钇对IMI829钛合金及Ti—14Al—21Nb合金显微组织和性能的影响

采用光学显微镜、扫描电和力学性能测试设备，研究了在ＩＭＩ８２９和Ｔｉ－１４Ａｌ－２１Ｎｂ合金中添加Ｙ，对合金显微组织遥影响。结果表明，在ＩＭＩ８２９和Ｔｉ－１４Ａｌ－２１Ｎｂ合金中添加Ｙ，可以细化这两种合金的组织和晶粒，使ＩＭＩ８２９－０．２Ｙ合金获得良好的室温力学性能和５５０℃蠕变性能，ｗｇｋｑＴｉ－１４Ａｌ－２１Ｎｂ－０．１Ｙ合金的高温力学性能得到改善。     

影响TiAl合金塑性的电子结构因素

应用ＥＨＴ紧束缚能带计算方法, 系统研究了Ｔｉ－４８Ａｌ－２Ｍ 为模型的γ－ＴｉＡｌ掺杂合金的电子结构。发现能有效地改善合金塑性的元素Ｖ、Ｃｒ、Ｍｎ 主要在两方面改变了γ－ＴｉＡｌ合金的电子结构,即改善Ｔｉ周围成键强度的各向均衡性和改变Ｔｉ、Ａｌ参与成键的电子分布,使成键电子云的球形化成分增大。研究结果表明Ｖ、Ｃｒ、Ｍｎ 等取代Ａｌ时成键的均衡性及电子云球形化均增大,从而有利于材料变形改善塑性,而加入Ｆｅ、Ｃｏ、Ｎｉ虽然改善电子云的球形化但却不利于成键强度的均衡性,因而对合金的塑性无明显改善。     

电感耦合等离子体原子发射光谱法测定Ti3Al基合金中钒、铬、锰、铁、铜、镍和锆的含量

<正>Ti3Al基合金是一种能在600℃~700℃之间使用的轻质结构材料,特别是通过添加铌等元素使合金的室温塑性和韧性有了较大的提高[1-2]。Ti3Al基合金的主要应用方向为低压涡轮导叶内环和高压压气机机匣等,这些合金的板材有可能在高超声速飞行器上使用,并用作碳化硅纤维增强复合材料的基体材料。通过优化合金成分设计、添加各种主量和微量元素合金化并控制合金中的杂质含量,可使Ti3Al基合金的性能大幅提高,适度的β稳定元素     

添加Al、Mg、W、Mo对烧结Nd-Fe-B磁体磁性能与显微组织的影响

研究了在烧结ＮｄＦｅＢ磁体晶间添加Ａｌ、Ｍｇ、Ｗ、Ｍｏ等合金元素对显微组织和磁性能的影响。实验结果表明：低熔点合金元素Ａｌ、Ｍｇ能显著提高ＮｄＦｅＢ磁体的矫顽力，略微降低剩磁，对磁体的热稳定性无影响；高熔点合金元素Ｗ、Ｍｏ在不降低剩磁的情况下亦能提高磁体的矫顽力，但效果不如Ａｌ、Ｍｇ明显。显微组织分析表明，在添加低熔点和高熔点合金元素的磁体晶间发现了两种不同的新相。矫顽力的提高可归于晶间新相的出现。进一步分析表明，与传统的合金化相比，对ＮｄＦｅＢ磁体晶间区域进行微合金化是改进ＮｄＦｅＢ磁体组织与性能的一种更为有效的手段。     

Ti-Al系金属间化合物的价电子结构分析

1　引言ＴｉＡｌ系金属间化合物因具有良好的高温性能与很低的密度在未来航空航天及兵工等方面有着美好的应用前景,但由于极低的室温脆性使其真正投入商用仍很困难.脆性一直是材料科学所关注的问题,这些年来虽在这方面做了大量工作,但大多研究仍停留在实验规律上[1].为深入理解脆性,从物理机理特别是化学键本质上探讨已势在必行.近年来已有人[2]从电子结构或电荷密度分布来解释ＴｉＡｌ的脆性本质,也有人[3]从价电子结构来分析Ｔｉ3Ａｌ的强韧性,但就整个ＴｉＡｌ系金属间化合物的全面分析而言,这些工作还缺乏系统性.固体与分子经验电子理论…     

机械合金化Mg/MmNi5-x(CoAlMn)x复合储氢合金的组织结构与吸氢特性

运用Ｘ射线衍射、扫描电及粒度分析等方法表征了机械合金化制备Ｍｇ／ＭｎＮｉ５－ｘ（ＣｏＡｌＭｎ）ｘ复合储氢合金的结构,通过ＰＣＴ曲线研究了基储氢性能。结果表明,在适当的球磨条件下能够获得纳米晶结构的Ｍｇ／ＭｎＮｉ５－ｘ（ＣｏＡｌＭｎ）ｘ复合储氢合金,ＭｍＮｉ５－ｘ（ＣｏＡｌＭｎ）ｘ合金相彘,复合储氢合金的活化性能及储氢量有明显提高。此外,还考察了Ｍｇ含量对复合储氢合金的组织结构及储氢性能的影响。     

铈在Fe-28Al合金中的作用

以稀土元素Ｃｅ为微合金化元素，研究了Ｃｅ对Ｆｅ３Ａｌ二元合金（Ｆｅ２８Ａｌ）室温力学性能的影响，采用光学显微镜、扫描电镜、透射电镜、Ｘ射线光电子能谱仪、等离子耦合光谱、Ｘ射线衍射仪以及俄歇能谱仪等现代微观分析手段，探讨了Ｃｅ微合金化对Ｆｅ３Ａｌ合金组织结构和力学性能影响的作用机制。研究结果表明，Ｃｅ的加入改善了合金的室温塑性和强度，并在合金中起到了脱硫、脱氧、改变夹杂物形态、细化晶粒以及表面改性等作用。此外还对富Ｃｅ相颗粒在合金中的形态分布作了分析。     

电感耦合等离子体原子发射光谱法测定哈氏合金中Cr、Fe、Mn、Mo、Ni的含量北大核心CSCD

哈氏合金（Hastelloy alloy）由Ni、Cr、Mo、Fe等元素组成,属于高等镍基合金,镍为面心立方结构,晶体学上的稳定性使得它能够比铁基合金容纳更多的合金元素[1]。哈氏合金作为高级镍基合金,在湿氧、亚硫酸、强氧化盐介质中都有优异的抗腐蚀性能[1],同时具有优良的强度、塑性、韧性、冶金稳定性、可加工性及可焊接性,已广泛应用于航空航天、核电及船舶等领域[2]。     

电化学法评估Ti-6Al-4V合金表面氧化膜之特性

Ｔｉ－６Ａｌ－４Ｖ合金因具有低密度,高强度,成为航太及生医方面重要使用的材料。此合金因表面层形成氧化膜的特性,更可广泛地应用于要求较高材料性能的环境上。近年来,更由于Ｔｉ－６Ａｌ－４Ｖ合金接近于人体骨骼的轻质结构,大量使用于骨料手术植入物。本研究即针对此种钛合金表面在盐酸及硫酸中的腐蚀及耐蚀行为进行评估。实验中,配合直流定电压及极化曲线扫描,观察出随时间而电流值增加之变化情况。此外,进行交流阻抗测     

铈对Zn-22%Al减振合金组织和力学性能的影响

借助于光学显微镜、透射电镜及扫描电镜,采用自然时效、人工时效等热处理工艺,研究了微量Ｃｅ对Ｚｎ－２２％Ａｌ减振合金显微组织和力学性能的影响,Ｃｅ具有细化Ｚｎ－２２％Ａｌ合金组织并障碍时效时晶粒长大和等轴程度降低的作用,在低于８０℃的温轧温度下效时,加Ｃｅ和不加Ｃｅ的Ｚｎ－２２％Ａｌ合金的强度不随时间的推移而变化。Ｃｅ还提高了Ｚｎ－２２％Ａｌ合金的强度和时效时力学性能的稳定性。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

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.     

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%).