bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Viscoelastic Deformation in Polymeric Glasses
Authors: Matsuoka Shiro 
Published: March 2011

AbstractThe dielectric, mechanical and volumetric relaxation data, and stress-strain data in tension, shear and uniaxial compression for polymeric glasses are compared. The relaxation phenomenon is viewed as a thermodynamically irreversible response to a perturbation in the configurational state. The relaxation behavior is apparently linear only in the limit of a very small perturbation, but otherwise generally nonlinear. Adam-Gibbs' entropy equation [1] has previously been shown to describe the dielectric and volumetric relaxation data better than Doolittle's free volume equation [2]. The temperature and the structure, i.e., history, dependence of mechanical relaxation time is shown to agree with the A-G theory better Than the Doolittle theory, in that the former predicts an Arrhenius type dependence on the temperature when the structural parameter, in this case the entropy, is fixed, while the latter predicts the temperature independence if the fractional free volume is fixed in the glassy state. The temperature dependence of the distribution of relaxation times is shown to agree qualitatively with the dynamic Ising model of Fredrickson and Andersen [3] (F-A model) involving the cooperativity of molecular motions in dense liquids.
Microstructure and Fracture of Engineering Polymers and Composites
Authors: Friedrich K. 
Published: March 2011

AbstractThe fracture properties of engineering polymers and composites are strongly affected by two major areas of influence. The first one covers the microstructural parameters of the material, whereas the second one includes the external testing conditions. In this contribution, it is mainly outlined how area one can determine the fracture characteristics. An introductory section illustrates the variety of microstructural details, for example molecular structure and semicrystalline polymer morphology, and filler related factors, such as volume fraction of reinforcing fibers, their orientation etc. In the following part, effects of these parameters on fracture mechanical properties are discussed. It is distinguished between the fracture behavior of unfilled engineering polymers, of short fiber reinforced, injection molded thermoplastics, and of continuous fiber composite laminates. In the latter group, special emphasis is given to the effect of new, high temperature resistant thermoplastic matrices, for instance PEEK, on the interlaminar fracture energy of the composites.
Fracture of Polymers Under Repetitive Loading
Authors: Sauer J. A. , Chen C. C. 
Published: March 2011

AbstractThe fracture surface morphology of various polymer specimens, fractured under alternating loading, has been examined by scanning electron microscopy. Illustrations are given of both typical and unusual fracture surfaces and the influence of such variables as composition, molecular weight, presence of a dispersed second phase and induced thermal effects is discussed.
Ultinite Mechanical Properties of Polymer Fibers a Theoretical Approach
Authors: Termonia Yves , Smith Paul 
Published: March 2011

AbstractA stochastic Monte-Carlo approach, based on the kinetic theory of fracture, has been used to study the axial maximum tensile strength of polymer fibers. The approach is entirely microscopic and the inhomogenous distribution of the external stress among atomic bonds near the chain ends is explicitly taken into account. Both primary and secondary bonds are assumed to break during fracture of the polymer fiber. The approach has been applied to perfectly oriented and ordered polyethylene and poly(p-phenylene-terephthalamide) fibers. The influence of the molecular weight, temperature ard strain rate on the axial tensile properties are presented.
Spectroscopic Characterization of the α⇌β Crystalline Phase Transition in Poly(Butylene Terephthalate) and its Copolymers with Poly(Tetramethylene Oxide).
Authors: Dobrovolny-Marand Eva , Hsu Shaw Ling 
Published: March 2011

AbstractThe stress-induced crystalline α⇌β phase transition found in poly(butylene terephthalate) and its copolymers with poly(tetramethylene oxide) has been studied by Fourier transform infrared spectroscopy coupled with mechanical measurements. The phase transformation behavior was explained in terms of a cooperative model which considered both intermolecular as well as intramolecular interactions within the crystal. It was shown that the strength of the intramolecular interactions increased with length of the hard segments and that the strength of the intermolecular interactions increased with perfection and lateral size of the crystals. The intermolecular interaction was assumed to be dominated by the interaction between neighboring terephthalate groups. The “mean” intramolecular energy was estimated at 0.40 Kcal/mole. This calculation was based on the potential energy of rotations of a carbonyl group about a benzene-carbonyl bond. Cooperativity between chains diminished when the surface to volume ratio increased above 2 x 10-2 Å-1.
Small-Angle Scattering from Disordered Systems
Authors: Schaefer Dale W. 
Published: March 2011

AbstractA general discussion of scattering from disordered materials is presented. The parameters which characterize structure are illustrated in real-space and are also identified in the reciprocal-space profile measured in a scattering experiment. Scattering from fractal objects is described in detail. To illustrate the interpretation of scattering data, the growth and structure of fumed silica is discussed. The flame growth of silica is explained in terms of monomer-cluster ballistic polymerization in the early stages and diffusion-limited aerosol aggregation in the latter stages.
Molecular Mechanism of Deformation in Epoxies – A Neutron Scattering Study
Authors: Wu Wen-Li 
Published: March 2011

AbstractNeutron scattering was used to investigate the molecular mechanism of large strain deformation in epoxies. Partially deuterated diglycidyl ether of bisphenol A (DGEBA) was cured with either tri- or di-amines of different molecular weights. The change of the average distance between crosslinks along the epoxy and the amine linkages could easily be determined from the shift in the positions of the scattering maxima. It was found that the average distance between crosslinks remained almost unchanged along both the amine and the epoxy linkages as the bulk material underwent a large deformation. The above results are discussed in terms of the functionality of the junctions as well as the molecular weight between crosslinks. Comparisons are also made between the solid state deformation results and those from swollen networks which did show a substantial increase inaverage distance between crosslinks.
An Automated Laboratory Apparatus for the Production of Rapidly Solidified Submicron Powders
Authors: Perel Julius , Mahoney John F. , Taylor Scott , Shanfield Zef , Levi Carlos 
Published: March 2011

ABSTRACTThe Electrohydrodynamic (EHD) method of spraying fine liquid droplets from a liquid state, in a vacuum environment, was developed and used to produce amorphous, microcrystalline, single crystal, bicrystalline and tricrystalline powders. Studies of these powders have contributed towards increasing the knowledge of extended solubility, nucleation, metastable phases, undercooling effects, etc. Coatings and films have been produced by collecting the liquid droplets before solidification. An automated instrument based upon the EHD method, the Micro-Particle Processor, is computer operated and allows a material scientist not completely acquainted with the EHD process to perform sophisticated experiments on materials of his choosing. Electron transparent powders close to 3μm and large powders up to l00μm have been collected and observed. Cooling rates above 107K/s have been achieved. Applications using powders include: new alloy compositions, use as AEM standards, in-situ remelt experiments in the electron microscope, etc.
Consolidation of Ni60Nb40 Metallic Glass Strips into Metal Matrix Composites
Authors: Cytron S. J. 
Published: March 2011

ABSTRACTTo fully utilize the promising mechanical properties of metallic glasses, consolidation techniques need to be developed to incorporate them into large bulk forms. This paper describes preliminary results on the consolidation of Ni60Nb40 metallic glass strips into an aluminum alloy matrix. The consolidation was achieved without the degradation of the metallic glass by employing a superplastic aluminum alloy as the matrix material. The consolidations were accomplished at a superplastic forming temperature compatible with the metal matrix material and sufficiently below the critical 650°C crystallization temperature of the Ni60Nb40 metallic glass. Initial studies employed an atuminum − 5% calcium − 5% zinc alloy as the metal matrix material.
Growth Kinetic Limitations During Rapid Solidification
Authors: Boettinger William J. 
Published: March 2011

ABSTRACTThe importance of growth kinetics in the development of the microstructure of rapidly solidified alloys is described. Growth kinetics are conveniently divided into diffusion kinetics and interface attachment kinetics. The former, which are used extensively for the analysis of slow rate solidification, can be extended to high solidification rates to predict some microstructural features; e.g., the limitations on eutectic growth rate which can promote the formation of metallic glass, and the reduction of microsegregation. At the highest rates interface attachment kinetics must be included. Some microstructural effects of the velocity dependence of the partition coefficient will be described.
Influence of Solidification Parameters on the Microstructure of Rapidly Quenched Fe-Ni-B Alloys
Authors: KÖster Uwe , Herold Ursula , Krause Dieter 
Published: March 2011

ABSTRACTThe microstructure of Fe-Ni-B alloys rapidly quenched by melt spinning has been investigated by means of light and electron microscopy. Depending on the surface velocity of the quenching wheel and the boron concentration a large variety of microstructures has been observed: increased solubility of boron, microstructures with different metastable crystalline compounds or metallic glasses.Plotting the as-cast microstructures versus the quenching rate has been found to be very useful for arranging the large amount of results and/or for predicting particular microstructures. Due to an extremely large gradient in the microstructure across the ribbon thickness this method of forming particular microstructures seems to be only of limited advantage. Controlled crystallization reactions of metallic glasses result in different, but more homogeneous microstructures.
New Magnetic Metallic Glasses with Reduced Metalloid Content
Authors: O'handley R. C. , Grant N. J. 
Published: March 2011

ABSTRACTSeveral new magnetic amorphous alloys containing early transition metals (TE) and having reduced metalloid (M) content have been melt spun. Some properties of three examples of this new class, 1) Co80Nb14B6, 2) Co84Nb10B6, and 3) Fe81Nb5B14, are presented. The dominant late transition meta1 (TL) content assures an appreciable magnetic moment while the presence of an early transition metal significantly enhances the stability against crystallization. Crystallization temperatures are 1) 742K, 2) 698K, and 3) 762K for the three alloys, respectively. X-ray diffraction patterns show the materials to be amorphous and to exhibit a large-r correlation length (approximately 2.0 A) that is shorter than is typiclly observed in TL80M20 glasses containing more than one transition meta) species (approximately 2.3 − 2.5A). The coercivities of the glassy compositions range from 30 to 70 m0e.
Thermal Expansion of Amorphous Iron-Chromium-Boron Alloys
Authors: Hunger G. , Bergmann H. W. , Mordike B. L. 
Published: March 2011

ABSTRACTIn amorphous iron-chromium alloys magnetic contraction is superimposed on the thermal expansion. Depending on the proportion of antiferromagnetic chromium the resultant coefficient of expansion is either positiv, negative or zero. The chromium content also changes the Curie temperature. Relaxation processes have a marked effect on the thermal expansion. Long term and short term expansion behaviour was compared and discussed. In addition the crystallization behaviour and mechanical properties of the alloys are reported.
Sorption of Hydrogen and Deuterium in a Glassy Pd-Si Alloy by a Bendingcantilever Method
Authors: Berry B.S. , Pritchet W.C. 
Published: March 2011

ABSTRACTThe dilatation caused by the sorption of H and D in amorphous samples of melt-spun Pd82Si18 and sputter-deposited Pd81Si19 has been measured at room temperature for ambient charging pressures P up to 760 torr. By comparison with the strength of the Gorsky relaxation, it is concluded that (a) the dilatations per hydrogen and deuterium atom are identical and independent of concentration and (b) the non-linearity of the dilatation vs. p1/2 isotherms is due solely to a deviation from Sieverts' law. The isotherms exhibit a distinct isotope-dependence, of a similar nature to that for crystalline Pd. A sputterdeposited film is found to dissolve more H or D than a melt-spun ribbon, due possibly to a less structurally-relaxed configuration.
Fretting of Amorphous Alloys
Authors: Becker Reinhard , Sepold Gerd 
Published: March 2011

ABSTRACTAmorphous surface layers produced by bonding metglas ribbons onto steel specimens were tested for their resistance to fretting. Friction and weight loss were determined and the worn surfaces were examined optically. There was no general tendency towards a better wear resistance of the tested amorphous metals as compared to crystallized metals or to a simple structural steel. The results will be discussed.
Environmental Cracking of Amorphous Alloys
Authors: Ashok S. , Slavin T. P. , Stoloff N. S. , Glicksman M. E. 
Published: March 2011

ABSTRACTSix amorphous metals have been tested in liquid metal environments or while charging with hydrogen. Differences in sensitivity to each environment are correlated with fractographic features. Evidence in support of enhanced shear as the mechanism of environmental cracking is presented.
Perpendicularly Crystallized Ribbons by Means of Rapid Solidifications from Melts
Authors: Tsuya Noboru , Ichi Arai Ken , Ohmori Kenji 
Published: March 2011

ABSTRACTSilicon-iron alloy ribbons containing around 6 wt% silicon and Sendust alloy ribbons in the crystalline state were prepared by a rapidly quenching roll method. In the as-prepared ribbons columnar grains about 1Oμm in diameter wer observed to grow from the surface to the middle part of the ribbon thickness. For the high silicon-iron ribbons annealed at 1200°C for 30 minutes the grain size was more than 1 mm and the texture was highly oriented to (100)[0kl] cube-on-face. The coercive force was 55 mOe for the 6.6Si 93.4Fe ribbons annealed at 1180°C for 60 minutes in vacuum, and the average magnetic iron loss W15/50 and W10/50 of the ribbons having the coercive force of 80 mOe was 0.7 Watt/kg and 0. 25 Watt/kg, respectively. For Sendust ribbons, the lowest coercive force was 8mOe when the ribbons was annealed at 1040°C for 30 minutes and then cooled at the rate of 60 deg/hour down to 550°C in vacuum. The recording heads made of laminated Sendust ribbons exhibit much better recording characteristics than ferrite heads, while frequency response remains flat.
Analysis of a Rapidly Solidified High-Phosphorus Austenitic Steel Containing an Amorphous Phase
Authors: Kelly T. F. , Olson G. B. , Vander Sande J. B. 
Published: March 2011

ABSTRACTRapid solidification of a high-phosphorus austenitic steel produces a fine cellular solidification structure containing an amorphous phase at the cell walls. The amorphous phase, which is stable to ∼500°C, is enriched in phosphorus and chromium, but contains significantly less phosphorus than conventional glass-forming alloys. Hot consolidation of powders produces a chemically-uniform metastable austenite which can be effectively precipitation hardened by phospho-carbides.
Grain-Coarsening Resistance and The Stability of Second-Phase Dispersions in Rapidly Solidified Steels
Authors: Olson G. B. , Ling H. C. , Montgomery J. S. , Vander Sande J. B. , Cohen M. 
Published: March 2011

ABSTRACTControl of alloy composition and processing to achieve grain coarsening resistance in rapidly solidified alloys is examined via the theory of grain boundary pinning and particle coarsening. The principles are illustrated for the case of manganese sulfides in steels. A thermodynamic survey of potential stable dispersed phases identifies TiN and rare-earth sulfides as particularly promising for alloy development via rapid solidification.
Microstructure of a Rapidly Solidified Al-Fe-Co-Ni Alloy
Authors: Sanders T. H. , Paris H. G. , Mullins J. W. 
Published: March 2011

ABSTRACTObservations made on different consolidated and wrought microstructures suggested that in addition to the simple variations in size and size distributions there were also differences in shape. Furthermore, clusters of oriented precipitates were often observed. The different particle morphologies were related to solidification rate effects. This paper describes the changes in microstructure which occur during the heating of rapidly solidified AI-3.3Fe-4.6Co-2.3Ni splat.
The β → α Transition in Rapidly Quenched Sn-Ge Alloys
Authors: Gallerneault W.M. , Smith R.W. 
Published: March 2011

ABSTRACTDilute Sn-Ge alloys were prepared as ribbons by meltspinning using a 4" copper drum. They were then transformed into grey tin at 242 K in the as-cast-condition, and after annealing. It is shown that germanium: (1) when in solid solution impedes β → α transformation; (2) when in solid solution cannot effect nucleation; and (3) has a solubility in α-Sn in excess of 1 wt. % Ge.In addition it is proposed that β → α transformation is restricted because the presence of germanium strengthens the β-Sn matrix.
RaneyR Type Nickel Catalysts From Rsr Atomization Of Al-Ni Powders
Authors: Brooks C. S. , Lemkey F. D. , Golden G. S. 
Published: March 2011

ABSTRACTThe synthesis and catalytic properties of hydrogenation catalysts of the RaneyR type derived from aluminum-nickel and aluminum-molybdenum-nickel RSR alloy powders have been evaluated. Two binary aluminum-nickel alloys, RSR 588, with 50 w/o Ni corresponding to currently available RaneyR commercial alloys, and RSR 587, with 28.5 w/o Ni corresponding to the proeutectic composition which produces exclusively Al3Ni as the precursor phase, were synthesized. One ternary, RSR 589, aluminum-molybdenum-nickel alloy with a nickel and molybdenum content to correspond to a commercial promoted RaneyR alloy was prepared.The hydrogenation catalytic activity for six organic compounds representing diverse functionalities was measured in a bench scale batch liquid slurry catalytic reaction. Each catalyst was suspended in an agitated solution of the reaction (0.8 to 5M) at 22°C under a constant hydrogen over pressure of 0.86 atmospheres. A declining pressure technique was also used as a measure of catalytic activity where the catalyst was suspended in an agitated solution of the three reactants at 80°C at an initial hydrogen pressure of four atmospheres. The reactants selected consisted of acetone, nitrobenzene, itaconic acid, butyronitrile, toluene, and dextrose. The organic functionalities hydrogenated consisted of the conversion of:(1) Carbonyl to alcohol(2) Nitro group to amine group(3) Double carbon bond to a single carbon bond(4) Nitrile group to an amine group(5) Aromatic to a hydroaromatic ring(6) Aldehyde to an alcohol.RSR 587 catalyst, containing 28.5 w/o nickel, provides superior hydrogenation rates over bulk cast RaneyR nickel catalysts by factors ranging from 2 to 20 for selected reactions. Rapid solidification followed by heat treatmen0t at 850°C of Al ∼42 w/o Ni powders yielded the greatest specific catalytic activity and provides a unique enrichment path for the formation of the peritectic phase, A13Ni, and subsequently the most active skeletal nickel pore structure with the least amount of waste aluminum.
Hot Consolidation/Devitrification of Metallic Glasses — Novel Multiphase Crystalline Alloys in Bulk Shapes With Technological Potentials
Authors: Ray Ranjan 
Published: March 2011

ABSTRACTIron, nickel and/or cobalt base metallic glasses with low contents of metalloids, predominantly boron, upon heat treatment at temperatures well above crystallization temperature of the glassy phase transform into ultra-finegrained (microcrystalline) alloys containing finely dispersed boride phases.Microcrystalline alloys devitrified from glassy phase are characterised by high strength, excellent thermal stability and superior corrosion/oxidation resistance. Mechanical properties of bulk microcrystalline alloys hot consolidated-devitrified from selected low metalloid metallic glass alloys are reported.
Micromechanisms of Crystallization in (Fe,Co,Ni)-Zr Metallic Glasses
Authors: Franke Hans-Georg , KÖster Uwe , Schroeder Hans-Werner , MÜller Johann 
Published: March 2011

ABSTRACTDepending on the Zr-concentration crystallization of (Fe-,Co,Ni)-Zr glasses has been found by TEM studies to occur by primary and polymorphic crystallization, however, not by eutectic crystallization reactions. Nucleation and growth rates of these ractions have been analyzed systematically. Thermal stability as indicated by orowth as well as nucleation rates decreases with increasing Zr-content and atomic number of the late transition metal. Using this knowledge on nucleation and orowth rates conditions for designing particular microstructures by crystallization reactions can be predicted.
Undercooling Behavior of Liquid Metals
Authors: Perepezko J. H. , Paik J. S. 
Published: March 2011

ABSTRACTThe undercooling of liquid metals is observed often, but is restricted by the catalysis of the most potent heterogeneous nucleation site in contact with the liquid. An experimental approach that yields large undercoolings involves the slow cooling from the melt of a dispersion of stabilized fine (5–20μ) liquid droplets. Droplet studies have extended measurements of the undercooling limit for low melting point metals to the range of 0.3 to 0.4 Tm. In droplets, surface coating and size characteristics usually limit the undercooling and control the uniformity of crystallization behavior. A nonuniform undercooling behavior can produce microstructural variations in powder samples with respect to metastable phases and solute segregation, but these variations can be diminished for isenthalpic solidification of hypercooled liquids. In alloys the trend in nucleation temperature can follow a similar pattern as the composition dependence of the liquidus. With highly undercooled droplets and even at modest ΔT (ΔT ≤ 0.lTm) with known heterogeneous sites, structural modifications such as extended solid solutions and metastable intermediate phases can be generated which are similar to those produced by rapid quenching techniques. These features highlight the importance of a high liquid undercooling as well as a high cooling rate in promoting effective rapid solidification processing treatments.
Phase Transformation Studies of Laser-Processed Fe-0.2%C-Cr Surface Alloys
Authors: Molian A. , Wang P. J. , Khan K. H. , Wood W. E. 
Published: March 2011

ABSTRACTPhase transformations in laser-processed Fe-0.2%C-Cr surface alloys with 5%, 10%, 20%, and 30%Cr were studied by light and electron microscopy.Alloys containing 5% and 10%Cr were found to be fully martensitic with a dislocated lath type substructure. Thin films of retained austenite and a homogeneous dispersion of fine carbides were observed at the lath boundaries and prior austenite grain boundaries. The alloy with a 20%Cr content showed a unique microstructure of twinnedaustenite needles in a dislocated ferrite matrix while the alloy containing 30%Cr exhibited a dislocated ferrite structure with M23C6 carbides.