YBa2Cu3Ox(123)超导体的微波焊接及其对微观结构的影响

对Ｙ－系（１２３）相超导材料的微波焊接进行了初步研究，结果表明微波快速焊接后的试样，经９６０℃空气中退火１５ｈ后炉冷，其Ｔ_c可恢复至８９．７Ｋ，比焊接前试样的Ｔ_c低１．６Ｋ。利用电子探针对焊接前后样品的显微结构进行了比较，发现焊区组织致密，但在后处理过程中超导相发生了再结晶，导致焊缝变宽，气孔因聚集而变大。同时用电子微探针分析仪发现，焊接后焊区普遍存在Ｙ₂ＢａＣｕＯ_x相、Ｂａ_2-yＣｕ_{y 关键词：}     

Ge/Au,Ge/Ag双层膜和Ge-Au,Ge-Ag合金膜中非晶Ge的晶化

本文对Ge/An,Ge/Ag,双层膜和Ge-An,Ge-Ag合金膜的退火过程进行了透射电子显微镜观测,对Ge/多晶Au(或Ag)还进行了加热过程的原位观测。观测表明,多晶Au和单晶Au膜的存在使非晶Ge的晶化温度T_c的下降显著不同,可由晶界三叉点等处为非晶Ge的有利形核位置来解释,双层膜的缩聚区中由于局域优先晶化的影响,不仅T_c(=100℃)比非缩聚区中(T_c=150℃)低,而且形成直径为1—2μm的Ge大晶粒,而Ge/多晶Ag和Ge/单晶Ag膜的T_c均约为280℃,合金膜中金属含量较低时(C_Au<17at％,C_Ag<18at％),T_c高于相应的Ge/多晶Au(Ag)膜;金属含量较高时,T_c低于Ge/多晶Au(Ag)膜。这说明过饱和金属原子的存在使得非晶Ge的晶化势垒大大降低。 关键词：     

CeCu2Si2和UBe13的超导理论(Ⅱ)——热力学量的计算

根据文献[1]中给出的模型和能隙方程,计算了超导态的热力学临界磁场,T_c处的比热跃变以及T_c以下的比热行为。结果表明:有关热力学量的临界值与实验结果定性相符;T_c以下的比热行为在整个温区与CeCu₂Si₂和UBe₁₃的实验结果符合。 关键词：     

McMillan Tc公式的解析推导(Ⅰ)——μ*=0情形

作者在μ^*=0情形,从Eliashberg方程解析地导出如下的T_c公式:T_c=αω_logexp{-b((1+cλ)/λ)},式中α=2γ/π,b=c=1;Inγ=C=0.5772是Euler常数。这个T_c公式只有在T_c=0.36/α(k)以下才是正确的,α是个大于1并随材料而异的常数。我们推测,当T_c超过上述范围后,T_c公式的函数结构很可能不同于McMillan T_c公式,至少α,b和c等参量不再是些不依赖于材料的常数了。 关键词：     

C-15结构(Hf,Zr,Ta)V2和(Hf,Zr,Nb)V2合金超导转变的压力效应研究

本文研究了C-15结构化合物(Zr_0.5Hf_0.5-xTa_x)V₂(x≤0.2)和(Hf_0.5Zr_0.5-xNb_x)V₂(x≤0.2)的超导转变温度T_c及其压力效应?T_c/?P。报道了实验方法与结果。与(Hf_1-xTa_x)V₂和(Zr_1-xTa_x)V₂的情况不同,在(Zr_0.5Hf_0.5-xTa_x)V₂中Ta的引入使常压下的T_c下降,然而(?)T_c/(?)P却大为提高。因此高压下Zr_0.5Hf_0.45Ta_0.05V₂的T_c反而比Hf_0.5Zr_0.5V₂更高。导出了一个基于角动量分波表象能带论方法的描述压力效应的新关系式。它指出导带电子波函数中的高角动量成分变化对T_c的压力效应影响比较重要。这个公式有助于理解上述复杂的实验现象,并能合理地解释某些元素(如Cs,Ba,La等)的T_c随压力剧增的事实。 关键词：     

非晶态超导体的转变温度Tc与原子质量的关系

本文探讨非晶态超导体的T_c与原子质量M之间的关系,发现在具有相同价电子数的同族元素中,超导T_c与原子质量的立方根成反比,即T_c∝l/M^1/3。讨论了晶态超导体的T_c问题,其中包括高T_c氧化物超导体。 关键词：     

表面与界面的绝缘铁磁理论

采用Green函数技术,我们讨论了温度从T=0直到T=T_c范围内铁磁体表面和界面的磁化强度随温度的变化情况,所得到表面磁化强度的结果与其他作者的结果一致;而在界面计算中,我们发现界面的T_c与体内的不同,并且找到了一个关系式:T_cc^A,T_c^B)。 关键词：     

YBa2Cu3Ox（123）超导体的微波焊接及其对微观结构的影响

对Ｙ－系（１２３）相超导材料的微波焊接进行了初步研究，结果表明微波快速焊接后的试样，经９６０℃空气中退火１５ｈ后炉冷，其Ｔｃ可恢复至８９．７Ｋ，比焊接前试样的Ｔｃ低１．６Ｋ。利用电子探针对焊接前后样品的显微结构进行了比较，发现焊区组织致密，但在后处理过程中超导相发生了再结晶，导致焊缝变宽，气孔因素聚集而变大。同时用电子微探针分析仪发现，焊接后焊区普遍存在Ｙ２ＢａＣｕＯｘ相、Ｂａ２－ｙＣｕｙＯｘ相和     

Bl结构MoNx薄膜的制备及物理性能研究

我们对以反应性溅射法制备的MoN_x薄膜测量了超导转变温度T_c,电阻率ρ(T)(从T_c起始到300K)。用X射线衍射技术、卢瑟福背散射(RBS)、俄歇谱仪和X射线光电子能谱(XPS)技术对这些样品进行了分析。实验结果表明T_c和ρ(T)随N含量改变而变化。当样品是B1结构时,T_c小于4.2K,而且样品内还有过量的N存在。俄歇分析表明,样品内有O,C杂质存在。这些因素都可能导致T_c很低,ρ(T)呈负的温度系数。 关键词：     

准静态颗粒介质的弹性势能弛豫分析

颗粒体系是典型的多体相互作用体系, 具有多重的能量亚稳态. 对于准静态颗粒体系, 引入构型颗粒温度T_c描述弹性势能涨落. 本文认为平衡的体系具有一定的构型颗粒温度T_a, 其量值反映了其结构特征. 当外界扰动激发的构型颗粒温度超出T_a时, 产生不可逆过程. 通过对应力松弛过程的分析, 发现(T_c-T_a)激发了弹性弛豫, 且(T_c-T_a)越大则松弛过程中应力变化越大, 最终构型颗粒温度T_c→T_a时,宏观应力松弛结束,体系达到新的能量亚稳态.     

Annealing effects on the microwave permittivity and permeability properties of Fe79Si16B5 microwires and their micowave absorption performances

This paper reports that amorphous magnetic microwires(Fe79Si16B5) have been fabricated by a melt-extraction technique and have been annealed at 600°C and 750°C respectively.Differential scanning calorimeter measurements show that nanocrystalline magnetic phase(α-Fe) has been formed in the amorphous matrix when it was annealed at 600°C.Hard magnetic phase(Fe2B) was formed in the microwires annealed at 750°C,which increases the magnetic coercivity.Microwave permittivity and permeability are found to be dependent on the microstructures.The permittivity fitting results show that multi Lorentzian dispersion processes exist.For microwires annealed at 750°C,their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600°C.The microwave absorption performance of microwires annealed at 600°C is found better than microwires annealed at 750°C.     

Phase Characterization of Diffusion Soldered Ni/Al/Ni Interconnections

The formation and growth of intermetallic phases in the Ni-Al system during a novel joining process for Ni/Ni interconnections based on diffusion soldering has been studied. The Ni/Al/Ni bonds were accomplished by isothermal solidification and subsequent interdiffusion of Ni and Al in the Ni/Al/Ni joints held at a temperature of 720°C. Optical and scanning electron microscopy, electron probe microanalysis and X-ray diffraction analysis were used to characterize the microstructural changes as a function of the reaction time. The following phases appeared sequentially: liquid Al → Al₃Ni → Al₃Ni₂ → AlNi (stoichiometric) → AlNi (Ni-rich) → AlNi₃. At intermediate stages two to four phases coexisted. The NiAl phase occurred in two variants, namely a Ni-rich AlNi (60 at.% Ni) and stoichiometric AlNi. The joining process was completed after 30 h of reaction. Then only AlNi₃ was present in the Ni/Al/Ni interconnection zone. The quality of the resultant bond and the high melting point of the AlNi₃ phase (1360°C) indicate a great potential of the diffusion soldering for the joining of heat dissipating devices used in electronics and electrotechnics.     

Residual stresses in ceramic-to-metal joints: diffraction measurements and finite element method analysis

The residual stress (RS) field in ceramic–metal diffusion bonds has been studied by spatial-resolved neutron strain scanning. Strain profiles were directly determined by neutron diffraction along selected lines perpendicular to the bonding interface of cube-shaped Ni/Si₃N₄ specimens. Finite element method (FEM) calculations were carried out to simulate the joining process and residual strains have been obtained among the whole body of specimens. The simulations were validated by comparison with the experimental strain data obtained by neutron and (previous) X-ray diffraction along some particular line of the specimen. Finally, the RS field across the whole sample was obtained from the FEM-calculated strain field, showing that neutron strain scanning combined with FEM analysis is a very useful technique to study the RS map in silicon nitride–metal diffusion bonds at both sides of the joining interface. Maxima of the axial stress were found at the lateral surface and close to the joining interface, being tensile for both ceramic and nickel. On the other hand, the largest radial stress at the joining interface was found at the centre of the specimen on the ceramic side. From the point of view of FEM analysis, it is shown that in order to simulate the joining process of nickel and silicon nitride, nickel must be considered as a ductile material having strain hardening and Si₃N₄ must be considered as purely elastic material having a nearly temperature-independent elastic modulus.     

Microwave-induced low-temperature crystallization of amorphous Si thin films

Microwave heating was utilized for low-temperature crystallization of amorphous Si (a-Si) films. Microwave heating lowered the annealing temperature and reduced the annealing time. By microwave heating the hydrogen in the amorphous films was diffused out long before the nucleation of polycrystalline Si (poly-Si). The combination of NiCl₂ coating on a-Si and microwave heating greatly reduced crystallization temperature. The combination of metal-induced crystallization and microwave-induced crystallization might be a useful technique to develop high-quality poly-Si films at low temperature.     

Cu/SiO2/Si(111)体系中Cu和Si的扩散及界面反应

室温下利用磁控溅射在p型Si(111)衬底上沉积了Cu薄膜. 利用X射线衍射和卢瑟福背散射分别对未退火以及在不同温度点退火后样品的结构进行了表征. 在此基础上，研究了Cu/SiO₂/Si(111)体系的扩散和界面反应. 实验结果表明：当退火温度高于450℃时出现明显的扩散现象，并且随着温度的升高，体系扩散现象会更加显著. 当退火温度低于450℃时没有铜硅化合物生成，当温度达到500℃时才有铜硅化合物生成. 关键词： 薄膜 扩散 界面反应 硅化物     

用磁分析法观察某些铁-镍-铝合金的脱溶过程

用热磁分析方法较仔细地观测了Fe-Ni-Al三元系合金沿β+β′两相区内某一结线上的几个不同成分的合金样品。淬火所得的成分接近Fe₂NiAl的过饱和固溶体在较高温度(～850℃)分解甚快,在一分钟内脱溶基本上完成。在850℃分出的β′相还含铁约35at.％,其居里点在400℃附近。在850℃经短时间回火继以水淬的合金,在600—700℃再经适当的回火,则首次回火所生成的β′相继续迅速分解,在不超过十分钟内损失大量的铁而变成非铁磁性的;其在室温的H_c可增到500奥斯特。这和Б.Г.Лившнц所提出的“继续脱溶”的假设相符。磁性观测的结果证明:β′相的继续脱溶是“可逆的”,就是说,把曾在600—700℃回火的合金重热至850℃时β′相能在几分钟内恢复850℃的平衡成分。Fe₂NiAl过饱和固溶体在较低温度(70O℃以下)分解极慢,并且其过程是明显地“不均匀”的。因此,这种合金不能通过高温淬火继以较低温度(600—700℃)回火的处理来获得高H_c的事实可以用单畴粒子的理论加以解释。     

Ti与莫来石陶瓷衬底的界面反应

在抛光的200℃莫来石陶瓷衬底上电子束蒸发淀积200nm的Ti膜，并在高真空中退火，利用二次离子质谱（SIMS）、俄歇电子能谱（AES）和X射线衍射分析（XRD）研究了从200—650℃Ti与莫来石的固相界面反应．结果表明，在淀积过程中，最初淀积的Ti与衬底表面的氧形成Ti—O键，并有微量元素态Al，Si原子析出，界面区很窄；450℃，1h退火后，界面区有所展宽，但变化不大；650℃，1h退火后，界面发生强烈反应，样品主要由TiO＋Ti，Ti₃Al，Ti₃Al＋TiSi₂和莫来石陶瓷衬底四层结构组成 关键词：     

磁控溅射方法制备垂直取向FePt/BN颗粒膜

用磁控溅射在热单晶MgO(100)基片上制备了［FePt/BN］多层膜，经真空热处理后，得到具有垂直取向L1₀-FePt/BN颗粒膜.X射线衍射结果和磁性测量的结果表明，［FePt(2nm)/BN(0.5nm)］₁₀和［FePt(1nm)/BN(0.25nm)］₂₀多层膜经700℃热处理1h后，均具有较好的(001)取向.［FePt(1nm)/BN(0.25nm)］₂₀垂直矫顽力达到522kA/m，剩磁比达到0.99，开关场分布S达到0.94，FePt晶粒平均尺寸约15—20nm，适合用于将来超高密度的垂直磁记录介质. 关键词： 磁控溅射 垂直磁记录 0-FePt/BN纳米颗粒膜')" href="#">L1₀-FePt/BN纳米颗粒膜     

Co掺杂纳米ZnO微结构的正电子湮没研究

利用正电子湮没技术研究了10 at.% Co掺杂的Co₃O₄/ZnO纳米复合物中退火对缺陷的影响. 利用X射线衍射(XRD)测量了Co₃O₄/ZnO纳米复合物的结构和晶粒尺寸. 随着退火温度升高,Co₃O₄相逐步消失,ZnO晶粒尺寸也有显著增加. 经过1000 ℃以上退火后,Co₃O₄相完全消失,并出现了CoO的岩盐结构. 正电子湮没寿命测量显示出Co₃O₄ /ZnO纳米复合物中存在大量的Zn空位和空位团. 这些空位缺陷可能存在于纳米复合物的界面区域. 当退火温度达到700 ℃后Zn空位开始恢复,空位团也开始收缩. 900 ℃以上退火后,所有空位缺陷基本消失,正电子寿命接近ZnO完整晶格中的体态寿命值. 符合多普勒展宽谱测量也显示Co₃O₄ /ZnO纳米复合物经过900 ℃以上退火后电子动量分布与单晶ZnO基本一致,表明界面缺陷经过退火后得到消除. 关键词： ZnO 界面缺陷 正电子湮没