Microwave-Assisted Synthesis of the Flexible Iron-based MIL-88B Metal–Organic Framework for Advanced Energetic Systems

The 3D metal–organic framework (MOF), MIL-88B, built from the trivalent metal ions and the ditopic 1,4-Benzene dicarboxylic acid linker (H₂BDC), distinguishes itself from the other MOFs for its flexibility and high thermal stability. MIL-88B was synthesized by a rapid microwave-assisted solvothermal method at high power (850 W). The iron-based MIL-88B [Fe₃.O.Cl.(O₂C–C₆H₄–CO₂)₃] exposed oxygen and iron content of 29% and 24%, respectively, which offers unique properties as an oxygen-rich catalyst for energetic systems. Upon dispersion in an organic solvent and integration into ammonium perchlorate (AP) (the universal oxidizer for energetic systems), the dispersion of the MOF particles into the AP energetic matrix was uniform (investigated via elemental mapping using an EDX detector). Therefore, MIL-88B(Fe) could probe AP decomposition with the exclusive formation of mono-dispersed Fe₂O₃ nanocatalyst during the AP decomposition. The evolved nanocatalyst can offer superior combustion characteristics. XRD pattern for the MIL-88B(Fe) framework TGA residuals confirmed the formation of α-Fe₂O₃ nanocatalyst as a final product. The catalytic efficiency of MIL-88B(Fe) on AP thermal behavior was assessed via DSC and TGA. AP solely demonstrated a decomposition enthalpy of 733 J g^?1, while AP/MIL-88B(Fe) showed a 66% higher decomposition enthalpy of 1218 J g^?1; the main exothermic decomposition temperature was decreased by 71 °C. Besides, MIL-88B(Fe) resulted in a decrease in AP decomposition activation energy by 23% and 25% using Kissinger and Kissinger–Akahira–Sunose (KAS) models, respectively.

     

Effect of Nano‐Copper Oxide and Copper Chromite on the Thermal Decomposition of Ammonium Perchlorate

The catalytic effect on the thermal decomposition behavior of ammonium perchlorate (AP) of p‐type nano‐CuO and CuCr₂O₄ synthesized by an electrochemical method has been investigated using differential scanning calorimetry as a function of catalyst concentration. The nano‐copper chromite (CuCr₂O₄) showed best catalytic effects as compared to nano‐cupric oxide (CuO) in lowering the high temperature decomposition by 118 °C at 2 wt.‐%. High heat releases of 5.430 and 3.921 kJ g⁻¹ were observed in the presence of nano‐CuO and CuCr₂O₄, respectively. The kinetic parameters were evaluated using the Kissinger method. The decrease in the activation energy and the increase in the rate constant for both the oxides confirmed the enhancement in catalytic activity of AP. A mechanism based on an electron transfer process has also been proposed for AP in the presence of nano‐metal oxides.     

Effect of copper chromite and copper chromitecopper oxide mixture catalysts on the thermal decomposition of ammonium perchlorate and composite solid propellant

Thermal decomposition of powdered ammonium perchlorate (AP), polystyrene (PS) and $\text{AP}\text{PS}$ propellant, catalysed by freshly-prepared CuCr₂O₄ and mixtures of CuCr₂O₄ and CuO, has been studied with a low concentration (1% by mass) of the catalysts. It appears that decomposition is increased due to heterogeneous catalysis. The kinetics of thermal decomposition of AP in the presence of CuCr₂O₄ in the orthorhombic region of AP have also been studied.     

Preparation and Characterization of Fe2O3/Ammonium Perchlorate (AP) Nanocomposites through Ceramic Membrane Anti‐Solvent Crystallization

A novel ceramic membrane anti‐solvent crystallization (CMASC) method was proposed to prepare Fe₂O₃/AP nanocomposites with core‐shell structure. For the preparation of Fe₂O₃/AP nanocomposites, several key advantages of the CMASC method are as follows. Firstly, both well‐dispersed Fe₂O₃ nanoparticles and the superfine AP preparation can be achieved at one step. Secondly, no non‐component of solid propellant was involved in this composite process. Thirdly, the size and morphology of Fe₂O₃/AP nanocomposites can be effectively controlled by using the ceramic membrane with regular pore structure as feeding template. The morphology and structure of Fe₂O₃/AP nanocomposites were characterized by inductively coupled plasma spectrophotometry (ICP), IR spectroscopy, SEM, and HRTEM. The results verified that the size and morphology of Fe₂O₃/AP nanocomposites are controllable, and the dispersion of Fe₂O₃ nanoparticles is greatly improved in Fe₂O₃/AP nanocomposites. Moreover, the thermal decomposition of the as‐prepared Fe₂O₃/AP nanocomposites was measured with TG‐DSC. The results showed that the Fe₂O₃ nanoparticles in Fe₂O₃/AP nanocomposites exhibit better catalytic activity on the thermal decomposition of AP. In addition, the mechanism was also discussed.     

Differential Scanning Calorimetric Study of HTPB based Composite Propellants in Presence of Nano Ferric Oxide

A comparative study of the thermal decomposition of ammonium perchlorate (AP)/hydroxy terminated polybutadiene (HTPB) based composite propellants has been carried out in presence and absence of nano iron oxide at different heating rates in a dynamic nitrogen atmosphere using differential scanning calorimetry. The pronounced effect was a lowering of the high temperature decomposition by 49 °C. A higher heat release up to 40% was observed in presence of nano ferric oxide (3.5 nm). The kinetic parameters were evaluated using the Kissinger method. The increase of the rate constant in the catalyzed propellant confirmed the enhancement of the catalytic activity of ammonium perchlorate. The scanning electron micrographs of nano Fe₂O₃ incorporated in HTPB revealed a well‐separated characteristic necklace‐like structure of α‐Fe₂O₃ particles at high magnification.     

Burning Characteristics and Thermochemical Behavior of AP/HTPB Composite Propellant Using Coarse and Fine AP Particles

The burning rate of AP/HTPB composite propellant increases with increasing AP content and with decreasing AP size. In addition, the burning rate can be enhanced with the addition of Fe₂O₃. The burning characteristics and thermal decomposition behavior of AP/HTPB composite propellant using coarse and fine AP particles with and without Fe₂O₃ at various AP contents were investigated to obtain an exhaustive set of data. As the AP content decreased, the burning rate decreased and the propellants containing less than a certain AP content self‐quenched or did not ignite. The self‐quenched combustion began at both lower and higher pressures. The lower limit of AP content to burn the propellant with coarse AP was lower than that with fine AP. The lower limit of AP content to burn was decreased by the addition of Fe₂O₃. The thermal decomposition behavior of propellants prepared with 20–80 % AP was investigated. The decrease in the peak temperature of the exothermic decomposition suggested an increased burning rate. However, a quantitative relationship between the thermochemical behavior and the burning characteristics, such as the burning rate and the lower limit of AP content to burn, could not be determined.     

Nanocobaltite: Preparation,Characterization, and their Catalytic Activity

Mixed transition metal oxides (MTMO) nanoparticles of 3rd‐series (NiCo₂O₄, CuCo₂O₄, and ZnCo₂O₄) were prepared by a co‐precipitation method. These were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The particle size was found to be in the order of 53.0, 43.4, and 21.2 nm, respectively. The thermolysis of ammonium perchlorate (AP), AP‐HTPB (hydroxyterminated polybutadiene) composite solid propellants (CSPs), and HTPB was found to be catalyzed with MTMOs and the burning rate of CSPs was also enhanced. TG and ignition delay study demonstrated that the higher temperature decomposition (HTD) of AP is catalyzed enormously by these catalysts and CuCo₂O₄ is the best candidate.     

Thermal Decomposition of AMMO/AP Composite Propellants

Thermal decomposition of AMMO/AP composite propellants was studied by DTA, TGA and DSC in helium atmosphere. The effects of accelerated aging at 347 K for 370 days on decomposition kinetics were also measured. AMMO/AP propellant showed two different decomposition steps, which were mainly the AMMO binder decomposed region and the reaction of AP dominated region. These regions were separated at around 20 % weight loss point at the condition used in this study. AMMO binder decomposition and AP decomposition were strongly related each other. The heat generated by the AMMO binder decomposition initiated and accelerated the thermal decomposition of AP. Although both Fe₂O₃ and CFe activated the thermal decomposition of AMMO/AP propellants, CFe mainly accelerated the decomposition of AMMO binder and Fe₂O₃ catalyzed the AP reactions which consisted of the AP decomposition and the reaction between decomposed AP and decomposed AMMO binder. AMMO/AP composite propellants were thermally stable even after aging at 347 K for 370 days.     

Effect of Fe2O3 in Fe2O3/AP Composite Particles on Thermal Decomposition of AP and on Burning Rate of the Composite Propellant

A technique of composite processing of Fe₂O₃ and ammonium perchlorate (AP) was employed in making the propellant. The effects of composite processing of Fe₂O₃ on catalytic activity, on the thermal decomposition of AP, and on the burning rate of the composite propellant were investigated in this paper. Fe₂O₃/AP composite particles were prepared by a novel solvent‐nonsolvent method. The results show that AP is successfully coated on the surface of Fe₂O₃. Composite processing of Fe₂O₃ and AP can improve the catalytic activity of Fe₂O₃. Fe₂O₃ exhibits better catalytic effect with increasing Fe₂O₃ content. The larger interface between Fe₂O₃ and AP and lower density of composite propellant (with the added Fe₂O₃/AP composite particles) are responsible for the enhancement of the catalytic activity of Fe₂O₃.     

Design of three dimensional flower-like MXene/manganese-cobalt spinel nanocomposites for efficient catalytic thermal decomposition of ammonium perchlorate

A series of MXene/MnCo₂O_4.5 nanocomposites was successfully prepared by hydrothermal, ice crystal template and physical blend methods, respectively. Various characterizations indicated that hydrothermal method could successfully loaded MnCo₂O_4.5 nanoparticles on the surface of MXene nanosheets to obtain MMC-W nanocomposites with 3D flower-like structure, which could give MMC-W large specific surface area. The HTD temperature and decomposition heat of AP with adding 2.0 wt% MMC-W could significantly decrease to 304.7 °C and increase to 1310.9 J g^-1, respectively. The lowest decomposition temperature (286.1 °C) and the highest heat release (1427.6 J g^-1) of AP could be obtained by adding 8.0 wt% and 4.0 wt% of MMC-W, respectively. Moreover, MMC-W (2.0 wt%) could also significantly reduce the E_a of pure AP by 118.3 kJ mol^-1 and increase the k value for AP by 11.2 times. The excellent catalytic performance of MMC-W was owing to the synergistic effect of nano-sized MnCo₂O_4.5 and MXene nanosheets. Owing to its high catalytic activity, MMC-W would be used as an excellent catalyst for ameliorating AP decomposition and supply an idea for the preparation of novel metal oxide nanoparticles.     

Preparation of Magnesium‐based Hydrogen Storage Materials and Their Effect on the Thermal Decomposition of Ammonium Perchlorate

Magnesium‐based hydrogen storage materials (MgH₂, Mg₂NiH₄, and Mg₂Cu‐H) were prepared and their structures were determined by XRD and ICP investigations. Mg₂NiH₄ has a monoclinic crystal structure and Mg₂Cu‐H is a mixture of MgCu₂ and MgH₂. The effects of magnesium‐based hydrogen storage materials on the thermal decomposition of ammonium perchlorate (AP) were studied by thermal analysis (DSC). It was found that magnesium‐based hydrogen storage materials show obvious boosting effects on the thermal decomposition of AP. The thermal decomposition peak temperature of AP was decreased, while the heat release of the decomposition of AP was increased. It was revealed that the effects of magnesium‐based hydrogen storage materials on the decomposition of AP become stronger with increasing content. The influence mechanism on the thermal decomposition of AP is suggested as follows: hydrogen released from magnesium‐based hydrogen storage materials and Mg, Ni, or Cu react with the decomposed products of AP.     

Well-dispersed ultrafine Mn3O4 nanoparticles on graphene as a promising catalyst for the thermal decomposition of ammonium perchlorate

Mn₃O₄–graphene (Mn₃O₄–GR) hybrids were synthesized using a one-step strategy under solvothermal conditions. During this process graphene oxide (GO) was reduced to GR and at the same time ultrafine Mn₃O₄ nanoparticles (NPs) with a size of ∼10 nm were uniformly anchored on the GR sheets. The Mn₃O₄–GR hybrids showed promising catalytic effects for the thermal decomposition of ammonium perchlorate (AP). The decomposition temperature was decreased by 141.9 °C and only one decomposing step was observed instead of common two in reported literature. This improved performance in the catalytic reaction is closely related to the synergistic effect of Mn₃O₄ and GR.     

Chemical and Textural Characterization of Iron Oxide Nanoparticles and Their Effect on the Thermal Decomposition of Ammonium Perchlorate

Metal oxide nanoparticles have been used as burning rate catalysts for ammonium perchlorate (AP) decomposition in composite solid propellants. Though most papers point to the efficiency of different sizes, shapes and compositions, the texture of the agglomerated particles plays an important role in the catalytic efficiency, but this aspect is not always discussed. In this paper, iron oxide and composite iron oxide/silica powders were synthesized in microemulsion systems and their effect on the decomposition of AP was investigated. X‐ray diffraction (XRD) analysis and Fourier transformed infrared spectroscopy (FT‐IR) showed that the synthesized powders have an amorphous to nanocrystalline pattern, with Fe₂O₃ composition. The use of different FT‐IR spectroscopic techniques – transmission, diffuse reflectance (DRIFT) and universal attenuated total reflectance (UATR) – allied to electron microscopy analysis allowed the characterization of the samples’ surface, indicating that silicon oxide forms a thick matrix that covers the iron oxide nanoparticles. Adsorption of N₂, light scattering and electron microscopy pointed that all samples are formed by mesoporous agglomerated nanoparticles containing micropores indicating that silicon oxide forms a thick matrix that covers the iron oxide nanoparticles. Adsorption of N₂, pointed that all samples show different microstructures and light scattering indicated results refer to agglomerated particles. Finally, the catalytic effect of the samples on the decomposition of AP was evaluated by thermogravimetric analysis coupled to differential thermal analysis (TG/DTA), showing that only the high temperature decomposition step of AP was affected by the catalyst, shifting to lower temperatures the higher the surface area of the synthesized iron oxide sample, regardless of the presence of the silica matrix.     

Synthesis and catalytic behaviors of cobalt nanocrystals with special morphologies

Cobalt nanocrystals with highly ordered snowflake-like, cauliflower-like, ball-like morphologies, and some less ordered shapes were prepared through the reduction of Co(NO₃)₂ by hydrazine hydrate in the solution of methanol, ethanol, ethylene glycol, and 1,2-propanediol. Based on the characterization results of X-ray powder diffraction and scanning electron microscope, crystal and morphologic structures of cobalt particles were correlated with the reaction conditions of temperature, Co(NO₃)₂ concentration, and the alcohols used. By changing temperature and/or Co(NO₃)₂ concentration, pure hexagonal close-packed (hcp) cobalt or a mixture of hcp and face-centered cubic (fcc) cobalt was obtained. The catalytic performance of as-prepared cobalt nanocrystals for the thermal decomposition of ammonium perchlorate (AP) was evaluated by differential scanning calorimetry. The decomposition temperature of AP was significantly decreased, and the apparent decomposition heat was over doubled when 2 wt.% cobalt was added into AP. Among the samples tested, snowflake-like cobalt showed the best performance in the aspect of decreasing the decomposition temperature of AP while the ball-like cobalt exhibited the highest apparent decomposition heat.     

Nanostructure composite ZnFe2O4–FeFe2O4–ZnO immobilized on glass: Photocatalytic activity for degradation of an azo textile dye F3B

An efficient and scalable one-pot synthetic method to prepare nanostructure composite of ZnFe₂O₄–FeFe₂O₄–ZnO (ZFZ) has been investigated. This method is based on thermal decomposition of iron(III) acetate and zinc acetate in monoethanolamine (MEA) as a capping agent. Moreover, thermogravimetric analysis (TG-DTG) was performed to determine the temperature at which the decomposition and oxidation of the chelating agents took place. ZFZ was immobilized on glass using doctor blade method and calcinated at different temperatures. The properties of the ZFZ nanocomposite have been examined by different techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance (DRS). FESEM shows that nanocomposite is monocrystallines and a narrow dispersion in size of 48 nm. XRD confirms that the prepared nanocomposite is composed of franklinite, ZnFe₂O₄ (54%), magnetite, FeFe₂O₄ (8%) and wurtzite, ZnO (48%). Photocatalytic activity of ZFZ immobilized on glass was carried out by choosing an azo textile dye, Reactive Red 195 (F3B) as a model pollutant under UV irradiation with homemade photocatalytic apparatus and the results indicated that ZFZ exhibited good photocatalytic activity.     

Synthesis of various CuO nanostructures via a Na3PO4–assisted hydrothermal route in a CuSO4–NaOH aqueous system and their catalytic performances

Various CuO nanostructures, including spherical, flower-like, cross-like, leaf-like, and elliptical structures, were obtained via a sodium phosphate (Na₃PO₄)–assisted hydrothermal route with CuSO₄ and NaOH as the copper and alkali sources, respectively. The presence of Na₃PO₄ is vital for the formation of various CuO nanostructures. The morphology of the CuO nanostructures is significantly influenced by the feeding concentration of the NaOH solution. The catalytic activity of the CuO products on the thermal decomposition of ammonium perchlorate (AP) was characterized by differential scanning calorimetry (DSC). Results showed that the addition of CuO nanostructures could dramatically decrease the high decomposition temperature of AP, thereby demonstrating their excellent catalytic activity for the thermal decomposition of AP.     

Facile Preparation of AP/Cu(OH)2 Core‐Shell Nanocomposites and Its Thermal Decomposition Behavior

Ammonium perchlorate (AP)/Cu(OH)₂ core‐shell nanocomposites were successfully synthesized using a facile ultrasonic assisted‐coprecipitation synthesis route. The obtained AP/Cu(OH)₂ nanocomposites were characterized by means of powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Its thermal decomposition was studied under the non‐isothermal conditions with thermogravimetric analysis and differential scanning calorimeter (TG‐DSC) techniques. In this procedure, SEM and TEM observations revealed that Cu(OH)₂ nanoparticles with an average size of 10–15 nm were uniformly deposited on the surface of AP particles. Detailed characterization results indicated that the existence of evidence of Cu(OH)₂. As expected, it was found that the AP/Cu(OH)₂ nanocomposites with mass fraction of 2 wt % Cu(OH)₂ remarkably decreased the peak temperature of high temperature decomposition of AP by 80.2 °C from approximately 441.3 °C to 361.1 °C. As compared with pure AP, the AP/Cu(OH)₂ nanocomposites show lower impact and friction sensitivity. These results may lead to potential applications of the AP/Cu(OH)₂ nanocomposites in the composite solid propellants for accelerating the thermal decomposition of AP.     

Synthesis of high purity 110 K phase in the Bi(Pb)-Sr-Ca-Cu-O superconductor by the sol-gel method

(BiPb)₂Sr₂Ca₂Cu₃O_x superconductor powders were synthesized by the sol-gel method using an aqueous solution of metal nitrates containing polyacrylic acid and tartaric acid as chelating agents. The conditions of the sol formation were determined and the thermal decomposition process of the gel precursor was examined. The effect of sintering temperature on the particle morphology was also investigated. High purity Bi(Pb)-Sr-Ca-Cu-O superconducting oxide powders with high-T_c phase could be obtained and they exhibited sharp superconducting transition with zero temperature of 105 K.     

Iron Nanoparticle Additives as Burning Rate Enhancers in AP/HTPB Composite Propellants

Burning rate measurements were carried out for ammonium perchlorate/hydroxyl‐terminated polybutadiene (AP/HTPB) composite propellants with iron (Fe) nanoparticles as additives. Experiments were performed in a strand burner at pressures from 0.2 to 10 MPa for propellants containing approximately 80 % AP and Fe nanoparticles (60–80 nm) at concentration from 0 to 3 % by weight. It was found that the addition of 1 % Fe nanoparticles increased burning rate by factors of 1.2–1.6. Because Fe nanoparticles are oxidized on the surface and have high surface‐to‐volume ratio, they provide a large surface area of Fe₂O₃ for AP thermal decomposition catalysis at the burning propellant surface, while also providing added energy release due to the oxidation of nanoparticle sub‐shell Fe. The increase in burning rate due to Fe nanoparticle content is similar to the increase in burning rate caused by the addition of iron oxide (Fe₂O₃) particles observed in prior literature.     

Preparation of spinel ferrites from citrate precursor route—A comparative study

Spinel ferrites MFe₂O₄ (M = Mn, Co, Ni, Cu) have been prepared from the thermolysis of transition metal bis(citrato)ferrates(III), M₃[Fe(C₆H₅O₇)₂]₂·xH₂O. Various physico-chemical studies, i.e. TG–DTG–DSC, XRD and Mössbauer spectroscopy have been employed for the investigation of the mode of decomposition and characterization of intermediates/products formed. After dehydration the anhydrous precursor undergoes an oxidative decomposition to yield α-Fe₂O₃ and respective metal oxide. Finally spinel ferrites, MFe₂O₄, are formed as a result of a solid-state reaction between the oxides at a much lower temperature (310–440 °C) and in less time as compared to that of the conventional ceramic method. SEM studies show these ferrites to be of nanosized. Ferrites obtained from the thermolysis of transition metal ferricitrate precursors show higher values of saturation magnetization than those got from respective ferrimalonate precursors, thus designating the former as novel materials to operate at high frequencies.