Synthesis and Characterization of Cobalt-Carbon Core-Shell Microspheres in Supercritical Carbon Dioxide System

研究了钴碳核壳微球在超临界二氧化碳体系中的合成过程. 在密闭的不锈钢高压反应釜中,适量的二茂钴和干冰在350 oC下,反应12 h后合成直径大约1 μm的钴碳核壳微球。通过X射线衍射、X射线光电子谱、透射电子显微镜、傅利叶红外光谱(FT-IR)以及拉曼光谱的分析,钴碳核壳微球是由直径小于1 μm的非晶钴核和厚度约为200 nm的非晶碳壳组成. 其生长机理可能是：二茂钴在超临界二氧化碳体系中的热分解,带单电子的碳原子或基团由于磁性作用沉积在磁性的钴核上. 由于非晶碳壳的存在,钴碳核壳微球的磁饱和强度141.     

催化剂对纳米非晶碳膜场发射性能的影响

利用微波等离子体增强化学气相沉积(MPECVD)法,在经处理的单晶硅衬底上沉积了纳米非晶碳薄膜.通过Raman、SEM、XRD表征,研究了催化剂对纳米非晶碳膜的生长速率及场发射性能的影响.结果表明,在制备纳米非晶碳膜时使用FeC13,作为催化剂可大幅提高其生长速率.在相同的制备条件下,与未加FeCl3催化剂制备的纳米非...     

空心微球/网络复合型碳泡沫材料制备与机理分析

在Klett等人于2000年制备的韧带网络型碳泡沫和Bruneten等人在2002年制备了一种空心微球碳泡沫材料结构的基础上,分别经过微观结构优化、碳化、石墨化处理,制备出了一种空心微球/网络复合型碳泡沫材料.扫描电镜和体视显微镜测试结果显示网络韧带和球形空腔呈现明显的空间周期性.X射线衍射(X-ray diffraction,XRD)图谱中,26°处的衍射峰表明该试样具有较高的石墨化特征.同时,对该材料的形成机理进行了分析. 关键词： 碳泡沫 微观结构优化 扫描电镜 X射线衍射     

金刚石镶嵌非晶碳膜表面形貌对场致电子发射的影响

用微波等离子体化学气相沉积设备，在经过不同研磨预处理的金属钼衬底上沉积出了表面形貌有较大差异的金刚石镶嵌非晶碳膜，分别用扫描电子显微镜（ＳＥＭ）、金相显微镜和Ｘ射线衍射谱（ＸＲＤ）以及Ｒａｍａｎ光谱对样品进行了分析测试．研究了各样品的场致电子发射特性，结果发现薄膜表面由大量镶嵌有金刚石小晶粒的非晶碳球组成，在我们的实验范围内，薄膜表面非晶碳球尺寸越小，场致电子发射效果越好     

非晶含氢碳膜的氧等离子体刻蚀性能研究

用苯作气源,采用电子回旋共振等离子体增强化学气相沉积方法制备了非晶含氢碳膜,并在该系统上用氧等离子体对这些碳膜进行了刻蚀性能的研究.实验中,测量了碳膜在不同氧压强、流量和微波功率下的刻蚀速率,研究了膜的沉积速率与它的刻蚀速率之间的关系.结果表明,膜的刻蚀速率与膜的生长条件密切相关;在低沉积速率下生长的非晶碳膜的刻蚀率低于常用的Novolak光刻胶.这种碳膜具有较强的耐刻蚀性能,可以用作微电子器件制造中的掩膜材料. 关键词：     

化学气相沉积法制备金刚石膜截面微区Raman分析

采用微区Raman散射分析方法研究化学气相沉积法制备的金刚石膜的横截面.金刚石膜从衬底面到生长面不同位置具有不同特征的Raman谱,依此对膜中的金刚石、石墨和非晶碳成分进行分析.衬底面附近区域对应金刚石膜生长过程的成核阶段,非晶碳成分含量较高,相应于1200—1600cm^-1波段较大的散射强度和存在较强的荧光背底.膜厚增大,非晶碳成分中sp³结构成分首先减少,而sp²结构成分和石墨成分的减少相对缓慢.而生长面附近区域只有比较单纯的晶体金刚石 关键词：     

空心阴极放电沉积氮化碳薄膜的结构和成键性质

利用空心阴极放电等离子体源在Si(100)衬底上沉积了氮化碳薄膜.用XRD,SEM,XPS及拉曼和红外吸收光谱对薄膜的结构、成分和化学键等进行了研究.XRD分析表明,制备的氮化碳薄膜为非晶结构.XPS分析证实了薄膜中以C—C,sp2CN和sp3CN键为主,并得出薄膜中的氮碳比为0.71,而sp3—CN相的含量也达到了0.39.拉曼和红外吸收光谱的结果也与XPS分析的键态结果一致.     

电子回旋共振等离子体增强化学气相沉积a-CFx薄膜的化学键结构

使用CHF₃和C₆H₆混合气体做气源,在一个电子回旋共振等离子体增强化学气相沉积装置中制备了氟化非晶碳(a-CF_x)薄膜.利用发射光谱研究了等离子体中形成的各种碳氟、碳氢基团随放电宏观参量的变化规律,对薄膜做了傅里叶变换红外光谱和X射线光电子能谱分析,证实等离子体中的CF₂,CF和CH基团是控制薄膜生长、碳/氟成分比和化学键结构的主要前驱物 关键词： 氟化非晶碳薄膜 电子回旋共振等离子体     

质量分离低能离子束沉积碳膜及离子轰击效应

用质量分离的低能离子束沉积技术得到了非晶碳薄膜,X射线衍射、Raman谱以及俄歇深度谱的线形表明,此种非晶碳膜中镶嵌着金刚石颗粒.碳离子的浅注入是该碳膜SP³形成的主要机理.从一个侧面说明了化学气相沉积法中偏压预处理增加金刚石成核的主要原因是因为离子轰击效应. 关键词： 非晶碳 离子轰击 质量分离低能离子束     

热丝CVD方法生长金刚石薄膜中石墨成份控制

 在用热丝CVD方法生长金刚石薄膜中，研究了生长条件对制备膜中石墨和非晶碳成份的影响，发现较高的碳源浓度或较低的衬底温度会使制备膜中非金刚石相碳成份增加。     

Using sonochemistry for the fabrication of hollow ZnO microspheres

Hollow ZnO microspheres assembled by nanoparticles have been prepared by a sonochemical synthesis at room temperature using carbon spheres as template. The growth process of the precursor was investigated. The prepared hollow spheres were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM). The diameter of the obtained hollow spheres is about 500 nm, and the walls are composed of numerous ZnO aggregate nanocrystallines with diameters of 90 nm. A possible growth mechanism for the formation of ZnO microspheres has been proposed, in which carbon spheres play a crucial role in the formation of the wurtzite hollow ZnO microspheres. The specific structure of the hollow spheres may find applications in nanoelectronics, nanophotonics and nanomedicine.     

Study on highly visible light active Bi-doped TiO2 composite hollow sphere

Bi-doped hollow titania spheres were prepared using carbon spheres as template and Bi-doped titania nanoparticles as building blocks. The Bi-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-vis diffuse reflectance spectrum (DRS) and X-ray photoelectron spectroscopy (XPS). The effects of Bi content on the physical structure and photocatalytic activity of doped hollow titania sphere samples were investigated. Results showed that there was an optimal Bi-doped content (4%) for the photocatalytic degradation of methylene blue (MB).     

Preparation, characterization and photocatalytic activity of the neodymium-doped TiO2 hollow spheres

Nd-doped titania hollow spheres were prepared using carbon spheres as template and Nd-doped titania nanoparticles as building blocks. The Nd-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The effects of Nd content on the physical structure and photocatalytic activities of doped titania hollow sphere samples were investigated. Results showed that there was an optimal Nd-doped content (3.9 at.%) for the photocatalytic degradation of dye X-3B (C.I. Reactive Red 2). The apparent rate constant of the best one was almost 9 times as that of P25 titania. The mechanism of photocatalytic degradation of dyes under visible light irradiation was also discussed.     

Synthesis of porous hollow silica spheres using polystyrene-methyl acrylic acid latex template at different temperatures

Porous hollow silica spheres were prepared by using polystyrene-methyl acrylic acid latex as a template and cetyltrimethylammonium bromide as a wall structure-directing agent starting from tetraethoxysilane. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-infrared spectroscopy (FT-IR) and nitrogen adsorption/desorption were used to characterize the hollow silica spheres. When silica-coated latex composites were prepared at room temperature, hollow silica spheres with micropores in the walls were formed after removing the latex templates by calcination. When silica-coated latex composites were aged at a higher temperature of 150 °C, intact mesoporous hollow silica spheres were formed after calcination treatment.     

A one-pot method to prepare N-doped titania hollow spheres with high photocatalytic activity under visible light

N-doped titania hollow spheres (NTHS) were prepared by a one-pot hydrothermal method using urea as precursor of nitrogen. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The photocatalytic activity of as-prepared titania hollow spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to non-doped titania hollow spheres and commercial P25 titania. Results indicated that the as-prepared NTHS showed highest photocatalytic activity.     

Synthesis, characterization and photodegradation study of mixed-phase titania hollow submicrospheres with rough surface

Titania hollow submicrospheres with mixed phase (anatase-brookite or anatase-rutile) were synthesized via the combination of hydrothermal treatment and calcination of submicrospheres consisting of a polystyrene core and an amorphous TiO₂ shell. After hydrothermal treatment, amorphous titania shell could be transformed to anatase-brookite shell consisting of loose packed titania nanocrystals, which could be further converted to anatase-brookite (below 700 °C) or anatase-rutile titania (700-800 °C) hollow spheres with rough surface via calcination. The loose packing of titania nanocrystals not only inhibited the transformation temperature from anatase to rutile, but also provided titania hollow submicrospheres with high photodegradation activity of Rhodamine B. The photocatalytic activity of titania hollow spheres increased firstly then decreased when the calcination temperature was varied in the range of 450-800 °C, while hollow spheres obtained via calcinating at 700 °C exhibited the highest photocatalytic activity, which was five times higher than that of counterpart without hydrothermal treatment.     

Preparation of Manganese Oxide Hollow Spheres Using pH-responsive Microgels as Templates

以pH响应型微凝胶为模板制备出了二氧化锰空心球材料,并利用XRD、TGA、SEM、FT-IR和TEM等手段对其进行了表征. 结果表明,通过调节KMnO₄的用量可以有效控制二氧化锰空心球的球壳厚度. 对洗脱后上层清夜中的pH响应型微凝胶进一步研究发现,部分微凝胶呈现出非可逆的膨胀-收缩转变,这一现象主要是由于其内部的交联程度不高造成的. 在对表征结果进行分析后提出了空心球结构的形成机理.     

金纳米空球的合成及其SERS效应

本文利用非晶硒溶胶作模板合成了金纳米空球,采用扫描电子显微镜(SEM)、X射线衍射(XRD)及拉曼光谱对其进行了表征,结果显示,所得到的金纳米空球呈多晶结构,粒径约为150 nm,壳层厚度约为25 nm,表面为颗粒状金原子团簇;将金纳米空心球组装到玻碳电极表面,以SCN-作为探针分子,初步探讨了金纳米空球的SERS效应,表明其具有较强的SERS活性。     

Stratified dust grains in the interstellar medium. III: Infrared cross-sections

We construct a model of interstellar dust in which H-rich amorphous carbon is deposited on silicate substrates in the interstellar medium, and is annealed to form H-poor amorphous carbon. The model grains are stratified spheres composed of hollow silicate cores coated with two carbonaceous layers, the inner layer of sp² carbon and the outer layer of sp³ carbon. Using an accurate method of computing the optical properties of such layered grains, we explore the consequences of varying the core-grain size distribution and the thicknesses of the carbonaceous layers on the resulting infrared extinction. We find a wide dispersion in the curve morphology that reflects the grain size distributions and the chemical composition of dust materials.     

A novel approach to fabrication of superparamagnetite hollow silica/magnetic composite spheres

We described a method for synthesizing hollow silica/magnetic composite spheres using sulfonic acid functionalized hollow silica spheres (SAFHSS) as templates. The Fe₃O₄ nanoparticles were deposited on or imbedded in the hollow silica shell by a precipitation reaction. The morphologies, composition and properties of the hollow composite spheres were characterized by transmission electron microscopy, Fourier transform infrared analysis, X-ray diffraction measurement and vibrating-sample magnetometry measurement. The results indicated crystal sizes and amount of the Fe₃O₄ nanoparticles on the SAFHSS. The magnetic properties of the hollow composite spheres were controlled by adjusting the proportion between Fe²⁺ and Fe³⁺ and iron ion total concentration. When appropriate loading species were added into the system, superparamagnetite hollow composite spheres were obtained. The method also could be applicable to prepare other superparamagnetite hollow silica/ferrite composite spheres.