Homogeneous(unseeded)precipitation of magnesium carbonate hydrates by the reaction of MgCl2 with Na2CO3 in supersaturated solutions between 273 and 363K was investigated.The compositions,morphologies and filtration ch...Homogeneous(unseeded)precipitation of magnesium carbonate hydrates by the reaction of MgCl2 with Na2CO3 in supersaturated solutions between 273 and 363K was investigated.The compositions,morphologies and filtration characteristics of the precipitates were studied in detail.The magnesium carbonate hydrates obtained at 313K and in the range of 343-363K showed good morphologies and filtration characteristics.Magnesium oxides(MgO)with high purity(97.6%-99.4%)were obtained by calcining magnesium carbonate hydrates at 1073K.展开更多
In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneo...In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneous precipitation method,using magnesium chloride hexahydrate(MgCl2.6H2O)and urea(CO(NH2)2)as reaction materials.Phase and morphology of the product were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.The results showed that well-crystallized plate-like Mg5(CO3)4(OH)2.4H2O can be prepared at the water bath temperature of 100°C,water bath time of 24 h,the aging time of 5 h after adding organic template agent.The investigation on organic template mediated mechanism shows that the template affects the crystal morphology by changing surface energy of different crystal plane.Through a preliminary study on the growth mechanism of the product,it is found that the generation of the plate-like Mg5(CO3)4(OH)2.4H2O could be explained by two-dimensional nucleation/step growth mechanism.展开更多
The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffracti...The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry （TG-DTG）. The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO3·Mg（OH）2·4H2O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1-1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies （E） were calculated by Flyrm-Wall-Ozawa method. It is obtained from Coats-Redfem＇s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.展开更多
Upsalite®is a mesoporous magnesium carbonate synthesized without using surfactants and therefore highly attractive from environmental and production economy points of view. The material has recently been sugge...Upsalite®is a mesoporous magnesium carbonate synthesized without using surfactants and therefore highly attractive from environmental and production economy points of view. The material has recently been suggested as drug delivery vehicle and as topical bacteriostatic agent. In order to continue exploring these and other bio-related applications of the material, primary biocompatibility studies are needed. Herein we present the first in vivo acute systemic toxicity and skin irritation analyses as well as in vitro cytotoxicity evaluations of Upsalite®. The material was found to be non-toxic for human dermal fibroblasts cells up to a concentration of 1000 μg/ml and 48 h exposure in contrast to the mesoporous silica material SBA-15, used as reference, which significantly affected cell viability at particle concentration of 500 and 1000 μg/ml after the same exposure time. Topical application of Upsalite®resulted in negligible cutaneous reactions in a rabbit skin irritation model and no evidence of significant systemic toxicity was found when saline extracts of Upsalite®were injected in mice. Injection of sesame oil extract, however, resulted in transient weight loss, most likely due to injection of particles, and not toxic leachables. The presented results form the basis for future development of Upsalite®and similar mesoporous materials in biomedical applications and further toxicity as well as biocompatibility studies should be directed towards specific areas of use.展开更多
Peculiar characteristics of soils of Zarafshan valley are salinity with carbonates. It is recommended to introduce large amount of manure or other organic fertilizers in these soils to improve soil reclamation. But cu...Peculiar characteristics of soils of Zarafshan valley are salinity with carbonates. It is recommended to introduce large amount of manure or other organic fertilizers in these soils to improve soil reclamation. But currently there is no possibility to collect so many organic fertilizers in Uzbekistan. That is why other ways of production of organic fertilizers for improving soil fertility were searched. In the experiment, the influence of composts was studied, which prepared from tobacco wastes and manure on agrochemical properties of soils of Zarafshan valley, and production of composts from these industrial wastes, two salted with magnesium carbonates and yield-capacity of com. With the problems that exist in Uzbekistan can be solved at once. These include problems of environmental contamination through wastes and ensuring with organic fertilizers in the irrigated soils. Introduction of composts in the doze of 30 t.ha1 separately and on the background of mineral-NPK （nitrogen, phosphorus and potassium） fertilizers increased the humus content, total NPK and mobile nutritious substances in soil. It is proved that composts, prepared from tobacco wastes with their effect on the yield capacity and quality ofcoru production, can successfully substitute manure. Composts positively influence on the balance of nutritious substances in the system of soil-corn.展开更多
Layered double hydroxides(LDHs)have received extensive attention in many fields such as catalysis,environmental management and medical applications.Typically,expensive soluble metal salts are commonly used as the star...Layered double hydroxides(LDHs)have received extensive attention in many fields such as catalysis,environmental management and medical applications.Typically,expensive soluble metal salts are commonly used as the starting materials for the synthesis of LDHs.Here,we report a novel synthesis route for Mg/Al-LDH by using inexpensive basic magnesium carbonate as the starting material.X-ray diffraction(XRD)and solid-state nuclear magnetic resonance(ssNMR)data show that LDHs with rich defects are formed rapidly at room temperature and good crystallinity can be obtained after further hydrothermal treatment.These results provide a simple,rapid and green preparation method for LDHs.展开更多
Using 1-butyl-3-methyl-imidazolium bromide （BM1MBr） as the supporting electrolyte and magne- sium as the sacrificial anode, a new and highly efficient electrochemically catalytic route was devel- oped for the synthe...Using 1-butyl-3-methyl-imidazolium bromide （BM1MBr） as the supporting electrolyte and magne- sium as the sacrificial anode, a new and highly efficient electrochemically catalytic route was devel- oped for the synthesis of cyclic carbonates from epoxides and CO2. Based on the cooperative action of BMIMBr and an electrogenerated magnesium salt obtained under a N2 atmosphere, CO2 reacted with a wide range of epoxides to readily generate cyclic carbonates in moderate to excellent yields under mild conditions.展开更多
Basic magnesium carbonate microspheres with a red blood cell （RBC）-like appearance and diameters of ~3μm were synthesized by amphiphilic molecule-participated self-assembly under hydrothermal conditions, In the sel...Basic magnesium carbonate microspheres with a red blood cell （RBC）-like appearance and diameters of ~3μm were synthesized by amphiphilic molecule-participated self-assembly under hydrothermal conditions, In the self-assembly, sodium dodecyl benzene sulfonate served as a template for the formation of Mg（OH）2 spherical micelles and also as a reactant precursor that releases CO2 to react with Mg（OH）2. The growth of the microspheres is driven by the continuous generation of new hydrophobic centers because of the consumption of hydrophilic poles （--SO3-）. The surfactant-directed self-assembly can be applied to the synthesis of other carbonate or metallic oxide self-assemblies, indicating that it is a universal self-assembly method for amphiphilic molecules.展开更多
Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining...Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining the precursor. In addition, the effect of MgO whisker addition on sintering and thermal shock resistance of refractory was also investigated. The results show that the thermal decomposition product is MgCO3·3H2O and its morphology is remarkably influenced by the types of additives, and magnesium carbonate whisker with the length of 10-60 μm and length-diameter ratio of 10-20 is successfully prepared when a type of soluble magnesium salt is added. MgO whisker with the length of 10-40 μm is derived from precursor with the heating rate of 1 ℃/min. The thermal shock resistance of refractory is significantly improved by the addition of MgO whisker due to its effect on binding and preventing crack expanding, and the proper amount of whisker addition is around 3%.展开更多
AM30 was inoculated by MgCO_(3) powder with different holding time.The influence of MgO decomposed by MgCO_(3)on the grain refinement effect was mainly discussed in the present study.Three sets of comparative samples ...AM30 was inoculated by MgCO_(3) powder with different holding time.The influence of MgO decomposed by MgCO_(3)on the grain refinement effect was mainly discussed in the present study.Three sets of comparative samples were prepared.They were AM30 alloy inoculated by MgO and pure Mg inoculated by MgO and MgCO_(3).The possible nucleating particles were observed and analyzed by EPMA and SEM.AM30 alloy could be effectively refined by either MgCO_(3)or MgO inoculation.Grain refining efficiency and fading effect of MgO inoculation were better than those of MgCO_(3) inoculation.However,pure Mg could not be refined by these two inoculants.Al is an indispensable element to determine the grain refinement of Mg alloys inoculated by either MgCO_(3)or MgO.MgO should not be the effective substrates forα-Mg phase.A novel grain refining mechanism of MgCO_(3) inoculation on AM30 alloy was proposed by combining experimental results with theoretical calculation,i.e.,MgAl_(2)O_(4) should be the potent nuclei ofα-Mg grain for the AM30 alloy in addition to Al_(4)C_(3).展开更多
Loose sand particles could be cemented to sandstone by bio-cement（microbial induced magnesium carbonate）. The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone c...Loose sand particles could be cemented to sandstone by bio-cement（microbial induced magnesium carbonate）. The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）, respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.展开更多
Micro/nano magnesium carbonate pentahydrate（MgCO3 ·5H2 O） with flower-like morphology was synthesized using magnesite as a substrate and potassium dihydrogen phosphate as an additive. The synthesized samples we...Micro/nano magnesium carbonate pentahydrate（MgCO3 ·5H2 O） with flower-like morphology was synthesized using magnesite as a substrate and potassium dihydrogen phosphate as an additive. The synthesized samples were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The influence of pyrolysis time on crystal morphology was explored. The formation mechanism was investigated on the basis of the characterized results and the crystal structure of MgCO3 ·5H2 O. The results showed that the flower-like MgCO3 ·5H2 O was 1.5-3.0 μm in length and 100-500 nm in diameter and was successfully obtained with a pyrolysis time of 30 min. The formation mechanism of flower-like MgCO3 ·5H2 O is suggested to be the selective adsorption of potassium dihydrogen phosphate on the surface. The process of flower-like crystal growth is as follows： amorphous nanoparticles formation, acicular and rod monocrystal formation, flower-like monocrystal formation, and flower-like polymers（MgCO3 ·5H2 O） crystallization. In the MgCO3 ·5H2 O crystal, the magnesium ion presents two different octahedral coordinations corresponding to2 26 Mg（H O）＋and2 2 2 4 23 [Mg（H O）（CO） ]--, and the chemical formula of the crystal is2 2 6 2 4 23 Mg（H O） Mg（H O）（CO）2.展开更多
This work involves the production of magnesium in the form of Mg(OH)_(2)from serpentinite rock(nickel mine tailing)material followed by conversion into MgCO_(3)using a pressurised fluidised bed(PFB)reactor operating a...This work involves the production of magnesium in the form of Mg(OH)_(2)from serpentinite rock(nickel mine tailing)material followed by conversion into MgCO_(3)using a pressurised fluidised bed(PFB)reactor operating at 400℃-600℃and pressures up to 2.85 MPa.Our approach is rooted in the thermodynamic fact that the reaction between Mg(OH)_(2)and gaseous CO_(2)forming MgCO_(3)and water releases significant amounts of heat.The main problem is,however,the chemical kinetics;the reaction is slow and has to be accelerated in order to be used in an economically viable process for large-scale(~1 Mt/a)CO_(2)sequestration.We have constructed a labscale PFB reactor test-setup for optimising the carbonation reaction.At high enough temperatures and conversion levels the reaction should provide the heat for the proceeding Mg(OH)_(2)production step,making the overall process energy neutral.So far we have been able to achieve a conversion degree of 26%at 500℃and 2.85 MPa after 30 min(particle size 125-212μm).In this paper the test facility and our latest results and progress on CO_(2)mineral carbonation are summarised.Also,the possible integration of the iron as a feedstock for iron and steel production will be briefly addressed.An interesting side-effect of this carbon dioxide capture and storage(CCS)route is that significant amounts of iron are obtained from the serpentinite rock material.This is released during the Mg(OH)_(2)production and can be of great interest to the iron-and steel producing sector,which at the same time is Finland’s largest CO_(2)producer.展开更多
A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The...A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The crystal structure, BET surface area and morphology of the produced cerium zirconium mixed oxides were characterized by X-ray diffraction （XRD）, Bru- mauer-Emmett-Teller （BET） and scanning electron microscopy （SEM） techniques. The reduction-oxidation behavior and oxygen storage capacity （OSC） performance were also studied by temperature programmed reduction （TPR） and oxygen pulse chemical adsorption methods. The XRD results demonstrated that the cerium zirconium mixed oxides obtained by both methods possessed struc ture of cubic solid solution phase. The fresh surface area calcinated at 600 ℃, aged surface area after 1000 ℃and OSC at 500 ℃ of cerium zirconium mixed oxides were determined to be 89.337, 34.784 ma/g, and 567 pmol O2/g for MHC method and 122.010, 46.307 m2/g, and 665 pmol O2/g for AAHC method, respectively.展开更多
Mg-4.0Zn alloy composite reinforced by NiO-coated CNTs （NiO@CNTs） was synthesized by combining ball-milling and a casting process. The yield strength （YS） and elongation to failure of the composite were dramatical...Mg-4.0Zn alloy composite reinforced by NiO-coated CNTs （NiO@CNTs） was synthesized by combining ball-milling and a casting process. The yield strength （YS） and elongation to failure of the composite were dramatically increased by 44.9% and 38.6%, respectively, compared to its alloy counterpart. The signifi- cantly eahanced mechanical properties of the as-synthesized composite are mainly ascribed to an improved interracial bond, grain refinement and good dispersion of CNTs in the matrix via. coating NiO on CNTs. It is shown that the NiO-nanolayer on the CNTs significantly enhances the interfacial bonding strength and effectively prevents the agglomeration of CNTs. NiO@CNTs are, therefore, expected to be a highly sustainable and dispersible reinforcement for magnesium matrix composites with superior performance.展开更多
To verify the formation behaviors and mechanisms of intra-granular acicular ferrite（ IAF） grains nucleated by Mg-Al-O in low carbon steel,the steels containing different Mg contents were refined in a vacuum inductio...To verify the formation behaviors and mechanisms of intra-granular acicular ferrite（ IAF） grains nucleated by Mg-Al-O in low carbon steel,the steels containing different Mg contents were refined in a vacuum induction furnace. The effect of Mg addition on the formation of IAF structure in Al-killed low carbon steel was investigated by optical microscope（ OM） and scanning electron microscope with energy dispersive X-ray spectroscope（ SEM-EDX）. It reveals that the IAFs are only detected in Mg-added steels,and the volume fraction of IAF increases with the Mg concentration from 8 × 10^（-6） to 26 × 10^（-6）. It shows that not only the MgO-Al_2O_3-MnS and MgO-Al_2O_3-P_2O_5 particles are the effective nucleation sites for IAF,but also the pure MgO·Al_2O_3 phase can promote the ferrite nucleation. A Mn-depletion zone（ MDZ） is characterized adjacent to the MgO-Al_2O_3-MnS,which is believed to be one of the possible mechanisms to explain the IAF nucleation. The MDZ around the MgO-Al_2O_3-MnS inclusion would be induced by the Mn S precipitation on the inclusion. It seems that the ability of Mg-containing inclusions to induce the nucleation of ferrite might be attributed to a new mechanism,i. e.,the Prich zone formed on a few Mg-Al-O inclusions might be another factor for promoting the IAF formation.展开更多
Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-mil...Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-milling was employed to pre-disperse CNTs on Zinc（Zn） flakes.Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes.The ultrasonic melt processing further dispersed CNTs in the Mg melt,especially tiny CNT clusters.Thus,a uniform dispersion of CNTs was achieved in the as-cast composites.Hot extrusion further improved the distribution of CNTs.CNTs increased both the strength and elongation of the matrix alloy.Notably,the elongation of the matrix alloy was enhanced by 40%.Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.展开更多
基金Supported by the National Natural Science Foundation of China （20876161） and the National Basic Research Program of China （2007CB613501, 2009CB219904）.
文摘Homogeneous(unseeded)precipitation of magnesium carbonate hydrates by the reaction of MgCl2 with Na2CO3 in supersaturated solutions between 273 and 363K was investigated.The compositions,morphologies and filtration characteristics of the precipitates were studied in detail.The magnesium carbonate hydrates obtained at 313K and in the range of 343-363K showed good morphologies and filtration characteristics.Magnesium oxides(MgO)with high purity(97.6%-99.4%)were obtained by calcining magnesium carbonate hydrates at 1073K.
基金Project(51374155)supported by the National Natural Science Foundation of ChinaProject(2014BCB034)supported by the Hubei Province Key Technology R&D Program,ChinaProject(2014CFB796)supported by the Natural Science Foundation of Hubei Province of China
文摘In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneous precipitation method,using magnesium chloride hexahydrate(MgCl2.6H2O)and urea(CO(NH2)2)as reaction materials.Phase and morphology of the product were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.The results showed that well-crystallized plate-like Mg5(CO3)4(OH)2.4H2O can be prepared at the water bath temperature of 100°C,water bath time of 24 h,the aging time of 5 h after adding organic template agent.The investigation on organic template mediated mechanism shows that the template affects the crystal morphology by changing surface energy of different crystal plane.Through a preliminary study on the growth mechanism of the product,it is found that the generation of the plate-like Mg5(CO3)4(OH)2.4H2O could be explained by two-dimensional nucleation/step growth mechanism.
基金Project(20876160) supported by the National Natural Science Foundation of China
文摘The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry （TG-DTG）. The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO3·Mg（OH）2·4H2O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1-1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies （E） were calculated by Flyrm-Wall-Ozawa method. It is obtained from Coats-Redfem＇s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.
基金The Swedish Research Council and the Swedish Energy Agency are gratefully acknowledged for financial supportthe China Scholarship Council(CSC)for financial support.
文摘Upsalite®is a mesoporous magnesium carbonate synthesized without using surfactants and therefore highly attractive from environmental and production economy points of view. The material has recently been suggested as drug delivery vehicle and as topical bacteriostatic agent. In order to continue exploring these and other bio-related applications of the material, primary biocompatibility studies are needed. Herein we present the first in vivo acute systemic toxicity and skin irritation analyses as well as in vitro cytotoxicity evaluations of Upsalite®. The material was found to be non-toxic for human dermal fibroblasts cells up to a concentration of 1000 μg/ml and 48 h exposure in contrast to the mesoporous silica material SBA-15, used as reference, which significantly affected cell viability at particle concentration of 500 and 1000 μg/ml after the same exposure time. Topical application of Upsalite®resulted in negligible cutaneous reactions in a rabbit skin irritation model and no evidence of significant systemic toxicity was found when saline extracts of Upsalite®were injected in mice. Injection of sesame oil extract, however, resulted in transient weight loss, most likely due to injection of particles, and not toxic leachables. The presented results form the basis for future development of Upsalite®and similar mesoporous materials in biomedical applications and further toxicity as well as biocompatibility studies should be directed towards specific areas of use.
文摘Peculiar characteristics of soils of Zarafshan valley are salinity with carbonates. It is recommended to introduce large amount of manure or other organic fertilizers in these soils to improve soil reclamation. But currently there is no possibility to collect so many organic fertilizers in Uzbekistan. That is why other ways of production of organic fertilizers for improving soil fertility were searched. In the experiment, the influence of composts was studied, which prepared from tobacco wastes and manure on agrochemical properties of soils of Zarafshan valley, and production of composts from these industrial wastes, two salted with magnesium carbonates and yield-capacity of com. With the problems that exist in Uzbekistan can be solved at once. These include problems of environmental contamination through wastes and ensuring with organic fertilizers in the irrigated soils. Introduction of composts in the doze of 30 t.ha1 separately and on the background of mineral-NPK （nitrogen, phosphorus and potassium） fertilizers increased the humus content, total NPK and mobile nutritious substances in soil. It is proved that composts, prepared from tobacco wastes with their effect on the yield capacity and quality ofcoru production, can successfully substitute manure. Composts positively influence on the balance of nutritious substances in the system of soil-corn.
基金supported by National Key R&D Program of China(2021YFA1502803)the National Natural Science Foundation of China(NSFC)(21972066 and 91745202)+3 种基金NSFC-Royal Society Joint Program(21661130149)Luming Peng thanks the Royal Society and Newton Fund for a Royal Society-Newton Advanced Fellowshipsupported by the Research Funds for the Frontiers Science Center for Critical Earth Material Cycling,Nanjing Universitya Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Layered double hydroxides(LDHs)have received extensive attention in many fields such as catalysis,environmental management and medical applications.Typically,expensive soluble metal salts are commonly used as the starting materials for the synthesis of LDHs.Here,we report a novel synthesis route for Mg/Al-LDH by using inexpensive basic magnesium carbonate as the starting material.X-ray diffraction(XRD)and solid-state nuclear magnetic resonance(ssNMR)data show that LDHs with rich defects are formed rapidly at room temperature and good crystallinity can be obtained after further hydrothermal treatment.These results provide a simple,rapid and green preparation method for LDHs.
基金supported by the National Natural Science Foundation of China(21303053)the Open Project of State Key Laboratory of Chemical Engineering(SKLChE-14C02)~~
文摘Using 1-butyl-3-methyl-imidazolium bromide （BM1MBr） as the supporting electrolyte and magne- sium as the sacrificial anode, a new and highly efficient electrochemically catalytic route was devel- oped for the synthesis of cyclic carbonates from epoxides and CO2. Based on the cooperative action of BMIMBr and an electrogenerated magnesium salt obtained under a N2 atmosphere, CO2 reacted with a wide range of epoxides to readily generate cyclic carbonates in moderate to excellent yields under mild conditions.
基金supported by the National Natural Science Foundation of China(No.21206191)the Science Foundation of China University of Petroleum,Beijing(No.2462013YXBS007)
文摘Basic magnesium carbonate microspheres with a red blood cell （RBC）-like appearance and diameters of ~3μm were synthesized by amphiphilic molecule-participated self-assembly under hydrothermal conditions, In the self-assembly, sodium dodecyl benzene sulfonate served as a template for the formation of Mg（OH）2 spherical micelles and also as a reactant precursor that releases CO2 to react with Mg（OH）2. The growth of the microspheres is driven by the continuous generation of new hydrophobic centers because of the consumption of hydrophilic poles （--SO3-）. The surfactant-directed self-assembly can be applied to the synthesis of other carbonate or metallic oxide self-assemblies, indicating that it is a universal self-assembly method for amphiphilic molecules.
基金Projects(50874130,50974034)supported by the National Natural Science Foundation of ChinaProject(FMRU2008K01)supported by the Open Research Fund of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education,Wuhan University of Science and Technology,China
文摘Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining the precursor. In addition, the effect of MgO whisker addition on sintering and thermal shock resistance of refractory was also investigated. The results show that the thermal decomposition product is MgCO3·3H2O and its morphology is remarkably influenced by the types of additives, and magnesium carbonate whisker with the length of 10-60 μm and length-diameter ratio of 10-20 is successfully prepared when a type of soluble magnesium salt is added. MgO whisker with the length of 10-40 μm is derived from precursor with the heating rate of 1 ℃/min. The thermal shock resistance of refractory is significantly improved by the addition of MgO whisker due to its effect on binding and preventing crack expanding, and the proper amount of whisker addition is around 3%.
基金the National Natural Science Foundation of China(51574127)Natural Science Foundation of Guangdong Province(2014A030313221).
文摘AM30 was inoculated by MgCO_(3) powder with different holding time.The influence of MgO decomposed by MgCO_(3)on the grain refinement effect was mainly discussed in the present study.Three sets of comparative samples were prepared.They were AM30 alloy inoculated by MgO and pure Mg inoculated by MgO and MgCO_(3).The possible nucleating particles were observed and analyzed by EPMA and SEM.AM30 alloy could be effectively refined by either MgCO_(3)or MgO inoculation.Grain refining efficiency and fading effect of MgO inoculation were better than those of MgCO_(3) inoculation.However,pure Mg could not be refined by these two inoculants.Al is an indispensable element to determine the grain refinement of Mg alloys inoculated by either MgCO_(3)or MgO.MgO should not be the effective substrates forα-Mg phase.A novel grain refining mechanism of MgCO_(3) inoculation on AM30 alloy was proposed by combining experimental results with theoretical calculation,i.e.,MgAl_(2)O_(4) should be the potent nuclei ofα-Mg grain for the AM30 alloy in addition to Al_(4)C_(3).
基金Funded by the National Natural Science Foundation of China(No.51072035)the Ph D Program’s Foundation of Ministry of Education of China(No.20090092110029)+2 种基金the Research Innovation Program for College Graduates of Jiangsu Province(No.CXZZ_0145)the Scientific Research Foundation of Graduate School of Southeast University(Nos.YBJJ1127 and YBPY1208)the Ph D Program’s Foundation Funded by the Science and Technology Review(kjdb2011001)
文摘Loose sand particles could be cemented to sandstone by bio-cement（microbial induced magnesium carbonate）. The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）, respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.
基金financially supported by the National Natural Science Foundation of China (No. 51074037)
文摘Micro/nano magnesium carbonate pentahydrate（MgCO3 ·5H2 O） with flower-like morphology was synthesized using magnesite as a substrate and potassium dihydrogen phosphate as an additive. The synthesized samples were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The influence of pyrolysis time on crystal morphology was explored. The formation mechanism was investigated on the basis of the characterized results and the crystal structure of MgCO3 ·5H2 O. The results showed that the flower-like MgCO3 ·5H2 O was 1.5-3.0 μm in length and 100-500 nm in diameter and was successfully obtained with a pyrolysis time of 30 min. The formation mechanism of flower-like MgCO3 ·5H2 O is suggested to be the selective adsorption of potassium dihydrogen phosphate on the surface. The process of flower-like crystal growth is as follows： amorphous nanoparticles formation, acicular and rod monocrystal formation, flower-like monocrystal formation, and flower-like polymers（MgCO3 ·5H2 O） crystallization. In the MgCO3 ·5H2 O crystal, the magnesium ion presents two different octahedral coordinations corresponding to2 26 Mg（H O）＋and2 2 2 4 23 [Mg（H O）（CO） ]--, and the chemical formula of the crystal is2 2 6 2 4 23 Mg（H O） Mg（H O）（CO）2.
基金funded(2008-2011)by the Academy of Finland—Sustainable Energy programme(SusEn).
文摘This work involves the production of magnesium in the form of Mg(OH)_(2)from serpentinite rock(nickel mine tailing)material followed by conversion into MgCO_(3)using a pressurised fluidised bed(PFB)reactor operating at 400℃-600℃and pressures up to 2.85 MPa.Our approach is rooted in the thermodynamic fact that the reaction between Mg(OH)_(2)and gaseous CO_(2)forming MgCO_(3)and water releases significant amounts of heat.The main problem is,however,the chemical kinetics;the reaction is slow and has to be accelerated in order to be used in an economically viable process for large-scale(~1 Mt/a)CO_(2)sequestration.We have constructed a labscale PFB reactor test-setup for optimising the carbonation reaction.At high enough temperatures and conversion levels the reaction should provide the heat for the proceeding Mg(OH)_(2)production step,making the overall process energy neutral.So far we have been able to achieve a conversion degree of 26%at 500℃and 2.85 MPa after 30 min(particle size 125-212μm).In this paper the test facility and our latest results and progress on CO_(2)mineral carbonation are summarised.Also,the possible integration of the iron as a feedstock for iron and steel production will be briefly addressed.An interesting side-effect of this carbon dioxide capture and storage(CCS)route is that significant amounts of iron are obtained from the serpentinite rock material.This is released during the Mg(OH)_(2)production and can be of great interest to the iron-and steel producing sector,which at the same time is Finland’s largest CO_(2)producer.
基金Project supported by Twelfth Five-Year National Science and Technology Pillar Program (2012BAE01B02)Eleventh Five-Year National 863 Program (2010AA03A405)
文摘A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The crystal structure, BET surface area and morphology of the produced cerium zirconium mixed oxides were characterized by X-ray diffraction （XRD）, Bru- mauer-Emmett-Teller （BET） and scanning electron microscopy （SEM） techniques. The reduction-oxidation behavior and oxygen storage capacity （OSC） performance were also studied by temperature programmed reduction （TPR） and oxygen pulse chemical adsorption methods. The XRD results demonstrated that the cerium zirconium mixed oxides obtained by both methods possessed struc ture of cubic solid solution phase. The fresh surface area calcinated at 600 ℃, aged surface area after 1000 ℃and OSC at 500 ℃ of cerium zirconium mixed oxides were determined to be 89.337, 34.784 ma/g, and 567 pmol O2/g for MHC method and 122.010, 46.307 m2/g, and 665 pmol O2/g for AAHC method, respectively.
基金supported by the National Key Research and Development Program(Nos.2016YFB0701201,2016YFB0701203)National Natural Science Foundation of China(Nos.51671101,51464034)+2 种基金Natural Science foundation of Jiangxi Province(No.20161ACB21003)Excellent Young Talent plan of Jiangxi Province(No.20162BCB23013)the Scientific Research Foundation of the Education Department of Jiangxi Province(Nos.GJJ151309,GJJ150010)
文摘Mg-4.0Zn alloy composite reinforced by NiO-coated CNTs （NiO@CNTs） was synthesized by combining ball-milling and a casting process. The yield strength （YS） and elongation to failure of the composite were dramatically increased by 44.9% and 38.6%, respectively, compared to its alloy counterpart. The signifi- cantly eahanced mechanical properties of the as-synthesized composite are mainly ascribed to an improved interracial bond, grain refinement and good dispersion of CNTs in the matrix via. coating NiO on CNTs. It is shown that the NiO-nanolayer on the CNTs significantly enhances the interfacial bonding strength and effectively prevents the agglomeration of CNTs. NiO@CNTs are, therefore, expected to be a highly sustainable and dispersible reinforcement for magnesium matrix composites with superior performance.
基金Item Sponsored by National Natural Science Foundation of China(51374059,51374060)Scientific Research Fund of Liaoning Provincial Education Department of China(2012221013)
文摘To verify the formation behaviors and mechanisms of intra-granular acicular ferrite（ IAF） grains nucleated by Mg-Al-O in low carbon steel,the steels containing different Mg contents were refined in a vacuum induction furnace. The effect of Mg addition on the formation of IAF structure in Al-killed low carbon steel was investigated by optical microscope（ OM） and scanning electron microscope with energy dispersive X-ray spectroscope（ SEM-EDX）. It reveals that the IAFs are only detected in Mg-added steels,and the volume fraction of IAF increases with the Mg concentration from 8 × 10^（-6） to 26 × 10^（-6）. It shows that not only the MgO-Al_2O_3-MnS and MgO-Al_2O_3-P_2O_5 particles are the effective nucleation sites for IAF,but also the pure MgO·Al_2O_3 phase can promote the ferrite nucleation. A Mn-depletion zone（ MDZ） is characterized adjacent to the MgO-Al_2O_3-MnS,which is believed to be one of the possible mechanisms to explain the IAF nucleation. The MDZ around the MgO-Al_2O_3-MnS inclusion would be induced by the Mn S precipitation on the inclusion. It seems that the ability of Mg-containing inclusions to induce the nucleation of ferrite might be attributed to a new mechanism,i. e.,the Prich zone formed on a few Mg-Al-O inclusions might be another factor for promoting the IAF formation.
基金supported by the National Natural Science Foundation of China(Grant No.51471059 and 51671066)the China Postdoctoral Science Foundation(Grant No.2014T70328)
文摘Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-milling was employed to pre-disperse CNTs on Zinc（Zn） flakes.Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes.The ultrasonic melt processing further dispersed CNTs in the Mg melt,especially tiny CNT clusters.Thus,a uniform dispersion of CNTs was achieved in the as-cast composites.Hot extrusion further improved the distribution of CNTs.CNTs increased both the strength and elongation of the matrix alloy.Notably,the elongation of the matrix alloy was enhanced by 40%.Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.
