A study of phosphate adsorption by different temperature treated hydrous cerium oxides

An alkaline precipitation method was introduced to produce hydrous cerium oxides.The prepared powder was characterized by Brunauer-Emmett-Teller（BET） nitrogen adsorption-desorption,X-ray diffraction（XRD）,Fourier transform infrared（FTIR） spectrometry,and thermal gravimetry（TG） approaches.The adsorbent has a chemical formula of CeO2·nH2O（n 2） and a cubic fluorite-type structure after high temperature treatment.Adsorption capacity of different temperature treated hydrous cerium oxides does not directly correlate with BET specific surface area.Phosphate adsorption isotherms follow the Langmuir equation below the treatment temperature of 800°C.Phosphate adsorption causes no change on the structure of a hydrous cerium oxides,and no signs of CePO4 precipitates are found.The ion-exchanging structure of hydrous cerium oxide plays a fundamental role in phosphate adsorption.The structure is highly temperature resistant and forms adsorption sites which adsorb both water and some anions.Complete loss of adsorption ability cannot be achieved unless the treatment temperature is higher than 1200°C.Mechanism study shows that the adsorption of phosphates is mainly an anion-exchange process.

Influence of silane coupling agent on the conversion film forming of galvanized steel treated with cerium salt

The influence of silane coupling agent on the film forming of galvanized steel treated with cerium salt was studied by scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）, and the corrosion resistance of conversion films was analyzed by electro interstitial scanning （EIS）. The results show that silane coupling agent KH-570 has significant influence on the compactness and homogeneity of cerium conversion films, and the process of film forming is promoted by increasing the content of tervalent and tetravalent cerium oxide. The impedance value of the cerium conversion film, especially modified with KH-570, is greater than that of the base metal, which reveals that it is necessary to add silane coupling agent to the film-forming solution in order to improve the corrosion resistance of the conversion film.

XPS characterization and corrosion resistance of cerium-treated magnesium coatings

Cerium conversion treatment was applied on magnesium coatings in a solution containing CeC13. The composition ot the cenum conversion layer on magnesium was investigated using X-ray photoelectron spectroscopy （XPS）, It was revealed that the composition predominately consisted of a three-valent state cerium compound with a relative abundance around 90%. Some of Ce^3＋ was oxidized to Ce^4＋. Electrochemical impedance spectroscopy results revealed that the total impedance of cerium-treated samples increased for a short immersion time in NaC1 solution before coating deteriorating. This deterioration was due to the coating porosity increasing and the breakdown of the conversion layer

Preliminary Study on Partially Metamict Allanite from Guposhan Granites

In this paper allanite from Guposhan granite complex was analysed with X-ray powder diffraction, infrared spectroscopy and Mossbauer spectroscopy, etc. and proved to be in a partially metamict state. However, after heating at 800 °C for 4h the allanite could be recovered to its crystalline state. Although the partially metamict allanite was anisotropic under polarizing microscope, it exhibited a few diffraction lines with lower intensity in its X-ray powder diagram than that in the crystalline state. Infrared spectra of the allanite showed lack of several strong absorption peaks and the bands shift into low frequency region. The characteristic Mossbauer spectrum parameters, I.S. values, of the allanite obviously decreased, while Q.S. values increased except for that of Fe3+ at M3 site. The metamictization of allanite results mainly from its lattice damage caused by decay of radioactive elements in the lattice. The partial metamictization of the allanite is not related with content of rare earth elements in it.

Effects of annealing on luminescence efficiency of large-size YAG:Ce crystal grown by temperature gradient techniques

YAG：Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique （TGT）. The effects of annealing on the luminescence efficiency of YAG：Ce crystal are investigated, and the optimal annealing temperature and atmosphere are obtained. The mechanism of variation behavior of the luminescence efficiency of YAG：Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed.

Spectral properties and energy transfer in YAlO_3 crystals doped with Ce ions and Mn ions

We report the luminescence properties and decay profiles of Ce：YAlO3, Mn：YAlO3, and Ce,Mn：YAlO3 crystals grown by Czochralski method. The spectroscopic properties show that both Mn2＋ ions and Mn4＋ ions exist in Mn：YA103 and Ce,Mn：YAlO3 crystals. The Mn2＋ ions have a broad emission band of 60 nm in Mn-doped YAlO3 crystal at 530 nm. The luminescence spectra also indicate that there is significant energy transfer between Ce3＋ and Mn4＋ in Ce,Mn：YA103 crystal. Because of the energy transfer, the first decay component in Ce,Mn：YAlO3 decreases from 24.5 to 10.8 ns, which is much faster than that of Ce：YAlO3.

Structure and heat capacity of the NaCeF_4 compound

This work continued our general research program on obtaining metallic cerium by electrodeposition from NaCeF4 dis-solved in different molten fluorides. The structure of NaCeF4 （cubic or hexagonal depending on the way of preparation） was estab-lished by DTA analysis, IR spectra and X-ray diffraction. The heat capacity （Cp） of NaCeF4 was measured by differential scanning calorimetry in the temperature range of 300-1093 K using the“step-method”. The Cp was fitted by an equation with a satisfactory re-sult. Heat capacity was compared with that calculated from the Neumann-Kopp rule （NKR） and the deviations observed were consis-tent with the stability of the NaCeF4 compound.