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Processing and characterization of ultra-high temperature oxide fiber-reinforced oxide ceramic matrix composites with improved thermomechanical properties

Kaya C. | Kaya F.

Conference Object | 2008 | Key Engineering Materials368-372 PART 2 , pp.1778 - 1781

A combined technique comprising electrophoretic deposition (EPD) and low-pressure infiltration was used for the fabrication of multi-layer woven mullite ceramic fabric reinforced alumina ceramic matrix composites (CMCs) for high temperature applications. Two different interface materials, NdPO 4 and ZrO2 were synthesised and used for coating the woven ceramic fibres by EPD. The manufactured CMC components with suitable interface material are targeted for use at 1300-1400°C in an oxidising atmosphere and have shown very good mechanical properties in multi-layer plate forms. Damage mechanisms, such as debonding, fibre fracture, delami . . .nation and matrix cracking within the composite plates subjected to flexural loading are analysed. It is shown that the composites with NdPO4 interface and 40 vol.% fibre loading have better mechanical properties in terms of strength and damage-tolerant behaviour. The final components produced are considered to be suitable for use as shroud seals and insulating layers for combustor chambers in aircraft engines Daha fazlası Daha az

Carbon nanotube-reinforced hydroxyapatite coatings on metallic implants using electrophoretic deposition

Kaya C. | Kaya F. | Cho J. | Roether J.A. | Boccaccini A.R.

Conference Object | 2009 | Key Engineering Materials412 , pp.93 - 97

Electrophoretic deposition (EPD) has been demonstrated to be a convenient processing technique to fabricate composite ceramic coatings containing ordered arrays of carbon nanotubes. In this investigation, EPD was used to coat Ti6Al4V medical implants with hydroxyapatite (HA) layers reinforced with surface functionalized multi-walled carbon nanotubes (MWCNTs). The functionalization of MWCNTs by treating them with an acid mixture was successfully achieved in order to create functional groups on the MWCNT surfaces enabling them to be homogeneously dispersed in water. The surface treatment was also used to induce the adsorption of HA na . . .noparticles on MWCNT surfaces. Some critical issues, such as microcracking and peeling of HA layers after EPD, were effectively solved by the use of MWCNTs Daha fazlası Daha az

Hydroxyapatite nano-barium-strontium-titaniumoxide composites

Demirkol N. | Kayali E.S. | Yetmez M. | Oktar F.N. | Agathopoulos S.

Conference Object | 2011 | Key Engineering Materials484 , pp.204 - 209

The aim of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from natural bovine bone and nano barium strontium titanium oxide (5 and 10 wt%). Compositions were mechanical alloyed and compacted to pellets. The samples were subjected to sintering at different temperatures between 1000°C and 1300°C. Compression strength, Vickers microhardness as well as density were measured. SEM and X-ray diffraction studies were also conducted. With increasing sintering temperature, microhardness, compression strength and density of composites increased. . . .With increasing addition of nano barium strontium titanium oxide (BST) to bovine hydroxyapatite (BHA), microhardness values of composites decreased at all sintering temperatures, but compression strength and density values of composites showed different tendency. Compression strengths of BHA-composites at low sintering temperatures were nearly the same, but their compression strengths at high sintering temperatures decreased with increasing nano BST addition. The best mechanical properties were obtained at 1300°C sintering temperature with BHA-5wt% nano BST. Microhardness and compression strengths values of these nano-oxide composites are generally higher than that BHA-composites produced by traditional methods. Adding of nano-oxides to BHA could be a valuable method to produce rigid and high load carrying ability when compared with BHA-composites produced by conventional methods. Nano-HA and nano-oxides composites could be even better. Those nano-nano studies are still in progress. © (2011) Trans Tech Publications, Switzerland Daha fazlası Daha az

Damage detection in fibre reinforced ceramic and metal matrix composites by acoustic emission

Kaya F.

Conference Object | 2010 | Key Engineering Materials434-435 , pp.57 - 60

In this work damage micro-mechanisms of two different types of fibre reinforced composites are investigated by acoustic emission, AE. Ceramic based oxide fibre reinforced mullite matrix composite and metallic based SiC fibre reinforced titanium matrix composites exhibit different fracture mechanisms during loading and AE technique could pinpoint these damage mechanisms based on the AE responses detected simultaneously. The results show that in a ceramic matrix composite, the identification of fibre fracture and matrix cracking requires careful analysis of the AE data as both fibres and matrix break in brittle manner. Whereas the sep . . .aration of fibre fracture from the ductile tearing of matrix ligaments could be easier in metallic based composites, such as titanium matrix composites. © (2010) Trans Tech Publications Daha fazlası Daha az

A new natural biomaterial: Sheep dentine derived hydroxyapatite

Akyurt N. | Yetmez M. | Karacayli U. | Gunduz O. | Agathopoulos S. | Gokce H. | ÖveÇoglu M.L.

Conference Object | 2012 | Key Engineering Materials493-494 , pp.281 - 286

Hydroxyapatite (HA) is a particularly attractive material for bone and tooth implants since it does not only closely resemble human tooth and bone mineral but it has also biologically proven to be compatible with these tissues. The applications of pure HA are restricted to non load bearing implants due to the poor mechanical properties of HA. Biomaterials of synthetic HA are highly reliable but the synthesis of HA is often complicate and expensive. Bioceramics of naturally derived biological apatites are more economic. Aim of the present work is to introduce sheep teeth dentine HA material as an alternative source of bioactive bioma . . .terials for grafting purposes. The work was started with such a way that extracted sheep teeth were cleaned. The teeth were calcinated at 850°C in air. It was seen that enamel matter was easily separated from dentine after calcination. The collected dentine parts were crushed and ball milled. The powder was pressed between hardened steel dies to produce samples suitable for compression and microhardness tests. The obtained powder compacts were sintered at different temperatures, specifically 1000, 1100, 1200, and 1300°C in air. Results of microhardness and compression strength (along with the statistical analysis of these results) as well as those of SEM and XRD analyses are presented. In the literature, there is very little information about the mechanical properties of dentine and enamel matter derived from sheep, bovine and human. The highest compression strength value in the present study was measured around 146 MPa (from human dentine derived HA the highest value was almost 60 MPa after sintering at 1300°C). The best microhardness in the present study was found as nearly 125 HV. The results of this study showed that the HA material produced from sheep tooth dentine can be qualified as a promising source of HA needed to produce bioactive ceramics. © (2012) Trans Tech Publications, Switzerland Daha fazlası Daha az

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