熔盐电解SiO2/C直接制备SiC纳米线

采用纳米SiO₂和酚醛树脂为原料制备酚醛树脂裂解碳纳米SiO₂复合阴极(硅碳物质的量的比为1:1),直接电解PFC/SiO₂复合阴极,在900℃熔融盐CaCl₂中,恒槽压2.0V下电解,制备出碳化硅纳米线。采用场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)及其附带的能谱仪、X射线分析衍射仪(XRD)和拉曼光谱(Raman)对产物的组成、形貌、微观结构等进行了表征。结果表明:碳化硅纳米线呈立方晶体结构,其直径为4~13nm,长可达数微米;室温下该纳米线在415nm和534nm附近有宽的发光峰。最后,讨论了碳化硅纳米线的生成机制。     

表面活性剂辅助合成CdWO4纳米棒和纳米线

以Na₂WO₄•2H₂O和CdCl₂ 为主要原料, 分别在十六烷基三甲基溴化铵(CTAB)和十二烷基苯磺酸钠(SDBS)表面活性剂中, 在180 ℃反应16 h, 水热制备了CdWO₄纳米棒和纳米线. 利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征, 并对其在室温下的发光特性进行了测定. 实验结果表明: 产物均为具有单斜结构的单相CdWO₄. 其中CdWO₄纳米棒具有单晶属性, 平均粒径约为63 nm, 长度近1 µm; 而CdWO₄纳米线具有多晶特性, 平均粒径约为12 nm, 长度达十几微米. 当激发波长为253 nm时均有460 nm强的发射峰, 其中CdWO₄单晶纳米棒的发光强度大于CdWO₄多晶纳米线. 分别对CdWO₄纳米棒和纳米线形成的可能机理进行了初步分析.     

表面活性剂辅助合成CdWO4纳米棒和纳米线

以Na₂WO₄•2H₂O和CdCl₂ 为主要原料, 分别在十六烷基三甲基溴化铵(CTAB)和十二烷基苯磺酸钠(SDBS)表面活性剂中, 在180 ℃反应16 h, 水热制备了CdWO₄纳米棒和纳米线. 利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征, 并对其在室温下的发光特性进行了测定. 实验结果表明: 产物均为具有单斜结构的单相CdWO₄. 其中CdWO₄纳米棒具有单晶属性, 平均粒径约为63 nm, 长度近1 µm; 而CdWO₄纳米线具有多晶特性, 平均粒径约为12 nm, 长度达十几微米. 当激发波长为253 nm时均有460 nm强的发射峰, 其中CdWO₄单晶纳米棒的发光强度大于CdWO₄多晶纳米线. 分别对CdWO₄纳米棒和纳米线形成的可能机理进行了初步分析.     

SiO2/Co3O4核壳催化剂对AP热分解的催化性能研究

采用改良的Stöber法制备粒径约为200 nm的单分散球形SiO₂颗粒,以此为内核,分别通过液相沉淀法和尿素均匀沉淀法制备包覆形式不同的新型SiO₂/Co₃O₄核壳式纳米催化剂。采用X-射线衍射分析(XRD)、透射电子显微镜(TEM)、红外光谱分析(IR)、拉曼光谱分析(Raman)、BET比表面积测试等手段对产物进行表征,利用差式扫描量热仪(DSC)考察SiO₂/Co₃O₄复合物对高氯酸铵(AP)热分解反应的催化作用,探讨不同包覆形式对其催化活性的影响。结果表明,两种方法制备得到的SiO₂/Co₃O₄复合物分别为层包覆和粒子包覆,比表面积大,具有明显的核壳结构,且粒子包覆形式的SiO₂/Co₃O₄对AP热分解反应的催化效果最好,使AP的高温分解温度降低了110 ℃,放热量增加了662 J·g^-1。     

核/壳型CdTe@SiO2荧光纳米复合粒子的制备与表征

利用反相微乳法, 以巯基乙酸修饰的水溶性CdTe量子点为核, 包覆SiO₂, 制备得到核壳型CdTe@SiO₂荧光纳米复合粒子. 用紫外-可见(UV-vis)分光光度计, 荧光(PL)分光光度计, 红外(FT-IR)光谱仪, 透射电子显微镜(TEM)等分析测试手段, 对得到的荧光纳米复合粒子的性能进行表征, 结果表明: 得到的CdTe@SiO₂纳米复合粒子是核壳型结构, 由SiO₂壳层包覆多个量子点, 其大小均匀, 水溶性好, 有效地提高了量子点的稳定性, 大大增强了其抗光漂白性能, 为该材料的进一步生物应用打下了良好的基础.     

反相微乳液法制备纳米SiO2的研究

在壬基酚聚氧乙烯5醚(NP-5)/环己烷/氨水的反相微乳液体系中，进行正硅酸乙酯(TEOS)的水解、缩合反应，得到粒径在30～50 nm的单分散纳米SiO₂胶体。红外光谱法(FTIR)及透射电子显微镜(TEM)观察证明了纳米SiO₂粒子的生成。反相微乳液体系相图的研究表明，水相为氨水比纯水有较窄的W/O型微乳区。氨水微乳液是碱催化TEOS水解、缩合制备纳米SiO₂粒子的适宜体系。当体系中TEOS的浓度增大时，粒子的粒径随之增大。降低NP-5     

自生纳米纤维增强SiO2气凝胶的制备及性能研究

采用溶胶-凝胶法和乙醇超临界干燥工艺制备ZrO_X/SiO₂复合气凝胶,再经1200℃高温热处理得到自生纳米纤维增强SiO₂复合气凝胶。利用扫描电子显微镜、透射电子显微镜、X射线衍射、热重和氮气吸附等手段对气凝胶的结构和性能进行了分析,并且测试了样品的压缩强度及真密度。实验结果表明：自生纳米纤维增强SiO₂复合气凝胶具有均匀的多孔网络结构,锆氧纳米纤维是以化学键连接复合的方式无序穿插在气凝胶中,对复合气凝胶的机械强度和隔热性能有明显的改善。经1200℃热处理后的ZrO_X/SiO₂复合气凝胶比表面积为827.22m₂·g^-1,压缩强度为9.68MPa,真密度为0.23g·cm^-3。     

SiO2/ZnO复合纳米粒子的制备及表征

采用双注控制沉积法(Controlled Double-Jet Precipitation,CDJP)将反应物添加到含有SiO₂的溶液中,通过直接的表面反应来制备单分散的SiO₂/ZnO复合纳米粒子,并对其进行了表征。透射电镜(TEM)观察表明,SiO₂表面有一层ZnO纳米颗粒或薄层。对复合纳米粒子SiO₂/ZnO进行X射线衍射(XRD)分析,复合颗粒的衍射峰与单独的氧化锌的衍射峰完全一致。能量弥散X射线法(EDX)分析表明,复合颗粒中含有Zn、Si、O元素。荧光光谱表明有ZnO的吸收峰。     

石墨基底对碳/碳化硼复合纳米绳形成的影响

利用邻碳硼烷(C₂H₁₂B₁₀)作为反应原料,二茂铁(C₁₀H₁₀Fe)作为催化剂,通过化学气相沉积法在石墨基片上生长出一种新颖的碳化硼纳米绳。用X射线衍射仪分析纳米绳的相结构,用场发射扫描电子显微镜(FESEM)和高分辨透射电子显微镜(HRTEM)观察纳米绳的微观形貌和结构,结果发现纳米绳的中心部分是碳化硼纳米线,在线的表面有非晶碳绳结,故纳米绳为碳/碳化硼复合物。研究了绳状产物的生长机理,表明石墨基片对产物的形成有至关重要的作用。     

Fe3O4磁性纳米粒子的超声包金及其表征

超声条件下, 在乙醇分散的3-氨丙基三乙氧基硅烷(APTES)功能化的磁性Fe₃O₄纳米粒子和四氯合金酸的混合溶液中滴加柠檬酸钠, 成功地制备了磁性Fe₃O₄/Au复合纳米粒子. 采用X射线粉末衍射仪(XRD)、紫外吸收可见光谱(UV-Vis)、带有电子能谱仪(EDS)的扫描电子显微镜(SEM)、透射电子显微镜(TEM)、光电子能谱(XPS)、超导量子干涉仪(SQUID)等方法, 对复合粒子的形态、结构、组成以及磁学性质进行了表征. 结果表明: 在此条件下制得的复合粒子粒径在30 nm左右, 室温下磁化强度可达63 emu/g.     

用透射电子显微技术研究Si3N4/纳米SiC复相陶瓷的微观结构与力学性能

利用透射电子显微镜,观察了Si3N4/纳米SiC复相陶瓷材料的显微结构特点、分析比较了纳米复相陶瓷与单相Si3N4陶瓷的显微结构差异、讨论了复相陶瓷材料的力学性能与其微观结构的关系,并提出在材料中引入纳米SiC粒子后,可以起到抑制Si3N4晶体长大,使材料的力学性能得到显著提高.     

Oscillations of open-circuit potential during immersion plating of silicon in CuSO4/HF solutions

The paper analyzes the nature of oscillations of open-circuit potential (OCP) during immersion plating of copper on silicon wafers. The oscillations are observed within well-determined interval of experimental conditions (composition of the electrolyte, doping level of silicon wafers, temperature, viscosity of electrolyte, etc.). Different to other known cases of the electrochemical oscillations, in the present case, there is no external source of the electrical current. We summarize here experimental findings relevant to this phenomenon and analyze possible reasons for the occurrence of the OCP oscillations. The effect is well fit by the general phenomenology of chaos-order transitions in complex chemical systems. We present a model for the oscillatory behavior which involves simultaneous reactions of Cu deposition and oxidation of silicon wafer, generation of local mechanical stress in the system, nonlinear electrochemical etching of silicon, localization of the electric field at the etched surface, etc. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 5, pp. 574–585. The text was submitted by the author in English. Deceased.     

XRD-Studies of SiC/Si layers on carbon substrates

Structural investigations of thin films of SiC, SiC with free silicon and various titanium suicides (TiSi₂, TiSi and Ti₅Si₃) are described. The crystal phases have been identified using X-ray diffractometry. The growth of reaction products from surface reactions between silicon and deposited titanium can be observed.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Magnetic transitions in the Gd5Si4−xPx (x = 0.5, 0.75, 1.25) phases. Magnetocaloric effect of the Gd5Si2.75P1.25 phase

The Gd₅Si_2.75P_1.25 phase with all interslab Si/P–Si/P dimers broken (Sm₅Ge₄-type structure) undergoes a ferromagnetic transition at 184 K. For this phase, the magnetocaloric effect in terms of the magnetic entropy change, ΔS, reaches the maximum value of −7.8 J/kg K at 177 K. Absence of a temperature-dependant structural transition, as confirmed by the low-temperature single crystal diffraction studies, together with the moderate value of ΔS points to the presence of a conventional magnetocaloric effect. Gd₅Si_3.5P_0.5 and Gd₅Si_3.25P_0.75, which are composites of the Gd₅Si₄- (all Si/P–Si/P dimers intact) and Sm₅Ge₄-type phases, possess two magnetic transitions associated with the two-phases. Introduction of P into Gd₅Si₄ lowers the Curie temperature from 336 K to 332 K in Gd₅Si_3.25P_0.75.     

Structural evolution of calcium-exchanged (NH4)2SiF6-dealuminated Y zeolite after various chemical treatments

The structural evolution of Y zeolite (Si/Al 2.17) weakly dealuminated by hexafluorosilicate (Si/Al 3.13), denoted Y_D, and exchanged with calcium (CaY_D), has been studied after acid–base treatments at 80 °C close to the cation exchange conditions. The stability of the samples was followed by X-ray diffraction and solid-state NMR of ²⁹Si and ²⁷Al; Y_D zeolite was completely destroyed by treatment with acid pH 2.5 and suffered serious degradation on treatment with alkali at pH 11.8. The introduction of calcium improved the stability of the zeolite in acid and base. In acid CaY_D was not destroyed until pH 1. At pH 2, silicon and aluminium were extracted and an amorphous phase was formed. Base treatment at pH 13 did not affect the calcium-exchanged zeolite.     

多孔硅镶嵌正丁胺/激光染料复合膜的荧光谱

多孔介质染料镶嵌膜有可能是发展固体染料激光器的一种途径[1].由于其所具有的微孔结构和大的比表面积,故使其成为激光染料理想的载体,以形成多孔硅基发光材料[2].　　我们用正丁胺作碳源,采用射频辉光(ＲＦ)放电法制备碳膜.利用正丁胺、Ｒ6Ｇ/聚乙二醇分别作碳源和蒸发源得到一种混合膜,如将其沉积在刚制备的新鲜多孔硅上则得到多孔硅镶嵌复合膜.本文着重研究了镶嵌于多孔硅中的正丁胺/Ｒ6Ｇ的荧光光谱,并考察了多孔硅衬底的改变对多孔硅镶嵌膜发光的影响.1　样品制备　　(1)多孔硅的制备　制备多孔硅(ＰＳ)所用的材料为(100)晶向的ｐ型单…     

多孔硅镶嵌正丁胺/激光染料复合膜的荧光谱

The photoluminescence (PL) of the compound films made by implanting n-butylamine/ Rhodamine into the porous silicon films was studied. Comparison and discussion of the difference of PL of the compound films and the dyes were carried out. The PL of the compound films with different substrates was measured.     

多重射流燃烧反应制备的TiO2/ SiO2纳米复合颗粒的形态和结构

TiO₂-SiO₂ nanocomposite particles were prepared in premixed H₂ / Air flame, and the morphology and structure of these nanocomposites were characterized by FTIR, XRD, TEM and HRTEM. The morphology of SiO₂ / TiO₂ nanocomposites was different from that of pure TiO₂ or SiO₂ nanoparticles, and the chemical bond of Ti-O-Si was found in the nanocomposites indicating that the TiO₂ / SiO₂ nanocomposites were not merely a physical mixture of TiO₂ and SiO₂. TiO₂ nanocrystalline grains with sizes of 1～2 nm were homogeneously dispersed in the amorphous SiO₂ matrix when TiCl₄ and SiCl₄ were mixed at molecular level in the flame. The particle size and rutile content decreased with increasing of SiO₂ molar ratio.     

多孔硅/TiO2纳米线光阳极的制备及其光电催化性能

使用金属辅助化学刻蚀(MACE)法与水热法,改变贵金属粒子的刻蚀时间,制备不同n型多孔硅/TiO_2纳米线光阳极。通过扫描电镜(SEM)和X射线衍射仪(XRD)对光阳极样品进行表征,结果显示多孔硅宏孔的尺寸会随着刻蚀时间延长而增大,由0.1μm变化到0.4μm,多孔硅表面长有TiO_2纳米线为金红石相及少量锐钛矿相。测试结果显示刻蚀35 min的多孔硅/TiO_2样品具有最高的减反射率,在模拟太阳光下具有较高的光电流(光电流密度)活性,且在1.5 V外加偏压下具有最高的光电催化活性。这是由于刻蚀35 min的多孔硅基底具有优异的减反射性能,同时多孔硅与Ti O_2纳米线复合形成光阳极之后具有异质结效应和窗口效应,使得多孔硅/TiO_2纳米线光阳极具有优异光电化学性能。