The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in Na...The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in NaF-AIF3 melts were calculated based upon this scheme. The thermodynamic mixing function for liquid NaF and solid AIF3, and liquidus data of NaF-AlF3 systems were calculated by using the above evaluated parameters. The results obtained are in good agreement with the experimental data.展开更多
Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed af...Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.展开更多
Fluoride removal by traditional precipitation generates huge amounts of a water-rich sludge with low quality, which has no commercial or industrial value. The present study evaluated the feasibility of recovering fluo...Fluoride removal by traditional precipitation generates huge amounts of a water-rich sludge with low quality, which has no commercial or industrial value. The present study evaluated the feasibility of recovering fluoride as low water content cryolite from industrial fluoride-containing wastewater. A novel pilot-scale reaction-separation integrated reactor was designed. The results showed that the seed retention time in the reactor was prolonged to strengthen the induced crystallization process. The particle size of cryolite increased with increasing seed retention time, which decreased the water content. The recovery rate of cryolite was above 75% under an influent fluoride concentration of 3500 mg/L, a reaction temperature of 50°C, and an influent flow of 40 L/hr. The cryolite products that precipitated from the reactor were small in volume, large in particle size, low in water content, high in crystal purity, and recyclable.展开更多
The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiom...The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^(-2),but the current density is above 200 mA·cm^(-2) under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.展开更多
This paper presents a comparative analysis of simulation processes of seasonal freezing-thawing of railway subgrade and permafrost degradation, with and without accounting for solar radiation. Also, the effect of sun ...This paper presents a comparative analysis of simulation processes of seasonal freezing-thawing of railway subgrade and permafrost degradation, with and without accounting for solar radiation. Also, the effect of sun screens to reduce the degradation of subgrade permafrost under different climatic conditions is numerically substantiated. And finally, the temperature criterion of the origination of permafrost is illustrated.展开更多
A smooth and timely fitting of a visually appealing,custom-made eye prosthesis after the loss of an eye is not only essential from a cosmetic point of view but above all facilitates good social and psychological rehab...A smooth and timely fitting of a visually appealing,custom-made eye prosthesis after the loss of an eye is not only essential from a cosmetic point of view but above all facilitates good social and psychological rehabilitation.Cryolite glass prostheses must be replaced at least once a year,PMMA prostheses polished once a year and renewed every five years.In children,especially in growth phases,the fit of the prosthesis should be checked at least every six months and adjusted,if necessary.Ocularists and ophthalmologists should determine an individual cleaning procedure together with the patient,which depends on both the prosthesis material and external factors.Complications such as allergic,giant papillary,viral,and bacterial conjunctivitis or even blepharoconjunctivitis sicca must be detected and treated at an early stage to avoid discomfort and to maintain the ability of prosthesis wear.In the case of inflammation-induced shrinkage of the conjunctival fornices or post-enucleation socket syndrome,surgical interventions are necessary.In summary,an early supply with an eye prosthesis,adequate treatment of complications,and attention to psychological aspects,form the basis for a successful long-term rehabilitation of anophthalmic patients.展开更多
The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste(IFCW). A two-step process, including ext...The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste(IFCW). A two-step process, including extraction and recovery, was developed to recover fluorine as synthetic cryolite from IFCW produced by the pesticide industry. The optimum conditions for extraction were found to be a temperature of 75℃, an initial p H(p Hi) of 12, a4-hr incubation time and a liquid-to-solid ratio of 40 m L/g; these conditions resulted in a fluorine extraction ratio of 99.0%. The effects of p H and the F/Al molar ratio on fluorine recovery and the compositional, mineralogical and morphological characteristics of the cryolite products were investigated. Field-emission scanning electron microscopy of recovered precipitates showed changes in morphology with the F/Al molar ratio. Coupling Fourier transform and infrared spectroscopy, X-ray diffraction indicated that the formation of Al F3-6was restricted as increasing p H. Both the amount of fluorine recovered and the quality of the cryolite were optimized at initial p H = 3 and a F/Al molar ratio 5.75. This study proposed a reliable and environmentally friendly method for the treatment of fluoridecontaining wastes, which could be suitable for industrial applications.展开更多
文摘The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in NaF-AIF3 melts were calculated based upon this scheme. The thermodynamic mixing function for liquid NaF and solid AIF3, and liquidus data of NaF-AlF3 systems were calculated by using the above evaluated parameters. The results obtained are in good agreement with the experimental data.
文摘Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.
基金supported by the Major Science and Technology Program of Hunan(China)(No.2009FJ-1009)
文摘Fluoride removal by traditional precipitation generates huge amounts of a water-rich sludge with low quality, which has no commercial or industrial value. The present study evaluated the feasibility of recovering fluoride as low water content cryolite from industrial fluoride-containing wastewater. A novel pilot-scale reaction-separation integrated reactor was designed. The results showed that the seed retention time in the reactor was prolonged to strengthen the induced crystallization process. The particle size of cryolite increased with increasing seed retention time, which decreased the water content. The recovery rate of cryolite was above 75% under an influent fluoride concentration of 3500 mg/L, a reaction temperature of 50°C, and an influent flow of 40 L/hr. The cryolite products that precipitated from the reactor were small in volume, large in particle size, low in water content, high in crystal purity, and recyclable.
基金financially supported by the National Basic Research Program of China(No.2013CB632606-1)the National Natural Science Foundation of China(No.51204044)
文摘The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^(-2),but the current density is above 200 mA·cm^(-2) under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.
文摘This paper presents a comparative analysis of simulation processes of seasonal freezing-thawing of railway subgrade and permafrost degradation, with and without accounting for solar radiation. Also, the effect of sun screens to reduce the degradation of subgrade permafrost under different climatic conditions is numerically substantiated. And finally, the temperature criterion of the origination of permafrost is illustrated.
文摘A smooth and timely fitting of a visually appealing,custom-made eye prosthesis after the loss of an eye is not only essential from a cosmetic point of view but above all facilitates good social and psychological rehabilitation.Cryolite glass prostheses must be replaced at least once a year,PMMA prostheses polished once a year and renewed every five years.In children,especially in growth phases,the fit of the prosthesis should be checked at least every six months and adjusted,if necessary.Ocularists and ophthalmologists should determine an individual cleaning procedure together with the patient,which depends on both the prosthesis material and external factors.Complications such as allergic,giant papillary,viral,and bacterial conjunctivitis or even blepharoconjunctivitis sicca must be detected and treated at an early stage to avoid discomfort and to maintain the ability of prosthesis wear.In the case of inflammation-induced shrinkage of the conjunctival fornices or post-enucleation socket syndrome,surgical interventions are necessary.In summary,an early supply with an eye prosthesis,adequate treatment of complications,and attention to psychological aspects,form the basis for a successful long-term rehabilitation of anophthalmic patients.
基金supported by the Hi-Tech Research and Development Program (863) of China (No. 2007AA061300)the Innovation Program of Undergraduate Students in Shanghai Province (No. 0400107092)Collaborative Innovation Center for Regional Environmental Quality
文摘The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste(IFCW). A two-step process, including extraction and recovery, was developed to recover fluorine as synthetic cryolite from IFCW produced by the pesticide industry. The optimum conditions for extraction were found to be a temperature of 75℃, an initial p H(p Hi) of 12, a4-hr incubation time and a liquid-to-solid ratio of 40 m L/g; these conditions resulted in a fluorine extraction ratio of 99.0%. The effects of p H and the F/Al molar ratio on fluorine recovery and the compositional, mineralogical and morphological characteristics of the cryolite products were investigated. Field-emission scanning electron microscopy of recovered precipitates showed changes in morphology with the F/Al molar ratio. Coupling Fourier transform and infrared spectroscopy, X-ray diffraction indicated that the formation of Al F3-6was restricted as increasing p H. Both the amount of fluorine recovered and the quality of the cryolite were optimized at initial p H = 3 and a F/Al molar ratio 5.75. This study proposed a reliable and environmentally friendly method for the treatment of fluoridecontaining wastes, which could be suitable for industrial applications.