bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure and Microanalysis Studies of some Lanthanum-Magnesium Based Hydrogen Storage Alloys
Authors: Zarpelon Lia Maria Carlotti , Ferreira Eliner Affonso , Takiishi Hidetoshi , de Faria Jr. Rubens Nunes
Published: March 2009

Microstructures and chemical compositions of some commercial La-Mg based alloys
have been investigated. The hydrogen storage alloys can be represented by the formulae La2Mgx,
La2Mgx-1Ni and LaMg2Ni9 (x=12 or 17). The determination of the microstructures and phase
compositions of these alloys has been carried out using scanning electron microscopy and energy
dispersive X-ray analysis.
The Design and Building of a Robot with Five Degrees of Freedom
Authors: Hwang Min Chan , Felszeghy Stephen F.
Published: March 2009

Automation engineering is interdisciplinary in its nature. One of the best ways for students to
experience this interplay among different disciplines is by building a robot. However, the complexity of
robotics puts the designing of a robot, from scratch, far beyond most students’ capabilities. It is also
impractical to expect the students to complete this type of a project alone. Hence, we delimit the
students’ project to one of producing a prototype design in collaboration with faculty, and we let the
students concentrate on manufacturing and assembling all the necessary parts to build the robot. The
objective of this paper is to present the many attributes of the robot we had to consider during the robot’s
design, including, the type of material used, the location and type of the joint bearings, the electronic
circuits, the control schemes, etc.
Evaluation of FDM Rapid Prototyping with ABSi Material for Airfoil Design
Authors: Daneshmand Saeed , Ahmadi Nadooshan A. , Aghanajafi C.
Published: March 2009

For faster new product introduction aerospace companies are interested in reducing the
time it takes to make wind tunnel models. The increased capability of rapid prototyping technologies
has made them attractive for this purpose. An experimental study was done of rapid prototyping
technology and their ability to make components for wind tunnel models in a timely and cost effective
manner. This paper discusses the application of wing-body-tail configuration constructed using fused
deposition method (FDM) for Subsonic and transonic wind tunnel testing. An experimental study was
undertaken comparing a rapid prototyping model constructed of FDM Technologies using ABSi
(Acrylonitrile butadiene styrene) to that of a standard machined steel model. Testing covered the
Mach range of Mach 0.3 to Mach 1.3 at an angle-of-attack range of + 4° to +26° at zero sideslip and at
angle of-sideslip ranges from –10 to +10 degrees at 16 degrees angle-of-attack.. Results from this
study show relatively good agreement between the two models. It can be concluded that FDM model
show promise in preliminary aerodynamic development studies and reduction in time and cost.
Application of Dynamic Masking on Rapid Prototyping
Authors: Chen Chien Nan , Hwang Sheng Jye , Lee Huei Huang , Huang Durn Yuan
Published: March 2009

In rapid prototyping (RP) technologies, curing of UV-curable photopolymers is
mainly achieved by the application of laser scanning with limited fabrication speed.
The dynamic masking approach can improve the fabrication speed; however, current
researches and available systems cure photopolymers with visible light rather than UV
light. In this research, we have attempted to develop a UV dynamic masking RP
system by implementing digital micro-mirror device (DMD) from digital light
processing (DLP) technology and TFT liquid crystal display (LCD) panel. A DLP
projector was disassembled and the main components were then recombined to form a
dynamic mask generator. Thus, this study has shown the feasibility of obtaining a UV
dynamic masking RP system that may be integrated for a UV-curable material
processing.
Manufacture of Dye-Sensitized Nano Solar Cells and their I-V Curve Measurements
Authors: Chen Yang Sian , Lee Jing Nang , Tsai Sheng You , Ting Chen Ching
Published: March 2009

The article presents a manufacturing process and their I-V curves measurements
of the dye-sensitized nano solar cells (DSSCs). The constituents of the produced DSSCs are
the photoelectrode, the dyes, the electrolyte, and the counter electrode. In process the constituents
are prepared for assembling individually. Four pieces of slight glass spacers around
the cell edges are sandwiched between the photoelectrode and the counter electrode to build a
gap. The gap is then filled in the liquid electrolyte, which is finished by mixing 0.5M KI and
0.05M I2 in solvent with ethylenecarbonate and propylenecarbonate in a 1 : 9 volume ratio. An
instrument for measurements of photoelectric conversion efficiency and a scanning absorption
spectrum analyzer, which used a metal halide lamp as the light source due to its better fitted
spectrum with the solar spectrum on purple and blue fields, are built in this work.
A Feasibility Study of Using X-Ray Computer Tomography for Ball Grid Array (BGA) Inspection
Authors: Lin Shin Chieh , Lu Hsin I
Published: March 2009

It is of interest to study the feasibility of using computing tomography technique on BGA
inspection. The effects of system parameters on the quality of the reconstructed images were studied
first. The system parameters studied are projection type, projection number, sensor number, and
filter. For fan beam projection, there are two additional parameters are studied. They are the fan beam
arc angle and the sensor geometry. It was found that the increase in projection number and sensor
number generally improve the quality of reconstructed image. The effects of sensor geometry and the
fan beam arc angle are not significant. BGA simulation test show the feasibility of using this
technique to detect the shape and location of defects inside the BGA.
Fabrication and Investigation of Curved PDMS Micro Nozzle/Diffuser
Authors: Chen Yu Tang , Hsu Chin Chun , Kang Shung Wen , Wu Lung Chi
Published: March 2009

This study describes the results on the fabrication, testing and analysis of curved micro
nozzle/diffuser. First, we use different polymers, SU-8 and polydimethylsiloxane (PDMS) for the
fabrication of curved micro nozzle/diffuser. By using the low-temperature bonding technique, we
can combine the structure with the glass and accomplish the component.
In order to understand the investigation and analysis of fluid dynamics characteristics, we
measure the pressure and flow of curved micro nozzle/diffuser and the commercially available
software CFD was adopted for analyzing the performance of straight and curved micro nozzle/
diffuser. If we have a given Reynolds number, the experimental data shows the pressure loss of the
diffuser is lower than that of the nozzle due to the change of momentum. Furthermore, the results
also indicate that the pressure loss coefficient of both curved nozzle and diffuser decrease with the
Reynolds number. All the experimental and numerical data Eventually are compared with each
other. The numerical data was found good agreement with previous analytic solution and
experimental results. In sum, the theoretical analysis and design basis from this study can be
formulated as the reference in the fabrication of micro nozzle/diffuser.
Thermodynamic Modelling of the Corrosive Deposits in Oxy-Fuel Fired Boilers
Authors: Bordenet B. , Kluger Frank
Published: March 2009

The aim to reduce the CO2-emissions has triggered the evaluation of new cycle concepts
for power plants. For the coal-fired power plants, the oxy-fuel firing is a promising option for CO2-
emission reduction. Here, the combustion takes place in a nitrogen-free atmosphere. The oxygen is
separated from the air and burned in near-stoichiometric conditions with the fuel. The gas
composition is significantly changed, when the combustion is changed from air-fired to oxy-fuel
fired condition. For lignite, the carbon dioxide content is raised from 15 to 59vol% and the watercontent
from 10 to ~32%. For the same fuel, the SO2-content in the flue gas increases by a factor of
3-4 to ~0.5%. These changed environmental boundary conditions will affect corrosion life of the
materials especially on the water walls and the heat exchanger surfaces.
Considering the significant changes in the combustion gas, the composition and the occurrence of
the corrosive deposits has been evaluated with the thermodynamic modelling program ‘FactSage’.
The chemical compositions of the deposits have been modelled for dried lignite from Germany. The
results exhibit that the oxy-fuel firing will give a significant change in the atmosphere as well as in
the deposit composition. Consequently, the corrosion rates of current used materials in air fired
boilers need to be evaluated for the application in oxy-fuel fired boilers.
Fireside Corrosion of Stainless and Low Alloyed Steels in a Waste-Fired CFB Boiler; The Effect of Adding Sulphur to the Fuel
Authors: Folkeson Nicklas , Pettersson J. , Pettersson C. , Johansson Lars Gunnar , Skog Erik , Andersson B.Å. , Enestam Sonja , Tuiremo Johanna , Jonasson Anna , Heikne Bengt , Svensson Jan Erik
Published: March 2009

Corrosion field tests have been carried out in the superheater region of a commercial
waste-fired 75MW CFBC boiler using air cooled probes. Exposure time was 24 and 1000 hours.
The effect of adding sulphur to the fuel on the corrosion of two high alloyed steels and a low
alloyed steel was studied. The fuel consisted of 50% household waste and 50% industrial waste.
The exposed samples were analyzed by ESEM/EDX and XRD. Metal loss was determined after
1000 hours. Both materials suffered significant corrosion in the absence of sulphur addition and the
addition of sulphur to the fuel reduced corrosion significantly. The rapid corrosion of the high
alloyed steel in the absence of sulphur addition is caused by the destruction of the chromiumcontaining
protective oxide by formation of calcium chromate. Adding sulphur to the fuel inhibited
chromate formation and increased the sulphate/chloride ratio in the deposit. Iron(II) chloride formed
on the low alloyed steel regardless of whether sulphur was added or not.
Altering Corrosion Response via Grain Boundary Engineering
Authors: Tan L. , Sridharan Kumar , Allen T.R.
Published: March 2009

Grain boundary engineering (GBE) was employed to improve the oxide exfoliation
resistance and mitigate oxide growth by optimizing the grain boundary character distribution.
Studies were performed on alloys of Incoloy 800H and Inconel 617. Alloys 800H and 617 were
selected due to their potential applications for the Generation IV nuclear power systems. The effect
of GBE on the corrosion response was evaluated using supercritical water exposure tests and cyclic
oxidation tests. The microstructure of the tested samples was analyzed by means of optical
microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, electron
backscatter diffraction, and gravimetry. The effects of thermal expansion mismatch and Cr
volatilization on the corrosion response are discussed.
Changes in Nanostructure of Wood Cell Wall during Deformation
Authors: Peura Marko , Andersson Seppo , Salmi Ari , Karppinen Timo , Torkkeli Mika , Hæggström Edward , Serimaa Ritva
Published: March 2009

The excellent mechanical properties of wood arise from its cellular and cell wall structure. X-ray scattering, ultrasound, and mechanical testing is combined to study the effects of strain on crystalline cellulose in wood. Results for dry and re-moistened softwood samples are reviewed and new results are presented for native, never-dried samples of Silver birch. When softwood is stretched parallel to the cell axis, the mean microfibril angle diminishes significantly in compression wood, but only slightly in clear wood. The cellulose chains in the crystallites elongate and their distance diminishes. In the never-dried Silver birch samples, axial strain caused the mode of the microfibril angle distribution to slightly decrease from the initial value of 14 degrees to 12 degrees. Unlike in softwood, in never-dried birch crystalline cellulose showed auxetic tensile behaviour. The distance of the chains increased and the X-ray Poisson ratio νca was negative, -0.3 ± 0.2. Dehydration of never-dried Silver birch caused no difference to the microfibril angle distribution.
1200-V, 50-A, Silicon Carbide Vertical Junction Field Effect Transistors for Power Switching Applications
Authors: Veliadis Victor , McNutt Ty , McCoy Megan , Hearne Harold , De Salvo Gregory , Clarke Chris , Potyraj Paul , Scozzie Charles
Published: March 2009

High-voltage normally-on VJFETs of 0.19 cm2 and 0.096 cm2 areas were manufactured in
seven photolithographic levels with no epitaxial regrowth and a single ion implantation event. A self
aligned guard ring structure provided edge termination. At a gate bias of -36 V the 0.096 cm2 VJFET
blocks 1980 V, which corresponds to 91% of the 12 μm drift layer’s avalanche breakdown voltage
limit. It outputs 25 A at a forward drain voltage drop of 2 V (368 A/cm2, 735 W/cm2) and a gate
current of 4 mA. The specific on-resistance is 5.4 mΩ cm2. The 0.19 cm2 VJFET blocks 1200 V at a
gate bias of -26 V. It outputs 54 A at a forward drain voltage drop of 2 V (378 A/cm2, 755 W/cm2) and
a gate current of 12 mA, with a specific on-resistance of 5.6 mΩ cm2. The VJFETs demonstrated low
gate-to-source leakage currents with sharp onsets of avalanche breakdown.
Semipolar Nitrides Grown on Si(001) Offcut Substrates with 3C-SiC Buffer Layers
Authors: Abe Yoshihisa , Komiyama Jun , Isshiki Toshiyuki , Suzuki Shunichi , Yoshida Akira , Ohishi Hiroshi , Nakanishi Hideo
Published: March 2009

The growth process of semipolar GaN(10-12) on Si(001) offcut substrates with 3C-SiC
buffer layers has been investigated. From XRD analysis, the difference in the crystal orientation
between GaN(10-12) and 3C-SiC(001) has been found to be around 8˚ toward the [110] direction of
the 3C-SiC templates. From TEM observations, a cubic-phase AlN seed layer is found to grow on
3C-SiC(001) templates, and the swift transition from the cubic phase to a hexagonal phase leads to the
stable growth of hexagonal nitrides. Using 8˚-offcut Si substrates, it is possible to obtain a mirror-like
surface of GaN(10-12) using an approximately 10-nm-thick AlN seed layer, which swiftly transitions
from cubic AlN to hexagonal GaN.
HRTEM Analysis of AlN Layer Grown on 3C-SiC/Si Heteroepitaxial Substrates with Various Surface Orientations
Authors: Isshiki Toshiyuki , Nishio Koji , Abe Yoshihisa , Komiyama Jun , Suzuki Shunichi , Nakanishi Hideo
Published: March 2009

Epitaxial growth of AlN was carried out by MOVPE method on SiC/Si buffered
substrates prepared by using various Si surfaces of (110), (211) and (001). Cross-sectional HRTEM
analyses of the interfaces between SiC buffer layer and AlN epitaxial layer disclosed characteristic
nanostructures related growth mechanism on the each substrate. In the case of Si(110) and Si(211)
substrate, hexagonal AlN grew directly on SiC(111) plane with AlN(0001) plane parallel to it. In
contrast, growth on Si(001) substrate gave complicate structure at AlN/SiC interface. Hexagonal
AlN didn’t grow directly but cubic AlN appeared with a pyramidal shape on SiC(001). When the
cubic AlN grew 10nm in height, structure of growing AlN crystal changed to hexagonal type on the
pyramidal {111} planes of cubic AlN.
A Silicon Carbide Accelerometer for Extreme Environment Applications
Authors: Rajgopal Srihari , Zula Daniel , Garverick Steven , Mehregany Mehran
Published: March 2009

A polycrystalline silicon carbide (poly-SiC) surface-micromachined capacitive
accelerometer is designed, fabricated and tested. Leveraging the superior thermo-mechanical and
chemical resistance properties of SiC, the device is a first step toward cost-effective implementation
of a new class of extreme environment accelerometers, for example for high temperature vibration
and shock measurements, even thought this initial work is at room temperature. The accelerometer
described herein is designed for a range of 5000 g and a bandwidth of 18 kHz, specifications
consistent with commercially available piezoelectric devices for high-level mechanical impact
measurements. Test results demonstrate the sensor achieving a resolution of 350 mg/√Hz at 1kHz
with a sensitivity of 12 μV/g and a bandwidth of 10 kHz at room temperature.
Consolidation of Amorphous Aluminum Alloy Powder by Equal Channel Angular Extrusion
Authors: Senkov O.N.
Published: March 2009

Semi-amorphous aluminum alloy powders produced by gas atomization were compacted using equal channel angular extrusion (ECAE) in the temperature range of 200-300°C. Microstructures of the compacts were studied after different levels of ECAE deformation, which allowed analysis of the mechanism of particle interactions, deformation and bonding during different stages of consolidation. Very non-homogeneous deformation of the compacted material was detected. At the temperatures of compaction, amorphous powder particles were much softer than fully crystalline powder particles, and they were severely deformed while the crystalline particles remained nearly spherical. Almost full consolidation occurred in regions predominantly consisting of amorphous and semi-amorphous powder particles at true strains of ~2. However, further excessive deformation led to strain localization and shear crack formation in the consolidated regions. Regions dominated by fully crystalline spherical particles with brittle intermetallic phases showed poor consolidation due to particle rotations and particle fracture; leading to weak particle bonding. The results show that consolidation is impeded by the presence of fully crystalline particles in the powder.
Nanostructures and Microhardness in Al and Al–Mg Alloys Subjected to SPD
Authors: Roven Hans Jørgen , Liu M. , Murashkin Maxim Yu. , Valiev Ruslan , Kilmametov A.R. , Ungár Tamás , Balogh L.
Published: March 2009

Nanostructures and microhardness of a commercial purity Al, three binary Al–Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion (HPT) at room temperature were comparatively investigated using high-resolution transmission electron microscopy, X-ray diffraction (XRD) and high-resolution XRD line profile analysis. The hardness values of HPT samples are twice to three times larger than that of the undeformed counterparts. Grain sizes measured by XRD are in the range 10–200 nm with typical average values ranging from 46 to 120 nm. The hardness values and the dislocation densities increased, whereas, the average grain size decreased significantly with increasing Mg contents. Typical dislocation densities are in the range 1.7 × 1014 m-2 – 2.3 × 1015 m-2. However, local densities in grain boundary and triple junction areas might be as high as 1017 m-2. The strengthening mechanisms contributing to high hardness may primarily be attributed to the cooperative interactions of high dislocation densities, grain boundaries and planar interfaces.
TEM Characterization of Two Spark Plasma Sintered Fe-1.5wt.%Mo Steels Stabilized with SiO2 and TiO2
Authors: Cabibbo Marcello
Published: March 2009

This paper presents a transmission electron microscopy study of two Fe-1.5wt.%Mo steels stabilized with 1.5wt.%SiO2 and 1.5wt.%TiO2,respectively, and compacted through spark plasma sintering. The microstructure inspections revealed that sintered FeMo+SiO2 is able to maintain a nanometric scale grained structure up to a sintering temperature of 815°C, while the steel modified with TiO2 retained its nanometric scale microstructure up to 900°C. The ultra-fine grained structure (within 100-150 nm) was also directly correlated to the grain boundary stability through systematic extinction contours survey. Local nano-welding phenomena shows the effective compacting process of the Fe-Mo powders during sintering. Residual nano-porosity was found to decorate most of the grain boundaries and the triple grain junctions in all the sintering conditions examined, although this nano-porosity accounted for values within 0.26% in volume fraction.
Damping of FeMo Alloys Obtained from SPS Sintering of Nanostructured Powders
Authors: Cabibbo Marcello , Deodati Paolo , Libardi S. , Molinari Alberto , Montanari Roberto , Ucciardello Nadia
Published: March 2009

Spark Plasma Sintering (SPS) of nanostructured FeMo powder produces samples with satisfactory density, however the final grain size critically depends on the sintering temperature. Two groups (sets A and B) of samples have been examined by means of internal friction (IF) and dynamic modulus measurements carried out in successive test runs on the same samples to assess their structural stability. Set A and B had been sintered at 1113 and 1128 K and had an average grain size of 100 nm and 1 µm, respectively. TEM and XRD have been performed on the samples in as-prepared condition and after IF measurements cycles. The samples with smaller grains are more stable and substantially are not affected by grain coarsening which, on the contrary, occurs in those with grains of larger size. The heating up to 923 K during the tests diminishes dislocation density in both the groups. An anomalous trend of resonance frequency during the first test run in samples of set A has been ascribed to the formation of small cracks relaxing internal stresses.
Microstructure and Mechanical Characterization of an Al-Zn-Mg Alloy after Various Heat Treatments and Room Temperature Deformation
Authors: Leo Paola , Cerri Emanuela , McQueen H.J. , Chiozzi Samanta
Published: March 2009

In this study, the effect of various solution and aging treatments on microstructure and mechanical properties of an as cast Al-5.5Zn-1.2Mg alloy has been investigated by optical microscopy, hardness measurements and room temperature tensile test. The solution heat treatments performed at temperatures between 400 and 490°C have little effects on hardness while electrical conductivity values increased at the lower temperature because of dissolved atoms and vacancy rich clusters. Concerning aging, only T6 improves mechanical properties of the undeformed alloy, while aging performed on tensile tested samples results in a decrease of hardness due to accelerated kinetics and heterogeneous nucleation of equilibrium phase stimulated by dislocation network. Tensile tested samples of the as cast alloy exhibits the fastest recrystallization time during annealing because of the absence of fine precipitates and the high strain hardening.
Features on Grain-Structure Evolution during Asymmetric Rolling of Aluminium Alloys
Authors: Farè Stefano , Vedani Maurizio , Angella Giuliano
Published: March 2009

The possibility of refining the grain structure of commercial Al-Mg-Si and Al-Mg-Mn alloys was evaluated using the asymmetric rolling technique in the severe plastic deformation regime. The study demonstrated that asymmetric rolling can readily promote the achievement of an ultrafine grained structure in the alloys investigated. Comparative analyses showed that by increasing the asymmetry ratio and by alternating the shear direction during rolling, higher hardness values and reduced crystallite size could be obtained in the alloys.
Developing Superplasticity in Metallic Alloys through the Application of Severe Plastic Deformation
Authors: Figueiredo Roberto B. , Kawasaki Megumi , Langdon Terence G.
Published: March 2009

Processing through the application of severe plastic deformation (SPD) provides an opportunity for achieving very significant grain refinement in bulk metals. Since the occurrence of superplastic flow generally requires a grain size smaller than ~10 µm, it is reasonable to anticipate that materials processed by SPD will exhibit superplastic ductilities when pulled in tension at elevated temperatures. This paper summarizes the fundamental principles of SPD processing and describes recent results demonstrating the occurrence of exceptional superplastic flow in these ultrafine-grained materials.
Finite Element Calculation of Sintering Deformation Using Limited Experimental Data
Authors: Pan Jing Zhe , Huang Ruo Yu
Published: March 2009

Predicting the sintering deformation of ceramic powder compacts is very important to manufactures of ceramic components. In theory the finite element method can be used to calculate the sintering deformation. In practice the method has not been used very often by the industry for a very simple reason – it is more expensive to obtain the material data required in a finite element analysis than it is to develop a product through trial and error. A finite element analysis of sintering deformation requires the shear and bulk viscosities of the powder compact. The viscosities are strong functions of temperature, density and grain-size, all of which change dramatically in the sintering process. There are two ways to establish the dependence of the viscosities on the microstructure: (a) by using a material model and (b) by fitting the experimental data. The materials models differ from each other widely and it can be difficult to know which one to use. On the other hand, obtaining fitting functions is very time consuming. To overcome this difficulty, Pan and his co-workers developed a reduced finite element method (Kiani et. al. J. Eur. Ceram. Soc., 2007, 27, 2377-2383; Huang and Pan, J. Eur. Ceram. Soc., available on line, 2008) which does not require the viscosities; rather the densification data (density as function of time) is used to predict sintering deformation. This paper provides an overview of the reduced method and a series of case studies.
When Should Microwaves Be Used to Process Technical Ceramics?
Authors: Binner Jon , Vaidhyanathan Bala
Published: March 2009

This paper attempts to shed light on why the stand alone microwave processing of technical ceramics, despite being one of the most popular field with respect to volume of research performed, is still struggling to achieve priority status with respect to commercialisation. To obtain some answers to this enigma and determine when microwaves should be used to process technical ceramics, three case studies are explored. The conclusion is that microwaves should be used to process technical ceramics when specific advantage can be taken of the intrinsic nature of microwave energy and not simply as an alternative energy source. In addition, it is concluded that from a commercialisation view point hybrid processing is often a better approach than the use of pure microwaves.
Slow Positron Beam Probe for the ZnO/Silicone under Proton Irradiation
Authors: Hao Ying Ping , Weng Hui Min , Li Chun Dong , Guo Wei Feng , Liu Jian Dang , Du Huai Jiang , Xiao Hai Ying , Ye Bang Jiao
Published: March 2009

The degradation of ZnO/Silicone coating system under 90keV proton irradiation varying from 5×1014cm-2 to 1×1016cm-2, was studied by slow positron annihilation spectrum. Effective diffusion length calculated by Variable energy positron fit (VEPFIT) shows a dramatically break in a dose of 1×1015cm-2. It is ascribed to the increase of crosslink density and decrease of free volume and hole during the proton irradiation. Furthermore, positron has shown a satisfying sensitivity in detecting the nano-scale defect on ZnO/Silicone system.
Hydrogen- and Corrosion-Related Defect Characterization of Iron and Steels Using a Slow Positron Beam
Authors: Wu Yi Chu , Chen C.Q. , Chen Y.Q. , Hu Y. , Cheng J. , Wang Shao Jie , Jean Yan Ching
Published: March 2009

Hydrogen- and corrosion -related defects of pure iron and AISI 304 and 316 stainless steels were investigated by measuring Doppler broadening energy spectra of positron annihilation. The significant increase in S-parameter after corrosion in iron was interpreted as due to the formation of defects and voids during corrosion processes. However, a decrease of the S-parameter in AISI 304 and 316 stainless steels after corrosion was interpreted as dissolution of passivity oxide film. Furthermore, similar results in iron and stainless steels after hydrogen-charging were observed. Hydrogen damage between the surface and the bulk has a significant variation with depth. The larger increase in S-parameter near the surface after hydrogen-charging mainly comes from the formation of large-size defects (e.g. voids); however the increase in S-parameter in the bulk after hydrogen-charging mainly comes from the production of small-size defects.
Positron Lifetime Study on Degradation of TiCrV Hydrogen Storage Alloy
Authors: Kawasuso Atsuo , Arashima Hironobu , Maekawa Masaki , Itoh Hideaki , Kabutomori Toshiki
Published: March 2009

Using positron lifetime spectroscopy, we examined the evolution of defects in the Ti24Cr36V40 alloy prepared by arc-melting method during hydriding cycles. We found that the positron lifetime increases with increasing the pressure swing cycles. This behavior is well correlated with the degradation of hydrogen transfer change with the pressure swing cycles. The prolonged positron lifetime is attributed to dislocation-related defects. Both dislocations and vacancies bound at dislocations may act as positron trapping centers. After the heat treatment at 400oC, a partial recovery of positron lifetime was observed.
Luminescence and Defect Study of Ce3+-Doped Lu3Al5O12 Phosphors
Authors: Zhong Y.R. , Yu R.S. , Li Z.X. , Wang Bao Yi , Wei Long
Published: March 2009

Cerium doped lutetium aluminium garnet (Lu3Al5O12:Ce, LuAG:Ce) displays particularly promising performance and has a great potential to be used in PET and SPECT. LuAG:Ce phosphors was synthesized with a simple sol-gel process. The structure was identified with XRD. Variations of luminescent properties and defects of LuAG:Ce phosphors with different heat-treatment temperatures and Ce3+-dope concentrations have been investigated, with the aid of emission spectra and positron annihilation lifetime measurements. The influence of defects on the luminescence properties was discussed.
Temperature and Pressure Measurements of PALS Spectra in Photonic Glasses
Authors: Jasińska Bożena , Śniegocka Monika , Reisfeld Renata , Zigansky Elena
Published: March 2009

The subject of investigation was porous glass produced using a sol-gel technique. ortho-Ps lifetimes and intensities in the material were determined as a function of temperature and pressure. Temperature was ranged from 100 to 500 K while the pressure from 0 to 1200 MPa. Nitrogen gas intercalation into pore structure was observed up to 100 MPa.
Positron Annihilation in Carbon Nanotubes
Authors: Guo Wei Feng , Chen Xiang Lei , Du Huai Jiang , Weng Hui Min , Ye Bang Jiao
Published: March 2009

Positron annihilation lifetime spectra have been measured in carbon nanotubes being pressed as a function of pressure up to 1536MPa. In addition, positron lifetime experiments for carbon nanotubes in vacuum, nitrogen and air have been performed respectively. Lifetimes have been obtained using LIFETIME program. The results display a single-component positron annihilation lifetime. Positron lifetime for carbon nanotubes decreases as the pressure increases, but lifetime is basically consistent after the pressure of 960MPa. Positron annihilation lifetime for carbon nanotubes in air is the shortest whereas the lifetime in vacuum the longest. We conclude that a positron annihilates with an electron on the external surface of carbon nanotubes.
Development of the Positron Facility at the Argonne National Laboratory’s 20 MeV Linac
Authors: Chemerisov S. , Jonah Charles D.
Published: March 2009

We present an update on positron-facility development at Argonne National Laboratory. We will discuss advantages of using low energy electron accelerator, present our latest results on slow positron production simulations, and plans for further development of the facility. We have installed a new converter/moderator assembly that is appropriate for our electron energy and that allows increasing the yield about an order of magnitude. We have obtained a Penning trap and buncher from LLNL that we plan to install. We have simulated the relative yields of thermalized positrons as a function of incident positron energy on the moderator. We use these data to calculate positron yields that we compare with our experimental data as well as with available literature data. We will discuss the new design of the next generation positron front end utilizing reflection moderation geometry.
Advanced Algorithms for PALS Analysis of Self-Assembled Amphiphiles
Authors: Pascual-Izarra Carlos , Dong Aurelia W. , Pas Steven J. , Boyd Ben J. , Drummond C.J. , Hill Anita J.
Published: March 2009

Self-assembled amphiphile systems are utilized in a wide variety of applications including drug delivery and energy storage. Nano-scale physical and chemical interactions govern the packing of self-assembled amphiphilic molecules, resulting in thermodynamically stable phases of defined geometries. Possible phases include micellar, hexagonal, cubic, lamellar and sponge phases. The internal nano-structure of the amphiphile self-assembly materials plays an important role in the properties of these systems and their application. To date small angle x-ray scattering (SAXS) has been the most common technique used to characterise their structure. We explore positron annihilation lifetime spectroscopy (PALS) as an alternative and/or complementary technique for this purpose, using the phytantriol/water system. While PALS is a well established technique for characterising many materials, the coexistence of aqueous and hydrophobic regions in a soft self-assembled amphiphile material poses a challenge to the analysis and interpretation of the results. In order to alleviate these difficulties we developed a computer program for general-purpose PALS data analysis called PAScual. Amongst the most salient features of this new code are the possibility to perform bounded fits and the option of using advanced algorithms to provide a more robust and unbiased fit: on the one hand, it incorporates a global nonlinear optimisation routine based on the Simulated Annealing algorithm and, on the other hand it gives information on the reliability of the results by means of a Markov Chain Monte-Carlo Bayesian Inference method. In this work we present the newly developed PALS data analysis techniques as well as the results for the phytantriol/water system, comparing them with additional data obtained from complementary techniques.
Collisions Involving Positrons and Positronium
Authors: Walters H.R.J.
Published: March 2009

The theoretical description of positron and positronium scattering by atoms within the context of the coupled pseuodostate approximation is briefly considered.
Photoluminescence and Structural Properties of ZnO Films Deposited on Si Substrates by Chemical Spray Deposition
Authors: Sali Samira , Tala-Ighil R. , Kermadi S. , Boumaour M. , Kechouane M.
Published: March 2009

The structure and photoluminescence (PL) of ZnO films deposited on Si (111) substrates by chemical spray deposition using aqueous solution of zinc acetate [Zn (CH3 CO2)2 , 2H2O] was investigated. It was found that these properties depend strongly on growth temperature and grain size. The samples grown at the optimum deposition conditions can generate stronger luminescence. It was revealed by X-ray diffraction that the preferred orientation of poly-crystals is along C-axis, with hexagonal wurtzite structure. PL spectroscopy results shows an evident ultra-violet (UV) emission observed near 380 nm with a broad low intensity band centred at 430 nm. The band was reported as being caused by the defects in the grain boundaries of ZnO.
Under optimum deposition conditions a low resistivity and a high optical transmittance of the order of 2.8×10−4 Ω cm and 90%, respectively, were obtained.
Effect of the Electrode Geometry on the Diffusion-Current Problem of the Rotating Porous Silicon Electrode in HF Solution
Authors: Cheggou Rabi , Gabouze N. , Kadoun A.
Published: March 2009

The basic voltammetric data of silicon/ fluoride-electrolyte interfaces available in the literature appear to be rather divers because of the large number of experimental parameters like semiconductor type, crystallographic orientation, fluoride acid concentration CF, pH and electrode rotation rate. In the present work we have studied the effects of parameters such as electrode rotating rate upon the voltammograms in order to show the electrode geometry effects on current transport through Si/HF interface. The decrease of the current experimentally observed after the initial current peak (Si/HF current-potential curve) is investigated. The origin of this behaviour lies in substitution of Si-H surface bond by SiO2 in the first seconds following the potential jump. The diffusion current problem of a rotating porous silicon electrode has been analysed based on the mass transfer equations for partially blocked electrode. The blocking parameter is calculated.
Optimization of DLC/PS Antireflection Coating Properties for Multicrystalline Silicon Solar Cells
Authors: Ait-Hamouda Kahina , Ababou A. , Gabouze N.
Published: March 2009

In this work, we report on the results of using a Diamond-Like Carbon / Porous Silicon (DLC/PS) double layer as antireflection coating to enhance the performance of multicrystalline silicon photovoltaic cells. DLC layers were obtained by Plasma Enhanced Chemical Vapor Deposition (PECVD) method. The properties of these layers were investigated in order to establish the optimum preparation conditions for solar cell applications. Then, thin films of combined porous silicon-DLC structure were fabricated for antireflection coating use. The spectral response of a solar cell based on multicrystalline silicon (mc-Si) coated with a PS layer, formed by electrochemical process was enhanced compared to a cell without porous silicon layer as emitter. Further improvements are obtained by a deposition of a thin DLC film. The results of the solar cell parameters before and after porous silicon formation and DLC coating are discussed.
Properties of Pt-Assisted Electroless Etched Silicon in HF/Na2S2O8 Solution
Authors: Megouda N. , Hadjersi T. , El Kachai O. , Boukherroub R. , Guerbous L.
Published: March 2009

The paper reports on hydrothermal electroless etching of high resistivity p-type Si(100) at 35°C. A thin layer of platinum (Pt) was deposited onto the silicon surface by evaporation under vacuum (~ 10-6 Torr) prior to immersion in a solution of HF/Na2S2O8. The HF concentration was kept at 22.5 M while the concentration of Na2S2O8 was varied from 0.03 to 0.18 M. The etching time was varied from 15 to 75 min. The morphology and optical properties of the etched layer as a function of oxidant concentration and etching time were investigated using scanning electron microscopy (SEM) and photoluminescence measurements.
Ti-Glass Biocomposite Coating Materials and their Crystallization Dynamics
Authors: Li Mu Qin , Qu Li Jie , Li Bin , Zhuang Ming Hui , Yang Shi Qin
Published: March 2009

Ti-bioglass was sprayed on Ti6Al4V substrate. The crystallization dynamics of Ti-bioglass was analyzed by differential scanning calorimetry(DSC). The structure and morphology of the coatings were studied by SEM, TEM and AFM. The results showed that new phase Ca5(PO4)3F formed at 695.2°C when bioglass crystallized. The formation activation energy was 147.76KJ/mol and the crystallization exponent was less than 3 (n<3). It indicated that the crystallization happened on the surface. When 20 wt% bioglass was mixed with Ti powders, the formation activation energy was 324.6KJ/mol and the crystallization exponent was larger than 3 (n>3), which indicated that an integrated crystallization happened. Micro- or nano-scale R-TiO2, A-TiO2 and Na2Ti6O13 crystals precipitated on the surface of the coating after crystallization treatment. These crystals have a function of self-seal on the cracks on the coatings and form a metallurgical interface between the substrate and the coating.
Gradient Rare-Earths Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding and its Bioactivity
Authors: Liu Qi Bin , Wu Ling , Yang Bang Cheng
Published: March 2009

A gradient bioceramic composite coating was prepared by wide-band laser cladding technique on TC4 alloy surface. The influence of rare earths oxide CeO2 on microstructure of bioceramic coating was studied. The experimental results indicated that CeO2 plays an important role in inducing HA + β-TCP formation. There is almost no HA+β-TCP in bioceramic coating without CeO2. When CeO2 content is higher than 0.2 wt.%, the amount of HA+β-TCP catalyzed by CeO2 gradually increases. The amount of HA+β-TCP becomes largest when CeO2 content is up to 0.4wt%. However, when CeO2 content ranges from 0.6 wt.% to 0.8 wt.%, the amount of synthesizing HA+β-TCP conversely goes down. Through cell culture experiment in vitro, the effect of bioceramic coating with different CeO2 contents on the expression of characteristic protein is investigated. The results show that the largest amount of expression of hydroxyproline(Hyp) at 2d and alkaline phosphatase(ALP) at 6d on coating is complied with 0.4wt.% CeO2, The result indicates that bioactivity of bioceramic coating is dependent on the amount of HA + β-TCP catalyzed by different CeO2 contents.
Study on Preparation and Properties of Nitric Oxide Releasing Polyurethane
Authors: Zhao Jian Hao , Tu Mei , Zeng Rong , Geng Jie , Cha Zhen Gang , Zhou Chang Ren
Published: March 2009

In this study, a novel nitric oxide (NO) endogenously releasing polyurethane (PU) material, i.e. PU-g-L-cysteine(PU-Cys), was synthesized by grafting L-cysteine on the film surface. Fluorescence analysis and a BCA method were used to characterize qualitatively and quantitatively the grafted L-cysteine. The results showed that L-cysteine was successfully immobilized on the PU film surface and the density of L-cysteine grafted was calculated to be 15.3nmol/cm2. The NO releasing behavior study of PU-Cys film demonstrated that endogenous NO could be continuously released from PU-Cys film and the accumulated releasing amount within 3h added up to 1.06nmol/cm2. The releasing rate of NO was well matchable to the self-releasing rate of resting platelets in human body. The results of dynamic blood clotting test and hemolysis ratio measurement showed that PU-Cys film had a better haemocompatibility than PU film, which might be the result of endogenously released NO inhibiting platelet adhesion and thrombus formation. Therefore, PU-Cys with the property of endogenous NO releasing is expected to be an ideal blood compatibility material in clinical application.
Flexibility Modification of Konjac Glucomannan Film by Deacetylation
Authors: Chen Yan , Lin Xiao Yan , Luo Xue Gang , Kang Ying Ting
Published: March 2009

Konjac glucomannan (KGM) were modified by deacetylation with sodium hydroxide, calcium hydroxide, sodium carbonate, sodium phosphate, respectively and mechanical properties of modified KGM films were investigated. The modification mechanism was explored by FTIR. Results show that deacetylation of KGM play an important role on the flexibility of the modified membranes, and the flexibilities vary with different modifiers. The flexibility of the films modified by sodium hydroxide is significantly higher than that of the others. The modified films with good flexibility were prepared by simple steps as follows: NaOH modifiers and KGM (1%) were added to water, stirred until the pH arrived at 9. And then the KGM swelled at the temperature of 50°C for 2 hours, the modified KGM sol was cast onto glass plates, the modified membranes were formed after dried at 50°C.
Designing Nano-Hydroxyapatite in the Polyelectrolyte Complex Macroporous Scaffold Based on Chitosan and Hyaluronic Acid
Authors: Chen Jing Di , Wang Ying Jun , Chen Xiao Feng
Published: March 2009

Owing to the unique characters of the hybrid scaffold components, a novel biodegradable porous composite scaffold was prepared. The nano hydroxyapatite (HAP) (73~136 nm) was crystallized in situ on the organic polyelectrolyte complex matrix through a biomimetic method. The polyelectrolyte complex composed of chitosan and hyaluronic acid had strong impacts on the formation of the nano HAP and directed in situ crystallization of the nano HAP as template. The in situ nano HAP reduced the interfacial energy and presented nano intensifier to the nano hybrid scaffold. Meanwhile, the scaffold kept high porosity.
Effects of bFGF and Collagen on the Construction of Tissue Engineering Cartilage In Vitro in the 3-D Culture System
Authors: Yu Li , Wu Feng Lin , Ma Tuan , Wu Min Ting , Zhou Li Li
Published: March 2009

Objective: To investigate effects of bFGF and collagen on tissue-engineered cartilage in pellet culture. Methods: Rabbit rib growth-plate chondrocytes were incubated in pellet culture. bFGF and Collagen was applied alone and in combination based on the results of previous search . The histological structure of neocartilage was observed by species stained with H＆E and Immunohistochemical analysis. The DNA content of neocartilage was measured by hoechst33258 dye. The production of matrix was estimated from the determination of hydroxyproline content and Alcian Blue method. Results: Chondrocytes formed cartilage-like tissue with distinct differentiated zones and regions. The DNA content of neocartilage was enhanced by bFGF and collagen. The production of collagen and PG was promoted by collagen. bFGF and collagen could suppress the expression of collagenⅠwhile they could decelerate the decrease of collagenⅡ. The combination of bFGF and collagen had synergistic effects. Conclusion: Pellet culture could maintain chondrocytes phenotype and enhance matrix production; bFGF could stimulate the proliferation of chondrocytes, collagen could stimulate the proliferation and the matrix production of chondrocytes, it also had a positive effect on the maintenance of cell phenotype, the combination of bFGF and collagen had synergistic effects on the maintenance of chondrocytes phenotype and the regeneration of cartilage.
Crosslinked Electrospun UPM/PHBV/PVP Fibers for Sustained Drug Release
Authors: Zhang Jing Jing , Liu Jun , Yu Hao , Zhang Yu , Zhu Mei Fang , Chen Yan Mo
Published: March 2009

Crosslinked UPM/PHBV/PVP fibers were successfully prepared using electrospinning process. The active pharmaceutical ingredient tetracycline hydrochloride (TH) was loaded onto the electrospun fibers through after-treatment method. Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) and in vitro dissolution tests were carried out to characterize the medicated electrospun fibers. The SEM and FTIR results clearly showed the difference between the UPM / PHBV and UPM/ PHBV/ PVPelectrospun fibers. The pharmaceutical tests results indicated that the fibers had good drug-loaded capability and sustained-release properties. The as-prepared fibers might find possible applications as wound dressings or transdermal drug delivery systems.
Effect of EDTA on Electrodeposition of Hydroxyapatite Coatings
Authors: Jiang Yong , Wang Xiao Xiang
Published: March 2009

Hydroxyapatite (HAP) coatings have been successfully electrodeposited on the titanium substrate by using Na2EDTA as chelate in electrolytes. The samples obtained were characterized by XRD and SEM. The XRD result indicated that the HAP crystals were preferentially oriented along c-axis. The SEM showed that the HAP crystals were rod like precipitates with a well-defined hexagonal cross section. The size of HAP crystals was well controlled by the addition of Na2EDTA and electrochemical parameters such as deposition times, pH value. It was discussed that the formation of Ca–EDTA complexes effectively restrained the growth of the HAP crystals.
AFM Study of Untreated and Treated Fibers of Mongolian Goat Cashmere
Authors: Javkhlantugs Namsrai , Ankhbayar Enkhbaatar , Tegshjargal Khishigjargal , Enkhjargal Damdin , Ganzorig Chimed
Published: March 2009

The morphological surface change of untreated and treated fibers of the Mongolian goat cashmere was investigated by atomic force microscopy (AFM) at ambient conditions. The cuticle scale heights of the Mongolian goat cashmere fibers were measured by the AFM for the fibers before and after treatment. The experimental results showed that the difference between the fine structure of the cuticle and surface roughness of untreated and treated fibers. We found that the surface morphological change of the cashmere fibers was strongly degraded after the bleaching process.