Combustion Agent Research Articles

Two-step preparation and characterization of Bi-2212 superconductors by the glycine-nitrate method

In order to prepare high-quality sub-stable copper oxide superconductor Bi-2212, the glycine-nitrate method combined with rapid sintering process was used in this paper. Firstly, the glycine-nitrate method was used to obtain highly active Bi-2212 precursor powders with uniform composition, and then Bi-2212 superconductor powders were prepared by rapid sintering. Glycine acted as a combustion agent while giving property of the complexation to ensure the homogeneity of multiple chemical components. The high-quality precursor powder was the basis for broadening the temperature interval of the pure phase of Bi-2212. And then the effects of precursor powder sampling pressure on Bi-2212 superconducting materials were systematically investigated. On this basis, the pure-phase temperature interval of Bi-2212 superconducting materials prepared by the nitroglycerin method was further investigated. The results showed that the increase of the sample preparation pressure can effectively optimize the crystallinity of Bi-2212, which no longer changed significantly after 300MPa. The pure phase temperature interval of Bi-2212 was 830~880 °C. The samples showed the characteristic lamellar morphology. The optimum sintering temperature was 850°C. The crystal integrity of Bi-2212 was destroyed under high temperature sintering conditions, and the two-dimensional properties were enhanced. The superconducting properties of Bi-2212 were acceptable, with a Tc, onset of 82.1K, Tc, zero of 72.4K, and ΔTc of 9.7K. This work largely reduces the difficulty in the preparation of the superconductors of Bi-2212, and it provides a good basis for the preparation of multi-component functional oxides by using the nitrate method.

Evaluation of the Combustion Properties and Catalytic Activity of MgAlB Energetic Ternary Particles

ABSTRACT Boron powder possesses significant potential for use as a combustible agent in energetic materials, owing to its superior combustion thermodynamic properties. However, the powder’s tendency to form an oxide layer on its surface results in delayed ignition, reduced combustion efficiency, and compromised energy advantage. To enhance the ignition and combustion properties of boron powder, we prepared boron-based energetic composites containing flammable metals (MgxAl1-xB2) through high-temperature sintering. These were then characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS). The combustion heat of these alloy powders were measured using an oxygen bomb calorimeter, while their catalytic performance on the thermal decomposition of ammonium perchlorate (AP) was analyzed using differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The results indicate that compared with boron, the MgxAl1-xB2 powders are more flammable, require less oxygen, exhibit a higher combustion efficiency and exothermic advantage. Especially, the Mg0.9Al0.1B2 and MgB2 alloy exhibit optimal combustion heat values of 39,094.92 and 37,693.90 J·g−1, respectively. They significantly enhance the thermal decomposition of AP and reduce the activation energy by over 20%.

Synthesis and Characterization of (Ni,Co)xMn0.25-xMg0.75Fe2O4 Nanoparticles

Ni-Co-Mn-Mg ferrite nanoparticles with the formula (Ni,Co)xMn0.25-xMg0.75Fe2O4 were synthesized in this work by employing the sol-gel auto-combustion process, with nitrates used as the cations source and citric acid (C6H8O7) as the combustion agent. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and a vibrating sample magnetometer (VSM) were used to characterize the structural, morphological, and magnetic properties of ferrite powders. The XRD measurements showed crystallite sizes ranging between 24 - 28 nm. The FE-SEM images show the presence of agglomeration as well as a non-homogeneous distribution of the samples. On the other hand, the stoichiometry of the reactant solutions that were used is in close agreement with the elemental analysis that was obtained from EDX showing that the composition was as expected. Manganese ferrite showed a decrease in magnetic parameters on magnesium doping, which was further enhanced in (Ni,Co)xMn0.25-xMg0.75Fe2O4 nanoparticles upon replacement of nonmagnetic manganese ions for nickel and cobalt ions. Results indicated that Ni-Co-Mn-Mg ferrite nanoparticles’ crystal morphology, structural, and magnetic properties were significantly influenced by the amounts of nickel and cobalt content.

A new method for predicting minimum ignition energy of environmentally friendly working fluids based on microscopic molecular structure

The issue of global warming prompts us to consider some questions related to energy supply and use. Organic Rankine Cycles (ORC) is a suitable technology for converting low-grade thermal energy into electrical energy, vital for conserving energy and mitigating emissions. Currently, most environmentally friendly working fluids are characterized by their flammability. Analyzing the minimum ignition energy (MIE) of these working fluids is crucial in guaranteeing secure utilization. This paper introduced a novel approach to predicting the MIE of flammable working fluids using microscopic molecular structure analysis. Firstly, the bond energy of molecules was derived by optimizing the microscopic molecular structure of prevalent combustible agents based on the density functional theory (DFT), which was employed to calculate the heat of combustion. Secondly, a mathematical model for predicting the MIE of combustible working fluids was constructed, drawing inspiration from the energy relationship during combustion. Then, the newly formulated model was used to predict the MIE of propane and nine other combustible working fluids, and the results were compared with the existing data. The results show that the predicted values of the MIE exhibit an impressive accuracy rate exceeding 95%. Finally, the MIE prediction model has been modified to provide higher prediction accuracy. This study is of great significance to ensure the safe application of combustible working fluids and to explore environmentally friendly alternatives.

Pore structure regulation of aluminum powder as a filler for high energy solid propellants

Aluminum (Al) powder, as a high-energy metal combustible agent, has advantages such as high calorific value and low cost. It has important research value in energetic materials. However, due to the Al2O3 layer on the surface of Al powder, the contact area between Al powder and oxidant components is reduced, resulting in a decrease in its energy release performance. In this paper, a modified Al powder with porous structure was prepared by chemical corrosion method to solve the problem that its small contact area with oxidant components affects its energy release performance. The study found that when the concentration of HF solution is 3.0 wt%, the removal effect of the oxide layer of Al powder is most effective, with a surface O element content of only 0.6 wt% and a uniform porous structure on the surface of Al powder. In addition, experiments have shown that nano CuO can be well filled into the pore structure of modified Al, increasing the contact area between Al powder and oxidant. This work provides a novel and simple research approach for effectively improving the energy release performance of Al based energetic materials.

A multi-criteria decision study with sensitivity analysis on a tri-generation system based on gas turbine fueled by wheat straw biomass

Wheat straw biomass plays a key role in the field of energy and developing different energy systems. A tri-generation system of power, hot air, and hot water has been developed and modeled in this research work based on a gas turbine unit fueled by wheat straw biomass. Although air usually is utilized as a combustion agent, this study has focused on the air, carbon dioxide, oxygen, and steam agents as the combustion agent in the gas turbine unit and compared their performances with respect to energy and environmental viewpoints. A multi-criteria decision-making analysis based on a sensitivity analysis has been carried out to compare the system performances in two cases of base case and normalized case (performance per mole of input agent). In base case, the system based on the steam agent has produced the maximum power (204.5 kW) and hot air (439 m3/min) and is the most efficient system (46.8 %) and has emitted the lowest emission (12.91 g/kW.min). This system was the best system according to the sensitivity analysis in the base case. In normalized case, the system based on the carbon dioxide agent has presented the best performance according to the sensitivity analysis because it requires the minimum required input agent. Normalized power of 24.6 kW/mol, normalized hot air of 0.65 m3/mol, and normalized hot water of 0.25 L/mol are presented by the system based on carbon dioxide.

Preparation of Primary Explosive by Self-assembly of Combustible and Oxidizing Agents under Acid.

In order to further explore the effect of ligands on the performance of primary explosives and gain a deeper understanding of the coordination mechanism, we designed furan-2-carbohydrazide (FRCA), a ligand, by using oxygen-containing heterocycles and carbohydrazide. Then, FRCA and Cu(ClO4)2 were used to synthesize coordination compounds [Cu(FRCA)2(H2O)(ClO4)2]·CH3OH (ECCs-1·CH3OH) and Cu(FRCA)2(H2O)(ClO4)2 (ECCs-1). The structure of the ECCs-1 was confirmed by single-crystal X-ray diffraction, IR and EA characterization. Further experiments on ECCs-1 show that ECCs-1 has good thermal stability, but is sensitive to mechanical stimuli (impact sensitivity = IS = 8 J, friction sensitivity = FS = 20 N). The predicted value of the detonation parameter is DEXPLO5 = 6.6 km s-1, PEXPLO5 = 18.8 GPa, but the ignition test, laser test, and lead plate detonation experiment show that ECCs-1 has excellent detonation performance, which is very worthy of attention.

Spectroscopic Characterization and Luminescence Study of Zinc Aluminate Nanocrystals Prepared by Microwave Combustion Method using Natural Black Pepper as Combustion Agent

Spectroscopic Characterization and Luminescence Study of Zinc Aluminate Nanocrystals Prepared by Microwave Combustion Method using Natural Black Pepper as Combustion Agent

Voltage-Mediated Enhances Lithium-Ion Storage in LiTiOPO4 by Combustion Method

Abstract LiTiOPO4 was prepared by solid-phase combustion method using citric acid as fuel. The LiTiOPO4 materials were characterized by X-ray diffraction test (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The XRD test showed that the synthesized samples were pure phases and the addition of different weight fractions of the combustion agent citric acid did not change the phase structure of the LiTiOPO4. The microscopic observations revealed that the LiTiOPO4 prepared after the addition of citric acid as a combustion agent was a sheet-like stacked structure. The electrochemical test results showed that the rate discharge capacity of LiTiOPO4 anode at 5000 mA g−1 maintains 184.7 mAh g−1 in the voltage range of 0.01–3.0 V and keeps at 147.2 mAh g−1 after 500 cycles. The LiTiOPO4 anode exhibits excellent cycling stability and good reversibility, which is attributed to the high crystallinity of LiTiOPO4 prepared by solid-phase combustion and the lamellar stacked layer structure that facilitates lithium-ion insertion/de-insertion.

Composition Analysis and Identification of Ancient Glass Products Based on Optimized BP_Adaboost Strong Classifier

Due to the different combustion agents used in the manufacture of glass in ancient China and abroad, there are apparent differences in the composition of ancient glass products in China and abroad. This paper presents a reduction analysis and identification of the composition of ancient glass products, which is of great significance to the study of the Silk Road and the history of the development of glass products. This paper analyzes and identifies the composition of ancient glass products based on the data of C questions of the CUMCM competition. The study first used a neural network optimized by a genetic algorithm to screen out the elements closely related to the weathering condition and used regression to reduce the composition of the weathered samples. The reduced samples were subclassified by systematic clustering according to their respective compositions, and high-potassium glass and lead-barium glass were classified into two subclasses each. The classification basis was reasonably clarified by factor analysis. Finally, the strong classifier was optimized to identify and classify the samples based on the unknown sample components. The correct identification rate reached 100%, which played a good role in distinguishing the weathered Chinese and foreign glass products.

Preparation and Properties of Pyrotechnic Binder Encapsulated α‐AlH3 Composites by Solvent/Anti‐solvent Method

AbstractAlpha‐aluminum hydride (α‐AlH3) is an ideal energetic combustion agent, but its poor stability and safety limit its application. Therefore, we prepare different composites by using the solvent/anti‐solvent method to coat different pyrotechnic binders on the surface of α‐AlH3. The vacuum stability test show that the minimum outgassing of Shellac‐coated α‐AlH3 composite is only 1.2 mL/g at 50 °C for 6 days. Due to the good electrical insulation properties of Viton, Viton‐coated α‐AlH3 composite have the highest E50 value of electrostatic sensitivity. In addition, the pyrotechnic binders coating not only protects the activity of the α‐AlH3 but also effectively increases its burning rate. Viton‐coated α‐AlH3 composite have more gaseous products and maximum flame area during combustion. This study illustrates that α‐AlH3 coated with pyrotechnic binders is a means to address its stability and safety, laying the foundation for its application in solid propellants.

Structural, magnetic and antibacterial studies of gadolinium doped cobalt ferrite nanoparticles synthesized at low temperature

In this work structural, magnetic and antimicrobial studies of gadolinium (Gd) doped cobalt ferrite nanopowder samples were synthesised through facile auto-combustion route using citric acid as combustion agent. The pristine nanopowders were sintered at 600 °C. X-ray diffraction (XRD), infrared spectroscopy (IR) measurements indicated the formation of a single spinel phase. The lattice constant gradually increased from 8.3801 Å to 8.3915 Å with increasing Gd concentration. The average crystallite size varied from 54 nm to 42.7 nm. The correlation between the cation distribution from XRD and the magnetic properties is discussed. The substitution of Gd ions significantly reduced the magnetisation from 60.6 to 36.6 emu g−1 and increased the coercivity. Antimicrobial activities of pure and Gd substituted cobalt ferrite are carried out against Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and also against fungi strain (Aspergillus niger) pathogens, suggesting that Gd substitution significantly improves the activity of cobalt ferrite nanopowders.

Characterization and luminescent properties of lanthanum borate prepared by solution combustion method

A series of LaBO3:Pr3+ luminescent materials were prepared by using lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and boric acid (H3BO3) as raw materials, glycine (C2H5NO2) as combustion agent and praseodymium nitrate hexahydrate (Pr(NO3)3·6H2O) as modifier. XRD, SEM, XPS, UV–vis DRS, PL and other characterization methods were used to analyze the phase structure, micro morphology and ionic valence of the luminescent materials, and the fluorescence properties of the materials were characterized in detail. The results showed that Pr3+ ions had entered into the lattice of LaBO3 after calcined at 850 °C for 4 h by solution combustion method. The macro particle size of the material was 790 nm, which belongs to submicron material. The valence state of rare earth ions was stable due to high temperature or other factors during the preparation process. The band gap of the powder was 6.62 eV. The fluorescence results showed that the main luminescence peak of LaBO3:Pr3+ powder was located at 670 nm at the excitation wavelength of 448 nm, and the luminescence intensity was the highest when the doping ratio was 0.03.

Effect of 5-Amino-1H-Tetrazole on Combustion Pyrolysis Characteristics and Kinetics of a Combustion Tear Gas Mixture

Taking the combustion tear gas mixture as the research object, the system formula was optimized by adding a different mass fraction of 5-amino-1H-tetrazole(5AT). TG-DSC, a thermocouple, and a laser smoke test system were used to characterize the characteristic combustion parameters such as combustion temperature and velocity, as well as the end-point effects such as smoke concentration and particle size. Starink’s method, the Flynn–Wall–Ozawa method, and the Coats–Redfern method were used to evaluate the pyrolysis kinetic parameters of the samples. The results show that when the mass fraction of 5-amino-1H-tetrazole in the system is 10%, the maximum combustion temperature of the sample decreases by nearly 70 °C and the smoke concentration increases by 12.81%. The kinetic study also found that with a different mass fraction of 5-amino-1H-tetrazole in the system, the main reaction model of the mixed agent in the first, third, and fourth stages of pyrolysis changed significantly, but for the second stage of sample pyrolysis, the main reaction model (the A4 model) showed a high degree of consistency, which can be considered as the thermal diffusion stage of the tear agent capsicum oleoresin (OC) (the temperature range is 220~350 °C), which is highly consistent with the results of the TG-DSC analysis. It was also confirmed that OC’s thermal diffusion is mainly concentrated in this stage. The results of this study show that adding an appropriate amount of the combustible agent 5-amino-1H-tetrazole to the combustion tear gas mixture can improve its combustion performance and smoking performance, which provides an important, new idea for the development of a new generation of safe, efficient, and environmentally friendly tear gas mixtures.

Enhanced combustion behavior of TKX-50/B/NC composites via electrospray

ABSTRACT TKX-50, as a representative of a new nitrogen-rich energetic compound, has attracted extensive interests due to its high energy and low sensitivity properties. As an important energetic material, combustible agent has great influence on improving the energy level of explosives and propellants. Boron powder has become the most potential combustible agent in energetic fields because of its unique performances. In this work, nano-boron-based microspheres containing TKX-50 are directly fabricated by electrospray deposition. The prepared microspheres showed high monodispersity with particle size ranging from ~1–3 μm. Thermal behavior results show that the mass gain of the electrostatically sprayed sample is 163.3%, which is much higher than that of pure boron and physically mixed samples. Combustion behavior tests show that electrosprayed microspheres exhibit outstanding performance in comparison to physical mixed sample, the peak pressure improved by 85%, the burning time decreased by 21% and the pressurization rate improved by 136%. These excellent properties are probably related to their uniform microstructure. Therefore, electrospray preparation of microspheres with controllable structure has a good application prospect in energetic materials.

A Facile Green Synthesis and Optical Characterization of Nano Zinc Aluminate Phosphor

This study presents a facile green synthesis of zinc aluminate nanophosphor by the microwave combustion method. Natural Piper nigrum seeds extract was used as a combustion agent. To study the effect of annealing temperature on structural, compositional, and optical properties of nano zinc aluminate, as-synthesized sample was further annealed at temperatures 700⁰C and 900⁰C. The structural and optical characterizations were carried out using XRD, UV-Vis DRS, FTIR, and PL spectroscopy. The XRD and FTIR confirmed the formation of nano zinc aluminate. The calculated average crystallite sizes were between 5-20 nm. The effective energy bandgap of prepared nano zinc aluminate was found to be 4.48 eV, larger than the bulk bandgap of zinc aluminate. Further, the effective band gap was increased with higher annealing temperatures. The PL spectra exhibited intense emission in the UV and blue region with weak emission in the red region.

A novel FEM-FVM coupled method of evaluating the explosion shock wave of a thermobaric bomb on the internal and external flow characteristics of aircraft

The high-temperature and high-pressure shock waves generated after the explosion of a thermobaric bomb have a considerable impact on the aerodynamic characteristics of aircraft. Taking a typical thermoelastic model as the object, the explosion process was calculated by LS-DYNA software. The obtained pressure–time history curve data were written into a UDF function and coupled with Fluent software. At the same time, the afterburning effect of the combustion agent was considered. The influence of the explosion effect on the flow field characteristics of an M6 wing and the inlet of a turboprop engine was evaluated. Thus, an FEM-FVM co-simulation method was established. The results showed that when affected by the explosion shock wave of a thermobaric bomb, the maximum changes in the lift, drag, and pitch moment of an M6 wing in a very short period of time are 29, 13, and 7 times those of the original, respectively, and the effect is mainly reflected in the first shock wave. For the flow field in the intake duct, the total pressure recovery coefficient of the outlet section is reduced by up to 68%, and the distortion rate is increased by up to 325%. This change may even lead to engine surge and shutdown. Moreover, regardless of internal or external flow, the high-temperature airflow after detonation also affects the thermal protection ability of the wing or the inlet profile. All these factors need to be considered comprehensively in the design phase of the aircraft.

Morphochemical investigation on the enrichment and transformation of hazardous elements in ash from waste incineration plants

The transformation of heavy metals in ash from waste incineration plants is significant for ash management. The migration behavior of trace elements in ash after combustion, semidry deacidification, fabric filtration, and chelating agent stabilization was investigated from one waste incineration plant. The hazardous elements Zn, Pb, and As were enriched in raw fly ash (ash produced at a combustion temperature of 850–1100 °C) due to their relatively high volatility. Mercury, Cd, and Pb were captured in fly ash2 and processed by activated carbon and fabric filters. The removal rate of As (71%) was the highest among all studied elements due to a large amount of quinquevalent As removed. However, the average removal rate of elements in fly ash was only 13%. In the finally obtained fly ash3 (after chelating agent stabilization), a larger particle size (~100 μm) was found than that of raw ash. Furthermore, fly ash3 contains HgSO4 and trivalent As, which are toxic and likely to be precipitated when the fly ash3 is next utilized or deposited in a landfill, causing environmental risks.

Fabrication of combustion pyrotechnics for laser and electromagnetic interference shielding

The contradiction between flammability and packing density is the technical bottleneck for combustible smoke agent. Herein, polyurethane (PU) foams with flammability and resilience were prepared with polyol and isocyanate as raw materials by chemical foaming method, then compounded with metal powders, polytetrafluoroethylene (PTFE), phthalic annychide (PA), etc. in a certain proportion and pressed into pyrotechnic grain to obtain eco-friendly combustion aerosols with compact density of about 1.15 g/cm3. The resulting combustion smoke agent combined the advantages of PU foam and pyrotechnic with easy ignition, large smoke production, long duration and low environmental pollution. The transmittance of aerosols for 532 nm and 1064 nm lasers was close to 0, and the EMI SE reached up to 65 dB and 35 dB in GPS band and X band, respectively. In addition, the resulting pyrotechnic grains exhibited good mechanical strength and elasticity for sample 1:25, with a compressive strength of 22 MPa and an elastic modulus of 195 MPa. The resulting combustion smoke agent is expected to play a potential role in the field of electromagnetic damage and protection.

Hydrogen-induced change of oxidation combustion characteristics of Al2Mg alloy

The effects of solid-state hydrogen introduction on the oxidation combustion property and mechanism of Al 2 Mg alloy were investigated by means of thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectrum. It was found that the starting combustion temperature of hydrogenated Al 2 Mg alloy is lowered by about 150 °C as compared with pristine Al 2 Mg alloy, due to its distinct phase composition of MgH 2 + Al as well as loose, porous and refined particle characteristics. The first-stage oxidation for the Al 2 Mg alloy hydride can be ascribed to the dehydrogenation of MgH 2 to form Mg followed by the reaction of Mg with oxygen to form MgO, which is entirely different from the oxidation mechanism of Al 2 Mg alloy. During the second-stage oxidation, MgAl 2 O 4 , γ-Al 2 O 3 and α-Al 2 O 3 were formed for both Al 2 Mg alloy and its hydride. However, almost no AlN can be generated for the Al 2 Mg alloy hydride with respect to Al 2 Mg alloy. • Solid-state hydrogen is introduced into Al 2 Mg alloy combustion agent. • The starting combustion temperature is reduced by 150 °C. • MgH 2 dehydrogenates and then reacts with oxygen during the first-stage oxidation. • Almost no AlN forms during the second-stage oxidation.