ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ under a pressure of 3.6 GPa. As the pressure increased to 3.9 GPa, the ZrSiO4 formation temperature was reduced to 815 ℃. The formation temperature for coesite was 990 ℃ under 3.9 GPa. The lower formation temperature for ZrSiO4, as compared to that for coesite, provided an experimental evidence that the coesite in the Earth＇s surface usually occurs as inclusions in ZrSiO4.
The cathode material Pr0.7Sr0.3Co1-yCuyO3-δ (y=0.05～0.3) was synthesized by a sol-gel method. X-ray diffraction indicated that the samples with y≤0.2 were single phase orthorhombic perovskite structure, but in the case of y=0.3, traces of a second phase were observed. The unit cell volumes increased with increasing copper content. The electrical conductivity decreased gradually with increasing Cu addition. The investigation of the electrochemical performance suggested that the sample with y=0.1 exhibited the lowest overpotential in all prepared Pr0.7Sr0.3Co1-yCuyO3-δ. With Pr0.7Sr0.3Co0.9Cu0.1O3-δ cathode and porous NiO/Ce0.8Sm0.2O1.9 anode, the single cell based on SDC thin film electrolyte was obtained by a simple dry pressing process. Maximum power densities of the cell were 406 and 481 mW·cm-2 at 700 and 750 ℃, respectively.
With the help of high-energy mechanical milling and a-SiO2 as the initial material, we investigated the synthesis of coesite at a high temperature and high pressure under the condition of adding a certain amount of hard Fe filling. The synthetic samples were measured by XRD and Raman spectroscopy. The results show that a small amount of small-sized coesite can be obtained under 2.5 GPa and 973 K.
WANG De-junLIU Xiao-meiZHU Cheng-junYAN Duan-tingLIU Fu-linSU Wen-hui
Ce0.85Sm0.15O1.925 （SDC） and La0.9Sr0.1Ga0.5Mg0.2O2.85 （LSGM） were synthesized using Glycine-Nitrate Process （GNP）, and the composite electrolytes were prepared by mixing SDC and LSGM. An X-ray diffraction pattern indicated that the mixture of SDC and LSGM consisted of their original phases after heating at 1450 ℃ for 10 h. The electronic conductivity of SDC-LSGM composite electrolytes were measured by direct current polarization method using Hebb-Wagner ion blocking cell at 700-800 ℃ in the oxygen partial pressure range of 104-10-20 MPa and compared with the results of SDC. Typical polarization curves, which were theoretically predicted, were observed on all the samples. The slopes of lgσe-lgPo2 plot for all the composite electrolytes agreed with the theoretically predicted value of-1/4 at some intermediate oxygen partial pressures and -1/6 at low oxygen partial pressure. The electronic conductivity of SDC-LSGM composite electrolytes decreased with the increase in LSGM content, whereas the ionic transport number ti of all the samples increased with the increase in LSGM content.
The mixtures of a-quartz and graphite powder with different mass ratios were, respectively, high-energetically mechanically milled and then treated under high pressure and high temperature. The influences of carbon content on the synthesis conditions of coesite were investigated. The experimental products were characterized by XRD, TEM, and Raman spectrometry. The results show that the existence of carbon can obviously inhibit the formation of coesite, and the higher the carbon content of the initial material, the higher the pressure for forming coesite.
WANG De-junLIU Xiao-meiZHU Cheng-junYAN Duan-tingLIU Yi-xinSUN YingLIU Fu-linSU Wen-hui
