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1
Content available remote

High Aspect Ratio Graphene Nanosheets Cause a Very Low Percolation Threshold for Polymer Nanocomposites

100%
Jan R., Habib A., Abbasi H.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
478-481
EN
Liquid exfoliated, high aspect ratio (1272) graphene nanosheets (GNS) are dispersed in thermoplastic polyurethane (TPU) to prepare range of nanocomposites. A three fold increase in direct current conductivity is recorded at 0.0055 volume fraction (V_{f}) of GNS-TPU composites as compared to pristine TPU. It is suggested that the percolation threshold for conducting network achieved at low filler loadings is due to the high aspect ratio and homogeneous dispersion of GNS within the polymer. The experimental results are interpreted using interparticle distance model and modified power law. The two models predict threshold filler loading in 0.015-0.001 range volume fraction GNS based on the average values of mean length and no. of layers per nanosheet. The experimental results favor modified power law as it relies on aspect ratio of fillers. A slight deviation in our study from modified power law may be due to aggregation in as prepared GNS.
2
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Investigation of the Delamination Factor of Glass Sphere and Silicon Particle Reinforced (GS-SCR) Hybrid Composite Material

100%
Dundar M., Ficici F., Ozen F., Unal H.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 3
595-597
EN
Reinforced polymer composite materials have opened a new era because they can substitute the conventional metallic materials. These materials have found numerous usage areas, especially in aviation, military and space applications due to such advantages as the high tensile strength, high modulus, high corrosion resistance and low density. However, during the assembly of parts from these materials, a huge amount of holes is required. There are problems during machining of reinforced polymer composite materials. Main reason behind these problems is the inhomogeneous microstructure. Some of these problems are burr, pullout, swelling, microcrack, rapid tool wear and delamination. Among the most important of these defects is the delamination damage. Delamination is a severe drilling failure. In this work, three different cutting speeds (15, 20, 25 m/min), three different feed rates (0.05, 0.10, 0.15 mm/rev) and three different cutting tool materials (Carbide, TiN Coated HSS and HSS) have been used. Effect of different feed rates, cutting speeds and tool materials on delamination is studied by drilling of %10 glass sphere- and %10 silicon particle-reinforced polypropylene hybrid composite material.
3
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Analysis of Surface Modification of GFRP and Influence on the Drilled Part Delamination

100%
Cavusoglu I., Durakbasa M., Cakir M.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 3
423-427
EN
Glass fibre reinforced plastics are especially used in aviation industry, marine applications, automobile industry and wind power plants. The shape of the products to be manufactured from glass fibre reinforced plastics materials can be easily produced by using different primary methods [J.-M. Bertholet, Composite Materials, Springer, New York 2012, p. 54]. Assembly is necessary to create the final products which have been fabricated from glass fibre reinforced plastics. Components manufactured from glass fibre reinforced plastics are drilled with CNC, during assembling process. Several kinds of defects occur around the hole after drilling the materials. Presence of defects influences the quality of holes and of the products. The aim of this study is to make comparison between modified and unmodified composite materials, both of which are formed of 30% of glass fibres and 70% of epoxy resin, in terms of delamination factor. Influence of surface modification is evaluated to identify optimum drilling parameters by using Taguchi orthogonal L18 matrix. Surface condition, drill diameter, spindle speed and feed rate are changed as process parameters in the experiments. According to the study, feed rate and spindle speed are the most influential parameters and the drill tool surface condition does not show any general change.
4
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Production and Characterization of Niobium Toughened Ti-TiAl₃ Metallic-Intermetallic Composite

63%
Yener T., Zeytın S.
Acta Physica Polonica A
|
2017
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vol. 132
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issue 3
941-943
EN
Ti-TiAl₃ in situ composites with 10 wt.% Nb were successfully prepared from Ti, Al, and Nb metallic powders by powder metallurgy processing technique of electric current activated/assisted sintering. The current and process time used for producing metallic-intermetallic composites were 2000 A and 90 s, respectively. In terms of fracture toughness, effects of addition of ductile niobium phase to Ti-TiAl₃ composites were investigated. According to SEM-EDS and XRD results, the synthesized composites mainly consisted of TiAl₃ matrix and dispersive Nb reinforcing phases, as well as ductile Ti phases. Hardness and fracture toughness values of the samples were measured by Vickers hardness tester under loads of 100 g and 10 kg, respectively. Fracture toughness value of TiAl₃ intermetallic composites was increased with Nb ductile phase addititon from 1.69± 0.05 MPa m^{1/2} to 5.23± 0.3 MPa m^{1/2}.
5
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Effect of Tetraethylene Glycol Dimethyl Ether on Electrical, Structural and Thermal Properties of PVA-Based Polymer Electrolyte for Magnesium Battery

63%
Gamal R., Sheha E., Shash N., El-Shaarawy M.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 3
803-810
EN
The aim of the contribution is to introduce a high performance magnesium conducting polymer electrolytes (PEs) comprising hybrid of poly(vinyl alcohol) (PVA), magnesium bromide (MgBr_2) and tetraethylene glycol dimethyl ether (TEGDME) as plasticizer are prepared at various compositions by solution cast technique. X-ray diffraction and thermogravimetric analyses suggest a substantial structural modification, decrease in crystallinity and various interactions in the polymer electrolyte components due to addition of TEGDME. Also there is a marked decrease in T_{g} with increasing TEGDME. The conductivity conformation with the addition of plasticizer which can be explained on the basis of dissociation of ion aggregates formed in PVA-MgBr_2 polymer electrolytes at higher concentrations of the salt. The ionic conductivity of the polymer electrolyte increased with addition of salt and plasticizer reached to the highest conductivity value of ≈ 10^{-6} S cm^{-1} at 0.8 ml TEGDME. The frequency dependence of AC conductivity obeys the Jonscher power law. The estimated value of Mg^{+2} ion transference number is found to be 0.68 for high conducting film. The open circuit voltage of a solid state battery which based on the optimum polymer electrolyte with a configuration Mg|PE|V_2O_5 is 1.5 V. Also this battery has exhibited a discharge capacity ≈3.78 mAh/g. The discharge characteristics are found to be satisfactory as a laboratory cell.
6
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Frequency Variation of Complex Permeability in Dual Ferrite Filler - Single Polymeric Matrix Composites

51%
Dosoudil R., Ušáková M., Sláma J., Grusková A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
621-624
EN
The frequency dependences of complex initial permeability for triple-component composite materials based on two different types of ferrite filler (MnZn and NiZn ferrite) and a nonmagnetic polymeric matrix (PVC) were studied in the frequency range of 10 kHz-1 GHz. The frequency dispersion of permeability is discussed by means of a dynamic model based on the superposition of the two types of magnetic resonance, the resonance of vibrating domain walls and the resonance of precessing magnetic moments in domains.
7
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Determination of the Young Modulus of Ti-TiAl₃ Metallic Intermetallic Laminate Composites by Nano-Indentation

51%
Yener T., Güler S., Siddique S., Walther F., Zeytin S.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
604-606
EN
Nano-indentation is an important technique to determine the Young modulus of multiphase materials where normal tensile tests are not appropriate. In this work, Ti-TiAl₃ metallic-intermetallic laminate composites have been fabricated successfully in open atmosphere using commercial purity Al and Ti foils with 250 μm and 500 μm initial thicknesses, respectively. Sintering process was performed at 700°C under 2 MPa pressure for 7.5 h. Mechanical properties including the Young modulus were determined after manufacturing. The Young moduli of metallic and intermetallic phases were determined as 89 GPa and 140 GPa, respectively. Microstructure analyses showed that aluminum foil was almost consumed by forming a titanium aluminide intermetallic compound. Titanium aluminides grow up through spherical shaped islands and metallic-intermetallic interface is a wavy form in Ti-Al system. Thus, the final microstructure consists of alternating layers of intermetallic compound and unreacted Ti metal. Microstructure and phase characterizations were performed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Hardness of test samples was determined as 600 HV for intermetallic zone and 130 HV for metallic zone by the Vickers indentation method.
8
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Ac Electrical Properties of Polystyrene/Ferroelectric Barium Stannate Titanate Ba(Ti_{0.9}Sn_{0.1})O₃ Ceramic Composite

51%
Al-Akhras M., Saq'an S., Ghadieh Z.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 1
447-449
EN
A composite of polystyrene (PS)/ferroelectric barium stannate titanate (BST) with different BST concentration was prepared. The dielectric properties were measured using HP low impedance frequency analyzer. It is found that samples behaved as an RC network. Composites become more capacitive than resistive with increasing frequency while resistance decreases with increasing BST ceramic concentration. Temperature effects were monitored throughout the annealing process. It is found that the capacity and the ac conductivity increased after annealing while the bulk resistance decreased. Our results suggest that, the obtained material is expected to be a promising candidate for electronic ceramics. The study provides a better understanding of the relationship among these parameters.
9
Content available remote

An Evaluation of Cu-B₄C Composites Manufactured by Powder Metallurgy

51%
Yener T., Altinsoy I., Yener S., Celebi Efe G., Ozbek I., Bindal C.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1045-1047
EN
In this study, the influences of B₄C ratios on some mechanical and physical properties such as relative density, microhardness and electrical properties of cold pressed Cu-B₄C composites were investigated. Curve fitting is applied for the estimation of electrical conductivity. Commercial copper powders with 40 μm particle size were reinforced with B₄C, with particle size of 40 μm, at ratios of 1, 2, 3 wt.%, for improving mechanical properties of copper used as electrical conductor. Cu-B₄C composites have been fabricated by powder sintering process at a temperature of 900°C for 2 h. The presence of Cu and B₄C, which are dominant components in the sintered composites, were confirmed by X-ray diffraction analysis technique and SEM-EDS. Scanning electron microscope (SEM-EDS) has shown that B₄C particles are distributed homogenously in the copper matrix. The relative densities of Cu and Cu-B₄C composites, sintered at 900°C, ranged from 95.7 to 91.6%. Microhardness of composites ranged from 84.5 to 94.6 HB. It was observed that cold pressed Cu-1 wt.% B₄C composites revealed promising physical properties. Results of electrical conductivity measurement of Cu-B₄C composite material are compared to the results of the model and the overall accuracy level above 96% is obtained.
10
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Complex Permeability of LiZn/MnZn/PVC Composite Materials

51%
Dosoudil R., Ušáková M., Grusková A., Sláma J.
Acta Physica Polonica A
|
2010
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vol. 118
|
issue 5
1049-1050
EN
The effect of particle content, size, and the fraction ratio of the double LiZn/MnZn ferrite filler in hybrid LiZn/MnZn/PVC composites on the frequency dispersion of complex permeability has been studied in the 1 MHz-3 GHz frequency range. The obtained relaxation type of permeability dispersion is due to the domain wall resonance, the natural ferromagnetic resonance, and the relaxation of magnetization rotation. The permeability and resonance/relaxation frequency of composites seem to be strongly affected by the change of particle content and fraction ratio of the double ferrite filler rather than by particle size.
11
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Electroconductive and Dielectric Properties of Composites Based on Bismuth Vanadate

51%
Torba J., Golubko N., Fortalnova E., Kaleva G., Safronenko M., Venskovskii N., Politova E.
Acta Physica Polonica A
|
2010
|
vol. 117
|
issue 1
24-26
EN
Ceramic composites (100 - n)Bi_{4}V_{2}O_{11-z}-nCe_{0.9}Gd_{0.1}O_{1.9} with n=0÷25 wt% were prepared and studied by the X-ray diffraction, dielectric spectroscopy, and impedance methods. Slight increase in the unit cell volume accompanied by monotonous decrease in temperatures and broadening of the α-β and β-γ phase transitions with increasing fluorite content was observed in the composites studied. Increase in melting temperatures of composites with n ≥ 10 with the retention of their high ionic conductivity was also proved.
12
Content available remote

The Electrical Properties of Some Composite Materials Based on Sodium and Tantalum Oxides

51%
Malaescu D., Grozescu I., Sfirloaga P., Vlazan P., Marin C.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 1
133-137
EN
Two samples of Na-Ta oxides were synthesized by the hydrothermal method at reaction temperatures of 160°C (sample A) and 200°C (sample B). For reference, a third sample of pure NaTaO₃ was prepared by the sol-gel method (sample C). Using X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance spectra and electric measurements, structural, morphologic, spectroscopic and electric properties of samples were investigated. The structural characterization by X-ray diffraction revealed that samples A and B are mixtures of Na-Ta oxides (including NaTaO₃ and other compounds), whilst sample C is pure NaTaO₃. UV-vis diffuse reflectance spectra allowed evaluation of the band gap energy (E_{g}), resulting in 3.88 eV for sample A, 3.93 eV for sample B and 4.1 eV for sample C. Electrical resistivity measurements, over the temperature range 300-450 K, showed a typical semiconductor behavior of the investigated samples, with the effective activation energy, E_{a} of 0.47 eV (sample A), 0.45 eV (sample B) and 0.82 eV (sample C). Based on the Mott variable range hopping model, the conductivity mechanism in the investigated samples was analyzed. The results shown that the density of states at the Fermi-level, N(E_{F}) is constant in the investigated temperature range and the typical values of N(E_{F}) are 0.713 × 10^{18} eV^{-1} cm^{-3} (sample A), 0.621 × 10^{18} eV^{-1} cm^{-3} (sample B) and 0.855 × 10^{17} eV^{-1} cm^{-3} (sample C). Other parameters of VRH model such as the hopping distance R and the hopping energy W have also been computed and the following values at the room temperature were obtained: R=15.7 nm and W=86 meV (for sample A); R=16.3 nm and W=89 meV (for sample B) and R=26.7 nm and W=147 meV (for sample C).
13
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Effect of Filler Mixture Ratio on Permeability of Multicomponent Soft Magnetic Composites

45%
Dosoudil R., Ušáková M., Grusková A., Sláma J.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
404-405
EN
Composites with hybrid LiZnTi ferrite/FeSiAl alloy filler and PVC polymer matrix were synthesized by thermal pressing process. The influence of the mixture ratio of hybrid filler on the frequency dispersion of complex permeability of the composites has been studied. The dispersion of permeability varied from resonance type to relaxation one with the configuration change from LiZnTi/PVC composite to FeSiAl/PVC one and was mainly due to the magnetic resonance phenomena such as domain wall and spin precession resonance and due to the eddy current effect.
14
Content available remote

Mössbauer and Magnetic Study of Fe+Vitroperm+Plastic System

45%
Brzózka K., Kollár P., Szumiata T., Sovak P., Füzer J., Fáberová M., Bureš R., Górka B., Gawroński M., Gzik-Szumiata M.
Acta Physica Polonica A
|
2014
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vol. 126
|
issue 1
148-149
EN
Phase composition and magnetization curves of the soft magnetic composites, fabricated by compaction of several kinds of powders mixed in various proportions, have been investigated by means of conversion electron Mössbauer spectroscopy and an alternating gradient force magnetometry. The results point to significant quantity of iron oxides - hematite and magnetite - at the surface of the samples. After the rubbing of thin surface layer, the relative content of oxides was distinctly reduced. Magnetic measurements revealed very similar characteristics of hysteresis curves for all the investigated materials.
15
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Imaging of Magnetic Domain Structure in FeSi/Mn_{0.8}Zn_{0.2}Fe₂O₄ Composite using Magnetic Force Microscopy

38%
Streckova M., Batko I., Batkova M., Bures R., Faberova M., Dzunda R., Hadraba H., Kubena I.
Acta Physica Polonica A
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2017
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vol. 131
|
issue 4
714-716
EN
Soft magnetic composite was prepared by coating the commercial FeSi powder by Mn_{0.8}Zn_{0.2}Fe₂O₄ (MnZn) ferrite, which serves as a potential dielectric phase. MnZn ferrite was prepared by the sol-gel method followed by the auto-self combustion process. The spinel structure of MnZn ferrite was analyzed by X-ray diffraction technique. The composite material was prepared by uniaxial compaction technique and sintered either by conventional or unconventional microwave method. The microwave sintering was applied in order to reduce a grain growth and decrease the overall sintering time. The microstructure of FeSi powder is formed by grains of different diameter. Magnetic force microscopy and scanning electron microscopy were used for an investigation of the correlation between the grain size, grain boundaries and magnetic domains. Magnetic force microscopy visualization of magnetic domains in the prepared soft magnetic composite brings insight into how the magnetically active coating (MnZn ferrite) influences the soft magnetic (FeSi) powder under the influence of the external magnetic field.
16
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High-Frequency Absorbing Performances of Carbonyl Iron/MnZn Ferrite/PVC Polymer Composites

38%
Dosoudil R., Ušáková M.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 4
687-689
EN
We have prepared composite materials with a mixture of carbonyl iron (CI) and manganese-zinc ferrite (MnZn) as filler and polyvinylchloride (PVC) as polymer matrix, and then electromagnetic wave absorption properties of CI/MnZn/PVC composites have been studied in the frequency range from 10 MHz to 6.5 GHz. Increasing carbonyl iron loading (to the detriment of MnZn ferrite) results in the rise of permeability and magnetic resonance loss (especially in GHz frequency range) which leads to the shift of absorption peak towards lower frequency and to the decrease of matching thickness. On the contrary, increasing MnZn ferrite loading (to the detriment of carbonyl iron) results in higher absorption bandwidth. The obtained results indicate that the prepared flexible composites may be useful as thin and/or wideband microwave absorbers.
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