煅烧条件对BaTiO3纳米粉体结构的影响

将溶胶-凝胶法制备的钛酸钡纳米粉体在不同的条件下煅烧，然后对粉体进行激光粒度分布、红外光谱（FT-IR）、X射线衍射（X-ray）、扫描电镜（SEM）等表征。实验结果表明：溶胶-凝胶法制备的样品在800℃左右的温度下煅烧2h，并在空气中冷却，可得到粒径分布窄、颗粒均匀、纯度高的钛酸钡纳米粉体。     

纳米二氧化锡粉体的超重力-水热法制备与表征

以SnCl₄·5H₂O和氨水为原料,用超重力-水热法制备了纳米SnO₂粉体。利用X射线衍射(XRD)、透射电镜(TEM)、高分辨透射电镜(HRTEM)和物理吸附仪(BET)等分析手段对其进行表征。考察了反应物浓度、反应温度和陈化时间等实验条件对纳米SnO₂粉体的晶体结构、粒度及分散性的影响。结果表明,在SnO₂溶液浓度为0.05mol/L、水热温度240～280℃以及陈化时间3～8h得到的粉体结晶性良好、比表面积大(90～170m²/g)、粉体的颗粒大小在2～6nm左右,并具有良好的分散性。     

固相法合成负热膨胀性粉体ZrW2O8

以分析纯ZrO2和WO3为原料,用固相法制备了负热膨胀材料ZrW2O8粉体.以X射线粉末衍射、扫描电子显微镜分别对粉体进行物相分析和形貌观测;通过高温X射线衍射以及Powder X软件计算不同温度下的晶胞参数,从而确定热膨胀系数.结果表明经1 220℃保温3 h制备出的高纯度ZrW2O8粉体为单一立方结构,平均粒径为0.5μm;ZrW2O8粉体有显著的负热膨胀特性,在室温到150℃范围内,所得ZrW2O8粉体热膨胀系数为-11.58×10-6K-1;200～500℃范围内,热膨胀系数为-3.77×10-6K-1;在整个温度范围内平均热膨胀系数为-6.31×10-6K-1.     

纳米HfO2粉体的制备工艺研究

该文以HfOCl2为原料，分别选用分子量为400、1000和6000的3种聚乙二醇(PEG)作分散剂，在70℃和25℃的反应温度条件下，采用反向滴定化学沉淀法制备出HfCh纳米粉体．X射线衍射(XRD)、透射电镜(TEM)的分析结果表明：在70℃的反应温度条件下，加入3种分散剂制备的HfO2粉体的平均晶粒度均小于50nm；用高分子量的分散剂PEG6000所制得的粉体晶粒度更加细小；PEG6000的加入量在0．5％～2．5％质量分数范围内变化对最终的粉体晶粒度影响不大；在25℃的反应温度条件下，加入同样分散剂制备的HfO2粉体的平均晶粒度更加细小，平均晶粒度在30nm左右．用TG／DSC结合XRD对纳米HfO2粉体的研究结果表明：HfO2纳米粉体的晶型转变温度比微米HfO2材料降低了251℃左右(由891℃降低至640℃)，并且在焙烧温度大于660℃时，生成了只有在高温高压条件下才能存在的斜方相HfO2．     

BaTiO3纳米粉体的一种制备技术及其影响因素

介绍了采用钛酸丁脂和氢氧化钡为原料，用溶胶凝胶法制备BaTiO3纳米粉体的过程及影响因素。最佳工艺条件为：加水量R=40，pH=9，煅烧温度900℃和加料速度40mL／min等。通过上述工艺，可以得到晶粒小、分散性好、低团聚的钛酸钡粉体，同时，对粉体的形貌、粒度大小、衍射花样、X射线衍射进行了分析。实验结果表明：本方法能够制得粒径20～80nm的钛酸钡粉体。     

ATO粉体的制备工艺及其导电性能的研究

以SnCl4·5H2O和SbCl3为原料,采用化学共沉淀法制备纳米ATO粉体,考察了pH值、氨水体积比、锑的掺杂量、煅烧温度及煅烧时间对粉体导电性能的影响.运用DDS-12A型数显电导率仪测试了ATO粉体的电导率,运用了X射线衍射(XRD)、扫描电镜(SEM)等测试方法对粉体的晶型、粒径及形貌进行了表征.研究结果表明,氨水体积比为1∶3,pH值为8,煅烧温度600℃,煅烧时间4 h时所制备的纳米ATO粉体电导率值最大,即导电性能最佳.     

两步热聚合法制备多孔氮化碳及其吸附性能

以三聚氰胺和氯化锂为原料,通过两步热聚合法制备了多孔氮化碳。通过扫描电镜(SEM)、X射线衍射(XRD)、红外光谱(FT-IR)、X射线光电子能谱(XPS)等对所制备多孔氮化碳的性能进行了表征,通过氮吸附法对样品的比表面积及孔结构进行了测试分析。结果表明:所制备的多孔氮化碳为石墨相,其比表面积达到了86.7 m2/g,远高于简单热聚合法制备的块状石墨相氮化碳(g-C_3N_4)。对亚甲基蓝的吸附动力学研究表明,g-C_3N_4对水中亚甲基蓝的吸附满足准二级动力学模型,多孔g-C_3N_4的吸附速率和吸附量远高于块状g-C_3N_4。     

PbTiO3纳米粉体的制备与X射线衍射分析

以醋酸铅和钛酸丁酯为原料,甲醇为溶剂,冰醋酸为催化剂,采用溶胶-凝胶法制备出PbT iO3干凝胶粉体,在高于450℃的不同温度下空气气氛中焙烧,得到PbT iO3纳米粉体.用X射线粉末衍射仪对粉体的晶态进行了表征,计算了不同焙烧温度下PbT iO3纳米晶的晶格常数和平均晶粒大小.分析表明:焙烧温度高于600℃时可形成单一四方相钙钛矿结构的PbT iO3纳米粉体,并且随热处理温度的升高,晶粒度增加.在450℃~800℃区间时,平均晶粒大小在35 nm~50 nm左右.     

热处理温度和气氛对BiFeO_3陶瓷物相的影响

用溶胶凝胶法制备了BiFeO3前驱体,经不同温度(500~800℃)、不同气氛(O2和N2)煅烧得到了BiFeO3粉体,并在O2或N2气氛条件下烧结制备了BiFeO3陶瓷。用X射线衍射对比研究了不同气氛条件下BiFeO3陶瓷的物相组成。结果显示,在O2或N2中700℃煅烧的BiFeO3粉体在N2中800℃烧结可以得到纯相的BiFeO3陶瓷。实验表明BiFeO3粉体的煅烧温度及烧结过程中采用的气氛对BiFeO3陶瓷的物相组成有重要影响。     

Sm-Gd掺杂CeO_2基纳米粉体的制备

采用均相沉淀法,以CO(NH2)2和(CH2)6N4为沉淀剂,Ce(NO3)3.6H2O,Sm2O3,Gd2O3为起始原料,经过700℃焙烧4.5h,分别制备了Sm,Gd掺杂及Sm和Gd共掺杂的CeO2基纳米粉体.利用X射线衍射、扫描电子显微镜和BET等方法,对焙烧粉体的物相、形貌、晶粒尺寸及比表面积进行分析表征.结果表明,通过控制反应条件可对粉体的形貌和粒径进行有效控制;当混合金属离子总浓度为0.04mol/L,起始沉淀剂浓度为0.5mol/L,pH值为6.8时所得前驱体粉末经过焙烧,其产物为具有立方萤石型晶体结构及良好相纯度和结晶性、粒度分布为21～28nm的球形纳米粉体.该方法不失为低温...     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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