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891.
S. Paschen E. Felder H.R. Ott 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):169-176
We present measurements of the specific heat, the electrical resistivity, the Hall effect, and the magnetic susceptibility
of CeAuAl3, a new heavy-electron compound that crystallizes in an ordered derivative of the tetragonal BaAl4-type structure. For comparison we have also done some of these measurements on the isostructural non-magnetic reference compound
LaAuAl3, which appears to be a simple metal. Below K, CeAuAl3 orders antiferromagnetically and below 1K, we encounter Fermi liquid behaviour with considerably enhanced effective masses,
i.e., a quadratic temperature dependence of the resistivity with a large prefactor and a sizable linear-in-T contribution to the specific heat. This linear-in-T contribution increases by more than a factor 50 from its value at to its value at . Consequently CeAuAl3 develops a heavy-electron ground state, coexisting with antiferromagnetic order. The small energy scales involved in the
problem make CeAuAl3 a good candidate for tuning it, by varying external parameters, towards a quantum critical point. At high temperatures we
observe local moment behaviour. From the temperature dependence of the magnetic susceptibility and the specific heat we have
derived the crystalline-electric-field-split level scheme of the J
=5/2 multiplet. Distinct features in the electrical resistivity provide additional evidence for this level splitting.
Received: 6 November 1997 / Accepted: 17 November 1997 相似文献
892.
S.A. van der Aart P. Verkerk W. van der Lugt R. Xu F. van der Horst R.L. McGreevy 《Physica B: Condensed Matter》1997,240(4):311-321
Neutron diffraction measurements on liquid KT1 alloys with 0, 1, and 5 at % Pd, respectively, show that the prepeak in the structure factor shifts from wave vector k=8.0 to 7.2 nm−1 with an increasing amount of Pd. This corresponds to a periodicity change from 0.96 to 1.07 nm in real space2. The structure of the liquid KT1 alloys is compared to the corresponding crystal structures, and some similarities are observed. Reverse Monte Carlo modelling indicates T1 clustering in the liquid alloy. Also in solid KTl Tl-clusters occur. The distance between the clusters increases with the addition of 5%. Pd. More information is needed to discriminate between various possible structures of the Tl clusters in the liquid alloy and to determine the position of Pd in these clusters. 相似文献
893.
Laser reactive sintering, i.e., laser-induced self-propagating reaction sintering synthesis was carried out on Ni–Al powder alloys. The exothermic behaviors for the alloys with different Al content were characterized by sintering temperature curves produced from reactive heat. The phases transformed from the sintered alloys were identified by X-ray diffraction. Properties and microstructure of the sintered alloys were studied. 相似文献
894.
Anna Bajorek Artur ChrobakGrażyna Chełkowska Marzena Kwiecień-Grudziecka 《Journal of magnetism and magnetic materials》2012
In the paper an influence of Gd/Y substitution on the magnetic properties and exchange interactions of the YxGd1−xNi3 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) polycrystalline compounds have been studied. The partial replacement of Gd by Y atoms is reflected in decreasing of the Curie temperature (TC) as well as decreasing of effective the magnetic moment (μeff). It has been shown that such a behaviour strongly depends on the magnetic interactions. Exchange coupling parameters of R–R (ARR), T–T (ATT) and R–T (ART) have been evaluated from M(T) magnetization curves (2–300 K, 2 T) based on the mean field theory (MFT) calculation. The magnetocaloric effect (MCE) has been estimated from the family of magnetic isotherms. The magnetic entropy indicates relatively small change with the Gd/Y substitution. The value of ΔSm(T,H) is higher for Gd-rich compounds and, respectively, decreases with Gd/Y substitution. 相似文献
895.
The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni–Ti–Pd, Ni–Ti–Pt, and Ni–Ti–Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives. 相似文献
896.
非晶态合金在力学性能、耐磨耐蚀性、磁性等方面比传统晶态合金具有显著优势,是一类有优良应用前景的新型结构与功能材料.非晶态合金与氢相互作用可以产生很多有趣的物理化学现象和应用.本文从物理基础和材料应用两个方面评述非晶态合金和氢相互作用的研究进展,在物理基础研究方面,从氢在非晶态合金中的存在状态出发,讨论氢在非晶态合金中的溶解、分布、占位和扩散等相关物理问题,进而分析氢对非晶态合金的热稳定性、磁性、内耗、氢脆等的影响.在材料应用研究方面,对非晶态储氢合金、非晶态合金氢功能膜、吸氢改善非晶态合金的塑性和玻璃形成能力、氢致非晶化、利用非晶态合金制备纳米储氢材料等方面的研究进展进行评述.最后总结并展望有关非晶态合金与氢相互作用的研究和应用. 相似文献
897.
There have been many interesting studies on high-entropy alloys(HEAs), also known as multi-component(MC) alloys(MCAs), in recent years. MC metallic-glasses(MGs) have shown the potential to express the advantages of MCAs and MGs in tandem. Amorphous phase formation rules are a crucial issue in the HEA and MCA field. For equal or near-equal atomic ratio alloys, mixed-entropy among the elements has a significant effect on the phase formation. This paper focuses on HEA amorphous phase formation rules. In the first two sections, the recent progress in amorphous phase formation in HEAs and MCAs is reviewed, including the effective factors and correlative parameters related to amorphous phase formation. In the third section, novel MCMGs including high-entropy(HE) bulk-metallic-glass(HE-BMG) and MCMG films developed in recent decades are summarized, and the giant-magnetic-impedance(GMI) effect of MC amorphous fibers is discussed. 相似文献
898.
《化学:亚洲杂志》2017,12(12):1400-1407
Noble metal nanoparticles (NPs) have recently received considerable attention from researchers working in the field of catalysis. However, the development of new methods allowing these materials to reach their maximum catalytic properties remains challenging. Nanoreactors could lead to dramatic improvements in activity with the help of the intrinsic confinement effect. In this study, we designed a series of yolk/shell FexOy/PdPt@CeO2 composites, where the FexOy NPs acted as a movable core, allowing for the uniform distribution of the PdPt alloys on the inner surface of the CeO2 shell. The high porosity and existence of hollow voids in the CeO2 shell allowed these FexOy/PdPt@CeO2 composites to be used as nanoreactors in catalytic reactions. As well this confinement effect, we identified two structural features that led to enhanced catalytic activity, including (i) the replacement of monometallic NPs with a bimetallic PdPt alloy and (ii) the replacement of a chemically inert support with a reactive CeO2 shell. The resulting nanoassembled catalysts displayed higher activities toward the catalytic reduction of dyes than the reference samples. Moreover, these catalysts were readily recovered and reused because of the magnetic FexOy core. 相似文献
899.
Soft magnetic properties of Co-based amorphous alloy of the composition Co67Fe4Ni2Si15B12 have been investigated by isothermal heat treatment up to the conventional crystallization temperature. In the as-cast condition the Curie temperature of the sample is 272 °C and saturation magnetization is 74 emu/g. Magnetic properties undergo variation depending on the heat treatment temperature. For the heat treatment temperatures of around 420 and 490 °C, superior soft magnetic properties are obtained. For both the temperatures initial permeability, μ′ reaches value up to ten times the value of permeability in the as-received samples. Annealing effect on giant magneto-impedance has been observed for the current-driving frequencies of 4.5 and 6 MHz. Field dependence of magneto-impedance shows hysteresis at low field, which is related to the changes in the magnetization process of the sample. 相似文献
900.
二溴邻羧基偶氮氯膦光度测定铝合金中微量锶 总被引:8,自引:0,他引:8
本介绍在一定量钙、钡共存下测定锶的新方法。在0.48mol/L H2SO4介质中,二溴邻羧基偶氮氯膦与锶形成2:1的蓝色络合物,最大吸收波长为630nm。摩尔吸光系数为3.2×10^4L.mol^-1.cm^-1,锶量在0-1mg/L范围内符合比耳定律,经过二氧化锰共沉淀分离富集后,可测定各种复杂铝合金样品中痕量锶。 相似文献