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.

Hydroxyapatite is a specific calcium phosphate phase that can occur naturally or can be synthesized using a variety of methods. Importantly it is similar in chemical and phase composition to the inorganic mineral component of bone and teeth. It has therefore been studied extensively as a biomaterial and has found applications alone or in combination with other materials to produce medical devices. This chapter reviews the various synthesis methods that have been utilised to produce hydroxyapatite, including comparisons with naturally occurring hydroxyapatites, the potential to substitute various ions in the hydroxyapatite structure, and the ability to control physical properties of the resulting material, including porosity and crystallite size and morphology. It also includes a review of the various methods for characterising these materials, including chemical, physical and biological characterisation. Although hydroxyapatite-based medical devices have been used clinically for many decades, it is clear that there is still much to learn about the factors such as composition and microstructure that can illicit various responses in vivo and how these may be best harnessed in the design of new materials for use as biomaterials.

Natural and Synthetic Hydroxyapatites

A process is disclosed for the preparation of a silicate and carbonate co-substituted calcium phosphate material. The process comprises the steps of: forming a silicon and optionally carbon-containing calcium phosphate precipitate by an aqueous precipitation method involving preparing an aqueous solution comprising phosphate ions, silicate ions, calcium ions and optionally carbonate ions, wherein the ratio of Ca/P and of Ca/(P+Si) in the solution is maintained above approximately 1.67; and heating the precipitate in an atmosphere comprising carbon and oxygen to form a silicate and carbonate co-substituted calcium phosphate material. The present invention also provides a synthetic carbonate and silicate co-substituted hydroxyapatite material, and process of formation, which may contain up to 2.86% by weight of silicon and up to 13% by weight of carbonate.

Substituted calcium phosphate materials

Researchers have used a variety of methods to enhance the performance of hydroxyapatite as a bone graft material including, among other methods, optimizing porosity, combining it with various proportions of other calcium phosphate phases such as β-TCP, or by adsorbing various growth factors to the surface. Another approach is to change the chemistry of hydroxyapatite. The modification of hydroxyapatite by the substitution of relatively small amounts (less than 2 wt%) of silicon, in the form of silicate ions, for phosphate ions significantly changes its properties. A variety of studies have reported the effect of silicon-substituted hydroxyapatite (Si-HA) ceramics on surface charge; grain size; dissolution in vitro and in vivo; osteoblast cell growth; bone repair in vivo. This updated 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. Since the original version of this chapter there have been a significant number of in vitro and in vivo studies that aim to understand what role silicate substitution may have on the biological behavior of hydroxyapatite. An overview of a related system, namely silicon-stabilized tricalcium phosphate is also provided. In addition to reviewing the current status of silicon-substituted calcium phosphate ceramics, this review finishes with a view of the future requirements of research in this field.

Iain R. Gibson

Papers

Natural and Synthetic Hydroxyapatites

Substituted calcium phosphate materials

1.20 Silicon-Containing Apatites

Effect of fluoride substitution on the biocompatibility of hydroxyapatite

Si ion concentration affects osteoblast gene expression