Oxidation kinetics and combustion of boron particles with modified surface

Thermal decomposition of ammonium perchlorate—A TGA–FTIR–MS study: Part I

Combustion of boron and boron–iron composite particles in different oxidizers

Ignition and combustion characteristics of amorphous boron and coated boron particles in oxygen jet

Effects of Ti and Mg particles on combustion characteristics of boron–HTPB-based solid fuels for hybrid gas generator in ducted rocket applications

Compound of magnesium and boron (MB) is promising to be the ideal substitute of amorphous boron which is usually used as the raw material of boron-based fuel-rich propellants. In this study, the physical characteristics of MB and amorphous boron were studied by the scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The thermal reaction characteristics and the ignition and combustion characteristics were investigated through TG/DSC experiments and laser ignition experiments. The experimental results show that the MB particle is much more regular than amorphous boron, which favors for the preparation of boron-based fuel-rich propellants. Magnesium exists in the form of elementary substance, and boron oxide is produced during the preparation of MB which results in the longer ignition delay time of MB. The content of magnesium and the pressure have effects on the MB combustion performance. Although the combustion of magnesium can provide much heat for the combustion of boron, MB with moderate content of magnesium shows the best combustion performance. On the contrast, the ignition delay time of MB is independent on the content of magnesium and the pressure.

Ignition and combustion characteristics of compound of magnesium and boron

High pressure DSC and simultaneous TG/DSC were used to study the different kinds of boron that was used in the fuel-rich propellant and the amorphous boron in different gases and different pressure. Also, some of the samples before the experiment and after the experiment were analyzed by the SEM. The results show that: (1) there is a big exothermic peak between 550 °C and 850 °C for all the samples because the combustion heat of boron is very high, and the exothermic peak appears in advance when the pressure or the oxygen concentration increases. (2) Although the reaction process of all the samples with air or oxygen could be divided into five stages, the reaction characteristics are different from each other. Especially, amorphous boron is much more active than the boron used in the fuel-rich propellant. (3) The exothermic peak at about 700 °C appears in advance, and the percentage conversion of boron decreases when the content of magnesium increases and boron–magnesium compound is used as the raw materials. (4) Some samples start to lose their mass for the sake of the evaporation of the (BO)n.

Thermal reaction characteristics of the boron used in the fuel-rich propellant

A facility was designed to collect the primary combustion products of boron-based fuel-rich propellants under different chamber pressures. The morphology and particle size of condensed-phase products were analyzed using a laser particle size analyzer and a scanning electron microscope (SEM), and chemical analysis of condensed-phase products was carried out by X-ray diffraction (XRD), laser Raman spectrometry, wet chemical analysis and elemental analysis. In addition, organics in condensed-phase products and gaseous products were analyzed by Fourier Transform Infrared Spectrometry (FTIR) and Gas Chromatography (GC), respectively. The results show that the condensed-phase products mainly consist of B, C, B4C (or B12C2), BN, Mg, MgO, MgAl2O4, Al, Al2O3, AlCl3, NH4[Mg(H2O)6]Cl3, NH4Cl and Fe3O4; there are large amounts of boron oxide and boron carbide in the condensed-phase products, which indicates that elemental boron is highly active during the primary combustion process; a higher chamber pressure may be disadvantageous to the secondary combustion efficiency because more inactive boron carbide, graphite and h-BN (especially boron carbide) are produced.

Chemical analysis of primary combustion products of boron-based fuel-rich propellants

Amorphous boron is usually employed as the most important fuel of boron-based fuel-rich propellants, and NH4ClO4 (AP), cyclotetramethylenetetranitramine (HMX), KClO4 and KNO3 are the solid oxidizers of most used in solid propellants. The mixtures of boron and different solid oxidizers with mass ratio 1:1 were prepared in this paper, and the effect of these oxidizers on the thermal oxidation and combustion performance of amorphous boron was studied by simultaneous thermogravimetry–differential scanning calorimeter–Fourier transform infrared spectroscopy and CO2 laser ignition experiments. The experimental results show that the main reactions during the heating process of B/AP and B/HMX samples are the decomposition of oxidizers, and the decomposition process of oxidizers rather than the decomposition temperature is affected by amorphous boron; boron could react with KClO4 and KNO3 violently with the release of large amounts of heat, and then both of the oxidizers, especially KClO4, have positive effect on the oxidation and combustion performance of amorphous boron.

Effect of solid oxidizers on the thermal oxidation and combustion performance of amorphous boron

Different boron-based fuel-rich propellants were prepared by replacing part of ammonium perchlorate with different content of cyclotrimethylenetrinitramine, cyclotetramethylenetetranitramine, potassium nitrate, and potassium perchlorate. The burning rate of the propellants under different pressures was measured in the strand burner, the combustion temperature of the propellants under 1 MPa was measured by microthermocouple, and differential scanning calorimetry/thermogravimetric analysis experiments of the propellants in argon atmosphere were carried out. The experimental results show that the effect of each oxidizer on the burning rate of the propellant is different; cyclotetramethylenetetranitramine and cyclotrimethylenetrinitramine could increase the combustion temperature and the gaseous products, whereas potassium nitrate, and potassium perchlorate have the opposite effect. The composition of the combustion products under different pressures was calculated based on the minimization of Gibbs free-ener...

Guo-qiang He

Papers

Ignition and combustion characteristics of compound of magnesium and boron

Thermal reaction characteristics of the boron used in the fuel-rich propellant

Chemical analysis of primary combustion products of boron-based fuel-rich propellants

Effect of solid oxidizers on the thermal oxidation and combustion performance of amorphous boron

Effect of Oxidizer on the Combustion Performance of Boron-Based Fuel-Rich Propellant