Is dark matter real or just a convenient hypothesis? Although it was first proposed almost a century ago, physicists have yet to uncover its true nature. Scientists from the Nicolaus Copernicus University are investigating the phenomenon using atomic clocks.

In this study, the effect of gas pressure on the shape and size of the AZ91 alloy powder produced by using the gas atomization method was investigated experimentally. Experiments were carried out at 820°C constant temperature in 2-mm nozzle diameter and by applying 4 different gas pressures (0.5, 1.5, 2.5 and 3.5 MPa). Argon gas was used to atomize the melt. Scanning electron microscope (SEM) to determine the shape of produced AZ91 powders, XRD, XRF and SEM-EDX analysis to determine the phases forming in the internal structures of the produced powders and the percentages of these phases and a laser measuring device for powder size analysis were used. Hardness tests were carried out to determine the mechanical properties of the produced powders. The general appearances of AZ91 alloy powders produced had general appearances of ligament, acicular, droplet, flake and spherical shape, but depending on the increase in gas pressure, the shape of the powders is seen to change mostly towards flake and spherical. It is determined that the finest powder was obtained at 820°C with 2 mm nozzle diameter at 3.5 MPa gas pressure and the powders had complex shapes in general.

Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 μm. It was expected that fraction of Nd2Fe14B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd2Fe14B phase tend to align to c-axis.

W artykule przedstawiono wyniki wstępnych badań laboratoryjnych nad opracowaniem metody oznaczania zawartości jednego z pierwiastków śladowych występujących w węglu kamiennym – bizmutu. Przedmiotem analizy były węgle kamienne typu 34 i 35 pochodzące z Jastrzębskiej Spółki Węglowej oraz otrzymane z nich popioły. Jednym z powodów do przeprowadzenia badań było szerokie zastosowanie bizmutu w wielu gałęziach przemysłu oraz umieszczenie go na liście pierwiastków deficytowych, co skłania do poszukiwania alternatywnych źródeł recyklingu tego pierwiastka. Badania zostały przeprowadzone z zastosowaniem techniki atomowej spektrometrii absorpcyjnej z atomizacją elektrotermiczną w pirokuwecie grafitowej. Przed przystąpieniem do analizy spektrometrycznej próbki poddano spopieleniu w temp. 800°C oraz mineralizacji mikrofalowej stosując metodę rozkładu próbek „na mokro” w systemie zamkniętym pod wysokim ciśnieniem. Do mineralizacji użyto mieszaniny kwasów HF oraz HNO3 w celu przeprowadzenia próbek do postaci kwaśnych roztworów. Metodykę pomiarową opracowano na podstawie dostępnych danych literaturowych oraz własnych obserwacji. W doświadczeniu zbadano wpływ dodatku modyfikatora oraz zmianę temperatur etapów: suszenia, spopielania, chłodzenia, atomizacji oraz wypalania. Wyniki przeprowadzonych badań wykazały, iż zastosowany modyfikator palladowy ograniczył reakcje uboczne i umożliwił odparowanie składników matrycy. Ponadto przedstawione w artykule warunki pomiaru pozwoliły na ustalenie liniowej krzywej kalibracji. Niestety, specyfika próbek węglowych nie pozwoliła na jednoznaczne i definitywne ustalenie metody oznaczania bizmutu w węglu kamiennym metodą ET-AAS.

With the recent advancement in technology for titanium metal powder injection molding and additive manufacturing, high yield and good flowability powder production is needed. In this study, titanium powder was produced through vacuum induction melting gas atomization with a cold crucible, which can yield various alloy compositions without the need for material pretreatment. The gas behavior in the injection section was simulated according to the orifice protrusion length for effective powder production, and powder was prepared based on the simulation results. The gas distribution changes with the orifice protrusion length, which changes the location of the recirculation zone and production yield of the powder. The produced powders had a spherical morphology, and the content of impurities (N, O) changed with the injected-gas purity.

Tin dioxide (SnO2) is an n-type semiconductor and has useful characteristics of high transmittance, excellent electrical properties, and chemical stability. Accordingly, it is widely used in a variety of fields, such as a gas sensor, photocatalyst, optoelectronics, and solar cell. In this study, SnO2 films are deposited by thermal atomic layer deposition (ALD) at 180°C using Tetrakis(dimethylamino)tin and water. A couple of 5.9, 7.4 and 10.1nm-thick SnO2 films are grown on SiO2/Si substrate and then each film is annealed at 400°C in oxygen atmosphere. Current transport of SnO2 films are analyzed by measuring current – voltage characteristics from room temperature to 150°C. It is concluded that electrical property of SnO2 film is concurrently affected by its semiconducting nature and oxidative adsorption on the surface.

The objective of this study was to deposit directly chromium with diamond nanoparticles (ND) on aluminum alloys and investigate the coating surface. The chromium coatings on aluminum alloys were obtained by electrochemical deposition. The coatings were doped with ND. The diamond nanoparticles were obtained by detonation synthesis. Chromium coatings were deposited on aluminum alloys with a silicon content of 7 % and 10 %. The ND concentration in the electrolyte was 25 g/l. The surface analysis was performed by means of Atomic force microscopy. The surface of the coating of chromium with ND on Al10Si is twice more even than that on Al7Si. The microstructure and microhardness were examined with a metallographic microscope and a microhardness tester. The microhardness of the coated samples is 9163 MPa compared to 893 MPa of uncoated aluminum samples. The thickness of the chromium coatings doped with diamond nanoparticles is between 45 – 55 μm. The coatings are dense, continuous and uniform with good adhesion to the substrate material.