bluuebunny/crossref_metadata_2025 huggingface dataset:
Lattice thermal vibration and its nonharmonic effect in Nd-doped rare-earth vanadates
Authors: Xia H.R. , Lu G.W. , Zhao P. , Sun S.Q. , Meng X.L. , Cheng X.F. , Qin L.J. , Zhu L. , Yang Z.H.
Published: May 2005

The 0.5 at.% Nd-doped gadolinium and yttrium orthovanadate, Nd:GdVO4 (NGV) and Nd:YVO4 (NYV), crystallize in the tetragonal space group I41/amd and are of a zircon-type structure with the lattice constants a = b = 0.7212(6) and c = 0.6348(3) nm for NGV and a = b = 0.7123(5) and c = 0.6292(5) nm for NYV. At high and room temperatures, the Raman spectra of NYV are much the same; however, the Raman spectra of NGV are different from those of NYV. The scattering intensity of NGV is largely stronger than that of NYV. Nonharmonic effect of the lattice thermal vibrations, including the thermal conductivity and expansion, is theoretically and experimentally discussed. The theoretical results roughly indicate that a crystal with the larger integrated intensities of the Raman-scattering peaks under the cutoff value of linear dependence of Debye frequency versus the temperature has the larger thermal conductivity. The experimental data of the thermal conductivity of the five samples show that the thermal conductivity of NGV is more outstanding than that of NYV in every direction. Compared the integrated intensity ratio IG/IY between the NGV and NYV Raman-scattering peaks under the cutoff wavenumber of Debye frequency with the ratio κG/κY of their crystal thermal conductivity, it may be seen that the Raman results are basically in agreement with the conductivity measurements within our experimental error. The experimental datum of the thermal conductivity of NYAG (Nd-doped yttrium aluminum garnet) with the cubic symmetry and stable laser properties and thermodynamics parameters, which is often considered as a comparable standard, approximately approaches to the average value of the NGV thermal conductivity in the a and c directions. The thermal-expansion data of NGV exhibit its small line-expansion coefficients, which imply that the large thermal conductivity is needed and existential and that NGV is more capable to bear a large temperature gradient, therefore, is also more suitable as a solid-state laser material than NYV crystals.
Damage Behavior of 200-nm Thin Copper Films Under Cyclic Loading
Authors: Zhang G.P. , Volkert C.A. , Schwaiger R. , Arzt E. , Kraft O.
Published: May 2005

Fatigue damage in 200-nm-thick Cu films was investigated and compared with the damage in thicker Cu films. The fatigued 200-nm-thick Cu films exhibited only a few, small extrusions and extensive cracking along twin and grain boundaries, whereas the thicker films showed many extrusions/intrusions and cracks lying along the extrusions rather than along the boundaries. This change in fatigue damage behavior with film thickness is attributed to the inhibition of dislocation mobility and the limited availability and activation of dislocation sources on the small length scale. It is argued that the decrease in film thickness and grain size inhibits the localized accumulation of plastic strain within grains, such as at extrusions/intrusions and in extended dislocation structures, and promotes the formation of damage such as cracks at twin and grain boundaries during fatigue. This effect is suggested as the likely cause for the increase in fatigue life with decreasing specimen dimensions.
Interfacial Bonding Behavior with Introduction of Sn–Zn–Bi Paste to Sn–Ag–Cu Ball Grid Array Package During Multiple Reflows
Authors: Shih Po-Cheng , Lin Kwang-Lung
Published: May 2005

Sn–8Zn–3Bi solder paste and Sn–3.2Ag–0.5Cu solder balls were reflowed simultaneously on Cu/Ni/Au metallized ball grid array (BGA) substrates to investigate the interfacial bonding behaviors for multiple reflow cycles at two different soldering temperature of 210 and 240 °C. The different intermetallic compounds that formed at the interface after one reflow cycle were respectively the island-shaped Ag–Au-Cu-Zn (near the solder) compounds and the Ni–Sn–Cu-Zn (near the metallized pad) compounds in 210 or 240 °C soldering systems. Layered Ag–Au–Cu–Zn, Ag5Zn8, and Ag–Zn–Sn compounds were also observed within the solder near the interface after single reflow cycle. After ten reflow cycles, the Ag–Au–Cu–Zn compounds significantly decomposed, while the Ag3Sn and Ni–Sn–Cu–Zn compounds coarsened obviously.
Study on Electronic Structure and Magnetic Properties of Ni3Fe Ferromagnetic Layer Adjacent to Cu
Authors: Bi Xiaofang , Yuan Xiaoyu , Gong Shengkai , Xu Huibin
Published: May 2005

The effect of a Cu layer on the electronic structure and magnetic properties of Ni3Fe was studied by employing the discrete-variational method in the framework of density-functional theory. Three models were established for Ni3Fe(6), Ni3Fe(3)/Cu(3)/Ni3Fe(3), and Ni3Fe(3)/Cu(3). The charge transfer, magnetic moment, and spin exchange split at the Fermi level were obtained for Fe and Ni atoms in a Ni3Fe layer. The related characterizations of Ni3Fe were estimated from those of Fe and Ni atoms. It was discovered that the magnetic properties of the Ni3Fe layer improved when adjacent to Cu layer due to the improvement of the corresponding properties of the Fe atoms in the Ni3Fe. However, the magnetic moment and the spin exchange split of the Ni atoms in the Ni3Fe decreased when the Ni3Fe was adjacent to a Cu layer.
Technique to Make Nano Carbon Tubes Buried Inside Rubber Composite Visible Using Femtosecond Pulse Laser Ablation
Authors: Saito Yasunori , Kobayashi Fumitoshi , Takeda Toshikazu , Takeuchi Akiko , Nomura Akio , Endo Morinobu
Published: May 2005

A method to observe the dispersion structure of carbon nanotubes buried inside a molding composite is described in this communication. The idea is that by utilizing the difference in ablation temperature between the tubes and the composite material, only the composite material, which has a lower ablation temperature, is ablated and buried tubes appear. This was applied to a rubber composite mixed with vapor-grown carbon fibers. A 150-fs pulse laser was prepared as an ablation source. In the ablation images observed with a field-emission secondary electron microscope, linear tubes, clusters, and connections of the tubes could be easily found in their original state.
Comparison of the High-Temperature Deformation of Alumina-Zirconia and Alumina-Zirconia-Mullite Composites
Authors: Chen Tiandan , Mecartney Martha L.
Published: May 2005

An alumina-based ceramic codispersed with 15 vol% zirconia and 15 vol% mullite (AZM) was synthesized by reactive processing, and the creep behavior was compared to alumina with 30 vol% zirconia (AZ). Constant stress compressive creep behavior for AZM exhibited a stress exponent of 2 and an activation energy of 770 KJ/mol, while a similar stress exponent but lower activation energy of 660 KJ/mol was found for AZ. The strain rate of AZM, however, was more than twice that of the AZ under the same deformation conditions, indicating a better potential for superplastic shape forming.
Properties of Indium Molybdenum Oxide Films Fabricated Via High-Density Plasma Evaporation at Room Temperature
Authors: Sun Shi-Yao , Huang Jow-Lay , Lii Ding-Fwu
Published: May 2005

The goal of this study was to determine the scattering mechanisms and investigate the optoelectronic properties of indium molybdenum oxide (IMO) films. IMO films were deposited from an In2O3/MoO3 target with a weight ratio of 99/1, 95/5 and 90/10 via high-density plasma evaporation at room temperature. Based on the structural, electrical and optical properties, this study proposed that the neutral complex [(2Mo‧In)Oi″]x dominated at high doping content and high oxygen content, whereas ionized complex Mo‧‧‧In Oi″]‧ dominated at low doping level or low oxygen content. Uniform 99/1 IMO films with minimum resistivity of 3.56 × 10−4 Ω cm (corresponding to a mobility of 14.6 cm2V−1s−1 and carrier concentration of 14.3 × 1020 cm−3) and average visible transmittance of ∼85% were produced at an optimum oxygen content of ∼9%. Average optical transmittance exceeding 80% was demonstrated, and a structural change appeared at low oxygen contents.
Characterization of Anatase Nanocrystal-Precipitated Coatings From (100 − x)SiO2·xTiO2 Gel Films Via The Sol-Gel Process with Boiling Hot Water Treatment
Authors: Matsuda Atsunori , Matoda Tatsuo , Kogure Toshihiro , Tadanaga Kiyoharu , Minami Tsutomu , Tatsumisago Masahiro
Published: May 2005

Considerable amounts of anatase nanocrystals were formed on the (100 − x)SiO2·xTiO2 coatings with x of 16.5 and 25 mol% with boiling water treatment, whereas the formation of anatase nanocrystals was not clearly observed for the coatings with x of 50 and 75 mol%. Despite the lower TiO2 content, the coatings with x of 16.5 and 25 mol% showed higher concentration of Si–O–Ti bonds among the coatings. Thus, the hydrolysis of Si–O–Ti bonds and resultant sites should facilitate the nucleation and growth of anatase nanocrystals. High transparency, high photocatalytic activity, and superhydrophilicity were demonstrated for the anatase nanocrystals-precipitated coatings.
Refractive Index and Low Dispersion Properties of New Fluorophosphate Glasses Highly Doped with Rare-Earth Ions
Authors: Choi J.H. , Shi F.G. , Margaryan A. , Margaryan A.
Published: May 2005

A new series of 0.4MgF2–0.4BaF2–0.1Ba(PO3)2–0.1Al(PO3)3 glasses highly doped with rare-earth dopants (RE; Nd2O3, Er2O3, and Yb2O3) have been successfully developed for laser applications. Linear refractive index, dispersion properties including Abbe number (ν), dispersion parameter (A′, B′), electronic osciallator energy (Eo), and electronic osciallator strength (Ed) were determined as a function of RE dopants. The refractive index (nD=1.5872 to 1.6047) was found to linearly increase with dopant concentrations irrespective of types of rare earth dopants, while the Abbe number (ν = 65.7 to 68.8) and dispersion parameters including A′ (∼62), B′, Eo (13 ± 0.5 eV), and Ed (19 ± 1 eV) exhibit a concentration independence. It is remarkable that the refractive index of those new glasses increased with increasing RE dopant concentration, while the relatively large Abbe number of those glasses was independent of dopant concentration. The dependence of refractive index (n) on RE cations with high polarizabilities are discussed in terms of molar volume (Vm) and molar refractivity (Rm). Electronic oscillator strengths (Ed), the average electronic energy gap (Eo), and their respective dependence on RE dopant concentration were also investigated using linear refractive index (n) and Abbe number (ν). Those results suggest the present new series of glasses are strong candidates for stable laser hosts with extremely low dispersion.
Hollow Mesoporous Spheres with Cubic Pore Network as a Potential Carrier for Drug Storage and its In Vitro Release Kinetics
Authors: Zhu Yu-Fang , Shi Jian-Lin , Li Yong-Sheng , Chen Hang-Rong , Shen Wei-Hua , Dong Xiao-Ping
Published: May 2005

The hollow mesoporous spheres (HMS) with cubic pore network have been synthesized via a simple two-step method. Two drugs of different molecules size, Aspirin and Gentamicin, were tested by one simple adsorption process. Up to 336 mg Aspirin molecules can be stored in 1.0 g HMS, while Gentamicin molecules of much larger size are much more difficult to be introduced into the pore channels of HMS. The same results can be obtained by using MCM-48 and MCM-41 as comparative mesoporous carriers. The HMS shows significantly higher storage amount of Aspirin than conventional MCM-48 and MCM-41 due to its hollow core structure. The release process of HMS-Aspirin, MCM-48-Aspirin and MCM-41-Aspirin are found to have a sustained-release property and follow a Fickian diffusion mechanism. Moreover, the HMS is suitable for storage of drug molecules of much smaller size.
Optical characteristics of photo-curable methacryl-oligosiloxane nano hybrid thick films
Authors: Eo Young-Joo , Kim Jeong Hwan , Ko Ji Hoon , Bae Byeong-Soo
Published: May 2005

In this paper, we report the fabrication the methacryl-oligosiloxane nano hybrid films from 3-(trimethoxysilyl)propyl methacrylate (MPTS) and diphenylsilanediol (DPSD), and the investigation of the tuneability of the optical characteristics of the films through the compositional change. The viscosity of the methacryl-oligosiloxane nano hybrid resin was altered at 102 intervals by the compositional modification without any drastic changes in the reaction parameters, and thickness-controlled (from 11 to 150 μm) and uniformly coated (less than 1 nm root-mean-square roughness) films were obtained through a single coating step. The refractive indices were tunable from 1.506 to 1.543, depending on composition. On the other hand, the thermo-optic coefficients remained constant (−2 × 10−4/°C), independent of composition. Also, we demonstrated a thick (170 μm) photo pattern with a high aspect ratio (3:1). Methacryl-oligosiloxane nano hybrid materials can be promising candidates for the optical applications due to easy and wide tuneability of their optical parameters.
Free-standing microscale structures of nanocrystalline zirconia with biologically replicable three-dimensional shapes
Authors: Zhao Junping , Gaddis Christopher S. , Cai Ye , Sandhage Kenneth H.
Published: May 2005

Microscale zirconia structures with intricate three-dimensional (3D) shapes and nanoscale features were synthesized using diatom (single-celled algae) microshells as transient scaffolds. After exposure to a zirconium alkoxide-bearing solution and firing at 550–850 °C, silica-based diatom microshells were coated with a thin, continuous nanocrystalline zirconia layer. Predominantly tetragonal or monoclinic zirconia could be produced with appropriate heat treatments. Selective silica dissolution then yielded freestanding zirconia micro-assemblies that retained the microshell shape and fine features. Such hybrid (biological/synthetic chemical) processing may be used to mass-produce nanostructured micro-assemblies with a variety of 3D, biologically replicable shapes and tailored compositions for use in numerous applications.
Patterning of sapphire substrates via a solid state conversion process
Authors: Park Hyoungjoon , Chan Helen M. , Vinci Richard P.
Published: May 2005

Nanopatterned sapphire substrates offer the potential for improved performance of devices based on III-V nitrides, e.g., light-emitting diodes and laser diodes. Due to the chemical stability and hardness of sapphire, however, surface patterning is a time-consuming and expensive process. Therefore, a novel method was utilized, whereby a surface coating of Al was deposited on a sapphire substrate and patterned into an array of square mesas using e-beam lithography. The lateral dimensions of each mesa were approximately 400 × 400 nm, and the average height was approximately 100 nm. The metallic film was subsequently subjected to an oxidation treatment at 450 °C for 24 h (a heat treatment which had previously been shown to minimize hillock formation). For the second heat treatment, which is necessary to induce migration of the sapphire interface and hence achieve solid state conversion, a range of temperatures (800–1350 °C) was explored. Results showed that for a heat-treatment time of 1 h, pattern retention was achieved for annealing temperatures less than or equal to 1250 °C. Successful epitaxial conversion of the patterned mesas to sapphire was confirmed using electron backscatter diffraction.
Nucleation efficiency of erbium and ytterbium fluorides in transparent oxyfluoride glass-ceramics
Authors: Dantelle G. , Mortier M. , Vivien D. , Patriarche G.
Published: May 2005

Oxyfluoride glasses (GeO2–PbO–PbF2) doped with erbium and/or ytterbium fluorides were prepared. Highly transparent glass-ceramics, containing β–PbF2 nanocrystallites, were successfully obtained by controlled glass devitrification and were studied as they could lead to promising optical applications. To characterize the samples, differential thermal analysis, x-ray diffraction, and transmission electron microscopy were performed, revealing a variation of the crystallites size, the crystallites number and β–PbF2 crystallization temperature according to the doping ion. Indeed, the analyses indicated differences between erbium and ytterbium fluorides in promoting the crystallization of the fluoride phase. Although both fluorides act as seeds for β–PbF2 heterogeneous nucleation, erbium fluoride has higher nucleation efficiency than ytterbium fluoride and runs the nucleation process in co-doped samples. Energy dispersive x-ray microanalysis insured high rare-earth segregation into the crystallites, proving the formation of a solid solution Pb1−x−yErxYbyF2 +x+y, also confirmed by the unit cell parameter study.
Absence of one-to-one correspondence between elastoplastic properties and sharp-indentation load–penetration data
Authors: Alkorta J. , Martínez-Esnaola J.M. , Sevillano J. Gil
Published: May 2005

The connection between parameters that can be measured by means of instrumented indentation with the real mechanical properties has been a matter of discussion for several years. In fact, even hardness is not a readily measurable magnitude since the real contact area depends on both the elastic and plastic properties of the sample. Recently, Dao et al. [ Acta Mater49, 3899 (2001)] proposed a method based on numerical fittings to calculate by a forward-reverse algorithm the elastoplastic properties of a sample from the load-penetration curve obtained with a sharp indenter. This work will show, in contrast, that it is not possible to measure uniquely these mechanical properties of a sample in that way.
Time-dependent incipient plasticity in Ni3Al as observed in nanoindentation
Authors: Wo P.C. , Zuo L. , Ngan A.H.W.
Published: May 2005

The time-dependent characteristics of incipient plasticity in Ni3Al during nanoindentation in the subcritical load regime were investigated statistically. The waiting time for incipient plasticity to occur at constant load was found to follow a Poisson-like distribution, with the peak shifting toward zero holding time as the load increased and eventually becoming an exponential distribution when the load was close to a critical value. The observed distribution of the strain burst waiting time at loads smaller than the critical value was inconsistent with the picture in which dislocations nucleated homogeneously out of the perfect crystal. The kinetics for the occurrence of strain burst in this case is thought to be governed by the accumulative growth of nucleation precursors.
Two-dimensional ordered polymer hollow sphere and convex structure arrays based on monolayer pore films
Authors: Li Yue , Cai Weiping , Duan Guotao , Cao Bingqiang , Sun Fengqiang
Published: May 2005

A two-step replication strategy to two-dimensional ordered polymer hollow sphere and convex structure arrays is presented based on polystyrene colloidal monolayer and inverse opal made of FeO(OH). We can control formation of a small hole on top of the hollow spheres by the concentration of polymer precursors, which could be of importance in selective permeability, nutrient and drug deliver, biotechnology, and even study of black-body irradiation in micro or nano space. In addition, the fabrication strategy is suitable for the most soluble polymer materials, which can solidify when they are concentrated.
Interlayer structure of organically modified montmorillonites: Effect of surfactant loading
Authors: Zheng Qiang , Xu Bo , Song Yihu , Yang Hongmei , Pan Yi
Published: May 2005

The surfactant cetyltrimethylammonium ion (CTA+) was confined within the galleries of montmorillonite (MMT) to obtain a series of organo-montmorillonites (C16-MMTs) through an ion-exchange intercalation reaction. The C16-MMT formed a single precipitate layer when CTA+ loading was 18.3 wt% but stratified at high loadings. The conformational disorder increased with increasing CTA+ loading. The upper precipitate was characterized by a larger gallery height and a higher surfactant loading in comparison with lower precipitate. The confined methylene chains adopted a lateral monolayer with a small percentage of conformation freedoms at CTA+ loading of 18.3 wt%. The intercalated methylene chains were arranged either in a lateral monolayer or in a tilted interdigitated bilayer at CTA+ loading of 24.7 wt% while in either a tilted interdigitated bilayer or a lateral bilayer at high CTA+ loadings. The different arrangements of methylene chains intercalated in the MMT galleries are believed to be the reason for the stratification.
Electrical conductivity changes in bulk Sn, and eutectic Sn-Ag in bulk and in joints, from aging and thermal shock
Authors: Guo F. , Lee J.G. , Hogan T. , Subramanian K.N.
Published: May 2005

Electrical conductivity of electronic interconnects made with Sn-based solders undergo a significant amount of deterioration during service. Several factors, such as anisotropy of Sn, coefficient of thermal expansion mismatches between the entities that make up the joint, and growth of intermetallic compounds present within the solder and solder/substrate interface, may contribute to the damage accumulation during thermal excursions and cause deterioration of properties. This study dealing with effects of aging and thermal shock on electrical conductivity, carried out with bulk Sn, and eutectic Sn–Ag in bulk and joint configurations, is aimed at evaluating the roles of the above factors on the deterioration of electrical conductivity from these thermal excursions.
Effect of Au distribution in NiO/Au film on the ohmic contact formation to p-type GaN
Authors: Yang Jiin-Long , Chen J.S. , Chang S.J.
Published: May 2005

The distribution of Au and NiO in NiO/Au ohmic contact on p-type GaN was investigated in this work. Au (5 nm) films were deposited on p-GaN substrates by magnetron sputtering. Some of the Au films were preheated in N2 ambient to agglomerate into semi-connected structure (abbreviated by agg-Au); others were not preheated and remained the continuous (abbreviated by cont-Au). A NiO film (5 nm) was deposited on both types of samples, and all samples were subsequently annealed in N2 ambient at the temperatures ranging from 100 to 500 °C. The surface morphology, phases, and cross-sectional microstructure were investigated by scanning electron microscopy, glancing incident angle x-ray diffraction, and transmission electron microscopy. I-V measurement on the contacts indicates that only the 400 °C annealed NiO/cont-Au/p-GaN sample exhibits ohmic behavior and its specific contact resistance (ρc) is 8.93 × 10−3 Ω cm2. After annealing, Au and NiO contact to GaN individually in the NiO/agg-Au/p-GaN system while the Au and NiO layers become tangled in the NiO/cont-Au/p-GaN system. As a result, the highly tangled NiO-Au structure shall be the key to achieve the ohmic behavior for NiO/cont-Au/p-GaN system.
Large-scale synthesis of highly aligned nitrogen doped carbon nanotubes by injection chemical vapor deposition methods
Authors: Liu J. , Czerw R. , Carroll D.L.
Published: May 2005

In this study, we compare the effects of pyridine (C5H5N) and pyrimidine (C4H4N2) precursors, using ferrocene as a metal source, in the production of nitrogen containing multiwalled carbon nanotubes. Using standard chemical vapor deposition techniques, highly aligned mats of carbon-nitrogen carbon nanotube were synthesized. The maximum nitrogen concentration in these materials is between 1% and 2% when pyridine is used as the precursor and can be increased to 3.2% when pyrimidine is used as the precursor. However, the electronic structure of both materials, as determined using scanning tunneling spectroscopy, suggests that the nitrogen is incorporated into the nanotube lattice in the same way for both precursors.
Modeling conical indentation in homogeneous materials and in hard films on soft substrates
Authors: Ni Wangyang , Cheng Yang-Tse
Published: May 2005

Dimensional analysis and finite element modeling were conducted to examine conical indentation in homogeneous materials and in hard films on soft substrates. In this paper, the solid materials modeled follow the incremental theory of plasticity with a von-Mises yield surface. The validity of the Oliver–Pharr method was examined. It was found that, for hard films on soft substrates, the Oliver–Pharr method is applicable only when the indentation depth is less than 10% of the film thickness. A linear relationship between the ratio of hardness to reduced modulus and the ratio of reversible work to total work was observed for conical indentation in homogeneous materials and in hard films on soft substrates. This relationship can be used to analyze instrumented indentation experiments.
Chemical disorder effects in transport and magnetic properties of perovskite manganite
Authors: Biswas Subhayan , Chatterjee Sandip , Chatterjee P. , Nigam A.K. , De S.K.
Published: May 2005

The dependence of the novel properties observed in colossal magnetoresistance (CMR) materials, other than average ionic radii 〈rA〉 and Mn valence ratio (Mn3+/Mn4+), was investigated through examination of the transport and magnetic properties of Pr0.65(Ca0.7Sr0.3)0.35MnO3, La0.123Pr0.527(Ca0.8Sr0.2)0.35MnO3, and Pr0.65(Ca0.866Ba0.134)0.35MnO3. The average ionic radii 〈rA〉 and valence ratio of all three samples have been kept equal. The results of this investigation indicate a more intense role of the nature of individual A-site cation and the lattice mismatch. A remarkably large magnetoresistance of the order of 108 at moderate magnetic field has been observed for Ba-doped sample.
Preparation of nanostructured titanium carbonitride particles by Mg-thermal reduction
Authors: Lee D.W. , Ahn J.H. , Kim B.K.
Published: May 2005

Nanostructured titanium carbonitride (TiC0.5N0.5) powders were synthesized by a Mg-thermal reduction process. The evaporated liquid solution made from TiCl4 + ¼C2Cl4 reacted with liquid magnesium protected with nitrogen gas. The extremely fine titanium carbonitride particles of about 50 nm were successfully produced by the reaction of Ti and C atoms released from chloride reduction with liquid magnesium and nitrogen gas. After the reduction process, the residual phases of MgCl2 and the excess Mg were removed by mechanical vacuum conditions. To obtain the maximized stoichiometry of product, the process optimization with thermodynamic study was performed with various experimental parameters such as reaction temperatures and solution feeding rates.
Thermal expansion of the new perovskite substrates DyScO3 and GdScO3
Authors: Biegalski M.D. , Haeni J.H. , Trolier-McKinstry S. , Schlom D.G. , Brandle C.D. , Graitis A.J. Ven
Published: May 2005

The thermal expansion coefficients of DyScO3 and GdScO3 were determined from298 to 1273 K using x-ray diffraction. The average thermal expansion coefficients of DyScO3 and GdScO3 were 8.4 and 10.9 ppm/K, respectively. No phase transitions were detected over this range, though the orthorhombicity decreased with increasing temperature. These thermal expansion coefficients are similar to other oxide perovskites (e.g., BaTiO3 or SrTiO3), making these rare-earth scandates promising substrates for the growth of epitaxial thin films of many oxide perovskites that have similar lattice spacing and thermal expansion coefficients.
Raman and cathodoluminescence spectroscopies of magnesium-substituted hydroxyapatite powders
Authors: Sprio S. , Pezzotti G. , Celotti G. , Landi E. , Tampieri A.
Published: May 2005

Stoichiometric and magnesium-substituted synthetic hydroxyapatite (HA) powders with different Mg contents were characterized by Raman and cathodoluminescence (CL) spectroscopies. The substitution of Ca ions by Mg is presently of great interest because it may improve activity in the first stage of the bone remodeling process. In this paper, we show new evidence that CL spectroscopy has the capability to detect the presence of crystal defects, related to the presence of magnesium substituting calcium in Mg-doped HA powders. The dependence of CL spectra of stoichiometric and magnesium-doped HA powders on their chemical composition was studied, and the results are compared with Raman analysis and data previously collected by other analytical tools. All the investigated powders showed five distinct CL bands; moreover, in magnesium-doped HA, an additional band at higher energy was found. The intensity ratios between selected CL bands showed some relationships with the powder crystallinity and the estimated amount of magnesium both in the HA lattice and in the amorphous surface layer; moreover the band observed only in magnesium-substituted powders could be directly related to the amount of magnesium entered into the HA lattice. Such results can contribute to improve the knowledge of the crystallographic structure of Mg-substituted hydroxyapatite.
Synchrotron x-ray scattering of ZnO nanorods: Periodic ordering and lattice size
Authors: Zhu Zuoming , Andelman Tamar , Yin Ming , Chen Tsung-Liang , Ehrlich Steven N. , O'Brien Stephen P. , Osgood Richard M.
Published: May 2005

We demonstrate that synchrotron x-ray powder diffraction (XRD) is a powerful technique for studying the structure and self-organization of zinc-oxide nanostructures. Zinc-oxide nanorods were prepared by a solution-growth method that resulted in uniform nanorods with 2-nm diameter and lengths in the range 10–50 nm. These nanorods were structurally characterized by a combination of small-angle and wide-angle synchrotron XRD and transmission electron microscopy (TEM). Small-angle XRD and TEM were used to investigate nanorod self-assembly and the influence of surfactant/precursor ratio on self-assembly. Wide-angle XRD was used to study the evolution of nanorod growth as a function of synthesis time and surfactant/precursor ratio.
A new high-strength spinodal alloy
Authors: Hanna James A. , Baker Ian , Wittmann Markus W. , Munroe Paul R.
Published: May 2005

Preliminary investigations of a new high-strength alloy of composition Fe30Ni20Mn25Al25 (at.%) are described in this paper. The as-cast alloy consisted of a periodic two-phase microstructure of interconnected, ∼50-nm-wide rods with fully coherent {100} interfaces, strongly suggestive of formation by a B2 to [(B2 + body-centered cubic (bcc)] spinodal decomposition. The (Ni,Al)-rich B2 and (Fe,Mn)-rich bcc phases differed in lattice parameter by <0.5%. Hardness and yield strength of the as-cast alloy were found to be approximately 500 VPN and 1500 MPa, respectively, and increased by more than 50% after annealing at 550 °C for several days. (Fe,Mn)-rich precipitates with a β–Mn structure were observed in the annealed material.
Influence of the substrate bias on the size and thermal stability of grains in magnetron-sputtered nanocrystalline Ag films
Authors: Almtoft K. Pagh , Bøttiger J. , Chevallier J. , Schell N. , Martins R.M.S.
Published: May 2005

The nanostructural evolution during heat treatments of direct-current magnetron-sputtered Ag films, deposited at room temperature at different substrate bias voltages, was experimentally studied. A growth chamber equipped with a magnetron and Kapton windows for in-situ x-ray diffraction was mounted on a six-circle goniometer at a synchrotron beam line. Bragg–Brentano x-ray diffraction was used to monitor the (111) Bragg peak during thermal annealing of the Ag films. In addition, to investigate the 〈111〉 fiber texture, one-dimensional pole figures were measured ex situ. The thermal stability of the nanostructure was sensitively dependent on the substrate bias voltage. Increasing the bias voltage resulted in significantly lower rates of grain growth, which we ascribe mainly to the formation of Ar bubbles. Furthermore, the grain size in the as-deposited films decreased with increasing bias voltage while the width of the one-dimensional pole figures increased.
Deposition of inorganic bronze coatings over ceramic foams
Authors: Mann M. , Shter G.E. , Grader G.S.
Published: May 2005

A method for applying conductive inorganic tungsten bronze (NaxWO3) coatings over ceramic foams is presented. The general basis of bronze coating involves an intermediate layer between the ceramic surface and the redox external agent (liquid or gas phase). The intermediate layer is a multifunctional element and its function depends on the agents involved in redox reaction. The bronze film is formed either on the intermediate layer or in place of it. The initial melt included Na2WO4, WO3, and NaCl. The reticulated ceramic foams, made from pure alumina (Al2O3), were prepared by a standard impregnation method. In all depositions, the temperature was above the melting point of the Na2WO4/WO3 system. The effect of NaCl content on the final coating properties was investigated in the 10–40 mol% range. The best results were obtained with hydrogen reduction of 40% NaCl in the melt. The bronze crystals size in the coating was 0.8–1.6 μm. The bronze layer was continuous throughout the foam. The obtained coating has a bright yellow-gold color, consistent with a stoichiometric parameter value (x) of 0.85–0.95. The resistivity of coated foams decreased from above 12 Ω mm to below 1 Ω mm when the NaCl concentration in the melts increased from 10% to 40%, respectively, due to improved continuity of the bronze crystals. These highly conductive, bronze-coated alumina foams, can potentially serve as high-temperature electrodes in aggressive conditions.
Exfoliated single molecular layers of Mn0.8PS3and Cd0.8PS3
Authors: Frindt R.F. , Yang D. , Westreich P.
Published: May 2005

The layered compounds MnPS3and CdPS3were exfoliated to form single molecular layers of Mn0.8PS3and Cd0.8PS3in suspension in water by ion exchange. The x-ray diffraction patterns of the two single-layer suspensions showed profound differences in some of the Bragg peaks, and we demonstrated that the differences are not due to the quality or size of the single layers, but are caused by structure factor modulations of the Warren tail for two-dimensional systems. We also demonstrated that the Cd or Mn vacancies generated in the exfoliation process are not ordered at long range, in contrast to an earlier report of vacancy ordering on intercalated MnPS3.
Synthesis of Au nanoclusters supported upon a TiO2 nanotube array
Authors: Liu Xi , Jaramillo Thomas F. , Kolmakov Andrei , Baeck Sung-Hyeon , Moskovits Martin , Stucky Galen D. , McFarland Eric W.
Published: May 2005

Gold nanoclusters were successfully deposited in the interior of TiO2 nanotubes fabricated as ordered arrays. This approach is a useful fabrication platform for miniature planar fuel cells, gas sensors, and heterogeneous catalysts. A pressure impregnation process was used to inject the titania and Au precursors into mesoporous alumina. After thermal treatment, Au nanoclusters were well-dispersed on the interior walls of nanotubular TiO2. The TiO2 nanotubes were shown by x-ray diffraction to be entirely anatase. Transmission electron microscopy imaging confirmed that 80% of the Au particles were 4.1 nm ± 2.0 nm in diameter. This material exhibited catalytic CO oxidation activity at low temperatures.
Platelet interlocks are the key to toughness and strength in nacre
Authors: Katti Kalpana S. , Katti Dinesh R. , Pradhan Shashindra M. , Bhosle Arundhati
Published: May 2005

Nacre, the inner layer of mollusk shells is a composite made of platelets of mineral aragonitic calcium carbonate with a few weight percent organic material sandwiched in between. The organic and nanostructural nuances are often suggested to be the reason for the extreme toughness of nacre. Here we report the presence of interlocks between platelets of nacre from red abalone. We also report and show, using three-dimensional finite element modeling, that interlocks are the key mechanism for the high toughness and strength of nacre. The observed rotation between platelet layers, which were earlier reported as defects of structure, are necessary for the formation of interlocks.
Band structure and bulk modulus calculations of germanium carbide
Authors: Mahmood A. , Sansores L. Enrique
Published: May 2005

Band-structure calculations of germanium carbide (GeC) show that it is a new indirect wide band gap semiconducting material, which crystallizes in both cubic and hexagonal phases. Through the density functional and total-energy technique in the generalized gradient approximation, the two polytypes 3C and 2H of GeC were studied. According to our calculations, it is a hard material with a percentage of covalency of about 80–90%. Important energy gaps were determined. The bulk modulus, density of states, and charge density were calculated. For the bulk modulus calculations, Murnaghan’s equation of state was used under elastic deformation to measure hardness. Our calculations showed that this semiconducting material crystallizes in zincblend (Eg = 1.76 eV) and wurtzite (Eg = 2.5 eV) structures.
Complex formation by bismuth and boron with fullerene (C60): A reaction that opens up a novel route for synthesis of C60–inorganic hybrid composites
Authors: Banerjee D. , Sahoo R. , Debnath R. , Pradhan B. , Kundu T.
Published: May 2005

A dark red colored composite of C60 and (zinc, bismuth) borate glass was synthesized by solid-state reaction between C60 and frits of the glass at 650–700 °C in an argon atmosphere completely free from oxygen and moisture. An unusual change in color and the absorption spectrum of the glass upon composite formation with C60 indicated that the incorporated C60 underwent some sort of interaction with the glass. Such fullerene molecules bonded to relatively smaller units of bismuth-boron network, were extracted out by eluting a powdered sample with toluene. The composite itself and the toluene extract there of, were then characterized by ultraviolet–visible–near-infrared, infrared, and mass spectral studies. The results showed that the bismuth ions of the bismuth-boron network were bonded with the C60 cages through direct donation of their lone pair of electrons to the latter. The phenomenon of addition of boron to C60 via an “oxygen bridge,” which was observed in our earlier work, was also detected in this case. Studies on the nonlinear optical properties of the composite exhibited a moderate value of third order nonlinear susceptibility χ(3) (1.5 × 10−11 esu) and optical limiting properties of the composite. The result showed that the material had the prospect of being used in nonlinear optical devices.
Microstructure and wear resistance of Cuss-toughened Cr5Si3/CrSi metal silicide alloys
Authors: Yin Y.X. , Wang H.M.
Published: May 2005

Wear-resistant Cu-based solid-solution-toughened Cr5Si3/CrSi metal silicide alloy with a microstructure consisting of predominantly the dual-phase primary dendrites with a Cr5Si3 core encapsulated by CrSi phase and a small amount of interdendritic Cu-based solid solution (Cuss) was designed and fabricated by the laser melting process using Cr–Si–Cu elemental powder blends as the precursor materials. The microstructure of the Cuss-toughened Cr5Si3/CrSi metal silicide alloy was characterized by optical microscopy, powder x-ray diffraction, and energy dispersive spectroscopy. The Cuss-toughened silicide alloys have excellent wear resistance and low coefficient of friction under room temperature dry sliding wear test conditions with hardened 0.45% C carbon steel as the sliding–mating counterpart.
Grain boundary self-diffusion in Ni: Effect of boundary inclination
Authors: Mendelev Mikhail I. , Zhang Hao , Srolovitz David J.
Published: May 2005

We examined the influence of the boundary plane on grain-boundary diffusion in Ni through a series of molecular dynamics simulations. A series of 〈010〉 ∑5 tilt boundaries, including several high symmetry and low symmetry boundary planes, were considered. The self-diffusion coefficient is a strong function of boundary inclination at low temperature but is almost independent of inclination at high temperature. At all temperatures, the self-diffusion coefficients are low when at least one of the two grains has a normal with low Miller indices. The grain boundary self-diffusion coefficient is an Arrhenius function of temperature. The logarithm of the pre-exponential factor in the Arrhenius expression was shown to be nearly proportional to the activation energy for diffusion. The activation energy for self-diffusion in a (103) symmetric tilt boundary is much higher than in boundaries with other inclinations. We discuss the origin of the boundary plane density–diffusion coefficient correlation.
Response of Juvenile Rainbow Trout to Turbulence Produced by Prismatoidal Shapes
Authors: Smith David L. , Brannon Ernest L. , Odeh Mufeed
Published: May 2005

Water velocity is a common measure of habitat suitability for salmonids. It is often noted that salmonid focal positions occur in low‐velocity areas adjacent to high‐velocity ones. Such locations are associated with increased turbulence. Turbulence in the stream regions typically occupied by salmonids is produced by flow separation around large objects such as rocks or on the riverbed. Turbulence has also been shown to increase the energetic cost of swimming for salmonids. Despite the link between cover and turbulence, no measurements of turbulence at the focal positions of juvenile salmonids have been reported in the literature. We measured turbulence at the focal positions of juvenile rainbow trout Oncorhynchus mykiss in a laboratory flume and found that those focal positions were characterized by low turbulence levels across a range of average velocities. Fish occupied highly turbulent locations if excessive average velocities were present. Eddy size, measured as the autocorrelation function of the velocity time series at a point, did not result in obvious correlations with focal position establishment, but it was correlated with turbulence levels. Turbulence provided some additional discriminatory resolution, allowing differentiation of potential focal positions of equal average velocities but different turbulence levels. Thus, accounting for turbulence levels may allow more accurate prediction of focal positions.
Transient gene expression of beta-glucuronidase in citrus thin epicotyl transversal sections using particle bombardment
Authors: Bespalhok Filho João C. , Kobayashi Adilson K. , Pereira Luiz F. P. , Galvão Rafaelo M. , Vieira Luiz G. E.
Published: May 2005

Studies were carried out to optimize the conditions for transient gene expression through particle bombardment on Carrizo citrange (Citrus sinensis x Poncirus trifoliata) thin epicotyl sections. The best conditions for transient GUS expression were: M-25 tungsten particles, 1550 psi helium pressure, 9 cm distance between specimen and DNA/particle holder and culture of explants in a high osmolarity medium (0.2 M mannitol + 0.2 M sorbitol) 4 h prior and 20 h after bombardment. Under these conditions, an average of 102 blue spots per bombardment (20 explants/plate) were achieved. This protocol is currently being used for transformation of Carrizo citrange and sweet orange (Citrus sinensis).
Sensitivity of the amphipod Tiburonella viscana (Platyischnopidae) to K2CR2O7
Authors: Abessa Denis M. S. , Sousa Eduinetty C. P. M.
Published: May 2005

The sensitivity of Tiburonella viscana to K2Cr2O7 was evaluated from 18 water-only toxicity tests. The mean 48h-LC50 was estimated as 11.217 ± 3.768 mg/l, and the warning limits were calculated (mean LC50 ± 2 SD) as being between 3.68 and 18.75 mg/l. These results are baseline for the species and can be used for future comparisons in toxicity tests.
Effect of biological variables and capture period on the proximate composition and fatty acid composition of the dorsal muscle tissue of Hypophthalmus edentatus (Spix, 1829)
Authors: Oliveira Edna Regina Netto de , Agostinho Angelo Antonio , Matsushita Makoto
Published: May 2005

This study analyzed the chemical composition of the dorsal muscle tissue of Hypophthalmus edentatus, in particular, fatty acids of the lipidic fraction, and its relationship with the biological variables and the capture period. The average values for moisture, ash, protein and total lipids were 63.15, 1.11, 14.27 and 17.24%, respectively. In the lipidic fraction, 35 fatty acids were identified, the most abundant being: 16:0, 18:1omega9, 18:0, 16:1omega7, 18:3omega3, DHA and EPA. The totals of respectively saturated, monounsaturated and polyunsaturated fatty acids were 41.15, 35.30 and 23.88%. The PUFA/SFA ratio was equal to 0.68 and the omega3/ omega6 ratio equal to 1.98. The PCA demonstrated that the long chain PUFAs contributed positively to the formation of the first axis. The CCA showed some effects of the biological factors (weight, reproductive cycle, sex) and the capture period on the variation of total lipids and some fatty acids.
Shelf life of custard apple treated with 1-methylciclopropene: an antagonist to the ethylene action
Authors: Benassi Guilherme , Correa Guilherme Augusto Simões Francischini , Kluge Ricardo Alfredo , Jacomino Angelo Pedro
Published: May 2005

Custard apple (Annona squamosa L.) presents very short storage life at room temperature, in part due to heavy losses in firmness. This process is associated with the production and action of the hormone ethylene. In order to retard the ripening evolution in custard apple, fruits were treated with the competitive ethylene antagonist 1-methycyclopropene (1-MCP) at concentrations of 0, 30, 90, 270 or 810 nL L-1 for 12 h at 25ºC and then stored at 25ºC for four days. The soluble solids content (SSC), firmness and percentage of ripe fruits (firmness < 0.5kg) were determined during the experimental period. There were no differences among treatments as to the SSC. Fruits treated with 810 nL L-1 of 1-MCP showed higher firmness than the control fruits. Both , non-treated or treated fruits with 30 or 90 nL L-1 ripened faster than fruits treated with 1-MCP at higher concentrations.
Effect of the medium composition on formation of amylase by Bacillus sp
Authors: Santos Eliana de Oliveira. , Martins Meire Lelis Leal
Published: May 2005

Studies on the alpha -amylase synthesis was carried out with a moderately thermophilic, facultatively anaerobic Bacillus sp, isolated from soil samples. The cells were cultivated in a complex medium containing soluble starch or maltose as carbon source. The levels of the alpha -amylaseactivity detected in culture supernatants varied greatly with the type of carbon source used. Maltose, soluble starch and citrate stimulated alpha -amylaseformation. Addition of exogenous glucose repressed formation of alpha -amylase, demonstrating that a classical glucose effect was operative in this organism. The concentration of yeast extract was found to be important factor in the alpha -amylase synthesis bythe isolate.The activity of the enzyme increased between 2 and 5 g/L yeast extract concentration and then fell very rapidly beyond this point. The best concentration of peptone to alpha-amylase formation was found to be around 10g/L.