Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffracti...Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffraction （XRD） demonstrated that 900＆#176;C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin （RCK）, whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin （CCK）. The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M？ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900＆#176;C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.展开更多
This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET （Fe73.5Si13.sBgNb3Cul） alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annea...This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET （Fe73.5Si13.sBgNb3Cul） alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annealed with the applied magnetic field show much higher resonance frequencies and have even higher permeability at higher frequencies than the samples annealed without the magnetic field and the non-annealed ribbons. MSssbauer spectroscopy had been employed to study the spatial distribution of the magnetic moments of five selected FINEMET alloy ribbons in different heat-treated conditions. The results show that an easy plane has been established after annealling in the magnetic field, while for the other ribbons this effect is not significant. Hence, the relationship between magnetic field annealing and high frequency property has been bridged by the bianisotropic theory.展开更多
Thin ferromagnetic films with in-plane magnetic anisotropy are promising materials for obtaining high microwave permeability. The paper reports a MSssbauer study of the field induced in-plane uniaxial anisotropy in el...Thin ferromagnetic films with in-plane magnetic anisotropy are promising materials for obtaining high microwave permeability. The paper reports a MSssbauer study of the field induced in-plane uniaxial anisotropy in electro-deposited FeCo alloy films. The FeCo alloy films were prepared by the electro-deposition method with and without an external magnetic field applied parallel to the film plane during deposition. Vibrating sample magnetometry and MSssbauer spectroscopy measurements at room temperature indicate that the film deposited in external field shows an in-plane uniaxial anisotropy with an easy direction coinciding with the external field direction and a hard direction perpendicular to the field direction, whereas the film deposited without external field does not show any in-plane anisotropy. MSssbauer spectra taken in three geometric arrangements show that the magnetic moments are almost constrained in the film plane for the film deposited with applied magnetic field. Also, the magnetic moments tend to align in the direction of the applied external magnetic field during deposition, indicating that the observed anisotropy should be attributed to directional ordering of atomic pairs.展开更多
The relationship between magnetostriction and structure of melt-spun Fes3Ga17 ribbons are investigated by XRD and M5ssbauer spectrum technique （MS）. As the heat-treatment temperature increases from 650℃ to 800℃, t...The relationship between magnetostriction and structure of melt-spun Fes3Ga17 ribbons are investigated by XRD and M5ssbauer spectrum technique （MS）. As the heat-treatment temperature increases from 650℃ to 800℃, the magnetostriction coefficient of Fes3Ga17 ribbon first increases and then decreases. The largest magnetostriction coeiffcient （-578.4 ppm） is achieved in those specimens quenched at 750oc. According to the XRD and MSssbauer spectrum anal- ysis, a small quantity of DO3 phase is precipitated in Fe83Ga17 ribbons when quenched from 650℃ and the DO3 phase is gradually transformed into B2-1ike phase if quenched at higher temperature. However, both DO3 and B2-1ike phases disappear when the temperature increases up to 800℃. From this point of view, B2-1ike phase might be beneficial to the enhancement of magnetostrictive properties of melt-spun ribbons.展开更多
The defects, the behavior of 3d electrons and the hyperfine interactions in binary Fe-Al alloys with different Al contents have been studied by measurements of positron lifetime spectra, coincidence Doppler broadening...The defects, the behavior of 3d electrons and the hyperfine interactions in binary Fe-Al alloys with different Al contents have been studied by measurements of positron lifetime spectra, coincidence Doppler broadening spectra of positron annihilation radiation and M？ssbauer spectra. The results show that on increasing the Al content in Fe-Al alloys, the mean positron lifetime of the alloys increase, while the mean electron density of the alloys decrease. The increase of Al content in binary Fe-Al alloys will decrease the amount of unpaired 3d electrons; as a consequence the probability of positron annihilation with 3d electrons and the hyperfine field decrease rapidly. M？ssbauer spectra of binary Fe-Al alloys with Al content less than 25 at.% show discrete sextets and these alloys make a ferromagnetic contribution at room temperature. The M？ssbauer spectrum of Fe70Al30 shows a broad singlet. As Al content higher than 40 at.%, the M？ssbauer spectra of these alloys are singlet, that is, the alloys are paramagnetic. The behavior of a 3d electron and its effect on the hyperfine field of the binary Fe-Al alloy has been discussed.展开更多
基金financially supported by Zhejiang Natural Science Foundation(No.Y1080393)Opening Foundation of State Key Laboratory of Clean Energy Utilization(No.ZJUEDU2012001)
文摘Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffraction （XRD） demonstrated that 900＆#176;C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin （RCK）, whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin （CCK）. The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M？ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900＆#176;C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.
基金supported by National Natural Science Foundation of China (Grant No.10774061)
文摘This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET （Fe73.5Si13.sBgNb3Cul） alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annealed with the applied magnetic field show much higher resonance frequencies and have even higher permeability at higher frequencies than the samples annealed without the magnetic field and the non-annealed ribbons. MSssbauer spectroscopy had been employed to study the spatial distribution of the magnetic moments of five selected FINEMET alloy ribbons in different heat-treated conditions. The results show that an easy plane has been established after annealling in the magnetic field, while for the other ribbons this effect is not significant. Hence, the relationship between magnetic field annealing and high frequency property has been bridged by the bianisotropic theory.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774061)
文摘Thin ferromagnetic films with in-plane magnetic anisotropy are promising materials for obtaining high microwave permeability. The paper reports a MSssbauer study of the field induced in-plane uniaxial anisotropy in electro-deposited FeCo alloy films. The FeCo alloy films were prepared by the electro-deposition method with and without an external magnetic field applied parallel to the film plane during deposition. Vibrating sample magnetometry and MSssbauer spectroscopy measurements at room temperature indicate that the film deposited in external field shows an in-plane uniaxial anisotropy with an easy direction coinciding with the external field direction and a hard direction perpendicular to the field direction, whereas the film deposited without external field does not show any in-plane anisotropy. MSssbauer spectra taken in three geometric arrangements show that the magnetic moments are almost constrained in the film plane for the film deposited with applied magnetic field. Also, the magnetic moments tend to align in the direction of the applied external magnetic field during deposition, indicating that the observed anisotropy should be attributed to directional ordering of atomic pairs.
基金Project supported by the National Basic Research Program of China (Grant No. 2010CB934602)
文摘The relationship between magnetostriction and structure of melt-spun Fes3Ga17 ribbons are investigated by XRD and M5ssbauer spectrum technique （MS）. As the heat-treatment temperature increases from 650℃ to 800℃, the magnetostriction coefficient of Fes3Ga17 ribbon first increases and then decreases. The largest magnetostriction coeiffcient （-578.4 ppm） is achieved in those specimens quenched at 750oc. According to the XRD and MSssbauer spectrum anal- ysis, a small quantity of DO3 phase is precipitated in Fe83Ga17 ribbons when quenched from 650℃ and the DO3 phase is gradually transformed into B2-1ike phase if quenched at higher temperature. However, both DO3 and B2-1ike phases disappear when the temperature increases up to 800℃. From this point of view, B2-1ike phase might be beneficial to the enhancement of magnetostrictive properties of melt-spun ribbons.
基金Supported by National Natural Science Foundation of China(10764001,51061002)Program for Science and Technology Innovation Team of Guangxi University
文摘The defects, the behavior of 3d electrons and the hyperfine interactions in binary Fe-Al alloys with different Al contents have been studied by measurements of positron lifetime spectra, coincidence Doppler broadening spectra of positron annihilation radiation and M？ssbauer spectra. The results show that on increasing the Al content in Fe-Al alloys, the mean positron lifetime of the alloys increase, while the mean electron density of the alloys decrease. The increase of Al content in binary Fe-Al alloys will decrease the amount of unpaired 3d electrons; as a consequence the probability of positron annihilation with 3d electrons and the hyperfine field decrease rapidly. M？ssbauer spectra of binary Fe-Al alloys with Al content less than 25 at.% show discrete sextets and these alloys make a ferromagnetic contribution at room temperature. The M？ssbauer spectrum of Fe70Al30 shows a broad singlet. As Al content higher than 40 at.%, the M？ssbauer spectra of these alloys are singlet, that is, the alloys are paramagnetic. The behavior of a 3d electron and its effect on the hyperfine field of the binary Fe-Al alloy has been discussed.
