低温熔盐铝电解的研究进展

综述了低温熔盐铝电解的研究进展.根据原料,将低温铝电解的研究划分为以先获得铝离子及铝的络合离子,再进行电解的传统低温铝电解和将固态Al2O3在低温熔盐中直接电化学还原的新低温铝电解.分析了传统方法电解质组成的改变对电解质物理化学性质的影响.指出了传统低温铝电解氧化铝的溶解度小且溶解速度慢、电解质导电性差以及阴极结壳是实现低温铝电解所要解决的主要问题,分析了新电解方法的缺点和解决手段,提出了今后的研究方向.     

Low Temperature Properties of Erbium In Gold

The properties of dilute alloys of Er in Au have been studied, principally below 100 mK, in connection with the use of this system in thermometry and in microcalorimetry for particle detection. Measurements are reported of (1) the magnetization at high temperatures and high field, (2) the magnetization in low fields with temperatures extending down to 0.1 mK, and (3) the heat capacity as a function of temperature and field at low temperatures. These measurements are analyzed to provide information of several properties of the Er³⁺ ion in the Au lattice, in particular, the crystal field parameters, the exchange interaction of the 4f electrons with the conduction electrons, and the spin glass freezing temperature.     

Low Temperature Properties and Superconductivity of LuB12

We have investigated the low temperature properties of LuB₁₂ by measuring its magnetic susceptibility, heat capacity, and electrical resistivity, as well as by point-contact spectroscopy using both the spear-anvil type technique and mechanically controllable break junctions. Our specific heat measurements and point - contact spectroscopy results indicate that LuB₁₂ is a simple weak-coupling BCS-type superconductor with T_C ≈ 0.4 K, a superconducting energy gap of 2 Δ ≈ 0.12 meV, and a very small critical field B_C ≈ 1 mT. From the dU/dI(U) characteristics in the superconducting state, the energy gap 2Δ, the critical current I_C and the Andreev-reflection excess current I_ex as a function of normal-state point contact resistance R_N have been determined. At low R_N all three parameters are strongly suppressed, possibly due to the self-magnetic field. At contacts with large R_N the model of resistively and capacitively shunted Josephson junctions (RCSJ) allowed us to estimate the superconducting current plasma frequency and the Josephson coupling energy. Moreover, from the d²U/d I²(U) spectra in the normal state the (point-contact) electron-phonon interaction function and the characteristic phonon energies of LuB₁₂ have been determined.     

Low Temperature Properties of a Superconducting Niobium Coaxial Cable

Semirigid coaxial cables with seamless metal shields are promising for readout from sensitive devices operating below liquid helium temperature. Low thermal conduction of such cables are also essential to reduce heat penetration into cryogenic temperature. We have developed thin semirigid coaxial cables employing niobium-titanium and niobium in both center and outer conductors, taking advantage of low thermal conductivity and extreme small electrical resistivity of superconductors. We assembled an adiabatic demagnetization refrigerator and measured thermal and electrical characteristics of those superconducting coaxial cables below T _c. Thin niobium coaxial cable with an outer diameter of 0.86 mm showed two-orders lower thermal conduction than expected, which is considered as the effect of impurity of niobium and forming process. Small attenuation was observed up to high frequency above 10 GHz at 3 K.     

抗温耐盐聚合物冻胶的低温合成及性能

以过硫酸铵/亚硫酸氢钠(APS/SHS)氧化还原体系为引发剂,利用丙烯酰胺(AM)、N,N-亚甲基双丙烯酰胺(MBA)等组成的共聚交联体系实现了黏弹性聚合物冻胶的低温聚合。探讨了单体、交联剂、引发剂用量及反应温度等合成条件对冻胶强度的影响,并采用环境扫描电子显微镜(ESEM)、红外光谱(FTIR)、热重-差热分析(TG-DSC)对聚合物冻胶进行了表征。确定其优化合成条件为:反应温度30℃,AM用量8wt%、MBA用量0.15wt%、引发剂(APS/SHS,质量比3∶2)用量0.15wt%(以反应物总质量计),在该条件下合成的聚合物冻胶强度较大、黏弹性较好。溶胀实验显示,在清水、1wt%NaCl、1wt%+0.5wt%CaCl2、5wt%NaCl、10wt%NaCl水溶液中浸泡6d的溶胀率分别为44%、50%、50%、62%和71%,最高可达1.71g/g,表明该聚合物冻胶具有一定的耐盐性。ESEM结果显示聚合物冻胶具有多孔结构,且孔隙度高,孔径分布均匀,溶胀性能良好;TG-DSC表明聚合物冻胶具有良好的热稳定性;岩心封堵实验表明该聚合物冻胶封堵效果良好,具有逐级封堵调剖特性。     

铝锆共掺杂氧化锌透明导电薄膜的低温制备及特性研究

利用直流磁控溅射法在室温玻璃衬底上制备出了可见光透过率高、电阻率低的铝锆共掺杂氧化锌(ZAZO)透明导电薄膜。讨论了溅射功率对ZAZO薄膜结构、形貌和光电性能的影响。实验结果表明,溅射功率对ZAZO薄膜的结构、形貌和电学性能有很大影响,而对其光学性能影响不大。扫描电子显微镜和X射线衍射仪研究结果表明,ZAZO薄膜为六方纤锌矿结构的多晶薄膜,具有垂直于衬底方向的c轴择优取向。当溅射功率为120 W时,薄膜的电阻率达到最小值5.28×10-4Ω.cm,其可见光区平均透过率超过94%。     

Thermal Properties of Two Materials Commonly Used in Low Temperature Laboratories

We carried out measurements of thermal conductance and thermal contact resistance of two materials commonly used in low temperature laboratories such as an Electro-Magnetic Interference (EMI) Filter and Stycast 2850 FT epoxy. Both samples were attached on a heat sink made of oxygen-free high thermal conductivity (OFHC) copper and characterized at temperatures between 0.3 K and 4.5 K, using a ³He refrigerator mounted on a pumped ⁴He cryostat. For the EMI filter we applied a varied input power from 0.25 up to 50 μW to the heater which is soldered to its central pin, whereas for a thin layer of Stycast sandwiched between a copper strap and the heat sink we applied an input power from 10 up to 810 μW. The temperature dependences obtained in each case were $K=3\,{\cdot}\,10^{-5}T^{2.3}~[\frac{\mathrm{W}}{\mathrm{K}}]$ , and $R_{K}=8.4\,{\cdot}\,10^{-3}T^{1.7}\ [\frac{\mathrm{W}}{\mathrm{cm}^{2}\,\mathrm{K}}]$ respectively.     

TLA掺量对湖沥青改性沥青高、低温性能的影响

为研究不同TLA掺量对湖沥青改性沥青高温、低温性能的影响,对TLA掺量为15%、25%、35%的湖沥青改性沥青分别采用动态剪切流变试验、蠕变及蠕变恢复试验来研究其高温性能;采用延度试验和BBR试验研究其低温性能。试验结果表明:老化前的湖沥青改性沥青以及RTFO老化后的湖沥青改性沥青的车辙因子G*/Sinδ值和破坏温度(fail temperature)都得到较大的提高,TLA掺量为35%比掺量为15%的湖沥青改性沥青的PG分级至少提高一个高温等级;随着TLA掺量的增加,湖沥青改性沥青的零剪切粘度逐渐变大,高温性能得到显著改善;但是湖沥青改性沥青的延度值和蠕变速率m却在减小,蠕变劲度s值在不断增大,表明TLA的加入对其低温性能是不利的。综合考虑高温、低温性能,建议TLA的合理掺量控制在25%~35%之间。     

Low Frequency Acoustic Resonance Studies

Fluid phase transitions in porous media are a powerful probe of the effect of confinement and disorder on phase transitions. Aerogel may provide a model system in which to study the effect of dilute impurities on a variety of phase transitions. In this paper we present a series of low frequency acoustic experiments on the effect of aerogel on the liquid–vapor phase transition. Acoustic resonators were used to study the liquid–vapor transition in two fluids (helium and neon) and in two different porosity aerogels (∼ 95% and ∼ 98%). While effective coexistence curves could be mapped out, the transition was sometimes difficult to pinpoint, leading to doubt as to whether this transition can be treated as an equilibrium macroscopic phase transition at all.     

Effect of Killer Impurities on Optical Properties of ZnO at Low Temperature

Optical characterizations for ZnO doped with killer impurities (Co or Fe or Ni) having doping concentrations 0.05–1.00% by weight have been carried out at 77 K. Optical properties such as excited state lifetime, trap-depth and decay constant values have been measured using the pulse excitation method. The effect of killer dopants, concentration of killer ions as well as the effect of temperature on various optical parameters values has been observed. Multi-exponential decay curves have been observed. Lifetime values are found to be in the micro- and nano-second time domain and a reverse trend is obtained with increase in concentration of killer impurities. With decreases in temperature from 300 to 77 K, lifetime shortening takes place. The effect of killer impurities is more prominent at higher concentrations. A mixed trend in decay constant values is observed with the increase proportional to the concentration of killer impurities. The values of the decay constant show a mixed effect with change in impurity concentrations. The value of the decay constant 0.76, corresponding to ZnO: Ni (0.7%) is the highest among all the doped ZnO phosphors.      

基于声学法测温的声波飞渡时间研究

声波飞渡时间的准确测量是声学法测温中影响温度场测温准确性的主要因素。采用互相关分析法计算单一频率声波信号及宽带频率声波信号的声波飞渡时间,仿真结果表明宽带频率信号由于具有较强的抗噪能力在计算声波飞渡时间时不受声波信号周期、信号延时时间等因素的限制,可用于工程实践。同时采用频率为40kHz的正弦波超声波探测器在均匀温场条件下对超声波信号的衰减程度进行试验研究,试验结果表明40kHz的正弦波超声信号在不经过放大处理条件下,其可测温场的距离仅为160mm。     

Installation of Relative Acoustic Gas Thermometry in the Low Temperature Range from 4.2 to 80 K

Measurement Techniques - A relative acoustic gas thermometry unit for reproducing and transmitting the unit of thermodynamic temperature, i.e., kelvin, in the low temperature range 4.2–80 K...     

面向低温环境的聚合物摩擦学性能及其改性研究进展

聚合物及其复合材料具有力学性能好、摩擦系数低、耐磨性能强等优点,常被应用于制造摩擦副关键基础件,如密封圈、齿轮、轴承保持架、转子叶片、活塞等.但迄今针对低温工况的聚合物摩擦学研究甚少,主要工作集中在常温和高温工况.面向低温环境的聚合物及其复合材料的摩擦学应用与相关制备、改性工艺的相关理论并不完备,极端服役环境下聚合物的摩擦学损伤失效机理还尚未完全清楚.此外,聚合物材料虽然具有众多优良的性能,但是其表面硬度低、温度影响大、易变形等缺点也同样明显,限制了其在低温摩擦学领域的应用,为此,研究者通过填充填料、表面处理等方法对聚合物进行了改性研究,取得了一定的成果.目前,由于航空航天等前沿技术的不断发展,聚合物在真空低温环境下的摩擦学性能受到了广泛关注,聚四氟乙烯、聚酰亚胺、聚醚醚酮等聚合物自润滑材料已被应用于空间飞行器领域来制作润滑和密封部件.研究者利用石墨、石墨烯、二硫化钼、芳纶纤维、玻璃纤维等对聚合物进行改性,制备了在低温环境下具有低摩擦系数、高耐磨性的聚醚醚酮/石墨、聚四氟乙烯/芳纶纤维、聚四氟乙烯/超高分子量聚乙烯等复合材料,促进了聚合物在低温摩擦学领域的应用.本文系统分析了低温环境下温度、环境介质、滑动速度、载荷、滑动方向等因素对聚合物摩擦学性能的影响,对面向低温环境的聚合物摩擦学改性进行了简要总结,以期促进聚合物低温环境下摩擦学应用及其相关研究的进一步发展.     

PECVD法低温淀积SiC_x薄膜的防水汽扩散性能研究

外界水汽和离子的扩散对集成电路和传感器等器件的性能及使用寿命有很大影响 ,利用无机钝化材料阻挡水汽和离子的扩散是常用的提高器件寿命和稳定性的方法。本文采用PECVD方法在较低的衬底温度条件下淀积碳化硅薄膜 ,利用各种方法研究了碳化硅薄膜的防潮性能。实验证明 ,碳化硅薄膜是一种良好的水汽扩散阻挡材料 ,其防潮能力达到甚至超过了集成电路生产中常用的氮化硅薄膜。并且 ,低温碳化硅薄膜具有非常好的化学稳定性和抗刻蚀能力 ,在各种微加工工艺中有广泛的应用前景。     

透明导电薄膜ZnO:Mn的低温制备及性能研究

利用直流磁控溅射法在室温玻璃衬底上制备出了可见光透过率高、电阻率低的掺锰氧化锌(ZnO:Mn)透明导电薄膜.实验制备的ZnO:Mn为六方纤锌矿结构的多晶薄膜,且具有垂直于衬底方向的c轴择优取向.实验结果表明,靶与衬底之间的距离对ZnO:Mn薄膜的生长速率、残余应力及电学性能有很大影响,而对薄膜的晶粒尺寸和光学性能影响不大.考虑薄膜的电学、光学及力学性能,认为靶与衬底之间的最佳距离为7.0 cm.在此条件下制备的ZnO:Mn薄膜的电阻率达到4.2×10-4 Ω·cm,可见光透过率为86.6％,丽残余应力仅为-0.025 GPa.     

低温等离子体处理对航空氟硅橡胶表面性能的影响

采用Ar,O2两种气氛对航空氟硅硫化橡胶(FS6265)表面进行低温等离子体(LTP)处理.用X射线光电子能谱(XPS)分析表面元素,测试表征了静态接触角、表面能及剥离强度;用扫描电子显微镜(SEM)及原子力显微镜(AFM)观察了表面形貌及表面粗糙度.结果表明:经Ar处理后,FS6265表面水接触角从101.5°降到19.0°,表面能从19.3mJ·m-2升高至73.2mJ·m-2;经O2处理后,水接触角降到25.5°,表面能升高至70.6mJ·m-2.SEM及AFM图像显示LTP处理后表面粗糙度增加.LTP处理后材料表面C、F元素含量下降,O元素含量大幅度提高,表面引入C-OH和C=O基团.LTP处理效果的时效性非常明显,FS6265经Ar,O2气氛处理后分别放置12,8h后表面性能的变化基本消失.     

Acoustic Properties of Amorphous Solids at Very Low Temperatures: The Quest for Interacting Tunneling States

We discuss the strain dependence of the acoustic properties of amorphous metals in both normal and superconducting states, in the temperature range 0.1 mK<T<1 K. A crossover is found when the strain energy is of the order of the effective interaction energy between tunneling systems at the corresponding temperature. Our results provide clear evidence for the interaction between tunneling systems, whose energy is in quantitative agreement with theoretical expectations, and reveal that without the knowledge of the corresponding strain dependences, the measured temperature dependences below ～50 mK of the acoustic properties of disordered solids are rather meaningless.     

LiV3O8纳米带的低温熔盐合成及其电化学性能

为了改进三聚钒酸锂作为锂离子电池正极材料的电化学性能,以LiNO3、LiCl和NH4VO3作为反应原料,通过一种简单的低温熔盐合成方法（LT-MSS）在250℃温度条件下制备得到带状LiV3O8纳米材料.X射线衍射（XRD）和X射线光电子能谱（XPS）分析结果表明所得产物为单斜相LiV3O8.扫描电镜（SEM）、透射电镜（TEM）和高分辨透射电镜（HRTEM）照片显示该产物为单晶纳米带形貌,沿[001]方向生长.电化学测试表明该产物储锂量高,循环性能良好.实验结果表明采用低温熔盐合成法制备LiV3O8能够有效提高所得产物的结构、形貌和电化学性能.     

低温推进剂的温度控制

通过对低温火箭三子级地面试验和多次飞行试验的分析及国外有关资料的报导，总结出影响低温推进剂温度的相关因素及控制方法，对新型的增压系统及温控技术进行了展望。