bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Crystal Structure of Ulm-16, A New Open Framework Fluorinated Gallium Phosphate with 16-Ring Channels
Authors: Loiseau Thierry , Férey Gérard 
Published: April 2011

AbstractThe synthesis and characterization of ULM-16, a new fluorinated gallophosphate Ga4(PO4)F2• 1.5 NC6H14• 0.5 H2O • 0.5 H3O, is described. This material is hydrothermally prepared at 180°C using cyclohexylamine as the structuring agent. It cristallizes in the orthorhombic space group Pbcn (n° 60) with a = 27.329(4) Å, b = 17.377(2) Å, c = 10.2124(5) Å, V = 4849.6 (9) Å3and Z = 8. The structure is built up from vertex-linked GaO4and PO4tetrahedra, GaO4F trigonal bipyramids and GaO4F2octahedra forming hexameric units and infinite double crankshaft chains (calledccor UUDD). The hexameric unit is similar to that found in ULM-3, ULM-4, ULM-5 and ULM-8. The two types of building units are fully connected by vertex-sharing with respect to a strict Ga-P alternation. The 3-D framework consists of cylindrical tunnels delimited by sixteen and six polyhedra running along [001]. The cyclohexylamine molecules are trapped in the wider pores and interact with the bridging fluorine atoms and hydration water through hydrogen bonds. The ULM-16 topology is closely related to that of ULM-5 where, in ULM-16, the infinite crankshaft chains replace the isolated D4R cages of ULM-5. TGA curve (under argon) indicates that the ULM-16 structure is intact up to 800°C. Structural relationships will be stated explicitly for the different structures of the ULM-n series containing the hexameric units.
A Rapid Supercritical Extraction Process for the Production of Silica Aerogels
Authors: Poco J. F. , Coronado P. R. , Pekala R. W. , Hrubesh L. W. 
Published: April 2011

AbstractSilica aerogels are a special class of porous materials in which both the pore size and interconnected particle size have nanometer dimensions. This structure imparts unique optical, thermal, acoustic, and electrical properties to these materials. Transmission electron microscopy and small angle x-ray scattering show that this nanostructure is sensitive to variations in processing conditions that influence crosslinking chemistry and growth processes prior to gelation. Recently, Lawrence Livermore National Laboratory (LLNL) has demonstrated that a Rapid Supercritical Extraction (RSCE) process can be used to prepare near-net shape silica aerogels in hours rather than days. Preliminary data from RSCE silica aerogels show that they have improved mechanical properties and slightly lower surface areas than their conventionally dried counterparts, while not compromising their optical and thermal performance.
Sol-Gel Polymerization of Tetraalkoxygermanium and Organotrialkoxygermanium Monomers
Authors: Baugher Brigitta M. , Loy Douglas A. 
Published: April 2011

AbstractWhile the sol-gel polymerizations of tetraalkoxy- and organotrialkoxysilanes have been extensively studied, there have been few reports of similar investigations with the analogous tetraalkoxygermanium and organotrialkoxygermanium compounds. Germanium alkoxides have received less attention due, in part to their higher cost, but also their greater reactivity towards hydrolysis and condensation reactions. Germanium oxide materials are potentially interesting because the Ge-O-Ge linkage is labile (compared with the siloxane bond in silica gels and polysilsesquioxanes) opening up the possibility of further chemical modification of the polymeric architecture. This may permit hydrolytic reorganization of germanium oxide networks under relatively mild conditions. In this paper, we will present the results of our investigations of the solgel polymerizations of tetraethoxygermanium 1, tetraisopropoxygermanium 2, and methyltriethoxy-germanium 3 to afford network materials as both xerogels and aerogels.
Activated Carbon Filaments with Mainly Mesopores
Authors: Lu Weiming , Chung D. D. L. 
Published: April 2011

AbstractActivated carbon filaments of diameter ∼ 0.1 μm, mean pore size (BJH) 65 Å, specific surface area 1540 m2/g and burn-off 64% (yield 36%) were obtained by activating carbon filaments of diameter ∼ 0.1 μm in CO2 + N2 (1:1) at 970°C for 100 min. Prior to this activation, the filaments were surface oxidized by exposure to ozone (0.3 vol.% in air) at 150°C for 3 min.
Upgrading of Heavy Oil From The San Joaquin Valley of California by Aqueous Pyrolysis
Authors: Reynolds John G. , Murray Ann M. , Nuxoll Eric V. , Fox Glenn A. , Thorsness Charles B. , Khan M. Rashid 
Published: April 2011

AbstractMidway Sunset crude oil and well-head oil were treated at elevated temperatures in a closed system with the presence of water. Mild to moderate upgrading, as measured by increase in API gravity, was observed at 400°C or above. Reduced pressure operation exhibited upgrading activity comparable to upgrading under normal aqueous pyrolysis conditions. Reduced pressure operation was obtained by the use of specific blending methods, a surfactant, and the proper amount of water. The use of metal complexes provided additional upgrading. The best of the minimum set tested was Co(ll) 2-ethylhexanoate. Fe, Zn, Mo, Cu, and Ni complexes also showed some levels of activity.
Flocculation of Colloidal Silica With Aluminum Fractal Polymers
Authors: Lartiges B. S. , Michot L. J. , Bottero J. Y. 
Published: April 2011

AbstractFlocculation of colloidal silica and Na-montmorillonite was investigated by 27A1 MAS NMR and XRD under various chemical conditions. The results showed that destabilization has many features in common with flocculation by addition of conventional organic polymers.
Quantitative Determination of Chromium Valence in Environmental Samples Using Xafs Spectroscopy
Authors: Peterson M. L. , Brown G. E. , Parks G. A. 
Published: April 2011

AbstractSynchrotron x-ray absorption fine structure (XAFS) spectroscopy provides quantitative information on the speciation of Cr in complex oxide samples, including the Cr(VI):Cr(III) ratio, without any sample pretreatment. We discuss several XAFS methods that can be used for this purpose, including: (1) measurement of the height of the pre-edge peak of Cr K-edge spectra which is caused by ls→3d electronic transitions occurring predominately in the Cr(VI)O4 tetrahedron; (2) fitting observed XANES spectra using combinations of experimental spectra from Cr(III)- and Cr(VI)-containing model compounds; (3) fitting observed EXAFS spectra using combinations of experimental spectra from Cr(III)- and Cr(VI)-containing model compounds; and (4) ab-initio modeling of observed Cr K-EXAFS spectra using theoretical phase-shift and amplitude parameters for Cr(III)O6 and Cr(VI)O4 models. The first method is shown to be the simplest and most accurate. The samples examined using these methods include highly pure model compounds, Cr3+2O3 and Na2Cr6+O4·4H42O, as well as more complex soil samples taken from Cr-contaminated industrial sites and Cr waste disposal pits. We present XAFS evidence for the reduction of Cr(VI) to Cr(III) after reaction with the Fe(Il)-bearing oxide magnetite, Fe3O4, and show that Cr associated with magnetite in soils is reduced, whereas that associated with non-Fe(II)-bearing silicate minerals is not. Also presented are ab-initio multiplescattering calculations of XANES spectra of an Cr(VI)O4 tetrahedron, which help explain the XANES features of this Cr species in solids and aqueous solutions.
The Evaluation of SrBi2Ta2O9 Films for Ferroelectric Memories
Authors: Gutleben C.D. 
Published: April 2011

AbstractFor use in ferroelectric memories, the layer structure ferroelectric SrBi2Ta2O9 (SBT) appears to have some stability-related advantages over the more commonly known PZT class of ferroelectrics. Currently we are evaluating the feasibility of integrating this material into a state of the art CMOS memory process. Our primary scientific goal is to identify the intrinsic limitations of SBT which may restrict the engineering applications of films grown by even perfectly optimized processes. To this end we have utilized a wide variety of microanalysis probes to examine polycrystaline SBT films grown under various conditions by both MOD and Flash MOCVD. We have found that X-ray diffraction methods must be supplemented by high resolution X-ray photoelectron spectroscopy (XPS) in order to fully analyze the secondary phases which are commonly incorporated in SBT films. The more complete knowledge of film microstructure that this provides has enabled us to relate phase structure to growth and annealing conditions. XPS has also given us some insight into the initial stages of the growth chemistry of SBT on various Pt surfaces.
Effect of Electrodes on Crystallization and Electrical Properties of Ferroelectric Pzt Films Deposited by Rf Magnetron Sputtering
Authors: Ea-Kim B. , Varniere F. , Hugon M. C. , Agius B. , Bisaro R. , Olivier J. 
Published: April 2011

AbstractThe electrical properties and crystallization process of Pb(Zr0.4, Ti0.6)O3or PZT thin films grown by rf magnetron sputtering, from ceramic target, on fiber-textured (111)Pt/TiN/Ti/SiO2/Si and polycrystalline RuOx/SiO2/Si have been studied. It is found that the amorphous as-deposited thin film, processed by rapid thermal annealing (RTA), is transformed to a perovskite PZT at about 700°C. It is pointed out that the “heating rates” to reach 700°C affect the electrical properties of such films: TEM analysis reveal different grain sizes as a function of the heating rate. The XRD show that an oriented (111) PZT is promoted when the film is annealed to the temperatures of 800°C for 5 secondes. For these annealing conditions, the electrical properties of such structure depend strongly on the deposition conditions of PZT. Our process studies show that a thin film PZT deposited on Pt or RuO1.65at 200°C and 1 Pa argon pressure gives good hysteresis loop with high values of Ps and Pr (about 20 and 30 μC/cm2on Pt and RuO1.65respectively) and low leakage current about 10−11A/cm2on Pt and 10−6A/cm2on RuO1.65.
Preparation and Pyroelectric Properties of La-Modified PbTiO8 Thin Films by Rf-Magnetron Sputtering
Authors: Kamada T. , Takayama R. , Tomozawa A. , Fujii S. , IIJIMA K. , Hirao T. 
Published: April 2011

AbstractHigh-quality La-modified PbTiO3 (Pb1−xLaxTi1−x/4O3; PLT) thin films were prepared by an rf-magnetron sputtering method. In this method, intermittent deposition was realized by periodical repetition of deposition and nondeposition processes. This deposition was found to enhance the horizontal grain growth of the films. The PLT thin films exhibit the phenomena named “self-polarization” and have high pyroelectric properties (pyroelectric coefficient γ of 5.0×10−8C/cm2K and low dielectric constant εr of 185) without a poling treatment. It was interestingly found that this self-polarization of the PLT thin films depends on the substrate temperature (Ts) and is based on a fairly small difference of the film composition (Pb/Ti). The pyroelectric properties were improved by means of addition of Mg to the PLT thin films. These thin films are expected to offer suitable materials for pyroelectric infrared (IR) sensors. High sensitive pyroelectric IR sensors (single element type and linear array type) were fabricated by using the PLT (x=0. 1) thin films with the new structures and the device processes. The sensors have remarkably high specific detectivity D* of 3.5×108 cm. Hz1/2/W and very fast response. A new compact IR sensing system using the linear array sensor (8 elements) has been developed for a new type of room air-conditioner.
Optical and Electrical Characterizations of Pzt Films With Different O/Pb Stoichiometry
Authors: Hugon M.C. , Kim B. Ea , Varniere F. , Agius B. , Masetti E. 
Published: April 2011

AbstractThin films were deposited by radio frequency (rf) magnetron sputtering on Pt/TiN/Ti/SiO2/Si substrates starting from a ceramic Pb(Zr0.4Ti0.6)O3 or metallic Pb1.1(Zr0.4Ti0.6) target. To promote the ferroelectric properties, films were successively processed by rapid thermal annealing (RTA). Before and after the RTA process, the film optical constants, in terms of refractive index and. extinction coefficient, were measured by spectroscopic ellipsometry and spectrophotometry and their values were related to the film composition determined by nuclear microanalysis with a precision better than ±2%. By adjusting the sputtering conditions, it was possible to grow different films with oxygen stoichiometry (O/Pb) in the range of 2.5-4.5. The electrical P-E characterization revealed a strong relation between the optical properties (film composition) before annealing and the hysteresis loop after annealing. This was mainly attributed to changes in the film oxidation during RTA and indicates that ferroelectric properties can be optimized adjusting the O/Pb ratio in the film.
Some new Results on Strontium Bismuth Tantalate Thin-Film Ferroelectric Memory Materials
Authors: Scott J. F. , Hartmann A. J. , Lamb R. N. , Ross F. M. , Vilbis A. DE , Araujo C. A. Paz De , Scott M. C. , Derbenwick G. 
Published: April 2011

Abstractreview is given, emphasizing electron microscopy, XPS, heavy-ion scattering, and very high frequency (1 MHz) hysteresis data, of the materials characteristics of thin films of SrBi2NbTaO9, SrBi2Ta2O9, and related titanates.
Yield Stress of Nano- and Micro- Multilayers
Authors: Hazzledine P. M. , Rao S. I. 
Published: April 2011

AbstractAn outline theory is given for the strengthening in polycrystalline and ‘single crystal’ multilayers. The model is based on the Hall-Petch theory applied to both the soft mode (in plane) and hard mode (cross plane) of deformation. In this theory the parameters to be evaluated are a Taylor factor M, the shear stress τ0 to move a dislocation within a multilayer and τ*, the shear stress needed to push a dislocation over a grain or interphase boundary. All three parameters are material- specific and attention is focussed on coherent multilayers of γ TiAl with micron thick layers and Cu-Ni with nanometer thick layers. M and some components of τ* are estimated classically. The remaining components of τ* and some components of τ0 are estimated from embedded atom simulations. The model captures the main experimental facts, that γTiAl is plastically very anisotropic with a rising yield stress as the lamellar thickness is refined and that Cu-Ni displays a peak in the yield stress at a layer thickness of approximately 10nm.
A Finite Element Study on Constrained Deformation in an Intermetallic / Metallic Microlaminate Composite
Authors: Heathcote J. , Odette G. R. , Lucas G. E. 
Published: April 2011

AbstractThe mechanical properties of intermetallic / metallic microlaminates were studied by determining the fundamental composite properties that control the fracture behavior: namely, the stress-displacement functions of the metal layers. Finite element methods were used to model the stress-displacement function of a constrained metal layer and to examine the effect of constituentproperties, residual stress, offset cracks in adjacent intermetallic layers, and debonding inclusions in the metal layer. Finally, FEM models representative of four specific microlaminates weredeveloped and the results were compared to experimentally determined σ(u)'s for those composites. Determining these fundamental composite properties and showing how they control the mechanical behavior gives insight into the optimum design of this composite system.
Impact Behavior of Extrinsically Toughened Discontinuously Reinforced Aluminum Composites
Authors: Irfan M. A. , Liou N. , Prakash V. 
Published: April 2011

AbstractDiscontinuously reinforced aluminum (DRA) composites with enhanced fracture toughness have recently been developed at ALCOA. The approach consists of producing a composite microstructure in which discrete ductile phases have been incorporated into the DRA through traditional powder processing routes. In the present paper, the high strain rate behavior of these toughened composites is investigated by obtaining (i) the dynamic flow characteristics at various levels of elevated strain rates using a split Hopkinson compression bar, and (ii) energy absorption during dynamic crack initiation and crack propagation using three-point bend specimens loaded on a modified Hopkinson bar configuration.
Microstructure and Thermal Conductivity of Thermal Barrier Coatings Processed by Plasma Spray and Physical Vapor Deposition Techniques
Authors: Ravichandran K. S. , Dutton R. E. , Semiatin S. L. , An K. 
Published: April 2011

AbstractThe temperature dependence of the thermal conductivity of multilayer coatings made by a plasma spray technique as well as some coatings made by physical vapor deposition (PVD) was investigated. The multilayer coatings consisted of a varying number of layers of Al2O3 and ZrO2 stabilized by 8%Y2O3. Plasma sprayed coatings exhibited a large reduction in thermal conductivity at all temperatures when compared to the bulk monolithic materials. This reduction was found to be due to porosity as well as thermal resistance brought about by interfaces in the coatings. A comparable reduction in thermal conductivity was achieved in monolithic ZrO2 as well as in a composite coating deposited by the PVD technique. Microstructural factors that may be responsible for this reduction are discussed.
Structural and Phase Transformations in Thin Film Ti-Aluminides and Ti/Al Multilayers
Authors: Banerjee R. , Swaminathan S. , Wheeler R. , Fraser H. L. 
Published: April 2011

AbstractMultilayered Ti/Al thin films (with nominally equal layer thickness of Ti and Al) have been sputter deposited on oxidized silicon substrates at room temperature. Transmission electron microscopy (TEM) and high resolution electron microscopy have been used to characterize the structure of these multilayers as a function of the layer thickness. Ti changed from an hcp to an fcc and back to an hcp structure on reduction of the layer thickness. Al too changed from an fcc to an hcp structure at a layer thickness of 2.5 nm. The observed structural transitions have been explained on the basis of the Redfield-Zangwill model. Subsequently Ti-aluminide thin films were deposited using a γ-TiAl target. These films were found to be amorphous in the as-deposited condition with crystallites of α-Ti(Al) embedded in the amorphous matrix. On annealing under a protective Ar atmosphere at a temperature of 550 °C, the Ti-aluminide film crystallized into a nanocrystalline two phase microstructure consisting of γ-TiAl and α2-Ti3Al. The crystallization of the aluminide film has been investigated in detail by in-situ annealing experiments on a hot stage in the TEM. The results of this investigation have been discussed in this paper.
Measuring Interfacial Fracture Toughness With The Blister Test
Authors: Hohlfelder R. J. , Luo H. , Vlassak J. J. , Chidsey C. E. D , Nix W. D. 
Published: April 2011

AbstractThe adhesion of thin films to substrates can be quantified using the blister test, which measures the crack extension force (G) required to propagate a crack along the film/substrate interface. We summarize the derivation of crack extension force for the blister test, and discuss how blister tests can be conducted by measuring only the pressure and volume of liquid injected into the test system. We describe a way to calculate the velocity of the interface crack front.Data from blister tests of acrylate films (14 μm thick) on nitride substrates are analyzed. The critical crack extension forces (GC) measured were 25 − 34 J/m2 for samples which had a commercial adhesion promoter at the interface, and 0.5 − 2.0 J/m2 without the adhesion promoter. GC was observed to increase with the velocity of the interface crack, and the dependence appears to obey a power-law.
Evolution of the Contact Area During an Indentation Process
Authors: Li Kangjie , Wu T. W. , Li J. C. M. 
Published: April 2011

AbstractThe evolution of the contact area during an indentation process has been examined by an a.c. technique and also by finite element analysis on five different bulk materials. The consistency of the results obtained by the two approaches not only show the validity and advantage of the a.c. technique but also corroborate the applicability of the elastic contact equation.
Micromechanical Tensile Testing
Authors: Greek S. , Ericson F. , Johansson S. , Schweitz J.-Å. 
Published: April 2011

AbstractA method is described where tensile tests can be performedin situon micromachined structures. The testing equipment consists of a testing unit mounted on a micromanipulator in a Scanning Electron Microscope (SEM). The fracture loads of micromachined beam structures made from thick and thin film polysilicon as well as from electrodeposited nickel and nickeliron alloy were measured, and the fracture strengths then calculated via measurements of the test structures’ initial cross-sectional areas. The statistical scatter of the polysilicon fracture strength values were evaluated by Weibull statistics. The mean fracture strength and the Weibull modulus, a measure of the scatter, were obtained
Simulation of Mechanical Deformation and Tribology of Nano-Thin Amorphous Hydrogenated Carbon (a:Ch) Films Using Molecular Dynamics
Authors: Glosli J. N. , Philpott M. R. , Belak J. 
Published: April 2011

AbstractMolecular dynamics computer simulations are used to study the effect of substrate temperature on the microstructure of deposited amorphous hydrogenated carbon (a:CH) films. A transition from dense diamond-like films to porous graphite-like films is observed between substrate temperatures of 400K and 600K for a deposition energy of 20 eV. The dense a:CH film grown at 300K and 20 eV has a hardness (˜50 GPa) about half that of a pure carbon (a:C) film grown under the same conditions.
Tribological Properties of Tetrahedral Carbon Films Deposited by Filtered Cathodic Vacuum Arc Technique
Authors: Shi X. , Tay B. K. , Flynn D. I. , Sun Z. 
Published: April 2011

AbstractTa-C films have been deposited using FCVA technique. The hardness and Young's modulus of the films on both silicon and sapphire substrates are determined by an ultra low load depth sensing nanoindenter to examine their dependence on the carbon ion energy. An optimum ion energy around 80 to 90 eV has been found, which coincides with the energy at which the sp3 content and film density reach maximum values. At this ion energy, the hardness, modulus and critical load of a 60 nm film on sapphire exhibit maximum values of 60 GPa, 580 GPa and 7 mN, respectively, whilst the frictional coefficient shows a minimum of 0.16.
Capillary Stress in Microporous Thin Films
Authors: Samuel J. , Hurd A. J. , Brinker C. J. , Frink L. J. Douglas , Swol F. Van 
Published: April 2011

AbstractDevelopment of capillary stress in porous xerogels, although ubiquitous, has not been systematically studied. We have used the beam bending technique to measure stress isotherms of microporous thin films prepared by a sol-gel route. The thin films were prepared on deformablesilicon substrates which were then placed in a vacuum system. The automated measurement was carried out by monitoring the deflection of a laser reflected off the substrate while changing the overlying relative pressure of various solvents. The magnitude of the macroscopic bending stress was found to reach a value of 180 MPa at a relative pressure of methanol, P/Po = 0.001. The observed stress is determined by the pore size distribution and is an order of magnitude smaller in mesoporous thin films. Density Functional Theory (DFT) indicates that for the microporous materials, the stress at saturation is compressive and drops as the relative pressure is reduced.