Daniel Guay

Structural and electrochemical properties of Ti–Ru–Fe–O alloys prepared by high energy ball-milling

The structural and electrochemical properties of the Ti–Ru–Fe–O system have been studied over the whole ternary metal compositional range, keeping constant the oxygen content at 30 at.%. The phase diagram was explored systematically by varying the composition of the material along one of the following axes: (i) constant Ru content of 16 at. %; (ii) constant Ti/Ru ratio of 2; (iii) constant Ti/Fe ratio of 1.6. For O/Ti ratios equal or below unity, the most prominent peaks observed in the x-ray diffraction patterns belong to a B2 structure. For O/Ti ratio larger than unity, stable titanium oxide phases are formed, which coexist with a cubic Fe-like or hcp-Ru like phases depending on the Fe/Ru ratio. Powder compositions with stoichiometry close to Ti 2 RuFeO 2 are of interest due to good electrocatalytic properties, long-term stability, and low Ru content.

Modified chloroaluminium phthalocyanine: an organic semiconductor with high photoactivity

The crystalline structure of chloroaluminum phthalocyanine (ClAlPc) is modified upon contact with an acidic solution (pH equals 3) containing 0.1 M of salts like KCl, KBr, KClO3, KBrO3 or NaHSO3. This modification is labelled H type on the basis of the film Q band shape. Even though the absorbances in the Q band region are the same for all the salts used in this work, the photoactivity of the transformed films varies greatly from one salt to another. Indeed, under 35 mW cm-2 white light illumination, short circuit photocurrents range from 0.25 mA cm-2 (NaHSO3) to 1.0 mA cm-2 (KCl) depending upon the salt used during the modification of ClAlPc. It is shown by electron diffraction, that transformations of the H type induce the same changes for all salts in the interplanar distances of the ClAlPc crystallites. It is probably the result of anion penetration into the film to compensate for the protonation of the macrocycles. This anion uptake in the ClAlPc structure is demonstrated by X-ray absorption in the case of KBr for which Br...C distances of 2.6 angstrom and Br...N distances of 4.2 angstrom are measured. The most photoactive H type transformations of ClAlPc are obtained in the presence of KCl, KBr and KClO3. They have a common point: a similar film morphology. For these salts, the long axis of the crystallites lies along a direction parallel to the substrate surface while it was perpendicular before the transformation. After the H-type modification with NaHSO3, the film morphology is similar to the one of the as-sublimed ClAlPc. NaHSO3 transformed films display the lowest photoactivity even if the crystallinity of those films is comparable, if not better, than the crystallinity of ClAlPc transformed with KCl.