Engineering Commons^™

Production Of Ethanol From Hardwood, Jay Mitchell

Electronic Theses and Dissertations

Diminishing crude oil and natural gas supplies, along with concern about greenhouse gas are major driving forces in the search for efficient renewable energy sources. The conversion of lignocellulosic biomass to energy and useful chemicals is a component of the solution. Ethanol is most commonly produced by enzymatic hydrolysis of complex carbohydrates to simple sugars followed by fermentation using yeast.

C₆H_l0O₅ + H₂O −Enxymes→ C₆H₁₂O₆ −Yeast→ 2CH₃CH₂OH + 2C0₂

In the U.S. corn is the primary starting raw material for commercial ethanol production. …

Reaction Mechanism Of V(Ⅳ)/V(Ⅴ) Redox Couple At Graphite Felt Composite Electrode Bonded With Conductive Carbon Plastic, Xiao-Gang Li, Ke-Long Huang, Liusu-Qin Liusu-Qin, Ning Tan, Li-Quan Chen

Journal of Electrochemistry

The rate-determining step of V(Ⅳ) /V(Ⅴ) redoxreaction was investigated at graphite felt(GF)composite electrode by various techniques: cyclic voltammetry,polarization curve and impedance spectroscopy.Cyclic voltammetry analysis indicated that V(Ⅳ) /V(Ⅴ) redox reaction at GF electrode is quasi reversible.Acertain chemical reaction step is suspected to follow the electron transfer step of this reaction.The Tafel slopevalue(0.124) obtained from the polarization curve agrees well with theoretical value(0.12),which supposingthe electron transfer step was the rate-determining step.Impedance Spectroscopies at various potentials werestudied and simulated by equivalentcircuits.The impedance value of the electron transfer step modified is greatlyhigher than the others,which shows that the electron transfer step is the …

Electrochemical Characterization Of Positive Electrode Material Lini_(1/3)Co_(1/3)Mn_(1/3)O_2 In Different Electrolytes, Jing-Jing Liu, Wei-Hua Qiu, Ling-Yan Yu, Hai-Lei Zhao, Tao Li

Journal of Electrochemistry

Cathode materials LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2) were prepared by low-heating solid-state reaction.The micro-structure and morphology of as-synthesized materials have been investigated by using XRD and SEM.The compatibilities of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2) with purchased LiPF_(6)/ EC+DMC+DEC electrolyte and prepared LiBOB/EC+DEC+EMC electrolyte have also been studied.The Li/LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2) batteries showed excellent electrochemical properties in the LiPF_(6)/ EC+DMC+DEC electrolyte.Reversible discharge capacities of 167、163、163、157、147mAh/g at 0.5C、1C、1.5C、2C、3C rate between 2.7~4.35 V,with stable cycling performances have been obtained.Comparatively,the specific capacity of 160 mAh/g at 0.5C was obtained in LiBOB/EC+DEC+DEC electrolyte,which was just a little lower than that in the other electrolyte.However,the high rate capability of the materials in LiBOB/EC+DEC+DEC was not as …

The Synthesis,Structure And Electrochemical Performances Of Lithium Iron Phosphate, Hui Xie

Journal of Electrochemistry

The lithium iron phosphate cathode materials were synthesized by solid-state reaction combined high-rate ball milling under the temperature ranging from 400 ℃ to 700 ℃.The crystalline structure,morphology of particles,and electrochemical performance of the sample were investigated by X-ray diffraction,scanning electron microscopy and charge-discharge test.The results showed that the sintering temperature had great influences on the crystal structure,morphology and electrochemical performances of LiFePO_(4).The sample synthesized under 600℃ showed the best charge-discharge performances with the first specific discharge capacity of(128.8) mAh/g and the 15~(th) specific discharge capacity of 129.1 mAh/g at 0.1C rate,each charge-discharge cycling efficiency being 99.7%.Also the sample showed good …

Synthesis Of Monolithic Carbon/Nickel Oxide Composite Electrode Material And Cyclic Voltammetry Characteristics, Tian-Ying Guo, Jing-Wei Zhu, Mou-Dao Song, Bang-Hua Zhang

Journal of Electrochemistry

Monolithic carbon/nickel oxide composite materials were synthesized by carbonization of phenol formaldehyde gels that were ion-exchanged with Ni~(2+).Atomic absorption spectroscopy and powder X-ray diffraction technique were used to characterize the chemical composition and physical structure of the materials.The nickel dope amount for this method can reach 5.9 %(by mass).Subsequent cyclic voltammetry experiments indicate that the materials exhibit best capacitive performance at the nickel content of 4.4 %.

Deep Treatment Of Pulping Wastewater Using Three Phase Fluidized Bed Electrode Reactor, Dan Wu

Journal of Electrochemistry

Treatment of pulping wastewater by using a novel electrochemical reactor,i.e.the three phase fluidized bed electrode,reactor were invesigated.The effects of air flow rate,applied voltage,pH value and FeSO_(4) concentration on electrolysis efficiency were investigated.It was clearly shown that the 20 V of voltage,0.3 m~(3) h~(-1) of air flow rate,1000 mg L~(-1) of FeSO_(4) concentration and pH≈2.5 were its best conditions.COD removal could be 70.1% under these conditions.

Electrochemical Behavior Of Buprofezin On Glass-Carbon Electrode, Qi Wang, Chang-Guo Chen

Journal of Electrochemistry

Electrochemical behavior of Bup has been investigated by means of cyclic voltammetry,linear sweep voltammetry,differential pulse voltammetry and square wave voltammetry.The results indicate that the electrochemical behavior of Bup on the surface of glassy carbon electrode is corresponding to a irreversible two-protons and two-electrons process with absrption.The square wave voltammetry for determination of Bup in actual samples has been established.

Facilitated Effect Of Ag To Oxygen Transportation In Pem Fuel Cell Air Cathodes, Hong-Feng Xu, Jian-Hua Dong, Xiang-Li Hou

Journal of Electrochemistry

Silver(Ag) was deposited in the pores of Nafion membrane by ion exchange and succedent hydrogen reduction;the structures of Nafion-Ag membrane were measured by TEM and XRD,the diffusion coefficients of oxygen in Nafion-Ag was determined by electrochemical limited current method.The results showed that after deposited silver,the pores in the Nafion were enlarged by silver grains;the oxygen diffusion coefficient was increased about four times.By introducing silver in the thin Nafion film around the cathode catalyst,the performance of PEM fuel cell have a evident increasing in high current density, which shows the facilitated effects of silver to oxygen transportation in PEM fuel cell.

Structure And Electrochemical Characteristics Of Lifepo_4 Prepared By The Polyacrylates-Pyrolysis-Reduction Method For Li-Ion Batteries, Li-Hong Yu, Yu-Liang Cao, Xiao-Fei Zhang, Han-Xi Yang, Xin-Ping Ai

Journal of Electrochemistry

The cathode material of olivine LiFePO_(4) was prepared by a novel method of polyacrylate-pyrolysis-reduction.XRD demonstrates that the material have the olivine structure.SEM photo shows an average particle-size of about 100 nm with a well distribution.Electrochemical test of cycling at a constant current reveals the discharge capacity of 138 mAh/g and a good cycling stability.It is a novel practicable technology to prepare LiFePO_(4) by using polyacrylate-pyrolysis-reduction method.

Stm Tip-Induced Nanostructuring-Replacement Method To Construct Pt Surface Nanostructures, Jin-Gang Wang, Jing Tang, Zhao-Bin Chen, Bing-Wei Mao

Journal of Electrochemistry

STM tip-induced surface nanostructuring based on "Jump-to-contact" mechanism is a nanostructuring technique that has the highest resolution in aqueous solutions.However,for metals that have high cohesive energy,atoms would transfer from surface to tip instead,which limits the wide application of this technique.In this paper,we present a two-step Nanostructuring-Replacement method to construct metal nanoclusters that cannot be obtained directly via the "Jump-to-contact" mechanism.The method is demonstrated to construct Pt nanoclusters that are of great interest in catalysis and electrocatalysis but cannot be constructed via the "Jump-to-contact" mechanism.Since Cu is the most intensively studied and successful system in the tip-induced nanostructuring,it is utilized as …

Preparation And Electrochemical Property Of Bam Boo-Shaped Silicon Nanotubes, Zeng-Tao Liu, Yan-Peng Fu, Chen Li, Yong Yang

Journal of Electrochemistry

A novel 1D bamboo-shaped silicon nanotubes was synthesized by chemical vapor deposition with Au catalyst and their electrochemical properties were primarily studied.The results showed that these silicon nanotubes were amorphous with the length about tens micrometer and the diameter about one hundred nanometer.Cyclic voltammetry studies showed that Li ions could intercalate into such silicon nanotubes at two location,i.e.,from the conjoint location and the wall of the hole.Meanwhile,the bamboo-shaped structure could help release the expansion of volume,which is usually serious in the lithium batteries.

Preparation And Electrochemical Characterization Of Anatase Tio_2 Nanotubes, Bin Cao, Jin-Wei Xu, Ling-Hong Ding, Wei-Feng Zhang

Journal of Electrochemistry

Titanium oxide nanotubes were prepared by hydrothermal treatment of anatase-type TiO_(2) powders and NaOH solution in an autoclave.Transmission Electron Microscopy and X-ray Diffraction showed that the product is anatase-type TiO_(2) nanotubes.The constant charge-discharge current and cyclic voltammetry exhibited the TiO_(2) nanotubes have a large initial lithium insertion capacity of 260 mA·h/g and good reversibility.This study indicates that TiO_(2) nanotubes might be a good negative electrode materical for second lithium battery in the future.

Fabrication Of Gold Electrode Array Based On Co_2 Laser Ablation, Wei Zhang, Jiang-Qun Xiao, Yong-Liang Zhou

Journal of Electrochemistry

A rapid process is described to produce single or multiple electrodes of any shape based on CO_(2) laser ablation for microfluidic chip.The method is as follow: coating a kind of material as sacrifice layer on a piece of glass with sputtered Cr and Au;designing the needed pattern on a computer;selecting proper parameters and ablating with CO_(2) laser;wiping of Au/Cr and sacrifice layer,and obtain electrodes at last.The microfluidic chip was gotten by reversely bonding with a piece of PDMS,and sealing around with PDMS prepolymer.The mask' effect is the main factor that influencing electrode quality.The width of electrodes could be 100 μm.Demonstrated …

Fabrication And Characterization Of Gadolinium Hexacyanoferrate Modified Electrode, Yan-Mao Shi, Pan Du, Ping Wu, Yao-Ming Zhou, Chen-Xin Cai

Journal of Electrochemistry

A new electroactive polynuclear inorganic compound of rare earth metal hexacyanoferrate,gadolinium hexacyanoferrate(GdCHF),was prepared by electrochemically deposition on the surface of a glassy carbon electrode with a potential cycling procedure.The result of SEM indicated that the GdHCF was in the form of particles adhered on the surface of electrode.There were two different shapes and sizes of GdHCF forming on the surface of electrode.FTIR spectrum of GdHCF showed a very strong and sharp peak,which located at 2062.5 cm~(-1) and corresponded to the stretching vibration of the C≡N group in the GdHCF.The cyclic voltammetric results indicated that the GdHCF/GC electrode exhibited two pairs …

Synergistic Functions Of Trimethl Phosphate And Vinylene Carbonate As Additives For The Li-Ion Batteries, Zhi-Yuan Tang, Yan-Bing He, Quan-Sheng Song, Yu-Hong Chen, Yuan-Gang Liu, Qiang Liu

Journal of Electrochemistry

The cooperative effects of trimethl phosphate and vinylene carbonate as additives for Li-ion batteries are investigated by using the cyclic voltammetry,electrochemical impedance spectroscopy and scanning electronic micro-photographs.The results show that the combination application of TMP and VC as additives for Li-ion batteries not only enhances safety of the batteries,but also improves their cycling performance.The reason may be ascribed to firstly VC being reduced and the reduction product polymerized to form excellent solid electrolyte interface(SEI) layer on the surface of graphite electrode during the first charge and discharge process,which prevents effectively the decomposition of TMP on the surface of the graphite …

Novel Electrochemical Method For Synthesis Of Nanostructured Materials Of Noble Metals Based On Poly(N-Vinylpyrrolidone) (Pvp), Wei Pan

Journal of Electrochemistry

Gold nanocrystals with controllable size were synthesized through a simple electroreduction method using poly(N-vinylpyrrolidone)(PVP) of different polymerization degree as both stabilizer and shape-controller for gold nanoclusters.Individual gold nanoparticles spontaneously assembled into the wire-and ring-shaped nanoparticle aggregates depending on the PVP's dynamic stretching and curling,and precursor nanoparticles grew into flat,single-crystalline nanoprisms with thickness of dozens of nanometers based on the oriented aggregation between particles.Besides,core-shell Au/Ag nanoparticles were conveniently synthesized through two-step electroreduction of noble metal ions in the presence of PVPK30.The electrochemical synthetic method based on PVP provides a new path for preparation of noble metal nanostructured materials with different shape …

Phase-Transfer Technique For Polymer-Protected Noble Metal Nanoparticles, Xing-Li Feng

Journal of Electrochemistry

A novel phase-transfer method was developed based on the decrease of PVP's solubility in water with increasing temperature,by means of which PVP-protected gold,silver and platinum nanoparticles can be conveniently transferred from aqueous phase to 1-butanol phase.Monodispersed metal nanoparticles were electrochemically synthesized at first in the aqueous,and then 1-butanol of appropriate volume was added to the aqueous phase.Heating the oil-water mixture to 80 ℃ under vigorous stirring would make metal nanoparticles leave the aqueous phase and enter into the 1-butanol phase,with high phasetransfer efficiency and without aggregation between nanoparticles.An electrochemical method to synthesize metal nanoparticles in the oil-water mixtures was further …

Study Of The Electrooxidation Of Glycerol On Oxide And Pd/C Composite Catalysts, Zhi-Yuan Yan, Chang-Wei Xu, Pei-Kang Shen

Journal of Electrochemistry

Oxide and Pd on carbon composite catalysts have been prepared by intermittent microwave heating(IMH) method.The performance of the catalysts for glycerol oxidation in alkaline solution is studied by electrochemical techniques.It is shown that the Pd/C catalyst is active for glycerol electrooxidation.However,the oxide-Pd/C catalysts are even better in terms of the onset potential that is more negative and peak current density.The ratio of oxide to Pd is optimized according to the electrochemical measurement.The results reveal that the addition of oxide into the Pd/C induces the synergistic effect for glycerol electrooxidation.

Electrochemical Properties Of The Modified Carbon Nanotubes, Chun-An Ma

Journal of Electrochemistry

Powder micro-electrodes were prepared from raw carbon nanotubes and carbon nanotubes modified by carboxyl.The electro-reduction properties of both the raw and open-ended carbon nanotubes in p-Nitrophenol solution were investigated.The FTIR spectrum result indicated that the functional groups are successfully fixed on the surface of the carbon nanotubes after nitric acid treatment.The cyclic voltammetry results show that the electrochemical activity of carboxyl-modified carbon nanotubes was improved.The mechanism of electro-(reduction) for the carbon nanotubes after acid treatment was discussed.

Posterminaries: After Nabarro, Alexander H. King

Alexander H. King

With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.

Oxidized Derivatives Of Ω-3 Fatty Acids: Identification Of Ipf 3Α-Vi In Human Urine, John A. Lawson, Seongjin Kim, William S. Powell, Garret Gerald A. Fitzgerald, Joshua Rokach

Chemistry and Chemical Engineering Faculty Publications

Isoprostanes (iPs) are prostaglandin-like molecules derived from autoxidation of polyunsaturated fatty acids (PUFAs). Urinary iP levels have been used as indices of in vivo lipid peroxidation. Thus far, it has only been possible to measure iPs derived from arachidonic acid in urine, because levels of iPs/neuroprostanes (nPs) derived from ω3-PUFAs have been found to be below detection limits of available assays. Because of the interest in ω3-PUFA dietary supplementation, we developed specific methods to measure nPF4α-VI and iPF3α-VI [derived from 4,7,10,13,16,19-docosahexaenoic acid (DHA) and 5,8,11,14,17-eicosapentaenoic acid (EPA)] using a combination of chemical synthesis, gas chromatography/mass spectrometry (GC/MS), andliquid chromatography tandem …

Anaerobic Catalytic Oxidation Of Hydrocarbons In Moving Heat Waves. Case Simulation: Propane Oxidative Dehydrogenation In A Packed Adiabatic V-Ti Oxide Catalyst Bed, Andrey N. Zagoruiko

Andrey N Zagoruiko

The model simulation study has shown that the anaerobic process of oxidative dehydrogenation of propane under periodic alteration of feeding between propane and air may be realized in adiabatic catalyst beds in stable continuous cyclic mode in two-reactor scheme. In case of appropriate choice of process parameters (cycle duration, feeding flow rates) the process appears to be autothermal, i.e. it does not require any inlet gas preheating for stable operation. Compared to similar steady-state adiabatic process, the proposed process is characterized with much lower maximum catalyst temperatures, giving the way to process pure propane without diluting it with inert gases, …

Semicrystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development And Macromolecular Design, Atsushi Hotta, Eric W. Cochran, Janne Ruokolainen, Vikram Khann, Glenn H. Fredrickson, Edward J. Kramer, Yong-Woo Shin, Fumihiko Shimizu, Anna E. Cherian, Phillip D. Hustad, Jeffrey M. Rose, Geoffrey W. Coates

Eric W. Cochran

We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic poly propylene-block-regioirregular poly propylene-block- isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90% elastic recovery at …

Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai

Kaitlin M. Bratlie

Catalytic hydrogen/deuterium exchange on a platinum (111) single crystal and its poisoning with carbon monoxide was studied using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), sum frequency generation vibrational spectroscopy (SFG), and mass spectrometry under reaction conditions at pressures in the mTorr to atmospheric range. At 298 K and in the presence of 200 mTorr of hydrogen and 20 mTorr of deuterium the surface is catalytically active, producing HD with activation energy of 5.3 kcal/mol. Addition of 5 mTorr of CO stops the reaction completely. In situ STM images reveal an ordered surface structure of chemisorbed CO. At 353 …

Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) vibrational spectroscopy and high-pressure scanning tunneling microscopy (HP-STM) have been used in combination for the first time to study a catalytic reaction. These techniques have been able to identify surface intermediates in situ during benzene hydrogenation on a Pt(111) single-crystal surface at Torr pressures.

Afci Quarterly Input – Unlv July 1 Through September 30, 2006, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt(100) and Pt(111) …

Posterminaries: The Scales Of Judgement, Alexander H. King

Alexander H. King

Materials scientists are generally well-versed in physics, and physics, above all, is a science of measurements. The first instinct of a physicist is to parse a problem in terms of its measurables in the dimensions of mass, length, and time, and it is the shifting of attention down the scale of length that particularly characterizes our present times as the Nano Age.

Calcined Temperatures Influence On Synthesis And Electrochemistry Charactarization Of Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_(2) For Li-Ion Batteries, Li-Qin Wang, Li-Fang Jiao, Hua-Tang Yuan

Journal of Electrochemistry

Layered Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_(2) materials have been prepared by a solid-state pyrolysis method.Experiments of XRD,SEM,cyclic voltammetry and charge/discharge cycling were carried out.It can be learned that when calclined at 800 ℃,the sample showed the highest first discharge capacity of 178.8 mAh·g~(-1) at a current density of 20 mA/g in the voltage range 2.3~4.6 V.

Investigation On The Resistance To Electrochemical Oxidation Of Carbon Nanotubes With Various Diameters, Yu-Yan Shao, Ge-Ping Yin, Yun-Zhi Gao, Peng-Fei Shi

Journal of Electrochemistry

The resistance to electrochemical oxidation of multi-wall carbon nanotubes(CNT) with various diameters is investigated by applying a fixed potential of 1.2 V(RHE) for 120 h in 0.5 mol L~(-1) H_(2)SO_(4).The oxidation current of CNTs decreases with their diameters,but CNTs between 10~20 nm in diameter(D1020) shows the lowest oxidation current.XPS analysis shows that,after oxidation,the increase in surface oxygen for D1020 is the smallest,implying that the oxidation degree for D1020 is the lowest.The conclusion can be reached that CNTs between 10~20 nm in diameter are the most resistant to electrochemical oxidation.The difference in electrochemical stability of CNTs is attributed to the difference …