Improvement of thermal decomposition properties of ammonium perchlorate particles using some polymer coating agents

This research aimed to investigate the optimum conditions for modification of thermal decomposition properties of ammonium perchlorate (AP) particles through microencapsulation techniques. A solvent/non-solvent method has been used to perform microencapsulation of AP particles with some polymer-coating agents such as viton A and nitrocellulose (NC). Differential scanning calorimetry, thermogravimetry, and scanning electron microscopy have been exploited to investigate the thermal properties, heat of decomposition, and coating morphology of pure and coated samples. The preliminary results revealed that AP microparticle could be effectively coated with both NC and viton, but the latter significantly and unfavorably attenuated heat of decomposition of AP so NC was chosen as an appropriate coating agent for modification of thermal properties of AP. The thermal analysis of NC-coated samples, prepared at optimized coating conditions, showed that its first stage decomposition temperature increases about 12 °C with respect to uncoated sample and reaches to 305 °C. Also, the apparent activation energy (E), ΔG ^≠, ΔH ^≠, and ΔS ^≠ of the decomposition processes of the pure and coated AP particles at the optimum conditions were obtained by non-isothermal methods that proposed by ASTM and Ozawa. Finally, the results of this investigation showed that microencapsulation of AP particles with fibrous NC enhance its heat of decomposition (~120 J g^?1) with no obvious effect on kinetic parameters and thermal decomposition temperature.     

Effect of catocene on the thermal decomposition of ammonium perchlorate and octogen

Simultaneous TG/DSC-FT-IR was employed to study the effect of catocene with a high concentration (5, 15, and 25 %) on the thermal decomposition of ammonium perchlorate (AP) and octogen (HMX) with different particle sizes. The experimental results show that catocene has effect on the thermal decomposition of AP and HMX, but the role that catocene playing changes with the concentration of catocene and the particle size of AP and HMX. High concentration of catocene (more than 15 %) benefits the decomposition of fine AP and HMX at low temperature, but has little effect on the decomposition of median and coarse AP. The thermal decomposition of HMX is affected by catocene mainly through increasing the heat release of the first decomposition step, while through both increasing the heat release and decreasing the decomposition temperature of the first decomposition step for the thermal decomposition of AP.     

Pure CuCr2O4 nanoparticles: Synthesis,characterization and their morphological and size effects on the catalytic thermal decomposition of ammonium perchlorate

In the present paper a pure phase of the copper chromite spinel nanoparticles (CuCr₂O₄ SNPs) were synthesized via the sol–gel route using citric acid as a complexing agent. Then, the CuCr₂O₄ SNPs has been characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the next step, with the addition of Cu–Cr–O nanoparticles (NPs), the effects of different parameters such as Cu–Cr–O particle size and the Cu/Cr molar ratios on the thermal behavior of Cu–Cr–O NPs + AP (ammonium perchlorate) mixtures were investigated. As such, the catalytic effect of the Cu–Cr–O NPs for thermal decomposition of AP was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA/DSC results showed that the samples with different morphologies exhibited different catalytic activity in different stages of thermal decomposition of AP. Also, in the presence of Cu–Cr–O nanocatalysts, all of the exothermic peaks of AP shifted to a lower temperature, indicating the thermal decomposition of AP was enhanced. Moreover, the heat released (ΔH) in the presence of Cu–Cr–O nanocatalysts was increased to 1490 J g⁻¹.     

Thermal decomposition of RDX/AP by TG–DSC–MS–FTIR

The method of TG–DSC–MS–FTIR simultaneous analysis has been used to study the thermal decomposition mechanism of the RDX/AP (1/2) mixture. TG–DSC showed that there were two mass loss processes for thermal decomposition of RDX/AP. The first one was mainly ascribed to the thermal decomposition of RDX. Addition of AP to RDX causes decomposition to take place abruptly, after melting, resulting in a very sharp and strong peak at lower temperature. The apparent activation energies, calculated by model-free Friedman method, of this process were negative. The second mass loss process of RDX/AP was confirmed to be the thermal decomposition of AP, catalyzed by RDX. This process can be divided into three stages, which were an nth-order autocatalytic and two one-dimensional diffusion stages, respectively. There was a competition among the formation reactions of N₂O, HNCO, and HCl for the first stage and between NO₂ and N₂O for the later two stages. The production of N₂O dominated in the second stage, while NO₂ did in the third stage.     

Thermal degradation and evolved gas analysis of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) during pyrolysis and combustion

The thermal degradation of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectroscopy (TG–FTIR–MS). Thermogravimetric analysis revealed that the thermal degradation process can be subdivided into three stages: sample drying (<200 °C), main decomposition (200–500 °C), and further cracking (>500 °C) of the polymer. The compound reached almost 800 °C during pyrolysis and combustion. The activation energy at the second step during combustion was slightly higher than that of pyrolysis emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, and hydrogen cyanide, and other gases during combustion and pyrolysis were detected by FTIR and MS spectra. It was observed that the intensities of CO₂, CO, HCN, and H₂O were very high when compared with their intensities during pyrolysis, and this was attributed to the oxidation of the decomposition product.     

A facile synthesis of boron nanostructures and investigation of their catalytic activity for thermal decomposition of ammonium perchlorate particles

In this research, ultrasound irradiation as a simple method was used to produce boron nanostructures. Reaction conditions such as boron concentration and sonication time show important roles in the size, morphology and growth process of the final products. The boron nanostructures (nanoparticles and nanorods) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, small-angle X-ray scattering and inductively coupled plasma atomic emission spectroscopy techniques. Primary evaluation of results showed that nanoparticles and nanorods of boron successfully have been prepared with 25–40 and 50–100 nm average particle size, respectively. These nanostructures (nanoparticles and nanorods) were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP) particles. Thermochemical decomposition behaviors of treated samples were characterized by thermal gravimetric analysis and differential scanning calorimetry techniques. Also, the kinetic parameters of thermal decomposition processes of pure and treated samples were obtained by nonisothermal methods proposed by Kissinger and Ozawa. However, boron nanoparticles with the smallest average particle size (25–40 nm) have the most significant catalytic effect including the decrease in decomposition temperature of AP + B nanocomposite by 100 °C, increase in the heat of decomposition from 580 to 1354 J g^?1 and decrease in activation energy from 207 to 110 kJ mol^?1.     

Thermal decomposition properties of guanidine nitrate and basic cupric nitrate

Characterized with a large gas production and low combustion temperature, the guanidine nitrate (GN) gas-generating agents are studied and applied widely. The determination factors of thermal decomposition properties of guanidine nitrate and basic cupric nitrate (GN/BCN) gas-generating agents for airbag application was investigated by the thermogravimetry–differential scanning calorimetry–mass spectrmetry–Fourier transform infrared spectroscopy (TG-DSC-MS-FTIR) and automatic calorimeter. Five different mass ratios were concerned. Our study showed that the onset reaction temperatures of GN/BCN mixtures were lower than that of individual GN and BCN. The thermal decomposition of GN/BCN mixtures could be divided into three stages, including the dissociation and escape of crystal water, solid (GN)-solid (BCN) phase reaction, and liquid (GN)-solid (BCN) phase reaction. When mass ratio of GN/BCN was 62.24/37.73, the largest value of the reaction heat was measured to 3152.7 J g^?1, with N₂ and H₂O as the major gases during thermal decomposition.     

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

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 analysis of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine

The melting temperature, melting enthalpy, and specific heat capacities (C _p) of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine (DIOIPF) were measured using DSC-60 Differential Scanning Calorimetry. The melting temperature and melting enthalpy were obtained to be 453.80 K and 33.22 J g^?1, respectively. The relationship between the specific heat capacity and temperature was obtained to be C _p/J g^?1 K^?1 = 2.0261 – 0.0096T + 2 × 10^?5 T ² at the temperature range from 320.15 to 430.15 K. The thermal decomposition process was studied by the TG–DTA analyzer. The results showed that the thermal decomposition temperature of DIOIPF was above 487.84 K, and the decomposition process can be divided into three stages: the first stage is the decomposition of impurities, the mass loss in the second stage may be the sublimation of iodine and thermal decomposition process of the side-group C₄H₂O₂N₂F, and the third stage may be the thermal decomposition process of both the groups –CH₃ and –CH₂OCH₂–. The obtained thermodynamic basic data are helpful for exploiting new synthetic method, engineering design, and commercial process of DIOIPF.     

Preparation and characterization of an active catalyst

As an active catalyst to promote thermolysis of ammonium perchlorate (AP), potassium lead hexanitrocobaltate(II) complex (K₂Pb[Co(NO₂)₆]) was synthesized by the direct deposition method and inverse microemulsion method. Its submicron, size, cube morphology, and crystal structure were investigated by SEM, TEM, and XRD analysis, respectively. Thermal decomposition of K₂Pb[Co(NO₂)₆] was studied by the TG/DSC-IR online system and XRD analysis. The catalyst was decomposed at about 300 °C; its gaseous products were NO₂, NO, and N₂O and its solid products were Pb₃O₄, Co₃O₄, PbO, CoO, and KNO₂. Because thermal decomposition of the catalyst was synchronous with low temperature decomposition of AP, thermolysis of AP was promoted remarkably. In particular, the gaseous products (NO _x ) could directly oxidize the absorbed NH₃. As a result, compared to the data of pure AP, the integral heat of AP added 3.0 wt% of the catalyst multiplied by 280 %, the maximum rate of heat release increased by 634 %. The decomposition of catalyzed AP ended at about 317 °C, at which only less than 30 % of pure AP decomposed.     

Effects of Aluminum on Thermal Decomposition of Hexogen/Ammonium Perchlorate

Thermogravimetry-differential scanning calorimetry-mass spectrometry-Fourier transform infrared spectrometry（TG-DSC-MS-FTIR） simultaneous analysis was used to study the effects of 10.7 μm and 40 nm Al on the thermal decomposition of the Hexogen/ammonium perchlorate（RDX/AP,1/2,mass ratio） mixture.TG-DSC results show that there are two mass loss processes for the thermal decomposition of RDX/AP/Al.The first one is mainly ascribed to the thermal decomposition of RDX.The reaction rate of RDX/AP/10.7 μm Al is so fast that the apparent activation energy,calculated by model-free Friedman method,is negative,which is the same as that of RDX/AP.30％（mass fraction） 40 nm Al added in RDX/AP change the activation energy from negative to positive value.The second mass loss process of the RDX/AP/A1 mixture is ascribed to the thermal decomposition of AP.This process can be divided into three stages for RDX/AP with and without Al.The kinetics model is not changed in the presence of micro-sized Al,while it is changed from CnB/D1/D1 to CnB/D1/D4 after the addition of 40 nm Al to RDX/AP.The reaction rate constant of the first stage and the end temperature of the second stage decrease,while the end temperatures of the third stage increase in the presence of 40 nm Al.The MS-FTIR results show there is a competition between the formation reactions of HNCO,N2O and NO2 during the second mass loss process.     

Decomposition of perfluoropolyether lubricants

Decomposition has been studied in the chemistry of perfluoropolyethers (PFPE), thus far no molecular structure information is reported. TG-MS is a tool to follow the off gassing of decomposition for clues. We selected two PFPEs that have different properties: Krytox® XHT-1000 and Fomblin Z60 heating to normal decomposition and catalytic decomposition in the presence of alumina powder. Comparing the decomposition fragment intensities, the molecular structure of the branched Krytox® XHT-1000 oil is more stable than the blocky Fomblin Z60. We see aluminum-containing fluorine fragments in the rapid decomposition of oils in contact with alumina powder. It has been suggested the formation of Al(O_6?n F _n ), where n = 1, 2, and 3, in which the fluorine atoms are selectively associated with aluminum atom. The major decomposition products are small and large fragments of fluorocarbons and perfluoroalkoxy. In the absence of alumina powder, Krytox XHT-1000 shows only a loss of 13 mass/% after several hours at 330 °C, whereas in the presence of 1 mass/% alumina powder the oil has rapidly decomposed to 67 mass/% of its original mass within 15 min. Fomblin Z60, a product might not be designed for high temperature, exposing to the same conditions at 330 °C for several hours and shows a loss of 98 mass/% alone, but in the presence of 1 mass/% alumina powder shows a loss of 98 mass/% in 3.6 min. When 3 mass/% of two new developmental additives were added to the both oils, the catalytic decomposition in the presence of 1 mass/% alumina powder was significantly reduced in Krytox® XHT-1000, showing only a loss of 23 mass/% in 4 h, but nearly all weight for Z60 in 60 min. In the oil grades that contain the new additives, we see the fragments of Al–O–S, and F–Al–O–S. The sulfur-containing compound has been reported ionically bonded to oxide in a tripod configuration of alumina surface, which shields the formation of Al–F.     

Effect of pressures on decomposition reaction kinetics of double-base propellant catalyzed with cerium citrate

The decomposition reaction kinetics of the double-base (DB) propellant (No. TG0701) composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG) and nitrocellulose (NC) with cerium(III) citrate (CIT-Ce) as a combustion catalyst was investigated by high-pressure differential scanning calorimetry (PDSC) under flowing nitrogen gas conditions. The results show that pressure (2 MPa) can decrease the peak temperature and increase the decomposition heat, and also can change the mechanism function of the exothermal decomposition reaction of the DB gun propellant under 0.1 MPa; CIT-Ce can decrease the apparent activation energy of the DB gun propellant by about 35 kJ mol⁻¹ under low pressure, but it can not display the effect under high pressure; CIT-Ce can not change the decomposition reaction mechanism function under a pressure.     

酒石酸铅锆的制备、表征及其燃烧催化作用

以酒石酸、硝酸氧锆和硝酸铅为原料,合成出了双金属盐酒石酸铅锆,采用有机元素分析、X射线荧光光谱和FTIR对其进行了表征。在程序升温条件下,利用TG/DTG、DSC、固相原位反应池/FTIR联用技术,研究了酒石酸铅锆的热行为和热分解机理,描述了酒石酸铅锆的热分解过程,分析得出其最终分解产物为ZrO2、PbO和C。利用螺压工艺制备了含酒石酸铅锆的推进剂样品,研究了酒石酸铅锆对双基系推进剂燃烧性能的影响,分析了其燃烧催化作用。结果表明,酒石酸铅锆对双基系推进剂的燃烧具有良好的催化作用,是一种高效的燃烧催化剂;酒石酸铅锆热分解的最终产物PbO是催化燃烧的主要活性物质,推进剂燃烧过程中形成了氧化铅-铅循环催化体系,而锆和碳则起辅助催化的作用。     

MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles with excellent catalytic activity in thermal decomposition of ammonium perchlorate

MnCo₂O₄ spinel nanoparticles (NPs) have been prepared using Aloe vera gel solution. The characterization of prepared spinel was performed applying Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron spectroscope, scanning electron microscope and dynamic light scattering. The results manifested that the prepared nanoparticles were mainly spherical plus minor agglomeration with average size distribution between 35 and 60 nm. The catalytic activity of the prepared nanoparticles upon thermal degradation of ammonium perchlorate (AP) was evaluated applying differential scanning calorimetry and thermogravimetry instruments. MnCo₂O₄ nanoparticles increased the released heat of AP from 450 to 1480 J g^?1 and decreased the decomposition temperature from 420 to 293 °C. The kinetic parameters obtained from Kissinger methods showed that the activation energy of AP thermal decomposition in the presence of MnCo₂O₄ NPs considerably decreased. Also, a mechanism has been proposed in the presence of catalyst for the process of thermal decomposition of AP.     

Thermal runaway reaction evaluation of two by-products mixed with cumene hydroperoxide in the oxidation tower

Oxygen (O₂) or air is widely used to produce cumene hydroperoxide (CHP) in the cumene oxidation tower. The aim of this study was applied to analyze thermal hazard of two by-products including alpha-methylstyrene (AMS) and acetophenone (AP) in a CHP oxidation tower. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were operated to evaluate thermal runaway reaction of CHP mixed with AMS and AP. Exothermic onset temperature (T ₀), maximum temperature (T _max), activation energy (E _a), etc., that were employed to prevent and protect thermal runaway reaction and explosion in the manufacturing process and storage area. In view of proactive loss prevention, the inherently safer handling procedure and storage situation should be maintained in the chemical industries. The T ₀ of 30 mass% CHP was determined to be 105 °C by DSC. Therefore, the T ₀ of 30 mass% CHP mixed with AMS was determined to be 60–70 °C by DSC. The exothermic reaction of CHP/AP and CHP/AMS by DSC under N₂ reaction gas is thermal decomposition of oxygen–oxygen bond (–O–O–) because of the anaerobic reaction.     

Synthesis,characterization and kinetic computations of fullerene (C60)–CuO on the mechanism decomposition of ammonium perchlorate

CuO, C₆₀–CuO, and Al/C₆₀–CuO nanostructures were synthesized and characterized by scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA) measurements were performed to study the influence of these additives on ammonium percolate (AP) thermal decomposition. From the comparison of DSC and TGA plots, the catalytic effect of CuO and C₆₀–CuO has been clearly noticed in which the lower temperature decomposition of AP was decreased from 331 °C to 315 °C, 310 °C, and 303 °C (in the presence of CuO, C₆₀–CuO, and Al/C₆₀–CuO, respectively) and the HTD was dropped from 430 °C (pure AP) to 352 °C, 335 °C, and 317 °C (for the compounds AP/CuO, AP/C₆₀–CuO, and AP/Al/C₆₀–CuO, respectively). The kinetics of the samples were investigated by isoconversional models and compared with an iterative procedure. The results of pure AP indicated a complex decomposition process involving three decomposition steps with specific reaction mechanism. The nanocatalysts incorporated in the AP have clearly affected its decomposition process in which the reaction mechanism and the number of stages were changed.     

Enhanced Thermal Decomposition Properties and Catalytic Mechanism of Ammonium Perchlorate over CuO/MoS2 Composite

In this report, CuO/MoS₂ composites were successfully prepared by the hydrothermal method where nano‐sized CuO was uniformly distributed on the surface of hierarchical MoS₂ substrates (CuO/MoS₂ composites). Their physicochemical properties and catalytic performance in ammonium perchlorate (AP) decomposition were investigated and characterized by XRD, SEM, TEM, BET, XPS, TG/DSC and combustion measurement. The results showed that it could decrease AP decomposition temperature at high decomposition stage from 416.5 °C to 323.5 °C and increase the heat release from 378 J/g (pure AP) to 1340 J/g (AP with catalysts), which was better than pure CuO nanoparticles (345.5 °C and 1046 J/g). Meanwhile, it showed excellent performance in combustion reaction either in N₂ or air atmosphere. The results obtained by photocurrent spectra, photoluminescence spectra and time‐resolved fluorescence emission spectra indicated that loading CuO mediated the generation rate and combination rate of electrons and holes, thus tuning the catalytic performance on AP decomposition. This study proved that employing the supports that can synergistically interact with CuO is an efficient strategy to enhance the catalytic performance of CuO.     

Characterization of herbal medicine with different particle sizes using pyrolysis GC/MS, SEM, and thermal techniques

Analytical techniques have been used to characterize compounds from herbal medicine, its products and extracts. The objective of this study was to characterize a variety of particle sizes of Erythrina velutina Willd powder. The samples used in the study were named MUF01 (710 μm), MUF03 (180 μm) and MUF05 (75 μm). The techniques employed were scanning electron microscopy (SEM), thermal analysis such as thermogravimetry (TG) and differential thermal analysis (DTA) together with pyrolysis coupled to gas chromatography/mass spectrometry (Pyr-GC/MS). SEM enabled us to detect the existence of divergences from the expected results from the granulometry process. Thermal analytical techniques (TG and DTA) showed the thermal decomposition profile, corresponding to physical and chemical phenomena. The chromatographic data relative to the peak area of the compounds analyzed evidenced quantitative differences in the chemical compositions of the samples MUF01, MUF03, and MUF05 at 300, 450 and 600 °C. Neophytadiene 2,6,10-trimethyl, 14 and 3-eicosyne were identified by Pyr-GC/MS at 300, 450 and 600 °C, and it classified the samples according the peak area values, which were MUF05 > MUF03 > MUF01. SEM, DTA and TG confirmed this through particle size uniformity, heat flow, and mass loss, respectively.     

Enhanced thermal and combustion resistance of cotton linked to natural inorganic salt components

A comparison of the thermal decomposition and combustion characteristics of raw and scoured cottons has demonstrated a mechanistic link caused by the presence of inorganic salts in raw cotton, which enhances resistance to heat and flame. Thermogravimetry, differential thermogravimetry, and microscale combustion calorimetry were used to examine the thermal decomposition kinetics and thermal stability of cotton. During pyrolysis, both raw cotton nonwoven and woven fabrics exhibited a slower decomposition with a larger initial weight loss and produced a greater char yield, as compared to the fabrics after scouring, which removes most inorganic components from cotton. The activation energy (E _a ) values, calculated using the Kissinger method, the Flynn–Wall–Ozawa method, and the modified Coats–Redfern method, were consistently determined to be smaller for raw cotton than for scoured cotton. The analyses of cotton fabrics heated at elevated temperatures by ¹³C CP/MAS NMR and ATR-FTIR showed that trace quantities of inorganic components promoted the formations of oxygenated moieties at low temperatures and aliphatic intermediate char. In the combustion, raw cotton exhibited a much smaller heat release capacity and a smaller total heat release than scoured cotton, indicating enhanced thermal stability when the inorganic components are intact.