Preparation and characterisation of Ag incorporated Al2O3 nanocomposite films obtained by sol‐gel method

Sol‐gel route has been applied for a deposition of the thin films of aluminum oxide and Ag embedded in Al₂O₃ films. The films are spin‐coated on Si and quartz substrates with the film thickness of 120 nm. XRD analysis has been used for the determination of the film structure. FTIR spectroscopy is applied for studying vibrational properties of the obtained coatings. Optical characterization is done by UV‐VIS spectroscopy. The formation of Ag nanoparticles has been confirmed by XRD and optical data. The sol‐gel process is found to be useful technology for incorporation of Ag nanoparticles in the metal oxide matrices. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Use of projection moiré for measuring the instantaneous out-of-plane deflections of composite plates subject to bird strike

For the new generation aircraft families, the use of fibre-reinforced plastics is considered for the leading edge of the wings. However, this leading edge is very prone to bird strike impact.This paper presents the use of the projection moiré technique to measure the instantaneous out-of-plane deflections of composite plates subject to bird strike. Very strict constraints with regard to (i) high-speed image acquisition, (ii) vibrations of the impact chamber, and (iii) projection and observation angles, complicated substantially the development of the set-up. Moreover, the high frame rates (12,000 fps) required a very intensive illumination.In the optimized configuration, a specially designed grating with gradually changing period is projected by means of special halide hydride lamps through one of the side windows of the impact chamber onto the composite plate riveted in a steel frame. The digital high-speed camera is mounted on the roof of the impact chamber and records through a mirror the object surface with the projected fringe pattern on it.Numerical routines based on local Fourier transform were developed to process the digital images to extract the phase and the out-of-plane displacements. The phase evaluation is possible due to the carrier frequency nature of the projected moiré pattern. This carrier frequency allows separation of the unwanted additive and multiplicative fringe pattern components in the frequency domain via the application of a proper mask. The numerical calculations were calibrated for the bird strike on an aluminum plate, where the plastic deformation could be checked after the test.     

Effect of annealing temperatures on properties of sol‐gel grown ZnO‐ZrO2 films

Mixed ZnO‐ZrO₂ films have been obtained by sol‐gel technology. By using spin coating method, the films were deposited on Si and glass substrates. The influence of thermal annealings (the temperatures vary from 400 °C to 750 °C) on their structural properties has been studied. The structural behavior has been investigated by the means of XRD and FTIR techniques. The results revealed no presence of mixed oxide phases, the detected crystal phases were related to the hexagonal ZnO and to crystalline ZrO₂. The sol‐gel ZnO‐ZrO₂ films showed polycrystalline structure with a certain degree of an amorphous fraction. The optical transmittance reached 91% and it diminished with increasing the annealing temperatures. The optical properties of the sol‐gel ZnO‐ZrO₂ films, deposited on glass substrates are excellent with high transparency and better then those of pure ZrO₂ films, obtained at similar technological conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of ZnO-TiO2 films obtained by sol-gel method

The sol-gel route has been applied to obtain ZnO-TiO₂ thin films. For comparison, pure TiO₂ and ZnO films are also prepared from the corresponding solutions. The films are deposited by a spin-coated method on silicon and glass substrates. Their structural and vibrational properties have been studied as a function of the annealing temperatures (400-750 °C). Pure ZnO films crystallize in a wurtzite modification at a relatively low temperature of 400 °C, whereas the mixed oxide films show predominantly amorphous structure at this temperature. XRD analysis shows that by increasing the annealing temperatures, the sol-gel Zn/Ti oxide films reveal a certain degree of crystallization and their structures are found to be mixtures of wurtzite ZnO, Zn₂TiO₄, anatase TiO₂ and amorphous fraction. The XRD analysis presumes that Zn₂TiO₄ becomes a favored phase at the highest annealing temperature of 750 °C. The obtained thin films are uniform with no visual defects. The optical properties of ZnO-TiO₂ films have been compared with those of single component films (ZnO and TiO₂). The mixed oxide films present a high transparency with a slight decrease by increasing the annealing temperature.     

Three-dimensional profilometry by symmetrical fringes projection technique

A precise interferometric method for three-dimensional surface measurements in a wide dynamic range is presented. The method is based on symmetrical two-spacing projection phase-stepping interferometry. Two approaches are proposed—one with double symmetrical illumination and the other with double symmetrical observation—which reduce influence of shadowing at investigation of complex surfaces and allow absolute coordinates estimation. The theoretical background, experimental check as well as accuracy and sensitivity assessment of the method are discussed. The proposed technique is especially useful for remote, non-destructive in-situ measurements of real objects—for example historical objects and monuments.     

Mössbauer spectroscopy of Zn<Subscript>x</Subscript>Mg<Subscript>1-x</Subscript> Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.74) nanostructures crystallized from borate glasses

Glasses in the system 51.7 B₂O₃/9.3 K₂O/1 P₂O₅/10.4 Fe₂O₃/(27.6 ? y) MgO/y ZnO (with y?=?0, 1, 2.5, 5, 7.5, 10, 13.8, and 20) were prepared by the conventional melt quenching method. The glass samples were thermally treated at 560 °C for 3 h in ambient conditions. Using ⁵⁷Fe Mössbauer spectroscopy, the effect of the substitution of MgO by ZnO in the glass network and the effect on the precipitated crystallized phase was studied. The results showed that the ratio of Zn²⁺:Mg²⁺ in the precipitated crystals increases with the ZnO concentration in the glass. The isomer shift values indicated that iron occurs as Fe³⁺, which is distributed at the tetrahedral (A) and the octahedral [B] sites. Introducing ZnO leads to a relative increase of the Fe³⁺ concentration at the B sites at the expense of that occupying the A sites. This indicates the precipitation of Zn_xMg_1-x Fe₂O₄ nanoparticles, where Zn²⁺ ions favorably occupy the A sites. The average hyperfine field of the samples showed a strong dependence on the Zn concentration. At the highest Zn concentration of 13.8 and 20 mol%, the samples are paramagnetic, while for the smaller ones, the samples are superparamagnetic.     

Binäre Systeme von Carcinogenen und verwandten Verbindungen in Beziehung zur krebserzeugenden Wirksamkeit: Mehrkernige aromatische Verbindungen,II

Zusammenfassung Es wird gezeigt, daß bei allen jenen bisher im Tierversuch und thermoanalytisch geprüften Gemischen aus einem starken und schwachen Carcinogen, welche Mischkristalle bilden, eine bereits bekannte Hemmung der Wirkung des starken Carcinogens durch das schwache eintritt. Daher scheint es, daß die thermische Analyse als Hilfsmittel für die Auffindung eines Anticarcinogens gegenüber einem bestimmten Carcinogen insofern in Betracht kommt, als bei zutreffender Mischkristallbildung eine wahrscheinliche Inhibitorwirkung der schwach oder womöglich nicht carcinogenen Verbindung gegenüber dem stärkeren Carcinogen vorausgesagt werden kann.Für eine Reihe zur Prüfung dieser Schlußfolgerung im Tierversuch geeignet scheinender Beispiele von bis jetzt auf krebserzeugende Wirkung noch nicht geprüften Gemischen wird Mischkristallbildung nachgewiesen.Geben ein starkes und ein schwaches Carcinogen anscheinend ein einfaches Eutektikum, so tritt in gewissen Fällen eine Inhibitorwirkung immer noch auf, in anderen jedoch nicht. In welcher Weise dies von der Beschaffenheit der Molekeln abhängt, läßt sich zur Zeit noch nicht angeben.Mit 18 Abbildungen6. Mitteilung über Carcinogene und strukturverwandte Verbindungen. 5. Mitteilung: Mh. Chem.85, 906 (1954).Teilweise vorgetragen vonA. M. auf der Generalversammlung des Veremes Österreichischer Chemiker in Klagenfurt am 21. September 1954: Österr. Chem.-Ztg.55, 258 (1954).— Über einige Ergebnisse dieser Arbeit wurde in der Österreichischen Biochemischen Gesellschaft am 28. Februar 1953 berichtet. Siehe auch Österr. Chem.-Ztg.53, 12 (1952).     

Electric conductivity of glasses in the system Na2O/CaO/SiO2/Fe2O3

The addition of polyvalent transition metal ions to the usually insulating traditional soda-lime-silica glasses can lead to semiconducting properties. We report on synthesis of glasses and glass-ceramics in a soda-lime-silicate based system containing Fe₂O₃ in the concentration range from 5 to 30 mol%. Two sub-systems were considered, in one of them the ratio [Na₂O]/[Fe₂O₃] was varied while in the other one, the ratio [SiO₂]/[Fe₂O₃] was changed. The phase composition of the synthesized products was characterized by X-ray diffraction and energy dispersive X-ray analysis, while the electrical properties were studied by impedance spectroscopy. Partially crystallized non-reduced samples are semiconducting even at room temperature while the glassy samples (both reduced and non-reduced) exhibit semiconducting properties at temperatures equal or larger than 100 °C. An attempt is done to predict the physical approximation explaining the conduction process in the glasses.