This paper presents the fabrication, modeling and testing of a metamaterial based passive wireless temperature sensor consisting of an array of closed ring resonators (CRRs) embedded in a dielectric material matrix. A mixture of 70 vol% Boron Nitride (BN) and 30 vol% Barium Titanate (BTO) is used as the dielectric matrix and copper washers are used as CRRs. Conventional powder compression is used for the sensor fabrication. The feasibility of wireless temperature sensing is demonstrated up to 200 C. The resonance frequency of the sensor decreases from 11.93 GHz at room temperature to 11.85 GHz at 200 C, providing a sensitivity of 0.462 MHz/C. The repeatability of temperature sensing tests was carried out to quantify the repeatability. The highest standard deviation observed was 0.012 GHz at 200 C.
Energy harvesting has been gaining significant interest as a potential solution for energizing next generation sensor and energy storage devices. The most widely investigated material for piezoelectric and pyro-electric energy harvesting to date is PZT (Lead Zirconate Titanate), owing to its good piezoelectric and pyro-electric properties. However, Lead is detrimental to human health and to the environment. Hence, alternative materials are required to be investigated for this purpose. In this paper, a lead free material Lithium Niobate (LNB) is reported as a potential material for pyro-electric energy harvesting. Although, it has lower pyro-electric properties than PZT, it has better properties than other lead free alternatives of PZT such as ZnO. In addition, LNB has a high curie point of 1142 °C, which makes it suitable for high temperature environment where other pyro-electric materials are not suitable. Therefore, a single crystal LNB has been investigated as a source of energy harvesting under alternative heating and cooling environment. A commercial 0.2 F super-capacitor was used as the energy storage device.
Development of new materials hold the key to the fundamental progress in energy storage systems such as Li-ion battery, which is widely used in modern technologies because of their high energy density and extended cycle life. Among these materials, porous carbon is of particular interest because it provides high lithiation and excellent cycling capability by shortening the transport length for Li<sup>+</sup> ions with large electrode/electrolyte interface. It has also been demonstrated that transition metal oxide nanoparticle can enhance surface electrochemical reactivity and increase the capacity retention capability for higher number of cycles. Here we investigate porous carbon/ceria (CeO<sub>2</sub>) nanoparticles composites as an anode material. The high redox potential of ceria is expected to provide a higher potential window as well as increase the specific capacity and energy density of the system. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) is used for material characterization, while battery analyzer is used for measuring the electrochemical performance of the battery.
Increasing demand for energy storage devices has propelled researchers for developing efficient super-capacitors (SC) with long cycle life and ultrahigh energy density. Carbon-based materials are commonly used as electrode materials for SC. Herein we report a new approach to improve the SC performance utilizing porous carbon /Cerium oxide nanoparticle (PC-CON) hybrid as electrode material synthesized via low temperature hydrothermal method and tetraethyl ammonium tetrafluroborate in acetonitrile as organic electrolyte. Through this approach, charges can be stored not only via electrochemical double layer capacitance (EDLC) from PC but also through pseudo-capacitive effect from CeO<sub>2</sub> NPs. The excellent electrode-electrolyte interaction due to the electrochemical properties of the ionic electrolyte provides a better voltage window for the SC. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD) measurements were used for the initial characterization of this PC/CeO<sub>2</sub> NPs hybrid material system. Electrochemical measurements of SCs was performed using a potentio-galvanostat. It is found that the specific capacitance was improved by 30% using PC-CON system compared with pristine PC system.
Electrochemical super-capacitors have become one of the most important topics in both academia and industry as novel energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been an increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles and portable electronics. These multifunctional structural super-capacitors provide lighter structures combining energy storage and load bearing functionalities. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area and fast ion diffusion rates. Scanning Electron Microscopy (SEM) and XRay Diffraction (XRD) measurements were used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing has been performed using a potentio-galvanostat. The results show that gold sputtered nanowire hybrid carbon fiber provides 65.9% better performance than bare carbon fiber cloth as super-capacitor.
Wireless passive temperature sensors are gaining increasing attention due to the ever-growing need of precise monitoring of temperature in high temperature energy conversion systems such as gas turbines and coal-based power plants. Unfortunately, the harsh environment such as high temperature and corrosive atmosphere present in these systems limits current solutions. In order to alleviate these issues, this paper presents the design, simulation, and manufacturing process of a low cost, passive, and wireless temperature sensor that can withstand high temperature and harsh environment. The temperature sensor was designed following the principle of metamaterials by utilizing Closed Ring Resonators (CRR) embedded in a dielectric matrix. The proposed wireless, passive temperature sensor behaves like an LC circuit that has a resonance frequency that depends on temperature. A full wave electromagnetic solver Ansys Ansoft HFSS was used to perform simulations to determine the optimum dimensions and geometry of the sensor unit. The sensor unit was prepared by conventional powder-binder compression method. Commercially available metal washers were used as CRR structures and Barium Titanate (BTO) was used as the dielectric materials. Response of the fabricated sensor at room temperature was analyzed using a pair of horn antenna connected with a network analyzer.
Lithium ion batteries (LIB) have been receiving extensive attention due to the high specific energy density for wide applications such as electronic vehicles, commercial mobile electronics, and military applications. In LIB, graphite
is the most commonly used anode material; however, lithium ion intercalation in graphite is limited, hindering the
battery charge rate and capacity. To overcome this obstacle, nanostructured anode assembly has been extensively
studied to increase the lithium ion diffusion rate. Among these approaches, high specific surface area metal oxide nanowires connecting nanostructured carbon materials accumulation have shown propitious results for enhanced lithium intercalation. Recently, nanowire/graphene hybrids were developed for the enhancement of LIB performance; however, almost all previous efforts employed nanowires on graphene in a random fashion, which
limited lithium ion diffusion rate. Therefore, we demonstrate a new approach by hydrothermally growing uniform
nanowires on graphene aerogel to further improve the performance. This nanowire/graphene aerogel hybrid not only uses the high surface area of the graphene aerogel but also increases the specific surface area for electrodeelectrolyte interaction. Therefore, this new nanowire/graphene aerogel hybrid anode material could enhance the
specific capacity and charge-discharge rate. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD)
are used for materials characterization. Battery Analyzer and Potentio-galvanostat are used for measuring the electrical performance of the battery. The testing results show that nanowire graphene hybrid anode gives significantly improved performance compared to graphene anode.