Synthesis thermal reductions

Application of carbo-thermal reduction. This is a synthesis process for the preparation of powders of carbides, nitrides and borides. Carbon may be graphite, coke, pyrolysed organic polymers. A reference process may be the Acheson process for the production of SiC ... 

In-situ synthesis of the clay stabilized Au nanoparticles was also carried out by dissolving 1.68 g of MgCl2-6H20 (8.26 mmol) in 20 mL of 3.8 mM solution of HAuCL followed by the addition of 2 mL of 3-aminopropyltrimethoxysilane. The yellow slurry obtained was stirred overnight at room temperature and then kept at 75 °C for 24 h. It slowly turned pink in colour due to the formation of gold nanoparticles by thermal reduction. The pink transparent film obtained was washed with ethanol and then dried again. 

Combs et al. have described an unprecedented in situ thermal reduction of the N-0 bond on microwave irradiation at 200 °C for 20 min in the synthesis of 2,4,5-triarylimidazoles from the parent keto-oximes and aldehydes [41]. A similar method has been extended to a short synthesis of lepidiline B (Scheme 10.18) and trifenagrel illustrating the utility of microwave technology [42]. 

Figure 5.8 Self-propagating synthesis of titanium nitride, carbide, or carbonitride via carbo-thermal reduction.

Thermal reduction method is limited by the requirement that the substrate must tolerate high temperature which may likely introduce many defects in to graphene sheets as well as the composites. As an alternative method, synthesis via chemical reduction was opted as it represents a very simple... 

The X-ray phase analysis confirmed that the synthesis products are TiC, ZrC, NbC and TaC carbides, which do not contain free carbon. Fineness of the carbides is determined by the grain size of the metal powder. The synthesis time depends on the diffusion rate of carbon into the volume of the grain or the crystallite. We used oxides of refractory metals as the starting materials for production of fine (1-5 pm) carbides. In this case the mass of the metallic calcium was increased taking into account its consumption for the calcium thermal reduction of the oxides. The presence of a higher amount of the calcium oxide in the salt melt did not incur large difficulties in the synthesis of the carbides and their washing with water to remove salts, because the calcium oxide easily dissolves in acidified water. This method of the carbide synthesis has been covered by a Russian Federation patent [6]. 

The reduction of porous silica with magnesium vapor is a highly exothermic reaction. The process with thermal moderators is an attractive route to generating highly mesoporous silicon (surface areas >500 m /g). Without thermal moderators, large batches of macroporous silicon can be generated by combustion synthesis. Electrochemical reduction with molten calcium or lithium salts rather than thermal reduction with magnesium is also under evaluation. The use of liquid aluminum to reduce mesoporous silica deserves much further study. 

Figure 7.13 Synthesis of Ag nanoparticles using a tubular microreactor via thermal reduction of silver pentafluoropropionate. (Reproduced from Ref [20].)...

Hoffmaim-La Roche has produced -carotene since the 1950s and has rehed on core knowledge of vitamin A chemistry for the synthesis of this target. In this approach, a five-carbon homologation of vitamin A aldehyde (19) is accompHshed by successive acetalizations and enol ether condensations to prepare the aldehyde (46). Metal acetyUde coupling with two molecules of aldehyde (46) completes constmction of the C q carbon framework. Selective reduction of the internal triple bond of (47) is followed by dehydration and thermal isomerization to yield -carotene (21) (Fig. 10). 

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