bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of [HCO3-+CO32−[ on Corrosion Crevice Repassivation Potential of Carbon Steel in Simulated Bentonite Environment
Authors: Fukuda Takanori , Akashi Masatsune
Published: April 2011

In order to evaluate the localized corrosion susceptibility of carbon steel in water containing bentonite, the critical pH for depassivation, pHd, the critical potential for crevice corrosion, ERCREV, and the free corrosion potential, Esp, were determined in simulated aqueous solutions of 1 to 100 mmol/L [HCO3- - CO32−], 1 to 1000 mmo!/L [NaCI], and pH of 7 to 12. The Following results were obtained; 1)ER, CREV. increases with increasing [HCO3− CO32−] concentration. The relationship can be described as a function of the ratio of [CI-I HCO3−- CO32−], 2)The Esp increases with increasing pH in the passive region, and 3)ThepHd shows [HCO3− - CO32−] concentration dependency. This paper also discusses the relationship between critical initiation potential for crevice corrosion of carbon steel, [CI-], and [HCO3− CO32−] anion. The crevice corrosion that occurs on passivated metals and alloys is characterized by determinable critical initiation potential that can be induced in a potential range nobler than its critical potential.
Coprecipitation of Sr, Ni and U with CaCO3: An Experimental Study
Authors: Carlsson Torbjörn , Aalto Hannu
Published: April 2011

At the Finnish candidate sites for a nuclear waste repository, calcite (CaCO3) is a common fracture mineral that may participate in coprecipitation processes. The objective of this preliminary work was to study the coprecipitation of the trace elements Sr, Ni, and U with CaCO3 under controlled conditions. The experiments were made in a titration vessel at room temperature under pure N2 or a 0.1 % CO 2/N2 mixture. The water phase contained CaCl2 (0.01M) and NaCl (0.05 M) to which trace amounts of Ni2+, Sr2+ and UO22+ were initially added. CaCO3 was precipitated by the addition of Na2CO3 and the use of CaCO3 seed crystals. When about 10−4 mol of precipitate had formed, the solution and solid phases were analysed with ICPMS. The results seem to indicate that Ni coprecipitated with CaCO3 under the experimental conditions, while U did not. In the case of Sr, further data are needed in order to make any conclusions from the experiments.
Durabilities and Microstructures of Radioactive Glasses for Immobilization of Excess Actinides at the Savannah River Site
Authors: Bibler N. E. , Ramsey W. G. , Meaker T. F. , Pareizs J. M.
Published: April 2011

This paper presents results of an investigation of the microstructures and durabilities of glasses for immobilization of excess Pu, Am, and Cm at the Savannah River Site (SRS). The glasses investigated had compositions based on commercial lanthanide glasses developed in the 1930's. All the glasses were prepared remotely in shielded cells and the analyses performed using instruments in radio hoods or benches. Durabilities were measured using the ASTM C-1285 standard leach test (PCT). Results for three glasses are presented. Two glasses contained 15 and 7 wt.% Pu, respectively. The third glass contained Am and Cm. The 15 wt% Pu glass was not completely amorphous and contained crystals of undissolved PuO2 and as well as dissolved PuO2. The 7 wt% Pu glass was completely amorphous. The Am/Cm glass contained <1 wt% actinides and was homogenous. The PCT tests for the Pu glasses indicated that B and Ba were leached congruently. Sm and Pu were leached at slower rates. In some cases release rates for specific Ba, Sm, and Pu isotopes were measured by analyzing the leachates by mass spectroscopy. For the Am-Cm glass release rates for B and Ba were equal indicating congruent dissolution. All three glasses were 25 to 50 times more durable than the borosilicate glasses developed at SRS for immobilization of the fission product HLW resulting from reprocessing operations at SRS.
Preparation of Titanium Hexacyanoferrate Microspheres (Diameter <70 μm) by Water Extraction Variant of Sol-Gel Process and its Application to Sorption of 137Cs from Nuclear Reactor Cooling Water
Authors: Deptula A. , Chmielewski A. G. , Lada W. , Olczak T.
Published: April 2011

Titanium hexacyanoferrate microspheres (diameter <70km) were obtained in the following steps: (1) extraction of chlorides from an aqueous solution of TiCl4 with long chain amine -Primene JMT- in paraffin diluent (the resulting sol has the concentration 320 g TiO2/dm3 and the mole ratio Cl-: Ti4+ = 1.83); (2) blending of titania sol with an aqueous solution of K4 Fe(CN)6. 3H2O (280 g/dm3) in order to obtain final sols with Fe(CN)64-: Ti4+ mole ratio of 0.05 - 0.1; (3) formation of multicomponent sol emulsion in 2-ethylhexanol-1 containing I vol. % of Ethomen S/15 (EH), (4) gelation of emulsion drops by extraction of water with partially dehydrated EH; (5) filtration and washing with acetone; (6) drying at 140°C using a special procedure elaborated on the basis of TG and DTA studies.

The final product is insoluble in water and exhibits high sorption efficiency of 137 Cs.
Natural Analog Support for Unsaturated Transport Modeling Using Data from the Akrotiri Archaeological Site
Authors: Murphy William M. , Pearcy English C.
Published: April 2011

A review of the natural analog study at the Akrotiri archaeological site is provided with regard to its use in support of long-term predictive modeling of chemical transport. Evidence for a plume of contaminants was collected using samples taken from the area under the location where artifacts were buried in silicic tuff for 3600 years. A transport model was developed using site characterization data, but no data for the plume. Qualitative data from the field support the model result that flux of metals from the artifacts was small. However, transient transport characteristics and the role of notable system heterogeneities and complexities were not fully represented by the model. The Akrotiri natural analog study indicates that long term releases and transport may be limited in an unsaturated repository site, but releases may be strongly affected by unknown processes or processes that are neglected in simplified models.
Uranium-Series Ages of Secondary Uranium Minerals with Applications to the Long-Term Evolution of Spent Nuclear Fuel
Authors: Finch R. J. , Suksi J. , Rasilainen K. , Ewing R. C.
Published: April 2011

Uranium-series activity ratios for U(VI) minerals from the Shinkolobwe mine in southern Zaire indicate that these minerals have not experienced significant preferential loss of uranium since their formation more than 100,000 years ago. The minerals examined include rutherfordine, UO2CO3, schoepite, [(UO2)8O2(OH)12]·12H2O, becquerelite, Ca[(UO2)6O4(OH)6]·8H2O, and uranophane, Ca[(UO2)2(SiO3OH)2]·5H2O. No correlation between mineral species and mineral age was evident. The oxidative dissolution of primary uraninite (UO2+x) has maintained ground waters supersaturated with respect to all of the secondary U(VI) minerals, providing an inexhaustible source of dissolved U6+ for mineral formation and growth. As long as uraninite persists in an oxidizing environment, the assemblage of secondary U(VI) phases is determined by local ground water chemistry (including transitory changes), but not necessarily a unidirectional reaction path towards equilibrium with U(VI) minerals of lower solubility. Thus the Shinkolobwe mine displays a complex assemblage of U(VI) minerals that reflects variations in the availability of dissolved elements besides U. Similarly, for a geologic repository exposed to oxidizing waters, the assemblage of corrosion products that will form during the corrosion of spent UO2 fuel is likely to be as complex as mineral assemblages found in natural uranium deposits under similar conditions.
Natural Occurrence and Stability of Pyrochlore in Carbonatites, Related Hydrothermal Systems, and Weathering Environments
Authors: Lumpkin Gregory R. , Mariano Anthony N.
Published: April 2011

Stoichiometric and non-stoichiometric (defect) pyrochlores crystallize during the magmatic and late magmatic-hydrothermal phases of carbonatite emplacement (T > 450–550 °C, P < 2 kb). Defect pyrochlores can also form at low temperatures in laterite horizons during weathering. After crystallization, pyrochlore is subject to alteration by hydrothermal fluids (T ∼ 550-200°C) and ground water. Alteration occurs primarily by ion exchange of low valence A-site cations together with O, F, and OH ions. The high valence cations Th and U are generally immobile; however, we have documented one example of hydrothermal alteration involving loss of U together with cation exchange at the B-site in samples from Mountain Pass, California. During laterite accumulation, the cation exchange rate of pyrochlore greatly exceeds the rate of matrix dissolution. The exceptional durability of pyrochlore in natural environments is related to the stability of the B-site framework cations. In carbonatites, defect pyrochlores may contain significant amounts of Si (up to 7.6 wt% SiO2) which is negatively correlated with Nb.
Postglacial Matrix Diffusion in a Boulder Sample
Authors: Rasilainen K. , Suksi J. , Hellmuth K.-H. , Lindberg A. , Kulmala S.
Published: April 2011

A boulder sample was studied for its unusual U content. Analyses of U-series nuclides within the rock matrix perpendicular to an assumed fracture face show abrupt pulse-like concentration distributions with very low concentrations of U daughters. Both Th-230/U-234 and Pa-231/U-235 activity ratios are low, indicating recent U accumulation into the rock. Matrix diffusion is tested as a possible cause for the experimental observations. We assume that the diffusion process was triggered and controlled by rock expansion, strong mixing of different water types and rapid land uplift at the end phase of the last glaciation.
An Early Review of the Performance Assessment in the Draft Compliance Certification Application for the Waste Isolation Pilot Plant
Authors: Lee William W.-L.
Published: April 2011

On March 31, 1995, tlhe IT. S. Department of Energy filed a draft application for certification of compliance with I the U. S. Environmental Protection Agency (USEPA) to show the Waste Isolation Pilot Plant's compliance with the USEPA's environmental standards, making the application the first of its kind. Demonstration of compliance is by performance assessment. This paper is an early review of the performance assessment in the draft application, by the Environmental Evaluation Group, an oversight group. The performance assessment in the draft application is incomplete. Not all relevant scenarios have been analyzed. The calculation of potential consequences often does not use experimental data but rather estimates by workers developing additional data. The final compliance application, scheduled for October 1996. needs to consider additional scenarios, and be fully based on experimental data.
Uncertainties in Nuclide Releases for a High-Level Waste Repository Backfill With Smectite Illitization
Authors: Hatano Y. , Hatano N. , Suzuki A.
Published: April 2011

Uncertainties in nuclide release calculations, based on the uncertainty in illitization rate for smectite backfill have been studied. This paper has three new features: (i) an analytical solution with temporal parameter changes, (ii) uncertainty study with respect to the rate of temporal changes, and (iii) using various data of illitization.

We show the following in this paper: (1) The uncertainty in nuclide releases is enhanced greatly in the case where the illitization period coincides with the transition time from solubility-limit source to exponentially decaying source; (2) The uncertainty in the retardation factor may have been overestimated in previous static analyses, leading to conclusions that the illitization problem is more vexing than it really is.
Scientific Basis for Storage Criteria for Interim Dry Storage of Aluminum-clad Fuels
Authors: Sindelar R. L. , Peacock H. B. , Lam P. S. , Iyer N. C. , Louthan M. R. , Murphy J. R.
Published: April 2011

An engineered system for dry storage of aluminum-clad foreign and domestic research reactor spent fuel owned by the United States Department of Energy is being considered to store the fuel up to a nominal period of 40 years prior to ultimate disposition. Scientifically-based criteria for environmental limits to drying and storing the fuels for this system are being developed to avoid excessive degradation in sealed and non-sealed (open to air) dry storage systems. These limits are based on consideration of degradation modes that can cause loss of net section of the cladding, embrittlement of the cladding, distortion of the fuel, or release of fuel and fission products from the fuel/clad system. Potential degradation mechanisms include corrosion mechanisms from exposure to air and/or sources of humidity, hydrogen blistering of the aluminum cladding, distortion of the fuel due to creep, and interdiffusion of the fuel and fission products with the cladding.

The aluminum-clad research reactor fuels are predominantly highly-enriched aluminumuranium alloy fuel which is clad with aluminum alloys similar to 1100, 5052, and 6061 aluminum. In the absence of corrodant species, degradation due to creep and diffusion mechanisms limit the maximum fuel storage temperature to 200°C. The results of laboratoryscale corrosion tests indicate that this fuel could be stored under air up to 200°C at low relative humidity levels (< 20%) to limit corrosion of the cladding and fuel (exposed to the storage environment through assumed pre-existing pits in the cladding). Excessive degradation of fuels with uranium metal up to 200°C can be avoided if the fuel is sufficiently dried and contained in a sealed system; open storage can be achieved if the temperature is controlled to avoid excessive corrosion even in dry air.
Design and Synthesis of Novel Side-Chain Polyquinolines and Polyimides for Second-Order Nonlinear Optics
Authors: Jen A. K-Y. , Chen T.-A. , Cai Y.-M.
Published: April 2011

Novel approaches to second-order nonlinear optical (NLO) side-chain polyquinolines and polyimides are described. The syntheses and the characterization of the polymers are detailed. The electro-optical coefficients (r33), temporal stability of dipole alignment, and other physical properties of the NLO polymers are presented.
Thermally Stable Polyimides for Second-Order Nonlinear Optics
Authors: Chen J. I. , Li L. , Marturunkakul S. , Kumar J. , Tripathy S. K. , Lindsay G. A. , Miller R. D.
Published: April 2011

A new class of nonlinear optical (NLO) polyimides incorporating a thermally stable chromophore has been synthesized and characterized. These polymers exhibit large and extremely
Contributions of Low-Lying Excited States to Optical Nonlinearities in Squaraines
Authors: Singer K. D. , Andrews J. H. , Khaydarov J. D. V. , Hull D. L. , Chuang K. C.
Published: April 2011

We measured the third-harmonic spectrum for a series of both centrosymmetric and noncentrosymmetric squaraine dyes in chloroform. By fitting the experimental dispersion of the third order susceptibility, γ, to a four-level sum-over-states model, we determined the strength and location of the lowest lying two-photon-like transition. In each case, we find that the lowest two-photon-like state appears just above the dominant linear absorption peak in energy and that the transition moment to that state makes a significant contribution to the nonlinearity, as do transition moments to one or more higher-lying two-photon-like states in the ultraviolet. The spectra of one centrosymmetric dye contains an additional feature evidencing a nonzero dipole moment difference between the ground and first excited state dipole moments (δμ) that we attribute to a conformational asymmetry. A noncentrosymmetric squaraine dye shows a similar feature, which, as expected, arises from its δμ. Effects of symmetry breaking are described.
Polymer Integrated Optic Zero-Gap Directional Coupler
Authors: Grote J. G.
Published: April 2011

Integrated optic zero-gap directional couplers (ZGDC‘s) offer orders of magnitude shorter device lengths than conventional directional couplers. Researchers are currently striving to simultaneously optimize several properties of nonlinear optical (NLO) polymers that are viewed essential for the fabrication of commercially viable polymer electro-optic devices, including high electro-optic activity, low propagation loss and high temperature poling retention. Fabrication of zero-gap directional couplers using NLO polymers show the potential to realize devices with interaction lengths as short as 100 μm, operating at TFL level switching voltages. Hence, NLO polymer ZGDC‘s will possess the ability to tolerate large propagation losses. This can allow the low propagation loss constraint for NLO materials to be relaxed significantly. Polymers with high electro-optic activity that might be rejected because of high propagation loss, could potentially be utilized for ZGDC switches. In addition, by using these devices as stand alone switches for the present (i.e., not integrating them with electronic circuits) the de-poling temperature constraint can also be significantly relaxed since neither solder baths nor high density interconnect (HDI) processes will be needed. These relaxed constraints should improve the chances for introduction of viable NLO polymer devices that can compete in the market place today, without being forced to wait for a material in which all properties have been optimized.
A Molecular Architectural Approach to Self-Assembled Monolayers as NLO Materials
Authors: Yang Xiaoguang , Smilowitz Laura , Buscher C. Thomas , McBranch Duncan , Robinson Jeanne , Li DeQuan
Published: April 2011

Self-assembled molecular architechtures of nonlinear optical (NLO) chromophores and their super-chromophores are discussed. The chromophores are derivatives of azobenzene sulfonates and the super chromophores are derivatives of calix[4]stilbazole and calix[4]stilbazolium. The studies of azobenzene sulfonates are aimed at understanding the surface coverage and molecular orientation in polar self-assembled monolayers (SAMs). The optimized molecular orientation was found to be 32±3 degree and the maximum surface coverage is approximately 2–4 molecules per nm2 depending on the molecular cross-section. The calixarene chromophores are macrocyclic compounds consisting of four simple D-π-A units bridged by methylene groups. These molecules were synthesized such that four D-π-A units of the calix[4]arene were aligned along the same direction with the calixarene in a cone conformation. Both simple and super-chromophores were subsequently fabricated into covalently bound selfassembled monolayers on the surfaces of fused silica and silicon. Spectroscopic second harmonic generation (SHG) measurements were carried out to determine the absolute value of the dominant element of the second-order nonlinear susceptibility, d33 = 60 pm/V at a fundamental wavelength of 890 nm. Furthermore, SHG imaging was employed to investigate the pattemed SAMs of NLO super chromophores.
Novel Piezoelectric Polyimides
Authors: Simpson Joycelyn O. , Welch Sharon S. , St.Clair Terry L.
Published: April 2011

This research focuses on the synthesis, processing, and characterization of novel high performance piezoelectric polymers. A series of polyimides containing pendant, polar trifluoro (-CF 3) and nitrile (-CN) groups have been synthesized, electroded and poled. Measurements of the piezoelectric sensor response are presented to demonstrate the relationship between dipole concentration and the level of piezoelectricity for these materials. An understanding of the effect of dipole concentration on piezoelectric properties will enable the molecular design of polymers possessing distinct improvements over state of the art piezoelectric polymers including enhanced polarizability, polarization stability at elevated temperatures, and increased mechanical integrity.
Electrical Communication Between Glucose Oxidase and Different Ferrocenylalkanethiol Chain Lengths
Authors: Rubin Shai , Bar Georg , Cutts Russell W. , Chow Jimmy T. , Ferraris John P. , Zawodzinski Thomas A.
Published: April 2011

We describe the factors affecting the electron transfer process between the different components of a self-assembled mixed monolayer. The system is comprised of mixed monolayers containing aminoalkanethiols (AMATs) and ferrocenylalkanethiols (FATs) of variable chain lengths. We study the effects of different ratio of the two mixed monolayer components on the permeability of the monolayer towards a Ru(NH3)6C13 redox probe. In order to study the electrical communication between the enzyme and the mediator molecules, the enzyme glucose oxidase (GOx) was attached to the AMAT sites to create a biosensor device. The relative efficiency of a biosensor of each chain-length combination of FAT and AMAT was examined. In light of this comparison, we consider the critical factors for efficient electron transfer between the ferrocene mediator and the GOx redox active site immobilized as part of the surface-confined system. We find that the biosensor response is greatest when the enzyme and the FATs are attached to the surface with different alkane chain lengths. We also find strong evidence for the existence of domains of FAT and AMAT in the mixed monolayer system.
Photoluminescence and Electroluminescence Quenching in 8-Hydroxyquinoline Aluminum Chelates
Authors: Zhang Xian-man , Higginson Keith A. , Papadimitrakopoulos Fotios
Published: April 2011

The present communication proposes a mechanism for photoluminescence (PL) and electroluminescence (EL) quenching in aluminum(III) 8-hydroxyquinoline (Alq3) chelates. Our experiments indicate that in the presence of moisture, ligand exchange of 8-hydroxyquinoline with water can occur. At elevated temperatures, the liberated 8-hydroxyquinoline undergoes a condensation reaction in the presence of traces of oxygen, generating a dark, non-emissive polymeric compound. Spectroscopic and electrochemical methods were used to determine the band gap and energy levels (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)) of this byproduct. Steady state PL experiments indicate that (0.5 to 1%) concentration of this byproduct, evenly dispersed in Alq3 films, results in dramatic PL quenching. Deliberate insertion of an approximately 50 Å thick film of this byproduct into the interface of a poly(p-phenylenevinylene)/Alq3 light emitting diode (LED) completely quenches the EL as well. Initial data suggest an energy transfer quenching mechanism.
Poly(3-Alkyl-Co-3,4-Dialkyltfiophfene) Copolymers: A Series of Conjugated Materials with Tunable Energy-Gap
Authors: Catellani M. , Luzzati S. , Botta C. , Stein P. C.
Published: April 2011

The copolymerization of 3-alkylthiophene and 3,4-dialkylthiophene units in well defined ratios leads to materials in which it is possible to modulate continuously the electronic properties such as the conjugation length and the energy-gap. The soluble materials have optical properties depending on the chemical composition of the chain. A macromolecular and optical characterisation has been performed on two copolymer series.
Assessment of Polyanilines as Alternative Anti-Corrosion Materials: A Theoretical Analysis of Metal-Polymer Adhesion.
Authors: Vallerio Robert , Keyer Roy , Grabania Steve , Landis Mary , Jansen Susan , Wei Yen
Published: April 2011

Current corrosion control methods use coatings which are toxic and environmentally hazardous materials, such as, chromium. More work needs to be done to find a substitute that is competitive with current industrial technologies. Many polymeric materials have been tested as possible alternatives to the present systems. These include polysiloxanes, polymer blends based on polymethylmethacrylate/polysiloxanes and co-polymers of these materials. [1] Oxidized and carbided metal surfaces have been analyzed as chromium substitutes as well. [2] So far the technology has not advanced to a industrially competitive level. Polyaniline is on of the most promising materials for environmentally safe corrosion control.
2,2'-Spaced-Dipyrroles: Electronic and Steric Effects of the Spacers on Bandgaps and Conductivities of the Corresponding Polymers
Authors: Berlin A. , Canavesi A. , Pagani G. , Schiavon G. , Zecchin S. , Zotti G.
Published: April 2011

Conjugated, conducting pyrrole-based polymers were obtained by electropolymerization of 2,2′-spaced-dipyrroles in which the spacer was a vinylene, or a cyanovinylene, or an azo group. In every case, the bandgap of the polymers is considerably narrower than that of polypyrrole.
Solvent, LICL, and Temperature Effects on the Morphological Structure and Electronic Properties of Polyaniline
Authors: Angelopoulos Marie , Liao Yun-Hsin , Furman Bruce , Graham Teresita
Published: April 2011

Extensive gel permeation chromatography coupled with surface structure measurements clearly indicate that polyaniline (pani) base has a tendency to aggregate as a result of interchain hydrogen-bonding. The aggregation is present in the solid state powder; the extent of aggregation is found to be significantly dependent on the synthetic conditions. Pani base powders having a high degree of aggregation have significantly reduced solubility. The degree of aggregation of pani base in solution is found to be dependent on the solvent, concentration, and temperature. As the solvent becomes a better solvent for the base material, the less aggregated is the structure. Solvents which can strongly interact with the polymer disrupt the aggregation. In addition, salts such as LiCl which complex the polymer via a “pseudo-doping” process, also disrupt the internal pani hydrogen-bonding and deaggregate the polymer. As the polymer is deaggregated to different levels by a solvent or by LiCl, the individual chains can better be solvated and thus a conformational change also occurs. The chains adapt a more expanded coil type of conformation. The degree of expansion depends on the solvation power of the solvent. As the level of deaggregation and subsequent chain expansion increases, a significant red shift is observed in the λmaximum of the exciton absorbance and the surface structure of the polymer becomes smoother. It is found that the LiCl induced morphological changes results in increased conductivity upon doping pani base with a protonic acid.
Superconductivity and Magnetism in C60 “Polymer”
Authors: Grigoryan L. S. , Tokumoto M.
Published: April 2011

A new aggregated form of C60, believed to be “polymer”, was prepared through the reaction of C60 with iodine. First, C60 was reacted with iodine to give iodine-doped C60 with magnetic transition around 60 K. After removal of the doped iodine, the sample showed some of the characteristic properties common to the other “polymer” forms of C60. Finally, this “polymer” sample was found to show superconductivity after doping with various alkali-metals (K, Rb, Rb/Cs). Magnetic and/or superconducting properties of these C60 “polymer” are compared with monomer C60
An Investigation into the Role of Incorporated Solvent (EtOH/H2O) Molecules on the Structure of Group 2 Metal bis(β- Diketonate) Complexes: Ramifications for CVD Precursors of Electronic Materials.
Authors: Otway David J. , Luten Henry A. , Malik K. M. Abdul , Hursthouse Michael B. , Rees William S.
Published: April 2011

The synthesis and characterization of thermally stable, volatile, group 2 element-containing complexes is an important prerequisite for the subsequent use of these compounds in chemical vapor deposition (CVD) of superconducting metal oxides (SMO) and other electronic materials, e.g., YBa2Cu3O7-δ. and CaGa2S4:Ce. The utilization of group 2 metal ethoxide compounds {[M(OEt)2(EtOH)4]n (where M = Ca, Sr or Ba)) as precursors to additional complexes is discussed. For example, the compounds [M(tmhd)(OEt)(EtOH)]n (Htmhd = 2,2,6,6- tetramethylheptane-3,5-dione) may be obtained by reacting one equivalent of Htmhd with the metal bis(ethoxide), and these also may be reacted further with functionalized alcohols, or a second β–diketone, to form heteroleptic compounds. Additionally, the preparation and characterization of some Lewis base adducted complexes have been examined with an emphasis on the role that water plays in their isolation.
Zinc Bis(Amide) Compounds Evaluated as Designed Precursors for Site-Selective P-type Doping of ZnSe
Authors: Gaul David A. , Just Oliver , Rees William S.
Published: April 2011

Zinc selenide doped with nitrogen deposited by organometallic vapor phase epitaxy (OMVPE) is one example which leads to a material that produces a blue emission. However, the effective incorporation of the nitrogen dopant into the zinc selenide lattice has not yet resulted in the demanded efficiency. One potential solution involves the design of a precursor introducing the nitrogen dopant bonded to zinc that survives the thermal decomposition process. Several new zinc bis(amide) compounds with the general formula Zn[N(R)(R′)]2 have been synthesized. Investigations into the thermal decomposition mechanisms of these compounds have provided insight into the potential usefulness of the designed precursor in the preparation of ZnSe:N.
MOCVD HTSC Precursor Delivery Monitored By UV Spectroscopy
Authors: Rappoli Brian J. , DeSisto William J.
Published: April 2011

UV spectroscopy has been used as an in situ diagnostic to measure the gas phase concentration of 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) complexes of Ba, Cu and Y in metalorganic chemical vapor deposition (MOCVD) bubbler effluent. These precursors for MOCVD synthesis of YBa2Cu37−δ (YBCO) show marked instability in gas phase concentration as a function of time during bubbler purge. The UV diagnostic technique has been applied to both a small scale test system and a commercial scale MOCVD reactor.
Boundary Layer Temperature Profile in Diamond CVD System Using Laser-Induced Fluorescence
Authors: Wang Qingyu , Lindsay Jon L. , Hofeldt David L.
Published: April 2011

The gas temperature of a radio-frequency thermal plasma has been measured by laser-induced fluorescence along the axis of the plasma jet near the substrate surface. The temperature was determined from the rotational population distribution of OH radicals. From the measured temperature profile, the freestream temperature was found to be about 3400 K and the boundary layer thickness was determined to be about 1 mm. A numerical model including carbonhydrogen- argon kinetics was used to predict species concentrations near the surface of the substrate. The results indicate that all CHa radical concentrations increase with freestream temperature for temperatures between 2500-4000 K. Of the C1 radicals, methyl has the highest concentration in this range in our system, which is consistent with other reports that methyl is an important diamond growth species.
A Grain Boundary Defect in Polycrystalline Films
Authors: Rutledge K. M. McNamara , Watkins G. D. , Zhou X.
Published: April 2011

Our studies primarily concern an S=1/2 electron paramagnetic resonance (EPR) at g=2.0028 with a pair of weaker partially resolved satellites that has been observed in polycrystalline diamond grown by chemical vapor deposition (CVD). These satellites can be shown to result from the forbidden Δm=±l nuclear spin flips of hydrogen during the EPR ΔM∼ 2Å away from the unpaired electron spin. It is suggested that hydrogen enters a vacancy-like stretched bond at a grain boundary, allowing the carbons to relax backward, one bonding to the hydrogen, the other with an unpaired electron in its dangling bond.
Influence Of Surface Terminating Species On Electron Emission From Diamond Surfaces
Authors: Thomas R. E. , Humphreys T. P. , Pettenkofer C. , Malta D. P. , Posthill J. B. , Mantini M. J. , Rudder R. A. , Hudson G. C. , Markunas R. J.
Published: April 2011

Changes in electron affinity on the C(001) surface of type Ifb diamonds have been studied using a variety of surface analytical techniques, including ultraviolet photoemission spectroscopy, secondary electron emission spectroscopy and constant initial states photoemission. Following H-plasma exposure, an intense low-energy emission peak was observed with all spectroscopies. The emission intensity associated with the chemisorbed hydrogen was found to be a linear function of surface hydrogen coverage. The proposed mechanism for the hydrogen induced changes in electron affinity is the creation of a dipole on the surface by the addition of hydrogen which opposes the surface potential of the bare surface. A total change in electron affinity of 2.2 eV was measured upon hydrogen termination of the clean 2x1 surface. Constant initial states photoemission demonstrates that the intense low-energy electron emission observed arises from electrons emitted from bulk states at the conduction band edge. Oxygen, as an electronegative species, was found to have the opposite effect and the electron affinity was increased by ∼3.7 eV upon oxygen termination relative to the clean 2x I surface.
Atomic and Electronic Structures of Grain Boundary in Chemical Vapor Deposited Diamond Thin Film
Authors: Zhang Y. , Ichinose H. , Ishida Y. , Ito K. , Nakanose M.
Published: April 2011

High resolution electron microscopy and electron energy-loss spectrometry were used to investigate both atomic and electronic structures of grain boundaries in diamond thin films grown by chemical vapor deposition. The atomic structures of {112}σ3 and {114}σ9 <110= tilt boundaries in diamond show different features from those in other diamond structure semiconductors. The electron energy-loss spectra recorded from the grain boundary regions show extra intensity near the energy-loss corresponding to carbon 1s-to-π*; transition, as compared to the spectra recorded from neighboring crystalline regions. This gives the evidence that the dangling bonds are not fully reconstructed along <110= direction in the boundary structure. Atomic models are constructed for these boundaries with the presence of non-tetracoordinated atoms. The stability of the boundary structure is explained by the π-like bonding between the nontetracoordinated atoms.
Electron Beam Activated Diamond Devices
Authors: Lin Shiow-Hwa , Sverdrup Lawrence H.
Published: April 2011

Diamond's unique properties are ideally suited for high power and high frequency electronic applications. Natural type Ila diamond wafers of various thicknesses and active areas were used to construct several electron beam activated diamond devices. Average voltage gradients in the diamond target on the order of a mega-volt per centimeter were obtained. Possibilities of improving the attainable average voltage gradient are discussed. Electron activation avoids the necessity of semiconducting doping of the active diamond devices. The electron bombardment on diamonds yields a current-voltage characteristics very similar to that of a bipolar transistor. In the experiments discussed here, the diamond conduction to bombarding current gain ranged from 1,000 to 3,000 depending upon the diamond thickness and the bombarding electron energy. The bombarded diamond on-state resistance is consistent with a simple carrier drift and space charge model. Maximum conduction current density achieved in diamond is 19kA/cm2. High power switching of greater than 25kW with less than 100ns risetime is demonstrated. An electron beam bombarded millimeter wave diamond device has generated more than one watt of power.
Auger Electron Spectroscopy of The CVD Diamond Surface Under Electron Exposure
Authors: Krainsky I. L. , Mearini G. T. , Asnin V. M. , Sun H. , Foygel M. , Petukhov A. G.
Published: April 2011

A simultaneous study of Auger spectra and secondary electron emission from the chemical vapor deposited diamond films under extended electron beam exposure is presented. Up to a 1.2 eV increase in energy of the carbon Auger peak accompanied by the decrease of the total secondary electron yield has been found. Exposure to hydrogen has resulted in recovery of the both Auger peak position and secondary yield. First-principles electronic structure calculations have been carried out to interpret the Auger peak shift. The effect is shown to be due to a change in the surface upper-valence band local density of states of the diamond crystal which is dependent on the extent of hydrogen coverage of the surface.
Electron Field Emission Properties of Diamond
Authors: Zhu W. , Kochanski G. P. , Jin S.
Published: April 2011

We have developed both experimental and numerical methods to collect and analyze field emission data from diamond samples. The diamond emitters are either films prepared by low pressure chemical vapor deposition (CVD) or powders synthesized by traditional high pressure high temperature (HPHT) processes. We established a strong correlation between the electric field required for emission and the defect densities in undoped or p-type doped diamond. We further found that ultrafine diamond particulate emitters offer substantially enhanced electron field emission properties at low electric fields compared to CVD diamond emitters. When subject to appropriate processing schemes, the particulate diamond emitters exhibit extremely low emission fields, typically 1-5 V/μm for a current density of 10 mA/cm2. These are believed to be the lowest-voltage field emitters ever reported.
Secondary Electron Emission Studies of Diamond Surfaces
Authors: Shih A. , Yater J. , Pehrsson P. , Butler J. , Hor C. , Abrams R.
Published: April 2011

Diamond exhibits high secondary-electron yields which vary strongly with sample preparation and sample treatment. In this study, we identify some of the factors that govern the secondary-electron emission yield of diamond. Comparative studies are made with polycrystalline diamond films having different dopants (boron or nitrogen), dopant concentrations and surface conditions (hydrogen-terminated or oxidized). In these studies, the total electron yield as a function of the incident-electron energy and the energy distribution of the secondary emitted electrons are measured. The results show that both electrical conductivity and hydrogen-termination play essential roles in the secondary-electron emission process. For hydrogen-terminated samples, the energy distribution shows a large and narrow peak at the onset of electron emission. The long mean-free path of the secondary electrons and the low or negative electron affinity are essential to the exceedingly high electron yield of diamond.
Measurement of Thermal Diffusivity of Cvd diamond films using modified ac calorimetry
Authors: Maesono Akikazu , Tye Ronald. P.
Published: April 2011

Many applications of thin films, especially for electronics devices, require that these materials, which are often anisotropic, have a very high thermal conductivity as well as uniform areal properties to ensure that reproducible performance be attained. These factors necessitate that measurements of thermal transport properties are required both to provide absolute application values for different heat flow directions as well as to evaluate uniformity and homogeneity of a wafer. For diamond, the combination of a very high thermal conductivity with limited size and form of available specimen presents unique challenges to the experimentalist. As a result, a modification of the ac calorimeter method has been developed to evaluate the thermal diffusivity of thin films.

Details of the technique will be provided together with examples of its use to evaluate thermal diffusivity and thermal conductivity of different CVD diamond film composites having thicknesses from 10µm to 600µm and free-standing films. In addition, results using this method will be compared. with those obtained by other techniques involved in a recent international round-robin measurements program designed to evaluate a potential standard method(s).
Kinetic Analysis of Solid-State Reactions: An Improved Analysis Method
Authors: Smith D. P. , Chaudhri M. M.
Published: April 2011

Many reactions of interest occur in the solid state, or with low mobility of the reactants or products, with the result that the physical mechanisms operative during the reaction determine the shape of the reaction rate-time profile; i.e. topochemistry is important. However, often improper account is taken of the physical mechanisms, resulting in erroneous values for the activation energy and kinetic constants.

An improved method of analysis is suggested, allowing the mechanisms of reaction to be determined explicitly. This thus allows the activation energy and kinetic constants to be determined with good theoretical justification. The method has been verified by studying the thermal decomposition of barium azide, where the activation energy was determined to better than 1%. The operative mechanisms so determined are in agreement with visual observations and the literature.
A Theoretical Study of BF + OH and BO + HF Reactions
Authors: Soto M. R.
Published: April 2011

The reactions of BF + OH and BO + HF are critical reactions in the reaction mechanism of fluorine-enriched boron combustion.1 In this study, ab initio multiconfigurational methods have been used to calculate energies, optimized geometries, harmonic vibrational frequencies and zero-point energies for reactants, products and intermediates of these reactions. Results for the following reactive pathways will be discussed:
High Pressure Ignition of Boron in Reduced Oxygen Atmospheres
Authors: Foelsche R. O. , Spalding M. J. , Burton R. L. , Krier H.
Published: April 2011

Boron ignition delay times for 24 μm diameter particles have been measured behind the reflected shock at a shock tube endwall in reduced oxygen atmospheres and in a combustion bomb at higher pressures in the products of a hydrogen/oxygen/nitrogen reaction. The shock tube study independently varies temperature (1400 – 3200 K), pressure (8.5, 34 atm), and ignition-enhancer additives (water vapor, fluorine compounds). A combustion chamber is used at a peak pressure of 157 atm and temperature in excess of 2800 K to study ignition delays at higher pressures than are possible in the shock tube.
Reaction Rate Modeling in the Deflagration to Detonation Transition of Granular Energetic Materials
Authors: Son S. F. , ASAY B. W , Bdzil J. B. , Kober E. M.
Published: April 2011

The problem of accidental initiation of detonation in granular material has been the initial focus of the Los Alamos explosives safety program. Preexisting models of deflagration-to-detonation transition (DDT) in granular explosives, especially the Baer & Nunziato (BN) model, have been examined. The main focus of this paper is the reaction rate model. Comparison with experiments are made using the BN rate model. Many features are replicated by the simulations. However, some qualitative features, such as inert plug formation in DDT tube-test experiments and other trends, are not produced in the simulations. By modifying the reaction rate model we show inert plug formation that more closely replicates the qualitative features of experimental observations. Additional improvements to the rate modeling are suggested.
Detonation and Deflagration Properties of Pyrotechnic Mixtures
Authors: Tanaka Katsumi
Published: April 2011

Theroretical calculation of detonation and deflagration properties of pyrotechnic mixtures have been performed including report charges and display charges. Calculation were performed with the KHT (Kihara-Hikta-Tanaka) code[l]. KHT results are compared with a modified version of the TIGER code[2] which allows calculation with 900 gaseous and 600 condensed product species at high pressure. Detonation properties computed by KHT and BKWS (Becker-Kistiakowskii-Wilson) give favorable agreement with experimental results of detonation velocity measurements. Hydrodynamic computation by one dimensional Lagrangian hydrodynamic code using the isentrope given by KHT constant volume explosion, indicated that experimental results for blast wave measurement for 30kg and 50kg of report charge were an incomplete reaction. Underwater detonation experiments with explosive charge of 25g, however, indicates a more energetic nature than the KHT prediction. This scale effect indicates complicated slow reactions and a number of condensed phase deflagration products of powder mixtures such as aluminum or titanium with oxidizers such as potassium perchlorate or nitrate salts as suggested by Hobbs et al[3].
Crystal Growth of Energetic Materials During High Acceleration
Authors: Lanzerotti M. Y. D. , Autera J. , Borne L. , Sharma J.
Published: April 2011

Studies of the growth of crystals of energetic materials under conditions of high acceleration in an ultracentrifuge are reported. When a saturated solution is accelerated in an ultracentrifuge, the solute molecules move individually through the solvent molecules to form a crystal at the outer edge of the tube if the solute is more dense than the solvent. Since there is no evaporation or temperature variation, convection currents caused by simultaneous movement of solvent and solute are minimized and crystal defects are potentially minimized. Crystal growth is controlled by the g-level of the acceleration. In addition, solution inclusions and bubbles migrate out of the saturated solution as a result of the pressure gradient induced by the g-force. We present results of TNT, RDX, and TNAZ grown at high g from various solutions.
Improved Monolithic Photovoltaic-Electrochromic Devices Incorporating an a-SiC:H Solar Cell
Authors: Bullock John N. , Bechinger Clemens , Xu Yueqin , Benson David K. , Branz Howard M.
Published: April 2011

In the tandem photovoltaic-electrochromic (PV-EC) device, a wide-gap, semitransparent, amorphous silicon-carbon alloy (a-SiC:H) photovoltaic device and an electrochromic optical transmittance modulator (EC device) are deposited sequentially to form a monolithic device on a single substrate. This device can be used as a “smart” window for active control of daylighting and building cooling load without an external electrical connection.

Last year we reported preliminary results on our development of a semi-transparent PV cell incorporating an a-SiC:H i-layer. Here we report our recent progress on the semitransparent PV component of a PV-EC device and development of a Li-based EC device that colors at voltages below 0.9 V. Finally, we discuss both recent progress and difficulties in integrating the two devices on one substrate.
Two-layer Model for Electroabsorption and Built-in Potential Measurements on a-Si:H pin Solar Cells
Authors: Jiang Lin , Schiff E. A.
Published: April 2011

Modulated Electroabsorption (EA) measurements have been widely used to estimate built-in potentials (Vbi) in semiconductor devices. The method is particularly simple in devices for which the built-in potential is dropped in a single layer of the device. However, experimental results in amorphous silicon and organic devices can involve at least 2 layers. In the present paper we consider the information which can be obtained about 2-layer semiconductor devices from electroabsorption measurements. In particular we describe a 2-layer EA model appropriate to a-Si:H based pin solar cells, for which both the p+ and i layers contribute to the EA signal. We present an analysis of capacitance and second harmonic measurements which yields the EA coefficient for the p+ layer of the device, and we present measurements on a-Si:H pin devices which appear consistent with this analysis. Wavelength dependent EA then yields the built-in potential across the 2-layer device.