bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combustion Synthesis of Sr-Substituted LaCo0.4Fe0.6O3 Powders
Authors: Kingsley J. J. , Chick L. A. , Coffey G. W. , McCready D. E. , Pederson L. R. 
Published: March 2011

ABSTRACTSr-substituted perovskite LaCo0.4Fe0.6O3 is known to have excellent mixed ionic and electronic conductivity and increased O2 sorption characteristics. These perovskites are usually prepared by lengthy solid-state reactions of the component oxides at temperatures near 1150°C, and often produce inhomogeneous, multi-phase powders. Presently, it has been prepared by the calcination of combustion-derived fine mixed oxides at 850°C in 6 hrs. Combustion reactions are carried out using precursor solutions containing the corresponding metal nitrates (oxidizers) and glycine (fuel) at 250°C. The metal oxides produced by this process and subsequent calcination were characterized by XRD, TEM and BET surface area analysis.
A Raman Spectroscopic Study of the Initial Stages of Hydrolysis Oftetraethoxysilane
Authors: Barrie J. D. , Aitchison K. A. 
Published: March 2011

ABSTRACTMultichannel detection Raman spectroscopy was used to follow the hydrolysis and condensation reactions of TEOS/ethanol solutions. Effects of alkoxide concentration, catalyst concentration, watenTEOS ratios, and temperature were studied. It was found that the initial oligomeric composition of hydrolyzed solution was dependent upon the amount of water added to the solution: not only did reaction rates differ, but so to did the reaction products. Higher water concentrations resulted in formation of an oligomer which may contain a trisiloxane ring.
Theoretical and Experimental Investigations of the Growth of Silica and Titania Particles in Low Molecular Weight Alcohols
Authors: Harris Michael T. , Basaran Osman A. , Byers Charles H. 
Published: March 2011

ABSTRACTSilica and titania particles are readily synthesized by the hydrolysis of alkoxides in various alcohols. The present research studies experimentally and models the chemistry and growth kinetics of silica and titania particles in low molecular weight alcohols (methanol, ethanol, 1-propanol, 1-butanol). The theoretical model is based on solving the hydrolysis and condensation kinetic expressions and applying the method of moments to expedite the solution of the governing population balance equation.
Chemical Processing of Ferroelectric Niobates Epitaxial Films
Authors: Hirano Shin-Ichi , Yogo Toshinobu , Kikuta Koichi , Urahata Hisanobu , Isobe Yasuhide , Morishita Toshiyuki , Ogiso Koji , Ito Yasuhiro 
Published: March 2011

ABSTRACTRecent achievements in the chemical processing of ferroelectric niobates epitaxial films are reported. The molecular level designing of the precursor solution was stressed as well as the control of key processing factors. Examples are presented for LiNbO3/Ti, K(Ta,Nb)O3 and (Sr,Ba)Nb2O6 films from metal alkoxide precursors. Crystalline epitaxial films with stoichiometry could be synthesized through control of the intermediate state of starting molecules in solution. Water vapor stream was found to play an important role in crystallizing gel films to desired phases at relatively lower temperatures.
Optimization of Sol-Gel Derived PZT thin Films by the Incorporation of Excess PBO
Authors: Teowee G. , Boulton J. M. , Uhlmann D. R. 
Published: March 2011

ABSTRACTA series of PZT precursor solutions was prepared which incorporated excess PbO to give the composition Pb1+xZr0.53Ti0.47O3+x, where 0 < × < 0.3. These solutions were spin coated on platinized Si wafers and fired at elevated temperatures up to 750C for 30 mins. After crystallization into single-phase perovskite, the films were studied using XRD, optical microscopy and electrical characterization techniques (hysteresis loops and dielectric properties). It was found that the presence of excess PbO significantly improved the PZT films in terms of phase assemblage, microstructure and electrical properties. Under optimized conditions, films with dielectric constants of around 3000 can be obtained.
Application of Ethanolamine Method FOB the Preparation of Indium Oxide-Based Sols And Films
Authors: Taiahashi Yasutaia , Hayashi Hideo , Ohya Yutaka 
Published: March 2011

ABSTRACTIt is found that ethanolamine method, recently developed by us, is very useful to form stable, concentrated (0.4–0.5M) indium oxide-based sols from which very uniform, transparent In2O3 and ITO films are obtained by dip-coating. Indium isopropoxide and acetate can be used as the starting materials. The optical and electrical properties of these films were examined. A transparent ITO film with the highest conductivity (3030 S/cm, after annealing at 0.05 torr-600°C for 60 min) was obtained from the acetate at 600°C. The films from the alkoxide had lower conductivities probably due to the impurities included in the alkoxide.
Structural and Electrical Properties of Mn-Co-Ni-O Thin Films Prepared by Dip-Coating Technique
Authors: Kaneko Shoji , Mazuka Naoto , Yamada Tamotsu 
Published: March 2011

ABSTRACTMn-Co-Ni-O thin films of metal atomic ratio 3.0 : 1.9 : 1.0 were prepared on glass substrates from methanol solutions of the corresponding metal β-diketonates by dip-coating. As-prepared films were heated at 900°C for 1 h mostly after being calcined at 450°C for 5 min. The film thickness increased with increasing concentration of the solution as well as the number of lifting times. However, the effect was not apparent with the sample prepared without calcination. The prepared films were observed to crystallize into a complicated spinel phase by the heating process at 900°C for 1 h. The surface of the dense film composed of particles of about 0.2 μm diameter, was almost even. The thermal and aging responses of electric resistance showed the film to be a good material as a thermistor.
Hydrolysis-Condensation of Alkyltin-Trialkoxides
Authors: Ribot François , Banse F. , Sanchez C. 
Published: March 2011

ABSTRACTBuSn(OPri)3 and BuSn(OAmt)3 have been synthesized according to a literature procedure. Their hydrolysis have been studied by 119Sn and 1H NMR spectroscopy. The former precursor yields only a closo-type oxo-hydroxo cation of formula [(BuSn)12O14(OH)6]2+. Investigation of the hydrolysis-condensation products of BuSn(OAmt)3 reveals expanded coordinenceabout the tin atoms from 4 to 5 and 6 when H2O/Sn>l. For butyltin tri-tert-amyloxide, condensation also promotes the formation of a cluster whose structure is as yet unknown.
Sol-Gel Derived PZT Fibers
Authors: Boulton J. M. , Teowee G. , Uhlmann D. R. 
Published: March 2011

ABSTRACTSol-gel routes were developed to prepare densified PZT fibers. The effects of the degree of hydrolysis and the addition of an organic polymer to the precursor sol on fiber forming ability were investigated. Results on the crystalline and microstructural development of gels and fibers are presented. The effects of the incorporation of excess PbO and sintering atmosphere are also discussed, particularly in relation to densification.
Sol-Gel Films With Tailored Microstructures
Authors: Logan Deborah L. , Ashley Carol S. , Jeffrey Brinker C. 
Published: March 2011

ABSTRACTThe refractive index and porosity of silicate films formed by dip-coating were tailored by varying the aging time of a two-step acid- and base-catalyzed sol to control the size and structure of the polymeric species prior to coating. 29Si NMR showed that there was a 2% increase in the total number of bridging oxygens with sol age, consistent with a cluster-cluster growth mechanism. However, several percent monomer remained regardless of aging. Dip-coated films were characterized by ellipsometry before and after heating to moderate temperatures at three rates. Sol aging prior to film deposition leads to greater film porosity, consistent with the concept of aggregation of fractal clusters, but only after a heat treatment to remove the organic species associated with incompletely hydrolyzed monomers from the pores.
Modeling and Experimental Investigations of Pressure Infiltration of Sol-Gel processed 3-D Ceramic Matrix Composites
Authors: Liu Hsien-Kuang , Parvizi-Majidi Azar 
Published: March 2011

ABSTRACTA parabolic rate kinetics model has been developed and verified by experiments for the pressure infiltration of textile ceramic matrix composites using sol-gel processing with added solid particles. Darcy's law and a global permeability of the whole system were adopted in the model. The permeability of the whole system consisting of fiber preform, compaction, and filter was derived from the individual permeabilities of the fiber preform and particle compaction inside the preform which were based on the Kozeny-Carman equation. Experiments were conducted using 3-D angle interlock woven carbon fiber preforms and silica sol containing silica particles of 0.25μm and 0.5μm sizes. The total infiltration time was inversely proportional to the constant processing pressure and increased significantly with reducing the solid particle size by a factor of two. This is because the permeability of particle compaction layer is the dominant term and it is proportional to the square of particle size.
Monitoring of Heteropolysiloxane Thin film Properties Using Rheological and Acoustic Characterization Methods
Authors: Guizard C. , Lacan P. , Saurel J. M. , Hajoub F. , Cot L. 
Published: March 2011

ABSTRACTThis paper emphasizes on the mechanical characterization of heteropolysiloxane (HPS) derived materials using rheology and acoustic microscopy methods. Dynamic rheological measurements have been performed at the sol and the gel stages with two different precursors. An organic gel-like behaviour has been brought into evidence related to the fact that several microns thick coated layers can be obtained with these materials. On the contrary acoustic analysis revealed a glass-like behaviour for the cured layers. These results confirm the interest of organic/inorganic polymers to design new materials with tailored properties.
Preparation of Aryl-Bridged Polysilsesquioxane Aerogels
Authors: Loy Douglas A. , Shea Kenneth J. , Russick Edward M. 
Published: March 2011

ABSTRACTWe report the preparation of a new class of organic/inorganic hybrid aerogels from aryl-bridged polysilsesquioxanes [1]. l,4-Bis(triethoxysilyl)benzene and 4,4'-bis(triethoxysilyl)-biphenyl were sol-gel processed to form phenyl- and biphenyl-bridged polysilsesquioxane gels (Figure 1, structures 1 and 2, respectively). The gels were then dried using supercritical carbon dioxide extraction. It was discovered that aryl-bridged polysilsesquioxane aerogels are indeed formed, but with a pronounced influence on surface area from the reaction conditions used in preparing the initial gels. Specifically, high surface aerogels ( up to 1750 m2/g) are obtained from gels prepared with either acid or base catalysts. With reduced concentrations of base catalyst, however, supercritical processing afforded phenyl-bridged xerogel-like materials, The materials were characterized by nitrogen sorption surface analysis, and by transmission electron microscopy.
Characterisation of Hydrolysed Alkoxysilanes and Zirconiumalkoxides for the Development of UV-Curable Scratch Resistant Coatings
Authors: Greiwe K. , Glaubitt W. , Amberg-Schwab S. , Piana K. 
Published: March 2011

ABSTRACTThe development of a new scratch resistant UV-curable coating system is described. The material can be applied to optical data discs by spin coating. The coating shows superior adhesion even without priming and good weathering performance especially on polycarbonate.The material is prepared from Zr(OPr)4 and 3-Methacryloxi-propyltrialkoxysilanes via sol-gel processing. Complexation of Zr(OPr)4 with methacrylic acid yields complexes which can be copolymlrized with the prehydrolyzed silane. The hydrolysis and self-condensation of the trialkoxysilanes were studied under different conditions. The consumption of water was studied by Karl-Fischer titration and the formation of oligomeric and polymeric species by GPC-measurements.
Molecular Design of Carboxylic Precursors for Zirconia
Authors: Apblett Allen W. , Lei Jin , Georgeva Galina D. 
Published: March 2011

ABSTRACTSeveral carboxylic acid derivatives of zirconium were investigated for their potential utility as precursors for zirconia fibers and thin films. The reactions of ZrOCl2· 8H2O and ZrCl4 with succinic acid, oxalic acid, maleic acid, benzene tetracarboxylic acid, 2-hydroxyiminopropionic acid, 3-hydroxybutyric acid, and β-alanine were performed and the thermal behavior of the products was investigated by thermal gravimetric analysis. The objective was to find preceramic compounds with low pyrolysis temperatures and physical properties suitable for materials processing.
High Temperature Stability of Oxycarbide Glasses
Authors: Zhang Hanxi , Pantano Carlo G. 
Published: March 2011

ABSTRACTThe stability of silicon oxycarbide glasses has been studied at temperatures up to 1500°C. The silicon oxycarbide glasses were synthesized using a sol/gel process. The pyrolysis treatment in argon influenced the structure and composition of the synthesized glasses, and in turn, their high temperature stability in oxidizing atmosphere. The oxycarbide glasses pyrolyzed at > 1000°C had lower hydrogen concentration and a more polymerized network structure, and thereby were more resistant to oxidation and crystallization at higher temperatures.
Boron Carbide Nitride Derived from Amine-Boranes
Authors: Bill Joachim , Riedel Ralf 
Published: March 2011

ABSTRACTAmine-boranes such as pyridine- or piperazine-borane can be converted into infusible polymers by thermal crosslinking at temperatures up to 420°C. Further rise of the temperature up to 1050° C in argon results in transformation of the polymers into black residues. Microstructural (TEM/EELS, ESCA) and chemical investigations indicate the presence of single phase boron carbide nitrides which exhibit a graphite-like, turbostratic structure with a homogeneous distribution of the elements B, N, and C. Subsequent annealing at 2200° C in argon gives rise to crystallization of the pyrolytic material generating the thermodynamically stable phases BN, C, and B4C.The semiconducting properties of the X-ray amorphous boron carbide nitride synthesized at 1050°C depend on the B/N/C-ratio which can be influenced a) by the type of amine-borane-precursor and b) by the applied atmosphere (Ar or NH3) during pyrolysis.The amine-boranes can be converted into boron carbide nitride- and BN-monoliths at 1050°C under argon or reactive gas (NH3), respectively. The monoliths are transformed into composites with 91% rel. density containing BN, C, and B4C when heated up to 2200° C.
New Routes to Group Iva Metal-Nitrides
Authors: Narula Chaitanya K. 
Published: March 2011

ABSTRACTThe reactions of TiCl4 with [(CH3)3Si]2NH have been examined under several reaction conditions. One of the reaction products, (CH3)3Si(H)NTiCl3, can be crystallized in 60% yield on reacting TiCl4 with TiCl4 with [(CH3)3Si]2NH in a 1:1 molar ratio in dichloromethane at -78°C. [(CH3)3Si(H)NTi(Cl2)(NH)]2TiCl2 is the primary product on increasing the amount of TiCl4 with [(CH3)3Si]2NH to two equivalents. (CH3)3Si(H)NTiCl3 and [(CH3)3Si(H)NTi(Cl2)(NH)]2TiCl2 form titanium nitride on pyrolysis at 600°C in an ammonia atmosphere.
Single-Component Routes to Perovsktte Phase Mixed Metal Oxides
Authors: Chandlertw Clive D. , Hampden-Smitht M. J. , Brinker C. J. 
Published: March 2011

ABSTRACTCrystalline perovskite phase mixed metal oxides have been prepared at low temperatures from single-component mixed metal-organic precursors specifically designed for this purpose. Pyridine solutions of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CMe2OH)2 where A = Pb, Ca, Sr, Ba; Me = methyl, react with metal alkoxide compounds such as B(OR')4, where B = Ti, Zr, Sn with the elimination of two equivalents of alcohol to form species with a fixed A:B stoichiometry of 1:1 according to the equation below.
Preparation of Titanium Carbonitride Coatings by the Sol-Gel Process
Authors: Zheng Haixing , Oka Kris , Mackenzie John D. 
Published: March 2011

ABSTRACTTi(NPri2)4 has been synthesized and used as a precursor for aminolysis andpolymerization by reaction with isopropylamine. The resultant dark red solution was utilized for dip coating of silicon substrates. Firing of these coatings in N2 or Ar produced dense and crack-free titanium carbonitride coatings.
Multicomponent Ceramic Powder Generation by Spray Pyrolysis
Authors: Lyons Shirley W. , Ortega J. , Wang L. M. , Kodas T. T. 
Published: March 2011

ABSTRACTWe have examined methods for controlling the morphology and microstructure of ceramic particles produced by spray pyrolysis. A variety of materials were examined including SrTiO3and BaTiO3 and the oxides of Al, Mg, Zn, Pd, V, Mo, and Bi. The morphology of the particles was influenced by using colloidal precursors in combination with molecular precursors for particle generation. Slow drying rates obtained by using high relative humidities and controlled axial temperature gradients did not influence particle morphology for the systems and conditions studied. The microstructure of Al2O3, V2O5, and PdO particles was controlled by varying the temperature to provide nanocrystalline or single-crystal particles. Evaporation and condensation of volatile species such as MoO3 and V2O5 dramatically modified particle microstructure and morphology.
An Electrochemical Study of the Au55(PPh3)12 Cl6 Cluster
Authors: Steggerda J. J. , Linden J. G. M. Van Der , Gootzen J. E. F. 
Published: March 2011

ABSTRACTVoltammetric studies of Au55(PPh3)12Cl6 (kindly provided by Prof. G. Schmid, Essen, Germany) in solutions of CH2Cl2 and THF with Pt electrodes show that the reduction of the cluster is a multistep, irreversible process. Precipitation of colloidal metal or any high molecular super-cluster is observed when stabilising. NBu+ –ions are absent and when the reduced solution is reoxidised.The parent cluster and the precipitate were studied by X-ray powder diffraction and UV-vis spectroscopy. The origin of the diffuse lines and the low-angle diffractions will be discussed. They suggest that the Au55 particles flocculate by changing their electric charge in the electrochemical redox reactions. The floc is unstable and congulates to particles of 25 Å and larger.
Giant Palladium Clusters: Synthesis and Characterization
Authors: Moiseev Ilya I. , Vargaftik Michael N. , Zamaraev Kirill I. , Kochubey Dmitry I. 
Published: March 2011

ABSTRACTA series of palladium clusters containing from 4 to some hundred Pd atoms in the metal skeleton was prepared and characterized with structural data as well as by chemical properties including catalytic activity. An agreement between X-ray and EXAFS data was obtained for single-crystal low-molecular clusters. Giant clusters approximated as Pd56L60(OCOCH3)180 (L=Phen, Bipy) and Pd561Phen60O60X60 (X = PF6, CIO4, SO4, BF4, CF3COO)were characterized with TEM, SAXS, EXAFS, NMR, and magnetic susceptibility data. The clusters consisting of close-packed metal core and L, X ligands at its periphery could be considered as a bridge between low-molecular clusters and the particles of colloidal metals.
Shape and Size Effect on Ultrafine Metallic Particles
Authors: Kimura Keisaku 
Published: March 2011

ABSTRACTThe effect of size and shape on the electronic state of ultrafine metallic particles is described with the critical review of so far proposed experimental and theoretical results. The temperature dependence of the spin susceptibility of small metal particles is presented as function of size, shape, spin-orbit interaction of the elements, and magnetic field strength. Based upon a proposed formula, the spin susceptibility of small Mg particles is precisely analyzed with the view point of shape effect. It is emphasized that the exogenous impurities have crucial effect. on the magnetic properties of small metal particles. It is clarified that the confusion in the magnetic experiments originates from the extrinsic magnetic effect. The deviation of the nature of chemical bond in small size systems from that in bulk is briefly outlined.
Sol-Gel Synthesis of Metal Oxide Clusters and Colloids
Authors: Livage J. , Sanchez C. , Toledano P. 
Published: March 2011

ABSTRACTThe hydrolysis and condensation of metal alkoxides M(OR)z allows the formation of oxopolymers or oxide colloids under mild conditions in solution. The molecular design of these precursors provides a chemical control over the formation of condensed phases. This can be conveniently performed via the chemical modification of alkoxides by nucleophilic species such as carboxylates or β-diketones. Condensation can be tailored with two chemical parameters; the hydrolysis ratio which leads to more condensed species and the amount of complexation which prevents condensation. Molecular clusters or colloidal particles can be obtained instead of precipitates. Moreover, non hydrolyzable complexing organic ligands lead to the formation of hybrid materials in which organic and inorganic moities are chemically bonded. These hybrid clusters and colloids are important starting points for producing solids and films with novel physical properties.
Conversion of (R4N+)4[S4M4(SPh)16]4− Molecular Solids to Bulk Metal Sulfides
Authors: Farneth W. E. , Herron N. , Wang Y. 
Published: March 2011

ABSTRACTIn this paper we report on the mechanism of the solid state conversion of a series of IINI precursors of general formula (R4N+)4[S4M4(SPh)16]4− (R=Me, Et; M=Cd, Zn) to the bulk metal sulfide structure. This family of cluster compounds was first reported by Dance et al [1]. On heating these solids in vacuum or inert atmosphere, we find that they convert to the corresponding extended metal sulfide lattice in two discrete reaction steps. The overall reaction appears to be general, but there are interesting differences in the rates and mechanistic details as R and M are varied. The first step, ˜200°C, can be characterized as a nucleophilic substitution or elimination initiated by the attack of a fragment of the anion cluster on the tetra-alkyl ammonium counterion. The intermediate solid produced in this step has been isolated and recrystallized. It consists of charge neutral M10S16Ph12 clusters that retain the cluster size present in the starting material but appear to aggregate to varying degrees in the solid or solution.
Preparation, Structure and Properties of Novel Bimetallic Au/Pd Colloids
Authors: Baddeley Christopher J. , Jefferson David A. , Lambert Richard M. , Ormerod R. Mark , Rayment Trevor , Schmid Günter , Walker Andrew P. 
Published: March 2011

ABSTRACTLigand-stabilized bimetallic Au/Pd colloids may be prepared from 180–200Å Au colloids which can be covered by Pd shells of varying thickness. They can be isolated as solid materials without agglomeration. HREM observations indicate a narrow particle size distribution and reveal a well-defined Au(core)/Pd(shell) structure. This is convincingly confirmed by EXAFS data. Thermal treatment leads to Au/Pd alloy formation at ≥ 500 K, as evidenced by the appearance of characteristic Au-Pd distances in the EXAFS.
Interdiffusion Between Mo and TiAl
Authors: Zhang Min-Xian , Hsieh Ker-Chang , Chang Y. Austin 
Published: March 2011

ABSTRACTDiffusion couple experiments were carried out for Mo/γ-TiAl at 900, 1000 and 1100°C for periods of time ranging from 121 to 553 hrs. Using the Boltzmann-Matano analysis, the two diagonal interdiffusion coefficients for the two phases formed in these couples were obtained assuming the cross diagonal terms to be negligible. These two phases are δ-(Mo, Ti)3Al and β-(Mo,Al)Ti. The three intrinsic diffusion coefficients were also obtained using the Darken-type relationships between the interdiffusion and intrinsic diffusion coefficients. The calculated interdiffusion coefficients from the three intrinsic diffusion coefficients are in reasonable accord with those obtained directly from the Boltzmann-Matano analysis.