The functionality of wood has evolved with time to adapt to the emerging needs of society.Carbonized wood-based composites have attracted tremendous interest in the fields of aerospace,military power,electric power,an...The functionality of wood has evolved with time to adapt to the emerging needs of society.Carbonized wood-based composites have attracted tremendous interest in the fields of aerospace,military power,electric power,and system electronic devices,especially at high temperatures.Nevertheless,their electrical conductivity and thermal stability characteristics are still far from satisfactory.Herein,an innova-tive wood-derived carbon-carbon nanotubes-pyrolytic carbon composites(WDC-CNTs-PyCs)is successfully fabricated by chemical vapor deposition and chemical vapor infiltration.The combination of wood-derived carbon(WDC),carbon nanotubes(CNTs),and pyrolytic carbon(PyC)has never been reported in any previous work.We have innovatively introduced PyC into the WDC by chemical vapor infiltration.CNTs promote the continuous deposition of PyC to form dense structures.WDC-CNTs-PyC demonstrates significant compressive strength(85.4 MPa)and excellent electrical conductivity(632 S cm^(-1)).The weight loss rate of WDC-CNTs-PyC is 6%after heating at 500℃ for 10 min in the air atmosphere.Furthermore,WDC-CNTs-PyC could resist oxyacetylene ablation above 2300℃ for 15 s.With excellent electrical conductivity,outstanding thermal stability,and mechanical properties,WDC-CNTs-PyC opens up a surprising strategy for efficiently fabricating various high-performance electronic device composites that could be used in high-temperature fields.展开更多
The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by ...The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by SEM and Raman spectroscopy. The influence of deposition time of PyC on the DC conductivity （ad） of A1203 filaments and complex permittivity of fabrics at X band （8.2-12.4 GHz） were investigated. The values of Crd and complex permittivity increase with increasing deposition time of PyC. The electron relaxation polarization and conductance loss were supposed to be contributed to the increase of ε＇ and ε＂, respectively. In addition, the reflection loss （RL） of fabrics was calculated. The results show that the microwave absorbing properties of Al2O3 fiber fabrics can be improved by PyC coatings. The best RL results are for 60 min-deposition sample, of which the minimum value is about -40.4 dB at about 9.5 GHz and the absorbing frequency band （AFB） is about 4 GHz.展开更多
The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst prop- erties, including acidity, pore si...The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst prop- erties, including acidity, pore size and supported metal on hydrocracking of pyrolytic lignin in supercritical ethanol and hydrogen were investigated at 260 ℃. A series of catalysts were prepared and characterized by BET, XRD, and NHa-TPD techniques. The results showed that enhancing the acidity of the catalyst without metal can promote pyrolytic lignin poly- merization to form more solid and condensation to produce more water. The pore size of microporous catalyst was smaller than mesoporous catalyst. Together with strong acid- ity, it caused pyrolytic lignin further hydrocrack to numerous gas. Introducing Ru into acidic catalysts promoted pyrolytic lignin hydrocracking and inhibited the polymerization and condensation, which caused the yield of pyrolytic lignin liquefaction product to increase significantly. Therefore, bifunctional catalyst with high hydrocracking activity metal Ru supported on materials with acidic sites and mesopores was imperative to get satisfactory results for the conversion of pyrolytic lignin to liquid products under supercritical conditions and hydrogen atmosphere.展开更多
Four kinds of carbon/carbon (C/C) composites, including the needled carbon fiber felt/the pyrolytic carbon (two different pyrolytic carbon microstructures), the chopped carbon fiber/the resin + pyrolytic carbon (PyrC)...Four kinds of carbon/carbon (C/C) composites, including the needled carbon fiber felt/the pyrolytic carbon (two different pyrolytic carbon microstructures), the chopped carbon fiber/the resin + pyrolytic carbon (PyrC), and the carbon cloth/PyrC, named as the composites 1#, 4#, 2#, and 3#, are prepared respectively. Effects of the preform and pyrolytic carbon structure on the thermophysical properties of 2D C/C composites are studied. The C/C composites possess low coefficient of thermal expansion (CTE). In a range of some temperatures, the negative expansion emerges in x-y direction for four C/C composites. From 0 to 900℃, the CTE is small and almost linear with the temperatures. The C/C composites have high thermal conductivities (TCs). As a function of temperature, TCs of the C/C composites are varied with the structures of preform and pyrc as well as the direction of heat transfer. In x-y and z direction, TCs differ greatly and that in x-y direction (25.6-174 W/m·K) is several times larger than that in z direction(3.5-50 W/m·K).展开更多
Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char(PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications ...Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char(PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications for pyrolytic char recovered is used for the removal of Cr(Ⅵ) in the wastewater effluent to control waste by waste. The surface chemistry properties of surface element distribution / concentration and chemical structure were examined for the pyrolytic char and the commercial activated carbon(CAC) respectively. The results showed that surfaces of PC possesses a large amount of ester and hydrocarbon graft, whereas there are mainly carbon functional components of C—OH, C O and COOH on the surface of CAC. Therefore the surface electronegativity of PC is lower than that of CAC in the water. The repulsive interactions between the surfaces of PC and the negatively charged Cr(Ⅵ) ion are weaker than that of CAC, which results in an intensification of the adsorption process by the utilization of PC. The adsorption isotherms of Cr(Ⅵ) ion on the two kinds of carbons were determined experimentally. The larger adsorption amount on the PC in the case of Cr(Ⅵ) may be attributed mainly to its special surface micro-chemical environment. The mechanism of the removal Cr(Ⅵ) from aqueous solution was assumed to be the integration of adsorption and redox reaction. The adsorption was the rate-controlled step for Cr(Ⅵ) removal. The adsorption of Cr(Ⅵ) was identified as pseudo-second-order kinetics. The rate constants of adsorption were evaluated.展开更多
The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon （PyC） layer has been discussed.With rising reaction te...The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon （PyC） layer has been discussed.With rising reaction temperature,the thickness of SiC layer increases and the SiC grain is coarsening.The apparent activation energy for the synthesis of SiC layer is about 103.3 kJ/mol.The oxidation resistance of carbon fiber can be improved by the SiC/PyC layers significantly.The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 300℃ higher than that of the uncoated carbon fiber.The oxidation of the SiC/PyC coated carbon fiber is owing to the diffusion of oxygen through the cracks generated by the mismatch of thermal expansion.展开更多
Bio-oil is a new liquid fuel produced by fast pyrolysis,which is a promising technology to convert bio-mass into liquid. Pyrolytic lignin extracted from bio-oil,a fine powder,contributes to the instability of bio-oil....Bio-oil is a new liquid fuel produced by fast pyrolysis,which is a promising technology to convert bio-mass into liquid. Pyrolytic lignin extracted from bio-oil,a fine powder,contributes to the instability of bio-oil. The paper presents the structural features of three kinds of pyrolytic lignin extracted from bio-oil with different methods(WIF,HMM,and LMM) . The pyrolytic lignin samples are characterized by Fourier transform infrared spectrometer(FTIR) and X-ray photoelectron spectroscopy(XPS) . FTIR data indicate that the three pyrolytic lignin samples have similar functional groups,while the absorption intensity is different,and show characteristic vibra-tions of typical lignocellulosic material groups O H(3340-3380 cm-1) ,C H(2912-2929 cm-1) and C O(1652-1725 cm-1) . Comparison in the region(3340-3380 cm-1) indicates that WIF has more O H stretch groups than HMM and LMM. The carbon spectra are fitted to four peaks:C1,C C or C H,BE 283.5 eV;C2,C OR or C OH,BE 284.5-285.8 eV;C3,C O or HO C OR,BE 286.10-287.10 eV;C4,O C O,BE 287.5-287.7 eV. The absence of C1,C C or C H indicates the dominant polymerization structure of aro-matic carbon in pyrolytic lignin samples. For HMM and WIF,C2a and C2b can not be separated,so there is no free hydroxyl group in the samples. The oxygen peaks are also fitted to four peaks:O1,OH,BE = 530.3 eV;O2,RC O,BE 531.45-531.72 eV;O3,O C O,BE = 532.73-533.74 eV;O4,H2O,BE 535 eV. The absence of O1 and O4 indicates that little hydroxyl groups and adsorbed water are present in the samples.展开更多
A self-designed experimental device was employed to simulate the pyrolytic dismantling process of selected electronic wastes(E-wastes), including printed wiring boards(PWBs)and plastic casings. The generated particula...A self-designed experimental device was employed to simulate the pyrolytic dismantling process of selected electronic wastes(E-wastes), including printed wiring boards(PWBs)and plastic casings. The generated particulate matter(PM) of different particle sizes, carbon monoxide(CO) and carbon dioxide(CO_2) were determined, and the corresponding emission factors(EFs) were estimated. Finer particles with particle sizes of 0.4–2.1 μm accounted for78.9% and 89.3% of PM emitted by the pyrolytic processing of PWBs and plastic casings,respectively, and the corresponding EFs were 9.68 ± 4.81 and 18.49 ± 7.2 g/kg, respectively.The EFs of CO and CO_2 from PWBs and plastic casings were 55.9 ± 26.9 and 1182 ± 439 g/kg,and 133.6 ± 34.6 and 2827 ± 276 g/kg, respectively. Compared with other emission sources,such as coal, biomass, and traffic exhaust, the EFs of E-wastes were relatively higher,especially for PM. There were significant positive correlations(p < 0.05) of the initial contents of carbon and nitrogen in PWBs with the related EFs of PM, CO, and CO_2, while the correlations for plastic casings were insignificant. The EFs of CO of PWBs were significantly positively correlated with the corresponding EFs of PM and the parent polycyclic aromatic hydrocarbons(PAHs); however, the same result was not observed for plastic casings.展开更多
The density functional theory has been successfully applied in analyzing pyrolytic carbon deposition by methane pyrolysis from the view of thermodynamics and kinetics based on a total number of 39 elementary reactions...The density functional theory has been successfully applied in analyzing pyrolytic carbon deposition by methane pyrolysis from the view of thermodynamics and kinetics based on a total number of 39 elementary reactions.M06-2X/def2-TZVP level was employed to optimize species structures and locate the transition states.The enthalpy changes and Gibbs free energy changes of all the reactions in the temperature range of 298.15–1800K were derived with optimized species.Results show that the reacting temperature should be above 1200 K based on the equilibrium constant analysis,which is consistent with the typical reaction temperature adopted in experiments.Potential energy surface profiles report that radical attacking reactions have lower energy barriers than those direct decomposition reactions,especially hydrogen radical attacking reactions.The energy barriers of the first steps,dehydrogenations of methane and ethylene,are 272.4 kJ·mol^(-1)and 288.9 kJ·mol^(-1)at 1200 K,which are very close to the experimental activation energy for methane pyrolysis.The most favorable decomposition reaction path is the path of hydrogen radical attacking reactions.The highest energy barrier of the path at 1200K is 185.7kJ·mol^(-1)presented by the C–H bond breaking in ethynyl attacked by hydrogen radical.展开更多
Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate...Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained from water extraction of bio-oil, methanol–water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecular weight distribution of high-molecular-weight pyrolytic lignin was relatively wider, among which the contents of dimers to pentamers all accounted for 12% –18%,while the low-molecular-weight pyrolytic lignin mainly consisted of trimers(75.38%). The pyrolytic lignins had similar basic structures, both of which contained syringyl and guaiacyl units, whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile,thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.展开更多
A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demons...A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demonstrated.The HOPG surface was modified preferentially by covalent bonding of a two-dimensional 4-aminophenyl monolayer employing diazonium chemistry.AuCl4 -ions were attached to the Ar-NH2 termination and reduced electrochemically.This results in the formation of Au nuclei that could be further grown into gold nanoparticles.The formation of polyaniline as the shell wrap of Au nanoparticle was established by localized electro-polymerization.These core-shell nanocomposites prepared were characterized by AFM and cyclic voltammetry.The results show that the gold-polyaniline core-shell composites on HOPG have a mean particle size of 100 nm in diameter and the polyaniline shell thickness is about 15 nm.展开更多
Pyrolytic carbon(PyC) coatings are deposited on the Nextel-440 fiber fabrics by chemical vapor deposition(CVD).The dielectric properties of the Nextel-440 fiber fabrics with PyC coatings(Nextel-440/PyC) are investigat...Pyrolytic carbon(PyC) coatings are deposited on the Nextel-440 fiber fabrics by chemical vapor deposition(CVD).The dielectric properties of the Nextel-440 fiber fabrics with PyC coatings(Nextel-440/PyC) are investigated in a temperature range from room temperature to 700℃ in X-band. Compared with the permittivity of the original Nextel-440 received,the complex permittivity of the Nextel-440/PyC(the real part εand the imaginary part ε), is significantly improved: εof the Nextel-440/PyC has a positive temperature coefficient, in contrast, εof the Nextel-440/PyC exhibits a negative temperature coefficient. Moreover, the reflection loss in units of d B is calculated. The results indicate that the microwave absorbing properties of the Nextel-440/PyC coatings is enhanced at 700℃ compared with that at lower temperatures.展开更多
A comparison of voltammetric behavior of bisoprolol fumarate (BF) at edge and basal plane pyrolytic graphite electrodes (EPPGE/BPPGE) has been made with single wall carbon nanotube modified glassy carbon. The electroc...A comparison of voltammetric behavior of bisoprolol fumarate (BF) at edge and basal plane pyrolytic graphite electrodes (EPPGE/BPPGE) has been made with single wall carbon nanotube modified glassy carbon. The electrochemical properties are investigated exercising the cyclic voltammetry and square wave voltammetry (SWV). Enhanced peak current associated with bisoprolol fumarate oxidation at EPPGE is due to its better electron transfer property. Quantification of bisoprolol fumarate was carried out at pH 7.2 at both the pyrolytic graphite electrodes. Well-defined peak has been observed at ~ 792 and 954 mV at EPPGE and BPPGE respectively for bisoprolol fumarate oxidation. The detection limit is found to be 2.8 × 10–7 M and 7.3 × 10–7 M for EPPGE and BPPGE respectively. A comparison of common quantification parameters for bisoprolol at carbon nanotube modified glassy carbon electrode and bare BPPGE and EPPGE has been made and it is observed that carbon naotube modified glassy carbon exhibits sensitivity and detection limit close to that observed at bare basal plane pyrolytic graphite electrode. The method developed is applicable for determination of bisoprolol fumarate in pharmaceutical preparations and real samples.展开更多
A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon sour...A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon source with nitrogen as dilution gas, and the pyrolytic carbon started to deposit on the carbon fiber surface when the deposition temperature was reached. The morphology of pyrolytic carbon was characterized by SEM, and the surface properties of carbon fibers before and after CVD were characterized by Raman spectroscopy. The experimental results show that the electric heating method is a novel method to fabricate C/C composite materials, which can form a dense C/C composite material in a short time. The order degree and the average crystallite size of the carbon fiber surface were decreased after the experiment.展开更多
This study aims to observe the durability of a pyrolytic carbon bileaflet mechanical valve prosthesis. The mechanical valves prosthesis was tested in vitro by the durability test instrument of valve prosthesis. Then i...This study aims to observe the durability of a pyrolytic carbon bileaflet mechanical valve prosthesis. The mechanical valves prosthesis was tested in vitro by the durability test instrument of valve prosthesis. Then in vivo, the durability of the implanted valves was observed with animal experiments and elinieal application. In the impact test for 5 min and durability test of 380 million eyeles in vitro, there was no the phenomenon of flyer, perforation and fracture observed, as well as no wear or pit found on the surface of valve leaflets. The valve leaflets could normally be turned on or off. The weight of the valve was（1.0031 ± 0.0004） g for 23 mm and（1.6003 ± 0.0002） g for 27 mm. The hydrodynamies test demonstrated that the valve prosthesis had still exeellent hemodynamic performance after the durability test. The animal autopsy showed that the valve leaflets could normally be turned on or off, and no wear was found. By follow-up of 62 patients implanted the valves, all patients had long-terms survival, no complication caused by valve was found. The age of the longest survival was more than 10 years. This study demonstrates that the new meehanieal valve prosthesis have excellent durable performance.展开更多
A method for determination of epinephrine（EP） in the presence of ascorbic acid （AA） and dopamine （DA） with bare pyrolytic graphite electrodes has been described for the first time. In pH 7.0 phosphate buffer sol...A method for determination of epinephrine（EP） in the presence of ascorbic acid （AA） and dopamine （DA） with bare pyrolytic graphite electrodes has been described for the first time. In pH 7.0 phosphate buffer solution, the linear relationship was observed between the reduction peak current of EP and its concentration over the range from 1×10^-4 to 5×10^-7 mol/L, the related coefficient is 0.9992 （N=8）.展开更多
An optical transmission method was used in-situ to measure the rate of pyrolytic deposition from Mn_2(CO)_(10) induced by a CW CO_2 laser. The effect of the laser intensity, Mn_2(CO)_(10) vapor pressure and added gase...An optical transmission method was used in-situ to measure the rate of pyrolytic deposition from Mn_2(CO)_(10) induced by a CW CO_2 laser. The effect of the laser intensity, Mn_2(CO)_(10) vapor pressure and added gases (CO, O_2 and Ar) on the deposition rate has been examined.展开更多
Chemical Vapor Infiltration (CVI) processes are the essential techniques for fabrication of high performance carbon carbon composites. Based on the polarized light and scanning electron analysis, the authors study th...Chemical Vapor Infiltration (CVI) processes are the essential techniques for fabrication of high performance carbon carbon composites. Based on the polarized light and scanning electron analysis, the authors study the micro morphology and texture characteristics of pyrolytic carbon deposited in CVI process, as well as the growth behavior of pyrolytic carbon. The research shows that Rough Laminar (RL) texture has the hierarchical and self similar structural features, which reflects the stage growth and self similar behavior during the growth course of pyrolytic carbon. According to the two growth features, a laminated growth model of pyrolytic carbon is proposed with the concept of Cone Growth Units (CGU). The laminated growth model can provide a fine description for the growth course of RL pyrolytic carbon. The model indicates that formation, developing and combination of local high order structures (such as CGU structures) are the essential factors for the growth of RL texture. Smooth Laminar (SL) texture and ISO carbon come into being with long range orderliness and isotropy structure respectively, which no local high orderliness intermediate involves in.展开更多
Highly oriented pyrolytic graphite (HOPG) is the substrate often used in scanningtunneling Ancroscopy (STM). It is well known that STM images of the basal plane of HOPG showsome unusual structUral patterns. In this le...Highly oriented pyrolytic graphite (HOPG) is the substrate often used in scanningtunneling Ancroscopy (STM). It is well known that STM images of the basal plane of HOPG showsome unusual structUral patterns. In this letter, we present in situ STM images of some unusualfeatures on HOPG in solutions, including normal or abnormal chain-like featUres and hexagonal oroblique superPeriodic structures. These features emerge both next to and apart from the step ofHOPG.展开更多
Huge amounts of Xanthoceras sorbifolia husks(XSH)are typically discarded after oil extraction.Since pyrolysis represents a promising solution to harness the bio-energy of XSH,in the present work the pyrolytic and kine...Huge amounts of Xanthoceras sorbifolia husks(XSH)are typically discarded after oil extraction.Since pyrolysis represents a promising solution to harness the bio-energy of XSH,in the present work the pyrolytic and kinetic characteristics of XSH and related crude cellulose extract(CCE)were studied considering different rates of heating(10,30 and 50℃ min^(-1)).The pyrolysis activation energy,pre-exponential factors and mechanism function were computed using different models namely Popescu,FWO(Flynn-Wall-Ozawa)and KAS(Kissinger-Akahira-Sunose).The pyrolysis process was articulated into three stages:dehydration(Stage I),primary devolatilization(Stage II),residual decomposition(Stage III).Marked variations in the average activation energy,thermal stability,final residuals and rate of reaction were noted.Stage II of XSH and CCE could be described by the Avramic-Erofeev equations.The average activation energies of XSH and CCE were found to be 269 and 296 kJ mol^(-1),respectively.展开更多
基金supported by the under Grant No.51872232,the Key Scientific and Technological Innovation Research Team of Shaanxi Province(No.2022TD-31)the Key R&D Program of Shaanxi Province(No.2021ZDLGY14-04)+2 种基金the National Training Program of Innovation and Entrepreneurship for Undergraduates(Grand No.XN2022023)the Joint Funds of the National Natural Science Foundation of China(Grant No.U21B2067)the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China(Grant No.136-QP-2015).
文摘The functionality of wood has evolved with time to adapt to the emerging needs of society.Carbonized wood-based composites have attracted tremendous interest in the fields of aerospace,military power,electric power,and system electronic devices,especially at high temperatures.Nevertheless,their electrical conductivity and thermal stability characteristics are still far from satisfactory.Herein,an innova-tive wood-derived carbon-carbon nanotubes-pyrolytic carbon composites(WDC-CNTs-PyCs)is successfully fabricated by chemical vapor deposition and chemical vapor infiltration.The combination of wood-derived carbon(WDC),carbon nanotubes(CNTs),and pyrolytic carbon(PyC)has never been reported in any previous work.We have innovatively introduced PyC into the WDC by chemical vapor infiltration.CNTs promote the continuous deposition of PyC to form dense structures.WDC-CNTs-PyC demonstrates significant compressive strength(85.4 MPa)and excellent electrical conductivity(632 S cm^(-1)).The weight loss rate of WDC-CNTs-PyC is 6%after heating at 500℃ for 10 min in the air atmosphere.Furthermore,WDC-CNTs-PyC could resist oxyacetylene ablation above 2300℃ for 15 s.With excellent electrical conductivity,outstanding thermal stability,and mechanical properties,WDC-CNTs-PyC opens up a surprising strategy for efficiently fabricating various high-performance electronic device composites that could be used in high-temperature fields.
基金Project (51072165) 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The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by SEM and Raman spectroscopy. The influence of deposition time of PyC on the DC conductivity （ad） of A1203 filaments and complex permittivity of fabrics at X band （8.2-12.4 GHz） were investigated. The values of Crd and complex permittivity increase with increasing deposition time of PyC. The electron relaxation polarization and conductance loss were supposed to be contributed to the increase of ε＇ and ε＂, respectively. In addition, the reflection loss （RL） of fabrics was calculated. The results show that the microwave absorbing properties of Al2O3 fiber fabrics can be improved by PyC coatings. The best RL results are for 60 min-deposition sample, of which the minimum value is about -40.4 dB at about 9.5 GHz and the absorbing frequency band （AFB） is about 4 GHz.
文摘The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst prop- erties, including acidity, pore size and supported metal on hydrocracking of pyrolytic lignin in supercritical ethanol and hydrogen were investigated at 260 ℃. A series of catalysts were prepared and characterized by BET, XRD, and NHa-TPD techniques. The results showed that enhancing the acidity of the catalyst without metal can promote pyrolytic lignin poly- merization to form more solid and condensation to produce more water. The pore size of microporous catalyst was smaller than mesoporous catalyst. Together with strong acid- ity, it caused pyrolytic lignin further hydrocrack to numerous gas. Introducing Ru into acidic catalysts promoted pyrolytic lignin hydrocracking and inhibited the polymerization and condensation, which caused the yield of pyrolytic lignin liquefaction product to increase significantly. Therefore, bifunctional catalyst with high hydrocracking activity metal Ru supported on materials with acidic sites and mesopores was imperative to get satisfactory results for the conversion of pyrolytic lignin to liquid products under supercritical conditions and hydrogen atmosphere.
文摘Four kinds of carbon/carbon (C/C) composites, including the needled carbon fiber felt/the pyrolytic carbon (two different pyrolytic carbon microstructures), the chopped carbon fiber/the resin + pyrolytic carbon (PyrC), and the carbon cloth/PyrC, named as the composites 1#, 4#, 2#, and 3#, are prepared respectively. Effects of the preform and pyrolytic carbon structure on the thermophysical properties of 2D C/C composites are studied. The C/C composites possess low coefficient of thermal expansion (CTE). In a range of some temperatures, the negative expansion emerges in x-y direction for four C/C composites. From 0 to 900℃, the CTE is small and almost linear with the temperatures. The C/C composites have high thermal conductivities (TCs). As a function of temperature, TCs of the C/C composites are varied with the structures of preform and pyrc as well as the direction of heat transfer. In x-y and z direction, TCs differ greatly and that in x-y direction (25.6-174 W/m·K) is several times larger than that in z direction(3.5-50 W/m·K).
文摘Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char(PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications for pyrolytic char recovered is used for the removal of Cr(Ⅵ) in the wastewater effluent to control waste by waste. The surface chemistry properties of surface element distribution / concentration and chemical structure were examined for the pyrolytic char and the commercial activated carbon(CAC) respectively. The results showed that surfaces of PC possesses a large amount of ester and hydrocarbon graft, whereas there are mainly carbon functional components of C—OH, C O and COOH on the surface of CAC. Therefore the surface electronegativity of PC is lower than that of CAC in the water. The repulsive interactions between the surfaces of PC and the negatively charged Cr(Ⅵ) ion are weaker than that of CAC, which results in an intensification of the adsorption process by the utilization of PC. The adsorption isotherms of Cr(Ⅵ) ion on the two kinds of carbons were determined experimentally. The larger adsorption amount on the PC in the case of Cr(Ⅵ) may be attributed mainly to its special surface micro-chemical environment. The mechanism of the removal Cr(Ⅵ) from aqueous solution was assumed to be the integration of adsorption and redox reaction. The adsorption was the rate-controlled step for Cr(Ⅵ) removal. The adsorption of Cr(Ⅵ) was identified as pseudo-second-order kinetics. The rate constants of adsorption were evaluated.
基金supported by the National Natural Science Foundation of China under Grant No.50832004the "111" Project under Grant No.B08040
文摘The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon （PyC） layer has been discussed.With rising reaction temperature,the thickness of SiC layer increases and the SiC grain is coarsening.The apparent activation energy for the synthesis of SiC layer is about 103.3 kJ/mol.The oxidation resistance of carbon fiber can be improved by the SiC/PyC layers significantly.The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 300℃ higher than that of the uncoated carbon fiber.The oxidation of the SiC/PyC coated carbon fiber is owing to the diffusion of oxygen through the cracks generated by the mismatch of thermal expansion.
基金Supported by State Key Development Program for Basic Research of China(2007CB210208)National Science and Technology Major Project of China(2008ZX07101)China Scholarship Council(CSC),Natural Science and Engineering Research Council of Canada(NSERC),BIOCAP,and Canadian Funding for Innovations(CFI)
文摘Bio-oil is a new liquid fuel produced by fast pyrolysis,which is a promising technology to convert bio-mass into liquid. Pyrolytic lignin extracted from bio-oil,a fine powder,contributes to the instability of bio-oil. The paper presents the structural features of three kinds of pyrolytic lignin extracted from bio-oil with different methods(WIF,HMM,and LMM) . The pyrolytic lignin samples are characterized by Fourier transform infrared spectrometer(FTIR) and X-ray photoelectron spectroscopy(XPS) . FTIR data indicate that the three pyrolytic lignin samples have similar functional groups,while the absorption intensity is different,and show characteristic vibra-tions of typical lignocellulosic material groups O H(3340-3380 cm-1) ,C H(2912-2929 cm-1) and C O(1652-1725 cm-1) . Comparison in the region(3340-3380 cm-1) indicates that WIF has more O H stretch groups than HMM and LMM. The carbon spectra are fitted to four peaks:C1,C C or C H,BE 283.5 eV;C2,C OR or C OH,BE 284.5-285.8 eV;C3,C O or HO C OR,BE 286.10-287.10 eV;C4,O C O,BE 287.5-287.7 eV. The absence of C1,C C or C H indicates the dominant polymerization structure of aro-matic carbon in pyrolytic lignin samples. For HMM and WIF,C2a and C2b can not be separated,so there is no free hydroxyl group in the samples. The oxygen peaks are also fitted to four peaks:O1,OH,BE = 530.3 eV;O2,RC O,BE 531.45-531.72 eV;O3,O C O,BE = 532.73-533.74 eV;O4,H2O,BE 535 eV. The absence of O1 and O4 indicates that little hydroxyl groups and adsorbed water are present in the samples.
基金supported by the Natural Science Foundation Committee of China(No.41390240)the National Basic Research Program of China(No.2014CB441101)
文摘A self-designed experimental device was employed to simulate the pyrolytic dismantling process of selected electronic wastes(E-wastes), including printed wiring boards(PWBs)and plastic casings. The generated particulate matter(PM) of different particle sizes, carbon monoxide(CO) and carbon dioxide(CO_2) were determined, and the corresponding emission factors(EFs) were estimated. Finer particles with particle sizes of 0.4–2.1 μm accounted for78.9% and 89.3% of PM emitted by the pyrolytic processing of PWBs and plastic casings,respectively, and the corresponding EFs were 9.68 ± 4.81 and 18.49 ± 7.2 g/kg, respectively.The EFs of CO and CO_2 from PWBs and plastic casings were 55.9 ± 26.9 and 1182 ± 439 g/kg,and 133.6 ± 34.6 and 2827 ± 276 g/kg, respectively. Compared with other emission sources,such as coal, biomass, and traffic exhaust, the EFs of E-wastes were relatively higher,especially for PM. There were significant positive correlations(p < 0.05) of the initial contents of carbon and nitrogen in PWBs with the related EFs of PM, CO, and CO_2, while the correlations for plastic casings were insignificant. The EFs of CO of PWBs were significantly positively correlated with the corresponding EFs of PM and the parent polycyclic aromatic hydrocarbons(PAHs); however, the same result was not observed for plastic casings.
基金supported by the National Natural Science Foundation of China(51821091 and 51472203)the “111”Project of China(Grant No.B08040)the Research Fund of State Key Laboratory of Solidification Processing(NWPU)of China(Grant No.142-TZ-2016)。
文摘The density functional theory has been successfully applied in analyzing pyrolytic carbon deposition by methane pyrolysis from the view of thermodynamics and kinetics based on a total number of 39 elementary reactions.M06-2X/def2-TZVP level was employed to optimize species structures and locate the transition states.The enthalpy changes and Gibbs free energy changes of all the reactions in the temperature range of 298.15–1800K were derived with optimized species.Results show that the reacting temperature should be above 1200 K based on the equilibrium constant analysis,which is consistent with the typical reaction temperature adopted in experiments.Potential energy surface profiles report that radical attacking reactions have lower energy barriers than those direct decomposition reactions,especially hydrogen radical attacking reactions.The energy barriers of the first steps,dehydrogenations of methane and ethylene,are 272.4 kJ·mol^(-1)and 288.9 kJ·mol^(-1)at 1200 K,which are very close to the experimental activation energy for methane pyrolysis.The most favorable decomposition reaction path is the path of hydrogen radical attacking reactions.The highest energy barrier of the path at 1200K is 185.7kJ·mol^(-1)presented by the C–H bond breaking in ethynyl attacked by hydrogen radical.
基金Supported by the National Science and Technology Supporting Plan Through Contract(2015BAD15B06)the National Natural Science Foundation of China(51276166)+1 种基金the National Basic Research Program of China(2013CB228101)Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization(2013A061401005)
文摘Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained from water extraction of bio-oil, methanol–water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecular weight distribution of high-molecular-weight pyrolytic lignin was relatively wider, among which the contents of dimers to pentamers all accounted for 12% –18%,while the low-molecular-weight pyrolytic lignin mainly consisted of trimers(75.38%). The pyrolytic lignins had similar basic structures, both of which contained syringyl and guaiacyl units, whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile,thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.
基金Project(50721003)supported by the Creative Research Group of National Natural Science Foundation of ChinaProject(50825102)supported by the National Science Fund for Distinguished Young Scholars,China
文摘A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demonstrated.The HOPG surface was modified preferentially by covalent bonding of a two-dimensional 4-aminophenyl monolayer employing diazonium chemistry.AuCl4 -ions were attached to the Ar-NH2 termination and reduced electrochemically.This results in the formation of Au nuclei that could be further grown into gold nanoparticles.The formation of polyaniline as the shell wrap of Au nanoparticle was established by localized electro-polymerization.These core-shell nanocomposites prepared were characterized by AFM and cyclic voltammetry.The results show that the gold-polyaniline core-shell composites on HOPG have a mean particle size of 100 nm in diameter and the polyaniline shell thickness is about 15 nm.
基金supported by the National Natural Science Foundation of China(Grant No.51072165)the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China(Grant Nos.KP201307 and SKLSP201313)
文摘Pyrolytic carbon(PyC) coatings are deposited on the Nextel-440 fiber fabrics by chemical vapor deposition(CVD).The dielectric properties of the Nextel-440 fiber fabrics with PyC coatings(Nextel-440/PyC) are investigated in a temperature range from room temperature to 700℃ in X-band. Compared with the permittivity of the original Nextel-440 received,the complex permittivity of the Nextel-440/PyC(the real part εand the imaginary part ε), is significantly improved: εof the Nextel-440/PyC has a positive temperature coefficient, in contrast, εof the Nextel-440/PyC exhibits a negative temperature coefficient. Moreover, the reflection loss in units of d B is calculated. The results indicate that the microwave absorbing properties of the Nextel-440/PyC coatings is enhanced at 700℃ compared with that at lower temperatures.
文摘A comparison of voltammetric behavior of bisoprolol fumarate (BF) at edge and basal plane pyrolytic graphite electrodes (EPPGE/BPPGE) has been made with single wall carbon nanotube modified glassy carbon. The electrochemical properties are investigated exercising the cyclic voltammetry and square wave voltammetry (SWV). Enhanced peak current associated with bisoprolol fumarate oxidation at EPPGE is due to its better electron transfer property. Quantification of bisoprolol fumarate was carried out at pH 7.2 at both the pyrolytic graphite electrodes. Well-defined peak has been observed at ~ 792 and 954 mV at EPPGE and BPPGE respectively for bisoprolol fumarate oxidation. The detection limit is found to be 2.8 × 10–7 M and 7.3 × 10–7 M for EPPGE and BPPGE respectively. A comparison of common quantification parameters for bisoprolol at carbon nanotube modified glassy carbon electrode and bare BPPGE and EPPGE has been made and it is observed that carbon naotube modified glassy carbon exhibits sensitivity and detection limit close to that observed at bare basal plane pyrolytic graphite electrode. The method developed is applicable for determination of bisoprolol fumarate in pharmaceutical preparations and real samples.
基金Funded by the National Natural Science Foundation of China(51165006)
文摘A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon source with nitrogen as dilution gas, and the pyrolytic carbon started to deposit on the carbon fiber surface when the deposition temperature was reached. The morphology of pyrolytic carbon was characterized by SEM, and the surface properties of carbon fibers before and after CVD were characterized by Raman spectroscopy. The experimental results show that the electric heating method is a novel method to fabricate C/C composite materials, which can form a dense C/C composite material in a short time. The order degree and the average crystallite size of the carbon fiber surface were decreased after the experiment.
文摘This study aims to observe the durability of a pyrolytic carbon bileaflet mechanical valve prosthesis. The mechanical valves prosthesis was tested in vitro by the durability test instrument of valve prosthesis. Then in vivo, the durability of the implanted valves was observed with animal experiments and elinieal application. In the impact test for 5 min and durability test of 380 million eyeles in vitro, there was no the phenomenon of flyer, perforation and fracture observed, as well as no wear or pit found on the surface of valve leaflets. The valve leaflets could normally be turned on or off. The weight of the valve was（1.0031 ± 0.0004） g for 23 mm and（1.6003 ± 0.0002） g for 27 mm. The hydrodynamies test demonstrated that the valve prosthesis had still exeellent hemodynamic performance after the durability test. The animal autopsy showed that the valve leaflets could normally be turned on or off, and no wear was found. By follow-up of 62 patients implanted the valves, all patients had long-terms survival, no complication caused by valve was found. The age of the longest survival was more than 10 years. This study demonstrates that the new meehanieal valve prosthesis have excellent durable performance.
基金supported by the National Natural Science Foundation of China(No.20335030)The Teaching and Research Award Program for 0utstanding Young Teachers in Higher Education Institutions of M0E ER,C.,the Natural Science Foundation of Gansu(No.3ZS051-A25-023)Key Laboratory of Ploymer Materials of Gansu Province
文摘A method for determination of epinephrine（EP） in the presence of ascorbic acid （AA） and dopamine （DA） with bare pyrolytic graphite electrodes has been described for the first time. In pH 7.0 phosphate buffer solution, the linear relationship was observed between the reduction peak current of EP and its concentration over the range from 1×10^-4 to 5×10^-7 mol/L, the related coefficient is 0.9992 （N=8）.
文摘An optical transmission method was used in-situ to measure the rate of pyrolytic deposition from Mn_2(CO)_(10) induced by a CW CO_2 laser. The effect of the laser intensity, Mn_2(CO)_(10) vapor pressure and added gases (CO, O_2 and Ar) on the deposition rate has been examined.
基金National Natural Science F oundation of China !( No.5 9882 0 0 4)
文摘Chemical Vapor Infiltration (CVI) processes are the essential techniques for fabrication of high performance carbon carbon composites. Based on the polarized light and scanning electron analysis, the authors study the micro morphology and texture characteristics of pyrolytic carbon deposited in CVI process, as well as the growth behavior of pyrolytic carbon. The research shows that Rough Laminar (RL) texture has the hierarchical and self similar structural features, which reflects the stage growth and self similar behavior during the growth course of pyrolytic carbon. According to the two growth features, a laminated growth model of pyrolytic carbon is proposed with the concept of Cone Growth Units (CGU). The laminated growth model can provide a fine description for the growth course of RL pyrolytic carbon. The model indicates that formation, developing and combination of local high order structures (such as CGU structures) are the essential factors for the growth of RL texture. Smooth Laminar (SL) texture and ISO carbon come into being with long range orderliness and isotropy structure respectively, which no local high orderliness intermediate involves in.
文摘Highly oriented pyrolytic graphite (HOPG) is the substrate often used in scanningtunneling Ancroscopy (STM). It is well known that STM images of the basal plane of HOPG showsome unusual structUral patterns. In this letter, we present in situ STM images of some unusualfeatures on HOPG in solutions, including normal or abnormal chain-like featUres and hexagonal oroblique superPeriodic structures. These features emerge both next to and apart from the step ofHOPG.
基金This study was supported by the Key Research and Development Program of Shandong Province(2019 GNC106084)the Key Research and Development Program of the Innovation Research Fund of Zhaoyuan Institute of Industrial Technology(9101-220193).
文摘Huge amounts of Xanthoceras sorbifolia husks(XSH)are typically discarded after oil extraction.Since pyrolysis represents a promising solution to harness the bio-energy of XSH,in the present work the pyrolytic and kinetic characteristics of XSH and related crude cellulose extract(CCE)were studied considering different rates of heating(10,30 and 50℃ min^(-1)).The pyrolysis activation energy,pre-exponential factors and mechanism function were computed using different models namely Popescu,FWO(Flynn-Wall-Ozawa)and KAS(Kissinger-Akahira-Sunose).The pyrolysis process was articulated into three stages:dehydration(Stage I),primary devolatilization(Stage II),residual decomposition(Stage III).Marked variations in the average activation energy,thermal stability,final residuals and rate of reaction were noted.Stage II of XSH and CCE could be described by the Avramic-Erofeev equations.The average activation energies of XSH and CCE were found to be 269 and 296 kJ mol^(-1),respectively.
