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The phase transformation of zirconia from tetragonal to monoclinic is characterized by UV Raman spectroscopy, visible Raman spectroscopy, and XRD. Electronic absorption of ZrO 2 in the UV region makes UV Raman spectroscopy more sensitive at the surface region than XRD or visible Raman spectroscopy. Zirconia changes from the tetragonal phase to the monoclinic phase with calcination temperatures elevated and monoclinic phase is always detected first by UV Raman spectroscopy for the samples calcined at lower temperatures than that by XRD and visible Raman spectroscopy. When the phase of zirconia changes from tetragonal to monoclinic, the slight changes of the phase at very beginning can be detected by UV Raman spectroscopy. UV Raman spectra clearly indicate that the phase transition takes place initially at the surface regions. It is found that the phase change from tetragonal to monoclinic is significantly retarded when amorphous Zr(OH) 4 was agglomerated to bigger particles and the particle agglomeration of amorphous zirconium hydroxide is beneficial to the stabilization of t-ZrO 2 phase.

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Framework titanium in Ti-silicalite-1 (TS-1) zeolite was selectively identified by its resonance Raman bands using ultraviolet (UV) Raman spectroscopy. Raman spectra of the TS-1 and silicalite-1 zeolites were obtained and compared using continuous wave laser lines at 244, 325, and 488 nm as the excitation sources. It was only with the excitation at 244 nm that resonance enhanced Raman bands at 490, 530, and 1125 cm -1 appeared exclusively for the TS-1 zeolite. Furthermore, these bands increased in intensity with the crystallization time of the TS-1 zeolite. The Raman bands at 490, 530, and 1125 cm -1 are identified as the framework titanium species because they only appeared when the laser excites the charge-transfer transition of the framework titanium species in the TS-1. No resonance Raman enhancement was detected for the bands of silicalite-1 zeolite and for the band at 960 cm -1 of TS-1 with any of the excitation sources ranging from the visible to UV regions. This approach can be applicable for the identification of other transition metal ions substituted in the framework of a zeolite or any other molecular sieve.

Framework titanium atoms in titanium-substituted silicalite (TS-1) can be identified by UV resonance Raman spectroscopy since the associated Raman bands at 1125, 530, and 490 cm(-1) (see figure) are observed only when the charge transfer transition associated with the framework Ti atoms is excited by a UV laser. Thus, framework Ti atoms can be distinguished from nonframework Ti atoms and other defect sites. This method can be applicable to identifying transition metal atoms in the frameworks of other molecular sieves.

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Anodic aluminum oxide (AAO) membranes were characterized by UV Raman and FT-IR spectroscopies before and after coating the entire surface (including the interior pore walls) of the AAO membranes by atomic layer deposition (ALD). UV Raman reveals the presence of aluminum oxalate in bulk AAO, both before and after ALD coating with Al2O3, because of acid anion incorporation during the anodization process used to produce AAO membranes. The aluminum oxalate in AAO exhibits remarkable thermal stability, not totally decomposing in air until exposed to a temperature >900 degrees C. ALD was used to cover the surface of AAO with either Al2O3 or TiO2. Uncoated AAO have FT-IR spectra with two separate types of OH stretches that can be assigned to isolated OH groups and hydrogen-bonded surface OH groups, respectively. In contrast, AAO surfaces coated by ALD with Al2O3 display a single, broad band of hydrogen-bonded OH groups. AAO substrates coated with TiO2 show a more complicated behavior. UV Raman results show that very thin TiO2 coatings (1 nm) are not stable upon annealing to 500 degrees C. In contrast, thicker coatings can totally cover the contaminated alumina surface and are stable at temperatures in excess of 500 degrees C.

Atomic layer deposition (ALD) on anodic aluminium oxide (AAO) is shown to be a facile, flexible route to the synthesis of catalytic membranes with precise control of pore wall composition and diameters. The oxidative dehydrogenation of cyclohexane was shown to depend strongly on pore diameter and to be more specific than similarly active alumina powder catalysts.Micro and mesoporous catalytic materials, predominantly in the form of zeolites, have gained wide acceptance as industrial catalysts for oil refining, petrochemistry, and organic synthesis, particularly for molecules with kinetic diameters below 1 nm. Here we report the first demonstration that ultra-uniform inorganic catalytic membranes, synthesized using a combination of anodic aluminum oxidation (AAO) [1-4] and atomic layer deposition (ALD) (a facile, flexible functionalization route) [5][6][7], have novel catalytic properties. Atomic level control of both the pore diameter and the pore wall composition along the entire pore length offers catalyst environments that include larger pores than conventional mesoporous materials (for efficient in-diffusion of large/elaborate molecular precursors or feedstock molecules, and for out-diffusion of large/ elaborate product molecules), tailored channel sizes and wall compositions (including tailored channel surfaces ranging from hydrophobic to hydrophilic in nature), catalyst mobility constraints to hinder agglomeration, and flow control of reagents in and out of the catalyst.Mesoporous and microporous catalytic material syntheses are often approached in a ''one step '' process (e.g.,). In this paper, we present an approach based on two steps: production of a stable mesoporous scaffold and then carefully controlled modification of the scaffold, where each step can be optimized independently. A related two step synthesis method utilizing a wet chemical modification method has been reported [12]. The modification method described here is based on gas phase deposition allowing directed control of the pore wall composition and diameter.AAO membranes are an appealing scaffold with highly-aligned, parallel pores and narrow pore diameter distributions. Electrochemical conditions can be arranged to produce most probable pore diameters in the range 20-400 nm [1-4, 13, 14] and membrane thicknesses in the range 0.5 to >250 lm. Prior catalytic studies using AAO showed interesting yield enhancements, but were limited to unreleased (pore blocked) films [15][16][17][18]. Moreover, as-grown AAO membranes suffer from poorly defined pore wall morphology and composition with significant (5%) amounts of incorporated electrolyte anions [19,20].For this work, highly-ordered, 70 lm thick AAO scaffolds produced in oxalic acid [13,14] are used. A typical plan view Secondary Electron Micrograph (SEM) of a scaffold is displayed in figure 1a. The hexagonal arrangement of pores (dark features) is clearly evident on this length scale; over longer distances the registry is less well defined. ALD was used to precisely control the chemical com...