10T强磁场下低温中和法制备亚微米Mn2O3的研究

利用XRD和TEM对无磁场和10T强磁场下低温中和法制备的试样进行了分析,结果表明:无磁场下,锰的沉淀物主要是锰的氢氧化物,而10T强磁场下,锰的沉淀物主要是30nm左右的锰的氧化物.此外,10T强磁场对锰的氧化物结晶度几乎没有影响.然后,对无磁场和10T强磁场下制备试样在无磁场中进行经不同温度(200、400和600℃)热处理2.0h后,利用XRD和SEM对热处理试样进行分析,检测结果表明,无磁场中对10T强磁场试样在600℃经热处理2.0h后,制备出了100nm左右的亚微米Mn2O3,并且其亚微米Mn2O3粒径分布很均匀.     

10T强磁场下低温中和法制备亚微米MnzO3的研究

利用XRD和TEM对无磁场和10T强磁场下低温中和法制备的试样进行了分析，结果表明：无磁场下，锰的沉淀物主要是锰的氢氧化物，而10T强磁场下，锰的沉淀物主要是30nm左右的锰的氧化物。此外，10T强磁场对锰的氧化物结晶度几乎没有影响。然后，对无磁场和10T强磁场下制备试样在无磁场中进行经不同温度（200、400和600℃）热处理2.0h后，利用XRD和SEM对热处理试样进行分析，检测结果表明，无磁场中对10T强磁场试样在600℃经热处理2.0h后，制备出了100nm左右的亚微米Mn2O3，并且其亚微米Mn2O3粒径分布很均匀。     

10T超导强磁场下中和法制备棒状α-Fe2O3的研究

利用XRD和SEM对无磁场和10T超导强磁场下通过中和法对Fe^3＋在80℃陈化6．oh制备的试样进行了分析，结果表明：无磁场下制备的纳米球形α-FeOOH颗粒粒度分布不均匀；10T超导强磁场下制备出了50hm左右的纳米球形α-FeOOH，其粒度分布均匀，并且纳米球形α-FeOOH呈现了线性聚合排列。此外，10T超导强磁场对纳米α-FeOOH的结晶度几乎没有影响．然后在无磁场中对无磁场和10T超导强磁场下制备的纳米旺α-FeOOH经800℃热处理2．0h后，利用XRD和SEM对热处理试样进行了分析，结果表明：前者制备出了粒度分布不均匀的纳米球形α-Fe2O3颗粒，后者制备出了棒状α-Fe2O3.     

10T强磁场下低温中和法沉淀锰（Ⅱ）离子的研究

利用XRD和TEM分别对无磁场和10T强磁场下低温中和法沉淀锰（Ⅱ）离子的沉淀物进行了分析，结果表明：无磁场下，锰（Ⅱ）离子的沉淀物主要是由颗粒状和短棒状的Mn（OH）2组成，随着陈化时间的延长，Mn（OH）2被空气中的氧气氧化为颗粒状的MnOOH，其粒度分布不均匀。10T强磁场下短时间内，强磁场加速了Mn（OH）2向MnOOH转变，并且制备出了30nm左右的颗粒状MnOOH，其粒度分布均匀。随着陈化时间的延长，物相几乎没有发生变化，但是MnOOH颗粒有所长大，其粒度也出现了不均匀分布。此外，10T强磁场对MnOOH晶化程度几乎没有影响。     

Effect of cooling rates on the microstructure of proeutectoid ferrite in Fe-0.76%C alloy under high magnetic field

研究了在12 T强磁场下冷却速率对Fe-0.76%C钢中先共析铁素体的显微组织和性能的影响,结果表明: 先共析铁素体晶粒的伸长方向与磁场方向的夹角随着冷速度的提高而增大,其原因是高速冷却时原子扩散减弱. 在冷却速率相同的条件下, 与非磁场热处理样品相比,强磁场热处理样品的先共析铁素体面积明显增加, 宏观硬度下降,因为强磁场使Fe-0.76%C钢表现出更明显的亚共析钢特征.     

电喷雾和二步热处理制备无硬团聚纳米氧化锌

通过电喷雾和二步热处理法制备得到无硬团聚的ZnO纳米微粒, 为制备无硬团聚氧化物纳米粉体提供了一种新方法. 试验采用添加适量PVP的Zn(CH₃COO)₂·2H2O的乙醇溶液作为电喷雾液体, 经过锥形喷雾得到均匀的微米级小液滴. 干燥后的喷雾产物先后在氮气炉和空气炉中分别600℃和400℃保温1h进行二步热处理. SEM、XRD测试结果表明, 使用该方法制备得到的ZnO纳米微粒粒度均匀, 结晶完整, 无硬团聚, 具有六角纤锌矿结构.     

强磁场下冷却速率对Fe-0.76%C钢先共析铁素体组织的影响

研究了在12T强磁场下冷却速率对Fe-0.76%C钢中先共析铁素体的显微组织和性能的影响,结果表明:先共析铁索体晶粒的伸长方向与磁场方向的夹角随着冷速度的提高而增大,其原因是高速冷却时原子扩散减弱.在冷却速率相同的条件下,与非磁场热处理样品相比,强磁场热处理样品的先共析铁素体面积明显增加,宏观硬度下降,因为强磁场使Fe-0.76%C钢表现出更明显的亚共析钢特征.     

新型纳米/亚微米纤维态催化剂的制备及表征

采用静电纺丝法以聚乙烯吡咯烷酮(PVP)和纳米T iO2为原料制备了一种新型纳米/亚微米纤维态催化剂。采用SEM、TEM、XRD、FT-IR对所制得的新型纳米/亚微米纤维态催化剂进行了表征,结果表明纤维直径随着纳米T iO2含量的增加而增加,纳米T iO2颗粒在PVP纤维基体中分散均匀,并且纳米T iO2颗粒和PVP分子形成了氢键。光催化性能测试结果表明纤维中纳米T iO2含量为20%时,紫外光照射80 m in对甲醛的光催化降解率达到了56.8%。     

强磁场对硅锰铸钢于A_1点附近等温珠光体相变的影响

通过开展12 T强磁下硅锰铸钢(50Si_2Mn_3)于A_1点温度附近不同等温时间的热处理试验,并对比强磁场与无磁场条件下等温珠光体相变试验结果,研究了磁场对珠光体转变量及组织形貌的影响。研究表明,对于50Si_2Mn_3在A1点以下较高温度范围内,强磁场可缩短珠光体相变的孕育期,促进硅锰铸钢珠光体转变,使其转变量明显增加;强磁场能够提高珠光体转变临界点,使50Si_2Mn_3在A1点以上等温过程中能够发生珠光体相变。     

稳恒强磁场热处理对钴铁氧体结构和磁性能的影响

在强磁场下对钴铁氧体纳米粉末压块进行了热处理,分析讨论了热处理温度和磁感应强度对钴铁氧体的结构和磁性能的影响.结果表明,强磁场退火有利于钴铁氧体结晶度的提高和磁性能的增强,在居里点附近550℃下磁场处理作用效果最强,磁场强度越大,作用效果越明显.     

Comparison of Mechanical and Superconducting Properties of YBaCuO and GdBaCuO Single Grains Prepared by Top-Seeded Melt Growth

It is known that mechanical properties of a high-temperature superconductor (HTS) can affect the superconducting behaviour of the material. In this study, the mechanical and basic superconducting properties of single-domain YBaCuO and GdBaCuO were determined and compared. The bulk single-grain superconductor samples were prepared by top-seeded melt growth process. Distribution of trapped fields in the samples was mapped using the Hall probe technique. Levitation force was assessed using a dynamometer. Phase composition of the samples, was characterised by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) measurements. Microstructure was studied using scanning electron microscopy (SEM) and optical microscopy. Microhardness and comprehensive strength of the prepared samples were measured at a room temperature. The GdBaCuO superconductor has shown higher average hardness than the YBCO sample; higher fragility was also observed by comprehensive strength measurement of both types. Maximum trapped magnetic field was 0.65 T at 77 K in the case of a Gd-based material. In comparison with YBaCuO, the values of the trapped magnetic field and levitation force of GdBaCuO were higher. The results obtained can be useful for rare earth element (RE) superconductor device engineering as well as for the research in the field of superconducting ceramics.     

组成对Bi系微晶玻璃超导纤维性能的影响

用熔体快速淬冷法制备了数种Ｂｉ（Ｐｂ）ＳｒＣａＣｕＯ玻璃，进而用动态加热荷重法将这些玻璃拉成纤维。用Ｘ射线衍射、差热分析、电子探针和能谱及电流测量、拉丝试验等手段研究了玻璃成分变化对成丝能力和晶化后超导性能的影响。结果表明，Ｓｒ、Ｃａ含量的变化不仅对超导性能，而且对玻璃成丝能力有很大影响。获得的超导纤维的最大长度为５３ｃｍ，在７７Ｋ和零磁场下超导短纤维的最高电流密度Ｊｃ＝１５Ａ／ｃｍ＾２。     

Dy掺杂La2／3Ca1/3MnO3锰氧化物制备及低磁场下电输运性质

用溶胶-凝胶法制备了系列掺杂（La1-xDyx）2/3Ca1／3MnO3多晶纳米晶体,粒度在100nm左右。对系列样品电输运性质的研究表明,（La1-xDyx）2/3Ca1／3MnO3体系的电输运行为对Dy掺杂量极为敏感。随着Dy含量的增加,样品的转变温度向低温方向移动,峰值电阻显著变大;随着磁场的增加,其转变温度向高温方向略有移动;磁场增加引起的材料磁有序状态提高,使材料的磁电阻进一步变大。     

Real-space observation of skyrmion lattice in helimagnet MnSi thin samples

Observing and characterizing the spin distributions on a nanometer scale are of vital importance for understanding nanomagnetism and its application to spintronics. The magnetic structure in MnSi thin samples prepared from a bulk, which undergoes a transition from a helix to a skyrmion lattice, was investigated by in situ observation using Lorentz microscopy. Stripe domains were observed at zero applied field below 22.5 K. A skyrmion lattice with 6-fold symmetry in real space appeared when a field of 0.18 T was applied normal to the film plane. The lattice constant was estimated to be 18 nm, almost identical to the helical period. In comparison with the marginally stable skyrmion phase in a bulk sample, the skyrmion phase was stable over a wide range of temperatures and magnetic fields in the thin samples.     

Self-assembly Routes towards Creating Superconducting and Magnetic Arrays

No Heading Using self-assembly from colloidal suspensions of polystyrene latex spheres we prepared well-ordered templates. By electrochemical deposition of magnetic and superconducting metals in the pores of such templates highly ordered magnetic and superconducting anti-dot nano-structures with 3D architectures were created. Further developments of this template preparation method allow us to obtain dot arrays and even more complicated structures. In magnetic anti-dot arrays we observe a large increase in coercive field produced by nanoscale (50–1000nm) holes. We also find the coercive field to demonstrate an oscillatory dependence on film thickness. In magnetic dot arrays we have explored the genesis of 3D magnetic vortices and determined the critical dot size. Superconducting Pb anti-dot arrays show pronounced Little-Parks oscillations in Tc and matching effects in magnetization and magnetic susceptibility. The spherical shape of the holes results in significantly reduced pinning strength as compared to standard lithographic samples. Our results demonstrate that self-assembly template methods are emerging as a viable, low cost route to prepare sub-micron structures.PACS numbers: 74.25Ha, 75.75+a.     

Self-assembly routes towards creating superconducting and magnetic arrays

Using self-assembly from colloidal suspensions of polystyrene latex spheres we prepared well-ordered templates. By electrochemical deposition of magnetic and superconducting metals in the pores of such templates highly ordered magnetic and superconducting anti-dot nano-structures with 3D architectures were created. Further developments of this template preparation method allow us to obtain dot arrays and even more complicated structures. In magnetic anti-dot arrays we observe a large increase in coercive field produced by nanoscale (50–1000nm) holes. We also find the coercive field to demonstrate an oscillatory dependence on film thickness. In magnetic dot arrays we have explored the genesis of 3D magnetic vortices and determined the critical dot size. Superconducting Pb anti-dot arrays show pronounced Little-Parks oscillations in T_c and matching effects in magnetization and magnetic susceptibility. The spherical shape of the holes results in significantly reduced pinning strength as compared to standard lithographic samples. Our results demonstrate that self-assembly template methods are emerging as a viable, low cost route to prepare sub-micron structures.     

Melt textured YBCO: High trapped fields and superconducting magnetic bearings

Bulk melt textured YBCO samples in the shape of discs were prepared by a top seeding method using Sm-123 crystals. The field distribution of the trapped field on the surface of the samples was measured at 77 K by means of a Hall probe. In single grains with diameter of 20 mm the trapped field reached maximum values up to 0.56 T at 77 K. Investigating the temperature dependence of the maximum trapped field, a value of 5.5 T at 30 K was found for the best sample. At the same temperature, degradation of the trapped field by a factor of about 10 was observed for a second sample after field cooling in a field of 7 T. This degradation is explained by damage to the sample due to magnetic stresses. At the centre of the sample a magnetic stress of 11 MPa is estimated to be responsible for this damage. Additionally YBCO material has been tested in a high speed motor with superconducting magnetic bearings (SMB) in order to demonstrate the passive stabilization properties of SMB. In first tests the shaft rotated with a speed of 12 000 rpm limited by air drag.     

水热合成CoFe_2O_4/Bi_(0.5)Na_(0.5)TiO_3颗粒磁电复合材料中的零偏置现象

通过水热法分别制备CoFe_2O_4和Bi0.5Na0.5TiO3纳米粉。将两种粉末均匀混合,经成型和共烧工艺制备了xCFO-(1-x)BNT颗粒复合磁电材料(质量分数x为0.3,0.4,0.5)。X射线衍射(XRD)和SEM扫描电子显微镜(SEM)分析表明,复合陶瓷保持了较纯净的钙钛矿(BNT)和尖晶石结构(CFO)。振动样品磁强计(VSM)测试表明,这种材料在室温下具有良好的铁磁性。当磁场频率为1KHz时,950℃烧结的复合磁电材料(x=0.3)具有最大的磁电转换系数,约为47.4mV/Oe·cm;且发现当磁场为零时,该复合材料磁电转换系数不为零,在谐振点处仍具有1.2V/Oecm的磁电转换系数。这是一种可以应用于零场和中频的磁电复合材料。     

Crystalline orientation of alumina ceramics prepared by electrophoretic deposition under a high magnetic field

Electrophoretic deposition (EPD) of alumina in a superconducting magnet was performed at various magnetic field strengths. A stable colloidal suspension of alumina appropriate for magnetic alignment was prepared in an ethanol medium by using a phosphate ester (PE) as a dispersant. The amount of PE appropriate for the stability of the alumina suspension was investigated by measuring the pH, zeta-potential and the relative density of the green compacts. The consolidation of alumina powder was performed by EPD under a magnetic field of 0–12 T. The degree of crystalline orientation of the sintered bodies was evaluated by X-ray diffraction (XRD) as a function of the applied magnetic field during deposition and the sintering temperature.     

Effect of Columnar Defects on Magnetization of Mesoscopic Superconductors

In this work we investigated magnetization and vortex configurations in mesoscopic superconducting samples in the presence of square columnar defects (CDs). We solved numerically the nonlinear TDGL equations for different samples to study magnetization as a function of the applied magnetic field. In calculations, we focused mainly on four samples with different numbers of CDs which have the same total surface area. In this way, the total superconducting area remained the same with increasing the number of CDs for a fixed sample size. We found that the superconducting regions still exist inside the sample at high applied magnetic fields with increasing the number of CDs but irreversible effects became increasingly prominent, when the field is returned to zero. The results are discussed in frame of surface and pinning effects in mesoscopic systems.