Sol-gel ZrO2 coatings for chemical protection of stainless steel

ZrO₂ coatings deposited on 316 L stainless steel sheets were synthesized by sol-gel method using Zr(OC₃H₇)₄ as precursor and isopropanol, glacial acetic acid, and water as solvents for application with ultrasounds. Different solutions for dip-coating were prepared with compositions varying between 0.025 and 0.9 mol/dm³ of ZrO₂. X-ray diffraction shows that the films densified at 800°C are crystalline with a tetragonal structure. The thickness of the coatings varied from 0.35–0.75 m. The influence of the ZrO₂ coatings on the corrosion behavior of stainless steel substrates in aqueous NaCl was studied through potentiodynamic polarization curves at 1 mV/s. The values of the electrochemical parameters allow for an explanation of the role of the films in the increased resistance of steel against corrosion in moderately aggressive environments.     

Diheterocyclic compounds from dithiocarbamates and derivatives thereof. VI. unsymmetrical N1,N4-Bis(2-benzazolyl)sulphanilamides

The title compounds 9 are readily synthesized from dithiocarbamic acid derivative 5 by stepwise formation of the heterocyclic rings. Differences in reactivity of dithiocarbamates and dithiocarbonimidates make group protection unnecessary.     

Adsorption voltammetric techniques for the determination of uranium(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone as complex forming reagent

Uranium (VI) can be determined by adsorptive voltammetric techniques, as its chloranilic acid complex, over a wide concentration range. Differential pulse polarography is useful for quantification of uranium between 0.1 and 1.5 mg/l; for the range from 10 to 500 g/l differential pulse voltammetry and for ultra-trace analysis between 0.024 and 40 g/l adsorptive stripping voltammetry are preferred. The standard deviation for the 3-detection limit of 24 ng/l uranium was found to be 8%. In the trace analysis of metals in aquatic environmental systems by adsorptive stripping voltammetry it is normally necessary to decompose polluted water samples by UV irradiation or microwave digestion. The advantage of the developed method is the fact that no sample pretreatment is necessary.Dedicated to Professor R. Geyer on the occasion of his 80th birthday     

Synthetic Strategies To Obtain V-P-O Open Frameworks Containing Organic Species as Structural Directing Agents. Crystal Structure of the V(IV)-Fe(III) Bimetallic Phosphate [H(3)N(CH(2))(2)NH(3)](2)[H(3)N(CH(2))(2)NH(2)][Fe(III)(H(2)O)(2)(V(IV)O)(8)(OH)(4)(HPO(4))(4)(PO(4))(4)].4H(2)O

A general synthetic approach to rationalize the solution preparative chemistry of oxovanadium phosphates containing organic species as structural directing agents is presented. Careful attention is payed to the hydrolysis and condensation processes involving the ionic species in solution, and a simple restatement of the partial charge model (PCM) has been used in order to organize the experimental results. The structure of a new V(IV)-Fe(III) bimetallic oxovanadium phosphate, [H(3)N(CH(2))(2)NH(3)](2)[H(3)N(CH(2))(2)NH(2)] [Fe(III)(H(2)O)(2)(V(IV)O)(8)(OH)(4)(HPO(4))(4)(PO(4))(4)].4H(2)O, has been determined by X-ray single crystal diffraction methods. This compound crystallizes in the monoclinic system, space group P2(1)/n and the cell dimensions are as follows: a = 14.383(3) ?, b = 10.150(2) ?, c = 18.355(4) ?, and beta = 90.39(3) degrees (Z = 2). The existence of a complex intercrossing channel system, including a very large channel of 18.4 ? of diameter (in which both water molecules and ethylenediamine species are located), is the more interesting feature of this structure. Thermal decomposition, including the dehydration/rehydration process, has been studied by thermal analysis and variable temperature X-ray powder diffraction techniques. A complementary SEM study of the different intermediate decomposition products is presented.     

Multi-technique surface characterization of bio-based films from sisal cellulose and its esters: a FE-SEM, μ-XPS and ToF-SIMS approach

Bio-based films were prepared from LiCl/DMAc solutions containing sisal cellulose esters (acetates, butyrates and hexanoates) with different degrees of substitution (DS 0.7–1.8) and solutions prepared with the cellulose esters and 20 wt% sisal cellulose. A novel approach for characterizing the surface morphology utilized field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and contact angle analysis. XPS and ToF-SIMS were a powerful combination while investigating both the ester group distribution on the surface and effects of cellulose content on the film. The surface coverage by ester aliphatic chains was estimated using XPS measurements. Fibrous structures were observed in the FE-SEM images of the cellulose and bio-based films, most likely because the sisal cellulose chains aggregated during dissolution in LiCl/DMAc. Therefore, the cellulose aggregates remained after the formation of the films and removal of the solvent. The XPS results indicated that the cellulose loading on the longer chain cellulose esters films (DS 1.8) increased the surface coverage by ester aliphatic chains (8.2 % for butyrate and 45 % for hexanoate). However, for the shortest ester chains, the surface coverage decreased (acetate, 42 %). The ToF-SIMS analyses of cellulose acetate and cellulose hexanoate films (DS 1.8) revealed that the cellulose ester groups were evenly distributed across the surface of the films.     

The interaction of cationic polymers with human hair

We present a combination of electrochemical methods, i.e. polyelectrolyte titration and streaming potential measurement, and AFM to characterise the adsorption and desorption behaviour and the morphology of a set of polyquaternium polymers on human hair. Specific charge density and molar mass are correlated to the amount of adsorbed polymer and the ease of desorption. Results are in line with a simple model of coulombic interaction between hair and polymer and are interpreted on this basis.