氧和铝在氧化铝中的自扩散参数评估

评估了氧和铝在Ａｌ２Ｏ３中的自扩散参数,分析了其扩散机理．得出：（１）在１７７０～２１００Ｋ 温度范围内,氧分压不超过１．０×１０５Ｐａ时,杂质总含量为３０×１０－６～５００×１０－６,Ｍｇ,Ｔｉ含量低于３０× １０－６的未掺杂Ａｌ２Ｏ３单晶中,氧的自扩散系数与温度的关系式,氧分压和扩散方向对该扩散系数 值影响不明显．（２）在１９４３～２１７８Ｋ范围,多晶Ａｌ２Ｏ３中铝的自扩散系数在１０－１５到１０－１４ｍ２／ｓ之间, 扩散活化能为 ４７７ ｋＪ／ｍｏｌ．（３）单晶Ａｌ２Ｏ３中主要杂质为ＴｉＯ２和 ＭｇＯ,掺Ｔｉ将降低氧的自扩散系 数,增加铝的自扩散系数;掺Ｍｇ使氧的自扩散系数略有增加;其他杂质对氧和铝在Ａｌ２Ｏ３中的 扩散系数影响不大．（４）氧和铝均通过空位扩散．     

片状SrTiO3晶体的合成及其反应机理

采用熔盐法分两步合成了片状SrTiO3晶体.研究了合成温度、熔盐种类对Sr3Ti2O7前驱体以及片状SrTiO3晶体形貌和尺寸的影响.在第1步过程中,低温下,首先生成亚微米级立方SrTiO3颗粒,随着温度的升高,SrTiO3颗粒逐渐生长成片状Sr3Ti2O7晶体.在第2步过程中,随着温度的提高,片状Sr3Ti2O7前驱体逐渐转变为片状SrTiO3晶体.熔盐的选择对片状SrTiO3晶体的最终形貌、尺寸有着显著的影响.以KCl作为熔盐,在1 200 ℃下合成的片状SrTiO3晶体边长为10～15 μm,而使用NaCl所得SrTiO3晶体边长为30～50 μm,宽厚比最高达到25∶1.片状SrTiO3晶体的形成机理是在高温条件下,由于熔盐中TiO2的作用,Sr3Ti2O7晶体中岩盐结构的SrO层被破坏,并以Sr2 、O2-形式溶出,剩余的SrTiO3结构重新叠合联结,产物基本保持原来Sr3Ti2O7片状晶体的外形,溶出的Sr2 、O2-与熔体中的TiO2反应生成SrTiO3.     

氧化钙部分稳定的氧化锆陶瓷渗氧机理的研究

本文采用渗氧池的方法研究了氧化钙-氧化锆陶瓷在960—1450℃的温度范围内的渗氧性,渗氧池一侧的氧分压(P′o_2)为10~(-3)～1大气压,另一侧的氧分压(P″o_2)为10~(-0)～10~(-4)大气压,单位时间单位面积渗氧量与(P′o_2~(1/n)-P″o_2~(1/n))成正比,其中指数项中的n值依赖于样品的微观结构和厚度,所导出的由内部扩散及表面反应混合控制的机理与实验结果一致,从而满意地解释了渗氧性对氧压依赖关系的特异规律,内部扩散及表面反应的活化能相近,约为200kJ/mol。     

铸造多晶硅生长过程中氧的传递过程研究

定向凝固法生长铸造多晶硅系统中,氧的平衡涉及到三个界面,它们是坩埚与熔体界面、熔体与气相界面以及晶体与熔体界面。因此氧的传递包含可能的三个过程:(1)氧从坩埚中向硅熔体中进行扩散;(2)氧的分凝导致氧从熔体中进入凝固的晶体中;(3)氧在熔体表面以SiO的形式挥发。     

Li_2O-Na_2O-Al_2O_3-SiO_2系玻璃中的Na~+自扩散

应用放射性同位素法,研究了xLi_2O·(31.8-x)Na_2O·5.8Al_2O_3·62.4SiO_2(mol%)系玻璃中的Na~+自扩散温度范围为250～450℃。从实测数据,用数值法与图解法求得Na~+的自扩散系数D_(Na)~*。根据玻璃的组成和扩散温度,D_(Na)~*值变化于8.8×10~(-8)～1.1×10~(-11)cm~2s~(-1)。随着玻璃中Na_2O含量的减少,D_(Na)~*逐渐降低,显示明显的双碱效应。由不同碱离子的Dietzel场强之差,讨论了这种双碱效应。D_(Na)~*随温度指数上升,符合Arrhenius方程。据此方程,应用最小二乘法,获得扩散活化能E和指数前项D_o,E值约为79～91kJ/mol。     

添质铝金红石(TiO2)单晶体焰熔法生长实验及机理

使用添加适量(原子分数为0 4%)Al2O3的金红石粉料,采用焰熔法成功地生长了尺寸为20mm×30mm的透明金红石单晶体,而采用相同工艺使用纯金红石粉料生长的晶体却是蓝黑色不透明的·添质铝在晶体生长过程中有如下作用:Al3 在晶体中取代Ti4 的位置,减少了氧的配位数,因而减少了晶体形成时对氧的需求,从而减少了由于Ti4 还原而形成的Ti3 和非本征氧空位的数量;由于Al3 半径小于Ti4 ,因此增加了正离子间距,使氧离子更易于迁移;形成添质后晶体的本征(固有)缺陷对Al′Ti V¨O,提供氧离子扩散通路·因此适量Al2O3的添加从宏观上增加了氧离子在晶体中的扩散速度,避免了大量色心的形成,从而在生长过程中可直接获得透明的金红石单晶体·     

SrTiO3:Ti3+晶体中朗德因子的研究

1引言 钛酸锶（SrTiO3）是一种重要的铁电晶体．它具有钙钛矿结构,在Tc=105K时有一个由立方到四角对称的结构相变．相变的结果使（Tio6）^9-八面体变为四角伸长的八面体（点群对称为D4h）．Ti^3＋离子在SrTiO3晶体中占据Ti^4＋离子位置．由于它所在的氧八面体为四角伸长,因此其基态为轨道双重态2^E,这个简并状态是不稳定的,会产生一个三角的Jahn—Teller畸变,使2^E态进一步劈裂成两个轨道单态．此时基态就为轨道单态,氧八面体也就变成斜方对称．电子顺磁共振（EPR）实验证实了这一点.     

氩气下Fe2O3-TiO2体系的固相反应

在氩气气氛下,采用扩散偶法研究了1323~1473K下的Fe2O3-TiO2体系的固相反应.使用电子探针对扩散偶的微观形貌进行观察,并对Fe、Ti离子的扩散摩尔分数曲线进行定量分析.动力学分析表明,氩气下体系的固相反应受铁、钛和氧离子的扩散控制.用Boltzmann-Matano法计算了体系的互扩散系数,其数量级在10-13~10-10cm2·s-1范围内,并随着温度和Ti离子摩尔分数的增大而升高.氩气气氛下体系的扩散活化能约为356.06 kJ·mol-1,远比空气下的大,表明外界气氛中氧分压对体系的反应机理有重要影响.     

锶离子在ZSM-5分子筛中的自扩散研究

用同位素示踪法研究了锶离子在ZSM-5分子筛中的自扩散过程:分快和慢的两步进行.控制速度的扩散方程为 D=4.9×10~(-11)exp(-E/RT)cm~2·sec~(-1) E=33kJ·mor~(-1)     

退火气氛对SrTiO3薄膜电学性能的影响

在不同的退火气氛下,采用金属有机物分解法在(111)Pt/Ti/SiO2/Si衬底上制备了SrTiO3薄膜材料,并对其结构和电学性能进行了研究。X射线衍射结果显示SrTiO3薄膜都呈现多晶立方钙钛矿结构。对比不同气氛下制备出的SrTiO3样品电学测量结果,发现在氧气氛中退火后,样品具有较低的漏电流和较好的介电性能,这可能是由于氧气氛中退火减少了SrTiO3薄膜内氧空位的浓度引起的。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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