bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractIn 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

AbstractIn 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

AbstractAn 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

AbstractA 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

AbstractCrystal 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

AbstractThe 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

AbstractThe 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

AbstractWe 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

AbstractWe 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

AbstractIn 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

AbstractA 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

AbstractSurface 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

AbstractWe 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

AbstractMembranes 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

AbstractWe 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

AbstractWe 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

ABSTRACTThe 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

ABSTRACTIn 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

ABSTRACTThe 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

ABSTRACTWe 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

ABSTRACTColloidal 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

ABSTRACTBoth 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

ABSTRACTTGA 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.