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Sphene (CaTiSiO5, i.e. CaO·TiO2·SiO2) ceramics were successfully developed via the polymer derived ceramics route, starting from a commercial silicone containing specific oxide fillers. The approach allowed the combination of synthesis, in conditions of high phase purity, and advanced manufacturing. In particular, the adopted starting materials enabled an easy preparation of pastes, to be used for direct ink writing (DIW) of three-dimensional reticulated scaffolds. Sphene scaffolds, after firing at 1300 °C, were always regular and crack-free, despite changes in the line spacing, resulting in variable porosity (from ≈ 59 to 74 %), and exhibited a compressive strength from 3.9 to 12.7 MPa. The porosity was actually hierarchical, considering the formation of ‘spongy’ struts. In vitro tests, with increasing immersion time in SBF solution, confirmed the bioactivity, combined with a quite slow ion release, useful to maintain the pH value at nearly physiological values. Additional biological tests, consisting of the seeding of scaffold with normal human adult dermal fibroblasts, showed adequate cell viability and no toxicity effect.

Sphene based glass-ceramics (CaTiSiO5), an excellent candidate for a host lattice of ceramic materials and for nuclear waste immobilization, has been prepared from a powder mixture of CaCO3, TiO2 and SiO2 using vibro-milling for homogenization. Starting powders were melted at 1400°C for 2 h, cooled to room temperature, grounded again, then crystallized by thermal treatment yielding a sphene glass-ceramic. The evolution of the phase composition during thermal treatment was investigated by X-ray powder diffraction (XRPD), FT-IR, Raman and thermal analyses (TG-DTA). Pure synthetic single phase sphene was formed at 800°C for 4 h, even it is very hard to obtain monophase powder at such low temperature. Powder morphology was analyzed by scanning electron microscopy (SEM). [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 45012]

Titanite is an important mineral in petrochronology studies. Understanding chemical signatures of titanite from different environments can provide significant data in unraveling the complex histories recorded in their textures and compositions. Using a database of over 8500 titanite analyses from both the literature (3829) and our own data (4900), we found that the ratio of Fe/Al is useful for separating igneous titanite (Fe/Al is typically close to 1:1 and almost always > 1:2) from metamorphic titanite (Fe/Al ratio is < 1:2) with few exceptions. Volcanic titanite grains can also be separated from plutonic titanite grains due to their shorter crystallization histories with compositions clustered more tightly in terms of Fe, Al, and F. Compositions of titanite from plutonic rocks often have later metamorphic or hydrothermal overgrowths that are not found on volcanic titanite. Fe/Al ratios in titanite from silica-undersaturated volcanic and plutonic rocks are typically > 1:2 and include titanite with the highest Fe/Al ratios. Although they overlap the field for normal igneous titanite, other elements (particularly high levels of Nb and low levels of Y) allow them to be separated. In most metamorphic rocks, the Fe/Al ratio is < 1:2 except for a few metamorphic titanite grains that formed in mafic rocks. Titanite from ultrahigh pressure metamorphic rocks (eclogite facies) tend to have the lowest Fe/Al ratios, typically < 1:8. Titanite from hydrothermal and pegmatitic environments scatter widely in terms of Fe/Al even within single grains due to crystallization from fluids with highly variable compositions. Charge balancing in metamorphic, hydrothermal, and pegmatitic titanite due to Fe+3 and Al+3 substitution into the Ti+4 site is largely accomplished by the coupled substitution of F− for O−2. However, in volcanic and plutonic titanite, the charge imbalance due to Fe+3 and Al+3 substitution appears to be mainly coupled with REE+3 or Y+3 substitution into the Ca+2 site with a lesser contribution from F−.

Surface modification of titanium-based implants has been extensively researched as an effective tool to generate a bioactive surface that helps to create a new bone and forms a natural bond at the interface between the implants and surrounding bone tissues. The present research is focused on the development of a new methodology to obtain sphene (CaTiSiO 5 ) biocoatings on titanium substrates. Based on previous results, where sphene coatings were obtained by a manual airbrush, the coating system was improved in order to have a full control of the process in terms of uniform morphology of the biocoating. The effectiveness of the coating system and deposition process is supported by microscopic analysis of the produced coatings, by surface roughness measurements of uncoated and coated substrates, and estimation of the adhesion strength between the coatings and the substrate. The results showed that the coatings had crack-free homogenous surfaces with ideal characteristics for orthopedic and dental implants in terms of adhesion strength and surface roughness.

Sphene (CaTiSiO5), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO3, TiO2 and SiO2 using vibro-milling for homogenization and activation of precursors. During the high-pressure and high-temperature synthesis (HPS) process at 4 GPa and 1,200 °C, sphene undergoes into phase transition, from room-temperature phase P21 /a to high-temperature phase A2/a. Evidence of that structural phase transition is given in this paper using infrared, Raman spectroscopy and X-ray powder diffraction. Rietveld refinement was employed to get the structural information of the synthesized powder. The most important structural change due to phase transition, the disappearance of the characteristic out-of-center distortion of the Ti atom and moving to the center of octahedra, was confirmed. HPS is an effective method for producing full-dense ceramics without any additives. Reduction of particle size occurred during high-pressure compaction. Microstructure and particle size of both phases were analyzed by scanning electron microscopy.

Mechanical activation of precursors has been used for the preparation of Cr-doped sphene ceramic pigments (CaTi1-yCrySiO5). Ceramic material has been prepared from a powder mixture of CaCO3, TiO2, SiO2 and Cr(NO3)center dot 9H(2)O using vibro-milling for homogenization and activation of precursors. The mechanochemical process initially yielded amorphous powders, which on further calcination, crystallized to yield Cr-doped sphene ceramic pigment. Phase evolution in CaTi1-yCrySiO5 composition with thermal treatment was investigated by X-ray powder diffraction (XRPD). Texture properties and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. UV/Vis reflectance spectra are used to determinate the behavior of the chromium ion. The color efficiency of pigments was evaluated by colorimetric analysis (CIE L * a * b system). Photoluminescence measurements were also performed. (c) 2013 Elsevier B.V. All rights reserved.

Sphene (CaTiSiO5), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO3, TiO2 and SiO2 using vibromilling for homogenization and activation of precursors. The mechanochemical process initially yielded amorphous powders, which on further calcination, crystallized to yield sphene ceramic. The evolution of the phase composition with thermal treatment was investigated by X-ray powder diffraction (XRPD). Powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. Rietveld refinement was employed to get the structural information of the synthesized powder. Densification and microstructure evolution was determined by means of density and scanning electron microscopy (SEM). The most favorable conditions for mechanical activation and synthesis of sphene based ceramic material are reported. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Lesnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method), the aim of this work was to study the structure of the sphene from the Lesnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lesnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.002)1.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.001)0.995 Si4+1.024 O2-5.

Hydroxyapatite (HAp) is commonly used to coat titanium alloys (Ti-6Al-4V) for orthopedic implants. However, their poor adhesion strength and insufficient long-term stability limit their application. Novel sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study is to use the novel sphene ceramics as coatings for Ti-6Al-4V. The sol-gel method was used to produce the coatings and the thermal properties, phase composition, microstructure, thickness, surface roughness and adhesion strength of sphene coatings were analyzed by differential thermal analysis-thermal gravity (DTA-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), atom force microscopy (AFM) and scratch test, respectively. DTA analysis confirmed that the temperature of the sphene phase formation is 875 degrees C and XRD analysis indicated pure sphene coatings were obtained. A uniform structure of the sphene coating was found across the Ti-6Al-4V surface, with a thickness and surface roughness of the coating of about 0.5-1 microm and 0.38 microm, respectively. Sphene-coated Ti-6Al-4V possessed a significantly improved adhesion strength compared to that for HAp coating and their chemical stability was evaluated by testing the profile element distribution and the dissolution kinetics of calcium (Ca) ions after soaking the sphene-coated Ti-6Al-4V in Tris-HCl solution. Sphene coatings had a significantly improved chemical stability compared to the HAp coatings. A layer of apatite formed on the sphene-coated Ti-6Al-4V after they were soaked in simulated body fluids (SBF). Our results indicate that sol-gel coating of novel sphene onto Ti-6Al-4V possessed improved adhesion strength and chemical stability, compared to HAp-coated Ti-6Al-4V prepared under the same conditions, suggesting their potential application as coatings for orthopedic implants.

The ceramic tile industry increasingly commits to modernisation and implementation of new technologies in the decoration process. Current demands of advanced processes in this fi eld, such as rotational decoration, inkjet printing, PVD (physical vapour deposition), laser systems, etc., led to a great interest in developing ceramic pigments with controlled composition and microstructure. These pigments are thermally and mechanically stable in the production cycles, have reproducible and multifunctional properties, and meet ecological and economic demands. The research work in this fi eld made the ceramic sector dynamic and competitive with regard to opening new markets.

Ceramic pigments with Cr-doped sphene structure (CaSn1-xCrxSiO5, CaTi1-xCrxSiO5) were synthesized by both spray drying an aqueous solution of precursor salts plus further calcining the resulting powders and conventional ceramic method. The thermal evolution of products was studied by X-Ray Powder Diffraction (XRPD). The powder morphology and chemical composition were analyzed by SEM-EDX. The color efficiency of pigments was evaluated by colorimetric analysis (CIELab system). Results showed that the spray drying process decreased the maximum firing temperature and increased the color efficiency of Cr-doped sphene pigments therefore enhancing a higher reactivity of powders compared with the solid state process.