快速凝固AlNiCuNd纳米/非晶复合材料的制备及显微组织研究

采用熔体单辊旋淬法制备了快凝Al87Ni7Cu3Nd3合金条带,利用差热扫描热力学(DSC)分析、X射线衍射(XRD)分析等手段对比研究了快凝合金条带及其不同退火态材料的晶化行为.选择合适工艺条件,对快凝合金条带进行等温加热退火,采用高分辨透射电镜(HRTEM)观察分析了等温退火态材料显微组织特征.结果表明,快凝Al87Ni7Cu3Nd3合金薄带呈现出完全均匀的非晶态结构.随加热温度升高,非晶态薄带的晶化过程包括两个主要的相转变: α-Al晶体从非晶基体中析出的初始晶化以及有Al3Ni,Al11Nd3和Al8Cu3Nd形成的第二次晶化过程.在低于310 ℃下加热,快速凝固Al87Ni7Cu3Nd3金属玻璃中发生的主要相转变是富Al非晶的初始晶化.110 ℃等温退火态薄带主要是由α-Al加残余非晶相的两相组成,α-Al晶体纳米颗粒均匀弥散分布在残余非晶基体上.而在310 ℃热暴露后的退火试样中,在除α-Al晶体外的残留非晶相中开始出现极少量的Al3Ni金属间化合物.     

Nd60Fe20Al8Co10B2大块非晶合金晶化过程中的结构及磁性能变化

利用吸铸的方法制备了Nd60Fe20Al8Co10B2大块非晶合金。采用示差扫描量热法(DSC)，X射线衍射(XRD)，扫描电子显微镜(SEM)和振动样品磁强计(VSM)研究了Nd60Fe20Al8Co10B2大块非晶合金在晶化过程中的微观结构及磁性能的变化情况。Nd60Fe20Al8Co10B2大块非晶合金在低于723K退火时，富Nd相和富Fe相的析出对于合金的矫顽力影响不大。但是，富Fe相的长大使合金的饱和磁化强度和剩磁下降明显。合金完全晶化后，硬磁性迅速消失。     

Nd60Fe20Al10Co10非晶粉末晶化过程及动力学研究

利用机械合金化制备出Nd60Fe20Al10Co10非晶粉末,采用示差扫描量热仪(DSC),X射线衍射(XRD)和振动样品磁强计(VSM)考察了Nd60Fe20Al10Co10非晶的晶化转变过程及其对磁性能的影响规律,用Kissinger方程计算了Nd60Fe20Al10Co10的晶化激活能,从晶化动力学的角度讨论了玻璃形成能力与晶化反应速率常数的关系。结果表明,Nd60Fe20Al10Co10合金的晶化过程为:非晶+α Fe→非晶+α Fe+Nd→非晶+α Fe+Nd+未知相Mx→α Fe+Nd+未知相Mx+Co2Nd+AlCo。晶化激活能E约为173kJ·mol-1。非晶相的的弛豫无序结构是Nd60Fe20Al10Co10具有硬磁性的原因。完全晶化后硬磁性迅速消失。     

Er对Al-Ni-Er-Zr非晶合金动力学特性的影响

采用单辊旋淬法首次制备了Al85Ni10ErxZr5-x(x=3,4,5)非晶合金,利用X射线衍射(XRD)证明Al85Ni10ErxZr5-x(x=4,5)结构为完全非晶态,Al85Ni10Er3Zr2合金为部分非晶。应用差示热分析法(DTA)测定该合金的热学参量,分析了其晶化过程。利用Kissinger法计算了非晶合金的晶化激活能。研究了Er的增加对于Al-Ni-Er-Zr系合金非晶形成能力和热稳定性的影响。结果表明:Er的增加提高了该合金体系非晶形成能力和热稳定性。     

Al89Gd7Ni3Fe非晶粉加压成块合金的组织结构与力学性能

研究了Al89Gd7Ni3Fe非晶粉末经不同温度热挤压成块后的组织形貌和相结构，分析了非晶的晶化过程，并考察了该合金的弯曲强度和疲劳性能。结果表明，不同温度热挤压成块合金组织均由面心立方的α-Al、二元金属间化合物Al3Gd和少量三元金属间化合物τ1相组成，α-Al晶粒细小，Al3Gd相呈等轴颗粒状，τ1相呈杆状分布，提高热挤压温度，有利于Al3Gd相的析出，不利于τ1相的形成。与普通沉淀硬化型Al合金相比，热挤压成块Al89Gd7Ni3Fe合金具有极高的强度和优良的抗疲劳性能，不同温度热挤压成块Al89Gd7Ni3Fe合金的弯曲强度均超过1000MPa，提高热挤压温度，合金的强度和疲劳性能也因金属间化合物Al3Gd相含量增加而改善。     

硼对硬磁性Nd60Fe20Al10Co10大块非晶合金的磁性与晶化行为的影响

利用示差扫描量热法，X射线衍射法和振动样品磁强计研究了少量B元素对Nd60Fe20All0Col0大块非晶合金的磁性和晶化行为的影响。研究表明，用B元素部分取代Nd元素后，其内禀矫顽力有所增大，饱和磁化强度降低。晶化后，Nd60Fe20All0Col0大块非晶合金退火折出的晶体相对硬磁性能无明显影响，而Nd58Fe20All0Col0B2合金退火析出非铁磁性的Nd1.lFe4B4相，使内禀矫顽力、饱和磁化强度、居里温度降低。     

添加镝的Nd-Fe-B纳米晶单相合金的微结构与磁性能研究

采用单辊快淬法制备了Nd12.3-xDyxFe79.7Zr0.8Nb0.8Cu0.4B6.0(x=0,0.5,1.5,2.5)合金纳米晶单相永磁薄带,研究了合金薄带晶化处理后,成分、组织结构与磁性能之间的关系.X射线衍射分析(XRD)表明,淬态合金主要由非晶相和Nd2Fe14B相组成,完全晶化后由Nd2Fe14B相和少量α-Fe组成.高分辨透射电镜(HRTEM)分析表明,经充分退火后,Nd2Fe14B晶体完整,晶粒间几乎没有边界相.随着Dy含量增加,晶粒尺寸细化,矫顽力大幅提高.x=0.5合金综合磁性能最佳,经过700℃晶化处理10min后,其磁性能为Jr=1.09 T,Hci=1048kA·m-1,(BH)max=169.5 kJ·m-3.     

Mg-Cu-Nd贮氢合金的微观组织结构及贮氢性能研究

采用熔体快淬法制备了(Mg72.2Cu27.8)90Nd10的非晶贮氢合金带,用DSC差热分析仪测定了非晶合金带的热稳定性和非晶形成能力,采用透射电镜TEM和X射线衍射仪表征了不同结晶程度的贮氢合金带的微观组织结构.结果表明:非晶(Mg72.2Cu27.8)90Nd10贮氢合金的晶化过程分为3个步骤:首先在170℃生成平均晶粒尺寸为5～10nm Mg2Cu相;当回火处理温度升高至210℃时,非晶(Mg72.2Cu27.8)90Nd10贮氢合金发生了第二步晶化反应,生成了α-Mg相;当回火处理温度升高到335℃以后,非晶贮氢合金已经完全晶化,生成了稳定的Mg2Cu,α-Mg和Cu5Nd相,晶化后的颗粒尺寸有50～80nm.对不同组织结构的(Mg72.2Cu27.8)90Nd10合金的贮氢性能测试表明:完全非晶状态的(Mg72.2Cu27.8)90Nd10合金具有最快的吸氢速率和最高的贮氢量(3.2%(质量分数)).     

Nd10.1Fe(83.7-x-y)CoxZryB6.2永磁材料结构和磁性能的研究

采用熔体快淬及晶化热处理工艺制备Nd10.1Fe(83.7-x-y)CoxZryB6.2纳米晶永磁材料. 在快淬速度为18 m·s-1时, 经710 ℃/4 min晶化处理后, Nd10.1Fe76Co5Zr2.7B6.2粘结磁体出现最佳磁性能, 分别为Br=0.67 T, JHc=754 kA·m-1, (BH)max=75.1 kJ·m-3. 粘结磁体的磁性能对于快淬速度非常敏感. 随着合金元素的添加, 出现最佳磁性能的快淬速度逐渐减少. 为了得到最佳磁性能, 除了选择合适的快淬速度外, 添加合适的合金元素变得非常重要.添加Zr元素抑制了亚稳相的析出以及细化了晶粒尺寸.比较不加Zr元素的Nd10.1Fe78.7Co5B6.2, 添加Zr元素晶化温度增加了9 ℃, 表明Zr元素也增加了快淬薄带的热稳定性.     

镁基非晶电极合金充放氢过程中的组织结构演变及其热力学计算

采用熔体快淬法制备了(Mg70.6Ni29.4)90Nd10的非晶贮氢合金带,用X射线衍射仪和高分辨电镜对该合金在充放电循环过程中的组织结构演变进行了动态跟踪。结果表明:非晶(Mg70.6Ni29.4)90Nd10贮氢合金在充放电循环过程中经过4个循环以后开始晶化,首先生成平均颗粒尺寸为5 nm左右的NdMg2Ni9相,经过6个循环以后开始出现Mg2Ni相,到第20个循环后,生成了稳定的Mg2Ni,α-Mg和Nd2H5相。这表明初生相NdMg2Ni9在充放电循环过程中逐渐转化为Mg2Ni,α-Mg和Nd2H5相。经过热力学计算进一步验证表明,非晶(Mg70.6Ni29.4)90Nd10合金在晶化过程中首先形成NdMg2Ni9相,因为它的自由能(ΔG=-15.2789 kJ.mol-1,T=300 K)与Mg-Ni相(ΔG=-8.2694 kJ.mol-1,T=300 K)和Mg-Nd相(ΔG=-13.29503 kJ.mol-1,T=300 K)相比是最低的。     

10,10-二吡啶甲基-9,10-二氢蒽的合成研究

蒽酮1和氯甲基吡啶盐酸盐2在甲苯中回流反应生成10,10-二吡啶甲基-9(10H)蒽酮(3),收率63％～68％;3用硼氢化钠还原生成10,10-二吡啶甲基-9,l0-二氢蒽-9-醇(4),收率87％～90％;蒽醇4在酸催化下发生歧化反应,得到还原产物10,10-二吡啶甲基-9,10-二氢蒽(5)和氧化产物蒽酮3.该歧化反应受催化剂、溶剂和反应温度等影响.当蒽醇4用三氟化硼为催化剂、甲苯为溶剂、回流反应,5的收率达到74％.所合成的新化合物都经1H NMR,13C NMR,MS和元素分析表征确认.     

10-Alkyl-10-demethylcolchicines

It is shown that colchicine ( 4 ) can regiospecifically be transetherified at C(10) by heating in ROH in the presence of (RO)₄M (M = Ti, Zr; cf. Scheme 2). (PrO)₄Zr in PrOH gives better yields than (PrO)₄Ti in PrOH, and also in the catalytic variant of the conversion is (PrO)₄Zr more effective than (PrO)₄Ti.     

One-pot synthesis of VO x /Al 2 O 3 as efficient catalysts for propane dehydrogenation

Vanadium oxides, as highly efficiently catalysts, are widely applied in various catalytic reactions, such as the dehydrogenation of light alkanes and epoxidation of alkenes. In this paper, a series of VO _x /Al ₂ O ₃ catalysts were fabricated by the 1-pot method for catalytic propane dehydrogenation. The results indicated that the VO _x /Al ₂ O ₃ catalysts with loading of 10 wt.% vanadium exhibited optimized catalytic performance. The as-prepared catalysts were characterized by N ₂ adsorption-desorption, XRD, TEM, H ₂ -TPR, and XPS to explore the texture properties, morphology, and electronic environment of vanadium. In addition, several vanadium catalysts were also prepared by the incipient wetness impregnation (IWI) method to compare their catalytic performance with the 1-pot synthesized catalysts. The catalysts synthesized by the 1-pot method exhibited higher selectivity of propylene and longer catalyst lifetime at high propane conversion when compared to the counterpart synthesized by the IWI method.     

Conducting polyfurans by electropolymerization of oligofurans

Polyfurans have never been established as useful conjugated polymers, as previously they were considered to be inherently unstable and poorly conductive. Here, we show the preparation of stable and conducting polyfuran films by electropolymerization of a series of oligofurans of different chain lengths substituted with alkyl groups. The polyfuran films show good conductivity in the order of 1 S cm^–1, good environmental and electrochemical stabilities, very smooth morphologies (roughness 1–5 nm), long effective conjugation lengths, well-defined spectroelectrochemistry and electro-optical switching (in the Vis-NIR region), and have optical band-gaps in the range of 2.2–2.3 eV. A low oxidation potential needed for polymerization of oligofurans (compared to furan) is a key factor in achievement of improved properties of polyfurans reported in this work. DFT calculations and experiments show that polyfurans are much more rigid than polythiophenes, and alkyl substitution does not disturb backbone planarity and conjugation. The obtained properties of polyfuran films are similar or superior to the properties of electrochemically prepared poly(oligothiophene)s under similar conditions.     

Diaryldichalcogenide radical cations

One-electron oxidation of two series of diaryldichalcogenides (C₆F₅E)₂ (13a–c) and (2,6-Mes₂C₆H₃E)₂ (16a–c) was studied (E = S, Se, Te). The reaction of 13a and 13b with AsF₅ and SbF₅ gave rise to the formation of thermally unstable radical cations [(C₆F₅S)₂]˙⁺ (14a) and [(C₆F₅Se)₂]˙⁺ (14b) that were isolated as [Sb₂F₁₁]^– and [As₂F₁₁]^– salts, respectively. The reaction of 13c with AsF₅ afforded only the product of a Te–C bond cleavage, namely the previously known dication [Te₄]²⁺ that was isolated as [AsF₆]^– salt. The reaction of (2,6-Mes₂C₆H₃E)₂ (16a–c) with [NO][SbF₆] provided the corresponding radical cations [(2,6-Mes₂C₆H₃E)₂]˙⁺ (17a–c; E = S, Se, Te) in the form of thermally stable [SbF₆]^– salts in nearly quantitative yields. The electronic and structural properties of these radical cations were probed by X-ray diffraction analysis, EPR spectroscopy, and density functional theory calculations and other methods.     

Microwave assisted synthesis of 10b-aza-10c-borapyrene

The synthesis of 10b-aza-10c-borapyrene, an analog of the polycyclic aromatic hydrocarbon pyrene with an internal boron–nitrogen bond, has been improved. We have dramatically reduced the reaction times and ease of workup for the synthesis of this molecule by using a microwave reactor and carefully controlling reaction conditions.     

Nonplanar aromatic compounds. 5. A atrategy for the synthesis of cis-10b,10c-dimethyl-10b,10c-dihydropyrenes. First crystal structure of a cis-10b,10c-dimethyl-10b,10c-dihydropyrene.

Through the use of a potentially removable tether, a heavily substituted 10b,10c-dimethyl-10b,10c-dihydropyrene (DMDHP), 20, was synthesized exclusively as the cis-isomer. It exists as the major component (20:1) in an equilibrium with its valence isomer syn-[2.2]metacyclophanediene 19. An X-ray crystal structure determination of 20, a cis-(2,7)-10b,10c-dihydropyrenophane, provided the first experimental measurements of the cis-DMDHP skeleton. The observed bond alternation in the [14]annulene was found to be larger than that of the corresponding trans-DMDHP framework. Prior MMPI calculations, on which previous discussion of the structure of the cis-DMDHP system had been based, are in very good agreement with the experimental results. Our own DFT calculations predict a more symmetric and more bond equalized structure than was observed in 20.