Thermodynamics of the formation of catalyst clusters for carbon nanotube growth

A fundamental thermodynamic model of formation of catalyst clusters for growing carbon nanotubes has been developed and model predictions have been compared with the experimental data. An expression for the size distribution function of clusters, depending on the conditions of their formation, is obtained. It is shown that surface tension plays an important role in the cluster formation. The surface tension coefficient for iron clusters at 950°C is determined.     

Oxidative dehydrogenation of ethylbenzene to styrene over ultra-dispersed diamond and onion-like carbon

The catalytic properties of sp³-hybridized ultra-dispersed diamond and sp²-hybridized onion-like carbon in the oxidative dehydrogenation of ethylbenzene to styrene were investigated, highlighting the structure sensitivity of the reaction. The sp³-carbon led initially to C-C cleavage and benzene formation, while a switchover of the main reaction pathway into the styrene formation occurred with time on stream due to the formation of surface sp² carbon, required for the selective styrene formation. This was confirmed by the behavior and the high stable styrene selectivity shown by onion-like carbons. High temperature oxygen pre-treatment created catalytically active species at the sp² carbon surface, confirming that a high thermal stability carbon-oxygen complex was the active surface site for forming styrene.     

New design of reactive distillation processes

A technological design of reactive distillation processes (catalytic distillation) is discussed that applies liquid-flooded catalytic zones with a cocurrent-cross flow of the liquid, into each of which only a portion of the vapor stream is passed from the zone located below. This allows the cross section of the catalytic zones to be multiply reduced and the local excessive heating in them to be completely eliminated.     

Numerical implementaion of a freezing-front model for water-saturated media that includes the dependence of the phase-transition temperature on the pressure and concentration

A computational algorithm is constructed for solution of the problem of freezing of water-saturated porous media with account for the dependence of the temperature of the phase transition of pore moisture on the pressure and the concentration of a dissolved impurity. The mathematical model of the process considered is based on a generalized formulation of the well-known Stefan problem. Examples convey results of computation.     

Heat resistance of nitrided layers on high-speed powder steels

Nitriding of cutting tools is used to improve their endurance. The small thickness of the nitrided layers does not make it possible to evaluate their heat resistance by the standard method. This has made it necessary to develop a method for independent determination of the heat resistance of nitrided layers on high-speed steels. This makes it possible to optimize the nitriding process, in particular, for improving the heat resistance of the layers. The present work is devoted to assessing the possibility of increasing the heat resistance of high-speed powder steels R6M5K5-MP and R9M4K8-MP by ion nitriding and to developing a method for evaluating the heat resistance of the nitrided layers. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 5–6, October, 1998.     

Production of Polikon carbon-filled conducting materials

The effect of disperse graphite on the kinetics and thermodynamics of formation of an ion-exchange matrix was investigated and the basic parameters for production of Polikon K carbon-filled material were selected. The effect of the filler on crosslinking and the yield of finished oligomer was established. Incorporation of colloidal graphite changes the dielectric properties of Polikon K material by increasing its conductivity. __________ Translated from Khimicheskie Volokna, No. 1, pp. 52–54, January–February, 2008.     

Basic principles for constructing controllable electrotechnical complexes for production of synthetic fibres and nonwoven materials

A concept for building the structure and studying controllable electrotechnical complexes for manufacturing equipment that increase the efficiency of saving energy and resources by optimizing the speed regimes is proposed. Selection of the velocity diagram of transportation, spinning, and winding of synthetic fibres and nonwovens should precede the process study to determine the optimum regime indexes.     

A method for protecting communicated information using neural-network detection

A method for protecting information transmitted via a communication channel is proposed. According to this method, data messaging is encoded by a change in the shape of pulse sequences and the messages are detected based on the neural-network method of signal identification. The efficiency of the method is analyzed in the case of multichannel transmitting of graphical information.