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  • High-performance ceramics  (1)
  • Industrial Chemistry and Chemical Engineering  (1)
  • Inorganic Chemistry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Synthese und Charakterisierung eines neuen gemischten Titan-Aluminium-Alkoxids (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1163-1167 
    Details
    ISSN: 0044-2313
    Keywords: Titanium-Aluminium Alkoxide ; Aluminium Titanate (Tialite) ; Ceramics Precursor ; X-Ray Structure Determination ; 1H/13C-NMR (2 D) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structural Characterization of a Novel Titanium-Aluminium AlkoxideThe novel Ti-Al-Alkoxide TiAl2(OiPr)10, was synthesized from aluminium turnings and titanium tetraisopropoxide in 2-propanol and isolated by subsequent fractionating distillation. Colourless prismatic crystals precipitated after 24 h at 20°C from the main fraction. They proved very moisture sensitive. The compound crystallizes in the monoclinc space group C2/c (no. 15) with a = 2303.1(4), b = 1097.2(3), c = 1685.0(3) pm, β = 104.32(1)° and Z = 4. The molecular structure exhibits a bent Al-Ti-Al′ unit, in which Al shows tetrahedral, but Ti octahedral1 coordination. The polyhedra are connected via cis-edges of the octahedron. The structure of the compound in solution was determined by NMR spectroscopy (1H, 13C, COSY) and proved to be identical to the structure in the solid state.
    Notes: Das neue Ti-Al-Alkoxid TiAl2(OiPr)10 wurde durch Umsetzung von Al-Spänen mit Titantetraisopropoxid in Isopropanol und anschließender fraktionierender Destillation dargestellt. Die nach 24 h bei 20°C aus der Hauptfraktion gebildeten farblosen, prismatischen Kristalle sind sehr hydrolyseempfindlich. Die Kristallstruktur konnte bei -83°C bestimmt werden: monokline Raumgruppe C2/c (Nr. 15) mit a = 2303,1(4), b = 1097,2(3), c = 1685,0(3) pm, β = 104,32(1)° und Z = 4. Die Molekülstruktur besteht aus einer gewinkelten Al-Ti-Al′-Einheit, in der Al tetraedrisch und Ti oktaedrisch koordiniert sind. Die verknüpfenden Kanten am Ti-Oktaeder sind cis angeordnet. Die Struktur der Verbindung in Lösung wurde NMR-spektroskopisch (1H, 13C, COSY) ermittelt und stimmt mit der Struktur im Einkristall überein.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230726
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  • 2
    Electronic Resource
    Electronic Resource
    Boron-modified polysilylcarbodi-imides as precursors for Si-B-C-N ceramics: Synthesis, plastic-forming and high-temperature behavior (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 725-734 
    Details
    ISSN: 0268-2605
    Keywords: precursor ; ceramic ; thermolysis ; silicon ; carbodi-imide ; boron ; hydroboration ; plastic forming ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, by two different reaction pathways, of boron-modified polysilylcarbodi-imides of general type {B[C2H4Si(R)NCN]3}n (R =­singly bonded organic ligand) and the plastic-forming and the thermal behavior of these polymers are described. Compounds {B[C2H4Si(R)NCN]3}n [2a, R = H; 2b, R = CH3; 2c, R = (NCN)0.5] can be obtained by treatment of the vinyl-substituted polysilylcarbodi-imides [(H2C=CH)(R)SiNCN]n [1a, R = H; 1b, R = CH3; 1c, R = (NCN)0.5] with borane dimethylsulfide BH3·S(CH3)2. The polysilylcarbodi-imides 1a-1c themselves are accessible via the reaction of vinyl-substituted chlorosilanes (H2C=CH)-­(R)SiCl2 with cyanamide H2N-C≡N in the presence of pyridine or by a non-oxide sol-gel process of vinylated chlorosilanes and bis(trimethylsilyl)carbodi-imide, (H3C)3SiN=C=NSi(CH3)3. In the second method for the synthesis of 2a-2c, hydroboration of vinyl-substituted chlorosilanes (H2C=CH)(R)SiCl2 with borane dimethylsulfide, borane trimethylamide or borane triethylamide to yield the tris[(chlorosilyl)ethyl]boranes B[C2H4Si(R)Cl2]3 (3a, R = H; 3b, R = CH3; 3c, R = Cl) is followed by treatment of the as-obtained compounds with bis(trimethylsilyl)carbodi-imide, which results in the formation of the hydroborated polysilylcarbodi-imides 2a-2c. The thermogravimetric behavior of the polymers 1a-1c and 2a-2c up to 2300°C is reported. It is shown that boron-modified polysilylcarbodi-imides are suitable precursors for the preparation of dense bulk ceramics. Therefore, the preparation of green bodies of the hydroborated polysilylcarbodi-imides 2a-2c by plastic forming (PF) is described. A series of experiments points to the fact that the microstructure of the as-obtained ceramic monoliths obtained by subsequent thermolysis of the plastic-formed green bodies is strongly influenced by the conditions during plastic forming. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    The Importance of Chemistry in the Development of High-Performance CeramicsDedicated to Professor Heinz Harnisch on the occasion of his 60th birthday (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 26 (1987), S. 371-381 
    Details
    ISSN: 0570-0833
    Keywords: High-performance ceramics ; Ceramics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Due to their mechanical, thermal and chemical stability, high-performance ceramics have a range of properties which makes it possible in many fields to go beyond the limits of use of the various classes of materials nowadays available. In spite of this favorable starting situation, the worldwide endeavors to introduce this new group of materials have suffered some setbacks in both conventional applications and in new technologies. The ultimate reason is that these materials are very brittle. After the introduction of fracture mechanics, designers in many fields have learned how to handle brittle materials and how to exploit the potential of their properties in components subject to extreme loadings. Materials scientists have also been very successful in developing ceramics with high strength and fracture toughness characteristics. Nevertheless, the field of use has hitherto been restricted, since, in many cases, the reliability of the components is inadequate. Small and very small defects, such as micropores and cracks, as well as any other chemical and physical inhomogeneity in the structure can cause catastrophic failure of the components due to the high brittleness. Since, on the one hand, these defects are as a rule caused by inadequate control of the process sequences and, on the other, the production processes comprise a large number of chemical process steps, it is to be hoped that consistent application of the way of thinking and procedures of a chemist will make an important contribution in overcoming these difficulties.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198703713
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