A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform inf...A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.展开更多
Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate ...Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.展开更多
The arc ignition based on charring conductive polymers has advantages of simple structure,low ignition power consumption and restart capacity,which bringing it broadly application prospect in hybrid propulsion system ...The arc ignition based on charring conductive polymers has advantages of simple structure,low ignition power consumption and restart capacity,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.In order to optimize the performance of arc ignition system,it is essential to have a deeper understanding of the ignition processes and ignition characteristics of charring conductive polymers.In this paper,the thermal decomposition,electrical conductivity and thermal conductivity characteristics of charring conductive polymers with different conductive additives and matrix materials were comprehensively evaluated.An experimental investigation was conducted to determine the ignition behaviors and characteristics of different charring conductive polymers in a visual ignition combustor.The experiment result showed that the ignition delay and external energy required for ignition are negatively correlated with voltage and initial temperature of the ignition grain,but positively correlated with oxidizer flow velocity.Compared with charring conductive polymers containing multi-walled carbon nanotube,the ignition delay of charring conductive polymers with carbon black is significantly higher and the pyrolysis time is relatively longer.However,the ignition and initial flame propagation of charring conductive polymers with carbon black is more violent and more inclined to carbon particle ignition.Finally,the restart characteristic of different charring conductive polymers was studied.The ignition delay and external energy required for ignition of different charring conductive polymers all reduced with the increasing of the number of ignitions.However,the ignition characteristics would not change a lot after repeated ignition.展开更多
The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of...The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.展开更多
To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together wit...To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.展开更多
Charring composites are widely used in the thermal protection system(TPS) to consume the intense aerodynamic heating during vehicle reentry. The ablation and thermal responses for the charring composites can be studie...Charring composites are widely used in the thermal protection system(TPS) to consume the intense aerodynamic heating during vehicle reentry. The ablation and thermal responses for the charring composites can be studied by using a numerical ablation model, in which the surface ablation and volume ablation could be taken into account. The coupling interactions among temperature, gas motion and interior pressure producing the pyrolysis gas could make the computation more complicated. A multi-physics model is developed to simulate the thermal response coupled with volume ablation and surface ablation. After studying four typical ablation cases, the model is validated, and then the heat transfer mechanisms in ablation are investigated. It is found that the viscous dissipation energy by the motion of pyrolysis gas can be neglected in the simulation. Also, the flow of pyrolysis gas plays an important role in the temperature response, especially under high heat flux condition.展开更多
A modified model of pyrolysis for charring materials in fire has been proposed in this note. In this model some special factors which show the effect on pyrolysis are considered, i.e. heat loss by convection and radia...A modified model of pyrolysis for charring materials in fire has been proposed in this note. In this model some special factors which show the effect on pyrolysis are considered, i.e. heat loss by convection and radiation caused by surface temperature rise and shrinkage of char surface are considered. Experimental device is designed specially for validating the reliability of the model. Effects of density of materials and heat radiation on pyrolysis of materials have also been investigated.展开更多
Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to t...Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.展开更多
In recent decades,annual urban fire incidents,including those involving ancient wooden buildings burned,transportation,and solar panels,have increased,leading to significant loss of human life and property.Addressing ...In recent decades,annual urban fire incidents,including those involving ancient wooden buildings burned,transportation,and solar panels,have increased,leading to significant loss of human life and property.Addressing this issue without altering the surface morphology or interfering with optical behavior of flammable materials poses a substantial challenge.Herein,we present a transparent,low thickness,ceramifiable nanosystem coating composed of a highly adhesive base(poly(SSS1-co-HEMA1)),nanoscale layered double hydroxide sheets as ceramic precursors,and supramolecular melamine di-borate as an accelerator.We demonstrate that this hybrid coating can transform into a porous,fire-resistant protective layer with a highly thermostable vitreous phase upon exposure to flame/heat source.A nanosystem coating of just~100μm thickness can significantly increase the limiting oxygen index of wood(Pine)to 37.3%,dramatically reduce total heat release by 78.6%,and maintain low smoke toxicity(CIT_G=0.016).Detailed molecular force analysis,combined with a comprehensive examination of the underlying flame-retardant mechanisms,underscores the effectiveness of this coating.This work offers a strategy for creating efficient,environmentally friendly coatings with fire safety applications across various industries.展开更多
In this study,the catalysis function of Na_(2)CO_(3) to the structural properties of xylan char was well investigated with Na_(2)CO_(3) on,and the electrochemical performance of xylan char as an anode material for sod...In this study,the catalysis function of Na_(2)CO_(3) to the structural properties of xylan char was well investigated with Na_(2)CO_(3) on,and the electrochemical performance of xylan char as an anode material for sodium-ion batteries was tested.The characterization of X-ray microscopy and scanning electron microscopy demonstrated that the morphological structure of xylan char was altered due to the addition of Na_(2)CO_(3) catalyst.The increasement of the Na_(2)CO_(3)/xylan ratio resulted in a slenderization of the triangular prism shape of the char skeleton and a reduction in porosity.X-ray diffraction analysis revealed that Na_(2)CO_(3) promoted the growth of the(004)crystal plane of graphite during xylan pyrolysis,while inhibiting the formation of the(100/101)crystal planes.Raman spectroscopy analysis indicated that the presence of Na_(2)CO_(3)had changed the graphitization degree of xylan char.Electrochemical tests further showed that char prepared with a Na_(2)CO_(3)/xylan mass ratio of 1∶1 exhibited the highest sodium storage capacity.This study provides a pathway for the rational design carbon materials derived from xylan for future applications in energy storage devices.展开更多
This work investigated the effect of Na_(2)CO_(3)on the char structures of cellulose and lignin,respective-ly,and examined the electrochemi-cal performance of the char by act-ing as an active material for coin cells.T...This work investigated the effect of Na_(2)CO_(3)on the char structures of cellulose and lignin,respective-ly,and examined the electrochemi-cal performance of the char by act-ing as an active material for coin cells.The morphology of char can be significantly steered by the con-centration of Na_(2)CO_(3).Scanning electron microscopy analysis demonstrated that the intro-duction of Na_(2)CO_(3)into cellulose at an appropriate concentration led to the formation of tubular structure on its surface after pyrolysis,whereas the tubular structure was absent in the lignin char with the addition of Na_(2)CO_(3)at any concentrations.X-ray diffraction and Ra-man spectroscopy characterizations revealed that all the obtained chars from both cellulose and lignin,with or without Na_(2)CO_(3),were ascribed to non-crystalline graphite.Nevertheless,the crystal orientation of graphite from cellulose and lignin changed after the catalysis of Na_(2)CO_(3).Further electrochemical tests showed that cellulose char had a higher sodium stor-age capacity than that of lignin char.The excellent electrochemical performance of carbon materials derived from cellulose might hold a prospective application in the field of energy storage.展开更多
Catalytic oxidation of NO at room temperature was carried out over nitrogen(N)-doped sludge char(SC)prepared from pyrolysis ofmunicipal sewage sludge,and urea was adopted as nitrogen source.The effects of different N-...Catalytic oxidation of NO at room temperature was carried out over nitrogen(N)-doped sludge char(SC)prepared from pyrolysis ofmunicipal sewage sludge,and urea was adopted as nitrogen source.The effects of different N-doping methods(one-step and two-step method),dried sludge(DS)/urea mass ratios(5:1,4:1,3:1,2:1,and 1:1),SC preparation procedures(pyrolysis only,pyrolysis with acid washing,and pyrolysis with KOH activation and acid washing),and different pyrolysis temperatures(500,600,700,and 800°C)on the catalytic oxidation of NO were compared to optimize the procedure for SC preparation.The results indicated that N-doping could obviously promote the catalytic performance of SC.The one-step method with simultaneous sludge pyrolysis(at 700°C),KOH activation,and N-doping(DS/urea of 3:1)was the optimal procedure for preparing the N-doped SC with the NO conversion rate of 54.7%,whereas the optimal NO conversion rate of SC without N-doping was only 47.3%.Urea worked both as carbon and nitrogen source,which could increase about 2.9%-16.5%of carbon and 24.8%-42.7%of nitrogen content in SC pyrolyzed at 700°C.N-doping significantly promoted microporosity of SC.The optimal N-doped SC showed specific surface areas of 571.38 m^(2)/g,much higher than 374.34 m^(2)/g of the optimal SC without N-doping.In addition,N-doping also increased amorphousness and surface basicity of SC through the formation of N-containing groups.Finally,three reaction paths,i.e.microporous reactor,active sites,and basic site control path,were proposed to explain the mechanism of N-doping on promoting the catalytic performance of NO.展开更多
The carbonization processing(Paozhi)in traditional Chinese medicine(TCM)represents a unique pharmaceutical technology where thermal modification of herbal materials enhances specific therapeutic properties,particularl...The carbonization processing(Paozhi)in traditional Chinese medicine(TCM)represents a unique pharmaceutical technology where thermal modification of herbal materials enhances specific therapeutic properties,particularly hemostatic and antioxidant effects.Despite centuries of empirical applications,the scientific basis underlying these enhanced bioactivities remains poorly characterized,particularly regarding the transformation and functionalization of active components during high-temperature carbonization.This study systematically investigates carbon dots(CDs),emerging carbon-based nanomaterials spontaneously formed during the carbonization process,as potential key bioactive constituents mediating the therapeutic actions of carbonized TCM.Through multidisciplinary analysis of pyrolysis-driven CD formation mechanisms,nanostructural evolution,and surface chemistry modulation,we demonstrate that CDs exhibit size-dependent fluorescence properties and redox-active surface functional groups that correlate with their observed biological effects.Crucially,the study establishes quantitative structure-activity relationships between CDs’quantum confinement characteristics(2–8 nm diameter),oxygencontaining surface moieties(carboxyl,hydroxyl groups),and their procoagulant/antioxidant capacities.By bridging traditional processing knowledge with nanotechnology insights,this work not only deciphers the“black box”of thermal processing in TCM but also proposes a nano-biointerface paradigm for understanding Paozhi mechanisms.The findings advance quality control strategies through CD-based spectral fingerprinting and open new avenues for developing nanoscale TCM derivatives with optimized therapeutic profiles.展开更多
Sewage sludge(SS)and SS impregnated with activating agents(ZnCl_(2) and KOH)were pyrolyzed in a fixed-bed reactor to produce gaseous fuel and activated char.The effects of heating rate,pyrolysis temperature and activa...Sewage sludge(SS)and SS impregnated with activating agents(ZnCl_(2) and KOH)were pyrolyzed in a fixed-bed reactor to produce gaseous fuel and activated char.The effects of heating rate,pyrolysis temperature and activator type on gas yields,pore structure and adsorption properties of activated char were systematically studied.The results demonstrated that increasing the pyrolysis temperature from 450℃ to 850℃ propo rtionally enhanced H_(2) and CO yields from the rapid pyrolysis of SS,while CH_(4) yield showed minimal variation between 650℃ and 850℃.ZnCl_(2) notably increased the CO yield,reaching71.9 ml·g^(-1)at 850℃,but caused a marked reduction in CH_(4) yield under the tested conditions.Similarly,KOH promoted CO yield at 750℃ and 850℃,with minimal impact on CH_(4) production.Both activators facilitated higher H_(2) yields in the range of 450-550℃,while the maximum H_(2) yield(109.8 ml·g^(-1))was observed at 850℃ in the absence of activator.The activated char derived from ZnCl_(2)-assisted pyrolysis exhibited well-developed micro-and mesopore structures,with specific surface areas ranging from 188.2 to 54.1 m^(2)·g^(-1)across pyrolysis temperatures of 450-850℃.When evaluated as adsorbents for methylene blue removal,activated char with greater specific surface area and total pore volume exhibited superior adsorption capacity.The adsorption process was well-described by the pseudo-second-order kinetic model.展开更多
In the current era of renewable energy prominence,the wide operational capacity of coal-fired boilers has emerged as crucial for ensuring the sustainability of power plants.However,attaining ultra-low nitrogen oxides(...In the current era of renewable energy prominence,the wide operational capacity of coal-fired boilers has emerged as crucial for ensuring the sustainability of power plants.However,attaining ultra-low nitrogen oxides(NO_x)emissions during periods of low-load operations presents a significant and persistent challenge for coal power enterprises.While techniques such as biomass re-burning and advanced re-burning have shown promise in enhancing NO reduction effciency above 800℃,their elevated levels of chlorine(Cl)and alkali metals pose potential risks to boiler equipment integrity.Therefore,this study proposes the utilization of biomass char derived from pyrolysis as a dual-purpose solution to enhance NO reduction efficiency while safeguarding boiler integrity during low-load operations.Findings indicate that pyrolysis treatment effectively reduces the Cl and alkali metal content of biomass.Specifically,it was determined that biomass char produced through deeply pyrolysis at 300℃achieves the highest NO reduction efficiency while minimizing the presence of harmful components.At a reduction temperature of 700℃,both re-burning and advanced re-burning techniques exhibit NO reduction efficiencies of 55.90%and 62.22%,which is already an ideal deficiency at low temperatures.The addition of water vapor at 700-800℃obviously avoids the oxidation of ammonia to NO in advanced reburning.Upon further analysis,denitrification efficiency in biomass char re-burning and advanced reburning is influenced not only by volatile content but also by physicochemical properties such as porosity and surface functional group distribution under certain reaction conditions.This study provides a theoretical framework for the industrial implementation of biomass char for NO control in coal-fired power plants,offering insights into optimizing NO reduction efficiency while mitigating potential risks to boiler equipment.展开更多
Improving crop productivity and soil fertility through the balanced application of inorganic and organic nutrient sources is a sustainable approach in modern agriculture.Char land soils,widely distributed in riverine ...Improving crop productivity and soil fertility through the balanced application of inorganic and organic nutrient sources is a sustainable approach in modern agriculture.Char land soils,widely distributed in riverine Bangladesh,are generally low in organic matter status and deficient in necessary nutrient elements for crop production.Addressing this challenge,the present study was conducted to investigate the effects of various organic nutrient sources with inorganic fertilizers on crop yields,nutrient uptake,and soil fertility in farm(L1)and char land(L2)of Brahmaputra River in Mymensingh,Bangladesh from 2022(Y1)to 2023(Y2).For each location,eight treatments viz.T1(Control),T2[100%recommended fertilizer dose(RFD)],T3(75%RFD),T4(75%N from RFD 25%N from cow dung),T5(75%+N from RFD 25%N from poultry manure),T6(75%N from RFD 25%N from vermicompost),T7(75%N from++RFD 25%N from household compost)and T8(75%N from RFD 25%N from rice straw compost)were arranged in++a randomized complete block design with three replications using Wheat–Mungbean–T.Aman rice cropping pattern where three way interaction was considered for results.Treatment T5 performed the best in both years in both locations as it enhanced the yield components(p 0.05)and caused yield increment over control.The yield improvement in<Char land soils was higher than that in farm soils.For all three crops,treatment T5 consistently augmented the uptake of nitrogen,phosphorus,potassium,and sulphur by different parts of the crops and improved soil fertility properties such as organic matter status,cation exchange capacity,total nitrogen,available phosphorus,and sulphur as well as exchangeable potassium in both locations in both years.Cost and return analysis of different treatments for the whole cropping system showed that the highest marginal benefit-cost ratio(16.35 and 15.07)and gross return(about Tk 768,595/ha and 728,341/ha)were obtained from the T5 treatment in farm soils and Char land soils,respectively.Followed by poultry manure,vermicompost performed well in addition to mineral fertilizers for improving crop yield and soil fertility but its economic efficiency was less due to high input cost.These findings may be useful to the smallholder farmers in char areas,who could benefit from increased productivity,reduced reliance on chemical fertilizers,and improved soil health,contributing to the long-term sustainability of char land agriculture.展开更多
Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high conce...Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.展开更多
Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differ...Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different macerals may provide insight into coal-forming processes. In this study, ESR data along with the H/C atomic ratio （to infer the aromatic fraction） are used to characterize coal samples with the aim of assessing a fire-origin for dominant inertinite macerals. A medium rank C bituminous Witbank No. 4 Seam Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich samples. The parent sample consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated samples comprise of 81 vol% total vitrinite （dominated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dominated by fusinite, semifusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sample, and 0.85 for the vitrinite-rich counterpart, suggesting the former sample is more aromatic. The ESR spectra obtained for the three samples were found to fit best using a Lorentzian distribution. The fit is noticeably better for the aromatic inertinite-rich sample, for which the spectrum is symmetric. This is attributed to pronounced electron mobility and exchange interactions. The higher radical content of the inertinite-rich and parent samples is attributed to the presence of specific inertinite macerals, namely： fusinite, semifusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sample, the dominant inertinite macerals are interpreted to have formed through charring of plant matter.展开更多
The instantaneous degradation of erosion surface of ethylene propylene diene monomer(EPDM)insulation subjected to the particle-laden flow in two operating conditions was measured by using a real-time X-ray radiography...The instantaneous degradation of erosion surface of ethylene propylene diene monomer(EPDM)insulation subjected to the particle-laden flow in two operating conditions was measured by using a real-time X-ray radiography system.The images of its erosion state and dynamic ablation rate were obtained.And the charring-layer was analyzed by using SEM and energy spectrum.The experimental results indicate that the erosion rate of EPDM insulation layer impacted by low speed and low concentration particle flow is relatively small in the 1st second since the motor starting,but increases rapidly in 1 to 2.5 s,while the erosion rate of EPDM insulation layer impacted by high speed and high concentration particle flow increases rapidly in the 1st second;the ablation rate at the section eroded intensively by particle flow increases at first,then decreases,and goes to stabilization after 4.5 s;the higher speed and concentration particle flow are,the deeper particles get into charring layer,which lead to more thermal increment and thinner charring layer.展开更多
基金the equipment support of Sharing Platform of Scientific Equipments,Ministry of Education's Research Center for Comprehensive Utilization and Clean Process Engineering of Phosphrous Resources,Sichuan University。
文摘A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.
基金the National Natural Science Foundation of China (No.51673059)the Science and Technology Planning Project of Henan Province (No. 212102210636)the Opening Project of Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices (East China University of Technology)。
文摘Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.
基金Supported by the Fundamental Research Funds for the Central Universities,China(No.30920041102)the National Natural Science Foundation of China(No.11802134).
文摘The arc ignition based on charring conductive polymers has advantages of simple structure,low ignition power consumption and restart capacity,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.In order to optimize the performance of arc ignition system,it is essential to have a deeper understanding of the ignition processes and ignition characteristics of charring conductive polymers.In this paper,the thermal decomposition,electrical conductivity and thermal conductivity characteristics of charring conductive polymers with different conductive additives and matrix materials were comprehensively evaluated.An experimental investigation was conducted to determine the ignition behaviors and characteristics of different charring conductive polymers in a visual ignition combustor.The experiment result showed that the ignition delay and external energy required for ignition are negatively correlated with voltage and initial temperature of the ignition grain,but positively correlated with oxidizer flow velocity.Compared with charring conductive polymers containing multi-walled carbon nanotube,the ignition delay of charring conductive polymers with carbon black is significantly higher and the pyrolysis time is relatively longer.However,the ignition and initial flame propagation of charring conductive polymers with carbon black is more violent and more inclined to carbon particle ignition.Finally,the restart characteristic of different charring conductive polymers was studied.The ignition delay and external energy required for ignition of different charring conductive polymers all reduced with the increasing of the number of ignitions.However,the ignition characteristics would not change a lot after repeated ignition.
基金the Fundamental Research Funds for the Central Universities(Grant No.30920041102)National Natural Science Foundation of China(Grant No.11802134).
文摘The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.
基金supported by the National Natural Science Foundation of China (Grant No. 51178115)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.
基金supported by the National Natural Science Foundation of China(Grant Nos.11672089&11732002)the Natural Science Foundation of Heilongjiang Province,China(Grant No.A2017003)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2017017)
文摘Charring composites are widely used in the thermal protection system(TPS) to consume the intense aerodynamic heating during vehicle reentry. The ablation and thermal responses for the charring composites can be studied by using a numerical ablation model, in which the surface ablation and volume ablation could be taken into account. The coupling interactions among temperature, gas motion and interior pressure producing the pyrolysis gas could make the computation more complicated. A multi-physics model is developed to simulate the thermal response coupled with volume ablation and surface ablation. After studying four typical ablation cases, the model is validated, and then the heat transfer mechanisms in ablation are investigated. It is found that the viscous dissipation energy by the motion of pyrolysis gas can be neglected in the simulation. Also, the flow of pyrolysis gas plays an important role in the temperature response, especially under high heat flux condition.
基金This work was supported by the National NaturalScience Foundation of China (Grant Nos. 59936140 and 50006012).
文摘A modified model of pyrolysis for charring materials in fire has been proposed in this note. In this model some special factors which show the effect on pyrolysis are considered, i.e. heat loss by convection and radiation caused by surface temperature rise and shrinkage of char surface are considered. Experimental device is designed specially for validating the reliability of the model. Effects of density of materials and heat radiation on pyrolysis of materials have also been investigated.
文摘Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.
基金the financial support from the National Natural Science Foundation of China(524B2168,U22A20149,52173081,and 52273275)。
文摘In recent decades,annual urban fire incidents,including those involving ancient wooden buildings burned,transportation,and solar panels,have increased,leading to significant loss of human life and property.Addressing this issue without altering the surface morphology or interfering with optical behavior of flammable materials poses a substantial challenge.Herein,we present a transparent,low thickness,ceramifiable nanosystem coating composed of a highly adhesive base(poly(SSS1-co-HEMA1)),nanoscale layered double hydroxide sheets as ceramic precursors,and supramolecular melamine di-borate as an accelerator.We demonstrate that this hybrid coating can transform into a porous,fire-resistant protective layer with a highly thermostable vitreous phase upon exposure to flame/heat source.A nanosystem coating of just~100μm thickness can significantly increase the limiting oxygen index of wood(Pine)to 37.3%,dramatically reduce total heat release by 78.6%,and maintain low smoke toxicity(CIT_G=0.016).Detailed molecular force analysis,combined with a comprehensive examination of the underlying flame-retardant mechanisms,underscores the effectiveness of this coating.This work offers a strategy for creating efficient,environmentally friendly coatings with fire safety applications across various industries.
基金supported by the Foundation Project of Jihua Laboratory(X200191TL200).
文摘In this study,the catalysis function of Na_(2)CO_(3) to the structural properties of xylan char was well investigated with Na_(2)CO_(3) on,and the electrochemical performance of xylan char as an anode material for sodium-ion batteries was tested.The characterization of X-ray microscopy and scanning electron microscopy demonstrated that the morphological structure of xylan char was altered due to the addition of Na_(2)CO_(3) catalyst.The increasement of the Na_(2)CO_(3)/xylan ratio resulted in a slenderization of the triangular prism shape of the char skeleton and a reduction in porosity.X-ray diffraction analysis revealed that Na_(2)CO_(3) promoted the growth of the(004)crystal plane of graphite during xylan pyrolysis,while inhibiting the formation of the(100/101)crystal planes.Raman spectroscopy analysis indicated that the presence of Na_(2)CO_(3)had changed the graphitization degree of xylan char.Electrochemical tests further showed that char prepared with a Na_(2)CO_(3)/xylan mass ratio of 1∶1 exhibited the highest sodium storage capacity.This study provides a pathway for the rational design carbon materials derived from xylan for future applications in energy storage devices.
基金supported by Foundation Project of Jihua Laboratory(X200191TL200).
文摘This work investigated the effect of Na_(2)CO_(3)on the char structures of cellulose and lignin,respective-ly,and examined the electrochemi-cal performance of the char by act-ing as an active material for coin cells.The morphology of char can be significantly steered by the con-centration of Na_(2)CO_(3).Scanning electron microscopy analysis demonstrated that the intro-duction of Na_(2)CO_(3)into cellulose at an appropriate concentration led to the formation of tubular structure on its surface after pyrolysis,whereas the tubular structure was absent in the lignin char with the addition of Na_(2)CO_(3)at any concentrations.X-ray diffraction and Ra-man spectroscopy characterizations revealed that all the obtained chars from both cellulose and lignin,with or without Na_(2)CO_(3),were ascribed to non-crystalline graphite.Nevertheless,the crystal orientation of graphite from cellulose and lignin changed after the catalysis of Na_(2)CO_(3).Further electrochemical tests showed that cellulose char had a higher sodium stor-age capacity than that of lignin char.The excellent electrochemical performance of carbon materials derived from cellulose might hold a prospective application in the field of energy storage.
基金supported by Shanghai Pujiang Program(No.22PJD001)the Fundamental Research Funds for the Central Universities(No.2232021G-11).
文摘Catalytic oxidation of NO at room temperature was carried out over nitrogen(N)-doped sludge char(SC)prepared from pyrolysis ofmunicipal sewage sludge,and urea was adopted as nitrogen source.The effects of different N-doping methods(one-step and two-step method),dried sludge(DS)/urea mass ratios(5:1,4:1,3:1,2:1,and 1:1),SC preparation procedures(pyrolysis only,pyrolysis with acid washing,and pyrolysis with KOH activation and acid washing),and different pyrolysis temperatures(500,600,700,and 800°C)on the catalytic oxidation of NO were compared to optimize the procedure for SC preparation.The results indicated that N-doping could obviously promote the catalytic performance of SC.The one-step method with simultaneous sludge pyrolysis(at 700°C),KOH activation,and N-doping(DS/urea of 3:1)was the optimal procedure for preparing the N-doped SC with the NO conversion rate of 54.7%,whereas the optimal NO conversion rate of SC without N-doping was only 47.3%.Urea worked both as carbon and nitrogen source,which could increase about 2.9%-16.5%of carbon and 24.8%-42.7%of nitrogen content in SC pyrolyzed at 700°C.N-doping significantly promoted microporosity of SC.The optimal N-doped SC showed specific surface areas of 571.38 m^(2)/g,much higher than 374.34 m^(2)/g of the optimal SC without N-doping.In addition,N-doping also increased amorphousness and surface basicity of SC through the formation of N-containing groups.Finally,three reaction paths,i.e.microporous reactor,active sites,and basic site control path,were proposed to explain the mechanism of N-doping on promoting the catalytic performance of NO.
基金supported by the Natural Science Foundation of Shandong Province(No.ZR2023ZD25)the Shandong Province Chinese Medicine Science and Technology Development Project(No.Q-2023107)the Taishan Scholars Project in Shandong Province(Nos.tstp202306 and tsqn202408246).
文摘The carbonization processing(Paozhi)in traditional Chinese medicine(TCM)represents a unique pharmaceutical technology where thermal modification of herbal materials enhances specific therapeutic properties,particularly hemostatic and antioxidant effects.Despite centuries of empirical applications,the scientific basis underlying these enhanced bioactivities remains poorly characterized,particularly regarding the transformation and functionalization of active components during high-temperature carbonization.This study systematically investigates carbon dots(CDs),emerging carbon-based nanomaterials spontaneously formed during the carbonization process,as potential key bioactive constituents mediating the therapeutic actions of carbonized TCM.Through multidisciplinary analysis of pyrolysis-driven CD formation mechanisms,nanostructural evolution,and surface chemistry modulation,we demonstrate that CDs exhibit size-dependent fluorescence properties and redox-active surface functional groups that correlate with their observed biological effects.Crucially,the study establishes quantitative structure-activity relationships between CDs’quantum confinement characteristics(2–8 nm diameter),oxygencontaining surface moieties(carboxyl,hydroxyl groups),and their procoagulant/antioxidant capacities.By bridging traditional processing knowledge with nanotechnology insights,this work not only deciphers the“black box”of thermal processing in TCM but also proposes a nano-biointerface paradigm for understanding Paozhi mechanisms.The findings advance quality control strategies through CD-based spectral fingerprinting and open new avenues for developing nanoscale TCM derivatives with optimized therapeutic profiles.
基金financially supported by the National Natural Science Foundation of China(U21A2062)National innovative training program for college students of China(202410792014)。
文摘Sewage sludge(SS)and SS impregnated with activating agents(ZnCl_(2) and KOH)were pyrolyzed in a fixed-bed reactor to produce gaseous fuel and activated char.The effects of heating rate,pyrolysis temperature and activator type on gas yields,pore structure and adsorption properties of activated char were systematically studied.The results demonstrated that increasing the pyrolysis temperature from 450℃ to 850℃ propo rtionally enhanced H_(2) and CO yields from the rapid pyrolysis of SS,while CH_(4) yield showed minimal variation between 650℃ and 850℃.ZnCl_(2) notably increased the CO yield,reaching71.9 ml·g^(-1)at 850℃,but caused a marked reduction in CH_(4) yield under the tested conditions.Similarly,KOH promoted CO yield at 750℃ and 850℃,with minimal impact on CH_(4) production.Both activators facilitated higher H_(2) yields in the range of 450-550℃,while the maximum H_(2) yield(109.8 ml·g^(-1))was observed at 850℃ in the absence of activator.The activated char derived from ZnCl_(2)-assisted pyrolysis exhibited well-developed micro-and mesopore structures,with specific surface areas ranging from 188.2 to 54.1 m^(2)·g^(-1)across pyrolysis temperatures of 450-850℃.When evaluated as adsorbents for methylene blue removal,activated char with greater specific surface area and total pore volume exhibited superior adsorption capacity.The adsorption process was well-described by the pseudo-second-order kinetic model.
基金supported by the Open Topics of State Key Laboratory of Clean and Efficient Coal-Fired Power Generation and Pollution Control(D2022FK103)National Natural Science Foundation of China(22278250)+1 种基金the Shanxi Province Science and Technology Cooperation and Exchange Special Program(202104041101014)the Shanxi Province Scholarship Council。
文摘In the current era of renewable energy prominence,the wide operational capacity of coal-fired boilers has emerged as crucial for ensuring the sustainability of power plants.However,attaining ultra-low nitrogen oxides(NO_x)emissions during periods of low-load operations presents a significant and persistent challenge for coal power enterprises.While techniques such as biomass re-burning and advanced re-burning have shown promise in enhancing NO reduction effciency above 800℃,their elevated levels of chlorine(Cl)and alkali metals pose potential risks to boiler equipment integrity.Therefore,this study proposes the utilization of biomass char derived from pyrolysis as a dual-purpose solution to enhance NO reduction efficiency while safeguarding boiler integrity during low-load operations.Findings indicate that pyrolysis treatment effectively reduces the Cl and alkali metal content of biomass.Specifically,it was determined that biomass char produced through deeply pyrolysis at 300℃achieves the highest NO reduction efficiency while minimizing the presence of harmful components.At a reduction temperature of 700℃,both re-burning and advanced re-burning techniques exhibit NO reduction efficiencies of 55.90%and 62.22%,which is already an ideal deficiency at low temperatures.The addition of water vapor at 700-800℃obviously avoids the oxidation of ammonia to NO in advanced reburning.Upon further analysis,denitrification efficiency in biomass char re-burning and advanced reburning is influenced not only by volatile content but also by physicochemical properties such as porosity and surface functional group distribution under certain reaction conditions.This study provides a theoretical framework for the industrial implementation of biomass char for NO control in coal-fired power plants,offering insights into optimizing NO reduction efficiency while mitigating potential risks to boiler equipment.
基金funded by Taif University,Saudi Arabia,Project No.(TU-DSPP-2025-30)The Science and Technology Fellowship Trust(SL No.39.00.0000.035.22.013.19.144)under the Ministry of Science and Technology of Bangladesh partially financed the current research。
文摘Improving crop productivity and soil fertility through the balanced application of inorganic and organic nutrient sources is a sustainable approach in modern agriculture.Char land soils,widely distributed in riverine Bangladesh,are generally low in organic matter status and deficient in necessary nutrient elements for crop production.Addressing this challenge,the present study was conducted to investigate the effects of various organic nutrient sources with inorganic fertilizers on crop yields,nutrient uptake,and soil fertility in farm(L1)and char land(L2)of Brahmaputra River in Mymensingh,Bangladesh from 2022(Y1)to 2023(Y2).For each location,eight treatments viz.T1(Control),T2[100%recommended fertilizer dose(RFD)],T3(75%RFD),T4(75%N from RFD 25%N from cow dung),T5(75%+N from RFD 25%N from poultry manure),T6(75%N from RFD 25%N from vermicompost),T7(75%N from++RFD 25%N from household compost)and T8(75%N from RFD 25%N from rice straw compost)were arranged in++a randomized complete block design with three replications using Wheat–Mungbean–T.Aman rice cropping pattern where three way interaction was considered for results.Treatment T5 performed the best in both years in both locations as it enhanced the yield components(p 0.05)and caused yield increment over control.The yield improvement in<Char land soils was higher than that in farm soils.For all three crops,treatment T5 consistently augmented the uptake of nitrogen,phosphorus,potassium,and sulphur by different parts of the crops and improved soil fertility properties such as organic matter status,cation exchange capacity,total nitrogen,available phosphorus,and sulphur as well as exchangeable potassium in both locations in both years.Cost and return analysis of different treatments for the whole cropping system showed that the highest marginal benefit-cost ratio(16.35 and 15.07)and gross return(about Tk 768,595/ha and 728,341/ha)were obtained from the T5 treatment in farm soils and Char land soils,respectively.Followed by poultry manure,vermicompost performed well in addition to mineral fertilizers for improving crop yield and soil fertility but its economic efficiency was less due to high input cost.These findings may be useful to the smallholder farmers in char areas,who could benefit from increased productivity,reduced reliance on chemical fertilizers,and improved soil health,contributing to the long-term sustainability of char land agriculture.
基金Sponsored by the National Nature Science Foundation of China(50876091)
文摘Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.
文摘Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experimental methods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different macerals may provide insight into coal-forming processes. In this study, ESR data along with the H/C atomic ratio （to infer the aromatic fraction） are used to characterize coal samples with the aim of assessing a fire-origin for dominant inertinite macerals. A medium rank C bituminous Witbank No. 4 Seam Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich samples. The parent sample consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated samples comprise of 81 vol% total vitrinite （dominated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dominated by fusinite, semifusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sample, and 0.85 for the vitrinite-rich counterpart, suggesting the former sample is more aromatic. The ESR spectra obtained for the three samples were found to fit best using a Lorentzian distribution. The fit is noticeably better for the aromatic inertinite-rich sample, for which the spectrum is symmetric. This is attributed to pronounced electron mobility and exchange interactions. The higher radical content of the inertinite-rich and parent samples is attributed to the presence of specific inertinite macerals, namely： fusinite, semifusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sample, the dominant inertinite macerals are interpreted to have formed through charring of plant matter.
基金Sponsored by the National Nature Science Foundation of China(50976095)
文摘The instantaneous degradation of erosion surface of ethylene propylene diene monomer(EPDM)insulation subjected to the particle-laden flow in two operating conditions was measured by using a real-time X-ray radiography system.The images of its erosion state and dynamic ablation rate were obtained.And the charring-layer was analyzed by using SEM and energy spectrum.The experimental results indicate that the erosion rate of EPDM insulation layer impacted by low speed and low concentration particle flow is relatively small in the 1st second since the motor starting,but increases rapidly in 1 to 2.5 s,while the erosion rate of EPDM insulation layer impacted by high speed and high concentration particle flow increases rapidly in the 1st second;the ablation rate at the section eroded intensively by particle flow increases at first,then decreases,and goes to stabilization after 4.5 s;the higher speed and concentration particle flow are,the deeper particles get into charring layer,which lead to more thermal increment and thinner charring layer.
