Magnesium(Mg)alloy is widely used in aerospace and automotive industries as an excellent lightweight metal material to reduce carbon emissions.The expansion of Mg alloy applications and the increasing demands for thes...Magnesium(Mg)alloy is widely used in aerospace and automotive industries as an excellent lightweight metal material to reduce carbon emissions.The expansion of Mg alloy applications and the increasing demands for these materials have significantly facilitated the generation of Mg alloy scrap.The recycling of Mg resources is crucial for promoting both environmental sustainability and economic viability.However,current recycling effect is unsatisfactory.Therefore,this paper provides a comprehensive review of the entire recycling process,including scrap classification,separation and sorting,pre-treatment,and recycling.This paper explores the generation of Mg alloy scrap and its reincorporation into industrial products.This review outlines various Mg scrap recycling technologies based on different phase states.These include liquid-state recycling(such as flux refining,impurity removal additives,fluxless refining,compound treatment,and direct remelting),solid-state recycling(involving hot extrusion,equal-channel angular pressing(ECAP),friction stir extrusion(FSE),and spark plasma sintering(SPS)),vapor-state recycling(comprising vacuum distillation and sublimation),electrochemical recycling(solid oxide membrane(SOM)electrolysis,RE-12TMelectrorefining,and non-aqueous solution electrorefining),and Mg secondary alloy development.The advantages and existing challenges associated with each method are compared and discussed,and the current obstacles to the future recycling of complex scrap are examined.展开更多
Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate...Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate than aluminum,and its greater complexity poses challenges to existing recycling processes.Although vacuum distillation can be used to recycle Mg alloy scrap,this requires optimizing and maximizing metal recirculation,but there has been no thermodynamic analysis of this process.In this study,the feasibility and controllability of separating inclusions and 23 metal impurities were evaluated,and their distribution and removal limits were quantified.Thermodynamic analyses and experimental results showed that inclusions and impurity metals of separation coefficient lgβ_(i)≤-5,including Cu,Fe,Co,and Ni below 0.001 ppm,could be removed from the matrix.All Zn entered the recycled Mg,while impurities with-1<lgβ_(i)<-5 such as Li,Ca,and Mn severely affected the purity of the recycled Mg during the later stage of distillation.Therefore,an optimization strategy for vacuum distillation recycling:lower temperatures and higher system pressures for Zn separation in the early stage,and the early termination of the recovery process in the later stage or a continuous supply of raw melt can also prevent contamination during recycling.The alloying elements Al and Zn in Mg alloy scrap can be further recovered and purified by vacuum distillation when economically feasible,to maximize the recycling of metal resources.展开更多
Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effe...Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effectively,even when the scraps are co-mingled and have higher costs for further sorting and separation.In this work,we explore an alloy design concept by creating a compositionally flexible domain that can recycle multiple alloy grades and yet maintain relatively consistent properties across chemical variations.This is demonstrated through the Fe-Cr-Ni-Mn system to identify compositionally flexible austenitic stainless steels(CF-ASS)and accommodate the recycling of mixed austenitic stainless steel scraps.Alloys within the nominal composition spaces exhibit relatively consistent mechanical properties and corrosion resistance despite significant variations in different alloy compositions.We illustrate how we can utilise the compositionally flexible austenitic stainless steels to recycle mixed 200 and 300-series stainless steel and ferronickel scraps,demonstrating its practical viability.While this demonstration focuses on the stainless steel system,the underlying principles can be extended to other systems related to mixed scrap recycling.展开更多
The present investigation studied the toxicity of soil contaminated by untreated discharge from a factory that recycles used plastics. The nearby agricultural areas and freshwater fish ponds were polluted with high co...The present investigation studied the toxicity of soil contaminated by untreated discharge from a factory that recycles used plastics. The nearby agricultural areas and freshwater fish ponds were polluted with high concentrations of Cu, Ni, and Mn. Water extracts from the contaminated soil retarded root growth of Brassica chinensis (Chinese white cabbage) and Cynodon dactylon (Bermuda grass) where their seeds were obtained commercially. The contaminated populations of C. dactylon, Panicum repen (panic grass), and Imperata cylindrica (wooly grass) were able to withstand higher concentrations of Cu. Ni, and Mn, especially C. dactylon, when compared with their uncontaminated counterparts. 1990 Academic Press, Inc.展开更多
Massive waste aluminum scraps produced from the spent aluminum products have high electron capacity and can be recycled as an attractive alternative to materials based on zerovalent iron(Fe^(0))for the removal of oxid...Massive waste aluminum scraps produced from the spent aluminum products have high electron capacity and can be recycled as an attractive alternative to materials based on zerovalent iron(Fe^(0))for the removal of oxidative contaminants from wastewater.This study thus proposed an approach to fabricate micron-sized sulfidated zero-valent iron-aluminum particles(S-Al^(0)@Fe^(0))with high reactivity,electron selectivity and capacity using recycled waste aluminum scraps.S-Al^(0)@Fe^(0)with a three-layer structure contained zero-valent aluminum(Al^(0))core,Fe^(0) middle layer and iron sulfide(FeS)shell.The rates of chromate(Cr(Ⅵ))removal by S-Al^(0)@Fe^(0)at pH 5.0-9.0 were 1.6-5.9 times greater than that by sulfidated zero-valent iron(S-Fe^(0)).The Cr(Ⅵ)removal capacity of S-Al^(0)@Fe^(0)was 8.2-,11.3-and 46.9-fold greater than those of S-Fe0,zero-valent iron-aluminum(Al^(0)-Fe^(0))and Fe^(0),respectively.The chemical cost of S-Al^(0)@Fe^(0) for the equivalent Cr(Ⅵ)removal was 78.5%lower than that of S-Fe^(0).Negligible release of soluble aluminum during the Cr(Ⅵ)removal was observed.The significant enhancement in the reactivity and capacity of S-Al^(0)@Fe^(0)was partially ascribed to the higher reactivity and electron density of the Al0core than Fe^(0).More importantly,S-Al^(0)@Fe^(0) served as an electric cell to harness the persistent and selective electron transfer from the Al^(0)-Fe^(0) core to Cr(Ⅵ)at the surface via coupling Fe^(0)-Fe^(2+)-Fe^(3+)redox cycles,resulting in a higher electron utilization efficiency.Therefore,S-Al^(0)@Fe^(0) fabricated using recycled waste aluminum scraps can be a cost-effective and environmentally-friendly alternative to S-Fe^(0) for the enhanced removal of oxidative contaminants in industrial wastewater.展开更多
The aim of this study was to determine the quality of rebar produced from recycled scrap metal collected throughout the country,and imported rebar sold in the Republic of Guinea.To do this,the samples were subjected t...The aim of this study was to determine the quality of rebar produced from recycled scrap metal collected throughout the country,and imported rebar sold in the Republic of Guinea.To do this,the samples were subjected to various mechanical tests involving traction,bending and microscopic analysis.In the Lambanyi and Casse Sonfonia samples,all the tensile strength values for diameters 12,14 and 16 were above 550 MPa.Conversely,the iron samples from Baillobaye and the 10 mm diameters of the samples from Casse Sonfonio and Lambanyi have less appreciable values.The limits of elasticity were determined.The various values found vary more or less from the conventional yield strength of the NF A35-016 reference supplied by CBITEC,which is 500 MPa.Microscopic analysis gives us an insight into the internal structure of the iron samples used.This study may provide the company and the vendors with an alternative for their improvements.展开更多
Recycling retired cars can relieve the environmental pollution and resource waste efficiently.However,a few publications can be found on the failure mechanisms and optimization method of recycling equipment,shredders....Recycling retired cars can relieve the environmental pollution and resource waste efficiently.However,a few publications can be found on the failure mechanisms and optimization method of recycling equipment,shredders.Thus,the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost.Failure types of shredder hammer are studied theoretically,and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer.The shredding process of metal scraps is analyzed by finite element method,and it can be divided into four stages based on the stress states：initial stage,collision stage,grinding stage and separation stage.It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head.Finally,it is determined that the hammer with two cutouts is the optimal structure for metal scraps,which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%.This study provides scientific basis for the industry application and theoretical foundation for further research.展开更多
A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, micro...A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, microstructure morphology and evolution mechanism of iron-rich phases in Mg-A1-Si alloy melts were studied, after AI-14Si-4Fe （wt%） alloys were added and dissolved completely. In the Mg-A1-Si alloys, iron has very little solubility and tends to combine with other elements to form intermetallic phases, which grow into a deposition layer due to the higher density. During the cooling and solidifying process of Mg-A1-Si melts, the needle-like AlsSiFe phase in AI-14Si-4Fe alloy evolved into blocky AI5Fe2 and Al0.7Fe3Si0.3 phases. Besides, the Fe levels of the Mg-AI-Si master alloys were reduced to 0.017 wt% from nominal content of 0.164 wt%. Based on the above results, this work carried out a semi-quantitative phase- compositions analysis for the deposition layer by relative intensity ratio （RIR） method, and evolution mechanism of the iron-rich phases had also been discussed. This study has paved a new way to regen- erate the scrap AI-Si-Fe alloys, which has a great significance of promoting the recycling of aluminum resources.展开更多
This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and oth...This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and other abandoned sites, as well as imported concrete reinforcing steel sold in the Republic of Guinea. To carry out this important work, a number of mechanical tensile and bending tests and a microscopic analysis combining two devices, an electron microscope and a photographic camera, were carried out. The samples were taken from sampling areas in the major communes of Conakry, namely: Casse Sonfonia, Matoto and Kagbélen. The tensile strength values of the large dimensions 20, 25, 28 and 32 are given in the tables.展开更多
基金supported by the Yunnan Province Nonferrous Metal Vacuum Metallurgy Top Team[grant number 202305AS350012]the Yunnan Province Yang Bin Scientist Workshop。
文摘Magnesium(Mg)alloy is widely used in aerospace and automotive industries as an excellent lightweight metal material to reduce carbon emissions.The expansion of Mg alloy applications and the increasing demands for these materials have significantly facilitated the generation of Mg alloy scrap.The recycling of Mg resources is crucial for promoting both environmental sustainability and economic viability.However,current recycling effect is unsatisfactory.Therefore,this paper provides a comprehensive review of the entire recycling process,including scrap classification,separation and sorting,pre-treatment,and recycling.This paper explores the generation of Mg alloy scrap and its reincorporation into industrial products.This review outlines various Mg scrap recycling technologies based on different phase states.These include liquid-state recycling(such as flux refining,impurity removal additives,fluxless refining,compound treatment,and direct remelting),solid-state recycling(involving hot extrusion,equal-channel angular pressing(ECAP),friction stir extrusion(FSE),and spark plasma sintering(SPS)),vapor-state recycling(comprising vacuum distillation and sublimation),electrochemical recycling(solid oxide membrane(SOM)electrolysis,RE-12TMelectrorefining,and non-aqueous solution electrorefining),and Mg secondary alloy development.The advantages and existing challenges associated with each method are compared and discussed,and the current obstacles to the future recycling of complex scrap are examined.
文摘Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate than aluminum,and its greater complexity poses challenges to existing recycling processes.Although vacuum distillation can be used to recycle Mg alloy scrap,this requires optimizing and maximizing metal recirculation,but there has been no thermodynamic analysis of this process.In this study,the feasibility and controllability of separating inclusions and 23 metal impurities were evaluated,and their distribution and removal limits were quantified.Thermodynamic analyses and experimental results showed that inclusions and impurity metals of separation coefficient lgβ_(i)≤-5,including Cu,Fe,Co,and Ni below 0.001 ppm,could be removed from the matrix.All Zn entered the recycled Mg,while impurities with-1<lgβ_(i)<-5 such as Li,Ca,and Mn severely affected the purity of the recycled Mg during the later stage of distillation.Therefore,an optimization strategy for vacuum distillation recycling:lower temperatures and higher system pressures for Zn separation in the early stage,and the early termination of the recovery process in the later stage or a continuous supply of raw melt can also prevent contamination during recycling.The alloying elements Al and Zn in Mg alloy scrap can be further recovered and purified by vacuum distillation when economically feasible,to maximize the recycling of metal resources.
基金financially supported by the National Key Research and Development Program(No.2023YFB3712403)the National Natural Science Foundation of China(Nos.52201112,52071066,U22A20106,and U22A20173).
文摘Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effectively,even when the scraps are co-mingled and have higher costs for further sorting and separation.In this work,we explore an alloy design concept by creating a compositionally flexible domain that can recycle multiple alloy grades and yet maintain relatively consistent properties across chemical variations.This is demonstrated through the Fe-Cr-Ni-Mn system to identify compositionally flexible austenitic stainless steels(CF-ASS)and accommodate the recycling of mixed austenitic stainless steel scraps.Alloys within the nominal composition spaces exhibit relatively consistent mechanical properties and corrosion resistance despite significant variations in different alloy compositions.We illustrate how we can utilise the compositionally flexible austenitic stainless steels to recycle mixed 200 and 300-series stainless steel and ferronickel scraps,demonstrating its practical viability.While this demonstration focuses on the stainless steel system,the underlying principles can be extended to other systems related to mixed scrap recycling.
文摘The present investigation studied the toxicity of soil contaminated by untreated discharge from a factory that recycles used plastics. The nearby agricultural areas and freshwater fish ponds were polluted with high concentrations of Cu, Ni, and Mn. Water extracts from the contaminated soil retarded root growth of Brassica chinensis (Chinese white cabbage) and Cynodon dactylon (Bermuda grass) where their seeds were obtained commercially. The contaminated populations of C. dactylon, Panicum repen (panic grass), and Imperata cylindrica (wooly grass) were able to withstand higher concentrations of Cu. Ni, and Mn, especially C. dactylon, when compared with their uncontaminated counterparts. 1990 Academic Press, Inc.
基金supported by the National Natural Science Foundation of China(No.42177358)the Natural Science Foundation of Guangdong Province(No.2023A1515011232)。
文摘Massive waste aluminum scraps produced from the spent aluminum products have high electron capacity and can be recycled as an attractive alternative to materials based on zerovalent iron(Fe^(0))for the removal of oxidative contaminants from wastewater.This study thus proposed an approach to fabricate micron-sized sulfidated zero-valent iron-aluminum particles(S-Al^(0)@Fe^(0))with high reactivity,electron selectivity and capacity using recycled waste aluminum scraps.S-Al^(0)@Fe^(0)with a three-layer structure contained zero-valent aluminum(Al^(0))core,Fe^(0) middle layer and iron sulfide(FeS)shell.The rates of chromate(Cr(Ⅵ))removal by S-Al^(0)@Fe^(0)at pH 5.0-9.0 were 1.6-5.9 times greater than that by sulfidated zero-valent iron(S-Fe^(0)).The Cr(Ⅵ)removal capacity of S-Al^(0)@Fe^(0)was 8.2-,11.3-and 46.9-fold greater than those of S-Fe0,zero-valent iron-aluminum(Al^(0)-Fe^(0))and Fe^(0),respectively.The chemical cost of S-Al^(0)@Fe^(0) for the equivalent Cr(Ⅵ)removal was 78.5%lower than that of S-Fe^(0).Negligible release of soluble aluminum during the Cr(Ⅵ)removal was observed.The significant enhancement in the reactivity and capacity of S-Al^(0)@Fe^(0)was partially ascribed to the higher reactivity and electron density of the Al0core than Fe^(0).More importantly,S-Al^(0)@Fe^(0) served as an electric cell to harness the persistent and selective electron transfer from the Al^(0)-Fe^(0) core to Cr(Ⅵ)at the surface via coupling Fe^(0)-Fe^(2+)-Fe^(3+)redox cycles,resulting in a higher electron utilization efficiency.Therefore,S-Al^(0)@Fe^(0) fabricated using recycled waste aluminum scraps can be a cost-effective and environmentally-friendly alternative to S-Fe^(0) for the enhanced removal of oxidative contaminants in industrial wastewater.
文摘The aim of this study was to determine the quality of rebar produced from recycled scrap metal collected throughout the country,and imported rebar sold in the Republic of Guinea.To do this,the samples were subjected to various mechanical tests involving traction,bending and microscopic analysis.In the Lambanyi and Casse Sonfonia samples,all the tensile strength values for diameters 12,14 and 16 were above 550 MPa.Conversely,the iron samples from Baillobaye and the 10 mm diameters of the samples from Casse Sonfonio and Lambanyi have less appreciable values.The limits of elasticity were determined.The various values found vary more or less from the conventional yield strength of the NF A35-016 reference supplied by CBITEC,which is 500 MPa.Microscopic analysis gives us an insight into the internal structure of the iron samples used.This study may provide the company and the vendors with an alternative for their improvements.
基金Supported by Innovation Team Development Plan(Grant No.IRT13087)Major Scientific and Technological Innovation Project in Hubei Province,China(Grant No.2015AAA014)Fundamental Research Funds for the Central Universities,China(Grant No.2015-yb-010)
文摘Recycling retired cars can relieve the environmental pollution and resource waste efficiently.However,a few publications can be found on the failure mechanisms and optimization method of recycling equipment,shredders.Thus,the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost.Failure types of shredder hammer are studied theoretically,and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer.The shredding process of metal scraps is analyzed by finite element method,and it can be divided into four stages based on the stress states：initial stage,collision stage,grinding stage and separation stage.It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head.Finally,it is determined that the hammer with two cutouts is the optimal structure for metal scraps,which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%.This study provides scientific basis for the industry application and theoretical foundation for further research.
基金supported by the National Natural Science Foundation of China(No.512711101)the National Basic Research Program of China (No.2012CB825702)
文摘A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, microstructure morphology and evolution mechanism of iron-rich phases in Mg-A1-Si alloy melts were studied, after AI-14Si-4Fe （wt%） alloys were added and dissolved completely. In the Mg-A1-Si alloys, iron has very little solubility and tends to combine with other elements to form intermetallic phases, which grow into a deposition layer due to the higher density. During the cooling and solidifying process of Mg-A1-Si melts, the needle-like AlsSiFe phase in AI-14Si-4Fe alloy evolved into blocky AI5Fe2 and Al0.7Fe3Si0.3 phases. Besides, the Fe levels of the Mg-AI-Si master alloys were reduced to 0.017 wt% from nominal content of 0.164 wt%. Based on the above results, this work carried out a semi-quantitative phase- compositions analysis for the deposition layer by relative intensity ratio （RIR） method, and evolution mechanism of the iron-rich phases had also been discussed. This study has paved a new way to regen- erate the scrap AI-Si-Fe alloys, which has a great significance of promoting the recycling of aluminum resources.
文摘This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and other abandoned sites, as well as imported concrete reinforcing steel sold in the Republic of Guinea. To carry out this important work, a number of mechanical tensile and bending tests and a microscopic analysis combining two devices, an electron microscope and a photographic camera, were carried out. The samples were taken from sampling areas in the major communes of Conakry, namely: Casse Sonfonia, Matoto and Kagbélen. The tensile strength values of the large dimensions 20, 25, 28 and 32 are given in the tables.
