Up to 1.5wt%of Cr(Ⅲ)salts(CrCl_(3),and Cr_(2)O_(3))and Cr(Ⅵ)salts(Na_(2)CrO_(4),and CaCr_(2)O_(7))were incorporated into red mud-based geopolymers,respectively.The solidification/stabilization,compressive strength,a...Up to 1.5wt%of Cr(Ⅲ)salts(CrCl_(3),and Cr_(2)O_(3))and Cr(Ⅵ)salts(Na_(2)CrO_(4),and CaCr_(2)O_(7))were incorporated into red mud-based geopolymers,respectively.The solidification/stabilization,compressive strength,and durability of the Cr-containing geopolymers were investigated.The experimental results indicate that the red mud-based geopolymer could effectively solidify/stabilize different types of Cr salts with solidification/stabilization rates of above 99.61%.Geopolymers are environmentally safe when the dosage of CaCr_(2)O_(7)is≤1.0wt%,or the dosage of CrCl_(3),Cr_(2)O_(3),and Na_(2)CrO_(4)is≤1.5wt%,respectively.The effects of Cr salts on the compressive strength varies with the type and content of Cr salts.The freeze-thaw cycle is more destructive to geopolymer properties than sulfate attack or acid rain erosion.The solidification/stabilization of Cr is mainly attributed to the following reasons:a)The chemical binding of Cr is related to the formation of Cr-containing hydrates(eg,magnesiochromite((Mg,Fe)(Cr,Al)_(2)O_(4)))and doping into N-A-S-H gel and C-A-S-H gel framework;b)The physical effect is related to the encapsulation by the hydration products(e g,N-A-S-H gel and C-A-S-H gel).This study provides a reference for the treatment of hazardous Cr-containing wastes by solid waste-based geopolymers.展开更多
The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWI fly ash with rich aluminum components, which was added as ba...The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWI fly ash with rich aluminum components, which was added as bauxite cement or metakaolinite instead, to form Friedel and Ettringite phases with high fixing capacities for heavy metals. The physical properties, heavy metals-fixing capacity, mineral phases and its vibration bands in the novel matrices were characterized by compressive strength, TCLP(toxic characteristic leaching procedure), XRD (x-ray diffraction) , DTG (derivative thermogravimetry), and FTIR (fourier transform infrared spectroscopy), respectively. The Tessier's five-step sequential extraction procedure was used to analyze the fractions of chemical speciation for Pb, Cd and Zn ions. The experimental results indicate that Friedel-Ettringite based novel solidification/stabilization matrices can incorporate Pb, Cd and Zn ions effectively by physical encapsulation and chemical fixation, and it exhibits a great potential in co-landfill treatment of MSWI fly ash with some heavy metals-bearing hazardous wastes.展开更多
One of the challenges faced by sewage sludge treatment and disposal is its higher water content,and how to efficient dewater those hazardous materials properly is welcome in practice. This study stabilized the sewage ...One of the challenges faced by sewage sludge treatment and disposal is its higher water content,and how to efficient dewater those hazardous materials properly is welcome in practice. This study stabilized the sewage sludge via the using of conventional curing agents and calcined aluminum salts,and the corresponding dewatering mechanisms and structural changes of the stabilized sludge were further comparable analyzed.Experimental results showed that wollastonite and kaolin exhibit a relative higher dewatering efficiency as compared to other conventional curing agents; however the releasing rate of heavy metals of Cu,Cr,Ni for kaolin solidification and Zn,Pb for wollastonite solidification is higher than the sludge samples solidified by other curing agents. For comparison,the sludge samples solidified by calcined aluminum salts (AS),calcium ash,Mg-based curing agent,tricalcium aluminate( C_3A) show a lower heavy metals leaching potential and unconfined compressive strength. In addition,the economic characteristics and local availability of AS,calcium ash,C_3A and CaO makes it have a broad prospect in extension and application. These findings are of great significance for stabilization and dewatering of sewage sludge.展开更多
This work experimentally examined the optimal proportioning of sludge curing agent for dewatered sludge curing on solidified sludge,two components sludge curing agent consisted of cement and slag,and three components ...This work experimentally examined the optimal proportioning of sludge curing agent for dewatered sludge curing on solidified sludge,two components sludge curing agent consisted of cement and slag,and three components consisted of cement,slag and inorganic salt. The results showed that,increasing of curing ages could increase unconfined compressive strength and reduce moisture content for solidified sludge. For the test of two components,the biggest unconfined compressive strength of the solidified sludge achieved to 543. 72 kPa and the minimum moisture content achieved to 3. 56% of 21 d. The optimum proportion of the sludge curing agent of two components is sludge: cement: slag = 1 ∶ 0. 05 ∶ 0. 2 which selected by Design-expert. It could rapidly increasing the unconfined compressive strength of solidified sludge when added three components sludge curing agent( sludge: cement: slag: MgSO4= 1 ∶ 0. 05 ∶ 0. 2 ∶ 0. 03) on sludge curing. The results showed that,curing ages of 7 d,the unconfined compressive strength could achieve to 126. 74 kPa,which was more than 11 times comparison with the solidified sludge curing by two components curing agent. Two or three components sludge curing agent all could stabilize the heavy metals on solidified sludge and the leaching of heavy metals was below the government standard,while the stability of the heavy metals was superior for three components sludge curing agent.展开更多
The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related ...The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related literature,this paper discussed the present situation about the treatment of the solid waste using stabilization/solidification technology;meanwhile we have a variety of outlooks on the future of the stabilization/solidification technology.展开更多
The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related ...The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related literature,this paper discussed the present situation about the treatment of the solid waste using stabilization/solidification technology;meanwhile we have a variety of outlooks on the future of the stabilization/solidification technology.展开更多
Quasi-solid-state lithium metal battery is a promising candidate for next generation high energy density and high safety power supply.Despite intensive efforts on electrolytes,uncontrolled interfacial reactions on lit...Quasi-solid-state lithium metal battery is a promising candidate for next generation high energy density and high safety power supply.Despite intensive efforts on electrolytes,uncontrolled interfacial reactions on lithium with electrolyte and patchy interfacial contacts still hinder its practical process.Herein,we bring in rationally designed F contained groups into polymer skeleton via in-situ gelation for the first time to establish quasi-solid-state battery.This method achieves a capacity retention of 90%after 1000 cycles at 0.5C with LiFePO_(4)cathodes.The interface constructed by polymer skeleton and reaction with–CF_(3)lead to the predicted solid electrolyte interface species with high stability.Furthermore,we optimize molecular reactivity and interface stability with regulating F contained end groups in the polymer.Comparisons on different structures reveal that high performance solid stable lithium metal batteries rely on chemical modification as well as stable polymer skeleton,which is more critical to construct robust and steady SEI with uniform lithium deposition.New approach with functional groups regulation proposes a more stable cycling process with a capacity retention of 94.2%at 0.5C and 87.6%at 1C after 1000 cycles with LiFePO_(4) cathodes,providing new insights for the practical development of quasi-solid-state lithium metal battery.展开更多
Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDAX) were used to study the microstructure,microsegregation, and fluid flow tendency of the superalloy Waspaloy in the mushy zone,which had b...Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDAX) were used to study the microstructure,microsegregation, and fluid flow tendency of the superalloy Waspaloy in the mushy zone,which had been solidified at different cooling rates. The investigation was accompanied with the calculation of Rayleigh numbers.It is found that Ti is the main segregating element and the content of Ti is the highest in the final liquid at the cooling rates of 3-6℃/min.The eta phase(η) precipitate presented in the residual liquid at the cooling rates higher than 6℃/min is responsible for the fluctuations in the curves of Ti content.The dendrite arm spacing is found to markedly decrease with the increase of cooling rate.The maximum relative Rayleigh number occurs at 10-20℃below the liquidus temperature at a cooling rate of 1℃/min,where the mushy zone is most unstable and fluid flow is most prone to occur.展开更多
Phase field investigation reveals that the stability of the planar interface is related to the anisotropic intensity of surface tension and the misorientation of preferred crystallographic orientation with respect to ...Phase field investigation reveals that the stability of the planar interface is related to the anisotropic intensity of surface tension and the misorientation of preferred crystallographic orientation with respect to the heat flow direction. The large anisotropic intensity may compete to determine the stability of the planar interface. The destabilizing effect or the stabilizing effect depends on the misorientation. Moreover, the interface morphology of initial instability is also affected by the surface tension anisotropy.展开更多
Based on theoretical analyses, the effect of electric current density on stability of solidification interface morphology of QAl 4 alloy was studied experimentally. The results show that the experimental results agree...Based on theoretical analyses, the effect of electric current density on stability of solidification interface morphology of QAl 4 alloy was studied experimentally. The results show that the experimental results agree well with the theoretical analyses, and the following conclusions can be drawn: the increase of electric current density improves the stability of the solidification interface morphology under the condition of no convection of the liquid metal. Otherwise this convection will slow down the trend of solidification interface developing to stability caused by increasing electric current density.展开更多
In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si) was made by using of micro-focus X-ray imaging.In both alloys,small spherical pores initially form in th...In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si) was made by using of micro-focus X-ray imaging.In both alloys,small spherical pores initially form in the melt far away from the eutectic solid-liquid (S/L) interface and then grow and coagulate during solidification.Some pores can float and escape from the solidifying melt front at a relatively high velocity.At the end of solidification,the remaining pores maintain spherical morphology in the near eutectic alloy but become irregular in the hypoeutectic alloy.This is attributed to different solidification modes and aluminum dendrite interactions between the two alloys.The mechanism of the porosity formation is briefly discussed in this paper.展开更多
This paper reports on laser surface remelting experiments performed on a Zn-2wt.%Cu hypoperitectic alloy by employing a 5kW CW CO2 laser at scanning velocities between 6 and 1207mm/s. The growth velocities of the mi- ...This paper reports on laser surface remelting experiments performed on a Zn-2wt.%Cu hypoperitectic alloy by employing a 5kW CW CO2 laser at scanning velocities between 6 and 1207mm/s. The growth velocities of the mi- crostructures in the laser molten pool were accurately measured. The planar interface structure caused by the high velocity absolute stability was achieved at a growth velocity of 210 mm/s. An implicit expression of the critical solidification velocity for the cellular-planar transition was carried out by nonlinear stability analyses of the planar interface. The results showed a better agreement with the measured critical velocity than that predicted by M-S theory. Cell-free structures were observed throughout the whole molten pool at a scanning velocity of 652 mm/s and the calculated minimum temperature gradient in this molten pool was very close to the critical temperature gradient for high gradient absolute stability (HGAS) of the η phase. This indicates that HGAS was successfully achieved in the present experiments.展开更多
Tin mine tailings(TMT)and fuming slag(FS)contain many heavy metals(As,Cr,Cu,Zn and Mn)that cause severe pollution to the environment.Herein,geopolymers were prepared using TMT,FS and flue gas desulfurization gypsum(FG...Tin mine tailings(TMT)and fuming slag(FS)contain many heavy metals(As,Cr,Cu,Zn and Mn)that cause severe pollution to the environment.Herein,geopolymers were prepared using TMT,FS and flue gas desulfurization gypsum(FGDG)to immobilize heavy metals,and their compressive strength and heavy metal leaching toxicity were investigated.It was first determined that T4F5(TMT:FS=4:5)sample exhibited the highest compressive strength(7.83 MPa).T4F5 achieved 95%immobilization efficiency for As and Cr,and nearly 100%for Cu,Zn and Mn,showing good immobilization performance.A series of characterization analyses showed that heavy metal cations can balance the charge in the geopolymer and replace Al in the geopolymer structure to form covalent bonds.In addition,about 2%–20%of heavy metal Fe was immobilized in hydration products,heavy metal hydroxides and non-bridging Si–O and Al–O coordination with silica-aluminate matrices.AsO_(3)^(3−) was oxidized into AsO_(4)^(3−),which may form Ca–As or Fe–As precipitates.Cr_(2)O_(7)^(2−)was converted to CrO_(4)^(2−)under alkaline environment and then combined with OH−to form Cr(OH)3 precipitates.Mn^(2+)may react directly with dissolved silicate to form Mn_(2)SiO_(4) and also form Mn(OH)_(2) precipitates.The unstable Mn(OH)_(2) can be further oxidized to MnO_(2).The heavy metal cations were immobilized in the silicoaluminate lattice,while the anions tended to form insoluble precipitates.These results may benefit the industry and government for better handling of TMT,FS and solid wastes containing the abovementioned five heavy metals.展开更多
Tip splitting instability of cellular interface morphology in directional solidification is analyzed based on the bias field method proposed recently by Glicksman. The physical mechanism of tip instability is explaine...Tip splitting instability of cellular interface morphology in directional solidification is analyzed based on the bias field method proposed recently by Glicksman. The physical mechanism of tip instability is explained by analyzing the interface potential, the tangential energy flux, and the normal energy flux. A rigorous criterion for tip-splitting instability is established analytically, i.e., the ratio of the cellular tip radius to the cellular width α 〉3/2/π≈ 0.3899, which is in good agreement with simulation results. This study also reveals that the cellular tip splitting instability is attributable to weak Gibbs–Thomson energy acting on the interface.展开更多
The solidification process of a conventional superalloy, IN718, was investigated by confocal scanning laser microscope (CSLM). The liquid fraction during solidification was obtained as a function of real time and te...The solidification process of a conventional superalloy, IN718, was investigated by confocal scanning laser microscope (CSLM). The liquid fraction during solidification was obtained as a function of real time and temperature in reference with the in-situ observation. The characteristics of L→γ transformation were analyzed and the γ growing rate of each stage was also calculated. Scheil equation was employed to predict the segregation behavior, and the predict results are in consistence with the experimental results. As a result, the confocal scanning laser microscope shows a great potential for solidification process research.展开更多
High-energy-density lithium metal batteries are the next-generation battery systems of choice,and replacing the flammable liquid electrolyte with a polymer solid-state electrolyte is a prominent conduct towards realiz...High-energy-density lithium metal batteries are the next-generation battery systems of choice,and replacing the flammable liquid electrolyte with a polymer solid-state electrolyte is a prominent conduct towards realizing the goal of high-safety and high-specific-energy devices.Unfortunately,the inherent intractable problems of poor solid-solid contacts between the electrode/electrolyte and the growth of Li dendrites hinder their practical applications.The in-situ solidification has demonstrated a variety of advantages in the application of polymer electrolytes and artificial interphase,including the design of integrated polymer electrolytes and asymmetric polymer electrolytes to enhance the compatibility of solid–solid contact and compatibility between various electrolytes,and the construction of artificial interphase between the Li anode and cathode to suppress the formation of Li dendrites and to enhance the high-voltage stability of polymer electrolytes.This review firstly elaborates the history of in-situ solidification for solid-state batteries,and then focuses on the synthetic methods of solidified electrolytes.Furthermore,the recent progress of in-situ solidification technology from both the design of polymer electrolytes and the construction of artificial interphase is summarized,and the importance of in-situ solidification technology in enhancing safety is emphasized.Finally,prospects,emerging challenges,and practical applications of in-situ solidification are envisioned.展开更多
The rapidly solidified powder of AlFeCrZrVSi aluminum alloy was prepared using multistage atomization and consolidated by hotextrusion, the evolution of microstructure of the extruded materials during thermal exposure...The rapidly solidified powder of AlFeCrZrVSi aluminum alloy was prepared using multistage atomization and consolidated by hotextrusion, the evolution of microstructure of the extruded materials during thermal exposure was studied with optical microscope, Xray diffraction and transmission electron microscope(TEM). The results show that the majority of dispersions present in the asextruded alloy are metastable Al12(Fe, Cr, V)3Si, which has excellent thermaldynamical stability and coarsening resistance; the coarsening ratecontrolling process of the Al12(Fe, Cr, V)3Si phase is considered to be diffusion of Fe atom along grain boundaries instead of bulk diffusion of Fe atom.展开更多
Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chrom...Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371 5 mg/L, 1 95 mg/L and 1 99 mg/L respectively Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.展开更多
Roadways excavated through a coal seam can exert an adverse effect on roadway stability. To investigate the effects of in-situ stress on roadway stability, numerical models were built and high horizontal stresses at v...Roadways excavated through a coal seam can exert an adverse effect on roadway stability. To investigate the effects of in-situ stress on roadway stability, numerical models were built and high horizontal stresses at varying orientations were applied. The results indicate that stress concentrations, roadway deformation and failure increase in magnitude and extent as the excavation angle with respect to the maximum horizontal stress increases. In addition, the stress adjacent to the coal-rock interface sharply varies in space and evolves with time; coal is much more vulnerable to deformation and failure than rock.The results provide insights into the layout of roadways excavated through a coal seam. Roadways should be designed parallel or at a narrow angle to the maximum horizontal stress. The concentrated stress at the top corner of the face-end should be reduced in advance, and the coal seam should be reinforced immediately after excavation.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.52074245,52374416 and 52202029)the China Postdoctoral Science Foundation(No.2022M721058)。
文摘Up to 1.5wt%of Cr(Ⅲ)salts(CrCl_(3),and Cr_(2)O_(3))and Cr(Ⅵ)salts(Na_(2)CrO_(4),and CaCr_(2)O_(7))were incorporated into red mud-based geopolymers,respectively.The solidification/stabilization,compressive strength,and durability of the Cr-containing geopolymers were investigated.The experimental results indicate that the red mud-based geopolymer could effectively solidify/stabilize different types of Cr salts with solidification/stabilization rates of above 99.61%.Geopolymers are environmentally safe when the dosage of CaCr_(2)O_(7)is≤1.0wt%,or the dosage of CrCl_(3),Cr_(2)O_(3),and Na_(2)CrO_(4)is≤1.5wt%,respectively.The effects of Cr salts on the compressive strength varies with the type and content of Cr salts.The freeze-thaw cycle is more destructive to geopolymer properties than sulfate attack or acid rain erosion.The solidification/stabilization of Cr is mainly attributed to the following reasons:a)The chemical binding of Cr is related to the formation of Cr-containing hydrates(eg,magnesiochromite((Mg,Fe)(Cr,Al)_(2)O_(4)))and doping into N-A-S-H gel and C-A-S-H gel framework;b)The physical effect is related to the encapsulation by the hydration products(e g,N-A-S-H gel and C-A-S-H gel).This study provides a reference for the treatment of hazardous Cr-containing wastes by solid waste-based geopolymers.
基金Funded by the National Natural Science Foundation of China(No.20477024)2003 Shanghai Education Research Fund
文摘The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWI fly ash with rich aluminum components, which was added as bauxite cement or metakaolinite instead, to form Friedel and Ettringite phases with high fixing capacities for heavy metals. The physical properties, heavy metals-fixing capacity, mineral phases and its vibration bands in the novel matrices were characterized by compressive strength, TCLP(toxic characteristic leaching procedure), XRD (x-ray diffraction) , DTG (derivative thermogravimetry), and FTIR (fourier transform infrared spectroscopy), respectively. The Tessier's five-step sequential extraction procedure was used to analyze the fractions of chemical speciation for Pb, Cd and Zn ions. The experimental results indicate that Friedel-Ettringite based novel solidification/stabilization matrices can incorporate Pb, Cd and Zn ions effectively by physical encapsulation and chemical fixation, and it exhibits a great potential in co-landfill treatment of MSWI fly ash with some heavy metals-bearing hazardous wastes.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51408159)the China Postdoctoral Science Foundation of China(Grant No.2013T60375 and 2012M520744)
文摘One of the challenges faced by sewage sludge treatment and disposal is its higher water content,and how to efficient dewater those hazardous materials properly is welcome in practice. This study stabilized the sewage sludge via the using of conventional curing agents and calcined aluminum salts,and the corresponding dewatering mechanisms and structural changes of the stabilized sludge were further comparable analyzed.Experimental results showed that wollastonite and kaolin exhibit a relative higher dewatering efficiency as compared to other conventional curing agents; however the releasing rate of heavy metals of Cu,Cr,Ni for kaolin solidification and Zn,Pb for wollastonite solidification is higher than the sludge samples solidified by other curing agents. For comparison,the sludge samples solidified by calcined aluminum salts (AS),calcium ash,Mg-based curing agent,tricalcium aluminate( C_3A) show a lower heavy metals leaching potential and unconfined compressive strength. In addition,the economic characteristics and local availability of AS,calcium ash,C_3A and CaO makes it have a broad prospect in extension and application. These findings are of great significance for stabilization and dewatering of sewage sludge.
基金Sponsored by the Technology Research Projects of Harbin Science and Technology Bureau(Grant No.2010AA4CS024)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.201192)+1 种基金the National Natural Science Key Foundation of China(Grant No.51206036)the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(Grant No.2013DX04)
文摘This work experimentally examined the optimal proportioning of sludge curing agent for dewatered sludge curing on solidified sludge,two components sludge curing agent consisted of cement and slag,and three components consisted of cement,slag and inorganic salt. The results showed that,increasing of curing ages could increase unconfined compressive strength and reduce moisture content for solidified sludge. For the test of two components,the biggest unconfined compressive strength of the solidified sludge achieved to 543. 72 kPa and the minimum moisture content achieved to 3. 56% of 21 d. The optimum proportion of the sludge curing agent of two components is sludge: cement: slag = 1 ∶ 0. 05 ∶ 0. 2 which selected by Design-expert. It could rapidly increasing the unconfined compressive strength of solidified sludge when added three components sludge curing agent( sludge: cement: slag: MgSO4= 1 ∶ 0. 05 ∶ 0. 2 ∶ 0. 03) on sludge curing. The results showed that,curing ages of 7 d,the unconfined compressive strength could achieve to 126. 74 kPa,which was more than 11 times comparison with the solidified sludge curing by two components curing agent. Two or three components sludge curing agent all could stabilize the heavy metals on solidified sludge and the leaching of heavy metals was below the government standard,while the stability of the heavy metals was superior for three components sludge curing agent.
文摘The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related literature,this paper discussed the present situation about the treatment of the solid waste using stabilization/solidification technology;meanwhile we have a variety of outlooks on the future of the stabilization/solidification technology.
文摘The number of hazardous waste in our country increased dramatically in recent years,stabilization/solidification technology begins to attract a wide spread attention by domestic scholars.Based on the domestic related literature,this paper discussed the present situation about the treatment of the solid waste using stabilization/solidification technology;meanwhile we have a variety of outlooks on the future of the stabilization/solidification technology.
基金support from the National Natural Science Foundation of China(52034011)the Fundamental Research Funds for the Science and Technology Program of Hunan Province(2019RS3002)+1 种基金the Central Universities of Central South University(Grant No.2018zzts133)Science and Technology Innovation Program of Hunan Province(2020RC2006).
文摘Quasi-solid-state lithium metal battery is a promising candidate for next generation high energy density and high safety power supply.Despite intensive efforts on electrolytes,uncontrolled interfacial reactions on lithium with electrolyte and patchy interfacial contacts still hinder its practical process.Herein,we bring in rationally designed F contained groups into polymer skeleton via in-situ gelation for the first time to establish quasi-solid-state battery.This method achieves a capacity retention of 90%after 1000 cycles at 0.5C with LiFePO_(4)cathodes.The interface constructed by polymer skeleton and reaction with–CF_(3)lead to the predicted solid electrolyte interface species with high stability.Furthermore,we optimize molecular reactivity and interface stability with regulating F contained end groups in the polymer.Comparisons on different structures reveal that high performance solid stable lithium metal batteries rely on chemical modification as well as stable polymer skeleton,which is more critical to construct robust and steady SEI with uniform lithium deposition.New approach with functional groups regulation proposes a more stable cycling process with a capacity retention of 94.2%at 0.5C and 87.6%at 1C after 1000 cycles with LiFePO_(4) cathodes,providing new insights for the practical development of quasi-solid-state lithium metal battery.
基金supported by the school fund of Nanjing University of Information Science and Technol ogy
文摘Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDAX) were used to study the microstructure,microsegregation, and fluid flow tendency of the superalloy Waspaloy in the mushy zone,which had been solidified at different cooling rates. The investigation was accompanied with the calculation of Rayleigh numbers.It is found that Ti is the main segregating element and the content of Ti is the highest in the final liquid at the cooling rates of 3-6℃/min.The eta phase(η) precipitate presented in the residual liquid at the cooling rates higher than 6℃/min is responsible for the fluctuations in the curves of Ti content.The dendrite arm spacing is found to markedly decrease with the increase of cooling rate.The maximum relative Rayleigh number occurs at 10-20℃below the liquidus temperature at a cooling rate of 1℃/min,where the mushy zone is most unstable and fluid flow is most prone to occur.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50401013)the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University of China (NWPU) (Grant No. KP200903)
文摘Phase field investigation reveals that the stability of the planar interface is related to the anisotropic intensity of surface tension and the misorientation of preferred crystallographic orientation with respect to the heat flow direction. The large anisotropic intensity may compete to determine the stability of the planar interface. The destabilizing effect or the stabilizing effect depends on the misorientation. Moreover, the interface morphology of initial instability is also affected by the surface tension anisotropy.
文摘Based on theoretical analyses, the effect of electric current density on stability of solidification interface morphology of QAl 4 alloy was studied experimentally. The results show that the experimental results agree well with the theoretical analyses, and the following conclusions can be drawn: the increase of electric current density improves the stability of the solidification interface morphology under the condition of no convection of the liquid metal. Otherwise this convection will slow down the trend of solidification interface developing to stability caused by increasing electric current density.
基金funded by the Natural Science Foundation of China under grant No:50771031GM Research Funding under contract No:GM-RP-07-211
文摘In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si) was made by using of micro-focus X-ray imaging.In both alloys,small spherical pores initially form in the melt far away from the eutectic solid-liquid (S/L) interface and then grow and coagulate during solidification.Some pores can float and escape from the solidifying melt front at a relatively high velocity.At the end of solidification,the remaining pores maintain spherical morphology in the near eutectic alloy but become irregular in the hypoeutectic alloy.This is attributed to different solidification modes and aluminum dendrite interactions between the two alloys.The mechanism of the porosity formation is briefly discussed in this paper.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 50201012 and 50471065).
文摘This paper reports on laser surface remelting experiments performed on a Zn-2wt.%Cu hypoperitectic alloy by employing a 5kW CW CO2 laser at scanning velocities between 6 and 1207mm/s. The growth velocities of the mi- crostructures in the laser molten pool were accurately measured. The planar interface structure caused by the high velocity absolute stability was achieved at a growth velocity of 210 mm/s. An implicit expression of the critical solidification velocity for the cellular-planar transition was carried out by nonlinear stability analyses of the planar interface. The results showed a better agreement with the measured critical velocity than that predicted by M-S theory. Cell-free structures were observed throughout the whole molten pool at a scanning velocity of 652 mm/s and the calculated minimum temperature gradient in this molten pool was very close to the critical temperature gradient for high gradient absolute stability (HGAS) of the η phase. This indicates that HGAS was successfully achieved in the present experiments.
基金financially supported by the National Key R&D Program of China(No.2019YFC1904202)the State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization,Kunming(No.CNMRCUKF20)the Center for Analysis and Testing of Kunming University of Science and Technology(No.2020P20171130007).
文摘Tin mine tailings(TMT)and fuming slag(FS)contain many heavy metals(As,Cr,Cu,Zn and Mn)that cause severe pollution to the environment.Herein,geopolymers were prepared using TMT,FS and flue gas desulfurization gypsum(FGDG)to immobilize heavy metals,and their compressive strength and heavy metal leaching toxicity were investigated.It was first determined that T4F5(TMT:FS=4:5)sample exhibited the highest compressive strength(7.83 MPa).T4F5 achieved 95%immobilization efficiency for As and Cr,and nearly 100%for Cu,Zn and Mn,showing good immobilization performance.A series of characterization analyses showed that heavy metal cations can balance the charge in the geopolymer and replace Al in the geopolymer structure to form covalent bonds.In addition,about 2%–20%of heavy metal Fe was immobilized in hydration products,heavy metal hydroxides and non-bridging Si–O and Al–O coordination with silica-aluminate matrices.AsO_(3)^(3−) was oxidized into AsO_(4)^(3−),which may form Ca–As or Fe–As precipitates.Cr_(2)O_(7)^(2−)was converted to CrO_(4)^(2−)under alkaline environment and then combined with OH−to form Cr(OH)3 precipitates.Mn^(2+)may react directly with dissolved silicate to form Mn_(2)SiO_(4) and also form Mn(OH)_(2) precipitates.The unstable Mn(OH)_(2) can be further oxidized to MnO_(2).The heavy metal cations were immobilized in the silicoaluminate lattice,while the anions tended to form insoluble precipitates.These results may benefit the industry and government for better handling of TMT,FS and solid wastes containing the abovementioned five heavy metals.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB610401)the National Natural Science Foundation of China(Grant No.51371151)the Free Research Fund of State Key Laboratory of Solidification Processing,China(Grant No.100-QP-2014)
文摘Tip splitting instability of cellular interface morphology in directional solidification is analyzed based on the bias field method proposed recently by Glicksman. The physical mechanism of tip instability is explained by analyzing the interface potential, the tangential energy flux, and the normal energy flux. A rigorous criterion for tip-splitting instability is established analytically, i.e., the ratio of the cellular tip radius to the cellular width α 〉3/2/π≈ 0.3899, which is in good agreement with simulation results. This study also reveals that the cellular tip splitting instability is attributable to weak Gibbs–Thomson energy acting on the interface.
基金Project(08dj1400402) supported by the Major Program for the Fundamental Research of Shanghai Committee of Science and Technology, China
文摘The solidification process of a conventional superalloy, IN718, was investigated by confocal scanning laser microscope (CSLM). The liquid fraction during solidification was obtained as a function of real time and temperature in reference with the in-situ observation. The characteristics of L→γ transformation were analyzed and the γ growing rate of each stage was also calculated. Scheil equation was employed to predict the segregation behavior, and the predict results are in consistence with the experimental results. As a result, the confocal scanning laser microscope shows a great potential for solidification process research.
基金supported by Beijing Municipal Natural Science Foundation(Z200011)National Key Research and Development Program of China(2021YFB2500300,2021YFB2400300)+8 种基金National Natural Science Foundation of China(22308190,22109084,22108151,22075029,and 22061132002)Key Research and Development Program of Yunnan Province(202103AA080019)the S&T Program of Hebei Province(22344402D)China Postdoctoral Science Foundation(2022TQ0165)Tsinghua-Jiangyin Innovation Special Fund(TJISF)Tsinghua-Toyota Joint Research Fundthe Institute of Strategic Research,Huawei Technologies Co.,LtdOrdos-Tsinghua Innovative&Collaborative Research Program in Carbon Neutralitythe Shuimu Tsinghua Scholar Program of Tsinghua University。
文摘High-energy-density lithium metal batteries are the next-generation battery systems of choice,and replacing the flammable liquid electrolyte with a polymer solid-state electrolyte is a prominent conduct towards realizing the goal of high-safety and high-specific-energy devices.Unfortunately,the inherent intractable problems of poor solid-solid contacts between the electrode/electrolyte and the growth of Li dendrites hinder their practical applications.The in-situ solidification has demonstrated a variety of advantages in the application of polymer electrolytes and artificial interphase,including the design of integrated polymer electrolytes and asymmetric polymer electrolytes to enhance the compatibility of solid–solid contact and compatibility between various electrolytes,and the construction of artificial interphase between the Li anode and cathode to suppress the formation of Li dendrites and to enhance the high-voltage stability of polymer electrolytes.This review firstly elaborates the history of in-situ solidification for solid-state batteries,and then focuses on the synthetic methods of solidified electrolytes.Furthermore,the recent progress of in-situ solidification technology from both the design of polymer electrolytes and the construction of artificial interphase is summarized,and the importance of in-situ solidification technology in enhancing safety is emphasized.Finally,prospects,emerging challenges,and practical applications of in-situ solidification are envisioned.
文摘The rapidly solidified powder of AlFeCrZrVSi aluminum alloy was prepared using multistage atomization and consolidated by hotextrusion, the evolution of microstructure of the extruded materials during thermal exposure was studied with optical microscope, Xray diffraction and transmission electron microscope(TEM). The results show that the majority of dispersions present in the asextruded alloy are metastable Al12(Fe, Cr, V)3Si, which has excellent thermaldynamical stability and coarsening resistance; the coarsening ratecontrolling process of the Al12(Fe, Cr, V)3Si phase is considered to be diffusion of Fe atom along grain boundaries instead of bulk diffusion of Fe atom.
文摘Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371 5 mg/L, 1 95 mg/L and 1 99 mg/L respectively Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.
基金provided by the Fundamental Research Funds for the Central Universities(No.2014QNA02)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT13098)+3 种基金the National Basic Research Program of China(No.2011CB201205)the National Natural Science Foundation of China(No.51404261)the Natural Science Foundation of Jiangsu Province(No.BK20140196)China PostdoctoralScience Foundation funded project(No.2014M551057)
文摘Roadways excavated through a coal seam can exert an adverse effect on roadway stability. To investigate the effects of in-situ stress on roadway stability, numerical models were built and high horizontal stresses at varying orientations were applied. The results indicate that stress concentrations, roadway deformation and failure increase in magnitude and extent as the excavation angle with respect to the maximum horizontal stress increases. In addition, the stress adjacent to the coal-rock interface sharply varies in space and evolves with time; coal is much more vulnerable to deformation and failure than rock.The results provide insights into the layout of roadways excavated through a coal seam. Roadways should be designed parallel or at a narrow angle to the maximum horizontal stress. The concentrated stress at the top corner of the face-end should be reduced in advance, and the coal seam should be reinforced immediately after excavation.