Hongxing Zheng

Phase Transition Behavior and Magnetocaloric Effect in a Heusler Ni50Mn37Sn13 Unidirectional Crystal

A unidireon heating, followed with a ferromagnetic- paramagnetic transition in austenite for the produced unidirectional crystal. Under a magnetic field change of 3 T, the total effective refrigeration capacity was strikingly enhanced up to 125 J/kg, nearly 64% higher than that of polycrystalline master alloy ctional crystal of Heusler Ni50Mn37Sn13 material was produced using a modified high-pressure optical zone-melting furnace. A structural transformation between weak-magnetization martensite and ferromagnetic austenite occurred first up(76 J/kg). The modified high-pressure optical zone-melting technique demonstrated high potentials for the fabrication of super-performance Heusler Ni-Mn-based magnetocaloric materials.

Magnetostructural Transition in Heusler Mn-Ni-In Melt-Spun Ribbons

The magnetostructural transition of Heusler Mn-Ni-In melt-spun ribbons was investigated in the present work. Experimental results show that the characteristic temperatures of martensitic transformation enhance with substituting Mn with Ni for constant indium levels in Mn50-xNi40+xIn10 (at.%, x=0,2,4) melt-spun ribbons. Meanwhile, the ribbons evolve from the bcc cubic L21-type structured austenite to fourteen-layered modulated (14M) monoclinic martensite at room temperature. The martensitic transformation happens prior to the magnetic transition of austenite in Mn46Ni44In10 and lead to a sharp decrease of magnetization discrepancy across the martensitic transformation. It is beneficial for the magnetic enhancement to keep high Mn content.

Optical Floating-Zone Crystal Growth of Heusler Ni-Mn-Sn Alloy

Heusler Ni-Mn-Sn unidirectional crystal was fabricated using optical floating zone furnace in the present work. Higher static argon pressure up to 7 bar was employed to suppress the volatilization, and meanwhile, a titanium bar was preheated to remove residual oxygen in the furnace chamber prior to the formal crystal growth. Experimental results show that the obtained Ni50Mn37Sn13 unidirectional crystal was β{110} preferentially oriented at the rate of 6 mm/h. Magnetization curves measured along different directions under a low magnetic field of 100 Oe demonstrates strong anisotropy.

Size Effect on the Phase Transformation of In-21at%Tl Nanowires

In this work, the interaction between the size effect and the thermomechanically induced phase transformation for SMAs composed of Indium-Thallium (InTl) is analyzed. An In-21at%Tl alloy is first fabricated, from which In-21at%Tl nanowires are subsequently produced. Using the mechanical pressure injection system, the bulk alloy is pressed into pores of an Anodized Aluminum Oxide (AAO) template to fabricate the nanowires. The diameter of these nanowires can be altered by changing the anodization parameters of the AAO templates (≈20nm–750nm). The critical diameter for which nanowires show a similar phase transformation behavior to the bulk alloy is experimentally determined to lie between 280nm and 750nm.Copyright