掺杂蓝青铜的Peierls相变及非线性电输运性质

对钾钼蓝青铜０．３ＭｏＯ３及其Ｎａ离子掺杂单晶Ｋ０．３－ｘＮａｘＭｏＯ３（ｘ＝０．０２，０．０５，０．１０）系列的Ｐｅｒｉｅｒｌｓ相变及７７Ｋ非线性电输运性质进行了系统研究，发现Ｎａ离子掺杂对Ｋ０．３ＭｏＯ３单晶的Ｐｅｉｅｒｌｓ相变温度无明显变化，本认为这是由于Ｎａ离子所起的两种相反作用的结果，Ｎａ离子掺杂使样品的半导体能隙和第一阈值电场均明显增大，用钉扎理论对后给予定性解释，非线性电荷密度波     

蓝青铜单晶(Rb0.3MoO3)的横向电流效应

文章采用熔融电解还原法制备纯的蓝青铜单晶Rb0.3MoO3,测量了该样品的低场电阻-温度关系和非线性电输运性质.在100 K以下,纯样品的ET1随温度的升高而增大.研究了蓝青铜Rb0.3MoO3在77.1K下电荷密度波的横向电流调制效应随着横向调制电流由零逐渐变大,样品的ET1呈减小变化,在定性上符合Radzihovsky等人的理论预期.     

钠紫青铜NaMo6O17的热电势研究

报道了在１０～３００Ｋ温度范围内，对准二维电荷密度波导体ＮａＭｏ６Ｏ７紫青铜热电势的测量结果，在８０Ｋ附近ＮａＭｏ６Ｏ１７的热电势发生突变是该物质存在Ｐｅｉｅｒｌｓ相变的又一个实验例证，温度高于８０Ｋ时，热电势可以用一个经验公式，Ｓ＝ＡＴ＋Ｂ／Ｔ来描述，而在温度低于３０Ｋ时，热电势可以拟合为：Ｓ＝ＡＴ＋ＢＴ＾３，说明总的热电势均存在着自载流子自身的热扩散和声子对载流子的散射两方面的贡献，但高温区和     

新六方钨氧化合物的合成与掺杂反应

亚稳态六方三氧化钨化合物(h-WO     

钨青铜陶瓷Sr0.5Ba0.5Nb2O6的制备结构与介电性能研究

采用固相反应法合成Sr0.5Ba0.5Nb2O6陶瓷,并对其结构、介电性能进行表征.研究结果表明,Sr0.5Ba0.5Nb2O6陶瓷为四方钨青铜结构单相,其在100℃附近存在一个明显的弥散介电峰,峰值随测试频率增加而减小,为典型的弛豫铁电相变.室温时,10kHz频率下,其介电常数约为450,介电损耗为0.121.     

钨青铜陶瓷Sr_(0.5)Ba_(0.5)N_2O_6的制备结构与介电性能研究

采用固相反应法合成Sr0.5Ba0.5Nb2O6陶瓷,并对其结构、介电性能进行表征.研究结果表明,Sr0.5Ba0.5Nb2O6陶瓷为四方钨青铜结构单相,其在100℃附近存在一个明显的弥散介电峰,峰值随测试频率增加而减小,为典型的弛豫铁电相变.室温时,10kHz频率下,其介电常数约为450,介电损耗为0.121.     

氢钨青铜的微波辅助合成

氢钨青铜是一类光学和电学性能都非常优异的应用前景广阔的材料.快速简便的合成方法对其实际应用具有非常重要的意义.通过微波加热辅助合成了单相的立方相氢钨青铜H0.25WO3,其空间群和晶胞参数分别为Im-3和a=0.767 3(1) nm.样品的微观形貌为均匀的片状颗粒,厚度约50 nm,边长约100～200 nm.该纳米...     

掺杂法制备低相变VO_2技术进展

VO2是一种性能优异的金属-半导体相变材料,通过掺入其他杂质元素,能有效改变其相变温度和光、电性能,应用前景广阔。本文综述了掺杂原理,杂质对VO2电学性能和光学性能的影响、常用的掺杂方法及效果,这对进一步研发应用具有重要意义。     

掺杂K_(0.22)WO_3的晶体结构

采用固态化学反应法制备了掺杂钾钨青铜(K1-xMx)0.22WO3(M=Na,Ca,Sr,Ba,Y和La;0x0.20).X射线衍射结果表明,在掺杂范围内,样品的晶体结构主相均为六方相,其中除Na以外,Ca,Sr,Ba,Y和La都能够部分替代K进入六方晶格中.通过对实验结果的分析,提出了由参数H(n,x,t)决定钨青铜类化合物掺杂机制的新观点.容忍因子t、化合价n和掺杂量x共同决定了此类材料的掺杂机制.对于不同的掺杂元素M,掺杂后样品(K1-xMx)0.22WO3的H在相同范围内时,其晶胞体积V随x的变化规律也相似.     

Ce对铝青铜合金粉体材料涂层微观组织结构的影响

利用等离子喷焊技术,将自主研究开发的多元铜合金粉体(含Ce和不含Ce)涂覆在45等对熔覆层表面微观组织观察,采用X射线衍射、表面EDS、EPMA等分析手段,研究Ce在多元铝青铜粉末熔覆层中的分布及其对微观组织结构的影响.结果表明:稀土Ce在多元铝青铜合金粉体材料涂层中以化合物的形式存在,主要富集在晶界,少量分布在晶粒内...     

微量元素Co对高铝青铜显微组织的影响

利用MEF3,XRD和EPMA对含Co质量分数为0%、1.5%、2.5%、5.0%和6.0%的Cu-14Al-X的高铝青铜试样进行显微组织,物相和微区成分分析.结果表明,在Co元素质量分数提高后,合金的显微组织形貌发生了明显的变化,出现了类梅花形的新相,主量相中各种相的比例发生了变化.     

铁磁自旋波对介观环中持续电流的影响：Ⅱ.Peierls失稳中magnon的作用

研究在Ｔｅｘｔｕｒｅ结构中自旋波的量子涨落（ｍａｇｎｏｎ）对具有Ｐｅｉｅｒｌｓ失稳性的介观环持续电流的影响，结果表明由于能隙的出现而使持续电流进一步的减少     

铝青铜合金粉末涂层制备中Fe元素的扩散特性

利用等离子喷焊和激光熔敷技术,将铝青铜合金粉末涂敷在45#钢表面,通过对涂层金相组织观察、界面金相观察、X-ray分析、表面EDS分析、对Fe元素的EPMA分析,研究Fe元素在铜合金涂层中的扩散特性.结果表明,采用等离子喷焊技术制备的涂层中,Fe元素从基材到合金涂层有较强烈持续的扩散过程;采用激光熔敷技术制备的涂层中,Fe元素在基体与合金涂层之间无明显的扩散现象.可见,Fe元素在等离子喷焊层中扩散率较高,在激光熔敷层中扩散率较低.     

新型高铝铜合金喷焊层的组织与形成过程

利用等离子喷焊技术在45#钢表面制备新型高铝铜合金(Cu-14Al-X)喷焊层.采用光学显微镜、场发射扫描电镜(SEM)、电子探针显微分析仪(EPMA)、X射线衍射仪(XRD)研究喷焊层金相组织特征、宏观硬度和显微硬度、喷焊层与基体的结合特点以及喷焊层形成过程.结果表明,该合金粉末喷焊层的重熔过程具有快速凝固的特征.在重结晶过程中,富含Fe、Co等元素的高熔点、高硬度相首先析出,在喷焊层中形成硬质相,使得合金喷焊层的宏观硬度和显微硬度均较普通铜合金涂层高,宏观硬度高达261 HV,显微硬度高达424.2 HV.     

Thermodynamic properties of the charge-density-wave transition in potasium blue brone

Thermodynamic properties of the charge-density-wave (CDW) transition in potassium blue bronze K_0.3MoO₃ are investigated by the measurement of specific heat. A second-order phase transition is observed at 177.5 K. The specific heat jump, and enthalpy and entropy changes associated with the transition are estimated. The results suggest that the lattice plays an important role in thermodynamics for this compound. Analysis of the data near CDW transition shows that width of critical region is about 6 K and the critical behavior belongs to the universality class of the three-dimensional XY model. Supported by the National Nature Science Foundation of China & Youth Foundation of Science of Shanghai Shi Jing: born in Mar. 1956, Accociate professor     

Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2CU12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2CU12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid △T=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of theZr41.3Ti14.2CU12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.     

Fe-C二元合金包晶相变的相场法模拟

以Fe-0.79 mol%C二元合金为例,采用多相场法,模拟研究了包晶相变过程中不同过冷度下奥氏体的演化过程,讨论了过冷度对奥氏体生长速度与形貌的影响.结果表明:包晶反应过程中,在界面迁移率与溶质富集的影响下,靠近三相节点处的部分δ相重熔,导致γ相向δ相内生长;当液相中的球状δ相表面发生包晶相变时,γ相作为一个外壳包围着δ相生长,最后在δ相周围形成一层γ相的核壳;随着过冷度的增加,包晶相变的驱动力增加,γ相的生长速度加快,γ相包围δ相的量越多。     

Influence of deformation on precipitation in AZ80 magnesium alloy

Precipitates in the conventionally processed (solution treatment followed by aging) AZ80 alloy are coarse, cellular, and incoherent. They nucleate and grow on the basal planes of the matrix or distribute discontinuously in the alloy. Their unique morphology and undesired distribution make them ineffective for precipitation strengthening. This condition, however, can be modified by applying selected deformation and heat treatment conditions. The effect of deformation and heat treatment on the morphology and distribution of precipitates has been studied. Deformation was introduced by hot extrusion, cold rolling, or equal channel angular pressing (ECAP). The microstructures were characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that cold deformation improved precipitation more significantly than hot deformation, and twinning promoted precipitation more effectively than slip. When ECAP was applied, the Bc-route induced more precipitates than the A-route.     

Y2O3掺杂对BaZrxTi1-xO3陶瓷介电性能的影响

研究BaZrxTi1-xO3 (x=0,0.1,0.2,0.3)陶瓷中掺杂0.1％(按物质的量计算,下同)Y2O3对铁电-顺电相变温度的影响.发现0.1％Y2O3的掺杂使BaTiO3的铁电-顺电相变的居里温度向高温偏移了约20℃,不同Zr含量的样品也发生了一定程度的高温偏移.在-40℃到140℃的测量温度范围内介电频率弥散现象极弱,峰值介电常数可以达到8000,损耗峰值为0.05以下.随Zr含量的增加,损耗峰快速移向低温.与文献报道的结果比较,证实Y以A位替代Ba为主.