Recent progress with tailored growth and post-process sorting enables carbon nanotube (CNT) assemblies with predominantly metallic or semi-conducting concentrations. Cryogenic and microwave measurements performed here show transport dimensionality and overall order increasing with increasing metallic concentration, even in atmospheric doping conditions. By 120 GHz, the conductivity of predominantly semi-conducting assemblies grew to 400% its DC value at an increasing growth rate, while other concentrations a growth rate that tapered off. A generalized Drude model fits to the different frequency dependent behaviors and yields useful quality control parameters such as plasma frequency, mean free path, and degree of localization. As one of the first demonstrations of waveguides fabricated from this material, sorted CNTs from both as-made and post-process sources were inserted into sections of practical micro-strip. With both sources, sorted CNT micro-strip increasingly outperformed the unsorted with increasing frequency-- illustrating that sorted CNT assemblies will be important for high frequency applications.
Conventional metal wires suffer from a significant degradation or complete failure in their electrical performance, when subjected to harsh oxidizing environments, however wires constructed from Carbon Nanotubes (CNTs) have been found to actually improve in their electrical performance when subjected to these environments. These opposing reactions may provide new and interesting applications for CNT wires. Yet, before attempting to move to any real-world harsh environment applications, for the CNT wires, it is essential that this area of their operation be thoroughly examined. To investigate this, CNT wires were treated with multiple combinations of the strongest acids and halogens. The wires were then subjected to conductivity measurements, current carrying capacity tests, as well as Raman, microscopy and thermogravimetric analysis to enable the identification of both the limits of oxidative conductivity boosting and the onset of physical damage to the wires. These experiments have led to two main conclusions. Firstly, that CNT wires may operate effectively in harsh oxidizing environments where metal wires would easily fail and secondly, that the highest conductivity increase of the CNT wires can be achieved through a process of annealing, acetone and HCl purification followed by either H2O2 and HClO4 or Br2 treatment.
1 January 2013 in Journal of Advanced Oxidation Technologies
Recently, many different plasma sources are being investigated for exhaust gases treatment, odor abatement, VOC removal, soil conditioning, surface decontamination or tissue disinfection and sterilization. Among many different plasma reactors investigated in laboratories, gliding arc discharges (GAD), dielectric barrier discharges (DBD), pulsed discharges (PD), atmospheric pressure glow discharges (APGD) and atmospheric pressure plasma jets (APPJ) seem to be the most promising for high pressure low temperature applications. They can be designed as multi-electrodes’ high power system that can be used in environment protection processes, like decontamination of large surfaces and treatment of large volume of polluted gases, as well as small size and low power devices for biomedical applications, like plasma healing, disinfection and sterilization. Paper presents review of power supply systems for cold plasma reactors. Dielectric Barrier Discharge (DBD), Gliding Arc Discharge (GAD) and atmospheric pressure plasma jet (APPJ) reactors with their supply systems have been discussed from the point view of their characteristics, possibility to control power to the discharge and efficiency. Taking into account the plasma reactor characteristics and nature (nonlinear resistive and/or capacitive) different solutions of power suppliers have been presented: transformer type, AC/DC/AC inverter, RF-frequency system and frequency resonant inverter.