2011, Vol.21, No.1

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

In this paper, firstly we have derived and presented the specific heat jump as a function of the critical temperature. Secondly, we have analyzed the sign and magnitude of the derived specific heat jump and predicted the expected experimental results. And lastly, we have compared the expected experimental results with the real experimental results. Theoretically derived specific heat jump is considerably compatible with the specific heat jump up and down phenomena of the YNi2B2C crystal. Especially, the remarkable theoretical prediction-that the specific heat would jump down during the normal state-to-superconducting state transition at extremely low temperatures-have been confirmed by the experimental results.

The re-crystallization process for recovering granular crystalline gypsum from phospho-gypsum have proposed. The process consists of two stages; at the first stage, needle-like fine gypsum is recovered with under-product of 325 mesh wet screening after the speedy hydration of dehydrated phospho-gypsum, and at the second stage, granular crystalline gypsum is recovered with upper-product of 325 mesh wet screening after dehydration and re-crystallization of the needlelike fine gypsum in Na2SO4 solution. This paper is mainly focused on the influence of dehydration time, cooling speed of temperature and re-crystallization temperature on the recovery of granular crystalline gypsum. And the re-crystallization velocity of needle-like fine gypsum at room temperature and the variation of Ca 2+ concentration of gypsum slurry during over all re-crystallization process were also discussed.

7Li Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in Li4P2O7 and LiFePO4 materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of LiFePO4 as cathode material. Li4P2O7 and LiFePO4 were prepared by a solid-state reaction. The 7Li MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in Li4P2O7 system. The 7Li MAS NMR spectra of in Li4P2O7 indicate that the lithium local environments in Li4P2O7 were not changed in the temperature range between 27oC and 97oC. Through this work, we confirmed that the small amount of Li4P2O7 less than 5.0 wt% in LiFePO4 could be clearly measured by the 7Li MAS NMR spectroscopy at high spinning rate over than 11 kHz.