Calcium carboaluminate was successfully prepared by a simple and efficient one-step method,and the effects of temperature,time,raw material ratio,carbonate type and heavy CaCO_(3)particle size on the products were inv...Calcium carboaluminate was successfully prepared by a simple and efficient one-step method,and the effects of temperature,time,raw material ratio,carbonate type and heavy CaCO_(3)particle size on the products were investigated in detail.The results show that increasing the temperature and extending the reaction time can enhance the yield and crystallisation degree of calcium carboaluminate.The proportion of Ca(OH)_(2),Al(OH)_(3)and CaCO_(3)is a pivotal factor in the synthesis of calcium carboaluminate.When the ratio of Ca(OH)_(2),Al(OH)_(3)and CaCO_(3)is 3:2:1,the diffraction peaks of calcium carboaluminate in the products are relatively sharp and strong.Furthermore,the purity and crystallinity of the synthesized calcium carboaluminate are higher when heavy CaCO_(3)with the particle size of 120 mesh is used as the carbonate raw material,in comparison to CO_(2),Na_(2)CO_(3)and light CaCO_(3).As results,a simple and efficient method for the synthesis of calcium carboaluminate is proposed,which will provide a solid experimental foundation and technical support for the industrial application of calcium carboaluminate in marine concrete.展开更多
In the past decade, progress in the field of biohydrometallurgy had been significant. A total of 17 novel biomining microorganisms were discovered, and eight copper heap bioleaching plants and 11 gold biooxidation pla...In the past decade, progress in the field of biohydrometallurgy had been significant. A total of 17 novel biomining microorganisms were discovered, and eight copper heap bioleaching plants and 11 gold biooxidation plants were established or expanded. In this review, it was summarized the physiological properties of the newly isolated biomining microorganisms and three novel microbial ecological methods for studying microbial community dynamics and structure. In addition, biohy- drometallurgy research on rare metals such as uranium, molybdenum, tellurium, germanium, indium, and sec- ondary rare metal resources, as well as heavy nonferrous metals such as copper, nickel, cobalt, and gold has been reviewed, with an emphasis on China. In future, further studies on bioleaching of chalcopyrite, rare metals, secondary resources from waste, and environmental pollution caused by resource utilization are necessary.展开更多
High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of mi...High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.展开更多
The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive spectrosco...The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and differential scanning calorimetry （DSC） analysis. The results indicate that the microstructure of the as-cast 7A55 aluminum alloy mainly consists of the dendritic network of aluminum solid solution, Al/AIZnMgCu eutectic phases, and intermetaUic compounds MgZn2, Al2CuMg, Al7Cu2Fe, and Al23CuFe4. After homogenization at 470℃ for 48 h, Al/AlZnMgCu eutectic phases are dissolved into the matrix, and a small amount of high melting-point secondary phases were formed, which results in an increasing of the starting melting temperature of 7A55 aluminum alloy The high melting-point secondary phases were eliminated mostly when the homogenization time achieved to 72 h. Therefore, the reasonable homogenization heat treatment process for 7A55 aluminum alloy ingots was chosen as 470℃/72 h.展开更多
Laser direct deposition （LDD） of metallic components is an advanced technology of combining CAD/CAM （computer aided design/computer aided manufacturing）, high power laser, and rapid prototyping. This technology us...Laser direct deposition （LDD） of metallic components is an advanced technology of combining CAD/CAM （computer aided design/computer aided manufacturing）, high power laser, and rapid prototyping. This technology uses laser beam to melt the powders fed coaxiaUy into the molten pool by the laser beam to fabricate fuUy dense metallic components. The present article mainly studies the LDD of Ti-6Al-4V alloy, which can be used to fabricate aircraft components. The mechanical properties of the Ti-6Al-4V alloy, fabricated by LDD, are obtained using the tension test, and the oxygen content of used powders and deposited specimens are measured. In the present article, it can be seen that the mechanical properties obtained using this method are higher than the ones obtained by casting, and equal to those got by wrought anneal. One aircraft part has been made using the LDD process. Because of this aircraft part, with sophisticated shape, the effect of the laser scanning track on the internal soundness of the deposited part was discussed.展开更多
The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical re...The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur, interface bonding was good, and the reinforcement particle was thermodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.展开更多
The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation tem...The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the swain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.展开更多
Up to now, the Pedgion magnesium reduction process is the dominating magnesium production process. In 2004, about 98% of raw magnesium is produced by Pedgion magnesium reduction process in China which equals to 60% of...Up to now, the Pedgion magnesium reduction process is the dominating magnesium production process. In 2004, about 98% of raw magnesium is produced by Pedgion magnesium reduction process in China which equals to 60% of the global output. It shows that the dolomite-ferrosilicon thermal reduction process is the most important method to produce magnesium in the world. Limited by the disadvantage of dolomite-ferrosilicon thermal reduction process, the magnesium producing process always followed by relatively severe pollution, while the resource utilizing efficiency keeps very low. With the rapid development of dolomite-ferrosilicon thermal reduction process in China, many research works have been done aiming at the process technology and the reduction theory, and the magnesium producing process has got great evolution. The history of dolomite-ferrosilicon thermal reduction process was introduced; the process character, the merits and which defects were also discussed. Defects in dolomite-ferrosilicon thermal reduction process were expatiated, and feasible method and idea to upgrade the process was put forward. The main problems and the potential troubles hindering the development of magnesium industry were analyzed. Finally, the probability to further improve the thermal reduction process and the effective approaches to develop Chinese magnesium industry were discussed.展开更多
Characteristic and hydrometallurgy processes for Baotou mixed-type rare earth concentrate, bastnasite, and ionic adsorption deposit in China were reviewed. The R ＆ D circumstance and new progresses in extraction and ...Characteristic and hydrometallurgy processes for Baotou mixed-type rare earth concentrate, bastnasite, and ionic adsorption deposit in China were reviewed. The R ＆ D circumstance and new progresses in extraction and separation of RE element in China were introduced. Moreover, the development trend of RE hydrometallurgy was predicted. The direction and emphasised fields of research and development are also brought forward as： to R ＆ D high efficient green progresses in hydrometallurgy and separation of RE ore, resolve the waste pollution problem of water, slagand gas, reduce the chemical material consumption and improve comprehensive efficiency of resources; to R ＆ D preparation technology for RE compounds with ultra high-purity and special physical property for extending application fields of RE.展开更多
Y2O3：Eu red phosphor for FED application was prepared by high temperature solid-state reaction. The In2O3 coating by precipitation method to the phosphor was applied and the analyses of XRD, Zeta potential, SEM, EDS ...Y2O3：Eu red phosphor for FED application was prepared by high temperature solid-state reaction. The In2O3 coating by precipitation method to the phosphor was applied and the analyses of XRD, Zeta potential, SEM, EDS and low voltage cathodoluminescence （CL） were conducted for investigating the coating effect. The results showed that In2O3 coating promoted the low voltage CL of the phosphor efficiently. The promotion was possibly due to the enhancement of the surface conductivity of the phosphor grains.展开更多
Ba-Al-S-Eu sputtering target for blue emitting phosphors was prepared by powder sintering method. XRD patterns showed that the main components of the target were barium tetra aluminum sulfide （BaAl4S7）, bariutm sulf...Ba-Al-S-Eu sputtering target for blue emitting phosphors was prepared by powder sintering method. XRD patterns showed that the main components of the target were barium tetra aluminum sulfide （BaAl4S7）, bariutm sulfide （BaS）, and europium sulfide （EuS）. In the samples, part of the barium and aluminum are formed into barium aluminum oxide （BaAl2O4） with the impurity element of oxygen. The PL characteristic spectra of the target showed the 470 nm blue emission obviously, and the Ba-Al-S thin films also transmitted a purple-blue emission at the position of 440 nm.The results indicated that this method was suitable for the fabrication of the Ba-Al-S：Eu sputtering target.展开更多
Analyzing raw material＇s structure and performance of bentonite from Panzhihua in Sichuan, the authors think that it is adequate for agglomerant of iron smelting. According to its composition and property we have res...Analyzing raw material＇s structure and performance of bentonite from Panzhihua in Sichuan, the authors think that it is adequate for agglomerant of iron smelting. According to its composition and property we have researched the purification and modification of I/S bentonite under conditions of different dispersants and sodium agent. XRD test result reveals that the essential minerals of Panzhihua bentonite are I/S mixed-layer ones, and FTIR analysis shows that when adding 1.5% sodium pyrophosphate to the bentonite slurry during purification, the composition of quartz in bentonite decreases to less than 4% and I/S is more than 90%. The optimized modification technic conditions are Na2CO3 （4%） and CMC-Na （3%） as modified agents, the clay and water are 10 vs. 1, and the temperature is 75℃. It is 40 min for stirring time and reacting time is 4 h. Under the conditions we can get the modified I/S bentonite with colloid index more than 500 nd/15 g.展开更多
Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synt...Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.展开更多
The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the...The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.展开更多
This paper focuses on the preparation of rare earth oxide products from rare earth chloride solutions during the rare earth extraction and separation processes,as well as the recycling of magnesium chloride solutions....This paper focuses on the preparation of rare earth oxide products from rare earth chloride solutions during the rare earth extraction and separation processes,as well as the recycling of magnesium chloride solutions.It proposes the idea of introducing spray pyrolysis technology into the rare earth extraction and separation processes.This paper briefly describes the development history of chloride spray pyrolysis technology,focusing on the research status and application progress of rare earth chloride solution and magnesium chloride solution spray pyrolysis technology,as well as spray pyrolysis equipment.The paper also analyzes the challenges and technical intricacies associated with applying spray pyrolysis technology to chloride solutions in the rare earth extraction and separation processes.Additionally,it explores future trends and proposes strategies to facilitate the full recycling of acids and bases,streamline the process flow,and enhance the prospects for green and low-carbon rare earth metallurgy.展开更多
The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of...The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of the precipitated phases,more Cr entered theκphase and a small amount of Cr solubilized in the matrix,which increase the hardness of theκand matrix and decrease the potential difference between theκand matrix.NAB alloy with Cr shows high erosion-corrosion resistance at high flow rate conditions,due to its lower phase potential difference and higher surface hardness.At the flow rate of 3 m·s^(-1),the corrosion rate is 0.076 mm·year^(-1),which is~20%lower than that of the unadded Cr sample.Moreover,the corrosion product film contains Cr_(2)O_(3)and Cr^(3+),which improves the densification of the film and raises alloy’s corrosion resistance with Cr addition.The combination of mechanical and corrosion resistant properties may qualify this alloy as a potential candidate material for sustainable and safe equipment.展开更多
Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elasti...Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elastic modulus and degradable properties.The Mg-3Zn-1Ca-0.5Sr(wt%)alloy is considered a competitor in the biomaterial field thanks to its unique composition of essential nutrients and excellent mechanical properties.However,the presence of coarse second-phase particles in the alloy accelerates its degradation rate and causes excessive gas formation during implantation,which restricts the alloy's potential for clinical device applications.In order to further optimize the properties of the alloy,extrusion combined with high-pressure torsion(HPT)was adopted for deformation processing.The results show that by optimizing the material processing means,the grain can be refined and broken,and the second-phase distribution can be improved,thus improving the microstructure,mechanical properties,and corrosion resistance of the alloy.After 15 cycles of HPT processing,the grains of the alloy are significantly refined to the nanometer scale,reaching approximately 98 nm.Additionally,the second-phase distribution is greatly improved,transforming the original streamlined structure into a more dispersed distribution.This change in microstructure leads to a significant strengthening effect on the alloy,with a noticeable increase in hardness from 60.3 HV in the as-extruded state to 98.5 HV.展开更多
The depression mechanism of sulfite ions on sphalerite and Pb^(2+)activated sphalerite in the flotation separation of galena from sphalerite still lacked in-depth insight.Therefore,the depression mechanism of sulfite ...The depression mechanism of sulfite ions on sphalerite and Pb^(2+)activated sphalerite in the flotation separation of galena from sphalerite still lacked in-depth insight.Therefore,the depression mechanism of sulfite ions on sphalerite and Pb^(2+)activated sphalerite in the flotation separation of galena from sphalerite was further systematically investigated with experiments and density functional theory(DFT)calculations.The X-ray photoelectric spectroscopy(XPS)results,DFT calculation results,and frontier molecular orbital analysis indicated that sulfite ions were difficult to be adsorbed on sphalerite surface,suggesting that sulfite ions achieved depression effects on sphalerite through other non-adsorption mechanisms.First,the oxygen content in the surface of sphalerite treated with sulfite ions in creased,which enhanced the hydrophilicity of the sphalerite and further increased the difference in hydrophilicity between sphalerite and galena.Then,sulfite ions were chelated with lead ions to form PbSO_(3)in solution.The hydrophilic PbSO_(3)was more easily adsorbed on sphalerite than galena.The interaction between sulfite ions and lead ions could effectively inhibit the activation of sphalerite.In addition the UV spectrum showed that after adding sulfite ions,the peak of perxanthate in the sphalerite treated xanthate solution was significantly stronger than that in the galena with xanthate solution,indicating that xanthate interacted more readily with sulfite ions and oxygen mo lecules within the sphalerite system,leading to the formation of perxanthate.However,sulfite ions hardly depressed the flotation of ga lena and could promote the flotation of galena to some extent.This study deepened the understanding of the depression mechanism o sulfite ions on sphalerite and Pb^(2+)activated sphalerite.展开更多
The diffusion of hydrogen-blended natural gas(HBNG)from buried pipelines in the event of a leak is typically influenced by soil properties,including porosity,particle size,temperature distribution,relative humidity,an...The diffusion of hydrogen-blended natural gas(HBNG)from buried pipelines in the event of a leak is typically influenced by soil properties,including porosity,particle size,temperature distribution,relative humidity,and the depth of the pipeline.This study models the soil as an isotropic porous medium and employs a CFD-based numerical framework to simulate gas propagation,accounting for the coupled effects of soil temperature and humidity.The model is rigorously validated against experimental data on natural gas diffusion in soil.It is then used to explore the impact of relevant parameters on the diffusion behavior of HBNG under conditions of low leakage flux.The results reveal distinct diffusion dynamics across different soil types:hydrogen(H_(2))diffuses most rapidly in clay,more slowly in sandy soil,and slowest in loam.At the ground surface directly above the leakage point,H_(2)concentrations rise rapidly initially before stabilizing,while at more distant surface locations,the increase is gradual,with delays that grow with distance.In particular,in a micro-leak scenario,characterized by a pipeline buried 0.8 m deep and a leakage velocity of 3.492 m/s,the time required for the H_(2)concentration to reach 1%at the surface,2 m horizontally from the leak source,is approximately 4.8 h for clay,5 h for sandy soil,and 7 h for loam.The time taken for gas to reach the surface is highly sensitive to the burial depth of the pipeline.After 18 h of diffusion,the surface H_(2)molar fraction directly above the leak reaches 3.75%,3.2%,and 2.75%for burial depths of 0.8,1.1,and 1.5 m,respectively,with the concentration inversely proportional to the depth.Soil temperature exerts minimal influence on the overall diffusion rate but slows the rise in H_(2)concentration directly above the leak as temperature increases.Meanwhile,the effect of soil humidity on H_(2)diffusion is negligible.展开更多
基金Funded by the National Nature Science Foundation of China(No.52078321)。
文摘Calcium carboaluminate was successfully prepared by a simple and efficient one-step method,and the effects of temperature,time,raw material ratio,carbonate type and heavy CaCO_(3)particle size on the products were investigated in detail.The results show that increasing the temperature and extending the reaction time can enhance the yield and crystallisation degree of calcium carboaluminate.The proportion of Ca(OH)_(2),Al(OH)_(3)and CaCO_(3)is a pivotal factor in the synthesis of calcium carboaluminate.When the ratio of Ca(OH)_(2),Al(OH)_(3)and CaCO_(3)is 3:2:1,the diffraction peaks of calcium carboaluminate in the products are relatively sharp and strong.Furthermore,the purity and crystallinity of the synthesized calcium carboaluminate are higher when heavy CaCO_(3)with the particle size of 120 mesh is used as the carbonate raw material,in comparison to CO_(2),Na_(2)CO_(3)and light CaCO_(3).As results,a simple and efficient method for the synthesis of calcium carboaluminate is proposed,which will provide a solid experimental foundation and technical support for the industrial application of calcium carboaluminate in marine concrete.
基金financially supported by the National High Technology Research and Development Program(Nos.2012AA061501,2012AA061502,and 2012AA061504)the National Basic Research Program of China(Nos.2010CB630905 and2010CB630906)and the National Natural Science Foundation of China(No.51404033)
文摘In the past decade, progress in the field of biohydrometallurgy had been significant. A total of 17 novel biomining microorganisms were discovered, and eight copper heap bioleaching plants and 11 gold biooxidation plants were established or expanded. In this review, it was summarized the physiological properties of the newly isolated biomining microorganisms and three novel microbial ecological methods for studying microbial community dynamics and structure. In addition, biohy- drometallurgy research on rare metals such as uranium, molybdenum, tellurium, germanium, indium, and sec- ondary rare metal resources, as well as heavy nonferrous metals such as copper, nickel, cobalt, and gold has been reviewed, with an emphasis on China. In future, further studies on bioleaching of chalcopyrite, rare metals, secondary resources from waste, and environmental pollution caused by resource utilization are necessary.
基金the project of National Key Laboratory for Precision Hot Processing of Metals,Harbin Institute of Technology(No.6142909190207)Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment(NSKL-HPFTE)(No.PETE-2019-KF01)。
文摘High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.
基金financially supported by the National Key Technologies R&D Program of China (No.2007BAE38B06)the National Natural Science Foundation of China (No.50904010)
文摘The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and differential scanning calorimetry （DSC） analysis. The results indicate that the microstructure of the as-cast 7A55 aluminum alloy mainly consists of the dendritic network of aluminum solid solution, Al/AIZnMgCu eutectic phases, and intermetaUic compounds MgZn2, Al2CuMg, Al7Cu2Fe, and Al23CuFe4. After homogenization at 470℃ for 48 h, Al/AlZnMgCu eutectic phases are dissolved into the matrix, and a small amount of high melting-point secondary phases were formed, which results in an increasing of the starting melting temperature of 7A55 aluminum alloy The high melting-point secondary phases were eliminated mostly when the homogenization time achieved to 72 h. Therefore, the reasonable homogenization heat treatment process for 7A55 aluminum alloy ingots was chosen as 470℃/72 h.
基金This work was supported by the National Natural Science Foundation of China （No. 50331010）
文摘Laser direct deposition （LDD） of metallic components is an advanced technology of combining CAD/CAM （computer aided design/computer aided manufacturing）, high power laser, and rapid prototyping. This technology uses laser beam to melt the powders fed coaxiaUy into the molten pool by the laser beam to fabricate fuUy dense metallic components. The present article mainly studies the LDD of Ti-6Al-4V alloy, which can be used to fabricate aircraft components. The mechanical properties of the Ti-6Al-4V alloy, fabricated by LDD, are obtained using the tension test, and the oxygen content of used powders and deposited specimens are measured. In the present article, it can be seen that the mechanical properties obtained using this method are higher than the ones obtained by casting, and equal to those got by wrought anneal. One aircraft part has been made using the LDD process. Because of this aircraft part, with sophisticated shape, the effect of the laser scanning track on the internal soundness of the deposited part was discussed.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50205005)
文摘The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur, interface bonding was good, and the reinforcement particle was thermodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.
基金This work was financially supported by the National Basic Research Program of China (No. G20000672).
文摘The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the swain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.
文摘Up to now, the Pedgion magnesium reduction process is the dominating magnesium production process. In 2004, about 98% of raw magnesium is produced by Pedgion magnesium reduction process in China which equals to 60% of the global output. It shows that the dolomite-ferrosilicon thermal reduction process is the most important method to produce magnesium in the world. Limited by the disadvantage of dolomite-ferrosilicon thermal reduction process, the magnesium producing process always followed by relatively severe pollution, while the resource utilizing efficiency keeps very low. With the rapid development of dolomite-ferrosilicon thermal reduction process in China, many research works have been done aiming at the process technology and the reduction theory, and the magnesium producing process has got great evolution. The history of dolomite-ferrosilicon thermal reduction process was introduced; the process character, the merits and which defects were also discussed. Defects in dolomite-ferrosilicon thermal reduction process were expatiated, and feasible method and idea to upgrade the process was put forward. The main problems and the potential troubles hindering the development of magnesium industry were analyzed. Finally, the probability to further improve the thermal reduction process and the effective approaches to develop Chinese magnesium industry were discussed.
文摘Characteristic and hydrometallurgy processes for Baotou mixed-type rare earth concentrate, bastnasite, and ionic adsorption deposit in China were reviewed. The R ＆ D circumstance and new progresses in extraction and separation of RE element in China were introduced. Moreover, the development trend of RE hydrometallurgy was predicted. The direction and emphasised fields of research and development are also brought forward as： to R ＆ D high efficient green progresses in hydrometallurgy and separation of RE ore, resolve the waste pollution problem of water, slagand gas, reduce the chemical material consumption and improve comprehensive efficiency of resources; to R ＆ D preparation technology for RE compounds with ultra high-purity and special physical property for extending application fields of RE.
基金Project supported by the National Natural Science Foundation of China (50272013 ,50372086)
文摘Y2O3：Eu red phosphor for FED application was prepared by high temperature solid-state reaction. The In2O3 coating by precipitation method to the phosphor was applied and the analyses of XRD, Zeta potential, SEM, EDS and low voltage cathodoluminescence （CL） were conducted for investigating the coating effect. The results showed that In2O3 coating promoted the low voltage CL of the phosphor efficiently. The promotion was possibly due to the enhancement of the surface conductivity of the phosphor grains.
基金supported by Provincial Natural Science Foundation of Beijing (3063022)
文摘Ba-Al-S-Eu sputtering target for blue emitting phosphors was prepared by powder sintering method. XRD patterns showed that the main components of the target were barium tetra aluminum sulfide （BaAl4S7）, bariutm sulfide （BaS）, and europium sulfide （EuS）. In the samples, part of the barium and aluminum are formed into barium aluminum oxide （BaAl2O4） with the impurity element of oxygen. The PL characteristic spectra of the target showed the 470 nm blue emission obviously, and the Ba-Al-S thin films also transmitted a purple-blue emission at the position of 440 nm.The results indicated that this method was suitable for the fabrication of the Ba-Al-S：Eu sputtering target.
文摘Analyzing raw material＇s structure and performance of bentonite from Panzhihua in Sichuan, the authors think that it is adequate for agglomerant of iron smelting. According to its composition and property we have researched the purification and modification of I/S bentonite under conditions of different dispersants and sodium agent. XRD test result reveals that the essential minerals of Panzhihua bentonite are I/S mixed-layer ones, and FTIR analysis shows that when adding 1.5% sodium pyrophosphate to the bentonite slurry during purification, the composition of quartz in bentonite decreases to less than 4% and I/S is more than 90%. The optimized modification technic conditions are Na2CO3 （4%） and CMC-Na （3%） as modified agents, the clay and water are 10 vs. 1, and the temperature is 75℃. It is 40 min for stirring time and reacting time is 4 h. Under the conditions we can get the modified I/S bentonite with colloid index more than 500 nd/15 g.
基金the National Key Research and Development Program of China(2022YFB3504503)the National Natural Science Foundation of China(52274355)the Gansu Province Science and Technology Major Special Project,China(22ZD6GD061).
文摘Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.
基金supported by the National Key Research and Development Program of China(2022YFB3505503)the National Natural Science Foundation of China(52201230)+2 种基金the Key R&D Program of Shandong Province(2022CXGC020307)the China Postdoctoral Science Foundation(2022M71204)the Beijing NOVA Program(Z211100002121092).
文摘The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.
基金supported by the National Key Research and Development Program of China(2022YFB3504501)the National Natural Science Foundation of China(52274355)。
文摘This paper focuses on the preparation of rare earth oxide products from rare earth chloride solutions during the rare earth extraction and separation processes,as well as the recycling of magnesium chloride solutions.It proposes the idea of introducing spray pyrolysis technology into the rare earth extraction and separation processes.This paper briefly describes the development history of chloride spray pyrolysis technology,focusing on the research status and application progress of rare earth chloride solution and magnesium chloride solution spray pyrolysis technology,as well as spray pyrolysis equipment.The paper also analyzes the challenges and technical intricacies associated with applying spray pyrolysis technology to chloride solutions in the rare earth extraction and separation processes.Additionally,it explores future trends and proposes strategies to facilitate the full recycling of acids and bases,streamline the process flow,and enhance the prospects for green and low-carbon rare earth metallurgy.
基金supported by Beijing Nova Program(No.20230484371)the National Key Research and Development Program of China(No.2021YFB3700700).
文摘The effect of Cr addition on nickel aluminium bronze(NAB)alloy microstructure,mechanical properties,and erosion-corrosion behaviour has been studied.The results show that Cr addition does not change the composition of the precipitated phases,more Cr entered theκphase and a small amount of Cr solubilized in the matrix,which increase the hardness of theκand matrix and decrease the potential difference between theκand matrix.NAB alloy with Cr shows high erosion-corrosion resistance at high flow rate conditions,due to its lower phase potential difference and higher surface hardness.At the flow rate of 3 m·s^(-1),the corrosion rate is 0.076 mm·year^(-1),which is~20%lower than that of the unadded Cr sample.Moreover,the corrosion product film contains Cr_(2)O_(3)and Cr^(3+),which improves the densification of the film and raises alloy’s corrosion resistance with Cr addition.The combination of mechanical and corrosion resistant properties may qualify this alloy as a potential candidate material for sustainable and safe equipment.
基金National Key Research and Development Program of China(2021YFB3701004)。
文摘Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elastic modulus and degradable properties.The Mg-3Zn-1Ca-0.5Sr(wt%)alloy is considered a competitor in the biomaterial field thanks to its unique composition of essential nutrients and excellent mechanical properties.However,the presence of coarse second-phase particles in the alloy accelerates its degradation rate and causes excessive gas formation during implantation,which restricts the alloy's potential for clinical device applications.In order to further optimize the properties of the alloy,extrusion combined with high-pressure torsion(HPT)was adopted for deformation processing.The results show that by optimizing the material processing means,the grain can be refined and broken,and the second-phase distribution can be improved,thus improving the microstructure,mechanical properties,and corrosion resistance of the alloy.After 15 cycles of HPT processing,the grains of the alloy are significantly refined to the nanometer scale,reaching approximately 98 nm.Additionally,the second-phase distribution is greatly improved,transforming the original streamlined structure into a more dispersed distribution.This change in microstructure leads to a significant strengthening effect on the alloy,with a noticeable increase in hardness from 60.3 HV in the as-extruded state to 98.5 HV.
基金financially supported by the National Natural Science Foundation of China(No.52074356)Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2023-06)+5 种基金the National Key R&D Program of China(No.2022YFC2904500)the Science and Technology Innovation Program of Hunan Province,China(No.2022RC1183)Changsha Science and Technology Project,China(Outstanding Innovative Youth Training Program)Innovation driven program of Central South University(No.2023CXQD002)National 111 Project(No.B14034)the Fundamental Research Funds for the Central Universities of Central South University Project(No.50621747)。
文摘The depression mechanism of sulfite ions on sphalerite and Pb^(2+)activated sphalerite in the flotation separation of galena from sphalerite still lacked in-depth insight.Therefore,the depression mechanism of sulfite ions on sphalerite and Pb^(2+)activated sphalerite in the flotation separation of galena from sphalerite was further systematically investigated with experiments and density functional theory(DFT)calculations.The X-ray photoelectric spectroscopy(XPS)results,DFT calculation results,and frontier molecular orbital analysis indicated that sulfite ions were difficult to be adsorbed on sphalerite surface,suggesting that sulfite ions achieved depression effects on sphalerite through other non-adsorption mechanisms.First,the oxygen content in the surface of sphalerite treated with sulfite ions in creased,which enhanced the hydrophilicity of the sphalerite and further increased the difference in hydrophilicity between sphalerite and galena.Then,sulfite ions were chelated with lead ions to form PbSO_(3)in solution.The hydrophilic PbSO_(3)was more easily adsorbed on sphalerite than galena.The interaction between sulfite ions and lead ions could effectively inhibit the activation of sphalerite.In addition the UV spectrum showed that after adding sulfite ions,the peak of perxanthate in the sphalerite treated xanthate solution was significantly stronger than that in the galena with xanthate solution,indicating that xanthate interacted more readily with sulfite ions and oxygen mo lecules within the sphalerite system,leading to the formation of perxanthate.However,sulfite ions hardly depressed the flotation of ga lena and could promote the flotation of galena to some extent.This study deepened the understanding of the depression mechanism o sulfite ions on sphalerite and Pb^(2+)activated sphalerite.
基金supported by the National Key Research and Development Program of China(No.2022YFB4002900).
文摘The diffusion of hydrogen-blended natural gas(HBNG)from buried pipelines in the event of a leak is typically influenced by soil properties,including porosity,particle size,temperature distribution,relative humidity,and the depth of the pipeline.This study models the soil as an isotropic porous medium and employs a CFD-based numerical framework to simulate gas propagation,accounting for the coupled effects of soil temperature and humidity.The model is rigorously validated against experimental data on natural gas diffusion in soil.It is then used to explore the impact of relevant parameters on the diffusion behavior of HBNG under conditions of low leakage flux.The results reveal distinct diffusion dynamics across different soil types:hydrogen(H_(2))diffuses most rapidly in clay,more slowly in sandy soil,and slowest in loam.At the ground surface directly above the leakage point,H_(2)concentrations rise rapidly initially before stabilizing,while at more distant surface locations,the increase is gradual,with delays that grow with distance.In particular,in a micro-leak scenario,characterized by a pipeline buried 0.8 m deep and a leakage velocity of 3.492 m/s,the time required for the H_(2)concentration to reach 1%at the surface,2 m horizontally from the leak source,is approximately 4.8 h for clay,5 h for sandy soil,and 7 h for loam.The time taken for gas to reach the surface is highly sensitive to the burial depth of the pipeline.After 18 h of diffusion,the surface H_(2)molar fraction directly above the leak reaches 3.75%,3.2%,and 2.75%for burial depths of 0.8,1.1,and 1.5 m,respectively,with the concentration inversely proportional to the depth.Soil temperature exerts minimal influence on the overall diffusion rate but slows the rise in H_(2)concentration directly above the leak as temperature increases.Meanwhile,the effect of soil humidity on H_(2)diffusion is negligible.
