15 February 2014, Volume 45 Issue 03
    

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    工艺 技术
  • Comprised of hot rolled material with high temperature coiling and normalization material for the production of high grade nonoriented silicon steel
    Tie YE ;
    . 2014, 45(03): 1-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Microstructure, texture and magnetic properties of high grade cold rolled nonoriented electrical steel which made of hot rolled material with high temperature coiling and with normalization were studied. Steels coiled in high temperature (at 750 ℃), stacked with insulation cover for 96 hours and air cooled to 100℃ were using to manufacture high grade nonoriented electrical steel. The process can replace the normalization process. There are a lot of recrystallized grains in the surface layer of the coil with high temperature coiling. These recrystallized grains included the dynamically recrystallized microstructure which formed by surface friction between the hot rolling rollers; formed by high temperature of the steel plate selves and formed by the coil stacked densely in the warehouse at 750 ℃. Texture types and orientation distribution density of hot rolled material with high temperature coiling and with normalization are similar. After recrystallization texture types and orientation distribution density are still similar. Goss texture promoted magnetic properties. The ratio of textures of [{100} +Goss]/ {111} reflects heritable and the higher the ratio, the better magnetic properties are in these steels tested.
  • Isolation, Purification and Structural Characterization of an acidic polysaccharide fraction from leaves of Eucommia ulmoides Oliver, named EOP-1
    . 2014, 45(03): 2-0.
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    The crude polysaccharide was extracted by hot water from leaves of Eucommia ulmoides Oliver. The deproteinization and decolorization of the polysaccharide was by Savage method and H2O2 method respectively. EOP-1 was purified by Sepharose CL-6B column chromatography from the crude polysaccharide. HPSEC-RI analysis showed that the melocular weigh of EOP-1 was about 6.0×105D. The structural features of polysaccharide EOP-1 were studied by partial acid hydrolysis and methylation methods, combined with GC-MS instrument, and the results indicate that EOP-1 is a kind of pectic polysaccharide which contained the main part of homogalacturonan fragments and the residues of sugar constituents were mainly D-GalpA, D-Galp, L-Araf and L-Rhap and the backbone was composed of 1,4-linked-D-GalpA and 1,4-D-Galp、1,6-D-Galp、1,5-L-Araf、1,2-L-Rhap were the mainly consititution of the branch, with a relative molar ratio of 45.11:35.9:0.9:10.5:6.9.
  • Study on the Improvement of Coating’s Mechanical properties by mechanical milling method
    Hong-Zhi TANG
    . 2014, 45(03): 3-0.
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    In this paper, we used 6 wt. % Al2O3-7 wt. % YSZ (AYSZ) to prepare the spraying precursor powder by the roller vibration milling. The resulting precursor became mechanical alloying, and formed AlxZr1-xO2-0.5x solid solution. Then, the precursor and 7wt. %YSZ powder were respectively sprayed by the high temperature plasma spraying to form AYSZ and YSZ coatings. The study results show that the grain size of the AYSZ coating is about 60 nm and the AYSZ coating has smaller internal crack without the cross-section, while the grain size of the YSZ coating is about 260 nm and the YSZ coating has wider and deeper internal crack with the obvious cross-section. Test results show that the properties of the AYSZ coating, like porosity, and mechanical properties, like elastic modulus and hardness, are higher than the YSZ coating’s. This paper is referential to the development of coating materials with high properties.
  • Influence of Technology Parameter on Resistivity of Boron Carbide Composities
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    . 2014, 45(03): 4-0.
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    The influence of technology parameter on resistivity of boron carbide/butyl rubber composites during the process of preparation is introduced. The resistivity dependency of different batches and the process of vulcanization and mixing are analyzed by preseting electrode in the composites. The results showed that: some difference of technology in the manufacturing process, the time and temperature of vulcanization, the change of mixing time and the rotor speed will bring obvious change of the conductive network structure. The change will influence the resistivity and the conductive property of composites.
  • Preparation and property of MCMB Fireproof Coating for Steel Structure
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    . 2014, 45(03): 5-0.
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    In this study, an waterborne flame-retardant coating was prepared with Mesocarbon Microbeads (MCMB), and the effect of the MCMB on the fireproof coating has been discussed. The results indicated that: the fire-retardant coating composed of MCMB has better dispersion in water. When the ratio of sericite/MCMB was 3:1, the char layer with compact and well-distributed pores was formed. At the same time, the char structure showed good adhesive properties and was tough enough to protect the steel structure , which effectively prevented heat transfer and thus reduced steel heating rate, improved the fire performance. And the steel structure reached 205℃ at 4200 seconds.
  • Preparation of Inverse-opal Hydrogel（IOH）Films by Using PS Nano-spheres as Templates
    Dong YI
    . 2014, 45(03): 6-0.
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    The monodisperse PS nanospheres with uniform size were prepared by dispersion polymerization. The effect of the amount of reactants on the size and distribution of the PS nanosphere was obtained by the method of orthogonal test and the controllable preparation of the PS nanosphere which size is between 150~350nm was achieved. A series of IOH films were prepared using PS nanospheres as templates and acrylamide/ acrylic acid as raw materials. The IOH films exhibit large variation range in Reflectance spectrum could be obtained when the sizes of PS templates are about 300nm. The IOH films prepared by this method show a good morphology.
  • Electrochemical Performance of Separator Coated with Different Particle Size Alumina
    Rui-jie XU; ;;;;
    . 2014, 45(03): 7-0.
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    In this paper, coating separator was prepared with different particle size alumina(Al2O3) and button cells were made. The electrochemical performances of the button cells were tested. The results showed that as coating dopant, the alumina powder with smaller particle size and narrow distribution could improve the separator performances. Its corresponding capacity retention rate was 96.3% after 30 charge-discharge cycles. The complex impedance and cyclic voltammograms were better than those of base polypropylene separator.
  • Comparative study of preparation and catalytic performance for dye degradation of modified PAN nanofiber Fe complexes
    Xue ting ZHAO;Yongchun Dong ;;;;
    . 2014, 45(03): 8-0.
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    Two kinds of polyacrylonitrile (PAN) fiber Fe complexes were prepared by amidoximation and coordination of ferric ions with PAN nanofibers and conventional PAN fibers as raw materials, respectively. The nitrile group conversion of two kinds of fibers and the variation of Fe content in their complexes were investigated and compared during amidoxime modification and coordination with ferric ions. Based on the characterization, two kinds of modified PAN fiber Fe complexes were used as the heterogeneous Fenton catalysts for the oxidative degradation of azo dye, Reactive Red 195. Their catalytic performance was studied in the dark or under visible irradiation. The results indicated that PAN nanofiber could amidoximate and coordinate with ferric ions more easily than conventional PAN fiber at the same conditions. However, the visible light adsorption of PAN nanofiber Fe complex was slightly lower than conventional PAN fiber. For the oxidative degradation of the dye, PAN nanofiber Fe complex has a much better catalytic activity and stability, especially in the dark.
  • Preparation and Properties of CsVO3/Polymer Composite Material
    Jie LI
    . 2014, 45(03): 9-0.
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    The interaction manners between three polymers and CsVO3 crystal surfaces were simulated. On the basis of theoretical calculation CsVO3/P(S-MMA) powder was prepared by ultrasonic-coupling and in-suit dispersion polymerization. And its film was obtained by spin coating. Their structure and properties were characterization. Results show that: Direct fabrication of the CsVO3/P(S-MMA) would be advantageous not only to avoid particle aggregation but also to further expand potential applications for flexible devices.
  • Preparation and Properties of La and Fe Co-doping TiO2/ACF composite photocatalyst
    . 2014, 45(03): 10-0.
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    La and Fe co-doping TiO2/ACF composite photocatalyst was prepared by sol-gel method with ACF. The photocatalytic activity of the composite photocatalyst under ultraviolet light was evaluated by degradation of formaldehyde．The results showed that the photocatalytic activities of La and Fe co-doping TiO2/ACF composite photocatalysts can be improved in appropriate amount. The photocatalystic activity of the La、Fe-TiO2/ACF composite photocatalyst co-doped with 0.5at% of La、0.5at% of Fe and calcined under 350℃ was the best, The degradation rate of formaldehyde examined at two hours of the reaction was 98.9％.
  • Dry sliding wear and friction performances of high velocity oxygen fuel (HVOF) sprayed chromium oxide coating
    . 2014, 45(03): 11-0.
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    Heat treatments of the HVOF sprayed chromium oxide coating were performed in chamber electric furnace. Effects of heat treatment temperature on dry tribological properties and wear mechanism of the coating were studied by microhardness testing machine, scanning electron microcopy (SEM), energy-dispersive spectroscopy (EDS) and friction wear testing machine. Results indicate that comprehensive wear & friction resistance of the coating after heat treatment at 500 ℃ are the best under the experimental condition in this paper. Heat treatment doesn’t alter wear mechanism of the coating. The main wear mechanisms of the coating are abrasive wear and slight spalling at 10N load, but at 25 N load, spalling is the main wear mechanism and abrasive wear also exist.
    • 研究 开发
  • STUDY ON THE CONDUCTED-NOISE SUPPRESSION PROPERTY OF FeCoB BASED MICROWAVE NOISE SUPPRESSOR
    Jing QIU
    . 2014, 45(03): 12-0.
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    To develop high performance microwave noise suppressor, the microwave noise suppressor based on a microstrip line using FeCoB based magnetic thin film are presented, whose noise suppression effects have been investigated. Effects of RF noise suppression on the process parameter and geometric dimension of noise suppressors were investigated. It was found that suitable low argon pressure is beneficial to the improvement of microwave noise suppression. In addition, the microwave noise suppression properties of RF noise suppressor could be tuned by controlling the geometric dimension of FeCoB based magnetic thin film and SiO2 dielectric layer, resulted from the FMR loss and eddy current loss. The Ploss/Pin of FeCoNiB thin film noise suppressor (length is 25 mm, width is 10 mm, thickness is 250 nm) reaches 75% at 3.4 GHz. These results show that the presented film noise suppressors have potential for the EMI design in the GHz frequency range.
  • Synthesis of titanium carbide coating on surface of graphite by molten salt media
    Jun DING
    . 2014, 45(03): 13-0.
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    Titanium carbide coating layer was synthesized on the surface of flaky graphite by reacting graphite with Ti powder in a NaCl-NaF binary salt at firing different temperatures for 3 h, and the surface of Graphite changed from hydrophobic to hydrophilic. The effects of raw material ratio and firing temperature on the surface modification of graphite powders were studied. The mass ratio of raw materials between Ti and salt was not a significant influence of the morphology of the titanium carbide layer, and small particles grew on the surface of graphite. The firing temperature had a significant effect on the morphology of the titanium carbide layer, and higher temperature conduced to crystal growth and particles size of 1-3 μm. The wettability angle was measured by the tableting method, and the wettability of modified graphite had greatly improved. The surface of graphite were evenly coated by titanium carbide particles, and the titanium carbide coating layer improved the oxidation resistance of the graphite material.
  • Friction and wear properties of PTFE composites containing CNT and graphene
    ;;;;;;
    . 2014, 45(03): 15-0.
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    Modified the surface of CNT and graphene by grafting carboxyl group and amino group, and prepared CNT/PTFE composites and graphene/PTFE composites. Improved the dispersion of nano-reinforcements in PTFE matrix and enhanced the interface bonding via inductive effect between surface functional groups in nano-reinforcements and fluorine atom in PTFE surface. The friction and wear research results shows that grafting amino group in nano-reinforcements’ surface improved composites’ friction and wear properties best, and unmodified reinforcements presented worst properties. Composites of 1wt.% reinforcements content showed the lest wear rate both CNT/PTFE composites and graphene/PTFE composites. CNT in PTFE matrix can effectively bear loads, avoid microscopic tearing resulted by shear force, so the wear rate of composites can reduce significantly, the largest decline was 69.6%; Apart from bearing load, graphene can also form a lubricating film, reducing the friction coefficient and the wear rate of the composite, of which the wear rate felled as much as 73.9%.
  • The Susceptibility Property and the Heat Treatment of Tourmaline from Houxianyu, Liaoning Province
    Yue-song WANG;Chuan xiu yunXi CAO;Huang du bin
    . 2014, 45(03): 16-0.
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    The tourmaline from Houxianyu, Liaoning Province was heated under different temperatures in oxidizing condition. The structure and phase changing after heating treatment were analyzed by optical microscope, XRF, XRD and IR spectroscopy. Magnetic susceptibility was also determined by the magnetic susceptibility testing instrument. The results showed that the black tourmaline is Dravite. Under the temperature of 700℃ the structure of tourmaline began to change and transformed to Anorthite and Hematite under the temperature of 800℃, sintering phenomenon is observed at the same time. The magnetic susceptibility of tourmaline had a negative correlation with the heating temperature. The low-frequency magnetic susceptibility got to lowest as 33.6*10-6cm3/g at 900℃. Its magnetic decrease is related to the phase and the ionic valency change.
  • Effect of ceramic fiber transition layer on the asymmetric filtration membrane of silicon carbide
    Yang-Shan SUN; ;; Xue-Liang YANG;Jia LIU;;jie YANG
    . 2014, 45(03): 17-0.
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    Abstract: The influence of ceramic fiber transition layer composed of mullite fibers and aluminosilicate fibers on the filter pressure drop and deposition of silicon carbide asymmetric filtration membrane used for high-temperature gas filtration were investigated.The surface morphology of the transition layer of ceramic fiber and the side morphology of the asymmetric filter membrane were tested by SEM.The thickness of ceramic fiber transition layer about 60μm between the support and the filtration membrane,which effectively prevent the small particle size of the particles to enter the pores of the supporting body and the actual thickness of the filtration membrane is reduced,thereby reducing the filter pressure drop of the filtration membrane,which is helpful to increase the filter life.Ceramic fiber transition layer also greatly improve the uniformity and integrity of the filtration membranes in the film-forming process.
  • Effect of chemical grafting on the surface structure of carbon fiber
    ; ;
    . 2014, 45(03): 18-0.
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    Chemical grafting is usually to modify the carbon fiber surface to improve interfacial adhesion properties of the carbon fiber/epoxy composite. XPS, Raman spectra, SEM and electronic universal testing machine were employed to characterize chemical states, morphology and interlaminar shear strength(ILSS) of untreated, oxidation, C2H8N2 reduction, C2H6O2 reduction carbon fiber surface. The results indicated that carbon fiber surface O/C ratio, the content of oxygen functional groups, the fiber surface roughness of carbon and the ILSS of irradiated carbon fiber/epoxy composite is increased after oxidation and chemical grafting on the surface of carbon fiber. Under the same conditions, the 1.2-Ethanediamine graft solutions can make the carbon fiber/epoxy composite ILSS is increased by the rate of 52.5% and the 1.2-Ethanediol graft solutions can make the carbon fiber/epoxy composite ILSS is increased by the rate of 47.9%, the 1.2-Ethanediamine graft solutions have ideal grafting effect on carbon surface.
  • Synthesis and Photoluminescence of a Full-color Emitting Phosphor Gd2MoB2O9:Eu3+,Tb3+ for White Light LEDs
    . 2014, 45(03): 19-0.
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    Abstract: The Eu3+and Tb3+co-doped barium magnesium silicate Gd2MoB2O9 phosphors, which can emit a full-colour light, are synthesized by high temperature solid state reaction, and their luminescence characteristics were investigated．The Gd2MoB2O9:Eu3+,Tb3+ emitted an intensive white light emission under excitation at 375 nm at room temperature. The spectra measurement show that the phosphors Gd2MoB2O9:Eu3+,Tb3+ emit three colours light peaked at 486nm, 543nm and 613nm, which are better suitable wavelength for composing white light. The excitation spectra having higher absorption between 250nm and 400nm, match with the UV-LED chips for white light emitting diode(w-LED).
  • Materials research of SF/COL/PLCL and SF/COL/PLLA electrospun three-dimensiona nanofiber scaffold
    . 2014, 45(03): 20-0.
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    Biocompatible and biodegradable PLCL and PLLA were used as material，Through the electrostatic spinning method, with a 70:30 as mass ratio of SF/COL and PLCL/PLLA blending preparation of nanofiber scaffold materials of different mass ratio. The methods of X-ray diffraction (XRD), thermogravimetric analysis on the physical and chemical properties of the composites were characterized and their performance were discussed and compared before and after cross-linking.Results show that SF/COL/polymer composite after its molecular structure and thermal stability change is not obvious,meanwhile, Crosslinked composite nanofibers stent beta degree, crystallinity and thermal stability increased before the crosslinking that can form stable conformation, thermal stability,so it can provide structure for certain cells in the tissue engineering support, which is expected to become a new type of tissue engineering scaffold material
  • Selective amorphization and novel coaxial structure formation of a single crystal Si nanowire induced by focused electron beam irradiation
    . 2014, 45(03): 21-0.
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    Structural instability of a single crystal Si nanowire at room temperature under focused electron beam irradiation was investigated by our developed In-situ transmission electron microscopy observation technique. It was observed that a series of intriguing changes such as preferential amorphization at the surface of Si nanowire, local bulging in the radial direction and formation of a novel three layers-packaged coaxial structure of Si nanowire with the increasing of electron doses during the irradiation.The possible mechanism for such phenomena was proposed and further discussed by completely new concepts of nanocurvature effect and energetic beam-induced athermal activation effect, while the current knock-on mechanism and electron beam heating effect seemed inadequate to explain these processes.
  • A study on corrosion behavior and electrochemical mechanism of nickel plated punched steel strip
    LI Chao qun ; ;
    . 2014, 45(03): 22-0.
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    The corrosion rate of nickel plated punched steel strip was measured by immersion corrosion test. The electrochemical corrosion behavior and mechanism of these Ni deposits in 5% NaCl media were investigated by using potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The results showed that the Ni deposit exhibits remarkably improved corrosion resistance. The higher corrosion resistance of nickel plated punched steel strip may be ascribed to the inherent nature of Ni and the more rapid formation of stable and continuous protective passive film. The results also revealed that the Ni deposited from citrate bath has higher polarization resistance, smaller corrosion current, higher charge transfer resistance and smaller corrosion rate, compared with that from Watts bath.
  • Characteristic of Heat Conduction in Nano-insulation Material
    Ya-Fen HAN ;
    . 2014, 45(03): 23-0.
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    In order to further investigate the heat conduction performance of aerogel nano-insulation material, this paper propose calculational model for solid and gas combined conduction in which the non-uniformity distribution of solid nanograin is taken into account. The thermal conductivity of nanograin of aerogel is simulated using Lattice Boltzmann Method. Based on the proposed structure model, the effects of density, porousity and non-uniformity distribution of solid nanograin on the thermal performance of aerogel are investigated.
    • 综述 进展
  • A review of hydroxyapatite microstructure regulation with hydrothermal method
    . 2014, 45(03): 24-0.
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    Due to the excellent biocompatibility and bioactivity, hydroxyapatite (HA) has been widely used in the fields of bone repair and substitute. However, the different microstructure has a great influence on the mechanical properties and biological properties, so it is critical to control the morphology and microstructure of HA. Hydrothermal method is an artificial environment of high temperature and high pressure, by adding Ca and P sources, synthetic crystalline apatite grains have higher crystallinity in the extreme conditions. Affected by biomimetic mineralization, organic polymer can be used in preparing novel morphology of apatite particles by hydrothermal method due to a mount of active groups for apatite orientated deposition. This paper summarized the methods of HA preparation by hydrothermal method using different kinds of organic template in recent years, and discussed the mechanism of organic template to control apatite grain size and morphology and forecasted the development trend of it.
  • Research Methods and Developments of NiCuZn Ferrite Sheet used in NFC
    Hong-Wei YANG
    . 2014, 45(03): 25-0.
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    Using of the NiCuZn ferrite sheet with high permeability and low loss in the Near Field Communication (NFC) is explained, as well as the process steps of sintering ferrite. The effect and using method of main composition and addition to this kind of NiCuZn ferrite is presented detailedly. The development status of homeland and abroad of the NiCuZn ferrite sheet is recommended, and pointing out the lack of research in the NiCuZn ferrite.
    • 研究 开发
  • The effects of technologic parameters on the rheological properties of the SiO2 / PEG disperse system and mechanism analysis
    Xin-Ya FENG;
    . 2014, 45(03): 27-0.
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    In this paper，the influence of synthesis temperature and dispersion time on the rheological properties of silica dispersions was studied with a stress controlled rheometer.The results show that as the synthesis temperature increases, the systems shows more obvious shear thickening and higher apparent viscosity, meanwhile,over dispersion time the systems shows less obvious shear thickening and smaller apparent rviscosity, The mechanism about the effect of the synthesis temperature and dispersion time on the rheological properties of silica dispersions was explored by future study,and the study shows that synthesis temperature and the dispersion time can change the content of the gas phase,which has some influence on the rheological properties of the dispersions,the properties of shear thickening improvemed and the apparent viscosity increased as the gas phase in the system increased.
  • Study on Magnetics and Optical Properties of transitionmetal Doped SnO2 Superlattice
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    . 2014, 45(03): 28-0.
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    The density of state (DOS), band structure, optical coefficient of n-layers transition metal Cr doped SnO2 superlattice are calculated using first-principles of density functional theory and full potential linearized augmented plane wave method (n=1, 2, 3). Generalized gradient approximations (GGA) are used for handling correlation energy. The result show that these several doping are all half-metallic. The magnetic moment and electroconductivity will be enhanced with the increase of n. The magnetic moment is contributed mainly by Cr-3d states and minority by O-2p states. Due to p-d hybridization, the doping-Cr makes the DOS of oxygen producing spin polarization. Because of the d-d transition of Cr atom, in 0~1.8eV, the position of first absorption peak will move back with the increase of n. In 1.8eV~7.0eV, the magnitude of the peak formed by p-d transition is augmented with the increase of n. In 7.0eV~17eV, the magnitude of the peak formed by p-s transition is reductive with the increase of n.
  • Effect of wheel speed and pressure difference on melt-spun NdFeB powders and die-upset magnets
    lai bin ;
    . 2014, 45(03): 29-0.
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    High-performance anisotropic NdFeB magnets can be prepared by hot deformation of melt-spun magnetic powders. Influence of wheel speed and pressure difference between the inside and outside of the quartz tube on melt-spun NdFeB powders and subsequent die-upset magnets was studied in this work. Increase of wheel speed can refine grain size of main phase（Nd2Fe14B） or increase the content of the amorphous phase, but the amorphous was harmful for the grain orientation in the hot deformation process and then texture formation. However, the lower wheel speed will result in the big size of grains and was also not helpful for the hot deformation and texture formation. Too high or too low wheel speed will reduce the romance Br and the maximum energy product (BH)m of the final deformed NdFeB magnets. The appropriate grain size with appropriate wheel speed in the melt-spun powders was 25-40nm. Reduce of pressure difference can also refine the grain size but not affect the content of the amorphous. When the pressure difference was lower than 0.07MPa, a new diffraction peak was found in the XRD spectrum and we think it may be a metastable phase. The content of the possible metastable phase increase with reduced pressure difference. The possible metastable phase will deteriorate the romance Br, the coercivity Hcj and the maximum energy product (BH)m of the deformed magnets. The best melt-spinning process conditions in the work were obtained as follows. The optimal wheel speed was 25m/s and the optimal pressure difference was 0.07MPa. The magnetic properties of deformed magnets from melt-spun powder in the preparation condition is: Br=12.93KGs，(BH)m=37.5MGOe，Hcj=11.56kOe.
  • The effects of the PLLA adhesion prevention membrane on the functions of late endothelial progenitor cells
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    . 2014, 45(03): 30-0.
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    Abstract：To investigate the effects of the PLLA adhesion prevention membrane on the functions of late endothelial progenitor cells (EPCs). The 3rd generation EPCs, namely late EPCs, was harvested and cell biological functions, such as proliferation, adhesion, migration, the ability of forming tubes, apoptosis and senescence were assayed with CCK-8, adhesion test, Boyden chamber assay, Matrigel, flow cytometry and β-Galactosidase staining, respectively. The late EPCs implanted on the PLLA adhesions prevention membrane exhibited decreased capabilities of proliferation, adhesion, migration and tube formation. In the mean time, PLLA increased the senescence of late EPCs but had no effect on cell apoptosis. Therefore, PLLA inhibits late EPC functions, which may be one of the mechanisms that PLLA adhesion prevention membrane prevents permanent adhesions.
  • Crystallization kinetics of melt-Spun Nd9Fe85.5-xCoxB5.5(x=3,5at%) amorphous ribbons
    Xin-cai LIU;PAN Jing
    . 2014, 45(03): 31-0.
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    The heating curves of Nd9Fe85.5-xCoxB5.5(x=3,5at%) amorphous alloy ribbons were measured by DSC protected by filling argon after vacuuming. The crystallization activation energy E, frequency factor Z, reaction rate constant K and Avrami exponent n of the two kinds of amorphous alloy ribbons were calculated according to the DSC curves. It is confirmed that the crystallization process changes from one step to two-steps with Co content increasing from 3at% to 5at%.And the higher Co content in the alloy, the higher crystallization activation energy E and crystallization reaction rate constant K of both the initial crystallization temperature Tx and the peak one Tp. This is the reason that the increase of frequency factor Z playes a key role. At the heating speed 10 k/min, the local Avrami exponent n of Nd9Fe82.5Co3B5.5 decreases sharply at first and then slow down with the increase of crystallization volume fraction x, but it rises again when x is more than 90%. It demonstrates that when x is less than 12%, the crystallization nucleation mainly in the three-dimensional nucleation mode, and it changes into the two-dimensional nucleation one when x is 12%~36%, after 36% it does in the one-dimensional nucleation one.
  • The study of magnetic properties and magnetization reversal mechanism of Gd doped FeCo thin films
    . 2014, 45(03): 32-0.
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    Gd doped magnetic FeCo thin films were fabricated by DC magnetron co-sputtering at ambient condition. The structure transition from nano-crystalline structure to crystalline structure were characterized by XRD upon increasing sputtering power. A spin reorientation transition from in-plane uniaxial anisotropy to perpendicular anisotropy was observed as the temperature decreasing to around 120 K for crystalline sample. While the SRT was absent in the nanocrystalline sample as the temperature decrease to the lowest available temperature of 100 K. The investigation of the angular dependence of coercivity indicates that the magnetization reversal mechanism of nanocrystalline FeCoGd film is domain-wall depinning or nucleation and coherent rotation when the applied field is close to the easy axis and hard axis, respectively.
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