Tin addition

Lead—Calcium-Tin Alloys. Tin additions to lead—calcium and lead—calcium—aluminum alloys enhances the mechanical (8) and electrochemical properties (12). Tin additions reduce the rate of aging compared to lead—calcium binary alloys. The positive grid alloys for maintenance-free lead—calcium batteries contain 0.3—1.2 wt % tin and also aluminum. 

Other Uses. The production of finished shapes from iron powder by compacting and sintering utilizes about 100,000 t of iron powder aimuaHy copper powder (2—10 wt %) is normally added as a sintering aid. Addition of 2% tin powder or equal amounts of tin and copper powder considerably lowers the sintering temperature and time of sintering at a cost saving. The tin addition also improves dimensional control. Iron powder plus 10 wt % powdered lead—tin metal is pressed and siatered to make pistons for use ia automotive hydrauHc brake cylinders. 

Table 16. Conductivity and Wrought Tensile Strength of Tin-Brasses Showing the Hardening Effect of Tin Additions...

Admiralty Brass and Naval Brass are 30 and 40% zinc alloys, respectively, to which a 1% tin addition has been added. Resistance to dezincification of Cu—Zn alloys is increased by tin additions. Therefore, these alloys are important for thein corrosion resistance in condenser tube appHcations. In these, as weU as the other higher zinc compositions, it is common to use other alloying additives to enhance corrosion resistance. In particular, a small amount (0.02—0.10 wt %) of arsenic (C443), antimony (C444), or phosphoms (C445) is added to control dezincification. When any of these elements are used, the alloy is referred as being "inhibited." For good stress corrosion resistance, it is recommended that these alloys be used in the fiiUy annealed condition or in the cold worked plus stress reHef annealed condition. 

Although aluminium is a base metal, it spontaneously forms a highly protective oxide film in most aqueous environments, i.e. it passivates. In consequence, it has a relatively noble corrosion potential and is then unable to act as an anode to steel. Low level mercury, indium or tin additions have been shown to be effective in lowering (i.e. making more negative) the potential of the aluminium they act as activators (depassivators). Each element has been shown to be more effective with the simultaneous addition of zinc . Zinc additions of up to 5% lower the anode operating potential, but above this level no benefit is gained . Below 0 9 7o zinc there is little influence on the performance of aluminium anodes . Table 10.10 lists a number of the more common commercial alloys. 

The current-time response of the system during Sn(Il) addition presents the same features as the mass intensity-time curve. For comparison the i-t curve for a blank experiment (only adsorbed methanol being present, no tin addition) is also shown in Fig. 4.6a. The observed response is not simply the sum of the individual responses of Sn(II) (Fig. 4.2b) and adsorbed methanol (see dashed curve in Fig. 4.6a), to the applied potential step. 

The identities of the products were confirmed by infrared spectroscopy and x-ray powder diffraction patterns. Physical data on the inorganic tin additives studied are given in Table II. 

Earlier studies at the ITRI have demonstrated the effectiveness of tin(IV) oxide, both in its anhydrous and hydrous forms, as a flame- and smoke-retardant additive for laboratory-prepared polyester resin formulations (J5j. In a recent study, carried out in collaboration with a major U.K. company, a number of inorganic tin additives have been incorporated into a commercial brominated polyester resin. Although this resin, which contains 28% by weight bromine, is intrinsically flame-retardant, giving samples with an 01 of ca. 41 and which meet the UL94-VO classification, formulations with improved flame and smoke properties are sought. 

Of the tin additives studied, the anhydrous and hydrated zinc stannates, ZnSnO and ZnSn(OH), respectively, are considerably more effective flame-retardant synergists with the bromine present in the plastic than 8-stannic acid (Figure 1). In line with this observation, oxidic tin-zinc systems have previously been found to exhibit superior flame-retardant properties to tin oxides alone (19-22). In addition, ZnSnO, gives higher values of 01 than Sb20, incorporation levels studied, and, in fact, the 1% ZnSnO - containing plastics outperform samples containing 2% Sb O,. 

Although there have been many studies on the mode of action of fire retardants generally, (J 6) the mechanistic behaviour of tin additives is less clear, and may depend on several factors including the ratio of halogen tin in the system. 

Hence, the tin additives may also be acting as condensed phase char promotors. 

In general, tin compounds do not exhibit flame-retardant properties in halogen-free polymer systems, unless the composition contains a high inorganic filler loading. However, tin additives often act as smoke suppressants in non-halogenated polymers. 

The Addition Formula for the Bessel Coefficients. In certain physical problems we have to reduce a Bessel coefficient of type, /n(i -(- ij) to a form more amenable to compulation. Wc shall now derive tin addition formula which is of great use in these circumstances. From the definition (25.0) we have the expansion... 

Davis 69) found no considerable variation in the o-xylene versus ethylbenzene ratio as a function of hydrogen pressure. He also observed that the relative amount of o-xylene from n-octane increased (a) with decreasing Pt loading of the catalyst (70) b) with increasing tin addition 69, 7J) (c) with the poisoning of the catalyst with thiophene (77) and d) if octenes or octynes... 

For the homologous azoalkanes ether, pentane, or petroleum ether may be used for extraction. The extraction solvent can be added before tin addition of hyjxxihlorite."... 

The second, which passes through a dimetallacyclopentane type intermediate [87], requires the presence of adjacent platinum atom assemblies. The mechanism should consequently be strongly inhibited by platinum site isolahon, due to tin addition or to catalyst poisoning by carbon. 

Also, materials with small amounts of TiN additions show lower friction in ball bearing applications leading to higher loading capacities of the bearings [525, 583],... 

Yaroshenko, V., Gogotsi, Y., Osipova, I., Effect of TiN addition on properties of silicon nitride based ceramics, in Ceramic Today - Tomorrow s Ceramics, ed. P. Vincenzini, Elsevier, Amsterdam, 2821-2830, 1991. 

Figure 6. Luminescence spectra of vanadyl naphthenate on LaY steam aged (A) without and (B) with tin addition. The excitation wavelength was 300 nm.

Spectral bands in the 500-575 nm region are quenched when the LaY zeolite is loaded with 1% tin, suggesting that tin addition minimizes V205 formation. Mossbauer studies have indicated that tin is in the +4 state after calcination (26-31) the reduction in intensity seen when comparing Figures 6a and 6b could be due to the formation of V+5-0-Sn+4 linkages (26). 

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