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Chemical precursors of high temperature superconductors were prepared by the controlled double-jet precipitation of their oxalates to obtain suspensions with submicron average crystal size, narrow crystal size distribution, desired chemical composition and internal structure. To improve mechanical and electrical properties of HTSC layers the chemical precursors of HTSC were doped by silver oxalates using the same method. This technique enables to achieve better mixing of reagents in compare with mixed oxide processing. The suspensions were coagulated, washed and coated on various substrates. During carefully controlled heat treatment the grains readily sintered and formed HTSC layers. The layers prepared by this technique showed some improvements in mechanical and electrical properties. When coated on silver substrate, high density layer and a strong bond between the HTSC layer and substrate were achieved

Controlled double-jet precipitation has been used to synthesize high-temperature superconductors (HTSCs). The cation and oxalic anion solutions were simultaneously separately introduced into the crystallizer with a stirred solution of gelatin under conditions where the temperature, excess of oxalic anions in solution, pH, reactant addition rate, type and amount of the growth restrainer were tightly controlled. The suspensions with submicron average grain size, narrow grain size distribution, and with high sinterability were used to prepare bulk specimens and films on various substrates. The sintered oxides were characterized by electrical resistivity and ac-susceptibility measurement. The superconducting properties of these samples were found to be comparable, if not superior, to those observed for samples produced by other conventional methods.

Oxidation of FeSO4 by air oxygen has been studied in aqueous solutions of constant acidity. The effect of various reaction conditions (of acidity, temperature, concentration of FeSO4, and of the air flow through the suspension) on the yield of various modifications of ferric oxide-hydroxides in the product mixture is described and the mechanism of the process is discussed. Reaction products prepared in the neutral and weakly alkaline solutions contain predominantly lepidocrocite (γ-FeOOH), amorphous Fe2O3.n H2O (ferrihydrite), at higher pH values also goethite (α-FeOOH) is formed. Their mutual ratios depend strongly on the solution acidity.

The effects of heatingα-Fe2O3 (hematite) prepared by oxidation precipitation of ferrous sulphate, at temperatures up to 700° C were studied. It was found that, in the course of heating, losses of structurally-bound water occured, accompanied by the formation and removal of pores, the lattice constants changed and the optical properties were modified, an effect which is important from the standpoint of the use of hematite as ferric pigment. With increasing annealing temperature, the complementary wavelength was shifted to higher values and the spectral purity of the pigment colour was decreased.

A method has been worked out for the reproducible preparation of Green Rust substances involving SO42-, Cl-, Br-, and I- anions. The chemical composition of the substances prepared has been followed in dependence on the synthesis conditions. The powder X-ray and electron diffraction patterns and infrared and Moessbauer spectra have been measured and discussed.

The kinetics of the reaction ofα-Fe2O3 (hematite) with K2CO3 was studied at 600–800 °C for hematite samples prepared in different ways. The results demonstrated that the hematite reactivity is not a simple function of the specific surface area (or particle size), but depends significantly on the sample preparation history, especially at lower reaction temperature. The effect of low-temperature sintering on the hematite reactivity is discussed.

Amorphous FeIII hydroxides prepared at pH = 6 differ from analogous precipitates obtained in alkaline media in that they have an increased content of anions bound in their structures, and crystallize less readily both in dry thermal treatment and under hydrothermal conditions. The shapes of DTA curves obtained for freshly prepared gels and for products of ageing in mother liquor are discussed, and the effect of the anions present on the course of thermal decomposition is assessed. Bildung und Kristallisation von FeIII-Hydroxiden. 2. Einflus der Fallungstemperatur und Natur des Ausgangs–FeIII-Salzes auf die Eigenschaften des in schwach saurem Medium dargestellten FeIII-Hydroxids Amorphe, bei pH = 6 dargestellte FeIII-Hydroxide unterscheiden sich von entsprechenden Niederschlagen aus alkalischen Medien durch einen zunehmenden Gehalt an Anionen in ihren Strukturen und kristallisieren weniger leicht sowohl bei trockner, thermischer Behandlung wie unter hydrothermalen Bedingungen. Die DTA-Kurven, die von frisch praparierten Gelen sowie von in Mutterlauge gealterten Produkten erhalten wurden und der Einflus der vorhandenen Anionen auf den Verlauf der thermischen Zersetzung werden diskutiert.

In den vorhergehenden Arbeiten wurde bei den kinetischen Untersuchungen der kontinuierlichen Hydrierung tablettierter Ni-Katalysator verwendet. Der Ni-Gehalt war in der gesamten Masse der Tablette gleich, wobei bei der Katalyse nur die Oberflachenschichten wirksam sind. Das Hauptziel der vorliegenden Arbeit war die Darstellung eines Ni-Katalysators durch die auf eine geeignete Weise durchgefuhrte Sattigung der extrudierten Kieselgur (Zylinderform). Am geeignetsten hinsichtlich der Eigenschaften des Ni-Katalysators erschienen zwei Verfahren, zunachst eine vielfache Sattigung extrudierter Kieselgur mit der Losung eines Ni-Salzes in Ammoniak, weiter eine Kombination der Sattigung mit dieser Losung und nachheriger Sattigung mit wasriger Ni(No3)2-Losung und Fallung mit einer Oxalsaure-Losung. Investigations of the Continuous Hydrogenation of Oils and Fatty Acids VI: Production of Pelleted Ni-Catalyst by Saturation of Extruded Kieselgur In the preceeding works pelleted Ni-catalyst was used for kinetic investigation of continuous hydrogenation. The nickel content was the same in the whole mass of the pellet, during catalysis however only the surface layers are effective. The main objective of the submitted work was the production of a Ni-catalyst by saturation of the extruded kieselgur (cylindric shape) by suitable means. With respect to Ni-catalyst properties two procedures seemed to be most suitable: At first a multiple saturation of extruded kieselgur with a Ni-salt solution in ammonia, furtheron combining the saturation with this solution and subsequent saturation with aqueous Ni(NO3)2-solution and precipitation by oxalic acid solution.

The kinetics of the reaction between α-Fe2O3 and K2CO3 have been investigated over the temperature range 600 to 800 °C, and the phase composition of the products has been determined. The reaction follows the rate law α = 1 - exp (-kτn). At molar ratios K : Fe 1, KFeO2 is the only product. At K : Fe 1, initially formed KFeO2 reacts with hematite to yield K2Fe4O7. The latter phase has been assigned a cubic structure with a = 1.681 ± 0.003 nm. based on X-ray powder diffraction patterns and Mossbauer spectra, the structure of K2Fe4O7 is proposed to be a cubic close-packed array of oxygen atoms, part of these being replaced by potassium atoms, with Fe atoms occupying the octahedral interstices.

The oxidation precipitation of aqueous solutions of iron(II) sulphate by oxygen gas was studied; the effect of pH, temperature, and presence of α-FeOOH and α-Fe2O3 crystal nuclei was examined and the conditions for the preparation of phase-pure α-Fe2O3 (hematite) were sought. The hematite prepared contained 3-5% structurally bonded water. The effect of the bonded water on the properties of the product is described and the way of the bonding in the structure is discussed.

The course of the transformation of synthetic γ-FeOOH (lepidocrocite) samples, prepared by different methods was investigated and the effect of a preliminary heat treatment of the initial material on the product phase composition and morphology studied. Both the goethite-tohematite ratio and the particle size of the products depend on the preparation method and on the preliminary heat treatment of the initial lepidocrocite. The results are discussed in terms of the dissolution of the less stable lepidocrocite followed by the crystallization of the more stable phases α-FeOOH and α-Fe2O3 from the solution. The final product phase composition and the particle size are affected considerably by a presence of goethite and/or hematite germs in the initial γ-FeOOH. Umwandlung von synthetischem γ-FeOOH (Lepidocrocit) in wasrigen Losungen von Eisen(II)-sulfat Der Verlauf der Umwandlung von synthetischem, nach verschiedenen Methoden dargestelltem γ-FeOOH (Lepidocrocit) in wasrigen Losungen von FeSO4 und der Einflus einer thermischen Vorbehandlung auf die Phasenzusammensetzung und Morphologie der Produktpartikel wurde untersucht. Die Gehalte an α-FeOOH und α-Fe2O3 sowie die Partikelgrosen der Produkte hangen sowohl vom Praparationsweg des Ausgangslepidocrocits wie auch von der thermischen Vorbehandlung ab. Die Ergebnisse werden als Auflosung des weniger stabilen Lepidocrocits und Kristallisation der stabileren Phasen α-FeOOH und α-Fe2O3 aus der Losung diskutiert. Die endliche Zusammensetzung der Produkte sowie ihre Partikelgrosen werden besonders durch die Anwesenheit von Keimen dieser Phasen im Ausgangs-γ-FeOOH beeinflust.

The thermal decomposition of synthetic lepidocrocite,γ-FeOOH, was studied using DTA, infrared and Mossbauer spectroscopy and X-ray diffraction, and the dependence of the phase composition of the dehydration products on the method of preparing the initialγ-FeOOH was described. The results demonstrated thatγ-Fe2O3 formed by dehydration ofγ-FeOOH consists of very small particles with a broad size distribution and that, depending on the method of preparation, the initialγ-FeOOH can contain a large amount of amorphous ferric hydroxide. A preparation method yieldingγ -FeOOH which is not contaminated with other ferric oxide-hydroxides is recommended.

Trickle bed reactor is one type of a unit in which heterogeneous catalytic reactions with contact of three phases gas and liquid on a solid catalyst surface can be materialized. In such reactor, reacting liquid flows downwards as a thin film on the catalyst pellets due to gravitation. Gas may flow either co or countercurrently, with the liquid product removed from the reactor bottom. This system has the advantage in perfect contact of reacting components and consequently, in high efficiency at minimum design requirements and costs.

Etude cinetique de la reduction dont la temperature varie de 240 a 330°C. Energie d'activation

In einem vereinfachten Reaktormodell wurde die Hydrierung von Olivenol auf Ni-Katalysator nach dem Rieselverfahren untersucht. Die Versuche erfolgten bei diskontinuierlicher Verfahrensweise auf tablettiertem Ni-Katalysator unter Eliminierung der Einflusse der auseren Diffusion und bei diskontinuierlicher Verfahrensweise unter Eliminierung der Einflusse der auseren sowie inneren Diffusion (Pulverkatalysator). Die gefundenen Werte des effektiven Faktors der auseren Diffusion ergaben, das der laminare Film auf der Oberflache der Tablette einen kleinen Widerstand gegenuber Stoffubertragung darstellt. Die Messungen des effektiven Faktors der inneren Diffusion ergaben, das der Grad der Ausnutzung der inneren Katalysatoroberflache bei der Hydrierung von Olen auf tablettiertem Ni-Katalysator niedrig ist. Investigations of Continuous Hydrogenation of Oils and Fatty Acids V: Degree of Utilization of Ni-Catalyst Surface During Hydrogenation Hydrogenation of olive oil by Ni-catalyst according to the trickling process was investigated in a simplified reactor model. The tests were carried out by discontinuous proceeding on pelletted Ni-catalyst with elimination of the influences of the outer diffusion and by discontinuous proceeding with elimination of the outer and internal diffusion (powdery catalyst). The obtained values of the effective factor of the outer diffusion showed that the laminar film on the surface of the pellets causes a small resistance to mass transfer. The measurements of the effective factors of the internal diffusion showed that the degree of the exploit of the internal catalyst surface during hydrogenation of oils on pelletted Ni-catalyst is low.

Developpement d'une methode de preparation mettant en jeu les anions SO 4 2− , Cl − , Br − et I − , des hydroxydes mixtes qui pourraient avoir la composition Fe (1−x) II Fe x III (OH) 2 •A xy (OH) x(1−y)

Cinetique etudiee de 600 a 800°C. Loi de vitesse. Suivant les proportions, les composes sont KFeO 2 ou K 2 Fe 4 O 7

Bei der Umwandlung von verschiedenen synthetischen γ-FeOOH- Proben in FeSO4-Losungen hangen die Gehalte der Endprodukte an α-FeOOH und α-Fe2O3 sowie deren Partikelgrosen vom Praparationsweg der Ausgangslepidocrocite ab.

Bei der Hydrierung der Octine (I) in n-Heptan oder Athanol bei 30°C (1 at) ist die Aktivitat eines Ni/Kieselgur-Katalysators stark von seinem Reduktionsgrad (Verhaltnis des Gehaltes an metallischem Ni zum Ni-Gesamtgehalt) abhangig; das Aktivitatsmaximum wird bei einem Reduktiongrad von 0,6 angenommen.