The Ni-based self-fluxing alloy coating containing RE was acquired by the technique of vacuum melting on the hypoeutectoid steel （Fe-0.45%C） matrix. By X-ray diffraction, SEM and EDX, the microstructure and phase st...The Ni-based self-fluxing alloy coating containing RE was acquired by the technique of vacuum melting on the hypoeutectoid steel （Fe-0.45%C） matrix. By X-ray diffraction, SEM and EDX, the microstructure and phase structure of section of coating and the microstructure near the interface between coating and matrix were investigated, and the effect of RE on microstructure of coating was also discussed. The results show that the microstructure of the NiCrBSi alloy coating is composed of Ni-based solid solution and a lot of massive, globular and needle secondary phases CrB, Ni3B, Cr7C3, Cr23C6 among the solid solution. The metallurgical binding between steel matrix and coating is realized. RE makes needle phase of alloy coating vanish. New phases of NiB and Cr6.5Ni2.5Si are precipitated from alloy coating, and secondary phases of alloy coating are sphericized. Consequently, RE also hinders the diffusion of Ni, Cr and Si atoms from coating to matrix and Fe atoms from matrix to coating, holds back the dilution of Fe for NiCrBSi alloy coating, and assures the chemical composition of the alloy coating.展开更多
To improve the heat transfer capability and the crystallization property of the traditional mold flux, CaF_2 was replaced with B_2O_3. Then, the influences of CeO_2 on the heat transfer and the crystallization of the ...To improve the heat transfer capability and the crystallization property of the traditional mold flux, CaF_2 was replaced with B_2O_3. Then, the influences of CeO_2 on the heat transfer and the crystallization of the CaF_2-bearing mold flux and the new mold flux with 10 wt% B_2O_3 were studied using a slag film heat flux simulator and X-ray diffraction(XRD). The results revealed that the addition of CeO2 reduced the heat transfer by increasing the solid slag thickness and the crystallization of two mold fluxes. However, CeO_2 had less effect on the B_2O_3-containing mold flux compared with the CaF_2-bearing mold flux. According to the analyses, the CeO_2 contents in the CaF_2-bearing mold flux and the B_2O_3-containing mold flux should not exceed 8 wt% and 12 wt%, respectively. Therefore, these experimental results are beneficial to improve and develop the mold flux for casting rare earth alloy steels.展开更多
Lithofacies structure of commercial cover flux and experimental slags were analyzed,and states of rare earth oxides in cover flux were studied. The results show that under the experiment conditions,the mineral structu...Lithofacies structure of commercial cover flux and experimental slags were analyzed,and states of rare earth oxides in cover flux were studied. The results show that under the experiment conditions,the mineral structures of original slags are mainly the calcium feldspar,a lot of magnesium olivine and Fe-bearing silicate. Rare earth oxides in the cover flux exist mainly as rare earth silicates. When the content of rare earth oxides reaches a certain value,rare earth oxides precipitate in molten cover flux. It means that the solubility of rare earth oxides is limited. Rare earth oxides may be partly substituted for CaO to form rare earth-silicate which may increase with the basicity reducing.展开更多
The effects of RE （rare earth） oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that: （1） The viscosity of mold fluxes is remarkably increased by RE oxide addition, es...The effects of RE （rare earth） oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that: （1） The viscosity of mold fluxes is remarkably increased by RE oxide addition, especially when the mass fraction of RE oxide is more than 10%. （2） By addition of RE oxide, precipitation of the insoluble particles with high melting point from the molten slag with the decreasing of the temperature leads to the increase of viscosity. Viscosity curve shows that RE oxide is soluble in some extent in mold fluxes. When RE oxide is in a state of supersaturation, the existence of insoluble particles also makes the viscosity of mold fluxes increase. （3） Not only the viscosity of mold fluxes can be reduced, but also the capacity to dissolve and absorb RE oxide can be increased by Li2O, B2O3 and BaO. However, the contents of Li2O, B2O3, and BaO should be controlled to suitable levels. （4） The solidification temperature of mold fluxes can be increased by the addition of RE oxide, which is unfavorable to heat transfer and lubrication of mold fluxes between steel shell and mold.展开更多
Ce3+-activated yttrium aluminum garnet (YAG) was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied...Ce3+-activated yttrium aluminum garnet (YAG) was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied in detail, especially the fluxes of alkali fluorides, which could enhance the emission intensity and change the wavelength of emission peaks. Among these YAG:Ce phosphors, the phosphor sintered with H3BO3 and NaF exhibited the strongest emission. The emission peaks of phosphors prepared with fluxes from LiF to KF were shifted to long wavelength. The effect of NaF concentration on the emission intensity of YAG:Ce was also investigated. The value of emission intensity reached the maximum when the concentration of NaF was 0.5%.展开更多
The luminescence of Eu2+ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from diffe...The luminescence of Eu2+ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu2+ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was en- hanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes (LED) combined with tricolor phosphors.展开更多
Long-lasting phosphor Y2O2S∶Eu 3+, Mg 2+, Ti 4+ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the...Long-lasting phosphor Y2O2S∶Eu 3+, Mg 2+, Ti 4+ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S∶Eu 3+x（0.01≤x≤0.10）. On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S∶ Eu 3+ crystal structure, Eu 3+ ions only replaced Y 3+ ions′ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm （5D1→7F2 transition） to 626 nm （5D0→7F2 transition）, and the maximum intensity was obtained when x=0.09 in Y2O2S∶Eu 3+x（0.01≤x≤0.10）. This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg 2+ or Ti 4+ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg 2+ and Ti 4+ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence （LLP） was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye （0.32 mcd·m -2）. Thus the LLP mechanism was analyzed.展开更多
The influences of the flux KCl or KF on the XRD spectra, cell parameters and crystal appearance, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ were studied. The results indicate that when 4.2%, 8.6%, 1...The influences of the flux KCl or KF on the XRD spectra, cell parameters and crystal appearance, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ were studied. The results indicate that when 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5%KF are respectively added into phosphor (La0.85Ce0.15) (Mg0.9Mn0.1)B5O10, compared with the normal card of JCPDS （No 35-120）, the intensity of XRD spectra is enhanced, the values corresponded to 17/28, 18/28, 16/28, 18/28 and 2/28 and the cell parameters diminish because of the flux KCl and KF. The use of 5% KCl a fraction of Cu monocrystals are observed in the phosphor. There are six hexagonal crystal-faces and eight triangular crystal-faces representing crystal-face index {100} and {111}. When 15% KCl is added to the phosphor, law of crystal plane and self-regulaton are formed, the emission intensity of Ce3+ 5d-4f ((（）2F5/2,) (（）2F7/2)) and Mn2+ （（（）4G） and （（）6S）） increases by 3.41 times and 2.36 times respectively.展开更多
The influences of the flux KCl or KF on the XRD patterns, cell parameters, crystal morphology, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ are studied. The results indicate that as 4.2%, 8.6%, 12.8% ...The influences of the flux KCl or KF on the XRD patterns, cell parameters, crystal morphology, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ are studied. The results indicate that as 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5% KF are added individually into the phosphor (La0.85Ce0.15) (Mg0.9Mn0.1) B5O10, some peaks of the XRD patterns are intensified and cell volumes are decreased. A small amount of Cu mono-crystal typed phase appears as more than 5% KCl is added. There are six hexagonal crystal-faces and eight triangular crystal-faces attributed to the {100} and {111} respectively. When 15% KCl is added into the phosphor, multi-faced regular crystals are formed and the crystal self-regulation appears. The emission intensity of 5d→4f ((（）2F5/2,) (（）2F7/2)) of Ce3+ and （（）4G→（）6S） of Mn2+ increases up 3.41 and 2.36 times respectively.展开更多
High calcination temperature is an important factor in the preparation process of CeMgAl 11O 19∶Tb 3+. To decrease the temperature, different fluxes (H 3BO 3, MgF 2 and AlF 3) were tested in order to compare their in...High calcination temperature is an important factor in the preparation process of CeMgAl 11O 19∶Tb 3+. To decrease the temperature, different fluxes (H 3BO 3, MgF 2 and AlF 3) were tested in order to compare their influence on the luminescence property and particle size distribution of CeMgAl 11O 19∶Tb 3+. The result shows that when the content of MgF 2 is 0.1 mol/mol, the intensity of luminescence can attain a maximum. Furthermore, MgF 2 can improve the particle size quality of the phosphor. So MgF 2 can take the place of the conventional flux H 3BO 3 to prepare high quality CeMgAl 11O 19∶Tb 3+ phosphor. In addition, the relation between phosphor property and content of AlF 3 was also studied. The crystal structure of the phosphor was analyzed by XRD method. The phase composition analysis shows that the reason of decrease of the brightness of CeMgAl 11O 19∶Tb 3+ phosphor is the emergence of TbAlO 3 and α-Al 2O 3 during the preparation process.展开更多
文摘The Ni-based self-fluxing alloy coating containing RE was acquired by the technique of vacuum melting on the hypoeutectoid steel （Fe-0.45%C） matrix. By X-ray diffraction, SEM and EDX, the microstructure and phase structure of section of coating and the microstructure near the interface between coating and matrix were investigated, and the effect of RE on microstructure of coating was also discussed. The results show that the microstructure of the NiCrBSi alloy coating is composed of Ni-based solid solution and a lot of massive, globular and needle secondary phases CrB, Ni3B, Cr7C3, Cr23C6 among the solid solution. The metallurgical binding between steel matrix and coating is realized. RE makes needle phase of alloy coating vanish. New phases of NiB and Cr6.5Ni2.5Si are precipitated from alloy coating, and secondary phases of alloy coating are sphericized. Consequently, RE also hinders the diffusion of Ni, Cr and Si atoms from coating to matrix and Fe atoms from matrix to coating, holds back the dilution of Fe for NiCrBSi alloy coating, and assures the chemical composition of the alloy coating.
基金financially supported by the National Natural Science Foundation of China (No. 51774024)
文摘To improve the heat transfer capability and the crystallization property of the traditional mold flux, CaF_2 was replaced with B_2O_3. Then, the influences of CeO_2 on the heat transfer and the crystallization of the CaF_2-bearing mold flux and the new mold flux with 10 wt% B_2O_3 were studied using a slag film heat flux simulator and X-ray diffraction(XRD). The results revealed that the addition of CeO2 reduced the heat transfer by increasing the solid slag thickness and the crystallization of two mold fluxes. However, CeO_2 had less effect on the B_2O_3-containing mold flux compared with the CaF_2-bearing mold flux. According to the analyses, the CeO_2 contents in the CaF_2-bearing mold flux and the B_2O_3-containing mold flux should not exceed 8 wt% and 12 wt%, respectively. Therefore, these experimental results are beneficial to improve and develop the mold flux for casting rare earth alloy steels.
文摘Lithofacies structure of commercial cover flux and experimental slags were analyzed,and states of rare earth oxides in cover flux were studied. The results show that under the experiment conditions,the mineral structures of original slags are mainly the calcium feldspar,a lot of magnesium olivine and Fe-bearing silicate. Rare earth oxides in the cover flux exist mainly as rare earth silicates. When the content of rare earth oxides reaches a certain value,rare earth oxides precipitate in molten cover flux. It means that the solubility of rare earth oxides is limited. Rare earth oxides may be partly substituted for CaO to form rare earth-silicate which may increase with the basicity reducing.
基金Project supported by the National Natural Science Foundation of China (50204005)
文摘The effects of RE （rare earth） oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that: （1） The viscosity of mold fluxes is remarkably increased by RE oxide addition, especially when the mass fraction of RE oxide is more than 10%. （2） By addition of RE oxide, precipitation of the insoluble particles with high melting point from the molten slag with the decreasing of the temperature leads to the increase of viscosity. Viscosity curve shows that RE oxide is soluble in some extent in mold fluxes. When RE oxide is in a state of supersaturation, the existence of insoluble particles also makes the viscosity of mold fluxes increase. （3） Not only the viscosity of mold fluxes can be reduced, but also the capacity to dissolve and absorb RE oxide can be increased by Li2O, B2O3 and BaO. However, the contents of Li2O, B2O3, and BaO should be controlled to suitable levels. （4） The solidification temperature of mold fluxes can be increased by the addition of RE oxide, which is unfavorable to heat transfer and lubrication of mold fluxes between steel shell and mold.
基金supported by the Science Technology Project of Zhejiang Province (2008C21153)the National Natural Science Foundation of China (60508014 and 50772102)+1 种基金Program for New Century Excellent Talents in University (NCET-07-0786)the Nature Science Foundation of Zhejiang Province (R406007)
文摘Ce3+-activated yttrium aluminum garnet (YAG) was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied in detail, especially the fluxes of alkali fluorides, which could enhance the emission intensity and change the wavelength of emission peaks. Among these YAG:Ce phosphors, the phosphor sintered with H3BO3 and NaF exhibited the strongest emission. The emission peaks of phosphors prepared with fluxes from LiF to KF were shifted to long wavelength. The effect of NaF concentration on the emission intensity of YAG:Ce was also investigated. The value of emission intensity reached the maximum when the concentration of NaF was 0.5%.
基金Project supported by the State Key Program for Basic Research of China (G1998061306)the National Natural Science Foundation of China (20071003, 20221101)the High Tech. Research of Zhejiang Province (2003C31029)
文摘The luminescence of Eu2+ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu2+ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was en- hanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes (LED) combined with tricolor phosphors.
文摘Long-lasting phosphor Y2O2S∶Eu 3+, Mg 2+, Ti 4+ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S∶Eu 3+x（0.01≤x≤0.10）. On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S∶ Eu 3+ crystal structure, Eu 3+ ions only replaced Y 3+ ions′ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm （5D1→7F2 transition） to 626 nm （5D0→7F2 transition）, and the maximum intensity was obtained when x=0.09 in Y2O2S∶Eu 3+x（0.01≤x≤0.10）. This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg 2+ or Ti 4+ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg 2+ and Ti 4+ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence （LLP） was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye （0.32 mcd·m -2）. Thus the LLP mechanism was analyzed.
文摘The influences of the flux KCl or KF on the XRD spectra, cell parameters and crystal appearance, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ were studied. The results indicate that when 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5%KF are respectively added into phosphor (La0.85Ce0.15) (Mg0.9Mn0.1)B5O10, compared with the normal card of JCPDS （No 35-120）, the intensity of XRD spectra is enhanced, the values corresponded to 17/28, 18/28, 16/28, 18/28 and 2/28 and the cell parameters diminish because of the flux KCl and KF. The use of 5% KCl a fraction of Cu monocrystals are observed in the phosphor. There are six hexagonal crystal-faces and eight triangular crystal-faces representing crystal-face index {100} and {111}. When 15% KCl is added to the phosphor, law of crystal plane and self-regulaton are formed, the emission intensity of Ce3+ 5d-4f ((（）2F5/2,) (（）2F7/2)) and Mn2+ （（（）4G） and （（）6S）） increases by 3.41 times and 2.36 times respectively.
文摘The influences of the flux KCl or KF on the XRD patterns, cell parameters, crystal morphology, and spectral properties of the phosphor LaMgB5O10∶Ce3+, Mn2+ are studied. The results indicate that as 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5% KF are added individually into the phosphor (La0.85Ce0.15) (Mg0.9Mn0.1) B5O10, some peaks of the XRD patterns are intensified and cell volumes are decreased. A small amount of Cu mono-crystal typed phase appears as more than 5% KCl is added. There are six hexagonal crystal-faces and eight triangular crystal-faces attributed to the {100} and {111} respectively. When 15% KCl is added into the phosphor, multi-faced regular crystals are formed and the crystal self-regulation appears. The emission intensity of 5d→4f ((（）2F5/2,) (（）2F7/2)) of Ce3+ and （（）4G→（）6S） of Mn2+ increases up 3.41 and 2.36 times respectively.
文摘High calcination temperature is an important factor in the preparation process of CeMgAl 11O 19∶Tb 3+. To decrease the temperature, different fluxes (H 3BO 3, MgF 2 and AlF 3) were tested in order to compare their influence on the luminescence property and particle size distribution of CeMgAl 11O 19∶Tb 3+. The result shows that when the content of MgF 2 is 0.1 mol/mol, the intensity of luminescence can attain a maximum. Furthermore, MgF 2 can improve the particle size quality of the phosphor. So MgF 2 can take the place of the conventional flux H 3BO 3 to prepare high quality CeMgAl 11O 19∶Tb 3+ phosphor. In addition, the relation between phosphor property and content of AlF 3 was also studied. The crystal structure of the phosphor was analyzed by XRD method. The phase composition analysis shows that the reason of decrease of the brightness of CeMgAl 11O 19∶Tb 3+ phosphor is the emergence of TbAlO 3 and α-Al 2O 3 during the preparation process.
