Chemistry Commons^™

Regional Scale Evidence For Improvements In Surface Water Chemistry 1990-2001, B. L. Skjelkvåle, J. L. Stoddard, D. S. Jeffries, K. Tørseth, T. Høgåsen, J. Bowman, J. Mannio, D. T. Monteith, R. Mosello, M. Rogora, D. Rzychon, J. Vesely, J. Wieting, A. Wilander, A. Worsztynowicz

United States Environmental Protection Agency: Publications

The main aim of the international UNECE monitoring program ICP Waters under the Convention of Long-range Transboundary Air Pollution (CLRTAP) is to assess, on a regional basis, the degree and geographical extent of the impact of atmospheric pollution, in particular acidification, on surface waters. Regional trends are calculated for 12 geographical regions in Europe and North America, comprising 189 surface waters sites. From 1990-2001 sulphate concentrations decreased in all but one of the investigated regions. Nitrate increased in only one region, and decreased in three North American regions. Improvements in alkalinity and pH are widely observed. Results from the ICP …

Synthesis Of Gold Nanoparticles Attached To Polypyrrole Nanofibers, Sunil K. Pillalamarri, Frank D. Blum, Massimo F. Bertino

Chemistry Faculty Research & Creative Works

Polypyrrole is a frequently studied conducting polymer due to its application in sensing and catalysis.1 Polypyrrole is considered among the most promising conductive polymers due to its stability and ease of conversion between conducting and insulating forms.2 Different chemical and electrochemical methods are generally used in the synthesis of polypyrrole.2 Despite many interesting applications, the use of polypyrrole is limited because of difficulty in processing it. Several approaches have been explored to improve the ability to process polypyrrole, including the use of emulsion, inverse emulsion, steric stabilizer, and microemulsion methods.1 Several reports have also been published on the synthesis of …

Copolymers And Blends Of Methyl Acrylate And Acrylic Isobutyl Poss Nanomaterials, Manikantan B. Nair, Frank D. Blum

Chemistry Faculty Research & Creative Works

Ultra-thin polymer films attached to solid substrates (supported films) have attracted significant interest in recent years. Supported films are used in the design of advanced materials like photoresists, lubricants and other electronic devices. Glass transition temperatures (Tgs) of supported polymer films have also been of significant interest. The Tg has been shown to depend on the thickness of the polymer film on the surface and the inherent nature of the surface. The effect of end-grafting of a polymer chain to a surface, on the Tg of the polymer has been studied previously.1 Reports on the study of glass transition behaviors …

Deuterium Nmr Studies Of Segmental Dynamics Of Anopore-Adsorbed Poly(Methyl Acrylate), Macduff O. Okuom, Frank D. Blum

Chemistry Faculty Research & Creative Works

Studies of segmental dynamics of polymers at interfaces provide a basis for understanding the properties of composite materials. Interfacial phenomena in multi-phase systems need to be understood as devices made from multi-phase polymeric systems become smaller. Various techniques have been used to investigate interfacial polymers at the air-polymer-solid interface; for example, ellipsometry,1 X-ray,2 and neutron reflectometry.3 These techniques typically characterize the structure (often the thickness) of the polymer layer and are normally used to determine the glass-transition temperature (Tg) through a break in the thicknesstemperature curve. There have been a few reports where the dynamics of polymers at the surface-air …

Effect Of Plasticizer On Pvac-D3 Dynamics Using 2h Solid-State Nmr, Rakesh R. Nambiar, Frank D. Blum

Chemistry Faculty Research & Creative Works

Poly(vinyl acetate) (PVAc) is an important polymer for use in many applications due to its various bulk and surface characteristics. The structure of poly(vinyl acetate) results in a relatively low glass transition temperature (Tg) and makes it important for processing and applications such as paints, adhesives, thin films and surface coatings. Poly(vinyl acetate) can also be easily plasticized, widening its range of applications. The term "plasticizer" refers to a species that will decrease Tg of a polymer.1 Polymer-plasticizer systems have been studied for years and continue to be of current interest. The effects of polymer-plasticizer interactions2 and plasticizer structure3 on …

Estimation Of Bound Carbonyls In Pmma-R-Ps Copolymers Adsorbed On Silica, Pavan K. Challa, Bing Zhang, Frank D. Blum

Chemistry Faculty Research & Creative Works

The adsorption of random copolymers on solid surfaces is essential for developing good properties in composite materials. A good control and understanding of interfaces allows tuning of the properties of the individual components. Interfacial polymers are important in many industrial applications such as photoresists, protective coatings, metal insulator and semi-conductor insulator junctions, metal-filled polymer composites and polymer-lined metal containers for protective food packaging. The effect of the drying process,1 configuration and tacticity,2 molecular mass, density of surface hydroxyls,3 and adsorbed amounts4 have already been studied for interfacial polymers. The thermal characterization for polystyrene,5 PMMA11 and PMMA-r- PS6 copolymers adsorbed on …

Predicted Properties Of Microhollow Cathode Discharges In Xenon, J. P. Boeuf, L. C. Pitchford, K. H. Schoenbach

Bioelectrics Publications

A fluid model has been developed and used to help clarify the physical mechanisms occurring in microhollow cathode discharges (MHCD). Calculated current-voltage (I-V) characteristics and gas temperatures in xenon at 100 Torr are presented. Consistent with previous experimental results in similar conditions, we find a voltage maximum in the I-V characteristic. We show that this structure reflects a transition between a low-current, abnormal discharge localized inside the cylindrical hollow cathode to a higher-current, normal glow discharge sustained by electron emission from the outer surface of the cathode. This transition, due to the geometry of …

Simulations Of Nanopore Formation And Phosphatidylserine Externalization In Lipid Membranes Subjected To A High-Intensity, Ultrashort Electric Pulse, Q. Hu, R. P. Joshi, K. H. Schoenbach

Bioelectrics Publications

A combined MD simulator and time dependent Laplace solver are used to analyze the electrically driven phosphatidylserine externalization process in cells. Time dependent details of nanopore formation at cell membranes in response to a high-intensity (100kV∕cm), ultrashort (10ns) electric pulse are also probed. Our results show that nanosized pores could typically be formed within about 5ns. These predictions are in very good agreement with recent experimental data. It is also demonstrated that defect formation and PS externalization in membranes should begin on the anode side. Finally, the simulations confirm that PS externalization is a nanopore facilitated event, rather than the …

Segmental Dynamics In Poly(Methyl Acrylate)-D3 On Strongly And Weakly Adsorbing Silica Surfaces, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

The segmental dynamics of a polymer on a solid surface appears to be significantly different than that in bulk. The strength of the interaction between polymer segments and a solid surface is likely to be an important factor affecting the segmental mobility of the polymers. Studies of polymers on a weakly adsorbing surface would provide additional understanding of their motional characteristics on surfaces. In a recent NMR study by Rivillon et al., chain dynamics was seen to be different for samples, even when there was no specific interaction with the surface. Peanasky et al. have found a restricted segmental dynamics …

Fourier Transform Infrared Analysis Of Hydroxyl Content Of Hydrothermally Processed Heteroepitaxial Barium Titanate Films, Sandeep K. Patil, Nipun Shah, Frank D. Blum, M. N. Rahaman

Chemistry Faculty Research & Creative Works

The concentration of hydroxyl (-OH) groups in epitaxial barium titanate (BaTiO3) films (thickness ≈ 200 nm), deposited on single-crystal strontium titanate (SrTiO3) at 150 °C by a hydrothermal technique, was investigated using x-ray photoelectron spectroscopy and Fourier transform infrared (FTIR) spectroscopy. After hydrothermal treatment, a broad FTIR resonance for the hydroxyl groups indicated a significant concentration of surface -OH groups in the films. The as-deposited films were subsequently treated hydrothermally with D2O, and the kinetics of the exchange reaction between -OH incorporated into the film and -OD from the D2O were studied using FTIR. For reactions carried out intermittently, the …

Nmr And Modulated Differential Scanning Calorimetry Of Adsorbed Poly(Methyl Acrylate) On Silica, Frank D. Blum, Burak Metin

Chemistry Faculty Research & Creative Works

The interaction between polymers and solid substrates can be studied by a variety of techniques. The results from different experiments can be affected by the nature of the polymer, surface, polymer-surface interactions and, also, the experiment. A great deal has been learned about the behavior of polymers at interfaces, but there is also much to be learned about the interactions and how they affect the physical properties of adsorbed polymers. In the present study, we report both deuterium nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry (MDSC) of poly(methyl acrylate) (PMA) adsorbed on Cab-O-Sil silica. The focus of this …

Coupled Electrical And Magnetic Properties In (La,Sr)Feo3-Δ, X.-D. Zhou, Qingsheng Cai, Jinbo Yang, M. S. Kim, William B. Yelon, William Joseph James, Y.-W. Shin, B. J. Scarfino, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

This article is aimed at studying the temperature dependence oxygen nonstoichiometry, magnetic moments, Fe³⁺ fraction, Néel temperature and conductivity of (La,Sr)FeO_3-δ. It is found that the magnetic properties in La_0.60 Sr_0.40 Fe_3-δ is determined by Fe³⁺ and its concentration, and the conductance is resulted from Fe⁴⁺ ions, which act as electron holes. Both of magnetic and electrical properties were directly governed by oxygen nonstoichiometry (δ). when δ=0.2, the compound has maximum Fe³⁺, the saturation magnetic moments and Néel temperature are 3.8 µB and 410 °C, both at the highest level, …

Study Of The Electronic Structure Of Cafeo₃, Jinbo Yang, M. S. Kim, Qingsheng Cai, X.-D. Zhou, Harlan U. Anderson, William Joseph James, William B. Yelon

Materials Science and Engineering Faculty Research & Creative Works

We have studied the charge disproportionation phenomenon in CaFeO3 using the local-spin density approximation with the on-site Coulomb interaction parameter U and exchange parameter J. The calculation reveals that the total number of the 3d electrons is about 5.1 for both Fe(1)(Fe5+) and Fe(2)(Fe3+) atoms, and that there are about 0.25 electron holes in the O-2p band. Therefore, the charge disproportionation can be more accurately described as 2d5L(Fe4+)=d5L2(Fe5+)+d5(Fe3+), where L denotes a hole in the oxygen 2p band, instead of 2d4(Fe4+)=d3(Fe5+)+d5(Fe3+). The hybridization between the Fe-3d and O-2p orbitals is stronger for Fe(1) than for Fe(2) due to the shorter …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski

Fuels Campaign (TRP)

This project examines inert fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations are used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of ²³⁹Pu. Ceramics are synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, are investigated in a manner to provide thermodynamic data necessary for …

The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James

Physics Faculty Research & Creative Works

The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1xCuxO3 (0<=x<=0.20) have been studied using neutron diffraction, magnetization, and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R[overline 3]c space-group from 10 K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the MnO bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x>=0.15 samples. The x=0.15 sample shows the highest MR([approximate]80%), which might result from the co-existence of Cu3-Cu2+ and the dilution effect of Cu-doping on the double exchange interaction

University Of Nevada, Las Vegas Transmutation Research Program: Annual Report Academic Year 2004-2005, Anthony Hechanova, Kathy Lauckner

Transmutation Research Program Reports (TRP)

It is my pleasure to present the UNLV Transmutation Research Program’s fourth annual report that highlights the academic year 2004 – 2005. Supporting this document are the many technical reports and scientific papers that have been generated over the past three years.

In the fourth year of our program, we added 11 new research tasks and saw the conclusion of 8 of the initial 16 independent student research tasks started in 2001 and 2002. In all, the program has sponsored to their conclusion 28 M.S. and 2 Ph.D. degrees. The program supported 58 graduate students and 13 undergraduates in 6 …

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

There is an active international interest in lead-bismuth eutectic and similar liquid lead systems because of the relevance to the transmutation of nuclear waste, fast reactors, and spallation neutron sources.

Materials in these systems must be able to tolerate high neutron fluxes, high temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge because the corrosive behaviors of materials in LBE are not well understood. Most of the available information on LBE systems has come from the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy

Transmutation Sciences Materials (TRP)

The primary objective of this task was to evaluate the effects of environmental and mechanical parameters on environment induced degradations of candidate target structural materials for applications in spallation-neutron-target systems. The materials selected for evaluation and characterization were martensitic stainless steels including Alloys HT-9, EP-823, and 422.

Accelerator-driven transmutation systems involve bombarding a target material such as molten lead-bismuth-eutectic (LBE) by a proton beam, thereby producing neutrons. The molten LBE target will be contained in a subsystem structural container made of a suitable material such as Alloys HT-9, EP-823, and 422. During the transmutation process, the target structural material may …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The corrosion of structural materials is a major concern for the use of lead-bismuth eutectic (LBE) systems for nuclear applications such as in transmuter targets or fast reactors. Corrosion in liquid metal systems can occur through various processes, including, for example, dissolution, formation of inter-metallic compounds at the interface, and penetration of liquid metal along grain boundaries. Predicting the rate of these processes depends on numerous system operational factors: temperature, system geometry, thermal gradients, solid and liquid compositions, and velocity of the liquid metal, to name a few. Corrosion, along with mechanical and/or hydraulic factors, often contributes to component failure. …

Development Of A Systems Engineering Model Of The Chemical Separations Process, Yitung Chen, Darrell Pepper, Sean Hsieh

Separations Campaign (TRP)

The chemical processing of used nuclear fuel is an integral component of any strategy for the transmutation of nuclear waste. Due to the large volume of material that must be handled in this first step of the transmutation process, the efficiency of the separations process is a key factor in the potential economic viability of transmutation strategies. The ability to optimize the chemical separation systems is vital to ensure the feasibility of the transmutation program.

Systems analysis, or total systems modeling, is one of the strongest tools available to researchers for understanding and optimizing complex systems such as chemical separations …

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth, Denis Beller

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process based on the traditional …

Development, Fabrication And Study Of Fullerene-Containing Carbon Material (Fcc) For Immobilization Of Iodine: Progress Report #1-4, Michael Savopulo, Boris E. Burakov

Separations Campaign (TRP)

During current reporting period the experiments on synthesis of ceramic-like material by conversion of iodine-doped FCC and activated carbon to Si_xC_y have been completed. Cold pressed granules of FCC and activated carbon were rinsed in water-ethanol solution of tetraethoxysilane (TEOS), Si(OC₂H₅)₄, and then used for further synthesis. All new samples obtained have been studied using precise powder XRD analysis.

Fundamental Chemistry Of U And Pu In The Tbp-Dodecane-Nitric Acid System: Quarterly Report, Kenneth Czerwinski, Cynthia-May Gong, Amber Wright

Separations Campaign (TRP)

The speciation of hexavalent U and tetravalent Pu will be examined in the TBPdodecane- nitric acid systems. This topic is chosen based on data needs for separation modeling identified by the AFCI. Emphasis will be placed on studying the influence of nitrate and acetohydroxamic acid on U and Pu speciation as well as conditions where a third phase forms in the organic phase. The organic phase will be 30 % TBP in dodecane. Equal volumes of aqueous and organic phase will be used. The speciation of the actinides in the aqueous and organic phase will be determined by a number …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 2nd Quarter Report, 2005, Clemens Heske

Fuels Campaign (TRP)

The goal of our project is to investigate interface corrosion processes in TRISO nuclear fuel particles. For this purpose, we are undertaking a detailed study of the interface formation between potential candidates for metallic fission products (Pd, Ag, and Cs), likely to diffuse from the kernel of the TRISO particles, with the TRISO coating layers. As a starting point, we are investigating the Pd/SiC interface and will extend our studies to Ag/SiC during our current summer research campaign. The experimental approach comprises the preparation of metal/SiC interfaces in-situ in our ultra-high vacuum system by electron-beam deposition. In order to understand …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 1st Quarter Report, 2005, Clemens Heske

Fuels Campaign (TRP)

In this project we utilize a combination of state-of-the-art soft X-ray spectroscopies to understand the chemical bonding between metal fission products (Pd and Ag) with coating layers in TRISO fuel particles (SiC and pyrocarbon). We are primarily focusing on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress. In the current first project year, we are beginning these investigations with the Pd/SiC interface, as discussed in the previous two quarterly reports. Our first experiments (both using our lab …

Interaction Between Metal Fission Products And Triso Coating Materials, Clemens Heske

Fuels Campaign (TRP)

The goal of this project is to elucidate the chemical bonding and interface formation of metal fission products with the coating materials used in state-of-the-art TRISO fuel particles. Particular emphasis is placed on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress. Furthermore, the chemical state of some of the metal fission products will be assessed.

This project studies the interface formation of Pd, Ag, and Cs with SiC and pyrolytic carbon. Using the TRISO coating materials (and …

Melting And Solidification Study Of Indium And Bismuth Nanocrystals Using Reflection High-Energy Electron Diffraction, Mohamed K. Zayed

Electrical & Computer Engineering Theses & Dissertations

As technology begins to utilize nanocrystals for many chemical, biological, medical, electrical, and optoelectrical applications, there is a growing need for an understanding of their fundamental properties. The study of melting and solidification of nanocrystals is of interest to fundamental understanding of the effect of reduced size and crystal shape on the solid-liquid phase transition. Melting and solidification of as-deposited and recrystallized indium and bismuth nanocrystals were studied using reflection high-energy electron diffraction (RHEED). The nanocrystals were thermally deposited on highly oriented 002-graphite substrate at different deposition temperatures. The growth dynamics of the nanocrystals was studied using in situ RHEED …

Studies On The Electrochemical Preparation And Electrochemical Properties Of Conducting Polymers——Brief Introduction To The Research Work Of Electrochemistry Of Conducting Polymers In Cas Key Laboratory Of Organic Solids(I), Yong-Fang Li

Journal of Electrochemistry

Conducting polymers have drawn much attention since the discovery of conducting polyacetylene in 1977, due to the novelty and curiosity of their structure and properties as well as their promising applications in many aspects. Among the studies of conducting polymers, the electrochemical preparation and electrochemical properties of conducting polymers are of special importance, because the electropolymerization is a main method for preparing conducting polymer films and the electrochemical properties are the basis for their applications in the fields of electrode materials for batteries, electrocatalysis, electrochromic display, etc. We are one of the earliest research groups in the world to perform …

Preparation And Photo-Catalyst Properties Of The α-Fe2O3-Tio2 Films On Sodium Alginate Polymer, Li-Qin Chen, Huai-Zhen Zhong, Ri-Yao Chen, Xi Zheng, Zhen Chen

Journal of Electrochemistry

Three new nano thin films of α-Fe₂O_3, TiO₂ and α-Fe₂O₃-TiO₂ by doping their powder with sodium alginate polymer were prepared. Surface structure and catalytic activities of the films were characterized by FTIR, XRD, PL, TEM and I-V techniques. The results of UV-visible absorption showed that the methylene blue was mineralized in aqueous of α-Fe₂O₃/SA, TiO₂/SA and (α-(Fe₂O₃))-TiO₂ /SA upon radiation with ultra violet light. α-Fe₂O₃ enhanced their photo-decolorized-activities by doping 15% TiO₂.

Electrochemical Behaviours Of Hemoglobin-Ddab-Modified Powder Microelectrode And The Application Of The Powder Microelectrode In Determination Of Nitric Oxide, Zhi-Mou Guo, Huan Liu, Jian Chen, Wen-Ting Zhang

Journal of Electrochemistry

The electrochemical behaviours of DDAB-Hb-PME were studied in this paper. The (apparent) surface concentration of Hb was enhanced greatly by using the powder microelectrode (technique). NO reacts with Hb and absorbs on the surface of the modified carbon powder. Therefore, the output of the electrode was enhanced greatly by employing PME with higher reaction surface (area). The sensitivity of DDAB-Hb-PME is 3.1 mA/μmol·L^-1·cm², which is much larger than the values obtained with the traditional electrodes. The detection limit is 9 nmol·L^-1 and the linear response range is 9～100 nmol·L^-1.