Spinel LiMn2O4 powders were prepared by solution combustion synthesis using nitrate and acetate salts as raw materials and urea as fuel. The phase composition of as-synthesized powders was identified by XRD and the microscopic structure was examined by SEM. Single-phase spinel LiMn2O4 was prepared when acetate salts were used, and the incorporation of nitrate salts resulted in the formation of Mn2O3. The products consisted of slight agglomerations of fine particles with the size of 50-200nm. It was found that the addition of nitrate salts increased the reaction rate and the yield of LiMn2O4 was depressed when more nitrate salts were used as a reactant.

Spinel LiMn2O4 was prepared by solution combustion synthesis. The effect of fuel content and calcination procedure on phase composition and microscopic structure of LiMn2O4 was studied. X-ray diffraction patterns showed that fuel content had no obvious influence on the grain size and phase purity of LiMn2O4. Higher calcination temperature led to higher phase purity, lager grain size, and better crystallization of resultant LiMn2O4. Below 600°C the effect of calcination time was inconspicuous, which became notable above 700°C. Scanning electron microscope images showed that nanocrystalline LiMn2O4 was obtained when the calcination temperature was lower than 600°C and the grain size increased at higher temperatures.

No abstract

Spinel LiMn2O4was synthesized by a solution combustion synthesis using lithium and manganese acetate as raw materials and acetic acid as fuel. The phase composition and micro morphology of the as-prepared products were determined by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD analysis suggested that the main phase of the products was LiMn2O4, but there was little impurity Mn2O3in the products. The relative content of Mn2O3was decreased gradually when the molar ratio of Li:Mn: acetic acid increased from 0.5:1:0.5 to 0.5:1:2, but increased again when the molar ratio of Li:Mn: acetic acid was 0.5:1:2.5. The purest product could be prepared when the molar ratio of Li:Mn: acetic acid=0.5:1:2. SEM investigation indicated that the typical crystal structure could not be investigated from the as-prepared products, and the particles were badly agglomerated. Electrochemical performance tests indicated that the specific capacity of the purest product was 108mAh/g. After 30 cycles, the capacity faded only 22% at the current density of 50mA/g, and the average charge/discharge efficiency was ~96%. At the current density of 75mA/g, the initial specific capacity of the purest product was only 72mAh/g, but after 30 cycles, the capacity retention was >92%, exhibiting a good cycling performance.

DEFORM is a software used for FEA (Finite Element Analysis) simulation. By using this software, I take a research on the procedure when a steel billet with defect of artificial loosening is drawn out in a simulated environment. Then I build a FEA model about the loosening and compaction of a large-sized rotor and stimulate the procedure in accordance with current craft card involving rotor forging. Finally, I get a result: the relative density of the loose area reaches up to 85% after the first drawing-out process (note: forging ratio 1.47). After simulating the procedure of chamfering on a billet which has been already drawn out, I found that chamfering had little substantial impact on the its loosening and compaction.