阶梯模冷却Mg_(68)Zn_(29)Y_3合金的组织及准晶相的形成

采用五层阶梯形模具冷却方法在Mg68Zn29Y3合金中制备了二十面体准晶相(I相)。通过扫描电镜、能谱分析仪和透射电子显微分析技术,观察了合金凝固组织和准晶相的形貌,并确定了准晶相成分及结构。结果表明:Mg68Zn29Y3三元合金在普通凝固-阶梯模冷却过程中,冷却速度对准晶相形貌、数量、大小和分布存在较为显著的影响;随着冷速的降低,准晶相的生长方式由细小弥散演变为粗大碎化,准晶晶粒尺寸由20μm逐渐长大至100μm以上;准晶相通过包晶反应形核、长大;合金凝固组织为MgZn+α-Mg+Zn60Mg30Y10。     

Mg-Zn-Zr-RE系镁合金中的稀土相分析

用光学显微镜、电子探针、X射线衍射及电手显微分析等手段研究了Mg Zn Zr RE合金铸态及挤压态的稀土相。在铸态组织中,稀土及锌均富集于晶界,形成三元金属间化合物Mg_3RE_2Zn_3(W)相及Mg_3REZn_6(Z)相,在0.8Y和0.79RE合金中以Z相为主,而在2.56RE合金中W相多于z相;挤压型材中均存在W和Z相。铸态合金经350℃保温并挤压后,合金发生如下相变:Mg+Mg_3REZn_6(Z)→MgZn+Mg_3RE_2Zn_3(W)实验测定了Z相为六方结构,其a=0.640～0.642nm,C=1.029～1.031nm。     

Mg-Zn-Y系合金的铸态组织及其相变点

采用Nikon Epiphot型光学显微镜、RigakuD／max-3C型X射线衍射仪（XRD）、带有能谱仪（EDS）的JEOL JSM-6700F型扫描电子显微镜（SEM）研究了高镁、低锌、低钇三元Mg-Zn-Y系合金的铸态组织及其分布特点。在铸态组织中，钇及锌均聚集于晶界。因此在Zn，Y含量相对低时，满足成分条件在晶界形成三元金属间化合物相的成分要求。合金中主要存在的三元相为W（Mg3Y2Zn3）相、Z（Mg3YZn6）相、X（Mg12YZn）相。结合差热分析进一步讨论了合金中相的变化温度。结果表明：W相的共晶熔化温度为520℃；Z相的相变温度为445℃；X相的熔化温度为540℃。     

时效处理对热挤压Mg-xZn(x=1,3,5)-Y合金组织与力学性能的影响

研究了时效处理对热挤压Mg-xZn(x=1,3,5)-Y合金显微组织和力学性能的影响。实验结果表明:挤压态Mg-xZn(x=1,3,5)-Y合金显微组织由α-Mg,Mg_3Zn_6Y和Mg_3Zn_3Y_2相组成。挤压后合金发生了动态再结晶,随着Zn含量的增加,合金中的Mg_3Zn_6Y相依次增加。经时效处理后,颗粒状的Mg_3Zn_6Y相沉淀析出,Mg_3Zn_3Y_2相也逐渐弥散析出。其中Mg-5Zn-Y合金经过温度为200℃,18 h的时效处理后,具有良好的综合力学性能,其抗拉强度,屈服强度和伸长率分别为375 MPa,258 MPa,23.5%。该合金拥有良好的力学性能主要是由于晶粒细化和Mg_3Zn_6Y相的沉淀强化。     

均匀化处理对Mg-Zn-Zr-RE合金挤压棒材显微组织和拉伸性能的影响

研究了Mg-Zn-Zr-RE合金挤压棒材的显微组织及拉伸性能。结果表明,挤压前未经均匀化处理的棒材的拉伸强度最高,而经380℃或400℃/18h均匀化处理后强度下降。均匀化处理时稀土化合物Mg3REZn_6(Z相)和Mg_3RE_2Zn_3(W相)大部分发生转变,形成MgZn相及二元Mg_(41)RE_5稀土相;同时,长时间均匀化处理使得合金的主要强化相MgZn(β相)明显长大,促使动态再结晶发生,从而使拉伸性能降低。     

T6处理后Al-Zn-Mg-Cu合金电子束焊接接头组织与织构的演变

采用扫描电镜、EBSD、透射电镜等方法研究了Al - Zn - Mg - Cu合金电子束焊接接头的微观组织特点,并分析了焊缝基体与熔合区在热处理前后织构的变化.结果表明,接头熔合区由尺寸约3～8 μm的等轴细晶组成,析出相沿晶界均匀分布,经T6处理后熔合区的晶粒尺寸无明显变化,晶界变细,沿晶界分布的连续析出相溶解,残余孤立的MgZn2析出相,尺寸约1～2 μm.基体主要织构为＜111＞和＜001＞丝织构,经T6(固溶时效)处理后,两种织构的含量无明显变化,织构强度略有下降,焊缝熔合区无明显的织构.     

生物材料用Mg-Y-Zn-Zr合金的微观结构及体外降解行为

通过向纯镁中添加微量的合金化元素（Y、Zn和Zr）,采用熔融浇铸法制备了名义成分为Mg1.5Y1.2Zn0.44Zr四元可降解镁合金生物材料,并对其进行了均匀化处理和挤压。 对这3种状态的镁合金进行了微观结构及在模拟体液(SBF)中体外降解行为的测试和分析,结果表明,合金主要由α-Mg基体和Mg12ZnY第二相组成;合金经过挤压后的组织得到了明显的细化;因此挤压后合金的降解性能得到明显改善;合金在模拟体液中生成的降解产物主要是含Ca和Mg的磷酸盐。     

钇对Nd-Fe-Al-Ni非晶合金热稳定性与晶化行为的影响

采用差示扫描量热法（DSC）、X射线衍射（XRD）和透射电镜（TEM）研究了Y对Nd-Fe-Al-Ni非晶合金热稳定性和晶化行为的影响。结果表明,淬火态的Nd60Fe20Al10Ni10-xYx（x=0,2）合金基本为非晶组织同时还含有少量的淬态相,Y的加入抑制了淬态相的析出。加入Y后,非晶合金的晶化开始温度和晶化峰值温度都向高温方向移动,证明其热稳定性提高。Y的加入改变了合金的晶化方式和最终晶化产物,使非晶基体中析出的晶化相更加弥散圆整细小。并且Y具有在化学上钝化氧杂质的作用,从而抑制了氧的有害作用。利用Kissinger方程获得了Nd60Fe20Al10Ni8Y2非晶合金的晶化开始和晶化峰值激活能分别为1.21和1.16 eV。     

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.     

钇对AZ91镁合金微观组织及腐蚀性能影响的研究

通过金相分析、扫描电镜析及化学成分分析等测试手段,对添加不同含量Y的AZ91镁合金的微观组织和腐蚀性能进行了研究。结果表明,加入Y后,合金中有稀土相Al4MgY生成,并显著细化了合金的微观组织,合金微观组织由典型的枝晶组织转变为细小的等轴晶组织,当Y含量达到1.52%时,合金组织的细化程度最大;Y的加入,减少了合金中的-βMg17Al12相,并使β相断续、弥散,同时合金的耐腐蚀性能提高,在3.5%NaCl水溶液腐蚀实验中,稀土含量为1.52%Y的合金耐腐蚀性能最好。     

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.     

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.     

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

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.     

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.     

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.