bluuebunny/crossref_metadata_2025 huggingface dataset:
Stresses During Micromolding of Metals at Elevated Temperatures: Pilot Experiments and a Simple Model
Authors: Meng W.J. , Cao D.M. , Sinclair G.B.
Published: May 2005

The Lithographie, Galvanoformung, Abformung (LIGA) technique is important for making metal-based high-aspect-ratio microscale structures (HARMS) and microdevices derived from metal-based HARMS. Recently, molding replication of HARMS made of Pb, Zn, and Al has been demonstrated, advancing LIGA technology from the state where only polymer-based HARMS could be replicated by molding. This demonstration offers a potential means for economical fabrication of a wide variety of metal-based microdevices. Micromolding of a metal requires heating the metal to be molded to a significant fraction of its melting temperature. At high temperatures, the strength of the mold insert itself will typically decrease. The insert strength thus places a limit on the range of materials that can be molded. In this paper, micromolding and tensile experiments on Pb were carried out. A simple mechanics model of the micromolding process was developed. This model relates the stresses on the insert during micromolding primarily to the yield strength of the molded metal and frictional tractions on the sides of the insert. Reasonable agreement was obtained between the Pb experiments and the model predictions. Ramifications for other material systems are discussed.
Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps
Authors: Farjas J. , Serra-Miralles J. , Roura P. , Bertran E. , Cabarrocas P. Roca i
Published: May 2005

Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 °C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At 100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.
Microstructure- and property-controllable NdAlNiCuFe alloys by varying Fe content
Authors: Zhang Z. , Zhao D.Q. , Wang W.H.
Published: May 2005

We report the formation of microstructure- and property-controllable Nd60Al10Ni10Cu20−xFex (0 ≤ x ≤ 20) alloys by varying the content of Fe element. The microstructure of the Nd-based alloy can be changed progressively from a full glassy state into a composite state with nanocrystalline particles in the glassy matrix and, finally, into a nanostructured state, accompanied by variation in magnetic property gradually from paramagnetic to hard magnetic. The role of Fe addition in the control of microstructure and magnetic property is clarified. We expect that the results would have implication in the development of the microstructure- and property-controllable functional materials for various applications.
Optical studies of polyvinylpyrrolidone reduction effect on free and complex metal ions
Authors: Kan Caixia , Cai Weiping , Li Cuncheng , Zhang Lide
Published: May 2005

Polyvinylpyrrolidone (PVP) reduction effect on free and complex Ag+ and Au3+ ions was studied from optical measurements by adding a metal precursor (K-30), commonly used as a stabilizer, to PVP. It was found that PVP has a strong reduction effect on free ionic metal, such as Ag+ ion in AgNO3, but much weaker on complex ionic metals, AuCl4− in HAuCl4 and Ag(NH3)2+ in Ag(NH3)2OH. This is explained based on the coordinative field of polar group in PVP molecules.
Distinctive characteristics of solid-state reactions in mechanically alloyed Ti–Al–Si–C powder mixtures
Authors: Zhou J.B. , Rao K.P.
Published: May 2005

Ti–Al–Si–C powder mixtures of two different compositions, namely, 58Ti–30Al–6Si–6C (at.%) and 50Ti–15Al–20Si–15C (at.%), were mechanically alloyed to investigate the solid-state reactions during such a process. The mechanically alloyed powders were characterized as a function of milling time by x-ray diffraction (XRD), scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy (TEM). XRD results showed that solid solutions of Ti were formed for a powder mixture of 58Ti–30Al–6Si–6C in about 20 h of milling, whereas Ti5(Al,Si)3 and Ti(Al,Si)C compounds started to form in the powder mixture of 50Ti–15Al–20Si–15C within just 5 h of milling. TEM observations demonstrated that the particle sizes were of nano and submicron scale in both cases. This investigation indicated that in mechanically alloyed Ti–Al–Si–C powder mixtures, the main solid-state reactions are due to interdiffusion and mechanically induced self-propagating reaction.
Parametric effects of low-temperature combustion synthesis of alumina
Authors: Chen Chien-Chong , Huang Kuan-Tung
Published: May 2005

The influences of parameters on the low-temperature combustion synthesis of alumina particles from reactant mixture of aluminum nitrate and combustion fuel were studied using the particle size of as-synthesized alumina particles as a performance index. First, when urea was used as combustion fuel, it produced a higher combustion temperature and a larger particle size than the case when carbohydrazide was the fuel. Next, the combustion in air yielded a flame propagating through the reactant mixture, in contrast to a flame simultaneously ruptured from the entire reactant when the combustion was conducted in nitrogen. The particle size of the product obtained in nitrogen was 40% smaller than that obtained in air. Increasing the heating temperature could increase the alumina particle size due to the sintering effect, while combustion failed if the heating temperature was too small. The addition of diluent, excess fuel, and gas-releasing agents reduced the particle size. The increase of stirring speed also reduced the particle size. Next, if the reactant density (the amount of reactant mixture in the reacting container) was below a certain threshold value, the combustion failed to ignite. Increasing the reactant density was found to reduce the particle size due to the simultaneous reduction of combustion time and temperature. Finally, a liquid–gas reaction model was proposed and solved to study the threshold of combustion parameters.
Crystallization kinetics and dielectric properties of nanocrystalline lead strontium barium niobates
Authors: Cheng Ching-Tai , Lanagan Michael , Lin Jiang-Tsair , Jones Beth , Pan Ming-Jen
Published: May 2005

The crystallization kinetics and phase developments of PbO–BaO–SrO–Nb2O5–B2O3–SiO2-based glass-ceramics was investigated. Lead strontium barium niobate, (Pb,Sr,Ba)Nb2O6, with a tetragonal tungsten-bronze structure formed as the major crystalline phase, which showed evidence of both surface and bulk crystallization. The results of the present study showed significant evidence of a change in crystallization mechanism between the as-heated surface and the interior of glass-ceramics. This effect could be attributed to a volatilization of PbO taken place readily on the surface region of sample during heating. The grain size of the bulk-nucleated (Pb,Sr,Ba)Nb2O6 crystals was substantially smaller than that of surface-nucleated crystals. This result facilitated meeting the capacitors as high energy density application due to the ultrafine grains (<60 nm) obtained. The dielectric constant increased from 27 for the as-quenched glass to 200 for a highly crystallized glass-ceramic, which was attributed to a significant volume fraction of (Pb, Sr, Ba) Nb2 O6 phase.
Elastic and structural properties of alkaline-calcium silica hydrogels
Authors: Phair John W. , Tkachev Sergey N. , Manghnani Murli H. , Livingston Richard A.
Published: May 2005

Brillouin scattering has been used to study the elastic properties of alkaline-calcium silica hydrogels synthesized from the precipitation of sodium silicate solution with calcium hydroxide. To the best of our knowledge, this is the first determination of the bulk elastic moduli for this type of alkaline-calcium silica hydrogel, also referred to as the alkali-silica reaction (ASR) gel. The measured bulk moduli for the alkaline-calcium silica hydrogels were found to be between 4 and 8 GPa for the gel containing 0.08 M Ca(OH)2 and between 10 and 25 GPa for the gel containing 0.8 M Ca(OH)2, increasing with increasing pressure. Fourier transform infrared measurements were made to correlate the moduli to the silica speciation and network formation within the gels as a function of Ca(OH)2 content. Significantly, for the concentrations considered, both the interconnection of the silica species and the bulk modulus increased with increasing Ca(OH)2 content. On this basis, Brillouin scattering was confirmed to be a useful method for distinguishing between the bulk moduli of alkaline-calcium silica hydrogels in terms of chemical composition. The potential for further characterization of ASR gels as a function of composition and water content by this technique is highly promising.
Influence of Zr additives on the microstructure and oxidation resistance of Cu(Zr) thin films
Authors: Liu C.J. , Chen J.S.
Published: May 2005

In this work, the microstructure and oxidation resistance of pure Cu, Cu(0.2 at.% Zr) and Cu(2.5 at.% Zr) alloy films deposited on SiO2/Si by sputtering were explored. Upon annealing, the Zr additives diffused to the free surface and reacted with the residual oxygen in the vacuum system. An additional ZrO2 layer formed and covered the Cu(2.5 at.% Zr) film surface after annealing at 700 °C for 30 min. Simultaneously, of the three films, the Cu(2.5 at.% Zr) film exhibited the highest degree of Cu(111) preferred orientation and the lowest degree of void growth upon annealing. Additionally, the Cu(2.5 at.% Zr) film pre-annealed at 700 °C showed a superior oxidation resistance when annealed at 200 °C in air for 15 min. Microstructure and oxidation resistance of Cu(Zr) alloy films were clearly affected by the ZrO2 layer formed via the segregation of Zr additives, and the connection is discussed.
Nanocrystalline TiO2 powders synthesized by in-flight oxidation of TiN in thermal plasma: Mechanisms of phase selection and particle morphology evolution
Authors: Oh Seung-Min , Li Ji-Guang , Ishigaki Takamasa
Published: May 2005

Titanium dioxide nanopowders were synthesized by in-flight oxidation of titanium nitride (TiN) in radio-frequency (rf) induction thermal plasma. The powders were characterized by x-ray diffraction, high-resolution transmission electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, and optical microscopy to reveal the mechanisms of phase selection and particle morphology evolution. The reaction began with surface oxidation of TiN particles, leading to the formation of core-shell composites with oxidized shells and TiN cores, followed by gas-phase condensation of TiO2 nanoparticles. Phase selection of the resultant TiO2 powders was found to largely depend on the oxidation potential of the thermal plasma rather than on the heat transfer itself. Anatase content of the products increased steadily with increasing the O2 input, and TiO2 nanoparticles (∼50 nm) containing ∼90% of anatase were obtained through O2/Ar plasma treatment. Phase-pure rutile nanoparticles (∼50 nm, on average) were also synthesized in H2/Ar plasma injected with O2 as the powder carrier gas.
The effect of abrasive hardness on the chemical-assisted polishing of (0001) plane sapphire
Authors: Zhu Honglin , Niesz Dale E. , Greenhut Victor A. , Sabia Robert
Published: May 2005

A series of abrasives with various hardness values including monocrystalline and polycrystalline diamond, α- and γ-alumina, zirconia, ceria, and silica were used to examine the concept of chemical-assisted polishing for finishing the (0001), c-plane (basal plane), of sapphire. Diaspore, a monohydrate of alumina, was also evaluated. Atomic force microscopy suggested that the hydrated layer of the c-plane surface was about 1 nm thick. Polishing experiments were designed to determine whether the chemically modified surface hydration layer forms on the basal plane in water. The results indicate that harder abrasives do not necessarily cause faster material removal and better surface finish for similar abrasive particle size. Abrasives with hardness equal to or less than sapphire such as α-Al2O3 and γ-Al2O3 achieved the best surface finish and greatest efficiency of material removal. It is proposed that the (0001) c-plane sapphire surface was modified by water to form a thin hydration layer with structure and hardness close to diaspore. This reaction layer can be removed by an abrasive that is softer than sapphire but harder than the reaction layer. α-Al2O3 was particularly effective. This result is attributed to adhesion between identical reaction layers on the basal planes of the alumina abrasive and the sapphire. This demonstrates that high removal rates and good surface finish can be achieved without costly diamond polishing.
Epitaxial Ti2GeC, Ti3GeC2, and Ti4GeC3 MAX-phase thin films grown by magnetron sputtering
Authors: Högberg H. , Eklund P. , Emmerlich J. , Birch J. , Hultman L.
Published: May 2005

We have grown single-crystal thin films of Ti2GeC and Ti3GeC2 and a new phase Ti4GeC3, as well as two new intergrown MAX-structures, Ti5Ge2C3 and Ti7Ge2C5. Epitaxial films were grown on Al2O3(0001) substrates at 1000 °C using direct current magnetron sputtering. X-ray diffraction shows that Ti–Ge–C MAX-phases require higher deposition temperatures in a narrower window than their Ti–Si–C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young’s modulus of 300 GPa, lower than that of Ti3SiC2. Four-point probe measurements yield resistivity values of 50–200 μΩcm. The lowest value is obtained for phase-pure Ti3GeC2(0001) films.
Orientation control of sol-gel-derived lead zirconate titanate film by addition of polyvinylpyrrolidone
Authors: Park Gun-Tae , Park Chee-Sung , Choi Jong-Jin , Kim Hyoun-Ee
Published: May 2005

Highly (100)- and (111)-oriented lead zirconate titanate (PZT) films with a thickness of 350 nm were deposited on platinized Si substrates through a single spinning of a PZT sol containing polyvinylpyrrolidone (PVP) as an additive. The crystallographic orientation of the film was strongly influenced by pyrolysis conditions after spin coating. When the spin-coated sol was pyrolyzed at temperatures above 320 °C for relatively long periods of time (>5 min), (111)-oriented film was formed after annealing at 700 °C for 10 min. On the other hand, when the same sol was pyrolyzed at 320 °C for short periods of time (<5 min), the film was strongly oriented to the (100) direction after annealing. Organic residues derived from PVP decomposition acted as nucleation sites for the (100) oriented grains during annealing after the pyrolysis. The effective d33 of the (100)-oriented PZT film (100 pC/N) was much higher than that of the (111)-oriented film (62 pC/N) with the same thickness.
Growth of rare-earth niobate-based pyrochlores on textured Ni–W substrates with ionic radii dependency
Authors: Bhuiyan M.S. , Paranthaman M. , Sathyamurthy S. , Goyal A. , Salama K.
Published: May 2005

Epitaxial films of rare-earth (RE) niobates, RE3NbO7 with pyrochlore structures, were grown on biaxially textured nickel–3 at.% tungsten (Ni–W) substrates using a chemical solution deposition process. A precursor solution of 0.3–0.50 M concentration of total cations was spin coated on to short samples of Ni–W substrates, and the films were crystallized at 1050–1100 °C in a gas mixture of Ar–4% H2 for 15 min. Detailed studies revealed that RE-niobates with ionic radius ratio RRE/RNb (R = ionic radius) from 1.23 to 1.40 (i.e., Sm, Eu, Gd, Ho, Y, and Yb) grow epitaxially with the pyrochlore structure. X-ray studies showed that the films of pyrochlore RE niobate films were highly textured with cube-on-cube epitaxy. Scanning electron and atomic force microscopy investigations of RE3NbO7 films revealed a fairly dense and smooth microstructure without cracks and porosity. The rare-earth niobate layers may be potentially used as buffer layers for YBa2Cu3O7−δ coated conductors.
Oxidation behavior of a pressureless sintered ZrB2–MoSi2 ceramic composite
Authors: Sciti Diletta , Brach Mylène , Bellosi Alida
Published: May 2005

Ultra-refractory ceramic composites of composition ZrB2 + (5 to 20) vol% MoSi2were produced by pressureless sintering at 1830 °C under argon atmosphere.Sintering cycles and microstructural analysis point out that at least 20 vol% molybdenum disilicide is necessary for obtaining a dense material. Thereafter, the composite 80 vol% ZrB2 + 20 vol% MoSi2 was used to test the thermal stabilityunder oxidizing environment. Oxidation tests were carried out in flowing syntheticair in a thermogravimetric analyzer from 700 to 1400 °C with exposure time of30 h. In the low-temperature range (700–1000 °C), the oxidation of the composite resembles that of monolithic ZrB2 ceramics, for temperatures >1200 °C the silica resulting from oxidation of molybdenum disilicide seals the sample surface, preventing zirconium diboride from fast degradation.
Evolution in friction and wear of Mg–SiCp composites: Influence of fretting duration
Authors: Kumar B.V. Manoj , Basu Bikramjit
Published: May 2005

In the effort toward achieving lightweight, wear-resistant, composite materials, considerable effort, in recent times, has been put forward to develop Mg–SiC composites. The detailed wear mechanism of these newly developed composites is still unclear, and most of the work on metal matrix composites (MMC) to date has concentrated on evaluating the wear behavior of Al-based MMCs. In the present work, the influences of fretting test duration on the evolution of frictional behavior as well as wear properties were studied. The experimental results revealed that fluctuations in friction curve are significantly suppressed with highest reinforcement content (26.3 wt%) in composites while considerable fluctuations continue to exist even after achieving steady state condition in base Mg. In all the fretting contacts, tribochemical reactions were observed to be dominant wear mechanisms. In the early stage of fretting, oxidative wear dominates due to formation of MgO. As the fretting continues, MgO undergoes tribochemical reaction and forms soft, viscous hydrated magnesia. For base Mg, surface fatigue cracks were observed after a threshold number of cycles. In composites, the soft, viscous triboproducts (hydrated MgO and dense hydrous magnesium silicate) smear on the worn surfaces and decrease the friction coefficient.
Fracture of SnBi/Ni(P) interfaces
Authors: Liu P.L. , Shang J.K.
Published: May 2005

Fracture resistance of the interface between electroless Ni(P) and the eutectic SnBi solder alloy was examined in the as-reflowed and aged conditions, to investigate the potential role of Ni in inhibiting interfacial segregation of Bi in SnBi–Cu interconnect. In the as-reflowed condition, the fracture resistance of the SnBi/Ni(P) interface was about the same as that of the SnBi/Cu interface. Upon aging at 120 °C for 7 days the fracture resistance of the SnBi/Ni(P) interface was much higher than that of the SnBi/Cu interface. Such a difference was shown to result from the difference in fracture mechanism as the crack remained along the solder–intermetallic interface in the aged SnBi–Ni interconnect but propagated along the intermetallic–substrate interface in the aged SnBi–Cu interconnect. While fracture of the intermetallic–substrate interface in SnBi–Cu interconnect was due to Bi segregation onto that interface, no Bi was detected at the intermetallic-substrate interface in SnBi–Ni interconnects, implying that Ni(P) was effective in inhibiting the interfacial segregation of Bi.
Synthesis of nanotabular barium titanate via a hydrothermal route
Authors: Yosenick Timothy J. , Miller David V. , Kumar Rajneesh , Nelson Jennifer A. , Randall Clive A. , Adair James H.
Published: May 2005

As layer thickness of multilayer ceramic capacitors decreases, nanoparticles of high dielectric materials, especially BaTiO3,are needed. Tabular metal nanoparticles produce thin metal layers with low surface roughness via electrophoretic deposition. To achieve similar results in dielectric layers requires the synthesis and dispersion of tabular BaTiO3nanoparticles. In the current study, the synthesis of BaTiO3was investigated using a hydrothermal route. Transmission electron microscopy and atomic force microscpy analyses show that the synthesized particles are single crystal with a 〈111〉 zone axis and a median thickness of 5.8 nm and face diameter of 27.1 nm. Particle growth is likely controlled by the formation of {111} twins and the synthesis pH, which stabilizes the {111} face during growth. With limited growth in the 〈111〉 direction, the particles develop a platelike morphology. Physical property characterization shows the powder is of high purity with low hydrothermal defect concentrations and controlled stoichiometry.
Effect of rotary-die equal channel angular pressing on the thermoelectric properties of a (Bi,Sb)2Te3 alloy
Authors: Sun Z.M. , Hashimoto H. , Keawprak N. , Ma A.B. , Li L.F. , Barsoum M.W.
Published: May 2005

A (Bi,Sb)2Te3 alloy powder was sintered via a pulse discharge sintering process followed by a rotary-die equal channel angular pressing (ECAP) process. It was found by x-ray diffraction analysis that the as-sintered material shows preferentially orientated microstructure, which were considerably eliminated by following ECAP processes. Generally, the Seebeck coefficient of the material was reduced by ECAP processing, which was attributed to the increased carrier concentration after the severe plastic deformation. Electrical conductivity increases after ECAP, which was also originated from the increased carrier concentration. The figure of merit of the material in different conditions shows higher value in the transverse direction. In the transverse samples, those after ECAP processing showed increased figures of merit, which reached 3.85 × 10−3/K in the material after 4 passes of ECAP.
Synthesis of ZnO nanorods by a hot-wall high-temperature metalorganic chemical vapor deposition process
Authors: Choi Young-Jin , Park Jae-Hwan , Park Jae-Gwan
Published: May 2005

ZnO nanorods with diameter of 30–200 nm were synthesized by a metalorganic chemical vapor deposition process in a hot-wall type chamber at elevated temperatures above 700 °C. At temperatures between 400 and 500 °C, ZnO thin films and wrinkles were synthesized. Above 500 °C, vertically aligned ZnO nanorods were grown on a Si and sapphire substrate without any catalysts. The range of diameter was 30–200 nm. When Au catalysts were deposited on the substrate prior to the deposition, nanocombs and nanosheets as well as nanorods were synthesized. In particylar, ZnO could be grown selectively along the pattern of the Au catalyst with the aid of a Au–Zn alloy.
Non-template synthesis of titania hollow spheres and their thermal stability
Authors: Wang Xin M. , Xiao Ping
Published: May 2005

Uniform and thermally stable spherical titania particles with hollow interiors were directly prepared by a novel solvothermal precipitation of TiCl4 in isopropanol without templates or shape-controller reagents. An average particle size of 700 nm to 1 μm was obtained. The hollow spheres consisted of pure anatase phase nanocrystals with an estimated crystallite size of 12–15 nm. Upon heating, the pure anatase phase was retained for temperatures up to 800 °C, which suggested that the spherical structure contributed to phase stability. This method is a promising process for industrial-scale preparation of titania hollow spheres.
Synthesis and thermoelectric properties of Bi2.5Ca2.5Co2Ox layered cobaltites
Authors: Guilmeau Emmanuel , Mikami Masashi , Funahashi Ryoji , Chateigner Daniel
Published: May 2005

Bi–Ca–Co–O polycrystalline materials with a layered structure were prepared. The synthesis of the sintered specimens from two starting compositions, Bi1.8Ca2Co2Oxand Bi2.5Ca2.5Co2Ox, revealed the latter is preferentially formed at high temperature(850 °C). The increase in sintering time was shown by growth of large platelike grains (up to 50 μm in diameter and several micrometers in thickness). The reaction mechanisms during the heat treatment and the preferential formation of the Bi2.5Ca2.5Co2Ox phase were observed by x-ray diffraction, thermogravimetry–differential thermal analysis, and scanning electron microscopy. These techniques supposed the presence of a liquid phase at high temperature, origin of a highly kinetic phase formation, and the growth of large grains. Interestingly the liquid phase reaction promotes an efficient stacking and sliding of grains during hot-forging treatment, and highly (00l) oriented materials were prepared. A relationship between thermoelectric performance, texture strength, and microstructure is clarified.
Effects of addition of ethanol on the infiltration pressure of a mesoporous silica
Authors: Kong Xinguo , Surani Falgun B. , Qiao Yu
Published: May 2005

The energy absorption behaviors of mesoporous silica particles immersed in aqueous solutions of ethanol were investigated. Addition of ethanol could significantly lower the infiltration pressure, which has great potential in developing selective protection systems. The ethanol concentration of the confined liquid inside the nanopores was higher than outside.
Relationships between initial unloading slope, contact depth, and mechanical properties for conical indentation in linear viscoelastic solids
Authors: Cheng Yang-Tse , Cheng Che-Min
Published: May 2005

Using analytical and finite element modeling, we studied conical indentation in linear viscoelastic solids with either displacement or load as the independent variable. We examine the relationships between initial unloading slope, contact depth, and viscoelastic properties for various loading conditions such as constant displacement rate, constant loading rate, and constant indentation strain rate. We then discuss whether the Oliver–Pharr method for determining contact depth, originally proposed for indentation in elastic and elastic-plastic solids, is applicable to indentation in viscoelastic solids. We conclude with a few comments about two commonly used experimental procedures for indentation measurements in viscoelastic solids: the “hold-at-peak-load” technique and the constant indentation strain-rate method.
Ductility of cold-rolled and recrystallized Ni3Al foils
Authors: Cui Chuanyong , Demura Masahiko , Kishida Kyosuke , Hirano Toshiyuki
Published: May 2005

The room-temperature ductility of 95% cold-rolled and recrystallized Ni3Al(Ni–24.0 at.% Al) foils was examined as a function of heat-treatment conditions. The cold-rolled, diffused Goss texture changed to a complicated, transitional texture in the early stage of grain growth and then returned to a similar diffused Goss texture in the late stage. With the texture evolution, the total area fraction of the tough grain boundaries (GBs) such as Σ1, Σ3, and Σ9 increased from 0.23–0.38 in the early stage to 0.56–0.73 in the late stage. Tensile and bending tests revealed that the ductility was drastically improved with the grain growth. The foils in the early stage fractured without showing yielding. In contrast, the foils in the late stage were very ductile, and the tensile elongation increased to 10% with the grain growth. It was confirmed that there was no in-plane anisotropy in ductility. The ductility improvement with the grain growth was ascribed to the increase in the area fraction of the tough GBs.
New type of bioactive materials: Hydroxyapatite/α-wollastonite composites
Authors: Ryu Hyun-Seung , Lee Jung Kun , Kim Hwan , Hong Kug Sun
Published: May 2005

A new type of bioactive materials, hydroxyapatite (HA)/α-wollastonite (α-Wol) composites, were prepared. The sintering behavior, phase evolution, and in vitro bioactivity of hydroxyapatite/α-wollastonite composites were examined. The properties of HA/α-Wol composites were quite different from those of HA ceramics or α-Wol ceramics. HA/α-Wol composites sintered 1300 °C for 2 h exhibited a dense microstructure consisting of grains in the range of 0.3–1.0 μm in diameter. During sintering, a complex phase evolution between HA and α-Wol was observed. At 1300 °C, the formation of the Si substituted HA and the additional α-tricalcium phosphate (TCP) were observed using Fourier transform infrared and x-ray diffraction analysis. Further heat treatment at 1350 °C transformed part of the HA and α-Wol into a new phase with the composition: Ca12P6Si2O31. The in vitro bioactivity of the HA/α-Wol composites with a weight ratio of 25:75 and 50:50 sintered at 1300 °C was better than that of α-Wol monophasic ceramics. This result revealed that the silica of α-Wol and the orthosilicate of Si substituted HA provided nucleation sites for the bonelike apatite layer. The phosphate present in the HA or α-TCP phases promoted the nucleation of a bonelike apatite layer on the surface of the composites. The dissolution rate of α-Wol phase in simulated body fluid was faster than α-TCP or HA phase. Therefore, HA/α-Wol composite is the bone replacement material of controllable bioactivity and degradation rate with relative content between HA and α-Wol phase.
An energy-based method to extract plastic properties of metal materials from conical indentation tests
Authors: Cao Yan Ping , Qian Xiu Qing , Lu Jian , Yao Zhen Han
Published: May 2005

Based on dimensional analysis and finite element computations, an energy-based representative strain for conical indentation in elastoplastic materials has been proposed to establish an explicitly one-to-one relationship between the representative stress σr, the indentation loading curvature C, and the ratio of reversible work We to total work Wt performed by the indenter, i.e., σr/C = F0(We/Wt), where σr is the flow stress corresponding to the representative strain. The relationship provides a very simple method to evaluate the representative stress σr from the three directly measurable quantities We, Wt, and C. Numerical examples and further theoretical analysis reveal that a unique, stable solution can be obtained from the present method for a wide range of material properties, including both highly plastic materials (e.g., Ni for which E/σy = 1070) and highly elastic materials (e.g., materials for which E/σy = 25 and n = 0.5), using indenters with different tip apex angles. Based on the representative strains and stresses given by two indenters with different tip apex angles, e.g., (σr,80, ϵr,80) and (σr,65, ϵr,65), the plastic properties of materials, i.e., the yield strength σy and strain hardening exponent n can be further determined.
Early stage soldering reaction and interfacial microstructure formed between molten Sn–Zn–Ag solder and Cu substrate
Authors: Yu Chang-Ho , Lin Kwang-Lung
Published: May 2005

The soldering reaction and interfacial microstructure formed between liquid Sn–Zn–Ag solder and Cu at the early stage of soldering at 250 °C for 15 s were studied primarily with the aid of transmission electron microscope (TEM). To achieve the early stage reaction information, the soldered specimens, 5 mm × 5 mm × 500 μm solder on 10 mm × 10 mm × 20 μm Cu, were rapidly quenched in liquid nitrogen after soldering. The results of TEM interfacial analysis show that a Cu–Zn reaction zone, consisting of β′–CuZn and γ–Cu5Zn8, formed near Cu while a Ag–Zn zone, consisting of γ–Ag5Zn8 and ϵ–AgZn3, formed near solder. The innermost layer adjacent to the Cu substrate is an amorphous Cu-Zn diffusion region that contains dispersed β′–CuZn nanocrystalline cells. The β′–CuZn also precipitates in the γ–Ag5Zn8 and ϵ–AgZn3 layer due to the supersaturation of Cu.
Effect of temperature on the cure shrinkage measurement of non-conductive adhesives for flip chip interconnects
Authors: Yu H. , Mhaisalkar S.G. , Wong E.H.
Published: May 2005

Non-conductive adhesive (NCA) flip chip interconnects are emerging as attractive alternatives to lead or lead-free solder interconnects due to their environmental friendliness, lower processing temperatures, and extendability to fine pitch applications. The electrical connectivity of a NCA interconnect relies solely on the pure mechanical contact between the integrated circuit bump and the substrate pad; the electrical conductivity of the contact depends on the mechanical contact pressure, which in turns depends to a large extend on cure shrinkage characteristic of the NCA. In addition, to reduce the cost and increase the output, NCA is usually ramped up to 200 °C and cured for 1 min during the assembly process. However, fast cure reaction poses a great challenge for the accurate measurement of cure shrinkage. In this paper, to precisely determine the cure shrinkage at high temperature, cure shrinkage was first measured at lower temperatures with slow reaction rate by means of thermomechanical analyzer and then extrapolated to high temperatures. With the increase of cure temperature, the maximum of degree of cure will increase, but the maximum cure shrinkage reduces due to the expansion of materials at higher cure temperature. Furthermore, the slopes of the linear relationship between the cure shrinkage and the degree of cure at different cure temperatures after gelation were found to be similar and independent of the cure temperature. The cure shrinkage from gel-point to complete curing was determined to be 4.275%.
Lead titanate glass-ceramics derived from a silicate-based melt
Authors: Sooksaen P. , Reaney I.M. , Sinclair D.C.
Published: May 2005

Glass composition 39PbO–1BaO–25TiO2–9.8Al2O3–24.2SiO2–1B2O3 (mol%) crystallized on heat treatment at ≥600 °C to form glass-ceramics whose majority phase was PbTiO3 (PT). At 600 °C, nano-size PT crystals (∼20–50 nm) with a c/a ratio of 1.000(1) were observed, but as heat-treatment temperature increased to 1000 °C, the crystal size and c/a ratio increased to ∼1.2 μm and 1.056(4), respectively. Permittivity measurements as a function of temperature revealed a broad peak at ∼400 °C associated with the nanocrystalline PT crystals, but it sharpened and increased in temperature as heat treatment temperature increased to 1000 °C. The causes of peak broadening and shift of Tc are believed to be due to either clamping of PT crystals by glass matrix, finite size effects due to their intrinsically small size, or the incorporation of dopant impurities such as Al, Si, or Ba ions in the PT phase.
Structure property relationships in the design of alloy composition: Moving beyond electron to atom ratios
Authors: Eberhart M.E. , Jones T.E. , Batchelder M.A. , Olson G.B.
Published: May 2005

A model explaining the variability of oxygen solubility in the transition metals is proposed in this article. It assumes that the energy of solution can be represented as the sum of the work required to embed an oxygen atom in the electron gas of the host lattice, plus the energy generated through the formation of an oxygen anion. The latter term is treated as nearly constant across the transition metal series, leaving the work term to account for the observed variations in oxygen solubility. This work, we argue, can be approximated by the ratio of the number of metal electrons excluded from the region around the oxygen atom to the Fermi energy density of states. In turn, the number of electrons excluded by oxygen is assumed to be proportional to the charge density at the octahedral interstitial site. These assumptions allow us to define a solubility parameter that is easily determined with first-principles methods. This parameter is shown to correlate well with experimental findings regarding oxygen solubility in transition metals. Supported by these findings, we use first principle methods to identify alloying elements likely to reduce the solubility of oxygen in niobium.
Nitrogen Application Increases Yield and Early Dry Matter Accumulation in Late‐Planted Soybean
Authors: Taylor R. Scott , Weaver David B. , Wood C. Wesley , van Santen Edzard
Published: May 2005

In double‐cropped soybean [Glycine max (L.) Merr.] planting is delayed, with a corresponding decrease in yield associated with photoperiod‐induced early flowering and reduced accumulation of dry matter during the vegetative growth period. Application of nitrogen (N) has been shown to improve yield of late‐planted soybean. We conducted a field study to determine the optimum economic rate of N that would stimulate early dry matter accumulation, and thus yield, in late‐planted soybean. The effects of three planting dates (mid‐June, late‐June, and mid‐July), two MG VIII cultivars (Kuell and Prichard), and five N rates (0, 25, 50, 75, and 100 kg ha−1) were studied for 2 yr at three Alabama locations (Fairhope, Shorter, and Crossville). Nitrogen application of 60 to 70 kg ha−1 maximized yield and R1 dry matter accumulation. However, N reduced nodule number and mass, but had no effect on R1 plant height, mature plant height, or seed quality, protein and oil content. Yield was reduced linearly by later planting, but there was no interaction between N rate and planting date for yield. Kuell was taller at maturity and had more R1 dry matter than Prichard, but Kuell yielded more than Prichard in only one environment and there was no cultivar × N rate interaction for yield. At current prices for N and soybean, we concluded that N can be a viable input for double‐cropped soybean at an optimal economic rate of 59 kg ha−1.
Minimum Number of Genes Controlling Cotton Fiber Strength in a Backcross Population
Authors: Meredith W. R.
Published: May 2005

Textile mills in the USA require strong cotton fiber (Gossypium hirsutum L.) for modern high‐speed textile operations. The primary objective of this study was to determine the inheritance of strength descending from FTA 263‐20 (FTA). FTA was developed by introgression into G. hirsutum from G. arboreum L., G. thurberii Todaro, and G. barbadense L. Five backcrosses (BCs) into ‘Deltapine 16’ (DP 16) followed by six BCs into DP 90ne were made. In 2001, three sets of 64 BC6 F2:F3 progenies were evaluated for strength. Significant variability for F2:F3 strength (F = 2.79), yield, three yield components, and four other fiber traits were detected. From a three replication test, strength gene number(s) estimates ranged from 1.10 to 1.29 and combined over sets was 1.23 genes. Average strength for the three BC5 parents was 10.3% greater than DP 90ne and yield was 16.9% less. Strength was highly correlated with lint percentage, boll weight, seed weight, and 2.5% span length. Gene numbers for these correlated traits ranged from 0.02 for micronaire to 1.04 for yield. A separate study involving the BC5 parents, ‘Deltapine 90’ (DP 90) and DP 90ne was used to determine the major physical components of strength. Fineness and individual fiber strength had no effect. Short fiber content significantly impacted strength as the three BC5 parents average short fiber was 6.7 versus 8.7% for the DP 90s. The BC5 parents average strength was 11% higher, 240 vs. 219 kN m kg−1, and its yield was 9.0% lower than DP 90ne. Probably a single major gene or closely linked cluster of genes resulted in increased fiber strength.
Effects of Salicylic Acid on Heat Tolerance Associated with Antioxidant Metabolism in Kentucky Bluegrass
Authors: He Yali , Liu Youliang , Cao Weixing , Huai Mingfang , Xu Baogang , Huang Bingru
Published: May 2005

Turf quality of Kentucky bluegrass (Poa pratensis L.) often declines during summer when temperatures exceed its optimum range. This study was designed to determine whether application of salicylic acid (SA) to the shoots and soil could improve heat tolerance of Kentucky bluegrass, and to investigate whether SA‐induced heat tolerance is related to changes in antioxidant activities. Effects of SA at different concentrations (0, 0.1, 0.25, 0.5, 1, and 1.5 mmol) on heat tolerance were examined in Kentucky bluegrass exposed to 46°C for 72 h in a growth chamber. Influences of SA on the production of active oxygen species (AOS), superoxide anion (O2·−), and hydrogen peroxide (H2O2), and activities of antioxidant enzymes, superoxide dismutase (SOD), and catalase (CAT), were examined. Among SA concentrations, 0.25 mmol was most effective in enhancing heat tolerance in Kentucky bluegrass, which was manifested by improved regrowth potential following heat stress of 72 h and maintenance of leaf water content at 77% during the 12‐h stress period similar to that under normal temperature conditions. The O2− generating rate increased significantly at 6 h of heat stress, and SOD activity increased significantly at 2 h but decreased to the control level at 6 h of heat stress in SA‐untreated plants. The SA application suppressed the increase of O2− generating rate and enhanced SOD activity significantly at 2 and 6 h of heat stress, respectively. The SA application decreased H2O2 level significantly at 2 and 12 h of heat stress, and increased CAT activity significantly within 12 h of heat stress. The results suggest that SA application enhanced heat tolerance in Kentucky bluegrass and SA could be involved in the scavenging of AOS by increasing SOD and CAT activities under heat stress.
Inheritance of Seed Zinc Accumulation in Navy Bean
Authors: Cichy Karen A. , Forster Shana , Grafton Kenneth F. , Hosfield George L.
Published: May 2005

Human zinc (Zn) deficiency is a widespread condition prevalent in people consuming grain and legume based diets. Dry beans (Phaseolus vulgaris L.) are frequently the major protein source in such diets. One way to reduce the incidence of Zn deficiency may be through the development of high Zn dry beans. Large variation for dry bean seed Zn concentration exists, which would aid in the development of Zn‐rich cultivars. The objectives of this study were to determine the inheritance of seed Zn levels in navy bean and to measure seed phytic acid (PA) levels in relationship to seed Zn concentration as an indicator of Zn bioavailability. A high seed Zn cultivar ‘Voyager’ and a low seed Zn cultivar ‘Albion’ were used to create the F2 and backcross populations that were field grown in 1999 and 2000. Seed Zn was measured in both years and seed phytic acid was measured in 1999. The results of this experiment suggest that a single dominant gene controls the high seed Zn concentration in the Voyager/Albion cross. In addition, phytic acid levels between the parent cultivars used in this study showed little variability and there was no strong correlation between seed Zn and PA concentrations. The development of dry bean cultivars with increased seed Zn levels should be possible through breeding.
Can Lignin Be Accurately Measured?
Authors: Hatfield Ronald , Fukushima Romualdo S.
Published: May 2005

Forages serve an important role in providing nutrients to ruminants while providing positive benefits to the environment. Forage cell wall digestibility is incomplete because of several structural features within the wall, but digestion is mostly inversely correlated with the amount of lignification that has occurred during cell wall development. Lignin is a hydrophobic polymer formed through enzyme‐mediated radical coupling of monolignols, mainly coniferyl and sinapyl alcohols. The polymer is highly resistant to degradation and generally passes through the ruminant unmodified. Though lignin is resistant to degradation, it is not easily quantified within various types of forages. Numerous methods have been developed over the years to measure lignin levels in different plant species. Most frequently used among workers involved with forage development or utilization are the acid detergent, Klason, and permanganate lignin methods. More recently, acetyl bromide has received attention as a possible lignin determination method. The acetyl bromide method is dependent on determining the absorbance of the extract in which all the lignin of a sample has been dissolved. Each of these methods gives different lignin values for the same type of forage sample. For example, acid detergent, Klason, permanganate, and acetyl bromide lignin methods give quite different values for alfalfa stems: 93, 145, 158, and 135 g lignin kg−1 cell wall, respectively. These differences can be even greater for grasses: 25, 77, 45, and 92 g kg−1 cell wall from corn (Zea mays L.) stalks analyzed by acid detergent, Klason, permanganate, and acetyl bromide lignin methods, respectively. This paper will discuss the different lignin determination methods and highlight the advantages and disadvantages of each as they relate to forage sample analysis.
Performance of Perennial Cool‐Season Forage Grasses in Diverse Soil Moisture Environments, Southern High Plains, USA
Authors: Lauriault L. M. , Kirksey R. E. , VanLeeuwen D. M.
Published: May 2005

A continuing need exists to evaluate grasses for irrigated pastures in new and marginal environments. Persistence and yield of Altai wildrye, Leymus angustus (Trin.) Pilg.; beardless wildrye, L. triticoides (Buckley) Pilg.; creeping foxtail, Alopecurus arundinaceus Poir.; grazing bromegrass, Bromus stamineus E. Desv.; intermediate‐pubescent wheatgrass, Elytrigia intermedia (Host) Nevski; meadow bromegrass, B. riparius (Rehmann); meadow fescue, Festuca pratensis (Huds.); orchardgrass, Dactylis glomerata (L.); prairie bromegrass, B. willdenowii (Kunth), syn. B catharticus Vahl var. catharticus; reed canarygrass, Phalaris arundinacea L.; RS wheatgrass, E. repens var. repens L. Desv. ex B.D. Jackson × Pseudoroegneria spicata (Pursh) A. Love; Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski; smooth bromegrass, B. inermis Leyss.; tall fescue, F. arundinacea Schreb.; tall wheatgrass, E. elongata (Host) Nevski; and western wheatgrass, Pascopyrum smithii (Rybd.) A. Love, sown in late summer 1997, were measured from 1999 to 2001 at Tucumcari, NM. Soil moisture treatments were (i) furrow irrigated once before each harvest, which is typical management; (ii) typical irrigation plus irrigated monthly during winter; and (iii) poorly drained, saline/sodic soil, irrigated less than once per cutting. Russian wildrye, RS wheatgrass, tall fescue, tall wheatgrass, and western wheatgrass maintained ground cover across soil moisture treatments. Stand development by Altai wildrye and smooth bromegrass was inconsistent across soil moisture treatments, but eventually complete. Beardless wildrye established stands only in poorly drained soil, while intermediate‐pubescent wheatgrass and meadow bromegrass did not establish well in that soil. No other species established or maintained satisfactory stands after 3 yr in any soil moisture treatment. Winter irrigation increased early‐season yield of intermediate‐pubescent wheatgrass, but decreased late‐season yields of several species, especially Altai wildrye. Distribution of tall wheatgrass and Altai wildrye yield appear complementary, and a binary mixture might provide uniform season‐long yields in this region.