Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Daniel Michalik"

Wpływ parametrów mielenia wysokoenergetycznego na właściwości proszków kompozytowych aluminiowo-ceramicznych DOI:10.15199/28.2015.4.3

  Fine-grained composites based on an aluminum matrix or its alloys, reinforced with submicron ceramic particles obtained by the powder metallurgy method are an alternative to the composites obtained by casting method and they can provide the submicrometer scale of reinforcement distribution. The aim of this study was to determine the impact of the milling parameters in a planetary mill on the formation and properties of the composite powder consisting of silumin, silicon nitride and glassy carbon. The analyzed parameters of milling are: the time of milling, the rotational speed, the diameter of the grinding media, the jar lining material and the diameter of the grinding bowl. Research methods enabling to determine the particle size distribution of the composite powder, the specific surface area, oxygen content in both, the metallic and silicon nitride powder, as well as phase composition changes induced by high-energy milling, were applied. The obtained results revealed a varying impact of milling parameters on the refining effect and on the properties of particulate material. High energy milling of the multi-component composite powder induced chemical reactions between the powder particles of various chemical composition and agglomeration of fine particles, with various intensity depending on the analyzed grinding parameters. Analogous milling of the sole silumin powder without ceramic reinforcement gave different results. Key words: MMCs (metal matrix composites), AMC (aluminum metal composites), mechanochemical processing, AL (AK12)-Si3N4 composites. Drobnoziarniste kompozyty na osnowie aluminium i jego stopów wzmacniane cząstkami ceramicznymi, stanowiące alternatywę dla kompozytów otrzymywanych metodami odlewniczymi, charakteryzuje submikroskopowy stopień rozdrobnienia i wysoka reaktywność. Celem prezentowanych badań było określenie wpływu parametrów mielenia w młynie planetarnym na powstawanie i właściwości proszku kompozytowego składająceg[...]

Effect of AlF3 and H3BO3 fluxes on the structure and optical properties of Ca-α-SiAlON:Eu2+ phosphor powders DOI:10.15199/28.2016.1.6

  The continuous increase in demand for electric power necessitates constant search for new energy-efficient and economical light sources. One of them are light-emitting diodes (LEDs), requiring further development of materials enabling generation of warm white light that could replace the conventional light sources used so far. Problems related to the use of white LEDs include relatively low efficiency and light quality. A material that is currently a subject of interest due to its optical properties is Eu2+ doped Ca-α-SiAlON. It is regarded as one of the materials that can potentially be used as a yellow phosphor in white LEDs. The broad emission spectrum of Ca-α-SiAlON:Eu2+, bearing similarities with YAG:Ce3+ emission, is characterized by an emission peak maximum located in the wavelength range of 570÷585 nm, which enables obtaining a high colour temperature of a white LED. This study investigates the effect of addition of 1÷5 wt % AlF3 and H3BO3 as fluxes on the optical properties of phosphors obtained at different temperature. The syntheses were conducted in the temperature range of 1450÷1650°C in an N2/CO atmosphere. On the basis of the examination of the powder phase composition (by XRD), morphology, and chemical composition in microareas (by SEM/EDS), and the comparison of the emission spectra of the Ca-α-SiAlON:Eu2+ powders with a different flux content, it was found that the addition of AlF3 had a positive effect on emission intensity and quality. Key words: phosphors, wLED, sialon, flux, optical properties.1. INTRODUCTION Practically since the invention of the light bulb by Thomas Alva Edison in 1879 and the replacement of the steam engine with the first electric engines in industrial applications, a continuous increase in electric power consumption has been observed. Even at that time Edison realized the significance of his invention and he initiated the establishment of the first public power plant in the world in[...]

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