bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanomaterials: Tin(IV) Sulfide Endo-and Exosemiconductors
Authors: Bowes Carol L. , Ozin Geoffrey A. 
Published: March 2011

ABSTRACTEndosemiconductors, materials produced when atom constituents of bulk semiconductors are reorganized into ordered arrays of single size and shape clusters encapsulated within a nanoporous host, are introduced with the report of a novel tin(IV) sulfide endosemiconductor synthesized by a two-step MOCVD-like self-assembly process. Template-mediated hydrothermal syntheses of phase-pure and large single crystal tin(IV) sulfide exosemiconductors, materials resulting from reorganization of those same atomic constituents into an open-framework crystalline nanoporous structure is also discussed. The properties of these nanomaterials are considered in terms of the degree of coupling between molecule-like constituent clusters, a concept which mediates the nanoworld of matter intermediate between molecular and bulk.
Infiltration/Pyrolysis Processing of Fiber-Reinforced Silicon Nitride
Authors: Schwab Stuart T. , Graef Renee C. , Blanchard Cheryl R. , Pan Yi-Ming , Davidson David L. 
Published: March 2011

ABSTRACTWhile its high-temperature strength, resistance to oxidation, and other properties make silicon nitride an attractive candidate for many advanced structural applications, its propensity for brittle failure has hindered its widespread adoption. One approach to avoiding brittle failure is through incorporation of continuous fiber-reinforcement; however, conventional (powderbased) methods of silicon nitride fabrication can degrade fibers and are not amenable to the production of complex shapes. The Southwest Research Institute has developed a number of polymeric precursors to silicon nitride which are available as thermosetting liquids, and we have shown that these materials can be used in combination with near net-shape manufacturing techniques to produce fiber-reinforced silicon nitride composites. Mechanical property tests conducted at room temperature suggest that these polymer-derived composites exhibit fracture behavior comparable to those produced through conventional techniques; micromechanical investigations conducted at 800°C indicate that non-brittle failure is maintained at elevated temperature.
Interface Structure of Si3N4 Matrix Composite with Nano-Meter Scale Sic Particles
Authors: Sasaki Gen , Suganuma Katsuaki , Fujita Teruaki , Hiraga Kenji , Niihara Koichi 
Published: March 2011

ABSTRACT²-Si3N4 matrix composites reinforced with nano-meter scale SiC particles were fabricated by hot-pressing the mixture of SiC and Si3N4 fine powders. Interface microstructure and crack propagation in the composite were observed by high resolution electron microscopy. The interface between SiC and Si3N4 had good coherence, but no preferred orientation was observed. At the interface between SiC and Si3N4, the (111) face of SiC particles was flat, and sometimes a disturbed lattice structure thinner than 1 nm was observed. Near the main cracks, the microcracking at fine SiC particles/Si3N4 matrix interface was frequently observed. The cracks propagated exactly along this interface. The interface microcracking seems to contribute to the improvement of fracture toughness.
Fabrication and Properties of Si3N4 with Rare Earth Apatite Grain Boundary Phases
Authors: Tiegs Terry N. , Nunn Stephen D. , Ploetz Kristin L. , Menchoffer Paul A. , Walls Claudia A. 
Published: March 2011

ABSTRACTThe rare earth-oxide and nitride apatites were examined as grain boundary phases in silicon nitride to assess their potential for developing high toughness materials using gas-pressuresintering. Densification was dependent on the quantity of additives used with high densities achieved at equivalent oxygen contents of ∼8%. Fracture toughnesses (KIc) up to 8-10 MPa√m were obtained for some compositions. Ambient temperature flexural strengths were in the range of 400-720 MPa; however, the strengths atelevated temperatures (1200ºC) were reduced from these values.
Formation and Densification of R-α'-SiAIONS (R = Nd, Sm, Gd, Dy, Er and Yb)
Authors: Wang P.L. , Sun W.Y. , Yen T.S. 
Published: March 2011

ABSTRACTThe densification behavior and formation characteristics of R-α'-Sialons (R = Nd, Sm, Gd, Dy, Er and Yb) hot-pressed in the temperature range of 1500ºC-1750ºC have been studied. The temperatures required for full densification decrease and the content of the α-Sialon phase increases with an increasing atomic number of R.
Parameters Affecting Pressureless Sintering of α'-Sialons with Lanthanide Modifying Cations
Authors: O'reilly K.P.J. , Redington M. , Hampshire S. , Leigh M. 
Published: March 2011

ABSTRACTμ-silicon nitride forms a range of solid solution Mx(Si,Al)12(0,N)16 where x = 2 and M is Li+, Ca2+, y3+ or certain lanthanide cations. This paper reports the formation of Ln-α'-sialons by the reaction of Si3N4 with AIN and Ln2O3 where Ln=Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. Transformation reactions of Nd, Sm, Gd, Ho, Er and Y cations occurring during liquid phase pressureless sintering are reported. The effects of the volume and viscosity of the liquid phase and the amountof secondary N-melilite on sintering are discussed.
Non-Oxide Additives As Sintering Aids For Si3N4-Based Ceramics
Authors: Ge C. , Xia Y. , Chen L. 
Published: March 2011

ABSTRACTThis article is a review of the selected activities since 1979 in using non-oxide additives as sintering aids for silicon nitride. Emphasis was placed on the work done in the authors' laboratory, and it is shown that ZrN and AIN in combined use can result in producing silicon nitride with good properties.
Corrosion of Silicon Nitride Ceramics by Nitric Acid
Authors: Kanbara Kunihiko , Uchida N. , Uematsu K. , Kurita T. , Yoshimoto K. , Suzuki Y. 
Published: March 2011

ABSTRACTCorrosion of silicon nitride was studied in boiling nitric acid to examine its feasibility as a drying pan material in the reprocessing of nuclear fuel. Unlike stainless steel (a conventional drying pan material), the weight loss and strength degradation were negligible in the concentration of nitric acid. The corrosion increased with decreasing concentration of nitric acid. At the concentration of 1-6N, the maximum losses of weight and strength were 0.8% and over 40%, respectively, in 200 h. Ionic species dissolved in nitric acid were determined by ICP analysis and were found to be accurately correlated to the weight loss and thickness of the corrosion layer determined by micrography. In the corrosion layer, grain boundary glassy phase was selectively dissolved. Strength loss was correlated to the weight loss and was ascribed to the reduced load bearing area due to corrosion.
The Effect of Polymers on Ceramic Suspension Rheology and Green Component Properties
Authors: Lewis Jennifer A. , Ogden Andrea L. , Schroeder David , Duchow Kirk J. 
Published: March 2011

AbstractCeramic suspensions were formulated based on an alumina/plasticized-polymer system. The total polymer volume in suspension was held constant, while the relative amount of high-to-low molecular weight polyvinyl butyral (PVB) in suspension was varied. Experiments were performed to elucidate the effects of polymer molecular weight and distribution on the rheological properties of these casting suspensions as well as on the green microstructure of tape-cast components. The polymer properties affected not only the suspension viscosity at a given shear rate as expected, but also the shear thinning behavior of each suspension. Tapes (thickness ≈ 250 μm) were cast from these suspensions and their properties were evaluated. Pore volume, a measure of the packing efficiency, was found to depend strongly on the polymer molecular weight and distribution. In addition, preliminary lamination studies revealed that dimensional stability and anisotropy were also affected by the relative amount of high-to-low molecular weight PVB. A direct correlation was shown to exist between the shear thinning behavior of these suspensions and the resulting dimensional anisotropy exhibited by the tapes cast from each of them. These results demonstrate that polymeric aids influence not only the suspension rheology, but the green component microstructure as well, and, hence, are an integral aspect of ceramic processing.
Extrusion Rheology and Structure of Alumina - Silicon Carbiide Composites
Authors: Blackburn S 
Published: March 2011

AbstractSilicon carbide fibre reinforced alumina compacts were formed by extrusion. The powder and fibre were pre-mixed and milled before high shear kneading to produce a homogeneous dispersion of up to 30 vol% chopped SiC fibre with high green density. The rheology of the paste was characterised using a physically based model. It is demonstrated that the pressure drop and constituent paste parameters are all systematically reduced with increasing fibre loadings for a given moisture content. It is suggested that particle packing theory in combination with fibre interactions within the paste and die system offers an explanation for the observed results.
Structure and Rheology of Cement-Based Systems
Authors: Banfill P.F.G. 
Published: March 2011

AbstractFresh concrete and mortar conform closely to the Bingham model, but the rheology of cement pastes is more complex and structural breakdown occurs. This can be explained by the existence of forces between the surfaces of individual particles which are less significant in the coarser grained materials. The requirements of apparatus to determine the rheology of these materials are described and typical results reported. The behaviour of the materials in practical applications such as pumping, vibration and trowelling can be explained by the rheological parameters so obtained, and a consistent view of the performance of cement based materials may be developed.
Interparticle Forces and the Rheology of Colloidal Dispersions
Authors: Costello Bernard A. de L. , Luckham Paul F. , Tadros Tharwat F. 
Published: March 2011

AbstractThe forces between mica surfaces bearing adsorbed layers of graft copolymers of either polyethyleneoxide/ polymethylmethacrylate in water or polyhydroxystearic acid / polymethylmethacrylate in decalin have been measured. The forces are repulsive in nature and in both cases commence at a surface separation of ˜ 25 nm. They may be described by scaling theory. The results are compared to the rheology of particles stabilised by the same copolymers, in particular to the elastic modulus. It is found that these two parameters scale in the same way, but quantitative comparison reveals that the modulus predicted from the particle forces is some 1 – 2 orders of magnitude greater than that measured experimentally.
Rheology Control in High Solids Solvent Borne Coatings Containing Polymer Microgels
Authors: Boggs L. J. , Rivers M. , Bike S. G. 
Published: March 2011

AbstractThe focus of this work is to determine the type of interparticle forces that are primarily responsible for the rheology control of high solids solvent borne coatings containing polymer microgels. Rheological behavior is an important consideration when formulating high solids coatings due to the relatively low viscosities required for sufficient atomization during spray application and the difficulty of preventing the film from sagging during the bake cycle. Rheology control agents such as microgels are used to modify rheological properties where solvent evaporation is insufficient during the bake cycle to prevent sagging.In this paper that describes the first phase of our work, we have characterized several microgel dispersions used as rheology control agents in high solids automotive topcoats using scanning electron microscopy (SEM) and steady shear viscosity measurements. The steady shear viscosity versus microgel volume fraction data was compared with the expected behavior of ideal hard sphere dispersions. One of the microgel dispersions showed very nearly ideal behavior while others deviated from the expected behavior at higher volume fractions. We have also investigated the steady shear behavior of increasing concentrations of microgel dispersions added to low molecular weight acrylic polymer, typical of resins used in high solids automotive coatings. These microgel dispersions induce a yield stress in the Newtonian resin that shows a strong dependence on microgel particle concentration.
Granular Fluids Rheometry
Authors: Meeten G H , Pafitis D 
Published: March 2011

AbstractMany functional fluids, such as cement slurries or drilling muds, contain high-density solids, typically grains of 10–100 micron in diameter, suspended in a liquid of much lower density. Coaxial cylinder rheometers, conventionally used for oilwell fluids and dense suspensions generally, are shown to give large errors owing to gravitational or centrifugal migration of the high-density solids. Further errors can arise from slippage between the fluid and the smooth walls of the rheometer.A modification is described to a coaxial cylinder rheometer, in which the fluid is circulated, using an external pump, through the sample cup and around the rotor/stator assembly. This circulation mixes and homogenises the fluid, prevents solids build-up in both the annular gap and the cup bottom, and provides an independently-controllable shear history. Thus stable and accurate data can be obtained for fluids which give measurement problems using standard rheometers.Results are given for various power-law/yield stress granular fluids.
Structural Network Model of Dense Suspension
Authors: Jiang W. , Yang Nanru , Wang Z. 
Published: March 2011

AbstractA structural network model for investigating dense suspension is introduced. The suspension may be considered as particle dispersion in liquid as a continuous phase and it is the combination of the three-dimensional arrangement of the fine particles and the forces acting between them that determines the physico-chemical behavior at all stages of the processing. The model assumes that microstructural features of dense suspension can be represented by simple linear network with a breakdown threshold. The conditions under which such a structural network model is valid for studying flow are discussed. The cement paste, asphalt, sand-water and clay-water system were investigated respectively using this model. An oscillating rheometer and a conventional rotational viscometer were used to carry out this study. The dynamical and viscoelastic properties of dense suspension were observed. All the qualitative features of the network results can be described theoretically by a statistical analysis of this problem. Soil mechanics principles which are focused on critical-state theory were applied to describe the stress-strain behavior of dense suspension.
The Resolution of Photoelectrochemically Etched Features
Authors: Cheng J. , Kohl P. A. 
Published: March 2011

ABSTRACTThe profiles of features etched photoelectrochemically in n-InP are studied to determine the factors which govern their distortions and to determine the factor limiting spatial resolution for etch depths in the 100–200−μm range. The optimal conditions for etching straight grooves using laser light are determined. The application to front-to-back mask registration will be discussed.
Laser Photochemical Etching of GaP in KOH Aqueous Solutions
Authors: Johnson A. Wayne , Tisone Gary C. 
Published: March 2011

ABSTRACTGallium phosphide is an important III-V semiconductor material for fabricating strained layer superlattices and high-speed and high-temperature microelectronics. Etching of this compound semiconductor with conventional techniques presents problems which may be solved by photon-induced electro-chemistry. We have shown that rapid localized etching of n-GaP in KOH can be driven with the UV lines of an argon-ion laser. The level and type of doping and the laser intensity determine the etch rates, which are nearly 60 nm/sec at 3500 Wcm−2 for n-doped material.
Deep-UV, Light-Assisted, Wet Etching of Compound Semiconductors
Authors: Podlesnik D. V. , Gilgen H. H. , Osgood R. M. 
Published: March 2011

ABSTRACTDeep-UV, laser-light-assisted, wet etching of compound semiconductors is reported. As ccmpared to results with visible light, the etching rates per unit power density in the ultraviolet are considerably faster; a factor of >30 is seen under typical conditions. A correlation between the UV absorption in different etching solutions and the light-enhanced etching rates is examined. Gratings with 100-nm resolution have been produced and high-aspect-ratio via-holes have been etched.
Single-Crystal Silicon Etching Characteristics Using Excimer Laser Cℓ2 GAS
Authors: Arikado T. , Sekine M. , Okano H. , Horiike Y. 
Published: March 2011

ABSTRACTSingle-crystal Si etching characteristics using an excimer laser (308 nm, XeCℓ) in the Cℓ2 gas have been studied. In lightly doped n-type and p-type Si, the etch rate of (100) is higher than that of (111), thus the (111) sidewall appears clearly for the irradiation to (100), while both orientations show almost the same etch rates in n+-doped Si. The n-type Si is etched spontaneously even by photo-dissociated Cℓ radicals generated in the gas phase, but no p-type Si etching occurs without direct irradiation. In addition, both types of etch rate-dependence on sheet resistance demonstrate that the number of electrons in the conduction band plays an essential role in the Si etching. This fact supports the field-assisted mechanism in the plasma etching proposed by Winters.
Spatial-Resolution Limits of Laser Patterning: Submicrometer Projection Microchemistry
Authors: Ehrlich D. J. , Tsao J. Y. 
Published: March 2011

ABSTRACTThe predictions of a simple two-dimensional model for the sensitivity to process contrast of direct-write and projection laser microchemistry are reviewed. Microchemical reactions excited by UV image projection are demonstrated using a 30X reduction reflecting system and excimer laser illumination. Well-resolved images with submicrometer features are obtained by: (1) reaction of an Al/O cermet, (2) projection doping of Si in BCl3,(3) projection etching of Pyrex glass in H2, and (4) reactive patterning of an organic bilayer. Linewidths of 0.5 – 0.2 μm have been demonstrated for projection imaging in these systems.
Laser-Assisted Local Etching of Gallium Arsenide
Authors: Takai M. , Tokuda J. , Nakai H. , Gamo K. , Namba S. 
Published: March 2011

ABSTRACTPyrolytic local etching of GaAs using focused Ar laser beams in C12 or CCl4 gas atmospheres has been performed to investigate the possibility of maskless etching processes by laser beams. Etching rates from 0.3 to 40 μ/scan with an etched linewidth down to 5 μ were obtained. In the case of CC1 4 , a carbon line buried in GaAs was obtained for a single scan of a laser beam at a pressure above 80 Torr with low scanning speeds or at a pressure above 120 Torr.
Sensitive, Non-Intrusive, In Situ Measurements of Plasma Electric Fields
Authors: Gottscho Richard A , Moore Cameron A. , Davis Glenn P. 
Published: March 2011

ABSTRACTWe report a new technique for the in situ, non-intrusive, and sensitive measurement of plasma electric fields with high spatial resolution. Fields as small as 40 V/cm can be characterized by spectrally resolving laser-induced fluorescence from Stark-mixed parity levels. The technique is demonstrated by exciting the A1 11−X 1Σ+ band system of BC1, produced in an rf discharge through BCI3. The characterization and absolute measurement of sheath fields, which have been elusive, are now possible. These fields are preeminent in governing charged particle transport to and between electrode surfaces and in maintaining the glow discharge.
Laser-Induced Oxidation and Crystallization of Thin Amorphous Sputtered Cr Films
Authors: Birjega M. I. , Constantin C. A. , Dinescu M. , Florescu I. Th. , Mihailescu I. N. , Nanu L. , Popescu-Pogrion N. , Sarbu C. 
Published: March 2011

ABSTRACTThe crystallization and oxidation processes of thin, free-standing (FS), sputtered Cr films under the action of cw CO2 laser irradiation were studied by transmission electron microscopy (TEM) and transmission electron diffraction (TED). The crystallization is induced at power densities above 28.65 W cm−2, dwell time of 1 s, and the oxidation at power densities of 48.1 W cm−2 and longer dwell times.
Wafer-Scale Laser Pantography: IV. Physics of Direct Laser-Writing Micron-Dimension Transistors
Authors: Herman Irving P. , Mcwilliams Bruce M. , Mitlitsky Fred , Wah Chin Hon , Hyde Roderick A. , Wood Lowell L. 
Published: March 2011

ABSTRACTThe processes involved in the fabrication of micron-dimension transistors and small-scale integrated circuits using only the technique of direct laser-writing by localized pyrolytic surface reactions are discussed. New experimental findings in the deposition of tungsten by silicon. surface reduction of tungsten hexafluoride and doped polysilicon are presented. The techniques used to fabricate laser beam-written n-MOSFET's are being extended to make unipolar JFET's and bipolar lateral pnp transistors.
Infrared Laser-Induced Heterogeneous Reactions: Fluence-dependent Branching Ratios in 2-Propanol with CuO
Authors: Farneth William E. , Zimmerman Patrick G. , Hogenkamp Derk J. 
Published: March 2011

ABSTRACTThe heterogeneous decomposition of 2-propanol vapor in the presence of CuO solid can be induced by irradiation with a pulsed CO2 laser. The reaction produces both propene and acetone. In contrast, the homogeneous multiphoton-induced decomposition of 2-propanol vapor yields only propene. The branching ratio ([hydrocarbon]/[acetone]) in the heterogeneous experiments has been examined as a function of laser pulse energy. While the yield of acetone increases monotonically with increasing fluence, yields of hydrocarbon show two distinctly different regimes of fluence dependence. Reactions have been run with both d8 and h8 2-propanol and on 1:1 mixtures. Neither reaction channel shows significant isotopic selectivity over a range of experimental conditions. This data will be discussed in light of a model that involves energy deposition in the solid, followed by either heterogeneous reaction of adsorbed material or energy transfer and subsequent multiphoton excitation of the alcohol vapor.
Local Doping of GaAs by Laser-Stimulated Diffusion From the Gas Phase
Authors: KrÄutle H. , Roth W. , Krings A. , Beneking H. 
Published: March 2011

ABSTRACTSemi-insulating GaAs as well as MOCVD GaAs layers have been doped in situ with Se in a MOCVD system. H2Se diluted in an H2 + AsH3 atmosphere, which avoids surface decomposition, is used as the doping source. The surface is heated locally for less than 1 μs with a 3-ns Nd-YAG-laser pulse (frequency doubled: λ = 532 nm, pulse ratio 5 s−1). During this short time adsorbed Se atoms are incorporated into the heated surface region.This process allows us to achieve heavily doped thin layers with Se concentrations in the order of 1021 cm−3. Outside the irradiated area the crystal remains undoped.Se concentrations measured with secondary ion mass spectroscopy (SIMS) and carrier concentrations measured with the van der Pauw method indicate the diffusion of adsorbed Se atoms into GaAs. The distribution and activation of Se depends on laser power and substrate temperature.
Doping of GaAs From Silane Decomposition Under Pulsed Laser Irradiation
Authors: Pribat D. , Dieumegard D. , Dessertenne B. , Chaplart J. 
Published: March 2011

ABSTRACTWe have studied silicon incorporation in GaAs subsequent to Nd-YAG laser irradiation through high pressure silane atmospheres. The process involves SiH4 pyrolysis at contact with a laser-melted GaAs surface, and incorporation of the released Si atoms in the melt. SIMS analyses have allowed us to study silicon incorporation as a function of SiH4 pressure, laser energy density and number of laser shots. The high sheet resistance of the doped layers indicates that the silicon atoms are poorly electrically activated. A compensation mechanism is discussed based on oxygen penetration from native GaAs oxide layers.