Effect of glycerin addition on the superconducting properties of MgB2

The effects of MgB 4 addition on the superconducting properties and the microstructure of in situ processed MgB 2 bulk superconductors were studied. MgB 4 powder of 1-20 wt.% was mixed with (Mg + 2B) powder and then pressed into pellets. The pellets of (Mg + 2B + xMgB 4 ) were heat-treated at 650 ℃ for 1 h in flowing argon. The powder X-ray diffraction (XRD) analysis for the heat-treated samples showed that the major formed phase in all samples was MgB 2 and the minor phases were MgB 4 and MgO. The full width at half maximum (FWHM) values showed that the grain size of MgB 2 decreased as the amount of MgB 4 addition increased. MgB 4 particles included in a MgB 2 matrix is considered to suppress the grain growth of MgB 2 . The onset temperatures (T c,onset ) of MgB 2 with MgB 4 addition (0-10 wt.%) was between 37-38 K. The 20 wt.% MgB 4 addition slightly reduced the T c,onset of MgB 2 to 36.5 K. This result indicates that MgB 4 addition did not influence the superconducting transition temperature (T c ) of MgB 2 significantly. On the other hand, the small additions of 1-5 wt.% MgB 4 increased the critical current density (J c ) of MgB 2 . The J c enhancement by MgB 4 addition is attributed not only to the grain size refinement but also to the possible flux pinning of MgB 4 particles dispersed in a MgB 2 matrix.

Section: Introductionmentioning

confidence: 99%

Enhanced critical current density of in situ processed MgB₂ bulk superconductors with MgB₄ additions

S.H.Kim¹,

Kang²,

Jun³

et al. 2017

“…The C doping to MgB 2 was known to be effective to increase the J c [16][17][18][19]. C was added to MgB 2 samples through the glycerin (C 3 H 8 O 3 ) treatment for B powder, which was already reported in our previous work [24,25]. B powder was mixed with a liquid glycerin, heated to 100 ℃, maintained at this temperature for appropriate time periods and dried at 200℃ for 20 h in a vacuum oven.…”

Section: Methodsmentioning

confidence: 99%

T_cand J_cdistribution in in situ processed MgB₂bulk superconductors with/without C doping

Kim¹,

Kim²,

Lim³

et al. 2014

Self Cite

Temperature dependence of magnetic moment (m−T) and the magnetization (M− ) at 5 K and 20 K of the in situ processed MgB 2 bulk pellets with/without carbon (C) doping were examined. The superconducting critical temperature (T c ), the superconducting transition width (∆T) and the critical current density (J c ) were estimated for ten test samples taken from the MgB 2 bulk pellets. The reliable m−T characteristics associated with the uniform MgB 2 formation were obtained for both MgB 2 pellets. The T c s and ∆Ts of all test samples of the undoped MgB 2 were the same each other as 37.5 K and 1.5 K, respectively. The T c s and ∆Ts of the C-doped MgB 2 were 36.5 K and 2.5 K, respectively. Unlike the m−T characteristics, there existed the difference among the M−H curves of the test samples, which might be caused by the microstructure variation. In spite of the slight T c decrease, the C doping was effective in enhancing the J c at 5 K.

“…The chemical solution method is an economical route for industrial fabrication. So far, many other groups have confirmed the effects of various organic or carbohydrate dopants of MgB 2 [2][3][4][5][6][7][8][9][10][11]. The study of carbon incorporation using malic acid can be advantageous because of the highly uniform mixing between the carbon and boron powders.…”

Section: Introductionmentioning

confidence: 99%

Magnesium diboride(MgB₂) wires for applications

Patel¹,

Kim²

2016

Field and temperature dependence of the critical current density, Jc, were measured for both un-doped and carbon doped MgB 2 /Nb/Monel wires manufactured by Hyper Tech Research, Inc. In particular, carbon incorporation into the MgB 2 structure using malic acid additive and a chemical solution method can be advantageous because of the highly uniform mixing between the carbon and boron powders. At 4.2 K and 10 T, Jc was estimated to be 25,000 -25,300 Acm -2 for the wire sintered at 600 o C for 4 hours. The irreversibility field, B irr , of the malic acid doped wire was approximately 21.0 -21.8 T, as obtained from a linear extrapolation of the J-B characteristic. Interestingly enough, the Jc of the malic acid doped sample exceeds 10 5 Acm -2 at 6 T and 4.2 K, which is comparable to that of commercial Nb-Ti wires.