β-SiC ceramic powders were obtained by pyrolyzing polycarbosilane in vacuum at 800-1200 °C. The β-SiC ceramic powders were characterized by TGA/DSC, XRD and Raman spectroscopy. The dielectric properties of β-S...β-SiC ceramic powders were obtained by pyrolyzing polycarbosilane in vacuum at 800-1200 °C. The β-SiC ceramic powders were characterized by TGA/DSC, XRD and Raman spectroscopy. The dielectric properties of β-SiC ceramic powders were investigated by measuring their complex permittivity by rectangle wave guide method in the frequency range of 8.2-18 GHz. The results show that both real part ε′ and imaginary part ε″ of complex permittivity increase with increasing pyrolysis temperature. The mechanism was proposed that order carbon formed at high temperature resulted in electron relaxation polarization and conductance loss, which contributes to the increase in complex permittivity.展开更多
Bi0.9La0.1Fe0.95Mn0.05O3 （BLFMO） ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/ substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by th...Bi0.9La0.1Fe0.95Mn0.05O3 （BLFMO） ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/ substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by thermo gravimetry analyser （TGA）, and the polycrystalline structure and smooth surface of BLFMO thin films were characterized by X-ray diffraction （XRD） and atomic force microscopy （AFM）, respectively. The remnant polarization （Pr） of the BLFMO films pyrolyzed at 420 ℃ is 21.2 μC/cm2 at the coercive field （Ec） of 99 kV/cm and the leakage current density is 7.1×10-3 A/cm2, which indicates that the BLFMO thin films display relatively good ferroelectric property at this temperature.展开更多
According to the Doehlert's matrix method, the adsorbent derived from sewage sludge was prepared through chemical activation under controlling the pyrolysis temperature and hold time. The characteristic parameters...According to the Doehlert's matrix method, the adsorbent derived from sewage sludge was prepared through chemical activation under controlling the pyrolysis temperature and hold time. The characteristic parameters including the total yield, adsorption of methylene blue, adsorption of iodine, BET surface area, micro-pore volume are 35%—49%, 16.5—38 mg/g, 285—362 mg/g, 185—359 m2/g, and 0.112—0.224 m3/g, respectively. According to the experimental data, the multi-linear regression method was adopted to fit the relations between the characteristic parameters and influential factors. At final, through optimization method, the optimal adsorbent is obtained when using 62 min as hold time and 1105K as pyrolysis temperature. Under the conditions, the adsorbent was produced and compared the characteristic parameters with model forecast value, the coherence is satisfied.展开更多
Activated carbon fiber/carbon nanotube(ACF/CNT) composites were fabricated by chemical vapor deposition(CVD) process.The effects of pyrolysis temperature on properties of ACF/CNT composites,including BET specific surf...Activated carbon fiber/carbon nanotube(ACF/CNT) composites were fabricated by chemical vapor deposition(CVD) process.The effects of pyrolysis temperature on properties of ACF/CNT composites,including BET specific surface area,mass increment rate and adsorption efficiency for rhodamine B in solution,were investigated by scanning electron microscopy.The results show that the pyrolysis temperature is a key factor affecting the qualities of ACF/CNT composites.The mass increment rate and BET specific surface area sharply decrease with the increase of pyrolysis temperatures from 550 ℃ to 850 ℃ and the minimum diameter of CNTs appears at 750 ℃.The maximum adsorption efficiency of ACF/CNT composites for rhodamine B is obtained at 650 ℃.ACF/CNT composites are expected to be useful in adsorption field.展开更多
Manure-derived biochar is widely used for soil remediation,yet the long-term effects of aging on the stability of its endogenous heavy metals remain unclear.This study aims to investigate how freeze-thaw(FT)cycle agin...Manure-derived biochar is widely used for soil remediation,yet the long-term effects of aging on the stability of its endogenous heavy metals remain unclear.This study aims to investigate how freeze-thaw(FT)cycle aging influences the physicochemical properties and endogenous heavy metal stability of chicken manure(CM)-derived biochars produced at different pyrolysis temperatures(350℃,550℃,and 750℃).By subjecting these biochars to accelerated FT aging,we compared changes in structural integrity and heavy metal speciation.FT cycles significantly induced physical fragmentation in porous biochar,reducing pH,graphitization,and stability while increasing the total specific surface area(SSA)and oxygen-containing functional groups.Biochars produced at higher pyrolysis temperatures demonstrated greater susceptibility to structural breakdown during FT aging,which led to increased leachability and phyto-availability of heavy metals.Chemical speciation analysis revealed that biochar produced at 750℃(CMB-750)experienced a pronounced transformation of heavy metals into less stable forms during FT aging,with acidsoluble(F1)fractions of Zn,Cu,Ni,Cr,Pb,and Cd in aged biochar(ACMB-750)increasing to 34.97%,18.06%,18.34%,13.16%,31.23%,and 6.31%,respectively.These findings highlight the risks of presuming that higher pyrolysis temperatures always enhance heavy metals retention and emphasize the importance of considering the entire biochar lifecycle,from fabrication and soil remediation to aging,when optimizing its safe and sustainable agricultural use.展开更多
Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new ap...Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.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
ZnO films were prepared at different substrate temperatures through spraying pyrolysis deposition of zinc chloride precursor onto glass substrate. Substrate temperature affects surface morphology of films and therefor...ZnO films were prepared at different substrate temperatures through spraying pyrolysis deposition of zinc chloride precursor onto glass substrate. Substrate temperature affects surface morphology of films and therefore their optical and electrical properties. All films are polycrystalline with Wurtzite crystal structure and preferentially grow along c-axis direction. Formation of ZnO rods start at about 500 °C. The diameter and length of rods deposited at 500 °C are350–500 and 550–700 nm, respectively. By increasing substrate temperature, film becomes more coverage and diameter of the rods reduces to 250–300 nm but their length increases to 1,000–1,200 nm, respectively. Optical transmission in visible region decreases with increasing substrate temperature. An ultraviolet emission and two visible emissions at 2.82 and2.37 eV are observed for photoluminescence spectra at room temperature. The resistivity of ZnO films increases with increasing substrate temperature due to surface morphology.展开更多
Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignit...Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignition temperature,burnout temperature,ignition index,burnout index,burnout ratio,combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis(TGA).The effects of pyrolysis temperature,heating rate,and pyrolysis time on yield,composition and calorific value of long flame coal derived semicokes were investigated,especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction(XRD) analysis of semicokes.The results show that the volatile content,ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces(PCFF) referring to China Standards GB/T 7562-1998.The pyrolysis temperature is the most influential factor among pyrolysis process parameters.As pyrolysis temperature increases,the yield,ignition index,combustion reactivity and burnout index of semicokes show a decreasing tend,but the ash content increases.In the range of 400 and 450 °C,the grindability of semicokes is rational,especially the grindability of semicokes pyrolyzed at 450 °C is suitable.Except for the decrease of volatile content and increase of ash content,the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char.It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.展开更多
Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by f...Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by fungi.However,the effects of biochar and soil type on the community,abundance,enzyme secretion,and necromass of fungi mediating SOC storage remain unclear.A mesocosm incubation experiment was conducted using forest and paddy soils from southern China to study the impact of biochars pyrolyzed at low(300℃BL)and high(700℃BH)temperatures on fungal abundance,community composition,necromass abundance,and C-degrading enzyme activities.The SOC retention ratio was higher under BL(84.0%)than under BH(76.3%).Addition of BL increased fungal abundance in the forest soil by 230%.In contrast,addition of BH decreased fungal abundance in the paddy soil by 20.8%.Biochar addition affected fungal necromass accumulation and oxidase activity and regulated SOC turnover.The high available C content and moderate liming effect of BL significantly increased fungal abundance and necromass abundance in the forest soil compared to the paddy soil.Moreover,after 16 weeks of incubation,BL addition decreased peroxidase activity by 32.1%in the forest soil due to the higher C use efficiency of fungi(i.e.,the enrichment of Talaromyces,Umbelopsis,and Trichoderma),decreasing C-degrading enzyme secretion and reducing SOC degradation compared to the paddy soil.However,BH addition increased the Fusarium abundance,which regulated the polyphenol oxidase activity and promoted SOC degradation in the paddy soil.We concluded that biochars could alter the soil environment and extracellular electron transfer to mediate fungal necromass content and C-degrading enzyme activities,thus affecting SOC storage in the forest and paddy soils.展开更多
Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-mod...Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.展开更多
Biochar(BC), known as the new black gold, is a stable, novel carbonaceous by-product that is synthesized through pyrolysis of biological materials in the absence of O_2.Recently, an emerging interest in the applicatio...Biochar(BC), known as the new black gold, is a stable, novel carbonaceous by-product that is synthesized through pyrolysis of biological materials in the absence of O_2.Recently, an emerging interest in the application of BC as a robust soil amendment has given rise to a broad research area in science and technology.It is considered a promising remediation option for heavy metal(HM)-contaminated soils to reduce HM bioavailability to plants.Remediation efficacy of BC depends on the porosity, composition,pyrolysis temperature, feedstock, and residence time of pyrolysis.This review article aimed to present an overview of BC use in the immobilization of HMs, i.e., Cd, As, Pb, Zn, Ni, Cu, Mn, Cr, and Sb, in contaminated soils.The remaining uncertain factors, including the specific soil HM immobilization mechanisms, long-term beneficial effects, and potential environmental risks associated with BC application are analyzed.Future research must be conducted to ensure that the management of environmental pollution is in accord with ecological sustainability and adaptation of the black gold biotechnology on a commercial basis for immobilization of HMs in contaminated soils.展开更多
The study on biochar derived from plant biomass for environmental applications is attracting more and more attention. Twelve sets of biochar were obtained by treating four phytoremediation plants, Salix rosthornii See...The study on biochar derived from plant biomass for environmental applications is attracting more and more attention. Twelve sets of biochar were obtained by treating four phytoremediation plants, Salix rosthornii Seemen, Thalia dealbata, Vetiveria zizanioides, and Phragmites sp., sequentially through pyrolysis at 500 °C in a N2 environment, and under different temperatures(500, 600, and 700 °C) in a CO2 environment. The cation exchange capacity and specific surface area of biochar varied with both plant species and pyrolysis temperature. The magnesium(Mg) content of biochar derived from T. dealbata(TC) was obviously higher than that of the other plant biochars. This biochar also had the highest sorption capacity for phosphate and ammonium. In terms of biomass yields, adsorption capacity, and energy cost, T. dealbata biochar produced at 600 °C(TC600) is the most promising sorbent for removing contaminants(N and P) from aqueous solution. Therefore, T. dealbata appears to be the best candidate for phytoremediation application as its biomass can make a good biochar for environmental cleaning.展开更多
Nowadays,iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water...Nowadays,iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water.In this study,boron-doped biochar(B-BC)was successfully prepared at various preparation conditions with the addition of boric acid.The as-prepared material has a more developed pore structure and a larger specific surface area(up to 897.97 m2/g).A series of characterization results shows that boric acid effectively activates biochar,and boron atoms are successfully doped on biochar.Compared with the ratio of raw materials,the pyrolysis temperature has a greater influence on the amount of boron doping.Based on Langmuir model,the maximum adsorption capacity of 800 B-BC1:2 at25℃,40℃,55℃ are 50.02 mg/g,95.09 mg/g,132.78 mg/g,respectively.Pseudo-second-order kinetic model can better describe the adsorption process,the adsorption process is mainly chemical adsorption.Chemical complexation,ions exchange,and co-precipitation may be the main mechanisms for Fe2+removal.展开更多
In this work, the effect of various effective dimensionless numbers and moisture contents on initiation of instability in combustion of moisty organic dust is calculated. To have reliable model, effect of thermal radi...In this work, the effect of various effective dimensionless numbers and moisture contents on initiation of instability in combustion of moisty organic dust is calculated. To have reliable model, effect of thermal radiation is taken into account. One- dimensional flame structure is divided into three zones： preheat zone, reaction zone and post-flame zone. To investigate pulsating characteristics of flame, governing equations are rewritten in dimensionless space-time （（, r/, ~） coordinates. By solving these newly achieved governing equations and combining them, which is completely discussed in body of article, a new expression is obtained. By solving this equation, it is possible to predict initiation of instability in organic dust flame. According to the obtained results by increasing Lewis number, threshold of instability happens sooner. On the other hand, pulsating is postponed by increasing Damk6hler number, pyrolysis temperature or moisture content. Also, by considering thermal radiation effect, burning velocity predicted by our model is closer to experimental results.展开更多
The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. ...The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.展开更多
Biochar, carbonaceous material produced from biomass pyrolysis, has been demonstrated to have electron transfer property(associated with redox active groups and multi condensed aromatic moiety), and to be also involve...Biochar, carbonaceous material produced from biomass pyrolysis, has been demonstrated to have electron transfer property(associated with redox active groups and multi condensed aromatic moiety), and to be also involved in biogeochemical redox reactions. In this study, the enhanced removal of Cr(VI) by Shewanella oneidensis MR-1(MR-1) in the presence of biochars with different pyrolysis temperatures(300 to 800 ℃) was investigated to understand how biochar interacts with Cr(VI) reducing bacteria under anaerobic condition. The promotion effects of biochar(as high as 1.07~1.47 fold) were discovered in this process, of which the synergistic effect of BMBC700(ball milled biochar) and BMBC800 with MR-1 was noticeable, in contrast, the synergistic effect of BMBCs(300–600 ℃) with MR-1 was not recognized. The more enhanced removal effect was observed with the increase of BMBC dosage for BMBC700 + MR-1 group. The conductivity and conjugated O-containing functional groups of BMBC700 particles themselves has been proposed to become a dominant factor for the synergistic action with this strain. And, the smallest negative Zeta potential of BMBC700 and BMBC800 is thought to favor decreasing the distance from microbe than other BMBCs. The results are expected to provide some technical considerations and scientific insight for the optimization of bioreduction by useful microbes combining with biochar composites to be newly developed.展开更多
The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil m...The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.展开更多
Polymer-derived ceramics(PDCs)pyrolyzed at high temperatures are promising electromagnetic wave(EMW)absorption materials for aerodynamically heated parts of aircraft under harsh environments.Nev-ertheless,high-tempera...Polymer-derived ceramics(PDCs)pyrolyzed at high temperatures are promising electromagnetic wave(EMW)absorption materials for aerodynamically heated parts of aircraft under harsh environments.Nev-ertheless,high-temperature pyrolysis results in a significant increase of electrical and dielectric proper-ties of the ceramics,causing extensive reflection of EMW.To address this challenge,boron nitride-coated carbon nanotubes(BN@CNTs)were fabricated and introduced into polymer-derived SiC(PDC-SiC)by py-rolyzing its precursor higher than 1200℃to form SiC-BN@CNT ceramic composites.The fabricated com-posites with 3 wt.%BN@CNTs pyrolyzed at 1200℃have an effective absorption bandwidth(EAB)of 4.2 GHz(8.2-12.4 GHz)at a thickness of 3.4 mm and the minimum reflection loss(RL min)of-57.20 dB.The ultra-broad EAB of 12.62 GHz(5.38-18 GHz)is obtained by simulation through periodic structure design-ing.The RL of the metamaterials was also measured using an arch testing method at a frequency range of 2-18 GHz and an EAB of 11.52 GHz(6.48-18 GHz)is obtained.The excellent absorption is attributed to the BN layer that limits the electrical conduction of the ceramic composites while retaining the high loss of CNTs.The introduction of BN@CNTs causes the refinement of SiC grains,which provides plenty of interfaces and enhances the interface polarization loss.This work successfully solves the problem that PDCs pyrolyzed at elevated temperatures cannot be used as EMW absorption materials by applying BN coating on CNTs served as absorbers for PDC-SiC.The results of this work greatly broaden the application scope of the PDC systems for EMW absorption.展开更多
Temperature is the determining factor of pyro-lysis,which is one of the alternative technologies for oil sludge treatment.The effects of final operating temper-ature ranging from 350 to 550uC on pyrolysis products of ...Temperature is the determining factor of pyro-lysis,which is one of the alternative technologies for oil sludge treatment.The effects of final operating temper-ature ranging from 350 to 550uC on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor.With an increase of temperature,the mass fraction of solid residues,liquids,and gases in the final product is 67.00%–56.00%,25.60%–32.35%,and 7.40%–11.65%,and their corresponding heat values are 34.4–13.8 MJ/kg,44.41–46.6 MJ/kg,and 23.94–48.23 MJ/Nm 3,respectively.The mass and energy tend to shift from solid to liquid and gas phase(especially to liquid phase)during the process,and the optimum temperature for oil sludge pyrolysis is 500uC.The liquid phase is mainly com-posed of alkane and alkene(C_(5)–C_(29)),and the gas phase is dominantly HC S and H 2.展开更多
基金Project (50572090) supported by the National Natural Science Foundation of ChinaProject (KP200901) supported by the Fund of the State Key Laboratory of Solidification Processing, China
文摘β-SiC ceramic powders were obtained by pyrolyzing polycarbosilane in vacuum at 800-1200 °C. The β-SiC ceramic powders were characterized by TGA/DSC, XRD and Raman spectroscopy. The dielectric properties of β-SiC ceramic powders were investigated by measuring their complex permittivity by rectangle wave guide method in the frequency range of 8.2-18 GHz. The results show that both real part ε′ and imaginary part ε″ of complex permittivity increase with increasing pyrolysis temperature. The mechanism was proposed that order carbon formed at high temperature resulted in electron relaxation polarization and conductance loss, which contributes to the increase in complex permittivity.
基金Project (11032010) supported by Key Project of National Natural Science Foundation of ChinaProjects (51072171, 61274107, 61176093, 11275163) supported by the National Natural Science Foundation of China+3 种基金Project (IRT1080) supported by Program for Changjiang Scholars and Innovation Research Team in UniversityProject (2012CB326404) supported by National Basic Research Program of ChinaProject (CX2011B248) supported by Hunan Provincial Innovation Foundation for PostgraduateProject (20104301110001) supported by the Doctoral Program of Higher Education of China
文摘Bi0.9La0.1Fe0.95Mn0.05O3 （BLFMO） ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/ substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by thermo gravimetry analyser （TGA）, and the polycrystalline structure and smooth surface of BLFMO thin films were characterized by X-ray diffraction （XRD） and atomic force microscopy （AFM）, respectively. The remnant polarization （Pr） of the BLFMO films pyrolyzed at 420 ℃ is 21.2 μC/cm2 at the coercive field （Ec） of 99 kV/cm and the leakage current density is 7.1×10-3 A/cm2, which indicates that the BLFMO thin films display relatively good ferroelectric property at this temperature.
文摘According to the Doehlert's matrix method, the adsorbent derived from sewage sludge was prepared through chemical activation under controlling the pyrolysis temperature and hold time. The characteristic parameters including the total yield, adsorption of methylene blue, adsorption of iodine, BET surface area, micro-pore volume are 35%—49%, 16.5—38 mg/g, 285—362 mg/g, 185—359 m2/g, and 0.112—0.224 m3/g, respectively. According to the experimental data, the multi-linear regression method was adopted to fit the relations between the characteristic parameters and influential factors. At final, through optimization method, the optimal adsorbent is obtained when using 62 min as hold time and 1105K as pyrolysis temperature. Under the conditions, the adsorbent was produced and compared the characteristic parameters with model forecast value, the coherence is satisfied.
基金Project(50802115) supported by the National Natural Science Foundation of ChinaProject(2010FJ4075) supported by the Science and Technology Plan of Hunan ProvinceProject(CDJJ-10010205) supported by Changsha University
文摘Activated carbon fiber/carbon nanotube(ACF/CNT) composites were fabricated by chemical vapor deposition(CVD) process.The effects of pyrolysis temperature on properties of ACF/CNT composites,including BET specific surface area,mass increment rate and adsorption efficiency for rhodamine B in solution,were investigated by scanning electron microscopy.The results show that the pyrolysis temperature is a key factor affecting the qualities of ACF/CNT composites.The mass increment rate and BET specific surface area sharply decrease with the increase of pyrolysis temperatures from 550 ℃ to 850 ℃ and the minimum diameter of CNTs appears at 750 ℃.The maximum adsorption efficiency of ACF/CNT composites for rhodamine B is obtained at 650 ℃.ACF/CNT composites are expected to be useful in adsorption field.
基金funded by the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01C737).
文摘Manure-derived biochar is widely used for soil remediation,yet the long-term effects of aging on the stability of its endogenous heavy metals remain unclear.This study aims to investigate how freeze-thaw(FT)cycle aging influences the physicochemical properties and endogenous heavy metal stability of chicken manure(CM)-derived biochars produced at different pyrolysis temperatures(350℃,550℃,and 750℃).By subjecting these biochars to accelerated FT aging,we compared changes in structural integrity and heavy metal speciation.FT cycles significantly induced physical fragmentation in porous biochar,reducing pH,graphitization,and stability while increasing the total specific surface area(SSA)and oxygen-containing functional groups.Biochars produced at higher pyrolysis temperatures demonstrated greater susceptibility to structural breakdown during FT aging,which led to increased leachability and phyto-availability of heavy metals.Chemical speciation analysis revealed that biochar produced at 750℃(CMB-750)experienced a pronounced transformation of heavy metals into less stable forms during FT aging,with acidsoluble(F1)fractions of Zn,Cu,Ni,Cr,Pb,and Cd in aged biochar(ACMB-750)increasing to 34.97%,18.06%,18.34%,13.16%,31.23%,and 6.31%,respectively.These findings highlight the risks of presuming that higher pyrolysis temperatures always enhance heavy metals retention and emphasize the importance of considering the entire biochar lifecycle,from fabrication and soil remediation to aging,when optimizing its safe and sustainable agricultural use.
文摘Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.
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.
文摘ZnO films were prepared at different substrate temperatures through spraying pyrolysis deposition of zinc chloride precursor onto glass substrate. Substrate temperature affects surface morphology of films and therefore their optical and electrical properties. All films are polycrystalline with Wurtzite crystal structure and preferentially grow along c-axis direction. Formation of ZnO rods start at about 500 °C. The diameter and length of rods deposited at 500 °C are350–500 and 550–700 nm, respectively. By increasing substrate temperature, film becomes more coverage and diameter of the rods reduces to 250–300 nm but their length increases to 1,000–1,200 nm, respectively. Optical transmission in visible region decreases with increasing substrate temperature. An ultraviolet emission and two visible emissions at 2.82 and2.37 eV are observed for photoluminescence spectra at room temperature. The resistivity of ZnO films increases with increasing substrate temperature due to surface morphology.
基金support from the Allocated Section of the Basic Fund for the Scientific Research and Operation of Central Universities of China (No.2009KH10)
文摘Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignition temperature,burnout temperature,ignition index,burnout index,burnout ratio,combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis(TGA).The effects of pyrolysis temperature,heating rate,and pyrolysis time on yield,composition and calorific value of long flame coal derived semicokes were investigated,especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction(XRD) analysis of semicokes.The results show that the volatile content,ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces(PCFF) referring to China Standards GB/T 7562-1998.The pyrolysis temperature is the most influential factor among pyrolysis process parameters.As pyrolysis temperature increases,the yield,ignition index,combustion reactivity and burnout index of semicokes show a decreasing tend,but the ash content increases.In the range of 400 and 450 °C,the grindability of semicokes is rational,especially the grindability of semicokes pyrolyzed at 450 °C is suitable.Except for the decrease of volatile content and increase of ash content,the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char.It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.
基金supported by the National Natural Science Foundation of China(Nos.32101397,42177195,42307527,and 42307567)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2021A1515011559,2024A1515012566,and 2023A1515012248)+1 种基金the Guangdong Foundation for Program of Science and Technology Research,China(No.2023B1212060044)GDAS'Project of Science and Technology Development,China(Nos.2023 GDASZH-2023010103 and 2020GDASYL-20200103074).
文摘Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by fungi.However,the effects of biochar and soil type on the community,abundance,enzyme secretion,and necromass of fungi mediating SOC storage remain unclear.A mesocosm incubation experiment was conducted using forest and paddy soils from southern China to study the impact of biochars pyrolyzed at low(300℃BL)and high(700℃BH)temperatures on fungal abundance,community composition,necromass abundance,and C-degrading enzyme activities.The SOC retention ratio was higher under BL(84.0%)than under BH(76.3%).Addition of BL increased fungal abundance in the forest soil by 230%.In contrast,addition of BH decreased fungal abundance in the paddy soil by 20.8%.Biochar addition affected fungal necromass accumulation and oxidase activity and regulated SOC turnover.The high available C content and moderate liming effect of BL significantly increased fungal abundance and necromass abundance in the forest soil compared to the paddy soil.Moreover,after 16 weeks of incubation,BL addition decreased peroxidase activity by 32.1%in the forest soil due to the higher C use efficiency of fungi(i.e.,the enrichment of Talaromyces,Umbelopsis,and Trichoderma),decreasing C-degrading enzyme secretion and reducing SOC degradation compared to the paddy soil.However,BH addition increased the Fusarium abundance,which regulated the polyphenol oxidase activity and promoted SOC degradation in the paddy soil.We concluded that biochars could alter the soil environment and extracellular electron transfer to mediate fungal necromass content and C-degrading enzyme activities,thus affecting SOC storage in the forest and paddy soils.
基金financially supported by the National Natural Science Foundation of China(42007181)Chinese Academy of Geological Sciences Basal Research Fund(CSJ-2024-03)National Key Research and Development Program of China(2023YFC3709104).
文摘Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.
基金supported by the China Scholarship Council(No.2014070067)the Science and Technology Overall Innovation Project of Shaanxi Province of China(No.2016KTCQ03-20)
文摘Biochar(BC), known as the new black gold, is a stable, novel carbonaceous by-product that is synthesized through pyrolysis of biological materials in the absence of O_2.Recently, an emerging interest in the application of BC as a robust soil amendment has given rise to a broad research area in science and technology.It is considered a promising remediation option for heavy metal(HM)-contaminated soils to reduce HM bioavailability to plants.Remediation efficacy of BC depends on the porosity, composition,pyrolysis temperature, feedstock, and residence time of pyrolysis.This review article aimed to present an overview of BC use in the immobilization of HMs, i.e., Cd, As, Pb, Zn, Ni, Cu, Mn, Cr, and Sb, in contaminated soils.The remaining uncertain factors, including the specific soil HM immobilization mechanisms, long-term beneficial effects, and potential environmental risks associated with BC application are analyzed.Future research must be conducted to ensure that the management of environmental pollution is in accord with ecological sustainability and adaptation of the black gold biotechnology on a commercial basis for immobilization of HMs in contaminated soils.
基金supported by the International Cooperative Project from the Ministry of Science and Technology of China(No.2010DFB33960)the National Key Technology R&D Program of China(No.2012BAC17B02)+1 种基金the Zhejiang Youth Creative Program(No.2012QNA6004)the Key Project from Zhejiang Science and Technology Bureau(No.2011C13015),China
文摘The study on biochar derived from plant biomass for environmental applications is attracting more and more attention. Twelve sets of biochar were obtained by treating four phytoremediation plants, Salix rosthornii Seemen, Thalia dealbata, Vetiveria zizanioides, and Phragmites sp., sequentially through pyrolysis at 500 °C in a N2 environment, and under different temperatures(500, 600, and 700 °C) in a CO2 environment. The cation exchange capacity and specific surface area of biochar varied with both plant species and pyrolysis temperature. The magnesium(Mg) content of biochar derived from T. dealbata(TC) was obviously higher than that of the other plant biochars. This biochar also had the highest sorption capacity for phosphate and ammonium. In terms of biomass yields, adsorption capacity, and energy cost, T. dealbata biochar produced at 600 °C(TC600) is the most promising sorbent for removing contaminants(N and P) from aqueous solution. Therefore, T. dealbata appears to be the best candidate for phytoremediation application as its biomass can make a good biochar for environmental cleaning.
基金the financial support by Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(No.Z019005)the Longjiang Scholars for young scientist。
文摘Nowadays,iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water.In this study,boron-doped biochar(B-BC)was successfully prepared at various preparation conditions with the addition of boric acid.The as-prepared material has a more developed pore structure and a larger specific surface area(up to 897.97 m2/g).A series of characterization results shows that boric acid effectively activates biochar,and boron atoms are successfully doped on biochar.Compared with the ratio of raw materials,the pyrolysis temperature has a greater influence on the amount of boron doping.Based on Langmuir model,the maximum adsorption capacity of 800 B-BC1:2 at25℃,40℃,55℃ are 50.02 mg/g,95.09 mg/g,132.78 mg/g,respectively.Pseudo-second-order kinetic model can better describe the adsorption process,the adsorption process is mainly chemical adsorption.Chemical complexation,ions exchange,and co-precipitation may be the main mechanisms for Fe2+removal.
文摘In this work, the effect of various effective dimensionless numbers and moisture contents on initiation of instability in combustion of moisty organic dust is calculated. To have reliable model, effect of thermal radiation is taken into account. One- dimensional flame structure is divided into three zones： preheat zone, reaction zone and post-flame zone. To investigate pulsating characteristics of flame, governing equations are rewritten in dimensionless space-time （（, r/, ~） coordinates. By solving these newly achieved governing equations and combining them, which is completely discussed in body of article, a new expression is obtained. By solving this equation, it is possible to predict initiation of instability in organic dust flame. According to the obtained results by increasing Lewis number, threshold of instability happens sooner. On the other hand, pulsating is postponed by increasing Damk6hler number, pyrolysis temperature or moisture content. Also, by considering thermal radiation effect, burning velocity predicted by our model is closer to experimental results.
基金financially supported by the Outstanding Youth Fund of the Natural Science Foundation of Jiangsu, China (No. BK20150050)the National Key Research and Development Program, China (No. 2016YFD0800204)+2 种基金the National Natural Science Foundation of China (No. 21677149)the Institute of Soil Science, Chinese Academy of Sciences (No. ISSASIP1616)the Key Program of Frontier Sciences, Chinese Academy of Sciences (No. QYZDJSSW-DQC035)
文摘The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.
基金The study was supported by the Natural Science Foundation of Tianjin(No.20JCZDJC00700)the National Natural Science Foundation of China(Nos.U1806216,41877372)+1 种基金the National Key R&D Program of China(No.2018YFC1802002)111 program,Ministry of Education,China(No.T2017002).
文摘Biochar, carbonaceous material produced from biomass pyrolysis, has been demonstrated to have electron transfer property(associated with redox active groups and multi condensed aromatic moiety), and to be also involved in biogeochemical redox reactions. In this study, the enhanced removal of Cr(VI) by Shewanella oneidensis MR-1(MR-1) in the presence of biochars with different pyrolysis temperatures(300 to 800 ℃) was investigated to understand how biochar interacts with Cr(VI) reducing bacteria under anaerobic condition. The promotion effects of biochar(as high as 1.07~1.47 fold) were discovered in this process, of which the synergistic effect of BMBC700(ball milled biochar) and BMBC800 with MR-1 was noticeable, in contrast, the synergistic effect of BMBCs(300–600 ℃) with MR-1 was not recognized. The more enhanced removal effect was observed with the increase of BMBC dosage for BMBC700 + MR-1 group. The conductivity and conjugated O-containing functional groups of BMBC700 particles themselves has been proposed to become a dominant factor for the synergistic action with this strain. And, the smallest negative Zeta potential of BMBC700 and BMBC800 is thought to favor decreasing the distance from microbe than other BMBCs. The results are expected to provide some technical considerations and scientific insight for the optimization of bioreduction by useful microbes combining with biochar composites to be newly developed.
基金This work was supported by National Priority Research and Development Program of China(2016YFD0600204)National Natural Science Foundation of China(41701264)+2 种基金Natural Science Foundation of Jiangsu Province,China(BK20170931)Natural Science Research Program(16KJB210005)Overseas Training Program and Priority Academic Program Development Funds(PAPD)of Jiangsu Higher Education Institutions.
文摘The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.
基金supported by the National Natural Science Foundation of China(Nos.52232005,52172104,and 52293370)Fundamental Research Funds for the Central Universities(China,Nos.3102020QD0411 and D5000220152)+1 种基金Fundamental Research Funds for the Central Universities(No.3102019TS0409)Cre-ative Research Foundation of Science and Technology on Thermo-Structural Composite Materials Laboratory.
文摘Polymer-derived ceramics(PDCs)pyrolyzed at high temperatures are promising electromagnetic wave(EMW)absorption materials for aerodynamically heated parts of aircraft under harsh environments.Nev-ertheless,high-temperature pyrolysis results in a significant increase of electrical and dielectric proper-ties of the ceramics,causing extensive reflection of EMW.To address this challenge,boron nitride-coated carbon nanotubes(BN@CNTs)were fabricated and introduced into polymer-derived SiC(PDC-SiC)by py-rolyzing its precursor higher than 1200℃to form SiC-BN@CNT ceramic composites.The fabricated com-posites with 3 wt.%BN@CNTs pyrolyzed at 1200℃have an effective absorption bandwidth(EAB)of 4.2 GHz(8.2-12.4 GHz)at a thickness of 3.4 mm and the minimum reflection loss(RL min)of-57.20 dB.The ultra-broad EAB of 12.62 GHz(5.38-18 GHz)is obtained by simulation through periodic structure design-ing.The RL of the metamaterials was also measured using an arch testing method at a frequency range of 2-18 GHz and an EAB of 11.52 GHz(6.48-18 GHz)is obtained.The excellent absorption is attributed to the BN layer that limits the electrical conduction of the ceramic composites while retaining the high loss of CNTs.The introduction of BN@CNTs causes the refinement of SiC grains,which provides plenty of interfaces and enhances the interface polarization loss.This work successfully solves the problem that PDCs pyrolyzed at elevated temperatures cannot be used as EMW absorption materials by applying BN coating on CNTs served as absorbers for PDC-SiC.The results of this work greatly broaden the application scope of the PDC systems for EMW absorption.
基金This work was supported by the National High-Tech Research and Development(863)Program of China(Grant No.2006AA06Z370).
文摘Temperature is the determining factor of pyro-lysis,which is one of the alternative technologies for oil sludge treatment.The effects of final operating temper-ature ranging from 350 to 550uC on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor.With an increase of temperature,the mass fraction of solid residues,liquids,and gases in the final product is 67.00%–56.00%,25.60%–32.35%,and 7.40%–11.65%,and their corresponding heat values are 34.4–13.8 MJ/kg,44.41–46.6 MJ/kg,and 23.94–48.23 MJ/Nm 3,respectively.The mass and energy tend to shift from solid to liquid and gas phase(especially to liquid phase)during the process,and the optimum temperature for oil sludge pyrolysis is 500uC.The liquid phase is mainly com-posed of alkane and alkene(C_(5)–C_(29)),and the gas phase is dominantly HC S and H 2.
