bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropy of Tensile Recovery Stress and Two Way Memory Effect of Cold Rolled Tini Sheet
Authors: Mulder J. H. , Thoma P. E. , Beyer J.
Published: March 2011

The texture of cold rolled and heat treated TiNi sheet has been measured and designated as {110}<110>p. The.anisotropy of the tensile recovery stress, the stress dependence of the transformation temperatures, and the development of the two-way memory effect during thermal fatigue have been measured. The resulting changes of texture after thermal fatigue are presented and explained. The observed effects are explained on the basis of the parent texture and the specific martensite variants which are formed according to the lattice correspondence between austenite and martensite.
A Martensite Peculiar to Thin Foils of a Ti50Ni49Fei Shape Memory Alloy
Authors: Tadaki Tsugio , Yamamoto Sukeyoshi , Shimizu Ken'ichi
Published: March 2011

A peculiar martensite found in thin foils of a Ti5oNi49Fei shape memory alloy has been examined by transmission electron microscopy and electron diffraction, which was entirely different from the R phase and the B19' and B19 martensites widely known so far in the Ti-Ni based alloys. The thin foil martensite is monoclinic with a=0.700nm, b=0.994nm, c=0.632nm and γ =94.4°. The lattice correspondence between the B2 parent phase and the martensite is as follows: <210>B2→ <100>M, <230>B2→ <010>m, <002>B2→ <001>m. The formation conditions and atom positions in the unit cell of the thin foil martensite are discussed.
Review of Phonon Behavior and Microstructural Development Leading to Martensitic Transformations in NixAl(100-x)Alloys
Authors: Tanner L. E. , Shapiro S. M. , Schryvers D. , Noda Y.
Published: March 2011

Elastic and inelastic neutron-scattering and high-resolution electron-microscopy examinations of the β2 (B2) phase of NixAl(100-x)alloys show a direct relationship between the anomalous changes in lattice dynamical behavior and the evolution of static premartensitic structural configurations as the β2 cools toward its martensitic transformation temperature,Ms. The resulting microstructure is a fine-scale mosaic assembly of nonuniformly distorted and modulated domains, in which {110}<110> shear-plus-shuffle displacements give rise to the {110}B2 micromodulations of ∼1.3 nm wavelength. These displacements are derived from the unusually low energy of the Σ4<ζζ0>–TA2phonon mode and its anomalous temperaturedependent incomplete softening at ζ = 0 (viz., the elastic constantC) and at ζ ≈ 0.16. These inhomogeneously strained domains (ISDs) are believed to be centered on low strain-amplitude defects. They are viewed as strain embryos of the product 7M(5, 2) martensite but are generally too weak to act as potent nucleation centers. Similar ISD configurations develop at defects with higher strain amplitudes (e.g., dislocations, grain boundaries) and these are the most likely sites for heterogeneous nucleation to occur.
Coherent Nucleation and Growth of Marte1Nite in B2 Nial Oberved in Computer Simulations
Authors: Clapp P. C. , Shao Y. , Rifkin J. A.
Published: March 2011

In atomistic simulations of B2 NiAl usirn Molecular Dynamics and Emxbedded Atom Method Ni-Al potentials, both thermally induoed and stress induced crent martensitic nucleation and growth processes of a tetragonal Llo phase have been observed, including the formation of self-accommodating martensite variants. Nucleation is found to occur only at special heterogeneous sites that can be well characterised. Prior to nucleation, clear evidence of the buildup of large amplitude localized soft modes can be seen. A discussion of the kinetics of these processes is presented.
Pushing The Limit to Achieve NiTi SMA Actuating Members that are Dimensionally Stable and have High Transformation Temperatures
Authors: Thoma Paul E. , Blok Alexander M. , Kao Ming-Yuan
Published: March 2011

In binary NiTi shape memory alloys (SMA), the highest martensite (M) and austenite (A) transformation temperatures (TT) occur in the annealed condition. The highest TT also occur in near equiatomic NiTi alloys that have an excess of Ti. However, the NiTi alloy composition and condition that have the highest TT produce actuating elements that are generally short lived, have poor mechanical properties, and plastically deform (creep) under low stress levels. Cold working the SMA followed by a memory imparting stress relieving heat treatment (HT) produces actuating elements that are long lived, have good mechanical properties, and are resistant to creep under moderate stress levels. However, in obtaining these desirable properties through thermal-mechanical processing, the M and A TT are significantly decreased, which limits the upper ambient temperature in which the actuating element can operate.

A dimensionally stable actuating member with high TT can be achieved by thermal cycling (under stress) a NiTi SMA wire that has received prior thermal-mechanical processing. Cycling under an applied axial stress can increase the M TT of a SMA wire. Data showing the influence of thermal cycling on the TT of axially stressed SMA wires, that were cold drawn followed by HT at different memory imparting temperatures, are presented and discussed. For a NiTi SMA wire (A finish TT = 111 °C in the annealed condition) having approximately 40% cold reduction in area, 400°C for 1 hour memory imparting HT, and 10 Ksi axial stress, the M start TT (Ms) and A finish TT (Af) increase from 26°C and 79°C respectively after 10 thermal transformation cycles to 62 °C and 83.5 °C respectively after 10,000 thermal transformation cycles.
Fabrication of A CU-AL-NI-MN Shape Memory Alloy
Authors: Wu Ming H. , Semiatin S.L. , Schetky L.M.
Published: March 2011

In the development of an optimized hot rolling process for a Cu-Al-Ni-Mn sheet alloy, the effects of the recrystallization texture on ductility and shape memory recovery were examined. The texture of samples rolled in the β phase region (750 °C) was characterized by martensitic (128) poles along the normal direction and (0018) poles inclined 60° from the normal to the rolling direction. The texture of samples rolled in the α+β region (600 °C) was slightly stronger but less symmetric. The shape memory recovery was more or less isotropic in the rolling plane, independent of the rolling conditions. However, improved bend ductility of 9.5% was observed along the rolling direction in specimens rolled at 750 °C with a reduction per pass of 27%.
High Temperature Shape Memory Alloys of Ni-Al Base Systems
Authors: Kainuma R. , Nakano H. , Oikawa K. , Ishida K. , Nishizawa T.
Published: March 2011

An attempt to develop a new type of high temperature shape memory alloys based on the Ni-Al system has been made through microstructural control. Addition of Fe or Mn to the binary Ni-Al alloy results in the formation of a ductile fcc phase in an extremely brittle P matrix phase, leading to an improvement in its ductility. These ductile alloys with β + γ two-phase structure in the Ni-Al-Fe, Ni-Al-Mn and Ni-Al-Mn-Fe systems exhibit a shape memory effect due to a thermoelastic martensitic transformation in the temperature range between -100°C and 700°C; besides, the transformation temperatures are easily controlled by annealing at an appropriate temperature. These alloys are expected to be a new group of shape memory alloys which operate at elevated temperatures.
Practical Application of Static Rock Breaker Using TiNi Shape Memory Alloy
Authors: Nishida M. , Kaneko K. , Takashima K. , Yamauchi K. , Inaba T.
Published: March 2011

A newly invented static rock breaker using TiNi shape memory alloy has been proposed. The breaker consisted of compressively pre-strained TiNi rods of 15mm in diameter and 29mm in height and a pair of two-layered wedge type platens of steel, and required no accessory equipments other than heating apparatus. The maximum breaking force per unit length of the breaker was 3 to 5MN/m. The total breaking force was about 300 to 900kN, depending on the number of TiNi rods used. To examine the practicality, the breaker has been applied to concrete wall of building, natural boulder, etc. It was confirmed that the breaker was not lack in terms of performance and was possible to control the direction of crack initiation and propagation. It can be concluded that TiNi shape memory alloy has a bright prospect as a solid pressure source.
Crystal Structure of ζ2' Martensite in Au-49.5at%Cd Alloy
Authors: Emura Yutaka , Ohba Takuya , Otsuka Kazuhiro
Published: March 2011

Crystal structure of the ζ2' martensite in a Au-49.5at%Cd ally has been analyzed by the single crystal x-ray diffraction method. The crystal lattice was trigonal and the lattice constants were a:0.8095(3) and c=o.57940(6) nm. There were 18 atoms in a unit cell. The space group was P3, which was different from that previously determined by Vatanayon and Hehemann. The structure was refined by the full matrix least squares method to a final R factor of 7.8% and a weighted R factor of 4.1%.
Deformation of Polydomain Phases
Authors: Roytburd A.L.
Published: March 2011

The thermodynamic theory of the deformation of heterophase solids containing polydomain phases is presented. The polydomain phases consisting of twins are considered. Elastic interaction between twins leads to the formation of an equilibrium polydomain structure. Its basic element is a polytwin: a plane-parallel plate consisting of alternating plane-parallel twins. In a uniform single crystal the polytwin structure is unstable and should disappear at any uniform external stress. But it can be stable in a heterophase system. The evolution of the equilibrium structure with the variation of the external stress exhibits reversible superplasticity and pseudoelasticity. Two contributions into total strain are considered: due to displacements of twin boundaries inside a polydomain (polytwin) phase and due to movement of interfaces between polydomain and matrix phases.
Fluorescence Probe Studies of Poly(Acrylic Acid) Interchain Complexation and Chain Rigidity Indyced by High Shear Flow. Influence of Molecular Environment
Authors: Kim Oh-Kit , Choi Ling-Siu
Published: March 2011

The mode and strength of poly(acrylic acid), PAA, interchain complexation was strongly influenced by the presence of salts and cationic surfactants. Addition of salts to the shearing PAA solution disrupted the complexation, while modification of the PAA with surfactant enhanced the complexation but only below a critical concentration that depended on the surfactant chain length and pH employed. The chain morphology developed by such interchain complexation of PAA is a rigid rod-like chain cluster. The PAA self-complexation in the presence of poly(ethylene oxide), PEO, is strongly affected by pH and PEO molecular weight. With a high molecular weight PEO, the PAA self-complexation is drastically suppressed, whereas the PAA complexation and thus, the chain rigidity is markedly enhanced in the presence of a low molecular weight PEO, probably due to physical crosslinking of the PEO between the elongated PAA molecules.
Lyotropic and Thermotropic Lrquid Crystals Under Shear Flow
Authors: Sirota E. B. , Safinya C. R. , Piano R. J. , Jeppesen C. , Bruinsma R. F.
Published: March 2011

We describe x-ray scattering studies of the nematic and smectic-A phases of the thermotropic liquid crystal 8CB and the Lα, and L3 (lamellar and sponge) phases of the lyotropic liquid crystal system: SDS, dodecane, pentanol and water. In the thermotropic system a series of orientational states of the nematic director is observed before entering the smectic-A phase where the smectic density wave and nematic director are oriented normal to the shear plane at high shear rates. In the lyotropic system lamellar fluctuations in the sponge phase (L3) become oriented by shear and in the lamellar phase (Lα) at high shear the layers orient preferentially along the velocity-gradient direction, in highly anisotropic cylindrical multilamellar liposome-like structures.
Light Scattering Near the Shear-Induced Critical Point in Nematic Liquid Crystals†
Authors: Olmsted Peter D. , Goldbart Paul
Published: March 2011

We study linear fluctuations about the steady states of thermotropic liquid crystals under planar sheax flow. Near the non-equilibrium critical point we find a single critical mode whose singular behavior at the critical point may be selectively probed by polarized light scattering. This critical mode is a combination of both amplitude and orientation fluctuations of the order parameter, which distinguishes it from conventional Ising-like critical modes, which are purely amplitude fluctuations. There are at least two distinct signatures of the critical point, depending on whether the critical strain rate is in the (material-dependent) strong or weak shear regimes.
Electrorheological Fluids: Structure Formation, Relaxation, and Destruction
Authors: Halsey Thomas C.
Published: March 2011

In a strong electric field, the qualitative behavior of electrorheological fluids is dominated by the dipolar interactions between the colloidal particles. When thermal effects can be ignored, the ground state of a system of dipolar particles is an ordered solid. However, long-range ordered structures are rarely seen in experiment. When a high electric field is applied to a fluid, dielectric columns oriented parallel to the field rapidly form. The relaxation of these columns is a much slower process. I calculate the shape of the columns formed and the time scale for the relaxation of the columnar structure. I also discuss how this structure formation is altered in the presence of a shear flow.
Sheared Suspensions II - Depletion Aggregation
Authors: Melrose J. R.
Published: March 2011

A Brownian dynamics algorithm described in the companion paper [1] is used to simulate sheared suspensions of particles interacting via a depletion potential. The shear and interaction forces interplay to give a complex non-equilibrium phase diagram: a variety of shear induced agglomerates form at low shear rate, but, for shear rates above a non-equilibrium phase boundary the agglomerates develop interfaces predominantly orientated parallel to the plane of shear gradient and flow.
Surface Tensions of Molten Polymers as a Function of Molecular Weight and Temperature.
Authors: Sauer Bryan B. , Dee Gregory T.
Published: March 2011

Surface tensions of viscous molten polymers were measured with the modified Wilhelmy method. Small diameter fibers were used as vertical surface tension probes giving rise to rapid equilibration of the wetting meniscus. Noise due to thermal convection currents was suppressed by the use of a baffle tube to protect the electro-balance which allowed us to extend our studies to temperatures exceeding 400°C. The precision of the surface tension measurement at T<350°C for n≤10,000 Poise is better than 0.5%. Discussion is made of the rate of meniscus equilibration as a function fiber diameter. The surface tensions of polystyrene(PS), polydimethylsiloxane(PDMS), poly(ethylene glycol)(PEG), poly(propylene glycol)(PPG), and polyethylene(PE) were determined as a function of MW and temperature in order to compare with theoretical predictions. The Cahn-Hilliard interfacial gradient theory is used in conjunction with equation of state models using pressure-volume-temperature data as the input. Good agreement with experiment is found using one adjustable parameter which is independent of MW, for both polar and non-polar polymers.
Equjlubrium Topologies of Associatxng Polymers
Authors: Baljon Arlette R. C. , Witten Thomas A.
Published: March 2011

We have developed a Monte-Carlo computer simulation to study associating polymer interactions. In our model we treat the associations as geometrical constraints. Each polymer chain contains two‘stickers’. The chains are treated as lattice selfavoiding random walks. Each sticker is constrained to be adjacent to one other sticker, but the stickers are free to exchange partners. This freedom to exchange results in an attraction between the chains, as anticipated by Cates and Witten.1 We find that in equilibrium the mutual excluded volume of two such chains passes from repulsive to attractive when the ratio of the sticker distance to the chain length is approximately 0.8. These results are independent of the chain length: they should apply to real polymers subject to these topological constraints in any good solvent at sufficiently high molecular weight.
The Conformation of Flexible Membranes
Authors: Lipowsky Reinhard , Cook-RÖder Joanna
Published: March 2011

Membranes such as lipid bilayers are highly flexible surfaces which determine the architecture of biological systems and provide a basic structural element for the mesophases of complex fluids1. Two aspects of their conformational behavior will be considered. First, the morphology of vesicles and membranes is briefly reviewed. Then, recent theoretical work on adhesion (or cohesion) phenomena which involve whole bunches of membranes will be discussed.
A Realistic Model for a Spin Glass
Authors: Given James A. , Stell George
Published: March 2011

We develop exact integral equations satisfied by the spin-spin correlation functions of a realistic spin glass model. This is done by considering the magnetic particles in a spin glass to be bound states of hard sphere ‘atoms’ and classical ‘spins’, the former of which are quenched in position, while the latter are allowed to equilibrate. We develop the replica Ornstein-Zernike (ROZ) equations, which are satisfied by the correlation functions of such a partly quenched mixture. We prove that two widely used OZ closures, the Percus-Yevick approximation and mean-spherical approximation are indifferent to quenched disorder, i.e., they give tihe same results for quenched and for fully annealed systems. We extend the ROZ equations to apply to the spin glass by using the proper interaction-site formalism. Preliminary numerical results are discussed.
Scattering Studies of the Isolated Red Blood Cell Skeleton, a Biological Two-Dimensional Polymer
Authors: Svoboda K. , Schmidt C.F. , Lei N. , Safinya C.R. , Block S.M. , Branton D.
Published: March 2011

We studied the conformation of the membrane skeleton of human red blood cells (RBC) after detergent extraction of RBC ghosts, using video microscopy, light scattering, and synchrotronbased small angle X-ray scattering (SAXS). RBC membrane skeletons are two-dimensionally connected, triangulated networks of flexible, polyionic proteins. Immediately after extraction, the skeletons exhibited large-scale thermal undulations and deformed strongly in weak shear flow. Screening of electrostatic repulsion by immersion in high ionic strength buffer led to shrinkage, while the shell-like conformations and the flexibility of the skeletons were preserved. Under high ionic strength conditions (1 M monovalent salt), the static structure factor,S(q), showed two power law regimesS(q) ∝q−α, with α <≈ 2.0 in the range of wave vectors 4×10−4Å−1<g< 8×10−4Å−1, and α = 2.3 ± 0.1 in the range of wave vectors 8×10−4Å−1<q< l×10−1Å−1. The same power law behavior was observed in low ionic strength buffer (25 mM salt) forq< 2×10−3Å−1. This result is not consistent with the occurence of a crumpling transition during skeleton shrinkage. The observed form of the static structure factor, with a transition between two regimes with different power law exponents, presents evidence for the theoretically predicted flat phase of 2D-polymers.
Low Temperature Routes to Cordierite-Like Ceramics using Chemical Processing
Authors: Zhang Zhi-Fan , Hoppe Martin L. , Rahn Jeffrey A. , Koo Sang-Man , Laine Richard M.
Published: March 2011

The reaction of SiO2 with basic magnesium compounds, in the presence of excess ethylene glycol, provides access to the hexacoordinate silicate complex, MgSi(OCH2CH2O)3. Alkali metal hydroxides provide access to pentacoordinate silicates of the type M2Si2(OCH2CH2O)5, where M = Li, Na, K, and Cs. Alumina also reacts with alkali metal hydroxides and ethylene glycol to give compounds of the type MAI(OCH2CH2O)2. HCl neutralization of the alkali metal silicates and aluminates provides the neutral metal glycolates of Si and Al. Stoichiometrically correct mixtures of these complexes form homogeneous, cordierite precursor solutions that are potentially useful for forming films, fibers and membranes of cordierite. These polymer-like materials can be heated directly in air to generate first α-cordierite and then µ-cordierite. Hydrolysis and condensation reactions, which occur in sol-gel processing, are not required. The phase transformations and chemical changes that occur during pyrolytic transformation of the preceramic materials to their target ceramic products were characterized. Methods developed during the course of these studies led to the development of heating schedules wherein well crystallized g.-cordierite could be formed at 850 °C.
High-Rate Formation of Nano-Scale Alumina Particles
Authors: Kilian A. , Reinhart L. , Davis A. , Morse T.F. , Paine D.C.
Published: March 2011

In this paper we report a new approach to the problem of high rate formation of nanophase powders. In our experiments we were able to make aluminum oxide particles in the size range from 5 to 140 nm (peaking sharply at 35 nm) at a rate of 3 g/min. The starting material was a mixture of aluminum-tri-sec-butoxide and sec-butanol. An aerosol was made from this solution and subsequently burned in a special torch, described below. The resulting particles were spherical and no necked regions were observable between them. In a practical application, our technique allows a large production rate while still approaching the ideal of nano-scale monodispersed particles. The work was extended to the formation of zirconium oxide particles with quite similar results in the size distribution.
Redox Effects in Self-Sustainiing Combustion Synthesis of Oxide Ceramic Powders
Authors: Chick L.A. , Maupin G.D. , Graff G.L. , Pederson L.R. , Mccready D.E. , Bates J.L.
Published: March 2011

The glycine/nitrate process (GNP) is a combustion synthesis method that is particularly useful for synthesizing ultra-fine, multi-component oxide powders. During the self-sustaining combustion, the precursor solution is rapidly converted into an oxide product with glycine serving as the fuel and nitrates providing the oxidant. This paper examines the effects of altering the fuel/oxidant ratio on the characteristics of the product. Examples discussed include La(Sr)CrO3 and La(Sr)FeO3 perovskites and NiO.
Homoepitaxial Alignment of SrTiO3 Thin Films Prepared by Metallo-Organic Decomposition.
Authors: Braunstein Gabriel , Paz-Pujalt Gustavo R.
Published: March 2011

We demonstrate the homoepitaxial growth of SrTiO3 prepared by the method of metallo-organic decomposition (MOD). Thin films of SrTiO3 are prepared by spin-coating and thermal decomposition of a solution of metallo-organic compounds, on single crystal, <100> oriented, SrTiO3 substrates and subsequently heat treated at temperatures ranging from 650°C to 1100°C for 30 minutes. Heat treatment at 1100°C results in the formation of single-crystal SrTiO3, perfectly aligned with respect to the underlying substrate.

Ion-channeling analysis shows that the transformation to singlecrystal material proceeds epitaxially from the coating-substrate interface towards the surface of the sample. Transmission electron microscopy (TEM) studies of partially regrown samples reveal two distinct phases: an epitaxially aligned single-crystal phase, adjacent to the substrate, and a polycrystalline phase on top. On the basis of these observations, it is proposed that the crystallization of the MOD films involves the competition between two processes: layer-by-layer solid phase epitaxy and random nucleation and growth of crystallites. Layerby- layer epitaxy is the predominant crystallization mechanism unless it is inhibited by extrinsic factors like the contamination of the interface between the MOD film and the single-crystal substrate.
Manipulating Solid-Surface Properties with Polymeric Agents
Authors: Watanabe H. , Patel S.S. , Argillier J.F. , Parsonage E.E. , Mays J. , Dan-Brandon N. , Tirrell M.
Published: March 2011

Colloidal processing offers a way to minimize undesired heterogeneities in the fabrication of advanced ceramics. Stable dispersions can be created by manipulation of interparticle potential. Adsorption of diblock copolymer amphiphiles provides a way to obtain long range repulsive interactions between particles, at comparatively low polymer coverage, thereby enabling suspension stabilization. In this study we investigate the relationship between copolymer structure and adsorbed layer characteristics, and specifically, the nature and range of interactions. We find that the surface density and interaction range are governed by a characteristic measure of the copolymer asymmetry. In the case of copolymers where one of the blocks is ionic, and therefore water soluble, we find a hysteresis in the interaction forces, indicating a meta-stable state of the polymer layer.
Mass Transfer Processes During Multicomponent Bender Thermolysis
Authors: Lewis Jennifer A. , Cima Michael J.
Published: March 2011

Both the binder viscosity and the % saturation will change during the removal of multicomponent binder systems. The effects of these changes were evaluated for the polyvinyl butyral (PVB) - dibutyl phthlate (DBP) system as the plasticizing constituent was selectively removed at isothermal conditions (Tiso < 170°C). Experiments were performed to determine the viscosities of the PVB-DBP system at various isotherms and at different concentrations of DBP. A scaling model was developed to determine the relative importance of capillary forces on the distribution of binder within ceramic compacts during thermolysis. This model was modified to account for the influence of fluid saturation on both the capillary driving force and the permeability of the wetting phase (i.e., binder). Two important results are derived from this analysis: (1) the change in binder viscosity affects the length scale (h) over which capillary forces act to redistribute the PVB-DBP to a greater degree than the change in saturation, and (2) the value of h can be significantly lower than the representative macroscopic dimension of the green compact and still permit a capillary-controlled distribution process for multicomponent binders.
Poly(Vinyl Butyral) Pyrolysis: Interactions with Plasticizer and Ain Ceramic Powder
Authors: Yan H. , Cannon W. R. , Shanefield D. J.
Published: March 2011

TGA and FTIR were employed to investigate the effects of dibutyl phthalate and butyl benzyl phthalate on the thermal degradation behavior of PVB, a binder used commonly for tape casting. Butyl benzyl phthalate was found to enhance the crosslinking of the PVB binder when heated in a nitrogen atmosphere during binder pyrolysis, which retarded its thermal degradation.

The interaction between AIN powder and PVB binder was also studied by using TGA, XPS and a special furnace for collecting residual carbon. Intrinsic char and gas phase mediated char were studied separately.
Binder System Containing Polycarbosilane and Polysiiazane for Injection-Molded Si3N4 Parts
Authors: Su Sophia R.
Published: March 2011

Polycarbosilane and polysilazane, precursors of SiC and Si3N4, have been incorporated into the binder system for injection-molded Si3N4-based parts. Property requirements for these precursors as the injection-molding binder are briefly described. The binder removal mechanism is proposed and discussed based on the experimental results. Instead, the gas diffusion effect, rather than fluid wicking, is a key factor. Controlling the thermal decomposition rate of the binder is the key for achieving crack-free dense sintered parts.
Surface Oxidation Kinetics of an a-Si3 N4 and an Amorphous Si3 N4 Powder
Authors: Wang Pu Sen , Malghan S. G. , Hsu S. M. , Wittberg T. N.
Published: March 2011

Surface oxidation kinetics of an a-Si3 N4 submicron size and an amorphous nano-size powder have been studied using x-ray photoelectron spectroscopy (XPS) and Bremsstrahlung-excited Auger electron spectroscopy (AES). The samples were oxidized by heating in air at temperatures between 850°C and 1000°C. The oxide thickness for each heating time and temperature was determined both from the relative 0 Is and N Is XPS peak intensities and from the Si02 and Si3 N4 Si KLL peak intensities. In each case, there was a good agreement between the oxide thickness value calculated from the XPS data and that obtained from the AES data. At these temperatures, oxidation followed a linear rate law. Activation energies of 15±1 kcal/mole and 27±1 kcal/mole were measured for the a-powder and the amorphous powder, respectively.
Novel Silicon Nitride Microstructures Through Processing of Phase Separated Polysilazane Gels
Authors: Lindquist David A. , Haggerty John S. , Rhine Wendell E. , Seyferth Dietmar
Published: March 2011

To date, processes used to synthesize to silicon nitride and silicon carbide ceramics from polysilazane preceramic polymers have focused on techniques which seek fully dense monoliths or matrices. An alternative approach, phase separation of polysilazane solutions using appropriate gelation agents, yields infusible preceramic monoliths having controlled two-phase microstructures. Subsequent removal of the solvent phase by supercritical fluid exchange leads to aerogels with defined pore structures. Controlled pore structures were explored as a means of providing diffusional pathways for reactant and product gases during pyrolysis. Resulting changes in the gel microstructure were followed by scanning electron microscopy and surface analysis by nitrogen desorption methods. It was found that micropores present in the unpyrolyzed gels are absent after pyrolysis, but that larger pore structures are maintained.
High Energy Ion Induced Decomposition and Diffusion in Thin Polymer Films
Authors: Venkatesan T. , Edelson D. , Brown W. L.
Published: March 2011

Electronic excitation in thin polymer films by MeV ion beams and on-line transient mass spectroscopy together provide a new opportunity for measuring the diffusion of molecules in polymers even when the diffusion coefficients are <∼ 10−10 cm2 s−1.With a quadrupole mass spectrometer, we have obtained transients of several molecular species from a variety of polymers bombarded by 2 MeV helium and argon ions.We have measured, for example, transient emission of D2, CO, CO 2, CD3OD, etc., from deuterated Poly(methyl methacrylate), PMMA.The beam fluences required for the measurements are sufficiently small that they cause minor perturbation in the structure of the film. The exciting ion pulse is typically 15 seconds wide with fast (<msec) rise and fall times. However, the emission signal of m−46 (COOD), for example, shows a slow build-up with a gradual fall after the beam is turned off with a tail lasting several seconds. The experimental data for the above molecule has been fitted to a one-dimensional diffusion model and the diffusion coefficient deduced from three different film thicknesses is ∼8−±2×10−11 cm2S−1 Since very thin films can be used in these experiments, still smaller D values are measurable. The sample requirements are simple and even the presence of pinholes will not affect the measurements significantly. Techniques that completely avoid any possible effects of ion damage tracks and an example where chemical reaction is the rate limiting step will be discussed.
Electron Energy Loss Spectroscopy of Polycrystalline and Ion Irradiated Ni-Al Alloys
Authors: Grunest L.A. , Barbour J.C. , Hung L.S. , Mayer J.W. , Ritsko J.J.
Published: March 2011

Ion beam modifications to thin film, polycrystalline Ni-Al alloys have been investigated using high resolution (0.1 eV FWHM) transmission electron energy loss spectroscopy (EELS). The ion induced modification of Ni3 AI,NiAI, Ni2Al3, and NiAl3 as measured by EELS, are compared to concurrent electron microscope diffraction analyses. The EELS coresub level spectra corroborate the NiAI3 to amorphous phase transition observed by diffraction, while the EELS valence spectra provide a signature for the Ni2Al3 to NiAl phase transformation. These results reflect the changes in the electronic states caused by changes in the crystal structure. In addition, perturbations to the electronic states are measured even when no change appears in the diffraction pattern (irradiated NiAl). Thus, high resolution EELS is shown to be a sensitive analytical technique for studying ion irradiated materials.
A General Treatment of Antiphase Domain Formation and Identification at Polar-Nonpolar Semiconductor Interfaces.
Authors: Pond R.C. , Gowers J.P. , Holt D.B. , Joyce B.A. , Neave J.H. , Larsen P.K.
Published: March 2011

Observations of antiphase disorder obtained using a new technique of transmission electron microscopy, in (100) epitaxial layers of GaAs:Ge produced by MBE are presented. The crystallographic origin of this type of disorder is analysed using a recently developed approach. It is shown that antiphase disorder can exist in epitaxial layers where the substrate orientation is of the form {hko}this is consistent with experimental observations that disorder is observed on (100) and (110) substrates, but not on (111) or (211), for example. Antiphase boundaries in {hko} specimens are shown to separate interfacial domains which are energetically degenerate and related by symmetry operations.
Metal Induced Grain Growth in Germanium and Silicon Thin Films.
Authors: Grovenor C.R.M. , Smith D.A.
Published: March 2011

Rapid grain growth has been induced in semiconductor films at relatively low temperatures by allowing contact with metals or metal/semiconductor eutectic melts. Mechanisms by which such enhanced grain growth can occur are discussed, and Diffusion Induced Boundary Migration has been shown to be a plausible explanation for the experimental observations from the Sn/Ge, Al/Ge and Au/Ge systems. Interface migration driven by the decrease in free energy during phase transformations however provides a better explanation of the large Si grains produced on heating the Au/Si samples.
Chemical Reaction at the Ni/Inp (110) and Ni/GaAs (110) Interfaces
Authors: Kendelewicz T. , Petro W. G. , Williams M. D. , Pan S. H. , Lindau I. , Spicer W. E.
Published: March 2011

The chemical reaction at the Ni/InP (110) and Ni/GaAs (110) interfaces produced by sequential deposition of thin Ni overlayers onto cleaved semiconductor surfaces has been investigated with valence band (VB) and core level photoemission and Auger spectroscopies using synchrotron radiation as the excitation source. By monitoring changes in the VB, P 2p, In 4d, Ga 3d, As 3d, and Ni 3p photoemission spectra and the lineshape of the P LVV Auger transition during the initial stage of Schottky barrier formation, we found that for both interfaces the first few Å of Ni react strongly with the surface resulting in the formation of a nickel phosphide or nickel arsenide. At the same time, segregation of metallic In or Ga is observed.
Photoemission Studies Of The CU-GaAs(ll0) Interface Formation
Authors: Pan S. H. , Kendelewicz T. , Petru W. G. , Williams M. D. , Lindau I. , Spicer W. E.
Published: March 2011

The cu-GaAS(ll0) interface formation nas been Studied with soft x-ray Photoemssion spectroscopy (SXPS) for Cu overlayers deposited at room temperature. Tne evolution of the tia 3a and As 3a spectra snow that strong interactions occur between Cu and the substrate during the formation of the Cu-GaAs interface. A cnemically smifted Ga 3d peak at 0.8 eV lower binging energy and strong moaification of the As 3d lineshape has been found. Detailed analysis nas shown that the dissociated As is preterentially segregated on the metal layer, but Ga remains mainly in the interfacial reion for trick Cu coverages (30 - 60 Å). Using a deconvolution tecnniqie we nave found that the final stabilized position of the interface Fermi level lies at about 0.9 eV below the conduction band minimum.
Residual Stresses in Co-Sputtered Films of Ta and Si on Substrates of Silicon and Oxide.
Authors: Goldsmith C. C. , Campbell D. R. , Mader S.
Published: March 2011

We have measured the stresses in TaSi. films both as a function of annealing temperature and of composition of the as-deposited films. Substrates of Si, polysilicon and SiO2 were used. The residual, room temperature stresses in samples annealed at 900°C are noticeably dependent on the initial Si/Ta ratio. This effect appears to to be related to microstructural differences between Si-rich and Ta-rich films. The stresses are largely due to the mismatch of thermal expansion coefficients (TEC) between the silicide and silicon although there is also evidence that samples annealed at lower temperatures (500°C) may have a sizable component of intrinsic stress as well. Despite tensile stresses as high as 1500 MPa, the x-ray topographs of Si wafers with patterned silicide/polysilicon structures show that no substrate dislocations are present after- annealing.
The Reaction between thin Ni and Co Films and their Disilicides
Authors: Cahoon E.C. , Comrie C.M. , Pretorius R.
Published: March 2011

Rutherford backscattering has been used to study metal/disilicide thin film interactions for Ni and Co. Upon heating, the metal first reacted with the disilicide to form Ni2Si and Co2Si, respectively. After complete consumption of the free metal, the monosilicide phase was found to form at temperatures between 350°C and 550°C. In the case of Co it was found that after all the metal had been converted to CoSi in this way, the reaction stopped. In the Si<>/NiSi2/Ni system, however, all the disilicide converted to NiSi, even though the thickness of the deposited metal was insufficient to account for this. For this to occur, the disilicide had to dissociate into NiSi and Si, with the excess silicon regrown epitaxially on the silicon substrate.

The stability of NiSi2 under various boundary conditions was investigated to determine the factors affecting dissociation. Partial dissociation was found to occur when the NiSi2/Ni reaction proceeded on an inert SiO2 substrate. The disilicide was stable, however, in the Si<>/NiSi/NiSi2 structure. Argon sputtering at temperature was found to induce complete dissociation of NiSi2 on single-crystal Si. We believe that the NiSi2 instability is due to the very small heat of formation from the monosilicide. In such a case, the thermodynamic driving forces are small enough that the reaction can be significantly influenced by the presence of kinetic barriers.
The Effect of Beam Species and Anneal History on Silicon Surface Damage Induced by Ion Beam Etching
Authors: Davis R. J. , Singh R. , Fonash S. J. , Caplan P. J. , Poindexter E. H.
Published: March 2011

Ion beam etching and reactive ion etching have been shown to significantly damage silicon surfaces. In this investigation, ion beam damage is examined as a function of ion beam type (1 keV Ne+, Ar+, and Kr+) and anneal history (temperatures of 500°, 800°, and 1000°C in ambient gases Ar,dN2, and Ar + H2 ). Damage at 1 keV, as characterized by currentvoltage and ESR measurements, appears to be roughly proportional to the inverse of ion size. Relatively long anneals at high temperatures (1 hr. at 800'-1000°C depending upon ambient) are found to be necessary to restore original surface characteristics.
Effect of Low Energy Hydrogen Implants on Damage Caused by Argon Ion Beam Etching
Authors: Climent A. , Wang J.-S. , Fonash S. J.
Published: March 2011

The dry etching technologies reactive ion etching (RIE) and ion beam etching (IBE) have both been shown to cause a damaged layer at silicon surfaces. It has been demonstrated that this damage can be annealed out or, alternatively, it can be passivated with low energy hydrogen implants from a Kaufman ion source. This study further explores the hydrogen passivation approach by focusing on the effect of hydrogen implantation on damage caused by argon ion beam etching. The lighter hydrogen ions are actually shown ta cause more extensive damage than the heavier argon ions. However, by using low-energy hydrogen implants all damage, that present from the Ar and that generated during the hydrogen implant, can be passivated.
Electrostatic Spray Deposition of Antimony Doped Tin Oxide on Soda-Lime Glass
Authors: Fabian D.J. , Colbow K. , Clayman B.P. , Mackintosh A. , Manning G. , Morrison S.R.
Published: March 2011

A technique for electrostatic spray deposition (ESD) of thin films onto a conducting substrate is described. The method, using a 60 kV corona has been tested for the preparation of heat-reflecting tin oxide coatings onto window glass by spraying solutions of hydrated tin tetrachloride with 1% antimony trichloride in ethyl acetate.

Uniformity of film, growth rate, conductivity, infrared reflectivity and light transmission in the visible are all examined and compare favourably with films produced by normal aerosol spray. Conductivity and infra-red reflectivity increase with the substrate temperature during ESD. This is similar to the observation for antimony-doped tin oxide films prepared on soda-lime glass by CVD; although this temperature dependence does not follow closely that reported for normal spray deposition.
Initial Phase formation at the Interface of Ni, Pd, or Pt and Si
Authors: Nemanich R. J. , Tsai C. C. , Stafford B. L. , Abelson J. R. , Sigmon T. W.
Published: March 2011

The initial phase formation at the interface of the near noble metals (Ni, Pd, and Pt) and Si is studied by Raman spectroscopy and Rutherford ion-backscattering. The results show that a crystalline Pd2Si forms immediately at the interface of Pd and Si while a disordered intermixed phase of composition ∼M2Si forms for Ni and Pt at 150°C. The results are discussed in terms of the disorder due to the kinetic process and the stability of the crystalline phase.
Preparation of Synthetic Quartz Aggregates under Pressure
Authors: Luan F. C. , Paterson M. S.
Published: March 2011

In 1965 Griggs and Blacic [1,2] proposed that there is a “hydrolytic weakening” process in quartz and silicates whereby the breaking of Si-O bonds, involved in the movement of dislocations, is facilitated by the presence of water. This proposal aimed to explain the observed dramatic weakening of quartz crystals when they are exposed to water in tests at high temperature, as well as the observed strong contrast in creep strength between dry natural quartz crystals and rapidly-grown synthetic quartz crystals containing traces of water. Such a “hydrolytic” process may also underlie the observed effects of water in accelerating other phenomena such as self-diffusion of oxygen in quartz, aluminium-silicon ordering in feldspars, slow crack propagation in silicates, and recrystallization in quartz. A review of this field is given in Reference 3.
Effect of Pressure Carbonization in Carbon/Carbon Composite Process (II)
Authors: Okamoto H. , Hosomura T. , Kosaka K.
Published: March 2011

We have found that pressurized carbonization cause the increase of carbon yield and the improvement of micro structure In the case of pitch resin. While the effects of pressurized carbonization on phenolic resin are not obvious.

In this study, carbonization and graphitization characteristics of phenolic resin were investigated experimentally. Phenolic resin specimens with and without iron powder addition were carbonized at the temperature of 650 °C under the pressure of atmospheric or 100MPa. Then each of them was heat-treated at the temperature of 1200, 1500 and 1900 °C respectively. Measurement of yield, density, x-ray diffraction and optical observation were carried out in the experiments. It is indicated from those results that pressurized carbonization of phenolic resin makes graphite crystallization progress and this effect is promoted by addition of iron powder.
Densification of Ceramics by Gas Overpressure Sintering
Authors: Gazza G. E. , Katz R. N.
Published: March 2011

The use of various gas pressure sintering (GPS) techniques for densifying ceramics are reviewed for both oxides and non-oxides. Variations of the process are discussed with respect to process parameters selected, process sequence, and microstructural development. Theoretical considerations underlying the technique are presented. GPS and hot isostatic pressing are compared and the advantages and disadvantages of each are briefly discussed.
Study of Glass Ceramic Diffusion During Hot Isostatic Pressing of Encapsulated PZT Ceramics
Authors: Leriche A. , Aleksandrowicz P. , Thierry B.
Published: March 2011

The development of high performance piezoelectric and dielectric ceramics needs a close control of density and microstructure. Hot isostatic pressing technique using glass encapsulation method allows to produce dense and complex shape ceramics with controlled grain size. However, diffusion phenomena occur at glass ceramic interface during HIP treatment.

In this study, the glass diffusion into PZT ceramics was examined for different glass types. We noted silicon species diffusion into ceramic and also lead migration into glass resulting from PZT decomposition.

HIP carried out with diffusion barrier surrounding ceramic samples allows to prevent such a diffusion.
X-Ray Induced Optical Absorption in Densified Silica Glass in the UV Region
Authors: Kitamura Naoyuki , Toguchi Yutaka , Kondoh Isao , Yamashita Hiroshi
Published: March 2011

X-ray induced optical absorption has been studied on silica glasses densified by hot isostatic pressing. Density of the glass increases up to about 1% in proportion to the operating pressure. Two main absorption bands centered at 5.8eV(215nm) and 4.8eV(260nm) are induced both in the densified and undensified glasses under the irradiation of X-rays at room temperature. The 5.8eV band is enhanced with the increase in density for the glass with low-OH content(<˜200ppm), but is decreased slightly for the glass with high-OH content(>˜200ppm). On the other hand, the 4.8eV band decreases with the increase in density irrespective of OH content, and reaches at a constant value above the densification of about 0.5%. It is found that these absorption bands originate in point defects in the glass and that the densification improves the optical durability of the glass against X-rays when hydroxyl impurities are contained in the glass.
Solid Gas Reaction Phase Diagram under High Gas Pressure - HIP Phase Diagram
Authors: Ishizaki Kozo
Published: March 2011

To evaluate which are the stable phases under high gas pressure conditions, a solid-gas reaction phase diagram under high gas pressure (HIP phase diagram) has been proposed by the author. The variables of the diagram are temperature, reactant gas partial pressure and total gas pressure. Up to the present time the diagrams have been constructed using isobaric conditions. In this work, the stable phases for a real HIP process were evaluated assuming an isochoric condition.

To understand the effect of the total gas pressure on stability is of primary importance: Two possibilities were considered and evaluated, those are: i) the total gas pressure acts as an independent variable, or ii) it only affects the fugacity values. The results of this work indicate that the total gas pressure acts as an independent variable, and in turn it also affects the fugacity values.
Characterization of Hot Isostatically Pressed Bi–Sr–Ca–Cu–O as a Function of Consolidation Variables
Authors: Goretta K. C. , Miller D. J. , Poeppel R. B. , Nash A. S.
Published: March 2011

Fully dense, bulk Bi2Sr1.7CaCu2Ox (2212) superconductor pellets were made by hot isostatic pressing in an inert atmosphere. Electron microscopy revealed that rotation and bending of the platelike 2212 grains were responsible for much of the densification. Under processing conditions of 825°C and 105 MPa, dense pellets were obtained in 15 min. Many dislocations, planar faults, and, perhaps, intergrowths of the Bi2Sr2CuOx phase were produced during pressing. The dislocations were largely present in subgrain boundaries when the pressing times were increased to 45–120 min.
Surface Engineering by HIP
Authors: Stephenson David J
Published: March 2011

Methods for surface treating and coating components by hot isostatic pressing are presented. It is shown that HIP'ing can improve the properties of conventional coatings and also be used to produce coatings that would be difficult to deposit by other techniques. The concept of using a combined coating and HIP treatment to modify surface properties by, for example, removing surface defects in metals and ceramics, is also discussed.