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Membranes consisting of uniform and vertically organized mesopores are promising systems for molecular filtration because of the possibility to combine high-flux and high-rejection properties. In this work, a new generation of mesoporous silica membranes (MSMs) have been developed, in which an organized mesoporous layer is directly formed on top of a porous ceramic support via a Stöber-solution pore-growth approach. Relevant characterization methods have been used to demonstrate the growth of the membrane separation layer and the effect of reaction time and the concentration of the reactants on the microstructure of the membrane. Compared to previous studies using the evaporation-induced self-assembly method to prepare MSMs, an important increase in water permeability was observed (from 1.0 to at least 3.8 L m -2 h -1 bar -1 ), indicating an improved pore alignment. The water permeability, cyclohexane permporometry tests, and molecular cut-off measurements (MWCO ≈ 2300 Da) were consistent with membranes composed of 2-3 nm accessible pores.

The structural evolution of sol-gel derived lead zirconate titanate (PZT) precursor films during and after physical drying was investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), selected area electron diffraction (SAED), and time-resolved X-ray diffraction (XRD). Films were deposited from initial 0.3 mol/dm(3) precursor sols with varying hydrolysis ratios. Zr-rich grains of 1-10 nm size, embedded in a Pb-, Zr-, and Ti-containing amorphous matrix were found in as-dried films. The Zr-rich regions were crystalline at hydrolysis ratios [H(2)O]/[PZT] < 27.6, and amorphous at ratios > 100. X-ray diffraction analysis of PZT and zirconia sols revealed that the crystalline nanoparticles in both sols are identical and are probably composed of nanosized zirconium oxoacetate-like clusters. This study demonstrates that time-resolved X-ray diffraction combined with electron energy loss spectroscopy mapping is a powerful tool to monitor the nanoscale structural evolution of sol-gel derived thin films., (© 2011 American Chemical Society)

Using a combination of TEM and XPS, we made an analysis of the complex high-temperature annealing effect on ultrathin titanium deuteride (TiD(y)) films evaporated on a Si(100) substrate and covered by an ultrathin palladium layer. Both the preparation and annealing of the TiD(y)/Pd bi-layer films were performed in situ under UHV conditions. It was found that the surface and bulk morphology of the bi-layer film as well as that of the Si substrate material undergo a microstructural and chemical conversion after annealing and annealing-induced deuterium evolution from the TiD(y) phase. Energy-filtered TEM (EFTEM) mapping of cross-section images and argon ion sputter depth profiling XPS analysis revealed both a broad intermixing between the Ti and Pd layers and an extensive inter-diffusion of Si from the substrate into the film bulk area. Segregation of Ti at the Pd top layer surface was found to occur by means of angle-resolved XPS (ARXPS) and the EFTEM analyses. Selected area diffraction (SAD) and XPS provided evidence for the formation of a new PdTi(2) bimetallic phase within the top region of the annealed film. Moreover, these techniques allowed to detect the initial stages of TiSi phase formation within the film-substrate interlayer.

The kinetics of thermal evolution of deuterium from ultrathin TiD(y)/Pd bilayer films has been studied by means of thermal desorption mass spectrometry (TDMS). Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, we made a study of the complex structural and chemical transformations of the TiD(y)/Pd film as a result of TDMS-induced evolution of deuterium and simultaneous annealing of this film. Both preparation and TDMS processing of the TiD(y)/Pd bilayer films were performed in situ under UHV conditions. It was found that the high-temperature TDMS processing of an ultrathin TiD(y)/Pd film, which was carried out in a relatively short time, leads to a significant film structure transformation. Energy-filtered TEM mapping of cross-section images and EDX analysis revealed extensive interdiffusion of Ti and Pd within the Ti-Pd bi-layer film. This process leads to a progressive change in chemical composition within the surface and subsurface area of the film during the TDMS processing. As the temperature of TDMS heating increases, segregation of Ti at the Pd top layer surface becomes significant. As a result, the kinetics of deuterium desorption is progressively changed during TDMS; at lower temperatures, the kinetics is limited by recombinative processes at the Pd surface, at temperatures beyond 500 K, it becomes dominated by interdiffusion of Ti into the Pd surface.

Using a combination of scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction and X-ray photoelectron spectroscopy (XPS), we made a comparative study of the high-temperature annealing impact on thin titanium deuteride (TiD(y)) films covered by an ultrathin Pd layer, and on Ti/Pd bilayer films. The bilayer films were prepared under ultrahigh vacuum conditions and were in situ annealed using the same annealing procedure. It was found that the surface and the bulk morphology of both films undergo different annealing-induced transformations, leading to an extensive intermixing between the Ti and Pd layers and the formation of a new PdTi(2) bimetallic phase. Energy-filtered TEM imaging and energy-dispersive X-ray spectrometry analysis, as well as XPS depth profiling all provided evidence of a different distribution of Pd and Ti in the annealed TiD(y)/Pd film compared with the annealed Ti/Pd film. Our results show that thermal decomposition of TiD(y), as a consequence of annealing the TiD(y)/Pd film, modifies the intermixing process, thereby promoting Ti diffusion into the Pd-rich top layer of the TiD(y) film and thus providing a more likely path for the formation of the PdTi(2) phase than in an annealed Ti/Pd film.

Thin titanium deuteride (TiD(y)) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiD(y) layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiD(y) films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiD(y) films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiD(y) (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiD(y) films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiD(y) film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiD(y) interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiD(y) and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiH(y) film. The XPS valence-band spectra of the Pd/TiD(y) interface reveal electronic features characteristic of a Pd-Ti bimetallic structure.