Oxygenated fuels are known to reduce particulate matter(PM)emissions from diesel engines.In this study,100%soy methyl ester(SME)biodiesel fuel(B100)and a blend of 10%acetal denoted by A-diesel with diesel fuel were te...Oxygenated fuels are known to reduce particulate matter(PM)emissions from diesel engines.In this study,100%soy methyl ester(SME)biodiesel fuel(B100)and a blend of 10%acetal denoted by A-diesel with diesel fuel were tested as oxygenated fuels.Particle size and number distributions from a diesel engine fueled with oxygenated fuels and base diesel fuel were measured using an Electrical Low Pressure Impactor(ELPI).Measurements were made at ten steady-state operational modes of various loads at two engine speeds.It was found that the geometric mean diameters of particles from SME and Adiesel were lower than that from base diesel fuel.Compared to diesel fuel,SME emitted more ultra-fine particles at rated speed while emitting less ultra-fine particles at maximum speed.Ultra-fine particle number concentrations of A-diesel were much higher than those of base diesel fuel at most test modes.展开更多
In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound c...In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.展开更多
The Fe_(949.7)Cr_(18)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2) amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel(HVOF)spray technique to enhance the corrosion resistance ...The Fe_(949.7)Cr_(18)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2) amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel(HVOF)spray technique to enhance the corrosion resistance of T91 stainless steel in liquid lead-bismuth eutectic(LBE).The corrosion behavior of the T91 steel and coating exposed to oxygen-saturated LBE at 400℃ for 500 h was investigated.Results showed that the T91 substrate was severely corroded and covered by a homogeneously distributed dual-layer oxide on the interface contacted to LBE,consisting of an outer magnetite layer and an inner Fe-Cr spinel layer.Meanwhile,the amorphous coating with a high glass transition temperature(Tg=550℃)and crystallization temperature(T_(x)=600℃)exhibited dramatically enhanced thermal stability and corrosion resistance.No visible LBE penetration was observed,although small amounts of Fe_(3)O_(4),Cr_(2)O_(3),and PbO were found on the coating surface.In addition,the amorphicity and interface bonding of the coating layer remained unchanged after the LBE corrosion.The Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.展开更多
Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio (OER...Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio (OER) is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.展开更多
We report the synthesis, characterisation and catalytic performance of two nature-inspired biomassderived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of...We report the synthesis, characterisation and catalytic performance of two nature-inspired biomassderived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of a real food waste(lobster shells) or by mimicking the composition of lobster shells using chitin and CaCO3 particles followed by acid washing. The simplified model of artificial lobster was prepared for better reproducibility. The calcium carbonate in both samples acts as a pore agent, creating increased surface area and pore volume, though considerably higher in artificial lobster samples due to the better homogeneity of the components. Various characterisation techniques revealed the presence of a considerable amount of hydroxyapatite left in the real lobster samples after acid washing and a low content of carbon(23%), nitrogen and sulphur(〈1%), limiting the surface area to 23 m^2/g, and consequently resulting in rather poor catalytic activity. However, artificial lobster samples, with a surface area of ≈200 m^2/g and a nitrogen doping of 2%, showed a promising onset potential, very similar to a commercially available platinum catalyst, with better methanol tolerance, though with lower stability in long time testing over 10,000 s.展开更多
Solid electrolytes(CeO2)0.7-x(MO)x (La2O3) 0.3(M = Mg,Ca,Sr)were synthesized.Their crystal structure,conductivity, XPS spectrum,ionic transferance number and the V-1 curve of the obtained fuel cell were measured.(CeO2...Solid electrolytes(CeO2)0.7-x(MO)x (La2O3) 0.3(M = Mg,Ca,Sr)were synthesized.Their crystal structure,conductivity, XPS spectrum,ionic transferance number and the V-1 curve of the obtained fuel cell were measured.(CeO2)0.7z (La2O3)0.3 doped with Ca2+,Mg2+,and Sr2+can perform the oxygen ionic electrolyte,and so enhance the open voltage and power output of the fuel cell.展开更多
Fe-based powder with a composition of Fe_(42.87)Cr_(15.98)Mo_(16.33)C_(15.94)B_(8.88)(at.%)was used to fabricate coatings by high-velocity oxygen fuel spraying.The effects of the spraying parameters on the...Fe-based powder with a composition of Fe_(42.87)Cr_(15.98)Mo_(16.33)C_(15.94)B_(8.88)(at.%)was used to fabricate coatings by high-velocity oxygen fuel spraying.The effects of the spraying parameters on the microstructure and the wear properties of the Fe-based alloy coatings were systematically studied.The results showed that the obtained Fe-based coatings with a thickness of about 400μm consisted of a large-volume amorphous phase and some nanocrystals.With increasing the fuel and oxygen flow rates,the porosity of the obtained coatings decreased.The coating deposited under optimized parameters exhibited the lowest porosity of 2.8%.The excellent wear resistance of this coating was attributed to the properties of the amorphous matrix and the presence of nanocrystals homogeneously distributed within the matrix.The wear mechanism of the coatings was discussed on the basis of observations of the worn surfaces.展开更多
High velocity oxygen fuel(HVOF)spraying process is commonly used to produce superalloy coatings.Inconel 625 coating was prepared on Q235B low carbon steel by HVOF.A series of experiments were conducted to examine the ...High velocity oxygen fuel(HVOF)spraying process is commonly used to produce superalloy coatings.Inconel 625 coating was prepared on Q235B low carbon steel by HVOF.A series of experiments were conducted to examine the surface and corrosion resistance properties of Inconel 625 HVOF coating.In this paper,potentiodynamic polarization tests and electrochemical impedance spectroscopy(EIS)tests were carried out to evaluate the corrosion resistance of Inconel 625 coating under simulated marine environment.The experiment-al results showed that Inconel 625 coating revealed low porosity and desired coating thickness.Shift in the corrosion potential(E_(corr))to-wards the noble direction combined with much low corrosion current density(i_(corr))indicating a significant improvement of HVOF Inconel 625 coating compared with the substrate.展开更多
Rare earth metal oxides(REMO) as cathode electrocatalysts in direct borohydride fuel cell(DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction...Rare earth metal oxides(REMO) as cathode electrocatalysts in direct borohydride fuel cell(DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.展开更多
Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new ca...Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.展开更多
To improve the corrosion resistance of coalbed methane drilling equipment,an AICoCrFeNiCu high entropy alloy coating was prepared on the AISI 4135(35CrMo)steel substrate by high velocity oxygen fuel(HVOF)technology,an...To improve the corrosion resistance of coalbed methane drilling equipment,an AICoCrFeNiCu high entropy alloy coating was prepared on the AISI 4135(35CrMo)steel substrate by high velocity oxygen fuel(HVOF)technology,and the coating was subjected to vacuum heat treatment(VHT)at different temperatures(500,700,900 and 1100℃).The corrosion test of the substrate and the coatings after VHT in coalbed methane drilling fluid was carried out.The results show that the HVOF sprayed AICoCrFeNiCu high entropy alloy(HEA)coating has a good bonding with the substrate,and the porosity of the coating is about 2.4%.There is partial segregation in the coating,and the coating mainly consists of body-centered cubic phase.The coating has good thermal stability,and the phase structure and microstructure of the coatings have changed after VHT at different temperatures.Compared with the substrate,the as-sprayed coating has better uniform corrosion resistance,and the corrosion resistance of the coating after VHT is further improved.After VHT at 500℃,the HVOF-sprayed AICoCrFeNiCu HEA coating has the best corrosion resistance.展开更多
The WC-lOCo-4Cr composite powder was synthesized firstly. Then the composite powder was agglomerated to prepare thermal spraying feedstock. The ultrafine/nanostructured WC-lOCo-4Cr coating was prepared by high velocit...The WC-lOCo-4Cr composite powder was synthesized firstly. Then the composite powder was agglomerated to prepare thermal spraying feedstock. The ultrafine/nanostructured WC-lOCo-4Cr coating was prepared by high velocity oxygen fuel thermal spraying. The phase constitution, elemental distribution and microstructure of the coating were characterized by X-ray diffraction and transmission electron microscopy, respectively. The wear resistance and corrosion resistance of the prepared composite coating were tested. The results show that the main phases of the coating include WC, binding phase with partial amorphous structure, with a little WC and Co(Cr)coexisting. The distributions of Co and Cr elements from the phase boundary to the eutectic area then to Co zone were analyzed quantitatively. The mechanisms for the formation of the microstructure and effects of Cr on the performance of the composite coating are proposed.展开更多
A significant fraction of the non-exhaust particulate matter emissions from vehicular traffic comprises fine particles from the wear debris of brake pads and discs.Recent studies have shown that these emissions can be...A significant fraction of the non-exhaust particulate matter emissions from vehicular traffic comprises fine particles from the wear debris of brake pads and discs.Recent studies have shown that these emissions can be consistently reduced by using wear resistant disc coatings.This study thoroughly analyses the debris produced by a low-met brake pad,which is dyno-bench tested against both cast iron and WC-CoCr-coated brake discs.To achieve this,particles in the size range of 2.5|im to 30 nm were collected and characterized.The results showed a consistent reduction in the particle emission as well as in the concentration of iron oxides,which are mainly released from the disc tribo-oxidation in the coated disc.Furthermore,a few tungsten carbides,released from the coating,were also observed in the wear fragments.The results of this study can be useful for improving the protective coating and consequently help in reducing particulate matter emission further.展开更多
Failure behavior of thermal barrier coatings on cylindrical superalloy tube was investigated under thermome- chanical fatigue (TMF). Two types of TMF tests, i.e. in phase (IP) and out of phase (OP), were perform...Failure behavior of thermal barrier coatings on cylindrical superalloy tube was investigated under thermome- chanical fatigue (TMF). Two types of TMF tests, i.e. in phase (IP) and out of phase (OP), were performed in the temperature range of 450-850℃. All tests were carried out under mechanical strain control at a given period of 300 s. The bond coat NiCrAIY was produced by high velocity oxygen fuel (HVOF), and the top coat 7%Y203-ZrO2 was deposited by air plasma spraying (APS). The testing results showed that the OP TMF life was longer than the IP TMF one under the same mechanical strain amplitude. Observations of the fractured specimens revealed that the interface damage and cracking behavior in the two phasing conditions were different. In OP loading, the top coat was cracked and detached from the bond coat while no spallation was found in the IP loading.展开更多
Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has b...Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiA1 catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of -3.7 nm. The half-wave potential of np PdCuTiA1 is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiA1 in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiA1 has been further rationalized through density functional theory calculations.展开更多
基金the National High Technology Research and Development Program of China(863 Program)(Grant No.2006AA06A305)the National Natural Science Foundation of China(Grant No.20807025)。
文摘Oxygenated fuels are known to reduce particulate matter(PM)emissions from diesel engines.In this study,100%soy methyl ester(SME)biodiesel fuel(B100)and a blend of 10%acetal denoted by A-diesel with diesel fuel were tested as oxygenated fuels.Particle size and number distributions from a diesel engine fueled with oxygenated fuels and base diesel fuel were measured using an Electrical Low Pressure Impactor(ELPI).Measurements were made at ten steady-state operational modes of various loads at two engine speeds.It was found that the geometric mean diameters of particles from SME and Adiesel were lower than that from base diesel fuel.Compared to diesel fuel,SME emitted more ultra-fine particles at rated speed while emitting less ultra-fine particles at maximum speed.Ultra-fine particle number concentrations of A-diesel were much higher than those of base diesel fuel at most test modes.
基金supports provided by the National Natural Science Foundation of China (No. 52075198)the National Key Research and Development Program of China (Nos. 2020YFB2008300 and 2020YFB2008304)+1 种基金the State Key Laboratory of High Performance Complex Manufacturing in CSU (No. Kfkt2019-01)the Analytical and Testing Center, HUST.
文摘In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.
基金financially supported by the National Natural Science Foundation of China (Nos. 52061135207, 51871016, 51921001, 5197011039, 5197011018, and U20b200318)the China Nuclear Power Technology Research Institute Co., Ltd
文摘The Fe_(949.7)Cr_(18)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2) amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel(HVOF)spray technique to enhance the corrosion resistance of T91 stainless steel in liquid lead-bismuth eutectic(LBE).The corrosion behavior of the T91 steel and coating exposed to oxygen-saturated LBE at 400℃ for 500 h was investigated.Results showed that the T91 substrate was severely corroded and covered by a homogeneously distributed dual-layer oxide on the interface contacted to LBE,consisting of an outer magnetite layer and an inner Fe-Cr spinel layer.Meanwhile,the amorphous coating with a high glass transition temperature(Tg=550℃)and crystallization temperature(T_(x)=600℃)exhibited dramatically enhanced thermal stability and corrosion resistance.No visible LBE penetration was observed,although small amounts of Fe_(3)O_(4),Cr_(2)O_(3),and PbO were found on the coating surface.In addition,the amorphicity and interface bonding of the coating layer remained unchanged after the LBE corrosion.The Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.
基金supported by the National Natural Science Foundation of China (No. 51177138)the Research Fund for the Doctoral Program of High Education of China (No.20100184110015)Sichuan Province International Technology Cooperation and Exchange Program (No. 2012HH0007)
文摘Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio (OER) is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.
基金the EU for the Intra European Marie Curie Research Fellowship (PIEFGA-2013-623227)
文摘We report the synthesis, characterisation and catalytic performance of two nature-inspired biomassderived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of a real food waste(lobster shells) or by mimicking the composition of lobster shells using chitin and CaCO3 particles followed by acid washing. The simplified model of artificial lobster was prepared for better reproducibility. The calcium carbonate in both samples acts as a pore agent, creating increased surface area and pore volume, though considerably higher in artificial lobster samples due to the better homogeneity of the components. Various characterisation techniques revealed the presence of a considerable amount of hydroxyapatite left in the real lobster samples after acid washing and a low content of carbon(23%), nitrogen and sulphur(〈1%), limiting the surface area to 23 m^2/g, and consequently resulting in rather poor catalytic activity. However, artificial lobster samples, with a surface area of ≈200 m^2/g and a nitrogen doping of 2%, showed a promising onset potential, very similar to a commercially available platinum catalyst, with better methanol tolerance, though with lower stability in long time testing over 10,000 s.
文摘Solid electrolytes(CeO2)0.7-x(MO)x (La2O3) 0.3(M = Mg,Ca,Sr)were synthesized.Their crystal structure,conductivity, XPS spectrum,ionic transferance number and the V-1 curve of the obtained fuel cell were measured.(CeO2)0.7z (La2O3)0.3 doped with Ca2+,Mg2+,and Sr2+can perform the oxygen ionic electrolyte,and so enhance the open voltage and power output of the fuel cell.
基金Item Sponsored by National Natural Science Foundation of China(51205001)Key Project of Natural Science of Education Department of Anhui Province of China(KJ2014A023)Scientific Research Starting Foundation of Anhui Polytechnic University of China(2012YQQ006)
文摘Fe-based powder with a composition of Fe_(42.87)Cr_(15.98)Mo_(16.33)C_(15.94)B_(8.88)(at.%)was used to fabricate coatings by high-velocity oxygen fuel spraying.The effects of the spraying parameters on the microstructure and the wear properties of the Fe-based alloy coatings were systematically studied.The results showed that the obtained Fe-based coatings with a thickness of about 400μm consisted of a large-volume amorphous phase and some nanocrystals.With increasing the fuel and oxygen flow rates,the porosity of the obtained coatings decreased.The coating deposited under optimized parameters exhibited the lowest porosity of 2.8%.The excellent wear resistance of this coating was attributed to the properties of the amorphous matrix and the presence of nanocrystals homogeneously distributed within the matrix.The wear mechanism of the coatings was discussed on the basis of observations of the worn surfaces.
基金supported by Zhejiang Provincial Natural Science Foundation of China(No.LTGC23E010001)the Youth Science and Technology Project of Zhejiang Provincial Administration for Market Regulation(No.QN2023427)Science and Techno-logy Project of State Administration for Market Regulation(No.2022MK054).
文摘High velocity oxygen fuel(HVOF)spraying process is commonly used to produce superalloy coatings.Inconel 625 coating was prepared on Q235B low carbon steel by HVOF.A series of experiments were conducted to examine the surface and corrosion resistance properties of Inconel 625 HVOF coating.In this paper,potentiodynamic polarization tests and electrochemical impedance spectroscopy(EIS)tests were carried out to evaluate the corrosion resistance of Inconel 625 coating under simulated marine environment.The experiment-al results showed that Inconel 625 coating revealed low porosity and desired coating thickness.Shift in the corrosion potential(E_(corr))to-wards the noble direction combined with much low corrosion current density(i_(corr))indicating a significant improvement of HVOF Inconel 625 coating compared with the substrate.
基金supported by Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry and National Natural Science Foundation of China (20803057)support by the National Self-determined and Innovative Research Funds of WUT
文摘Rare earth metal oxides(REMO) as cathode electrocatalysts in direct borohydride fuel cell(DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.
基金The authors are grateful for the financial support from FORMAS:Swedish Research Council for Sustainable Development(No.2020-02302)(Nescup project)The research also received funding from European Union's Horizon 2020 research and innovation programme(No.954377)(nPETS project).
文摘Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3706600)the National Natural Science Foundation of China(Grant Nos.52175196 and 52275218)the Fundamental Research Funds for Central Universities(Grant No.265QZ2021008).
文摘To improve the corrosion resistance of coalbed methane drilling equipment,an AICoCrFeNiCu high entropy alloy coating was prepared on the AISI 4135(35CrMo)steel substrate by high velocity oxygen fuel(HVOF)technology,and the coating was subjected to vacuum heat treatment(VHT)at different temperatures(500,700,900 and 1100℃).The corrosion test of the substrate and the coatings after VHT in coalbed methane drilling fluid was carried out.The results show that the HVOF sprayed AICoCrFeNiCu high entropy alloy(HEA)coating has a good bonding with the substrate,and the porosity of the coating is about 2.4%.There is partial segregation in the coating,and the coating mainly consists of body-centered cubic phase.The coating has good thermal stability,and the phase structure and microstructure of the coatings have changed after VHT at different temperatures.Compared with the substrate,the as-sprayed coating has better uniform corrosion resistance,and the corrosion resistance of the coating after VHT is further improved.After VHT at 500℃,the HVOF-sprayed AICoCrFeNiCu HEA coating has the best corrosion resistance.
基金financially supported by the National Natural Science Foundation (No. 51601004)the Key Program of National Natural Science Foundation (No. 51631002)the National Science Fund for Distinguished Young Scholars (No. 51425101)
文摘The WC-lOCo-4Cr composite powder was synthesized firstly. Then the composite powder was agglomerated to prepare thermal spraying feedstock. The ultrafine/nanostructured WC-lOCo-4Cr coating was prepared by high velocity oxygen fuel thermal spraying. The phase constitution, elemental distribution and microstructure of the coating were characterized by X-ray diffraction and transmission electron microscopy, respectively. The wear resistance and corrosion resistance of the prepared composite coating were tested. The results show that the main phases of the coating include WC, binding phase with partial amorphous structure, with a little WC and Co(Cr)coexisting. The distributions of Co and Cr elements from the phase boundary to the eutectic area then to Co zone were analyzed quantitatively. The mechanisms for the formation of the microstructure and effects of Cr on the performance of the composite coating are proposed.
文摘A significant fraction of the non-exhaust particulate matter emissions from vehicular traffic comprises fine particles from the wear debris of brake pads and discs.Recent studies have shown that these emissions can be consistently reduced by using wear resistant disc coatings.This study thoroughly analyses the debris produced by a low-met brake pad,which is dyno-bench tested against both cast iron and WC-CoCr-coated brake discs.To achieve this,particles in the size range of 2.5|im to 30 nm were collected and characterized.The results showed a consistent reduction in the particle emission as well as in the concentration of iron oxides,which are mainly released from the disc tribo-oxidation in the coated disc.Furthermore,a few tungsten carbides,released from the coating,were also observed in the wear fragments.The results of this study can be useful for improving the protective coating and consequently help in reducing particulate matter emission further.
基金financially supported by the Center for Interfacial Materials,Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences
文摘Failure behavior of thermal barrier coatings on cylindrical superalloy tube was investigated under thermome- chanical fatigue (TMF). Two types of TMF tests, i.e. in phase (IP) and out of phase (OP), were performed in the temperature range of 450-850℃. All tests were carried out under mechanical strain control at a given period of 300 s. The bond coat NiCrAIY was produced by high velocity oxygen fuel (HVOF), and the top coat 7%Y203-ZrO2 was deposited by air plasma spraying (APS). The testing results showed that the OP TMF life was longer than the IP TMF one under the same mechanical strain amplitude. Observations of the fractured specimens revealed that the interface damage and cracking behavior in the two phasing conditions were different. In OP loading, the top coat was cracked and detached from the bond coat while no spallation was found in the IP loading.
文摘Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiA1 catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of -3.7 nm. The half-wave potential of np PdCuTiA1 is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiA1 in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiA1 has been further rationalized through density functional theory calculations.