanocomposites: a review

Tissue engineering aims at developing functional substitutes for damaged tissues and organs. Before transplantation, cells are generally seeded on biomaterial scaffolds that recapitulate the extracellular matrix and provide cells with information that is important for tissue development. Here we review the nanocomposite nature of the extracellular matrix, describe the design considerations for different tissues and discuss the impact of nanostructures on the properties of scaffolds and their uses in monitoring the behaviour of engineered tissues. We also examine the different nanodevices used to trigger certain processes for tissue development, and offer our view on the principal challenges and prospects of applying nanotechnology in tissue engineering.

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Nanotechnological strategies for engineering complex tissues.

Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials.

Ultralight and Highly Compressible Graphene Aerogels

Sandwich structures are the ideal materials to use for many engineering applications since they are lightweight, strong, and stiff. While sandwich structures are mechanically advanced, their acoustic properties are not ideal since they are excellent sound radiators. Therefore by studying their wave number characteristics, the acoustic properties of sandwich structures can be improved to help mitigate noise propagation. This study used several different combinations of carbon fiber‐epoxy, glass fiber‐epoxy, and aluminum face sheets with honeycomb and Rohacell foam core materials. These beams were vibrated with an electro‐dynamic shaker, while the vibration response was measured at numerous equidistant points along the beam with a micro‐accelerometer. Results showed the frequency response functions, which were transformed to the wave number/frequency domain yielding dispersion plots. From this plot one can calculate the coincidence frequency of the sandwich structure, which determines how and when the structure will radiate noise. Experimental results showed that thin aluminum face sheets with Rohcell 51 WF foam core had the greatest noise mitigation properties with a coincidence frequency of approximately 4500 Hz. Furthermore, it is shown that the experimental wave speed values agree with analytical methods. [Work supported by The Boeing Company.]

Noise mitigation and wave number characterization in sandwich structures.

Although polyetherimide (PEI) has attracted attention owing to its good dielectric properties, superior mechanical properties, and thermal/chemical stabilities, there is still a lack of methodology to fabricate PEI films in desired shapes directly on devices. In this study, a dispenser printing method to fabricate sophisticated 2D PEI structures is introduced. As dispenser printing is a solution-based process, PEI ink is prepared by dissolving PEI in N-methyl pyrrolidone (NMP). The printing conditions are controlled by optimizing the pneumatic pressure and viscosity of the inks with various ratios of PEI and NMP, followed by a two-step heat treatment to develop fine PEI films. The dielectric constant of the PEI film increases from 2.28 to 2.61 with the corresponding secondary heating time of 1–5 h, which is much lower than the theoretical value owing to the free volume and loosely entangled polymer chains generated from the shear forces in printing and solvent evaporation. Furthermore, the film exhibits anisotropic mechanical properties in different printing directions, stemming from the alignment effect of the polymer molecules. It is believed that the developed PEI films and the facile methodology can be diversely tuned to provide new insights into material utilization, further extending the application fields. 

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐printed Polyetherimide Films using Two‐step Thermal Treatment

Structural components subjected to cyclic stress can succumb to fatigue and fail at stress levels much lower than what is expected under static loading conditions. Such fatigue behavior in nanotube structures has never been reported, albeit its importance in practical devices incorporating nanotube components. In particular, cyclic compression loaded vertically aligned nanotube structures could find various applications as electro-mechanical systems. Here, this work reports the mechanical response from repeated high compressive strains on freestanding, long, vertically aligned multiwalled carbon nanotube membranes and show that the arrays of nanotubes under compression behave very similar to soft tissue and exhibit viscoelastic behavior. Under compressive cyclic loading, the mechanical response of nanotube blocks shows initial preconditioning, hysteresis characteristic of viscoeleastic materials, nonlinear elasticity, stress relaxation, and large deformations. Furthermore, no fatigue failure is observed even at high strain amplitudes up to half million cycles. The outstanding fatigue life and extraordinary soft tissue-like mechanical behavior suggest that properly engineered carbon nanotube structures could mimic artificial muscles, and their added high electrical and thermal conductivity could make excellent candidates for uses as compliant electrical contact brushes, probe cards and electromechanical systems.Copyright © 2007 by ASME

Visco-Elastic Properties of Aligned Multi-Walled Carbon Nanotube Blocks

http://irep.iium.edu.my/100943/2/100943_Characterization%20of%20dioxane-based_SCOPUS.pdf

Characterization of dioxane-based and soda-based extraction of lignin from oil palm empty fruit bunches as reinforcement in polylactic acid bio-composite

This study involves the investigation of spherically shaped filler diameter and interphase effects on the Young's modulus
of micro and nano size silicon dioxide (SiO 2 ) particle reinforced epoxy composite materials. Specifically, 10μm and
80nm size SiO 2 particles and Epon 862 epoxy are chosen as fillers and a matrix material, respectively. While 10μm and
80nm SiO 2 particles are dispersed in the epoxy through a direct shear mixing method, nano-composites are fabricated
with hardener at desirable ratios. Both micro- and nano-composites are prepared at 2 different particle loading fractions
for tensile testing. It is observed that the nano-composites show significant increase in Young's modulus over micro-composites,
showing a linear increase as particle volume fraction increases. This could indicate that for nano-composites,
the interphase region between the particle and matrix can considerably affect their mechanical properties. Here, we
develop a finite element analysis (FEA) model to investigate the interphase effect on the Young's modulus of both
micro- and nano-composites. This model demonstrates how to estimate the effective volume fraction of a particle as
filler using a combined experimental/numerical approach. The effective volume fraction is shown to be important in
predicting the mechanical response of nano-scale particles reinforced composite materials.

Jonghwan Suhr

Papers

Noise mitigation and wave number characterization in sandwich structures.

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐printed Polyetherimide Films using Two‐step Thermal Treatment

Visco-Elastic Properties of Aligned Multi-Walled Carbon Nanotube Blocks

Characterization of dioxane-based and soda-based extraction of lignin from oil palm empty fruit bunches as reinforcement in polylactic acid bio-composite

Characterization of particle diameter and interphase effects on Young's modulus of SiO 2 /epoxy particulate composites