bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub-part-per-trillion detection and analysis of submicrometer particles in integrated circuit processing chemicals
Authors: Xu D. , Pinizzotto R. F. , Sees J. A.
Published: March 2008

We have developed a new technique for the analysis of particulate contaminants in liquids (or gases) with an elemental detectability limit as low as 0.1 parts per trillion, and a particle concentration detectability limit as low as 1 particle/ml for particles greater than 0.2 μm in diameter. Samples are prepared using extraction replication and analyzed using analytical transmission electron microscopy. The methodology has been applied to the analysis of H2O2 and HF, important chemicals in integrated circuit fabrication. The new methodology should become an important tool in the identification of submicron-sized particles which adversely affect integrated circuit fabrication.
Accuracy in the experimental calorimetric study of the crystallization kinetics and predictive transformation diagrams: Application to a Ga–Te amorphous alloy
Authors: Clavaguera N. , Clavaguera-Mora M. T. , Fontana M.
Published: March 2008

The uncertainties inherent to experimental differential scanning calorimetric data are evaluated. A new procedure is developed to perform the kinetic analysis of continuous heating calorimetric data when the heat capacity of the sample changes during the crystallization. The accuracy of isothermal calorimetric data is analyzed in terms of the peak-to-peak noise of the calorimetric signal and base line drift typical of differential scanning calorimetry equipment. Their influence in the evaluation of the kinetic parameter is discussed. An empirical construction of the time-temperature and temperature-heating rate transformation diagrams, grounded on the kinetic parameters, is presented. The method is applied to the kinetic study of the primary crystallization of Te in an amorphous alloy of nominal composition Ga20Te80, obtained by rapid solidification.
Preparation of refractory carbide fibers by thermal decomposition of transition metal (Ti, Zr, Hf, Nb, Ta) alkoxide-cellulose precursor gel fibers
Authors: Kurokawa Y. , Kobayashi S. , Suzuki M. , Shimazaki M. , Takahashi M.
Published: March 2008

Gel fibers have been prepared by extruding cellulose acetate spinning solution into transition metal (Ti, Zr, Hf, Nb, Ta) acetone solution as a coagulation bath. Gel formation must be due to the coordination of metal to OH and CO groups on the pyranose ring. The resultant gel fibers have been converted into carbide fibers by pyrolyzing them in Ar and N2 atmospheres at temperatures lower than for powder processing. This precursor gel can give a molecular scale mixture of metal and carbon sources.
Texture development in Bi2Te3during hot forging
Authors: Gonzalez E. J. , Blendell J. E. , Cline J. P. , Ritter J. J. , Maruthamuthu P. , Nelson E. H. , Horn S. B.
Published: March 2008

The development of crystallographic texture in hot-forged polycrystalline Bi2Te3samples was studied. Texture was evaluated with the use of the March–Dollase model in conjunction with a Rietveld analysis of x-ray diffraction data. It was determined that during forging a strong (0001) texture develops along the loading axis. The magnitude of the (0001) texture increases systematically with the amount of height reduction during hot-forging. The correlation between the observed deformation and the March–Dollase texture model suggests that grain rotation is the primary mechanism for texture development in Bi2Te3.
Importance of soft solution processing for advanced inorganic materials
Authors: Yoshimura Masahiro
Published: March 2008

Based upon the analysis of materials cycling and processing on the earth, a thermodynamic concept for energetical and environmental problems has been proposed. It concludes that solution processing using aqueous solutions should be the most important processing even for advanced materials. According to this concept, energetical and environmental features of soft solution processing (SSP) are discussed in general, using also some particular examples, such as BaTiO3. Applications of the SSP are shown with special emphasis on hydrothermal and/or electrochemical synthesis of thin films and integration issues. Soft solution processing allows one to fabricate in aqueous solutions shaped/sized/oriented ceramics in only one step, without excess energies for firing/sintering or melting and without expensive equipment, providing an environmentally friendly route for the preparation of advanced ceramic materials.
Sol-gel control of the micro/nanostructure of functional ceramic-ceramic and metal-ceramic composites
Authors: Colomban Philippe
Published: March 2008

The problems encountered to tailor simultaneously various specific chemical or physical properties are discussed. Selected polymeric precursors used in association with fine powders allow the control of the nano/microstructure of composites and hence the preparation of functional (FGM) and hierarchical reinforced (HRC) composites, making it possible to combine several kinds of fibers, interphases, and matrices in the same composite (hot microwave absorbent), to control the fiber/matrix interface (long life times composites), to achieve net-shape sintering of 3D composite matrices, and to prepare thick films of metal-ceramic composites with tailored microwave absorption (radar stealthiness).
Formation mechanism of fine anatase crystals from amorphous titania under hydrothermal conditions
Authors: Yanagisawa Kazumichi , Yamamoto Yuichi , Feng Qi , Yamasaki Nakamichi
Published: March 2008

Crystallization of amorphous titania prepared by hydrolysis of ethoxide was accelerated even by a small amount of water in the vapor phase. The existence of water promoted the change of localized structure of the amorphous titania to anatase structure, which resulted in acceleration of anatase nucleation. The anatase crystals grew in steam by solid-state epitaxial growth, but stopped growing in a short time. The growth of anatase crystals under hydrothermal conditions could be divided into the following two stages: the first stage with fast growth rate by the solid-state epitaxial growth and the second stage with slow growth rate by the dissolution and deposition process.
Preparation and electrical conductivity of three types of antimonic acid films
Authors: Ozawa Kiyoshi , Sakka Yoshio , Amano Muneyuki
Published: March 2008

Three types of antimonic acid (Sb2O5 · nH2O) films, (111)-oriented and nonoriented polycrystalline films of cubic Sb2O5 · nH2O and amorphous Sb2O5 · nH2O films, were prepared on quartz glass substrates with a spin-coating technique using aqueous slurries, which were formed by reacting H2O2 with metallic Sb powder or Sb(O-n-C3H7)3. The morphologies and structures of the films were observed, and the electrical conductivity of the films was determined at 20 °C in the relative humidity range 9–100%. The electrical conductivity of the (111)-oriented film, which increases from 1.69 × 10−5 to 2.89 × 10−3 S cm−1 as the relative humidity changes from 11 to 85%, is approximately one order of magnitude larger than those of the nonoriented and amorphous films.
Low temperature solid-state epitaxy of LiNbO3 films by a dipping-pyrolysis process using Li-trifluoroacetate
Authors: Manabe T. , Yamaguchi I. , Kondo W. , Kumagai T. , Mizuta S.
Published: March 2008

Epitaxially grown LiNbO3 thin films were prepared on sapphire(012) (R-plane) substrates by a dipping-pyrolysis process using two kinds of lithium sources, i.e., Li-2-ethylhexanoate and Li-trifluoroacetate, which are pyrolyzed in air to Li2CO3 and LiF, respectively. Crystallization temperature and alignment of LiNbO3 films on sapphire(012) were found to depend greatly on the Li sources. Dominantly [100]-oriented epitaxial LiNbO3 films were crystallized at around 600 °C using 2-ethylhexanoate, whereas dominantly [012]-oriented epitaxial LiNbO3 films resulted at a temperature as low as 400 °C using trifluoroacetate.
Preparation of fine-grained monoclinic zirconia ceramics by colloidal processing
Authors: Uchikoshi T. , Sakka Y. , Ozawa K. , Hiraga K.
Published: March 2008

Fine-grained monoclinic zirconia ceramic was made from well-dispersed zirconia sol prepared by the hydrolysis of zirconium chloride oxide octahydrate. Dechlorinated and concentrated zirconia sol was consolidated by pressure filtration. The relative green density of the compact was improved by the following cold isostatic pressing treatment at 400 MPa. The compact was densified by pressureless sintering to >98% of theoretical density in air at 1100 °C, which is lower than that of monoclinic to tetragonal transformation of pure zirconia. The average grain size of the sintered monoclinic zirconia ceramics was 92 nm.
Crystallization of titania in liquid media and photochemical properties of crystallized titania
Authors: Yin Shu , Inoue Yuichi , Uchida Satoshi , Fujishiro Yoshinobu , Sato Tsugio
Published: March 2008

Titania gels in liquid media crystallized from amorphous to anatase at temperatures as low as 120 °C, while the onset of crystallization in air was 370 °C. The crystallization rate in water was much faster than in methanol and n-hexane, and the crystallite size of anatase prepared in water was larger than of those prepared in organic solvents. The crystallized powders were capable of efficient hydrogen evolution following band gap irradiation in the presence of a sacrificial hole acceptor such as methanol. The photocatalytic activity of powder crystallized in methanol was superior to those prepared in water and air.
Glycothermal synthesis of rare earth iron garnets
Authors: Inoue Masashi , Nishikawa Toshihiro , Inui Tomoyuki
Published: March 2008

The reactions of rare earth (RE) acetates with iron acetylacetonate in 1,4-butanediol at 300 °C (glycothermal reaction) yielded two novel phases depending on the ionic size of the RE element: one was obtained for Er-Lu and the other for Tb and Dy. The former phase was hexagonal REFeO3, while the latter phase has not been identified. The reaction of Y or Ho acetate yielded the mixture of these two phases. When the reactions were carried out in the presence of seed crystals of yttrium aluminum garnet (Y3Al5O12), these phases were not formed but RE iron garnet (RE3Fe5O12) grew on the seed, which suggests that spontaneous nucleation of RE iron garnet does not occur, but crystal growth proceeds easily under the glycothermal conditions. Hydrothermal reaction of the same starting materials yielded a mixture of Fe2O3 and an amorphous RE phase.
Functionally graded SrTiO3–BaTiO3 thin films prepared by the hydrothermal-electrochemical method under flowing solution
Authors: Yoshimura Masahiro , Suchanek Wojciech , Watanabe Tomoaki , Sakurai Bungo , Abe Masanori
Published: March 2008

BaTiO3, SrTiO3, and BaxSr1−x TiO3 thin films, as well as multilayers in the SrTiO3-BaTiO3 system, have been prepared on Ti substrates in newly constructed flow-system equipment by the hydrothermal-electrochemical method. The synthesis parameters (temperature of 120–200 °C, flow rate of 1–50 cm3/min) allow fabrication of dense, single-phase films with different morphology by controlling nucleation and/or growth rates. The flow system enables also an easy fabrication of SrTiO3/BaTiO3 and BaTiO3/SrTiO3 multilayers with variable chemical composition and microstructure across the film thickness. The multilayers can be prepared in only one experiment by simply changing the kind of flowing solution and/or adjusting the processing conditions.
Pure tetravalent nickel in γ-type nickel oxyhydroxide as secondary battery electrode
Authors: Han Kyoo-Seung , Yoshimura Masahiro , Yoon Joo-Byoung , Choy Jin-Ho , Park Kwang-Ja
Published: March 2008

Pure tetravalent nickel in γ-type cobalt substituted nickel oxyhydroxide, Ni0.70Co0.30O2K0.30(H2O)0.42, could be obtained by the “chimie douce” reaction. The presence of tetravalent nickel is confirmed by comparing the Ni K-edge XANES spectrum of the sample with those of reference compounds having various nickel valency and similar layer structure. The Co K-edge XANES spectrum indicates that the trivalent cobalt remains unchanged regardless of the nickel valency. The structural modification during chimie douce reaction observed from XRD patterns and the result of iodometric titration are consistent with the Ni and Co K-edge XANES data.
Synthesis of metal oxide thin films by liquid-phase deposition method
Authors: Deki Shigehito , Aoi Yoshifumi
Published: March 2008

A novel wet process to synthesize metal oxide thin films has been developed. The process is called the Liquid-Phase Deposition (LPD) method. In this method, metal oxide or hydroxide thin films are formed on the substrate through the ligand-exchanging (hydrolysis) equilibrium reaction of metal-fluoro complex species and the F− consumption reaction of a F− scavenger. The LPD method is a unique soft solution process, and is performed by very simple procedures. In this paper, we develop a method of preparing composite oxide thin films, Pt-dispersed titanium oxide, and iron-nickel binary oxide thin films.
Soft process for the intercalation of ammonium cations into vanadium oxide
Authors: Inagaki Michio , Nakamura Tomoyuki , Shimizu Akira
Published: March 2008

A soft process for the intercalation of different ammonium cations into vanadium pentoxide was developed. By refluxing an aqueous solution containing ammonium, tetramethylammonium (CH3)4N+, and tetraethylammonium (C2H5)4N+with V2O5powders, intercalation compounds containing corresponding ammonium cations were obtained. The compound with aniline C6H5NH2was also synthesized by the same process. The compounds with (CH3)4N+, (C2H5)4N+, and also C6H5NH2had diffraction patterns consisting of very sharp00llines. The spacing for sandwiching the intercalates (the identity period), (CH3)4N+, (C2H5)4N+, and C6H5NH2, was 1.29, 1.31, and 1.39 nm, respectively.
Cryosol method: A novel powder processing technique based on ion-exchange phenomena
Authors: Vertegel A. A. , Kalinin S. V. , Oleynikov N. N. , Metlin Yu. G. , Tretyakov Yu. D.
Published: March 2008

A novel technique has been suggested for synthesis of highly dispersed oxide powders. The method is based on the treatment of aqueous solution of a multivalent metal nitrate (or chloride) by anion-exchange resin in the OH− form. The presented technique yields a stable colloid solution of the corresponding hydroxide with concentration up to 1 M. The subsequent freeze-drying and thermal dehydration results in very fine powder of metal oxide. The individual and multicomponent oxides obtained by the cryosol method were shown to possess unusual properties due to their high dispersity and chemical homogeneity.
Large size plasma generation using multicathode direct current geometry for diamond deposition
Authors: Baik Young-Joon , Lee Jae-Kap , Lee Wook-Seong , Eun Kwang Yong
Published: March 2008

The deposition area of diamond film is increased by applying a geometry of multiple cathodes and a single anode in direct current (dc) plasma assisted chemical vapor deposition (PACVD). Each cathode is made of Ta and connected independently to its own dc power supply. The operating pressure is 1.3 × 104 Pa (100 Torr), and methane-hydrogen mixed gas is used as reaction gas. The voltage and the current applied to each cathode are 650 V and 4 A, respectively. The transition from a diffuse glow to an arc is prevented by maintaining cathode temperatures above 2000 °C, which inhibits carbon deposition on the cathodes. Translucent diamond film of 3 in. diameter, thicker than 200 μm, is grown using seven cathodes with 3% CH4–H2 mixed gas for 110 h. The deposition area can be increased further by increasing the number of cathodes.
Tetragonal-orthorhombic phase transition in YBaCuO thin films observed by perturbed angular correlation spectroscopy
Authors: Platzer R. , Dumkow I. D. , Tom D. W. , Gardner J. A. , Tate J.
Published: March 2008

Oxygen-deficient, tetragonal thin films of YBa2Cu3O6+x with x ≈ 0.25, quenched from the deposition temperature, change to the oxygenated, orthorhombic phase with x ≈ 1, between 200 °C and 400 °C in flowing oxygen. The transition is not reversible in flowing oxygen, and cannot be completely reversed by cooling in flowing argon. We do not observe a transition of the orthorhombic films to the tetragonal phase up to 800 °C in flowing oxygen. We observe that the major impurity phases to appear under nonoptimal annealing conditions are oriented phases of YcuO2 and BaCu2O2, with Y2BaCu2O5 and Y2Cu2O5 conspicuously absent. These conclusions have been drawn from a study that uses perturbed angular correlation spectroscopy to probe the local microstructure of the films.
Structural characterization of Yba2Cu3O7–δ/Y2O3 composite films
Authors: Broussard P. R. , Wall M. A. , Talvacchio J.
Published: March 2008

Using 4-circle x-ray diffraction and transmission electron microscopy, we have studied the microstructure and in-plane orientation of the phases present in thin film composite mixtures of Yba2Cu3O7–δ and Y2O3. We see a high degree of in-plane orientation and have verified a previous prediction for the in-plane order of Y2BaCuO5 on (110) MgO. Transmission electron microscopy shows the composite films to be a mixture of two phases, with YBCO grain sizes of ≈1 μm. We have also compared our observations of the in-plane order to the predictions of a modified near coincidence site lattice model.
Thermodynamically stable tungsten ohmic contacts to n-In0.53Ga0.47As
Authors: Chen D. Y. , Chang Y. A. , Swenson D. , Shepherd F. R.
Published: March 2008

Based on a thermodynamic assessment of the W–In–Ga–As quaternary system, the metal W was selected as a thermodynamically stable ohmic contact material to n-In0.53Ga0.47As. As-deposited contacts (on n ∼ 1.4 × 1018 cm−3 In0.53Ga0.47As) had average specific contact resistances of 7 × 10−7 Ω ·cm2 as measured using the transmission line model. The contact resistances remained unchanged after rapid thermal annealing at 400 °C for 1 min or at 600 °C for 1 min, and exhibited no degradation in electrical properties even after long-term annealing at 500 °C for 100 h. Transmission electron microscopic examination of the contacts showed no interfacial reaction. The present investigation demonstrates the power of thermodynamics in identifying stable ohmic contacts to multicomponent semiconductors.
Effect of Ba2+ on dielectric and electrostrictive properties of (Pb1 − xBax)0.96Y0.02(Zr0.75Ti0.25)0.98Nb0.02O3 ceramics
Authors: Yoon Ki Hyun , Kim Yong Woon , Kang Dong Heon
Published: March 2008

(Pb1−xBax) (Zr0.75Ti0.25)O3 ceramics were modified with Y3+ and Nb5+, and their dielectric and electrostrictive properties were investigated as a function of x (0.23 ≤x ≤ 0.33). With increasing Ba2+ content, the axial length (a) was increased and distortion of rhombohedral angle (90°-α) approached to zero, resulting in the increased symmetry of the (Pb1−xBax)0.96Y0.02(Zr0.75Ti0.25)0.98Nb0.02O3 structure. As the Ba2+ content increased, the maximum dielectric constant decreased and the curve of field-induced strain became a parabolic one with lower hysteresis of strain. When 25−27 mol% of Ba2+ was substituted on the Pb2+ sites, the specimens showed excellent electrostrictive properties which were 1.04−1.17 × 10−3 of longitudinal strain and 12–18% of hysteresis of strain at 10 kV/cm.
Thin film scratch testing in two dimensions—Experiments and analysis
Authors: de Boer Maarten P. , Nelson John C. , Gerberich William W.
Published: March 2008

We have modified the microscratch test to create a near plane strain loading condition. In the Microwedge Scratch Test (MWST), a wedge-shaped diamond indenter tip is drawn along a fine line (i.e., narrow strip of film), while simultaneously being driven into the line. We compare microwedge scratching of zone 1 (voided grain boundaries) and zone T (metallurgical grain boundaries) thin film specimens of sputtered tungsten on thermally grown SiO2. Symptomatic of its weak grain boundaries, the zone 1 film displays three separate crack systems. Because of its superior grain boundary strength, the zone T film displayed only one of these—an interfacial crack system. By correlating fracture phenomena to signature events in the load-displacement curve, we develop governing equations for propagating interfacial cracks, including expressions for strain energy release rate, bending strain, and mode mixity. Grain boundary fracture causes zone 1 films to spall before a stable crack is formed. Zone T films survive the bending strains, and hence adhesions may be inferred from stable crack growth mechanics. We conclude by contrasting and comparing experimental results for plane strain indentation versus plane strain scratching.
Role of ozone in reactive coevaporation of lead zirconate titanate thin films
Authors: Torii Kazuyoshi , Yano Fumiko , Fujisaki Yoshihisa
Published: March 2008

The role of ozone in the reactive coevaporation of the lead zirconate titanate thin film was investigated by depositing films at various growth rates with various ozone fluxes or molecular oxygen fluxes on unheated substrates and then crystallizing them using rapid thermal annealing. The oxidation state of lead in the as-deposited film was determined from the ratio of the ozone to the total metal fluxes. The amount of atomic oxygen supplied to the surface of the film was at least 103 times larger when the deposition was done using ozone rather than molecular oxygen. When the ozone flux was more than one-third of the total metal flux, well-oxidized films were obtained. To ensure obtaining well-oxidized film, the ozone flax should be more than twice as much.
Laser-induced structural transformations in MoO3 investigated by Raman spectroscopy
Authors: Haro-Poniatowski E. , Julien C. , Pecquenard B. , Livage J. , Camacho-López M. A.
Published: March 2008

The glass-crystalline transformation induced by laser irradiation is studied in MoO3. Before crystallization we have found that the system evolves from a low temperature glass phase to a high temperature glass phase. The crystallization kinetics depend strongly on the initial irradiation power. The power densities needed to induce the phase transformations, of the order of 15 W/mm2, are relatively low and suggest the possibility of using this material as a data storage medium.
Influences of pileup on the measurement of mechanical properties by load and depth sensing indentation techniques
Authors: Bolshakov A. , Pharr G. M.
Published: March 2008

Finite element simulation of conical indentation of a wide variety of elastic-plastic materials has been used to investigate the influences of pileup on the accuracy with which hardness and elastic modulus can be measured by load and depth-sensing indentation techniques. The key parameter in the investigation is the contact area, which can be determined from the finite element results either by applying standard analysis procedures to the simulated indentation load-displacement data, as would be done in an experiment, or more directly, by examination of the contact profiles in the finite element mesh. Depending on the pileup behavior of the material, these two areas may be very different. When pileup is large, the areas deduced from analyses of the load-displacement curves underestimate the true contact areas by as much as 60%. This, in turn, leads to overestimations of the hardness and elastic modulus. The conditions under which the errors are significant are identified, and it is shown how parameters measured from the indentation load-displacement data can be used to identify when pileup is an important factor.
Relationships between acoustic emission signals and physical phenomena during indentation
Authors: Bahr D. F. , Gerberich W. W.
Published: March 2008

A commercial piezoelectric acoustic emission transducer has been used in conjunction with nanoindentation techniques to study the relationship between acoustic emission signals and discrete physical events to identify the type and strength of an event. Indentations into tungsten and iron single crystals have been used to study dislocation generation and passive film failure. In addition, indentations made into a thin nitride film on sapphire have been used to cause film delaminations. Parameters such as signal rise time and frequency for a piezoelectric sensor are related to sample geometry, and not to the type of event which caused the acoustic emission signal. As a possible calibration for acoustic emission sensors, the most meaningful parameter is the acoustic emission energy, which has been shown to scale with the elastic energy released during the event. The measured values of elastic energy released correspond very closely to those calculated using Hertzian contact mechanics.
Optimization of the extraction of aluminum sulfate and ammonium aluminum sulfate alums from aluminum dross tailings
Authors: Mohamed M. A. , Kassim M. E. , El-katatny E. A.
Published: March 2008

Aluminum dross tailings, an industrial waste from the Egyptian Aluminium Company (Egyptalum), were used to produce two types of alums, namely, aluminum sulfate alum and ammonium aluminum alum via two separate processes. The first process involved leaching the impurities using dilute H2SO4 at different solid/liquid ratios and temperatures in the form of soluble sulfates. Some dissolved aluminum was recovered as ammonium aluminum sulfate. The second process involved extraction of aluminum sulfate from the purified dross produced after leaching. This was carried out under atmospheric pressure using different concentrations of H2SO4. Influence of temperature, time of reaction, and acid concentration on leaching and extraction processes were studied. X-ray diffraction, atomic absorption spectrometry, and thermal analysis techniques were used.
Oxygen diffusivity in MoO3 as determined by a temperature programmed method
Authors: Clair Todd P. St. , Restad Jill M. , Oyama S. Ted
Published: March 2008

A temperature programmed method for determining diffusivities has been previously applied to oxygen diffusivity in V2O5. In this communication we extend the method to the case of oxygen diffusivity in MoO3. The reduction of MoO3 to MoO2 using NH3 is utilized to obtain experimental parameters such as the temperature of reduction and the activation energy for oxygen diffusion. These parameters are in turn used to solve Fick's equation for the oxygen diffusivity D0. The utility of this temperature programmed method for obtaining diffusivities has now been clearly established by extension to MoO3.
Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium
Authors: Weber W. J. , Ewing R. C. , Catlow C. R. A. , de la Rubia T. Diaz , Hobbs L. W. , Kinoshita C. , Matzke Hj. , Motta A. T. , Nastasi M. , Salje E. K. H. , Vance E. R. , Zinkle S. J.
Published: March 2008

This review provides a comprehensive evaluation of the state-of-knowledge of radiation effects in crystalline ceramics that may be used for the immobilization of high-level nuclear waste and plutonium. The current understanding of radiation damage processes, defect generation, microstructure development, theoretical methods, and experimental methods are reviewed. Fundamental scientific and technological issues that offer opportunities for research are identified. The most important issue is the need for an understanding of the radiation-induced structural changes at the atomic, microscopic, and macroscopic levels, and the effect of these changes on the release rates of radionuclides during corrosion.
Nanoscale liquid phase epitaxy between Si and Au nanoparticles
Authors: Wakayama Yutaka , Fujinuma Haruko , Tanaka Shun-ichiro
Published: March 2008

A self-assembly technique was used for fabrication of a Si/metal interface in nanometer scale. Fine particles of gold of nanometer-order diameter were generated by a gas-phase condensation method and deposited on a Si substrate. Through a heat treatment and a cooling process, a nanoscopic Si–Au composite structure was formed on the surface of the Si substrate. Then, surface diffusing Si atoms played an important role for fabrication of the Si–Au structure which were epitaxially grown projecting onto the substrate. Furthermore, the Si/Au interface was atomically flat with no mixed-layer formation, and the Au nanoparticles also had the same crystal orientation as that of the Si dots in spite of a large lattice constant mismatch between them. This structure was considered to be fabricated as a result of minimization of the total surface and interface energy of the Si/Au system.
Investigation of ordering kinetics in Cu3Au with the tomographic atom probe
Authors: Duval S. , Chambreland S. , Loiseau A. , Blavette D.
Published: March 2008

Kinetics of congruent ordering in Cu3Au at 350 °C was investigated by means of a three-dimensional atom probe. This instrument, called a Tomographic Atom Probe (TAP), enables atomic resolution images of a small volume (10 × 10 × 100 nm3) of the material reconstructed in the three dimensions of space. The time evolution of ordered domains at 350 °C shows that at1/2law is followed as soon as 5 min. For this aging time, the nucleus diameter is close to 1.7 nm. This scaling law was observed even before domains came into contact (t= 50 min). Competitive growth was observed to start as soon as 5 min. The number density was observed to decrease rapidly up tot= 50 min. A slower decrease was observed when domains begin to impinge. Experimental conditions and requirements as well as advantages of TAP as compared to HREM for the study of ordering are discussed in detail.
Elastic stress in composite FeTi hydrogen storage materials
Authors: Tessier P. , Schulz R. , Ström-Olsen J. O.
Published: March 2008

A simple model of the elastic stress in a composite hydrogen absorbing material is developed to account for the hydrogen storage properties of nanocrystalline FeTi with a network of intergranular phase having a wide storage site energy distribution. The model accounts for the equilibrium properties of nanocrystalline FeTi hydrogen absorbers made by ball-milling such as the narrowing of the miscibility gap and changes in plateau pressure. A second model is proposed for disconnected inclusions of the second phase. The effect of chemical disorder is also briefly examined.
Variations in the synthesis of barium hexaferrite doped with iridium and its effect in the catalytic combustion of hydrocarbons
Authors: Pierre A. C. , Favre A. , Guilhaume N.
Published: March 2008

This paper discusses the influence of the synthesis technique on the porous structure, phase transformation, and catalytic properties of barium hexaferrite. Barium hexaferrite was synthesized by two different citrate gel methods. The first one involved metal salts, citric acid, and ammonia, while the second dispersed the same components in a polyacrylamide gel. X-ray diffraction analysis was used to determine the nature of the phase while the Brunauer, Emmett, and Teller (BET) analysis was used to study the porous structure of the material which were heat-treated at 700 °C, 900 °C, and 1200 °C. The catalytic activity of all materials in the combustion of methane was also measured.
Preparation of silver particles by spray pyrolysis of silver-diammine complex solutions
Authors: Kieda N. , Messing G. L.
Published: March 2008

A novel precursor solution system, containing NH3 as a complexing agent, was used for the production of Ag powders by spray pyrolysis. Solutions of Ag2CO3, Ag2O, and AgNO3 with NH4HCO3 were used in this study. Ag powders were obtained at unexpectedly low temperatures, i.e., 400 °C or less. The Ag powders with a shell-like morphology were obtained from Ag2CO3 and Ag2O solutions, whereas dense Ag particles of about 1 μm diameter were obtained from AgNO3–NH4HCO3 solution. These morphologies are explained in terms of NH3 release during spray pyrolysis.
Secondary ion mass spectrometry study of erbium diffusion in lithium niobate crystals
Authors: Caccavale F. , Segato F. , Mansour I. , Almeida J. M. , Leite A. P.
Published: March 2008

A systematic investigation of erbium diffusion in lithium niobate (LiNbO3) crystal as a function of crystal cut-direction, diffusion process parameters (temperature and time), and initial film thickness is reported. Depth concentration profiles of erbium are obtained by secondary ion mass spectrometry (SIMS). Combining experimental data with diffusion theory, the relevant diffusion parameters are derived. Diffusion from an infinite source of erbium ions is studied to evaluate the solid solubility lower limit of Er in LiNbO3. A thin film diffusion regime, with complete depletion of ion source, is also investigated. A comparison of Er diffusion with Er/Ti codiffusion in LiNbO3 crystals is reported.
Electron energy-loss study of titania particles
Authors: Gonzalez R. J. , Ritter A. L.
Published: March 2008

Small titania particles, prepared by hydrolysis and condensation using in situ steric stabilization, have been studied by high-energy, transmission, electron energy-loss spectroscopy. Electron diffraction patterns and energy-loss spectra as a function of momentum transfer were measured for as-prepared particles (amorphous titania), particles annealed at 600 °C (primarily anatase), and particles annealed at 1000 °C (primarily rutile). The energy-loss spectra at low momentum disagreed with the loss function calculated from optical data (rutile) and disagreed with theory (rutile and anatase). The data was fit by an Elliot-like model for a resonant exciton interacting with a continuum of levels. The translational effective mass of the exciton derived from the fitting was quite large, indicating that it was self-trapped.
Morphology control and texture of hematite particles by dimethylformamide in forced hydrolysis reaction
Authors: Kandori Kazuhiko , Ohkoshi Naoki , Yasukawa Akemi , Ishikawa Tatsuo
Published: March 2008

The effects of dimethylformamide (DMF) on morphology and texture of hematite particles produced from a forced hydrolysis reaction of FeCl3–HCl solution were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetry and differential thermal analysis (TG-DTA), N2and H2O adsorption, and zeta potential measurements. The morphology of synthetic hematite particles was concentration dependent; they changed from large sphere with a diameter of ca. 600 nm to diamond-like shape with increasing DMF concentration in the aging solution accompanying a reduction of their size to 80 nm without incorporation of DMF in the particles. This fact was explained by an acceleration of phase transformation from β–FeOOH to hematite with an elevation of the solution pH owing to dimethylamine produced from a hydrolysis of DMF at an elevated temperature. TEM and XRD suggested that the diamond-like hematite particles formed above 6–10 vol% DMF possess a single-crystal nature. Gas adsorption technique revealed that the particles produced above 10 vol% DMF possess a high thermal stability. TG and FTIR indicated that the hematite particles produced with DMF contained small amounts of OH_ions in the lattice though they provided a single-crystal nature.
Epitaxial growth of β–SiC on silicon by bias-assisted hot filament chemical vapor deposition from solid graphite and silicon sources
Authors: Woo H. K. , Lee C. S. , Bello I. , Lee S. T.
Published: March 2008

Epitaxial β–SiC film has been grown on a mirror-polished Si(111) substrate using bias-assisted hot filament chemical vapor deposition (BA-HFCVD) at a substrate temperature of 1000 °C. A graphite plate was used as the only carbon source, and hydrogen was the only feeding gas to the deposition system. Atomic hydrogen, produced by hot filaments, reacted with the graphite to form hydrocarbon radicals which further reacted with the silicon substrate and deposited as β–SiC. The effect of negatively biasing the substrate is the key factor for epitaxial growth. Under the same growth conditions without negative bias, polycrystalline β–SiC resulted.
Bismuth quantum-wire arrays fabricated by a vacuum melting and pressure injection process
Authors: Zhang Zhibo , Ying Jackie Y. , Dresselhaus Mildred S.
Published: March 2008

Ultrafine bismuth nanowire arrays were synthesized by injecting its liquid melt into nanochannels of a porous anodic alumina template. A large area (1 cm × 1.5 cm) of parallel wires with diameters as small as 13 nm, lengths of 30–50 μm, and packing density as high as 7.1 × 1010 cm−2 has been fabricated. X-ray diffraction patterns revealed these nanowires, embedded in the insulating matrix, to be essentially single crystalline and highly oriented. The optical absorption spectra of the nanowire arrays indicate that these bismuth nanowires undergo a semimetal-to-semiconductor transition due to two-dimensional quantum confinement effects.
Aluminum borate in the combustion synthesis of alumina/boride composite
Authors: Liu Yonghe , Yin Sheng , Guo Zhimeng , Hoyi Lai
Published: March 2008

The formation mechanism of aluminum borate in the combustion synthesis of Al2O3/B4C composite with Al, B2O3, and C as starting materials is proposed. Based on the formation mechanism, several approaches taken to eliminate them are discussed. The unconverted B2O3 is the major cause of the formation of 9Al2O3 · 2B2O3 when the reaction proceeds in the SHS mode. The amount of 9Al2O3 · 2B2O3 formed is very sensitive to the excess B2O3 to the stoichiometry 4Al + 2B2O3 + C and influenced by the size of B2O3 powder. The high dispersion of the reactants is helpful in prompting the thermite reaction to consume B2O3 and hence inhibiting the aluminum borate formation.
Formation of silicon carbide and amorphous carbon films by pulse biasing silicon to a high voltage in a methane electron cyclotron resonance microwave plasma
Authors: Volz K. , Ensinger W. , Reiber W. , Rauschenbach B. , Stritzker B.
Published: March 2008

Silicon was pulse biased to −45 kV in a methane plasma generated by microwave excitation in the electron cyclotron resonance (ECR) mode. Hydrocarbon ions were accelerated in the electrical field and implanted into the silicon. Rutherford backscattering (RBS) measurements showed that it is possible to incorporate a concentration of up to 95 at.% C into the Si. Cross-section transmission microscopy (XTEM) showed that the resulting surface layer was amorphous. Annealing at 1250 °C resulted in the formation of 10 to 60 nm thick, crystalline SiC layers.
Effects of substrate pretreatment and methane fraction on the optical transparency of nanocrystalline diamond thin films
Authors: Bhusari D. M. , Yang J. R. , Wang T. Y. , Chen K. H. , Lin S. T. , Chen L. C.
Published: March 2008

Optical transmittance of the nanocrystalline diamond films has been studied as a function of grain size of the diamond powder used for substrate pretreatment and the methane fraction in the source gas. It has been observed that for CH4 fractions below 13%, the films grown on substrates pretreated with finer diamond powder are more transparent, while this trend reverses for CH4 fractions above 13%. These variations in the transparency of the films correlate very well with their corresponding surface roughness. Nanocrystalline/amorphous diamond films with transmittance of greater than 80% beyond 700 nm and with average surface roughness as low as 61 Å have been obtained for CH4 fractions as high as 42% in the source gas. Interestingly, these films do not show an obvious presence of any graphitic carbon, and the structural ordering of the amorphous sp3-bonded phase also seems to be insensitive to the CH4 content of the source gas.
Effect of noble metals on selective detection of liquid petroleum gas by SnO2
Authors: Phani A. R. , Pelino M.
Published: March 2008

The present investigation deals with the electrical response of doped SnO2 to improve the selectivity for liquid petroleum gas (LPG) in the presence of CO and CH4, by utilizing noble metal sensitizers such as Pd, Pt, and Rh. SnO2 with the addition of Pd (1.5 wt. %) or Pt (1.5 wt. %) sintered at 800 °C which have shown high sensitivity toward LPG with no cross interference of CO and CH4 at an operating temperature of 350 °C. The results suggest the possibility of utilizing the sensor for the detection of this hydrocarbon gaseous mixture. X-ray diffraction studies have been carried out to evaluate the crystallite size as a function of sintering temperature; x-ray photoelectron spectroscopy studies have been carried out to define the possible chemical species involved in the gas-solid interaction and the sensitivity enhancing mechanism of the SnO2/Pd sensor element toward LPG.
Silicon carbide grown by liquid phase epitaxy in microgravity
Authors: Yakimova R. , Syväjärvi M. , Lockowandt C. , Linnarsson M. K. , Radamson H. H. , Janzén E.
Published: March 2008

6H and 4H polytype silicon carbide (SiC) layers have been grown on ground and under microgravity conditions by liquid phase epitaxy (LPE) from a solution of SiC in Si-Sc solvent at 1750 °C. The effects of gravity on the growth parameters and material characteristiques have been studied. The growth rate, Sc incorporation, and the structural defects are modified in reduced gravity conditions, while the polytype reproduction of the substrate is not affected. The results obtained are intriguing as to further experiments providing objects for carrier lifetime measurements.
Polycarbodiimide and polyimide/cyanate thermoset in situ molecular composites
Authors: Wiff D. R. , Lenke G. M. , Fleming P. D.
Published: March 2008

The synthesis of polycarbodiimide and polyimide in a cyanate resin precursor was achieved. A unique procedure for achieving a high molecular weight of the molecular composite reinforcement molecules was demonstrated. In spite of phase separation being present during the processing, the final cured composites were transparent. The enhanced mechanical properties and the presence of a single Tg, which increases with rigid rod content, were indications that a molecular composite was achieved. The agreement between measured mechanical properties and those predicted using molecular mechanics simulations CERIUS2 software was encouraging.
Compositional and physical changes on perovskite crystal surfaces
Authors: Chen S. P.
Published: March 2008

The surface composition of BaTiO3, SrTiO3, and CaTiO3 perovskite (100) surface is determined by shell-model calculations. The TiO2-terminated surface is energetically favorable for BaTiO3 and SrTiO3, which is consistent with experimental observations on SrTiO3. On the other hand, the CaO-terminated surface is preferred for CaTiO3 where Ca2+ is the smallest 2+ cation in these titanates. Ions on (100) surface rumple and induce surface dipoles. The surface ferroelectric polarization stabilizes the surface and changes its sign as the surface composition changes from TiO2 to CaO. This phenomenon is expected to affect the stability and properties of epitaxial films on perovskite substrates.
Microstructural development of SCS-6 SiC fibers during high temperature creep
Authors: Giannuzzi Lucille A. , Lewinsohn Charles A. , Bakis Charles E. , Tressler Richard E.
Published: March 2008

Microstructural development of SCS-6 SiC fibers induced by creep deformation at 1400 °C is presented. Grain growth occurs in all SiC regions of the fiber during creep. Portions of the SiC4 region transform from βSiC to αSiC growing at the expense of the βSiC. The SiC1 through SiC3 regions of the fiber consist of a distinct (C + βSiC) two-phase region. The grain growth of the βSiC grains in the two-phase region is not as extensive as in the SiC4 region, suggesting that the presence of excess carbon may inhibit the growth of βSiC.
Fabrication of dense nanocrystalline ZrO2−3 wt. % Y2O3 by hot-isostatic pressing
Authors: Chaim R. , Hefetz M.
Published: March 2008

Amorphous to nanocrystalline ZrO2−3 wt. % Y2O3 powders were formed by chemical precipitation from mixed nitrate salt solutions. The powders were cold pressed and presintered in air for 2 to 6 h within the temperature range of 1100 °C and 1300 °C. Hot isostatic pressing was performed for 2 to 3 h within the temperature range of 1150 °C to 1350 °C in argon pressure of 150 MPa. Fully dense pellets with grain size of 22 nm to 45 nm were formed by application of low presintering temperatures.
Early age microstructure of the paste-aggregate interface and its evolution
Authors: Zampini Davide , Shah Surendra P. , Jennings Hamlin M.
Published: March 2008

The sequence of microstructural changes occurring at the wet paste-aggregate interface is documented at an age as early as 5 min using the environmental scanning electron microscope (ESEM). Unlike other microscopic techniques, the ESEM allows pastes of normal water: cement ratio to be observed at early ages without reducing the paste to a powder. Evolution of the paste-aggregate microstructure is followed up to an age of 24 h. The region adjacent to the aggregate surface contains a phase with a morphology referred to as a “sheaf of wheat” morphology. The same interfacial region in a 10-day-old specimen has a microstructure similar to the interfacial transition zone (ITZ) reported in the literature. Variations of the “sheaf of wheat” morphology due to original water-to-cement ratio, mixing energy, incorporation of silica fume, and drying are documented. As revealed by energy dispersive x-ray analysis (EDS), the microstructure contains significant amounts of calcium and silica. These results indicate that the observed morphology is likely to be a calcium silicate hydrate (C-S-H) product that is a precursor to type I C-S-H. A description of the evolution of the observed microstructural features is presented. The “sheaf of wheat” morphology appears to be a general precursor to morphologies commonly seen in mature pastes.
Atomic force microscope investigation of the thermal stability of thin TiSi2 films
Authors: Amorsolo Alberto V. , Funkenbusch Paul D. , Kadin Alan M.
Published: March 2008

The thermal stability of TiSi2 films on Si has been studied using the atomic force microscope (AFM). Changes in the surface roughness, film morphology, and sheet resistance were monitored during a series of rapid thermal annealing treatments. A linear increase of the root-mean-square (rms) roughness with time was observed during the early stages of degradation, in agreement with a surface diffusion model of thermal grooving, followed by an apparent saturation roughness that was attributed to the effective rupture of the film.
Solid-phase reactions in Ir/(111)Si systems studied by means of x-ray emission spectroscopy
Authors: Kurmaev E. Z. , Galakhov V. R. , Shamin S. N. , Rodríguez T. , Almendra A. , Sanz-Maudes J. , Göransson K. , Engström I.
Published: March 2008

High energy resolved x-ray emission spectroscopy with variable electron beam excitation is applied for study of solid-phase reactions in the Ir/(111)Si system as a function of annealing temperature. The formation of Ir silicides as a function of depth is studied by measurements of Si L2,3 x-ray emission valence spectra at different electron excitation energies (3–10 keV), and the results are compared with those of Rutherford backscattering.
Laser synthesis and crystallization of nanocomposite Si/C/N powder
Authors: Pan Zhengwei , Li Hualun , Zhang Litong
Published: March 2008

Ultrafine preceramic Si/C/N composite powders have been prepared from hexamethyldisilazane (HMDS) by laser-induced gas phase reaction, using a new kind of tworeaction-zone reactor which could efficiently increase laser efficiency and production yield compared with a one-reaction-zone reactor. The as-formed products were nanosized (50–80 nm), amorphous powders containing Si–C and Si–N bonds homogeneously mixed with some excess carbon. The production yield was in the range of 88–120 g/h. Changes of chemical composition and crystallization of the powders during heat treatment at 1350 and 1550 °C under nitrogen for 1 h were studied.