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  • 1
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The two-point bend strength and the fracture toughness of a series of soda–potassia–silicate and soda–potassia–calcia–silicate glass fibres have been measured. There is a clear variation of mean strength with composition for the soda–potassia–silicate glasses, however, there is much less variation of mean strength with composition for the soda–potassia–calcia–silicate glasses. There is also a greater variation of fracture toughness with composition for the soda–potassia–silicate glasses than for the soda–potassia–calcia–silicate glasses. The mean strength, fracture toughness and inferred flaw sizes for the soda–potassia–calcia–silicate glasses are all less than the equivalent values for the soda–potassia–silicate glasses. These results are related to the structural models and durability of the glasses tested.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 2929-2935 
    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 A study of the stability relations of pure silica phases is described. It is shown that although cristobalite can be produced from pure quartz by heating it is not possible to produce tridymite in this fashion; a flux or mineralizer is required for tridymite formation and even in this case cristobalite is produced before any tridymite is observed. Thus it is concluded that the stability relations for the silica minerals proposed by Fenner are incorrect and that tridymite is not a stable phase in the pure silica system.
    Type of Medium: Electronic Resource
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  • 3
    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 Directed melt oxidation (DMOX) of pure aluminium has been used to produce Al/Al2O3 composites by growth into a particulate alumina filler in the absence of any dopants apart from a β-Al2O3 impurity in the filler. The microstructural development and mechanisms of growth of these composites have been investigated. It is shown that the Al2O3 filler used in this work has both chemical and physical effects on the reaction process. The β-Al2O3 impurity introduces sodium into the system; this increases the wettability of alumina (both filler and oxidation reaction product) by molten aluminium, and initiates DMOX reactions. In addition, the filler particle size has an effect on the directed oxidation reaction. If the particle size is too fine, no oxidation growth takes place. Filler particles limit the ingress of oxygen through the reaction front so that AIN instead of Al2O3 may be formed in regions behind the main reaction front. Although such AIN production is seen when magnesium is used as a dopant to initiate DMOX reactions in the Al/Al2O3 system, it is more marked with sodium, because the latter has a greater effect on the wettability of alumina by aluminium.
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  • 4
    ISSN: 1572-8943
    Keywords: cristobalite inversion ; quartz ; silica polymorphism ; tridymite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The cristobalite α-β inversion has been studied using DSC on cristobalites produced by firing high purity quartz with and without addition of a mineraliser. If no mineraliser was used, the inversion temperatures and hysteresis on heating and cooling increased with firing temperature. Firing time had little or no effect on inversion temperature. When a mineraliser was used, the same general trend was observed with increases in firing time at low temperatures leading to splitting of the inversion peak. The amount of mineraliser added had little effect. Tridymite inversions were also observed. The results are explained in terms of the degree of order of the cristobalite structure.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Stress intensity factors at any point on the crack front of penny and half-penny shaped cracks subjected to stress gradients are presented. The SIF's which are exact for a penny shaped crack are based on the well known solution for a point load acting normally to such a crack. The line load solution which is derived from this is different in form to those given by previous workers and is more readily integrated to give SIF's for stress gradient loading. This is demonstrated by the derivation of a general equation for the SIF at any point on a penny-shaped crack due to polynomial stress gradients. These results are extended to produce a similarly general, albeit approximate, equation for the SIF at any point on the circumference of a half-penny crack due to polynomial loading. The usefulness of the approach developed here is further indicated by the derivation of an approximate SIF for exponential stress gradients over a half-penny crack.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7111-7118 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The liquid jet impact technique has been used extensively for the quantitative study of rain impact. Most of this work has been for normal impact. Although some angled impact studies have been pursued using jets, these have been purely of a qualitative nature. This paper develops the theory of angled drop impact. This allows the establishment of a method of correlating between angled drop and jet impact and obtaining "equivalent drop'' curves for jet impact. The correlation is also applied to normal impact. For normal impact it is shown that the previously published equivalent drop curves need to be modified especially at low velocities. The results for both normal and angled impact are discussed with reference to the details of the jet profile, and it is shown that angled jets may be considered as having an average equivalent drop size. The theory of angled impact also explains the shape of damage marks produced by impact and why the amount of damage decreases so rapidly with increasing angle.
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  • 7
    Publication Date: 2013-01-30
    Description: Vitrification is used for the immobilization and conditioning of high-level waste (HLW) arising from the reprocessing of spent nuclear fuel in the UK. Vitrification is also under consideration for the immobilization of certain intermediate-level wastes (ILW), where there may be advantages of volume reduction and removal of uncertainties in long-term waste behaviour, compared to encapsulation in a cement grout. This paper gives an overview of recent work into the chemical durability of UK vitrified wasteforms to inform the technical specification for the disposal facilities for these waste products and the treatment of their long-term behaviour in post-closure performance assessment. This has included: (1) measurements of the initial glass dissolution rates of a simulated HLW Magnox waste glass in a range of groundwater types representative of potential UK host geologies and in simulated high pH near-field porewaters relevant to potential disposal concepts, using Product Consistency Test type-B (PCT-B) at 40°C; and (2) durability testing of three simulant ILW glasses in a saturated calcium hydroxide buffered solution to simulate conditions in cement-based disposal vaults, using PCT-B tests at 50°C. The experimentally defined initial rate of HLW Magnox waste glass dissolution in a range of simulated groundwater compositions appears to be similar regardless of the ionic strength and major element composition of the solution. The release of caesium from HLW Magnox waste glass appears to be sensitive to solution composition. Caesium is selectively retained in the glass compared to other soluble components in the two low ionic strength solutions, but is released at similar rates to other soluble components in the three groundwaters and Ca(OH) 2 solution. Whether this change in caesium retention is an ionic strength effect or is related to changes in the nature of the surface alteration layer formed on the glass, has yet to be established. For HLW Magnox waste glass, dissolution is accelerated at high pH in NaOH solution, however, the presence of calcium acts to mitigate the effects of high pH, at least initially. In Ca(OH) 2 solution, calcium is found to react with all the glasses studied leading to the formation of calcium-containing alteration products. The initial dissolution behaviour in Ca(OH) 2 solution varies with glass composition and in particular appears to be sensitive to the boron content.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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  • 8
    Publication Date: 2012-12-01
    Description: Vitrification is used for the immobilization and conditioning of high-level waste (HLW) arising from the reprocessing of spent nuclear fuel in the UK. Vitrification is also under consideration for the immobilization of certain intermediate-level wastes (ILW), where there may be advantages of volume reduction and removal of uncertainties in long-term waste behaviour, compared to encapsulation in a cement grout. This paper gives an overview of recent work into the chemical durability of UK vitrified wasteforms to inform the technical specification for the disposal facilities for these waste products and the treatment of their long-term behaviour in post-closure performance assessment. This has included: (1) measurements of the initial glass dissolution rates of a simulated HLW Magnox waste glass in a range of groundwater types representative of potential UK host geologies and in simulated high pH near-field porewaters relevant to potential disposal concepts, using Product Consistency Test type-B (PCT-B) at 40°C; and (2) durability testing of three simulant ILW glasses in a saturated calcium hydroxide buffered solution to simulate conditions in cement-based disposal vaults, using PCT-B tests at 50°C.The experimentally defined initial rate of HLW Magnox waste glass dissolution in a range of simulated groundwater compositions appears to be similar regardless of the ionic strength and major element composition of the solution. The release of caesium from HLW Magnox waste glass appears to be sensitive to solution composition. Caesium is selectively retained in the glass compared to other soluble components in the two low ionic strength solutions, but is released at similar rates to other soluble components in the three groundwaters and Ca(OH)2 solution. Whether this change in caesium retention is an ionic strength effect or is related to changes in the nature of the surface alteration layer formed on the glass, has yet to be established. For HLW Magnox waste glass, dissolution is accelerated at high pH in NaOH solution, however, the presence of calcium acts to mitigate the effects of high pH, at least initially. In Ca(OH)2 solution, calcium is found to react with all the glasses studied leading to the formation of calcium-containing alteration products. The initial dissolution behaviour in Ca(OH)2 solution varies with glass composition and in particular appears to be sensitive to the boron content.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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