bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydration Reactions and Etrringite Formation in Selected Cementitious Coal Conversion By-Products
Authors: Solem Jody K. , McCarthy Gregory J.
Published: March 2011

Cementitious reactions and ettringite formation, which occur when water is added to high-calcium fly ash, to many dry flue gas desulfurization solids, and to two of the residues from the emerging “clean coal” technologies, fluidized bed combustion and limestone injection multiphase burner, have been studied. The parameters varied included water to solid ratio and curing time. Crystalline reactants and products were monitored by X-ray powder diffraction. The amount of ettringite, the principal crystalline cementitious reaction product, was determined after three months of curing. Results are discussed in terms of available Ca, Al and S in each by-product and w/s ratio.
Deformation Twinning, Slip, Martensite Formation and Crack Inhibition in the B2-Type Zr50Pd35Ru15 Alloy
Authors: Waterstrat R.M. , Bendersky L.A. , Kuentzler R.
Published: March 2011

Enhanced room temperature toughness of the Zr50Pd35Ru15B2 phase alloy was found to be a result of the activation of an additional deformation mode besides the b=[001] dislocation slip mode - {114}-type mechanical twinning. The twinning is a true one, i.e. there is no change in the ordered crystal structure. Another additional mode of plastic deformation, expected for more Pd rich alloys, is the formation of stress-induced martensite. The martensite was found to have a CrBtype structure.
Microstructure, Phase Stability, Mechanical Properties, and Shape Memory Characteristics of Ni-Fe-AI-B Alloys
Authors: George E. P. , Liu C. T. , Sparks C. J. , Kao Ming-Yuan , Horton J. A. , Kunsmann Henry , King Todd
Published: March 2011

Conventionally cast and hot-rolled Ni-Fe-AI-B alloys containing 4-20 at.% Fe, 23.9- 31.5 at.% Al, and 300 wppm B were investigated in this study. After oil quenching from 1300°C, all the alloys—except SMA-15 (27A1-14Fe)—have at least a two-phase microstructure, one phase of which is martensite with the characteristic plate morphology, and the other a globular second phase distributed throughout the microstructure. The amount of second phase generally increases with increasing Fe content. Alloys containing less than 14% Fe were found to be quite brittle at room temperature, indicating that a ductile second phase is at least partly responsible for the improved room-temperature ductility in the high-Fe alloys. The best tensile ductility (12%) was obtained in SMA-17 (23.9AI-20Fe) which was shown by X-ray diffraction to consist of 40% (mostly disordered) fcc [(Ni,Fe)3 (AI,Fe)] + 30% (partly ordered) bct martensite + 30% B2. Differential scanning calorimetry showed that the transformation temperatures for this alloy were MP = 65°C and AP = 95°C. Room-temperature tensile strains of 2-3% could be almost completely recovered in SMA-17 by heating for 3 min. at 600°C with the load removed. Upon subsequent cycling (i.e., strain-anneal cycling), the amount of strain recovery increased dramatically from 70% in the first cycle to nearly 100% after 4-5 cycles, indicating that cold work may help in improving the shape memory characteristics of this alloy. SMA-15 was found to have significantly higher transformation temperatures (Mp = 143°C and Ap = 170°C) than SMA-17; however, it is relatively brittle compared to SMA-17.
Study of Transformation-Induced Ductility in Polycrystalline Nickel Aluminide
Authors: Murthy Ananda S. , Goo Edward
Published: March 2011

Nickel aluminide intermetallic compounds are of interest due to their good high temperature properties. However, they are associated with room temperature brittleness. A method for enhancing the room temperature ductility of polycrystalline NiAI in the composition range of 62-65 at.% by using the martensitic transformation is presented. Transformationinduced ductilities up to 4.5% in specimens with coarse grains have been obtained in our investigation. The effects of Ni concentration, grain size and quenching rate from the parent B2 phase are studied and optimized to induce maximum transformation ductility. The original excellent high temperatu re properties are restored from the ‘soft’ room temperatu re martensitic phase by heating to an appropriate temperature to revert to the equilibrium phases.
The Influence of the Microstructure of CU-ZN-AL Shape Memory Alloy on Mechanical Hysteresis
Authors: Buffard L. , Charbonnier P. , Roucau C. , Dubois B.
Published: March 2011

Cu-Zn-Al shape memory alloys may offer good thermomechanical properties for industrial applications. However, it is important to control transformation temperatures,the aging and the fatigue behaviour.

We compare in this paper the effects of two thermomechanical treatments on industrial springs:

“Direct” treatment consists in homogenization in β phase, annealing and training.

“Inverse” treatment consists in homogenization in β phase, training and annealing.

A correlation between electron microscopy observations and D.S.C. experiments shows that heterogeneous ordered state (β+y2+β3) in Cu25%wtZn9%wtAl is an essential parameter influencing mechanical hysteresis.
The Effect of Some Factors on Ms and Sme in Ce-TZP Ceramics
Authors: Jiang Bohong , Tu Jinbiao , Hsu T.Y. , Xu Zuyao , Qi Xuan , Zheng Xiuhua , Zhong Jiaxiang
Published: March 2011

As known to all,shape memory behaviour has been observed in a variety of metallic alloys. This phenomenon, however, is not only observed in that field but also in other materials recently, such as in polymers,intermetallic compounds and ceramics, especially in zirconia ceramics.

Swain [1] observed the shape recovery of a bent magnesia-partiallystabilized zirconia (Mg-PSZ) bar upon heating above a certain temperature. The maximum deflection which was nearly completely recovered on heating is about 300 μm.

Chen et al [2] investigated the pseudoelasticity and shape memory effect (SME) in ceria-stabilized tetragonal zirconia polycrystals (Ce- TZP) containing 12 mol% CeO2.Wang et al [3] also observed the SME in Ce-TZP containing 10 mol% CeO2,.Here we would like to introduce some of results conducted recently in our group on SHE in Ce-TZP ceramics.
On the Electronic Nature of Phase Transformations in Ti-Me Shape Memory Compounds
Authors: Shabalovskaya S. A.
Published: March 2011

Binary or quasi-binary compounds TI-Me (where Me stands for Fe, Co, Ni, Pd. Pt and Au, or Ni with one of the above metals) with the B2 (CsCl) structure are known to undergo martensitic transformations of two types: B2-B19'(B19) and B2-R, with an Intermediate precursor charge-density-wave Incommensurate phase IS. Analysis of both experimental and theoretical data enabled us to establish empirical relations between the transformation temperatures: Ms(B2-B19') and TIs(B2-1S), and fundamental parameters of both electronic and crystal structures of the compounds, such as the lattice parameters, the shift of the d-band in the compound with respect to that in the pure Me, the compound's d-band width, the Ti site-projected d-densities of states at the Fermi level In the compound and BCC Ti, and the temperature of β-β allotropic transformation In pure Ti. This correlation is based on localization of the Me d-bands in the compounds. As a result the Me-Me interaction becomes less important, and the interatomic interactions are controlled by d-d (Ti-Ti) and sp-d (Me-Ti) bonds. The Fermi levels are dominated by the Ti d-states, which control the lattice dynamics as well. The latter is also reflected in closeness of the C' moduli and similar values of the phonon frequencies In Ti and the TiNi compound. Since the intermediate IS phase results from a frozen phonon mode and Is controlled by the electron-phonon interaction, the B2-IS transition temperature can be correlated with the Debye Temperature, θD as: TIS=λθD. Estimates based on experimental data show that for Ti-Ni alloys λ < 1.3. A decrease of λ upon alloying with Fe stabilizes the B2 phase.
Effect of Vacancy Clustering on Stabilization of Martensite in Copper Based Shape Memory Alloys
Authors: Kong Yingjie , Jiang Bohong , Hsu T.Y. , Wang Baoyi , Wang Tianming
Published: March 2011

Vacancy behaviors during ageing of Cu-26Zn-4A1 and Cu-14Al-4Ni alloys have been investigated and compared by means of positron annihilation (PA) and electrical resistivity measurement. For ageing in martensitic state after direct quenching, it is observed that the S parameter values of Cu-Zn- Al specimens, measured in liquid nitrogen, increase at first and then decrease, while those of Cu-Al-Ni remain unchanged. The activation energies calculated from the S parameter for increasing and decreasing stages are o.4lev and o.63ev respectively, and the former can be corresponding to the formation energy of vacancy clustering, while the latter may be regarded as the migration energy of effective vacancies. A mechanism is put forward that the clustering of quenched-in vacancies results in a decreasing of the ordering degree and a reduction of the stored energy in martensite, which is responsible for the early stage of the stabilization of martensite in Cu-Zn-Al alloys. However, the fact that Cu-Al-Ni alloy is not subject to the stabilization is assumed to be owing to the immobility of supersaturated vacancies in its martensitic state which may be associated with the strong binding force between Ni and Al atoms.
MÖssbauer Study of a Tinife Shape Memory Alloy.
Authors: Jimenez M. , Marquina V. , Aburto S. , Marquina M.L. , Gomez R. , Rios-Jara D.
Published: March 2011

MÖssbauer spectroscopy is very sensitive to structural transitions that may occur during a phase change of the type known to arise in the shape memory TiNiFe alloy. In this work we present the results of resistance vs temperature, differential scanning calorimetry (DSC) and Mössbauer spectroscopy (MS) measurements in Ti50Ni47Fe3 sample. The resistance vs temperature curve shows the usual sharp increase associated to the B2 → R transition at Tp = 245 K and then raises until a maximum is attained at ∼ 150 K. The DSC curve shows a peak maximum at the same temperature where the resistivity starts to increase. The room temperature Mössbauer spectrum consists of a single line, indicating that the iron atoms have cubic surroundings. As temperature is lowered, a small asymmetric quadrupole doublet begins to develop. The isomer shift (I.S.) and quadrupole splitting (ΔQ) values of this doublet increase with decreasing temperature until almost constant values are achieved at temperatures ∼ 100 K. We relate the changes in the Mössbauer spectra with previously proposed charge density wave induced premartensitic transition.
Thermodynamics, Phase Equilibria and Martensitic Transformation in Fe-Mn-Si Alloys
Authors: Forsberg Annika , Ågren John
Published: March 2011

The thermodynamic properties of the Fe-Mn-Si system are analyzed by means of thermodynamic models for the individual phases. Special attention is paid to γ → ε martensitic transition. A complete set of parameters, from which arbitrary sections of the phase diagram as well as the Ma and As temperatures may be calculated, has been obtained.
Fe-Mn-Si Based Shape Memory Alloys
Authors: Otsuka H.
Published: March 2011

Fe-Mn-Si based alloys are non-thermoelastic shape memory alloys which utilize the stress-induced transformation from γ austenite to ε martensite. After these shape memory alloys are deformed at room temperature, they recover their original shape when heated to 473K or higher. Fe-Mn-Si based alloys contain 15% to 33% Mn, 5% to 6% Si, 0% to 13% Cr, and 0% to 10% Ni in weight. Mn and Si are indispensable for the development of shape memory effect (SME). The amounts of these elements require to be adjusted so that the Neel temperature (TN) lies lower than Ms temperature and the Ms lies just below room temperature. Though the volume of stress-induced martensite is only 20 to 30%, a thermomechanical treatment called “training” has made it possible for the alloy to recover from a tensi le deformation exceeding 3%. Today, the use of the shape memory al loys for steel pipe joints is being studied. They have already been put into practical use for an auxiliary bicycle part to clamp the frame.
Electron Microscopy of Stress-Induced Martensite and Pretransition Microstructures in Ni62.5Al37.5
Authors: Schryvers D. , Tanner L.E.
Published: March 2011

Static configurations of stress-induced martensite and pretransition microstructures in Ni62.5A137.5 have been studied with conventional as well as high resolution electron microscopy using single crystal TEM specimens containing defect sites of extremely high stress intensity. From images of different regions around such defects it can be concluded that the austenite lattice develops transverse displacement modulations with increasing amplitude and correlation directly related to the {110}<110> shear-plus-shuffle displacements required to form the martensite structures. Different steps in this transition sequence are presented and discussed.
Thermal Hysteresis in Ni-Ti and Ni-Ti-X Alloys and Their Applications
Authors: Suzuki Yuichi , Horikawa Hiroshi
Published: March 2011

The first practical shape memory alloy, NITINOL, has a transformation thermal hysteresis(Hs) of about 30K and a monoclinic martensite structure. The first application of this alloy was a pipe coupling. Although various ideas were proposed on thermal actuators, they were not easily industrialized at least partly because the amount of Hs of the binary Ni-Ti alloy was too large. While the reduction of Hs is not so easy as transformation temperature control, the alloy was improved in terms of Hs through the discovery of new martensite phases. The first Hs reduction was realized in a Ni-Ti-Cu alloy. The copper addition changes the martensite structure to orthorhombic and reduces Hs to 10-15K. The alloy was first applied to a thermal actuator in automobile fog-lamps. Subsequently the R-phase transformation was identified in the binary alloy under the combination of cold working and a heat treatment at relatively low temperatures. Hs was further reduced to 2K in the R-phase transformation. The R-phase transformation is also featured by an excellent fatigue life which reaches one million cycles. The small Hs and long repetition life rapidly widened the application field of shape memory actuators. An expansion of Hs up to 100K was also achieved by a combination of fine dispersion of niobium and cold working. At present, the Hs of the Ni-Ti base alloys ranges from 2K to 100K. An appropriate alloy system can be selected according to applications. The binary alloy has found a wider application field in the super elastic application. In this paper, we summarize the progress in the modification of Hs and present recent applications of each transformation.
Development of a Retractable Bone Probe Using Shape Memory Alloys
Authors: Ley Timothy J. , Stice James D.
Published: March 2011

A unique superelastic NiTi Retractable Bone Probe was designed which can diagnose anatomical structures not previously possible. A number of design considerations which entered into the final device configuration will be discussed. Potential applications for this new probe will be presented.
Cycling Times of Thin-Film NiTi on Si
Authors: Jardine A. Peter
Published: March 2011

The thermo-mechanical properties of NiTi are well known for bulk material although its deposition and utilization as a thin film are still in their earliest stages. The deposition of thin-films of Shape Memory Effect NiTi onto Si(100) wafers offers several advantages over bulk NiTi, including fast response times and comparitively large transformation forces, and so is a promising candidate as a micro-actuator for MicroElectroMechanical (MEMS) systems as well as in strain measurements. The response time for a variety of NiTi layers were modelled under different boundary conditions and show response times similar to the acoustic velocities for one micron thick NiTi.
Shear-Enhanced Structure and Dynamics in Semidilute Polymer Solutions
Authors: Dixon P. K. , Pine D. J. , Wu X.-L.
Published: March 2011

We present elastic light scattering measurements of a semidilute polymer solution under shear flow. The basic symmetries observed in the shear-enhanced structure factor agree with the predictions of recently proposed theoretical models. The enhancement appears to be due to a coupling between the polymer concentration and shear flow through the concentration-dependent viscosity and normal stress coefficients. We also found an unexpected long wavelength peak in the shear-enhanced structure factor. Transient scattering measurements upon the cessation of shear have revealed the origin of this peak. The polymer solution demonstrates two modes of relaxation for concentration fluctuations in equilibrium due to a coupling between collective diffusion and stress relaxation. The transient scattering measurements indicate that the mechanism that couples the concentration fluctuations to the shear flow, and thereby enhances concentration fluctuations, selectively enhances only the slower of the two equilibrium modes. This selective enhancement generates the long wavelength peak in the shear-enhanced structure.
Rheo-Optics of an Augned Thermotropic Liquid Crystalline Polymer
Authors: Srinivasarao Mohan , Garay Raul O. , Winter H. Henning , Stein Richard S.
Published: March 2011

Rheo-optical studies on aligned and unaligned melts of a main chain thermotropic polyester with flexible spacers are discussed in terms of the predictions of the Ericksen-Leslie equations. It is shown, using conoscopy, that the director is flowaligning at temperatures close to TNI and nonflow-aligning close to a smectic to nematic (TSN) phase transition. The implications of these results are discussed in terms of the change in sign of one of the Leslie viscosity coefficients and interpreted in the framework of the Ericksen-Leslie Theory.
Phase Diagram of a Lattice Model for Ternary Mixtures of Water, Oil, and Surfactants
Authors: Laradji Mohamed , Guo Hong , Grant Martin , Zuchkermann Martin J.
Published: March 2011

Large scale Monte-Carlo simulations have been performed on a lattice model for a three component system of water, oil, and surfactants to obtain the phase equilibria and scattering behavior for a wide range of temperatures and chemical potentials. We observed that this model has a rich phase behavior, namely a water-oil phase coexistence, a microemulsion phase, a lamellar phase, and a square phase. This phase diagram is consistent with experiments, and is in qualitative agreement with a model of Gompper and Schick [ Phys. Rev. Lett. 62, 1647 (1989)].
Virial Expansions for Low Dimensional Ferrofluids
Authors: Widom M. , Zhang H.
Published: March 2011

Ferrofluids are colloidal suspensions of magnetic particles which we model as a dilute gas of dipolar hard spheres. At low particle density the osmotic pressure and magnetic susceptibility may be expanded in a virial series. We evaluate the second virial coefficients for fluids confined to a line, or to a plane, as well as ordinary three dimensional fluids in ellipsoidal containers. We focus our attention on anisotropy of the magnetic susceptibility and point out the role of particle chaining in determining the magnetic anisotropy of low dimensional ferrofluids.
Instabolotoes of a Ferrofludd Droplet in Alternatong and Rotatong Maghietic Fields
Authors: Bacrl J.-C. , PerZynski R. , Salin D. , Čebers A. O.
Published: March 2011

For the first time, response of magnetic fluid microdrops to time dependent magnetic fields are tested in two different experimental conditions (rotating field, crossed static and alternating fields). In both cases, a new shape instability is observed leading to cog-wheels either rotating either motionless. A simple model account for the stability range of oblate ellipsoidal shapes and for the lateral peak instability leading to the cogs which crown the cog-wheel.
Sheared Suspensions I - Electrorheology and Depletion Aggregation
Authors: Melrose J. R.
Published: March 2011

Idealised models of sheared suspensions are studied by computer simulation. In this and the companion paper [1], non-equilibrium phase diagrams are evaluated for two models: one for electrorheology (this paper), the other for aggregation due to depletion (companion paper [1]). Distinct structural phases and their associated rheology are reported.
Flocculation and Coalescence of Oil-in-Warer Emulsions
Authors: Bibette J.
Published: March 2011

Emulsions are commonly made of macrosized droplets dispersed in a continuous solvent. These systems are subject to two types of instabilities. One is reversible: flocculation, the other is irreversible: coalescence. The reversible flocculation induced by excess surfactant is studied. It is shown that an attractive interaction arises from depletion of surfactant micelles and leads to a fluid-solid phase transition. The sensitivity of this phase transition to the oil droplet diameter leads to a fractionated crystallisation method for purifying in size highly polydisperse emulsions. These well characterized systems are used to study the stability of the film against coalescence. Two distinct regimes of coalesence are found. One is driven by the surfactant chemical potential and occurs in a dilute emulsion. The other is driven by the water chemical potential and takes place in a concentrated emulsion which ressembles a biliquid foam.
Brillouin Scattering from Gels
Authors: Mallamace F. , Micali N. , Vasi C. , Sciortino F. , Bansil R. , Pajevic S.
Published: March 2011

We have investigated the question of heterogeneity in gels using Brillouin scattering, depolarized Rayleigh scattering and dynamic light scattering measurements on methylmethacrylate (MMA) gels crosslinked with varying amount of ethylene-dimethacrylate (EDMA). We find that the k dependence of the phase velocity changes on increasing the cross-link content. For higher concentrations of crosslink we observe maxima and minima in the k dependence of the phase velocity which e associate with spatial inhomogeneities in the gel, with the formation of regions of low and high cross-link density, respectively. This micro-phase separation occurs around crosslink content of 3-4 %. At this same concentration depolarized Rayleigh measurements show a marked decrease in the number of MMA side groups capable of rotating.
Morphologies in Blends of Diblock Copolymer and Homopolymer: Morphology Diagrams and the Intermaterial Dividing Surface
Authors: Winey Karen I.
Published: March 2011

Binary blends of diblock copolymer (AB) and homopolymer (hA) self assemble upon solvent evaporation into a great variety of microphase separated morphologies. The ordered lamellar, bicontinuous double diamond, cylindrical and spherical morphologies were observed by TEM and SAXS in our studies, as well as a range of micellar morphologies.

The mean curvature (H) and the area per copolymer junction (σj), which characterize the intermaterial dividing surface, increased with increasing homopolymer concentration in the blend and/or with decreasing homopolymer molecular weight. These trends were generally obeyed both between and within ordered morphology types. The increase in H and σjwas related to an increased degree of mixing between the homopolymer and the block of the copolymer.

Two types of isothermal morphology diagrams were constructed to consolidate the extensive morphological data and to illustrate the general morphological transitions in AB/hA blends. The constant molecular weight morphology diagrams illustrated the interdependence of the copolymer composition and the homopolymer concentration. The constant copolymer composition diagrams emphasized the importance of the relative homopolymer molecular weight and the overall blend composition.
Interlayer Diffusion in Langmuir-Blodgett Multilayers
Authors: Foster Mark D. , Vierheller Timothy R. , Schmidt Albert , Mathauer Klemens , Knoll Wolfgang , Wegner Gerhard , Satija Sushil , Majkrzak Charles
Published: March 2011

Interlayer diffusion in Langmuir-Blodgett multilayers containing Cadmium Arachidate (CdA), polyglutamate (PG) copolymers, or both, was investigated using neutron and x-ray reflectometry. Measurements from multilayers comprised only of CdA or PG revealed that little interdiffusion occurred upon annealing at 70°C or 84°C. However, some relaxation of the intralayer microstructure in the PG samples was observed at both temperatures. In contrast, the neutron reflectivity of a multilayer sandwich containing a bilayer of PG between two multilayers of CdA showed gradual and progressive change with annealing at both temperatures for annealing times of up to several hours. This change is surprising as PG is expected to act as a barrier to interdiffusion of the CdA molecules at these temperatures.
Adsorption Kinetics of Polyvinyl Acetate Adsorbed at the Solid-Liquid Interface
Authors: Terashima H. , Kanehashi K. , Imai N.
Published: March 2011

The kinetics of adsorption of polyvinyl acetate at the solid-liquid interface has been studied to verify the correctness of a description in a paper [Peterson and Kwel, J.Phys.Chem. 65, 1330(1961)] : “the initial rate of adsorption of polyvinyl acetate was found to be rapid”. This is inconsistent with the widely accepted knowledge that polymer adsorption is a slow process. Polyvinyl acetate (Mw = 124,800) was adsorbed from benzene (0.001 to 0.05 mg ml−1) onto mica at 295.5 K. The adsorbed amount per unit area i.e. adsorbance has been determined as a function of incubation time using an ultramicrobalance [Mettler UM3]. The results obtained show that the adsorbance rises rapidly at the beginning of adsorption and then reaches an apparent plateau, where the adsorbance still increases at negligibly slow rate in comparison with the initial rate. The Peterson and Kwei's results have been confirmed to be correct. We regarded the plateau as an adsorption equilibrium and constructed adsorption isotherms, in which the Peterson and Kwei's results were incorporated. These isotherms are found to be less dependent on concentration in the dilute region concerned. This dependency is in agreement with the prediction of the Scheutjens and Fleer theory based on the loop-train-tail model.
Exclusion of Spherical Particles from the Nematic Phase of Reversibly Assembled Rod-Like Particles
Authors: Madden Thomas L. , Herzfeld Judith
Published: March 2011

The open-ended aggregation of amphiphilic molecules in aqueous solution generates a broadly polydisperse population of elongated particles that form a variety of partially ordered phases. Herzfeld and coworkers have shown that the phase behavior of these binary systems is well described by self-consistently combining scaled-particle theory for the effects of excluded volume in fluid dimensions, a simple cell model for the effects of excluded volume in positionally ordered dimensions, a mean-field treatment of soft-interactions, and a phenomenological model of aggregate formation. We have now extended this model to ternary systems. We find that the addition of spherical particles to a solution of rod-forming particles induces a very wide isotropic-nematic coexistence region in which a relatively dilute isotropic solution with little aggregation separates from a rather concentrated nematic solution that almost completely excludes the spherical solutes. The magnitude of this effect depends on the relative diameters of the two solutes.
Nonthermal Microwave Plasma Synthesis of Crystalline Titanium Oxide & Titanium Nitride Nanoparticles
Authors: Mehta Prabhjot , Singh A. K. , Kingon A. I.
Published: March 2011

We report the nonthermal synthesis of ultrafine crystalline nanoparticles of titanium oxide and titanium nitride. The nanoparticles are formed by gas phase reactions between precursor gases dissociated in the microwave plasma. For the production of titanium nitride, titanium tetraisopropoxide (TTIP) and ammonia or nitrogen precursor gases are used. For titanium oxide production TTIP and oxygen are used as precursor gases. In both cases ultrahigh purity argon serves as a carrier gas and diluent.Transmission electron microscopy (TEM) revealed that the titanium nitride powders so formed were either cubic (TiN) or tetragonal (Ti2N) depending on the operational conditions, particularly the relative nitrogen gas flow rates. Ammonia gas was found to be a much more reactive nitrogen source than molecular nitrogen gas. For the titanium oxide growth an excess of oxygen was utilized to achieve TiO2. Powders collected from the gas phase corresponded to the rutile (tetragonal) phase. However, powders collected from the cavity walls corresponded to the high temperature and pressure (orthorhombic) 13-TiO2. There was also evidence of a polytypically modulated phase of TiO2, with the observed c-periodicity double the parent c-periodicity of the rutile phase. Using a low oxygen flow rate during powder formation led to the formation of orthorhombic Ti3O5 “powders”. The powders were easily sinterable by in situ electron beam annealing in the electron microscope, with an estimated temperature of around 550°C. This is much lower than the temperatures normally required to sinter these materials.
Synthesis and Characterization of Pure Barium Ferrite Prepared by a Glycine - Metal Nitrate Combustion Method
Authors: Wade Manson L. , Agresti David G.
Published: March 2011

A combustion-synthesis method [Chick et al., Materials Letters 10, 6 (1990)] has been adapted for the efficient preparation of pure barium ferrite particles, BaFe12O19. Solutions of Ba(NO3)2 and Fe(NO3)3 · 9H2O were mixed in stoichiometric amounts and glycine (aminoacetic acid) was then added according to the desired glycine / nitrate ratio. The solution was heated to around 200°C, when combustion occured, yielding a highly magnetic ash, which XRD suggests consists of extremely fine-grained γ-Fe2O3 and Ba3Fe2O6. Subsequent heat-treatments of 1050°C for 1.5 hr or 1200°C for 1 hr converted the ash to pure barium ferrite, as determined by XRD and Mdssbauer spectroscopy. Single-crystal platelets of barium ferrite, identified by SEM, varied dramatically in size with heat-treatment (diameter ∼0.2 pm and 6 μm, respectively), as did coercivity, measured by VSM (∼5000 Oe and 2500 Oe, resp.), while magnetization was unaffected.
A Novel Co-Precipitation Route for the Synthesis of Fine Mixed-Oxide Powders
Authors: Pathak Amita , Pramanik P
Published: March 2011

A new co-precipitation technique for the preparation of fine ceramic mixed-oxide povders using a mixture of (NH4)HCO3, triethylamine and formaline in presence of soluble polymers, like polyvinyl alcohol (PVA). The mixture is chemically equivalent to one mole of triethylamnroniumcarbonate (TEAC). The mixed-oxide ccmpositions synthesized and characterized are - MN2O4 [Spinels; where M = Ni(II), Cu(II), Zn(II), Co(II) and N = Fe(III), tr(III)]; M3Fe5O12 [Garnets; where M = Y(III), Gd(III)] and RBa2Cu3O7+δ [Ceramic superconductors; where R = rare-earths]. The final product is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy for microanalysis (EDX) and scanning electron microscopy (SEM).
Crystalline Phases During the Melting of Bi2Sr2CaCu2OX
Authors: Xu Ming , Polonka J. , Goldman A. I. , Finnemore D. K. , Li Qiang , Laabs F. C.
Published: March 2011

The melting of Bi2Sr2CaCu2Ox material has been studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in order to study the phases that formed in the high temperature regions. Two distinct phases of (Sr1-xCax)CuO2 and (Sr1-xCax)2CuO3 have been observed in the Bi-rich matrix depending upon quenching temperatures. Crystallization from the melt by fast cooling usually produce the co-existence of Bi (2201) and these Sr-Ca-Cu-O phases.
Issues Concerning the Chemical Synthesis of Ceramic Superconducting Coatings in the Bi-Sr-Ca-Cu-O System with High Critical Current Densities.
Authors: Golden S. J. , Vaidya K. J. , Bloomer T. E. , Lange F. F. , Clarke D. R.
Published: March 2011

Superconducting thin films of the two Cu-layer phase in the Pb-doped Bi- Sr-Ca-Cu-O system have been fabricated on {100} LaAlO3 single crystals by the metalorganic deposition (MOD) from ethyl hexanoate precursors. Some of the major issues pertinent to the synthesis of high quality films have been studied.

Thin films of composition Bi1.8Pb0.3Sr1.6CaCu2Ox given heat treatments in air at 850–860 °C for several hours had sharp resistive transitions with a Tc of 85–89 K. The zero-field transport critical current densities were in the range of 1–4×105 A.cm−2 at 77 K and 106 A.cm−2 at 45 K in 200–300 nm thick films. In contrast to caxis oriented films grown on (100) MgO, X-ray pole figures show that the polycrystalline films grown on (100) LaAlO3 are epitaxial, a result confirmed by electron channeling patterns.
Synthesis of C-oriented YbBa2Cu3O7-δ Films on Single and Polycrystalline Substrates by Oxidation of Liquid Alloys
Authors: Luo J. S. , Merchant N. , Maroni V. A. , Gruen D. M. , Tani B. S. , Sandhage K. H. , Craven C. A.
Published: March 2011

Textured superconducting films of YbBa2Cu3O7-δ supported on single and polycrystalline substrates were prepared by oxidation of a liquid precursor alloy. The substrates were coated by dipping them into a molten alloy (YbBa2Cu3, m.p. ∼870°C), withdrawing them from the melt, then oxidizing the adhering liquid alloy layer to the corresponding oxide phase, i.e., YbBa2Cu3O7-δ. Samples prepared in this way exhibited a superconducting transition at ∼80 K following annealing in pure O2 at 500°C. With SrTiO3 (100) and MgO (100) substrates, evidence was seen for the epitaxial growth of YbBa2Cu3O7-δ crystals having their c-axis parallel to the [100] direction of the substrate. For polycrystalline MgO, x-ray diffraction and microstructural examination showed that the high-Tc crystallites in the films were also oriented with their c-axis perpendicular to the substrate surface, but the a and b axes directions were randomly oriented rather than epitaxial.
Chemical Beam Deposition of Y2O3 Thin Films with An Ecr
Authors: Massimo Maurice , Varhue Walter , Adams Edward , Titcomb Stephen
Published: March 2011

Stoichiometric thin films of Y2O3 have been deposited on Si at substrate temperatures as low as 300 °C by plasma enhanced chemical vapor deposition using an electron cyclotron resonance (ECR) source. The yttrium source was an organo-metallic compound which was sublimated and fed with He carrier gas into the reactor chamber. Good capacitance-voltage characteristic curves were obtained for the dielectric film and a relative electrical permittivity of 9.9 was measured. This technique is a useful means of depositing oxide ceramic films at low substrate temperatures.
Oxidation Behaviour of Ieabct Deposited NiCoCrAlY-ZrO2·y2O3 Coating
Authors: Huang N. K. , Wang D. Z. , Feng Z. R.
Published: March 2011

The oxidation behaviour of NiCoCrAlY-ZrO2·y2O3 coatings produced by using an ion-electron-atom beams combination technique (IEABCT) was studied after air exposure at 1100 °C for up to 300 hours. It was found that pores were dispersed in the coating, especially in the interface between coating and substrate, and no spallation or separation of the ceramic layer from the metallic bond layer were observed. The composition and morphology of the coatings before and after oxidation exposure in air at 1100 °C for 300 hours were examined by microscopy and electron microprobe analysis (EMPA).
Preparation and Characterization of Sic From Alkoxide-Derived Polymeric Precursors
Authors: Jiang Zhiping , Rhine Wendell E.
Published: March 2011

Crystalline SiC was prepared by carbothermic reduction of alkoxide-derived polymeric precursors under a flow of argon at 1400-1600°C. The pyrolysis products from the precursors with a molecular source of carbon, i.e., (R1)x(R2)ySiO1.5(Rl=phenyl; R2=propyl, vinyl), showed different morphologies from those of the precursors derived from TEOS and a polymeric source of carbon (polyfurfuryl alcohol). Furthermore, the pyrolysis chemistry of theses precursors and the microstructure of their corresponding pyrolysis products were studied by means of FTIR, TGA, XRD, SEM, BET, elemental analyses, etc.
Settling Behavior of Alumina Dispersions and Resultant Green Body Characteristics: Solvent, Binder, and Dispersant Competition in Model Systems
Authors: Parker Anthony A. , Tsai Mei-Yuan , Biresaw Girma , Stanzione Todd T. , Armstrong George H. , Marcinko Joseph J.
Published: March 2011

The chemical functionality of binders, dispersants, and solvents will influence competitive adsorption/desorption behavior on alumina powder, and hence will affect both slurry and ultimate green tape properties. Given that multiple competitive interactions are common to most dispersions, it is usually difficult to ascertain mechanisms from simple settling density experiments. However, this problem can be partially overcome with the choice of model systems that minimize the number of competitive processes. This criterion is met to a first approximation with a model system of toluene solvent, polystyrene binder, and a C8 aliphatic dispersant with an anchor group of variable functionality. Plateau adsorption concentrations from settling experiments in toluene show that surface coverage for efficient dispersants is typically achieved at about 6μmoles/m2. Less efficient dispersants adsorb at higher plateau concentrations, and are eventually displaced after repeated washing steps in toluene. The settling densities of dispersions prepared with C8 dispersants are consistently higher than densities achieved in toluene alone, and as seen in a case study with n-octylsilane, the settling densities are independent of the presence of polystyrene. Green bodies cast from a polystyrene/Al2O3 slurry also show increased densities in the presence of n-octylsilane dispersant. However, despite the apparent low levels of interaction between polystyrene and n-octylsilane in the dispersion state, solid state NMR and dynamic mechanical results show that the solid state molecular motional behavior of polystyrene is strongly affected by the presence of n-octylsilane dispersant.
Biaxial Alignment of High-Tc Superconductor Polycrystals V: Micrographic Evidence for Biaxial Alignment in (Eu. 92 Yb.08)Ba2Cu30x [123(Eu)]
Authors: Zhang Jian-Zhong , Zhang Xin-Yu , Wang Sheng-Qi , Zhang Baoshan , Markiewicz Robert S. , Giessen Bill C.
Published: March 2011

The new biaxial alignment technique based on a combination of magnetic field and mechanical force alignment (acting normal to each other) has been applied for the first time to an RE-123 superconductor ceramic, where RE - Eu .92 Yb .08. Biaxial (and hence triaxial) alignment was achieved, at least in the surface layer, as demonstrated by XRD and observation of the twin boundary pattern.
A Process for Producing “Granular Single Crystals” of Ceramics from Polycrystals by Biaxial Alignment, Demonstrated for High-Tc Superconductors
Authors: Hidalgo Rafael , Zhanl Xin-Yu , Wang Sheng-Qi , Zhang Baoshan , Zhang Jian-Zhong , Chen Feng , Finn C. , Markiewicz Robert S. , Giessen Bill C.
Published: March 2011

A recently developed method for producing triaxial alignment of single crystalline grains may be applicable to ceramics other than the high-Tc cuprate superconductors for which it was designed as a means of reducing the grain boundary weak links due to grain orientational misfit. This technique uses a suitable combination of a mechanical force and a magnetic field acting on the moment of a rare earth element incorporated into the ceramic; a "granular single crystal" is thus formed. A detailed step-by-step procedure is presented here to facilitate use of the new approach.
Effect of Forming Techniques on the Orientation of Platelet Composites
Authors: Chou Yeong-Shyung , Green David J.
Published: March 2011

Two forming techniques, i.e., slip casting and dry compaction, have been employed to make SiC(platelet)-A1203 composites. The orientation of SiC platelets in the composites, before and after hot pressing, was studied using optical microscopy and a pole-figure X-ray device. It was found that the preferred orientation in the dry-pressed green bodies increased with increasing pressure, whereas the platelets in the slip cast bodies were close to a random orientation. The pressure during the hot pressing process did, however, align the platelets of slip-cast composites during densification. Optical micrographs confirmed the platelets tend to align with their faces perpendicular to the hot pressing direction. The effect of platelet size on the orientation was also investigated. X-ray analysis showed that small platelets (∼ 1.6 μm) do not give rise to preferred orientation both in green and hot pressed bodies; whereas larger platelets (∼24 μm) with larger aspect ratio do yield a stronger preferred orientation. The causes for the platelet alignment will be discussed.
Pyrolysis of Organometallic Precursors As A Route to Novel Ceramic Materials
Authors: Interrante Leonard V. , Schmidt Wayde R. , Marchetti Paul S. , Maciel Gary E.
Published: March 2011

Homogeneously mixed nanocrystalline composites incorporating SiC, Si3N4, AIN, BN and TiN, and SiC/AIN solid solutions were prepared from mixtures of known precursors to the separate components and specially prepared singlesource precursors. These novel materials are of potential interest as tough, abrasion-resistant coatings, continuous fibers and matrices for high temperature composites and, possibly, superplastic ceramics. Solid state NMR spectroscopy along with other chemical and materials characterization methods have been employed in studies of the precursor-to-ceramic conversion process and the characterization of the final ceramic products. The results of these studies are described and their implications with respect to the relationship between precursor structure, pyrolysis chemistry and the final ceramic composition and microstructure are discussed.
Solid Freeform Fabrication of Ceramics Using Selective Laser Sintering and Selective Area Laser Deposition
Authors: Lakshminarayan Uday , Zong Guisheng , Thissell W. Richards , Marcus Harris L.
Published: March 2011

Solid Freeform Fabrication (SFF) is a new computer fabrication technique that does not require any part specific tooling. The starting material can be either solid, liquid or gaseous. The part can be made from metallic, ceramic, polymeric or a composite material. The concept is to use a solid modeling system to define the part of interest and to reduce the model to a set of toggle point data that totally define the geometry. In Selective Laser Sintering the sectioned component is then combined with a rastered laser system that impinges on the precursor powder materials in a layered reconstruction of the three dimensional CAD designed part. The part is then formed in this manner. This approach to producing the part involves a great deal of understanding of the laser materials interactions, the appropriate choice of materials specific to this processing and how the total process integrates. Application to ceramic powders will be described. An alternative approach to SFF is Selective Area Laser Deposition where the three dimensional part is made from the gas phase. The initial gas deposition studies involving deposition of carbon from hydrocarbons will be discussed. For both of the above SFF approaches the laser beam powder and gas phase interactions and the microstructure of the resulting three dimensional forms as a function of system parameters will be described.
Formation and Stabilization of Extended Defects in Zirconia Titanate Microwave Ceramics
Authors: Christoffersen Roy , Davies Peter K.
Published: March 2011

The low-temperature, Zr/Ii ordered, form of zirconium titanate has been investigated using high-resolution transmission electron microscopy in order to characterize the incommensurate structure of phases with compositions ZrTiO4 to near Zr5Ti7O24. Electron diffraction reveals that compositions with Zr:Ti between 5:7 and 1:1 have incommensurate superstructures, and phases close to 1:1 are commensurate with an a-axis repeat 2× that of the disordered structure. High-resolution images show that the a-doubling in ZrTiO4 corresponds to a new structure, one that consists of two Zr-rich, distorted octahedral layers alternated with two Ti-rich octahedral layers. The incommensurate compositions are composed of blocks of the 1:1 structure intercalated with blocks of the commensurate 5:7 structure, the latter having a tripled a-repeat and a ZTTZTT sequence of cation layers. The intercalation can be described as an “interface-modulated” structure resulting from the quasi-periodic insertion of (100) faults with displacement vector ℝ= -l/3aord in the ordered 5:7 phase. Although their spacing is variable, the faults are uniformly distributed in such a way as to produce incommensurate satellite reflections.
A Study of the Thermolysis Behaviour of Pmma in Polymer/SiO2-PbO-B2O3 Glass Powder Mixtures
Authors: Aruchamy A. , Blackmore K. A. , Zelinski B. J. J. , Uhlmann D. R. , Booth C.
Published: March 2011

The binder burn-out behavior in PMMA/glass powder composites was studied as a function of glass composition in the PbO-SiO2-B203 system. The PbO content was varied to obtain glasses having optical basicities in the range of 0.62-0.81. TGA measurements on PMMA/glass composites show that the main decomposition end temperatures of PMMA increase with decreasing PbO content, and therefore, decreasing optical basicity. This indicates that PMMA interacts strongly with more acidic surfaces. The effect of the milling fluid was also studied. Milling in toluene does not significantly alter the behavior. Milling in water of a PbO-rich glass leads to significant leaching of lead. During drying, the leached lead deposits on the glass particle surfaces and drastically alters the thermal behaviour of the glass powder and PMMA/glass composites.
Coating of Silicon Nitride with Sintering Aid
Authors: Joshi P. N. , Mccauley R. A.
Published: March 2011

Commercially available silicon nitride powders were coated with various metal oxides with the help of metal-organic surfactants in an aqueous medium. A surfactants could also act as a dispersant. The coatings were studied by XPS, TEM and accoustophoresis and the mechanism for formation of these coatings is proposed. The amount of sintering aid incorporated was determined by the surface area and surface chemistry of the nitride powder, the pH of the solution, the structure of the surfactant and the surface charge behavior of the powder and the coating. Multicomponent coatings were also possible by precise control of these parameters. The sintering behavior of the coated powders and the properties of the sintered material were promising.
In-Situ Preparation of TiC/Al2O3, TiN/Al2O3 and TiN/AIN Composites From Alkoxide-Derived Precursors
Authors: Jiang Zhiping , Rhine Wendell E.
Published: March 2011

The reaction between furfuryl alcohol (FuOH) and the hydrolysis product of a mixture of Ti(O-n-Bu)4 and Al(O-sec-Bu)3 (AI:Ti=1:1) resulted in the formation of soluble polymeric solids. Pyrolysis of these polymers in argon yielded TiC/A2O3 composite at 1250 °C. When these polymers were pyrolyzed in ammonia, TiN/AI2O3 or TiN/AIN composite was formed. All these composites showed fine microstructure and excellent homogeneity. Furthermore, the structure and pyrolysis chemistry of these polymeric precursors as well as the microstructure of the pyrolysis products were studied by means of FTIR, TGA, XRD, SEM, TEM, STEM, Auger, elemental analyses etc.