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Featured researches published by K.W. Zhou.


Journal of Rare Earths | 2009

Study on stability of RECo5 phases (RE=Dy, Gd)

Qiming Zhu; Y.H. Zhuang; Jianlie Liang; Junqin Li; K.W. Zhou; Jianqiu Deng

Abstract The eutectoid decomposition reaction that occurred in RECo5 phases (RE=Dy and Gd) at low temperature was discussed and confirmed by X-ray powder diffraction (XRD), differential thermal analysis, and scanning electron microscopy. The decomposition temperature of the GdCo5 and DyCo5 were identified as 805.8 and 900 °C, respectively. The GdCo5 and DyCo5 phases could not be found in the isothermal section of Gd-Dy-Co ternary system at 800 K. Reasons for the absence of the RE2Co7 phase in the XRD patterns were discussed in detail.


Rare Metals | 2006

Influence of Carbon on the Giant Magnetocaloric Effect of LaFe11.7Si1.3

Junqin Li; Fusheng Liu; Weiqin Ao; Y.H. Zhuang; K.W. Zhou

The influences of carbon on phase formation, Curie temperature, and magnetic entropy change of the NaZn13-type LaFe11.7Si1.3 were investigated. Seven carbon-containing alloys, LaFe11.7Si1.3C(subscript x) with x=0, 0.03, 0.06, 0.10, 0.20, 0.30, and 0.50, respectively, were prepared for this investigation. Experimental results show that addition of a small amount of carbon in LaFe11.7Si1.3 is favorable for the formation of the NaZn13-type structure of LaFe11.7Si1.3C(subscript x). The lattice constant increases with C addition and x increases in the alloy because of the introduction of C as interstitial atoms. The Curie temperature of LaFe11.7Si1.3C(subscript x) increases from 194 K to 225 K as x increases from 0 to 0.5. Large magnetic entropy changes were observed in these carbon-containing alloys LaFe11.7Si1.3C(subscript x) because of their first-order structural/magnetic transition. The maximum magnetic entropy change of 27.5 J•kg^(-1)•K^(-1) at 202 K for the 0-1.56 T magnetic field change was observed in the alloy with x=0.06. The large magnetic-entropy changes corresponding to low magnetic field change, and the low cost of the material of LaFe11.7Si1.3C(subscript x) makes it a promising candidate to be used as magnetic refrigerants in the corresponding temperature range.


Journal of Rare Earths | 2006

Structure and Magnetocaloric Effect in Tb(Co1-xSnx)2 Alloys

Y.H. Zhuang; Jianqiu Deng; Junqin Li; K.W. Zhou; Qiming Zhu

Abstract The phases and magnetocaloric effect in the alloys Tb(Co 1- x Sn x ) 2 with x = 0, 0.025, 0.050, 0.075, 0.100 were investigated by X-ray diffraction analysis and magnetization measurement. The substitution of Sn in TbCo 2 was limited. The cubic MgCu 2 -type structure for the sample of TbCo 2 was confirmed by the results of X-ray powder diffraction and the rest samples consist of the TbCo 2 phase mainly, together with some TbCo 3 and Tb 5 Sn 3 impurity phases. The impurity phases increase with the increase of Sn contents. The magnetic phase transition in all samples keeps second-order transition. T C increases slightly by Sn substitution from 230 K of the alloy with x = 0 to 233 K of the alloy with x =0.050 and then a slight decrease for higher concentration of x . The maximum magnetic entropy change in the samples Tb (Co 1- x Sn x ) 2 with x = 0, 0.025, 0.050, 0.075 are 3.44, 2.29, 1.64, 1.16 J·kg −1 ·K −1 , respectively, with the applied field change from 0 to 2.0 T.


Journal of Rare Earths | 2008

Phase structure and magnetocaloric effect of (Tb1–xDyx)Co2 alloys

Y.H. Zhuang; Xiang Chen; K.W. Zhou; Kefeng Li; Chunhua Ma

Abstract Phase structure and magnetocaloric effect of (Tb 1– x Dy x )Co 2 alloys with x =0, 0.2, 0.4, 0.6, 0.8, and 1.0 were investigated using X-ray diffraction analysis, differential thermal analysis, and magnetization measurement. The samples were single phase with cubic MgCu 2 -type structure; with the increase of Dy content, T C decreased from 240 K (TbCo 2 ) to 130 K (DyCo 2 ), and the maximum magnetic entropy change |Δ S M,max | increased from 3.133 to 8.176 J/kg·K under low magnetic field of 0–2 T. The Arrott plot and the change of |Δ S M,max | showed that magnetic phase transition from second order to first order occured with the increase of Dy content between x =0.6 and 0.8.


Solid State Communications | 2006

Magnetocaloric effects in (Gd1−xTbx)Co2

K.W. Zhou; Y.H. Zhuang; Junqin Li; Jianqiu Deng; Q.M. Zhu


Journal of Alloys and Compounds | 2010

Martensitic transition and magnetocaloric properties in Ni45Mn44−xFexSn11 alloys

J.L. Yan; Z.Z. Li; X. Chen; K.W. Zhou; S.X. Shen; H.B. Zhou


Journal of Alloys and Compounds | 2007

Magnetic phase transition and magnetocaloric effect in (Gd1−xTbx)5Si1.72Ge2.28 compounds

J.Q. Deng; Y.H. Zhuang; J.Q. Li; K.W. Zhou


Journal of Alloys and Compounds | 2006

The isothermal section of the Gd–Dy–Co ternary system at 800 K

Y.H. Zhuang; Q.M. Zhu; Junqin Li; K.W. Zhou; J.Q. Deng; Wei He


Journal of Alloys and Compounds | 2006

The 500 °C isothermal section of the Gd-Tb-Co ternary system

K.W. Zhou; Y.H. Zhuang; Junqin Li; Q.M. Zhu; J.Q. Deng


Journal of Alloys and Compounds | 2011

Isothermal section of the YCoV ternary system at 500 C

X. X. Wei; J.L. Yan; H.W. Du; C.L. Wu; K.W. Zhou; Ya Hui Zhuang; J.Q. Li

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