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.

A systematic study of the stability of potassium/carbonate co-substituted hydroxyapatite has been carried out, with samples synthesized by aqueous precipitation according to the chargebalanced mechanism: Ca10-xKx(PO4)6-x(CO3)x(OH)2 Samples up to x=10 were prepared and their stability determined by heating at a range of temperatures in both air and CO2 environments Results showed that whilst samples up to x=10 can be prepared phase-pure, the stability of these materials is strongly dependent on sintering temperature with the full range of compositions only being stable at 600°C in CO2 The c unit cell parameter increases linearly with x, and, for a fixed composition, decreases linearly with temperature indicating loss of carbonate from the A-site FTIR showed that samples contained carbonate at both A- and B-sites, and that carbonate content increased with x

Synthesis and Stability of Potassium/Carbonate Co-Substituted Hydroxyapatites

The bone graft system comprises a solid inorganic component, which is bone graft material, and a hydrogel. The hydrogel contains >2ppm of silicon ions, calculated as parts by weight of Si per million of the aqueous component of the hydrogel. Preferably, the solid inorganic component comprises hydroxyapatite or a silicon-containing hydroxyapatite, and may be a silicon- containing hydroxyapatite having a Ca/P ratio in the range 2.05 to 2.55 and a Ca/(P + Si) molar ratio less than 1.66. Bone healing is promoted by delivery of silicon ion release from the hydrogel and by the solid inorganic component stimulating cell behaviour.

Bone graft system

High temperature phase transactions in CA3(PO4)2 measured by neutron diffraction

Researchers have used a variety of methods to enhance the performance of hydroxyapatite (HA) as a bone graft material. These include, among other methods, porosity optimization, in combination with various proportions of other calcium phosphate phases such as beta-tricalcium phosphate (β-TCP), or by adsorption of various growth factors on the surface. Another approach is to change the chemistry of HA. The modification of HA by the substitution of relatively small amounts (<2 wt%) of silicon, in the form of silicate ions, for phosphate ions effects a significant change in its properties. A variety of studies have reported the effect of silicon-substituted HA (Si-HA) ceramics on surface charge, grain size, dissolution in vitro and in vivo, osteoblast cell growth, and bone repair in vivo. This review summarizes these studies, including the synthesis of Si-HA, the formation of Si-HA coatings and porous scaffolds, and their biological behavior, and attempts to correlate physiochemical properties with in vitro and in vivo observations. An overview of a related system, namely silicon-stabilized TCP, is also provided. In addition to reviewing the current status of silicon-substituted calcium phosphate ceramics, this chapter offers a view of the future requirements of research in this field.

Silicon-Containing Apatites

The sintering behaviour of a number of commercially produced 8 mol% yttria-stabilized zirconia powders has been studied. The effect of different sintering regimes on the density and microstructure of the sintered ceramic was determined using density measurements, scanning electron microscopy (SEM) and dilatometry. The chemical homogeneity, particle size and the morphology of the as-received powder were related to the sintering behaviour of the different commercial powders. Powders prepared via a route which involved a spray-drying step sintered more readily than those prepared without a spray-drying step. Plasma-derived powders did not sinter to as high an apparent density as co-precipitated powders. The effect of sample density on the ionic conductivity of sintered YSZ ceramics was studied using a.c. impedance spectroscopy. This technique allowed separation of the bulk and grain-boundary components, enabling clear intepretation of the effects of sample porosity of the conduction pathways. Ceramics prepared from the three different powders achieved a bulk ionic conductivity of ∼16 S cm-1 at 1000 °C for sintered densities of 95% or greater. The results obtained are compared to values reported for a variety of other commercial powders. © 1998 Kluwer Academic Publishers

Iain R. Gibson

Papers

Synthesis and Stability of Potassium/Carbonate Co-Substituted Hydroxyapatites

Bone graft system

High temperature phase transactions in CA3(PO4)2 measured by neutron diffraction

Silicon-Containing Apatites

Sinterability of commercial 8 mol% yttria-stabilized zirconia powders and the effect of sintered density on the ionic conductivity