Papers by Keyword: Calcium Silicate

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Authors: Noriyuki Mifune, Yoshio Harada
Abstract: The applicability of 2CaO·SiO2-CaO·ZrO2 ceramic coatings as thermal barrier coatings (TBCs) was investigated. Coatings consisting of various ratios of 2CaO·SiO2-CaO·ZrO2 bond-coated with NiCrAlY were prepared using the plasma spray process. The structure of the coatings was characterized by scanning electron microscopy and X-ray diffraction analysis. The resistance of the coatings to thermal shock was evaluated with acoustic emission techniques under a thermal cycle from 1273 K to room temperature, and the hot corrosion resistance of the coatings was investigated with V2O5 and Na2SO4 at 1273 K for 3 h. The 2CaO·SiO2-10~30mass%CaO·ZrO2 coatings had excellent thermal shock resistance, because the coatings contained a vertical micro-crack in a single flattened ceramic particle. These coatings possessed excellent corrosion protection preventing direct contact between the corrosive ashes and a NiCrAlY bond coating. The CaO in the coating reacted with vanadium compounds and inhibited the penetration of corrosive ashes to the bond coating. The developed 2CaO·SiO2-20mass%CaO·ZrO2 thermal barrier coating on stationary vanes was evaluated in an actual gas turbine. The ceramic coating did not separate from the bond coating and reacted with SOx in combustion gas to produce a stable sulfate (CaSO4), which fixed in the coating. The TBC effectively protected the metal substrate of the vanes in practical operating condition for 25,000 h.
Authors: M. Motisuke, R. García Carrodeguas, Cecília A.C. Zavaglia
Abstract: On this study the influence of silicon dopping on the properties of the final calcium phosphate cement were analysed and compared to the ones of the conventional Si and Mg-free α-TCP cement. In spite of silicon doping, Si-α-TCP calcination temperature (1400°C) was higher than the one used for conventional α-TCP (1300°C) as a result of Mg contamination on the commercial precursor used on the Si-α-TCP synthesis. Because of the high temperature used, Si-α-TCP sample was difficult to mill. Even after 1 week milling, the particle size achieved was 12µm while Si-free α-TCP reached 7.7µm. Consequently, the reactivity of both powders was different. In conclusion, the properties of Si-α-TCP cement were not satisfactory for clinical application. In order to do it so, it is essential to enhance the powder reactivity by reducing Mg contamination, lowering the sintering temperature and reducing the particle size to, then, achieve the desired reactivity and compressive strength.
Authors: Priya Saravanapavan, S. Verrier, Larry L. Hench
Authors: El-Sayed Ghaith, Toshihiro Kasuga, Masayuki Nogami
Abstract: Amorphous calcium silicate coating on a metallic titanium substrate for hard tissue replacement was prepared by a sol-gel method. Calcium silicate film was deposited on a titanium substrate by a spin-coating technique and subsequently heated at 500°C for 2 h in air. The deposited film, which was dense, had thickness of about 800 nm and strongly adhered to the substrate. Biomimetic apatite-forming ability of the deposited films was examined by soaking in simulated body fluid (SBF). Thin film X-ray diffractometry and scanning electron microscopy showed the formation of apatite on the surface after 10 days of soaking in SBF.
Authors: Ping Li, Zhang Wang, Fei Luo, Xiu Feng Xiao
Abstract: A novel and facile process called “alternative loop immersion method” formed bioactive and biocompatible Zn-doped calcium silicate coating over the drug-loaded titania nanotube arrays to improve the properties of drug release. The samples were characterized by scanning electronic microscope (SEM), x-ray diffraction (XRD) and fourier transform infrared (FT-IR). The results show that TNTs modified by Zn-doped calcium silicate coating possess improved drug release characteristics with reduced burst release (from 83% to 66%) and prolonged drug release (from 11 days to over 15 days). This approach provides an alternative to tailor the surface of TNTs and offer considerable propects for diverse biomedical applications.
Authors: Simone Sprio, Anna Tampieri, Elena Landi, Gian Carlo Celotti, Daniele Dalle Fabbriche
Abstract: The present work deals with the preparation and characterization of ceramic composites for the substitution of load-bearing bone portions, made of hydroxyapatite (HA) and bioactive β- calcium silicate (β-Ca2SiO4) as a reinforcing phase. The composite materials were prepared by Fast Hot-Pressing technique (FHP), which allowed the rapid sintering of monolithic ceramics at temperatures up to 1500 °C, well above the commonly adopted temperatures for sintering of hydroxyapatite (1200-1300 °C), in order to achieve the densification of the reinforcing phase also. XRD analysis reported no formation of secondary phases other than HA and β-Ca2SiO4, after FHP cycles. Flexural strength tests were performed on selected samples sintered at different temperatures: the composite materials exhibited increased mechanical resistance compared to samples constituted of HA only. These preliminary results confirmed that composites of HA and β- Ca2SiO4 are promising for the development of bioactive load-bearing ceramic bone substitutes.
Authors: Xuan Yong Liu, Xue Bin Zheng, Chuan Xian Ding
Authors: A.L. Oliveira, Manuela E. Gomes, P.B. Malafaya, Rui L. Reis
Authors: Aleš Břenek, Vojtěch Václavík, Tomáš Dvorský, Jaromír Daxner, Vojtech Dirner
Abstract: The article deals with energy rehabilitation of a building with damaged waterproofing of its lower structure. The reference construction is made of fired bricks, whose functional properties are perfectly fine, but the thermal insulation properties are insufficient for this time. The most common solution of such a problem is the application of a thermal insulating material based on expanded polystyrene on the building envelope. Unfortunately, these solutions often entail the risk of moisture problems in places that appeared to be dry before. The article compares the current solution with the new one relying on material based on calcium silicate [4] with high moisture transport capabilities as an alternative insulation of these buildings.
Authors: Farah Atiqah Abdul Azam, Hamisah Ismail, Roslinda Shamsudin, Zalita Zainuddin, Muhammad Azmi Abdul Hamid
Abstract: The morphology and surface topography of calcium silicate coated on Ti6Al4V implant were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction analysis (XRD) respectively. The surface of titanium alloy plates was mechanically ground with 320, 800 and 1200 grits of SiC abrasive paper followed by surface polishing into mirror-like finish. The synthesized β-CaSiO3 was deposited onto the Ti6Al4V substrate using electron beam evaporator. After coating, calcium silicate was heat treated at 500 °C for 1 hour. Characterization of the calcium silicate coated on Ti6Al4V substrate using e-beam evaporation technique demonstrated that 5 wt% of PVA addition was able to improve the coating-to-substrate adhesion.
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