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The most common type of container glass which is landfilled in the UK is soda-limesilica glass, comprising typically 7I-75wt% silica, 12-I6wt% soda and 1O-15wt% lime. Considering its chemical similarity to that of the fluxing materials commonly used in whiteware bodies, it is sensible to investigate the use of SLS waste glass as replacement for these fluxes in whitewares. The present study aimed at the incorporation of colourless SLS waste glass into a standard whiteware formulation (Le. 50wt% kaolinite clay, 25wt% quartz and 25wt% nepheline syenite) as a flux, and at the examination of the microstructural development on firing. Bulk samples with two (e.g. clay and quartz, SLS glass and clay, etc.), three (standard and fully SLS-fluxed whiteware) and four (mixed nepheline syenite SLS glass as flux system) components were studied in depth. After firing 3h at 1100°C, batches containing 6.25wt% SLS glass and 18.75wt% nepheline syenite attained open-pore closure and a bulk density of 2.40 g/cm3 , comparable to that of the standard body fired at 1200°C. SLS glass softens and melts, conferring early densification and overfiring on whitewares fired at commercially-applied firing temperatures. Severe bloating ruled out the use of higher amounts of SLS glass. The microstructural evolution examined using XRD, SEMlEDS, and TEMIEDS revealed the formation of a variable composition plagioclase, wollastonite, and cristobalite in batches containing SLS glass, in addition to primary and secondary mullites, partially dissolved quartz, and a glassy matrix as found in the standard whiteware. Na+ and Ca2+ions from SLS glass migrate towards clay mineral relicts to form plagioclase, limiting the extent of mullite crystallization in SLS containing batches. Wollastonite and cristobalite crystallize from the devitrification of SLS glass. The flexural strength of the body containing 6.25wt% SLS glass fired at 1l00°C (-71.2 MPa) was higher, modulus of elasticity slightly lower, and fracture toughness comparable to those of the standard whiteware body fired at 1200°C. The Weibull modulus of the partially SLS-fluxed whiteware was lower due to the presence of crystals inhomogeneously distributed over a complex microstructure. From the physical and mechanical properties investigated in this study, SLS glass can be used as part of the fluxing system of some fully densified whitewares.

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Mullite is considered a promising candidate for ceramic recuperators in turbo propelled engines, due to its low thermal conductivity, adequate thermal shock resistance, low cost, low density, thermodynamic stability, and reasonable strength at high temperatures. Unfortunately, the limited fracture toughness of mullite (~1.8-2.8 MPa m1/2) is considered too low. A reliable way of improving fracture toughness in a range of materials has been to tailor the microstructure to contain elongated grains capable of bridging cracks. In this thesis the tailoring of mullite microstructures using a range of processing methods is reported: reactive sintering of mixtures of alumina and silica, sol-gel synthesis of mullite and the use of sol-gel derived additives to enhance the sintering of commercial mullite powders. The differences in morphologies produced as well as the influence on indentation fracture toughness is described. The addition of ceria stabilised zirconia has been shown to improve the room temperature toughness of mullite to 4.7 MPa m1/2. In this work the toughening mechanisms of this and two other mullite zirconia composites (monoclinic zirconia and yttria stabilised zirconia) are investigated, as well as the effect of temperature on the toughness of the composites. It is unknown what effect the addition of the zirconia materials to mullite has on the other properties of the material. In this work the effect on the creep resistance is investigated, with mechanistic observations presented.

High temperature nanoindentation has been employed to study the influence of temperature on mechanical properties of ceramics in Ti1-xAlxN system. The temperature had a strong effect on the hardness of the bulk single crystal TiN (TiNbulk), leading to a drop from 21.4 ± 0.4 GPa at 22 °C to 13.7 ± 0.4 GPa at 350 °C. Plastic deformation of TiNbulk mainly occurred along the (110) crystallographic planes, over the temperature range 22 °C - 350 °C, suggesting that the drop in hardness with the temperature was attributed to a change of ease of plastic slip. Hardness of magnetron sputtered Ti0.66Al0.34N coatings dropped with temperature in a similar manner to TiNbulk, although from a higher starting value. Approaching the compositional atomic ratio Al : Ti = 1:1, maximum hardness was reached and the thermal stability of hardness improved. It was proposed that the high hardness stability with the temperature of magnetron sputtered coatings is linked to the presence of the two crystallographic domains, fcc TiN and stabilized fcc AlN. The small difference between the lattice parameters of these phases seems to be accommodated by distortion of lattices, in order to form coherent boundaries between domains. It has been shown that stabilised fcc AlN formed during deposition and remained in the structure after annealing at 600 °C. Aluminium addition increased the activation energy for slip from 0.75 eV for TiNbulk to 1.26 eV for Ti0.48Al0.52N coatings. These values indicate the deformation took place by lattice controlled dislocation glide mechanism. The hardness of industrial cathodic arc Ti0.4Al0.6N films decreased with temperature in a similar way to TiNbulk, although at higher values. High deposition energies promoted fcc AlN alongside fcc TiN, and a change of growing direction from (200) to (111). The differences in structure and mechanical properties attributed to different physical vapour depositions are presented.

Batches of film-formers were created via emulsion polymerisation from a formulation supplied by Celanese. These film-formers were then incorporated into a formulation as supplied by St. Gobain Vetrotex which is used in industry to produce a working glass fibre size. Initial studies were undertaken to determine the location of the constituent species present in the size to produce an image of its structure. The film-former formulation was then altered to produce a range of physical properties. The performance of sizes produced from these film-formers were then investigated in the areas of clarity, film formation, wetting ability and strength. Alterations to the size formulation was then undertaken to determine whether this produced any effect in the performance of the size over some of the same areas of investigation. The conclusions drawn are listed below:• The coupling agent species present in the size formulation migrates to the glass interface of the size during drying.• A minor amount of lubricant migrates to the air interface of the size during drying.• Migration of species in the size only occurs during drying when the size is in its liquid state.• The molecular weight and particle size of a film-former is directly related to the initiator and first stage monomer concentrations respectively.• The molecular weight of a film-former does not alter the size's ability to form a continuous film if dried under suitable conditions. Film-formers with large particle sizes produce inhomogeneous films due to incomplete diffusion occurring during film formation.• The inhomogeneity of films with larger particle sizes present produces an increasingly optically active film with an increased wet-out rate.• The molecular weight and particle size of a film-former do not alter the corresponding sizes ability to wet a bare glass fibre due to the large amount of water present in the size formulation.• A size can be redistributed following successive re-wetting and drying under certain conditions.•The stiffness of a size is directly related to the molecular weight of the sizes film-former.• An inhomogeneous, discontinuous size will be formed with excessive deviation from the size formulation.• An excess of coupling agent is present in the standard size formulation.

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No description available.

Investigations are carried out into the mass gain behaviour of fired clay ceramics following drying (130°C) and reheating (SOO°C), and the application of these mass gain properties to the dating of archaeological ceramics using a modified rehydroxylation dating (RHX) methodology, a component based approach. Gravimetric analysis is conducted using a temperature and humidity controlled glove box arrangement (featuring a top-loading balance) on eighteen samples of varied known ages and contexts; this occurs following transfer from environmentally controlled chambers where subsamples of these samples are aged at three temperatures (2S0C, 3SoC, 45°C) following drying and reheating. The sample set consists principally of post-medieval bricks, but also includes some post-medieval pottery as ·well as both Etruscan and Roman ceramics. A suite of techniques are applied to characterise these ceramics, including XRO, FTIR, p-XRF, thin-section petrography, BET analysis, TG-MS and permeametry. Significant findings are presented related to the drying of samples, the causes of poor mass gain behaviour, the mass gain behaviour following drying at 130°C and the chemisorption processes involved, the relationship between the mass gain behaviour following heating at 130°C and SOO°C, the appropriate models and descriptors of this behaviour, as well as the relationship Of the mass gain behaviour to the chemical, mineralogical, and structural properties of the ceramic involved. For RHX dating, a component based approach is presented and applied. The results are inconclusive, with the estimated ages of most samples generally far too large, neither confirming the effectiveness of a component based approach nor the use of a tA1/4 or tA1/n model. The effects of a range of factors (uncertainties, contamination, mineral alteration, short term heating effect) on the estimated ages are examined and discussed.

No description available.