Combustion boron

Site and Mode of Boron Combustion in the Combustion Wave... 

Boron is one of the essential materials for obtaining high specific impulse of a ducted rocket However, the combustion efficiency of boron-containing gas-generating pyrolants is low due to incomplete combustion of the boron particles in the ramburner.[i3-i l Fig. 15.20 shows the combustion temperature ofa boron-containing pyrolant with and without boron combustion as a function of air-to-fuel ratio, 8. A typical boron-containing pyrolant is composed of mass fractions of boron particles b(0-30), ammonium perchlorate ap(0.40), and carboxy-terminated polybutadiene ctpb(0-30). If the boron particles burn completely in the ramburner, the maximum combustion temperature reaches 2310 K at 8 = 6.5 and v = Mach 2 p =... 

Fig. 15.20 Theoretical flame temperature versus air-to-fuel ratio of a boron-containing pyrolantwith and without boron combustion.

MPa) under conditions of sea-level flight However, if no boron combustion occurs, the temperature decreases to 1550 K under the same flight conditions. The combustion efficiency of boron particles is an important parameter for obtaining high specific impulse of ducted rockets. 

Schadow, K., Boron Combustion Characteristics in Ducted Rockets, Combustion Science and Technology, Vol. 5, 1972,... 

Schadow, K., Experimental Investigation of Boron Combustion in Air-Augmented Rockets, AIAA Journal, Vol. 7, 1974,... 

The molecules involved are relatively small, so that CBS procedures were feasible for these calculations. For boron combustion, we initially used both the CBS-Q and the B3PW91 techniques [93], but changed to the superior CBS-QB3 when it became available [94-96], and continuted with it for the aluminum work [97], At this level, the average absolute error in AHf (determined from formation reactions) was less than 2.0 kcal/mole [96,97]. The same accuracy was achieved for AH(298 K), AH(2000 K) and AG(298 K) for the combustion steps examined. It was observed that AH changes very little, by an average of less than 2.0 kcal/mole, in going from 298 K to 2000 K. In contrast, AG(2000 K) can differ quite significantly from AG(298 K), and tends to be less accurate. (Fortunately... 

Borovinskaya, I. P., Merzhanov, A. G., Novikov, N. P., and Filonenko, A. K., Gasless combustion of mixtures of powdered transition metals with boron. Combust. Explos. Shock Waves, 10,2 (1974). 

Mukasyan, A. S., Characteristics and mechanism of silicon and boron combustion in nitrogen. Ph.D. Dissertation, Institute of Chemical Physics, USSR Academy of Science (1986). 

NITRITO POTASICO (Spanish) (7758-09-0) Noncombustible, but many chemical reactions can cause fire and explosions. A powerful oxidizer. Reacts with acids, acid fumes, producing nitrous fumes. Violent reaction with many substances, including reducing agents, alcohols, ammonium salts, amines, boron, combustible materials, ethers, finely divided metals, organic substances, nitric acid, potassium, sulfuric acid. Incompatible with ammonium sulfate, barium sulfide, potassium amide. Decomposes or may explode in elevated temperatures. 

Boron Nitride Nanoparticles of boron nitride powders (a-BN) can be obtained by choosing the proper terms of elemental boron combustion in gaseous or liquid nitrogen or boron anhydride (B2O3) combustion by the mode called SHS with a reduction stage [43]. In the first case, the agglomerates of BN nanoparticles can be separated by means of chemical dispersion (chemical-thermal method of the... 

Li, LiN, MgB, Sn, Pb, and so on. For the first time, P-BN (wurtzite-like form) was discovered at X-ray analysis of boron combustion products in the mixture with metal magnesium. In those experiments, was also detected as thin... 

But it should be noted that the experiments with boron combustion in liquid nitrogen in sealed reactors were rather dangerous. In some experiments, the pressure leaps higher than 20 kbar resulted in combustion transition to detonation and even the installation destruction as well as acid treatment of the reaction products was followed by shots with flame. Obviously, some by-products or intermediate ones as explosive azides can be formed at fast cooling of the reactive mass. 

Considering the results of these experiments, we can assume that boron combustion at high nitrogen pressures corresponds to the elemental combustion model of the second type, namely, the model of high-temperature melting. 

In general, elemental boron and boron compounds have been the subject of many studies involving propulsion systems due to the very high heats of combustion. However, due to some combustion problems, the theoretical benefits of boron and its compounds have rarely been delivered. The main limitations for boron combustion are (i) ignition delay due to the presence of an oxide layer on the surface of... 

---