Fluoride fluxes

Gl ss-Ionomers. Glass-ionomers show fluoride release at levels that are usually higher than those found in composite materials. The fluoride is found within the aluminosihcate glass, which is melted with fluoride fluxes and ground to form powder filler. The fluoride is added as calcium fluoride [7789-75-5] aluminum fluoride [15098-87-0] and sodium fluoride [7681-49-4] in a combined proportion of approximately 20% by weight in the final powder (284,285). 

Because barium titanate has interesting properties, many methods have been used to grow single crystals of this compound. One of the most popular techniques, using a potassium fluoride flux, was first employed by Remeika.1... 

From solution in an oxide or fluoride flux by cooling. 

In parallel to the work on zinc phosphate cements, porcelain dental cements also were developed. Steenbock [23] was the first to produce silicophosphate dental cement using 50 wt% concentrated phosphoric acid solution and an aluminosilicate glass. Schoenbeck [24] introduced fluoride fluxes in these glasses and vastly improved the dental cements. Fluorides lower the temperature of fusion of the glasses used in forming these cements. The same fluorides impart better translucency to the cement, and have some therapeutic effects. As a result, fluorides have become a part of modern dental cements. 

For the fluorometric method, uranium is concentrated by co-precipitation with aluminum phosphate, dissolved in diluted nitric acid containing magnesium nitrate as a salting agent, and the co-precipitated uranium is extracted into ethyl acetate and dried. The uranium is dissolved in nitric acid, sodium fluoride flux is added, and the samples fused over a heat source (EPA 1980). 

Use Principal source of fluorine and its compounds by way of hydrogen fluoride, flux in open-hearth steel furnaces and in metal smelting, in ceramics, for synthetic cryolite, in carbon electrodes, emery wheels, electric arc welders, certain cements, dentifrices, phosphors, paint pigment, catalyst in wood preservatives, optical equipment. 

The most popular and elegant specimen preparation technique introduced by Claisse 17] is based on fusion of solid specimens with lithium tetraborate. The method was used with great success in our laboratory for the rapid quantitative X-ray fluorescence analysis of silicates, bricks, refractories, limes, iron, and manganese ores. The use of lithium tetraborate and lithium fluoride flux systems was therefore examined first. 

Lee SH, Jung DS, Han JM, Koo HY, Kang YC (2009) Fine-sized Y3AI5O12 Ce phosphor powders prepared by spray pyrolysis from the spray solution with barium fluoride flux. J Alloy Compd 477 776-779... 

Boron oxide Calcium fluoride Lead oxide, red Sodium nitrate flux, ceramic glazes Aluminum fluoride flux, ceramics Aluminum orthophosphate flux, copper soldering Triethylamine flux, enamels... 

Aluminum fluoride Lithium fluoride flux, hard solder Potassium fluoride flux, magnesium prod. 

If low impurity levels are required, the method of preparing the fluoride for the electrolytic method is not as critical as for the Ca reduction method - at least with respect to the O content of CeFs. In the electrolytic method Ce02 or Ce203 is added to the fluoride flux, and it is the oxide which is reduced to the metal. For the Ca reduction method the O content of the fluoride is quite critical since any oxide present in the fluoride will end up in the metal. Furthermore, as noted by Carlson et al. (1960) the fluoride flux may serve to extract some of the impurities. These authors found that the levels of C, N, O, F, Mg and Ni in a Y-Mg alloy are reduced by extraction with a fused salt. Similarly, in the electrolytic preparation one might expect that the long contact time of the metal with the fluoride flux may decrease the level of some impurities in the metal. This behavior of the fluoride flux, however, may lead to difficulties if the flux is contaminated from the previous runs, since continued use would saturate the flux with certain impurities, and they would no longer be extracted, and even might be introduced into the next metal sample. 

The electrolytic method is by far the cheapest method for preparing these metals. For Ce Morrice et al. (1961) report that only 7.5 kw-hours are required to prepare 1 kg Ce, and at a cost of 5 cents per kw-hour it would cost 0.38 to prepare this Ce. This figure does not include the cost of the starting Ce203 or Ce02, the fluoride flux, the equipment and heating costs, since these would be comparable to costs of similar items in the Ca reduction method. 

To move now to the aluminum industry, a similar question was being asked, although the context of the question was different. Aluminum is produced by the electrolytic reduction of aluminum oxide/fluoride fluxes at temperatures of about 1(X)0°C, less than the maximum temperatures of a blast furnace (about 1300 °C). The reductant is the carbon anode which is a block of calcined carbon weighing about 1 tonne which has to be inserted into the electrolytic cell. From time to time, these anodes would fail and fall into the molten electrolyte from which they would have to be extracted (a procedure not looked upon with favor within the industry). A major cause of this problem was eventually associated with the presence of sodium (less so with potassium) within the calcined coke. The question to be solved at that time was how does sodium cause degradation and weakening of the carbon anode. 

In an attempt to propose a solution to the two first issues, the present study will endeavor exploring the effects of crystallization on BAM s PL by treating the phosphor with fluoride fluxes LiF and MgF2 chosen on the basis of their low volatility at high temperature, resistance to reducing treatment and presumed non-reactivity towards BAM. Despite its low temperature of decomposition (100 °C), the effect of NH4F, commonly used as a flux, will be also explored. 

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