Advanced microwave-assisted production of hybrid electrodes for energy applications

Carbon nanotubes are one of the most prominent materials in research for creating electrodes for portable electronics. When coupled with metallic nanoparticles the performance of carbon nanotube electrodes can be dramatically improved. Microwave reduction is an extremely rapid method for producing carbon nanotube-metallic nanoparticle composites, however, this technique has so far been limited to carbon nanotube soot. An understanding of the microwave process and the interactions of metallic nanoparticles with carbon nanotubes have allowed us to extend this promising functionalisation route to pre-formed CNT electrode architectures. Nanoparticle reduction onto pre-formed architectures reduces metallic nanoparticle waste as particles are not formed where there is insufficient porosity for electrochemical processes. A two-fold increase in capacitive response, stable over 500 cycles, was observed for these composites, with a maximum capacitance of 300 F g−1 observed for a carbon Nanoweb electrode.

Monitoring and analysis of respiratory patterns using microwave doppler radar

 Noncontact detection characteristic of Doppler radar provides an unobtrusive means of respiration detection and monitoring. This avoids additional preparations, such as physical sensor attachment or special clothing, which can be useful for certain healthcare applications. Furthermore, robustness of Doppler radar against environmental factors, such as light, ambient temperature, interference from other signals occupying the same bandwidth, fading effects, reduce environmental constraints and strengthens the possibility of employing Doppler radar in long-term respiration detection, and monitoring applications such as sleep studies. This paper presents an evaluation in the of use of microwave Doppler radar for capturing different dynamics of breathing patterns in addition to the respiration rate. Although finding the respiration rate is essential, identifying abnormal breathing patterns in real-time could be used to gain further insights into respiratory disorders and refine diagnostic procedures. Several known breathing disorders were professionally role played and captured in a real-time laboratory environment using a noncontact Doppler radar to evaluate the feasibility of this noncontact form of measurement in capturing breathing patterns under different conditions associated with certain breathing disorders. In addition to that, inhalation and exhalation flow patterns under different breathing scenarios were investigated to further support the feasibility of Doppler radar to accurately estimate the tidal volume. The results obtained for both experiments were compared with the gold standard measurement schemes, such as respiration belt and spirometry readings, yielding significant correlations with the Doppler radar-based information. In summary, Doppler radar is highlighted as an alternative approach not only for determining respiration rates, but also for identifying breathing patterns and tidal volumes as a preferred nonwearable alternative to the conventional - ontact sensing methods.

The use of home experimentation kits for distance students in first-year undergraduate electronics

Laboratory and practical classes are an important part of the education of students in electronics and electrical engineering. "Hands-on" experience is critical for any engineer working in these fields in particular. For many years, delivering engineering practicals to distance-education students has been a tremendous challenge for universities. For a number of years now, students enrolled in the common first-year electronics course by distance mode at Deakin University have received a home experimentation kit. Using the kit and a laboratory manual, students are required to complete a number of experiments based on components included in the kit. The kit supports a full range of practical activities for digital electronics, and a more limited range of activities for analog electronics. With the kit, off campus students are supplied software for simulating AC electronic circuits, such as amplifiers and rectifiers. In this report we examine the past use of this kit and software,
review anecdotal student experiences with the package, and propose changes to it and to other curriculum resources, aiming to enhance the use of the kit by distance students. Key curriculum resources planned are a web-based 'companion' for the components in and the use of the kit, and two additions to the kit itself: a battery powered function generator, and a PC-based oscilloscope.

Conducting polymer coated fabrics for potential applications in microwave frequencies : a study of electromagnetic properties

The microwave reflection, transmission and complex permittivity of paratoluene-2-sulfonic acid doped conducting polypyrrole (PPy/pTSA) coated Nylon-Lycra textiles in the 1-18 GHz frequency were investigated. The real part of permittivity increased with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity showed a frequency dependent change throughout the tested range. All the samples had higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeded 80% for the highly pTSA doped samples coated for 3 hours.

Characterization of conducting polymer coated fabrics at microwave frequencies

Purpose – The purpose of this paper is to investigate microwave reflection, transmission, and complex permittivity of p-toluene-2-sulfonic acid doped conducting polypyrrole coated nylon-lycra textiles in the 1-18?GHz frequency with a view to potential applications in the interaction of electromagnetic radiation with such coated fabrics.

Design/methodology/approach – The chemical polymerization of pyrrole is achieved by an oxidant, ferric chloride and doped with p-toluene sulfonic acid (pTSA) to enhance the conductivity and improve stability. Permittivity of the conducting textile substrates is performed using a free space transmission method accompanied by a mathematical diffraction reduction method.

Findings – The real part of permittivity increases with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity shows a frequency dependent change throughout the test range. All the samples have higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeds 80 percent for the highly pTSA doped samples coated for 3?h.

Originality/value – A non-contact, non-destructive free space method thin flexible specimens to be tested with high accuracy across large frequency range. The non-destructive nature of the experiments enables investigation of the stability of the microwave transmission, reflection, absorption and complex permittivity values. Moreover, mathematical removal of the diffraction enables higher accuracy.

The influence of polymerization time and dopant concentration on the absorption of microwave radiation in conducting polypyrrole coated textiles

Temperature changes in conducting polypyrrole/para-toluene-2-sulphonic acid (PPy/pTSA) coated nylon textiles due to microwave absorption in the 8–9 GHz and 15–16 GHz frequency ranges were obtained by a thermography station during simultaneous irradiation of the samples. The temperature values are compared and related to the amounts of reflection, transmission and absorption obtained with a non-contact free space transmission technique, indicating a relationship between microwave absorption and temperature increase. Non-conductive samples showed no temperature increase upon irradiation irrespective of frequency range. The maximum temperature difference of around 4 °C in the conducting fabrics relative to ambient temperature was observed in samples having 48% absorption and 26.5 ± 4% reflection. Samples polymerized for 60 or 120 min with a dopant concentration of 0.018 mol/l or polymerized for 180 min with a dopant concentration of 0.009 mol/l yielded optimum absorption levels. As the surface resistivity decreased and the reflection levels increased, the temperature increase upon irradiation reduced.

A new H.E.L.P kit for teaching practical AC electronics to undergraduate distance students

An important part of educating students in electronics and electrical engineering is laboratory practicals. Providing effective practical experience to students by distance education has always been a significant challenge to the engineering educator. Deakin University has for many years taught practicals in basic digital electronics to off-campus students by means of a kit. The same students have performed related exercises in analogue electronics, which require generating and measuring AC signals, by means of either software simulations or on-campus attendance at lab classes. This year, for the first time, off-campus students are being provided with a new kit, which contains a low-cost, battery-powered AC signal generator, and an interface that allows a PC to be used as an oscilloscope. This kit allows the off-campus student further flexibility in learning basic electronics.

Characteristcs of conducting textiles in the microwave frequency range

This investigation of textiles coated with a polymer that conducts electricity showed that they can be used for effectively reflecting and absorbing microwaves. These conducting textiles are an economical, flexible and lightweight alternative to traditional materials for electromagnetic interference shielding of, for instance, sensitive electronic equipment.

Investigation into and control of microwave induced thermal run-away

Analyses the mechanisms that cause thermal run-away in some materials. A control strategy was devised to provide effective temperature control independent of material characteristics. The set of control criteria derived from mathematical models allowed the control limits of a microwave processing system to calculated.

Microwave dielectric properties of PTFE/rutile nanocomposites

The effects of nano-size rutile filler on the microwave dielectric properties of PTFE composites were investigated and the results were compared with that of micron size rutile filled composites. Nano-size rutile powder was prepared through sol–gel route and the filled PTFE composites were fabricated through SMECH process. Different characterization techniques such as powder X-ray diffraction, SEM, BET, TEM and TG/DSC were employed to analyze the nature of ceramic filler. The dielectric properties of filled composites were evaluated at microwave frequency region using waveguide cavity perturbation technique. Different theoretical models have been employed to predict the variation of dielectric constant with respect to filler loading. The moisture absorption characteristics of nano-rutile filled PTFE composites were measured as per IPC-TM-650 2.6.2 standards. Composites show high dielectric constant at X-band frequency region with relatively high loss tangent compared to micron size counterpart.

Microwave-accelerated 1,3-dipolar cycloaddition for the formation of fused [n]polynorbornanes

Microwave irradiation induces the 1,3-dipolar cycloaddition of cyclobutane epoxides with norbornenes to afford [n]polynorbornane scaffolds. Greatly enhanced reaction rates and significantly reduced levels of decomposition were observed.

Preparation, characterization and dielectric properties of temperature stable SrTiO3/PEEK composites for microwave substrate applications

Poly(ether ether ketone) (PEEK) is a potential candidate for electronic applications due to its low permittivity, low loss, high melting point, better chemical resistance, excellent insulating properties and easy processibility. Present paper discusses the preparation and characterization of SrTiO3 filled PEEK composite for microwave substrate applications. The dielectric constant, dielectric loss and temperature variation of dielectric constant of the composites have been studied up to 1 MHz using an Impedance Analyzer. Different theoretical approaches have been employed to predict the effective permittivity of composite systems and the results are compared with that of the experimental data. The crystallinity of the bulk composite is studied by X-ray diffraction studies. Scanning electron microscopic technique has been employed to study the dispersion of the particulate filler in PEEK matrix. Vickers hardness of pure and filled PEEK composite has been measured using Microhardness Tester. The effect of particle size on the dielectric as well as mechanical properties of SrTiO3/PEEK composite system is also studied by incorporating micronsize and nanosize fillers. Present study shows that a temperature stable composite can be realized by judiciously selecting appropriate filler concentration in the PEEK matrix.