Mechanical Engineering Commons^™

Synthesis And Characterization Of One Dimensional Boron-Based Nanomaterials, Rui Li

Theses and Dissertations

One dimensional (1D) metal borate and boride nanomaterials have attracted tremendous attention due to their good chemical inertness, high-temperature stability, excellent mechanical properties, and low thermal expansion coefficient.

Beta-BaB2O4 (BBO) is a well-known nonlinear optical material with a high second-order nonlinear susceptibility, wide transparency range, and high damage threshold. Using a low temperature, organic-free hydrothermal technique, single-crystalline barium polyborate Ba3B6O9(OH)6 (BBOH) nanorods were synthesized. It was found that BBO nanospindles can be achieved by annealing the BBOH nanorods at a relatively low temperature of 810 oC. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were …

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-Gd_0.1Ce_0.9O_2−δ (Ni-GDC) anode was prepared using freeze drying tape casting, while the hierarchically porous cathode with nano-size Sm_0.5Sr_0.5CoO₃ (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 50 nm in the cathode promote …

Can Silver Be A Reliable Current Collector For Electrochemical Tests?, Yunhui Gong, Changyong Qin, Kevin Huang

Faculty Publications

The true functionality of a current collector employed in electrochemical cells is to ensure a low- resistance steady electrons flow between the cell and instrumentation without involving in any local electrochemical reactions of the electrode. In this study, we investigated the effect of curing temperature of a common current collector, silver, on the polarization area specific resistance (ASR) of a cathode. The results explicitly showed that at least one order of magnitude lower ASR for a cathode with Ag cured at 800°C than that cured at 650°C of the same cathode configuration. Microscopic analysis of the 800°C-cured cells revealed a …

Atomistic Investigation Of Scratching-Induced Deformation Twinning In Nanocrystalline Cu, Junjie Zhang, Tao Sun, Yoganda Yan, Dong Shen, Xiaodong Li

Faculty Publications

Deformation twinning is an important deformation mode of nanocrystalline metals. In current study, we investigate the scratching-induced deformation twinning in nanocrystallineCu by means of molecular dynamics simulations. The tribological behavior, the deformation mechanisms, the formation mechanism of deformation twins, and the grain size dependence of the propensity of deformation twinning are elucidated. Simulation results demonstrate that deformation twinning plays an important role in the plastic deformation of nanocrystallineCu under nanoscratching, in addition to dislocation activity and grain boundary-associated mechanism. The nucleation of initial twinning partial dislocations originates from the dissociation of lattice partial dislocations that emit from grain boundary triple …

Enhanced Methanol Oxidation And Co Tolerance Using Ceo2-Added Eggshell Membrane-Templated Pd Network Electrocatalyst, Qunwei Tang, Zhengping Mao, Shuguo Ma, Kevin Huang

Faculty Publications

Macroporous Pd and CeO₂-added Pd network catalysts have been synthesized using eggshell membrane (ESM) as a template for enhanced methanol oxidation and CO tolerance. The microstructural characterization revealed a hierarchically ordered macroporous network of Pd reproducing the fibrous structure of ESM for a Pd-only catalyst, and a flower-like CeO₂-decorated Pd morphological architecture for the CeO₂-added Pd catalyst synthesized by a precipitation method. XRD patterns indicated Pd and CeO₂ phases with good crystallinity. The cyclic voltammetry studies showed an enhanced electrocatalytic activity for methanol oxidation in acidic aqueous medium. Because of the preferential formation …

Energy Storage Characteristics Of A New Rechargeable Solid Oxide Iron-Air Battery, Xuan Zhao, Nansheng Xu, Xue Li, Yunhui Gong, Kevin Huang

Faculty Publications

Cost effective and large scale energy storage is critical to renewable energy integration and smart-grid energy infrastructure. Rechargeable batteries have great potential to become a class of cost effective technology suited for large scale energy storage. In this paper, we report the energy storage characteristics of a newly developed rechargeable solid oxide iron–air battery. Investigations of the battery’s performance under various current densities and cycle durations show that iron utilization plays a determining role in storage capacity and round-trip efficiency. Further studies of the battery's cycle life reveal a unique charge-cycle originated degradation mechanism that can be interpreted by a …

H3Po4-Imbibed Three-Dimensional Polyacrylamide/Polyacrylamide Hydrogel As A High-Temperature Proton Exchange Membrane With Excellent Acid Retention, Qunwei Tang, Guoging Qian, Kevin Huang

Faculty Publications

We herein report the use of polyacrylamide/polyacrylamide interpenetrating polymer network (PAM/PAM IPN) hydrogel as a matrix to imbibe proton conducting H₃PO₄, forming a robust proton exchange membrane (PEM) suitable for high-temperature PEM fuel cells by combining excellent acid retention, simple synthesis, and low cost. Its extraordinary ability to absorb large quantity of aqueous solution is fully utilized to achieve high H₃PO₄ loading, showing a proton conductivity of 0.0833 S cm−1 at 183 °C in dry air. The synthesized membrane also shows excellent acid retention even under mechanical load and high humidity. These profound …

Characterization Of Ba1-X-YCaXSrYTio3 Perovskites As Pb-Free Dielectric Materials, Lingling Zhang, Siwei Wang, Xusheng Wang, Kevin Huang

Faculty Publications

Use of lead-containing piezoelectric components in electrical and electronic devices has been banned on the EU market since July 1st, 2006. Development of lead-free high performance piezoelectric materials to meet the strong market demand is therefore imperative. In this paper, we report a systematic study on the structural, dielectric and ferroelectric properties of one class of lead-free piezoelectric materials, Ba_1-x-yCa_xSr_yTiO₃ (x = 0-0.4, and y = 0-0.2) ceramics, using techniques such as XRD, SEM, impedance analyzer, and ferroelectric analyzer. It is found that with increasing Sr concentration in Ba …

Order-Disorder Transition Of Aragonite Nanoparticles In Nacre, Zaiwang Huang, Xiaodong Li

Faculty Publications

Understanding nacre’s bottom-up biomineralization mechanism, particularly, how individual aragonite platelets are formed, has long remained elusive due to its crystallographic peculiarity and structural complexity. Here we report that crystallographic order-disorder transition can be triggered within individual aragonite platelets in pristine nacre by means of heat treatment and/or inelastic deformation, offering a unique opportunity to discriminate mysterious aragonite nanoparticles in transmission electron microscopy. Our findings unambiguously uncover why aragonite nanoparticles in pristine nacre have long been inaccessible under TEM observation, which is attributed to the monocrystal-polycrystal duality of the aragonite platelet. The underlying physical mechanism for why an individual aragonite platelet …

High Co2 Permeation Flux Enabled By Highly Interconnected Three-Dimensional Ionic Channels In Selective Co2 Separation Membranes, Lingling Zhang, Nansheng Xu, Xue Li, Siwei Wang, Kevin Huang, William H. Harris, Wilson K. S. Chiu

Faculty Publications

Abatement of CO₂ emissions from existing fossil-fueled power plants is currently the sole near-term solution to stabilize CO₂ concentration in the atmosphere. Separation and capture of CO₂from process streams of these power plants is the first step toward this effort. In this paper, we report a high flux membrane consisting of highly and efficiently interconnected three-dimensional ionic channels prepared from a combined “co-precipitation” and “sacrificial-template” synthesis. The membranes exhibit remarkable CO₂ permeation characteristic, achieving a CO₂ flux density two orders of magnitude higher than other similar systems reported in the literature. The experimental results …

Sr2Fe1.5Mo0.5O6-Δ – Sm0.2Ce0.8O1.9 Composite Anodes For Intermediate-Temperature Solid Oxide Fuel Cells, Beibei He, Ling Zhao, Shuxiang Song, Tong Liu, Fanglin Chen, Changrong Xia

Faculty Publications

Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) perovskite is carefully investigated as an anode material for solid oxide fuel cells with LaGaO₃-based electrolytes. Its electronic conductivity under anodic atmosphere is measured with four-probe method while its ionic conductivity is determined with oxygen permeation measurement. Samaria doped ceria (SDC) is incorporated into SFM electrode to improve the anodic performance. A strong relation is observed between SDC addition and polarization losses, suggesting that the internal SFM-SDC contacts are active for H₂ oxidation. The best electrode performance is achieved for the composite with 30 wt% SDC addition, resulting …

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 to date for the cells with metal oxide anodes at this …

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_{3 …}

Dual Mode Sensing With Low-Profile Piezoelectric Thin Wafer Sensors For Steel Bridge Crack Detection And Diagnosis, Lingyu Yu, Sepandarmaz Momeni, Valery Godinez, Victor Giurgiutiu, Paul Ziehl, Jianguo Yu

Faculty Publications

Monitoring of fatigue cracking in steel bridges is of high interest to many bridge owners and agencies. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In this paper, we presented a dual mode sensing methodology integrating acoustic emission and ultrasonic wave inspection based on the use of low-profile piezoelectric wafer active sensors (PWAS). After introducing the research background and piezoelectric sensing principles, PWAS crack detection in passive acoustic emission mode is first presented. Their acoustic emission detection capability has been validated …

Piezoelectric Wafer Active Sensors In Lamb Wave-Based Structural Health Monitoring, Lingyu Yu, Victor Giurgiutiu

Faculty Publications

Recent advancements in sensors and information technologies have resulted in new methods for structural health monitoring (SHM) of the performance and deterioration of structures. The enabling element is the piezoelectric wafer active sensor (PWAS). This paper presents an introduction to PWAS transducers and their applications in Lamb wave-based SHM. We begin by reviewing the fundamentals of piezoelectric intelligent materials. Then, the mechanism of using PWAS transducers as Lamb wave transmitters and receivers is presented. PWAS interact with the host structure through the shear-lag model. Lamb wave mode tuning can be achieved by judicious combination of PWAS dimensions, frequency value, and …

Spotlight On Usc: Mechanical Engineering, Allison Marsh

Section 3: Imaging the Fast Moving

No abstract provided.

Investigation Of Carbon Corrosion Resistance Of Cnt Containing Electrode, Diana Larrabee, William A. Rigdon, Eli Mcpherson, Joshua Sightler, Xinyu Huang

Faculty Publications

Carbon support corrosion is one of the major degradation mechanisms of polymer electrolyte membrane (PEM) fuel cell. Carbon oxidation occurs in PEM electrode and is accelerated at high potential created by adverse operating conditions and improper distribution of reactants and products [1, 2, 3]. Carbon corrosion can lead to the thinning of the electrode layer and severe performance degradation. The detailed mechanisms of carbon support corrosion induced performance loss are still not fully understood; it is believed that the following events contribute to the decay: (1) structural collapse of the porous electrode due to the loss of carbon; (2) carbon …

Dual Mode Sensing With Low-Profile Piezoelectric Thin Wafer Sensors For Steel Bridge Crack Detection And Diagnosis, Lingyu Yu, S. Momeni, V. Godinez, Victor Giurgiutiu, Paul Ziehl, J. Yu

Faculty Publications

Monitoring of fatigue cracking in steel bridges is of high interest to many bridge owners and agencies. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In this paper, we presented a dual mode sensing methodology integrating acoustic emission and ultrasonic wave inspection based on the use of low-profile piezoelectric wafer active sensors (PWAS). After introducing the research background and piezoelectric sensing principles, PWAS crack detection in passive acoustic emission mode is first presented. Their acoustic emission detection capability has been validated …

Aerosol-Assisted Synthesis Of Monodisperse Single-Crystalline Α-Cristobalite Nanospheres, Xingmao Jiang, Lihong Bao, Yung-Sung Cheng, Darren R. Dunphy, Xiaodong Li, C. Jeffrey Brinker

Faculty Publications

Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity nanocrystalline α-cristobalite is important for catalysis, nanocomposites, advanced polishing, and understanding silica nanotoxicology.

One-Step Infiltration Of Mixed Conducting Electrocatalysts For Reducing Cathode Polarization Of A Commercial Cathode-Supported Sofc, Nansheng Xu, Xue Li, Xuan Zhao, Hailei Zhao, Kevin Huang

Faculty Publications

Infiltrating fine-grained electrocatalyst particles of either ion conducting or mixed electron and ion conducting (MEIC) material into a ceramic porous electrode scaffold has proven a very effective way to improve electrode performance for low to intermediate temperature solid oxide fuel cells (SOFCs). We report here one-step infiltration of MEIC fine particles, La_0.6Sr_0.4CoO_3-δ (LSCo) and SrCo_0.8Fe_0.2O_3-δ (SCF), into a commercial cathode substrate. A comparative study shows that the cathode polarization can be considerably reduced by a factor of 17 to 28 and 28 to 49 from 1000 to 700 ³C by …

A Novel Solid Oxide Redox Flow Battery For Grid Energy Storage, Nansheng Xu, Xue Li, Xuan Zhao, John B. Goodenough, Kevin Huang

Faculty Publications

In this work we report proof-of-concept of a novel redox flow battery consisting of a solid oxide electrochemical cell (SOEC) integrated with a redox-cycle unit. The charge/discharge characteristics were explicitly observed by operating between fuel cell and electrolysis modes of the SOEC along with “in-battery” generation and storage of H₂ realized by an in situ closed-loop reversible steam-metal reaction in the redox-cycle unit. With Fe/FeO as the redox materials, the new storage battery can produce an energy capacity of 348 Wh/kg-Fe and round-trip efficiency of 91.5% over twenty stable charge/discharge cycles. This excellent performance combined with robustness, environmental friendliness …

Synthesis, Structural, Optical And Mechanical Characterization Of Srb2O4 Nanorods, Rui Li, Lihong Bao, Xiaodong Li

Faculty Publications

Single crystalline strontium borate (SrB₂O₄) nanorods were synthesized for the first time via a facile sol–gel route at low temperature. The SrB₂O₄ nanorods have a good crystalline nature with the growth direction along the [511] orientation and they are transparent from the ultraviolet to the visible regimes. Nanoscale three-point bending tests were performed directly on individual nanorods to probe their mechanical properties using an atomic force microscope. The elastic modulus of SrB₂O₄ nanorods was measured to be 158.2 ± 2.8 GPa, exhibiting a significant increase compared with other borate nanostructures …

In Situ Synthesis Of Ultrafine Ss-Mno2/Polypyrrole Nanorod Composites For High-Performance Supercapacitors, Jianfeng Zang, Xiaodong Li

Faculty Publications

We report a remarkable observation that is at odds with the established notion that β-MnO₂ was regarded as an undesirable candidate for supercapacitor applications. The specific capacitance of β-MnO₂ can reach as high as 294 F g⁻¹, which is comparable to the best crystallographic structure, like α-MnO₂. The key is to substantially decrease the size of β-MnO₂ powders to ultra small regime. We demonstrate a facile, simple, and effective approach to synthesizing ultrafine (<10 nm in diameter) β-MnO₂/polypyrrole nanorod composite powders for high-performance supercapacitor electrodes. Our observation may encourage a revisit of the other good …

Characteristics Of The Hydrogen Electrode In High Temperature Steam Electrolysis Process, Chao Jin, Chenghao Yang, Fanglin Chen

Faculty Publications

YSZ-electrolyte supported solid oxide electrolyzer cells (SOECs) using LSM-YSZ oxygen electrode but with three types of hydrogen electrode, Ni–SDC, Ni–YSZ and LSCM–YSZ have been fabricated and characterized under different steam contents in the feeding gas at 850°C. Electrochemical impedance spectra results show that cell resistances increase with the increase in steam concentrations under both open circuit voltage and electrolysis conditions, suggesting that electrolysis reaction becomes more difficult in high steam content. Pt reference electrode was applied to evaluate the contributions of the hydrogen electrode and oxygen electrode in the electrolysis process. Electrochemical impedance spectra and over potential of both electrodes …

A Generic Bamboo-Based Carbothermal Method For Preparing Carbide (Sic, B4C, Tic, Tac, Nbc, TiXNb1-XC, And TaX Nb1-XC) Nanowires, Xinyong Tao, Yiping Li, Jun Du, Yang Xia, Yingchao Yang, Hui Huang, Yongping Gan, Wenkui Zhang, Xiaodong Li

Faculty Publications

Finding a general procedure to produce a whole class of materials in a similar way is a desired goal of materials chemistry. In this work, we report a new bamboo-based carbothermal method to prepare nanowires of covalent carbides (SiC and B₄C) and interstitial carbides (TiC, TaC, NbC, Ti_xNb_1−xC, and Ta_xNb_1−xC). The use of natural nanoporous bamboo as both the renewable carbon source and the template for the formation of catalyst particles greatly simplifies the synthesis process. Based on the structural, morphological and elemental analysis, volatileoxides or halides assisted …

Sr2Fe1.5Mo0.5O6 As Cathodes For Intermediate-Temperature Solid Oxide Fuel Cells With La0.8Sr0.2Ga0.87Mg0.13O3 Electrolyte, Guoliang Xiao, Qiang Liu, Fei Zhao, Lei Zhang, Changrong Xia, Fanglin Chen

Faculty Publications

The performance of Sr₂Fe_1.5Mo_0.5O₆ (SFMO) as a cathode material has been investigated in this study. The oxygen ionic conductivityof SFMO reaches 0.13 S cm^-1 at 800°C in air. The chemical diffusion coefficient (D_chem) and surface exchange constant (k_ex) of SFMO at 750°C are 5.0 x 10^-6 cm² s^-1 and 2.8 x 10^-5 cm s^-1, respectively, suggesting that SFMO may have good electrochemicalactivity for oxygen reduction. SFMO shows a thermal expansion coefficient (TEC) of 14.5 x 10^-6 K^-1 the …

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.

Optical Cell For Combinatorial In Situ Raman Spectroscopic Measurements Of Hydrogen Storage Materials At High Pressures And Temperatures, Jason R. Hattrick-Simpers, Wilbur S. Hurst, Sesha S. Srinivasan, James E. Maslar

Faculty Publications

An optical cell is described for high-throughput backscattering Raman spectroscopic measurements of hydrogen storagematerials at pressures up to 10 MPa and temperatures up to 823 K. High throughput is obtained by employing a 60 mm diameter × 9 mm thick sapphire window, with a corresponding 50 mm diameter unobstructed optical aperture. To reproducibly seal this relatively large window to the cell body at elevated temperatures and pressures, a gold o-ring is employed. The sample holder-to-window distance is adjustable, making this cell design compatible with optical measurement systems incorporating lenses of significantly different focal lengths, e.g., microscope objectives and single element …

Mechanical Characterization Of Polymer Electrolyte Membrane With Optical Methods, Xinyu Huang, Luis Alva, Jay Neutzler

Faculty Publications

Mechanical properties of polymer electrolyte membrane have important implications in the endurance of many electrochemical energy conversion devices [1]. Mechanical experiments are effective method to reveal discrete damage developed in the membrane by quantifying the change of mechanical strength and toughness. Regular strain measurement methods are overly intrusive to the thin and relatively fragile polymer electrolyte membrane; hence optical-based minimal invasive stress/strain measurement methods are studied.

Effective Ionic Conductivity Of A Novel Intermediate-Temperature Mixed Oxide-Ion And Carbonate-Ion Conductor, Xue Li, Guoliang Xiao, Kevin Huang

Faculty Publications

A systematic investigation on the effective ionic conductivity (σ_m) of a novel intermediate-temperature mixed oxide-ion and carbonate-ion conductor MOCC consisting of a ceria phase and a carbonate phase is reported. The study explicitly shows that the observed remarkable temperature-dependent σ_m is primarily the result of softening/melting of the carbonate phase as the physical state of the carbonate phase transforms from solid, softened to molten. Differential scanning calorimetry analysis complements the understanding of the observed electrical behavior by revealing temperatures of melting and solidification in agreement with the onset temperatures of σ_m. In addition, the …