Ba0.4Sr0.6Co1-xFexO3-δ系阴极材料的制备和表征

采用甘氨酸-硝酸盐(GNP)法合成了中温固体氧化物燃料电池阴极材料Ba_0.4Sr_0.6Co_1-xFe_xO_3-δ(x=0.0～0.8)系列粉体。利用XRD和SEM对材料的结构和微观形貌进行分析,用直流四端子法测量了烧结陶瓷体在中温(450～800 ℃)范围内的电导率。结果表明,制备的样品为单一钙钛矿相,随着Fe含量增加,XRD衍射峰值向高角度方向稍有偏移。电导率随着温度及Fe含量的变化出现极大值,在x＜0.2时,Ba_0.4Sr_0.6Co_1-xFe_xO_3-δ系列烧结体在中温(450～800 ℃)区的电导率,随Fe掺入量的增大而增大,x=0.2样品的电导率最高,800 ℃时达244.7 S·cm^-1,远超过文献报道值,进一步增大Fe含量导电性能变差。     

Pr0.6-xNdxSr0.4FeO3-δ电极材料的光谱及性能研究

以柠檬酸-硝酸盐自蔓延燃烧法合成了ABO₃型钙钛矿结构的Pr_0.6-xNd_xSr_0.4FeO_3-δ(x=0.0～0.6)系列稀土复合氧化物粉体。利用傅立叶变换红外光谱(FTIR)和激光共焦拉曼光谱(LRS)对产物的晶体结构进行了表征。分别采用热膨胀仪测定烧结陶瓷体的热膨胀系数(TEC)；TG-DTA记录材料的热稳定性；XRD研究阴极材料与中温电解质Sm_0.2Ce_0.8O_1.9(SDC)及La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ(LSGM)的化学相容性；SEM观察阴极/电解质复合材料的断口形貌。结果表明，该系列样品在高、低温热循环过程中化学稳定、晶型稳定；在室温至1 100 ℃范围内的平均热膨胀系数为1.16 × 10^-5 K^-1，与SDC及LSGM的热膨胀系数十分接近。阴极/电解质混合粉体1 200 ℃煅烧10 h，XRD未检测到新物质；SEM显示复合层断面界面清晰，没有相互扩散现象。该体系有望成为以SDC或LSGM为电解质的中温固体氧化物燃料电池合适的阴极材料。     

中温天然气燃料电池复合阳极NiO-La0.75Sr0.25Cr0.5Mn0.5O3-δ-Ce0.8Sm0.2O2-δ的制备和性能研究

采用共压-共烧结的方法制备了以NiO-La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ-Ce_0.8Sm_0.2O_2-δ复合阳极为支撑、以Ce_0.8Gd_0.2O_2-δ(GDC)为电解质、以La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ(LSCF)-Ce_0.8Gd_0.2O_2-δ(GDC)为复合阴极的单电池,在400～700 ℃范围内,以加湿天然气(3% H₂O)为燃料气,氧气为氧化气,测试了电池的放电性能。利用XRD、SEM、EDX等手段对复合阳极进行结构、化学相容性、微观型貌和碳元素分析。分析结果表明,符合阳极具有较好的化学相容性,且阳极和阴极具有较好的孔隙、孔道结构。EDX测试结果表明有少量的碳沉积。在600 ℃进行了电池的稳定性测试。测试结果表明,该电池在13 h的测试过程中功率无明显衰减,具有较好的稳定性。复合阳极单电池在600 ℃得到最大电流密度,为215.49 mA·cm^-2;最大功率流密度为44.85 mW·cm^-2。     

BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)的制备及性能研究

采用高温固相反应法制备了质子导体BaCe_0.8-xNb_xGd_0.2O_3-δ(0≤x≤0.45)。结合XRD、SEM、EIS等技术对其物相、微观形貌、稳定性及电导率进行了研究。结果表明,在1 600 ℃烧结5 h制备的质子导体BaCe_0.8-xNb_xGd_0.2O_3-δ(0≤x≤0.45)均能保持主相为斜方晶的钙钛矿结构。Nb的加入可明显提高烧结样品的致密性及在CO₂和水蒸气气氛下的稳定性。在湿润H₂/Ar(0.4%,V/V)气氛中800 ℃下,x=0.1样品的电导率为5.73 mS·cm^-1,电导活化能为0.35 eV,与x=0的样品相当。     

低热固相反应法在多元金属复合氧化物合成中的应用—锂离子电池正极材料LiCo0.8Ni0.2O2的合成、结构和电化学性能的研究

以氢氧化锂、醋酸钴、醋酸镍和草酸为原料,采用低热固相反应法制备了锂离子电池正极材料LiCo_0.8Ni_0.2O₂的前驱体。该前驱体在不同温度下焙烧制得LiCo_0.8Ni_0.2O₂粉体样品。通过XRD和SEM技术对样品的结构和颗粒形貌进行了分析;采用BET法、激光散射技术和恒电流间歇滴定法(GITT)分别对比表面积、粒度分布和扩散系数等理化参数进行了测试。结果表明,样品颗粒是由许     

La1-xSrxFeO3-δ系钙钛矿材料的表征和性能

采用甘氨酸-硝酸盐(GNP)法合成了中温固体氧化物燃料电池阴极材料La_1-xSr_xFeO_3-δ(x=0.0~0.6)系列粉体。用FTIR、TG-DTA、XRD等对产物形成过程及结晶学特征进行了研究，考察了合成样品与Sm_0.2Ce_0.8O_1.9(SDC)的化学相容性；利用碘滴定法测定了该系列产物中Fe元素的平均表观化合价和氧的非化学计量值。结果表明，所合成的系列样品均形成具有ABO₃型结构的钙钛矿固溶体。随A位取代Sr含量的增加，IR谱图上560 cm^-1附近B-O键伸缩振动的红外吸收峰蓝移，意味着钙钛矿产物中Fe-O键的共价性成分增强。实验还发现，Fe元素的平均化合价先随样品中Sr含量的增加而升高，并以La_0.6Sr_0.4FeO_3-δ样品达最高，而后降低；样品中氧的非化学计量值则随掺Sr量的增加单调增大。四探针法电导测量结果表明，在x≤0.4时，La_1-xSr_xFeO_3-δ系列陶瓷烧结体在中温(450~800 ℃)区的电导率，随Sr掺入量的增大而增大，La_0.6Sr_0.4FeO_3-δ样品的电导率最高，进一步增大Sr含量导电性能变差。在低温段，样品的导电行为符合小极化子导电机制。该系列材料与SDC电解质材料具有良好的化学相容性。     

天然气中温SOFC阳极材料铒掺杂的氧化铈的制备与性能研究

采用溶胶-凝胶法合成了新型中温固体氧化物燃料电池(IT-SOFC)阳极材料Ce_1-xEr_xO_y(x=0.00,0.10,0.15,0.20,0.25,0.30)(EDC),并采用共压-共烧结法制备了以NiO-EDC复合阳极为支撑、以Ce_0.8Gd_0.2O_2-δ(GDC)为电解质、以La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ(LSCF)-GDC为复合阴极的单电池。利用XRD和SEM等方法对阳极材料EDC进行了晶相结构、微观形貌和化学相容性等分析。在400~700 ℃范围内,以加湿天然气(3% H₂O)为燃料气,氧气为氧化气测试了电池的电化学性能。结果表明：EDC阳极材料具有良好的孔道结构;11种不同阳极组成的单电池中50%(质量分数)NiO-50%(质量分数)Ce_0.85Er_0.15O_y(E15C85)阳极支撑的单电池具有最佳的电化学性能,在650 ℃时其最大电流密度为117.84 mA·cm^-2和最大比功率为24.37 mW·cm^-2。     

天然气和甲烷固体氧化物燃料电池中的Ni-LCCM-GDC阳极性能研究

采用溶胶-凝胶法合成了纳米粉体La_1-xCe_xCr_0.5Mn_0.5O_3-δ(x=0.05,0.10,0.15,0.20)(LCCM),并采用共压-共烧结法制备了以复合阳极Ni-La_0.9Ce_0.1Cr_0.5Mn_0.5O_3-δ-Ce_0.8Gd_0.2O_2-δ(GDC)为支撑、GDC为电解质、La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ(LSCF)-GDC为复合阴极的单电池。利用XRD和SEM等方法对阳极材料进行了晶相结构、化学相容性、微观形貌分析。在500~750 ℃范围内,分别以湿天然气(3% H₂O)和甲烷为燃料气,氧气为氧化气测试了单电池的电化学性能,同时检测了以甲烷为燃料气的阳极尾气组成。结果表明：复合阳极材料具有良好的化学相容性;阳极和阴极具有较好的孔隙结构。以天然气和甲烷为燃料气的单电池在700 ℃时最大电流密度分别为131.96 mA·cm^-2,162.36 mA·cm^-2; 最大比功率分别为28.61 mW·cm^-2,31.03 mW·cm^-2。在500~750 ℃范围内阳极尾气中均检测出CO,CO₂,在700 ℃时CO,CO₂含量达到最大值,分别为2.39254%,6.20891%。     

单相Ba2Ti9O20柠檬酸凝胶法制备、表征及介电性能

采用柠檬酸凝胶法两步热处理工艺制备了单相Ba₂Ti₉O₂₀。干凝胶在750 ℃热处理得到了物相为BaTi₅O₁₁和Ba₄Ti₁₃O₃₀、尺寸为30～50 nm的前驱体粉体。纳米前驱体具有高表面活性，促使单相Ba₂Ti₉O₂₀在1 200 ℃热处理温度下形成。两步热处理所得的粉体比一步热处理所得的粉体具有更好的烧结和介电特性，两步热处理所得的粉体，在1 250 ℃烧结4 h，可获得理论密度为97%的Ba₂Ti₉O₂₀微波介质陶瓷，其介电性能：ε_r=38.5，Qf=19 320 GHz，τ_f=8.7×10^-6 ℃^-1。     

La1-xCaxFeO3-δ系阴极材料的GNP法合成及电性能研究

采用甘氨酸-硝酸盐(GNP)法合成了LaFeO₃及La_1-xCa_xFeO_3-δ(x=0.1～0.5)系列粉体，用TG-DTA、XRD、TEM、SEM等对产物形成过程及微结构进行了表征。结果表明，所合成的系列样品均形成钙钛矿结构的单相固溶体。在x≤20mol%的Ca含量范围内，产物为正交钙钛矿结构；当x>30mol%时，转变为立方钙钛矿相。相同条件下产物的衍射峰强度、晶胞体积及晶粒尺寸都随Ca含量的增大而减小。采用直流四端子法测量了烧结体在中温(450～800 ℃)区的电导率。掺杂使样品导电能力显著增强，电导率随Ca²⁺掺入量的增大先增大后减小，La_0.6Ca_0.4FeO_3-δ样品的电导率最高。在低温段，各样品的导电行为符合小极化子导电机制，导电活化能为13.67～22.70 kJ·mol^-1。     

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.