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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 18 (1991), S. 47-52 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A 29Si and 27Al magic angle spinning nuclear magnetic resonance study is reported for differently synthesized mullites. The 29Si MAS NMR spectra of all samples are essentially identical. They consist of a main resonance at -86.8 ppm, a shoulder around -90 ppm and a second resonance at -94.2 ppm. The main resonance is interpreted as being due to a sillimanite-type geometry around Si and the second one is tentatively assigned to a Si environment typical for mullite. The 27Al MAS NMR spectra of sinter- and fused-mullite measured at different Larmor frequencies revealed clearly the presence of three distinct Al sites in mullite, i.e. of octahedral (M1), tetrahedral (M2) and distorted tetrahedral (Al*) sites.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract This paper presents a solid state 1H, 23Na, 29Si, and 119Sn nuclear magnetic resonance (NMR) study of sorensenite. New 29Si NMR data for two related pyroxenoids, wollastonite and pectolite, are included for comparison. By more sensitively probing chemical bonding, the element-specific NMR observations both complement and reinforce the x-ray diffraction results. The role of hydrogen and its interactions with neighboring atoms in sorensenite is further clarified. The wollastonite and pectolite 29Si spectra resolve for the first time all three crystallographic sites and their comparison with sorensenite reveals subtle, systematic differences in sites along the pyroxenoid chains. Effects of corner-shared BeO4 tetrahedra on 29Si shifts show that sorensenite may also be viewed as a more polymerized silicoberyllate.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 16 (1989), S. 752-756 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract 29Si MAS NMR spectra of synthetic akermanite, Ca2MgSi2O7, exhibit a splitting into three or more lines in the stability feld of the low-temperature incommensurate phase. With increasing temperature, these lines continuously merge into a single line which is then characteristic of the high-temperature, melilite-type structure. The data point to the non-equivalence of Si sites in the low-temperature phase and the gradual structural changes as the phase transition temperature is approached.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 341-348 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Magnetic resonance imaging (MRI) has been used to study solid rocket propellants and liner material. The samples studied were simulants, used mainly for safety reasons, of real systems using ammonium sulfate in place of the energetic materials. The polymeric binder was hydroxy-terminated poly(butadiene) (HTPB) reacted with isopherone diisocyanate. MRI was used to observe variations in intensity in the simulant samples due to differing percentages of solids loading. It also showed the homogeneous intensity obtained for an unfilled sample used for comparison with the 82% filled material. The liner material, HTPB and dimeryl diisocyanate, was imaged despite its relative rigidity observed from its short T2 value. Samples of poly(alkylene) oxide simulants were imaged, and various bubbles and regions of filler inhomogeneity were observed. These defects were correlated with photo-micrographs of the sample. MRI can be used to image real systems of solid rocket components. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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