To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)w...To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)wt.%are added to the alloy.The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM,EDS and TEM.Results show the addition of La decreases the segregation of elements and increases the amount ofγ/γ′eutectics of the as-cast alloy,and in the interdendritic region,the growth of eutectics is accompanied by the growth of strip clusters composed of Ni_(5)La and Ni_(3)Ta.As the La content in the alloy increases,the proportion of Ni_(5)La in the cluster increases.After heat treatment,incipient melting occurs in the cluster regions,leading to an increase in microporosity compared to the original as-cast samples.Furthermore,the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one,and it changes their composition from Ni_(5)La and Ni_(3)Ta to a combination of Ni_(5)La,Ni_(3)Ta,and MC carbides.展开更多
Lanthanum oxalate hydrate La2（C2O4）3·10H2O,the precursor of La2O3 ultrafine powders,was prepared by impinging stream reactor method with PEG 20000 as surfactant.Thermal decomposition of La2（C2O4）3·10H2O ...Lanthanum oxalate hydrate La2（C2O4）3·10H2O,the precursor of La2O3 ultrafine powders,was prepared by impinging stream reactor method with PEG 20000 as surfactant.Thermal decomposition of La2（C2O4）3·10H2O from room temperature to 900 °C was investigated and intermediates and final solid products were characterized by FTIR and DSC-TG.Results show that the thermal decomposition process consists of five consecutive stage reactions.Flynn-Wall-Ozawa（FWO） and Kissinger-Akahira-Sunose（KAS） methods were implemented for the calculation of energy of activation（E）,and the results show that E depends on α,demonstrating that the decomposition reaction process of the lanthanum oxalate is of a complex kinetic mechanism.The most probable mechanistic function,G（α）=[1-（1＋α）1/3]2,and the kinetic parameters were obtained by multivariate non-linear regression analysis method.The average E-value that is compatible with the kinetic model is close to value which was obtained by FWO and KAS methods.The fitting curve matches the original TG curve very well.展开更多
Oleic acid (denoted as OA) surface-caped lanthanum borate nanorods, abbreviated as OA/LaBO3·H2O, were prepared via hydrothermal method. The microstructures of the as-prepared OA/LaBO3·H2O nanorods were chara...Oleic acid (denoted as OA) surface-caped lanthanum borate nanorods, abbreviated as OA/LaBO3·H2O, were prepared via hydrothermal method. The microstructures of the as-prepared OA/LaBO3·H2O nanorods were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The friction and wear properties of OA/LaBO3·H2O nanorods in rapeseed oil were evaluated with a four-ball tribo-tester. The results show that the as-prepared OA/LaBO3·H2O nanorods are hydrophobic and display nanorods morphology with uniform diameter of about 50 nm and length of up to 500 nm. In the meantime, OA/LaBO3·H2O nanorods can obviously improve the anti-wear and friction-reducing capacities of rapeseed oil, and the optimal anti-wear and friction-reducing properties of rapeseed oil were obtained at an OA/LaBO3·H2O content of 1% (mass fraction).展开更多
The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the ...The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.展开更多
Using SEM and EDS some particles containing La and P were discovered in low oxygen and sulfur purity steel with lanthanum. In these particles low melting point elements such as As and Sb also were detected. According ...Using SEM and EDS some particles containing La and P were discovered in low oxygen and sulfur purity steel with lanthanum. In these particles low melting point elements such as As and Sb also were detected. According to the result of simulative calculation of segregation, it is shown that La and P enrich so strongly in the process of solidification that their concentrations can satisfy thermodynamic condition to forme LaP compound or meet the requirements to forme eutectic phase in the last stage of solidification. Therefore, the particles are concluded as LaP compound or eutectics, which exist on grain boundary mainly.展开更多
A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorp...A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICE It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.展开更多
China is quite poor in argent resource. Roughly 80% of this industrial argent is imported every year. In order to improve the situation, we took advantage of rare earth (RE) mineral resource and successfully developed...China is quite poor in argent resource. Roughly 80% of this industrial argent is imported every year. In order to improve the situation, we took advantage of rare earth (RE) mineral resource and successfully developed the non-argent Lanthanum-tellurium-copper alloy as a substitute for industry argent-copper. In our research, we were able to successfully apply rare earth lanthanum to copper alloy. The defects as porosity, inclusion, etc. originating from nonvacuum melting processing were controlled. Fine grain was obtained. Meanwhile, the comprehensive properties of the copper alloy, such as strength, conductivity and thermal conductivity were improved. The research results in increasing conductivity and thermal conductivity by 5% and 15%, respectively, while the tensile strength is increased by 6% higher than Ag-Cu alloy. The anti-electric corrosion property is good, and there is no argent-cadmium steam population originating from the electric arc effect. The addition of lanthanum further reduces the content of oxygen and hydrogen. The optimum quantity of the addition of RE lanthanum in the copper alloy is 0.010% - 0.020% .展开更多
The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersiv...The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.展开更多
Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% ...Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% La were evaluated by various tests such as copper-accelerated acetic acid salt spray testing（CASS）, immersion test in 3.5% NaCl solution, electrochemical tests including weak polarization curves and electrochemical impedance spectroscopy（EIS） tests, scanning electron microscope（SEM） test and X-ray diffraction（XRD） test.It was found that the corrosion resistance of galvalume coating could be improved by adding proper amounts of La.Meanwhile, the mechanism of the improvement of corrosion resistance by La addition was discussed.展开更多
The interaction relation between lanthanum and the constituent elements of Sn-Pb alloy system was analyzed by using the thermodynamic models including Miedema formation energy model for binary system, Tanaka modificat...The interaction relation between lanthanum and the constituent elements of Sn-Pb alloy system was analyzed by using the thermodynamic models including Miedema formation energy model for binary system, Tanaka modification by excess entropy and the Chou geometric model for ternary system. The thermodynamic calculaton results show that lanthanum has higher affinity for Sn in the Sn-Pb system. This is an important foundation for the improvement of the metallurgical properties of Sn-Pb solder alloy by adding rare earth elements.展开更多
The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and solu...The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and soluble protein increase to a certain degree and then decrease under La3+ Ce3+ Zn2+ stress, while there is a constantly dropping tendency under Cr6+ stress. The four ions have different effects on protective enzyme systems of Potamogeton malaianus. They can induce rises of the activities of catalase (CAT) and peroxides (POD) at lower concentration, however, with the increase of ions concentration, the activities decline. The change of SOD activity is exactly opposite to that of CAT and POD activity. It falls at first and rises later. An increasing tendency of MDA content appears with the increasing concentration. The toxicities of La3+, Zn2+, Ce3+ and Cr6+ become more serious in the order. The lethal concentration of Cr6+ to Potamogeton malaianus ranges from 0.5 to I mg(-1) that of Ce3+ and Zn2+ ranges from 3 to 5 mg(-1) and that of La3+ ranges from 7 to 10 mg(.)L(-1). The toxic mechanism of La3 + and Ce3+ is similar to that of Cr6+ and Zn2+.展开更多
基金funded by the National Science and Technology Major Project of China(Grant No.J2019-Ⅵ-0023-0139)。
文摘To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)wt.%are added to the alloy.The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM,EDS and TEM.Results show the addition of La decreases the segregation of elements and increases the amount ofγ/γ′eutectics of the as-cast alloy,and in the interdendritic region,the growth of eutectics is accompanied by the growth of strip clusters composed of Ni_(5)La and Ni_(3)Ta.As the La content in the alloy increases,the proportion of Ni_(5)La in the cluster increases.After heat treatment,incipient melting occurs in the cluster regions,leading to an increase in microporosity compared to the original as-cast samples.Furthermore,the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one,and it changes their composition from Ni_(5)La and Ni_(3)Ta to a combination of Ni_(5)La,Ni_(3)Ta,and MC carbides.
基金Project (IRT0974) supported by Program for Changjiang Scholars and Innovative Research Team in University,ChinaProject (50974098) supported by the National Natural Science Foundation of China
文摘Lanthanum oxalate hydrate La2（C2O4）3·10H2O,the precursor of La2O3 ultrafine powders,was prepared by impinging stream reactor method with PEG 20000 as surfactant.Thermal decomposition of La2（C2O4）3·10H2O from room temperature to 900 °C was investigated and intermediates and final solid products were characterized by FTIR and DSC-TG.Results show that the thermal decomposition process consists of five consecutive stage reactions.Flynn-Wall-Ozawa（FWO） and Kissinger-Akahira-Sunose（KAS） methods were implemented for the calculation of energy of activation（E）,and the results show that E depends on α,demonstrating that the decomposition reaction process of the lanthanum oxalate is of a complex kinetic mechanism.The most probable mechanistic function,G（α）=[1-（1＋α）1/3]2,and the kinetic parameters were obtained by multivariate non-linear regression analysis method.The average E-value that is compatible with the kinetic model is close to value which was obtained by FWO and KAS methods.The fitting curve matches the original TG curve very well.
基金Project(50975282)supported by the National Natural Science Foundation of China
文摘Oleic acid (denoted as OA) surface-caped lanthanum borate nanorods, abbreviated as OA/LaBO3·H2O, were prepared via hydrothermal method. The microstructures of the as-prepared OA/LaBO3·H2O nanorods were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The friction and wear properties of OA/LaBO3·H2O nanorods in rapeseed oil were evaluated with a four-ball tribo-tester. The results show that the as-prepared OA/LaBO3·H2O nanorods are hydrophobic and display nanorods morphology with uniform diameter of about 50 nm and length of up to 500 nm. In the meantime, OA/LaBO3·H2O nanorods can obviously improve the anti-wear and friction-reducing capacities of rapeseed oil, and the optimal anti-wear and friction-reducing properties of rapeseed oil were obtained at an OA/LaBO3·H2O content of 1% (mass fraction).
文摘The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.
基金Project supported by the Ministry of Science and Technology of China (2002BA315A-5)
文摘Using SEM and EDS some particles containing La and P were discovered in low oxygen and sulfur purity steel with lanthanum. In these particles low melting point elements such as As and Sb also were detected. According to the result of simulative calculation of segregation, it is shown that La and P enrich so strongly in the process of solidification that their concentrations can satisfy thermodynamic condition to forme LaP compound or meet the requirements to forme eutectic phase in the last stage of solidification. Therefore, the particles are concluded as LaP compound or eutectics, which exist on grain boundary mainly.
基金supported by the National Major Research Plan for Water Pollution Control and Treatment of China (No.2008ZX07101-015)
文摘A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICE It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.
基金Project supported by the National Scientific and Technological Achievements Spread Project (2004EC00299)Science and Technology Type Middle and Small Business Technique Invention Fund (04C26225121390)
文摘China is quite poor in argent resource. Roughly 80% of this industrial argent is imported every year. In order to improve the situation, we took advantage of rare earth (RE) mineral resource and successfully developed the non-argent Lanthanum-tellurium-copper alloy as a substitute for industry argent-copper. In our research, we were able to successfully apply rare earth lanthanum to copper alloy. The defects as porosity, inclusion, etc. originating from nonvacuum melting processing were controlled. Fine grain was obtained. Meanwhile, the comprehensive properties of the copper alloy, such as strength, conductivity and thermal conductivity were improved. The research results in increasing conductivity and thermal conductivity by 5% and 15%, respectively, while the tensile strength is increased by 6% higher than Ag-Cu alloy. The anti-electric corrosion property is good, and there is no argent-cadmium steam population originating from the electric arc effect. The addition of lanthanum further reduces the content of oxygen and hydrogen. The optimum quantity of the addition of RE lanthanum in the copper alloy is 0.010% - 0.020% .
基金Project supported by the Ministry of Science and Technology of China (2002BA315A-5)
文摘The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.
文摘Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% La were evaluated by various tests such as copper-accelerated acetic acid salt spray testing（CASS）, immersion test in 3.5% NaCl solution, electrochemical tests including weak polarization curves and electrochemical impedance spectroscopy（EIS） tests, scanning electron microscope（SEM） test and X-ray diffraction（XRD） test.It was found that the corrosion resistance of galvalume coating could be improved by adding proper amounts of La.Meanwhile, the mechanism of the improvement of corrosion resistance by La addition was discussed.
文摘The interaction relation between lanthanum and the constituent elements of Sn-Pb alloy system was analyzed by using the thermodynamic models including Miedema formation energy model for binary system, Tanaka modification by excess entropy and the Chou geometric model for ternary system. The thermodynamic calculaton results show that lanthanum has higher affinity for Sn in the Sn-Pb system. This is an important foundation for the improvement of the metallurgical properties of Sn-Pb solder alloy by adding rare earth elements.
文摘The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and soluble protein increase to a certain degree and then decrease under La3+ Ce3+ Zn2+ stress, while there is a constantly dropping tendency under Cr6+ stress. The four ions have different effects on protective enzyme systems of Potamogeton malaianus. They can induce rises of the activities of catalase (CAT) and peroxides (POD) at lower concentration, however, with the increase of ions concentration, the activities decline. The change of SOD activity is exactly opposite to that of CAT and POD activity. It falls at first and rises later. An increasing tendency of MDA content appears with the increasing concentration. The toxicities of La3+, Zn2+, Ce3+ and Cr6+ become more serious in the order. The lethal concentration of Cr6+ to Potamogeton malaianus ranges from 0.5 to I mg(-1) that of Ce3+ and Zn2+ ranges from 3 to 5 mg(-1) and that of La3+ ranges from 7 to 10 mg(.)L(-1). The toxic mechanism of La3 + and Ce3+ is similar to that of Cr6+ and Zn2+.
