Dissolution Mechanisms of Oxides and Titanate Ceramics — Electron Microscope and Surface Analytical Studies

Turner, Peter S.; Jones, Colin F.; Myhra, Sverre; Neall, F. B.; Pham, Duy Khanh; Smart, Roger St. C.

doi:10.1007/978-94-009-1035-5_41

Cited by 13 publications

(12 citation statements)

References 17 publications

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“…This dependence is not observed during the initial kinetic regime of MgO dissolution [11,12]. Protonation of oxide sites (eqs.…”

Section: Dissolutionmentioning

confidence: 87%

“…A dramatic restructuring of the smooth, nearly perfect (100) MgO smoke faces occurs before any significant dissolution (i.e. < 1 monolayer) can be measured [11,12]. It seems clear that surface diffusion of cationic and anionic species across the surface must be a rapid process in comparison to dissolution during the initial stage of interaction with water or acid.…”

Section: O>(s) + H + (Aq) -+ Oh(s)mentioning

confidence: 99%

“…In each case, it was assumed that the density of reactive sites per unit area is constant and independent of the extent of dissolution or of pH. * This assumption is certainly not true of the initial stages of dissolution of MgO where the reactivity is govemed by the rapidly changing structure of the oxide surface [11,12,14]. A dramatic restructuring of the smooth, nearly perfect (100) MgO smoke faces occurs before any significant dissolution (i.e.…”

Section: O>(s) + H + (Aq) -+ Oh(s)mentioning

confidence: 99%

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Quantum chemical modelling case studies relevant to metal oxide dissolution and catalysis

Gerson

Jones

Simpson

et al. 2001

Ionics

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Abstract. Over the past 20 years quantum-chemical methods have been developed sufficiently so that they can now be applied to the elucidation of the complex mechanistic processes that occur during metal oxide dissolution and catalysis reactions. Many of the reactions occurring during these processes are not directly accessible to experimental techniques and therefore quantum-chemical modelling can be applied to probe the individual reaction steps involved in the overall mechanism.Quantum chemistry provides the means of calculating the electronic properties of solids (e.g. band structures) structural properties of solids and surfaces (for instance surface relaxation and rumpling) heats of formation and reaction, activation energies, spectroscopic excitation energies and vibrational frequencies. Three case studies are described, which have been chosen to cover a range of quantum chemical applications and methodologies. These case studies are a) the dissolution mechanism of MgO, b) the parameterisation of titanium dioxide for the determination of electronic properties and c) the mechanism and energetics of adsorption of Pd onto rutile. These case studies utilise Hartree-Fock semiempirical and ab initio quantum-chemical methods as well as density functional methodologies. A range of model types are used, namely cluster models embedded in pseudo-atoms, 3-dimensional periodic models and 2-dimensional periodic surface models.

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“…This dependence is not observed during the initial kinetic regime of MgO dissolution [11,12]. Protonation of oxide sites (eqs.…”

Section: Dissolutionmentioning

confidence: 87%

Section: O>(s) + H + (Aq) -+ Oh(s)mentioning

confidence: 99%

Section: O>(s) + H + (Aq) -+ Oh(s)mentioning

confidence: 99%

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Quantum chemical modelling case studies relevant to metal oxide dissolution and catalysis

Gerson

Jones

Simpson

et al. 2001

Ionics

View full text Add to dashboard Cite

show abstract

“…Additionally, there will be aqueous attack on the silica network and establishment of local equilibrium concentrations of silicaceous species, as in the case of glass dissolution [12], i.e., Given a supply of anionic oxidants, transport through the oxide is driven by the field, E>10 9 V/m, for the as-received system. During the growth phase of less than 20 ms, the thickness of the oxide layer may increase by a factor of 10, at which point the field is of the order of 10 8 V/m.…”

Section: Anodic Oxidation Of Simentioning

confidence: 99%

Tip-induced Local Anodic Oxidation: Nanolithography and Nanobiotechnology

Myhra

2007

Nanobiotechnol

Self Cite

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Nanolithographic patterning of Si and a-C type diamond-like carbon (DLC) films by local anodic aqueous electro-oxidation can produce structures that are laterally differentiated in geometry and surface chemistry. The processing is most conveniently carried out on a scanning probe platform, with the probe tip effectively being a traveling electrode, thus defining the lateral extent and location of the oxidative reaction. A similar process has been demonstrated based on electron beam patterning in an environmental SEM. Tip-induced patterning of Si in combination with existing chemical functionalization procedures provides a route for taking the current generation of biotechnological devices from the micro-to the nanoscale. In the case of DLC, nano-/microlithography may extend processes and devices in biotechnology to a carbon-based material.

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“…The authors proposed a base catalysed hydrolysis and ion exchange model to account for their observations, whereby surface Ca 2+ is released to solution via exchange with H + and Ti-O-Ti surface species are converted to Ti-OH species via reaction with OH-and H20. The overall reaction can be written as follows (Pham et al 1989):…”

Section: Perovskite Ceramics and Natural Samplesmentioning

confidence: 99%

Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms

Lumpkin

Smith

Gieré

et al. 2004

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A number of polyphase or single-phase ceramic waste forms have been considered as options for the disposal of nuclear waste in geological repositories. Of critical concern in the scientific evaluation of these materials is their performance in natural systems over long periods of time (e.g., 103 to 106 years). This paper gives an overview of the aqueous durability of the major titanate host phases for actinides (e.g., Th, U, Np, Pu, Cm) and important fission products (e.g., Sr and Cs) in alternative crystalline ceramic waste forms. These host phases are compared with reference to some basic acceptance criteria, including the long-term behaviour determined from studies of natural samples. The available data indicate that zirconolite and pyrochlore are excellent candidate host phases for actinides. These structures exhibit excellent aqueous durability, crystal chemical flexibility, high waste loadings, and well-known processing conditions. Although both pyrochlore and zirconolite become amorphous due to alphadecay processes, the total volume swelling is only 5-6% and there is no significant effect of radiation damage on aqueous durability. Hollandite also appears to be an excellent candidate host phase for radioactive Cs isotopes. Brannerite and perovskite, on the other hand, are more prone to alteration in aqueous fluids and have a lower degree of chemical flexibility. With the exception of hollandite, many of the properties of these potential host phases have been confirmed through studies of natural samples.

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Dissolution Mechanisms of Oxides and Titanate Ceramics — Electron Microscope and Surface Analytical Studies

Cited by 13 publications

References 17 publications

Quantum chemical modelling case studies relevant to metal oxide dissolution and catalysis

Quantum chemical modelling case studies relevant to metal oxide dissolution and catalysis

Tip-induced Local Anodic Oxidation: Nanolithography and Nanobiotechnology

Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms

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