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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3447-3450 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The internal friction (IF) and elastic modulus were measured for bulk samples of nano-ZrO2 from −200 °C to room temperature. An IF peak located on a high background was found for as-compacted bulk nano-ZrO2. At the same time, a large modulus defect appeared. After annealing, the IF background decreased substantially and both the IF peak and the modulus defect disappeared. When the sample was heat treated according to the schedule 700 °C/15 h+900 °C/21 h+1100 °C/18 h, the modulus jumped a factor of 2 comparison with the modulus of an as-compacted sample. The modulus of as-compacted nano-ZrO2 was higher than that of coarse-grained ZrO2 at low temperature. The origin of the IF peak is associated with the atomic relaxation in boundaries. The dramatic increase of the modulus for the annealed nano-ZrO2 is mainly induced by the enhancement of the binding force and the decrease of the mobility of atoms and bonds in boundaries.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2709-2711 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical absorption properties were investigated for mesoporous silica loaded with different amounts (up to 5% in weight) of silver (Ag) nanoparticles (less than 4 nm in diameter) into its pores. In contrast to the previously reported glasses containing Ag particles, in this Ag particle-loaded silica no apparent surface plasmon resonance peak of Ag particle, other than an absorption edge, was observed. This composite exhibits the optical features of a semiconductor with direct band gap. The absorption edge shifts in the range from about 200 to about 700 nm with an increasing Ag loading amount up to 5% in weight, and hence, is controllable. Adsorption of oxygen in air on the surface of Ag particles within the pores, and scattering inside the porous structure were used to explain these results. © 1998 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5453-5456 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fluorescence phenomena of nanostructured Al2O3 without doping and after doping of nano-Fe2O3 (4.61 and 48.01 wt %) were systematically investigated. The results show that a new fluorescence band with a peak position of about 17 500 cm−1 occurs for boehmite, η-Al2O3 and γ-Al2O3 and it disappears for α-Al2O3. This band can be attributed to fluorescence of Fe3+ in the systems with low-order degree (boehmite, η- and γ-Al2O3 and interfaces), which arises from 6A1→4T1 d5 electron transitions of Fe3+.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5185-5188 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy levels of defect states in nanometer-sized amorphous silicon nitride solids were systematically studied in terms of ultraviolet emission spectra. Six emission bands were observed, corresponding to 3.2, 2.8, 2.7, 2.4, 2.3, and 2.0 eV, respectively. With increasing the heat-treated temperature from room temperature to 1000 °C in low vacuum, these emission bands became high. For the specimen heated at 1000 °C, a new emission band of 3.0 eV appeared. The appearance of these emission bands is closely related to the formation of the energy levels of the defect states in the energy gap. The origin of these emission bands are discussed in detail.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1186-1189 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline TiO2 powder with a grain size of 9.8 nm was prepared by the hydrothermal precipitation method. Thermal desorption in the powder and compacted TiO2 samples has been studied by differential scanning calorimetry and thermogravimetric analysis. An endothermic peak was observed on these samples and the peak can be attributed to thermal desorption. The desorption enthalpy per gram of adsorbates in the compacted sample is larger than that in the powder one and it continues to increase with the compacting pressure. A tentative model has been proposed to explain the increase in desorption enthalpy due to compaction. © 1996 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6313-6316 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dangling bonds in pellets made by compacting nanometer-sized silicon nitride (NASN) grains are studied by electron-spin resonance (ESR). The ESR results of NASN show that the number of dangling bonds in NASN is about three orders of magnitude higher than that of coarse-grained silicon nitride. It is also observed that compaction pressure and thermal treatment temperature affect the type and the number of dangling bonds. An explanation is presented for the changes in the dangling bonds caused by the processes of compaction and thermal treatment.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1572-1574 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanoscaled AgxAu1−x (0.2〈x〈0.8) alloy particles were synthesized by putting gold and silver particles into pores of monolithic mesoporous silica by soaking and annealing method. It has been found that in optical absorption spectrum, the surface plasmon resonance (SPR) maximum of AgxAu1−x alloy particles can shift from about 524 nm (SPR maximum of Au nanoparticles) to about 400 nm (SPR maximum of Ag nanoparticles) with increasing concentration of Ag in AgxAu1−x alloy particle. The simulation of optical absorption spectrum of AgxAu1−x alloy particles was conducted based on Mie theory. The calculated values are found to be consistent with the experimental results. © 2000 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 174-176 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we report the observation of an ultraviolet (UV) photoluminescence (PL) emission at around 330 nm in porous silica prepared by the sol–gel process. Upon a posttreatment which leads to OH adsorption, the intensity of the observed UV PL emission increases significantly. It is shown that this behavior is associated with the increase of OH groups adsorbed on the surface of porous silica. We suggest that the observed UV PL emission originates from the nonbridging oxygen hole centers generated from surface hydroxyls. The mechanism of the UV PL emission is expressed tentatively by combining the nonbridging oxygen centers charge modification model and the vibrative absorption of a SiO2 network containing water. © 2001 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 495-497 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence study was performed on indium–oxide (INO) nanoparticles dispersed within pores of mesoporous silica, annealed at different temperatures (from 500 to 850 °C). It was found that, for the dispersed INO nanoparticles, there exists a broad luminescence band, consisting of three peaks at about 430, 480, and 520 nm, spanning the whole visible region, in contrast to the aggregates of INO nanoparticles which exhibit no luminescence. This band increases with rise of annealing temperature up to 650 °C, at which the band reaches maximum. When annealing temperature is 700 °C, the whole band redshifts and peaks at about 545 nm. Annealing at higher temperatures leads to additional redshift and decrease of the luminescence band. It has been shown that the luminescence in this study is associated with the size and the structure of the INO particles within pores of porous silica. The peaks at 430, 480, and 520 nm originate from amorphous INO particles about 2, 4, and 6 nm in diameter. The 545 nm peak is attributed to crystallized INO particles with larger size. © 1999 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2586-2588 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAs nanocrystals embedded in SiO2 matrix have been fabricated by a radio-frequency magnetron co-sputtering technique without postannealing. X-ray photoelectron spectra and Raman spectroscopy strongly suggest the existence of InAs nanocrystals in the SiO2 matrix. From the optical absorption spectrum, the absorption edge exhibits a very large blueshift of 3.3 eV with respect to that of bulk InAs. The double-peak ultraviolet photoluminescence is observed. Our experimental results show that this double-peak phenomenon originates from the radiative recombination of the quantum-confined electron-heavy hole excitons and electron-split-off hole excitons. © 1997 American Institute of Physics.
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