Flux composition

As manufactured, potassium fluoroaluminate fluxes typically contain a mixture of KAIF4 and K2ALF5, where the K2ALF5 may or may not be hydrated. During the brazing 

In fact, flux manufacturers choose the ratio of KAIF4 and K3 AlFg based on the eutectic AIF3 — KF phase diagram (see below), which was first constructed in 1932 [72] and further investigated and refined in 1966 [73]. 

A potassium fluoroaluminate flux must coutaiu more than just the pure phases - and it must contain these phases in an extremely precise ratio - in order to work effectively and to meet the conditions for eutectic formation which controls the melting point. 

Furthermore, the presence of K2AIF5 is necessary to achieve the proper ratio of KAIF4 and K3ALF6 at brazing temperature, the necessary condition to form the eutectic. This can be explained more thoroughly by examining the following scheme  

Flux Components-Phase Transformation During Brazing M or Minor 

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Uses. Lithium fluoride is used primarily in the ceramic industry to reduce firing temperatures and improve resistance to thermal shock, abrasion, and acid attack (see Ceramics). Another use of LiF is in flux compositions with other fluorides, chlorides, and borates for metal joining (17) (see Solders). 

The atom flux sputtered from a solid surface under energetic ion bombardment provides a representative sampling of the solid. Sputtered neutral mass spectrometry has been developed as method to quantitatively measure the composition of this atom flux and thus the composition of the sputtered material. The measurement of ionized sputtered neutrals has been a significant improvement over the use of sputtered ions as a measure of flux composition (the process called SIMS), since sputtered ion yields are seriously affected by matrix composition. Neutral panicles are ionized by a separate process after sputter atomization, and SNMS quantitation is thus independent of the matrix. Also, since the sputtering and ionization processes are separate, an ionization process can be selected that provides relatively uniform yields for essentially all elements. 

The domain for c-BN formation and the solubility conditions are strongly influenced by the flux composition. In the catalytic process h-BN is mixed with the catalyst or just only brought into contact. In some experiments it has also been shown that c-BN can nucleate on substrates placed in the reaction chamber [156] (Fig. 11). 

This stereotyped expression was perhaps fortunate, inasmuch as a new fluxing composition, which turned out to be the only feature of the invention the court considered patentable, was not included in the stated objects of the invention. Even more fortunate was the statement The composition of the welding medium is of the utmost importance. ... 

Just what did the trial court do with the patent It held first of all, that an invention of great merit had been made and recognized that the patentees had been able, by the use of their improved fluxing composition, to conduct their electric arc-welding operation without glare, with no open arc, no splatter, and very little, if any, smoke. Further the performance achievement was held to be far superior to what had gone be-... 

The primary use of lithium fluoride is in the ceramic industry. It reduces the firing temperature and improves the resistance to abrasion, acid attack and thermal shocks. It is essential component of the fluorine cell electrolyte. An addition of small amount (1-1.5%) to KHF2 HF electrolyte improves the wettability of the carbon anodes and lowers the tendency of the cell to polarize. Another important use of LiF is in flux compositions containing chlorides, borates and other fluorides. Lithium fluoride windows made from high purity crystals are used for X-ray monochromators, UV, visible or IR regions [18]. 

Before samples can be analysed by INAA, they must be submitted to neutron irradiation. The interaction between neutrons and different elements in the sample, makes some of them become y-active and so measurable by a y-spectrometer. It depends on what kind of heavy metals are present in the sample, on the neutron flux and the neutron flux composition and on the cross-section of the relative n-y nuclear reactions. The neutron irradiation of the quartz microfibre filters is performed at the TRIGA MARK II nuclear research reactor at the ENEA... 

In this paper, recent work on the viscosity of mold flux compositions is reviewed, and a relation to describe the temperature dependence of viscosity is discussed. This relation is based on the Clausius-Clapeyron Equation and was originally developed by Kirchoff and Rankine to describe the temperature dependence of vapor pressure. 

The viscosity of twenty flux compositions determined earlier ( ) were used to evaluate the Kirchoff-Rankine Equation. The compositions of these fluxes are given in Table I with a summary of the viscosities given in Table II. The flux viscosity data was fitted to the Kirchoff-Rankine equation as... 

To complete this text we offer a selection of exercises. Some of the exercises are of a theoretical nature and we ask you to verify some of the equations presented in the text or to derive established results in other ways. In other exercises we invite you to extend the theoretical treatments in ways that we have not considered in detail (although in some cases the results are available in the literature). Still other exercises are of a computational nature and we invite you to compute mass transfer coefficients, molar fluxes, composition profiles, and other quantities. In order to gain some familiarity with the various methods described in the text we strongly recommend solving the computational problems. Hand calculation is extremely instructive but does get to be a bit tiresome after a while. There are also exercises that require you to evaluate papers in the literature. Finally, we have provided exercises that can be assigned as term projects for students, perhaps as a replacement for a final examination. 

Flores, J.H. et al. Ultrahltration of White Riesling juice Effect of oxidation and pre-UF juice treatment on flux, composition, and stability. Am. J. Enol. Vitic., 39, 180,1988. 

Claes, S., Vandezande, R, Mullens, S. et al. 2010. High flux composite PTMSP-silica nanohybrid membranes for the pervaporation of ethanol/water mixtures, 351 ... 

Sample type Flux composition Flux sample ratio (by wt)... 

Particular attention must be given to transfer pipework where seam-welded pipe runs are used. In such cases, experience from the American power industry steam reheat line catastrophic failures should be borne in mind. The critical factors identified are weld geometry, weld metal and flux compositions and pipe ovality. Generally, older CRU units utilise seamless pipe in this service but some instances are known, particularly in larger capacity units, where seam-welded pipe is in service. Where necessary, this factor can be taken into account in the assessment procedure described below. Seam welds are subject to the full pressure hoop stress, as well as to many of the system loads. Failure of such a weld is likely to lead to a full-scale rupture, rather than a leak. Accordingly, they must be treated as critical items for assessment, and replacement, rather than repair, should be considered the ultimate outcome. 

The unusual solubility of gases and vapors in perfluoropolymers has several applications relevant to membrane gas separations. Perfluoropolymers have solubility selectivities that are significantly different from those of hydrocarbon-based polymers. The amorphous perfluoropolymers can be fabricated into thin, high-flux composite membranes, which possess the excellent chemical and thermal stability. Typical reported pure gas permeabilities and selectivities of these fine amorphous perfluoropolymers are shown in Table 16.8 [33]. 

In the case of Y123, variation of the initial flux composition is advantageous in the preparation of thick crystals by the self-flux method (sect. 5.1) or in the control of crystalline film orientation in the LPE method (sect. 5.4). However, for LRl 23 crystals the control of liquid composition is crucial even for their superconductivity enhancement. 

Synthesis of high-flux composite membranes requires deposition of a selective, ultra-thin skin on a highly permeable support. The most common methods for formation of composite membranes include interfadal polymerization, casting, plasma polymerization, and solution coating. 

As mentioned previously, it is important to heat the flux sufficiently to activate it (make it chemically reactive) and to burn off the activators by the end of the soldering process. This is true even of no-clean solder chemistries. If an unactivated, insufficiently heated no-clean solder flux is left on a board, the weak organic acids in the flux residue could cause long-term corrosion. Usually temperatures between 80° and 150°C (depending on the flux composition) are sufficient to activate a flux fully. Avoid pooling flux. To minimize the possibiiity of corrosion. 

Zhuge, J., Gou, J., Chen, R.-H., Gordon, A., Kapat, J., Hart, D., Ibeh, C., 2012a. Fire retardant evaluation of carbon nanofiber/graphite nanoplatelets nanopaper-based coating under different heat fluxes. Composites Part B Engineering 43, 3293—3305. 

M. Kojima, F. Watanabe, A. Toukana, H. Nojiri and K. Yamasoe, Flux Composition for Brazing of Aluminum Material and Method for Brazing of Aluminum Material, European Patent Application EP 0936024 Al. 

Fluxes. Ingredient in many flux compositions, and in some printed circuit boards. ... 

Several excellent texts devote chapters to fluxes [105-108] and, although somewhat dated, one text [109] hsts many formulations from patent literature. Patents and Material Safety Data Sheets (MSDS) are additional sources of flux compositions however, it should be recalled that many suppliers keep their formulations proprietary. 

Flux Composition and Corresponding Soldering Method. US Patent 5,615,827, 1997. 

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