Phasenänderungen im System Er2O3—TiO2

Zusammenfassung Röntgenographische und Gefügeuntersuchungen werden im System Er₂O₃–TiO₂ durchgeführt und ein Phasendiagramm im Solidusbereich ermittelt. Der Homogenitätsbereich der Pyrochlor-(von 33,3 Molprozent bis 50 Molprozent Er₂O₃) und der Fluoritphase (von 50 Molprozent bis 57 Molprozent Er₂O₃) wird bei 1550°C bestimmt.

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Phase transformations in the system Er₂O₃—TiO₂

The system Er₂O₃–TiO₂ has been investigated by microscopic and X-ray procedures. A phase diagram for the solidus range has been proposed. The pyrochlore phase is homogeneous from 33.3 to 50 mole% Er₂O₃ at 1550°C. Beyond 50 and up to 57 mole% Er₂O₃, the fluorite phase is homogeneous.

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Mit 2 Abbildungen     

Experimental analysis of contact for the indentation of a flat rounded punch

The ‘plane vs. plane’ contact involving flat punches has been the subject of many investigations, even in recent years, mainly due to the crucial role that such components play in phenomena, such as fretting fatigue and indentation tests. While the problem has been deeply approached from a theoretical point of view, there is a noteworthy lack of experimental verifications due to the limited number of laboratory techniques capable of supplying detailed information about contact parameters. In order to make a partial contribution towards gaining an understanding of such problems, this study proposes the investigation of flat rounded punch contact with an ultrasound-based technique, which exploits the properties of ultrasonic waves to be differently reflected by a contact interface depending on its stress state. A suitable setup was built in such a way as to ensure a good level of control of contact conditions, and the interface was scanned with a high-frequency ultrasonic transducer so as to acquire the reflection data. While the graphic processing of the ultrasonic coefficient of reflection may easily be displayed as a ‘contact map’, the quantitative accuracy of the method was also investigated by comparing experimental results with those obtained from a Finite Element model of the system. The results show a good level of agreement between the two approaches, thus confirming that the ultrasonic technique can be effectively employed to investigate many contact problems which to date have never (or scarcely) been experimentally validated.     

Formation and structure elucidation of two novel spiro[2H-indol]-3(1H)-ones

The molecular structures of two byproducts 1,1'-diphenyl-3',4'-dihydrodispiro[indole-2,2'-furan-5',2'-indole]-3,3'(1H, 1'H)-dione (3) and 1,5'-diphenyl-4',5'-dihydro-3'H-spiro[indole-2,2'-pyrano[3,2-b]indol]-3(1H)-one (4), which accompanied the rearrangement of 3-hydroxy-3-methyl-1-phenylquinoline-2,4(1H,3H)-dione (1) to 2-hydroxy-2-methyl-1-phenyl-1,2-dihydro-3H-indol-3-one (2), have been elucidated by NMR, MS, and X-ray diffraction.     

4‐Aminopyridinium hydrogen maleate

The title compound, C₅H₇N₂⁺·C₄H₃O₄⁻, crystallizes in space group P2₁ with one ion pair in the asymmetric unit. The hydrogen maleate anion possesses nearly planar geometry and displays an extremely short intramolecular O—H...O hydrogen bond, with an O...O distance of 2.4198 (19) Å. Classical N—H...O hydrogen bonds, together with short C—H...O contacts, generate an extensive hydrogen‐bonding network.     

Self condensation of enamines mediated by acetylation. A novel approach to 1-(azol-5-yl)-(1E,3Z)-butadiene-4-N,N-dimethylamines

Novel self-condensation of 3-(azol-5-yl)-1,1-dimethylenamines has been found to form new C-C bonds leading to 2,4-(1,2,3-triazole-1,2,3-thiadiazole-3-phenylisothiazole)-(1E,3Z)-5-yl-butadiene-1-amines. The discovered reaction represents a new example of C-H functionalization in unsaturated systems and can serve an efficient synthetic approach to rational design of new 2,4-(diazole-5-yl)-dieneamines.     

Preparative and Structural Studies of trans-Tetrachloro and Tetrabromodipyridinemolybdate(III) and Tungstate(III)

The first products of reactions between (PyH)₃MoX₆ (PyH = pyridinium, C₅H₆N⁺; X = Cl, Br) and pyridine are trans-(PyH)MoCl₄Py₂ and trans-(Py)₂HMoBr₄Py₂. Trans-(Py)₂H MoCl₄Py₂ can be obtained from the cold solution of trans-(PyH)MoCl₄Py₂ in pyridine. NaBH₄ suspended in the mixture of isopropanol and pyridine reduces WX₄Py₂ to trans-(Py)₂HWX₄Py₂ (X = Cl, Br). Trans-(Py)₂HMX₄Py₂ (M = Mo, W; X = Cl, Br) decompose at room temperature to trans-(PyH)MX₄Py₂. Four trans-(Py)₂HMX₄Py₂ compounds are isostructural and three of them crystallize in the triclinic unit cell. Pairs of trans-(PyH)MCl₄Py₂ and (PyH)MBr₄Py₂ have nearly equal sequence of interplanar spacings. Crystal structure of trans-(Py)₂HWCl₄Py₂ has been solved. The compound has a triclinic P1 space group with: a = 9.373(3), b = 9.563(3), c = 15.009(6) Å, α = 78.21(1), β = 77.94(2), γ = 78.63(2)° and Z = 2. Two independent WCl₄Py₂^? groups are located on the symmetry center. Average W? Cl and W? N (pyridine) bond lengths are 2.435(5) and 2.18(2) Å. The cation (Py)₂H⁺ contains a hydrogen bond between pyridinium ion and pyridine. The N? N distance is 2,76 Å. (PyH)MX₄Py₂ react with pyridine giving mer-MX₃Py₃ (M = Mo, W; X = Cl, Br).