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  • 1
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 72, No. 6 ( 2023), p. 067502-
    Abstract: Microelectronic devices have a wide range of application prospects. In order to make microelectronic devices that have excellent high-frequency characteristics, developing of soft magnetic films with high saturation magnetization, low coercivity and high resistivity becomes the key to the research. In this work, Fe-Fe〈sub〉3〈/sub〉N soft magnetic films with different numbers of N atoms are prepared by radio-frequency atomic source assisted vacuum thermal evaporation. Among them, the RF atom source provides N atoms with higher chemical activity than N molecules, which reduces the formation energy between Fe atoms and N atoms. The vacuum thermal evaporation is beneficial to accurately controlling the growth rate, impurity concentration and composition ratio of multiple compounds of the film at the atomic level. The combination of the two Fe aom and N atom is easier to form nitrides with Fe atoms. Thus in this way the Fe-N films with stable structure are obtained. In the prepared Fe-Fe〈sub〉3〈/sub〉N soft magnetic film, the introduction of N atoms makes the surface of the film more uniform, resulting in the increase of density. Compared with Fe, surface roughness is reduced by two times, and the crystallinity is obviously enhanced. Owing to the high saturation magnetization, the content of Fe〈sub〉3〈/sub〉N phase is increased by 29% and the (102) orientation of Fe〈sub〉3〈/sub〉N increases to 0.64. Therefore the directionality of the magnetic moment arrangement is improved. Comparing with Fe film, the saturation magnetization of the film is increased by 55.2%, reaching 1705.6 emu/cm〈sup〉3〈/sup〉. In addition, with the increase of the (102) orientation of Fe〈sub〉3〈/sub〉N, a large number of lattice mismatches are produced, which impedes the growth of Fe and Fe〈sub〉3〈/sub〉N grains and reduces the grain size and anisotropy of the film. Thus the coercivity of the film decreases. The coercivity (50.3 Oe) is 68.6% lower than that of the Fe film. At the same time, the larger lattice mismatch results in the increase of heterointerface, which promotes the carrier scattering and increases the resistivity of Fe-Fe〈sub〉3〈/sub〉N thin film. The resistivity (8.80 μΩ·m) of Fe-Fe〈sub〉3〈/sub〉N thin film is 7 times higher than that of Fe thin film. Therefore, this research provides a new method for studying and developing soft magnetic films with high saturation magnetization, low coercivity and high resistivity.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2023
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  • 2
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 9 ( 2018), p. 097501-
    Abstract: In order to tune the crystalline texture evolution and magnetic properties of the Sm-Fe film, molecular beam vapor deposition method is used to fabricate the Sm-Fe films. Sm content, thickness, and high magnetic field are used to affect the crystalline texture and magnetic properties. X-ray diffraction is used to analyze the texture evolution. Atomic force microscope is used to observe the surface morphology and roughness. Energy-dispersive X-ray spectroscopy is used to measure the compositions of the film. Vibrating sample magnetometer is used to test the magnetic properties. The results show that the crystalline textures are tuned through the Sm content. The crystalline texture evolution and high magnetic field have significant effect on the magnetic properties of the Sm-Fe film. The Sm-Fe film with 5.8% atomic content is of bcc crystal structure and is of amorphous structure with 33.0% Sm. Neither the thickness nor the high magnetic field has an influence on the crystalline texture. The surface roughness and particle size on the surface of the amorphous film are smaller than those of the crystal film. A 6 T high magnetic field increases the surface particle size and reduces the surface roughness. Saturation magnetization Ms of the amorphous film is 47.6% lower than that of the crystal film (1466 emu/cm3, 1 emu/cm3=410-10 T). The 6 T high magnetic field reduces the Ms of crystal and amorphous film by about 50%. The coercivity Hc values of the Sm-Fe films are in a range of 6-130 Oe (1 Oe=103/(4) A/m). The Hc of the amorphous film is higher than that of the crystal film. The 6 T high magnetic field increases the Hc of the crystal film and reduces the Hc of the amorphous film. The highest reduction is 95%. The anisotropy of the crystal film transforms to isotropy of the amorphous film. High magnetic field increases the anisotropy of the crystal film. The squareness of the crystal film is much higher than that of the amorphous film. High magnetic field has a significant effect on the measured magnetic field to obtain saturation magnetization in the film. This measured saturation magnetic field increases in the amorphous film and decreases in the crystal film after the high magnetic field has been exerted during the film growth. These results indicate that the Sm content and high magnetic field can be used to tune the crystal textures and magnetic properties of the Sm-Fe films.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2018
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  • 3
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 66, No. 2 ( 2017), p. 027401-
    Abstract: Ag-Cu alloys are used as both decorative materials because of beautiful appearance, and conductors due to excellent combinations of strength and electrical conductivity. The strength and electrical conductivity of Ag-Cu alloy are closely related to precipitation behavior of Cu-rich phase in Ag matrix. The morphology, size and volume fraction of Cu-rich phase have been highly concerned. In this work, a series of aging temperatures is used in both supersaturated solid-solution and cold-rolled Ag-7wt.%Cu samples to investigate the relationship between the precipitation behavior of Cu-rich phase and property by using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and properties measurements (hardness and resistivity). The DSC results of as-solid-solution Ag-7wt.%Cu alloy show a distinct exothermic precipitation reaction of Cu out of Ag matrix ranging from 300 C to 350 C, and the activation energy is estimated to be (1111.6) kJ/mol according to Kissinger equation. Because of the existence of deformation energy, the DSC results of cold-rolled Ag-7wt.%Cu sample show a distinct exothermic precipitation reaction of Cu from Ag matrix between 290 C and 330 C, and the activation energy is (12812) kJ/mol. XRD analysis indicates that the dissolved Cu in Ag is dependent on ageing temperature, and the change of solubility of Cu in Ag is calculated by XRD curve. Microstructural analysis demonstrates that spherical Cu-rich phases are precipitated from Ag-matrix at 450 C in both solid-solution and cold-rolled Ag-7wt.%Cu alloys. Moreover, the banded structure of Cu-rich phase is found in the solid-solution sample after being aged at 450 C. The deformation twinning Ag is found in the cold-rolled sample. The precipitation and dissolution of Cu-rich phase in Ag matrix play important roles in the resistivity and microhardness. With ageing temperature increasing (ageing temperatures range from 200 to 450 C), the electrical resistivity of as-solid-solution aged sample decreases and the microhardness increases, however, both electrical resistivity and microhardness of as-cold-rolled aged sample decrease. With ageing temperature increasing further (over 450 C), the electrical resistivity increases and the microhardness decreases in both aged samples. Because of the formations of dislocation and deformation twinning Ag, the microhardness of cold-rolled sample reaches to 217 HV, which is higher than that of solid-solution sample. Strengthening and electrical resistivity models are built based on the microstructural characterization and concentration contributions. These theoretical predictions are in good agreement with experimental values. Our model demonstrates that the precipitation and dissloution of Cu in Ag significantly affect the electrical conductivity, and dislocation and deformation twinning play important roles in microhardess in Ag-Cu alloy. This work clarifies the influencing mechanism of different microstructures on the microhardness and resistivity of Ag-Cu alloy.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2017
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  • 4
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 70, No. 21 ( 2021), p. 214401-214401
    Type of Medium: Online Resource
    ISSN: 1000-3290
    Language: English
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2021
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  • 5
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 70, No. 21 ( 2021), p. 218102-
    Abstract: M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide’s amount, size, morphology and distribution in the microstructure contribute much to the wear resistance of high chromium cast irons. In the present paper, a two-dimensional microscopic cellular automaton model for the growth of the faceted M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide together with the austenitic dendrite grains in an Fe-4%C-17%Cr ternary alloy is developed to obtain the evolution of M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide grain morphology, the concentration redistribution and their interaction during the growth of M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide and austenite grains, and also the total influence on the final M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbides’ size. The model includes the effect of latent heat release on the temperature drop. The grain growth velocity is determined by both the diffusion of C solute and the diffusion of Cr solute at the S/L interface. The equilibrium concentration in liquid cells is interpolated from the tablulated solidification path which is prescribed by Gulliver-Scheil approximation coupling with the thermodynamic equilibrium calculation. The morphology of the faceted M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide is maintained through setting its neighborhood relations and optimizing its shape factor at grain growth. The results show that the individual grain growth velocity for M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide and austenite increases with the increase of the supersaturation and Peclet number of solute C and Cr. The austenite precipitation and grain growth obviously speed up the growth velocity of M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide grains. While with the austenite grains gradually touching and enveloping the M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide grain, the growth velocities for both kinds of grains decrease. The rejection of solute C and Cr during austenite grain growth complements the absorption of solute C and Cr during M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide grain growth, thus promoting their growth. The predicted cooling curve fits with the evolution tendency of the experimental one. The predicted final solidification microstructure and M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbide amount in volume fraction are in agreement with the experimental ones. Furthermore, both C solute concentration distribution and Cr solute concentration distribution in both residual liquid and austenite are consistent with the predictions by the Gulliver-Scheil, partial equilibrium and lever rule model.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2021
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  • 6
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 70, No. 21 ( 2021), p. 214401-
    Abstract: Electricity power has served as an essential source in our daily life. However, some remote areas that are difficult to be covered by the power grid, are still facing a serious shortage of electricity for outdoor equipment such as field monitors. Off-grid power is the alternative power in such areas, but there arise apparently economic and environmental problems. Therefore, the development of portable, pollution-free and sustainable power supply equipment has vital research significance. In this paper, based on the radiative cooling and greenhouse effects, a passive thermoelectric system without any active energy input is proposed. A square copper plate coated with a thin film of acrylic acid doped with SiO〈sub〉2〈/sub〉 particles, with an average emissivity value of 0.937, is selected as a radiative cooling material. The commercial polyolefin film with a thickness of 0.12 mm is selected as a greenhouse material. The radiative cooling effect cools the cold end of the thermoelectric generator (TEG) during the nighttime, the greenhouse effect during the daytime is utilized to increase the temperature of the hot end of the TEG. The radiative cooling effect and the greenhouse effect both result in the increase of the temperature difference between the cold and hot ends, and thus obtaining the output power. During the period of time from June 17 to June 21, 2020, the performance of the designed system at the location of Shaanxi, China was evaluated experimentally, and the weather condition effects were also studied. The experimental results show that a stable temperature drop of ~1.1 ℃ of the cold end is achieved via the radiative cooling effect at night. Owing to the greenhouse effect, the temperature increase of the hot end reaches a maximum value of 13.9 ℃. When the average ambient humidity decreases from 45% to 20%, the average temperature difference between the hot end and cold end of the thermoelectric module increased from 1.6 to 1.9 ℃ throughout the day, and the average power increased from 47.8 to 67.3 mW/m〈sup〉2〈/sup〉, indicating that the equipment can have better power generation performance under the condition of 20% ambient humidity. The device developed in this work realizes all-day passive output and shows that it has potential applications in off-grid power supplies.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2021
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  • 7
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2016
    In:  Acta Physica Sinica Vol. 65, No. 16 ( 2016), p. 166101-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 16 ( 2016), p. 166101-
    Abstract: The initial growing dendrite is influenced significantly by the complicated solidification conditions in continuously oscillating mold. The uneven growth of dendrite causes some defects seen commonly such as internal crack, subsurface porosity, subsurface inclusion and other defects of continuous casting billet. The induced initial defects in mold can be expanded and propagated in the following process such as secondary cooling, straightening, rolling and other subsequent handling procedure and then evolve into serious defects that can restrict the development and the quality refinement of final steel products. The mechanical stress caused by mold oscillation and the melt flowing is a crucial factor that leads to the uneven microstructure growth of initial solidifying shell in continuous casting mold. In this work, we simulate the growth and the morphology evolution of primary dendrites in mold area by using the cellular automaton (CA) method in combination with the actual conditions for continuously cast low carbon billet (Fe-0.6 wt.%C). Further, the mechanical state of initial dendrite is analyzed by regarding primary dendrite as a cantilever beam and its mechanical stress is calculated by combining thermo-physical properties and flow rate of steel based on the principle of materials mechanics to shed light on the formation of initial defects formation in mold area of continuous casting process. The results show that the solute concentration of initial dendrite tip gradually increases with undercooling from 2 to 10 K, and the maximum concentration rises by 0.07% when the increment of undercooling is 2 K. The length of dendrite arm increases significantly with undercooling from 2 to 6 K. However, the length of dendrite arm remains steady in a stable growth rate of 0.08 mms-1 when the undercooling is enhanced from 6 to 10 K. The increase of undercooling reduces the bending stress at dendrite root when the flow rate of molten steel is improved from 0.13 to 0.33 ms-1, while the mechanical stress continuously increases with the growth of primary dendrite at a constant undercooling. The bending stress of dendrite root has a high possibility to exceed its critical fracture strength under the condition of undercooling below 6 K or dendrite grow up more than 1 s. The primary dendrite is likely to be fractured and form initial defects of billet.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
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  • 8
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 64, No. 10 ( 2015), p. 103401-
    Abstract: For α-boron, R3m group, Lennard-Jones (L-J) pair potential function is fitted, and a pairwise many-body potential is constructed. For constructing both interatomic potentials, only the atomic average cohesive energy and geometric information are needed. And the cohesive energy and geometry of α-boron crystal are calculated by first-principles code Castep. The fitting procedure for the potentials is as follows. For L-J potential, the minimum of the function is set to be located at the nearest neighbors. For the pairwise many-body potential, L-J potential is minimal, and the form of the function is chosen as a piecewise function, which consists of the L-J function and polynomial function. The minima of L-J potential are located at the distances between the different neighbors of atoms, and the potential barriers are at the midpoints of the distances of the two neighbor minima. L-J potential, L-J pair potential, and Tersoff potential for boron are tested and compared with each other, by energy minimization method in molecular dynamics (MD) simulation. The radial distribution function is used to analyze the structure obtained from the simulation results obtained by using different potentials. The results show that the structure after minimization deviates significantly from the initial crystal of α-boron by L-J potential, and final structure is consistent well with the initial ideal crystal, with L-J potential used. The NVT ensemble is used in MD simulation, where the temperature is set to be 2000 K, and the α-boron crystal experiences the thermodynamic evolutions for 10 fs and 100 fs, to obtain the deviated initial structures. Then the minimization by MD simulation is made to test the three potentials, which also shows that the L-J potential can give the much better result than the other two potentials.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2015
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  • 9
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 63, No. 18 ( 2014), p. 187101-
    Abstract: The effect of S impurity on adhesion of Fe(110)/Al2O3(0001) interface is studied by the first-principles plane wave pseudopotential method within the density functional theory. It is shown that S impurity prefers to occupy the site of Fe3 at Fe(110)/Al2O3(0001) interface substitutionally due to the smallest interface segregation energy. The adhesion of Fe(110)/Al2O3(0001) interface is mainly governed by the interaction between Fe and O atoms on both sides of interface. The calculation results of the partial density of states, Mulliken overlap population and the electron density all suggest that Fe-O interaction is weakened by the segregated S impurity at Fe/Al2O3 interface, and the presence of S impurity gives rise to stronger electrostatic repulsion between Fe and O atoms across Fe/Al2O3 interface, which all leads to a reduced adhesion for Fe/Al2O3 interface. As a result, the results obtained by the first principles can give us a deeper understanding of the mechanism of a reduced interface adhesion and the oxidation film spallation by the segregation of S impurity at FeCrAl alloy interface.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2014
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  • 10
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 64, No. 11 ( 2015), p. 116601-
    Abstract: In this paper, the model of metalic melt shearing flow near the surface is established, and the effect of shearing flow on solidification microstructure of the metal is also analyzed. Calculated results based on A356 alloy melt show that in the laminar flowing melt, the shear stress decreases with increasing length along the vertical direction of the surface of the slope, and the shear stress first decreases rapidly and then stabilizes with increasing length along the flowing direction of the surface of the slope; while in the turbulent flowing melt, the shear stress firstly decreases rapidly and then stabilizes with increasing length along the vertical direction of the surface of the slope, and increases with increasing length along the flowing direction of the surface of the slope. The shear stress at the same position in the melt on the surface of the slope increases with increasing angle of the slope; the shear stress acting on the columnar crystal in the melt on the surface of the slope increases with decreasing length along the vertical direction of the surface of the slope. The shear stress acting on the columnar crystal at the same position in the melt on the surface of the slope increases with increasing angle of the slope; with the increase of the length along the flowing direction, the shear stress acting on the columnar crystal rapidly decreases first and then stabilizes in the laminar flowing melt on the surface of the slope, while the shear stress increases in the turbulently flowing melt on the surface of the slope. Based on the theoretical calculation, the maximum shear stress acting on the columnar crystal in the melt during the shearing flow near the surface of the metalic melt is lower than the yield strength of α-Al grain, so the shear stress induced by shearing flow cannot break the columnar crystal, and only by sweeping the grain into the melt to induce the multiplication of grain, which agrees with the experimental results. So, the proposed model can explain the constitutive relations of the metalic melt shearing flow near the surface and the effect of shear stress on the solidification microstructure.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2015
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