bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon Carbide Growth:C/Si Ratio Evaluation and Modeling
Authors: Pons Michel , Nishizawa Shin Ichi , Wellmann Peter J. , Blanquet Elisabeth , Chaussende Didier , Dedulle Jean Marc , Madar Roland
Published: March 2009

Modeling and simulation of the SiC growth processes, Physical Vapor Transport (PVT), Chemical Vapor Deposition (CVD), are sufficiently mature to help building new process equipment or up-scaling old ones. It is possible (i) to simulate accurately temperature and deposition distributions, as well as doping (ii) to quantify the limiting phenomena, (iii) to understand the important role of different precursors in CVD and hydrogen additions in PVT. The first conclusion of this paper is the importance of the "effective" C/Si ratio during CVD epitaxy in hot-wall reactors and its capability to explain the doping concentrations. The second conclusion is the influence of the C/Si ratio in alternative bulk growth technique involving gas additions.
Damage-Free Planarization of 2-Inch 4H-SiC Wafer Using Pt Catalyst Plate and HF Solution
Authors: Okamoto Takeshi , Sano Yasuhisa , Hara Hideyuki , Arima Kenta , Yagi Keita , Murata Junji , Mimura Hidekazu , Yamauchi Kazuto
Published: March 2009

We report a damage-free and efficient planarization process for silicon carbide (SiC) using
platinum as a catalyst in hydrofluoric acid (HF) solution. In previous studies, 4H-SiC (0001) on-axis
wafers were planarized by this process and an extremely flat surface was obtained. However,
electronic device substrates require off-axis wafers. In the present study, 4H-SiC (0001) 8° off-axis
Si-face wafers were planarized using a Pt catalyst plate and HF solution. In the first trial using these
wafers, the surface roughness worsened and a diagonal pattern was observed by phase-shift
interference microscopy. The pattern seemed to have been formed when the Pt plate morphology was
transcribed onto the wafer. The removal rate of the 8° off-axis Si-face wafer is much greater than that
of the on-axis Si-face wafer. Thus, we concluded that the use of a smoother catalyst plate would be
necessary to obtain a smooth 8° off-axis Si-face wafer surface. Improving the Pt plate morphology by
hand lapping also improved the surface roughness of the processed wafer as compared with the
preprocessed surface. The maximum height of the surface irregularity (peak-to-valley, P-V) and
root-mean-square roughness were improved to 0.513 nm and 0.044 nm, respectively, as determined
by atomic force microscopy (2×2 μm2).
Temperature Dependence of Plasma Chemical Vaporization Machining of Silicon and Silicon Carbide
Authors: Sano Yasuhisa , Watanabe Masayo , Kato Takehiro , Yamamura Kazuya , Mimura Hidekazu , Yamauchi Kazuto
Published: March 2009

Silicon carbide (SiC) is a promising semiconductor material for power devices. However, it
is extremely hard and chemically stable; thus there is no efficient method of machining it without
causing damage to the machined surface. Plasma chemical vaporization machining (PCVM) is
plasma etching in atmospheric-pressure plasma. PCVM has a high removal rate because the radical
density in atmospheric-pressure plasma is much higher than that in conventional low-pressure
plasma. Although it was found that the machining characteristic of SiC by PCVM had stronger rf
power dependence than that of Si, it has not been clear whether it is radical density dependence or
temperature dependence. In this paper, the temperature dependences of the PCVM of Si and SiC are
examined using pipe electrode apparatus. As a result, it is found that the removal rate of SiC has a
much stronger temperature dependence than that of Si and that the surface roughness of the SiC Si
face becomes worse as the etching temperature increases whereas that of the C face does not increase
at etching temperatures of up to 360°C.
An Examination of Material-Related Performance in SiC Heated Elements for IR Emitter and Sensor Applications
Authors: Chen Li , Mehregany Mehran
Published: March 2009

Micro-hotplate platforms, including the heating and sensing resistors, are fabricated by
surface micromachining techniques from nitrogen-doped, polycrystalline SiC films deposited by
low-pressure chemical vapor deposition. The resulting heated elements are operated without the need
for metal electrodes. For comparison, platinum is also used as the heating/sensing resistor on top of
otherwise similar SiC micro-hotplates. After characterizing the fundamental thermal transient
response of the resulting micro-hotplates, accelerated aging tests are carried out by increasing the
input power until the heating resistors fail. Material-related kinetic degradation analysis is conducted
to estimate the life time of such elements as infrared emitters.
Mechanical Properties of Poly 3C-SiC Thin Films According to Carrier Gas (H2) Concentration
Authors: Chung Gwiy Sang , Han Ki Bong
Published: March 2009

This paper presents the mechanical properties of 3C-SiC thin film according to 0, 7, and 10
% carrier gas (H2) concentrations using Nano-Indentation. When carrier gas (H2) concentration was
10 %, it has been proved that the mechanical properties, Young’s Modulus and Hardness, of 3C-SiC
are the best of them. In the case of 10 % carrier gas (H2) concentration, Young’s Modulus and
Hardness were obtained as 367 GPa and 36 GPa, respectively. When the surface roughness according
to carrier gas (H2) concentrations was investigated by AFM (atomic force microscope), when carrier
gas (H2) concentration was 10 %, the roughness of 3C-SiC thin was 9.92 nm, which is also the best of
them. Therefore, in order to apply poly 3C-SiC thin films to MEMS applications, carrier gas (H2)
concentration’s rate should increase to obtain better mechanical properties and surface roughness.
Reliability Aspects of High Voltage 4H-SiC JBS Diodes
Authors: Brosselard Pierre , Camara Nicolas , Jordá Xavier , Vellvehi Miquel , Bano Edwige , Millan José , Godignon Philippe
Published: March 2009

1.2 kV and 3.5 kV JBS diodes have been fabricated using the same technology process.
After 50 hours of DC stress, 1.2 kV diodes do not exhibit any degradation in forward mode whereas
the 3.5 kV JBS diodes show a degradation after ten hours. This behaviour has been confirmed by
the formation of Stacking Faults clearly illustrated by electroluminescence microscopy in 3.5 kV
JBS diodes, whereas it is not the case for the 1.2 kV JBS diodes.
Distribution of Forward Voltage of SiC Schottky Barrier Diode Using Ti Sintering Process
Authors: Kuroda Kenichi , Matsuno Yoshinori , Ohtsuka Kenichi , Yutani Naoki , Shikama Shozo , Sumitani Hiroaki
Published: March 2009

The forward current density-voltage (JF-VF) characteristics of SiC Schottky barrier diodes
(SBDs) with an epilayer thickness between 9.6 and 10 μm and donor concentration (ND) ranging from
4.0x1015 to 5.7x1015 cm-3
was evaluated. It was found that the Schottky barrier height (Φb) can be
stabilized by Ti sintering process and the forward current (IF) abruptly rises at the same knee voltage
for all samples. On the other hand, the on-resistance (Ron) and VF were dispersed. The instability
corresponds to the values calculated by the dispersion of ND, substrate resistivity and substrate
thickness.
3.3 kV-10A 4H-SiC PiN Diodes
Authors: Brosselard Pierre , Camara Nicolas , ul Hassan Jawad , Jordá Xavier , Bergman Peder , Montserrat Josep , Millan José
Published: March 2009

An innovative process has been developed by Linköping University to prepare the 4HSiC
substrate surface before epitaxial growth. The processed PiN diodes have been characterized in
forward and reverse mode at different temperature. The larger diodes (2.56 mm2) have a very low
leakage current around 20 nA @ 500V for temperatures up to 300°C. A performant yield (68%) was
obtained on these larger diodes have a breakdown voltage superior to 500V. Electroluminescence
characteristics have been done on these devices and they show that there is no generation of
Stacking Faults during the bipolar conduction.
Challenges in Integration of Piezoelectric Ceramics in Micro Electromechanical Systems
Authors: Dorey R.A.
Published: March 2009

Lead zirconate titanate (PZT) thick films, a few tens of micrometres thick, are of technological interest for integration with microsystems to create micro electromechanical systems (MEMS) with high sensitivity and power output. This paper examines the challenges faced in integrating thick film PZT with other materials to create functional micro devices. Thermal, chemical and mechanical challenges associated with integration will be examined and potential solutions explored.
Ceramic and Glass Matrix Composites Containing Carbon Nanotubes
Authors: Cho Johann , Boccaccini Aldo Roberto
Published: March 2009

Carbon nanotubes (CNTs) are promising reinforcing elements for structural composites due to their remarkable mechanical properties. The impressive electrical and thermal properties of this new form of carbon also make CNTs containing composites ideal candidates for multifunctional applications. In the past decade, researchers have investigated CNTs as toughening inclusions to overcome the intrinsic brittleness of ceramics and glasses. Although there are numerous investigations available in the literature, a significant progress has not occurred or it has been rather slow compared to advances in the field of CNT/polymer matrix composites. This paper reviews current trends in research and development efforts on the use of CNTs for fabrication of ceramic and glass matrix composite materials. The review includes a summary of key issues related to the optimisation of CNT-based composites and an overview of investigations dealing with processing techniques developed to optimise dispersion quality, interfaces and density. The mechanical properties of as-produced composites are discussed and a comprehensive comparison of data available for different matrix materials is presented. Finally, the potential applications of the resulting CNT/inorganic matrix composites and the scope for future developments in the field are highlighted.
Defects in Electron Irradiation Te-Doped GaSb Studied by Positron Lifetime Spectroscopy
Authors: Li H. , Ke J.Y. , Pang J.B. , Wang Bo , Wang Z.
Published: March 2009

Defects induced by electron irradiation in Te-doped liquid-encapsulated Czochralski–grown GaSb were studied by the positron lifetime spectroscopy. The lifetime measurements under room temperature indicated there were VGa-related defects with a characteristic lifetime of 298 ps in the heavily Te-doped as-grown GaSb samples. The average lifetime increased with the increase of irradiation dose in lightly Te-doped GaSb,but the behavior was opposite in the heavily Te-doped samples. It should be due to the shift of Fermi level in heavily Te-doped GaSb and the occurrence of gallium vacancies in different charge states. In the temperature dependence measurements carried out on heavily Te-doped samples, we observed positron shallow trap, and this shallow trap should be attributed to positrons forming hyrogenlike Rydberg states with GaSb antisite defects.
The Calculation of Positron Lifetime in Ni3Al Alloy
Authors: Chen Xiang Lei , Guo Wei Feng , Du Huai Jiang , Weng Hui Min , Ye Bang Jiao
Published: March 2009

Superposed-neutral-atom model and the finite-difference method (SNA-FD) are used to calculate the positron lifetime of different sizes and types of vacancy clusters in Ni3Al alloy. The calculated positron bulk lifetime in Ni3Al agrees well with the experimental results mentioned in literatures. The positron lifetimes of vacancy clusters with the same amount of vacancy but different components are also calculated. The results show that the positron lifetime is different when its components are different. The positron lifetimes of vacancy clusters with a single element but different sizes are also calculated. The result shows that the positron lifetime is almost a constant when its component is only Al vacancy, but the positron lifetime will increase at first and trend to be a constant when its component is only Ni vacancy.
Defects in Carbon Allotropes Studied by Positron Annihilation
Authors: Huang Yu Yang , Chen Zhen Ying , Wei Ya Qin , Li Yu Xia , Deng Wen
Published: March 2009

Slow positron beam technique has been employed to study the defects of graphite, nanophase C, as well as the structural changes in un-doped, B-doped and S-doped diamond films with annealing temperatures. The results show that the concentration of defects in nanophase C is higher than that in graphite. The vacancy concentration in the S-doped diamond film is higher than that in un-doped one. The addition of small amount of B atoms leads to the decrease of the vacancy concentration in the film. The vacancy concentration in un-doped diamond film would decrease after annealing at temperature below 600°C, while vacancy concentration will increase after annealing at temperatures above 900°C. The vacancy concentration in the 40 Ω cm B-doped diamond film decreases at annealing temperatures higher than 200°C.
Tungsten Oxide Nanostructures Growth in HFCVD System by Slow Positron Beam
Authors: Lou J. , Ye B.J. , Wang X.P. , Weng H.M. , Du Huai Jiang , Zhang Z.B.
Published: March 2009

Tungsten oxide (WOx) nanostructures were prepared by a hot filament chemical vapor deposition (HFCVD) system. Two series of samples were synthesized by adjusting filaments temperature (Tf) and oxygen gas concentration (OGC). The crystallinity and stoichiometry were highly related to Tf and OGC. The evolution of stoichiometry and types of defects was illuminated by slow positron implantation spectroscopy (SPIS). A turning point of Tf=1750°C was found that at this point the crystallinity and stoichiometry natures were the best. In order to develop the chemical phase from substoichiometric to stoichiometric, the oxygen gas concentration in the mixture gas during deposition should be raised to an appropriate level.
Formation of Ordered Pores Determined by Positronium Time of Flight Spectroscopy
Authors: Qin Xiu Bo , Yu Run Sheng , Kurihara Toshikazu , Cao Xing Zhong , Wang Bao Yi , Wei Long
Published: March 2009

We prepared a series of mesoporous silica films to study the structural information of ordered pores by positronium Time of Flight (Ps-TOF) spectroscopy. By changing the ratio of surfactant to silicon source, the pore structure is tuned. Results show that once ordered pores are formed, clear Ps TOF peak is observed. And the film with less distributed pore geometry leads to a narrowed Ps TOF peak.
Temperature Dependence of Free Volume in Epoxy/Rectorite Nanocomposites by Positron Annihilation
Authors: Zhang Ming , Wang Shao Jie , Liu L.M. , Fang Peng Fei
Published: March 2009

Recently polymer nanocomposites[1,2] have been receiving special attention because of its advantages and unique properties in comparison to the traditional polymer composites.The structural transformation of Epoxy (cured by polyamide) and epoxy/Rectorite nanocomposite(with 0.5% rectorite content) is studied by PALS as a function of temperature from 30K to 490K. For Epoxy and Epoxy/Rectorite nanocomposite, the glass transition temperature (Tg) is observed to be 270K and 260K, the second transition temperature (Tγ) is 160K and 120K, the viscous flow temperature (Tf) is the same as 380K. The result shows that properties of the free-volume in nanocomposite have been changed by the rectorite platelets fully separated in material at low temperature. At the same time, we find that the intensity of o-Ps decreases with increase of the temperature at the softening temperature above the Te.
Freezing of Nanodroplets: Phase Transition of Organic Liquids Confined in Nanopores Studied by Positron Annihilation Spectroscopy
Authors: Dutta Dimple P. , Sharma S.K. , Maheshwari P. , Sudarshan K. , Pujari P.K.
Published: March 2009

Behavior of solids and liquids confined in nano domain has great relevance in fundamental research as well as applications in nanotribology, nanofabrication, membrane separation, interfacial adhesion and lubrication. In this work, we have studied phase transition behavior of different organic liquids confined in nanopores of ZSM-5 zeolite and silica using temperature dependent positron annihilation Doppler broadening and lifetime spectroscopy. It is observed that the freezing and melting properties of liquids confined in nanopores are different from their bulk behavior. The liquid molecules (isopropanol) that feel more attractive interaction with the pore wall show an increase in freezing temperature. Similarly, a liquid like benzene which is weakly attractive with pore wall as compared to its solid phase show a decrease in its freezing point under confinement. The confining pore diameters are in the range of 10-60 Å. It was observed that the shift in phase transition temperature does not follow classical Gibbs-Thomson relation.
Positronium Molecule Formation on Al (111)a
Authors: Deng S.H.M. , Cassidy D.B. , Mills A.P.
Published: March 2009

A single crystal Al (111) sample cleaned by repeated cycles of ion bombardment and annealing was irradiated by a subnanosecond high density positron beam [1] and the resulting positronium lifetime spectra were measured using single shot positron annihilation lifetime spectroscopy (SSPALS) [2]. We observed the amount of positronium emitted dependence on the incident positron beam density, which indicates the formation of positronium molecules (Ps2) at the Al (111) surface [3]. The Ps2 formation probability appears to be extremely sensitive to surface contamination and further experiments under improved vacuum conditions are planned to clarify this effect.
Momentum Distributions of Ortho-Positronium Dependent on Electronic State at Free Volume Walls in Insulators
Authors: Sato K. , Murakami Hideoki , Ito Kenji , Hirata Kouichi , Kobayashi Yoshinori
Published: March 2009

Age-momentum correlation (AMOC) spectroscopy, which can sensitively probe momentum distributions of positrons and positronium (Ps), was conducted for studying the pick-off process of the triplet bound state ortho-Ps (o-Ps) with electrons at the walls of the free volume holes. Influences of different chemical elements forming free volume and the size of the free volume are investigated. It is found that the momentum distribution of o-Ps pick off annihilation sensitively depends on the electronic state. The feasibility of the chemical analysis relevant to the free volume in insulating materials is discussed.
The Interface of Multi-Phase Polymer Systems Studied by Positron Annihilation
Authors: Yu Wen , Chen Zhe , Fang Peng Fei , Wang Shao Jie
Published: March 2009

MA-g-HDPE and PA6-MMT were selected to improve the compatibility of HDPE and PA6. Positron annihilation lifetime spectroscopy (PALS) and optical microscopy were utilized to characterize the interface of the blends.
Atomic Scale Study of Surface Structures and Phase Transitions with Reflection High-Energy Positron Diffraction
Authors: Kawasuso Atsuo , Fukaya Yuki , Hashimoto M. , Ichimiya Ayahiko , Narita H. , Matsuda I.
Published: March 2009

In this work, we studied a few surfaces, of which the structures have not yet been revealed, using reflection high-energy positron diffraction (RHEPD). We studied the Ge(111)/Pb and Ge(111)/Sn surfaces that exhibit the phase transition from 3×3 to √3×√3 periodicities at around 200K. We found that in both phases the equilibrium positions of Pb and Sn adatoms are conserved. That is, in the unit-cell, one of three adatoms is located upper position and two of them are located lower positions (one-up-two-down). The phase transition is interpreted in terms of an order-disorder type. We furthermore studied the quasi-one dimensional Si(111)/In surface which exhibits the metal-insulator transition at around 120K. The high temperature phase is well explained as the zigzag chain structure. We found that a dynamic atomic displacement which leads to the formation of hexagon structure occur below 120 K. We confirmed the appearance of the band gap using the surface structure determined from the RHEPD rocking curves.
Future Material Systems: Requirements and Applications
Authors: Kasper Erich , Müssig Hans Joachim , Grimmeiss Hermann G.
Published: March 2009

Requirements and applications for three different scenarios in material science of microelectronics are discussed. Dimension scaling continous at the same pace (More Moore) by changing to immersion lithography and later to extreme ultraviolet lithography. The functionality of system on chip solutions will be increased by heterogeneous technologies combined with a microelectronics core ( More than Moore). Material science and physical understanding of new device principles started well in advance to judge difficulties and options. The strong links to economy are illustrated by a simple model of exponential growth.
On Similar Electrical, Optical and Structural Properties of MOS Structures Prepared on a-Si:H/c-Si, Porous Silicon/c-Si, and c-Si
Authors: Pinčík Emil , Kobayashi Hikaru , Brunner Róbert , Takahashi Masao , Rusnák Jaroslav , Jergel Matej
Published: March 2009

The paper presents results of research of similar electrical, optical and structural properties of three types of MOS structures prepared on different Si-based semiconductors. Electrical interface properties are investigated by institutionally produced equipment with Charge Version of Deep Level Transient Spectroscopy and time domain C-V. X-ray diffraction at grazing incidence angles is applied to control their structural properties. Optical properties of selected structures are investigated by photoluminescence measurements at liquid helium temperature (approx. 6K in cryostat). Dominant interest is focused on analysis of both electrical properties of MOS porous silicon based structures prepared on p-type crystalline Si and photoluminescence signals of the structures observed around 1.1 eV, respectively.
Such parameters as Fermi level position, flat-band voltage, surface potential, position of deep level hole traps, and acceptor density are calculated for various conditions as defined by sample ambient, temperature, and light illumination. Following two main findings are analyzed: i) total suppression of large C-V hysteresis due to suitable illumination and ii) recovering of part of detected interface states in the dark.
Properties of CdS Thin Films Grown by Chemical Bath Deposition as a Function of Bath Temperature
Authors: Moualkia H. , Hariech S. , Aida M.S.
Published: March 2009

The present work deals with the preparation and characterization of cadmium sulfur (CdS) thin films. These films are prepared by chemical bath deposition on the well cleaned glass substrates. The thickness of the samples was measured by using profilometer DEKTAK, structural and optical properties were studied by X-ray diffraction analysis, and UV-visible spectrophotometry. The optical properties of the films have been investigated as a function of temperature. The band gap energy and Urbach energy were also investigated as a function of temperature. From the transmittance data analysis the direct band gap ranges from 2.21 eV to 2.34 eV. A dependence of band gap on temperature has been observed and the possible raisons are discussed. Transmission spectra indicates a high transmission coefficient (75 %). Structural analysis revealed that the films showed cubic structure, and the crystallite size decreased at a higher deposition temperature.
Water Molecule Sensitive Layers Deposited from Hexamethyldisiloxane/Oxygen Mixture at Low Temperature
Authors: Guermat N. , Bellel A. , Sahli Salah , Segui Y. , Raynaud Patrice
Published: March 2009

Humidity sensors are widely used in industry production, process control, environment monitoring, medical and electrical applications. In this study, water molecule sensitive layers have been elaborated by plasma enhanced chemical vapor deposition PECVD technique, from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) in different proportions. The films were deposited on a comb-shape aluminum electrode evaporated on glass substrate. Electrical and structural characteristics of the elaborated humidity sensors were evaluated by humidity-impedance characteristics, infrared spectroscopy FTIR and ellipsometric analysis. Electrical analysis showed that the elaborated humidity sensor exhibited a detectable response to relative humidity ranging from 35 to 95%. However, increasing O2 concentration in the mixture during deposition, leads to a significant decrease of the sensor sensibility. A sensor elaborated with pure vapor of HMDSO exhibited a better sensibility. FTIR analysis revealed that increasing O2 concentration induces a decrease of methyl groups CH3 and the formation of Si-O groups leading to film densification. Besides, the values of the refractive index deduced from ellipsometric data indicated that the refractive index increases with increasing the O2% in the mixture. This observation may be considered as further evidence to film densification.
Effect of Process Conditions on Microstructure and Properties of Bioactive Glass
Authors: Chen Xiao Feng , Hu Jing , Zhao Na Ru , Meng Yong Chun , Li Yu Li
Published: March 2009

The bioactive glass is used widely as bone-repairing material due to its excellent bioactivity, biocompatibility and the function for bone restoration, which depended, to a great extent, on the composition, microstructure of the glass and the process conditions. In this study, effect of process conditions (the melting temperature and time) on compositions, microstructure and the properties of bioactive glass was analyzed using EDS, Density measurement, XRD and FTIR techniques. The results indicated that compositions and microstructure changed because of the selective evaporation of constituent and the change in homogeneity of components.The bioactivities of the glasses prepared under different process conditions were characterized by immersing the glass particles in simulated body fluid (SBF) combined with FTIR technique. The results indicated that hydroxyl-carbonate-apatite (HCA) layer formed on the surface of the samples after 24 hours soaking in SBF. A quantitative method was used to compare the bioactivity of samples. It indicated the different preparation processes had influence on the bio-mineralization properties. Then the optimal preparation condition (1450°C, 30min) was obtained.
Toughness Analysis of Cannon Bone Based on Microstructural Model
Authors: Chen Bin , Sun Shi Tao , Peng Xiang He
Published: March 2009

As a typical biological material, bone possesses high fracture strength and fracture toughness, which are closely related to its exquisite microstructure. SEM observation of a cannon bone shows that the bone is a kind of layered bioceramic composite consisting of hydroxyapatite sheets and collagen matrix. The hydroxyapatite sheets are of long and thin shape, distributing in parallel. The fracture toughness of the bone is analyzed with the representative model of the hydroxyapatite sheets and the concept of maximum pullout energy. It is shown that the lathy shape as well as the parallel distribution of the hydroxyapatite sheets increases the pullout energy and endows the bone with high fracture toughness.
Effect of Microstructure and Texture on Corrosion Resistance of Magnesium Alloy
Authors: Xin Ren Long , Wang Mao Yin , Gao Jia Cheng , Liu Pei , Liu Qing
Published: March 2009

Magnesium alloys are considered as candidate materials for biodegradable implants. However, the key issue is that they corrode too fast in physiological environment. The aim of this study is to investigate the effect of microstructure and texture of magnesium alloys on their corrosion resistance. Magnesium alloy AZ31 extruded rod, hot rolled sheet and extruded sheet with different initial microstructure and texture were prepared. Then they were immersed in conventional simulated body fluid (SBF) for several days for corrosion evaluation. The corrosion products and precipitates on their surfaces were examined by scanning electron microscopy (SEM). The preliminary results showed that the initial microstructure and texture of AZ31 alloys has considerable effect on the weight loss rate of the alloys, suggesting that it is possible to enhance the corrosion resistance of AZ31 alloys through tailoring the microstructure and texture of the alloys.
Phase Transformation of Biomedical Metastable β Titanium Alloy during Aging
Authors: Guo Ai Hong , Cui Wen Fang , Wu Yi Zhou , Liu Xiang Hong , Zhou Lian
Published: March 2009

A kind of metastable β type Ti-30Nb-13Zr-0.5Fe (wt.%) alloy for biomedical application was newly designed and developed. In order to exam the phase transformation during aging and its effects on the mechanical properties, the alloy was β solubilized and aged at 350°C-550°C for 4 hours. The microstructures were observed by OM and TEM, and the phase structures were identified by XRD. The tensile tests were performed with various aged microstructures. The results show that a lot of ω phase precipitates during aging at 350°C, leading to the increase of strength and elastic modulus and drastic decrease of plasticity. Aging at 450°C, dot α phase uniformly precipitates from metastable β phase. The good combination of high strength 、high plasticity and low elastic modulus was obtained under this aging condition. With increasing aging temperature and aging time α precipitations coarsen and precipitation free zones (PFZ) along prior β grain boundaries form, which are the main reasons to lower the strength and plasticity.
Effect of Red Mud on Mechanical Properties of Loess–Containing Aluminosilicate Based Cementitious Materials
Authors: Wan Jian Hua , Sun Heng Hu , Wang Ying Ying , Li Chao
Published: March 2009

The effect of the thermal treated red mud on mechanical properties of loess –containing aluminosilicate based cementitious materials is investigated. And the characteristic of hydration production is tested using XRD, SEM and EDAX methods. The results show that the thermal treated red mud not only has excellent cementitious properties but also can improve the mechanical properties of loess –containing aluminosilicate based cementitious materials. Moreover when the content of red mud is 5%, the improved effect is optimal. On the one hand, the alkaline ingredients of red mud can promote abundant ettringites to produce at early ages. And the ettringites contribute to early strength of the cementitious material. On the other hand, the content of red mud is too high to improve the long-term strength.
Study on the Electrochemical Behavior of Ferric Stearate and its Electro-Catalytic Oxidation of Hydrogen Peroxide
Authors: Liang Li Li , Luo Xue Gang , Lin Xiao Yan
Published: March 2009

A ferric stearate electrode was made by doctor-blade methods using the Fluorine tin oxide (FTO) conductive glass. The electrochemical behavior of ferric stearate electrode was studied by the cyclic voltammetry. The electro-catalytic effects of ferric stearate on H2O2 were also investigated by cyclic voltammetry.
Enhancement Corrosion Resistance of (3–Glycidoxylpropyl)- Silsesquioxane Hybrid Films and its Validation by Gas-Molecule Diffusion Coefficients Using MD Simulation
Authors: Xie Gang , Wang Peng , Hu Li Jiang
Published: March 2009

Based on silsesquioxanes (SSO) derived from hydrolytic condensation of (–glycidoxylpropyl) trimethoxysilane (GPMS) and tetraethoxysilane (TEOS), two hybrid films, f-GPMS-TEOS-SSO (f-GTS) modified with 10 wt-% TEOS and f-GTS modified with 50 wt-% DGEBA (f-GTSD), were prepared. The anticorrosion properties (corrosion potential, Ecorr, and corrosion current density, Icorr) of the bare aluminum alloy (AA) and the two films on AA were tested by electrochemical measurements with typical potentiodynamic polarization curves. The Icorr values of three samples were significantly different with the order of f-GTSD<f-GTS<AA， which implies that the DGEBA addition in the f-GTSD coating indeed enhances the electrochemical corrosion resistance. Two different 3D-amorphous cubic unit cells, cell(f-GTS) and cell(f-GTSD), as models were employed to investigate self-diffusion coefficients by MD simulation for the NO2, SO2 and H2O molecules. All the three self-diffusion coefficients of NO2, SO2 and H2O diffusing in cell(f-GTSD) were less than the coefficients in cell(f-GTS), which validates the corresponding anticorrosion-experiment results. Two reasons that the addition of DGEBA in the system of f-GTS lead to the decrease of the gas self-diffusion coefficient compared to the f-GTS system were discussed.
Preparation, Characterization and Oxidation Mechanism Study of Biomorphic Porous Carbon Coated with SiC Gradient Coating
Authors: Wu Ming Jian , Gao Peng Zhao , Liu Yan Li , Xiao Han Ning
Published: March 2009

A biomorphic porous carbon coated with gradient SiC coating (SiC/BPC) was prepared by controlled carbonizing native pine under Ar atmosphere and then processed with precursor infiltration-pyrolysis (PIP) of organosilan. Microstructure and component of SiC/BPC were performed by SEM, EDS (attached with line scanning program) and XRD. The non-isothermal oxidation properties and mechanism of SiC/BPC were studied by TGA. The kinetic parameters were calculated through model-functions methods. Experimental results showed that SiC/BPC has a topologically uniform interconnected porous network microstructure, the SiC coating was amorphous and combines well with the carbon surface, which improved the oxidation resistance of BPC material about 150K. The non-isothermal oxidation reaction of SiC/BPC exhibited the characteristic of self-catalytic, the oxidation mechanism of SiC/BPC was 2-D diffusion, decelerator -t curve, the kinetic parameters are lgA/min-1= 15.483；E/kJ•mol-1 = 287.49.
Photo-Oxidative Degradation of Metallocene Linear Low-Density Polyethylene
Authors: Bai Fu Chen , Zhang Chun Xiao , Zhang Xi Yao , Liu Jian , Tian Wei
Published: March 2009

Films of linear-low density polyethylenes, made from metallocene catalyst and Ziegler-Natta catalyst , were exposed to accelerate photo-oxidation conditions. The investigations were focused on the changes of the physical and chemical structures and elongation at break occurring in the photo-oxidation process. The results showed that ethylene-hexene m-LLDPE was more favorer to photo-oxidize than ethylene-octene LLDPE. The other two ethylene-ocetene m-LLDPEs were comparable to LLDPE with the same comonomer. The oxidation rate of LDPE is slower than those of all the LLDPEs.
Preparation and Photocatalytic Activity of Fe-Doped TiO2 Nanopowders
Authors: Ren Bai Xiang , Teng Hong Hui
Published: March 2009

(0-2%) Fe-doped TiO2 nanopowders were prepared by sol-gel method. The Size, structure, appearance, the light absorption and hydroscopicity properties were characterized by XRD, TEM, UV-Vis and FTIR. The photocatalytic degradation of crystal violet under UV over catalyst was used as a probe reaction to evaluate their photocatalytic activity, the dependence of photocatalytic properties on Fe doping content and roasting temperature were also discussed. The results show that the process of phase transfer of TiO2 from anatase to rutile was promoted by doping Fe, 1.5% Fe3+-doped TiO2 nanoparticles formed many defects at grain boundaries, inhibited effectively the recombination of the photoproduced e-/h+, improved the efficiency of photons, enhanced the absorbing water function of catalyst, and 1.5% Fe3+-doped TiO2 revealled strongly absorption in UV and widened obviously absorption in Vis. Photocatalytic degradation ratio of crystal violet (4mg/L) on 1.5% Fe3+-doped TiO2 was increased 30% than pure TiO2.
Influence of Silver / CNTs on Epoxide Resin Based Conductive Adhesive
Authors: Liang Shu Quan , Tang Yan , Zhang Yong , Jie Zhong , Tan Xiao Pin
Published: March 2009

Silver / CNTs was prepared by ball milling method and was used as filler to reinforce epoxide resin based conductive adhesive. The effect of content and dispersion state of the filler on tensile strength, tensile modulus, fracture extensibility and electrical resistance of the composites were studied. The results indicated that the filler could be dispersed well in epoxide resin matrix by ultrasonic method and the mechanical and electrical properties was improved greatly. The best content of the silver / CNTs was 0.75 wt% (considering of CNTs weight percentage), when the tensile strength, tensile modulus and fracture extensibility increased 42.6%, 18.8% and 115.3% respectively. With the increase of silver/CNTs, the conductivity of the matrix increased significantly. The micro structure analyses showed that the silver-covered CNTs worked as conductive channel and the electrons were easy to transfer through silver powder by CNTs network.
Fabrication of Plasma Treated Nano Zinc Oxide/PP/PLA Composites Filaments Using Melt Spinning
Authors: Zhang Ying Chen , Wu Hong Yan , Qiu Y.P.
Published: March 2009

The Melt spinning technique of Nano Zinc Oxide/PP/PLA composites filaments fabricated by plasma treated Nano Zinc Oxide（NZOP） was studied in the present investigation. The experimental results showed that the physical and mechanical properties of Nano Zinc Oxide/PP/PLA composites filaments depended on the following factors of the percentage of NZOP, the percentage of maleic anhydride (MAH), the plasma treatment parameters, helium gas flow rate, output power, sample treatment or stationary time and oxygen gas flow rate. Among them the oxygen gas flow rate had the significant influence on the filament properties of tensile modulus, the yield strength, the melting temperature and the crystallization temperature. Stepwise multiple regressions orthogonal design method of system optimization was used to determine the percent of contribution of each factor. It was found that the four indicators were different by these analyses. The experimental results indicated that the optimized conditions by stepwise multiple regressions were better than that by traditional analysis.
Analysis of Improved Photoelectric Properties of Copper Phthalocyanine/C60 Organic Solar Cells: Effects of Substrate Temperature
Authors: Zhou Wen Jing , Shi Wei Min , Wu Li
Published: March 2009

Organic photovoltaic(OPV) cells are rapidly gaining attention due to their potential to be fabricated at low cost in thin, flexible, and light-weight forms. For efficient generation of photo-induced charges,C60 has been indispensable electron acceptors in building heterojunctions with various suitable electron donors, such as CuPc, and Alq3 was always used as a new buffer layer to improve the degradation of heterojunction conductivity upon oxygen permeation
In this work, the photoelectric properties of organic solar cells(ITO/CuPc/C60/ Al) were studied with a focus on the effect of substrate temperature. All the organic layers and the aluminum cathode were prepared onto ITO substrates by vacuum deposition at various substrate temperatures from room temperature to 363°CK. With increasing the substrate temperature , an improvement in crystallization of bilayer films(CuPc/C60) was observed by AFM. The results showed the photoconduction of the bilayer films increased because the bilayr films were well oriented, and the carrier mobility of the films were enhanced withby the increase of the substrate temperature.
One-Step Sintering of CoSb3 Thermoelectric Material and Cu-W Alloy by Spark Plasma Sintering
Authors: Zhao De Gang , Wang Li , Cai Yan Hong , Jiang Wan , Chen Li Dong
Published: March 2009

In this study, we designed a suitable electrode material was designed, Cu-W alloy, which achieved a good thermal match with CoSb3 thermoelectric (TE) material. By means of spark plasma sintering (SPS), Cu-W alloy was introduced into CoSb3/Ti/Cu-W TE element successfully. Finite element analysis showed that the maximum thermal residual stress appeared at the cylindrical surface zone close to the CoSb3/electrode interface. SEM and EPMA results showed that an intermetallic compound (IMC) layer formed at the CoSb3/Ti interface and EDS analysis confirmed the IMC layer was TiSb phase. Shear tests showed that the shear strength of CoSb3/Ti/Cu70W30 joint was about 50Mpa. The potential profile of the interface area was measured by the four-probe method and the result showed no abrupt change in voltage was found around the interface. The high temperature reliability evaluation showed the joint had high thermal duration stability.
Effect of B2O3 on Long-Last Phosphorescence of SrAl2O4:Eu2+,Dy3+
Authors: Wang Yu Hua , Song Xin Yu , Zhang Shui He
Published: March 2009

A series of Sr0.95Al2O4:Eu2+0.02, Dy3+ 0.03•nB2O3 (0≤n≤0.30) were prepared by a solid state reaction. The role of B2O3 on the photoluminescence (PL) properties of Sr0.95Al2O4:Eu2+0.02, Dy3+0.03 were evaluated with UV emission spectra and decay curves. B2O3 significantly improved the emission intensity and persistent luminescence time. The crystal environment and defects induced by B3+ doping were detected with IR spectra, thermoluminescence and positron annihilation (PA) methods. Some Al3+ were substituted by B3+ and a kind of defect complex cluster responsible for the long decay time was formed when the substitution of Al3+ by B3+ occurs.
Polyamide as a Matrix for the Creation of Form-Stable Phase Change Materials
Authors: Guo Jing , Li Nan
Published: March 2009

Phase change materials (PCMs) with storing and releasing energy properties have been widely used in lots of fields such as solar energy storing, smart housing, thermo-regulated fibers, and agricultural greenhouse. Here, PCMs based on polyamide 6 (PA6) blended with Polyethylene glycol (PEG) was studied. In order to improve the compatibility between PA6 and PEG, a PA6-PEG block copolymer was synthesized and added to the blends. The structure and properties of the block copolymer were determined by Fourier Transform Infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and optics microscope (OM). The results of DSC analysis showed that tThe copolymer block is phase separated. DSC results also showed that the phase transition temperature of the blend is different from that of pure PEG, indicating the interaction occurrence between PEG and PA6 by using PA6-PEG block copolymer, the latent heat of PEG/PA6 blend increased with the mass percent of PEG. The results of tThermal cycling tests showed that the blend as a PCM has good long-term thermal reliability.
Structural Study on Ammonia Borane for Hydrogen Storage
Authors: James W.J. , Jagat L. , Cai Q. , Yelon W.B. , Yang J.B.
Published: March 2009

Ammonia borane(BH3NH3) is a promising hydrogen storage material because of its high gravimetric (19.6 wt% H2) and volumetric hydrogen density with an accompanying moderate decomposition temperature. Previously reported structures determined by using x-ray and neutron diffraction on hydrides show differences in bond lengths and atomic coordination. Here, the crystal structures of fully and half deuterated ammonia borane were investigated as a function of temperature using powder neutron diffraction. The neutron diffraction patterns show a significant difference due to large difference in the scattering length of D and H. It is evident that an order-disorder phase transition occurs around 225 K for all compounds. At low temperature, the compound crystallizes in the orthorhombic structure with space group Pnm21 and gradually transforms to a high temperature disordered tetragonal structure with space group I/4mm at about 225K. The differential scanning calorimetry studies confirm this phase transformation and also indicate that all compounds melt and decompose at above 370 K. The c cell parameter remains unchanged in the orthorhombic phase from 16 K to 200K and increases liaa nearly above 225K. As the temperature is increased, the BH3-NH3 groups start to reorient along the c axis, and the D/H atoms become disordered, leading to the tetragonal phase transition around 225K.
Application of ANN Back-Propagation for Fracture Design Parameters in Extra-Low Cycle Rotating Bending Fatigue
Authors: Duan Hong Yan , Li You Tang , Zhang Jin , He Gui Ping
Published: March 2009

The fracture problems of ecomaterial (aluminum alloyed cast iron) under extra-low cycle rotating bending fatigue loading were studied using artificial neural networks (ANN) in this paper. The training data were used in the formation of training set of ANN. The ANN model exhibited excellent in results comparison with the experimental results. It was concluded that predicted fracture design parameters by the trained neural network model seem more reasonable compared to approximate methods. It is possible to claim that, ANN is fairly promising prediction technique if properly used. Training ANN model was introduced at first. And then the Training data for the development of the neural network model was obtained from the experiments. The input parameters, notch depth, the presetting deflection and tip radius of the notch, and the output parameters, the cycle times of fracture were used during the network training. The neural network architecture is designed. The ANN model was developed using back propagation architecture with three layers jump connections, where every layer was connected or linked to every previous layer. The number of hidden neurons was determined according to special formula. The performance of system is summarized at last. In order to facilitate the comparisons of predicted values, the error evaluation and mean relative error are obtained. The result show that the training model has good performance, and the experimental data and predicted data from ANN are in good coherence.
Electrochemical Performance of Tin-Aluminum Thin Film Anodes for Lithium Ion Battery
Authors: Yu Hong Wen , Hu She Jun , Hou Xian Hua , Ru Qiang , Zhao Ling Zhi , Li Wei Shan
Published: March 2009

Tin and tin-aluminum thin film anodes for lithium ion battery are deposited on a copper substrate by radio frequency (RF)-magnetron sputtering at room temperature. Charge/discharge characteristics are compared. It is indicateds that tin-aluminum anode has higher capacity and better cycle performance than that of pure tin anode. XRD shows that tThe tin-aluminum thin film is a mischcrystal alloy. The first discharge capacities of tin and tin-aluminum are 750mAh/g and 1205mAh/g respectively. After 30 times charge/discharge, the specific capacity of tin-aluminum anode is 780mAh/g. , compared with 530mAh/g for pure tin anode. From above results, tThe mischcrystal alloying tin with aluminum has effectively improved the electrochemical performance of tin anode. The tin-aluminum mischcrystal alloy will be a promising anode material for lithium ion battery.
Nanocomposite Hydride LaNi5/A- and Mg2Ni/A-Type Materials (A=C, Cu, Pd)
Authors: Jurczyk Mieczyslaw , Nowak Marek , Okonska Izabela , Smardz Lewlaw , Szajek A.
Published: March 2009

In this work, we have synthesized LaNi5/A and Mg2Ni/A (A = graphite, copper or palladium) nanocomposites. The A elements were distributed on the surface of ball milled alloy particles homogenously and role of these particles is to catalyze the dissociation of molecular hydrogen on the surface of studied alloy. Mechanical coating with graphite or palladium effectively reduced the degradation rate of the studied electrode materials. Results showed a significant broadening of the valence bands of studied nanocomposites compared to those obtained by theoretical band calculations. The reasons responsible for the band broadening of the nanocrystalline LaNi5- and Mg2Ni-type alloys are probably associated with a strong deformation of the nanocrystals in the mechanically alloyed (MA) samples. Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded. The valence band spectra of the MA samples could be also broadened due to an additional disorder introduced during formation of the nanocrystalline structure.