Jihua Gou

Synergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymer composite

The present work studies the synergistic effect of carbon nanofiber (CNF) and carbon nanopaper on the shape recovery of shape memory polymer (SMP) composite. The combination of CNF and carbon nanopaper was used to improve the thermal and electrical conductivities of the SMP composite. The carbon nanopaper was coated on the surface of the SMP composite in order to achieve the actuation by electrical resistive heating. CNFs were blended with the SMP resin to improve the thermal conductivity to facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electroactive responses.

EXPERIMENTAL DESIGN AND OPTIMIZATION OF DISPERSION PROCESS FOR SINGLE-WALLED CARBON NANOTUBE BUCKY PAPER

This paper presents a new processing method to produce nanotube reinforced composites by using single-walled nanotube (SWNT) bucky paper as reinforcement. The SWNT bucky paper is an entangled mat of SWNTs, which is a highly porous mesh structure. To successfully produce SWNT bucky paper reinforced composites, it is essentially important to prepare a high-quality bucky paper. In this study, the quality of the bucky paper related to the dispersion of nanotubes within the bucky paper, which was quantitatively-characterized with rope size distribution and pore size distribution. An experimental study was conducted to investigate the effects of various process parameters on the dispersion of nanotubes using design of experiments (DOEs) approach. Based on the experimental analysis, the dispersion process of nanotubes within the bucky paper was optimized by selecting appropriate process parameters.

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

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.

Electrical properties and shape-memory behavior of self-assembled carbon nanofiber nanopaper incorporated with shape-memory polymer

The present paper studies the electrical and shape-memory behavior of self-assembled carbon nanofiber (CNF) nanopaper incorporated with shape-memory polymer (SMP). The morphology and structure of the self-assembled nanopapers were characterized with scanning electron microscopy (SEM). A continuous and compact network was observed from the SEM images, which indicates that the CNF nanopaper could have highly conductive properties. The electrical conductivity of the CNF nanopaper was measured by the four-point probe method and its temperature coefficient effect was studied. Finally, the actuation of SMP was demonstrated by the electrical resistive heating of the CNF nanopaper.

Damping augmentation of nanocomposites using carbon nanofiber paper

Vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the nanocomposites through integrating carbon nanofiber paper into traditional glass fiber reinforced composites. The carbon nanofiber paper had a porous structure with highly entangled carbon nanofibers and short glass fibers. In this study, the carbon nanofiber paper was employed as an interlayer and surface layer of composite laminates to enhance the damping properties. Experiments conducted using the nanocomposite beam indicated up to 200-700% increase of the damping ratios at higher frequencies. The scanning electron microscopy (SEM) characterization of the carbon nanofiber paper and the nanocomposites was also conducted to investigate the impregnation of carbon nanofiber paper by the resin during the VARTM process and the mechanics of damping augmentation. The study showed a complete penetration of the resin through the carbon nanofiber paper. The connectivities between carbon nanofibers and short glass fibers within the carbon nanofiber paper were responsible for the significant energy dissipation in the nanocomposites during the damping tests.

Nanopaper enabled shape-memory nanocomposite with vertically aligned nickel nanostrand: controlled synthesis and electrical actuation

The present work studies the synergistic effect of self-assembly multi-walled carbon nanotube (MWCNT) nanopaper and sub-micro nickel nanostrand on the electrical properties and electro-active recovery behavior of shape memory polymer (SMP) nanocomposite. The combination of MWCNT nanopaper and nickel nanostrand is used to improve the electrical and thermal conductivities of the SMP nanocomposite. The electrical MWCNT nanopaper was coated on the surface to achieve the shape recovery of the SMP nanocomposite induced by electricity. Electromagnetic nickel nanostrands were blended with and, vertically aligned into the SMP resin in a magnetic field, to improve the thermal conductivity. The vertically aligned nickel nanostrands will facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electrical actuation. Furthermore, they have little negative effect on recovery behavior, resulting in the nanocomposite having an approximately 100% recovery ratio undergoing cyclic deformation.

Gas-Induced Formation of Cu Nanoparticle as Catalyst for High-Purity Straight and Helical Carbon Nanofibers

The facile preparation of high-purity carbon nanofibers (CNFs) remains challenging due to the high complexity and low controllability in reaction. A novel approach using gas-induced formation of Cu crystals to control the growth of CNFs is developed in this study. By adjusting the atmospheric composition, controllable preparation of Cu nanoparticles (NPs) with specific size and shape is achieved, and they are further used as a catalyst for the growth of straight or helical CNFs with good selectivity and high yield. The preparation of Cu NPs and the formation of CNFs are completed by a one-step process. The inducing effect of N(2), Ar, H(2), and C(2)H(2) on the formation of Cu NPs is systematically investigated through a combined experimental and computational approach. The morphology of CNFs obtained under different conditions is rationalized in terms of Cu NP and CNF growth models. The results suggest that the shapes of CNFs, namely, straight or helical, depend closely on the size, shape, and facet activity of Cu NPs, while such a gas-inducing method offers a simple way to control the formation of Cu NPs.

Correlation of nitrogen related traps in InGaAsN with solar cell properties

The thermal annealing of nitrogen related traps in p-type InGaAsN and GaAsN is investigated by deep level transient spectroscopy (DLTS). Upon annealing, an apparent recovery of the photovoltaic properties correlates with changes in the DLTS data observed for InGaAsN and GaAsN diodes and solar cells, revealing that a nitrogen related E1 (EC−0.20eV) center has an important role in governing the solar cell performance. The large electron capture cross section (∼8.9×10−15cm2) of this center indicates that this defect may act as an efficient recombination center. Therefore, its complete removal by annealing or by some other process is essential for the high performance of GaInAsN solar cells. The internal quantum efficiency data were modeled to quantify the change in material properties associated with this improvement upon annealing. Annealed cells with indium impurity (InGaAsN) show a slightly higher photoresponse, which could be due to low scattering caused by In–N pair formation after annealing.

Mechanical behavior of nanostructured materials

This Special Issue presents recent research advances in various aspects of advanced nanomaterials including synthesis, micro- and nanostructures, mechanical properties, modeling, and applications for material nanotechnology community. In particular, it aims to reflect recent advances in mechanical behaviors, for example, stiffness, strength, ductility, fatigue, and wear resistance, of various nanomaterials including nanocrystalline, inorganic, nonmetallic nanomaterials, composites with nanosized fillers, and biomaterials with nanosized structures. The role of this Special Issue is to bridge the gaps among fabrication techniques, experimental techniques, numerical modeling, and applications for some new nanomaterials and to investigate some key issues related to the mechanical properties of the nanomaterials. It brings together researchers working at the frontier of the mechanical behavior of nanomaterials...

Synergistic effect of carbon nanofiber and sub-micro filamentary nickel nanostrand on the shape memory polymer nanocomposite

This work studies the synergistic effect of carbon nanofiber (CNF) and sub-micro filamentary nickel nanostrand on the thermal and electrical properties, as well as the electro-active shape memory behavior, of a shape memory polymer (SMP) nanocomposite. The combination of electrical CNF and electromagnetic nickel nanostrand is used to render insulating thermo-responsive SMPs conductive. Subsequently, the shape memory behavior of the SMP can be activated by the electrical resistive heating. It is shown that sub-micro filamentary nickel-coated nanostrands significantly improved the electrical conductivity to facilitate the actuation of the SMP nanocomposite despite the low nanostrand volume content and low electrical voltage. Also the CNFs are blended with the SMP resin to facilitate the dispersion of nanostrands and improve the thermal conductivity to accelerate the electro- and thermo-active responses.