高温相变蓄热电采暖器蓄放热特性的实验研究

本文对自研得高温相变蓄热电采暖器的蓄放热性能进行了实验研究,表明该电采暖器蓄热密度高,蓄放热性能稳定;针对放热末期散热进行了空气通道强化散热实验研究,结果表明其内部结构合理,蓄热时隔热性能好,放热时放热速率可满足普通取暖要求。     

2003年度诺贝尔物理学奖漫谈

简要介绍了奖金获得者Alexei A Abrikosov，Vitaly L Ginzburg和Anthony J Leggett在超导体和超流体理论方面开拓性的贡献，特别着重于他们所发展的理论的背景和重要性，文章还简要谈及2003年度诺贝尔物理学奖给我们带来的启示。     

Mössbauer study of 1/8 anomaly in La2−x Ba x CuO4

The measurements of Mössbauer effect, magnetic susceptibility and muon spin relaxation have been carried out for the high-T _c superconductor La_2?x Ba _x CuO₄. The intensity of Mössbauer doublet spectrum of the sample of x～1/8 begins to decrease rapidly at a certain temperature T _m, which we define as a magnetic transition temperature T _Möss. This temperature almost agrees with T _μSR determined from muon spin relaxation. The quadrupole doublet disappears at low temperature below T _m but a clearly splitted spectrum is not observed even at 4.2 K, which indicates a peculiar magnetic state with a wide distribution of internal magnetic field. Around x～1/8, the superconducting critical temperature T _c and T _m are competed each other. In conclusion, superconductivity disappears around 1/8 hole concentration and a peculiar magnetic state such as spin density wave appears.     

高温超导制冷机直接冷却中界面热阻的辨识与实验研究

本文给出了三种提高YBCO块材在外磁场中悬浮力的方法 .第一种方法是增强外磁场 ,对于此方法 ,本文研究了一块直径为 30mm的圆柱状YBCO块材分别在圆柱状NdFeB永磁体和NdFeB永磁导轨上的悬浮力 .测量结果表明在 77K温度下YBCO块在圆柱状NdFeB永磁体上的最大悬浮力为 5 0N ,在NdFeB永磁导轨上的最大悬浮力为 10 3.0N .第二种方法是提高YBCO块材自身的性能 ,包括临界电流密度、俘获磁通和块材尺寸 ,对于此方法 ,本文仅研究了块材尺寸对悬浮力的影响 .三块直径分别为 30mm、35mm、4 0mm的圆柱状YBCO块材在NdFeB永磁导轨上的悬浮力被测量 ,77K温度下 5mm悬浮间距时的悬浮力分别为 10 3.0N、134.5N、175 .0N .第三方法是将YBCO块材变成准永久磁体 ,此种情况下 ,直径为 4 0mm的圆柱状YBCO块材在 77K温度下 5mm悬浮间距时的悬浮力高达 2 18.3N .高温超导材料和低温技术的发展 ,促进了制冷机直接冷却高温超导磁体的发展 .在高温超导直接冷却系统中 ,减小和控制界面热阻成了实现超导直接冷却的关键 .界面热阻机制相当复杂 ,虽然可以用公式进行预测 ,但是最可靠的还是通过实验进行测量 .本文介绍了界面热阻测量的基本原理和实验装置 ,提出一种基于导热反问题的参数辩识方法 ,并用这种方法处理了氮化铝 (AlN)与高温超     

YBCO熔融织构准单晶中的进氧和脱氧扩散研究

采用热重法研究了YBCO熔融织构准单晶中氧的化学扩散过程. 与以往的实验不同，采用固定 氧偏压变化温度的方法获得氧浓度梯度. 拟合实验所得重量等温弛豫曲线可知，在375—600 ℃温区内，熔融织构准单晶的氧化学扩散系数比单晶体高出约50％，但都约为10^{-10c m2s-1，激活能为～1eV. 对YBCO熔融织构准单晶中的进氧和脱氧研 究表 明两者具有相同的速率，证实实验过程中环境氧分压的改变会导致进氧和脱氧过程不一致. 关键词： 高温超导 氧扩散 熔融织构 热重法}     

Alkali Lithosilicates: Renaissance of a Reputable Substance Class with Surprising Luminescence Properties

A hitherto unknown synthetic access to alkali lithosilicates, a substance class first described by Hoppe in the 1980s, is reported. With the synthesis and characterization of NaK₇[Li₃SiO₄]₈, a new representative has been discovered, expanding the family of known alkali lithosilicates. Astonishingly, NaK₇[Li₃SiO₄]₈ and the already established alkali lithosilicates Na[Li₃SiO₄] as well as K[Li₃SiO₄] display unforeseen luminescence properties, when doped with Eu²⁺. Na[Li₃SiO₄]:Eu²⁺ exhibits an ultra‐narrow blue, K[Li₃SiO₄]:Eu²⁺ a broadband, and NaK₇[Li₃SiO₄]₈:Eu²⁺ a yellow‐green double emission upon excitation with near‐UV to blue light. Consequently, all of the investigated substances of this class of compounds are highly interesting phosphors for application in phosphor converted LEDs.     

Thermally stable coherent domain boundaries in complex-structured Cr2Nb intermetallics

The strength and hardness of nanostructured materials are significantly enhanced owing to the large amount of grain boundaries (GB) produced by a reduced grain size. The thermal stability of the GB is a key to maintaining the grain size and thus the strength/hardness in nanostructured materials at high temperatures. In this work, coherent domain boundaries (DB) were introduced by compressive processing to sub-divide a complex-structured intermetallic Cr₂Nb into nanograins of size down to 2 nm. These DB persisted after an annealing of 10 h at 1273 K. The coherent DB have been investigated by aberration-corrected high-resolution transmission electron microscopy and first-principles calculations. The high thermal stability is evidently a result of low formation energies of the DB.     

Accumulation features and TL of TLD-500 detectors in a wide temperature range at pulsed and continuous high-dose irradiation

The results of a comparative research of thermoluminescence (TL) of TLD-500 detectors based on anion-defective corundum irradiated with continuous and pulsed X-ray and pulsed electron beams in a range of doses of 0.3 ÷ 10⁷ Gy, dose rates of 0.02–2.6·10¹¹ Gy/s, and in a temperature range of 300–950 K are presented. It is found that, in contrast to continuous irradiation, upon pulsed irradiation with a duration of 10 ns and dose rate of P_P ≥ 5·10⁶ Gy/s, the first linear region of dose dependences for TL peaks at 450, 580 and 830 K is, instead of saturation, followed by a second one with a smaller slope at doses near 2, 200 and 10³ Gy. Moreover, the slope of the second region increases with growing P_P. It was also found that dose dependence for the peak at 830 K in the area of the first linear region at 10–10³ Gy remains invariable at P_P ≤ 10¹⁰ Gy/s. It is shown that the upper limit of doses registered by TLD-500 detectors can be increased to 2·10³ and 6·10⁶ Gy for continuous and pulsed irradiation, respectively. New broadband UV luminescence with a maximum hν = 4.1 eV and half width H = 0.85 eV was registered within the TL peak spectrum at 830 K. Besides, the optical depletion spectrum in which a single band with hν = 5.2 eV and H = 1.6 eV is observed was investigated for a trap causing a peak at 830 K.     

Electrotransport properties of a high-temperature phase of CsH<Subscript>2</Subscript>PO<Subscript>4</Subscript> and composite systems with silicon dioxide at different humidities

Investigations of the electrotransport and thermodynamic properties of CsH₂PO₄ and composite systems (1 ? x)CsH₂PO₄?xSiO₂ (x=0–0.5) synthesized on the basis of silicon dioxide with different magnitude of the specific surface area are conducted while varying the partial pressure of water vapor. It is demonstrated that the superionic phase transition, which is observed in CsH₂PO₄ at a temperature of 230°C, has nothing to do with the process of dehydration. A strong surface interaction of the salt with the matrix is discovered in composites of different compositions synthesized on the basis of uniformly porous silicon dioxides with specific surface areas of 41–520 m₂ g^?1 and the value of pH ～7. The interaction is found to lead to dehydration and to small values of conductivity in the systems heated to temperatures in excess of 230°C. An analysis of the dehydration products is conducted and conditions conducive to the existence of phases with certain compositions are determined.