The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship betwe...The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship between the spheroidization grade of liguid iron treated by different nodulizers and holding time were obtained. The results show that the more the remains of the rare earth, the longer the anti-degradation time, the liquid iron was treated either by Y-Mg-Si or by Ce-Mg-Si nodulizer. When the rare earth remains are above certain quantity, the spheroidization grade starts to decline. When liquid iron treated by either Y-Mg-Si or Ce-Mg-Si nodulizer with proper remains of rare earths about 0.04% 0.06%(mass fraction), the anti-degradation is the best, and the remains of Mg being about 0.04% -0.07% (mass fraction). Rare earths-Mg nodulizer with moderate RE remains is better than that of Mg-Si nodulizer in anti-degradation property. However, Y-Mg-Si nodulizer with moderate remins of Re is better than Ce-Mg-Si nodulizer. Sometimes Ce-Mg- Si nodulizer can be used for the production of heavy section nodular cast iron.展开更多
The effects of rare earths (RE) and its complex with extract from seaweed (Lamiaria japonica) on the growth and immunization of penaeid shrimp (Penaeus vannamei) were investigated. The results show that the survival r...The effects of rare earths (RE) and its complex with extract from seaweed (Lamiaria japonica) on the growth and immunization of penaeid shrimp (Penaeus vannamei) were investigated. The results show that the survival rate, body length and weight of the shrimp treated by RE and its complex with extract from seaweed are higher than those of the control, and that the activities of the phenoloxidase (PO), lysozyme (LSZ), superoxide dismutase (SOD), peroxidase (POD), acid phosphatase (ACP) and alkaline phosphatase (ALP) in the shrimp treated by RE and the complex are also much higher than those from the control.展开更多
Rare earths in ores, altered and unaltered sericite phyllite, altered and unaltered dacite porphyry were determined in order to examine behaviors of rare earths in hydrothermal alteration associating with ore-forming ...Rare earths in ores, altered and unaltered sericite phyllite, altered and unaltered dacite porphyry were determined in order to examine behaviors of rare earths in hydrothermal alteration associating with ore-forming processes of Yinshan deposit. It is not sufficient to show the mobility only by the absolute abundance of trace elements changes before and after alteration. This can simply result from dilution or concentration if other elements are added to or removed from the rock. As shown by that in Yinshan deposit, less than 20% of the increment of RE was caused by the 'condensed' of leaching some of major elements (e.g. Si, Na) from the rock. The principal factor which should be responsible for the higher contents of RE in altered rock is the addition of RE into the rock by hydrothermal fluids. Eu is selectively leached from the altered sericite phyllite by a mild acidity and reducing fluid which is characterized by much lower LRE/HRE ratio and a large positive Eu anomaly. A major effect on the RE patterns is the tendency to develop relatively flatter chondrite-normalized patterns. The RE characteristics may be used to distinguish between small and large ore bodies at a later stage of exploration.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
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 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
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
The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the r...The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.展开更多
Ce (Ⅳ) nitrato complexes were adsorbed on two anion exchangers based on polyvinyl pyridine (PVP) and quatemized PVP incorporated into porous silica matrix. The effect of nitric acid concentration (0.5~6 mol...Ce (Ⅳ) nitrato complexes were adsorbed on two anion exchangers based on polyvinyl pyridine (PVP) and quatemized PVP incorporated into porous silica matrix. The effect of nitric acid concentration (0.5~6 mol·L^-1) and temperature (278 ~318 K) on Ce( Ⅳ ) sorption efficiency was investigated. Sorption increased with increasing nitric acid concentration, indicating that [Ce(NO3)6]^2- complex is the main adsorbed Ce(Ⅳ) species. Oxidation of sorbents by adsorbed Ce ( Ⅳ ) species resulting in Ce ( Ⅲ ) release to the solution was observed. Pyridine based anion exchangers exhibited higher oxidation stability compared to the commercial strong base anion exchanger. Ce( Ⅳ ) reduction was temperature dependent and obeyed pseudo-first-order reaction kinetics. Column separation of Ce ( Ⅳ ) from La ( Ⅲ ) and Y ( Ⅲ ) was carried out from 6 mol·L^-1 nitric acid with PVP based anion exchanger. Reasonable Ce (Ⅳ) breakthrough capacity (0.7 mol·kg^-1 PVP) was achieved. No remarkable decrease of capacity was observed within 3 consequent runs. In contrast, Ce (Ⅲ) leakage due to reduction decreased and breakthrough capacity slightly increased. This effect was more pronounced with increasing temperature. Regeneration with 0.1 mol·L^- 1 nitric acid was successful (recovery 100% ± 4% ) and Ce solution of high purity ( 〉 99.97% ) with respect to La and Y content was gained.展开更多
On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE) could promote the growth of crops and increase their yield. The effects of extraction f...On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with RE on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The resuits showed that the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88 %, 52.30%, 49.52%, and 22.88 %, respectively, for chlorpyrifos, dichlorvos, omethoate, and dimethoate, and those by the complex decreased by 95.99%, 54.23%, 48.79%, and 25.66%, respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach sprayed with the complex were decreased by 90.64% and 76.56%, respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d. The fresh weight of brassica chinensis and cabbage increased by 28.62% and 18.72%, and their dry weight increased by 44.49% and 14.74%, respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia chinese were decreased by 36.36% and 50.00%, respectively, and their rate of decrease in cabbage was 40.00% and 75.00%, respectively, on 5th day after spraying with the complex, when compared with those in the vegetable from control. These results suggest that this complex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables.展开更多
The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE a...The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro alloy action effect. The improved steel making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.展开更多
The effect of the mixed rare earths of Ce on the phase transformation in ascast ZA 27 alloy during compressive was investigated under 37 MPa and at 160 deg C by X-raydiffraction technique and SEM. The results showed t...The effect of the mixed rare earths of Ce on the phase transformation in ascast ZA 27 alloy during compressive was investigated under 37 MPa and at 160 deg C by X-raydiffraction technique and SEM. The results showed that the as cast microstructure of ZA 27-RE alloyconsisted of a dendritic Al-rich alpha' surrounded by Zn-rich beta' phase, interdendritic epsilonphase and Zn-rich eta phase together with a complex Z phase which was a complex constitute compound,(RE,Cu)Al_5Zn_(16), dispersed in crystal interfaces or branch crystal interfaces and stable duringcompressive creep test at 160 deg C. The phase transformations of ZA 27-RE alloy, decomposition ofbeta' phase arid four transformation, were delayed by the addition of rare earths, also the lamellarstructure and the spheroidized structure in ZA 27-RE alloy were finer than in ZA 27 alloy duringcompressive creep test at 160 deg C at the same creep time, and the compressive creep resistance ofZA 27-RE alloy was higher than that of ZA 27 alloy.展开更多
The influence of rare earth on the friction and wear characteristics of magnesium alloy AZ91 and AM60 were studied. The results show that the wear resistance properties of rare earth magnesium alloys are better than t...The influence of rare earth on the friction and wear characteristics of magnesium alloy AZ91 and AM60 were studied. The results show that the wear resistance properties of rare earth magnesium alloys are better than those of matrix alloy under the testing conditions. The anti wear behaviour of AZ91 alloy is much better than that of AM60 alloy. In dry sliding process,magnesium alloys undergo a transition from mild wear to severe wear. The addition of rare earths refine the structure of alloys, improve the comprehensive behaviors of magnesium alloys, increase the stability of oxidation films on worn surfaces, enhance the loading ability of rare earth magnesium alloys, and delay the transition from mild wear to severe wear effectively.展开更多
Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of...Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.展开更多
Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, ...Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHC Ⅱ to PS Ⅱ, excitation energy distribution from PS Ⅰ to PS Ⅱ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PS ⅡDCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order: Ce〉Nd 〉La〉 control. However, the photoreduction activities of spinach PS I almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.展开更多
文摘The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship between the spheroidization grade of liguid iron treated by different nodulizers and holding time were obtained. The results show that the more the remains of the rare earth, the longer the anti-degradation time, the liquid iron was treated either by Y-Mg-Si or by Ce-Mg-Si nodulizer. When the rare earth remains are above certain quantity, the spheroidization grade starts to decline. When liquid iron treated by either Y-Mg-Si or Ce-Mg-Si nodulizer with proper remains of rare earths about 0.04% 0.06%(mass fraction), the anti-degradation is the best, and the remains of Mg being about 0.04% -0.07% (mass fraction). Rare earths-Mg nodulizer with moderate RE remains is better than that of Mg-Si nodulizer in anti-degradation property. However, Y-Mg-Si nodulizer with moderate remins of Re is better than Ce-Mg-Si nodulizer. Sometimes Ce-Mg- Si nodulizer can be used for the production of heavy section nodular cast iron.
基金Project supported by Qingdao Scientific Research Program (03 2 HH 3) and Shandong Scientific Foundation (2004ZRB01001)
文摘The effects of rare earths (RE) and its complex with extract from seaweed (Lamiaria japonica) on the growth and immunization of penaeid shrimp (Penaeus vannamei) were investigated. The results show that the survival rate, body length and weight of the shrimp treated by RE and its complex with extract from seaweed are higher than those of the control, and that the activities of the phenoloxidase (PO), lysozyme (LSZ), superoxide dismutase (SOD), peroxidase (POD), acid phosphatase (ACP) and alkaline phosphatase (ALP) in the shrimp treated by RE and the complex are also much higher than those from the control.
文摘Rare earths in ores, altered and unaltered sericite phyllite, altered and unaltered dacite porphyry were determined in order to examine behaviors of rare earths in hydrothermal alteration associating with ore-forming processes of Yinshan deposit. It is not sufficient to show the mobility only by the absolute abundance of trace elements changes before and after alteration. This can simply result from dilution or concentration if other elements are added to or removed from the rock. As shown by that in Yinshan deposit, less than 20% of the increment of RE was caused by the 'condensed' of leaching some of major elements (e.g. Si, Na) from the rock. The principal factor which should be responsible for the higher contents of RE in altered rock is the addition of RE into the rock by hydrothermal fluids. Eu is selectively leached from the altered sericite phyllite by a mild acidity and reducing fluid which is characterized by much lower LRE/HRE ratio and a large positive Eu anomaly. A major effect on the RE patterns is the tendency to develop relatively flatter chondrite-normalized patterns. The RE characteristics may be used to distinguish between small and large ore bodies at a later stage of exploration.
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.
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.
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.
文摘The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.
基金Project supported bythe Japan Societyfor the Promotion of Science (JSPS)
文摘Ce (Ⅳ) nitrato complexes were adsorbed on two anion exchangers based on polyvinyl pyridine (PVP) and quatemized PVP incorporated into porous silica matrix. The effect of nitric acid concentration (0.5~6 mol·L^-1) and temperature (278 ~318 K) on Ce( Ⅳ ) sorption efficiency was investigated. Sorption increased with increasing nitric acid concentration, indicating that [Ce(NO3)6]^2- complex is the main adsorbed Ce(Ⅳ) species. Oxidation of sorbents by adsorbed Ce ( Ⅳ ) species resulting in Ce ( Ⅲ ) release to the solution was observed. Pyridine based anion exchangers exhibited higher oxidation stability compared to the commercial strong base anion exchanger. Ce( Ⅳ ) reduction was temperature dependent and obeyed pseudo-first-order reaction kinetics. Column separation of Ce ( Ⅳ ) from La ( Ⅲ ) and Y ( Ⅲ ) was carried out from 6 mol·L^-1 nitric acid with PVP based anion exchanger. Reasonable Ce (Ⅳ) breakthrough capacity (0.7 mol·kg^-1 PVP) was achieved. No remarkable decrease of capacity was observed within 3 consequent runs. In contrast, Ce (Ⅲ) leakage due to reduction decreased and breakthrough capacity slightly increased. This effect was more pronounced with increasing temperature. Regeneration with 0.1 mol·L^- 1 nitric acid was successful (recovery 100% ± 4% ) and Ce solution of high purity ( 〉 99.97% ) with respect to La and Y content was gained.
基金Project supported by the Natural Scientific Foundation of Shandong Province (Z 2004D05) and Qingdao City (05-2-NS-21)
文摘On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with RE on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The resuits showed that the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88 %, 52.30%, 49.52%, and 22.88 %, respectively, for chlorpyrifos, dichlorvos, omethoate, and dimethoate, and those by the complex decreased by 95.99%, 54.23%, 48.79%, and 25.66%, respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach sprayed with the complex were decreased by 90.64% and 76.56%, respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d. The fresh weight of brassica chinensis and cabbage increased by 28.62% and 18.72%, and their dry weight increased by 44.49% and 14.74%, respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia chinese were decreased by 36.36% and 50.00%, respectively, and their rate of decrease in cabbage was 40.00% and 75.00%, respectively, on 5th day after spraying with the complex, when compared with those in the vegetable from control. These results suggest that this complex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables.
文摘The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro alloy action effect. The improved steel making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.
文摘The effect of the mixed rare earths of Ce on the phase transformation in ascast ZA 27 alloy during compressive was investigated under 37 MPa and at 160 deg C by X-raydiffraction technique and SEM. The results showed that the as cast microstructure of ZA 27-RE alloyconsisted of a dendritic Al-rich alpha' surrounded by Zn-rich beta' phase, interdendritic epsilonphase and Zn-rich eta phase together with a complex Z phase which was a complex constitute compound,(RE,Cu)Al_5Zn_(16), dispersed in crystal interfaces or branch crystal interfaces and stable duringcompressive creep test at 160 deg C. The phase transformations of ZA 27-RE alloy, decomposition ofbeta' phase arid four transformation, were delayed by the addition of rare earths, also the lamellarstructure and the spheroidized structure in ZA 27-RE alloy were finer than in ZA 27 alloy duringcompressive creep test at 160 deg C at the same creep time, and the compressive creep resistance ofZA 27-RE alloy was higher than that of ZA 27 alloy.
文摘The influence of rare earth on the friction and wear characteristics of magnesium alloy AZ91 and AM60 were studied. The results show that the wear resistance properties of rare earth magnesium alloys are better than those of matrix alloy under the testing conditions. The anti wear behaviour of AZ91 alloy is much better than that of AM60 alloy. In dry sliding process,magnesium alloys undergo a transition from mild wear to severe wear. The addition of rare earths refine the structure of alloys, improve the comprehensive behaviors of magnesium alloys, increase the stability of oxidation films on worn surfaces, enhance the loading ability of rare earth magnesium alloys, and delay the transition from mild wear to severe wear effectively.
文摘Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.
基金Project supported by the National Natural Science Foundation of China (20671067, 30470150)
文摘Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHC Ⅱ to PS Ⅱ, excitation energy distribution from PS Ⅰ to PS Ⅱ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PS ⅡDCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order: Ce〉Nd 〉La〉 control. However, the photoreduction activities of spinach PS I almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.