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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3159-3162 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We calculate the deuterium electric field gradient in the HD and D2 molecules at various internuclear separations by making use of a previously proposed variation–perturbation method. We calculate DEFG values at internuclear separations R=1.2, 1.3, 1.4, 1.5, and 1.6. We also calculate the average values for the vibrational ground state v=0 and for the vibrational states J=0, J=1, and J=2 of the HD and D2 molecules. The vibrational averaged DEFG value is very close to the equilibrium value at R=1.4 due to accidental cancellation of different contributions. The difference between our result and other theoretical values is about 2.5%.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A spatially variant dielectric Ca–Mg–silicate (CMS)/Bi–Ba–Nd–titania (BBNT) composite, in which periodic BBNT inclusions were embedded in the CMS matrix, was fabricated using the thermoplastic extrusion. The co-firing behavior of the composite was evaluated in terms of its shrinkage compatibility, thermoplastic compatibility, and chemical compatibility. The noticeable shrinkage mismatch between CMS and BBNT materials was observed. Such shrinkage mismatch strongly affected the interfacial bonding types of the composites. The good interfacial bonding was observed for the composite having BBNT inclusions in the CMS matrix; however, the interfacial cracking and matrix cracking for the opposite design (i.e., CMS inclusions in the BBNT matrix). In addition, the (Ca, Zn)-rich glassy phase in the CMS region migrated into the BBNT region, forming an interfacial reaction layer. The dielectric properties of the CMS, BBNT, and CMS–BBNT mixture were measured to evaluate the spatially variant dielectric CMS/BBNT composite as a novel dielectric substrate.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A coextrusion process was used to fabricate three-directionally macrochanneled tetragonal zirconia polycrystals (TZP) with a calcium phosphate coating layer. The three-directionally connected structure was built by a unique alignment and a lamination of the TZP surrounded by calcium phosphate and carbon black filaments. After a thermal treatment (binder burnout and sintering), a 52 vol% array of 290 μm, three-directionally connected macrochannels, which were clad on the inside with bioactive calcium phosphate, had formed on the sintered TZP body. For a comparison, porous calcium phosphate with a similar structure was also fabricated. The compressive strength (96 MPa) of the three-directionally macrochanneled TZP with a bioactive calcium phosphate layer was much higher than that (24 MPa) of the three-directionally macrochanneled calcium phosphate.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The oxidation behavior and its effect on the mechanical properties of fibrous monolith Si3N4/BN after exposure to air at temperatures ranging from 1000° to 1400°C for up to 20 h were investigated. After exposure at 1000°C, only the BN cell boundary was oxidized, forming a B2O3 liquid phase. With increasing exposure temperature, the Si3N4 cells began to oxidize, forming crystalline Y2Si2O7, SiO2, and silicate glass. However, in this case, a weight loss was observed due to extensive vaporization of the B2O3 liquid. After exposure at 1400°C, large Y2Si2O7 crystals with a glassy phase formed near the BN cell boundaries. The oxidation behavior significantly affected the mechanical properties of the fibrous monolith. The flexural strength and work-of-fracture decreased with increasing exposure temperature, while the noncatastrophic failure was maintained.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A coextrusion process was used to fabricate macrochannelled hydroxyapatite (HA). To improve the powder characteristics, the HA powder was calcined at 900°C in air for 1 h. A feedrod composed of HA (shell) and carbon black (core) was coextruded at 120°C through a symmetric 8:1 square reduction die. After the first coextrusion, the individual pieces were bundled, warm-pressed, and then coextruded again. After removing the binder, the billet was sintered at 1350°C for 1h in air. Uniform, 27 vol% macrochannels with a diameter of 270 μm were formed in the dense HA through removal of the carbon black. The compressive strength of the test specimens was strongly dependent on the macrochannel direction due to the stress concentrations related to the macrochannel geometry.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The oxidation behaviors of monolithic Si3N4 and nanocomposite Si3N4-SiC with Yb2O3 as a sintering aid were investigated. The specimens were exposed to air at temperatures between 1200° and 1500°C for up to 200 h. Parabolic weight gains with respect to exposure time were observed for both specimens. The oxidation products formed on the surface also were similar, i.e., a mixture of crystalline Yb2Si2O7 and SiO2 (cristobalite). However, strength retention after oxidation was much higher for the nanocomposite Si3N4-SiC compared to the monolithic Si3N4. The SiC particles of the nanocomposite at the grain boundary were effective in suppressing the migration of Yb3+ ions from the bulk grain-boundary region to the surface during the oxidation process. As a result, depletion of yttribium ions, which led to the formation of a damaged zone beneath the oxide layer, was prevented.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 5639-5644 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report theoretical results of the electric field gradient at the position of the deuterium nucleus in the DF molecule. The purpose of the calculation is the evaluation of a correction term to the expectation value of the electric field gradient with respect to a linear combination of atomic orbitals-molecular orbital self-consistent field (LCAO-MO SCF) function proposed by Ransil. Our method is based on a variation-perturbation method that was proposed previously. The expectation value of q0D (el) is qD =−2.8964, the corrected value is qD (el)=−2.9056, and the experimental value is qD (exp)=−2.9241 (all values are expressed in terms of atomic units). The difference between our theoretical value and the experimental result is 0.6%.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fluoridated hydroxyapatite (FHA) powders were fabricated by a solid-state reaction, and their dense bodies were obtained by sintering at 1350°C. The biological performance of FHAs was evaluated and compared with that of pure hydroxyapatite (HA). The fluoridation of FHAs was confirmed by the changes in their lattice parameters. Human osteoblast-like cells attached and proliferated well on all of the FHAs, including pure FA. The proliferation and differentiation levels of the cells on FHAs were similar to those on pure HA. This finding suggests that the FHAs possess cell viability and activity comparable to pure HA, and thus are potentially applicable as hard tissue substitutes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fluor-hydroxyapatite (FHA) fabricated by a reaction between fluorapatite (FA) and hydroxyapatite (HA) was mixed with ZrO2 to produce FHA–ZrO2 composites. When the relative amount of FA to HA increased, the decomposition of the composite was decreased gradually because of the formation of thermally stable FHA solid solutions. With such suppression of decomposition, the FHA–ZrO2 composites retained fully densified bodies. As a result, significant enhancements in mechanical properties, such as hardness, flexural strength, and fracture toughness, were achieved as the relative amount of FA to HA increased. The highest values in strength and toughness were 220 MPa and 2.5 MPa·m1/2, respectively, with FHA–40 vol% ZrO2 composites. In vitro proliferation of osteoblast-like cells (MG63) on the composites showed behavior similar to that observed on pure HA and FHA. Alkaline phosphatase (ALP) activity of the growing cells (HOS) on the composites was slightly down-regulated compared with that on pure HA and FHA at prolonged periods.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The oxidation behavior of reaction-bonded silicon carbide (RBSC) and the effect of oxidation on the room-temperature flexural strength of RBSC were investigated. Four different types of RBSC, each having various SiC particle-size distributions and free silicon contents, were exposed to air at 1300°C for up to 200 h. Parabolic weight gains, with respect to oxidation time, were observed in all the specimens. The strength of the RBSC increased after oxidation for up to 50 h, because of the blunting of cracks by the silica layer that was formed on the surface. However, with further oxidation, the beneficial role of the oxide layer was negated by the cracks that were newly generated on the surface because of the thermal mismatch between the substrate and the silica layer. The amount of free silicon had a negligible effect on the strength retention of the specimens after the oxidation processes.
    Type of Medium: Electronic Resource
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