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1.
快速凝固TiAl基合金稀土相显微组织的研究   总被引:1,自引:1,他引:0  
利用两种不同的快速凝固方法对TiAl-RE合金中稀土相的显微组织进行了研究并与铸态组织进行对比,选择的快速凝固方法为溶体旋转法(MS)和锤钻法(HA),试验结果表明,随着材料冷却速度的变化稀土相的显微组织发生了很大的变化,由铸态完全分布于晶粒边界之上过渡到锤砧法极细的层片和弥散分布的颗粒组织,选区电子衍射结果表明,稀土相的衍射斑点与AlCe金属间化合物一致。  相似文献   

2.
失活加氢精制催化剂中硫铁相的高分辨透射电镜研究   总被引:1,自引:1,他引:0  
利用高分辨透射电镜(HRTEM)结合X射线能谱仪(EDS)和选区电子衍射(SAED)分析,对运转后的加氢精制催化剂中含有的微量未知相的化学组成、晶体结构进行了研究.通过X射线能谱仪确定该未知相主要成分为硫和铁.根据选区电子衍射结果,该硫铁相为单晶结构.采用样品倾转的方法,获得3幅不同取向的选区电子衍射图,根据衍射谱中衍射斑点对应的晶体学信息及3幅电子衍射图取向间的夹角关系,确定该硫铁化合物属于正交晶系的硫化亚铁,分子式为Fe0.91S.该催化剂应用于高温高压下的加氢环境中,其中原料油中的酸性物质,尤其是环烷酸对加氢设备材质的腐蚀是导致硫铁化合物相形成的主要原因,并由此探讨了硫铁化合物相的形成机制.  相似文献   

3.
用透射电镜对在氩气中电离溅射沉积于碳膜上的Ag超微粒进行了直接研究。通过明场象和电子衍射观察分析发现,在溅射入射角为60°时,经不同的出射角收集,形成的超微粒的粒径、粒径分布、形态和物相结构各有不同。  相似文献   

4.
基于前文错流移动床反应器模型方程,模拟计算并分析了该类反应器中气、固相流动对热煤气脱硫等非催化气固反应过程的影响。研究表明,床层在床深方向按反应速率的快慢可分为粗脱区和精脱区,在颗粒流动方向上气相浓度差异较大,并主要体现在粗脱区内,床层出口处颗粒转化率呈现较大分布,反应器内气固交错流动、气相浓度和颗粒转化率共同作用( 于气固反应速率) 等因素是造成过程特征的主要因素。因此反应器优化应满足对两相流动的优化,将粗脱区设置成错流移动床而精脱区设置成固定床,并使粗脱区内颗粒流速沿气流方向逐渐减小,以减小出口颗粒转化率的分布并提高颗粒利用率,同时沿颗粒流动方向应逐渐减小过床气流体积分率以利于床内气固反应速率的均一分布。由此指出对该类床型其底部渐缩下料段和过床气流对床内颗粒流动的影响以及床层结构及颗粒流动对过床气流分布的影响研究的必要性。  相似文献   

5.
建立了两段式气流床煤气化炉内气固两相流动的三维计算流体力学(CFD)模型,将气体视为连续介质,在Euler坐标系下考察气相的运动;将颗粒视为离散体系,在Lagrange坐标系下研究颗粒的运动。利用所建CFD模型对基本设计尺寸和操作条件下的两段式气流床煤气化炉内气固两相流动进行了模拟,给出了两段式气流床煤气化炉内的气固两相流动的规律和颗粒的分布规律。在此基础上,针对不同的结构(喉口直径变化)和不同的操作条件(两段气固进料量变化)进行了一系列的模拟比较。结果表明,喉口直径的变化对于炉内气固两相流动及颗粒分布有重要影响。随着喉口直径减小,喉口附近区域的气相回流增强,颗粒运动轨线变得更加曲折,颗粒分布发生明显变化。两段气固流量的改变可以明显改变炉内气固流动,随着一段反应区的气固流量增加和二段反应区气固流量减小,一段反应区内的气相回流更加显著, 二段反应区气相回流减弱,颗粒螺旋上升运动增强,反应器边壁处颗粒浓度增大,颗粒沉积现象减弱。  相似文献   

6.
本文用电子衍射径向分布函数测定了稀土顺1,4聚丁二烯的原子间距分布。从电子衍射实验强度曲线的傅里叶变换得到的RDF曲线上,具有二个分子内峰和三个分子间峰。说明在熔点以上,处于非晶态的顺1,4聚丁二烯中不同程度的存在分子链间的局部有序性。  相似文献   

7.
张业  孙予罕  钟炳 《燃料化学学报》2001,29(Z1):154-156
采用类凝胶-超临界流体干燥法制备了超细Mo-Co-K催化剂,并运用TEM和选区电子衍射技术对制得的催化剂进行了表征.结果表明,制得的催化剂由属于超细粒子范畴的片状微晶和球状小颗粒组成,进一步经选区电子衍射技术分析,前者归属为MoO3物相,后者归属为CoMoO4物相.  相似文献   

8.
Ti+(100keV,3×1017cm-2)注入H13钢,表面注入层的化学组成和微观结构发生了很大的变化,俄歇分析表明,注入元素Ti在钢表面层的剖面含量分布呈近似高斯分布,在40nm处原子数分数达到其峰值(25%),离子束真空碳化导致在钢的表面形成一层约20nm的“渗碳层”。透射电镜分析表明,表面层的微观形貌由注入前的板条状马氏体结构转变成注入后的微胞状结构,电子衍射则进一步证实,表面层已出现非晶化,并且有TiC析出  相似文献   

9.
电子辐照对聚反式1,4-丁二烯晶型转变的影响   总被引:3,自引:0,他引:3  
由于晶体结构对高分子性能有较大影响,因此研究其晶体结构具有重要意义.目前,已发现聚反式1,4-丁二烯(PTBD)存在两种晶型结构[1],分别为单斜相和六方相,在低温下主要为单斜相,高温下主要为六方相.在一定温度下,单斜相和六方相可发生可逆的相转变[2].本文以透射电镜为主要手段,在电子射线辐照下,研究单斜相向六方相的转变过程,不仅摄得样品的单斜相和六方相电子衍射谱,而且还拍摄到两相共存的电子衍射谱.1 PTBD的晶型转变Fig.1 DSCthermalgramofPTBDScanrate:10℃…  相似文献   

10.
使用X射线粉末衍射(XRD)表征了电弧炉熔炼的Gd5Si2Ge2.2合金的相组成,结果表明Gd5Si2Ge2.2合金主要由Gd5Si2Ge2相和GdGe相构成。扫描电镜(SEM)分析表明,Gd5Si2Ge2晶粒内部有大量规则分布的线状特征;透射电镜(TEM)研究发现了Gd5Si2Ge2相的基体上存在两种不同形态的线条组织,选区电子衍射证明两种不同形态的线条组织既非第二相也非孪晶;根据高温原位金相观察的结果推测,该线状组织是在液-固相变过程中形成的。  相似文献   

11.
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.  相似文献   

12.
KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.  相似文献   

13.
Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.  相似文献   

14.
The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.  相似文献   

15.
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.  相似文献   

16.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion.  相似文献   

17.
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.  相似文献   

18.
An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.  相似文献   

19.
20.
A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.  相似文献   

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