bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intergranular Microstructure and Oxidation Behaviour of Si3N4 Ceramics Formed with Y2O3, Al2O3 AND ZrO2
Authors: Falk L.K.L. , EngstrÖm E.U. , Rundgren K. 
Published: March 2011

ABSTRACTAnalytical electron microscopy, X-ray diffractometry and secondary ion mass spectrometry (SIMS) have been used to characterize the intergranular microstructure of nitrided pressureless sintered (NPS) Si3N4 ceramics and the phase transformations which occur in the intergranular regions during oxidation. The phase transformations, which take place after crystallisation of the residual intergranular glass, are caused by an inward transport of oxygen and result in the development of sub-scalar phase gradients. Cubic Y2O3 stablized ZrO2 partitions from the oxynitride liquid phase sintering medium when a small amount of ZrO2(+ 3 mol% Y2O3) is added together with the Y2O3 and Al2O3 sintering additives. The latter material has a reduced oxidation resistance, presumeably due to the high oxygen conductivity of the cubic ZrO2 structure.
Partial Devitrification of Sintered Silicon Nitride During Static Fatigue Testing
Authors: Braue W. , Quinn G. D. 
Published: March 2011

ABSTRACTThe static fatigue behavior of sintered Y2O3/A12O3-fluxed Si3N4 in air is controlled by slow crack growth or creep fracture. Partial devitrification of the amorphous grain boundary phase at 1000°C and 1100°C improves the static fatigue resistance with specimens surviving up to 1500 hrs. during stress rupture experiments. In this study the early stages of partial devitrification during static fatigue testing at 1000°C are investigated by conventional and analytical transmission electron microscopy with emphasis on nucleation and growth of δ-Y2Si2O7 and X1-Y2SiO5 and possible constraints from different stress states. The results show that the stress state does not affect the nature of the secondary phase assemblage. However, the amount of crystallization is higher within the tensile region of the flexural specimens than in areas which experienced compressive stresses.
Role of Sintering Parameters on Microstructure Development and Mechanical Properties of Sinter/hip Silicon Nitride
Authors: Kühne Arnd , Oberacker Rainer , Grathwohl Georg 
Published: March 2011

ABSTRACTSinter/HIP consolidation with systematic variation of all relevant process parameters was performed for low additive (Y2O3-A12O3) silicon nitride material. With SEM-investigations as well as bending and creep tests the relevance of process parameters on microstructure development and mechanical properties was studied.
Deformation and Toughness of α-Silicon Nitride Single Crystals
Authors: Suematsu H. , Petrovic J. J. , Mitchell T. E. 
Published: March 2011

ABSTRACTVickers and Knoop indentation methods were used to determine the deformation behavior and fracture toughness of single crystal α-Si3N4at room temperature. The tests were performed on (0001), (1100) and (1120) faces; both hardness and toughness values were found to be independent of orientation within statistical variations. Thus, the mechanical properties of silicon nitride are essentially isotropic at room temperature.Single crystals of α-Si3N4were also compressed at 1760 and 1820°C at a strain rate of The sample tested at 1760°C showed yielding at a stress of 200MPa but it fractured before indicating a significant amount of plastic deformation. On the other hand, the sample compressed at 1820°C deformed to a strain of 2.7% at a stress of 4OMPa before fracturing. A significant density of dislocations was observed by transmission electron microscopy. From conventional g.b analysis, the Burgers vector of the dislocations was determined to be 1/3<1120>. From the line direction of the dislocations, the primary slip system of α-Si3N4is determined to be {1101}<1120>.
Damage Resistance of In Situ Reinforced Silicon Nitride
Authors: Li Chien-Wei , Gasdaska Charles J. , Goldacker Jeffrey , Lui Siu-Ching 
Published: March 2011

ABSTRACTThe room temperature fracture behavior for in situ reinforced (ISR) silicon nitride is correlated to its microstructure and R-curve behavior. The relation of strength to fracture origin suggests that stable growth of the intrinsic flaw precedes catastrophic fracture. Grainbridging that generates a rising bridging stress behind the crack-tip has been proposed as the cause for stable crack growth, which in turn reduces the strength dependency on initial flaw size. As a result of strong bridging by the acicular β-Si3N4 grains, ISR Si3N4 is characterized for high Weibull modulus. At elevated temperatures, the material's tensile creep rupture behavior follows the Monkman-Grant type plot. A tensile creep rate of -10−9s−1 at 1260°C/250 MPa, 1300°C/180 MPa, and 1350°C/90 MPa has been recorded. This relatively strong creep resistance is related to the sliding-resistance of the acicular grains and the properties of the amorphous film between the grains in ISR Si3N4.
Oxidation Behaviour of Zirconia-Sialon Composites
Authors: Cheng Yibing , Thompson Derek P. 
Published: March 2011

ABSTRACTIn yttria densified ZrO2-sialon composites, an increase in β′:O′-sialon ratio results in a structural change in the zirconia phase because an increasing amount of nitrogen dissolves in the zirconia structure as the overall composition becomes increasingly nitrogen rich. Both ZrN and nitrogen-containing zirconia (N-ZrO2) are observed in the β′-ZrO2 composite and these phases show a poor oxidation performance above 600°C. However, the introduction of small amounts of O′ phase into the β′-ZrO2 composite has provided an effective oxygen-rich barrier to reduce the diffusion rate of nitrogen in zirconia and therefore O′-β′-ZrO2 composites showed superior oxidation resistance compared with β′-ZrO2 materials at temperatures between 600 and 1200°C.
Factors Affecting the Extensional Flow of Crowded Suspensions for the Manufacture of thin Wall Ceramic Bodies
Authors: Greener James , Evans Julian R.G. 
Published: March 2011

AbstractProcedures for the manufacture of thin wall ceramic components from particulate suspensions using plastic forming methods which employ extensional flows are described. These include vacuum forming, blow moulding and film blowing. In order to understand how to select materials and to adjust the composition of such suspensions, the factors which control suspension rheology are identified. The measurement of extensional viscosity of ceramic suspensions is reported and compared with shear flow measurements.
Characterization of Monodisperse Aqueous Latex Dispersions Prepared with N-Isopropylacrylamide
Authors: Kiminta D. , Costello B. , Lenon S. , Luckham P.F. 
Published: March 2011

AbstractPoly-N-isopropylacrylamide (poly-NIPAM) is a water soluble nonionic polymer that exhibits a lower consolute solution temperature (LCST) of about 31°C. This paper describes the preparation and characterization of a monodisperse, hydrophilic polymer latex of poly-NIPAM, crosslinked by N,N'-methylenebisacrylamide. The presence of these crosslinking moieties will prevent dissolution of the particles at low temperatures; rather the particles will be swollen with solvent such that a microgel is formed. The swelling and rheological behaviour of the latex has been studied. The results show that at high temperatures the particles are ˜ 30 nm whilst at 25°C, the particles were ˜ 130 nm in diameter. This four fold increase in the particle diameter correspond to a ˜ sixty fold increase in volume. The rheological properties, both continuous and oscillatory shear, of these systems have also been studied and is strongly temperature dependant, reflecting the changes in phase volume of the NIPAM latex.
Rheology of YBa2Cu3O7−x Precursors
Authors: Green Timothy M. , Akinc Mufit 
Published: March 2011

AbstractNitrate and acetate precursors to Ba2Cu3O7−x (123) are prepared using a molten salt technique. The viscosity and shear stress of the paste are controlled by evaporation of water from the paste. The pastes contain ˜20 - 80 volume percent solids. Rheometry over strain rates of 0 - 200 sec−1 shows both systems are shear-thinning. Both systems are thixotropic. The nitrate system may be described by a two-stage Bingham Plastic model, the acetate by a Hershel-Bulkley model. The existence of more than one region of flow behavior suggests that there are at least two mechanisms which contribute to flow. In the low strain rate region, flow resistance is due to the existence of flocs in the colloidal assembly. At higher strain rates, flow is probably controlled by interlaminar drag interactions. Precursors produced by both methods have been used to form fibers of YBa2Cu3O7−x, by ram extrusion.
Theoretical and Empiriical Modeling of the Rheology of Fresh Cement Pastes
Authors: Karam Gebran N. 
Published: March 2011

AbstractThe most important property of cements and concretes after strength is the workability, which is controlled by the rheological characteristics of the mix. Theoretical modeling having proved complicated and in some cases mathematically untractable, cement specialists have concentrated on empirical based models for the last two decades. The major theoretical contributions to date on the properties of colloidal and concentrated suspensions are summarized and a general framework for theoretical modeling of cement viscosity is established. The empirical modeling and the experimental investigation of the rheological properties of fresh cements are reviewed and discussed. A semi-empirical model is proposed and its validity tested in the interpretation of some published experimental results.
The Interaction of Polymer Dispersions with Portland Cement Paste
Authors: Su Z. , Bijen J.M.J.M. , Fraaij A.L.A. 
Published: March 2011

AbstractResearch has been done on the interaction of two types of polymer dispersions, a styrene acrylate (SA) and a polyvinylidene chloride (PVDLC), with portland cement by means of a COULTER particle size analyzer and a filtration technique. It was found that over 50% of the polymer SA particles were adsorbed onto the cement surface, the others did not adhere to cement grains and remained dispersed in the mixing water. However, the polymer dispersion PVDLC caused a quick flocculation and coagulation of cement grains and stiffening of the paste. Hardly any free polymer particles of this polymer were found in the liquid phase.
Constitutive Behavior of Semi-Solid Metal Alloy Slurries
Authors: Kumar Pratyush , Martin Christophe L. , Brown Stuart 
Published: March 2011

AbstractThe constitutive flow behavior of semi-solid metal alloy slurries has been modeled using an internal variable framework. The formulation represents the primary flow response of these materials: history dependence (thizotvopy), steady state shear rate thinning (pseudoplasticity) and constant internal structure shear rate thickening (dilatancy). The flow response at any given structure has been decoupled from structure-dependent response in carefully controlled rapid transient experiments done on a computer-controlled, high temperature, Couette geometry rheomneter. The data for Sn-15wt%Pb correlates well with the model.
Crystallization in Suspensions of “Hard” Colloidal Spheres
Authors: Ackerson Bruce J. 
Published: March 2011

Extended AbstractSubmicron diameter polymethylmethacrylate (PMMA) particles suspended in a solvent mixture of tetralin and decalin have been observed to undergo a crystal to liquid phase transformation as a function of particle volume fraction[1]. This thermodynamic phase transformation and other measurements of the crystal structure [2], sedimentation rates [1], and response of particle microstructure to shear flow [3] suggest hard sphere behavior for the interparticle interactions.
Orientational Ordering of Rigid Rod Polymers in Shear Flow
Authors: Vugmeister B.E. , Wang C. , Ou-Yang H.D. 
Published: March 2011

AbstractWe present the results of experimental and theoretical study of the orientational ordering of rigid rod like polymers in the presence of shear flow. Shear induced birefringence was measured to determine the dependence of orientational order parameter S=<3cos2θ−l>/2 on the shear rate at different values of the volume fraction. Experimental results are discussed in terms of an approximate solution of the rotational diffusion equation in the presence of shear flow based on the construction of the effective interaction energy.
Direct Holographic Processing Using Laser Chemistry
Authors: Gilgen H. H. , Podlesnik D. , Chen C. J. , Osgood R. M. 
Published: March 2011

ABSTRACTBy using two interfering laser beams to initiate localized chemical reactions at an interface, very high resolution, maskless microfabrication can be done over relatively large substrate areas. The resulting deposited or etched patterns can be used in a variety of electrooptical and electronic applications. In addition, this type of fabrication, which can be monitored in real time, provides insight into many new interfacial phenomena.
Plasma-Initiated Laser Deposition of Polycrystalline and Monocrystalline Silicon Films
Authors: Gee J. M. , Hargis P. J. , Carr M. J. , Tallant D. R. , Light R. W. 
Published: March 2011

ABSTRACTIn this paper we report a new method of silicon deposition using the interaction between the radiation from a pulsed-ultraviolet excimer laser and the plasma species produced in a glow discharge in silane (SiH4). Examination of the deposited film by laser Raman spectroscopy and by transmission electron microscopy revealed that the morphology ranged from polycrystalline silicon at laser fluences of 0.13–0.17 J/cm2 to epitaxial silicon at fluences of 0.4–0.6 J/cm2 . Growth rates of 100 nm/min for polycrystalline silicon and 30 nm/min for monocrystalline silicon were achieved.
Localized Photoprocesses at Semiconductor-Electrolyte Interfaces Using a Programmable Laser Spot Scanner
Authors: Kavassalis C. A. , Longendorfer D. H. , Lelievre R. A. , Rauh R. D. 
Published: March 2011

ABSTRACTA highly focused laser can be used to perform spatially selective photoelectrochemistry at semiconductor-electrolyte interfaces. These processes may be used for imaging (etching, deposition, etc.) or for nondestructive mapping of semiconductor properties from photoelectric response. A programmable laser scanner is described which can be used for both. An example of imaging is given for photoelectrochemical etching of pits in CdSe electrodes, which may be applied to archival data storage. Nondestructive evaluation is shown for a CdS crystal, in which the lateral distribution of subband gap photovoltage response is related to surface states incurred by polishing damage.
Excimer-Laser-Initiated, Dry Etching of Single Crystal GaAs
Authors: Brewer P. , Halle S. , Osgood R. M. 
Published: March 2011

ABSTRACTGas-phase UV-initiated (193 nm) photodissociations of methyl (CH3) and trifluoromethyl (CF3) containing compounds have been investigated for the dry etching of single crystal GaAs substrates. Etching rates of greater than 1 μ/min. have been observed. Etching rates and surface profiles will be discussed in terms of crystal orientation, reactive etching fragments, and laser-surface interactions. Products of the etching reactions have been examined by UV absorption, mass spectrometry and laser-induced fluorescence techniques. Applications to large scale and micron dimension etching processes will be briefly discussed.
Laser-Induced Chemical Etching of Solids: Promises and Challenges
Authors: Chuang T. J. 
Published: March 2011

ABSTRACTRecent studies have shown the potential of laser-induced chemical etching to become a powerful technique for processing electronic materials. In this paper, the unique strengths and limitations of the laser chemical approach are examined. Some photon-enhanced reaction mechanisms, in particular silicon-halogen reactions, are discussed to illustrate the many facets of the electronically, vibrationally and thermally activated surface processes. It is suggested that the field-assisted diffusion mechanism proposed by Winters, Coburn and Chuang may also be applicable to some photon-induced etching reactions. In addition, the salient features of the laser and the plasma-assisted etching methods are compared. The challenges to resolve certain fundamental and practical difficulties involved in developing the laser technique for processing technology are also outlined.
Laser-Induced Deposition of Silicon Films and Cars Diagnostics
Authors: Hanabusa M. , Kikuchi H. 
Published: March 2011

ABSTRACTVarious laser-based deposition methods for preparation of silicon films have been reviewed briefly with emphasis on laser chemical vapor deposition (CVD). The main body of this paper is concerned with CO2laser CVD of silane. This is interesting because the observed dependence of deposition rates on laser wavelengths indicates that gas-phase reactions are involved in deposition processes and therefore we can apply a powerful new diagnostic means, coherent anti-Stokes Raman spectroscopy (CARS), to examine gas-phase dynamics. From N2CARS thermometry the CO2laser beams were found to raise the temperature of the gas containing silane, when they were tuned to absorption lines of SiH4. Silane CARS spectra were characterized by a complicated profile with double peaks. We interpreted the shape of the spectra as arising from excitation of rotational levels following gas-phase reactions. Applying this interpretation, we can judge how SiH4molecules are disturbed differently according to CO2laser wavelengths and a distance from a substrate.
Real-Time Diagnosis of Etching and Deposition Processes by Spectroscopic Ellipsometry
Authors: Aspnes D. E. , Chang R. P. H. 
Published: March 2011

ABSTRACTRecent advances in instrumentation and data analysis have made spectroscopic ellipsometry a routine analytic tool with submonolayer sensitivity for monitoring and controlling cleaning, etching, deposition, or other processes that take place in relatively high-pressure or reactive environments. We discuss representative applications in chemical etching, plasma processing, and MOCVD to illustrate analytical procedures and to indicate other potential uses of the technique. The possibility of extracting surface information already carried in the polarization state of the processing laser beam is also discussed.
Mechanism of Laser-Assisted Evaporation of II-VI Semiconductors
Authors: Cheung J. T. 
Published: March 2011

ABSTRACTThe evaporation mechanism of CdTe, HgTe and HgO.7CdO.3Te under high power laser irradiation was investigated using mass spectroscopy. Results were compared to thermal evaporation. Thermal evaporation yields Te molecules and Cd(Hg) atoms. In the case of HgTe and Hgo.7Cdo.3Te, the evaporation is noncongruent. Evaporation induced by the irradiation of 1.06 μm Nd:YAG laser pulses evolves atomic Hg, Cd and Te congruently. The dissociative and congruent nature of this process makes it a very attractive technique for depositing thin films.
Ion Dynamics in Low Frequency RF Plasmas
Authors: Gottscho Richard A. , Flamm Daniel L. , Burton Randolph H. , Donnelly Vincent M. 
Published: March 2011

ABSTRACTWe describe the use of time-resolved laser-induced fluorescence (TRLIF) and plasma-induced emission (PIE) spectroscopy in studying the dynamics of ion transport, formation, and loss in low frequency RF plasmas, used in plasma etching and deposition. N2+ and Cl2+ ions formed in N2, Cl2, and N2/Cl2 discharges were monitored as a function of both position between the electrodes and magnitude of the applied rf potential. In the discharge center, TRLIF was used to measure ground state ionic lifetimes. In N2/Cl2 mixtures, N2+ was found to charge exchange rapidly with Cl2 and Cl to form Cl2+ and Cl+. In the electrode sheaths, the ion response to the applied potential was evident from periodic depletion of the ion concentration as a result of acceleration by the field. From the spatial variation in the ion concentration time dependence, we deduce that the sheaths expand and contract with the same period as the applied potential.
Recent Advances in Laser-Enhanced Plating
Authors: Von Gutfeld R. J. , Gelchinski M. H. , Vigliotti D. R. , Romankiw L. T. 
Published: March 2011

ABSTRACTA summary of the recent work on laser-enhanced gold plating is presented. The purpose of the study has been to obtain rapid maskless plating on thick metal samples. Results will be described on the plating rates for a variety of laser and electrical parameters. The most recent work on a laser-jet plating system will be discussed. With this system, rates of up to 30 μm/s have been achieved on 8 mil thick Be-Cu samples.
Pyrolytic Laser Activation Of Cds Thin Film Photoconductors
Authors: Kitai A. H. , Wolga G. J. 
Published: March 2011

ABSTRACTCdS and CdS:Ag thin films, deposited at room temperature, were irradiated using an argon-ion laser, causing them to become photoconductive in the path of the laser beam. Physical deformation of the thin films is reported, and the optical and electrical properties of the photoconductive devices thus fabricated are described. We suggest this as a means to fabricate small area, patterned photoconductors with the benefit of maskless, low temperature processing.
Primary and Secondary Ion Deposition of Epitaxial Semiconductor Films From Laser-Induced Plasmas
Authors: Lubben D. , Barneti S.A. , Suzuki K. , Greene J.E. 
Published: March 2011

ABSTRACTPrimary and secondary ion deposition of epitaxial semiconductor films from laser-induced plasmas is reported Laser plasmas were generated by focusing 15 ns, 107 to 108 W/cm2 pulses of 5 eV photons from a KrF excimer laser onto Ge and Si wafer targets. Time-of-flight, current-voltage, and film thickness measurements at secondary (i.e., ion) targets indicated that the ions were emitted, with an average energy of ∼40 eV, in a distribution which was strongly peaked in the normal direction. Primary ion deposition was performed by placing substrates on an ion target/substrate heater biased to give additional ion acceleration as required. Secondary deposition was achieved by biasing the ion target, in this case a wafer of the same material as the laser target, sufficiently negative to sputter target material onto a third electrode. Epitaxial Si on (100) Si and Ge on (100) Si and (100) GaAs were obtained by both methods. Hall effect measurements on heteroepitaxial Ge grown at 1 μm/hr on GaAs substrates by primary deposition showed thatfthe films were p-type with hole concentrations of ∼1018 cm−3 and mobilities of ∼150 cm2/V-sec.
A Model for the Laser-Induced Chemical Vapor Deposition of Hydrogenated Amorphous Silicon
Authors: Meunier M. , Flint J.H. , Adler D. , Haggerty J.S. 
Published: March 2011

ABSTRACTWe propose a model for laser-induced chemical vapor deposition in which the growth of hydrogenated amorphous silicon (a-Si:H) thin films is rate-controlled by the gas phase homogeneous thermal dissociation of SiH4 The gas temperature is determined by a steady-state balance between energy absorbed from the laser and energy lost by thermal conduction.The film properties are primarily controlled by the substrate temperature.