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1.
用真空电弧熔炼法制备了Ce2Co17-xMx(M=Ga,Al和Si)化合物。通过X射线衍射和磁性测量手段,研究了非磁性替代原子Ga,Al和Si的加入对Ce2Co17化合物的剧里温度和饱和磁化强度的影响,其中Si在Ce2Co17化合物中的固溶度最小,并使居里温度和饱和磁化强度下降幅度最大。  相似文献   

2.
纳米复合固体超强酸SO42-/CoFe2O4的制备和表征   总被引:26,自引:0,他引:26  
采用纳米化学制备技术合成了新型的纳米复合固体超强酸催化剂SO4^2-/CoFe2O4。用XRD、TEM、XPS、红外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明:所研制的SO4^2-/CoFe2O42催化剂为晶态纳米粒子(〈50nm),比表面积很大(157m^2.g^-1),SO4^2-与氧化物的金属离子呈无机齿螯合状配位化合物的结合形式。以乙酸乙酯合成为模型反应考究了该催化剂的催化活  相似文献   

3.
3d过渡金属掺杂TiO2纳米晶膜电极的光电化学研究   总被引:16,自引:0,他引:16  
应用原子力显微镜和X射线粉末法对3d过渡金属离子Cr(Ⅲ),Fe(Ⅲ),Mn(Ⅱ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)和Zn(Ⅱ)掺杂TiO2纳米晶粒(简写为M^3d-TiO2)作了表征,并用光电化学方法研究了M^3d-TiO2纳米结构多孔膜电极。实验结果表明,M^3d-TiO2纳米粒子的颗粒较均匀,粒径约为15nm,其晶型为锐钛矿和板铁矿的混晶。在所研究的M^3d-TiO2中,只有Zn^2+-T  相似文献   

4.
采用XRD,顺磁共振(ESR),Mossbauer和或温还原(TPR)技术对负截型Cu-Fe-O(Ⅰ),Cu-Fe-Co-O(Ⅱ)催化剂的固相结构及热稳定性进行了研究。结果发现,(Ⅰ)中主要存在Fe2CuO4,CuO和颗粒度小于13nm的Fe2O3相。随着焙烧温度的升高,CuO晶相逐渐消失,Fe2CuO4的晶相长大。(Ⅱ)中Ce的存在,能提高Cu^2+的浓度,抑制CuO和Fe2CuO4晶相的生成,  相似文献   

5.
纳米复合固体超强酸SO42-/CoFe2O4的制备和表征   总被引:27,自引:0,他引:27  
采用纳米化学制备技术合成了新型的纳米复合团体超强酸催化剂SO42-/CoFe2O4。用XRD、TEM、XPS、红 外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明:所研制的SO42-/CoFe2O4催化剂为晶态纳 米粒子(< 50nm),比表面积很大(157m2· g-1),SO42-与氧化物的金属离子呈无机双齿螯合状配位化合物的结 合形式。以乙酸乙酯合成为模型反应考察了该催化剂的催化活性,比较了酸性和酸强度,推断出该催化剂的酸 强度H0<-14.5。  相似文献   

6.
化学自组装法制备钡铁氧体亚微空心球   总被引:8,自引:0,他引:8  
描述了一种基于化学自组装制备钡铁氧体亚微空心球的新颖方法, 即以聚(苯乙烯-共-丙烯酸)乳胶粒子为模板, 利用酸醇相互作用, 将在聚乙二醇水溶液中得到的钡铁氧体前驱物包覆在模板粒子上, 形成聚(苯乙烯-共-丙烯酸)/钡铁氧体前驱物核壳纳米复合粒子. 复合粒子经历750 ℃的热处理, 可获得主晶相为BaFe12O19的钡铁氧体亚微空心球. 该空心球有可能在微波吸收、电磁流变等领域得到重要应用.  相似文献   

7.
六角晶系铁氧体BaZn2Fe16O27的XRD分析及其微波电磁特性   总被引:4,自引:0,他引:4  
在BaO-ZnO-Fe2O3三元系统中,利用固相反应法合成了W型六角晶系铁氧体BaZn2Fe16O27,采用扫描电镜(SEM)和X射线衍射法(XRD)对该化合物进行了形貌观察和物相分析,并报道了其特征X射线衍射数据。对BaZn2Fe16O27的微波电磁参数也进行了测试。  相似文献   

8.
在纳米晶Co—Mo/Ni复合电极上的析氢反应   总被引:3,自引:0,他引:3  
虞慰曾  马洁 《电化学》1996,2(1):47-53
采用复合电镀的方法将不同球磨时间制备的高催化活性的纳米晶Co-Mo合金粉直接镀在电极表面,用稳态极化曲线及交流阻抗技术测试了这些电极析氢的电化学活性,并用X射线衍射,透射电镜及X射线光电子能谱,扫描电镜监测了Co-Mo合金粉的物相结构,晶粒尺寸和复合镀的成份,形貌,实验结果表明,Co-Mo纳米晶合金粉有较高的析氢催化活性,球磨使钴钼粉合金化成为纳米晶,一方面增加了复合镀层的真实表面积,另一方面由于  相似文献   

9.
采用共学沉淀并加法制备了B位掺杂烧绿石型稀土复合氧化物纳米微晶Y2Sn2-xFex7O-δ。制备的纳米微晶属于立方晶系,Fd3m,晶胞参数和掺杂量呈线性关系。通过Mossbauer,TG-DTA,气相色谱和γ射线辐照等技术研究了纳米微晶对CO的催化选择性能。  相似文献   

10.
纳米级钡铁氧体的原子力显微镜分析及微波性能的研究   总被引:2,自引:0,他引:2  
卓长平  张雄 《分析测试学报》2005,24(3):14-17,21
采用溶胶-凝胶法制备掺杂钡离子的纳米六角晶型铁氧体.采用X衍射仪对其物相进行鉴定,利用原子力显微镜对不同方法制得的试样粒径进行了分析研究,最后用网络分析仪对铁氧体在1~6 GHz范围内的微波性能进行分析,结果表明:实验制得粉体为M型钡铁氧体,利用乙醇分散的稀浓度的试样能在原子力显微镜下很好地观察到颗粒的粒径,其平均粒径为52.68 nm左右,并且实验制得的纳米M型钡铁氧体具有较大的介电损耗和磁损耗,具有良好的吸波性能.  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.
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   

14.
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   

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.
N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).  相似文献   

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