bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphologies in Blends of Diblock Copolymer and Homopolymer: Morphology Diagrams and the Intermaterial Dividing Surface
Authors: Winey Karen I. 
Published: March 2011

AbstractBinary 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

AbstractInterlayer 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

AbstractThe 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

AbstractThe 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

ABSTRACTWe 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

ABSTRACTA 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

ABSTRACTA 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

ABSTRACTThe 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

ABSTRACTSuperconducting 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

ABSTRACTTextured 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

ABSTRACTStoichiometric 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

ABSTRACTThe 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

ABSTRACTCrystalline 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTA 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

ABSTRACTTwo 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

ABSTRACTHomogeneously 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

ABSTRACTSolid 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

ABSTRACTThe 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

ABSTRACTThe 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.