Now, a rapidly growing concern for the environmental protection and resource utilization has stimulated many new activities in the in dustrialized world for coping with urgent environmental problems created by the ste...Now, a rapidly growing concern for the environmental protection and resource utilization has stimulated many new activities in the in dustrialized world for coping with urgent environmental problems created by the steadily increasing consumption of industrial products. Increasingly stringent r egulations and widely expressed public concern for the environment highlight the importance of disposing solid waste generated from industrial and consumable pr oducts. How to efficiently recycle and tackle this problem has been a very impo rtant issue over the world. Designing products for recyclability is driven by environmental and economic goals. To obtain good recyclability, two measures can be adopted. One is better recycling strategy and technology; the other is design for recycling (DFR). The recycling strategies of products generally inclu de: reuse, service, remanufacturing, recycling of production scraps during the p roduct usage, recycle (separation first) and disposal. Recyclability assessment is a very important content in DFR. This paper first discusses the content of D FR and strategies and types related to products recyclability, and points out th at easy or difficult recyclability depends on the design phase. Then method and procedure of recyclability assessment based on ANN is explored in detail. The pr ocess consists of selection of the ANN input and output parameters, control of t he sample quality and construction and training of the neural network. At la st, the case study shows this method is simple and operative.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acousti...The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.展开更多
Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generato...Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.展开更多
Massive amounts of low-grade tin middlings have been produced from tin tailings,in which arsenic and tin are worthy to be recycled.Owing to high sulfur content in these tin middlings,a novel self-sulfurization roastin...Massive amounts of low-grade tin middlings have been produced from tin tailings,in which arsenic and tin are worthy to be recycled.Owing to high sulfur content in these tin middlings,a novel self-sulfurization roasting was proposed to transform,separate and recover arsenic and tin in this research.There was no extra curing agent to be added,which decreased the formation of pollutant S-containing gas.The self-sulfurization process involved a two-stage roasting of reduction followed by sulfurization.First in reduction roasting,FeAsS decomposed to FeS and As and the As then transformed to As_(4)(g)and As_(4)S_(4)(g),via which the arsenic was separated and recovered.The arsenic content in the first residue could be decreased to 0.72 wt.%.Accompanied with it,the FeS was firstly oxidized to Fe_(1−x)S and then to SO_(2)(g)by the coexisted Fe_(2)O_(3),and finally reduced and combined with the independent Fe_(2)O_(3)to form Fe_(1−x)S.In the followed sulfurization roasting,the Fe_(1−x)S sulfurized SnO_(2)to SnS(g),due to which tin could be recovered and its content in the second residue decreased to 0.01 wt.%.This study provided an efficient method to separate and recover arsenic and tin from low-grade tin middlings.展开更多
The utilization of arsenic-containing gold dressing tailings is an urgent issue faced by gold production companies worldwide.The thermodynamic analysis results indicate that ferrous arsenate(FeAsO_(4)),pyrite(FeS_(2))...The utilization of arsenic-containing gold dressing tailings is an urgent issue faced by gold production companies worldwide.The thermodynamic analysis results indicate that ferrous arsenate(FeAsO_(4)),pyrite(FeS_(2))and sodium cyanide(NaCN)in the arsenic-containing gold metallurgical tailings can be effectively removed using straight grate process,and the removal of pyrite and sodium cyanide is basically completed during the preheating stage,while the removal of ferrous arsenate requires the roasting stage.The pellets undergo a transformation from magnetite to hematite during the preheating process,and are solidified through micro-crystalline bonding and high-temperature recrystallization of hematite(Fe_(2)O_(3))during the roasting process.Ultimately,pellets with removal rates of 80.77% for arsenic,88.78% for sulfur,and 99.88% for cyanide are obtained,as well as the iron content is 61.1% and the compressive strength is 3071 N,meeting the requirements for blast furnace burden.This study provides an industrially feasible method for treating arsenic-containing gold smelting tailings,benefiting gold production enterprises.展开更多
Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scan...Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF2, CaSO4, Me（OH）, （M： Fe, Cr, Ni）, and the content of CaF2 is high in the sludge. The melting point of pickling sludge is about 1350℃ and the viscosity is about 0.14 Pa.s at 1450 ℃, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF4 and A1F3 generated through the reactions of CaF2 with SiO2 and Al2O3. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.展开更多
A large amount of coal gangue from coal mining and processing is regarded as waste and usually stockpiled directly. In order to recycle the valuable elements from the coal gangue, an integrated process is proposed. Th...A large amount of coal gangue from coal mining and processing is regarded as waste and usually stockpiled directly. In order to recycle the valuable elements from the coal gangue, an integrated process is proposed. The process consists of three steps: 1concentrating alumina from the coal gangue via activation roasting followed by alkali leaching of Si O2 which produces alumina concentrate for alumina extraction by the Bayer process; 2) synthesizing tobermorite whiskers from the filtrated alkali liquo containing silicate via a hydrothermal method and reusing excess caustic liquor; and 3) enriching titanium component from the Baye process residue by sulfuric acid leaching. Alumina concentrate with 69.5% Al_2O_3 and mass ratio of alumina to silica(A/S) of 5.9pure 1.1 nm tobermorite whisker and TiO_2-rich material containing 33% TiO_2 are produced, respectively, with the optimal parameters Besides, the actual alumina digestion ratio of alumina concentrate reaches 80.4% at 270 oC for 40 min in the Bayer process.展开更多
Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption...Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption of production. However, the cost of the feedstock for additive manufacturing and the additive manufactured parts is usually very high, which hinders the further application of additive manufacturing, especially for the metal additive manufacturing. The concept of circular metal additive manufacturing involves the recycling of the metal feedstock and the additive manufactured parts leading to the truly zero waste production and the most energy saving. This paper reviews the technologies that help the formation of a circular metal additive manufacturing through recycling of the feedstocks and the damaged metal parts. Reactive metals, such as titanium, tend to be contaminated easily during handling and production. Recycling of the titanium for achieving a circular titanium additive manufacturing is reviewed in detail.展开更多
In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was...In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was investigated,and a series of analytical technologies were used to reveal process mechanism.The results indicate that LiMn_(2)O_(4) can be effectively separated from graphite via flotation after the roasting.The flotation grade of LiMn_(2)O_(4) was significantly increased from 63.10%to 91.36%after roasting at 550℃for 2 h.The TG-DTG analysis demonstrates that the difficulty in flotation separation of LiMn_(2)O_(4) from graphite is caused by the organic binder and electrolytes coating on their surfaces.The XRD,SEM,XPS,and contact angle analyses confirm that the organic films on the surfaces of those materials can be effectively removed by roasting,after which the wettability of LiMn_(2)O_(4) is regained and thus the surface wettability difference between the cathode and anode materials is increased significantly.The closed-circuit flotation test indicates that a LiMn_(2)O_(4) sample with high grade of 99.81%is obtained,while the recovery of LiMn_(2)O_(4) is as high as 99.40%.This study provides an economical and eco-friendly way to recycling waste LIBs.展开更多
The crushing performance of printed circuit board (PCB) was studied on several crushers. The results show that PCB is a material which is difficult to crush. The crushing performance of PCB with disk crusher, especial...The crushing performance of printed circuit board (PCB) was studied on several crushers. The results show that PCB is a material which is difficult to crush. The crushing performance of PCB with disk crusher, especially vibration grinding, which has cut or impact action, excels that of jaw crusher or roller crusher. The PCB scrap is worthwhile to recycle using variety of modern characterization methods. When compared with natural resources, this material stream remains a rich precious metal and nonferrous metals. In PCB scrap, metals account for 47% of the total material composition, in which there exists 19.66% copper, 11.47% iron, 3.93% lead, 300 g/t gold and 510 kg/t silver, etc. In addition, the PCB scrap contains 27% of plastics and 26% of refractory oxides.展开更多
Asphalt mixture pavement reheating is one of the important steps in hot in-place recycling(HIR).To improve the heating speed of asphalt pavement in HIR,based on the numerical analysis model of asphalt mixture heating ...Asphalt mixture pavement reheating is one of the important steps in hot in-place recycling(HIR).To improve the heating speed of asphalt pavement in HIR,based on the numerical analysis model of asphalt mixture heating process,a new multi-layer low-temperature heating method(MLHM)was proposed.Considering input heat flux,the thermal capacity and thermal resistance of asphalt mixture,the heat transfer model was established based on energy conservation law.By heating the asphalt mixture in layers,it changes the situation that the heat energy can only be input from the upper surface of the asphalt mixture pavement.Through the simulation of the heating method of asphalt mixture in the existing technology,the result shows that the existing heating methods lead to serious aging or charring of the asphalt mixture.By MLHM,the upper and the bottom of the asphalt mixture are heated at the same time,and the heating temperature is lower than other heat methods,which not only reduces the heating thickness and increases the heating area of the asphalt mixture pavement,but also improves the heating speed,saves the energy resource and ensures the heating quality.Especially,by MLHM,the heating uniformity is better and speed is faster.展开更多
In this study,we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers.The objectives of the study were to investigate the effect of ...In this study,we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers.The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers.The reinforced plastics were recycled;the recycling efficiency was determined and the recovered fibers were sized using 1 wt%and 3 wt%concentration of(3-aminopropyl)triethoxysilane.We characterized the morphologies utilizing the electron spectroscopy for chemical analysis(ESCA),atomic force microscopy(AFM),FTIR-attenuated total reflection(ATR)spectroscopy and scanning electron microscopy(SEM).Although the surface of the fibers had no cracks,there was evidence of contaminations which affected the interfacial properties and the quality of the fibers.Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration.The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.展开更多
Thermodynamic calculation on the smelting slag of direct recycling of electric arc furnace stainless steelmaking dust was presented. An induction furnace was used to simulate electric arc furnace smelting to recover t...Thermodynamic calculation on the smelting slag of direct recycling of electric arc furnace stainless steelmaking dust was presented. An induction furnace was used to simulate electric arc furnace smelting to recover the metals from the dust. The elements of iron, chromium and nickel in the ingot and the components of metal oxides in the slag were analyzed. The thermodynamic model for FeO Cr 2O 3 MgO SiO 2 slag was set up and the active concentrations of substances in the slag at 1 550 ℃ were determined by thermodynamic calculation according to the experimental data. The results show that the apparent equilibrium constant and quantitative distribution of chromium between slag and steel are unstable and affected by the mass ratios of pellets to start iron and metal reducing agent to the pellets. In order to get satisfactory chromium recovery from the direct recycling of electric arc furnace stainless steelmaking dust, it is important to ensure the mass ratio of pellets to the steel below 0.20 and the mass ratio of metal reducing agent to pellets over 0.18 in practical smelting runs.展开更多
Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufac...Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufacturing method named ＂W3T4＂ was proposed to improve the performances of interracial transition zone （ITZ） between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate （RA） replacement and 10% PHS ＋ 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope （SEM）. The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.展开更多
Physical and chemical properties of electric arc furnace （EAF） dust from Tianjin seamless Pipe Company were measured and analyzed. The zinc leaching tests in alkaline medium were carried out under variation of leach...Physical and chemical properties of electric arc furnace （EAF） dust from Tianjin seamless Pipe Company were measured and analyzed. The zinc leaching tests in alkaline medium were carried out under variation of leaching agent concentration, leaching temperature, leaching cumulative time and solid-to-liquid ratio. The thermodynamics and kinetics of the zinc leaching process were also analyzed. The results show that the EAF dust contains 10% （mass fraction） zinc and the median particle size is 0.69 μm. The zinc recovery of 73.4% is obtained tinder the condition of 90 ℃, 6 mol/L NaOH, and 60 min leaching time. With the increase of concentration of NaOH and the cumulative time, zinc leaching will be significantly increased. The kinetics study demonstrates that the leaching reaction is chemically controlled and the reaction activation energy is 15.73 kJ/mol.展开更多
A close-looped process based on the membrane separation and electrolysis is proposed to regenerate the copper etchant in-situ, recover copper on-site and reuse it. It is characterized by selective separation of copper...A close-looped process based on the membrane separation and electrolysis is proposed to regenerate the copper etchant in-situ, recover copper on-site and reuse it. It is characterized by selective separation of copper from the spent etchant, which is accomplished by the ion exchange membrane-electrowinning, and at the same time the other components useful for etching are reclaimed. The experiments show that at least 90 % of electricity efficiency for copper removal can be maintained and the optimum condition for membrane-electrowinning is: cell voltage 2 -2.5 V, operating temperature 40 - 50 ℃ and current density 500 - 1 500 A/m2. The regenerated etchant can be suc cessfully reused to etch copper after adjusting its composition to the normal range, and its recycling property is as good as that of the fresh etchant after 50 times of use-disposal-regeneration cycles.展开更多
文摘Now, a rapidly growing concern for the environmental protection and resource utilization has stimulated many new activities in the in dustrialized world for coping with urgent environmental problems created by the steadily increasing consumption of industrial products. Increasingly stringent r egulations and widely expressed public concern for the environment highlight the importance of disposing solid waste generated from industrial and consumable pr oducts. How to efficiently recycle and tackle this problem has been a very impo rtant issue over the world. Designing products for recyclability is driven by environmental and economic goals. To obtain good recyclability, two measures can be adopted. One is better recycling strategy and technology; the other is design for recycling (DFR). The recycling strategies of products generally inclu de: reuse, service, remanufacturing, recycling of production scraps during the p roduct usage, recycle (separation first) and disposal. Recyclability assessment is a very important content in DFR. This paper first discusses the content of D FR and strategies and types related to products recyclability, and points out th at easy or difficult recyclability depends on the design phase. Then method and procedure of recyclability assessment based on ANN is explored in detail. The pr ocess consists of selection of the ANN input and output parameters, control of t he sample quality and construction and training of the neural network. At la st, the case study shows this method is simple and operative.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Projects(52274143,51874284)supported by the National Natural Science Foundation of China。
文摘The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.
基金Generalitat Valenciana(GVA)and Spanish Ministry of Science and Innovation(Grant Nos.TED2021-130879 B-C21,CIACIF/2021/286,PID2023-151110OB-I00,and CIPROM/2022/3)to provide funds for conducting experiments and software licensessupported by the National Research Foundation,Prime Minister's Office,Singapore under its Campus for Research Excellence and Technological Enterprise(CREATE)programme。
文摘Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.
基金Project(52174384)supported by the National Natural Science Foundation of ChinaProject(LZB2021003)supported by Fundamental Research Funds for the Central Universities,China。
文摘Massive amounts of low-grade tin middlings have been produced from tin tailings,in which arsenic and tin are worthy to be recycled.Owing to high sulfur content in these tin middlings,a novel self-sulfurization roasting was proposed to transform,separate and recover arsenic and tin in this research.There was no extra curing agent to be added,which decreased the formation of pollutant S-containing gas.The self-sulfurization process involved a two-stage roasting of reduction followed by sulfurization.First in reduction roasting,FeAsS decomposed to FeS and As and the As then transformed to As_(4)(g)and As_(4)S_(4)(g),via which the arsenic was separated and recovered.The arsenic content in the first residue could be decreased to 0.72 wt.%.Accompanied with it,the FeS was firstly oxidized to Fe_(1−x)S and then to SO_(2)(g)by the coexisted Fe_(2)O_(3),and finally reduced and combined with the independent Fe_(2)O_(3)to form Fe_(1−x)S.In the followed sulfurization roasting,the Fe_(1−x)S sulfurized SnO_(2)to SnS(g),due to which tin could be recovered and its content in the second residue decreased to 0.01 wt.%.This study provided an efficient method to separate and recover arsenic and tin from low-grade tin middlings.
基金Project(52274343)supported by the National Natural Science Foundation of ChinaProjects(2023YFC3903900,2023YFC3903904)supported by the National Key R&D Program of China。
文摘The utilization of arsenic-containing gold dressing tailings is an urgent issue faced by gold production companies worldwide.The thermodynamic analysis results indicate that ferrous arsenate(FeAsO_(4)),pyrite(FeS_(2))and sodium cyanide(NaCN)in the arsenic-containing gold metallurgical tailings can be effectively removed using straight grate process,and the removal of pyrite and sodium cyanide is basically completed during the preheating stage,while the removal of ferrous arsenate requires the roasting stage.The pellets undergo a transformation from magnetite to hematite during the preheating process,and are solidified through micro-crystalline bonding and high-temperature recrystallization of hematite(Fe_(2)O_(3))during the roasting process.Ultimately,pellets with removal rates of 80.77% for arsenic,88.78% for sulfur,and 99.88% for cyanide are obtained,as well as the iron content is 61.1% and the compressive strength is 3071 N,meeting the requirements for blast furnace burden.This study provides an industrially feasible method for treating arsenic-containing gold smelting tailings,benefiting gold production enterprises.
基金Project(2010JM7010)supported by the Natural Science Foundation of Shaanxi Province,ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,ChinaProject supported by the Technology Foundation for Selected Overseas Chinese Scholars,Department of Human Resources and Social Security of Shaanxi Province,China
文摘Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF2, CaSO4, Me（OH）, （M： Fe, Cr, Ni）, and the content of CaF2 is high in the sludge. The melting point of pickling sludge is about 1350℃ and the viscosity is about 0.14 Pa.s at 1450 ℃, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF4 and A1F3 generated through the reactions of CaF2 with SiO2 and Al2O3. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.
基金Projects(51234008,51174230)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0515)supported by the Program for New Century Excellent Talents in University,ChinaProject supported by Co-Innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources,China
文摘A large amount of coal gangue from coal mining and processing is regarded as waste and usually stockpiled directly. In order to recycle the valuable elements from the coal gangue, an integrated process is proposed. The process consists of three steps: 1concentrating alumina from the coal gangue via activation roasting followed by alkali leaching of Si O2 which produces alumina concentrate for alumina extraction by the Bayer process; 2) synthesizing tobermorite whiskers from the filtrated alkali liquo containing silicate via a hydrothermal method and reusing excess caustic liquor; and 3) enriching titanium component from the Baye process residue by sulfuric acid leaching. Alumina concentrate with 69.5% Al_2O_3 and mass ratio of alumina to silica(A/S) of 5.9pure 1.1 nm tobermorite whisker and TiO_2-rich material containing 33% TiO_2 are produced, respectively, with the optimal parameters Besides, the actual alumina digestion ratio of alumina concentrate reaches 80.4% at 270 oC for 40 min in the Bayer process.
基金Project(51922108)supported by the National Natural Science Foundation of ChinaProject(2019JJ20031)supported by Hunan Natural Science Foundation,ChinaProject(2019SK2061)supported by Hunan Key Research and Development Program,China。
文摘Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption of production. However, the cost of the feedstock for additive manufacturing and the additive manufactured parts is usually very high, which hinders the further application of additive manufacturing, especially for the metal additive manufacturing. The concept of circular metal additive manufacturing involves the recycling of the metal feedstock and the additive manufactured parts leading to the truly zero waste production and the most energy saving. This paper reviews the technologies that help the formation of a circular metal additive manufacturing through recycling of the feedstocks and the damaged metal parts. Reactive metals, such as titanium, tend to be contaminated easily during handling and production. Recycling of the titanium for achieving a circular titanium additive manufacturing is reviewed in detail.
基金Project(2021JJ20062) supported by the Natural Science Foundation of Hunan Province,ChinaProject(2019XK2304) supported by Landmark Innovation Demonstration Project of Hunan Province,China+3 种基金Project(2022GK4058) supported by High-tech Industry Science and Technology Innovation Leading Project of Hunan Province,ChinaProject(2020CX038) supported by the Innovation Driven Project of Central South University,ChinaProject(2019YFC1907301) supported by the National Key R&D Program of ChinaProject(202006375018) supported by the China Scholarship Council。
文摘In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was investigated,and a series of analytical technologies were used to reveal process mechanism.The results indicate that LiMn_(2)O_(4) can be effectively separated from graphite via flotation after the roasting.The flotation grade of LiMn_(2)O_(4) was significantly increased from 63.10%to 91.36%after roasting at 550℃for 2 h.The TG-DTG analysis demonstrates that the difficulty in flotation separation of LiMn_(2)O_(4) from graphite is caused by the organic binder and electrolytes coating on their surfaces.The XRD,SEM,XPS,and contact angle analyses confirm that the organic films on the surfaces of those materials can be effectively removed by roasting,after which the wettability of LiMn_(2)O_(4) is regained and thus the surface wettability difference between the cathode and anode materials is increased significantly.The closed-circuit flotation test indicates that a LiMn_(2)O_(4) sample with high grade of 99.81%is obtained,while the recovery of LiMn_(2)O_(4) is as high as 99.40%.This study provides an economical and eco-friendly way to recycling waste LIBs.
文摘The crushing performance of printed circuit board (PCB) was studied on several crushers. The results show that PCB is a material which is difficult to crush. The crushing performance of PCB with disk crusher, especially vibration grinding, which has cut or impact action, excels that of jaw crusher or roller crusher. The PCB scrap is worthwhile to recycle using variety of modern characterization methods. When compared with natural resources, this material stream remains a rich precious metal and nonferrous metals. In PCB scrap, metals account for 47% of the total material composition, in which there exists 19.66% copper, 11.47% iron, 3.93% lead, 300 g/t gold and 510 kg/t silver, etc. In addition, the PCB scrap contains 27% of plastics and 26% of refractory oxides.
基金Project(2017JM5077)supported by the Natural Science Basic Research Plan in Shaanxi Province,ChinaProjects(300102259109,300102259306)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Asphalt mixture pavement reheating is one of the important steps in hot in-place recycling(HIR).To improve the heating speed of asphalt pavement in HIR,based on the numerical analysis model of asphalt mixture heating process,a new multi-layer low-temperature heating method(MLHM)was proposed.Considering input heat flux,the thermal capacity and thermal resistance of asphalt mixture,the heat transfer model was established based on energy conservation law.By heating the asphalt mixture in layers,it changes the situation that the heat energy can only be input from the upper surface of the asphalt mixture pavement.Through the simulation of the heating method of asphalt mixture in the existing technology,the result shows that the existing heating methods lead to serious aging or charring of the asphalt mixture.By MLHM,the upper and the bottom of the asphalt mixture are heated at the same time,and the heating temperature is lower than other heat methods,which not only reduces the heating thickness and increases the heating area of the asphalt mixture pavement,but also improves the heating speed,saves the energy resource and ensures the heating quality.Especially,by MLHM,the heating uniformity is better and speed is faster.
基金Project(S2598445)supported by the Project for Cooperative R&D between Industry,Academy and Research Institute Funded by the Korea Ministry of SME and Startups in 2018
文摘In this study,we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers.The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers.The reinforced plastics were recycled;the recycling efficiency was determined and the recovered fibers were sized using 1 wt%and 3 wt%concentration of(3-aminopropyl)triethoxysilane.We characterized the morphologies utilizing the electron spectroscopy for chemical analysis(ESCA),atomic force microscopy(AFM),FTIR-attenuated total reflection(ATR)spectroscopy and scanning electron microscopy(SEM).Although the surface of the fibers had no cracks,there was evidence of contaminations which affected the interfacial properties and the quality of the fibers.Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration.The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.
文摘Thermodynamic calculation on the smelting slag of direct recycling of electric arc furnace stainless steelmaking dust was presented. An induction furnace was used to simulate electric arc furnace smelting to recover the metals from the dust. The elements of iron, chromium and nickel in the ingot and the components of metal oxides in the slag were analyzed. The thermodynamic model for FeO Cr 2O 3 MgO SiO 2 slag was set up and the active concentrations of substances in the slag at 1 550 ℃ were determined by thermodynamic calculation according to the experimental data. The results show that the apparent equilibrium constant and quantitative distribution of chromium between slag and steel are unstable and affected by the mass ratios of pellets to start iron and metal reducing agent to the pellets. In order to get satisfactory chromium recovery from the direct recycling of electric arc furnace stainless steelmaking dust, it is important to ensure the mass ratio of pellets to the steel below 0.20 and the mass ratio of metal reducing agent to pellets over 0.18 in practical smelting runs.
基金Project(51178417)supported by the National Natural Science Foundation of ChinaProject(2012R10025)supported by the Qianjiang Talent Plan of Zhejiang Province,China+2 种基金Project(2012HY006B)supported by the Marine Cross-Guide Research Funds of Zhejiang University,ChinaProject(2013FZA4015)supported by the Fundamental Research Funds for the Central Universities,ChinaProject supported by the Department of Construction of Zhejiang Province,China
文摘Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufacturing method named ＂W3T4＂ was proposed to improve the performances of interracial transition zone （ITZ） between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate （RA） replacement and 10% PHS ＋ 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope （SEM）. The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.
基金Project(20876014) supported by the National Natural Science Foundation of China
文摘Physical and chemical properties of electric arc furnace （EAF） dust from Tianjin seamless Pipe Company were measured and analyzed. The zinc leaching tests in alkaline medium were carried out under variation of leaching agent concentration, leaching temperature, leaching cumulative time and solid-to-liquid ratio. The thermodynamics and kinetics of the zinc leaching process were also analyzed. The results show that the EAF dust contains 10% （mass fraction） zinc and the median particle size is 0.69 μm. The zinc recovery of 73.4% is obtained tinder the condition of 90 ℃, 6 mol/L NaOH, and 60 min leaching time. With the increase of concentration of NaOH and the cumulative time, zinc leaching will be significantly increased. The kinetics study demonstrates that the leaching reaction is chemically controlled and the reaction activation energy is 15.73 kJ/mol.
文摘A close-looped process based on the membrane separation and electrolysis is proposed to regenerate the copper etchant in-situ, recover copper on-site and reuse it. It is characterized by selective separation of copper from the spent etchant, which is accomplished by the ion exchange membrane-electrowinning, and at the same time the other components useful for etching are reclaimed. The experiments show that at least 90 % of electricity efficiency for copper removal can be maintained and the optimum condition for membrane-electrowinning is: cell voltage 2 -2.5 V, operating temperature 40 - 50 ℃ and current density 500 - 1 500 A/m2. The regenerated etchant can be suc cessfully reused to etch copper after adjusting its composition to the normal range, and its recycling property is as good as that of the fresh etchant after 50 times of use-disposal-regeneration cycles.
