掺杂的PZT95/5陶瓷粉体性能

掺杂对PZT95/5压电陶瓷粉体的性能有较大影响.采用溶胶-凝胶法制备PZT95/5粉体,选择不同掺杂物进行改性,研究其对粉体的粒度均匀性、分散性、合成纯度等性能影响.结果表明,不同掺杂物在一定程度上都可提高溶胶的分散性;掺杂Nb5+以可溶性铌盐(C10H8N2O33Nb2)液相引入时,合成粉体的分散效果和合成纯度都要比以固相Nb2O5粉体引入时好;中性掺杂物SiO2具有降低合成温度和抑制烧绿石相形成的作用,且合成粉体的粒度均匀、分散性好.     

高性能锆钛酸铅(PZT)粉体的水热法合成及其压电陶瓷性能研究

以氧氯化锆、钛酸四丁酯、硝酸铅为前驱物,采用两步水热法合成钙钛矿结构的Pb Zr0.52Ti0.48O3粉体并制备陶瓷样品.通过XRD、SEM及电学性能等测试,系统研究了矿化剂浓度对PZT粉体结晶性、形貌以及最终烧结陶瓷样品电学性能的影响,初步探讨了PZT粉体在不同碱度下的生长机理.实验结果表明,较低碱度条件有助于制备结晶性良好、单一分散的立方体形貌的PZT粉体,由该粉体烧结的陶瓷样品的电学性能(d33=310 p C/N,kp=53.2%,ε33T/ε0=1 358,tanδ=0.005)明显优于高碱度水热条件制备粉体所烧结的陶瓷及传统固相法制备的陶瓷的压电性能(d33=223 p C/N,kp=40%,ε33T/ε0=1 330,tanδ=0.004).     

La0.5Sr0.5CoO3多晶靶材的制备研究

为制备出纯度高、单一物相、致密的、符合后期PLD(Pulsed Laser Deposition)镀膜所用要求的LSCO (La0.5Sr0.5CoO3)靶材,对LSCO的制备方法及其过程进行了分析研究.采用半共沉淀法,LSCO前驱物经900 ℃预烧、研磨,可制得纯度高、物相单一的LSCO粉体;用干压方法成型,在不同的温度下对其烧结,通过研究烧结体的XRD图谱、吸水率和密度并结合LSCO粉体的DSC-TG曲线,确定出制备LSCO多晶靶材的最佳烧结温度为1200～1250 ℃,比用固相法制备粉体的靶材烧结温度降低了100～150 ℃.     

改性Pechini法制备BaTi2O5陶瓷及其优异电学性能研究

利用改性Pechini法制备了 BaTi2O5(BT2)粉体,采用傅里叶红外光谱仪、X射线衍射仪(XRD)、冷场发射扫描电子显微镜(FESEM)和同步热分析仪测试了 BT2粉体的物相结构与反应机理.结果表明,采用以柠檬酸为螯合剂的溶胶制备BT2粉体的最佳煅烧温度为850℃.粉体经1200℃的常压固相烧结得到BT2陶瓷,...     

柠檬酸燃烧法制备钙钛矿结构二元稀土氧化物LaYbO_3粉体的研究

钙钛矿结构二元稀土氧化物由于优异的物理性能可以作为质子导体、闪烁体和磁介质等材料,因此对其制备过程的研究是物性研究的前提.本文采用了柠檬酸盐燃烧法进行了钙钛矿结构二元稀土氧化物LaYbO3的制备.通过对前驱体在不同温度下进行煅烧处理,结合XRD分析,得到了前驱体随着加热温度改变的物相组成变化.并通过采用SEM观察对不同温度下获得的纯相粉体的微观形貌,得到了粉体微观形貌随煅烧温度的改变情况.结果表明,采用柠檬酸燃烧法700℃下便可获得单相LaYbO3粉体,粉体的粒度在100-200nm范围内.由于采用水作溶剂,粉体有团聚现象存在.     

钛酸锶钡粉体晶化过程和物相结构研究

应用传统陶瓷制备工艺制备出Ba0.6Sr0.4TiO3(BST)粉体,在600~1 140℃范围内对粉体按不同温度煅烧,用X射线衍射分析各煅烧温度下制备出粉体的物相结构,用TG/DTA研究了粉体在煅烧过程中的晶化过程.实验结果表明:粉体在600~900℃煅烧过程中出现3个不同的中间相,900℃附近这些中间相基本消失,BST钙钛矿相开始形成,经过1 000℃煅烧2.5 h,BST粉体已经显示为完全的钙钛矿相,其晶格常数a和c分别为0.397 4 nm和0.398 4 nm,晶胞体积为0.062 9 nm3.随着煅烧温度的升高,粉体的晶格常数和晶胞体积逐渐减小.     

钛酸钡纳米粉体的制备与X射线衍射分析

采用溶胶—凝胶法,以醋酸钡和钛酸丁酯为原料,冰醋酸为催化剂,制备了BaTiO3干凝胶,干凝胶在700℃以上温度焙烧,得到单一物相的BaTiO3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BaTiO3粉体的晶格常数,以及不同焙烧温度下BaTiO3粉体的晶粒大小.分析表明:BaTiO3粉体随温度的升高,晶体结构由立方逐渐向四方转变,晶粒度增加,热处理温度在700℃~900℃时,平均晶粒在40 nm~80 nm范围.     

铁酸铋陶瓷的制备及其磁电性能研究

采用低温固相法制备BiFeO_3前驱体,经煅烧得到BiFeO_3粉体,并在不同温度下烧结制得BiFeO_3陶瓷。分析前驱体的热分解过程、粉体和陶瓷的物相组成及陶瓷的磁性能和介电性能。结果表明,采用低温固相法制备的BiFeO_3前驱体,经700℃煅烧可制得基本为单相的BiFeO_3粉体,再经800℃烧结可以制得体积密度较大的BiFeO_3陶瓷,其在室温下不表现宏观磁性;BiFeO_3陶瓷的介电常数和介电损耗均随其烧结温度的升高而下降。     

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。     

水热法制备纳米复合粉体催化剂

纳米复合粉体是催化反应生产纳米材料的常见催化剂,其颗粒大小和分散程度在纳米材料的制备中起到关键作用。本文采用水热法重结晶制备SiO2负载型纳米复合粉体,研究水热反应温度对催化剂物相的影响,并用该催化剂通过化学气相沉积法成功生长出碳纳米管。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-