The response of powder of the Nickel-based superalloy CM247LC to a range of Hot Isostatic Pressing (HIPping) conditions and post-HIP heat treatments has been investigated as a preliminary step in the assessment of net shape HIPping as a possible process-route for component production. A HIPping pressure of 150MPa was used at temperatures of 1100°C, 1200°C, 1260°C and 1320°C. 1260°C as-HIPped specimens had the best tensile and HCF fatigue properties at both room temperature and 750 °C; the influence of post-HIP solution treatment conditions and of subsequent ageing on the properties of samples which had been HIPped at 1260 °C was thus investigated. A solution treatment at 1100 °C for 1h followed by forced air cooling and ageing at 870 °C for 16h resulted in the optimum tensile, high cycle fatigue at both room temperature and 750 °C. The optimized microstructure consists of a ‘necklace’ structure of coarse γ′ particles along the grain boundaries; cuboidal γ′ distributed inside grains with hyper-fine γ′ precipitated in γ channels; and fine carbides homogeneously disperse in the matrix. The properties of samples with this microstructure were comparable with those of cast, directionally solidified CM247LC. Solution treatment at 1260 °C gives better creep resistance at 760 °C/ 350MPa. It was also concluded that with gas-atomised powder, solution treatment must be carried out below the HIP temperature to minimise porosity. Analytical scanning electron microscopy showed that Hf-rich inclusions, some of which had alumina cores, initiated failure in almost all tensile samples and in all fatigue samples. It was shown that this type of inclusion can be avoided by removal of Hf from the alloy; but the removal of Hf – which is added to the alloy to improve castings – degrade the creep properties over the temperature range of 700 °C to 950 °C and the stress range of 150 MPa to 550 MPa. Further work is required to assess the influence on the tensile and fatigue properties.

The present investigation has been focused on the design, deposition and characterisation of novel low-friction, wear-resistant multilayer nanocomposite CrAlTiCN coatings. Systematic materials characterisation and property evaluation were conducted on the as-deposited and oxidation-tested CrAlTiCN coatings, and the results are presented and discussed. It is possible to generate novel CrAlTiCN coatings with the carbon content up to 24.34 at% by closed-field unbalanced magnetron sputtering of graphite target. The microstructure of the CrAlTiCN coatings mainly depends on their carbon content. When the carbon content is low, carbon atoms are mainly dissolved in the fcc metastable phase (Cr, Al, Ti) (C, N); when the carbon content is high, the major carbon atoms will form amorphous carbon with a C-C bond state and in a sp\(^2\) dominated graphitic environment. Both the hardness and brittleness of CrAlTiCN coatings reduce with increasing the carbon content. When tested at room temperature under unidirectional sliding conditions, the friction coefficient and wear of the CrAlTiCN coatings decrease with the carbon content, and the thermal stability of CrAlTiCN coatings is similar to the CrAlTiN coating but better than graphite-like carbon coatings. The good performance of the new CrAlTiCN coatings can be attributed to the optimised design of the coating system: the Cr/Al for oxidation resistance, the amorphous C for lowfriction and the multi-layered nano-composite microstructure for high toughness.

There is an urgent desire to move from lead-based piezoelectric materials to lead-free alternatives. One of the most promising lead-free materials has been reported to be zBao.7oCao.3oTi0J-(1-z) BaZro.2oTio.soOJ (abbreviated as zBCT-(1-z)BZT) system, which has comparable piezoelectric performance to lead-based materials. However, there is a lack of systematic research to investigate the effects of fabrication on the structural and functional properties of this zBCT -(1-z)BZT system. In this work, the end member Bai-xCaxTiOJ (x=0-0.30) and BaZryTii-y03 (ji=0-0.30) systems have been investigated. The phase transition diagrams of the two systems have been successfully established by measuring temperature dependent Raman spectroscopy and functional properties. The optimized fabrication procedure for forming single phased Bao.7oCao.3oTi0J and BaZro.2oTio.soOJ ceramics by solidstate methods, has been applied as a novel way to form zBCT-(1-z)BZT (O:Sz:~:J) ceramics by sintering the pre-calcined Bao.7oCao.3oTi0J and BaZro.2oTio.soOJ powders. A new phase diagram of the zBCT-(1-z)BZT (0$z:S1) has been constructed by combing structural and functional property measurements. It indicates a vertical orthorhombic phase region separating rhombohedral and tetragonal phases below the Curie temperature. The highest piezoelectric properties have been observed for z=0.5 ceramics at room temperature, due to the increased potential polarization directions in the vicinity of the orthorhombic to tetragonal phase boundary.

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The current work proposes a novel approach to the production of sorbent materials, which integrates recycling of calcium silicate-based industrial residues and sequestration of carbon dioxide in the process of accelerated carbonation. The concept was tested on model substrates of suitable mineralogy, namely Portland cement and dicalcium silicate, which were carbonated, and examined by nitrogen adsorption, XRD, NMR, SEM, TG-DTA analytical techniques. The carbonated materials were evaluated in batch sorption studies with the solutions of cadmium, lead, nickel, cobalt, zinc, strontium and cesium. The findings of the structural examination indicated the transformation of nesosilicate-type calcium silicates during carbonation into polymerized Ca-silicate frameworks, aragonite (in carbonated cement only) and calcite. The NMR investigation, for the first time, described in detail the nature of polymerized silicates (predominantly Q3 and Q4 silicon environment) in carbonated cement and dicalcium silicate. The carbon dioxide uptake measured by thermogravimetric analysis was equivalent to 480 kg/t and 370 kg/t of CO2 reacted with dicalcium silicate and Portland cement, respectively. Batch sorption experiments demonstrated better metal removal efficiencies by carbonated cement, particularly for cadmium and cesium. It was concluded that the metal removal mechanisms ranged from adsorption (e.g. ion-exchange, complexation, isomorphic substitution) to surface and bulk precipitation. The main solubility-limiting phases identified for cadmium, lead, strontium and zinc were otavite CdCO3 (only detected in carbonated cement), (hydro-)cerussite, strontianite, and hydrozincite. Cobalt, nickel, cesium were selectively sorbed within the Si-rich phase of both carbonated cement and dicalcium silicate. The leach study demonstrated an adequate containment of sorbed/precipitated metals within carbonated cement (= 2.5% leached) and carbonated dicalcium silicate (= 12% leached) in water. Metal mobility, however, increased during the exposure to acidic conditions, with = 5% of cadmium, lead, cobalt, nickel and 15- 75% of zinc, cesium, strontium being mobilized into leachates.