沉淀法合成纳米CeO2及其性能

以Ce(NO3)3·6H2O为铈源,(NH-4)2CO3·H2O为沉淀剂,并加入少量PEG4000作为分散剂,采用液相沉淀法制备前驱体Ce2(CO3)3·H2O,前驱体经热处理合成了纳米CeO2.通过XRD,DTA/TG,TEM,BET及杂质含量分析,并根据XRD线宽法,按Scherrer公式计算平均晶粒尺寸,结合相对密度的测定研究了在不同热处理温度下纳米CeO2性能的变化.结果表明前驱体经300℃焙烧1 h已完全形成CeO2,属于立方晶系,空间群为Fm3m,原生晶粒粒径为5 nm左右,颗粒粒径为20 nm左右,比表面积达140.61 m2/g,孔径分布为5～15 nm,孔径峰值为9.3 nm,纯度≥99.97%;随焙烧温度提高,将引起CeO2晶粒尺寸和相对密度显著增大,比表面积减少.     

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...     

离子交换均匀沉淀法合成纳米CeO 2研究

以Ce(NO3)3.6H2O、Na2CO3为原料,采用新型弱酸性阳离子交换树脂均匀沉淀法制备CeO2前驱体,经500℃焙烧1～4h后获得了高纯度的纳米CeO2晶体.用热重分析、X射线衍射、扫描和透射电子显微镜等对前驱体和样品的形貌和粒径分布进行了表征,并对涉及的均匀沉淀机理进行了探讨.结果表明,制备的CeO2纳米晶体属立方晶系,样品分散性好,平均粒径为30～50nm.离子交换树脂均匀沉淀法具有操作简单易行,成本低,同时避免使用有机溶剂和表面活性剂,污染小,后处理容易,离子交换树脂可再生重复使用等优点.     

直接沉淀法纳米氧化锌的制备及表征

以ZnCl2.2H2O和无水(NH4)2CO3为原料,采用直接沉淀法制备了纳米氧化锌.TG-DTG-DTA、IR分析结果表明,前驱体为碱式碳酸锌[Zn5(OH)6(CO3)2].前驱体经300℃煅烧1 h、2 h、3 h后分别得到粒径不同的纳米氧化锌.用XRD、TEM和BET等进行表征,300℃煅烧2 h得到的纳米氧化锌的最小粒径约为8 nm,最大约为15 nm,平均粒径约为12 nm,比表面积为80.56 m2/g,纯度达99.9%以上,结果较为满意.     

氧化铜纳米粉的制备及分散方法

以CuSO4·5H2O为原料,首先制备出碱式碳酸铜前驱体.在350℃焙烧1h后,制备出 氧化铜纳米粒子,经XRD和TEM检测,粒径为30nm.在十二烷基苯磺酸钠水溶液中加入氧 化铜纳米粉,用稀HNO3,调节介质pH=3.0,得到均匀分散的氧化铜纳米粉水溶胶.     

不同液相法制备CeO2粉体的对比研究

以Ce(NO3)3.6H2O为铈源,采用液相法中的氨水沉淀法、碳酸氢铵沉淀法和借助微波的溶胶凝胶法分别制备了纳米CeO2粉体。利用XRD、TEM对所得粉体进行分析表征,从晶粒大小、分散性、形貌等方面进行了对比研究,结果表明氨水沉淀法制得的CeO2粉体为球状,平均一次粒径最小仅为9.5 nm,且分散性最好。利用IR确定了碳酸氢铵沉淀法中前驱体的物相组成,并讨论了棒状CeO2的形成过程,发现在形貌上与其前驱体具有继承性。     

纳米ZnO的制备与表征

以ZnAc2.2H2O、(NH4)2CO3为原料,采用沉淀法制备了纳米ZnO.以TG-DTA、IR、XRD、TEM和BET等测试方法研究了纳米ZnO粉体的结构和形貌特性.结果表明,前驱物[Zn5(OH)6(CO3)2]经300℃焙烧2 h,得到的纳米ZnO为六方晶系,粒子为球形,最小晶粒约为5 nm,最大约为28 nm,大部分集中在16~20 nm之间,平均晶粒为19.4 nm,90%的纳米晶粒≤24 nm,粒度分布均匀,分散性良好.探讨了反应物浓度、物料配比和焙烧温度等对样品的影响.     

ZnC2O4·2H2O和CuC2O4·2H2O纳米晶的超声波固相化学反应合成与结构表征

在近室温下通过固相反应合成ZnC2 O4·2H2 O和CuC2 O4·2H2 O纳米超细化合物 ,用X射线粉末衍射 (XRD)和透射电子显微镜 (TEM)对其物相、晶粒形貌和晶粒大小进行了表征 .结果表明 ,所得产物为颗粒大小均匀、平均粒径分别为 30nm和 4 0nm左右的纳米粉体     

用乙二醇为介质制备纳米氧化镁

用乙二醇为溶剂,Mg(NO3)2·6H2O为前驱物盐,NaOH和Na2CO3水溶液为沉淀剂,制备纳米MgO粉体,对样品进行了XRD、TEM、SEM表征.结果发现,煅烧前的沉淀物分别为纳米Mg(OH)2和Mg5(CO3)4(OH)2·4H2O,此沉淀物在430℃和530℃煅烧1.5 h,均得到晶粒较细、比表面积较大的纳米MgO粉体,其中最小晶粒尺寸和最大比表面积值分别为5.2 nm和259.8 m2·g-1.由Mg(OH)2分解得到的是重质MgO,由Mg5(CO3)4(OH)2·4H2O分解得到的是轻质MgO,且制得的MgO均保持了与相应沉淀物相似的形貌.     

NiFe2O4纳米晶的合成及焙烧动力学

以α-Fe2O3和NiO粉体为原料,NaCl为稀释剂,利用固相机械化学反应,在高能球磨作用下合成了NiFe2O4纳米晶.采用X射线衍射分析了合成NiFe2O4的过程和不同焙烧温度对晶粒尺寸的影响,计算了前驱体热处理过程晶粒长大的活化能.研究结果表明:制备的NiFe2O4纳米晶的晶粒尺寸为20～30 nm;焙烧温度越高,晶粒尺寸越大;NiFe2O4晶粒长大的表观活化能为16.7 kJ/mol,这表明热处理过程的晶粒长大主要以界面扩散为主.     

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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