Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg...Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg(OH)_(2)layer,especially that formed in a natural condition,cannot provide desirable corrosion resistance in the community of corrosion and protection.Here,several Mg(OH)_(2)coatings were prepared by changing the pH values of sodium hydroxide solutions.These coatings were composed of innumerable nanoplatelets with different orientations and showed distinguished capability in corrosion resistance.The nanoplatelets were well-oriented with their ab-planes parallel to,instead of perpendicular to,the magnesium alloy surface by raising the pH value to 14.0.This specific orientation resulted in the optimal coating showing long-term corrosion protection in both in vitro and in vivo environments and good osteogenic capability.These finds manifest that the environment-friendly Mg(OH)_(2)coating can also provide comparable and better corrosion protection than many traditional chemical conversion films(such as phosphate,and fluoride).展开更多
The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wast...The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wastewater treatment filed was comprehensively commentated.Meanwhile,the prospects of application were discussed.Considering the magnesium resources in China were characterized with rich classes,abundant reserves,vast distribution and high quality,it's important to make great efforts to research and exploit magnesium products,especially the exploitation of their meticulous use way.It had the practical significance for the sustainable development of economy in China.展开更多
To further enhance the corrosion resistance of the porous micro-arc oxidation(MAO) ceramic layers on AZ31 magnesium alloy, superhydrophobic Mg-Al layered double hydroxide(LDH) coating was fabricated on MAO-coated AZ31...To further enhance the corrosion resistance of the porous micro-arc oxidation(MAO) ceramic layers on AZ31 magnesium alloy, superhydrophobic Mg-Al layered double hydroxide(LDH) coating was fabricated on MAO-coated AZ31 alloy by using in-situ growth method followed by surface modification with stearic acid. The characteristics of different coatings were investigated by XRD, SEM and EDS. The effect of the hydrothermal treatment time on the formation of the LDH coatings was studied. The results demonstrated that the micro-pores and cracks of MAO coating were gradually sealed via in-situ growing LDH with prolonging hydrothermal treating time. Electrochemical measurement displayed that the lowest corrosion current density, the most positive corrosion potential and the highest impedance modulus were observed for superhydrophobic LDH/MAO coating compared with those of MAO coating and LDH/MAO coating. Immersion experiment proved that the superhydrophobic LDH/MAO coating with the active anti-corrosion capability significantly enhanced the long-term corrosion protection for MAO coated alloy.展开更多
Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant sol...Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties(e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index(LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.展开更多
In this work, we demonstrate an in situ phase conversion from basic magnesium chloride(BMC) into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of...In this work, we demonstrate an in situ phase conversion from basic magnesium chloride(BMC) into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of magnesium hydroxide whiskers prepared at different reaction temperature, alkali concentration and organic solvent were analyzed by X-ray diffraction(XRD) and scanning electronic microscope(SEM). It was found that when one of the organic solvents such as absolute ethyl alcohol, butanol, polyethylene glycol(PEG-400), acetone, et al. was selected as the template, the precursor BMC can transform into whisker-like magnesium hydroxide through precipitate transformation in low temperature and non-hydrothermal system. It can be reasonably explained that the regulation of Mg^2+ solubility by those organic solvents and the sustained release of Mg^2+ dissolution by organic adsorption played a significant role in the formation of magnesium hydroxide whisker via BMC whisker as the precursor.展开更多
Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurr...Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurry bubble column reactor was described,and a reliable computational model was developed.The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance.The results show that the mass transfer process of CO2 absorbed by Mg(OH)2 slurry is mainly liquid-controlled,and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient.High concentration of CO2 has an adverse effect on its absorption because it leads to the fast deposition of MgCO3·3H2O crystals on the surfaces of unreacted Mg(OH)2 particles,reducing the utilization ratio of magnesium hydroxide.Meanwhile,high CO3^2– ion concentration limits the dissolution of MgCO3 to absorb CO2 continually.Concentration of 0.05 mol/L Mg(OH)2,15%vol CO2 gas and operation temperature at 35℃are recommended for this CO2 capture system.展开更多
The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composit...The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composite were firstly subjected to a homogenization heat treatment at 450 ℃ and then an open-die forging at 450 ℃. The results indicated that the presence of reinforcing particles led to grain refinement and improvement of dynamic recrystallization. The forging process was more effective to eliminate the porosity in the cast alloy workpiece. Microhardness of the forged composite was increased by up to 80% and 16%, in comparison with those of the cast and forged alloy samples, respectively. Ultimate tensile strength and maximum tensile strain of the composite were improved by up to 45% and 23%, compared with those of the forged alloy in similar regions. These enhancements were respectively 50% and 37% in the compression test. The composite exhibited a fatigue life improvement in the region with low applied strain;however, a degradation was observed in the high applied strain region. Unlike AZ31 B samples, tensile, compressive and high cycle fatigue behaviors of the composite showed less sensitivity to the applied strain, which can be attributed to the amount of porosity in the samples before and after the hot-forging.展开更多
In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxide...In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.展开更多
Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a su...Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a surface modifier, magnesium chloride hexahydrate in the presence of ethanol as a precursor, and sodium hydroxide as a precipitant. The products were characterized by Fourier transform infrared spectroscopy(FTIR), Field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD), and thermogravimetry-differential scanning calorimetry(TG-DSC). Compatibility with organic solutions was determined by sedimentation tests. The prepared nanoparticles exhibited regular hexagonal lamella with an average diameter of 30 nm when OA is added to the reaction system; this result indicates that OA regulates the morphology of the Mg(OH)_2nanoparticles.XRD revealed that the high-purity Mg(OH)_2product presents a brucite structure, and the I_(001)/I_(101) of hydrophobic Mg(OH)_2(0.86) was higher than that of the blank Mg(OH)_2(0.63). FTIR analysis showed that OA bonded to the surface of the Mg(OH)_2. Compared with the blank Mg(OH)_2product, the product obtained through the proposed method possesses excellent hydrophobic properties, including a high water contact angle of 101.4° and good compatibility with liquid paraffin. TG-DSC analysis indicated that the total percentage of mass loss of hydrophobic Mg(OH)_2(40.88%) was higher than that of the blank Mg(OH)_2product(33.18%). The in situ surface modification method proposed in this work presents potential use in the large-scale production of Mg(OH)_2nanoparticles.展开更多
8-hydroxyquinoline(8-HQ)intercalated layered double hydroxides(LDH)film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy.The LDH,LDH/sol-gel,and LDH@HQ/sol-gel ...8-hydroxyquinoline(8-HQ)intercalated layered double hydroxides(LDH)film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy.The LDH,LDH/sol-gel,and LDH@HQ/sol-gel coatings were analyzed using the scanning electron microscopy(SEM),field emission scanning electron microscopy(FESEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),atomic force microscopy(AFM),and electrochemical impedance spectroscopy(EIS)methods.The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets.The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings.Also,almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness.Although the LDH film had the same impedance behavior as the alloy sample in 3.5wt%NaCl solution,its corrosion resistance was much higher,which could be due to its barrier properties as well as to the trap-ping of the chloride ions.Similar to the LDH film,the corrosion resistance of the LDH/sol-gel composite diminished with increasing the ex-posure time.However,its values were much higher than that of the LDH film,which was mainly related to the sealing of the solution path-ways.The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.展开更多
The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis(diphenyl phosphate) (BDP) and resorcinol bis(diphenyl phosphate) (RDP)] combined with magn...The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis(diphenyl phosphate) (BDP) and resorcinol bis(diphenyl phosphate) (RDP)] combined with magnesium hydroxide (MH) in polyamide 6 (PA6) have been investigated. Combining 5 wt% BDP, 50 wt% MH imparts a limiting oxygen index (LOI) of 40.9% and UL94 V-0 rating to PA6, meanwhile the peak rate of smoke release (pRSR), total release of smoke (TSR) and Izod notched impact strength are 41%, 33% and 233% relative to the corresponding value of 55 wt% MH without BDP, respectively. Dynamic mechanical analysis (DMA) indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP. Furthermore, based on the comprehensive analysis of thermogravimetry (TG), cone calorimeter and SEM-EDX investigations, possible flame retardancy and smoke suppression mechanisms were revealed. Besides the fuel dilution and barrier effect of MH, the combination of MH and RDP shows an additional flame inhibition effect. The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.展开更多
Poly[bis(phenoxyphosphazene)](PBPP) and magnesium hydroxide(MH) are used as a flame retardant blend with low-density polyethylene(LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-L...Poly[bis(phenoxyphosphazene)](PBPP) and magnesium hydroxide(MH) are used as a flame retardant blend with low-density polyethylene(LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-LDPE blend composites on flame retardance and electron beam irradiation. The structure, morphology,and properties of the blend composites irradiated by an electron beam to different absorbed doses were characterized. The results indicated that PBPP provides lubrication during processing. As the PBPP content in the blend increases the melt flow rate at 20 phr MH, meaning the material is easier to process. The higher the PBPP content, the higher the limiting-oxygen index. The elongation at the break of the PBPP containing composites(at 50 phr MH) was evidently higher than the non-PBPP ones at different absorbed doses by electron beam irradiation. The thermogravimetric analysis results indicated that the improved mechanical property, resulting from electron-beam irradiation, could be attributed to the consumption of PBPP.展开更多
A novel EVA/unmodified nano-magnesium hydroxide (NMH)/silicone rubber ternary nanocomposite was prepared by using a special compound flame retardant of NMH and silicone rubber (CFR). The flammability of the ternar...A novel EVA/unmodified nano-magnesium hydroxide (NMH)/silicone rubber ternary nanocomposite was prepared by using a special compound flame retardant of NMH and silicone rubber (CFR). The flammability of the ternary composite was studied by cone calorimeter test (CCT). Synergistic effect on flame retardancy was found between silicone rubber and NMH. EVA/CFR ternary nanocomposite showed the lowest peak heat release rate (PHRR) and mass loss rate (MLR) among the samples of virgin EVA, EVA composites. The synergistic flame retardancy of silicone rubber and NMH in EVA system is attributed to the enhanced char layers in the condensed phase that prevents the heat and mass transfer in the fire.展开更多
Mg(OH)2 nano-particles with fiber-like morphology were prepared by chemical precipitation process,with the bittern from Qinghai Salt Lakes used as Mg2+ raw material and ammonia water as precipitator. The influence of ...Mg(OH)2 nano-particles with fiber-like morphology were prepared by chemical precipitation process,with the bittern from Qinghai Salt Lakes used as Mg2+ raw material and ammonia water as precipitator. The influence of aging procedure on the Mg(OH)2 crystal was investigated by TEM and crystalline size calculation. The Mg(OH)2 nano-particles were characterized by XRD,SEM,TEM and TG-DTA methods. The results indicate that the Mg(OH)2 nano-particles with perfect crystal are obtained after aging procedure above 50 ℃,and the grain size increases with increasing aging temperature and prolonging aging time. Mg(OH)2 particles with fiber-like morphology,20-60 nm in diameter and 300-500 nm in length are observed,Mg(OH)2 will decompose into MgO at temperature range 347-623 ℃.展开更多
The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that ...The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that the calculated IEP values with the modified Yoon′s equation agreed well with the experimental ones. With the increase of the ionic radius of monovalent anions (Cl -, Br -, I -) the ζ potential decreased. The same was true for CO 2- 3, SO 2- 4 but the sign of the Y- potential reversed from positive to negative. For Al 3+ , Ca 2+ , Mg 2+ , however, the ζ potential increased with the increase of the concentration of Al 3+ , Ca 2+ , Mg 2+ .展开更多
The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV inc...The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV increased with the increase of the ratio of Al/Mg and with the peptizing temperature. AlIV originated from the so-called Al13 polymer with the structure of one Al tetrahedron surrounded by twelve Al octahedrons.展开更多
Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of th...Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of the variable charge component. The calculated values with modified Yoon's equation agreed with the experimental values.展开更多
Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at d...Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at different pH values (pH range from 8.0 to 12.0). The surface properties of grafted γ-APS on MH surface as a function of solution pH value were studied using elemental analysis,Fourier transform infrared spectroscopy and zeta potential measurement. The results show that hydrolysis and condensation of γ-APS are activated in alkaline solution and lead to multilayer adsorption of γ-APS molecules on the surface of MH. The type of adsorption orientation of γ-APS on MH surface is a function of coverage density that is altered by changing solution pH value. At low coverage density (e.g. 55 nm-2),γ-APS molecules are preferentially adsorbed to the surface with the silicon moiety towards the surface,and increasing coverage density (e.g. 90 nm-2) leads to parallel orientation. At an even higher coverage density (e.g. 115 nm-2),γ-APS molecules bond to the surface with the amino moiety towards the surface.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
Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, el...Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy(SEM), film thickness meter, X-ray diffraction (XRD), energy disperse spectroscopy(EDS) and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,52271073)the Sichuan Science and Technology Program(2024NSFJQ0034)+3 种基金the Central Government Guided Special Program(No.2021ZYD0049)the Young Elite Scientists Sponsorship Program by CAST(YESS,2018QNRC001)the GDPH Supporting Fund for Talent Program(KY0120220137)the Scientific and Technological Projects of Guangzhou,China(202002030283).
文摘Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg(OH)_(2)layer,especially that formed in a natural condition,cannot provide desirable corrosion resistance in the community of corrosion and protection.Here,several Mg(OH)_(2)coatings were prepared by changing the pH values of sodium hydroxide solutions.These coatings were composed of innumerable nanoplatelets with different orientations and showed distinguished capability in corrosion resistance.The nanoplatelets were well-oriented with their ab-planes parallel to,instead of perpendicular to,the magnesium alloy surface by raising the pH value to 14.0.This specific orientation resulted in the optimal coating showing long-term corrosion protection in both in vitro and in vivo environments and good osteogenic capability.These finds manifest that the environment-friendly Mg(OH)_(2)coating can also provide comparable and better corrosion protection than many traditional chemical conversion films(such as phosphate,and fluoride).
基金Supported by The National Science Research Guidance Plan Project of Education Department in Hebei Province (Z2009110 )The Science & Technology Research and Development Guidance Plan of Baoding City in 2009 (the Second Batch) (09ZF075)The Natural Science Funds of Hebei Province (B2005000105)
文摘The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wastewater treatment filed was comprehensively commentated.Meanwhile,the prospects of application were discussed.Considering the magnesium resources in China were characterized with rich classes,abundant reserves,vast distribution and high quality,it's important to make great efforts to research and exploit magnesium products,especially the exploitation of their meticulous use way.It had the practical significance for the sustainable development of economy in China.
基金Project(17JS083) supported by the Key Laboratory Program of Shaanxi Education Department,ChinaProject(2016JZ018) supported by the Key Program of Natural Science Research of Shaanxi Province,ChinaProject(51701162) supported by the National Natural Science Foundation of China
文摘To further enhance the corrosion resistance of the porous micro-arc oxidation(MAO) ceramic layers on AZ31 magnesium alloy, superhydrophobic Mg-Al layered double hydroxide(LDH) coating was fabricated on MAO-coated AZ31 alloy by using in-situ growth method followed by surface modification with stearic acid. The characteristics of different coatings were investigated by XRD, SEM and EDS. The effect of the hydrothermal treatment time on the formation of the LDH coatings was studied. The results demonstrated that the micro-pores and cracks of MAO coating were gradually sealed via in-situ growing LDH with prolonging hydrothermal treating time. Electrochemical measurement displayed that the lowest corrosion current density, the most positive corrosion potential and the highest impedance modulus were observed for superhydrophobic LDH/MAO coating compared with those of MAO coating and LDH/MAO coating. Immersion experiment proved that the superhydrophobic LDH/MAO coating with the active anti-corrosion capability significantly enhanced the long-term corrosion protection for MAO coated alloy.
基金Supported by the National Natural Science Foundation of China(21376229)the Science and Technology of Shanxi Province(2015031019-5)the Natural Science Foundation for Young Scientists of Shanxi Province(2015021033)
文摘Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties(e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index(LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.
基金Supported by the National Basic Research Program of China(2010CB933501,2013CB934302)the Outstanding Youth Fund(21125730)+3 种基金the National Science Foundation Grant(21273237,21103191)the Knowledge Innovation Program of the Chinese Academy of Sciences(KJCX2-YW-N50,KJCX2-EW-J02)the Technology Key Project of Fujian Province(2013H0058)the Fund of Fujian Key Laboratory of Nanomaterials(2006L2005)
文摘In this work, we demonstrate an in situ phase conversion from basic magnesium chloride(BMC) into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of magnesium hydroxide whiskers prepared at different reaction temperature, alkali concentration and organic solvent were analyzed by X-ray diffraction(XRD) and scanning electronic microscope(SEM). It was found that when one of the organic solvents such as absolute ethyl alcohol, butanol, polyethylene glycol(PEG-400), acetone, et al. was selected as the template, the precursor BMC can transform into whisker-like magnesium hydroxide through precipitate transformation in low temperature and non-hydrothermal system. It can be reasonably explained that the regulation of Mg^2+ solubility by those organic solvents and the sustained release of Mg^2+ dissolution by organic adsorption played a significant role in the formation of magnesium hydroxide whisker via BMC whisker as the precursor.
基金Project(21878338)supported by the National Natural Science Foundation of ChinaProject(2015BAL04B02)supported by the National key Technology R&D Program of China+1 种基金Project(2018K2038)supported by the key Research and Development Project of Hunan Province,ChinaProject supported by Hunan Collaborative Innovation Center of Building Energy Conservation&Environmental Control,China
文摘Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurry bubble column reactor was described,and a reliable computational model was developed.The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance.The results show that the mass transfer process of CO2 absorbed by Mg(OH)2 slurry is mainly liquid-controlled,and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient.High concentration of CO2 has an adverse effect on its absorption because it leads to the fast deposition of MgCO3·3H2O crystals on the surfaces of unreacted Mg(OH)2 particles,reducing the utilization ratio of magnesium hydroxide.Meanwhile,high CO3^2– ion concentration limits the dissolution of MgCO3 to absorb CO2 continually.Concentration of 0.05 mol/L Mg(OH)2,15%vol CO2 gas and operation temperature at 35℃are recommended for this CO2 capture system.
文摘The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composite were firstly subjected to a homogenization heat treatment at 450 ℃ and then an open-die forging at 450 ℃. The results indicated that the presence of reinforcing particles led to grain refinement and improvement of dynamic recrystallization. The forging process was more effective to eliminate the porosity in the cast alloy workpiece. Microhardness of the forged composite was increased by up to 80% and 16%, in comparison with those of the cast and forged alloy samples, respectively. Ultimate tensile strength and maximum tensile strain of the composite were improved by up to 45% and 23%, compared with those of the forged alloy in similar regions. These enhancements were respectively 50% and 37% in the compression test. The composite exhibited a fatigue life improvement in the region with low applied strain;however, a degradation was observed in the high applied strain region. Unlike AZ31 B samples, tensile, compressive and high cycle fatigue behaviors of the composite showed less sensitivity to the applied strain, which can be attributed to the amount of porosity in the samples before and after the hot-forging.
基金Vietnam National University-Ho Chi Minh City under grant number A2020-16-01.
文摘In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.
基金Supported by the National Natural Science Foundation of China(No.21376229)
文摘Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a surface modifier, magnesium chloride hexahydrate in the presence of ethanol as a precursor, and sodium hydroxide as a precipitant. The products were characterized by Fourier transform infrared spectroscopy(FTIR), Field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD), and thermogravimetry-differential scanning calorimetry(TG-DSC). Compatibility with organic solutions was determined by sedimentation tests. The prepared nanoparticles exhibited regular hexagonal lamella with an average diameter of 30 nm when OA is added to the reaction system; this result indicates that OA regulates the morphology of the Mg(OH)_2nanoparticles.XRD revealed that the high-purity Mg(OH)_2product presents a brucite structure, and the I_(001)/I_(101) of hydrophobic Mg(OH)_2(0.86) was higher than that of the blank Mg(OH)_2(0.63). FTIR analysis showed that OA bonded to the surface of the Mg(OH)_2. Compared with the blank Mg(OH)_2product, the product obtained through the proposed method possesses excellent hydrophobic properties, including a high water contact angle of 101.4° and good compatibility with liquid paraffin. TG-DSC analysis indicated that the total percentage of mass loss of hydrophobic Mg(OH)_2(40.88%) was higher than that of the blank Mg(OH)_2product(33.18%). The in situ surface modification method proposed in this work presents potential use in the large-scale production of Mg(OH)_2nanoparticles.
文摘8-hydroxyquinoline(8-HQ)intercalated layered double hydroxides(LDH)film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy.The LDH,LDH/sol-gel,and LDH@HQ/sol-gel coatings were analyzed using the scanning electron microscopy(SEM),field emission scanning electron microscopy(FESEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),atomic force microscopy(AFM),and electrochemical impedance spectroscopy(EIS)methods.The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets.The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings.Also,almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness.Although the LDH film had the same impedance behavior as the alloy sample in 3.5wt%NaCl solution,its corrosion resistance was much higher,which could be due to its barrier properties as well as to the trap-ping of the chloride ions.Similar to the LDH film,the corrosion resistance of the LDH/sol-gel composite diminished with increasing the ex-posure time.However,its values were much higher than that of the LDH film,which was mainly related to the sealing of the solution path-ways.The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.
基金Chinese 973 National Key Scientific Project(No.2011CB606002)Key Project in Science and Technology of Guangdong Province(No.2010B010800018)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Department of Education of Guangdong Province(No.cxzd1008)
文摘The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis(diphenyl phosphate) (BDP) and resorcinol bis(diphenyl phosphate) (RDP)] combined with magnesium hydroxide (MH) in polyamide 6 (PA6) have been investigated. Combining 5 wt% BDP, 50 wt% MH imparts a limiting oxygen index (LOI) of 40.9% and UL94 V-0 rating to PA6, meanwhile the peak rate of smoke release (pRSR), total release of smoke (TSR) and Izod notched impact strength are 41%, 33% and 233% relative to the corresponding value of 55 wt% MH without BDP, respectively. Dynamic mechanical analysis (DMA) indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP. Furthermore, based on the comprehensive analysis of thermogravimetry (TG), cone calorimeter and SEM-EDX investigations, possible flame retardancy and smoke suppression mechanisms were revealed. Besides the fuel dilution and barrier effect of MH, the combination of MH and RDP shows an additional flame inhibition effect. The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.
基金Supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XDA02040300)
文摘Poly[bis(phenoxyphosphazene)](PBPP) and magnesium hydroxide(MH) are used as a flame retardant blend with low-density polyethylene(LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-LDPE blend composites on flame retardance and electron beam irradiation. The structure, morphology,and properties of the blend composites irradiated by an electron beam to different absorbed doses were characterized. The results indicated that PBPP provides lubrication during processing. As the PBPP content in the blend increases the melt flow rate at 20 phr MH, meaning the material is easier to process. The higher the PBPP content, the higher the limiting-oxygen index. The elongation at the break of the PBPP containing composites(at 50 phr MH) was evidently higher than the non-PBPP ones at different absorbed doses by electron beam irradiation. The thermogravimetric analysis results indicated that the improved mechanical property, resulting from electron-beam irradiation, could be attributed to the consumption of PBPP.
基金This work was subsidized by the Special Funds for Major State Basic Research Projects(No.2005CB623800).
文摘A novel EVA/unmodified nano-magnesium hydroxide (NMH)/silicone rubber ternary nanocomposite was prepared by using a special compound flame retardant of NMH and silicone rubber (CFR). The flammability of the ternary composite was studied by cone calorimeter test (CCT). Synergistic effect on flame retardancy was found between silicone rubber and NMH. EVA/CFR ternary nanocomposite showed the lowest peak heat release rate (PHRR) and mass loss rate (MLR) among the samples of virgin EVA, EVA composites. The synergistic flame retardancy of silicone rubber and NMH in EVA system is attributed to the enhanced char layers in the condensed phase that prevents the heat and mass transfer in the fire.
基金Project supported by Promoting Program of National Engineering Laboratory for Vacuum Metallurgy
文摘Mg(OH)2 nano-particles with fiber-like morphology were prepared by chemical precipitation process,with the bittern from Qinghai Salt Lakes used as Mg2+ raw material and ammonia water as precipitator. The influence of aging procedure on the Mg(OH)2 crystal was investigated by TEM and crystalline size calculation. The Mg(OH)2 nano-particles were characterized by XRD,SEM,TEM and TG-DTA methods. The results indicate that the Mg(OH)2 nano-particles with perfect crystal are obtained after aging procedure above 50 ℃,and the grain size increases with increasing aging temperature and prolonging aging time. Mg(OH)2 particles with fiber-like morphology,20-60 nm in diameter and 300-500 nm in length are observed,Mg(OH)2 will decompose into MgO at temperature range 347-623 ℃.
文摘The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that the calculated IEP values with the modified Yoon′s equation agreed well with the experimental ones. With the increase of the ionic radius of monovalent anions (Cl -, Br -, I -) the ζ potential decreased. The same was true for CO 2- 3, SO 2- 4 but the sign of the Y- potential reversed from positive to negative. For Al 3+ , Ca 2+ , Mg 2+ , however, the ζ potential increased with the increase of the concentration of Al 3+ , Ca 2+ , Mg 2+ .
基金This research is supported by NNSFC No:20273041.
文摘The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV increased with the increase of the ratio of Al/Mg and with the peptizing temperature. AlIV originated from the so-called Al13 polymer with the structure of one Al tetrahedron surrounded by twelve Al octahedrons.
文摘Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of the variable charge component. The calculated values with modified Yoon's equation agreed with the experimental values.
基金Projects(50574104 50574102) supported by the National Natural Science Foundation of China
文摘Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at different pH values (pH range from 8.0 to 12.0). The surface properties of grafted γ-APS on MH surface as a function of solution pH value were studied using elemental analysis,Fourier transform infrared spectroscopy and zeta potential measurement. The results show that hydrolysis and condensation of γ-APS are activated in alkaline solution and lead to multilayer adsorption of γ-APS molecules on the surface of MH. The type of adsorption orientation of γ-APS on MH surface is a function of coverage density that is altered by changing solution pH value. At low coverage density (e.g. 55 nm-2),γ-APS molecules are preferentially adsorbed to the surface with the silicon moiety towards the surface,and increasing coverage density (e.g. 90 nm-2) leads to parallel orientation. At an even higher coverage density (e.g. 115 nm-2),γ-APS molecules bond to the surface with the amino moiety towards the surface.
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Project(12504230006) supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy(SEM), film thickness meter, X-ray diffraction (XRD), energy disperse spectroscopy(EDS) and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.