Key Engineering Materials Vols. 434-435

Abstract: In this paper, the green RBSC was prepared by gel casting process. The influences of the monomer content (MBAM and AM) and monomer ratio (MBAM to AM) on the flexural strength were investigated. The results indicated the flexural strength of green body was up to 8MPa and the micro- structures were homogeneous. The green RBSC bodies were machined by CNC grinding machine with diamond-coated grinding tools. Machining tests showed the green component could be machined without appended defects. It was found that green machining as a ‘top-down’ approach was a potential alternative for the rapid fabrication of complex-shaped ceramics, especially for some one-of-a-kind products.

Abstract: Based on the Al2O3-ZrO2-SiO2 system, the conventional pre-sintering samples were reheated by microwave to investigate the influence of microwave to the thermodynamic equilibrium and phase equilibrium relationships. It was found that microwave can accelerate transitions to thermodynamic equilibrium. The phase equilibrium of the samples prepared by microwave heating was identical with the traditional phase diagram. In addition, the amount of tetragonal zirconia in the prepared samples remained constant as the microwave heating time prolonging. All of the observed phenomenon can be explained by microwave nonthermal effects.

Abstract: A solvothermal method to synthesize barium titanate nanoparticles is employed. In this method many raw materials such as oleic acid, surfactant, sodium hydroxide, alkali barium acetate, alcohol, tetrabutyl titanate are used. When the samples are collected, oleic acid which has mush an account will cover the whole particles. To make the samples cleaner, nitric acid is used to transition oleic acid to elaidic acid which is lighter than water then it will float up to be removed. In the progress to wash off the oleic acid the particles were found to reunite unusually: bigger and cubic particles are formed and the shape seems like single crystal but they are reunitions indeed, we used HTEM to prove this. It means self–assembling might happen through the progress, the spontaneous polarization orient, polarity of molecules will affect this progess.

Abstract: Lanthanum aluminate powders were prepared via a polymer complexing method by using PEG as complexing agent. The LaAlO3 powder was characterized by XRD and SEM. The influence of processing parameters such as molar ratio of PEG monomers to metal cations (PEG:Men+) and aging process on the phase purity and powder morphology were investigated. The calcined powder with the PEG:Men+ ratio larger than 2:1 may contain the secondary phase, namely La2O3. The formation of phase pure LaAlO3 powder occurs when the PEG:Men+ ratio is 1:1 or enough gelation time is involved. Although the phase pure powder is obtained by this PEG method, all the single phase LaAlO3 powders are found to have seriously aggregated particles. The weakly agglomerated powder morphology is only found in the powders which contain La2O3.

Abstract: The present article reports the results of studies related to the synthesis of nano-crystalline alumina powder by combustion process using different combustion aids. Aluminium nitrate as oxidant and urea as fuel were used as reagents. Starch and ammonium nitrate were compared as combustion aids. The results showed that employment of starting fuel with combustion aids resulted in synthesizing nano-crystalline alumina powder with small crystalline size (<20 nm) and fine agglomerates. By using combustion aid, the energetics of the combustion reaction has been changed. The different selection of combustion aid determines the characteristics of the as-synthesized powders.