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Ammonium Perchlorate Decomposition in Nano-titania

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22/01/18 Chemistry Reference this

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Thermal decomposition of ammonium perchlorate in the presence of commercial nano-titania

Mostafa Mahinroosta*

 

Abstract

Addition of metal and metal oxide nanoparticles (especially transition metal oxides) to ammonium perchlorate improves its thermal decomposition via decreasing the high temperature of decomposition. Two mechanisms including electron-transfer and proton-transfer have been proposed for thermal decomposition of ammonium perchlorate. In this research field, nanometer transition metal oxides have attracted a growing attention. Titanium dioxide exists under three crystalline forms of rutile, anatase, and brookite. All three forms occur naturally but the latter is rather rare and has no commercial interest. Anatase becomes more stable than rutile when the particle size is decreased below 14 nm. In the present study, commercial nano-titania with an average particle size of 10-25 nm was added to ammonium perchlorate. Catalytic effect of the titania nanoparticles on the thermal decomposition of ammonium perchlorate was evaluated. Some samples of ammonium perchlorate consisting of various mass loadings of nano-titania were prepared. Thermogravimetry analysis results indicate that addition of titania nanoparticles to ammonium perchlorate lessens decomposition temperature of ammonium perchlorate. The most decrease in the decomposition temperature was 61 °C and observed in the presence of 3 wt.% of nanometer titanium dioxide.

Keywords: Titania; Ammonium perchlorate; Thermal decomposition; Nanostructure.

1. Introduction

Over the past few years, nanoparticles of many different compounds and combinations have received considerable attention in the scientific and engineering research fields [1]. Nanometer materials exhibit a much larger surface area for a certain mass or volume compared to conventional particles [2]. The oxide nanoparticles are the materials with good electrical, optical, magnetic, and catalytic properties that are different from their bulk counterparts [3]. Reduction in the particle size lessens the transient heat conduction travel through the particle over time, and an increase in the surface-to-volume ratio leads to better dispersion of the particles in the mixture, increasing the reactant sites. Finally, the nanometer particles can have completely different surface chemistry, often better than their micron-sized counterparts [4]. Among these nanostructure oxides, titanium dioxide or titania (TiO2) nanostructures have emerged as one of the most promising materials because of their potential for gas sensors, especially for humidity and oxygen detection [2, 3, 5], optical devices [3, 5, 6], photocatalysis [2, 3, 6], fabricating capacitors in microelectronic devices due to its unusually high dielectric constant [3, 6], pigments [2, 7], adsorbents [7], and solar cells [5]. A relatively low level of TiO2 is needed to achieve a white opaque coating which is resistant to discoloration under ultraviolet light. TiO2 pigment is used in many diverse products, such as paints, coatings, glazes, enamels, plastics, papers, inks, fibers, foods, pharmaceuticals or cosmetics. Pure titanium dioxide is colorless in the massive state, non-toxic, thermally stable, inert versus acids, alkalis and solvents, and insoluble. It exists under three fundamental crystalline phases: rutile which is the most stable and the most abundant form, anatase (octahedrite) and brookite. All three forms occur naturally but the latter is rather rare and has no commercial interest. Anatase becomes more stable than rutile when the particle size is decreased below 14 nm. Generally speaking, the functional properties of nano-TiO2 are influenced by a large number of factors such as particle size, surface area, synthesis method and conditions, and crystallinity [2].

The presence of nano metals and metal oxides especially transition metal oxides as the nanocatalyst in solid propellant formulations tailors the thermal decomposition of ammonium perchlorate (AP in short). Thermal decomposition improvement of AP as a powerful oxidizer salt has attracted many attentions [1, 4, 8-10]. Decrease amounts of decomposition temperature of AP in the presence of the different nano metal and metal oxides are summarized in Table 1.

Table 1 is here

Vargeese [26] showed that significant reduction in activation energy indicates a strong catalytic activity of TiO2 on the thermal decomposition of AP. Fujimura and Miyake [27] studied the effect of specific surface area of TiO2 on the thermal decomposition of AP and concluded that the thermal decomposition temperature of AP decreases when the specific surface area of TiO2 increases.

The catalytic effect of commercial nanometer titanium dioxide on the thermal decomposition of AP is investigated within the scope of this study.

2. Materials and methods

2.1. Materials

Ammonium perchlorate (monomodal 120 µm) was purchased from Merck. Commercial nano-TiO2 in anatase form was purchased from Pishgaman Company located in Mashhad, Iran (Figure. 1). Its purity was more than 99%. Chemical composition and physical properties of nano-TiO2 are given in Tables 2 and 3, respectively.

Table 2 is here

Table 3 is here

2.2. Methods

2.2.1. X-ray diffraction analysis

X-ray diffraction (XRD) patterns of TiO2 nanoparticles was performed with a Philips PW 1800 powder X-ray diffractometer using CuKα radiation at 40 kV and 30 mA.

2.2.2. Transmission Electron Microscopy

Transmission electron microscopy (TEM) image of nano-TiO2 was prepared on a Philips transmission electron microscope operated at an accelerating voltage of 100 kV.

2.2.3. Thermogravimetry analysis

The thermal decomposition processes of the samples were characterized by thermogravimetry analysis (TGA) using Dupont 2000 instrument at a heating rate of 10 °C/min until temperature of 600 °C.

2.2.4. Sample preparation

The AP was mixed with various mass loadings of TiO2 nanoparticles namely 1, 2, and 3 wt.% to prepare the samples for thermal decomposition study. Theses samples were labeled as AP1T (AP+1% nano-TiO2), AP2T (AP+2% nano-TiO2), and AP3T (AP+3% nano-TiO2). Before thermal decomposition experiments using TGA technique, the samples were homogenized.

3. Results and discussion

3.1. Characterization of nanostructure

The TEM analysis was performed to confirm the actual size of the particles and the distribution of the crystallites. It is clear from the micrograph that the average size of the particles is located in range of 10-25 nm. TEM image of TiO2 nanoparticles is shown in Figure 2. Clear spherical structure can be seen from this figure. Figure 3 shows the X-ray diffractogram of the commercial nano-TiO2. It can be obviously seen that that diffraction peaks appear in the pattern associated with the anatase phase with proper crystalline nature. A very strong anatase peak is observed at 2ÆŸ of 25.25°, assigned to (101) plane. Other anatase peaks are observed at 2ÆŸ of 37.7° (004), 47.7° (200), 53.54° (105), and 62.32° (204).

3.2. Catalytic activity of nano-titania

Figure 4 shows the TGA curve for the thermal decomposition of pure AP. As can be seen in figure 4, the first exothermic peak is appeared in temperature of 327 °C that accompanied by a weight loss of 18 wt.%. This peak can be related to the partial decomposition of AP and the formation of some NH3 and HClO4 via dissociation and sublimation. The second exothermic peak is occurred in temperature of 411 °C. The weight loss in this stage is about 92 wt.% that is corresponding to complete decomposition of transition products to volatile products. Figure 5 presents the TGA curves associated with thermal decomposition of AP in the presence of 1, 2, and 3 wt.% of TiO2 nanoparticles. From this figure, it is clear that the partial decomposition of AP in the presence of 1, 2, and 3 wt.% of TiO2 nanoparticles is happened in a temperature much lower than 327 °C. Also, complete decomposition of AP in the presence of 1, 2, and 3 wt.% of TiO2 nanoparticles is occurred in temperatures of 370, 360, and 350 °C, respectively that accompanied by decrease of 41, 51, and 61°C, respectively. It is obvious that addition of nano-sized TiO2 to AP has deep effect on the exothermic decomposition of AP. According to these results, it can be concluded that the catalytic effect of nano-sized TiO2 is observed mainly on high-temperature decomposition process and not on the initial stages of decomposition.

3.3. Mechanism of thermal decomposition of AP

Based on the recent studies, two main mechanisms have been suggested for thermal decomposition of AP [11, 16, 17, 21]:

First mechanism: electron transfer from perchlorate ion to ammonium ion which is as follows:

ClO4+NH3+→ClO40+NH40

NH40→NH3+H

ClO40+ClO4=ClO4+ClO40

HClO4+H→H2O+ClO3

Second mechanism: proton transfer from ammonium ion to perchlorate ion which is as follows:

NH4ClO4(s) →NH4++ClO4→NH3(s) +HClO4(s) →NH3(g) +HClO4(g)

For first mechanism, it is proposed that the rate-determining stage is electron transfer and inasmuch as the p-type semiconductors have positive holes, they can accept the released electron from perchlorate ion. Thus, these catalysts accelerate the electron transfer.

eoxide+ClO4→Ooxide+ClO3→1/2O2+ClO3+eoxide

in which eoxide is a positive hole in the valence band of the oxide and Ooxide is an abstracted oxygen atom from oxide. It is clear that this mechanism includes two steps: 1) oxidation of ammonia and 2) dissociation of ClO4 species into ClO3 and O2.

In first step, metal oxides exhibit high catalytic activity in ammonia oxidation and in second step metal oxides accept the released electron from ammonia oxidation that may promote the dissociation of ClO4 into ClO3 and O2.

For second mechanism, steps (I)-(III) have been proposed. In step (I), the ammonium and perchlorate ions are paired. Step (II) is started with proton transfer from NH4+ cation to ClO4 anion and the molecular complex is formed that then is decomposed into NH3 and HClO4 in step (III). The molecules of NH3 and HClO4 react in adsorbed layer on the perchlorate surface or they are desorbed and sublimed that is accompanied by interactions in gas phase.

NH4+ClO4 ↔ NH3-H-ClO4 ↔ NH3-HClO4 ↔ NH3(a)+HClO4(a)

(I) (II) (III) ↕ ↕

NH3(g)+HClO4(g)

At low temperature (<350 °C), the surface reaction is performed more rapidly than the sublimation in gas phase and by-products such as O2, N2O, Cl2, NO, and H2O are formed.

Based on proton transfer, during high-temperature decomposition, the nanoparticles adsorb the reactive molecules on their surface and catalyze the reaction. The existence of more holes in p-type semiconductor catalysts is responsible for the increasing of the AP decomposition.

In this study, the mechanism of thermal decomposition of AP in the presence of the TiO2 nanoparticles can be explained as follows:

Titanium has the electronic configuration of [Ar]3d24s2. Experiments have demonstrated that it can form both +3 and +4 oxidation state, so it can lose 3 or 4 electrons to form cations. The +4 state is the most common and stable, because it is able to form an octet. The +3 state is less stable (more reactive) because it leaves a single d electron in the valence orbital.

Ti4+ cation in TiO2 structure has s and d-type orbitals with 3d04s0 electronic configuration. These orbitals have not been filled with electrons and provide a useful space for electron transfer in AP thermal decomposition and play the role of a bridge. By accepting transferred electrons resulted from ClO4 degradation, ClO4 degradation is promoted. On the other hand, TiO2 nanoparticles have high specific surface area and large amount of surface active sites that increase adsorption of reactive molecules in gas phase to the surface and promote the redox reactions between them.

4. Conclusions

The results of thermogravimetry analysis show that the nanometer titanium dioxide has significant catalytic effect on the thermal decomposition of ammonium perchlorate. The presence of nano-sized titanium dioxide improves significantly the thermal decomposition of ammonium perchlorate. With increase of content of nanometer titanium dioxide, the decrease in decomposition temperature of ammonium perchlorate becomes greater.

References

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[2] Marie-Isabelle, B: Nano-TiO2 for solar cells and photocatalytic water splitting: scientific and technological challenges for commercialization. The Open Nanoscience Journal, 5, 64-77 (2013).

[3] Suresh, S: Synthesis and electrical properties of TiO2 nanoparticles using a wet chemical technique. American Journal of Nanoscience and Nanotechnology, 1(1), 27-30 (2013).

[4] Demko, AR, Johnson, M, Allen, TW, Reid, DL, and Seal, S: Comparison of commercially available and synthesized titania nano-additives on the burning rate of composite HTPB/AP propellant samples. Spring technical meeting of the central states section of the combustion institute, April 22-24 2012.

[5] MortezaAli, A, and Saeideh, RS: Study of growth parameters on structural properties of TiO2 nanowires. Journal of Nanostructure in Chemistry, 3, 35 (2013).

[6] Karimi, L and Zohoori, S: Superior photocatalytic degradation of azo dyes in aqueous solutions using TiO2/SrTiO3 nanocomposite. Journal of Nanostructure in Chemistry, 3, 32 (2013).

[7] Vijayalakshmi, R and Rajendran, V: Synthesis and characterization of nano-TiO2 via different methods. Archives of Applied Science Research, 4(2), 1183-1190 (2012).

[8] Goncalves, RFB, Rocco, AFF and Iha, K: Thermal decomposition kinetics of aged solid propellants based on ammonium perchlorate-AP/HTPB binder. INTECH, doi: 10.5772/52109.

[9] Rodic, V: Effect of titanium (IV) oxide on composite solid propellant properties. Scientific Technical Review, 62(3-4), 21-27 (2012).

[10] Matthew, AS, Eric, LP, Carro, R, David, LR and Sudipta, S: Multi-parameters study of nanoscale TiO2 and CeO2 additives in composite AP/HTPB solid propellants. Propellants, Explosives, Pyrotechnics, 35(2), 143-152 (2010).

[11] Chen, W, Li, F, Liu, L and Li, Y: Synthesis of nano-yttria via a sol-gel process based on hydrated yttrium nitrate and ethylene glycol and its catalytic performance for thermal decomposition of NH4ClO4. Journal of Rare Earths, 24, 543-548 (2006).

[12] Zhenye, MA, Fengsheng, L and Aisi, C: Preparation and thermal decomposition behavior of TMOs/AP composite nanoparticles. Nanoscience, 11(2), 142-145 (2006).

[13] Yanping, W, Junwu, Z, Xujie, Y, Lude, L and Xin, W: Preparation of NiO nanoparticles and their catalytic activity in the thermal decomposition of ammonium perchlorate. Thermochimica Acta, 437, 106-109 (2005).

[14] Hungzhen, D, Xiangyang, L, Guanpeng, L, Lei, X and Fengsheng, L: Synthesis of Ni nanoparticles and their catalytic effect on the decomposition of ammonium perchlorate. Materials processing technology, 208, 494-498 (2008).

[15] Guorong, D, Xujie, Y, Jian, C, Guohong, H, Lude, L and Xin, W: The catalytic effect of nanosized MgO On the decomposition of ammonium perchlorate. Powder Technology, 172, 27-29 (2007).

[16] Satyawati, SJ, Prajakta, RP and Krishnamurthy, VN: Thermal decomposition of ammonium perchlorate in the presence of nanosized ferric oxide. Defence Science Journal, 58(6), 721-727 (2008).

[17] Shusen, Z and Dongxu, M: Preparation of CoFe2O4 nanocrystallites by solvothermal process and its catalytic activity on the thermal decomposition of ammonium perchlorate. Hindawi Publishing Corporation Journal of Nanomaterials, (2010). doi:10.1155/2010/842816.

[18] Han, A, Liao, J, Ye, M, Li, Y and Peng, X: Preparation of Nano-MnFe2O4 and its catalytic performance of thermal decomposition of Ammonium perchlorate. Chinese Journal of Chemical Engineering, 19, 1047-1051 (2011).

[19] Yifu, Z, Xinghai, L, Jiaorong, N, Lei, Y, Yalan, Z and Chi, H: Improve the catalytic activity of α-Fe2O3 particles in decomposition of ammonium perchlorate by coating amorphous carbon on their surface. Journal of Solid State Chemistry, 184, 387-390 (2011).

[20] Yu, Z, Chen, L, Lu, L, Yang, X and Wang, X: DSC/TG-MS study on in situ catalytic thermal decomposition of ammonium perchlorate over CoC2O4. Chinese Journal of Catalysis, 30(1), 19-23 (2009).

[21] Alizadeh-Gheshlaghi, E, Shaabani, B, Khodayari, A, Azizian-Kalandaragh, Y and Rahimi, R: Investigation of the catalytic activity of nano-sized CuO, Co3O4 and CuCo2O4 powders on thermal decomposition of ammonium perchlorate. Powder Technology, 217, 330-339 (2012).

[22] Wang, J, He, S, Li, Z, Jing, X, Zhang, M and Jiang, Z: Synthesis of chrysalis-like CuO nano-crystals and their catalytic activity in the thermal decomposition of ammonium perchlorate. J. Chem. Sci., 121, 1077-1081 (2009).

[23] Liu, T, Wang, L, Yang, P and Hu, B: Preparation of Nanometer CuFe2O4 by auto-combustion and its catalytic activity on the thermal decomposition of ammonium perchlorate. Materials Letters, 62, 4056-4058 (2008).

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[26] Vargeese, A: Effect of anatase-brookite mixed phase titanium dioxide nanoparticles on the high temperature decomposition kinetics of ammonium perchlorate. Materials Chemistry and Physics, 139(2-3), 537-542 (2013).

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Figure legends

Figure 1. Commercial nano-TiO2 used in this study

Figure 2. TEM image of TiO2 nanoparticles

Figure 3. XRD patterns of TiO2 nanoparticles

Figure 4. TGA curve related to pure AP

Figure 5. TGA curves related to (a) AP1T, (b) AP2T, and (c) AP3T

Table 1. Reported data from the literature on the decrease in AP decomposition temperature in the presence of different nano metal and metal oxides.

Nanocatalyst

Preparation method

Amount (wt.%)

Decrease in decomposition temperature (°C)

Reference

Nano-yttria

Sol-gel

5

114.6

[11]

CuO/AP composite nanoparticles

A novel solvent-nonsolvent method

95.83

[12]

Co2O3/AP composite nanoparticles

A novel solvent-nonsolvent method

137.11

[12]

NiO nanoparticles

Solid-state reaction

2

93

[13]

Ni nanoparticles

Hydrogen plasma method

2-5

92-105

[14]

Nano-sized MgO

Sol-gel

2

75

[15]

Nano-sized α-Fe2O3

Electrochemical method

2

59

[16]

Nanometer CoFe2O4

Polyol-medium solvothermal

2

112.8

[17]

Nano-MnFe2O4

Co-precipitation phase inversion

3

77.3

[18]

Nano-MnFe2O4

Low-temperature combustion

3

84.9

[18]

Sphere-like α-Fe2O3

NH3·H2O and NaOH solution to adjust the pH value

81

[19]

pod-like α-Fe2O3

NH3·H2O and NaOH solution to adjust the pH value

72

[19]

Nanometer CoC2O4

Co-precipitation

2

104

[20]

Nano-sized CuO

Sol-gel

90.47

[21]

Nano-sized Co3O4

Sol-gel

92.07

[21]

Nano-sized CuCo2O4

Sol-gel

102.78

[21]

CuO nanocrystals

Simple chemical deposition

2

85

[22]

Nanometer CuFe2O4

Auto-combustion method

2

105

[23]

Co nanoparticles

Hydrogen plasma

2

145.01

[24]

Cu-Co nanocrystal

Hydrazine reduction in ethylene glycol

1

96

[25]

Cu-Fe

1

89

Cu-Zn

1

114

Table 2. Chemical composition of nano-TiO2

Element

Mg

Nb

Al

S

Si

Ca

Amount (ppm)

<=67

<=82

<=19

<=128

<=116

<=75

Table 3. Physical properties of nano-TiO2

Bulk density (g/cm3)

Actual density (g/cm3)

Average particle size (nm)

Specific surface area (m2/g)

Color

0.24

3.90

10 to 25

200 to 240

white

1

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