bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Laser Ablation and Vaporization of PbZr0.54Ti0.66O3: Laser Fluence and Ambient Gas Effects
Authors: Leuchtner R.E. , Horwitz J.S. , Chrisey D.B.
Published: March 2011

A systematic study of the gas phase products observed from the pulsed laser vaporization of a PbZro.54Ti0.46O3target was performed as a function of laser fluence and ambient gas pressure. At low fluences, ≤0.3 J/cm2, only Pb and PbO were observed, while at higher fluences, between 0.3 - 1.3 J/cm2, neutral atomic species Pb, Zr, and Ti were detected. Small oxide molecules and atomicions were also observed. These regimes are associated with two ejection mechanisms: thermal evaporation and ablation, respectively. No direct evidence of chemical reactions was found over the gas pressure range explored (0-5 mTorr). Within the 25 cm reaction cell distance however, the addition of both inert and reactive gases greatly changed the velocity distributions of the ejected species. The decrease in velocity (energy) as a function of gas pressure was due to physical scattering and could be modeled as a pseudo-first order bimolecular collision process. The scattering rate increased linearly with the physical cross-section of the background gas and was independent of the kinetic energy of the ablated species.
Electrooptic Properties of Pzt thin Films for Image Storage Applications
Authors: Dimos D. , Schwartz R.W.
Published: March 2011

The photocurrent responses, photo-induced changes in hysteresis behavior, and electrooptic (birefringence) effects of sol-gel derived PZT films have been characterized as part of an effort to evaluate ferroelectric films for image storage and processing applications.
Microstructural Characterization of Epitaxial Bottom Electrodes, Buffered Layers, and Ferroelectric thin Films
Authors: Rou Shang Hsien , Graettinger T. M. , Chow A. F. , Soble C. N. , Lichtenwalner D. J. , Auciello O. , Kingon A. I.
Published: March 2011

Three subjects are covered in this paper. First, a set of criteria are established to explain how epitaxial growth can be achieved for sol-gel processed ferroelectric thin films. These criteria describe the conversion of amorphous films to epitaxial films. Second, we report the microstructures of ion beam sputtered buffer layers, (100) MgO on (100) Si, and epitaxial bottom electrodes, (100) Pt on (100) MgO and (111) Pt on (0001) A12O3, for the integration of ferroelectric films with various types of substrates. Third, microstructures of the multilayered epitaxial films, (001) YBa2Cu307-δ on (100) KNbO3/(100) MgO and (100) KNbO3 on (100) MgO/(100) Si, are characterized. The results indicate that high quality epitaxial multilayered films can be obtained under the proper processing conditions.
Ferroelectricity of Lanthanum-Modified Lead-Titanate Thin Films Deposited on Nickel Alloy Electrodes
Authors: Ogawa Toshio , Shindou Satoshi , Senda Atsuo , Kasanami Tohru
Published: March 2011

Lanthanum-modified lead-titanate (Pbo.85Lao.1Ti03) thin films were fabricated by rf magnetron sputtering on various kinds of substrates such as single-crystal MgO (100), r-plane sapphire and SI (100) with an MgO thin film layer. All the films were able to be evaluated using nickel alloy electrodes which possess low reactivity with PbO, excellent heat-resistance and oxidation-resistance. The quality of these films was affected by the kind of substrate and crystal orientation of nickel alloy electrode used. Furthermore, by controlling the crystal orientation of the alloy electrode, films on Si (100) with an MgO (100) layer showed good ferroelectricity.
Yb3+ Sensitised Er3+ Doped Silica Optical Fibre with Ultra High Transfer Efficiency and Gain
Authors: Townsend J. E. , Barnes W. L. , Crubb S. G.
Published: March 2011

Efficient 1.54 μm emission under 1064nm excitation of Er3+/Yb3+ codoped silica fibre is reported. The energy transfer efficiency from Yb3+ to Er3+, of at least 85%, even under high inversion, is comparable to that in multicomponent glass fibres. Fibre design parameters are discussed and results presented. Small signal gain of ˜ 45dB is also measured and a power amplifier giving 145mW output power demonstrated.
Optical Properties of Materials for Optical Amplifiers at 1.3 μM
Authors: Hessen B. , Sunshine S. A. , Schneemeyer L. F. , Neeves A. E. , Reed W. A.
Published: March 2011

We describe the preparation and near Infra-Red fluorescence characteristics of a series of transition metal (V2+, Ni2+, Cr4+) doped crystalline inorganic materials. Within isostructural series, the effect of changes in the host lattice on the transition metal fluorescence has been investigated. This allows selection and fluorescence tuning of transition metal ion/crystalline host combinations of possible use for optical amplification in the 1.31 μm telecommunication window
Site-Selective Specirdsmpy of Thulium-Doped Glasses
Authors: Pearson A. , Lincoln J. R. , Brocklesby W. S. , Carte J. N.
Published: March 2011

Laser operation has been demonstrated in Tm3+-doped optical fibres at several useful wavelengths, including 2.3μm, 2μm, 1.47μm and 800nm, and visible upconversion fluorescence observed in silica and ZBIAN hosts. The ground-state Stark structure is ∼600cm−1 wide, resulting in broad tuning ranges for the lasers studied so far. As several of these laser are operated quasifour level using the ground state multiplet, the structure of this multiplet influences the laser transitions significantly. We Ipresent site-selective line-narrowed fluorescence studies of thulium in ZBLAN1 and silica-based hosts at low temperatures, which show detail of Stark levels not present in the room-temperature luminescence spectrum. Comparison of these data for Tmi: ZBLAN with the performance of fibre lasers and amplifiers based on the 800nm transition explains aspects of the laser performance such as tuning range, and optimum pump wavelength for amplifiers. In addition these data give information about the site-to-site disorder within the inhcmogeneous line.
Optical properties of silica glasses having O2 and Cl2 molecules
Authors: Awazu Koichi , Kawazoe Hiroshi , Muta Ken-ichi
Published: March 2011

Oxygen or chlorine was incorporated into silica glasses by sintering porous soot rods under 02/He or C12/He atmosphere. In case of oxygen, the Schumann-Runge band of 02 molecule was found in VUV region. An absorption band at 4. 8eV having 1. 9eV emission was generated with irradiation of excimer laser. We proposed that such optical properties were due to 02 molecule trapped in glass because they were similar to photochemistry of 02 molecule in the gas phase which could be shown as:

When silica glasses were fabricated under chlorine ambient, a minor fraction was found to be present as Cl2 molecule trapped in the glass, which gives the absorption band at 3.8eV.
Glasses for Nonlinear Optics
Authors: Newhouse M. A.
Published: March 2011

Our work, in which we have studied optical nonlinearity trends in oxide glasses and the fabrication of optical fibers from high nonlinearity glasses, is reviewed. An oxide glass with a nonresonant nonlinearity Kerr coefficient g equal to 125 × 10−20 cm2/W, which is approximately fifty times larger than that of silica, was identified. Single-mode optical fibers have been fabricated from such high nonlinearity glasses. The predicted enhanced nonlinear properties of the fibers have been demonstrated without any significant degradation due to the nonlinear resonant process of two-photon absorption.
Fused Coupler Optical Switch Using a Photochromic Material
Authors: Kobayashi Yuji , Hosoya Toshifumi , Nonaka Tsuyoshi , Matsuda Yasuo
Published: March 2011

An optical switch based on a single-mode fused coupler has been fabricated. The switch is worked by light induced refractive index change of an organic photochromic compound as cladding material in the coupling region. The splitting ratio of optical output at 1.3 μ m wavelength light can change 44.5%. The optical loss in the switch is less than 0.4
Synthesis, Characterization, and Optical Properties of Inorganic Polymer Films
Authors: Exarhos Gregory J. , Samuels William D. , Burton Sarah D.
Published: March 2011

The linear and non-linear optical response of phosphazene and siloxane polymers and cyclic precursors is influenced by the nature of chemical groups substituted onto the heteronuclear backbone chains. Polymer mechanical properties, chemical stability, and solubility also are affected. Significant variations in both second and third order susceptibilities have been measured for various substituted phosphazene materials. The electron donating tendency of substitutional groups appears to correlate with the measured non-linear optical properties determined by SHG and DFWM experiments in these systems where d¦-p¦ bonding along the polymer chain is important. Approaches to the synthesis, and deposition of these materials as thin films will be discussed. Variations in optical properties are highlighted for several model systems in terms of substitutional group perturbation to the chemical bonding between the chain heteroatoms.
Local structure around Er in MeV Er-implanted silica
Authors: Polman A. , Marcus M. A. , Jacobson D. C. , Poate J. M.
Published: March 2011

Amorphous SiO2 films, 10 μm thick, were grown on Si(100) substrates and subsequently implanted with 5.0×1015 Er ions/cm2 at an energy of 3.5 MeV. When optically pumped at λ = 488 nm, the implanted films show a sharply peaked photoluminescence spectrum centred around λ. = 1.54 μm, corresponding to an intra-4f transition of Er3+. Thermal treatment at temperatures above 700 °C is needed to anneal out the implantation-induced defects and attain a maximum PL intensity and luminescence lifetime (15 ms). Extended x-ray absorption fine structure (EXAFS) spectra of Er-implanted bulk silica samples (3.4×1016 ions/cm2, 2.9 MeV) indicate that the Er has six O first neighbours at a distance around 2.25 Å. The results are similar to those for bulk samples doped with Er in the molten phase.
Optical Characteristics of Planar Waveguides in Simox Structures
Authors: Reed G T , Rickman A G , Weiss B L , Namavar F , Cortesi E , Soref R A
Published: March 2011

Results are presented for the propagation loss of planar optical waveguides fabricated in SIMOX structures with Si overlayers whose thickness varies from 0.57 μm to 6.0 μm. The results demonstrate that thick Si overlayers are required to produce propagation losses below 1 dB/cm. In addition, the results of the coupling between two vertically integrated waveguides formed using two buried SiO2 layers are also reported.
Investigations on Hydraulically Reactive Glasses in the system CaO-AL2O3-SLO2
Authors: Hommertgen C. , Odler I.
Published: March 2011

A series of glasses in the system CaO-Al2O3-SiO2 was synthetized and studied with respect to their hydraulic reactivity. Generally, the initial reactivity is greater but the developed maximum strength is lower in glasses yielding a hydrogarnet phase, as compared to those yielding gehlenite hydrate. Another factor that determines initial reactivity appears to be the cooling rate of the glass melt. After longer hydration times the strength of glass cement pastes starts to decline, apparently due to a recrystallization of the hydrates formed initially.
Synthesis and Properties of Poly(Vinyl Alcohol)/Calcium Aluminate Nanocomposites
Authors: Messersmith Phillip B. , Stupp Samuel I.
Published: March 2011

This paper describes the synthesis, structure and properties of a new layered nanocomposite which may have applications in cementitious systems. This material is one example of a new class of materials which consist of inorganic crystals containing intercalated organic polymer. The nanocomposite is synthesized by precipitating Ca2Al(OH)6[X]·nH2O (X=OH−, CO3−2) in the presence of poly(vinyl alcohol) (PVA). X-ray diffraction analysis indicates that the nanocomposite consists of calcium aluminate layers separated by interlayers containing anions, water and PVA. The intercalation of PVA can only be accomplished during crystal growth and is accompanied by an expansion in layer spacing from ˜8 Å to ˜18 Å. The nanocomposite exhibited enhanced thermal stability and when compacted into a cylinder was found to have more than twice the compressive strength than the pure calcium aluminate.
Multivariate Statistical Analysis of the Wfarddc North American Fly Ash Database
Authors: Pietersen Hans S. , Vriend Simon P. , Mccarthy Gregory J.
Published: March 2011

The database of chemical, mineralogical and physical characteristics of North American Fly ashes, assembled by the WFARDDC in North Dakota, was analyzed using multivariate statistics. Prior to the multivariate analysis, the data were rearranged in subgroups containing information on bulk-chemistry, glass chemistry, mineralogy and ASTM physical test results. These groups were analyzed individually. The multivariate technique used was Fuzzy C-Means Cluster Analysis, combined with Non-Linear Mapping. Analysis of the data-set indicates a relation between glass network former and network modifier content. The database shows that a subdivision on the basis of bulk CaO (< 11%; 11–20%; >20%) correlates well with the ASTM C618 Σ(SiO2 +Al2O3 +Fe2O3) and/or specific gravity. Mineralogical data indicate a subdivision into clusters containing varying amounts of mullite, quartz and/or ferrite spinel and a variety of Ca-containing minerals; high CaO ashes usually have high Ca-mineral contents. Of the CaO containing minerals, only portlandite contributed slightly to the compressive strength as defined by ASTM C618. Analysis of glass chemistry reveals smaller differences in absolute amounts of major oxides than would be expected on the basis of bulk chemistry alone. Surprisingly, the total glass content does not contribute significantly to 28 day compressive strength; multiple regression analysis only indicates a significant relation of particle size and specific gravity with the ASTM Pozzolanic Activity Index (portland cement). The Pozzolanic Activity Index with lime seems to be of limited importance in evaluating the performance of fly ashes as mineral admixtures in concrete. On the basis of the statistical analysis, suggestions for selection of important classifying variables are made.
Magnetic Properties of Low-Ca Fly Ash: A Rapid Tool for Fe-Assessment and a Survey for Potentially Hazardous Elements
Authors: Dekkers M.J. , Pietersen H.S.
Published: March 2011

Between 20 and 50 per cent of the total iron in low-Ca fly ashes resides in low-substitution magnetite spinel with Curie temperatures in between 565 and 590°C. A TEM study reveals that the spinel consists of aggregates of closely spaced spherules of 10 – 30 nm in diameter, which is in complete agreement with rock magnetic determinations. The low-field magnetic susceptibility correlates extremely well with total iron and fairly well with specific heavy metals. Measurement of the magnetic susceptibility may serve as a rapid tool for the evaluation of the speciation of these heavy metals in fly ash.
Inertial Effects in the Dynamics of Martensitic Phase Boundaries
Authors: Truskinovsky Lev
Published: March 2011

Localized phase transitions, as well as shock waves, can be modeled by material discontinuities satisfying appropriate jump conditions. One can show that the classical system of Rankine-Hugoniot jump conditions is incomplete in the case of subsonic phase boundaries. The supplementary condition which generalizes the condition of phase equilibrium, can be obtained from the traveling wave solution of the truly dynamic system of equations describing the interface structure.
Elastic Isotropy in Martensitically Transforming FCC Alloys
Authors: Li J. , Chopra H.D. , Tanner L. , Wuttig M.
Published: March 2011

The nature of the premartensitic state is still under debate. It is becoming evident that alloys which transform into a long period polymorph display the equivalent precursor strain modulations in the parent phases. The situation in alloys which transform in the center of the BZ is less clear, however. On the basis of electron microscopic [1,2,3] and X-ray diffraction data [4], it has been proposed for Fe-Pd alloy that the parent state consists of a coherent mixture of tetragonally distorted variants which may form a transitional phase. The interpretation is substantially based on the observation of 110 diffuse scattering and the softening of the elastic constant ½(C11 -C12) [1,2,5,6,7]. We have performed TEM studies of In-Tl alloys and investigated the low frequency mechanical response of In-Tl, In-Cd and Fe-Pd alloys. The phase diagrams of the three alloys [8,9,10], schematically presented in Fig. 1, show the common FCC-FCT martensitic transformation. Our studies indicate isotropic "elastic" softening and show that 111 streaking is present as well. This paper presents the mechanical results and their preliminary interpretation.
Shape Memory Behavior and Mechanical Properties of NiMn and Ni(Mn,X) Alloys
Authors: Yang W.S. , Mikkola D.E.
Published: March 2011

Potential high transition temperature shape memory alloys based on NiMn have been studied with emphasis on the shape recovery, transformation temperatures and mechanical properties. Binary NiMn, which has been reported to be brittle, has a low shape recovery, but this can be increased with Al or Ti additions. Also, the transformation temperature can be changed and the room temperature ductility improved by ternary element additions. The various substitutional solute characteristics affecting the shape recovery, the transformation temperatures, and the ductility have been examined.
Orthorhombic Martensite, Intermetallic Precipitates and Retained Austenite in Ti-Rich Ti(Ni+Cu) Sputtered thin Films
Authors: Chang L. , Grummon D. S.
Published: March 2011

Periodic multilayered titanium-rich Ni-Ti thin films were prepared by magnetron sputtering from alternating Ni45Ti50Cu5 alloy and pure titanium targets, with an alloy-layerfl'i-layer thickness ratio of 9:1. The microstructure, martensite transformation behavior, and precipitate and defect structures were studied in films which had been annealed at 923K for one hour and furnace cooled at <20 K/min. Energy dispersive X-ray fluorescence measurements showed that the resulting films had a hyperstoichiometric titanium content of approximately 51 atomic percent. Ti2Ni precipitates were found in the annealed structures which were oriented with [1 1 0 ]Ti2Ni parallel to [110]B2 and (001)Ti2Ni parallel within +/− 10 to (001)B2. Differential scanning calorimetry (DSC) revealed an unusually low transformation enthalpy for the martensite reaction in the film (9.1 J/g as opposed to 20.7 J/g for the alloy sputtering target), and a significant fraction of residual B2 austenite was found at temperatures well below the nominal Mf. The martensite transformation was found to occur in two steps involving, on cooling, the initial formation of an orthorhombic martensite prior to transformation to the monoclinic martensite phase at low temperature.
Theory of Pre-Martensitic Effects in Alloys with ω- Transformation
Authors: Vul David A.
Published: March 2011

It is shown that the phonon dip in the longitudinal phonon branch L[111] in the metals Zr, Hf, Ti, Nb results in an oscillating component in static displacement field around a point defect. The oscillations have the wave vector 2/3(111) and occur in four rod-like shape regions along <111> directions. The value of the oscillations is much smaller then whole atomic displacements. Anomalies of the elastic diffuse scattering intensity from β-phase alloys based on the metals are explained as caused by the scattering on these distorted regions around solutes.
SMA and SME in Cu-Zn-Al Alloys: Local Studies inα, ε, T Space
Authors: Amengual A. , Isalgué A. , Lovey F.C. , Marco F. , Torra V.
Published: March 2011

The use of Cu-Zn-Al single crystals (electronic concentration e/a= 1.48) and of a high resolution equipment allows to study the evolution of one or few martensite domains. This kind of study proves the existence of intrinsic thermoelasticity, the differences between different friction processes (interface movements and nucleation) and also the coherence of the hysteresis loops obtained through mechanical stress or temperature. The different evolutions linked to the creation of dislocations or to the change of é precipitates can clearly be seen during the cycling. The observations allow to establish a model of the material behaviour consistent with experimental observation.
Effect of Superelastically Deforming NiTi Surface Microalloys on Fatigue Crack Nucleation in Copper.
Authors: Grummon D. S. , Nam S. , Chang L.
Published: March 2011

Alloys based on near-equiatomic NiTi are capable of thermoelastic martensite transformations which give rise to shape memory and superelasticity (pseudoplasticity) effects. In particular, at temperatures above Ms and Af but below Md, NiTi alloys can deform by mechanisms of stressinduced martensite transformation and may display large anelastic strains which involve little or no deformation by slip. Under these conditions, the strain-controlled fatigue resistance of NiTi alloys may be exceptionally high [1]. In contrast, fcc metals like copper will, during strain controlled fatigue, eventuate severe plastic strain localization in the form of persistent slip bands (PSBs), whose behavior at free surfaces is intimately associated with fatigue crack initiation [2]. It is well known that fatigue crack initiation in fcc metals can be delayed by modifying surfacebreaking PSB structure or environment [3,4]. However, any attempt to strengthen the surface region in order to impede surface expression of persistent slip bands must contend with the large subsurface strain localizations enforced by the PSBs, which subject the film to strain cycling at roughly the characteristic PSB shear strain amplitude. Thermoelastic nickel-titanium alloys, capable of pseudoplastic straining, may be uniquely suited to the role of surface protection in situations where fatigue crack initiation is associated with PSB interaction with the external environment. In the present work, thin surface microalloys of NiTi, produced by ion sputtering, have been applied to polycrystalline copper fatigue specimens that were subsequently subjected to both monotonic loading, and fatigue under plastic strain control to produce mature PSB structures in the bulk material. Optical and scanning electron microscopy studies are described which assess the effect of the NiTi surface microalloy on the behavior of PSBs in the near surface region, and the attendant effect of the films on surface behavior of persistent slip bands. Although the results are incomplete with respect to the effects of the film on fatigue crack initiation, it has been shown for the first time that martensite transformation can be stress-induced (at temperatures above Ms) in a thin NiTi film on a plastically deforming substrate. This finding augurs well for the potential of such films to effectively suppress slip band penetration during low cycle fatigue.
Electric Transport Properties of a NiTi Shape Memory Alloy Under Applied Stress.
Authors: Airoldi G. , Riva G. , Ranucci T. , Vicentini B.
Published: March 2011

It is well known that mechanical properties of Shape Memory Alloys are strongly dependent upon the test temperature (T) respect to transformation temperatures: the stress-strain curves however hinder the true deformation processes acting.

Electrical resistance(ER), a physical property sensibly affected by electronic structure modifications, traditionally used to follow the growth of thermal martensite, is here investigated to follow the modifications of a NiTi alloy, in an initial single phase structure, under applied stress. ER measurements are here detected with the aim to distinguish different deformation processes at four test temperatures Ti (i=1,..,4): in martensitic phase,either at T1 <Mf or at T2<As within the hysteresis cycle; in parent phase, either at Af<T3 or at Ms<T4 within the hysteresis cycle, where T2 = T4. Results are examined in comparison with previous obtained data and discussed at the light of imprinted deformation.
The Influence of Thermomechanical Treatment on R–Phase Transition and Shape Memory Effect
Authors: Jinfang Guo , Yuying Cheng , Ming Zhu , Long Shen , Guansen Yuan
Published: March 2011

This paper discussed the influence of cold working and annealing process on R–phase SME in an equiatomic TiNi alloy by means of tensile test, phase transformation, temperature measurement, and shape recovery examination. The results show that the increase in cold deformation of TiNi alloy got the increase in both tensile strength and R–phasc transition (TR–Ms). As R–phase becomes stable, the SME will be improved and the decay of memory effect will also be controlled at fatique test. The increase in annealing temperature got the decrease in R–phase transition range. In that case the stability of R–phase and the SME of the alloy also become bad. When annealing at 600°C, the recrystallization occurs no R–phase is found. Surely the SME of alloy becomes bad.
Material Characterization of Rapidly Solidified Ti-Ni-Cu Alloys
Authors: Furuya Y. , Matsumoto M. , Masumoto T.
Published: March 2011

Material properties of of rapidly solidified(RS),Ti5øNi5ø-xCux(X=O-2Oat%) alloys,i.e., thermoelasatic transformation temperature,transformation strain vs. temperature hysteresis, strength.ductility,themal fatigue resistance and corrosion resistance etc. were investigated. Specimens of thin ribbon were prepared by using melt-spinning machine with single Cu rolls at the cooling rate of about 40 m/sec. In the range of Cu content over lOat%,rapidly solidified (RS)ribbons were producible as a very thin plate and showed high ductility(i.e.180° bending). From the measurements of transformation strain vs. temperature hysteresis under small stress a bout 60MPa,transformation strain shows the maximum at Cu=5at%,and its transformtion temperature range nΔ(=Af-Mf) decreased with increasing Cu content to minimum value of 6.5K at Cu=17 at%. Thermal fatigue resistance was improved very much about ten times,futhermore,corrosion resistance was also improved over 100 times as much as conventionally processed(i.e. melting→ mechanically worked) material. It can be concluded that the functional superioity of RS meltspun Ti5øNi5ø-xCux ribbon exists in the range of Cu content over 10 at%. The reason of abovementioned remarkable improvements of material properties of RS TiNiCu alloys is discussed by relating with the observed unique fine columnar microstructures having strong crystal anisotropy and homogeneouss smooth surface.
From a Seed to a Need: the Growth of Shape Memory Applications in Europe.
Authors: Humbeeck Ir. J. Van
Published: March 2011

A more systematic marketing research approach has finally revealed good ideas anticipating a market need for the use of shape memory alloys. The success of those new ideas, prototypes and applications are analysed in terms of “the value of the function”, defined as the importance of the function divided by the cost of providing the function. A high importance and/or a low cost of the function are thus the basic requirements for the successful introduction of shape memory applications. Attention is also paid to the way how the 4 P's, product, price, place, promotion (the marketing mix) are applied by the European companies. Those different items will be illustrated on the basis of some small-, medium- and largescale applications, used in different markets. “to the point research”, fundamental and applied, on material properties as well as on manufacturing (cost reduction) is being discussed as the key factor to increase the function value.
The Interior of the Pseudoelastic Hysteresis
Authors: Fu Senlin , Müller Ingo , Xu Huibin
Published: March 2011

An interesting problem within the research on shape memory is provided by the investigation of the pseudo-elastic hysteresis loop that accompanies the strain-induced austenitic-martensitic phase transition. Miller [1] suggested by thermodynamic arguments that the size of that loop should be related to the coherency energy at interfaces between martensite and austenite. That proposition received a boost when Müller & Xu [2] showed that the same thermodynamic arguments predicted the onset of internal yield and recovery inside the hysteresis loop on a well-definqd line of unstable phase equilibrium. Recently Fu, Müller and Xu [3] have reported results with improved specimens and methods of observation that may help to understand the nature of metastability inside the hysteresis loop.
Aging Effects of Cu-Zn-Al Shape Memory Alloys Studied by the Alchemi Measurements
Authors: Shimizu K. , Nakata Y. , Yamamoto O.
Published: March 2011

The aging effects of two kinds of Cu-Zn-Al shape memory alloys (Cu-ll.4 Zn-18.7A1 (A) and Cu-ll.2Zn-17.lAl (B) in at%) have been examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atom location by channeling enhanced microanalysis (ALCHEMI). In the directly quenched (D.Q.) state, alloy A was the parent phase, Ms being 253 K, and alloy B was the martensite phase. The alloy B was subjected another quenching treatment as follows: It was once quenched into an oil bath at 423 K and held for 300 s, followed by quenching into iced water (step quench (S.Q.) ). The D.Q. alloy B did not exhibit the reverse transformation because of a stabilization of the martensbite phase, but the S.Q. alloy B did and its As temperature of the reverse transformation was raised with the progress of aging at the martensitic state. Fraction of Zn atoms at the Cu(2) site examined by the ALCHEMI measurements was almost the same in the parent phase of D.Q. alloy A and its aged one, indicating no change in Cu and Zn atom sites, while it was gradually decreased in S.Q. alloy B with the progress of aging. The fraction of Zn atoms in D.Q. alloy B was much lower than those in the S.Q. alloy B and its aged one. TEM observation of the S.Q. alloy B revealed that stacking faults as the lattice invariant shear in the M18R martensites decreased in the density with the progress of aging. The decrease in the fraction of Zn atoms and in the density of stacking faults well corresponds to the increase in As temperature, and thus the martensite stabilization was attributed to a disordering between Cu and Zn atoms and to an annihilation of stacking faults.
Two - Step Martensitic Transformations in TiNi(10% Cu) Shape Memory Alloys
Authors: Moberly Warren J. , Duerig T.W. , Proft J.L. , Sinclair R.
Published: March 2011

Third element additions to TiNi provide a wide range of modifications of its shape memory properties. The advantages of Cu additions are to provide a more narrow hysteresis, less sensitivity to the Ti::Ni(+Cu) ratio of the temperature at which martensite starts to form (Ms), a larger strength differential between the austenite and martensite phases, and superior fatigue resistance. The substitution of a few atomic percent Cu for Ni does not significantly alter the crystal structure of either the cubic B2 austenite nor the monoclinic B19ʹ martensite phases; however, the addition of greater than 10% Cu results in an orthorhombic B19 martensite phase. For the case of 10% Cu, a two-step martensitic transformation occurs upon cooling, with the cubic austenite transforming to the orthorhombic B19 martensite and subsequently to the monoclinic B19ʹ martensite. As a result of this two-step crystallographic transformation, material properties such as resistivity and shape change also exhibit a two-step transformation.

In situ transmission electron microscopy heating and cooling experiments are used to observe the two-step martensitic transformation and to establish an orientation relationship between the B19 orthorhombic and the B19ʹ monoclinic structures. Strain vs temperature Ms tests establish the relative shape changes associated with both the cubic-to-orthorhombic transformation and the orthorhombic-to-monoclinic transformation. Similar Ms tests, where an applied load is removed during the transformation, establishes a crystallographic dependence between the two shape changes. Whereas binary TiNi is "trained" to undergo a specific shape change, this ternary TiNiCu alloy has a "natural" direction associated with the second step of its shape change.
Aging Effects in Ni-36% Al Shape Memory Alloy
Authors: Angst David R. , Kao Ming-Yuan , McKinney Bryan L.
Published: March 2011

Samples of Ni-36 at% Al which were hot rolled, then solutionized at 1230°C and quenched, exhibited reversible transformations between the low-temperature, martensitic phase and the high temperature, austenitic phase. The initial peak transformation temperatures on heating (AP), cooling (MP), and the heats of transformation (ΔH) determined by differential scanning calorimetry (DSC) were ∼121°C, 119°C and 4 J/g, respectively for the as-solutionized material.

Decreases in transformation temperatures and heats after aging at 350°C were also determined using differential scanning calorimetry (DSC), and microhardness testing (DPH). The DPH values plotted against age time showed two distinct peaks, a result similar to precipitation hardening in other Al alloys.
Ordered Structure of Copolyesters Having Mesogenic Components
Authors: Niki Akihiro , Hasegawa Hirokazu , Hashimoto Takeji
Published: March 2011

Ordered structures of the multiblock copolyesters composed of p-quarterphenyl (DHQ, rigid segments) and poly(ethylene adipate) (flexible segments) were investigated by means of WAXD and SAXS. It was found that only the DHQ segments crystallize but the poly(ethylene adipate) segments hardly crystallize which make this copolyester a good thermoplastic elastomer. The copolyesters exhibit microphase separation above the melting temperature of the DHQ segments.
Study of the Reduction of Turbulent Drag by Photon Correlation Spectroscopy
Authors: Tong P. , Goldburg W. I. , Huang J. S.
Published: March 2011

Turbulent drag reduction in a dilute polymer solution has been studied using the technique of photon-correlation homodyne spectroscopy to measure velocity differences in a concentric cylinder cell, in which the inner cylinder rotates. A large anisotropic suppression of turbulent velocity differences is found in the bulk region of the turbulent fluid. The suppression effect occurs at various length scales up to ∼ 1 mm, which is far beyond the Kolmogorov dissipation length ℓd (∼ 0.04 mm). The large-scale velocity fluctuations are suppressed, but their statistical properties remain unchanged. The small-scale fluctuations, on the other hand, are damped out much more strongly, resulting in a different functional form for the velocity density function. The latter observation is consistent with the notion that the polymer-turbulence interaction causes a truncation of the turbulent energy cascade at small scales.
Colloidal Dynamics from Forced Rayleigh Scattering
Authors: Gochanour C. , Mazur S. , Wolfe M.S.
Published: March 2011

Colloidal suspensions are remarkable analogues of molecular fluids. In particular, at high volume fraction (Φv) they share two characteristic features with super-cooled molecular liquids: the appearance of two distinct modes of translational motion (fast and slow diffusive modes), and a critical retardation of the latter as Φv approaches random close packing (a colloidal “glass transition”). These phenomena have been studied extensively by photon correlation spectroscopy (PCS) [1-4] and are the subject of many theoretical analyses [5-12]. This paper concerns the use of forced Rayleigh scattering (FRS) to address questions not resolved by existing data or theory. We report: 1) properties of a hydrophobic silica colloid bearing photoactive azo-dye groups suitable for FRS studies, and 2) preliminary results from FRS measurements which reveal some unanticipated features regarding the transition from short-time to long-time self-diffusion at small k.
The Use of Mechanical Property Measurements to Characterize Gels and Gelation Processes
Authors: Yang Y. , Ichise N. , Li Z. , Yuan Q. , Mark J. E. , Chan E. K. M. , Alamo R. G. , Mandelkern L.
Published: March 2011

There are a variety of gels (highly swollen solids) that are of considerable interest to polymer scientists, materials scientists, and ceramists. One type consists of typical organic polymers such as polyethylene or polystyrene, in networks which are formed by means of physical cross links, such as crystallites or physical aggregates. Such gels are thermoreversible in that liquefaction occurs upon heating. Another type consists of chain-like structures permanently bonded into covalent networks. These permanently branched and cross-linked chains can be either organic (phenol-formaldehyde resins, epoxies, etc.), or inorganic [silica (SiO2), titania (TiO2), zirconia (ZrO2), etc.] Both the organic and inorganic covalent types have been used to prepare aerogels, and the inorganic ones are now much used to prepare high-tech ceramics by the new sol-gel route.

In the case of the thermoreversible, organic polymer gels, moduli can be measured as a function of concentration, temperature, and structural characteristics of the polymer (molecular weight, molecular weight distribution, and nature and degree of any chain branching). Such equilibrium results give information on the nature of the gels, including the influence of morphology, and the presence of dangling-chain irregularities. Measurements carried out as a function of time, for example, on polyethylene homopolymers and copolymers, can give information about their gelation kinetics.

In the case of the ceramic materials, the evolution of the shear modulus with time is very useful in establishing induction times, rates of gelation, and aging effects. Correlation of such information with results of scattering studies can give much insight into the nature of the sol-gel process.
Sol-Gel Diagram of Silica-Siloxane Mixtures. Percolation Approach
Authors: Cohen-Addad J.P.
Published: March 2011

The property of elasticity and the effect of swelling of mechanically induced silica-siloxane mixtures are interpreted within a percolation framework. This approach is illustrated by varying the specific amount of adsorbed polymer upon the silica surface of aggregates.
Structure of The Diblock Co-Polywer Aggregates in Solution
Authors: Huang J. S. , Fetters L. J. , Sung J. , Lin H. Y. , Richter D. , Hadjichristidis N. , Farago B. , Gast A. P.
Published: March 2011

We have employed a variety of scattering techniques to study the structure of diblock copolymer aggregates in solution The system of interest is an anionically prepared poly(styrene-isoprene) diblock copolymer (PS-PI) with well defined molecular weight and composition. When the diblock copolymer is added to decane, which dissolves the polyisoprene but not the polystyrene, we observe that polymeric micelles form at concentrations above a critical micellar concentration. The aggregation number is determined by light scattering and neutron scattering to be roughly 120. The micellar aggregate consists of a spherical polystyrene core with a mean radius of 105 A surrounded by a PI corona. The size distribution is quite narrow (<10%). The PS core is swollen with the solvent by roughly a factor of 2 in volume. By combining dynamic light scattering and SANS, we determined the thickness of the corona to be 50 A, which is 70% larger than the radius of gyration of a free PI chain of the same molecular weight in a good solvent. Furthermore, SANS measurements suggest that the aggregates form an ordered phase at the nominal cross-over concentration as it is expected for a highly functionalized star-branched macromolecules in solution.
Microphase Separatxon of Charged Diblock Copolymers
Authors: Marko J. F. , Rabin Y.
Published: March 2011

The microphase segregation properties of diblock copolymers composed of a neutral polymer joined to a polyelectrolyte are described. For weakly charged diblocks under melt conditions, we have constructed a theory of weak concentration fluctuations and have used it to study the spinodal instabiity to microphase separation that is driven by incompatibility of the polyion and neutral blocks. As in polyelectrolyte melts, the charging has a strong compatibilizing effect because of the large counterion entropy cost of phase separation. The electrostatic interactions also introduce a new length scale, the Debye screening length, which competes with the free chain radius to determine the microphase wavelength. A scaling theory of the strongly-segregated phase indicates that the salt-free microphases cannot have sharp interfaces beyond a threshold number of charges per chain.
The Polyelectrolyte Brush: Poor Solvent
Authors: Ross Richard S. , Pincus Phil
Published: March 2011

We investigate the end grafted polyelectrolyte brush in the poor solvent regime of the corresponding neutral polymer system. Using Poisson-Boltzmann theory for the electrostatics and Flory-Huggins-mean-field theory for the excluded volume and Van-der-Waals-like monomer interactions, we find the existence of a first order phase transition to a collapsed state for moderate to highly charged polyelectrolytes in the poor solvent regime. Irreversibilities in the disjoining pressure between planar grafted surfaces are predicted. For polyelectrolytes grafted to spherical and cylindrical surfaces with small radii of curvature, the phase transition is predicted to become second order in the infinite molecular weight limit. A phase diagram for the entire poor solvent regime is given.
Selective Formation of Radicals at Polymer-Solvent Interface. A Direct Determination of Solvent Penetration into a Porous Network
Authors: Korb J.-P. , Chachaty C.
Published: March 2011

This work shows that, in studies on porous disordered organic material such as cross-linked resin of poly(4- vinylpyridine, one has to consider a possible interfacial adsorption of solvents. We propose the nuclear relaxation associated with ESR of y-ray induced radicals as an efficient method to estimate the extent of solvent penetration into the interface of the polymer network. This method is however limited to the case where free radicals resulting from solvent-substrate interactions can be selectively generated at interfaces.
Complexing Blends of an Ionomer and a Rigid Rod Polymer
Authors: Shao L. , Weiss R. A. , Lundberg R. D.
Published: March 2011

A unique, molecular architecture was developed based on a hydrocarbon soluble backbone with a liquid crystalline side group. Lightly sulfonated polystyrene (SPS) ionomer was complexed with poly(y-benzyl-L-glutamate) (PBLG), an amine terminated synthetic polypeptide, by solution blending in either THF or chloroform. Complexation first occurred by proton transfer from the pendent acid to the amine terminal group. A secondary interaction involved hydrogen-bonding between the sulfonic acid and the carbonyl group on the PBLG chain. This material will have the potential as a molecular composite and unusual solution behavior was observed when the interaction occurred.
The Effect of Molecular Architecture on the Phase Diagram and Mobility of a Polymer Blend Exhibiting a Lower Critical Solution Temperature: Cycles Mixed with Linear Chains.
Authors: Santore Maria M. , McKenna Gregory , Han Charles
Published: March 2011

We examine the role of molecular architecture on the phase diagram of the PS/PVME (poly[styrenel /poly[vinyl methyl ether]) blend, a mixture which in previous studies with linear chains exhibited a lower critical solution temperature, (LCST) i.e. it phase separated on heating. In this investigation, two blends with components exceeding the critical molecular weight for entanglement were compared: one consisting of linear PS and PVME and a second with cyclic PS and linear PVME. Cloud point experiments over a broad composition range reveal that the blend containing cyclic PS undergoes phase separation at temperatures 7-8 °C higher than the analogous linear blend. In other words, the mixture of cycles and linear chains is more thermodynamically stable than the mixture of two linear chains.

The LCST nature of the system facilitates examining chain mobility by considering the phase separation kinetics. Time-resolved light scattering studies of blends near their critical compositions tracked the spinodal decomposition following a rapid temperature jump from the one-phase to the two-phase region. An analysis of the scattering intensity growth ultimately led to mutual diffusion coefficients whose temperature dependence confirmed the observed cloud points. An approximation of the second derivative of the free energy function based on SANS studies of the linear PS/PVME blend allowed us to estimate mutual mobilities. The values determined for the cycle-containing blend were considerably lower than those for the blend of linear chains at these molecular weights.
Cellular Automaton Simulation of Polymers
Authors: Smith M. A. , Bar-Yam Y. , Rabin Y. , Margolus N. , Toffoli T. , Bennett C. H.
Published: March 2011

In order to improve our ability to simulate the complex behavior of polymers, we introduce dynamical models in the class of Cellular Automata (CA). Space partitioning methods enable us to overcome fundamental obstacles to large scale simulation of connected chains with excluded volume by parallel processing computers. A highly efficient, two-space algorithm is devised and tested on both Cellular Automata Machines (CAMs) and serial computers. Preliminary results on the static and dynamic properties of polymers in two dimensions are reported.
Threshold Fracture of Networks
Authors: Mazich K. A. , Smith C. A.
Published: March 2011

We discuss the threshold fracture energy, GO, of networks over a wide range of cross-link density. C, for networks with an average number of main chain steps, ςc, that compare favorably with the entanglement spacing, ςc, follow the 1/2 power law, Go - ς1/2. Two views of molecular fracture, one a chain-breaking mechanism and the other a suction process, produce the 1/2 power law. For lightly cross-linked networks (ςc ≫ ςe), Go appears to decrease with increasing ςc. Trapped entanglements limit the extensibility and fracture energy of these networks. Consideration of rupture of trapped entangled chains gives Go -ςc-1/2; this form agrees reasonably well with data at high ςc.
Preparation and Cracterization of Alu1Inur Titanate Plabra Spray Powder
Authors: Shyu L. J. , Brice V. T. , Cambria F. M. , Su B. M. , Tirendi C. , Wandass J.
Published: March 2011

Aluminum titanate ceramic powder, used in plasma spray coating as a wear resistant material, was prepared from a gel precursor followed by high temperature calcination. The chemically derived gel was made from aluminum sulfate and titanium isopropoxide in an oxalic acid aqueous system. The soluble complex was studied by 13C NMR spectroscopy which showed that the mole ratio of oxalic acid bound to Al and Ti was 2:1. A coprecipitation took place when ammonium hydroxide was added. The gel was examined by solid-state NMR spectroscopy which suggested that aluminum titanium hydroxyl oxalate was present with Al in a distorted octahedral environment. EDX mapping showed that Al and Ti were evenly distributed throughout the gel particles. Thermal analysis indicated that dehydration and combustion of organic groups took place between 100 and 400 ° C. Gel which was heat treated at 1500 °C was identified as a pure AI2TiO5 crystalline phase by XRD.
Synthesis of Rare-Earth-Based Oxides for the Ceramic Industry: From Laboratory to Pilot Plant
Authors: Balachandran U. , Donris S. E. , Lanagan M. T. , Poeppel R. B. , Tourre J. M. , Golowski J. W.
Published: March 2011

A wide variety of compounds, e.g., superconductors, chromites, and manganites, can be synthesized by spray drying a mixture of salts or a combination of salts and sols in a flash dryer. The process ensures good control of stoichiometry, morphology, particle size, and surface area. Appropriate particle-growth and synthesis heat treatments of these fine powders have been conducted, and the resultant powders have been evaluated for possible applications in fuel cells and superconductors. The process has been scaled up to a pilot-plant capacity of ≈40 kg per day.