bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of the Effectiveness of Certain High Performance Coatings in Preventing Hot Corrosion Degradation of Ti-Aluminide Alloys
Authors: Tomasz Dudziak , Wilson Alasdair , Ahmad Haifa G. , Datta Psantu K.
Published: September 2009

This paper originates from a large EU programme designed to produce high performance coatings with superior mechanical and corrosion resistance properties to enhance high temperature corrosion behaviour of TiAl based alloy (Ti45Al8Nb).The paper here is concerned with studies of the hot corrosion behaviour of Ti – Aluminide alloys (Ti45Al8Nb mainly -TiAl with small amount 2 (Ti3Al)) coated with three coatings: (1) TiAlYN/CrN coating, (2) CrAl with 2%YN addition [1,2] (3) TiAlN with Al2O3 overlayer. Hot corrosion was induced by spraying salts mixture of 80%Na2SO4/20%NaCl with melting point around 700oC [1] [2] on heated sample surfaces, and subsequently heating the sprayed samples in a furnace at 750oC for various times. The extent of degradation, assessed by weight changes and examination by OM (Optical Microscope), SEM (Scanning Electron Microscope), and EDX (Energy Dispersive X-Ray Analysis) indicated that all samples suffered hot corrosion attack to various degrees. TiAlN with Al2O3 overlayer had the best corrosion resistance.We shall discuss these results within a mechanistic framework of hot corrosion degradation and describe their implications.
Spectrum Analysis of Acoustic Emission Signal Obtained during Breakaway Oxidation of 2.25Cr-1Mo Steel
Authors: Jha B.B. , Mishra Barada Kanta , Ojha S.N.
Published: September 2009

Frequency spectrum analysis of acoustic emission (AE) signal has been carried out during breakaway oxidation and internal cracking of oxide scales formed on 2.25Cr-1Mo steel. Three regions viz pre-breakaway, post-breakaway and internal cracking of scales have been distinguished based upon thermogravimetric analysis and SEM/EPMA observations. The frequency pattern of the AE signal obtained in three different regions shows three different characteristic features. Frequency spectra based upon the predominant frequencies have been correlated with the physical phenomena occurring during the course of oxidation.
Structural and Morphological Studies of TiO2 Films for Dye-Sensitized Solar Cell Applications
Authors: Huda Abdullah , Rini Ari Sulistyo , Ya Mohd. Zulfa , Yarmo Mohd Ambar
Published: September 2009

Titanium dioxide has been successfully synthesized via an evaporation-induced self-assembly method. Here, TiCl4 was chosen as a precursor and CTAB as a surfactant. The SEM images revealed that hydrochloric acid, added during reaction, obviously enlarges the particle size of TiO2 since a larger size was obtained. The X-ray diffraction (XRD) results confirmed the appearance of both the anatase and rutile structures of TiO2 after titania film was calcined at 450°C for 1 hour. The TEM results showed that the evaporation temperature had no significant impact upon the particle size of TiO2.
INVITED PAPER: Agrifood Nanotechnology: A Tiny Revolution in Food and Agriculture
Authors: Shrivastava Siddhartha , Dash Debabrata
Published: September 2009

Nanotechnology focuses on special properties of a material which emerge from nanometer size—is becoming one of the most promising scientific fields of research in decades. The realisation that the nano-scale has certain properties needed to solve important biomedical challenges and cater to unmet biomedical needs is driving nano-biosystem research. Proper nutrition and a clean environment promote human health. Nanotechnologies are only used to a limited extent at the moment for achieving these aims although it has the potential to revolutionize agriculture and food systems. We will see increasing uses of tools and techniques developed by nanotechnology to detect carcinogenic pathogens and biosensors for improved and contamination free food and agricultural products. This article will review some of the current nanotechnology research that is applicable to agriculture and food technology and project what the future will bring to the newly emerging field of Agrifood Nanotechnology.
The Synthesis, Stability and Shrinkage of Hollow Nanoparticles: An Overview
Authors: Belova Irina V. , Evteev Alexander V. , Levchenko Elena V. , Murch Graeme E.
Published: September 2009

Recently, there has been a great deal of interest in the properties of hollow nanoparticles for use in advanced technologies. The diffusion phenomenon known as the Kirkendall effect features in one of the important experimental methods of synthesis of hollow binary nanoparticles. Diffusion naturally features prominently in shrinkage mechanisms of hollow nanoparticles. In this paper, we summarize the progress made so far in understanding the formation and shrinkage by diffusion processes of hollow nanoparticles and their apparent stability.
Synthesis and Structural Evaluation of Nanocrystalline Hydroxyapatite Obtained by Mechanochemical Treatment in Polyamide6 Vials
Authors: Nasiri-Tabrizi Bahman , Shokuhfar Ali , Ebrahimi-Kahrizsangi Reza
Published: September 2009

Among various biocompatible materials, hydroxyapatite (HA) is widely used in medical applications. Hydroxyapatite can be used as temporary substitute material for the human bone. Despite of the risk of contamination during milling, the mechanochemical method shows higher reproducibility and low processing cost. In this investigation, the mechanochemical method has been carried out to produce nanocrystalline powders of hydroxyapatite using two experimental procedures (HA1: CaHPO4 + Ca (OH) 2; HA2: CaCO3 + CaHPO4) in polymeric and metallic vials at different milling time. The Effects of milling time, milling media and also chemical composition of initial materials on the crystallinity and morphological properties of obtained materials using X-ray diffraction (XRD) and transmission electron microscopy (TEM) were studied. Appropriate equation and graphs for determining crystallinity degree were used. The obtained results show that the crystallites sizes are within the nanometer range and also indicated that nanocrystalline hydroxyapatite with spherical morphology and high crystallinity degree can be produced much better in polymeric vials; therefore using polymeric vials with high wear resistance can have better performance during the mechanochemical process for the production of high quality nanocrystalline hydroxyapatite. Further work is needed to expand the idea for mass production.
Nanofluid Droplet Evaporation Kinetics and Wetting Dynamics on Flat Substrates
Authors: Moffat J.Ross , Sefiane Khellil , Shanahan Martin E.R.
Published: September 2009

An experimental investigation into the evaporation of sessile nanofluid droplets is reported in this paper. The effect of nano-particle addition on the evaporative behaviour is studied using ethanol and Titanium Oxide nano-particles. The results show that a distinct ‘stick-slip’ pinning behaviour is observed when nano-particles are added to the base liquid. Increasing the nano-particle concentration was found to enhance the ‘stick-slip’ behaviour. This behaviour is attributed to the effects of evaporatively driven particle accumulation near the contact line. This in turn leads to an increase in localised viscosity, and an enhancement of contact line pinning.
Diffusion-Controlled Electrosynthesis of Nanoporous Electrodes for Electrochemical Supercapacitors
Authors: Jacob Gideon Moses , Zhitomirsky Igor
Published: September 2009

Nanostructured manganese dioxide films were obtained by electrosynthesis using 0.02-0.15 M KMnO4 solutions. The diffusion-controlled deposition mechanism is based on the reduction of anionic MnO4- at the cathode surface. The method allowed the fabrication of porous films for application in electrochemical supercapacitors (ES). It was shown that film porosity is beneficial for the charge transfer during deposition, crack prevention in thick films and electrolyte diffusion in fabricated ES electrodes. Porous nanostructured films showed good capacitive behavior in the 0.1 M Na2SO4 electrolyte in a voltage window of 1V. The specific capacitance decreased with increasing scan rate due to the diffusion limitation in the porous manganese dioxide electrodes
Tensile Properties of Open Cell Ceramic Foams
Authors: Dlouhý Ivo , Řehořek Lukáš , Chlup Zdeněk
Published: September 2009

Full understanding of response of highly porous (cellular) ceramic foams to different mechanical loading conditions is important because of their potential use in industry, medical and other applications. Technique of tensile test of ceramic foam materials has been developed and first knowledge is described in the paper. Tested material was based on alumina ceramic; it was manufactured by slurry coating of polyurethane foam. Two cell sizes were included into the study 10 and 60 PPI. Testing procedure consists from fixation of ceramic foam into aluminium pots by suitable adhesive. Tensile test results generated using two specimen sizes with cross-section 10x10 and 15x15 mm have been statistically analysed. Basic fractographic analysis was applied to get corresponding figure about specimens behaviour during tensile loading.
Qualifying Glass Surfaces by Scratch Test with Integrated Image Processing
Authors: Maros Maria Berkes , Fazekas Attila , Barkóczy Péter , Szeghalmy Szilvia , Koncsik Zsuzsanna
Published: September 2009

Residual stresses of production origin superimposed with the operational stresses influences the reliability of glass products. The most widely used procedures for their detection and qualification are optical methods that can not be utilized for testing of non-transparent glasses. A recently developed glass qualifying procedure based on scratch test with integrated image processing is applicable for evaluating the residual stresses in surface of both the transparent and non-transparent glasses. The reliability of the suggested test method is greatly dependent on the information content provided by the involved image analysis procedure. The current paper introduces the principle, and methodology of the test method, furthermore presents the latest results gained by applying an improved algorithm of the image processing.
Ceramic Materials for Ballistic Protection
Authors: Klement Richard , Krestan Jan , Rolc Stanislav
Published: September 2009

The ballistic performance of ceramic materials was investigated. Various types of ceramic-metals and ceramic-laminate composites were prepared. Their ballistic resistances against AP small arms ammunition of protection level 2 and 3 according to NATO Standardization Agreement STANAG 4569 were investigated. For the ballistic performance assessment V50 test method was used. From economical, technological, and ballistic point of view as optimal solution sandwich structure consisting of alumina front-face layer and aramid or duralumin backing layer was found.
Effect of Low Temperature Degradation on Scratch Behaviour of 3Y-TZP
Authors: Hvizdoš Pavol , Chintapalli Ravikiran , Valle Jorge , Anglada Marc
Published: September 2009

Effect of low-temperature degradation of 3Y-TZP ceramics (polycrystalline zirconia stabilized by 3mol% of yttria) on contact damage resistance has been studied applying scratch testing technique. Friction properties and damage mechanisms have been investigated for various degrees of hydrothermal ageing, i.e. for different grain sizes and crystallography, and for different thickness of the degraded surface layer. The onset of plastic damage, catastrophically cracking, grain pull-out, spalling and chipping due to top layer debonding have been identified. The contact damage micromechanisms corresponding to various degrees of degradation have been studied in detail by interferometry and microscopy.
Observation of Thermophysical and Tribological Properties of CNT Reinforced Si3N4
Authors: Koszor Orsolya , Lindemann Andre , Davin François , Balázsi Csaba
Published: September 2009

Thermophysical and tribological measurements have been performed on carbon nanotube added silicon nitride composites. Higher thermal conductivity values were observed in the case of the sample with CNT than for the reference sample. As was observed from tribological measurements, nanocomposite Si3N4 without carbon nanotubes shows a higher friction coefficient than carbon nanotube - Si3N4. The results of wear study indicate that the Si3N4 ball (used as static partner) was more damaged with MWCNTs addition nanocomposite than with pure Si3N4 ceramic. A pronounced difference was observed in the wear rate: there was a much higher wear for carbon nanotube - Si3N4 than for Si3N4 without MWCNTs.
The Compressibility Behaviour of a New Generation of Coated Metal/Ceramic Composite Powders
Authors: Bidulská Jana , Kvačkaj Tibor , Actis Grande Marco , Bidulský Róbert
Published: September 2009

The present work deals with the compressibility behaviour of a new generation of coated metal/ceramic composite powders. A commercial 316L stainless steel powder was coated with the alumina layer by an aqueous sol-gel colloidal process and then metal/ceramic composite materials were produced with core/shell structure. The powders were uniaxially cold pressed in a cylindrical die in the range from 200 to 1000 MPa. In order to reach the best green density, composite powders have been added with 1% in weight of lubricant. The compressibility behaviour was analysed using the equation P = P0.exp (-K.pn). P0 is the relative apparent density and p is applied pressure; K and n are the parameters with defined physic-metallurgical substance. The values of the parameters K and n were determined by regression analyses. The correlation coefficients r of experimental compaction curves were up to 0.98. The results showed that difference between metal/alumina weight ratios affected the compressibility parameters as well as compressibility curves.
Fractography of Dynamic Crack Propagation in Silicon Crystal
Authors: Sherman Dov
Published: September 2009

The phenomena occurring during rapid crack propagation in brittle single crystals were studied by cleaving silicon specimens on the low energy cleavage planes under tensile and bending. The experiments revealed new phenomena not previously reported, and new crack path instabilities in particular. The well defined boundary conditions of the tested specimens and crack velocity measurements enabled rationalization of the observed phenomena and the velocity-surface instabilities relationship in particular. In contrast to amorphous materials, the observed instabilities are generated at relatively low velocity, while at high velocity the crack path remains stable. No evidences for mirror, mist, and hackle instabilities, typical in amorphous materials, were found.
pH Effect on Electrophoretic Deposition in Non-Aqueous Suspensions and Sintering of YSZ Coatings
Authors: Xu Hui , Shapiro Ian P. , Xiao Ping
Published: September 2009

Yttria stabilized zirconia (YSZ) particle suspension in acetylacetone (ACAC) was deposited onto Fecralloy substrates by using EPD and then constrained sintered at 1200°C. Before EPD, the operational pH value of the suspension was adjusted with addition of acetic acid or base triethanolamine (TEA). The effect of suspension pH on the deposition of EPD coatings was studied with respect to the suspension stability, coating density and microstructure. Results showed that the zeta potential decreased to close to zero with the increase of pH value from 4.4 to 7.4, then increased with further increase of the pH. This ‘U’ shape zeta potential-pH relationship was probably resulted from the adsorption of TEA. This reduced the degree of particle coagulation and increased the packing density of the EPD coatings; therefore, promoted the sequent sintering of coatings which was evaluated by micro-hardness.
Monitoring Constrained Sintering of YSZ Coatings Using Fluorescence Spectroscopy and Micro-Hardness
Authors: Shapiro Ian P. , Zhao Xiao Feng , Xu Hui , Xiao Ping
Published: September 2009

The constrained sintering behavior of yttria stabilized zirconia coatings containing 1 wt. % alumina produced using electrophoretic deposition has been studied. Coatings have been characterized by scanning electron microscopy, micro-hardness and fluorescence spectroscopy after sintering in air at 1100°C and 1200°C. These coatings were compared with those that additionally contained 1 wt. % soda-lime glass. Micro-hardness and fluorescence spectroscopy are shown to accurately monitor the density of the coatings. Fluorescence spectroscopy showed that the density across the coating is even, as expected from modelling literature. The addition of 1 wt. % of soda-lime glass is shown to improve the sintered density of coatings.
Electrophoretic Deposition of Natural Hydroxyapatite
Authors: Javidi Mehdi , Javadpour Sirus , Bahrololoom Mohammad Ebrahim , Ma Jan
Published: September 2009

Natural hydroxyapatite has been electrophoretically deposited on medical grade 316L stainless steel. Stable suspensions were prepared by mixing 40 g/L milled natural hydroxyapatite powder in isopropyl alcohol and stabilized by polyethylenimine as dispersing agent and binder. The stability of suspensions was investigated by measuring zeta potential. It was found here that the suspension which was stabilized with 4 g/L polyethylenimine revealed a high value of zeta potential and stability. Deposition was achieved on the cathode at constant voltages of 30, 60, and 90 V for 1 to 5 minutes. After deposition, the samples were dried at room temperature for 24 hours and deposition weight, roughness, and thickness of the coatings were measured. The surface morphology of the coated samples was studied by a scanning electron microscope. The results of the electrophoretic deposition process showed that the sample coated at 60 V and 3 minutes led to an adherent, continuous, and crack-free coating. The coating efficiency and thickness increased with increasing deposition time and yielded to saturation at the constant applied voltage. Also, the current density decreased and yielded to saturation at the constant applied voltage during electrophoretic deposition.
Textured α-Alumina through Electrophoretic Deposition and Templated Grain Growth
Authors: Zhang Li , Kanjarla Anand Krishna , Vleugels Jef , Van der Biest Omer
Published: September 2009

The development of texture was studied during electrophoretic deposition in alumina suspensions containing plate shaped alumina particles. The mechanism of platelet orientation during EPD was examined with respect to the influence of the electric field, gravity and hydrodynamic forces. This was realized by using two different deposition cells, with vertically or horizontally positioned deposition electrode. The texture of the green deposit was further enhanced during sintering by templated grain growth in which the platelet shaped alumina particles were growing at the expense of the fine grained matrix. The sharp ‘fiber texture’ obtained after templated grain growth during sintering of the deposit was characterized by means of x-ray diffraction and Electron Backscatter Diffraction (EBSD).
Threshold Value of Particle Concentration in EPD: Experimental Evidence with TiO2 Organic Suspensions
Authors: Radice Simona , Mischler Stefano , Michler Johann
Published: September 2009

This study was triggered by our experience on electrophoretic deposition (EPD) with different suspension systems showing evidence of a particle concentration threshold, below which no deposit was formed. In this study, the role of particle concentration in the mechanism of EPD was investigated with a model system, consisting of isopropanol suspensions with TiO2 nanosized particles (d50 = 130 nm). The investigated concentration range was 0.01 - 0.4 vol% TiO2. Constant voltage EPD tests with variable particle concentration were performed for 1 min under different applied voltages (25 - 300 V corresponding to 62.5 - 750 V/cm). A longer deposition time (30 min) was tested for a lower concentration value (0.003 vol% TiO2). The deposition process was evaluated in situ by means of the current measured during EPD. The deposits obtained were characterized by weight and profile measurements and scanning electron microscope (SEM).
The results confirmed the finding of a lower limit value of particle concentration, determining a threshold in the formation of an EPD coating. Above this threshold, proportionality between deposited mass and particle concentration was observed, in agreement with the equation of Hamaker. Below this threshold, the proportionality was lost with evidence of a lack of coating formation. A possible interpretation for this experimental finding was provided.
Electrophoretic and Electrolytic Deposition of Gold Nanoparticles on a Graphite Carbon Plate
Authors: Watanabe Hideo , Fuji Masayoshi , Tada Atsuko , Takahashi Minoru
Published: September 2009

Nobel metal particles with nanometer size have attracted keen interest because of, for example, their high catalytic activity to be applied for industrial applications. In this study, nano-sized gold particles were deposited onto a graphite carbon plate by two approaches: 1) electrophoresis of colloidal gold nanoparticles, 2) electrolysis of chlorauric acid. For former case, commercially-available gold nanoparticle and anionic mercapto ligand-stabilized gold nanoparticles, synthesized by citric acid reduction of chlorauric acid, were used. Size and morphology of the gold particles deposited were characterized by scanning electron microscopy. Electrolytic deposition resulted in larger gold particles around tens to hundreds nm in size. Electrophoretic deposition accomplished particle sizes smaller than 15 nm, which basically reflected the size of colloidal gold particles used.
Carbon Nanotube-Reinforced Hydroxyapatite Coatings on Metallic Implants Using Electrophoretic Deposition
Authors: Kaya Cengiz , Kaya Figen , Cho Johann , Roether Judith A. , Boccaccini Aldo Roberto
Published: September 2009

Electrophoretic deposition (EPD) has been demonstrated to be a convenient processing technique to fabricate composite ceramic coatings containing ordered arrays of carbon nanotubes. In this investigation, EPD was used to coat Ti6Al4V medical implants with hydroxyapatite (HA) layers reinforced with surface functionalized multi-walled carbon nanotubes (MWCNTs). The functionalization of MWCNTs by treating them with an acid mixture was successfully achieved in order to create functional groups on the MWCNT surfaces enabling them to be homogeneously dispersed in water. The surface treatment was also used to induce the adsorption of HA nanoparticles on MWCNT surfaces. Some critical issues, such as microcracking and peeling of HA layers after EPD, were effectively solved by the use of MWCNTs.
New Method for Improving Properties of Polymer Composites by Using Organic Inorganic Hybrid Polymers
Authors: Pilz Monika , Männle Ferdinand , Simon Christian R. , Trevor Susannah L. , Bu Huai Tian , Tanem Bjørn S.
Published: September 2009

Polymer materials are utilized in an increasing number of categories of products, such as components for cars, boats, airplanes, within the electronics industry and other advanced industry as well as in paints and other coatings, for special packaging etc. The uses of polymer materials in new categories of products are only limited by the product properties. It is thus a continuous need for developing polymer products with improved properties like increased scratch resistance, improved weather resistance, increased UV resistance, chemical resistance and antioxidation.
In addition to pure polymer materials, new products based on hybrid organic inorganic materials involving macromolecules with inorganic core and organic branches have been developed.
In this paper, organic inorganic hybrid polymers (HP) are prepared based on a new technology and applied as additives for polymer products like thermoset plastics and in lacquers and other types of coatings for surface protection. Used in appropriate amounts and with suitable particle size, such hybrid polymers contribute to a significant improvement of the properties of the plastic material or the lacquer, hereunder an increased wear resistance/scratch resistance and/or weather resistance.
It is shown that HP additives are suitable for a number of applications within organic chemistry and in particular within polymer chemistry and can be used as a stabilizer for thermoplastics with a broader range of utility than known mono-functional stabilizers.
Preparation and Characterization of Polysulfone Membranes Containing Ag Nanoparticles by a Convenient Ultraviolet Irradiation Technique
Authors: Gaina Viorica , Gaina Constantin , Olaru Mihaela
Published: September 2009

A novel silver/polysulfone nanocomposite membrane was prepared by a convenient ultraviolet irradiation technique, through in situ reduction of silver salt (AgNO3) added to a solution of commercial UDEL polyethersulfone dissolved in N-methyl-2-pyrrolidinone (NMP). The UV-reduction of Ag+ to Ag0 nanoparticles was confirmed by means of UV-vis spectroscopy, from aggregation phenomena. The effects of dispersion of silver nanoparticles within polysulfone matrix were investigated by means of ATR-FTIR, dynamic mechanical thermal analysis and differential scanning calorimetry. Using X-ray diffraction, it was shown that annealing produced silver crystallites of 70-90 nm across, which are partially textured in “sheetlike” {110} planes.
Metal Oxide Mineral Filler Containing Polymer Nanocomposites
Authors: Merijs Meri Remo , Shutka Andris , Zalite Ilmars , Bledzki Andrzej K.
Published: September 2009

Metal oxide mineral filled polycarbonate (PC) nanocomposites have been investigated. Plasma-chemical synthesis has been used to obtain metal oxide nanoparticles (MON). Melt mixing has been utilized to obtain PC/MON composites with regularly organized nanostructure. Consequently, an increasing in MON content caused a small decrease of surface and volume resistivities and an increase of nanocomposites magnetic activity.
Electronic Structures and Surface States of ZnO Finite Well Structures
Authors: Lin Kuo Feng , Hsieh Wen Feng
Published: September 2009

Electronic band structures and surface states were investigated for ZnO finite wells or slabs grown along <0001> and <1-100> directions using tight binding representation. The dangling bonds on two end-surfaces caused surface bands for different directions grown slabs, of which the wavefunctions tend to localize at the end surfaces. The increasing splitting of the degenerate surface bands at the Γ point was observed decreasing with the thickness of the nonpolar [1-100] slab. And, the quantum confinement effect is distinctively enhanced by the extra electron-field induced in the <0001> grown finite well with the polar end-surfaces.
Some SiAlONs Prepared from Nanopowders by Spark Plasma Sintering
Authors: Zalite Ilmars , Zilinska Natalja , Šteins Ints , Krastins Janis
Published: September 2009

Different compositions of α- and α-/β- SiAlON materials have been prepared from separate nanopowders and their composites: Si3N4 – AlN, Si3N4, Al2O3 and Y2O3, produced by the method of plasma-chemical synthesis. Compositions have been sintered by spark plasma sintering (SPS) method in vacuum at 1700 °C with a heating rate of 100 °C/min and holding time of 5 min. The densification behaviour of the materials at these sintering conditions depends insignificantly on the powder composition. It is possible to obtain dense ceramic materials with relatively fine-grained structure (200-400 nm) and good mechanical properties from nanosized powders at relatively low temperatures (1400-1600 °C). The holding time at applied compacting conditions is still too short to ensure the formation of α- SiAlON phase corresponding to the phase diagram. All samples consist of β- SiAlON’s of differing composition and this is the reason for relatively low hardness of samples (HV5 = 15,6-16,9 GPa).
Hybrid Glass Mat Reinforced Polypropylene-Montmorillonite Nanocomposites
Authors: Plummer Christopher J. G. , Dalle Vacche Sara , Houphouët-Boigny Chrystèle , Michaud Véronique , Månson Jan Anders E.
Published: September 2009

Although addition of montmorillonite (MMT) clay to isotactic polypropylene (iPP) results in large increases in the melt viscosity at low shear rates, satisfactory impregnation of glass mats is obtained with iPP/MMT under conditions typical of industrial processing, and the MMT is well dispersed throughout the resulting composites. However, the MMT is also shown to retard relaxation of the glass mat, leading to non-uniform through-thickness glass fiber distributions. Thus, depending on the initial lay-up and hence on the initial surface fiber concentration, the bending modulus of the consolidated specimens may either increase or decrease with increasing matrix MMT content, whereas the tensile modulus remains consistent with the predictions of micromechanical models based on the assumption of a uniform glass fiber distribution. The presence of matrix-rich layers at surfaces of specimens containing MMT is also shown to promote crack initiation and induce premature failure in flexural tests.
Magnetically Responsive Nanocomposite Materials for Bioapplications
Authors: Safarik Ivo , Safarikova Mirka
Published: September 2009

Magnetic nano- and microparticles have already found many important applications in various areas of biosciences, medicine, biotechnology, environmental technology etc. These smart materials exhibit different types of response to external magnetic field. In most cases they can be described as composite materials, where the magnetic properties are caused by the presence of iron oxides nano- or microparticles. Such materials can be efficiently separated from difficult-to-handle samples and targeted to the desired place, applied as contrast agents for magnetic resonance imaging, used to generate heat during exposure to alternating magnetic field or to modify biomolecules and biological structures.
Conductivity Study of Co3O2BO3 and Co3-xFexO2BO3 Oxyborates
Authors: Kazak N.V. , Ivanova N.B. , Rudenko V.V. , Ovchinnikov S.G. , Vasil’ev A.D. , Knyazev Yu.V.
Published: September 2009

Single crystals of cobalt oxyborates Co3O2BO3 and Co3-xFexO2BO3 were synthesized. The crystal structure and electric properties were investigated. The difference in the electrical resistivity behaviors was found. For parent Co3O2BO3 nor simple activation law, nor Mott variable range hopping (VRH) are acquirable to describe the experimental data in wide temperature region. In contrast for Co3-xFex O2BO3 Mott’s variable-range hopping conductivity clearly dominates.
Phase Transformations in Nd2/3Ca1/3MnO3: Effect of Y Substitution
Authors: Fertman Elena , Beznosov Anatoly , Desnenko Vladimir , Kajňaková Marcela , Feher Alexander
Published: September 2009

It was found that below the room temperature both parent Nd2/3Ca1/3MnO3 and doped (Nd0.9Y0.1)2/3Ca1/3MnO3 compounds exhibit a sequence of phase transformations: charge ordering, structural transformation of O-O type within the orthorhombic structure, and three magnetic transitions. Three different types of long-range magnetic order co-exist in (Nd0.9Y0.1)2/3Ca1/3MnO3 at low temperatures (as it was earlier found in Nd2/3Ca1/3MnO3): the antiferromagnetic orderings of PCE and DE types existing below ~110 K and ~60 K, respectively, and the ferromagnetic one of B type existing below ~42 K. Charge ordering occurs at 290 K in the doped compound. Diluting of Nd subsystem by Y in the parent perovskite has opposite effects on the temperatures of magnetic and charge orderings: the temperatures of all magnetic transformations are reduced in the doped compound by 20-30 K, while the charge ordering one increases by 80 K. A relationship between evolution of the phase transformation temperatures and crystal and electronic structures of the compound are analyzed.
Influence of Magnetism on Interaction Energy between 3d Impurities and Hydrogen in Palladium Crystal in the Presence of Vacancies
Authors: Isaeva Leyla E. , Bazhanov D.I. , Kulkov S.S. , Kulkova S.E. , Abrikosov Igor A.
Published: September 2009

In this paper we have studied from first-principles the effect of magnetism on the hydrogen-metal interaction and the binding properties of palladium with 3d-alloying atoms in the presence of vacancies induced during hydrogenation process. Our first-principles calculations were carried out by means of state of the art ab-initio method based on density functional theory and all-electron PAW-potentials. We have analyzed the changes of the atomic and electronic structures of palladium crystal induced by the presence of substitutional 3d-alloying atoms, interstitial hydrogen and structural defect (palladium vacancy). The obtained results have shown that magnetism can strongly affect the hydrogen-metal interaction in palladium based alloys. We have also demonstrated that the presence of vacancies in the palladium matrix can alter the interaction energy between hydrogen and alloying transition metal atoms.
Neutron Reflectivity on Polymer Multilayers Doped with Magnetic Nanoparticles
Authors: Douadi-Masrouki Siham , Frka-Petesic Bruno , Sandre Olivier , Cousin Fabrice , Dupuis Vincent , Perzynski Regine , Cabuil Valerie
Published: September 2009

The aim of this work is to elaborate nanocomposite thin films sensitive to a magnetic field by incorporating magnetic nanoparticles in a symmetrical diblock copolymer matrix organized in lamellae on plane substrates. On the one hand, the symmetrical diblock copolymer P(n-BMA)-b-PS is synthesized by ATRP and characterized by several methods. On the other hand, nanoparticles made of maghemite -Fe2O3 are functionalized with PS using the “grafting from” technique in order to make them compatible with polystyrene and to insert them in PS lamellae. Composite films are elaborated by “spin coating” a solution containing both the -Fe2O3@PS core-shell nanoparticles and the copolymer onto a silicon substrate. After annealing, these films are characterized mainly by AFM and neutron reflectivity to investigate the lamellar order.
Effect of Surfactant Excess in Non-Polar Ferrofluids Probed by Small-Angle Neutron Scattering
Authors: Petrenko V.I. , Avdeev M.V. , Aksenov V. L. , Bulavin L.A. , Rosta L.
Published: September 2009

The microstructure of ferrofluids (magnetite/oleic acid/benzene) with an excess of free oleic acid is investigated by small-angle neutron scattering (SANS). For such excess higher than 25 vol. % a sharp break in the stability of ferrofluids occurs followed by coagulation and precipitation. Below this value the influence of the surfactant excess on the stability of ferrofluids is insignificant; neither particle aggregation nor surfactant agglomeration is observed. The interaction of free acid molecules in the ferrofluids is compared with that in pure benzene solutions. A significant increase in the attraction is observed for acid molecules in the ferrofluids, which is related to the loss of magnetic fluids stability at high excess of acid.
Nanostructures Based on Glasses Doped with 3d and 4f Elements
Authors: Ivanova O.S. , Edelman I.S. , Ivantsov R.D. , Zabluda V. , Zaikovskiy V. , Stepanov S.
Published: September 2009

Nano-composite structures based on potassium-aluminum-germanium glasses doped simultaneously with Fe and rare earth (RE) oxides - Gd, Tb, Dy, Ho, or Yb were studied for the first time. Samples were fabricated by glass technology and subjected to an additional thermal treatment at different regimes. Formation of magnetic nanoparticles was revealed with transmission electron microscope. Morphology and space distribution of nanoparticles in the glasses as well as optical and magneto optical spectra have been shown to be dependent on the additional treatment regime and almost independent of the type of the rare earth element.
Metamaterials Fabricated of Amorphous Ferromagnetic Microwires: Negative Microwave Permeability
Authors: Ivanov Andrei V. , Galkin V.Yu. , Ivanov V.A. , Petrov D.A. , Rozanov Konstantin N. , Shalygin A.N. , Starostenko S.N.
Published: September 2009

Microwave permeability of glass-coated ferromagnetic amorphous microwire exhibiting a weak negative magnetostriction has been studied. The diameter of the microwire was about 20 m and the diameter of the metal core was about 12 m. The microwire was wound to comprise a 7/3 washer-shaped composite sample with the volume fraction of magnetic constituent of about 10%. The permeability of the composite sample was measured in a coaxial line in the frequency range from 0.1 to 10 GHz. The composite was found to exhibit a negative permeability within the frequency range from approximately 0.7 to 1.5 GHz, with the permeability being as low as −0.4. Therefore, microwire-based composites, particularly, crossed arrays of microwires may be employed to develop metamaterials for microwave applications. In the composite, the negative microwave permeability is due to the natural ferromagnetic resonance and the negative microwave permittivity is due to the inherent inductance of the wire. Such metamaterials are advantageous in simple design, isotropic in-plane performance, and possible tunability of performance by external magnetic bias. However, for a feasible metamaterial fabricated from microwire arrays, the wires have to exhibit higher magnitude of the ferromagnetic resonance, higher quality factor, and higher resonance frequency.
Microwave Properties of Sandwich Structure Based on Iron and Barium Nanoparticles
Authors: Babushkin A.V.
Published: September 2009

The high frequency intrinsic and effective permeability was calculated for spherical iron and barium particles in a nonmagnetic matrix (epoxy resin) by using the combination of Landau-Lifshitz-Gilbert equation and extended Bruggeman’s effective medium theory with the consideration of the skin effect. It was found that the microwave properties of the composite were influenced by many parameters, such as damping parameter, volume fractions and size of magnetic components. The sandwich microwave absorber with reflection loss < −10 dB over the range of 6-22 GHz was achieved. The thickness of absorber is only 4.25 mm.
Electron Spin Resonance in EuB6
Authors: Semeno A.V. , Glushkov V.V. , Bogach A.V. , Sluchanko N.E. , Dukhnenko A.V. , Fillippov V.B. , Shitsevalova N.Y. , Demishev S.V.
Published: September 2009

Cavity measurements of a high frequency (60 GHz) electron spin resonance (ESR) have been carried our for a single crystal of EuB6 at temperatures 4.2-50K in magnetic field up to 7 T, which has been aligned along [001] crystallographic direction. The influence of the experimental geometry on the parameters of the resonance line has been studied. It is found that in conditions of a homogeneous magnetic field the ESR spectrum in EuB6 is formed by a single resonance line at all temperatures including the ferromagnetic ordering region. The presence of the gradient of the magnetic field in the sample causes strong broadening of the resonance line at low temperatures and even may induce a double peak ESR structure. The analysis of the linewidth temperature dependence in EuB6 shows the anomalous growth of the line width below Curie temperature TC ~15 K.
High Frequency Magnetoimpedance of FeNi/Cu/FeNi Sensitive Elements with Different Geometries
Authors: Volchkov Stanislav O. , Svalov Andrey V. , Kurlyandskaya G.V.
Published: September 2009

In this work magnetoimpedance (MI) behaviour was studied experimentally for Fe19Ni81(175 nm)/Cu(350 nm)/Fe19Ni81(175 nm) sensitive elements deposited by rf-sputtering. A constant magnetic field was applied in plane of the sandwiches during deposition perpendicular to the Cu-lead in order to induce a magnetic anisotropy. Sandwiches with different width (w) of FeNi parts were obtained. The complex impedance was measured as a function of the external magnetic field for a frequency range of 1 MHz to 700 MHz for MI elements with different geometries. Some of MI experimental data are comparatively analysed with finite elements numerical calculations data. The obtained results can be useful for optimization of the design of miniaturized MI detectors.
Pulsed Laser Deposited Y3Fe5O12 Films for Magnetostatic Wave Band Pass Filters
Authors: Manuilov S.A. , Fors Rickard , Khartsev S.I. , Grishin A.M.
Published: September 2009

Y3Fe5O12 (YIG) films were pulsed laser deposited onto the Gd3Ga5O12(111) substrates. Processing conditions were optimized to obtain films with a narrow ferromagnetic resonance (FMR) linewidth: 0.9 Oe in 1.22 μm thick YIG at 9 GHz. Due to sharp film-to-substrate interface YIG films remain strained hence possess unusually high lattice mismatch induced uniaxial anisotropy Hu = - 880 Oe. We fabricated and tested magnetostatic surface wave (MSSW) band pass hybrid-type filters with YIG film lain on transducers alumina board. MSSW filter with antennas areal size of 2 mm2 at 7.5 GHz shows insertion loss – 9 dB and a resonant 3 dB bandwidth as narrow as 12.5 MHz.
Shear Thickness Modes in a Presence of Magnetoelastic Waves Parallel to a Surface Guided by Ferromagnetic Film
Authors: Gareeva Z.V. , Doroshenko R.A.
Published: September 2009

Thickness modes of magnetoelastic waves (MEW) guided by ferromagnetic film have been investigated. Propagation of two mutually perpendicular MEW one of which is parallel to a normal to the surface has been considered. It has been shown that resonant frequencies of standing MEW depend on the wave number of a wave propagating along a surface. Plots illustrating dependence of thickness shear modes upon wave vector kz of MEW traveling in a surface plane have been presented.
Microwave Heating of Metallic Powders
Authors: Buchelnikov Vasiliy D. , Lousguine-Luzgin D.V. , Bychkov Igor V. , Anzulevich A.P.
Published: September 2009

It is known from experimental data that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present paper we investigate theoretically the mechanisms of penetration of microwave radiation through a layer of metallic powder and microwave heating of such system.
Multi-Channel High-Tc SQUID System for Bio-Applications
Authors: Hatsukade Yoshimi , Noda K. , Masaki S. , Yoshida S. , Tanaka Saburo
Published: September 2009

high-Tc SQUID, magnetometer, bio-magnetism, multi-channel, rat MCG.
Abstract. Three-channel directly-coupled-type high-Tc SQUID magnetometer array, with pick-up coil size of 1.5 mm2 comparable to the lift-off distance of the developed multi-channel SQUID system, was designed. In this design, two slits were introduced in the SQUID ring to improve the inductive coupling between the pick-up coil and the SQUID ring to obtain the field sensitivity of about 700 fT/Hz1/2. With the SQUID array that was mounted on the multi-channel SQUID system, the measurements of magnetocardiogram of rat were demonstrated to evaluate the system performance.
Superconducting Gap of Fe-Intercalated TiSe2 Observed Using Ultrahigh-Resolution Photoemission Spectroscopy
Authors: Kuznetsova T.V. , Grebennikov Vladimir I.
Published: September 2009

Ultrahigh-resolution photoemission spectroscopy of 1T-Fe0.5TiSe2 was performed in order to study the changes in the density of states across the superconducting transition. We observed the gap about 2 meV in spectrum measured at 4.5 K.
Low Temperature Heat Capacity Study of Nd3Ni13-xCoxB2 Series
Authors: Arauzo Ana B. , Bartolomé Juan , Rillo Conrado , Rubín Javier
Published: September 2009

The Low Temperature Heat Capacity of the layered structure Nd3Ni13-xCoxB2 (x = 0, 1, 3, 6, 8, 11 and 13) solid solutions has been measured from 350 mK to 300 K. For high Co content (x ≥ 8), a hyperfine contribution has been explained as due to hyperfine fields of 112.4 kG for Co and 3.68 MG for Nd. The electronic heat capacity contribution reveals an increase of the density of states at the Fermi level as the Co content is increased. For x = 0 a low dimensionality magnetic transition attributed to the Nd sublattice is observed. The substitution of Ni by Co (1  x < 3) induces interaction disorder on the Nd sublattice. For Nd3Ni13B2 an estimation is given for the molecular field of Hm = 54 kG and the exchange constant of J/kB = 4.1 K.
Magnetic Anisotropy in 2H-NbSe2 Electron Irradiated Single Crystals
Authors: Bartolomé Juan , Bartolomé E. , Eremenko V.V. , Ibulaev V.V. , Sirenko Valentyna , Petrusenko Yu.T.
Published: September 2009

The anisotropic magnetic properties of the metallic layered compound with hexagonal crystal structure 2H-NbSe2 are investigated as a function of their dependence on high-energy electron irradiation. Pauli paramagnetism of free electrons is shown to dominate the magnetic susceptibility, P. The anisotropy is related to spin-orbit effects on the hybridized electronic states. Irradiation affects the density of states at the Fermi surface, increasing both P and the anisotropy. Below a threshold temperature, TS=54 K, the paramagnetic contribution, which increases with the dose, is ascribed to dangling bonds, nanotubes and nanorods generated by irradiation.
Hall Effect in LaB6 and NdB6
Authors: Anisimov M.A. , Bogach A.V. , Glushkov V.V. , Demishev S.V. , Samarin N.A. , Shitsevalova N.Y. , Sluchanko N.E.
Published: September 2009

To shed more light on the peculiarities of ground state formation in RB6 Hall effect in NdB6 and LaB6 has been investigated on the single crystals at temperatures 2K<T<300K in magnetic fields H < 80kOe. The Hall coefficient RH and resistivity ρ have been measured by the sample rotation technique in fixed magnetic field to be perpendicular to the axis of rotation (<110> for LaB6 and <100> for NdB6). A very similar temperature behavior of RH(T) with the step–like anomaly near T ~ 25K has been established for both magnetic NdB6 and diamagnetic LaB6 at intermediate temperatures T>10K. The temperature independent behaviour of Hall coefficient (RH(LaB6) ~ –3.6•10-4 cm3/C, RH(NdB6) ~ –3.7•10-4 cm3/C) observed in the interval 10K<T<20K allowed to estimate the reduced charge carriers’ concentration n/nR ≈ 1.21±0.03 (nR– the concentration of La (Nd) ions). The Hall mobility μH = RH(T)/ρ(T) estimated for LaB6 and NdB6 was shown to be well fitted by the power law μH ~ T-α where α(LaB6) ≈ 1.5, α(NdB6) ≈ 0.6 at the intermediate temperatures 50K<T<300K and α(LaB6) ≈ 3 in the range 20K<T<50K. The drastic decrease of both the Hall mobility μH and the exponent α is discussed in terms of the magnetic scattering enhancement of conduction electrons on the localized 4ƒ–states of Nd3+ ions.
Influence of Electron Correlations on Magnetic Properties in Transition Metals in View of Degeneration
Authors: Shilov V.E. , Shilova E.V.
Published: September 2009

Transition from high-spin state to low-spin state is considered in this work. The self - energy in one-loop approximation was calculated. The three – orbital periodic Anderson-Hubbard model is used to obtain an initial segment of an optical branch in view of degeneration. The possibility of experimental verification of the received result by a method of non-elastic dispersion of slow neutrons is mentioned.
Impurity Assisted Interlayer Exchange Coupling in Iron/Silicon Multilayers
Authors: Men'shov V.N. , Tugushev V.V. , Kulatov E.T.
Published: September 2009

The model of exchange coupling between ferromagnetic metal layers across a non-degenerate semiconductor spacer with point-like defects is considered. Calculation of an asymptotic behavior of the exchange integral is carried out. The exchange integral is found to alternate its sign depending on the position and filling of the deep impurity energy levels into the spacer. The results provide a basis for interpretation of recent experiments in iron/silicon multilayers.