Iosif D. Rosca

Carbon Nanotube Composites for Wideband Millimeter-Wave Antenna Applications

In this paper, we explore using carbon nanotube (CNT) composite material for wideband millimeter-wave antenna applications. An accurate electromagnetic model of the composite antenna is developed using Microwave Studio for numerical analysis. Good agreement between computed and measured results is shown for both copper and CNT antennas, and their performance is compared. The CNT antenna shows stable gain and radiation patterns over the 24 to 34 GHz frequency range. The dispersion characteristics of the CNT antenna show its suitability for wideband communication systems. Using a quarter-wave matched T-junction as feed network, a two-element CNT antenna array is realized and the performance is compared with a copper antenna. The housing effect on the performance of the CNT antenna is shown to be much lower than for the copper antenna.

Full-Composite Fractal Antenna Using Carbon Nanotubes for Multiband Wireless Applications

In this letter, single-wall carbon nanotube (CNT) composite materials are explored for the design of multiband antennas. An accurate electromagnetic (EM) model of the modified Sierpinski fractal composite antenna is developed using Microwave Studio for numerical analysis. For antenna fabrication, we printed CNT on both sides of a substrate and then cut out the desired antenna pattern using a high-precision milling machine. The CNT material was hardened by resin infiltration in order to be processed on the milling machine. The CNT antenna shows satisfactory gain and radiation patterns for UHF-RFID (900 MHz), Bluetooth (2.4 GHz), and WLAN (5.5 GHz) applications. Good agreement between computed and measured results is observed.

Reinforced Continuous Carbon-Fiber Composites Using Multi-Wall Carbon Nanotubes for Wideband Antenna Applications

We explore using reinforced continuous carbon fiber (RCCF) composite for wideband antennas in wireless applications. We use composite material as the radiating element for a wireless applications. An electromagnetic (EM) model of the composite antenna is developed using Microwave Studio for numerical analysis. An RCCF composite sample is prepared including up to 2% multiwall carbon nanotube (MWCNT) to enhance the conductivity. The anisotropic conductivity of the resulting material is determined by measurement using standard waveguide setups. The reflection coefficient, radiation pattern and gain of the composite antenna are investigated. The frequency- and time-domain dispersions are found for the composite antenna to show its suitability for ultrawideband (UWB) communication systems. It is observed that RCCF/MWCNT composite is an effectively alternative to metal for the antenna structure.

The effect of carbon nanotubes on epoxy matrix nanocomposites

The paper concerns thermal properties of epoxy/nanotubes composites for aircraft application. In this work, influence of carbon nanotubes on thermal stability, thermal conductivity, and crosslinking density of epoxy matrix was determined. Three kinds of nanotubes were used: non-modified with 1- and 1.5-μm length, and 1-μm length modified with amino groups. Scanning electron microscopy observations were done for examining dispersion of nanotubes in the epoxy matrix. Glass transition temperature (Tg) was readout from differential scanning calorimetry. From dynamic mechanical analysis, crosslinking density was calculated for epoxy and its composites. Also, thermogravimetric analysis was done to determine influence of nanotubes addition on thermal stability and decomposition process of composites. Activation energy was calculated from TGA curves by Flynn–Wall–Ozawa method. Thermal diffusivity was also measured. SEM images proved the uniform dispersion of carbon nanotubes without any agglomerates. It was found that nanotubes modified with amino groups lead to the increase of epoxy matrix crosslinking density. The significant increase in Tg was also observed. On the other hand, addition of carbon nanotubes leads to the decrease of thermal stability of polymer due to the increase of thermal diffusivity.

Multiwall Carbon Nanotube–Epoxy Composites With High Shielding Effectiveness for Aeronautic Applications

Using mass-produced multiwall carbon nanotubes (MWCNTs) from different providers, we have fabricated nanocomposites with high and nearly constant shielding effectiveness (SE) over a wide frequency range up to 26.5 GHz. The MWCNT weight fraction and sample thickness were lower than 10% and 2 mm, respectively. The fabrication process and percolation curves are described. A high dc conductivity of 239.1 S/m was achieved at an MWCNT loading of only 8% by weight. The effect of aspect ratio on shielding performance is addressed. By comparing the measured SE of the composite with predictions from a model of the measurement setup using Microwave Studio, the effective conductivity of the nanocomposite was determined. Since the thickness is very important for shielding analysis, the SE/unit thickness diagram was calculated by using the effective parameters of samples. The results were verified experimentally by measuring the SE of samples with different thicknesses.

Conductive carbon fiber composite materials for antenna and microwave applications

In this paper, the use of carbon fiber composite (CFC) materials is investigated for building antennas and microwave circuits, by replacing the metal with CFC. Two kinds of composite materials are investigated, namely reinforced continuous carbon-fiber (RCCF) composites and carbon nanotube (CNT) composites. We use RCCF composite to build ultra-wideband antennas. The effect of the anisotropic conductivity tensor of RCCF composite on the antenna performance is investigated. As one of the most highly-conductive composites, single wall carbon nanotube (SWCNT) buckypapers are used to build composite antennas. A new fabrication method is proposed to print arbitrarily-shaped full-composite SWCNT antenna on any type of substrate. Various types of SWCNT antennas are fabricated for different wireless antenna applications. Good agreement is demonstrated between simulated and measured performance for all these composite antennas.

Nonmetallic Dielectric Resonator Antenna Using Carbon Nanotube Composite Materials

In this letter, we present a nonmetallic antenna for wireless applications comprising a circular disk dielectric resonator (DR) on a duroid substrate, with carbon nanotube (CNT) composite material. The radiation characteristics of the proposed DR-CNT antenna such as impedance bandwidth and peak gain are studied both numerically and experimentally. The effect of the ohmic losses in the CNT composite on the antenna efficiency is investigated. The DR-CNT antenna has useful gain and radiation characteristics over the operating frequency band near the resonance of DR, and therefore the proposed antenna is a good candidate for wireless applications requiring a nonmetallic antenna.

Anisotropic carbon fiber nanocomposites for mechanically reconfigurable antenna applications

We demonstrate the potential use of reinforced continuous carbon fiber composite (RCCFC) material for building reconfigurable antennas. The frequency and polarization agility characteristics of the proposed antennas are obtained by the rotation of the antenna ground plane which is made of anisotropic conductive RCCFC material. The anisotropic RCCFC ground plane provides a mode filter mechanism in the proposed antennas. The mechanical and chemical strength of RCCFC materials along with the promising radiation characteristics of the RCCFC antennas make the proposed composite antenna very suitable for radio cognitive and military applications.

Carbon-fiber nanotubes for X-band conformal antenna applications

Metals are commonly used in antenna structures for the radiating element and the ground plane. However, the cost, fabrication procedure, weight or corrosion resistance can limit the usefulness of metal antennas. Some recent studies have used various composite materials as replacements for metals [1]-[3]. In [1], a conducting-polymer patch antenna is proposed. A conductive textile coated with carbon nanotubes (CNTs) and gold is used to fabricate a patch antenna in [2]. Inkjet printing is applied to fabricate high-conductive material antenna in [3]. Advanced carbon-fiber composite materials are being used in the aerospace industry as a good replacement for metals because of their outstanding mechanical properties. Carbon-fiber composites have lower electrical conductivity than metals, as so the shielding effectiveness is of concern for electromagnetic compatibility (EMC) applications. In [4], we investigated the carbon-fiber materials for the radiating element of an RFID antenna. It was observed that carbon-fiber composite can be efficiently used in such a resonant antenna. Very recently, we explored the use of reinforced carbon fiber composites for wideband applications [5]. Conformal antennas are extensively used in mobile and vehicular systems such as aircraft and automobiles [6]. Being compatible with inkjet printing technique, CNT is of much more interest for antenna fabrication among other kinds of composites. Recently, CNT patch antennas have been effectively used for conformal applications [7] in which using metals is not desirable.

MoonDust Lunar Dust Simulation and Mitigation

The feasibility of extended exploration and human presence on the Moon and Mars depends critically on dealing with various environmental factors, and especially on the effects of dust. One of the most restricting facets of lunar surface exploration, as experienced by the prior Apollo landed missions, is the fine lunar dust, its high adherence, and its restrictive friction-like action. Moreover, the lunar dust particle size distribution extends generally into the submicron range, where it could potentially have toxic effects on exposed astronauts through their respiratory system. MoonDust is a project being performed in collaboration with the Canadian Space Agency to study the effects of lunar dust on optics and mechanical elements, and to develop innovative nano-filtration solutions to extend their operational lifetime within a lunar and/or Mars environment. To assist this work, a small lunar environment simulation vacuum chamber is being developed at MPBC, to enable the study of lunar dust effects on optics elements and rotary mechanisms, at pressures brought down below 10 -5 Torr. The developed simulator includes an injection system for lunar dust simulants, an excimer UV laser-light source for vacuum UV (VUV), and various diagnostic ports for relevant optical and electrical measurements. The MoonDust innovative dust mitigation solution exploits key characteristics of the lunar dust while incorporating nano-filtration technologies based on carbon nanotubes (CNT) materials. The aim is to minimize the required consumables while providing high capacity and high efficiencies for the more dangerous submicron particles. This paper reports on the development of the lunar environmental chamber and the associated lunar dust simulator. Some of the preliminary trial experimental results for filters based on CNTs for optical devices and rotary mechanical joint protection are also presented.