Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

https://www.researchgate.net/file.PostFileLoader.html?id=526892a1d4c118a61d4360bd&assetKey=AS%3A272155479085058%401441898330516

Porosity of 3D biomaterial scaffolds and osteogenesis.

Surface treatments of titanium dental implants for rapid osseointegration

Macroporous ceramics with pore sizes from 400 nm to 4 mm and porosity within the range 20%–97% have been produced for a number of well-established and emerging applications, such as molten metal filtration, catalysis, refractory insulation, and hot gas filtration. These applications take advantage of the unique properties achieved through the incorporation of macropores into solid ceramics. In this article, we review the main processing routes that can be used for the fabrication of macroporous ceramics with tailored microstructure and chemical composition. Emphasis is given to versatile and simple approaches that allow one to control the microstructural features that ultimately determine the properties of the macroporous material. Replica, sacrificial template, and direct foaming techniques are described and compared in terms of microstructures and mechanical properties that can be achieved. Finally, directions to future investigations on the processing of macroporous ceramics are proposed.

/pdf/processing-routes-to-macroporous-ceramics-a-review-1urld578zq.pdf

Processing Routes to Macroporous Ceramics: A Review

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2008.0151

Biomaterials in orthopaedics.

Silicate-substituted calcium phosphates have been shown to result in enhanced biological performance compared to the corresponding, silicate-free, calcium phosphates. We have produced a range of silicate-substituted alpha-TCP compositions using two different synthesis methods and two different substitution mechanisms. Single phase compositions were only observed for a silicate substitution of 1.3 wt% by both solid state synthesis and aqueous precipitation synthesis, although the latter was the result of a design composition with a higher silicate substitution (3 wt%). The silicate substitution resulted in small changes in the unit cell parameters of the alpha-TCP. More importantly, this small level of silicate substitution had a strong effect on the thermal stability of the alpha-TCP phase, with the silicate substitution stabilising the alpha-polymorph to lower temperatures. This has an immediate advantage in that the quenching conditions are not as critical for the production of silicate-substituted alpha-TCP compositions compared to silicate-free alpha- TCP.

Synthesis and Phase Stability of Silicate-Substituted α-Tricalcium Phosphate

The pro-angiogenic potential of copper ions could increase the viability of bone forming cells within a bone substitute scaffold, and so hasten healing, by stimulating infiltration of blood vessels into the scaffold. Copper-doped hydroxyapatite with x = 0, 0.5, 0.75 and 1 in the nominal formula Ca10(PO4)6CuxOyHz was prepared by solid state synthesis. Lattice parameters increased as x was increased, consistent with formation of Cu-O species on hydroxyl sites. In FT-IR spectra, the OH stretch (3572 cm-1) and the OH libration (631 cm-1) decreased in intensity as x was increased, and a band at 771-778 cm-1 was assignable to a Cu-O stretch, characteristic of Cu+ bands between 3140 and 3450 cm-1 related to copper-disturbed OH stretching vibrations. In UV visible spectra, bands between 400 and 800 nm were assignable to d-d transitions of Cu2+. Therefore we propose that Cu is present in these materials both as Cu+ and Cu2+.

https://www.hilarispublisher.com/open-access/preparation-of-copperdoped-hydroxyapatite-with-varying-x-in-the-composition-2090-5025.S1-005.pdf

Preparation of Copper-Doped Hydroxyapatite with Varying x in the Composition Ca10(PO4)6CuxOyHz

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

Ac impedance spectroscopy and neutron powder diffraction have been used to study the high temperature behaviour of defective fluorite solid electrolytes. In yttria-stabilised zirconia with an yttrium content of 15 mol% YO1.5 there is a marked change in conductivity behaviour at around 650 °C, with a decrease in activation energy of 0.15 eV. Structural studies confirm that this is due to a change in the bulk of the sample with the disappearance of diffuse scattering peaks and marked changes in the behaviour of the isotropic temperature factors at the same temperature. These results indicate that the change in activation energy of yttria-stabilised zirconia at 650 °C is due to an order-disorder transition involving local defect clusters. In studies of zirconia co-doped with yttrium and niobium, activation energy for conduction is found to rapidly increase with the concentration of the trivalent yttrium Saturation doping is reached at about 20–30 % of yttrium and activation energy only increases slightly with doping. Introduction of pentavalent niobium at this level of doping serves to decrease activation energy, although it also decreases conductivity slightly. The low and high temperature activation energies converge as the saturation regime is approached. These observations seem to suggest that ordering of defect clusters into microdomains increases activation energy for ionic motion. At low defect concentrations and high temperatures, this local ordering breaks down and the activation energy for conduction decreases.

Oxide Ion Transport in Highly Defective Cubic Stabilized Zirconias

Silicate substituted hydroxyapatite bioceramics have been shown to enhance bone repair in vivo compared to hydroxyapatite (HA), although the amount of silicate ions that can be substituted alone into the hydroxyapatite structure is limited to approximately 5.2 wt%, or 1.6 wt% Si. This study describes the substitution of greater levels of silicate ions via co-substitution of silicate ions with trivalent yttrium ions, without resulting in the formation of any secondary phases. This substitution mechanism involves a coupled substitution of yttrium and silicate ions for calcium and phosphate ions, respectively, and enables a level of silicate substitution up to approximately 9 wt%. Two different substitution mechanisms result in subtle differences in the crystal structure. When the mechanism xY3+ + xSiO4 4- was used, a small decrease in the a-axis, but no change in the c-axis, of the unit cell compared to HA was observed. In contrast, when the mechanism x/2Y3+ + xSiO4 4- was used, a significant increase in the c-axis of the unit cell was observed, compared to HA. XRF analysis and FTIR spectroscopy supported the proposed substitution mechanisms. These novel substitution mechanisms not only enable greater levels of silicate-substitution in HA to be prepared, but also allow the production of compositions with the same level of silicate substitution, and with subtle differences in chemical structure.

Iain R. Gibson

Papers

Synthesis and Phase Stability of Silicate-Substituted α-Tricalcium Phosphate

Preparation of Copper-Doped Hydroxyapatite with Varying x in the Composition Ca10(PO4)6CuxOyHz

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

Oxide Ion Transport in Highly Defective Cubic Stabilized Zirconias

Synthesis of Novel High Silicate-Substituted Hydroxyapatite by Co-Substitution Mechanisms