bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Twist Drill’s Geometry for Cast Iron
Authors: Zheng Xiao Hu , Zhang Hong Zhou , Xue Kai , Chen Ming , Zhang Yun Shan
Published: March 2010

A new special drill is developed for iron cast drilling. The special drill has double point angle and 0°chisel rake angle which can decrease cutting force, tool wear and cutting temperature. Drilling performance is evaluated by trust force, torque, tool wear. The results indicate that new special drill is suitable for iron cast drilling with small cutting force and long tool life.
The Application of FEM in Micro-Cutting and The Study of Key Technique
Authors: Pang Y.C. , Li Y.
Published: March 2010

The application of finite element method (FEM) in conventional machining simulation has been carried on for a long time. But in micro-cutting, due to the unique mechanism of micro-cutting, such as size effect, round tool edge, minimum chip thickness and microstructure effect, there are still some bottleneck problems need to address. So this paper focuses on the current state-of-the-art surrounding the application of FEM in micro-cutting, and discusses some key techniques such as material model, chip separation, and chip-tool interaction in detail. Finally, future work of FEM simulation for the micro-cutting is recommended.
Effect of Tool Coating on High Speed Milling Microwave Printed Circuit Board
Authors: Zhao Xin , Xu Feng , Wu Xin , Zang Xiao Jun , Li Ying
Published: March 2010

The aluminum base microwave printed circuit board has the wide application foreground in high-tech fields. But the insulating layer of PCB is a difficult-to-machining material. In this paper, the experimental research on the wear mechanics and cutting coating comparison in high speed milling of the Rogers 6002 micro wave PCB. TiN and TiAlN coated cemented carbide cutting tool are select to milling the micro wave PCB. The effect of milling parameters and cutting length on cutting force is investigated. SEM is used to observe the wear morphology of the flank face of cutting tools. Research results show the wear mechanisms of coated tool include abrasive wear and adhesive wear. TiAlN coating is more suitable for high milling the insulating layer of microwave PCB because of its high hardness and wear resistance. The research results are contributive to choose proper high-speed cutting tools and parameters.
An Extended Role-Based Access Control Model for CSCW Systems
Authors: Chen Bing
Published: March 2010

Due to the increasing threat of network attacks, network and information security is an upmost concern for CSCW. Traditional Role-Based Access made focus on the typical roles divided according to organizational roles in CSCW. It is insufficient to have role permissions based on object types for collaborative environments. An extended role-based access control model is proposed in this article to expand role to construct the hierarchy of security domain for CSCW. The total CSCW system was called security domain. Subdomain roles inherit security domain roles. Atomic domain roles inherit subdomain roles under role constrains. All extended role and role constraint are partial ordering and are used to restrict the range of access control for all CSCW participants.
Experimental Study for the Cutting Forces during Sawing Granite with Diamond Circular Saw Blades
Authors: Wang Jing Kun , Ai Xing , Xu Guo Jun , Zhang Jin Sheng
Published: March 2010

The granite cutting processing using diamond circular saw blades is the most extensive application processing methods. The cutting force is measured at different cutting depth ap, sawing feed rate vf and linear velocity v when the granite is cut by diamond circular saw blade by orthogonal experimental method. And the sawing force empirical formulas relative to these three variables are educed. We can obtain the experimental results as follows. The radial force Fn is greater than the tangent force Ft when ap is smaller than the circular saw blade diameter. The corresponding Fn and Ft are all smaller as the feed rate is greater at the same circular saw blade diameter. The cutting forces increase obviously as the cutting depth increases at the same circular saw blade diameter and feed rate.
Numerical Simulation and Experimental Investigation of the Gas-Liquid-Solid Three-Phase Flow Outside of the Abrasive Water Jet Nozzle
Authors: Hou Rong Guo , Huang Chuan Zhen , Zhu Hong Tao , Zhao Qing Zhi
Published: March 2010

Simulation of the gas-liquid-solid three-phase flow field of outside the abrasive water jet(AWJ) nozzle is studied by the computed fluid dynamic software- FLUENT, and the velocity field of the three-phase flow is obtained, the velocity value of the flow between the nozzle and work-pieces is also obtained. Serial experiments have been done to verify the simulation method. In the experiments, the impact force signal of the AWJ outside the nozzle is collected by the piezoelectricity ergometer, then it is filtered by the vibration signal and dynamic signal software. The testing values are transformed to the velocity values, which will be compared with the simulation values. The comparison result indicates that the value of the simulation is changing similarly with the experiment value, and both value is almost the same, which proves that the simulation method is successful, the simulation model and the boundary conditions are right.
Processing Methodology to Embedding NiTi Shape Memory Fibers into a Polymer-Based Composite Plate
Authors: Leite Boniek Evangelista , De Macedo Rafael Feliciano , Amorim Júnior Wanderley Ferreira , de Araújo Carlos José
Published: March 2010

The objective of this work was the development of a processing methodology for embedding NiTi fibers into a polymer-based composite plate. A carbon fiber reinforced polymer (CFRP) prepreg and NiTi thin wires were used. A uniaxial hot press was prepared to be used in the composite processing. Two prototypes were fabricated to provide fiber alignment and fixation fixture. A CFRP composite plate without fiber and another with NiTi fibers were processed. Micrometers and a universal materials testing machine were used to measure the plate thickness and Young's modulus. It was possible to develop a processing methodology for embedding NiTi fibers into a polymer-based composite plate. The CFRP plate without fiber presented almost no variation in plate thickness and Young's modulus measurement thus enabling the CFRP manufacture by the hot uniaxial press. The fiber fixation fixture developed was able to produce CFRP-NiTi fiber hybrid composites with different number of fibers embedded, the spacing distance between fibers was at least 1 mm and the fiber alignment was achieved.
Investigation of Quasicrystal-Reinforced Aluminium Metal Matrix Composite by Hot Extrusion
Authors: Passos Tibério Andrade , Gomes Rodinei Medeiros , Melo Tadeu Antônio de Avezedo , de Lima Severino Jackson Guedes
Published: March 2010

The use of quasicrystalline alloys as reinforcement material is due to the fact that they posses high hardness and low coefficient of friction. For this purpose was used compaction/extrusion equipment with which it was possible to observe a tendency toward increase in the mechanical strength from 72MPa (0% reinforcement) to 129Mpa (6% reinforcement).
Preliminary Results of Stress Recovery of Constrained NiTi SMA Wire for Aerospace Applications
Authors: Santos Júlio Cesar , Da Silva Antunes Andre , Pinheiro Afonso Paulo Monteiro , Kabayama Leonardo Kyo , Rigo Odair Doná , Otubo Jorge
Published: March 2010

The rocket propellant ignition system uses electro-explosive device actuated by wire electrode. Those wires are usually made by Fe-Ni based alloy with controlled thermal expansion inserted into a ceramic feed-through and are connected to thin resistive wire which is heated through the passage of an electrical current for propellant ignition. The contact between ceramic feed-through and wires should be reliable since sometimes it could fail. A novel alternative process is to use SMA wires taking into account the shape recovery effect constraining the wire inside the feed-through. The recovery stress of 326 MPa for 4% pre-strain should be enough to constrain the wire inside the feed-trough avoiding the gas leakage.
Thermal Activation of CFRP with Embedded NiTi Shape Memory Wires
Authors: Vilar Zoroastro Tôrres , de Araújo Carlos José , Dos Reis Rômulo Pierre Batista
Published: March 2010

The possibility of uniting two or more different materials to obtain structures capable to feel and adapt to environmental alterations and operational conditions, has been leading to the development of active composites with functional properties that makes possible the control of shape, vibration, rigidity and/or structural integrity monitoring. These characteristics are very well accepted in modern technological applications. In this context, active composites were manufactured using pre-impregnated (Pre-Pregs) of carbon fiber reinforced polymer (CFRP) and NiTi shape memory alloy (SMA) thin wires in different conditions. The functional capacity of the obtained CFRP-NiTi smart composites was verified through detection of buckling and thermal contraction/expansion effects by electrical heating of the NiTi wires inside the CFRP matrix. Although the NiTi wires represent a minimum volumetric fraction in the CFRP-NiTi produced systems, its influence was evidenced.
Dynamic Properties of NiTi Shape Memory Alloy and Classic Structural Materials: A Comparative Analysis
Authors: Da Silva Niédson José , Grassi Estephanie Nobre Dantas , de Araújo Carlos José
Published: March 2010

Shape Memory Alloys (SMA) are smart materials that have attracted increasing attention due to their superior damping properties when compared to conventional structural materials. These functional materials exhibit high damping capacity during phase transformation as well as in the low temperature martensitic state. In this work NiTi SMA, commercial aluminum, stainless steel and brass were submitted to dynamic mechanical analysis (DMA) in a single cantilever mode. Small beam specimens were manufactured to accomplish the DMA tests. The studied NiTi presented a damping capacity peak during phase transformation, being much higher than damping of conventional materials. NiTi SMA also showed an increase of storage modulus after conversion of low temperature phase to high temperature phase while an almost linear decrease is observed for the conventional materials studied.
Precipitates Formation in Ti-Ni Equiatomic Alloys due to Annealing Heat Treatment
Authors: Oliveira Carlos Augusto Nascimento , De Pina Euclides Apolinário Cabral , Gonzalez Cezar Henrique , de Araújo Carlos José , Filho U.S.L. , de Araújo Filho Oscar Olimpio
Published: March 2010

The use of smart material such as Ti-Ni in actuators application requires an intense mechanical and metallurgical investigation to understand its behavior. This paper studies martensitic transformation using DSC and X-ray diffraction techniques to compare shape memory parameters in Ti-50.2%Ni (A1) and equiatomic Ti-50.0%Ni (A2) Alloys. The as as-received samples were submitted to annealing at 400°C and 500°C for 24 hours then quenched in at 25°C. The influence of heat treatment on martensitic transformations temperatures and the appearance of R-phase were analyzed using DSC and X-ray diffraction.
Comparison between the Flexibility of Three Different Types of Rotary NiTi Endodontic Instruments
Authors: Viana Ana Cecília Diniz , Bahia Maria Guiomar de Azevedo , Buono Vicente Tadeu Lopes
Published: March 2010

The aim of this study was to characterize metallurgical properties and the dimensions of three types of rotary NiTi endodontic instruments and to establish a correlation between these characteristics and the flexibility of the instruments. Their chemical composition and constitution were characterized by energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD). Transformation temperatures were assessed by means of differential scanning calorimetry (DSC). Computer software was used to analyse images of the longitudinal and transverse sections for determining instrument diameter and cross-sectional area at 3mm from the tip. The flexibility of the instruments was evaluated in bending tests performed according to the ISO 3630-1 specification, in which the instruments are clamped at 3mm from their tip and bent by 45° along their longitudinal axis. The values of bending moment at 45° were correlated with instrument diameter and cross-sectional area at 3mm from the tip. The results of EDX, XRD and DSC showed that physical and chemical properties of the materials differed slightly among the files analyzed. A direct relationship was found between bending moment and the geometric characteristics of the instruments. Resistance to bending of NiTi root canal instruments depended on their geometrical shapes and metallurgical properties, but the cross-sectional configuration can be seen as an important parameter affecting this property.
Vibration Attenuation in an Epoxy Smart Composite Beam with Embedded NiTi Shape Memory Wires
Authors: Dos Reis Rômulo Pierre Batista , Souto Cícero da Rocha , de Araújo Carlos José , Silva Antonio Almeida , da Silva Edson Paulo
Published: March 2010

Shape memory alloys (SMA) are thermo-responsive materials where deformation can be induced and recovered through temperature changes. Therefore, SMA are considered smart materials. In this work, an epoxy beam reinforced by NiTi SMA wires was developed. This active composite contains five pre-trained NiTi SMA wire actuators, evenly distributed along the neutral plane of the epoxy beam, which can be activated by resistive heating. The results of different ways for electrical activation of the smart composite in a simply clamped mode are discussed. It was possible to demonstrate the viability of this concept for attenuation of mechanical vibrations by controlled electrical heating of the NiTi wire actuators.
The Influence of Cyclic Straining in Torsion on Fatigue Resistance and Torsional Properties of ProTaper NiTi Endodontic Instruments
Authors: Martins Renata de Castro , Bahia Maria Guiomar de Azevedo , Buono Vicente Tadeu Lopes
Published: March 2010

This study evaluated the influence of cyclic straining in torsion on fatigue resistance and torsional properties of ProTaper (S1, S2, F1, F2, F3) NiTi instruments. The mechanical behavior was evaluated by means of torsion and bending tests, performed according to ISO 3630-1 specification, while the fatigue resistance was evaluated using a bench test device employing an artificial canal with 5mm curvature radius and angle of curvature of 45º. The dimensional aspects, diameter (D3) and cross-sectional area (A3) at 3mm from the tip of the instruments were determined by means of image analysis of optical and scanning electron microscopy (SEM). The surface characteristics of instruments before and after they were submitted to cyclic straining in torsion and the morphological aspects of the fractured surfaces were analyzed by SEM. The maximum torque and the bending moment at 45º were higher for instruments with larger D3 and A3. The F1 and F2 instruments followed the Coffin-Manson’s relation, i.e., their number of cycles to failure (NCF) varied inversely with the strain amplitude. With the exception of S1 and S2 instruments, there was a tendency of decreasing the maximum torque after the instruments have been submitted to cyclic straining in torsion. With the exception of S1 instruments, there was a tendency of decreasing the NCF after torsional cycling. The analyses by SEM showed the presence of longitudinal cracks on the instruments previously cycled in torsion. The morphological aspects of the fractured surfaces of instruments tested in torsion or flexural fatigue did not changed by the cyclic straining in torsion. These changes in mechanical properties with torsional cycling can be related to the generation of imperfections such as longitudinal cracks on the instruments.
Cyclic Stress-Strain Response of Superelastic Polycrystalline Cu-12wt%Al-0.5wt%Be Alloy
Authors: França Fabio José Carvalho , Guedes Nilmário Galdino , de Lima Severino Jackson Guedes , Melo Tadeu Antônio de Avezedo , Gomes Rodinei Medeiros
Published: March 2010

The effect of cyclic deformation on the stability of superelasticity was investigated for the Cu-12wt%Al-0.5wy%Be alloy. The loading and unloading cyclic tensile tests were performed at room temperature and at 57oC with the maximum constant strain of 4%. The effect of holding the applied strain for a period of time on the superelastic properties was also investigated. It was confirmed that the total volume fraction of the retained martensite changes with time after unloading cycle, leading to the reduction of the residual strain. Additionally, the residual strain increases as the loading cycle of the applied strain is kept constant for a period of time.
Synthesis and Atomic Force Microscopy Contact Current Images of Aluminum Doped ZnO Thin Films
Authors: Muñoz Aguirre N. , Rivera-López J. Eduardo , Martínez Pérez L. , Tamayo Meza Pedro A.
Published: March 2010

Aluminum doped ZnO thin films were synthesized by the water-mist assisted spray pyrolysis technique. The structural characterization by means of X-Ray diffraction measurements is reported. By means of Atomic Force Microscopy, the superficial electrical characteristics of the thin films are studied. Specifically, contact current images are shown and discussed. It is important to emphasize that in spite of no voltage is applied to the Atomic Force Microscopy contact conductive tip, current images are getting.
Structural Characterization of Poly(Sodium 4-Styrene Sulfonate)/CdS Semiconductor Nanoparticle Composites
Authors: Espe Matthew P. , Ortiz-Colon Saida Y. , Ponce Arturo , Ziolo Ronald F.
Published: March 2010

The properties of polymer/semiconducting nanoparticle (NP) composites-materials used in hybrid, bulk-heterojunction photovoltaic materials-are dependent on the interaction of the NPs and polymer. Composite films of water soluble polymers and CdS NPs have been produced both by synthesizing the NPs within the polymer matrix and by adding the CdS NPs, containing a capping agent, to the polymer. The composites have been characterized by microscopy as well as 1H, 13C and 113Cd solid-state NMR. When synthesizing the NPs within the polymer, the polymer matrix plays a role in the cadmium sulfide NP nucleation, growth and structure. In the blended system, the dominant interaction between the glycerol capping agent and sulfonated polymer is observed to be hydrogen bonding.
Effect of Type and Concentration of Ionomer Compatibilizer on the Hdpe/ Ionomer/ Clay Nanocomposites Morphology
Authors: López-García S. , Sánchez-Valdés Saul , Ramos de Valle L.F.
Published: March 2010

A study of the effect of an ionomer compatibilizer (surlyn® 9520 and 9721, both with zinc as the neutralizing cation) on the morphology and properties of a high density polyethylene (HDPE) - montmorillonite clay nanocomposite was carried out. The nanoclay used was cloisite 20A®. Polyethylene /Ionomer /Clay nanocomposites were prepared via melt mixing in a twin screw extruder. The nanoclay dispersion and exfoliation were examined through X-Ray Difraction (XRD) and Scanning Electron Microscopy (SEM). TGA was carried out to determine the effect of nanoclay on the thermal stability of the HDPE nanocomposites. Results showed that both ionomers impart a marked compatibility between the polymer and the nanoclay, promoting the exfoliation of the nanoclay within the HDPE matrix. Nonetheless, ionomer 9520 (with the higher degree of neutralization) at 10 and 12 wt% content produced completely exfoliated morphologies, whereas, the ionomer 9721 produced a lesser degree of exfoliation with few tactoids.
Dielectric Properties of PMMA-SiO2 Hybrid Films
Authors: Morales-Acosta M.D. , Quevedo-López M.A. , Alshareef Husam N. , Gnade B.E. , Ramírez-Bon R.
Published: March 2010

Organic-inorganic hybrid films were synthesized by a modified sol-gel process. PMMA-SiO2 films were prepared using methylmethacrylate (MMA), tetraethil-orthosilicate (TEOS) as silicon dioxide source, and 3-trimetoxi-silil-propil-methacrylate (TMSPM) as coupling agent. FTIR measurements were performed on the hybrid films to confirm the presence of PMMA-SiO2 bonding. In addition, metal-insulator-metal (MIM) devices were fabricated to study the dielectric constant of the films as function of frequency (1 KHz to 1 MHz). Electrical results show a weak trend of the dielectric constant of the hybrid films with MMA molar ratio. More importantly, the PMMA-SiO2 hybrid films showed a higher dielectric constant than SiO2 and PMMA layers, which is likely due to the presence of additional C-O-C bond.
Preparation of Electrospun Barium Titanate – Polyvinylidene Fluoride Piezoelectric Membranes
Authors: Corral-Flores Verónica , Pérez-Herrera Jessica J. , Torres-Moye Enrique , Romero-García Jorge , Bueno-Baqués Darío , Ziolo Ronald F.
Published: March 2010

Piezoelectric fibrous membranes of barium titanate (BTO) – polyvinylidene fluoride (PVDF) nanocomposites were studied. BTO nanoparticles of about 40 nm were synthesized by the sol-gel method and mixed in PVDF–dimethyl formamide solutions at 0, 0.1, 1 and 3 wt.% relative to the polymer weight. The suspensions were electrospun using a horizontal set-up with an applied voltage of 15 kV. The samples were heat treated for 24 hours at 100°C in air to increase the crystallinity of the polymer. The heat treatment induced a phase transformation from α to β phase in the pure polymer sample, while the nanocomposite membranes did not undergo such phase transformation. It was found that the addition of nanoparticles affected not only the morphology and diameter of the fibers, but also the content of beta phase of the polymer. In order to pursue the crystallization of β phase, additional samples were prepared by surface modification of the BTO nanoparticles and the addition of tetraisopentyl ammonium chloride. The best results were obtained with the last additive, which lead to the crystallization of only β phase and a homogeneous fibrous morphology. All these aspects were strongly correlated and consequently, governed the ferroelectric behavior of the samples.
Synthesis and Characterization of Branched Gold Nanoparticles
Authors: Mayoral Alvaro , Vazquez-Duran Alma , Heinze Stefan G. , José-Yacamán Miguel
Published: March 2010

In this work we present the synthesis of branched gold nanoparticles based on the seed mediated growth technique. The materials have been characterized by advanced electron microscopy techniques in order to elucidate morphology, size and internal structure.
Preparation of Nano-Ceramics via Aqueous Sol-Gel Method Modified with Surfactants: An Overview
Authors: Perera Yibran
Published: March 2010

The present paper shows an overview related to the preparation and characterization of different nano-materials such as: silica, alumina, di- and tri-calcium silicates and a composite in the ternary CaO-SiO2-Al2O3 system. These nano-materials are related to the construction area so some basic tests are carried out to evaluate their cementitious and/or pozzolanic behavior. The nano-ceramics have been synthesized via hydrolysis and condensation of aqueous sol-gel method modified with surfactants using different precursors such as: tetraethyl orthosilicate (TEOS), calcium nitrate tetrahydrate (Ca(NO3)2.4H2O), sodium silicate (Na2O.SiO2), aluminum nitrate nonahydrate (Al(NO3)3•9H2O) and an industrial aluminum hydroxide (gibbsite). The synthesis parameters such as: pH, temperature, kind of surfactants, etc., are reported. To characterize the structural, chemical composition, particle size and morphology of the nanoparticles, different techniques such as: Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM) are used.
On the Influence of Silver Nanoparticles Size in the Electrical Conductivity of PEDOT: PSS
Authors: Melendez Rebeca G. , Moreno Karla J. , Moggio Ivana , Arias Eduardo , Ponce Arturo , Llanera Irantzu , Moya Sergio E.
Published: March 2010

In this paper, we studied the influence of the silver nanoparticles size on the electrical conductivity of PEDOT:PSS in Ag(PEDOT:PSS) films. The silver nanoparticles were synthesized in presence of PEDOT:PSS by varying the molar ratio between AgNO3 and the reducing agent (NaBH4). Both the particle size determined by TEM and the plasmon band obtained by UV-Vis spectroscopy were found to be strongly dependent on the reducing agent concentration. The electrical conductivity increases inversely with the concentration of reducing agent from 5.24 x 10-4 up to 1.63 S/cm; three orders of magnitude higher than pristine PEDOT:PSS.
Ferromagnetic Nanomaterials Obtained by Thermal Decomposition of Ferrocene
Authors: Koprinarov Nikola , Konstantinova Mariana , Marinov Miko
Published: March 2010

Ferromagnetic micro and nano particles that are chemically resistant have been obtained by thermal decomposition of ferrocenes in a tightly closed chamber at high pressures. The investigation is focused on the influence of decomposition temperature, work atmosphere, temperature-change rate and process duration. According to the conditions, Fe3C, Fe3O4 and pure α-Fe particles have been created. Their composition and structure have been studied by Mössbauer spectroscopy, Scanning and Transmission Electron Microscopy, Electron Probe X-ray Micro Analysis and Energy Dispersive X-ray Spectrometry. In a tightly closed chamber, all components obtained during the decomposition process remain there. This difference to the widely-used Chemical Vapor Deposition method is very important. It inhibits the decomposition process and growth of ordered structures, preventing the end materials to be separated from each other. During the process, iron is liberated from the ferrocene molecule. Experiments have shown that it is highly chemically active to carbon and oxygen. For example, creation of carbide occured in conditions that are not allowed according to the iron-carbon phase diagram valid for bulk iron. Parallel to the reaction of iron with carbon (according to work atmosphere), the surplus of carbon atoms causes emerging of carbon nanoparticles.
Investigation of ZrN Hard Coatings Obtained by Cathodic Arc Evaporation
Authors: Kakanakov Roumen , Bahchedjiev H. , Kolaklieva Lilyana , Cholakova T. , Evtimova Svetla , Polychroniadis Efstathios K. , Pavlidou Eleni , Tsiaousis Ioannis
Published: March 2010

Zirconium nitrides (ZrN) coatings have shown better quality in comparison to titanium nitrides (TiN) ones regarding the application in the mechanical processing of aluminum and titanium alloys. This work presents the results from investigation on properties of ZrN-based coatings intended for industrial application. The ZrN and ZrTiN hard coatings in a thickness of (3 5) m were obtained on stainless steel substrates by cathodic arc evaporation method. The coating hardness in the range of 25-32 GPa was evaluated using the Vickers measurement technique. The coating properties were studied in relation to the surface morphology by Atomic force microscopy (AFM) and Scanning electron microscopy (SEM). The analyses showed that the number and size of the macroparticles decrease when N2 pressure increases in the deposition chamber. X-ray diffraction analysis (XRD) was performed to identify the crystallographic structure, preferred orientation and stress of the ZrN coatings.
Vacancy Mediated Diffusion at Surface-Confined Atomic Intermixing
Authors: Michailov Michail
Published: March 2010

The present study deals with diffusion behavior of adsorbed atoms on stepped crystal surfaces. In volume-immiscible systems, two-dimensional (2D) atomic intermixing at epitaxial interface could be completely blocked on step-free surface domains. This is a result of high diffusion barrier for direct atomic exchange between adsorbed layer and substrate. In that case, diffusion takes place exclusively across the steps of atomic terraces. In such systems, dynamic competition between energy gain by mixing and substrate strain energy results in diffusion scenario where adsorbed atoms form alloyed stripes in the vicinity of terrace edges. At high temperatures, the stripe width increases and finally completely destroys the terraces. This process leads to formation of alloyed 2D atomic islands on top of pure substrate layer. The atomistic Monte Carlo simulations reveal vacancy-mediated mechanism of diffusion inside atomic terraces as a result of spontaneous generation of vacancies at high temperature. Being in agreement with recent experimental findings, the observed surface-confined alloying opens up a way various surface pattern to be configured at different atomic levels on the crystal surface.
Characterization and Ethanol Sensing Properties of Pt-Doped Sn-O-Te Thin Films
Authors: Georgieva Biliana , Podolesheva Irena , Spasov Georgi
Published: March 2010

Thin films (40-60 nm) prepared by co-evaporation of Sn and TeO2 were studied as ethanol gas sensors. In the as-deposited state, the films thus obtained are amorphous and consist of mixed Te and Sn oxides, doped with Te, Sn, and/or SnTe (depending on the atomic ratio between Sn and Te (RSn/Te)), due to interaction between the two substances during the co-deposition. After stepwise thermal treatment of films with RSn/Te ≈ 2.3 up to 360oC (by 40oC steps, for 15 minutes at each temperature) nanocrystalline films, built up of a mixture of SnO2, TeO2 and unstoichiometric Sn oxide were obtained. The Pt-doping was realized by thermal evaporation in a separate vacuum cycle, after the annealing. To study the film composition and structure as well as the volume distribution of the elements different electron microscopy techniques (TEM, SAED) and analytical methods (EDS in SEM, AES) were applied.
The sensitivity towards ethanol vapours was investigated as a function of the substrate temperature (T) in the range from 20oC to 200oC. High sensitivity has been observed for Pt-doped films at T = 120oC. No cross sensitivity to relative humidity (RH [%]) was observed at this temperature. Further improvement of the sensitivity could be obtained by optimization of the thermal processing, Pt-doping and working temperature.
About the Surface Hardening of Tool Steels by Electrical Discharge Treatment in Electrolyte
Authors: Krastev Dimitar , Yordanov Boyan
Published: March 2010

In this study are given some results about the influence of electrical discharge treatment in electrolyte on the microstructure of high speed steel HS 6-5-2. The metallic surface after electrical discharge treatment in electrolyte has a different structure in comparison with the metal matrix, which determines different properties. It is observed remarkable increasing of hardness, strength and corrosion resistance related to the nonequilibrium phase transformations and the obtained finecrystalline microstructure.
Pressureless Sintering of Boron Carbide-Based Superhard Materials
Authors: Radev Dimitar D.
Published: March 2010

Boron carbide-based materials B4C-MexBy were densified by pressureless sintering in a vacuum furnace. Some transition metal carbides (TiC, ZrC, HfC, Cr3C2 and WC) from groups IV-VI were used as sintering aids. The optimal sintering temperature in the range 2220-2250oC was used for any composition. Here we show the possibilities to activate the mass transport of the B4C by the mechanism of liquid phase sintering. The method of reactive sintering of B4C in the presence of additives of some transition metal carbides allows in situ synthesis of dense B4C-MexBy materials. Structural properties and fracture toughness of the B4C-based composite materials were discussed. The properties of some of these materials and the possibilities for their application are also discussed.
Thickness-Dependent Interface Parameters of Silicon Oxide Films Grown on Plasma Hydrogenated Silicon
Authors: Alexandrova S. , Szekeres A.
Published: March 2010

In the present paper we discuss the defects at the oxide/Si interface and the structure of silicon oxide films grown on plasma hydrogenated (100) and (111)Si. The effect of oxide thickness ranging from 7 to 40 nm on the interface parameters was examined. Electrically active defects were characterized through C-V and G-V measurements. The dependence of the refractive index on oxide thickness was studied. Information on the oxide structure was inferred through the refractive index evaluated from ellipsometric measurements. From both, the electrical and optical results a characteristic oxide thickness was found, below which the oxide structure is different from SiO2, most probably SiOх. It is related to a modified Si surface during the pre-oxidation plasma treatment and its value depends on Si orientation and pre-clean conditions. A characteristic oxide thickness of 13 nm was found for Si hydrogenated without heating and, of 9 nm for Si hydrogenated at 300oC.
An Arc Discharge by Closely Situated Electrodes for Synthesis of Nanostructures
Authors: Koprinarov Nikola , Marinov Miko , Konstantinova Mariana
Published: March 2010

Geometry of electrodes, distance between them, work atmosphere and ambient temperature are the important factors, which determine quantity and variety of structures synthesized via arc discharge. Usually, electrodes of different cross-section are placed away from each other, allowing a large vapor stream directed into the reactor inside to be obtained. Generally, the anode is thinner than the cathode; it heats up to a high temperature, sublimates and supplies the carbon vapor required for nanoparticle synthesis. In contrast to this commonly used approach, when electrode dimensions are appropriately chosen and electrodes placed closely together, temperature interaction between them becomes considerable, discharge area constrains and hot electrodes can be used as heaters for the evaporation of materials of high melting point.
Preparation and Characterization of Al2O3 Thin Films for Catalytic Activity Studies
Authors: Atanasova Genoveva , Guergova Desislava , Stoychev Dimitar , Radić Nenad , Grbić Boško , Stefanov Plamen
Published: March 2010

In the present work, the surface properties of various Al oxide films were investigated. The oxide films were produced on a stainless steel by spray pyrolysis and cathodic deposition methods. The films obtained represent typical layers that can be used as a support in model systems to investigate alumina-based catalysts. Information about the chemical environment of the Al and O ions in the oxide films depending on the preparation conditions has been deduced from the binding energies of the Al 2p and O 1s electron core levels and corresponding Auger parameters.
Stress, Texture and Phase Transformation in Titanium Thin Films
Authors: Chakraborty Jay , Kumar Kishor , Ranjan R. , Chowdhury Sandip Ghosh , Singh S.R.
Published: March 2010

{111} fiber textured face centered cubic (fcc) titanium has been found to coexist with the {0002} fiber textured hexagonal close packed (hcp) titanium in polycrystalline titanium (Ti) thin films (thickness: 144 nm to 720 nm) deposited on Si (100) substrate by magnetron sputtering. X-ray diffraction investigation confirms that relative phase fraction of such metastable fcc Ti phase decreases with increasing film thickness indicating thickness dependent fcc-hcp phase transformation of titanium. Texture development in hcp Ti phase was due to film microstructure (thickness effect) rather than the phase trans-formation. Diffraction stress analysis (by d-sin2 method) indicates that fcc to hcp phase transformation is also accompanied by the reduction of compressive stress in the hcp Ti phase with increasing film thickness. Strain energy calculations for both phases of titanium indicate that fcc Ti is a more stable phase compared to hcp Ti at relatively low film thickness (144 nm to 432 nm). It has been concluded that film stress favours fcc to hcp phase transformation towards the higher film thickness. Reverse transformation (hcp to fcc) occurs towards the lower film thickness.
Calculation Methods to Determine Crystallographic Elements: Interface Plane, Surfaces Plane and Twinning Elements, Based on Electron Diffraction Orientation Measurements by SEM and TEM
Authors: Esling Claude , Zhang Yu Dong , Muller Jacques , Zhao Xiang , Zuo Liang
Published: March 2010

In the present work, we summarize three calculation methods to determine some specific crystallographic elements based on electron diffraction orientation measurements by SEM and TEM. The first one is to determine the plane indices of the faceted interfaces where the orientation relation¬ships (ORs) between the adjacent crystals are reproducible. To acquire the orientation data, we need to prepare only one sample surface but not two perpendicular sample surfaces as usually required in the standard double trace method. The second is to characterize the surface crystalline planes and directions of a faceted nano-particle under TEM imaging and diffraction mode. With the determination of the edge trace vectors and then the plane normal vectors in the screen coordinate system of TEM, their Miller indices in the crystal coordinate system can be calculated through coordinate trans¬formation. The third method is to determine the twin type and the twinning elements based on the orientation information acquired by SEM EBSD measurements from the two twinned crystals through misorientation calculations. These methods will facilitate related studies.
Effect of Texture on Damping Behaviour in an AZ80 Alloy
Authors: Gan Wei Min , Maawad Emad , Chang Hai , Fan G.D. , Randau Christian , Zheng Ming Yi , Wu Kun , Brokmeier Heinz Günter
Published: March 2010

An extruded AZ80 Mg alloy was utilized to investigate the texture effect on the damping behavior. Results showed that different input textures had great effect on the damping behaviour by strain-depended test, but did not showed strong influence on the temperature-depended behaviour which has been discussed.
Texture Development in Zr-Based Alloys by High-Temperature Forging as Indicator of Interaction between Plastic Deformation and α↔β Phase Transform Actions
Authors: Isaenkova Margarita , Perlovich Yuriy , Fesenko Vladimir , Kropachev Sergey , Krymskaya Olga
Published: March 2010

Deformation behavior of Zr-based alloys by forging under conditions of α↔β phase transformations was considered as applied to model samples and real semi-products. Model samples were deformed by uniaxial compression at temperatures of β- and (α+β)-regions of the phase diagram Zr-Nb. Mechanisms, responsible for plastic deformation of alloys by different temperature-rate regimes, were determined on the basis of textures, arising in deformed samples. Among these mechanisms there are crystallographic slip in grains of β-Zr and α-Zr as well as mutual displace¬ments of crystallites along interphase boundaries. The latter mechanism sharply intensifies under conditions of α«β phase transformations and lies in the basis of superplasticity. An input of each mechanism into plastic deformation of material depends on the temperature-rate regime of compression and determines its anisotropy.
Determination of Grain Size for Different Texture Components by Statistical Fluctuations of Intensity, Registered in the Course of Texture Measurement
Authors: Krymskaya Olga , Isaenkova Margarita , Perlovich Yuriy
Published: March 2010

The method for grain size determination by statistical fluctuations of X-ray intensity, registered during measurement of texture pole figures, was developed. Niobium and bronze rods as well as tubes from Zr-1%Nb alloy, subjected to annealing at different temperatures, were studied. Description of the method, pole figures (PF), X-ray intensity distribution within PF circular sections, grain size values and their errors are presented.
Formation of Substructure and Texture in Dual-Phase Steels due to Thermal Treatment
Authors: Masimov M. , Klein Helmut
Published: March 2010

Microstructure and texture formation in DP steels obtained by thermal treatment at temperatures of 780 °C i.e. between Ac1 and Ac3 and at 900 °C, i.e. above Ac3 and following different cooling techniques were studied by means of X-ray and electron diffraction techniques. The formation of the different structure constituents as well as substructure parameters such as blocks size and misorientation between them induced by thermal treatment was detailed analyzed. Various methods – conventional X-ray methods, high-energy synchrotron radiation and EBSD measuring – the texture of the bcc phase were applied in order to investigate their influence on the results. Beside texture heredity, a softening of the initial texture components induced by cold rolling and of related anisotropy of steels due to thermal treatment was estimated.
Effect of Texture on Tensile Properties of an ECAP-Processed MA2-1 Magnesium Alloy
Authors: Serebryany Vladimir , Ivanova T.M. , Savyolova T.I. , Dobatkin Sergey V.
Published: March 2010

Various equal channel angular pressing (ECAP) regimes by routes A and Bc were applied to a commercial MA2-1 (Mg-5wt.%Al-1wt.%Zn-0.4wt.%Mn) alloy for the development of texture which is different from the one of conventionally extruded and annealed alloy. In order to avoid the grain-size effect, the ECAP-processed alloy was annealed to coarsen the grains. The alloy texture before and after the ECAP was determined by the approximation of the X-ray measured pole figures with the canonical normal distributions of central type. The ECAP implementation results in the formation of ultra-fine grained structure of the alloy with an average grain size of 2.0-2.4 µm. The ECAP also drastically changes the initial axial texture characterized by a sharp basal component by splitting it into several more scattered orientations. The degree of the orientation scattering depends on the ECAP regime and route. The annealing of alloy after ECAP results in the grain size growth to the initial state of the extruded and annealed alloy. In addition to that the texture changes of the ECAP-processed alloy after annealing, unlike the structure changes, don’t result in texture of the initial state. The mechanical tensile properties of the annealed alloy substantially depend on the preceding ECAP routes. The yield strength of the annealed alloy decreases after all routes of ECAP. On the contrary, the uniform elongation compared with the one of the initial state of the alloy decreases after 4A route and increases after 4Bc route of ECAP. The effect of the texture and structure on the yield strength and tensile elongation of the alloy after ECAP and annealing was estimated using calculation of the generalized Schmid factors for specific preferred orientations of the active deformation systems and Hall-Petch relationship.
Surface Texture Modification for Improved Roping Behaviour of Aluminium Alloy 6016
Authors: Bennett Tricia A. , Petrov Roumen H. , Kestens Leo
Published: March 2010

The effect of two different intermediate annealing (IA) treatments on texture banding in a roping prone aluminium alloy was investigated. It was found that texture banding occurred in the final annealed material that underwent an IA treatment consisting of slow heating in which there was significant interaction between the recrystallizing grains and the particles in the material. A more uniform distribution of orientations in the final annealed material was obtained in the case of an IA treatment with fast heating so that there was no significant effect of particles on recrystallization.
A New Approach to Calculate the γ Orientation Maps in Steels
Authors: Blaineau Pierre , Germain Lionel , Humbert Michel , Gey Nathalie
Published: March 2010

We propose a new approach to automatically reconstruct the  orientation map from the ’ map inherited by the bainitic or martensitic ’ phase transformation. Our model comprises two main steps (1) identification of reliable fractions of parent grains – each  fraction orientation is determined from neighbouring variants related to a unique  orientation with a low tolerance angle; (2) expansion of these fractions by collecting adjacent variants being in orientation relation (OR) with the  orientation of the initial fraction - using now a higher tolerance around the strict OR. The code was tested on ’ maps we built from reference  maps to control some characteristics of the transformation, i.e. the type of OR used, the spread around OR, the number of inherited variants. The results show that even with a large spread around OR, the shape and orientation of most of the  grains are accurately calculated.
Elementary Facet Method for Grain Boundary Plane Determination by 3D EBSD
Authors: Chou C.T. , Gholinia Ali
Published: March 2010

A new method, the elementary facet method for the grain boundary (GB) orientation measurement using three dimensional EBSD data obtained from serial sectioned sample surfaces, has been applied to a nickel superalloy sample. The principles of this method are described and a part of results obtained are given.
EBSD Study of Substructure and Texture Formation in Dual-Phase Steel Sheets for Semi-Finished Products
Authors: Masimov M. , Peranio N. , Springub B. , Roters Franz , Raabe Dierk
Published: March 2010

Using SEM/EBSD the substructure and texture evolution in dual phase steels in the first steps of the process chain, i.e. hot rolling, cold rolling, and following annealing were characterized. In order to obtain dual phase steels with high ductility and high tensile strength an industrial process was reproduced by cold rolling of industrially hot rolled steel sheets of a thickness of 3.75 mm with ferrite and pearlite morphology down to a thickness of 1.75 mm and finally annealing at different temperatures. Such technique allows a compilation of ferrite and martensite morphology typical for dual phase steels. Due to the competition between recovery, recrystallization and phase trans-formation during annealing a variety of ferrite martensite morphologies was produced by promoting one of the mechanisms through the variation of technological parameters such as heating rate, intercritical annealing temperature, annealing time, cooling rate and the final annealing temperature. Annealing induced changes of the mechanical properties were determined by hardness measurements and are discussed on the basis of the results of the substructure investigations.
Microstructural and Textural Aspects of Shear Banding in Plane Strain Deformed Fcc Metals
Authors: Paul Henryk
Published: March 2010

Periodic crystal lattice rotations within compact clusters of shear bands, developed in copper, have been characterized over a range of scales by optical microscopy, high resolution FEG-SEM-EBSD and TEM orientation mapping, to examine the role of local lattice re-orientation on slip propagation across pre-existing barriers to dislocation motion. Two different cases were analysed in detail. The single crystal analysis addresses the relation between the crystallographic microtexture and microstructure development due to the crystal anisotropy after a strain path change. All the changes in strain path directly lead to crystallite subdivisions and strain localization in the form of macroscopically visible bands of different morphology at the micro scale. The elongated cell substructure formed during primary straining was the source of anisotropy after changing deformation path. It is thought that the presence of this structure (here subcells) as barriers to dislocation motion is crucial for the occurrence of shear banding. The analysis of pure polycrystalline copper has been focused on the influence of local lattice re-orientations within particular grains on slip propagation across grain boundaries. The crystal lattice rotated in such a way that one of the {111} slip planes became nearly parallel to the direction of maximum shear (due to the actual state of anisotropy). A natural consequence of this rotation was the formation of a specific microtexture which facilitated slip propagation across grain boundaries.