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Full-Text Articles in Mechanical Engineering

Optimization Of Microfluidic Chip Fabrication Via Femtosecond Laser Ablation, Kenneth Aycock Apr 2018

Optimization Of Microfluidic Chip Fabrication Via Femtosecond Laser Ablation, Kenneth Aycock

Senior Theses

Microfluidic devices have become staple tools in biomedical research and have a promising future as low cost, point-of-care (POC) diagnostic devices. Despite the advancements in microfluidic device technology, the manipulation and fabrication of these systems can be tedious and expensive. Repeatable techniques in which computer-aided designs are translated into microfluidic systems in a matter of minutes are highly desirable both for researchers and manufacturers. Laser ablation of tape substrates has shown promise in producing cost-effective, rapidly manipulable devices, but the work done thus far has utilized continuous wave lasers that perform suboptimally due to the relatively short wavelengths used and ...


La0.6Sr1.4Mno4+Δ Layered Perovskite Oxide: Enhanced Catalytic Activity For The Oxygen Reduction Reaction, Yarong Wang, Zhibin Yang, Fanliang Liu, Chao Jin, Jiao Wu, Ming Shen, Ruizhi Yang, Fanglin Chen Jan 2015

La0.6Sr1.4Mno4+Δ Layered Perovskite Oxide: Enhanced Catalytic Activity For The Oxygen Reduction Reaction, Yarong Wang, Zhibin Yang, Fanliang Liu, Chao Jin, Jiao Wu, Ming Shen, Ruizhi Yang, Fanglin Chen

Faculty Publications

Efficient electrocatalysts for the oxygen reduction reaction (ORR) is a critical factor to influence the performance of lithium–oxygen batteries. In this study, La0.6Sr1.4MnO4+δ layered perovskite oxide as a highly active electrocatalyst for the ORR has been prepared, and a carbon-coating layer with thickness <5 nm has been successfully introduced to enhance the electronic conductivity of the as-prepared oxide. XRD, XPS, Raman, SEM and TEM measurements were carried out to characterize the crystalline structure and morphology of these samples. Rotating ring-disk electrode (RRDE) technique has been used to study catalytic activities of the as-prepared catalysts for the ORR in 0.1 M KOH media. RRDE results reveal that carbon-coated La0.6Sr1.4MnO4+δ exhibits better catalytic activity for the ORR. For the carbon-coated La0.6Sr1.4MnO4+δ, the ORR proceeds predominately via a direct four electron process, and a maximum cathodic current density of 6.70 mA cm ...


Characterization Of 3d Interconnected Microstructural Network In Mixed Ionic And Electronic Conducting Ceramic Composites, William M. Harris, Kyle S. Brinkman, Ye Lin, Dong Su, Alex P. Cocco, Arata Nakajo, Matthew B. Degostin, Yu-Chen Karen Chen-Wiegart, Jun Wang, Fanglin Chen, Yong S. Chu, Wilson K. S. Chiu May 2014

Characterization Of 3d Interconnected Microstructural Network In Mixed Ionic And Electronic Conducting Ceramic Composites, William M. Harris, Kyle S. Brinkman, Ye Lin, Dong Su, Alex P. Cocco, Arata Nakajo, Matthew B. Degostin, Yu-Chen Karen Chen-Wiegart, Jun Wang, Fanglin Chen, Yong S. Chu, Wilson K. S. Chiu

Faculty Publications

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications ...


Low Frequency Energy Scavenging Using Sub-Wave Length Scale Acousto-Elastic Metamaterial, Raiz U. Ahmed, Sourav Banerjee Jan 2014

Low Frequency Energy Scavenging Using Sub-Wave Length Scale Acousto-Elastic Metamaterial, Raiz U. Ahmed, Sourav Banerjee

Faculty Publications

This letter presents the possibility of energy scavenging (ES) utilizing the physics of acousto-elastic metamaterial (AEMM) at low frequencies (<∼3KHz). It is proposed to use the AEMM in a dual mode (Acoustic Filter and Energy Harvester), simultaneously. AEMM’s are typically reported for filtering acoustic waves by trapping or guiding the acoustic energy, whereas this letter shows that the dynamic energy trapped inside the soft constituent (matrix) ofmetamaterials can be significantly harvested by strategically embedding piezoelectric wafers in the matrix. With unit cell AEMM model, we experimentally asserted that at lower acoustic frequencies (< ∼3 KHz), maximum power in the micro Watts (∼35µW) range can be generated, whereas, recently reported phononic crystal based metamaterials harvested only nano Watt (∼30nW) power against 10KΩ resistive load. Efficient energy scavengers at low acoustic frequencies are almost absent due to large required size relevant to the acoustic wavelength. Here we report sub wave length scale energy scavengers utilizing the coupled physics of local, structural and matrix resonances. Upon validation of the argument through analytical, numerical and experimental studies, a multi-frequency energy scavenger (ES) with multi-cellmodel is designed with varying geometrical properties capable of scavenging energy (power output from ∼10µW – ∼90µW) between 0.2 KHz and 1.5 KHz acoustic frequencies.


Design, Fabrication, And Properties Of 2-2 Connectivity Cement/Polymer Based Piezoelectric Composites With Varied Piezoelectric Phase Distribution, Xu Dongyu, Cheng Xin, Sourav Banerjee, Huang Shifeng Jan 2014

Design, Fabrication, And Properties Of 2-2 Connectivity Cement/Polymer Based Piezoelectric Composites With Varied Piezoelectric Phase Distribution, Xu Dongyu, Cheng Xin, Sourav Banerjee, Huang Shifeng

Faculty Publications

The laminated 2-2 connectivity cement/polymer based piezoelectric composites with variedpiezoelectric phase distribution were fabricated by employing Lead Zirconium Titanate ceramicas active phase, and mixture of cement powder, epoxy resin, and hardener as matrix phase with a mass proportion of 4:4:1. The dielectric, piezoelectric, and electromechanical coupling properties of the composites were studied. The composites with large total volume fraction ofpiezoelectric phase have large piezoelectric strain constant and relative permittivity, and thepiezoelectric and dielectric properties of the composites are independent of the dimensional variations of the piezoelectric ceramic layer. The composites with small total volume fraction of piezoelectric ...


A Platinum Nanowire Network As A Highly Effective Current Collector For Intermediate Temperature Solid Oxide Fuel Cells, Hanping Ding, Xingjian Xue Jan 2014

A Platinum Nanowire Network As A Highly Effective Current Collector For Intermediate Temperature Solid Oxide Fuel Cells, Hanping Ding, Xingjian Xue

Faculty Publications

We report the fabrication and evaluation of a platinum nanowire network as a highly efficient current collector for solid oxide fuel cells (SOFCs). The ink of carbon-black supported platinum nanoparticles was sprayed onto the cathode. After firing, the carbon black was oxidized and disappeared as carbon dioxide gas while the platinum nanoparticles connect with one another, forming a tree-branch-like nanowire network. The diameters of the nanowires range from 100 nm to 400 nm. Compared to a conventional platinum paste current collector, the polarization resistance of the PrBaCo2O5+δ (PBCO) cathode with a nanowire current collector was reduced ...


Modeling Of Chemical-Mechanical Couplings In Anode-Supported Solid Oxide Fuel Cells And Reliability Analysis, Xinfang Jin, Xingjian Xue Jan 2014

Modeling Of Chemical-Mechanical Couplings In Anode-Supported Solid Oxide Fuel Cells And Reliability Analysis, Xinfang Jin, Xingjian Xue

Faculty Publications

Oxygen ionic transport in conducting ceramics is an important mechanism enabling solid oxide fuel cell (SOFC) technology. The multi-physicochemical processes lead to the fact that the distribution of oxygen vacancy site fraction is not uniform in a positive-electrode electrolyte negative-electrode (PEN) assembly. Different oxygen vacancy concentrations induce different volumetric expansion of ceramics, resulting in complicated chemical–mechanical coupling phenomena and chemical stress in SOFCs. In this research, a mathematical model is developed to study oxygen ionic transport induced chemical stress in an SOFC. The model is validated using experimental polarization curves. Comprehensive simulations are performed to investigate chemical stress distribution ...


Influence Of Crystal Structure On The Electrochemical Performance Of A-Site-Deficient Sr1-SNb0.1Co0.9O3-Δ Perovskite Cathodes, Yinlong Zhu, Ye Lin, Xuan Shen, Jaka Sunarso, Wei Zhou, Shanshan Jiang, Dong Su, Fanglin Chen, Zongping Shao Jan 2014

Influence Of Crystal Structure On The Electrochemical Performance Of A-Site-Deficient Sr1-SNb0.1Co0.9O3-Δ Perovskite Cathodes, Yinlong Zhu, Ye Lin, Xuan Shen, Jaka Sunarso, Wei Zhou, Shanshan Jiang, Dong Su, Fanglin Chen, Zongping Shao

Faculty Publications

The creation of A-site cation defects within a perovskite oxide can substantially alter the structure and properties of its stoichiometric analogue. In this work, we demonstrate that by vacating 2 and 5% of Asite cations from SrNb0.1Co0.9O3-δ (SNC1.00) perovskites (Sr1-sNb0.1Co0.9O3-δ,s = 0.02 and 0.05; denoted as SNC0.98 and SNC0.95, respectively), a Jahn–Teller (JT) distortion with varying extents takes place, leading to the formation of a modified crystal lattice within a the perovskite framework. Electrical conductivity, electrochemical performance, chemical ...


Micro Modeling Study Of Cathode/Electrolyte Interfacial Stresses For Solid Oxide Fuel Cells, Xinfang Jin, Xingjian Xue May 2013

Micro Modeling Study Of Cathode/Electrolyte Interfacial Stresses For Solid Oxide Fuel Cells, Xinfang Jin, Xingjian Xue

Faculty Publications

Delamination of the cathode/electrolyte interface is an important degradation phenomenon in solid oxide fuel cells (SOFCs). While the thermal stress has been widely recognized as one of the major reasons for such delamination failures, the role of chemical stress does not receive too much attention. In this paper, a micro-model is developed to study the cathode/electrolyte interfacial stresses, coupling oxygen ion transport process with structural mechanics. Results indicate that the distributions of chemical stress are very complicated at the cathode/electrolyte interface and show different patterns from those of thermal stress. The maximum principal stresses take place at ...


The Effect Of Isostatic Pressing On The Dielectric Properties Of Screen Printed Ba0.5Sr0.5Tio3 Thick Films, Siwei Wang, Lingling Zhang, Jiwei Zhai, Fanglin Chen Jan 2013

The Effect Of Isostatic Pressing On The Dielectric Properties Of Screen Printed Ba0.5Sr0.5Tio3 Thick Films, Siwei Wang, Lingling Zhang, Jiwei Zhai, Fanglin Chen

Faculty Publications

Ba0.5Sr0.5TiO3 thick films with B2O3–Li2O glass sintering aid were prepared by the screen printing method on Al2O3 substrates. A 200 MPa isostatic pressure was applied to the films before sintering. After being sintered at 950C, lower porosity and denser microstructure was obtained compared with the films without isostatic pressing. The dielectric constant and dielectric loss were 238 and 0.0028, respectively. A tunability of 61.7% was obtained for the isostatic pressed films, a 27.8% enhancement compared to unpressurized films. These results ...


High Performance Low Temperature Solid Oxide Fuel Cells With Novel Electrode Architecture, Yu Chen, Qian Liu, Zhibin Yang, Fanglin Chen, Minfang Han Dec 2012

High Performance Low Temperature Solid Oxide Fuel Cells With Novel Electrode Architecture, Yu Chen, Qian Liu, Zhibin Yang, Fanglin Chen, Minfang Han

Faculty Publications

In this study, we have fabricated high performance low temperature solid oxide fuel cells (LT-SOFCs) with both acicular anodes and cathodes with thin Gd-doped ceria (GDC) electrolyte film. The acicular Ni-Gd0.1Ce0.9O2−δ (Ni-GDC) anode was prepared using freeze drying tape casting, while the hierarchically porous cathode with nano-size Sm0.5Sr0.5CoO3 (SSC) particles covering an acicular GDC skeleton was prepared by a combination of freeze drying tape casting and self-rising approaches. The acicular electrodes with 5–200 μm pores/channels enhance mass transport, while SSC particles of about ...


A Ceramic-Anode Supported Low Temperature Solid Oxide Fuel Cell, Hanping Ding, Junjie Ge, Xingjian Xue Mar 2012

A Ceramic-Anode Supported Low Temperature Solid Oxide Fuel Cell, Hanping Ding, Junjie Ge, Xingjian Xue

Faculty Publications

We report the fabrication and evaluation of a ceramic-anode supported button cell LSCM-SDC/SDC/PBSC (thickness 400 μm/20 μm/20 μm). The anode/electrolyte assembly LSCM-SDC/SDC was co-fired at low temperature of 1250°C, where a slight amount of CuO was mixed with LSCM. The CuO (20.3 wt%) were impregnated into the porous substrate to enhance current collecting effect. The cell exhibited power density of 596 mWcm−2 and 381 mWcm−2 at 700°C with wet hydrogen and methane as the fuel respectively, where the silver paste was used as current collectors, the highest performance up ...


A New Approach For The Preparation Of Variable Valence Rare Earth Alloys From Nano Rare Earth Oxides At A Low Temperature In Molten Salt, Milin Zhang, Yongde Yan, Wei Han, Xing Li, Zhiyao Hou, Yang Tian, Ke Ye, Lihong Bao, Xiaodong Li, Zhijian Zhang Feb 2012

A New Approach For The Preparation Of Variable Valence Rare Earth Alloys From Nano Rare Earth Oxides At A Low Temperature In Molten Salt, Milin Zhang, Yongde Yan, Wei Han, Xing Li, Zhiyao Hou, Yang Tian, Ke Ye, Lihong Bao, Xiaodong Li, Zhijian Zhang

Faculty Publications

The solubility of RE2O3 (RE = Eu, Sm, and Yb) with variable valence in molten salts is extremely low. It is impossible to directly obtain variable valence metals or alloys from RE2O3 using electrolysis in molten salts. We describe a new approach for the preparation of variable valence rare earth alloys from nano rare earth oxide. The excellent dispersion of nano–Eu2O3 in LiCl–KCl melts was clearly observed using a luminescent feature of Eu3+ as a probe. The ratio of solubility of nano-Sm2O3/common Sm2O ...


High Conductivity Solid Oxide Electrolyte Composite-Laminates Utilizing Scandia/Ceria Co-Doped Zirconia Core With Yttria Stabilized Zirconia Outer Skins, Jay Neutzler, Xinyu Huang, Joshua Sightler, Yan Chen, Nina Orlovskaya Jan 2011

High Conductivity Solid Oxide Electrolyte Composite-Laminates Utilizing Scandia/Ceria Co-Doped Zirconia Core With Yttria Stabilized Zirconia Outer Skins, Jay Neutzler, Xinyu Huang, Joshua Sightler, Yan Chen, Nina Orlovskaya

Faculty Publications

Increasing the conductivity of electrolytes in lower temperature Solid Oxide Fuel Cells (SOFC) is of great importance. However, there are several challenges that are to be addressed, which include phase stability of electrolyte’s crystal structure, chemical stability in both oxidizing and reducing environments, and maintaining mechanical integrity and high ionic conductivity over time.


Optimization Design Of Electrodes For Anode-Supported Solid Oxide Fuel Cells Via Genetic Algorithm, Junxiang Shi, Xingjian Xue Dec 2010

Optimization Design Of Electrodes For Anode-Supported Solid Oxide Fuel Cells Via Genetic Algorithm, Junxiang Shi, Xingjian Xue

Faculty Publications

Porous electrode is the critical component of solid-oxide fuel cells (SOFCs) and provides a functional material backbone for multi-physicochemical processes. Model based electrode designs could significantly improve SOFC performance. This task is usually performed via parameter studies for simple case and assumed property distributions for graded electrodes. When nonlinearly coupled multiparameters of electrodes are considered, it could be very difficult for the model based parameter study method to effectively and systematically search the design space. In this research, the optimization approach with a genetic algorithm is demonstrated for this purpose. An anode-supported proton conducting SOFC integrated with a fuel supply ...


Accelerated Testing Method For Pem Fuel Cell Based Uninterrupted Power Supply Systems, Xinyu Huang, Xiaofeng Wang Jan 2007

Accelerated Testing Method For Pem Fuel Cell Based Uninterrupted Power Supply Systems, Xinyu Huang, Xiaofeng Wang

Faculty Publications

Proton exchange membrane fuel cell based power systems are on the verge of commercialization for a number of niche applications where batteries are traditionally used. Uninterrupted power supply (UPS) for wireless communication towers and broadband network relay utilities is one of the targeted application of fuel cell power systems with capacity ranging from one to serveral kilowatts. It is believed that fuel cell based UPS systems can offer considerable advantage when extended backup time is desirable. In order to replace the well-known battery based UPS systems, the reliability and perofrmance of fuel cell based UPS system need to be thoroughly ...


Mechanics Of Hydrogenated Amorphous Carbon Deposits From Electron-Beam-Induced Deposition Of Paraffin Precursor, W. Ding, D. A. Dikin, X. Chen, R. D. Piner, R. S. Ruoff, E. Zussman, X. Wang, Xiaodong Li Jul 2005

Mechanics Of Hydrogenated Amorphous Carbon Deposits From Electron-Beam-Induced Deposition Of Paraffin Precursor, W. Ding, D. A. Dikin, X. Chen, R. D. Piner, R. S. Ruoff, E. Zussman, X. Wang, Xiaodong Li

Faculty Publications

Many experiments on the mechanics of nanostructures require the creation of rigid clamps at specific locations. In this work, electron-beam-induced deposition(EBID) has been used to depositcarbonfilms that are similar to those that have recently been used for clamping nanostructures. The film deposition rate was accelerated by placing a paraffin source of hydrocarbon near the area where the EBIDdeposits were made. High-resolution transmission electron microscopy, electron-energy-loss spectroscopy, Raman spectroscopy, secondary-ion-mass spectrometry, and nanoindentation were used to characterize the chemical composition and the mechanics of the carbonaceous deposits. The typical EBIDdeposit was found to be hydrogenated amorphous carbon (a-C:H ...


Mechanics Of Composite Materials In Fuel Cell Systems, Kenneth Reifsnider, Xinyu Huang, G. Ju, Matthew Feshler, K. An Jan 2005

Mechanics Of Composite Materials In Fuel Cell Systems, Kenneth Reifsnider, Xinyu Huang, G. Ju, Matthew Feshler, K. An

Faculty Publications

The science and technology that are fundamental to the concept of composite materials are also the foundation for the construction and function of fuel cells and fuel cell systems. The present paper outlines this relationship in the context of the physics and chemistry that are enabled by the specific selection and arrangement of constituents of the “functional composite” fuel cell. General principles of operation are described, and fundamental issues are defined that must be addressed by the composites community if the fuel cell science and engineering is to advance. Examples of several types of functional composite fuel cells are presented ...