本文研究了4d过渡族金属Zr取代(Mn,Fe)2 (P,Si)合金中Fe原子对其晶体结构、居里温度、热滞以及磁热性能的影响规律。结果显示,当Zr取代10at.%的Fe时,可将MnFeP0.65Si0.35原始样品的热滞由18 K降低至1.5K,大大提高其相变的可逆性。然而,...本文研究了4d过渡族金属Zr取代(Mn,Fe)2 (P,Si)合金中Fe原子对其晶体结构、居里温度、热滞以及磁热性能的影响规律。结果显示,当Zr取代10at.%的Fe时,可将MnFeP0.65Si0.35原始样品的热滞由18 K降低至1.5K,大大提高其相变的可逆性。然而,当Zr原子的含量增加至20 at.%时,热滞出现了上升,这主要由于过量的Zr造成了Mn5Si3型第二相的出现,消耗了主相中的部分Si原子所致。与此同时,随着Zr含量的增加,居里温度逐渐上升。这是由于Zr取代部分Fe原子削弱了(Mn,Fe)2 (P,Si)合金中Fe-Si的化学键合作用,增强了铁磁相的稳定性,从而提高了该合金的居里温度。此外,Zr掺杂的(Mn,Fe)2 (P,Si)合金仍然表现出较强的磁热性能。因此,Zr掺杂的(Mn,Fe)2 (P,Si)合金因其具有较小的热滞、可调的居里温度以及优异的磁热性能有望应用于室温磁制冷和能量转换领域。 Theinfluence of 4d transition metal Zr substitution on the structure,magnetoelastic transition and magnetocaloric properties has been investigatedfor the MnFe1-xZrxP0.65Si0.35alloys. The substitution for Fe by 10 at.% Zr significantly diminishes the thermalhysteresis (ΔThvs) from 18 to 1.5 K and hence greatlyenhances the reversibility of the magnetoelastic transition. However, a furtherincrease in the Zr content to 20 at.% deteriorates the thermal hysteresis. Thisis due to the formation of Mn5 Si3-type impurity phase, which depletes the Si atoms in the main phase. The Curietemperature (TC) is raised with the increasing Zrcontent. This is due to the Zr-induced weakening of the Fe-Si covalent bonding,which stabilizes the ferromagnetic state and thus increases the TC.Additionally, the giant magnetocaloric effect (MCE) is retained in theZr-substituted samples. Consequently, the combination of small ΔThvs,tunable TC and giant MCE has made the Zr-substituted (Mn,Fe)2 (P,Si) promising for room-temperature magnetic refrigerationand energy conversion applications.展开更多
磁制冷是一种利用材料的磁热效应进行制冷的新型制冷技术,相比于传统气体压缩制冷,因其绿色环保、高效节能等优点而备受关注。在众多磁相变合金材料中,人们对Mn_2Sb基亚铁磁相变合金研究甚少。文章研究了Cr取代Mn后亚铁磁性Mn_(2-x)Cr_x...磁制冷是一种利用材料的磁热效应进行制冷的新型制冷技术,相比于传统气体压缩制冷,因其绿色环保、高效节能等优点而备受关注。在众多磁相变合金材料中,人们对Mn_2Sb基亚铁磁相变合金研究甚少。文章研究了Cr取代Mn后亚铁磁性Mn_(2-x)Cr_xSb_(0.95)In_(0.05)(x=0.05,0.09,0.13)合金的磁性和磁热性能。室温XRD数据表明合金在室温附近以四角Cu_2Sb型结构为主相。由于反铁磁中有高磁响应,因此从XRD图谱中能观察到少量的铁磁MnSb杂相。随着温度的降低,在这些合金中,发生了亚铁磁到反铁磁的一级磁致弹性转变。同时,在亚铁磁区域观察到两个自旋重新取向转变。由于反铁磁-亚铁磁的转变过程中磁化强度突变,使得在Mn_(1.91)Cr_(0.09)Sb_(0.95)In_(0.05)合金中在0~10 k Oe的磁场变化中获得高达1.63 J/kg·K的大磁熵变。目前的研究可能有助于研究和开发新的磁性冷材料。展开更多
Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attr...Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system.展开更多
文摘本文研究了4d过渡族金属Zr取代(Mn,Fe)2 (P,Si)合金中Fe原子对其晶体结构、居里温度、热滞以及磁热性能的影响规律。结果显示,当Zr取代10at.%的Fe时,可将MnFeP0.65Si0.35原始样品的热滞由18 K降低至1.5K,大大提高其相变的可逆性。然而,当Zr原子的含量增加至20 at.%时,热滞出现了上升,这主要由于过量的Zr造成了Mn5Si3型第二相的出现,消耗了主相中的部分Si原子所致。与此同时,随着Zr含量的增加,居里温度逐渐上升。这是由于Zr取代部分Fe原子削弱了(Mn,Fe)2 (P,Si)合金中Fe-Si的化学键合作用,增强了铁磁相的稳定性,从而提高了该合金的居里温度。此外,Zr掺杂的(Mn,Fe)2 (P,Si)合金仍然表现出较强的磁热性能。因此,Zr掺杂的(Mn,Fe)2 (P,Si)合金因其具有较小的热滞、可调的居里温度以及优异的磁热性能有望应用于室温磁制冷和能量转换领域。 Theinfluence of 4d transition metal Zr substitution on the structure,magnetoelastic transition and magnetocaloric properties has been investigatedfor the MnFe1-xZrxP0.65Si0.35alloys. The substitution for Fe by 10 at.% Zr significantly diminishes the thermalhysteresis (ΔThvs) from 18 to 1.5 K and hence greatlyenhances the reversibility of the magnetoelastic transition. However, a furtherincrease in the Zr content to 20 at.% deteriorates the thermal hysteresis. Thisis due to the formation of Mn5 Si3-type impurity phase, which depletes the Si atoms in the main phase. The Curietemperature (TC) is raised with the increasing Zrcontent. This is due to the Zr-induced weakening of the Fe-Si covalent bonding,which stabilizes the ferromagnetic state and thus increases the TC.Additionally, the giant magnetocaloric effect (MCE) is retained in theZr-substituted samples. Consequently, the combination of small ΔThvs,tunable TC and giant MCE has made the Zr-substituted (Mn,Fe)2 (P,Si) promising for room-temperature magnetic refrigerationand energy conversion applications.
文摘磁制冷是一种利用材料的磁热效应进行制冷的新型制冷技术,相比于传统气体压缩制冷,因其绿色环保、高效节能等优点而备受关注。在众多磁相变合金材料中,人们对Mn_2Sb基亚铁磁相变合金研究甚少。文章研究了Cr取代Mn后亚铁磁性Mn_(2-x)Cr_xSb_(0.95)In_(0.05)(x=0.05,0.09,0.13)合金的磁性和磁热性能。室温XRD数据表明合金在室温附近以四角Cu_2Sb型结构为主相。由于反铁磁中有高磁响应,因此从XRD图谱中能观察到少量的铁磁MnSb杂相。随着温度的降低,在这些合金中,发生了亚铁磁到反铁磁的一级磁致弹性转变。同时,在亚铁磁区域观察到两个自旋重新取向转变。由于反铁磁-亚铁磁的转变过程中磁化强度突变,使得在Mn_(1.91)Cr_(0.09)Sb_(0.95)In_(0.05)合金中在0~10 k Oe的磁场变化中获得高达1.63 J/kg·K的大磁熵变。目前的研究可能有助于研究和开发新的磁性冷材料。
基金the support from SOLVE: The Virtual Lab @ NITK (Grant number: No.F.16-35/2009-DL, Ministry of Human Resources Development)
文摘Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system.
