金属氧化物掺杂改善LiFePO4电化学性能

采用氧化物前驱体对磷酸铁锂(LiFePO₄)进行少量金属离子掺杂，并用XRD，SEM和恒电流充放电对掺杂的LiFePO₄进行了研究。结果表明，少量的掺杂离子在很大程度上提高了LiFePO₄的电化学性能，特别是大电流放电性能。1.0 mol%的Nb⁵⁺掺杂LiFePO₄的0.1 C放电容量约150 mAh·g^-1；即使在3 C倍率下放电，也有117 mAh·g^-1的容量。掺杂的效果与掺杂离子的半径、价态密切相关，半径小、价态高的离子对提高LiFePO₄的电化学性能有利。在掺杂量较小时(<2.0 mol%)，掺杂效果与掺杂离子的浓度关系不大。     

掺杂F-,Sr2+的氧化铈紫外屏蔽和氧化催化性研究

采用沉淀法合成F-,Sr2+单掺杂和共掺杂的氧化铈,探讨了不同掺杂离子对氧化铈紫外屏蔽性能和氧化催化性能的影响.XRD结果表明,F-,Sr2+单掺杂或共掺杂的CeO2均为立方萤石结构,但衍射峰因掺杂离子的不同而稍有偏移.UV-Vis光谱表明,F-,Sr2+单掺杂和共掺杂的氧化铈的紫外屏蔽性能均优于纯氧化铈.共掺杂氟锶后的氧化铈的氧化催化性明显比纯氧化铈的弱,但是,单掺杂氟离子或锶离子的氧化铈的氧化催化性比纯氧化铈的强.     

La或N掺杂SiC纳米线的制备、场发射性能及第一性原理计算

采用化学气相沉积法和气相掺杂法, 分别制备了La 或N掺杂的SiC 纳米线. 利用场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)、高分辨透射电子显微镜(HRTEM)、X射线能量色散谱(EDS)分析和X射线衍射(XRD)等测试手段对两种产物的微观形貌、元素组成和物相结构进行了系统表征. 以合成产物作为阴极, 对其场发射性能进行测试, 结果表明: SiC 纳米线的开启电场值和阈值电场值由未掺杂的2.3、6.6 V·μm^-1分别降低为1.2、5.2 V·μm^-1(La 掺杂)和0.9、0.4 V·μm^-1(N 掺杂). 采用Material Studio 软件中的Castep 模块建立(3×3×2)晶格结构模型, 对未掺杂、La 或N掺杂SiC 的能带结构和态密度进行计算, 结果显示: La或N掺杂后, 在费米能级附近产生了新的La 5d或N 2p掺杂能级, 导致禁带宽度(带隙)变窄, 使得价带电子更容易跨越禁带进入导带, 从而改善SiC纳米线的场发射性能.     

掺杂态聚苯胺的性能及其防腐应用研究进展

聚苯胺具有良好的导电性和独特的掺杂-解掺杂特性,成为近年来备受关注的导电高分子材料,其特有的抗划伤、抗点蚀和钝化性能使其在金属防腐领域拥有巨大的应用前景。聚苯胺结构中苯环的存在,使得其分子链具有较大刚性,而分子间氢键又导致其难溶、难熔、可加工性能较差,严重制约了聚苯胺的应用。掺杂过程能有效改善聚苯胺的某些性能,或赋予其新的功能,扩展聚苯胺的应用。本文综述了聚苯胺的掺杂方式、掺杂机理、聚苯胺防腐材料的制备方法,以及其在金属防腐领域的应用,展望了聚苯胺的研究和应用前景。     

li+掺杂对casio3∶pb2+,mn2+晶体结构及荧光性能的影响

li+掺杂;偏硅酸盐;晶体结构;荧光性能     

陶瓷基钛掺杂硅胶块体吸附剂研究

以陶瓷纤维纸为基材, 顺次经水玻璃、酸性硫酸氧钛溶液浸渍共沉淀制得新型蜂窝状陶瓷基钛掺杂硅胶块体吸附剂. FTIR谱在波数954 cm^－1附近的特征吸收峰表明钛掺杂硅胶中存在Si-O-Ti键; XRD谱显示掺杂材料为无定型非晶相材料; SEM显示钛掺杂硅胶粒子较好地分散在陶瓷纤维表面及其空隙中; 用EDS及XPS揭示了材料的组成和钛原子含量, 根据钛掺杂前后XPS中Si2p, O1s, Ti2p 3/2电子结合能变化以及²⁹Si MAS NMR中硅原子化学位移差异, 进一步表明钛原子替代硅原子进入了四面体骨架; BET分析显示掺杂材料以中孔为主. 与硅胶相比, 由于钛掺杂, 其比表面积、孔容增大, 吸附性能、耐热性能增强.     

铝钴复合掺杂的氢氧化镍的制备及其电性能

低热固相反应;氢氧化镍;电化学性能;复合掺杂     

MoO3氧化物掺杂改善LiFePO4 / 乙炔黑电化学性能研究

采用MoO₃氧化物前驱物对磷酸铁锂(LiFePO₄)进行少量的掺杂，并用XRD、SEM、CV及恒流充放电测试对产物进行了研究。研究表明，少量的掺杂并未影响到LiFePO₄的晶体结构，但却能够在一定程度上改善LiFePO₄的电化学性能。其中650 ℃焙烧的1% Mo掺杂的LiFePO₄材料性能较好，该材料在以0.2 C的倍率充放电时，充放电曲线具有平稳的电压平台和较大的充放电容量，首次放电容量能达到     

Fe3+-H掺杂TiO2光催化剂的制备、表征与催化性能

Fe3+-H掺杂TiO2光催化剂的制备、表征与催化性能;二氧化钛;掺杂;光催化;铁离子;等离子体     

氯钯共掺对Cs2TiBr6光电性能影响的第一性原理计算

全无机无铅钙钛矿Cs₂TiBr₆具有光电特性良好、带隙可调和环境友好等优点,是一种潜力巨大的光吸收材料。为改善Cs₂TiBr₆的相关性能,我们采用基于第一性原理的方法,针对Pd、Cl掺杂的Cs₂TiBr₆钙钛矿结构进行了研究。结果表明,用Pd取代Ti后产生杂质带,将原来间接带隙的Cs₂TiBr₆转变为直接带隙材料。用25.0% Pd掺杂后,晶体带隙值降低26%,掺杂后的晶体在320~415 nm近紫外光区吸收能力加强约50%,在645~900 nm的红外光区及近红外光区的光吸收能力加强约134%。在此基础上,将Cl与25.0% Pd共掺杂时,Cl掺杂不仅可以把Pd的形成能在单掺的基础上减小约9%,而且Cl的不同掺杂位置对材料的光电性能也有一定的影响。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

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.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

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.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.