Structure and properties of ANOF Layers

Oxide layers produced by ANOF technique show other structures and properties than such ones anodized as usual. Some characteristic mechanical, electrical and chemical properties are described. Their dependence on structure is discussed.     

Application Fields of ANOF Layers and Composites

Anodic oxidation by spark discharge (ANOF) produces e.g. Al₂O₃ layers containing up to 25% α-Al₂O₃ on the average if carried out on Al (Kurze et al. (1) and corresponding oxide layers with special outstanding properties on other barrier layer forming metals esp. Ta, Ti, Zr, Nb(Cb) (Kurze) et al. (2), (3), (4); Schneider (1), (2)). There is a wide field of application possibilities of such layers and composites of them with the bearing metals and other materials, e.g. in the fields of electrical engineering, electronics, medicine and vacuum engineering etc. This is the last one of three general ANOF papers published in this journal (Krysmann et al.; Dittrich et al.).     

Process characteristics and parameters of Anodic Oxidation by spark discharge (ANOF)

Process characteristics and parameters of ANOF as well as that special logarithmic relation of the layer formation parameters which is valid for the spark region are discussed. By calorimetric investigation it can be shown that the greatest share of electric energy will be transformed to heat and that the current quantity of ≈ 1.1.A · s · cm⁻² is characteristic for the incubation period before spark discharge during the gas — solid reaction of aluminium coating.     

Photochrome Eigenschaften von γ-bestrahlten Claciumfluoridkristallen mit Lanthan-Dotierung

The preparation of La-doped CaF₂ crystals is described. Their photochromic properties in the UV and visible spectral range are investigated. Furtheron their use for information storage is discussed and their capacity compared with the reported characteristics of additively coloured crystals.     

Zum Zusammenhang von Verfärbungserscheinungen und Gitterdeformationen in synthetischen Quarzeinkristallen

Synthetic quartz monocrystals with fringes of smoky colouration perpendicular to the growth direction show maxima of the reflected intensity of X-rays (reflection 0003) on places where the absorption of visible light varies strongly. Detectable components of the displacement vektor are parallel to the growth direction. In strongly coloured regions the lattice is expanded.     

Dislocation Photoconduction and Related Dislocation Memory Effects in KCl Crystals

Two types of memory phenomena are discussed, both related to dislocation photoconduction of highly pure and coloured KCl crystals, using the combination of Lyman- and F-illuminations. A very simplified explanation of the dislocation memory effects is given taking into consideration possible changes in the direction of the photocurrents. Some considerations may be of interest for the explanation of photoplastic effects.     

Brown colour of ruby

The defects characteristic of brown pure ruby crystals coloured by specific growth conditions, annealing and irradiation are described. The comparsion of UV- and X-rayed crystals is given. Brown or yellow colour is attributed to the O⁻ centre which is formed by the electron transfer from O²⁻.     

Coloured coatings containing mixed transition metal oxides

Glass coloured coatings of M_nO_m---N_pO_q---SiO₂ (M, N = Fe, Co, Ni, Mn, Cr) prepared on soda-lime-silica flat glasses by the sol-gel route using the dip-coating technique.

The optical properties of these films were investigated by spectrophotometry and the optical parameters obtained allowed the colouration mechanism acting in each case to be determined as well as a comparison to be made with the parameters on the single TMO coloured films. Colour coordinates were calculated in every case.

On the other hand coatings have been prepared consisting of two different single TMO films. The corresponding mixed coatings were compared with these double films, showing different behaviours and widening the colour spectrum of glass TMO coatings.     

Coloured zirconia

This paper deals with the growth of coloured zirconium oxide crystals, cubic stabilized with yttrium oxide. The host material–zirconia–is colourless. To generate colourations minor concentrations of 3d- and 4f-elements are incorporated into the lattice. The resulting colours are dependent on the ions' valence and the local crystal symmetry. Both, the possibility to change the ions' valence by heat treatment, and the possibility to change the local crystal symmetry by alteration of the starting yttria concentration, are discussed in the following.     

Growth of 2-methyl-4-nitroaniline (MNA) crystals by the bridgman method

Organic single crystals of 2-methyl-4-nitroaniline (MNA) up to 3 mm in diameter and 20 mm in length have been successfully grown by the Bridgman method using the purified reagent by sublimation. The crystals are transparent and yellow in colour by controlling the growth conditions. In the spectra of yellow coloured crystals no absorption peak is observed until about 450 nm. Also, the crystals of MNA have the two cleavage planes (311 ) and (010).     

Precision lattice parameter determination of coloured quartz monocrystals

Several possibilities for the determination of relative lattice parameter changes and for the absolute measurement of lattice parameters are discussed. Special attention has been given to a measuring device for the high-precision lattice parameter determination according to the BOND method. This device allows to determine the lattice parameters with a relative accuracy of 2 × 10⁻⁷. As an example the methods discussed are applied to the investigation of a smoky coloured quartz crystal plate and the results obtained by them were compared.     

Temperature distribution in growing semi-transparent crystals (II). Comparison of theory with experiments

Calculated temperature difference between the liquid/solid interface and bulk of the melt was compared with the wide-angle scattering (celluae density) of Al₂O₃ and YAG crystals. Celluae free coloured crystals were grown using higher energy losses from the upper part of the crystal and the melt. Colourless crystals were successfully grown under opposite conditions. The results are in accordance with the calculated temperature differences which are proportional to the actual temperature gradient at the interface.     

A Variable Tilt Smectic A Electro-Optic Effect Giving Stored Colours

A smectic A phase was aligned with a uniformly high tilt such that it appeared coloured between crossed polarisers. By applying an electric field the tilt angle of the structure increased progressively giving a Newton Spectrum series of colours. The colours remain on removal of the drive voltage.     

Optical absorption property of glasses coloured with Cd (S, Se, Te)

In the glasses coloured with Cd (S, Se, Te), the dependence of the absorption coefficient () on photon energy (E) and temperature (T) has been determined. Some results that differ from the Urbach rule were obtained.     

Crystal and molecular structure of tetrachloro tetraaquo-(1,8,10,17-tetraazacyclooctadecane-9,10-dithione) dicopper (II)

Tetradentate bioactive macrocyclic thiourea 1,8,10,17-tetraazacyclooctadecane-9,18-dithione(L) has been complexed with copper chloride dihydrate yielding bluish green coloured paramagnetic complex of orthorhombic geometry. The composition and tentative environment around Cu(II) is assigned on the basis of elemental analysis, IR, ESR spectra, X-ray diffraction and magnetic studies.     

Novel carbon materials obtained by reactions of C60 fullerene with phosphorus at high temperature

C₆₀ fullerene reacted with phosphorus at high temperatures to graphitic materials with strongly differing properties. Several spectroscopic investigations as Raman, ESR, XPS and ³¹P-NMR as well as TEM and ESEM have shown that the structural order of the mostly micro-crystalline materials increased with increasing reaction temperatures and decreasing phosphorus content. At suitable preparation conditions carbon nanotubes are formed, which are disordered in most cases, but partly exhibit high structural order (single-wall nanotubes), too. The prepared materials are very hard, e.g. harder than silica, intensely coloured and electrically conductive. Their hardness decreased with rising phosphorus content, and their conductivity increased with decreasing phosphorus content.     

On the structural characterization of solid state reaction product of cadmium carbonate and 8-hydroxyquinoline

The formation of coordination compound of cadmium carbonate and 8-hydroxyquinoline has been studied in solid state. The light yellow coloured crystals of this compound have been grown in non-aqueous media for X-ray studies. The crystal system and lattice parameters have been determined by powder technique of X-ray diffraction. Infrared spectral study of the complex was carried out in order to study the mode of linkage. Molecular distortion due to coordination has been discussed.     

Aus flüssiger Phase abgeschiedene,dotierte VO2-Schichten und deren Widerstands-Temperatur-Verhalten

The preparation of VO₂ layers by a liquid-phase process is described. Undoped VO₂ layers and layers doped with Al and W are prepared, respectively. The resistance-temperature behaviour of the layers was investigated: The VO₂ layers reach nearly the quality of monocrystalline material. The recrystallization of the VO₂ layers is of great importance for the effectiveness of doping.     

Chemistry of cultural glasses: the early medieval glasses of Monselice's hill (Padova, Italy)

To investigate the mechanisms of deterioration of historical glasses, under natural evolution, some early medieval glasses from the archaeological site of the Monselice's hill have been analysed. By an archaeological approach, developed at the Dipartimento di Scienze dell'Antichità, University of Padova, the glasses were dated between the VI and the beginning of the VII century and they were ascribed to the same artist or school. By a geological approach, developed at the Dipartimento di Mineralogia e Petrologia, University of Padova, it was found that some pieces of glasses, from the same archaeological site, were made of silica, rich in sodium and calcium, with iron and manganese. The composition was analogous the one of glasses produced during Roman empire, using `natron' (Na<sub>2</sub>CO<sub>3</sub>·NaHCO<sub>3</sub>·2H<sub>2</sub>O) as melting agent and glasses produced during medieval age, in the Mediterranean basin, using plant ash like `Salsola Kali' as melting agent. It was also found that there was a surface layer, with a special lamellar structure, easy to remove. The surface layer was found poor in alkali and alkaline-earth elements. By surface and microscopic analyses (optical microscopy, SEM-EDS, microRaman, XPS, SIMS and Mössbauer) it has been found that all the samples have a composition rich in silica, sodium and calcium except one that, unexpectedly, was rich in potassium and poorer in sodium. This sample, as composition, seems just like medieval glasses produced north of the Alps, using plant ash like ferns as melting agent. In all the samples the surface layers have less alkaline elements and the depletion goes to ten μm of depth. The extreme consequence of this depletion is the formation, in some samples, of an alteration layer, easy to remove, that the XPS analyses tell us it is made of very hydrated silica. The surface layers show a little accumulation of calcium. The calcium ion is also present in some birefringent crystal aggregates immersed in the glass that, in some samples, are around one mm large. These aggregates have a circular shape, with a nucleation centre in them. By microRaman spectroscopy it was found that the crystal aggregates are made of vateritic and calcitic calcium carbonate. By Mössbauer spectroscopy it was found that in the flat yellow coloured glasses, richer in iron, the Fe(III) species predominates. Instead in the pale green ones, poorer in iron, the Fe(II) prevails.     

As2S3 and AgI thin layers as ion sensitive membranes

The possibilities of using thin layers of As₂S₃ and AgI as ion sensitive membranes for ion selective field-effect transistors (ISFETs) are investigated. The thin films have been prepared by vacuum deposition on static and rotating substrates. The As₂S₃ layers were additionally doped with silver. The influence of the type of substrates and preparation conditions on electrochemical properties of the layers was studied. Electrochemical measurements revealed a reasonable sensitivity of chalcogenide and halide layers to silver and iodide ions, respectively. The near Nernstian behavior of sensitivity of As₂S₃ layers to Ag⁺ ions and of AgI layers to I⁻ ions is observed. The results obtained are promising for the development of ISFETs.