AlCl(3) solution was analyzed at concentrations from 0.02 to 100 mM using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS), and the dissolution state of aluminum ions is discussed. Results obtained using ESI-Q-MS were consistent with those obtained using (27)Al nuclear magnetic resonance ((27)Al NMR). Aluminum species existed mainly as positively charged monomeric aluminum hydroxide coordinated with several water molecules in solution. The complexation of chloride ions by aluminum ions differed between the positive and negative ion modes. Chemical reactions that partially modified chemical forms of species through ESI-Q-MS measurement were also observed. In the same aluminum chloride solution, using ESI-TOF-MS and ESI-Q-MS/MS studies, the disagreement of the reports is discussed. It is concluded that ESI-TOF-MS might show also the gas-phase reaction in the mass spectrometer but the dissolution state of aluminum species can be shown by ESI-Q-MS.
The application of electrospray ionization mass spectrometry (ESI-MS) for aluminum speciation in the positive and negative ion modes was discussed. Aluminum nitrate, perchlorate and sulfate solutions were measured by ESI-MS. In the positive ion mode, aluminum species containing anions (Al-L; L=NO3, ClO4 and SO4) were identified, while [Al(OH)2(H2O)n]+ (n=2-4) were the main species. The affinity of the anions with Al3+ estimated by ESI-MS was consistent with the hardness of the anions (hard and soft acids and bases principle) and the results from 27Al nuclear magnetic resonance studies. This indicates that the results observed from the positive ion mode preserved the chemical state of aluminum in the solution. In the negative ion mode, [Al(OH)4-nLn]- (n=0-2, L=NO3, ClO4) were the main species, which were considered to be converted from positive aluminum species, [Al(OH)(H2O)n]+ (n=2-4), by the successive addition of anions. Anions did not only attach to one aluminum ion but also bridged two aluminum ions. In Al2(SO4)3 solution, the behavior of SO4(2-) in the negative ion mode differed from that of NO3- and ClO4-. This may reflect the affinity of SO4(2-) with Al3+ in the solution or in the mass spectrometer or in both. Finally, detection mechanisms for the aluminum species in the solution are proposed for both the positive and negative ion modes. It is shown that ESI-MS can be used to observe the interaction between Al3+ and anions. We show the importance of the interpretation of the results by ESI-MS for obtaining new information of the metal species in the solution.
We have developed a new ecofriendly fabrication process for porous ceramics using hydraulic alumina (HA) and water. In the present study, we fabricated porous alumina ceramics using this new process. A boehmite gel 3D network was formed by the hydration of HA in HA slurry. The HA slurry was hardened by the formation of this 3D network. Even without the addition of an organic binder, green bodies containing the 3D network demonstrated high compressive strength. Furthermore, the water acted as a fugitive material in the green bodies.Consequently, the open porosity of sintered alumina ceramics could be controlled over a wide range of 56.6 69.1÷ by addition of water (ratio of water to HA powder: 1.0 to 2.0 by weight) without the use of organic fugi tive materials. The results of evolved gas analysismass spectrometry measurements showed that the emissions from the hardened green body mostly consisted of water. Consequently, the new fabrication process for porous alumina ceramics was confirmed to be ecofriendly.
A slurry used to produce dense green compacts by slip casting should exhibit low viscosity, high solids content, and good dispersion. Slurries with good characteristics were produced in the present study by adding oligosaccharide alcohol to an Al 2 O 3 slurry with an NH 4 ؉ salt of poly(methacrylic acid) (NH 4 ؉ -PMA). The role of NH 4 ؉ -PMA and oligosaccharide alcohol in the Al 2 O 3 slurry was examined by DTA, -potential measurement, high-pressure liquid chromatography, and viscometry. The viscosity of the slurry with NH 4 ؉ -PMA and oligosaccharide alcohol was lower than that of the slurry with NH 4 ؉ -PMA at a high solids content. Oligosaccharide alcohol did not interact with the Al 2 O 3 surface. However, the Al 2 O 3 slurry with NH 4 ؉ -PMA was influenced by the addition of oligosaccharide alcohol. We found that the dispersibility of the slurry was greatly improved by adding oligosaccharide alcohol. The transmittance of the Al 2 O 3 ceramics produced by slip casting using the slurry with both NH 4 ؉ -PMA and oligosaccharide alcohol was higher than that of ceramics produced by slip casting using the slurry with NH 4 ؉ -PMA alone. The increased optical property resulted from low viscosity, which was attributed to the addition of oligosaccharide alcohol, at a high solids content.
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