Engineering Science and Materials Commons^™

Fast And Accurate Evaluation Of Lifepo4 Cathode Materials By Single Particle Microelectrode, Fu-Qing Wang, Yi-Min Wei, Yu-Zhuan Su, Bing-Wei Mao, Kai Wu, Feng-Gang Zhao, Chun-Lei Chen, Xing-Lu Li, Jin Chong

Journal of Electrochemistry

Single particle microelectrode enables to evaluate the electrochemical responses for single particle of active material without binder and conductive agent. Thus, the influences of additive and electrode structure on the electrochemical performance of active materials can be ignored. Furthermore, this technology can be used to evaluate active materials fast. Therefore, single particle microelectrode allows fast and accurate determination of the intrinsic performance of active material. Cyclic voltammogram (CV), cycle performance, and kinetic behavior of LiFePO4 cathode materials were evaluated by the single particle microelectrode. CV curve of LiFePO4 particle with a pair of oxidation and reduction peaks was obtained with …

Special Issue: Electrochemistry Of Carbon Materials, Chen Wei

Journal of Electrochemistry

Carbon materials are traditional electrode materials due to their excellent electrical conductivities, high electrochemical stabilities and wide potential windows. Glassy carbon, graphite, various activated charcoals, carbon fibers etc. have been widely used in electrochemistry serving as electrode substrates or supports. In addition to their applications in basic electrochemistry, carbon materials have also played important roles in electrochemical energy storage and conversion. In recent years, various types of carbon structures, from zero-dimensional carbon nanodots, one-dimensional nanotubes, two-dimensional graphene to three-dimensional porous carbons, have attracted increasing attention in electrochemical field. It has been found that carbon materials have outstanding properties as advanced …

Applications Of Carbon Materials In Electrochemical Energy Storage, Ji Liang, Lei Wen, Hui-Ming Cheng, Feng Li

Journal of Electrochemistry

An electrode material for electrochemical energy storage is one of the key components for high performance devices. In a variety of electrochemical energy storage systems, carbon materials, especially the lately emerged carbon nanomaterials including the carbon nanotube and graphene, have been playing a very important role and brought new vitality to the development and demonstration of the broad application prospects. In this review, we summarize the applications of various carbon materials in the typical electrochemical energy storage devices, namely lithium/sodium ion batteries, supercapacitors, and lithium-sulfur batteries, as well as flexible electrochemical energy storage and electrochemical catalysis. A perspective of novel …

Colloidal Ionic Supercapacitors, Kun-Feng Chen, Dong-Feng Xue

Journal of Electrochemistry

Supercapacitors have high power density and long cycle life compared with battery systems, but they still suffer from low energy density at the same time. In order to increase the energy density of supercapacitors, we have developed a new type of pseudocapacitor, called colloidal ion supercapacitor, which can directly use commercial metal salts as electrode materials and form electroactive matter by in-situ electrochemical reactions without the need of additional materials synthesis processes. Colloidal ion supercapacitor can fully utilize the redox reaction of metal cations with multiple oxidation states, which can completely release the stored electrical energy of multiple-valence cations, leading …

Electrodeposition Of Lanthanum In Deep Eutectic Solvents, Li Wang, You-Jun Fan, Lu Wei, Hai-Xia Liu, Shi-Gang Sun

Journal of Electrochemistry

With the choline chloride/urea deep eutectic solvents (DESs) as the medium, the olive-like lanthanum particles with uniform shape and size were successfully prepared through a potentiostatic deposition method. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). At the same time, the effect of deposition potential, temperature and time on the size and morphology of samples was investigated. The results demonstrated that the optimum conditions for the preparation of olive-like lanthanum particles were as follows: deposition potential of -1.7 V, temperature of 80 ^oC …

Synthesis Of Porous Carbon Nanosheets And Its Application In Sodium-Ion Battery, Jing-Fei Zhang, Jing Lu, Xiao-Yu Yang, Yun-Di Huang, Lin Xu, Dong-Mei Sun, Ya-Wen Tang

Journal of Electrochemistry

Owning to sodium’s high abundance, relatively low cost, similar chemical properties to Li and very suitable redox potential of E0(Na+/Na) = -2.71 V versus SHE which is only 0.3 V above that of lithium, rechargeable sodium ion battery hold much promise as potential alternatives to current lithium ion batteries for energy storage applications. Carbon material is regarded as the most promising anode candidate for sodium ion battery. Particularly, carbon nanosheet with porous structure and high conductivity is expected to have improved sodium ion storage properties. In this paper, we present a two-step pyrolysis-based method for facile synthesis of porous carbon …

Carbon Aerogel/Nickel Foam As Electrode For High-Performance Supercapacitor, Zhong Wu, Xin-Bo Zhang

Journal of Electrochemistry

Herein, a facile synthesis has been explored to prepare carbon aerogel/Ni foam. Graphene oxide, resorcinol and formaldehyde serve as precursors and polymerize in-situ on the Ni foam after hydrothermal synthesis at 85 oC. After lyophilization treatment, the carbon aerogel/Ni foam with porous structure can be obtained. Electrochemical investigations reveal that the carbon aerogel/Ni foam exhibits superior performances in both aqueous and organic electrolytes involving high specific capacitance and long-term cycling stability. The excellent properties can be ascribed to the unique formation and porous structure, which allows more effective transportations of electron and electrolyte ion.

Effect Of Mno2 Content On Electrochemical Capacitance Behavior Of Active Carbon Electrode, Kun Shen, Xian-Liang Zhou, Qi-Shun Duan

Journal of Electrochemistry

In this work, the manganese dioxide (MnO₂) materials were prepared by solution approach at low temperature, thermal decomposition and electrochemical deposition. The actived carbon (AC) and MnO₂ composite electrodes were used for aqueous supercapacitors. The morphologies and structures of the prepared materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the electrochemical behaviors were tested by cyclic voltammetry (CV) and galanostatic charge-discharge tests. Electrochemical test data show that the maximum specific capacitances of 151, 172 and 141 F•g^-1 were obtained with the contents of MnO₂ being 70, 60 and 70% in …

Progress Of Self-Supported Supercapacitor Electrode Materials Based On Carbon Substrates, Shui-Jian He, Wei Chen

Journal of Electrochemistry

Self-supported electrode materials have been widely used in supercapacitors. Carbon materials are promising substrates in building self-supported electrode materials attributed to their diverse structures, rich resource, relatively low cost and high stability. Combined with our own research in this field, we summarize here the recent progress on the synthesis of self-supported electrode materials and their supercapacitance properties. The overall synthetic strategy could be divided into two categories: “top-down” and “bottom-up”. We hope this review is helpful for the development and application of renewable sources in self-supported electrode materials.

Turning An Organic Semiconductor Into A Low-Resistance Material By Ion Implantation, Beatrice Fraboni, Alessandra Scidà, Piero Cosseddu, Yongqiang Wang, Michael Nastasi, Silvia Milita, Annalisa Bonfiglio

Nebraska Center for Energy Sciences Research: Publications

We report on the effects of low energy ion implantation on thin films of pentacene, carried out to investigate the efficacy of this process in the fabrication of organic electronic devices. Two different ions, Ne and N, have been implanted and compared, to assess the effects of different reactivity within the hydrocarbon matrix. Strong modification of the electrical conductivity, stable in time, is observed following ion implantation. This effect is significantly larger for N implants (up to six orders of magnitude), which are shown to introduce stable charged species within the hydrocarbon matrix, not only damage as is the case …

Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu

Doctoral Dissertations

A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.

In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The comparison …

Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker

Theses and Dissertations

The importance of a reliable and safe way to store energy, and allow for on-demand usage, has led to much research in the field of secondary battery development. The thesis herein explores a technology that has shown promising results when implemented in large-scale energy grid applications. Though the technology has proven viable in both load-leveling on existing grids as well as serving to legitimize renewable energy sources, the development of such advanced battery systems is not without challenge. Sodium-sulfur (NaS) secondary cells have shown promising results when implemented in the aforementioned energy storage applications. One of the main drawbacks to …

Chemical And Electronic Structure Of Surfaces And Interfaces In Cadmium Telluride Based Photovoltaic Devices, Douglas Arthur Duncan

UNLV Theses, Dissertations, Professional Papers, and Capstones

The surface and interface properties are of the upmost importance in the understanding, optimization, and application for photovoltaic devices. Often the chemical, electronic, and morphological properties of the films are empirically optimized, however when progress slows, a fundamental understanding of these properties can lead to breakthroughs. In this work, surfaces and interfaces of solar cell-relevant films are probed with a repertoire of X-ray analytical and microanalysis techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), X-ray emission (XES) spectroscopies, and atomic force (AFM) and scanning electron (SEM) microscopies.

Silicon-based devices currently dominate the solar market, which is rather inflexible …

Process Development For Compression Molding Of Hybrid Continuous And Chopped Carbon Fiber Prepreg For Production Of Functionally Graded Composite Structures, Corinne Marie Warnock

Master's Theses

Composite materials offer a high strength-to-weight ratio and directional load bearing capabilities. Compression molding of composite materials yields a superior surface finish and good dimensional stability between component lots with faster processing compared to traditional manufacturing methods. This experimental compression molding capability was developed for the ME composites lab using unidirectional carbon fiber prepreg composites. A direct comparison was drawn between autoclave and compression molding methods to validate compression molding as an alternative manufacturing method in that lab. A method of manufacturing chopped fiber from existing unidirectional prepreg materials was developed and evaluated using destructive testing methods. The results from …

An Approach To Model Plastic Deformation Of Metallic Plates In Hypervelocity Impact Experiments, Shawoon Kumar Roy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Space structures are subjected to micro-meteorite impact at extremely high velocities of several kilometers per second. Similarly, design of military equipment requires understanding of material behavior under extremely high pressure and temperature. Study of material behavior under hypervelocity impact (HVI) poses many challenges since few researchers so far have approached this problem. Material models, equations of the state, and fracture mechanics are not well understood under these conditions.

The objective of this research is to present an approach for studying plastic deformation of metallic plates under HVI conditions. A two-stage light gas gun can be used to simulate these conditions …

The Influence Of Iron On Arctic Thule Migration Patterns, Alina T. Aquino

UNLV Theses, Dissertations, Professional Papers, and Capstones

Arctic scholars have yet to fully understand the reasons behind the migration of Thule culture from the western to the eastern Arctic. This rapid movement across such a vast area into environmentally diverse regions marks a critical period of cultural change that is usually summarized by two theoretical positions. Ecological theories postulated environmental changes placed selective pressures on traditional food sources that required Thule hunters to follow migrating prey. Theories that focused on material acquisition alternately proposed the Thule followed the trail of meteoric iron eastward into northwestern Greenland.

This research sought to examine the eastward Thule migration from another …

Crystalline Phase Change In Steel Alloys Due To High Speed Impact, Muna Slewa

UNLV Theses, Dissertations, Professional Papers, and Capstones

The effect of hypervelocity projectile impact on the crystalline grain structure near the target impact location of A36 steel has been studied. A36 steel is a mostly single phase body centered cubic material (BCC). Impact velocities ranged from 3.54 to 6.70 km/sec. Target materials were studied before and after impact to determine if these impact conditions result in a phase change of the A36. Scanning electron microscopy, electron back-scatter diffraction, and x-ray diffraction methods were used to investigate deformation, lattice defects, twinning, and phase transformation. A limited number of impacted targets made from 304L and HY100 steels were also examined. …

Experimental Investigation And Thermal Modeling On Electro Discharge Drilling Of Pcd, Farnaz Nourbakhsh

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This study presents an experimental investigation and finite element simulation of Electro Discharge Drilling (ED-Drilling) of Polycrystalline Diamond (PCD). PCD has many outstanding properties including uniformly high hardness, high wear resistance and strong corrosion which are the main causes of widely using PCD. While PCD has many advantages and an important role in industrial applications, its high level of hardness and wear resistance cause this material to be difficult to form and machine by using traditional machining methods. EDM as a nontraditional machining process is an effective method among other non-traditional methods for PCDs due to its low cost and …

Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck

Electronic Theses and Dissertations

Little is known about the impact of additive manufacturing in the spare part supply chain. A few studies are available, but they focus on specific parts and their applications only. A general model, which can be adapted to different applications, is nonexistent. This dissertation proposes a decision making framework that enables an interested practitioner/manager to decide whether using additive manufacturing to make spare parts on demand is economical when compared to conventional warehousing strategy. The framework consists of two major components: a general discrete event simulation model and a process of designing a wide range of simulation scenarios. The goal …

Effect Of Processing History And Material Properties On The Growth Of Wrinkle Amplitude, Yu-Cheng Chen

Doctoral Dissertations

Wrinkling has been employed by many organisms to form unique topography, such as fingerprints, gut villi, and surface of flower petal cells. The wavy wrinkle structure provides friction enhancement, surface area increase, optical, and wetting properties improvement. Inspired by Nature, scientists have created wrinkles synthetically and proposed numerous uses for them. However, wrinkling surfaces encounters limitations on achieving massive area and high amplitude-to-wavelength ratio (aspect ratio). The three phase contact line wrinkling technique creates well-defined wrinkles in a continuous fashion, and has great potential to scale-up for massive production. In addition to the velocity dependent adhesion force, we find the …

Development Of Proton Conduction Membranes In Application Of Vanadium Flow Battery, Le-Tu Qingge, Wei-Nan Guo, Ping Liu, Bao-Guo Wang

Journal of Electrochemistry

The polymeric hydrophilic/hydrophobic interactions into membrane formation were introduced. A general and straightforward strategy for preparing membranes with nanometer-scale pores was suggested by utilization of hydrophilic/hydrophobic interactions to generate phase separation and removal of polyion aggregates through water immersion. Poly(vinylidene fluoride) (PVDF) and sodium allyl sulfonate (SAS) serve as the membrane material and pore-generator, respectively, resulting in chemically stable and oxidation-resistant membranes with various potential applications. Following the same procedure invented to produce the laboratory-scale membranes, the scale-up process to manufacture large-area membranes was completed. The obtained membrane exhibited the conductivity of 3.5×10-2 S•cm^-1, thickness of 100 μm, …

Review For Applications Of "Lead Carbon" Batteries In Energy Storage System, Yong-Quan Ma, Ke Ke, Da-Ming Gu

Journal of Electrochemistry

Three types of “lead carbon” batteries are introduced by comparing their advantages and disadvantages. Then their applications in energy storage system (ESS), especially in the field of renewable energy power generation, are discussed. The prospects and potential applications of “lead carbon” batteries in EES for electric power supply system are analyzed by combining the state-of-the-art techniques in this field.

Preparation And Performance Of Lithium-Rich Manganese Layered Materials 0.6li[Li1/3mn2/3]O2·0.4linixmnyco1-X-Yo2(X < 0.6, Y > 0), Hai-Lan Feng, Ya-Fei Liu, Yan-Bin Chen

Journal of Electrochemistry

Lithium-rich manganese based cathode materials 0.6Li[Li_1/3Mn_2/3]O₂•0.4LiNi_xMn_yCo_1-x-yO₂ (x < 0.6, y > 0) were synthesized by carbonate co-precipitation and high temperature solid-state reaction. The structures and morphologies of the as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). The results of high temperature in-situ XRD test show that the lattice parameters change significantly with increasing temperature and Ni content. The cation mixing gets serious and the spinel phase appears in the high Ni content samples when the temperature is up to 800 oC. Under voltages ranging from 2.0 to …

Sulfonated-Graphene/Nafion Composite Membrane For All Vanadium Redox Flow Batteries, Da-Wei Yang, Yan-Qing Dong, Jing-Min Fan, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

Nafion membrane has been widely used in fuel cells due to its good proton conductivity, chemical and mechanical stabilities. However, the well-developed water channels in Nafion membrane have restricted its application in all vanadium redox flow batteries owing to the high permeation of vanadium ions and the cost. In this work, the water adsorption rate, resistivity and transference number of vanadium ions of sulfonated-graphene/Nafion composite membrane were investigated and compared with those of Nafion membrane in an effort to overcome the abovementioned drawbacks. It was found that the area resistivity and permeation rate of sulfonated-graphene/Nafion composite membrane were significantly reduced …

Short Review On Electrochemical Energy Storage, Hong Li, Ying-Chun Lyu

Journal of Electrochemistry

Energy storage is a critical supporting technology in many fields such as energy, information, transportation, and healthcare, aerospace, advanced manufacture, advanced equipment, national security. Electrochemical energy storage technique has been widely applied and is developing continuously. In this article, the energy storage mechanism, technical indicators and technology ready level in electrochemical energy storage are summarized. Mainly based on lithium ion batteries, untraditional electrochemical issues in electrochemical energy storage devices are described from the perspective of fundamental science. These issues deal mainly with thermodynamics, kinetics, size effect, asymmetric system, asymmetric reaction path, surface phenomenon, hybrid ion transportation, and solid state battery. …

Latest Progresses In Vanadium Flow Battery Technologies And Applications, Xiao-Li Wang, Yu Zhang, Hua-Min Zhang

Journal of Electrochemistry

With virtues of high safety, long cycle life, friend environment and state of charge easy monitoring, vanadium flow battery has become an effective technique for large scale energy storage. United States, Japan, Europe and other developed countries are actively promoting the developments of vanadium flow battery technology and related equipments. In this paper, the performance of containerized vanadium flow battery, which was newly developed by Rongke Power (RKP) and Dalian Institute of Chemical Physics, was introduced. The operation data of 5 MW/10 MWh vanadium flow battery energy storage station was displayed. Finally, it is pointed out that reducing the cost, …

Preparations And Properties Of Polybenzimidazole/Polyvinylbenzyl Crosslinked Composite Membranes For High Temperature Proton Exchange Membrane Fuel Cells, Jin-Kai Jin-Kai, Yong-Yi Jiang, Wang-Zhen Wang-Zhen, Xiao-Jin Li, Zhi-Gang Shao, Bao-Lian Yi

Journal of Electrochemistry

In order to increase the chemical stability of polybenzimidazole (PBI) membrane, a highly stable polymer, poly vinylbenzyl chloride (PVBC), was chosen as the macromolecular crosslinker, and 1H-1,2,4-triazol was adopted to prepare the crosslinked PBI-based membranes. The influence of the PVBC amount on membrane characteristic was investigated in detail. The results indicated that the crosslinked structure of the membrane effectively improved the chemical stability, and at the same time, the membrane presented good mechanical property and proton conductivity. The fuel cell performance for the membrane was tested with hydrogen and oxygen single cell without humidification at 150 oC, and the maximum …

Impact Of Water Content On The Performance Of Lifepo4 Based Lithium-Ion Battery, Jun-Ting Niu, Lin Sun, Shu-Wen Kang, Zhen-Wei Zhao, Zi-Feng Ma

Journal of Electrochemistry

Through different dry conditions and measuring by moisture test instrument, cathode pole pieces with different water contents of 0.3‰ ~ 0.7‰ were obtained to prepare lithium-ion batteries. Cycling performance and high rate performance at 1C ~ 5C discharge rates were tested. Moreover, ASR performances of LiFePO4 base lithium-ion batteries after 200 cycles with different water contents were investigated by EIS. The results showed that the cycle performance and rate performance were closely related to the water content of the electrode. When the water content went up to 0.6‰ the cycle stability and rate performance fell. Meanwhile, the internal resistance and …

Application Of Pd/Graphene Modified Electrode In The Detection Of 4-Chlorophenol, Peng Shi, Bo-Xuan Wang, Quan-Lin Song, Hui Wang, Xin Liu, Zhao-Yong Bian

Journal of Electrochemistry

The Pd/graphene composites were synthesized by a modified Hummers method and NaBH4 reduction process, and then were characterized using XRD, SEM, XPS, and TEM. The Pd/graphene modified glassy carbon electrode (Pd/graphene/GCE) was prepared based on this method. Cyclic voltammetry was used to study the optimum operation conditions for the 4-chlorophenol detection. It was shown that the surface of the graphene was smooth and Pd nanoparticles were uniformly dispersed on graphene. The average particle size was calculated to be 6.5 ± 0.05 nm. These nanoparticles exhibited high catalytic activity and sensitivity toward chlorophenols. PBS with a concentration of 0.1 mol?L-1 at …

Research Progress Of Secondary Sodium-Air Batteries, San-Pei Zhang, Zhao-Yin Wen, Jun Jin, Xiang-Wei Wu, Ying-Ying Hu, Mei-Fen Wu

Journal of Electrochemistry

Rechargeable sodium-air batteries have been the focus in the fields of batteries and energy storage recently, owing to their high specific energy density (1600 Wh?kg-1), an equilibrium discharge potential of 2.3 V and earth-abundant sodium element. However, research on sodium-air cells is still in an infant age and presents many scientific issues. Based on recently reported work and our own experience on sodium-based batteries, this review summarizes the research progress related to the critical scientific issues of secondary sodium-air batteries and the application prospect of sodium-air battery.