In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural prope...In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural properties of schist subjected to four conditions were investigated:freeze-thaw cycles in air(FTA),freeze-thaw cycles in water(FTW),dry-wet cycles(DW),and dry-wet-freeze-thaw cycles(DWFT).Uniaxial compressive strength(UCS),water absorption,ultrasonication,low-field nuclear magnetic resonance,and scanning electron microscopy analyses were conducted.The integrity attenuation characteristics of the longitudinal wave velocity,UCS,and elastic modulus were analyzed.The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist.The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media(R2>0.97).Different media affected the schist deterioration and half-life,with the FTW-immersed samples having a half-life of 28 cycles.Furthermore,the longitudinal wave velocity decreased as the number of cycles increased,with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles.Moreover,the damage variables of compressive strength and elastic modulus increased with the number of cycles.After 40 cycles,the schist exposed to FTW exhibited the highest damage variables and saturated water content.展开更多
Cadmium(Cd)or excess copper(Cu)has a great impact in terms of toxicity on living organisms as it severely affects crop growth,yield and food security;thus,warranting appropriate measures for the remediation of Cd or C...Cadmium(Cd)or excess copper(Cu)has a great impact in terms of toxicity on living organisms as it severely affects crop growth,yield and food security;thus,warranting appropriate measures for the remediation of Cd or Cu polluted soils.Phytoextraction of heavy metal(HM)using tolerant plants along with organic chelators has gained global attention,and this study provided further insights into this issue.Pot experiments were performed to evaluate the effects of different types of chelators[ethylenediamine tetraacetic acid(EDTA),ethylenediamine disuccinic acid(EDDS)and citric acid(CA)]to improve the phytoextraction capacity of Ricinus communis L.for the metals Cd and Cu.Contaminated soil from a copper smelter was used in this study.A rhizon soil sampler was used to determine the metal concentrations in soil pore water.The results indicated that R.communis was an adequate candidate for chelator induced phytoextraction under the experimental conditions and that EDDS would be a good candidate chelator for the phytoextraction of Cu in soils.EDTA addition obviously improved the uptake of Cd and Cu in R.communis;however,it posed the greatest risk because the concentration of HMs in soil pore water was very high even after 40 days.Compared with EDTA and EDDS,CA had few effects on Cd or Cu uptake in R.communis.Linear relationships between the metal uptake in R.communis shoots and the maximum HM concentrations in soil pore water under HM,2.5,5,and 10 mmol·kg^(-1) treatments were typically observed.From the results of this study,it could be concluded that EDDS treatments played a promising role in increasing the uptake of Cd or Cu and reducing its phytotoxicity.EDDS application could be an effective approach for the phytoextraction of Cd or Cu from polluted soils by growing Ricinus communis L.展开更多
To improve the practical application of carbon steel,developing a superhydrophobic coating with outstanding mechanical properties is essential for effective corrosion resistance protection.Here,we obtained a robust su...To improve the practical application of carbon steel,developing a superhydrophobic coating with outstanding mechanical properties is essential for effective corrosion resistance protection.Here,we obtained a robust superhydrophobic anti-corrosion coating with a cauliflower structure by co-depositing the lauric acid with Ni ions and Mn ions onto a carbon steel through electrodeposition method.As demonstrated by the results,superhydrophobic Ni/Mn alloy(SNMAmit)displays a multi-hierarchical micro/nano cauliflower structure under the synergy of optimal parameters,exhibiting superb superhydrophobicity with contact angle of 161.9°and sliding angle of 6.2°.Surprisingly,the Tafel polarization curves in 3.5%NaCl showed that the corrosion potential of SNMAmit coating was 476 mV,and the corrosion current density was reduced from 1.39×10^(−5)to 5.89×10^(−7)A/cm^(2).The reduced corrosion current density of superhydrophobic Ni/Mn alloy(SNMA)indicates that SNMA coating can significantly enhance the anti-corrosion properties of carbon steel.In addition,after being subjected to various damages such as blade scraping,tape cyclic peeling,acid and alkalis,sandpaper cyclic abrasion,high temperatures,ultrasound,and graphite contaminant,SNMA showed good mechanical stability,interference resistance,heat resistance,and self-cleaning properties,which made it suitable for hostile conditions.展开更多
Expanded polystyrene (EPS) is a common type of microplastics (MPs) often found in coastal areas especially aquaculture areas.It is considered as an important site for microbial colonization and biofilm formation,as we...Expanded polystyrene (EPS) is a common type of microplastics (MPs) often found in coastal areas especially aquaculture areas.It is considered as an important site for microbial colonization and biofilm formation,as well as a carrier of pollutants like heavy metals.However,the dynamic changes of bacterial communities attached to EPS and their interaction with heavy metals are still poorly unknown.In this study,a one-year field exposure experiment was conducted at an aquaculture farm near Donghai Island,in Leizhou Bay,Zhanjiang,Guangdong,in South China Sea.The bacterial communities attached to EPS MPs were examined by 16S r DNA high-throughput sequencing,and the relationships between bacterial biofilms and heavy metals were explored.The results show that there were notable seasonal variations in the bacterial diversity of EPS MPs.Species biodiversity was the highest in summer and the lowest in winter.The greatest number of bacterial species and lowest level of uniformity were observed in the spring.The bacterial community structure changed with exposure time,and the most significant difference in the 12-month group (P<0.05) was found.The dominant bacterial species attached to EPS MPs were mainly Proteobackteria and Firmicutes at the phylum level,and Pseudomonas and Exiguobacterium were dominant at the genus level.Furthermore,EPS MPs acted as transport carriers for potential pathogenic bacteria.High correlations were found between bacterial species and the total concentration of heavy metals on EPS MPs,as well as their speciation fractions.Different chemical speciation of heavy metals migrated and altered over seasons within biofilms,which would further exacerbate the ecological risks.展开更多
Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c...Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.展开更多
Mg-based amorphous alloys exhibit efficient catalytic performance and excellent biocompatibility with a promising application probability,specifically in the field of azo dye wastewater degradation.However,the problem...Mg-based amorphous alloys exhibit efficient catalytic performance and excellent biocompatibility with a promising application probability,specifically in the field of azo dye wastewater degradation.However,the problems like difficulty in preparation and poor cycling stability need to be solved.At present,Mg-based amorphous alloys applied in wastewater degradation are available in powder and ribbon.The amorphous alloy powder fabricated by ball milling has a high specific surface area,and its reactivity is thousands of times better than that of gas atomized alloy powder.But the development is limited due to the high energy consumption,difficult and costly process of powder recycling.The single roller melt-spinning method is a new manufacturing process of amorphous alloy ribbon.Compared to amorphous powder,the specific surface area of amorphous ribbon is relatively lower,therefore,it is necessary to carry out surface modification to enhance it.Dealloying is a way that can form a pore structure on the surface of the amorphous alloys,increasing the specific surface area and providing more reactive sites,which all contribute to the catalytic performance.Exploring the optimal conditions for Mg-based amorphous alloys in wastewater degradation by adjusting amorphous alloy composition,choosing suitable method to preparation and surface modification,reducing cost,expanding the pH range will advance the steps to put Mg-based amorphous alloys in industrial environments into practice.展开更多
Half-Heusler(HH)compounds have emerged as promising candidates for high-temperature thermoelectric power generation;however,their mechanical properties in service environments have been scarcely reported.In this study...Half-Heusler(HH)compounds have emerged as promising candidates for high-temperature thermoelectric power generation;however,their mechanical properties in service environments have been scarcely reported.In this study,the temperature dependences of the mechanical responses and failure mechanisms of an n-type ZrNiSn-based HH compound(Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015))were systematically evaluated through high-temperature compression tests and microfractographic characterization.The test results indicated that the elastic modulus and ultimate compressive strength of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)decreased with increasing temperature.The stress-strain behavior of the material changed from linear(300,500,and 700 K)to nonlinear(900 and 1100 K).Microfractography observations revealed that increasing the temperature reduced the strength of the grain boundary as well as aggravated oxidation and segregation on the fracture surface,which significantly impacted the macro-compressive behavior of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)at elevated temperatures.Finally,a stress-strain relationship for the ZrNiSnbased HH was proposed to describe the change in the compressive response from linear to nonlinear with increasing temperature.The present study elucidates the load-carrying and failure mechanisms of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)within its operational temperature range,providing valuable guidance for the mechanical design of HH thermoelectric devices over their entire service temperature range.展开更多
The direct oxidation of methane to methanol(DOMM) has been recognized as a significant technology for efficiently utilizing low-concentration coalbed methane(LCMM) and supplying liquid fuel.Herein,the noble metals(Pt,...The direct oxidation of methane to methanol(DOMM) has been recognized as a significant technology for efficiently utilizing low-concentration coalbed methane(LCMM) and supplying liquid fuel.Herein,the noble metals(Pt,Pd and Ru) modified Cu/alkalized sepiolite(CuX/SEPA) catalysts were prepared and used for the DOMM in a gas-phase system at low temperatures.The CuRu/SEPA exhibited the highest methanol production of 53 μmol·g^(-1)·h^(-1) and methanol selectivity of 90% under the optimal reaction conditions.Various characterizations demonstrated that the addition of Ru promoted the formation of Cu^(2+)and the contraction of Cu—Si/Al bonds to reduce the distance between framework Al atoms of SEPA to further generate more Al pairs,which facilitated the formation of reactive dicopper species([Cu_(2)O]^(2+)or [Cu_(2)O_(2)]^(2+)).Investigation of the reaction mechanism revealed that [Cu_(2)O]^(2+) or [Cu_(2)O_(2)]^(2+) species could adsorb and activate methane to form CH_(3)O^(*) species and ultimately generated methanol with the assistance of water.展开更多
Correction to:Rare Met.https://doi.org/10.1007/s12598-021-01815-z In the original publication,Fig.5 was published with few mistakes.The correct version of Fig.5 is given in this correction.
The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The result...The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The results indicated that Ce microalloying improved the hot ductility of S32654 throughout the entire deformation temperature range.Specifically,the addition of Ce greatly enhanced the hot ductility in the low(850–900℃)and high(1100–1250℃)temperature ranges,but only slightly increased that in the medium temperature range(900–1100℃).At 850–900℃,Ce addition not only reduced the sulfur(S)content and suppressed the S segregation at the grain boundary,but also promoted the formation of slip bands and deformation twins,apparently improving the hot ductility.At 900–1100℃,Ce addition promoted the nucleation of intergranularσphases and dynamic recrystallization(DRX)grains,which have adverse and beneficial effects on the hot ductility,respectively.As the temperature increased,the precipitation tendency presented a first increasing and then decreasing trend around 1000℃,while the DRX gradually increased.Accordingly,the improvement degree of Ce on the hot ductility first weakened and then enhanced.At 1100–1250℃,Ce significantly promoted the DRX to form more fine and uniform deformation structure,thereby remarkably increasing the cracking resistance and then the hot ductility.展开更多
Proton exchange membrane fuel cells(PEMFCs)have gained increasing interests as promising power sources due to their ability to convert hydrogen and oxygen directly into electricity with high efficiency and zero greenh...Proton exchange membrane fuel cells(PEMFCs)have gained increasing interests as promising power sources due to their ability to convert hydrogen and oxygen directly into electricity with high efficiency and zero greenhouse gas emissions.Bipolar plates(BPs)are considered as a critical component of PEMFCs,serving to collect current,separate gases,distribute the flow field,and conduct heat.This paper reviews the technical status and advancements in BP materials,with special focus on strategies for enhancing interfacial contact resistance(ICR)and corrosion resistance through conductive polymer(CP)coatings.First,commonly used BP materials in PEMFCs are summarized.Then,the advantages and limitations of various coatings for metallic BPs are discussed.Finally,recent progress in CP coatings for metallic BPs,aimed at achieving high corrosion resistance and low ICR,is comprehensively reviewed.展开更多
The metal triazole(MTA)-based MOFs were found to preferentially adsorb O-rich species,which had enhanced electrocatalytic oxygen reduction reactions(ORR)and stabilized the O-containing species during the discharge and...The metal triazole(MTA)-based MOFs were found to preferentially adsorb O-rich species,which had enhanced electrocatalytic oxygen reduction reactions(ORR)and stabilized the O-containing species during the discharge and charge processes in Li-O_(2)battery.However,the MOFs exhibited low electron conductivity and poor electron transfer interface in the electrocatalysis,limiting the electrocatalytic activity.To address this issue,a nanocomposite with the Co-MTA-coated carbon nano tubes(Co-MTA-C)was constructed,which formed the three-dimensional conductivity network connected with the intersecting carbon nano tube(CNT).In this composite,the electron-rich Co-MTA interacted with the highly conductive CNT,resulting in a charge redistribution.Optimized the electronic structure of the Co center through compositional modifications presented a high valence compared to the pure MOFs.In situ X-ray absorption spectroscopy revealed a direct reaction of Co sites with intermediates such as LiO_(x),leading to the formation of nanosheet array discharge products.The battery based on optimized CoMTA-C demonstrated fast kinetics and superior stability,with a low overpotential of 1.13 V,high specific capacity of 9057 mAh g^(-1),and long-term durability of 600 cycles.It provides a facile and effective strategy for enhancing the electrocatalytic performance through rational tuning of high-conductivity substances.展开更多
The distribution and source of the solvent-extractable organic and inorganic components in PM2.5 （aerodynamics equivalent diameter below 2.5 microns）, and PM10 （aerodynamics equivalent diameter below 10 microns） f...The distribution and source of the solvent-extractable organic and inorganic components in PM2.5 （aerodynamics equivalent diameter below 2.5 microns）, and PM10 （aerodynamics equivalent diameter below 10 microns） fractions of airborne particles were studied weekly from September 2006 to August 2007 in Beijing. The extracted organic and inorganic compounds identified in both particle size ranges consisted of n-alkanes, PAHs （polycyclic aromatic hydrocarbons）, fatty acids and water soluble ions. The potential emission sources of these organic compounds were reconciled by combining the values of n-alkane carbon preference index （CPI）, %waxCn, selected diagnostic ratios of PAHs and principal component analysis in both size ranges. The mean cumulative concentrations of n-alkanes reached 1128.65 ng/m3 in Beijing, 74% of which （i.e., 831.7 ng/m3） was in the PM2.5 fraction, PAHs reached 136.45 ng/m3 （113.44 ng/m3 or 83% in PM2.5）, and fatty acids reached 436.99 ng/m3 （324.41 ng/m3 or 74% in PM2.5）, which resulted in overall enrichment in the fine particles. The average concentrations of SO42-, NO3-, and NH4＋ were 21.3 ± 15.2, 6.1 ±1.8, 12.5 ± 6.1 μg/m3 in PM2.5, and 25.8±15.5, 8.9± 2.6, 16.9±9.5 μg/m3 in PM10, respectively. These three secondary ions primarily existed as ammonium sulfate （（NH4）2SO4）, ammonium bisulfate （NH4HSO4） and ammonium nitrate （NH4NO3）. The characteristic ratios of PAHs revealed that the primary sources of PAHs were coal combustion, followed by gasoline combustion. The ratios of stearic/palmitic acid indicated the major contribution of vehicle emissions to fatty acids in airborne particles. The major alkane sources were biogenic sources and fossil fuel combustion. The major sources of PAHs were vehicular emission and coal combustion.展开更多
The solvent extractable organic compounds （SEOC）, including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, and dicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing, were measured ...The solvent extractable organic compounds （SEOC）, including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, and dicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing, were measured via gas chromatography-mass spectrometry for determining the characteristics and sources of these organic pollutants. The concentrations of total n-alkanes, PAHs, and organic acids before Chinese Spring Festival Eve （1025.5, 95.9, and 543.3 ng/m3, respectively） were higher than those after （536.6, 58.9, and 331.8 ng/m3, respectively）, n-Aalkanes and PAHs had much higher concentration in nighttime than those in daytime because of high relative humidity and low wind speed during the night. Combustion of coal and exhaust emission were major sources of n- alkanes. It could be concluded by the characteristic ratios that the primary source of PAHs in fine particles was the combustion of coal, but the combustion of gasoline was in the next place. The ratios of C18：0/C16 indicated the contribution of vehicular emissions to the fatty acids. Dicarboxylic and aromatic acids were abundant in daytime than in nighttime because these acids were secondary organic acid and the photochemical degradation of aromatic hydrocarbons was the main source.展开更多
Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limitin...Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.展开更多
Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry.The results showed substantially more severe pollutio...Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry.The results showed substantially more severe pollution in Beijing.Of the 14 compounds detected,the total average concentration was 100 ng/m^3 in Beijing,compared with 11.6 ng/m^3 in Xinglong.More specifically,concentration of nitro-aromatic compounds(NACs)(81.9 ng/m^3 in Beijing and 8.49 ng/m^3 in Xinglong) was the highest,followed by aromatic acids(14.6 ng/m^3 in Beijing and 2.42 ng/m^3 in Xinglong) and aromatic aldehydes(3.62 ng/m^3 in Beijing and 0.681 ng/m^3 in Xinglong).In terms of seasonal variation,the highest concentrations were found for 4-nitrocatechol in winter in Beijing(79.1±63.9 ng/m^3) and 4-nitrophenol in winter in Xinglong(9.72±8.94 ng/m^3).The analysis also revealed diurnal variations across different seasons.Most compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating intensity.While some presented higher levels during the day,which attributed to the photo-oxidation process for summer and more biomass burning activities for autumn.Higher concentrations appeared in winter and autumn than in spring and summer,which resulted from more coal combustions and adverse meteorological conditions.The significant correlations among NACs indicated similar sources of pollution.Higher correlations presented within each subgroup than those between the subgroups.Good correlations between levoglucosan and nitrophenols,nitrocatechols,nitro salicylic acids,with correlation coefficients(r) of 0.66,0.69 and 0.69,respectively,indicating an important role of biomass burning among primary sources.展开更多
A TIA1N/MoS2-Ti coating was developed to improve the tribological characteristics of a single TiAlN coating. The MoS2-Ti layer was deposited by a DC magnetron sputtering system on the hard TiAIN coated SKD-11 steel su...A TIA1N/MoS2-Ti coating was developed to improve the tribological characteristics of a single TiAlN coating. The MoS2-Ti layer was deposited by a DC magnetron sputtering system on the hard TiAIN coated SKD-11 steel substrate. The titanium content in the MoS2-Ti layer was 11.3 at.% determined by EPMA. The surface morphology was observed by FE-SEM. The TiAlN layer exhibited excellent adhesion and hardness. However, the deposition of an MoS2-Zi layer on the TRAIN led to a significant improvement in tribological properties without affecting the adhesion to the substrate. The MoS2-Ti layer significantly decreased the friction coefficient of the TiAIN coating, and the drop was 48% after MoS2-Ti deposition. Also, the MoS2-Ti layer remarkably decreased the wear rate of the TtA1N coating.展开更多
Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the ran...Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.展开更多
Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal ...Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance.Herein,the thermoelectric properties of nominal Bi_(1-x)Cu_(x)Se samples were studied as the functions of the content of Cu additive and temperature.It is found that Cu additives in BiSe(1)profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process,(2)increase considerably the effective mass and thus the Seebeck coefficient,and(3)yield point defects and Cu-Se secondary phases that effectively scatter heat-carrying phonons.As a result,the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT~0.29 in Bi_(1-x)Cu_(x)Se(x=0.03)sample at 467 K in parallel to the pressure direction and a zT~0.20 at 468 K in the perpendicular direction.展开更多
To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate（APP）, the UV-curable pentaerythritol triacrylate（PETA） was used to microencapsulate APP via the UV curing polymerization met...To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate（APP）, the UV-curable pentaerythritol triacrylate（PETA） was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP（PETA-APP） was characterized by Fourier transform infrared spectroscopy（FTIR）, scanning electron microscopy（SEM）, and thermogravimetric（TG） analysis. PETA-APP was used as intumescent flame retardant（IFR） alone to flame retard polypropylene（PP）. The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index（LOI）, vertical burning test（UL-94） and cone calorimeter（CC） test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate（HRR）, mass loss rate（MLR） and smoke production rate（SPR） of PP/PETAAPP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy（XPS） tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42171108 and 42101136)Sichuan Science and Technology Program(Nos.2024NSFSC2007 and2025YFHZ0273)Natural Science Starting Project of SWPU(No.2024QHZ029)。
文摘In cold regions,slope rocks are inevitably impacted by freeze-thaw,dry-wet cycles and their alternating actions,leading to strength weakening and pore degradation.In this study,the mechanical and microstructural properties of schist subjected to four conditions were investigated:freeze-thaw cycles in air(FTA),freeze-thaw cycles in water(FTW),dry-wet cycles(DW),and dry-wet-freeze-thaw cycles(DWFT).Uniaxial compressive strength(UCS),water absorption,ultrasonication,low-field nuclear magnetic resonance,and scanning electron microscopy analyses were conducted.The integrity attenuation characteristics of the longitudinal wave velocity,UCS,and elastic modulus were analyzed.The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist.The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media(R2>0.97).Different media affected the schist deterioration and half-life,with the FTW-immersed samples having a half-life of 28 cycles.Furthermore,the longitudinal wave velocity decreased as the number of cycles increased,with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles.Moreover,the damage variables of compressive strength and elastic modulus increased with the number of cycles.After 40 cycles,the schist exposed to FTW exhibited the highest damage variables and saturated water content.
基金Supported by the Joint Funds of the National Natural Science Foundation of China(U2340219)。
文摘Cadmium(Cd)or excess copper(Cu)has a great impact in terms of toxicity on living organisms as it severely affects crop growth,yield and food security;thus,warranting appropriate measures for the remediation of Cd or Cu polluted soils.Phytoextraction of heavy metal(HM)using tolerant plants along with organic chelators has gained global attention,and this study provided further insights into this issue.Pot experiments were performed to evaluate the effects of different types of chelators[ethylenediamine tetraacetic acid(EDTA),ethylenediamine disuccinic acid(EDDS)and citric acid(CA)]to improve the phytoextraction capacity of Ricinus communis L.for the metals Cd and Cu.Contaminated soil from a copper smelter was used in this study.A rhizon soil sampler was used to determine the metal concentrations in soil pore water.The results indicated that R.communis was an adequate candidate for chelator induced phytoextraction under the experimental conditions and that EDDS would be a good candidate chelator for the phytoextraction of Cu in soils.EDTA addition obviously improved the uptake of Cd and Cu in R.communis;however,it posed the greatest risk because the concentration of HMs in soil pore water was very high even after 40 days.Compared with EDTA and EDDS,CA had few effects on Cd or Cu uptake in R.communis.Linear relationships between the metal uptake in R.communis shoots and the maximum HM concentrations in soil pore water under HM,2.5,5,and 10 mmol·kg^(-1) treatments were typically observed.From the results of this study,it could be concluded that EDDS treatments played a promising role in increasing the uptake of Cd or Cu and reducing its phytotoxicity.EDDS application could be an effective approach for the phytoextraction of Cd or Cu from polluted soils by growing Ricinus communis L.
基金the National Natural Science Foundation of China(U21A2057)the Natural Science Foundation of Chongqing(No.cstc2021jcyj-msxmX1139)the Science and Technology Research Program of Chongqing Municipal Education Commission(Nos.KJZD-M202301201 and KJZD-K202304502).
文摘To improve the practical application of carbon steel,developing a superhydrophobic coating with outstanding mechanical properties is essential for effective corrosion resistance protection.Here,we obtained a robust superhydrophobic anti-corrosion coating with a cauliflower structure by co-depositing the lauric acid with Ni ions and Mn ions onto a carbon steel through electrodeposition method.As demonstrated by the results,superhydrophobic Ni/Mn alloy(SNMAmit)displays a multi-hierarchical micro/nano cauliflower structure under the synergy of optimal parameters,exhibiting superb superhydrophobicity with contact angle of 161.9°and sliding angle of 6.2°.Surprisingly,the Tafel polarization curves in 3.5%NaCl showed that the corrosion potential of SNMAmit coating was 476 mV,and the corrosion current density was reduced from 1.39×10^(−5)to 5.89×10^(−7)A/cm^(2).The reduced corrosion current density of superhydrophobic Ni/Mn alloy(SNMA)indicates that SNMA coating can significantly enhance the anti-corrosion properties of carbon steel.In addition,after being subjected to various damages such as blade scraping,tape cyclic peeling,acid and alkalis,sandpaper cyclic abrasion,high temperatures,ultrasound,and graphite contaminant,SNMA showed good mechanical stability,interference resistance,heat resistance,and self-cleaning properties,which made it suitable for hostile conditions.
基金Supported by the Hainan Province Science and Technology Special Fund (No.ZDYF2022SHFZ317)the Guangdong Province Key Laboratory of Applied Marine Biology (No.2023B1212060047)the Program for Scientific Research Start-up Funds of Guangdong Ocean University (No.060302332301)。
文摘Expanded polystyrene (EPS) is a common type of microplastics (MPs) often found in coastal areas especially aquaculture areas.It is considered as an important site for microbial colonization and biofilm formation,as well as a carrier of pollutants like heavy metals.However,the dynamic changes of bacterial communities attached to EPS and their interaction with heavy metals are still poorly unknown.In this study,a one-year field exposure experiment was conducted at an aquaculture farm near Donghai Island,in Leizhou Bay,Zhanjiang,Guangdong,in South China Sea.The bacterial communities attached to EPS MPs were examined by 16S r DNA high-throughput sequencing,and the relationships between bacterial biofilms and heavy metals were explored.The results show that there were notable seasonal variations in the bacterial diversity of EPS MPs.Species biodiversity was the highest in summer and the lowest in winter.The greatest number of bacterial species and lowest level of uniformity were observed in the spring.The bacterial community structure changed with exposure time,and the most significant difference in the 12-month group (P<0.05) was found.The dominant bacterial species attached to EPS MPs were mainly Proteobackteria and Firmicutes at the phylum level,and Pseudomonas and Exiguobacterium were dominant at the genus level.Furthermore,EPS MPs acted as transport carriers for potential pathogenic bacteria.High correlations were found between bacterial species and the total concentration of heavy metals on EPS MPs,as well as their speciation fractions.Different chemical speciation of heavy metals migrated and altered over seasons within biofilms,which would further exacerbate the ecological risks.
基金financially supported by the National Key R&D Program of China (No.2021YFA1200203)the National Natural Science Foundation of China (Nos.51922026 and 51975111)+1 种基金the Fundamental Research Funds for the Central Universities (No.N2202015,N2002005,and N2105001)the 111 Project of China (No.BP0719037 and B20029)。
文摘Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.
基金supported by the National Natural Science Foundation of China(Grant No.52071276)the Natural Science Foundation of Chongqing,China(Grant No.CSTB2022NSCQ-MSX0440)the Fundamental Research Funds for the Central Universities(Grant No.SWUXDJH202313,SWU-KQ22083).
文摘Mg-based amorphous alloys exhibit efficient catalytic performance and excellent biocompatibility with a promising application probability,specifically in the field of azo dye wastewater degradation.However,the problems like difficulty in preparation and poor cycling stability need to be solved.At present,Mg-based amorphous alloys applied in wastewater degradation are available in powder and ribbon.The amorphous alloy powder fabricated by ball milling has a high specific surface area,and its reactivity is thousands of times better than that of gas atomized alloy powder.But the development is limited due to the high energy consumption,difficult and costly process of powder recycling.The single roller melt-spinning method is a new manufacturing process of amorphous alloy ribbon.Compared to amorphous powder,the specific surface area of amorphous ribbon is relatively lower,therefore,it is necessary to carry out surface modification to enhance it.Dealloying is a way that can form a pore structure on the surface of the amorphous alloys,increasing the specific surface area and providing more reactive sites,which all contribute to the catalytic performance.Exploring the optimal conditions for Mg-based amorphous alloys in wastewater degradation by adjusting amorphous alloy composition,choosing suitable method to preparation and surface modification,reducing cost,expanding the pH range will advance the steps to put Mg-based amorphous alloys in industrial environments into practice.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.U2141208 and 12141203)Shengqiang Bai acknowledges the support from the International Partnership Program of the Chinese Academy of Sciences(Grant No.121631KYSB20200012).
文摘Half-Heusler(HH)compounds have emerged as promising candidates for high-temperature thermoelectric power generation;however,their mechanical properties in service environments have been scarcely reported.In this study,the temperature dependences of the mechanical responses and failure mechanisms of an n-type ZrNiSn-based HH compound(Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015))were systematically evaluated through high-temperature compression tests and microfractographic characterization.The test results indicated that the elastic modulus and ultimate compressive strength of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)decreased with increasing temperature.The stress-strain behavior of the material changed from linear(300,500,and 700 K)to nonlinear(900 and 1100 K).Microfractography observations revealed that increasing the temperature reduced the strength of the grain boundary as well as aggravated oxidation and segregation on the fracture surface,which significantly impacted the macro-compressive behavior of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)at elevated temperatures.Finally,a stress-strain relationship for the ZrNiSnbased HH was proposed to describe the change in the compressive response from linear to nonlinear with increasing temperature.The present study elucidates the load-carrying and failure mechanisms of Zr_(0.5)Hf_(0.5)NiSn_(0.985)Sb_(0.015)within its operational temperature range,providing valuable guidance for the mechanical design of HH thermoelectric devices over their entire service temperature range.
基金financial assistance from the Anhui Provincial Major Science and Technology Project(202003a05020022)the Institute of Energy,Hefei Comprehensive National Science Center(21KZS219)。
文摘The direct oxidation of methane to methanol(DOMM) has been recognized as a significant technology for efficiently utilizing low-concentration coalbed methane(LCMM) and supplying liquid fuel.Herein,the noble metals(Pt,Pd and Ru) modified Cu/alkalized sepiolite(CuX/SEPA) catalysts were prepared and used for the DOMM in a gas-phase system at low temperatures.The CuRu/SEPA exhibited the highest methanol production of 53 μmol·g^(-1)·h^(-1) and methanol selectivity of 90% under the optimal reaction conditions.Various characterizations demonstrated that the addition of Ru promoted the formation of Cu^(2+)and the contraction of Cu—Si/Al bonds to reduce the distance between framework Al atoms of SEPA to further generate more Al pairs,which facilitated the formation of reactive dicopper species([Cu_(2)O]^(2+)or [Cu_(2)O_(2)]^(2+)).Investigation of the reaction mechanism revealed that [Cu_(2)O]^(2+) or [Cu_(2)O_(2)]^(2+) species could adsorb and activate methane to form CH_(3)O^(*) species and ultimately generated methanol with the assistance of water.
文摘Correction to:Rare Met.https://doi.org/10.1007/s12598-021-01815-z In the original publication,Fig.5 was published with few mistakes.The correct version of Fig.5 is given in this correction.
基金financially supported by National Natural Science Foundation of China(grant nos.52325406,52374334,and U1860204)Joint Program of Science and Technology Plans in Liaoning Province(grant nos.2023JH2/101700244 and 2023JH2/101800045)+1 种基金Fundamental Research Funds for the Central Universities(grant no.N2430002)Program of Introducing Talents of Discipline to Universities(grant no.B21001).
文摘The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The results indicated that Ce microalloying improved the hot ductility of S32654 throughout the entire deformation temperature range.Specifically,the addition of Ce greatly enhanced the hot ductility in the low(850–900℃)and high(1100–1250℃)temperature ranges,but only slightly increased that in the medium temperature range(900–1100℃).At 850–900℃,Ce addition not only reduced the sulfur(S)content and suppressed the S segregation at the grain boundary,but also promoted the formation of slip bands and deformation twins,apparently improving the hot ductility.At 900–1100℃,Ce addition promoted the nucleation of intergranularσphases and dynamic recrystallization(DRX)grains,which have adverse and beneficial effects on the hot ductility,respectively.As the temperature increased,the precipitation tendency presented a first increasing and then decreasing trend around 1000℃,while the DRX gradually increased.Accordingly,the improvement degree of Ce on the hot ductility first weakened and then enhanced.At 1100–1250℃,Ce significantly promoted the DRX to form more fine and uniform deformation structure,thereby remarkably increasing the cracking resistance and then the hot ductility.
基金supported by the National Natural Science Foundation of China under Grant Nos.12102310 and U21A20113the Guangdong Basic and Applied Basic Research Foundation under Grant No.2020A1515110818+2 种基金the Inovation Team Project for Colleges and Universities of Guangdong Province under Grant No.2023KCXTD030the Key Project of Biomedicine and Health in Colleges and Universities of Guangdong Province under Grant No.2021ZDZX2055the Medical Science and Technology Research Fund of Guangdong Province under Grant No.A2022004.
文摘Proton exchange membrane fuel cells(PEMFCs)have gained increasing interests as promising power sources due to their ability to convert hydrogen and oxygen directly into electricity with high efficiency and zero greenhouse gas emissions.Bipolar plates(BPs)are considered as a critical component of PEMFCs,serving to collect current,separate gases,distribute the flow field,and conduct heat.This paper reviews the technical status and advancements in BP materials,with special focus on strategies for enhancing interfacial contact resistance(ICR)and corrosion resistance through conductive polymer(CP)coatings.First,commonly used BP materials in PEMFCs are summarized.Then,the advantages and limitations of various coatings for metallic BPs are discussed.Finally,recent progress in CP coatings for metallic BPs,aimed at achieving high corrosion resistance and low ICR,is comprehensively reviewed.
基金financially supported by the National Natural Science Foundations of China(No.12304037)the Interdisciplinary Intelligence Super Computer Center of BNUZH
文摘The metal triazole(MTA)-based MOFs were found to preferentially adsorb O-rich species,which had enhanced electrocatalytic oxygen reduction reactions(ORR)and stabilized the O-containing species during the discharge and charge processes in Li-O_(2)battery.However,the MOFs exhibited low electron conductivity and poor electron transfer interface in the electrocatalysis,limiting the electrocatalytic activity.To address this issue,a nanocomposite with the Co-MTA-coated carbon nano tubes(Co-MTA-C)was constructed,which formed the three-dimensional conductivity network connected with the intersecting carbon nano tube(CNT).In this composite,the electron-rich Co-MTA interacted with the highly conductive CNT,resulting in a charge redistribution.Optimized the electronic structure of the Co center through compositional modifications presented a high valence compared to the pure MOFs.In situ X-ray absorption spectroscopy revealed a direct reaction of Co sites with intermediates such as LiO_(x),leading to the formation of nanosheet array discharge products.The battery based on optimized CoMTA-C demonstrated fast kinetics and superior stability,with a low overpotential of 1.13 V,high specific capacity of 9057 mAh g^(-1),and long-term durability of 600 cycles.It provides a facile and effective strategy for enhancing the electrocatalytic performance through rational tuning of high-conductivity substances.
基金supported by the Science and Technology Project of Beijing (No. D09040903670902)the Chinese Academy of Sciences for Key Topics in Innovation Engineering (No. KZCX2-YW-Q02-03)the Basic Research and Development Program (973) of China (No.2007CB407303)
文摘The distribution and source of the solvent-extractable organic and inorganic components in PM2.5 （aerodynamics equivalent diameter below 2.5 microns）, and PM10 （aerodynamics equivalent diameter below 10 microns） fractions of airborne particles were studied weekly from September 2006 to August 2007 in Beijing. The extracted organic and inorganic compounds identified in both particle size ranges consisted of n-alkanes, PAHs （polycyclic aromatic hydrocarbons）, fatty acids and water soluble ions. The potential emission sources of these organic compounds were reconciled by combining the values of n-alkane carbon preference index （CPI）, %waxCn, selected diagnostic ratios of PAHs and principal component analysis in both size ranges. The mean cumulative concentrations of n-alkanes reached 1128.65 ng/m3 in Beijing, 74% of which （i.e., 831.7 ng/m3） was in the PM2.5 fraction, PAHs reached 136.45 ng/m3 （113.44 ng/m3 or 83% in PM2.5）, and fatty acids reached 436.99 ng/m3 （324.41 ng/m3 or 74% in PM2.5）, which resulted in overall enrichment in the fine particles. The average concentrations of SO42-, NO3-, and NH4＋ were 21.3 ± 15.2, 6.1 ±1.8, 12.5 ± 6.1 μg/m3 in PM2.5, and 25.8±15.5, 8.9± 2.6, 16.9±9.5 μg/m3 in PM10, respectively. These three secondary ions primarily existed as ammonium sulfate （（NH4）2SO4）, ammonium bisulfate （NH4HSO4） and ammonium nitrate （NH4NO3）. The characteristic ratios of PAHs revealed that the primary sources of PAHs were coal combustion, followed by gasoline combustion. The ratios of stearic/palmitic acid indicated the major contribution of vehicle emissions to fatty acids in airborne particles. The major alkane sources were biogenic sources and fossil fuel combustion. The major sources of PAHs were vehicular emission and coal combustion.
基金supported by the National Basic Re-search Program (973) of China (No. 2007CB407303)the National Natural Science Foundation of China (No.40525016)the Hi-Tech Research and Development Program (863) of China (No. 2006AA06A301).
文摘The solvent extractable organic compounds （SEOC）, including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, and dicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing, were measured via gas chromatography-mass spectrometry for determining the characteristics and sources of these organic pollutants. The concentrations of total n-alkanes, PAHs, and organic acids before Chinese Spring Festival Eve （1025.5, 95.9, and 543.3 ng/m3, respectively） were higher than those after （536.6, 58.9, and 331.8 ng/m3, respectively）, n-Aalkanes and PAHs had much higher concentration in nighttime than those in daytime because of high relative humidity and low wind speed during the night. Combustion of coal and exhaust emission were major sources of n- alkanes. It could be concluded by the characteristic ratios that the primary source of PAHs in fine particles was the combustion of coal, but the combustion of gasoline was in the next place. The ratios of C18：0/C16 indicated the contribution of vehicular emissions to the fatty acids. Dicarboxylic and aromatic acids were abundant in daytime than in nighttime because these acids were secondary organic acid and the photochemical degradation of aromatic hydrocarbons was the main source.
基金financially supported by the National Natural Science Foundation of China(Nos.50933005 and 51121001)the Program for Changjiang Scholars and Innovative Research Teams in Universities of China(IRT 1026)
文摘Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.
基金supported by the National Key R&D Program of China (No:2017YFC0210000)the Ministry of Science and Technology of China (No:2016YFC0202001).
文摘Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry.The results showed substantially more severe pollution in Beijing.Of the 14 compounds detected,the total average concentration was 100 ng/m^3 in Beijing,compared with 11.6 ng/m^3 in Xinglong.More specifically,concentration of nitro-aromatic compounds(NACs)(81.9 ng/m^3 in Beijing and 8.49 ng/m^3 in Xinglong) was the highest,followed by aromatic acids(14.6 ng/m^3 in Beijing and 2.42 ng/m^3 in Xinglong) and aromatic aldehydes(3.62 ng/m^3 in Beijing and 0.681 ng/m^3 in Xinglong).In terms of seasonal variation,the highest concentrations were found for 4-nitrocatechol in winter in Beijing(79.1±63.9 ng/m^3) and 4-nitrophenol in winter in Xinglong(9.72±8.94 ng/m^3).The analysis also revealed diurnal variations across different seasons.Most compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating intensity.While some presented higher levels during the day,which attributed to the photo-oxidation process for summer and more biomass burning activities for autumn.Higher concentrations appeared in winter and autumn than in spring and summer,which resulted from more coal combustions and adverse meteorological conditions.The significant correlations among NACs indicated similar sources of pollution.Higher correlations presented within each subgroup than those between the subgroups.Good correlations between levoglucosan and nitrophenols,nitrocatechols,nitro salicylic acids,with correlation coefficients(r) of 0.66,0.69 and 0.69,respectively,indicating an important role of biomass burning among primary sources.
文摘A TIA1N/MoS2-Ti coating was developed to improve the tribological characteristics of a single TiAlN coating. The MoS2-Ti layer was deposited by a DC magnetron sputtering system on the hard TiAIN coated SKD-11 steel substrate. The titanium content in the MoS2-Ti layer was 11.3 at.% determined by EPMA. The surface morphology was observed by FE-SEM. The TiAlN layer exhibited excellent adhesion and hardness. However, the deposition of an MoS2-Zi layer on the TRAIN led to a significant improvement in tribological properties without affecting the adhesion to the substrate. The MoS2-Ti layer significantly decreased the friction coefficient of the TiAIN coating, and the drop was 48% after MoS2-Ti deposition. Also, the MoS2-Ti layer remarkably decreased the wear rate of the TtA1N coating.
基金The Hi-Tech Research and Development Program (863) of China (No. 2002AA601290) and the National Natural ScienceFoundation of China (No. 20247012 50578155)
文摘Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.
基金the Graduate Scientific Research and Innovation Foundation of Chongqing,China(No.CYB 19064)the National Natural Science Foundation of China(Nos.51772035,11674040,51472036 and 51672270)+4 种基金the Fundamental Research Funds for the Central Universities(No.106112017CDJQJ308821)the Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSW-SLH016)the CSC Scholarship(No.201806050180)2019 ITS Summer Fellowship,the Natural Science Foundation of Chongqing,China(No.cstc2019jcyj-msxmX0554)the Starting Research Fund from Chongqing University。
文摘Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance.Herein,the thermoelectric properties of nominal Bi_(1-x)Cu_(x)Se samples were studied as the functions of the content of Cu additive and temperature.It is found that Cu additives in BiSe(1)profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process,(2)increase considerably the effective mass and thus the Seebeck coefficient,and(3)yield point defects and Cu-Se secondary phases that effectively scatter heat-carrying phonons.As a result,the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT~0.29 in Bi_(1-x)Cu_(x)Se(x=0.03)sample at 467 K in parallel to the pressure direction and a zT~0.20 at 468 K in the perpendicular direction.
基金financially supported by the National Natural Science Foundation of China(Nos.50933005,51121001)the Program for Changjiang Scholars and Innovative Research Team in Universities(IRT1026)
文摘To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate（APP）, the UV-curable pentaerythritol triacrylate（PETA） was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP（PETA-APP） was characterized by Fourier transform infrared spectroscopy（FTIR）, scanning electron microscopy（SEM）, and thermogravimetric（TG） analysis. PETA-APP was used as intumescent flame retardant（IFR） alone to flame retard polypropylene（PP）. The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index（LOI）, vertical burning test（UL-94） and cone calorimeter（CC） test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate（HRR）, mass loss rate（MLR） and smoke production rate（SPR） of PP/PETAAPP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy（XPS） tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.
