Indium-doped induced aluminum thermal oxidizer and method of making

Abstract

The application provides a preparation method of an indium-doped induced aluminum thermal oxidant, which is used for synthesizing an indium-doped iron oxide rich in oxygen vacancies and high-valence iron species, the oxidant is an indium-doped induced high-valence iron oxide, and the doping molar percentage of indium in the indium-doped iron oxide is 0.5%-10%. The preparation method comprises the following steps: (1) preparation of an indium-doped iron oxide precursor: dissolving an iron source and an indium source in deionized water according to the above molar ratio, adding a mineralizer and a precipitator, stirring at 200-800 rpm for 0.5-1 h to form a mixed uniform solution; after the mixed uniform solution is subjected to a hydrothermal reaction, the solution is sequentially subjected to cooling, filtration, washing with deionized water and ethanol, and drying at 40-80 DEG C for 6-24 h to prepare the precursor; and (2) high-temperature calcination of the precursor, and then grinding to 100 mesh to obtain an indium-doped iron oxide powder.

Description

Technical Field

[0001] This invention relates to a method for preparing metal oxides, and more particularly to an indium-doped aluminothermic oxidant and its preparation method. Background Technology

[0002] Thermite is a mixture of metal reducing agents and metal oxide oxidizing agents. After ignition, it undergoes a violent redox reaction, releasing a large amount of heat and producing high-temperature molten metal. Traditional thermite commonly uses iron oxide as an oxidizing agent. This system has readily available raw materials and a large heat release, but it also has some inherent defects: First, its reaction requires a high ignition temperature to start, which requires high ignition energy; second, the reaction propagation rate is relatively slow, and incomplete combustion often occurs, resulting in reduced energy release efficiency; in addition, due to the dense oxide layer on the surface of aluminum powder, the reaction in the micron-sized thermite system is divided into solid-solid reaction stage and solid-liquid reaction stage, resulting in the ignition energy of the thermite being not concentrated.

[0003] Studies have shown that cation doping of iron oxide can effectively regulate its crystal structure, oxygen vacancy concentration, and electronic properties. Indium (In) doping can not only reduce the band gap of iron oxide and enhance its redox activity, but also introduce more defects in the crystal lattice as reactive sites. These properties are expected to fundamentally improve the thermodynamic and kinetic processes of the aluminothermic reaction. Summary of the Invention

[0004] The present invention aims to provide a method for preparing an indium-doped aluminothermic oxidant. This method is used to synthesize indium-doped iron oxides rich in oxygen vacancies and high-valence iron species. The oxidant is an indium-doped high-valence iron oxide, and the molar percentage of indium in the indium-doped iron oxide is 0.5% to 10%. The preparation method includes the following steps: (1) Preparation of indium-doped iron oxide precursor: Iron source and indium source are dissolved in deionized water according to the above molar ratio, mineralizing agent and precipitant are added, and the mixture is stirred at 200~800 rpm for 0.5~1h to form a homogeneous solution; the homogeneous solution is subjected to hydrothermal reaction, and then cooled, filtered, washed with deionized water and ethanol in sequence, and dried at 40~80℃ for 6~24h to obtain the precursor; (2) The precursor was calcined at high temperature and then ground to 100 mesh to obtain indium-doped iron oxide powder.

[0005] Furthermore, the molar percentage of indium in the indium-doped iron oxide is preferably 4% to 8%.

[0006] Further, the iron source mentioned in step (1) is one or more of ferric chloride hexahydrate, ferric nitrate nonahydrate, or ferric sulfate.

[0007] Further, the indium source mentioned in step (1) is one or more of indium nitrate, indium chloride, or indium sulfate.

[0008] Furthermore, the mineralizing agent mentioned in step (1) is ammonium fluoride, and the amount used is 1 to 2 times the total number of moles of metal ions.

[0009] Further, the precipitant in step (1) is urea, and the concentration of urea in the mixed solution is 0.1~0.2 mol / L.

[0010] Furthermore, the temperature of the hydrothermal reaction in step (1) is 120~180℃, and the reaction time is 4~12h.

[0011] Furthermore, the high-temperature calcination temperature in step (2) is 400~600℃, the heating rate is 2~10K / min, and the holding time is 1~4h.

[0012] The present invention also provides an indium-doped aluminothermic oxidant, characterized in that the oxidant lattice has oxygen vacancies generated by the synergistic induction of indium doping and fluorine ions, and high-valence iron species generated by local charge compensation.

[0013] Furthermore, when the oxidant is mixed with aluminum powder to undergo an aluminothermic reaction, the abundant oxygen vacancies can lower the migration barrier of lattice oxygen, allowing the solid-solid reaction and solid-liquid reaction of the aluminothermic agent to occur simultaneously.

[0014] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention induces the formation of high-valence iron species and abundant oxygen vacancies in the iron oxide lattice through indium doping. High-valence iron has a higher oxidation potential and can provide stronger oxidation ability as an oxidant; oxygen vacancies significantly reduce the migration barrier of lattice oxygen and enhance the intrinsic reactivity of the material; the two work synergistically to fundamentally reduce the activation energy of the aluminothermic reaction. (2) The aluminothermic oxidant of the present invention can carry out solid-solid reaction and solid-liquid reaction simultaneously, thereby improving the energy release efficiency of the aluminothermic reaction. Attached Figure Description

[0015] Figure 1 The image shows the XRD pattern of the product from Comparative Example 1.

[0016] Figure 2 The image shows the DSC curve of the product from Comparative Example 1.

[0017] Figure 3 The image shows the XRD pattern of the product from Example 1.

[0018] Figure 4 This is the DSC curve of the product of Example 1.

[0019] Figure 5 The image shows the XRD pattern of the product from Example 2.

[0020] Figure 6 This is the DSC curve of the product of Example 2.

[0021] Figure 7 The image shows the XRD pattern of the product from Example 3.

[0022] Figure 8 This is the DSC curve of the product of Example 3.

[0023] Figure 9 The image shows the XRD pattern of the product from Example 4.

[0024] Figure 10 This is the DSC curve of the product of Example 4.

[0025] Figure 11 The image shows the XRD pattern of the product from Example 5.

[0026] Figure 12 This is the DSC curve of the product from Example 5.

[0027] Figure 13 The image shows the XRD pattern of the product from Example 6.

[0028] Figure 14 The image shows the DSC curve of the product from Example 6. Detailed Implementation

[0029] Example 1: An aluminothermic oxidant based on indium doping-induced high-valence iron oxide mainly includes the following steps: (1) Weigh 2.70g FeCl3·6H2O (iron source) and 0.06g In(NO3)3 (indium source), dissolve in 350mL deionized water, at which time the molar ratio of In:Fe is about 1:100, that is, the molar percentage of indium doping is 1.0%; add 1.1g NH4F and 3g urea to the solution; NH4F is a mineralizing agent, the amount of which is about 1.5 times the total number of metal ions; urea is a precipitant, the concentration of which in the mixed solution is about 0.14mol / L; stir at 500rpm for 30min to form a homogeneous solution, transfer the solution to a 50mL polytetrafluoroethylene-lined reactor, and hydrothermally react in an oven at 160℃ for 5h. After the reaction is completed, cool naturally to room temperature, vacuum filter, wash 3 times each with deionized water and ethanol, place the obtained filter cake in an oven at 50℃ and dry for 12h to obtain precursor powder; (2) The precursor powder was placed in a muffle furnace and heated to 500°C at a heating rate of 5K / min. The temperature was maintained at this temperature for 2 hours and then naturally cooled to room temperature. The calcined product was then ground to 100 mesh to obtain reddish-brown indium-doped iron oxide powder.

[0030] Example 2 differs from Example 1 only in step (1). The amount of In(NO3)3 added in step (1) is adjusted to 0.12 g, so that the In:Fe molar ratio is 1:25, that is, the molar percentage of indium doping is 4.0%. The remaining process steps, parameters and reagents are exactly the same as in Example 1.

[0031] Example 3 differs from Example 1 only in step (1). The amount of In(NO3)3 added in step (1) is adjusted to 0.18g, so that the In:Fe molar ratio is 1.5:25, that is, the molar percentage of indium doping is 6.0%. The remaining process steps, parameters and reagents are exactly the same as those in Example 1.

[0032] Example 4 differs from Example 1 only in step (1). The amount of In(NO3)3 added in step (1) is adjusted to 0.24g, so that the In:Fe molar ratio is 2:25, that is, the molar percentage of indium doping is 8.0%. The remaining process steps, parameters and reagents are exactly the same as those in Example 1.

[0033] Example 5 differs from Example 1 only in step (1), where the iron source in step (1) is replaced with Fe(NO)3·9H2O of equal molar iron content. All other process steps, parameters, and reagents used are identical to those in Example 1.

[0034] Example 6 differs from Example 1 only in step (2). The calcination temperature in step (2) is adjusted to 600℃ and the holding time is 2h. All other process steps, parameters, and reagents used are exactly the same as in Example 1.

[0035] Comparative Example 1 differs from Example 1 only in that In(NO3)3 is not added in step (1). The remaining process steps, parameters, and reagents are exactly the same as in Example 1.

[0036] The oxidant powders prepared in each example and comparative example were simply physically mixed with spherical aluminum powder with a particle size of 1-3 μm at a stoichiometric ratio of Fe2O3:Al = 1:1 to prepare a series of thermite samples. XRD and DSC curves were obtained for each sample. Figures 1 to 14 As shown.

[0037] like Figure 1 , 3As shown in Figures 5, 7, and 9, the XRD patterns of Comparative Example 1 and Examples 1-4 all conform to the main phase characteristics of iron oxide, and no impurity phase diffraction peaks of elemental indium or indium oxide were detected, confirming that indium has been completely dissolved into the iron oxide lattice. It is noteworthy that as the molar percentage of indium doping increased from 1.0% (Example 1) to 8.0% (Example 4), the diffraction peak intensity of the product progressively decreased, and at 2... θ The amorphous diffuse scattering background (broad peak) gradually increases in the 15°~30° region. Figure 9 This phenomenon is most pronounced in (Example 4). This is attributed to In 3+ with Fe 3+ The ionic radius mismatch triggers severe lattice distortion, disrupting local long-range crystalline order. This low crystallinity and microscopic disorder induced by indium doping depth theoretically spontaneously accompany the generation of high-density oxygen vacancy defects and unevenly distributed charge species, thus providing numerous kinetic active sites for the macroscopic aluminothermic reaction. (Comparison) Figure 3 and Figure 13 It can be seen that when the calcination temperature is increased from 500℃ to 600℃, the diffraction peaks of the product become sharp again, and the crystallinity is significantly improved, indicating that high-temperature heat treatment has a significant annealing repair effect on lattice defects. Therefore, controlling the calcination temperature within the range of 400~600℃ is the key process window for maintaining the high defect activity state of the oxidant. 2 θ The diffraction angle is the angle between the diffracted beam (scattered light) and the original straight-line direction of the incident beam.

[0038] The DSC thermal analysis curve of the composite aluminothermic agent is as follows: Figure 2 , 4 As shown in 6, 8, 10, 12, and 14. From Figure 2 It can be seen that the undoped Comparative Example 1 exhibits only a weak solid-solid reaction exothermic response near 620°C, accompanied by a severe endothermic valley of metallic Al melting at 660°C. Its main exothermic peak lags behind 900°C and has a broad peak shape, indicating that the traditional system suffers from high ignition energy barriers and slow exothermic kinetics. After introducing indium doping, the reaction kinetics of the system are significantly reconstructed. For example... Figure 4 As shown in Example 1, a highly explosive and sharp solid-solid exothermic peak erupts at a low temperature of 610°C, indicating that lattice defects significantly reduce the reaction initiation energy barrier, achieving a concentrated and advanced release of energy. With the indium doping content controlled at 4.0%~8.0% (Examples 2~4), Figure 6 , 8(10) The exothermic peak of the solid-liquid reaction near 900°C shows a significant progressive narrowing and intensity jump, with a substantial shortening of the half-width at half-maximum (HWHM). This directly confirms the synergistic effect of the high oxidation potential of high-valence iron species and the reduction of the lattice oxygen migration barrier by oxygen vacancies, resulting in a qualitative improvement in the aluminothermic reaction rate and energy release efficiency. Furthermore, compared to... Figure 6 and Figure 14 It can be seen that after increasing the calcination temperature to 600°C (Example 6), the main exothermic peak shows a significant trend of crystallization and passivation, with a decrease in peak height and a widening of the crystallization reaction range. This is completely consistent with the trend observed in XRD of high-temperature thermal repair of lattice defects and reduction of active site density. The above thermal analysis results scientifically confirm that the indium-doped defect-state iron oxide constructed by the method of the present invention at 400~600°C (preferably 500°C) can fundamentally improve the combustion and explosion kinetics of thermite.

Claims

1. A method for preparing an indium-doped induced aluminothermic oxidant, characterized in that, The preparation method is used to synthesize indium-doped iron oxides rich in oxygen vacancies and high-valence iron species. The oxidant is an indium-doped high-valence iron oxide, and the molar percentage of indium in the indium-doped iron oxide is 0.5%~10%. The preparation method includes the following steps: (1) Preparation of indium-doped iron oxide precursor: Iron source and indium source are dissolved in deionized water according to the above molar ratio, mineralizing agent and precipitant are added, and the mixture is stirred at 200~800 rpm for 0.5~1h to form a homogeneous solution; the homogeneous solution is subjected to hydrothermal reaction, and then cooled, filtered, washed with deionized water and ethanol in sequence, and dried at 40~80℃ for 6~24h to obtain the precursor; (2) The precursor was calcined at high temperature and then ground to 100 mesh to obtain indium-doped iron oxide powder.

2. The preparation method according to claim 1, characterized in that, The preferred molar percentage of indium in the indium-doped iron oxide is 4% to 8%.

3. The preparation method according to claim 1, characterized in that, The iron source mentioned in step (1) is one or more of ferric chloride hexahydrate, ferric nitrate nonahydrate, or ferric sulfate.

4. The preparation method according to claim 1, characterized in that, The indium source mentioned in step (1) is one or more of indium nitrate, indium chloride, or indium sulfate.

5. The preparation method according to claim 1, characterized in that, The mineralizing agent mentioned in step (1) is ammonium fluoride, and the amount used is 1 to 2 times the total number of moles of metal ions.

6. The preparation method according to claim 1, characterized in that, The precipitant in step (1) is urea, and the concentration of urea in the mixed solution is 0.1~0.2 mol / L.

7. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction in step (1) is 120~180℃ and the reaction time is 4~12h.

8. The preparation method according to claim 1, characterized in that, The high-temperature calcination in step (2) is carried out at a temperature of 400~600℃, a heating rate of 2~10K / min, and a holding time of 1~4h.

9. An indium-doped induced aluminothermic oxidant prepared by the preparation method according to any one of claims 1-6, characterized in that, The oxidant has oxygen vacancies induced by the synergistic effect of indium doping and fluorine ions in its crystal lattice, as well as high-valence iron species generated by local charge compensation.

10. The indium-doped induced aluminothermic oxidant according to claim 9, characterized in that, When the oxidant is mixed with aluminum powder to undergo an aluminothermic reaction, the abundant oxygen vacancies can lower the migration barrier of lattice oxygen, allowing the solid-solid reaction and solid-liquid reaction of the aluminothermic agent to occur simultaneously.

Images