bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous Emission of Positronium Negative Ions from Tungsten (100) Surface
Authors: Nagashima Yasuyuki , Hakodate Toshihide , Miyamoto Ayaka , Michishio Koji
Published: March 2009

Recently, we have observed spontaneous emission of positronium negative ions from polycrystalline tungsten surface. In the present work, we have extended the study to the emission from tungsten single crystal. The emission from tungsten (100) surface plane has been confirmed. The fraction of positrons yielding the ions at the target surface was ()4102.02.1−×±.
Prospects for Laser Spectroscopy of Ps2
Authors: Cassidy D.B. , Deng S.H.M. , Greaves R.G. , Lopez-Valdez N. , Meligne V. , Tom H.W.K. , Mills A.P.
Published: March 2009

Recent observations of molecular positronium (Ps2) were based on a correlation between changes in positronium (Ps) lifetime spectra associated with the density of an incident positron beam and the population of a positronium (or positron) surface state. While the evidence for molecule formation is compelling it is nevertheless an indirect observation, and has not provided any information about the properties of Ps2 beyond its likely creation. Here we discuss the prospects for a direct observation via laser spectroscopy of a predicted 1S2P excited molecular state. Such a measurement would provide a direct and unambiguous signal of Ps2 formation and would also allow us to determine some properties of the molecule, namely the lifetime of the excited state and the 1S1S-1S2P energy interval.
n-Nonadecane Embedded in Mesopores
Authors: Zaleski Radosław , Goworek Jacek
Published: March 2009

The ordering of n-nonadecane confined in the pores of MCM-41 silica was investigated by Positron Annihilation Lifetime Spectroscopy. No irradiation effects caused by the positron source were observed. The ortho-positronium components found in the lifetime spectra correspond to the free volumes observed in the bulk alkane plus additional space at the interface between n-nonadecane and the silica wall. Phase transitions rigid-rotator and rotator-liquid were shifted towards lower temperatures by 28 and 16 degrees respectively.
Investigation of Interfacial Interaction and Microstructure for Epoxy/CNTs Nanocomposites by PALS
Authors: Zhou Wei , Yue Shao Jie , Wang Jun Jun , Wang Bo , Zheng Ya Ping
Published: March 2009

Epoxy nanocomposites with multi-walled carbon nanotubes (MWNTs) were prepared. The interaction between MWNTs and epoxy matrix and microstructure were systematically investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the positron annihilation technology (PAT) respectively. The glass transition temperatures were determined by the variation of the free volume size.
Open-Nano Pores in Natural Minerals Studied by Positron Lifetime Spectroscopy
Authors: Yoshizawa K. , Sato K. , Murakami Hideoki , Shikazono N. , Fujimoto K. , Nakata M.
Published: March 2009

Positron lifetime spectroscopy was conducted for natural minerals to investigate open-nano pores. Positronium (Ps) formation occurs with ortho-positronium (o-Ps) intensities ranging from a few % to 20 % and size distributions of nano pores are evaluated from o-Ps lifetimes. The results will be discussed with respect to formation processes of nano pores influenced by earth's environment.
Influence of Sintering Temperature on Defects in Porous Silica Monoliths Studied by Positron Annihilation Techniques
Authors: Huang Yu Yang , Xiong Chao , Wang Yu Xin , Lu Yan Qiong , Deng Wen
Published: March 2009

Positron lifetime and coincidence Doppler broadening spectra for porous silica calcined at temperatures from 900 to 1500 oC have been measured. As the sintering temperatures increasing from 900 to 1000 oC, the height of the peaks of the ratio curves decrease, and the τ3 increases, which is due to the exclusion of the gas and the organic substance out of the cavities. As the sintering temperatures increasing from 1000 to 1250 oC, some of the defects were recovered, the grains of low quarts appearing and growing. This gives rise to the increase of the height of the peak of the ratio curve, and the decrease of lifetime (τ1,τ2 and τ3). As the sintering temperatures increasing from 1250 to 1500oC, the height of the peak of the ratio curve decreases, and the lifetime increases due to the phase transition of low quartz to cristobalite.
Porous Structure of Mesoporous Silica Studied by Positron Annihilation Lifetime Spectroscopy
Authors: Xi Yang , Hao Wei Chang , Wang Dan Ni , Wang Tian Min , Yu Run Sheng , Wang Bao Yi , Wei Long
Published: March 2009

In this paper, a series of mesoporous silica particles with different pore diameters were fabricated using tetraethyl orthosilicate (TEOS) as the network precursor, hexadecyl trimethyl ammonium bromide (CTAB) as a structure directing agent and 1,3,5-Trimethylbenzene (TMB) as a pore enlarge reagent. Compared with SAXRD and BET, the PALS may not only show the mesoporous information but also provide the structure information of microporous.
Influence of Temperature on Intratrack Processes and Ps Formation and Behaviour in Liquid Water
Authors: Stepanov Sergey V. , Duplâtre Gilles , Byakov Vsevolod , Subrahmanyam V.S. , Zvezhinskiy Dmitry , Mishagina A.S.
Published: March 2009

Positron annihilation lifetime (PAL) spectra are measured in liquid water in the temperature range 2 – 930C. The spectra are treated by taking into account intratrack reactions and assuming that radical reactions with Ps are diffusion-controlled (the respective temperature dependences obeying the Stokes-Einstein law). Equilibrium Ps bubble parameters are obtained.
Positron Method for Diagnostics of Carcinogens
Authors: Byakov Vsevolod , Stepanov Sergey V. , Stepanova O.P.
Published: March 2009

A method for detection of carcinogenic properties of chemical substances based on the Ps formation mechanism is briefly discussed.
Positronium Formation in Room Temperature Ionic Liquids
Authors: Hirade Tetsuya
Published: March 2009

Positron annihilation age-momentum correlation measurements (AMOC) were performed for room temperature ionic liquids (IL) to investigate positronium (Ps) formation process. The solvation time of free electrons in IL is longer than in usual molecular liquids. And hence IL is very useful materials to investigate fast reactions such as Ps formation. On the other hand, Ps formation is a good tool to investigate the dry electrons. The para-Ps annihilation lifetime is about 125ps and then the effect of dry electrons should be seen on the S(t) parameters made by the age-momentum correlation measurements. The slow Ps formation was observed in the room temperature ionic liquids.
4-Channel Digital Positron Lifetime Spectrometer for Studying Biological Samples
Authors: Sane Petri , Kilpeläinen Simo , Tuomisto F.
Published: March 2009

In this work a novel detector setup for PALS-studies on biomolecular materials is presented. When pursuing optimal detecting efficiency and lifetime component resolution one must make compromises when using only one detector pair. With smaller scintillation heads the resolution is higher, but the detecting efficiency decreases and vice versa. When measuring biological materials that do not withstand long measurement periods, sacrifices are made for gaining efficiency. The price of this optimization is low resolution of the lifetime components, namely separating the always present water’s lifetime component of ~1.8 ns from the actual material’s lifetime component, typically >2 ns. A solution to this problem is measuring the annihilation spectra with two individual detector pairs simultaneously. Using analog setup, it would require duplicate ADC-hardware that are both expensive and degrade by time. With a fully digital setup, the need for hardware is smaller and the precision of the setup is constant during its service life.
Positronium Thermalization Process in Nanoporous Materials and its Influence on the Shape of PALS Spectrum
Authors: Kansy Jerzy , Zaleski Radosław
Published: March 2009

A new method of analysis of PALS spectra of porous materials is proposed. The model considers both the thermalization process of positronium inside the pores and the pore size distribution. The new model is fitted to spectra of mesoporous silica MCM-41 and MSF. The resulting parameters are compared with parameters obtained from fitting the “conventional” models, i.e. a sum of exponential components with discrete or/and distributed lifetimes.
Positronium in Alkanes at High Pressure of Argon and Nitrogen
Authors: Zgardzińska Bożena , Goworek Tomasz , Wawryszczuk Jan
Published: March 2009

Positron lifetime spectra were measured for several alkanes under high pressure of argon and nitrogen. In the case of argon intercalation, the dependence of melting temperature on pressure is nonmonotonous, while in nitrogen this effect does not appear.
Seeking the Good Fitting Procedure of PALS Polymer Spectra
Authors: Laforest Nicolas , De Baerdemaeker Jérémie , Bas Corine , Dauwe Charles
Published: March 2009

Positron annihilation lifetime measurements on polymethylmethacrylate (PMMA) at low temperature were performed. Different discrete fitting procedures have been used to analyze the experimental data. It shows that the extracted parameters depend strongly on the fitting procedure. The physical meaning of the results is discussed. The blob model seems to give the best annihilation parameters.
Analysis of Radiation Induced Phenomena in a Polymer Electrolyte Membrane with Positron Annihilation Technique
Authors: Honda Yoshihide , Kimura N. , Pujari P.K. , Isoyama G. , Tagawa Seiichi , Miyauchi H. , Shibahara Y. , Sodaye H.S. , Akiyama Y. , Izumi Y. , Nishijima S.
Published: March 2009

Positron annihilation techniques were applied for irradiated Nafion-117 to investigate deterioration process in PEM. There were no significant changes in lifetime of positron/positronium, whereas the S-parameter showed fairly good correlation with proton conductivity.
The Effect of Anneal on PP and PA Blends Studied by Positron
Authors: Rong W. , Fang Peng Fei , Wang Q. , Chen Zhe , Wang Shao Jie
Published: March 2009

The anneal effect of PP/PA/MMT blends had been studied by positron annihilation lifetime spectra (PALS). The o-Ps lifetime and intensity of unannealed blends were linearly additive basis on the PA weight fraction, which was coincident to the simple compound rule. However, the o-Ps intensity of the samples decreased after samples annealed.
Positron Annihilation and Chemistry of Groups in Hyperbranched Polymers
Authors: Gong Wei , Mai Yi Yong , Zhou Yong Feng , Qi Ning , Wang Bo , Yan De Yue
Published: March 2009

In this paper, both lifetime and intensity in hyperbranched polymers were measured by using positron annihilation lifetime spectroscopy (PALS) measurements. Ortho-positronium properties upon the degree of branching (DB) have been studied; o-Ps lifetimes maintain a constant while an increase in o-Ps intensities has been detected with DB increasing. Which is inconsistent with author’s prediction and indicate that interactions between positronium and the free-volumes are strongly depend on not only the free-volume size properties but also its chemistry environment, due to the variations in the distribution of the different ending groups: –OH and -CH3, caused by DB changes in hyperbranched polymers. The present works demonstrate that in the polar-polymeric application of PALS, effects of the distribution of polar groups should be properly taken into consideration.
The Influence of Acrylic Acid Groups on the Microstructure of HDPE/PS/Clay System Studied by Positron Annihilation
Authors: Wang Hong Mei , Chen Zhe , Wang Peng Fei , Wang Shao Jie
Published: March 2009

Two types of composites－high density polyethylene/polystyrene (HDPE/PS) with clay, and high density polyethylene grafted with acrylic acid/PS (PEAA/PS) with clay－were prepared via melt compounding. X-ray diffraction (XRD) results revealed that the dispersion of clay in compatibilized blends was better than immiscible blends. Positron annihilation lifetime spectroscopy (PALS) has been utilized to investigate the microstructure of two types of composites. The ortho-positronium (o-Ps) intensity for PEAA/PS was lower than that for HDPE/PS. The results provided evidence that the chain segments with carboxyl group would be easier to intercalate the gallery of silicates.
Resonant Positron Annihilation on Molecules
Authors: Young J.A. , Surko C.M.
Published: March 2009

At incident positron energies below the threshold for positronium atom formation, there are many cases in which annihilation rates for molecules are far in excess of that possible on the basis of simple two-body collisions. We now understand that this phenomenon is due to positron attachment to molecules mediated by vibrational Feshbach resonances. The attachment enhances greatly the overlap of the positron with molecular electrons and hence increases the probability of annihilation. Furthermore, measurements of the annihilation spectra as a function of incident positron energy provide a means of measuring positron-molecule binding energies. In this paper we present an overview of our current understanding of this process, highlighting key results and discussing outstanding issues that remain to be explained.
Influence of Free Volume on Damping Properties for CIIR and CIIR/PEA Investigated by Positron
Authors: Zhu Yu Chan , Wang Bo , Zhou Wei , Wu Jin Rong , Huang Guang Su
Published: March 2009

The effect of the free volume on damping properties for CIIR (Chlorinated isoprene-isobutylene rubber) and CIIR/PEA (polyethylacrylate) were investigated by positron annihilation lifetime spectroscopy and DMA, respectively. The DMA results indicate that the tanδ peaks of CIIR and CIIR/PEA both have very broad covering temperature range. The tanδ peak of CIIR/PEA shifts to higher temperature region which indicates that the CIIR/PEA has better damping property in high temperature region that CIIR. From PALS results, we found that the lifetime of o-Ps in CIIR and CIIR/PEA both exhibit broad glass transition. It is interestingly that the glass transition region of CIIR/PEA also shifts to higher temperature than CIIR. This character of the free-volume is well in agreement with the damping properties obtained by DMA. It indicates that the free volume has close relationship with damping mechanism for CIIR and CIIR/PEA.
Positron Beam Characterization of Silica Thin Films with Structurally Ordered Porosity
Authors: Yu R.S. , Qin X.B. , Wang Q.Z. , Zhang Z. , Zhong Y.R. , Li Z.X. , Wang Bao Yi , Wei Long , Jia Q.J. , Kurihara T.
Published: March 2009

Well-ordered 2-dimensional (2D) hexagonal and 3-dimensional (3D) cubic mesoporous silicon oxide thin films prepared using triblock Poly(ethylene oxide)-Poly(Propylene oxide)-Poly(ethylene oxide) copolymer species (P123, F127) as the structure-directing agents, are studied by positron beam analysis in parallel with X-ray reflection measurements. It is observed that in the two films with equivalent porosity and pore size (normal to the film surface direction), the shape of mesopores considerably affects positron annihilation behavior. The narrowed positron annihilation Doppler broadening in the 2D hexagonal mesoporous film may suggest a higher positronium formation probability there, owing to a larger effective open volume area originated from the extension of pore channels parallel to the film substrate.
Silicon Nitride Surface Modification and Cell Adhesion
Authors: Zhao Yi , Lv Xiao Ying , Jiang Zheng Lin , Li Xia , Huang Yan , Wang Zhigong
Published: March 2009

Silicon microelectrode arrays (Si MEAs) have great potential in recording of neural activity; the biocompatibility of silicon nitride has gained much attention as a part of Si MEAs. In this study, we used alternating polycations, polyethyleneimine (PEI), and polyanions, gelatin, to fabricate multilayer films built up by LbL deposition on silicon nitride wafers. Then the samples surfaces were characterized by contact angle system and atomic force microscopy (AFM). The amount of proteins adsorbed on silicon nitride and modified silicon nitride were measured by a modified Coomassie brilliant blue (CBB) protein assay. Cell culture results showed that the modified silicon nitride could increase the adhesion ability of the hippocampal neurons.
Biomimetic Synthesis of Tooth-Like Hydroxyapatite under Organic Polymer Monolayer
Authors: Tian Kun , Shuai Hui Min , Yang Xiao Min
Published: March 2009

Based on the basic theory of molecular recognition , we design a organic molecules model to induce the crystallization of hydroxyapatite to synthesized tooth-like calcium phosphate/hydroxyapatite under a controllable way in vitro. The cross-linking of collagen on the dentin surface and extraneous collagen was optimized by varying the molar ratio of N,N-(3-dimethylaminopropyl)- N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) at a constant EDC concentration. CaCl2 and Na3PO4-12H2O solutions were added after the crosslinking process. X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis of organic protein monolayer for samples. The obtained composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX). XPS and FTIR analysis showed the surface organic compositions in experimental group is higher than that of normal dentin and decalcified dentin surface. The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there were column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. This study showed that the specific organic molecule model can be used as a potential effective crystal growth modifier.
Quantification of BSA in Tissue Engineered Medical Products by ELISA — Problems and Solutions
Authors: Fang Yu , Du Xiao Dan , Xi Ting Fei , Feng Xiao Ming , Chen Zhen , Zhang Zhi Xiong
Published: March 2009

Aim In this study, the adaptability of an ELISA kit for quantification the residual BSA in TEMPs, the influence of rinsing protocol on reducing the residual BSA in TEMPs and the effectiveness of ultra-filtration on reducing the matrix effects of TEMPs immersion on BSA quantitative by ELISA were discussed. Methods Three kinds of TEMPs used in this study were: tissue engineered skin (TES), recombination human acellular dermal matrix (rhADM) and combination chitosan tissue engineered skin (cC-TES). The devices were rinsed according to the Directions for Use firstly. To investigating the influence of rinsing protocol on reducing the residual BSA in TEMPs, TES were rinsed by two different protocols separately. Then TEMPs immersions were prepared according to ISO10993.12, physiological saline (NS) was used as immersion medium. BSA concentration in immersions and filtrate were determined by using the “Quantitative measure of residual BSA ELISA kit” (detection range was 12.5-200ng/mL, manufactured by WUXI BOSHENG MEDICAL BIO-TEC DEVELOPMENT CO., LTD. As suspected to have some matrix effect on BSA quantification by ELISA kit, rhADM immersion was ultra-filtrated before detection. Results The results showed good correlation between dilution factors and the A450nm of TES and cC-TES immersions, correlation coefficient (r) was 0.9943±0.0007 and -0.9835±0.0037, respectively. No significant effect on BSA detection was found when NS was used as immersion medium. Comparing the results of protocol 1 and 2, the A450nm of TES immersion was significantly decreased after rising by protocol 2. After ultra-filtration, the correlations between absorption and dilution factors of rhADM immersion were improved significantly; the correlation coefficient (r) was raised from -0.7264±0.0089 to -0.9606±0.0039. Conclusions The quantitative ELISA kit was considered to be adaptability for detect the BSA in TEMPs. Different rinsing protocol may obviously affect on reducing the residual BSA in TEMPs. The matrix effects of rhADM immersion can be reduced obviously by using ultrafiltration.
Protein Adsorption Behaviors on PLLA Surface Studied by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D)
Authors: Zeng Rong , Zhang Yi , Tu Mei , Zhou Chang Ren
Published: March 2009

The adsorption of two different proteins (bovine serum albumin (BSA) and collagen-I) onto poly (L-lactic acid) (PLLA) surface was investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). It’s found that protein characteristics would greatly affect the adsorption kinetics, structure and viscoelastic properties of adsorbed protein layers. Compared with BSA, collagen-I trended to form a loose, dissipative layer with a slower adsorption rate and larger adsorption reversibility, which is consistent with AFM observation. The results provided some valuable information for controlling the structure and properties of adsorbed proteins to develop an alternative surface-modification approach for biomaterials.
Improved HA Coating on Titanium Substrate Using Induction Heating and Hydrothermal Treatment Methods
Authors: Zou Chun Li , Xiong Xin Bo , Zeng Xie Rong
Published: March 2009

An adherent apatite coating was deposited on titanium substrate through the three steps. First, titanium substrate was modified in 10M NaOH solution at 60°C, and then immersed in acidic solution of calcium phosphate resulting in the deposition of monetite (CaHPO4) coating using induction heating technique. Finally the monetite crystals were transformed to HA by a hydrothermal process at 160°C for 2 hours. Composition、morphology and structure of the initial and final coatings were identified using X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS). The final coating consisted of compact HA crystals and these HA apatite crystals stacked tightly and kept the initial morphology of the monetite crystals. The coating adhesion measured using scratch test was 25.25N. In conclusion, hydrothermal treatment and induction heating techniques are effective surface coating methods that improve bonding to titanium substrate.
Study on Polylactide/Poly(ether block amide) Composite Biomaterials and Shape-Memory Effect
Authors: Zhang Wei , Chen Long , Zhang Yu
Published: March 2009

Melt blending of PLA and biodegradable PE-b-A has been performed in an effort to toughen the PLA. With the PE-b-A contents increasing, the elongation at break of composites increased and the brittle break became ductile break. When the PE-b-A content is 10%, the tensile strength of composite is similar with neat PLA, and the elongation increased significantly. The composites showed wonderful shape-memory effect. The composites occurred to deformation upon tensile load, and recovered to original shape quickly with temperature increasing. PE-b-A acts as stress concentrator in system with the stress release locally and energy-dissipation process. These will prevent PLA matrix from breaking under high deformation and make the PLA molecular orientation. Consequently, releasing the stress by heating up the material will reform the shape back to the original shape.
Construction of Two-Gene Modified Artificial Bone by Using Recombinant Adenovirus
Authors: Duan Chun Guang , Meng Guo Lin , Liu Jian , Hu Yun Yu , Li Bao Feng , Li Dan , Bai Jian Ping , Bi Long , Liu Min
Published: March 2009

Large osseous defects are difficult to treat because of deficient blood supply on the defected area. To get sufficient blood supply, we designed to establish the adenovirus simultaneously encoding both VEGF and Ang-1 (pAd-VIA) to accelerate the formation of new vessels in the process of bone defect repair. The construction of the adenovirus was performed according to the method reported by Tong-Chuan HE with a tiny modification. Three kinds of adenoviruses were acquired. They are adenovirus pAd-VIA simultaneously encoding VEGF and Ang-1, adenovirus pAd-VEGF encoding VEGF, and adenovirus pAd-Ang-1 encoding Ang-1. The adenovirus prepared in this study could successfully transfer VEGF and Ang-1 into mesenchymal stem cells(MSCs) with high efficiency. Two-gene modified artificial bone was established by use of these adenovirus. In the end, the two-gene modified artificial bone was proved to have good biocompatibility and biological function. Study reports presented here will pave the way for further exploration of vascularization in the process of large osseous defects repair.
Preparation of Tetracalcium Phosphate and the Effect on the Properties of Calcium Phosphate Cement
Authors: Kai Dan , Fan Hong Song , Li Dong Xiao , Zhu Xiang Dong , Zhang Xing Dong
Published: March 2009

In the present study, three types of tetracalcium phosphate (TTCP) were prepared by solid-solid reaction or co-precipitation method and by different cooling modes. The effect of TTCP on the performance of calcium phosphate cement (CPC) was investigated. The result showed that the characteristic of TTCP varied with preparation method and played an important role in CPC performance. A solid-solid reacted TTCP yielded smaller particle size and resulted in bad workability and mechanical strength of CPC. The fast cooling of sintering TTCP by liquid nitrogen could avoid the decomposition of TTCP and make pure TTCP. TTCP prepared by wet-precipitation could improve performance of CPC and was promising to optimization of CPC.
Anticorrosion Behaviors of Quaternary Polyethyleneimine in Acidic Environment
Authors: Zhang Xin , Wu Xue Dong , Li Jian Zhong , Wang Hui , Dai Dan , Song Zhen Lun
Published: March 2009

Polymeric compounds are of great interest as corrosion inhibitors in acidic environment due to their inherent stability. Polymeric film is effectively used for the protection of metals partly owing to their capacity to act as a physical barrier between the metal surface and the corrosive environment.
In this paper, a cation polyelectrolyte inhibitor (Quaternary Polyethyleneimine, QPEI) was prepared. The quality and inhibition efficiency of QPEI self-adsorbed films were studied by polarization curve and electrochemical impedance spectroscopy, respectively. The compositions and morphologies of the polymer film on the steel surface were examined with the aids of SEM and XPS, respectively. The results showed that QPEI could greatly retard the corrosion of iron in sulfuric acid, which was attributed mainly to the protective QPEI film formed on the surface. Meanwhile, the inhibition of QPEI could be supposed as a mixed process, in which both cathodic and anodic corrosions were simultaneously restrained. Based on the results of XPS and SEM, it could be evidenced that the QPEI can form a protective polymer layer on the metal surface by adsorption.
Production of Magnesium Alloy Billets by Semisolid Continuous Casting
Authors: Kido Futoshi , Motegi Tetsuichi
Published: March 2009

In order to produce AZ91 and AZ31 magnesium alloy billets semisolid continuous casting by using an inclined cooling plate was carried out. The molten magnesium alloy in an electric furnace was flowed on the inclined cooling plate and then poured in a tundish. The slurry prepared using this process was solidified by drawing a dummy bar from a water-cooled copper mold, consequently producing a billet. As a result, we could produce the magnesium alloy billets by semisolid continuous casting. Magnesium alloy billets with refined and globular primary α crystals were successfully and continuously cast by optimizing the solidification conditions. In this case, the grain size of AZ91 billets was about 55μm and that of AZ31 billets was 50μm. The AZ91 billets produced by semisolid continuous casting were employed in thixocasting experiments. The experiments revealed that thixocasting could produce the mobile phone casings with spherical primary α crystals at 858K. Moreover, we proved that the difference of shot cycle did not influence the microstructures for up to 251 shots.
Effect of TiO2 on the Thermal Conductivity of Eco-Friendly Silica Bricks Fabricated by Yellow River Silt
Authors: Yang Jian Ying , Xu Li Hua , Hao Hong Shun , Yang Shu Ming
Published: March 2009

Silt from the Yellow River was mixed with a certain amount of SiO2 powder to fabricate eco-friendly silica bricks and different amounts of TiO2 were added to ameliorate the thermal conductivity of the bricks. Results showed that the phases of as-fabricated silica bricks are cristobalite and tridymite with cristobalite predominating. With increasing amounts of TiO2, the bulk density and thermal conductivity of the samples increase. Although the bulk density (1.65~1.76 g/cm3 ) than the ideal density 1.85 g/cm3, the thermal conductivity is significantly ameliorated. The thermal conductivity of the sample with 1.5% TiO2 addition is 2.11 W/m.°C, which is nearly three times higher than that of commercial silica bricks (0.8 W/m.°C).
Degradation of Harmful Gases in Air by Ce3+/TiO2 Complex Nanomembrane
Authors: Li Ling , Peng Li Ping
Published: March 2009

. The Ce3+/TiO2 complex membrane made from Ce3+on the TiO2 framework with the activity of photocatalysis were prepared. The degradation behavior of the best mass ratio of Ce3+/TiO2 complex membrane , and the influences of the diameters of particles of Ce3+/TiO2 complex membrane on the degradation of the harmful gases under 254nm and 365nm ultraviolet light or natural light in room were investigated. AFM result showed that the Ce3+/TiO2 complex membrane were composed of nanoparticles with 10nm~50nm diameters of particles. The experimental results revealed that the smaller the nanoparticles in Ce3+/TiO2 complex membrane, the greater the degradation degree was. The best mole ratio of Ce3+ and TiO2 was 5% and the best mass ratio of Ce3+/TiO2 and formaldehyde were 7.06 under 254nm and 365nm ultraviolet and 23.55 under the natural light in room after 24h when the degradation percents of formaldehyde were more than 90%. Same as above conditions ammonia were 8.76 and 25.79 and benzene were 15.65 and 35.32. The degradation percents of Ce3+/TiO2 complex membrane to harmful gases were higher about 3 times under 254nm and 365nm ultraviolet than under the natural light in room.
Study on Properties of Quasi Solid Polymer Electrolyte Based on PVdF-PMMA Blend for Dye-Sensitized Solar Cells
Authors: Yang Yan , Tao Jie , Ma Li
Published: March 2009

Poly(vinylidene fluoride)(PVDF) is photochemically stable even in the presence of TiO2 and Pt nanoparticles, and poly(methacrylate)(PMMA) has good solvent retention. The quasi-solid electrolytes based on PVDF-PMMA blend polymer were prepared in this work by soaking a porous membrane in an organic electrolyte solution containing the I−/I3− redox couple. The as-prepared electrolytes were characterized by means of Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope respectively. Moreover, the conductivity and the voltage-current curves of the electrolytes were measured by electrochemical workstation. The results indicated that the optimum blend proportion of PVDF and PMMA was 6:4. The porous structure prepared with the addition of propanetriol was beneficial to ion diffusion and thus enhanced the conductivity of the electrolytes. The gel polymer electrolyte had a conductivity of 0.14 mS•cm-1 under the ambient atmosphere. Furthermore, electrolytes were assembled to fabricate DSSCs and the performance of the cells was tested. The good properties with the open-circuit voltage of 0.60V and the short-circuit current of 1.1mAcm-2 were achieved upon illumination with visible light.
Preparation and Research on TiO2/SiO2 Nanofilm with High Transmittance on Solar Cell Glass
Authors: Li Ling , Xiang Hang
Published: March 2009

TiO2/SiO2 complex nanofilm with high transmittance on solar cell glass was prepared by sol-gel method. Particle diameters, surface structures, the thickness of nanofilm and the transmittance of light from 400nm to 1100nm were tested with AFM, UV2550 and other instruments. The mole percents of TiO2 in SiO2 and their ratio influences on the transmittance of glass, aging ability and other properties of nanofilm were investigated. The AFM photos demonstrated that the TiO2/SiO2 film with high transmittance were composed of nanoparticles with 10nm to 30 nm diameters and their structures were meshes with many holes whose diameters were from 300nm to 500nm. The results revealed that as the mole percents of TiO2 in SiO2 increased the transmittance of solar cell glass with TiO2/SiO2 nanofilm decreased but the aging, adhering and wearing abilities increased and as the diameters of nanoparticles decreased the transmittances of solar cell glass with TiO2/SiO2 nanofilm increased under the condition of TiO2/SiO2 nanofilm with meshes of 300nm to 500m diameters of holes. When the mole percents of TiO2 in SiO2 were 0.1%~0.3%, the average diameters of particles in TiO2/SiO2 nanofilm were about 10nm and the structures of TiO2/SiO2 nanofilm were the meshes with many gaps and the diameters of holes were 300nm to 500nm. The increased transmittances were the greatest about 3.6%, increased value of solar cell efficiency about 3.8% and the aging, adhering and wearing abilities of TiO2/SiO2 nanofilm were best for 20 year life through rapid aging tests.
Segregation Effect on Nanoscale Mg - Based Hydrogen Storage Materials
Authors: Nowak Marek , Okonska Izabela , Smardz Lewlaw , Jurczyk Mieczyslaw
Published: March 2009

The nanocrystalline Mg-based metal hydrides offer a breakthrough in prospects for practical applications. In this work, we study experimentally the structure, electrochemical properties and surface segregation effect of nanocrystalline and microcrystalline Mg2M alloys and Mg2M/M’ (M=Cu, Ni; M’=C, Ni, Pd) nanocomposites. These materials were prepared by mechanical alloying (MA). In the nanocrystalline Mg2Cu powder, discharge capacity up to 30 mA h g-1 was measured. It was found that nickel substituting copper in Mg2Cu1-xNix alloy greatly improved the discharge capacity of studied material. In nanocrystalline Mg2Ni powder, discharge capacities up to 100 mA h g-1 were measured. Additionally, it was found that mechanically coated Mg-based alloys with graphite, nickel or palladium have effectively reduced the degradation rate of the studied electrode materials. Finally, the properties of nanocrystalline alloys and their nanocomposites are compared to that of microcrystalline samples. X-ray photoelectron spectroscopy studies showed that the surface segregation of Mg atoms and valence band width in the nanocrystalline Mg2M alloy are greater compared to those observed in microcrystalline Mg2M. Especially, a strong surface segregation of Mg atoms was observed for the Mg2Ni/M’ composites. In that case, Mg atoms strongly segregate to the surface and form a Mg based oxide layer under atmospheric conditions. The lower lying Ni and M’ atoms form a metallic subsurface layer and could be responsible for the observed relatively high hydrogenation rate. Furthermore, the valence band broadening observed in the nanocrystalline Mg2Ni alloys and Mg2Ni/M’ composites could also significantly influence their hydrogenation properties.
Synthesis and Transport Properties of Polycrystalline Co-Filled Type-I Clathrate Compound (Sr,Ba)8Ga16Ge30
Authors: Wang Li , Zhao De Gang , Shi Xiao Ya , Jiang Wan , Chen Li Dong
Published: March 2009

Ga-substituted Ge based type-I clathrates with the general formula A8X16Y30 display promising thermoelectric performance. Using high purity elemental Sr, Ba, Ga, and Ge as starting materials, polycrystalline co-filled type-I clathrate compound (Sr,Ba)8Ga16Ge30 were successfully achieved by combining melting and Spark Plasma Sinter (SPS) method. The temperature dependence of thermal conductivity, electronic conductivity and Seebeck coefficient were reported. The calculated ZTmax is 0.28 at 700K. Enhanced thermoelectric performance would be expected through adjusting Sr/Ba ratio and framework atoms.
Effects of Mg2+ Doping on the Properties of LiFePO4 Synthesized via Hydrothermal Route
Authors: Liang Guang Chuan , Zhi Xiao Ke , Ou Xiu Qin , Wang Li
Published: March 2009

Mg2+ doped LiFePO4 was synthesized from Li3PO4, FeSO4 and MgSO4 by a hydrothermal synthesis at 150 °C（Li1-xMgxPO4, x=0.00, 0.01,0.02,0.04,0.06）. The samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and charge-discharge test. The results showed that Mg2+ dissolved in the LiFePO4 lattice. When the content is in the range of 0 to 6 mol%, Mg2+ caused the shrinkage of LiFePO4 cell volume. The capacity of doped and undoped samples at low discharging rate was similar, about 145mAhg-1 for 0.2C. But the sample doped with 2-4 mol% Mg2+ has higher capacity and longer cycle lifetime than the undoped one at 5C.
PVDF-PAn Co-Polymer with High Permittivity Fabricated by Emulsion Polymerization
Authors: Guo Yan , Luo D.B. , Pan Dong , Liu Han Xing
Published: March 2009

With eEmploying dichloromethane as solvent, sodium dodecanesulphonate as surface active agent, ammonium persulphate as oxidizer, PAn was introduced into PVDF and co-polymer with high relative permittivity reaching to 280 was obtained by emulsion polymerization. By detecting the structural information and electrical property through FT-IR, XRD, SEM, informations about the co-polymers were presented and in this paper. By adjusting the quantity of aniline in polymerization and the concentrations of protonic acid in the post processing, polymers with different electric properties could bewere compared and analyzed. It was The SEM images and XRD patterns showed the crystallization and microstructure information of the co-polymers in comparison. Particularly, the SEM images showed that the PVDF-PAn co-polymers had homogeneous properties in certain constitute range and as a result of emulsion, spherical PAn-PVDF media was fabricated. After robber mixing procedure at certain temperature, the PAn had a relatively average-fine dissolving in the PVDF, which overcame the difficulty of dissolving PAn oin other substrateance. This ensured the fine property for the matrix material in composites. The XRD pattern showed, wWith the increasing of the introduction quantity of PAn, the crystallization of the entire material complex had been raised greatly.
Fabrication and Properties of Aluminum Nitide Ceramics Doped Carbon Nanotubes
Authors: Li Bao Ping , Niu Ben , Wang Jie Qiang , Li Ping , Wang Sun Hao
Published: March 2009

Aluminum nitride ceramics doped carbon nanotubes were fabricated by dispersed multi-walled carbon nanotubes (MWNTs) into AlN powders homogenously. The densification, electric resistance, thermal conductivity and relative dielectric constant of AlN ceramics were investigated. It was found that MWNTs additives could purify the grain boundaries. Furthermore, it induced the increase of the thermal conductivity and the decrease of the relative dielectric constant. However, the linear shrinkage and electric resistance decreased with increasing MWNTs amount. AlN ceramics with high thermal conductivity and low relative dielectric constant were obtained without apparent decrease of electric resistivity.
Synthesis of Carbon Nanofibers: A Catalyst Derived from Cupric Carbonate Basic during Acetylene Decomposition
Authors: Yu Li Yan , Sui Li Na , Cui Zuo Lin
Published: March 2009

Two types of helical and straight carbon nanofibers, have been synthesized by the decomposition of acetylene using cupric carbonate basic as catalyst precursor at low temperature. The obtained carbon nanomaterials were characterized by transmission electron microscope, scanning electron microscope, and X-ray power diffraction. The size of the catalyst nanoparticles remaining inside the resultant nanofibers was determined. The carbon nanofiber diameters, ranging from 30 to 400 nm, closely correlated with the size of the catalytic nanoparticle. The growth mechanism of carbon nanomaterials was also studied. The nanocopper particle size had a considerable effect on the morphology of carbon nanofibers. The helical carbon nanofibers with a symmetric growth mode were synthesized with the nanocopper catalyst particles having a grain size less than 50 nm. When the average catalyst particle size determined was around 50–300 nm, the straight carbon nanofibers were obtained dominantly.
Self-Assembly Growth and Size Control of Silver Nanocrystals for Nonvolatile Memory Applications
Authors: Wang Li , Sun Hong Fang , Zhou Hui Hua , Zhu Jing
Published: March 2009

A film with a single-layer of size controlled silver nanocrystals embedded in silicon dioxide (SiO2) dielectric film by magnetic sputtering has been fabricated for nonvolatile memory applications. The effects of sputtering power, deposition time and substrate temperature on Ag nanocrystals formation were investigated. Transmission electron microscopy (TEM) images showed the as-prepared Ag nanocrystals had high uniformity in their size and distribution. The relationship between Ag nanocrystal size, density and electron storage capability as well as date retention time has been discussed.
Porosity Ratio and Anti-Corrosion Properties of Cr/CrN Films Synthesized by Unbalanced Magnetron Sputtering
Authors: Wu Yan Ping , Leng Yong Xiang , Gui Xian , Sun Hong , Huang Nan , Zhu Sheng Fa , Zhang Peng Cheng , Bai Bin
Published: March 2009

In the present paper, Cr, CrN single-layer films and Cr/CrN multilayer films were deposited on iron and silicon wafer substrates by means of unbalanced magnetron sputtering. The film thickness was measured using surface profile meter. The porosity ratio was calculated using coulometric method based on the polarization curves obtained in the 30g/L NaCl solution at room temperature. Moreover, the corrosion resistance of the sample in a 350°C water vapor atmosphere was also analyzed. The thickness of all films ranged from 1.03 to 1.54 micrometer. The porosity ratio of the Cr and CrN single-layer film were 3.72% and 5.83%, respectively. The porosity of the Cr/CrN multilayer film decreased to 0.39%. The results showed that the Cr/CrN multilayer films had better protection than the Cr and CrN single-layer films.
Fast Removal of Pb2+ from Aqueous Solution by Water Insoluble Konjac Glucomannan
Authors: Luo Xue Gang , Liu Feng , Lin Xiao Yan
Published: March 2009

Konjac glucomannan (KGM) was converted into water insoluble konjac glucomannan (WIKGM) by treating with NaOH through completely deacetylated reaction. Adsorption study was carried out for the adsorption of Pb2+ from aqueous solution using water insoluble konjac glucomannan. The influences of pH, contact time, temperature and initial Pb2+ concentration on the absorbent were studied. Results of kinetic data showed that the Pb2+ adsorption rate was fast and good correlation coefficients were obtained for the pseudo second-order kinetic model. The equilibrium process was described well by the Langmuir isotherm model with maximum adsorption capacity of 9.18 mg/g on WIKGM at 25°C.
Effect of C Content on Properties and Microstructure of Steel-Bonded Cemented Carbide GT35 Produced by In Situ Reduction of Ilmenite
Authors: Wu Yi , Wang Xin , Long Fei , Shen Yu Fang , Zou Zheng Guang
Published: March 2009

Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ carbothermic reduction and vacuum pressureless sintering. The effects of C content on the mechanical properties and microstructures of GT35 composites were investigated. As an excellent reducer, carbon provides an impetus for a series of reductive process. C content determines the melting point of the steel matrix, and directly affects the mechanism of dissolving and segregating of TiC particles, forming a netlike microstructure. Besides, the liquid steel whose viscosplasticity is determined by C content was coated on the surface of the composite and refrained the release of CO. The results showed that the good mechanical properties of steel-bonded cemented carbide GT35 composite were obtained with 0.9wt.% C at the same sintering conditions and the density reached 6.12g/cm3, the average bending strength was over 1229MPa after heat treatment, the mean hardness HRC was 69.4. It also showed that in-situ reduction of natural limonite was a feasible way to fabricate good performance GT35 composite with a relatively low cost.
Nano Effects of Helium-Plasma Treatment Nano-SiO2 Sol-Gel Coating UHMWPE Filaments
Authors: Zhang Ying Chen , Zhu Hai Yan , Wu Hong Yan , Qiu Y.P.
Published: March 2009

The effects of helium-plasma treatment on tensile deformation of nano-SiO2 sol-gel coating UHMWPE filaments (HONSUHMWPE) were studied and a new concept for the nano-structural interphase between fiber surface and nano-coating was provided. The tensile test results showed that in addition to the enhanced ductility of UHMWPE filaments by nano-SiO2 sol-gel coating UHMWPE filaments treated by helium-plasma, the activation volumes of UHMWPE filaments untreated and treated with helium-plasma ranging from 1101.875 to 16603.07(nm)3 by following Eyring’s equation were important descriptors for the properties of the nano-structural interphase between fiber surface and nano-coating, From the results of SEM and FTIR, it was observed that the remarkable uniform dispersion of the nano-SiO2 coating of the UHMWPE filaments modified with helium plasma not only introduced the activated functional groups, but also formed a protective layer on the fiber surfaces.
Oretical Analysis of Filtration Purification of Mg Scrap Melt
Authors: Sun Ji Yun , Long Si Yuan , Zha Ji Li , Wang Yun , Chan Raymond
Published: March 2009

Mg scrap is notorious for the high cost and serious pollution of its recycling process due to the good wettability and similar density of Mg melt to its solid inclusions. To support the sustainable growth of Mg industry and application, intensive effort has been contributed to the development high efficiency, flux-free purification techniques for Mg scrap recycling. In the present study, the purification of Mg scrap melt via filtration was theoretically analyzed by multi-phase fluid hydrodynamics. The relationships between the nozzle size in the filtration medium, melt penetrating-through speed and other filtration parameters were formulated. To provide a guideline to filtration engineering, the influence of processing parameters on the filtering efficiency were discussed.
Application Study of Polypropylene Fiber Reinforced Concrete Railway Tunnel Lining Structure within Hard Rock Mass Using Wet-Sprayed Technique
Authors: Zhou Tai Quan , Hua Yuan
Published: March 2009

The wet sprayed concrete technique has good virtue of improving the working condition within the tunnel, fewer reflective concrete loss and higher sprayed concrete quality. The concrete mixed with polypropylene fiber could improve the concrete inner structure, the flexural strength, tensile strength and anti-penetrating ability. The application of the wet sprayed polypropylene fiber reinforced concrete in the construction of tunnel lining structure could improve the stability of tunnel rock mass. The nonlinear finite element analysis is performed on rock mass stability of the railway tunnel lining structure and the rock mass stability is analyzed both for the un-lining tunnel and the lining tunnel. The computation result shows that the rock mass plasticity zone distribution with the lining structure is fewer than that without lining structure. To measure the deformation behavior, tunnel deformation measurement sensors are installed in the railway tunnel transverse section. The measured railway tunnel deformation result also shows that the lining structure deforms little and the rockmass is in stable state.
Preparation of Semi-Solid Billet of ZW61 Alloy by Equal Channel Angular Extrusion
Authors: Huang Z.H. , Chen Rongshi , Han En-Hou
Published: March 2009

Strain induced and melt activated (SIMA) is used for the preparation of semi-solid billet through equal channel angular extrusion (ECAE) as strain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment, by which semi-solid billet with fine spherical grains can be prepared. As comparison, extruded ZW61 alloy is also remelted to the semi-solid state. Furthermore, both of the semi-solid isothermal treatment microstructures in as-cast and extruded ZW61 alloy are discussed. ECAE process is found more potential for semi-solid thixoforming for as-cast ZW61 alloy.