Mechanical properties of ultra-high pressure sintered sphene (CaTiSiO5)
01 Dec 2016-Processing and Application of Ceramics (National Library of Serbia)-Vol. 10, Iss: 4, pp 295-298
TL;DR: In this paper, the nano-mechanical properties of sphene sintered under ultra-high pressures in the order of 4 GPa were investigated using indentation techniques and an indentation hardness of 6.6 GPa and reduced elastic modulus of 112.3 GPa was reported at maximum load of 7 mN.
Abstract: The investigation of nano-mechanical properties of sphene sintered under ultra-high pressures in the order of 4 GPa is done using indentation techniques. An indentation hardness of 6.6 GPa and reduced elastic modulus of 112.3 GPa is reported at maximum load of 7 mN. The material exhibits a high elastic recovery (∼59.1%) and the nature of deformation mechanism has been comprehended from the plastic work ratio. In addition, the fracture toughness of the material is also evaluated using indentation crack length method.
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TL;DR: In this paper, the authors used a Berkovich indenter to determine hardness and elastic modulus from indentation load-displacement data, and showed that the curve of the curve is not linear, even in the initial stages of the unloading process.
Abstract: The indentation load-displacement behavior of six materials tested with a Berkovich indenter has been carefully documented to establish an improved method for determining hardness and elastic modulus from indentation load-displacement data. The materials included fused silica, soda–lime glass, and single crystals of aluminum, tungsten, quartz, and sapphire. It is shown that the load–displacement curves during unloading in these materials are not linear, even in the initial stages, thereby suggesting that the flat punch approximation used so often in the analysis of unloading data is not entirely adequate. An analysis technique is presented that accounts for the curvature in the unloading data and provides a physically justifiable procedure for determining the depth which should be used in conjunction with the indenter shape function to establish the contact area at peak load. The hardnesses and elastic moduli of the six materials are computed using the analysis procedure and compared with values determined by independent means to assess the accuracy of the method. The results show that with good technique, moduli can be measured to within 5%.
22,557 citations
TL;DR: In this article, the authors proposed a new theory of elastic contact, which is more closely related to real surfaces than earlier theories, and showed how the contact deformation depends on the topography of the surface, and established the criterion for distinguishing surfaces which touch elastically from those which touch plastically.
Abstract: It is usually assumed that the real area of contact between two nominally flat metal surfaces is determined by the plastic deformation of their highest asperities. This leads at once to the result that the real area of contact is directlyproportional to the load and independent of the apparent area-a result with many applications in the theories of electric contacts and friction. Archard pointed out that plastic deformation could not be the universal rule, and introduced a model which showed that, contrary to earlier ideas, the area of contact could be proportional to the load even with purely elastic contact. This paper describes a new theory of elastic contact, which is more closely related to real surfaces than earlier theories. We show how the contact deformation depends on the topography of the surface, and establish the criterion for distinguishing surfaces which touch elastically from those which touch plastically. The theory also indicates the existence of an 'elastic contact hardness', a composite quantity depending on the elastic properties and the topography, which plays the same role in elastic contact as the conventional hardness does in plastic contact. A new instrument for measuring surface topography has been built; with it the various parameters shown by the theory to govern surface contact can be measured experimentally. The typical radii of surface asperities have been measured. They were found, surprisingly, to be orders of magnitude larger than the heights of the asperities. More generally we have been able to study the distributions of asperity heights and of other surface features for a variety of surfaces prepared by standard techniques. Using these data we find that contact between surfaces is frequently plastic, as usually assumed, but that surfaces which touch elastically are by no means uncommon in engineering practice.
5,371 citations
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...Greenwood and Williamson have proposed [11] a model in which it is indicated that if γ > 1, the material is predominantly plastic whereas if γ < 0....
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...Apart from this, the materials with high H/E are said to possess high wear resistance [15] and the HPS sphene with a H/E ratio of around 0....
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TL;DR: In this paper, tetragonal-zirconia-polycrystalline (TZP) powder coated with Al2O3 was used to improve the mechanical properties of a bioceramic material.
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...2 MPa·m) indicating a possible potential use in biomedical applications [13,14]....
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TL;DR: It is demonstrated that the newly developed CaTiSiO(5) ceramics possess excellent chemical stability and bioactivity, suggesting their potential use in skeletal tissue regeneration and as coating onto currently available orthopedic/dental implants.
Abstract: Calcium silicate (CaSiO(3)) is regarded as a potential bioactive material. However, its poor chemical stability and cytocompatibility limits its biological applications. The aim of this study is to incorporate Titanium (Ti) into CaSiO(3) to produce a ceramic with improved chemical stability and biological properties. Sphene (CaTiSiO(5)) ceramics were prepared by sintering sol-gel-derived CaTiSiO(5) powder compacts and their chemical stability was assessed by measuring the ions released and weight loss after soaking CaTiSiO(5) in simulating body fluid for 1, 3, 7, and 14 days. Results indicated that CaTiSiO(5) has a significantly improved chemical stability, compared with CaSiO(3). The ability of CaTiSiO(5) ceramics to support human bone-derived cells (HBDC) attachment, proliferation, and differentiation was assessed using scanning electron microscopy, MTS, and alkaline phosphatase activity assays, respectively. CaTiSiO(5) ceramics supported HBDC attachment and significantly enhanced their proliferation and differentiation, compared with CaSiO(3) ceramics. Taken together, this study demonstrates that the newly developed CaTiSiO(5) ceramics possess excellent chemical stability and bioactivity, suggesting their potential use in skeletal tissue regeneration and as coating onto currently available orthopedic/dental implants.
119 citations
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...in coefficients in contrast to HAP and CaSiO3 coatings [3]....
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