There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

/pdf/carbon-based-supercapacitors-produced-by-activation-of-1wqrpq3luo.pdf

Carbon-based Supercapacitors Produced by Activation of Graphene

Free-standing paper-like or foil-like materials are an integral part of our technological society. Their uses include protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, electronic or optoelectronic components, and molecular storage. Inorganic 'paper-like' materials based on nanoscale components such as exfoliated vermiculite or mica platelets have been intensively studied and commercialized as protective coatings, high-temperature binders, dielectric barriers and gas-impermeable membranes. Carbon-based flexible graphite foils composed of stacked platelets of expanded graphite have long been used in packing and gasketing applications because of their chemical resistivity against most media, superior sealability over a wide temperature range, and impermeability to fluids. The discovery of carbon nanotubes brought about bucky paper, which displays excellent mechanical and electrical properties that make it potentially suitable for fuel cell and structural composite applications. Here we report the preparation and characterization of graphene oxide paper, a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets. This new material outperforms many other paper-like materials in stiffness and strength. Its combination of macroscopic flexibility and stiffness is a result of a unique interlocking-tile arrangement of the nanoscale graphene oxide sheets.

Preparation and Characterization of Graphene Oxide Paper

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

Crystallization and orientation studies in polypropylene/single wall carbon nanotube composite

Poly(vinyl alcohol) (PVA) composite films using poly(vinyl pyrrolidone) (PVP) and sodium dodecyl sulfate (SDS)-covered, well dispersed single wall carbon nanotubes (SWNT) exhibit significant improvement in tensile strength and modulus as compared to the control PVA and PVA/ PVP/SDS films. The evidence of load transfer to the nanotubes in the composite film has been obtained from the shift in the Raman SWNT D* band peak position.

Poly(vinyl alcohol)/SWNT Composite Film

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Polyacrylonitrile Single‐Walled Carbon Nanotube Composite Fibers

The use of carbon nanotubes for piezoresistive strain sensors has acquired significant attention due to its unique electromechanical properties. In this comprehensive review paper, we discussed some important aspects of carbon nanotubes for strain sensing at both the nanoscale and macroscale. Carbon nanotubes undergo changes in their band structures when subjected to mechanical deformations. This phenomenon makes them applicable for strain sensing applications. This paper signifies the type of carbon nanotubes best suitable for piezoresistive strain sensors. The electrical resistivities of carbon nanotube thin film increase linearly with strain, making it an ideal material for a piezoresistive strain sensor. Carbon nanotube composite films, which are usually fabricated by mixing small amounts of single-walled or multiwalled carbon nanotubes with selected polymers, have shown promising characteristics of piezoresistive strain sensors. Studies also show that carbon nanotubes display a stable and predictable voltage response as a function of temperature.

/pdf/a-review-carbon-nanotube-based-piezoresistive-strain-sensors-tulig9lhts.pdf

A Review: Carbon Nanotube-Based Piezoresistive Strain Sensors

Single wall carbon nanotube films (bucky paper) have been prepared using aqueous dispersions containing 0, 3, 6, and 10 M nitric acid. With increasing nitric acid concentration, film tensile strength increased from 10 to 74 MPa, tensile modulus from 0.8 to 5.0 GPa, while in-plane dc electrical conductivity decreased from 3 × 104 S/m to 1.2 × 104 S/m. In-plane storage modulus exhibited no decrease in the measured temperature range (room temperature to 200 °C). Raman spectroscopy showed that nitric acid treatment results in the loss of the small diameter tubes. This was consistent with the X-ray diffraction observation, which showed that with increasing nitric acid concentration, (10) and (11) SWNT d spacings increased from 1.23 to 1.29 nm and from 0.74 to 0.87 nm, respectively. Morphological changes in the film have been monitored using scanning electron microscopy.

Tao Liu

Papers

Crystallization and orientation studies in polypropylene/single wall carbon nanotube composite

Poly(vinyl alcohol)/SWNT Composite Film

Polyacrylonitrile Single‐Walled Carbon Nanotube Composite Fibers

A Review: Carbon Nanotube-Based Piezoresistive Strain Sensors

Properties and Structure of Nitric Acid Oxidized Single Wall Carbon Nanotube Films