Antimony decomposition

France M R, Buchanan J W, Robinson J C, Pullins S FI, Tucker J T, King R B and Duncan M A 1997 Antimony and bismuth oxide clusters growth and decomposition of new magic number clusters J. Phys. Chem. A 101 6214... 

Antimony Oxide as a Primary Flame Retardant. Antimony oxide behaves as a condensed-phase flame retardant in cellulosic materials (2). It can be appHed by impregnating a fabric with a soluble antimony salt followed by a second treatment that precipitates antimony oxide in the fibers. When the treated fabric is exposed to a flame, the oxide reacts with the hydroxyl groups of the cellulose (qv) causing them to decompose endothermically. The decomposition products, water and char, cool the flame reactions while slowing the production and volatilization of flammable decomposition products (see Flaa retardants for textiles). 

Either mechanism can be used to describe how antimony—halogen systems operate in both the condensed and vapor phases. In the condensed phase a chat that is formed during the reaction of the polymer, antimony trioxide, and the halogen reduces the rate of decomposition of the polymer therefore, less fuel is available for the flame (16). 

The fine antimony mist formed from the decomposition of the trichloride also participates in the flame-inhibiting process, deactivating oxygen, hydrogen, and hydroxyl radicals. 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

Semiconductor and Solar Cells. High purity (up to 99.9%) antimony has a limited but important appHcation in the manufacture of semiconductor devices (see Semiconductors). It may be obtained by reduction of a chemically purified antimony compound with a high purity gaseous or soHd reductant, or by thermal decomposition of stibine. The reduced metal may be further purified by pyrometaHurgical and zone melting techniques. 

High purity stibiae is used as an -type, gas-phase dopant for Si in semiconductors (14). Low temperature distillation of stibiae at <53.3 kPa (400 torr) yields a product that on decomposition gives metallic antimony having less than 8 x lO " % impurity (18). A method for determining quantities of stibiae in the neighborhood of 0.1 mg/m in air has been reported (19). 

Antimony Pentachloride. Antimony(V) chloride [7647-18-9], SbQ, is a colorless, hygroscopic, oily Hquid that is frequently yeUow because of the presence of dissolved chlorine it caimot be distilled at atmospheric pressure without decomposition, but the extrapolated normal boiling point is 176°C. In the soHd, Hquid, and gaseous states it consists of trigonal bipyramidal molecules with the apical chlorines being somewhat further away than the... 

The thermal decomposition of trialkyl antimony dihaUdes has been used for the preparation of chloro-, bromo-, and iodostibines (106) ... 

Antimony-based passivation was introduced by Phillips Petroleum in 1976 to passivate nickel compounds in the FCC feed. Antimony is injected into the fresh feed, usually with the help of a carrier such as light cycle oil. If there are feed preheaters in the unit, antimony should be injected downstream of the preheater to avoid thermal decomposition of the antimony solution in the heater tubes. 

The role of Lewis acids in the formation of oxazoles from diazocarbonyl compounds and nitriles has primarily been studied independently by two groups. Doyle et al. first reported the use of aluminium(III) chloride as a catalyst for the decomposition of diazoketones.<78TL2247> In a more detailed study, a range of Lewis acids was screened for catalytic activity, using diazoacetophenone la and acetonitrile as the test reaction.<80JOC3657> Of the catalysts employed, boron trifluoride etherate was found to be the catalyst of choice, due to the low yield of the 1-halogenated side-product 17 (X = Cl or F) compared to 2-methyI-5-phenyloxazole 18. Unfortunately, it was found that in the case of boron trifluoride etherate, the nitrile had to be used in a ten-fold excess, however the use of antimony(V) fluoride allowed the use of the nitrile in only a three fold excess (Table 1). 

Figure 6.4 shows the change in the sensor conductivity as a function of temperature. Curve / shows the dependence of sensor resistivity with temperature when the sensor is positioned in evacuated installation. The introduction of antimony hydride was made at temperature - 75°C bringing about no change in resistivity. When the temperature of the sensor was increased up to - 20 C there were no effects detected on its resistivity caused by antimony hydride. Only at higher temperatures one can observe deviation of dependence RiT) from curve 1 which is caused by decomposition of SbHa on ZnO. These results led to experiments on emission of H-atoms in a special vial when Sb-film treated by H-atoms was kept at a room temperature and sensors were kept at the temperature of - 80 C. Under these conditions, as is shown by above reasoning. 

Gillespie, R. J. et al., J. Chem. Soc., Chem. Comm., 1977, 595-597 Although stable at below -40°C in absence of moisture, it will explode if warmed rapidly (>20°C/h). Explosive decomposition of the solid difluoride oxide at -196°C occurs on contact with mercury, or antimony pentafluoride or arsenic pentafluoride [1], The fluoride explodes at about 0°C, and also in contact with arsenic pentafluoride in absence of hydrogen fluoride at -78°C [2],... 

Volatile decomposition products may include HC1, HCN, nitrogen oxides (NO ), benzene, and oxides of arsenic, antimony, or lead. 

Ylides from R N2. This reagent is more effective than bis(acetylacetonate)-copper(II) (5, 244) for generation of carbenes from diazo compounds.2 The decomposition proceeds at a lower temperature, even at room temperature. The mild conditions are particularly useful in the preparation of heat-sensitive ylides, such as those of antimony, bismuth, and tellurium. 

The kinetics of the thermally induced homogeneous decomposition of phosphine (PH3) have not yet been studied. The species PH2, PH and P2 are formed on flash photolysis of PH3 and could be identified by their absorption spectra63. There are proposals as to the mechanism of the consecutive process after the photochemical primary step, but nothing is known about the kinetic parameters of these reactions. With arsine and antimony hydride only the heterogeneous decomposition has been studied64,65. 

The pyrolysis was studied in a toluene carrier flow system over the temperature range 475-603 °C. Most runs were carried out at 16-17 torr with a contact time of 1-2 sec. He ratio % decomposition (gas anaiysis)/% decomposition (antimony recovered from reaction zone) varied from 0.91 at 475 °C to 0.75 at 603 °C. Apparent first-order rate coefficients based on both metal and gas analysis increased with decreasing alkyl concentration (log k/log[Sb(CH3)3] = 0.28 at all temperatures). Corrected for this effect, fc24t0rr/ 6torr = 1-3, indicating a small uni-molecular pressure effect. 

Diammino-antimony Trichloride, [Sb(NH3)2]Cl3.—This derivative is prepared by passing ammonia gas over molten antimony trichloride or warm antimony pentachloride.1 It is a yellowish-white semi-crystalline substance, which is volatile without decomposition and is attacked by hydrochloric acid, with formation of the compound NH4Cl.SbCl3. 

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