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A. Dulęba, M. Cholewa and D. Scelina

integrated composite material structures under different fabrication processing. Composites. Part A. Previatali, B., Pocci, D. & Taccardo, C. (2008). Application of traditional investment casting process to aluminium matrix composites. Composites. Part A, 39. Cholewa, M. (2005). The kinetic solidification of dispersive composites , ZN nr 1672. Gliwice: Silesian University of Technology. Lee, J. C., Ahn, J., Shim, J. H., Shi, Z., Lee, H. I. (1999). Control of the interface in SiC/Al

Open access

Martin Florovič, Róbert Szobolovszký, Jaroslav Kováč, Jaroslav Kováč, Aleš Chvála, Jean-Claude Jacquet and Sylvain Laurent Delage

Abstract

GaN-based HEMTs’ high potential is deteriorated by self-heating during the operation, this has influence on the electrical properties as well as device reliability. This work is focused on an average channel temperature determination of power AlGaN/GaN HEMT prepared on SiC substrate using quasi-static and pulsed I-V characterization. There was analyzed the drain current change relation to temperature dependent electrical HEMT parameters such as source resistance, threshold voltage, saturation velocity, resp. leakage current which allows to calculate an average channel temperature versus dissipated power for various ambient temperature. Differential temperature of investigated device with and without heatsink was determined. Obtained results were discussed using simulated spatial temperature distribution.

Open access

N. Guskos, E. Anagnostakis, G. Zolnierkiewicz, J. Typek, A. Biedunkiewicz, A. Guskos and P. Berczynski

Abstract

Two nanocrystalline samples of TiC+SiC+20%C (sample 1) and Si3N4+Si(C,N)+Ti(C,N)+1%C (sample 2) were prepared by non-hydrolytic sol-gel method. The latter sample was produced from sample 1, by subjecting it to additional annealing at high temperature. XRD measurements showed the presence of aggregates of cubic SiC+TiC nanoparticles (10 to 30 nm in size). In both samples, a very narrow electron paramagnetic resonance (EPR) line originating from localized magnetic centers was centered at g eff∼2. At T = 130 K, we registered the linewidths ΔH pp = 1.41(2) G and ΔH pp = 2.92(2) G for the sample without and with thermal annealing, respectively. For the non-annealed sample, the resonance line was fitted by a Lorentzian line in the low temperature range, and by a Dysonian line above 70 K, which indicates a significant change in electrical conductivity. Therefore, thermal annealing can significantly improve the transport properties of samples. An analysis of the temperature dependence of the EPR parameters (g-factor, linewidth, integrated intensity) showed that thermal annealing has a significant impact on the reorientation processes of localized magnetic centers.

Open access

K. Labisz, T. Tański, D. Janicki, W. Borek, K. Lukaszkowicz and L. A. Dobrzański

Abstract

In this paper are presented the investigation results concerning microstructure as well as mechanical properties of the surface layer of cast aluminium-silicon-copper alloy after heat treatment alloyed and/ or remelted with SiC ceramic powder using High Power Diode Laser (HPDL). For investigation of the achieved structure following methods were used: light and scanning electron microscopy with EDS microanalysis as well as mechanical properties using Rockwell hardness tester were measured. By mind of scanning electron microscopy, using secondary electron detection was it possible to determine the distribution of ceramic SiC powder phase occurred in the alloy after laser treatment. After the laser surface treatment carried out on the previously heat treated aluminium alloys, in the structure are observed changes concerning the distribution and morphology of the alloy phases as well as the added ceramic powder, these features influence the hardness of the obtained layers. In the structure, there were discovered three zones: the remelting zone (RZ) the heat influence zone (HAZ) and transition zone, with different structure and properties. In this paper also the laser treatment conditions: the laser power and ceramic powder feed rate were investigated. The surface laser structure changes in a manner, that there zones are revealed in the form of. This carried out investigations make it possible to develop, interesting technology, which could be very attractive for different branches of industry.

Open access

Y. Nakafushi, K. Matsuda and M. Nose

Abstract

FIn this work, AlN/SiCN composite coatings were deposited by r.f.-reactive sputtering method using a facing target-type sputtering (FTS) apparatus with composite targets consisting of Al plate and SiC chips in a gaseous mixture of Ar and N2, and investigated their mechanical properties and microstructure. The indentation hardness (HIT) of AlN/SiCN coatings prepared from composite targets consisting of 8 ~32 chips of SiC and Al plate showed the maximum value of about 29~32 GPa at a proper nitrogen gas flow rate. X-ray diffraction (XRD) patterns for the AlN/SiCN composite coatings indicated the presence of the only peeks of hexagonal (B4) structured AlN phase. AlN coatings clarified the columnar structure of the cross sectional view TEM observation. On the other hand, microstructure of AlN/SiCN composite coatings changed from columnar to equiaxed structure with increasing SiCN content. HR-TEM observation clarified that the composite coatings consisted of very fine equiaxial grains of B4 structured AlN phase and amorphous phase.

Open access

P. Ambroza, S. Bockus and L. Kavaliauskiene

Microstructure and properties of structural steel subjected to overlay welding with secondary materials powder is investigated. Crushed glass, grinding wheels (SiC), hard metals plates, high speed steel and cast iron chips as well as marble powders were used in automatic overlay welding of steel by low carbon wire. Powder spread over the steel surface and melted by continuously supplied wire arc enabled to obtain layers with graphite and carbides inclusions in the matrix; hardness of the matrix depends on the phases contained in it: martensite, troostite and residual austenite as well as secondary carbides. Depending on materials used for overlay welding the layers were obtained which abrasive wear resistance became equal to that of high alloyed hardened tool steel. Wear of these layers is much more less in comparison with low alloyed hardened tool steel.

Open access

J.T. Bonarski, L. Tarkowski, S. Pawlak, A. Rakowska and Ł. Major

Abstract

Performed investigations and obtained results concerned the analysis of residual stresses in near-surface areas of coppercorundum (Cu-Al2O3) composite and silicon carbide (SiC) samples. X-ray diffraction and acoustic tomography techniques, as well as the suitable calculation procedures, allowed to locate sample-areas with extreme values of stresses residing in the examined materials. The registered texture-stress characteristics reflects inhomogeneity of the samples structure identified by means of acoustic tomography. Obtained results provide valuable information on anisotropy of physical properties of structural elements produced by the technologies applied to the examined samples.

Open access

Justyna Brzezińska

Bibliography Damon J., 2012, Wykluczenie , Oficyna Naukowa, Warszawa. http://stat.gov.pl/obszary-tematyczne/warunki-zycia/ubostwo-pomoc-spoleczna/zasieg-ubostwa-ekonomicznego-w-polsce-w-2015-r-,14,3.html (dostęp: 20.05.2017). Lister R., 2007, Bieda , Wydawnictwo Sic!. Szarfenberg R., Żołędowski C., Theiss M. (red.), 2010a, Polityka publiczna wobec ubóstwa i wykluczenia społecznego, Elipsa, Warszawa. Szarfenberg R., Żołędowski C., Theiss M. (red.), 2010b, Ubóstwo i wykluczenie społeczne – perspektywa poznawcza , Elipsa, Warszawa.

Open access

Assen Ignatov, Daniel Mitev, Rob Berkelder and Paul van der Poel

Pozvetek

Bledi srakoper Lanius isabellinus gnezdi v širokem pasu od Irana prek osrednje Azije in severne Kitajske do Mongolije. Prezimuje v osrednji in vzhodni Afriki, Pakistanu in Indiji. V Evropi se redno pojavlja, predvsem med koncem aprila in začetkom junija ter med začetkom septembra in koncem novembra. Pojavljata se (pod)vrsti isabellinus in phoenicuroides. V srednji in jugovzhodni Evropi so znana opazovanja iz Avstrije (3), Romunije (1) in Grčije (8). Avtorji prispevka predstavljajo prvi opazovanji za Bolgarijo, in sicer je bil 24. 5. 2010 na gori Slavjanka opazovan drugoletni samec nedoločene (pod)vrste, 28. 9. 2014 na jezeru Durankulak pa odrasel samec (pod)vrste isabellinus. Opazovanji je kot prvo in drugo za državo potrdila bolgarska komisija za redkosti BUNARCO.

Open access

K. Gawdzińska, L. Chybowski and W. Przetakiewicz

Abstract

Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC). A certificate of non-combustibility test of cast aluminum-ceramic foam for marine applications was included inside the paper. The composite foam was prepared by the gas injection method, consisting in direct injection of gas into liquid metal. Foams with closed and open cells were examined. The foams were foaming with foaming gas consisting of nitrogen or air. This work is one of elements of researches connected with description of properties of composite foams. In author's other works acoustic properties of these materials will be presented.