铈对M2高速钢凝固组织的作用

研究了Ｃｅ对Ｍ２高速钢凝固组织的影响及其作用机制。发现Ｃｅ在高速钢中可减轻Ｗ,Ｍｏ等合金元素的偏析,使共晶碳化物量减少并细化;Ｃｅ主要偏聚在晶界共晶碳化物与奥氏体的界面上,并有部分Ｃｅ参与形成含Ｃｅ的Ｍ２Ｃ碳化物;Ｃｅ促进共晶碳化物在高温加热时的断网和团球化。     

稀土元素在高速钢晶界偏聚的研究

材料的晶界状态对材料的性能有很大的影响,元素在晶界偏聚对材料性质的影响是冶金和材料科学的重要课题。合金元素和杂质元素在晶界偏聚,使晶界的化学成分发生变化,影响晶界移动、晶粒长大、元素沿晶界扩散、沿晶界的破断等现象,从而影响材料的机械性质、化学性质以及电学性质等。溶解在铁中的铈因原子半径远大于铁而产生较大的点阵畸变能,这将促使它们偏聚在晶界上。我们曾指出,铈和镧能够使硫的偏聚减     

镧对Al—Si合金锶和钠变质的影响

在含有变元素锶或钠的铸造Ａｌ－Ｓｉ－Ｃｕ－Ｍｇ合金中添加微量镧，发现合金组织中同时存在在富镧和锶的化合物，而镧和钠不存在这种作用，在富镧的化合物中没有钠的富集，因此镧对锶和钠变质存在不同程度的影响。     

镧对Al－Si合金锶和钠变质的影响

在含有变质元素锡或钠的铸造Ａｌ－Ｓｉ－Ｃｕ－Ｍｇ合金中添加微量镧，发现合金组织中同时存在富镧和银的化合物，而镧和钠不存在这种作用，在富镧的化合物中没有钠的富集，因此镧对锶和钠变质存在不同程度的影响。     

Studies of surface alloy as high efficient electrocatalyst for glyoxylic acid synthesis

运用电化学方法，研制了三种表面合金（ＰｂＳｂＰｔ／ＧＣ，ＳｂＰｔ／ＧＣ，ＰｂＰｔ／ＧＣ）电催化剂，发现在草酸还原生成乙醛酸的电有机合成中这些表面合金电催化剂有较高的活性，其起始还原电位分别比在Ｐｂ阴极上（１．１Ｖ）提前了０．４８～０．７０Ｖ。这三种表面合金电催化剂的活性次序为：ＰｂＳｂＰｔ／ＧＣ＞ＳｂＰｔ／ＧＣ＞ＰｂＰｔ／ＧＣ。红外光谱结果表明，在这些表面合金电极上草酸还原产物主要为乙醛酸。     

铝锂合金中铈与杂质含量对延伸率及再结晶的作用

研究了铈及有害杂质含量对２０９０及８０９０铝锂合金薄板延伸率和再结晶状态的影响，得出了再结晶组织参数与板材横向延伸率之间的关系。Ｃｅ的微合金化作用在含一定量Ｆｅ、Ｓｉ杂质的２０９０合金和含一定量Ｎａ、Ｋ杂质的８０９０合金中表现得比较明显，当各种杂质共存且含量较高时，Ｃｅ对８０９０合金的延伸率仍有一定的有利作用。随Ｃｅ及杂质含量变化，若两类合金的再结晶体积、粗晶体积及晶粒平均宽度增加，则其延伸率下降，随晶粒长宽比增加，２０９０合金的延伸率增加而８０９０合金的延伸率下降。     

镧在钴基超合金GH188中的作用及分配

本文研究了镧在钴基超合金GH188中的作用及其分配。镧在基体及M_6C相中的分配大约为9:1,大部分镧偏聚在晶界处。在该合金中镧化物主要是La_2O_3和La_2O_2S;用X射线和扫描电镜发现.该合金在空气中于900～1200℃经0～100h的氧化特性遵循一般的抛物线氧化规律,添加镧可提高氧化激活能值,其氧化皮主要由(Co、Ni)Cr_2O_4和一定量的Cr_2O_3及βCo组成,而铬离子在Cr_2O_3中的扩散是控制氧化速率的因素。镧能显著改善该合金氧化皮的致密性、连续性、稳定性和粘附力,并能提高其持久强度和持久塑性。     

稀土对莱氏体钢共晶碳化物粒化的影响

研究了稀土对莱氏体钢中共晶碳化物热处理粒化的影响，探讨了稀土元素的作用机制。结果表明：稀土细化了莱氏钢中奥氏体晶粒和共晶碳化物，使离异共晶数量增多，减少了Ｃｒ、Ｍｏ合金元素偏析，并使Ｍ７Ｃ３（Ｍ＝Ｆｅ、Ｃｒ）碳化物中孪晶等晶格缺陷增多，从而降低碳化物的稳定性，促进了共晶碳化物的粒化动力学过程，得到良好的粒化效果。     

WC-8Co硬质合金中稀土添加剂的作用

以混合稀土氧化物为添加剂，在真空炉中于０２Ｐａ、１３７０℃下经液相烧结３０ｍｉｎ制备加稀土的ＷＣ８ＣｏＲ硬质合金试样。Ｘ射线衍射、扫描电镜和磁性测定的结果表明，稀土提高ＷＣ８Ｃｏ硬质合金的表面宏观压应力是强化合金的重要因素，其阻止粘结相（γ相）的ｆｃｃ→ｈｃｐ转变对合金强韧性的作用甚微。稀土对ＷＣＣｏ硬质合金显微结构参数无明显影响，也无Ｗ溶质对γ相的附加固溶强化效果     

熔融织构生长强磁浮YBCO超导块材的取向和结构

采用熔融织构生长法结合顶部Ｓｍ１２３籽晶技术，成功地制备了直径为２０ｍｍ的ＹＢＣＯ超导块材。该块材具有极强的磁性能。用Ｘ射线θ／２θ扫描和Φ扫描分析其结构表明，样品在三维方向上具有很强的择优取向，其ｃ、ａ、ｂ轴方向分别与Ｓｍ１２３籽晶的ｃ、ａ、ｂ轴方向一致，并具有类似单晶的结构特点。     

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.     

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.     

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.     

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%).     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

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.