The phase selection of ternary intermetallic compound τphase (Mg32(Al, Zn)49 ) and φ phase (Al2Mg5Zn2) in high zinc magnesium alloys was studied by using scanning electron microscope, X-ray diffractometer and differ...The phase selection of ternary intermetallic compound τphase (Mg32(Al, Zn)49 ) and φ phase (Al2Mg5Zn2) in high zinc magnesium alloys was studied by using scanning electron microscope, X-ray diffractometer and differential scanning calorimeter, etc. The results indicate that, when adding element Si in Mg-8Zn-4Al-0.3Mn (ZA84) alloy, φ phase is promoted, whereas τ phase is inhibited. The Chinese script-type Mg2Si and matrix microstructure are greatly refined, the formation of τ phase is facilitated and φ phase is restrained when modifier Al-AlP master alloy is added in ZA84 alloy containing Si. The kinetics study of phase selection indicates that there is a critical degree of undercooling of the melt. If the undercooling exceeds the critical value, τ phase preferentially forms while φ phase is restrained; otherwise, φ phase preferentially forms while τ phase is restrained.展开更多
With N,N′-dimethylpiperazine（DMPIP） as the structure-directing agent, a zinc phosphate [Zn6（H2O）P5O20] [C5N2H14] [C6H16N2]0.5·3H2O（1） with a novel three-dimensional（3D） open-framework architecture was hy...With N,N′-dimethylpiperazine（DMPIP） as the structure-directing agent, a zinc phosphate [Zn6（H2O）P5O20] [C5N2H14] [C6H16N2]0.5·3H2O（1） with a novel three-dimensional（3D） open-framework architecture was hydrothermally synthesized. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by ICP, NMR, and TG analyses. Compound 1 crystallized in the triclinic space group P1（No.2） with a=0.9984（2） nm, b=1.2354（3） nm, c=1.2384（3） nm, α=88.32（3）°, β=74.57（3）°, γ=75.81（3）° and Z=2. The alternation arrrangement of tetrahedral Zn units[ZnO4 and ZnO3（H2O）] and PO4 units forms an anionic 3D open framework containing intersecting 16-, 10- and 8-ring channels. Water molecules, diprotonated DMPIP, and diprotonated N-methyl-piperazine（MPIP） decomposed from DMPIP, are located in the channels and interact with the host framework via H-bonds. Compound 1 transforms to another new phase（compound 2） upon calcination at 200―350℃ with the removal of the water coordinated to Zn atoms in the lattice. The phase transformation of compound 2 was further studied.展开更多
The modified Siemens process,which is the major process of producing polycrystalline silicon through current technologies,is a high temperature,slow,semi-batch process and the product is expensive primarily due to the...The modified Siemens process,which is the major process of producing polycrystalline silicon through current technologies,is a high temperature,slow,semi-batch process and the product is expensive primarily due to the large energy consumption.Therefore,the zinc reduction process,which can produce solar-grade silicon in a cost effective manner,should be redeveloped for these conditions.The SiCl2 generation ratio,which stands for the degree of the side reactions,can be decomposed to SiCl4 and ZnCl2 in gas phase zinc atmosphere in the exit where the temperature is very low.Therefore,the lower SiCl2 generation ratio is profitable with lower power consumption.Based on the thermodynamic data for the related pure substances,the relations of the SiCl2 generation ratio and pressure,temperature and the feed molar ratio（n（Zn）/n（SiCl4） are investigated and the graphs thereof are plotted.And the diagrams of Kpθ-T at standard atmosphere pressure have been plotted to account for the influence of temperature on the SiCl2 generation ratio.Furthermore,the diagram of Kpθ-T at different pressures have also been plotted to give an interpretation of the influence of pressure on the SiCl2 generation ratio.The results show that SiCl2 generation ratio increases with increasing temperature,and the higher pressure and excess gas phase zinc can restrict SiCl2 generation ratio.Finally,suitable operational conditions in the practical process of polycrystalline silicon manufacture by gas phase zinc reduction of SiCl4 have been established with 1200 K,0.2 MPa and the feed molar ratio（n（Zn） /n（SiCl4）） of 4 at the entrance.Under these conditions,SiCl2 generation ratio is very low,which indicates that the side reactions can be restricted and the energy consumption is reasonable.展开更多
Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we pr...Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH_4 Cl–NH_3·H_2 O solution. The thermodynamics and phase conversion of Zn_2 Si O_4 to zinc oxide(ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn_2 Si O_4 mole ratio(n(Ca O)/n(Zn_2 Si O_4)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn_2 Si O_4 was first converted to Ca_2 Zn Si_2 O_7 and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn_2 Si O_4 to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.展开更多
Electrochemical impendence spectroscopy （EIS） is applied to investigate the dissolution behavior of Al-Zn alloys in 3% NaCl solution at different polarization potentials. A new reaction model is proposed, and the ac...Electrochemical impendence spectroscopy （EIS） is applied to investigate the dissolution behavior of Al-Zn alloys in 3% NaCl solution at different polarization potentials. A new reaction model is proposed, and the activation mechanism of zinc in Al-Zn alloys is achieved. There are three intermediates in the dissolution process： Znad^＋, Znad^2＋ and Alad^＋, ,of which only Zni can activate Al-Zn alloys. Most Znnd^＋ is produced by β-phase,and the alloys with 2. 3% - 3. 8% （wt） Zn dissolve rapidly. The Al-Zn alloys of heart-shaped EIS are active in 3% NaCl solution, thus EIS characteristic can be used to distinguish the activa-tion of Al-Zn alloys.展开更多
An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting ...An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of（NH_4）_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for（NH_4）_2SO_4 and zinc mixed in a molar ratio of 1.4：1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.展开更多
Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choice of cathode materials with satisfactory ...Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choice of cathode materials with satisfactory cycling performance. Here, we report a porous V2O5 nanofibers cathode with high Znstorage performance in an aqueous Zn(CF3SO3)2 electrolyte. We propose a reaction mechanism based on phase transition from orthorhombic V2O5 to zinc pyrovanadate on first discharging and reversible Zn^2+ (de)intercalation in the open-structured hosts during subsequent cycling. This open and stable architecture enables a high reversible capacity of 319 mAh g^-1 at 20 mAg^-1 and a capacity retention of 81% over 500 cycles. The remarkable electrochemical performance makes V2O5 a promising cathode for aqueous zinc-ion batteries.展开更多
Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction ...Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction （XRD） ,scanning electron microscope （SEM） and glow discharge optical emission spectrometry （GDOES）. It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.展开更多
The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded...The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.展开更多
The paper presents the calculation results on the construction of solidus lines of phase diagrams for some binary metal systems based on cadmium, zinc and tellurium. The investigations have been carried out using the ...The paper presents the calculation results on the construction of solidus lines of phase diagrams for some binary metal systems based on cadmium, zinc and tellurium. The investigations have been carried out using the phase equilibrium thermodynamics and known liquidus lines. By the calculation method the solidus lines of phase diagrams of the Cd-Na, Cd-Tl, Te-Ga, Te-As, Te-Cu and Zn-Sn systems were constructed in the temperature range from the base component melting point to the eutectic transformation temperature. In the Cd-Tl, Te-As, Te-Cu and Zn-Sn systems a retrograde solubility of the second component in the solid phase was observed. The temperature and maximum solubility values at the retrograde behavior of solidus lines, as well as, the limiting solubility values of components at eutectic transformation in the systems based on Cd, Zn and Te were determined.展开更多
Superlattice phase transformation, occurred in the solute enriched region caused by diffusion induced grainboundary migration (DIGM), was found in two kinds of diffusion couples which consist of: (1) low carbon highst...Superlattice phase transformation, occurred in the solute enriched region caused by diffusion induced grainboundary migration (DIGM), was found in two kinds of diffusion couples which consist of: (1) low carbon highstrength steel with hot dipped zinc coating, and (2) commercial pure iron with galvanized zinc coating after isothermally diffusion annealed at different temperatures (500, 560 and 580℃) with various durations. The product of thetransformation is an ordered phase with Li2 superlattice structure which was identified through the analysis by SEM,TEM and AEM. The ordered phase resulted from transformation occurred in the alloyed areas generated by DIGMand DIR The zinc content in this phase is variable, it approaches the stoichiometric composition Fe3Zn as the diffusion time is sufficiently prolonged. The mechanism of the transformation in connection with the process of DIGMand DIR was discussed. DIGM DIR and DIP (diffusion induced phase transformation) are three interrelatedprocessed originated from grain boundary diffusion.展开更多
基金Project(50571092) supported by the National Natural Science Foundation of ChinaProject(0523020500) supported by the Excellent Young Scholars Foundation of Henan Province, China
文摘The phase selection of ternary intermetallic compound τphase (Mg32(Al, Zn)49 ) and φ phase (Al2Mg5Zn2) in high zinc magnesium alloys was studied by using scanning electron microscope, X-ray diffractometer and differential scanning calorimeter, etc. The results indicate that, when adding element Si in Mg-8Zn-4Al-0.3Mn (ZA84) alloy, φ phase is promoted, whereas τ phase is inhibited. The Chinese script-type Mg2Si and matrix microstructure are greatly refined, the formation of τ phase is facilitated and φ phase is restrained when modifier Al-AlP master alloy is added in ZA84 alloy containing Si. The kinetics study of phase selection indicates that there is a critical degree of undercooling of the melt. If the undercooling exceeds the critical value, τ phase preferentially forms while φ phase is restrained; otherwise, φ phase preferentially forms while τ phase is restrained.
基金Supported by the National Natural Science Foundation of China(No.20871051)the Scientific and Technological Planning Project of Jilin Province,China(No.20080504)
文摘With N,N′-dimethylpiperazine（DMPIP） as the structure-directing agent, a zinc phosphate [Zn6（H2O）P5O20] [C5N2H14] [C6H16N2]0.5·3H2O（1） with a novel three-dimensional（3D） open-framework architecture was hydrothermally synthesized. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by ICP, NMR, and TG analyses. Compound 1 crystallized in the triclinic space group P1（No.2） with a=0.9984（2） nm, b=1.2354（3） nm, c=1.2384（3） nm, α=88.32（3）°, β=74.57（3）°, γ=75.81（3）° and Z=2. The alternation arrrangement of tetrahedral Zn units[ZnO4 and ZnO3（H2O）] and PO4 units forms an anionic 3D open framework containing intersecting 16-, 10- and 8-ring channels. Water molecules, diprotonated DMPIP, and diprotonated N-methyl-piperazine（MPIP） decomposed from DMPIP, are located in the channels and interact with the host framework via H-bonds. Compound 1 transforms to another new phase（compound 2） upon calcination at 200―350℃ with the removal of the water coordinated to Zn atoms in the lattice. The phase transformation of compound 2 was further studied.
基金Supported by the Provincial personnel training funds(kksy201352109)the National Natural Science Foundation of China(51374118)
文摘The modified Siemens process,which is the major process of producing polycrystalline silicon through current technologies,is a high temperature,slow,semi-batch process and the product is expensive primarily due to the large energy consumption.Therefore,the zinc reduction process,which can produce solar-grade silicon in a cost effective manner,should be redeveloped for these conditions.The SiCl2 generation ratio,which stands for the degree of the side reactions,can be decomposed to SiCl4 and ZnCl2 in gas phase zinc atmosphere in the exit where the temperature is very low.Therefore,the lower SiCl2 generation ratio is profitable with lower power consumption.Based on the thermodynamic data for the related pure substances,the relations of the SiCl2 generation ratio and pressure,temperature and the feed molar ratio（n（Zn）/n（SiCl4） are investigated and the graphs thereof are plotted.And the diagrams of Kpθ-T at standard atmosphere pressure have been plotted to account for the influence of temperature on the SiCl2 generation ratio.Furthermore,the diagram of Kpθ-T at different pressures have also been plotted to give an interpretation of the influence of pressure on the SiCl2 generation ratio.The results show that SiCl2 generation ratio increases with increasing temperature,and the higher pressure and excess gas phase zinc can restrict SiCl2 generation ratio.Finally,suitable operational conditions in the practical process of polycrystalline silicon manufacture by gas phase zinc reduction of SiCl4 have been established with 1200 K,0.2 MPa and the feed molar ratio（n（Zn） /n（SiCl4）） of 4 at the entrance.Under these conditions,SiCl2 generation ratio is very low,which indicates that the side reactions can be restricted and the energy consumption is reasonable.
基金financially supported by National Program on Key Basic Research Project of China (973 Program, No. 2014CB643403)the Postdoctoral Foundation of Central South University
文摘Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH_4 Cl–NH_3·H_2 O solution. The thermodynamics and phase conversion of Zn_2 Si O_4 to zinc oxide(ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn_2 Si O_4 mole ratio(n(Ca O)/n(Zn_2 Si O_4)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn_2 Si O_4 was first converted to Ca_2 Zn Si_2 O_7 and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn_2 Si O_4 to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.
基金National Natural Science Foundation of China(Nos.51204147,51274175,51574206,51574207)Program for International S&T Cooperation Projects of China(No.2014DFA50320)+1 种基金Program for International S&T Cooperation Projects of Shanxi Province(No.201381017)Technological Projects of Shanxi Province(No.20150313002-3)
文摘Electrochemical impendence spectroscopy （EIS） is applied to investigate the dissolution behavior of Al-Zn alloys in 3% NaCl solution at different polarization potentials. A new reaction model is proposed, and the activation mechanism of zinc in Al-Zn alloys is achieved. There are three intermediates in the dissolution process： Znad^＋, Znad^2＋ and Alad^＋, ,of which only Zni can activate Al-Zn alloys. Most Znnd^＋ is produced by β-phase,and the alloys with 2. 3% - 3. 8% （wt） Zn dissolve rapidly. The Al-Zn alloys of heart-shaped EIS are active in 3% NaCl solution, thus EIS characteristic can be used to distinguish the activa-tion of Al-Zn alloys.
基金financially supported by the National Natural Science Foundation of China(Nos.51204054 and 51574084)the Fundamental Research Funds for the Central Universities of China(No.N150204009)the National Basic Research Priorities Program of China(No.2014CB643405)
文摘An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of（NH_4）_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for（NH_4）_2SO_4 and zinc mixed in a molar ratio of 1.4：1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.
基金financially supported by Tianjin Natural Science Foundation (No. 18JCZDJC31100)MOST(2017YFA0206700 and 2016YFA0202503)+1 种基金MOE(B12015)the Fundamental Research Funds for the Central Universities
文摘Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choice of cathode materials with satisfactory cycling performance. Here, we report a porous V2O5 nanofibers cathode with high Znstorage performance in an aqueous Zn(CF3SO3)2 electrolyte. We propose a reaction mechanism based on phase transition from orthorhombic V2O5 to zinc pyrovanadate on first discharging and reversible Zn^2+ (de)intercalation in the open-structured hosts during subsequent cycling. This open and stable architecture enables a high reversible capacity of 319 mAh g^-1 at 20 mAg^-1 and a capacity retention of 81% over 500 cycles. The remarkable electrochemical performance makes V2O5 a promising cathode for aqueous zinc-ion batteries.
文摘Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction （XRD） ,scanning electron microscope （SEM） and glow discharge optical emission spectrometry （GDOES）. It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.
文摘The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.
文摘The paper presents the calculation results on the construction of solidus lines of phase diagrams for some binary metal systems based on cadmium, zinc and tellurium. The investigations have been carried out using the phase equilibrium thermodynamics and known liquidus lines. By the calculation method the solidus lines of phase diagrams of the Cd-Na, Cd-Tl, Te-Ga, Te-As, Te-Cu and Zn-Sn systems were constructed in the temperature range from the base component melting point to the eutectic transformation temperature. In the Cd-Tl, Te-As, Te-Cu and Zn-Sn systems a retrograde solubility of the second component in the solid phase was observed. The temperature and maximum solubility values at the retrograde behavior of solidus lines, as well as, the limiting solubility values of components at eutectic transformation in the systems based on Cd, Zn and Te were determined.
文摘Superlattice phase transformation, occurred in the solute enriched region caused by diffusion induced grainboundary migration (DIGM), was found in two kinds of diffusion couples which consist of: (1) low carbon highstrength steel with hot dipped zinc coating, and (2) commercial pure iron with galvanized zinc coating after isothermally diffusion annealed at different temperatures (500, 560 and 580℃) with various durations. The product of thetransformation is an ordered phase with Li2 superlattice structure which was identified through the analysis by SEM,TEM and AEM. The ordered phase resulted from transformation occurred in the alloyed areas generated by DIGMand DIR The zinc content in this phase is variable, it approaches the stoichiometric composition Fe3Zn as the diffusion time is sufficiently prolonged. The mechanism of the transformation in connection with the process of DIGMand DIR was discussed. DIGM DIR and DIP (diffusion induced phase transformation) are three interrelatedprocessed originated from grain boundary diffusion.
