Chloride-, sulfate-, and perchlorate-exchanged forms of hydrotalcite have been prepared and their layer spacings determined after equilibration in hydrous atmospheres and after heat-treatments up to the temperature of decomposition in the range 300–400°C. The initial carbonate form of hydrotalcite and also brucite, for purposes of comparison, have been similarly studied. Only chloride-hydrotalcite and brucite exhibit a single phase stable to the decomposition temperature. The other anionic forms exhibit various phases with different layer spacings which are interpreted in terms of the size, orientation, and stability of the anions and, in some cases, the presence of additional water. A regularly interstratified form of sulfate-hydrotalcite (layer spacing = 19.80 Å) is obtained at room temperature and relative humidity <50%; at higher humidities, a fully hydrated phase is obtained, and at 50°C a collapsed form is obtained. In the preparation of perchlorate-hydrotalcite, an interstratified phase (layer spacing = 17.0 Å) was recognized with alternating carbonate and Perchlorate layers, although the evidence is less certain.

Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

We have measured the growth rate of silicon nanowires (SiNWs) in the diameter range of 3 to 40 nm (8.4 nm on average), which were grown by chemical vapor deposition (CVD) at temperatures between 365 °C and 495 °C. It is found that SiNWs with smaller diameters grow slower than those with larger ones, and a critical diameter at which growth stops completely exists. The growth rate of the thinner SiNWs stronger depends on growth temperature than that of thicker ones in previous studies. We discuss the dependence by thermodynamics theory.

We have shown previously the results from out-of-plane and in-plane X-ray scattering /diffraction measurements together with transmission electron microscope and X-ray reflectance measurements and shown that they are effective in characterization of a periodic porous silica low-k film [1]. In the present work, we report the results on pore-size distribution, pore-diameter anisotropy, and size and macroscopic isotropy of domain structure.

In a simulated engineered barrier system consisting of a simulated HLW glass doped with Pu, a compacted bentonite and water under reducing conditions, migration tests of Pu from the glass into the bentonite through water were performed. The following results were obtained: (1) The presence of bentonite enhances the glass dissolution while it has no remarkable influence on the concentration of Pu dissolved species in the solution. (2) Only a small part of the leached Pu, which may correspond to the dissolved species, can diffuse into the bentonite with the apparent diffusion coefficient of 3×10−14m2/s. (3) Interactions between the glass and the bentonite have no remarkable influence on the diffusion of Pu.

The objective of this study is to evaluate the effects of water redox conditions and of the presence of iron corrosion products (magnetite) on the release of actinides from HLW glasses. Static corrosion tests were performed on a simulated HLW glass doped with Pu and Np in deionized water in the presence of magnetite under oxidizing and reducing conditions. The tests under oxidizing conditions were performed in air, while the tests under reducing conditions were performed in mixed gas (Ar+5%H2) atmosphere.

The following results were obtained: (1) The presence of magnetite enhances formation of colloids containing Pu and Np in the leachates under both redox conditions. (2) Redox conditions have no remarkable influence on the release of Pu. (3) The reducing conditions combined with the presence of magnetite cause a decrease in the concentrations of Np dissolved species, which is probably the result of the reduction of Np(V) to Np(IV) at the magnetite surface.

Silicide reaction between co-deposited TiSix layers and Si was studied. It was shown that an amorphous TiSix layer, with x − 0.5–1, deposited between amorphous Si and the Ti film led to a significant reduction in the observed C49→C54 TiSis transformation temperature. Amorphous TiSix layers generated by the pre-deposition of Ti and pre-annealing also enhanced the nucleation of the C54-TiSi2 phase. The efficacy of the interfacial TiSix layer was demonstrated on undoped and heavily doped n- and p-type α-Si, but was found to be absent on single crystal Si. Possible mechanisms of these phenomena are discussed.

Titanium disulfide films were prepared by plasma CVD. Crystalline orientation of layered TiS2 was investigated in relation to deposition rate, film thickness, and kinds of substrate. The preferred orientation of TiS2 basal plane perpendicular to substrates was obtained on the films with their thickness of more than ca. 10 μm at the deposition rate of ca. 4 ⊠ 10−3 g/cm2·h on all kinds of substrate. This orientation resulted in a large discharge capacity in a lithium battery cathode application.