Activation Energy Of Thermal Decomposition Research Articles

Construction of rGH/NTO 3D-network composite with improved energy release efficiency and significantly reduced corrosiveness of 3-nitro-1,2,4-triazole-5-one

3-Nitro-1,2,4-triazole-5-one (NTO) is a high-energy insensitive explosive with broad application prospects. However, due to the slow energy release kinetics, high decomposition temperature and unsatisfactory safety performance, its effective application is affected. In this paper, a reduced graphene oxide hydrogel (rGH)/NTO composite material was prepared to improve both the physical and chemical properties of NTO. The morphology and structure of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that the rGH/NTO composites did not undergo polymorphic transformation during the preparation process. At the same time, the three-dimensional (3D) network structure formed by rGH can reduce the initial temperature and activation energy of NTO thermal decomposition, and significantly increase the energy release rate. In addition, combined with experiments and DFT theoretical calculations, it is verified that the synergistic effect of the composite material reduces the corrosivity of NTO and increases the insensitivity, thereby improving the effective safety performance. Therefore, the synergistic effect of 3D network structure composite strategy is expected to be extended to the multi-performance control of energetic materials.

Surface modification of nitrocellulose by interfacial self-assembly of metal-phenolic network for enhanced thermal stability and eco-friendly propulsion energy

Metal-phenolic networks (MPNs) have received widespread interest owing to their ability to incorporate metal ions and phenolic ligands in a modular manner. However, the effect of MPNs on nitrocellulose (NC), an energetic material for propulsion, has not been extensively investigated. Herein, we fabricated MPN-coated NC fibers (NC@MPN) and confirmed the successful coating and homogeneous distribution of MPN on the surface of NC through Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, scanning electron microscopy (SEM) and Energy Dispersive spectroscopy (EDS). The thermal stability of NC was enhanced as evidenced by differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC) and the ignition point test. The thermal decomposition activation energy of NC@MPN can reach 200.73 kJ•mol−1, 7.50 % higher than that of NC primitive fiber (186.72 kJ•mol−1). The ARC tests demonstrate that the implementation of MPN coating prolonged the time of entering the adiabatic section by 5.4 °C and the forecast temperatures for TD8 and TD24 have increased by 4.6 and 4.8 °C, respectively. Additionally, the ignition point was also raised by 2 °C. The aforementioned three experimental results provide evidence for the enhanced thermal stability conferred by MPNs. Besides, thermogravimetric analysis (TGA) results demonstrate a reduction in the residue from thermal decomposition. The present study presents a simple and robust coating strategy for the modular surface engineering of energetic materials, which significantly improves thermal stability and reduces the residues of thermal decomposition.

Effect of internal phase particle size on properties of site mixed emulsion explosive at plateau environment

To study the effect of internal particle size on the microstructure properties and thermal decomposition characteristics of site mixed emulsion explosive at different altitudes. Site mixed emulsion explosive was prepared with different shear rate. The particle size, viscosity, sensitized bubbles, detonation velocity and peak pressure of the emulsion explosive were tested after stored at different simulated altitudes. The thermal decomposition characteristics of emulsion matrix prepared at three different rotational speeds were measured by thermogravimetric analyzer and kinetic analysis was performed by non-isothermal model Kissinger–Akah–Sunose (KAS) method. The results show that with the increase in altitude, the internal phase size showed a trend of first increasing and then decreasing, and the number of sensitized bubbles within the emulsion explosive decreases. At an altitude of 0 m, the detonation velocity and peak overpressure of the emulsion explosive prepared by 1600 r min−1 increased 4.78% and 29.09%, respectively compared with 1200 r min−1, and at an altitude of 4500 m, the detonation velocity increased 11.87%, the peak overpressure increased 43.98%. The thermal decomposition activation energy of the emulsion matrix at 1600 r min−1 increased 13.14% compared to 1200 r min−1. It shows that in the production of site mixed emulsion explosive at high altitude, reducing the particle size of the internal phase of emulsion explosives in a certain range can effectively improve the performance of emulsion explosives.

Thermal decomposition behavior of Mountain Pass rare earth concentrate in air/CO2 atmosphere

The Mountain Pass mine is recognized as one of the world’s primary sources of rare earth minerals. These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate, which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process. An efficient, clean, and economical process called the "combined method" was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate (MPREC). The main steps of this process include weak oxidation atmosphere roasting, step leaching of hydrochloric acid, solid-liquid separation, the monazite slag with sulfuric acid roasting water leaching, etc. In this paper, the roasting process of MPREC under a weak oxidation atmosphere was investigated. The study examines the thermal decomposition kinetics, phase transition process, and leaching behavior of MPREC in air/CO2 atmosphere. Results show that, the activation energy (Ea) for MPREC thermal decomposition in air and CO2 atmosphere are 146 and 320 kJ/mol, respectively. At temperature above 500 °C in air or above 700 °C in CO2 atmosphere, REOF are generated from bastnaesite through an in-situ reaction with CaO, which is decomposed from CaCO3, to form CaF2 and rare earth oxide (REO). Thus, F is regulated into solid phase. In an oxidizing atmosphere, the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ). In contrast, the oxidation of Ce(Ⅲ) in a CO2 atmosphere is significantly inhibited. At 700 °C, the oxidation rate of Ce in air is 74.09%, while in a CO2 atmosphere, it is only 33.83%. The hydrochloric acid leaching experiment shows that, the leaching rate of rare earth after roasting at 600 °C under an air atmosphere reaches to 82.9%, and it reaches 87% after roasting at 800 °C under a CO2 atmosphere. The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.

Nano-clay treatment of jute fiber for reinforcement in polymer composites: Mechanical, morphological, and thermo-kinetic analysis

Natural fibers have demonstrated exceptional properties that can be utilized as a viable and environmentally reliable material for reinforcement in polymer composites replacing their synthetic counterparts creating numerous environmental problems. Jute fiber is a prominent natural fiber that has been successfully applied for manufacturing noble natural fiber-based composites. This article describes the advantages and comparison between two surface treatment techniques that is alkali treatment and nano-clay treatment of jute fiber to enhance the properties for producing improved composite material. FTIR, SEM, AFM, and TGA have been utilized to compare and study how different surface treatment methods affect jute fiber. Isoconversional methods FWO and KAS are applied for the thermos-kinetic analysis and evaluation of activation energy of thermal decomposition. More than 30% increase in peak activation energy has been observed (120 KJ/mole to 160 KJ/mol). Alkali–nano-clay treated jute fiber exhibits nearly 32% improvement (405 MPa to 535 MPa) in tensile strength, 24% increment (11.85 GPa to 14.69 GPa) in tensile modulus, and 15% improvement (1.4 gm/cm3 to 1.61 gm/cm3) in fiber density as compared to that of untreated jute fiber. This study validates that nano-clay treatment has shown promising results and can improve the overall properties of natural fibers significantly.

Synthesis, self-assembly and surface-active properties of alkyl halide mediated imidazolium monomeric surfactants

Two imidazolium monomeric surfactants, that is, 1-tetradecyl-1H-imidazole [14IM] and 1-hexadecyl-1H-imidazole [16IM] has been synthesized and characterized by 1H NMR,13C NMR, FTIR, HRMS spectroscopies and thermogravimetric analysis (TGA) for number and types of protons and carbon, functional groups, estimation of molecular weight and thermal stability of these compounds. The conductivity was measured in double distilled water at four different temperatures, 288, 293, 298, and 303 K. The results showed that these surfactants behave as weak electrolytes. The density and viscosity data have shown the existence of strong interactions between imidazolium surfactants and solvent (water) molecules. The results obtained from Root’s equation indicate that surfactant–solvent interactions are important than surfactant–surfactant interactions in dilute solutions, that is, below critical micellar concentration. The values of constants obtained from Einstein and Moulik equations have revealed that there was stronger and significant interaction between imidazolium surfactants and water molecules below critical micellar region. The surface tension parameters have indicated that these surfactants are good contenders to lower the surface tension of air/water interface. The results obtained from surface tension data have shown that standard change in free energy of micellization (ΔG°mic) and adsorption (ΔG°ads) were negative, indicating that these surfactants molecules have spontaneous tendencies to form micelles in solution at higher concentration and to get adsorb at the air/water interface at lower concentration. The TGA has indicated good thermally stability and activation energy for thermal decomposition was found in the range of 37.26.26–98.20.20 kJ/mol.

Study on controlling factors and developing a quantitative assessment model for spontaneous combustion hazard of coal gangue

Developing a quantitative hazard assessment model for spontaneous coal gangue combustion is imperative to ensuring the safety of coal mining operations. In this study, eight types of coal gangue from different coalfields were used to determine the controlling factors for spontaneous combustion. A variety of physical and chemical characterization methods were employed to investigate the physical and chemical characteristics of the samples. Based on the experimental results, six key parameters were identified, namely the aliphatic C–H components, pyrite sulfur content, physical oxygen absorption capacity, ash content, ignition point temperature, and activation energy for thermal decomposition. The results show that the spontaneous combustion hazard of coal gangue is positively correlated with the first three of these and is negatively correlated with the rest. Using the entropy-weight method combined with the analytic hierarchy process, appropriate weighting factors for each parameter were obtained and used to establish a quantitative assessment model for the spontaneous combustion hazard of coal gangue. This model is expected to enhance the current industrial best practices for the prevention and control of spontaneous coal gangue combustion.

Micromodulation of dual-shell CL-20/desensitizer interface based on in-situ assembly of tea polyphenols

Although the research on CL-20 crystals has reached a high level, the property of the explosive-desensitizer interface is a key concern for composite explosive applications. Herein, inspired by super adhesion performance on cup, the in-situ assembly ability of tea polyphenol (TP) was utilized to enhance the surface performance and desensitize CL-20. The five kinds of core-dual-shell composites were fabricated by the “one-pot” water suspension method under the influence of ionic charge, -OH bonding, and the structure like suction cup of ivy. They were characterized by SEM, XPS, TG-DSC, XRD, and mechanical sensitivity device. The morphology and surface analysis results indicated that TP and desensitizer were evenly coated on the surface of CL-20, forming a core-dual-shell structure. This provided a great structural contribution to its security. The thermal analysis results suggested that TP/microcrystalline wax (MW) was endowed with thermal decomposition activation energy (Ea) of CL-20 from 190.92 kJ/mol up to 200.99 kJ/mol. While, the Ea of CL-20/TP, CL-20/TP/GO, CL-20/TP/TPU, and CL-20/TP/TPU-PDA were only 189.33 kJ/mol, 190.61 kJ/mol, 199.77 kJ/mol, and 184.75 kJ/mol, respectively. Meanwhile, the TP/GO film reduced Tp0 of CL-20 from 218.15 ℃ to 208.21 ℃ and Tb from 220.27 ℃ to 210.14 ℃, respectively. Besides, the XRD results confirmed that the five films had not caused a transformation of the ε-CL-20 crystal phase, which afforded process safety support for the further application of these composite particles. Due to the properties of MW and the advantages of dual-shell composite structural, the TP/MW film brought mechanical sensitivity of CL-20 from 60 N and 3.5 J to 336 N and 8.97 J, closing to the level of PBXs with 95% LLM-105% and 5% ternary composite (11 J). These safety parameters indicate materiel of moderate sensitivity that possibly can be handled in accordance with standard procedures. Moreover, the particle coated with TP/TPU-PDA possessed better free-running property. These findings can provide reference for the large-scale application of CL-20.

Novel protonated LiCoO2 as a catalyst for the thermal decomposition of ammonium perchlorate

ABSTRACT LiCoO2 (LCO) powders were protonated and their catalytic activity on the thermal decomposition of ammonium perchlorate (AP) was tested using differential scanning calorimetry and thermogravimetric analysis. Powders were characterized using SEM, XRD, and BET surface area analysis to quantify the morphology and structure. The thermal analysis showed that protonated powders enhanced the catalytic activity in AP decomposition over commercial and unmodified LiCoO2, Fe2O3 and Co3O4 catalyst powders. The activation energies were investigated using the model-free Kissinger method, and the possible mechanisms governing the catalytic activity are discussed. The activation energies of AP thermal decomposition were decreased significantly by the use of these protonated catalysts. For neat AP, commercial LCO, and protonated LCO the activation energy for LTD and HTD were: 104 ± 5 kJ/mol and 143 ± 4 kJ/mol, 89 ± 4 kJ/mol and 92 ± 14 kJ/mol, and 76 ± 6 kJ/mol and 98 ± 7 kJ/mol respectively. We believe the hydrogen and vacancies in the protonated lattice act as reaction sites for the decomposition of AP.

The impact of oxygen-clustering on the transformation of electrochemically-derived graphite oxide framework

Oxygen-clustering in graphene oxide is the activated process of diffusion of oxygen functionalities: hydroxyls and epoxides, to form clusters and to trigger sp2 percolation, a key element for electrical conductivity. Impact of oxygen-clustering is thoroughly analyzed in electrochemically-derived graphite oxide (EGO), amine-functionalized frameworks (EGOF), and their pyrolyzed forms. Amine pillars within EGOF were suspected to amplify oxygen-clustering in EGOF as onset temperature of thermal decomposition was smaller in EGOF than in EGO. Thermochemical analysis proves that pillars within EGOF significantly augment oxygen-clustering aiding the reduction mechanism as inferred by the activation energy of thermal decomposition. Defective oxygen-clustering mechanism is evidenced using multiple techniques, including XRD, and is harnessed to enhance nitrogen doping. The pyrolytic morphological transformation from lamellae of EGOF into ravioli is revealed through SEM. A labyrinthic network of array prismatic dislocations provides stability to pyrolyzed EGOF ravioli whilst confining long chains of electron delocalization (localized π-orbitals), as unprecedently confirmed by HR-TEM/EELS and conductive AFM (C-AFM). Oxygen-clustering not only improves nitrogen doping in ravioli, but also improves density of array prismatic dislocations, which ultimately boosts Faradaic redox activity as observed in cyclic voltammetry (CV). Results show that Faradaic response originating from redox-active nitrogen groups predominantly relies on abundance of extended localized π-orbitals, which are geometrically and chemically confined within ravioli array prismatic dislocations. Our first-of-a-kind HR-TEM/EELS, C-AFM, and CV comparative and correlative analysis of pyrolyzed forms of EGO, EGOF, and their oxygen-clustered derivatives, confirms emergent role of confined electron delocalizations in amplifying Faradaic redox activity.

Assessment of self‐heating and spontaneous combustion of Napier grass using thermogravimetric analysis

AbstractNapier grass is a potential solid biofuel that can be used as a renewable energy resource. Nevertheless, its tendency for self‐heating and the subsequent self‐ignition remain unknown, which are common problems in solid fuel. In this work, thermal decomposition characteristics of Napier grass in air and inert conditions were investigated using thermogravimetric analysis (TGA) and the pertinent kinetic parameters were established using model‐free methods. The average activation energy of Napier grass thermal decomposition is 285 and 382 kJ/mol under oxidative and inert conditions, respectively. The linear plot obtained through model‐free methods shows a high linear correlation coefficient at conversion ranges of 0.2–0.7 during combustion and 0.4–0.6 during pyrolysis. The ignition and burnout temperatures were evaluated, and ignition index of Napier grass was established. Average ignition temperature obtained for air was 217°C while 200°C for inert condition. The burnout temperatures between 691 and 984°C were observed. This research facilitates in understanding fire threat posed by tendency of Napier grass to self‐heat and provides valuable information for safe conditions of Napier grass storage and transportation.

Effects of Overload on Thermal Decomposition Kinetics of Cross-Linked Polyethylene Copper Wires.

During an overload fault in an energized wire, the hot metal core modifies the structure of the insulation material. Therefore, understanding the thermal decomposition kinetics of the insulation materials of the overloaded wire is essential for fire prevention and control. This study investigates the thermal decomposition process of new and overloaded cross-linked polyethylene (XLPE) copper wires using thermogravimetry-Fourier-transform infrared spectroscopy and cone calorimetry. The thermal decomposition onset temperature and activation energy of the overloaded XLPE insulation materials were reduced by approximately 15 K and 20 kJ mol-1, respectively, and its reaction mechanism function changed from D-ZLT3 to A2 (0 < α < 0.5). The FTIR shows that the major spectral components produced during the pyrolysis of the XLPE insulation material are C-H stretching, H2O, CO2, C-H scissor vibrations, and C=O and C=C stretching. Additionally, the four functional groups in the PE chains produced the spectral components in the following decreasing order of wavenumber: C-H stretching > CO2 > C-H scissor vibration > C=O and C=C stretching.

Precursor decomposition mechanism of In2O3 powder for oxide ceramic targets

In this study, precursor decomposition as well as nucleation and growth processes during the preparation of In2O3 powders via chemical precipitation were investigated. This is to provide guidance for the preparation of high-quality In-based oxide target powders. In-situ phase and microstructure evolution during thermal decomposition of precursors were analyzed. In addition, decomposition behavior of precursors at different heating rates was explored. Results show that amorphous In(OH)3 precursor powder gradually decomposes and transforms into crystalline In2O3 powder during heating process. Its degree of crystallinity increases with the increase in temperature. Fine and homogeneous In2O3 powder with average grain size of 54.46 nm was obtained by holding the powder at 770 °C for 3 h. The decomposition of precursors at any given heating rate can be divided into two stages: (i) dehydration and (ii) nucleation and crystallization. However, higher heating rate clearly results in temperature hysteresis effect, the occurrence of decomposition reaction at higher temperature, and an increase in the maximum reaction rate of decomposition reaction. Moreover, activation energy of thermal decomposition was obtained using model-free transformation method. Decomposition reaction model of In(OH)3 precursor was established using model-fitting method. It was deduced that first-stage reaction mechanism is three-dimensional diffusion. Reaction rate in this stage is controlled by product layer diffusion. Furthermore, second-stage reaction mechanism is random nucleation and subsequent growth. Reaction rate in this stage is controlled by nucleation and growth rates.

Thermal decomposition of n-hexane in organic Rankine cycle: a study combined ReaxFF reactive molecular dynamic and density functional theory

The thermal decomposition mechanism of n-hexane is investigated by using density functional theory and ReaxFF force field. The initial decomposition reactions, the effect of temperature on thermal decomposition and first-order kinetics are analyzed. The results show that the C-C bonds in n-hexane molecule are more easily decomposed than that of C-H bonds, and the breakage of C3-C4 bond is the main initial decomposition reaction. The main decomposition products of n-hexane are H2, CH4, C2H2, C2H4, C2H6, and C3H6. The decomposition rate of n-hexane is accelerated by temperature. The apparent activation energy and pre-exponential factor of n-hexane thermal decomposition are 209.8 kJ mol−1 and 1.1 × 1013 s−1, respectively.

Investigation of Curing Process and Thermal Behavior of Copolymers Based on Polypropylene Glycol Fumarate and Acrylic Acid Using the Methods of DSC and TGA.

In this work, the possibility of preparation of copolymers of three-dimensional crosslinked structure based on polypropylene glycol fumarate and acrylic acid is shown. The initial reagent polypropylene glycol fumarate has been synthesized by polycondensation reaction of fumaric acid and propylene glycol. The curing process of polypropylene glycol fumarate and acrylic acid at various mole concentrations was studied using DSC method at isothermal and dynamic regimens. Curing in isothermal condition was carried out at temperatures of 60 °C, 70 °C, and 80 °C. Residual reactivity was evaluated at a dynamic regimen within the temperature range from 30 °C to 200 °C at a constant heating rate. On the basis of calorimetric studies, the thermal effects and kinetic parameters of the reaction (conversion, reaction rate, activation energy) have been determined. Thermal behavior of cured samples of p-PGF-AA was estimated using dynamic thermogravimetry (TGA). According to TGA data, the process of decomposition of the studied copolymers proceeds in several stages. Based on the results obtained, the activation energies of thermal decomposition were calculated using the iso-conversional methods of Kissinger-Akakhira-Sunose and Friedman.

Preparation and performance study of sedum multiceps-like biomimetic structure TKX-50 with various particle sizes

Biomimetic structures often endow materials with excellent performance. In order to explore the impact of biomimetic structures on the performance of energetic materials, the sedum multiceps-like bionic structure dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) was constructed by self-assembly technology, and controllable particle size adjustment was achieved. Moreover, the effects of solvent ratio, solute content, stirring flow field, and temperature on the quality of sedum multiceps-like TKX-50 crystals were explored, and the formation mechanism of sedum multiceps-like TKX-50 crystals was analyzed. Then, the crystal morphology, crystal form and particle size distribution of sedum multiceps-like TKX-50 were characterized, furthermore, the thermal properties and mechanical sensitivity of sedum multiceps-like TKX-50 were emphatically studied. The results showed that the sedum multiceps-like biomimetic structure TKX-50 was assembled from needle shaped or sheet shaped small particle crystals, and the sedum multiceps-like structure did not change the explosive crystal form of TKX-50. What's more, the thermal decomposition activation energy of the prepared sedum multiceps-like TKX-50 crystal was at least 157.30 kJ⋅mol−1 and at most 185.27 kJ⋅mol−1, and the thermal energy was greatly affected by particle size. In addition, the minimum and maximum ultimate impact energy of the sedum multiceps-like TKX-50 crystals are 20 J and 55 J. The ultimate impact energy of the sedum multiceps-like TKX-50 crystal with different particle sizes is higher than that of the raw TKX-50 (15 J). As a consequence, the sedum multiceps-like bionic structure effectively improves the energy release of TKX-50, reduces the impact sensitivity, and improves the uniformity of particle size distribution.

Mechanical properties, thermal stability, and mechanism of main‐chain polybenzoxazine composites fabricated based on multi‐scale effects and surface functionalization of graphene oxide nanosheets

AbstractPolybenzoxazine (PBZ) has been recognized as a potential substitute for traditional phenolic resin. However, poor flexibility and low heat resistance limited obviously the application of PBZ. Herein, graphene oxide (GO) nanosheet and its amino‐rich derivatives (fGO‐g‐SiO2) with multi‐scale surfaces were designed, synthesized and incorporated into main‐chain PBZ through in‐situ polymerization to fabricate PBZ composites. The morphology, mechanical properties, and thermal stability of the composites were systematically investigated using x‐ray diffraction (XRD), contact angle tests, field emission scanning electron microscopy (FESEM), tensile and impact tests, and thermogravimetric analysis (TGA). FTIR and XRD analyses confirmed the multi‐scale surfaces of GO derivatives and ordered structures, respectively. The size of the in‐situ grown SiO2and the thickness of GO coated on PBZ were estimated as 6.5 and 19.07 nm, respectively. The contact angle test revealed thatfGO‐g‐SiO2and BZ had the closest solid surface energy of 32.002 and 43.519 mN/m, respectively, among the components of the composites. The impact and tensile evaluation revealed the highest impact, tensile strength and Young's modulus of 16.75 kJ/m2, 107.24 MPa and 3.17 GPa, respectively for 1.2%fGO‐g‐SiO2/PBZ composite. The modified Halpin‐Tsai equation was also utilized to develop a predictive function for the tensile strength. FESEM offGO‐g‐SiO2/PBZ composites indicated that the multi‐scale effect and amination effectively improved the restriction of GO derivatives on crack propagation in PBZ composites and played a more significant role in crack deflection and bridging. In addition, the highest thermal decomposition activation energy of 166.94 kJ/mol was achieved for 1.2%fGO‐g‐SiO2/PBZ composite.HighlightsGraphene oxide (GO) nanosheets were incorporated into main‐chain polybenzoxazine (PBZ) to improve its mechanical properties and heat resistance.GO with multi‐scale structure and amino‐rich interface were designed, synthesized to improve the interface interactions with PBZ matrix.The GO with multi‐scale structure and amino‐rich interface showed excellent similarity in the term of solid surface energy with benzoxazine oligomers.The morphology, mechanical and thermal stability of resulting PBZ composites was systematically investigated by using experimental and mathematical model to elucidate the relationships between the structure and properties.The composites exhibited excellent mechanical and thermal properties, and it is expected to be used as advanced engineering material in demanding environments.

Synthesis of Hybrid Cellulose Acetate Membranes and Application of the Flynn-Wall-Ozawa Isoconversional Method

The synthesis of hybrid materials is a promising alternative in the production of materials with optimized properties. In this context, the classic cellulose acetate membranes are being modified. It is worth mentioning that knowing the thermal stability of cellulosic materials is an essential factor in their use since organic polymers have low thermal resistance, limiting their applicability. This work evaluates the synthesis and the study of the thermal degradation kinetics of hybrid cellulose acetate membranes. The synthesis was carried out using the sol-gel process, with the phase inversion technique, through the reaction of cellulose acetate with organometallic precursors: tetraethyl orthosilicate, TEOS; 3-aminopropyl triethoxysilane, APTES, and titanium isopropoxide, TiPOT, in fixed composition. Thermal characterization was performed with thermogravimetric analysis at different heating rates under a nitrogen atmosphere. The kinetic parameter of thermal decomposition activation energy, Ea, was estimated with the isoconversional method proposed by Flynn-Wall-Ozawa (FWO). The degradation kinetics shows that the change in the chemical composition of the samples directly interferes with their thermal properties. Thus, it is possible to observe that the activation energy found for the reference sample, AC-Pure, in the first and second batches was 233.5 and 219.05 kJ/mol, respectively. The composition modification results in an increase in activation energy, in which sample B0//100-30 recorded 310.31 and 226.05 kJ/mol in the first and second batches; and sample B100//0-30 reached 452.73 and 424.74 kJ/mol. It is clear that the increase in the thermal resistance of the samples is associated with the change in the chemical composition and must be attributed to the increase in the TEOS content in the composition due to the formation and increase in the presence of siloxane groups in the material.

Preparation and Properties of Ultra-fine HNS-IV

Ultra-fine 2,2’,4,4’,6,6’- Hexanitrostilbene (HNS-IV) was obtained by HNS-II by vibration cavity comminute. This method uses only alcohol and deionized water, which can be viewed as a green technology. The morphology, particle size, specific surface area, thermal decomposition property and the threshold energy for slapper detonator were compared between HNS-IV and HNS-II in this paper. Results show that after HNS pulverizing, the particle size decreased from 27.18μm to 1.44μm, the specific surface area increased from 0.73m2•g−1 to 9.10m2•g−1. DSC analysis shows that the decomposition peak temperature Td decreases and the melting temperature Tm increases after pulverizing. It is speculated that in the explosive reaction with very high heating rate, the enthalpy of decomposition will be increased by pulverizing, which will be more conducive to detonation growth and explosive reaction. According to the calculation of thermal decomposition kinetics, the decomposition and activation energy Ea of HNS decreases after pulverizing, and the thermal decomposition reaction rate of HNS-IV increases when the temperature is less than 409.6°C. The initiation threshold test of the impact plate shows that the 50% initiation threshold energy of HNS- II is 1.242J, and the 50% initiation threshold energy of HNS-IV is 0.558J, and the initiation threshold for slapper detonatorer is significantly reduced by 55%. This means that the ultra-fine HNS-IV is very suitable as the main ingredient in the booster in the EFI initiation.

Reaction kinetics, pyrolytic behavior and product characterization of dewatered solids from spent fermentation coir wastes using a fixed batch reactor

Solid residues after pretreatment and hydrolysis of coir pith and Bit fiber waste was dewatered, dried and pyrolyzed at 300, 350, and 400 °C using a fixed bed batch pyrolyzer. The products were characterized using ultimate analysis, FTIR and GCMS. Bit fiber yielded more bio-oil (26.3 %), rich in 4-Methoxy phenol (60.94 %) and a Higher Heating Value of 27.06 MJ kg−1. Coir pith bio-oil with Higher Heating Value of 27.16 MJ kg−1, was rich in 2-Methoxy Phenol, which are principal lignin degradation products. Non condensable gases included mixture of methane, carbon dioxide and isomers of butene. Activation energy for thermal decomposition was studied using Coats and Redfern model from thermogravimetric data at heating rates of 10 and 15 k min−1, which showed two major phases of decomposition. Activation energy was higher for devolatilization phase of bit fiber waste (132 kJ/ mol) owing to higher percentage of lignin than in coir pith waste (Ea = 114 kJ/ mol).