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Properties of Al–Al2O3 composites synthesized by spark plasma sintering method

Garbiec D., Jurczyk M., Levintant-Zayonts N., Mościcki T.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 4

933--939

EN

This work presents fabrication and characterization of Al–Al2O3 composite materials with a 5%, 10%, 15% and 20% volume fraction of reinforcing phase particles. The spark plasma sintering method was applied for the purpose of fabricating these materials. The obtained Al–Al2O3 composites were characterized with an porosity from 1.27% to 5.07%. It was proven that as the content of hard ceramic particles increases in the composite, its density, hardness, and compression as well as tensile strength increase. The conducted study showed that a composite with 20% alumina content is characterized by a larger hardness (1355 MPa) and compression strength (247 MPa).

2

Modelling of plasma formation during nanosecond laser ablation

Mościcki T., Hoffman J., Szymański Z.

Archives of Mechanics

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2011

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Vol. 63, nr 2

99-99

EN

The interaction of laser beam with a target and next with the evaporated material is studied theoretically. In the case of a nanosecond laser pulse with 1064 nm wavelength, the ablation is thermal and therefore the interaction of the laser beam with a target is studied with the use of thermal model. The model which describes both the target heating, formation of the plasma and its expansion consists of equations of conservation of mass, momentum and energy and is solved with the use of Fluent software package. The calculations show a sharp increase of the plume temperature and pressure after plasma formation and following it, a considerable increase of the velocity of plasma plume. Maximum plasma pressure of 2 ×108 Pa, temperature of 61 500 K and front velocity of 3.8 × 104 m ź s-1 have been found. The results show that the Mie absorption cannot be neglected in the phase of plasma formation. The shape of the plume and plasma front velocity obtained from the model are close to that observed in the experiment carried out in similar conditions.

3

Deposition of thin hydroxyapatite films by 335 nm Nd:YAG laser ablation

Jedyński M., Hoffman J., Mościcki T., Mróz W., Burdyńska S., Diduszko R., Kołodziejczak P., Szymański Z.

Materials Science Poland

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2010

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Vol. 28, No. 3

693--702

EN

The characteristics of hydroxyapatite (Ca10(PO4)6(OH)2) thin films deposited by the pulsed laser deposition technique have been describrd. The laser used was a Nd:YAG, operating at the wavelength of 355 nm. All films were deposited at room temperature, either in ambient water vapour or in vacuum, and were annealed, after deposition in air, at 600 °C. Next, they were examined with the use of an X-ray diffractometer, Fourier transform infrared spectrometer, atomic force microscope, micro scratch tester and scanning electron microscope. The analyses showed that crystalline films exhibiting very strong adhesion to the substrate have been obtained.

4

Net emission coefficients of low temperature thermal iron-helium plasma

Mościcki T., Hoffman J., Szymański Z.

Optica Applicata

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2008

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Vol. 38, nr 2

365-373

EN

Poland Net emission coefficients of low temperature thermal iron-helium plasma mixture at atmospheric pressure are presented. The calculations are made assuming the plasma is in the local thermodynamic equilibrium at a pressure of 0.1 MPa. The results are presented for several values of helium mass fraction in the mixture (between 0 and 1), for a temperature range 3000-25000 K and three characteristic plasma dimensions; 0 - corresponding to the optically thin case, and 1 mm and 10 mm. The values of net emission coefficients allow the estimations of total radiation losses in iron-helium plasmas.

5

Spawanie stopu magnezu AM20 laserem CO2

Kalita W., Kołodziejczak P., Hoffman J., Mościcki T., Szymański Z.

Przegląd Mechaniczny

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2003

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nr 7-8

48-51

6

Dynamics of the plasma plume induced during laser welding

Mościcki T., Hoffman J., Szymański Z.

Optica Applicata

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2003

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Vol. 33, nr 2-3

433-443

EN

The dynamics of the plasma plume produced during laser welding is quite complex. The keyhole wall oscillates and this results in oscillations of the plasma plume over the keyhole mouth. The metal vapour, which appears in irregular bursts, interacts with the shielding gas flowing from the opposite direction. In the present work, temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, without being diluted by the shielding gas. The results, together with the analysis of the colour pictures from streak camera, allow interpretation of the dynamics of the plasma plume. No apparent mixing of metal vapour and the shielding gas has been observed. In typical bursts the electron density determined from the Stark broadening of Ar I lines varies from 0.9×1023 m–3 near the metal surface to 0.5×1023 m–3 at a distance of 1.5 mm from the surface. Assuming that argon is not mixed with the metal vapour and is in local thermal equilibrium these electron densities correspond to temperatures 12.7 kK and 11.5 kK, respectively. In strong bursts the electron density varies, along the same distance, from 1.6×1023 m–3 to 0.6×1023 m–3 , which corresponds to the temperatures of 14.2 kK and 11.8 kK, respectively.