Search results for " Aluminium"
showing 10 items of 42 documents
Application of electrochemical impedance for characterising arrays of Bi2S3 nanowires
2015
Abstract Electrochemical Impedance Spectroscopy (EIS) was used to characterise the electrical properties of bismuth sulphide (Bi2S3) nanowires (NWs) templated within anodic aluminium oxide (AAO) membranes. A specially engineered cell, with a nominal electrolyte volume of 0.1–0.2 ml, was used to hold and measure the electrochemical impedance of the fragile NW/AAO samples. An equivalent circuit model was developed to determine the filling density of nanowires within the porous templates. The EIS method can be utilised to probe the nanowire filling density in porous membranes over large sample areas, which is often unobtainable using electron microscopy and conductive atomic force microscopy t…
Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR methods
2020
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Radiation Induced Defects in Yttrium Aluminium Perovskite
2000
The yttrium aluminium perovskite single crystals YAlO3 (YAP) doped with rare -earth ions belong to the most prospective materials of solid-state laser engineering. Laser based of YAlO3 crystals have the advantage in comparison with yttrium aluminium garnet (YAG). The main of them consists in anisotropy of optical properties [1], which are stipulated by the low symmetry of orthoaluminate crystals. Continuos wave (CW) laser action at 549.6 nm was achieved in 1% Er:YAP crystal at below 77 K [2]. The YAP:Nd allows to obtain a CW generation at 1079 nm, 1340 nm and 1440 nm [3, 4]. It is known, that the color center can completely suppress laser generation in the crystal.
Evidence for a Double Doping Regime in Nd:YAG nanopowders
2009
Nanopowders of Yttrium Aluminium Garnet doped with neodymium (Nd:YAG) were investigated by X-Ray Absorption Fine Structure (XAFS) at the Nd LIII-edge in the 1.3 - 20.8 % doping range. XANES spectra appear similar in the full range of the Nd concentration. However, a significant decrease in the white line intensity of XANES is revealed as the quantity of Nd doping ions increases. Plotting the white line intensity as a function of Nd doping ions reveals two linear trends with two different slopes, identifying a threshold value where the neodymium concentration reaches 5 at.% This experimental finding provides support for the existence of a double doping regime in Nd:YAG nanopowders.
On microstructural phenomena occurring in friction stir welding of aluminium alloys
2006
Abstract The results of experimental activity on friction stir welding (FSW) of aluminum alloys are reported. Butt joints of two different materials, namely AA2024-T4 and AA7075-T6, were investigated from a metallurgical point of view. Grain dimensions and insoluble particle densities were investigated both in the parent materials and in the joints. Furthermore, the effect of post-welding heat treatments on the joint strength was studied.
Electrochemically-induced TiO2 incorporation for enhancing corrosion and tribocorrosion resistance of PEO coating on 7075 Al alloy
2018
Abstract 7075 Al alloy was PEO-treated in a silicate based electrolyte containing 3 g l-1 potassium titanyl oxalate using unipolar and bipolar pulsed current waveforms. The coating formed by the bipolar waveform with the wider cathodic pulses showed volcano-like surface morphology with no evidence of large pores at the metal/coating interface. It revealed the highest corrosion performance due to the synergistic effect of TiO2 incorporation and structural/morphological features along with a better passivation behavior indicating no pitting susceptibility. For this coating, the tribocorrosion tests showed no potential drop during sliding under 1 N with the lowest volume loss of 0.022 mm3.
Structure and Phase Changes in Natural and Synthetic Magnesium Aluminum Spinel
2015
Natural spinel crystals from Ural and Pamir deposits and synthetic magnesium aluminium spinel single crystals with different stoichiometry (MgO.nAl2O3 ) grown by Verneuil method were used. The photoluminescence (PL), its excitation (PLE) and optical absorption of stoichiometric and nonstoichiometric magnesium aluminium spinel crystals containing the chromium and manganese ions and defects produced by fast neutron irradiation( fluence up to 1020cm-2, E>0.1 MeV) are investigated. The broadening of R- and N-lines takes place in synthetic stoichiometric spinel. Structure of synthetic nonstoichiometric spinels (n>1) has to be more disordered, since in addition to the site exchange …
Thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) filled with cerium-doped yttr…
2016
This paper reports on the thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) composites filled with cerium-doped yttrium aluminium garnet (Ce:YAG) at different contents ranging between 0.1 and 5 wt%, and prepared by melt compounding. The interaction between PMMA and the filler was much stronger than that between PC and the filler, and this resulted in a significant improvement in the dynamic mechanical properties of the PMMA composites. The presence of filler did not significantly increase the thermal stability of the PC, while an observable increase in the thermal stability was only observed at higher filler loadings for …
Co-precipitation synthesis of neodymium-doped yttrium aluminium oxides nanopowders: Quantitative phase investigation as a function of joint isotherma…
2007
Abstract Neodymium-doped yttrium aluminium nanopowders with nominal Nd:Y:Al ratio equal to X:3–X:5 (where X = 0, 0.006, 0.012, 0.024, 0.048, 0.081, 0.096, 0.171, 0.192, 0.384, 0.540 and 0.720) were prepared by the co-precipitation method and subjected to five cumulative stages of isothermal treatment in the temperature range from 900 to 1050 °C. The phase evolution of the oxides were investigated quantitatively by the X-ray powder diffraction approach using the Rietveld method of analysis. An almost single phase cubic garnet structure was attained at temperatures as low as 900 °C for specimens with neodymium loading less than ca. 6 at.% with respect to total (Nd + Y) atoms. Isothermal treat…
A new fixture for FSW processes of titanium alloys
2010
FSW of titanium alloys is nowadays one of the most challenging welding operations, even with a solid state process, due to the thermo-mechanical and thermo-chemical characteristics of such materials. Due to the relevant application of titanium alloys in the aeronautic and aerospace industries, in the recent years few attempts were carried out to develop FSW processes aimed to maximize the mechanical performances of the welded parts. In the paper a new fixture is presented allowing obtaining effective FSW joints of titanium blanks, which were investigated through mechanical and metallurgical tests highlighting the peculiarities of FSW of titanium alloys.