Burning Time Research Articles

Co-combustion of bituminous coal and industrious sludge under non-isothermal and isothermal conditions: Thermal behaviors, kinetic analyses, and heavy metals migration

Considering the environmental pollution caused by the direct stacking or landfilling of various sludge, the combustion characteristics of bituminous coal, Fe-rich industrious sludge, and their blend were studied using thermogravimetric analysis at non-isothermal and isothermal conditions. It was found that the volatile matter in sludge with low C/H ratios will be released and burned in the low-temperature stage, then the generated heat will promote extra heat for the combustion of fixed carbon in coal when the addition of sludge was greater than 60%. The used Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods were more accurate for coal, sludge, and their blend with low sludge addition. After comparing the activation energy, a suitable addition of sludge was found to improve the combustion and kinetic characteristics of fixed carbon but do less help to volatile matter in coal. As to the heavy metals emission, the synthetic effect of the blend combustion enhanced the Pb emission when sludge addition was more than 60% but almost did not affect Cr, Ni, Zn, and Cu. By sampling dynamically during the co-combustion, it was found that the leaching toxicity of heavy metals was greatly related to the combustion degree. The stabilization of Al, Ca, Cr, and Zn was finished as their leaching toxicity decreased to a constant value before the burnout of fixed carbon (100∼120s) while that of Ni was slightly delayed, especially when the coal was added. Besides, the leaching concentration of Cu gradually increased with combustion time and its stabilization cost more time. Such a time-controlled combustion strategy may also be worthy of further research to help dispose of other solid wastes with similar composition.

Diagnostic investigation of devolatilization, ignition, and flame fluctuation during laminar oxy-coal combustion

The rapid development of measurement technology has created possibilities for the advancement of intelligent combustion diagnostics. The high-speed OH-PLIF was used to investigate homogeneous ignition and combustion characteristics of gas-solid two-phase flame in a laminar flow reactor of oxy-coal combustion. The primary focus is to investigate the physico-chemical processes of gas-solid interaction during the early stages of combustion. The image processing was employed to analyze the flame features and then obtain the ignition mechanism, OH distribution, species radiations, and fluctuation frequency. Results show that the homogeneous reaction dominates the ignition and volatile combustion at the early stages of oxy-coal flame. The ignition delay time and volatile burning time decrease with the increasing gas temperatures and oxygen concentrations. The fluctuation dominant frequency increases from 190.5 Hz to 243.2 Hz at the ambient temperature from 1200 to 1800 K. The dominant frequency stabilizes between 243.2 Hz and 243.5 Hz at the ambient temperature from 1500 to 1800 K. The dominant frequency undergoes a shift to a maximum limit of 243.5 Hz from 1200 to 1800 K. When the oxygen concentration increases from 20 % to 40 %, the dominant frequency continues to rise from 244.8 Hz to 268.7 Hz.

Effect of flame heating on thermal runaway propagation of lithium-ion batteries in confined space

As the thermal runaway (TR) of lithium-ion batteries (LIBs) may be induced in enclosed systems, thermal hazards from the ceiling fire contribute to the TR propagation in battery module. However, the characteristic of TR propagation in confined space, especially the heating effect of battery flame, is still unclear. To fill the knowledge gaps, a refined study has been conducted with LiFePO4 battery modules in a confined space. The TR propagation behavior, battery temperature, propagation time and the heat transfer are analyzed quantitatively with different plate heights and heating modes. The results show the TR propagation occurs at 2, 5 and 10 cm plate height while no propagation at higher height. The lower height leads to the increasing of flame heating effect and decreasing of TR propagation time. The flame heating reduces the demand of the heat transferred through the conduction for TR propagation. Further, the heat from ceiling flame has little change with different heights as it is mainly depended on the combustion time. Finally, the heating power of ceiling flame is analyzed and the maximum increases from 1400.3 to 2594.6 W when height decreases from 15 to 2 cm, while it is higher with continuous heating.

The effect of initial conditions (temperature and pressure) on combustion of Fe-coated-aluminum hydride nanoparticles using the molecular dynamics approach

Highly combustible elements like beryllium, lithium, Al, Mg, and Zn have the highest combustion, increasing the heat in explosives and propellants. Al can be used because of its greater availability. Reducing the size of Al nanoparticle (NP) increases the combustion rate and decreases the combustion time. This paper studied the effect of initial conditions on the phase transition (PT) and atomic stability times of Fe-coated-aluminium hydride (AlH3) NPs. The molecular dynamics (MD) technique was used in this research. The microscopic behavior of structures was studied by density (Den.), velocity (Vel.), and temperature (Tem.) profiles. Heat flux (HF), PT, and the atomic stability of the structure were examined at different initial pressures (IP) and initial temperatures (IT). According to the achieved results, Den., Vel., and Tem. values had a maximum value of 0.025 atoms/Å3, 0.026 Å/ps, and 603 K. By increasing IT in the simulation box to 350 K, HF in the samples increases to 75.31 W/m2. Moreover, the PT time and atomic stability time by increasing IP reach to 5.93 ns and 8.96 ns, respectively. Regarding the importance of the phenomenon of heat transfer and PT of nanofluids (NFs), the findings of this study are predicted to be useful in various industries, including medicine, agriculture, and others.

Analysis of carbon nano particle variant as the propellant fuel to increase specific impulses of rockets

Background: This study compares propellant fuels’ specific thrust and impulse parameters using nanocarbon variant fuels from coconut shells and coal. Specific impulses and impulses are essential parameters that determine rocket performance. The specific thrust and impulses are influenced by fuel type, material composition, heat flow, and burning time parameters. The characteristics of nanocarbon as a fuel are proven to have high-value features and a long combustion time. This parameter is essential to add value to specific thrusts and impulses. Methods: The method to prove the quality of solid fuel material was done experimentally. The composition of the propellant fuel variant mixed with NH4ClO4 as an oxidizer through the printing process and sample testing was carried out using scanning electron microscope (SEM), X-ray diffraction analysis (XRD), combustion time, and specific impulse tests. Results: Test results with the composition of CBK2 (Coconut Shell + NH4ClO4 + Binder + Al = 15: 70: 10: 5) produced a specific impulse of 267 seconds or an increase of 37 seconds without carbon. CBB2 (Coal + NH4ClO4 + Binder + Al = 15: 70: 10: 5) produced a specific impulse of 261 seconds or an increase of 31 seconds. Conclusions: The composition of nanocarbon as a solid fuel propellant has been proven to increase a rocket’s thrust and specific impulses. After all the material variants have been tested for thrust and specific impulse, the best rocket propellant is CBK2.

Study of the influence of external heat and mass exchange on the features of combustion and extinction of gas suspensions of carbon particles

In the work, the regularities of the influence of heat and mass exchange of gas suspensions of carbon particles with the external gas environment on the processes of ignition, burning and quenching at different mass concentrations of carbon fuel are studied. A monodisperse gas suspension of carbon particles located in a gas heated to a high temperature, which contains an oxidant, is considered. As a result of the conducted physical and mathematical modeling, the following characteristics of high-temperature processes were determined: induction period, burning time and time of complete transformation of particles, critical parameters of ignition and extinction of particles. The influence on these characteristics of the initial particle diameter, mass concentration and temperature of the surrounding gas was analyzed. It was found that the external heat and mass exchange has a slight effect on the induction period and critical parameters of the ignition of gas suspensions, but it has a sufficiently strong effect on the characteristics of the combustion and extinguishing processes. The existence of an upper limit for fuel concentrations and particle diameters at which complete combustion of gas suspensions is not observed in the absence of external mass transfer is proved. Ranges of mass concentrations were found for which complete conversion of carbon fuel burning in the form of gas suspensions is carried out. It is shown that for open gas suspensions, the range of mass concentrations, where complete transformation of particles is observed, expands to the side of large values. The diameters of the particles characterizing the quenching of gas suspensions, taking into account the external mass transfer, are smaller, as a result of a greater supply of oxygen to the volume of the gas suspension.

Characteristics of fires in coal mine roadways and comparative analysis of control effectiveness between longitudinal ventilation and cross-section sealing

Enhancing ventilation velocity and constructing sealing walls are prevalent strategies aimed at managing fires in coal mine roadways. To assess the efficacy of these control tactics, this study investigates the fire characteristics with varying heat release rates (HRR) using a 1:10 experiment and numerical simulations. Results reveal that an increase in the HRR corresponds to a decrease in ceiling temperature, alongside an increase in both smoke back-layering length and critical velocity. Longitudinal ventilation proves effective in lowering ceiling temperature and inhibiting upstream smoke propagation from fire source, but it does not extinguish the fire, instead reducing downstream visibility and escalating risk downstream of fire. When the actual velocity exceeds 3.1 m/s, it effectively prevents smoke backflow in a fire of 10 MW. Cross-section sealing works by reducing oxygen levels within roadway to suffocate the fire. As the sealing ratio increases, flame inclination angle and burning time decline, whereas ceiling temperature rises. When it exceeds 75%, CO concentration sharply rises and fire enters the extinguishment phase, if ratio is 100%, fire with higher HRR are extinguished more quickly. This study provides valuable insights into roadway fire control: longitudinal ventilation aids personnel evacuation, while cross-sectional sealing effectively extinguishes fires in unpopulated spaces.

Survey of burning rate measurements in small solid rocket motors

Burning rate plays a crucial role in determining the performance of solid rocket motors (SRMs). In the traditional approach for solid propellant propulsion, technical activities regarding burning rates are developed at three different operational levels: (i) Strand burners or laboratory-scale devices in general; (ii) Small-scale motors (SSMs); And (iii) full-size or end-item rocket motors. While strand burners are extensively used for propellant development (formulation exploration, ingredients screening, performance verification, and production control) and relatively little is done experimentally at the full-size motor level (being large-scale experimentation too expensive and dangerous), a lot is usually carried out at SSM level to obtain burning rate information under motor operating conditions. In the introductory part of this work, burning rate fundamentals are recalled and burning rate measurement devices are quickly summarized. Then, a survey of subscale motors is conducted and several automated procedures to deduce burning rate from SSM testing are analyzed. Data reduction methods commonly used by leading European companies are based on the thickness-over-time (TOT) definition. Attention is dedicated to procedures used in Italy and France for quality control of the European space launchers (solid propellant boosters of Ariane family and core solid rocket motors of VEGA family). In addition, automated data reduction methods based on mass balance (MB) and often used in USA are investigated. Specific features and general trends of the tested industrial procedures are pointed out. Since for any tests the actual burning rates are unknown, results can only be compared based on the statistical quality of the deduced ballistic data. Mainly reproducibility, ease of application, and suitability for automated computer implementation are of interest to industrial users. The effects of test variability, input data quality, and data reduction methods on result reproducibility are discussed with reference to fire tests of the successful Ariane-5 solid boosters. The systematic analysis of industrial data conducted in this work suggests that improving the actual mix reproducibility and quality of experimental data is more important than perfecting the current data reduction methods. Moreover, the international trends suggest that the fundamental TOT procedures are being replaced by MB procedures or advanced TOT procedures with burning times evaluated using pressure integrals.

Experimental study on the effect of phase change material on thermal runaway characteristics of lithium-ion battery under different triggering methods

Although paraffin (PA) is a commonly used phase change material (PCM) for lithium-ion battery thermal management, its flammability may increase the risk of thermal runaway. This paper investigates the influence of PA on the thermal runaway, and the highly effective flame retardant hexa-phenoxy-cyclotriphosphazene (HPCP) was employed to suppress PA combustion and mitigate the thermal runaway hazard. Penetration and heating were used to induce thermal runaway. The battery surface temperature, the material temperature and the flame condition were recorded. The results show that penetration caused more violent reactions than heating, the battery temperature of penetration was 25 % higher than that of heating, while heating led to more harmful flame with a flame temperature over 1000 °C. PA delayed the onset of thermal runaway by 58.7 %, however, the higher temperature and longer burning time were a sign of increased danger. HPCP inhibited PA combustion, reducing the burn time by 35.7 %, while HPCP/PA delayed thermal runaway and controlled the battery flame, with a minimum of 43.5 % reduction in flame height. This study may provide a reference for the safe design of thermal management system for lithium-ion battery.

Living with visible scars: The social stigmatization of burn survivors.

Objective: To assess the social stigmatism, in adult burn survivors with visible scars, that they face in the society. Study Design: Cross-sectional study. Setting: Department of Plastic Surgery and Burns, Sheikh Zayed Medical College and Hospital, Rahim Yar Khan. Period: May 2022 to April 2023. Material & Methods: The study included 64 participants aged 16 to 55 years who were awaiting reconstructive surgery and had experienced visible scarring from burns for over six months. Data on perceived stigmatization were collected using the Perceived Stigmatization Questionnaire (PSQ). The demographic profile, burn characteristics, and socio-economic factors of the participants were also analyzed. Statistical analysis was performed using SPSS 27, including post-stratification chi-square tests. Results: Of the 64 participants, 87.5% reported experiencing perceived stigmatization, with gender being a significant factor. Notably, 91.7% of females reported stigmatization, compared to 75% of males. Marital status, educational level, scarred body parts, visibility of scars in public, and age at the time of burn were also strongly associated with perceived stigmatization. The study revealed the mean scores for three domains: Absence of friendly behavior (2.58 ± 0.64), Confused/Staring behavior (3.15 ± 0.57), and Hostile behavior (2.19 ± 0.72). Conclusion: This study underscores the prevalence of perceived stigmatization among burn survivors, particularly those with visible scars on their face and hands. The findings emphasize the importance of social support and awareness campaigns in mitigating these challenges. Greater efforts are needed to address the psychosocial issues faced by burn survivors and promote empathy and inclusivity in society. Further research is crucial to understanding the experiences of burn survivors from diverse backgrounds.

Formulation and Physical Quality Testing of Candles Combining Essential Oils of Red Roses (Rose Hybrid) and White Roses (Rose Alba) as Aromatherapy

Background: There are many aromatherapy options on the market, one of which is in the form of aromatherapy candles. Aromatherapy candles are made using several ingredients and use essential oils that have an aromatherapy scent, a combination of red rose and white rose essential oils. These essential oils are used not only for the treatment and prevention of disease, but also for their effects on mood, emotions, and a sense of well-being.
 Method: In this experimental study, a comparative test was carried out between 5 concentration variations of red rose and white rose essential oils with F1 = 1%:5% ; F2= 2%:4% ; F3= 3%:3% ; F4= 4%:2% ; and F5= 5%:1%, using the same basis. Then an evaluation was carried out by testing the physical quality of the candle aromatherapy preparations which included organoleptic tests, melting point tests, burn time tests, and hedonic tests. 
 Result: The organoleptic test on formulas 1 and 5 produced an even color, no cracks and a characteristic odor, but in formulas 2,3 and 4 the color was uneven and there were depressions. In the melting point test, all formulas are within the standard candle time range, namely 540C, the average burn time test is not more than 2 hours and the preference test is on formula 5.
 Conclusion: The final result is a formula that meets all testing standards, namely 5%:1% formula 5, in which the ratio of essential oils of red roses and white roses is and the ratio of paraffin and stearic acid is 54%:40%.

Utilization of Wasted Cooking Oil and Essential Oil of Sweet Orange Peel (Citrus sinensis) as Aromatherapy Candles

<p><strong>Abstract.</strong> Utilizations of waste cooking oil can be projected to be candles. Sweet orange (<em>Citrus sinensis</em>) peel, considering the large amount of this abandoned waste, also can be utilized as essential oil. This research was conducted to examine the production of aromatherapy candles by purifying the wasted cooking oil and adding the sweet orange peel essential oil. Steam distillation method was used to extract essential oils by determining the effect of raw material conditions on the yield obtained. The essential oils obtained from fresh peel was 1.87% of yield with 94.37% limonene, while dry one was 2.16% yield with 94.67% limonene by GC-MS analysis. Adsorption method by activated carbon was carried out to purify the wasted cooking oil as candle materials, varied by 7%, 10%, and 13% mass of activated carbon. The addition of the highest mass of activated carbon gave the lowest absorbance and indicated that the purified oil was the brightest. Utilization of refined wasted oil was mixed with stearin and sweet orange peel essential oil of 2%, 4%, and 6% by weight as aromatherapy candle product. Characteristics of candle was investigated by analyzing the melting point, burning time, organoleptic, and preference test for respondents and resulted that all characters meet Indonesian National Standard. Purification of wasted cooking oil varied by activated carbon mass influenced the color of the candles. The addition of essential oils influenced the smell, melting point and burning time of candle, the essential oil addition makes lower melting point and faster burning time.</p><p><strong>Keywords:</strong></p><p align="left">Aromatherapy Candles, Sweet Orange Peel Essential Oil, Wasted Cooking Oil</p><p><strong><br /></strong></p>

Electrostatic Spraying Microspheres of Nano Boron and Its Constant-Volume Combustion with Potassium Nitrate

ABSTRACT The nanometer boron (nB) powders have become the most promising high-energy additive in the field of fuel-rich solid propellants due to their extremely high gravimetric and volumetric calorific value. However, further applications are limited by its disadvantages such as easy agglomeration, easy oxidation, high ignition temperature, and incomplete energy release. Herein, nB powders were pre-agglomerated into microspheres by electrostatic spray method using fluoropolymer (F2602) as binders. The morphology and structure of the samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray energy spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and Brunauer-Emmett-Teller (BET). Results showed that the pre-agglomerated nB microspheres had good dispersion, high sphericity, and no surface oxide. The thermal performance and combustion performance of the samples were characterized by a synchronous thermal analyzer and combustion pressure test device. Results showed that the nB microspheres had the highest oxidation weight gain within 1000°C and lowest activation energy compared to the same scale micron boron. In addition, the microspheres significantly shorten the combustion time and improve the combustion efficiency.The pressurization rate of nB microspheres is 4.12 times that of micron boron powders and 2.85 times that of nB powders. These excellent properties may be related to its unique spherical porous structure. Therefore, the preparation of nB microspheres with controllable structure by electrostatic spraying has a good application prospect.

Flame propagation modes for iron particle clusters in air, Part II: Transition from continuous to discrete propagation mode under strong convection effects

Combustion of iron powder is a promising option for clean and sustainable generation of heat and power. However, a fundamental understanding of the flame propagation mode is missing, especially under strong convection effects. In part I of this work, we analyzed the modes of flame propagation under weak convection effects and estimated the discreteness parameter as a ratio of the particle burn time to the conduction timescale. We found that both, the selection of temperature at which thermal properties are evaluated, and the selected length scale, are critical for a reliable prediction of the transitional particle spacing indicating the transition from the continuous to the discrete mode. In this paper, we extend our previous work by studying the effect of convection on inter-particle heat and mass transfer using boundary layer resolved numerical simulations. It is shown that for increasing convection, iron flames transition from the continuous to the discrete mode at higher particle distances. Taking into account both diffusion and convection-dominated heat transfer, an extension for the scaling of transitional particle spacing of part I is proposed. Furthermore, since iron flames could experience varying ranges of particle distances at different velocities in a practical flame, a regime diagram is constructed which is based on the Péclet number and the particle spacing with a boundary separating the two modes of flame propagation. The regime diagram offers orientation for simulations of large-scale flames using Euler–Lagrange methods where boundary layers around the particles are not resolved.

Preparation of Ar–P–N-structured flame retardant via Kabachnik–Fields reaction for fire safety and mechanical reinforcement of polyurethane

Fire safety of polyurethanes (PUs) has limited their further practical applications. To address this problem, we designed novel phosphorus-based flame retardants (P-FR) by incorporating aryl (Ar) groups via Kabachnik–Fields reaction, realizing π–π interaction-reinforced Ar2 and Ar5. Total heat release and peak heat release rate of PU/Ar5, whose flame-retardancy-index of 5.02 due to reduced combustion time, decreased 23.24 and 9.23 %, respectively, compared with neat PU. Moreover, UL94 rating for PU/Ar5 was improved from V-2 to V-0. These results demonstrate that Ar5 effectively generate a barrier effect that blocks oxygen, fuel, and heat. Sluggish mobility and phase transition are responsible for such enhancement due to a delay effect with the existence of π–π interactions and steric hindrance. Encouragingly, tensile strength and toughness of PU/Ar5 were greatly improved by 1345.8 and 670.3 %, respectively, compared with neat PU. We believe that this study could provide a promising method for introducing specific function to flame retardants to enhance fire safety and mechanical properties of composites.

Dissociation of methane and carbon dioxide hydrates: Synergistic effects

The dissociation and combustion of methane hydrate samples were studied experimentally in a laboratory-scale combustion chamber with variable thermal conditions. The temperature in the combustion chamber was varied from 800 °C to 1000 °C to reproduce high-potential reactors and combustion chambers. Ignition delays, combustion times, and combustion product compositions were determined for gas hydrates in the form of granules and tablets. Synergistic effects were analyzed from the simultaneous dissociation of methane and carbon dioxide hydrate samples. Critical conditions were determined in which carbon dioxide prevented methane ignition. The definable parameters were determined as functions of the arrangement schemes of two gas hydrates and input experimental parameters, and the corresponding predictive mathematical expressions were obtained. Methane hydrate granules were found to ignite significantly faster than methane hydrate tablets. An increase in the temperature in the combustion chamber was proved advisable in the case of methane hydrate tablets. Granulated hydrate samples ignited consistently in a wide range of temperatures, and the ignition delay times changed negligibly with varying temperature. The methane hydrate combustion stability was analyzed, and a model was developed describing the patterns and predicting the carbon dioxide hydrate flow rate required for fire suppression. Finally, conditions were identified in which the synergistic effects of simultaneously dissociating hydrates with flammable and nonflammable gases would make it possible to effectively manage their safe and sustainable application in the energy industry.

Synthesis and Characterization of Flame Retarded Rigid Polyurethane Foams with Different Types of Blowing Agents.

In this study, rigid polyurethane foams modified with non-halogenated flame retardant were obtained. The foams were synthesized using two systems containing different blowing agents. In the first one, cyclopentane and water were used as a mixture of blowing agents, and in the second one, only water was used as a chemical blowing agent. The systems were modified with the additive phosphorus flame retardant Roflam F5. The obtained modified foams were tested for their flammability and basic properties, such as apparent density, closed-cell contents and analyses of the cell structures, thermal conductivity, mechanical properties, and water absorption. Increasing the content of Roflam F5 caused a decrease in temperature during the combustion of the material and extended the burning time. The addition of 1.0 wt.% phosphorus derived from Roflam F5 caused the modified rigid polyurethane foam to become a self-extinguishing material. The increase in the content of Roflam F5 caused a decrease in the total heat release and the maximum heat release rate during the pyrolysis combustion flow calorimetry. The foams with the highest content of flame retardant and foamed with a chemical-physical and chemical blowing agent had a lower total heat release by 19% and 11%, respectively, compared to reference foams.

Phase change and combustion of iron particles in premixed CH[formula omitted]/O[formula omitted]/N[formula omitted] flames

Metal powder is a promising carbon-free and recyclable energy carrier. Direct combustion of the micron-sized iron particles involves complex physical and chemical processes, such as heat transfer, surface reaction, and phase change. In this work, computational modelling of these processes is investigated and validated against experiments. A single iron particle combustion and phase change model is proposed in an Eulerian–Lagrangian framework. The new phenomenological model considers five stages, i.e., solid phase oxidation, melting of iron oxides and raw iron, liquid phase oxidation, cooling of liquid iron oxides, and solidification of super-cooled liquid iron oxides. The proposed model is first validated and then adopted in simulations of micron-sized iron particle combustion in premixed CH4/O2/N2 flames to study the effects of ambient temperature and oxygen concentration on single iron combustion. Results show that the new model is capable of replicating the melting, heterogeneous surface reaction, cooling, and solidification processes. Two-stage solidification is observed in experiments and modelled in simulations. This two-stage solidification includes a fast solidification with a significant temperature rise (∼150–200 K) and a thermal equilibrium solidification featuring a constant temperature and a slight particle radiant intensity decrease. In addition, a diffusion-controlled mechanism is identified during the melting process, in which the oxygen concentration dominates the melting time and the subsequent burning time. Furthermore, it is found that the reaction between iron and CH4/O2/N2 flame products, such as CO2 and H2O, plays a non-negligible role in the iron combustion process.

Fire Performance of Cotton Fabrics Coated with 10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) Zr-Based Metal-Organic Frameworks.

We investigated the performance of cotton fabrics coated with DOPO-HQ and Zr-based Metal-organic Frameworks when exposed to fire. The chemical structure of the cotton fabrics before and after the coating was characterized using FTIR spectroscopy, and the surface morphology of cotton and their combustion residues was probed via scanning electron microscopy. In our experiments, we used flammability tests and thermogravimetric methods to understand the burning behavior of the coated fibers, as well as their thermal stability. The cotton fabrics coated with DOPO-HQ and Zr MOFs exhibited shorter combustion times, had better thermal degradation properties, promoted the creation of heat-insulating layers, and exhibited improved smoke suppression behavior.

Preparation of NCh-B and NCh-B-Ti nanocomposites and their ignition and combustion performances

To overcome the agglomeration and insufficient combustion of nano-boron (n-B) powders, this study successfully prepared two novel types of boron-based nanocomposites using the acoustic resonance technology, namely high-substitute nitrochitosan/nano-boron (NCh-B) with ratios of 1:3, 1:5, 1:7 and 1:9, and nitrochitosan/nano-boron powder/nano-titanium (NCh-B-Ti) with Ti contents of 5 wt%, 10 wt%, 15 wt% and 20 wt%. The structural morphologies, laser ignition and combustion properties of the composites were systematically investigated. The results suggest that the addition of NCh can significantly improve the dispersion of n-B. NCh-B exhibited a higher combustion performance than n-B, as evidenced by their ignition delay and flame areas. When the laser power density was 81 W, NCh-B5-Ti15% exhibited a combustion time and an ignition delay of 240 ms and 5.5 ms respectively, which were higher and lower than those of NCh-B5 (199 ms and 17 ms, respectively). Furthermore, NCh-B5-Ti15% displayed a lower ignition delay than both n-B powders (12 ms) and NCh-B (11 ms), as well as brighter flames and a larger combustion area. Therefore, the addition of n-Ti can promote the combustion of n-B powders, with the combustion products of NCh-B-Ti including H3BO3, B2O3, TiB2, and TiO. This study provides a new method for improving the ignition performance and combustion efficiency of n-B powders.