A.A.Hanna
,
M.Sh.Khalil
,
H.I.Saleh
,
A.F.Ali
材料科学技术（英文）
A series of chemical compositions based on Cr, Fe and O with Zn as a partially substituting ion has been prepared in the general formula ZnxCr1-xFe2O by coprecipitation method using NH4OH as the precipitating agent at pH=10.3. The prepared samples were identified by both thermal analysis (DTA and TGA) and X-ray diffraction (XRD). It was found that no single phase was obtained for any of the studied compositions but a mixture of different phases was observed, depending on the molar percentage of zinc ion substitution as well as on the sintering temperature. The temperature dependence of the electrical conductivity, σ, of the prepared samples was plotted between 25 and 680℃. It was observed that the electrical conductivity increased with temperature for both samples with x=0.00 and 0.80 Zn ion content while it was nearly temperature independent for samples with intermediate Zn concentration x=0.2 and 0.5 mol fraction. The activation energy, Ea, calculated from the linear relation, lgσ-1000/T for the final mixtures (sintered at 1300℃) was calculated.
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A.A.Hanna
,
A.I.M.Akarish
,
S.M.Ahmed
材料科学技术（英文）
Phosphogypsum (PG) derived from the dissolution of phosphate ore in H2SO4 has been characterized by using chemical and thermogravimetric analyses, X-ray diffraction and infrared spectrum to give an idea about the future utilization of this waste material. The PG under the investigation was free from the radioactive elements and Cd and contained about 141×10-6 rare earth elements in total, which favors the utilization of this material. PG was formed mainly of gypsum, little anhydrite and quartz and rare kaolinite. It exhibited two large endothermic peaks corresponding to the dehydration of the sample and a small one which may be attributed to the liberation of the residual water that may be found in the soluble anhydrite. Also, an exothermic peak was observed which may be related to the transformation of soluble (γ-anhydrite) to insoluble β-anhydrite. PG exhibited the same absorption bands as that observed for chemical CaSO4.2H2O and natural gypsum samples besides the appearance of a weak band at 840 cm-1 which characterizes the vibration of H2PO4- group.
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