Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical...Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical oven. The magnetic properties of the resulting specimens have been analyzed and discussed as a function of the grain size and the particles’ morphology. The partial formation of garnet and orthoferrite phases was revealed on the obtained powder through microstructural analyses after 9 h of ball milling. The milled powders were transformed into the orthoferrite phase after the SPS-treatment at 700°C and 900°C. Magnetic-saturation studies revealed magnetic responses up to 12.7 emu/g for specimens SPS-treated at 700°C, whereas 2.1 emu/g for samples SPS-treated at 900°C. Conventionally treated specimens at 700°C developed 0.36 emu/g of magnetization, while 0.93 emu/g was registered for those treated at 900°C.展开更多
This article represents a pioneering study centered on the corrosion kinetics of untreated and thermally processed mechano-synthesized Al_(x)Cr_(y)Ni_(z) two-dimensional decagonal quasicrystalline structure and crysta...This article represents a pioneering study centered on the corrosion kinetics of untreated and thermally processed mechano-synthesized Al_(x)Cr_(y)Ni_(z) two-dimensional decagonal quasicrystalline structure and crystalline approximants.It sheds light on the distinguished corrosion behavior of untreated and heat-treated mechano-synthesized Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2)alloys,including a wide diversity of miscellaneous intermetallic phases.A comprehensive characterization was performed to analyze crystallographic structure and thermal characteristics of Al_(x)Cr_(y)Ni_(z) powder particles.Electrochemical evaluations of the mechano-synthesized Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) specimens and their heat-treated counterparts were conducted under cyclic potentiodynamic polarization tests with 0.1 mol/L Na_(2)SO_(4)(pH=2) and 3.5%NaCl(pH=8.5) electrolytes at room temperature,respectively.Al_(72)Cr_(15)Ni_(13) two-dimensional decagonal quasicrystalline phase was attained following 6 h mechanosynthesis and subsequent annealing treatment at 1035℃.There is no evidence of quasicrystal formation in the Al_(86)Cr_(12)Ni_(2) alloy system after 6 h mechano-synthesis and successive thermal processing at 445 and 570℃.In this study,we conducted the first investigation into electrochemical performance of both Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) intermetallics.Both Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) alloys develop a protective passive film in 0.1 mol/L Na_(2)SO_(4) electrolyte.It was determined that 6 h mechano-synthesized Al_(72)Cr_(15)Ni_(13) sample,subjected to annealing at 1035℃,stands out in the Al-Cr-Ni alloy systems for applications necessitating exceptional corrosion resistance,passivation behavior,and minimal susceptibility to pitting corrosion when compared to other tested counterparts.This alloy is characterized by a corrosion current density of 3.73μA/cm^(2) and a corrosion potential of-0.16 V(vs.Ag/AgCl),revealing a remarkably stable passive film up to a current density of 0.02 A/cm^(2) and a potential of 2.41 V(vs.Ag/AgCl)within 0.1 mol/L Na_(2)SO_(4) medium.Likewise,it exhibited a drastically diminished corrosion current density of 11.65μA/cm^(2) and a reduced corrosion potential of-0.27 V(vs.Ag/AgCl)within 3.5%NaCl electrolyte,attributed to the formation of two-dimensional decagonal quasicrystalline phase and hexagonalδ-Al_(3)Ni_(2) crystalline approximant at 1035℃.It also encompassed a re-passivation current density and potential of 50.35μA/cm^(2)and-0.04 V(vs.Ag/AgCl),respectively,within the latter solution.Its corrosion mechanism may be ascribed to a two-step surface precipitation process:initially,Al dissolves into a hydroxide,succeeded by the formation and precipitation of Al oxides,such as NaAlO_(2) and Al_(2)O_(3)·xH_(2)O.展开更多
文摘Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical oven. The magnetic properties of the resulting specimens have been analyzed and discussed as a function of the grain size and the particles’ morphology. The partial formation of garnet and orthoferrite phases was revealed on the obtained powder through microstructural analyses after 9 h of ball milling. The milled powders were transformed into the orthoferrite phase after the SPS-treatment at 700°C and 900°C. Magnetic-saturation studies revealed magnetic responses up to 12.7 emu/g for specimens SPS-treated at 700°C, whereas 2.1 emu/g for samples SPS-treated at 900°C. Conventionally treated specimens at 700°C developed 0.36 emu/g of magnetization, while 0.93 emu/g was registered for those treated at 900°C.
文摘This article represents a pioneering study centered on the corrosion kinetics of untreated and thermally processed mechano-synthesized Al_(x)Cr_(y)Ni_(z) two-dimensional decagonal quasicrystalline structure and crystalline approximants.It sheds light on the distinguished corrosion behavior of untreated and heat-treated mechano-synthesized Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2)alloys,including a wide diversity of miscellaneous intermetallic phases.A comprehensive characterization was performed to analyze crystallographic structure and thermal characteristics of Al_(x)Cr_(y)Ni_(z) powder particles.Electrochemical evaluations of the mechano-synthesized Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) specimens and their heat-treated counterparts were conducted under cyclic potentiodynamic polarization tests with 0.1 mol/L Na_(2)SO_(4)(pH=2) and 3.5%NaCl(pH=8.5) electrolytes at room temperature,respectively.Al_(72)Cr_(15)Ni_(13) two-dimensional decagonal quasicrystalline phase was attained following 6 h mechanosynthesis and subsequent annealing treatment at 1035℃.There is no evidence of quasicrystal formation in the Al_(86)Cr_(12)Ni_(2) alloy system after 6 h mechano-synthesis and successive thermal processing at 445 and 570℃.In this study,we conducted the first investigation into electrochemical performance of both Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) intermetallics.Both Al_(72)Cr_(15)Ni_(13) and Al_(86)Cr_(12)Ni_(2) alloys develop a protective passive film in 0.1 mol/L Na_(2)SO_(4) electrolyte.It was determined that 6 h mechano-synthesized Al_(72)Cr_(15)Ni_(13) sample,subjected to annealing at 1035℃,stands out in the Al-Cr-Ni alloy systems for applications necessitating exceptional corrosion resistance,passivation behavior,and minimal susceptibility to pitting corrosion when compared to other tested counterparts.This alloy is characterized by a corrosion current density of 3.73μA/cm^(2) and a corrosion potential of-0.16 V(vs.Ag/AgCl),revealing a remarkably stable passive film up to a current density of 0.02 A/cm^(2) and a potential of 2.41 V(vs.Ag/AgCl)within 0.1 mol/L Na_(2)SO_(4) medium.Likewise,it exhibited a drastically diminished corrosion current density of 11.65μA/cm^(2) and a reduced corrosion potential of-0.27 V(vs.Ag/AgCl)within 3.5%NaCl electrolyte,attributed to the formation of two-dimensional decagonal quasicrystalline phase and hexagonalδ-Al_(3)Ni_(2) crystalline approximant at 1035℃.It also encompassed a re-passivation current density and potential of 50.35μA/cm^(2)and-0.04 V(vs.Ag/AgCl),respectively,within the latter solution.Its corrosion mechanism may be ascribed to a two-step surface precipitation process:initially,Al dissolves into a hydroxide,succeeded by the formation and precipitation of Al oxides,such as NaAlO_(2) and Al_(2)O_(3)·xH_(2)O.
