On-Line, Real-Time Diagnostics of a Single Fluid Atomization System

A drop tube-Impulse Atomization technique was used to produce copper droplets. In this method, energy is transferred to a liquid by plunger movement resulting in spherical droplets emanating from orifices. A mathematical model of the evolution of droplet velocity and temperature at various heights for different sized droplets was developed. A two-color pyrometer, DPV-2000, and a shadowgraph were used to measure droplets radiant energy, diameter and velocity. The temperature values from the model were used to assess the two color pyrometer assumption over the temperature range of measurement. The DVP 2000 measurements were found to be dependent of droplet size wavelength and position of droplets below the atomizing nozzle. By calibrating the instrument for effective emissivity over the range of measurements, the thermal history of droplets may be recorded using a single color pyrometer approach

Dendrite growth in undercooled Al-rich Al-Ni melts measured on Earth and in Space

The dendrite growth velocity in Al₇₅Ni₂₅ melts has been measured in a containerless procedure as a function of undercooling using an electromagnetic levitation technique both in the Earth laboratory and in Space on board the International Space Station. The growth shows an anomalous behavior inasmuch as the growth velocity decreases with increasing undercooling, confirming previous experiments on Earth. Within the scatter of experimental data, results obtained on Earth and in Space do not show significant differences. Thus, convection effects as the origin of the anomalous growth characteristics can be excluded. However, high-speed video recording exhibits multiple nucleation events in front of the growing solid-liquid interface. This effect is identified as the origin of the anomalous dendrite growth characteristics in undercooled melts of Al-rich Al-Ni melts

Containerless Solidification and Characterization of Industrial Alloys

Containerless solidification using electromagnetic levitator (EML), gas atomization and an instrumented drop tube, known as impulse atomization is investigated for Al-Fe and AlNi alloys. The effects of primary phase and eutectic undercooling on the microstructure of AlFe alloys are investigated using the impulse drop tube and parabolic flight. The TEM characterization on the eutectic microstructure of impulse-atomized Al-Fe powders with two compositions showed that the metastable AlmFe formed in these alloys. Also, the growth undercooling that the dendritic front experiences during the solidification of the droplet resulted in variation of dendrite growth direction from to . For Al-4 at%Fe, it was found that in reduced-gravity and in the impulse-atomized droplets the primary intermetallic forms with a flower-like morphology, whereas in the terrestrial EML sample it has a needle like morphology. For Al-Ni, the effect of primary phase undercooling on dendrite growth velocity under terrestrial and reduced-gravity condition is discussed. It is shown that under terrestrial conditions, in the Ni-rich alloys with increasing undercooling the growth velocity increases, whereas in the Al-rich alloys the growth velocity decreases. However, the Al-rich alloy that was studied in reduced-gravity showed similar behavior to that of Ni-rich alloys. Furthermore, the effect of cooling rate on the phase fractions and metastable phase formation of impulse-atomized Al-Ni alloys is compared with EML. A microsegregation model for the solidification of Al-Ni alloys is applied to impulse atomized powders. The model accounts for the occurrence of several phase transformations, including one or several peritectic reactions and one eutectic reactionPeer Reviewe

Microstructural analysis of rapidly solidified aluminium-nickel alloys

Powders of Al-50 wt-%Ni and Al-36 wt-%Ni were produced using the impulse atomisation technique, a rapid solidification technique. The molten droplets were cooled in flight by the stagnant helium or nitrogen in the atomising chamber. The resulting powders were sieved into different size ranges. X-ray diffraction and neutron diffraction were used in order to quantify the phase fractions in the samples. Profile refinement, using the computer software GSAS, was used to calculate the weight fraction of the existing phases, namely Al3Ni2, Al3Ni and Al, as a result of different processing parameters. The Scheil-Gulliver model was applied to investigate the extent to which it can predict phase fractions in the Al-Ni system. In Al-50 wt-%Ni, by increasing cooling rate, the ratio of Al3Ni to Al3Ni2 approaches that of Scheil-Gulliver\u2019s prediction. Opposite behaviour was observed in Al-36 wt-%Ni. In addition, from the profile refinement, the effect of composition and cooling rate on the lattice parameter of Al3Ni2 was investigated. In Al-36 wt-%Ni, the c/a ratio is significantly smaller than the stoichiometric c/a ratio of Al3Ni2, and it decreases with increasing cooling rate. On the other hand, for Al-50 wt-%Ni, the c/a ratio is much closer to the stoichiometric value and it increases with increasing cooling rate.Peer reviewed: YesNRC publication: Ye

Microstructural analysis of rapidly solidified aluminium–nickel alloys

International audienc

Molecular, serological and transmission electron microscopic analysis of the barley yellow dwarf virus- PAV and the cereal yellow dwarf virus-RPV in canary seed ( Phalaris canariensis L.)

Canary seed ( Phalaris canariensis L.) is a cereal crop belonging to the tribe Phalarideae of the Poaceae family. A prevailing virus infection, which causes dwarfing of plants and yellowing of leaves, was observed in canary seed fields in the Tekirdag province of Turkey. The aim of this study was to identify, clone and sequence the cereal viruses naturally occurring on P. canariensis by employing serological tests as DAS-ELISA and TAS-ELISA tests combined with transmission electron microcopy (TEM) and molecular analysis. One hundred and one plant samples showing symptoms were collected and tested serologically using polyclonal antisera against Barley yellow dwarf virus -PAV (BYDV-PAV) and Cereal yellow dwarf virus -RPV (CYDV-RPV). The results of both immunoassays showed that 48% of the samples were infected with BYDV-PAV, 2% with CYDV-RPV and 14% were mixed infection. 36% of the samples were uninfected or infected at level below detection. Aphid transmission experiments revealed that barley (cv. Rubina) exhibited characteristic of CYDV-RPV. Investigations of infected canary grass seedlings using transmission electron microscopy (TEM) supported the findings of serological tests and revealed the presence of isometric particles of approximately 25 nm in diameter. These results were also confirmed by using BYDV-PAV and CYDV-RPV specific primers. Sequence analysis of cDNA and probable translation products revealed a high level of homology to BYDV-PAV and CYDV-RPV isolates found in other plant species. The sequence data obtained from this research were deposited in the EMBL/GenBank Data Libraries under the accession nos. EGO19056 and EF372272