Chemistry Commons^™

The Study On Fabricating Thin Electrodes For Polymer Electrolyte Membrane Fuel Cells (Pemfc), Yong-Sheng Yang, Jing-Hua Liu, Chang-Peng Liu, Gong-Quan Sun, Chang-Zhi Li, Tian-Hong Lu

Journal of Electrochemistry

To lower platinum loading in electrodes for polymer electrolyte membrane fuel cell, a new thin electrode fabrication technique (TEFT) was developed in this work. A series of low Pt loading electrodes with smooth and uniformed surface were fabricated by the TEFT. As a result, the maximum power density of the cell with platinum loading of 1 mg/cm² and Nafion 117 membrane as electrolyte was up to 0.3 W.cm^-2. Moreover, the effects of PTFE and Nafion content in cathodes on the performance of PEMFC with low Pt loading electrodes (1 mg Pt/cm²) were examined systematically.

Studies Of The Preparation Of Electrodes From Lead Carbonate For Lead-Acid Battery Ⅱ. The Preparation Of Paste Electrodes, Zhong-Xu Dai, Di-Hua Wang, Hao-Hao Ke, Jin-Yun Zou, Yun-Hong Zhou

Journal of Electrochemistry

The positive and negative pastes were prepared by mixing PbCO₃ and H₂SO₄ solution as well as relative additives, respectively. The effects of the various formation methods and the charge/discharge conditions on discharge capacity and active material utilization of both electrodes were examined. The results indicate that the performance of the positive electrode formed at 2.0 mA/cm² is better than that formed at higher current density under the same charge/discharge condition, the PAM utilization reaches 74.4 % under discharging at 2.0 mA/cm²; and the property of the negative electrode formed by unsymmetrical square wave …

Inhibition Of N,N'-O-Phenylen-Bis(3-Methoxysalicylidenimine) On Copper In Halide Solutions, Hou-Yi Ma, Shen-Hao Chen, Zhen-Lan Quan, Lin Niu, Shu-Lan Li

Journal of Electrochemistry

Inhibition of N,N'-o-phenylen-bis(3-methoxysalicylidenimine) (V-o-Ph-V) on corrosion and anodic disslution of copper in neutral NaCl and NaBr solutions was investigated in terms of potentiostatic steady-state polarization and A.C. impedance techniques. The inhibition mechanism of V-o-Ph-V to copper corrosion was interpreted in detail by comparing the electrochemical behaviors of copper in halide solutions with or without V-o-Ph-V. Besides, the inhibition effect of self-assembled V-o-Ph-V film on copper corrosion in NaCl was also studied.

Study On Preparation Of Coarse And Fine γ-Lialo2 Mixed Powder Used For Mcfc Matrix, Hua-Xin Lin, Bao-Lian Yi, Lian-Ying Kong, En-Jun Zhang, Li Zhou, Feng-Xia Wang

Journal of Electrochemistry

Coarse α-LiALO₂ powder was transferred completely to γ-LiAlO₂ at 900 ℃ for ten hours. Fine γ-LiALO₂ powder was prepared by “chloride” synthesis. MCFC matrix was fabricated by mixing the coarse and fine γ-LiALO₂ powder and by tape cast. The out'put voltage of the cell assembled with the matrix was 0.85 and 0.75 V respectively at 200 and 300 mA/cm ², and power density was about 250 mW/cm². The performance of the matrix fabricated with the mixed powder was obviously more advanced than that of the matrix fabricated with only coarse γ-LiALO₂ powder.

Fabrication And Examination Of Reduced Temperatrue Solid Oxide Fuel Cell Using A Supported Thin Ysz Electrolyte Substrate, Yi-Huang Zhang, Yong-Lei Dong, Yi Jiang, Zhi-Gui Lu, Jing-Wang Yan

Journal of Electrochemistry

By using a cost-effective wet process,dense yttria stabilized zirconia (YSZ) films on Ni-YSZ anode substrates have been prepared successfully. The YSZ film was characterized to be around 10 μm in thickness, sufficiently dense, uniform and crack free. A single solid oxide fuel cell fabricated from the supported YSZ film electrolyte on the anode substrate and a LSM cathode prepared on the YSZ film was tested. The power density reached to 0.1 W/cm² at 800 ℃, showing a reasonable performance. Further analysis on both electrodes shows that the anodic overpotential was much larger than IR drop (including YSZ resistance and …

High-Performance Liquid Chromatographic Separation Of The Enantiomers Of Unusual Α-Amino Acid Analogues, Antal Péter, Edit Olajos, Richard Casimir, Dirk Tourwé, Quirinus B. Broxterman, Bernard Kaptein, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

The direct and indirect stereochemical resolution of the enantiomers of ring- and α-methyl-substituted phenylalanines and phenylalanine amides was attempted by high-performance liquid chromatographic methods. The direct separation was carried out on two chiral stationary phases, the crown-ether- based Crownpak CR (+), and the teicoplanin-based Chirobiotic T, while the indirect resolution was performed by applying pre-column derivatization with 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (GITC) and Nα- (2,4-dinitro-5-fluorophenyl)-L-alanine amide (Marfey's reagent, FDAA). The Chirobiotic T column was efficient in the separation of ring- and α-methyl- substituted phenylalanine analogues but was ineffective for the amides of these analogues. The Crownpak CR (+) column separated the ring-substituted …

Hydrogen Bonding In Alcohol Clusters: A Comparative Study By Infrared Cavity Ringdown Laser Absorption Spectroscopy, Robert A. Provencal, Raphael N. Casaes, Katja Roth, Joshua B. Paul, Chris N. Chapo, Richard J. Saykally, Gregory S. Tschumper, Henry F. Schaefer

Chemistry Faculty Research & Creative Works

Infrared cavity ringdown laser absorption spectroscopy has been used to study the O-H stretching vibrations of jet-cooled ethanol and butanol clusters. Three bonded O-H stretches were attributed to the ethanol dimer, indicating the presence of more than one conformer in the molecular beam. One unresolved feature was measured for both the trimer and tetramer. To facilitate spectral assignment, the vibrational frequencies and intensities have been calculated for the ethanol dimer using second-order Moller-Plesset perturbation theory. Three bonded O-H stretches have also been measured for the butanol dimer, suggesting that more than one conformer is present in the molecular beam. Vibrational …

Sol-Gel Ph Sensors And Sol-Gel Metal-Removing Sorbents, Dong Liu

Dissertations and Theses

Sol-gel silica is a porous glasslike material that can be prepared at room temperature. In this work, sol-gel method was employed to develop sol-gel sensors for pH measurement and sol-gel silica sorbents for removal of heavy metals.

Sol-gel pH sensors were prepared by entrapping pH indicators in porous solgel silica films. The feasibility of developing optical pH sensors with linear response over a wide pH range by using mixtures of multiple indicators was demonstrated. Theoretical criteria and experimental procedures for selecting indicators and determining optimum ratios of indicators were discussed. A linear response over 4.5 pH units was obtained for …

Quantum Calculations On The Vibrational Predissociation Of Nebr2: Evidence For Continuum Resonances, Thomas Alex Stephenson, N. Halberstadt

Chemistry & Biochemistry Faculty Works

Quantum mechanical calculations on the vibrational predissociation dynamics of NeBr2 in the B electronic state have been performed and the results compared with both experimental data and other computational studies. For vibrational levels with v less than or equal to 20 we find that the vibrational state dependence of the predissociation lifetimes is in qualitative agreement with experimental measurements, as are the calculated Br-2 fragment rotational distributions. For higher vibrational levels, the B <-- X excitation profiles are well represented by a sum of two Lorentzian line shapes. We attribute this result to the presence of long-lived resonances in the dissociative continuum that are reminiscent of long-lived dissociative trajectories in previous classical studies of NeBr2. (C) 2000 American Institute of Physics. [S0021-9606(00)00205-1].

Degradation Of N-Hexadecane And Its Metabolites By Pseudomonas Aeruginosa Under Microaerobic And Anaerobic Denitrifying Conditions, Chawala Chayabutra, Lu-Kwang Ju

Chemical, Biomolecular, and Corrosion Engineering Faculty Research

A strategy for sequential hydrocarbon bioremediation is proposed. The initial O-2-requiring transformation is effected by aerobic resting cells, thus avoiding a high oxygen demand. The oxygenated metabolites can then be degraded even under anaerobic conditions when supplemented with a highly water-soluble alternative electron acceptor, such as nitrate. To develop the new strategy, some phenomena were studied by examining Pseudomonas aeruginosa fermentation. The effects of dissolved oxygen (DO) concentration on n-hexadecane biodegradation were investigated first. Under microaerobic conditions, the denitrification rate decreased as the DO concentration decreased, implying that the O-2-requiring reactions were rate limiting. The effects of different nitrate and …

Observations Of Particulates Within The North Atlantic Flight Corridor: Polinat 2, September-October 1997, J. D. Paladino, Donald E. Hagen, Philip D. Whitefield, Alfred Raymond Hopkins, Otmar Schmid, M. R. Wilson, Hans Schlager, Peter Schulte

Physics Faculty Research & Creative Works

This paper discusses particulate concentration and size distribution data gathered using the University of Missouri-Rolla Mobile Aerosol Sampling System (UMR-MASS), and used to investigate the southern extent of the eastern end of the North Atlantic Flight Corridor (NAFC) during project Pollution From Aircraft Emissions in the North Atlantic Flight Corridor/Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (POLINAT 2/SONEX) from September 19 to October 23, 1997. The analysis presented in this paper focuses on "the corridor effect," or enhancement of pollutants by jet aircraft combustion events. To investigate the phenomena, both vertical and horizontal profiles of the corridor, and regions …

Lifetime Effects On The Dissociation Of Core-Excited N2 And Co Molecules, N. Saito, A. Hempelmann, F. Heiserq, Oliver Hemmers, K. Wieliczek, J. Viefhaus, U. Becker

Environmental Studies Faculty Publications

Vibrational-resolved ion and ion-pair yield spectra of N₂ and CO taken at their 1s⃗π^* resonance excitations reveal decay-channel-dependent core hole lifetimes. The linewidths of the yield spectra tend to be shortened when the number of electrons ejected in the deexcitation process increases, finally becoming narrower than the total ion yield or absorption natural lifetime width of the core-excited states of N₂ and CO, respectively. In contrast to this, the linewidths of the yield spectra for the singly charged molecular ions, N₂⁺ and CO⁺, are shown to be broader than their corresponding natural linewidths. …

9-Phenyl-3,4,4a,9a-Tetrahydrotriptycene And 9-Phenyl-1,2,3,4,4a,9a-Hexahydrotriptycene, John Masnovi, Shaoming Duan, Ronald J. Baker

Chemistry Faculty Publications

The structure of 9-phenyl-3,4,4a,9a-tetrahydrotriptycene, C26H22, (I), exhibits regiochemistry consistent with a stepwise mechanism for its formation from photocycloaddition of 1,3- cyclohexadiene and 9-phenylanthracene. Bond distances involving the bridgehead C atoms are similar in (I) and the hydrogenated derivative, 9-phenyl-1,2,3,4,4a,9a-hexahydrotriptycene, C26H24, (II), with bonds to the quaternary-C atoms exhibiting significant elongation [1.581 (2) A Ê in (I) and 1.585 (2) A Ê in (II)]. The molecular geometry precludes significant overlap between the phenyl groups and the interannular bonds in both compounds, indicating that the origin of the bond lengthening is steric in nature.

Thermodynamic Stability Of Sn4, Sn5, Sn6, And Sn7 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, R W. Schmude, J E. Kingcade, Karl A. Gingerich

Chemistry Faculty Publications

The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of Sn[sub n] (n=1-7) under equilibrium conditions above liquid tin or a tin-gold alloy, contained in a graphite Knudsen cell. From the all-gas analyzed equilibria the following atomization enthalpies Δ[sub a]H[sub 0][sup °](Sn[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup °](Sn[sub n]), in kJ mol-1, have been obtained: Sn[sub 4], 750.2±14 and 450.6±14; Sn[sub 5], 990.2±22 and 512.3±22; Sn[sub 6], 1349.7±28 and 452.8±28; Sn[sub 7], 1644.2±37 and 460.0±37. The atomization energies are compared with available …

Knudsen Cell Mass Spectrometric Investigation Of The B2n Molecule, Giovanni Meloni, M Sai Baba, Karl A. Gingerich

Chemistry Faculty Publications

High-temperature Knudsen cell mass spectrometry has been used to study the equilibria involving the B2Nmolecule over the Si–BN system. Thermal functions needed in the evaluation of the mass spectrometric equilibrium data have been calculated from available experimental and theoretical molecular parameters. The enthalpy changes for the reactions2B(g)+Si2N(g)=B2N(g)+2Si(g),and BN(s)+B(g)=B2N(g)have been measured. The following atomization enthalpy,ΔaHo0,and enthalpy of formation,ΔfHo298.15,in kJ mol⁻¹, of1045.5±18 and551.3±18 for theB2N molecule have been determined from these reactionenthalpies. Atomization energies of similar molecules have been compared and discussed.

Thermodynamic Study Of The Gaseous Molecules Al2n, Aln, And Al2n2 By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

The Knudsen effusion mass spectrometric method has been employed to measure the equilibrium partial pressures of the Al2N molecule over the AlN–Au–graphite system. Theoretical computations were carried out to determine the structure, molecular parameters, and thermodynamic properties of Al2N. The partial pressures have been combined with the calculated thermal functions to determine the atomization enthalpy,ΔaHo0, and enthalpy of formation,ΔfHo298.15, in kJ mol⁻¹, of 783.2±15 and 342.7±15 for Al2N, respectively. Upper values for the dissociation energy of AlN, Do0(AlN,g)⩽368±15 kJ mol−1, and for the atomization enthalpy of Al2N2, ΔaHo0(Al2N2,g)⩽1402 kJ mol−1 have been obtained. These results are discussed and …

Solidification/Stabilization Of Lead And Chromium With The Aid Of Bagasse As An Additive To Portland Cement, Michael A. Janusa

Faculty Presentations

No abstract provided.

Abstracts Of Student-Faculty Publications

The Corinthian

Abstracts of Student-Faculty Publications

Ground-State Properties And Excited-State Reactivity Of 8-Quinolate Complexes Of Ruthenium(Ii), Dean Johnston

Chemistry Faculty Scholarship

In an effort to explore new systems with highly reducing excited states, we prepared a series of Ru(II) complexes of the type Ru(L)(2)quo(+) (L = bpy (2,2'-bipyridine), phen (1,10-phenanthroline), dmphen (4,7-dimethyl-1,10-phenanthroline), tmphen (3,4,7,8-tetramethyl-1,10-phenanthroline); quo(-) = 8-quinolate) and investigated their photophysical and redox properties. The absorption and emission spectra of the Ru(L)(2)quo(+) are significantly red-shifted relative to those of the parent complexes Ru(L)(3)(2+), with emission maxima in the 757-783 nm range in water. The Ru(L)(2)quo(+) systems are easily oxidized with E(1/2)(Ru(III/II)) values ranging from +0.62 to +0.70 V vs NHE, making the emissive Ru --> phen MLCT (metal-to-ligand charge transfer) excited …

Double Cysteine Mutations In Staphylococcal Nuclease: The Effect Of Artificially Introduced Disulfide Bonds On Protein Structure And Stability, Anna Terry

Inquiry: The University of Arkansas Undergraduate Research Journal

Since a protein's function depends on its structure, basic research in protein structure facilitates the solution of many practical problems, such as the synthesis of more effective medicines. With this larger goal in sight, the purpose of this research project is to understand better the chemical principles that underlie protein structure and stability. Disulfide bonds are a potentially stabilizing feature of many proteins. They may form between cysteine residues in close proximity to one another if the orientation is favorable. Often found in proteins produced by organisms that grow at high temperatures, disulfide bonds may anchor side chains together, making …

Atomization Enthalpies And Enthalpies Of Formation Of The Germanium Clusters, Ge5, Ge6, Ge7, And Ge8 By Knudsen Effusion Mass Spectrometry, Karl A. Gingerich, R W. Schmude, M Sai Baba, Giovanni Meloni

Chemistry Faculty Publications

The high-temperature mass spectrometric method was employed to measure the equilibrium partial pressures of small germanium clusters above liquid germanium contained in a graphite Knudsen cell. These data were combined with new thermal functions, calculated from recent theoretical and spectroscopic molecular parameters, to evaluate the atomization enthalpies and enthalpies of formation of Ge[sub 5]-Ge[sub 8]. Mass spectrometric equilibrium data available in literature were also reevaluated. The following atomization enthalpies, Δ[sub a]H[sub 0][sup o](Ge[sub n],g) and enthalpies of formation Δ[sub f]H[sub 298.15][sup o](Ge[sub n],g), in kJ mol-1, have been obtained: Ge[sub 5], 1313±27 and 548±27, Ge[sub 6], 1649±33 and 583±33, Ge[sub …

Characterization Of Chimeric Lipopolysaccharides From Escherichia Coli Strain Jm109 Transformed With Lipooligosaccharide Synthesis Genes (Lsg) From Haemophilus Influenzae, Nancy J. Phillips, T. J. Miller, J. J. Engstrom, William Melaugh, R. Mclaughlin, M A. Apicella, B W. Gibson

Chemistry Faculty Publications

Previously, we reported the expression of chimeric lipopolysaccharides (LPS) in Escherichia coli strain JM109 (a K-12 strain) transformed with plasmids containing Haemophilus influenzae lipooligosaccharide synthesis genes (lsg) (Abu Kwaik, Y., McLaughlin, R. E., Apicella, M. A., and Spinola, S. M. (1991) Mol. Microbiol. 5, 2475–2480). In this current study, we have analyzed the O-deacylated LPS and free oligosaccharides from three transformants (designated pGEMLOS-4, pGEMLOS- 5, and pGEMLOS-7) by matrix-assisted laser desorption ionization, electrospray ionization, and tandem mass spectrometry techniques, along with composition and linkage analyses. These data show that the chimeric LPS consist of the complete E. coli LPS core …

Solid State Phase Transitions Characterized By Esr And Xas, Juana Vivó Acrivos

Faculty Publications, Chemistry

Measurements of the relaxation time,  of electron systems to a disturbance, by two different spectroscopic methods are examined in detail, with the purpose to establish how the presence of fluctuations near a solid state phase transition are made evident in insulators, conductors and superconductors. The absolute temperature and the relaxation time determine the thermodynamic stability of the electronic system near a phase transition by the Uncertainty Principle. At a given temperature T, Landau and Lifshitz obtain the stability from the lower limit of the uncertainty in entropy in units of the Boltzmann constant, S/kB << 1 when T  >> 3.82 K ps. Magnetic resonance …

Photoabsorption Spectra Of Argon Cation Clusters: Monte Carlo Simulations Using Many-Body Polarization, Jose A. Gascon, Randall W. Hall

Collected Faculty Scholarship

A simple, semiempirical model that includes many-body polarization is used to study the ground and excited stateproperties of Ar+N clusters (N=3–23) at 80 K. For purposes of comparison, a model that does not include many-body polarization is used to study clusters with N=3–27.Monte Carlo simulations are used to calculate the average properties of these clusters. The model is similar to one previously used to study argon cation clusters without many-body polarization. The photoabsorptionspectrum is in good agreement with experiment; in particular, the photoabsorptionspectra for cluster sizes 4–10 do not show the blueshift that is seen with models that do not …

Hammett Correlations Of The Amide Proton Chemical Shift In A Series Of 1-Tosyl-3-(4-Substituted Phenyl)Ureas, Frank L. Setliff, Melody K. Harrison

Journal of the Arkansas Academy of Science

No abstract provided.

Preparation Of An Electrophilic 3-Methylindole Derivative: Difficulties In Forming A Stable, Suitable Material For The Preparation Of Tryptophan, Jason Boggs, Mariah Mcmasters, Robert W. Curley Jr., Michael J. Panigot

Journal of the Arkansas Academy of Science

In an attempt to prepare stereoselectively beta-deuterated tryptophan, N-protected indole-3-methanol compounds were prepared with model studies being done on undeuterated material. Conversion of these compounds to electrophilic species proved exceptionally difficult and resulted in very low yields or recovered starting material only. A summary of the current results utilizing N-tosyl indole-3-methanol will be presented as well as efforts using N-Boc indole-3-methanol.

Spin-Exchange Term In The Solvent Equation Of State Near The Critical Point For Electron Transfer Reactions, Juana Vivó Acrivos

Faculty Publications, Chemistry

Phenomenological Equations of State (EOS) for fluids near their critical point have been obtained using literature compression factor data, Zc = Pc Vc/(n R Tc) = 0.40 to 0.10 in Table I (Pc, Vc/n, Tc are the pressure, volume per n mole, and the absolute temperature of the fluid at the critical point). The objective is to explain the deviations from the van der Waals value, Zc(vdW) = 3/8 (-70 % for molten Se and alkali metals up to 6 % for molten Pb, Hg, and In) by including in the commonly used phenomenological thermodynamic relations a term which explicitly …

Aqueous Equilibria: Acids, Bases, And Solubility. A General Chemistry Laboratory Experiment, Michael A. Janusa

Faculty Publications

We refer to two major types of general chemistry freshman laboratory experiments: discovery and cookbook. The typical Freshman enrolled in general chemistry has the skills to perform an experiment that is somewhere between cookbook and discovery, and we have developed a laboratory experiment that is midway between these extremes. This experiment aids the student's understanding of the concept of aqueous equilibria. In this experiment, students are asked to prepare and measure the pH of a variety of acidic and basic solutions. Students are also asked to calculate pH values from literature dissociation constants and dissociation constants from their experimental pH …

Solidification / Stabilization Of Lead With The Aid Of Bagasse As An Additive To Portland Cement, Michael A. Janusa

Faculty Publications

Solidification/stabilization (S/S) of hazardous waste is a widely used technology; therefore, it is crucial to evaluate its effectiveness and make attempts to improve the technique. A better matrix for S/S of hazardous waste was designed that is effective and economically feasible. This was accomplished by adding bagasse (byproduct of milling or diffusing sugar cane) to the waste/cement matrix. Lead nitrate was used as the model heavy metal waste with a 10or 15% lead by weight to cement loading. Samples were cured for 7, 14, and 28 days at 24°C. Samples containing bagasse typically resulted in TCLP (modified) extract lead concentrations …

Palladium-Catalyzed Carboxylative Coupling Of Allylstannanes And Allyl Halides, Russell J. Franks

Faculty Publications

A three-component carboxylative coupling between allyl halides, allylstannanes, and CO2 to produce allyl esters is catalyzed by Pd and Pt phosphine complexes. Allyl chloride and allyltributylstannane are thus converted to propenyl butenoate in excellent yield. Cross coupling of two different allyl components produces a nearly statistical mixture of all four possible esters. Tentative mechanistic pathways for the catalytic reaction are proposed.