Papers by Keyword: Calcium Fluoride

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Authors: Mahmoud Azami, Sasan Jalilifiroozinezhad, Masoud Mozafari
Abstract: In this research, a novel biphasic solid solution consisted of Calcium fluoride (CF) and fluorinated-hydroxyapatite (FHAp) was successfully synthesized through a modified precipitation method using buffer solution. The obtained results confirmed the formation of biphasic nanocrystalline powder composed of about 46% CF and 54% (w/w%) FHAp. This product can be considered as an osteoconductive dental filler or implant with the ability of dental carries prevention due to release of fluorine ions. Herein, the usage of buffer solution for this purpose not only can produces biphasic powder but also provides the possibility of establishment of a continuous synthesis method without manual interfere for adjusting pH of the reactor.
626
Authors: Hong Ming Wang, Xiang Zhu, Gui Rong Li, Li Li Yang, Cong Xiang Peng, Chang Chen Qu
Abstract: To reduce the pollution caused by employing CaF2 as fluxing agent in metallurgical flux, boron sludge is used as fluxing agent to substitute for CaF2. The melting temperatures of CaO-SiO2-Fe2O3-boron sludge system were investigated. The melting temperature of CaO-SiO2-Fe2O3-boron sludge slag system is increased with the increase of ω (CaO)/ω (SiO2) at first, and then fluctuates at about 1430°C. Moreover, the melting temperature of CaO-SiO2-Fe2O3-boron sludge system is decreased with the increase of boron sludge content at first and then increased, 7% content of boron sludge has the best fluxing effect and the melting temperature is1445°C. As a conclusion, the fluxing effect of boron sludge is close to CaF2, boron sludge may be considered to substitute for CaF2.
382
Authors: Hong Ming Wang, Li Li Yang, Hua Zhu, Yong Qi Yan
Abstract: B2O3 is employed as fluxing agent of high basicity CaO-based flux to substitute for CaF2. The effects of B2O3 and CaF2 on the metallurgy properties of CaO-based flux were investigated. The results indicate that the fluxing action of B2O3 is better than that of CaF2. For the high basicity CaO-based flux, when CaF2 is substituted with B2O3, the melting temperature can be decreased remarkably. Especially, when the mass ratios of CaO/SiO2 are in range of 5.25~8.0, the flux melting temperature is lower than 1300 °C. The inflection point temperature of flux viscosity-temperature curve is lowered remarkably when B2O3 is employed to substitute for CaF2. Meanwhile, the desulfurization capacity of flux can be improved markedly when CaF2 is substituted with equal mass of B2O3.
966
Authors: Ji Wang Yan, Junichi Tamaki, Katsuo Syoji, Tsunemoto Kuriyagawa
95
Authors: Hong Ming Wang, Ting Wang Zhang, Li Li Yang, Yong Qi Yan, Hua Zhu
Abstract: To avoid slag sticking onto the ladle snorkel during the CAS-OB refining and alloying process, CaO-B2O3 and CaO-CaF2 were respectively employed as modifiers added into the ladle slag. The desulfurization capability of modified slag was investigated. The results of experiments on sulphur partition equilibrium between metal and slag indicate that the sulphur content of metal can be further decreased by the modified slag. When CaO-B2O3 is used as additive and the mass ratio of CaO to B2O3 is 1:1, the desulfurization ratio of slag to liquid steel is 50%, the final sulphur content can be controlled at 0.002%. The efficiency of desulfurization is fine. When CaO- CaF2 is employed as additive and the mass ratio of CaF2 to CaO is 2:8, the final sulphur content of metal can be controlled lower than 0.004%, the efficiency of desulfurization is also acceptable.
962
Authors: Hong Ming Wang, Ting Wang Zhang, Hua Zhu, Yong Qi Yan, Yi Nan Zhao
Abstract: To avoid slag sticking onto the snorkel during CAS-OB ladle refining process, B2O3-CaO(mass ratio equals 1:1) and CaF2-CaO(mass ratio equals 1:1) were respectively employed as modifiers added to decrease the viscosity of ladle slag. The rotary cylinder method was adopted in the viscosity measurements. The results showed that the modifiers could decrease the viscosity of ladle refining slag remarkably. At 1500°C, the viscosity of ladle slag without any modifiers is about 6.0 Pa·s. But by adding more than 10mass% CaO-B2O3 or CaO-CaF2, the slag viscosity at 1500°C could be decreased lower than 1.0 Pa·s. The mechanism of modifiers decreasing the slag viscosity was analyzed.
2647
Authors: Zhao Hui Zhang, Bai Long Liu, Yun Ren
Abstract: Preparation of the tundish coverture fluxes by the blast furnace slag can recycle utilization of solid wastes discharged from iron and steel industry. Calcium fluoride and magnesia can play an important role for the basic performance of tundish coverture fluxes. The impact on the melting temperature, viscosities and surface tension of the tundish coverture fluxes from the content of calcium fluoride and magnesia were studied. The results showed that: When the content of CaF2 increased from 10% to 25%, the melting temperature, the viscosity and the surface tension were decreased by 50°C, 0.3 Pa·S and 0.039 N/m respectively. The viscosity was brought down of 0.02 Pa·S, the surface tension was increased by 0.03 N/m, and the difference between the lowest and highest melting temperature was about 3°C when the content of MgO changed from 5% to 11%.
96
Authors: Dan Hua Zhao, Xiao Jun Liu, Xiu Lian Zhang, Wei Yin
Abstract: A new hybrid material of CaF2/ABB6B (CFAB) was developed by the template-free hybridization of acid brilliant blue 6B (ABB6B) with CaF2. The composition and structure of the material were determined and characterized. In contrast to conventional sorbents, the hybrid material contains lots of negative charges as the basis of specific adsorption. The efficient removal of cationic dyes of victoria blue B (VBB), ethyl violet (EV) and basic brilliant blue BO (BBBO) indicates that it has an improved adsorption capacity and selectivity with a short removal time less than 5 min; while the hybrid sorbents fit the Langmuir isotherm model. Instead of using ABB6B reagent, an ABB6B-producing wastewater was reused to prepare the cost-effective sorbent, and the equilibrium adsorption capacities of which reached 46.29 mg•g-1, 24.81 mg•g-1 and 30.40 mg•g-1 for VBB, EV and BBBO, respectively. The sorbent was then used to treat the actual wastewater samples with satisfactory results of over 96% decolonization and 82% COD-decreasing. This work has developed a simple and eco-friendly method for synthesizing a practical and efficient sorbent. The results shown that the hybrid adsorption material has ideal decolorization and COD lowering efficiency and a good application prospect in dye industrial wastewater treatment.
2338
Authors: L.S. Ozyegin, Faik N. Oktar, Simeon Agathopoulos, S. Salman, Y. Bozkurt, Niyazi Eruslu
Abstract: Composites of calcinated bovine bone derived hydroxyapatite (BHA) doped 0.5 and 1 wt% CaF2 were prepared by sintering. The production of BHA from natural sources is preferred due to money and time saving reasons. Scanning electron microscopy (SEM) and X-ray diffraction analysis together with measurements of density and compression strength were carried out in the produced samples. The experimental results indicated that compression strength of the composites increase when sintering temperature increases. The best compression strength was achieved after sintering at 1200°C for 0.5% CaF2 addition. The results are in agreement with densification measurements and microstructure analysis. With regards to the amount of CaF2, the results indicate that small additions of F, lower than 0.5%, can further improve the mechanical properties of HA.
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Authors: Siraprapa Srithongsuk, N. Anuwongnukroh, Surachai Dechkunakorn, Toemsak Srikhirin, Peerapong Tua-Ngam
Abstract: Objective: This study aimed to investigate fluoride release, flexural strength and surface characteristics of three orthodontic acrylic resins (A) blended with (1) sodium fluoride powder (NaF), (2) calcium fluoride powder (CaF2), and (3) glass ionomer cement powder (GIC). Material & Methods: Acrylic resin was blended with NaF, CaF2 , and GIC to make orthodontic acrylic plates. Each sample group was divided into subgroups at fluoride concentrations 5%, 10% and 20%. The acrylic resin was cured in a round stainless steel mold and kept in a bottle with 10 ml. deionized water then kept in an incubator at 37oC. The deionized water, changed every day, was tested for fluoride release up to six mo by Orion machine. For the flexural strength test, the samples were cured in a stainless steel mold, 64 mm. long, 10 mm. wide and 3.3 mm. high according to standard of ISO 20795-2 and testing was done up to 6 mo in deionized water. Scanning electron microscope determined surface characteristics after being blended. Results: Fluoride release was observed from orthodontic acrylic plates blended with NaF, CaF2 and GIC. The results of the A-NaF and the A- CaF2 group decreased fluoride level greatly at day 2, but the A-GIC group was observed at day 7. The A-NaF group and the A-GIC group could not detect fluoride level after mo 4 and 2, respectively. The A-CaF2 group found greater long term fluoride release than the A-NaF and the A-GIC group especially at 20% concentration (up to six mo). Significant differences (p<0.05) of fluoride release level (ppmF) among the A-NaF, A-GIC, and A-CaF2 groups at 5% concentration in every time point from day 1 to the mo 5, but not significant in mo 6 similar to the 10% concentration comparison. Whereas, comparing the 20% concentration among groups, significant differences (p<0.05) were found between groups in all periods of time (from the day 1 to mo 6). When comparing the different concentrations of 5%, 10%, and 20% in each group, significant differences (p<0.05) were found in every concentration at every time period of the A-GIC group from day 1 to mo 2, in the A-CaF2 group from day 1 to mo 6 and in the A-NaF group from day 1 to mo 4. Conclusion: Fluoride release was observed from orthodontic acrylic plates blended with NaF, CaF2 and GIC. The longest duration of fluoride release from orthodontic acrylic plates was found in the CaF2 group followed by the NaF and GIC groups. The flexural strength in every group decreased over time. This result implied that the flexural strength decreased during fluoride release. The acrylic surface was seen to be porous in every period of the fluoride release process.
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