Jiesheng Wang

Room‐Temperature Tunneling Behavior of Boron Nitride Nanotubes Functionalized with Gold Quantum Dots

One-dimensional arrays of gold quantum dots (QDs) on insulating boron nitride nanotubes (BNNTs) can form conduction channels of tunneling field-effect transistors. We demonstrate that tunneling currents can be modulated at room temperature by tuning the lengths of QD-BNNTs and the gate potentials. Our discovery will inspire the creative use of nanostructured metals and insulators for future electronic devices.

Diameter-Dependent Bending Modulus of Individual Multiwall Boron Nitride Nanotubes

The mechanical properties of individual multiwall boron nitride nanotubes (MWBNNTs) synthesized by a growth-vapor-trapping chemical vapor deposition method are investigated by a three-point bending technique via atomic force microscopy. Multiple locations on suspended tubes are probed in order to determine the boundary conditions of the supported tube ends. The bending moduli (EB) calculated for 20 tubes with diameters ranging from 18 to 58 nm confirm the exceptional mechanical properties of MWBNNTs, with an average EB of 760 ± 30 GPa. For the first time, the bending moduli of MWBNNTs are observed to increase with decreasing diameter, ranging from 100 ± 20 GPa to as high as 1800 ± 300 GPa. This diameter dependence is evaluated by Timoshenko beam theory. The Youngs modulus and shear modulus were determined to be 1800 ± 300 and 7 ± 1 GPa, respectively, for a trimmed data set of 16 tubes. The low shear modulus of MWBNNTs is the reason for the detected diameter-dependent bending modulus and is likely due to the presence of interwall shearing between the crystalline and faceted helical nanotube structures of MWBNNTs.

Multiwalled Boron Nitride Nanotubes: Growth, Properties, and Applications

This chapter provides a comprehensive review on the current research status of boron nitride nanotubes (BNNTs), especially the multiwalled nanostructures. Experimental and theoretical aspects of the properties, synthesis, and characterization of BNNTs, as well as their potential mechanical, electronic, chemical, and biological applications are compiled here.

Introduction to B–C–N Materials

B–C–N is an emerging material system consisting of novel nanostructures of boron (B), carbon (C), boron nitride (BN), carbon nitride (CN x ), boron-carbon nitride (B x C y N z ), and boron carbide (B x C y ). These B–C–N materials are sometimes called as frontier carbon materials, because of their flexibility in forming materials of various types of hybridizations similar to those in the pure carbon system. This chapter provides a concise introduction on all these materials. Readers are referred to various references and other chapters compiled in this book for further reading.

Controlled Growth of Carbon, Boron Nitride, and Zinc Oxide Nanotubes

Nanotubes represent a unique class of materials in which all atoms are located near the surface. Since electrons flowing through nanotubes are confined near the surface, nanotubes are attractive for sensing biological and chemical molecules. In addition, their tubular structures enable nanofluidic devices that are useful for novel sensing applications. In this paper, we will discuss current applications and the latest advancements on the growth of carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs), and ZnO nanotubes (ZnONTs). First, CNT growth is highly controlled by regulating the effective catalysts and the dissociative adsorption of the hydrocarbon molecules during chemical-vapor deposition growth. Second, we have achieved low temperature growth of vertically aligned BNNTs at 600 degC , the first success of growing pure BNNTs directly on substrates at temperatures about half of those reported so far. Finally, we have developed an original approach for growing ZnONTs without catalyst or template. Robust, controllable growth techniques for nanotubes are necessary in order to fully realize their sensing potential.

Growth of Carbon, Boron Nitride and ZnO Nanotubes for Biosensors

Summary It was shown that the progress in growing nanostructures affects our ability to use them for applications. In CNTs, growth is easy and controllable, leading to a wealth of study on biological applications. BNNTs, being similar to CNTs but more robust, are a promising material. Until recently, the difficulty of their growth has limited their use, but we have found easier, low-temperature growth methods that should help expand the scope of their application. Finally, ZnO materials are desired for their hydrophilic natures, their tubular structures and wide energy band gaps. These nanotubes can now be grown single-crystal by conventional thermal CVD methods, and, as continuing refinements of the growth techniques take place, they will find more and more use in biological applications. Acknowledgments This work is supported by Michigan Tech Research Excellent Funds, the US Department of Army (Grant No. W911NF-04-1-0029 through the City College of New York), National Science Foundation CAREER Award (Award number 0447555, Division of Materials Research), the U.S. Army Research Laboratory and the Defense Advanced Research Projects Agency (Contract number DAAD17-03-C-0115), and the Center for Nanophase Materials Science (CNMS) sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy, under Contract No. DE-AC05-00OR22725 with UT-Battelle, LLC.

Testing Multiwall Carbon Nanotubes on Ion Erosion for Advanced Space Propulsion

Are carbon nanotubes more resistant than diamonds against ion erosion? Here, we report an evaluation of multiwall carbon nanotubes (MWNTs) as the protective coating against plasma erosion in advanced space propulsion systems. We have compared polycrystalline diamond films with MWNTs, amorphous carbon (a-C) and boron nitride (BN) films. Two types of MWNTs were investigated including vertically aligned (VA) MWNTs, and those horizontally laid on the substrate surfaces. Only diamond films and VA-MWNTs survived erosion by 250 eV krypton ions of a flight-quality Hall-effect thruster. VA-MWNTs are found to bundle at their tips after ion erosion.

Induction annealing and subsequent quenching : effect on the thermoelectric properties of boron-doped nanographite ensembles.

Boron-doped nanographite ensembles (NGEs) are interesting thermoelectric nanomaterials for high temperature applications. Rapid induction annealing and quenching has been applied to boron-doped NGEs using a relatively low-cost, highly reliable, laboratory built furnace to show that substantial improvements in thermoelectric power factors can be achieved using this methodology. Details of the design and performance of this compact induction furnace as well as results of the thermoelectric measurements will be reported here.

Growth of Single Crystalline ZnO Nanotubes and Nanosquids

The growth of ZnO nanotubes and nanosquids is obtained by conventional thermal chemical vapor deposition (CVD) without the use of catalysts or templates. Characterization of these ZnO nanostructures was conducted by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and photoluminescence (PL). Results indicate that these ZnO nanostructures maintain the crystalline structures of the bulk wurtzite ZnO crystals. Our results show that rapid cooling can be used to induce the formation of ZnO nanotubes and ZnO nanosquids. The self-assembly of these novel ZnO nanostructures are guided by the theory of nucleation and the vapor-solid crystal growth mechanism.

Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates

For the first time, patterned growth of boron nitride nanotubes (BNNTs) on Si substrates has been achieved by catalytic chemical vapor deposition (CCVD). Following the boron oxide chemical pathway and our growth vapor trapping approach, high quality and quantity BNNTs can be produced. Effective catalysts have been found to facilitate the growth of BNNTs, while some critical parameters of the synthesis have also been identified to control the quality and density. The success of patterned growth of high quality BNNTs not only explains the roles of the effective catalysts during the synthesis process, but could also be of technologically important for future device fabrication.