Nanometric mixed iron-titanium oxides were prepared by mechanical milling with a view to determining their ability to act as anodic materials in lithium cells. At a TiO 2 /Fe 2 O 3 mole ratio of 0.4, a solid-state reaction occurs that leads to the formation of Fe 5 TiO 8 , which possesses a spinel-like structure; at lower ratios, however, the structure retains the hematite framework. Li/g-Fe 2 O 3 cells exhibit poor electrochemical reversibility; by contrast, Ti-containing electrodes possess improved cycling properties. Changes in the electrodes upon cycling were examined by X-ray photoelectron spectroscopy ͑XPS͒. XPS data confirm the participation of electrolyte in the electrochemical reaction and the different type of electrochemical reversibility exhibited by samples. Both processes were influenced by the presence of titanium. Titanium dioxide, in the presence of iron oxides, seems to be inactive to the electrochemical process. Based on the step potential electrochemical spectroscopy ͑SPES͒ curves and photoelectron spectra obtained, the presence of Ti increases the reversibility of the redox reactions undergone by the electrolyte during discharge/charge processes. The increased active-material/electrolyte/inactive-material interaction which is reported here offers new perspectives for the use of well-known transition oxides as anode materials in Li-ion batteries.

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An analytical procedure for the analysis of lipophilic extractives from wood and pitch deposits is described in this paper. It comprises a rapid gas chromatographic method that enables the analysis of a high number of samples in a short period of time. Short-length, high-temperature capillary columns with thin films and high temperature-programming rates were preferred for the rapid analysis of wood extractives since they enable elution and separation of compounds within a wide molecular mass range (from fatty acids to sterol esters and triglycerides) in the same chromatographic analysis in a short period of time. Several examples of analysis of extractives from pine and eucalypt woods and pitch deposits in an eucalypt kraft pulp, are shown. On the other hand, a simple fractionation method using solid-phase extraction (SPE) in aminopropyl cartridges is described for the preparative scale separation and fractionation of wood lipophilic extractives into major lipid classes. The SPE advantages include smaller sample and solvent requirements and ease of use compared to conventional solvent extraction techniques.

Magnetite, goethite, and lepidocrocite thin films have been electrochemically grown on titanium substrates by the anodic oxidation of ferrous ions in a 0.01 M FeSO 4 ͑NH 4 ͒ 2 SO 4 •6H 2 O + 0.04 M CH 3 COOK, pH 6.0, aqueous solution. It is demonstrated that the deposition potential can be used as a tool to tune the obtainment of the different pure phases of the iron oxide-oxyhydroxides thin films. Results of an exhaustive structural characterization, a morphological study, and X-ray photoelectron spectroscopy characterization are presented.

SummaryThe composition of lipophilic extractives in the chloroform soluble fraction of the acetone extract from Eucalyptus globulus wood has been examined. The lipid extract was fractionated by solid-phase extraction on aminopropyl-phase cartridges into four different fractions of increasing polarity. The total lipid extract and the resulting fractions were analyzed by gas chromatography and gas chromatography-mass spectrometry, using high temperature capillary columns. The main compounds identified included sterols, sterol esters, fatty acids, steroid ketones, hydrocarbons and triglycerides. Minor compounds such as fatty alcohols, mono-and diglycerides, waxes and tocopherols were also identified among the lipids from E. globulus wood.

ZnO/CdS core/shell nanorod arrays were fabricated by a two-step method. Single-crystalline ZnO nanorod arrays were first electrochemically grown on SnO(2):F (FTO) glass substrates. Then, CdS nanocrystals were deposited onto the ZnO nanorods, using the successive ion layer adsorption and reaction (SILAR) technique, to form core/shell nanocable architectures. Structural, morphological and optical properties of the nanorod heterojunctions were investigated. The results indicate that CdS single-crystalline domains with a mean diameter of about 7 nm are uniformly and conformally covered on the surface of the single-crystalline ZnO nanorods. ZnO absorption with a bandgap energy value of 3.30 ± 0.02 eV is present in all optical transmittance spectra. Another absorption edge close to 500 nm corresponding to CdS with bandgap energy values between 2.43 and 2.59 eV is observed. The dispersion in this value may originate in quantum confinement inside the nanocrystalline material. The appearance of both edges corresponds with the separation of ZnO and CdS phases and reveals the absorption increase due to CdS sensitizer. The photovoltaic performance of the resulting ZnO/CdS core/shell nanorod arrays has been investigated as solar cell photoanodes in a photoelectrochemical cell under white illumination. In comparison with bare ZnO nanorod arrays, a 13-fold enhancement in photoactivity was observed using the ZnO/CdS coaxial heterostructures.