Y.H. Zhuang

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

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.

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

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.

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

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.

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

Abstract The isothermal section of the phase diagram of the Gd–Tb–Co ternary system at 500xa0°C was investigated by X-ray powder diffraction, differential thermal analysis and metallographic analysis techniques. In this isothermal section, there are nine single-phase regions, eight two-phase regions and none three-phase region. No ternary compound was found. The compounds Gd 2 Co 17 and Tb 2 Co 17 , Gd 2 Co 7 and Tb 2 Co 7 , GdCo 3 and TbCo 3 , GdCo 2 and TbCo 2 , Gd 4 Co 3 and Tb 4 Co 3 , Gd 12 Co 7 and Tb 12 Co 7 , Gd 3 Co and Tb 3 Co, Gd and Tb form a continuous series of solid solutions. In addition, we experimentally determined the vertical section of pseudobinary system and the Curie temperature of Gd 1− x Tb x Co 2 ( x from 0 to 1) series alloys.

Intermetallics and phase transformations of the Zr-1.0Sn-0.3Nb-0.3Fe-0.1Cr alloy

Intermetallics and phase transformations of the zirconium-based alloy, Zr-1.0Sn-0.3Nb-0.3Fe-0.1Cr, were investigated by conventional X-ray diffraction (XRD), differential scanning calorimetry (DSC), and dilation measurement. Three types of precipitates, namely, (ZrNb)2Fe, Zr(CrFe)2, and Zr3Fe, were detected by XRD. The cubic Ti2Ni-type (ZrNb)2Fe was found to be the main precipitate in the alloy, and it was proposed to dissolve at 861°C, whereas Zr3Fe dissolved at 780°C and Zr(CrFe)2 at 814°C. No precipitates were observed at a temperature higher than 900°C. The transformation-start temperature of α-Zr → β-Zr was reconfirmed to be 780°C, and the end temperature of α-Zr → β-Zr was determined to be 955°C. The dilation result also revealed that the martensitic transformation-start temperature, Ms, and the finish temperature, Mf, of this alloy were 741°C and 645°C, respectively.

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

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.

The influence of Co substitution on the magnetocaloric effect of Gd(Al,Fe)2

The magnetocaloric effect (MCE) in samples GdAl1.7(Fe1 xCox)0.3 with x= 0, 0.1, 0.2, 0.3 and 0.4 were investigated by x-ray diffraction (XRD) and magnetization measurements. It was found that five samples crystallize well in the MgCu 2-type structure. The lattice parameter and the values of Curie temperature decrease with increasing Co content, whereas the magnetic-entropy change and cooling capacity increase. In the magnetic-field change of 2.0 T the maximum of the magnetic-entropy change and refrigerant capacity in sample GdAl1.7Fe0.7Co0.3 reach 4.8 J kg 1 K 1 and 88.3 J kg 1 , respectively. The maximum of the magnetic-entropy change is comparable to that of Gd metal (3.8 J kg 1 K 1 in 1B = 1.5 T).

Phase equilibria in Nb-Y-Si ternary system at 873 K

Abstract The isothermal section of the Nb-Y-Si ternary system at 873 K was investigated over the whole concentration range mainly by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). This isothermal section consisted of 10 single-phase regions, 17 two-phase regions, and 8 three-phase regions. The existence of the binary compounds, i.e., Y 5 Si 3 , Y 5 Si 4 , YSi, Y 3 Si 5 , YSi 2 , Nb 5 Si 3 and NbSi 2 at 873 K was confirmed. On the basis of XRD patterns, the structure types of Y 5 Si 4 , Y 3 Si 5 and YSi 2 were discussed. No ternary compound and no detectable solid solubility in the binary compounds were found.

Magnetocaloric effect of (Tb1–xCex)Co2 alloys in low magnetic field

Abstract The phases in alloys (Tb1–xCex)Co2 with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5 were investigated by X-ray diffraction analysis, and the magnetocaloric effect for x=0–0.4 was studied by magnetization measurement. The samples were almost single phase with MgCu2-type cubic structure. The magnetization decreased with the increase of Ce. The Curie temperatures (Tc) of Tb1–xCexCo2 alloys with x from 0.1 to 0.4 were 180, 165, 160 and 152 K, respectively. For x=0.5 in the range from 100 K to 230 K, the point of magnetic transition was not obvious, and thus this article did not discuss the magnetocaloric effects for x=0.5. The maximum magnetic entropy change decreased with the increase of Ce content. The results of Arrott plots showed that the magnetic phase transition was second-order magnetic phase transition in those alloys.

Crystal structural refinement for NdAlSi

Abstract The compound NdAlSi was studied using X-ray powder diffraction technique and refined by the Rietveld method. The compound NdAlSi has tetragonal α-ThSi 2 -type structure, space group 14 1 /amd (No.141), Z = 4, and the lattice parameters a = 0.41991(1) nm, c = 1.44916(3) nm. The Smith and Snyder figure of merit F N is F 30 = 103.1(36). The R -factors of Rietveld refinement are R p = 0.113 and R wp = 0.148, respectively. The X-ray powder diffraction data is presented in this article.