斯特林制冷机直线电机磁性材料模拟分析与应用

直线电机磁性材料的选择对斯特林制冷机的性能具有重要影响。应用电机电磁场理论和有限元分析方法,建立动磁式直线电机的电磁场模型,基于Ansoft Maxwell软件对几种常用磁性材料的电磁场进行有限元分析,得到了相应的电磁推力和磁感应强度分布。经过分析比较,选择铷铁硼、铁钴钒和硅钢作为电机磁性材料,研制的斯特林制冷机应用于5L深冷冰箱,获得了-150℃的低温环境,对应温度的制冷量为7W。     

Ecological optimization for an irreversible magnetic Ericsson refrigeration cycle

An irreversible Ericsson refrigeration cycle model is established, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leakage, and the efficiency of the regenerator are taken into account. Expressions for several important performance parameters, such as the cooling rate, coefficient of performance （COP）, power input, exergy output rate, entropy generation rate, and ecological function are derived. The influences of the heat leakage and the time of the regenerative processes on the ecological performance of the refrigerator are analyzed. The optimal regions of the ecological function, cooling rate, and COP are determined and evaluated. Furthermore, some important parameter relations of the refrigerator are revealed and discussed in detail. The results obtained here have general significance and will be helpful in gaining a deep understanding of the magnetic Ericsson refrigeration cycle.     

Performance characteristics and parametric optimization of an irreversible magnetic Ericsson heat-pump

Taking into account the finite-rate heat transfer in the heat-transfer processes, heat leak between the two external heat reservoirs, regenerative loss, regeneration time, and internal irreversibility due to dissipation of the cycle working substance, an irreversible magnetic Ericsson heat-pump cycle is presented. On the basis of the thermodynamic properties of magnetic materials, the performance characteristics of the irreversible magnetic Ericsson heat-pump are investigated and the relationship between the optimal heating load and the coefficient of performance (COP) is derived. Moreover, the maximum heating load and the corresponding COP as well as the maximum COP and the corresponding heating load are obtained. Furthermore, the other optimal performance characteristics are discussed in detail. The results obtained here may provide some new information for the optimal parameter design and the development of real magnetic Ericsson heat-pumps.     

Laser chemical processing of magnetic materials for recording-head application

A laser-induced thermochemical reaction has been used to etch single crystalline magnetic ferrite for industrial application to recording-head processing. Scanning focused Ar-ion laser irradiation to ferrite in flowing aqueous solutions of KOH or H₃PO₄ resulted in etch rates of 350–400 m/s with aspect ratios of up to 40. Metal-In-Gap (MIG) head structures with Sendust (FeAlSi) have been successfully fabricated using laser chemical processing. The MIG head fabricated by laser chemical processing showed better performance than that by conventional mechanical machining.Presented at LASERION '93, June 21–23, 1993 München (Germany)     

New developments in technologically important magnetic materials

In the past decade there has been a number of new developments in magnetic materials that should pave the way for expanded applications. These include: highly oriented high induction silicon steel; new varieties of permalloys, especially near 65% Ni; amorphous soft magnetic materials of the type (Fe, Co, Ni)₈₀ (P, B, Al)₂₀ produced by continuous rapid quenching; rare earth-cobalt permanent magnets with _iH_c to 150 kA/m and (BH)_max to 200 kJ/m³; ductile chromium cobalt iron permanent magnets with properties comparable to the alnicos; new families of ductile semihard magnets particularly for miniature self-latching dry reed contacts; and a new memory technology based on magnetic bubbles. These new developments will be discussed along with prospects for future applications.     

New mechanisms for magnetic anisotropy in localised S-state moment materials

Anisotropic versions of the familiar (RKKY) indirect exchange between localised S-state magnetic moments in metals can arise in a number of ways. There are two basic mechanisms, viz. (i) from anisotropic s-d interactions such as dipolar coupling and (ii) in higher orders of perturbation theory with the conduction electron spin-orbit interaction. Applications to particular materials are briefly considered.     

A new method to study complex materials in solid state chemistry: application to chalcogenide materials

We show that a combined application of Mössbauer spectroscopy and other experimental tools such as X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy and nuclear magnetic resonance provides a coherent picture of the local electronic structure in chalcogenide materials. In order to develop this idea we propose an analysis of the Sn, Sb and Te local electronic structures for three different systems of materials. The first example concerns the In–Sn–S system. We show that Li insertion in In₁₆Sn₄S₃₂ leads to changes of the Sn oxidation states from Sn(IV) to Sn(II). The second example concerns materials of the Tl–Sb–S system. We show that variations of the ¹²¹Sb Mössbauer isomer shift and surface of the first peak of the X‐ray absorption spectra at the Sb L_III edge can be linearly correlated because of the main influence of the Sb 5s electrons. This is explained by changes in the local environment of the Sb atoms. The last example concerns the crystalline phases of the Tl–Sn–Te system. The formal oxidation numbers of the Te atoms are determined from ¹²⁵Te Mössbauer spectroscopy and X‐ray photoelectron spectroscopy. They are related to the different types of bonds involving the Te atoms in the Tl–Sn–Te compounds.     

Anisotropic and vector hysteresis model for magnetic materials application to a cubic textured NiFe sheet

Nowadays, several research teams are involved in vector and anisotropic hysteresis modelling of soft magnetic materials. In this paper a new model is presented. It is based on the Preisach model, but uses a four-state vector operator. The model is applied to a cubic textured NiFe sheet and verified for unixial and rotating exciting field. At high induction level the behaviour of the material is well described. However, discrepancy with experiment is observed at low induction. This phenomena is currently under analysis in order to adapt the model for such working conditions.     

Optical properties of some magnetic materials for coherent magnetic vibrations

In this communication we report experimental results concerning optical properties of magnetic crystals such as rare-earth iron garnets and orthoferrites doped with semimetals such as bismuth and tin. The components of the dielectric tensor of the doped magnetic material exhibit favourable magnetic properties. Such kinds of materials are employed for generating coherent magnetic vibrations having amplitudes sufficiently large for detection.     

A thermal entangled quantum refrigerator based on a two-qubit Heisenberg model with Dzyaloshinskii-Moriya interaction in an external magnetic field

Based on an isotropic two spin-1/2 qubits Heisenberg model with the Dzyaloshinskii-Moriya interaction in an external magnetic field, we have constructed an entangled quantum refrigerator. Expressions for the basic thermodynamic quantities, i.e., the heat exchanged, the net work input, and the coefficient of performance, are derived. Some intriguing features and their qualitative explanations in zero and non zero magnetic fields are given. The influence of the thermal entanglement on the refrigerator is investigated. The results obtained here have general significance and will be helpful to understand the performance of an entangled quantum refrigerator.     

斯特林制冷机采用不同工质应用于冰箱温区的性能研究

基于斯特林冷循环应用于冰箱制冷的优点,对应用于冰箱领域的斯特林制冷机采用氦气、氢气、空气三种不同工质在相应工况下的性能进行了理论分析和实验研究.研究结果表明,斯特林制冷机实际运行过程中要比理想模型复杂得多,且在冰箱制冷温区(-80℃以上),氢气是最佳的选用工质,其次是氦气,空气性能较差.     

Coupled-dipole method for magnetic and negative-refraction materials

We present a derivation of the coupled-dipole method, also called discrete dipole approximation, for scatterers with arbitrary dielectric permittivity and magnetic permeability. We discuss the numerical implementation of the method and illustrate its application to magnetic and negative-refraction materials.     

Some inequalities for magnetic and dielectric materials

Arguments based on thermodynamics lead to upper bounds on observable quantities like magneto or electrostriction or magnetoelectric susceptibilities.     

High-frequency nanostructured magnetic materials for integrated inductors

Electroplating is compatible with the deposition of relatively thick layers i.e. several μm to 10s- of μm. However eddy current losses mean that thick layers will have an inferior frequency response. We have used a low content phosphorous bath together with pulse reverse plating to generate Co-rich and Co-deficient multi-nanolayers of CoP having improved saturation magnetisation and a better frequency response. The plating parameters have been optimised in order to produce a material with low loss, and a high permeability of around 700 retained up to 103 MHz for a sample with a thickness of 1.7 μm and a resistivity of 136 μΩ cm.     

Trapping energy of a magnetic monopole in magnetic materials

Analytical methods to investigate the interaction of magnetic monopoles with known magnetic media have been developed. Trapping energies of monopoles inside ferro-magnetic or super onducting materials of size greater than about 10⁻⁶ cm are found to be of the order of several kiloelectron volts. These are two to three orders of magnitude higher than in paramagnetic materials. Thus if stable magnetic monopoles exist at all in the universe, they are perhaps trapped in these magnetic materials. The effect of the finite size of the magnetic bodies is taken into account explicitly in our calculations of the trapping energy.     

High magnetic field effects in some metallic magnetic materials

An account is given of the following magnetic properties in high magnetic fields: (1) Magnetic isotherms of pure nickel and Ni-Pd alloys near the Curie points; the exchange splitting energies deduced on this basis are discussed. (2) Metamagnetic transitions in internal fields for the rare earth-cobalt compounds R Co₂. (3) Metamagnetic transitions in external fields for Co(S, Se)₂ and ordered FePt₃.     

On the disaccommodation of the complex susceptibility in an alternating magnetic field

Néel's theory is used to derive the expression describing the disaccommodation of the complex initial susceptibility in an alternating field in dependence on temperature, frequency of the field and concentration of relaxators. In addition to the disaccommodation of the real part the relaxation of the imaginary part of the initial susceptibility and that of the loss angle are predicted. The physical meaning of derived expressions have been discussed and the phenomena which can influence the aftereffect measurements have been mentioned.     

New materials for optical cooling

Well-characterized solid-state laser materials are evaluated for performance in optical refrigeration as well as radiation-balanced laser systems. New figures-of-merit are developed and applied to ytterbium-doped materials. Superior performance is predicted for high-cross-section tungstate materials. Photothermal deflection experiments on samples of Yb³⁺-doped KGd(WO₄)₂ confirm anti-Stokes fluorescence cooling. This is the first observation of optical cooling in a crystal. Received: 1 February 2000 / Revised version: 15 June 2000 / Published online: 13 September 2000     

New nanohybrid materials for biophotonics

Hybrid nanomaterials were prepared by one- and two-step procedures in the absence of water. Femtosecond laser ablation of a ZnO target in absolute ethanol afforded a colloidal ZnO solution. Dye molecules were grafted onto the ZnO nanoparticle surface by mixing the ZnO solution with an ethanol solution of tetramethylrhodamine B isothiocyanate or rhodamine B. Formation of strongly facetted nanohybrid particles with the average size of 21 nm was observed by HRTEM measurements. Ablation of ZnO in the presence of the dyes afforded nanohybrids with the average size of 12 nm. The occurrence of energy transfer from the ZnO nanoparticles towards the attached dye molecules was demonstrated by photoluminescence spectroscopy of the nanohybrids after single and multi-photon excitations. In particular, two-photon absorption of the nanohybrids ZnO core gave rise to emission of the grafted dyes. PACS 81.07.Bc; 81.07.Nb; 78.67.Bf; 78.55.Et; 81.15.Fg