bluuebunny/crossref_metadata_2025 huggingface dataset:
Criteria for Accurate Measurement of Charge-Pumping Current in 4H-SiC MOSFETs
Authors: Okamoto Dai , Yano Hiroshi , Hatayama Tomoaki , Uraoka Yukiharu , Fuyuki Takashi
Published: March 2009

This paper describes the influence of the geometric component in the charge-pumping
measurement of 4H-SiC MOSFETs. Charge-pumping measurements were conducted on 4H-SiC
MOSFETs with and without NO annealing. Charge-pumping measurements with different pulse-fall
times revealed that the geometric component exists in 4H-SiC MOSFETs and is especially large in
the unannealed MOSFETs. A sufficiently long fall-time is needed to minimize its effect, which is
expected to be 1–10 μs for 4H-SiC MOSFETs with a gate length of 10 μm.
Optimization of 4H-SiC MOS Properties with Cesium Implantation
Authors: Wang Y. , Khan T. , Chow T. Paul
Published: March 2009

The effect of incorporation of cesium with implantation on the electrical characteristics
of SiO2/4H-SiC interface has been evaluated using MOS capacitors. With a cesium dosage of 1012
and 3x1012 cm-2 on deposited oxide re-oxidized in steam, effective oxide charge densities of -
1.4x1012 and -7.5x1011 cm-2 respectively were extracted and a cesium implant activation percentage
of 33% was estimated from flatband voltage shift. Also, corresponding interfacial state densities of
2.5x1013 and 1.8x1013 cm-2-eV-1 near the conduction band edge were extracted from High-Low
frequency C-V technique, showing a decreasing Dit with increasing Cs dosage.
A Study of Deep Energy-Level Traps at the 4H-SiC/SiO2 Interface and Their Passivation by Hydrogen
Authors: Allerstam Fredrik , Sveinbjörnsson E.Ö.
Published: March 2009

This study is focused on characterization of deep energy-level interface traps formed
during sodium enhanced oxidation of n-type Si face 4H-SiC. The traps are located 0.9 eV below the
SiC conduction band edge as revealed by deep level transient spectroscopy. Furthermore these traps
are passivated using post-metallization anneal at 400°C in forming gas ambient.
Improved Properties of AlON/4H SiC Interface for Passivation Studies
Authors: Wolborski M. , Martin D.M. , Bakowski Mietek , Hallén Anders , Katardjiev Ilia
Published: March 2009

Aluminium oxynitride (AlON) films of variable composition were grown by reactive
sputter deposition in a N2/O2 ambient at room temperature and studied for device passivation. The
films were deposited on Si and 4H-SiC substrates as well as on SiC PiN diodes. The
AlON/SiO2/SiC stack provided superior interface properties compared to the AlON/SiC structure.
Samples with 8% oxygen content, in the AlON film, and subjected to a UV exposure prior to
deposition, exhibited the smallest net positive interface charge. A large net negative interface
charge was observed for samples with 10% oxygen content and for the samples with 8% oxygen
content and subjected to a RCA1 surface clean, prior to deposition. Diodes passivated with AlON
films demonstrated reduced leakage current compared to as-processed diodes.
SiC Epitaxial Growth on Multiple 100-mm Wafers and its Application to Power-Switching Devices
Authors: Burk Albert A. , O'Loughlin Michael  J. , Sumakeris Joseph J. , Hallin C. , Berkman Elif , Balakrishna Vijay , Young Jonathan , Garrett Lara , Irvine Kenneth G. , Powell Adrian R. , Khlebnikov Y. , Leonard R.T. , Basceri C. , Hull Brett A. , Agarwal Anant K.
Published: March 2009

The development of SiC bulk and epitaxial materials is reviewed with an emphasis on epitaxial growth using high-throughput, multi-wafer, vapor phase epitaxial (VPE) warm-wall planetary reactors. It will be shown how the recent emergence of low-cost high-quality 100-mm diameter epitaxial SiC wafers is enabling the economical production of advanced wide-bandgap Power–Switching devices.
Correlation between Thermal Oxide Breakdown and Defects in n-Type 4H-SiC Epitaxial Wafers
Authors: Soloviev Stanislav I. , Matocha Kevin , Dunne Greg , Stum Zachary
Published: March 2009

In this work, the correlation between thermal oxide breakdown and dislocations in n-type
4H-SiC epitaxial wafers has been investigated. Thermal oxide was grown by oxidation in N2O at
1250°C followed by annealing in NO atmosphere. The electron beam induced current (EBIC)
technique was employed to find correlations between the electrically active defects in epitaxial
layers and regions where the oxide breakdowns occurred. The test measurements of leakage
currents in MOS devices were performed in order to correlate the leakage currents with number of
defects in the epi-layer detected by EBIC technique.
Reliability of Thermal Oxides Grown on n-Type 4H-SiC Implanted with Low Nitrogen Concentration
Authors: Senzaki Junji , Shimozato Atsushi , Fukuda Kenji , Arai Kazuo
Published: March 2009

Reliability of thermal oxides grown on the n-type 4H-SiC substrates implanted by
nitrogen ion with low doping levels equal to or less than 1x1018 cm-3 has been investigated. The
surface morphology becomes rough by the nitrogen implantation and the post implantation
annealing. The field-to-breakdown value decreases with increase in the nitrogen concentration.
The average EBD values are 11.6 MV/cm, 11.3 MV/cm and 10.7 MV/cm for the samples without the
implantation and with the nitrogen implantation of doping levels of 1x1017 cm-3 and 1x1018 cm-3,
respectively. The time-to-breakdown values were also degraded with the increase of the nitrogen
implantation doping level. The reliability degradation of thermal oxides is caused by the
implantation-induced breakdown factor.
The Impact of Chemical-Mechanical Polishing on Defective 4H-SiC Schottky Barrier Diodes
Authors: Lee Kung Yen , Chen Wen Zhou , Capano Michael A.
Published: March 2009

In this article, the correlation of surface morphological defects and barrier-height
inhomogeneities with the electrical characteristics of defective 4H-SiC Schottky barrier diodes
(SBDs) before and after chemical-mechanical polishing (CMP) is investigated. The forward
characteristics, an ideality factor and a single barrier height of a SBD, remain the same after CMP,
so that CMP does not affect SBD characteristics. Most barrier-height inhomogeneities are
eliminated or improved after CMP. Therefore, leakage current induced by barrier-height
inhomogeneities are improved by CMP as well. In addition, about 40% of SBDs with carrots inside
the active areas exhibits double barriers before CMP. This excludes that carrots are a cause of
barrier-height inhomogeneities. In reverse-bias mode, CMP reduces reverse leakage current at low
bias and increases breakdown voltage due to the reduction of thermionic field emission and
elimination of local enhanced electric fields.
Electric Discharge Machining for Silicon Carbide and Related Materials
Authors: Yamaguchi Satarou , Noro Toshiya , Takahashi Hideaki , Majima Hideyoshi , Nagao Yoshihisa , Ishikawa Katsuhiko , Zhou You , Kato Tomohisa
Published: March 2009

In order to cut the ingots and slabs of the silicon carbide (SiC), we developed the new
method of electric discharge machining (EDM). EDM is usually used for the machining of the
metals, and if it is electric conductive material, it is effective for the machining. However, if the
electrical resistivity of SiC is high, the electric current cannot be large enough for and the EDM,
and we failed the machining of SiC. Therefore, we use three methods to keep higher electric
conduction. One is photoconductive, the second is high electric field effect and it is called
avalanche effect, and the third is high temperature effect because usually the resistivity is low when
the semiconductor or insulation materials are in high temperature. Thus, we applied three method,
and finally can cut the SiC slabs of the resistivity of the order of 10 Ωm, which is almost 1000 times
higher than that of the ordinary EDM at least. The flatness of the cutting surface is the same of the
metals’ and the cutting rate for the SiC ingots is 10 times higher than that of diamond saw. This
technique will be effective for the related materials of SiC, such as diamonds and GaN.
Cross-Sectional TEM Analysis of Structural Change in 4H-SiC Single Crystal Irradiated by Femtosecond Laser Pulses
Authors: Kawahara Hiroyuki , Okada Tatsuya , Kumai Ryota , Tomita Takuro , Matsuo Shigeki , Hashimoto Shuichi , Yamaguchi Makoto
Published: March 2009

We carried out cross-sectional transmission electron microscopy (TEM) investigation of
femtosecond laser-induced ripples formed on 4H-SiC single crystal surface. Here, we paid attention
to the crystal structures underlying the coarse and fine ripples and the three-dimensional distribution
of amorphous phase. Conventional and high-resolution TEM analyses made clear that a continuous
amorphous layer approximately of 50 nm thick exist at the topmost region of both coarse and fine
ripples. The result strongly suggests that the fundamental surface deformation process is common for
coarse and fine ripples, even though the factors which determine their periods are different.
Challenges for Improving the Crystal Quality of 3C-SiC Verified with MOSFET Performance
Authors: Nagasawa Hiroyuki , Yagi Kuniaki , Kawahara Takamitsu , Hatta Naoki , Abe Masayuki , Schöner Adolf , Bakowski Mietek , Ericsson Per , Pensl Gerhard
Published: March 2009

In 3C-SiC MOSFETs, planar defects like anti-phase boundaries (APBs) and stacking-faults (SFs) reduce the breakdown voltage and induce leakage current. Although the planar defect density can be reduced by growing 3C-SiC on undulant-Si substrate, specific type of SFs, which expose the Si-face, remains on the (001) surface. Those SFs increase the leakage current in devices made with 3C-SiC. In order to eliminate the residual SFs, an advanced SF reduction method involving polarity conversion and homo-epitaxial growth was developed. This method is called switch-back epitaxy (SBE) and consists of the conversion of the SF surface polarity from Si-face to C-face and following homo-epitaxial growth. The reduction of the SF density in SBE 3C-SiC results in a tremendous improvement of the device performance. The combination of the achieved blocking voltage with the demonstrated high current capability indicates the potential of 3C-SiC vertical MOSFETs for high and medium power electronic applications such as electric and hybrid electric vehicle (EV/HEV) motor drives.
Critical Technical Issues in High Voltage SiC Power Devices
Authors: Agarwal Anant K. , Burk Albert A. , Callanan Robert , Capell Craig , Das Mrinal K. , Haney Sarah K. , Hull Brett A. , Jonas Charlotte , O'Loughlin Michael  J. , O`Neil Michael , Palmour John W. , Powell Adrian R. , Richmond Jim , Ryu Sei Hyung , Stahlbush Robert E. , Sumakeris Joseph J. , Zhang Q. Jon
Published: March 2009

In this paper, we review the state of the art of SiC switches and the technical issues which
remain. Specifically, we will review the progress and remaining challenges associated with SiC
power MOSFETs and BJTs. The most difficult issue when fabricating MOSFETs has been an
excessive variation in threshold voltage from batch to batch. This difficulty arises due to the fact that
the threshold voltage is determined by the difference between two large numbers, namely, a large
fixed oxide charge and a large negative charge in the interface traps. There may also be some
significant charge captured in the bulk traps in SiC and SiO2. The effect of recombination-induced
stacking faults (SFs) on majority carrier mobility has been confirmed with 10 kV Merged PN
Schottky (MPS) diodes and MOSFETs. The same SFs have been found to be responsible for
degradation of BJTs.
Development of Large Area (up to 1.5 cm2) 4H-SiC 10 kV Junction Barrier Schottky Rectifiers
Authors: Hull Brett A. , Sumakeris Joseph J. , O'Loughlin Michael  J. , Zhang Q. Jon , Richmond Jim , Powell Adrian R. , Paisley Michael J. , Tsvetkov Valeri F. , Hefner A. , Rivera Angel
Published: March 2009

DC characteristics and reverse recovery performance of 4H-SiC Junction Barrier Schottky (JBS)
diodes capable of blocking in excess of 10 kV with forward conduction of 20 A at a forward voltage
of less than 4 V are described. Performance comparisons are made to a similarly rated 10 kV
4H-SiC PiN diode. The JBS diodes show a significant improvement in reverse recovery stored
charge as compared to PiN diodes, showing half of the stored charge at 25°C and a quarter of the
stored charge at 125°C when switched to 3 kV blocking. These large area JBS diodes were also
employed to demonstrate the tremendous advances that have recently been made in 4H-SiC
substrate quality.
Effect of the Doping Concentration and Space of Both p-Grid and Field Limiting Ring on 4H-SiC Junction Barrier Schottky Diode with Single Ion Implantation Process
Authors: Kang In Ho , Song Jae Yeol , Joo Sung Jae , Bahng Wook , Kim Sang Cheol , Kim Nam Kyun
Published: March 2009

The effect of the doping concentration and space of both p-grid and FLR on the electrical
performances of 4H-SiC JBS diode has been investigated. A 4H-SiC JBS diode with the p-grid space
of 3um, the FLR space of 3um, and the doping concentration of 5E18cm-3 showed the highest
blocking voltage of 1500V.
Extremely Uniform, High Quality SiC Epitaxy on 100-mm Substrates
Authors: Sumakeris Joseph J. , Henning Jason , O'Loughlin Michael  J. , Sriram Saptharishi , Balakrishna Vijay
Published: March 2009

We have developed a horizontal hot-wall reactor for growing extremely uniform epilayers on 100-mm diameter SiC substrates using a novel supplemental reagent source. Doping and thickness variations of 2% and 1% s / mean, respectively, have been demonstrated. The typical defect density is 2 cm-2. We describe the growth cell in detail and discuss the development of the design and process to produce these very uniform epilayers.
Bimetallic PdZn Nanoparticles for the Partial Hydrogenation of Phenylacetylene
Authors: Engels Volker , Wheatley Andrew E.H. , Berenguer-Murcia Angel , Jefferson David A. , Johnson Brian F.G.
Published: March 2009

Novel catalytic systems based on PdZn alloys have been synthesized by polyol reduction over the entire compositional range [1, 2] and characterized by means of HRTEM, EDS and ICP. The expected bulk compositions were reproducible to within a 2 mol% margin and the purified particle suspensions stable for several months after preparation. The EDS results indicated the presence of considerable amounts of oxygen, especially in those samples containing high fractions of zinc. The particle size distributions were shown to be narrow and the mean sizes slightly decreased with higher molar fractions of palladium (diameter range 2.6 to 3.2 nm). In the catalytic hydrogenation of phenylacetylene, a strong dependence of the substrate conversion time on the Pd concentration was established, and selectivity towards the semihydrogenation product (styrene) was found to be close to 100 %. The selectivity dropped only shortly before the initial substrate was fully depleted.
FeCrAl Alloys Produced by Roll-Bonding and Annealing of Al(RE)-Clad Stainless Steel: How Addition of Hf and Zr Affects their Oxidation Behaviour
Authors: Pilone D. , Felli F. , Bernabai U.
Published: March 2009

The process involving cold rolling and annealing of Al-steel-Al sandwiches allows to produce an alloy containing more than 7 wt.% of Al. Unfortunately many α-Al2O3 scales tend to spall during thermal cycling because of thermal expansion mismatch between the alloy and the scale. Small additions to the ferritic stainless steel of oxygen reactive elements are known to improve the adhesion of α-Al2O3 scales. In this work hafnium and zirconium were added to the aluminium foil before roll bonding and their behaviour during the diffusion bonding was evaluated. This novel doping method was proven to be effective in improving scale adhesion and alloy lifetime. Moreover it allows to overcome problems related to steel alloying with reactive elements and reduces the quantity of expensive reactive elements that needs to be added to the steel foil.
A Multipass ECAP Study of Modified Aluminium Alloys
Authors: Cerri Emanuela , De Marco P.P. , Leo Paola
Published: March 2009

ECAP (Equal Channel Angular Pressing) is a very interesting method for modifying microstructure in producing UFG (Ultra Fine Grained) materials. It consists of pressing test samples through a die containing two channels, equal in cross section and intersecting at an angle Φ. As a result of pressing, the sample theoretically deforms by simple shear and retains the same cross sectional area to repeat the pressing for several cycles. 2-D and 3-D FEM simulations of both one and four ECAP passes of two modified aluminium alloys were performed in order to investigate the deformation state of processed workpiece and, moreover, the effect of the different alloy related Strain Hardening Rate (SHR), die geometry (in terms of variation of channel outer angle) and friction on deformation distribution and magnitude. FEM results showed a lower equivalent plastic strain on the outer side of both cross and longitudinal sections of the billets after one and four passes. Microhardness tests performed on the same sections of ECAP processed billets supported these findings. Moreover, FEM analysis indicated that an higher SHR means a greater strain inhomogeneity on cross section of the processed billet. The same effect was observed by increasing the channel outer angle by computing friction.
Oxidation Behaviour and Thermal Stability of Nanocomposited Ti-Al-Si-B-N and Ti-Cr-B-N Coatings
Authors: Fabrizi A. , Paternoster C. , Cecchini R. , Kiryukhantsev-Korneev P.V. , Sheveyko A. , Cabibbo Marcello , Haidopoulo Marie , Spigarelli Stefano
Published: March 2009

Thin nanostructured Ti-B-N-based films are known for their excellent mechanical properties and their stability at high temperature in oxidizing atmosphere. In the present work, nanostructured Ti-Al-Si-B-N and Ti-Cr-B-N coatings deposited on AISI 304 stainless steel by ion implantation have been characterized. To evaluate the oxidation resistance and thermal stability, the coatings were annealed at 900°C in vacuum and in air for 4 hours. The mechanical properties, phase composition and micro-structure of as-deposited and annealed coatings were addressed. The coatings showed a complex multilayered structure and a substantial change of their mechanical properties, due to the new structure and to the phases formed after air annealing.
Pre-Primary Stage of Low Strain Rate Creep in Metals
Authors: Kloc Luboš , Sklenička Václav
Published: March 2009

Primarystageofcreepprocessisaperiodwhenthecreeprateisdecreasingduetomi-crostructuredevelopment.Thedislocationdensityevolvestothedynamicequilibriumvaluerelatedtotheappliedstress.Inlow-strainratecreepexperiments,similarstageofdecreasingstrainrateisobservedalongwithapparenttransitiontosteadystate.Nevertheless,deeperanalysisofthevariousparametersofthestageshowsthatthesubstanceoftheprocessmustbedifferent.Themainreasonsare:i)thestrainistoosmallfordislocationsubstructurerearrangement,ii)stressandtemperaturedependenciesofthetransitionstrainandrelaxationtimeoftheprocessdoesnotcorrespondtoanyoftheknownprimarycreepprocesses,iii)thestrainreachedduringthestageisalmostfullyrecoverable,sothatthedeformationisratheranelasticthanplasticone.Thetransitionstrainobservedinlowstrainrateexperimentsthusshouldbetreatedasaspecial“pre-primary”stage,whiletheapparentsecondary(steadystate)stageisinfactpartoftheprimarycreepstage.
Backstress, the Bauschinger Effect and Cyclic Deformation
Authors: Kassner Michael E. , Geantil P. , Levine L.E. , Larson B.C.
Published: March 2009

Backstresses or long range internal stresses (LRIS) in the past have been suggested by many to exist in plastically deformed crystalline materials. Elevated stresses can be present in regions of elevated dislocation density or dislocation heterogeneities in the deformed microstructures. The heterogeneities include edge dislocation dipole bundles (veins) and the edge dipole walls of persistent slip bands (PSBs) in cyclically deformed materials and cell and subgrain walls in monotonically deformed materials. The existence of long range internal stress is especially important for the understanding of cyclic deformation and also monotonic deformation. X-ray microbeam diffraction experiments performed by the authors using synchrotron x-ray microbeams determined the elastic strains within the cell interiors. The studies were performed using, oriented, monotonically deformed Cu single crystals. The results demonstrate that small long-range internal stresses are present in cell interiors. These LRIS vary substantially from cell to cell as 0 % to 50 % of the applied stress. The results are related to the Bauschinger effect, often explained in terms of LRIS.
Role of Boundaries in Control of Deformation Rate and Strength of Crystalline Materials
Authors: Blum Wolfgang
Published: March 2009

Plastic deformation of crystalline materials is not controlled by interaction among free dislocations only, but the interaction of free dislocations with internal boundaries. i) Low-angle boundaries: Modeling of deformation of pure materials with conventional grain size on the basis of structure evolution indicates that low-angle boundaries act as obstacles of free dislocations. The migration of the low-angle boundaries constitutes an essential recovery process determining the deformation resistance in the steady state. ii) High-angle boundaries: Severe plastic deformation transforms low-angle boundaries into high-angle ones. They differ in obstacle and recovery characteristics from low-angle boundaries, which explains the special properties of ultrafine-grained and nanocrystalline materials with regard to strength, strain rate sensitivity and ductility. iii) Phase boundaries in Ni-base superalloys enhance the strengthening by hard phases with strengthening by dense dislocation networks serving to reduce coherency stresses. It is concluded that internal boundaries play a crucial role in controlling the evolution of structure and strength in crystalline materials.
Organic Materials for Large Area Electronics
Authors: Friend Richard
Published: March 2009

Organic materials have been developed to operate as the active semiconductor in a wide range of semiconductor devices, including light-emitting diodes, LEDs, field-effect transistors, FETs, and photovoltaic diodes, PVs. The ability to process these materials as thin films over large areas makes possible a range of applications, currently in displays, as LEDs and as active matrix FET arrays, and solar cells. This article reviews developments in semiconductor physics of these materials and in their application in semiconductor devices
Deposition of Titanium Nitride Thin Films onto Silicon by RF Reactive Magnetron Sputtering
Authors: Saoula Nadia , Henda K. , Kesri R.
Published: March 2009

The properties of TiN films deposited by magnetron sputtering are related to their deposition conditions. The elaboration of our films has been carried out by RF-Magnetron Sputtering (13.56 MHz) from a titanium metallic target in reactive N2/Ar gas mixture. The main variables investigated are the composition of the Ar/N2 gas mixture, the total pressure, the deposition time, the discharge power but in this work the attention is given to the effect of the substrate bias voltage.
A study is carried out the effects of these variations on the film growth rates, the film thickness and the properties of TiN films. The deposited films were characterized by energy dispersive spectroscopy (EDS), and observed by means of atomic force microscopy (AFM).
Characterization of SiOF Thin Films Deposited by PECVD from Hexamethyldisiloxane in Mixture with Oxygen and CF4
Authors: Chabane R. , Sahli Salah , Zenasni A. , Raynaud Patrice , Segui Y.
Published: March 2009

Thin SiOF films were elaborated in microwave excited DECR plasma reactor (Distributed Electron Cyclotron Resonance) from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) (in 1: 9 proportion) with the presence of various CF4 concentrations. The fluorine contents in the films composition were adjusted by the CF4 gas flow ratio (in the range of 10 - 70%). The refractive index and the deposition rate were estimated from ellipsometric data and the film chemical structure was studied by FTIR analysis technique. The deposition rate increases with increasing CF4 flow and then decreases after reaching a maximum value for 20% of CF4. The decrease in the deposition rate may be attributed to the etching effect by CF4 plasma during the deposition process. As the additive fluorine concentration increases, the intensity of Si–F peak stretching vibrations located at 930 cm-1 increases and the frequency of the Si–O stretching vibration mode centered at 1060 cm-1 shifts towards higher wavenumber.
Cyclohexyl Methacrylate with Tetra (Ethylene Glycol) Dimethacrylate in Tertahydrofuran Radical Copolymerization
Authors: Fasla Asmahane , Ould Kada Seghier , Seghier Zoubida , Périchaud Alain
Published: March 2009

Free-radical copolymerization of cyclohexyl methacrylate (CHMA) and tetra (ethylene glycol) dimethacrylate (TtEGDMA) were carried out at 60 °C in tetrahydrofuran solution in presence of 2,2-azobisisobutyronitrile. The random copolymers were prepared with nominal crosslinking ratios, X of 1, 5 and 10% mol TtEGDMA / mol CHMA. The copolymers were characterized by 13C NMR spectroscopy. The copolymers was characterized by 13C RMN analysis and determined the copolymers composition. The monomer reactivity ratios r1 (TtEGDMA) and r2 (CHMA) were determined with the linearized copolymerization equations of the Fineman–Ross methods (r1 = 1.77 and r2 = 0.48) and Kelen–Tüdös (r1 = 1.81 and r2 = 0.46). Parameters of Alfrey-Price Q1 = - 1.10 (specific activity) and e1= - 0.64 (polarity) for TtEGDMA.
Comparative Study between Two Polymers of Arylene-Vinylene Units: Electrochemical, Spectroscopic Characterization and Resistivity Measurements
Authors: Mosbah S. , Zbiri I. , Bencharif L.
Published: March 2009

Two arylenevinylenes compounds formed with thienyl or furyl units substituted by a cyano group at the ethylene linkage were studied by direct anodic oxidation in CH2Cl2/Bu4NBF4 0,2M medium on platinum electrode using cyclic voltammetry method. By applying a sequential linear potential scan rate of 100 mV.s-1 between 0-1,6 V versus Ag /Ag+ (0,1 M) / CH2Cl2, these two organic compounds could be polymerized. The electrosynthetized conducting polymers were also prepared by potentiostatic method then characterized by IR and UV spectroscopies and their conductivity was evaluated.
Fabrication of Novel Cellulose/Chitosan Artificial Skin Composite
Authors: Fu Li Na , Wang Wei , Yu Long Jiang , Zhang Sheng Min , Yang Guang
Published: March 2009

Skin wounds, burns and scars represent a major burden upon world healthcare costs. The successful creation in vitro of skin substitutes has been the focus of a concentrated research activity for the last 30 or more years, culminating in some success for its translation into the clinical setting. In this paper, a novel artificial skin of bacterial cellulose has been biosynthesized by Acetobacter xylinum and modified by chitosan. BC is thought as an optimal substrate material of artificial skin. It is thought to be an interesting material for using as a substratum of artificial skin because it could provide moist environment to a wound resulting in a better wound healing. But BC has no antimicrobial activity to reduce the probability of wound infection. To achieve antimicrobial activity of BC, it was modified by chitosan due to its antibiotic activity. The structure and components were characterized by FTIR and ESEM. The results indicated the nano-composites of BC and chitosan are promising and potential for wound dressings.
Silsesquioxane Materials as Sun Protection Factor Ingredients and as Films for Greenhouse Covers
Authors: Chen Ping , Liu Tao , Wang Di , Liu Yu , Hu Li Jiang
Published: March 2009

Using polyhedral oligomeric silsesquioxanes (POSS) derived from the hydrolytic condensation of (3–methacryloxypropyl)trimethoxysilane (MPMS), vinyltrimethoxysilane (VMS), and (3-glycidoxypropyl)trimethoxysilane (GPMS), three hybrid nanofilms, f-MP (film-MPMS-POSS), f-GP and f-VP, were prepared using sol-gel and crosslinking processes. The average transparency (AT) and absorption coefficents (AC) of the films were measured in the ranges of 280-2500 nm. Two film transparency applications are described in this work: 1) The AT values of the POSS films in the range of the ultraviolet B (UV-B) spectrum (280–320 nm) (a skin cancer-causing agent) and 2) the AT values in the visible light (VIS) region (400-750 nm) and the near infrared (NIR) region (750-2500 nm) (providing crops growth energy and the improvement of the photosynthetic process efficiency). The AT values of the POSS films in the UV-B range are only about 13%, indicating these films can provide a physical barrier to block UV-B absorption by the skin, and therefore are possible POSS materials for sunscreen ingredients. The AT values in the VIS region are 95.13%, 89.16% and 91.60%, respectively, and the AT values in the near infrared (NIR) region (750-2500 nm) are 95.39%, 93.11% and 90.50%, respectively. These high AT films are good candidates for greenhouse covers. The AT values among the three films in the 280-2500nm region are different and exhibit varied selectivity for absorbed spectra due to the dissimilar sizes of organic branches covalently bonded to the silica network in the film structure.
Preparation and Properties of Calcium Phosphate Cement Containing ZnO Whisker
Authors: Guo Ya Meng , Li Dong Xu , Li Yan Bao
Published: March 2009

Calcium phosphate cement (CPC) is a self-hardening material for bone repairing. ZnO whisker is a new type reinforced materials lately, which is acerose single crystal fiber. In this study, ZnO whisker was added into the CPC with different ratios, and each specimen kept at 37 oC in 100% humidity for 24 hrs. The phase and microstructure of the calcium phosphate pastes were investigated using X-ray diffraction and scanning electron microscopy, respectively. It has been found that ZnO whisker could supply nucleating center, TTCP and DCPA could be much easier to form HA around the ZnO whisker. The adding amount of ZnO whisker is a key factor that determines the mechanical properties.
Fabrication Idea Two-Dimensional Photonic Crystals by Growing Freshwater Pearls Induced by Rare Earth Cerium
Authors: Shi Wei Lin , Jin Ye Fei , Li Jie Ru
Published: March 2009

Recently, biological system has revealed astonishing complex photonic structures. Freshwater pearls shows striking optical effects, such as reflection and interference, which closely related to its nanometer-scale multiplayer structure. In this paper, we tried to fabricate idea biological two-dimensional (2D) photonic crystals by growing freshwater pearls induced by Rare Earth Elements (REE) Cerium at a concentration of 1.2 mg•L-1. Comparing with the reference pearls cultured in nature freshwater, the superficial microstructure of REE pearls and their glossiness have taken large changes. The nacre of the REE pearls is structured 2D periodic photonic crystals layered structure, and each layer is composed by regular aragonite sheets, while the nature pearls has a mesa structure made of the spindly blocks, which were investigated by means of scanning electron microscopy (SEM). The glossiness of the pearls corresponds with the microstructure, the REE pearls possessing idea photonic crystals have higher glossiness than that of the nature pearls, which attribute to the strong interference effect of light on the photonic structure of REE pearls. It also provides an opportunity to grow perfect photonic crystals by culturing water pearls.
Surface Characteristics and Hemocompatibility of Modified NiTi Alloy Intravascular Stents
Authors: Ni Ya Ru , Huang Hai Rong , Lu Chun Hua , Xue Jun Kai , Xu Zhong Zi
Published: March 2009

TiO2, ZrO2 and titanium oxide in deficiency oxygen environment were used to modify the surface of biomedical NiTi stents. The coatings were prepared by vacuum deposition. The surface microstructures and characteristics, blood compatibility of the modified stents in simulated body fluids were assessed using scanning electron microscopy (SEM), hemolysis test, coagulation test and blood platelet adhesion test. The hemocompatiblity of the modified stents were all improved by layer coating. Enhancement of blood compatibility was believed to stem from the improved surface water affinity and hemolysis resistance of the layer, and titanium oxide in deficiency oxygen environment displayed better. This study indicated that layer coating was a promising effective modification method for improving the surface properties of biomedical NiTi alloy intravascular stents. As a coating materials，titanium oxide in deficiency oxygen environment was better than TiO2 and ZrO2.
Study on Biomineralization of Poly (Vinyl Alcohol) Film via a Biomimetic Process
Authors: Guo Yue Wen , Li Ling Li , Li Guang , Jiang Jian Ming
Published: March 2009

Organic polymer–hydroxyapatite (HA) hybrid was expected as a promising bone substitute. In this work, poly(vinyl alcohol) (PVA) was used as a polymer substrate and the PVA-HA hybrid was prepared by a biomimetic process. The resultant PVA-HA composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. It was found that HA could deposite on PVA surface when PVA soaked in water for a little swelling and then was carried out CaP treatment previously. The formed HA showed bone-like structure and had a good interaction with PVA substrate. The resultant hybrid might exhibit good osteoconductivity and biocompatibility, and could be expected as a useful scaffold for bone tissue regeneration.
Property and Influence of Membrane on the Absorption Efficiency of Sulfur Dioxide from Flue Gas
Authors: Xue Juan Qin , Wang Yu Jie , Wang Kong Fen , Zhou Zhou
Published: March 2009

The method of wettability of solid-liquid interface is used to examine the differences of the liquid membranes formed by hydrophilic or hydrophobic membranes with different size and different materials, the influence of the characteristics of membrane modules in the process of desulfurization is studied. The method of accelerating the renewing rate of liquid membrane is proposed. The results show that the hydrophobic liquid membrane leads to higher renewing rate and absorption efficiency of sulfur dioxide and the hollow fiber membrane of polypropylene has higher adsorption efficiency. The dynamic contact angle of the same hollow fiber membrane is increasing with the number of the fibers leading to the increase of the diffusing resistance of liquid between the fibers. In order to accelerate the renewing rate of the liquid membrane, the concentration of the medium should be decreased under the condition of high absorption capacity.
Preparation of Porous Titanium by a Novel Foaming Process and MG63 Cell Behavior In Vitro
Authors: Chen Yue Jun , Feng Bo , Weng Jie , Qu Shu Xin , Wang Jian Xin , Lu Xiong
Published: March 2009

A novel two-step foaming process has been developed to prepare the porous titanium implant. By using H2O2 and stearic acid as foaming reagent ordinally, a foamed structure with an open, interconnected pore morphology was obtained. The mechanical property was determined by compressive test. In vitro study was conducted to evaluate the ability of the porous titanium to support the growth and differentiation of Human osteosarcoma cell line MG63. The results show that the porous titanium has better interconnection compared to that obtained by traditional slurry foaming and its compressive strength and Young’s modulus were approximate 23.6 MPa and 2.1 GPa, respectively. Cell culture experiment results indicate that the porous titanium has good biocompatibility and acid-alkali treatment facilitates the adherence and proliferation of cells.
Fabrication and Antibacterial Performance of Bio-Graded Nano-Composite Materials by Using Inkjet Printing Method
Authors: Zhu Dong Bin , Xu An Ping , Qu Yun Xia , Mi Zhi Mei , Li Jian Qiang
Published: March 2009

The graded composite materials were fabricated by direct inkjet printing of nano-electropolar mineral and nano-hydroxyapatite powders for the study of inhibiting function on streptococcus mutans, which is a primary pathogen for human dental caries. The electropolar mineral can be utilized in many fields due to its spontaneous permanent polarity and far infrared emission properties. In this study, the graded distribution of the streptococcus mutans on the surface of graded composite materials was investigated by energy dispersion spectrometry, and the mechanism of which is that the streptococcus mutans was remained in the culture of pH at about 8.5 self-adjustment induced by the electropolar mineral. This culture inhibits growth and acid production of streptococcus mutans. Therefore, this composite materials have inhibitory effects on streptococcus mutans, and can be used as a promising biomaterial for preventing human teeth from caries.
Study on the Hemolysis Rate and Cytotoxicity Test of Porous Ultramicron HA Containing Mg
Authors: Li Xing Yi , Liu Guo Quan , Yuan Shi Dan , Zhang Ling , Meng Xiang Cai
Published: March 2009

The Nano-HA powder was prepared by chemical precipitation. Magnesium powders were used to make porous ultramicron HA ceramic, and the biological properties of which were investigated by hemolysis rate and cytotoxicity tests. The experimental results shows that the hemolysis rate of the nano-HA powder and porous ultramicron HA ceramic were all less than 5% and none of them showed cytotoxicity. The results indicated that nano-HA and porous ultramicron HA ceramic were provided with good biocompatibility.
Effects of Exercise on Antitumor Efficacy of DHAQ-Loaded PLA-PLL-RGD Nanoparticles in Hepatocellular Carcinoma
Authors: Liu Pei Feng , Wang Hong Zhi , Zhang Jun , Yu Hui , Li Yao Gang , Duan You Rong
Published: March 2009

This study mainly describes the synthesis of Arginine-Glycine-Aspartic (RGD) peptide modification of copolymer: poly(lactic acid-co-L-lysine) (PLA-PLL- RGD) and preparation of mitoxantrone(DHAQ)-loaded PLA-PLL-RGD nanoparticles (DHAQ-NP), and researches the effects of exercise on antitumor efficacy of DHAQ-NP in hepatocellular carcinoma. Experimental results show that compared with DHAQ-only group, the DHAQ concentration of tumor in Exercise+DHAQ-NP and DHAQ-NP groups up-regulate significantly. Tumor volume and weight of mice were significantly decreased in the DHAQ-NP and Exercise+DHAQ-NP groups as compared to with the Control group. Suggesting that DHAQ-NP can effectively inhibit the growth of hepatocellular carcinoma. Compared with DHAQ-NP group, the DHAQ concentration, tumor volume of Exercise+DHAQ-NP group have no significant changes. This suggests exercise can not significantly influence the antitumor efficacy of DHAQ-NP. These studies are essential to fully understand the safety and application of exercise as a supportive intervention in targeted therapies.
Surface Modification of Chitosan Membranes by Oxygen Plasma Treatment
Authors: Zhao Na Ru , Wang Ying Jun , Ren Li , Chen Xiao Feng
Published: March 2009

Chitosan membranes were prepared by solvent cast method. In order to increase cell adhesion of the chitosan membranes, oxygen plasma treatment was applied to improve the hydrophilicity of the surface of chitosan membranes. The surface properties were characterized by scanning electron microscopy (SEM), contact angle analyzer, X-ray photoelectron spectroscopy (XPS). The effects of exposure time, plasma generating power, and chamber pressure on water contact angle of the chitosan membranes were investigated. The water contact angle of chitosan membranes decreased from 94.1° to 49.2° after plasma treatment. Which suggested the surfaces became more hydrophilic. XPS analysis showed that the oxygen content and the ratio of O/C increased markedly after oxygen plasma treatment. Furthermore, it was found that C-H bonds were broken with oxygen plasma treatment. C-OH group had been increased after plasma irradiation.
Effect of High Temperature on Morphology and Structure of Nano-Hydroxyapatite/Collagen Composite
Authors: Song Qiang , Hu Kun , Cui Fu Zhai , He Zhou Ying
Published: March 2009

Nano-hydroxyapatite/collagen composite was processed at room temperature, 180°C, 200°C and 220°C under atmosphere for 10 min respectively. The morphology of the samples was characterized by scanning electron microscopy (SEM). The structure and components of the samples were investigated by energy dispersive spectrograph (EDS), X-ray powder diffractometer (XRD) and Fourier transform infrared (FTIR). The results of SEM and EDS for nHAC changed greatly at 200°C and 220°C in comparison with room temperature. The morphology and structure of nHAC at 180°C were similar to those at room temperature. It was demonstrated that nHAC possessed thermal stability in morphology and structure.
Microstructure and Toughness Mechanism of Shank Bone
Authors: Chen Bin , Peng Xiang He , Sun Shi Tao , Luo Ji
Published: March 2009

Scanning electron microscope (SEM) observation was performed and showed that shank bone is a kind of bioceramic composite consisting of laminated hydroxyapatite and organic materials. The hydroxyapatite layers are parallel with the surface of the bone and consist of numerous thin and long hydroxyapatite sheet fibers. The hydroxyapatite sheet fibers in different hydroxyapatite make a little angle with each other and compose a kind of screwy microstructure. The maximum pullout force of the screwy microstructure was investigated and compared with that of parallel microstructure. It shows that the maximum pullout force of the screwy microstructure is markedly larger than that of the parallel microstructure, which was experimentally validated.
Influence of pH Value Stability on the Biomineralization of Bioglass
Authors: Ma Qiang , Wang Ying Jun , Zheng Hua De , Ning Cheng Yun , Chen Xiao Feng
Published: March 2009

Papers reported that the pH value was rising slowly with the prolonging of soaking time when bioglass was studied into simulated body fluids, and it influenced the formation of apatite layer on the surface of bioglass obviously. An Intelligent Multi-parameter in vitro Simulated Evaluation （IMSE system） was used to study the bio-mineralization properties of 58S bioglass. The deposition of apatite formation on the surface of bioglass (BG) from dynamic r-SBF was studied systemically with IMSE system, which could control and stable such parameters as temperature, fluid rate, ion concentrations and pH value etc. precisely. Results showed that the rate of apatite formation was slowed down when pH value was stabled at about 7.35.
Synthesis and Characterization of Titania Nanoribbons for Lithium Selective Adsorption
Authors: Zhang Qin Hui , Li Shao Peng , Sun Shu Ying , Yin Xian Sheng , Yu Jian Guo
Published: March 2009

Mesoporous titania nanoribbons are synthesized via an optimized soft hydrothermal process and the derived titania ion-sieves with lithium selective adsorption property are accordingly prepared via a simple solid-phase reaction between Li2CO3 and TiO2 nanomaterials followed by the acid treatment process to extract lithium from the Li2TiO3 ternary oxide precursors. The physical chemistry structure are characterized by XRD, TEM/HRTEM, SAED and N2 adsorption-desorption analysis; and the lithium selective adsorption properties are tested by the adsorption isotherm measurement and demonstrated with the distribution coefficient of a series of alkaline and alkaline-earth metal ions. Though the high temperature calcinations and lithium insertion-extraction process resulted in the agglomeration of nanostructure to large bulky particles, it implied that that the low-dimensional titania nanoribbons might be functionalized to lithium ion-sieves with remarkable adsorption capacity and selectivity, promising in the utilization of lithium extraction from aqueous resources including brine or seawater.
Miscibility Evaluation of LDPE/EVA Blends Filled with Lignin by Rheological Properties and FT-IR
Authors: Zhou Jian , Luo Xue Gang
Published: March 2009

Lignin, one kind of byproduct of pulp-making industry, is used for the preparation of blends with LDPE/EVA by torque rheometer through the measuring maximal torque, balanced torque and plasticized time to confirm the optimum processing conditions. The miscibility, which is mainly dependent on the occurrence of lignin-polymer interactions of hydrogen bond, is characterized by Fourier infrared spectroscopic analysis (FT-IR). The results indicate that the rheological properties of lignin filled blends with 50~55N•maximal torque, 11~12N•m balanceable torque and 60~70s plasticized time are obtained under the conditions of 20 parts lignin blending with the LDPE and EVA proportion of 55/45 with 10 parts compatibilizer at 150°C. The FT-IR figures show that the hydrogen bond between compatibilizer and lignin or polymer is formed resulting from that the characteristic absorption peak of carbonyl at 1725~1800cm-1 disappears and hydroxide at 3438~3440cm-1 increases.
Preparation of Titania Cloth Using Cellulose Fabric as the Template
Authors: Chen Xiao Jun , Wang Biao , Wang Hua Ping , Duan Qiong Juan
Published: March 2009

Titania cloth was successfully prepared by the process comprising the steps of (1) immersing a cellulose fabric into titanium compound solution and (2) heating the impregnated fabric under controlled conditions. Several methods such as TG-DTA measurement， X-ray power diffraction (XRD), scanning electron microscope (SEM) were used to characterize the structure and properties of TiO2 cloth. And the TiO2 cloth sintered at 500°C exhibited the highest photodegradation efficiency of MB relative to the other samples.
Synthesis of TiO2 Nanorod-Assembled Microspheres from TiCl3 and its Photocatalytic Activities
Authors: Huang Xiang Ping , Wang Zhao , Mao Feng , Wei Hui Li , Zhang Chang Yuan
Published: March 2009

Pure rutile TiO2 nanorod-assembled microspheres were synthesized on a large scale without templates or surfactants by hydrolysis of TiCl3 in ethanol and HCl mixed solution at 180°C.The spheres exhibit unique three-dimensional hierarchical architectures with significantly improved photocatalytic activities in visible light.
Hydrothermal Synthesis of Self-Assembled-Microfibers with Rutile Single Crystal Titania Nanorods
Authors: Wang Zhao , Mao Feng , Huang Xiang Ping , Wei Hui Li , Zhang Chang Yuan
Published: March 2009

Single crystal rutile TiO2 microfibers have been synthesized by hydrothermal method using TiCl3 as titanium source. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal that the microfibers with average diameter of 15 μm and length of 1~2 mm are self-assembled by single crystal TiO2 nanorods and well-dispersed. The bandgap Eg of microfibers is about 3.0 eV by UV-vis adsorption spectrum.
Synthesis of O'-SiAlON/SiC Ecomaterials by Using Non-Traditional Resources: Yangtze River Sand
Authors: Hao Hong Shun , Xu Li Hua , Liu Ming , Zhang Xiao Meng , Yang Jian Ying , Guo Yu Juan
Published: March 2009

O'-SiAlON/SiC ecomaterials were synthesized by using the Yangtze River sand that containing abundant Si and Al elements as the major raw material with minor additives through the carbothermal reduction nitridation route combined with colloidal process. This study realized the conversion of ecomaterials from non-traditional resources, Yangtze River sand. Orthogonal design was adopted to optimize the colloidal process parameters. The green compact with the largest bulk density was obtained when the solid volume loading is 50%, the addition mass fraction of SL is 0.8%, the addition mass fraction of CMC is 0.05%, the ball milling time is 10 h, the pH value is 9 and particle size distribution is multi-peak in the colloidal process. The effects of reduction agent, flowing rate of N2, sintering temperature during carbothermal reduction nitridation process on the microstructure of as-fabricated SiAlON materials were explored. The XRD results indicated that when sintering temperature is 1450°C, maintaining time is 6 h, flowing rate of N2 is 1.0 L/min and carbon black is selected as reduction agent, O-SiAlON/SiC composites was successfully synthesized. The SEM images showed the densificated microstructure and uniform grains with the short column shape.