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  • 1
    Electronic Resource
    Electronic Resource
    Electrolyte wetting effects in the comparative polarization behaviour of the hydrogen evolution reaction at Ni-Mo-Cd electrodes in KF · 2HF and KOH · 2H2O melts (1995)
    Springer
    Journal of applied electrochemistry 25 (1995), S. 6-14 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In the electrolyte process of fluorine production from KF · 2HF melts at 85° C, unusually high polarization arises both at the cell anodes (carbon) and cathodes (mild steel) at moderate current densities. The anomalous polarization behaviour in fluorine evolution at carbon anodes has been extensively studied but much less is known about the origin of hyperpolarization in hydrogen evolution at the cathodes. Here, the results of comparative polarization studies at a Ni-Mo-Cd composite cathode material in a KF · 2HF melt and a corresponding aquo-analogue melt of KOH · 2H2O are reported. Large differences are observed which are attributed to the different wetting characteristics of these two melts at the interface of the Ni-Mo-Cd cathodes that are microporous. Such electrode material also offers a major improvement of cathode polarization over that at mild steel surfaces. Conclusions on wetting effects are based on: (i) a comparative determination of hydrogen-bubble contact angles at the electrode in the two melts and (ii) an evaluation of the double-layer capacitances of the electrode interfaces with the two melts as determined by the fast potential-relaxation method, at short times after current interruption. The apparent double-layer capacitances at a given electrode are very different in the two melts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251258
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  • 2
    Electronic Resource
    Electronic Resource
    Arsenic poisoning effects on cathodic polarization and hydrogen adsorption at platinum and steel electrodes in KF · 2HF melts (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 803-814 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract It is demonstrated how the presence of arsenic species in the KF · 2HF melt employed as the electrolyte in fluorine production cells greatly affects the electrocatalytic behaviour of the steel electrodes that are used as cathodes. Effects of the introduction of As2O3, AsF3 and AsF5 as the sources of catalyst poison species have been studied. Such species influence the electrode kinetics of the cathodic hydrogen evolution reaction (h.e.r.) and the adsorption of the overpotential-deposited (o.p.d.) H intermediate. Using Pt, as a model electrocatalyst surface, these effects were quantitatively studied by means of potential-relaxation transients, Tafel relations and cyclic voltammetry, the latter enabling changes of underpotential-deposited C (u.p.d.) H coverage due to the presence of As species to be evaluated. By means of simulation of the potential-relaxation behaviour, information on rate constants, coverages by o.p.d. H and As species were also derived. The presence of As at Pt cathodes suppresses the u.p.d. H adsorption and modifies the o.p.d. H behaviour and the associated pseudocapacitance. The presence and generation of As(−iii) species, as AsH3, in the evolved hydrogen gas was demonstrated by means of Marsh's test. The contact-angles of hydrogen bubbles generated in the h.e.r. at mild-steel electrode surfaces were also determined comparatively in relation to observed sluggish hydrogen bubble detachment from the electrode surfaces when As species were present.Ex situ XPS analysis confirmed the presence of As species on the electrode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683742
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of Some Parameters on the Synthesis of ZrO2 Nanoparticles by Heating of Alcohol–aqueous Salt Solutions (1999)
    Springer
    Journal of nanoparticle research 1 (1999), S. 349-352 
    Details
    ISSN: 1572-896X
    Keywords: alcohol–aqueous salt solutions ; ZrO2 ; nanoparticles ; aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Parameters that influence ZrO2 (3-mol% Y2O3 stabilized) nanoparticles prepared by heating of alcohol–aqueous salt solutions were investigated. It revealed that the kind of alcohol used significantly affected the particle size and morphology of the as synthesized nano-ZrO2 powders. The ratio of alcohol to water (R/H) was also important to conduct the gelation process. The dispersion and sintering behavior of the powder could be optimized via aging. By carefully controlling the process, weakly agglomerated ZrO2 nanoparticles with an average particle size of 13-nm (TEM) were achieved. The classical DLVO theory was employed to clarify the effect of solvent on powder morphology, an aging mechanism was proposed as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010056830551
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  • 4
    Electronic Resource
    Electronic Resource
    Nanocrystalline NiZn ferrite synthesized by high energy ball milling (1999)
    Springer
    Journal of materials science 18 (1999), S. 1781-1783 
    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:1006639530050
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  • 5
    Electronic Resource
    Electronic Resource
    Silicon carbide-toughened zirconia ceramics (1996)
    Springer
    Journal of materials science 31 (1996), S. 957-962 
    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 Tetragonal zirconia polycrystalline (TZP) ceramics containing SiC reinforcement in the form of fine particles (nano-scale), particles (micro-scale), whiskers and platelets were synthesized by hot-pressing. The effects of morphology and grain size of SiC reinforcement on the strength and fracture toughness at room temperature were investigated. The addition of SiC (in whatever form) caused decreases in strength and toughness at room temperature with the exception of whisker-reinforced materials. Toughness fell off with increasing temperature, but nevertheless retained about one-half of the room-temperature value for that particular SiC reinforcement. However, the whisker- and particle-reinforced materials had higher K lc values at high temperature than fine particle- or platelet-reinforced materials, with values in excess of 7 MPa m1/2 at 1000 °C. The microstructure was examined for SiC whisker-reinforced/TZP materials by TEM and HREM, to examine the nature of the whisker/zirconia interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352896
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  • 6
    Electronic Resource
    Electronic Resource
    Microstructure and mechanical properties of nanoscale SiC/Ca α-SiAlON composites (1997)
    Springer
    Journal of materials science 32 (1997), S. 3263-3269 
    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 Ceramic composites comprising nanoscale (less than 200 nm) silicon carbide particles distributed in a matrix of calcium α-SiAlON (α′) have been prepared by uniaxial hot pressing, and the reaction sequence, during densification of a sample containing 20 wt% SiC, has been investigated in the temperature range 1400–1800°C. Samples containing up to 20 wt% SiC were produced to near full density by pressure sintering at temperatures as low as 1600°C for 1 h. For samples with higher SiC contents subjected to a similar treatment, there was residual porosity which was detrimental to the mechanical properties. The SiC was preferentially distributed intergranularly within the α-SiAlON and was effective in controlling grain growth of the α-SiAlON during processing. There was an increase in the uniformity of the grain structure and a significant refinement of the grain size of the composite microstructures with increasing SiC content. The hardness and the three-point bending strength of the composite samples increased markedly with increasing SiC content up to a level of 20 wt%. For a sample containing 20 wt % SiC, the bending strength was about ∼1.5 times that of single-phase α-SiAlON. For samples with higher SiC contents, the rate of increase in hardness was diminished and the bending strength decreased because of incomplete densification. The initial improvement in fracture strength with increasing SiC content is plausibly attributable to the uniform refined grain structure of the composite materials, assuming that the maximum flaw size scales with the grain size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018627507245
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  • 7
    Electronic Resource
    Electronic Resource
    Mössbauer studies of R(Fe1−x Mn x )2 (R = Tb, Ho) intermetallic compounds (1995)
    Springer
    Journal of materials science 14 (1995), S. 705-707 
    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/10.1007/BF00253377
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  • 8
    Electronic Resource
    Electronic Resource
    Preferred orientation in hot-pressed Ca α-SiAlON ceramics (1996)
    Springer
    Journal of materials science 15 (1996), S. 1447-1449 
    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/10.1007/BF00275302
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  • 9
    Electronic Resource
    Electronic Resource
    Phase transformation in the Al2O3–ZrO2 system (1998)
    Springer
    Journal of materials science 33 (1998), S. 1399-1403 
    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 Co-precipitation methods have been used to produce 20 mol% Al2O3–80 mol% ZrO2 mixed oxides, from aqueous solutions of zirconium oxychloride and aluminium chloride, followed by precipitation with ammonia. The resulting gel was calcined at increasing temperatures, and X-ray diffraction confirmed that the structure remained amorphous up to 750°C and then crystallized as a single-phase cubic zirconia solid solution, but with a reduced unit-cell dimension. At higher temperatures, the unit-cell dimension increased and, above 950°C, this phase started to transform to a tetragonal zirconia (t-ZrO2) phase, again of reduced cell dimensions compared with t-ZrO2, with simultaneous appearance of small amounts of θ-Al2O3. Above 1100°C, the tetragonal phase transformed to monoclinic zirconia on cooling, and the amount of θ-Al2O3 increased. Above 1200°C, the θ-Al2O3 transformed to the stable α-Al2O3. These results confirm that aluminium acts as a stabilizing cation for zirconia up to temperatures of about 1100°C. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004327104481
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  • 10
    Electronic Resource
    Electronic Resource
    Localized superplastic deformation of nanocrystalline 3Y-TZP ceramics under cyclic tensile fatigue at ambient temperature (1998)
    Springer
    Journal of materials science 33 (1998), S. 2719-2723 
    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 Cyclic tensile fatigue tests were performed on 100±20 nm, and 0.35 μm 3Y-TZP ceramic specimens at room temperature. Localized superplastic deformation of the grains in the 100 nm material at and near to the fracture surfaces was first identified by AFM imaging. Slip band-like microfeatures, similar to those reported on some metals, were also unexpectedly seen to develop on the side faces. In contrast, the 0.35 μm specimens retained their equiaxed grain morphology after undergoing similar testing conditions. The micromechanisms underlining these phenomena were discussed. Grain boundary diffusion of the respective atomic species is reasoned to be the major governing process in operation. And the contribution of a dislocation slip mechanism is considered to play a possible or parallel role. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004390227100
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