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The conditions for the synthesis of aluminum tungstate Al2(WO4)3 and aluminum niobate AlNbO4 were clarified using hydrothermal treatment and post-heating. Single-phase Al2(WO4)3 can be synthesized through the hydrothermal treatment of the starting materials at a mixing ratio of Al:W = 5:5 at 250 °C for 5 h and post-heating at 840 °C for 6 h. The AlNbO4 was synthesized using the same method, under a hydrothermal treatment of Al:Nb = 2:8 and post-heating. As a result of investigating the products under various mixing conditions based on the synthesis of pure Al2(WO4)3 and AlNbO4, Nb could not be doped into Al2(WO4)3, but W-doped AlNbO4 was synthesized. The electric conductivity was measured for several samples of sintered W-doped AlNbO4, and the results showed that the electrical conductivity was improved within a higher temperature region by doping with W.

In this study, detailed surface reaction mechanisms for CO/O2 system on Pt/Al2O3 and Rh/Al2O3 have been developed based on the measurements of gaseous and surface species. The conventional conversi...

Ultra-precision machining of single crystalline sapphire was performed using a polycrystalline diamond (PCD) micro-milling tool. Examination of the machining characteristics indicates that a high-quality surface with a nanometre-scale surface roughness can be obtained when the removed chips are thin enough to achieve ductile-mode machining. Although a high-quality surface was successfully machined, the surface roughness gradually deteriorated and the actual depth of the machined groove became shallower as the machining distance increased because of the build-up of material adhering to the surface of the tool. To retain the milling capabilities of the PCD tool, an electrochemical-assisted surface reconditioning process has been proposed. The reconditioning technique was found to be effective in removing the surface contaminant without causing damage to the edges of the tool.

In this study, reaction characteristics of C2H4/O2 and C3H6/O2 on practical Pt/Al2O3 monolith catalyst are investigated, and a simplified microkinetic surface reaction mechanism is proposed by taking the observed surface species and their occupied active surface sites into account. Importance of more than one active PGM surface site occupations at the adsorption step of C2H4 or C3H6 and multiple-sited stable intermediate CHx species are considered. Gas phase experimental results show that the light-off temperature as well as complete conversion temperature of both C2H4/O2 and C3H6/O2 mixture shift to lower side with the increase in oxygen concentration. The surface species analyses show the presence of stable intermediate CHx species and linearly adsorbed CO on the platinum surface. Numerically simulated light-off performance with the proposed reaction mechanism shows good agreement with the experimental results of C2H4/O2 and C3H6/O2. Moreover, simulation results also agree well with the additional experimental results with multiple gas compositions and validate the proposed detailed reaction mechanism.

In this study, gas entrainment characteristics of a diesel spray injected by a group of closely spaced two-orifices (group-hole nozzle) were investigated. Both free and wall-impinging sprays were considered. The gas entrainment characteristics of the group-hole nozzle spray were compared to those of single-hole nozzle sprays: one has the same total hole area with the group-hole nozzle, and the other has the same hole diameter. The gas entrainment characteristics of diesel sprays were investigated using a particle image velocitmetry technique coupled with a laser induced fluorescence technique (LIF-PIV technique). The spray tip penetration of the group-hole nozzle was the shortest among the applied nozzles in a free spray condition, while it was the longest in a wall-impinging condition. In the free spray condition, the gas entrainment of the spray was enhanced by the group-hole nozzle due to extensive momentum exchange with surrounding gas and superposed gas entrainment motion of the two-jets injected by the group-hole nozzle. After wall-impingement, the group-hole nozzle spray showed a stronger wall-jet vortex and increased gas entrainment compared to the single-hole nozzle sprays due to enhanced spray/wall interaction caused by the momentum interaction of the two-jets from the group-hole nozzle. Asymmetric shape of the group-hole nozzle spray resulted in an asymmetric gas velocity distribution of the spray both in the free and wall-impinging conditions.

This paper describes an investigation of the flame structure of wall-impinging diesel sprays injected by group-hole nozzles in a constant-volume combustion vessel at experimental conditions typical of a diesel engine. The particular emphasis was on the effect of the included angle between two orifices (0–15 deg. in current study) on the flame structure and combustion characteristics under various simulated engine load conditions. The laser absorption scattering (LAS) technique was applied to analyze the spray and mixture properties. Direct flame imaging and OH chemiluminescence imaging were utilized to quantify the ignition delay, flame geometrical parameters, and OH chemiluminescence intensity. The images show that the asymmetric flame structure emerges in wall-impinging group-hole nozzle sprays as larger included angle and higher engine load conditions are applied, which is consistent with the spray shape observed by LAS. Compared to the base nozzle, group-hole nozzles with large included angles yield higher overall OH chemiluminescence intensity, wider flame area, and greater proportion of high OH intensity, implying the better fuel/air mixing and improved combustion characteristics. The advantages of group-hole nozzle are more pronounced under high load conditions. Based on the results, the feasibility of group-hole nozzle for practical direct injection diesel engines is also discussed. It is concluded that the asymmetric flame structure of a group-hole nozzle spray is favorable to reduce soot formation over wide engine loads. However, the hole configuration of the group-hole nozzle should be carefully considered so as to achieve proper air utilization in the combustion chamber. Stoichiometric diesel combustion is another promising application of group-hole nozzle.

An evaporation process plays an important role on the combustion and emission formation processes in a direct injection (D. I.) gasoline engines. An experimental study was conducted on the evaporation process of the non-axisymmetric wall-impinging spray injected by the hole type injector for a D. I. gasoline engine. For the quantitative measurement of the vapor of the non-axisymmetric spray, the image processing technique using the Laser Absorption Scattering (LAS) principle was newly developed. The total amount of fuel vapor in the whole spray was obtained from the optical thickness image of the vapor and the Lambert Beer's law. The amount of fuel vapor in the wall-impinging spray is decreased compared with the free spray. In addition, the amount of fuel vapor is decreased as the distance between nozzle tip and the impingement wall is decreased.

Al 2 (MoO 4 ) 3 could be synthesized using two different methods, the traditional solid-state reaction and the hydrothermal reaction with post-heating. For preparation by the solid-state reaction, the starting materials were Al(OH) 3 and MoO 3 . TG-DTA results suggested that the reaction temperature of the solid-state reaction should be more than 973 K for crystallization of Al 2 (MoO 4 ) 3 . In contrast, the hydrothermal technique required crystallization at lower temperatures. SEM photographs indicate that while the former yields larger particles, the latter yields finer and well-shaped particles. It is hoped that Al 2 (MoO 4 ) 3 obtained by this method will find applications in the manufacture of ceramic devices.