Distribution Of Metal Cations Research Articles

Stoichiometric synthesis of pure NiFe2O4 spinel from layered double hydroxide precursors for use as the anode material in lithium-ion batteries

A pure NiFe 2 O 4 spinel has been prepared from an Ni–Fe 2+ –Fe 3+ –LDHs precursor under mild conditions for use as the anode material in Li-ion batteries. XRD, elemental analysis and a combination of TG–DTG–DTA and evolved gas mass spectrometry (EGMS) were carried out to characterize the calcined products. The main factors, affecting the electrochemical performance of the materials, were investigated. The material calcined at 700 °C for 3 h performs best with an initial discharge capacity of 1239 mAh g −1 and a reversible capacity of 701 mAh g −1 . The major advantage of the LDHs precursor method for the synthesis of NiFe 2 O 4 is that it uses a readily available precursor and affords a spinel with a small particle size and uniform distribution of metal cations, hence, resulting in a good electrochemical performance.

Light-switched metal-tunneling across a π-basic tube of 1,3-alternate-calix[4]arenes

Three 1,3-alternate-calix[4]arenes ( 1 ∼ 3 ) bearing two anthracenyl groups at one side and two propoxyl or ethoxyethoxyl groups at the other side were synthesized. The aim of this molecular design is to reversibly change the metal-binding ability of the anthracene-linked side through their photoinduced cycloaddition and reverse thermal decomposition. Since certain metal cations tend to pass from one side to the other side across a π-basic calix[4]arene tube, one can expect that a light-triggered metal tunneling for this molecule. In compounds 1 and 2 the rate of the metal tunneling was faster than the 1H NMR time-scale and the distribution of metal cations between two sides could not be determined. In a 3·Ag + complex the coalescence temperature appeared at −20°C and Ag + is bound to the ethoxyethoxyl side more than to the anthracenyl side in the dark. After photoirradiation Ag + was exclusively bound to the photocycloaddition side. These results support the view that compound 3 behaves like a mechanochemical “syringe”, the action of which is controllable by light.

Charting cation migration in a nickel exchanged zeolitic catalyst: An in situ rietveld X‐ray study

X‐ray diffractograms of an active zeolite catalyst (see figure) can yield information concerning the distribution of metal cations within the framework of the catalyst. When thse measurements are carried out during catalysis, the migration of the ions can be followed and the occupation of various sites examined. equation image

The number of sodium ions in the hydrogenation-active center of Y zeolite

1. The authors have determined the numbers of Na+ ions in the large structure gaps in decationized specimens of Y zeolite. 2. They derive an expression for the distribution of metal cations over the large gaps in Y zeolite. 3. On the basis of the proposed model, they show that the active center of NaY zeolite contains one or two Na+ ions.