首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 973 毫秒
1.
应用硝酸钇水溶液和冰乙酸为水解剂,通过丙醇锆控制水解的溶胶凝胶法制备稳定的溶胶先驱物.研究表明:氧化物、水及酸的含量是影响氧化锆溶胶稳定性和胶凝时间的主要因素,而在溶胶中加进高聚物能够延长胶凝时间和调节溶胶粘度.氧化钇稳定的氧化锆膜是通过将多孔αAl2O3衬底插入溶胶中,然后干燥和灼烧而制得.实验发现,为避免操作过程中出现裂纹和针孔要注意下述几点:(1)需要合适的溶胶浓度和粘度;(2)支撑体应有平滑的表面和窄的孔尺寸分布,并用高聚物溶液涂敷表面进行预处理;(3)在相对湿度3376%的气氛下干燥;(4)加热速率要低,特别在灼烧的早期阶段.  相似文献   

2.
萘和丙烯的异丙基化反应是连串反应,生成不同烷基化程度的异构体。其中,2,6-二异丙基萘(2,6.diisopropylnaphthalene,简称2,6-DIPN)是制备高分子单体2,6.萘二甲酸的前体。采用水汽脱铅丝光沸石(SDHM)进行萘的择形异丙基化反应合成2,6-DIPN,效果优于用盐酸脱铝得到的丝光沸石。综合考察了影响SDHM催化性能的主要因素,优化后的处理条件为:水汽脱铝温度450℃,通水汽时间1.5h,灼烧温度450℃及灼烧时间6h。同时考察了丝光沸石中Na2O含量对SDHM催化性能的影响,发现较低的Na2O含量有利于提高沸石的活性、选择性和进一步脱铝。  相似文献   

3.
首次用草酸共沉淀法和柠檬酸络合法分别制得了两种甲烷氧化偶联反应催化剂镧锰酸盐前驱体LaMn(C2O4)2.58H2O和LaMn(Cit)23HNO36H2O。通过元素分析、红外光谱、热重-差热等手段对这两个前驱体进行了表征,并对在1270°C灼烧后的两种样品进行了X-射线衍射分析、比表面测定和催化性能测试。  相似文献   

4.
本实验,首先根据铈易被氧化成四价铈的性质,使Ce(OH)3lfnywx o C(OH)4.须稀酸(PH≈2.5)中,Ce(OH)4不溶解,而E(OH)3能溶解,使铈与其他轻稀土元素得到初级分离,再根据四价铈容易被磷酸三丁酯(TBP)萃取的性质,使铈得到进一步纯化,后经草酸沉淀、过滤、灼烧得到纯的二氧化铈。  相似文献   

5.
杨木制取高质量颗粒活性炭的研究   总被引:2,自引:1,他引:2  
研究利用杨木和杨树枝丫材,制取高质量颗粒活性炭的工艺,先把杨树枝杈烧成木炭,再把木炭粉碎,添加复合粘结剂,混合成型,炭化和多步活化,制得高品位颗粒活性炭,其关键技术是使用了复合粘结剂和独特的加工方法,按本方法制得的杨木颗粒活性炭碘吸附值1354mg/g,亚甲基兰吸附值16mL/0.1g(240mg/g),苯吸附率34.8%,强度(硬度)95%,灼烧残渣(灰分)0.83%。这些指标达到或超过不定型椰  相似文献   

6.
固相法制备氧化铁纳米粒子   总被引:8,自引:0,他引:8  
采用固相法制备了氧化铁的纳米粒子,并对其进行了XRD谱图表征,发现产物氧化铁的晶型与灼烧温度及灼烧时间有关,随着灼烧温度的升高和灼烧时间的延长,氧化铁的晶型从γ型向α型转变。同时讨论了温度、时间等条件对产品粒径、产率等因素的影响。  相似文献   

7.
火焰原子吸收光谱法测定人参和西洋参中微量元素   总被引:9,自引:2,他引:9  
采用干法灰化法处理样品,用HNO3溶解灼烧后的残渣,用火焰原子吸收光谱法测定溶液中Zn、Cu、Fe、Mn、Co、Ni、Ca、Mg、Cd、Pb等10种微量元素的含量.方法简便、快速,并获得满意结果.  相似文献   

8.
采用均匀沉淀和直接沉淀2种方法合成了纳米TiO2,对所得产物进行了透射电镜和粒度分布的测试.结果表明:均匀沉淀法制备的纳米TiO2粒度分布均匀,团聚少,并且粒径较小,大约在20nm左右,基本呈球形;直接沉淀法制备的纳米TiO2粒度分布不够均匀,团聚现象比较严重,有较大颗粒存在,粒径在40nm左右,近似呈球形.对均匀沉淀法制得的TiO2前驱物采用不同的灼烧温度和灼烧时间,得到了不同晶型和粒径的TiO2粉体.对相同灼烧温度、不同灼烧时间的TiO2进行了XRD测试.并从均匀沉淀法制备的不同粒径的金红石型纳米TiO2中选取3种不同粒径的样品,进行了表面光电压测试和分析.  相似文献   

9.
采用重量分析法测定盐酸乙脒中难挥发杂质的含量。将2.0g盐酸乙脒样品放入恒重瓷坩埚内,将其在电炉上炭化1.0h后转入马弗炉,700℃高温下灼烧1.5h。结果表明,盐酸乙脒平均灰分为0.6%,当盐酸乙脒中含有氯化钠时,灰分升高,且氯化钠添加量与灰分呈高度正相关关系(相关系数r^2=0.998)。  相似文献   

10.
本文采用FTIR技术测定了共聚物的组成,用Fineman—Ross法、最小二乘曲线拟合法(NLS法)、置信区间法计算了甲基丙烯酸三甲基锡酯(TMTM)、三乙基锡酯(TETM),三丁基锡酯(TBTM)和三苯基锡酯(TPTM)与甲基丙烯酸甲酯(MMA)的竟聚率,NLS法的数值分别为:r1=1.07,r2=0.63(TMTM/MMA);0.87,0.62(TETM/MMA);0.62,0.58(TBTM/MMA);0.68,0.60(TPTM/MMA),并计算了各单体的Q和e值,讨论了不同取代基结构对其共聚合相对活性的影响.  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.
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   

13.
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   

14.
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   

15.
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-  相似文献   

16.
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-  相似文献   

17.
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  相似文献   

18.
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  相似文献   

19.
<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  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号