超临界流体触媒作用下石墨-金刚石转变

 研究了超临界流体CO₂在石墨-金刚石转变中的触媒作用。实验中，采用Ag₂O作为流体触媒的先驱材料，在7.7 GPa压力下，Ag₂O在1 200 ℃分解成Ag和O₂，O₂与石墨套管在高温高压下反应形成CO₂超临界流体。研究结果表明，在7.7 GPa和1 500 ℃以上温度条件下，石墨在CO₂流体触媒的作用下可转变为金刚石晶体，在1 500～1 700 ℃温度范围内合成出的金刚石具有完好的八面体形貌，与天然金刚石的生长特征非常相似。     

Pd41Ni10Cu28P21大块非晶合金结构与晶化过程

采用水淬的方法获得了Pd41Ni10Cu28P21大块非晶合金.结果表明,这一合金体系具有很强的玻璃形成能力,其约化的玻璃转变温度Trg为0.714.结构分析显示,Pd41Ni10Cu28P21非晶合金比以往所报道的Pd40Ni40P20非晶具有更接近于"冻结"液态的密堆积结构.非晶的晶化实验表明,晶化初期多种晶相同时结晶析出.低于710K退火非晶样品,亚稳相形成,继续提高退火温度亚稳相消失.此外,从热力学和动力学角度就Cu部分替代Ni对合金的玻璃形成能力的影响进行了探讨.     

Superconductivity and Fermi Surface Anisotropy in Transition Metal Dichalcogenide NbTe_2

Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has been placed upon WTe_2 and MoTe_2, which exhibit non-trivial topology both in single layer and bulk as well as pressure induced or enhanced superconductivity. We study another distorted IT material NbTe_2 through systematic electrical transport measurements. Intrinsic superconductivity with onset transition temperature(T_c~(onset)) up to 0.72 K is detected where the upper critical field(H_c) shows unconventional quasi-linear behavior,indicating spin-orbit coupling induced p-wave paring. Furthermore, a general model is proposed to fit the angledependent magnetoresistance, which reveals the Fermi surface anisotropy of NbTe_2. Finally, non-saturating linear magnetoresistance up to 50 T is observed and attributed to the quantum limit transport.     

Advanced high-pressure transport measurement system integrated with low temperature and magnetic field

We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Condition User Facilities in the Huairou District of Beijing, China. To demonstrate the capabilities of the system for condensed matter research,the emergence of some pressure-induced phenomena and physics related to superconductivity found previously is also introduced, and then a perspective for such an advanced high-pressure system is presented.     

Kinetics of the glass Transition of the Zr41Ti14Cu12.5Ni10Be22.5 Alloy Solidified in a Drop Tube

Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass-forming alloy with different sizes are solidified in a drop tube containerless process.The glass transition temperature Tg of Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres solidified with different cooling rates is investigated by using a differential scanning calorimeter.It was found that all the amor phous spheres show an increase of Tg with the heating rate.The glassy spheres have a unique value for the glass transition activation energy Eg=435.50kJ/mol,which is independent of cooling rate q.The insensitivity of Tg to q is interpreted by an extension of the free volume model for flow.     

Structural relaxation of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) bulk metallic glass under high pressure

Zr41Ti14Cu12.5Ni10Be22.5bulk metallic glass (BMG) is annealed at 573 K under 3 GPaand its structural relaxation is investigated by X-ray diffraction, ultrasonic study, compression as well as sliding wear measurements. It is found that after the ZrTiCuNiBe BMG sample was annealed under high pressure, the mechanical properties were improved. Moreover, the BMG with relaxed structure exhibits markedly different acoustic properties. These results are attributed to the fact that relaxation under high-pressure results in a microstructural transformation in the BMG.     

高温高压下采用非金属触媒合成金刚石 *

综述了在非金属触媒作用下石墨-金刚石转变的研究进展 ,为更好地了解非金属触媒对石墨 金刚石转变的作用机理提供了最新相关文献中的典型例子和当前的实验研究结果 .另外 ,通过计算石墨-金刚石相变中碳原子跃迁的激活能和相变几率比较了高温高压下采用碳酸盐、硫酸盐和磷等非金属触媒对石墨-金刚石相变的影响 ,发现触媒的类型对相变激活能的影响非常明显 ,同时给出了采用这些非金属触媒合成金刚石的转变几率.     

抵御大变形超导体的发现

超导体在压力的作用下会产生原子间距的缩小,进而导致晶格参数的改变,甚至能使其原子排列规律变化,引发结构相变.超导体的超导电性是一种演生现象,是由超导体中所包含的电荷、自旋、轨道、晶格等多种相互作用的自由度所决定的.因此,当超导体在外部压力作用下发生晶体结构的变化,通常都会引起超导电性的改变,尤其超导转变温度的变化.本文介绍近年发现的一类能够抵御大变形的超导体(robust super-conductivity against volume shrinkage, RSAVS)——这类超导体在压力作用下,即使发生很大的体积压缩,其超导转变温度仍保持不变.这种奇异的能抵御压缩变形的稳定超导电性最初是在对高熵合金的高压研究中观察到的,后续研究发现在广泛应用的商业化NbTi合金以及Nb, Ta等金属元素超导体中也具有这种可抵御大变形的超导电性.分析结果显示,这类超导体都具有体心立方晶体结构,并由过渡族金属元素构成.这种超导体的发现为统一理解“什么因素决定了超导体的超导转变温度?”这一关键问题提出了新的研究课题和挑战.     

注入Mo 在Zr57Nb5Cu15.4Ni12.6Al10非晶合金中的扩散

通过二次离子质谱仪(SIMS)研究了Mo在Zr57Nb5Cu15.4Ni12.6Al10非晶合金中的扩散,并计算出其扩散激活能Q和前置系数D0分别为1.95 eV和1.13×10-5 m2s-1.根据Stokes-Einstern关系式研究了玻璃转变温度以下593-673 K之间Zr57Nb5Cu15.4Ni12.6Al10非晶合金的黏滞特性,得到的黏滞系数从593 K的1.07×1010Poise降到673 K的1.42×108 Poise.