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Soft and hard soldering methods
Published in Andrew Livesey, Alan Robinson, The Repair of Vehicle Bodies, 2018
The properties required for an effective flux for brazing aluminium and its alloys are as follows: The flux must remove the oxide coating present on the surfaces to be joined. It is always important that the flux be suitable for the parent metal, but especially so in the joining of aluminium-magnesium alloys.It must thoroughly wet the surfaces to be joined so that the filler metal may spread evenly and continuously.It must flow freely at a temperature just below the melting point of the filler metal.Its density, when molten, must be lower than that of the brazing alloy.It must not attack the parent surfaces dangerously in the time between its application and removal.It must be easy to remove from the brazed assembly. Many types of proprietary fluxes are available for brazing aluminium. These are generally of the alkali halide type, which are basically mixtures of the alkali metal chlo-rides and fluorides. Fluxes and their residues are highly corrosive and therefore must be completely removed after brazing by washing with hot water.
Dielectric Properties
Published in Daniel D. Pollock, PHYSICAL PROPERTIES of MATERIALS for ENGINEERS 2ND EDITION, 2020
In an ionic crystal, such as an alkali halide, the ionic displacement is determined by equating the forces involved: () Kx =eEloc;x=eEloc/K
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Published in E R Pike, High-power Gas Lasers, 1975, 2020
Although the mechanism of formation of XeF* in an e-beam excited gas mixture is not fully understood, some reasonable explanation of the XeF laser can be obtained on the basis of presently available information. Production of XeF* in a direct reaction of the xenon metastable atom Xe* (3P2) with a halogen-containing molecule is well known (Velazco and Setser 1975) since it is very similar to the reaction of an alkali metal atom with a halogen forming an alkali halide. In e-beam excited Xe gas, Xe* metastables are formed via Xe+, since the primary mechanism of energy deposition by the high-energy electrons of the e-beam is by ion-electron pair production.
Thermo-acoustical studies of zinc oxide nano particles dispersed nematic liquid crystals mixtures in the temperatures range 283.15 K318.15K
Published in Liquid Crystals, 2022
Poonma Malik, Sandeep Kumar, Arun Upmanyu, Pankaj Kumar, Praveen Malik
The value of Sharma constant (S0) for 8 CB and 8CB + 0.5% ZnO, 8CB + 2.0% ZnO and 8CB + 5.0% ZnO liquid crystal mixtures in the given temperature range is recorded in Tables 1-4. The close inspection of tables reveals that S0 is on the average constant around 1.11 ± 0.01 and it well matches with the reported values of S0 for the liquid crystals [27]. The constancy of S0 also confirmed that it can be treated as molecular constant for pure and ZnONPs doped 8 CB LC mixtures like solid, liquids and polymers [27,39–43]. The calculated values of θ are defined as the difference between C1 and δ. In the present work, the value of θ is positive for all the samples. It indicates that C1 is greater than δ for all the liquid mixtures. The close look of Tables (1–4) reveals that the C1 exceeds δ by unity i.e.C1≅δ +1. This is in agreement with results reported for alkali halide crystal by Keer [36] on the basis of thermodynamical consideration.
Convective and Radiative Heat Transfer in Molten Salts
Published in Nuclear Technology, 2020
Figure 9 shows the reflectivity values of LiF, NaF, and KF. Since the radiation properties for KF are not publicly available in the literature, radiation-related properties for another similar (in terms of the crystal structure) alkali halide, KCl, are used as references. Considering the mass (or molar) fraction of KF in FLiNaK and the value of spectral emissive power in the infrared region, it is unlikely that this approximation would lead to a large uncertainty in the current radiative heat transfer estimation. The reflectivity of FLiNaK is estimated by the number density average of the constituents as
Radiolytic Production of Fluorine Gas from MSR Relevant Fluoride Salts
Published in Nuclear Science and Engineering, 2023
Lance Davis, Ralph Hania, Dennis Boomstra, Dillon Rossouw, Florence Charpin-Jacobs, Jan Uhlir, Martin Maracek, Helmut Beckers, Sebastian Riedel
Radiolysis, the phenomenon of relevance in this work, is the chemical bond cleaving effect induced by ionizing radiation occurring in molecular materials and salts, including the halide salts intended for use in MSRs. The conventional description of radiation-induced damage in halide salt crystals starts with a primary process that involves creation of interstitials (H-centers) and vacancies (F-centers) in the halide sublattice,2,6–8 referred to as primary defects, with an insignificant effect on the cation sublattice.9,10 Complex intermediate processes follow (described in detail elsewhere11), leading to a late stage in which extended defects are created in the form of metallic colloidal precipitates and atomic or molecular halogen (bubbles), by aggregation of F-centers and H-centers, respectively.6,7,10,12 The halogen bubbles are able to coalesce and diffuse to the grain boundaries of the salt through a similar mechanism as that of dislocation loop punching, observed for gases in irradiated metals,11,13,14 and escape from the crystal surface. Additionally, as the halide salt is subjected to progressive radiation damage, interactions between primary and extended defects lead to the formation and growth of vacancy voids.7,8 In Ref. 15, a mechanism is proposed in which the halogen bubbles/gas in irradiated halide salt are/is expected to grow to a stable size at relatively low irradiation dose, whereas vacancy voids grow in a progressive logarithmic manner with increasing irradiation dose.7,15 As the vacancy voids grow within the salt crystal, they collide with the finely dispersed halogen bubbles, absorbing the halogen bubbles and filling the void with halogen gas. When the dimensions of the gas-filled vacancy voids exceed the mean distance between metallic colloids and halogen bubbles (gas) in the crystal lattice, the halogen gas and metallic colloids interact within the vacancy void resulting in a powerful recombination reaction.8 It should be stated that this overview of the halide salt radiolysis process is largely based on studies of alkali halide salts, and although the overall process is expected to be similar for divalent (and higher valency) halide salts due to the lesser role of the cation sublattice, there are notable deviations, particularly in the intermediate radiolysis stages. These deviations/differences are discussed in other work.16–18