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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 398-404 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For polymer composites to be used in electronic packaging, they must have a good combination of thermal and dielectric properties. A composite of aluminum-nitride (AlN) particles dispersed around polystyrene matrix particles has been synthesized in this study. The purpose of using this microstructure is to improve the thermal properties of the polymer at the low-filler content with a minimal increase in the dielectric constant of the polymer composite. The dielectric relaxation behavior of polystyrene–AlN composites has been investigated with broadband dielectric relaxation spectroscopy. The experimental results indicate that the dielectric property of polystyrene–AlN composites is a function of polystyrene particle size, AlN filler concentration, temperature, and frequency under this dispersion state. The dependence of Maxwell–Wagner–Sillars or interfacial polarization of polystyrene–AlN composites on AlN volume fraction has also been studied. The Davidson–Cole equation is used to fit the experimental Cole–Cole plot. © 2000 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1008-1014 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we report the development of Fe modified BaTiO3 using sol-gel technique and present results of structural and dielectric studies to establish its suitability for pyroelectric sensor applications. Fine powders of Fe modified BaTiO3 were prepared by sol-gel process using barium acetate, iron isopropoxide, and titanium isopropoxide. X-ray structural analyses of the BaTiO3 with different proportion of Fe ion suggest the formation of single-phase compounds having tetragonal structure at a relatively low temperature around 750 °C for 4 h. The particle size of the powder was found to be in nm range. The sintering temperature of 1250 °C for the above calcined powder was considerably lower than the powders made by the conventional methods. The ferroelectric to paraelectric phase transition of Ba(Fe, Ti)O3 ceramics was studied using the dielectric measurement. The value of dielectric constant for Fe modified BaTiO3 was found to be lower than pure BaTiO3 and the transition temperature shifted towards the lower temperature side with an increase in Fe ion concentration. A combination of low dielectric constant and a low transition temperature makes Fe modified BaTiO3 materials attractive for room temperature pyroelectric sensor applications. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1826-1828 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric behavior of nanostructured diamond films has been investigated by using an impedance analyzer up to 500 °C. Impedance data are presented in the form of the Cole–Cole plot. It is found that: (i) the resistivity contributed both from bulk grain interior and grain boundary decreases with increasing temperature; (ii) above 250 °C, the impurities at grain boundaries are thermally activated, and thus contribute to the dielectric relaxation; and (iii) the electrical conductivity of diamond films follows an Arrhenius law with an activation energy transition from 0.13 to 0.67 eV at 250 °C. Similar activation energy is found for the Arrhenius plot of relaxation frequencies from 0.14 to 0.73 eV. The dielectric transition is explained as the change of crystal field caused by the thermal expansion or by surface bond contraction of nanosized particles. © 2001 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 19 (2000), S. 1139-1141 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1999), S. 509-518 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract FeSbO4-based semiconducting ceramics used as a promising candidate for sensing liquid-petroleum gas (LPG) are presented here for the first time. Precursor powders of FeSbO4 were prepared by two different methods (i.e., ball-milling and chemical coprecipitation). The solid-state reaction in the Fe2O3-Sb2O3 system was investigated by means of thermal gravimetric-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). Based on our experimental results and previous work, the diffusion of antimony oxide onto α-Fe2O3 is assumed to be a controlling step of the solid-state reaction. Scanning electron microscopy (SEM) and the BET method were used to characterize the samples calcined at 550 to 1000 °C. It was found that a sudden change in specific surface area, crystallite size and particle size takes place between 550 °C calcining and 600 °C calcining, which has an obvious influence on gas-sensing properties. FeSbO4-based sensors operating at 370 °C show a high sensitivity and selectivity to liquid-petroleum gas (LPG) over H2 CO or i-C4H10. Addition of Pd shows a fair increase in sensitivity to LPG, but a remarkable improvement in response and recovery times which is advantageous for its practical application.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 18 (1999), S. 1675-1677 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH4 and H2 on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH4 and H2 on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH4 during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH4 in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically.
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  • 8
    Publication Date: 2003-11-03
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 9
    Publication Date: 2000-07-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 10
    Publication Date: 2003-01-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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