bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Reducing Sodium Chloride Concentration on the Results of Coulomb Electric Flux
Authors: Lu Ming , Yang Yi Bo , Li Jia Cheng , Guo Wen Ying
Published: April 2011

For reducing the consumption and pollution of the sodium chloride (NaCl), the effect of reducing the NaCl concentration on the result of coulomb electric flux were studied. Three typical proportions of concrete and mortar were used to investigate the effects on the results of coulomb electric flux when the NaCl solution is from 3.0% to 1.0% and 0.5% by mass, respectively. The coulomb electric flux for 6h and 18h and chloride ion penetration depth for18h were studied in this experiment. The results are as followings: (1) it is a little effect on the 6h and 18h coulomb electric flux value of concrete and mortar to use1.0% by mass NaCl solution instead of 3.0% by mass NaCl solution, and the error is less than 5%. It was suitable to use 1.0% NaCl solution by mass. (2)The influence of water-binder ratio (W/B) and test time on coulomb electric flux is related to the porosity and pore connectivity. The lower the W/B, the smaller the coulomb electric flux is; the ratio of coulomb electric flux of 18h to that of 6h was about 2.8 ~ 3.0, and the ratio increases with the water-binder ratio. (3) It is not suitable to use the test results of mortar specimens to count the results of concrete specimens, but can use the results of mortar specimens to estimate the anti-chloride performance of different binder. The suggested test method is that using 0.5% or 1.0% by mass NaCl solution, water-binder ratio is 0.38 and binder-sand ratio is between 1:1.5 and 1:1.8. The best binder-sand ratio and other test parameter need to be determined by more research.
Effect of Oxygen Ions Diffusion on Steel Corrosion in Concrete
Authors: Bai Jun Ying , Ai Hong Mei , Lu Pu Guang
Published: April 2011

Oxygen ions are the necessary condition for steel corrosion which occurs when the steel’s passive film is destroyed. Oxygen ions diffusion directly influences steel corrosion rate. The paper, starting from the steel corrosion mechanism, summarized the testing technology and the research progress of oxygen ions diffusion coefficient, analyzed the influencing factors and studied further the effect of oxygen ions diffusion on steel corrosion in concrete. The testing technology of oxygen ion diffusion coefficient is combined with the testing method of steel corrosion rate, and the relationship between oxygen ions diffusion coefficient and steel corrosion rate are established.
The Water Extraction Method to Evaluate the Content of Soluble Alkali in Mortar
Authors: Pu Qi , Jiang Lin Hua , Xu Jin Xia , Chu Hong Qiang , Xu Yi
Published: April 2011

A new method was presented to study the content of the soluble alkali in mortar. The method was based on mixing powdered sample with distilled water with two water-solid ratios and measur-ing the pH of the suspension. According to the measurement result of the suspension, the content of soluble alkali in mortar was calculated. The parameters such as water-solid ratio and measuring ac-curacy which affected the calculated result were investigated. The calculated result of the content of soluble alkali in mortar was compared with the result of flame photometry. The calculation was in good agreement with the result of flame photometry.
Preparation and Properties of Heat Durable N:TiO2 Antibacterial Nano-Ceramics
Authors: Zhang Guang Lei , Qin Guo Qiang , Yang Jin Hui
Published: April 2011

As a new type of environmental pollutant reduction technology, semiconductor nano-TiO2 photocatalytic technology has attracted widely attention in recent years. In order to overcome the disadvantage of pure TiO2 photocatalyst in lower utilization of solar energy and heat durability, the sol-gel method followed by co-precipitation method was employed to synthesize ZnO packed N:TiO2 nano-powders, and EDS, XRD, SEM, UV-VIS analysis as well as detection of degradation rate of methyl orange were used to characterize the composition, phase, micro-morphology and the photocatalytic properties of the nano-powders. The results showed that the excitation band of the composite powders extended from the UV region to the visible light zone, indicating a remarkable improvement of the photocatalytic activities of TiO2 composite powders under both visible light and UV irradiation. After calcined at 950°C, the composite powders still remained mixed crystal structures of anatase and rutile phases with the diameter of the composite powder being about 60nm. After coated with ZnO, the heat durability of the N-doped nano-TiO2 composite powders was significantly improved 250°C.
Diffusion of Multi-Ionic Species in Recycled Aggregate Concrete
Authors: Damrongwiriyanupap Nattapong , Liang Yu Chang , Xi Yun Ping
Published: April 2011

In recent years, recycled aggregate concrete has been used in reinforced concrete structures. Concrete structures exposed to chloride environment often encountera premature deterioration due to corrosion of steel reinforcement. In order to avoid unplanned maintenances or repairs, it is necessary to develop a reliable prediction model for the chloride diffusion in concrete. The basic formulation of the transport theory will be presented first and then its application to Recycled Aggregate Concrete (RAC) will follow. Chloride diffusion in RAC is different from the diffusion in regular concrete, because the material parameters of RAC such as chloride diffusion coefficient are different from those of regular concrete. In this paper, a multi-scale and multi-phase model will be developed to characterize theinternal structure of the recycled aggregate with a layer of residual cement paste on the surface of natural aggregate and another layer of surface treatment material on the surface of the residual cement paste. The multi-scale and multi-phase model will also be used to characterize the chloride diffusion coefficient of RAC. The numerical analysis of the diffusion equations is performed by using finite element method.
Study on Slag-Based Geopolymer Hydration Process
Authors: Wang Qing , Ding Zhao Yang , Zhang J. , Qiu L.G. , Sui Zhi Tong
Published: April 2011

As environment-friendly or green cement, the geopolymer cementitious material has high early age strength, good volume stability and durability. In this paper, the mechanical properties of geopolymer hydrates at different hydrating ages were studied by changing the oxide content of raw material. The results showed that the chemical-combined water kept increasing as hydrating age prolonged, and reached the maximum at n(SiO2)/n(Al2O3)=3.9, n(H2O)/n(SiO2)=2.3 and n(Na2O)/n(Al2O3)=0.6. With the development of hydration, the pH value of geopolymer paste showed fluctuated: pH value kept increased at the age of 1d～3d, then decreased at the age of 3d～7d, at the age of 7d～14d the pH value increased again and at last it remained constant at the age of 14d～28d. 28d compressive strength of geopolymer paste reached the maximum as chemical-combined water content was 0.09g～0.10g and pH value was 10～11.
Production of Magnesium Titanate-Based Nanocomposites via Mechanochemical Method
Authors: Fahami Abbas , Ebrahimi-Kahrizsangi Reza , Nasiri-Tabrizi Bahman
Published: April 2011

The mechanical activation was employed to study the phase evolution of the Mg–TiO2–CaHPO4–CaO nanocrystalline system. The powders mixture with certain weight percent was grinded. Thermal annealing process at 650°C, 900°C and 1100°C temperatures resulted in generation of different compounds like MgTiO3/MgO/Hydroxyapatite (HAp) and MgTiO3/MgO/β-TCP and MgTiO3/Mg2TiO4/MgO/β-TCP, respectively. The compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The consequences of XRD analysis revealed that by increasing temperature, some composites with different morphological and structural features were detected. Beside, due to decomposing of HAp around 800°C, HAp converted to whitlockite (β-TCP) with growth of temperature. According to SEM and TEM observations, it was found that the synthesized powder contained large agglomerates which significant content of finer particles and agglomerates with spherical morphology. Because magnesium titanates based dielectric materials are useful for electrical applications, the electrical property of HAp has been proved, and the incorporation of these materials could result in new nanocrystalline dielectric materials.
Biomechanical Characterization of a Cervical Corporectomy Using Porcine Specimens, Following an Experimental Approach
Authors: Hernández-Gómez Luis Héctor , Beltrán-Fernández Juan Alfonso , Urriolagoitia-Calderón G. , González-Rebatú A. , Galán Vera M. M. , Urriolagoitia-Sosa G.
Published: April 2011

In this paper, the interaction among cervical vertebrae, a cervical plate and a bone graft implant, which is developed in a Corporectomy, is analyzed in an experimental form. In the case of specific damaged vertebra, its replacement is one of the alternative solutions. However, the displacement between the vertebral adjacent facets and the bone graft is a critical parameter which has to be evaluated in order to ensure the stability of the spine. Besides, it is advisable to make a precise evaluation of the structural integrity of the arrangement. For this study, porcine cervical vertebrae (C3-C5) were instrumented in order to replace a damaged C4 vertebra. This arrangement was tested under compression. The experimental observations were complemented with a numerical model. The displacements between the vertebral facets and the bone graft were measured. They are lower than 3 mm in order to develop stability in the spine. Besides, the proposed arrangement has structural integrity and the surgical procedure is simplified, as no wires are used.
Study of the Properties of Al2O3-Ag Nanopowders Produced by an Innovative Thermal Decomposition–Reduction and Silver Nitrate Reduction Methods
Authors: Jastrzębska Agnieszka Maria , Kunicki Antoni Ryszard , Olszyna Andrzej Roman
Published: April 2011

The present study is concerned with the morphology, physical properties and biocidal activity of Al2O3-Ag nanopowders produced by two methods: thermal decomposition-reduction and the silver nitrate reduction. The innovative method of thermal decomposition-reduction has been described in our earlier publication and is protected by our patent application, whereas the silver nitrate reduction method is commonly used in industry at the present. The nano-powders produced by these two methods differ considerably from one another in terms of their morphology and physical properties. The proposed method of thermal decomposition-reduction gives Al2O3-Ag nano-powders which are not only much less agglomerated with the average agglomerate sizes below 1 µm, but also the average size of their particles is considerably smaller (below 60 nm). Moreover, their specific surface is larger (above 200 m2g-1) and they have good bactericidal and fungicidal properties.
Experimental Characterization of Hydrogen Embrittlement in API 5L X60 and API 5L X80 Steels
Authors: Araújo Bruno Allison , Travassos Gabriel Dias , Silva Antonio Almeida , Vilar Eudésio Oliveira , Carrasco Jorge Palma , de Araújo Carlos José
Published: April 2011

The present work aims to study the hydrogen embrittlement process in API 5L X60 and API 5L X80 steels. The tests were performed using two kinds of hydrogen sources to work with two conditions of hydrogen damage: environmental hydrogen embrittlement and internal hydrogen embrittlement. The mechanical behavior of API 5L X60 and API 5L X80 steels in tensile tests, with and without hydrogen, were studied. Under environmental hydrogen embrittlement conditions, the API 5L X60 steel presented a softening process observed by the decrease in yield strength and increase in its deformation. The API 5L X80 steel was more susceptible to the phenomenon due the deformation decrease of hydrogenated samples. In notched samples, both steels were susceptible to embrittlement as shown by the decrease in elongation. Under internal hydrogen embrittlement conditions, in both steels the changes in deformation were significant and can be attributed to changes in the hydrogen trapping due to the hydrogenation process used, the chemical composition and microstructure. It was observed that the fracture surface morphology of hydrogenated samples of both steels was ductile by microvoids coalescence, and that the distribution of dimples per unit area was higher in the API 5L X60 steel. It can be concluded, as reported in the literature, that the reversible hydrogen trapping observable in environmental hydrogen embrittlement is more damaging than irreversible hydrogen trapping, observable in internal hydrogen embrittlement.
Corrosion Monitoring in Marine Environment Using Wavelet Description
Authors: Kuzmanić Ivca , Vujović Igor , Šoda Joško
Published: April 2011

The paper proposes a method, the so-called wavelet description, for corrosion monitoring in marine environment which is based on taking the energy difference contained in energy from coefficients derived by applying complex wavelet transforms. Then the rms value of coefficients has been accounted that form an illumination-independent energy representation of corroded and corrosion-free parts. The robustness on illumination variations has been achieved because by applying the proposed algorithm the energy representation enables reduction of the noise, since getting the difference of two subsequent images leaves only greater values of differences.
Comparative Analysis of Vaporization Rates of 5456 Aluminum Alloying Elements during CO2 Laser Welding
Authors: Achebo Joseph I. , Oghoore O.
Published: April 2011

In this paper, the vaporization rates of Mg2+ and Al+ alloying elements of a 5456 aluminum plate were investigated using the CO2 laser welding process. The models proposed and used by Block-Bolten and Eagar in 1984 and Zhao and DebRoy in 2003 were applied with experimental results generated from this study. The vaporization rate of Mg2+ ions and Al+ ions using the equations proposed by Block-Bolten and Eagar gave 8.76 μgs-1cm-2 and 0.0465 μgs-1cm-2 respectively, whereas the equation proposed by Zhao and DebRoy gave 6.7 μgs-1cm-2 and 0.016 μgs-1cm-2 respectively. These values are within the reported values obtained by Block-Bolten and Eagar (1984). The heat transfer coefficient for Mg2+ and Al+ ions were also obtained. The vapor bubble radius including the surface tension and buoyancy forces were examined. The evaporative power and energy losses as a result of these bubbles’ collapse were calculated. The paper clearly shows the comparative analysis of alloying elements’ vaporization process in the aluminum metal heating process.
Electromagnetic Characteristics of Iron-Based Microwave Absorbing Materials
Authors: Yang R.B. , Juan K.Y. , Tsay Chien Yie , Liang W.F. , Lin Chung Kwei
Published: April 2011

Nowadays human are exposed to an environment filling with electromagnetic waves over a wide frequency range. The electromagnetic properties of microwave absorbing materials plays an important role in the performance of civilian electromagnetic interference (EMI) shielding at low frequency range and military stealth technology at high frequency one. The electromagnetic properties include complex permittivity and permeability and its combination determines the electromagnetic wave absorption ability of a material. Complex permittivity and permeability can be measured by three different methods, i.e., free-space method, coaxial/waveguide method, and resonant cavity perturbation method. The first one requires a large space, expensive equipment, and not suitable for academic usage. In the present study, using coaxial/waveguide and resonant cavity perturbation methods, electromagnetic characteristics of iron-based microwave absorbing materials will be obtained and its microwave absorption performance will be investigated. In addition, a comparison between the measurements by these two methods will be addressed.
Fabrication of Complex-Shaped SiC Parts Based on Polymerization -Induced Phase Separation and Pyrolysis Technique
Authors: Qiao Guan Jun , Xu Shun Jian , Li Jie , Liu Gui Wu
Published: April 2011

A route based on a technique of polymerization - induced phase separation and pyrolysis (PIPSP) has been developed to fabricate complex-shaped SiC parts. The capability of this process to produce complex component shapes has been demonstrated, and corresponding reactive mechanisms have been also discussed. Three types of porous carbon preforms, i.e. mesoporous carbon monoliths (MCMs), hierarchical porous carbon monoliths (HCMs) and porous carbon foam (PCFs) were obtained, which has different pore size distributions. The pore structures of the preforms can be controlled through changing starting mixture composition and polymerizing conditions. The apparent porosity of the preform was changed from 19.9 to 60%, which was a key parameter to obtain dense SiC parts. After reactive infiltration of the preform with Si, the SiC parts were obtained. Geometry of SiC parts were controlled by molds. The dimension shrinkage of SiC parts was less than 3% before/after siliconization and no distortion occurred. Compared with other molds assistance route, the wax mold assistance route was a most potential technique to fabricate SiC parts industrially because of its suitable forming precision, recycled mold materials and low-cost. The mechanism of the reactive infiltration of MCMs was different from that of the reactive infiltration of preforms with bigger pore size, i.e. the pore channels of MCMs were restructured at transitional stage of reaction.
Fabrication of SiC and SiC/ Aluminum-Silicon Composites from Rattan Charcoal
Authors: Lin Yung Jen , Lo Xiao Wen
Published: April 2011

Bio-structured carbon was obtained by carbonization of rattan in Ar. Then, the charcoal was reacted with Si at 1500 °C to form SiC. It was also reacted with Si and 2024 aluminum alloy at 1400°C for various times to form composites. The results showed that the SiC was beta phase and had the structure of rattan. SiC whiskers were also found on the inner surfaces of the pore channels (vessels) of rattan structure. The bulk density of the porous SiC was 1.5 g/cm3 and its open porosity was 44%. On the other hand, the charcoal embedded in Si powder and 2024 alloy was converted into SiC/aluminum-silicon composite after heat treatment. The charcoal was reacted to form SiC first. Then, Al-Si alloy infiltrated into the pores of the porous SiC to form composites. When the alloy composition was Al-20 at% Si, the composite obtained after 5 hours of reaction had bulk density of 2.3 g/cm3, open porosity of 19%, compressive strength of 316 MPa and bending strength of 138 MPa.
Surface-Texturing of Single-Crystalline Silicon Wafers
Authors: Lin Jian Yang , Chang Pai Yu , Hu Chih Kai , Wu Bin Hon
Published: April 2011

In this work, alkaline-based anisotropic etchants, tetramethylammonium hydroxide (TMAH) and potassium hydroxide (KOH)/isopropyl alcohol (IPA) solutions, have been used for the surface texturing of the single-crystalline silicon wafers used for solar cells. The pyramid morphology produced by the surface texturing can reduce the surface reflection of the incident light and increase the light absorption so that the efficiency of the solar cells can be increased. The experimental data shows that the optimized surface texturing has been obtained with 5 wt. % TMAH anisotropic etching at 80 °C. The surface reflectance of the polished front surface can be reduced to 17 % and the surface reflectance of the unpolished backside surface can be reduced to 3 %, respectively. This result shows that the anisotropic etching can effectively reduce the surface reflectance. While for the surface texturing with KOH/IPA mixture, the front surface reflectance can only be reduced to 35 % and the backside surface reflectance can only be reduced to 5 %, respectively. Besides, debris of Si nano-crystals exists around the pyramid base area when texturing with the KOH/IPA mixture.
Resistive Oxygen Gas Sensing Behavior of Zirconia-Doped Ceria
Authors: Chang Kai Hsin , Liu Chin Lung , Chan Ya Ting , Tsai Wen Cheieh , Chen Chin Yi
Published: April 2011

In the present study, nanocrystalline ceria powder and 10 mol% zirconia-doped ceria (10ZDC) powder were prepared by co-precipitation method from cerium nitrate and zirconium nitrate precursors. The resulting particles with irregular shapes were printed onto alumina substrate for the investigation of oxygen gas sensing behavior. The coating morphology of 10ZDC with a network structure revealed a better connection enhancing the sensing properties. Zirconia doping tended to inhibit the grain growth and decrease the lattice constant of ceria. Such effects may improve the electrical conductivity of 10ZDC under different oxygen partial pressures and shorten the response time of 10ZDC to the change of oxygen partial pressure.
AZ80 Mg Alloy Synthesized by Spray Forming and its Extrudability
Authors: Wang Shih Han , Tsao Chi Y.A.
Published: April 2011

Magnesium materials are gaining an increasing interest especially in transportation industries. The goals are the reduction of fuel and the reduction of the green house gas CO2. To achieve these goals, the weight of vehicles must be reduced. Compared to Al based materials, Mg based materials offer the possibility of saving up to 30% in weight. Unfortunately the latter suffer from poor workability. The workability of AZ91B has been proven to be improved significantly by employing the rapid solidification process, Spray Forming. In this study, the AZ80 Mg alloy was synthesized via Spray Forming process. The microstructures were characterized and compared with conventionally cast materials. The workability of the spray-formed AZ80 Mg alloys was studies via a simple extrusion process. The effects of the extrusion speed and temperature on the workability were investigated.
Microstructures and Mechanical Properties of Dissimilar Metal Weld A508/52M/316L Used in Nuclear Power Plants
Authors: Fang Ke Wei , Li Guan Jun , Li Guang Fu , Yang Wu , Zhang Mao Long , Sun Zhi Yuan
Published: April 2011

The microstructures and mechanical properties of a dissimilar metal weld A508/52M/316L used in the primary water system of pressurized water reactor (PWR) nuclear power plants were investigated. The weld exhibits complicated microstructures, with significant change around the interfaces A508/52M and 52M/316L. The variations of main elements in 52M weld metal are greater than those in the A508 and 316L, with significant changes in the zones closed to the interfaces. The bulk 52M weld metal has higher and more uneven hardness than both of the base metals A508 and 316L. The HAZ of A508 exhibits the highest hardness value in the weld. The area around the A508/52M interface is the most weak part for stress corrosion cracking (SCC) resistance of the weld in simulated PWR primary water at 290°C. SCC was only found in the specimens tested at +200mV(SHE) but not in those tested at both -780mV and Ecorr (about -500mV).
Microstructure Evolution of a Fine Grain Al-50wt%Si Alloy Fabricated by High Energy Milling
Authors: Wang Fei , Wang Ya Ping
Published: April 2011

Microstructure evolution of high energy milled Al-50wt%Si alloy during heat treatment at different temperature was studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that the size of the alloy powders decreased with increasing milling time. The observable coarsening of Si particles was not seen below 730°C in the high energy milled alloy, whereas, for the alloy prepared by mixed Al and Si powders, the grain growth occurred at 660°C. The activation energy for the grain growth of Si particles in the high energy milled alloy was determined as about 244 kJ/mol by the differential scanning calorimetry (DSC) data analysis. The size of Si particles in the hot pressed Al-50wt%Si alloy prepared by high energy milled powders was 5-30 m at 700°C, which was significantly reduced compared to that of the original Si powders. Thermal diffusivity of the hot pressed Al-50wt%Si alloy was 55 mm2/s at room temperature which was obtained by laser method.
Solid Welding Conditions for Seam and Hollow Extrusion Process of 7075 Aluminum Alloy
Authors: Hsu Quang Cherng , Kuo Kun Hong , Hsu Chi Peng
Published: April 2011

Direct extrusion by porthole – bridge die configuration has been successfully used to fabricate products with hollow cross sections for 6000 series aluminum alloys. However, if for 7000 series aluminum alloys, this situation alerts since different alloy composition such as Cu causing hollow extrusion failed due to not enough welding strength in seam. In order to determine the solid welding conditions during hollow extrusion with porthole die structure for high strength aluminum alloy, an easy tooling configuration has been designed. The proposed method is easy and cheap because there is no necessary to conduct experiment in controlled environment such as in vacuum chamber of Gleeble test or in a protective atmosphere. A seam and hollow extrusion for square tube has been conducted to obtain the welding strength comparison to the proposed solid welding method which shows good agreement.
Study on the Modification of TiN and CrN Binary Films
Authors: Zhou Tao , Nie Pu Lin , Cai Xun
Published: April 2011

With the development of modern science and technology, the elements such as Al, Si, Mo, C, B will be doped into the TiN and CrN binary films to improve their properties. In this work, a series of Ti-X-N and Cr-X-N films were prepared under the various N2 partial pressures，bias voltages and substrate temperatures by reactive magnetron sputtering using the mosaic target and multi-targets systems. The composition, microstructure, mechanical properties and thermal stability of the films were investigated using EDS, XRD, XPS, AFM, nano-indentation, scratch and thermal stability test. The results indicated that the doping element content, microstructure and mechanical properties of the films can be easily regulated through the deposition parameters, such as the N2 partial pressure，bias voltages and so on. The superhard Ti-Si-N and Ti-Al-N films with the nanohardness of more than 40GPa can be achieved, especially when the lower N2 partial pressure is used.
Influence of Co Moment on Magnetic Properties of Co2Sm2W3O14 Tungstate
Authors: Urbanowicz P. , Tomaszewicz Elzbieta , Groń Tadeusz , Duda Henryk , Pacyna Andrzej W. , Mydlarz Tadeusz , Fuks H. , Kaczmarek Slawomir M.
Published: April 2011

The Co2Sm2W3O14 compound crystallizes in the orthorhombic system, and melts congruently at 1443 K. The magnetic measurements showed that Co2Sm2W3O14 is a paramagnet in the temperature range 4.2-225 K showing both the residual magnetic interactions since the paramagnetic Curie-Weiss temperature   0 and the uncompensated temperature independent contributions of magnetic susceptibility since 0  0. The Brillouin fit of the Landé factor revealed an increase of the orbital contribution to the total magnetic moment of the compound what seems to be responsible for its hard and spontaneous magnetization at low temperatures.
Magnetic Properties of Fe-Nb-B-Re (Re=Y, Gd) Bulk Nanocrystalline Alloys
Authors: Chrobak Artur , Haneczok G. , Chełkowska Grażyna , Bajorek Anna , Kansy Jerzy , Hanc Artur
Published: April 2011

Magnetic properties of the Fe76.2Nb5.7B13.3Gd4.8, Fe69.6Nb5.2B12.2Gd13, Fe76.2Nb5.7B13.3Y4.8, Fe69.6Nb5.2B12.2Y13 bulk nanocrystalline alloys (mould casting technique) are presented and discussed. Measurements were carried out by the means of SQUID magnetometer (temperature range 2 K – 400 K, field up to 7 T) and magnetic balance (temperatures up to 1100 K). Microstructure was studied by the Mössbauer spectroscopy at room temperature. It was shown that the samples are nonocrystalline with α-Fe and different Fe-B, Y/Gd-Fe or Y/Gd-Fe-B compounds. The preparation method as well as the Gd addition causes a magnetic hardening of the studied alloys.
Disorder-Sensitive Superconductivity and Bonding Network in the Iron-Silicide Superconductor Lu2Fe3Si5
Authors: Okuyama H. , Takase K. , Takano Yoshiki , Watanabe Tadataka , Yoshida Fumiko , Moriyoshi Chikako , Kuroiwa Yoshihiro
Published: April 2011

We performed experimentally the electron-density mapping on the crystal structure of the iron-based superconductor Lu2Fe3Si5 which revealed the Fe-Si covalent-bonding network with the fully ionized Lu-sites. And, for Lu2Fe3Si5, we investigated the effect of Fe- and Si-site substitutions on the superconductivity. The Fe-site-substitution study revealed that, in addition to the disorder-sensitive superconductivity, the additionally-provided 3d electrons or holes tend to be itinerant rather than localized. Taking into account that the localized magnetic moments introduced on the Lu-sites are inactive as magnetic pair breakers, the present results suggest that, in Lu2Fe3Si5, the Fe-Si bonding network should be the playground for the exotic superconductivity which is characterized by the sign-reversed superconducting gap function.
Anisotropy of Photoluminescence in Layered Semiconductors ReS2 and ReS2:Au
Authors: Lin Der Yuh , Huang Tung Pai , Wu Fan Lei , Lin Chih Ming , Huang Ying Sheng , Tiong Kwong Kau
Published: April 2011

The optical anisotropy properties of rhenium disulphide (ReS2) and Au-doped rhenium disulphide (ReS2:Au) have been investigated by polarization-dependent photoluminescence (PL). Because the excitonic transitions show strong polarization dependences in the near-infrared region, we used polarization-dependent PL measurements in the range between 0° and 180° to characterize the unique polarization property of ReS2 and ReS2:Au, and identify the origin of the excitonic transitions. It was observed that the variation in the amplitude of PL excitonic transitions with different polarization characteristics follows the Malus rule. In comparison with the undoped ReS2, the PL spectra of Au-doped sample show not only the main excitonic transitions near the direct band edge but also some extra transitions owing to the doping effects.
Amorphous Shell Formation on the Iron Particles during Mechanosynthesis in Fe2O3/Fe/(Ga,Al) Mixtures
Authors: Kiseleva Tatiana Yu. , Novakova Alla A. , Gendler Tatiana S.
Published: April 2011

Amorphous shell formation on the Fe-particles surface in course of mechanochemical nanocomposite synthesis in Fe2O3+Fe, Fe2O3+Al+Fe, and Fe2O3+Ga+Fe powders mixtures have been observed by Mössbauer spectroscopy and magnetic measurements.
A Model for the Growth of Fe2B Layers on a Steel Substrate: Effect of the Surface Boron Concentration
Authors: Keddam Mourad , Chegroune Redoune
Published: April 2011

The growth kinetics of Fe2B layers formed at the surface of AISI 1018 was simulated. The paste-boriding (with a paste thickness of 4 mm) was applied to produce the Fe2B phase at the material surface; considering four temperatures (1123, 1173, 1223 and 1273 K) for 2, 4, 5, 6 and 8 h. The suggested model was based on the mass balance equation at the (Fe2B /substrate) interface. As a fitting parameter of the model, the surface boron concentration (12.16 wt. %B) was obtained in order to predict with a good agreement the experimental parabolic growth constants at the (Fe2B /substrate) interface derived from the literature. An expression of the parabolic growth constant at the (Fe2B /substrate) interface was obtained as a function of the two parameters: and . In addition, a relationship of the Fe2B layer thickness was also deduced that showed a good concordance with the experimental results from the literature.
Successive Magnetic Transitions on Single Crystal Cu3(OH)4SO4
Authors: Hara Shigeo , Sato Hirohiko
Published: April 2011

Cu3(OH)4SO4, a parallel Cu (S = 1/2) triple chain system, is an interesting magnet because an idle-spin state is expected on the central chain. We have succeeded in growing high-quality single crystals of Cu3SO4(OH)4 by a hydrothermal method from copper sulfate and copper hydroxide. We measured field dependence of the magnetization on a single crystal under various directions of magnetic field up to 7 T. We found a clear magnetic anisotropy and confirmed that the existence of the easy axis lies in the ac plane. Under magnetic fields parallel to the c-axis and the a-axis at 2.5 K, we observed field-induced successive magnetic transitions. In the case of B//c, two anomalies of the magnetization are observed at 0.9 and 1.7 T, On the other hand, there are broad anomalies in the magnetization at 3.7 and 5.6 T in the case of B//a.
Single-Crystal Synthesis and Structure Refinement of Na0.44MnO2
Authors: Akimoto Junji , Hayakawa Hiroshi , Kijima Norihito , Awaka Junji , Funabiki Fuji
Published: April 2011

Single crystals of Na0.44MnO2 (=Na4Mn9O18) have been synthesized by a flux method at 1173 K for the first time. The crystal structure of Na0.44MnO2 has been refined by single-crystal X-ray diffraction method. The framework structure consists of double and triple rutile-type chains of edge-sharing MnO6 octahedra and a single chain of edge-sharing MnO5. The Mn-O bond distance and bond valence analyses revealed the manganese valence Mn3+/Mn4+ ordering in the Na0.44MnO2 structure.
A Study of Exchange Interactions in R(FeCo)11TiCy (R=Y or Pr) Compounds
Authors: Cizmas Corneliu Bazil , Bessais Lotfi
Published: April 2011

The exchange interactions in PrFe11-xCoxTiCy (x=0÷2, y≤1), are analyzed on the basis of the structural and magnetic properties of polycrystalline samples. The magnetic properties of polycrystalline isomorphous compounds YFe11-xCoxTiCy have been used in order to determine the T (T=Fe+Co) sub-lattice contributions, such as the T sub-lattice mean magnetic moment and the T-T exchange interaction strength. The exchange coupling parameters JTT, JRT and the recurrent molecular field coefficients nTT, nRT have been calculated in the molecular field approximation (MCA). The effects of Co content and carbonation on the R-T (T=Fe+Co) and on the T-T exchange interactions are analyzed.
Role of Transition Elements in Stability of Magnesium Hydride: A Review of Theoretical Studies
Authors: Shelyapina Marina G. , Fruchart Daniel
Published: April 2011

During the last decades hydrogen has attracted worldwide attention as an energy carrier. MgH2 is one of the most promising materials for hydrogen storage due to its high hydrogen uptake, large reserves and low cost. However, the potential for practical use of MgH2 is severely limited because of its high temperature of hydrogen discharge, slow desorption kinetics and a high reactivity toward air and oxygen. Nevertheless, the transition metals doping of Mg greatly enhances the kinetics of hydrogen uptake and release and in particular cases decreases its stability. Despite a huge number of experimental studies fundamental aspects of these phenomena remain unclear. Theoretical researches could provide an insight in metal-hydrogen bonding that governs both the thermodynamic stability and the hydrogen sorption kinetics. In this paper a brief review of the recent theoretical works concerning the influence of transition metals on the electronic structure and stability of magnesium hydride MgH2 is given.
Pauli Paramagnetism of the Novel Uranium Intermediate Phase UCo3-xGex (0.2 ≤ x ≤ 0.4)
Authors: Soudé Arnaud , Tougait Olivier , Pasturel Mathieu , Kaczorowski Dariusz , Noël Henri
Published: April 2011

The new compound UCo3-xGex with x = 0.4 was prepared by direct solidification of the corresponding liquid phase, followed by annealing at 973 K. Single crystal X-ray diffraction carried out at room temperature showed that it crystallizes with the hexagonal space group P63/mmc (n°194) and the unit-cell parameters a = 4.890(5) Å and c = 16.405(5) Å. The substitution of Co atoms by germanium atoms in UCo3 (PuNi3 structure type) yields stabilization of the CeNi3 structure. The homogeneity range, evaluated by energy dispersive spectroscopy analysis, extends from x = 0.2(1) to 0.4(1). The electronic properties were investigated by means of DC magnetic susceptibility and DC electrical resistivity measurements. The phase is a Pauli paramagnet and exhibits electrical conductivity characteristic of strongly disordered metals.
Neutrons Not Entitled to Retire at the Age of 60: More than Ever Needed to Reveal Magnetic Structures
Authors: Ritter Clemens
Published: April 2011

In 1949 Shull et al. [1] used for the first time neutrons for the determination of a magnetic structure. Ever since, the need for neutrons for the study of magnetism has increased. Two main reasons can be brought forward to explain this ongoing success: First of all a strong rise in research on functional materials (founding obliges) and secondly the increasing availability of easy to use programmes for the treatment of magnetic neutron diffraction data. The giant magnetoresistance effect, multiferroic materials, magnetoelasticity, magnetic shape memory alloys, magnetocaloric materials, high temperature superconductivity or spin polarized half metals: The last 15 years have seen the event of all these “hot topics” where the knowledge of the magnetism is a prerequisite for understanding the underlying functional mechanisms. Refinement programs like FULLPROF or GSAS and programs for magnetic symmetry analysis like BASIREPS or SARAH make the determination of magnetic structures accessible for non specialists. Following a historical overview on the use of neutron powder diffraction for the determination of magnetic structures, I will try to convince you of the easiness of using magnetic symmetry analysis for the determination of magnetic structures using some recent examples of own research on the rare earth iron borate TbFe3(BO3)4 and the rare earth transition metal telluride Ho6FeTe2.
Crystal Growth, Structure, and Incoherent Metallic Behaviour of FeCrAs
Authors: Wu Wen Long , McCollam Alix , Swainson Ian P. , Julian Stephen R.
Published: April 2011

There is growing interest in a possible connection between incoherent metallic conduction and high temperature superconductivity, that is exemplified by the behaviour of the parent compounds of the new iron-pnictide high-temperature superconductors. We have recently discovered very incoherent behaviour in the non-superconducting arsenide, FeCrAs. This material shows a non-metallic resistivity that rises with decreasing temperature without saturation or a gap, over three decades of temperature, from 80 mK to 800 K. We briefly review this behaviour, and address the question of disorder: how to test for the presence of disorder in a system where the scattering rate inferred from the resistivity is highly abnormal, and how to produce single crystals with low levels of disorder. Our discussion will focus on magnetic properties. FeCrAs is a partly frustrated magnetic system with a Nèel temperature TN that depends on sample quality, a sample-dependent spin freezing temperature TF < TN, and magnetic hysteresis that depends strongly on preparation conditions due to ferromagnetic minority phases in disordered samples.
High Effective Thermoelectrics Based on the Mg2Si-Mg2Sn Solid Solution
Authors: Fedorov Mikhail I. , Zaitsev Vladimir K. , Isachenko Grigory N.
Published: April 2011

The complex study of the thermoelectric properties in solid solutions between compounds Mg2X (X=Si, Ge, Sn) was accomplished. Analysis of the features of band structure, thermal conductivity and electrical properties in the wide range of temperature and carrier concentration has shown that the most effective thermoelectric can be achieved in the Mg2Si-Mg2Sn solid solution. Energy spectrum and carrier concentration optimization, and, also, lattice thermal conductivity minimization allowed to establish the most effective compounds for the thermoelectrics of n- and p- type. Thermoelectrics with the maximum dimensionless figure of merit of more than 1.2 and average ZT0.9 (in the temperature range 300-800K) were obtained with developed synthesis and doping techniques. These materials are cheap, wide spread and environment friendly, have non-toxic initial components. It is very favorable for practical application.
Microstructures and Thermoelectric Properties of (Bi2Te3)1-X/(CdTe)x Composites
Authors: Gao Horng Jyh , Huang Wu Ruei , Wu Ching Cherng , Kuo Yung Kang , Ho Ching Hwa
Published: April 2011

In this study, Bi2Te3 was selected as a matrix material and an immiscible semiconductor material CdTe with a wider energy band gap was precipitated to form microstructures in it. For this purpose, a series of two-component composites (Bi2Te3)1-x/(CdTe)x, with x = 0.01, 0.05, 0.1, 0.15, 0.2 were prepared by melting, high speed rocking and quenching technique. The composition and microstructure of these two-component composites were examined by X-ray and SEM. Thermoelectric properties including Seebeck coefficient, electric resistivity, and thermal conductivity were measured from 30 K to 400 K. The compositional and temperature dependence of the microstructure and thermoelectric properties of (Bi2Te3)1-x/(CdTe)x composites were discussed. It is found that (Bi2Te3)0.99/(CdTe)0.01 exhibits a better thermoelectric performance than that of Bi2Te3 at elevated temperatures. The figure of merit (ZT) of (Bi2Te3)0.99/(CdTe)0.01 is about 0.64 at 400 K.
Piezoreflectance and Raman Characterization of Mo1−xWxS2 Layered Mixed Crystals
Authors: Dumcenco Dumitru O. , Su Yu Chen , Wang Yi Ping , Chen Kuei Yu , Huang Ying Sheng , Ho Ching Hwa , Tiong Kwong Kau
Published: April 2011

A systematic optical characterization of a series of Mo1-xWxS2 (0 ≤ x ≤ 1) layered mixed crystals grown by chemical vapour transport method were carried out by using piezoreflectance (PzR) and Raman scattering measurements. From a detailed lineshape fit of the PzR spectra over an energy range from 1.6 to 5.0 eV, the energies of the band-edge excitonic and higher lying interband transitions were determined accurately. The transition energies and their splittings vary smoothly with the tungsten composition x indicating that the nature of the band structure is similar for the Mo1-xWxS2 series compounds. The peaks of the two dominant first-order Raman-active modes, and , and several second-order bands are observed in the range of 250-450 cm-1. The peaks corresponding to mode show a one-mode type behavior, while the peaks of mode demonstrate two-mode type behavior for the entire series of Mo1-xWxS2 crystals. These behaviors were discussed on the basis of the lattice vibrational properties of 2H-MoS2 and 2H-WS2 compounds.
Clear Cell Basal Cell Carcinoma
Authors: Sarma Deba P. , Olson Daniel , Olivella Jennifer , Harbert Tracey , Wang Bo , Ortman Stephanie
Published: April 2011

Introduction. Clear cell basal cell carcinoma (BCC) is an uncommon and unusual variant of BCC, which is characterized by a variable component of clear cells. The pathogenesis of this histological variant and its clinical significance has not been clarified. Differentiation of this uncommon variant of BCC from other clear cell tumors is important for the treatment.
Case Presentation. A 65-year-old male presented with a 0.9 cm dome-shaped lesion on his upper chest. A shave biopsy revealed a dermal basaloid tumor that comprised nests with a peripheral palisading pattern, retraction artifacts, and striking clear cell changes. Histopathologic examination, along with findings from immunohistochemical studies and special staining of the clear cells, supports the diagnosis of clear cell basal cell carcinoma.
Conclusion. Clear cell BCC is a rare and unusual variant of BCC. The underlying pathogenesis of this subtype is unclear; however, accurate identification may affect treatment and prognosis.
Unexplained cough: pericardial cyst innocent bystander or culprit?
Authors: Orrange Sharon Elizabeth , Saxon Leslie A. , Baydur Ahmet , McFadden P. Michael
Published: April 2011

Pericardial cysts are rare mediastinal cysts and an uncommon cause of cough. Patients are often asymptomatic but can present with cough, dyspnea and atypical chest pain. We describe the case of a 30 year old female with a 3 month history of unexplained cough. Extensive workup and empiric treatment for the standard causes of cough were unsuccessful. More detailed workup including bronchoscopy, endoscopy, pulmonary function testing and otolaryngology evaluation was normal. Computed tomographic (CT) scan and Magnetic resonance imaging (MRI) of the chest revealed a 5.8 cm pericardial cyst in the left cardiophrenic angle. Video assisted thorascopic surgery (VATS) was performed for removal of the cyst and the cough resolved completely postoperatively.
Recurrent Hypothermia and Hypoglycemia as the Initial Presentation of Hepatitis C
Authors: Senadhi Viplove
Published: April 2011

Hepatitis C most commonly manifests with asymptomatic elevations in transaminase levels or in advanced stages, may present with hepatic encephalopathy or ascites. We report the first case in the literature, in which the initial manifestation of hepatitis C induced chronic liver disease was recurrent hypoglycemia and hypothermia. In our case, the hypoglycemia was induced by glycogen depletion from hepatitis C induced chronic liver disease. In chronic liver disease, glycogen stores are depleted from extensive fibrosis and it has been shown that glycogen depletion may herald hepatic encephalopathy, which later manifested in our patient.
Massively Dilated Right Atrium Masquerading as a Mediastinal Tumor
Authors: Schroeter Thomas , Doll Nicolas , Subramanian Sreekumar , Mohr Friedrich W. , Borger Michael A.
Published: April 2011

Severe tricuspid valve insufficiency causes right atrial dilatation, venous congestion, and reduced atrial contractility, and may eventually lead to right heart failure. We report a case of a patient with severe tricuspid valve insufficiency, right heart failure, and a massively dilated right atrium. The enormously dilated atrium compressed the right lung, resulting in a radiographic appearance of a mediastinal tumor. Tricuspid valve repair and reduction of the right atrium was performed. Follow up examination revealed improvement of liver function, reduced peripheral edema and improved New York Heart Association (NYHA) class. The reduction of the atrial size and repair of the tricuspid valve resulted in a restoration of the conduit and reservoir function of the right atrium. Given the chronicity of the disease process and the long-standing atrial fibrillation, there is no impact of this operation on right atrial contraction. In combination with the reconstruction of the tricuspid valve, the reduction atrioplasty will reduce the risk of thrombembolic events and preserve the right ventricular function.
Significant Stenoses of Twin Circumflex Arteries Accompanied by Heart Failure: A Rare Coronary Artery Anomaly
Authors: Cicek Davran , Gokay Seher , Eldem Halil Olcay , Muderrisoglu Haldun
Published: April 2011

Although coronary artery anomalies may cause some clinical symptoms, most are incidentally discovered as benign findings on coronary angiograms. A circumflex coronary artery anomalously originating from the right sinus of Valsalva is the most common coronary anomaly. However, a double circumflex coronary artery, both stenotic in their mid portions, resulting in symptomatic heart failure is a rare clinical and angiographic condition. In this case, we present a 71-year-old male patient admitted to our clinic with the diagnosis of acute heart failure. Angiography revealed stenotic double circumflex arteries, arising from the left and right sinus of Valsalva, and the patient was treated by percutaneous coronary intervention.
Wine and Society - Welcome Editorial
Authors: Trevisan Maurizio
Published: April 2011

Wine, its production and consumption, has accompanied western civilization for thousands of years. Since the early sign of its production in the Fertile crescent area, approximately 6000-8000 years ago, the culture of wine has spread out through the middle east, the Nile valley and the Mediterranean basin. Wine became part of the recorded history in ancient Egypt were it was used as part of religious ceremonies and by the Pharaos and the elite.