Addition Of CaF2 Research Articles

酸化鉄含有モールドフラックスの光吸収に対するCaF<sub>2</sub>の影響およびその放射伝熱評価

Optical properties were measured for synthesised mould flux containing iron oxides, and radiative heat transfer from the steel shell to the mould was estimated to investigate the effect of CaF2 additions to mould fluxes on heat transfer in continuous casting process from the perspective of absorption by iron oxides. The sample compositions were designed so that T.CaO/SiO2=1 and Fe2O3 concentration was 1 mass%. All the glassy samples show optical properties and radiative heat transfer similar to each other, suggesting that there is no effect of CaF2 on the basicity of flux. In addition, there was no change in the absorption wavelength and the absorptivity by divalent Fe ion, suggesting that the coordination of Fe ions and the electric charge strength do not change with additions of fluoride. On the other hand, crystallised samples show reflectivity increase and transmissivity decrease with increasing CaF2 concentration, resulting in the decrease of the radiative heat transfer. The fluoride facilitates the crystallization of the flux, and induces a decrease in radiative heat transfer. The Fe ions were mainly contained in the glassy portion rather than in crystals (cuspidine or CaF2) in the crystallised samples. To optimize the refractive index in the glassy portion is a possible way to reduce further radiative heat transfer of mould flux containing iron oxides.

溶銑の脱りん速度に及ぼすCaF<sub>2</sub>添加量，温度，塩基度，生石灰粒径の影響

溶銑の脱りん速度に及ぼすCaF<sub>2</sub>添加量，温度，塩基度，生石灰粒径の影響

Research of boron removal from polysilicon using CaO–Al2O3–SiO2–CaF2 slags

Purification process of MG-Si was limited by the difficulties involved in reducing boron content. The possibility of removing impurity boron (B) in MG-Si using CaO–Al2O3–SiO2–CaF2 slags was investigated in the present study. Different from traditional research methods, the whole melting process was carried out under atmosphere condition, which was closer to the actual production conditions. The thermodynamic and kinetic mechanisms of B removal were analyzed. Based on the ionic structure theory, the relation between ionic structure of slags at high temperature and optical basicity can be explained firstly. The parameters, including the slag optical basicity, melting time and CaF2 content were discussed. The boron content was reduced from original 25 ppmw to 4.4 ppmw through 120 min melting with the optical basicity of 0.551 and 5 wt% CaF2 additions.

Effect of oxide and fluoride addition on electrolytic preparation of Mg–La alloy in chloride molten salt

Mg–La alloys were prepared by constant voltage electrolysis in the molten salt system of MgCl2–LaCl3–KCl at 750 °C, with a graphite crucible as the anode and a tungsten rod as the cathode. The effect of oxide and fluoride addition on the electrolysis was investigated comprehensively. X-ray diffraction (XRD) was used to characterize some of the Mg–La alloy products and the sludges. As the content of MgO or La2O3 in the electrolyte increased, both the current efficiency and the mass of alloy product decreased, indicating that both MgO and La2O3 may take part in the reactions in the electrolyte. When the same mass of the oxide was added, compared with La2O3, MgO had a more pronounced effect on both the current efficiency and the mass of alloy product. XRD studies confirmed the formation of LaOCl when MgO or La2O3 was added into the electrolyte. The formation of LaOCl sludge would be the main reason for the negative effect of the oxide addition on both the current efficiency and the mass of alloy. In the electrolytic system, the addition of CaF2 was not helpful to suppress the negative effect of MgO on the electrolysis, probably due to the complex reactions of the La compounds in the electrolyte.

Self-Lubricating Behavior of ZrO<sub>2</sub>(Y<sub>2</sub>O<sub>3</sub>)-Mo-CaF<sub>2</sub>-Graphite Composite

t is of great importance to find ways to lubricate ZrO2ceramic. In this paper, a kind of ZrO2 matrix high temperature self-lubricating compositewith addition of CaF2 and graphite as lubricants was prepared by hot-pressing. It was found that the tribological properties of ZrO2(Y2O3)-CaF2-graphiteshow a good tribological behavior both at low temperature and high temperatures. The low friction coefficients of ZrO2 (Y2O3)-Mo-CaF2-graphite at high temperatures were due to the perfect lubricity of CaMoO4 which was formed on the worn surface at high temperatures.

W and two-dimensional WO3/W nanocrystals produced by controlled self-sustaining reduction of sodium tungstate

Abstract

Synthesis, characterization and bioevaluation of partially stabilized cements for medical applications

Abstract Materials for dental applications, i.e., white mineral trioxide aggregate (WMTA) and partial stabilized cements (PSC) were obtained using the sol-gel method. The presence of ZnO or/and CaF2 additions in the starting mixture induced changes in the composition, morphology and grindability of PSCs as compared with WMTA. The presence of foreign elements (Zn or F) in the crystalline lattice of mineralogical phases, increased their grindability. Thermal analysis (TG&DTA) was used to assess the kinetics of hydration process in binding systems based on WMTA/PSCs. The presence of foreign elements in PSCs systems increases the reactivity vs. water of these materials and consequently, the compressive strength developed after 28 days of hardening at 37°C are higher as compared with WMTA. The in vitro bioevaluation results (trypan blue staining, eukaryotic cells cycle assay by flowcytometry) accounted for a high biocompatibilty of the obtained materials demonstrating their potential use for biomedical applications.

Effect of Premelted Calcium-Magnesium-Aluminate Flux on Magnesia Carbon Brick

The novel Calcium-Magnesium-Aluminate (CMA) based premelted fluxes with different concentrations of MgO are developed and their corrosion to MgO/C brick is compared with traditional fluxing practice based on CaF2 addition. Results show that the corrosion of the MgO/C brick can be reduced obviously with initial high content of MgO employed in CMA. Additionally, the corrosion could be decreased correspondingly with the increase of MgO content in CMA fluxes, and the working lifetime of ladle slag zone can be extended by adding CMA flux.

Wear behavior of cold pressed and sintered Al2O3/TiC/CaF2-Al2O3/TiC laminated ceramic composite

A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure. Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear. Al2O3/TiC ceramic was also cold pressed and sintered for comparison. Friction analysis of the two ceramics was then conducted via a wear-and-tear machine. Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum, respectively. Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite. Under the friction load, the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits. This process formed a smooth, self-lubricating film, which led to better anti-wear properties. Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

Silicomanganese production utilising low grade manganese nodules leaching residue

The use of washed leached manganese nodules residue (WMNR), generated by reductive roasting ammoniacal leaching of manganese nodule, for production of standard grade silicomanganese (Si16Mn63), via carbothermic reduction smelting in electric arc furnace was described. The lower Mn/Fe ratio of WMNR was improved by its blending with Mn ore. Various parameters, such as Mn/Fe, Mn/Si, coke addition, CaF2 addition and holding time, were varied to optimise process to produce the desired grade of silicomanganese. Under optimised set of conditions, a charge mix with Mn/Fe≥3·5 and Mn/Si≥2·5 at basicity {(CaO+MgO)/SiO2} of 0·2 and R ratio {(CaO+MgO)/Al2O3} of 1·8 produced the standard grade silicomanganese in 15 min holding time with >77% Mn recovery. Excess coke (110% of stochiometric amount) in the smelting and CaF2 additions to the tune of 4 wt-% (WMNR–Mn ore blend) during the holding time, improved the metallic yield and manganese recovery.

Fabrication of transparent Nd:YAG ceramic by vacuum sintering with CaF2 additive

Abstract Neodymium-doped yttrium aluminum garnet (Nd:YAG) ceramics were fabricated via a solid-state reaction method using high-purity Y2O3, Al2O3 and Nd2O3 powders as the raw materials. The mixed powder compacts were sintered at 1 750 °C for 5 h under vacuum. The Nd:YAG bulk without doped CaF2 was opaque. A transparent Nd:YAG ceramic was obtained with tiny amounts of CaF2 addition. The bulk had a uniform microstructure containing grains with an average size of 20 μm. No porosity could be detected in the sintered bulk. The maximum optical transmittance of the sample is 44 % in the visible range.

Effect of CaF2 Addition on the Viscosity and Structure of CaO–SiO2–MnO Slags

Effect of CaF2 Addition on the Viscosity and Structure of CaO–SiO2–MnO Slags

Application and Research on Reducing Reaction of Boron Slag in the Steelmaking Engineering

Analyzed the reaction between slag and liquid iron and done a lot of experiments in the Lab to find the effect of many factors. It shown that putting into CaO to low the reaction activity with small amount of calcium oxide added, it can make the expansion in reaction to be inhibited, and improve the content of CaO in further. Silicate is high melting point material in the reaction product. After the reaction it reduce the slag fluidity to the slag with addition of CaF2, which can further improve the effect of reduction reaction.

Activities of FexO in Industrial Slags Used for External Removal of Phosphorous from Hot Metal

AbstractIn order to obtain a physicochemical knowledge of complex industrial slags, the activities of FexO in the industrial slags used for external dephosphorization of hot metal performed at practical steelmaking plants in Japan were measured by means of a solid-oxide galvanic cell in a temperature range between 1523 K and 1673 K. XRD study showed the presence of solid phases in all the slags, showing the heterogeneous character of the slags employed. With respect to the effect of CaF2 on FexO activity, the FexO activities of the heterogeneous slags were correlated with the ratio X(FeO)/X(CaF2). High X(FeO)/X(CaF2) values corresponded to high FeO activity. This tendency is interpreted based on the phase relationship in a CaO-CaF2-FexO ternary system. A favorable condition for external dephosphorization with less addition of CaF2 is discussed.

Effect of CaF2 surface layers on the friction behavior of copper-based composite

The paper studies the effect of the process parameters for the production of new copper-based bearing composite materials doped with nickel and molybdenum, with CaF2 additions (DN5M3KF9) as a solid lubricant, on the structurization and tribotechnical properties at high-speed friction (bearings perform at a sliding speed of 6 m/sec and a pressure up to 38.5 MPa in air). The study focuses on the distribution of CaF2 in the composite with a Cu–Ni–Mo matrix, its role in self-lubrication of the material, and the behavior of CaF2 in the friction area under extreme operating conditions. It is shown that the solid lubricant is evenly distributed over the contact surfaces as it piles up over the entire friction area during high-speed friction. It is established that the tribofilms formed in the presence of the CaF2 solid lubricant provide high wear resistance of copper-based materials.

High-temperature tribological behavior of ZrO2–MoS2–CaF2 self-lubricating composites

It is of great significance to find ways to control the high-temperature friction and wear of ceramic materials. In this paper, a ZrO2 matrix high temperature self-lubricating composite with addition of MoS2 and CaF2 as lubricants were prepared using hot pressing method by tailoring the composition of CaF2. The wear and friction behavior of the composites was investigated from room temperature to 1000 °C. The ZrO2–MoS2–CaF2 composites against SiC ceramic exhibited excellent self-lubricating and anti-wear properties at a wide temperature range. At 1000 °C, the ZrO2–10MoS2–10CaF2 (wt.%) composite has a very low coefficient of friction of about 0.27 and wear rate of 1.54 × 10−5 mm3/(N m). The low friction and wear were attributed to a new lubricant CaMoO4 which formed on the worn surfaces at high temperatures.

Effects of mix activated fluxes coating on microstructures and mechanical properties of tungsten inert gas welded AZ31 magnesium alloy joints

The effects of mix activated fluxes on the penetrations, microstructures and mechanical properties of tungsten inert gas (TIG) welded AZ31 magnesium alloy joints were studied. The results showed that an increase in the amount of TiO2 coating improved the weld penetration and depth/width ratio of the TIG welded AZ31 magnesium alloy seams. The α-Mg grains of the fusion zone (FZ) became fine gradually with the addition of CaF2 coating but coarsened sharply when the amount of TiO2 coating was over 70%. In addition, the porosities and total length of solidification cracks in the FZ were reduced by the CaF2 and TiO2 coatings. The ultimate tensile strength value of the welded joints increased with the addition of TiO2 coating but decreased sharply when more TiO2 coating was adopted.

Liquidus Temperature Depression in Cryolitic Melts

The electrolyte in Hall-Heroult cells for the manufacture of primary aluminum nominally contains only cryolite (Na3AlF6) with additions of AlF3, CaF2, and Al2O3. However, impurities are present, entering the process with the feedstock. The effect on the liquidus temperature by the impurities cannot be calculated correctly by the well-known equation for freezing-point depression in binary systems simply because the electrolyte cannot be regarded as a binary system. By extending the equation for freezing-point depression to the ternary system NaF-AlF3-B, it appeared that the acidity of the impurity B plays a major role. Some calculations were made using an ideal Temkin model, and for most types of impurities, the effect on the liquidus temperature will be larger in an industrial electrolyte than what can be estimated from the equation for freezing-point depression in cryolite. Experimental data on the liquidus temperature in the system Na3AlF6-AlF3-Al2O3-CaF2-MgF2 show that the effect of MgF2 on the liquidus temperature increases strongly with decreasing NaF/AlF3 molar ratio, and it is suggested that MgF2 forms an anion complex, probably MgF42−.

Microstructure and tribological properties of laser-clad Ni–Cr/TiB2 composite coatings on copper with the addition of CaF2

In this study, Ni–Cr/TiB2 metal matrix composite (MMC) coatings with the addition of a little CaF2 (2wt.%) were successfully fabricated on a Cr–Zr–Cu alloy substrate by laser cladding process with powder mixtures of Ni, Cr, TiB2 and CaF2 as the precursor materials. The MMC coatings were free of defects and the interfacial substructure between the MMC coatings and the copper substrate was epitaxial, with excellent bonding by the strong metallurgical interface. The microstructure, phase and tribological properties were investigated by means of optical microscopy (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM), as well as dry sliding wear test. Results show that the influence of TiB2 on the microstructure and tribological properties of the coatings was significant. The microstructure of the coatings was mainly composed of dendrites, cystiform-dendrites and particles. The dendritic microstructural features of the MMC coatings could be changed into particles by increasing TiB2 to 20wt.%. The laser-clad Ni–Cr/TiB2 MMC coatings on copper with the addition of CaF2 exhibited higher microhardness and better wear resistance than pure copper substrate. The highest microhardness was up to 946HV0.1 which was improved 8 times compared to the original substrate. The friction coefficient of the laser-clad Ni–Cr–20wt.%TiB2–2wt.%CaF2 coating was reduced significantly to about 0.24, and a relatively smooth wear surface could be observed.

Research on Properties of AlN-Mo Composite Ceramic

With CaF2 and CaCO3 as sintering additives, AlN-Mo composite was prepared using hot pressed sintering technique. The phase composition and morphology of AlN-Mo composite ceramics were analyzed using XRD and SEM, respectively. The experimental results show that when CaF2 and CaCO3 additives is in a range of 1~3wt%, the thermal conductivity AlN-Mo composites increases with increasing of the CaF2 content; With the increasing of CaCO3 content, first increases and then decreases. Sintering additives in a certain type and content, the thermal conductivity of AlN-Mo composite ceramics with 20 vol% Mo is higher than containing 18 vol% Mo. The dielectrical property of AlN-Mo composite ceramics was also discussed. The addition of CaF2 can decrease the dielectric constant of AlN-Mo composite ceramics.