https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

Nanotechnology is being used to enhance conventional ceramic and polymeric water treatment membrane materials through various avenues. Among the numerous concepts proposed, the most promising to date include zeolitic and catalytic nanoparticle coated ceramic membranes, hybrid inorganic–organic nanocomposite membranes, and bio-inspired membranes such as hybrid protein–polymer biomimetic membranes, aligned nanotube membranes, and isoporous block copolymer membranes. A semi-quantitative ranking system was proposed considering projected performance enhancement (over state-of-the-art analogs) and state of commercial readiness. Performance enhancement was based on water permeability, solute selectivity, and operational robustness, while commercial readiness was based on known or anticipated material costs, scalability (for large scale water treatment applications), and compatibility with existing manufacturing infrastructure. Overall, bio-inspired membranes are farthest from commercial reality, but offer the most promise for performance enhancements; however, nanocomposite membranes offering significant performance enhancements are already commercially available. Zeolitic and catalytic membranes appear reasonably far from commercial reality and offer small to moderate performance enhancements. The ranking of each membrane nanotechnology is discussed along with the key commercialization hurdles for each membrane nanotechnology.

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A review of water treatment membrane nanotechnologies

▪ Abstract This account reviews the discovery, synthesis, properties, and the latest research advances of carbon nanotubes developed over the past 12 years. Because of their remarkable electronic and mechanical properties, carbon nanotubes are unique and exciting. The field has been developed rapidly, and the number of publications per year is increasing almost exponentially. Various technological applications are likely to arise using nanotubes for fabrication of flat panel displays, gas storage devices, toxic gas sensors, Li+ batteries, robust and lightweight composites, conducting paints, electronic nanodevices, etc. Further experimental and theoretical research is still necessary so that novel technologies will become a reality in the early twenty-first century.

Science and Technology of the Twenty-First Century: Synthesis, Properties, and Applications of Carbon Nanotubes

[*] Dr. J.-Y. Choi, H.-J. Shin, S.-M. Yoon Display Device and Processing Laboratory Samsung Advanced Institute of Technology PO Box 111, Suwon 440-600 (Republic of Korea) E-mail: jaeyoung88.choi@samsung.com Prof. Y. H. Lee, S. J. Chae, F. Gunes, Dr. K. K. Kim, E. S. Kim, G. H. Han, S. M. Kim, H.-J. Shin BK21 Physics Division Sungkyunkwan Advanced Institute of Nanotechnology Center for Nanotubes and Nanostructured Composites Sungkyunkwan University Suwon 440-746 (Republic of Korea) E-mail: leeyoung@skku.edu M. H. Park, Prof. C. W. Yang Department of Advanced Materials Engineering Sungkyunkwan University Suwon 440-746 (Republic of Korea)

Synthesis of Large‐Area Graphene Layers on Poly‐Nickel Substrate by Chemical Vapor Deposition: Wrinkle Formation

Recent research and development has been incredibly successful at advancing the capabilities for vacuum electronic device (VED) sources of powerful terahertz (THz) and near-THz coherent radiation, both CW or average and pulsed. Currently, the VED source portfolio covers over 12 orders of magnitude in power (mW-to-GW) and two orders of magnitude in frequency (from ; 10 THz). Further advances are still possible and anticipated. They will be enabled by improved understanding of fundamental beam-wave interactions, electromagnetic mode competition and mode control, along with research and development of new materials, fabrication methods, cathodes, electron beam alignment and focusing, magnet technologies, THz metrology and advanced, broadband output radiation coupling techniques.

Vacuum Electronic High Power Terahertz Sources

Vertically aligned carbon nanotubes were synthesized on Ni-deposited Si substrates using microwave plasma-enhanced chemical vapor deposition. The grain size of Ni thin films varied with the rf power density during the rf magnetron sputtering process. We found that the diameter, growth rate, and density of carbon nanotubes could be controlled systematically by the grain size of Ni thin films. With decreasing the grain size of Ni thin films, the diameter of the nanotubes decreased, whereas the growth rate and density increased. High-resolution transmission electron microscope images clearly demonstrated synthesized nanotubes to be multiwalled.

Controlling the diameter, growth rate, and density of vertically aligned carbon nanotubes synthesized by microwave plasma-enhanced chemical vapor deposition

A novel slow-wave vacuum electron device circuit, consisting of a half-period-staggered double-vane array and a high-aspect ratio sheet electron beam, has been conceived for a high-power wideband submillimeter-wave generation. A particle-in-cell simulation, which is based on a finite-difference time-domain algorithm, has shown that this circuit has a very wide intrinsic bandwidth (in excess of 50 GHz around the operating frequency of 220 GHz) with a moderate gain of 13 dB/cm. Moreover, the saturated conversion efficiency is predicted to be 3%-5.5% over the operating band corresponding to an output power of 150-275 W, assuming a beam power of 5 kW. Of particular importance, this structure is based on the TE-fundamental mode interaction, thereby avoiding the complex over moding instabilities that usually cause spurious signal oscillation in conventional high-aspect-ratio structures. This planar circuit has simple 2-D geometry that is thermally and mechanically robust as well as being compatible with conventional microfabrication techniques. This concept is expected to open numerous opportunities in potential applications of versatile electronic devices in the low-millimeter- and submillimeter-wave regions.

Phase-Shifted Traveling-Wave-Tube Circuit for Ultrawideband High-Power Submillimeter-Wave Generation

Aligned carbon nanotubes were synthesized on Ni-coated Si substrates using microwave plasma-enhanced chemical vapor deposition. The surface morphology of Ni thin films was varied with the rf power density during the rf magnetron sputtering process. It was found that the growth of carbon nanotubes was strongly influenced by the surface morphology of Ni thin film. Pure carbon nanotubes were synthesized on Ni thin film with uniformly distributed grain sizes, whereas large amounts of carbonaceous particles were produced in addition to the nanotubes, when the nanotubes were grown on Ni thin film with widely distributed grain sizes. With decreasing Ni-grain size, the diameter of nanotubes decreased and the length increased. High-resolution transmission electron microscope images clearly demonstrated the nanotubes to be multiwalled, and the graphitized structures were confirmed from the Raman spectra. Efficient field emission was observed from the diode structure with the nanotube tips.

Effect of surface morphology of Ni thin film on the growth of aligned carbon nanotubes by microwave plasma-enhanced chemical vapor deposition

We report efficient wideband amplification of terahertz frequency electromagnetic waves from sequential electron-plasmon coupling along a half-period staggered double grating structure. Numerical eigenmode calculations show that the fundamental plasmonic band has a strong symmetric TE-mode, with a significant longitudinal electric field component, that is confined to the electron beam channel. A particle-in-cell simulation analysis with a single frequency excitation, combined with a short pulse broad spectrum drive, confirms that this terahertz plasmonic circuit produces three or four orders of magnitude power amplification with up to 30% bandwidth and 3%–5.5% saturated energy conversion efficiency.

Intense wideband terahertz amplification using phase shifted periodic electron-plasmon coupling

The 0.22 THz vacuum electronic circuits fabricated by UV lithography molding and deep reactive ion etching processes are under investigation for submillimeter wave applications. Eigenmode transient simulations show that, accounting for realistic values of our currently achievable fabrication tolerances, the transmission, and dispersion properties of the operation modes of a TE-mode, staggered, double grating circuit are maintained within less than 1 dB and 2% deviation, respectively. Scanning electron microscopy and atomic force microscopy analyses of the fabricated circuit samples demonstrate that both of the microelectromechanical system fabrication approaches produce circuits with ±3–5 μm dimensional tolerance and ∼30 nm surface roughness.

Young-Min Shin

Papers

Controlling the diameter, growth rate, and density of vertically aligned carbon nanotubes synthesized by microwave plasma-enhanced chemical vapor deposition

Phase-Shifted Traveling-Wave-Tube Circuit for Ultrawideband High-Power Submillimeter-Wave Generation

Effect of surface morphology of Ni thin film on the growth of aligned carbon nanotubes by microwave plasma-enhanced chemical vapor deposition

Intense wideband terahertz amplification using phase shifted periodic electron-plasmon coupling

Terahertz vacuum electronic circuits fabricated by UV lithographic molding and deep reactive ion etching