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1.
超临界流体干燥制备纳米MnxOy   总被引:3,自引:0,他引:3  
以硝酸锰和氨水为主要原料,用“溶胶-凝胶”法结合“超临界流体干燥”技术制备纳米MnxOy气凝胶,在800℃下煅烧MnxOy气凝胶,用XRD和TEM进行表征,重点考察超临界干燥、煅烧工艺对MnxOy气凝胶晶态、形貌和尺寸的影响。结果表明,采用超临界干燥,可制得分散性好的疏松棕黑色Mn3O4球形颗粒,其粒径介于10~30hm之间;在800℃下热处理,Mn3O4球形颗粒进一步氧化转变为米粒状Mn2O3颗粒,粒径也相应增大。  相似文献   

2.
溶胶凝胶和超临界干燥法制备纳米TiO_2粉体   总被引:1,自引:0,他引:1  
以钛酸丁酯 (Ti(OR) 4 )为原料 ,采用溶胶凝胶法及超临界流体干燥技术制备了纳米TiO2 粉体。采用正交设计法研究了操作条件对反应的影响 ,筛选出了最佳工艺条件。TEM检测表明 ,优化条件下制得的二氧化钛粉体粒径为 11~ 12 .3nm ,且随热处理温度的升高粒径变化不大 ,但团聚加重。XRD结果表明 ,当热处理温度为 5 0 0℃时晶粒为锐钛型 ;当煅烧温度为 80 0℃时晶粒转化为金红石型。BET结果表明 ,二氧化钛气凝胶颗粒的比表面积可高达5 5 6m2 /g ;但随煅烧温度的升高 ,比表面积下降迅速 ;在 5 0 0℃时 ,比表面积只有 94 .6m2 /g。  相似文献   

3.
溶胶凝胶和超临界干燥法制备纳米TiO2粉体   总被引:9,自引:1,他引:8  
以钛酸丁酯(Ti(OR)4)为原料,采用溶胶凝胶法及超临界流体干燥技术制备了纳米TiO2粉体。采用正交设计法研究了操作条件反应的影响,筛选出了最佳工艺条件。TEM检测表明,优化条件下制得的二氧化钛粉体粒径为11-12.3nm,且随热处理温度的升高粒径变化不大,但团聚加重。XRD结果表明,当热处理温度为500℃时晶粒为锐钛型;当煅烧温度为800℃时晶粒转化为金红石型。BET结果表明,二氧化钛气凝胶颗粒的比表面积可高达556m^2/g;但随煅烧温度的升高,比表面积下降迅速;在500℃时,比表面积只有94.6m^2/g。  相似文献   

4.
以无机盐TiCl4为前躯体,采用溶胶 凝胶法结合超临界干燥技术制备超细TiO2气凝胶,并采用XRD和TEM技术进行表征。结果表明,采用该法,可制得流动性好的白色球形α TiO2气凝胶颗粒,其平均粒径约为20nm。  相似文献   

5.
溶胶—凝胶法制备α—TiO2气凝胶   总被引:2,自引:3,他引:2  
以无机盐TiCl4为前躯体,采用容胶—凝胶法结合超临界干燥技术制各超细TiO2气凝胶,并采用XRD和TEM技术进行表征。结果表明,采用该法,可制得流动性好的白色球形α—TiO2气凝胶颗粒,其平均粒径约为20nm。  相似文献   

6.
为了提高聚酰亚胺(PI)气凝胶的光催化活性,采用两步复合的方法制备CPI/PI气凝胶复合材料。首先以3,3′,4,4′-联苯四甲酸二酐和4,4′-二氨基二苯醚为前驱体,采用乙醇超临界干燥技术得到PI气凝胶,并将PI气凝胶在600℃煅烧成含氮的碳化PI气凝胶(CPI);然后将CPI气凝胶与PI气凝胶前驱体复合并经超临界干燥制备CPI/PI气凝胶复合材料。对PI和CPI/PI气凝胶的表面形貌、比表面积、力学性能和光催化性能进行表征分析。结果表明:CPI/PI气凝胶具有良好的多孔结构,比表面积达到245 m~2/g, PI气凝胶的力学性能优异(弹性模量在10 MPa以上);煅烧后的CPI有效提高了PI气凝胶对土霉素溶液的光催化效率并具有良好的循环再生稳定性能,5次循环使用后土霉素溶液降解率为76%。  相似文献   

7.
以溶胶凝胶法为基础,采用正硅酸乙酯(C8H20O4Si)、硝酸铝(Al(NO3)3·9H2O)为主要原料,借助X射线衍射仪进行检测,系统研究了pH值、煅烧温度对生成3∶2型莫来石以及生成过程的影响。结果表明:莫来石凝胶介于单相凝胶和双相凝胶的混合尺度,pH值在4~10范围内均可生成莫来石,煅烧温度为1175 ℃时出现明显的莫来石化;pH=4时,不利于无定形硅的转化;在pH值为5~9范围、煅烧温度1200 ℃时完全莫来石化,且生成的莫来石结晶度总体变小,晶胞参数上下波动。莫来石的生成经历了无定形硅和铝的氧化物到铝硅尖晶石再到莫来石的过程。  相似文献   

8.
纳米级锂离子电池正极材料LiCoO2的制备及表征   总被引:1,自引:0,他引:1  
LiCoO2是锂离子电池中最有前途的正极材料之一,近年来人们对它进行了广泛的研究.这里我们通过两种不同的湿化学方法首次合成了纳米级的LiCoO2:溶胶—凝胶法(方法B)和一种改进了的溶胶—凝胶法(方法C)。为了便于比较,我们也采用了固相反应法(方法A)。用DTA,IR,XRD,TEM等技术对前驱体和LiCoO2纳米颗粒进行了表征.结果表明在600℃煅烧时可以得到晶化程度较好的LiCoO2纳米颗粒,方法A和方法B得到了直径大约为100和40nm的球状颗粒,而方法C主要得到球形颗粒,同时伴有少量小棒形颗粒生成,直径约为50nm。电化学测试表明方法C得到的产物具有最好的性能。  相似文献   

9.
Co-Nd复合氧化物纳米微粒的制备及初步表征   总被引:2,自引:0,他引:2  
利用溶胶-凝胶法制备钴钕的前驱体,利用差热分析(DTA)确定前驱体的分解温度,并在不同温度下对前驱体进行煅烧,得到四种不同的黑色粉体,分别对它们进行红外光谱分析,并用透射电子显微镜对600℃和1000℃产物的形貌、粒径进行表征.结果表明,微粒形状为类球形,平均粒径小于100nm.  相似文献   

10.
以廉价的无机盐为原料,用溶胶-凝胶法结合超临界干燥技术制备超细氧化铝前驱体微粉,用TEM,XRD技术对其进行表征。结果表明,采用该法,可制得白色、分散性好的γ-AIOOH超细微粉。  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
何延凌 《科技信息》2008,(4):258-258
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.  相似文献   

14.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

15.
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。  相似文献   

16.
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.  相似文献   

17.
本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。  相似文献   

18.
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.  相似文献   

19.
20.
The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to  相似文献   

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