The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification proc...The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.展开更多
Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve ...Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.展开更多
Effect of graphene nanoplatelets(GNPs)addition on mechanical properties of magnesium–10wt%Titanium(Mg–10Ti)alloy is investigated in current work.The Mg-(10Ti+0.18GNPs)composite was synthesized using the semi powder ...Effect of graphene nanoplatelets(GNPs)addition on mechanical properties of magnesium–10wt%Titanium(Mg–10Ti)alloy is investigated in current work.The Mg-(10Ti+0.18GNPs)composite was synthesized using the semi powder metallurgy method followed by hot extrusion.Microstructural characterization results revealed the uniform distribution of reinforcement(Ti+GNPs)particles in the matrix,therefore(Ti+GNPs)particles act as an effective reinforcing filler to prevent the deformation.Room temperature tensile results showed that the addition of Ti+GNPs to monolithic Mg lead to increase in 0.2%yield strength(0.2%YS),ultimate tensile strength(UTS),and failure strain.Scanning Electron Microscopy(SEM),Energy-Dispersive X-ray Spectroscopy(EDS)and X-Ray Diffraction(XRD)were used to investigate the surface morphology,elemental dispersion and phase analysis,respectively.展开更多
The research on electrocatalysts with relatively lower price than Pt and excellent electrocatalytic performance for the cathode oxygen reduction reaction(ORR) and anode methanol oxidation reaction(MOR) is vital for th...The research on electrocatalysts with relatively lower price than Pt and excellent electrocatalytic performance for the cathode oxygen reduction reaction(ORR) and anode methanol oxidation reaction(MOR) is vital for the development of direct methanol fuel cells(DMFCs). In this work, we develop a cyanogel-reduction method to synthesize reduced graphene oxide(rGO) supported highly dispersed PdNi alloy nanocrystals(PdNi/rGO) with high alloying degree and tunable Pd/Ni ratio. The large specific surface area and the d-band center downshift of Pd result in excellent activity of Pd4 Ni1/rGO nanohybrids for the ORR. The modification of Pd electronic structure can facilitate the adsorption of CH3 OH on Pd surface and the highly oxophilic property of Ni can eliminate/mitigate the COadsintermediates poisoning, which make PdNi/r GO nanohybrids possess superior MOR activity. In addition, rGO improve the stability of PdNi alloy nanocrystals for the ORR and MOR. Due to high activity and stability for the ORR and MOR, PdNi/rGO nanohybrids are promising to be an available bifunctional electrocatalyst in DMFCs.展开更多
A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the in...A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the internal structure,the friction surface,and the wear debris were characterized by scanning electron microscopy,X-ray diffraction,and Raman spectroscopy.Compared with the original 7075 aluminum alloy,the hardness and elastic modulus of the 7075 Al/GNPs composite were found to have increased by 29%and 36%,respectively.The results of tribological experiments indicated that the composite also exhibited a lower wear rate than the original 7075 aluminum alloy.展开更多
Although graphene oxide(GO)has emerged as an excellent lubricant additive in water,there remain great challenges in their practical application due to high production costs.By taking into account the low cost and also...Although graphene oxide(GO)has emerged as an excellent lubricant additive in water,there remain great challenges in their practical application due to high production costs.By taking into account the low cost and also its excellent tribological properties,it is likely that nano-SiO_(2)can be used as a lubricant additive to partially replace GO.Hence,this paper aims to explore the tribological properties of nano-SiO_(2)incorporated in GO nanofluids for partial GO replacement by investigating the friction coefficient and wear volume of the prepared SiO_(2)/GO hybrid nanofluids for magnesium alloy/steel sliding pairs.The experiments reveal that the SiO_(2)/GO hybrids retain low friction coefficients as compared to individual GO or SiO_(2)at all test conditions in this study.However,as for the bearing capacity test,all samples can provide a low wear volume under the loads of 1 and 3 N.With the increase of the normal load,there is considerable differences in the anti-wear behavior.Compared with that of individual GO nanofluids,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by50.5%at 5 N and by 49.2%at 8 N.Furthermore,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by46.3%under the rigorous conditions,as compared to individual GO nanofluids.The findings provide new insights into developing carbon nanomaterial-based hybrid nanofluids for magnesium alloy formation.展开更多
Non-noble metal-based catalysts,especially stable ones,have gained increasing attentions in the field of electronically catalytic hydrogen evolution reaction(HER).In this work,an N-doped carbon confined Co–Ni alloy w...Non-noble metal-based catalysts,especially stable ones,have gained increasing attentions in the field of electronically catalytic hydrogen evolution reaction(HER).In this work,an N-doped carbon confined Co–Ni alloy with reduced graphene oxide(rGO) decoration(CoNi@N-C/rGO) was fabricated for HER.The prepared catalyst exhibited excellent HER activity in an acidic electrolyte(Tafel slope of ~133.7 m V).The results showed that the enhanced HER performance of the nanostructures is attributed to the chemical and electronic synergic effect between the confined Co–Ni alloy and r GO.Stability tests,realized via longterm potential cycles and extended electrolysis,provided the confirmation of the exceptional durability of the catalyst,which originated from the confining effect of the N-doped carbon shell.This versatile method provides a strategy for designing stable non-precious metal electrocatalysts confined by carboncoating.展开更多
To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sh...To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.展开更多
Photothermal therapy becomes a hotspot in the treatment of bone tumors. Magnesium and its alloys are regarded as potential bone implants for their favorable mechanical property and biodegradable in vivo. However, ther...Photothermal therapy becomes a hotspot in the treatment of bone tumors. Magnesium and its alloys are regarded as potential bone implants for their favorable mechanical property and biodegradable in vivo. However, there is few research devoted to fabricating a photothermal coating on Mg alloy. In the present study, reduced graphene oxide coating with a strong photothermal effect was prepared on the surface of AZ31via two steps. Firstly, graphene oxide coating was deposited on the surface via electrophoresis deposited(GO#), followed by a reduction process of the graphene oxide coating in ultrapure water(rGO#). GO# and rGO# coatings were characterized by SEM, Raman, XRD, FTIR,and XPS. The results revealed that, compared with GO# coating, the content of oxygen-containing(C-O/C-O-C, C=O, O-C=O) groups on rGO# coating was significantly decreased. rGO# coating was found tightly adhered to AZ31 substrate. According to the first-principles calculations, the well-bonded heterostructure between MgO and rGO is the main reason for the strong bonding force. Moreover, the prepared rGO# coating showed a superior photothermal effect, which brings a new strategy to the treatment of bone tumors with Mg-based implants.展开更多
In this study, two nano-derivatives from nano-Graphene oxide (GO) were synthesized. Regarding to GON and GOS by reaction GO with 2-amino ethanol and 2-marcapto ethanol respectively, the GO, GON, GOS were characterized...In this study, two nano-derivatives from nano-Graphene oxide (GO) were synthesized. Regarding to GON and GOS by reaction GO with 2-amino ethanol and 2-marcapto ethanol respectively, the GO, GON, GOS were characterized by FTIR, XRD and FSEM. Evaluation prepared compound to inhibitors corrosion for Carbon steel in acidic media at (1 - 6 ppm) concentration and different temperature 298, 308, 318, 328 K. The electrochemical technique used Tafel plot to measure the efficiency of inhibitor. It was observed that the corrosion rate and charge transfer of the carbon steel for the inhibitor increase with increase of temperature and decrease with increase of the inhibitor concentration in the same temperature. The GON had inhibition efficiency reached 96.96% for the 6 ppm concentration at 298 K.展开更多
Advancing efficient and affordable electrocatalysts to boost the oxygen evolution reaction(OER)is pivotal for sustainable green hydrogen production.Herein,we propose the fabrication of nickel-iron alloy nanoparticles-...Advancing efficient and affordable electrocatalysts to boost the oxygen evolution reaction(OER)is pivotal for sustainable green hydrogen production.Herein,we propose the fabrication of nickel-iron alloy nanoparticles-encapsulated on N-doped vertically aligned graphene array on carbon cloth(NiFe@NVG/CC)as a highly active three-dimensional(3D)catalyst electrode for OER.In 1 M KOH,such NiFe@NVG/CC demonstrates outstanding catalytic performance,necessitating merely overpotential of 245 mV for achieving a current density of 10 mA·cm^(−2),a remarkably low Tafel slope of 36.2 mV·dec^(−1).Furthermore,density functional theory calculations validate that the incorporate of N species into graphene can reinforce the electrocatalytic activity though reducing the reaction energy barrier during the conversion of*O to*OOH intermediates.The outstanding performance and structural benefits of NiFe@NVG/CC offer valuable insights for the development of innovative and efficient electrocatalysts for water oxidation.展开更多
The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging (500℃ for 15 rain), the hardness and the conductivity of the alloy rap...The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging (500℃ for 15 rain), the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.展开更多
Testing results shows that alloying with Ce and Y improves the hardness and softens temperature of cold worked Cu-Cr-Zr alloys obviously, while the conductivity was fluctuant with the variation of RE content. Observat...Testing results shows that alloying with Ce and Y improves the hardness and softens temperature of cold worked Cu-Cr-Zr alloys obviously, while the conductivity was fluctuant with the variation of RE content. Observation and analysis indicate that micro-dosage RE elements helps to refine microstructure and morphology of Cu-Cr-Zr-RE alloys, suppress microstructure coarsening and improves homogeneous level of Cu-Cr-Zr alloys. Alloying with 0.01% Ce causes about 1% IACS increment of conductivity, and reduces about 2%~3.5% IACS conductivity after alloying with 0.03%~0.04% RE (Ce or Ce+Y) for Cu-Cr-Zr alloys. The microstructure of as-cast Cu-Cr-Zr alloy is refined after alloying with 0.01% Ce while the plasticity is improved slightly. Alloying with 0.01%~0.04% RE improves the softening temperature of deformed Cu-Cr-Zr alloys about 20~40 K; hardness is also improved about 20~35 HV. Test data indicate that alloying with Ce+Y raises softening temperature and hardness of Cu-Cr-Zr alloys more notably than alloying with pure Ce.展开更多
Phases of Cu-(0.4%-2.0%) Cr-(0.05%-0.16%) Zr alloys were analyzed in both as cast and deformed state. Solute-rich clusters of Cr, which was supposed to form during aging treatment, were observed in as cast state; ...Phases of Cu-(0.4%-2.0%) Cr-(0.05%-0.16%) Zr alloys were analyzed in both as cast and deformed state. Solute-rich clusters of Cr, which was supposed to form during aging treatment, were observed in as cast state; along with the morphology character, corresponding preferential orientation of Cr phase in as cast state was also investigated. Precipitates were observed to distribute in the matrix with a bimodal distribution, viz. coarse precipitates with dimension larger than several hundred nanometers and fine precipitates with size of 2- 10 nm. Three types of intermetallics, the common compound of Cu51Zr14, correspondingly infrequent Cu5Zr and rare Cu5Zr3, were characterized in different samples.展开更多
The non-linear relationship between parameters of rapidly solidified agingprocesses and mechancal and electrical properties of Cu-Cr-Zr alloy is available by using asupervised artificial neural network (ANN). A knowle...The non-linear relationship between parameters of rapidly solidified agingprocesses and mechancal and electrical properties of Cu-Cr-Zr alloy is available by using asupervised artificial neural network (ANN). A knowledge repository of rapidly solidified agingprocesses is established via sufficient data learning by the network. The predicted values of theneural network are in accordance with the tested data. So an effective measure for foreseeing andcontrolling the properties of the processing is provided.展开更多
The effects of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding were investigated employing Brinell-hardness testing unit, abrasion examination machine, electronic alm...The effects of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding were investigated employing Brinell-hardness testing unit, abrasion examination machine, electronic almighty testing machine and X-ray stress analyzer. Tensile fracture surfaces of the alloy were characterized by scanning electronic microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). The results showed that, after deep cryogenic treatment, σb and σ0.2 increased 23 MPa and 21 MPa respectively, the wear rate of the alloy exhibited the trend of decrease with the decreasing temperature and increasing time of deep cryogenic treatment, and the surface residual stress of the alloy was partially eliminated by deep cryogenic treatment.展开更多
The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were ex- plored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions ...The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were ex- plored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}〈331〉 and {110}〈112〉 were predominated, whereas, those of {113}〈332〉 and {112}〈111〉 were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (〉0.5wt%). However, in the samples with a lower Zr content (〈0.1wt%), the texture contents of {113}〈332〉, {112}〈111〉, and {111}〈110〉 were in the majority.展开更多
Nano graphene platelet(Gr)reinforced nano composites with a zinc–aluminum alloy(ZA27)matrix were produced by powder metallurgy at four different mass ratios(0.5wt%,1.0wt%,2.0wt%and 4.0wt%)and three different sinterin...Nano graphene platelet(Gr)reinforced nano composites with a zinc–aluminum alloy(ZA27)matrix were produced by powder metallurgy at four different mass ratios(0.5wt%,1.0wt%,2.0wt%and 4.0wt%)and three different sintering temperatures(425,450,and 475°C).In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure,the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope.Hardness,transverse rupture,and abrasion wear tests were performed to determine the mechanical properties.According to the test results,the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased.However,when the composites produced in different reinforcement ratios were evaluated,the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.展开更多
基金the National Natural Science Foundation of China(Grant number 51771178)Shaanxi Outstanding Youth Fund project(Grant number 2021JC-45)+2 种基金Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007)the Major Program of Science and Technology in Shaanxi Province(Grant number20191102006)Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019)。
文摘The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.
文摘Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.
基金The present work was supported by the National Natural Science Funds of China(No.50725413)the Ministry of Science and Technology of China(MOST)(No.2010DFR50010 and 2011FU125Z07)Chongqing Science and Technology Commission(CSTC2013jcyjC60001).
文摘Effect of graphene nanoplatelets(GNPs)addition on mechanical properties of magnesium–10wt%Titanium(Mg–10Ti)alloy is investigated in current work.The Mg-(10Ti+0.18GNPs)composite was synthesized using the semi powder metallurgy method followed by hot extrusion.Microstructural characterization results revealed the uniform distribution of reinforcement(Ti+GNPs)particles in the matrix,therefore(Ti+GNPs)particles act as an effective reinforcing filler to prevent the deformation.Room temperature tensile results showed that the addition of Ti+GNPs to monolithic Mg lead to increase in 0.2%yield strength(0.2%YS),ultimate tensile strength(UTS),and failure strain.Scanning Electron Microscopy(SEM),Energy-Dispersive X-ray Spectroscopy(EDS)and X-Ray Diffraction(XRD)were used to investigate the surface morphology,elemental dispersion and phase analysis,respectively.
基金the National Natural Science Foundation of China (21473111)the Fundamental Research Funds for the Central Universities (GK201701007)
文摘The research on electrocatalysts with relatively lower price than Pt and excellent electrocatalytic performance for the cathode oxygen reduction reaction(ORR) and anode methanol oxidation reaction(MOR) is vital for the development of direct methanol fuel cells(DMFCs). In this work, we develop a cyanogel-reduction method to synthesize reduced graphene oxide(rGO) supported highly dispersed PdNi alloy nanocrystals(PdNi/rGO) with high alloying degree and tunable Pd/Ni ratio. The large specific surface area and the d-band center downshift of Pd result in excellent activity of Pd4 Ni1/rGO nanohybrids for the ORR. The modification of Pd electronic structure can facilitate the adsorption of CH3 OH on Pd surface and the highly oxophilic property of Ni can eliminate/mitigate the COadsintermediates poisoning, which make PdNi/r GO nanohybrids possess superior MOR activity. In addition, rGO improve the stability of PdNi alloy nanocrystals for the ORR and MOR. Due to high activity and stability for the ORR and MOR, PdNi/rGO nanohybrids are promising to be an available bifunctional electrocatalyst in DMFCs.
基金This work was financially supported by the Program for New Century Excellent Talents in University(No.NCET-11-0951).
文摘A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the internal structure,the friction surface,and the wear debris were characterized by scanning electron microscopy,X-ray diffraction,and Raman spectroscopy.Compared with the original 7075 aluminum alloy,the hardness and elastic modulus of the 7075 Al/GNPs composite were found to have increased by 29%and 36%,respectively.The results of tribological experiments indicated that the composite also exhibited a lower wear rate than the original 7075 aluminum alloy.
基金supported by the National Natural Science Foundation of China (No. 52001028)the Education Commission of Chongqing Municipality (No. KJQN20210141)the Chongqing Science and Technology Commission (Nos. cstc2020jcyj-msxmX0544 and cstc2019jcyj-msxm X0510)
文摘Although graphene oxide(GO)has emerged as an excellent lubricant additive in water,there remain great challenges in their practical application due to high production costs.By taking into account the low cost and also its excellent tribological properties,it is likely that nano-SiO_(2)can be used as a lubricant additive to partially replace GO.Hence,this paper aims to explore the tribological properties of nano-SiO_(2)incorporated in GO nanofluids for partial GO replacement by investigating the friction coefficient and wear volume of the prepared SiO_(2)/GO hybrid nanofluids for magnesium alloy/steel sliding pairs.The experiments reveal that the SiO_(2)/GO hybrids retain low friction coefficients as compared to individual GO or SiO_(2)at all test conditions in this study.However,as for the bearing capacity test,all samples can provide a low wear volume under the loads of 1 and 3 N.With the increase of the normal load,there is considerable differences in the anti-wear behavior.Compared with that of individual GO nanofluids,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by50.5%at 5 N and by 49.2%at 8 N.Furthermore,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by46.3%under the rigorous conditions,as compared to individual GO nanofluids.The findings provide new insights into developing carbon nanomaterial-based hybrid nanofluids for magnesium alloy formation.
基金financial support from the National Natural Science Foundation (21676129,21607063)the Science & Technology Foundation of Zhenjiang (GY2016021,GY2017001,GY2017009)Postgraduate Innovation Project of Jiangsu Province (KYLX16_0912)
文摘Non-noble metal-based catalysts,especially stable ones,have gained increasing attentions in the field of electronically catalytic hydrogen evolution reaction(HER).In this work,an N-doped carbon confined Co–Ni alloy with reduced graphene oxide(rGO) decoration(CoNi@N-C/rGO) was fabricated for HER.The prepared catalyst exhibited excellent HER activity in an acidic electrolyte(Tafel slope of ~133.7 m V).The results showed that the enhanced HER performance of the nanostructures is attributed to the chemical and electronic synergic effect between the confined Co–Ni alloy and r GO.Stability tests,realized via longterm potential cycles and extended electrolysis,provided the confirmation of the exceptional durability of the catalyst,which originated from the confining effect of the N-doped carbon shell.This versatile method provides a strategy for designing stable non-precious metal electrocatalysts confined by carboncoating.
基金financially supported by the National Natural Science Foundation of China(NOs.21303157 and51771164)the Natural Science Foundation of Hebei Province(No.E2019203161)Scientific Research Projects in Colleges and Universities in Hebei Province(No.QN2016002)
文摘To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.
基金financially supported by the National Natural Science Foundation of China (31771044)China Postdoctoral Science Foundation (2019M662830)+2 种基金Shanghai Committee of Science and Technology,China (19JC1415500,18ZR1445000)International Partnership Program of Chinese Academy of Sciences (GJHZ1850)Natural Science Foundation of Guangdong Province,China (2020A1515011447)。
文摘Photothermal therapy becomes a hotspot in the treatment of bone tumors. Magnesium and its alloys are regarded as potential bone implants for their favorable mechanical property and biodegradable in vivo. However, there is few research devoted to fabricating a photothermal coating on Mg alloy. In the present study, reduced graphene oxide coating with a strong photothermal effect was prepared on the surface of AZ31via two steps. Firstly, graphene oxide coating was deposited on the surface via electrophoresis deposited(GO#), followed by a reduction process of the graphene oxide coating in ultrapure water(rGO#). GO# and rGO# coatings were characterized by SEM, Raman, XRD, FTIR,and XPS. The results revealed that, compared with GO# coating, the content of oxygen-containing(C-O/C-O-C, C=O, O-C=O) groups on rGO# coating was significantly decreased. rGO# coating was found tightly adhered to AZ31 substrate. According to the first-principles calculations, the well-bonded heterostructure between MgO and rGO is the main reason for the strong bonding force. Moreover, the prepared rGO# coating showed a superior photothermal effect, which brings a new strategy to the treatment of bone tumors with Mg-based implants.
文摘In this study, two nano-derivatives from nano-Graphene oxide (GO) were synthesized. Regarding to GON and GOS by reaction GO with 2-amino ethanol and 2-marcapto ethanol respectively, the GO, GON, GOS were characterized by FTIR, XRD and FSEM. Evaluation prepared compound to inhibitors corrosion for Carbon steel in acidic media at (1 - 6 ppm) concentration and different temperature 298, 308, 318, 328 K. The electrochemical technique used Tafel plot to measure the efficiency of inhibitor. It was observed that the corrosion rate and charge transfer of the carbon steel for the inhibitor increase with increase of temperature and decrease with increase of the inhibitor concentration in the same temperature. The GON had inhibition efficiency reached 96.96% for the 6 ppm concentration at 298 K.
基金the National Natural Science Foundation of China(Nos.52202214,52001059,52001059,and 52202215)Sichuan Natural Science Foundation(No.23NSFSC3565)+1 种基金China National Postdoctoral Program for Innovative Talents(No.BX2021053)China Postdoctoral Science Foundation(No.2021M700680).
文摘Advancing efficient and affordable electrocatalysts to boost the oxygen evolution reaction(OER)is pivotal for sustainable green hydrogen production.Herein,we propose the fabrication of nickel-iron alloy nanoparticles-encapsulated on N-doped vertically aligned graphene array on carbon cloth(NiFe@NVG/CC)as a highly active three-dimensional(3D)catalyst electrode for OER.In 1 M KOH,such NiFe@NVG/CC demonstrates outstanding catalytic performance,necessitating merely overpotential of 245 mV for achieving a current density of 10 mA·cm^(−2),a remarkably low Tafel slope of 36.2 mV·dec^(−1).Furthermore,density functional theory calculations validate that the incorporate of N species into graphene can reinforce the electrocatalytic activity though reducing the reaction energy barrier during the conversion of*O to*OOH intermediates.The outstanding performance and structural benefits of NiFe@NVG/CC offer valuable insights for the development of innovative and efficient electrocatalysts for water oxidation.
基金This work was supported by the National“863”High Pro-gram of China(No.2002AA331112)the Doctorate Foun-dation of Northwestern Polytechnical University(CX200409)the Science Research Foundation of Henan University of Science and Technology(No.2004ZY039).
文摘The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging (500℃ for 15 rain), the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.
基金Project supported by National High-Tech Research and Development Program of China (2004AA3Z1460)
文摘Testing results shows that alloying with Ce and Y improves the hardness and softens temperature of cold worked Cu-Cr-Zr alloys obviously, while the conductivity was fluctuant with the variation of RE content. Observation and analysis indicate that micro-dosage RE elements helps to refine microstructure and morphology of Cu-Cr-Zr-RE alloys, suppress microstructure coarsening and improves homogeneous level of Cu-Cr-Zr alloys. Alloying with 0.01% Ce causes about 1% IACS increment of conductivity, and reduces about 2%~3.5% IACS conductivity after alloying with 0.03%~0.04% RE (Ce or Ce+Y) for Cu-Cr-Zr alloys. The microstructure of as-cast Cu-Cr-Zr alloy is refined after alloying with 0.01% Ce while the plasticity is improved slightly. Alloying with 0.01%~0.04% RE improves the softening temperature of deformed Cu-Cr-Zr alloys about 20~40 K; hardness is also improved about 20~35 HV. Test data indicate that alloying with Ce+Y raises softening temperature and hardness of Cu-Cr-Zr alloys more notably than alloying with pure Ce.
基金This work was supported by the stae“863 plan”,under Grant No.2002AA331112by the Major Science and Technology Project of Henan Province,China,under Grant No.0122021300.
文摘Phases of Cu-(0.4%-2.0%) Cr-(0.05%-0.16%) Zr alloys were analyzed in both as cast and deformed state. Solute-rich clusters of Cr, which was supposed to form during aging treatment, were observed in as cast state; along with the morphology character, corresponding preferential orientation of Cr phase in as cast state was also investigated. Precipitates were observed to distribute in the matrix with a bimodal distribution, viz. coarse precipitates with dimension larger than several hundred nanometers and fine precipitates with size of 2- 10 nm. Three types of intermetallics, the common compound of Cu51Zr14, correspondingly infrequent Cu5Zr and rare Cu5Zr3, were characterized in different samples.
基金This project is financially suported by the State"863 Plan"(No.2002AA331112)
文摘The non-linear relationship between parameters of rapidly solidified agingprocesses and mechancal and electrical properties of Cu-Cr-Zr alloy is available by using asupervised artificial neural network (ANN). A knowledge repository of rapidly solidified agingprocesses is established via sufficient data learning by the network. The predicted values of theneural network are in accordance with the tested data. So an effective measure for foreseeing andcontrolling the properties of the processing is provided.
基金[This work was financially supported by the National Natural Science Foundation of China (No. 50175080) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (SRFDP: No. 20030056003).]
文摘The effects of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding were investigated employing Brinell-hardness testing unit, abrasion examination machine, electronic almighty testing machine and X-ray stress analyzer. Tensile fracture surfaces of the alloy were characterized by scanning electronic microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). The results showed that, after deep cryogenic treatment, σb and σ0.2 increased 23 MPa and 21 MPa respectively, the wear rate of the alloy exhibited the trend of decrease with the decreasing temperature and increasing time of deep cryogenic treatment, and the surface residual stress of the alloy was partially eliminated by deep cryogenic treatment.
文摘The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were ex- plored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}〈331〉 and {110}〈112〉 were predominated, whereas, those of {113}〈332〉 and {112}〈111〉 were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (〉0.5wt%). However, in the samples with a lower Zr content (〈0.1wt%), the texture contents of {113}〈332〉, {112}〈111〉, and {111}〈110〉 were in the majority.
基金Kirikkale University BAP Unit within the scope of project numbered 2018/043
文摘Nano graphene platelet(Gr)reinforced nano composites with a zinc–aluminum alloy(ZA27)matrix were produced by powder metallurgy at four different mass ratios(0.5wt%,1.0wt%,2.0wt%and 4.0wt%)and three different sintering temperatures(425,450,and 475°C).In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure,the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope.Hardness,transverse rupture,and abrasion wear tests were performed to determine the mechanical properties.According to the test results,the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased.However,when the composites produced in different reinforcement ratios were evaluated,the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.