Physical Sciences and Mathematics Commons^™

17th International Herman F. Mark Symposium: Polypropylene - A Material Of The Future, Otto Vogl, Helga Roder

Otto Vogl

No abstract provided.

Molecular-Dynamics Study Of Phase Transitions In Alkali Azides, M. M. Ossowski, John R. Hardy, Robert W. Smith

Physics Faculty Publications

An account is presented of our studies of the order-disorder phase transitions in KN₃, RbN₃, and CsN₃. These are based on parameter-free interionic potentials based on the Gordon-Kim modified electron-gas formalism extended to molecular ions. We performed static structural relaxations and supercell molecular dynamics and predicted with reasonable accuracy the temperatures for the onset of the transitions. In particular, we address the question of how the N₃^- ions reorient to yield the transitions. We found the existence of NaCl-type high-temperature phases in disordered KN₃ and RbN₃ and argue that this …

Thermal Degradation Of Blends Of Polystyrene And Poly(Sodium 4-Styrenesulfonate) And The Copolymer, Poly(Styrene-Co-Sodium 4-Styrenesulfonate), Qiang Yao, Charles Wilkie

Chemistry Faculty Research and Publications

The thermal degradation of blends and copolymers of styrene with styrenesulfonic acid has been studied using thermogravimetric analysis, TGA/FTIR, and cone calorimetry. The blends have enhanced thermal stability relative to virgin polystyrene but there is no enhancement in thermal stability for the copolymers. Apparently, it is necessary to have adjacent sulfonic acid groups in order to permit the formation of a graphite-like char which can provide thermal protection to the polymer. It is necessary to have a good match in degradation temperatures of the two components if one is to have significantly enhanced thermal stability.

Further Studies On Fire Retardant Polystyrene By Friedel–Crafts Chemistry, Zhitao Wang, David D. Jiang, Charles Wilkie, Jeffery W. Gilman

Chemistry Faculty Research and Publications

The combination of a copolymer of 4-vinylbenzyl alcohol and styrene with 2-ethylhexyldiphenylphosphate (DPP) and with metal chlorides has been studied by TGA, radiative gasification, Cone Calorimetry, and oxygen index measurements. Evidence is presented in support of a cross-linking reaction with the additives and the copolymer, which proceeds through a Friedel–Crafts mechanism. This approach reduces the peak heat release rate (HRR) by 60% as measured in the Cone Calorimeter. There is a significant reduction in the mass loss rate during the thermal degradation, and evidence of char formation is observed in the radiative gasification experiments.

Alkyl Nitrates During The Prophet ’98 Summer Intensive, Kristi A. Ostling

Masters Theses

As part of the PROPHET intensive held at the University of Michigan Biological Station in northern Michigan, a gas chromatography system for making fast-turnaround measurements of C1 to C5 alkyl nitrates was developed and deployed from July 19 to August 21, 1998. Every 30 minutes, samples were automatically acquired on a small Tenax trap made from silicosteel column and injected on a GC column by thermal desorption prior to ECD detection. Tests performed to measure breakthrough and on-trap destruction indicated no breakthrough for C3, C4, and C5 nitrates and excellent stability for these compounds on the trap. Chromatographic resolution of …

Tga/Ftir: An Extremely Useful Technique For Studying Polymer Degradation, Charles A. Wilkie

Chemistry Faculty Research and Publications

Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy, TGA/FTIR, has been used to probe the degradation of several polymeric systems. These include poly(methyl methacrylate) in the presence of various additives, graft copolymers of acrylonitrile-butadiene-styrene and styrene-butadiene with sodium methacrylate and styrene with acrylonitrile, blends of styrene-butadiene block copolymers with poly(vinylphosphonic acid) and poly(vinylsulfonic acid), and cross-linked polystyrenes. Additives may interact with poly(methyl methacrylate) by coordination to the carbonyl oxygen to a Lewis acid and the subsequent transfer of an electron from the polymer chain to the metal atom or by the formation of a radical which can trap the degrading …

Enantioseparation Of Alkylaryl Sulfoxides Using Capillary Zone Electrophoresis, Chad Snyder

Masters Theses & Specialist Projects

Alkylaryl sulfoxides possess a chiral sulfur atom easily identifiable by capillary zone electrophoresis (CZE). Separation of chiral alkylaryl sulfoxides has already been accomplished by modified method of CZE known as micellar electrokinetic chromatography (MEKC). However, no articles have been published on the enantioseparation of alkylaryl sulfoxides using capillary zone electrophoresis.

A series of sulfoxides were synthesized, purified and identified via NMR. Enantioseparation was performed using CZE employing a 10 mmol. Phosphate buffer (pH 4.0, 25% acetonitrile, 2% sulfated-β-cyclodextrin). Synthesis of these sulfoxides will be presented along with the results of the procedure’s optimization. Separation of the sulfoxide enanitomers relies on …

A Study Of The Thermal Properties Of Peti-5/Im7, Yan Tang

Masters Theses & Specialist Projects

PETI-5 (Phenylethynyl-terminated polyimide) is a substance that shows a great deal of potential in the high-speed aircraft and the aerospace industry. PETI-5 has been used for the High Speed Civil Transport (HSCT), a supersonic passenger aircraft in development at NASA. In this project, four staging samples, one fresh sample, one fully cured sample and one partially cured sample were analyzed and compared using thermal analytical techniques. The sample staged at 450°F with full vacuum showed the highest thermal properties among four staging samples. The results indicated that vacuum is helpful in improving the thermal stability of PETI-5. The mechanism of …

The Studies Of The (Photo) Electrochemical Character On The Electrodeposited Silver Indium Selenium Thin Films, Shaoai Xie

Journal of Electrochemistry

A photoelectrochemical cell(PEC) is constructed,using an AgInSe 2 film photoanode made from electrodeposition and a platinium electrode in aqueous polyiodide or polysufide electrolyte. The V oc and I sc of PEC have been tested and measured, and the effect of chemical decoration on the photoanodes also studied.

A Novel Reaction Region Moving Electrode System For Electrochemical Power Sources, Jinkua You, Que Tu, Zhengjian Wang, Jie Sun, Zugeng Lin

Journal of Electrochemistry

In most of practical rechargeable batteries, charging/discharging process is always concerned with phase_transformation in the solid state. Due to the irreversibility of the phase_transformation, the cyclic performance of the rechargeable batteries are limited. In this paper, a novel reaction_region moving counter electrode system is constructed in our laboratory. The electrode system is operated at room temperature and cycled in solid_liquid phase during charging/discharging processes. With this electrode, the metal_complexes are firstly deposited(i.e. charging process) on the nearest working electrode and gradually extended to those another working electrodes several centimeters away from the counter electrode. The deposite is dissolved again into …

The Preparation Of Flexible Polymeric Anode And The Measurement Of Its Protective Ability For Cathodic Protection, Ailing Du, Heming Zhang, Mingzong Zhang

Journal of Electrochemistry

The flexible electrode,whose shape can be changed freely,was made of ethenyl copolymer and conductive component and proper amount of additive for cathodic protection.The resistance of electrode was measured.In low concentration of H 2SO 4,the flexible electrode can be used as auxiliary anode to protect the carbon steel.The protection ability of the flexible auxiliary anode was measured too.

Electrochemical Studies Of Metal Complexes In Solution, Yexiang Tong, Beisheng Kang, Qiqin Yang

Journal of Electrochemistry

The prospectus of electrochemical studies of metal complexes in solution have been introduced as a background of our research work. The electrochemical behaviors of the metal complexes and clusters have been investigated by many kinds of electrochemical methods.The content includes the standard electrode potential and the related equilibrium constant, electrochemical kinetics and the related behavior of structure, electrocatalysis and electrosynthesis of metal complexes. The electrode reaction mechanisms of the complexes have been approached. The methods for measuring some thermodynamic and kinetic parameters of the complexes are also given. Electrochemical studies would provid many kinds of important information for studying the …

Electro Oxidation Of Phenol On Sno_2/Ti Electrodes Prepared By Thermal Oxidation, Qingsong Zhang, Huihuang Wu

Journal of Electrochemistry

A SnO 2/Ti electrode prepared by thermal oxidation was used as the anode for galvanostatic electrolysis in acidic solution containing phenol, the time_dependances of phenol concentration,chemical oxygen demand in solution(COD)and instantaneous current efficiency were determined during electrolysis.The results show that with the SnO 2/Ti anode instead of Pt,the COD significantly decreases at the same charge passage, and average current efficiency of oxidation increases by three times The mechanism for phenol oxidation at two electrodes was discussed.

Study On Electrochemical Reduction Properties Of Nitrobenzene, Chuna Ma, Wenkui Zhang, Hui Huang, Yongping Gan

Journal of Electrochemistry

The electrochemical reduction characteristics of nitrobenzene was extensively investigated by using the techniques such as quasi_steady_state polarization,cyclic voltammetry,fast linear potential sweep method and chronoamperometry in this paper.The electroanalytic properties of Cu,Cu_Hg and Cu_Ni electrodes were evaluated.Based on the study of the transient steping behaviour of nitrobenzene to PAP,the reduction mechanism was discussed.The results showed that the transition steps existed on the electrochemical reduction of nitrobenzene in acidic solution,the reactant is also absorbed on electrodes surface. The control step in the reduction of nitrobenzene was ascribed to the diffusion of nitrobenzene and its electrochemical reductive products in the acid solution.

Investigation Of Sodium Hypophosphite Anodic Oxidizing Behavior In The Process Of Acid Electroless Nickel Deposition, Meiyuan Wang, Yafei Kuang, Yan Xu

Journal of Electrochemistry

The anodic oxidizing behavior of sodium hypophosphite in the process of electroless nickle deposition(pH=5.5) was investigated with the linear potential sweep method and alternating current impedance.The results indicated that,the oxidation of NaH 2PO 2 was a complicated electrochemical process and affected by the concentration of NaH 2PO 2, the temperature of the bath,the sweep rate and the existence of nickel ion. The NaH 2PO 2 electrooxidation reaction was very likely preceded by heterogeneous interface transformation process,which might be the control step of the whole anodic process.

The Electrochemical Behaviors Of Superoxide Dismutase At Promoter Modified Gold Electrode, Xiaqin Wu, Xiaoyun Meng, Zhesu Wang, Zongrang Zhang

Journal of Electrochemistry

The electron_transfer process of superoxide dismutase was investigated by cyclic voltammetry at the 4,4'_dithiodipyridine,L_cysteine,histidine and arginine modified gold wire electrodes repectively.The quasi_reversible behavior was observed at L_cysteine modified gold electrode.An irreversible electrochemical behavior has been observed at hisdinine modified gold wire electrode.

Aes Multi_Layer Structural Analysis Of Si Based Anodic Porous Alumina Films And Studies On Its Formation Mechanism, Junhui Wu, Jianping Zou, Qing Zhu, Ximao Bao

Journal of Electrochemistry

nm aluminum films were deposited onto a p_type,0.5 Ω·cm, 〈100〉 oriented silicon wafers using electron beam evaporation technique.Then,the wafers was immersed in 15 wt% H 2SO 4 for porous_type over_anodization under a constant voltage of DC 60V.During the anodization,the temperature of the electrolyte was maintained at 0 ℃.The obtained samples were investigated by means of transmission electron microscopy,scanning electron microscopy,and AES depth profile for multi_layer structural information.In addition, the basic anodic formation mechanism of the Si_based aluminum films was brielfly discussed.

High Performance Proton Exchange Membrane Fuel Cells, Jingrong Yu, Baolian Yi, Ming Han, Xiaoliang Cheng, Zhigang Shao, Jingxin Zhang

Journal of Electrochemistry

Proton_exchange membrane fuel cells(PEMFC) using a perfluorosulfonic acid proton exchange membrane as an electrolyte can simplify water and electrolyte management.In this paper,the effects of thickness of PEM on the performance of PEMFC were studied.The Nafion_112 PEM and low platinum loading E_TEK electrode yielded very high power density,of the order of 0.95 W/cm 2.The energy_conversion efficiency,the degree of platinum utilization and stability for PEMFC using Nafion 112 and E_TEK electrode were also investigated.

Surface Enhanced Raman Spectroscopic Study Of Scn - Adsorbed At The Copper And Gold Nanowire Arrays, Jianlin A Yao, Guoping Pan, Kuanhong Xue, Yong Xie, Jing Tang, Bin Ren, Dongmei Sun, Bingwei Mao, Zhongqun Tian

Journal of Electrochemistry

Two_dimensional arrays of Cu and Au nanowires have been fabricated by template synthesis method, using the anodic aluminum oxidation films as the template. The morphology of the nanowire array was monitored by atomic force microscope (AFM) in the dissolution processes of the alumina film. Based on the probe molecule strategy, the spectral feature of SCN - adsorbed at the Cu and Au nanowires with different diameters has been investigated by surface enhanced Raman spectroscopy (SERS). The results reveal that the intensity of the SERS bands depends on the length of the exposed nanowires. The C≡N stretching vibration frequency (ν CN …

Characterization And Electrochemical Behaviour Of Ce(Ⅲ) Amino Acid Imidazole Ternary Complexes, Huixia Wu, Zemin Wang, Haifeng Yang, Zongrang Zhang

Journal of Electrochemistry

Two Ce(Ⅲ)_amino acid_imidazole teranry complexe were synthesized,These complexes have the composition of Ce(Trp) 3IM(NO 3) 3·3H 2O and Ce(Phe) 3IM(NO 3) 3 respectively. The IR spectra indicate that the carboxy group of amino_acid and the N atoms of imidazole are coordinated with Ce(Ⅲ) ion.Cyclic voltammetry was used to study the electrochemical behaviour of Ce(Ⅲ) ion,the mixture of Ce(Ⅲ) with ligands,and Ce(Ⅲ) binary or ternary complexes. Within the scan range of -0.1 to 1.10 V (vs.SCE),both of ternary complexes depicted completely irreversible electron transfer process.

Studies On Methods Of Fuel Cells Electrodes Preparation, Jun Gu, Sheng Sui, Guangqiang Li, Zhitong Sui

Journal of Electrochemistry

In fuel cells,the structure of electrodes is an important factor which effect the cell performance.To improve the structure and the performance of electrodes,a new method of providing fuel cell electrodes is proposed in this paper.PTFE(polytetrafluoroethylene) and ethyne black was ground for about half an hour in a high_speed grinder,then the catalyst was added into the grinder and milled for an hour.This milled catalyst was transferred into a mixer followed by the addition of surface_active agent. After a suspension was formed,it was filtered under vacuum condition.Then a thin uniform filter_cake of the catalyst was formed,which was rolled together with a current_collecting …

Prparation Of Nanocrystaline Tio_2(Anatase)With High Thermal And Textural Sability By Electrochemical Method, Daobao Chu, Xingfu Zhou

Journal of Electrochemistry

Titanium alkoxides were prepared by anodic dissolution of metallic titanium in absolute ethanol in the presence of HN(C 2H 5) 2·HCl (electro_conductive additives).The solution was directly hydrolyzed to prepare nanocrystalline of TiO 2 (about 10nm)by a sol_gel process.The precursor gels was calcined at T =450 ℃ and 720 ℃for 30 min,and nanocrystalline of TiO 2 (anatase) with high textural and thermal stability was obtained.FTIR,XRD,TEM,were used to characterize the structure of titanium alkoxides and nanocrystalline of TiO 2.The characteristics of nanocrystalline of TiO 2 was depended on the properties of titanium alkoxides.The Ti(OEt) 4 as a source of titanium yielded the …

Studies Of The Electrode Preparation Of Electrode From Lead Carbonate For Lead Acid Battery Ⅰ The Activation Of The Pme, Zhongxu Dai, Dihua Wang, Junwei Jiang, Yunhong Zhou, Jinyun Zou

Journal of Electrochemistry

Lead carbonate which was an intermediate product in lead hydrometallurgy without pollution of lead vapor and sulfur dioxide was selected as electrode material of lead_acid batteries. In the present work,the performances of PbO 2/PbSO 4 or PbSO 4/Pb electrode transformed from PbCO 3 have been investigated by powder microelectrode technique combined with cyclic voltammetry.The results show that the CV characteristics of either negative or positive electrode prepared from PbCO 3 is as good as that of both electrodes made from lead oxide produced by mill machine,when a powder microelectrode with PbCO 3 transformed into PbSO 4 in 1.0 mol/L H …

Photoelectrochemical Studies On The Tio_2 Nanostructured Porous Film Sensitized By Cyanine Dye, Li Zhang, Maizhi Yang, Xuebin Qiao, Yanzhong Hao, Enqing Gao, Shengmin Cai

Journal of Electrochemistry

The photoelectrochemical behaviors of the TiO 2 nanostructured porous film sensitized by cyanine dye were investigated in this paper.The results showed that the excitaed state level matched the conduction band edge of TiO 2 nanoparticle.Therefore the sensitization of the dye can increase the photocurrent intensity of the TiO 2 nanostructured electrode obviously and results in a red-shift of optical absorption from the ultra_violet region to the visible.As a result,the light_to _electricity conversion efficiency was improved evidently,the maximum value of IPCE has reached 12.1%.

A Gas Analysis Method For Determining The Perchlorate Current Efficiency And Other Applications, Zhigang Shao, Baolian Yi

Journal of Electrochemistry

A method for determining the current efficiency by means of measuring the flow capacity of the cell gas in a perchlorate cell has been proposed. The perchlorate cell system was equipped with an oxygen cathode or a Na + ion exchange membrane. This method is simple and convenient as well as accurate in the evaluation of the perchlorate current efficiency in the perchlorate cell as compared with the traditional methods of analysis. It is useful in the investigation of electrochemical problems with high perchlorate concentration,as well as for the assessment of electrocatalytic performance of anode materials.With an oxygen cathode in …

Subsidence, Mixing, And Denitrification Of Arctic Polar Vortex Air Measured During Polaris, M. Rex, R. J. Salawitch, G. C. Toon, B. Sen, J. J. Margitan, G. B. Osterman, J. F. Blavier, R. S. Gao, Stephen G. Donnelly Ph.D., E. Keim, J. Neuman, D. W. Fahey, C. R. Webster, D. C. Scott, R. L. Herman, R. D. May, E. J. Moyer, M. R. Gunson, F. W. Irion, A. Y. Chang, C. P. Rinsland, T. P. Bui

Chemistry Faculty Publications

We determine the degree of denitrification that occurred during the 1996-1997 Arctic winter using a technique that is based on balloon and aircraft borne measurements of NOy, N2O, and CH4. The NOy/N2O relation can undergo significant change due to isentropic mixing of subsided vortex air masses with extravortex air due to the high nonlinearity of the relation. These transport related reductions in NOy can be difficult to distinguish from the effects of denitrification caused by sedimentation of condensed HNO3. In this study, high-altitude balloon measurements are used to define the properties of air masses that later descend in the polar …

A Study Of Cartenoids Uptake In Human Subjects And Their Metabolites, Yin Chen

FIU Electronic Theses and Dissertations

In this study, a metabolite of lutein was tentatively shown to result from oxidation of lutein by performing a reduction reaction. The result is important evidence that supports the hypothesis that lutein functions as an antioxidant in the human body. In a long term of dietary supplementary study of zeaxanthin in a human subject, the expected increase in the serum concentration of the supplement was accompanied by an increase in serum concentration of several metabolites. A six-month low dose dietary supplementation with lutein in 2 2 human subjects was performed with an expected result in increase of the serum concentration …

Stereoselective Determination Oftrihexyphenidyl In Human Serum By Lc–Esi–Ms, Vladimı́R Čápka, Yan Xu, Yong Hong Chen

Chemistry Faculty Publications

The antiparkinsonian drug trihexyphenidyl (THP) is currently manufactured and administered as a racemate. However, stereochemistry can play significant role in the drug’s pharmacokinetics, biotransformation, metabolism, interaction with cellular and tissue components and overall effect on human body. It is necessary to consider such a drug as a mixture of two compounds (drug enantiomers), with their own effect on the human body. The present paper describes a simple and sensitive LC–MS method for the stereoselective determination of THP in human serum. In this study, the sample was prepared by a solid-phase extraction (SPE) procedure. The enantiomer separation was done using native …

Confined Water In Hydrophobic Nanopores: Dynamics Of Freezing Into Bilayer Ice, Jan Slovak, Kenichiro Koga, Hideki Tanaka, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Molecular dynamics simulations for a thin film of water confined to a slit nanopore are performed in order to investigate the dynamic process of crystallization of the system. The system upon freezing creates a bilayer ice crystal composed of two layers of hexagonal rings. We perform one simulation at T=257 K during which the system remains a supercooled liquid state, and another one at T=253 K during which the system freezes. Many patterns of molecular arrangement are found upon freezing, and an account is given of the origin of multiple peaks in the distributions of binding energy and …

Imaging Point Defects In A Liquid Environment: A Model Afm Study, Kenichiro Koga, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Effects of the liquid on atomic force microscopy (AFM) imaging are examined for a model system consisting of a hexagonal flake of seven Lennard-Jones (LJ) atoms as a multiatom tip, a monolayer of LJ crystal containing a single point defect as a substrate, and three-site model water as the liquid. A previous simulation [Koutsos et al., Europhys. Lett. 26, 103 (1994)] has shown that the true atomic resolution of a point defect cannot be achieved in vacuum by use of the multiatom tip. Here we examine the feasibility of such atomic resolution when both the tip and substrate are immersed …