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This research focused on the synthesis of ultrafine Ni–Co composite powder prepared using a freeze-drying technique. In the process of freeze-drying, the Ni–Co powder was prepared by freeze-drying the precursor from simple NiC 2 O 4 and CoC 2 O 4 powders. Thermal decomposition of the amorphous freeze-dried precursor powder produced the ultrafine Ni–Co composite powder. To assure process control and product characterization, the freeze-dried precursor and the final products were analyzed by means of XRD, SEM, TEM, and IR. The results showed that the freeze-dried powder existed in a non-hygroscopic and non-crystalline state. The final product of the experiments was a Ni–Co composite powder, which existed in the form of a single crystalline state and represented fine, homogeneous, spherical particles, reaching a size range of approximately 40–70 nm. The freeze-dried powder was composed of [Ni(NH 3 ) 6 ] 2+ and [Co(NH 3 ) 6 ] 3+ .

Nanoparticles of cerium oxide were prepared by common precipitation method using cerium nitrate solution and ammonia reagent. Cerium oxide particles with different morphologies were synthesized through adjusting pH values of the solution. TEM and BET results showed that spherical crystal was gained in acid solution, with the specific surface of 148.1944 m2·g−1. The cerium oxide appeared in the form of spherical and rod-like grains under neutral condition, and the specific surface changed to 114.7975 m2·g−1. Moreover, in alkaline solution, cerium oxide powders were exhibited in rod-like form with the specific surface of 106.2465 m2·g−1. Precipitation formation mechanism of different morphologies was also discussed, which followed decomposition precipitation mechanism and topology reaction mechanism in acid and alkaline solution, respectively.

Fluorocarbon-modified silica membranes were deposited on gamma-Al2O3/alpha-Al2O3 supports by the sol-gel technique for hydrogen separation. The hydrophobic property, pore structure, gas transport and separation performance, and hydrothermal stability of the modified membranes were investigated. It is observed that the water contact angle increases from 27.2+/-1.5 degrees for the pure silica membranes to 115.0+/-1.2 degrees for the modified ones with a (trifluoropropyl)triethoxysilane (TFPTES)/tetraethyl orthosilicate (TEOS) molar ratio of 0.6. The modified membranes preserve a microporous structure with a micropore volume of 0.14 cm3/g and a pore size of approximately 0.5 nm. A single gas permeation of H2 and CO2 through the modified membranes presents small positive apparent thermal activation energies, indicating a dominant microporous membrane transport. At 200 degrees C, a single H2 permeance of 3.1x10(-6) mol m(-2) s(-1) Pa(-1) and a H2/CO2 permselectivity of 15.2 were obtained after proper correction for the support resistance and the contribution from the defects. In the gas mixture measurement, the H2 permeance and the H2/CO2 separation factor almost remain constant at 200 degrees C with a water vapor pressure of 1.2x10(4) Pa for at least 220 h, indicating that the modified membranes are hydrothermally stable, benefiting from the integrity of the microporous structure due to the fluorocarbon modification.