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  • 1
    Electronic Resource
    Electronic Resource
    An integrated dynamic model for the volcanic activity at Poas volcano, Costa Rica (1987)
    Springer
    Bulletin of volcanology 49 (1987), S. 588-598 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A dynamic model for the activity of Poas Volcano, Costa Rica, is proposed. Data collected during a three-year period show that the volcanic processes occur within a small hydrothermal system. Heat is supplied by a magma body in the conduit and is transferred to the surface by fluid convection. Within a given volume of rock, pore pressure builds up due to the upward motion of fluids and the increase in vapor pressure when the temperature rises above the boiling point. Ultimately, the system becomes unstable when the pore pressure overcomes the total pressure. This leads to the assumption that the kinetic and thermal energies are proportional to the depth at which the mechanical equilibrium is disturbed. Laboratory experiments were performed by heating samples of the crater lake deposits. The preliminary results of these experiments show significant analogies with the low-energy activity of the volcano. Following this model we estimated that a phreatic explosion which reaches 200 m in height (comparable to the one observed by Francis et al. in 1978) originates at a depth of 70 m and a temperature of 180° C; these values agree with those reported in the literature. In addition, “magmatic” sulfur, which partitions into the rising hydrothermal fluids, reacts at lower temperature and higher $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{f} O_2$$ to produce pockets of liquid sulfur in the conduit deposits and the lava dome. These pockets are subsequently erupted forming the pyroclastic sulfur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01079964
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of humidity on the electrical response of porous BaTiO3 ceramics (1999)
    Springer
    Journal of materials science 18 (1999), S. 1297-1299 
    Details
    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
    URL: http://dx.doi.org/10.1023/A:1006662805186
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  • 3
    Electronic Resource
    Electronic Resource
    Multilayer piezoelectric devices based on PZT (1996)
    Springer
    Journal of materials science 7 (1996), S. 55-60 
    Details
    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 A PZT 53/47 was obtained by a modified chemical route. Small-particle-size powders were allowed to obtain high solid content, non-aqueous slips with Newtonian behaviour. The use of both the tape-casting technique and the common multilayer ceramic fabrication process led to a high-density multilayer ceramic body without cracks or delaminations, and a homogeneous microstructure. The architecture of multilayer piezoelectrics has an important effect on the clamping of resonance modes, particularly on planar modes, by modifying the nature of the electrode and the effect of the polarization procedure. This fact is corroborated by the dielectric and piezoelectric properties measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194094
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric and microstructural properties of sintered BaTiO3 ceramics prepared from different TiO2 raw materials (1991)
    Springer
    Journal of materials science 26 (1991), S. 3257-3263 
    Details
    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 BaTiO3 ceramics, sintered from powders previously synthesized using TiO2 of different characteristics, have been studied. The microstructural development depended on the crystalline nature and impurity types and levels, when the same sintering schedules were applied. Anatase leads to BaTiO3 powders which showed a controlled grain growth after sintering. Rutile with very low impurity levels gave materials in which a non-uniform grain growth was promoted. Dielectric constant and loss tangent were measured and correlated with the density and microstructure. From these correlations, it seems that the raw materials' nature has a greater effect on the dielectric properties that the sintering schedule of a given material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01124671
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  • 5
    Electronic Resource
    Electronic Resource
    Phase transition and electrical conductivity in the system YMnO3-CaMnO3 (1999)
    Springer
    Journal of materials science 34 (1999), S. 2565-2568 
    Details
    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 Solid solution formation between the ferroelectric hexagonal compound YMnO3 and the semiconducting perovskite compound CaMnO3 has been studied in the Y-rich region of the pseudobinary system. The materials were prepared by reaction of the corresponding oxides and the calcium carbonate for obtaining the corresponding phases and subsequent sintering of the pressed powders in the 1400–1525 °C-temperature range. Their ceramic characteristics were established. Samples with relative density 〉98% Dth were obtained. The hexagonal symmetry of the pure yttrium manganite changes to an orthorhombic one, isostructural with that of the GdMnO3 compound, for ∼32 mol % CaMnO3. The incorporation of the Ca cation causes an increasing in the compactness of the lattice cell, promoting a rise in the apparent density, despite of the smaller atomic weight of the Ca cation against that of the Y one, until the transition to the orthorhombic lattice occurs. Subsequent increase in the Ca amount lead to a decrease in the theoretical density. The electrical conductivity of the solid solutions increases strongly from 100 to the 90/10 Y/Ca composition, and more moderately for higher Ca amounts. Conductivity values as high as 10−2 S · cm−1 were measured on the denser samples. The activation energy for conduction suffers a corresponding decrease when the Ca amount is increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004692430582
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  • 6
    Electronic Resource
    Electronic Resource
    Off-diagonal long-range order in Little's model (1972)
    Springer
    Journal of low temperature physics 7 (1972), S. 119-127 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Various authors have shown, using nonrigorous arguments, that the one-dimensional model of Little cannot exhibit off-diagonal long-range order (ODLRO) at nonzero temperatures. Hohenberg has proven that ODLRO cannot exist at nonzero temperatures in any one- or two-dimensionalhomogeneous system. Bychkovet al. have shown that the nonhomogeneity in the Little model may produce peculiar forms of ODLRO. Using Bogoliubov's inequality, we prove that such ODLRO vanishes at nonzero temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00629123
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation, microstructural development and dielectric properties of Pb(Mg1/3Nb2/3)O3-Pb(TixZr1−x)O3 multilayer ceramic capacitors (1994)
    Springer
    Journal of materials science 29 (1994), S. 4999-5004 
    Details
    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 Multilayer ceramic capacitors based on PMN-PZT solid solutions have been prepared using a 70 % Ag-30% Pd alloy as internal electrode. Some interaction of the electrode-dielectric with Ag+ diffusion into the dielectric was observed. The Ag+ diffusion influenced the normal microstructural development present in the PMN-PZT ceramics. In spite of this, the dielectric behaviour of a five active layers capacitor sintered at 1050 °C for 2 h in air showed a capacitance of 120 nF, an effective dielectric constant maximum of ~200 000 and dielectric losses of about 3% near room temperature and 1 kHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01151090
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  • 8
    Electronic Resource
    Electronic Resource
    Microstructure and properties of K2O doped superconducting YBa2Cu3O7−x (1994)
    Springer
    Journal of materials science 29 (1994), S. 5997-6003 
    Details
    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 K doped YBa2Cu2O x powders have been obtained by incorporating K2CO3 to previously coprecipitated amorphous hydroxide mixtures. Synthesis was performed at 900
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366885
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  • 9
    Electronic Resource
    Electronic Resource
    Phosphor-doped BaTiO3: Microstructure development and dielectric properties (1995)
    Springer
    Journal of materials science 30 (1995), S. 3799-3804 
    Details
    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 phosphor cation retards BaTiO3 formation during the first reaction stage, and favours Ba2TiO4 formation. As a consequence, the end of the reaction is only accomplished at 1150 °C. The average particle size of the synthesized powder, after attrition milling was 〈1.0 μm. Isopressed bars were sintered from 1200–1400 °C. Dilatometric measurements showed the existence of two sintering mechanisms; these were confirmed by means of isothermal sintering experiments. Microstructural development at low sintering temperature differs from that corresponding to higher ones. Very high permittivity values were measured in the 1325–1350 °C sintered samples. This anomalous dielectric behaviour is associated with the presence of phosphor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01153937
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  • 10
    Electronic Resource
    Electronic Resource
    Processing and microstructure of porous and dense PZT thick films on Al2O3 (1995)
    Springer
    Journal of materials science 30 (1995), S. 5399-5404 
    Details
    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 processing of porous PZT thick-film ceramics on Al2O3 has been studied. The films were screen-printed from a thixotropic ink of PZT with a 58% solids content. The thick films were sintered between 1000 and 1150°C for 2 h. The sintered films show a 10 μm thickness and an average pore diameter ranging from 1–2 μm. The PZT forms a continuous skeleton that can be filled with the desired polymer. Dense and continuous PZT films were fabricated by screen-printing PZT ink on previously electroded Al2O3 substrates with Ag/Pd 70/30 paste. Densification of the PZT was obtained by sintering near the liquidus temperature of the Ag-Pd system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351550
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