Steel H13 was put in non toxic salt bath with addition of CeO 2 for co diffusion of sulfur, nitrogen and carbon and followed by oxidation treatment. The effect of rare earths on the improvement of wear resistance a...Steel H13 was put in non toxic salt bath with addition of CeO 2 for co diffusion of sulfur, nitrogen and carbon and followed by oxidation treatment. The effect of rare earths on the improvement of wear resistance and high temperature oxidation resistance of steel H13 was studied using scanning electron microscope, energy dispersive spectrometry and X ray diffraction. The results show that compared to the surface treatment without rare earth addition, the treatment with addition of rare earths improves the wear resistance and high temperature resistance to oxidation of steel H13. Under the conditions of 30 N and 2 h, the wear weight loss was decreased by 40%, and the friction coefficient was reduced from 0 25 to 0 22; whereas for 150 N and 0 2 h, the wear weight loss was decreased by 24%, and the friction coefficient was reduced from 0 35 to 0 32. For the oxidation at 700 ℃ and 4 h, the rate of weight gain decreased to only about 1/30 of that without rare earths.展开更多
The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer...The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer by LRSP of RE containing coating. The RE in the steel surface can react with oxygen and sulphur, then be dissolved in the grains or grain boundaries, and form intermetallic compounds RE 2Fe 17 . The addition of RE by LRSP has very strong effects on the properties of steel surface.展开更多
By means of inoculating, the effects of rare earths, N and RE N joint inoculants on the content and surface morphology of graphite of high CE gray cast irons were studied The results indicate that RE, N, and espec...By means of inoculating, the effects of rare earths, N and RE N joint inoculants on the content and surface morphology of graphite of high CE gray cast irons were studied The results indicate that RE, N, and especially RE N joint inoculants make the content of graphite decrease; N and RE N joint inoculants could make the surface of graphite rougher and the heads of graphite flake passive展开更多
The effects of rare earths on precipitation of NbC in austenite and ferrite have been investigated. The results show that precipitation of NbC is promoted in ferrite but retarded in austenite. The fit to different mod...The effects of rare earths on precipitation of NbC in austenite and ferrite have been investigated. The results show that precipitation of NbC is promoted in ferrite but retarded in austenite. The fit to different models by using the least square technique indicates that the addition of RE changes the rate constant of precipitation rather than the kinetic mechanism of precipitation.展开更多
The stability constants of ML binary system and MLL′(M=La^3+～Yb^3+, Y^3+ and Ca^2+; L=DLmalic aicd, L′=Lhydroxyproline) ternary system were determined by pHpotentiometric method under the simulating physiological c...The stability constants of ML binary system and MLL′(M=La^3+～Yb^3+, Y^3+ and Ca^2+; L=DLmalic aicd, L′=Lhydroxyproline) ternary system were determined by pHpotentiometric method under the simulating physiological condition(37 ℃, I=015 mol/L NaCl). The complex species MpLqL′rHs(abbr as pqrs) in the sytems were ascertained by program COMPLEX. The results show that there are three species(1101, 1100 and 1200) in ML binary system and one species(1010) in ML′ binary system. In addition to the above four species, a new species, 1112 was found in the MLL′-ternary system, which is the only species of mixed ligands. Rare earth ions form more stable complexes than calcium ion does and the stability differences between their complexes in the ternary system are less than that in the binary system. The distributions of all the species in LaLL′-ternary system vs pH are discussed.展开更多
A fast EDXRF analysis by using radioisotope, 241 Am as an exciting source and high purity Ge as a planar detector in heavy rare earth separation processes by solvent extraction has been investigated Applying th...A fast EDXRF analysis by using radioisotope, 241 Am as an exciting source and high purity Ge as a planar detector in heavy rare earth separation processes by solvent extraction has been investigated Applying the method, heavy rare earth chloride aqueous samples in Er/Tm and Y/Er separation processes were off line analyzed The results show that the method can be used for a wide range of rare earth concentration(0 1 g/L～300 g/L) with high accuracy展开更多
By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic mangane...By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic manganese steel was investigated The results show that the constitutional supercooling of austenitic manganese steel during solidification can be improved and the dendritic crystals can be grown facilely, melted, isolated and multiplied by adding RE(Ce) In the melt the alloying elements Ti and C can form TiC directly which acts as nucleus of cementite and causes both primary and eutectic cementite to be granulated and refined so that the cementite network in this steel can be eliminated展开更多
The research on the influence of RE on the directional solidified microstructure of tin lead alloy reveals that the addition of RE can cause chopping and irregular lamellar and smaller lamellar spacing. When RE conte...The research on the influence of RE on the directional solidified microstructure of tin lead alloy reveals that the addition of RE can cause chopping and irregular lamellar and smaller lamellar spacing. When RE content increases, the microstructure changes to peritectic structure. Moreover, the eutectic point of Sn Pb alloy deviates because the affinity of RE for Sn, which results in the existence of primary Pb rich phases contained hypocutectic grown layers. Sn RE intermetallic compound has no effect on the solidification of Sn Pb alloy.展开更多
The influence of mixed RE with c Ce 45%(mass fraction) on the high temperature mechanical properties and microstructure of ZA 27 alloys was investigated. The results show that RE elements can react with ele...The influence of mixed RE with c Ce 45%(mass fraction) on the high temperature mechanical properties and microstructure of ZA 27 alloys was investigated. The results show that RE elements can react with elements Al, Zn, Cu etc. to form some complex compounds which have high hardness and hot hardness and can disperse in grain boundaries or between dendrite crystals, so that the alloy can be refined and the deformation of matrix and the movement of grain boundaries at high temperature are hindered. The appropriate addition amount of RE can result in increase of tensile strength by about 30% and hardness by 25% and only a little decrease of elongation, but impact toughness has been improved at 150 ℃. It is also found that the strength at room temperature changes little although the plasticity and impact toughness decrease slightly.展开更多
Magnesium sulfate was proposed to be leaching agent to deal with the ion-adsorption type rare earths ore to reduce or even eliminate ammonia?nitrogen emissions. The effects of temperature, particle size and stirring s...Magnesium sulfate was proposed to be leaching agent to deal with the ion-adsorption type rare earths ore to reduce or even eliminate ammonia?nitrogen emissions. The effects of temperature, particle size and stirring speed on rare earth leaching process and the leaching behaviors of the single rare earth element were investigated in order to reveal the rare earth leaching characteristics. Besides, the comparison of leaching effects between magnesium sulfate and ammonium sulfate was also studied. The results showed that the rare earth leaching process could be well described with inner diffusion control model and the apparent activation energy was 9.48 kJ/mol. The leaching behaviors of the single rare earth element were brought into correspondence with rare earths. Moreover, when the concentration of leaching agent was 0.20 mol/L, the rare earth leaching efficiency could all reach above 95% and the leaching efficiency of aluminum impurities could be restrained by 10% using magnesium sulfate compared with ammonium sulfate.展开更多
In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynami...In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.展开更多
By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were perfor...By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were performed on undoped and doped bulk α Mg for comparison.The results showed that Al atoms segregated at GBs in AZ91 alloys.When RE atoms were added,they also segregated at GBs,and their segregation is stronger than Al atoms＇.Therefore,RE atoms retard the segregation of Al atoms.Calculations of interaction energy indicated that Al atoms repelled each other,and could form ordered phase with host Mg atoms.On the contrary to the case of Al,RE atoms attracted each other,they could not form ordered phase with Mg,but could form clusters.Between RE and Al,there existed attractive interaction,and this attractive interaction was the origin of Al11RE3 precipitation.Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.展开更多
Carbon fibers （CF） were surface treated with air-oxidation and rare earths （RE）, respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroeth...Carbon fibers （CF） were surface treated with air-oxidation and rare earths （RE）, respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE （CF/PTFE） composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.展开更多
The effects of rare earths on the properties of the microarc oxidation（MAO） coating on a magnesium alloy were investigated by means of scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,...The effects of rare earths on the properties of the microarc oxidation（MAO） coating on a magnesium alloy were investigated by means of scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,and electrochemistry methods.The results show that a nice and compact MAO coating was successfully obtained when the magnesium alloy was treated in nitrate solutions as the pre-treatment of MAO.However,the MAO was not successfully completed for the silicate electrolytes with the addition of rare earths.After the magnesium alloy being treated by rare earth nitrate,the obtained MAO coating has advantages such as uniform distribution of thickness,improved corrosion resistance,and nice-uniform surface,as compared with the untreated magnesium alloy.In addition,the time of non-ESP,the voltage and current density of the MAO process obviously decrease.Cerium oxide doped on the surface of the magnesium alloy can significantly improve the corrosion resistance of the MAO coating and decrease the current density of the MAO process,as compared with lanthanum oxide,whereas the doped rare earths have no significant effect on the components of the MAO coating.展开更多
Effect of cerium （Ce^3＋） on growth and photosynthesis in rape seedlings exposed to two levels of ultraviolet-B radiation （UV-B, 280 - 320 nm） was studied with hydroponics under laboratory conditions. The growth o...Effect of cerium （Ce^3＋） on growth and photosynthesis in rape seedlings exposed to two levels of ultraviolet-B radiation （UV-B, 280 - 320 nm） was studied with hydroponics under laboratory conditions. The growth of rape seedlings exposed to two levels of UV-B irradiation （0.15 and 0.35 W· m^-2/T2） was both heavily restrained. The aboveground growth indices including stem （plant） height, leaf number, leaf area, leaf fresh/dry weight and stem fresh/dry weight were obviously decreased by 13.2% - 44.1% （T1） and 21 .4% - 49.3% （T2）. Compared to CK, and except active absorption area of roots, the belowground indices main root length, root volume and fresh/dry weight by 14.1% -35.6% （T1） and 20.3% - 42.6% （T2）, respectively. For Ce ＋ UV-B treatments, the aboveground and belowground growth indices were decreased by 4.1% - 23.6%, 5.2% -23.3% （Ce＋T1） and 10.8% -28.4%, 7.0% -27.8% （Ce ＋T2）, lower than those of UV-B treatments mentioned above. These results show that Ce has protective effect on plant against injury of UV-B radiation. Furthermore, the protective effect of Ce on seedlings exposed to T1 level of UV-B radiation is superior to T2 level. Chlorophyll content, net photosynthesis rate, transpiration rate, stomatal conductance and water use efficiency in UV-B treatments decrease dramatically, whereas intercellular CO2 concentration increases. Although these indices in Ce ＋ UV-B treatments decrease compared with those of CK, the decrease in Ce ＋ UV-B treatments are lower than those in UV-B treatment. This phenomenon indicates that the ecophysiological protective effect of Ce is based on improving photosynthesis in plants. The dynamic curves of photosynthesis indices show that the course of light-repair is shortened and the injury to rape seedlings by UV-B radiation stress is alleviated by Ce.展开更多
The diffusion coefficient of carbon in surface layer of steel-20 rare earth carburixed at 880 degreesC and 900 degreesC for 8 h was calculated by substituting the measured layer depths into the diffusion equation. The...The diffusion coefficient of carbon in surface layer of steel-20 rare earth carburixed at 880 degreesC and 900 degreesC for 8 h was calculated by substituting the measured layer depths into the diffusion equation. The mathematical model of the transfer coefficient of carbon was deduced based on the kinetics of weight gain during gas carburizing. The calculated results show that the main reason why the gas carburizing process is accelerated is due to the obvious increase in the diffusion coefficient and transfer coefficient of carbon resulted from the addition of RE.展开更多
Magnetic refrigeration is a revolutionary, efficient, environmentally friendly cooling technology, which is on the threshold of commercialization. The magnetic rare earth materials are utilized as the magnetic refrige...Magnetic refrigeration is a revolutionary, efficient, environmentally friendly cooling technology, which is on the threshold of commercialization. The magnetic rare earth materials are utilized as the magnetic refrigerants in most cooling devices, and for many cooling application the Nd2Fe14B permanent magnets are employed as the source of the magnetic field. The status of the near room temperature magnetic cooling was reviewed.展开更多
The density of states （DOS） of 17 kinds of rare earths （RE） doped rutile TiO2 was by using first-principles density functional theory （DFT） calculation. The band gap widths of RE doped futile TiO2 were important...The density of states （DOS） of 17 kinds of rare earths （RE） doped rutile TiO2 was by using first-principles density functional theory （DFT） calculation. The band gap widths of RE doped futile TiO2 were important factors for altering their absorbing wavelengths. The results show that RE ions could obviously reduce the band gap widths and form of energy of ruffle TiO2 except Lu, Y, Yb and Sc, and the order of absorbing wavelengths of RE doped ruffle TiO2 were the same as that of the results of calculation. The ratio of RE dopant was another important factor for the photo catalytic ＇activity of RE doped rutile TiO2, and there was an optimal ratio of dopant. There was a constant for predigesting the calculation difficulty, respectively, which were 0.5mol.% and 100 mol^-1 under supposition. The band gap widths of RE doped rutile TiOz by DFT calculation were much larger than that by experiment. Finally, by transferring the calculation values to experiment values, it could be found and predicted that RE enlarged obviously the absorbing wavelengh of ruffle TiO2. In addition, the degree of RE ions edging out the Ti atom using the parameters of RE dements was computed.展开更多
Carbon fibers （CFs） were surface treated with air-oxidation, rare earths （RE） after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites fi...Carbon fibers （CFs） were surface treated with air-oxidation, rare earths （RE） after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites filled with carbon fibers treated with different treatment methods. Tribological properties of the PTFE composites, sliding against GCr15 steel under water-lubricated condition, were investigated on a reciprocating ball-on-disk UMT-2MT tribometer. The worn surfaces of the composites were examined using scanning electron microscopy. Experimental results reveal that RE treatment is superior to air oxidation in promoting tribological properties of CF reinforced PTFE （CF/PTFE） composite. The friction and wear properties of PTFE composite filled with RE treated CF are the best of the PTFE composites. RE treatment is more effective than air oxidation to improve the tribological properties of CF/PTFE composite owing to the effective improvement of interfacial adhesion between carbon fibers and PTFE matrix.展开更多
The effects of composite rare earths La+Ce on properties of CuZnAl shape memory alloys were studied bymetallograph examination, tensile and bending tests, electric resistivity measurements, EDS and SEM. The test resul...The effects of composite rare earths La+Ce on properties of CuZnAl shape memory alloys were studied bymetallograph examination, tensile and bending tests, electric resistivity measurements, EDS and SEM. The test resultsshow that the grain size of CuZnAl shape memory alloys could be diminished effectively and the mechanical propertiesimproved obviously by the addition of composite rare earths La+Ce (La: Ce=1: 1). Meanwhile, the excellent shapememory properties remained unchanged. The results of microanalyses indicate that the composite rare earths were segregated at grain boundaries and impeded the grain growth, leading to the improvement of the mechanical properties ofCuZnAl alloys. If the amount of composite rare earths La+Ce was greater than 0. 10%, the shape memorial propertiesbecame poor.展开更多
文摘Steel H13 was put in non toxic salt bath with addition of CeO 2 for co diffusion of sulfur, nitrogen and carbon and followed by oxidation treatment. The effect of rare earths on the improvement of wear resistance and high temperature oxidation resistance of steel H13 was studied using scanning electron microscope, energy dispersive spectrometry and X ray diffraction. The results show that compared to the surface treatment without rare earth addition, the treatment with addition of rare earths improves the wear resistance and high temperature resistance to oxidation of steel H13. Under the conditions of 30 N and 2 h, the wear weight loss was decreased by 40%, and the friction coefficient was reduced from 0 25 to 0 22; whereas for 150 N and 0 2 h, the wear weight loss was decreased by 24%, and the friction coefficient was reduced from 0 35 to 0 32. For the oxidation at 700 ℃ and 4 h, the rate of weight gain decreased to only about 1/30 of that without rare earths.
文摘The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer by LRSP of RE containing coating. The RE in the steel surface can react with oxygen and sulphur, then be dissolved in the grains or grain boundaries, and form intermetallic compounds RE 2Fe 17 . The addition of RE by LRSP has very strong effects on the properties of steel surface.
文摘By means of inoculating, the effects of rare earths, N and RE N joint inoculants on the content and surface morphology of graphite of high CE gray cast irons were studied The results indicate that RE, N, and especially RE N joint inoculants make the content of graphite decrease; N and RE N joint inoculants could make the surface of graphite rougher and the heads of graphite flake passive
文摘The effects of rare earths on precipitation of NbC in austenite and ferrite have been investigated. The results show that precipitation of NbC is promoted in ferrite but retarded in austenite. The fit to different models by using the least square technique indicates that the addition of RE changes the rate constant of precipitation rather than the kinetic mechanism of precipitation.
文摘The stability constants of ML binary system and MLL′(M=La^3+～Yb^3+, Y^3+ and Ca^2+; L=DLmalic aicd, L′=Lhydroxyproline) ternary system were determined by pHpotentiometric method under the simulating physiological condition(37 ℃, I=015 mol/L NaCl). The complex species MpLqL′rHs(abbr as pqrs) in the sytems were ascertained by program COMPLEX. The results show that there are three species(1101, 1100 and 1200) in ML binary system and one species(1010) in ML′ binary system. In addition to the above four species, a new species, 1112 was found in the MLL′-ternary system, which is the only species of mixed ligands. Rare earth ions form more stable complexes than calcium ion does and the stability differences between their complexes in the ternary system are less than that in the binary system. The distributions of all the species in LaLL′-ternary system vs pH are discussed.
文摘A fast EDXRF analysis by using radioisotope, 241 Am as an exciting source and high purity Ge as a planar detector in heavy rare earth separation processes by solvent extraction has been investigated Applying the method, heavy rare earth chloride aqueous samples in Er/Tm and Y/Er separation processes were off line analyzed The results show that the method can be used for a wide range of rare earth concentration(0 1 g/L～300 g/L) with high accuracy
文摘By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic manganese steel was investigated The results show that the constitutional supercooling of austenitic manganese steel during solidification can be improved and the dendritic crystals can be grown facilely, melted, isolated and multiplied by adding RE(Ce) In the melt the alloying elements Ti and C can form TiC directly which acts as nucleus of cementite and causes both primary and eutectic cementite to be granulated and refined so that the cementite network in this steel can be eliminated
文摘The research on the influence of RE on the directional solidified microstructure of tin lead alloy reveals that the addition of RE can cause chopping and irregular lamellar and smaller lamellar spacing. When RE content increases, the microstructure changes to peritectic structure. Moreover, the eutectic point of Sn Pb alloy deviates because the affinity of RE for Sn, which results in the existence of primary Pb rich phases contained hypocutectic grown layers. Sn RE intermetallic compound has no effect on the solidification of Sn Pb alloy.
文摘The influence of mixed RE with c Ce 45%(mass fraction) on the high temperature mechanical properties and microstructure of ZA 27 alloys was investigated. The results show that RE elements can react with elements Al, Zn, Cu etc. to form some complex compounds which have high hardness and hot hardness and can disperse in grain boundaries or between dendrite crystals, so that the alloy can be refined and the deformation of matrix and the movement of grain boundaries at high temperature are hindered. The appropriate addition amount of RE can result in increase of tensile strength by about 30% and hardness by 25% and only a little decrease of elongation, but impact toughness has been improved at 150 ℃. It is also found that the strength at room temperature changes little although the plasticity and impact toughness decrease slightly.
基金Project(2015BAB16B01)supported by the National Science and Technology Support Program of China
文摘Magnesium sulfate was proposed to be leaching agent to deal with the ion-adsorption type rare earths ore to reduce or even eliminate ammonia?nitrogen emissions. The effects of temperature, particle size and stirring speed on rare earth leaching process and the leaching behaviors of the single rare earth element were investigated in order to reveal the rare earth leaching characteristics. Besides, the comparison of leaching effects between magnesium sulfate and ammonium sulfate was also studied. The results showed that the rare earth leaching process could be well described with inner diffusion control model and the apparent activation energy was 9.48 kJ/mol. The leaching behaviors of the single rare earth element were brought into correspondence with rare earths. Moreover, when the concentration of leaching agent was 0.20 mol/L, the rare earth leaching efficiency could all reach above 95% and the leaching efficiency of aluminum impurities could be restrained by 10% using magnesium sulfate compared with ammonium sulfate.
基金Projects(50664004,50474022,50574069) supported by the National Natural Science Foundation of ChinaProjects(Q959612,Q972026) supported by the Natural Science Foundation of Jiangxi Province,China
文摘In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.
基金Project supported by the National Natural Science Foundation of China(50671069,50571071)Science Research Plan of Liaoning Province Education Bureau(05L297)+1 种基金Postdoctor Science Foundation of China(2004036113)the Doctor Starting Project and the Experiment Center of Shenyang Normal University
文摘By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were performed on undoped and doped bulk α Mg for comparison.The results showed that Al atoms segregated at GBs in AZ91 alloys.When RE atoms were added,they also segregated at GBs,and their segregation is stronger than Al atoms＇.Therefore,RE atoms retard the segregation of Al atoms.Calculations of interaction energy indicated that Al atoms repelled each other,and could form ordered phase with host Mg atoms.On the contrary to the case of Al,RE atoms attracted each other,they could not form ordered phase with Mg,but could form clusters.Between RE and Al,there existed attractive interaction,and this attractive interaction was the origin of Al11RE3 precipitation.Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.
基金Project supported by the National Natural Science Foundation of China (50275093)
文摘Carbon fibers （CF） were surface treated with air-oxidation and rare earths （RE）, respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE （CF/PTFE） composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.
文摘The effects of rare earths on the properties of the microarc oxidation（MAO） coating on a magnesium alloy were investigated by means of scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,and electrochemistry methods.The results show that a nice and compact MAO coating was successfully obtained when the magnesium alloy was treated in nitrate solutions as the pre-treatment of MAO.However,the MAO was not successfully completed for the silicate electrolytes with the addition of rare earths.After the magnesium alloy being treated by rare earth nitrate,the obtained MAO coating has advantages such as uniform distribution of thickness,improved corrosion resistance,and nice-uniform surface,as compared with the untreated magnesium alloy.In addition,the time of non-ESP,the voltage and current density of the MAO process obviously decrease.Cerium oxide doped on the surface of the magnesium alloy can significantly improve the corrosion resistance of the MAO coating and decrease the current density of the MAO process,as compared with lanthanum oxide,whereas the doped rare earths have no significant effect on the components of the MAO coating.
文摘Effect of cerium （Ce^3＋） on growth and photosynthesis in rape seedlings exposed to two levels of ultraviolet-B radiation （UV-B, 280 - 320 nm） was studied with hydroponics under laboratory conditions. The growth of rape seedlings exposed to two levels of UV-B irradiation （0.15 and 0.35 W· m^-2/T2） was both heavily restrained. The aboveground growth indices including stem （plant） height, leaf number, leaf area, leaf fresh/dry weight and stem fresh/dry weight were obviously decreased by 13.2% - 44.1% （T1） and 21 .4% - 49.3% （T2）. Compared to CK, and except active absorption area of roots, the belowground indices main root length, root volume and fresh/dry weight by 14.1% -35.6% （T1） and 20.3% - 42.6% （T2）, respectively. For Ce ＋ UV-B treatments, the aboveground and belowground growth indices were decreased by 4.1% - 23.6%, 5.2% -23.3% （Ce＋T1） and 10.8% -28.4%, 7.0% -27.8% （Ce ＋T2）, lower than those of UV-B treatments mentioned above. These results show that Ce has protective effect on plant against injury of UV-B radiation. Furthermore, the protective effect of Ce on seedlings exposed to T1 level of UV-B radiation is superior to T2 level. Chlorophyll content, net photosynthesis rate, transpiration rate, stomatal conductance and water use efficiency in UV-B treatments decrease dramatically, whereas intercellular CO2 concentration increases. Although these indices in Ce ＋ UV-B treatments decrease compared with those of CK, the decrease in Ce ＋ UV-B treatments are lower than those in UV-B treatment. This phenomenon indicates that the ecophysiological protective effect of Ce is based on improving photosynthesis in plants. The dynamic curves of photosynthesis indices show that the course of light-repair is shortened and the injury to rape seedlings by UV-B radiation stress is alleviated by Ce.
文摘The diffusion coefficient of carbon in surface layer of steel-20 rare earth carburixed at 880 degreesC and 900 degreesC for 8 h was calculated by substituting the measured layer depths into the diffusion equation. The mathematical model of the transfer coefficient of carbon was deduced based on the kinetics of weight gain during gas carburizing. The calculated results show that the main reason why the gas carburizing process is accelerated is due to the obvious increase in the diffusion coefficient and transfer coefficient of carbon resulted from the addition of RE.
基金Project supported bythe U.S .Department of Energy ,Office of Basic Energy Sciences , Materials Science and Engineering Division and Astronautics Corporation of America , Milwaukee , Wisconsin
文摘Magnetic refrigeration is a revolutionary, efficient, environmentally friendly cooling technology, which is on the threshold of commercialization. The magnetic rare earth materials are utilized as the magnetic refrigerants in most cooling devices, and for many cooling application the Nd2Fe14B permanent magnets are employed as the source of the magnetic field. The status of the near room temperature magnetic cooling was reviewed.
基金supported by the Education Commission of Sichuan Province of China (2006A099)the National Defense Basic Research Foundation of China (A3120080126)
文摘The density of states （DOS） of 17 kinds of rare earths （RE） doped rutile TiO2 was by using first-principles density functional theory （DFT） calculation. The band gap widths of RE doped futile TiO2 were important factors for altering their absorbing wavelengths. The results show that RE ions could obviously reduce the band gap widths and form of energy of ruffle TiO2 except Lu, Y, Yb and Sc, and the order of absorbing wavelengths of RE doped ruffle TiO2 were the same as that of the results of calculation. The ratio of RE dopant was another important factor for the photo catalytic ＇activity of RE doped rutile TiO2, and there was an optimal ratio of dopant. There was a constant for predigesting the calculation difficulty, respectively, which were 0.5mol.% and 100 mol^-1 under supposition. The band gap widths of RE doped rutile TiOz by DFT calculation were much larger than that by experiment. Finally, by transferring the calculation values to experiment values, it could be found and predicted that RE enlarged obviously the absorbing wavelengh of ruffle TiO2. In addition, the degree of RE ions edging out the Ti atom using the parameters of RE dements was computed.
基金Project supported bythe National Natural Science Foundation of China (50275093)
文摘Carbon fibers （CFs） were surface treated with air-oxidation, rare earths （RE） after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites filled with carbon fibers treated with different treatment methods. Tribological properties of the PTFE composites, sliding against GCr15 steel under water-lubricated condition, were investigated on a reciprocating ball-on-disk UMT-2MT tribometer. The worn surfaces of the composites were examined using scanning electron microscopy. Experimental results reveal that RE treatment is superior to air oxidation in promoting tribological properties of CF reinforced PTFE （CF/PTFE） composite. The friction and wear properties of PTFE composite filled with RE treated CF are the best of the PTFE composites. RE treatment is more effective than air oxidation to improve the tribological properties of CF/PTFE composite owing to the effective improvement of interfacial adhesion between carbon fibers and PTFE matrix.
文摘The effects of composite rare earths La+Ce on properties of CuZnAl shape memory alloys were studied bymetallograph examination, tensile and bending tests, electric resistivity measurements, EDS and SEM. The test resultsshow that the grain size of CuZnAl shape memory alloys could be diminished effectively and the mechanical propertiesimproved obviously by the addition of composite rare earths La+Ce (La: Ce=1: 1). Meanwhile, the excellent shapememory properties remained unchanged. The results of microanalyses indicate that the composite rare earths were segregated at grain boundaries and impeded the grain growth, leading to the improvement of the mechanical properties ofCuZnAl alloys. If the amount of composite rare earths La+Ce was greater than 0. 10%, the shape memorial propertiesbecame poor.
