TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing Ti...TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.展开更多
To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxida...To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxidation stage,CeO_(2) accelerated the formation of a multiphase glass layer on the coating surface.The maximum oxidation rates of CeO_(2)-HfB2-SiC coatings with 1%,3%,and 5%CeO_(2) were 24.1%,20.3%,and 53.2%higher than that of the unmodified HfB2-SiC coating,respectively.In the stable oxidation stage,the maximum oxidation rates of coatings with 1%and 3%CeO_(2) decreased by 31.4%and 21.9%,respectively,demonstrating adequate inert protection.CeO_(2) is a“coagulant”and“stabilizer”in the composite glass layer.However,increasing the CeO_(2) content accelerates the reaction between the SiO_(2) glass phase and SiC,leading to a higher SiO_(2) consumption and reduced self-healing ability of the glass layer.The 1%CeO_(2)-60%HfB2-39%SiC coating showed improved glass layer viscosity and stability,moderate SiO_(2) consumption,and better self-healing ability,significantly boosting the oxidation protection of the coating.展开更多
To improve the high-temperature oxidation resistance of TiAlNb9 alloy,a Cr-Al-Y co-deposition coating was prepared on the alloy surface by the pack cementation method.The microstructure of the coating was analyzed by ...To improve the high-temperature oxidation resistance of TiAlNb9 alloy,a Cr-Al-Y co-deposition coating was prepared on the alloy surface by the pack cementation method.The microstructure of the coating was analyzed by scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer,and the high-temperature oxidation properties of the substrate and coating at 1273 K were compared and studied.The results show that the Cr-Al-Y coating is about 30μm in thickness,and it has a dense structure and good film-substrate bonding.The coating includes an outer layer composed of TiCr_(2),TiCr,Ti_(4)Cr,and(Ti,Nb)Cr_(4) phases as well as an inner layer composed of Ti_(2)Al,and Nb-richγ-TiAl interdiffusion zone.The TiAlNb9 substrate forms an oxide layer composed of TiO_(2) and Al_(2)O_(3) at 1273 K.Due to its loose and porous structure,TiO_(2) oxide film cannot effectively isolate the internal diffusion of element O,resulting in continuous oxidation damage to the substrate.The Cr-Al-Y co-deposition coating forms a dense Cr_(2)O_(3) and Al_(2)O_(3) oxide layer during oxidation,effectively preventing the internal diffusion of element O and significantly improving the high-temperature oxidation resistance of the substrate alloy.展开更多
To improve the high-temperature service properties of coppery tuyere,Co06 coating with a Ni60A interlayer was prepared on copper by plasma cladding.Ni60A interlayer acted as a bridge to promote the element diffusion,t...To improve the high-temperature service properties of coppery tuyere,Co06 coating with a Ni60A interlayer was prepared on copper by plasma cladding.Ni60A interlayer acted as a bridge to promote the element diffusion,thus achieving metallurgical bonding.Due to the strengthening effect ofγ-Co,Cr_(23)C_(6)and Cr_(7)C_(3)phases,the wear resistance of Co06–Ni60A coating was much higher than that of copper substrate.As the temperature increased,the wear resistance of coating decreased first and then increased.The coating exhibited better wear resistance at 600℃ due to the oxidation wear mechanism.Compared with copper substrate and Ni60A,the oxidation resistance of Co06 was increased by 6.0 and 1.9 times,respectively.For melting loss resistance,Co06–Ni60A coating was superior to Ni60A single-layer coating,but the molten iron can still form a micro-metallurgical bonding with the coating surface.展开更多
Laser shock peening(LSP)was used to enhance the high-temperature oxidation resistance of laser melting deposited Ti45Al8Nb alloy.The microstructure and high-temperature oxidation behavior of the as-deposited Ti45Al8Nb...Laser shock peening(LSP)was used to enhance the high-temperature oxidation resistance of laser melting deposited Ti45Al8Nb alloy.The microstructure and high-temperature oxidation behavior of the as-deposited Ti45Al8Nb alloy before and after LSP were investigated by scanning electron microscopy,X-ray diffraction,and electron backscatter diffraction.The results indicated that the rate of mass gain in the as-deposited sample after LSP exhibited a decrease when exposed to an oxidation temperature of 900℃,implying that LSP-treated samples exhibited superior oxidation resistance at high temperatures.A gradient structure with a fine-grain layer,a deformed-grain layer,and a coarse-grain layer was formed in the LSP-treated sample,which facilitated the diffusion of the Al atom during oxidation,leading to the formation of a dense Al_(2)O_(3)layer on the surface.The mechanism of improvement in the oxidation resistance of the as-deposited Ti45Al8Nb alloy via LSP was discussed.展开更多
The high-temperature oxidation resistance of AISI 321 stainless steel used in solar thermal power heat exchangers determines its service life.In this study,aluminizing and subsequent laser shock peening(LSP)treatments...The high-temperature oxidation resistance of AISI 321 stainless steel used in solar thermal power heat exchangers determines its service life.In this study,aluminizing and subsequent laser shock peening(LSP)treatments were employed to improve the high-temperature oxidation resistance of AISI 321 stainless steel at 620°C.These two treatments decreased the oxidation rate of AISI 321 steel.Specifically,the optimal oxidation resistance was observed in aluminized steel before oxidation for 144 h owing to the increased entropy of the LSP-treated specimen.After 144 h,LSP-treated steel achieved the best oxidation resistance because of the formation of a protectiveα-Al2O3film.Moreover,the large amount of subgrain boundaries formed on the aluminized layer of the LSP-treated samples could act as short-circuit paths for the outward diffusion of Al,facilitating the rapid nucleation ofα-Al2O3.Meanwhile,the aluminized layer could isolate the contact between the oxidation environment and matrix,thereby decreasing the oxidation rate.Furthermore,the minimum oxidation parabolic constant was calculated for LSP-treated steel(6.45787×10^(-14)),which was 69.18%and 36.36%that of aluminized and 321 steel,respectively,during the entire oxidation process.Therefore,the combination of aluminizing and LSP treatments can improve the high-temperature oxidation resistance of 321 stainless steel,providing a new idea for its surface treatment to achieve a long service life at high temperatures.展开更多
To protect carbon materials from oxidation, mullite/SiC coatings were prepared on graphite by chemical vapor reaction (CVR) and slurry sintering. The XRD analyses show that the phase of the outer-layer coating is comp...To protect carbon materials from oxidation, mullite/SiC coatings were prepared on graphite by chemical vapor reaction (CVR) and slurry sintering. The XRD analyses show that the phase of the outer-layer coating is composed of SiO2 and mullite, and the inner-layer coating is mainly composed of β-SiC. The anti-oxidation behavior of the coating and the Rockwell hardness (HRB) of the coating after oxidation were investigated. The oxidation test shows that the as-prepared multi-layer coating exhibits excellent antioxidation and thermal shock resistance at high temperature. After oxidation at 1150 ℃ for 109 h and thermal shock cycling between 1150 ℃ and room temperature for 12 times, the mass gain of the coated sample is 0.085%. Meanwhile, the indentation tests also demonstrate that the as-prepared coating has good bonding ability between the layers.展开更多
The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the...The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the Ni Al phase is formed. It is also found that the Ni2Al3 phase completely turns into Ni Al phase after oxidizing treatment for 100 h and above. The Ni Al coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.展开更多
[Objective] The aim was to study on the oxidation resistance of flavonoids in Chinese jujube stone. [Method] The extract of flavonoids from Chinese jujube stone was added to fresh rapeseed oil and lard to explore the ...[Objective] The aim was to study on the oxidation resistance of flavonoids in Chinese jujube stone. [Method] The extract of flavonoids from Chinese jujube stone was added to fresh rapeseed oil and lard to explore the oxidation resistance of flavonoids; the removal rates of it to O2-·,DPPH· and ·OH were also studied. [Result] The flavonoids from Chinese jujube stone had good oxidation resistance on rapeseed oil and lard,and the effects showed dose-dependent; citric acid and vitamin C appeared synergistic effects to the flavonoids; in free-radical reaction experiment,the flavonoids from Chinese Jujube stone also showed strong scavenging ability on O2-·,DPPH· and ·OH,in addition,the scavenging ability increased with concentration increasing. [Conclusion] The result of this study had provided theoretical basis for the further development and utilization of Chinese jujube resource.展开更多
Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employ...Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employed to investigate the oxidation resistance of the composite coatings. The results revealed that the applied Al2O3/Au nano-laminated composite coatings improved the oxidation and spallation resistance of the stainless steel substrate significantly. The mechanism accounting for oxidation resistance was related with the suppression of inward oxygen diffusion and selective oxidation of Cr in the substrate. The mechanism accounting for spallation resistance was attributed to the relaxation of thermal stress by the nano-laminated structure.展开更多
To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carb...To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carbon foams were characterized by scanning electron microscopy and X-ray diffraction, respectively. Oxidation resistances of uncoated and coated boron-modified carbon foams were investigated at 873 K in air. The results showed that as-received B2O3 coating could protect boron-modified carbon foams from oxidation at 873 K. B2O3-coated carbon foam doped with 7% B2O3 （mass fraction） （BO-7） had better oxidation resistance, exhibiting mass loss of 17.40% after oxidation at 873 K for 120 min. The melting glass layer formed on the surface of BO-7 could prevent oxygen from diffusing into boron-modified carbon foams substrate during oxidation to some extent.展开更多
[Objective] The aim was to research the influences of different formulations on oxidation resistance of PVDF hollow fiber membrane.[Method]The immersion precipitation phase inversion method was employed to make castin...[Objective] The aim was to research the influences of different formulations on oxidation resistance of PVDF hollow fiber membrane.[Method]The immersion precipitation phase inversion method was employed to make casting solution with different formulations into hollow fiber membrane.The membrane was immersed in 1% NaClO solution for testing its performance changes.[Result]The membrane made by materials with bigger molecular weight had better oxidation resistance performance;the surfactant tween-80 could increase water flux,but lead to lower rupture intension;Pore-forming agent PEG400 do better than PVP in the oxidation resistance of membrane.[Conclusion]This study will provide a good idea for the development of the PVDF membrane with high oxidation resistance.展开更多
A1 and N were introduced into copper substrate using plasma immersion ion implantation （PIII） in order to enhance its hardness and oxidation resistance. The dosage of N ion is 5 × 1016 cm-2, and range of dosage...A1 and N were introduced into copper substrate using plasma immersion ion implantation （PIII） in order to enhance its hardness and oxidation resistance. The dosage of N ion is 5 × 1016 cm-2, and range of dosage of A1 ion is 5× 1016-2× 1017 cm-2. The oxidation tests indicate that the copper samples after undergoing PIII possess higher oxidation resistance. The degree of oxidation resistance is found to vary with implantation dosage of AI ion. The antibacterial tests also reveal that the plasma implanted copper specimens have excellent antibacterial resistance against Staphylococcus aureus, which are similar to pure copper.展开更多
We studied the oxidation resistance of graphene-coated Cu surface and its layer dependence by directly growing monolayer graphene with different multilayer structures coexisted, di- minishing the influence induced by ...We studied the oxidation resistance of graphene-coated Cu surface and its layer dependence by directly growing monolayer graphene with different multilayer structures coexisted, di- minishing the influence induced by residue and transfer technology. It is found that the Cu surface coated with the monolayer graphene demonstrate tremendous difference in oxidation pattern and oxidation rate, compared to that coated with the bilayer graphene, which is considered to be originated from the strain-induced linear oxidation channel in monolayer graphene and the intersection of easily-oxidized directions in each layer of bilayer graphene, respectively. We reveal that the defects on the graphene basal plane but not the boundaries are the main oxidation channel for Cu surface under graphene protection. Our finding indicates that compared to putting forth efforts to improve the quality of monolayer graphene by reducing defects, depositing multilayer graphene directly on metal is a simple and effective way to enhance the oxidation resistance of graphene-coated metals.展开更多
Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance a...Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance are analyzed. The （Nb,Ti）ss, β-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 exist in Nb-22Ti-16Si-6Cr-3Al-4Hf alloy, while （Nb,Ti）ss, α-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 are present in Nb-22Ti-16Si-6Cr-3Al-4Hf-lB and Nb-22Ti-16Si-6Cr-3Al-4Hf-2B alloys. The oxidation of Nb-Ti-Si-based ultrahigh-temperature alloys is dominated by the diffusion of oxygen through （Nb,Ti）ss. Compared to boron-free alloys, the boron-containing alloys have significantly lower oxidation rate when oxidized at 1 200 ℃ for less than 50 h, but, for more than 50 h, their oxidation resistance deteriorates.展开更多
Nb-16Si-24Ti-6Cr-6A1-2Hf-xCe （x =0, 0.05, 0.1,02.5, 0.5, 1 （%, atom fraction）） in situ composites were prepared by arc melting The microstmcture and the effect of rare earth element cerium on 1250℃ oxidation resi...Nb-16Si-24Ti-6Cr-6A1-2Hf-xCe （x =0, 0.05, 0.1,02.5, 0.5, 1 （%, atom fraction）） in situ composites were prepared by arc melting The microstmcture and the effect of rare earth element cerium on 1250℃ oxidation resistance of the composites were investigated with scanning electron microscopy （SEM） and X-ray energy disperse spectrum （EDS）, as well as X-ray diffraction （XRD）. The experimental results showed that the high temperature oxidation resistance of the alloy was improved by adding a proper amount of cerium （Ce）. The effect of Ce was considered as the concurrent of the following three factors： first, the oxide of Ce formed in the interface reduced the internal oxidation rate; second, the lath shaped oxide containing Ce increased the cracking resistance and reduced the expansion of the oxide scale; and third, the decrease of the sificide volume fraction on account of Ce addition reduces the power of the sample resisting oxygen penetration.展开更多
Nb-22Ti-14Si-2Hf-2Al-xCr （x=2, 6, 10, 14, 17 at%） alloys are prepared by arc-melting under argon atmosphere. Microstructural characteristics, mechanical properties and oxidation resistance of the arc-melted alloys a...Nb-22Ti-14Si-2Hf-2Al-xCr （x=2, 6, 10, 14, 17 at%） alloys are prepared by arc-melting under argon atmosphere. Microstructural characteristics, mechanical properties and oxidation resistance of the arc-melted alloys are investigated. At 2 at% Cr content, the microstructure is composed of Nbss, Nb3Si and a small quantity of Nb5Si3, when the Cr contents increase, Nb3Si disappears. For the high Cr content （x ≥ 10 at%） alloys, besides the Nbss and Nb5Si3, Cr2Nb is also detected. With the increase of Cr content, the volume fractions of Cr2Nb and Nb5Si3 increase, while that of Nbss increases firstly and then begins to degrade when the Cr content is higher than 6 at%. For the alloy with 2 at% Cr, the room temperature fracture toughness is about 14.5 MPa·m1/2, but badly decreases to about 8.5 MPa·m1/2, when the Cr contents increase. Vickers hardness of Nbss tends to increase linearly from about 400 to 500, while that of silicides is not sensitive to Cr contents, about 950. The appearance of Cr2Nb phase significantly improves the high temperature oxidation resistance of the alloys with high Cr contents. The isothermal oxidation tests show that the oxidation kinetics of the alloys with various Cr contents follows parabolic oxidation kinetics.展开更多
In order to improve the oxidation resistance properties of 30 at.% Mo5Si3/MoSi2 composite at high temperature in air, a molybdenum disilicide coating was prepared on its surface by a molten salt technology. XRD and SE...In order to improve the oxidation resistance properties of 30 at.% Mo5Si3/MoSi2 composite at high temperature in air, a molybdenum disilicide coating was prepared on its surface by a molten salt technology. XRD and SEM analysis showed that only tetragonal MoSi2 phase existed in the coating after being siliconized for 5 h at 900℃. The oxidation film formed on the uncoated sample was not dense, so that oxygen diffused easily through it. The volatilization of MoO3 resulted in the oxidation film separating from the substrate. The MoSi2 coating was proved to be an effective method to prevent 30 at.% Mo5Si3/MoSi2 composites from being oxidized at 1200℃. A dense glassy SiO2 film was formed on the MoSi2 coating surface, which acted as a barrier layer for the diffusion of oxygen atoms to the substrate. The 30at.% MosSi3/MoSi2 composites with a MoSi2 coating showed much better oxidation resistance at high temperature.展开更多
Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain meth...Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.展开更多
The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were desig...The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were designed by the Box-Behnken method of design of experiments(DOE).The alloying elements show complicated effects on the mass gain due to oxidation,depending on the alloy composition.Al reduces the mass gain largely.The other elements except Al do not appear to exert a strong effect on the oxidation rate on average,but their influences are shown clearly in the alloys with a low Al content.Co,W,and Ta reduce the oxidation rate,while Cr,Mo,and Ti promote oxidation.Ta is the most effective element in reducing the oxidation rate of the alloy with a low Al concentration.It is confirmed that a continuous Al2O3 layer is essentially required for high oxidation resistance.The oxide scale of easily oxidized alloys has various oxides such as NiCr2O4,NiAl2O4,NiO,Cr2O3,CrTaO4,and TiO2.展开更多
基金supported by the Original Exploratory Program of the National Natural Science Foundation of China(No.52450012)。
文摘TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.
文摘To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxidation stage,CeO_(2) accelerated the formation of a multiphase glass layer on the coating surface.The maximum oxidation rates of CeO_(2)-HfB2-SiC coatings with 1%,3%,and 5%CeO_(2) were 24.1%,20.3%,and 53.2%higher than that of the unmodified HfB2-SiC coating,respectively.In the stable oxidation stage,the maximum oxidation rates of coatings with 1%and 3%CeO_(2) decreased by 31.4%and 21.9%,respectively,demonstrating adequate inert protection.CeO_(2) is a“coagulant”and“stabilizer”in the composite glass layer.However,increasing the CeO_(2) content accelerates the reaction between the SiO_(2) glass phase and SiC,leading to a higher SiO_(2) consumption and reduced self-healing ability of the glass layer.The 1%CeO_(2)-60%HfB2-39%SiC coating showed improved glass layer viscosity and stability,moderate SiO_(2) consumption,and better self-healing ability,significantly boosting the oxidation protection of the coating.
基金National Natural Science Foundation of China(52161009)Innovation Project of Postgraduate Students in North Minzu University(YCX24104)。
文摘To improve the high-temperature oxidation resistance of TiAlNb9 alloy,a Cr-Al-Y co-deposition coating was prepared on the alloy surface by the pack cementation method.The microstructure of the coating was analyzed by scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer,and the high-temperature oxidation properties of the substrate and coating at 1273 K were compared and studied.The results show that the Cr-Al-Y coating is about 30μm in thickness,and it has a dense structure and good film-substrate bonding.The coating includes an outer layer composed of TiCr_(2),TiCr,Ti_(4)Cr,and(Ti,Nb)Cr_(4) phases as well as an inner layer composed of Ti_(2)Al,and Nb-richγ-TiAl interdiffusion zone.The TiAlNb9 substrate forms an oxide layer composed of TiO_(2) and Al_(2)O_(3) at 1273 K.Due to its loose and porous structure,TiO_(2) oxide film cannot effectively isolate the internal diffusion of element O,resulting in continuous oxidation damage to the substrate.The Cr-Al-Y co-deposition coating forms a dense Cr_(2)O_(3) and Al_(2)O_(3) oxide layer during oxidation,effectively preventing the internal diffusion of element O and significantly improving the high-temperature oxidation resistance of the substrate alloy.
基金supported by the University Synergy Innovation Program of Anhui Province(Grant Nos.GXXT-2023-025 and GXXT-2023-026)Natural Science Foundation of Anhui Province(Grant Nos.2008085ME149,2308085QE132 and 2308065ME171)Anhui University Scientific Research Project(Grant Nos.2022AH040247,2023AH051660,2023AH051670 and 2023AH051671).
文摘To improve the high-temperature service properties of coppery tuyere,Co06 coating with a Ni60A interlayer was prepared on copper by plasma cladding.Ni60A interlayer acted as a bridge to promote the element diffusion,thus achieving metallurgical bonding.Due to the strengthening effect ofγ-Co,Cr_(23)C_(6)and Cr_(7)C_(3)phases,the wear resistance of Co06–Ni60A coating was much higher than that of copper substrate.As the temperature increased,the wear resistance of coating decreased first and then increased.The coating exhibited better wear resistance at 600℃ due to the oxidation wear mechanism.Compared with copper substrate and Ni60A,the oxidation resistance of Co06 was increased by 6.0 and 1.9 times,respectively.For melting loss resistance,Co06–Ni60A coating was superior to Ni60A single-layer coating,but the molten iron can still form a micro-metallurgical bonding with the coating surface.
基金supported by the Class Ⅲ Peak Discipline of Shanghai,China-Materials Science and Engineering(High-Energy Beam Intelligent Processing and Green Manufacturing).
文摘Laser shock peening(LSP)was used to enhance the high-temperature oxidation resistance of laser melting deposited Ti45Al8Nb alloy.The microstructure and high-temperature oxidation behavior of the as-deposited Ti45Al8Nb alloy before and after LSP were investigated by scanning electron microscopy,X-ray diffraction,and electron backscatter diffraction.The results indicated that the rate of mass gain in the as-deposited sample after LSP exhibited a decrease when exposed to an oxidation temperature of 900℃,implying that LSP-treated samples exhibited superior oxidation resistance at high temperatures.A gradient structure with a fine-grain layer,a deformed-grain layer,and a coarse-grain layer was formed in the LSP-treated sample,which facilitated the diffusion of the Al atom during oxidation,leading to the formation of a dense Al_(2)O_(3)layer on the surface.The mechanism of improvement in the oxidation resistance of the as-deposited Ti45Al8Nb alloy via LSP was discussed.
基金Supported by National Natural Science Foundation of China(Grant Nos.52075048,51675058,12232004)Hunan Provincial Excellent Youth Project of the Education Department(Grant No.21B0304)+2 种基金Natural Science Foundation of Hunan Province(Grant No.2023JJ30025)Science and Technology Innovation Program of Hunan Province(Grant No.2023RC1058)Scientific Research Innovation Project for Graduate Student of Changsha University of Science and Technology(Grant No.CLSJCX22096)。
文摘The high-temperature oxidation resistance of AISI 321 stainless steel used in solar thermal power heat exchangers determines its service life.In this study,aluminizing and subsequent laser shock peening(LSP)treatments were employed to improve the high-temperature oxidation resistance of AISI 321 stainless steel at 620°C.These two treatments decreased the oxidation rate of AISI 321 steel.Specifically,the optimal oxidation resistance was observed in aluminized steel before oxidation for 144 h owing to the increased entropy of the LSP-treated specimen.After 144 h,LSP-treated steel achieved the best oxidation resistance because of the formation of a protectiveα-Al2O3film.Moreover,the large amount of subgrain boundaries formed on the aluminized layer of the LSP-treated samples could act as short-circuit paths for the outward diffusion of Al,facilitating the rapid nucleation ofα-Al2O3.Meanwhile,the aluminized layer could isolate the contact between the oxidation environment and matrix,thereby decreasing the oxidation rate.Furthermore,the minimum oxidation parabolic constant was calculated for LSP-treated steel(6.45787×10^(-14)),which was 69.18%and 36.36%that of aluminized and 321 steel,respectively,during the entire oxidation process.Therefore,the combination of aluminizing and LSP treatments can improve the high-temperature oxidation resistance of 321 stainless steel,providing a new idea for its surface treatment to achieve a long service life at high temperatures.
基金Project (2012M511752) supported by China Postdoctoral Science FoundationProject (2011CB605801) supported by the National Basical Research Program of China+3 种基金Project (2012QNZT004) supported by the Fundamental Research Funds of the Central Universities, ChinaProject supported by the Freedom Explore Program of Central South University, ChinaProject (CSUZC2012026) supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University, ChinaProject supported by the Postdoctoral Science Foundation of Central South University, China
文摘To protect carbon materials from oxidation, mullite/SiC coatings were prepared on graphite by chemical vapor reaction (CVR) and slurry sintering. The XRD analyses show that the phase of the outer-layer coating is composed of SiO2 and mullite, and the inner-layer coating is mainly composed of β-SiC. The anti-oxidation behavior of the coating and the Rockwell hardness (HRB) of the coating after oxidation were investigated. The oxidation test shows that the as-prepared multi-layer coating exhibits excellent antioxidation and thermal shock resistance at high temperature. After oxidation at 1150 ℃ for 109 h and thermal shock cycling between 1150 ℃ and room temperature for 12 times, the mass gain of the coated sample is 0.085%. Meanwhile, the indentation tests also demonstrate that the as-prepared coating has good bonding ability between the layers.
基金Projects(CKJB201205,QKJB201202,YJK201307)supported by the Nanjing Institute of Technology,China
文摘The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the Ni Al phase is formed. It is also found that the Ni2Al3 phase completely turns into Ni Al phase after oxidizing treatment for 100 h and above. The Ni Al coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.
基金Supported by Tarim University President Fund for Innovation Group Program (TDZKCX08001)~~
文摘[Objective] The aim was to study on the oxidation resistance of flavonoids in Chinese jujube stone. [Method] The extract of flavonoids from Chinese jujube stone was added to fresh rapeseed oil and lard to explore the oxidation resistance of flavonoids; the removal rates of it to O2-·,DPPH· and ·OH were also studied. [Result] The flavonoids from Chinese jujube stone had good oxidation resistance on rapeseed oil and lard,and the effects showed dose-dependent; citric acid and vitamin C appeared synergistic effects to the flavonoids; in free-radical reaction experiment,the flavonoids from Chinese Jujube stone also showed strong scavenging ability on O2-·,DPPH· and ·OH,in addition,the scavenging ability increased with concentration increasing. [Conclusion] The result of this study had provided theoretical basis for the further development and utilization of Chinese jujube resource.
基金Project (50771021) supported by the National Natural Science Foundation of China
文摘Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employed to investigate the oxidation resistance of the composite coatings. The results revealed that the applied Al2O3/Au nano-laminated composite coatings improved the oxidation and spallation resistance of the stainless steel substrate significantly. The mechanism accounting for oxidation resistance was related with the suppression of inward oxygen diffusion and selective oxidation of Cr in the substrate. The mechanism accounting for spallation resistance was attributed to the relaxation of thermal stress by the nano-laminated structure.
基金Projects(51072107,51272213,51221001)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities of China("111" Project)
文摘To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carbon foams were characterized by scanning electron microscopy and X-ray diffraction, respectively. Oxidation resistances of uncoated and coated boron-modified carbon foams were investigated at 873 K in air. The results showed that as-received B2O3 coating could protect boron-modified carbon foams from oxidation at 873 K. B2O3-coated carbon foam doped with 7% B2O3 （mass fraction） （BO-7） had better oxidation resistance, exhibiting mass loss of 17.40% after oxidation at 873 K for 120 min. The melting glass layer formed on the surface of BO-7 could prevent oxygen from diffusing into boron-modified carbon foams substrate during oxidation to some extent.
基金Supported by Sichuan Provincial International S&T Cooperation Program(No.2008HH0012)Cooperation Research Program of Sichuan University and Hitachi Company(No.07H372)~~
文摘[Objective] The aim was to research the influences of different formulations on oxidation resistance of PVDF hollow fiber membrane.[Method]The immersion precipitation phase inversion method was employed to make casting solution with different formulations into hollow fiber membrane.The membrane was immersed in 1% NaClO solution for testing its performance changes.[Result]The membrane made by materials with bigger molecular weight had better oxidation resistance performance;the surfactant tween-80 could increase water flux,but lead to lower rupture intension;Pore-forming agent PEG400 do better than PVP in the oxidation resistance of membrane.[Conclusion]This study will provide a good idea for the development of the PVDF membrane with high oxidation resistance.
基金Project(9231083) supported by Yunnan Aerospace Industry Corporation Contract Research,ChinaProject(9220061) supported by City University of Hong Kong Donation Research Grant,China
文摘A1 and N were introduced into copper substrate using plasma immersion ion implantation （PIII） in order to enhance its hardness and oxidation resistance. The dosage of N ion is 5 × 1016 cm-2, and range of dosage of A1 ion is 5× 1016-2× 1017 cm-2. The oxidation tests indicate that the copper samples after undergoing PIII possess higher oxidation resistance. The degree of oxidation resistance is found to vary with implantation dosage of AI ion. The antibacterial tests also reveal that the plasma implanted copper specimens have excellent antibacterial resistance against Staphylococcus aureus, which are similar to pure copper.
文摘We studied the oxidation resistance of graphene-coated Cu surface and its layer dependence by directly growing monolayer graphene with different multilayer structures coexisted, di- minishing the influence induced by residue and transfer technology. It is found that the Cu surface coated with the monolayer graphene demonstrate tremendous difference in oxidation pattern and oxidation rate, compared to that coated with the bilayer graphene, which is considered to be originated from the strain-induced linear oxidation channel in monolayer graphene and the intersection of easily-oxidized directions in each layer of bilayer graphene, respectively. We reveal that the defects on the graphene basal plane but not the boundaries are the main oxidation channel for Cu surface under graphene protection. Our finding indicates that compared to putting forth efforts to improve the quality of monolayer graphene by reducing defects, depositing multilayer graphene directly on metal is a simple and effective way to enhance the oxidation resistance of graphene-coated metals.
基金Foundation item： National Natural Science Foundation of China （50671081）
文摘Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance are analyzed. The （Nb,Ti）ss, β-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 exist in Nb-22Ti-16Si-6Cr-3Al-4Hf alloy, while （Nb,Ti）ss, α-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 are present in Nb-22Ti-16Si-6Cr-3Al-4Hf-lB and Nb-22Ti-16Si-6Cr-3Al-4Hf-2B alloys. The oxidation of Nb-Ti-Si-based ultrahigh-temperature alloys is dominated by the diffusion of oxygen through （Nb,Ti）ss. Compared to boron-free alloys, the boron-containing alloys have significantly lower oxidation rate when oxidized at 1 200 ℃ for less than 50 h, but, for more than 50 h, their oxidation resistance deteriorates.
基金Project supported by the National"863"Project (2003AA305810)
文摘Nb-16Si-24Ti-6Cr-6A1-2Hf-xCe （x =0, 0.05, 0.1,02.5, 0.5, 1 （%, atom fraction）） in situ composites were prepared by arc melting The microstmcture and the effect of rare earth element cerium on 1250℃ oxidation resistance of the composites were investigated with scanning electron microscopy （SEM） and X-ray energy disperse spectrum （EDS）, as well as X-ray diffraction （XRD）. The experimental results showed that the high temperature oxidation resistance of the alloy was improved by adding a proper amount of cerium （Ce）. The effect of Ce was considered as the concurrent of the following three factors： first, the oxide of Ce formed in the interface reduced the internal oxidation rate; second, the lath shaped oxide containing Ce increased the cracking resistance and reduced the expansion of the oxide scale; and third, the decrease of the sificide volume fraction on account of Ce addition reduces the power of the sample resisting oxygen penetration.
基金National Natural Science Foundation of China (51101005)
文摘Nb-22Ti-14Si-2Hf-2Al-xCr （x=2, 6, 10, 14, 17 at%） alloys are prepared by arc-melting under argon atmosphere. Microstructural characteristics, mechanical properties and oxidation resistance of the arc-melted alloys are investigated. At 2 at% Cr content, the microstructure is composed of Nbss, Nb3Si and a small quantity of Nb5Si3, when the Cr contents increase, Nb3Si disappears. For the high Cr content （x ≥ 10 at%） alloys, besides the Nbss and Nb5Si3, Cr2Nb is also detected. With the increase of Cr content, the volume fractions of Cr2Nb and Nb5Si3 increase, while that of Nbss increases firstly and then begins to degrade when the Cr content is higher than 6 at%. For the alloy with 2 at% Cr, the room temperature fracture toughness is about 14.5 MPa·m1/2, but badly decreases to about 8.5 MPa·m1/2, when the Cr contents increase. Vickers hardness of Nbss tends to increase linearly from about 400 to 500, while that of silicides is not sensitive to Cr contents, about 950. The appearance of Cr2Nb phase significantly improves the high temperature oxidation resistance of the alloys with high Cr contents. The isothermal oxidation tests show that the oxidation kinetics of the alloys with various Cr contents follows parabolic oxidation kinetics.
文摘In order to improve the oxidation resistance properties of 30 at.% Mo5Si3/MoSi2 composite at high temperature in air, a molybdenum disilicide coating was prepared on its surface by a molten salt technology. XRD and SEM analysis showed that only tetragonal MoSi2 phase existed in the coating after being siliconized for 5 h at 900℃. The oxidation film formed on the uncoated sample was not dense, so that oxygen diffused easily through it. The volatilization of MoO3 resulted in the oxidation film separating from the substrate. The MoSi2 coating was proved to be an effective method to prevent 30 at.% Mo5Si3/MoSi2 composites from being oxidized at 1200℃. A dense glassy SiO2 film was formed on the MoSi2 coating surface, which acted as a barrier layer for the diffusion of oxygen atoms to the substrate. The 30at.% MosSi3/MoSi2 composites with a MoSi2 coating showed much better oxidation resistance at high temperature.
基金supported financially by Komatsu of Japan,grant number31370011370804,in Shandong University,China.
文摘Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.
基金financially supported by the Fundamental R&D Program for Core Technology of Materials(No.10041233)the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)(No.20174030201620)。
文摘The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were designed by the Box-Behnken method of design of experiments(DOE).The alloying elements show complicated effects on the mass gain due to oxidation,depending on the alloy composition.Al reduces the mass gain largely.The other elements except Al do not appear to exert a strong effect on the oxidation rate on average,but their influences are shown clearly in the alloys with a low Al content.Co,W,and Ta reduce the oxidation rate,while Cr,Mo,and Ti promote oxidation.Ta is the most effective element in reducing the oxidation rate of the alloy with a low Al concentration.It is confirmed that a continuous Al2O3 layer is essentially required for high oxidation resistance.The oxide scale of easily oxidized alloys has various oxides such as NiCr2O4,NiAl2O4,NiO,Cr2O3,CrTaO4,and TiO2.
