RESUMEN
Mg77+xNi20-xLa3 (x = 0, 5, 10, 15) alloys were successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction and scanning electron microscope. The effects of nickel content on the microstructure and hydrogen storage kinetic of the as-cast alloys were investigated. The results showed that the alloys are composed of a primary phase of Mg2Ni, lamella eutectic composites of Mg + Mg2Ni, and some amount of LaMg12 and La2Mg17. Nickel addition significantly improved the hydrogen-absorption kinetic performance of the alloy. At 683 K, Mg77Ni20La3 alloy and Mg82Ni15La3 alloy underwent hydrogen absorption and desorption reactions for 2 h, respectively, and their hydrogen absorption and desorption capacities were 4.16 wt.% and 4.1 wt.%, and 4.92 wt.% and 4.69 wt.%, respectively. Using the Kissinger equation, it was calculated that the activation energy values of Mg77Ni20La3, Mg82Ni15La3, Mg87Ni10La3 and Mg92Ni5La3 alloys were in the range of 68.5~75.2 kJ/mol, much lower than 150~160 kJ/mol of MgH2.
RESUMEN
A method for analyzing volatile constituents from plant leaves with gas chromatography/mass spectrometry (GC/MS) coupled with solid-phase microextraction (SPME) was developed. The volatile compounds from the plant leaves inside a sealed flask maintained at 45 degrees C in a water bath were efficiently extracted with Polyacrylate (85 microm) SPME fibers prior to perform GC/MS analysis. The GC/MS analysis indicated that the volatile compounds from the plant leaves which is easy to be damaged by Tetraychus vienneis include relative large amounts of cis-3-hexenyl ester acetic acid, cis-3-hexenyl ester butanoic acid and alpha-famesene. These compounds were preliminarily confirmed to be accountable for attracting Tetraychus vienneis. This finding may lead to identify biological species for preventing and treating Tetraychus vienneis.
