Der Einfluß einer mechanischen Bearbeitung auf die thermische Zersetzung von Hydrargillit

Influence of Mechanical Activation on Thermal Decomposition of Gibbsite The influence of mechanical activation on structure and reactivity of gibbsite in dependence on stress mechanism (pressure stress and shearing in vibration-mills, shock stress in disintegrators) is investigated. With increasing mechanical treatment the degree of order is decreased. Mechanically disturbed gibbsite shows changed decomposition series. After mechanical activation and short-time heating there are formed nearly X-ray amorphous Al₂O₃ with high spec. surfaces. It is possible to transform these alumina into pseudo-boehmite with a very low alkali content. The transformation into pseudo-boehmite is dependent on the degree of order of the mechanically pretreated gibbsite and is independent of the spec. surface of X-ray amorphous Al₂O₃. The products can be used for the preparation of adsorbents and catalyser components.     

Die Sublimation und thermische Zersetzung von TeJ4 und die Existenz von TeJ2 in der Gasphase

The Sublimation and the Thermal Decomposition of TeJ₄ and the Existence of TeJ₂ in the Gaseous Phase The sublimation and the decomposition of TeJ₄ have been investigated. For the sublimation and the decomposition reactions and the values of enthalpy and entropy were derived (see ?Inhaltsübersicht”?). The existence of TeJ₂ in the gaseous phase was demonstrated by equilibrium measurements and chemical transport experiments.     

Die thermische Zersetzung von Bariumazid-Einkristallen, 5. Mitt.: Der Einfluß der Korngröße auf die thermische Zersetzung von Bariumazid

Decomposition studies on ground samples of anhydrous Ba(N₃)₂ with defined particle size are described. The kinetic equations derived for single crystals hold for the decomposition of powders too. The far faster decomposition of powders is caused both by the increased numberN ₀ of potential nuclei forming sites and the larger specific surfaceF ₀/V ₀, whereas the rate constantsk ₁ andk ₂ for nucleation and linear nucleus growth, resp., and their respective activation energies coincide with the data for single crystals. The proportionality between the rate of decomposition and the specific surface is confirmed experimentally and thereby a further proof of the geometric decomposition model is established. Independent of particle size and temperture always 75% of the azide are transformed into nitride during thermal decomposition, this value corresponding exactly to the theoretical one. It is shown experimentally that with decomposition conditions no reaction takes place between metallic Ba and N₂ in its electronic ground state and therefore the mechanism proposed for nitride formation is confirmed.     

Dynamisch thermische analyse der Zersetzung von K2SiF6

Thermal decomposition of K₂SiF₆ is a complicated process depending on several parameters, the combination of which cause difficulty in comparing the results obtained from different methods. An experimental method for the study of small quantities of material is described. This allows direct comparison with thermoanalytical results. The influence of experimental conditions is discussed. The decomposition of K₂SiF₆ is a model for other complexes which produce easily hydrolysed products during thermal reaction. The course of thermal decomposition of K₂SiF₆ is described up to complete vaporisation of the products at 1200°C.     

Einfluß von Gitterstörungen des Graphits auf die Bildung von Graphithydrogensulfat

Influence of Lattice Defects of Graphite on the Formation of Graphite Hydrogensulfate Various natural and synthetic graphites were oxidized with chromic acid in sulfuric acid to the 1st stage of graphite hydrogensulfate with the intent of determining the inhibition of intercalation by lattice defects. More oxidant than required by stoichiometry is consumed because slow total oxidation to CO₂ is superimposed even at room temperature. The activation energy for total oxidation is reduced by lattice defects. With some graphites, separation of the intercalation reaction from total oxidation was accomplished using calorimetry. The reaction enthalpy in the oxidation of well-crystallized graphites to the graphite salt is ?3.05 kJ/mol C.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 5. Mitt.: Primärprozesse der thermischen Zersetzung von Natriumazid

Zusammenfassung Elektronische Zustände des Natriumazides werden durch ein Energiebandmodell charakterisiert, dem mittlere spektroskopische Eigenschaften zugrunde liegen. Unter Verwendung von UV-Absorptionsspektren sowie der in der 2. Mitt. ber. Polarisationsund Gitterenergie kann mit Hilfe eines Kreisprozesses das Bandmodell vervollständigt werden. Ein Vergleich mit den elektronischen Daten der Natriumhalogenide ergibt, daß sich das NaN₃, wenn man von den feinstrukturellen Eigenschaften, die zur Zersetzung führen, absieht, natriumhalogenidähnlich verhält. Weiters werden Studien über elektronische Primärprozesse bei der thermischen Zersetzung mitgeteilt. Als geschwindigkeitsbestimmender Primärschritt wird ein Elektronentransfer von Azid-Ionen zu Elektronenfallen angenommen. Wie eine quantenmechanische Betrachtung gestörter Gitterpotentiale zeigt, ergeben kationische Fremdionen, anionische Leerstellen und Oberflächen Elektronenfallen, während kationische Leerstellen und anionische Fremdionen Streustellen für Elektronen und Excitonen darstellen. Auf der Basis eines Störzentrengases kann eine Geschwindigkeitsgleichung für den Primärschritt abgeleitet werden, die qualitativ durch Umsatz/Zeit-Kurven belegt wird. Diese wurden durch Registrierung der bei der Zersetzung entstehenden Stickstoff-Druck-Zunahme gewonnen. Durch Zersetzung von NaN₃-Präparaten mit verschiedenen Gitterfehlern wird gezeigt, daß mit steigendem Einbau von kationischen Fremdionen, anionischen Leerstellen sowie einer Vergrößerung der Oberfläche die autokatalytische Zersetzung beschleunigt und mit steigendem Einbau von anionische Fremdionen die Reaktion verzögert wird. In der Sprache der Festkörperchemie entspricht dies einer Variation der Keimbildungsperiode.

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Electronic states of sodium azide are characterized by an energy band model, based on mean spectroscopic properties. Using UV-absorption-spectra and the calculated polarization and lattice energies (see paper 2) the band model can be completed by means of a cyclic process. A comparison with the electronic data of sodium halogenides shows that sodium azide behaves similar neglecting the microstructural properties leading to the decomposition. Moreover, studies on electronic primary processes during thermal decompositions are reported on. An electron transfer from azide ions to electron traps is assumed to be a rate determining step. As shown by a quantum mechanical consideration of disturbed lattice potentials cationic impurities, anionic vacancies and surfaces give rise to electron traps, whereas cationic vacancies and anionic impurities represent defraction centers for electrons and excitons. Based on imperfections behaving like a gas a rate equation for the primary step can be derived, which is proved qualitatively by pressure/timecurves. By decomposing samples of sodium azides with various lattice defects it is shown that with increasing amounts of cationic impurities, anionic vacancies and an increase of the surface, the autocatalytic decomposition is accelerated, whereas with increasing amount of anionic impurities the reaction is slowed down. In decomposition chemistry this corresponds to a variation of the nucleiation period.

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Mit 9 Abbildungen     

Zum Einfluß von Zusätzen auf die Hydratation von Tricalciumsilicat (Ca3SiO5)

On the Influence of Admixtures on the Hydration of Tricalcium Silicate (Ca₃SiO₅) The influence of several compounds (alcohols, ketones, organic acids and the ir salts, cation exchange resin) on the hydration of tricalcium silicate was investigated by means of differential calorimetric analysis (DCA). The acceleration and retardation of this reaction found in these experiments are discussed on the basis of Ca(OH)₂ solubility, the pH of the solution and the rate of conversion of a C? S? H rich in CaO into a C? S? H poor in CaO at the surface of the C₃S grains.     

Über die thermische Zersetzung der Hydraziniumpentafluorometallate N2H6MF5 des Eisens,Vanadiums und Aluminiums

On the Thermal Decomposition of Hydraziniumpentafluorometallates N₂H₆MF₅ of Iron, Vanadium and Aluminium The thermal decomposition of the hydraziniumpentafluorometallates of N₂H₆FeF₅, N₂H₆VF₅ and N₂H₆AlF₅ has been investigated by thermoanalytical, X-ray and i.r. spectroscopic methods. The thermal decomposition leads to ammonium compounds forming in consequence of disproportionation of the hydrazinium cation into ammonia and nitrogen. Under quasi-isobaric conditions a multistage decomposition mechanism has been detected. No hydrolysis reactions have been observed. In the iron system a partial reduction of Fe^III takes place. Consequently NH₄Fe₂F₆ is formed which decomposes via (NH₄)_1?xFeF_4?x (x = 0.6-0.8) with HTB-structure into FeF₃ and FeF₂. In the aluminium and vanadium system the formation of tetragonal (NH₄F)_y · MF₃-phases (y = 0.2-0.8) as intermediates has been observed. Final products of decomposition are VF₃ and α-AlF₃.     

Zum Einfluß der Halogenmodifizierung auf das acide Verhalten von γ-Al2O3

Influence of Modification of γ-Alumina by Halides on the Acidic Behaviour The influence of modification of γ-alumina by Cl and F on the acidic properties was studied by means of i.r. spectroscopic methods using ammonia as probe molecule. The measurements show a significant rise in Lewis acidity.     

Über basische Aluminiumsalze und ihre Lösungen. VII. Zum Einfluß der Herstellungsbedingungen,der Konzentration und der Alterungszeit auf die Zusammensetzung von Lösungen basischer Aluminiumsalze

Basic Aluminium Salts and their Solutions. VII. Influence of Preparation, Concentration, and Aging on the Constitution of Solutions of Basic Aluminium Salts 0.1 to 4 molar basic aluminium chloride solutions – prepared by dissolving aluminium metal in substoichiometric quantities of hydrochloric acid and 10^?4 to 0.2 molar basic solutions of aluminium chloride and perchlorate – prepared by adding alkali to the solutions of the neutral salts were investigated for the kinetics of their reactions with ferrone and by ²⁷Al NMR spectroscopy. In all solutions the contents of polymeric species decreases at equal basicity with increasing aluminium concentration. On the other hand the Al₁₃O₄₀ complex is only formed in solutions prepared by addition of alkali. The differences of composition are confirmed by the aging behaviour of the solutions.     

Über den Einfluß von Substitution auf die Kristallstruktur von SrNi2P2

About the Effect of Substitution on the Crystal Structure of SrNi₂P₂ With several series of mixed crystals the effect of substitution on the crystal structure of SrNi₂P₂ (polymorphic, the structures are variants of the ThCr₂Si₂ type) is investigated by X-ray methods. In the compound Ni completely can be substituted by Co and Cu respectively and also P by As; in Sr_1–xCa_xNi₂P₂ there is a gap of the miscibility between 0.3 ≤ x ≤ 0.6. A low substitution of the several elements more than proportionally changes the structure parameters. In this range the mixed crystals with Ca, Cu, and As, respectively, undergo first order phase transitions with significant changes of the bond distances, which will be interpreted by the results of band structure calculations.     

Komplexchemie P-reicher Phosphane und Silylphosphane. X [1] Zum Einfluß der Komplexierung auf die Reaktivität des [(Me3Si)2P]2PH

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. X. The Influence of the Formation of Complex Compounds on the Reactivity of [(Me₃Si)₂P]₂PH Whereas [(Me₃Si)₂P]₂PH 1 by BuLi is attacked at the PH group to give [(Me₃Si)₂P]₂PLi 2 , the related chromium carbonyl complex (Me₃Si)P^IV ? ²P^IV(H) ? ³P^III(Si? Me₃)₂ · Cr(CO)₄ 3 with BuLi yields Li(Me₃Si)¹P^IV ? ²P^IV(H) ? ³P^III(SiMe₃)₂ · Cr(CO)₄ 4 by cleaving a Si? P bond at the chromium substituted ¹P atom. Dissolved in ether, 4 is stable for a longer time, while under comparable conditions 2 forms Li₃P₇ which is not obtained from 4 . MeOH in 3 cleaves selectively the Me₃Si groups from the complex substituted P atom yielding (Me₃Si)(H)¹P^IV ? ²P^IV(H) ? ³P^III(SiMe₃)₂ · Cr(CO)₄ 5 and HP^IV ? ²P^IV(H) ? ³P^III(SiMe₃)₂Cr(CO)₄ 6. 5 and 6 seem to be stable in contrast to the uncoordinated triphosphanes which are not known.