Thermal degradation metals

Products of thermal degradation metal chlorides produced fiom thermal stabilizers, products of degradation of some antioxidants, hydrogen chloride (autocatalytic product of PVC degradation)... 

A new versatile solution based strategy for in situ preparation of metal-organic molecular precursors based on butyldithiocarbamic acid has been reported. Carbon disulfide (CS2) and 1-butylamine undergo a facile reaction producing butyldithiocarbamic acid which reacts with a variety of metal oxides and hydroxides to form thermally degradable metal-organic molecular precursors. This approach has been used for the fabrication of CIGSSe based absorber layer in thin film solar cells. In a... 

Anionic Polymerization of Cyclic Siloxanes. The anionic polymerization of cyclosiloxanes can be performed in the presence of a wide variety of strong bases such as hydroxides, alcoholates, or silanolates of alkaH metals (59,68). Commercially, the most important catalyst is potassium silanolate. The activity of the alkaH metal hydroxides increases in the foUowing sequence LiOH < NaOH < KOH < CsOH, which is also the order in which the degree of ionization of thein hydroxides increases (90). Another important class of catalysts is tetraalkyl ammonium, phosphonium hydroxides, and silanolates (91—93). These catalysts undergo thermal degradation when the polymer is heated above the temperature requited (typically >150°C) to decompose the catalyst, giving volatile products and the neutral, thermally stable polymer. 

In a reactor at low pressure (0.2-0.3 MPa) and moderate temperature (375 °C) the PVC is chemically and thermally degraded. A particular feature of the process is that the chlorine in the PVC reacts in part with the fillers in PVC and is neutralised with the formation of CaCl2. In similar vein, metal stabilisers in PVC are converted into the respective metal chlorides (lead, cadmium, zinc and/or barium). At current PVC waste compositions these chlorides consist of 60% lead which can be purified and re-used. The reaction in the end results in the following solid, liquid and gaseous products. 

The effects of aluminium, zinc, iron, nickel and copper powders on the thermal degradation of waste PS were studied. The results showed that the catalytic effects of metal powders were related to their activities. The catalytic effects increased with increasing activities of metals. It was suggested that PS degraded through a transient intermediate in the presence of metal powders and that the degradation of the transient intermediate was the rate-determining step. 10 refs. 

Similarly, Pd, Ag, and Pd-Ag nanoclusters on alumina have been prepared by the polyol method [230]. Dend-rimer encapsulated metal nanoclusters can be obtained by the thermal degradation of the organic dendrimers [368]. If salts of different metals are reduced one after the other in the presence of a support, core-shell type metallic particles are produced. In this case the presence of the support is vital for the success of the preparation. For example, the stepwise reduction of Cu and Pt salts in the presence of a conductive carbon support (Vulcan XC 72) generates copper nanoparticles (6-8 nm) that are coated with smaller particles of Pt (1-2 nm). This system has been found to be a powerful electrocatalyst which exhibits improved CO tolerance combined with high electrocatalytic efficiency. For details see Section 3.7 [53,369]. 

Figure 2. TCS-D strategy. A resin layer is produced outside each support particle. Metallation-reduction of the polymer shell will lead to size-controlled metal nanoclusters. Gentle thermal degradation of the organic shell will lead to size-controlled metal nanoclusters, expected to be evenly dispersed on the support particles surface.

Increase the oxidation rate of polymers, e.g. metal ions which increase the hydroperoxide decomposition rate. Photodegradation and thermal degradation are enhanced by transition metal ion containing pro-oxidants, such as iron dithiocarbamate (as opposed to nickel dithiocarba-mate, which acts as a photo-antioxidant). 

L. Costa, G. Camino and L. Trossaarelli, "Thermal Degradation of Fire Retardant Chloroparaffin - Metal Compound Mixtures - Part I. Antimony Oxide,"Polym. Degradation and Stability, 5, 267 (1983). 

A study was made of the thermal degradation behaviour of PS foams used as patterns in the lost foam process for metal casting. The data indicated that the thermal degradation of the pattern had a strong effect on mould filling and casting quality. The use of other types of foam such as PE, PP, PMMA and styrene-methyl methacrylate copolymers to overcome problems encountered with PS foam patterns is discussed. 7 refs. 

Strength, brittleness, and solvent permeability properties are limited because of lack of control of the ceramic composition on a macro- and microlevel. Even small particle sizes are large compared with the molecular level. There have been a number of attempts to produce uniform ceramic powders including the sol-gel synthesis in which processing involves a stable liquid medium, coprecipitation in which two or more ions are precipitated simultaneously. More recently, Carraher and Xu have used the thermal degradation of metal containing polymers to deposit metal atoms and oxides on a molecular level. 

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