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It is of great interest to develop metal-free electrocatalysts derived from cheap and environmental friendly biomass for oxygen reduction reaction (ORR). Here we report a facile method to prepare graphene-like N-doped carbons with a high degree of graphitization and large surface area using chitosan as precursor and FeCl 3 as soft template. The graphitization degree, surface area and the N species can be simply adjusted by controlling the annealing temperature. The soft template induced sample annealed at 800 °C (STS800) exhibits more positive onset potential than the samples annealed at 600 °C and 1000 °C (−0.08 V compared to −0.12 V and −0.15 V), which demonstrates that all of the high degree of graphitization, large surface area and the high percentages of pyridinic-N and graphitic-N play curial roles in the good ORR activity. The value of onset potential for STS800 is just 25 mV negative than that for Pt/C (−0.08 V to −0.055 V) and the ORR current density at merely −0.3 V for STS800 (−2.16 mA cm −2 ) is larger than that for Pt/C (−2.12 mA cm −2 ), which indicates its superior ORR activity even compared to Pt/C. Besides, the current for STS800 retains 95% at −0.2 V in 30000 s while that for Pt/C just retains 88%, which reveals its longer durability. With the addition of 3 M methanol, the CV curve of STS800 shows no noticeable current attenuation, indicating its good methanol tolerance. The excellent ORR activity, good methanol tolerance, and long durability demonstrate that STS800 could be a promising alternative for costly Pt-based electrocatalysts. [ABSTRACT FROM AUTHOR]

• Multi-color phosphorescent CDs were prepared. • These phosphorescent CDs accelerated the production of 1O 2. • Graphitization degrees and amounts of C O on RTP were first elucidated. • The proposed multi-color CDs showed the application of LED lamps. Room-temperature phosphorescence with multiple-color activated the widespread interest owing to their promising applications, howbeit, there still exist the insurmountable challenge, especially for elucidating their photoluminescence mechanism and tunable emissions. Here we systematically proposed several carbon dots (CDs) with different degrees of graphitization and amounts of carbonyl while sulfuric acid and ethanol played the critical roles. In brief, sulfuric acid functioned as the carbonization and strong oxidization reagent, while the increasing volumes of ethanol gradually reduced the boiling point of the reactions. Significantly, the energy of these phosphorescent CDs transferred from their excited triplets to oxygen molecules once they were irradiated by UV in aqueous, resulting in the production of the singlet oxygen to oxidize 3,3′,5,5′-tetramethylbenzidine. This finding indirectly provided the evidence for the existence of the phosphorescence rather than delayed fluorescence. Towards the photoluminescence mechanism, their fluorescence of CDs was originated from π-π* transition of C C in the carbon cores and n-π* transition of C O on the surfaces, while RTP was mainly attributed to n-π* transition of the carbonyls. The further evidence suggested that the CDs with different graphitization degrees and amounts of C O regulated their multiple-color phosphorescence. Besides, we employed these CDs for information encryption and preparing LED lamps. [ABSTRACT FROM AUTHOR]

Effects of viscosity index improver on morphology and graphitization degree of diesel particulate matter were investigated. Three lubricating oils with different viscosity were tested and compared in a two cylinder, four stroke, direct injection diesel engine. 5.0 wt. % and 10 wt. % viscosity index improver were added into lubricating oil to improve the viscosity-temperature performance respectively. Transmission Electron Microscope and Raman spectroscopy were employed to analyze the primary particle size distribution and graphitization degree of diesel particles from different lubricating oils. The primary particles size distribution conformed to Gaussian distribution. When the higher viscosity lubricating oil was used, the primary particle boundaries tend to be clearer and the mean diameter is smaller at 1600 rpm and 2200 rpm. As to the graphitization degree, the ratio of the D 1 band to G band areas (A D1 /A G ) increased with the increasing viscosity at 1600 rpm and 2200 rpm, indicating that the graphitization degree was lower when the higher viscosity lubricating oil was used. [ABSTRACT FROM AUTHOR]

Iron oxide/carbon nanofibers (FeO x /CNFs) were prepared by electrospinning FeCl 3 ·6H 2 O-polyacrylonitrile (PAN) precursors and heat treating at 400, 600, 800, 1000 °C. As carbonization temperature increased, granular FeO x gradually migrated from nanofiber interior with effectual contacts between electrolyte and active materials rising at first and then falling; Oxidation states of iron in FeO x /CNFs changed from Fe 2 O 3 to FeO and Fe with an improvement of capacity retention and an extra reversible capacity catalyzed by Fe; Graphitization process of carbon matrices proceed with less defective structures and heteroatom contents, leading to an increase of conductivity and a diminution of irreversible reactions during cycling. As systematically studied and compared in electrochemical performance, FeO x /CNFs with FeO, Fe state, highly graphitized carbon matrices and migration structure with FeO and Fe both embedded in and dispersed on carbon matrices presented stable cycling performance with a reversible capacity of ∼674 mAhg −1 after 60 cycles and outstanding rate capability. The above trade-off study of all the cooperative factors that affected the electrochemical property might make an effective guidance for preparation of promising FeO x /CNF anodes. [ABSTRACT FROM AUTHOR]

The porous carbon is considered to be one of the most suitable materials for volatile organic compounds (VOCs) adsorption and separation. Revealing the adsorption behavior and molecular interaction mechanism is of great significance for the preparation and synthesis of porous carbon adsorbents. Herein, we investigated detailed mechanistic effects of graphitization degrees and surface oxygen heteroatoms of porous carbon on their benzene and ethanol adsorptive separation performance by combining experiments and theoretical calculations. The results show that graphitized carbon surface has a stronger van der Waals interaction with benzene molecules compared to the disordered carbon surface, and thus exhibit a higher benzene adsorption performance and benzene/ethanol selectivity. While the introduction of oxygen functional groups enhances electrostatic affinity of porous carbon surface, resulting in higher ethanol adsorption capacity and ethanol/benzene selectivity under the entire pressure range. Subsequent theoretical calculations studied the adsorption behaviors of benzene and ethanol molecules in porous carbon models (with different graphitization degrees and oxygen contents) from the perspective of the weak interactions, and found the different molecular configurations of benzene and ethanol is the main leading cause of their different adsorption preferences. This study provided mechanistic insights on how the graphitization degrees and oxygen heteroatoms affected the capture and separation properties of porous carbon, which would further provide a rational alternative strategy in the preparation and synthesis of porous carbons for the effective gas mixture capture and separation. • The vital role of graphitization degrees and surface oxygen heteroatoms on VOCs adsorptive separation is proved. • Provide a molecular perspective on the adsorption behavior of VOCs in porous carbons. • The intrinsic enhancement mechanism in adsorption and separation process was clarified. • Provide a rational alternative strategy in preparation and synthesis of porous carbons. [ABSTRACT FROM AUTHOR]

Carbon felt electrodes for vanadium redox flow batteries are obtained by the graphitization of polyacrylonitrile based felts at different temperatures. Subsequently, the surface of the felts is modified via thermal oxidation at various temperatures. A single-cell experiment shows that the voltage efficiency is increased by this treatment. Electrode potentials measured with reference electrode setup show that this voltage efficiency increase is caused mainly by a reduction of the overpotential of the negative half-cell reaction. Consequently, this reaction is investigated further by cyclic voltammetry and the electrode activity is correlated with structural and surface chemical properties of the carbon fibers. By Raman, X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy the role of edge sites and oxygen containing functional groups (OCFs) for the electrochemical activity are elucidated. A significant activity increase is observed in correlation with these two characteristics. The amount of OCFs is correlated with structural defects (e.g. edge sites) of the carbon fibers and therefore decreases with an increasing graphitization degree. Thus, for the same thermal oxidation temperature carbon fibers graphitized at a lower temperature show higher activities than those graphitized at a higher temperature. [ABSTRACT FROM AUTHOR]

In this work, bamboo-shaped, multi-walled carbon nanotubes were synthesized via methane decomposition over a Ni-Co-Fe tri-metallic catalyst at 1000 °C. The nitrogen absorption (BET), X-ray diffraction (XRD), and particle size analysis results of the catalyst were used to demonstrate the surface area, size distribution, and crystallinity of the sample. The scanning electron microscopy (SEM) micrographs of the nanocarbons deposited via methane decomposition indicated that highly uniform carbon nanotubes were grown on the surface of the tri-metallic catalyst. The transmission electron microscopy (TEM) images showed that the carbon nanotubes were multi-walled and bamboo-shaped with a diameter of ~20 nm. Raman spectra revealed the graphitization degree of the CNTs with an I/ I of 1.84, indicative of the crystallinity of CNTs with structural defects. The thermal analysis shows the high oxidation stability of the multi-walled carbon nanotubes. [ABSTRACT FROM AUTHOR]

The roles of graphitization degree and surface functional groups of N-doped activated biochar are key concerns for phenol removal from wastewater. In this study, N-doped activated biochars with different doping ratios and activation levels were prepared to adsorb phenol. As the doping ratio rises, the surface N content and I D /I G value increased, and the surface O content decreased. The adsorption capacities were 126.5–170.7 (high activation level) and 100.6–117.9 mg/g (low activation level), and declined with the increase of doping ratio. The density functional theory calculation results show that the surface functional groups are beneficial to phenol adsorption to different degrees. N-5-pyrrolic (−66.6 KJ/mol) and N-Q (−56.9 and −58.0 KJ/mol) groups play the most important role among N functional groups, followed by N-X (−54.6 and −56.6 KJ/mol) group, while the N-6 (−54.5) and N-5-pyridones (−52.5 KJ/mol) groups play the least important role. The phenol adsorption energies of biochar with –C O, –COOH and –OH are − 262.2, − 57.7 and − 53.2 KJ/mol, respectively. With the degree of graphitization decreases, the adsorption energy first increase then dramatically declines which implies a mildly defect in the graphite structure is beneficial to adsorption, but serious defect is harmful even with the help of functional groups. Therefore, the declined adsorption performance of biochar with higher doping ratio is due to the decrease of surface O content and graphitization degree. This study offers theoretical support for the target regulation of biochar with high adsorption performance for wastewater treatment. • Functional groups contribute more than N functional groups in phenol adsorption. • The strongest adsorption is found when phenol is adsorbed by biochar with –C O. • N-5 and N-Q play the most vital role in phenol adsorption among N functional groups. • The adsorption energy first rises then drop with the higher degree of graphitization. [ABSTRACT FROM AUTHOR]

• The addition of alcohol fuels increases the graphitization degree of particles. • The C–H/C = C ratio increases with the use of low- to high-carbon chain alcohols. • The sp3/sp2 ratio are consistent with the changing trend of A D1 /A G for particles. • The D1-FWHM has an important effect on the oxidation activity of the particles. Alcohol fuels can effectively reduce particle emissions of diesel engines. However, the effects of lower and higher alcohols on the microscopic physicochemical properties of the particles, such as the graphitization degree, surface aliphatic C–H functional groups, O/C ratio, and the carbon atom hybridization is still unclear. Moreover, the relationship between microscopic physicochemical properties and particle oxidation activity has not been systematically studied. Therefore, the alcohol-diesel mixtures with different carbon chain lengths and the same oxygen content were used as the fuel for commercial diesel engines in this research, such as methanol/diesel mixture (M10), n-butanol/diesel mixture (NB25), and n-octanol/diesel mixture (NO45), and the pure diesel (D100) was used as a reference. The physicochemical properties of different fuel particles under two loads were analyzed using Raman spectroscopy, Fourier Transform Infrared, and X-ray photoelectron spectroscopy. The results showed that as the load increased, the A D1 /A G of the particles decreased, which meant that the graphitization degree increased. Moreover, the addition of alcohol fuel will increase the graphitization degree of the particles. In addition, the addition of alcohol fuel will reduce the aliphatic C–H functional groups and the O/C ratio on the surface of the particles. However, with the use of M10 to NO45, the aliphatic C–H functional groups continued to increase, while the O/C ratio first decreased and then increased, and the NB25 particle had the smallest O/C ratio. Through the Partial Least Square analysis, it was found that the fringe length and fringe separation distance had the most significant impact on the activation energy of the particles. Interestingly, among the characteristic parameters of Raman spectroscopy, the D1-full width at half maximum had the largest contribution to the activation energy. [ABSTRACT FROM AUTHOR]

• The addition of DMM has a stable and higher proportion of regular soot. • The use of DMM has lower amounts of C H groups. • O/C rate and sp3/sp2 rate have the lowest effect on the apparent activation energy (Ea). • The sequence degree of soot structure (A D /A G) has the large influence on Ea. Physicochemical properties of soot, such as graphitization degree and surface functional groups of dimethoxymethane (DMM)–diesel blends, have been conducted with Raman spectrum, FT-IR (Fourier transform infrared spectroscopy), and XPS (X-ray photoelectron spectroscopy), respectively. The experimental samples are collected in a four-cylinder, turbocharged engine at two different speeds (2200 and 1400 rpm), different loads (1.2 and 0.6 MPa), and different fuels (D100, DMM6.4, and DMM13). The results show that with the increase in loads, the difference of graphitization degree is gradually disappeared with different fuels, and a higher graphitization degree can be obtained. Moreover, the use of DMM reduces the proportion of unsaturated fuels, thereby leading to lower amounts of C H groups. In terms of oxygenated surface functional groups' content of particulate matter (PM), the C O functional group accounts for 4%-12%, the COO functional group accounts for 1%-4%, and the C O functional group accounts for 3%-8%. Sensitivity analysis of the microscopic properties of soot found that the O/C ratio and sp3/sp2 ratio have the lowest effect on the apparent activation energy (Ea) of soot. And A D1 /A G , A D2 /A G , and A D4 /A G significantly affect Ea. [ABSTRACT FROM AUTHOR]

The microstructure and texture of C/C composites with a resin-derived carbon, a rough laminar (RL) pyrocarbon and a smooth laminar pyrocarbon, before and after braking tests, were investigated by Raman spectroscopy. The full width at half maximum (FWHM) of the D-band indicates the amount of defects in the in-plane lattice, while the G-to-D band intensity (peak area) ratios ( I/ I) is used to evaluate the degree of graphitization. The results show that the FWHM of D-band of sample with RL pyrocarbon changes greatly from 36 cm to 168 cm after braking tests, which indicates that a large number of lattice defects are produced on its wear surface. However, the graphitization degree of resin-derived carbon sample rises significantly, because the I/ I increases from 0.427 to 0.928. Braking tests under normal loading conditions, involving high temperature and high pressure, produce a lot of lattice defects on the wear surface, and induce the graphitization of the surface. Sample with RL pyrocarbon having a low hardness is easy to deform, and has the most lattice defects on the wear surface after braking. While raw materials with resin-derived carbon have the lowest graphitization degree which rises greatly during braking. [ABSTRACT FROM AUTHOR]

Abstract: Ternary intercalation compounds of carbon fiber (ICCF) were successfully synthesized by soaking pitch-based carbon fibers in solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF) containing dissolved alkali metals (lithium, sodium, or potassium). ICCF with stage-1 and random stage was synthesized in alkali metal–DME and potassium–THF systems using different types of carbon fibers. However, ICCF with stage-1 could not be synthesized in lithium– or sodium–THF systems using carbon fibers with a low graphitization degree. Furthermore, the influence of the graphitization degree in the synthesis of ICCF was discussed. The graphitization degree of the host carbon fiber, in addition to the dimensions and steric structure of the intercalated complex affected the formation of TICCF. [Copyright &y& Elsevier]

Abstract: The structure and the oxidation activity of the solid carbon produced from catalytic decomposition of methane at different temperatures were investigated using TEM, XRD, Raman and TPO techniques. The results show that the graphitization degree of the solid carbon is increased with decomposition reaction temperature. The addition of ethylene or acetylene to methane can change the growth way of the solid carbon and decrease their graphitization degree. The average oxidation temperature of the solid carbon has a close relationship with the corresponding graphitization degree. The addition of ethylene or acetylene to methane can decrease the average oxidation temperature of the solid carbon. [Copyright &y& Elsevier]

High density graphite is widely used in friction and sealing area. The pore structure inside, which were mainly affected by molding method, has a great effect on its thermophysical properties and friction performance. Herein, isostatic pressing, compression molding and hot molding method were utilized in our work to prepare high density graphite with different pore structure in order to study the relationship between pore structure and the comprehensive property. The results showed that the properties of graphite vary significantly in different directions, which was mainly affected by porosity, pore size distribution, the specific surface area, pore shape and fractal dimension. The influence mechanism of three graphite materials with different pore structures on thermophysical properties was delved, and the correlation between the comprehensive properties of graphite materials and their pore structures was verified. The in-plane comprehensive properties of hot molding graphite were the best, the graphitization degree was the highest (75.4%) and the total porosity was the lowest (15.08%). Especially, according to the pore structure analysis of the graphite, we found a positive correlation between the fractal dimension and the friction and wear properties of the graphite materials. Furthermore, research of pore structure explained the properties of graphite materials and proved the potential application of graphite in friction and sealing fields. [Display omitted] • Graphite with different pore structures were prepared by different forming process. • The evolution of pore structure was deduced during the preparation of graphite products. • Pore structure characteristic parameters effect the comprehensive property of graphite. • Hot Molding can improve the orientation and degree of graphitization of the graphite. • Fractal dimension was positively correlated with the friction and wear properties. [ABSTRACT FROM AUTHOR]

Abstract: Effects of graphite crucible on mass transport and crystal growth process has been investigated in the fabrication of SiC single crystal by the seeded sublimation growth method. Different graphitization degrees of the crucibles were obtained by heat treatment at various temperatures between 2100 and 2300 °C. The crucibles were subjected to SEM and XRD in which the graphitization degree was determined quantitatively. The experimental results indicate that the graphite crucible plays an important role in the SiC crystal growth by providing carbon. High crystal growth is obtained by using the untreated crucibles (corresponding to low graphitization degree), which contributes to the reaction activity between Si and graphite of the crucible. Increasing the graphitization degree results in degradation in crystal growth, even in the graphitization of the SiC seed crystal. [Copyright &y& Elsevier]

• Soot exhibited higher graphitization degrees along the after-treatment system components. • Aliphatic C–H groups in soot more likely to oxidize than other surface functional groups. • Soot particles further transformed in the exhaust after-treatment system. • Activation energies of soot oxidation determined 132–190 kJ/mol by the Arrhenius model. The primary objective of the present study is to investigate the variations of soot particles' oxidation reactivity along the components of the exhaust after-treatment system in a diesel engine and analyze its quantitative correlation with surface functional groups (SFGs) and graphitization degree. Soot particles generated from a 16-cylinder turbocharged diesel engine were sampled thoroughly before and after the diesel oxidation catalyst (DOC), as well as after a catalyzed diesel particulate filter (CDPF). Using a set of characterization techniques of Fourier transform infrared (FTIR), Raman spectroscopy and Thermal gravimetric analyzer (TGA), the surface functional groups (SFGs), graphitization degree and oxidation reactivity of soot particle samples along the exhaust after-treatment system components were examined. Results showed that, for all conditions, soot oxidation activation energies increased almost linearly along the after-treatment system, indicating that soot particles became more and more stable, with the inherent graphitization degree achieved the highest right after the CDPF. Meanwhile, the combined characterization results also indicated that amorphous carbon and reactive light volatile fractions have been removed or oxidized via passing through the DOC and CDPF monolith. It was thus concluded that the higher oxidation activity of soot particles was characterized by lower graphitization degree and higher aliphatic C-H group concentration. The catalyst components in the after-treatment systems (DOC and CDPF) effectively increases the graphitization of the exhaust particles, leaving more stable particles that would require much higher energies from active regeneration or more powerful catalysts on the CDPF wall surface to clean them up. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-N X /C-NC1100 with high graphitization is prepared via a stepwise pyrolysis method. • Fe-N X /C-NC1100 achieves a high density of active sites under harsh thermal treatment. • Fe-N X /C-NC1100 shows superior ORR stability with 25 mV loss of E 1/2 after 30 K cycles. • Fe-N X /C-NC1100 reserves 71 % of activity after 100 h at 0.5 V in H 2 -air fuel cell test. • Stability enhancement is ascribed to the strong antioxidant ability of NC support. Metal-nitrogen/carbon (M-N X /C) materials have been hailed as promising electrocatalysts toward oxygen reduction reaction (ORR). However, most reported promising Fe-N X /C catalysts are prohibited by their low stability in acidic media. Here we report a rational stepwise pyrolysis strategy for stabilizing isolated Fe-N X sites on highly graphitized N-doped carbon (NC) supports. The NC support derived from a harsh thermal treatment of 1100 °C can apparently enhance the graphitization degree of catalysts. The targeted catalyst, Fe-N X /C-NC1100 achieved a half-wave potential (E 1/2) of 0.811 V and displayed superior stability in both ORR (only 25 mV loss of E 1/2 after 30000 cycles) and fuel cell (71 % current retention at a voltage of 0.5 V after 100 h) tests. High graphitization degree of carbon support was responsible for the enhancement of stability, which empowers strong antioxidant ability to Fe-N X /C catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • The double-cavity yolk-shell Fe 3 O 4 @C microspheres are successfully synthesized. • The optimized reflection loss has reached −58.44 dB with the thickness of 1.9 mm. • Effective bandwidth is 6.0 GHz (12.0–18.0 GHz) covering the whole Ku band. • Carbonization temperature has great influence on impedance matching. Carbon electromagnetic wave (EMW) absorbing materials are often limited in performance improvement due to their excessive conductivity and single loss mechanism. And the introduction of magnetic components with rational construction of microstructure is evolved as an effective approach to reinforcing the electromagnetic properties of carbon-based microwave absorbers. For the first time, a double-cavity yolk-shell hollow Fe 3 O 4 @C (H-Fe 3 O 4 @C) microwave absorber is fabricated via a "coating–coating–etching" method, by controlled high-temperature carbonization. The resultant carbon shell is actually composed of different contents of amorphous carbon and graphite, which has a powerful influence on the graphitization degree. When H-Fe 3 O 4 @C microspheres are carbonized at 650 ℃, the optimized reflection loss (RL) has reached −58.44 dB and the effective bandwidth is 6.0 GHz (12.0–18.0 GHz) covering the whole Ku band with the thickness of merely 1.9 mm (filler loading: 30 wt%), which is better than most carbon-based absorbing materials reported yet. The outstanding EMW absorbing properties are ascribed to the multiple reflections and scattering arising from the designed double-cavity yolk-shell structure, the multi-interface polarization between Fe 3 O 4 /air and C/air, and the good impedance matching relating to the proper carbonization degree of carbon component at 650 °C. [ABSTRACT FROM AUTHOR]

As the heterogeneous Fenton reactions are always restricted by the unsatisfied reduction efficiency of Fe(III) and ineffective consumption of H 2 O 2 , many strategies have been developed. In this work, we prepared hydrothermal carbons (HTC) with different graphitization degrees using glucose under different hydrothermal times, and then they were combined with ferrihydrite (Fh). Interestingly, although 30%HTC/Fh has much better BPA degradation efficiency than Fh (26 times larger of calculated degradation rate constants), the decomposition rate of H 2 O 2 in the former system is lower. The generated Fe(II) of HTC/Fh is much higher than that of Fh during the heterogeneous Fenton reactions, and the degradation of BPA is almost unaffected by p-benzoquinone (scavenger of superoxide radicals (O 2 •- )) while greatly inhibited by isopropanol (scavenger of hydroxyl radicals (HO • )). These results indicate that HTC act as electron donors due to the abundant carbon-centered persistent free radicals (PFRs) to directly reduce Fe(III) to Fe(II) and therefore decrease the H 2 O 2 consumption by Fe(III), which subsequently inhibits the generation of less active O 2 •- . HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh.2 O 2 . HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this paper, the Pure-DLC, B 4 C-DLC and Si-DLC films were deposited on the AISI 304 stainless steel by unbalanced magnetron sputtering method. The tribological behaviors of the films sliding against SiC and Si 3 N 4 balls were tested by a ball-on-disc tribometer under high relative humidity (90%). The results showed that the tribological behaviors for the films sliding against SiC exhibits more excellent than the corresponding film sliding against Si 3 N 4 , mainly showing lower friction coefficients and wear rates, narrower wear widths as well as lower fluctuant friction curves. There are two main reasons for the results. On the one hand, the films sliding against SiC ball exhibit the superior graphitization degree, smaller size of microcrystalline graphite and smaller disorder and sp2 hybrid bond content. On the other hand, the films sliding against Si 3 N 4 ball show more abrasive particles during the friction process, which leads to the adsorbate of films on the surface to be more easily desorbed so that the σ bond reacted easily with water vapor and oxygen is more exposed and forms a strong covalent bond. Unlabelled Image • The SiC and Si 3 N 4 balls exhibit different tribological properties under different environments. • The Pure-DLC, B 4 C-DLC and Si-DLC film sliding against SiC ball presents excellent tribological properties. • The Pure-DLC sliding against SiC possess lower friction coefficient and disc wear rate. • The tribological mechanism for the films sliding against SiC and Si 3 N 4 were discussed. [ABSTRACT FROM AUTHOR]

• The influence of graphitization degree on HTGR reactor physics calculation is studied. • The k eff can be underestimated if graphitization degree is not taken into account. • The result is of significance for graphite reactors. Nuclear graphite is widely used in traditional and advanced nuclear reactors. Especially in High Temperature Gas-cooled Reactors (HTGRs), nuclear graphite is the main composition of fuel element and reflector. The graphite cross section data libraries used in practical reactor physics calculations are generally evaluated from ideal single crystal graphite material. However, the actual nuclear graphite is not ideal but contains a certain proportion of amorphous carbon, which is measured as graphitization degree. By this short paper, it is shown that the graphitization degree of nuclear graphite has a considerable influence on HTGR reactor physics calculation. The observation would be important for the engineering design of various types of graphite reactors. [ABSTRACT FROM AUTHOR]

An experimental study was performed by employing a seal pair of phenolic resin impregnated graphite and high chromium martensitic stainless steel 9Cr18. A purpose-built test rig was designed and fabricated to study the effect of face temperature on the surface morphology of a seal ring made of phenolic resin impregnated graphite with different graphitization degrees for varying PV values (pressure × velocity). As revealed by the results, the effect of rotational speed on heat generation between the two mating surfaces was more significant than that of fluid pressure. The effects of surface frictional temperature between the two faces were found different when the phenolic resin impregnated graphite ring with different graphitization degrees. The worn surfaces of the phenolic resin impregnated graphite rings were examined with the assistance of scanning electron microscopy and 3D measuring laser microscopy to investigate the wear mechanism for these different mating rings. Both adhesive and abrasive wear mechanisms were discovered under the working conditions. It was found out that the phenolic resin impregnated graphite ring with a high degree of graphitization was worn more severely at high PV values. Under the conditions of high speeds or high PV values, the phenolic resin impregnated graphite with fine and compact graphite matrix particles, medium degree of graphitization, high thermal conductivity and hardness is the top choice. ∙ This paper studies the effect of face temperature under different PV values on frictional characteristics of impregnated phenolic resin graphite rings with different graphitization degrees. ∙The influence mechanism of PV values on face temperature of mechanical seal is revealed. And the effects of face temperature on phenolic resin graphite stationary rings with different graphitization degrees are studied. ∙This paper provides some important conclusions for choosing the proper phenolic resin impregnated graphite stationary ring under the conditions of high speeds or high PV values. [ABSTRACT FROM AUTHOR]

Graphene nanoribbon (GNR) is an important candidate for future nanoelectronics due to its high carrier mobility and dimension-controlled band gap. Polymer-templated growth is a promising method toward high quality and massive production of GNRs. However, the obtained GNRs so far are still quite defective. In order to rationally control the crystallinity of the synthesized GNRs, herein we systematically investigate the effect of polymer chemical structure on their templated growth of GNRs. We studied the morphology/dimensions, composition, graphitization degree, and electrical conductivity of GNRs derived from four different types of electrospun polymers. The four polymers polystyrene (PS), poly(vinyl alcohol) (PVA), polyvinylphenol (PVP), and Novolac (a phenolic resin) are chosen to investigate the effect of metal binding and the effect of aromatic moieties. We found that metal-binding functional groups are crucial for obtaining uniform and continuous GNRs. On the other hand, a polymer with aromatic moieties leads to a higher sp(2) percentage in the resulting GNRs, showing a higher graphitization degree and electrical conductivity.