Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases a...Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases and the precipitation of secondary phases,driven by changes in the chemical environment,often mediated by hydrothermal fluids.The Bailongshan Li deposit,located in the West Kunlun region of northwest China,is a significant geological formation known for its rich lithium content and associated rare metals such as tantalum,niobium,and tin.This study investigates the coupled dissolution-precipitation processes that have played a crucial role in the mineralization of this deposit,focusing on key minerals,including cassiterite(Cst),columbite-group minerals(CGM),and elbaite(Elb).Using a combination of petrographic analysis,back-scattered electron(BSE)imaging,cathodoluminescence(CL)imaging,and micro X-ray fluorescence(XRF)mapping,we examined the textural and chemical characteristics of these minerals.Our findings reveal intricate patchy zoning patterns and element distributions(indicated by the Nb,Ta,W,Mn,Fe,Hf,Ti for CGM;Hf,Ti Rb,W,Nb,Ta for Cst;Ti,Zn,Fe,W,Hf,Mn,K for Elb)that indicate multiple stages of mineral alteration driven by fluid-mediated processes.The coupled dissolution-precipitation mechanisms observed in the Bailongshan deposit have resulted in significant redistribution and enrichment of economically valuable elements.The study highlights the importance of hydrothermal fluids in altering primary mineral phases and precipitating secondary phases with distinct compositions.These processes not only modified the mineralogical makeup of the pegmatite but also enhanced its economic potential by concentrating rare metals.Signatures of coupled dissolutionprecipitation processes can serve as an essential tool for mineral exploration,guiding the search for high-grade zones within similar pegmatitic formations.展开更多
In this work,accelerated sintering of Y_(2)O_(3)dispersion strengthened tungsten alloy with a well-regulated structure was achieved by a novel dissolution-precipitation strategy.As indicated,yttrium oxide was firstly ...In this work,accelerated sintering of Y_(2)O_(3)dispersion strengthened tungsten alloy with a well-regulated structure was achieved by a novel dissolution-precipitation strategy.As indicated,yttrium oxide was firstly dissolved into the lattices of W powder precursor during the thermal plasma synthesis process in a one-step and ultra-fast way,and then homogeneously precipitated out within W grains during sintering.The theoretical calculation reveals that the formation process of Y_(2)O_(3)dispersoids enhanced the driving force of densification by increasing the sintering stress and declining the macroscopic viscosity,resulting in improved diffusion ability for the W skeleton.The microstructural investigation further confirmed the occurrence of mass inter-diffusion at the W-Y_(2)O_(3)interface,which provides a fast diffusion pathway for W atoms,and is responsible for the accelerated densification kinetics.Being sintered at 1600℃ for 1 h,the as-obtained alloy possesses a high relative density of 98.26%,together with a refined grain size of 970 nm for W and 50 nm for intragranular Y_(2)O_(3),respectively.展开更多
Peculiar hierarchical microstructures in creatures inspire modern material design with distinct functionalities.Creatures can effortlessly construct sophisticated yet long-range ordered microstructure across bio-membr...Peculiar hierarchical microstructures in creatures inspire modern material design with distinct functionalities.Creatures can effortlessly construct sophisticated yet long-range ordered microstructure across bio-membrane through ion secretion and precipitation.However,microstructure biomimicry in current technology generally requires elaborate,point-by-point fabrication.Herein,a spontaneous yet controllable strategy is developed to achieve surface microstructure engineering through a natural surface phenomenon similar to ion secretion-precipitation,that is,coupled dissolution-precipitation.A series of hierarchical microstructures on mineral surfaces in fluids with tunable morphology,orientation,dimension,and spatial distribution are achieved by simply controlling initial dissolution and fluid chemistry.In seawater,long-range ordered film of vertically aligned brucite flakes forms through interfacial dissolution,nucleation,and confinement-induced orientation of flakes with vertically grown{110}plane,on the edge of which,fusiform aragonite epitaxially precipitates.With negligible initial surface dissolution,prismatic aragonite epitaxially grows on a calcite polyhedron-packed surface.By tuning fluid chemistry,closely packed calcite polyhedron and loosely packed calcite micro-pillars are engineered through rapid and retarded precipitation,respectively.Surprisingly,the spontaneously grown microstructures resemble those deliberately created by human or found in nature,and tremendously modulate surface functionality.These findings open new possibilities for facile and customizable engineering of microstructural surfaces,hierarchical heterostructures,and biomimetic materials.展开更多
In order to improve the densification of Si_(3)N_(4) bonded SiC refractories and reduce the nitriding temperature of Si powder,Si_(3)N_(4) bonded SiC refractories were produced by reaction sintering at 1350℃ for 5 h ...In order to improve the densification of Si_(3)N_(4) bonded SiC refractories and reduce the nitriding temperature of Si powder,Si_(3)N_(4) bonded SiC refractories were produced by reaction sintering at 1350℃ for 5 h under a carbon embedded atmosphere,using SiC particles and fine powder,and Si powder as the main raw materials,and introducing Ti-Si-Fe alloy extracted from high-titanium blast furnace slag to partially replace the Si powder.The effects of the Ti-Si-Fe alloy addition(0,1.8%,3.6%,5.4%,and 7.2%,by mass)on the nitriding behavior of Si powder,as well as on the mechanical properties and microstructure of the material were investigated,and the nitriding reaction sintering mechanism was also explored.The results show that:(1)with the increase of the Ti-Si-Fe alloy addition,the cold mechanical properties and the hot modulus of rupture of the refractories are obviously improved,and the refractoriness under load exceeds 1700℃;the property enhancement slows down with Ti-Si-Fe alloys addition above 3.6%;(2)Ti-Si-Fe alloy promotes the complete nitridation of Si powder and the reaction sintering of the material at a lower temperature;the volume growth during the nitridation process of the Ti-Si-Fe alloys and Si powder can effectively fill pores,nitriding products improve the bonding state between aggregates and matrix,and that inside matrix,thereby increasing the densification and improving the mechanical properties of the material;(3)after the introduction of Ti-Si-Fe alloys,the liquid phase rich in Ti,Si,N,and Fe components is formed in the reaction system;besides the traditional VS and VLS mechanisms,the dissolution-precipitation mechanism plays a leading role in the formation of short columnar β-Si_(3)N_(4) and granular TiN;and the cross-linked α-Si_(3)N_(4) whisker,short columnar β-Si_(3)N_(4) and granular TiN enhance the mechanical properties of the material.展开更多
Clay minerals constitute an important component of the soil system and knowledge of their role in soil fertility is imperative for sustainable soil management and productivity. The aim of this work is to overview the ...Clay minerals constitute an important component of the soil system and knowledge of their role in soil fertility is imperative for sustainable soil management and productivity. The aim of this work is to overview the influence of clay minerals on some major soil fertility attributes. The rationale for carrying out this work is that most soil fertility studies rarely incorporate soil mineralogy. Clay minerals, through their physical and chemical properties, affect soil fertility by controlling nutrient supplies and availability, through the sequestration and stabilization of soil organic matter, by controlling soil physical properties through microaggregate formation, by influencing soil acidity and controlling soil microbial population and activity. The main processes involved in these relationships are dissolution-precipitation and adsorption-desorption processes, alongside mechanisms involving the formation of short-range-ordered phases. Although the determination of soil mineralogical properties is very costly and time-consuming, information about a soil’s mineralogy is imperative for a holistic understanding and proper management of soil fertility. Therefore, the development of rapid, low-cost, reliable and efficient techniques of soil mineralogical analysis, directly applicable to soil fertility investigations, constitutes a major challenge. Also, future research should investigate the relationships between clay minerals and soil nitrogen vis-à-vis sequestration and stabilization. Lastly, clay minerals should be considered in studies dealing with soil quality assessment, especially in the choice of soil quality indicators.展开更多
The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestit...The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestite in mild condition was described.Sr element remained in precipitation with formation of Sr(OH)2,while S element entered into leachate with formation of Na2SO4.The effects of initial concentration of NaOH,conversion temperature,liquid-to-solid(L/S)ratio and conversion time on Sr/S ratio of samples for celestite conversion were systematically investigated by experiments.The results demonstrated that the efficiency of Sr/S isolation increased with the initial concentration of NaOH,L/S ratio and conversion time,and decreased with conversion temperature.The maximum conversion ratio of Sr(OH)2 was 93.88%under the optimum condition,whose Sr/S ratio of sample could reach to 41.16.It illustrated that better isolation efficiency of celestite could be achieved in alkaline treatment.The results of SEM-EDS analyses demonstrated that the conversion reaction was a dissolution-precipitation process.展开更多
Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite （CHap） are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage ...Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite （CHap） are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage increases with decreasing pH values and reaches a maximum at pH=2-3. Under some conditions, the lead residual concentration is below national integrated wastewater discharge standard, even drinking water standard. The removal behavior is a complicated non-homogeneous solid/liquid reaction, which can be described by two stages from kinetic point of view. At the earlier stage, reaction rate is so fast that its kinetic course is intricate, which requires further study. At the latter stage, the rate of reaction becomes slow and the process of reaction accords with one order reaction kinetic equation. Experimental results show that the relationship between reaction rate constant k1 and temperature T accords to Arrhenius Equation, and the activation energy of sorption （Ea） is 11.93 kJ/mol and frequency factor （A） is 2.51 s^-1. X-ray diffraction （XRD）, scanning electron microscopy with an energy dispersive X-ray fluoresence spectrometer （SEM-EDS） and toxicity characteristic leaching procedure （TCLP） test were conducted in this work. It is indicated that the main mechanism is dissolution-precipitation, accompanying with superficial sorption.展开更多
Hierarchically nanostructured porous carbonated hydroxyapatite coatings (HNPCs) on Ti6Al4V substrate were fabricated by a two-stage application route: fabrication of nacre coatings (NCs) on Ti6Al4V substrate by electr...Hierarchically nanostructured porous carbonated hydroxyapatite coatings (HNPCs) on Ti6Al4V substrate were fabricated by a two-stage application route: fabrication of nacre coatings (NCs) on Ti6Al4V substrate by electrophoretic technique, and conversion of NCs to HNPCs in a phosphate buffer solution (PBS) by microwave irradiation method. Their samples were characterized by using XRD, FT-IR, SEM, TEM, and N2 adsorption-desorption isotherms. The results show that the microwave irradiation technique improves obviously the conversion rate of NCs to HNPCs as compared with conventional method. After soaking the NCs in the PBS, calcium ions are released from the nacre particles and react with phosphate ions to form carbonated hydroxyapatite nanoparticles. These nanoparticles aggregate to form the plate-like carbonated apatite. The mesopores with a size of about 3.9 nm and macropores with the diameters of 1~4μm exist within and among the carbonated apatite plates, respectively. Simulated body fluid immersion tests reveal that the HNPCs have a good in vitro bioactivity.展开更多
基金jointly supported by the National Natural Science Foundation of China(Nos.42250202,92162323,42272075)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.24lgqb001)+1 种基金the Natural Science Foundation Project of Guangdong Province(No.2022A1515010003)the Guangdong Province Introduced Innovative R&D Team of Big Data—Mathematical Earth Sciences and Extreme Geological Events Team(No.2021ZT09H399)。
文摘Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases and the precipitation of secondary phases,driven by changes in the chemical environment,often mediated by hydrothermal fluids.The Bailongshan Li deposit,located in the West Kunlun region of northwest China,is a significant geological formation known for its rich lithium content and associated rare metals such as tantalum,niobium,and tin.This study investigates the coupled dissolution-precipitation processes that have played a crucial role in the mineralization of this deposit,focusing on key minerals,including cassiterite(Cst),columbite-group minerals(CGM),and elbaite(Elb).Using a combination of petrographic analysis,back-scattered electron(BSE)imaging,cathodoluminescence(CL)imaging,and micro X-ray fluorescence(XRF)mapping,we examined the textural and chemical characteristics of these minerals.Our findings reveal intricate patchy zoning patterns and element distributions(indicated by the Nb,Ta,W,Mn,Fe,Hf,Ti for CGM;Hf,Ti Rb,W,Nb,Ta for Cst;Ti,Zn,Fe,W,Hf,Mn,K for Elb)that indicate multiple stages of mineral alteration driven by fluid-mediated processes.The coupled dissolution-precipitation mechanisms observed in the Bailongshan deposit have resulted in significant redistribution and enrichment of economically valuable elements.The study highlights the importance of hydrothermal fluids in altering primary mineral phases and precipitating secondary phases with distinct compositions.These processes not only modified the mineralogical makeup of the pegmatite but also enhanced its economic potential by concentrating rare metals.Signatures of coupled dissolutionprecipitation processes can serve as an essential tool for mineral exploration,guiding the search for high-grade zones within similar pegmatitic formations.
基金supported by the National Natural Science Foundation of China(Nos.52130407,52174342)Beijing Natural Science Foundation(No.2232044).
文摘In this work,accelerated sintering of Y_(2)O_(3)dispersion strengthened tungsten alloy with a well-regulated structure was achieved by a novel dissolution-precipitation strategy.As indicated,yttrium oxide was firstly dissolved into the lattices of W powder precursor during the thermal plasma synthesis process in a one-step and ultra-fast way,and then homogeneously precipitated out within W grains during sintering.The theoretical calculation reveals that the formation process of Y_(2)O_(3)dispersoids enhanced the driving force of densification by increasing the sintering stress and declining the macroscopic viscosity,resulting in improved diffusion ability for the W skeleton.The microstructural investigation further confirmed the occurrence of mass inter-diffusion at the W-Y_(2)O_(3)interface,which provides a fast diffusion pathway for W atoms,and is responsible for the accelerated densification kinetics.Being sintered at 1600℃ for 1 h,the as-obtained alloy possesses a high relative density of 98.26%,together with a refined grain size of 970 nm for W and 50 nm for intragranular Y_(2)O_(3),respectively.
基金National Key R&D Program of China,Grant/Award Number:2021YFB2600900National Science Fund for Distinguished Young Scholars of China,Grant/Award Number:51925903+3 种基金National Natural Science Foundation of China,Grant/Award Numbers:52108195,U21A20150Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20210264Natural Sciences and Engineering Research Council of CanadaCanada Research Chairs Program。
文摘Peculiar hierarchical microstructures in creatures inspire modern material design with distinct functionalities.Creatures can effortlessly construct sophisticated yet long-range ordered microstructure across bio-membrane through ion secretion and precipitation.However,microstructure biomimicry in current technology generally requires elaborate,point-by-point fabrication.Herein,a spontaneous yet controllable strategy is developed to achieve surface microstructure engineering through a natural surface phenomenon similar to ion secretion-precipitation,that is,coupled dissolution-precipitation.A series of hierarchical microstructures on mineral surfaces in fluids with tunable morphology,orientation,dimension,and spatial distribution are achieved by simply controlling initial dissolution and fluid chemistry.In seawater,long-range ordered film of vertically aligned brucite flakes forms through interfacial dissolution,nucleation,and confinement-induced orientation of flakes with vertically grown{110}plane,on the edge of which,fusiform aragonite epitaxially precipitates.With negligible initial surface dissolution,prismatic aragonite epitaxially grows on a calcite polyhedron-packed surface.By tuning fluid chemistry,closely packed calcite polyhedron and loosely packed calcite micro-pillars are engineered through rapid and retarded precipitation,respectively.Surprisingly,the spontaneously grown microstructures resemble those deliberately created by human or found in nature,and tremendously modulate surface functionality.These findings open new possibilities for facile and customizable engineering of microstructural surfaces,hierarchical heterostructures,and biomimetic materials.
文摘In order to improve the densification of Si_(3)N_(4) bonded SiC refractories and reduce the nitriding temperature of Si powder,Si_(3)N_(4) bonded SiC refractories were produced by reaction sintering at 1350℃ for 5 h under a carbon embedded atmosphere,using SiC particles and fine powder,and Si powder as the main raw materials,and introducing Ti-Si-Fe alloy extracted from high-titanium blast furnace slag to partially replace the Si powder.The effects of the Ti-Si-Fe alloy addition(0,1.8%,3.6%,5.4%,and 7.2%,by mass)on the nitriding behavior of Si powder,as well as on the mechanical properties and microstructure of the material were investigated,and the nitriding reaction sintering mechanism was also explored.The results show that:(1)with the increase of the Ti-Si-Fe alloy addition,the cold mechanical properties and the hot modulus of rupture of the refractories are obviously improved,and the refractoriness under load exceeds 1700℃;the property enhancement slows down with Ti-Si-Fe alloys addition above 3.6%;(2)Ti-Si-Fe alloy promotes the complete nitridation of Si powder and the reaction sintering of the material at a lower temperature;the volume growth during the nitridation process of the Ti-Si-Fe alloys and Si powder can effectively fill pores,nitriding products improve the bonding state between aggregates and matrix,and that inside matrix,thereby increasing the densification and improving the mechanical properties of the material;(3)after the introduction of Ti-Si-Fe alloys,the liquid phase rich in Ti,Si,N,and Fe components is formed in the reaction system;besides the traditional VS and VLS mechanisms,the dissolution-precipitation mechanism plays a leading role in the formation of short columnar β-Si_(3)N_(4) and granular TiN;and the cross-linked α-Si_(3)N_(4) whisker,short columnar β-Si_(3)N_(4) and granular TiN enhance the mechanical properties of the material.
文摘Clay minerals constitute an important component of the soil system and knowledge of their role in soil fertility is imperative for sustainable soil management and productivity. The aim of this work is to overview the influence of clay minerals on some major soil fertility attributes. The rationale for carrying out this work is that most soil fertility studies rarely incorporate soil mineralogy. Clay minerals, through their physical and chemical properties, affect soil fertility by controlling nutrient supplies and availability, through the sequestration and stabilization of soil organic matter, by controlling soil physical properties through microaggregate formation, by influencing soil acidity and controlling soil microbial population and activity. The main processes involved in these relationships are dissolution-precipitation and adsorption-desorption processes, alongside mechanisms involving the formation of short-range-ordered phases. Although the determination of soil mineralogical properties is very costly and time-consuming, information about a soil’s mineralogy is imperative for a holistic understanding and proper management of soil fertility. Therefore, the development of rapid, low-cost, reliable and efficient techniques of soil mineralogical analysis, directly applicable to soil fertility investigations, constitutes a major challenge. Also, future research should investigate the relationships between clay minerals and soil nitrogen vis-à-vis sequestration and stabilization. Lastly, clay minerals should be considered in studies dealing with soil quality assessment, especially in the choice of soil quality indicators.
基金Project(2015-GX-108A)supported by Qinghai Provincial Science and Technology Support Program,China
文摘The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestite in mild condition was described.Sr element remained in precipitation with formation of Sr(OH)2,while S element entered into leachate with formation of Na2SO4.The effects of initial concentration of NaOH,conversion temperature,liquid-to-solid(L/S)ratio and conversion time on Sr/S ratio of samples for celestite conversion were systematically investigated by experiments.The results demonstrated that the efficiency of Sr/S isolation increased with the initial concentration of NaOH,L/S ratio and conversion time,and decreased with conversion temperature.The maximum conversion ratio of Sr(OH)2 was 93.88%under the optimum condition,whose Sr/S ratio of sample could reach to 41.16.It illustrated that better isolation efficiency of celestite could be achieved in alkaline treatment.The results of SEM-EDS analyses demonstrated that the conversion reaction was a dissolution-precipitation process.
文摘Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite （CHap） are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage increases with decreasing pH values and reaches a maximum at pH=2-3. Under some conditions, the lead residual concentration is below national integrated wastewater discharge standard, even drinking water standard. The removal behavior is a complicated non-homogeneous solid/liquid reaction, which can be described by two stages from kinetic point of view. At the earlier stage, reaction rate is so fast that its kinetic course is intricate, which requires further study. At the latter stage, the rate of reaction becomes slow and the process of reaction accords with one order reaction kinetic equation. Experimental results show that the relationship between reaction rate constant k1 and temperature T accords to Arrhenius Equation, and the activation energy of sorption （Ea） is 11.93 kJ/mol and frequency factor （A） is 2.51 s^-1. X-ray diffraction （XRD）, scanning electron microscopy with an energy dispersive X-ray fluoresence spectrometer （SEM-EDS） and toxicity characteristic leaching procedure （TCLP） test were conducted in this work. It is indicated that the main mechanism is dissolution-precipitation, accompanying with superficial sorption.
基金Supported by National Natural Science Foundation of China (No.51002095)Innovation Foundation of Shanghai Education Committee (No.11YZ86)
文摘Hierarchically nanostructured porous carbonated hydroxyapatite coatings (HNPCs) on Ti6Al4V substrate were fabricated by a two-stage application route: fabrication of nacre coatings (NCs) on Ti6Al4V substrate by electrophoretic technique, and conversion of NCs to HNPCs in a phosphate buffer solution (PBS) by microwave irradiation method. Their samples were characterized by using XRD, FT-IR, SEM, TEM, and N2 adsorption-desorption isotherms. The results show that the microwave irradiation technique improves obviously the conversion rate of NCs to HNPCs as compared with conventional method. After soaking the NCs in the PBS, calcium ions are released from the nacre particles and react with phosphate ions to form carbonated hydroxyapatite nanoparticles. These nanoparticles aggregate to form the plate-like carbonated apatite. The mesopores with a size of about 3.9 nm and macropores with the diameters of 1~4μm exist within and among the carbonated apatite plates, respectively. Simulated body fluid immersion tests reveal that the HNPCs have a good in vitro bioactivity.
