Browsing by Subject "Magnesium"

Now showing 1 - 4 of 4

Open Access
Effect of processing options on ultra-low-loss lead-magnesium-niobium titanate thin films for high density capacitors
(Elsevier, 2013) Chen W.; McCarthy, K.G.; O'Brien, S.; Çopuroǧlu, Mehmet; Cai, M.; Winfield, R.; Mathewson, A.
This work studies the impact of annealing temperatures on PMNT (lead-magnesium niobate-lead titanate, Pb(Mg0.33Nb 0.67)0.65Ti0.35O3) thin films grown on a silicon substrate. The electrical properties of the thin films, such as dielectric constant and loss tangent, are shown to depend strongly on the annealing temperature, with the best electrical properties being achieved at the highest annealing temperature. It is seen that the perovskite phase is highest in the sample annealed at 750 C indicating that a relatively high temperature is necessary for complete transition of PMNT to the perovskite phase. The sample annealed at 400 C exhibits the lowest loss tangent of approximately 0.007 at a frequency of 1 MHz. © 2012 Elsevier B.V.
Open Access
Induction of triacylglycerol production in Chlamydomonas reinhardtii: comparative analysis of different element regimes
(Elsevier, 2014) Çakmak, Z. E.; Ölmez, T. T.; Çakmak, T.; Menemen, Y.; Tekinay, T.
In this study, impacts of different element absence (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) on element uptake and triacylglycerol production was followed in wild type Chlamydomonas reinhardtii CC-124 strain. Macro- and microelement composition of C. reinhardtii greatly differed under element regimes studied. In particular, heavy metal quotas of the microalgae increased strikingly under zinc supplementation. Growth was suppressed, cell biovolume, carbohydrate, total neutral lipid and triacylglycerol levels increased when microalgae were incubated under these element regimes. Most of the intracellular space was occupied by lipid bodies under all nutrient starvations, as observed by confocal microscopy and transmission electron micrographs. Results suggest that sulfur, magnesium and phosphorus deprivations are superior to nitrogen deprivation for the induction triacylglycerol production in C. reinhardtii. On the other hand, FAME profiles of the nitrogen, sulfur and phosphorus deprived cells were found to meet the requirements of international standards for biodiesel.
Open Access
Peculiar piezoelectric properties of soft two-dimensional materials
(American Chemical Society, 2016-06) Sevik, C.; Çakır, D.; Gülseren, O.; Peeters, F. M.
Group II-VI semiconductor honeycomb monolayers have a noncentrosymmetric crystal structure and therefore are expected to be important for nano piezoelectric device applications. This motivated us to perform first-principles calculations based on density functional theory to unveil the piezoelectric properties (i.e., piezoelectric stress (e11) and piezoelectric strain (d11) coefficients) of these monolayer materials with chemical formula MX (where M = Be, Mg, Ca, Sr, Ba, Zr, Cd and X = S, Se, Te). We found that these two-dimensional materials have peculiar piezoelectric properties with d11 coefficients 1 order of magnitude larger than those of commercially utilized bulk materials. A clear trend in their piezoelectric properties emerges, which originates mainly from their mechanical properties. We establish a simple correlation between the piezoelectric strain coefficients and the physical properties, as the natural elemental polarizabilities, the Bader charges, and lattice constants of the individual M/X atoms and MX monolayers.
Open Access
Sorption studies of Cs+, Ba2+, and Co2+ ions on bentonite using radiotracer, ToF-SIMS, and XRD techniques
(De Gruyter Oldenbourg, 2001) Shahwan, T.; Erten H. N.
The sorption behaviour of Cs+, Ba2+, and Co2+ ions on bentonite were investigated using the radiotracer method, Time of Flight-Secondary Ion Mass Spectroscopy (ToF-SIMS), and X-Ray Diffraction (XRD). The sorption of Cs+ and Ba2+ were exothermic while sorption of Co2+ was endothermic. The sorption data were well described by Freundlich and Dubinin-Radushkevich isotherms. According to ToF-SIMS results Na+ and Mg2+ were the primary exchanging ions in bentonite. The XRD spectra showed that no structural changes were associated with the sorption of Cs+ and Co2+, and BaCO3 precipitate was formed upon the sorption of Ba2+ on bentonite.