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  • 2010-2014  (11)
  • 2000-2004  (82)
  • 1
    Digitale Medien
    Digitale Medien
    Nanocages of layered BN: Super-high-pressure nanocells for formation of solid nitrogen (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 8523-8532 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We observed high N contents inside BN fullerenelike multilayered nanocages (ca. 30–100 nm) formed by reacting CNx nanotubes (x≤0.1) and B2O3 in a N2 atmosphere at 1985–2113 K. High-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy, energy dispersion x-ray spectroscopy, electron diffraction analysis, spatially resolved energy-filtered TEM, and in situ TEM electron irradiation studies suggest that super-high pressures (of several GPa) are generated inside nanocages, responsible of crystallizing gaseous nitrogen trapped within the BN shells. In addition, high-pressure-induced phase transformation of graphiticlike BN into diamondlike cubic BN occurs inside the nanocages. Thus, BN nanocages play an unusual role of super-high-pressure nanocells. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1469599
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  • 2
    Digitale Medien
    Digitale Medien
    Valence evaluation of cerium ions in Ce-doped α-sialon by electron energy loss spectra (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5469-5472 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: For a long time cerium ions, both Ce3+ and Ce4+, have not been considered to be able to enter the interstitial sites in an α-sialon structure until recent successes in the preparation of cerium-doped α-sialon materials using CeO2 as the starting powder. It is then of great importance and necessity to know the chemical valence of these incorporated cerium ions. Meanwhile, the specific structure of the interstices in α-sialon provides quite a different chemical environment upon which the electronic structures of cerium ions could be different from those ever reported in, for instance, metallic compounds and oxides. Electron energy loss spectra (EELS) in the M-edge region of rare-earth elements carries information on the initial state 4f occupancy. We have acquired and examined the M4,5-edge spectra of cerium at different locations in the microstructure. It has been found that all the Ce(IV) ions in the intergranular glass and the majority inside the α-sialon crystals have been reduced to Ce(III) while there exist inside the crystal cerium ions showing 4f0 initial-state peaks on the EELS spectrum. The 4f0 peak locates at about 0.6 eV higher in energy than that for CeO2. An increased and possibly by far the highest weight of f0 state is derived for Ce(IV) ions in α-sialon. The spectral evidences confirm the general suggestion of the unstability of Ce(IV) ions with silicon nitride. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1365433
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  • 3
    Digitale Medien
    Digitale Medien
    High-resolution transmission electron microscopy of cubic Si3N4 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3070-3072 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A cubic Si3N4 phase/nanostructure has been characterized by means of high-resolution analytical electron microscopy. The specimen prepared from β-Si3N4 powders at a high pressure and temperature by shock wave compression contained nanometer-sized Si3N4 crystallites. The results of nano-beam electron diffraction analysis and high-resolution lattice images as well as computer simulations revealed that the Si3N4 crystallites had a cubic symmetry with spinel structure. The electron energy loss spectrum suggested that the chemical compositions of these nanostructures were close to Si3N4. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1287765
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  • 4
    Digitale Medien
    Digitale Medien
    Si3N4/SiC interface structure in SiC-nanocrystal-embedded α-Si3N4 nanorods (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1515-1519 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Si3N4/SiC interface structure in SiC-nanocrystal-embedded α-Si3N4 nanorods was studied by high-resolution transmission electron microscopy. The SiC-nanocrystal-embedded α-Si3N4 nanorods were synthesized by the method of carbothermal reduction of SiO in pure N2 atmosphere, while the SiC nanocrystals were produced from a substitution of SiC for Si3N4. Between SiC and Si3N4, there are three kinds of plane configurations and a set of orientation relationships, i.e., [11¯0]SiC//[0001]Si3N4 and nearly (111)SiC//(101¯0)Si3N4 with low-angle discrepancy of either 3° or 5°. The origin of the low-angle discrepancies was explained in terms of a reciprocal lattice theory for heteroepitaxial interfaces. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1428106
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  • 5
    Digitale Medien
    Digitale Medien
    Nanobelts of the dielectric material Ge3N4 (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4565-4567 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ge3N4 nanobelts 30–300 nm in width were synthesized by thermal reduction of a mixed Ge+SiO2 powder in NH3 atmosphere. These nanobelts were studied by high-resolution transmission electron microscope equipped with an x-ray energy dispersive spectrometer. In these synthesized nanobelts, the existence of α and β phases of Ge3N4 was identified. The α phase exhibiting slight difference from an ideal α-Ge3N4 phase was also found in the present Ge3N4 material. The mechanism of formation of the Ge3N4 nanobelts is discussed. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1428634
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  • 6
    Digitale Medien
    Digitale Medien
    Insights into the structure of BN nanotubes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1979-1981 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The following features of multiwalled BN nanotubes were discovered using a field emission high-resolution analytical transmission electron microscope: (i) coexistence of hexagonal and rhombohedral stacking in nanotube shell assembly; (ii) flattening of nanotube cross section, which makes possible clear atomic resolution of the core structure in a three-shelled nanotube; and (iii) change in chirality of tubular layers from armchair to zigzag arrangement in a 30° double-walled nanotube kink, as revealed by atomically resolved images of tube wall segments. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1313251
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  • 7
    Digitale Medien
    Digitale Medien
    ZnO nanobelts grown on Si substrate (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 144-146 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using infrared irradiation to heat an industrial brass (Cu–Zn alloy) disk in moderate vacuum, ZnO nanobelts were directly prepared on a Si substrate. The nanobelts had a single-crystal hexagonal structure and grew along the [0001] direction. The nanobelts had two distinct widths along their entire length. Photoluminescence measurement showed that the nanobelts had an intensive near-band ultraviolet emission at 379 nm. Large-area growth and high quality indicate that the prepared ZnO nanobelts have potential application in optoelectronic devices. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1492008
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  • 8
    Digitale Medien
    Digitale Medien
    Unique morphologies of boron nitride nanotubes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 415-417 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Unusual morphological features of boron nitride nanotubes produced via metal–oxide-promoted high-temperature syntheses from carbon nanotubes, boron oxide, and nitrogen were observed using high-resolution transmission electron microscopy. The tubes normally displayed open ends and preferentially two or four tubular layers as revealed by statistical analysis of 600 nanotubes. In addition, the total amount of tubes with even number of shells (61% occurrence) markedly prevailed over that with odd number of shells (39%). All three characteristics are exceptional for BN compared to other layered materials which may be assembled in tubules. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1385188
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  • 9
    Digitale Medien
    Digitale Medien
    Field emission from individual B–C–N nanotube rope (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 1083-1085 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The field-emission characteristics of individual ropes made of B–C–N nanotubes were measured in situ in a low-energy electron point source microscope. The tungsten field emission tip of the microscope was used as a movable electrode, approaching the rope, and acting as an anode during field-emission measurements. The atomic structure and chemical composition of the ropes were analyzed by high-resolution transmission electron microscopy and electron energy-loss spectroscopy. The tubes assembled within the ropes typically revealed open-tip ends, a small number of layers and zigzag chirality. We found that the field-emission properties of the B–C–N nanotube ropes are competitive with conventional C nanotubes, with the expected additional benefit that the B–C–N ropes exhibit higher environmental stability. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1497194
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  • 10
    Digitale Medien
    Digitale Medien
    Incorporation of Cerium Ions into α'-SiAlON (2003)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 237 (Apr. 2003), p. 31-36 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/46/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.237.31.pdf
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