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Wyświetlanie 1-15 z 178
Tytuł:
ZnO Nanopowders as Chemical Sensor to Malathion Vapor
Autorzy:
Al-Mohammad, A.
Darwich, R.
Rukiah, M.
Abo Shaker, S.
Kakhia, M.
Powiązania:
https://bibliotekanauki.pl/articles/1195948.pdf
Data publikacji:
2014-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.16.Be
84.37.+q
81.20.Ev
81.20.Wk
07.07.Df
Opis:
Thick films of zinc oxide (ZnO) nanopowders have been prepared by high energy ball-milling for various spans of mill time (3-18 h). The morphology and crystal structure of the prepared ZnO powder were characterized by scanning electron microscope and X-ray diffraction. The ZnO thick films were then used to construct a gas sensor for O,O-dimethyl dithiophosphate of diethyl mercaptosuccinate (malathion) at different operating temperatures. The sensor response at 100 ppm of malathion was found to reach a maximum as large as 80 at 6 h of high energy ball-milling, four times larger than that found for ethanol. Scanning electron microscope observation of the granular state and pore size distribution analyses indicated that increasing high energy ball-milling time gave rise especially to an increase in the volume of pores in the pore size range of 6-35 nm. It is suggested that such a change in nanostructure is responsible for the marked promotion of the response to malathion.
Źródło:
Acta Physica Polonica A; 2014, 125, 1; 131-134
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
What Is Unique About Mechanochemical Reactions?
Autorzy:
Takacs, L.
Powiązania:
https://bibliotekanauki.pl/articles/1383095.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
82.33.Pt
82.30.-b
Opis:
Mechanochemical reactions can provide compounds, phases, and microstructures that are essentially different from the products of ordinary reactions. In this paper, the origin of this uniqueness is discussed in light of the recent advances of the field. It is claimed that the local availability of large batches of energy, well above kT, is the key feature of mechanochemical reactions. As a consequence, reactions that cannot occur thermally become possible, similarly to the reactions induced by the energy of photons in photochemistry. However, the situation is more complex, as macroscopic deformation affects many defect sites simultaneously. The direction of the mechanical load relative to the orientation of a molecule or the crystallographic axes of a solid can be important. Many mechanochemical reactions of organic compounds take place at low milling energy that is not sufficient to break primary bonds, but the gentle mechanical grinding can influence the relative position of macromolecules, leading to the formation of unique cocrystals and compounds. In inorganic systems, unusual products form due to forced mixing and the high defect density generated by intense milling.
Źródło:
Acta Physica Polonica A; 2014, 126, 4; 1040-1043
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Use of Mechanical Alloying for Production of Aluminium Matrix Composites with Non-Agglomerated Nanodiamond Reinforcing Particles
Autorzy:
Popov, V.
Prosviryakov, A.
Sagalova, T.
Többens, D.
Kiryukhantsev-Korneev, Ph.
Powiązania:
https://bibliotekanauki.pl/articles/1375581.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Ni
81.20.Ev
Opis:
Agglomeration is the main problem that prevents large-scale implementation of nanodiamonds in the production of composites. Mechanical alloying was applied for crushing the agglomerates and to obtain uniform distribution of the primary nanodiamond particles in aluminium matrix composites. The commonly used X-ray diffraction method fails to detect non-agglomerated diamond nanoparticles 5 to 6 nm in size, if they are incorporated in a metal matrix. Synchrotron radiation was used for the identification of non-agglomerated nanodiamonds. Scanning electron microscopy and synchrotron investigation showed that mechanical alloying does not lead to transformation of the diamond structure into other allotropic forms of carbon and the nanodiamond reinforcing particles are uniformly distributed in the aluminium matrix.
Źródło:
Acta Physica Polonica A; 2014, 126, 4; 1008-1011
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical and Experimental Determination of the Sound-Absorbing Property Class of Acoustic Barriers
Autorzy:
Turkiewicz, J.
Wszołek, G.
Powiązania:
https://bibliotekanauki.pl/articles/1359889.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.55.Ev
43.50.Gf
Opis:
The currently applicable PN-EN 1793-1 standard concerning anti-noise devices on roads recommends for acoustic barriers built along traffic routes to have panels characterized by good sound-absorbing properties. The sound-absorbing properties of these panels (wall elements) are to be specified by giving the values of the single-number sound absorption evaluation index $DL_α$ and the absorption property class determined in accordance with the PN-EN 1793-3:2001 standard. Continuous regular acoustic studies of new materials heretofore not used in anti-noise protections are conducted in the Department of Mechanics and Vibroacoustics at AGH. This paper presents the findings of research that started with different porous materials physical absorption coefficient tests. The purpose of these preliminary tests was to pick out materials with best sound-absorbing properties from the group of acoustically tested materials. The chosen materials could be used as a sound-absorbing lining on panels (wall elements) used in the design of acoustic barriers. On the basis of the obtained results, two materials with values of the average physical sound absorption coefficient higher than 0.5 ($α_{favg}$>0.5) were picked out for further acoustic tests. This paper presents results of studies that had the final effect consisting in determining the values of the single-number sound absorption evaluation index $DL_α$ and the absorption property class for two prototype panels of an acoustic barrier the sound-absorbing lining of which was made up of materials chosen after preliminary acoustic studies. The determination of sound-absorbing property classes was carried out both theoretically and experimentally. In order to be possible to reduce the costs of acoustic tests in the future, particularly of new materials in regard to which there is a margin of uncertainty of whether their sound-absorbing properties meet expectations, the authors determined sound-absorbing property classes of acoustic barriers theoretically and then compared theoretical results with the results of experimental tests.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-127-A-130
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Structural Properties of Fe-Ti-B Based Alloys Produced by Mechanical Alloying
Autorzy:
Kon, O.
Sen, U.
Powiązania:
https://bibliotekanauki.pl/articles/1401329.pdf
Data publikacji:
2015-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
06.30.Dr
62.20.Qp
Opis:
In the present study, the production of Fe-Ti-B based alloys was realized and their structure and properties were investigated. Mechanical alloying proceeds by the continual cold welding and fracturing of the constituent mixture of Ti+4B+5Fe powder when subjected to the large compressive forces of a high speed mill. The powder charge together with 7 mm diameter steel balls were loaded into a tool steel grinding container at approximately 350 RPM for 20 h. The samples were shaped as cylinder of Ø15×8 mm dimensions by uniaxial pressing at 450 MPa. Then, the green body materials were produced by sintering at 1100°C for 1-4 h in argon atmosphere. The morphology of composite materials was investigated by optical microscopy and scanning electron microscopy and phase analysis was realized by x-ray diffraction analysis. The bulk densities of the materials were measured using by Archimedes method. Also, the micro-hardness of the samples was measured by Vickers indentation technique. As a result, Fe, iron boride (FeB, Fe₂B) and titanium boride (TiB₂) phases were detected in the phase analysis of the Fe-Ti-B based materials. The hardness of the materials was measured between 1107 $HV_{0.05}$ and 1551 $HV_{0.05}$, depending on sintering time. The densities of the samples were determined between 4.205 g/cm³ and 4.219 g/cm³.
Źródło:
Acta Physica Polonica A; 2015, 127, 4; 1214-1217
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Spark Plasma Sintering of Silicon Carbide Ceramics Using Alumina
Autorzy:
Unlu, M.
Goller, G.
Yucel, O.
Sahin, F.
Powiązania:
https://bibliotekanauki.pl/articles/1216300.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
81.05.Je
Opis:
SiC ceramics were fabricated by spark plasma sintering technique with the use of $Al_2O_3$ additive. The sintering process was carried out at three different temperatures in the range of 1700-1800C applying two different pressures 40 and 80 MPa under vacuum atmosphere. The effect of additive, different temperatures and pressures on densification behaviour, density, Vickers hardness, fracture toughness, and microstructure were examined. The hardness and fracture toughness of the samples were evaluated by the Vickers indentation technique. Microstructure of spark plasma sintered SiC samples were characterized by using scanning electron microscopy technique. The highest value of fracture toughness $5.9 ± 0.2$ MPa $m^{1/2}$ was achieved with the addition of 5 vol.% $Al_2O_3$.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 257-259
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Porosity Evaluation during ECAP in Aluminium PM Alloy
Autorzy:
Bidulská, J.
Kvačkaj, T.
Bidulský, R.
Actis Grande, M.
Powiązania:
https://bibliotekanauki.pl/articles/1418956.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Bx
81.07.Bc
81.20.Ev
81.40.-z
Opis:
The main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (Al-Mg-Si-Cu-Fe) was used as investigated material. After applying different pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventilated furnace at 400C for 60 min. Sintering was carried out in a vacuum furnace at 610C for 30 min. The specimens were processed by single equal channel angular pressure pass. A significant disadvantage of powder metallurgy processing methods is the presence of porosity. Pores act as crack initiators and, due to their presence, the distribution of stress is inhomogeneous across the cross-section and leads to reduction of the effective load bearing area. The equal channel angular pressure process, causing stress distribution in deformed specimens, made the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores. The proposed safety diagram includes the combined effect of stress and strain behaviour during equal channel angular pressure. The "safety line" eliminates and quantifies the effect of large pores as a potential fracture initiation sites with respect to the mechanical viewpoint.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 553-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Kinetics of Spinel Formation of Algerian Halloysite by Differential Thermal Analysis
Autorzy:
Heraiz, M.
Sahnoune, F.
Belhouchet, H.
Raghdi, A.
Ouali, A.
Powiązania:
https://bibliotekanauki.pl/articles/1033398.pdf
Data publikacji:
2017-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.70.Pg
81.20.Ev
82.20.-w
Opis:
The kinetics of spinel (Al-Si) crystallization from Algerian halloysite (DD1) was investigated using differential thermal analysis. Experiments were carried out on samples between room temperature and 1400°C with constant heating rate from 2 to 20°C min¯¹. The activation energies measured from isothermal and non-isothermal treatments were 1054.85 and 1140 kJ mol¯¹, respectively, for the spinel (Al-Si) formation. The Avrami constant n obtained by the Ligero method and the m parameter obtained by the Matusita method were about 2 for spinel crystallization. This value indicates that the crystallization mechanism of Al-Si spinel phase proceeds by bulk nucleation of the phase formation with a constant number of nuclei and that the three-dimensional growth of crystals is controlled by diffusion.
Źródło:
Acta Physica Polonica A; 2017, 131, 1; 139-142
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Process Parameters of EDM on the Surface Roughness of Aluminum Matrix Composites Reinforced with SiC Particulates
Autorzy:
Feray Guleryuz, L.
Ozan, S.
Kasman, S.
Ipek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399967.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Ni
81.20.Ev
81.20.Wk
Opis:
This paper investigates the effect of electrical discharge machining parameters on the surface roughness as an alternative method for machining of $Al//SiC_{p}$ metal matrix composites produced with the powder metallurgy. Current, electrode type, pulse-on-time, particle reinforcement weight ratio and voltage were used as the process parameters. An experimental plan $(L_{18})$ was constituted by using the Taguchi orthogonal design. Results of experiments showed that pulse-on-time (34%) and current (31.26%) is the most influencing parameters. Besides this, the percentage contribution of particle reinforcement on the surface roughness is 6.71%.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 421-423
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Electronic and Electrochemical Properties of the $LaNi_5$-Based Alloys
Autorzy:
Szajek, A.
Jezierski, A.
Nowak, M.
Jurczyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810498.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
81.20.Ev
Opis:
Mechanical alloying was used to synthesize $LaNi_5$-type hydrogen storage materials. X-ray diffraction analysis showed that, after 30 h milling, the starting mixture of the elements was decomposed into an amorphous phase. Following the annealing in high purity argon at 700°C for 0.5 h, X-ray diffraction confirmed the formation of the $CaCu_5$-type structures. The nanocrystalline materials were used as negative electrodes for a $Ni-MH_x$ battery. A partial substitution o Ni by Al or Mn in $LaNi_{5-x}M_x$ alloy leads to an increase in discharge capacity. On the other hand, the alloying elements such as Al, Mn and Co greatly improved the cycle life of $LaNi_5$ material. For example, in the nanocrystalline $LaNi_{3.75}Mn_{0.75}Al_{0.25}Co_{0.25}$ powder, discharge capacities of up to 258 mA h $g^{-1}$ (at 40 mA $g^{-1}$ discharge current) were measured. The band structure ab initio calculations showed that 3g sites are preferred by Al, Co, and Mn atoms in the unit cell.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 247-250
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Electrical Properties of Some Composite Materials Based on Sodium and Tantalum Oxides
Autorzy:
Malaescu, D.
Grozescu, I.
Sfirloaga, P.
Vlazan, P.
Marin, C.
Powiązania:
https://bibliotekanauki.pl/articles/1398686.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
81.20.Fw
72.20.Ee
72.80.Tm
Opis:
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 $0.713 \times 10^{18} eV^{-1} cm^{-3}$ (sample A), $0.621 \times 10^{18} eV^{-1} cm^{-3}$ (sample B) and $0.855 \times 10^{17} eV^{-1} cm^{-3}$ (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).
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 133-137
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effects of Chemical Composition on Soft Magnetic Materials Behaviour
Autorzy:
Bidulský, R.
Actis Grande, M.
Ferraris, L.
Ferraris, P.
Bidulská, J.
Powiązania:
https://bibliotekanauki.pl/articles/1533981.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.-y
81.20.Ev
81.40.Rs
Opis:
The main aim of the presented work was to study the effects of chemical composition on the magnetic properties (in terms of B-H characteristics) of an insulated iron powder compound with various addition of the aluminium alloy (0, 5 and 10 wt%). The magnetic properties of the powder were significantly influenced by density and "sintering" effects. The addition of aluminium alloy maintaining suitable values of coercive force, remanence and core losses; this makes the modified insulated iron powder compound a promising soft magnetic material in several applications.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 802-803
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Temperature on Grain Size of $SnO_2$ Nanoparticles Synthesized by Sol-Gel Method
Autorzy:
Köse, H.
Aydin, A.
Akbulut, H.
Powiązania:
https://bibliotekanauki.pl/articles/1218824.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
81.20.Fw
81.20.Ev
Opis:
Tin dioxide nanoparticles were synthesized by sol-gel method and calcined at different temperatures in the range 350-750°C. The $SnO_2$ precursor solution was prepared from $SnCl_2$·$2H_2O$ (tin (II) chloride dihydrate), and chloride ions were removed from the solution before the sol-gel synthesis was applied. $SnO_2$ powders were characterized by thermal analyses, X-ray diffraction, field emission gun-scanning electron microscopy, and energy dispersive X-ray spectroscopy, and grain size of nanoparticles were determined by using the Debye-Scherrer formula.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 345-347
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 178

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