Use of Fluxes

Essentials of Inorganic Materials Synthesis, First Edition. C.N.R. Rao and Kanishka Biswas. 2015 John Wiley Sons, Inc. Published 2015 by John Wiley Sons, Inc. 

FIGURE 10.4.1 Phase diagram of K S/S system (From Ref. 10, Chem. Mater, 2 (1990) 353. 1990 American Chemical Society). 

FIGURE 10.4.2 Structure of Rb SnjP Se j, viewed down the t-axis. AH atoms are labelled. Disordered atoms are omitted for clarity. Rb blue, Sn yellow, P black, Se red (From Ref. 11, Angew. Chem. Int. Ed, 50 (2011) 8834. 2011 Wiley-VCH Verlag GmbH Co. K GaA). (See insert for colour representation of the figure.) 

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Table 4.2 gives a summary of methods for sample decomposition [36 K)]. Fluxes are particularly important for inorganic materials. The use of fluxes is limited by the reaction of trace elements within the crucibles and by the high blank levels in the fluxing materials themselves. 

Quantitative Estimation by Sis Dry Method—Ae-saying.—The fourth sad last method of estimating the amount of gold in an ore or alloy, is by the use of fluxes and fire. It is therefore termed the dry method, and formerly even the separation of the silver was effected without a liquid solvent, by one or other of the dry processes described in connection with the operation of parting ou the large scale but now the agency of an acid solution is employed in the last part of the process. 

Locher (LSI) reviewed ways of decreasing the energy consumption in cement manufacture to values substantially below those characteristic of modern Portland cement production. They included the use of fluxes to lower the burning temperature, the production of cements containing more reactive forms of belite or based on belite together with highly reactive phases, replacement of alite by the chloride-containing phase, alinite, and the use of composite cements. 

The burning temperature for production of Portland cement clinker can be decreased by about 150°C through the use of fluxes, but opinions have differed as to the energy saving thereby obtainable, Klemm and Skalny (K52), who reviewed the subject, estimated it at 630kJkg" . Christensen and Johansen (C56) considered that this figure, while possibly realistic for an inefficient, wet process kiln, was unlikely to be so for a modern, precalciner-preheater kiln, in which heat recovery is efficient. They considered a value of lOSkJkg" more realistic. 

Table 3.1 summarizes the lithographic properties of methacrylate polymers 54). These polymethacrylates all exhibit similar UV absorptions with optical densities of 0.27-0.47 xm" at 215 nm, which is considerably less than that of AZ1350J in the near-UV region (0.87 jim at 405 nm). This low absorption represents ineflScient use of flux and is one reason for the low sensitivity of the system. 

Thomas LH (1949) Elliptic Problems in Linear Differential Equations over a Network. Watson Sci Comput Lab Report, Columbia University, New York Thuburn J (1993) Use of flux-limited scheme for vertical advection in a GCM. Q J R Meteorol Soc 119 469-487... 

In the determination of the number of fissions in an irradiated sample by the use of flux monitors, account must be taken of the flux depression in the sample due to self-shielding to obtain an effective flux. Also, the capture cross sections of the monitors and the fission cross sections of the sample are neutron energy dependent. It is, therefore, necessary to know the eneigy distribution of the neutrons or the neutron temperature and to determine effective cross sections (Section IV). This can be done by using two monitors such as cobalt and samarium, the one monitor being used to determine the neutron temperature corresponding to the neutron distribution as described by Fritze et al. (35). 

The use of fluxes rather than conventional pathways provides a very flexible framework which together with the concepts of flux-generating and regulatory steps (as defined in Section II) provides a solid foundation for subsequent quantitative analysis. 

Systems developed for tin component lead finishes exhibit some problems. Flagging and icicles (excess solder condition) at the end of leads are particularly difficult to control and very troublesome for automatic and even hand insertion. The use of flux sprayed into the exit of the wave alleviates the problem, but also causes major contamination and maintenance problems. However, the use of nitrogen, instead of flux, results in a more uniform solder coating as icicles draw up on leads under inerted conditions. A number of these tinning systems are commercially available. 

The thermal modeling strategy explored appropriate use of flux or temperature boundary conditions as model inputs and the resulting model outputs. Due to the directional nature and the non-linearities inherent in the problem, prior spreadsheet calculations were of limited use for predicting local system temperatures. Use of system heat balance temperatures in the model ensured that an internally consistent set of temperature inputs was applied to the model. The model temperature outputs and heat balance temperatures were input into a spreadsheet calculation to predict model heat fluxes. This spreadsheet result was used to benchmark the model s estimate of system heat fluxes. 

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