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High-Tc superconducting Bi-2223/Ag blistering band


Law gisCCO-2223/Ag (Bi a 2223/Ag) strip production process in the Health 9 blistering occurs, it is a value mattress attention to technical problems. Bi 2223g in the manufacture of a strip, the Mao I; were deposited with the Mu end, the nominal composition Bi, ff'b. , Sr. , Ca = ? u, Ox, after the two roasting total amount of carbon units 2.0x10 ~. This precursor powder,[link widoczny dla zalogowanych], cooking is a major titanite 2212, also contains a step amount of CaO | and the CuO phase. The powder into the outer diameter of 6mm, inner diameter 4mm, tweezers tube, the Wu bulk density of about 50% of theoretical density. Follow-up processes include stretch-ling for the 1.6mm diameter round wire, and then flat rolled into a thickness of 0.15mra, a width of 35mm strip. At a temperature of 820 ~ 840 ℃ under the conditions of sintering length O7 ~ 15 (K'm strip sample,[link widoczny dla zalogowanych], the atmosphere was air, INI a 7.5% O: and oxygen, which asked for rolling and suppression: a very narrow range of heating rate variation, which is 50 ℃ / h to l50 ℃ m. The basic process includes 3 times to ask for the duration of the sintering step 50 ~ 100h, followed by the intermediate rolling and pressing (with the material I) . Another process is 250 ℃ m speed quickly heated to the sintering temperature, exposure to cool a few minutes, and rolled before the first sintering, and the rest the same process with the former (with wood Ⅱ). X-ray diffraction (XR.D), scanning electron microscopy (SEM), optical microscopy and electron probe was stone block X-ray microanalysis (EPMA) examination of tissue samples, and in advance 1/3Hp +2 / 3Nq, -I ~ OH solution to remove corrosion wallet sets. With 3eolJXA a 8600 electronic microscope and energy dispersive spectroscopy (EDs) of the system to a 2223 strip characterization of Bj's chemical properties. in accordance with the basic process out of the band processing The first one I material sintering process, the able to observe two different patterns of behavior of a swelling and blistering. in expansion mode, increasing the thickness of the sample the same shape; thickness of the growth of very small, less than the initial thickness of 10%. In blistering mode,[link widoczny dla zalogowanych], flat central part of the sample length along the strip into a hollow cylinder rules. In the sample out of the side and end of the first part of the small Island. in injury status annealing, the bulk sample ten centimeters long flat section of the separation of some short rounded body composition, they are just a few millimeters distance from the break .3.5 lPiIn ', wide strip of the cylinder diameter of about i.6ram. It know, the side tilting Island Formation and the internal gas pressure caused by the deformation of wallet sets of related articles prisoners. In this case,[link widoczny dla zalogowanych], the top and bottom of the sheath plane strain occurs without any external constraints; side of the end of the first exception, and many plane intertwined. The fact that the basic process in accordance with the process I strip out, the swelling and blistering two actions are dependent on heating rate of horizontal (∞, and specimen length (L), thermal processing and handling composition of the atmosphere does not affect the strip act. has been found that the faster heating rate and the length of the larger sample,[link widoczny dla zalogowanych], then sample more severe blistering and bubbling lower the temperature. in the heating rate of 250 ℃ / rain, the sample length about 10cm, the minimum temperature of foaming 600 ℃. In order to remove moisture and reduce the carbon content will be prepared prior to processing powder in the drying temperature of 835 ℃, but this does not prevent foaming. In addition, studied the strip rolling state of pre-annealing at 500-700 ℃ for the impact of blistering heat. The fact that the baking powder made of 4 strips, even at the highest heating rate (250 ℃ h ~ ir-) and the sintering temperature (835 ℃) under. Annealing can eliminate foaming; low temperature annealing can completely eliminate blistering. XILD analysis confirmed. forming the state of the ceramic cylinder is mainly a 2212 phase composition of Bi, because the deformation of pre-Ling highly textured. in the subsequent sintering process occurred Bj 2223 a 2212 change to a large ground delays. even after 190h annealing long asked, in fact, no change in the state to retain a majority of Bi 2212 phase. Facts show that. even if the sintering for up to 190h, cylindrical samples is not high critical current density (Jc ≈ 5. 0A afraid). At the 1st sintering pressed into the flat after the strip after I have completely suppressed The performance is, Tc ≈ 110K, Jc (3 ~ 5) x103 ~ ∞. Ⅱ strip after the full processing and heat treatment with good superconducting properties, including non-foaming, critical current density than l × 10 one. A Chuan (Huang Jinchang)

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