The goals are to explore the world of Micro-Electro-Mechanical Systems (MEMS) by understanding its design and fabrication aspects ...
(IT-NEWSWIRE.COM, February 13, 2018 ) Nanoelectromechanical Systems-Global Market Status and Trend Report 2013-2023 offers a comprehensive analysis on Nanoelectromechanical Systems industry, standing on the readers perspective, delivering detailed market data and penetrating insights. No matter t
Nanoelectromechanical systems (NEMS) are a class of devices integrating electrical and mechanical functionality on the nanoscale. NEMS form the logical next miniaturization step from so-called microelectromechanical systems, or MEMS devices. NEMS typically integrate transistor-like nanoelectronics with mechanical actuators, pumps, or motors, and may thereby form physical, biological, and chemical sensors. The name derives from typical device dimensions in the nanometer range, leading to low mass, high mechanical resonance frequencies, potentially large quantum mechanical effects such as zero point motion, and a high surface-to-volume ratio useful for surface-based sensing mechanisms. Uses include accelerometers, or detectors of chemical substances in the air. As noted by Richard Feynman in his famous talk in 1959, Theres Plenty of Room at the Bottom, there are many potential applications of machines at smaller and smaller sizes; by building and controlling devices at smaller scales, all ...
A drive circuit for and method of driving a piezoelectric actuator utilizes an impedance coupled to the piezoelectric actuator, wherein the impedance and the piezoelectric actuator together form a tank circuit that has a resonant frequency. A first circuit is provided that drives the actuator at the resonant frequency and a second circuit is further provided that selectively operates the first circuit in one of at least two modes of operation including a first mode that causes the actuator to be energized at a first duty cycle and a second mode that causes the actuator to be energized at a second duty cycle.
Carbon nanotubes and graphene have many interesting properties. To exploit the properties in applications their synthesis and incorporation in devices has to be understood and controlled. This thesis is based on experimental studies on synthesis of carbon nanotubes and fabrication of nanoelectromechanical systems from carbon nanotubes and graphene. Vertically aligned nanotube arrays with heights over 800 µm have been grown using acetylene with iron as catalyst on alumina support using thermal chemical vapor deposition. By varying the partial pressure of acetylene it was found that the addition-rate of carbon was proportional to the coverage of acetylene molecules on the catalyst nanoparticle. In certain conditions the macroscopic pattern of the catalyst areas influenced the microscopic properties of the carbon nanotubes. It was shown that the initial carbon-precursor flow conditions could determine the number of walls produced. The amount of carbon incorporated into nanotubes was constant but ...
On January 8, 2007, at the CES show in Las Vegas, Nevada, Freescale Semiconductor announced the availability of three new micro-electro-mechanical system (MEMS) triple-axis acceleration sensors. Freescale is a major supplier of MEMS acceleration sensors for automotive applications, but the three new sensors extend Freescales capabilities into a wide variety of consumer applications. They feature low-power, zero-g detect for freefall protection, a small footprint for portable applications and a self-test function. There are many potential applications for MEMS accelerometers in consumer products. One example is hard disk drive protection in portable electronic devices such as MP3 players or PDAs. Zero-g detection provides a logic interrupt signal when all three axes are at zero-g. Advanced motion sensing then detects when a device is falling so that steps can be taken to prevent damage to hard drives or other sensitive electronic components. Another example is game controllers. Heightened multi-axis
Acreo is a well reputable MEMS design house, contracted by leading MEMS manufacturers, that offer custom MEMS design of sensors and actuators, including electronics, test and calibration routines for production. We are especially well known for our work on inertial MEMS sensors (gyros and accelerometers). Micro-Electro-Mechanical Systems, or MEMS, is a technology that allows microfabrication of miniaturized mechanical and electro-mechanical elements i.e., devices and structures. Using MEMS, a vast number of microsensors have been demonstrated with performances exceeding those of their macroscale counterparts; temperature, pressure, inertial forces, chemical species, magnetic fields, radiation, etc. MEMS technology has become a standard tool for building microsensors for navigation and motion tracking based on inertial phenomena; RF micro switch; interdigital electrodes for various bio-chemical measurements; bio-array reaction vessel that can be sealed with magnetic particles, packaging and assembly of
For measuring angular rate, numerous types of gyroscopes have been realized over the past years using MEMS technology, where current state-of-the-art MEMS gyroscopes show formidable performance in range, resolution and noise floor [12-15]. MEMS gyroscopes are typically no haltere-based systems, are generally heavily underdamped2 and operate at rather high frequencies. By contrast, the flys haltere system is a close to critically damped system and operates around the flys wing beat frequency (130-150 Hz) [9]. Obviously, the flys haltere system has developed under evolutionary pressure and therefore addresses the sensory needs of the fly. As a result, not only the operation principle is different from those generally used in MEMS gyroscopes, but also the performance may score high on metrics other than generally used for MEMS gyroscopes. For example, bandwidth and response time may be far more essential for flies than (bias-)stability and noise floor, as the halteres have been proven to aid in ...
received the B.S. and M.S. degrees (with high honors) in electrical and electronics engineering from Middle East Technical University (METU), Ankara, Turkey, in 2010 and 2012, respectively. He is currently working toward the Ph.D. degree in electrical and computer engineering at the University of California at Davis, Davis, CA, USA. He was a Research Assistant with the Micro-Electro-Mechanical Systems Research and Applications Center, METU, between 2010 and 2013. He has been a Graduate Research Assistant with the University of California at Davis since 2013. His research interests include MEMS sensors and analog integrated circuits.. An Ultrasonic Implantable for Continuous In Vivo Monitoring of Tissue Oxygenation [BPN871] ...
Caltech researchers are working on developing a MEMS-based (Micro-Electro-Mechanical System) brain-computer interface, with initial designs proving promisi
Microelectromechanical systems manufacturers, exporters, companies, sellers, OEM suppliers directory. Find the best Microelectromechanical systems business partners & shopping resources from this electronics & computer products portal. (Microelectronics : Microelectromechanical systems)
Abstract:. Despite of decades of research in conventional drug delivery systems many challenges are unconfronted in treatment of chronic diseases at a personalized medicine level. So there is a need for development of targeted and efficient drug delivery systems at such levels of treatment. Microelectromechanical systems have some unique characteristics like analyte sensitivity, electrical responsiveness, temporal control and sizes similar to cells and organelles that has led to engineering of implants for drug delivery in various chronic diseases.Targeting can be achieved through the use of this technology as the drugs are released at the site of action as well as in minimal effective concentrations, thus avoiding side-effects also. This review gives a general overview about the Bio Microelectromechanical systems used in targeting with some relevant examples. Hence Microelectromechanical systems prove to be a promising contender for development of drug delivery systems and targeting in ...
Many surveying engineering applications require the knowledge of the orientation parameters of instruments. One can use inertial measurement units (IMUs) to determine that. IMUs are combinations of several inertial sensors and comprise at least an accelerometer and a gyroscope. Therefore, they can detect accelerations and angular rates in a three-dimensional space. As micro-electro-mechanical systems, the sensors are increasingly getting smaller and lighter, but without being reduced in their accuracy. The smaller size facilitates diverse placing of the sensors, which allows a variety of uses. Moreover, several low-cost IMUs have been devised since the development of single-board computers.. The main objectives of this work are to determine tilts using a low-cost IMU, and the accuracy of the sensor. Furthermore, it studies general IMU applications in surveying engineering, and examines whether low-cost versions are applicable.. To fulfil the objectives, the study was based on a selected low-cost ...
TY - JOUR. T1 - Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies. AU - Wang, Zenghui. AU - Jia, Hao. AU - Zheng, Xuqian. AU - Yang, Rui. AU - Wang, Zefang. AU - Ye, G. J.. AU - Chen, X. H.. AU - Shan, Jie. AU - Feng, Philip X.L.. PY - 2015/1/21. Y1 - 2015/1/21. N2 - We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ∼100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ∼200 nm down to ∼20 nm clearly exhibit elastic characteristics transitioning from ...
The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, Si x N y /Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described.
We report a MEMS (Micro-Electro-Mechanical Systems)-based microbial fuel cell (MFC) that produces a high power density. The MFC features 4.5-μL anode/cathode chambers defined by 20-μm-thick photo-definable polydimethylsiloxane (PDMS) films. The MFC uses a Geobacter-enriched mixed bacterial culture, anode-res
Surface micromachining of micro-electro-mechanical systems (MEMS) has inherent limitations that can lead to mechanisms having an undesirable amount of clearance in revolute and prismatic joints. In micro devices, where actua-tion of the mechanisms is often limited by the displacement capabilities of actuators, the effects of joint clearances become significant. This paper details a modeling technique that is suited to the particular sources of clearance found in surface-micromachined mechanisms. Clearance vector models are used where the clearances are represented as vectors having variable lengths and directions. The preci-sion error of any point on any rigid link can be determined, in addition to the error in link angles, by comparison with the ideal (zero clearance) model. A bistable compliant mechanism is used as an example.
BISAC: SCI055000. Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. Electromechanical actuators directly transform input electrical energy into mechanical energy. Piezoelectric and electrostrictive ceramics are widely used in applications requiring high generative force, high frequency operation, accurate displacement, quick response time, or small device size. This book presents important progress in growth and structure-property studies in ferroelectrics with a high Curie temperature (Tc). (Imprint: Nova). ...
Research Interests: Design and fabrication of microsensors, microactuators, and micro-electro-mechanical systems (MEMS) for a variety of applications such as inertial sensing, environmental sensing, scanning microscopy, microfluidics, microoptics, and biomedical instrumentation; Development of manufacturing processes using combinations of traditional and novel materials and techniques, for example, micro-electro-discharge machining and microplasmas; Design of interface circuits for MEMS and development of co-fabrication techniques for circuits and MEMS ...
Linde Electronics, the global electronics business of The Linde Group, has strengthened its material support for electronics manufacturing by announcing a strategic partnership with Pelchem, the global fluorochemicals specialist, to accelerate the development of Micro-Electro-Mechanical Systems (MEMS).
The investigators are studying motivational interviewing (MI). MI is a counseling method to help people adopt healthy behaviors. The investigators will test whether MI improves patients accurate use of glaucoma eye drops. The investigators will train eye clinic staff called glaucoma educators to use MI. Up to 250 patients at 3 clinics will be recruited. All patients will receive their usual eye care. Based on chance, some patients will also be supported by a glaucoma educator. The groups will be compared on medication adherence using micro-electro-mechanical system(MEMS). MEMS are electronic bottle caps that track when a medication bottle is opened. Patients will be aware that their medication use is tracked. The groups will also be compared on treatment value, outcomes, and cost. The investigators will also collect data on variables that may predict medication adherence ...
All participants will continue to take the anti-HIV medication regimen prescribed by their health care provider. However, participants will be asked to keep one medication type in a bottle that has a special Micro-Electro-Mechanical System (MEMS) cap. This electronic cap will record each time the participant opens the bottle. Participants will meet with study staff for MEMS cap data collection once weekly for the first 4 weeks, every 2 weeks up to Week 12, and then every 4 weeks thereafter.. EC will consist of 30- to 45-minute counseling sessions about medication adherence. Participants will meet in person with a counselor for the first five sessions, occurring at baseline and Weeks, 1, 2, 6, and 11. An additional five counseling sessions will be conducted by phone during Weeks 4, 9, 15, 19, and 23. Participants receiving mDOT will have their doses of HIV medication delivered to them by an mDOT worker for the first 24 weeks of treatment. Participants will select a time and location to meet with ...
TY - GEN. T1 - Manufacture of SU-8 micro-grippers for mechanical characterization of gut epithelial cells. AU - Mackay, R. E.. AU - Le, H.R.. AU - Keatch, R.P.. AU - Zhao, Qi. PY - 2009. Y1 - 2009. N2 - This paper describes the manufacture of an integrated micro-electro-mechanical system (M EMS) to be used for small scale tissue manipulation. The micro-grippers are to be used to test the mechanical cell adhesion properties of the gut epithelium. In the majority of sporadic colon cancers the Adenomatous Polyopsis Coli (APC) protein is mutated or missing. Mutations of APC occur extremely early in the development of cancer, before formation of polyps. The following paper looks at the manufacturing processes for SU-8 micro-grippers. The micro-gripper structure has been successfully fabricated as a single structure not incorporating conduction paths. A number of sacrificial layers have been examined for compatibility with the SU-8 development. The sacrificial layer will be removed to leave a ...
The growing research in the applications of magnetically patterned thin film permanent magnets (PM) for lab-on-chip micromanipulation of various microscopic objects and for micro-electro-mechanical systems (MEMS) increases the demand for characterization of the magnetic space field distribution produced by such PMs. In the present work calculations are made for different patterns and magnetization distributions of Nd-Fe-B anisotropic films deposited onto 100 mm Si substrates using high rate triode sputtering. Space resolved magnetic imaging techniques utilizing magneto-optical indicator films (MOIF) were applied for the visualization of the magnetic field microdistribution with a resolution of the order of 1 micrometer. Both uniaxial and planar MOIF calibrated with the aid of a known external field were used to achieve quantitative measurements. Deviation of the data measured for real samples from the results of calculations performed for the idealized case of a uniform material are revealed. ...
Thus, the main innovation of this study is the fusion of NIRS technology with other emerging techniques such as the so-called MEMS (Micro-Electro-Mechanical System)-NIRS or hyperspectral image, which uses low cost, smaller size and faster than traditional sensors. Further, the combination NIRS-image not only allows to obtain spectral information using near-infrared radiation, but also spatial content, i.e., a visual representation of product characteristics similar to that provided by a satellite image . Not only does this combination provide general information about moisture, proteins, sugars or fatty acids, but it also shows other parameters such as the highly valued level of intramuscular fat or internal fruit damage, she said ...
Thus, the main innovation of this study is the fusion of NIRS technology with other emerging techniques such as the so-called MEMS (Micro-Electro-Mechanical System)-NIRS or hyperspectral image, which uses low cost, smaller size and faster than traditional sensors. Further, the combination NIRS-image not only allows to obtain spectral information using near-infrared radiation, but also spatial content, i.e., a visual representation of product characteristics similar to that provided by a satellite image . Not only does this combination provide general information about moisture, proteins, sugars or fatty acids, but it also shows other parameters such as the highly valued level of intramuscular fat or internal fruit damage, she said ...
Thus, the main innovation of this study is the fusion of NIRS technology with other emerging techniques such as the so-called MEMS (Micro-Electro-Mechanical System)-NIRS or hyperspectral image, which uses low cost, smaller size and faster than traditional sensors. Further, the combination NIRS-image not only allows to obtain spectral information using near-infrared radiation, but also spatial content, i.e., a visual representation of product characteristics similar to that provided by a satellite image . Not only does this combination provide general information about moisture, proteins, sugars or fatty acids, but it also shows other parameters such as the highly valued level of intramuscular fat or internal fruit damage, she said ...
Thus, the main innovation of this study is the fusion of NIRS technology with other emerging techniques such as the so-called MEMS (Micro-Electro-Mechanical System)-NIRS or hyperspectral image, which uses low cost, smaller size and faster than traditional sensors. Further, the combination NIRS-image not only allows to obtain spectral information using near-infrared radiation, but also spatial content, i.e., a visual representation of product characteristics similar to that provided by a satellite image . Not only does this combination provide general information about moisture, proteins, sugars or fatty acids, but it also shows other parameters such as the highly valued level of intramuscular fat or internal fruit damage, she said ...
Microfluidics is generally used to describe any technology that moves microscopic and nano-scale quantities of fluid through channels on a MEMS (Micro-Electro-Mechanical System). Devices in this realm are expected to have the capabilities to accurately…. ...
Associate Professor Reza Ghodssi (ECE/ISR) has been named as an associate editor for the Journal of Biomedical Microdevices, effective May 1, 2008. Ghodssi is also affiliated with the Fischell Department of Bioengineering. Biomedical Microdevices is the first journal to focus on biomedical applications of micro- and nanotechnology. It covers research in the diagnostic and therapeutic applications of Micro-Electro-Mechanical Systems, microfabrication, and nanotechnology. Topics include design, characterization, testing, modeling and clinical validation of microfabricated systems, and their integration on-chip and in larger functional units. The interests of the journal include systems for neural stimulation and recording; bioseparation technologies such as nanofilters and electrophoretic equipment; miniaturized analytic and DNA identification systems; biosensors; microtechnologies for cell and tissue research; tissue engineering; cell transplantation and the controlled release of drugs and ...
This study presents an effort to explore the exploitation of dynamic instabilities and bifurcations in micro-electro-mechanical systems to realize novel methods and functionalities for mass sensing and detection. These instabilities are induced by exciting a microstructure with a nonlinear forcing composed of a dc parallel-plate electrostatic load and an ac harmonic load. The frequency of the ac load is tuned to be near the fundamental natural frequency of the structure (primary resonance) or its multiples (subharmonic resonance). For each excitation method, local bifurcations, such as saddle-node and pitchfork, and global bifurcations, such as the escape phenomenon, may occur. This work aims to explore the utilization of these bifurcations to design novel mass sensors and switches of improved characteristics. One explored concept of a device is a switch triggered by mass threshold. The basic idea of this device is based on the phenomenon of escape from a potential well. This device has the ...
Control of biomolecular transport is essential to the advancement of nanokinematic systems whether for molecular cargo delivery in sensing or assembly processes, or as a means to interface micro-electro-mechanical systems with the nanoscale regime. Actin-myosin and nanotubule-kinesin systems represent two protein-based systems being explored as basic building blocks for realization of linear and rotary biomolecular motors based on biological nanoscale transport phenomena. While macroscopic electro-motility assays have been documented in the literature, harnessing this biological nanokinematic system to achieve spatially addressable transport of cargo on the micrometer scales of an integrated chip surface is of significant interest. In this work, we undertake a fundamental exploration of the interaction of microscale localized electric fields with the nanoscale actin-myosin motility assay. Electric fields established with arrays of integrated electrode structures under the assayed surface are used to
The microvascular network is a simple but critical system that is responsible for various important biological mechanisms in the bodies of all animals. The ability to generate a functional microvessel in vitro not only makes it possible to engineer vital tissue of considerable size but also serves as a platform for biomedical studies. In this study, we propose a simple method for fabricating customized cylinder micro-scaffolds for the in vitro development of microvascular networks. By integrating micro-electro-mechanical systems techniques with thermal reflow, we design and fabricate a micro-scale hemi-cylinder photoresist template. Then, a replica mold of polydimethylsiloxane, produced by casting, is used to generate microvascular network scaffolds of poly(lactide-co-glycolide) (PLGA). We selected the human umbilical vein endothelial cell (HUVEC) as our model endothelial cell, seeded it onto both sides of the PLGA scaffold, and cultured it using a traditional approach with no pumping system. ...
REMOTE-CONTROLLED insects may sound like the stuff of science fiction, but they have already been under development for some time now. In 2006, for example, the Defense Advanced Research Projects Agency (DARPA, the Pentagons research and development branch) launched the Hybrid Insect Micro-Electro-Mechanical Systems program, whose ultimate aim is to turn insects into unmanned aerial…. ...
This paper introduces a differential vibrating beam MEMS accelerometer demonstrating excellent long-term stability for applications in gravimetry and seismology. The MEMS gravimeter module demonstrates an output Allan deviation of 9 μGal for a 1000 s integration time, a noise floor of 100 μGal/√Hz, and measurement over the full ±1 g dynamic range (1 g = 9.81 ms−2). The sensitivity of the device is demonstrated through the tracking of Earth tides and recording of ground motion corresponding to a number of teleseismic events over several months. These results demonstrate that vibrating beam MEMS accelerometers can be employed for measurements requiring high levels of stability and resolution with wider implications for precision measurement employing other resonant-output MEMS devices such as gyroscopes and magnetometers.
A microelectromechanical systems (MEMS) device utilizing an aluminum fluoride layer as an etch stop is disclosed. In one embodiment, a MEMS device includes a first electrode having a first surface; and a second electrode having a second surface facing the first surface and defining a gap therebetween. The second electrode is movable in the gap between a first position and a second position. At least one of the electrodes includes an aluminum fluoride layer facing the other of the electrodes. During fabrication of the MEMS device, a sacrificial layer is formed between the first and second electrodes and is released to define the gap. The aluminum fluoride layer serves as an etch stop to protect the first or second electrode during the release of the sacrificial layer.
We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencie Editors Choice: Making sense of nanosensors and devices
0061] Referring to FIGS. 14A and 14B, a nanoelectromechanical device 1202 is shown according to an exemplary embodiment. The device 1202 includes a plurality of contacts 1232, shown as first through third contacts 1232a-1232c, spaced along the length of a surface 1228 and at least one variable actuator 1230 configured to deflect the nanotube 1210 into contact with the surface 1228 along a variable length thereby making 0, 1, 2 . . . n connections. The nanotube 1210 is supported at a first end 1212 by a first support structure 1220. As shown in the embodiment of FIG. 14A, the actuator 1230 is configured to apply a variable force on the nanotube 1210, thereby causing the nanotube 1210 to couple to the surface 1228. A low force is shown to cause the nanotube 1210 to buckle at a first buckling location 1218a and to couple to a first contact 1232a. A high force (shown in dashed lines) causes the nanotube 1210 to buckle at a second buckling location 1218b and to also couple to a second contact 1232b. ...
Nanoelectromechanical (NEM) memory cells are provided by anchoring a conductive nanometer-scale beam (e.g., a nanotube) to a base and allowing a portion of the beam to move. A charge containment layer is provided in the vicinity of this free-moving portion. To read if a charge is stored in the charge containment layer, a charge is formed on the beam. If a charge is stored then forces between the charged beam and the charge containment layer will displace the free-moving portion of the beam. This movement may be sensed by a sense contact. Alternatively, the beam may contact a sense contact at an ambient frequency when no charge is stored. Changing the amount of charge stored may change this contact rate. The contract rate may be sensed to determine the amount of stored charge.
Rapid development of micro-fabrication technology, once considered exclusively for aerospace navigation, is now regarded for a wide range of applications, including autonomous vehicle navigation, underwater and industrial applications. Microelectromechanical systems (MEMS)-based gyroscope employs a resonating mass (resonator) to detect changes in motion, which is the central element of the gyroscope. MEMS resonator energy loss is the primary barrier towards achieving navigation-grade precision, so predicting resonators vibration characteristics is critical for minimizing energy loss. MEMS high-precision resonators also need to keep operating in high vacuum to ensure no energy loss due to air damping. This project will seek a MEMS high-precision and ultra-low damping resonator design that can operate in wafer-scale vacuum-sealed environment and packaging. This design is expected to create a major technological shift in motion sensing; at an attractive unit cost, it is expected to create a ripple ...
We present the magnetic characterization of cobalt wires grown by focused electron beam-induced deposition (FEBID) and studied using static piezoresistive cantilever magnetometry. We have used previously developed high force sensitive submicron-thick silicon piezoresistive cantilevers. High quality polycrystalline cobalt microwires have been grown by FEBID onto the free end of the cantilevers using dual beam equipment. In the presence of an external magnetic field, the magnetic cobalt wires become magnetized, which leads to the magnetic field dependent static deflection of the cantilevers. We show that the piezoresistive signal from the cantilevers, corresponding to a maximum force of about 1 nN, can be measured as a function of the applied magnetic field with a good signal to noise ratio at room temperature. The results highlight the flexibility of the FEBID technique for the growth of magnetic structures on specific substrates, in this case piezoresistive cantilevers. ...
Gas permeability through damage networks in composite laminates is the key issue for the applicability of high-performance composites to the cryogenic propellant tanks of space launch vehicles. A simple model for the gas permeability induced by multilayer matrix cracks in composite laminates is proposed based on the leak conductance at crack intersections, which is an extension of the model by Kumazawa et al (AIAA J. 41, 2037-2044, 2003). Experimental evidence on the gas permeability mechanisms is summarized and reflected in the present model. In order to include the effects of applied loadings and damage sizes on the gas permeability, the leak conductance is assumed to be a function of the average crack opening displacements of the matrix cracks and the crack intersection angles. The leak conductance factor was empirically obtained as a function of the crack intersection angle, and the comparison of the gas permeability between the predictions based on the developed model and the experimental results
The piezoresistive effect is a change in the electrical resistivity of a semiconductor or metal when mechanical strain is applied. In contrast to the piezoelectric effect, the piezoresistive effect causes a change only in electrical resistance, not in electric potential. The change of electrical resistance in metal devices due to an applied mechanical load was first discovered in 1856 by Lord Kelvin. With single crystal silicon becoming the material of choice for the design of analog and digital circuits, the large piezoresistive effect in silicon and germanium was first discovered in 1954 (Smith 1954). In conducting and semi-conducting materials, changes in inter-atomic spacing resulting from strain affect the bandgaps, making it easier (or harder depending on the material and strain) for electrons to be raised into the conduction band. This results in a change in resistivity of the material. Within a certain range of strain this relationship is linear, so that the piezoresistive coefficient ρ ...
In this late-start Tier I Seniors Council sponsored LDRD, we have designed, simulated, microfabricated, packaged, and tested ion traps to extend the current quantum simulation capabilities of macro-ion traps to tens of ions in one and two dimensions in monolithically microfabricated micrometer-scaled MEMS-based ion traps. Such traps are being microfabricated and packaged at Sandias MESA facility in a unique tungsten MEMS process that has already made arrays of millions of micron-sized cylindrical ion traps for mass spectroscopy applications. We define and discuss the motivation for quantum simulation using the trapping of ions, show the results of efforts in designing, simulating, and microfabricating W based MEMS ion traps at Sandias MESA facility, and describe is some detail our development of a custom based ion trap chip packaging technology that enables the implementation of these devices in quantum physics experiments.
TY - JOUR. T1 - Phosphoric acid doped imidazolium polysulfone membranes for high temperature proton exchange membrane fuel cells. AU - Yang,Jingshuai. AU - Li,Qingfeng. AU - Jensen,Jens Oluf. AU - Pan,Chao. AU - Cleemann,Lars Nilausen. AU - Bjerrum,Niels J.. AU - He,Ronghuan. PY - 2012. Y1 - 2012. N2 - A novel acid-base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i.e. methyl (MePSU), ethyl (EtPSU) and butyl (BuPSU) imidazoliums, as revealed by 1H NMR spectra. The imidazolium polysulfone membranes are then doped with phosphoric acid and used as a proton exchange membrane electrolyte in fuel cells. An acid doping level of about 10-11mol H3PO4 per mole of the imidazolium group is achieved in 85wt% H3PO4 at room temperature. The membranes exhibit a proton conductivity of ...
Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices that show the highest power densities compared to the other type of fuel cell. In this work, nanocomposite membranes used for proton exchange membrane fuel cells as poly(vinyl alcohol)/La2Ce2O7 (PVA-LC) with the aim of increasing the water uptake and proton conductivity. Glutaraldehyde (GA) was used as cross linking agent of PVA matrix. PVA-LC nanocomposite membranes have been prepared with solutions casting method. The significant improvement has been achieved via the synergetic combination of organic and inorganic phases. Nanocomposite membranes were structurally, morphologically and electrochemically considered by FTIR, SEM and ELS, respectively. The results exhibited that the proton conductivity and the water uptake of the nanocomposite membranes were higher than that of the PVA membrane. PVA-LC nanocomposite membranes containing 4 wt.% of La2Ce2O7 nanoparticles displayed a high proton conductivity (0.019 S/cm). The highest
TY - JOUR. T1 - Liquid water flooding in a proton exchange membrane fuel cell cathode with an interdigitated design. AU - Kang, Simo. AU - Zhou, Biao. AU - Cheng, Chin-Hsiang. AU - Shiu, Huan Ruei. AU - Lee, Chun I.. PY - 2011/12/1. Y1 - 2011/12/1. N2 - In this paper, we studied the liquid water flooding process in the flow field of a proton exchange membrane fuel cell with an interdigitated design by using a multi-phase three-dimensional fuel cell cathode side model with a porous layer. The commercial CFD software package fluent (ANSYS Canonsburg, PA, USA) was used with a user-defined function. The results indicate that the general liquid water flooding process inside of this type of cathode design can be classified into three phases (the porous layer phase, the channel phase, and the drainage phase), and the details of liquid water behavior during this flooding process can be well understood and explained using the air-liquid interaction. Also, a liquid water avalanche phenomenon was ...
An alignment structure for a proton exchange membrane fuel cell is disclosed, which is used to accurately position a proton exchange membrane fuel cell onto a fuel cell manufacturing tool. The proton
TY - JOUR. T1 - Impedance characterization of high temperature proton exchange membrane fuel cell stack under the influence of carbon monoxide and methanol vapor. AU - Jeppesen, Christian. AU - Polverino, Pierpaolo. AU - Andreasen, Søren Juhl. AU - Araya, Samuel Simon. AU - Sahlin, Simon Lennart. AU - Pianese, Cesare. AU - Kær, Søren Knudsen. PY - 2017/8. Y1 - 2017/8. N2 - This work presents a comprehensive mapping of electrochemical impedance measurements under the influence of CO and methanol vapor contamination of the anode gas in a high temperature proton exchange membrane fuel cell, at varying load current. Electrical equivalent circuit model parameters based on experimental evaluation of electrochemical impedance spectroscopy measurements were used to quantify the changes caused by different contamination levels. The changes are generally in good agreement with what is found in the literature. It is shown that an increased level of CO contamination resulted in an increase in the high ...
TY - JOUR. T1 - Optimal design of baffles locations with interdigitated flow channels of a centimeter-scale proton exchange membrane fuel cell. AU - Jang, Jiin Yuh. AU - Cheng, Chin Hsiang. AU - Huang, Yu Xian. PY - 2010/1/1. Y1 - 2010/1/1. N2 - In the present study, the simplified conjugate-gradient method (SCGM) is combined with commercial CFD code to build an optimizer for designing the baffles locations with interdigitated channels of a centimeter-scale proton exchange membrane fuel cell (PEMFC). Using the optimizer, the locations of the baffles are adjusted toward the maximization of the average current density of the flow field. The approach is developed by using the commercial CFD code as the direct problem solver, which is able to provide the numerical solutions for the three-dimensional mass, momentum and species transport equations as well as to predict the electron conduction and proton migration taking place in a PEMFC. Results show that the optimal design process of the locations of ...
TY - JOUR. T1 - Pre-oxidized and nitrided stainless steel alloy foil for proton exchange membrane fuel cell bipolar plates. Part 2. T2 - Single-cell fuel cell evaluation of stamped plates. AU - Toops, Todd J.. AU - Brady, Michael P.. AU - Tortorelli, Peter F.. AU - Pihl, Josh A.. AU - Estevez, Francisco. AU - Connors, Daniel. AU - Garzon, Fernando. AU - Rockward, Tommy. AU - Gervasio, Don. AU - Mylan, William. AU - Kosaraju, Sree Harsha. PY - 2010/9/1. Y1 - 2010/9/1. N2 - Thermal (gas) nitridation of stainless steel alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant nitride containing surface layers (Cr2N, CrN, TiN, V2N, VN, etc.) of interest for fuel cells, batteries, and sensors. This paper presents results of proton exchange membrane (PEM) single-cell fuel cell studies of stamped and pre-oxidized/nitrided developmental Fe-20Cr-4V weight percent (wt.%) and commercial type 2205 stainless steel alloy foils. The single-cell fuel cell ...
Fuel cells are a promising technology to deal with energy sustainability, especially for mobility purposes the Proton Exchange Membrane Fuel Cell and hydrogen produced from biomass could be coupled to overcome the amount of CO2 emissions. In order to improve fuel cells performances the search for new electrocatalysts has a great importance in this technology the challenge for a fuel cell catalyst that is less poisoned by CO is one of the most important field in low temperature fuel cell developments that use alcohol and hydrocarbons as primary fuels. In this work PtSm, PtTb, PtDy, PtU, PtRuMo and PtRuDy systems have been synthesized by the colloid method, investigated by the following techniques: X-rays fluorescence analysis (XFA), X-rays powder diffraction (XRD), X-rays photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), cyclic voltammetry (CV) and polarization curves (Exi). The results obtained in this work shows that ...
Previous theoretical studies have shown that piezoelectric proton exchange membrane fuel cells (PZT-PEMFCs) might solve water flooding problems and increase cell performance. The innovative design of PZT-PEMFCs results in more oxygen being compressed into the catalyst layer. This enhances the electrochemical reaction and the current density, especially at a high PZT vibration frequency (64 Hz). In this investigation, a single, valveless PZT-PEMFC experimental fuel cell is built. The results are then compared with those of previous theoretical studies. This study includes an analysis of PZT vibration frequencies, and cell operation temperatures. A Nafion 212 membrane with a reaction area of 2 cm × 2 cm is used to measure the voltage and average current density under different temperatures and vibration frequencies. When the PZT device moves upward and increases the chamber volume, a diffuser directs most of the air to the outlet. In the valveless PZT-PEMFC, both a nozzle and diffuser are used. ...
Proton Exchange Membrane Fuel Cell (PEMFC) uses hydrogen and oxygen for fuel, the whole energy conversion process almost has no negative impact on the environment. The PEM fuel cell stack with the advantages of low-operating temperature, high current density and fast start-up ability is considered to be the next generation of new electric vehicle power. However, due to the limited current output, it is difficult for a single cell to meet the practical application requirements. The actual fuel cell stack is formed by many single cells assembled together. The assembly process is often related to load transfer, material transfer, energy exchange, multi-phase flow, electrochemical reaction and other factors. The performance of MEA (Membrane Electrode Assembly), sealing gaskets and other components will change during the assembly process, which makes the fuel cell stack assembly process more complex. The assembly load of large stack and the inside interface pressure homogeneity significantly affect ...
Proton exchange membrane fuel cells suffer from reversible performance loss during operation caused by the oxidation of the Pt catalyst which in turn reduces the electrochemically active surface area. Many fuel cell manufacturers recommend using short circuiting during the operation of the fuel cell to improve the performance of the cells over time. However, there is lack of understanding on how it improves the performance as well as on how to optimise the short circuiting strategy for different fuel cell systems. We present a simple procedure to develop an optimised short circuiting strategy by maximising the cumulative average power density gain and minimising the time required to recover the energy loss during short circuiting. We obtained average voltage improvement from 10 to 12% at different current densities for a commercial H-100 system and our short circuiting strategy showed ∼2% voltage improvement in comparison to a commercial strategy. We also demonstrated that the minimum short ...
In this article, one-phase and three dimensional computational fluid dynamics analysis was utilized to investigate the effect of annular field pattern of proton exchange membrane fuel cells (PEMFC) with different geometry on the performances and species distribution. This computational fluid dynamics code is used for solving the equation in single domain namely the flow field, the mass conservation, the energy conservation, the species transport, and the electric/ionic fields under the assumptions of steady state and non-isothermal. The introduced cell consist of different novelties, such as the way in which reactant gases are supplied to the flow field, the design of the flow field geometry for both anode and cathode and the membrane electrode assembly design and the length and occupied volume decreases up to 40%. Obtained results showed that generation of fuel cells with annular shaped geometry with the same active area and inlet area gave intensively higher current density compared with conventional
The Report Global PEMFC (Proton Exchange Membrane Fuel Cells) Market 2015-2019 provides information on pricing, market analysis, shares, forecast, and company profiles for key industry participants. - MarketResearchReports.biz. About PEMFC. PEMFC are devices that generate electricity through an electrochemical process involving oxidation of electrolytes placed between the anode and the cathode. Fuel cells are generally categorized based on the type of electrolyte used. PEMFC use an acidic water-based polymer membrane with platinum-based electrodes. It operates at low temperatures and caters effectively to dynamic power requirements. The chemical source of PEMFC, which is hydrogen, needs to be extremely pure because of its operating temperature and use of precious metal-based electrodes. PEMFC is a fuel-cell technology that is used extensively in light duty and material handling vehicles.. View Full Report at http://www.marketresearchreports.biz/analysis/280607. Technavios analysts forecast the ...
The Report Global PEMFC (Proton Exchange Membrane Fuel Cells) Market 2015-2019 provides information on pricing, market analysis, shares, forecast, and company profiles for key industry participants. - MarketResearchReports.biz About PEMFC PEMFC are devices that generate electricity through an electrochemical process involving oxidation of electrolytes placed between the anode and the cathode. Fuel cells are generally categorized based on the type of electrolyte used. PEMFC use an acidic water-based polymer membrane with platinum-based electrodes. It operates at low temperatures and caters effectively to dynamic power requirements. The chemical source of PEMFC,…. Read More ...
Gas diffusion electrodes (GDEs) prepared by a novel automatic catalyst spraying under irradiation (ACSUI) technique are investigated for improving the performance of phosphoric acid (PA)-doped polybenzimidazole (PBI) high temperature proton exchange membrane fuel cell (PEMFC). The physical properties of the GDEs are characterized by pore size distribution and scanning electron microscopy (SEM). The electrochemical properties of the membrane electrode assembly (MEA) with the GDEs are evaluated and analyzed by polarization curve, cyclic voltammetry (CV) and electrochemistry impedance spectroscopy (EIS). Effects of PTFE binder content, PA impregnation and heat treatment on the GDEs are investigated to determine the optimum performance of the single cell. At ambient pressure and 160 o C, the maximum power density can reach 0.61 W cm-2, and the current density at 0.6 V is up to 0.38 A cm-2, with H /air and a platinum loading of 0.5 mg cm-2 on both electrodes. The MEA with the GDEs shows good ...
This work highlights the gains of an innovative model-based control approach applied to a proton exchange membrane fuel cell (PEMFC) system, included in a stand-alone hybrid generator. This approach proposes a multivariable setpoint tracking of the PEMFC output power and temperature. The freshness of this approach is based on the combination of a nonlinear model-based predictive control strategy (NMPC) and a global linearizing control (GLC) algorithm. The performance of the proposed control strategy is confirmed thanks to simulations of varying control scenarios. Results show good performance in setpoint tracking, disturbances rejection and robustness against plant/model mismatch in presence of noisy signals. Moreover, for similar setpoint point tracking accuracy, the proposed control strategy appears to be four times faster than a classical multivariable NMPC strategy. According to real-time application objectives, this control strategy appears as a promising option to be implanted in the overall
Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphite content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for
TY - JOUR. T1 - ZIF derived PtNiCo/NC cathode catalyst for proton exchange membrane fuel cell. AU - Hanif, Saadia. AU - Shi, Xuan. AU - Iqbal, Naseem. AU - Noor, Tayyaba. AU - Anwar, Rehan. AU - Kannan, A. M.. PY - 2019/12/5. Y1 - 2019/12/5. N2 - High performance cathode catalysts with minimum platinum amount for the electrocatalyzed oxygen reduction reaction (ORR) in PEMFCs remain as a significant challenge for commercial application. Zeolitic Imidazolate Framework (ZIF) based catalyst can provide void 3D framework of N-doped nano-porous carbon for promising ORR activity. Here we report a bimetallic pyrolyzed NiCo-ZIF supported fine Pt/Pt alloy electrocatalyst for ORR. After pyrolysis, nano-porous carbon is obtained with well dispersed Pt/Pt alloy nanoparticles (˜ 3 nm). This catalyst shows superior performance and stability in acidic medium against the commercial catalyst comprising of Pt/C. In a single cell PEMFC, high peak power density value of 1067 mW. cm−2 is attained at 70 °C by ...
Sustained potential oscillations are experimentally observed in a proton exchange membrane fuel cell with PtRu as anode catalyst and with H2/108ppm CO as the anode feed when operating under a constant current density mode. These oscillations appear at fuel-cell temperatures below 70°C. A threshold value exists for both the current density and the anode flow rate at a given fuel-cell temperature for their onset. The temperature dependence of the oscillation period shows an apparent activation energy around 60 kJ/mol. The potential oscillations are believed to be due to the coupling of anode electro-oxidation of H2 and CO on the PtRu catalyst surface, on which OHad is formed more readily, i.e., at lower overpotentials. A simple kinetic model is provided that can reproduce the observed oscillatory phenomenon both qualitatively and quantitatively.
Publishers Accepted Manuscript: Study of acetylene poisoning of Pt cathode on proton exchange membrane fuel cell spatial performance using a segmented cell system ...
Proton Exchange Membrane Fuel Cells (PEMFC) are promising energy converters, but still suffer from a short life duration. Applying Prognostics and Health M
The Global Proton Exchange Membrane Fuel Cells Industry 2015 Market Research Report is a professional - Market Research Reports and Industry Analysis
TY - JOUR. T1 - Experimental analysis of a dimensionless number in the cathode channels of a polymer electrolyte membrane fuel cell with different head losses. AU - Han, S. H.. AU - Kim, K. R.. AU - Ahn, D. K.. AU - Choi, Y. D.. PY - 2010/1/1. Y1 - 2010/1/1. N2 - This study investigates the effects of stoichiometry, humidity, cell temperature, and pressure on the performance and the flooding of the proton exchange membrane fuel cell. Values of stoichiometry are 1.5, 2.0, and 2.5 at cell temperatures of 50, 55, and 60°C, respectively. This study shows that the dimensionless flooding value (FV) is a function of the stoichiometry, humidity, temperature, and pressure. The FV is calculated by using the measured values of temperature, humidity, pressure, and flowrate of the cathode. The effect of the dimensionless number on the flooding of the cathode in the proton exchange membrane fuel cell is analysed in this study. The effects of air stoichiometry, cell temperature, and air humidity are also ...
MAHRENI, Mahreni and MOHAMAD, Abu Bakar and KADHUM, Abdul Amir Hasan. and Daud, Wan Ramli Wan (2010) NANOCOMPOSITE ELECTROLYTE MEMBRANE FOR MODERATE TEMPERATURE AND LOW RELATIVE HUMIDITY HYDROGEN PROTON EXCHANGE MEMBRANE FUEL CELL (HPEMFC) APPLICATlON. Departement Of Chemical Engineering, ITB. ...
In this paper, a fault tolerant control (FTC) strategy for proton exchange membrane (PEM) fuel cells based on the use of virtual actuators and the Takagi- Sugeno (TS) approach is proposed. The overall solution relies on adding a virtual actuator in the control loop to hide the fault from the controller point of view, allowing it to see the same plant as before the fault, such that the stability and some desired performances are preserved. The proposed methodology is based on the use of a reference model, where the resulting nonlinear error model is brought to a Takagi-Sugeno form using a gridding approach. The TS model is suitable for designing a controller using linear matrix inequalities (LMI)-based techniques, such that the resulting closed-loop error system is stable with poles placed in some desired region of the complex plane. Simulation results are used to show the effectiveness of the proposed approach ...
The report documents the study on a hydrogen proton exchange membrane (PEM) fuel cell powered unmanned aerial vehicle (UAV) named Kenyalang-1. Common aircraft utilize internal combustion engines (ICE) as main power source for the propulsion system. However, ICE imposes negative impact towards the environment due to the pollution produced through carbon emission, initiating green house effect, global warming, and health problems. Researchers have started to develop interest on the possibilities of using alternative energies to replace ICE aircraft propulsion system. Due to the relatively new nature of the technology, there is a need for a research on the development of a ftiel cell electrical propulsion system. The objectives of this project are to design and to develop a fuel cell propulsion system that operates using a 500 W hydrogen PEM fuel cell as the main power generator for a UAV. The research is important to determine the capability of the propulsion system to power a custom designed and ...
A pre-spiral bundle for making a spiral wrapped cylindrical fuel cell and cylindrical fuel cells made using the pre-spiral bundle. The pre-spiral bundle comprises a sleeve defining a hydrogen flowpath. The sleeve comprises a proton exchange membrane encapsulating a substantially planar anode in ionic communication with a catalytically effective amount of a noble metal
In the Experimental Section, paragraph 3, the fifth sentence should read: The scattering patterns were integrated to generate an I vs q curve, where I is the intensity of scattered X-rays and q is the scattering vector r, q is calculated from scattering angle θ and the wavelength of the X-ray beam λ by the equation q= 4πsin (θ)/λ. The remaining two sentences of that paragraph should be disregarded.. Figure 5 in the original manuscript should be replaced by the new version of Figure 5 shown below. Figure 5 in the published article is the relation between scattering intensity and the scattering angle, rather than q [calculated as q=4πsin (θ)/λ], due to an oversight by the author. The caption remains the same and is included for completeness.. The author apologises for these oversights. ...
Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature inside the fuel cell. Experimental results demonstrate that temperature was generally linearly related to resistance and that accuracy and sensitivity were within 0.5 °C and 1.68×10-3/°C, respectively. The best experimental performance was 9.37 mW/cm2 at an H2/O2 dry gas flow rate of 30/30 SCCM. Fuel cell temperature during operation was 27 °C, as measured using thermocouples in contact with the backside of the electrode. Fuel cell operating temperature measured in situ was 30.5 °C.
EFC Fuel Cell Hardware includes a conditioned MEA (Membrane Electrode Assembly) installed inside the hardware utilizing ElectroChems proprietary technology for leak-tight performance.. ElectroChems EFC Fuel Cell Hardware is used by many of our global customers as the standard they utilize in the development of their membrane electrode assemblies (MEA). They are completely assembled fuel cells for any researcher to utilize for the understanding the basic operation of a fuel cell. It helps the researcher to understand the effect of gas flow rate, pressure, and its impact on performance. The EFC fuel cell hardware is quality control tested prior to shipment - and is sent with a performance curve based on that testing.. ...
In the present study, sulfonated polysulfone (SPSU)/layered double hydroxide (LDH) composite membranes for use in proton exchange membrane fuel cells (PEMFCs) were investigated. Polysulfone (PSU) was sulfonated with trimethylsilyl chlorosulfonate in 1,2 dichlo In the present study, sulfonated polysulfone (SPSU)/layered double hydroxide (LDH) composite membranes for use in proton exchange membrane fuel cells (PEMFCs) were investigated. Polysulfone (PSU) was sulfonated with trimethylsilyl chlorosulfonate in 1,2 dichloroethane at room temperature. Composite membranes were prepared by blending different amount (0, 1, 2, and 5%) of LDH nanoparticles with SPSU in dimethylacetamide (DMAc). The membranes were prepared by the casting method and the samples obtained were characterized by XRD, FTIR spectroscopy. The thermal behavior for all samples was evaluated by thermogravimetrical analysis (TGA). Finally electrochemical impedance spectroscopy (EIS) was used to study the membranes electrical properties. ...
Catalysts play an essential role in nearly every chemical production process. Platinum supported on high surface area carbon substrates (Pt/C) is one of the promising candidates as an electrocatalyst in low temperature polymer electrolyte fuel cells. Developing the activity of the Pt/C catalyst with narrow Pt particle size distribution and good dispersion has been a main concern in current research.. In this study, the main objective was the development and characterization of inexpensive and effective nanophase Pt/C electrocatalysts. A set of modified Pt/C electrocatalysts with high electrochemical activity and low loading of noble metal was prepared by the impregnation-reduction method in this research. The four home-made catalysts synthesized by different treatments conditions were characterized by several techniques such as EDS, TEM, XRD, AAS, TGA, BET and CV.. Pt electrocatalysts supported on acid treatment Vulcan XC-72 electrocatalysts were produced successfully. The results showed that Pt ...
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Direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutral-state electrolyte of 0.1 M [PO4] tot was studied with five different anode electrocatalysts (Pt, PtRu, PtNi, Au, PdAu) at a temperature of 37 oC and at a glucose concentration of 0.1 M. The cathode catalyst in each test was Pt supported on carbon (60 wt.%). Four anode electrocatalysts (supported on carbon) had a total metal content of 40 wt.% while the fifth anode material of PtRu had a higher content of 60 wt.%. Moreover, in order to show the influence of the metallic content on the fuel cell performance, anode catalysts with 60 wt.% (Pt) and 10wt.% (PtNi) were tested. The operation of the AEMFC was controlled by means of an in-house-made electronic load with PI-controller (i.e. a feedback controller that has proportional and integral action on control error signal) either at constant current (CC) or at constant voltage (CV). The primary objective was to characterize the Coulombic efficiency (CE) based on the exchange of ...
This work covers the direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutralstate electrolyte of 0.1 M [PO4] (tot) having two high-performing anode electrocatalysts (Pt and PtNi) at 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was a Pt supported on carbon (60 wt.%). The PtNi/C had a total metal content of 40 wt.% and the Pt/C 60 wt.%. The operation of the AEMFC was controlled by means of an in-house made electronic load with PI-controller (i.e. a feedback controller, which has proportional and integral action on control error signal). There were two primary objectives with this study. At first, to find out how the electrode modifications of the anode (i.e. by increasing the thicknesses of these electrodes by adding extra carbon) affect the Coulombic efficiency (CE, based on the exchange of two electrons) and the specific energy (SPE, Wh kg(-1)) values of the direct glucose AEMFC. Secondly, investigate how a two-stage fuel cell system ...
To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid-base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characterizations and fuel cell technologies. To optimize the membrane properties, high molecular weight polymers with synthetically modified or N-substituted structures have been synthesized. Techniques for membrane casting from organic solutions and directly from acid solutions have been developed. Ionic and covalent cross-linking as well as inorganic-organic composites has been explored. Membrane characterizations havebeenmadeincluding spectroscopy,wateruptake and acid doping, thermal and oxidative stability, ...
Fuel cells, using hydrogen as energy carrier, allow chemically‑stored energy to be utilized for many applications, including balancing the electrical grid and the propulsion of vehicles. To make the fuel cell technology more accessible and promote a sustainable energy society, this thesis focuses on alternative polymer electrolytes, as they can potentially lead to a lower cost and a more environmentally‑friendly fuel cell. The main subject is anion exchange membrane fuel cells (AEMFCs), for which the importance of gas diffusion electrode morphology and platinum electrode reactions are investigated. Properties of the membrane such as water flux during operation are evaluated. Furthermore, novel polymer electrolytes are studied: variations of poly(phenylene oxide)‑based membranes in AEMFCs; and cellulose‑based membranes in a proton exchange membrane fuel cell (PEMFC).. The AEMFC results show that the performance is dependent on the electrode morphology. Electrochemical experiments in a ...
Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE materials. Unlike PEMFCs, there is not an ideal AEM material that provides efficient ion transport, while being mechanically robust and chemically stable under strong alkaline conditions. The objectives of this dissertation are to
TY - JOUR. T1 - Emerging Porous Solid Electrolytes for Hydroxide Ion Transport. AU - Kang, Dong Won. AU - Kang, Minjung. AU - Yun, Hongryeol. AU - Park, Hyein. AU - Hong, Chang Seop. N1 - Publisher Copyright: © 2021 Wiley-VCH GmbH. PY - 2021/5/10. Y1 - 2021/5/10. N2 - Anion exchange membrane fuel cells (AEMFCs) offer several advantages over proton exchange membrane fuel cells, such as the use of a non-precious metal catalyst, but these cells suffer from various issues related to OH--conducting electrolytes, including low conductivity and the formation of K2CO3 salt. These issues need to be resolved for the widespread use of AEMFCs. Recently, many studies have focused on developing excellent ion-conductive electrolytes using porous materials based on metal-organic and covalent organic frameworks. However, most of this research is biased toward proton-conducting electrolytes; to the best of the authors knowledge, reviews addressing OH--conducting electrolytes using porous materials have not been ...
In transportation research programs, two types of fuel cells are under primary consideration for application in heavy-duty vehicles: Phosphoric acid (PAFC) and proton exchange membrane (PEM). The following discussion will include the main differences between the phosphoric acid and proton exchange membrane fuel cells and explain the differences between their applications in transportation research. A central focus of this paper will be the application of PAFC technology in a 40 foot transit bus program with which TMC is currently associated, and a discussion of the PEM technology and its potential for heavy-duty transit applications. Included will be a discussion of the fuels which can potentially be used with fuel cells such as methanol, natural gas, ethanol, hydrogen, and finally, an overview of technical challenges related to the fuel cell ...
In the last two decades, capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be promising for various ultrasound imaging and chemical sensing applications. Although holding many benefits for ultrasound imaging, CMUTs have certain weaknesses such as the relatively low output pressure at transmission, which hinder their development in the diagnostic imaging application. In the sensing area, CMUTs have shown attractive features such as high mass sensitivity, miniaturized array configuration, and ease of functionalization. However, their potential for humidity sensing is less explored. The objectives of this thesis lie in two aspects. One is to offer a solution to overcome the limitation of low output pressure, and the other is to develop CMUTs as resonant gravimetric humidity sensors. The major efforts are made on the second task. For the first objective, a novel dual-element ultrasonic transducer is proposed. It incorporates two transducer technologies by using a ...
FABRICATION OF NOVEL NANOMATERIALS FOR POLYMER ELECTROLYTE MEMBRANE FUEL CELLS AND SELF-CLEANING APPLICATIONS , FABRICATION OF NOVEL NANOMATERIALS FOR POLYMER ELECTROLYTE MEMBRANE FUEL CELLS AND SELF-CLEANING APP... , کتابخانه دیجیتال دانشگاه آزاد اسلامی خوراسگان
STUDY OF SPEEK-BASED PROTON EXCHANGE MEMBRANES FOR FUEL CELL APPLICATIONS.POMPES PAR TRANSITIONS MULTIPLES , STUDY OF SPEEK-BASED PROTON EXCHANGE MEMBRANES FOR FUEL CELL APPLICATIONS.POMPES PAR TRANSITIONS MUL... , کتابخانه دیجیتال دانشگاه آزاد اسلامی خوراسگان