纳米CeO2对Ni基合金激光熔覆层的组织与耐蚀性的影响

利用5 kWCO2激光器,在Q235低碳钢表面熔覆微米或纳米CeO2/Ni基合金复合材料,制备了涂层。利用光学显微镜、扫描电镜和X射线衍射仪分析了熔覆层的组织和相结构,利用CHI604b型电化学分析仪测定了熔覆层的阳极极化曲线。结果表明：加入微米CeO2的熔覆层组织明显细化,并出现大量的等轴晶,加入纳米CeO2的熔覆层等轴晶更加细小,并且组织致密;加入微米CeO2后Ni基合金熔覆层主要相结构的为γ-Ni,Cr23C6,CeNi3,γ-CeO2,Ni3Si和Ni3B等相,加入纳米CeO2的熔覆层中出现γ-Ni,Cr23C6,CeNi3,CeNi5,Ni3Si和Ni3B等相;当纳米CeO2的添加量为1.5%时,熔覆层的耐蚀性能大幅度提高,并且形成相对稳定的钝化膜。     

Y2O3:Eu纳米晶的硝基取代苯甲酸配合物固相热解制备和性能

以苯甲酸、邻硝基苯甲酸、间硝基苯甲酸、对硝基苯甲酸、3,5 二硝基苯甲酸等为配体制备了Y3+、Eu3+二元配合物,配合物中Y3+与Eu3+的摩尔比为9：1.利用这些配合物的爆炸式热分解特性通过固相热解反应制备了一系列Y2O3:Eu纳米晶.透射电镜观察,可以看出所得纳米晶呈球形,粒度介于40～60 nm,X射线衍射分析表明实验所得纳米晶属立方晶系,粒径与电镜观察所得结果基本一致；Eu3+的引入并不影响Y2O3的晶相组成；配体类型对纳米晶的结构没有显著影响,不过相对于硝基取代苯甲酸配合物,苯甲酸配合物热解所得Y2O3∶Eu纳米晶团聚严重；退火温度显著影响纳米晶粒度,退火温度高,纳米晶粒度大,反之亦然.荧光光谱测定表明所有Y2O3∶Eu纳米晶具有相似的发光行为,其中以苯甲酸配合物分解所得Y2O3:Eu纳米晶发光性能最为优越.     

尿素水解法制备球形磁性Al2O3复合材料

利用酸化法在磁性Fe3O4纳米粒子表面包覆SiO2膜,制备了Fe3O4/SiO2复合粒子。然后将该复合粒子超声分散在尿素和铝盐的混合溶液中,利用油中成型法制备出球形纳米磁性Al2O3复合材料,通过水热焙烧等工序处理得γ-Al2O3。实验中采用XRD、TEM、BET、AGM等方法对复合粒子的性能进行了表征,探讨了制备过程对产物晶型的影响、产物的孔结构变化和磁学性能。另外添加的SiO2膜阻止了磁性Fe3O4纳米粒子的进一步团聚,使得Fe3O4纳米粒子保持较小尺寸并均匀分散在产物中,复合材料表现出超顺磁性;同时SiO2膜防止了磁核部分与Al2O3包覆层在高温焙烧时发生反应;还起到加强粘结的作用,使得Al2O3在使用过程中不容易脱落。     

纳米Y_2O_3对14CrSiMnV硬质合金涂层耐磨耐热氧化性影响

利用激光熔覆表面复合纳米Y_2O_3颗粒的14CrSiMnV铁基合金粉体,制备了14CrSiMnV硬质合金钢涂层。研究了纳米Y_2O_3对涂层微观结构、微观硬度、耐热以及耐滑动摩擦的影响。结果表明:在合金涂层成型过程中,添加小于1%(质量分数)纳米Y_2O_3可以促进涂层组织中的树状晶向等轴晶转变,且减少涂层在600℃高温条件的氧化腐蚀现象,改善表面滑动摩擦的塑性剥离,从而使涂层拥有更好的耐热性能和耐滑动摩擦性能。     

Y2O3:Eu纳米晶的硝基取代苯甲酸配合物固相热解制备和性能

以苯甲酸、邻硝基苯甲酸、间硝基苯甲酸、对硝基苯甲酸、3，5－二硝基苯甲酸等为配体制备了Y^3 、Eu^3 二元配合物，配合物中Y^3 与Eu^3 的摩尔比为9：1，利用这些配合物的爆炸式热分解特性通过固相热解反应制备了一系列Y2O3：Eu纳米晶。透射电镜观察，可以看出所得纳米晶呈球形，粒度介于40－60nm，X射线衍射分析表明实验所得纳米晶属立方晶系，粒径与电镜观察所得结果基本一致；Eu^3 的引入并不影响Y2O3的晶相组成；配体类型对纳米晶的结构没有显著影响，不过相对于硝基取代苯甲酸配合物，苯甲酸配合物热解所得Y2O3：Eu纳米晶团聚严重；退火温度显著影响纳米晶粒度，退火温度高，纳米晶粒度大，反之亦然。荧光光谱测定表明所有Y2O3：Eu纳米晶具有相似的发光行为，其中以苯甲酸配合物分解所得Y2O3：Eu纳米晶发光性能最为优越。     

α,β,γ,δ,ε,η-Bi_2O_3电子结构和光学性质的第一性原理研究

基于密度泛函理论的CASTEP模块研究了α,β,γ,δ,ε和η-Bi_2O_3晶型,计算分析了其几何结构、能带结构、电子态密度和光学性质.结果表明,α,ε和η相均为层状结构,其中,α和ε相为单层—Bi—O—结构,而η相为双层—Bi—O—结构;β,γ和δ相为—Bi_m—O_n—交错结构,其中δ相交错尤为密集,呈现导体特性.各晶相的导带均由Bi 6p态构成,价带由O__(2p)态起主导作用.电势电位分析结果表明,6种晶相价带电位均在H_2O/O_2之下,具有强氧化能力,与实验报道的光催化氧化能力大小顺序γ-Bi_2O_3β-Bi_2O_3α-Bi_2O_3δ-Bi_2O_3一致,而导带还原电位低于H_2/H_2O,预测纯Bi_2O_3很难具备催化产氢能力.光学性质分析发现,γ和δ相的起始响应波长较大,说明其应具备红外激发的性质.这些结果可为获得偏红外激发和较宽光谱响应的Bi_2O_3材料研究提供理论基础,为研发和应用Bi_2O_3及其复合物提供重要的指导.     

纳米晶Y_2O_3∶Eu~(3+)的合成及其热分析动力学

以Y(NO3)3、Eu2O3、CO(NH2)2为原料,使用超声波作用下的均匀沉淀法合成了纳米晶荧光粉Y2O3∶Eu3+。利用不同升温速率的热重及差热分析研究了纳米晶Y2O3∶Eu3+的合成动力学及晶粒生长动力学。研究表明,纳米晶Y2O3∶Eu3+的前驱体分解过程可分为3个步骤,利用Doyle-Ozawa法和Kissinger法分别计算了各个反应阶段的表观活化能,用Kissinger法确定每个反应阶段的反应级数和频率因子,并给出了各个阶段的动力学方程。根据晶粒生长动力学理论计算纳米荧光粉Y2O3∶Eu3+晶粒生长活化能为17.80kJ·mol-1,表明热处理过程中纳米晶粒的长大为扩散生长机制。     

气态环己烷催化氧化制丁二酸酐的研究- TiO2-Al2O3纳米复合载体对目标反应的影响

采用溶胶-凝胶法,在γ-A l2O3载体上负载纳米TiO2,制得一系列纳米复合载体.用正交实验法对催化剂载体进行优化筛选,借助DTA-TG、IR、TEM等表征手段研究了催化剂载体的晶型结构转变,表面形貌及纳米复合载体粒径.结果表明:在实验条件下,复合载体的晶型结构、粒径大小、TiO2的负载量、乙醇与钛酸丁酯的物质的量之比、焙烧温度等对催化性能均有不同程度的影响.     

纳米Y2O3:Eu3+超声辐射沉淀制备及其性能研究

采用超声辐射沉淀法以草酸为沉淀剂制备出纳米Y2O3:Eu^3 粉体。利用XRD、TG-DTA、TEM等手段对其进行了表征．并对其光谱特性进行了研究。结果表明：将超声辐射引入普通沉淀法中,可显著提高粉体性能,所得纳米Y2O3:Eu^3 为球形,粒度分布均匀,粒径约为38～45nm,与微米晶相比,该纳米晶的发射光谱发生蓝移,激发光谱发生红移。     

高分子自组装Mn2O3花瓣状纳米带、纳米线的研究

通过控制热处理工艺条件, 利用Mn(CH3COO)2和具有特殊空间构型的聚乙烯醇(PVA), 在600 ℃合成了类花瓣状Mn2O3纳米带和纳米线结构. SEM, XRD表征分析证明Mn2O3纳米带结构为方铁锰矿晶型结构, 沿(222)方向择优生长. 分析了热处理工艺对一维纳米结构的影响机制. 初步探讨了Mn2O3一维纳米结构的生长机理.     

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%.     

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.     

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.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.