Table 2 - uploaded by Qiang Yao
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The oxidation characteristics of boron particles, boron-A with the diameter of 2.545 μm and boron-B with the diameter of 10.638 μm, at low temperature (<1500 K) have been investigated by thermogravimetry (TG) coupled with simultaneous differential scanning calorimetry (DSC), infrared and mass spectra. A rapid oxidation stage of boron particles, fol...
Contexts in source publication
Context 1
... impurities in the boron-A and boron-B, as shown in Table 2, were detected by inductively coupled plasma mass spectrometry (ICPMS). The mainly impurity content in bo- ron-A or boron-B is carbon. ...
Context 2
... this weight loss could be eliminated by normalization of the TG curves. The other is caused by re- leasing CO 2 , product of the reaction between the impurity of carbon in the boron particles, seen in Table 2, and the oxy- gen. Since the TG-MS curves of CO 2 in Figure 4 show that the rates of releasing CO 2 are similar to the DTG curves respectively. ...
Citations
... Multiple research efforts reviewed recently [1] aimed to improve boron's ignition and combustion efficiency, including preparing composites [9][10][11][12] washing its surface oxide and hydroxide off with a solvent [13,14], and coating boron with oxidizers [14,15], binders [16][17][18], fluoride materials [19,20], fluoropolymers [12], and metals [21,22]. Different types of boron powders (fine [23][24][25][26], coarse [27,28], amorphous [8,29,30], crystalline [31,32], etc.) were used in different experiments. In a recent study, boron powders with different characteristics were examined, and it was established that such powders are mostly micron-sized agglomerates of finer primary particles [33,34]. ...
... Researchers have found that particle size and specific surface area of boron powders have a strong effect on the oxidation onset temperature observed in TG experiments [32,48,49]. This is broadly explained by the increase in the heterogeneous oxidation rate for greater reactive surface areas, and many models were developed focused on finding the correct functional form for this size dependence [1,32,33]. ...
... Researchers have found that particle size and specific surface area of boron powders have a strong effect on the oxidation onset temperature observed in TG experiments [32,48,49]. This is broadly explained by the increase in the heterogeneous oxidation rate for greater reactive surface areas, and many models were developed focused on finding the correct functional form for this size dependence [1,32,33]. The crystallinity of boron powders may also play a role in their reactivity [49,50]. ...
... The exothermic temperature of the 13 μm sample ranges from 587.9 to 840.9 °C, covering 253 °C, which exceeds the temperature range of the smaller boron particles. This indicates that increasing the particle diameter reduces the heat release peak and the heat release efficiency, consistent with the literature [38] . Note: T i , initial reaction temperature ( °C); T e , final reaction temperature ( °C); T p , peak temperature ( °C); Q , heat release (J ·g −1 ). ...
... Теоретический прирост массы при полном окислении бора составляет около 218%. В термическом анализе при нагреве порошка бора в кислороде до температуры 1000 • C увеличение массы бора составляет ∼ 140% [6], а при нагреве в воздухе до 1500 • C прирост массы бора составляет ∼ 160% [7]. Таким образом, в реакцию окисления вступает не более 75 и 82 mass.% ...
The use of aluminum borides is a promising direction in the development of modern fuel compositions and aircraft. The paper presents experimental data on the kinetics of oxidation of micro-sized powders of aluminum, amorphous boron, aluminum borides AlB2 and AlB12 in air when heated at a constant rate of 10 °C/min., as well as the results of laser ignition of high-energy materials based on ammonium perchlorate, ammonium nitrate, inert and active combustible binders containing these metal powders. It was found that the use of boron-based powders makes it possible to reduce the temperatures of the onset and intensive oxidation, and to increase their completeness of oxidation in comparison with pure aluminum. The obtained dependences of the ignition delay time on the heat flux density showed that AlB2 and AlB12 powders included in the HEM based on ammonium perchlorate, ammonium nitrate, and an active binder are the most effective metal fuels in terms of reducing the ignition delay time and the heat input.
... A slight decrease in mass was noticed when heated up to 100 °C. This can be attributed to the hygroscopic nature of the initial oxide layer present on B. During storage of B, particle surface will slowly oxidize to form a thin oxide layer of several to hundreds of nanometers [20][21][22]. The oxide layer will then react with water vapor in the presence of air to form boric acid (H 3 BO 3 ) or metaboric acid (HBO 2 ). ...
Nano-materials are potential substitutes for micro-sized solid propellant ingredients for improving energy density and reaction activity. So far, several nano-carbides act as accelerants for boron (B) oxidation reaction but their promotive effects and corresponding action mechanisms have rarely been reported. In this work, four nano-carbides [nano-boron carbide (nB4C), nano-titanium carbide (nTiC), nano-zirconium carbide (nZrC), and nano-silicon carbide (nSiC)] were evaluated by thermogravimetric differential scanning calorimetry-combined thermal analysis system and thermodynamic software FactSage 6.2. Among the four nano-carbides, nTiC ranked as the best accelerant by reducing the initial oxidation temperature of B by 10.7% and increasing heat release by 16.0%. By comparison, nB4C and nZrC were ranked as second and third best accelerants with abilities of decreasing the initial oxidation temperature (by 5.4% and 3.3%, respectively) and raising heat release (both by 6.2%). On the other hand, though nSiC slightly decreases the initial oxidation temperature of B, heat release of B + nSiC was lower than that of original B. The action mechanisms of nano-carbides were found complex, and one nano-carbide can accelerate B oxidation following one or several approaches. First, the nano-carbide can be oxidized before B to offer extra heat and induce the oxidation of B. The produced gaseous oxidation product CO2 by nano-carbide may then help break down the liquid oxide film deposited on B particle surface. Third, the reaction between nano-carbide and B would generate borides, which may diminish accumulated liquid oxide film at low temperatures. Finally, the corresponding oxide will be produced to catalyze the oxidation of B. Overall, these findings look promising for future performance improvement of B-based solid propellants.
