bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromium and Lanthanum on Transition Alumina Surfaces: The Role of Bulk Point-Defect Distributions on Catalytic Activity
Authors: Rashkeev S. N. , Sohlberg K. , Glazoff M. V. , Novak J. , Pennycook S. J. , Pantelides S. T.
Published: April 2011

We employ a combination of Z-contrast scanning transmission electron microscopy (Z-STEM) and first-principles density-functional calculations to investigate the interaction between metal atoms and cubic alumina catalytic supports. We show that there are two observed La sites at the porous γ- alumina surface, and that single La atoms do not exhibit a tendency to cluster. Cr behaves very differently from La - it has a tendency to cover the alumina surface in ordered, periodic raft-like patches. The degradation of the chromia/alumina catalyst is related to the possibility for the chromium to move away from the surface into the bulk, and the activation barrier for such a process is higher in η- alumina than in γ- alumina, i.e., η- alumina is a more durable support for chromium catalyst.
Characterization of Porous Pt/Al2O3 Films Produced by Hybrid Gas-to-Particle Conversion and Chemical Vapor Deposition
Authors: Nguyen Quynh T. , Ehrman Sheryl H.
Published: April 2011

A hybrid process, based upon gas-to-particle conversion and chemical vapor deposition, is presented as an alternative technique for producing porous films with the main advantage of solvent-free, low-substrate temperature operation. Starting from precursors of platinum acetylacetonate and aluminum acetylacetonate, nanoparticles were produced by chemical reaction followed by gas-to-particle conversion. Downstream of this reaction zone, these nanoparticles were collected via thermophoresis onto a cooled substrate forming a porous, nanocermet film that may have possible uses in catalytic, sensor, or coating applications.

In this study, Pt/Alumina nanocermet films were produced by two routes: either simultaneous precursor injection processing or a layer-by-layer approach. Energy-dispersive X-ray spectroscopy revealed that this hybrid process results in reasonable control of the amount of Pt within each sample. From transmission electron spectroscopy images taken of films produced by simultaneous processing, Pt nanoparticles appear to be co-agglomerated with alumina. The results may identify changes that can be made to the process to improve properties, such as catalytic activity, in the nanocermet films.
HRTEM Study of the Extended Defect Structure in Epitaxial Ba0.3Sr0.7TiO3 Thin Films Grown on (001) LaAlO3
Authors: Lu C.J. , Bendersky L.A. , Chang K. , Takeuchi I.
Published: April 2011

The defect structure of a 350-nm-thick epitaxial Ba0.3Sr0.7TiO3 thin film grown on (001) LaAlO3 has been investigated using conventional and high-resolution transmission electron microscopy. The predominant defects in the film are threading dislocations (TDs) with Burgers vectors b = <100> and <110>. A high density of extended stacking faults (SFs) with displacement vectors R = (1/2)<110> were also observed in the near-interface region of the film. The faults are associated with dissociated dislocations and partial halfloops. Some findings about dislocation dissociation and the atomic structure of the (1/2)<110> faults are observed for the first time in perovskites to our knowledge. The mechanisms for the generation, dissociation and evolution of the TDs as well as for the formation mechanism of the SFs are discussed.
The Effect of Changing Epitaxial Strain on Colossal Magnetoresistance Thin Films
Authors: Dale Darren , Fleet Aaron , Brock J.D. , Suzuki Y.
Published: April 2011

We have studied the properties of epitaxial La(1-x)SrxMnO3 (x=0.3, 0.5) epitaxial thin films grown on BaTiO3 and SrTiO3. Significant modifications of properties are observed in magnetization and resistivity versus temperature experiments. These modifications occur at temperatures corresponding to structural phase transitions in the substrate. The x=0.5 composition is particularly sensitive to changes in the epitaxial strain state, exhibiting a direct correlation between changes in strain, magnetization and resistivity. Strain can also be induced in BaTiO3 by the inverse piezoelectric effect, which results in as much as a 13% decrease in the resistivity of the film.
Metalorganic chemical vapor deposition of aluminum oxide on silicon nitride
Authors: Dasgupta Anindya , Chowdhuri Abhijit Roy , Takoudis Christos G.
Published: April 2011

Thin films of aluminum oxide were deposited on silicon nitride thin films using trimethylaluminum and oxygen at 0.5 Torr and 300 °C. Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopic (XPS) analyses of these films showed no aluminum silicate phase at the film-substrate interface. The O/Al ratio in the deposited film was found to be higher than that in stoichiometric Al2O3 indicating the presence of excess oxygen. FTIR spectroscopy and XPS of the annealed samples did not show any formation of silicon oxide, oxynitride or silicate at the aluminum oxide/silicon nitride interface. In contrast to aluminum oxide on clean silicon substrates, using ultrathin silicon nitride as a barrier layer could prevent excess oxygen migration towards the Si substrate and formation of any interfacial layers.
The Effect of the Surface Layer on the Dielectric Constant of (Pb, La)TiO3 Thin Films
Authors: Yu G.L. , Xiao D.Q. , Meng L.L. , Yu P. , Zhu J.G.
Published: April 2011

(Pb, La)TiO3 (PLT) ferroelectric thin films are one of the promising candidates for applications in dynamic random memory and pyroelectric detectors, etc. However, the chemical composition in the surface layer of thin films is usually different from that in the “bulk” region of the thin films. For instance, it has been reported that there is Pb, Ti, or La enrichment in the surface layer of the (Pb, La)TiO3 thin films. According to a numerical modeling using effective-medium theory, which was developed in our group, we discussed the effect of the surface layer on the dielectric constant of (Pb, La)TiO3 thin films. The effect of Pb, Ti, or La enrichment in the surface layer on the dielectric constant of PLT thin films was discussed. And a case of the “upgraded” and the “down-graded” thin films was expatiated and discussed.
Nanocrystallisation and Nanoquasicrystallisation in (Ti/Hf)-Zr-(Ni/Cu) Ternary Alloys
Authors: Basu Joysurya , Louzguine D.V. , Inoue A. , Ranganathan S.
Published: April 2011

The applicability of the confusion principle and size factor in glass formation has been explored by following different combinations of isoelectronic Ti, Zr and Hf metals. Four alloys of nominal composition Zr41.5Ti41.5Ni17, Zr41.5Hf41.5Ni17, Zr25Ti25Cu50 and Zr34Ti16Cu50 have been rapidly solidified to obtain an amorphous phase and their crystallisation behaviour has been studied. The Ti-Zr-Ni alloy crystallises in three steps. Initially this alloy precipitates icosahedral quasicrystalline phase, which on further heat treatment precipitates cF96 Zr2Ni phase. The Zr-Hf-Ni alloy can not be amorphised under the same experimental conditions. The amorphous Zr-Ti-Cu alloys at the initial stages of crystallisation phase-separateinto two amorphous phases and then on further heat treatment cF24 Cu5Zr and oC68 Cu10Zr7 phase are precipitated. The lower glass-forming abilityof Zr-Hf-Ni alloy and the crystallisation behaviour of the above alloys has been studied. The rationale behind nanoquasicrystallisation and the formation of other intermetallic phases has been explained.
Synthesis and Evaluation of Resins for Actinide Separations
Authors: Noyes K. L. , Charton N. , Draye Micheline , Czerwinski K. R.
Published: April 2011

Molecular imprinting techniques have shown great promise for applications in chemical separations, including those involving lanthanides and actinides. This work examines the production of a selective resin for Am separations. Due to practical difficulties, resins were not imprinted with Am, rather 3 resins were created with each of Sm, Nd, and Pr as the template ions. An analogous “blank” or unimprinted resin was also created. The nitrate salt of the target metal ion was dissolved in CH2Cl2 and the resin was created around the ions to provide a unique structure based upon each metal. These resins were synthesized by a radical polymerization method, producing a reusable organic solid. The resins were qualified by obtaining values for their proton exchange capacities and data to define their complexation thermodynamics. Proton exchange capacities were determined using an indirect titration and were found to be 10.08 meq/g for the Sm-imprinted resin, 7.25 meq/g for the Nd resin, and 7.14 meq/g for the Pr resin. Data for the resins' thermodynamics were obtained at pH 1–7 in steps of 0.5 units. Results show that the templated resins rapidly removed the target actinide from aqueous solution under experimental conditions. Best separation results for Am from Eu and Gd were obtained with the Nd imprinted resin.
Synthesis of Uranium Phosphate Phases and Potential Retardation Effects on Spent Fuel Radionuclide Migration
Authors: Turner A. S. , Wronkiewicz D. J.
Published: April 2011

The UO2 in spent nuclear fuel is unstable in the oxidizing conditions within the volcanic tuffs at the proposed nuclear repository at Yucca Mountain, Nevada. Over time, the UO2 will oxidize and corrode, releasing actinides and fission products to the surrounding environment. However, uranyl (U6+) phosphates (autunite, phurcalite, sodium autunite, etc.) are stable in such an oxidizing environment. The mobility of released radionuclides may be greatly retarded if they can be incorporated into these naturally stable phosphate phases, while the complex structures, variable chemical compositions, and natural analogue occurrences of the uranyl phosphates suggests such a process is favorable. Current tests have focused on synthesizing such phases by reacting uranium oxynitrate or UO3 with a calcium, sodium, or potassium phosphate and a base (if necessary) in a Teflon reaction vessel. Excess water is added, and the solution is heated at 90°C for 7, 35, or 182 days. SEM analyses have confirmed that various uranium phosphate crystalline solids have formed. XRD results indicate that tests using two different calcium phosphorus source materials, Ca2P2O7 and Ca10(OH)2(PO4)6, have both created synthetic phosphuranylite, Ca(UO2)[(UO2)3(OH)2(PO4)2] 2*12H2O. The formation of this phase is appears to be kinetically favored over other similar phases. Results utilizing sodium phosphates, NaH2(PO4)*H2O and Na2HPO4, have produced sodium autunite (NaUO2PO4*2H2O), but other phases are probably also present. Test results utilizing potassium phosphate, K3PO4, were inconclusive. Experiments using surrogate radionuclides are currently being performed in order to determine whether radionuclides, such as 239Pu, 137Cs, and 99Tc, released from corroded spent nuclear fuel can become incorporated into the crystalline structure of specific uranium phosphate phases, effectively limiting any further migration.
Host Phases for Actinide Elements in the Metallic Waste Form
Authors: Janney D. E.
Published: April 2011

Argonne National Laboratory has developed an electrometallurgical process for conditioning spent sodium-bonded metallic reactor fuel prior to disposal. A waste stream from this process consists of stainless steel cladding hulls that contain undissolved metal fission products such as Tc, Ru, Rh, Pd, and Ag; a small amount of undissolved actinides (U, Np, Pu) also remains with the hulls. These wastes will be immobilized in a waste form whose baseline composition is stainless steel alloyed with 15 wt% Zr (SS-15Zr). Scanning electron microscope (SEM) observations of simulated metal waste forms (SS-15Zr with up to 11 wt% actinides) show eutectic intergrowths of Fe-Zr-Cr-Ni intermetallic phases with steels. The actinide elements are almost entirely in the intermetallics, where they occur in concentrations ranging from 1–20 at%. Neutron- and electron-diffraction studies of the simulated waste forms show materials with structures similar to those of Fe2Zr and Fe23Zr6.

Dissolution experiments on simulated waste forms show that normalized release rates of U, Np, and Pu differ from each other and from release rates of other elements in the sample, and that release rates for U exceed those for any other element (including Fe). This paper uses transmission electron microscope (TEM) observations and results from energy-dispersive X-ray spectroscopy (EDX) and selected-area electron-diffraction (SAED) to characterize relationships between structural and chemical data and understand possible reasons for the observed dissolution behavior.

Transmission electron microscope observations of simulated waste form samples with compositions SS-15Zr-2Np, SS-15Zr-5U, SS-15Zr-11U-0.6Rh-0.3Tc-0.2Pd, and SS-15Zr-10Pu suggest that the major actinide-bearing phase in all of the samples has a structure similar to that of the C15 (cubic, MgCu2-type) polymorph of Fe2Zr, and that materials with this structure exhibit significant variability in chemical compositions. Material whose structure is similar to that of the C36 (dihexagonal, MgNi2-type) polymorph of Fe2Zr was also observed, and it exhibits less chemical variability than that displayed by material with the C15 structure. The TEM data also demonstrate a range of actinide concentrations in materials with the Fe23Zr6 (cubic, Mn23Th6-type) structure.

Microstructures similar to those produced during experimental deformation of Fe-10 at% Zr alloys were observed in intermetallic materials in all of the simulated waste form samples. Stacking faults and associated dislocations are common in samples with U, but rarely observed in those with Np and Pu, while twins occurred in all samples. The observed differences in dissolution behavior between samples with different actinides may be related to increased defect-assisted dissolution in samples with U.
Stability and Aging of Candidate Alloys for the Yucca Mountain Project: CALPHAD Results
Authors: Turchi P. E. A. , Kaufman L. , Liu Zi-Kui
Published: April 2011

The CALPHAD approach is applied to the study of stability and aging of several Ni-Cr-Mo alloys similar to those considered for use in waste disposal containers for the Yucca Mountain Project (YMP). The stability of occurring phases in the as-fabricated materials must be investigated since their precipitation with time at temperature can reduce their corrosion resistance and mechanical properties. We first show that excellent agreement exists between assessed and calculated phase diagrams for the three major binary alloys, Ni-Cr, Ni-Mo, and Cr-Mo, and for the ternary Ni-Cr-Mo alloy. Then we present a comparative study of phase fractions versus temperature for the nominal composition of several multi-component Ni-Cr-Mo alloys. Finally we discuss the aging properties of the Ni2Cr-ordered phase in Ni-Cr and in Ni-Cr-Mo alloys, and of the complex P phase in Alloy 22.
Extension of the Modified Associate Species Thermochemical Model for High-Level Nuclear Waste: Inclusion of Chromia
Authors: Besmann Theodore M. , Spear Karl E. , Vienna John D.
Published: April 2011

The successful thermochemical model based on the modified associate species approach for the Na2O-Al2O3-B2O3-SiO2 base glass system has been extended to include a critical constituent, Cr2O3. This includes the Cr2O3-Al2O3 solid solution. For the liquid, and potentially glass phase when undercooling is allowed to occur, the model uses the relative simple, modified associate species method to allow accurate determination of phase relations, including liquidus surfaces. It also allows prediction of chemical activities and vapor pressures, which can be important in both processing and in modeling long-term waste form stability.
Dissolution Behavior and Fission Product Release from Irradiated Thoria-Urania Fuel in Groundwater at 90°C
Authors: Jerden James L. , Cunnane J. C.
Published: April 2011

The dissolution behavior and fission-product release from irradiated thoria-urania fuel was studied by immersing fuel samples in J-13 well water at 90°C. The samples are from the Shippingport Light Water Breeder Reactor and consist of binary solid solutions of (U,Th)O2 with UO2 contents varying from 2.0 to 5.2 Wt.%. The post-irradiation U isotopic composition of the samples used in our experiments is: 87.3% 233U, 10.4% 234U, 1.8% 235U, and <0.5% 238U, 236U, 232U. Burn up values for the samples range from 22.3 to 40.9 megawatt-days per kg-metal. Our tests were performed on polished disks and on crushed and sieved samples in stainless-steel reaction vessels with air-filled head-space. After 196 days of reaction, samples showed no evidence for corrosion at the micrometer scale. Concentration ranges (μgL-1) of key radionuclides in filtered (∼5 nm pore size) leachates were: 0.1 – 15 90Sr, 0.9 – 7.0 99Tc, 0.1 – 35.2 137Cs,<0.2 – 0.8 233U, <0.1 – 0.7 232Th. Concentrations of 237Np, 239Pu, 240Pu and 241Am were all <0.2 μgL-1. The relatively high concentrations of the fission products 90Sr and 137Cs occur early during leaching and decrease for later samplings. Matrix dissolution rates for the irradiated thoria-urania samples range from ∼3x10-3 to <3×10-5 mg m-2day-1 and are at least two orders of magnitude lower than those measured for UO2 spent fuels under similar experimental conditions.
Microstereolithography: a Review
Authors: Bertsch Arnaud , Jiguet Sébastien , Bernhard Paul , Renaud Philippe
Published: April 2011

Microstereolithography is a technology at the interface of the microengineering and rapid prototyping domains. It has evolved from the stereolithography technique, and is also based on a light-induced layer-stacking manufacturing. As the resolution of the microstereolithography technique is far better than the one of rapid prototyping technologies, this technique is of particular interest in the microengineering domain where its 3D capability allows the production of components no other microfabrication technique can create.

The first developments of the microstereolithography technique have started in 1993 and different research teams have developed machines since, using different approaches. This paper reviews the major microstereolithography processes developed until now.

Microstereolithography is starting to be a commercially available manufacturing process. As the market for miniaturized products grows rapidly, there is an increasing need for highresolution small size prototype parts. If the production of small mechanical components is the first commercial application of microstereolithography, this technology can also produce useful components for the microrobotic, microfluidic, microsystems and biomedical fields. Current research in the microstereolithography field is focused on using ceramic composites as material to manufacture complex three-dimensional parts that can be sintered to produce pure alumina microcomponents.
Direct Fabrication of Patterned Functional Ceramic Films by Soft Solution Processing without Post-Firing
Authors: Yoshimura Masahiro , Watanabe Tomoaki , Fujiwara Takeshi , Teranishi Ryo
Published: April 2011

We are proposing an innovative concept and technology, Soft Solution Processing (SSP) for ceramics, which aims to achieve direct fabrication of shaped, sized, located, oriented ceramic materials from solutions without firing and/or sintering. We have successfully fabricated thin and thick films of BaTiO3, SrTiO3, BaWO4, SrMoO4, LiCoO2, and LiNiO2 by SSP in aqueous solutions from room temperature to 200 °C. In these experiments, interfacial reactions between a solid reactant (substrate) and component(s) in a solution have been designed and realized. By locally activating the reaction and moving the reaction point dynamically in these reactions, we can produce patterned ceramics directly in solution without masking, etching, pattern forming, or any post-heating such as firing or sintering. In this paper we present recent results for patterned ceramic films of PbS, CdS, and LiCoO2. The processes used to produce these films are entirely new, and represent the first examples of successful direct patterning of ceramics from solutions. In previous reports, heating processes have been essential for synthesis and/or sintering of powders and precursors to obtain patterns in ceramic materials. Such processes inevitably cost environmentally and economically. In contrast, our method, where no firing is needed, provides an environmentally and economically less expensive alternative.
Direct-Write Process for UV-Curable Epoxy Materials by Inkjet Technology
Authors: Voit W. , Rao K. V. , Zapka W.
Published: April 2011

We demonstrate drop-on-demand inkjet printing technique to be a high throughput method for the patterned deposition of UV-curable epoxy materials. Different multi-nozzle printheads have been used to produce epoxy droplets with controlled volume in the range from 15 to 180 pl, and to apply the droplets with high placement accuracy. For a large dot grid pattern, which was printed by addressing 126 individual ink channels, standard deviations of σx = 2.3 μm and σy = 2.6 μm have been achieved for the error in dot placement. The deposited epoxy dots were found to form planar convex lenses with a focal length of 142 μm. In addition, we have successfully printed magnetic nanoparticles in a carrier fluid with the drop-on-demand printheads, as a step towards the production of composites.
Fabrication Of Mesoscale Energy Storage Systems By Laser Direct-Write
Authors: Arnold Craig B. , Wartena Ryan C. , Swider-Lyons Karen E. , Piqué Alberto
Published: April 2011

Over the last two decades, there has been a trend towards the development of smaller and more autonomous electronic devices, yet the question of how to power these microdevices with correspondingly small power sources remains. To address this problem, we employ a laser forward-transfer process in combination with ultraviolet laser micromachining, to fabricate mesoscale electrochemical power sources, such as microbatteries and micro-ultracapacitors. This direct-write laser-engineering approach enables the deposition of battery materials (hydrous ruthenium oxide, manganese oxide, lithium cobalt oxide, etc.) under ambient temperature and atmospheric conditions, resulting in films with the desired morphological and electrochemical properties. Planar and stacked cell configurations are produced and tested for their energy storage and power delivery capabilities and exhibit favorable performance in comparison to current battery technology.
Laser Direct-Write Of Alkaline Microbatteries
Authors: Arnold Craig B. , Piqué Alberto
Published: April 2011

We are developing a laser engineering approach to fabricate and optimize various types of alkaline microbatteries. Microbattery cells are produced using a laser forward transfer process that is compatible with the materials required to make the anode, cathode, separator and current collectors. The use of an ultraviolet transfer laser (wavelength = 355 nm, 30 ns FWHM) enables other operations such as surface processing, trimming and micromachining of the transferred materials and substrate and is performed in situ. Such multi-capability for adding, removing and processing material is unique to this direct-write technique and provides the ability to laser pattern complicated structures needed for fabricating complete microbattery assemblies. In this paper, we demonstrate the production of planar zinc-silver oxide alkaline cell by laser direct-write under ambient conditions. The microbattery cells exhibit 1.5–1.6 V open circuit potentials, as expected for the battery chemistry and show flat discharge behavior under constant current loads.
Versatile Nanodeposition of Dielectrics and Metals by Non-contact Direct-Write Technology
Authors: Wanzenboeck H. D. , Langfischer H. , Harasek S. , Basnar B. , Hutter H. , Bertagnolli E.
Published: April 2011

Direct-write techniques allow processing in the nanometer range and have become powerful methods for rapid prototyping of microelectronic circuits and micro-electro-mechanical systems (MEMS). Chemical reactions are initiated by a focused beam leading to deposition of solid material on literally any surface. We have used this method to deposit metals such as tungsten and dielectrics such as silicon oxide using a focused ion beam (FIB) with 10 to 50 kV acceleration voltage. Controlled guidance of the beam allows deposition of both metallic and dielectric material with features in the 100 nm range. The deposition of separate structures of metallic and dielectric material deposited next to each other is shown on samples of different roughness. 3-dimensional exemplary prototypes in the sub-μm range and multilayer structures demonstrate the versatility of this method for prototyping and mix-and-match approaches with commercial semiconductor devices. A characterization of the deposited material was performed to clarify chemical composition and surface morphology of deposited structures. The deposition parameters were found to influence the chemical composition and electronic properties of the material. Direct-write deposition of dielectrics and metals by FIB allows fabrication of 3-dimensional prototypes with custom-tailored material properties.
Two-Photon Laser Micro-Nano Fabrication; Understanding from Single-Voxel Level
Authors: Kawata Satoshi , Sun Hong-Bo
Published: April 2011

For laser nanofabrication using two-photon photopolymerization, a deep understanding of the nature of focal spots that are related to two-photon excitation is essential for achieving a high spatial resolution in three dimensions. Here we report the use of a technology we call ascending scan for characterizing the three-dimensional size and shape of single polymerization elements (voxels), and introduce several features of voxels that have not been fully noticed before. These findings are important for tailoring nanofeatures according to design.
Structural and Morphological Study of Zirconia and Titania Sol-Gel Monolayered Films Supported on Soda-Lime Glass Substrates
Authors: Cueto Luisa F. , Sánchez Enrique , Torres-Martínez Leticia M. , Hirata Gustavo A.
Published: April 2011

Sol-Gel, dip-coated titaniumIV and zirconiumIV dioxide monolayered films were deposited on soda-lime glass using titanium and zirconium acetylacetonates as precursors, respectively, and their structural and morphological characterization carried out. The films were heat-treated at different temperatures, 25°C, 150°C, 300°C, and 500°C and, according to Low-angle X-Ray Diffraction analyses (XRD), it was found that TiO2 (anatase) and tetragonal zirconia were present on the substrate, when heated at 500°C. Yoshida and Yajima's method, based on optical information given by the films transmittance UV-Vis spectra, was used to estimate film thickness, refractive index, and, using the Lorentz-Lorentz relationship, their volume fraction. Film thinning and phase formation with increasing temperature was observed, and both titania and zirconia films showed similar behavior during firing. Smooth films with a roughness value of around 2 nm are obtained for the two cases as indicated by Atomic Force Microscopy (AFM) of the surface. Also, formation temperature at around 500°C resulted in the optimum condition to obtain clean stoichiometric TiO2 and ZrO2 thin films on glass substrates as confirmed by X-Ray Photoelectron Spectroscopy (XPS) measurements.
Microfrictional Properties of Titanium Carbide
Authors: Ahmed Syed Imad-Uddin , Bregliozzi Giuseppe , Haefke Henry
Published: April 2011

The tribological issues associated with silicon-based microelectromechanical systems (MEMS) are well known. A popular solution to improve the tribological behavior is to apply different kinds of thin films. One film material, shown to have favorable properties in specialty applications, and which may also be suited for MEMS, is titanium carbide (TiC).

This paper examines the microfrictional properties of titanium carbide surfaces with two surface roughnesses sliding against polished 2 mm diameter TiC counterbodies. A comparison of the microfrictional behavior is made with various other surfaces sliding against the same material. Results indicate that the microfriction of smooth TiC sliding against a smooth TiC surface is low and similar to silicon or TiC sliding against a hydrophobic self-assembled monolayer. However, friction increases when the polished TiC ball slides against a rough TiC surface. Experiments at various relative humidities show that friction increases with increase in the relative humidity for two smooth TiC surfaces sliding against one another, but is reduced at higher relative humidity if the surface of one of the sliding partners is considerably rough.

This microfrictional study shows that TiC is well suited for microtribological applications. However, for optimal performance, the surface characteristics need to be tailored to the operating conditions.
Corrosion Protection of Materials by Applying Nanotechnology Associated Studies
Authors: Asmatulu Ramazan , Claus Richard O.
Published: April 2011

Corrosion usually takes place and degrades material surfaces based on environmental chemistry. There are several popular ways of decreasing corrosion rates to improve the lifetime of materials and devices. As recently determined, some methods may incorporate nanostructured materials processing approaches. These include surface treatment methods, nanocomposite thin film coatings, top layer coatings and thermal barrier coatings. Test results show that the corrosion performance of materials is significantly improved as compared to materials processed using conventional methods. In the present paper, some of these studies will be analyzed, and the obtained corrosion results will be evaluated in detail for the future of corrosion processes.
Fe3O4 Ultrafine Particles with Narrow Size Distribution from Polymer-Metal Complex Gels
Authors: Huang Cheng , Yang C. Z. , Chen L.
Published: April 2011

Although studies on the Fe3O4 magnetic particle formation have been markedly advanced by the strenuous efforts of numerous researchers, the preparation and formation of ultrafine Fe3O4 particles with narrow size distribution still remain as an open area due to their broad applications, especially in biomedical fields such as target drug delivery and medical imaging. A new method for the titled template-mediated synthesis of Fe3O4 ultrafine magnetite particles (several tens of nanometers) with narrow size distribution from a polymer matrix has been investigated. Hydrazine hydrate was used as a reducing agent to prepare the poly(itaconic acid-co-acrylic acid) gel-supported iron metallic nanoclusters, which served as nuclei, and were later transferred into ultrafine iron oxide powders in NaOH base solution. The morphology, particle size, structure and magnetic properties, as well as the formation of the particles with narrow size distribution, were investigated by means of transmission electron microscopy, selected area electron diffraction, laser light scattering, wide-angle X-ray diffraction, Fourier-transform infrared spectroscopy, and electron spectroscopy for chemical analysis, as well as magnetic measurements, respectively. It was revealed that the Fe3O4 ultrafine particles prepared from the Fe3+-poly(itaconic acid-co-acrylic acid) complex gel system kept narrow size distribution, which originated from the oxidation and aggregation growth of the primary particles, and the metallic iron nanoclusters would act as “templates” in the later magnetite particles growth stage. This new attempt of template-mineralization of Fe3O4 ultrafine particles in our preparation was proved to be effective for preparing template-mediated ultrafine magnetite particles with narrow size distribution quickly, which could also be used to prepare other kinds of inorganic particles.
Preparation and Microstructure Control of Protein Thin Films Deposited by Pulsed Laser Deposition and Via Colloid Chemical Routes
Authors: Nakayama Sayuri , Taketani Ichiro , Nagare Sanshiro , Senna Mamoru
Published: April 2011

Protein thin film (mainly silk fibroin) was prepared by pulsed laser deposition (PLD) with 1064nm IR-beam and via colloid chemical routes. Thickness, surface roughness, and microstructures of the deposited film were examined by quartz crystal microbalance sensor, field emission scanning electron microscope (FE-SEM), and atomic force microscope (AFM). The laser power density was varied systematically for PLD to control the microstructures of the film and the secondary structure (β-sheet, α-helix, or random coil) of the protein. Secondary structure of the target and film was examined by FT-IR. Films prepared by PLD comprise by agglomerated particles with their primary particle size around 30nm. The size of the primary particles was uniform, especially for the film prepared at low laser power density. At low laser power density, proportion of β-sheet increased and that of random coil decreased. Proportion of random coil was also increased by the wet colloidal process. PLD with low power density is most suitable to preserve the secondary structure in the protein thin film.
Systematic Molecular Control of Interfacial Structure in Nanoporous Carbons
Authors: Jian Kengqing , Crawford Gregory P. , Hurt Robert H.
Published: April 2011

The present paper describes a new concept of synthesizing nanoporous carbons that allows control not only of the pore structure, but also of the molecular structure of the internal surfaces. Interfacial molecular control is achieved through the use of discotic liquid crystalline precursors whose molecular orientation on the substrate material is known or can be determined by simple measurements on flat substrate test samples. Here a suite of nanoporous (mesoporous) carbons are synthesized from various porous glass and silica gel templates, and a model is developed to predict the carbon properties from template properties thus allowing systematic template selection.
Intrinsic Friction of Monolayers Adsorbed on Solid Surfaces.
Authors: Bénichou O. , Cazabat A.M. , De Coninck J. , Moreau M. , Oshanin G.
Published: April 2011

We review recent results on intrinsic frictional properties of adsorbed monolayers, composed of mobile hard-core particles undergoing continuous exchanges with a vapor phase. In terms of a dynamical master equation approach we determine the velocity of a biased impure molecule - the tracer particle (TP), constrained to move inside the adsorbed mono-layer probing its frictional properties, define the frictional forces exerted by the monolayer on the TP, as well as the particles density distribution in the monolayer.
Prediction of Transport Properties of Nanosystems and Their Use for Virtual Fabrication of Nanomaterials
Authors: Pozhar Liudmila A.
Published: April 2011

Fundamental statistical-mechanical expressions for transport coefficients describing transport processes in spatially inhomogeneous systems (such as nanofluids, interfacial systems, atomic clusters, etc.) and derived by the use of the functional perturbation theory (FTP) due to Pozhar and Gubbins (PG) are simplified for the use in engineering and technology. Together with explicit expressions for the charge transport properties of quantum inhomogeneous systems (such as semiconductor quantum dots, wells and wires, artificial atoms/molecules etc.) derived recently, these expressions form a basis for development of algorithms and codes to realize a virtual (i.e., fundamental theory-based, computational) synthesis of nanomaterials with predesigned transport properties for novel nanocluster- or nanopore- based catalysts and adsorbents, integrated nanocircuits, nanoheterostructures, etc.
Aging Effects in Suspensions of Silica Particles
Authors: Selimovic Seila , Hu Yue
Published: April 2011

In our study of the aging phenomena in silica suspensions we immersed precipitated silica particles in methyl-terminated PDMS (silicone oil), mineral oil, and glycerol/water and measured their viscoelastic properties as a function of time. We found that the samples based on silicone oil, initially of a pasty consistence, became fluid-like after a period of about three weeks. Aqueous samples aged much faster than the oily samples. Samples containing mineral oil did not exhibit any changes in viscosity and elasticity. In this paper we discuss a possible mechanism for these aging behaviors.
Slow Relaxation of Spin-Cast Poly(methyl methacrylate) Confined in Thin Films
Authors: Richardson Helen , Sferrazza Michele , Keddie Joseph L.
Published: April 2011

Although the volume relaxation of bulk homopolymer glasses is thoroughly understood, many questions remain about the volume relaxation of polymers cast from solvent. Furthermore, in polymer thin films, the possible effects of confinement, surfaces and interfaces on relaxation are largely unexplored. Measurements of the film thickness of spin-cast poly(methyl methacrylate) thin films over extended periods of time, using spectroscopic ellipsometry, reveal that the characteristic time for relaxation increases with film thickness. This result is consistent with the idea of enhanced molecular mobility in thin films, and it might reflect the conformation and a reduced extent of entanglements of the polymers when spin-cast from dilute solution.
Dimensional Crossover in the Growth of Depletion Zone in a Rectangular Capillary: Experiments and Monte Carlo Simulations
Authors: Park Sung Hyun , Peng Hailin , Argyrakis Panos , Taitelbaum Haim , Kopelman Raoul
Published: April 2011

The diffusion-limited kinetics of the growth of depletion zone around a static point trap in a thin, long stripe geometry was studied using a laser photobleaching experiment of fluorescein dye inside a rectangular capillary. The dynamics of the depletion zone was monitored by the θ-distance, defined as the distance from the trap to the point where the reactant concentration has been depleted to the specific fraction of its initial bulk value. A dimensional crossover from two dimensions to one dimension, due to the finite width of the reaction zone, was observed. The crossover seems to occur for all θ values concurrently when the depletion zone touches the boundary for the first time, suggesting that the boundary information spreads faster than diffusion. Monte Carlo simulations were performed to support the experimental results. The crossover time (τc) is found to scale with the width (L) of the rectangular reaction zone as τc ∼ L2, as expected from the Einstein's diffusion law.
An Intermediate TCE Nanocomposite Coating for Thermal Barrier Coatings
Authors: Gregory Otto J. , Downey Markus A. , Wnuk Steve , Wnuk Vince
Published: April 2011

A NiCoCrAlY /Al2O3 nanocomposite coating was developed for Inconel 718 substrates to improve thermal barrier coatings (TBC's) based on thermally sprayed NiCoCrAlY and alumina. This intermediate TCE coating was deposited by rf sputtering techniques and was instrumental in increasing the fatigue life of both TBC's and thermal spray instrumentation. Combinatorial chemistry techniques were employed to screen a large number of NiCoCrAlY / Al2O3 compositions to yield an optimal composite coating such that the TCE of the metallic bond coat was matched to the ceramic top coat. The resulting combinatorial libraries were thermally fatigued and the composition of the library with the longest fatigue life was determined by X-ray energy dispersive analysis (EDS). A sputtering target of the optimal composition was fabricated by thermal-spraying a mixture of NiCoCrAlY and alumina to simulate the results from the combinatorial chemistry experiments and form a nanocomposite with the desired properties. The sputtered intermediate TCE coating improved the fatigue life of the TBC's by 160% when compared to as-sprayed TBC's formed on Inconel 718 substrates. When a thermally grown oxide was formed on the surface of NiCoCrAlY bond coated substrates prior to deposition of the intermediate TCE coating, a 200% increase in fatigue life was realized. Techniques for extending the fatigue life of other thermal barrier coating systems using this approach will be discussed.
Multilayer structure, stress reduction and annealing of carbon film.
Authors: Ha Peter C.T. , McKenzie D. R. , Doyle D. , McCulloch D. G. , Wuhrer Richard
Published: April 2011

Carbon films deposited by filtered cathodic arc show a high compressive stress which limits their thickness because of delamination. We study three methods of relieving the stress in these films. We first determine the dependence of the stress on DC bias up to bias voltages of 1200V and show that the formula of Davis provides a good fit to the data including the stress maximum in the region of 150–200V and the progressive decrease in stress at higher voltages. In the second method, plasma immersion ion implantation (PIII) was used to create multilayer of alternating high density, high stress (PIII on) films and lower density, low stress (PIII off) films. This method enabled thicker structures to be produced. In the third method we made multilayers using amorphous silicon and carbon layers. Annealing of these layers showed that the stress could be reduced to very low values because of the ability of the silicon layers to absorb compressive stress by contracting after the annealing step. The microstructural effects of PIII were studied by transmission and scanning electron microscopy.
The early stages of stress development during epitaxial growth of Ag/Cu multilayers
Authors: Labat S. , Bocquet F. , Bigault T. , Roussel L. , Mikaelian G. , Alfonso C. , Charai A. , Thomas O.
Published: April 2011

The early stages of stress development during epitaxial growth of metal layers with a large misfit in lattice parameters still need in-depth understanding. In this particular study we have focused on Ag-Cu system, which is immiscible and exhibit a large 14% misfit in lattice parameters. Ag/Cu multilayers have been grown by ultrahigh-vacuum evaporation on Si (111) maintained at -20°C, 35°C or 110°C. The thickness of the individual layers is about 100 Å. All the films present the same (111) orientation with a well defined in-plane orientation: <110> Cu or Ag // <110> Si. The stress was monitored during growth with a home-made laser curvature measurement device. The stress vs thickness behaviour is highly asymmetric when comparing Ag/Cu and Cu/Ag. Indeed Ag grown on Cu does not develop any measurable stress at any thickness or temperature, whereas Cu grows on Ag under tensile temperature and thickness-dependent stress. The temperature dependence of this stress relaxation cannot be interpreted with a standard relaxation model including dislocation motion. A possible way to understand the stress temperature dependence is to consider the evolution of microstructure during growth.
Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization
Authors: Aubin V. , Caurant D. , Gourier D. , Baffier N. , Esnouf S. , Advocat T.
Published: April 2011

Progress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.
Experimental and Computational Studies of Ion-Solid Interactions in Silicon Carbide
Authors: Weber William J. , Gao Fei , Devanathan Ram , Jiang Weilin , Zhang Yanwen
Published: April 2011

Experimental and computational results on ion-beam-induced defect production, damage accumulation, and thermal recovery in SiC are reviewed. The accumulation and recovery of disorder on the Si and C sublattices have been determined experimentally by ion-channeling methods. Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies. Energetic Si and C collision cascades, with energies up to 50 keV, primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters. Overlapping of Si and C cascades results in the interaction of defects and clusters that stimulates cluster growth and produces long-range structural disorder. For energetic Au cascades, nanoscale amorphous clusters are produced directly within about 25% of the Au cascades, along with point defects and smaller clusters. The disordering behavior and the changes in volume and elastic modulus obtained experimentally and from molecular dynamics simulations are in good agreement, thus providing atomic-level interpretation of experimentally observed features. Simulations of close-pair production and recombination in SiC indicate that the activation energies for recombination of most close pairs range from 0.24 to 0.38 eV. Multiaxial channeling measurements indicate annealing below 300 K results in relaxation of some interstitials to lower-energy configurations. Long-range migration energies for interstitials and vacancies have likewise been determined by computational methods.
REACE: A New Algorithm for Low Energy Ion Implantation Simulation.
Authors: Shi Xiaokang , Yu Min , Shi Hao , Huang Ru , Zhang Xing , Wang Yangyuan , Zhang Jinyu
Published: April 2011

A new method for the acceleration of MD (molecular dynamics) simulation of ion implantation into crystalline targets is presented, named REACE (Rare Event Algorithm with Cascade Effect). This method can speed up the MD simulation of ion implantation with cascade processes. As a result, the time required to perform a simulation with high precision and dose effect is drastically reduced. And many details producing statistical noise in the simulation are simulated in the REACE and help it to be more reasonable and reliable.
The Role Of Ge In Cluster Formation In B And Bf2 Implanted Si Wafers After Ge Pre-Amorphization
Authors: Alper Sahiner M. , Magee Charles W. , Downey Daniel F. , Arevalo Edwin , Woicik Joseph C.
Published: April 2011

Cluster formation in high dose B, BF2 implanted Si wafers is an important problem in silicon doping, since it is one of the leading causes of the electrical deactivation of the dopant. In this study, we used Ge pre-amorphized, ultra low energy B and BF2 implanted Si wafers in order to probe these clusters from a local structural point of view. Ge K-edge x-ray absorption spectroscopy (XAFS) is a powerful tool in obtaining local structural information around the Ge atom. The effects of different implant species with various implant doses and annealing conditions on the cluster formation are presented using Ge K-edge multi-shell XAFS analysis. The non-linear least-squares fits to the Ge K-edge Fourier Transformed (FT) XAFS data using calculated standards from multiple scattering simulations around the Ge atom reveal formed Ge-B clusters for the Rapid Thermal Processing (RTP) annealed wafers. The results also indicate the laser annealing process on the other hand is blocking the formation of these Ge induced Ge-B clusters.